Search PubMed⌕ Search

Biomedical subjects

P Thomopoulos

Publications and source records attributed to P Thomopoulos.

At least 73 records · Page 4Linked to original sources
PubMed1980

Insulin receptors in acute and chronic lymphoid leukaemias.

Normal lymphocytes lack insulin receptors. The binding of this hormone was studied in twelve patients with acute lymphoblastic leukaemia (ALL) and fourteen patients with chronic lymphocytic leukaemia (CLL). Lymphoblasts from ALL have been found to possess hormone receptors with properties identical to those of the known target cells for insulin: specificity, pH and temperature dependence, and ligand-induced increase in dissociation rate. All patients with ALL displayed insulin receptors on their lymphoblasts. The null-type cells possessed higher numbers of binding sites than the T-type cells, without overlapping of the values. In the fourteen patients with CLL, eight had low levels of insulin receptors on their lymphocytes while six showed a complete lack of such binding sites. Our results suggest that measurement of insulin binding might be a useful non-immunological marker for the classification of human leukaemias.

Adult↗
PubMed1980

Insulin receptors and protein synthesis in bone marrow cells and reticulocytes.

Normal rabbit bone marrow erythroid cells have been found to possess insulin receptors. Their number shows an inverse relationship with the stage of differentiation, ranging from 20,000 sites/cell in the less mature to 8,000 sites/cell in the more mature cells. In addition, insulin rapidly stimulates the incorporation of leucine into protein in these cells and in rabbit, human, and rat peripheral blood reticulocytes. In rat reticulocytes, the concentration range of the hormone required for this phenomenon is from 25 to 625 microU/ml.

Animals↗
PubMed1979

Insulin receptors in cultured mouse retinal cells.

The binding of 125I-insulin to uncloned and cloned cultures of mouse retinal cells has been investigated. At 15 degrees C, binding of the hormone reached a steady state by 60 min, while at 37 degrees C equilibrium was reached earlier but at a lower level than at 15 degrees C. Porcine insulin, porcine proinsulin and guinea pig insulin displaced labelled insulin in proportion to their known biological potency. A sharp pH dependence of the hormone binding was observed with an optimum at pH 7.8. The dissociation rate of the 125I-insulin was increased in the presence of unlabelled hormone, suggesting the existence of negative cooperatively in the insulin-receptor interaction. The availability of established retinal cell lines with insulin receptors should facilitate the study of the insulin-retina interactions in a controlled in vitro system.

Animals↗
PubMed1978

Stimulation of triacylglycerol synthesis in rat adipocytes by plasma very-low-density lipoproteins.

The effect of human plasma lipoproteins on lipogenesis from glucose has been studied in isolated rat adipocytes. The very-low-density lipoproteins increased lipogenesis specifically, whereas low-density lipoproteins and high-density lipoproteins were without effect. Such stimulation could be reproduced with partially delipidated very-low-density lipoproteins. Nod-esterified fatty acids and glycerol were also without effect. Pretreatment of the adipocytes with trypsin did not alter the effect of very-low-density lipoprotein. The presence of Ca2+ was required for the full activation of lipogenesis. The synthesis of acylglycerol fatty acids and of acylglycerol glycerol were equally increased. The effect of very-low-density lipoprotein was not additive to that of insulin. It is suggested that very-low-density lipoprotein may directly stimulate lipogenesis in fat-cells, particularly in states when the lipoproteins are present at high concentration in the circulation.

Adipose Tissue↗
PubMed1976

Insulin receptors in normal and transformed fibroblasts: relationship to growth and transformation.

The insulin receptors in normal and transformed lines of mouse Balb/3t3 fibroblasts have been studied. In the normal fibroblasts, the binding of insulin was low in growing cells and increased 2-9 fold in confluent stationary cells. Insulin binding was increased whether growth arrest was due to contact inhibition of growth or serum starvation. When serum-starved cells were stimulated to grow by the addition of fresh serum, insulin binding declined. In cells transformed by simian virus 40, Kirsten, Moloney, and Harvey sarcoma viruses, methylcholanthrene, X rays, or spontaneously, the binding was low, in the same range as growing normal cells. In simian virus 40-transformed cells, insulin binding increased 4 fold as the cells reached higher densities in culture. No relationship to changes in cell size was found. The differences in binding were due to changes in the concentration of the receptors, without changes in their affinity for the hormone.

Blood↗
PubMed1975

Iodine-induced thyrotoxicosis in apparently normal thyroid glands.

Although iodine-induced thyrotoxicosis was reported to occur in patients with obvious underlying thyroid disorders, it is not known to occur in patients with apparently normal thyroid glands. From ten such cases evidence is presented that thyrotoxicosis: a) appeared during treatments by iodide or organic-iodine-containing drugs, in the absence of any past history of thyroid disorder; b) was accompanied by almost undetectable radioidine uptake which nevertheless could be activated by TSH; c) subsided spontaneously within a few weeks or months after stopping the high intake of iodine; d) and left, after a period of hypothyroidism, an apparently normal thyroid gland which had resumed normal size, function, uptake, and suppressibility.

Adult↗
PubMed1973

Studies on mono- and diiodohistidine. I. The identification of iodohistidines from thyroidal iodoproteins and their peripheral metabolism in the normal man and rat.

The problem as to whether iodohistidines are normally biosynthetized in thyroglobulin and thyralbumin has been examined both in man and the rat. Evidence has been obtained for the first time that diiodohistidine (DIH) is present in both species in these two iodoproteins. The biosynthesis of monoiodohistidine (MIH) in the thyroglobulin of the normal rat has been confirmed and extended to rat thyralbumin and to human thyroid iodoproteins. THE IODOHISTIDINE IDENTIFICATION IS BASED ON FIVE ORIGINAL METHODS INCLUDING: (a) the preparation of stable and radioiodine-labeled iodohistidines; (b) the protection of the labile iodohistidines during the iodoprotein enzymatic hydrolysis; (c) the isolation of iodohistidines by ion-exchange resin chromatography; (d) their separation from each other and from iodinated cationic butanol-insoluble compounds by Sephadex G-10 chromatography; and (e) their purification by successive crystallizations to a constant specific activity. Iodohistidine levels (in percent of protein radioactivity from iodide given in vivo) were found comparable in man and the rat. However, the values (mean +/-SE) for thyroglobulin (MIH, 0.61+/-0.10%; DIH, 0.050+/-0.015%) and for thyralbumin (MIH, 2.61+/-0.57%; DIH, 0.28+/-0.09%) differ significantly (P < 0.05). Iodohistidines are stable during in vitro exposure to iodotyrosine dehalogenase preparations. In contrast to iodotyrosines the iodohistidines when given in vivo to man either orally or intravenously were in large part recovered in 24-h urines.

Administration, Oral↗