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1.
Experiments were conducted on rats during the early postnatal period; a study was made of the membrane potential (MP) establishment of the fibers of the skeletal muscles of the neck, the anterior and the posterior limbs. At birth the most mature were the muscles of the neck, and the least -- the muscles of the posterior limb. Establishment of the stationary MP level in the muscles of the neck occurred during the first week after birth, in the muscles of the anterior limbs -- by the 10th-12th day, and of the posterior limbs -- by the 15th-20th day. The order of maturation of various groups of the skeletal muscles was associated with the peculiarities of the neuro-trophic influences at various age periods. Muscles of the neck were characterized at all the developmental stages by a rhythmic low-frequency electromyographic activity. In the muscles of the limbs the rhythmic electromyographic activity was transformed into the discharge high-frequency activity by the period of termination of increase of the MP of the muscles.  相似文献   

2.
The time course of changes in the hand muscle activity and the grip force before the hit of an object falling from different heights into a cup held between the thumb and the forefinger was analyzed in three variants of the experiment: (1) the subject saw the object falling; (2) the subject did not see the object falling but initiated the fall; and (3) the subject had no information on either the falling or its start. In the third variant, the muscle activity and the grip force changed in response to the object hitting the cup. In the second variant, the muscle activity and the grip force began to change 200–280 ms before the hit, this time being independent of height from which the object fell. In the first variant, the anticipatory changes began 150 ms after the object started falling and did not depend on the height of the falling within the rage 30–50 cm. If the object fell from a height of 70–105 cm, the changes in the muscle activity and the grip force began a fixed time before the object hit the cup, which did not depend on the height from which the object fell. Thus, when the object fall from small heights, the timing of the increase in the grip force was mainly determined by the moment when the object began moving; at large heights, the increase in the grip force was related to the presumed moment of the hit.  相似文献   

3.
Ab initio molecular orbital calculations were made for the various types of structures of the pore of the ion channel and the results were applied to the permeability model by Hille, an extension of the Eyring rate theory. In Hille's model, ion passage through the channel is regarded as a kinetic process. Accordingly, it is thought that the interaction energy between cation and ligand, the easier the passage is, due to the lower activation energy. The calculated interaction energy was in the order Li+ greater than Na+ greater than K+ for all models. The optimum size of the pore determined from the interaction energy depends on the structure of the filter. The size for the pentagon was largest, followed by the hexagon and tetragon. On the other hand, the size depends hardly at all on the kind of ligand molecules. In the case of the tetragon, the sizes for the Na and K channels were nearly the same as those estimated from the model building and inhibitor-blocking experiment. The interaction energy between the ionized carboxyl group and the cation was extremely large, clearly reflecting the experimental fact that the carboxyl group in the pore has an important role in making the passage of the cation through the channel easier by dehydrating the water molecules. By analysis of the interaction energy, it was revealed that the contribution of the electrostatic energy was predominant, although the contributions of the other effects might not be negligible. Among these effects, the value of the charge transfer energy is largest, and this is noteworthy in connection with the selective transmission of cations through the overlap of orbitals. It is concluded that the quantum-chemical indices such as interaction energy and the electronic charge calculated by the sophisticated ab initio method help to shed light on the nature of the pore of the ion channel.  相似文献   

4.
In the first part of the paper, the results of the investigation of the rhodopsin arrestin interaction are presented. The results were mainly obtained with the technique of the selective labelling of the rhodopsin and arrestin SH-groups and the rhodopsin limited proteolysis. These results are discussed in the frame of the latest data on the three-dimensional structure of arrestin. In the second part of the paper, results of the antigenic properties of arrestin (S-antigen) and its role in the pathogenesis of the retina diseases are summarized. The data on the role of the autoimmune processes in the pathogenesis of diabetic retinopathy are presented. We have also described the results of the use of the elaborated technique of the immune diagnostics in the prognosis of the diabetic retinopathy and retinopathy of the premature babies.  相似文献   

5.
纵坑切梢小蠹蛀梢期空间分布   总被引:11,自引:0,他引:11  
在昆明地区,纵坑切梢小蠹(Tomicus piniperda)成虫蛀梢多集中在蛀干木附近。种群密度以蛀干木为中心向周围是指数递减,散布半径约30m。在蛀虹梢过程中,该种群逐渐向新区扩张。在树冠内,纵坑切梢小蠹主要分布在4—10轮枝上。第7轮技虫口百分率最高。6—7轮枝受害率最大。树冠上层受害较其下属于重。从树冠水平层次考察,树冠外层虫量相对集中,约为树冠中、内层虫量之和。树冠内层虫量最少。纵坑切梢小蠹在树冠内的种群分布系由梢径、种群密度、蛀梢行为、降落方式、光照等因素综合影响的结果。  相似文献   

