Hazzard assessment and cytogenotoxic effects of different concentrations of mercury chloride sterilant using an onion (Allium cepa) assay

Hazzard assessment and cytogenotoxic effects of different concentrations of mercury chloride sterilant using an onion (Allium cepa) assay | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Hazzard assessment and cytogenotoxic effects of different concentrations of mercury chloride sterilant using an onion (Allium cepa) assay DAVID ADEDAYO ANIMASAUN, PETER ADEOLU ADEDIBU, SAHEED OLAREWAJU AFOLABI, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3821770/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract The Allium cepa assay represents a crucial in vivo model for evaluating the cytotoxicity and genotoxicity of substances. This study investigated the cytogenotoxicity potential of mercury chloride (HgCl 2 ), a laboratory disinfectant and catalyst, using an Allium cepa assay. Mitotic slides were prepared from onion root tip cells grown on media supplemented with different concentrations of HgCl 2 (0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%). The slides were observed to evaluate cytogenotoxicity based on measurements of the mitotic index, mitotic inhibition percentage, clastogenic alterations, and root length over 10 days. The results suggest that the concentrations used may harm the cell, leading to adverse impacts on the mitotic index, mitotic inhibition, root growth and chromosome structure. Different chromosomal aberrations, such as bridge formation, fragmentation, wandering chromosomes, stickiness, binucleus formation and micronucleus formation, were detected depending on the concentration. Although lower concentrations (0.2–0.4%) had fewer effects on the cells, they still had a significant cytogenotoxic effect ( p < 0.05 ) compared to that of the control (0.0%). The higher the concentration was, the greater the effects on clastogenic changes. The observed abnormalities in both mitotic spread and root growth indicate that mercury chloride is cytotoxic even at low concentrations and can cause mitotic-depressive effects at higher concentrations. The results of this investigation can be used as a guide to guarantee sufficient safety precautions for people and organs during the regular use of HgCl 2 . Allium cepa cytotoxicity assay mercury chloride mitotic index mitotic inhibition chromosome aberrations Figures Figure 1 Figure 2 Figure 3 1. Introduction Cytotoxicity describes the harmful impact of chemical agents on living cells. An agent may also be genotoxic if it induces genetic changes within a cell, resulting in a mutation, a condition that can be fatal or extremely harmful to different systems. This alteration may produce permanent and heritable effects on DNA, impacting either the organism's somatic or germ cells, which can be passed down to future generations (Sainis et al . 2016; Banti and Hadjikakou 2019 ). Cytological examination of either mitotic or meiotic behaviour is a reliable way of measuring mutagenic potential (Aslantürk 2018 ). Cytotoxicity testing holds great significance in the biological assessment of chemicals in cells. The extent of cytotoxicity and damage to cellular structure and physiology, such as disruption of the cell membrane, inhibition of protein synthesis, and irreversible binding to receptors, can be determined by conducting tests on chemicals, drugs, and extracts. Therefore, rapid, accurate and cost-effective cytotoxicity assays that evaluate toxicity to whole organisms by examining their impact in vivo or/ in vitro are needed (Ishiyama et al. 1996 ; Asita and Matebesi 2010 ; Sahu et al. 2014 ; Chrysouli et al. 2018 ). The use of assays can be invaluable in determining the effects of chemicals or biologics in living tissues. Cytotoxicity assays aim to affect various cellular mechanisms, such as cell membrane permeability, ATP production, enzyme activity, coenzyme production, and nucleotide uptake activity (Aslantürk 2018 ). Onion ( Allium cepa ) is a suitable model for experimentally determining the in vivo cytotoxicity of chemicals and complex mixtures (Lerda et al. 2010 ; Tedesco and Laughinghouse 2012 ; Sainis et al . 2016; Milionis et al . 2018). The A. cep a assay is considered a cost-effective and easy-to-use screening method that surpasses other short-term screening methods requiring prior preparation of test samples and the inclusion of exogenous metabolic systems. This assay can evaluate the toxicity and genotoxicity of substances (Banti and Hadjikakou 2019 ). This includes assessing chromosomal irregularities and mitotic anomalies (Leme and Marin-Morales 2009 ; Lerda et al. 2010 ; Bakare et al. 2012 ; Khalil et al. 2016 ). The Allium cepa test is commonly used to evaluate the harm caused by mutagens to DNA. This test has also been effective at screening the cytotoxicity of chemical agents and studying the genotoxicity of environmental pollutants (Fernandes et al. 2007 ; Asita and Matebesi 2010 ; Milionis et al . 2018). The Allium cepa assay is significantly correlated with mammalian testing systems. Bakare et al. ( 2012 ) used this assay to evaluate the cytogenotoxicity induced by e-waste leachate. Kaymak and Goc-Rasgele ( 2009 ) explored the genotoxicity of Raxil by using the Allium cepa assay. Metin and Bürün (2008) investigated the cytogenetic effects of aqueous extracts of Urginea maritime L. on chromosomes using an Allium cepa assay. Mercuric chloride (HgCl 2 ) is a chemical compound consisting of mercury and chlorine atoms. It is a laboratory reagent regularly used as a catalyst for converting acetylene to vinyl chloride, the precursor for polyvinyl chloride synthesis (Simon et al. 2006 ). In addition, HgCl 2 functions as a depolarizer in batteries. Due to its effectiveness as a germicide, it is frequently used to sterilize the surfaces of explants and workspaces in plant tissue culture laboratories before culture inoculation. Moreover, it is employed in dental amalgam fillings (Bengtsson and Hylander 2017) as well as in energy-efficient light bulbs (Bjorklund et al . 2017). During the Middle Ages, Arab physicians employed HgCl 2 to sterilize wounds. This practice persisted for several decades, even throughout the twentieth century, although it was ultimately deemed unsafe for modern medicinal use (Maillard et al . 2007). Although HgCl 2 is considered toxic and should not be handled carelessly, it is required for the daily operation of many laboratories and factories, and some individuals are exposed to this chemical daily during their work. The increasing concern about contamination from mercury compounds in laboratories and the environment is of global significance. HgCl 2 is a highly corrosive and toxic substance that can cause acute and cumulative poisoning (US Environmental Protection Agency 2010 ). Mercury poisoning can occur not only through ingestion but also through skin absorption into the bloodstream, resulting in detrimental effects on the kidneys and nervous system (Oriquat et al . 2012). Exposure to HgCl 2 can lead to various symptoms, including skin rashes, vision impairment, memory loss, and mental disorders (Health Canada 2008 ; US Environmental Protection Agency 2010 ). Traces of mercury have been identified in cosmetics, skin-lightening products, and even in fish and algae from polluted aquatic environments (Clarkson 2002 ; Silva-Pereira 2005). The absorption rate varies based on the amount of mercury compound present, the duration of exposure, and the concentration of the compound. Assays aimed at detecting genotoxic molecules entail analysing the levels of DNA damage in exposed cells. This damage can arise due to chromosomal breakage, encompassing both single- and double-strand breaks, loss of excision repair, cross-linking, point mutations, and structural as well as numerical chromosomal aberrations (Chrysouli et al. 2018 ; Banti and Hadjikakou 2019 ). In most scenarios, negative alterations in genetic material can give rise to a range of disorders. Numerous methods for conducting in vitro and in vivo toxicological tests have been developed to evaluate the genotoxicity of chemicals. Hence, this study aimed to assess the toxic impact of different concentrations of HgCl 2 on the occurrence of mitotic indices (%), chromosomal aberrations (%), nuclear abnormalities (%), and micronuclei (%) at various mitotic stages using the Allium cepa model. 2. Materials and methods 2.1 Plant material preparation and treatments Bulbs of onions ( Allium cepa ) were sourced from a market in Ilorin, Nigeria, for this study. After being left to dry in the sun for five days and then cleared, healthy bulbs of approximately equal sizes were selected for the experiment. Mercury chloride (HgCl 2 ) was purchased from Sigma Aldrich (USA) and was used at concentrations of 0.2, 0.4, 0.6, 0.8, and 1% w/v to create a concentration gradient for the examination of cytogenotoxicity in Allium cepa . Deionized water was used as the control (0.0%). The bulbs were prepared by removing the dry, scaly brown covering leaves and the old roots attached to the basal stem, leaving the ring of the primordial roots intact. The toxicity of the HgCl 2 solution on root growth and in vivo induction of Allium cepa chromosomal aberration was evaluated following the methods outlined by Khalil et al. ( 2009 ). The basal stem of the onion bulbs was suspended in 50 ml conical tubes for each of the tested concentrations of HgCl 2 , with five replicates for each chloride concentration and for the control. The sample was kept at a temperature of 27 ± 1°C in a dark laboratory cupboard. The treatment solutions were changed every other day, and onion bulbs were carefully examined daily to monitor root emergence, which aided in identifying the growth-inhibiting impact of HgCl 2 at various concentrations for 10 days. 2.2 Root harvest and slide preparation When the roots of Allium cepa had grown to a length of approximately 3 cm, the root tips were excised using sterilized scissors. The tips are then collected and labelled in specimen tubes according to the treatments. Harvesting of the root tips was performed in the morning between 9:00 a.m. and 10:00 a.m. to collect cells that were actively undergoing cell division. The pretreatment of roots and slide preparation followed the Asita and Matebesi ( 2010 ) protocol, with a few modifications. The root tips were pretreated with Para-dichlorobenzene for four hours. The treated root tips were then extracted from the solution with forceps, rinsed twice in double distilled deionized water and subsequently transferred to a tube containing freshly prepared ethanol:glacial acetic acid fixatives (3:1, v/v) for 24 hours. The root tips were rinsed with ice-cold distilled water after being removed from the fixative. Following this, the tips were hydrolysed in a watch glass with 5 N HCl for 10 minutes at room temperature, after which the HCl was discarded. Next, the tips were transferred to clean microscopic slides, and 1–2 mm of the growing tip was removed while the tips were retained and the other root parts discarded. Then, 2% acetocarmine was added to cover the tip, which was left for 10 minutes before being covered with a coverslip. The root tips were then squashed in 45% acetic acid and stained through gentle tapping until a turbid suspension was formed, and the slide was covered with a cover slit in preparation for microscopic observation. 