Reproductive cycle and growth of the sand dollar Scaphechinus griseus inhabiting Japanese surf clam Pseudocardium sachalinense fishing grounds in Tomakomai,southwest Hokkaido,Japan

Fisheries Science - Bioturbation by the sand dollar Scaphechinus griseus is suspected to inhibit the recruitment of Pseudocardium sachalinense, a commercially important bivalve. This study aimed to...     

Reproductive biology of the female Japanese mantis shrimp Oratosquilla oratoria (Stomatopoda) in relation to changes in the seasonal pattern of larval occurrence in Tokyo Bay, Japan

ABSTRACT:   The reproductive traits and the monthly larval abundance of the mantis shrimp Oratosquilla oratoria were investigated in Tokyo Bay, Japan, in 2002. The goal of the study was to elucidate the cause of changes in the monthly pattern of larval abundance from the 1980s to the 1990s as these changes relate to variation in the stock size of the adult shrimp. Oogenesis was divided into 10 stages by histological observation. The developmental stage of oocytes in an individual's ovary was synchronous, suggesting that almost all the oocytes in an ovary are spawned at the same time. The size at first maturity was estimated to be 7 ≤ body length ( BL ) < 8 cm. Fecundity was expressed as a function of BL , ranging from 19 300 eggs for 8 cm BL to 92 100 eggs for 14 cm BL . Small female shrimps (<10 cm BL ) spawned around August. Most large female shrimps (≥10 cm BL ) spawned around May, and some large female shrimps also spawned until September. Although most large female shrimps spawned in spring, the larval abundance was low before July and high from August onwards. The results suggest that a substantial decrease in the stock size of large individuals causes the low larval abundance before July.     

Purification and properties of pyrethroid carboxyesterase in rat liver microsome

Pyrethroid carboxyesterase which hydrolyzes the esters of chrysanthemumic acid was purified from rat liver microsome by cholic acid solubilization, ammonium sulfate fractionation, heat treatment, and DEAE-Sephadex A-50 column chromatography. The 45-fold purified enzyme (38% yield) is likely to consist of single protein, as evidenced by polyacrylamide gel disc electrophoresis and Sephadex G-100 column chromatography, and had a molecular weight of approximately 74,000 and a K_m of 0.21 mM. It is susceptible to inhibition by organophosphates and carbamate insecticides and insensitive to pCMB, mercuric ion, and cupric ion. It is capable of hydrolyzing trans isomers of synthetic pyrethroids much more rapidly (five to ten times) than the cis counterparts. The purified pyrethroid carboxyesterase is apparently identical in nature with malathion carboxyesterase and with p-nitrophenyl acetate carboxyesterase.     

Contribution of insulin to the ascorbate recycling system in the chicken liver

The effect of insulin on the ascorbate recycling system in the chicken liver was examined. First, insulin was injected subcutaneously into the chicken, and liver glutathione‐dependent dehydroascorbate reductase (GSH‐DHAR) activity was determined. Insulin increased liver GSH‐DHAR activity, but did not affect plasma and liver ascorbate concentration. Dehydroascorbate increased plasma and liver ascorbate levels, and liver GSH‐DHAR activity. However, distinct changes in plasma insulin level were not observed by dehydroascorbate injection. In addition, reduction of external dehydroascorbate in cultured chicken hepatocytes could not be observed in an insulin‐deprived culture, although the cells reduced external dehydroascorbate in a serum‐free culture with insulin. We concluded that insulin affects the ascorbate recycling system as an essential factor in the chicken liver.     

Pathogenesis-related gene expression in rice is correlated with developmentally controlled Xa21-mediated resistance against Xanthomonas oryzae pv. oryzae

Disease resistance mediated by the resistance gene Xa21 is developmentally controlled in rice. We examined the relationship between Pathogenesis Related (PR) defense gene expression and Xa21-mediated developmental disease resistance induced by Xanthomonas oryzae pv. oryzae (Xoo). OsPR1a, OsPR1b, and OsPR1c genes were cloned and their induction was analyzed, in addition to the OsPR10a gene, at the juvenile and adult stages in response to a wildtype Xoo strain that induces a resistance response (incompatible interaction) and an isogenic mutant Xoo strain that does not (compatible interaction). We found that the adult stage leaves are more competent to express these OsPR1 genes and that the Xa21 locus is required for the highest levels of induction.     

