施肥对稻米品质和产量影响的研究

通过1985～1087年的多点田间试验和盆栽试验,探索了施氮量,施氮时期,氮、磷、钾三要素及其组合方式,基肥种类以及稀土微肥对稻米产量和品质的影响,为优质稻合理施肥提供了理论依据。     

Soil nitrogen distribution and deposition on shortgrass prairie adjacent to a beef cattle feedyard

Cattle feedyards can impact local environments through emission of ammonia and dust deposited on nearby land. Impacts range from beneficial fertilization of cropland to detrimental effects on sensitive ecosystems. Shortgrass prairie downwind from an adjacent feedyard on the southern High Plains of Texas, USA changed from perennial grasses to annual weeds. It was hypothesized that N enrichment from the feedyard initiated the cascade of negative ecological change. Objectives were to determine the distribution of soil nitrogen and estimate N loading to the pasture. Soil samples were collected from 119 locations across the pasture and soil total N (TN), nitrate-N and ammonium-N (AN) determined in the top 30 cm. Soil TN concentration decreased with distance downwind from the feedyard from 1.6 ± 0.2 g kg⁻¹ at 75 m to 1.2 ± 0.05 g kg⁻¹ at 582 m. Nitrate-N concentration decreased within 200 m of the feedyard and changed little at greater distances. Ammonium-N concentration decreased linearly (P < 0.001) with increasing distance from the feedyard from 7.9 ± 1.7 mg kg⁻¹ within 75 m from the feedyard to 5.8 ± 1.5 mg kg⁻¹ at more than 550 m from the feedyard; however, distance only explained 12% of the variability in AN concentration. Maximum nitrogen loading, from 75 to 106 m from the feedyard, was 49 kg ha⁻¹ year⁻¹ over 34 years and decreased with distance from the feedyard. An estimate of net dry deposition of ammonia indicated that it contributed negligibly to N loading to the pasture. Nitrogen enrichment that potentially shifted vegetation from perennial grasses to annual weeds affected soil N up to 500 m from the feedyard; however, measured organic and inorganic N beyond that returned to typical and expected levels for undisturbed shortgrass prairie.

日本晴与5个优良恢复系的多态性标记筛选及遗传差异分析

遗传基因的分离需要供、受体亲本间较大的遗传差异.该文利用均匀分布于水稻12条染色体的429个SSR标记,分析了日本晴与5个自育优良恢复系之间的多态性标记及分布密度,进而评价它们间的遗传差异性.结果显示,日本晴与西恢18号、缙恢35、R225、R232和R250之间的多态性标记数分别为263,253,253,255和240个;多态率分别为61.31%,58.97%,58.97%,59.44%和55.94%;每个标记间的平均物理距离分别为1.59,1.61,1.62,1.62和1.72 Mb.每个SSR位点可检测到的等位基因数目为2~5个,平均每对SSR引物检测到2.35个等位基因.各亲本之间的遗传距离在0.121 7~0.896 7之间,日本晴与5个恢复系间的平均遗传距离为0.857 6.聚类分析也将日本晴与5个恢复系分为两大亚类,表明它们之间存在极大的遗传差异.这些材料和结果对水稻遗传基因的分离具有重要意义.     

一种简便高效的PCR辅助选择技术在杂交水稻转Xa21基因育种中的应用

介绍了一种在杂交水稻转Xa21基因育种中使用的PCR分子标记辅助选择技术.该技术结合测交和半粒种子法可以快速准确地筛选出转Xa21基因纯合株系和转[ WTBX〗Xa21基因杂交稻,大大提高育种效率,对培育抗白叶枯病杂交稻具有重要的应用价值.     

Long-term persistence of multi-drug-resistant Salmonella enterica serovar Newport in two dairy herds

OBJECTIVE: To evaluate the association between maintaining joint hospital and maternity pens and persistence of multi-drug-resistant (MDR) Salmonella enterica serovar Newport on 2 dairy farms. DESIGN: Observational study. SAMPLE POPULATION: Feces and environmental samples from 2 dairy herds. PROCEDURE: Herds were monitored for fecal shedding of S enterica Newport after outbreaks of clinical disease. Fecal and environmental samples were collected approximately monthly from pens housing sick cows and calving cows and from pens containing lactating cows. Cattle shedding the organism were tested serially on subsequent visits to determine carrier status. One farm was resampled after initiation of interventional procedures, including separation of hospital and maternity pens. Isolates were characterized via serotyping, determination of antimicrobial resistance phenotype, detection of the CMY-2 gene, and DNA fingerprinting. RESULTS: The prevalence (32.4% and 33.3% on farms A and B, respectively) of isolating Salmonella from samples from joint hospital-maternity pens was significantly higher than the prevalence in samples from pens housing preparturient cows (0.8%, both farms) and postparturient cows on Farm B (8.8%). Multi-drug-resistant Salmonella Newport was isolated in high numbers from bedding material, feed refusals, lagoon slurry, and milk filters. One cow excreted the organism for 190 days. Interventional procedures yielded significant reductions in the prevalences of isolating the organism from fecal and environmental samples. Most isolates were of the C2 serogroup and were resistant to third-generation cephalosporins. CONCLUSIONS AND CLINICAL RELEVANCE: Management practices may be effective at reducing the persistence of MDR Salmonella spp in dairy herds, thus mitigating animal and public health risk.     