2.3 Scoring of slides and data analysis Several replicates were conducted to obtain cells at different stages of mitosis. The slides were observed using a light microscope, starting with the lowest objective lens (×10) and progressing steadily to higher objectives. The mitotic index was calculated with a ×40 objective by observing dividing and nondividing cells and noting chromosomal anomalies. Using a digital camera attached to the microscope's eyepiece, images of chromosomes were captured at each stage of mitosis. Approximately 300 cells were screened in three randomly selected areas per slide. Two slides were examined for each bulb, and five replicates were performed, resulting in a total of 3,000 cells per treatment. The following parameters were assessed: (a) the mitotic index (MI); (b) the frequency of cells displaying chromosome aberrations (CAs), which include bridges, fragments, sticky chromosomes, polar deviation, pulverization, and others; and (c) the frequency of micronucleus (MN) formation. Cytotoxicity determination A comparison was conducted to analyse the behaviour and morphology of chromosomes in cells exposed to HgCl 2 or without such exposure (control). For cells that displayed mitotic irregularities, changes in the mitotic index, chromosome damage or cell death, the HgCl 2 dosage was considered cytotoxic. The toxicity parameters evaluated included the mitotic index (MI) and the occurrence of different chromosome aberrations (CAs), including sticky chromosomes, pulverization, bridge formation, fragmentation, and polar deviation. Additionally, the presence of micronuclei (MNs) was examined among the treatment groups. The mitotic index (MI) was determined according to Eq. (1) suggested by Sehgal et al. ( 2006 ). Chromosomal aberrations (CAs) refer to alterations in either the structure or total number of chromosomes (karyotypes) following exposure to a chemical agent. Mitotic inhibition was measured using the method of Fiskejo (1993) (2). The frequency of MNs was evaluated as ‰ MNs in interphase cells per 1000 cells, as outlined by Pavlica et al . (2000). Representative micrographs demonstrating frequent abnormalities. $$\text{M}\text{i}\text{t}\text{o}\text{t}\text{i}\text{c} \text{i}\text{n}\text{d}\text{e}\text{x}= \frac{\text{D}\text{i}\text{v}\text{i}\text{d}\text{i}\text{n}\text{g} \text{c}\text{e}\text{l}\text{l}\text{s} \text{i}\text{n} \text{a}\text{l}\text{l} \text{p}\text{h}\text{a}\text{s}\text{e}\text{s}}{\text{T}\text{o}\text{t}\text{a}\text{l} \text{n}\text{u}\text{m}\text{b}\text{e}\text{r} \text{o}\text{f} \text{c}\text{e}\text{l}\text{l}\text{s}} \times 100$$ $$\text{M}\text{i}\text{t}\text{o}\text{t}\text{i}\text{c} \text{i}\text{n}\text{h}\text{i}\text{b}\text{i}\text{t}\text{i}\text{o}\text{n}= \frac{\text{m}\text{i}\text{t}\text{o}\text{t}\text{i}\text{c} \text{i}\text{n}\text{d}\text{e}\text{x} \text{i}\text{n} \text{t}\text{h}\text{e} \text{c}\text{o}\text{n}\text{t}\text{r}\text{o}\text{l} – \text{m}\text{i}\text{t}\text{o}\text{t}\text{i}\text{c} \text{i}\text{n}\text{d}\text{e}\text{x} \text{o}\text{f} \text{t}\text{e}\text{s}\text{t} \text{c}\text{o}\text{n}\text{c}\text{e}\text{n}\text{t}\text{r}\text{a}\text{t}\text{i}\text{o}\text{n}}{\text{M}\text{i}\text{t}\text{o}\text{t}\text{i}\text{c} \text{i}\text{n}\text{d}\text{e}\text{x} \text{o}\text{f} \text{t}\text{h}\text{e} \text{c}\text{o}\text{n}\text{t}\text{r}\text{o}\text{l}} \times 100$$ 2.4 Data analysis All experiments were carried out in five replicates. The data were evaluated for analysis of variance (ANOVA) using SPSS version 20 (IBM Corp. Armonk, NY. USA). The significance level between the treatment means was determined using Tukey's honest significant difference (HSD) test at a p value of less than 0.05. 3. Results The effects of different levels of HgCl 2 on root growth are illustrated in Fig. 1 . An inhibitory impact on the growth of onion bulbs was observed at all five doses. Onions treated with lower concentrations (0.2% and 0.4%) demonstrated delayed rooting, whereas higher concentrations (0.6%, 0.8%, 1%) exhibited significantly delayed emergence of roots. In the replicates where the onions underwent no HgCl 2 treatment (control setup), the root growth was optimal. Onions commenced sprouting on the third day and reached a length exceeding 1 cm. The delay in root emergence increased with increasing HgCl 2 concentration. Even at the 10-day mark, the average root lengths of the untreated control and those treated with 0.2 and 0.4% HgCl 2 were 9.28, 5.16, and 4.18 cm, respectively. However, higher dosages significantly inhibited root growth. The most detrimental effect was observed in samples treated with 1.0% HgCl 2 , in which the length of the roots was less than 2 cm on the 10th day (Fig. 2 ). Analysis of the cytological impacts of different concentrations of HgCl 2 revealed a direct relationship between the number of dividing cells, the percentage of mitotic cells, and the percentage of mitotic inhibition (Table 1 ). A lower concentration (0.2 and 0.4%) resulted in a greater number of actively dividing cells, while the number of cells undergoing division decreased as the concentration increased. Additionally, the untreated bulbs (control) contained the greatest quantity of dividing cells in various phases. Similarly, the percentage of mitotic index (%MI), which indicates the proportion of actively dividing cells in comparison to the total number of cells observed, decreased proportionally with concentration. In this study, the MI was used as a quantitative measurement of cell division rates, which decreased as the concentration of HgCl 2 increased. In contrast, the percentage of mitotic inhibition showed a concentration-dependent pattern. Increased concentrations of HgCl 2 resulted in greater mitotic inhibition. Thus, as the concentration increased, cellular division was increasingly inhibited. Table 1 Cytological effects of exposure to varying concentrations of HgCl 2 on A. cepa mitotic cells. HgCl 2 concentrations (%) Total number of cells Dividing cells Mitotic index (%) Mitotic inhibition (%) Control 2957.64a 413.35a 14.01a 0.00f 0.2 2972.81a 361.44b 12.16ab 13.20de 0.4 2413.66a 277.36c 11.49bc 17.99d 0.6 2433.33a 237.66cd 9.77c 30.26c 0.8 2341.33a 117.41e 5.01d 64.24ab 1.0 2129.66a 61.33f 2.89de 79.37a The values designated by different superscript letters in each column are significantly different from each other at a level of p < 0.05 . Cytological analysis revealed various types and frequencies of chromosomal abnormalities in the root meristem of A. cepa treated with varying concentrations of HgCl 2 , a surface sterilization agent commonly used in industry or laboratories. The observed normal division and chromosomal aberration data are shown in Figs. 3 a and 3 b, while Table 2 presents the findings. The frequency of chromosomal aberrations, including anaphase bridge, stickiness, C-mitosis, chromosome fragmentation, and micronucleus formation, exhibited notable differences among the various concentrations of HgCl 2 . Anaphase bridges, characterized by incomplete segregation of nuclear material to the poles owing to persistent DNA entanglement between sister chromatids, were more evident in onion root cells treated with higher concentrations (0.6-1.0%) of HgCl 2 . The pattern is consistent for all the other identified abbreviations. Exposing root cells to elevated concentrations of HgCl 2 leads to an increased occurrence of chromosomal aberrations. Table 2 Chromosome aberration of A. cepa mitotic cells in response to exposure to varying concentrations of HgCl 2 . HgCl 2 Conc. (%) Total number of counted cells a Anaphase bridge Stickiness Fragment Micronucleus Others b % Chromosome aberration 0.0 2957.64a 1.00d 9.01e 0.00c 5.11de 4.20cd 0.65 0.2 2972.81a 11.13c 24.16cd 13.20b 6.24cd 2.91cd 1.94 0.4 2413.66a 8.33cd 21.49cde 7.99bc 14.25bc 3.83cd 2.32 0.6 2433.33a 31.56ab 19.77de 10.26b 11.25c 8.25bc 3.32 0.8 2341.33a 43.45a 45.01b 64.24a 23.25b 11.48b 8.00 1.0 2129.66a 33.42a 102.89a 79.37a 42.45a 36.15a 13.82 a The average total number of mitotic cells counted for each HgCl 2 treatment was determined in three replicates. b Other observed chromosomal aberrations include nuclear abnormalities, binucleated cells, irregular prophase, polyploidy, pulverization, anaphase lagging chromosome, multipolar cells, and polyploidy. The values designated by different superscript letters in each column are significantly different from each other at a level of p < 0.05 . Low concentrations (0.2–0.4%) of HgCl 2 resulted in chromosome genotoxicity and damage in treated cells. Nevertheless, such concentrations are toxic to cells, causing chromatin to become sticky clumps, which may lead to sterility and chromosome fragmentation (Table 2 ). Moreover, a concentration of 0.4% resulted in the development of micronuclei in a considerable number of cells, with an even greater amount being found in those exposed to 0.6%. A small number of chromosomal aberrations, such as irregular prophase, anaphase lagging and pulverization, were observed in the root cells of onions that were not treated. Nevertheless, with higher concentrations of HgCl 2 , their frequency increased. Exposure to 0.6-1.0% HgCl 2 resulted in increased frequencies of multipolar cells, binucleated cells, and nuclear abnormalities in the treated bulbs. Essentially, the investigation revealed a substantial percentage of chromosome abnormalities, signifying cytogenotoxicity for HgCl 2 concentrations ranging from 0.6-1.0%. The order of aberrations triggered by interventions was 0.0 < 0.2%<0.4%<0.6%<0.8%<1.0%, indicating that high concentrations are associated with a greater risk of harm and genotoxicity. 