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Biomedical subjects

B Shafer

Publications and source records attributed to B Shafer.

4 recordsLinked to original sources
PubMed1978

Monoamine oxidase activity in different density gradient fractions of human platelets.

Monoamine oxidase (MAO) activity measured in human platelets is reportedly altered by such drugs as epinephrine, lithium carbonate, and imipramine, and also reduced in a number of clinical disorders. To evaluate whether MAO activity might differ in platelet subpopulations, density gradient centrifugation with arabino-galactan was used to prepare four platelet fractions that differed in weight and volume. MAO activity in the lightest and smallest platelet subpopulation was approximately one-half that in the heaviest and largest subpopulation. Because platelet weight and size are thought to be related to platelet age, it is possible that some drug effects on platelet MAO activity might represent changes in platelet turnover. Factors other than platelet turnover rates may contribute to individual differences in platelet MAO activity, however, since one group of individuals with markedly reduced platelet MAO activity exhibited no shift in the proportion of lighter versus heavier platelets nor in the relative amount of MAO activity in each density gradient subfraction.

Blood Platelets↗
PubMed1978

Heterogeneity of human whole blood platelet subpopulations. II. Use of a subhuman primate model to analyze the relationship between density and platelet age.

A subhuman primate model was developed to ascertain whether or not platelet heterogeneity could be explained by aging in the peripheral circulation. Density-dependent platelet cohorts, postulated to represent cells of different ages, were isolated on isosmolar arabinogalactan gradients and labeled with radiochromium. Mean platelet lifespan was measured for the different density cohorts, and simultaneous sequential density distribution analysis was performed to follow changes in cell density during aging. The average mean lifespan of light platelets was 74.6 hr, compared to 313.6 hr for heavy platelets. After injection, labeled light platelets were recovered only in the gradient light region, in contrast to labeled heavy platelets, which were initially restricted to the dense region and progressively migrated to the light region during their lifespan. This study supports the hypothesis that platelet age in unstressed primates correlates with cell density and provides a rationale for the use of "age-dependent" markers to estimate platelet turnover rates.

Animals↗