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Biomedical subjects

C W Scott

Publications and source records attributed to C W Scott.

At least 55 records · Page 3Linked to original sources
PubMed1985

Phosphorylation of type II regulatory subunit of cAMP-dependent protein kinase in intact smooth muscle.

A monoclonal antibody was used to quantitate changes in the extent of phosphorylation of the type II regulatory subunit of cAMP-dependent protein kinase in intact bovine tracheal smooth muscle. The autophosphorylated and nonphosphorylated forms of the regulatory subunit (RII) were separated in sodium dodecyl sulfate-polyacrylamide gels and identified by immunoblot analysis. Addition of cAMP to tissue extracts resulted in rapid dephosphorylation of RII (t 1/2 = 20s at 4 degrees C) while addition of MgATP caused complete conversion to the phosphorylated form. Under basal conditions, 56% of RII in intact muscle was phosphorylated when the tissue was homogenized under conditions which fully inhibit protein kinase and phosphatase activities. Incubation with isoproterenol caused a dose-dependent decrease in the phosphorylation state of RII (EC50 = 5 X 10(-8) M). Incubation with high concentrations of isoproterenol, 1-methyl-3-isobutylxanthine, or forskolin caused maximal decreases in the phosphorylated form to 12-18% of the total RII. The effect of isoproterenol was rapid (t 1/2 = 15 s at 37 degrees C), reversible, and could be blocked with the antagonist propranolol. Contraction of the smooth muscle with K+ or low (less than 1 microM) concentrations of carbachol had no effect on the phosphorylation level. A decrease in the basal phosphorylation level to 41% was observed with 10 microM carbachol which was additive with the dephosphorylation produced by isoproterenol. The time course of isoproterenol-induced dephosphorylation of RII paralleled that of muscle relaxation, consistent with a role of cAMP-dependent protein kinase activation in relaxation of smooth muscle.

Adenosine Triphosphate↗
PubMed1985

Monoclonal antibodies as probes of structure, function and isoenzyme forms of the type II regulatory subunit of cyclic AMP-dependent protein kinase.

We have attempted to review studies which have utilized monoclonal antibodies in the analysis of various aspects of type II cAMP-dependent protein kinase. It is readily apparent that the monoclonal antibodies directed against RII can be used in a number of ways to assess the structure and function of this protein. Monoclonal antibodies have been used to identify specific structural aspects of the protein, down to the level of amino acid sequence. These have included identification of relationships between several functional domains and the antigenic sites recognized by different antibodies. Monoclonal antibodies also have been used to specifically identify distinct isoenzyme forms of RII. The antibodies were shown to have virtually complete specificity for heart-type RII despite relatively few amino acid substitutions in neural-type RII. This discrimination was utilized to show that purified brain RII is composed of a small fraction of protein similar to the heart isozyme while the bulk of the protein is a distinct isozyme form. It is anticipated that future studies using antibodies specific for individual forms will be a valuable approach to analyzing the distribution and functions of different forms. Monoclonal antibodies have also been used as probes of RII in tissue extracts to examine phosphorylation of this subunit in intact tissue. Monoclonal antibodies should continue to provide powerful probes of the structure and function of this and other protein kinases.

Animals↗
PubMed1984

Reconstitution of catecholamine-stimulated binding of guanosine 5'-O-(3-thiotriphosphate) to the stimulatory GTP-binding protein of adenylate cyclase.

The stimulatory GTP-binding protein (Gs) of adenylate cyclase, purified from rabbit liver, and beta-adrenergic receptors, partially purified 1000-4000-fold from turkey erythrocyte plasma membranes, were coreconstituted into unilamellar phospholipid vesicles. The molar ratio of Gs to receptors in the vesicles varied from 3 to 10 in different preparations, as measured by guanosine 5'-O-(3-[35S]thiotriphosphate) [( 35S]GTP gamma S) binding to Gs and [125I]iodocyanopindolol binding to receptors. Activation of reconstituted Gs by GTP gamma S was stimulated up to 10-fold by the addition of the beta-adrenergic agonist (-)-isoproterenol. Activation was assayed functionally by reconstitution with the catalytic unit of adenylate cyclase. Because of the relative purity of this preparation, the quasi-irreversible binding of [35S]GTP gamma S could also be measured in the vesicles and was shown to parallel the functional activation of Gs under all conditions. Most of the assayable Gs in the vesicles could interact with the receptors and undergo agonist-stimulated activation. Agonist-stimulated activation and [35S]GTP gamma S binding were complete in less than 3 min, even under suboptimal conditions, and could go to completion in less than 20 s under maximal stimulation. Agonist-stimulated binding did not require appreciable free Mg2+ (less than 0.1 mM). Activation in the absence of agonist was stimulated by free Mg2+, but maximal activation took up to 10 min in the presence of 50 mM MgCl2. Reconstitution increased the stability of Gs to thermal denaturation. The addition of beta-adrenergic agonist further stabilized Gs, presumably by the formation of a stable agonist-receptor-Gs complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Alcohol oxidase assembles post-translationally into the peroxisome of Candida boidinii.

