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Fish are exposed to many kinds of environmental stressors and the chances of succumbing to infectious diseases may be increased a result. For example, an acute increase in temperature can induce numerous physiological changes in the body. In the present study, we examined the redox state in response to a severe acute stress resulting from heat shock in teleost coho salmon (Oncorhynchus kisutch). The plasma lipid peroxides levels in fish gradually increased after heat shock treatment. By 2.5 h post-heat stress, plasma glutathione (GSH) levels had decreased, but they had returned to basal levels by 17.5 h post-stress. Plasma superoxide dismutase activities in stressed fish were significantly increased compared with those in control fish at 17.5 h post-stress, but had returned to basal levels by 48 h post-stress. Expression levels of hepatic GSH and heat shock protein 70 gradually increased after heat shock treatment. These results concerning the changing patterns of multiple important redox-related biomarkers suggest that severe thermal stressors can affect the redox state and induce oxidative stress in ectothermal animals, such as fish, in vivo. Hence, manipulation of appropriate thermal treatment may possibly be useful to control fish fitness., Graphical abstract, Highlights • The plasma lipid peroxides levels gradually increased after heat shock. • The plasma glutathione levels had decreased, but they had returned to basal levels. • The plasma superoxide dismutase activities were increased. • The hepatic glutathione and heat shock protein 70 levels gradually increased. • Severe thermal stressors can affect the redox state and might induce oxidative stress.

We investigated the potential for exploiting Stevia rebaudiana stem (SRS) waste as a source of edible plant-based antioxidants finding for the first time that the hot water extract of SRS had significantly higher antioxidant activity against fish oil oxidation than that of the leaf, despite SRS extract having lower total phenolic content, DPPH radical scavenging activity and ORAC values. To locate the major antioxidant ingredients, SRS extract was fractionated using liquid chromatography. Five phenolic compounds (primary antioxidant components in activity-containing fractions) were identified by NMR and HR-ESI-MS: vanillic acid 4-O-β-d-glucopyranoside (1), protocatechuic acid (2), caffeic acid (3), chlorogenic acid (4) and cryptochlorogenic acid (5). Further analysis showed that, among compounds 2-5, protocatechuic acid had the highest capacity to inhibit peroxides formation, but exhibited the lowest antioxidant activities in DPPH and ORAC assays. These results indicate that SRS waste can be used as strong natural antioxidant materials in the food industry.

Angiotensin-I-converting enzyme (ACE) plays a crucial role in the crisis of hypertension. Some peptides that originate from protease hydrolysates are known to suppress ACE activity in vitro and in vivo. Here, we investigated whether trypsin hydrolysate of oyster Crassostrea gigas showed hypotensive activity and ACE inhibition. The hydrolysate significantly suppressed systolic blood pressure and ACE activity in spontaneously hypertensive rats following a one-shot oral administration and a long-term feeding experiment lasting 9 weeks. Each hydrolysate from oyster tissue showed ACE inhibitory activity, indicating the hypotensive effect was due to synergism. One potent ACE inhibitory peptide, Asp-Leu-Thr-Asp-Tyr, was identified from the hydrolysate of the striate muscle, and the peptide exhibited hypotensive activity in vivo. Protease digestion analysis suggested that Asp-Tyr could be the real effector of this penta-peptide in vivo.

Growth in fish is regulated by the growth hormone (GH)-growth hormone receptor (GHR)-insulin-like growth factor-1 (IGF-1) axis. However, the effect of severe acute stressors on the GH-IGF-1 axis in fish is not well understood. The present study determined the changes in mRNA expression of growth-related genes gh, ghr, and igf and the redox state in coho salmon (Oncorhynchus kisutch), in response to severe acute stress. Severe stress consisted of exposure to heat shock (adequate rearing temperature +11 °C for 2 h). The plasma expression patterns of redox state-related biomarkers, such as glutathione, lipid peroxides, and superoxide dismutase, in response to heat shock suggest that heat shock might induce oxidative stress in fish. After exposure to heat shock, ghr mRNA levels in the pituitary glands and liver increased, whereas levels decreased 48 h post-stress. Hepatic igf1 mRNA expression levels gradually decreased in response to the stressor. On the other hand, the pituitary gh mRNA expression did not change in response to the stressor. These findings showed that a heat shock-induced oxidative stress could affect the redox state and the expression of several growth-related genes in coho salmon. The results of this study also suggest that the expression of several growth-related genes in fish may be affected differently by the types and strength of stress.

