OBJECTIVETo explore the relationship between contractile characteristics and fiber type conversion in hind-limb unloading mice soleus.

METHODSAfter 28-day hind-limb unloading and muscle atrophy, we used the method of isolated muscle perfusion with different stimulated protocols to determine the changes in contractile characteristics including the isometric twitch force and tetanus force and fatigue index of slow twitch muscle in mice. The muscle myofibrillar composition and fiber type conversion were detected by immunofluorescence staining and real-time PCR.

RESULTSThe isometric twitch force and the tetanus force and fatigue index were decreased progressively in 28-day unloaded mice soleus, with the increase in fast twitch fiber subtype and the decrease in slow twitch fiber subtype.

CONCLUSIONThe alteration of contractile characteristics is relevant to the slow-to-fast fiber conversion in mice soleus after 28-day hind-limb unloading.

Animals ; Hindlimb Suspension ; physiology ; Mice ; Mice, Inbred C57BL ; Muscle Contraction ; physiology ; Muscle Fatigue ; physiology ; Muscle Fibers, Fast-Twitch ; physiology ; Muscle Fibers, Slow-Twitch ; physiology ; Muscle, Skeletal ; pathology ; physiology ; Muscular Atrophy

Akt, a key protein of cell survival, can promote cell growth and survival by activations of various cellular protective factors. Ischemic preconditioning (IP) has been known to reduce ischemic injury through upregulation of phosphorylation of Akt (p-Akt). CuZn-superoxide dismutase (SOD-1), an antioxidant enzyme, scavenges reactive oxygen species and protects cell from oxidative stress by increasing the activaiton of Akt. The present study was performed to examine the effects of IP on the expression of p-Akt and SOD-1 in the ischemicreperfused rat skeletal muscles. Thirty weeks old male SD rats were divided into 4 groups, such as controls, IP, 4 hour ischemia and 4 hour ischemia with IP. For IP, commom iliac artery was occluded three times for 5 min ischemia followed by 5 min reperfusion using rodent vascular clamps. Ischemia was induced by occlusion on the same artery for 4 hours. The Tibialis anterior and Soleus were removed at 0, 1, 3, and 24 hours of reperfusion. The expressions of p-Akt (Ser 473) and SOD-1 were examined with immunohistochemistry and Western blot analysis.In the IP group, the p-Akt and SOD-1 were increased, compared to the control group. In the ischemia group, the p- Akt and SOD-1 were decreased, compared to the control group, and were more abundant when reperfusion time were increased. IP increased the p-Akt and SOD-1 after 4 hour ischemia, and the p-Akt and SOD-1 were higher in Soleus compared to Tibialis anterior. These findings suggest that IP increases p-Akt and expression of SOD-1 in the ischemic-reperfused rat skeletal muscles, and that upregulations of p-Akt and SOD-1 induced by IP were higher in the red muscle fiber, Soleus, than the white muscle fiber, Tibialis anterior.
Animals ; Arteries ; Blotting, Western ; Cell Survival ; Humans ; Iliac Artery ; Immunohistochemistry ; Ischemia ; Ischemic Preconditioning ; Male ; Muscle Fibers, Fast-Twitch ; Muscle Fibers, Slow-Twitch ; Muscle, Skeletal ; Oxidative Stress ; Phosphorylation ; Rats ; Reactive Oxygen Species ; Reperfusion ; Rodentia ; Up-Regulation

The internal anal sphincter (IAS) plays an important role in the maintenance of fecal continence since it generates tone and is responsible for > 70% of resting anal pressure. During normal defecation the IAS relaxes. Historically, tone generation in gastrointestinal muscles was attributed to mechanisms arising directly from smooth muscle cells, ie, myogenic activity. However, slow waves are now known to play a fundamental role in regulating gastrointestinal motility and these electrical events are generated by the interstitial cells of Cajal. Recently, interstitial cells of Cajal, as well as slow waves, have also been identified in the IAS making them viable candidates for tone generation. In this review we discuss four different mechanisms that likely contribute to tone generation in the IAS. Three of these involve membrane potential, L-type Ca²⁺ channels and electromechanical coupling (ie, summation of asynchronous phasic activity, partial tetanus, and window current), whereas the fourth involves the regulation of myofilament Ca²⁺ sensitivity. Contractile activity in the IAS is also modulated by sympathetic motor neurons that significantly increase tone and anal pressure, as well as inhibitory motor neurons (particularly nitrergic and vasoactive intestinal peptidergic) that abolish contraction and assist with normal defecation. Alterations in IAS motility are associated with disorders such as fecal incontinence and anal fissures that significantly decrease the quality of life. Understanding in greater detail how tone is regulated in the IAS is important for developing more effective treatment strategies for these debilitating defecation disorders.
Anal Canal ; Defecation ; Fecal Incontinence ; Gastrointestinal Motility ; Interstitial Cells of Cajal ; Membrane Potentials ; Motor Neurons ; Muscle, Smooth ; Muscles ; Myocytes, Smooth Muscle ; Myofibrils ; Quality of Life ; Receptor, Platelet-Derived Growth Factor alpha ; Tetanus

