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Biomedical subjects

R E Fellows

Publications and source records attributed to R E Fellows.

At least 55 records · Page 3Linked to original sources
PubMed1976

Covalent structure of apolipoprotein A-II from Macaca mulatta serum high-density lipoproteins.

The covalent structure of apolipoprotein A-II, isolated from the serum high-density lipoprotein of a single male Rhesus monkey (Macaca mulatta), was determined. The amino acid sequence of this 77-residue polypeptide is: less than Glu-Ala-Glu-Glu-Pro5-Ser-Val-Glu-Ser-Leu10-Val-Ser-Gln-Tyr-Phe15-Gln-Thr-Val-Thr-Asp20-Tyr-Gly-Lys-Asp-Leu25-Met-Glu-Lys-Val-Lys30-Ser-Pro-Glu-Leu-Gln35-Ala-Gln-Ala-Lys-Ala40-Tyr-Phe-Glu-Lys-Ser45-Lys-Glu-Gln-Leu-Thr50-Pro-Leu-Val-Lys-Lys55-Ala-Gly-Thr-Asp-Leu60-Val-Asn-Phe-Leu-Ser65-Tyr-Phe-Val-Glu-Leu70-Arg-Thr-Gln-Pro-Ala75-Thr-Gln-COOH. A comparison of this structure to that of the monomeric form of human apolipoprotein A-II reveals a high degree of homology except for six conservative amino acid replacements (positions 3, 6, 40, 53, 59, and 71). Of particular structural significance is the replacement of cysteine by serine in position 6. This explaines why Rhesus A-II exists in monomeric form, contrary to the established dimeric nature of the human protein.

Amino Acid Sequence↗
PubMed1976

Localization and specificity of binding of subprimate placental lactogen in rabbit tissues.

A search for specific placental lactogen binding was undertaken in tissues obtained from late pregnant rabbits using the placental lactogens from sheep, cows, and human beings. 125I-labeled ovine lactogen exhibited highest specific binding to the adrenal gland (57.8%), followed by liver (21.5%), ovary (19.9%), mammary gland (15.9%), uterus (12.2%), kidney (8.8%), brain (8.5%), and adipose tissue (7.9%). In liver and mammary gland, the displacement curves for ovine and human lactogen were identical to that for bovine prolactin, indicating that they share the same receptor site. Although the displacement curve for bovine lactogen was parallel to that of the other lactogens the bovine hormone is less active in the radioreceptor assay.

Adrenal Glands↗
PubMed1976

Circulating placental lactogen levels in dairy and beef cattle.

Levels of bovine placental lactogen (bPL) have been measured in the serum of dairy and beef cattle and in the milk and amniotic fluid of pregnant animals with a highly specific radioimmunoassay. In both dairy and beef cows, serum bPL levels remain low (less than 50 ng/ml) during the first two trimesters and then rise rapidly between 160 and 200 days of gestation to a plateau. The bPL levels do not decline prior to parturition. During the last trimester, serum levels in dairy cows, 1103+/-342 ng/ml, are significantly higher than those in beef cattle, 650+/-37 ng/ml (P less than 0.01); furthermore, dairy cows having a high milk production also tend to have high bPL levels. Serum levels are almost twice as high in twin pregnancies and are not correlated with fetal sex or birth weight. bPL levels in milk and amniotic fluid from dairy cattle during the last trimester are approximately 86% and 25% of the serum values, respectively, suggesting that bPL enters these fluids by passive diffusion.

Amniotic Fluid↗
PubMed1976

Ovine placental lactogen: acute effects on intermediary metabolism in pregnant and non-pregnant sheep.

The intravenous administration of ovine placental lactogen to pregnant and non-pregnant sheep produced significant acute decreases in plasma free fatty acid, glucose and amino nitrogen concentrations. Plasma insulin concentrations decreased 1 h after administration of ovine placental lactogen and then increased significantly above baseline concentrations. The results suggest that, like human placental lactogen, ovine placental lactogen is important in the modulation of intermediary metabolism during pregnancy. The sheep is an excellent animal model for the investigation of the physiology of placental lactogen.

Amino Acids↗
PubMed1975

Development of the sheep as an animal model to study placental lactogen physiology.

Ovine placental lactogen, purified from term sheep cotyledons, has been found to have chemical and biologic properties similar to those of human placental lactogen, ovine growth hormone, and ovine prolactin. OPL stimulates lactation in vivo and in vitro and binds to prolactin and growth hormone membrane receptors. Its binding to growth hormone receptors is approximately 20 times greater than that of hPL, suggesting that its somatotrophic potency is greater than that of hPL. Preliminary in vivo studies in the sheep indicate that oPL affects maternal carbohydrate, lipid, and protein metabolism and that its effects are, in part, similar to those of hPL and growth hormone.

Animals↗
PubMed1975

Growth hormone covalently bound to sepharose or glass. Analysis of ligand release rates and characterization of soluble radiolabeled products.

Purified boveine growth hormone labeled enzymatically with iodine-125 was covalently coupled to cyanogen bromide activated Sepharose 4B gel and to diazotized zirconia-clad glass beads. Under the conditions employed, an average of 0.8 and 7.3 mg of hormone were bound per ml of Sepharose and glass, respectively. When the conjugates were incubated in Krebs-Ringer bicarbonate buffer (pH 7.4), three separate radioactive species were detected in the incubation supernatant by chromatography on Sephadex G-75. The elution volumes of two of the species were identical with those of 125-I-labeled growth hormone and Na-125I controls, while the third component eluted as a moleucle of intermediate size. The rate of release of each species from the solid matrix was linear with time over 4 days and increased with temperature from 4 to 37 degrees. Although significantly less growth hormone was released from glass (0.14%/day) than from Sepharose (0.40%/day) at 37 degrees, active hormone in amounts sufficient to be detectable in a biological assay was nevertheless liberated from the former after as little as 4 hr of incubation. By contrast, the rate of release of 125-Iminus- and the intermediate-size compound from glass was significantly greater than from Sepharose, suggesting that protein bound to glass supports is more susceptible to degradation from exposure to ionizing radiation.

Animals↗