中国南方天然常绿阔叶林枯叶分解的养分元素变化

中国南部的天然常绿阔叶林中,不同的初始条件下研究了栲树叶的重量损失和养分释放.对构成森林的13个树种的叶子也用枯叶袋法进行了研究.两年后栲树叶的分解率为53％～67％,其他13个种的叶分解率为59％～96％.两年间落叶树种叶子的重量损失大于常绿树种.分解叶的氮磷含有率随实验时间逐渐增加,而钾、钠、钙和镁的含有率却在降低.氮和磷的释放慢于更具活动性的元素,如钾、钠、钙和镁.分解率与最初的氮和磷的含有率成正相关.     

Identification of low-molecular weight glutenin subunits of wheat associated with bread-making quality

Although it is known that the compositions of low‐molecular weight glutenin subunits (LMW‐GSs) are important factors for bread‐making quality of wheat, it is still not clear which LMW‐GSs confer improved bread‐making quality and how those LMW‐GSs interact with high‐molecular weight (HMW) GSs. Using a hard red winter wheat line with good bread‐making quality and a Japanese wheat cultivar with poor quality as well as their progeny we identified LMW‐GSs associated with the bread‐making quality. One such LMW‐GS, KS2, which had a molecular weight of 42 kDa and was allelic to HS1, was associated with bread‐making quality. Furthermore, by using four recombinant inbred lines with different HMW‐GS and LMW‐GS combinations, KS2 and HMW‐GS 5+10 showed interaction effects on the bread‐making quality. Two‐dimensional polyacrylamide gel electrophoresis (Page) analysis showed that KS2 consists of two protein components and that HS1 is composed of three components. The N‐terminal amino acid sequences of the five components were identical to the most frequently analysed sequence of LMW glutenin components.     

Live offspring from cryopreserved embryos following in vitro growth, maturation and fertilization of oocytes derived from preantral follicles in mice

This study was undertaken to examine pre- and postimplantation developmental potency of cryopreserved embryos that had undergone in vitro growth (IVG), maturation (IVM) and fertilization (IVF) of oocytes from the preantral follicle stage. An oocyte culture system for IVG and IVM was used in oocyte-granulosa cell complexes (OGCs) derived from preantral follicles in 12-day-old mice. The rate of oocyte maturation was improved by the addition of gonadotropins (FSH/LH) and cytokines (IGF-I/SCF) to culture medium for IVG. During culture for IVG, estradiol-17β and progesterone concentrations increased progressively to the latter period of culture. This culture system enabled IVG, IVM, IVF and pre- and postimplantation development. From 90 cryopreserved 2-cell stage embryos transferred into recipients after warming, 10 live pups were produced. Cryopreservation of embryos by vitrification at the 2-cell stage showed no harmful effect on development to the blastocyst stage or on the cell numbers of the inner cell mass (ICM) and trophectoderm (TE). This study demonstrated that embryos derived from oocytes grown in vitro have tolerance for vitrification and competence to develop to term after warming. This IVG-IVM-IVF technology combined with embryo cryopreservation might be useful for assisted reproduction in mice.     

Polymorphisms in the bovine hemoglobin‐beta gene provide evidence for gene‐flow between wild species of Bos (Bibos) and domestic cattle in Southeast Asia

The electrophoretic variation in bovine hemoglobin‐beta (HBB) is one of the most investigated genetic markers. The presence of a unique HBB variant, HBB^X, in Southeast Asian cattle has been reputed as a sign of gene‐flow from wild bovine species. In this study, we analyzed the DNA sequences of HBB genes in domestic and wild bovine species to verify this belief. Isoelectric focusing of HBB chain revealed that the HBB^X in domestic cattle had dimorphism and was separated into HBB^X1 and HBB^X2. The HBB^X1 had the same DNA sequence of the common HBB variant in gayal (Bos gaurus frontalis), while some of the HBB^X2 were identical with that of Cambodian banteng (Bos javanicus birmanicus). As a result, we confirmed that the bovine HBB variants can be a good indicator of introgression between wild and domestic cattle. The HBB^X1 was always predominant to HBB^X2 in the continental populations, suggesting that the gaur had contributed to the gene pool of domestic cattle in this region much more than the banteng. On the other hand, the mitochondrial DNA analysis could not detect gene‐flow from wild species. Autosomal markers that can trace the phylogeny between alleles are suitable for the assessment of bovine interspecific introgression.     

