“中国春”小麦不同缺体的RAPD分析

利用ＰＣＲ－９０Ａ型ＤＮＡ扩增仪，对７个中国春小麦缺体核ＤＮＡ进行了扩增。结果显示，中国春小麦缺体核ＤＮＡ的ＲＡＰＤ产物可分为二种类型：（１）所有供试材料均能扩增出的片段，代表了核ＤＮＡ在进化上的保守性。有一个引物检测到这类片段。（２）全部供试材料间存在的差异片段，这类片段是用来基因定位的主要依据。另外，建立中国春小麦缺体系统的ＲＡＰＤ指纹图谱对研究小麦的系统进化也将有重要意义     

禁抗前后规模鸡场环境中金黄色葡萄球菌和大肠杆菌对15种抗菌药的敏感性比较

为了解规模鸡场两种环境细菌在禁抗前后耐药性的变化,以评估使用抗菌药对养殖场用药的影响,通过对禁抗前以及禁抗6个月后规模鸡场的环境进行采样,培养分离大肠杆菌和金黄色葡萄球菌(金葡菌),然后针对15种常见抗菌药物开展药敏试验,并对敏感性进行比对。结果显示:禁抗前规模鸡场分离的大肠杆菌对妥布霉素、林可霉素、头孢拉定、卡拉霉素等较敏感,而对磺胺异噁唑、土霉素、头孢唑林和青霉素等耐药;金葡菌对头孢曲松、卡拉霉素、头孢唑啉、氟苯尼考等较敏感,而对土霉素、磺胺异噁唑、庆大霉素、妥布霉素等耐药。禁抗6个月后,两种细菌对大部分抗菌药的敏感性都有不同程度的增加,但对土霉素、磺胺异噁唑、氟苯尼考、青霉素等的敏感性增加不多甚至有降低。结果表明禁抗总体上可以增强鸡场环境中两种细菌对抗菌药的敏感性,降低耐药性。本文为指导规模鸡场禁用和科学使用抗菌药物提供了数据支持。     

全球基因I型非洲猪瘟病毒流行与疫苗研究进展

非洲猪瘟病毒已在我国定殖并形成较大污染面,国内样品中发现基因I型非洲猪瘟病毒,提示当前临床中实际流行的病毒种群更加复杂。基因I型毒株从1957年传入葡萄牙后,研究人员就开始对其进行研究。多年来,国外对基因I型毒株的流行分布情况特别是弱毒疫苗进行了大量研究,但国内目前尚无这方面的分析讨论。为此,作者就基因I型非洲猪瘟病毒流行与疫苗研究现状进行综述,以期为我国非洲猪瘟的科学防控提供参考。     

Oral administration of L-citrulline changes the concentrations of plasma hormones and biochemical profile in heat-exposed broilers

We examined the effects of oral administration of L-citrulline (L-Cit) on plasma metabolic hormones and biochemical profile in broilers. Food intake, water intake, and body temperature were also analyzed. After dual oral administration (20 mmol/head/administration) of L-Cit, broilers were exposed to a high ambient temperature (HT; 30 ± 1°C) chamber for 120 min. Oral administration of L-Cit reduced (p < .001) rectal temperature in broilers. Food intake was increased (p < .05) by heat stress, but it was reduced (p < .05) by L-Cit. Plasma levels of 3,5,3′-triiodothyronine, which initially increased (p < .0001) due to heat stress, were reduced (p < .01) by oral administration of L-Cit. Plasma insulin levels were increased by heat exposure (p < .01) and oral L-Cit (p < .05). Heat stress caused a decline (p < .05) in plasma thyroxine. Plasma lactic acid (p < .05) and non-esterified fatty acids (p < .01) were increased in L-Cit-treated heat-exposed broilers. In conclusion, our results suggest that oral L-Cit can modulate plasma concentrations of major metabolic hormones and reduces food intake in broilers.     

The effects of maxillary nerve block,ethmoidal nerve block and their combination on cardiopulmonary responses to nasal stimulation in anesthetized Beagle dogs

ObjectiveTo describe an approach for ethmoidal nerve block (E_BLOCK) and to compare the effects of a maxillary nerve block (M_BLOCK), E_BLOCK and their combination (M-E_BLOCK) on heart rate (HR), systolic (SAP), mean (MAP), diastolic (DAP) arterial pressures and respiratory rate (f_R) during nasal stimulation in dogs.Study designProspective, blinded, randomized, crossover placebo-controlled study.AnimalsBeagle dogs (five cadavers, nine live dogs), with a median (interquartile range) weight of 10.5 (10.3–11.0) kg.MethodsThe accuracy of iohexol injections (each 1 mL) at the maxillary and ethmoidal foramina in cadavers was evaluated using computed tomography. Then, anesthetized dogs were administered four bilateral treatments separated by 1 week, saline or 2% lidocaine 1 mL per injection: injections of saline at the maxillary and ethmoidal foramina (Control), injections of lidocaine at the maxillary foramina and saline at the ethmoidal foramina (M_BLOCK), injections of saline at the maxillary foramina and lidocaine at the ethmoidal foramina (E_BLOCK) and injections of lidocaine at all foramina (M-E_BLOCK). The ventral nasal meatus was bilaterally stimulated using cotton swabs, and HR, SAP, MAP, DAP and f_R were continuously recorded. Values for each variable were compared before and after stimulation using Wilcoxon signed-rank test. Changes in variables among treatments were analyzed using Mann–Whitney U and Kruskal–Wallis tests (p ≤ 0.05).ResultsComputed tomography revealed iohexol distribution around the openings of the target foramina in all cadavers. In living dogs, HR, SAP, MAP, DAP and f_R significantly increased after stimulation within each treatment (p < 0.03). Physiologic responses were significantly attenuated, but not absent, in the M-E_BLOCK [HR (p = 0.019), SAP, MAP, DAP and f_R (all p ≤ 0.001)] compared with those in the Control.Conclusions and clinical relevanceConcurrent injections of lidocaine at the maxillary and ethmoidal foramina attenuated HR, arterial pressure and f_R responses to nasal stimulation in Beagle dogs.     

