Survival and behavior patterns associated with hypoxia at different life stages of the pen shell Atrina cf. japonica.

Pen shell (Atrina cf. japonica) resources have been devastated in Ariake Bay, Japan, and to facilitate the recovery of this species, there is an urgent need to fully understand the factors contributing to its high levels of mortality. Pen shells living in natural waters grow through successive life stages, and environmental factors may affect these bivalves differently at different stages. Accordingly, to elucidate the causes of mortality in natural waters, it is necessary to gain an understanding of the quantitative effects of environmental factors on bivalves at each life stage. In this study, we sought to determine the differential effects of hypoxic conditions on 1-year-old (average shell length: 93.9 mm) and 2-year-old (146.5 mm) pen shells bred under artificial conditions. We exposed shells of each age group to six different dissolved oxygen (DO) concentrations for 96 h and monitored their behavior and survival rate. Based on the survival status, we estimated the lethal DO concentrations that induced 50%, 95%, and 5% mortality (LC50, LC95, and LC5, respectively) at each age. We found that for 1-year-old shells, the LC50 values at 48, 72, and 96 h were 0.51, 0.74, and 0.84 mg/L, respectively, whereas the corresponding values for 2-year-old shells were 0.74, 1.27, and 1.80 mg/L. Furthermore, we found that for 1- and 2-year-old shells, the estimated ranges from LC95 to LC5 at 48, 72, and 96 h were 0.39-0.68, 0.62-0.88, and 0.64-1.12 mg/L, and 0.31-1.75, 0.77-2.09, and 1.29-2.53 mg/L, respectively. Under low DO concentrations (0.47 to 1.93 mg/L and 0.49 to 3.30 mg/L for 1- and 2-year-old shells, respectively), we observed pen shells with more than half of their shell length protruding above the substrate. In addition to age and body size, the 1- and 2-year-old pen shells used in the present study also differed with respect to reproductive status, with 7.6% of 1-year-old and 96.7% of 2-year-old shells considered to be fully ripe. Collectively, our observations indicate that 2-year-old pen shells are less tolerant to hypoxic conditions than are 1-year-old pen shells, and we suspect that the differences in hypoxic tolerance could be attributable to differences in the physiological status of the pen shells during gonadal development. We believe the findings of this study will make an important contribution to enhancing our understanding of the effects of hypoxia on the viability of A. cf. japonica in natural waters.

Possible mediators involved in decreasing peripheral vascular resistance with blackcurrant concentrate (BC) in hind-limb perfusion model of the rat.

We analyzed mechanisms decreasing hind-limb perfusion pressure (PP) with blackcurrant concentrate (BC) in the rat. The decrease in PP with BC was abolished by endothelial removal, nitroarginine plus tetraethylammonium, nitroarginine plus catalase or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one as an inhibitor of guanylyl cyclase and potassium channel(s), and accompanied by the increased cyclic GMP level. Partial but significant inhibition caused by KCl was observed during contraction. Authentic H2O2 decreased the PP in a sensitive manner to catalase and tetraethylammonium. The decrease in PP with BC in the presence of nitroarginine was significantly attenuated by diverse potassium channel blockers. Two delphinidins of 4 anthocyanins purified from BC definitely decreased the PP through similar mechanisms to BC. These results suggest that the decreased PP with BC is possibly mediated by endothelial NO and H2O2, and partially through the activation of diverse potassium channels, and that 2 delphinidins play a major role as active components of BC.

Novel physiological function of fructooligosaccharides.

Two key properties of short chain fructooligosaccharides (sc-FOS) which lead to physiological functions are indigestibility in the small intestine and fermentability in the colon. Sc-FOS is converted into short chain fatty acids (SCFAs) by intestinal bacteria in the colon and absorbed. Through the metabolic pathway, sc-FOS improves gastrointestinal (GI) condition such as relief from constipation, formation of preferable intestinal microflora and intestinal immunomodulation those are known as prebiotics' function. Besides improvement of GI condition, dietary sc-FOS influences on calcium and magnesium absorption in the colon. A major mineral absorption site is the small intestine, but the colon also works as a Ca and Mg absorption site with an aid of SCFAs made from sc-FOS. Furthermore dietary sc-FOS influences on bioavailability of soy-isoflavones. Plasma and urinal concentration of Genistein and Daidzein, aglycones of Daidzin and Genistin, are higher in the rat fed with sc-FOS than the control rat. An additive effect of dietary isoflavone and sc-FOS was observed on the bone mineral density in OVX mice and moreover sc-FOS increased ceacal beta-glycosidase activity and equol production. These results suggest that FOS increase the bioavailability of isoflavones.

Anti-cariogenic properties of a water-soluble extract from cacao.

The addition of a water-soluble extract from cacao-extracted powder (CEPWS) to a cariogenic model food, a white chocolate-like diet that contains 35% sucrose, significantly reduced caries scores in SPF rats infected with Streptococcus sobrinus 6715, compared to control rats fed a white chocolate-like diet. CEPWS markedly inhibited water-insoluble glucan (WIG) synthesis through crude glucosyltransferases (GTFs) from Streptococcus sobrinus B13N in vitro. GTF-inhibitor(s) in CEPWS was prepared through three-step fractionation, and was termed CEPWS-BT, which is a high molecular weight (>10 kDa) heat-stable matrix of sugar, protein, and polyphenol. When the inhibitory effect of CEPWS-BT on glucan synthesis was examined using the purified GTF-I, GTF-T, and GTF-U enzymes from S. sobrinus B13N, significant reduction in GTF-I and GTF-T activity as a result of adding CEPWS-BT at low concentrations was observed. These results suggest that the addition of CEPWS to cariogenic food could be useful in controlling dental caries.