Transformation of leukotriene D4 catalyzed by lysosomal cathepsin H of rat liver

Among several intracellular protease tested, cathepsin H transformed leukotriene D4 to E4 with a release of glycine in a stoichiometric quantity. Under the optimal conditions the rate of leukotriene D4 transformation by cathepsin H was about 3% of the hydrolysis rate of alpha-N-benzoyl-DL-arginine-2-naphthylamide which is commonly utilized as a very efficient substrate to test the peptidase activity of the enzyme. Leukotriene C4 was not transformed to leukotriene D4 by cathepsin H. Neither cathepsin B nor C was active with leukotrienes C4 and D4.     

Relative Activities of NAD- and NADP-Isocitric Dehydrogenases in Bean Mitochondria Modified by Glycerol or NADP

Mitochondria from cotyledons of Vigna sesquipedalis (L.) Fruwirth (starchy seed) showed no NAD-isocitric dehydrogenase (NAD-IDH) activity by the methods which have been known to be useful for the detection of NAD-IDH in mitochondria of plants including castor bean and alaska pea. When the Vigna cotyledon mitochondria were treated with glycerol, NAD-IDH activity appeared and NADP-isocitric dehydrogenase (NADP-IDH) activity was inhibited. The inhibition of mitochondrial NADP-IDH by glycerol was overcome by the addition of excess NADP.On the other hand, NADP-IDH activity in the soluble fraction of cell components was only slightly inhibited by glycerol and no NAD-IDH activity was elicited.It was postulated that NADP-IDH in mitochondria is converted to NAD-IDH by glycerol and back to NADP-IDH with NADP by the alteration in the spatial configuration of the enzyme. However, there could be 2 proteins as the other possibility.The NADP-IDH in the soluble fraction which is not subject to such alteration is different from the mitochondrial NADP-IDH.     

Studies of cloned simian immunodeficiency virus-specific T lymphocytes. gag-specific cytotoxic T lymphocytes exhibit a restricted epitope specificity.

CD8+ CTL inhibit the replication of HIV and simian immunodeficiency virus of macaques (SIVmac) in PBL and, therefore, are likely to play an important role in containing the spread of the AIDS virus in infected individuals. We have generated a series of gag-specific lytic T lymphocyte clones from PBL: of an SIVmac-infected rhesus monkey. These T cell clones are CD3+CD8+ and are MHC class I-restricted in their target specificity. They are, therefore, CTL. Interestingly, all gag-specific CTL clones, as well as the gag-specific lytic activity of PBL of this monkey, demonstrated specificity for a single 25 amino acid fragment of the SIVmac gag protein. Moreover, they were restricted in their lytic function by a single MHC class I allele. These findings illustrate a powerful method for cloning AIDS virus-specific T lymphocytes and demonstrate a remarkably restricted epitope specificity of this AIDS virus-specific CTL response.     

Effect of dimethyl sulfoxide on cytosolic ionized calcium concentration and cytoskeletal organization of hepatocytes in a primary culture

The addition of dimethyl sulfoxide (DMSO) to a chemically defined, serum free medium prolonged hepatocytes survival in primary culture. DMSO exposure had a remarkable effect on morphological change and F-actin filaments distribution of hepatocytes. When hepatocytes were cultured in a medium containing 2% DMSO, the cells showed a compact and cubical shape and intracellular F-actin filaments were mainly observed in a ring-like fashion around the intercellular space. After exposure to DMSO, fibronectin fibers in the interspace between cell and substratum were not apparent. Exposing the hepatocytes to DMSO also caused a sharp increase in cytosolic free ionized calcium ([Ca2+]). The initial increase in [Ca2+]i following the addition of DMSO was not attenuated by the chelation of extracellular Ca2+ with EGTA. The Ca2+ signal in the absence of extracellular Ca2+ was transient and returned to the basal levels within 1-2 min, while it was maintained at a high steady state in the presence of extracellular Ca2+. These results suggest that DMSO may be able to increase [Ca2+]i by two mechanisms, by the release of the ion from intracellular pools and, by the stimulation of influx across the plasma membrane. The increase in [Ca2+]i induced by DMSO treatment may play a role in prolonging hepatocyte survival in culture, since [Ca2+]i is one of the most important dynamic second messengers in various cellular metabolic processes.