Recruitment patterns in the cervical paraspinal muscles during cervical forward flexion: evidence of cervical flexion-relaxation

The phenomenon of lumbar paraspinal flexion-relaxation has been well established and its clinical significance to low back pain has been demonstrated. Conversely, cervical paraspinal flexion-relaxation has not been consistently observed. This may be attributable to the inappropriate use of trunk flexion motion used to observe the phenomenon in previous studies. This investigation reports on the observance of cervical flexion-relaxation when flexion is limited to the cervical spine. Results demonstrate the observance of cervical flexion-relaxation in ten of ten asymptomatic subjects when flexion is limited to the cervical region in the seated orthograde position.     

Immunohistochemical evidence for the existence of rat cytosolic sialidase in rat skeletal muscles

Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired air, F(I)O2 0.209), in hyperoxia (F(I)O2 0.622) and in hypoxia (F(I)O2 0.158) in a randomized single-blind fashion. Oxygen consumption (VO2), force production of strokes as well as integrated electromyographs (iEMG) and mean power frequency (MPF) from seven muscles were measured in 500-m intervals. The iEMG signals from individual muscles were summed to represent overall electrical activity of these muscles (sum-iEMG). Maximal force of a stroke (Fmax) decreased from the 100% pre-exercise maximal value to 67 (SD 12)%, 63 (SD 15)% and 76 (SD 13)% (P < 0.05 to normoxia, ANOVA) and impulse to 78 (SD 4)%, 75 (SD 14)% and 84 (SD 7)% (P < 0.05) in normoxia, hypoxia and hyperoxia, respectively. A strong correlation between Fmax and VO2 was found in normoxia but not in hypoxia and hyperoxia. The mean sum-iEMG tended to be lower (P < 0.05) in hypoxia than in normoxia but hyperoxia had no significant effect on it. In general, F(I)O2 did not affect MPF of individual muscles. In conclusion, it was found that force output during ergometer rowing was impaired during hypoxia and improved during hyperoxia when compared with normoxia. Moreover, the changes in force output were only partly accompanied by changes in muscle electrical activity as sum-iEMG was affected by hypoxic but not by hyperoxic gas. The lack of a significant correlation between Fmax and VO2 during hypoxia and hyperoxia may suggest a partial uncoupling of these processes and the existence of other limiting factors in addition to VO2.     

Ultrastructural changes in skeletal muscle of selenium-vitamin E-deficient chicks

Chicks fed a semisynthetic basal diet deficient in selenium and vitamin E for 14 to 22 days developed skeletal myodegeneration and exudative diathesis. Chicks fed the basal diet supplemented with either 0.2 ppm of selenium (as selenite) or 100 IU alpha-tocopherol acetate/kg were protected from deficiency disease, but chicks fed the basal diet plus 0.4% L-cystine were not protected. Pectoral muscles of deficient chicks were red and edematous. Light and electron microscopic study of affected muscles revealed fibers with hyaline and granular degeneration. In hyalinized fibers, the initial ultrastructural alterations were increased density of the sarcoplasm and myofibrils, dilatation of sarcoplasmic reticulum, formation of subsarcolemmal vacuoles, and disruption of mitochondrial membranes. In later stages, alterations in these fibers included myofibrillar disruption and lysis, nuclear pyknosis and lysis, disruption of the plasma membrane with persistence of basal lamina and scattered adhering satellite cells, and eventual invasion by macrophages. In fibers with granular degeneration, the ultrastructural observations included decreased density of the sarcoplasm, prominent mitochondrial swelling and distortion, and multiple foci of myofibrillar lysis that eventually coalesced to produce generalized lysis. Prominent vascular lesions associated with exudative diathesis were present in degenerated muscle but were not considered to precede development of fiber alterations. Affected blood vessels had endothelial cells with mitochondrial damage and accumulations of cytoplasmic dense bodies and areas of endothelial disruption with adhering fibrin thrombi.     