An improved dry ash procedure for the detection of titanium dioxide in cattle feces

We improved the dry ash procedure for detecting titanium dioxide (TiO₂) in cattle feces containing chromium dioxide (Cr₂O₃). First, the effect of amount of sodium sulfate (Na₂SO₄) on the recovery of TiO₂ from cattle feces that contained Cr₂O₃ was evaluated. Average recovery of TiO₂ at the 2.5 g Na₂SO₄ level was significantly higher (P < 0.0001) than that at 0.75 g Na₂SO₄. Second, the effect of Cr₂O₃ concentration on the recovery of TiO₂ of cattle feces by using two levels of Na₂SO₄ addition was examined. The recovery of TiO₂ decreased with the increase in the amount of Cr₂O₃ at the 0.75 g Na₂SO₄ level but was consistently high at 2.5 g Na₂SO₄. Third, the recovery of Cr₂O₃ from cattle feces was checked. The recoveries of TiO₂ and Cr₂O₃ were high enough at the 2.5 g Na₂SO₄ level. Fourth, the improved dry ash procedure (5 mL of concentrated H₂SO₄ and 2.5 g of Na₂SO₄ were used for sample digestion) was compared to the wet ash procedure. Average recovery of TiO₂ by the improved dry ash procedure was significantly higher (P = 0.0077) than that by the wet ash procedure. Thus, the improved dry ash procedure can be used for TiO₂ analysis in cattle feces containing Cr₂O₃.     

Genome‐wide association study for fatty acid composition in Japanese Black cattle

Fatty acid composition is one of the important traits in beef. The aim of this study was to identify candidate genomic regions for fatty acid composition by genome‐wide association study with 50 K single nucleotide polymorphism (SNP) array in Japanese Black cattle. A total of 461 individuals and 40 657 SNPs were used in this study. We applied genome‐wide rapid association using mixed model and regression (GRAMMAR) and genomic control approaches to estimate the associations between genotypes and fatty acid composition. In addition, two SNPs in fatty acid synthase (FASN) (T1952A) and stearoyl‐CoA desaturase (SCD) (V293A) genes were also genotyped. Association analysis revealed that 30 significant SNPs for several fatty acids (C14:0, C14:1, C16:1 and C18:1) were located in the BTA19 FASN gene located within this region but the FASN mutation had no significant effect on any traits. We also detected one significant SNP for C18:1 on BTA23 and two SNPs for C16:0 on BTA25. The region around 17 Mb on BTA26 harbored two significant SNPs for C14:1 and SNP in SCD in this region showed the strongest association with C14:1. This study demonstrated novel candidate regions in BTA19, 23 and 25 for fatty acid composition.     

The assessment of genetic diversity within and among the eight subpopulations of Japanese Black cattle using 52 microsatellite markers

Japanese Black cattle are at risk for genetic homogeneity due to intensive use of a few sires. Therefore, assessment of the actual genetic diversity of this breed is important for future breeding plans. In the present study, we investigated the genetic diversity within and among eight subpopulations of Japanese Black cattle using 52 microsatellite markers. The parameters for genetic diversity of Japanese Black cattle were comparable to those of other cattle breeds, suggesting that the relatively high genetic diversity of the breed. However, upon comparison among the eight subpopulations, the Hyogo subpopulation showed markedly low genetic diversity. The results of the pairwise F_ST values, phylogenetic network and structure analysis indicated that the Hyogo population has remarkably high level of genetic differentiation from other populations, while Yamagata, Niigata, Hiroshima and Kagawa populations have low levels of genetic differentiation. Furthermore, multidimensional scaling plots indicated that individuals in some subpopulations were separated from individuals in the other subpopulations. We conclude that while the overall genetic diversity of Japanese Black cattle is still maintained at a relatively high level, that of a particular subpopulation is significantly reduced, and therefore the effective population size of the breed needs to be controlled by correct mating strategies.     

