Protective effect of quercetin and thymoquinone against genotoxicity and oxidative stress induced by ZnO nanoparticles in the Wistar rat model.

Zinc oxide nanoparticles (ZnO-NPs) are increasingly used in a variety of consumer and other commercial products. Hence, man faces the risk of exposure to ZnO-NPs and the consequent adverse health effects. Mitigation/prevention of such effects using natural products has drawn the attention of scientists. Therefore, the aim of the present study has been to find the toxic effects associated with exposure to ZnO-NPs, and the protective role of the phytochemicals thymoquinone (TQ) and quercetin (QCT) in the rat model. ZnO-NPs were administered to male Wistar rats through oral route; TQ / QCT was concurrently administered through intra-peritoneal route. The response in the animal was analyzed adopting chromosomal aberration test, micronucleus test, and comet assay of bone marrow cells to assess the genotoxicity, and biochemical assays of superoxide dismutase (SOD), catalase (CAT), lipid peroxidation (LPO), total extractable protein of liver, and reduced glutathione (GSH) of liver homogenate to monitor the changes in the antioxidant defense mechanism in response to the oxidative stress. Treatment of 300 mg/kg body weight (bw) of ZnO-NPs produced adverse effects on all aspects analyzed viz., structural chromosomal aberrations, micronuclei formation, DNA damage, SOD, catalase, lipid peroxidation, GSH, and extractable total protein of liver. Co-treatment of TQ / QCT offered protection against the toxicity induced by ZnO-NPs. The most optimum doses of TQ and QCT that offered the best protection were 18 mg/kg bw and 500 mg/kg bw, respectively. The study reveals that TQ / QCT supplementation is beneficial in the context of toxic effects of ZnO-NPs.

Nizatidine interacts with ct-DNA causing genotoxicity and cytotoxicity: an assessment by in vitro, in vivo, and in silico studies.

H2 receptor antagonists are the medication given for treating stomach ulcers, but lately, reports have shown their role in healing several malignant ulcers. The present work entails the interaction of H2 blocker nizatidine with calf thymus (ct)-DNA for determining the binding mode and energetics of the interaction. Multi-spectroscopic, calorimetric, viscometric and bioinformatic analysis revealed that nizatidine interacted with ct-DNA via groove-binding mode and is characterised by exothermic reaction. Moreover, assessment of genotoxic potential of nizatidine in vitro was carried out in peripheral human lymphocytes by alkaline comet assay. DNA damage occurred at high concentrations of nizatidine. Genotoxicity of nizatidine was also evaluated in vivo by assessing cytogenetic biomarkers viz. micronuclei formation and chromosomal aberration test. Nizatidine was able to induce micronuclei formation and chromosomal damage at high dose. Additionally, cytotoxic activity of nizatidine was determined in cancer cell lines, namely HeLa and HCT-116 and compared with the normal human cell line HEK-293 employing MTT assay. It was observed that nizatidine was more toxic towards HeLa and HCT-116 than HEK-293. Cell morphology analysis by compound inverted microscopy further strengthens the finding obtained through MTT assay.

Antioxidant thymoquinone and eugenol alleviate TiO2 nanoparticle-induced toxicity in human blood cells in vitro.

Titanium dioxide (TiO2) nanoparticles (NPs) are used extensively in a variety of commercial, industrial, and medical products, due to which human exposure is inevitable. This study aimed to explore the potential of eugenol and thymoquinone (TQ), two well-known antioxidants, in counteracting the NP-induced toxicity in human blood cells in vitro. Fresh lymphocytes and erythrocytes were isolated from volunteer human blood donors and incubated with 50 µg/mL of TiO2 NPs in the presence and absence of 50 µM of TQ and 20 µg/mL of eugenol for 3 h. Results showed that NP-treatment-induced hemolysis, oxidative stress, lactate dehydrogenase (LDH) leakage, and reduced ATPase activity in the erythrocytes. In the lymphocytes treated with NPs alone (50 µg/mL), cytotoxicity in MTT assay and DNA damage in comet assay were observed; in addition, mitochondrial membrane potential collapsed and ADP/ATP ratio increased indicating mitochondrial function impairment. However, in the presence of antioxidants, all these NP-induced changes were mitigated significantly. The results were more significant when both antioxidants eugenol and TQ were given together. Thus, it seems that antioxidants eugenol and TQ can be used as a protective agent against TiO2 NP-induced toxicity.

