Proteolytic degradation of myofibrillar components by carp cathepsin L

Carp cathepsin L, which is the best candidate to produce textural change in the arai-treated carp fillet, exhibited maximum hydrolytic activity for Z-Phe-Arg-MCA and soluble casein at pH 5·0–5·5. The proteolytic action of the enzyme was evaluated by complete degradation of various carp myofibrils at pH 5·0 over 30 min and by potent degradation of the same proteins at pH 5·5–6·0 over 20 h. All myofibrillar components were partially degraded by the enzyme at pH 6·5–7·0, but varying amounts of them remained undegraded after 20 h. These findings indicate that carp cathepsin L degrades not only carp myofibrillar components but also their resultant products between pH 5·0 and 7·0 and that it markedly acts on myosin heavy chain, α-actinin and troponin-T and -I. Carp cathepsin L likely contributes to postmortem muscle tenderisation of carp fillet over an extensive pH range during storage. © 1998 SCI.     

Juvenile masu salmon in a regulated river

We examined the relationship between the physical environment and habitat use of juvenile masu salmon, Oncorhynchus masou, in the Nobori River in Hokkaido, Japan to provide a perspective for the conservation of fish habitat in regulated streams. The study was undertaken during the autumn and winter, with an emphasis on the hierarchy of three spatial scales: microhabitat, channel‐unit and reach scales. The microhabitat‐scale analysis indicated juvenile masu salmon preferred a midstream habitat type, with a greater depth (Avg. ± SD: 35.4 ± 14.2 cm) and high (43.4 ± 23.1 cm s^?1) and uniform current velocities during the autumn, and a channel margin habitat type with a moderate current (about 20 cm s^?1) and submerged cover during winter. In addition, different cover types have different roles in determining juvenile salmon distributions during winter. Grass cover had extremely high carrying capacities, whereas coarse substrate cover provided winter habitat for larger juvenile salmon. Channel‐unit scale analyses showed that abundance of juvenile salmon tended to be higher in pools than runs in the autumn through winter. Reach‐scale analysis showed that abundance and mean body length of juvenile salmon significantly differed between differently regulated reaches during winter, associated with the dominant cover type in each reach. This study demonstrated that the habitat conditions determining juvenile masu salmon distribution differ according to the season and scale of analysis. Therefore, for conservation of fish communities, it is important to evaluate and conserve or create fish habitats in regulated reaches, with a focus on the hierarchy of spatial scales and seasonal differences. Copyright © 2007 John Wiley & Sons, Ltd.     

Role of matrix metalloproteinase-7 in angiogenesis associated with age-related macular degeneration

To investigate the possible role of matrix metalloproteinase-7 in choroidal neovascularization associated with age-related macular degeneration, immunoelectron microscopy using ultrathin frozen sections and conventional transmission electron microscopy were performed in subfoveal fibrovascular membranes from patients with age-related macular degeneration. immunoelectron microscopy revealed that matrix metalloproteinase-7 was expressed within basal laminar deposits and amorphous materials around the retinal pigment epithelial cells. The results support a role for matrix metalloproteinase-7 in the development of choroidal neovascularization in age-related macular degeneration.     

Crack-tip dislocation nanostructures in dynamical fracture of fcc metals : Amolecular dynamics study

Dynamic behavior of dislocations near a crack tip in an fcc lattice, studied through parallel molecular dynamics (MD) simulation with visualization facilitated by newly developed software, reveals three-dimensional features of dislocation nucleation and subsequent entanglement. Results obtained for copper and aluminum show multiple emissions of dislocation loops from the crack tip and incipient evolution of plastic deformation during crack extension. 〈100〉 dislocations are found to be emitted in aluminum at zero temperature, which however are unstable and subsequently disassociate into bundles of \langle110\rangle dislocations. This revised version was published online in June 2006 with corrections to the Cover Date.     

The effect of transition metal stearates on the photodegradation of polyethylene

The effect of a series of transition metal (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) stearates on the photodegradation of a high-density polyethylene was examined mainly by changes in the carbonyl IR absorption of the sample films. Electron spin resonance (ESR) and luminescence spectra of the samples containing the copper stearate were measured. The photochemical reaction of the copper stearate was examined by IR and UV-visible spectroscopies. The iron stearate was the most effective at an early stage of the photodegradation of the polymer, and vanadium and manganese stearates accelerated it, while the copper stearate retarded it. The other metal stearates showed no applicable effect on the photodegradation. The relative intensity of the ESR spectra of the photoirradiated samples and that of the emission spectra of the unirradiated samples at ca. 350 nm decreased with increasing concentration of the copper stearate. An absorption peak at 1580 cm^?1 decayed, and a new peak at 1740 cm^?1 appeared with photoirradiation of the copper stearate. Absorption peaks of the copper stearate at 252 and 665 nm decayed also rapidly with photoirradiation of the copper stearate in THF solution. The results suggest that one of the main retardative functions of the copper stearate in the photodegradation of polyethylene was an ultraviolet absorber.     

Low-temperature thermoelectric properties of α- and β-Zn4Sb3 bulk crystals prepared by a gradient freeze method and a spark plasma sintering method

The low temperature thermoelectric properties of Zn₄Sb₃ samples prepared by the gradient freeze (GF) method and sintering have been characterized. With decreasing temperature a dramatic rise in the thermal expansion is observed associated with the structural transition from β- to α-phase; Δl/l=2.8×10⁻⁴ at T_s^GF=257.4 K for GF and Δl/l=1.6×10⁻⁴ at T_s^S=236.5 K for sintered samples. Enhancement is observed in electrical conductivity and p-type thermopower at T_s^GF and T_s^S, while a reduction is observed in the magnetic susceptibility. The GF sample exhibits higher thermoelectric performance than the sintered sample. The power factor of the α-phase in the GF sample is twice as large as that of the β-phase; it exceeds 20 μW/cm·K² between 120 and 240 K, indicating that the α-phase Zn₄Sb₃ is one of the prime candidates for thermoelectric materials for cryogenic use.