乳酸菌噬菌体的分离及生物学特性鉴定

为了解乳酸菌噬菌体的生物学特性,并为制定乳酸菌发酵生产过程中噬菌体污染的防控措施提供试验数据和参考,本研究通过斑点试验和双层琼脂平板法,以干酪乳杆菌（L. casei） ATCC 393、戊糖乳杆菌（L. pentosus） KLDS 1.0413、短小乳杆菌（L. brevis） ATCC 367为指示菌从乳制品、泡菜样品中分离乳酸菌噬菌体,通过透射电镜观察噬菌体形态,噬菌体基因组限制性内切酶作用分析其包装机制,并进行宿主范围和一步生长曲线的测定,SDS-PAGE分析噬菌体结构蛋白,对获得的噬菌体进行生物学特性鉴定。结果显示,分离获得3株烈性乳酸菌噬菌体,依次命名为Lc、Lpen和Lbre。电镜结果显示,噬菌体Lc、Lpen均由多面体头部和非收缩性尾部组成,而噬菌体Lbre由多面体头部和收缩性尾部组成。根据形态学分析,Lc和Lpen属于长尾噬菌体科（Siphoviridae）,B1类,Lbre属于肌尾噬菌体科（Myoviridae）,A1类。噬菌体基因组经限制性内切酶作用后,核酸电泳结果显示,噬菌体Lc、Lpen基因组均为异质平末端,其包装机制属满头包装,即pac-型,而Lbre含有黏性末端,其包装机制属于cos-型。宿主范围测定结果显示,噬菌体Lc、Lbre对宿主专一,而Lpen宿主谱较广。一步生长曲线显示,噬菌体Lc、Lpen和Lbre潜伏期分别为60、45和150 min,裂解期分别为45、90和105 min,裂解量分别为47、24和30 PFU/cell。SDS-PAGE分析显示,噬菌体Lc结构蛋白有7个,主要结构蛋白分子质量约为50 ku;噬菌体Lpen和Lbre结构蛋白均有5个,主要结构蛋白分子质量分别约为55和50 ku。综上,本研究分离获得3株乳酸菌烈性噬菌体,并对其主要生物学特性进行鉴定,对了解乳酸菌噬菌体及后续乳酸菌噬菌体污染的防治提供了试验数据和理论依据。     

猪丹毒和猪肺疫混合感染综合诊治

疫病一直是生猪养殖中影响猪群健康的重要因素,受到疾病影响的猪群会给养殖户带来巨大的经济损失,严重阻碍养殖业的发展。该文将简要概述猪丹毒和猪肺疫的病理状况,分析猪丹毒和猪肺疫混合感染的发病特征和临床症状,并研究综合诊治猪丹毒和猪肺疫混合感染的方法,降低猪丹毒和猪肺疫混合感染对生猪养殖的影响。     

一种时间阈值自动调整的测频方法设计与实现

由于多周期同步频率测量方法对测频率在低频段的范围有一定限制,提出了一种时间阈值自动调整的改进型多周期同步频率测量方法。当被测频率超出低频段测量范围时,该方法通过有规律地延长时间阈值,拓展了在低频段被测频率的范围。结合MSP430单片机丰富的硬件资源,解决了测频模块硬件实现中的频率范围超出判断、时间阈值自动延长等关键问题,提出了合理的解决方案,并对其进行了软硬件设计。经实验测试,该方法实现了频率的测量,并拓展了低频段频率测量的范围。     

R~*树结点的主元分界分裂方法

为降低R*树结点重叠度,提高其空间利用率,通过结点特征点集方差及各子特征点集方差之和建立主元分析和结点分裂之间的联系,基于主元分析算法对特征点集进行降维处理,计算特征点集的主元向量,过特征点集中心且正交于该向量建立分界面对特征点集进行划分,将各簇数据的中心作为结点分裂的初始分裂中心,实现R*树结点分裂。实验证明,该算法具有较高的结点分裂效率,使得R*树结点重叠度降低,分裂结果较合理,显著提高了R*树构造效率和k近邻查询效率。     

新型山药收获机下支撑支架的设计与分析

山药收获机下支撑支架是根据主旋转支撑装置的离地高度和开沟深度设计的,在实际作业过程中,链刀切削阻力、螺旋刀切割阻力、输送机构支撑力、油缸的推拉力最终都由下支撑支架承载,作用力较为复杂,容易发生变形和断裂;且链刀切入土壤产生的振动、链节和链轮齿的啮合会给链传动带来工作的不平稳性和有规律的振动,可能会引起共振。为此,在进行山药收获机工作装置设计时,首先采用有限元方法对下支撑支架进行静力学分析,并在静力学分析的基础之上对其进行预应力模态分析,以评估设计的合理性,对结构进行优化。