Stress relaxation of wood during elevating and lowering processes of temperature and the set after relaxation II: consideration of the mechanism and simulation of stress relaxation behavior using a viscoelastic model

Previously we showed that the relaxation modulusEt of water-saturated wood during temperature reduction maintained its initial value despite the decrease in temperature, although during temperature elevationEt showed a marked decrease. In the present study, to clarify the mechanism of relaxation during temperature elevation and reduction, Young's modulus was measured in stress relaxation experiments with changes in temperature, and relaxation behavior was simulated using a Maxwell model consisting of five elements. Furthermore, the dynamic Young's modulus and dynamic loss modulus were measured during both temperature elevation and reduction. The results obtained suggested that the unique relaxation behavior during temperature reduction was caused by decreases in Young's modulus and coefficient of viscosity (i.e., an increase in fluidity) compared with those during elevation of temperature. The decrease in Young's modulus and increase in fluidity were considered to be due to an unstable structure in wood that occurred during temperature reduction. This unstable structure probably develops in the nonequilibrium state of temperature toward a true equilibrium state. Wood should be more unstable during temperature reduction than during temperature elevation because of the decrease in molecular motion when the temperature is lowered.Part of this report was presented at the 49th annual meeting of the Japan Wood Research Society, Tokyo, April 1999     

Mechanical properties of wood swollen in organic liquids with two or more functional groups for hydrogen bonding in a molecule

The modulus of elasticity and the modulus of rupture during static bending in the radial direction, and the viscoelastic properties in the radial direction in the temperature range 20°–100°C of hinoki (Chamaecyparis obtusa) swollen in organic liquids with two or more functional groups in a molecule were compared with those of wood swollen by moisture. The wood swollen in organic liquids in or near the swelling equilibrium, but not that swollen in organic liquids distant from the swelling equilibrium, showed higher moduli of elasticity and rupture than the wood swollen to a similar degree by moisture. This suggests that wood exists in an unstable state as it approaches the swelling equilibrium, rendering it highly flexible and weak. During the first viscoelastic measurements for wood swollen in various organic liquids, thermal softening was observed in 40°–60°C range and above 80°C, though this softening disappeared during the second measurement. The softening observed in the 40°–60°C range and above 80°C was thought to have been caused by the redistribution of liquid toward the equilibrium state at a higher temperature and the swelling accompanying an elevated temperature, respectively.Part of this report was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999     

Changes in the mechanical properties of wood during a period of moisture conditioning

Changes in the modulus of elasticity (MOE), modulus of rupture (MOR), and stress relaxation in the radial direction of wood (hinoki:Chamaecyparis obtusa) moisture-conditioned by the adsorption process from a dry state and by the desorption process from a moisture content slightly below the fiber saturation point were investigated. The MOE and MOR of wood conditioned by the adsorption process showed significant increases during the later stages of conditioning when the moisture content scarcely changed. However, with the desorption process they did not increase as much during later stages of conditioning, though they increased during early stages of conditioning when the moisture content greatly decreased. The stress relaxation of wood decreased with an increase in the conditioning period with both the adsorption and desorption processes. These results suggest that wood in an unstable state, caused by the existing state of moisture differed from that in a true equilibrium state shows lower elasticity and strength and higher fluidity than wood in a true equilibrium state. Furthermore, the present study demonstrates that the unstable states of wood induced during the course of drying, desorption, and possibly adsorption of moisture are slowly modified as wood approaches a true equilibrium state.     

Complete mitochondrial DNA sequence of the Japanese flying fish <Emphasis Type="Italic">Cypselurus hiraii</Emphasis>

ABSTRACT:   In this study, to develop a technique that enables authentication of processed seafood, the complete nucleotide sequence of the mitochondrial genome for the Japanese flying fish Cypselurus hiraii was determined. Three segments spanning the entire genome were amplified using polymerase chain reaction, and products were subsequently used as templates for direct sequencing with 60 primers. The genome (16 528 base pairs) was found to contain the same 37 genes (two ribosomal RNA, 22 transfer RNA, and 13 protein-coding genes) as those found in other vertebrate mitochondrial genomes, with the gene order being identical to that typical of vertebrates. A major non-coding region between the tRNA^Pro and tRNA^Phe genes (868 base pairs) appears to be the control (D-loop) region, as it has several conserved blocks characteristic of control regions.     

