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Biomedical subjects

J B Hunt

Publications and source records attributed to J B Hunt.

48 records · Page 3Linked to original sources
PubMed1979

Identification of four major classes of sulfhydryl groups in human blood platelets. Ferricyanide titration of spin-labeled platelets.

Human blood platelets have been labeled with the sulfhydryl-specific spin labels, 4-iodoacetamido-2,2,6,6-tetramethylpiperidine-1-oxyl and 3-maleimido-2,2,5,5-tetramethylpyrrolidine-1-oxyl. First, the ESR spectra of platelets labeled with either reagent revealed two classes of sulfhydryl groups, a mobile class and an immobile class. Second, when spin-labeled platelets were titrated with high concentrations of potassium ferricyanide (greater than 10(-3) M), there was a decrease in the peak heights of the mobile class of sulfhydryl groups due to dipole-dipole exchange. Third, plots of peak heights of the mobile class versus ferricyanide concentration revealed three classes of mobile sulfhydryl groups compared to a single immobile class. This technique may be used to show the relative locations of spin-labeled groups on cell surfaces.

Blood Platelets↗
PubMed1979

Synthesis and use of a new spin-labeled analogue of ADP with platelet-aggregating activity.

A new spin-labeled derivative of ADP, 2-(4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl)thioadenosine-5'-diphosphate, has been synthesized. The compound causes both the reversible and irreversible phases of aggregation of human blood platelets at concentrations similar to those required for similar phases of aggregation by ADP itself. The spin-labeled ADP also rivals ADP as a substrate for pyruvate kinase. The interaction of intact human blood platelets and of isolated platelet membranes with the platelet-aggregating spin-labeled derivatives of ADP has been studied. The dramatic decrease in the ESR signal of the spin label is primarily due to chemical reduction of the nitroxide, rather than immobilization of the label. When platelets and spin-labeled ADP are mixed, a rapid burst of nitroxide reduction occurs, followed by a much slower reduction similar in time course to that seen for other spin labels. The rapid burst of reduction, but not the slow reduction, is inhibited by adenosine, an inhibitor of ADP-induced platelet aggregation, and by sulfhydryl-blocking agents. Experiments conducted with Ellman's reagent and platelet membranes or washed platelets revealed a 10 to 30% increase in the number of reactive membrane sulfhydryl groups when ADP was present. These results indicate that there is an increase in the number of reactive sulfhydryl groups on the platelet surface when platelets or membranes are stimulated by ADP.

Adenosine Diphosphate↗
PubMed1978

Fast neutron sensitivities of Geiger-Mueller counter gamma dosemeters.

The sensitivities to 4.2 and 5.5 MeV neutrons of different types of energy-compensated Geiger-Mueller counters used in mixed field dosimetry were measured using a field produced by the 2H(d, n)3He reaction with an isotropic gamma-dose component. Further results are presented on sensitivities to 14.7 MeV neutrons.

Fast Neutrons↗