Effect of intermittent starvation on growth and some antioxidant indexes of Macrobrachium nipponense (De Haan)

The effect of different periods of starvation (0, 2, 4 and 8 days) followed by re-feeding on growth, feed utilization, oxygen consumption and some immune indexes [reactive oxygen intermediates (ROIs), activities of superoxide dismutase (SOD) and catalase (CAT)] was evaluated over an 18-day experimental period in shrimp Macrobrachium nipponense (De Haan) that had an initial body weight of 0.52 g. As a result of compensatory growth, indicated by an increase in specific growth rate (SGR), feeding rate (FR) and feed conversion efficiency (FCE) after re-feeding, final body weight of shrimp starved for 2 days (0.63 g) and 4 days (0.65 g) did not differ ( P >0.05) from the control group (0.64 g), with feed withholding for 8 days presenting a significant lower value (0.63 g). Oxygen consumption rate (OCR) decreased during the starvation period in all groups, followed by a gradual increase to a similar ( P >0.05) value than found in the control group (0.47 mg kg⁻¹ h⁻¹) at the end of the experiment. Although ROIs and the activity of SOD and CAT fluctuated during starvation in the feed-deprived groups, values at the termination of the experiment were comparable ( P >0.05) to those found for the control group.     

关于人工鱼礁的基本设计与管理问题的探讨

为保证人工鱼礁业的健康稳定发展,使人工鱼礁产生更好的生态效益、经济效益和社会效益,最大程度地发挥人工鱼礁的效能,文章就人工鱼礁材料的选择、人工鱼礁的设计提出了一些技术要求,并对人工鱼礁建成后的管理提出建设性意见。     

基于文献计量分析我国玉米黑穗病研究现状

以《中国期刊全文数据库》的数据为检索对象,采用文献计量学的方法,从年度载文量、核心作者群、合作度、主要产出单位及区域、期刊分布等方面对玉米丝黑穗病研究文献进行统计,进一步分析国内该领域的研究热点从而揭示近10a来我国对玉米丝黑穗病研究的现状和发展趋势     

石灰性潮土对氮肥连续施用的环境承受力

本文在冬小麦-夏玉米→春玉米轮作条件下,通过肥料长期定位试验,研究了北京地区石灰性潮土对氮肥连续施用的环境承受力。结果表明,常量氮肥(N 一年169 kg·hm~(-2))与不施氮相比,在60 cm 以下土层 NO_3~--N 含量无显著差异,没有污染地下水,而在两倍于常量的施氮量(N 一年338 kg·hm~(-2))条件下,80～100 cm 土层的 NO_3~--N 含量比常量施氮显著增加,在雨季或灌水量较大及长期淋洗条件下有可能污染地下水。通过本试验并参考有关研究结果,将该土壤对氮肥的环境承受力定为 N 一年203 kg·hm~(-2)。研究还表明,适量施用有机肥及磷、钾肥能协调土壤对作物的养分供应,增加作物产量,提高肥料利用率,从而减少 NO_3~--N对地下水污染的可能性。     

High prevalence and widespread distribution of multi-resistant Escherichia coli isolates in pigs and poultry in China

Escherichia coli play an important ecological role within resistant bacteria populations, and can be used as a bio-indicator of antimicrobial resistance. The aim of the present study was to use this feature of E. coli to investigate the prevalence of antimicrobial resistance and the degree of cross-species transmission of bacteria in pigs and poultry in China. A total of 592 E. coli strains, isolated from pigs and poultry (healthy and diseased animals), were tested for resistance to 22 antimicrobials representing eight antimicrobial drug types.E. coli isolates had high rates of resistance to ampicillin (99.5%), doxycycline (95.6%), tetracycline (93.4%), trimethoprim–sulfamethoxazole (74.3%), amoxicillin (65.1%), streptomycin (54.7%), and chloramphenicol (50.2%). Resistance to cephalosporins, quinolones, and aminoglycosides was also quite prevalent. The majority (81%) of isolates demonstrated multi-antimicrobial resistance, most commonly to 5–6 different antimicrobial types. One isolate was resistant to all 22 antimicrobials. Twenty-two cultures exhibiting multi-antimicrobial resistance were analysed by pulsed-field gel electrophoresis (PFGE) to assess their distribution between farms. Three distinct PFGE types were identified, indicating inter-farm transmission of multi-antimicrobial resistant bacteria. The study confirmed the presence and transmission of multi-antimicrobial-resistant E. coli strains amongst pigs and poultry in China and highlights the urgent need for appropriate monitoring programmes.     

