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S Hatfield

Publications and source records attributed to S Hatfield.

5 recordsLinked to original sources
PubMed1978

The effects of different levels of selenium administered to rats in drinking water on distribution and glutathione peroxidase.

Studies were conducted in an attempt to define a biochemical index of selenium toxicity rather than weight loss, liver disease and death. Rats, maintained on selenium deficient diets, received in drinking water various levels of selenium as Na2SeO3(0.1, 1.0, 1.5, 2.0 ppm). Changes in selenium dependent glutathione peroxidase (GSH-Px) activities and specific activities (nCi75Se/ug Se) were determined in liver, kidney and plasma at baseline and two and ten weeks after repletion. In intial selenium deficient rats, GSH-Px activities were markedly depressed and specific activities elevated as compared to 0.1 ppm controls. After two weeks, liver and plasma GSH-Px activiities increased, and plasma, liver and kidney specific activities decreased in a concentration dependent manner. In kidney, there were no differences in enzyme activity at either two or ten weeks. At ten weeks, liver GSH-Px activities continued to increase in the 1.0 ppm group, but were depressed at both the 1.5 and 2.0 ppm levels. Specific activities were also depressed in liver and excretion was not increased at these levels. This suggests a biochemical toxicity in liver at levels above 1.0 ppm after ten weeks, prior to the onset of gross pathological changes.

Animals↗
PubMed1976

Activation of purified human T cells by mitogens: diminished mitogen-induced deoxyribonucleic acid synthesis in human T cells compared with autologous peripheral blood lymphocytes.

Human thymus-derived (T) cells were isolated from peripheral blood after rosette formation with neuraminidase-treated sheep erythrocytes (SRBC). After separation on Ficoll-hypaque, SRBC were removed from T cells by treatment with tris(hydroxymethyl)aminomethane-NH4Cl. Human T cells and autologous peripheral blood lymphocytes (PBL) were then incubated with phytohemagglutinin, concanavalin A, or pokeweed mitogen. Human T cells, in the absence of other cell types, responded with less deoxyribonucleic acid (DNA) synthesis (measured by uptake of [3H]thymidine) than equal numbers of autologous PBL. Further experimentation established that, compared with autologous PBL, the diminished capacity of human T cells to be activated by mitogens was due neither to differences in the mitogen dose-response relationship nor to the time of peak DNA synthesis of T cells or autologous PBL. Fragments or components of SRBC were not detected on human T cells, and treatment of the T cell-SRBC mixture with tris(hydroxymethyl)aminomethane-NH4Cl did not contribute to the results. Increased cell density or a period of preculture before addition of mitogen also did not influence the degree of decreased DNA synthesis in human T cells compared with the response of autologous PBL incubated with the same mitogens. When mixed with the cells remaining at the Ficoll-media interface, purified human T cells did not suppress the mitogenic response of this cell mixture to PHA or concanavalin A. The data indicated that human T cells, in the absence of other cell types, were activated by mitogens to a lesser degree than autologous PBL. Furthermore, T cells responded with DNA synthesis after direct T cell-mitogen interaction.

Cell Separation↗
PubMed1976

Activation of purified human thymus-derived (T) cells by mitogens. II. Monocyte- macrophage potentiation of mitogen-induced DNA synthesis.

Thymus-derived (T) cells from peripheral blood were purified by rosette formation with neuraminidase-treated sheep red blood cells (SRBC) and centifugation on Ficoll-Hypaque. T cells recovered from the pellet were freed of SRBC by treatment with Tris-NH4Cl. T cells purified by this method showed a diminished ability to take up 3H-thymidine (3H-TdR) after mitogen stimulation when compared to the mitogenic response of an equal number of autologous peripheral blood mononuclear lymphocytes (PBL). Autologous monocytes restored the capacity of purified T cells to take up 3H-TdR in the presence of phytohemagglutinin (PHA) or Concanavalin A (Con A). The effect was proportional to the number of monocytes added. Similar restorative effects could be obtained with allogeneic or xenogeneic monocytes. These data suggest that the mitogenic stimulation of human PBL and Con A may reflect the participation of more than one cell type: the T cells and monocyte and that the genetic origin of the monocyte is not critical for augmentation of the mitogenic activation of human T cells.

Animals↗