Platelet regeneration time and late occlusion of aortocoronary saphenous vein bypass grafts.

The half-time for platelet regeneration was estimated in 16 patients with aortocoronary vein grafts by the use of a non-radioisotopic technique based on the permanent inhibition by acetylsalicylic acid of lipid peroxidation by platelets. Ten patients had patent grafts after 6 years; in the other six at least one graft had become occluded between 2 and 6 years after the operation as shown by serial angiography. The mean half-time (+/- the standard error) for platelet regeneration was reduced to 2.5 +/- 0.2 days (P less than 0.002) in the group with occluded grafts as compared with 3.3 +/- 11 healthy volunteers. These results suggest a relation between late graft occlusion and platelet turnover and support the idea that patients with aortocoronary vein grafts could benefit from platelet suppressive therapy. Finally, the method employed appears to be a useful and simple way of evaluating platelet function in vivo.     

Substrate specificity and adenosine triphosphatase activity of the ATP-dependent deoxyribonuclease of Bacillus subtilis

Studies on the specificity of the ATP-dependent DNase of Bacillus subtilis 168, carried out with pure enzyme at the optimal conditions for its action, have shown that the substrate is double-stranded linear DNA. Linear single-stranded DNA (separated strands of B. subtilis DNA and linear phage fd DNA) is not attacked, neither are there any circular forms (supercoiled or nicked simian virus 40 and circular single-stranded fd DNAs). The double-stranded DNA can be completely hydrolysed, the limit products being, almost exclusively, mononucleotides. The presence of terminal phosphate residues in the substrate (either at the 3' or the 5' end) is not necessary for enzyme action. This DNase appears therefore to be an exonuclease processively liberating mononucleotides from both strands of the native linear DNA. ATP (indispensable for the DNase reaction) is also hydrolysed by the enzyme, to ADP and inorganic orthophosphate (Pi) in the presence of DNA. The apparent Km for ATP, in the ATPase reaction, is 0.15 mM. At high ATP concentrations, which inhibit the DNase activity, there is activation of the ATPase reaction. Three molecules of ATP are consumed for each DNA phosphodiester bond split, at optimal conditions for DNase activity.     

Characterization of dicyclohexylcarbodiimide binding sites in beef-heart mitochondria.

Binding studies with [¹⁴C]-dicyclohexylcarbodiimide showed the presence of binding sites in the beef-heart mitochondrial membrane at a concentration of 1.8 nmol/mg protein (1.4 sites per cytochrome a+a₃). Saturation of these sites correlated with the inhibition of the ATPase activity. The maximum binding capacity could be related with the amount of F₁-ATPase in mitochondria from various tissues.     

Effects of a neurotoxin isolated from the sea anemone, Anemonia sulcata, at frog neuromuscular junction (author's transl)]

ATX II is a toxin extracted from tentacles of Anemonia sulcata. It was known that this protein displays neurotoxic effects on frog isolated neuromuscular preparation (Fig. 1, 2) and that muscular contractures observed with ATX II are blocked by d-tubocurarine (Fig. 3) or on a 40-days-denervated gastrocnemius (Fig. 4). Part of these experiments has already appeared. 1. These effects of ATX II depend on calcium concentration in the bathing medium, as is the case for transmitter release. The same results were observed when we substituted strontium to calcium. 2. On an intact sciatic sartorius preparation, ATX II does not act on the amplitude of the miniature endplate potentials (mepps, Fig. 6). The muscular action potential is not modified by this toxin. 3. ATX II increases the frequency of the mepps (Fig. 5). The evoked transmitter release (quantal content) after ATX II is also largely increased (Fig. 7). 4. In conclusion, it is suggested that ATX II acts indirectly on the muscle through an increase in acetylcholine release from the motor nerve terminals.     

The isolation and properties of a denitrifying bacterium of the genus Flavobacterium

A previously undescribed denitrifying bacterium was isolated from soil. The cells are small gram-negative rods, asporogenous, and non-motile. Colonies become yellow after long exposure to light. This colouring is due to the production of a carotenoid pigment. The organism shows no fermenting activity, and grows only in the presence of one of the following electron acceptors: NO _inf2 ^sup- , N₂O, and O₂. It does not reduce nitrate. It gives a positive oxidase test and has a cytochrome c and catalase. It requires no growth factors, is a chemoorganotroph and uses only sugars as carbon and energy supply. The DNA base composition is 40.8 moles percent GC. Although presenting the physiological characteristics of a pseudomonad, the organism described has been placed in the genus Flavobacterium because of its pigmentation and its low GC percentage.     

Changes in fibrinolysis components during short-term adaptation to high altitude]

In studying hemocoagulation in dogs under conditions of Frunze (760 m above the sea level) and Tuya-Ashu (3200 m above the sea level) it was shown that in the "emergency" phase of adaptation (the first three days) there was seen activation of fibrinolysin and profibrinolysin with depression of antifibrinolysins and inhibitors of profibrinolysin activators. The concentration of plasma fibrinogen at that period decreased by 100 mg%, which could promote an increase in the vascular permeability and improvement of oxygen approach to the tissues. Later, along with elevation of fibrinolysin and profibrinolysin activators there was a marked increase in the level of fibrinolysis inhibitors. Correlation of all the fibrinolysis components was established at a new level.     

Action of thrombin on ovine, bovine and human pituitary growth hormones.

1. This communication reports the action of bovine thrombin on ovine, bovine and human growth hormones. Thrombin cleavage was shown to be restricted to a single homologous peptide bond in all three growth hormones (at sequence positions 133--134 of the ovine and bovine hormones). 2. Ovine growth hormone was the most sensitive to the action of thrombin, bovine growth hormone was attacked to a relatively less extent, and human growth hormone was the most resistant to the enzyme. 3. After reduction and carbamidomethylation of the disulfide bonds in thrombin modified ovine growth hormone, the two fragments (residues 1--133 and 134--191) were isolated. The large NH2-terminal thrombin fragment of the hormone (residues 1--133) was found to be inactive in the rat tibia test, whereas a tryptic fragment (residues 96--133) isolated in an independent way gave measurable responses.     

Oxidation of methanol,formaldehyde and formic acid by methanol-utilizing yeast

Methanol-utilizing yeast,Candida boidini 11 Bh, characterized by high tolerance to methanol during growth, displays even higher tolerance when the oxidation rate by intact cells is tested. Low respiration activity is found even at 22% v/v of methanol. The half-saturation constant was 17–18mM. The half-saturation constants for the two oxidation intermediates, formaldehyde and formic acid were 3.6–4.0 and 30–33mM, respectively. When applied together with standard concentration of methanol, very low concentrations of both intermediates stimulated the oxidation rate. These results are discussed in connection with the relationship between growth and oxidation, the tolerance to high concentrations of inhibitory products and the mechanism of inhibition.