Isometric and Isotonic Relaxation in Venous Smooth Muscle

The time course of relaxation under isometric and isotonic conditions was studied in preparations of rat portal vein which maintained regular phasic contractions in solutions with increased [K⁺] and [Ca²⁺]. It was found that the smooth muscle during isotonic lengthening was able to carry the afterload for a period of time which was longer than expected from the control isometric response. The difference was largest for afterloads corresponding to about half the isometric peak force. The terminal decline in force was identical in afterloaded and purely isometric responses. Inhibitory influences of isotonic shortening causing increased rates of relaxation, as reported for striated muscles, were not observed. The differences in the course of relaxation between isotonic and isometric responses of portal vein could not be attributed to variations in membrane excitation. It also appears that the differences are not due to changes in release or uptake of activator calcium, or to presence of viscous elements in the tissue. It is suggested that the ability of the smooth muscle to carry load over a relatively long period during isotonic relaxation may be attributed to the characteristics of the instantaneous force-velocity relations in the force range above P₀.     

Non-Hyperbolic Force-Velocity Relationship in Single Muscle Fibres1

The force-velocity relation has been studied in sixteen single fibres from frog semitendinosus muscle with particular attention to the high-force portion of the curve. The force-velocity curve was hyperbolic except for a reversal of curvature near 80 % measured isometric tension (P₀). Rectangular hyperbolas fitted (linear, least-squares method) these data well only when values below 0.78 P₀ were considered. Extrapolation of these hyperbolas above 0.78 P₀ gave predicted isometric tensions (P*₀) which averaged 32±6% above the measured P₀ values. Hill's constants (1.84°C) for these hyperbolas were: a/P*₀=0.177±0.021, b = 0.329±0.035 M.L./sec, V_max=1.91±0.074 M.L./sec. The reversal of curvature persisted when force-velocity data were obtained using: 1 or 60 min response intervals, afterloaded isotonic responses, grid stimulation, electrically induced contractures and bundles of fibres. The reversal of curvature diminished when force-velocity data were obtained from slightly stretched fibres (about 2.3 μm sarcomere length as compared to 2.1 μm in the control). The results indicate that sarcomere length redistributions probably do not account for the non-hyperbolic force-velocity relation. An explanation for the behavior based on the geometry of the contractile filament lattice is discussed.     

Effect of Contractions in Vitroon Glycogen Content and Glycogen Synthetase Activity in Muscle

The influence of contraction on the content of glycogen in muscle as well as on the activity of the glycogen synthetase enzyme (EC 2.4. 1. 11.)—rate-limiting for glycogen synthesis—has previously been investigated in vivo. In the present study this influence was studied in vitro, where interference of epinephrine and insulin on the the effects of contraction is more easily excluded. Electrically stimulated intact levator ani muscle preparations from prepubertal rats were used (Arvill, Acta endocr. 1967. 56. suppl. 122). Glycogen content decreased during 15 min of intermittent tetanization (10 slmin). There was no change in synthetase activity during the contractions. For the period following contractions an increase in the per cent active I-form of the enzyme was found after 1, 2, 10 and 180 min. Resynthesis of glycogen was shown after 30–180 min. An inverse relation between % I-form and glycogen content was found when data from 1–10 min after contractions were plotted together with the data from unstirnulated muscles. During repeated single twitches (1/s) for 60 min there was an enhanced penetration of xylose-¹⁴C and a higher rate of incorporation of glucose-¹⁴C into glycogen compared to control muscles. The present results are in good agreement with those previously obtained in vivo. Thus, the influence of contractions in vivo could be demonstrated also in vitro.     

Ultrastructural Observations on Smooth Muscle Tumors

The ultrastructure of a series of primary and metastatic smooth muscle tumors is reviewed. Myofilaments and other smooth muscle features were present in all primary leiomyosarcomas of the soft tissues and uterus. They were also present but were less plentiful in most of the metastatic leiomyosarcomas. Electron microscopy is therefore a useful method to establish the diagnosis of a suspected leiomyosarcoma. Stromal tumors of the gastro-intestinal tract may require correlated immunocytochemical and ultrastructural studies for their identification: 9 of the 50 cases examined were positive with immunostaining for S-100 protein, and 16 tumors with epithelioid transformation did not show evidence of smooth muscle differentiation by electron microscopy.     

Smooth Muscle Antibodies in Complicated Early Pregnancies*

ABSTRACT: The titer, immunoglobulin class, and staining pattern of smooth muscle antibodies (SMA) were assayed by indirect immunofluorescence in 15 patients with threatened abortion, 46 patients with spontaneous abortion, and 45 normal pregnant women in the first trimester to investigate possible abnormality of humoral immunity. An increased incidence of moderate and high titer SMA was found in both abnormal groups. SMA were mainly of the IgG class and gave a “vessel wall” staining pattern in immunofluorescence. This staining pattern suggests non-actin specificity of SMA. The more precise characterization of the antigen specificity of SMA in complications during pregnancy requires further investigation.     

