Relationships between body size and secondary sexual characters,and sperm characters in male Dolly Varden char (Salvelinus malma)

In Salmonidae, subordinate males are exposed to higher risks of sperm competition than dominant males and thus are expected to improve the sperm characteristics (sperm concentrations, sperm velocity and sperm longevity). In this study, we investigated the relationships between body size and secondary sexual characters (breeding colour, hump height and snout length), and sperm characteristics of one‐year‐old (newly matured) Dolly Varden char. Small males displayed higher sperm concentrations than large males. Moreover, males with dull breeding colours, but not with lesser snout length and hump height, displayed an increased sperm velocity compared to males with bright colours, suggesting a trade‐off between sperm quantity and the investment in breeding colour. In addition, sperm longevity decreased as sperm swimming velocity increased. These findings indicate that small males with dull breeding colours improve the quantity and quality of their sperm to a great extent to enhance their chances of reproductive success.     

Potential negative impacts of introduced rainbow trout on endangered Sakhalin taimen through redd disturbance in an agricultural stream, eastern Hokkaido

Nomoto K, Omiya H, Sugimoto T, Akiba K, Edo K, Higashi S. Potential negative impacts of introduced rainbow trout on endangered Sakhalin taimen through redd disturbance in an agricultural stream, eastern Hokkaido.
Ecology of Freshwater Fish 2010: 19: 116–126. © 2009 John Wiley & Sons A/S
Abstract –  Sakhalin taimen ( Hucho perryi ) populations have decreased in Hokkaido, northernmost Japan, primarily because of overexploitation and habitat degradation. Here we document another threat to this species, that of spawning redd superimposition by artificially introduced rainbow trout ( Oncorhynchus mykiss ). Sakhalin taimen and rainbow trout are the only spring-spawning salmonid species in Hokkaido. In 2006–2008, spawning activities of both these species were observed in a Hokkaido stream, and it was determined that their spawning periods overlapped during mid-late April. They also spawned at similar water velocities, depths and substrate compositions. Although female Sakhalin taimen were larger than female rainbow trout, their egg burial depths were nearly identical. During the observation period, rainbow trout redds were approximately five times more abundant than Sakhalin taimen redds, and about 30% of the observed Sakhalin taimen redds were superimposed by rainbow trout redds. The high degree of spatial and temporal overlap in spawning, the similar egg burial depths of both species, and the high proportion of superimposed redds suggest that the introduced rainbow trout impact the endangered Sakhalin taimen in Hokkaido, and possibly, in other areas where the two species occur together.     

Prevalence of Dirofilaria immitis infection in living raccoon dogs assessed by hematological examination

The prevalence of Dirofilaria immitis in free-ranging raccoon dogs (Nyctereutes procyonoides viverrinus) was examined in the southeast region of Kanagawa Prefecture, Japan, using a rapid immunomigration (RIM) test kit. Between April 2007 and March 2010, we examined 108 raccoon dogs rescued and housed by the Kanazawa Zoological Garden. D. immitis infection was found in 8 (7.4%) raccoon dogs. This is the first report to reveal the prevalence of D. immitis infection in living raccoon dogs. The prevalence of the infection was lower than previously reported values obtained on postmortem examination. One reason might be that the present study included young raccoon dogs infected with immature worms. Significant high-risk areas of D. immitis infection in the raccoon dogs were not observed.     

ROS-generating mitochondrial DNA mutations can regulate tumor cell metastasis

Mutations in mitochondrial DNA (mtDNA) occur at high frequency in human tumors, but whether these mutations alter tumor cell behavior has been unclear. We used cytoplasmic hybrid (cybrid) technology to replace the endogenous mtDNA in a mouse tumor cell line that was poorly metastatic with mtDNA from a cell line that was highly metastatic, and vice versa. Using assays of metastasis in mice, we found that the recipient tumor cells acquired the metastatic potential of the transferred mtDNA. The mtDNA conferring high metastatic potential contained G13997A and 13885insC mutations in the gene encoding NADH (reduced form of nicotinamide adenine dinucleotide) dehydrogenase subunit 6 (ND6). These mutations produced a deficiency in respiratory complex I activity and were associated with overproduction of reactive oxygen species (ROS). Pretreatment of the highly metastatic tumor cells with ROS scavengers suppressed their metastatic potential in mice. These results indicate that mtDNA mutations can contribute to tumor progression by enhancing the metastatic potential of tumor cells.     

Identification of Antiviral Agents Targeting Hepatitis B Virus Promoter from Extracts of Indonesian Marine Organisms by a Novel Cell-Based Screening Assay

The current treatments of chronic hepatitis B (CHB) face a limited choice of vaccine, antibody and antiviral agents. The development of additional antiviral agents is still needed for improvement of CHB therapy. In this study, we established a screening system in order to identify compounds inhibiting the core promoter activity of hepatitis B virus (HBV). We prepared 80 extracts of marine organisms from the coral reefs of Indonesia and screened them by using this system. Eventually, two extracts showed high inhibitory activity (>95%) and low cytotoxicity (66% to 77%). Solvent fractionation, column chromatography and NMR analysis revealed that 3,5-dibromo-2-(2,4-dibromophenoxy)-phenol (compound 1) and 3,4,5-tribromo-2-(2,4-dibromophenoxy)-phenol (compound 2), which are classified as polybrominated diphenyl ethers (PBDEs), were identified as anti-HBV agents in the extracts. Compounds 1 and 2 inhibited HBV core promoter activity as well as HBV production from HepG2.2.15.7 cells in a dose-dependent manner. The EC₅₀ values of compounds 1 and 2 were 0.23 and 0.80 µM, respectively, while selectivity indexes of compound 1 and 2 were 18.2 and 12.8, respectively. These results suggest that our cell-based HBV core promoter assay system is useful to determine anti-HBV compounds, and that two PBDE compounds are expected to be candidates of lead compounds for the development of anti-HBV drugs.     

Granulocyte colony-stimulating factor has no adverse effects on atherosclerotic lesions in high cholesterol-fed miniature Swine

Granulocyte colony-stimulating factor (G-CSF) is widely used to mobilize peripheral blood stem cells, and expected to restore cardiac function for patients with coronary artery diseases as a consequence of progression of atherosclerosis. Safety issues related to the administration of G-CSF to these patients, however, are still under study. The animal model for atherosclerosis was produced by feeding miniature swine a high-cholesterol diet for 3 months. G-CSF (5 or 10 microg/kg/day) was given to the animal model by daily subcutaneous injections for 10 days and 20 main arteries were evaluated pathologically. In addition, the general toxicological effects were studied on clinical signs, body weight, hematology, blood chemistry and pathology. In the G-CSF-treated groups, a variety of changes related to the major pharmacological activity of G-CSF including an increase in white blood cell (WBC) counts were observed. In many arteries, atherosclerotic lesions similar to Type I-V of the proposed classification by the American Heart Association were observed. No effects of the G-CSF treatment were seen on the histopathological findings, incidence, severity or distribution of atherosclerotic lesions. In addition, no infiltration of neutrophils to the lesions was observed. These findings suggest that the administration of G-CSF causes neither exacerbation or modification of atherosclerotic lesions nor adverse changes despite that a sufficient increase in WBC counts could be achieved in the peripheral blood.