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D K Saxena

Publications and source records attributed to D K Saxena.

At least 19 recordsLinked to original sources
PubMed2005

Validation of Drosophila melanogaster as an in vivo model for genotoxicity assessment using modified alkaline Comet assay.

The single cell gel electrophoresis or Comet assay is one of the most popular techniques for genotoxicity assessment. The present study was undertaken to validate our previously modified version of the Comet assay for genotoxicity assessment in Drosophila melanogaster (Oregon R(+)) with four well-known mutagenic and carcinogenic alkylating agents, i.e. ethyl methanesulfonate (EMS), methyl methanesulfonate (MMS), N-ethyl-N-nitrosourea (ENU) and cyclophosphamide (CP). Third instar larvae (74 +/- 2 h) of D.melanogaster were fed different concentrations of EMS, MMS, ENU and CP (0.05, 0.5 and 1.0 mM) mixed standard Drosophila food for 24 h. At 98 +/- 2 h, the anterior midgut from control and treated larvae were dissected out, single-cell suspensions were prepared and Comet assay was performed. Our results show a dose-dependent increase in DNA damage with all the four alkylating agents, in comparison to control. The lower concentration (0.05 mM) of the test chemicals, except MMS, did not induce any DNA damage in the gut cells of the exposed larvae. When comparison of Comet parameters was made among the chemicals, MMS was found to be the most potent genotoxicant and ENU the least. The present study validated our previous observation and shows that D.melanogaster is a sensitive and suitable model for the in vivo assessment of genotoxicity using our modified alkaline Comet assay.

Alkylating Agents↗
PubMed2005

Genotoxicity of industrial solid waste leachates in Drosophila melanogaster.

The potential toxicity of industrial solid wastes is a major environmental concern. The present study evaluated the genotoxicity of industrial waste leachates on the gut cells of Drosophila melanogaster (Oregon R+), using a modified alkaline comet assay. Leachates were prepared from control soil and solid wastes generated by a flashlight battery factory, a pigment plant, and a tannery, using different pHs (7.0, 4.93, and 2.88). Newly emerged first instar Drosophila larvae (22 +/- 2 hr) were transferred to standard Drosophila diet containing 0.05%, 0.1%, 0.5%, 1.0%, and 2.0% of the leachates, and allowed to grow. At 96 +/- 2 hr, the anterior midgut of control and treated larvae was dissected out; single cell suspensions were prepared; and the comet assay was performed on the cells. All the leachates produced significant (P < 0.05), dose-dependent increases in DNA damage, in the gut cells. Leachates prepared at pH 7.0 were significantly less genotoxic than leachates prepared at pH 4.93 or 2.88. A comparison of the comet parameters among the exposed groups indicated that leachates of the pigment plant solid waste produced the least DNA damage, while leachates prepared from the flashlight battery factory solid waste were the most genotoxic. The present study indicates that leachates of solid wastes from flashlight battery factories, pigment plants, and tanneries possess genotoxic activity and that D. melanogaster is a useful in vivo model for assessing the genotoxicity of these potential environmental contaminants.

Animal Feed↗
PubMed2004

Correlation of chlorinated pesticides concentration in semen with seminal vesicle and prostatic markers.

Semen samples of fertile and infertile men were analysed by gas liquid chromatography (GLC) for the presence of dichlorodiphenyltrichloroethane (DDT) and its metabolites (1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene) (pp'-DDE); (1,1,1-trichloro-2,2-bis(p-chlorophenyl ethane) (pp'-DDT); (1,1-dichloro-2,2 bis(p-chlorophenyl) ethane) (pp'-DDD); (1,1,1-trichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl) ethane) (op'-DDT), hexachlorocyclohexane (HCH) and its isomers alpha (alpha), beta (beta), gamma (gamma), delta (delta) and aldrin. The biochemical analysis of seminal vesicle and prostatic marker was done by spectrophotometer. The concentrations of alpha-, beta-, gamma-HCH, pp'-DDE and pp'-DDD were higher in the semen of infertile than in that of fertile men. An elevation in the fructose level along with decrease in the gamma-glutamyl transpeptidase and acid phosphatase activity was noticed in infertile men as compared to fertile subjects. The data showed correlation between alpha-, beta-, gamma-HCH, pp'-DDE, pp'-DDD and seminal vesicle marker fructose and prostatic marker gamma-gluatamyl transpeptidase and acid phosphatase in infertile men. The study suggests that the chlorinated pesticides may influence the semen quality by affecting the seminal and prostatic functions in infertile men.