The effects of a hot water extract of the stem of Stevia rebaudiana on the smooth muscle of isolated guinea pig ileum were investigated. The butyl alcohol layer of the extract antagonized the contractions of the isolated guinea pig ileum induced by histamine (1 x 10(-5) M) and acetylcholine (1 x 10(-5) M) in a concentration-dependent manner. The butyl alcohol layer of the extract also showed inhibition of CaCl(2) (1 x 10(-3)-3.8 x 10(-1) M)-induced contractions. The antagonism of the extract was considered to be non-specific, but this action might be related to an influx of extracellular Ca(2+). With column chromatography preparation, the active component was assumed to be as stevioside. The antagonistic effects exerted by the stem extract of Stevia rebaudiana contributed to the gastroprotective activity of the extract in animals fed dietary histamine.

Stevia extract was made from stevia stem by extraction with boiling water and fermentation. The protective effect of a Stevia extract on rainbow trout (average weight, 12 g) fed 1% of dietary histamine for 4 weeks was investigated. Administration of dietary histamine to trout did not result in a reduction in growth rate or feed consumption but caused a gastric abnormality, e.g. exfoliation of the mucosal epithelium and atrophy of mucosal lamina propria. Stevia extract protected gastric tissue from histamine-induced damage. Pepsin activity in gastric fluid increased and liver alpha-tocopherol content was reduced after histamine treatment, but Stevia treatment prevented these abnormalities. The results suggest that the stevia extract might protect the rainbow trout stomach from histamine toxicity.

The present study's aim was to investigate change of fatty acid composition of white adipose tissue with increasing age in Syrian hamster fed continuously alfalfa (LU) or cereal based diet (F2). A total of 43 Syrian hamsters with male and female, 22 head maintained with mating between sibling in a close herd fed F2 (GN) and 21 head selected for long-term for large number of weaning pups per a mater using GN fed LU (ALF), were used. Fatty acid composition in adipose tissues taken from the back leg subcutaneous depot, periphery of kidney and reproductive organs at 3, 8 and 13 weeks of age were determined by using a gas chromatograph. Carbon (C)18:0 in GN tended to decrease and C18:1 increased significantly with increasing age, suggesting that Δ9-desaturase had related adaptively. C18:3 in ALF increased significantly with increasing age. The present results indicate that, although the composition in unsaturated fatty acid (USFA) in both herds was different, the ratio of USFA to saturated fatty acid increased with increasing age suggesting that USFA in GN fed F2 was at a high level compared with in ALF fed LU.

Information on the metabolism of exogenous histamine in fish is of much concern regarding the effect of dietary histamine on fish. Histamine catabolic enzymes, diamine oxidase and histamine N-methyl transferase were measured in the tissues of rainbow trout. Diamine oxidase was detected in the stomach, pylorus caeca and intestine. Histamine N-methyl transferase was detected only in the liver. A change in the contents of histamine and its metabolites was observed in the tissues of rainbow trout after oral administration of histamine. A large amount of imidazole acetic acid was observed in the serum, kidney, liver and muscle. On the other hand, 1-methyl histamine was detected only in the liver. Histamine and its metabolites, imidazole acetic acid and 1-methyl histamine were metabolized and diminished within 48 hr in all tissues. These results showed that histamine was metabolized by two metabolic routes in rainbow trout. One is the main pathway producing imidazole acetic acid by intestinal diamine oxidase and the other is the complementary pathway producing 1-methyl histamine by liver N-methyl-transferase.