4. Discussion This study revealed chromosomal irregularities in mitotic cells of Allium cepa when exposed to different concentrations of HgCl 2 . The results revealed a range of chromosomal abnormalities at various stages of mitosis in onion roots exposed to the chemical, indicating that this chemical can be used as a sterilizer or disinfectant alone or in combination with other chemicals as a catalyst (Simon et al. 2006 ) and has genotoxic and mutagenic properties (Silva-Pereira 2005; Shalan 2022 ). The genotoxicity of mercury primarily results from its capacity to react with the sulfhydryl groups of tubulins. This process inhibits spindle function and results in various forms of chromosomal aberrations, and this chemical can also induce polyploidy (De Flora et al. 1994 ; Silva-Pereira et al. 2005 ). Moreover, mercury triggers free radical production by generating osmotic stress (Ehrenstein et al . 2002; Durak et al . 2010), which prompts apoptosis and consequent DNA damage (Hossain et al . 2021). Thus, the potential of HgCl 2 to cause disruptions in the sequential and directional process of mitotic cell division/cycle progression suggests cyto- and genotoxicity. These effects can be inferred from the mitotic indices of the plants, as well as the various clastogenic and aneugenic events observed in the roots exposed to HgCl 2 . According to Schurz (2000), mercury may hinder cellular antioxidant mechanisms, leading to cell degeneration and, ultimately, necrosis. Boujbiha et al . (2009) confirmed that HgCl 2 is the most harmful mercury compound due to its strong affinity for proteins. They found that cells exposed to any amount of HgCl 2 experienced detrimental consequences, indicating that the chemical is hazardous to living tissues. In this study, even at a low concentration of 0.2% w/v, considerable chromosome damage was detected, implying that prolonged exposure to the substance might be hazardous, given its potential for penetrating the skin and causing adverse effects on the body's organs and genetic system (Su et al. 2008 ; Oriquat et al . 2012). However, despite the potential risks associated with HgCl 2 , various laboratories, hospitals, and industries continue to use this material for different purposes (Dadar et al . 2016; Bengtsson and Hylander 2017; Bjorklund et al . 2017). This poses a threat to personnel who may be exposed to the chemical's harmful genotoxic effects. In a study conducted by Hwang et al. ( 2013 ), the toxic effects of HgCl 2 on keratinocytes and the subsequent impact on the expression of certain genes were demonstrated. The authors observed cell death and disruption of the cell membrane structure caused by the harmful effects of HgCl 2 . Several decades ago, Sander et al. ( 1978 ) reported the occurrence of chromosomal damage during the mitotic process in barley exposed to mercury chloride. The results from the present study were consistent with earlier research. HgCl 2 toxicity was found to cause several chromosomal abnormalities, including fragmentation, lagging, stickiness, bridge formation, polyploidy, binucleation, and nuclear budding. These abnormalities could lead to DNA damage, alterations in the genetic system, and mutations or disorders (Chrysouli et al. 2018 ). As demonstrated in the present study, high levels of HgCl 2 hinder cellular division, leading to significant occurrences of diverse clastogenic changes and reducing the mitotic index. These findings support previous reports (Nefic et al. 2013 ; Sabeen et al. 2020 ) that suggest a correlation between high accumulation of heavy metals in plant roots and chromosomal irregularities, such as a decreased mitotic index, increased frequency of chromosome lagging, bridge formations, and nuclear lesions. These aberrations can interfere with cell division and result in disorders and even the death of cells. The occurrence of anaphase bridges, a decreased mitotic index, chromosome lag, and other chromosomal aberrations observed in this study is contingent on concentration. These findings are consistent with the findings of Ping et al. ( 2012 ), who revealed that the genotoxicity induced by Euphorbia hirta extract also hinges on the concentration. The occurrence of chromosome bridging is attributed mainly to chromosome stickiness, which leads to delayed separation and unsuccessful detachment of these adhesive chromosomes. Internally within or between chromatids, chromosomal structures become bridged through a combination of homologous and nonhomologous chromosome exchanges, usually due to dicentric formation or defective replication processes. These events can result in disorders (Feretti et al. 2007 ). Chromosomes can become adhesive in two ways: through contraction or condensation, DNA depolymerization and partial dissolution of nucleoproteins. This study demonstrated a high rate of stickiness, suggesting the harmful impact of HgCl 2 on nuclear materials, which may cause irreversible damage and cell death. Additionally, the occurrence of unaligned chromosomes suggested impaired organization and function of the spindle apparatus caused by HgCl 2 . The different degrees of C-mitosis detected in onion root cells suggest the presence of harmful substances in the growth media (Bonciu et al . 2018). The Allium cepa test demonstrated a substantial correlation with potential impacts in mammals (Khalil et al. 2016 ; Milionis et al. 2018), and because the assay can be employed without ethical concerns, it functions as a valuable model for assessing cytotoxicity. The Allium cepa test has been utilized to evaluate the possible chemical impacts of chromosomal aberrations and cytotoxicity (Bakare et al. 2012 ; Sabeen et al. 2020 ). In these previous studies, the authors reported considerable chromosome distortion and cytotoxicity when high levels of chemicals were applied. The results of this study may hold weight for tissue culturists, microbial laboratory technologists, patients, and industrial workers who are at risk of HgCl 2 toxicity due to their occupation. Information regarding the cytotoxicity of HgCl 2 could therefore serve as a vital reference for ensuring adequate safety measures for those frequently working with this compound. Such measures are crucial given the documented potential for harm to essential bodily organs (Saljooghi and Delavar-mendi 2013; Mohamed et al. 2019 ). 5. Conclusion The present study explored the cytotoxic impact of different HgCl 2 concentrations on onion root tips by identifying numerous chromosomal abnormalities, including lagging chromosomes, chromosome bridges in various stages of cell division, vagrants, sticky chromosomes, binucleated cells, chromosome fragmentation, and loculated nuclei. The majority of the induced abnormalities exhibited concentration dependence. However, the data have shown that concentrations as low as 0.2% can result in harmful effects, leading to cytotoxicity. HgCl 2 caused significant clastogenic changes in onion root tip cells, which suggested that it interferes with cell growth and the cell cycle, possibly affecting the genetic system and behaviour of the cells. The data gathered on HgCl 2 toxicity in this study can serve as a point of reference to ensure the implementation of appropriate safety measures by those who frequently use HgCl 2 to prevent harm to vital organs. Declarations Author Contributions DAA, PAA, SI and RK designed the study. All the authors carried out the cytogenetic studies. DAA and PAA analysed the data. DAA, SAO KAA and RK interpreted the results and validated the correctness of the information. All the authors prepared and vetted the final manuscript. Conflict of Interest The authors declare no potential conflicts of interest. Funding Information No funding was received for this study. Data Availability Statement The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request Plant Ethics: The study protocol comply with relevant institutional, national, and international guidelines and legislation. 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Combined assay of cell viability and in vitro cytotoxicity with a highly water-soluble tetrazolium salt, neutral red and crystal violet. BioloPharm Bull. 19 (11) 1518–1520 Kaymak F, Goc-Rasgele P 2009 Genotoxic effects of raxil on root tips and anthers of Allium cepa L. Caryologia, 62(1) 1–9. Khalil A, Maslat A, Hafez A., Mizyed S and Ashram M 2009 Genotoxicity of different tert-butyl calyx [4] crowns. Zeitschrift für Naturforschung C, 63 167–175. Khalil AM, Salman WK and Al-Qaoud KM 2016 Preliminary evaluation of acute cytogenotoxicity of a novel phenylboronic acid derivative; 2- (bromoacetamido) phenylboronic acid using the Allium cepa chromosome aberrations assay. Caryologia 70(1) 34–41 Leme DM and Marin-Morales MA 2009 Allium cepa in environmental monitoring: A review on its application. Mutat. Res. 682 71–81. Lerda D, Biagi BM, Pelliccioni P and Litterio N 2010 Allium cepa as a biomonitor of ochratoxin a toxicity and genotoxicity. Plant. Biol. 12(4) 685–688. Metin M and Bürün B 2008 Cytogenetic effects of Urginea maritime L. aqueous extracts on the choromosomes by using Allium test method. Caryologia 61(4) 342–348. Milionis I, Banti CN, Sainis I, Raptopoulou CP et al . 