Reinnervation of motor endplates and increased muscle fiber size after human insulin-like growth factor I gene transfer into the paralyzed larynx

Current surgical strategies for the treatment of laryngeal paralysis are limited by the muscle atrophy associated with denervation. Moreover, attempts at reinnervation have not effected significant change in surgical outcome. To address this clinical problem, we have developed a rat laryngeal paralysis model to study novel gene transfer strategies. Using this model, the human insulin-like growth factor I (hIGF-I) gene was introduced into paralyzed rat laryngeal muscle to assess the benefit of sustained local hIGF-I production. A muscle-specific nonviral vector containing the alpha-actin promoter and hIGF-I gene was used in formulation with a polyvinyl-based delivery system and injected into paralyzed adult rat laryngeal muscle. Twenty-eight days after a single injection, gene transfer efficiency, muscle fiber size, motor endplate length, and nerve-to-motor endplate contact were evaluated. Gene transfer was detected in 100% of injected animals by PCR. Gene transfer with expression, as measured by RT-PCR for hIGF-I mRNA, occurred in 81.3 % of injected animals. When compared with controls, hIGF-I-transfected animals presented a significant increase in muscle fiber diameter [17.56 (+/-0.97 SD) microm versus 14.70 (+/-1.43 SD) microm; p = 0.0002], a significant decrease in motor endplate length [20.88 (+/-1.42 SD) microm versus 25.41 (+/-3.19 SD) microm; p = 0.0025], and a significant increase in percentage of endplates with nerve contact (20.3% (+/-13.9 SD) versus 4.4% (+/-4.2 SD); p = 0.0079). In the context of laryngeal paralysis, gene therapy represents a tremendous opportunity to augment current surgical treatment modalities by preventing or reversing muscle atrophy, and by enhancing nerve sprouting and reinnervation.     

d-Tubocurarine accentuates the burn-induced upregulation of nicotinic acetylcholine receptors at the muscle membrane

BACKGROUND: Increases in acetylcholine receptors (AChRs) at the muscle membrane, induced by burn injury, have been associated with a hyperkalemic response to succinylcholine and resistance to d-tubocurarine-like drugs. Muscle relaxants often are administered to burn-injured patients in the intensive care unit to facilitate mechanical ventilation. This study in rats tested whether continuous administration of d-tubocurarine in subparalytic doses exaggerates the upregulation of AChRs induced by burn trauma. Subparalytic doses were used to avoid the confounding effects of immobilization. METHODS: Three days after an approximate 50% body surface area burn or sham injury, the animals received an infusion of 3.03 +/- 0.05 micrograms/h of d-tubocurarine or equal volume of saline directly to the left gastrocnemius muscle via catheter connected to a subcutaneously implanted osmotic pump. After 7 days of d-tubocurarine or saline infusion, the AChRs were quantitated using 125I-alpha-bungarotoxin. The AChRs on the d-tubocurarine or saline-infused left gastrocnemius were compared to the contralateral gastrocnemius in the same group. The right or left gastrocnemius AChRs were compared to the ipsilateral muscles between groups. These intra- and intergroup comparisons allowed the delineation of the effects of catheter irritation, burns, or d-tubocurarine on AChRs. RESULTS: Daily examination of the withdrawal response to toe-pinch revealed no evidence of paralysis. Weight loss in the burn-injury animals receiving d-tubocurarine or saline was similar, confirming that the infusion of d-tubocurarine did not impair the mobility of the animals to move and feed. The plasma d-tubocurarine concentration after 7 days of infusion was 26.0 +/- 12 ng/ml (mean +/- SE). Regardless of burn or sham injury or of d-tubocurarine or saline infusion, the concentration of AChRs on the left was consistently greater than in the contralateral right gastrocnemius muscles within the same group, indicating that manipulation of the area alone can result in upregulation of AChRs. The AChRs in the right gastrocnemius of burn-injured animals were greater than those in the same muscle of sham-injured animals, regardless of saline (7.24 +/- 0.9 vs. 5.7 +/- 0.5 fmoles/mg protein, P = 0.06) or d-tubocurarine (7.3 +/- 0.4 vs. 5.7 +/- 0.5, P < 0.05) infusion to the burn-injury groups. AChRs in the left gastrocnemius of burn-injury animals receiving d-tubocurarine were significantly greater than those in burn- or sham-injury animals receiving saline (13.9 +/- 1.1 vs. 9.8 +/- 1.2 and 7.1 +/- 0.5 fmoles/mg protein, respectively, P < 0.05). CONCLUSIONS: Burn-induced upregulation of AChRs is accentuated by infusion of subparalytic doses of d-tubocurarine. Concomitant administration of d-tubocurarine to burn-injured patients may result in further exaggeration of the aberrant responses to neuromuscular relaxants.     

