Regeneration of muscle fibers in the extensor digitorum longus muscle of the aged rat

Regeneration of muscle fibers was observed in the extensor digitorum longus (EDL) muscle of aged (24 and 27 months) Wistar rats. The aged muscles consisted almost exclusively of medium-sized muscle fibers. In addition to degenerating and/or atrophied muscle fibers, very small muscle fibers <10 mum in diameter were observed in some muscle bundles which sporadically distributed in the muscle. In the degenerating muscle fibers, satellite cells mostly appeared to be normal, possibly surviving within the scaffold of basal lamina to form new (regenerating) muscle fibers. However, some of the satellite cells were degenerated and destroyed, suggesting the decrease in number of muscle fibers. On the other hand, very small muscle fibers existed between small and/or medium-sized muscle fibers or in the wide interstitial spaces between them solitarily or in small groups. In addition, immature muscle cells having a centrally located nucleus and sporadically distributed myofilaments were observed among the small and/or medium-sized muscle fibers and partially lacked a layer of basal lamina. These immature muscle cells were often closely apposed to fibroblasts with some slender cytoplasmic processes and/or to each other without an interposing basal lamina. These findings suggest that in addition to satellite cells within the basal lamina tubes, some of the regenerating muscle fibers in the aged EDL muscle may be originated from mesenchymal cells such as fibroblasts in the interstitial spaces.     

Fine structural study of the regeneration of muscle fibers in the rat soleus muscle during aging

We examined the regeneration of muscle fibers in the soleus muscle of mature (12 months) and aged (24 and 27 months) rats by using electron microscopy. In both mature and aged muscles, regenerating muscle fibers were mainly formed within the scaffolds of basal laminae after necrosis. In the aged muscle, however, satellite cells within the scaffolds were occasionally destroyed, and immature muscle cells occurred in and around muscle bundles. These findings suggest that new muscle fibers formed in the interstitial spaces may contribute to the total number of regenerated muscle fibers. The origin of the immature muscle cells is briefly discussed.     

Scanning electron microscopic study of muscle spindles in the tenuissimus muscle of the Chinese hamster: with reference to the outer capsule, inner capsule and fusimotor endings

The outer capsule, inner capsule and fusimotor endings of muscle spindles in the tenuissimus muscle of mature Chinese hamsters were examined by scanning electron microscopy (SEM). The thin and long tenuissimus muscle was transversely cut into several segments, and the segments were longitudinally or obliquely cut with a razor blade to mechanically remove the spindle sheath (outer capsule). These specimens were treated with 8 N HCl at 60 degrees C to isolate the muscle spindles and clearly expose the internal structures such as the inner capsule and fusimotor endings innervating intrafusal muscle fibers. The spindle sheath was about 1 mm long and at the equator about 50 microm in diameter. Within the outer capsule, cells of the inner capsule in the equatorial region were polygonal in shape, and continuously surrounded the axial bundle like a sleeve. This continuous sheath became sieve-like in the juxta-equatorial region, depending on the twining of thin and flattened cytoplasmic extensions and/or processes of the cells. Owing to the continuous inner capsular sheath in the equatorial region, the arrangement of sensory endings were not visualized under SEM. Fusimotor endings observed in the juxta-equatorial and polar regions consisted of poorly-developed subneural apparatuses with predominantly pit-like and short slit-like junctional folds.     

Modeling of surface myoelectric signals. I. Model implementation

The relationships between the parameters of active motor units (MU's) and the features of surface electromyography (EMG) signals have been investigated using a mathematical model that represents the surface EMG as a summation of contributions from the single muscle fibers. Each MU has parallel fibers uniformly scattered within a cylindrical volume of specified radius embedded in an anisotropic medium. Two action potentials, each modeled as a current tripole, are generated at the neuromuscular junction, propagate in opposite directions and extinguish at the fiber-tendon endings. The neuromuscular junctions and fiber-tendon endings are uniformly scattered within regions of specified width. Muscle fiber conduction velocity and average fiber length to the right and left of the center of the innervation zone are also specified. The signal produced by MU's with different geometries and conduction velocities are superimposed. Monopolar, single differential and double differential signals are computed from electrodes placed in equally spaced locations on the surface of the muscle and are displayed as functions of any of the model's parameters. Spectral and amplitude variables and conduction velocity are estimated from the surface signals and displayed as functions of any of the model's parameters. The influence of fiber-end effects, electrode misalignment, tissue anisotropy, MU's location and geometry are discussed. Part II of this paper will focus on the simulation and interpretation of experimental signals.     

