Basal levels and responses to glucose infusion of plasma glucose and insulin in beef steer before and after the end of the growing phase on pasture

We examined the effect of grazing during the growing phase on plasma glucose and insulin behavior at the end of the growing phase and at the early stage of the subsequent fattening phase in beef steers. From 13 to 45 weeks of age (growing phase), crossbred beef steers were grazed with minimal supplement (group G: n = 5) or housed while being fed on hay and concentrate (group H: n = 5). Following this phase, both groups were housed for finishing (fattening phase). At the end of the growing phase, group G showed faster plasma glucose disappearance after intravenous glucose infusion, with a smaller plasma insulin response, compared with group H. At the third week of the fattening phase, group G still showed higher glucose tolerance, although they experienced abrupt changes in nutritional and environmental factors. The results suggest that grazing during the growing phase probably improves the glucose tolerance and insulin response to glucose infusion in steers compared with animals that were housed during the corresponding period, and the improved properties may persist at least a few weeks after the commencement of fattening.     

Calcium metabolism of pregnant rats fed a vitamin D-depleted diet

The effects of vitamin D (VD) deficiency on calcium (Ca) metabolism during pregnancy were evaluated in rats fed VD-repleted (VD-repleted rats) and VD-depleted (VD-depleted rats) diets. In the VD-depleted rats, the plasma concentrations of 1,25-dihydroxyvitamin D and Ca decreased severely, whereas the parathyroid hormone concentrations increased. The Ca contents of the feces of the VD-depleted rats were higher than those of the VD-repleted rats. The fetal Ca contents of the VD-repleted and VD-depleted rats increased continuously, but that of the VD-depleted rats was lower. These data reveal that VD deficiency during pregnancy induces severe hypocalcemia due to reduced intestinal absorption of Ca and elevated fetal demand for Ca.     

Behavior and mutation of <Emphasis Type="Italic">Ralstonia solanacearum</Emphasis> in <Emphasis Type="Italic">Solanum toxicarium</Emphasis> grown in aseptic culture

To study the behavior and mutation of Ralstonia solanacearum in Solanum toxicarium, which is resistant to bacterial wilt, S. toxicarium was grown in aseptic culture and inoculated with R. solanacearum. Although 60%–80% of the inoculated plants were wilting after 2 to 3 days, most wilted plants had recovered by 20 days after inoculation. The pathogen was reisolated from over 98% of inoculated plant stems, but the percentage of recovery decreased the closer the isolation sites were toward the upper stem sections. Three colony types, characterized as fluidal white, nonfluidal red, and a mixture of fluidal white and nonfluidal red, were reisolated from the stems. Nonfluidal red colonies were less virulent on tomato plants than fluidal white colonies.     

Effects of thiophanate-methyl and azoxystrobin on the composition of Cercospora kikuchii populations with thiophanate-methyl-resistant strains

Azoxystrobin was recently registered in Japan for the control of purple seed stain of soybean caused by Cercospora kikuchii, because the pathogen has developed resistance to thiophanate-methyl. To investigate the effects of these fungicides on the frequency of C. kikuchii strains resistant to thiophanate-methyl and on the genotype structure of the population, we sowed purple-stained seeds, approximately 40% of which were infected with resistant strains, as inocula with asymptomatic seeds and applied thiophanate-methyl and azoxystrobin during the reproductive growth of soybeans. The isolation frequency of resistant strains increased more than 99% by thiophanate-methyl but was not significantly increased by azoxystrobin. In amplified fragment length polymorphism (AFLP) DNA fingerprinting, genotypic diversity was significantly decreased by thiophanate-methyl but was not affected by azoxystrobin. In addition, the similarity of the AFLP genotype structure was increased by thiophanate-methyl but not by azoxystrobin. These results suggest that thiophanate-methyl selectively inhibited the proliferation of sensitive strains, which resulted in a small number of genotypes, most of which were resistant strains. Azoxystrobin was found to nonselectively inhibit proliferation of the pathogen, which retained a large number of genotypes including thiophanate-methyl-sensitive or thiophanate-methyl-resistant strains or both. The nucleotide sequence data for the cytochrome b gene are available in the DDBJ/EMBL/GenBank databases under accession number AB231863.     

A PCR-based epidemiological survey of Hepatozoon canis in dogs in Nigeria

The prevalence of Hepatozoon canis infections in dogs in Nigeria was surveyed using molecular methods. DNA was extracted from blood samples obtained from 400 dogs. A primer set that amplified the Babesia canis 18S rRNA gene, which has high similarity to the H. canis 18S rRNA gene, was used for the PCR. As a result, samples from 81 dogs (20.3%) produced 757 bp bands, which differed from the 698 bp band that corresponded to B. canis infection. The sequence of the PCR products of 10 samples were determined, all of which corresponded with the H. canis sequence.     

Dysregulated metabolism and behaviors by disrupting gut microbiota in prenatal and neonatal mice

The live microbiota ecosystem in the intestine plays a critical role in maintaining the normal physiological and psychological functions in both animals and human beings. However, the chronic effect of microbiota disturbances during prenatal and neonatal developing periods on animal's health remains less studied. In the current study, pregnant ICR mice were fed with an antibiotic diet (7-g nebacitin [bacitracin-neomycin sulphate 2:1]/kg standard diet) from day 14 of conception, and their offspring were provided with the same diet till the termination of the experiments. Dams treated with antibiotics showed increased body weight along with enlarged gut. Antibiotic-treated offspring revealed decreased bodyweight, increased food, water, and sucrose intake. Administration of antibiotics affected corticosterone responsivity to acute 20 min restraint challenge in male pups. In behavior tests, female pups showed decreased movement in open field while male pups revealed decreased latency to open arms in elevated plus maze test and immobility time in tail suspension test. Together, these results suggested that early antibiotic exposure may impact on the food intake, body weight gain, and emotional behavior regulation in mice.     

Application of laser-assisted zona drilling to in vitro fertilization of cryopreserved mouse oocytes with spermatozoa from a subfertile transgenic mouse

Development of assisted reproductive technologies is necessary to obtain fertilized oocytes in a subfertile transgenic mouse strain. Here, we showed the application of laser-assisted drilling of the zona pellucida to in vitro fertilization of cryopreserved mouse oocytes with sperm from subfertile transgenic mice (C57BL/6N-Tg(UCP/FAD2)U8 strain). After cryopreservation by vitrification, the recovery and survival rates of the zona-drilled mouse oocytes were 97% (97/100) and 94% (91/97), respectively. In vitro fertilization of the cryopreserved zona-drilled mouse oocytes with sperm from the subfertile transgenic mice was greatly facilitated (60%, 55/91) compared to that of the cryopreserved zona-intact mouse oocytes (11%, 81/768). In vitro fertilized embryos that developed to the 2-cell stage were again cryopreserved by vitrification, and after warming they were transferred into recipient females. Subsequently, six viable offspring were delivered, and all were confirmed to be transgenic mice. These results indicate that laser-assisted zona drilling of oocytes combined with cryopreservation by vitrification may be a useful approach for large-scale production of in vitro fertilized embryos for managing transgenic mouse strains with reproductive disabilities such as subfertile sperm.