Prahlad K. Seth

Free Radical-Generated Neurotoxicity of 6-Hydroxydopamine

Abstract: Albino rats were lesioned bilaterally with 6‐hydroxydopamine (6‐OHDA) hydrochloride (4 µg/µl, dissolved in saline with 0.1% ascorbic acid) into the striatum, and 72 h after the injection, levels of lipid peroxidation, GSH, superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), lipid class, membrane fluidity, and intracellular calcium concentrations were studied and the results were compared with those in the sham‐operated controls. The malonaldialdehyde level and the level of conjugated dienes were increased by 43 and 40%, respectively, in corpus striatum, and GSH, SOD, and GSH‐Px levels were decreased (24–30%) following 6‐OHDA treatment. Total phospholipid content was also decreased (18%), whereas cholesterol content remained unaffected. Among the different phospholipids only phosphatidylcholine and phosphatidylinositol were decreased in level. Membrane fluidity was decreased (23%), whereas the intracellular calcium concentration was elevated (100%) in corpus striatum compared with control rats. The results suggest that these alterations in membrane‐related events by 6‐OHDA could be due to free radical generation.

The effect of smoking and eating habits on DNA damage in Indian population as measured in the Comet assay

This study was undertaken with the aim of assessing the status of DNA damage in a normal healthy Indian population. The 62 male volunteers in this study belonged to the smoking, non-smoking, vegetarian and non-vegetarian categories, were well educated and aged between 23 and 57 years. The data revealed significant differences in the extent of DNA damage in the smokers versus non-smokers as well as between the vegetarians and non-vegetarians. A significant difference was also observed amongst the different groups of smokers depending on the extent of smoking. An age-dependent effect in DNA damage was also observed. This preliminary study has, for the first time, revealed differences in the extent of DNA damage in the normal Indian population depending on their eating and smoking habits as well as age.

Gender-related differences in basal DNA damage in lymphocytes of a healthy Indian population using the alkaline Comet assay.

The Comet assay, a sensitive, rapid and non-invasive technique, measures DNA damage in individual cells and has found wide acceptance in epidemiological and biomonitoring studies to determine the DNA damage resulting from lifestyle, occupational and environmental exposure. The present study was undertaken to measure the basal level of DNA damage in a normal, healthy Indian male and female population. Out of the 230 volunteers included in this study, 124 were male and 106 were female. All the individuals belonged to a comparable socio-economic background and aged between 20 and 30 years. They were also matched for their smoking and dietary habits. The period of sample collection was also matched. The results revealed a statistically significant higher level of DNA damage in males when compared to females as evident by an increase in the Olive tail moment [3.76+/-1.21 (arbitrary units) for males as compared to 3.37+/-1.47 for females (P<0.05)], tail DNA (%) [10.2+/-2.96 for males as compared to 9.40+/-2.83 for females (P<0.05)] and tail length (microm) [59.65+/-9.23 for males and 49.57+/-14.68 for females (P<0.001)]. To our knowledge, this report has, for the first time demonstrated significant differences in the basal level of DNA damage between males and females in a normal healthy Indian population.

Nitrite content and antioxidant enzyme levels in the blood of schizophrenia patients

