Maternal antibody passively transferred interferes with rabies vaccination in hamsters

Transference and interference of maternal immunity to offspring after rabies vaccination were studied in hamsters. Females were vaccinated or not before mating and offspring were vaccinated at the age of 7, 14, 21 and 30 days. Other pups were maintained as controls. Thirty days after vaccination pups were challenged intracerebrally with CVS virus. Mouse neutralization tests were used to verify antibody titers. Mortality of 97.0, 76.9, 60.9 and 24.0% was observed in pups vaccinated at 7, 14, 21 and 30 days respectively, born from vaccinated dams, while in pups from non-vaccinated dams, mortality was 51.4, 28.6, 8.7 and 0.0%. Statistically significant associations were found between mortality and age at vaccination, by simple linear regression with y=-3.1169x + 120.8 (p = 0.008; r2=0.98) for litters vaccinated and born from vaccinated dams and y=-2.2541x + 62.7495 (p = 0.03; r2=0.93) for pups vaccinated and born from non-vaccinated dams. Immunological response to vaccination in pups born from vaccinated mothers was delayed 11 days, when compared to that observed in pups of non-vaccinated mothers.     

Salmonella contamination in commercial layer feed in Japan

A total of 4,418 samples of commercial layer feeds obtained in 1998 were investigated for the presence of salmonellae. A total of 146 strains of salmonellae which consisted of 32 serovars, including 20 strains of Salmonella Enteritidis, were isolated from 143 feed samples.     

Root and stem rot of chrysanthemum caused by five <Emphasis Type="Italic">Pythium</Emphasis> species in Japan

Root and stem rot with wilt of above ground parts of cultivated chrysanthemums was first found in Ibaraki, Toyama and Kagawa prefectures, Japan in 2002 and 2003. Pythium species were isolated from the diseased tissues and identified as P. dissotocum, P. oedochilum, P. sylvaticum, P. ultimum var. ultimum and asexual strains of P. helicoides based on their morphologies and sequences of rDNA-ITS region. All the Pythium species were strongly pathogenic to chrysanthemums in pot conditions and were reisolated from the inoculated plants. Because Pythium root and stem rot of chrysanthemum has never been reported in Japan, we propose that this is a new disease that can be caused by the five Pythium species.     

Characterizing Submergence Survival Strategy in Rice Via Chlorophyll Fluorescence

Rice plants cope with flash floods using either an ‘escape strategy’ involving rapid shoot elongation or a ‘quiescence strategy’ involving survival underwater with minimal activity. To clarify the differences in the response of leaf photosynthesis properties to conditions during and after submergence, two rice cultivars were compared: a non‐shoot‐elongating cultivar IR 67520‐B‐14‐1‐3‐2‐2 (IR67520) and a shoot‐elongating cultivar IR72442‐6B‐3‐2‐1‐1 (IR72442). Twenty‐three‐day‐old seedlings were submerged in 80‐cm‐deep water for 14 days. During submergence, the chlorophyll contents of the upper fully expanded leaf (5th leaf) and newly developed leaf later (6th leaf) and the maximal quantum yield of photosystem II (F_v/F_m) of the fifth leaf decreased earlier in IR72442 than in IR67520. In the submerged sixth leaf, F_v/F_m was higher in IR72442 than in IR67520 at early measurement. Although F_v/F_m of the sixth leaf in submerged IR67520 increased substantially from 2 days post‐submergence, IR72442 decreased because of leaf chlorosis. Therefore, a non‐shoot‐elongating cultivar coped with submergence by inhibiting photodamage and maintaining high chlorophyll content in the leaves. The shoot‐elongating cultivar was able to maintain the photosynthetic capacity of the newly developed leaf during submergence by prompt reduction of chlorophyll and chlorophyll fluorescence in the leaf that developed before submergence.     

Heat budget and statistical analysis of the relationship between stream temperature and riparian forest in the Toikanbetsu River basin, northern Japan

Riparian forests greatly influence aquatic ecosystems by providing shade cover, which controls water temperature and limits primary production. We examined the relationship between forest cover and summer stream temperature in northernmost Japan. Heat budget and statistical analyses were employed and the results were compared. Heat budget analysis revealed that the water temperature would decrease almost linearly from 29°C to 25°C with an increase in forested reaches along a 3.2 km stretch of the river. Multiple regression analysis by the stepwise method chose only open channel length as a variable to explain the variation in maximum stream temperature. A sharp increase in stream temperature was noted when riparian forest cover was removed in short lengths, of up to 1.0km; this increasing trend gradually flattened as the length of open stretch increased. Thus, even small openings in the riparian canopy resulted in drastic rises in summer stream temperature. The maximum summer temperatures estimated by the two methods were coincided, and can therefore be accurately estimated by regression analysis. Retrospective analysis based on the regression equation showed that the maximum summer temperature in 1947 was 6°C lower than at present, and that a sharp increase occurred from 1947 to 1960, a period of rapid expansion of agricultural land development in the watershed.     

