首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The paper shows that formulated by I. P. Pavlov principles of higher nervous activity are quite fruitful even today in investigations into the problems associated with contemporary new physiological trends as, for instance, cognitive processes. Special attention is paid to study of the principles of neurophysiological organisation of the mechanisms carrying out analysing and synthesising activities. I. P. Pavlov was the first to indicate the important role of frontal cortex in these processes.  相似文献   

2.
大学生自我心理治疗的过程、评定和原则   总被引:1,自引:1,他引:0       下载免费PDF全文
本文论述了大学生自我心理治疗一般过程中的四个阶段,自我心理治疗效果的评定方式、指标和评定依据,以及自我心理治疗的七个原则。  相似文献   

3.
4.
The molecular details of antigen processing and presentation by MHC class I and class II molecules have been studied extensively for almost three decades. Although the basic principles of these processes were laid out approximately 10 years ago, the recent years have revealed many details and provided new insights into their control and specificity. MHC molecules use various biochemical reactions to achieve successful presentation of antigenic fragments to the immune system. Here we present a timely evaluation of the biology of antigen presentation and a survey of issues that are considered unresolved. The continuing flow of new details into our understanding of the biology of MHC class I and class II antigen presentation builds a system involving several cell biological processes, which is discussed in this Review.  相似文献   

5.
microRNAs (miRNAs) and small interfering RNAs (siRNAs), which constitute two major classes of endogenous small RNAs in plants, impact a multitude of developmental and physiological processes by imparting sequence specificity to gene and genome regulation. Although lacking the third major class of small RNAs found in animals, Piwi-interacting RNAs (piRNAs), plants have expanded their repertoire of endogenous siRNAs, some of which fulfill similar molecular and developmental functions as piRNAs in animals. Research on plant miRNAs and siRNAs has contributed invaluable insights into small RNA biology, thanks to the highly conserved molecular logic behind the biogenesis and actions of small RNAs. Here, I review progress in the plant small RNA field in the past two years, with an emphasis on recent findings related to plant development. I do not recount the numerous developmental processes regulated by small RNAs; instead, I focus on major principles that have been derived from recent studies and draw parallels, when applicable, between plants and animals.  相似文献   

6.
Christensen AC 《Genetics》2000,155(3):999-1004
I have used an exercise involving domestic cats in the General Genetics course at the University of Nebraska-Lincoln for the past 5 years. Using a coherent set of traits in an organism familiar to the students makes it easy to illustrate principles of transmission and population genetics. The one-semester course consists primarily of sophomores and juniors who have either taken a one-semester introductory biology course, a one-semester cell biology course, or have a strong high school biology background. The students are given a handout and asked to determine the genotype at seven unlinked loci of at least one cat. To fill out the form, the students have to grasp such concepts as dominance, incomplete dominance, temperature-sensitive mutations, epistatic interactions, sex linkage, and variable expressivity. Completing the form reinforces these concepts as they observe the cat's phenotype and fill in the genotype. I then analyze the collected data and use it in my lectures on population genetics to illustrate the Hardy-Weinberg equilibrium, calculate allele frequencies, and use statistics. This allows the students to look at population genetics in a very positive light and provides concrete examples of some often misunderstood principles.  相似文献   

7.
In search of general generative principles I start from the postulate of a reality which comprises both materialistic and psychic aspects. This overall reality, described by others as the world of archetypes, is not directly accessible to sensory perception. Yet, by studying archetypical manifestations, it is possible to distinguish different structures or generative principles in it. Comparison of three models, which depict developmental processes in different disciplines, shows that they have the same basic structure. The effects of the archetypes involved can be described as four general generative principles: 1st the principle of wholeness (connection and integration of conflicting opposites), 2nd the principle of complementation and compensation (periodic change of opposite influences); 3rd the enstructuring principle (relative stability or spatial aspect of a manifest structure), and 4th the principle of gesture (change or temporal aspect of that structure).  相似文献   

8.
9.
Characterizing the N-terminal processing motif of MHC class I ligands   总被引:2,自引:0,他引:2  
Most peptide ligands presented by MHC class I molecules are the product of an intracellular pathway comprising protein breakdown in the cytosol, transport into the endoplasmic reticulum, and successive N-terminal trimming events. The efficiency of each of these processes depends on the amino acid sequence of the presented ligand and its precursors. Thus, relating the amino acid composition N-terminal of presented ligands to the sequence specificity of processes in the pathway gives insight into the usage of ligand precursors in vivo. Examining the amino acid composition upstream the true N terminus of MHC class I ligands, we demonstrate the existence of a distinct N-terminal processing motif comprising approximately seven residues and matching the known preferences of proteasome and TAP, two key players in ligand processing. Furthermore, we find that some residues, which are preferred by both TAP and the proteasome, are underrepresented at positions immediately preceding the N terminus of MHC class I ligands. Based on experimentally determined aminopeptidase activities, this pattern suggests trimming next to the final N terminus to take place predominantly in the endoplasmic reticulum.  相似文献   

