Growth hormone secretion during longterm incubation of the pituitary of the Japanese eel,Anguilla japonica

Growth hormone (GH) secretion from organ-cultured pituitaries of the eel (Anguilla japonica) was studied during incubation in a defined medium for 2 weeks, using a homologous radioimmunoassay which does not distinguish between the two molecular forms of eel GH. The total amount of GH secreted increased gradually during the incubation period; so that the amount of GH released on day 14 was about 30 times greater than that on day 1. On day 14, the proportion of GH released relative to the total amount of GH present (the sum of GH released into the medium and residual content in the pituitary) was 96% and the amount produced on day 14 was 4 times greater than the content in the unincubated pituitary. Somatostatin (SRIF, 1.8 × 10^-7 M) inhibited the increase in GH release. On day 7, the proportion of GH released by pituitaries treated with SRIF (28%) was less than that released by the control pituitary (91%). There was no significant difference in GH release between the pituitaries incubated in isotonic medium (300 mOsm) and those in hypotonic medium (240 mOsm) for 2 weeks except for the first 3 days, when the pituitaries in hypotonic medium secreted significantly greater amounts of GH than those incubated under isotonic condition. Hypertonic medium (350 mOsm) had no effect on GH release except for significant inhibition on days 6 and 14. When secretion of the two forms of GH (GH I and II) was examined after separation by polyacrylamide gel electrophoresis followed by densitometry, slightly more GH I tended to be secreted than GH II during the culture period, although the effects of SRIF and osmolality of the media on GH I release were similar to those on GH II. It is concluded that GH secretion and production in the eel is mainly under the inhibitory control of hypothalamus, and that osmolality has a minimum influence on the GH release.     

Distribution of adipocyte-related cells in skeletal muscle of rainbow trout Oncorhynchus mykiss

Adiponectin is one of the adipokines secreted mainly from adipocytes in mammals. In rainbow trout, however, adiponectin is highly expressed in skeletal muscle. Although it has been suggested that fish skeletal muscle contains adipocytes, their endocrine function and distribution are poorly understood. Recently, an EST analysis of rainbow trout found that heart-type fatty acid binding protein (H-FABP), a member of the intracellular fatty acid binding protein family, encodes an adipose-specific gene. In this study, we produced anti-adiponectin and H-FABP antibodies and investigated the distribution of adipocytes and related cells in skeletal muscle of rainbow trout. The adiponectin signal was detected at around 75 kDa in muscle in Western blotting. Since the molecular mass of rainbow trout adiponectin is around 25 kDa, this 75 kDa band would be a trimer. For H-FABP, the signal band was detected at around 15 kDa. Immunohistochemistry of skeletal muscle sections indicated that adiponectin and H-FABP signals were present outside of muscle cells and throughout the muscle tissues, suggesting the existence of adipocyte-related cells in these regions. These results will contribute to our understanding of energy metabolism in fish skeletal muscle.     

Accumulation of gamma-oryzanol in teleost

Japanese people consume crop bran, which contains relatively high amounts of gamma-oryzanol (ORZ), as foodstuffs and food materials. We have recently confirmed that ORZ inhibits NF-κB activation, activates peroxisome proliferator-activated receptor gamma (PPARγ), and increases plasma adiponectin levels. ORZ is therefore expected to improve lipid and carbohydrate metabolisms and various inflammatory diseases, i.e., metabolic syndrome including type 2 diabetes. ORZ administration also allowed fish, such as rainbow trout, yellowtail, and red sea bream, to accumulate protein through enhancement of lipid and carbohydrate metabolisms. In the present study, we have investigated ORZ accumulation levels in mouse and rainbow trout administered ORZ-containing feed. Although mouse muscle and liver hardly contained ORZ, muscle tissues of every fish species accumulated higher amounts of ORZ. These findings suggest that rainbow trout, red sea bream, and yellowtail accumulate ORZ in muscle.     