Acid Phosphatase↗
PubMed2003

Evaluation of toxic potential of captan: Induction of hsp70 and tissue damage in transgenic Drosophila melanogaster (hsp70-lacZ) Bg9.

The study investigated the working hypothesis that a widely used fungicide captan exerts toxic effects on nontarget organisms. Transgenic Drosophila melanogaster (hsp70-lacZ) was used as a model by assaying stress gene expression as an endpoint for cytotoxicity and also to evaluate whether stress gene expression is sufficient enough to protect and to prevent tissue damage against toxic insult of the chemical. The study was further extended to understand the effect of the pesticide on development, life cycle, and reproduction of the organism and finally to evaluate a concentration of the chemical to be nontoxic to the organism. The study showed that (i) captan causes cytotoxicity at and above 0.015 ppm; (ii) at 0.0015 ppm captan, absence of hsp70 expression in the exposed organism was evaluated as the concentration referred to as no observed adverse effect level (NOAEL) for Drosophila; (iii) emergence pattern of flies was affected only at the highest concentration of captan by 4 days, while hatching and survivorship were unaffected even at this concentration; (iv) reproductive performance was significantly affected only at 125.0 and 1250.0 ppm captan, while in the lower dietary concentrations no such deleterious effects were observed; (v) at 1250.0 ppm, hsp70 failed to protect the cells from toxicant assault after 48 h exposure, thus leading to tissue damage as revealed by Trypan Blue staining. The present study shows the cytotoxic potential of captan and further reveals the application of stress genes in determining NOAEL and its expression as bioindicator of exposure to environmental contaminants.

Animals↗
PubMed2003

Argemone oil induced cellular damage in the reproductive tissues of transgenic Drosophila melanogaster: protective role of 70 kDa heat shock protein.

We explored the reproductive toxicity of argemone oil and its principal alkaloid fraction in transgenic Drosophila melanogaster (hsp70-lacZ) Bg(9). The toxicity of argemone oil has been attributed to two of its physiologically active benzophenanthridine alkaloids, sanguinarine and dihydrosanguinarine. Freshly eclosed first instar larvae of transgenic Drosophila melanogaster were transferred to different concentrations of argemone oil and its alkaloid fraction contaminated food. Virgin flies that eclosed from the contaminated food were pair-mated to look into the effect on reproduction. The study was further extended by investigating hsp70 expression and tissue damage in larval gonads, genital discs, and reproductive organs of adult fly. Our results showed that argemone oil was more cytotoxic than its principal alkaloid fraction. Moreover, it was the male fly that was more affected compared to its opposite number. The accessory glands of male reproductive system of the fly, which did not express hsp70, exhibited severe damage as evidenced by Trypan blue staining. This prompted us to explore the ultrastructural morphology of the gland, which showed acute signs of necrosis in both the cell types as evident by necrotic nuclei, higher vacuolization, and disorganized endoplasmic reticulum, decrease in the number of Golgi vesicles and disorganized, loosely packed filamentous structures in the lumen of the accessory gland, at the higher concentrations of the adulterant. The study showed the reproductive toxicity of argemone oil and its alkaloid fraction in transgenic Drosophila melanogaster and further confirmed the cytoprotective role of hsp70.

Alkaloids↗
PubMed2003

Heat shock response: hsp70 in environmental monitoring.

Heat shock proteins (Hsps) are a ubiquitous feature of cells in which these proteins cope with stress-induced denaturation of other proteins. Among the different families of Hsps, the 70 kDa family (hsp70) is the most highly conserved and has been most extensively studied. Apart from their primary role in cellular defense under stress condition, a number of studies in recent years have shown the immense potential of hsp70 in pollution monitoring using even transgenic approach both in vivo and in vitro. This article reviews the recent developments in the widespread application of hsp70 in environmental risk assessment.

Animals↗
PubMed2003

Correlation of lead and cadmium in human seminal plasma with seminal vesicle and prostatic markers.

The objective of this study was to investigate the correlation between lead and cadmium with seminal vesicle and prostatic markers. Semen samples categorized into fertile and infertile were evaluated for the presence of lead and cadmium and biochemical markers in the seminal plasma. Associations between lead and fructose, acid phosphatase and gamma-glutamyl transpeptidase (gamma-GT) were observed. However, no such relationships were noticed for cadmium. It is concluded that lead may be one of the pollutants indirectly affecting semen quality by altering the functions of accessory sex glands.