6.
This paper reports a quantitative study of the effect of ring substituents in the 1-position of the aromatic ring on the rate of monophenol hydroxylation and o-diphenol oxidation catalyzed by tyrosinase. A possible correlation between the electron density of the carbon atom supporting the oxygen from the monophenolic hydroxyl group and the V Mmax values for each monophenol was found. In the case of o-diphenols the same effect was observed but the size of the side-chain became very important. NMR studies on the monophenols justified the sequence of the V Mmax values obtained. As regards the o-diphenols, on the other hand, only a fair correlation between NMR and V Dmax values was observed due to the effect of the molecular size of the ring substituent. From these data, it can be concluded that the redox step (k33) is not the rate-determining step of the reaction mechanism. Thus, the monophenols are converted into diphenols, but the order of specificities towards monophenols is different to that of o-diphenols. The rate-limiting step of the monophenolase activity could be the nucleophilic attack (k51) of the oxygen atom of the hydroxyl group on the copper atoms of the active site of the enzyme. This step could also be similar to or have a lower rate of attack than the electrophilic attack (k52) of the oxygen atom of the active site of oxytyrosinase on the C-3 of the monophenolic ring. However, the rate-limiting step in the diphenolase activity of tyrosinase could be related to both the nucleophilic power of the oxygen atom belonging to the hydroxyl group at the carbon atom in the 3-position (k32) and to the size of the substituent side-chain. On the basis of the results obtained, kinetic and structural models describing the monophenolase and diphenolase reaction mechanisms for tyrosinase are proposed.  相似文献   

7.
A study was made of the accumulation of antibodies in the blood serum and the secretions of the respiratory tracts of persons immunized with the living influenza vaccine. The duration of inductive phase and the dynamics of the antibody accumulation in the secretions occurred irrespective of their initial level in the blood sera, this pointing to the autonomic character of the local immunity system. On the other hand the functional condition of the system of local immunity influenced the intensity of the antibody formation in the system of the general immunity. If before the immunization the antibody titre in the secretions were 1:4 and greater, the antibody accumulation in the blood sera took place less intensively. An analogous phenomenon was also observed when the antibodies were absent in the secretions before the immunization, but their formation took place as soon as the first week after it. The mechanism of this peculiar "competition for the antigen" of the systems of local and general immunity consisted in the neutralization of the influenza virus in the area of the porta of infection.  相似文献   

8.
Because of their great abundance and amenability to fully automated genotyping, single-nucleotide polymorphisms (SNPs) and simple insertion/deletion are emerging as a new generation of markers for positional cloning. Although the efficiency and cost associated with the markers are important in the mapping of human disease genes, the power to detect the linkage between the marker and the disease locus, as well as the accuracy of the estimation of the map location of the disease gene, dictate the selection of the markers. Both the power and the accuracy depend not only on the type of the markers but also on other factors, such as the age of the disease mutation, the magnitude of the genetic effect, the marker-allele distribution in the population, mutation rates of marker loci, the frequency of the disease allele, the recombination fraction, and the methods for mapping the human disease genes. In this article, we develop a mathematical framework and the analytical formulas for calculation of the power and the accuracy and investigate the impact that the aforementioned factors have on the power and the accuracy, by using two population-based gene-mapping methods-likelihood-based linkage-disequilibrium mapping and the transmission/disequilibrium test, for both biallelic SNPs and microsatellites. These studies provide not only guidance in selection of the markers and in the design of the sample scheme for positional cloning but also insight into the biological bases of the mapping of human disease genes.  相似文献   

9.
水文变异下的黄河流域生态流量   总被引:2,自引:0,他引:2  
张强  李剑锋  陈晓宏  江涛 《生态学报》2011,31(17):4826-4834
使用t检验和Mann-Whitney U检验对黄河干流7个水文站月均流量进行水文变异分析,探讨了水文变异成因,在此基础上,确定变异前各月月均流量序列最适概率分布函数,将概率密度最大的月平均流量定义为河道内生态流量。经与Tennant法、最小月平均流量发和逐月径流法比较,考虑水文变异的河道内生态流量计算方法是可行、合理的。水文变异后,黄河干流7水文站月均流量普遍减少,月均流量满足河道内生态流量的频率降低。研究结果表明,人类活动是黄河生态系统水环境恶化的重要原因。在流域生态管理中,确保变异后生态流量满足频率与变异前相当。研究对于理解在当前气候变化与人类活动双重影响下,干旱半干旱区流域水资源科学管理具有一定理论与现实意义。  相似文献   

