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Biomedical subjects

J C Robinson

Publications and source records attributed to J C Robinson.

At least 163 records · Page 9Linked to original sources
PubMed1977

Effect of manganese(ous) and sulfate on activity of human placental glucose 6-phosphate-dependent form of glycogen synthase.

The human placental glucose-6-P-dependent form of glycogen synthase, in the absence of glucose-6-P, can be activated by MnSO4. Separately, Mn2+ and SO4(2-) have no significant effect. In the presence of glucose-6-P, Mn2+ activates the enzyme, but SO4(2-) inhibits; MnSO4 synergetically increases the enzyme activity. Mn2+ reduces the Ka for glucose-6-P to one-tenth of the control value; SO4(2-) increases the Ka 5-fold; however, MnSO4 has no effect on Ka. MnSO4, like glucose-6-P, increases the Vmax of the enzyme in the presence of its substrate, UDP-glucose; it slightly increases the Km for UDP-glucose. In the presence of glucose-6-P, Mn2+ increases and SO4(2-) decreases the Vmax of the enzyme, but neither has an effect on the Km for UDP-glucose. At physiological concentrations of UDP-glucose and glucose-6-P, either Mn2+ or MnSO4 at concentrations less than 1 mM increases the enzyme activity as much as 8 mM glucose-6-P does. At physiological concentrations of UDP-glucose and glucose-6-P, Mn2+ or MnSO4 reverses the inhibition of the enzyme by ATP.

Chlorides↗
PubMed1977

Total conversion of glycogen synthase from the I- to the D-form by a cyclic AMP-independent protein kinase from rabbit skeletal muscle.

A newly discovered cyclic AMP-independent protein kinase, which catalyzes the total conversion of glycogen synthase from the I- to the D-form, has been isolated from rabbit skeletal muscle. This enzyme, designated glycogen synthase kinase, is separable from cyclic AMP-dependent protein kinase by column chromatography on phosphocellulose. Synthase kinase and cyclic AMP-dependent protein kinase are distinct in their specificity for protein substrates, the effects of cyclic AMP and the inhibitor of cyclic AMP-dependent protein kinase on their activities, and the extent to which they phosphorylate I-form glycogen synthase. The phosphorylation of I-form enzyme by synthase kinase results in the incorporation of 4 mol of phosphate/85,000 subunit; however only two of the phosphate sites seem predominantly to determine glucose-6-P dependence. The resulting multiply phosphorylated enzyme, which is highly dependent on glucose-6 P for activity, has a phosphate content comparable to the D-form enzyme isolated from rabbit muscle.

Animals↗
PubMed1977

Risks of BCG intralesional therapy: an experience with melanoma.

A nearly fatal allergic reaction to intratumor BCG injections was associated with a complete remission of recurrent malignant melanoma. Clinical course and histologic sections suggested both anaphylactic and Arthus reactions. The occurrence of reactions at BCG injection sites as well as at uninjected sites of tumor suggests common BCG and melanoma antigens. The management of events involved in this often fatal postimmunotherapy complication involves the early administration of parenteral fluids, antituberculous therapy, antihistamines, and possible steroids. The prophylactic use of antihistamines and an in-hospital administration of intralesional BCG immunotherapy are strongly suggested. In the future, prophylactic INH may prove to be both therapeutically efficacious and protective against infectious complications.

Anaphylaxis↗
PubMed1977

Induction of placental alkaline phosphatase in choriocarcinoma cells by 5-bromo-2'-deoxyuridine.