A fiber laser with a comb-like spectrum

An unpolarized comb-like spectrum is emitted from a fiber laser constructed from a Nd-doped silica fiber connected to an undoped high-birefringence fiber. Depending on the overall birefringence of the high-birefringence fiber, spectral spacings of 0.8 nm to 4 nm between two adjacent wavelengths were obtained, with as many as eight simultaneous discrete peaks. No intracavity polarizing elements were used, and the observed spectral characteristics are due to parasitic reflections at the interface between the two fibers     

An ultrastructural study of age-related changes in mouse olfactory epithelium

Transmission and scanning electron microscopic examinations were undertaken to detail changes in the olfactory epithelium (OE) resulting from the ageing process. Samples were prepared from 3% glutaraldehyde/1% formaldehyde perfused mice aged 6 months and 29-30 months. Compared to OE from young adults, a number of striking changes were apparent in tissue from older animals. The most obvious of these were extensive local accumulations of large inclusion bodies, totally disrupting the normal morphology of such affected areas of olfactory epithelium. Even in areas where these deposits were absent, other significant signs of ageing were noted in the seemingly unaffected OE of all older mice studied. Quantitative analysis of semi-thin resin sections revealed that the OE of aged mice was significantly reduced in thickness, and with significantly fewer olfactory sensory neurons, irrespective of whether or not inclusions were present. In addition, pale cells, which have been suggested to be a form of degenerating cells, were more abundant in aged OE. The straight, sharp boundary between respiratory and olfactory epithelia which is seen in young adults became irregular and disrupted with age due to an intermingling of the respiratory and olfactory cells. Such structural alterations may parallel olfactory dysfunction reputed to occur in older mammals.     

胆管细胞癌浸润性生长的电镜观察

本文报道了亚硝基吗啉诱发的大鼠浸润性胆管癌的超微形态结构，发现浸润癌细胞胞浆内存在大量纤维性成分，细胞间隙明显增宽，癌细胞核拉长，胞浆伸出伪足，提示其阿米巴样运动，并以此方式实现浸润性生长，最后突破基底膜，直至伸抵邻近血管。本文所观察到的３例胆管癌，其细胞极向性及细胞间连结均保持完好，属分化较高类型。     

Study of the Action of Static and Dynamic Fusimotor Fibers With a Mechanical Model of the Mammalian Muscle Spindle

A model of the mammalian muscle spindle having three distinct parts is proposed. The three parts, which consist of a mechanical filter, a transducer, and an encoder, are closely related with their physiological counterparts. A study of the generator potentials for the primary and secondary endings of the spindle was performed by means of an analog computer simulation of the model. The afferent responses of the spindle under a phasic stretch with and without fusimotor fibers simulation are also studied. Finally, frequencygrams (see text) are obtained under the condition of ?1 (dynamic) stimulation acting on both nuclear bag and nuclear chain fibers. The model yields results that are directly comparable with physiological data obtained under similar conditions.     

Novel muscle spindles containing muscle fibers devoid of sensory innervation in the extensor digitorum longus muscle of aged rats

We examined the structural features of muscle spindles at the equatorial and juxtaequatorial regions in the extensor digitorum longus muscle of adult (12 months) and aged (25 months) rats. In aged muscle spindles, the lamellated layers of the spindle capsule were a little increased in number compared to those in the adult ones. Two novel muscle spindles were observed in the aged muscle. In one muscle spindle, the spindle capsule contained four thin intrafusal muscle fibers invested by the inner capsule and two muscle fibers between the layers of the spindle capsule. Serial semithin sections revealed that the latter lacked the investment of the spindle capsule at the polar region. The other muscle spindle contained four intrafusal muscle fibers: two thin sensory-innervated muscle fibers invested by the inner capsule and two thick muscle fibers similar in structural features to neighboring extrafusal muscle fibers and lacking sensory innervation within the wide periaxial space. These findings suggest that two muscle fibers between the layers of the spindle capsule may be invested by the newly formed capsular cells during aging, while two thick fibers within the periaxial space may fail to receive the sensory innervation during the early development and follow the course of extrafusal fiber differentiation.     