Abstract.Rationale: Recent studies have suggested augmentation in the inflammatory response as well as involvement of nitric oxide (NO) in mood disorders. Polymorphonuclear leukocytes (PMN), NO and free radicals have been associated with inflammatory response; however, the status of NO in the PMN has not been investigated so far in schizophrenia patients. Objectives: The present study was undertaken to investigate levels of nitrite (a metabolite of NO), malonaldehyde (MDA, lipid peroxidation product) and antioxidant enzymes such as superoxide dismutase (SOD), catalase and glutathione peroxidase (Gpx) in the PMN of schizophrenia patients. Methods: Patients with schizophrenia (n=62) were diagnosed according to DSM-IV and were free of anti-psychotic medications/ECT for at least 3 months. Mean age of the patients was 29.06±1.17 years, with a male to female ratio of 4:1, and mean duration of illness was 3.7±0.6 years. The control group consisted of 82 healthy subjects with a mean age of 37.0±1.26 and a male to female ratio of 5:1. PMN were isolated from the blood. Nitrite, MDA and antioxidant enzymes were estimated by standard biochemical techniques in the PMN of normal healthy controls and schizophrenia patients. Platelet and plasma nitrite levels were also estimated in controls and schizophrenia patients. Results: Nitrite content in the PMN was reduced to 68%, while plasma and platelet nitrite content in schizophrenia patients was not significantly changed in comparison to controls. Malonaldehyde (MDA) content in PMN was significantly augmented in schizophrenia patients but activity of SOD, catalase and Gpx remain unaltered. Conclusion: Results obtained indicate a significant decrease in NO synthesis and an increase in MDA in the PMN of schizophrenia patients, while antioxidant enzyme activities were not altered in the PMN of schizophrenia patients. This suggests that the decrease in PMN NO synthesis by PMN might lead to oxidative stress in schizophrenia patients.

Oxidative stress-mediated neurotoxicity of cadmium

Young albino rats were administered cadmium i.p. (0.4 mg/kg body weight) for a period of 30 days and membrane fluidity, intracellular calcium level, MDA level, phospholipids, (phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, phosphatidylserine and sphingomyelin) and reduced glutathione were studied in olfactory bulb, cerebellum and rest of brain. A decrease in membrane fluidity was observed in all the brain regions studied, maximum being in olfactory bulb (21%). Intracellular calcium (Ca+2)i level was increased significantly in olfactory bulb (150%) followed by rest of brain (98%) and cerebellum (71%) in Cd-exposed rats in comparison with controls. A significant decrease in phosphatidylcholine (27%) and phosphatidylethanolamine (22%) was observed in olfactory bulb, while other phospholipids remained unaffected. TBA reactivity was increased in olfactory bulb (77%), cerebellum (35%) and rest of brain (27%). Reduced glutathione level was also decreased in different brain regions. The results suggest that the effect of cadmium in brain is region-specific and most pronounced in olfactory bulb.

Microbial degradation of acrylamide monomer.

Acrylamide, a neurotoxic monomer with extensive industrial applications was found to be degraded by the microorganisms present in a tropical garden soil. A bacterium capable of degrading acrylamide was isolated from this soil by enrichment. It was found to be aerobic, gram-negative, motile, short rod and identified as Pseudomonas sp. The bacterium degraded high concentrations of acrylamide (4 g/l) to acrylic acid and ammonia which were utilized as sole carbon and nitrogen source for growth. An amidase was involved in the hydrolysis of acrylamide, which could act on other short chain amides like formamide and acetamide but not on acrylamide analogues: methacrylamide and N,N-methylene bis-acrylamide. The enzyme was sensitive to catabolite repression by succinate both in presence as well as absence of nitrogen source.

Effect of lead exposure on the immune response of some occupationally exposed individuals

Lead is a ubiquitous pollutant in the industrial environment, which poses serious threats to human health. In the past 20 years increasing attention has been paid to the effects of lead exposure on health. This toxic metal alters the immune response of animals as well as humans. To study the immunological effects of occupational exposure to lead, we examined lymphocyte proliferation, natural killer (NK) cell cytotoxicity and interferon-gamma production with peripheral blood mononuclear cells (PBMCs) of individuals occupationally exposed to lead. We selected three different groups of individuals exposed to lead: three-wheeler drivers (30), battery workers (34) and silver jewelery makers (20); and unexposed healthy volunteers (30) as control for comparison. Our results indicate that though lymphocyte proliferation to phytohaemagglutinin (PHA) is inhibited in lead exposed individuals as compared with unexposed volunteers, there is no correlation between inhibition of lymphocyte proliferation and blood lead level. NK cell cytotoxicity remains unaffected in individuals exposed to lead as compared with controls. On the other hand, we observed that interferon-gamma (IFN-gamma) was significantly elevated in T cell mitogen, PHA, stimulated PBMCs culture supernatant of lead exposed individuals. We found significant positive correlation between blood lead levels and IFN-gamma produced in culture supernatant on stimulation with PHA. In brief, this study demonstrates that lead can affect the immune response of the occupationally exposed individuals such as three-wheeler drivers, battery reconditioning workers and silver jewelery makers.

