Initiation of the extrinsic pathway of coagulation. Association of factor VIIa with a cell line expressing tissue factor

We have examined initial assembly of the extrinsic pathway of blood coagulation on cell surfaces with radiolabeled human factor VIIa and a human fetal lung cell line possessing abundant functional tissue factor activity. Binding of factor VIIa to these cells was observed and was time- and temperature-dependent. Binding of factor VIIa was quantitatively equivalent at 37 and 6 degrees C, although the kinetics of binding differed. The radiolabeled ligand bound by the cell was indistinguishable by sodium dodecyl sulfate-polyacrylamide gel analysis from the factor VIIa offered. Factor VIIa binding was influenced by calcium ions. The binding appears to involve at least two classes of calcium-dependent binding sites. Optimal binding occurred at 2 mM calcium for both classes of sites, and there was inhibition of binding to the high affinity sites at higher calcium. Association of factor VIIa was specific, saturable, had a Kd of 123 +/- 37 pm, and factor VIIa interacted with about 100,000 binding sites per cell. Once established, specific binding was rapidly reversible. Direct cellular binding of human factor X also was observed and was calcium, time- and temperature-dependent. Factor X binding was specific and saturable with half-maximal binding at 87.6 +/- 27.4 nM to 6.03 +/- 1.03 X 10(6) sites per cell. Specific high affinity binding of factor VIIa correlated with generation of factor Xa. A direct linear relationship was observed at low factor VIIa binding; however, at higher bound factor VIIa, the relationship was nonstoichiometric, i.e. less factor Xa was formed per mole of factor VIIa. Expression of specific binding sites for factors VIIa and X provides further substantiation for the molecular assembly hypothesized to initiate the extrinsic coagulation protease cascade on cells.     

Obligatory amino acids in primitive proteins

Conformational similarity among amino acid residues, a property derived by analysing (φ, ψ)-probability distributions of 20 proteinous amino acids from 38 different globular proteins, is used to arrive at a set of six ‘obligatory’ amino acids of primitive proteins. The amino acids Ser, Val, Leu, Asp, Gly and Pro have been argued to be ‘obligatory’ and to represent, conformationally, the remaining amino acids. The reasons for consideration of these six residues as ‘obligatory’ are discussed. Methods to check the validity of our proposition are suggested.     

The biological effects in animals related to the accident at the Chernobyl Atomic Electric Power Station. 1. The experimental model. The radiation loads on animals kept continuously under external and internal radiation exposure in the area of the Chernobyl Atomic Electric Power Station]

Irradiation conditions in which laboratory animals were kept in experimental laboratories of Chernobyl and Kiev after the accident at the Chernobyl A.P.S. are described. The data are presented on the spectral structural and activity of radionuclides in the diet as well as in the organs and tissues of the animals. The radiation loads have been estimated with regard to an external gamma component and the internal one contributed by the incorporated radionuclides. It has been shown that radiation doses received by the animals during their lifetime due to these contributions do not exceed units of cGy.     

The biological action of low-level radiation

On the basis of their own data and the literature the authors have analyzed the mechanism of biological action of low-level radiation on cells. In studying the harmful effect of gamma-radiation (10-40 cGy) on HeLa cells it was shown that damages occurred in 12 postirradiation generations. Analysis of cell distribution within the colonies has demonstrated that the share of colonies with low cell content and the number of giant cell increase. These data indicate that low-level radiation causes reproductive cell death that can occur not immediately but in later generations.     

Comparison of two techniques for quantifying environmental contaminants in human serum

Peak area matching and linear regression were used to quantify eight chlorinated pesticides and polychlorinated biphenyls (as Aroclor 1260) in human serum. There are no statistically significant differences in data obtained by these two quantifying techniques which were indicated by the paired t-test. For chlorinated pesticides, p = 0.053-0.62, and for polychlorinated biphenyls (as Aroclor 1260), p = 0.64. Analyte residues for the chlorinated pesticides ranged from 0.5 ppb for hexachlorobenzene (HCB) to 186 ppb for dichlorodiphenyldichloroethylene (DDE). Analyte residues for the polychlorinated biphenyls (as Aroclor 1260) ranged from 5-114 ppb. The absolute mean percent difference between the two quantifying techniques ranged from 0.06% for DDE to 8.06% for dieldrin (HEOD) among the chlorinated pesticides. The absolute mean percent difference between the two quantifying techniques for the polychlorinated biphenyls (as Aroclor 1260) was 3.4%. Peak area matching and linear regression were found to be comparable for quantifying these environmental residues in serum when the following conditions apply: 1) the concentration of the chlorinated pesticides is greater than or equal to 0.5 ppb (e.g., HCB, hexachlorocyclohexane (HCCH), oxychlordane (OC), heptachlor epoxide (HE), transnonachlor (TN), HEOD, and dichlorodiphenyltrichloroethane (DDT); 2) the concentration of the chlorinated pesticide is greater than or equal to 3 ppb (e.g., DDE); and 3) the total concentration of polychlorinated biphenyls (e.g., as Aroclor 1260) is greater than or equal to 5 ppb.     

In vivo protein synthesis from 14C-substrates in porcine tissues during the transition to postnatal development

[2-14C] leucine, [1-14C] alanine, [1-14C] glucose, [1-14C] lactate and [1-14C] pyruvate utilization in the protein synthesis has been studied in vivo at early stages of postnatal development of piglets. It has been established, that during the first 24 hours after birth the protein synthesis intensity, judging by [2-14C] leucine incorporation, in liver, skeletal muscle, duodenal wall and subcutaneous tissue of piglets increases 5, 7, 6.5 and 2.1 times respectively. At the age of 1-2 h the radioactive carbon incorporation from [1-14C] glucose into the brain proteins is more pronounced than into the proteins of liver and skeletal muscle. During the first days of life the intensity of the label incorporation from [1-14C] glucose into liver and skeletal muscle proteins of piglets is enhanced, whereas in brain it remains at the same level. The degree of 14C carbon incorporation from [1-14C]-alanine, [1-14C] pyruvate and [1-14C] lactate into the liver and skeletal muscle proteins of 5-days-old piglets is approximately the same, 14C substrates of protein synthesis in brain and subcutaneous adipose tissue having some peculiarities.