Primate brain tolerance to temporary focal cerebral ischemia during isoflurane- or sodium nitroprusside-induced hypotension

Isoflurane has properties that suggest it may provide cerebral protection from ischemia. This study compared, in primates, neurologic outcome after a 45-min period of temporary focal ischemia during hypotension induced with either isoflurane or sodium nitroprusside (SNP). Fourteen macaque monkeys were studied. Seven animals received halothane and seven isoflurane anesthesia during surgical preparation. After transorbital exposure of the middle cerebral artery (MCA), in the halothane group, the inspired halothane was reduced to 0.75% and the mean blood pressure (BP) reduced to 50 mmHg by the infusion of SNP. In the isoflurane group, the isoflurane was titrated to reduce mean BP to 50 mmHg. Stable hypotension was maintained for 90 min, which included a 45-min period of MCA occlusion. Monitoring included intraarterial blood pressure, arterial blood gases, EEG, somatosensory evoked potentials (SEP), and temperature. After the procedure the animals were allowed to awaken and were assessed neurologically every 8 h. On the third postoperative day, they were reanesthetized and underwent magnetic resonance imaging (MRI) and SEP recording. Thereafter, they were killed with iv KCl and the brains fixed for neuropathology. All animals survived the surgical procedure, but two animals receiving halothane and none receiving isoflurane died prematurely (P less than 0.2). The SEP disappeared in all animals within 10 min of MCA occlusion and then returned partially or completely. There was no difference between groups in neurologic scores, in the size of the lesion as assessed by MRI (isoflurane 15.7 +/- 6%, halothane/SNP 10.5 +/- 4%), or in the extent or severity of the neuropathologic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors influencing erythrocyte choline concentrations

Choline concentrations in human erythrocytes increase after freezing and thawing, during incubation in Krebs-phosphate for 30 min or on storage at 0 degrees C for 3-24 hr. The increase is prevented by protein precipitation by 10% perchloric acid, 10% zinc hydroxide, 10% sodium tungstate or boiling in water. It is not prevented by EDTA (10 mM) and is increased by oleate (5 mM). We suggest that the increase is due to the action of phospholipase D on erythrocyte phospholipids.

Pharmacokinetics of vasopressin and atrial natriuretic peptide in anesthetized rabbits

The elimination from plasma of the peptide hormones vasopressin (VP) and atrial natriuretic peptide (ANP) as well as the time course of release and elimination of these hormones after a physiological stimulus were studied in anesthetized rabbits. As an inverse relationship was found to exist between carotid sinus pressure and plasma IR-ANP, a decrease in carotid sinus pressure to 60 mm Hg was used to stimulate ANP as well as VP release. The elimination of VP after iv injection involved a rapid initial phase and a slow late component, with corresponding half-life (t1/2) values of 0.9 and 5.4 min, respectively. After reduction of carotid sinus pressure to 60 mm Hg, plasma VP increased significantly within 1 min and reached a maximum at 10 min. When carotid sinus pressure was increased to 160 mm Hg to inhibit VP release, the t1/2 of VP was 1.3 min. The t1/2 of immunoreactive (IR) ANP after iv infusion was 1.2 min. Plasma IR-ANP was significantly increased 2 min after carotid sinus pressure was decreased, and a maximum was observed at 10 min. The t1/2 of IR-ANP after elevation of carotid sinus pressure to 160 mm Hg was 3.2 min. These studies indicate that both VP and IR-ANP are rapidly eliminated in the anesthetized rabbit.

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.