栗疫菌弱毒力特征的传递及其影响因素

栗疫菌 (Cryphonectriaparasitica)弱毒力 (hypovirulence)的本质是菌体中含有一种弱毒性病毒 (cryphonectriahypovirulenceviruses ,CHV)dsRNA(Choietal,1992 ;Morrisetal,1979)。栗疫菌的弱毒力菌株 (H菌株 )一般都具有将强毒力 (virulent)菌株 (V菌株 )转化为弱毒力菌株的能     

水杨酸和乙烯在烟草抗黑胫病中的作用

5mmol/L水杨酸或1g/L乙烯外源处理可诱导烟草对黑胫病的抗性，推迟植株死亡。不能积累水杨酸的转nahG基因植株和不表现乙烯应答反应的转etr1-1基因植株对黑胫病的抗性显著弱于野生型植株。组成性积累高水平水杨酸的转entC和pmsB基因植株对黑胫病的抗性明显强于野生型植株。这些结果说明水杨酸和乙烯增强烟草对黑胫病的抗性，减缓黑胫病的扩展。0．5mmol/L KCN连续浇灌植株4天或浸溃叶片2，4h均不能恢复转nahG基因植株丧失的对黑胫病的抗病性。此结果进一步支持关于KCN处理不能恢复转nahG基因植株丧失的对真菌病害抗病性的假说。     

Evaluating the probiotic potential and adhesion characteristics of Bacillus spp. isolated from the intestine of Rhynchocypris lagowskii Dybowski

Probiotics have been widely used in aquaculture worldwide especially in China as antibiotics have been banned in aquaculture. In the present study, 27 potential strains were isolated from Rhynchocypris lagowskii Dybowski intestinal tract towards the assessment of their probiotic potential. Two potential probiotics were finally screened from the 27 candidate strains according to the results of enzyme-producing ability, in vitro against pathogens ability and antibiotic sensitivity test. The 2 potential probiotics were identified and confirmed on the basis of their colony morphology, biochemical characteristics, and 16S rRNA sequencing. The probiotic strains, LSG2-3–2 and LSG3-6, were identified to be Bacillus methylotrophicus and B. tequilensis, respectively. Further studies showed that LSG2-3–2 and LSG3-6 had excellent tolerance to high temperature (80℃), low pH (3–5), bile salts (0.3%), intestinal juice (10%), and gastric juice (0.5%). The adhesion rates of LSG2-3–2 and LSG3-6 in the in vitro intestinal mucosal adhesion model were 17.74% and 24.04%, respectively. Analysis of their bacteria surface adhesive proteins revealed that the lectins on the bacterial surface of LSG2-3–2 and LSG3-6 were mainly protein and glycoprotein properties, respectively. The adhesion receptor components in the mucus proteins of the two strains were all protein properties. The results of the inhibitory adhesion test indicated that LSG3-6 had a higher inhibitory effect on Aeromonas hydrophila and LSG2-3–2 had a better inhibitory effect on A. veronii. The biosafety assay confirmed that the isolates were not pathogenic to the host fish. Based on the presently observed characteristic features, it can be concluded that LSG2-3–2 (B. methylotrophicus) and LSG3-6 (B. tequilensis) retrieved from the digestive tract of R. lagowskii can be used for the healthy breeding and disease prevention of R. lagowskii.

     

关于收敛群的几条性质

得到了Ｒ＾ｎ上收敛群中元素的一些性质，利用这些性质证明了收敛群中某些子群的一些极大性质。     

Reevaluation of the Dietary Protein Requirement of Japanese Flounder Paralichthys olivaceus

An experiment was conducted to determine the dietary protein requirement by different analysis methods and to study the effects of dietary protein levels on growth performance and body composition in Japanese flounder Paralichthys olivaceus fed white fish meal and casein-based diets for 8 wk. After a 1-wk conditioning period, one of six isocaloric diets containing 30, 36, 42, 48, 54, and 60% crude protein (CP) was fed to fish at approximately 4–5% of wet body weight on a dry matter basis to triplicate groups of 15 fish averaging 13.3 ± 0.06 g (mean ± SD). After 8 wk of the feeding trial, weight gain (WG) and feed efficiency (FE) from fish fed 48% CP diet were similar to those from fish fed 42% and 54% CP diets, and were significantly higher than those from fish fed 30, 36 and 60% CP diets ( P < 0.05). Fish fed 48 and 54% CP diets had a significant higher specific growth rate (SGR) than did fish fed 30 and 36% CP diets ( P 0.05). Protein efficiency ratio (PER) was inversely related to the dietary protein level. No significant differences existed in hematocrit (PCV) and survival rate among the dietary treatments. Broken-line model analysis indicated that the optimum dietary protein level could be 44.0 ± 3.0% for maximum WG in Japanese flounder. Polynomial regression analysis of the dose-response showed that maximum WG occurred at 50.2% ( R² = 0.94) based on WG, and the second-order polynomial regression analysis with 95% confidence limits revealed that the range of minimum protein requirement was between 38.9% and 40.3% based on WG. Therefore, these findings suggest that the optimum dietary protein requirement for maximum growth of Japanese flounder is greater than 40%, but less than 44% CP in the fish meal and casein-based diets containing 17.0 kJ/g of energy.