Inhibition of ADP-induced platelet aggregation by reduced factor Xa

Treatment of blood coagulation factor Xa with insolubilized hexyl-agarose derivative of prostaglandin E1 (PGE1) results in the generation of two sulfhydryl groups in the protein molecule. The reduced factor Xa was found to be a potent inhibitor of platelet aggregation and thromboxane A2 synthesis induced by ADP. In contrast to the inhibition of thromboxane formation, the reduced factor Xa had no effect on the formation of PGE2 indicating that thromboxane synthetase might be selectively inhibited by the reduced factor Xa. Incubation with oxidized glutathione reversed the inhibitory activity of factor Xa previously exposed to the insolubilized hormone. Soluble PGE1 also reduces factor Xa, but more slowly than the insolubilized PGE1. PGE1 also exhibits reducing ability as tested with redox dyes. Reduction of factor Xa by dithiothreitol also transformed the coagulation factor into an inhibitor of platelet aggregation and thromboxane A2 formation. These experiments indicate that reduction of factor Xa leads to a reversible alteration of the molecule which inhibits platelet aggregation induced by ADP. This effect of reduced factor Xa is probably mediated through the inhibition of thromboxane A2 synthesis.     

Effect of 3-phenylindole on lipophilic ion and carrier-mediated ion transport across bilayer lipid membranes

The physical effects of 3-phenylindole, an antimicrobial compound which interacts with phospholipids, on ion transport across phosphatidylcholine-cholesterol bilayers have been investigated using three lipophilic ions and one ion-carrier complex. It was found that 3-phenylindole increased membrane electrical conductance of positively charged membrane probes and decreased electrical conductance of negatively charged probes. The enhancement of conductance detected by nonactin-K+ complex and tetraphenylarsonium+ was several orders of magnitude, whereas the suppression of conductance due to tetraphenylborate- and dipicrylamine- was less than a factor of ten. Presence of 3-phenylindole in aqueous phase slightly decreased adsorption of tetraphenylborate- and dipicrylamine- at the membrane surface. From the voltage dependence of the steady-state conductance it was shown that 3-phenylindole induced kinetic limitation of membrane transport of potassium mediated by nonactin. No such limitation was found in the case of tetraphenylarsonium+ transport. These results are shown to be consistent with the present concept of ion diffusion in membranes and the assumption that 3-phenylindole decreases the electric potential in the membrane interior. The asymmetry of the effect of 3-phenylindole on the magnitude of conductance changes for positively and negatively charged membrane permeable ions is also discussed as a reflection of the discreteness of both the absorbed 3-phenylindole and lipid dipoles.     

Haematological studies on the prewintering and wintering frog, Rana esculenta

1. A study of the haematology of the frog Rana esculenta including erythrocyte count (RBC), haemoglobin content (Hb), haematocrit (HCT), mean cell volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC) and erythrocyte size as a function of prewinter and winter was made. 2. The RBC count and Hb were significantly higher in contrast to MCV and MCH values during prewinter in both sexes. 3. The surface area to volume ratio was higher in prewinter whereas the length to width ratio (eccentricity) of the cytosome and nucleus was significantly higher during winter in both sexes. 4. Sexual differences in the erythrocyte count, Hb content and the surface area to volume ratio were also observed. 5. The physiological significance of these observations are reported for Rana esculenta.     

Multivariate analyses of Canadian and Japanese populations ofGlycyphagus destructor (Schrank) (Acarina,Glycyphagidae)

Summary Two multivariate statistical procedures were used to determine the basic trends of morphologic and geographic variations between males of a common stored-grain mite,Glycyphagus destructor (Schrank) collected from Canada and Japan. All analyses were carried out on physical measurements of 25 morphological features. Three principal component analyses bases on the Canadian (50 specimens), Japanese (50 specimens) and the combined populations from the 2 countries (100 specimens) revealed that the first component, accounting for 40% of the variability in all 3 solutions represented a measure of the morphologic dimension of the body. The second component, which explained over 18% of the variability, is a measure of the leg dimension. Smaller clusters of variates characteristic of the population from each county were also evident. Discriminant analysis, performed with the Canadian and Japanese populations, identified the variates that differed between the 2 populations and provided an approximate appraisal of interrelations. The general conclusion based on these analyses is that the Canadian and the Japanese populations are morphologically distinct. The difference is most evident in the diameters of genu 2, lengths of the sensory seta W_I, lengths of the body, and the distances between the vertical external setae. Contribution No. 446, from Research Station, Canada Department of Agriculture, Winnipeg, Manitoba, Canada.     