10.
The following conclusions may be drawn from the results in this work. The respiratory cycles are formed by the neuronal machinery in the reticular formation under the posterior part of the vagal motor nucleus. The motor neurones or the neuronal networks composing the motor nucleus of the respiratory muscles tonically discharge the action potentials, when the neurones or the networks are released from the inhibitory influences of the interneurones connecting the neuronal machinery to the motor neurones. Furthermore, the interneurones probably generate the tonic discharges after removing the inhibitory influences of the other interneurones or the neuronal machinery on them. A reflex mouth closing is elicited by a mechanical stimulus applying on the upper lip. The motor neurones of the m. adductor mandibulae are activated via only one synapse in the reflex. The reflex action potentials recorded from the motor nerve reduce in amplitude at the resting phase of the nerve in the respiratory cycles. These results suggest that the respiratory motor neurones are by nature spontaneous generators of the tonic action potentials and, in the time of the normal breathing, the tonic activity is interrupted by an inhibitory influence of the neuronal machinery generating the respiratory cycles.  相似文献   

11.
银杏套细胞发育的解剖学研究   总被引:3,自引:2,他引:1  
银杏套细胞起源于近雄配子体表达的颈卵器母细胞周围细胞,中央细胞形成时,套细胞呈明显的一层,围绕颈卵器紧密排列,随着颈卵器的发育,套细胞体积逐渐地大,细胞质变浓厚,细胞质中脂滴增多,套细胞和中央细胞的接触壁开始出现局部加厚,在颈卵器发育的泡沫化阶段,套细胞和中央细胞的接触壁不均匀加厚较为显著,在较薄的区域可见胞间连丝,受精前,套细胞中液泡增多,脂滴迅速减少,造淀粉体增大,套细胞与卵细胞的接触壁的不均匀加厚非常明显,精核进入颈卵器以后,卵细胞与套细胞的接触壁和卵细胞的质膜之间形成一个薄厚不均的间隔层,受精卵分裂时,受精卵细胞与套细胞接触壁的凹陷处可见许多小泡和内质网,游离核期时,套细胞内出现大量小液泡,细胞内含物迅速消失,套细胞外形变长,胚胎长出颈卵器后,套细胞逐渐解体消失。  相似文献   

12.
On lines of the mice genetically differing on the sensitivity on emotional stress (steady--of the mouse of the line C57BL/6 or sensitive--of the mouse of the line BALB/c), the research of the development of the adaptive reactions in the system of the blood on the emotional stress influencing animals on the background of the preliminary irradiation in a low dose (0.9 Gy) is carried out. The unirradiated mice of the line C57BL/6 adequately reacted on the stress, that was shown in a moderate behavioural reaction during the period of stress, and the development of high-grade adaptive reactions in the hemopoietic system. Among the mice of the line C57BL/6 in conditions of the combined influence of ionizing radiation and of the emotional stress was not revealed of the infringements of the adaptive reactions of the hemogenesis. As opposed to these data, among unirradiated mice of the line BALB/c the sharply expressed behavioural reactions during the stress were marked, that was accompanied by incomplete development of the adaptive reactions in the system of a blood on the stress. Under the influence of stress on the previously irradiated animal line BALB/c was observed the inhibition of the medullar hemopoiesis.  相似文献   

13.
A universal procedure for controlling the sylphon hermeticity is discussed. Travelling sylphon or membrane diaphragms in combination with a dublicate sylphon are used as a separating element at the border of the separating media, e. g. the medium transporting through the valve and the environmental air. Pneumatic pressure higher than the working pressure of the separating medium is created inside the space between the working and the dublicate sylphons. If the hermeticity of one of the above sylphons is broken, the excessive pressure inside the space between them is reduced which is automatically stated by means of a pneumatic probe. Because of detection of the breach in the hermeticity of one of the sylphons in proper time, when the second sylphon is safe, the contact of the transporting medium with the environmental air is prevented. The described procedure for controlling the hermeticity is universal since it provides the use of the probes working only under the pressure independent of the type and physico-chemical properties of the separating medium. One of the important advantages of the new procedure is also the fact that the working sylphon appears to be empty since the outer with respect to it pressure of the separating medium is practically balanced by the pressure created in the sylphon space.  相似文献   

