Role of integrins in differentiation of chick retinal pigmented epithelial cells in vitro

When retinal pigmented epithelial cells (PEC) of chick embryos are cultured under appropriate conditions, the phenotype changes to that of lens cells through a process known as transdifferentiation. The first half of the process, characterized by dedifferentiation of PEC, is accompanied by a marked decrease in adhesiveness of PEC to collagen type I- or type IV-coated dishes. To understand the underlying mechanisms of this change, we analyzed the expression of integrins, which are major receptors for extracellular matrix components. Northern blot analysis with cDNA probes for chicken α3, α6, α8, αv, β1 and β5 integrin mRNA showed that the genes for all these integrins are transcribed at similar levels in PEC and dedifferentiated PEC (dePEC). Further analysis of β1 integrin, which is a major component of integrin heterodimers, showed that although the protein amount of β1 integrin was not changed, its localization at focal contacts seen in PEC was lost in dePEC. When anti-β1 integrin antibody was added to the PEC culture medium, a decrease of cell-substrate adhesiveness occurred, followed by a gradual change in both morphology and gene expression patterns to ones similar to those of dePEC. These findings suggest that an appropriate distribution of β1 integrin plays an essential role in maintaining the differentiated state of PEC through cell-substrate adhesion.     

Studies on the Sulfite Reducing System of Algae

Sulfite reductase using reduced methyl viologen as an electron donor was purified about 94-fold from a red alga, Porphyra yezoensis. The enzyme was ultracentrifugically homogenous and could reduce sulfite to sulfide quantitatively with an uptake of six electrons. The enzyme had a pH optimum in the vicinity of 7.5. The Km for sulfite was determined to be 6.5×l0^?4m. The purified preparation of the algal reductase showed its absorption maximum at 385 mμ and slight shoulders at 408, 456, 485, 600 and 664 mμ in addition to an intense peak at 278 mμ. Metal analysis of the purified enzyme suggested the presence of iron and copper in the molecule. NADPH, NADH or the reduced form of spinach ferredoxin could not be a direct electron donor for the purified algal sulfite reductase.     

Fallback Foods of Red Leaf Monkeys (Presbytis rubicunda) in Danum Valley, Borneo

Animals in Southeast Asia must cope with long periods of fruit scarcity of unpredictable duration between irregular mast fruiting events. Long-term data are necessary to examine the effect of mast fruiting on diet, and particularly on the selection of fallback foods during periods of fruit scarcity. No such data is available for colobine monkeys, which may consume substantial amounts of fruits and seeds when available. We studied the diet of red leaf monkeys (Presbytis rubicunda, Colobinae) in Danum Valley, Sabah, northern Borneo, using 25 mo of behavioral observation, phenology and vegetation surveys, and chemical analysis to compare leaves eaten with nonfood leaves. The monkeys spent 46% of their feeding time on young leaves, 38% on seeds, 12% on whole fruits, 2.0% on flowers, 1.0% on bark, and 1.2% on pith. They spent more time feeding on seeds and whole fruit when fruit availability was high and fed on young leaves of Spatholobus macropterus (liana, Leguminosae) as fallback foods. This species was by far the most important food, constituting 27.9% of the total feeding time, and the feeding time on this species negatively correlated with fruit availability. Consumed leaves contained more protein than nonconsumed leaves, and variation in time spent feeding on different leaves was explained by their abundance. These results suggest that red leaf monkeys show essentially the same response to the supra-annual increase in fruit availability as sympatric monogastric primates, increasing their seed and whole-fruit consumption. However, they depended more on young leaves, in particular Spatholobus macropterus, as fallback foods during fruit-scarce periods than did gibbons or orangutans. Their selection of fallback food appeared to be due to both nutrition and abundance.     

Effects of dipeptides having a C-terminal lysine on the cholesterol 7alpha-hydroxylase mRNA level in HepG2 cells

Inducing expression of the cholesterol-catabolizing enzyme cholesterol 7alpha-hydroxylase (CYP7A1) in the liver can be an effective strategy in preventing hypercholesterolemia and atherosclerosis. We used HepG2 cells to investigate the effects of 1 mM dipeptides having a C-terminal lysine group on the CYP7A1 mRNA level. We found that the dipeptides Asp-Lys, Glu-Lys, and Trp-Lys significantly increased the CYP7A1 mRNA level.     