Effect of environmental conditions on sclerotia and cleistothecia production in aspergillus

Summary Literature pertaining to sclerotial Aspergilli has been reviewed in brief. Observations on the effect of certain environmental conditions viz. pH, light, temperature of incubation, oxygen-deficient conditions and various relative humidity values on sclerotia production byAspergillus niger van Tieghem, (two strains),A. flavus Link (two strains),A. sclerotiorum Hüber (one strain) andA. paradoxus Fennell &Raper (one strain) and on cleistothecia production byA. nidulans (Eidam)Wint. (one strain) have been presented. Optimum pH for sclerotia or cleistothecia production was 7.5. In other respects sclerotia and cleistothecia behaved similarly. In general, condition showing maximum sclerotia or cleistothecia production was the one that showed maximum vegetative growth. Certain strains of the same species reponded differently to the same condition. Light completely inhibited sclerotia formation in one strain ofA. flavus. InA. paradoxus, in general, conditions favouring sclerotia production were those that inhibited (or retarded) the formation of conidial heads and the yellow pigment in the medium. Oxygen-deficient conditions inhibited or retarded sclerotia or cleistothecia formation. Production of sclerotia and cleistothecia increased with an increase in relative humidity values. No definite correlation could be observed between extent of sporulation and sclerotia or cleistothecia production except in case of relative humidity. Parallelism in the behaviour of sclerotia and cleistothecia production inAspergillus lends further support in favour of the hypothesis that in this genus sclerotia are sterile stromata.     

Induction of alveolar epithelial injury by phospholipase A2

Severe damage to the alveolar type I epithelial cell is a characteristic morphological feature of lung injury due to numerous cases. It is postulated that excess phospholipase A2 (PLA2) activity might be responsible for these changes, as one of the naturally occurring products of this enzyme, lysophosphatidylcholine (lysoPC) has been shown to cause selective injury to the type I pneumonocyte when it is instilled into the lower air spaces of the lung. To further investigate this potential mechanism of type I epithelial cell toxicity, we have measured the epithelial permeability-surface area product (PS) for [14C]sucrose as well as whole-lung lysoPC content at several times after instilling PLA2 (Naja naja venom) into either the air spaces or the perfusate of an isolated hamster lung preparation. As a molar percentage of total phospholipids, the normal hamster lung contains approximately 1.5% lysoPC, and this value is not affected by fluid filling of the air spaces or perfusion of the excised lung for periods up to 90 min. When 0.15 U/ml PLA2 is instilled into the air spaces, lung lysoPC content increases to approximately 2.5% and there are barely detectable increases in [14C]sucrose PS. With air space PLA2 concentrations of 0.30 U/ml, lysoPC content increases to between 4 and 5%, [14C]sucrose PS increases by greater than a factor of 10, and flooding of the alveolar spaces occur. Ultrastructural studies of similarly treated lungs show widespread but selective damage to the type I epithelial cells. These same biochemical and functional changes are not seen when the same concentrations of PLA2 are added to the lung perfusate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Complete cDNA sequence of bovine alpha 1-antitrypsin.

A cDNA clone coding for the entire bovine alpha 1-antitrypsin molecule has been isolated from a lambda gt11 bovine liver cDNA library using a human alpha 1-antitrypsin cDNA as a probe. The bovine cDNA was sequenced by the dideoxynucleotide chain termination method. Comparison of the translated amino acid sequence of the bovine alpha 1-antitrypsin with those of the human, baboon, sheep, rat and mouse demonstrates the preservation of most of the critical structural determinants. The bovine and the sheep molecules have a sequence homology of 94% and both the molecules contain four cysteine residues; there is only one cysteine in the others.