Adult↗
PubMed2002

Toxicity of argemone oil: effect on hsp70 expression and tissue damage in transgenic Drosophila melanogaster (hsp70-lacZ) Bg9.

The effect of argemone oil on hsp70 expression and tissue damage was investigated by studying beta-galactosidase activity, Western blotting and hybridization, and trypan blue staining in the larval tissues of transgenic Drosophila melanogaster (hsp70-lacZ)Bg9. Different concentrations of argemone oil were mixed with food and third-instar larvae were allowed to feed on them for different time intervals (2, 4, 24, and 48 h). Argemone oil was found to induce hsp70 even in the lowest concentration of the adulterant while maximum tissue damage was observed in the higher two treatment groups. Malpighian tubules and midgut tissue reflected maximum damage as evidenced by both high beta-galactosidase activity and trypan blue staining in these tissues. A prior temperature shock treatment to the larvae was enough to protect the larvae from argemone oil-induced tissue damage as evidenced by little or no trypan blue staining. The present study suggests the cytotoxic potential of argemone oil and further strengthens the evidence for the use of hsp70 as a biomarker in risk assessment.

Animals↗
PubMed2002

Are germ cell factors essential in the testicular enlargement after neonatal hypothyroidism recovery? A study using W/Wv mutant mice model.

We examined the issue of whether germ cell factors are required for testicular enlargement that occurs after recovery from neonatal hypothyroidism. Experiments were performed using W/Wv mutant mice (lacking germ cells) and normal mice (ICR). The pups in experimental group (neonatal hypothyroid) received 6 propyl 2-thio-uracil (PTU) treatment, administered by adding 0.1% (w/v) to the water provided to the mother from day 1 of birth through day 25 postpartum, while the pups of control group received drinking water only. Mice were sacrificed at the age of day 25, 50 and 90, in the case of ICR mice, or at day 25 and 90 in the case of W/Wv mutant mice. In both groups, early hypothyroidism caused a partial recoverable decrease in body growth and testicular development. Both ICR and W/Wv mutant mice, those recovered from neonatal hypothyroidism showed an increase in testis weights, the number of Sertoli cells, and the diameter of the semniferous tubules. This study demonstrates that neonatal hypothyroidism led recovery caused testicular enlargement not only in ICR mice but also in germ cell depleted W/Wv mutant mice. Hence these findings deny direct involvement of the germ cell factors in the process of testicular enlargement in recovered mice even in vivo, and reaffirm the notion that thyroid hormone directly regulates the dynamics of Sertoli cell maturation.

Animals↗
PubMed2002

Behaviour of a sperm surface transmembrane glycoprotein basigin during epididymal maturation and its role in fertilization in mice.

Basigin (bsg) is a transmembrane glycoprotein belonging to an immunoglobulin superfamily and is localized on the surface of the sperm tail. The behaviour of bsg during epididymal maturation and its role in fertilization were examined using an anti-bsg antibody. Spermatozoa from caput, corpus and cauda epididymides were immunostained by indirect immunofluorescence (IIF). Immunostaining revealed that bsg is localized on the principal piece of caput spermatozoa and the molecule was found on the middle piece during transit in the corpus and cauda epididymides. Concomitantly, the molecular mass of bsg was reduced from 37 kDa (testis) to 26 kDa (cauda epididymidis). IVF experiments were designed to assess the effect of anti-bsg antibody on the fertilization events. Anti-bsg antibody significantly inhibited primary binding to the cumulus-invested oocytes with intact zonae pellucidae in a dose-dependent manner. Consequently, the fertilization rate of cumulus-invested oocytes with intact zonae pellucidae was also inhibited. The bsg molecule was also detected on the head of live capacitated spermatozoa by IIF under IVF conditions. These findings indicate that testicular bsg is a glycosylated protein that undergoes molecular processing and deglycosylation during its transit in the epididymis. The bsg molecule that was detected on the sperm head after capacitation may facilitate the primary binding or might be involved in distinct events required for primary binding of spermatozoa to the zona pellucida during capacitation and sperm-cumulus interaction.

