In vitro differentiation inhibits the migration of cultured neonatal rat cortical astrocytes transplanted to the neonatal rat cerebrum.

Neonatal rat astrocytes transplanted into the rat cerebrum migrate extensively. However, few of the molecular signals determining this migration have been defined. In the present study, in vitro modifications were designed to examine whether differentiation prior to transplantation would affect the magnitude or pattern of astrocyte migration in the neonatal host brain. Here, cortical astrocytes were collected from the brains of rats 1-3 days postpartum and purified by culturing them in DME medium supplemented with 10% calf serum. After 14-21 days, astrocytes were labelled with fluorescein-tagged latex microspheres for 16 hr; the label was then removed and replaced with either fresh medium or fresh serum-free medium plus 1 mM dbcAMP. After 48 hr, cells were harvested and then transplanted into the right frontal cerebrum of neonatal rats at 3 days postpartum by injection with a hand-held Hamilton syringe. Animals were sacrificed at 3, 6, 9, 15, 21 and 28 days after inoculation and their brains examined with fluorescence microscopy. Astrocytes not exposed to dbcAMP prior to implantation migrated along the corpus callosum, internal capsule, glial limitans, ventricular linings and the hippocampal structure. They also appeared to migrate in a radial fashion toward the periphery from the ventricular lining. Astrocytes treated with dbcAMP prior to transplantation did not appear to migrate into the neonatal parenchyma, remaining confined to the injection site for at least 6 days. Migration then appeared to commence at a normal rate after 9 days. Thus, neonatal cortical migrate outward in a pattern similar to that defined by the radial glia. Astrocytes differentiated by dbcAMP treatment, however, do not appear to migrate to any large degree in the neonatal brain until the treatment effect diminishes, suggesting that differentiation may represent an end-point to glial migration in the neonatal host brain.

Hemodynamic effects of high dose pentobarbital: studies in elective neurosurgical patients.

High dose barbiturate therapy has been used clinically for about 10 years. However, the hemodynamic consequences of such therapy have not been well defined in humans. We therefore examined the effects of a brief (30-minute), high dose (0.6 mg/kg/minute or 18 mg/kg total) infusion of pentobarbital in nine otherwise healthy patients (aged 20 to 30) scheduled to undergo operation for the removal of large or deeply seated arteriovenous malformations. Monitored variables included intravascular pressures, cardiac output, arterial and mixed venous blood gases and hematocrit, and the electroencephalogram (EEG). After a brief rest period and the collection of control data, pentobarbital infusion was begun, muscle relaxants were given, and normocarbia was maintained by mask ventilation. Because our primary intent was to examine the effects of the drug on the heart and arterial circulation, lactated Ringer's solution was infused continuously to keep pulmonary capillary wedge pressure (PCWP) at control values in an attempt to keep constant the ventricular "preload" (although PCWP is only an approximation of the true preload). Drug infusion resulted in progressive EEG suppression ending in a pattern of deep burst suppression (1 to 3 bursts/minute) at t = 30 minutes, with measured plasma pentobarbital concentrations (in four patients) of 34 +/- 4 micrograms/ml (mean +/- SD). There were no changes in PaO2, PaCO2, or pH, nor were there any changes in PCWP. The cardiac index did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of carotid artery transection resulting from a stab wound to the ear.

Emergency treatment of penetrating injury to the internal carotid artery at the skull base and within the temporal bone is difficult due to problems of exposure and control of this vessel. A successful method of management of a patient whose carotid artery was completely transected by a stab wound to the ear is presented. This involved gaining proximal vascular control in the neck and distal control intracranially. Indications for extracranial-intracranial vascular bypass procedures are discussed.