Dietary supplementation with cellooligosaccharide improves growth performance in weanling pigs

Nondigestible oligosaccharides are not digested in the small intestine, but are fermented by bacteria colonizing in the large intestine. Physiological effects of non‐digestible oligosaccharides have been considered to be conferred by the fermentation of bacteria colonizing in the large intestine. Because cellooligosaccharide is a non‐digestible oligosaccharide, various physiological effects are expected. However, physiological functions of cellooligosaccharide are not well understood. This experiment was conducted to clarify the effect of dietary supplementation with cellooligosaccharide on the growth performance in weanling pigs. The result showed that average daily gain was significantly higher (P < 0.05) in pigs fed a diet supplemented with cellooligosaccharide than in pigs without cellooligosaccharide. There was a tendency to increasing average daily feed intake in pigs with cellooligosaccharide, though the significant difference was not detected (P = 0.18). Feed efficiency and nutrient digestibility of feces and ileum were not changed by feeding cellooligosaccharide. In addition, blood urea nitrogen was significantly higher (P < 0.05) in pigs fed the diet supplemented with cellooligosaccharide than in pigs without cellooligosaccharide. The concentrations of acetic and iso‐valeric acids in the cecum of pigs fed the diet with cellooligosaccharide tended to be higher (P < 0.10) than those without cellooligosaccharide. The results obtained in this study demonstrated that dietary supplementation with cellooligosaccharide improves growth performance in weanling pigs.     

Ruminal epithelial insulin‐like growth factor‐binding proteins 2, 3, and 6 are associated with epithelial cell proliferation

The aim of this study was to identify factors that regulate ruminal epithelial insulin‐like growth factor‐binding protein (IGFBP) expression and determine its role in rumen epithelial cell proliferation. Primary bovine rumen epithelial cells (BREC) were incubated with short‐chain fatty acids (SCFAs) at pH 7.4 or 5.6, lactate, lipopolysaccharide (LPS), insulin‐like growth factor‐I (IGF‐I), ‐II (IGF‐II), or recombinant bovine IGFBP2 (rbIGFBP2). The mRNA expression levels of IGFBP in BREC were analyzed using quantitative real‐time polymerase chain reaction (qRT‐PCR). The proliferation rate of BREC was analyzed using a WST‐1 assay. IGFBP2 gene expression tended to be lower with SCFA treatment (p < .1), and IGFBP6 gene expression was significantly lower with SCFA treatment (p < .05). IGFBP3 and IGFBP6 gene expression tended to be higher with d ‐Lactate treatment (p < .1). IGFBP3 gene expression was significantly higher (p < .05) with LPS treatment. BREC treated with IGF‐I grew more rapidly than vehicle control‐treated cells (p < .01); however, recombinant bovine rbIGFBP2 inhibited IGF‐I‐induced proliferation. IGF‐II and/or rbIGFBP2 did not affect BREC proliferation. Taken together, SCFA treatment decreased IGFBP2 and IGFBP6 expression in rumen epithelial cells, and lower expression of these IGFBP might promote rumen epithelial cell proliferation by facilitating IGF‐I.     

In-straw cryoprotectant dilution for bovine embryos vitrified using Cryotop

The aim of this study was to develop an in-straw dilution method suitable for 1-step bovine embryo transfer of vitrified embryos using the Cryotop vitrification-straw dilution (CVSD) method. The development of embryos vitrified using the CVSD method was compared with those of embryos cryopreserved using in-straw vitrification-dilution (ISVD) and conventional slow freezing, outside dilution of straw (SFODS) methods. In Experiment 1, in vitro-produced (IVP) embryos cryopreserved using the CVSD method were diluted, warmed and exposed to the dilution solution at various times. When vitrified IVP embryos were exposed to the dilution solution for 30 min after warming, the rates of embryos developing to the hatched blastocyst stage after 72 h of culture (62.0-72.5%) were significantly lower (P<0.05) than those of embryos exposed to the solution for 5 and 10 min (82.4-94.3%), irrespective of supplementation with 0.3 M sucrose in the dilution solution. In Experiment 2, the rate of embryos developing to the hatching blastocyst stage after 48 h of culture in IVP embryos cryopreserved using the SFODS method (75.0%) was significantly (P<0.05) lower than those of embryos cryopreserved using the CVSD and ISVD methods (93.2 and 97.3%, respectively). In Experiment 3, when in vivo-produced embryos that had been cryopreserved using the CVSD, ISVD and SFODS methods and fresh embryos were transferred to recipient animals, no significant differences were observed in the conception and delivery rates among groups. In Experiment 4, when IVP embryos derived from oocytes collected by ovum pick-up that had been cryopreserved using the CVSD and ISVD methods and fresh embryos were transferred to recipient animals, no significant differences were observed in the conception rates among groups. Our results indicate that this simplified regimen of warming and diluting Cryotop-vitrified embryos may enable 1-step bovine embryo transfer without the requirement of a microscope or other laboratory equipment.     

