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Biomedical subjects

S F Speckart

Publications and source records attributed to S F Speckart.

7 recordsLinked to original sources
PubMed1979

Alterations in platelet surface sialytransferase activity and platelet aggregation in a group of cancer patients with a high incidence of thrombosis.

Platelet aggregation, platelet surface sialic acid, and platelet surface sialytransferase activity were studied in a group of 12 cancer patients with a high incidence of thrombosis. These patients demonstrated accelerated coagulation, increased Factor VIII antigen and restocetin cofactor, and enhanced adenosine 5'-diphosphate-induced platelet aggregation. Platelet exogenous sialytransferase activity was increased in cancer patients (117.6 +/- 14 pmol/10(9) platelets) as compared to controls (59.0 +/- 4.3 pmol/10(9) platelets, p less than 0.01). Platelet exogenous sialytransferase activity and platelet aggregation were inhibited by aspirin. Thrombosis and bleeding have complicated the clinical course of half of these patients. This platelet membrane analysis provides additional data which may be related to current observations of increased levels of plasma sialytransferase activity and serum sialic acid in cancer patients.

Adult↗
PubMed1978

Different effects of concanavalin A and E-phytohemagglutinin upon lymphocyte glycosyltransferase activities.

We have studied glycosyltransferase activities in human lymphocytes stimulated with the plant mitogens E-phytohemagglutinin or concanavalin A (Con A) and have compared the results with activities found in resting lymphocytes. Compared to resting lymphocytes, Con A-stimulated lymphocytes possess an enhanced capacity to transfer the sugars, sialic acid, galactose, and N-acetyl-glucosamine from their respective nucleotide donors to both endogenous cellular acceptors and added exogenous glycoprotein acceptors. The enhanced glycosyltransferase activity induced by Con A is not inhibited by puromycin despite effective inhibition of de novo protein synthesis, indicating that synthesis of new glycosyltransferase enzymes is not necessary for the observed increases in glycosylation activity. By contrast to the findings in Con A-stimulated cells, the corresponding glycosyltransferase activities of E-phytohemagglutinin-stimulated lymphocytes do not differ from those of unstimulated lymphocytes. These data indicate that individual plant lectins have different effects on the biosynthesis of complex saccharides by cultured human lymphocytes.

Cell Membrane↗
PubMed1977

Leukemic reticuloendotheliosis: "hairy cell leukemia," functional and structural features of the abnormal cell in a patient with profound leukocytosis.

The development of profound leukocytosis in a patient with leukemic reticuloendotheliosis (LRE) enabled us to obtain purified LRE cells for the investigation of their structural and functional characteristics. The LRE cells of our patient bore surface immunoglobulin and had complement receptors but did not bear Fc receptors and did not form rosettes with sheep erythrocytes. By electron microscopy, the cells were observed to contain typical ribosome lamella structures and to phagocytize both 0.81 micron latex particles and complement-coated zymosan particles. They were adherent to both glass and nylon wool fibers. The mitogenic response to erythroagglutinating phytohemagglutinin was normal to magnitude but delayed chronologically. The binding of 125I-labeled plant lectins was used to characterize the surface topography of LRE cells. Results of these studies indicated that the LRE cell surface differed significantly from the surface of normal T and B lymphocytes and chronic lymphatic leukemia cells. The LRE cells were capable of both stimulating and responding in a one-way mixed lymphocyte culture. However, the LRE cells were not active as effector cells of either cell-mediated lympholysis, a T cell function, or antibody-dependent cellular cytotoxicity, a null cell function. In contrast, they were effector cells of lectin-induced cellular cytotoxicity showing that they did possess the capacity to function as cytotoxic effector cells. These data indicated that the LRE cells in our patient had surface and functional characteristics of both lymphocytes and monocytes.

Binding Sites↗
PubMed1977

Excretion of DNA by purified human lymphocyte subpopulations.

A large proportion of DNA synthesized in vitro by human lymphocytes stimulated with plant mitogens or specific antigens is selectively excreted from the cells. To determine if DNA excretion differs among various types of lymphocytes, we examined purified human lymphocyte subpopulations for DNA synthesis and excretion in response to stimulation by L-PHA. The relative proportion of newly synthesized DNA that is excreted by unseparated mononuclear cells, macrophage-depleted cells, T, and B lymphocytes is identical despite great differences in the magnitude of their responses. Low levels of both DNA synthesis and excretion by macrophage-depleted cells and B cells can be increased by reconstitution with macrophages and T cells, respectively. These data indicate that DNA exretion is a general property of lymphocytes stimulated to undergo DNA synthesis by plant mitogens.

Antigens↗