Physical and chemical characteristics of the blackened portion of Japanese persimmon (Diospyros kaki)

The heartwood of the Japanese persimmon tree (Diospyros kaki) becomes black on rare occasions and has been highly esteemed as a substitute for ebony. We attempted to clarify how the physical, mechanical, chemical, and biodegradation properties differ between sapwood and blackened heartwood. The specific gravity, equilibrium moisture content, modulus of rupture, and modulus of elasticity in the blackened heartwood were higher, and the loss tangent was lower, than those in sapwood. Furthermore, the blackened portion was more resistant to fungal and termite attacks. A section of heartwood was dark-brown, and the specific gravity and mechanical properties of this portion were slightly lower than those in sapwood. The dark-brown portion was speculated to be a sign or interrupted state of fungal attack. The blackening substance was bound tightly to cell wall components and could not be extracted with any of the organic solvents used. The findings of trace element analysis using inductively coupled plasma-mass spectrometry showed that the boron content was markedly high in the blackened portion. The findings obtained here suggest a role of boron in the antifungal properties and the blackening phenomenon of Japanese persimmon.Part of this work was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

Erratum to: Mechanical properties of wood in an unstable state due to temperature changes,and analysis of the relevant mechanism III: Effect of quenching on stress relaxation of chemically modified woods

In order to understand the mechanism of destabilization occurring when wood is quenched, we applied chemical modifications, and controlled the number of moisture adsorption sites in wood. The degree of destabilization was evaluated according to the fluidity (1-E _t/E ₀), increase in fluidity, and relative fluidity in relation to the nonmodified wood, and was discussed by comparing these quantities with the hygroscopicity or swelling of wood. We found that destabilization of chemically modified wood was lower than that in nonmodified wood, and the amount of adsorbed water controlled the magnitude of flow of wood. Moreover, according to the analysis of water state by the Hailwood-Horrobin equation, it was shown that the function of dissolved water to the fluidity is almost identical for both chemical modifications, whereas hydrated water has more effect on acetylated wood than on formaldehydetreated wood. We speculate that the motion of water molecules due to quenching accompanied with the redistribution of energy resulting from the exchange of their potential energy and movement to attain a new balance, and the introduced acetyl groups and cross-linking restrict the water molecule movement. An erratum to this article is available at .     

Use of trioxane for improvement of hygroscopic and acoustic properties of wood for musical instruments

Summary As a reagent source for the formalization of wood, trioxane was used instead of conventional paraformaldehyde. From preliminary experiments it became apparent that trioxane depolymerizes to formaldehyde by heating in the presence of some metallic salts. Formalization of wood with trioxane was carried out under the catalysis of sulfur dioxide (SO₂) along with these salts. The hygroscopic and acoustic properties were considerably improved by the treatment. Especially when the reaction was catalyzed by a combination of SO₂ and Fe₂(SO₄)₃, the antiswelling efficiency (ASE) reached nearly 70%, the specific dynamic Young's modulus (E/) in the radial direction increased about 20%, and the loss tangent (tan ) decreased about 30% and 50% in the longitudinal and radial directions, respectively. In this case, the modulus of rupture did not appreciably decrease in the radial direction. This is comparable to the most prominent results obtained so far by SO₂ catalyzed formalization with tetraoxane. It can be concluded that trioxane is very effective as a reagent source for formalization. The increase in acoustic converting efficiency, , of about twofold in the radial direction and decrease in hygroscopicity of more than 60% should not only enrich the sound volume of musical instruments but also stabilize their tone quality against humidity changes.     

Effects of impregnation of simple phenolic and natural polycyclic compounds on physical properties of wood

The impregnation of various simple phenolic and natural polycyclic compounds into wood was investigated from the viewpoints of vibrational property and dimensional stabilizing effect. When simple phenolic compounds were impregnated, the loss tangent (tan ) in the longitudinal direction increased linearly with increasing weight gain. Meanwhile, among the natural polycyclic compounds hematoxylin decreased the tan drastically by impregnation. It was suggested that the five hydroxyl groups and the pyran ring oxygen in the hematoxylin molecule contribute to formation of the crosslinkage-type hydrogen bonds between wood components. The rigidity of hematoxylin molecules may also be important. By impregnation of about 10% catechol, resorcinol, and saligenin, a 40% level of antiswelling efficiency (ASE) was attained, although a significant dimensional stabilizing effect was not observed after impregnation of natural polycyclic compounds.Part of this work has been published as a Rapid Communication inMokuzai Gakkaishi 43(12). It was also presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998     

Rhodococcus equi in the soil environment of horses in Inner Mongolia, China

Little is known about the distribution of Rhodococcus equi in the soil environment of native horses in China. One hundred and eight soil samples were collected from native-horse farms in the Hulun Beier grasslands of eastern Mongolia, the Xilin Goler grasslands of southern Mongolia, and Tongliao City in Inner Mongolia, China. The isolation rates of R. equi from soil samples from the Hulun Beier and Xilin Goler grasslands ranged from 25.9% to 30.0%. In contrast, isolation rates from soil samples from Tongliao City were as high as 82.3% and the mean number of R. equi in soil samples from Tongliao City was 10 times more than those of samples from the grasslands. The 488 isolates were examined using PCR for the presence of genes that encode virulence-associated 15-17 kDa antigen protein (VapA) and the 20 kDa antigen protein (VapB). All isolates were negative for virulence-associated proteins. Plasmid profiles of these avirulent isolates showed that cryptic plasmids of various sizes were present with an incidence of 13.3% to 21.5%. The results of the present study contrast with those of our recent study (J. Vet. Med. Sci. 67:611-613, 2005), in which we reported that R. equi was absent from Mongolian horses in Ulaanbaatar, Mongolia. It is suggested that the difference between the results of these two studies is due to the mobile pasturing system in Mongolia and nonmobile pasturing system in Inner Mongolia.     

