Amino acids and collagen-induced platelet aggregation. Lack of effect of three amino acids that are elevated in homocystinuria.

Arterial thrombosis frequently occurs in homocystinuric children whose plasma levels of homocystine, homocysteine, and methionine are elevated. Since platelet aggregation is important in the pathogenesis of arterial thrombosis, we wondered whether the elevated concentrations of these amino acids might predispose to arterial thrombosis by enhancing platelet aggregation. Addition of the above amino acids to normal platelet-rich plasma to achieve concentrations within or above the range found in homocystinuric children had no effect on collagen-induced platelet aggregation.

Failure of methylhistidines to inhibit platelet aggregation at concentrations found in uremic plasma.

Methylhistidines are among the amino acids which are present in increased concentrations in the plasma of severely uremic patients who may have a hemorrhagic diathesis. Histidine contains an imidazole ring, and our previous work has shown inhibition of collagen-induced platelet aggregation by imidazole in concentrations as low as 0.5 mM.

Modoc viral infections in the deer mouse Peromyscus maniculatus.

The pathogenesis of Modoc virus and its mechanism of transmission were investigated in Peromyscus maniculatus gambeli (deer mouse) as a model to understand the natural history of this virus. Animals were readily infected by the intranasal or subcutaneous route of inoculation. Virus could be detected by direct isolation techniques in many organs and body fluids during the first 7 to 9 days after intranasal inoculation.

Characterization of persistent Modoc viral infections in Syrian hamsters.

Adult Syrian hamsters were readily infected by intranasal inoculation with Modoc virus. Viremias were detected 2 to 6 days after infection and peak viremia titers (10(6.2) plaque-forming units/ml of blood) occurred 4 days postinoculation.

In vitro studies with Modoc virus in Vero cells: plaque assay and kinetics of growth, neutralization, and thermal inactivation.

A sensitive and quantitative assay system is described for plaquing Modoc virus in Vero cells. Neutralizing antibodies to Modoc virus could be detected by using this in vitro system by their interference with viral plaque formation. Virus was readily neutralized within 30 min at 37 C by a 1:10 dilution of hyperimmune hamster serum.

A new enzymatic assay for guanosine 3':5'-cyclic monophosphate and its application to the ductus deferens of the rat.

A sensitive enzymatic procedure has been developed for the determination of guanosine 3':5'-cyclic monophosphate (cyclic GMP). It is based on the conversion of cyclic GMP to GMP by cyclic nucleotide phosphodiesterase and on the transfer of (32)P from [gamma-(32)P]ATP to GMP by the action of a specific ATP:GMP phosphotransferase (EC 2.7.