Newer laboratory approaches for assessing visual dysfunction.

The crucial point that will be emphasized throughout this report is the potential utility of analyzing visual cortical receptive field (RF) properties of the single-cell level as a sensitive and reliable neurotoxicity screening tool. Numerous studies employing exposure of kittens to altered visual environments during the critical period have demonstrated that particular classes of RFs can be selectively affected while sparing others. There has been a rapid proliferation of new methods used to investigate such effects. An important current trend involves the development of multidisciplinary combinations of approaches. The various maneuvers reviewed here seem adaptable to studying neurotoxic insult of the sensitive properties of cortical visual neurons, particularly in the cat or monkey. Conceivably, a general disruption of cortical RF properties might be expected following toxic exposure since individual RF properties are generally not determined by completely independent mechanisms. In fact, some toxicants might produce a general degradation of RF properties akin to the electrophysiological results reported for long-term dark rearing or binocular deprivation

Dialyzable factor in human serum of platelet origin stimulates endothelial cell replication and growth

Porcine aortic endothelial cells were isolated and maintained in Dulbecco's modified Eagle's medium (DME medium)/10% citrate-treated human plasma. They were stimulated by DME medium/10% human serum to grow from a density of 10,100 +/- 500 per well to a final density of 83,000 +/- 1,800 per well over a 9-day period. On the other hand these cells grew poorly (11% increase) in DME medium/10% human platelet-poor plasma prepared without chelating agents and containing platelet factor 4 at 18 ng/ml by radioimmunoassay. Dialysis of the human serum (M(r) cutoff, 3,500) eliminated all the stimulatory activity. The activity recovered from the dialysate stimulated growth when added to endothelial cultures in conjunction with either dialyzed serum or platelet-poor plasma alone. The dialyzable factor could be obtained directly from platelets; both acetic acid extracts and boiled NaCl extracts stimulated porcine aortic endothelial cell replication. Gel filtration chromatography on Sephadex G-15 showed that the endothelial growth factor had a molecular weight of 700. Partially purified material induced a concentration-dependent stimulation of porcine aortic endothelial cell replication in the presence of DME medium alone; however, simultaneous incubation with platelet-poor plasma resulted in a much greater response. Fibroblast growth factor isolated from bovine brain was found to be mitogenic only in the presence of nondialyzed serum or of the dialyzable factor together with plasma. In the absence of this serum factor, fibroblast growth factor had no effect. We conclude that human serum contains a potent endothelial cell mitogen of platelet origin. Human plasma that is devoid of platelet content does not stimulate endothelial cell growth. This growth factor may be an important stimulant of the endothelial cell response to vascular wall injury

Atmospheric Evolution

Earth's atmosphere has evolved as volatile species cycle between the atmosphere, ocean, biomass and the solid Earth. The geochemical, biological and astrophysical processes that control atmospheric evolution are reviewed from an "Earth Systems" perspective, with a view not only to understanding the history of Earth, but also to generalizing to other solar system planets and exoplanets.Comment: 34 pages, 3 figures, 2 tables. Accepted as a chapter in "Encyclopaedia of Geochemistry", Editor Bill White, Springer-Nature, 201