14.
15.
Analysis of the biometric parameters of dunlins is based on data of 496 adult birds and 214 birds in their second year of life captured during the spring migration in the years 2002–2014 in the floodplain of the Pripyat River in southern Belarus. The average size of the dunlins caught in this area shows that the majority of birds correspond to the parameters of the nominate subspecies (C. a. alpina). We have not found any statistically significant differences between the age groups in all morphometric parameters except for the length of the wing, which in the birds in their second year of life is slightly smaller than in adults. Both the adult dunlins and the yearlings have two peaks in the distribution of biometric parameters, such as the bill length to the nostril, the bill length to the feathering, the total length of the head with the bill, and the length of the wing, which is associated with differences in the size of males and females. We have noted an increase in the average bill length to the nostril, bill to feathering length, and the total length of the head with the bill, as well as the wing length in the adult birds captured during the spring migration. These values are especially significant in the last five days of May. The body mass index of the dunlins passing through the floodplain of the Pripyat River increases intensively during the migration, which can partly be attributed to the later migration of large birds (females). However, the main reason for the increase in the body mass index is that the birds migrating later in spring have higher energy reserves compared with the earlier migrants. At the end of the migration period, in the floodplain of the Pripyat River, the body mass indices of dunlins are very high. This suggests that birds leaving the stopover site in southern Belarus in early June have sufficient energy resources to reach the nesting places in one nonstop flight.  相似文献   

16.
目的:对枕骨斜坡骨性结构及周围毗邻关系的解剖学测量,为经口咽入路行枕骨大孔扩大术提供详尽的解剖学数据及理论依据。方法:①选取成人干燥颅骨标本40例,分别测量斜坡颅底内面、颅底外面的长度;斜坡咽结节处宽度、斜坡最小厚度、中部厚度和最大厚度;斜坡与水平面的夹角;颈动脉管外口内缘、颈静脉孔内外口内缘、破裂孔内外口内缘、舌下神经内外口内缘、寰枕关节内缘与斜坡中线的距离。②选取完整头颈部标本20例,观察斜坡与周围血管神经的毗邻关系。结果:①斜坡颅底内面长(40.1±2.5)mm,外面长(28.2±3.1)mm;斜坡中部宽度(18.8±2.5)mm,;最小厚度(6.8±2.3)mm,;中部厚度(9.8±2.2)mm,最大厚度(11.5±1.7)mm;咽结节至枕骨大孔前缘距离(12.8±1.5)mm。②斜坡与水平面的夹角(46.8±4.5)°。③颈动脉管外口内缘距离斜坡中线(26.1±3.1)mm,颈静脉孔内口内缘距离斜坡中线(21.8±2.5)mm,颈静脉孔外口内缘距离斜坡中线(25.1±2.7)mm,破裂孔内口内缘距离斜坡中线(10.5±2.9)mm,破裂孔外口内缘距离斜坡中线(11.8±2.5)mm,舌下神经管内口内缘距离斜坡中线(13.8±2.3)mm,舌下神经管外口内缘距离斜坡中线(21.1±2.3)mm,寰枕关节内缘距离斜坡中线(10.5±2.3)mm。④斜坡上部距离后方基底动脉(7.6±1.0)mm,距离后方脑桥(8.3±1.2)mm,斜坡中部距离后方延髓脑桥沟(13.5±1.7)mm,斜坡下部距离后方延髓(6.5±0.8)mm。⑤斜坡上部与后方硬脑膜之间间隙为(1.8±0.2)mm,斜坡中部与后方硬脑膜之间间隙为(1.3±0.1)mm,斜坡下部与后方硬脑、脊膜之间间隙为(1.3±0.1)mm。⑥在斜坡开骨窗的宽度为20mm,高度为15mm,深度为6mm,可以满足经口咽入路枕骨大孔扩大术的要求,并有可靠的安全性。结论:本研究通过对斜坡骨性结构及周围毗邻关系的测量与观察,为临床斜坡区手术提供解剖学数据。  相似文献   