Candida yeasts rapidly form peroxisomes of simple function and composition when grown on methanol. Because the induction is both massive and rapid, this system may be useful for a detailed dissection of peroxisomal biogenesis. We report procedures to express peroxisomal proteins in cells and spheroplasts of Candida boidinii to stabilize peroxisomes in a lysate of spheroplasts and to obtain an enriched peroxisomal fraction. With these techniques we have been able to study the assembly of alcohol oxidase, a homo-octomeric flavoprotein, into the organelle in vivo. The primary translation product of alcohol oxidase comigrates on sodium dodecyl sulfate-polyacrylamide gels with the mature subunit. Pulse-chase experiments indicate that the newly synthesized monomer of alcohol oxidase has a half-life of about 20 min in intact cells and 13 min in spheroplasts before conversion to octomer. The monomer first appears in a high speed supernatant of a lysate of spheroplasts and then chases into a purified peroxisomal fraction before or during its octomerization. There is no detectable intermediary organelle involved in this process.

Alcohol Oxidoreductases↗
PubMed1981

Extramedullary blast transformation in the central nervous system in idiopathic myelofibrosis.

Idiopathic myelofibrosis (IM) is a myeloproliferative syndrome characterized by anemia, fibrosis of the bone marrow, variable proliferation of megakaryocytes, myelocytic and erythrocytic precursors, and splenomegaly. Extramedullary hematopoiesis can develop in diverse areas. Unlike in chronic granulocytic leukemia, transformation to acute leukemia is uncommon in IM. Transformation to acute leukemia is usually accompanied by the findings of progressive increase in blasts in peripheral blood or bone marrow [1]. We have recently treated a patient with an unusual transition from IM to acute leukemia in whom leukemic transformation began in the central nervous system.

Central Nervous System Diseases↗
PubMed1980

The effects of commercial coaching or the NBME Part I Examination.

A total of 55 second-year medical students from the University of Alabama in Birmingham utilized the services of a commercial test-coaching company to assist them in preparations for the June 1977, 1978, and 1979 National Board of Medical Examiners Part I examination. These students scored significantly higher on the examination than students with comparable basic science grade-point averages. Students were surveyed to determine the nature of the course and to identify the salient points which they believed contributed to higher Part I scores. The study raises questions concerning the impact of commercial coaching on the licensure process for both domestic students and students of foreign medical schools entering the U.S. medical profession.

Achievement↗
PubMed1976

How many doctors?

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Health Planning↗
PubMed1975

Harmful effect of megadoses of vitamins: electroencephalogram abnormalities and seizures induced by intravenous folate in drug-treated epileptics.

Folic acid was administered intravenously during constant EEG monitoring to eight epileptic subjects who had received diphenylhydantoin therapy for more than 1 year. Six of the subjects displayed low folate levels by Lactobacillus casei assay in plasma and/or whole blood. Six patients received 75 mg of folate intravenously over a 30-min period without clinical effect of EEG change. One patient exhibited an increase in spike discharges on the EEG in comparison to the baseline pattern, but no clinical change or seizure while receiveing 150 mg of folate in a 30-min period. One patient displayed a 2-sec burst of spike and slow wave activity on the EEG after receiveing 7.2 mg of folate in a 3-min period. A tonic-clonic seizure occured after the infusion of 14.4 mg of folate, and again after infusion of 19.2 mg of folate. There appear to be wide variation in the ability of drug-treated epileptic subjects to tolerate infusions of folic acid. These variations help explain conflicting reports in the literature concerning the effect of folic acid administration on seizure control. Megadoses of folic acid should be employed with great caution in all subjects, but particularly among epileptics. Information is lacking as to whether folate might induce seizures in certain ostensibly normal individuals. It is postulated that folic acid exerts a direct effect among sensitive subjects on existing pathways concerned with the metabolism of folate, histidine, or other important brain metabolites. The mechanism of the anticonvulsant action of diphenylhdantoin remains unknown, but there is considerable evidence to suggest that it interferes with the deamination of histidine.

Adolescent↗