Investigation of relationships between cell and pulp properties in Eucalyptus by examination of within-tree property variations

 Relationships between cell and pulp properties were investigated by examining the within-tree property variations in Eucalyptus camaldulensis and Eucalyptus globulus. Properties investigated included proportions of ray and axial parenchyma, thickness of cell walls and cell wall percentages. The characteristics of the ray and axial parenchyma (their proportions and wall thickness) were found to have a significant influence on all measured pulp properties, including paper strength properties. Multiple regression of pulp properties in relation to cell properties revealed that nearly all measured pulp properties were explained by cell properties at the 1% significance level. It was concluded, therefore, that all cell types are important for predicting pulp properties, and it is strongly recommended that tree breeding programs for Eucalyptus include the measurement of all cell types. Received 6 July 1999     

Effect of shoot size and phenological variation of host plants on the spatial patterns of cynipid galls

The effects of shoot size and differences in budburst phenology ofQuercus serrata trees on the spatial patterns of galls were investigated for two cynipid species: the sexual generation ofAndricus moriokae and the agamic generation ofAphelonyx glanduliferae. There were marked differences in budburst phenology, but these did not affect the gall density on the tree. The galls of both cynipids showed a contagious distribution in their respective trees, but different abundance patterns under high gall density. The mean number of galls ofA. glanduliferae over a shoot size range was positively correlated with shoot size. More galls ofA. moriokae appeared on larger shoots on trees on which many buds had started growing before oviposition by the agamic adults. In the case of a tree on which a few buds had burst by the time of oviposition, the mean numbers ofA. moriokae galls on shoots of particular size ranges depended on the frequency of shoots in the size class. These results suggest that, although these cynipids prefer to attack larger shoots within a host tree, they may exhibit plasticity in their preference in response to changes in budburst phenology of the host plant relative to the time of oviposition.     

Effects of light and microsite conditions on tree size of 6-year-old Cryptomeria japonica planted in a group selection opening

We examined the extent to which direct and indirect measures of light and microsite conditions could explain variation in tree height and diameter at the base of 6-year-old Cryptomeria japonica trees planted in a group selection opening of about 0.32 ha on a steep slope at Shiiba, Miyazaki Prefecture, southern Japan. We first used the gap light index (GLI) and soil thickness (ST) as directly measured indices. For an indirect measure of light, we used a between-cohort competition index (BCI) estimated from the position and total height of residual trees. For indirect measures of microsite, we examined topographic indices (slope, plan and profile curvature, average slope gradient, and relative elevation) derived from digital elevation models (DEMs) with different resolutions ranging from 2 to 10 m. The multiple linear regression using GLI and ST explained about 45% of variation in tree size, while simple regression using only GLI explained about 35%. The contribution of ST was about half of GLI. The multiple regressions using BCI and the topographic indices did not explain any more variation than using BCI alone (R ² of about 0.26). We conclude that microsite conditions with shallower soil and steeper slope have negative effects on tree growth in group selection openings, although the relative importance is smaller than light conditions. More comprehensive studies considering several openings with more heterogeneous topography including different species are needed to generalize our growth prediction using the indirect measures, which are useful for practical forest management.     

Fundamental studies on wood/cellulose-plastic composites: effects of composition and cellulose dimension on the properties of cellulose/PP composite

Although wood/cellulose-plastic composites (WPC) of low wood/cellulose content have been more accepted worldwide and are promoted as low-maintenance, high-durability building products, composites containing high wood/cellulose content are not yet developed on an industrial scale. In this study, flow properties, mechanical properties, and water absorption properties of the compounds of cellulose microfiber/polypropylene (PP) and maleic anhydride-grafted polypropylene (MAPP) were investigated to understand effects of the high cellulose content and the dimensions of the cellulose microfiber. The molding processes studied included compression, injection, and extrusion. It was found that fluidity is not only dependent on resin content but also on the dimension of the filler; fluidity of the compound declined with increased fiber length with the same resin content. Dispersion of the composite was monitored by charge-coupled device (CCD) microscope. Increasing the plastic content in the cellulose-plastic formulation improved the strength of mold in addition to the bond development between resin and filler, and the tangle of fibers. The processing mode affected the physicomechanical properties of the cellulosic plastic. Compression-molded samples exhibited the lowest modulus of rupture (MOR) and modulus of elasticity (MOE) and the highest water absorption, while samples that were injection-molded exhibited the highest MOR (70 MPa) and MOE (7 GPa) and low water absorption (2%).