Avian predation on wild and cultured sea urchin <Emphasis Type="Italic">Strongylocentrotus intermedius</Emphasis> in a rocky shore habitat

ABSTRACT:   The present study reports the annual variation in consumption of the sea urchin Strongylocentrotus intermedius by avian predators on a rocky shore where the culture of sea urchins has been conducted. Carrion crow and a few gull species were the most abundant avian predators and consumed a large number of sea urchins. Crows consumed mostly natural sea urchins, approximately 36 kg ww/ha per year on the intertidal rocky bench, but the gull species consumed mostly cultured sea urchins, approximately 100 kg ww/ha per year in the culture area. The seasonal variation in the amount of sea urchins consumed by crows was higher than that by the gull species, presumably because of the difference in foraging behavior in association with the seasonal tidal cycle. The natural sea urchins consumed are an allochthonous input from the subtidal to the intertidal habitat, and thus, crow predation may not affect the natural and the cultured populations of the sea urchin. The gull species consumed much of the cultured sea urchin, and thus, may be regarded as an effective predator causing damage to sea urchin culture. The results suggest that further studies are needed to determine why the gull species selectively feed on cultured sea urchins.     

Suppression of MyoD induces spontaneous adipogenesis in skeletal muscle progenitor cell culture

The degree of intramuscular adipose tissue accumulation is one of the factors affecting meat quality. Accumulation of adipocytes is also observed under the pathological condition of skeletal muscle such as muscular dystrophy and sarcopenia. The origin of adipocytes seen in skeletal muscle is mesenchymal progenitor cells that can give rise to both adipocytes and fibroblasts. In the present study, we demonstrated that siRNA-mediated suppression of MyoD expression in rat skeletal muscle progenitor cell culture, which comprises both myogenic satellite cells and mesenchymal progenitor cells, resulted in diminished myotube formation and an unexpected spontaneous appearance of white adipocytes. Suppressing myomaker expression also resulted in complete absence of myotube formation without reducing MyoD expression, but no adipogenesis was seen in this scenario, indicating that decline in MyoD expression rather than decreased myotube formation is necessary to induce adipogenesis. In addition, spontaneous adipogenesis induced by suppressing MyoD expression in culture was inhibited by the conditioned medium from control culture, indicating that anti-adipogenic factor(s) are secreted from MyoD-positive myogenic cells. These results indicate the presence of regulatory mechanism on adipogenesis by myogenic cells.     

Oral administration of L-citrulline changes the concentrations of plasma hormones and biochemical profile in heat-exposed broilers

We examined the effects of oral administration of L-citrulline (L-Cit) on plasma metabolic hormones and biochemical profile in broilers. Food intake, water intake, and body temperature were also analyzed. After dual oral administration (20 mmol/head/administration) of L-Cit, broilers were exposed to a high ambient temperature (HT; 30 ± 1°C) chamber for 120 min. Oral administration of L-Cit reduced (p < .001) rectal temperature in broilers. Food intake was increased (p < .05) by heat stress, but it was reduced (p < .05) by L-Cit. Plasma levels of 3,5,3′-triiodothyronine, which initially increased (p < .0001) due to heat stress, were reduced (p < .01) by oral administration of L-Cit. Plasma insulin levels were increased by heat exposure (p < .01) and oral L-Cit (p < .05). Heat stress caused a decline (p < .05) in plasma thyroxine. Plasma lactic acid (p < .05) and non-esterified fatty acids (p < .01) were increased in L-Cit-treated heat-exposed broilers. In conclusion, our results suggest that oral L-Cit can modulate plasma concentrations of major metabolic hormones and reduces food intake in broilers.