Characterization of two putative mechanosensitive channel proteins of Campylobacter jejuni involved in protection against osmotic downshock

Acute hypotonic stress becomes a threat to the survival of bacteria in the environment. Mechanosensitive channels play an essential role in the maintenance of bacterial cell integrity during hypoosmotic shock. A database search suggested that Campylobacter jejuni, a major worldwide cause of bacterial gastroenteritis in humans, possesses two putative mechanosensitive channels, designated Cjj0263 and Cjj1025, in C. jejuni strain 81-176. Osmotic downshock experiments demonstrated that a mutant lacking Cjj0263 showed a severe defect in survival of hypoosmotic shock, while a mutant lacking Cjj1025 exhibited the same survival capacity as the wild type. We further examined the colonization ability of each mutant using the one-day old chick model. Cjj0263 or Cjj1025 mutants were able to colonize chick ceca at the same level as the wild type, but a Cjj0263 Cjj1025 double mutant revealed significantly reduced ability to colonize chick ceca. To examine whether C. jejuni that have grown in the digestive tract of chicks are protected against acute hypotonic stress, bacteria in ceca were directly exposed to water. The wild type was able to survive acute osmotic downshift, but the Cjj0263 mutant suffered a substantial loss of viability when subjected to a rapid osmotic downshock. Immunoblot analysis suggested that both Cjj0263 and Cjj1025 were glycosylated via the N-linked protein glycosylation pathway, but glycan modification of these proteins was unlikely to have a major effect on their function and stability. Our data suggest that Cjj0263, a mechanosensitive channel, has a pivotal role in protection against hypoosmotic stress experienced during environmental transmission.     

Optimization of a protocol for cryopreservation of mouse spermatozoa using cryotubes

The rapid increase in the number of genetically modified mouse strains has produced a high demand for their frozen spermatozoa from laboratories and mouse banking facilities. Historically, plastic straws have been used preferentially as containers for frozen mammalian spermatozoa because spermatozoa frozen in plastic straws have a high survival rate after thawing. However, plastic straws are more fragile and are used less often than the cryotubes used for conventional cell freezing. In this study, we sought to develop a new protocol for sperm freezing using cryotubes as the container to increase the accessibility of mouse sperm cryopreservation. Epididymal spermatozoa were collected from mature ICR or C57BL/6J (B6) males and were suspended in 18% raffinose and 3% skim milk solution. We then optimized the following conditions using the sperm survival rate as an index: 1) distance of cryotubes from the surface of the liquid nitrogen at freezing, 2) volume of the sperm suspension in the cryotube and 3) temperature of warming sperm during thawing. The best result was obtained when cryotubes containing 10 μl of sperm suspension were immersed 1 cm below the surface of the liquid nitrogen and then thawed at 50 C. The fertilization rates using spermatozoa frozen and thawed using this method were 63.1% in ICR mice and 28.2% in B6 mice. The latter rate was increased to 62.3% by adding reduced glutathione to the fertilization medium. After embryo transfer, 68% and 62% of the fertilized oocytes developed into normal offspring in the ICR and B6 strains, respectively. These results show that cryotubes can be used for cryopreservation of mouse spermatozoa under optimized conditions. This protocol is easy and reproducible, and it may be used in laboratories that do not specialize in sperm cryopreservation.     

Genetic organization and preferential distribution of putative pilus gene clusters in Streptococcus suis

Recent analyses of Streptococcus suis isolates using multilocus sequence typing (MLST) suggested the importance of sequence type (ST) 1 and ST27 complexes for animal hygiene and public health. In this study, to investigate whether pilus-associated genes in S. suis can be used as novel genetic markers for important clonal groups, we examined the correlation between STs and putative pilus-associated gene profiles in S. suis. Genomic searches using sequenced genomes and sequence data determined in several isolates revealed the presence of at least four distinct putative pilus gene clusters in S. suis (srtBCD, srtE, srtF, and srtG clusters). On the basis of the presence or absence of genes in the four clusters, 108 S. suis isolates from various origins were classified into 12 genotypes (genotypes A–L). Genotypes A and B, which possessed srtBCD plus srtF clusters and srtF plus srtG clusters, respectively, were the most common in isolates from diseased pigs and humans, and 29.9% and 59.8% of the isolates belonged to genotypes A and B, respectively. In contrast, only 4.8% and 28.6% of isolates from healthy carriers were genotypes A and B, respectively. MLST analysis showed the associations of genotypes A and B with ST1 and ST27 complexes, respectively. In addition, srtBCD and srtG clusters were preferentially distributed to ST1 and ST27 complex members, respectively. These results suggest that profiling of selected pilus-associated genes could be used as an easy screening method to monitor isolates important for S. suis infection.