Biomedical subjects

R Sinha

Publications and source records attributed to R Sinha.

219 records · Page 13Linked to original sources

PubMedDate not supplied

A study of gender-based cytochrome P4501A2 variability: a possible mechanism for the male excess of bladder cancer.

One hypothesis for the well known gender difference in bladder cancer risk is that males and females metabolize carcinogens differently. The caffeine breath test (CBT) was performed on a group of healthy men and women to determine whether there was a gender difference in P4501A2 activity. Results consistent with previous data suggest an elevation of CBT in men were observed, although this increase was not statistically significant. Among women, however, there was a significant difference between nulliparous and parous women(P = 0.03). Parous women had CBT values similar to men, whereas the results of women who had never given birth were lower. Confirming earlier studies, women taking oral contraceptives had low CBT values. Our data suggest an effect of recent caffeine consumption, with heavy coffee drinkers having higher rates of caffeine clearance. Adjustment for other weak effects, such as age, exposure to environment cigarette smoke, history of smoking, recent meat and cruciferous vegetable consumption, and use of alcohol or other medications, did not alter these findings. The finding of a difference between parous and nulliparous women requires further study.

Adult↗

PubMedDate not supplied

Determinants of plasma vitamin E in healthy males.

Vitamin E or tocopherol, a known antioxidant, may play a role in the etiology of chronic diseases such as cancer and heart disease. This study examined both "internal" (lipids, lipoproteins, and apoproteins) and "external" (dietary components, physical activity, and body mass index) factors which may influence plasma alpha-tocopherol and gamma-tocopherol levels. Analyses were done using dietary questionnaires and plasma obtained from 65 nonsmoking male volunteers aged 30-59 years. Forty-six men did not take any supplements while 19 took supplements containing vitamin E. A positive correlation (r = 0.32; P < 0.01) between vitamin E intake and alpha-tocopherol status [(ratio of plasma alpha- or gamma-tocopherol/(total triglycerides + total cholesterol)] and a negative correlation (r = -0.33; P < 0.007) between intake and gamma-tocopherol status were observed. The main internal factors, or determinants, for plasma alpha-tocopherol for nonsupplement users were plasma triglycerides and apoproteins, apoA1 and apoB, but neither lipids nor apoproteins appeared to affect tocopherol levels in supplement users. External determinants of alpha-tocopherol status in nonsupplement users were vitamin E intake, total fat intake, and body mass index, while in supplement users only vitamin E intake was important. Both vitamin E intake and alcohol intake appeared to affect plasma gamma-tocopherol status in a negative manner.

Adult↗

PubMedDate not supplied

Isolation and identification of selenium-labeled proteins in the mouse kidney.

Selenium is a potent chemopreventive agent; however, the mechanisms for its chemopreventive activities remain elusive. Selenium binds to several proteins, some of which require selenium for functional activity. In this study, two 58kDa selenium-labeled proteins were identified in mouse kidney using a 75Se labeling method. The proteins were partially purified using Sephadex G.150 gel filtration, DEAE-Sephadex A-50 ion-exchange chromatography and one- / two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (1D-/2D-SDS-PAGE). The two proteins migrated at 58kDa on 2D-SDS-PAGE and differed only slightly in their pI values; i.e., 6.2 and 6.6, respectively. The polyclonal antibodies raised in rabbits against the 58kDa proteins electro-eluted from the 1D-SDS-PAGE of the DEAE purified fraction, recognized both protein spots on 2D-SDS-PAGE gel. The in situ enzymatic digestion of the two proteins separated in 2D-SDS-PAGE gels, followed by microsequencing of the peptides, resulted in the identification of these two proteins as related to human lipoamide dehydrogenase and thiol: protein disulfide oxidoreductase (TPDO). In common, both these proteins have a bis (cysteinyl) sequence motif cys-X-X-cys (for lipoamide dehydrogenase it is cys-X-X-X-X-cys) which is also an integral part of several other proteins such as thioredoxin, protein disulfide isomerase, endoplasmic reticulum protein (ERp72), selenoprotein W, 56kDa acetaminophen binding protein and formate dehydrogenase. This sequence motif acts as an active redox center for majority of the proteins mentioned above, that may be controlling the oxidation/reduction of proteins in vivo. How and why selenium is binding to proteins with this common sequence motif needs further investigation.

Amino Acid Sequence↗