Coenzyme Q10 protects isolated human blood cells from TiO2 nanoparticles induced oxidative/antioxidative imbalance, hemolysis, cytotoxicity, DNA damage and mitochondrial impairment.

TiO2 NPs have been investigated for their toxic potential and studies have reported their toxicity is due to generation of oxidative stress. In the present study, we investigated the toxicity of TiO2 NPs and explored the potential of well-known antioxidant coenzyme Q10 (CoQ10) in counteracting the NP-induced toxicity in isolated human blood cells. When the isolated blood cells were treated with varying concentrations of TiO2 NPs (25-100 µg/ml), only 50 µg/ml dose induced statistically significant hemolysis in erythrocytes and cytotoxicity in lymphocytes (p < 0.05). None of the concentrations induced any significant increase in platelet aggregation. To investigate the protective effect of CoQ10, we incubated the isolated blood cells with 50 µg/ml of TiO2 NPs in the presence and absence of 25 µM of CoQ10 for 3 h. Hemolysis, oxidative stress, LDH leakage and ATPase enzyme activity were studied in erythrocytes; cytotoxic and DNA damaging potential of NPs were determined in lymphocytes, along with mitochondrial membrane potential (MMP) and ADP/ATP ratio. Hemolysis, generation of oxidative stress, LDH leakage and reduced ATPase activity were observed in the erythrocytes treated with NPs alone (50 µg/ml), the results were statistically significant at p < 0.05. Oxidative stress was evident by increased levels of malonaldehyde, indicating lipid peroxidation and generation of reactive oxygen species including hydrogen peroxide, together with statistically significant decrease in the activities of catalase and superoxide dismutase and reduced glutathione levels. In the lymphocytes treated with NPs alone (50 µg/ml), cytotoxicity in MTT assay and DNA damage in comet assay were observed; in addition, mitochondrial membrane potential collapsed and ADP/ATP ratio increased indicating mitochondrial function impairment. However, in the presence of CoQ10, hemolysis, oxidative stress and LDH leakage in the erythrocytes and lymphocyte cytotoxicity and DNA damage were drastically reduced, enzyme activities, MMP and ADP/ATP ratio were restored towards normal levels. TiO2 NPs induce cytotoxicity, damage DNA in lymphocytes, and induce oxidative/anti-oxidative imbalance in erythrocytes. Antioxidant CoQ10 protects erythrocytes and lymphocytes from toxicity induced by TiO2 NPs.

Lead and zinc interactions - An influence of zinc over lead related toxic manifestations.

BACKGROUND: Interaction between metals is known from earlier studies, in which one metal influences the absorption and functional role of other. Lead is known to cause debilitating effects in living organisms and also prevents several essential trace metals from functioning normally. METHODS: The relevant literature using the key words lead toxicity, lead zinc interaction, zinc nutrition and the ability of zinc to act against lead has been reviewed. RESULTS: Role of several nutrients in reducing the manifestations of toxic metals have been elucidated recently. Lead damages bio-membranes, causes cognitive disabilities and disturbs the normal process of DNA replication and transcription. Zinc on the other hand helps in proper maintenance of the cellular membranes and plays an important role as a metal cofactor in most of the proteins vital for membrane integrity. Zinc has essential role in cognitive functioning, zinc finger proteins and significantly neutralizes most toxic effects of lead. CONCLUSION: Increased lead exposure and limited resources for tackling lead poisoning may cause an increased possibility of future environmental emergencies. Interactions between essential nutrient metals and non-essential toxic metals may act as important factor which can be used to target the metal toxicities. An assumption is made that the lead toxicity can be reduced by maintaining the status of essential trace metals like zinc.