Fruiting and flushing phenology in Asian tropical and temperate forests: implications for primate ecology

In order to understand the ecological adaptations of primates to survive in temperate forests, we need to know the general patterns of plant phenology in temperate and tropical forests. Comparative analyses have been employed to investigate general trends in the seasonality and abundance of fruit and young leaves in tropical and temperate forests. Previous studies have shown that (1) fruit fall biomass in temperate forest is lower than in tropical forest, (2) non-fleshy species, in particular acorns, comprise the majority of the fruit biomass in temperate forest, (3) the duration of the fruiting season is shorter in temperate forest, and (4) the fruiting peak occurs in autumn in most temperate forests. Through our comparative analyses of the fruiting and flushing phenology between Asian temperate and tropical forests, we revealed that (1) fruiting is more annually periodic (the pattern in one year is similar to that seen in the next year) in temperate forest in terms of the number of fruiting species or trees, (2) there is no consistent difference in interannual variations in fruiting between temperate and tropical forests, although some oak-dominated temperate forests exhibit extremely large interannual variations in fruiting, (3) the timing of the flushing peak is predictable (in spring and early summer), and (4) the duration of the flushing season is shorter. The flushing season in temperate forests (17–28 % of that in tropical forests) was quite limited, even compared to the fruiting season (68 %). These results imply that temperate primates need to survive a long period of scarcity of young leaves and fruits, but the timing is predictable. Therefore, a dependence on low-quality foods, such as mature leaves, buds, bark, and lichens, would be indispensable for temperate primates. Due to the high predictability of the timing of fruiting and flushing in temperate forests, fat accumulation during the fruit-abundant period and fat metabolization during the subsequent fruit-scarce period can be an effective strategy to survive the lean period (winter).     

Fused p47phox and p67phox truncations efficiently reconstitute NADPH oxidase with higher activity and stability than the individual components

Activation of the neutrophil NADPH oxidase occurs via assembly of the cytosolic regulatory proteins p47(phox), p67(phox), and Rac with the membrane-associated flavocytochrome b(558). Following cell-free activation, enzymatic activity is highly labile (Tamura, M., Takeshita, M., Curnutte, J. T., Uhlinger, D. J., and Lambeth, J. D. (1992) J. Biol. Chem. 267, 7529-7538). To try to stabilize the activity and investigate the nature of the complex, fusion proteins between p47N-(1-286) and p67N-(1-210) were constructed. In a cell-free system, a fusion protein, p67N-p47N, had an 8-fold higher efficiency and produced a higher activity than the individual proteins, and also resulted in an 8-fold improved efficiency for Rac and a lowered K(m) for NADPH. O(2) generating activity was remarkably stabilized by using p67N-p47N. The cytosolic proteins fused in the opposite orientation, p47N-p67N, showed similar activity and stability as individual proteins, but with a 4-fold improved efficiency compared with the individual cytosolic factors. In the system efficiency for Rac and affinity for NADPH were also higher than those with the nonfused components. Interestingly, the p67N-p47N showed nearly full activation in the absence of an anionic amphifile in a cell-free system containing cytochrome b(558) relipidated with phosphatidylinositol- or phosphatidylserine-enriched phospholipid mixtures. From the results we consider multiple roles of anionic amphifiles in a cell-free activation, which could be substituted by our system. The fact that a fusion produces a more stable complex indicates that interactions among components determine the longevity of the complex. Based on the findings we propose a model for the topology among p47N, p67N, and cytochrome b(558) in the active complex.     