Increased capillarity in leg muscle of finches living at altitude

An increased ratio of muscle capillary to fiber number (capillary/fiber number) at altitude has been found in only a few investigations. The highly aerobic pectoralis muscle of finches living at 4,000-m altitude (Leucosticte arctoa; A) was recently shown to have a larger capillary/fiber number and greater contribution of tortuosity and branching to total capillary length than sea-level finches (Carpodacus mexicanus; SL) of the same subfamily (O. Mathieu-Costello, P. J. Agey, L. Wu, J. M. Szewczak, and R. E. MacMillen. Respir. Physiol. 111: 189-199, 1998). To evaluate the role of muscle aerobic capacity on this trait, we examined the less-aerobic leg muscle (deep portion of anterior thigh) in the same birds. We found that, similar to pectoralis, the leg muscle in A finches had a greater capillary/fiber number (1.42 +/- 0.06) than that in SL finches (0.77 +/- 0.05; P < 0.01), but capillary tortuosity and branching were not different. As also found in pectoralis, the resulting larger capillary/fiber surface in A finches was proportional to a greater mitochondrial volume per micrometer of fiber length compared with that in SL finches. These observations, in conjunction with a trend to a greater (rather than smaller) fiber cross-sectional area in A than in SL finches (A: 484 +/- 42, SL: 390 +/- 26 micrometer2, both values at 2.5-micrometer sarcomere length; P = 0.093), support the notion that chronic hypoxia is also a condition in which capillary-to-fiber structure is organized to match the size of the muscle capillary-to-fiber interface to fiber mitochondrial volume rather than to minimize intercapillary O2 diffusion distances.     

Relationship of visual assessments of feeder lamb muscularity to differences in carcass yield traits

We examined the relationship between visual differences in muscle thickness among feeder lambs and subsequent differences in carcass composition. Medium-framed, crossbred feeder lambs (n = 120) were selected at two commercial feedlots to exhibit distinct phenotypic differences in muscularity. The lambs were assigned scores (ranging from 1 to 9; 1 = extremely thin, 5 = average, 9 = extremely thick) for muscle thickness and were sampled serially on d 0, 14, 28, and 42 of the trial. After recording yield grades, one side of each carcass was deboned, and the soft tissues from the entire side were ground, sampled, and analyzed for lipid and moisture content. The opposite side was fabricated into boneless, closely trimmed (.25 cm maximum fat depth) subprimal cuts. When lambs of the same frame size were compared at the same live weight, greater muscle thickness was associated with greater (P < .05) fat-free muscle mass. Correspondingly, thickly muscled lambs produced carcasses of a given weight that had a higher (P < .05) composite yield of lean meat and a lower (P < .05) proportion of trimmable fat compared with carcasses of thinly muscled lambs. When comparisons were made at the same percentage of extractable fat in the carcass, greater muscle thickness was associated with heavier (P < .05) live and carcass weights, increased (P < .05) fat-free muscle mass, and increased (P < .05) weights of trimmed, boneless subprimal cuts. Results suggest that visual assessments of muscle thickness in feeder lambs, as applied in this study, are indicative of commercially important differences in carcass yields of lean meat.     

Characterization of monomeric and homodimeric forms of osteoclastogenesis inhibitory factor

