The ICR/f rat is a recessive-type hereditary cataractous strain. We previously reported that this mutant differs from normal in the composition of lens crystallins.1) Analysis of the cataractous lens crystallins showed remarkable decreases in g-, bB1-and bA3-crystallin contents. Also, the calcium content in the cataractous lenses was about 10-fold higher than in the normal lenses. Two-dimensional electrophoresis of the cataractous lens proteins revealed the loss of b-and acrystallins and the appearance of new polypeptides.The major classes of crystallins are the a-crystallins which are molecular chaperones related to the small heatshock proteins, 2) and the b-and g-crystallins.3) The b-and gcrystallin superfamilies are characterized by four Greek key motifs in their amino acid sequences. The b-crystallins also have amino-and carboxy-terminal extensions designated as "arms". All b-crystallins have N-terminal extensions of 10 to 58 amino acids in length, and the subtype of bB-crystallin has C-terminal extensions of approximately 15 amino acids.3,4) g-Crystallins lack these N-and C-terminals. While b-crystallins form mixtures of homodimers, heterodimers, and higher order oligomers, 5) the native g-crystallins are characterized as monomers.3) It has been hypothesized that the extensions function to stabilize the intermolecular interaction between b-crystallins and to prevent their random aggregation.3) Thus some research has examined the possible function of b-crystallin N-terminal extensions in stabilizing the structure of b-crystallin oligomers. 6,7)Calpain (EC 3.4.22.17) is a non-lysosomal cysteine-protease activated by calcium. The ubiquitous m-and m-calpains, by far the best characterized calpains, are heterodimers comprising distinct but quite homologous 80-kDa "large" Lsubunits and a common 30-kDa "small" S-subunit. On exposure to calcium at concentrations of 5-50 mM (for m-calpain) and 200-1000 mM (for m-calpain), these calpains are activated and partially autolyzed.8) m-Calpain has been found in lenses of all species examined so far. David et al. have reported that the amino acid sequence of the N-terminal of bcrystallins in the insoluble protein fraction of lens from rodent cataractous lenses is very similar to the N-terminal of bcrystallin polypeptides degraded partially by the purified mcalpain. 11,12) This result suggests that endogenous calpain cleaves the N-terminal extension of b-crystallin, and the resulting N-terminal-missing b-crystallins aggregate randomly. Cysteine protease inhibitors suppressed this proteolysis and temporarily prevented the progression of cataract formation caused by various inducers in vitro.13) In addition, incubation of total soluble proteins from young mouse and rat lenses with the purified m-calpain, [11][12][13] or activation of endogenous lens calpain in a soluble fraction by calcium, caused the insolubilization of crystallins and an increase in the turbidity of the fraction. 9) On the other hand, David et al. reported that 120 mM KCl (the concentration in normal lenses)...

Effect of fl uvial and geomorphic disturbances on habitat segregation of tree species in a sedimentation-dominated riparian forest in warm-temperate mountainous region in southern Japan Abstract We investigated habitat segregation and patterns of species diversity of trees in relation to variations in fl uvial and geomorphic disturbances (erosion or sedimentation) along a longitudinal stream gradient from V-shaped valley to alluvial fan and between valley and adjacent hill slopes in a warm-temperate mountainous riparian forest in Kyushu, southwestern Japan. We longitudinally divided the riparian area into four geomorphic zones: V-shaped valley (VV-zone), upper fan (UF-zone), middle fan (MFzone), and lower fan (LF-zone). We surveyed the distribution of tree species (diameter at breast height ≥3 cm) in the four riparian zones and in additional plots on hill slopes (SL-zone) representing the broader, nonriparian forest matrix. Detrended correspondence analysis ordination demonstrated variations in species composition along the longitudinal stream gradient. Species guild analysis based on the detection of the species preferred zone by a bootstrap method revealed a guild structure corresponding to each geomorphic zone. The four riparian zones were differentiated from the SL-zone by having a low proportion of SL-guild species and a high proportion of infrequent species that were characterized by deciduous leaf habit. The LF-zone was the most differentiated and was characterized by low tree density and specialist species established on the fl at and unstable soil surface created by frequent deposition of sediment. The UF-and MF-zones were characterized by a high tree density and species richness (particularly of infrequent species) established on the stable ground surface of a high alluvial terrace. Microsite heterogeneity produced by channel formation may also maintain a high species diversity in the riparian zones.

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