Pulak Lahiri

Lindane (γ-HCH) causes reproductive failure and fetotoxicity in mice

Abstract Lindane (γ-Hexachlorocyclohexane) was orally given to pregnant Swiss female mice at various stages of pregnancy. During early pregnancy (1–4 days of gestation), the insecticide caused total absence of any implantation site, while given during mid pregnancy (6–12 days of gestation), lindane caused total resorption of fetuses. Lindane administration during late pregnacy (14–19 days of gestation) resulted in death of all pups either within 12 h (high-dosed group) or 5 days (low-dosed group) of parturition. Body weight of such pups were also highly reduced. When estrogen was given together with lindane at early pregnancy, implantation was normal, although subsequent fetal development was adversely affected. Progesterone, unlike estrogen, could not correct lindane-induced failure in implantation. On the other hand, when estrogen and progesterone were simultaneously given to lindane-fed mice during early pregnancy, both implantation and subsequent fetal development became comparable to normal mice. The insecticide besides being fetotoxic, thus appears to cause steroid hormone deficiency resulting in reproductive and developmental failure.

Hematological changes produced by lindane (γ-HCH) in six species of birds

Abstract Hematological changes were studied after oral administration of lindane (γ-hexachlorocyclohexane) at 5 mg/kg body weight twice in 1 week in 6 species of agriculturally important birds: house sparrow, baya weaver bird, common myna, rose-ringed parakeet, blue rock pigeon and domestic duck. Lindane induced anemia in the birds as judged by reduced RBC count, hematocrit and hemoglobin content with corresponding changes in MCV, MCH and MCHC. Bleeding and clotting time were markedly prolonged. Splenic cell counts were decreased with marginal increase of splenic weight in most of the lindane fed birds. Total leucocyte counts were increased while the differential counts of WBC show marked heterophilia and eosinophilia with a decrease in monocyte, lymphocyte and basophil numbers. Domestic duck appears to be somewhat resistant compared to the wild birds studied. Besides anemia the results suggest both immunosuppression and stress effects and indicate that early hematological changes induced by lindane may serve as an initial warning for pesticide toxicity.

Effect of lindane on mitochondrial side-chain cleavage of cholesterol in mice.

Cholesterol side-chain cleavage of mitochondria, the key rate limiting step in steroid biosynthesis in ovarian tissues, was studied in female Swiss mice fed lindane (gamma-hexachlorocyclohexane) at various doses and over varying periods. The insecticide adversely affected cholesterol side-chain cleavage of the ovary as judged by decreased conversion of this sterol to pregnenolone and subsequently to progesterone in a dose-dependent manner. The formation of pregnenolone was maximally inhibited (75% inhibition) at the highest intake of insecticide with simultaneous inhibition of its conversion to progesterone. At all doses, the rate of inhibition of pregnenolone formation was comparatively higher than its conversion to progesterone. The significant inhibition of cholesterol side-chain cleavage by lindane and resultant decrease in the rate of steroidogenesis in the ovary would account for the observed gonadal hormone deficiency and related reproductive disorders in the lindane-fed mice.

Suppression of adrenocortical function in female mice by lindane (γ-HCH)

Abstract Lindane (γ-HCH) given to adult female mice orally at various doses and over varying periods adversely affected adrenocortical function. Adrenal weights decreased and both fasciculata and reticularis zones markedly regressed. Histopathological lesions were also noted and plasma and glandular glucocorticoid contents were significantly reduced. Simultaneously an increase in cholesterol and a decrease in ascorbic acid content of the adrenal glands were noticed. The adrenotoxic effect of this chlorinated insecticide possibly results from depressed corticoid production in situ and /or suppressed activity of enzyme(s) that catalyze the peripheral transformation of steroids.