2018 Silver ciprofloxacin (CIPAG): a successful combination of chemically modified antibiotic in inorganic-organic hybrid. J. Biol. Inorg. Chem. 23(5) 705–723. Maillard AP, Fraise PA and Lambert J 2007 Principles and practice of disinfection, preservation and sterilization. John Wiley & Sons. Oxford: p. 4. Mohamed NA, Ali AM, Bakhoum SA, Abdel-Kader HH and Ahmed MA 2019 Monitoring of oxidative stress biomarkers and toxicity of lead and mercury in catfish of Lake Mariout, Egypt: the role of Meso- 2,3- Dimercaptosuccinic acid (DMSA) Egyp. J. Aqu. Bio. Fish. 23(2) 165–182. Nefic H, Musanovic J, Metovic A and Kurteshi K 2013 Chromosomal and nuclear alterations in root tip cells of Allium cepa L. induced by alprazolam. Med. Arch. 67(6) 388. Oriquat GA, Saleem TH, Naik RR, Moussa SZ and Al-Gindy RM 2012 A sub-chronic toxicity study of mercuric chloride in the rat. Jordan J. Biol. Sci. 5(2) 141–146 Pavlica M, Besendorfer V, Roša J and Papeš D 2000 The cytotoxic effect of wastewater from the phosphoric gypsum depot on common oak ( Quercus robur L.) and shallot ( Allium cepa var. ascalonicum). Chemosphere 41(10) 1519–1527. Ping YK, Darah I, Yusuf UK, Yeng C and Sasidharan S 2012 Genotoxicity of Euphorbia hirta : An Allium cepa Assay. Molecules 17(7) 7782–7791. https://doi.org/10.3390/molecules17077782 Sabeen M, Mahmood Q, Ahmad Bhatti Z, Faridullah Irshad M, et al. 2020 Allium cepa assay based comparative study of selected vegetables and the chromosomal aberrations due to heavy metal accumulation. Saudi. J. Biolo. Sci . 27(5) 1368–1374. https://doi.org/10.1016/j.sjbs.2019.12.011 Sahu SC, Njoroge J, Bryce SM, Yourick JJ and Sprando RL 2014 Comparative genotoxicity of nanosilver in human liver HepG2 and colon Caco2 cells evaluated by a flow cytometric in vitro micronucleus assay. J. Appl. Toxicol. 34 1226–1234. Saljooghi AS and Delavar Mendi F 2013 The effect of mercury in iron metabolism in rats. J. Clin. Toxicol. S3 1–5. https://doi.org/10.4172/2161-0495.S3-006 Sander C, Nillan RA, Kleinhof SA and Big BK 1978 Mutagenic and chromosome breaking effects of mercury chloride in barley and human leucocyte. Mut. Res. 50 67–76. Schurz F, Sabater-Vilar M and Fink-Gremmels J 2000 Mutagenicity of mercury chloride and mechanisms of cellular defence: the role of metal-binding proteins. Mutagenesis 15 525–530. Sehgal R, Roy S and Kumar VL 2006 Evaluation of cytotoxic potential of latex of Calotropis procera and podophyllotoxin in Allum cepa root model. Biocell 30(1) 9–13. Shalan MG 2022 Amelioration of mercuric chloride-induced physiologic and histopathologic alterations in rats using vitamin E and zinc chloride supplement. Heliyon 8(12) e12036. Silva-Pereira LC, Cardoso PCS, Leite DS, Bahia MO et al . 2005 Cytotoxicity and genotoxicity of low doses of mercury chloride and methylmercury chloride on human lymphocytes in vitro. Braz. J. Med. Biolog. Res. 38 901–907 Simon M, Jönk P, Wühl-Couturier G and Halbach S 2006 Mercury, mercury alloys, and mercury compounds. In: Ullmann's Encyclopedia of Industrial Chemistry. (6th ed.). Wiley-Interscience, New York, pp. 15264–15295 https://doi.org/10.1002/14356007.a16269.pub2 Sainis I, Banti CN, Owczarzak AM and Kyros et al. L 201. New antibacterial, non-genotoxic materials, derived from the functionalization of the anti-thyroid drug methimazole with silver ions. J. Inorg. Biochem. 160 114–124. Su L, Wang M, Yin ST, Wang HL et al . 2008 The interaction of selenium and mercury in the accumulations and oxidative stress of rat tissues. Ecotoxicol. Environ. Saf. 70(3) 483–489. Tedesco BS and Laughinghouse IV HD 2012 Bioindicator of genotoxicity: The Allium cepa Test. InTech. https://doi.org/10.5772/31371 US Environmental protection agency, 2010, http://www.epa.gov/hg/effects.htm (accessed on 10th August 2023). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 19 Mar, 2024 Reviews received at journal 01 Mar, 2024 Reviewers agreed at journal 26 Feb, 2024 Reviewers agreed at journal 23 Feb, 2024 Reviewers agreed at journal 29 Jan, 2024 Reviewers invited by journal 26 Jan, 2024 Editor assigned by journal 15 Jan, 2024 Submission checks completed at journal 15 Jan, 2024 First submitted to journal 29 Dec, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3821770","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":267110658,"identity":"826d063b-0663-4179-bfa9-fe3fe0ed5765","order_by":0,"name":"DAVID ADEDAYO ANIMASAUN","email":"data:image/png;base64,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","orcid":"","institution":"University of Ilorin","correspondingAuthor":true,"prefix":"","firstName":"DAVID","middleName":"ADEDAYO","lastName":"ANIMASAUN","suffix":""},{"id":267110660,"identity":"4eeb98bd-da6e-4d5f-8501-251aad070649","order_by":1,"name":"PETER ADEOLU ADEDIBU","email":"","orcid":"","institution":"University of Ilorin","correspondingAuthor":false,"prefix":"","firstName":"PETER","middleName":"ADEOLU","lastName":"ADEDIBU","suffix":""},{"id":267110663,"identity":"c1d2c280-8029-4bfe-bf9a-81b8d4a0b99d","order_by":2,"name":"SAHEED OLAREWAJU AFOLABI","email":"","orcid":"","institution":"University of Ilorin","correspondingAuthor":false,"prefix":"","firstName":"SAHEED","middleName":"OLAREWAJU","lastName":"AFOLABI","suffix":""},{"id":267110665,"identity":"b2b13e03-79ba-4a2a-9604-ec7591deced1","order_by":3,"name":"KHADIJAH ABDULHAMID ABDULKAREEM","email":"","orcid":"","institution":"University of Ilorin","correspondingAuthor":false,"prefix":"","firstName":"KHADIJAH","middleName":"ABDULHAMID","lastName":"ABDULKAREEM","suffix":""},{"id":267110667,"identity":"50b1f0f8-cb4d-4da8-a3c3-1d6e4b731f80","order_by":4,"name":"SARAFADEEN IBRAHIM","email":"","orcid":"","institution":"University of Ilorin","correspondingAuthor":false,"prefix":"","firstName":"SARAFADEEN","middleName":"","lastName":"IBRAHIM","suffix":""},{"id":267110668,"identity":"8dfa2ca4-281a-4110-b6a7-09bc4e2a0b2e","order_by":5,"name":"RAMAR KRISHNAMURTY","email":"","orcid":"","institution":"University of Ilorin","correspondingAuthor":false,"prefix":"","firstName":"RAMAR","middleName":"","lastName":"KRISHNAMURTY","suffix":""}],"badges":[],"createdAt":"2023-12-29 15:44:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3821770/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3821770/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":49882462,"identity":"0b493c50-54a0-4c7e-8fb4-072f167aa73b","added_by":"auto","created_at":"2024-01-19 16:34:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":10993,"visible":true,"origin":"","legend":"\u003cp\u003eVariations in root lengths of \u003cem\u003eAllium cepa\u003c/em\u003e bulbs were observed under different concentrations of HgCl2. The mean value of five replicates ± SE is presented. The root number was determined by counting at least 0.5 cm long roots after ten days of treatment.\u003c/p\u003e","description":"","filename":"Onlinedrawingimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3821770/v1/1ba5585ff726367b89121e69.png"},{"id":49882464,"identity":"df4c2d3a-6e92-49a9-b0e3-9a53a7fb5efa","added_by":"auto","created_at":"2024-01-19 16:34:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":205089,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eAllium cepa\u003c/em\u003e\u0026nbsp;root formation in response to exposure to varying concentrations of HgCl\u003csub\u003e2 \u003c/sub\u003ein 10 days after treatment.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3821770/v1/3373e550a39d48191cb797ab.png"},{"id":49882463,"identity":"1b78a760-5c7d-4cb7-8c8f-9be5b8fed757","added_by":"auto","created_at":"2024-01-19 16:34:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2870633,"visible":true,"origin":"","legend":"\u003cp\u003e3a. Microscopic appearance of normal interphase and actively dividing cells in \u003cem\u003eAllium. cepa\u003c/em\u003e root tip meristematic region (a) Interphase; (b) Prophase; (c) Metaphase; (d) Anaphase; and (e) Telophase.\u003c/p\u003e\n\u003cp\u003e3b: Representative microscopic appearance of the nuclear abnormalities in the\u0026nbsp;\u003cem\u003eAllium cepa\u003c/em\u003e\u0026nbsp;root tip cells exposed to different concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e which is used as a sterilant in laboratories. (a): Irregular metaphase; (b): sticky anaphase; (c): sticky chromosome at prophase; (d): anaphase bridge; (e): condensed nucleus prophase; (f): polyploidy; (g): sticky metaphase; (h): telophase with vagrant chromosome; (i): nuclear buds; (j): binucleated cell; (k): delayed anaphase; (l): chromosome mis-segregation and fragmentation.\u003c/p\u003e","description":"","filename":"floatimage243.png","url":"https://assets-eu.researchsquare.com/files/rs-3821770/v1/8f5918d088df72f9147deeee.png"},{"id":49882983,"identity":"0b00c4f3-4c64-4025-9773-24a9e6d4c4be","added_by":"auto","created_at":"2024-01-19 16:42:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2652629,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3821770/v1/dbda8c3c-2963-43ae-a00b-54e0b5e5d8c9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eHazzard assessment and cytogenotoxic effects of different concentrations of mercury chloride sterilant using an onion (Allium cepa) assay\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCytotoxicity describes the harmful impact of chemical agents on living cells. An agent may also be genotoxic if it induces genetic changes within a cell, resulting in a mutation, a condition that can be fatal or extremely harmful to different systems. This alteration may produce permanent and heritable effects on DNA, impacting either the organism's somatic or germ cells, which can be passed down to future generations (Sainis \u003cem\u003eet al\u003c/em\u003e. 2016; Banti and Hadjikakou \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Cytological examination of either mitotic or meiotic behaviour is a reliable way of measuring mutagenic potential (Aslant\u0026uuml;rk \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Cytotoxicity testing holds great significance in the biological assessment of chemicals in cells. The extent of cytotoxicity and damage to cellular structure and physiology, such as disruption of the cell membrane, inhibition of protein synthesis, and irreversible binding to receptors, can be determined by conducting tests on chemicals, drugs, and extracts. Therefore, rapid, accurate and cost-effective cytotoxicity assays that evaluate toxicity to whole organisms by examining their impact \u003cem\u003ein vivo\u003c/em\u003e or/\u003cem\u003ein vitro\u003c/em\u003e are needed (Ishiyama et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Asita and Matebesi \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Sahu et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Chrysouli et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe use of assays can be invaluable in determining the effects of chemicals or biologics in living tissues. Cytotoxicity assays aim to affect various