PURPOSE: The purpose of this study was to characterize structural changes in the pulmonary vasculature in congenital diaphragmatic hernia (CDH) complicated by persistent pulmonary hypertension (PPH) with particular emphasis on adventitial thickness. METHODS: Victorian blue Van Gieson (VVG) staining and immunostaining with antialpha smooth muscle actin (ASMA) were performed on lung tissues obtained at autopsy from 23 patients with CDH complicated by PPH and 11 age-matched control tissues of sudden infant death syndrome patients (SIDS). The degree of medial and adventitial thickening was measured in pulmonary arteries with an external diameter (ED) of less than 75 microm, 75 to 100 microm, 100 to 150 microm, 150 to 250 microm, 250 to 500 microm, and greater than 500 microm by IPS-4.01 image analyzer and compared statistically. The degree of medial thickening and adventitial thickening was also measured in pulmonary veins with an ED of less than 100 microm, 100 to 200 microm, and greater than 200 microm. To determine whether the characteristic structural changes were size related, each was related to ED. The area of adventitia and media of the pulmonary arteries and veins was measured using image analyzer. RESULTS: There was a significant increase in medial and adventitial thickness in arteries of all sizes in CDH patients compared with controls (P < .01). The degree of adventitial area was significantly increased for arteries of all sizes (P < .01) and the degree of medial area was significantly increased only for arteries less than 100 microm size (P < .05) in CDH patients compared with controls. Calculation of the areas of the various components in the wall of each artery showed that for small arteries (<100 microm ED), the area of the lumen was smaller, and the areas of the media and adventitia were larger in CDH patients compared with controls (P < .01). There was a significant increase in adventitial thickness and area in veins of all sizes in CDH patients compared with controls (P < .01). The adventitial thickness of pulmonary veins were ED of less than 100 microm: CDH, 13.5 microm +/- 3.5; control, 9.21 microm +/- 2.0; ED 100 to 200 microm: CDH, 21.3 microm +/- 7.5; control, 13.0 microm +/- 4.8; ED greater than 200 microm: CDH, 34.4 microm +/- 12.5; control, 22.3 microm +/- 4.2. CONCLUSIONS: The present study provides the first quantitative demonstration of structural alterations in pulmonary veins in addition to pulmonary arteries in CDH complicated by PPH. The structural remodeling of the pulmonary vein is perhaps as a result of an increase in transvascular pressure in PPH.     

Muscle fiber length and moment arm coordination during dorsi- and plantarflexion in the mouse hindlimb

The purpose of this study was to test the hypothesis that muscle fiber length and joint moment arm are combined in such a way that maximum muscle force is produced during locomotion. Plantarflexor (soleus, SOL and medial gastrocnemius, MG) and dorsiflexor (extensor digitorum longus, EDL and tibialis anterior, TA) muscle architecture in the mouse was measured along with their associated moment arms. Fiber length varied significantly between muscles ranging from 5.7 +/- 0.2 mm (MG) to 7.6 +/- 0.2 mm (TA). Plantarflexor moment arms were over twice as large as dorsiflexor moment arms (1.88 +/- 0.06 mm vs. 0.84 +/- 0.03 mm) suggesting a greater muscle length change with joint angle for plantarflexors compared to dorsiflexors. Using a simple muscle-joint model, the active sarcomere length range in these muscle groups was calculated and proved to be quite similar between functional groups. The active range for dorsiflexors was 2.2-2.4 microns, while the active range for plantarflexors was 2.2-2.5 microns, indicating that both muscle groups operate primarily near the plateau of their length tension-relation. Finally, when calculating force produced by muscles during locomotion, the combination of moment arm and fiber length measured in all muscle groups yielded muscle-joint systems that produced near maximal forces at the velocities modeled. These data indicate that fiber length and moment arm appear to be coordinated to yield the greatest possible force production during locomotion.     

Stress-induced alterations of somatodendritic 5-HT1A autoreceptor sensitivity in the rat dorsal raphe nucleus--in vitro electrophysiological evidence

The role of trauma in the etiology of temporomandibular disorders (TMD) is controversial. The objectives of this study were to compare presenting signs, symptoms, and diagnoses in patients who had motor vehicle accident trauma-related TMD to patients who had nontrauma-related TMD. Files of 50 trauma and 50 matched nontrauma TMD patients were reviewed. Information concerning presenting pain, temporomandibular joint (TMJ) and related symptoms, examination findings, and diagnoses was recorded. Posttraumatic TMD patients reported higher facial (P = .006) and headache (P = .0001) pain ratings, neck symptom frequency (P < .01), ear-related symptoms (P = .02), sleep disturbance (P < .001), and occupational and avocational disability frequencies (P < .0001). They had greater masticatory muscle (P < .001), neck muscle (P < .001), and TMJ tenderness (P = .01) scores and myofascial pain (P = .006) and arthralgia/capsulitis (P = .008) diagnoses. The nontrauma group had more subjective (P = .02) and objective (P = .05) TMJ crepitus and higher self-reports of parafunctional jaw habits (P = .05). Trauma may be an important etiologic factor for some TMD patients.     