10.
Disentangling the relative importance and potential interactions of selection and genetic drift in driving phenotypic divergence of species is a classical research topic in population genetics and evolutionary biology. Here, we evaluate the role of stochastic and selective forces on population divergence of a colour polymorphism in seven damselfly species of the genus Ischnura, with a particular focus on I. elegans and I. graellsii. Colour-morph frequencies in Spanish I. elegans populations varied greatly, even at a local scale, whereas more similar frequencies were found among populations in eastern Europe. In contrast, I. graellsii and the other five Ischnura species showed little variation in colour-morph frequencies between populations. F(ST)-outlier analyses revealed that the colour locus deviated strongly from neutral expectations in Spanish populations of I. elegans, contrasting the pattern found in eastern European populations, and in I. graellsii, where no such discrepancy between morph divergence and neutral divergence could be detected. This suggests that divergent selection has been operating on the colour locus in Spanish populations of I. elegans, whereas processes such as genetic drift, possibly in combination with other forms of selection (such as negative frequency-dependent selection), appear to have been present in other regions, such as eastern Europe. Overall, the results indicate that both selective and stochastic processes operate on these colour polymorphisms, and suggest that the relative importance of factors varies between geographical regions.  相似文献   

11.
The plasma membrane (PM) is a highly heterogenous structure intertwined with the cortical actin cytoskeleton and extracellular matrix. This complex architecture makes it difficult to study the processes taking place at the PM. Model membrane systems that are simple mimics of the PM overcome this bottleneck and allow us to study the biophysical principles underlying the processes at the PM. Among them, cell-derived giant plasma membrane vesicles (GPMVs) are considered the most physiologically relevant system, retaining the compositional complexity of the PM to a large extent. GPMVs have become a key tool in membrane research in the last few years. In this review, I will provide a brief overview of this system, summarize recent applications and discuss the limitations.  相似文献   

12.
Spore morphology of thirteen species of the genus Bryum Hedw. were observed by LM and SEM. The results show that the ornamentation of spore exine could be divided into three types: Type I , blunt at the top of baculate processes, to which four species belong: Bryum argenteum, B. lonchocaulon , B. uliginosum and B. arcticum. Type Ⅱ, sharp or with small processes at the top of baculate processes, represented by seven species: B. pallescens, B. caespiticium, B. pallens, B. pseudotriquetrum, B. paradoxum, B. alpinum and B. thomsoii. Type Ⅲ, expanded into hemispherical-shaped at the top of baculate processes, represented by two species: B.coronatum and B.sauteri. The Bryum species may also be divided into three groups according to the variation of spore diameter. Group I , with spore diameter under 10 μm, including one species, B. uliginosum. Group Ⅱ, with spore diameter 11~20 μm, including seven species: B. argenteum, B. alpinum, B. coronatum, B. pallens, B.paradoxum, B.sauteri, B.thomsonii. Group Ⅲ, spore diameter 21~30 μm, with five species: B. pallescens, B. caespiticium, B. pseudotriquetrum, B. lonchocaulon, B. arcticum. There are resemblances of spore morphology and exine ornamentation among the thirteen species. In the view of palynology, the genus Bryum is a natural taxon which is more advanced than the genus Pohlia Hedw. But spores of thirteen species are different at some characters such as diameter, shape ofproximal leptoma, etc., which indicates the genetic differentiation in the genus Bryum.  相似文献   

13.
Receptors have fascinated biologists for more than a century and they have fascinated me for the entirety of my own research career. The seven transmembrane receptors, also known as G protein coupled receptors, represent the largest of the several families of plasma membrane receptors, comprising more than a thousand genes and regulating virtually all known physiological processes in mammals. Moreover, they represent one of the commonest targets of currently used drugs. I have spent the entirety of my research career working on these receptors. Here I set down some personal reflections on the evolution of the field during the past 35 years, hanging the thread of the story on some of the work from my own laboratory.  相似文献   

14.
Receptors have fascinated biologists for more than a century and they have fascinated me for the entirety of my own research career. The seven transmembrane receptors, also known as G protein coupled receptors, represent the largest of the several families of plasma membrane receptors, comprising more than a thousand genes and regulating virtually all known physiological processes in mammals. Moreover, they represent one of the commonest targets of currently used drugs. I have spent the entirety of my research career working on these receptors. Here I set down some personal reflections on the evolution of the field during the past 35 years, hanging the thread of the story on some of the work from my own laboratory.  相似文献   

