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Biomedical subjects

S Ellis

Publications and source records attributed to S Ellis.

At least 271 records · Page 15Linked to original sources
PubMed1978

Differences in dihydroergotamine antagonism of glucose release by catecholamines, glucagon and adenosine 3',5'-monophosphate in rabbit liver slices.

1 Quantitative studies were made on the glucose release from rabbit liver slices in vitro induced by a range of concentrations of (-)-adrenaline (Ad), (-)-isoprenaline (Iso), glucagon and adenosine 3',5'-monophosphate (cyclic AMP) in the presence and absence of several concentrations of dihydroergotamine (DHE). 2 DHE (3.16 X 10(-6) M) shifted the Ad log concentration-response (LCR) curve to the right and also reduced the maximum response; at a higher concentration (3.16 x 10(-5) M) it produced a greater shift to the right of the LCR curve and caused a reduction in the slope and a larger depression of the maximal responses. The LCR curve to Iso was similarly affected by this higher concentration of DHE. 3 DHE (1 X 10(-5) M) produced no significant effect on the LCR curves of glucagon or cyclic AMP and even at 1 x 10(-4) M DHE caused only a slight depression of the maximal responses to both agonists without any modification of the lower major portions of the curves. 4 These data indicate a selective antagonism by DHE at the rabbit liver adrenoceptor and, since the maximal responses to catecholamines were depressed by a lower concentration of DHE than was required to produce a slight depression of the responses to glucagon and cyclic AMP, the antagonism of DHE against catecholamines does not appear to be at a site beyond the formation of cyclic AMP, but rather at a site more intimately related to the adrenoceptor.

Animals↗
PubMed1978

Identification of a tripeptidyl aminopeptidase in the anterior pituitary gland: effect on the chemical and biological properties of rat and bovine growth hormones.

The NH2-terminal heterogeneity which is generated in bovine GH during its extraction from mildly acidified pituitary homogenates is attributable to a newly identified peptidase. The beta-naphthylamide of Phe-Pro-Ala, modeled after the NH2-terminal tripeptide sequence of the phenylalanyl monomer of bovine growth hormone, was cleaved by the peptidase into the tripeptide and B-naphthylamine and served as a substrate for assay of the eznyme. However, the B-naphthylamide of Ala-Phe-Pro, modeled after the NH2-terminal tripeptide sequence of the alanyl monomer, was not cleaved. In harmony with this specificity, the peptidase cleaved 11 tripeptides sequentially from the NH2-terminus of the phenylalanyl monomer of bovine GH but none from the alanyl monomer. Six of the tripeptides nearest the NH2-terminus were unequivocally identified and their sequences were consistent with the NH2-terminal octadecapeptide sequence of the phenylalanyl monomer of bovine GH. Five additional peptides were by composition consistent with their being tripeptides derived from residues 19--33. Because of the apparent specificity for the hydrolytic release of tripeptides and inability to cleave substituted tripeptidyl derivatives, the enzyme is considered to be a tripeptidyl aminopeptidase. In its hydrolysis of phenylalanyl monomers of rat growth hormone, a similar number of tripeptides was released, associated with which there was a 70% loss of biological activity but no reduction in immunological activity. The enzyme could be solubilized by extraction with 1% Triton X-100 at pH 3.0, precipitated between 2 and 3 M (NH4)2SO4, and further purified by gel filtration on G-75 in M/10 acetic acid. The enzyme has a mol wt of 57,000 and is optimally active at pH 4. It can be differentiated from cathepsin D by its insensitivity to inhibition by pepstatin.

Animals↗
PubMed1977

Metabolic and cardiovascular effects of carbuterol and metaproterenol.

Metabolic and cardiovascular responses to selective beta-adrenergic bronchodilators, carbuterol and metaproterenol, were studied during an asymptomatic period in 8 male subjects with bronchial asthma diagnosed as mile to moderate. On separate days each individual received either placebo, carbuterol 2 mg, carbuterol 4 mg, or metaproterenol 20 mg orally in a double-blind fashion. Subsequently, metabolic and cardiovascular responses were measured periodically for 5 hr. Carbuterol 2 mg was indistinguishable from placebo except for small elevations of glucose at 3 and 4 hr. Carbuterol 4 mg produced significant increases in glucose, insulin, lactate, and free fatty acids as well as in pulse rate and arterial pulse pressure. Metaproterenol produced increases only in plasma glucose and insulin. The majority of patients reported drug-related side effects which were all mild, after taking either carbuterol 4 mg or metaproterenol 20 mg. Fewer subjective side effects were noted with carbuterol 2 mg. These findings indicate that a 2-mg dose of carbuterol can be administered to typical asthmatic subjects without significant subjective or objective side effects. The larger dose (4 mg) may be accompanied by a greater frequency of side effects.

