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Biomedical subjects

H Mohan

Publications and source records attributed to H Mohan.

At least 19 recordsLinked to original sources
PubMed1996

Caffeine as an antioxidant: inhibition of lipid peroxidation induced by reactive oxygen species.

Caffeine (1,3,7-trimethyl xanthine), an ingredient of coffee, has been investigated for its potential antioxidant activity against oxidative damage to rat liver microsomes. Such damage was induced by three reactive oxygen species of cardinal importance in causing membrane damage in vivo namely hydroxyl radical (.OH), peroxyl radical (ROO.) and singlet oxygen (1O2). The results obtained showed that caffeine was an effective inhibitor of lipid peroxidation, at millimolar concentrations, against all the three reactive species. The extent of inhibition was high against peroxidation induced by .OH, medium against 1O2 and low against ROO. In general, the antioxidant ability of caffeine was similar to that of the established biological antioxidant glutathione and significantly higher than ascorbic acid. Investigations into the possible mechanisms involved in the observed antioxidant effect reveal that the quenching of these reactive species by caffeine may be one of the possible factor responsible. The rate constant of caffeine with .OH was 7.3 x 10(9) M-1 s-1 and with 1O2 it was 2.9 x 10(7) M-1 s-1. Considering their potential for damage, half-life estimates and generation in biological systems, the ability of caffeine to inhibit oxidative damage induced by these reactive species in membranes suggest one more positive attribute of caffeine, whose daily intake as coffee may be considerable in most populations.

Animals↗
PubMed1996

Mechanisms of protection by buthionine sulphoximine against gamma-ray-induced micronuclei in polychromatic erythrocytes of mouse bone marrow.

The effect of pretreatment with buthionine sulphoximine (BSO) on the radiosensitivity of mouse bone marrow cells was studied using the in vivo micronucleus test. Varying concentrations of BSO were injected into mice by intraperitoneal injection 2 h before irradiation, and the frequency of micronuclei in polychromatic erythrocytes (MnPCEs) of bone marrow were scored. Treatment with BSO resulted in a significant reduction (41% at 20 mg/kg body weight) in the frequency of micronuclei induced by 1 Gy gamma-rays. Reduction was observed in cells sampled at 24, 30 and 48 h postirradiation with no apparent effect on the ratio of poly- to normo-chromatic erythrocytes in BSO-treated versus control groups. Glutathione levels in the bone marrow of BSO-treated animals 2 h after a single injection were found to be unaltered. The protective effect of BSO was not observed if it was given either immediately or 2 h after irradiation. Based on these and earlier findings it seemed as if BSO molecules may be involved in physicochemical reactions with reactive species generated in the system by irradiation. BSO showed relatively high reaction rate constants with hydroxyl radical (.OH, 2.5 x 10(9) dm3 mol-1s1, calculated on the basis of competition kinetics) and with singlet oxygen (1O2, 4.3 x 10(7) dm3 mol-1s-1 but a lower rate constant with hydrated electrons (< or = 5.0 x 10(6) dm3 mol-1s1). Based on half-life estimates, transients formed and potential for damage to biomolecules, .OH and 1O2 seemed to be the possible species responsible. In vitro studies reveal that BSO has significant abilities to protect DNA against single-strand breaks and lipid peroxidation induced by 1O2 in microsomal membranes. This supports our hypothesis that BSO may be involved in scavenging the reactive species generated and that besides .OH, 1O2 may also be a major player in radiation damage.

Animals↗
PubMed1994

Addition of e-aq and H atoms to hypoxanthine and inosine and the reactions of alpha-hydroxyalkyl radicals with purines. A pulse radiolysis and product analysis study.