15.
本文提出和论述了岛礁型海洋生物保护区(IMPA)设计和管理的7条原则;生物多样性和稀缺性,生境典型性和完整性,物种-面积关系,海-陆生态交错带,人工自然化,生态脆弱性和自养型经济。并且结合我国第一个国家级海洋生物保护区-南麂列岛自然保护区(NINR)设计和规划的实践,说明如何实施这些原则。  相似文献   

16.
《Ecological Indicators》2008,8(2):115-122
Criteria and indicators (C&I) have emerged as a powerful tool in implementing sustainable forest management. In a relatively short period, around 150 countries have adopted C&I. Some processes have used C&I in forest management and produced progress reports. Six of the seven thematic areas common to all processes are also being used as a basis for reporting progress towards sustainable forest management [e.g., the Food and Agriculture Organization of the United Nations (FAO) in its Global Forest Resource Assessment 2005]. However, there are significant problems in the wider application of C&I. A number of countries are not using C&I at all, and in some countries where they are being used, it is not done in an effective manner. Areas that need improvement in order to promote the use of C&I include: (1) strengthening concepts and definitions; (2) rationalising criteria and indicators; (3) further research on indicators; and (4) utilising C&I in more effective ways. The future development of C&I must be based on an active link between research effort and operational needs in order to prevent a waste of resources and effort. Some of the research undertaken to date has led to the adoption of innovative approaches to optimise resource use and simplify application. This paper identifies areas needing more research and draws from ongoing work to show where progress is being made.  相似文献   

17.
Krasnovskiĭ AA 《Biofizika》2004,49(2):305-321
The primary mechanisms for the photodynamic action of pigments and dyes, the principles of their division into mechanisms of type I and type II, and the role of these processes in biological systems are reviewed. Singlet oxygen is considered to be an indicator of the mechanisms of photodynamic reactions. The methods of its detection are described, which are based on the use of chemical traps, measurements of infrared phosphorescance at 1270 nm, and the registration singlet oxygen-sensitized delayed fluorescence caused by the summation of the energy of two singlet oxygen molecules by one dye molecule.  相似文献   

18.
Numerous cell membrane associated processes, including signal transduction, membrane sorting, protein processing and virus trafficking take place in membrane subdomains. Protein-protein interactions provide the frameworks necessary to generate biologically functional membrane domains. For example, coat proteins define membrane areas destined for sorting processes, viral proteins self-assemble to generate a budding virus, and adapter molecules organize multimolecular signalling assemblies, which catalyse downstream reactions. The concept of raft lipid-based membrane domains provides a different principle for compartmentalization and segregation of membrane constituents. Accordingly, rafts are defined by the physical properties of the lipid bilayer and function by selective partitioning of membrane lipids and proteins into membrane domains of specific phase behaviour and lipid packing. Here, I will discuss the interplay of these independent principles of protein scaffolds and raft lipid microdomains leading to the generation of biologically functional membrane domains.  相似文献   

19.
首次研究了7种凤仙花属(ImpatiensL.)植物茎的解剖学及细胞组织中草酸钙结晶的特征.结果表明,7种凤仙花属植物茎的解剖学结构非常近似,而茎中草酸钙结晶特征则差异显著,7种凤仙花属植物茎中均有草酸钙针晶,根据草酸钙结晶形态特征的不同,将针晶分为3种类型,即针晶束、针晶簇和散针晶.其中,黄金凤、长角凤仙花、锐齿凤仙花和红纹凤仙花有针晶束分布,而湖北凤仙花、紫花黄金凤和窄萼凤仙花则无针晶束分布,只有针晶簇或散针晶分布;此外,针晶的形态、长度、排列方式及丰富程度等在不同的物种中亦有差异.草酸钙结晶特征对凤仙花属植物的分类具有一定的科学意义.  相似文献   

20.
This article introduces a collection of seven papers that offer anthropological examinations of contemporary food‐related practices in the Australasian‐Pacific region. The collection is based on those presented in the panel ‘Eat me! An anthropological examination of food’ at the Australian Anthropological Society Annual Conference, La Trobe University, Melbourne, 2001. I set out the ethnographic terrain of food in processes of contemporary Australian cultural production, introduce the articles and then briefly discuss the three key themes of the collection. These are the trajectory of grand processes, such as colonialism, in the intimate movements of daily life; the reproduction of social forms via socialities relating to food and commensality; and the (sensory) manifestation and embodiment of epistemes (such as gender) in food‐ and consumption‐related values and practices.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号