Effects of felodipine on left ventricular systolic and diastolic performance in congestive heart failure

We studied the effects of a dihydropyridine calcium blocker, felodipine, on left ventricular (LV) contractile performance and diastolic filling dynamics in conscious dogs with pacing-induced congestive heart failure (CHF) before and after autonomic blockade. Eleven conscious dogs were instrumented to measure micromanometer LV and left atrial (LA) pressure (P) and to determine LV volume (V) from three dimensions. CHF was induced by 4 to 5 weeks of right ventricular pacing. After CHF, the mean LV end-diastolic (ED) P increased (9.7 +/- 2.9 vs. 27.9 +/- 6.8 mm Hg, P < .05), LVEDV and end-systolic (ES) V increased and stroke volume (SV) decreased (15.3 +/- 2.4 vs. 9.6 +/- 3.0 ml, P < .05). The time constant of LV relaxation (T) (25.9 +/- 2.9 vs. 37.9 +/- 5.1 msec, P < .05) and LVES wall stress (WS) (63.4 +/- 21.0 vs. 74.6 +/- 23.7 g/cm2, P < .05) also increased. After CHF, felodipine (25 nmol/kg i.v., plasma concentrations 17.4 +/- 3.2 nmol/L) produced significant decreases in LVESP (119 +/- 12 vs. 96 +/- 11 mm Hg, P < .05), arterial elastance, total systolic resistance (TSR) (0.11 +/- 0.04 vs. 0.07 +/- 0.03 mm Hg/ml/min, P < .05) and LVESWS (74.6 +/- 23.7 vs. 60.2 +/- 17.3 g/cm2, P < .05). Felodipine increased the slopes of the ESP-V relation (5.6 +/- 1.5 vs. 7.8 +/- 0.7 mm Hg/ml, P < .05), the dP/dtmax-EDV relation (51.4 +/- 6.1 vs. 85.3 +/- 10.1 mm Hg/ml sec, P < .05) and the stroke work-EDV relation (69.8 +/- 7.1 vs. 78.9 +/- 7.1 mm Hg, P < .05) and shifted all three relations to the left, indicating enhanced contractile performance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Contractile studies of single human skeletal muscle fibers: a comparison of different muscles, permeabilization procedures, and storage techniques

The study of single muscle fibers has improved our understanding of muscle physiology and pathology. To compare three techniques for fiber preparation and storage, biopsies were obtained from the tibialis anterior and vastus lateralis muscles of a hemiparetic patient and a control subject. Single fibers were prepared with: (1) chemical skinning (CS) and storage at -20 degrees C; (2) chemical skinning followed by sucrose (SU) incubation and storage at -80 degrees C; or (3) freeze-drying (FD) and -80 degrees C storage. Cross-sectional area (CSA), resting, maximal (P0), and specific tension (P0/CSA), and maximum shortening velocity (V0) were determined in 189 cells. CSA was similar in all groups. Resting tension was higher and P0 and P0/CSA lower after FD. In general, V0 was the same in all groups. Our data suggest that CS and SU preserve the properties of single muscle fibers better than FD. SU may allow longer storage of fibers.     

Evidence for a striatal NMDA receptor modulation of nigral glutamate release. A dual probe microdialysis study in the awake freely moving rat

Insulin-like growth factor I (IGF-I) peptide levels have been shown to increase in overloaded skeletal muscles (G. R. Adams and F. Haddad. J. Appl. Physiol. 81: 2509-2516, 1996). In that study, the increase in IGF-I was found to precede measurable increases in muscle protein and was correlated with an increase in muscle DNA content. The present study was undertaken to test the hypothesis that direct IGF-I infusion would result in an increase in muscle DNA as well as in various measurements of muscle size. Either 0.9% saline or nonsystemic doses of IGF-I were infused directly into a non-weight-bearing muscle of rats, the tibialis anterior (TA), via a fenestrated catheter attached to a subcutaneous miniosmotic pump. Saline infusion had no effect on the mass, protein content, or DNA content of TA muscles. Local IGF-I infusion had no effect on body or heart weight. The absolute weight of the infused TA muscles was approximately 9% greater (P < 0.05) than that of the contralateral TA muscles. IGF-I infusion resulted in significant increases in the total protein and DNA content of TA muscles (P < 0.05). As a result of these coordinated changes, the DNA-to-protein ratio of the hypertrophied TA was similar to that of the contralateral muscles. These results suggest that IGF-I may be acting to directly stimulate processes such as protein synthesis and satellite cell proliferation, which result in skeletal muscle hypertrophy.     