Accumulation and depletion kinetics of erythromycin in rainbow trout (Oncorhynchus mykiss)

Erythromycin is an antimicrobial agent recommended for the control and treatment of diseases caused by gram-positive bacteria. Few studies, however, have determined the metabolic and pharmacokinetic aspects of this antimicrobial agent in fish. The aim of the present study, therefore, was to determine the accumulation and depletion time of erythromycin after administration of medicated feed containing 52 mg kg(-1) body weight day(-1) for 8 days in rainbow trout (Oncorhynchus mykiss). Results were analyzed following the European Agency for Evaluation of Medicinal Products guidelines. We measured a withdrawal time of 187°C-day (°C-day=water temperature×days), lower than the value (500°C-day) recommended by Council Directive 2004/28/EC for veterinary medicinal products. Our results provide data to establish therapeutic regimens for the use of erythromycin in aquaculture.     

盐碱土中可培养中度嗜盐菌的研究

为了调查大庆盐碱地的中度嗜盐菌资源,采集重度盐碱化的土壤样本进行嗜盐微生物的分离纯化,获得45株中度嗜盐细菌。形态学特征显示,40%菌落呈黄色,其余为乳白色;细胞为直线或弯曲的杆状,G+和G-细菌比例为19:26。进一步的生理生化特征分析筛选出8株进行16S rDNA基因序列的测定及系统发育分析。结果表明,它们分别属于Bacillus(3株),Halomonas(2株)和Alkalibacillus(3株)属的菌株。菌株15-2应为现有种Bacillus agaradhaerens,X10-1(或X10-7)可能为Bacillus属潜在的新种,15-7(或X10-2)可能为Halomonas潜在的新种,有待于进一步的验证。研究虽然仅获得了有限的中度嗜盐菌资源,但却丰富了我们对大庆盐碱土中可培养中度嗜盐菌多样性的认识,为今后合理开发和利用大庆地区的嗜盐微生物资源提供了素材和参考。     

In vitro effects of reactive oxygen metabolites, with and without flunixin meglumine, on equine colonic mucosa

OBJECTIVE: To determine effects of reactive oxygen metabolites (ROMs), with and without flunixin meglumine, on equine right ventral colon (RVC) in vitro. ANIMALS: 18 healthy horses and ponies. PROCEDURES: In 3 groups of 6 animals each, short-circuit current and conductance were measured in RVC mucosa in Ussing chambers. The 3 groups received physiologic saline (0.9% NaCl) solution, IV, 10 minutes before euthanasia and tissue incubation in Krebs-Ringer-bicarbonate (KRB) solution; flunixin meglumine (1.1 mg/kg, IV) 10 minutes before euthanasia and tissue incubation in KRB solution; or physiologic saline solution, IV, 10 minutes before euthanasia and incubation in KRB solution with 2.7 x 10(5)M flunixin meglumine. Incubation conditions included control (no addition) and ROM systems, including addition of 1 mM xanthine and 80 mU of xanthine oxidase (to produce the superoxide radical), 1 mM H(2)O(2), and 1 mM H(2)O(2) and 0.5 mM ferrous sulfate (to produce the hydroxyl radical). RESULTS: All ROMs that were added or generated significantly increased the short-circuit current except in tissues coincubated with flunixin meglumine, and they induced mild epithelial vacuolation and apoptosis, but did not disrupt the epithelium nor change conductance, lactate dehydrogenase release, or [(3)H]mannitol flux. CONCLUSIONS AND CLINICAL RELEVANCE: Responses to ROMs could be attributed to increased chloride secretion and inhibited neutral NaCl absorption in equine RVC, possibly by stimulating prostaglandin production. The ROMs examined under conditions of this study could play a role in prostaglandin-mediated colonic secretion in horses with enterocolitis without causing direct mucosal injury.     

Neonatal adaptation to stress of parturition and dystocia

The fetal animal undergoes a tremendous transition from intrauterine to extrauterine life at parturition. In this article, the maternal-fetal interactions of parturition are discussed with the aim of examining the normal stress reactions of parturition. Dystocia is discussed from the standpoint of additional distress of the newborn, with an aim toward the development of rational therapeutic support.