Functional Asymmetry in the Innervation of Smooth Muscle Organs

We studied functional asymmetry in the innervation of smooth muscle organs (right and left ureter, and right and left fallopian tubes). Asymmetry in the innervation of the right and left ureter is provided by activation of the purinergic system. Asymmetry in the innervation of the fallopian tubes is determined by the purinergic and serotoninergic mechanisms.__________Translated from Byulleten Eksperimentalnoi Biologii i Meditsiny, Vol. 139, No. 2, pp. 128–132, February, 2005     

Ultrastructural Changes of the Smooth Muscle in Esophageal Atresia

Esophageal atresia (EA) with or without tracheo-esophageal fistula (TEF) is a relatively rare congenital anomaly. Despite the advances in the management techniques and neonatal intensive care, esophageal dysmotility remains a very common problem following EA/TEF repair. Our current study aimed to describe the most significant ultrastructural changes of the smooth muscle cells (SMCs) trying to highlight some of the underlying mechanisms of esophageal dysmotility following EA/TEF repair. Twenty-three biopsies were obtained from the tip of the lower esophageal pouch (LEP) of 23 patients during primary repair of EA/TEF. Light microscopic examination was performed with hematoxylin and eosin (HE), and Van Gieson’s stains. Ultrastructural examination was done using transmission electron microscopy (TEM). Histopathological examination showed distortion of smooth muscle layer and deposition of an abundant amount of fibrous tissue in-between smooth muscles. Using TEM, SMCs exhibited loss of the cell-to-cell adhesion, mitochondrial vacuolation, formation of myelin figures, and apoptotic fragmentation. There were also plasmalemmal projections and formation of ghost bodies. Interestingly, SMCs were found extending pseudopodia-like projections around adjacent collagen fibers. Engulfed collagen fibers by SMCs underwent degradation within autophagic vacuoles. Degeneration of SMCs and deposition of abundant extracellular collagen fibers are prominent pathological changes in LEP of EA/TEF. These changes might contribute to the pathogenesis of esophageal dysmotility in patients who have survived EA/TEF.     

基于熵的动态收缩sEMG信号疲劳特征分析

频谱分析方法常被用来检测肌肉疲劳过程。本文将频率分析和非线性动力学方法结合起来，基于表面肌电（sEMG）信号在不同频率分布不均匀的特点将信号能量分解到不同频带。以此计算功率谱／小波包和熵相结合的功率谱熵／小波包熵来衡虽系统的复杂度，进而衡量肌肉的疲劳程度，为用EMG信号研究动态收缩过程中的肌肉疲劳程度提供了新的分析手段和方法。文中方法也适用于萁它生物医学信号的分析。     

The Evolution of Vascular Smooth Muscle Responses to Histamine and 5-Hydroxytryptamine

Studies on the vascular smooth muscle responses to histamine and 5-hydroxytryptamine and on the distribution of these amines in different tissues were performed in several species of reptiles. The responses to adrenaline, noradrenaline and acetylcholine were studied for comparison. Vascular actions were recorded both in vivo as changes in systemic arterial blood pressure and in vitro as changes in vascular resistance in perfused preparations. The specificity of the action of each drug was evaluated by means of pharmacological blocking agents. Tissue levels of histamine and 5-hydroxytryptamine were determined spectrofluorometrically. Fluorescence microscopy was used for histochemical localization of the histamine stores. The results indicate that histamine and 5-hydroxytryptamine exert dual actions (inhibitory and stimulatory) on reptilian vascular smooth muscles which have thus acquired response patterns towards these amines similar to those found in mammals. Inhibitory as well as stimulatory actions of adrena line, noradrenaline and acetylcholine are also present in reptiles. Levels of 5-hydroxytrypt amine are apparently low in most tissues, whereas many species show very high tissue levels of histamine. Histamine, except that of the stomach, is mainly located in tissue mast cells and blood basophils. Nutritional-dependent variations in mast cell number are parallelled by varia tions in tissue histamine content. By comparing the present results with those previously ob tained in jawless vertebrates, fish and amphibians, a general outline of the evolution of vascular actions and tissue stores of histamine and 5-hydroxytryptamine is presented.     

微小核糖核酸对血管平滑肌细胞表型转换影响的研究进展

血管平滑肌细胞(VSMC)作为血管中膜的主要构成细胞,其功能作用与其表型变化密切相关。合成表型具有增生及迁移能力,是各种心血管及周围血管病发生发展的主要病理基础,而收缩表型对维持血管弹性和收缩功能至关重要。较多微小核糖核酸(microRNAS,miRNAS)可通过相关途径和方式调控VSMC表型转换,从而在机体病理生理变化中发挥重要作用。本文综述涉及上述调节的miRNA研究的有关进展。     

The Role of Intramural Noradrenaline in the Potassium Induced Contracture of Non-Estrogenized Smooth Muscle

The influence of intramural noradrenaline on potassium induced contractures was studied in isolated preparations of the uterus and the portal vein of the rat. Uterine strips of oophorectomized rats responded with contraction followed by transient relaxation when immersed in a medium containing 127 mM potassium chloride. Reserpinization or blockade of β-adrenoceptors with propranolol greatly diminished the transient relaxation. In the isolated portal vein, both noradrenaline depletion with reserpine and α-adrenoceptor blockade (phentolamine) reduced the active tension produced in response to the isotonic potassium solution. These results suggest that intramural noradrenaline plays a significant role in the development of contractures evoked by potassium in the uterus and the portal vein of the rat. In the uterus, the released noradrenaline counteracts the development of active tension, whereas in the portal vein, noradrenaline has a contractile effect which is added to that of potassium. Estrogen treatment reduced (portal vein) or abolished (rat uterus) the contractile effects of intramural noradrenaline. The adrenolytic effect of estrogen is possibly due to reduction in the release of noradrenaline from the sympathetic nerve-endings.