Animals↗
PubMed2001

Effect of three chlorinated pesticides on hsromega stress gene in transgenic Drosophila melanogaster.

Expression of hsromega stress gene in the third-instar larvae of 951-lacZ2 (hsromega-lacZ having-844pb sequence) and 498-lacZ1 (hrsomega-lacZ having -498bp sequence) strains of Drosophila melanogaster at LC(50) and lower dietary concentrations of hexachlorocyclohexane (HCH) pentachlorophenol (PCP), and endosulfan was examined in relation to larval mortality by beta galactosidase activity, vital dye staining, and salivary gland polytene chromosome puffing. Our results showed that both HCH and PCP at lower concentrations evoked strong hsromega stress gene expression in the larval tissues while endosulfan did not. On the other hand, puffing data revealed that endosulfan at lower doses, induced well-developed puff at the resident site (93D) of the hsromega gene but the transgenic sites (30B in 951-lacZ2 and 44B in 498-lacZ1 strain) did not show any well-developed puff. Regression in hsromega stress gene expression in 951-lacZ2 strain at LC(50) concentrations of HCH and PCP after 48 h was concurrent with extensive tissue damage as evident by trypan blue staining. Similarly, strong hsromega expression was accompanied by insignificant trypan blue staining in the larval tissues of this strain after shorter duration of exposure (2-12 h) to these toxicants. Although endosulfan under similar experimental condition did not induce hsromega, strong trypan blue staining indicated extensive tissue damage after 48 h of exposure. The present study suggests that all the three toxicants pose cytotoxic potential to Drosophila. While protective role of this stress gene was evident at the initial stages of exposure, extensive tissue damage in the later stages of intoxication accompanied by autorepression of hsromega led to larval mortality. The study further suggests that -844bp upstream sequence of the gene is adequate for hsromega inducibility against HCH and PCP but not for endosulfan for which responsive elements may be searched further upstream.

Animals↗
PubMed2001

Chlorpyrifos-induced hsp70 expression and effect on reproductive performance in transgenic Drosophila melanogaster (hsp70-lacZ) Bg9.

Expression of hsp70 in the third-instar larval tissues of transgenic Drosophila melanogaster (hsp70-lacZ) following dietary exposure to organophosphate insecticide chlorpyrifos for various time intervals was investigated. Effect of the chemical on different developmental stages of the fly was also evaluated by looking at survivorship, hatchability, emergence, fecundity, fertility, and reproductive performance. Our results showed that the toxicant evokes profound cytotoxic effect as evidenced by dark blue staining in salivary gland, proventriculus, brain ganglia, and midgut in the lowest concentration of the chemical following 24 and 48 h of exposure. On the other hand, a significant increase (61%) in hsp70 expression in the above larval tissues was observed in the next higher concentration of the toxicant after 6 h exposure when compared with that of the lowest dose. A further increase in exposure time caused 100% larval mortality. Similarly, larvae exposed to higher concentrations of the toxicant, exhibited 100% mortality within 1 h of treatment. The insecticide caused a delay in emergence and a severe reduction in survivorship of the flies in a dose-dependent manner with 100% mortality within a day of exposure in the highest dosed group. A delay in emergence by 3 days was evident even in the lowest concentration of the chemical. A drastic effect of the chemical on hatchability was found in the highest dosed group with 100% embryonic mortality at post-16 stage of the embryo. Reproductive performance was significantly affected even in the lowest dosed group. The present study suggests that certain larval tissues of Drosophila, a nontarget organism, are vulnerable to chlorpyrifos as evidenced by hsp70 expression. Further, the adverse effect of the toxicant is reflected on various stages of development of the fly including reproductive performance.

Animals↗
PubMed2001

Effect of lead and chromium on nucleic acid and protein synthesis during sperm-zona binding in mice.

Lead and chromium are ubiquitous environmental pollutants and their effects on reproductive physiology as shown by animal experiments and human studies is well documented. The present study was conducted to ascertain the role of these metals on gamete physiology during the sperm-zona binding process, Superovulated ova and capacitated sperm from BALB/c mice were exposed to lead (0.0, 0.2, 0. 5, 1.0 and 2.0 microg/ml) or chromium (0.0, 5.0, 10.0 and 20.0 microg/ml) for 2 h in the culture medium. The sperm that became attached to the ova in the presence of these metals were scored. Synthesis of DNA, RNA and protein was assessed during this process by labelling the cells with [3H]thymidine (20 microCi/ml), [3H]uridine (50 microCi/ml) and [35S]methionine (10 microCi/ml) in the culture medium after exposure to the metals for 2 h. Our studies show a significant dose-dependent decrease in the number of sperm attaching to the ova in both exposed groups along with a decrease in the incorporation of radiolabelled thymidine, uridine and methionine. The results indicate that DNA, RNA and protein synthesis under sperm-zona binding conditions are affected by the presence of these two metals. The physiology of the gametes is altered resulting in a low frequency of sperm attachment to the ova, which in turn leads to a risk of reproductive failure.