Microbial and chemical properties of <Emphasis Type="Italic">aji-no-susu</Emphasis>, a traditional fermented fish with rice product in the Noto Peninsula,Japan

Aji-no-susu is a Japanese fermented fish product prepared from salted horse mackerel Trachurus japonicus, and cooked rice. We studied the organic acid and free amino acid contents and microflora in 12 aji-no-susu products to clarify their features as a lactic-acid-fermented food. Salinity of the samples was approximately 7.0% (rice portion) and 6.0% (fish portion) (w/w). Water activity was approximately 0.9, and pH was approximately 4.4 and lower. In the rice portions, lactic acid content was very high (57 mg/g sample). The predominant amino acids were alanine (2.3 mg/g rice portion) and lysine (2.1 mg/g). In the case of long-fermented (4 and 12 months) aji-no-susu, a high content of gamma-aminobutyric acid (GABA, 1.5 and 1.4 mg/g) was detected. Total viable counts in rice and fish portions were 7.7 and 7.4 log colony-forming units (cfu)/g, respectively. The number of lactobacilli in the rice and fish portions was 7.3 and 7.1 log cfu/g, respectively. Yeasts were detected in eight samples. Furthermore, acid-tolerant lactic acid bacteria (LAB) (Lactobacillus plantarum), GABA-producing LAB (Lactobacillus sp.), and halophilic or halo-tolerant yeast (Debaryomyces hansenii) were isolated and identified. Results in this study indicate that aji-no-susu is a typical traditional lactic-acid-fermented fish product.     

Effect of Lherzolite on Chemical Fractions of Cd and Zn and their Uptake by Plants in Contaminated Soil

Immobilizing materials such as lherzolite could reduce metal bioavailability but the effectiveness of lherzolite on the extractability and bioavailability of cadmium (Cd) and zinc (Zn) is rarely investigated. We conducted a greenhouse experiment to investigate the effect of 5% application of lherzolite to a contaminated soil on the chemical fractionation of Cd and Zn and their uptake by radish (Raphanus sativus L.) and Japanese mustard spinach (Brassica rapa L. var. perviridis). Both plants were grown in a highly contaminated (with Cd and Zn) sandy loam soil. Plants were cultivated consecutively three times in the same pots. After the third cultivation, soil samples were collected and analyzed by sequential extraction procedure into five operationally defined fractions (F1—exchangeable, F2—carbonate-bound, F3—oxides-bound, F4—bound with organic matter, and F5—residual). Addition of lherzolite to soil decreased 50% of exchangeable (F1) Cd but it increased the carbonate (F2), oxide (F3), and organic (F4) fraction Cd. For Zn, application of lherzolite resulted into the reduction of both F1 (87%) and F2 (33%) fractions but it increased the F3, F4, and F5 fractions. The reduction in exchangeable fraction of Cd and Zn in the soil resulted in higher plant growth and lower concentrations of both Cd (64% to 92%) and Zn (78% to 99%) in plant tissues of both plant species grown. We may thus conclude that application of lherzolite resulted into lower availability of these metals in the soil leading to lower uptake of Cd and Zn by plant roots, lower toxicity, and ultimately higher plant growth.     

Effects of the feeding of wild Yeso sika deer (Cervus nippon yesoensis) on the prevention of damage due to bark stripping and the use of feeding sites

Feeding sites for wild Yeso sika deer around Lake Akan, Japan, were established. Effects on the number of deer using the feeding sites, the prevention of bark stripping damage, the amount of feeding, and eating time in a 5‐year period (1999–2003) were evaluated. The number of deer using feeding sites increased with years during the feeding period. The damaged tree ratio after the initiation of feeding markedly decreased compared with 16.5% before the initiation of feeding. After the start of feeding, there were no trees with damage the entire circumference. According to tree species, the number of damaged trees of Ulmus laciniata Mayr as a percentage of all investigated trees was high (5.2%). The total amount of beet pulp feeding increased with the feeding year, showing 4.5‐fold increase. At feeding sites in deer culling, eating behavior was observed during the night. The preventive effects on bark stripping damage continued during the 5‐year feeding period. However, with the course of feeding years, the number of deer using feeding sites and the level of feeding increased.