Changes in muscle morphology, electromyographic activity, and force production characteristics during progressive strength training in young and older men

Effects of a 10-week progressive strength training program composed of a mixture of exercises for increasing muscle mass, maximal peak force, and explosive strength (rapid force production) were examined in 8 young (YM) (29+/-5 yrs) and 10 old (OM) (61+/-4 yrs) men. Electromyographic activity, maximal bilateral isometric peak force, and maximal rate of force development (RFD) of the knee extensors, muscle cross-sectional area (CSA) of the quadriceps femoris (QF), muscle fiber proportion, and fiber areas of types I, IIa, IIb, and IIab of the vastus lateralis were evaluated. Maximal and explosive strength values remained unaltered in both groups during a 3-week control period with no training preceding the strength training. After the 10-week training period, maximal isometric peak force increased from 1311+/-123 N by 15.6% (p <.05) in YM and from 976+/-168 N by 16.5% (p <.01) in OM. The pretraining RFD values of 4049+/-791 N*s(-1) in YM and 2526+/-1197 N*s(-1) in OM remained unaltered. Both groups showed significant increases (p < .05) in the averaged maximum IEMGs of the vastus muscles. The CSA of the QF increased from 90.3+/-7.9 cm2 in YM by 12.2% (p <.05) and from 74.7+/-7.8 cm2 in OM by 8.5% (p <.001). No changes occurred in the muscle fiber distribution of type I during the training, whereas the proportion of subtype IIab increased from 2% to 6% (p < .05) in YM and that of type IIb decreased in both YM from 25% to 16% (p < .01) and in OM from 15% to 6% (p < .05). The mean fiber area of type I increased after the 10-week training in YM (p < .001) and OM (p < .05) as well as that of type IIa in both YM (p < .01) and OM (p < .01). The individual percentage values for type I fibers were inversely correlated with the individual changes recorded during the training in the muscle CSA of the QF (r=-.56, p < .05). The present results suggest that both neural adaptations and the capacity of the skeletal muscle to undergo training-induced hypertrophy even in older people explain the gains observed in maximal force in older men, while rapid force production capacity recorded during the isometric knee extension action remained unaltered during the present mixed strength training program.     

Developmental expression and location of IGF-I and IGF-II mRNA and protein in skeletal muscle

To investigate the role of IGF in muscle development in vivo, developmental expression and location of IGF-I and -II protein and mRNA were examined in fetal, postnatal, and adult skeletal muscle. Muscle tissue was collected from 30-, 44-, 59-, 68-, 75-, 89-, and 109-d porcine fetuses, 21-d neonatal pigs, and 6-mo-old (adult) pigs. Relative amounts of IGF-II mRNA peaked (P < .05) in 59-d fetal muscle and decreased thereafter. Inversely, muscle IGF-I expression increased (P < .05) to maximal levels around birth. For in situ hybridization, frozen muscle tissue sections (10 microm) were hybridized with a hydrolyzed form of the same riboprobes or incubated with polyclonal or monoclonal antibodies to IGF-I or -II, respectively. The majority of IGF-I and IGF-II mRNA was localized to developing muscle fibers, whereas little signal was found in the surrounding connective tissues. Immunofluorescent localization of IGF-I and -II confirmed that muscle IGF are present in developing muscle fibers. Collectively, these data show that IGF-I and -II are expressed and produced primarily in muscle cells within developing muscle tissue and support the hypothesis that IGF-I and -II modulate fetal muscle development.     