In vitro activity of 24 antimicrobial agents against Staphylococcus and Streptococcus isolated from diseased animals in Japan

A total of 88 Staphylococcus and 61 Streptococcus isolates from diseased animals throughout Japan were examined in 2000 for the minimum inhibitory concentrations of 24 different antimicrobials by the agar dilution method standardized by the Japanese Society of Chemotherapy. The resistance rates to aminobenzylpenicillin (36.4%) and benzylpenicillin (35.2%) were high in Staphylococcus isolates, and those to oxytetracycline (45.9%) and kanamycin (21.3%) were high in Streptococcus isolates. Two isolates resistant to oxacillin harbored the mecA gene. One was Staphylococcus epidermidis derived from a pig with arthritis, and the other Staphylococcus cohnii from a head of cattle with mastitis.     

Effect of supplemented sericin on the development,cell number,cryosurvival and number of lipid droplets in cultured bovine embryos

Sericin was investigated as an alternative to fetal bovine serum (FBS) for bovine embryo culture. In vitro matured oocytes were developed using 0.05%, 0.1% or 0.15% sericin. The developmental rate, cryosurvival rate and blastulation time of these embryos were compared with those of embryos developed using 5% FBS. The number of lipid droplets was compared among the blastocysts developed using 5% FBS, using 0.05% sericin and in vivo. The rate of cleavage and blastocyst formation was similar among all groups. Blastulation occurred significantly earlier in the embryos developed using 5% FBS than in those developed using sericin at any concentration (P < 0.05). At 72 h after thawing, the cryosurvival rate of the blastocysts developed using 5% FBS and 0.05% sericin were significantly higher compared with those developed using 0.1% and 0.15% sericin (P < 0.05). The blastocysts developed using 0.05% sericin and in vivo produced a significantly fewer number of medium and large lipid droplets than those developed using 5% FBS. These results suggest that the blastocysts developed using 0.05% sericin show characteristics similar to those of the blastocysts developed in vivo and that the use of sericin as an alternative to FBS is feasible.     

Effect of cultivar maturity period on the growth and yield of potato plants grown from microtubers and conventional seed tubers

Potato plants of early cultivars grown from microtubers have been reported to have a much lower growth vigor and produce lower yields than microtubers of late cultivars. This study intended to clarify the field performance of plants grown from directly planted microtubers of cultivars with different maturity periods, with a special attention to early cultivars. The experiments were conducted at Hokkaido University, Japan, over four years. Microtubers and conventional seed tubers of the early cultivar Kitaakari, late cultivars Konafubuki and Norin 1, and very late breeding line IWA-1 were planted, and the plant growth and tuber yields were analyzed. The microtuber plants of Kitaakari had a lower initial increase in leaf area index than conventional seed tuber plants, but at the maximum shoot growth had the same leaf area index. This pattern was also observed in the other cultivars. Tuber initiation and tuber bulking occurred on average five days later in microtuber plants than in conventional seed tuber plants of cultivar Kitaakari. At maximum shoot growth, microtuber plants had on average 65% of tuber dry weight of conventional seed tuber plants, with small variation among cultivars. Irrespective of maturity period, microtuber plants showed a higher tuber increase after maximum shoot growth, achieving around 86% of tuber dry weight of conventional seed tuber plants at harvest. From the results of this study we conclude that microtuber plants of early and late cultivars have a similar yield potential relative to conventional seed tuber plants, and microtubers of both early and late cultivars might be used as an alternative seed tuber source for potato production, if necessary.