cellular mechanisms, such as cell membrane permeability, ATP production, enzyme activity, coenzyme production, and nucleotide uptake activity (Aslant\u0026uuml;rk \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Onion (\u003cem\u003eAllium cepa\u003c/em\u003e) is a suitable model for experimentally determining the \u003cem\u003ein vivo\u003c/em\u003e cytotoxicity of chemicals and complex mixtures (Lerda et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Tedesco and Laughinghouse \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Sainis \u003cem\u003eet al\u003c/em\u003e. 2016; Milionis \u003cem\u003eet al\u003c/em\u003e. 2018). The \u003cem\u003eA. cep\u003c/em\u003ea assay is considered a cost-effective and easy-to-use screening method that surpasses other short-term screening methods requiring prior preparation of test samples and the inclusion of exogenous metabolic systems. This assay can evaluate the toxicity and genotoxicity of substances (Banti and Hadjikakou \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). This includes assessing chromosomal irregularities and mitotic anomalies (Leme and Marin-Morales \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Lerda et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Bakare et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Khalil et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The \u003cem\u003eAllium cepa\u003c/em\u003e test is commonly used to evaluate the harm caused by mutagens to DNA. This test has also been effective at screening the cytotoxicity of chemical agents and studying the genotoxicity of environmental pollutants (Fernandes et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Asita and Matebesi \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Milionis \u003cem\u003eet al\u003c/em\u003e. 2018). The \u003cem\u003eAllium cepa\u003c/em\u003e assay is significantly correlated with mammalian testing systems. Bakare et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) used this assay to evaluate the cytogenotoxicity induced by e-waste leachate. Kaymak and Goc-Rasgele (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) explored the genotoxicity of Raxil by using the \u003cem\u003eAllium cepa\u003c/em\u003e assay. Metin and B\u0026uuml;r\u0026uuml;n (2008) investigated the cytogenetic effects of aqueous extracts of \u003cem\u003eUrginea maritime\u003c/em\u003e L. on chromosomes using an \u003cem\u003eAllium cepa\u003c/em\u003e assay.\u003c/p\u003e \u003cp\u003eMercuric chloride (HgCl\u003csub\u003e2\u003c/sub\u003e) is a chemical compound consisting of mercury and chlorine atoms. It is a laboratory reagent regularly used as a catalyst for converting acetylene to vinyl chloride, the precursor for polyvinyl chloride synthesis (Simon et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). In addition, HgCl\u003csub\u003e2\u003c/sub\u003e functions as a depolarizer in batteries. Due to its effectiveness as a germicide, it is frequently used to sterilize the surfaces of explants and workspaces in plant tissue culture laboratories before culture inoculation. Moreover, it is employed in dental amalgam fillings (Bengtsson and Hylander 2017) as well as in energy-efficient light bulbs (Bjorklund \u003cem\u003eet al\u003c/em\u003e. 2017). During the Middle Ages, Arab physicians employed HgCl\u003csub\u003e2\u003c/sub\u003e to sterilize wounds. This practice persisted for several decades, even throughout the twentieth century, although it was ultimately deemed unsafe for modern medicinal use (Maillard \u003cem\u003eet al\u003c/em\u003e. 2007).\u003c/p\u003e \u003cp\u003eAlthough HgCl\u003csub\u003e2\u003c/sub\u003e is considered toxic and should not be handled carelessly, it is required for the daily operation of many laboratories and factories, and some individuals are exposed to this chemical daily during their work. The increasing concern about contamination from mercury compounds in laboratories and the environment is of global significance. HgCl\u003csub\u003e2\u003c/sub\u003e is a highly corrosive and toxic substance that can cause acute and cumulative poisoning (US Environmental Protection Agency \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Mercury poisoning can occur not only through ingestion but also through skin absorption into the bloodstream, resulting in detrimental effects on the kidneys and nervous system (Oriquat \u003cem\u003eet al\u003c/em\u003e. 2012). Exposure to HgCl\u003csub\u003e2\u003c/sub\u003e can lead to various symptoms, including skin rashes, vision impairment, memory loss, and mental disorders (Health Canada \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; US Environmental Protection Agency \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Traces of mercury have been identified in cosmetics, skin-lightening products, and even in fish and algae from polluted aquatic environments (Clarkson \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Silva-Pereira 2005). The absorption rate varies based on the amount of mercury compound present, the duration of exposure, and the concentration of the compound.\u003c/p\u003e \u003cp\u003eAssays aimed at detecting genotoxic molecules entail analysing the levels of DNA damage in exposed cells. This damage can arise due to chromosomal breakage, encompassing both single- and double-strand breaks, loss of excision repair, cross-linking, point mutations, and structural as well as numerical chromosomal aberrations (Chrysouli et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Banti and Hadjikakou \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In most scenarios, negative alterations in genetic material can give rise to a range of disorders. Numerous methods for conducting \u003cem\u003ein vitro\u003c/em\u003e and \u003cem\u003ein vivo\u003c/em\u003e toxicological tests have been developed to evaluate the genotoxicity of chemicals. Hence, this study aimed to assess the toxic impact of different concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e on the occurrence of mitotic indices (%), chromosomal aberrations (%), nuclear abnormalities (%), and micronuclei (%) at various mitotic stages using the \u003cem\u003eAllium cepa\u003c/em\u003e model.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Plant material preparation and treatments\u003c/h2\u003e \u003cp\u003eBulbs of onions (\u003cem\u003eAllium cepa\u003c/em\u003e) were sourced from a market in Ilorin, Nigeria, for this study. After being left to dry in the sun for five days and then cleared, healthy bulbs of approximately equal sizes were selected for the experiment. Mercury chloride (HgCl\u003csub\u003e2\u003c/sub\u003e) was purchased from Sigma Aldrich (USA) and was used at concentrations of 0.2, 0.4, 0.6, 0.8, and 1% w/v to create a concentration gradient for the examination of cytogenotoxicity in \u003cem\u003eAllium cepa\u003c/em\u003e. Deionized water was used as the control (0.0%). The bulbs were prepared by removing the dry, scaly brown covering leaves and the old roots attached to the basal stem, leaving the ring of the primordial roots intact. The toxicity of the HgCl\u003csub\u003e2\u003c/sub\u003e solution on root growth and \u003cem\u003ein vivo\u003c/em\u003e induction of \u003cem\u003eAllium cepa\u003c/em\u003e chromosomal aberration was evaluated following the methods outlined by Khalil et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). The basal stem of the onion bulbs was suspended in 50 ml conical tubes for each of the tested concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e, with five replicates for each chloride concentration and for the control. The sample was kept at a temperature of 27\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u0026deg;C in a dark laboratory cupboard. The treatment solutions were changed every other day, and onion bulbs were carefully examined daily to monitor root emergence, which aided in identifying the growth-inhibiting impact of HgCl\u003csub\u003e2\u003c/sub\u003e at various concentrations for 10 days.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Root harvest and slide preparation\u003c/h2\u003e \u003cp\u003eWhen the roots of \u003cem\u003eAllium cepa\u003c/em\u003e had grown to a length of approximately 3 cm, the root tips were excised using sterilized scissors. The tips are then collected and labelled in specimen tubes according to the treatments. Harvesting of the root tips was performed in the morning between 9:00 a.m. and 10:00 a.m. to collect cells that were actively undergoing cell division. The pretreatment of roots and slide preparation followed the Asita and Matebesi (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) protocol, with a few modifications. The root tips were pretreated with Para-dichlorobenzene for four hours. The treated root tips were then extracted from the solution with forceps, rinsed twice in double distilled deionized water and subsequently transferred to a tube containing freshly prepared ethanol:glacial acetic acid fixatives (3:1, v/v) for 24 hours. The root tips were rinsed with ice-cold distilled water after being removed from the fixative. Following this, the tips were hydrolysed in a watch glass with 5 N HCl for 10 minutes at room temperature, after which the HCl was discarded. Next, the tips were transferred to clean microscopic slides, and 1\u0026ndash;2 mm of the growing tip was removed while the tips were retained and the other root parts discarded. Then, 2% acetocarmine was added to cover the tip, which was left for 10 minutes before being covered with a coverslip. The root tips were then squashed in 45% acetic acid and stained through gentle tapping until a turbid suspension was formed, and the slide was covered with a cover slit in preparation for microscopic observation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Scoring of slides and data analysis\u003c/h2\u003e \u003cp\u003eSeveral replicates were conducted to obtain cells at different stages of mitosis. The slides were observed using a light microscope, starting with the lowest objective lens (\u0026times;10) and progressing steadily to higher objectives. The mitotic index was calculated with a \u0026times;40 objective by observing dividing and nondividing cells and noting chromosomal anomalies. Using a digital camera attached to the microscope's eyepiece, images of chromosomes were captured at each stage of mitosis. Approximately 300 cells were screened in three randomly selected areas per slide. Two slides were examined for each bulb, and five replicates were performed, resulting in a total of 3,000 cells per treatment. The following parameters were assessed: (a) the mitotic index (MI); (b) the frequency of cells displaying chromosome aberrations (CAs), which include bridges, fragments, sticky chromosomes, polar deviation, pulverization, and others; and (c) the frequency of micronucleus (MN) formation.