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Biomedical subjects

R E Steele

Publications and source records attributed to R E Steele.

At least 91 records · Page 5Linked to original sources
PubMed1978

Modified bases in the DNAs of unicellular eukaryotes: an examination of distributions and possible roles, with emphasis on hydroxymethyluracil in dinoflagellates.

The occurrence of small amounts of one or more of several modified bases in the DNA of an organism is widespread in nature. Prominent among these bases are 5-methylcytosine, N6-methyladenine and 5-hydroxymethyluracil. All can be found in varying amounts in DNA of viral, prokaryotic and eukaryotic origin. In some organisms, modified nucleotides comprise a large fraction of DNA nucleotides and in others there is complete replacement of one of the common four nucleotides by a modified one. This article discusses the distributions and possible roles of the several modified bases found in prokaryote and eukaryote DNAs. Emphasis is given (1) methylcytosine in a broad variety of eukaryotes, (2) methyladenine in certain protozoa and protophyta and (3) hydroxymethyluracil in dinoflagellates. Attention is focused on the phenomenology and the possible consequences of the presence of hydroxymethyluracil in DNA.

Adenine↗
PubMed1977

Interrelationships of sodium transport and carbon dioxide production by the toad bladder: response to changes in mucosal sodium concentration, to vasopressin and to availability of metabolic substrate.

Active sodium transport and CO2 production were measured simultaneously in toad bladders mounted in membrane chambers. The rate of sodium transport was varied by changing the concentration of sodium in the mucosal bath (substitution with choline), by adding vasopressin, by adding metabolic substrates and by adding malonate, and the ratio of the change of sodium transport and CO2 production was determined Mean values for deltaNa/deltaCO2 (equiv/mole) were: Na in equilibrium choline 18.3 +/- 1.1; vasopressin 15.5 +/- 2.8; and pyruvate (corrected for the increment in "nontransport" CO2) 15.4 +/- 3.5. Based on previously determined values for the respiratory quotient (R.Q.), calculated mean values for deltaNa/deltaO2 ranged between 15.5 and 18.5 equiv/mole. It appears that basal metabolism does not contribute to metabolism supporting sodium transport when the rate of sodium transport is varied. "Transport" metabolism appears much more responsive to changes in the availability of endogenous and exogenous substrates than does "nontransport" metabolism. We conclude that "transport" and "nontransport" metabolism are functionally separated in the toad bladder.

Animals↗
PubMed1977

Relative importance of 5alpha reduction for the androgenic and LH-inhibiting activities of delta-4-3-ketosteroids.

The significance of 5alpha reduction of c19, delta1,4-3-ketosteroids in regulating growth of the rat ventral prostate (VP) was examined. The androgenic and LH-inhibiting activities of a C19 delta1,4-3-detosteroid which does not undergo appreciable 5alpha reduction were compared with those of its 5alpha reduced analogue and those of testosterone (T). In intact rats M (17beta-hydroxy-17alpha-methyl-androsta-1:4-dien-3-one) caused a suppression of VP weights and plasma testosterone concentrations, and in castrated rats suppressed plasma LH concentrations. M was considerably less androgenic and moderately less potent as an inhibitor of LH secretion than either T or the 5alpha reduced analogue of M [17beta-hydroxy-17alpha-methyl-5alpha-androst-1-ene-3-one; (5alphaM)]. 5alphaM was found to be at least as androgenic and as active as an inhibitor of LH as T, suggesting that the weak activity of M may be attributable to a lack of reduction to 5alphaM. Following incubation of 3H-M with VP minces, over 96% of the radioactivity recovered corresponded with M by TLC. Under identical conditions 32-48% of the radioactivity recovered from incubations with 14C-T corresponded with 5alpha reduced metabolites of T. This study demonstrates the importance of 5alpha reduction for both the androgenic and LH-inhibiting activities of delta4-3-ketosteroids.

Anal Canal↗
PubMed1976

Integrated concentrations of luteinizing hormone and puberty.

Integrated serum concentrations of luteinizing hormone have been compared among 30-minute collections from 10 boys (6-18 years old) and 5 girls (5-11 years old). This study suggests that perpubertal as well as pubertal boys have greater mean integrated concentrations of LH during sleep than during waking. One of two pubertal girls had greater concentrations of LH during sleep, while three prepubertal girls did not.

Adolescent↗