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Biomedical subjects

A Koul

Publications and source records attributed to A Koul.

26 records · Page 2Linked to original sources
PubMed1990

Inhibition of arylhydrocarbon hydroxylase and cytochrome P-450 by 20-methylcholanthrene and phenobarbital in guinea pig on excessive doses of ascorbic acid.

Treatment of guinea pigs on adequate ascorbic acid (AA) with 20-methylcholanthrene (MCA) and phenobarbital (PB) significantly increased hepatic arylhydrocarbon hydroxylase (AHH), cytochrome P-450 and cytochrome-b5 activities. In lungs, only MCA treatment significantly enhanced the activities of AHH, cytochrome P-450 and cytochrome b5. In animals on excessive doses of AA, there was inhibition of hepatic AHH, cytochrome P-450 and cytochrome b5 levels by treatment with these xenobiotics. Also, inhibition was observed in pulmonary AHH and cytochrome P-450 levels. The relevance of these observations in excessive AA-fed guinea pigs to carcinogenesis requires further extensive investigations.

Animals↗
PubMed1989

Prevalence of hepatitis B surface antigen in Kashmiri blood donors.

Eighty eight of 7900 healthy blood donors screened for hepatitis B surface antigen (HBs Ag) carrier state by reversed passive haemagglutination assay were found to be positive. The positivity was significantly more in rural donors (P less than 0.001) as compared to urban donors. False positive results are seen only with 1.13 per cent of the sera tested.

Adult↗
PubMed1987

Effect of excessive intake of ascorbic acid on hepatic and extra-hepatic phase I and phase II drug metabolism in rat.

Guinea pig is the animal model of choice for studies on effects of ascorbic acid (AA). However, rat is one of the largely used animals for investigations related to chemical carcinogenesis. Therefore, the present study was designed to evaluate the changes induced by high intake of the vitamin in xenobiotic and carcinogen metabolizing status of the organs. Male Wistar rats, dosed daily with 50 mg AA/100 g body weight for 10 weeks, demonstrated a small non-significant increase in hepatic, pulmonary and colon cytochrome P-450 (Cyt. P-450) contents, which was accompanied with a significant increase in hepatic and pulmonary arylhydrocarbon hydroxylase (AHH) activities. Phase II enzymes of drug metabolism responded in different ways to increased intake of AA. UDP-glucuronyltransferase (UDPGT) activity was unaffected in liver and colon, but it was increased (p less than 0.005) in lung. Activities of glutathione S-transferase (GST) were decreased in the three organs. Inducibility of AHH by 3-methylcholanthrene (MCA) or phenobarbital (PB) was largely reduced due to AA feeding. Besides this, MCA and PB had differential effects on enzymatic levels in AA fed rats. When compared with our earlier observations in guinea pig, it was found that rat responded similarly to guinea pig to increased intake of AA with regard to hepatic AHH, Cyt. P-450, UDPGT and GST, pulmonary AHH, Cyt. P-450 and Cyt. b5, and all studied colon enzymes, except GST.

Animals↗
PubMed1986

Effect of large doses of ascorbic acid on the hepatic and extra-hepatic drug-metabolizing enzymes in guinea pig.

Water solubility and non-toxic properties of ascorbic acid are taken as criteria for beneficial effects of large doses of the vitamin. In the present study, male guinea pigs, dosed daily with 15, 30 or 50 mg/100g body weight for 10 weeks, demonstrated no differences in effect on liver and lung weights, body growth and microsomal protein contents of liver and lung when compared with controls. When guinea pigs were fed excessive ascorbic acid, there was a small non-significant increase (p less than 0.05) in hepatic and pulmonary cytochrome P-450, and significant increase (p less than 0.05) in hepatic cytochrome b5 which was accompanied with a significant increase in arylhydrocarbon hydroxylase activity in the two organs. Activity of NADPH-dependent cytochrome c-reductase was decreased in liver and remained unaffected in lung and colon. Drug detoxifying enzymes responded in different ways to increased intake of ascorbic acid. Activity of UDP-glucuronyltransferase remained unchanged on feeding excessive ascorbic acid, whereas glutathione S-transferase was decreased significantly in liver and was unaltered in lung and colon. Reduced glutathione was decreased only in the lung. The observed changes in drug activating and detoxifying enzymes appear to be important from drug pharmacokinetics and carcinogenesis point of view.

Animals↗
PubMed1979

A nonfunctioning paraganglioma of vagus nerve: an ultrastructural study.

The clinical, histological, and ultrastructural aspects of a cervical paraganglioma of the vagus nerve, in a 66-year-old white man, have been discussed in detail. Ultrastructurally, the tumor chief cells contained characteristic membrane-bound and dense-cored neurosecretory granules which ranged in size from 85 millimicron to 190 millimicron. Unlike earlier ultrastructural reports, the present study showed the presence of sustentacular or supporting cells. These cells were smaller, darker, polymorphic, and were commonly located at the periphery of a single or group of chief cells. Furthermore, unlike earlier reports on vagal paragangliomas, nonmyelinated nerve fibers and an occasional axon were identified in the present fine structure study.

Aged↗
PubMed1979

Olfactory neuroblastoma (esthesioneuroblastoma): a light and ultrastructural study of two cases.

Olfactory neuroblastoma is a malignant neoplasm with a varied biological behavior. Its clinical course is unpredictable and there is no correlation between its microscopic features and biological behavior. The present study deals with light and ultrastructural characteristics of two cases of olfactory neuroblastoma of the nasal cavity. In one patient, the definitive diagnosis was established on the basis of ultrastructural features of the lesion. The most consistent fine structural findings were the presence of intracytoplasmic densecored neurosecretory granules, "true" and "pseudo-" rosettes, and the neuritic processes emanating from the tumor cells. On the basis of their biochemical, histochemical, and ultrastructural characteristics, olfactory neuroblastomas are similar to neuroblastomas arising from the adrenals or sympathetic nervous system. These findings, therefore, support the hypothesis that olfactory neuroblastomas are most likely of neural crest origin and thus belong to a group of neoplasms collectively known as "apudomas" or neurocristomas. The literature review strongly favors combined surgery and postradiation as the most effective treatment of olfactory neuroblastoma.

Aged↗