Chemosensitization of Therapy Resistant Tumors: Targeting Multiple Cell Signaling Pathways by Lupeol, A Pentacyclic Triterpene.

BACKGROUND: The resistance of cancer cells to different therapies is one of the major stumbling blocks for successful cancer treatment. Various natural and pharmaceuticals drugs are unable to control drug-resistance cancer cell's growth. Also, chemotherapy and radiotherapy have several side effects and cannot apply to the patient in excess. In this context, chemosensitization to the therapy-resistant cells by non-toxic phytochemicals could be an excellent alternative to combat therapy-resistant cancers. OBJECTIVE: To review the currently available literature on chemosensitization of therapy resistance cancers by Lupeol for clinically approved drugs through targeting different cell signaling pathways. METHODS: We reviewed relevant published articles in PubMed and other search engines from 1999 to 2019 to write this manuscript. The key words used for the search were "Lupeol and Cancer", "Lupeol and Chemosensitization", "Lupeol and Cell Signaling Pathways", "Cancer Stem Cells and Lupeol" etc. The published results on the chemosensitization of Lupeol were compared and discussed. RESULTS: Lupeol chemosensitizes drug-resistant cancer cells for clinically approved drugs. Lupeol alone or in combination with approved drugs inhibits inflammation in different cancer cells through modulation of expression of IL-6, TNF-α, and IFN-γ. Lupeol, through altering the expression levels of BCL-2, BAX, Survivin, FAS, Caspases, and PI3K-AKT-mTOR signaling pathway, significantly induce cell deaths among therapy-resistant cells. Lupeol also modulates the molecules involved in cell cycle regulation such as Cyclins, CDKs, P53, P21, and PCNA in different cancer types. CONCLUSION: Lupeol chemosensitizes the therapy-resistant cancer cells for the treatment of various clinically approved drugs via modulating different signaling pathways responsible for chemoresistance cancer. Thus, Lupeol might be used as an adjuvant molecule along with clinically approved drugs to reduce the toxicity and increase the effectiveness.

Influence of zinc levels on the toxic manifestations of lead exposure among the occupationally exposed workers.

Lead and zinc are usually found at the same occupational places and occur as co-contaminants. Effects of lead toxicity are detrimental on human health as it is probable carcinogen and impairs normal growth and development. On the other hand, zinc is an important nutritional element, the deficiency of which causes debilitating effects on growth and development. The purpose of this study was to examine the possible association of blood lead and zinc levels and any influence of zinc over DNA damage, blood cell membrane aberration and oxidative stress among lead and zinc co-exposed workers. Atomic absorption spectroscopy was used for lead and zinc measurement and comet assay for DNA damage assessment. Haematological aberrations were studied using light and electron microscopy (LM and EM) followed by electron density X-ray spectroscopy (EDS) and elemental mapping. Occupational exposure was observed to cause significant elevation in blood lead levels among workers. This elevation in lead levels and associated DNA damage among workers was significantly high in comparison to controls. Further light and electron micrographs of red blood cells revealed significant morphological alterations associated with increased lead ions in workers. It was clear from SEM-based elemental maps and EDS graphs that elevated lead levels were associated with low levels of zinc. The results suggest that lead absorption is highly influenced due to zinc levels in body which has an impact over DNA damage, blood cell aberration and oxidative stress caused by lead exposure. Efforts are going on to understand the role of other trace metals on lead toxicity in order to develop a sustainably nutrition-based therapeutic intervention. Graphical abstract.

Evaluation of DNA interaction, genotoxicity and oxidative stress induced by iron oxide nanoparticles both in vitro and in vivo: attenuation by thymoquinone.

