Microbial distribution and function across wheat rhizosphere with oxamide and ammonium sulfate as N sources

Analysis of the effect of slow-releasing N fertilizers on microbial parameters of the rhizosphere soil is essential for their effective use. This investigation revealed the comparative effects of oxamide and ammonium sulfate as different N sources on some selected microbial parameters as well as the pH in the rhizosphere of wheat (Triticum aestivum cv. Nourin No. 61). The study was conducted on a Japanese upland alluvial soil using a rhizobox system. In the central compartment (CC) of the rhizoboxes treated with oxamide and ammonium sulfate, four wheat seedlings were grown for 53 d. In either of the treatments, the pH of the rhizosphere soil increased with the increase in the distance from the CC. In contrast, nitrate production, bacterial and fungal numbers, microbial biomass nitrogen, and β-acetylglucosaminidase activity decreased with the increase in the distance, with the highest values of the respective parameters being recorded in the CC. However, remarkable changes of these microbial parameters were found within a distance of 1–2 mm from the CC to the distant compartments. Thus the results indicated that pH, bacterial number, and nitrate production were high in the oxamide treatment. In contrast, higher fungal number, microbial biomass N, and .B-acetylglucosaminidase activity were associated with the ammonium sulfate treatment. It was assumed that the significant (p<O.05) effect of the rhizosphere on microbial activities varied with the treatments.     

鲤疱疹病毒Ⅱ型对异育银鲫背鳍细胞的显微形态与免疫基因表达水平的影响

为研究鲤疱疹病毒Ⅱ型(Cy HV-2)体外感染复制特征以及异育银鲫抗病毒免疫应答反应。本实验采用组织块培养法建立了异育银鲫背鳍细胞的原代培养体系。结果显示,在10 d左右可观察到组织块迁移分离出新的单层细胞,3周左右细胞可覆盖底部面积为25cm2培养瓶的底部;经Cy HV-2悬液感染离体培养的原代细胞,3 d后病毒滴度增殖至106拷贝/m L;在病毒感染6 d后出现典型的细胞病变效应;Cy HV-2感染原代细胞后,分析前期通过鱼体水平实验鉴定出的与该病毒感染相关的免疫基因:PNP5a、MPO、MHCⅠ、LYZ-C、IL-11、ITLN、PNP5a和DUSP,Real-time Rt-PCR结果显示大部分基因在细胞水平均有显著性的上调,与鱼体水平实验结果一致。本研究建立了原代培养的异育银鲫背鳍细胞,用于构建体外感染Cy HV-2病毒的细胞模型,为深入研究Cy HV-2的感染复制规律及其与宿主的相互作用关系,以及细胞水平筛选抗病毒药物实验奠定了基础。     

Effect of atropine and pyridostigmine on growth hormone response to GH-releasing peptide-2 and GH-releasing hormone in swine

To investigate the effects of high and low somatostatinergic tone on GH-releasing peptide-2 (GHRP-2) and GH-releasing hormone (GHRH)-induced growth hormone (GH) secretion in swine, we examined GHRP-2- and GHRH-induced GH secretion after pretreatment with atropine or pyridostigmine. Pretreatment of swine with atropine (80 µg/kg bodyweight (BW), intravenous (i.v.)) 15 min before i.v. administration of saline, GHRP-2 (30 µg/kg BW), GHRH (1 µg/kg BW) or a combination of GHRP-2 and GHRH, reduced plasma GH area under the curve ( P  < 0.05), completely blocked GH response to GHRH, and attenuated GH response to GHRP-2 and GHRH combined ( P  < 0.05), without affecting GH response to GHRP-2 only. A synergistic effect of GHRP-2 and GHRH was not observed. In contrast, pretreatment of swine with pyridostigmine (100 µg/kg BW, i.v.), under the same pretreatment conditions as above, increased plasma GH concentration ( P  < 0.01), augmented GH response to GHRP-2 ( P  < 0.05), and GHRP-2 and GHRH combined ( P  < 0.05), but did not affect GH response to GHRH. These results suggest that the cholinergic muscarinic agents atropine and pyridostigmine modulate the GH response to GHRP-2 and GHRH, and that GHRP-2 acts antagonistically on the inhibitory effect of somatostatin in swine.     

Pancreatic insulin secretory response and insulin action in heat-exposed sheep given a concentrate or roughage diet

The effects of heat exposure and type of diet on the insulin secretory response to glucose and glucose disposal in response to insulin action in female sheep were investigated employing hyperglycemic and euglycemic clamp techniques. Animals were divided into concentrate and roughage diet groups, and were maintained at the same intake levels of metabolizable energy and crude protein in both diets. Each diet group was subjected to either thermoneutral (20°C, 70% RH) or hot (30°C, 70% RH) environment, followed by glucose clamp experiments.

Heat-exposed sheep showed significant increases in respiration rates (P<.001) and rectal temperature (P<.05). Plasma glucose concentrations in the basal conditions were lower (P<.01) in the hot environment than in the thermoneutral environment, but there was no significant difference in basal levels of plasma insulin between the environmental treatments. In the hyperglycemic clamp experiment, mean plasma insulin increments increased (P<.05) during the heat exposure period across diet treatments. The ratio of mean plasma insulin increment to glucose infusion rate tended to be higher (P<.07) in the hot environment than in the thermoneutral environment, but diet treatment did not affect the ratio of mean plasma insulin increment to glucose infusion rate. The euglycemic clamp technique showed that glucose infusion rates remained unchanged among treatments. Insulin secretion response to glucose could be stimulated in the hot environment.     

Effects of Chinese herbal medicine and cold exposure on plasma glucose,leucine and energy metabolism in sheep

An experiment was carried out to assess the feeding effect of Chinese herbal medicine on N balance, ruminal fermentation characteristics, kinetics of plasma glucose, leucine and energy metabolism in sheep kept at thermoneutral environment (23°C) or exposed to cold (2–4°C). Four sheep were subjected to either mixed hay (MH‐diet) or hay supplemented with 2% of a traditional nourishing Chinese herbal medicine mixture (Astragalus root, Angelica root and Atractylodes rhizome; CHM‐diet) over two 23‐day periods using a crossover design. Cold exposure was conducted for 5 days. The isotope dilution of [U‐¹³C]glucose with open circuit calorimetry was used to determine the turnover and oxidation rates of plasma glucose and metabolic heat production. The rate of plasma leucine turnover was measured with an isotope dilution method using [1‐¹³C]leucine. N intake was higher, N excretion through faeces was lower and N digestibility was higher for the CHM‐diet than the MH‐diet. Rumen pH was lower, concentration of rumen NH₃ was higher, concentrations of rumen total VFA and acetate tended to be higher and propionate was higher for the CHM‐diet compared with the MH‐diet. Turnover rate of plasma glucose was higher for the CHM‐diet than the MH‐diet and increased during cold exposure. Oxidation rate of plasma glucose did not differ between diets and also between environments. Turnover rate of plasma leucine was higher for the CHM‐diet compared with the MH‐diet but remained similar between environments. Heat production was greater for the CHM‐diet than the MH‐diet and increased during cold exposure. No significant diet × environment interaction was detected. The present results demonstrated that plasma glucose and energy metabolism were enhanced by both Chinese herbal medicine and cold exposure; plasma leucine metabolism was enhanced by Chinese herbal medicine but with lack of change in response to cold exposure in sheep under the conditions of the current experiment.