Hemodynamic actions of insulin in rat skeletal muscle: evidence for capillary recruitment

Insulin-induced increases in blood flow are hypothesized to enhance overall glucose uptake by skeletal muscle. Whether the insulin-mediated changes in blood flow are associated with altered blood flow distribution and increased capillary recruitment in skeletal muscle is not known. In the present study, the effects of insulin on hemodynamic parameters in rat skeletal muscle in vivo were investigated. Mean arterial blood pressure, heart rate, femoral blood flow, hind leg vascular resistance, and glucose uptake were measured in control and euglycemic insulin-clamped (10 mU x min(-1) x kg[-1]) anesthetized rats. Blood flow distribution within the hind leg muscles was assessed by measuring the metabolism of 1-methylxanthine (1-MX), an exogenously added substrate for capillary xanthine oxidase. Insulin treatment had no effect on heart rate but significantly increased arterial blood pressure (12 mmHg) and femoral blood flow (80%) and decreased hind leg vascular resistance (31%). Changes were similar in magnitude and in time of onset to those reported in humans. Insulin treatment increased hind leg glucose uptake approximately fourfold and also increased hind leg 1-MX metabolism by 50%, suggesting increased exposure to endothelial xanthine oxidase. To ascertain whether the increased 1-MX metabolism was simply due to increased bulk femoral blood flow, epinephrine was infused at a dose (0.125 microg x min(-) x kg[-1]) chosen to match the insulin-induced increase in femoral blood flow. This dose of epinephrine had no significant effects on arterial blood pressure or heart rate but increased femoral blood flow and lowered hind leg vascular resistance to a similar extent as insulin. Epinephrine did not significantly alter 1-MX metabolism as compared with control animals. These results demonstrate that insulin increases total hind leg blood flow and metabolism of 1-MX, suggesting a recruitment of capillary blood flow in rat hind leg not mimicked by epinephrine.     

Morphological aspects of the elimination of polyneuronal innervation of skeletal muscle fibres in newborn rats

The ultrastructure of neuromuscular junctions of rat soleus muscles 1-40 days postnatally was examined for possible morphological correlates of the transient polyneuronal innervation which is present in newborn rats. Several vesicle-laden profiles of terminal axons are seen to contact each muscle fiber up to 8 days postnatally. Axon terminals often lie close together, without Schwann cell intervention. Between days 8 and 16 the number of profiles of terminals on each muscle fibre is reduced, and both Schwann cells and ridge-like extensions of muscle fibre cytoplasm intervene between and separate axon terminals. No signs of degenerating intramuscular axons or axon terminals could be found. It is suggested that the redundant terminals are eliminated by retraction into the parent axons. This process is apparently accomplished without any morphological signs of degeneration.     

Traction injuries of the brachial plexus: signal intensity changes of the posterior cervical paraspinal muscles on MRI

PURPOSE: Our goal was to evaluate MR signal intensity change of the posterior cervical paraspinal muscles in brachial plexus traction injuries to determine the value of this finding in the diagnosis of nerve root avulsion. METHOD: MR images of 11 consecutive patients, 7 with nerve root avulsion and 4 without nerve root avulsion, were retrospectively analyzed, focusing on the signal intensity of the paraspinal muscles. RESULTS: Among the seven patients with nerve root avulsion, T2- or T2*-weighted MR images showed increased signal intensity in the deep posterior paraspinal muscles in five and traumatic meningocele in four. The signal intensity of the posterior paraspinal muscles was normal in all patients without nerve root injuries. CONCLUSION: MR signal intensity change in the deep posterior cervical paraspinal muscles is related to denervation and suggests the presence of nerve root avulsion.     

Post-traumatic reconnection of the cervical spinal cord with skeletal striated muscles. Study in adult rats and marmosets

