Search PubMed⌕ Search

Biomedical subjects

R Kumar

Publications and source records attributed to R Kumar.

At least 1,441 records · Page 80Linked to original sources
PubMed1980

Enterohepatic physiology of 1,25-dihydroxyvitamin D3 metabolites in normal man.

Within 6 hr of the intravenous administration of radiolabeled 1,25(OH)2D3 to five normal vitamin D-replete human subjects, 15.6% of the injected dose appeared in bile as polar metabolites of 1,25(OH)2D3. Of the injected dose, 27% and 7.5% appeared in the feces and urine, respectively, at 24 hr. In another two subjects, biliary radioactivity was sampled at two jejunal sites separated by a distance of 40 cm; a 24.8% decrease in radioactivity over this segment of bowel was noted. These data demonstrate that products of 1,25(OH)2D3 are excreted in normal human bile. Furthermore, these products are reabsorbed as such or as free 1,25(OH)2D3 in the intestine and re-excreted as polar products in bile. Our data suggest that there is an enterohepatic circulation of the products of 1,25(OH)2D3 in normal man.

Adult↗
PubMed1979

Hepatic silver binding protein (Ag BP) from sparrow (Passer domesticus).

A silver binding protein (Ag BP) has been identified in the liver of sparrows administered a tracer dose of 110mAg. The protein as purified by gel-filtration shows a major absorption maximum at 260 nm and a minor one at 225 nm. It has a mol.wt of 9500 daltons and is stable when exposed to high temperature (64 degrees C for 15 min) as well as to acidic pH (2.2).

Animals↗
PubMed1979

Sources of variation in locomotor activity and stereotypy in rats treated with d-amphetamine.

Rats injected with doses of d-amphetamine 0--5.0 mg/kg were observed continuously in either an enclosed Y-maze or on an elevated Y-shaped platform. Patterns of increased walking and stereotypy were unaffected by the type of apparatus, but rearing remained totally suppressed at all dose levels on the elevated platform. In the second experiment, groups of rats where given single short tests in the enclosed Y-maze, which was novel to them. The stimulant actions of d-amphetamine on locomotion were obscured by high baseline levels of motor activity induced by the novel environment. Continuous measurements of habituated rats may provide a more sensitive means of evaluating stimulant actions of drugs in screening tests. The observed changes in patterns of onset and offset of increased locomotion and of stereotypy were consistent with the view that these types of behaviour are, to some extent, independently, mediated.

Animals↗
PubMed1979

Aldolase and dehydrogenase activities in Spirillum bengal.

Spirillum bengal is unable to grow on sugars, but can utilize different organic acids as carbon sources. Dehydrogenase activities were tested with different substrates and were found highest with lactate, glutamate, acetate, succinate and malate. A low aldolase activity was also detectable.

Cell-Free System↗
PubMed1979

Experimental cryptococcosis in normal and B-cell-deficient mice.

B-cell-deficient mice were prepared by administration of rabbit anti-mouse-mu antiserum to newborn animals within 12 h of birth onwards. Such immunodeficient animals, along with the normal controls, were infected intravenously with Cryptococcus neoformans. There was no difference in the mortality pattern, viable count of cryptococci in different organs, delayed-type hypersensitivity reaction, and antigen level in the sera of control and B-cell-deficient animals. Antibodies were absent in B-cell-deficient animals but were present in low titers in control animals. It is concluded that antibodies are not involved in protection of mice infected with C. neoformans.

Animals↗
PubMed1979

In vivo 24-hydroxylation of 25-hydroxyvitamin D3 in enterocolectomized rats.

To determine if the renal 25-hydroxyvitamin D3 24-hydroxylase is active in addition to the intestinal 25-hydroxyvitamin D3 24-hydroxylase in vivo in the rat, radiolabeled 25-hydroxyvitamin D3 was administrated to normocalcemic, vitamin D-replete, enterocolectomized rats. Substantial amounts of 24,25-dihydroxyvitamin D3 were detected and the identity of the isolated plasma 24,25-hydroxyvitamin D3 region in these animals were confirmed by coelution on high pressure liquid chromatography and periodate cleavage. This suggests that both intestinal and renal 25-hydroxyvitamin D3 24-hydroxylases are active in vivo in the rat.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