17.
The development of the egg-apparatus (consisted of an egg cell and two synergids) of rice ( Oryza sativa L. ) was studied at the uhrastructural level. The walls of the egg cell and synergids, immediately after their formation, possessed numerous plasmodesmata. Plasmodesmata were also present on walls between the egg cell and synergids. During the enlargement phase of the egg cell and synergids, the walls at the tip region began to loosen and vesiculate. By the time the embryo sac became mature, the part of the wall of the egg cell and synergids, facing the chalaza, disappeared. Consequently, the tip regions of the egg cell and synergids were only protected by a plasma membrane. When the embryo sac reached full maturity, the upper and middle region of the wall of the synergids broke up into pieces. At that time one synergid began to degenerate. Plasmodesmata persisted at the hook region of the wall of both the egg cell and synergids. Most plastids in the egg cell contained starch grains that persisted throughout the period of the embryo sac development. Starch grains in the plastids of the synergids appeared only before the time when the two polar-nuclei moved into the region above the egg-apparatus. They then disappeared and did not appear again until the embryo sac had reached full maturity. The size and location of the vacuoles in the egg cell were different from those in the synergids. The time of formation was also different. Vacuoles in the egg cell formed late in comparison with the synergids. Vacuoles in the chalazal region of the egg cell (especially at the early stage of the embryo sac development) were much larger than those in the micropylar region. Vacuoles in the synergids tended to concentrate mainly in the chalazal region. There was a peak period of lipid formation in the two synergids. The peak appeared when the embryo sac neared maturity. At the early stage of development, the nuclei of the synergids were elliptical in shape and were situated at the central region near the micropyle. The shape of the nuclei at the late stage of development became less regular and tended to move more towards the micropylar region. Changes in the uhrastructure of the egg cell and synergids of rice appeared to be closely related to the metabolic processes controlling the embryo sac formation and development.  相似文献   

18.
The effects of villosity and distension on the absorptive and secretory flux in the small intestine were investigated theoretically in a simplified model. In the case of low epithelial permeability, villosity increases both fluxes by surface enlargement, but in the case of high epithelial permeability, this occurred only if the intervillous spaces are very narrow. Otherwise, the flux is reduced due to the intervillous diffusion resistance, which is more effective than the enlargement of the surface area in that case. Distension increases the fluxes due to the additional surface exposed, by opening the intervillous spaces. In the case of low epithelial permeability this increase exceeds that expected from the enlargement of the smooth inner cylindrical surface area. In the case of high epithelial permeability, however, the increase of the fluxes exceeds surface enlargement only in the first phase, just after opening the intervillous spaces. Otherwise, the increase of the flux is less, since the hindrance by the intervillous diffusion resistance is more effective than the increase of the smooth inner cylindrical surface area. In the intervillous spaces the concentration gradient is non-linear with the steepest slope at the entrance due to the permeation through the lateral surfaces of the villi. The gradient approaches linearity in the center of broad intervillous spaces and becomes steeper when the width decreases and the epithelial permeability increases. In rat small intestine broad intervillous spaces are formed at the front sides of the trapezoidal villi by the predominant circular distension. The diffusion resistance in these spaces and the increase of the supravillous diffusion resistance weaken the increase of the absorptive and secretory flux by distension, especially in the case of high epithelial permeability.  相似文献   

19.
慈竹的数量生态研究   总被引:1,自引:0,他引:1       下载免费PDF全文
 慈竹生态研究的结果如下:(1)用逐步回归分析模型分析,慈竹竹丛密度仅与土壤厚度关系密切.慈竹高度、胸径与海拔成正相关。(2)用逐步回归法分析笋生长量与气候因子间的关系,证明笋的逐日生长量与湿度,温度和降雨量有较密切关系,笋在一天内有两个生长高峰。(3)自然条件下,出笋数主要与土厚密切相关,退笋数受母竹高和出笋数所制约,好笋数主要受土厚和竹高影响。  相似文献   

20.
The duration of the cellular cycle and the diurnal rhythm of the amount of mitosis were studied in young rats in normality and under the influence of thyroxin. The parenchymal and connective-tissue cells of the liver and cells of the liver and the cells of the oesophagus epithelium basal layer were studied. It was found that under the influence of thyroxin there occured a shortening of the periods of the cellular cycle and a 3--6 h shift to the left of the diurnal rhythm curve of the amount of mitoses. In thyroxinized animals the 21--95% increase of the amount of mitoses in the period of maximum values of the mitotic index during a day was observed as compared with control animals. A conclusion is made about the diurnal rhythm of sensitivity of G0-phase cells to the synchronizing factor, suggesting the decisive significance of the state of the cell population in the interaction of the tissue and hormone cells. The data obatained in the work show that the thyroid hormones regulate the cellular reproduction in the organism by stimulating the cells in the division cycle, synchronization of greater amount of cells by the moment of beginning of the mitotic cycle at a definite time of day and by shortening the period of the cell mitotic cycle.  相似文献   

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