Iron oxide nanoparticles (IONPs) are known to induce cytotoxicity in various cancer cell lines through the generation of reactive oxygen species (ROS). However, the studies on its potential to induce toxicity in normal cell lines and in vivo system are limited and ambiguity still exists. Additionally, small molecules are known to interact with the DNA and cause damage to the DNA. The present study is designed to evaluate the potential interaction of IONPs with DNA along with their other toxicological effects and subsequent attenuation by thymoquinone both in vitro (primary lymphocytes) and in vivo (Wistar rats). IONPs were characterized by TEM, SEM-EDS, and XRD. The results from DNA interaction studies showed that IONPs formed a complex with DNA and also got intercalated between the base pairs of the DNA. The decrease in percent cell viability of rat's lymphocytes was observed along with an increase in ROS generation in a dose-dependent manner (50, 100, 200, 400 and 800 µg/ml of IONPs). The genetic damage in in vivo might be due to the generation of ROS as depletion in anti-enzymatic activity was observed along with an increase in lipid peroxidation in a dose-dependent manner (25, 50, 100 mg/kg of IONPs). Interestingly, supplementation of thymoquinone in combination with IONPs has significantly (P < 0.05) attenuated the genetic and oxidative damage in a dose-dependent manner both in vitro and in vivo. It can be concluded that thymoquinone has the potential to attenuate the oxidative stress and genetic toxicity in vitro and in vivo.

Evaluation of cytotoxic activity and genotoxicity of structurally well characterized potent cobalt(II) phen-based antitumor drug entities: An in vitro and in vivo approach.

Cobalt (II) phen-based drug candidates of the formulation Co(phen)2Cl2,1, Co(phen)2L, 2 where L = 1H-pyrazole-3,5-dicarboxylic acid were synthesized and thoroughly characterized by spectroscopic methods and single X-ray crystallography. DNA binding interaction of 1 and 2 was carried out employing biophysical techniques {UV-visible, fluorescence, thermal denaturation and cyclic voltammetry} to validate their potential to act as antitumor agents. The interpretations of these biophysical studies of 1 and 2 supported the non-covalent intercalative binding mode; furthermore, a higher binding trend of 2 was observed as compared to 1, phen and 1H-pyrazole-3,5-dicarboxylic acid alone. Cleavage studies of 1 and 2 with pBR322 were assessed by gel electrophoresis and it was observed that both drug candidates cleave DNA by hydrolytic pathway involving hydroxyl radical (OH). Cytotoxic activity of 1 and 2 against human cancer cell lines [MCF-7 (breast), HeLa (cervical), MIA-PA-CA 2 (pancreatic), A-498 (kidney), Hep-G2 (hepatoma)] was evaluated by SRB assay. The obtained results showed that drug candidate 1 showed significantly low GI50 value (<10 µg/ml) against MCF-7 and HeLa cell lines. However, candidate 2 revealed excellent cytotoxicity (<10 µg/ml) against all the tested cancer cell lines. The in vivo genotoxicity of 2 was evaluated by micronucleus (MN) test and chromosomal aberration (CA) in bone marrow cells of the Wistar rats to check cobalt(II)-induced systemic toxicity. The results showed that no significant chromosomal aberrations and micronucleus formation was observed at 5 mg/kg and 10 mg/kg in presence of drug candidate 2 implicating that it could be administered safely at a low dosage. However, an elevated percentage of chromosomal aberration and micronucleated polychromatic erythrocytes (MNPCE) was observed only at higher doses (20 mg/kg and 40 mg/kg) of drug candidate 2.

Protective role of nimbolide against chemotherapeutic drug hydroxyurea induced genetic and oxidative damage in an animal model.