Reflecting Rubber Characteristics of Anisotropic Sheets and Measurement of Complex Permittivity Tensor

Complex values of the permittivity tensor of robber sheets which are manufactured by the rolling process were estimated by the least-squares method using the reflection coefficient measured for normal incidence. First, the frequency characteristics of the reflection coefficients of a rubber sheet backed by thin aluminum were measured from 8.5 to 10.5 GHz by changing the rolling angle relative to the incident electric field. Next, the elements of the permittivity tensor were determined by the least-squares method from many data of measured reflection coefficients of the samples. Five kinds of rubber sheets containing carbon particles or fibers were selected, and circular pieces 30 cm in diameter were measured by this method. The complex permittivity tensors including off-diagonal elements were thus obtained, and the principal directions of the tensor were calculated from the measured permittivity tensor. The following facts were found through this analysis: The permittivity element in the rolling direction is about five times larger and the off-diagonal elements are small compared with the diagonal elements. The principal direction of the real part is different from that of the imaginary part for a certain kind of rubber sheet mixed with carbon particles.     

Characteristics of the carcinogenic action of methyl(acetoxymethyl)nitrosamine and DNA repair in rats of different ages

A pattern of DNA methylation and carcinogenesis has been studied in young (3 month-old) and old (14 month-old) female rats following a single intravenous injection (13 mg/kg) of methyl(acetoxymethyl)nitrosamine (DMN-OAc). The incidence of various tumours as well as the incidence of tumours in some peculiar sites were found to be similar in young and old DMN-OAc-treated rats. The life time of old rats was less than that in young animals; the average period of tumour detection was also shorter in old rats. In both young and old animals the highest concentrations of methylated purines were found in lung and kidney DNA. However, the level of DNA methylation in old rats was higher than in corresponding tissues of young animals. Efficiency of O6-meG repair in methylated template DNA was found to be the highest in liver extracts of 1- and 12-month-old rats. Further, by the age of 2 years, the activity of O6-meGT decreased. The findings suggest that different age periods could be characterized by different efficiency of DNA alkylation, synthesis and repair.     

老龄大鼠脑缺血再灌注海马神经元iNOS的表达及超微结构改变

目的：观察老年大鼠脑缺血再灌注后海马神经元诱导型一氧化氮合酶（induced nitric oxide synthase iNOS）的表达及超微结构变化。方法：建立老年大鼠不完全性全脑缺血动物模型，应用免疫组织化学染色和透射电镜，观察海马神经元iNOS的表达及超微结构变化。结果：缺血30min后再灌注24h组海马神经元iNOS活性显著升高；缺血30min再灌注21h和48h组中量表达；假手术组、缺血30min即刻取材、再灌注1h、6h、96h组iNOS几乎无表达；再灌注超过48h组海马神经元损伤较重。结论：NO是脑缺血后神经元迟发性死亡的重要因素之一。     

结合问题特征利用SE-Tree反向深度求解冲突集的方法

基于模型诊断是人工智能领域内的一个重要研究方向,求解极小冲突集在基于模型诊断中有着重要应用.在对结合CSISE-Tree求解冲突集方法深入研究的基础上,根据冲突集求解特征重构了结合枚举树的计算冲突集的过程,提出基于深度优先反向搜索求解冲突集的方法.针对CSISE-Tree方法求解时占用内存空间与元件总数指数级相关的缺点,构建反向深度搜索方法减小求解时所占用内存空间;针对CSISE-Tree方法不能对部分非极小的冲突集进行剪枝的问题,给出对非冲突集和更多非极小的冲突集进行剪枝的方法,有效减少了求解时调用SAT(Boolean SATisfiability problem)求解器的次数;实验结果表明,与CSISE-Tree方法相比,本文提出的方法求解效率有明显的提升,并避免了求解时的内存爆炸问题.     

