Astrocyte cultures from adult rat brain. Derivation, characterization and neurotrophic properties of pure astroglial cells from corpus callosum.

It has not as yet been routinely possible to derive primary cultures of glial cells from adult rat brain tissue even when adopting strategies that have proven successful with perinatal tissue. We now report that in response to a surgical lesion and a period of postoperative 'priming' in vivo, proliferating cultures of astroglial cells can be derived from the normally quiescent glia of the corpus callosum region of the adult rat brain. In such cultures the predominance of astroglia and the virtual absence of oligodendroglia and neurons has been established by the use of a variety of cell-type specific antisera. Fibroblasts, the only other cell type identified, when not numerous could be successfully eliminated by treatment of the cultures with anti-Thy-1 antibodies and guinea pig complement. Pure astroglial cells from adult brain have been sub-cultured and maintained for up to 4 months in vitro, providing suitable quantities of cells for studies on the trophic interaction between glia and neurons. In long-term culture the adult astrocytes maintain a flattened undifferentiated morphology but readily assume a stellate shape with long branching processes upon the addition of a crude homogenate from bovine pituitary.

Dissociation of spontaneous and mating induced ovulation by frontal hypothalamic deafferentations in the rat.

Different types of anterior hypothalamic deafferentations have been used to investigate the nervous pathways involved in spontaneous and mating-induced ovulation in the rat. Knife cuts which circumscribed the suprachiasmatic nuclei on all but their ventral surface and either their rostral or caudal poles prevented spontaneous ovulation, but the rats were sexually receptive (copulation plugs and sperm in the smear), and mating induced ovulation. Similar types of cut extended dorsally so as to sever the continuity between the preoptic area and the mediobasal hypothalamus also prevented spontaneous ovulation, and although these rats were also receptive, mating did not induce ovulation. Two possible explanations are considered: either (i) that difference between the effects of the two types of cut is a direct function of the differing proportions of gonadotrophic hormone-containing axons severed, or (ii) cuts in the region of the suprachiasmatic nuclei specifically impair a mechanism for the maintenance of diurnal rhythms, to which the abnormality in gonadotrophin control is secondary.

Release of beta-thromboglobulin from human platelets by therapeutic intensities of ultrasound.

The effects of therapeutic intensities of ultrasound on human platelets in whole blood were investigated by monitoring the release of the platelet specific protein beta-thromboglobulin (beta-TG). More beta-TG was released as the intensity of the ultrasound was increased and also as the driving frequency was decreased from 3.0 to 0.75 MHz. Some beta-TG was released at spatially-averaged intensities as low as 0.6 W/cm2 at 0.75 MHz, a value significantly lower than that observed for the onset of aggregation of platelet rich plasma (obtained from the same volunteer) in the same exposure system. Liberation of beta-TG by ultrasound was diminished but not abolished in the presence of inhibitors which rendered the platelets functionally inert. Our data suggests that beta-TG is liberated in two ways, firstly as a result of platelet disruption by cavitation, and subsequently by potent aggregating agents, liberated in parallel with beta-TG, inducing the physiological release reaction in adjacent platelets. The low therapeutic intensities and short exposure times (30 s or less) necessary to liberate beta-TG from normal human platelets in vitro, suggests that patients with abnormally sensitive platelets and/or 'hypercoagulable state' could be at risk if subjected to high therapeutic intensities of ultrasound.