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1.
The incidence of headshaking in domestic fowls (Gallus domesticus) is influenced by both social and environmental factors; it was more frequent in larger groups and in subordinate birds, and it could be greatly increased by exposure to disturbing stimuli. The findings are not readily explained by earlier suggestions that it is a response to frustration of movement, that it serves to increase sensory input under conditions of social isolation in barren surroundings, or that it is a displacement reaction to conflict situations. Evidence is presented to show that it occurred in contexts demanding increased attention, for example, upon the presentation of novel or disturbing stimuli, and it is proposed that headshaking is an “alerting response”.  相似文献   

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3.
On the basis of completed experimental research on intact nodes of Ranvier in isolated nerve fibres we decided that outcome in perinodal space during excitation potassium ions accumulation realized some important functions: it decreased the potassium ions outflow from axoplasma; it caused prolonged postspike depolarization; it activated action of electrogenic membranous Na-K pump; it predetermined the generation of prolonged components of posttetanic hyperpolatisation that appeared as a supplementary factor for potassium ions reabsorbing in cytoplasm; it did underlie the mechanisms of repeated and rhythmic activity and others.  相似文献   

4.
Persson I 《Bioethics》1999,13(3-4):294-305
Peter Singer has argued that nothing done to a fetus before it acquires consciousness can harm it. At the same time, he concedes that a child can be harmed by something done to it when it was a non-conscious fetus. But this implies that the non-conscious fetus can be harmed. The mistake lies in thinking that, since existence can be intrinsically bad for a being only if it is conscious, it can be harmed only if it is conscious. In fact, its being harmed only implies that it could have been conscious (and led a good life).  相似文献   

5.
The effect of esophageal chalone on epithelial cell reproduction in the esophagus was studied. Lyophilized aqueous extract from the esophagus was used. The following properties of the esophageal preparation have been revealed: it is water-soluble; it is present in the same tissue where it acts; it has tissue-specific effect (the preparation does not act on the mitotic and radioactive index in the epithelial crypts of the small intestine); its action is short-term and reversible; its effect on DNA division and synthesis in the esophageal epithelial cells is dose-dependent. Therefore, it is suggested that the esophageal preparation contains a chalone.  相似文献   

6.
H. Maldiney 《PSN》2007,5(1):23-30
This paper reflects on one of Ludwig Binswanger’s best-known essays, in an effort to clarify the mode of existence of the person within the oneiric world and, therefore, the manifestation mode of that world itself. The author argues that what matters most in the expression of that world is not that it consists of images, but that it is devoid of syntax. This makes it both global and perfective and explains why nothing in it is actually determined by the ego of the dreamer. Its space has no horizon, no perspective and no vantage point, and its temporality is in gestation (chronogenetics), with no concept of the separation of present, past and future. It is characterised by process and lacking in structure. In addition, it is strangely familiar, because it echoes the past in a way that indicates inevitable fate. While the dreaming ego is well folded into that world, its mode of existence remains impersonal; it doesn’t decide for itself, and it doesn’t confront what is coming. The strangeness encountered is not that of the Other, but that of the stranger the ego perceives within itself. Dreaming, therefore, offers the opportunity for human beings to experience existence when it is still undecided — Freud called it the id and Schelling Gemüt — in a place where the ego has not yet become a person. It is only in the waking world that people can integrate their still inchoative egos and give them a destination.  相似文献   

7.
When China turned its back on the Cultural Revolution, it aimed to build a thriving capitalist sector. It got one. Now, it wants a world-class research enterprise. How far has it progressed in the biosciences, how did it get there, and how far does it have to go?  相似文献   

8.
A study was made of the effects of isothiobarbamine and guthimine (10 and 50 mg/kg, respectively) on the content of cAMP and cGMP in the brain cortex (BC) and hippocamp under normal conditions and hypoxia. Isothiobarbamine did not change the content of both cyclic nucleotides under normoxia, whereas under hypoxia it reduced the level of the cyclic nucleotides in the BC and raised it in the hippocamp. Guthimine increased their content in the BC and did not change it in the hippocamp under normoxia, whereas under hypoxia it increased the cAMP content in the hippocamp and did not change it in the BC. The cGMP content descended in both the structures under study.  相似文献   