In an attempt to clarify the function of the suboccipital muscles, we performed morphological observation of the suboccipital muscles for variations in the muscle belly and compared the morphology of their muscle fibers in terms of cross-sectional area by immunostaining with anti-myosin heavy chain antibodies. The cadavers of 25 Japanese individuals were used: 22 for morphological examinations and three for histological examinations. Among samples of the rectus capitis posterior major muscle (RCPma) and rectus capitis posterior minor muscle (RCPmi), 86.4% had a typical muscle appearance with a single belly, and 13.6% had an anomalous morphology. None of the samples of the obliquus capitis superior (OCS) or obliquus capitis inferior (OCI) muscles had an anomalous appearance. Measurement of cross-sectional area revealed that fast-twitch muscle fibers in the RCPma and OCI had a significantly greater cross-sectional area than those of the RCPmi and OCS. The cross-sectional area of intermediate muscle fibers was also significantly greater in the OCS than in the RCPma, RCPmi, and OCI. The cross-sectional area of slow-twitch muscle fibers was significantly greater in the OCS than in the RCPma, RCPmi, and OCI, and the RCPmi showed a significantly greater cross-sectional area for slow-twitch muscle fibers than did the RCPma, and OCI. Our findings indicate that the RCPmi and OCS exert a greater force than the RCPma and OCI, and act as anti-gravity agonist muscles of the head. Prolonged head extension in individuals with anomalous suboccipital muscle groups could result in dysfunction due to undue stress.
Antibodies ; Asian Continental Ancestry Group ; Cadaver ; Classification* ; Head ; Headache ; Humans ; Muscle Fibers, Fast-Twitch ; Muscle Fibers, Slow-Twitch ; Muscles

Under physiological conditions, the motility of smooth muscle in digestive tract is mainly regulated by enteric nervous system (ENS). However, how neural signal is transmitted to smooth muscle is not fully understood. Autonomic nerve endings in the smooth muscle layer form large number of varicosities which contain neurotransmitters. It was considered that nerve pulses arriving at the varicosities may cause the release of neurotransmitters, which may diffuse to the smooth muscle cells to induce contractile or relaxant responses. Over the past decade, a new understanding of the neurotransmission between ENS and smooth muscle has emerged, which emphasizes the role of a functional syncytium consisting of the interstitial cells of Cajal (ICC), the platelet-derived growth factor receptor α positive (PDGFRα) cells and the smooth muscle cells. Within the syncytium, purine neurotransmitters bind to P2Y1 receptors on PDGFRα cells, activating small-conductance calcium activated potassium channel (SK3) to hyperpolarize PDGFRα cells, and thus hyperpolarize smooth muscle cells through gap junction, resulting in relaxation of smooth muscle. In this paper, we review the research progress in the field of inhibitory purinergic neurotransmission in the gastrointestinal tract.
Interstitial Cells of Cajal ; Muscle, Smooth ; Myocytes, Smooth Muscle ; Receptor, Platelet-Derived Growth Factor alpha ; Synaptic Transmission

Gastrointestinal smooth muscle layer contains two kinds of interstitial cells with special differentiation, i.e., interstitial cells of Cajal (ICC) and platelet-derived growth factor receptor α-positive (PDGFRα) cells. The ICC and PDGFRαcells contact with smooth muscle cells (SMCs) by gap junctions and regulate contractive function of the SMCs. Therefore, these three kinds of cells constitute a functional syncytium, i.e., the SMC, ICC and PDGFRαcells syncytium (SIP syncytium). Various neurotransmitters, humoral factors, endogenous bioactive molecules, as well as drugs regulate gastrointestinal motility through the SIP syncytium. In this review, we introduce the concept of SIP syncytium and summarize functions of the syncytium, as well as its physiological and pathological significances.
Gastrointestinal Motility ; Giant Cells ; Humans ; Interstitial Cells of Cajal ; Muscle, Smooth ; Myocytes, Smooth Muscle ; Receptor, Platelet-Derived Growth Factor alpha

Angiomyofibroblastoma is a recently described mesenchymal tumor characterized by unique morphologic features, a propensity to arise in the vulva, and a non-aggressive beni-gn biologic behavior. It is typically well circumscribed and superficially located tumor and its cellularity is variable with hypercellular and hypocellular areas composed of bland-looking, pump stromal cells showing the immunophenotype of vimentin-/desmin - positive, and muscle specific actin(MSA)-/alpha-smooth muscle actin(ASMA) - negative. Spindle or plasm-acytoid cells are the characteristic cell types of most tumors. It is similar to an aggressive pelvic angiomyxoma in histology. Because of histologic similarity and differences in the clinical course and treatment, distinction from aggressive angiomyxoma was needed. It rep-resents new type in the expanding spectrum of tumors of which myofibroblasts constitute an integral component. We experienced a case of angiomyofibroblastoma of the vulva occuring in a 42 years old woman. The lesion was relatively well encapsulated mass(3 X 1.5 X 0.9 cm in dimension), showing intimate admixture of hypercellular and hypocellular area. The tumor contained prominent, somewhat ectatic vessels surrounded by smooth muscle cells, some of which blend or fan out from the muscular walls of the vessels. The margin was relatively free from tumor cells. At immunohistochemical stain, vimentin and desmin was diffuse and weak positive, smooth muscle actin was very a few and weak positive in tumor cells.
Actins ; Adult ; Desmin ; Female ; Humans ; Muscle, Smooth ; Myocytes, Smooth Muscle ; Myofibroblasts ; Myxoma ; Stromal Cells ; Vimentin ; Vulva*