Nimbolide is known to be an antioxidant found in neem plant. Hydroxyurea is a medication frequently used in sickle-cell disease, different cancers and HIV infection. The present study aimed to evaluate the adverse effect of HU and possible amelioration by nimbolide in Wistar rats. To test our hypothesis, we performed genotoxicity tests, biochemical assays, and histopathological studies. We observed that HU caused higher levels of genotoxicity in the treated animals. The observed genetic and oxidative damage might be due to the presence of reactive species as HU increased the level of the malondialdehyde-a biomarker of oxidative damage. Interestingly, co-treatment of animals with HU and nimbolide showed a lower level of damage. We conclude that nimbolide significantly protects the cells from the adverse effect of HU and could be considered as a potential adjuvant for the patients under HU therapy.

Possible role of zinc in diminishing lead-related occupational stress-a zinc nutrition concern.

Lead and zinc are mostly present at the same occupational source and usually found as co-contaminants. Lead is known to associate with detrimental effects to humans. Zinc however is an essential nutrient and its deficiency causes debilitating effects on growth and development. Besides, it acts as core ion of important enzymes and proteins. The purpose of this study was to examine if zinc concentrations are associated with blood lead levels and if zinc may prevent lead-induced DNA damage. Blood samples were collected from 92 workers as participants occupationally exposed to lead or lead and zinc and 38 comparison participants having no history of such exposure. Lead and zinc levels were determined from blood by atomic absorption spectrophotometry and genetic damage was assessed by comet assay. Correlation was calculated by Spearman's rho. Lead concentrations were observed to increase among workers with increase in years of exposure. There was a significant difference (p < 0.001) in blood lead levels between workers and controls. In addition, significant difference (p < 0.001) in the genetic damage was observed among workers and controls. A clear effect of increased occupational exposure was visible among workers. Multiple regression analysis further reveals the positive effect of lead, while as the inverse effect of zinc on DNA damage. The results suggest that zinc may influence body lead absorption and may have a role in preventing the genetic damage caused by lead.

A comprehensive biological insight of trinuclear copper(II)-tin(IV) chemotherapeutic anticancer drug entity: in vitro cytotoxicity and in vivo systemic toxicity studies.

Cisplatin (cis-diamminedichloroplatinum(II), CDDP) causes severe systemic toxicity, which limits its application in cancer treatment. Nevertheless, incorporation of endogenously present essential metal ions (copper) in anticancer drug regimes in a heterometallic ligand scaffold can substantially modulate the toxic effects of non-essential metals (platinum), thereby reducing unwanted toxic side effects. A chiral l-tryptophan derived [bis(1,2-diaminobenzene) copper(II)] chloride complex [CuSn2(Trp)] was previously synthesized by us as an active chemotherapeutic agent. Furthermore, we have explored CuSn2(Trp) induced in vitro cytotoxicity in a panel of human cancer cell lines and in vivo acute and systemic toxicities in healthy female Rattus norvegicus (Wistar) rats. MTT assay showed that CuSn2(Trp) exhibits strong anticancer potency against ovarian (PA-1) and prostate carcinomas (PC-3) but lower potency towards liver (HepG2) and breast carcinomas (MCF-7). Further, flow cytometric analysis demonstrated that CuSn2(Trp) kills PA-1 cells dose-dependently after 48 h treatment. Fluorescence microscopy and western blotting revealed that the plausible mechanism behind CuSn2(Trp) cytotoxicity was apoptosis, which was substantiated by cleavage of caspase-3 and poly-(ADP-ribose) polymerase (PARP). Furthermore, it has lower toxicity than CDDP in rats as evident from its eight fold (98.11 mg kg(-1)) more medial lethal dose (LD50) than CDDP (12 mg kg(-1)). Besides, the safety profile of CuSn2(Trp) was also established and no measurable DNA damage, nephrotoxicity, hepatotoxicity and neurotoxicity were observed when assessed as a function of oxidative stress markers in contrast to CDDP at equivalent lower doses. Our findings are of high importance in the context of further in vivo cancer studies on the CuSn2(Trp) drug entity.

