ULTRASTRUCTURE OF CHLORELLA PYRENOIDOSA AS AFFECTED BY ENVIRONMENTAL CHANGES

Chlorella pyrenoidosa (van Niel's strain) was cultured in four environmental conditions: light-glucose, light-galactose, dark-glucose, and dark-galactose. The gradual change in structure was observed when the cultures were transferred from light to darkness (dark adaptation). Cells grown in light contained well-developed chloroplasts and the normal cytoplasmic sub-units. During the transition to the complete heterotrophic mode of nutrition, the chloroplast regressed to the proplastid stage with a gradual reduction in thylakoid number. A prolamellar body was noted in the most regressed proplastid condition and plastid storage material was observed in all stages. The cell wall thickened during the transition. Cells adapted to darkness on galactose exhibited abundant cytoplasmic storage material with osmiophilic properties.     

Effects of chorda tympani nerve anesthesia on taste responses in the NST

Human clinical and psychophysical observations suggest that the taste system is able to compensate for losses in peripheral nerve input, since patients do not commonly report decrements in whole mouth taste following chorda tympani nerve damage or anesthesia. Indeed, neurophysiological data from the rat nucleus of the solitary tract (NST) suggests that a release of inhibition (disinhibition) may occur centrally following chorda tympani nerve anesthesia. Our purpose was to study this possibility further. We recorded from 59 multi- and single- unit taste-responsive sites in the rat NST before, during and after recovery from chorda tympani nerve anesthesia. During anesthesia, average anterior tongue responses were eliminated but no compensatory increases in palatal or posterior tongue responses were observed. However, six individual sites displayed increased taste responsiveness during anesthesia. The average increase was 32.9%. Therefore, disinhibition of taste responses was observed, but infrequently and to a small degree in the NST At a subset of sites, chorda tympani-mediated responses decreased while greater superficial petrosal-mediated responses remained the same during anesthesia. Since this effect was accompanied by a decrease in spontaneous activity, we propose that taste compensation may result in part by a change in signal-to-noise ratio at a subset of sites.      

Enhanced adhesion of polymorphonuclear leukocytes to anoxic cultured vascular endothelium

This study showed that the adherence of human polymorphonuclear leukocytes (PMN) to monolayer cultures of human umbilical vein endothelial cells (HUVEC) was increased when the latter were rendered anoxic. This adhesion was greater after 4-5 h than after 8 h of anoxia, but even at 8 h was significantly above the level of adhesion to HUVEC maintained under normoxic conditions for the same period. The changes in adhesion were not dependent on the viability of HUVEC during anoxia. Anoxia-induced adhesion was prevented by addition of cycloheximide (5 micrograms/ml) to the cultures, suggesting that it depended on HUVEC protein synthesis. Enhanced adhesion was also prevented by addition of a monoclonal antibody directed against the cytokine, interleukin-1 alpha (IL-1 alpha). These findings are consistent with a role of endogenous IL-1 alpha as a mediator of the anoxia-induced adhesion of PMN to HUVEC.