OBJECTIVETo study the effect of testosterone propionate (TP) on the distribution pattern of calcitonin gene-related peptide (CGRP) in two types of motoneuron (Mn) pools in rats.

METHODThe double labeling of cholera toxin B subunit coupled with colloidal gold (CB-Au) retrograde identification combining with immunocytochemistry was mainly used to reveal the distribution pattern of CGRP-like immunoreactivity (CGRP-LI) and its changes in the motoneuron pools labeled by CB-Au.

RESULTTP injected intramuscularly 28 days later significantly decreased CGRP expression in Mn pool innervating extensor digitorum longus (EDL, fast-twitch), comparing with corresponding control and castration group respectively (P < 0.001), while no significant effect on Mn pools innervating soleus (SOL, slow-twitch, P > 0.05) was observed.

CONCLUSIONEDL-Mn pool is more sensitive to testosterone propionate than SOL-Mn pool in regulating CGRP expression.

Animals ; Calcitonin Gene-Related Peptide ; drug effects ; metabolism ; Male ; Motor Neurons ; drug effects ; metabolism ; Muscle Fibers, Fast-Twitch ; cytology ; drug effects ; Muscle Fibers, Slow-Twitch ; cytology ; drug effects ; Rats ; Rats, Wistar ; Testosterone Propionate ; pharmacology

The gastrointestinal motility is regulated by extrinsic and intrinsic neural regulation. Intrinsic neural pathways are controlled by sensory input, inter-neuronal relay and motor output. Enteric motor neurons release many transmitters which affect post-junctional responses. Post-junctional responses can be excitatory and inhibitory depending on neurotransmitters. Excitatory neurotransmitters induce depolarization and contraction. In contrast, inhibitory neurotransmitters hyperpolarize and relaxe the gastrointestinal smooth muscle. Smooth muscle syncytium is composed of smooth muscle cells, interstitial cells of Cajal and platelet-derived growth factor receptor alpha-positive (PDGFRalpha+) cells (SIP syncytium). Specific expression of receptors and ion channels in these cells can be affected by neurotransmitters. In recent years, molecular reporter expression techniques are able to study the properties of ion channels and receptors in isolated specialized cells. In this review, we will discuss the mechanisms of ion channels to interpret the post-junctional responses in the gastrointestinal smooth muscles.
Gastrointestinal Motility ; Giant Cells ; Interstitial Cells of Cajal ; Ion Channels ; Motor Neurons ; Muscle, Smooth ; Myocytes, Smooth Muscle ; Neural Pathways ; Neurotransmitter Agents ; Receptors, Platelet-Derived Growth Factor

Prenatal development of the thoracic aorta of the human during the period ranging from gestation weeks 7 (C-R length 20mm) to 30 (C-R length 260mm) was examined by transmission electron microscopy and the following results were obtained. The early form of cuboidal or columnar endothelial cells at 7-9 weeks of gestation changed gradually to typical flat endothelial cells at 12-14 weeks of gestation. At 9 weeks of gestation, the mesenchymal cells begin to differentiate to myoblasts, which have small clusters of myofilaments with dense bodies and rough endoplasmic reticulum. And from 14 weeks the differentiating cells begin to form a parallel concentric lamellar structure. At 12th week of gestation, elastic fibers were first seen in subendothelial connective tissue and the intercellular spaces between smooth muscle cells. Elastic fibers appeared as small globular shape which composed of a central core of elastic and peripheral microfibrils. From this period the amount of elastic fibers and their aggregation increases gradually in both the subendothelial space and the intercellular spaces between smooth muscle cells. At 30th week of gestation, subendothelial elastic fibers almost completed the internal elastic lamina and also well formed elastic laminae were seen between the smooth muscle cells adjacent to endothelial cells. However, in the space between the smooth muscle cells near the adventitia the elastic lamina formation is delayed. In the adventitia elastic fiber were scanty but collagen fibers are abundant.
Adventitia ; Aorta, Thoracic* ; Collagen ; Connective Tissue ; Elastic Tissue ; Endoplasmic Reticulum, Rough ; Endothelial Cells ; Extracellular Space ; Fetus* ; Humans* ; Microfibrils ; Microscopy, Electron, Transmission ; Myoblasts ; Myocytes, Smooth Muscle ; Myofibrils ; Pregnancy