Extreme winter aggregation of invasive rainbow trout in small tributaries: implications for effective control

Because of their high economic and recreational value, salmonids have been extensively introduced worldwide and are responsible for significant impacts on native ecosystems. However, effective methods for controlling or eradicating introduced populations of salmonids are still limited, particularly in large river systems. Here, we demonstrated that invasive rainbow trout Oncorhynchus mykiss immigrated to and extremely aggregated in small tributaries during the winter, which can be utilized for effective population control. Seasonal census was conducted in 10 small tributaries of the Otofuke River in the Tokachi River basin, central Hokkaido, Japan. Winter abundance was 8–125 times higher than summer abundance in four of the tributaries where water velocities were low. Relatively large individuals (200–350 mm) aggregated in several pools at an unusually high density (>2–3 individuals/m² or 170–440 individuals per pool). Females were common in the small tributaries in the winter, but not in the summer. Therefore, removal of invasive rainbow trout may be best practised in such small tributaries during early winter. Because many stream fishes overwinter in specific, often limited, habitats, more attention should be paid to such winter habits in the effective management of non-native fish species.     

Comparative analysis of complete orthologous centromeres from two subspecies of rice reveals rapid variation of centromere organization and structure

Centromeres are sites for assembly of the chromosomal structures that mediate faithful segregation at mitosis and meiosis. This function is conserved across species, but the DNA components that are involved in kinetochore formation differ greatly, even between closely related species. To shed light on the nature, evolutionary timing and evolutionary dynamics of rice centromeres, we decoded a 2.25‐Mb DNA sequence covering the centromeric region of chromosome 8 of an indica rice variety, ‘Kasalath’ (Kas‐Cen8). Analysis of repetitive sequences in Kas‐Cen8 led to the identification of 222 long terminal repeat (LTR)‐retrotransposon elements and 584 CentO satellite monomers, which account for 59.2% of the region. A comparison of the Kas‐Cen8 sequence with that of japonica rice ‘Nipponbare’ (Nip‐Cen8) revealed that about 66.8% of the Kas‐Cen8 sequence was collinear with that of Nip‐Cen8. Although the 27 putative genes are conserved between the two subspecies, only 55.4% of the total LTR‐retrotransposon elements in ‘Kasalath’ had orthologs in ‘Nipponbare’, thus reflecting recent proliferation of a considerable number of LTR‐retrotransposons since the divergence of two rice subspecies of indica and japonica within Oryza sativa. Comparative analysis of the subfamilies, time of insertion, and organization patterns of inserted LTR‐retrotransposons between the two Cen8 regions revealed variations between ‘Kasalath’ and ‘Nipponbare’ in the preferential accumulation of CRR elements, and the expansion of CentO satellite repeats within the core domain of Cen8. Together, the results provide insights into the recent proliferation of LTR‐retrotransposons, and the rapid expansion of CentO satellite repeats, underlying the dynamic variation and plasticity of plant centromeres.     

Local factors affecting winter habitat use of non-native rainbow trout in a boreal stream in northern Japan

Ichthyological Research - Despite its potential use for population control, the winter ecology of nonnative fishes is still poorly understood due to the difficulty of conducting field surveys. In...     

Synthesis and optimization of 4,5,6,7-tetrahydrooxazolo[4,5-c]pyridines as potent and orally-active metabotropic glutamate receptor 5 negative allosteric modulators

We describe here the design, synthesis and characterization of a series of 4,5,6,7-tetrahydrooxazolo[4,5-c]pyridines as metabotropic glutamate receptor (mGluR) 5 negative allosteric modulators (NAMs). Optimization of the substituents led to the identification of several compounds with good pharmacokinetic profiles, including long half life and high oral bioavailability, in both rats and monkeys. The receptor occupancy test in the rat cortex revealed favorable brain penetration of these compounds. The reprsentative compound 13 produced oral antidepressant-like effect in the rat forced swimming test (MED: 0.3 mg/kg, q.d.).     

Recombinant human progranzyme 3 expressed in Escherichia coli for analysis of its activation mechanism

Gr3 is reported to play an important role in defense against viral infection. Although it is known that Gr3 is synthesized as a proenzyme and activated in the cytotoxic granules of NK cells and CTL, the activation mechanism is not clearly understood. In an attempt to analyze the activation mechanism of human Gr3, a recombinant pro‐Gr3 was expressed in the periplasm of E. coli and purified to homogeneity. On SDS‐PAGE the recombinant pro‐Gr3 showed a slightly higher molecular weight than the enzymatically active Gr3, because the former possesses a small propeptide at its N‐terminal. The recombinant pro‐Gr3 was enzymatically inactive. It could be activated by treatment with cathepsin C, which concomitantly decreased the molecular weight to that of active Gr3. The proteolytic reaction of cathepsin C did not continue after one dipeptide had been removed, indicating that the recombinant pro‐Gr3 had the native conformation without any refolding process. The recombinant pro‐Gr3 would be a valuable tool for analyzing the activation mechanism and exploring other activating enzymes besides cathepsin C.