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCytotoxicity determination\u003c/strong\u003e \u003cp\u003eA comparison was conducted to analyse the behaviour and morphology of chromosomes in cells exposed to HgCl\u003csub\u003e2\u003c/sub\u003e or without such exposure (control). For cells that displayed mitotic irregularities, changes in the mitotic index, chromosome damage or cell death, the HgCl\u003csub\u003e2\u003c/sub\u003e dosage was considered cytotoxic. The toxicity parameters evaluated included the mitotic index (MI) and the occurrence of different chromosome aberrations (CAs), including sticky chromosomes, pulverization, bridge formation, fragmentation, and polar deviation. Additionally, the presence of micronuclei (MNs) was examined among the treatment groups. The mitotic index (MI) was determined according to Eq.\u0026nbsp;(1) suggested by Sehgal et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Chromosomal aberrations (CAs) refer to alterations in either the structure or total number of chromosomes (karyotypes) following exposure to a chemical agent. Mitotic inhibition was measured using the method of Fiskejo (1993) (2). The frequency of MNs was evaluated as \u0026permil; MNs in interphase cells per 1000 cells, as outlined by Pavlica \u003cem\u003eet al\u003c/em\u003e. (2000). Representative micrographs demonstrating frequent abnormalities.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv id=\"Equa\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\text{M}\\text{i}\\text{t}\\text{o}\\text{t}\\text{i}\\text{c} \\text{i}\\text{n}\\text{d}\\text{e}\\text{x}= \\frac{\\text{D}\\text{i}\\text{v}\\text{i}\\text{d}\\text{i}\\text{n}\\text{g} \\text{c}\\text{e}\\text{l}\\text{l}\\text{s} \\text{i}\\text{n} \\text{a}\\text{l}\\text{l} \\text{p}\\text{h}\\text{a}\\text{s}\\text{e}\\text{s}}{\\text{T}\\text{o}\\text{t}\\text{a}\\text{l} \\text{n}\\text{u}\\text{m}\\text{b}\\text{e}\\text{r} \\text{o}\\text{f} \\text{c}\\text{e}\\text{l}\\text{l}\\text{s}} \\times 100$$\u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Equb\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\text{M}\\text{i}\\text{t}\\text{o}\\text{t}\\text{i}\\text{c} \\text{i}\\text{n}\\text{h}\\text{i}\\text{b}\\text{i}\\text{t}\\text{i}\\text{o}\\text{n}= \\frac{\\text{m}\\text{i}\\text{t}\\text{o}\\text{t}\\text{i}\\text{c} \\text{i}\\text{n}\\text{d}\\text{e}\\text{x} \\text{i}\\text{n} \\text{t}\\text{h}\\text{e} \\text{c}\\text{o}\\text{n}\\text{t}\\text{r}\\text{o}\\text{l} \u0026ndash; \\text{m}\\text{i}\\text{t}\\text{o}\\text{t}\\text{i}\\text{c} \\text{i}\\text{n}\\text{d}\\text{e}\\text{x} \\text{o}\\text{f} \\text{t}\\text{e}\\text{s}\\text{t} \\text{c}\\text{o}\\text{n}\\text{c}\\text{e}\\text{n}\\text{t}\\text{r}\\text{a}\\text{t}\\text{i}\\text{o}\\text{n}}{\\text{M}\\text{i}\\text{t}\\text{o}\\text{t}\\text{i}\\text{c} \\text{i}\\text{n}\\text{d}\\text{e}\\text{x} \\text{o}\\text{f} \\text{t}\\text{h}\\text{e} \\text{c}\\text{o}\\text{n}\\text{t}\\text{r}\\text{o}\\text{l}} \\times 100$$\u003c/div\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Data analysis\u003c/h2\u003e \u003cp\u003eAll experiments were carried out in five replicates. The data were evaluated for analysis of variance (ANOVA) using SPSS version 20 (IBM Corp. Armonk, NY. USA). The significance level between the treatment means was determined using Tukey's honest significant difference (HSD) test at a \u003cem\u003ep\u003c/em\u003e value of less than 0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eThe effects of different levels of HgCl\u003csub\u003e2\u003c/sub\u003e on root growth are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. An inhibitory impact on the growth of onion bulbs was observed at all five doses. Onions treated with lower concentrations (0.2% and 0.4%) demonstrated delayed rooting, whereas higher concentrations (0.6%, 0.8%, 1%) exhibited significantly delayed emergence of roots. In the replicates where the onions underwent no HgCl\u003csub\u003e2\u003c/sub\u003e treatment (control setup), the root growth was optimal. Onions commenced sprouting on the third day and reached a length exceeding 1 cm. The delay in root emergence increased with increasing HgCl\u003csub\u003e2\u003c/sub\u003e concentration. Even at the 10-day mark, the average root lengths of the untreated control and those treated with 0.2 and 0.4% HgCl\u003csub\u003e2\u003c/sub\u003e were 9.28, 5.16, and 4.18 cm, respectively. However, higher dosages significantly inhibited root growth. The most detrimental effect was observed in samples treated with 1.0% HgCl\u003csub\u003e2\u003c/sub\u003e, in which the length of the roots was less than 2 cm on the 10th day (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAnalysis of the cytological impacts of different concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e revealed a direct relationship between the number of dividing cells, the percentage of mitotic cells, and the percentage of mitotic inhibition (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). A lower concentration (0.2 and 0.4%) resulted in a greater number of actively dividing cells, while the number of cells undergoing division decreased as the concentration increased. Additionally, the untreated bulbs (control) contained the greatest quantity of dividing cells in various phases. Similarly, the percentage of mitotic index (%MI), which indicates the proportion of actively dividing cells in comparison to the total number of cells observed, decreased proportionally with concentration. In this study, the MI was used as a quantitative measurement of cell division rates, which decreased as the concentration of HgCl\u003csub\u003e2\u003c/sub\u003e increased. In contrast, the percentage of mitotic inhibition showed a concentration-dependent pattern. Increased concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e resulted in greater mitotic inhibition. Thus, as the concentration increased, cellular division was increasingly inhibited.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCytological effects of exposure to varying concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e on \u003cem\u003eA. cepa\u003c/em\u003e mitotic cells.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHgCl\u003csub\u003e2\u003c/sub\u003e concentrations (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal number of cells\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDividing cells\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMitotic index (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMitotic inhibition (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eControl\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2957.64a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e413.35a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.01a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.00f\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2972.81a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e361.44b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12.16ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e13.20de\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2413.66a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e277.36c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11.49bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e17.99d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2433.33a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e237.66cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.77c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30.26c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2341.33a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e117.41e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.01d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e64.24ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2129.66a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e61.33f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.89de\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e79.37a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eThe values designated by different superscript letters in each column are significantly different from each other at a level of \u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eCytological analysis revealed various types and frequencies of chromosomal abnormalities in the root meristem of \u003cem\u003eA. cepa\u003c/em\u003e treated with varying concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e, a surface sterilization agent commonly used in industry or laboratories. The observed normal division and chromosomal aberration data are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, while Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the findings. The frequency of chromosomal aberrations, including anaphase bridge, stickiness, C-mitosis, chromosome fragmentation, and micronucleus formation, exhibited notable differences among the various concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e. Anaphase bridges, characterized by incomplete segregation of nuclear material to the poles owing to persistent DNA entanglement between sister chromatids, were more evident in onion root cells treated with higher concentrations (0.6-1.0%) of HgCl\u003csub\u003e2\u003c/sub\u003e. The pattern is consistent for all the other identified abbreviations. Exposing root cells to elevated concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e leads to an increased occurrence of chromosomal aberrations.