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关键词： 饲料   食品检验   食品检验   细菌纲   分析   定义   验证   抽样方法   沙门氏菌属   食品   微生物分析   测试   农产品   测定   微生物学   试验  

标准号: BS EN ISO 6579-2002

摘要： This International Standard specifies a horizontal method for the detection of Salmonella, including Salmonella Typhi and Salmonella Paratyphi. Subject to the limitations discussed in the Introduction, this International Standard is applicable to — products intended for human consumption and the feeding of animals; — environmental samples in the area of food production and food handling.

关键词： 浦乳动物细胞   分泌   乙型肝炎病毒   表面S+PreS1融合抗原   理化性状   生物学性状   N-末端序列   免疫原性  

摘要： 研究了哺乳动物细胞(转基因GdSS1-18细胞系)分泌的乙型肝炎(乙肝)病毒表面S+PreS1融合抗原(SS1)纯品的理化及生物学性状,结果表明:经HPLC柱层析呈现一个对称峰,证明HBsAg颗粒所带电荷的均一性;SDS-PAGE出现P24及P27条带,未出现Gp30的条带,凝胶扫描分析其各条带分别各占22 3%、77 7%、0%;West ernblot试验证实,P27和Gp30能与S及S1抗体结合,而P24条带仅能与S抗体结合,表明S、PreS1是特异性条带;N-末端的氨基酸序列与所用目的基因编码的序列相同;乙肝SS1融合抗原在4℃储存较稳定。动物实验结果表明:与单纯含S基因的参比疫苗相比,含SS1融合基因疫苗免疫Balb/c小鼠既产生S抗体,又产生S1抗体,S抗体的ED50滴度与参比疫苗相似,S1抗体产生早于S抗体。

关键词： 焦虑   动物模型   神经生物学   惊愕反应   僵滞  

摘要： 1研究背景和理论基础[1～5] 急性焦虑和恐惧(fear)是人类乃至所有高等脊椎动物最为常见的情绪体验,其作用对生存或者说激活生物防御行为系统十分重要,可保护动物或人类抵抗潜在的环境威胁.自上世纪80年代起,生物精神病学领域对建立焦虑等精神疾病的模型来研究其病因学、症状学和治疗学倾注了大量投入,以实验动物大鼠为例,当遇到猫或潜在伤害刺激时,会表现为静止不动和僵滞(freeze),即除了呼吸活动外,没有任何运动表现,更进一步还可表现为恐惧诱导性惊愕(fear-potentiated startle)、痛觉丧失(analgesia)、自主神经变化和一些体内激素释放增加,以求增加生存的机会.在人类,则表现为主观性恐惧状态,并以此阐述急性焦虑、惊恐或创伤后应激障碍(PTSD)等一系列焦虑谱性障碍的病理机制.

关键词： mammalian sialidase   molecular cloning   gene structure and expression   molecular properties   transgenic expression  

摘要： This review summarizes the recent research development on mammalian sialidase molecular cloning. Sialic acid-containing compounds are involved in several physiological processes, and sialidases, as glycohydrolytic enzymes that remove sialic acid residues, play a pivotal role as well. Sialidases hydrolyze the nonreducing, terminal sialic acid linkage in various natural substrates, such as glycoproteins, glycolipids, gangliosides, and polysaccharides. Mammalian sialidases are present in several tissues/organs and cells with a typical subcellular distribution: they are the lysosomal, the cytosolic, and the plasma membrane-associated sialidases. Starting in 1993, 12 different mammalian sialidases have been cloned and sequenced. A comparison of their amino acid sequences revealed the presence of highly conserved regions. These conserved regions are shared with viral and microbial sialidases that have been characterized at three-dimensional structural level, allowing us to perform the molecular modeling of the mammalian proteins and suggesting a monophyletic origin of the sialidase enzymes. Overall, the availability of the cDNA species encoding mammalian sialidases is an important step leading toward a comprehensive picture of the relationships between the structure and biological function of these enzymes.

关键词： 创新研究群体   研究方向   动物病毒   分子生物学   预防兽医学  

摘要： 童光志博士领导的研究小组近十年来一直坚持不懈地从分子生物学水平对动物病毒病进行广泛而深入的研究,取得了丰硕的成果。他本人曾两次赴美留学都如期而归,扎根于我国畜牧兽医科研领域,其精神难能可贵。在学术方面。

关键词： 中学   生物教学   研究性学习   生物学网站  

摘要： 生物学是研究生命现象与生命活动规律的科学。在中学必修的基础课程中,生物学是最引人入胜的学科之一。她与人类的生活、生产有着密切的联系,其中的基因科学是目前最活跃的科技热点。因此,生物学是学生进行研究性学习时选题的热点。