Olfactory ensheathing cell transplantation restores functional deficits in rat model of Parkinson's disease: a cotransplantation approach with fetal ventral mesencephalic cells

Different strategies have been worked out to promote survival of transplanted fetal ventral mesencephalic cells (VMCs) using trophic and nontrophic support. Olfactory ensheathing cells (OECs) express high level of growth factors including NGF, bFGF, GDNF, and NT3, which are known to play important role in functional restoration or neurodegeneration. In the present investigation, an attempt has been made to study functional restoration in 6-hydroxydopamine (6-OHDA)-lesioned rat model of Parkinsons disease (PD) following cotransplantation of VMC and OECs (cultured from olfactory bulb, OB) in striatal region. The functional restoration was assessed using neurobehavioral, neurochemical, and immunohistochemical approach. At 12 weeks, post-transplantation, a significant recovery (P < 0.001) in D-amphetamine induced circling behavior (73%), and spontaneous locomotor activity (SLA, 81%) was evident in cotransplanted animals when compared with 6-OHDA-lesioned animals. A significant restoration (P < 0.001) in [3H]-spiperone binding (77%), dopamine (DA) (82%) and 3,4-dihydroxy phenyl acetic acid (DOPAC) level (75%) was observed in animals cotransplanted with OECs and VMC in comparison to lesioned animals. A significantly high expression and quantification of tyrosine hydroxylase (TH)-positive cells in cotransplanted animals further confirmed the supportive role of OECs in viability of transplanted dopaminergic cells, which in turn may be helping in functional restoration. This was further substantiated by our observation of enhanced TH immunoreactivity and differentiation in VMC cocultured with OECs under in vitro conditions as compared to VMC alone cultures. The results suggest that cotransplantation of OECs and VMC may be a better approach for functional restoration in 6-OHDA-induced rat model of Parkinsons disease.

BEHAVIORAL, NEUROCHEMICAL, AND NEUROMORPHOLOGICAL EFFECTS OF DELTAMETHRIN IN ADULT RATS

The neurotoxic action of a synthetic pyrethroid, a deltamethrin formulation (Decis), was studied in adult rats. Adult male albino rats received deltamethrin in formulation at a dose of 7.0 mg/kg body weight/d in corn oil orally for 15 d. Deltamethrin-exposed rats exhibited a decrease in body weight from d 9 onward, which was significantly lowered at d 15 of exposure. Administration of deltamethrin markedly increased the wet weight of the hippocampus and pons medulla region without much affecting the weight of frontal cortex, corpus striatum, hypothalamus, and cerebellum. A significant increase in the activity of monoamine oxidase was observed in frontal cortex, hippocampus, and cerebellum, and acetylcholinesterase activity was markedly increased in frontal cortex, corpus striatum, hippocampus, cerebellum, and pons medulla. The activity of Na+,K(+)-ATPase showed marked decrease in frontal cortex, hippocampus, and cerebellum following deltamethrin exposure. The polyamine concentration in brain regions was significantly affected, and all three polyamines showed marked alterations in the cerebellum. Deltamethrin significantly increased the spontaneous locomotor activity and aggressive behavior. Maze learning was markedly decreased. Morphological changes in Purkinje neurons in the cerebellum were observed in deltamethrin-exposed rats. Results suggest significant neurochemical and neuromorphological changes, which may culminate in perturbed synaptic function following deltamethrin exposure in rats.

Degradation of some phthalic acid esters in soil

Abstract The biodegradation of three phthalic acid esters (PAEs)—dimethyl phthalate (DMP), dibutyl phthalate (DBP) and di(2-ethyl hexyl)phthalate (DEHP)—was studied in a garden soil. The degradation rates of DMP and DBP were greater than that of DEHP under aerobic conditions. Anaerobiosis created by flooding greatly retarded the degradation of the three PAEs. The results suggest that microflora, especially bacteria, are actively involved in the degradation of the three phthalate esters.