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChromosome aberration of \u003cem\u003eA. cepa\u003c/em\u003e mitotic cells in response to exposure to varying concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHgCl\u003csub\u003e2\u003c/sub\u003e Conc. (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal number of counted cells\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAnaphase bridge\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStickiness\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFragment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMicronucleus\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eOthers\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e% Chromosome aberration\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2957.64a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.00d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.01e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.00c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.11de\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.20cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.65\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2972.81a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.13c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24.16cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e13.20b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.24cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.91cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.94\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2413.66a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.33cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.49cde\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.99bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14.25bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.83cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e2.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2433.33a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.56ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19.77de\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.26b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11.25c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.25bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e3.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2341.33a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43.45a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e45.01b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e64.24a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e23.25b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e11.48b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e8.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2129.66a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.42a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e102.89a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e79.37a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e42.45a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e36.15a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e13.82\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003csup\u003ea\u003c/sup\u003eThe average total number of mitotic cells counted for each HgCl\u003csub\u003e2\u003c/sub\u003e treatment was determined in three replicates. \u003csup\u003eb\u003c/sup\u003eOther observed chromosomal aberrations include nuclear abnormalities, binucleated cells, irregular prophase, polyploidy, pulverization, anaphase lagging chromosome, multipolar cells, and polyploidy. The values designated by different superscript letters in each column are significantly different from each other at a level of \u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eLow concentrations (0.2\u0026ndash;0.4%) of HgCl\u003csub\u003e2\u003c/sub\u003e resulted in chromosome genotoxicity and damage in treated cells. Nevertheless, such concentrations are toxic to cells, causing chromatin to become sticky clumps, which may lead to sterility and chromosome fragmentation (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Moreover, a concentration of 0.4% resulted in the development of micronuclei in a considerable number of cells, with an even greater amount being found in those exposed to 0.6%. A small number of chromosomal aberrations, such as irregular prophase, anaphase lagging and pulverization, were observed in the root cells of onions that were not treated. Nevertheless, with higher concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e, their frequency increased. Exposure to 0.6-1.0% HgCl\u003csub\u003e2\u003c/sub\u003e resulted in increased frequencies of multipolar cells, binucleated cells, and nuclear abnormalities in the treated bulbs. Essentially, the investigation revealed a substantial percentage of chromosome abnormalities, signifying cytogenotoxicity for HgCl\u003csub\u003e2\u003c/sub\u003e concentrations ranging from 0.6-1.0%. The order of aberrations triggered by interventions was 0.0\u0026thinsp;\u0026lt;\u0026thinsp;0.2%\u0026lt;0.4%\u0026lt;0.6%\u0026lt;0.8%\u0026lt;1.0%, indicating that high concentrations are associated with a greater risk of harm and genotoxicity.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThis study revealed chromosomal irregularities in mitotic cells of \u003cem\u003eAllium cepa\u003c/em\u003e when exposed to different concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e. The results revealed a range of chromosomal abnormalities at various stages of mitosis in onion roots exposed to the chemical, indicating that this chemical can be used as a sterilizer or disinfectant alone or in combination with other chemicals as a catalyst (Simon et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) and has genotoxic and mutagenic properties (Silva-Pereira 2005; Shalan \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The genotoxicity of mercury primarily results from its capacity to react with the sulfhydryl groups of tubulins. This process inhibits spindle function and results in various forms of chromosomal aberrations, and this chemical can also induce polyploidy (De Flora et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Silva-Pereira et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Moreover, mercury triggers free radical production by generating osmotic stress (Ehrenstein \u003cem\u003eet al\u003c/em\u003e. 2002; Durak \u003cem\u003eet al\u003c/em\u003e. 2010), which prompts apoptosis and consequent DNA damage (Hossain \u003cem\u003eet al\u003c/em\u003e. 2021). Thus, the potential of HgCl\u003csub\u003e2\u003c/sub\u003e to cause disruptions in the sequential and directional process of mitotic cell division/cycle progression suggests cyto- and genotoxicity. These effects can be inferred from the mitotic indices of the plants, as well as the various clastogenic and aneugenic events observed in the roots exposed to HgCl\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eAccording to Schurz (2000), mercury may hinder cellular antioxidant mechanisms, leading to cell degeneration and, ultimately, necrosis. Boujbiha \u003cem\u003eet al\u003c/em\u003e. (2009) confirmed that HgCl\u003csub\u003e2\u003c/sub\u003e is the most harmful mercury compound due to its strong affinity for proteins. They found that cells exposed to any amount of HgCl\u003csub\u003e2\u003c/sub\u003e experienced detrimental consequences, indicating that the chemical is hazardous to living tissues. In this study, even at a low concentration of 0.2% w/v, considerable chromosome damage was detected, implying that prolonged exposure to the substance might be hazardous, given its potential for penetrating the skin and causing adverse effects on the body's organs and genetic system (Su et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Oriquat \u003cem\u003eet al\u003c/em\u003e. 2012). However, despite the potential risks associated with HgCl\u003csub\u003e2\u003c/sub\u003e, various laboratories, hospitals, and industries continue to use this material for different purposes (Dadar \u003cem\u003eet al\u003c/em\u003e. 2016; Bengtsson and Hylander 2017; Bjorklund \u003cem\u003eet al\u003c/em\u003e. 2017). This poses a threat to personnel who may be exposed to the chemical's harmful genotoxic effects.\u003c/p\u003e \u003cp\u003eIn a study conducted by Hwang et al. (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), the toxic effects of HgCl\u003csub\u003e2\u003c/sub\u003e on keratinocytes and the subsequent impact on the expression of certain genes were demonstrated. The authors observed cell death and disruption of the cell membrane structure caused by the harmful effects of HgCl\u003csub\u003e2\u003c/sub\u003e. Several decades ago, Sander et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1978\u003c/span\u003e) reported the occurrence of chromosomal damage during the mitotic process in barley exposed to mercury chloride. The results from the present study were consistent with earlier research. HgCl\u003csub\u003e2\u003c/sub\u003e toxicity was found to cause several chromosomal abnormalities, including fragmentation, lagging, stickiness, bridge formation, polyploidy, binucleation, and nuclear budding. These abnormalities could lead to DNA damage, alterations in the genetic system, and mutations or disorders (Chrysouli et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). As demonstrated in the present study, high levels of HgCl\u003csub\u003e2\u003c/sub\u003e hinder cellular division, leading to significant occurrences of diverse clastogenic changes and reducing the mitotic index. These findings support previous reports (Nefic et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Sabeen et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) that suggest a correlation between high accumulation of heavy metals in plant roots and chromosomal irregularities, such as a decreased mitotic index, increased frequency of chromosome lagging, bridge formations, and nuclear lesions. These aberrations can interfere with cell division and result in disorders and even the death of cells. The occurrence of anaphase bridges, a decreased mitotic index, chromosome lag, and other chromosomal aberrations observed in this study is contingent on concentration. These findings are consistent with the findings of Ping et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), who revealed that the genotoxicity induced by \u003cem\u003eEuphorbia hirta\u003c/em\u003e extract also hinges on the concentration.