关键词： Animals   Models, Immunological   rac GTP-Binding Proteins/metabolism   rho GTP-Binding Proteins/metabolism   Signal Transduction/immunology   Signal Transduction/physiology   T-Lymphocytes/enzymology   T-Lymphocytes/physiology  

摘要： Experiments with cell lines have unveiled the implication of the Rho/Rac family of GTPases in cytoskeletal organization, mitogenesis, and cell migration. However, there have not been adequate animal models to investigate the role of these proteins in more physiological settings. This scenario has changed recently in the case of the T-cell lineage after the generation of animal models for Rho/Rac family members, their regulators, and effectors. These studies have revealed the implication of these GTPases on multiple regulatory layers of T-cells, including the coordination of cytoskeletal change, activation of kinase cascades, stimulation of calcium fluxes, and the induction of gene expression. These pathways affect the transition of different T-cell maturation stages, the positive/ negative selection of thymocytes, T-cell responses to antigens, and the homeostasis of peripheral T-lymphocytes. Moreover, these animals have revealed interesting cross-talks between Rho/Rac pathways and other signal transduction routes that participate in lymphocyte responses. (C) 2002 Wiley Periodicals, Inc.

关键词： ISOPODA   REPRODUCTION   CRUSTACEA -- Behavior   SEXUAL behavior in animals  

摘要： Mating systems of many symbiotic crustaceans are characterised by a high degree of mate guarding. A peculiar case of mate guarding has been reported for small symbiotic janirid isopods where males mate with immature females. Field samples of individual hosts and laboratory experiments were conducted to reveal the mating behaviour of the symbiont in a natural environment, that is, on their hosts. Along the coast of the Magellan Strait, Chile, the janirid isopod Iais pubescens was frequently found on the shore-living isopod Exosphaeroma gigas. Symbiont prevalence (percent hosts occupied) was high at eight of the nine sampling sites. Mean symbiont intensity was very low at one site ( < < 1 individual host(-1)), intermediate at two sites (1-10 individuals host(-1)) and high at the other sites (10-40 individuals host(-1)). The mean sex ratio (males:females) was male biased at most sampling sites (n = 7). Females of I. pubescens reached substantially larger sizes (1.5-3.0 mm body length, BL) than males (1.1-1.9 mm BL). The majority of males were carrying small juveniles (66.15%), and males with juveniles were significantly larger than males without juveniles - this suggests that males prefer virgin juveniles to adult females an that they compete for small juveniles. In laboratory observations, males were seen to manipulate the marsupium of adult females that were about to release small juveniles. Males obtained virgin juveniles in this manner. Juveniles were carried for similar to7 days, and they moulted shortly before being fertilised and released by males. The high proportion of juveniles carried by males in the field (68.2%) supports previous observations that males initially are not able to distinguish male and female juveniles. It is suggested that the mating system of symbiotic janirid isopods with long-term sperm storage and continuous receptivity in females and male mating with virgin females has evolved in response to highly unpredictable encounter probabilities

关键词： melatonin receptors   suprachiasmatic nucleus   pars tuberalis   cyclic AMP signaling pathway  

摘要： The pineal hormone, melatonin, is an important regulator of seasonal reproduction and circadian rhythms. Its effects are mediated via high-affinity melatonin receptors, located on cells of the pituitary pars tuberalis (PT) and suprachiasmatic nucleus (SCN), respectively. Two subtypes of mammalian melatonin receptors have been cloned and characterized, the MT1 (Mel(1a)) and the MT2 (Mel(1b)) melatonin receptor subtypes. Both subtypes are members of the seven-transmembrane G protein-coupled receptor family. By using recombinant melatonin receptors it has been shown that the MT1 melatonin receptor is coupled to different G proteins that mediate adenylyl cyclase inhibition and phospholipase Cbeta activation. The MT2 receptor is also coupled to inhibition of adenylyl cyclase and additionally it inhibits the soluble guanylyl cyclase pathway. In mice with a targeted deletion of the MT1 receptor, the acute inhibitory effects of melatonin on SCN multiunit activity are completely abolished, while the phase-shifting responses to melatonin (given in physiological concentrations) appear normal. Furthermore, melatonin inhibits the phosphorylation of the transcription factor cyclic AMP response element binding protein, induced by the pituitary adenylate cyclase-activating polypeptide in SCN cells predominantly via the MT1 receptor. However, a functional MT2 receptor in the rodent SCN is partially able to compensate for the absence of the MT1 receptor in MT1 receptor-deficient mice. These findings indicate redundant and non-redundant roles of the receptor subtypes in regulating SCN function. In the PT, a functional MT1 receptor is essential for the rhythmic synthesis of the clock gene product mPER1. Melatonin produces a long-lasting sensitization of adenylyl cyclase and thus amplifies cyclic AMP signaling when melatonin levels decline at dawn. This action of melatonin amplifies gene expression rhythms in the PT and provides a mechanism for reinforcing rhythmicity in peripheral tiss