Dissociation of the Factor-VIII complex during clotting: role of thrombin and phospholipids

Abstract. To study the dissociation of the two moieties of the factor-VIII complex during clotting, plasma, concentrate and serum were chromatographed on 4% agarose. In plasma and concentrate factor-VIII coagulant activity (VIII C), factor-VIII coagulant antigen (VIII C:Ag), and factor-VIII-related antigen (VIII R:Ag) eluted together in the void volume, but some VIII C: Ag eluted after the void volume. The amount of VIII C:Ag eluting after the void volume was made smaller by adding proteinase inhibitors. In serum nearly all VIII C:Ag eluted after the void volume.
From factor-VIII complex immunoadsorbed by means of an antibody against VIII R:Ag no VIII C:Ag was dissociated by thrombin or by thrombin and physiologic CaCl₂ concentrations. Radiolabelled human thrombin did not bind to the VIII C:Ag of immunoadsorbed factor-VIII complex. VIII C:Ag displaying VIII C was dissociated from immunoadsorbed factor-VIII complex by human brain thromboplastin or by phosphatidyl-serine.
Our results suggest that VIII C:Ag and VIII R:Ag dissociate during clotting. This dissociation seems not to be mediated by thrombin, but may be mediated by phospholipids.     

Restoration of blood supply and intensity of phospholipid metabolism in various parts of the postischemic rat brain

A marked increase in the blood supply to the cerebral hemispheres, diencephalon, and mesencephalon and a simultaneous decrease in blood supply to the cerebellum and medulla were observed 15 min after restoration of the blood flow through the common carotid arteries, which had been arrested by application of ligatures. The blood supply after 60 min was restored completely in all parts of the brain except the cerebral hemispheres. Complete restoration of the intensity of phospholipid metabolism also was found in parts of the brain in which it had been considerably depressed during the period of ischemia.Laboratory of Regulation of Brain Metabolism, Academician I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR V. N. Chernigovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 87, No. 2, pp. 139–142, February, 1979.     

Effect of polychlorinated biphenyls (PCBs) administration on phospholipid biosynthesis in rat liver

The effect of PCBs or phenobarbital on the biosynthesis of phospholipids in hepatic endoplasmic reticulum of rats was studied by the intraperitoneal injection of [³²P]orthophosphate, [Me?¹⁴ C]choline or [2?³H]glycerol. Significant increases in liver microsomal phospholipid content after the administration of either PCBs or phenobarbital indicated the actual proliferation of endoplasmic reticulum membranes. The rate of both [³²P] and [¹⁴C] incorporations into microsomal choline-containing phospholipids, such as phosphatidylcholine, sphingomyelin and lysophosphatidylcholine, was reduced to one fifth by PCBs administration compared with control animals. The incorporation of [³²P]orthophosphate into phosphatidylethanolamine or other phospholipid classes was less or not affected, respectively, by PCBs administration. The specific inhibitory effect of PCBs on the incorporation into cholinecontaining phospholipids was not observed when [2?³-H]glycerol was used as a precursor. Phenobarbital administration, however, increased significantly the rate of [³²P] incorporation into liver phospholipids, especially phosphatidylcholine. It is suggested that the increase in microsomal phospholipid content by PCBs administration is not due to the stimulation of synthesis but to the inhibition of the catabolism of membrane phospholipids and that the increase in content caused by phenobarbital is due at least in part, to the stimulation of synthesis. The possible site(s) of PCBs-induced inhibition of phospholipid biosynthesis in rat liver is discussed.     

In vitro cytotoxicity of polychlorinated biphenyls (aroclors 1016, 1242, 1254 and 1260) and their effect on phospholipid and neutral lipid composition of Chinese hamster ovary (CHO-K1) cells

Cytotoxicity of 4 Aroclors (1016, 1242, 1254 and 1260) was compared in Chinese hamster ovary (CHO-K1) cells in Ham's F-12 medium. When parameters of toxicity were cell numbers or tissue protein, 50% lethality occurred at Aroclor concentrations between 30 and 45 ppm. An in vitro clonal assay with CHO-K1 cells was a sensitive indicator of cytotoxicity of the polychlorinated biphenyls (PCBs). From EC₅₀ values (concentration that allowed 50% survival of formed colonies), cytotoxicity was lower with Aroclor 1016 (32 ppm) and higher with Aroclors 1254 (27 ppm) and 1260 (28 ppm). In cells exposed 24 h to a marginally cytotoxic dose (20 ppm) of each Aroclor, phospholipid (PL) thin-layer chromatography (TLC) showed an increase in phosphatidylcholine (PC) and a decrease in phosphatidylethanolamine (PE) and diphosphatidylglycerol (DPG). Neutral lipid (NL) TLC of cells given Aroclors 1242, 1254 or 1260 showed a 3–4-fold increase in triglyceride (TG) and a similar reduction in cholesteryl esters (CE); in contrast to Aroclor 1016 which produced no change in TG and a smaller (2-fold) reduction in CE. Cholesterol and free fatty acid fractions were unaffected by any of the Aroclors. The TG:PL ratio remained unchanged in cells given Aroclor 1016, but increased 3–4-fold with Aroclors 1242, 1254, or 1260. Compared to total values in the untreated controls, CHO-K1 cells contained less neutral lipid and more phospholipid only with Aroclor 1016.These results support the concept that differences in the behavior of Aroclor 1016 are related to its PCB composition. Changes in membrane PL and NL components, observed at marginally cytotoxic levels of each Aroclor, provided further evidence that the PCBs may affect membrane integrity and associated metabolic functions.     