Effect of lindane on clutch size and level of egg yolk protein in domestic duck

Lindane (gamma-hexachlorocyclohexane) was administered to laying ducks (Anas platyrhynchos domesticus) in 3 doses viz. (1) 20 mg/kg body weight daily, (2) 20 mg/kg body weight thrice weekly and (3) 20 mg/kg body weight twice weekly for 8 weeks. Egg laying was immediately stopped for 3 weeks in the first 2 groups and when resumed it became highly irregular with clutch size drastically reduced (1 against 7 of control ducks). The initial delay was absent in the 3rd group and reduction in clutch size was also marginal (5 against 7). Laying frequencies were 8.3%, 11.7% and 40% in Groups 1, 2 and 3 birds respectively against 50% frequency of the normal ducks. Hepatic, plasma and ovarian vitellogenin levels were substantially reduced in the first 2 groups. At the same time liver RNA level was markedly reduced. Ovary of such birds lack mature vitellogenic follicles and the thecal layer of moderately differentiated oocytes became highly atrophic. Stilbestrol (50 mg/kg body wt--single injection) administration to lindane fed pauci-layer ducks restored egg laying within 24 h, with return of a normal level of plasma vitellogenin and hepatic RNA. The results suggest that lindane induced estradiol insufficiency causes inhibition of hepatic RNA and yolk protein synthesis, thereby preventing transformation of moderately differentiated oocytes to mature vitellogenic follicles, delaying ovulation and thus drastically reducing clutch size.

Thyroidal influence on the cell surface GM1 of granule cells: Its significance in cell migration during rat brain development

Summary1.No difference was observed in thein vitro growing ability of granule cells isolated from hypothyroid or normal rat brain. When granule cells were taken from hypothyroid rat brain and grown in normal culture medium containing 10% fetal calf serum, they behaved similarly to the granule cells obtained from normal rat brain.2.In both cases there were progressive losses ofin vitro growing ability of the granule cells with the age of the animal and it became impossible to grow them when derived from 21 days or older animals.3.A marked decrease in cell surface GM1 was observed when the cells were maintained under thyroid hormone-deficient conditions in culture.4.Anti-GM1 antibody was found to inhibit significantly the migration of granule cells along the astrocyte fibers.5.These results indicate that GM1 has an important role in thyroid hormone-dependent postnatal brain maturation in rat.

Use of high-performance liquid chromatography for assay of glutamic acid decarboxylase. Its limitation in use for post-mortem brain.

Rat brain, obtained 10 min after death, contained high levels of endogenous gamma-aminobutyric acid (GABA) and glutamic acid. Incubation of this brain homogenate at 37 degrees C indicated decrease of GABA with time due to degradation by GABA-transaminase. Reported high-performance liquid chromatographic (HPLC) methods for glutamic acid decarboxylase (GAD) assay depend on the difference between the GABA content of the reaction mixture after and before the incubation period. None of the methods considered the degradation of GABA during incubation. Furthermore, during determination of the Michaelis constant (KM) for the reaction none of them considered the endogenous substrate. Here we have focused on these factors which seriously affect the maximum velocity (Vmax) and KM values during GAD assay by the HPLC technique. By a simple and rapid HPLC technique we have measured GAD activity in post-mortem rat brain after removing endogenous glutamic acid by charcoal treatment and using gabaquline to prevent GABA degradation during incubation period. By this method a Vmax value of 46 +/- 4 nmol/h/mg protein and a KM value of 7.5 +/- 0.6 mM were observed for GAD activity of crude brain homogenate. For a comparative study, we have carried out radiometric assay of GAD activity from the same sample and observed a Vmax of 48 +/- 6 nmol/h/mg protein and KM of 6.9 +/- 0.4 mM.

Insecticide induced hematological changes in pigeons

Hematological responses of bluerock pigeon (Columba livia Gmelin) were studied after oral administration of chlordane (a cyclodiene) fenitrothion (a phosphothioate) and carbaryl (a carbamate) for one week. Comparable hematological disorders were induced by these insecticides which include reduction in total count of peripheral erythrocytes, hemoglobin content, hematocrit and total cellularity of spleen. Total count of peripheral leucocytes, on the otherhand, increased with marked heterophilia together with lymphopenia and monocytopenia. Both bleeding and clotting time became conspicuously prolonged in the experimental birds. The results indicate potential to use hematological responses for rapid on the spot assay of insecticide toxicity in non-target animals.

Bay K8644 like activity of an antibody against a 60 kDa tubular membrane protein

Partial purification of the dihydropyridine receptor from rat skeletal muscle demonstrated mainly a 60 kDa band in SDS-polyacrylamide gel. An antibody raised against that protein behaved as a calcium channel agonist viz. Bay K8644. The affinity purified antibody, when added to cultured heart cells, increased the beat rate 40-80% depending on the titer of the antiserum. The antibody also woke up the beats of the cells previously blocked with the channel antagonist, nifedipine. Immunoblot analysis indicated that the receptor of this antibody in heart cell membrane is also a 60 kDa protein.