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

PURPOSE: This study was conducted to determine whether low intensity regular exercise following dexamethasone treatment could attenuate steroid-induced muscle atrophy. METHOD: 36 Wistar-rats(90-110g) were divided into six groups: control group(C), dexamethasone treatment group(D), sedentary group after normal sedentary period(C+S), sedentary group after dexamethasone treatment period(D+S), exercise group after normal sedentary period(C+E), and excercise group after dexamethasone treatment period(D+E). D, D+S, and D+E groups received dexamethasone injection(5mg/Kg) for seven days whereas C, C+S, and C+E groups received normal saline injection. Both C+E and D+E groups ran on a treadmill for 60 minutes/day(20minutes/4hours) at 15m/min and a 10degreegrade for seven recovery days. RESULT: Post-weight(body weight before muscle dissection) of D group significantly decreased by 16.03%, and that of D+E group significantly increased by 15.51% compared with pre-weight(body weight before steroid treatment). Type II muscle(plantaris and gastrocnemius) weights of D group were significantly lower than those of C group. Myofibrillar protein contents of type II muscles of D group tended to decrease comparing with C group. In D+E groups, body weights and relative weights of typeII muscles(muscle weight(mg)/post-weight(g)) tended to increase comparing with D+S group. CONCLUSION: It is suggested that steroid- induced muscle atrophy can be ameliorated through low intensity regular exercise after dexamethasone treatment.
Animals ; Body Weight ; Dexamethasone ; Muscle Fibers, Fast-Twitch ; Muscles* ; Muscular Atrophy ; Rats* ; Weights and Measures

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

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

BACKGROUNDAge-associated decrease in type IIA/B human skeletal muscle fibers was detected in human biopsies in our previous study. The relationship between change in muscle fiber typing and bone mineral density (BMD) is, however, unknown either cross-sectionally or longitudinally. We therefore conducted a cross-sectional study to investigate their correlation using human muscle biopsies.

METHODSForty human subjects aged (53.4 ± 20.2) years were recruited. Histomorphometric parameters of their muscle biopsies were measured by ATPase staining and image analysis, including average area percentage, fiber number percentage, mean fiber area, and area percentage of connective tissues. Hip and spine BMD was measured by dual-energy X-ray absorptiometry. Partial correlation with adjusting age was performed.

RESULTSType IIB muscle fiber was found positively correlated with hip BMD irrespective to age and demonstrated significantly stronger relationship with BMD among all fiber types, in terms of its cross-sectional area (r = 0.380, P = 0.029) and size (r = 0.389, P = 0.025). Type IIA muscle fibers associated with hip BMD in mean fiber area only (r = 0.420, P = 0.015).

CONCLUSIONSType IIB muscle fiber may play an important role in maintaining bone quality. This may also be a relatively more sensitive fiber type of sarcopenia and osteoporosis. These findings further consolidate the muscle-bone relationship.

Adult ; Age Factors ; Aged ; Aged, 80 and over ; Bone Density ; physiology ; Female ; Humans ; In Vitro Techniques ; Male ; Middle Aged ; Muscle Fibers, Fast-Twitch ; cytology ; metabolism ; Prospective Studies ; Young Adult