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L Pickart

Publications and source records attributed to L Pickart.

32 records · Page 2Linked to original sources
PubMed1980

Evidence for a low-molecular-weight plasma peptide which stimulates chick chondrocyte metabolism.

Plasma contains a number of insulin-like activities (ILA) of molecular weights 7,000 to 90,000 (somatomedins and insulin-like proteins) which stimulate cellular metabolism and may function as growth factors. We have found evidence for the presence of an 800 Dalton peptide in human plasma which markedly stimulates the metabolism of chick chondrocytes. This peptide was extracted from human Cohn fraction IV-1 by procedures similar to those used for somatomedin isolations. At the Sephadex G-50 column separation step, the fraction with molecular weights of 300-1,000 was found to markedly stimulate chick chondrocyte metabolism. Rechromatography on Sephadex G-25 concentrated activity in peptides of molecular weight of about 800. An HPLC separation on a silica C-18 reverse phase column gave elution of the active peptide at 18% acetonitrile in water. This bioactivity appears to be a peptide which is free of lipids, carbohydrates, nucleic acids, metal ions, and immunoreactive insulin. This factor markedly increased the metabolism of cultured chick chondrocytes, but had only marginal activity on rat chondrocytes. When added at 1 microgram/ml to chick chondrocytes cultured in F-12 medium plus 1.5% fetal calf serum, the HPLC-purified activity increased DNA synthesis 7.3-fold, lipid synthesis 10.2-fold, and lactate production 2.9-fold after 48 h incubation. However, unlike somatomedins A and C, this factor did not displace insulin from placental membranes. These results suggest that low-molecular-weight peptides, which are smaller than the somatomedins, may contribute to the total ILA of human plasma.

Animals↗
PubMed1980

Improved recovery of somatomedin activity from plasma by prolonged formic acid extraction.

Recovery of somatomedin activity from plasma fractions was increased approximately 5-fold by prolonged extraction of isolates with formic acid. Extraction for 72 hours enhanced the yields of active peptides in the 6,000, 8,000 and > 20,000 dalton range. Yields of smaller peptides were similar following short (2 hrs) and long (72 hrs) extraction periods. Active fractions obtained after prolonged extraction possessed sulfation activity and insulin-receptor affinity comparable to somatomedin isolated during short extraction with formic acid.

Animals↗
PubMed1979

Effect of transition metals on recovery from plasma of the growth-modulating tripeptide glycylhistidyllysine.

Isolation and purification of growth-modulating peptides from biological sources is often accompanied by excessive losses of bioactive material. During the isolation of a growth-modulating tripeptide glycylhistidyllysine (GHL) from human plasma, copper and iron were found to co-isolate with the peptide. Studies with [3H]GHL demonstrated that these metals interfere at several steps of the procedure for the isolation of GHL from plasma (gel filtration chromatography, high-pressure silica-gel). Removal of these metals with an insoluble chelating resin (Cellex 100) enhanced recovery of [3H]GHL from plasma 8-fold. These results suggest that removal of transition metals may aid in the recovery of peptides which are difficult to isolate from biological sources.

Chelating Agents↗
PubMed1979

Suppression of tumor-associated hyperfibrinogenemia and free fatty acidemia with p-phenoxybenzalbutyrate (clofibrate).

Previous work in our laboratory has indicated that free fatty acids stimulate synthesis of fibrinogen by the liver. The effect of the hypolipidemic agent clofibrate on hyperfibrinogenemia associated with tumors was evaluated by monitoring clofibrate-induced changes in plasma fibrinogen concentration and biosynthesis of the protein in Buffalo rats implanted with a localized, nonmetastasizing neoplasm derived from a tumorigenic hepatoma cell line (HTC4). In tumor-bearing animals not treated with clofibrate, cancer growth was associated with elevated rates of fibrinogen synthesis and a doubling of plasma fibrinogen concentrations. Plasma free fatty acid concentrations and serum free fatty acid/albumin molar ratios were also increased in tumor-bearing rats. Treatment with clofibrate in doses which normalized the plasma free fatty acid/albumin ratio also prevented the tumor-associated rise in plasma fibrinogen. Rates of fibrinogen synthesis were lowered significantly in clofibrate-treated animals. Tumor growth was not affected by clofibrate. These results indicate that hyperfibrinogenemia associated with nonmetastasizing tumors may reflect changes in lipid metabolism which are neutralized by clofibrate. Thus, treatment with clofibrate or other hypolipidemic agents should be evaluated in cancer patients with elevated plasma fibrinogen levels and their attendant complications.

Animals↗
PubMed1978

Surface analysis and depth profiles of calcium in hepatoma cells during pyruvate-induced DNA synthesis.

Induction of DNA synthesis is associated with increased uptake of calcium in cultured cells. Calcium distribution within the plasma membrane and adjacent cytoplasmic layers of hepatoma cells was investigated with X-ray photoelectron spectroscopy and oxygen plasma etching. Cells in minimal growth medium initiate active DNA synthesis 16 h after addition of sodium pyruvate. Cells stimulated with pyruvate and pyruvate-free controls were analysed by X-ray photoelectron spectroscopy--oxygen plasma etching at 0--40 A (layer I), 0--450 A (layer II) and 0--4000 A (layer III from the outer cell surface. Calcium concentrations were elevated in induced cells compared with controls: +20% in layer I, +60% in layer II, and +300% in layer III. As the plasma membrane is 90--120 A thick, these results indicate that pyruvate-induced DNA synthesis is preceded by an increase in calcium, most marked in the cytoplasm subjacent to the plasma membrane, moderate at its inner surface, and minimal at its outer surface.

Animals↗
PubMed1976

Serum protein synthesis in mutant mice with abnormal hepatic endoplasmic reticulum.

Severe ultrastructural abnormalities of liver endoplasmic reticulum have been described in newborn mice homozygous for radiation-induced deletion alleles at the colour locus. The ultrastructural defects were accompanied by deficiencies of several enzymes and lowered serum protein levels. Studies on serum protein synthesis were undertaken to see if decreased rates of synthesis, especially of constituents thought to be synthesized on membrane-bound ribosomes, were the cause of the deficiencies. Although decreases or absence of several serum proteins were shown, radiopulse-immunoprecipitation studies of albumin and fibrinogen synthesis suggested that the decreased synthesis rates were a secondary defect. Serum glycoproteins were not altered more than other constituents in the mutant material.

Albinism↗
PubMedDate not supplied

Dog allergy, a model for allergy genetics.

Experimental sensitization in dogs has revealed that the capacity to produce high levels of IgE against a variety of allergens (high IgE responders), an essential characteristic of the atopic state, is a genetic trait inherited in a dominant manner. In high IgE responder dogs spontaneous development of IgE to inhaled allergens, such as house dust mites, on the other hand, represents an apparent phenotype very similar to that observed in human atopic families. The full potential of the high IgE response gene appears to be fulfilled only under some conditions such as early and repeated exposition to allergens. It is therefore quite possible that the true phenotype of human atopy would also be inherited in a dominant fashion but not constantly expressed. This would explain why the increase in the prevalence of allergic diseases started long before the environmental factors currently accused could have been at play. This hypothesis, which can be verified experimentally, has important implications for the future of allergy.

Animals↗