Experimental muscle pain increases the human stretch reflex

In this study we investigated the effect of human experimental muscle pain on H- and stretch reflexes as indicators of changes in muscle spindle sensitivity. Fourteen healthy, male volunteers participated in the study. Muscle pain was produced by infusion of 5% hypertonic saline over a period of 10-15 min in m. soleus and in m. tibialis anterior. Reflexes were elicited in the relaxed and active soleus muscle (10-15 Nm ankle torque) before, during and after muscle pain. Control measurements were made with infusions of 0.9% isotonic saline. Surface electromyograms (EMG) were measured from the soleus muscle, and torque was measured from the ankle joint. With pain in the soleus muscle the mechanical stretch reflex response (ankle torque) increased significantly (P = 0.0007) as compared to before pain. With pain in the tibialis anterior muscle both the mechanical and EMG responses increased significantly (P = 0.001; P = 0.0003) as compared to before pain. The H-reflex showed no significant changes during the infusions in either muscles. This study has demonstrated a muscle pain-related increase in the amplitude of the stretch reflex without a corresponding increase in the H-reflex amplitude. One explanation could be an increased dynamic sensitivity of the muscle spindles during muscle pain caused by an increased firing rate in the dynamic gamma-motoneurones. However, the data could not support the vicious cycle model because the excitability of the alpha-motoneurone pool was unchanged.     

Desensitization of mutant acetylcholine receptors in transgenic mice reduces the amplitude of neuromuscular synaptic currents

While the slow onset of desensitization of nicotinic acetylcholine receptors (AChRs), relative to the rate of acetylcholine removal, excludes this kinetic state from shaping synaptic responses in normal neuromuscular transmission, its role in neuromuscular disorders has not been examined. The slow-channel congenital myasthenic syndrome (SCCMS) is a disorder caused by point mutations in the AChR subunit-encoding genes leading to kinetically abnormal (slow) channels, reduced miniature endplate current amplitudes (MEPCs), and degeneration of the postsynaptic membrane. Because of this complicated picture of kinetic and structural change in the neuromuscular junction, it is difficult to assess the importance of the multiple factors that may be responsible for the reduced endplate current amplitudes, and ultimately the clinical syndrome. In order to address this we have used a transgenic mouse model for the SCCMS that has slow AChR ion channels and reduced endplate responsiveness in the absence of any of the degenerative changes. We found that the reduction in MEPC amplitudes in these mice could not be explained by either reduced AChR number or by reduced AChR channel conductance. Rather, we found that the mutant AChRs in situ manifested an activity-dependent reduction in sensitivity that caused diminished MEPC and endplate current amplitude with nerve stimulation. This observation demonstrates that the basis for the reduction in MEPC amplitudes in the SCCMS may be multifactorial. Moreover, these findings demonstrate that, under conditions that alter their rate of desensitization, the kinetic properties of nicotinic AChRs can control the strength of synaptic responses.     

Meat tenderness and the calpain proteolytic system in longissimus muscle of young bulls and steers

The objectives of this study were to examine the effects of castration on the calpain proteinase system (mu-calpain, m-calpain, and calpastatin) activities and meat tenderness. Six each, MARC III bulls and steers were slaughtered at approximately 12 mo of age. Longissimus muscle samples were obtained for determining myofibril fragmentation index, Warner-Bratzler shear force, and sensory panel evaluation at 1, 7, and 14 d postmortem, and mu- and m-calpain and calpastatin activities at 24 h postmortem. Bulls produced leaner carcasses with lower (P < .05) quality grades than did steers. Meat from bulls had higher (P < .05) shear force values than meat from steers; however, sensory panelists were unable (P > .05) to detect differences in tenderness or other sensory traits between bulls and steers. Activities of mu- and m-calpain were not affected (P > .05) by castration; however, calpastatin was higher (P < .05) in muscles from the bull carcasses. Lower (P < .05) myofibril fragmentation index values indicate that less proteolysis occurred in muscle from bulls than in muscle from steers during the first 7 d postmortem. Greater calpastatin 24-h activity may be associated with the increased shear force of meat from bulls.     

Murine endodermal F9E cells, derived from the teratocarcinoma line F9, contain high basal levels of retinoic acid receptors (RARs and RXRs) but are not sensitive to the actions of retinoic acid

We observed differences in the capillary architecture of the skeletal muscles that have different fiber metabolism. The soleus, the vastus intermedius and the tibialis anterior muscles of adult Wistar rats were prepared using two different techniques. Samples for adenosine triphosphatase (ATPase) staining were prepared following Dubovitz's method, and the distributions of fiber type, Types 1, 2A and 2B, were analyzed. Then, corrosion casts of capillary architecture of these muscles prepared following Murakami's method were observed with a scanning electron microscope (SEM) and compared with the fiber distribution. The fiber type composition of the soleus muscle showed Type 1 (slow-twitch) dominance and that of the vastus intermedius and the tibialis anterior muscle showed Type 2 (fast-twitch) dominance. The capillaries of the soleus muscle were tortuous, and this was thought to be advantageous for blood supply. In contrast, the capillaries of the vastus intermedius and tibialis anterior muscles had a relatively parallel pattern. Additionally, two different patterns of capillary architecture that appeared to correspond to certain metabolic characteristic of different muscle fiber types were preserved with corrosion casting. In conclusion, comparative studies on capillary architecture of the skeletal muscles are useful for analyses of its function.     

