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关键词： 分子生物学   技术应用  

关键词： transposable elements   reverse transcription   genome structure   human mutation   mouse mutation  

摘要： L1 retrotransposons comprise 17% of the human genome. Although most L1s are inactive, some elements remain capable of retrotransposition. LI elements have a long evolutionary history dating to the beginnings of eukaryotic existence. Although many aspects of their retrotransposition mechanism remain poorly understood, they likely integrate into genomic DNA by a process called target primed reverse transcription. L1s have shaped mammalian genomes through a number of mechanisms, First, they have greatly expanded the genome both by their own retrotransposition and by providing the machinery necessary for the retrotransposition of other mobile elements, such as Alus. Second, they have shuffled non-L1 sequence throughout the genome by a process termed transduction. Third, they have affected gene expression by a number of mechanisms. For instance, they occasionally insert into genes and cause disease both in humans and in mice. L1 elements have proven useful as phylogenetic markers and may find other practical applications in gene discovery following insertional mutagenesis in mice and in the delivery of therapeutic genes.

关键词： 微生物分析   食品检验   微生物   大肠杆菌   大肠杆菌   试样制备   定义   定义   试样   水平的   饲料   验证   肉制品   食品   生化分析法   试验报告   肉   薄膜材料   抽样方法   微生物学   试验   调查  

标准号: ISO 16649-1-2001

摘要： This part of ISO 16649 specifies a horizontal method for the enumeration of β-glucuronidase-positive Escherichia coli in products intended for human consumption or for the feeding of animals. It uses a colony-count technique after resuscitation using membranes and incubation at 44 ℃ on a solid medium containing a chromogenic ingredient for detection of the enzyme β-glucuronidase. WARNING — Strains of Escherichia coli which do not grow at 44 ℃ and, in particular, those that are p-glucuronidase negative, such as Escherichia coli O157, will not be detected.

关键词： Ascidian Halocynthia aurantium   Bacillus   Biological activity   Microorganisms from marine environment   Pseudoalteromonas  

摘要： The taxonomy and biological activity of 176 heterotrophic microorganisms associated with the ascidian Halocynthia aurantium from the coastal waters of Peter the Great Bay (Sea of Japan) were studied. In the microbial community, bacteria of the genera Pseudoalteromonas (38% of all strains studied) and Bacillus (25%) prevailed and showed high biological activity. Bacteria of Pseudoalteromonas were capable of extracellular hydrolases production and exhibited high antibiotic and antimicrobial properties. Five Pseudoalteromonas strains were capable of restriction enzyme production. A significant proportion of the pseudoalteromonads inhibited growth of Proteus vulgaris and Candida albicans (81 and 84%, respectively). Spore-forming bacteria of Bacillus were capable of chitin hydrolysis and extracellular inducible RNAses production (23%). They were active against Staphylococcus aureus and Bacillus subtilis (39 and 23%, respectively). Bacillus pumilus strain KMM 1364 showed hemolytic activity and antagonistic properties against S. aureus and was found to produce surface active glycolipids and surfactinlike cyclic depsipeptides.

关键词： 动物遗传育种   研究攻关   农业   分子生物学  

摘要： 农业是我国12亿人口赖以生存的基础。发展动物农业对提高人民生活水平、保持社会安定团结具有重要的战略意义。根据美英等西方发达国家政府和世界粮农组织(FAO)的预测,21世纪全球动物农业90％的品种都将通过分子育种

关键词： amphibians   UV-B radiation   endocrine-disrupting chemicals   declines   review  

摘要： Statistical meta-analysis of large and diverse data sets has indicated that amphibians have been declining worldwide since the 1960s. Exposure to UV-B radiation (280-320 nm) and endocrine-disrupting chemicals (EDCs) have been considered as possible hypotheses to explain the observed declines. Equivocal conclusions have been reached with respect to the effects of UV-B on amphibian populations. Field and laboratory studies employing both ecologically relevant and enhanced UV-B levels have been conducted using a variety of amphibian species and reports differ with respect to the most sensitive developmental stage and the ultimate implications. UV-B radiation has also been shown to interact with other stressors (e.g., pesticides, polycyclic aromatic hydrocarbons, low pH) resulting in decreased survivorship for several amphibian species. Limited evidence of reproductive toxicity of xenobiotics in amphibians exist;however, early exposure to EDCs could cause abnormal development of the amphibian reproductive s ystem, inhibit vital hormone messages that drive metamorphosis, and ultimately contribute to the decline of some amphibian populations. The available evidence suggests that more than one agent is contributing to amphibian population declines and the following review narrows the focus to address the existing data on the effects of UV-B, alone and in combination with other stressors, and EDCs on amphibian survivorship and development.

关键词： 动物学   生物学   高等学校   教材   CT   S016585   动物学   CT   S066582   生物学  

关键词： 试样制备   水平的   食品检验   试样   试验报告   肉制品   肉   饲料   生化分析法   调查   验证   试验   微生物   微生物学   定义   大肠杆菌   大肠杆菌   微生物分析   食品   抽样方法  

标准号: ISO 16649-2-2001

摘要： This part of ISO 16649 specifies a horizontal method for the enumeration of β-glucuronidase-positive Escherichia coli in products intended for human consumption or for the feeding of animals. It uses a colony-count technique at 44 ℃ on a solid medium containing a chromogenic ingredient for detection of the enzyme β-glucuronidase. WARNING — Strains of Escherichia coli which do not grow at 44 ℃ and, in particular, those that are β-glucuronidase negative, such as Escherichia coli 0157, will not be detected.

关键词： Chestnut blight   Evolution   Fungus   Insect transmission   RNA   Virus  

摘要： Virtually every type of organism may serve as a host for viruses. In some hosts, virus presence may be considered beneficial to humans;in other hosts, viruses are considered detrimental. Examples of viruses that are considered beneficial to humans include those that are used for biological control of organisms that themselves are considered detrimental to humans, such as plant pathogenic fungi. Viruses are extremely variable in terms of morphology, structure, and genome organization. However, viruses that attack hosts from different kingdoms may be related, deriving from the same phylogeny. This paper summarizes some of the properties of three related families of viruses that attack hosts in different kingdoms: the animal-infecting Picornaviridae, the plant-infecting Potyviridae, and the fungus-infecting Hypoviridae. Properties of these viruses that set them apart from each other and factors that may affect their evolution are discussed.

关键词： Microgravity   Space flight   Vertebrates   Frogs   Tadpoles   Embryos   Rats  

摘要： Despite the sentimental appeal of human visits to the moon, people have only been transients in space. And yet, even their transient visits have started to demonstrate some curious biological paradoxes. For example, it is well known that an astronaut in space lose about 1 percent of the mineral density in their heel bone per month. But bone-forming cells do not show the same reduction when raised in tissue culture in space. The take-home message for our author is that biological processes that occur above the cellular cannot be predicted from the responses of their cells or tissues alone. To start to answer questions—indeed, to know what questions to ask—biologists are sending animals into space to study the effects of microgravity on their growth and development. The author discusses the surprising results of some of these experiments, which may have implications for the successful colonization of space someday in the future. People, says the author, will not have conquered the space environment until they can safely complete a life cycle in that setting.