9.
This article explores the social benefits and moral arguments in favour of women and couples freezing eggs and embryos for social reasons. Social IVF promotes equal participation by women in employment; it offers women more time to choose a partner; it provides better opportunities for the child as it allows couples more time to become financially stable; it may reduce the risk of genetic and chromosomal abnormality; it allows women and couples to have another child if circumstances change; it offers an option to women and children at risk of ovarian failure; it may increase the egg and embryo pool. There are strong arguments based on equal concern and respect for women which require that women have access to this new technology. Freezing eggs also avoids some of the moral objections associated with freezing embryos.  相似文献   

10.
骨性关节炎是影响人类健康及生活质量的最常见关节疾病之一,是一种以骨关节软骨退行性变和继发性周围骨质增生为特点的慢性关节疾病,又被称为退行性关节炎.多发于中老年人群,常累及全身骨关节中的脊柱、髋关节和膝关节等负重较大的关节,导致受累关节僵硬、变形,从而使关节功能受到严重影响,影响患者的生活质量。常见症状为受累关节疼痛,活动受限,休息后缓解及晨起关节僵硬感。由于人口老龄化加重,导致其发病率连年增加。但由于其病因及病机复杂多样,目前医学界还没有确切的结论,导致缺乏有效的治疗手段,本文就近几年来文献中提及的骨性关节炎病因及病机做一综述,有利于我们继续探索,早日认清这种疾病,治愈这种疾病,提高患者生活质量。  相似文献   

11.
In E. coli, Se-3 aminopropylselenocysteine or selenahomolysine (SeHL) does not affect intracellular lysine transport, i.e. it cannot bind E. coli lysine transport systems. In CHO cells it inhibits cationic aminoacid transport system, but only in the presence of Na+, this indicating that it behaves like polar neutral aminoacids. On the other hand, it poorly affects leucine transport both in the presence and in the absence of Na+. SeHL is not activated by aminoacyl-tRNA synthetase preparations from bacterial and mammalian sources, thus it cannot be utilized for protein synthesis.  相似文献   

12.
An established ethical principle of biomedical research involving human subjects stipulates that risk to subjects should be proportionate to an experiment's potential benefits. Sometimes this principle is imprecisely stated as a requirement that 'risks and benefits' be balanced. First, it is noted why this language is imprecise. Second, the persistence of such language is attributed to how it functions as a rhetorical trope. Finally, an argument is made that such a trope is infelicitous because it may not achieve its intended persuasive purposes. More importantly, it should be avoided because it masks the important role that chance plays in clinical research. Risk is the possibility of harm. As a precondition of harm it is unintended and undesirable in projects of biomedical research. It requires ethical vigilance. As a vehicle of chance, however, it is both intended and desirable. It requires methodological appreciation.  相似文献   

13.
Like any other society France is increasingly diversified culturally and in terms of collective identities. Clearly it is a multicultural, multi-identificational society, but it is not often willing to discuss openly the changes needed to accommodate its diversity and its de facto multicultural character. Michel Wieviorka has been courageous in trying to launch this crucial debate. In France his work is often appreciated but it is also often held to be ‘politically incorrect’ precisely because it questions the validity of the French republican model and its adequacy for the deep social changes at work in French society, and also because it raises the issue of the necessity of building a French multiculturalism. In this article the most important insights of Wieviorka's perspectives on multiculturalism are presented and some of the problems it implies are discussed.  相似文献   

14.
本文通过新疆种植黑加仑和天然黑加仑的脂肪油、八种微量元素、十七种氨基酸以及维生素C的含量进行测定比较,得出:天然黑加仑脂肪油含量为17.9%,种植黑加仑脂肪油含量为12.9%,其中,天然黑加仑脂肪油中,r-亚麻酸的含量为19.02%,而种植黑加仑中,其含量为10.20%,天然黑加仑中K,Na,Ca,Cu,Zn的含量比种植黑加仑含量高,但同时Fe,Mn,Mg元素的含量却比种植黑加仑含量低。种植黑加仑的维生素C含量为99.6mg/g,天然黑加仑的含量为108mg/g,天然黑加仑的氨基酸的总量为1.63%,种植黑加仑为1.55%。  相似文献   