Inversion of the current-distance relationship by transientdepolarization

The objective of this research was to develop a technique to excite selectively nerve fibers distant from an electrode without exciting nerve fibers close to the electrode. The shape of the stimulus current waveform was designed based on the nonlinear conductance properties of neuronal sodium channels. Models of mammalian peripheral myelinated axons and experimental measurements on cat sciatic nerve were used to determine the effects of subthreshold polarization on neural excitability and recruitment. Subthreshold membrane depolarization generated a transient decrease in neural excitability and thus an increase in the threshold for stimulation by a subsequent stimulus pulse. The decrease in excitability increased as the duration and amplitude of the subthreshold depolarization were increased, and the increase in threshold was greater for fibers close to the electrode. When a depolarizing stimulus pulse was applied immediately after the subthreshold depolarization, nerve fibers far from the electrode could be stimulated without stimulating fibers close to the electrode. Subthreshold depolarizing prepulses inverted the current-distance relationship and allowed selective stimulation of nerve fibers far from the electrode     

Directed Motility of Hygroresponsive Biomimetic Actuators

The capability of cellulose microfibrils to elicit directionality by anisotropically restricting the deformation of amorphous biogenic matrices is central to the motility of many plants as motoric and shape‐restoring elements. Herein, an approach is described to control directionality of artificial composite actuators that mimic the hygroinduced motion of composite plant tissues such as the opening of seed pods, winding of plant tendrils, and burial of seed awns. The actuators are designed as bilayer structures where single or double networks of buried parallel glass fibers reinforce the composite. By anisotropically restricting the expansion along certain directions they also effectively direct the mechanical reconfiguration, thereby determining the mechanical effect. A mathematical model is developed to quantify the kinematic response of fiber‐reinforced actuators. Within a broader context, the results of this study provide means for control over mechanical deformation of artificial dynamic elements that mimic the oriented fibrous architectures in biogenic motoric elements.     

人参皂甙Rb1促进老年大鼠睾丸间质细胞睾酮产生和StAR蛋白表达

目的:探讨人参皂甙Rb1对老年大鼠间质细胞增殖及睾酮产生的影响,分析人参皂甙Rb1对睾酮提升作用的机制.方法:体外分离培养老年大鼠睾丸间质细胞,培养液中分别加入不同浓度RB1,MTT法测定细胞增殖改变,ELISA法测定培养上清中睾酮水平,用RT-PCR分析间质细胞StAR基因和P450scc基因表达,western b...     

Scattering from composite materials: a first-order model

The nonspecular electromagnetic scattering from finite composite laminates is investigated. The composite material is modeled as planar lamina composed of undirectional collimated fibers with regular spacings between the elements. The fibers, perfectly or partially conductive, are assumed to be embedded in a resin matrix translucent to electromagnetic radiation. For the partially conductive case, the Schelkunoff Ansatz is used. The case of two-plied laminates with skewed fiber orientation is discussed. The mathematical formulation is based on the electric-field integral equation solved with an entire-domain Galerkin expansion. Results are obtained for laminates with both finite and infinite numbers of elements. For the latter, the Floquet-Galerkin solution for periodic structures is used. The effect of truncation of the panels is discussed for arbitrary angles of illumination. It is shown that in many cases implementation of the Floquet-Galerkin solution using diagonal system matrices yields accurate results for the nonspecular cross sections of the laminates. The theoretical results are confirmed by experimental data     

折射率引导型光子晶体光纤的研究进展和应用

折射率引导型光子晶体光纤具有许多传统光纤不具有的特点，为光通信及光传感器系统的设计提供了一种新的选择。介绍了这类光纤的导光原理、制作方法和最新的研究进展与相关应用。     

Analysis of fields and coupling associated with optical fibers withpower-law profiles

The fundamental mode fields of optical fibers are of importance for various applications. The field and relevant properties are directly related to the index profile of the fiber itself. In practice, index profiles for many fibers can be represented by power-law functions. Within the framework of a field approximation method the authors systematically study fundamental mode fields of optical fibers with clad power-law profiles, as well as coupling occurring between two such fibers