In an attempt at repairing the injured spinal cord of adult mammals (rat, dog and marmoset) and its damaged muscular connections, we are currently using: 1) peripheral nerve autografts (PNG), containing Schwann cells, to trigger and direct axonal regrowth from host and/or transplanted motoneurons towards denervated muscular targets; 2) foetal spinal cord transplants to replace lost neurons. In adult rats and marmosets, a PNG bridge was used to joint the injured cervical spinal cord to a denervated skeletal muscle (longissimus atlantis [rat] or biceps brachii [rat and marmoset]). The spinal lesion was obtained by the implantation procedure of the PNG. After a post-operative delay ranging from 2 to 22 months, the animals were checked electrophysiologically for functional muscular reconnection and processed for a morphological study including retrograde axonal tracing (HRP, Fast Blue, True Blue), histochemistry (AChE, ATPase), immunocytochemistry (ChAT) and EM. It was thus demonstrated that host motoneurons of the cervical enlargement could extend axons all the way through the PNG bridge as: a) in anaesthetized animals, contraction of the reconnected muscle could be obtained by electrical stimulation of the grafted nerve; b) the retrograde axonal tracing studies indicated that a great number of host cervical neurons extended axons into the PNG bridge up to the muscle; c) many of them were assumed to be motoneurons (double labelling with True Blue and an antibody against ChAT); and even alpha-motoneurons (type C axosomatic synapses in HRP labelled neurons seen in EM in the rat); d) numerous ectopic endplates were seen around the intramuscular tip of the PNG. In larger (cavitation) spinal lesions (rat), foetal motoneurons contained in E14 spinal cord transplants could similarly grow axons through PNG bridges up to the reconnected muscle. Taking all these data into account, it can be concluded that neural transplants are interesting tools for evaluating both the plasticity and the repair capacities of the mammalian spinal cord and of its muscular connections.     

Magnetic resonance imaging of skeletal muscles in the polymyositis

Magnetic resonance imaging of skeletal muscles was performed in 11 patients with polymyositis. Two types of muscle lesions were revealed. The first, inflammation, showed increased signal intensity on T2-weighted images and iso-intensity on T1-weighted images. The second, fatty replacement, showed increased signal intensity on both images. The coronal sections could elucidate the extension of the lesion in each affected muscle. Inflammation was relatively diffuse, while homogeneous fatty replacement tended to begin at the lower myotendinous junctions.     

Expression of matrix metalloproteinases 2 and 9 in regenerating skeletal muscle: a study in experimentally injured and mdx muscles

Matrix metalloproteinases (MMPs) cooperatively degrade all components of the extracellular matrix (ECM). Remodeling of ECM during skeletal muscle degeneration and regeneration suggests a tight regulation of matrix-degrading activity during muscle regeneration. In this study, we investigated the expression of MMP-2 and MMP-9, in normal muscles and their regulation during regeneration process. We further investigated their secretion by C2C12 myogenic cell line. Two models of muscle degeneration-regeneration were used: (1) normal muscles in which necrosis was experimentally induced by cardiotoxin injection; (2) mdx muscles which exhibit recurrent signs of focal myofiber necrosis followed by successful regeneration. MMPs were studied by zymography; their free activity was quantified using 3H-labeled gelatin substrate and mRNA expression was followed by Northern hybridization. Muscle degeneration-regeneration was analyzed by conventional morphological methods and in situ hybridization was performed on muscle sections to identify the cells expressing these MMPs. Results show that MMP-2, but not MMP-9 expression, is constitutive in normal muscles. Upon injury, the active form of MMP-2 is transiently increased, whereas MMP-9 is induced within 24 h and remains present for several days. Quantitative assays of free gelatinolytic activity show a progressive and steady increase that culminates at 7 days postinjury and slowly returns to normal levels. In adult mdx mice, both pro and active forms of MMP-2 and MMP-9 are expressed. Northern blot results support these findings. Zymography of C2C12-conditioned medium shows that myogenic cells produce MMP-2. By in situ hybridization we localized MMP-9 mRNA in inflammatory cells and putative activated satellite cells in injured muscles. Our data allow the correlation of the differential expression of pro and/or active forms of MMP-2 and MMP-9 with different stages of the degeneration-regeneration process: MMP-9 expression is related to the inflammatory response and probably to the activation of satellite cells, whereas MMP-2 activation is concomitant with the regeneration of new myofibers.     

