Oxyhemoglobin was injected intracisternally into three baboons, and methemoglobin into one baboon, in an attempt to mimic the prolonged cerebral arterial spasm sometimes seen after subarachnoid hemorrhage due to aneurysm rupture. Cerebral angiography was performed for up to 7 days after injection of hemoglobin, and the degree of vasospasm was estimated from the angiograms. Oxyhemoglobin caused slight arterial narrowing, which lasted for 3 days. Methemoglobin had no significant effects. Motor neurological deficits and histopathological signs, characteristic of prolonged cerebral vasospasm, were not observed. It was concluded that hemoglobin alone is not capable of causing the cerebral vasospasm syndrome in these experimental animals.

SummaryHuman blood platelets resuspended in calcium-free Krebs solution accumulated radioactive L-leucine and L-arginine. The tissue/medium concentration ratio (Ci/Co) was greater than 10:1 when Co was 10–7 M or lower. Accumulation was inhibited by incubation at 4° C, the presence of metabolic inhibitors or platelet soniñcation at the beginning of the experiment. It is considered that these compounds are accumulated by energy-dependent processes against a concentration gradient.In the presence of 19 other amino acids accumulation of leucine or arginine was greatly reduced. Under these conditions some incorporation of radioactivity into proteins occurred. However, incorporation was small. Both compounds were incorporated similarly despite the fact that arginine is metabolized to ornithine, whilst leucine has no detectable metabolites. This fact is discussed in relation to the possible physiological significance of platelet protein synthesis.