Molecular cloning and characterization of a cDNA encoding ent-cassa-12,15-diene synthase, a putative diterpenoid phytoalexin biosynthetic enzyme, from suspension-cultured rice cells treated with a chitin elicitor

We have isolated and characterized a cDNA encoding a novel diterpene cyclase, OsDTC1, from suspension-cultured rice cells treated with a chitin elicitor. OsDTC1 functions as ent-cassa-12,15-diene synthase, which is considered to play a key role in the biosynthesis of (-)-phytocassanes recently isolated as rice diterpenoid phytoalexins. The expression of OsDTC1 mRNA was also confirmed in ultraviolet (UV)-irradiated rice leaves. In addition, we identified ent-cassa-12,15-diene, a putative diterpene hydrocarbon precursor of (-)-phytocassanes, as an endogenous compound in the chitin-elicited suspension-cultured rice cells and the UV-irradiated rice leaves. The OsDTC1 cDNA isolated here will be a useful tool to investigate the regulatory mechanisms of the biosynthesis of (-)-phytocassanes in rice.     

Food conditions, competitive regime, and female social relationships in Japanese macaques: within-population variation on Yakushima

Feeding conditions, competitive regime, and female social relationships of Japanese macaques (Macaca fuscata) on Yakushima were compared between the two habitats at two different altitudes (coniferous forest, 1,000–1,200 m and coastal forest, 0–200 m). Fruit availability was higher in the coastal forest. There was no consistent difference in the frequency of agonistic interactions within a group during feeding between the two habitats. The coastal forest evoked stronger inter-group contest competition compared to the coniferous forest as evidenced by a higher inter-group encounter rate and a higher proportion of aggressive encounters to non-aggressive ones. Birth rate was higher in larger groups compared to smaller ones in the coastal forest, but did not differ in the coniferous forest. In spite of these differences in competitive regime, no variation in female social relationships was observed, such as direction and concentration on particular individuals in grooming, linearity in dominance rank, counter-attack, and support of juvenile kin during agonistic interactions. The present results indicate that the female social relationships of Japanese macaques are robust and do not change according to changes in the current environment.     

Purification and characterization of macrolide 2''-phosphotransferase type II from a strain of Escherichia coli highly resistant to macrolide antibiotics

Hyperimmune and high-titered polyclonal pneumococcal antisera, specific for cross-reactive types within groups, were produced in adult rabbits. Purified capsular polysaccharide was injected intravenously into adult rabbits. One week later, these rabbits were given multiple intravenous injections of formalin-inactivated pneumococci of the cross-reactive type by an established method. Each of the resultant antisera were specific for the cross-reactive type indicating that the previous injection of the polysaccharide had induced epitope-specific tolerance. This method was successful for production of antisera against pneumococcal types 6A, 6B, 9N, 9V, 19F and 19A. Polyclonal rabbit pneumococcal antisera have some advantages over murine monoclonal antibodies for serologic studies and this method should be applicable for producing type-specific antibodies to cross-reactive polysaccharides of clinical interest. Further, this method is simpler and generally produces higher titered monovalent (factor) reagents than absorbed antisera.     

Mechanism of glucan-induced agglutination in Streptococcus mutans. I. Binding of radioactive glucan to whole cells of S. mutans OMZ-176.

The binding of radioactive glucan to Streptococcus mutans cells, which are agglutinated by dextrans, was examined. The glucan was synthesized from sucrose by extracellular glucosyltransferases from S. mutans FA-1 and was highly branched at C-3 and C-6 of D-glucose residues, containing 17% of a (1 leads to 3)inter-chain residues. Binding of glucan to whole cells of S. mutans OMZ-176, which were agglutinated by addition of glucan or Dextran T2000, was irreversible and followed saturation type kinetics; saturation was achieved at approximately 110 ng of glucan per ml. About 14 ng of glucan were bound per mg of the cells at the saturated concentration. The heated cells of this organism, however, had a relatively low ability of glucan-binding, compared with the freshly prepared and lyophilized cells. Binding to the heated cells was entirely of a non-saturation type. Binding of Dextran T2000 or T10 was determined by competition between the labeled glucan and unlabeled Dextrans for the binding site(s). Both Dextrans and glucan from S. mutans FA-1 were bound to the same site(s). Other organisms, which did not undergo glucan- and Dextran-induced agglutination, had a relatively lower ability of glucan-binding than S. mutans, which was agglutinated.