Effect of feeding rice whole crop silage on growth rate,levels of vitamin A, β‐carotene,vitamin E and IGF‐1 in plasma and skeletal muscle protein degradation in Japanese black calves

This study evaluated the effects of rice whole crop silage (RWCS) on growth, plasma levels of vitamin A, β‐carotene, vitamin E and IGF‐1, and expression of genes involved in muscle protein degradation and synthesis in Japanese Black calves. Eleven calves were divided into RWCS (fed RWCS ad libitum and concentrate, n = 5) and control groups (fed hay ad libitum and concentrate, n = 6). Final body weight and dairy gain were significantly larger in the RWCS group compared with the control group. Plasma β‐carotene and vitamin E concentrations were significantly higher in the RWCS group compared with control group. Although plasma vitamin E concentration in the RWCS group significantly increased from 4 to 9 months of age, it did not increase in the control group. At 6 months of age in the RWCS group, ubiquitin B (p < 0.05) and calpain 1 (p = 0.097) mRNA expression were lower than control group, but they were not different between groups at 9 months of age. These results indicate that RWCS increases plasma β‐carotene level and promotes muscle growth because of a decrease in the rate of protein degradation, but the effect is lost with the increase in plasma vitamin E level.     

Allelic frequencies and association with carcass traits of six genes in local subpopulations of Japanese Black cattle

Marker‐assisted selection (MAS) is expected to accelerate the genetic improvement of Japanese Black cattle. However, verification of the effects of the genes for MAS in different subpopulations is required prior to the application of MAS. In this study, we investigated the allelic frequencies and genotypic effects for carcass traits of six genes, which can be used in MAS, in eight local subpopulations. These genes are SCD, FASN and SREBP1, which are associated with the fatty acid composition of meat, and NCAPG, MC1R and F11, which are associated with carcass weight, coat color and blood coagulation abnormality, respectively. The frequencies of desirable alleles of SCD and FASN were relatively high and that of NCAPG was relatively low, and NCAPG was significantly associated with several carcass traits, including carcass weight. The proportions of genotypic variance explained by NCAPG to phenotypic variance were 4.83 for carcass weight. We thus confirmed that NCAPG is a useful marker for selection of carcass traits in these subpopulations. In addition, we found that the desirable alleles of six genes showed no negative effects on carcass traits. Therefore, selection using these genes to improve target traits should not have negative impacts on carcass traits.     

Impacts of Ambient Ozone and/or Acid Mist on the Growth of 14 Tree Species: An Open-Top Chamber Study Conducted in Japan

Young trees of 14 species were exposed to ambient ozone (O₃), (charcoal-filtered air [CF] or non-filtered air [NF]) and/or acid mist (pH 5 or 3: SO₄ ^2?, NO₃ ^?, Cl^? at equivalent 1:2:1 ratio) over three seasons (from June 1993 to November 1995) using tunnel-type open-top chambers at two sites (Abiko: 25 m a.s.l. and Akagi: 540 m a.s.l.) in Japan. Ambient, 12-hr (0600–1800) mean O₃ concentration for April–September during the period of experiment at Akagi (41 ppb) was 40 % higher than that at Abiko (30 ppb). The NF- and CF-chambers had 90 % and 30 % of ambient O₃, respectively. Significant decreases in biomass in the NF treatments were observed in Pinus densiflora, Larix k aempferi, Picea abies, Abies firma, Abies homolepis, Abies veitchii, Cryptomeria japonica, Populus maximowiczii, Betula platyphylla, Fagus crenata and Zelkova serrata as compared with the CF treatment. These results indicate that the current ambient level of O₃ in Japan is high enough to have adverse effects on the growth of all tree species examined, except Pinus thunbergii, Chamaecyparis obtusa and Quercus mongolica. Increasing acidity of mist caused no growth decreases in all tree species examined. However, the growth decreases by O₃ were greater at pH 3 mist treatment than at pH 5 mist treatment on Abies veitchii and Fagus. This suggested that the O₃ effect on tree growth can be exacerbated by the deposition of acid mist, possibly associated with nitrate.