Iron induced genotoxicity: attenuation by vitamin C and its optimization.

Vitamin C (VC) is a well-known antioxidant and strong free radical scavenger. Its antioxidant activity is useful for protection of cellular macromolecules, particularly DNA, from oxidative damage induced by different agents. This study was undertaken to evaluate the optimum level of VC in attenuating the chromosome aberrations (CAs) and DNA damage after iron sulfate (FeSO4) acute administration in Wistar rats. The results exhibited that the increase of CAs and DNA damage induced by FeSO4, 200 mg Fe/kg, could be reduced significantly by VC pretreatment at the dose of 500 mg/kg (p<0.001), but not in the 100 mg/kg group. The findings provide evidence that VC at the dose of 500 mg/kg exerted a possible protective effect against FeSO4 induced CAs and DNA damage. The possible mechanisms of VC may be attributed to its property as a free radical scavenger or to its indirect action in reducing the level of reactive oxygen species (ROS).

Cytogenetic evaluation of cadmium chloride on Channa punctatus.

The aim of present study was to evaluate the genotoxic effect of heavy metal in Channa punctatus through the micronucleus test, chromosomal aberrations and sister chromatid exchange. The fish were kept separately in 0.5, 1.0, 2.0 and 5.0 ppm cadmium chloride for 3 days. For micronucleus test blood was collected from caudal vein and smeared on clean slides fixed in methanol and stained with 2% Giemsa. Mean frequency of micronuclei observed was 0.10, 0.15, 0.24, 0.34 and 0.39 in control, 0.5, 1.0, 2.0 and 5.0 ppm CdCl2 respectively. In vivo chromosome preparation from kidney tissues was carried out. The mean frequency of cells with aberrations observed was 0.13, 0.20, 0.34, 0.60 and 0.95 in control, 0.5,1.0, 2.0 and 5.0 ppm CdCl2 respectively. Likewise the mean frequency of SCE observed was 0.05, 0.16, 0.36, 0.44 and 0.52 in control, 0.5, 1.0, 2.0 and 5.0 ppm CdCl2 respectively. It has been revealed from the results of this study that cadmium produced genotoxic effects in fish.

Cytogenetic evaluation of Fansidar on human lymphocyte chromosomes in vitro.

Fansidar is a fixed combination of two antimalarial agents a diaminopyrimidine (Pyrimethamine) and a sulphonamide (Sulphadoxine) in the ratio 1:20- that have been used extensively worldwide for the treatment of Chloroquine resistant Plasmodium falciparum malaria, toxoplasmosis and Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome. This study examined the effect of Fansidar on chromosomes in human lymphocyte culture. Fansidar was added to peripheral blood lymphocyte cultures in vitro at four different concentrations: 5,15, 25 and 50 microl in the ratio 1:20, 3:60, 5:100 and 10:200 microg ml(-1). Result shows that this drug induces moderate increase in the frequency of gaps, breaks and rearrangements. Therefore it can be concluded that Fansidar has moderate clastogenic effect on human chromosomes in vitro.

Anticlastogenic action of vitamin C against genotoxicity of estrogenic drug diethylstilbestrol (DES) in the human lymphocyte chromosomes.

Several sex steroids and estrogenic drugs are genotoxic in varying conditions and cause oxidative stress, which has been a field of interest to study the molecular mechanism of the genetic damage. Among the estrogenic drugs, a strong toxic effect is exerted by diethylstilbestrol (DES). In the present study it has been attempted to study its genotoxic effects in human lymphocyte assay system along with ameliorative or anticlastogenic effects of vitamin C. The drug was used with different dosage of concentrations on human lymphocytes administered in vitro. The parameters used were Sister Chromatid Exchanges (SCEs) and Chromosomal Aberrations (CAs). Higher levels of clastogeny and SCEs have been observed indicating significant damaging effect by the drug. Interesting ameliorating effects were observed in the presence of vitamin C which is a well-known antioxidant. The results support the possibility of practical application of natural protectors against the mutagenic/oenotoxic action of chemical mutagens.

