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Biomedical subjects

R G Mason

Publications and source records attributed to R G Mason.

At least 73 records · Page 4Linked to original sources
PubMed1975

Some interactions of blood with tubular biomaterials.

Native human blood was exposed to polyethylene, poly(vinyl chloride), and Silastic tubing for varying time intervals, following which the relative degree of activation of the intrinsic coagulation system and alterations in cell counts were determined. The effects of pre-exposure of Silastic to purified albumin, high-density lipoprotein, or protein polysaccharide upon subsequent reactivity of blood with these surfaces was determined. In addition, the effects of aspirin, dextran, heparin, and Warfarin on reactivity of blood with Silastic were determined. In each case, changes in coagulation and cell counts were correlated with ultrastructural features of test surfaces following their exposure to blood. Pre-exposure of Silastic to purified proteins had relatively little effect upon subsequent reactivity with blood, while the presence of antithrombotic agents produced numerous changes.

Animals↗
PubMed1975

Reactivity of blood with biomaterials in vitro: evaluation of some in vitro test systems for estimation of the blood compatibility of biomaterials.

Several different in vitro tests designed to estimate the degree of compatibility of blood with biomaterials have been examined to determine possible effects of donor or donor-material interaction. Statistical evaluation of data was performed, and adequate data were collected with each different test system to render such evaluation meaningful. Isolated examples of donor and donor-material interaction were detected, but these proved to be minor or insignificant in each case. Data are presented for each of the in vitro test systems examined to indicate the number of replicate determinations required for observed differences to be significant at the 5% level.

Biocompatible Materials↗
PubMed1975

Characterization of human platelets separated from blood by ADP-induced aggregation.

Separation of platelets from plasma is achieved by adding ADP (final concentration 10-5 M) to platelet-rich plasma and allowing aggregates to form. Aggregates are removed quickly by brief, gentle centrifugation, washed two to three times with 0.9% NaCl (saline), and then incubated for 10 minutes in the presence of apyrase, albumin and calcium. Platelet aggregates deaggregate completely during this incubation period. The platelet suspension is then subjected to 1100g for 12 minutes, gently resuspended in a small volume of saline, and finally diluted with an appropriate medium to the desired concentration. The entire separation procedure requires approximately 30 minutes. Platelets obtained by this procedure are a) comparable in aggregability to the platelet preparations obtained by gel filtration, b) have normal intracellular amounts of ATP and ADP, and c) except for slight dilatation of the surface-connected canalicular system, have normal ultrastructural appearance. When suspended in an appropriate medium, these separated platelets take up serotonin 14-C and subsequently release it in nearly normal quantities when exposed to thrombin, collagen or ADP.

Adenosine Diphosphate↗
PubMed1975

Hemoglobin J-Chicago (beta76(E20) Ala yields Asp): a new hemoglobin variant resulting from substitution of an external residue.

An electrophoretically fast-moving hemoglobin variant was found in a 2-yr-old boy who was referred for evaluation with findings of iron deficiency anemia. The anemia was corrected, and no hematologic abnormality remained after treatment with iron. Oxygen affinity of the blood was normal, and no evidence was found of instability of the variant hemoglobin. Structural studies demonstrated a substitution of aspartic acid for alanine at beta76 (E20). This change did not appear to cause any functional disruption of the hemoglobin in this patient, as would be predicted by the position of the affected animo acid residue on the surface of the molecule.

1-Propanol↗
PubMed1974

Sites of acetylation of sickle cell hemoglobin by aspirin.

Aspirin acetylates a variety of sites on both the alpha and beta chains of hemoglobin S. Nevertheless, the vast majority of acetyl groups become attached to three loci: betaLys 59, betaLys 144, and alphaLys 90. These observations reveal some molecular details of this transacylation reaction and suggest interesting possibilities for its extension to other acylsalicylates with a variety of different structures.

Aspirin↗
PubMed1974

Venous thrombosis on prosthetic surfaces. Evolution and blood coagulation studies in a nonhuman primate model.

Thrombi deposited on prosthetic devices in the superior vena cava of the rhesus monkey were studied by morphologic and biochemical technics. Glass or silicone-coated glass (SCG) rings were implanted for 30 minutes to 14 days. Thrombus was deposited on the surface of each prosthetic device, and deposition was much greater and more rapid on glass surfaces than on SCG surfaces. On SCG surfaces, initial deposits consisting of single platelets, small platelet aggregates and erythrocytes were seen by scanning electron microscopy. These were followed by larger platelet aggregates, fibrin and, much later, leukocytes. Transmission electron micrographs revealed disintegration of the platelets forming aggregates and an osmiophilic deposit on the prosthetic surface. Shortened partial thromboplastin times were observed in all test animals but the sham-operated one, and therefore may be predictive of thrombus formation.

Animals↗
PubMed1974

Comparison of certain functions of human platelets separated from blood by various means.

Human platelets separated from blood by six different methods have been compared for aggregability, adhesion to glass, adenine nucleotide content and release, and adenosine triphosphatase and cholinesterase activities. Methods of separation of platelets from blood included three differential centrifugation technics, gel filtration and two albumin density gradient methods. Platelets prepared by the different methods aggregated comparably except those separated by albumin density gradient technics which tended to be hyporeactive. Differences in adhesion to glass, adenine nucleotide content and release, and monitored enzyme activities of the various platelet preparations were noted in several cases but were not marked in general. Ultrastructural studies, reported elsewhere, revealed that platelets separated by the method of Mustard or by gel filtration were less altered morphologically than those separated by the other methods. Platelets separated from blood by gel filtration also appeared somewhat superior functionally to platelets separated by other methods.

Adenosine Diphosphate↗