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Biomedical subjects

S Ellis

Publications and source records attributed to S Ellis.

At least 37 records · Page 2Linked to original sources
PubMed1979

Characterization of Azotobacter vinelandii deoxyribonucleic acid and folded chromosomes.

The properties of Azotobacter vinelandii deoxyribonucleic acid (DNA) and folded chromosomes were studied and compared to those of Escherichia coli as a standard. Based on melting temperature and buoyant density measurements, the guanosine + cytosine content of purified A. vinelandii DNA was 65%, whereas that of E. coli DNA was 50%. The results of renaturation studies showed that the unique DNA sequence lengths of the two organisms were similar with Cot1/2 values of 7.3 +/- 0.4 mol.s/liter and 7.5 +/- 0.3 mol.s/liter, respectively, for A. vinelandii and E. coli. Folded chromosomes of A. vinelandii sedimented in a centrifugal field at a rate identical to those derived from E. coli, 1,600 to 1,700S. Based on the DNA content per cell and the mass of a single genome, A. vinelandii contains at least 40 chromosomes per cell.

Azotobacter↗
PubMed1979

Growth hormone control of glucose oxidation pathways in hypophysectomized rats.

An in vivo response of glucose oxidation to growth hormone has been demonstrated. Hypophysectomized rats were found to oxidize glucose at rates significantly higher than normal rats. Treatment with growth hormone 1 h before injection of 14C-U-glucose, 14C-6-glucose, or 14C-1-glucose caused a return to a normal oxidation pattern. This acute response was independent of insulin action but clearly time-dependent since no change from untreated hypophysectomized rats appeared when growth hormone was given at various times prior to administration of labeled glucose. The response observed for 14C-6-glucose was comparable to that observed for 14C-1-glucose with regard to dynamics but differed with respect to total 14C recovered as 14CO2. The cumulative percent 14CO2 recovered from oxidation of 14C-6-glucose 1 h after growth hormone injection exceeded that recovered from oxidation of 14C-1-glucose. These results suggest a change in glucose oxidation by a route that cannot be explained solely by changes in either the hexose monophosphate or Embden-Meyerhof pathways.

Animals↗
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↗