Adrenergic beta-Agonists↗
PubMed1977

Catecholamine-induced changes in plasma glucose and insulin levels in the unanesthetized rabbit.

Isoproterenol (ISO) produced dose-related increases in plasma immuno-reactive insulin (IRI) levels in unanesthetized rabbits, whereas epinephrine produced no significant changes. Dose rats of ISO or glucose that produced similar peak increases in glucose levels also produced similar increases in plasma IRI, but the responses to ISO occurred later and were of longer duration than the responses to glucose. Propranolol blocked the increase in plasma IRI produced by ISO, but the ISO-induced rise in plasma glucose was antagonized imcompletely. These data provide supporting evidence for the suggestion that the hyperglycemic activity of ISO in vivo is limited by concurrent ISO-induced changes in peripheral IRI levels.

Animals↗
PubMed1977

Cholesterol determination in high-density lipoproteins separated by three different methods.

We describe a simplified method for measuring high-density lipoprotein cholesterol in serum after very-low- and low-density lipoproteins have been precipitated from the specimen with sodium phosphotungstate and Mg2+. Values so obtained correlate well with values obtained with the heparin-Mn2+ precipitation technique (r = 0.95, CV less than 5% in 66% of the subjects studied and between 5 and 10% in the remaining ones) or by ultracentrifugal separation (r = 0.82, CV less than 5% in 80% of the subjects studied and between 5 and 10% in the remaining ones). Our precipitation technique is more appropriate for routine clinical laboratory use.

Adult↗
PubMed1977

In vivo response of ornithine decarboxylase activity to growth hormone as demonstrated by oxidation of L-ornithine-1-14C in hypophysectomized rats.

An in vivo response of ornithine decarboxylase activity to growth hormone has been demonstrated. In hypophysectomized rats, found to oxidize ornithine at rates comparable to those of normal rats, an acute treatment of growth hormone 4 hours before injection of L-ornithine-1-14C caused a 39% increase in the peak specific activity of carbon dioxide and a 24% increase in the 14CO2 recovered in 5 hours. However, response was not observed when growth hormone was administered chronically rather than acutely.

Animals↗
PubMed1976

Plasma vasopressin and renin activity in women exposed to bed rest and +Gz acceleration.

To study the effect of prolonged recumbency on plasma vasopressin and renin activity, eight women (23-34 yr) were subjected to 17 days of absolute bed rest. The +3 Gz tolerance of the subjects was tested before and after 14 days of bed rest. From day 2 and through day 17 of bed rest, plasma arginine vasopressin (AVP) levels were reduced 33%. Plasma renin activity (PRA) increased 91% (P less than 0.05) above ambulatory control values from days 10 through 15 of bed rest. When compared to precentrifuge values, exposure to +3 Gz prior to bed rest provoked a 20-fold rise (P less than 0.05) in mean plasma AVP but resulted in only a slight increase in PRA. After bed rest, acceleration increased plasma AVP 7-fold (P less than 0.02); however, the magnitude of this increase was less than the post +3Gz value obtained prior to bed rest. After bed rest, no significant rise was noted in PRA following +3 Gz. This study demonstrates that prolonged bed rest leads to a significant rise in the PRA of female subjects, while exposure to +Gz acceleration provokes a marked rise in plasma AVP.

Adult↗
PubMed1975

Amino terminal residue heterogeneity of bovine and ovine growth hormones as revealed by polyacrylamide gel electrophoresis.

Prolonged electrophoresis (4 to 16 h) of bovine and ovine growth hormones on analytical polyacrylamide gels in Tris-EDTA-borate buffers of pH 7.6 to 8.1 resulted in the separation of alanyl, phenylalanyl, and methionyl terminal polypeptide chains of these hormones similar to that obtained by isoelectric focusing in Ampholine pH gradients. Their relative anodic mobilities were methionyl greater than phenylalanyl greater than alanyl. The mobilities of the respective monomers were inversely related to their isoionic points as determined by isoelectric focusing in Ampholine pH gradients. The resolution of the different monomers is attributed to differences in the dissociation constants of the amino groups of the alanyl, phenylalanyl and methionyl terminal residues. Rat growth hormone, which consists of monomers with only a phenylalanyl amino terminus, did not display heterogeneity on gel electrophoresis. The applicability of employing polyacrylamide gel electrophoresis for the assessing of amino terminal residue heterogeneity is noted.

Alanine↗