Effect of oxymetholone on SCE frequency in human lymphocyte chromosomes in vitro.

Genotoxicity evaluation of a commonly used synthetic androgen, Oxymetholone, was carried out in human peripheral blood lymphocytes in vitro. Sister chromatid exchange (SCE) was used as genetic end point. The concentrations of the drug were determined after observing its effects on the mitotic index. A wide range of concentrations, i.e., 25, 50, and 100 micro g/ml of the drug, were used to determine the genotoxic effects in the absence as well as in the presence of rat liver microsomal activation system (S9 mix). The drug did not induce any significant increase in the SCE frequency at any of the concentrations either in the presence or in the absence of S9 mix. The maximum value of SCE was observed in the absence of S9 mix at 100 microg/ml concentration (i.e., 1.38+/-0.080/cell), which was not significant statistically. Moreover, the drug was not effective in increasing the SCE frequency even in the presence of S9 mix. The maximum value of SCE (i.e., 1.78+/-0.103/cell) was observed at 50 microg/ml of concentration in the presence of S9 mix. A dose relationship was also not observed. It was concluded that Oxymetholone does not affect the genetic material in human lymphocytes at a wide range of concentrations in the SCE assay.

Evaluation of genotoxic potential of synthetic progestins-norethindrone and norgestrel in human lymphocytes in vitro.

The genotoxicity study of two widely used contraceptive synthetic progestins, i.e. norgestrel and norethindrone was carried out on human lymphocyte chromosomes using chromosomal aberrations (CA), sister chromatid exchanges (SCE) and cell growth kinetics as parameters. The study was carried out both in the presence as well as in the absence of metabolic activation (S(9) mix). The lymphocytes were exposed to three different concentrations of the drugs (20, 40 and 75 microg/ml for norethindrone and 10, 25 and 50 microg/ml for norgestrel) for three different durations (24, 48 and 72 h). The drug norethindrone was found to be non-genotoxic at any concentration and at any exposure duration either in the presence or in the absence of S(9) mix. But another drug norgestrel was found to affect the genetic material. It induces CA, SCE at significant level, and inhibits lymphocyte proliferation at 25 and 50 microg/ml of concentrations only. In the presence of S(9) mix the values obtained for CA, SCE and mitotic index (MI) were more significant. A time and dose relationship was also observed. It was concluded that norgestrel itself and possibly its metabolites are potent mutagens beyond a particular dose in human lymphocytes.

Genetic analysis of fragile X-syndrome.

Fragile X-syndrome is the most common inherited cause of mental retardation. The key clinical features of the fragile X-syndrome in males are mental retardation, a long face with large everted ears and large testes. The disorder is associated with a visible fragile site at Xq27.3 at FMR-1 loucs with the amplification of (CGC) n repeat sequence. The early diagnosis of affected individuals are carriers who are not aware of their high risk of having an affected child is important for proper management and counselling.

Genotoxic effects of estradiol-17beta on human lymphocyte chromosomes.

The cytogenetic effect of a hormonal steroid, estradiol-17beta, was assessed in peripheral blood human lymphocyte culture. Sister chromatid exchanges (SCE) and chromosome aberrations (CA) were scored as genetic end points. Significant induction of CA was observed at 25 microg/ml and 50 microg/ml concentrations of estradiol-17beta in the absence of microsomal activation. The drug was effective in all treatments in the presence of rat liver S(9) microsomal fraction (S(9) mix) and exhibited increased frequency of chromosomal aberrations. The drug was effective in increasing the SCE frequency which was found to be maximum at the dose of 50 microg/ml concentration (i.e., 4.34+/-1.22) both with and without metabolic activation. It was found that estradiol-17beta itself and possibly its metabolites are potent mutagens beyond a particular dose in human lymphocytes.