Growth of choriocarcinoma cells in the presence of 5-bromo-2'-deoxyuridine (BrdUrd) results in a 30- to 40-fold increase in alkaline phosphatase activity. The effects of BrdUrd is specific for phosphatase with an alkaline pH optimum. The induction by BrdUrd is probably not due to the production of an altered enzyme, since the induced enzyme resembles the basal enzyme in thermal denaturation and kinetic properties. Enzyme induction can be prevented by thymidine but not by deoxycytidine or deoxyuridine. The induction of alkaline phosphatase appears to require incorporation of the BrdUrd into cellular DNA. The presence of BrdUrd in the growth medium is not necessary for alkaline phosphatase induction in proliferating cells containing BrdUrd-substituted genomes. However, enzyme induction and maintenance of the induced levels of alkaline phosphatase in nonproliferating cells containing BrdUrd-substituted DNA requires the presence of the analogues in the medium. The induction of alkaline phosphatase by BrdUrd in probably an indirect process.

Alkaline Phosphatase↗
PubMed1976

Cigarette smoking and the young: a national survey.

Cigarette smoking behaviour among the young was examined in the light of the responses of over 78 000 students to a 1972 questionnaire survey of Canadian schools. As few as 2% (8-year-old girls) and as many as 60% (16 year--old boys) were smoking one or more cigarettes per week. The prevalence of smoking was higher than that reported in earlier studies. Students, particularly girls, were beginning to smoke at progressively earlier ages. Some differences in smoking behaviour were found between regions, language groups and groups of children whose parents did or did not smoke. Recognition of immediate rather than long-term effects of smoking on health was reported as an important consideration in not smoking.

Achievement↗
PubMed1976

Synthesis of alpha subunit of human chorionic gonadotrophin by presumptive HeLa cells.

Several cell lines, originally thought to be derived from a human placenta at term but possibly HeLa-contaminated, have been studied. These cells secrete a protein indistinguishable immunochemically from the alpha subunit of chorionic gonadotropin but not the beta subunit of chorionic gonadotropin or placental lactogen. Complete chorionic gonadotropin was detected but amounted to less than 1% of the level of the alpha subunit. The cells also produce an alkaline phosphatase similar to placental alkaline phosphatase in immunochemical, gel-electrophoretic, and heat-denaturation properties. They induce tumor growth when inoculated into nude mice. These cells are aneuploid and have a model chromosome number of 66. The common HeLa karyologic markers, designated 1, 2, and 3, and A-type glucose-6-phosphate dehydrogenase are present in these cells. HeLa cells have not previously been shown to secrete the alpha subunit of hCG.

Alkaline Phosphatase↗
PubMed1976

Monoamine oxidase in rat placenta, human placenta, and cultured choriocarcinoma.

The activity of monoamine oxidase (MAO), an enzyme which metabolized catecholamines and indoleamines, was determined in rat placenta at various stages of gestation, in human term placenta, and in choriocarcinoma grown in culture. From Day 15 to Day 20 of gestation the specific activity (units/mg protein) of MAO in rat placenta increased at least 3-fold; from Day 20 to the time of parturition, it decreased about 50%. The specific activity of MAO in human placenta at term was about 50%. The specific activity of MAO in human placenta at term was about 8 times higher than that of rat placenta at term. No MAO activity was found in choriocarcinoma grown in culture.

Animals↗
PubMed1976

Studies on the nicotine exposure of individual smokers. I. Changes in mouth-level exposure to nicotine on switching to lower nicotine cigarettes.

Twenty-four subjects smoked two brands of filter-tipped cigarettes delivering different amounts of nicotine, on the following 4-week schedule: 1. Smoking their usual brand for 1 week. 2. Smoking another brand similar in size, but delivering less nicotine, for 2 weeks. 3. Reverting to their usual brand for 1 week. The amount of nicotine entering the mouth, defined as the mouth-level exposure, was estimated from a determination of the amount of nicotine trapped in the filter of each cigarette smoked. The results indicate a substantial variation in mouth-level exposure for the subjects studied, even among smokers of cigarettes that deliver similar amounts of nicotine when smoked on a machine under standard conditions. For the majority of subjects, however, changing to a lower nicotine cigarette reduced the total daily mouth-level exposure to nicotine and, therefore, presumably the total tar intake.

Adult↗