Animals↗
PubMed2001

Effect of endosulfan during fetal gonadal differentiation on spermatogenesis in rats.

Pregnant rats were exposed to endosulfan (1 or 2 mg/kg per day) from day 12 of gestation through parturition. Male neonates were fostered to untreated dams. At 100 days of age, the male offspring were sacrificed. Exposure to endosulfan during fetal gonadal differentiation altered the process of spermatogenesis by affecting testicular lactate dehydrogenase and sorbitol dehydrogenase. Reduction in spermatid count in testis and sperm count in cauda epididymis was observed. Testis, epididymis and seminal vesicle showed significant decrease in weights in both the treated groups while no effect on prostate weight was recorded. Hence it can be suggested that endosulfan interferes in the process of spermatogenesis. The overall toxicity was dose dependent.

Journal Article↗
PubMed2001

Inhibition of mouse fertilization in vivo by intra-oviductal injection of an anti-equatorin monoclonal antibody.

The monoclonal antibody mMN9 recognizes an antigenic molecule, equatorin, which is localized at the equatorial segment of the mammalian sperm acrosome. Our previous results using an IVF system indicated that mMN9 blocked sperm-oocyte fusion. Antibody-containing and control solutions were injected directly into the right and left oviductal ampullae, respectively, of anaesthetized female mice to assess the effect of mMN9 on fertilization in vivo. After hCG treatment, the females were mated, and their oviductal eggs and implanted embryos were examined. mMN9 was retained in the oviductal lumen at 20 h after injection. The rates of fertilization and concomitant pregnancy were significantly lower than in the control side (P < 0.05). In addition, histological studies showed no evidence of pathological changes in the female reproductive tract after the injections. These results indicate that mMN9 inhibits mouse fertilization significantly under in vivo conditions and that this injection method should be useful for studying the effects of antibodies and agents on fertilization in vivo.

Animals↗
PubMed2001

Protein expression and cell organelle behavior in spermatogenic cells.

Spermatogenic cells stage-specifically produce a wide variety of proteins during spermatogenesis, wherein protein expression is coordinated with cell organelle behavior. It has been shown that the Golgi apparatus and the endoplasmic reticulum (ER) are uniquely coordinated with the expression of an immunoglobulin super-family protein, flagellar plasma membrane MC31 (MC31/CE9), and a molecular chaperone, calmegin, respectively. When the Golgi apparatus begins to generate sperm components in the primary spermatocytes, it actively engages in producing proteins for the acrosome in round spermatids and for the flagellum in elongating spermatids. Structurally, the Golgi apparatus is reduced in size during meiotic division, moves from the apical to the basal region (cytoplasmic lobe) when spermatids differentiate from round to elongating phase, and then collapses in the late maturation phase. The ER is distributed uniformly over the entire cytoplasm of spermatocytes and round spermatids, and then moves distally toward the cytoplasmic lobe along the bundles of microtubule, called the manchette, in elongating spermatids. The ER is resorbed into the radial body in late maturation spermatids. MC31/CE9 expresses strong immunostaining twice on the Golgi apparatus during spermatogenesis, first in early pachytene spermatocytes and then in early elongating spermatids. Calmegin expression exactly parallels ER behavior. This mini-review focuses on the unique relationships in spermatogenic cells, particularly those between protein expression and cell organelle behavior.

Acrosome↗
PubMed2001

Internet: a major resource for toxicologists.

Use of the Internet in developing countries is now growing faster. Internet has created a new conduit not only for communication but also in the access, sharing and exchange of information among scientists. The Internet is now viewed as the world's biggest library where retrieval of scientific literature and other information resources are possible within seconds. Large volumes of toxicological information resources are available on the Internet. This review outlines some sites that may be of great importance and useful to the toxicologist.

Internet↗