\u003c/p\u003e \u003cp\u003eThe occurrence of chromosome bridging is attributed mainly to chromosome stickiness, which leads to delayed separation and unsuccessful detachment of these adhesive chromosomes. Internally within or between chromatids, chromosomal structures become bridged through a combination of homologous and nonhomologous chromosome exchanges, usually due to dicentric formation or defective replication processes. These events can result in disorders (Feretti et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Chromosomes can become adhesive in two ways: through contraction or condensation, DNA depolymerization and partial dissolution of nucleoproteins. This study demonstrated a high rate of stickiness, suggesting the harmful impact of HgCl\u003csub\u003e2\u003c/sub\u003e on nuclear materials, which may cause irreversible damage and cell death. Additionally, the occurrence of unaligned chromosomes suggested impaired organization and function of the spindle apparatus caused by HgCl\u003csub\u003e2\u003c/sub\u003e. The different degrees of C-mitosis detected in onion root cells suggest the presence of harmful substances in the growth media (Bonciu \u003cem\u003eet al\u003c/em\u003e. 2018). The \u003cem\u003eAllium cepa\u003c/em\u003e test demonstrated a substantial correlation with potential impacts in mammals (Khalil et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Milionis \u003cem\u003eet al.\u003c/em\u003e 2018), and because the assay can be employed without ethical concerns, it functions as a valuable model for assessing cytotoxicity. The \u003cem\u003eAllium cepa\u003c/em\u003e test has been utilized to evaluate the possible chemical impacts of chromosomal aberrations and cytotoxicity (Bakare et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Sabeen et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In these previous studies, the authors reported considerable chromosome distortion and cytotoxicity when high levels of chemicals were applied.\u003c/p\u003e \u003cp\u003eThe results of this study may hold weight for tissue culturists, microbial laboratory technologists, patients, and industrial workers who are at risk of HgCl\u003csub\u003e2\u003c/sub\u003e toxicity due to their occupation. Information regarding the cytotoxicity of HgCl\u003csub\u003e2\u003c/sub\u003e could therefore serve as a vital reference for ensuring adequate safety measures for those frequently working with this compound. Such measures are crucial given the documented potential for harm to essential bodily organs (Saljooghi and Delavar-mendi 2013; Mohamed et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThe present study explored the cytotoxic impact of different HgCl\u003csub\u003e2\u003c/sub\u003e concentrations on onion root tips by identifying numerous chromosomal abnormalities, including lagging chromosomes, chromosome bridges in various stages of cell division, vagrants, sticky chromosomes, binucleated cells, chromosome fragmentation, and loculated nuclei. The majority of the induced abnormalities exhibited concentration dependence. However, the data have shown that concentrations as low as 0.2% can result in harmful effects, leading to cytotoxicity. HgCl\u003csub\u003e2\u003c/sub\u003e caused significant clastogenic changes in onion root tip cells, which suggested that it interferes with cell growth and the cell cycle, possibly affecting the genetic system and behaviour of the cells. The data gathered on HgCl\u003csub\u003e2\u003c/sub\u003e toxicity in this study can serve as a point of reference to ensure the implementation of appropriate safety measures by those who frequently use HgCl\u003csub\u003e2\u003c/sub\u003e to prevent harm to vital organs.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDAA, PAA, SI and RK designed the\u0026nbsp;study. All the authors carried out the cytogenetic studies. DAA and PAA\u0026nbsp;analysed\u0026nbsp;the data.\u0026nbsp;DAA, SAO KAA and RK interpreted the results and validated the correctness of\u0026nbsp;the\u0026nbsp;information.\u0026nbsp;All the authors prepared and vetted the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no potential\u0026nbsp;conflicts\u0026nbsp;of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding was received for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePlant Ethics:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study protocol comply with relevant institutional, national, and international guidelines and legislation.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAsita AO and Matebesi LP 2010 Genotoxicity of hormoban and seven other pesticides to onion root tip meristematic cells. Afri. J. Biotechnol. 9(27) 4225\u0026ndash;4232.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAslant\u0026uuml;rk OS 2018 In vitro cytotoxicity and cell viability assays: principles, advantages, and disadvantages. In: Genotoxicity - \u003cem\u003eA predictable risk to our actual world\u003c/em\u003e. (1st Ed) (eds) Larramendy ML and Soloneski S. IntechOpen Ltd. London, UK. pp. 122. Available at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.5772/intechopen.71923\u003c/span\u003e\u003cspan address=\"10.5772/intechopen.71923\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBakare AA, Adeyemi AO, Adeyemi A, Alabi OA and Osibanjo O. 2012 Cytogenotoxic effects of electronic waste leachate in \u003cem\u003eAllium cepa\u003c/em\u003e. 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InTech. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5772/31371\u003c/span\u003e\u003cspan address=\"10.5772/31371\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUS Environmental protection agency, 2010, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.epa.gov/hg/effects.htm\u003c/span\u003e\u003cspan address=\"http://www.epa.gov/hg/effects.htm\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (accessed on 10th August 2023).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-toxicology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Toxicology](https://link.springer.com/journal/44339)","snPcode":"44339","submissionUrl":"https://submission.springernature.com/new-submission/44339/3","title":"Discover Toxicology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Allium cepa, cytotoxicity assay, mercury chloride, mitotic index, mitotic inhibition, chromosome aberrations","lastPublishedDoi":"10.21203/rs.3.rs-3821770/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3821770/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe \u003cem\u003eAllium cepa\u003c/em\u003e assay represents a crucial \u003cem\u003ein vivo\u003c/em\u003e model for evaluating the cytotoxicity and genotoxicity of substances. This study investigated the cytogenotoxicity potential of mercury chloride (HgCl\u003csub\u003e2\u003c/sub\u003e), a laboratory disinfectant and catalyst, using an \u003cem\u003eAllium cepa\u003c/em\u003e assay. Mitotic slides were prepared from onion root tip cells grown on media supplemented with different concentrations of HgCl\u003csub\u003e2\u003c/sub\u003e (0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%). The slides were observed to evaluate cytogenotoxicity based on measurements of the mitotic index, mitotic inhibition percentage, clastogenic alterations, and root length over 10 days. The results suggest that the concentrations used may harm the cell, leading to adverse impacts on the mitotic index, mitotic inhibition, root growth and chromosome structure. Different chromosomal aberrations, such as bridge formation, fragmentation, wandering chromosomes, stickiness, binucleus formation and micronucleus formation, were detected depending on the concentration. Although lower concentrations (0.2\u0026ndash;0.4%) had fewer effects on the cells, they still had a significant cytogenotoxic effect (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e) compared to that of the control (0.0%). The higher the concentration was, the greater the effects on clastogenic changes. The observed abnormalities in both mitotic spread and root growth indicate that mercury chloride is cytotoxic even at low concentrations and can cause mitotic-depressive effects at higher concentrations. The results of this investigation can be used as a guide to guarantee sufficient safety precautions for people and organs during the regular use of HgCl\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","manuscriptTitle":"Hazzard assessment and cytogenotoxic effects of different concentrations of mercury chloride sterilant using an onion (Allium cepa) assay","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-19 16:34:33","doi":"10.21203/rs.3.rs-3821770/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-03-19T08:59:58+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-03-01T22:05:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"81b56cc0-91d5-475b-9ee8-4e29960d5051","date":"2024-02-26T18:06:40+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"077ede97-a7bd-46a8-afe5-5de03852bf55","date":"2024-02-23T20:33:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"79662fdc-9d7b-4c2c-8e54-a81886d77d8a","date":"2024-01-29T08:46:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-01-26T15:28:30+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-01-15T06:33:47+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-01-15T06:30:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Toxicology","date":"2023-12-29T15:41:22+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-toxicology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Toxicology](https://link.springer.com/journal/44339)","snPcode":"44339","submissionUrl":"https://submission.springernature.com/new-submission/44339/3","title":"Discover Toxicology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"326f58bf-f236-4595-a759-f690fb5d5a68","owner":[],"postedDate":"January 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-05-14T11:08:10+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-19 16:34:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3821770","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3821770","identity":"rs-3821770","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}