von Willebrand factor binds specifically to sulfated glycolipids

The human plasma glycoprotein Factor VIII/von Willebrand factor (vWF) binds specifically and with high affinity to sulfatides (galactosylceramide-I3-sulfate). vWF does not bind to gangliosides, neutral glycolipids, phospholipids, or cholesterol 3-sulfate. Although the largest oligomers of vWF bind preferentially to sulfatides, vWF monomers and dimers also bind but with reduced affinity. vWF binding is inhibited at high ionic strength or low pH, by some sulfated polysaccharides and by antibodies to vWF. Binding of vWF to sulfatides is probably responsible for its agglutination of aldehyde-fixed erythrocytes and may play a role in vWF-induced platelet adhesion or platelet aggregation.     

Effect of chlorine dioxide on selected membrane functions of Escherichia coli

The mode of action of chlorine dioxide on Escherichia coli was assessed by studying outer membrane permeability to macromolecules and potassium, and observing effects on respiration. The results indicate that gross cellular damage involving significant leakage of intracellular macromolecules does not occur. There was a substantial efflux of potassium, however, and respiration was inhibited even at sublethal doses. It was concluded that the inhibition of respiration, which could be due to the damage to the cell envelope, was not the primary lethal event. Observations of the efflux of K⁺ strongly implicate the loss of permeability control as the primary lethal event at the physiological level, with nonspecific oxidative damage to the outer membrane leading to the destruction of the trans-membrane ionic gradient.     

Enzyme kinetics of a highly purified mitochondrial creatine kinase in comparison with cytosolic forms

Summary Mitochondrial creatine kinase (CK) purified from canine myocardium showed a single protein band on SDS-PAGE and was free of MMCK. Its amino acid composition was different than MMCK or BBCK and did not react to antiserum to MMCK or BBCK. Using purified mitochondrial, MM and BBCK, the velocity of reaction (V) was estimated for creatine phosphate (CP), creatine (C), adenosine triphosphate (ATP) and adenosine diphosphate (ADP) over a wide range of concentrations including those at V_max. The values for K_m (mM/L) derived from Lineweaver-Burke plots are shown: The affinity of mitochondrial CK for C is much greater than MMCK which is compatible with the energy shuttle hypothesis, namely ATP is converted by mitochondrial CK to CP, and then diffuses to the myofibril for conversion to ATP for utilization.     

Corticotropin-releasing factor (CRF) stimulates locomotor activity in intact and hypophysectomized newts (Amphibia)

Locomotor activity of rough-skinned newts (Taricha granulosa) was significantly higher in intact and hypophysectomized males injected intracranially with 100 ng CRF (ovine corticotropin-releasing factor) than in those injected with 10 ng CRF or saline. In addition, an injection of corticosterone or dexamethasone failed to stimulate newt locomotor activity. These results provide evidence that CRF can act independently of pituitary hormones to stimulate locomotor activity in a nonmammalian vertebrate.     

Molecular heterogeneity of creatine kinase isoenzymes

The [32P]phosphoamino acids in proteins of first trimester and term-cultured human placentas have been separated and their relative amounts were measured. A significant phosphorylation of tyrosine residues could be detected in the cultured placental tissue at different stages of gestation. The phosphotyrosine accounts for 2-4% of the total acid-stable phosphate in the phosphoamino acids after partial acid hydrolysis. The difference in the extent of [32P]tyrosine in various placentas seems to be a function of biological variation of the individual placentas, rather than a function of placental age and stage of gestation. In contrast, a significant difference in the phosphorylation ratio of serine and threonine could be measured between first trimester and term placentas. As more evidence is accumulating that protein phosphorylation of tyrosine is involved in the processes of cellular growth and proliferation, our findings of the relatively high tyrosine phosphorylation in human placenta strongly suggest that this type of protein phosphorylation may play an important role in the placental growth and development. Furthermore, these findings may correlate with the existence of the endogenous RNA virus-like particles found in normal human placenta.     

Hypoxanthine: Guanine phosphoribosyltransferase mutants in Saccharomyces cerevisiae

Summary Yeast mutants lacking activity of the enzyme hypoxanthine: guanine phosphoribosyltransferase (H:GPRT) have been isolated by selecting for resistance to 8-azaguanine in a strain carrying the wild type allele, ade4 ⁺ of the gene coding for amidophosphoribosyltransferase (PRPPAT), the first enzyme of de novo purine synthesis. The mutants excrete purines and are cross-resistant to 8-azaadenine. They are recessive and represent a single complementation group, designated hpt1. Ade4-su, a prototrophic allele of ade4 with reduced activity of PRPPAT, is epistatic to hpt1, suppressing purine excretion and resistance to azaadenine but not resistance to azaguanine. The genotype ade2 hpt1 does not respond to hypoxanthine. Hpt1 complements and is not closely linked to the purine excreting mutants pur1 to pur5. Hpt1 and pur6, a regulatory mutant of PRPPAT, are also unlinked but do not complement, suggesting a protein-protein interaction between H:G-PRT and PRPPAT. Mycophenolic acid (MPA), an inhibitor of de novo guanine nucleotide synthesis, inhibits the growth of hpt1 and hpt1 ⁺. Xanthine allows both genotypes to grow in the presence of MPA whereas guanine only allows growth of hpt1 ⁺. Activity of A-PRT, X-PRT and H:G-PRT is present in hpt ⁺. Hpt1 lacks activity of H:G-PRT but has normal A-PRT and X-PRT.     

Effect of Externally Applied Pressure on Femoral Vein Blood Flow

The effect of incremental increases in external pressure, applied to the leg, on blood volume flow in the femoral vein was studied in dogs. Clinical investigation of external pressure increases was also carried out on nine patients undergoing surgery for varicose veins. An external pressure between 5 and 15 mm. Hg caused a sustained increase in mean femoral vein flow both in a control and in the compressed limb. Above 15 mm. Hg external pressure flow decreased in the compressed limb but was maintained at an increased level in the control limb.If external compression is to be used to prevent and treat deep vein thrombosis its application must be carefully controlled.