Brain tolerance to middle cerebral artery occlusion during hypotension in primates

The aim of this study was to determine the duration of middle cerebral artery occlusion required to produce significant ischemic damage when the occlusion occurs during controlled systemic hypotension. In 21 anesthetized cynomolgus monkeys, an IV infusion of sodium nitroprusside was used to lower the mean arterial blood pressure to 45-50 mmHg for 90 minutes. Middle cerebral artery occlusion for 15, 30, 45, or 60 minutes was performed during the hypotensive period. Neurological function was then evaluated every 8 hours for a total of 72 hours. At the end of the observation period, the monkeys were again anesthetized, magnetic resonance imaging was performed, and the brain was perfused with 10% buffered formalin. Neurological deficits were observed after 30 minutes, but not after 15 minutes, of middle cerebral artery occlusion, and rapidly increased in incidence and severity when the duration of occlusion was increased. After 60 minutes of occlusion, all the monkeys exhibited severe deficits. Four monkeys died during the observation period--two in each of the 45- and 60-minute occlusion groups. Histopathological examination revealed that little or no ischemic damage resulted from a 15-minute occlusion during hypotension. However, severe ischemic damage began to occur after only 30 minutes of occlusion, and all monkeys subjected to middle cerebral artery occlusion for 60 minutes developed extensive regions of infarction. The size and incidence of these infarctions correlated well with the lesions observed in the magnetic resonance images. These results demonstrate that the duration of middle cerebral artery occlusion that produces cerebral infarction in primates is drastically reduced when the occlusion occurs at hypotensive levels commonly employed during neurovascular surgical procedures.

Resistance of schedule-induced behaviours to hippocampal lesions

It has been reported that electrolytic lesions of the hippocampus accelerate the onset of schedule-induced drinking (SID) and also lead to significant increases in adrenal weights [2]. In the present experiment three groups of Long Evans rats received electrolytic or 6-Hydroxydopamine or sham lesions of the hippocampus and one group received electrolytic cortical lesions. Half of each group were tested 1 hr/day for 10 days under scheduled food delivery and the other half received food in a single presentation. It was found that both electrolytic hippocampal and cortical lesions reduced the level of SID compared with sham and 6-Hydroxydopamine lesions which did not differ from each other. However, there is support for the suggestion that hippocampal catecholamine neurones are involved in corticosterone regulation as shown by a significant increase in plasma corticosterone levels in non-scheduled, 6-Hydroxydopamine lesioned rats.

Experimental study in rabbits of the antishock effect of anisodamine (654-2), and its mechanism of action

The antishock effect of anisodamine (654-2) was observed in different kinds of experimental shock in groups of rabbits--due to late hemorrhage, superior mesenteric artery occlusion, and septic shock from peritonitis. The drug 654-2 significantly alleviated the progress of shock and increased the survival rate of the animals. The therapeutic effect of 654-2 was much better than that of other vasoactive drugs commonly used, such as norepinephrine, phenoxybenzamine, dopamine, and aramine. The antishock mechanism of 654-2 is probably partly due to its protective action on intestinal shock in preventing its effects becoming irreversible. The antishock action of 654-2 both by basic research workers and clinicians merits further study.

Anal lesions complicating Crohn disease

Of 503 patients with Crohn disease seen at the New York Hospital-Cornell Medical Center, 138 (28%) developed an anorectal abscess, anal fissure, or anal fistula during the course of their disease. In 9.3% of patients the anal lesion preceded the onset of intestinal symptoms by two weeks to 12 years. Patients in our series with large bowel disease were twice as likely to develop an anal lesion as were patients with small bowel disease. Likewise, patients with large bowel disease were twice as likely to have had an anal lesion as a presenting symptom. A patient with an anal lesion, however, was more apt to develop small bowel disease simply because the small bowel was a far commoner site of Crohn disease in this series. The cause of the anal lesions is still not clear. Specific evidence of Crohn disease was not found in histological examination of material from any of the patients.