Acetylcholine receptor and calcium leakage activity in nondystrophic and dystrophic myotubes (MDX)

To determine whether the lack of dystrophin alters the occurrence of calcium leakage activity (CLA) and acetylcholine receptor (AChR) activity, the frequency of each event class was determined from several cell attached patches on nondystrophic and dystrophic (mdx) myotubes. The frequency of CLA observed in the presence of ACh was significantly (P < 0.05) elevated in mdx myotubes, an effect which was partly due to a significant (P < 0.05) increase in the proportion of cell attached patches that exhibited 100% CLA with no AChR activity. Areas of mdx and nondystrophic membrane that exhibited reduced or absent AChR activity had significantly (P < 0.01) and substantially elevated calcium leakage event frequencies. This inverse and discontinuous relationship between CLA and AChR activity provides further evidence that some CLA in dystrophic muscle is produced by clusters of AChRs that form unusual physical associations with the dystrophic cytoskeleton during the processes associated with receptor localization and stabilization.     

Investigation in real time of the effect of gravitation on human spermatozoa and their tendency to swim-up and swim-down

The purpose of this study was to investigate the laterality of muscle fiber conduction velocity in biceps brachii for badminton players, who have stronger arm in the handedness side for long term training. The muscle fiber conduction velocity was calculated from the propagation time of the action potentials along the muscle fibers and the electrode separation using cross-correlation method. For badminton players, significant lateral differences (e.g. right side skillful) were observed in the upper arm girth (P < 0.01) and isokinetic peak torque at 0, 10, 20, 30, 40 rpm (P < 0.01). For control subjects, significant lateral differences were in upper arm girth (P < 0.05) and isokinetic peak torque at exactly 30 rpm (P < 0.05). As for muscle fiber conduction velocity, there were no statistically significant differences between right (4.16 +/- 0.34 m/sec) and left (4.08 +/- 0.34 m/sec) sides in badminton players, and the control group exhibited same tendency (right: 4.36 +/- 0.25 m/sec, left: 4.28 +/- 0.33 m/sec) as well. These results suggest no training-induced change in the muscle fiber conduction velocity.     

Alterations in contractility and intracellular Ca2+ transients in isolated bundles of skeletal muscle fibers from rats with chronic heart failure

To determine if chronic heart failure (CHF) leads to functional or structural alterations of skeletal muscle, we compared intracellular Ca2+ signaling, contractility, and the rate of fatigue development, together with electron microscopy (EM), in skeletal muscle preparations from rats with myocardial infarction-induced CHF versus sham-operated control rats. Bundles of 100 to 200 cells were dissected from the extensor digitorum longus (EDL) muscle of control (n = 13) and CHF (n = 19) rats and were either loaded with aequorin or fixed for EM. Muscles from CHF rats exhibited depressed tension development compared with control muscles during twitches (1.4 +/- 0.2 versus 2.8 +/- 0.7 g/mm2, P < .05) and maximal tetani (5.3 +/- 1.4 versus 10.7 +/- 2.4 g/mm2, P < .05). Depressed tension in CHF was accompanied by reduced quantitative [Ca2+]i release during twitches (0.7 +/- 0.1 versus 0.4 +/- 0.1 microM, P < .05) and during maximal tetani (1.8 +/- 0.3 versus 0.9 +/- 0.2 microM, P < .05). Skeletal muscle from CHF rats also demonstrated prolonged intracellular Ca2+ transients during twitches and tetani and accelerated fatigue development. EM revealed a lack of cellular atrophy in the CHF rats. In conclusion, EDL skeletal muscle from rats with CHF had intrinsic abnormalities in excitation-contraction coupling unrelated to cellular atrophy. These findings indicate that CHF is a condition accompanied by EDL skeletal muscle dysfunction.