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Biomedical subjects

J Pick

Publications and source records attributed to J Pick.

27 records · Page 2Linked to original sources
PubMed1976

Kinetics of fibrinogen and platelet adherence to biomaterials.

The initial task was to establish a conceptually and materially simple test procedure that could quantitate and evaluate the thrombogenic potential of a biomaterial surface. Since the primary events of thrombus formation on prosthetic surfaces are believed to involve the deposition of a plasma protein monolayer followed by platelet adhesion to its fibrinogen component, it seemed reasonable to focus on the binding kinetics of fibrinogen and platelets to a commonly used biomaterial. Employing solutions of 125I-fibrinogen in buffered saline, the adsorption characteristics of several types of biomedical tubing could be compared, and the competition and exchange among plasma proteins at surface binding sites of PVC were evaluated. Human platelets with 51Cr were found to adhere to PVC surfaces proportional to surface fibrinogen concentration, but only in the presence of plasma; the circulation of labelled platelets in buffered saline only resulted in significant adherence to the native surface, while surface fibrinogen was inhibitory. Physiological concentrations of albumin were the most effective in preventing both fibrinogen adsorption and platelet adherence. The most important consequence of this work, perhaps, is the many avenues of future experimentation discovered from this methodological approach, not only in the thrombogenic evaluation of a specific biomedical surface, but also in the delineation of thrombogenic sequelae in general.

Adhesiveness↗
PubMed1965

The fine structure of sympathetic neurons in x-irradiated frogs.

The effects of whole body x-irradiation on the fine structure of sympathetic neurons were studied in 15 unanesthetized adult frogs (Rana pipiens), as seen at intervals ranging from 1 hour to 2 weeks after single exposures to 1000 r and 2000 r. Using standard procedures, the lumbar sympathetic ganglia of experimental and 20 control animals were prepared for electron microscope examination. Radiation produced conspicuous but irregular and variable deterioration, swelling, and clearing of neuronal lysosomes. These changes may have been due to an increased permeability of lysosomal membranes, causing the entry of fluid into lysosomes and their swelling and deterioration, but a pronounced escape of lysosomal enzymes into the cytoplasm was questionable. Less frequent were the dilatation and the parallel layering or complete fusion and tight packing of the rough-edged endoplasmic reticulum. The number of vacuoles, probably derived from Golgi cisternae, was somewhat increased. These vacuoles were conjectured to serve the "sequestration" of damaged cytoplasmic areas. Abnormal amounts of presumptive glycogen granules occupied some axons of myelinated and unmyelinated fibers, especially of presynaptic nerve fibers. This was assumed to be due to a decreased breakdown of glycogen and probably caused the interruption of the transmission of nerve impulses in presynaptic fibers. The maximal incidence of these alterations seemingly occurred 8 days after exposure to 1000 r, and 1 hour after x-irradiation with 2000 r. Signs of recovery appeared 2 weeks after exposure to 2000 r.

Animals↗