FACTORS INFLUENCING THE SIZE, COMPOSITION AND METABOLISM OF VERY LOW DENSITY LIPOPROTEINS IN THE RAT

The composition of very low density lipoproteins (VLDL), secreted by the perfused rat liver, varied considerably depending on the fatty acid in the perfusing medium. Plasma VLDL metabolism was more rapid in female than in male rats.     

顺铂及其类似物与人红细胞膜磷脂相互作用的研究

本文采用IR和^31P NMR方法研究了顺铂及其类似物与人红细胞膜磷脂的相互作用。与对照相比，顺铂及其类似物加入人红细胞膜以后，使得红外波谱的1300－953cm^-1频区发生明显改变。结果分析提示，顺铂等铂配合物通过静电相互作用和某些配位的方式，即主要与磷脂的极性头部相互作用，12小时动力学实验进一步表明顺铂的作用是一个可恢复的作用过程，而其它的铂配合物的作用则不可恢复。^31P NMR实验得到与IR分析相似的结果，对此进行了讨论。     

Procoagulant activity of partial thromboplastin (cephalin) reagent and its phospholipid composition

The relationship between the phospholipid composition of successive batches of the standardised partial thromboplastin reagents produced in the National (UK) Reference Laboratory for Anticoagulant Reagents and Control and their procoagulant activity in the kaolin-activated partial thromboplastin time test (APTT) has been investigated.

Separation and quantitation of individual lipid classes was achieved by the use of a modified high pressure liquid chromatographic technique to provide more rapid and improved separation of the lipid classes.

Many batches of human brain partial thromboplastin reagent, of comparable activity in the standardised APTT technique, were investigated. Considerable variation was found in total lipid concentration of partial thromboplastin extracts with identical procoagulant properties. The coefficient of variation of individual components showed that phosphatidyl serine was the most consistently represented class amongst reagents studied. Phosphatidyl serine inhibited or promoted clotting activity in the APTT according to its concentration.     

Relation of somal lipid synthesis to the fast axonal transport of protein and lipid

The role of somal lipid synthesis in the fast axonal transport of protein and lipid was examined in vitro utilizing spinal/sciatic nerve preparations of bullfrog. Inhibition of phospholipid synthesis in dorsal root ganglia by the amphiphilic cation, fenfluramine (0.1-2.0 mM) was monitored as decreased incorporation of [3H]choline into phosphatidyl choline. This inhibition was directly proportional to a decrease in the amount of [3H]protein undergoing fast axonal transport, the two variables being related by a slope close to unity. [3H]Choline-labeled lipid undergoing fast transport in the axon was unaffected by inhibition of somal phospholipid synthesis. Levels of fenfluramine up to 1.0 mM had no effect on uptake or incorporation of [3H]leucine. Selective exposure of desheathed nerve trunks to 1.0 mM fenfluramine had no effect on [3H]protein translocation, indicating that local phospholipid synthesis is not required to maintain ongoing transport in the axon. Inhibition of cholesterol synthesis in the ganglia with the analog 20,25-diazacholesterol also resulted in depression of [3H]protein transport. Since synthesis of both phospholipid and cholesterol are required at the level of the ganglion, it is suggested that the initiation of fast axonal transport of protein is dependent on the assembly of lipoprotein structures in the soma.     

Biochemical transmethylation of lipids and neuropeptidergic stimulation of pituitary hormone secretion

S-adenosyl-l-methionine-dependent methylation of membrane phosphatidylethanolamine to phosphatidylcholine has been shown to exist in a number of tissues including pituitary gland and to play important roles in receptor-mediated functions. The possible role of this phospholipid methylation reaction in pituitary hormone secretion has been studied. To this end, the ability of thyrotropin-releasing hormone (TRH) to release thyrotropin (TSH) and prolactin and the ability of luteinizing hormone-releasing hormone (LH-RH) to release luteinizing hormone (LH) were evaluated after inhibition of pituitary phospholipid methylation. Both TRH and LH-RH stimulated the release of their corresponding pituitary hormone in a dose-dependent manner and this stimulatory effect was inhibited in the presence of phospholipid methylation inhibitors. Non-specific stimulation of TSH release by 55 mM KCl or 0.1 mM veratridine, however, was not affected by the methylation inhibitors. The data suggest that phospholipid methylation may participate in receptor-mediated release of pituitary hormones.