15.
Most of the major livestock breeding organizations in the world are actively involved in using the emerging tools for genome analysis to obtain a better understanding of the molecular architecture of their favourite production traits. This is bound to generate a considerable amount of novel biological information that will provide a competitive advantage to those that have access to it. At present, the preferred avenue to exploit this information is via marker-assisted selection (MAS), and several breeding organisations are starting to implement MAS in breeding programs. However, it seems unlikely that the exploitation of genomics information will be limited to MAS in the future. Even though it is difficult to anticipate the ultimate impact of genomics on animal production, it would be very surprising if it were not to revolutionize this industry as it is already revolutionizing the biomedical and plant breeding industries.  相似文献   

16.
Statistical hypothesis testing is commonly used inappropriately to analyze data, determine causality, and make decisions about significance in ecological risk assessment. Hypothesis testing is conceptually inappropriate in that it is designed to test scientific hypotheses rather than to estimate risks. It is inappropriate for analysis of field studies because it requires replication and random assignment of treatments. It discourages good toxicity testing and field studies, it provides less protection to ecosystems or their components that are difficult to sample or replicate, and it provides less protection when more treatments or responses are used. It provides a poor basis for decision‐making because it does not generate a conclusion of no effect, it does not indicate the nature or magnitude of effects, it does not address effects at untested exposure levels, and it confounds effects and uncertainty. Attempts to make hypothesis testing less problematical cannot solve these problems. Rather, risk assessors should focus on analyzing the relationship between exposure and effects, on presenting a clear estimate of expected or observed effects and associated uncertainties, and on providing the information in a manner that is useful to decision‐makers and the public.  相似文献   

17.
粘虫的迁飞发生区及其分布的数学模型   总被引:1,自引:0,他引:1  
邬祥光 《生态学报》1981,1(4):327-334
粘虫(Mythimna separata Walker)的年周期远距离迁飞,早已为我国多数昆虫学者所证实(林昌善等、1963、1964;马世骏;1963;陈永林等,1963;李光博等,1964;陈瑞鹿等;1965;李绵春等,1965)。作者亦曾于1962年全国昆虫学会及1963年广东省植保学会上提出数据,同意此观点。并作出全国粘虫迁飞发生区地图,综合粘虫的水平迁飞及垂直迁飞为害实况,绘出福建南部,广东中、南部,广西中、南部,云南南部为第一次发生区,2—3月幼虫为害小麦。山东南部,河南中、南部,陕西东、南角西至贵州、四川、云南的平坝地  相似文献   

18.
As an embryo gastrulates or makes neural tissue it shortens across the dorso-ventral axis and extends dramatically along the perpendicular, antero-posterior axis, resulting in the embryo doubling in length. This process is known as convergent extension and it is so powerful in remodelling tissue that it is used time and again during development. New research in Drosophila melanogaster and other model organisms is shedding fresh light on how it happens.  相似文献   

19.
In chicken embryo pancreas on the 19th day the activity of alpha-amylase and especially of lipase is very low; it increases soon after until it reaches its highest level in 36 hours old chick. Then it falls considerably on the 2nd and 10th day of normal diet; finally it starts again: in fact in three months old chickens the activity of alpha-amylase is equal to thirty-six hours old chick's, while lipase's is lower than this last one.  相似文献   

20.
Ecological restoration是现代生态学最活跃的关键行动之一, 在我国被译为“生态恢复”。经查验其英语涵义和演变过程, 建议正名为“生态重建”, 指在人为辅助下的生态活动。而“生态恢复”(recovery)在国际文献中指没有人直接干预的自然发生过程, 二者不容混淆。作者强调自然恢复和生态重建的三类时间尺度, 即地质年代尺度(千、万、亿年)自然生态系统世代交替和演替尺度(十、百、千年)和生态建设时间尺度(一、十、百年)。前二者为自然恢复尺度。三者相差2-3个数量级或更多。人类不能超尺度地依赖自然恢复能力, 自然与人为时间尺度的不匹配是自然恢复难以满足人类社会生态需求的根本原因。作者质疑“以自然恢复为主”和“从人工建设转向自然恢复为主的转变”提法。认为把生态重建的责任推诿给自然去旷日持久地恢复, 是不负责任和不作为的逻辑和有悖于“谁破坏, 谁补偿; 谁污染, 谁治理; 谁享用, 谁埋单”的全球环保公理和生态伦理观念。除恢复重建自然的生态系统外, 还要发展人工设计生态方案等未来生态重建途径。  相似文献   

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