Aim: The angiotensin-I-converting enzyme (ACE) inhibitory and antihypertensive activities of wakame hydrolysates have been investigated in several studies. Methods: Wakame (Undaria pinnatifida) was hydrolyzed using 17 kinds of proteases and the inhibitory activity of the hydrolysates for ACE was measured. Of these hydrolysates 4 with potent ACE inhibitory activity were administered singly and orally to spontaneously hypertensive rats (SHR). Results: The systolic blood pressure of SHR decreased significantly after single oral administration of protease S ‘Amano’ and proleather FG-F hydrolysates (10 mg protein/kg body weight). In a long-term feeding experiment, 7-week-old SHR were fed standard chow supplemented with protease S ‘Amano’-derived wakame hydrolysates for 10 weeks. In SHR fed the 1 and 0.1% wakame hydrolysates, elevation of systolic blood pressure was still significantly suppressed for 7 weeks. Conclusions: The hydrolysates derived from wakame by protease S ‘Amano’ have a powerful ACE-inhibitory activity (IC50 = 86 µg protein/ml) and were effective in spite of their slight bitterness as ‘physiologically functional food’ with antihypertensive activity.

SUMMARY: Changes in distribution of dietary α-tocopherol at 100 mg per 100 g of diet to organic tissues and to serum lipoproteins were investigated on Japanese flounder Paralichthys olivaceus. α-tocopherol had been transported to and preserved more positively in the gonad during the reproduction period. During maturity serum α-tocopherol had partly combined with the vitellogenin-like parts that diminished after the spawning period. Conversely, serum α-tocopherol after the spawning period partly combined with lipoprotein that increased after the spawning period. The prosperity and decline of different types of lipoproteins induced α-tocopherol distribution changes at the end of the spawning period.

ステビア茎粗抽出物は強い抗酸化活性を示した.その活性は抗酸化指数で葉に比べ5倍程度高く,現在ほとんど利用されていない茎の新たな利用価値を提示した.ステビア抽出末はマイワシ油およびリノール酸に対して100ppmの添加で抗酸化効果を発現した.その効果は同濃度のBHT,α-Tocに匹敵する強さを示した.ステビア抽出末はα-Tocおよびクエン酸を併用することにより抗酸化効果が増強された.ステビア抽出末の抗酸化有効成分は主として透析外液(分画分子量500)に存在した.外液濃縮物を逆相カラムクロマトグラフィー.薄層クロマトグラフィーで分画し,複数の有効画分を認めた.その多くは,ポリフェノール化合物であったが,最も強い効果を示した成分にはカリウムが高濃度で存在した.

ステビア抽出末に強い抗酸化活性を認め,その活性の最も強い画分には高濃度のカリウムの存在が認められたことから,カリウム塩を含む9種類の無機塩の抗酸化効果を調べた.その結果,K2CO3,KHCO3,Na3PO4,Na2CO3およびKClにリノール酸に対する抗酸化効果を認めた.NaCl,CaCl2,MgCl2およびMgSO4には抗酸化効果は認められなかった.K2CO3は60ppm(カリウム濃度として)以上の濃度で抗酸化効果を示し,最も強力であった.α-Tocと併用することでその効果は向上したが,クエン酸とでは向上は認められなかった.ステビア抽出末の抗酸化作用機構について,フリーラジカル捕捉効果,スーパーオキシド捕捉効果および金属キレート作用について調べた.ステビア抽出末の抗酸化効果は主としてフリーラジカルの捕捉効果に因るもので,スーパーオキシドの消去能も補足的に関わっているものと考えられた.

Lipid and fatty acid compositions of cultured and wild coho salmon were compared. Tri-glyceride (TG) was the main component of lipids in all the tissues investigated. TG contents of ordinary and dark muscles (ca. 90%) were higher than those of liver, gonad and viscera (50-70%). The main fatty acids of cultured fish were C16:0, C18:1, C20.3 and C22:6, while those of wild fish were C16:0, C18:1, C20:1, C22:1 and C22:6. The fatty acids such as C20:1 and C22:1 were higher in wild fish than in cultured fish. Monoenoic fatty acids were the main components of fatty acids in ordinary muscle, dark muscle, viscera, integument, head and bone, and testis. Polyenoic fatty acids were higher in liver and ovary than in the other tissues.