The reactions of hydrated electrons e-aq with hypoxanthine and inosine were followed using pulse radiolysis methods. In a neutral solution the electron adduct of inosine is immediately protonated at the heteroatoms of the purine ring by water (k >> 2.5 x 10(6)s-1) to give In(N,O-H).. These N,O-protonated intermediates have a single absorption maximum at 300 nm. In basic solution the protonation of the electron adduct of inosine by water leads to other intermediate products with an absorption maximum at 350 nm. These intermediates are believed to be the C-protonated electron adducts of inosine (In(N,O-H).). In (N,O-H). and In(C-H). differ strongly in their ability to reduce p-nitroacetophenone (PNAP). In(N,O-H). are strong reductants and reduce PNAP quantitatively to PNAP.-. Based on the pH dependence of PNAP.- yields, two types of tautomers of In(C-H). could be distinguished. One of the tautomers can reduce PNAP, albeit with slower rate than In(N,O-H)., the other tautomer has no reducing properties. The latter is the one with the higher pKa and therefore thermodynamically more stable. The absorption spectrum of the intermediates produced in the reaction of e-aq with hypoxanthine at neutral pH is very similar to that of In(N,O-H). with a maximum at 300 nm. However, no build-up at 350 nm was observed in basic solution as in the case of the electron adduct of inosine. The reaction of H atoms with inosine produces in basic solution intermediate radicals with the same absorption spectrum as the C-protonated electron adducts of inosine. It is suggested that both the reactions of e-aq and H. with inosine in basic solution produce the same radical, namely the H-adduct of inosine (In(C-H)) with the highest pKa. alpha-Hydroxyalkyl radicals were found to react very slowly with purine bases and nucleosides in neutral to basic solutions. In acidic solution their reactivity increases and a number of rate constants were determined by pulse radiolysis measurements at pH 0.4. The intermediates from the reaction of 2-hydroxy-2-propyl radicals with inosine could be observed pulse spectrometrically in neutral and in basic solutions. In basic solution this reaction leads to intermediates with the same absorption maximum at 350 nm as that of the H-adduct of inosine. Furthermore, the yield of acetone was found to increase strongly in basic pH.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetophenones↗
PubMed1993

Diagnostic and prognostic role of CRP and m-ESR in neonatal septicemia.

Serial estimation of CRP and m-ESR was done in 65 clinically suspected cases of septicemia and 25 healthy controls. Of these 65, 12 (18%) had a negative CRP test at the time of diagnosis and rest all had significantly elevated CRP and m-ESR compared to matched controls at the time of diagnosis. A persistently negative CRP test indicated bad prognosis. With treatment a declining trend of CRP was seen in survivors, but in deteriorating/expired babies the levels kept on increasing. However, m-ESR had no prognostic significance.

Blood Sedimentation↗
PubMed1990

Circulating iso and auto antibodies to human spermatozoa in infertility.

Blood samples from 50 couples of unexplained primary infertility and 25 healthy fertile couples were tested for antispermatozoa antibodies (ASA) by gelatin agglutination test and sperm immobilising complement dependent cytotoxicity test. The incidence of sperm agglutinating and sperm immobilising antibodies was found to be 14 per cent and 10 per cent respectively in infertile couples. Agglutinating antibodies were detected in 18 per cent males and 16 per cent of females while cytotoxic antibodies were found in 14 per cent males and 10 per cent of females. Only 4 per cent of the normal fertile couples taken as a control group showed positive ASA, hence the difference in incidence of positive ASA between the infertile and fertile couples was found to be statistically significant. Also, the agglutination test was observed to be more sensitive than the cytotoxicity test.

Agglutination Tests↗
PubMed1990

Placental pathology in pre-eclampsia eclampsia syndrome.

Quantitative analysis of placental pathology was carried out on 20 placentae from various grades of pre-eclampsia eclampsia syndrome and 20 placentae from control group. Placental weights were lower in the study group. The gross abnormalities noted were the placental infarcts, retroplacental haematoma and calcification. The striking villous lesions observed in the study group were cytotrophoblastic cell proliferation, thickening of villous basement membrane and paucity of vasculosyncytial membrane and these findings correlated well with the severity of maternal disease. These vascular villous lesions were considered secondary to uteroplacental ischaemia.

Basement Membrane↗