Habitat management of little terns in Japan’s highly developed landscape

The little tern (Sterna albifrons) is a species of shorebird that nests in colonies on sandy beaches and riverbanks with little vegetation cover. In Japan, the natural breeding habitats of the terns have decreased drastically, and the species is listed under the category “vulnerable” in the Red List of the Government of Japan. To reduce the effects of habitat loss on the terns, conservationists are attempting to create and manage artificial colony sites in highly developed landscapes, such as reclaimed lands located in Tokyo Bay, central Japan. We present the factors that contribute to breeding success for this species and the habitat characteristics related to nest-site selection in the artificial colony sites along Tokyo Bay. Our data show that around 3 ha of a building rooftop without vegetation cover could sustain more than 2000 little tern nests. We found a strong positive relationship between colony size and hatching success, observing that a colony size of more than 100 lowered predation rates of eggs. On sites built upon white crushed-concrete, nest densities were high and predation rates of eggs were low. We also found that feeding rates were affected by foraging habitats, of which the best types were the shoreline of sandy beaches and mud flats. The 40 km dispersal range of the breeding terns, inferred from distribution data, should be considered when establishing a network of the multiple colony sites.     

Fast‐to‐slow shift of muscle fiber‐type composition by dietary apple polyphenols in rats: Impact of the low‐dose supplementation

Our previous studies demonstrated that an 8‐week intake of 5% (w/w) apple polyphenol (APP) in the diet improves muscle endurance of young‐adult rats. In order to identify a lower limit of the dietary contribution of APP to the effect, the experiments were designed for lower‐dose supplementation (8‐week feeding of 0.5% APP in AIN‐93G diet) to 12‐week‐old male Sprague‐Dawley rats. Results clearly showed that the 0.5% APP diet significantly up‐regulates slower myosin‐heavy‐chain (MyHC) isoform ratios (IIx and IIa relative to total MyHC) and myoglobin expression in lower hind‐limb muscles examined (P < 0.05). There was a trend to increased fatigue resistance detected from measurements of relative isometric plantar‐flexion force torque generated by a stimulus train delivered to the tibial nerve (F(98, 1372) = 1.246, P = 0.0574). Importantly, there was no significant difference in the animal body‐phenotypes or locomotor activity shown as total moving distance in light and dark periods. Therefore, the present study encourages the notion that even low APP‐intake may increase the proportions of fatigue‐resistant myofibers, and has promise as a strategy for modifying performance in human sports and improving function in age‐related muscle atrophy.     

Dissolution of polystyrene into p-cymene and related substances in tree leaf oils

We examined the dissolution of polystyrene into p-cymene and related substances to develop an alternative method for the recycling of expanded polystyrene. The dissolving power of p-cymene [212.0 g (100 g solvent)⁻¹] to polystyrene at 50°C compared favorably with those of 2-p-cymenol [156.7 g (100 g solvent)⁻¹], (R)-limonene and its structural isomers [181.7–197.1 g (100 g solvent)⁻¹], and Abies leaf oil [84.7 g (100 g solvent)⁻¹]. The favorable solubility of polystyrene into p-cymene can be explained by the solubility parameter. p-Cymene and polystyrene can be recovered almost quantitatively from the polystyrene solution by simple steam distillation.     

Effect of temperature decrease on oocyte development,sex steroids,and gonadotropin β-subunit mRNA expression levels in female Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis>

To improve understanding of the mechanism of early ovarian development in eels, the effects of water temperature decrease on oocyte development, plasma levels of sex steroids [estradiol 17β (E2), testosterone (T), 11-ketotestosterone (11-KT)], and gonadotropin β-subunit [follicle-stimulating hormone (FSHβ), luteinizing hormone (LHβ)] messenger RNA (mRNA) expression levels were investigated. A total of 27 female Japanese eels Anguilla japonica were divided into initial, control, and test (water temperature decrease) groups. Starting on 22 September 2009, eels in the test group were reared in a tank with gradual temperature decrease from 25°C to 15°C over 39 days, while the control group was maintained at 25°C. The test group accumulated more oil droplets in their oocytes than did the other groups. Levels of sex steroids, especially 11-KT, were higher in the test group. In contrast, FSHβ and LHβ mRNA expression levels were lower in the test group. These results suggest that water temperature decrease only induced an early stage of ovarian development that was partly affected by an 11-KT increase. For further maturation, other environmental factors related to induction of gonadotropin increase appear to be needed.     

Effects of androgen on plasma levels of adrenocorticotropic hormone and cortisol during transportation in goats

Previously, we demonstrated that plasma cortisol (Cor) levels were increased by road transportation in castrated male goats, but the extent of the increase was significantly reduced by 5alpha-dihydrotestosterone (DHT) implantation. This study aims to clarify whether the reduction of Cor secretion by androgen during transportation results from reduced plasma adrenocorticotropic hormone (ACTH). Castrated goats were implanted separately with cholesterol (Cho), testosterone (T) or DHT, followed by transportation. Plasma Cor levels increased during transportation regardless of hormone treatment, but the levels in T and DHT treated animals were lower than those in animals treated with Cho. Plasma ACTH levels also increased during transportation, and those in T treated animals were significantly lower than in those treated with Cho. However, plasma ACTH levels in DHT treated animals varied among the animals and did not differ from those in Cho treated animals. Significant and highly positive correlations between the logarithm of plasma ACTH levels and plasma Cor levels were found in every treatment group. The areas under the regression curves between plasma ACTH levels and plasma Cor levels associated with T and DHT treatments were significantly lower than those with Cho treatment. In conclusion, T was shown to reduce ACTH secretion in response to transportation in castrated goats. However, this suppression of the increase in Cor secretion during transportation by androgen is suggested to be mainly a result of suppression of the responsiveness of the adrenal cortex to ACTH.     

Correlation between skeletal muscle fiber type and free amino acid levels in Japanese Black steers

Free amino acids are important components of tastants and flavor precursors in meat. To clarify the correlation between muscle fiber type and free amino acids, we determined the concentrations of various free amino acids and dipeptides in samples of different muscle tissues (n = 21), collected from 26‐month‐old Japanese Black steers (n = 3) at 2 days postmortem. The proportions of the myosin heavy chain (MyHC), slow (MyHC1) and fast (MyHC2) isoforms were determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). The contents of free amino acids and dipeptides were measured by high performance liquid chromatography (HPLC). The MyHC isoform composition varied among the tissue samples. The MyHC1 proportion ranged from 6.9% ± 3.9% to 83.3% ± 16.7%. We confirmed that there was a strong positive correlation between MyHC1 composition and total free amino acid concentrations, including those for two dipeptides. Among the 31 measured free amino acids and dipeptides, 11 showed significant positive correlations and five showed significant negative correlations with MyHC1 composition. These results suggest that a high MyHC1 content induces high free amino acid contents in bovine muscles possibly because of greater oxidative metabolism. This high level of free amino acids could contribute to the intense flavor of meat that is rich in slow‐twitch fibers.