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Biomedical subjects

B Shane

Publications and source records attributed to B Shane.

103 records · Page 6Linked to original sources
PubMed1975

Assessment of vitamin B 6 status. Studies on pregnant women and oral contraceptive users.

The vitamin B6 status of 10 pregnant women (third trimester), 9 oral contraceptive agent users, and 12 notnpregnant women (controls) was investigated over a 10-week period by means of the erythrocyte glutamate-oxaloacetate transaminase (E-GOT) activation test and by measurements of whole blood pyridoxal phosphate levels. Blood pyridoxal phosphate levels in oral contraceptive agent users (7.6 plus or minus 1.1 ng/ml) were significantly lower than in the control group (9.6 plus or minus 1.7 mg/ml)indicating a relative vitamin B6 deficiency. Pyridoxal phosphate levels in pregnant women(5.1 plus or minus 1.3ng/ml) were even lower; in fact, no overlap was found in individual mean values between the pregnant and control groups. The E-GOT activation test did not indicate a vitamin deficiency in the pregnant women or in oral contraceptive agent users and the E-GOT activation factor did not correlate with blood pyridoxal phosphate levels unless results obtained after pyridoxine hydrochloride (20 mg/day) administration were included. The E-GOT activation test appears to be a poor indicator of vitamin B6 status, except in pronounced deficiency as it is less responsive to vitamin depletion than blood pyridoxal phosphate levels, and suffers from relatively large variations in individual control values. This may be a result of factors unrelated to vitamin B6 as blood pyridoxal phosphate levels remained fairly constant in the individuals investigated.

Adolescent↗
PubMed1975

The anti-folate effect of methionine on bone marrow of normal and vitamin B12 deficient rats.

The effects of dietary vitamin B12 and methionine deficiency, and the in vitro addition of methionine, homocysteine, or folic acid on the methylation of dUMP to dTMP were studied in rat bone marrow culture. Vitamin B12 or methionine deficiency had no effect on the methylation reaction or on bone marrow folate levels although the vitamin B12 content in bone marrow was reduced in vitamin B12 deficiency. In vitro addition of vitamin B12 or folic acid also had no effect on the methylation of dUMP. In vitro addition of methionine reduced the methylation of dUMP and increased the proportion of 5-methyltetrahydrofolate at the expense of other folate coenzymes. The reason for this 'anti-folate' effect of methionine, which is the opposite to that found in liver, was not clear. The presence of 5,10-methylenetetrahydrofolate reductase and 5-methyltetrahydrofolate-homocysteine methyltransferase were confirmed in rat bone marrow and they were inhibited by S-adenosylmethionine and methionine, respectively, in a similar fashion to that found with the liver enzymes. Homocysteine had no effect on the proportions of the various folate coenzymes in bone marrow but did inhibit the incorporation of deoxyuridine and deoxythymidine into DNA. It appeared that homocysteine exerted at a non-folate dependent step beyond the formation of dTMP.

Animals↗
PubMed1975

Stimulatory effects of peptides on growth of the free-living nematode Caenorhabditis briggsae.

Evidence is presented that peptide products of hydrolysis of casein, including some di- and tripeptides, but not the constituent amino acids, can stimulate growth of C. briggsae in defined basal medium supplemented with cytochrome C and B-sitosterol. Peptide activity may raise from amino acid imbalances in the medium which causes competitive inhibition of uptake of essential amino acids. Such activity precludes facilitation of heme transport as the sole function of growth factor in C. briggsae. This is the first report in a nutritional role of peptides in invertebrate metazoa.

Amino Acids↗
PubMed1972

Purification and characterization of lysosomal -glucuronidase from human placenta.

1. Subcellular fractions of human placenta were prepared by nitrogen-bomb homogenization and differential centrifugation. 2. beta-Glucuronidase from placental lysosomes was purified 2100-fold on a protein basis. 3. The lysosomal enzyme, at different stages of purification, was characterized by using 4-methylumbelliferyl beta-d-glucuronide and phenolphthalein beta-d-glucuronide as substrates. 4. Only one isoenzyme of beta-glucuronidase was found in placenta; the enzyme in the endoplasmic reticulum appeared to be the same as the lysosomal enzyme. 5. The isoenzyme contained in normal plasma was different from that of the placenta. 6. The elevated beta-glucuronidase activity found in plasma obtained during pregnancy was due to increased activity of the normal plasma isoenzyme; no contribution was made by placental isoenzyme. 7. Plasma contained a heat-stable, non-diffusible activator of placental beta-glucuronidase. 8. A heat-stable competitive inhibitor of placental and plasma beta-glucuronidase was also present in plasma.

Centrifugation↗