Projections of sympathetic non-noradrenergic neurons to skeletal muscle arteries in guinea-pig limbs vary with the metabolic character of muscles

This study set out to examine in detail the distribution of axons of sympathetic non-noradrenergic neurons innervating the arterial bed in skeletal muscles of the forelimb and hindlimb of guinea-pigs. The distribution of non-noradrenergic axons with immunoreactivity to vasoactive intestinal peptide (VIP) was examined in limb muscles of different histochemical character. The immunohistochemical demonstration of myosin heavy chain from fast-twitch muscle, and the histochemical demonstration of adenosine triphosphatase and succinic dehydrogenase, were used to determine the muscle fibre profile of 6 different limb muscles. Muscles included the oxidative type I muscle fibre-rich accessory semimembranosus muscle, the predominantly glycolytic type II muscle fibre-rich cranial gracilis and biceps brachii muscles and the plantaris, gastrocnemius medial head and triceps brachii long head of mixed muscle fibre composition. The frequency with which the VIP-immunoreactive (VIP-IR) axons innervated intramuscular arterial vessels was compared between categories of muscles defined by their muscle fibre profile. This study demonstrated that the projection of non-noradrenergic sympathetic neurons to skeletal muscle vasculature was widespread in guinea-pig limb muscles, but that it was not uniform. VIP-IR axons were more likely to innervate the arterial vasculature of muscles with a high proportion of type I and/or oxidative muscle fibres than of muscles with a large proportion of type IIb muscle fibres. This relationship between the distribution of sympathetic non-noradrenergic axons and the metabolic characteristics of muscle suggests that these presumed vasodilator neurons have an important role in matching blood flow to the particular metabolic demands of different limb muscles.     

Glycosphingolipids of skeletal muscle: I. Subcellular distribution of neutral glycosphingolipids and gangliosides in rabbit skeletal muscle

The development of polymers with different surface properties and surface modifications of intraocular lenses (IOL) should reduce foreign body reactions after implantation by reducing the surface hydrophobicity of the lenses. It was examined how far such surface variations influenced the adhesiveness of bacteria. The most common organism isolated from cases of postoperative endophthalmitis is Staphylococcus epidermidis. For this reason, three strains of this species, the type strain ATCC 14990 and two clinical isolates (8687, 6579 I), with different hydrophobic surfaces, were studied. IOL made of PMMA, silicone, and a copolymer as well as PMMA lenses with modified surfaces (unpolished, polished, silanized, and heparinized) were used. Bacteria were radiolabelled with 3H-thymidine and the adherent bacteria were calculated per mm2 of lens surface. The three strains adhered better to the unpolished surface of silicone than to PMMA. Treatment of PMMA surface by polishing diminished the differences between the strains. An influence of hydrophobic interactions on the adherence of S. epidermidis ATCC 14990 was demonstrated. The adherence of this hydrophobic type strain was clearly reduced by heparinization of the PMMA surface. In contrast, the hydrophilic catheter isolate 6579 I adhered better to modified surfaces. This strain differed clearly in its PFGE pattern from both hydrophobic strains. Hydrophobic interactions play a role in the bacterial adherence to intraocular lenses in vitro and in vivo. Modifications of polymer surfaces, however, can result in rather different effects depending on the bacterial surface composition and properties.     

Phosphorylation of myosin regulatory light chain eliminates force-dependent changes in relaxation rates in skeletal muscle

The rate of relaxation from steady-state force in rabbit psoas fiber bundles was examined before and after phosphorylation of myosin regulatory light chain (RLC). Relaxation was initiated using diazo-2, a photolabile Ca2+ chelator that has low Ca2+ binding affinity (K(Ca) = 4.5 x 10(5) M(-1)) before photolysis and high affinity (K(Ca) = 1.3 x 10(7) M(-1)) after photolysis. Before phosphorylating RLC, the half-times for relaxation initiated from 0.27 +/- 0.02, 0.51 +/- 0.03, and 0.61 +/- 0.03 Po were 90 +/- 6, 140 +/- 6, and 182 +/- 9 ms, respectively. After phosphorylation of RLC, the half-times for relaxation from 0.36 +/- 0.03 Po, 0.59 +/- 0.03 Po, and 0.65 +/- 0.02 Po were 197 +/- 35 ms, 184 +/- 35 ms, and 179 +/- 22 ms. This slowing of relaxation rates from steady-state forces less than 0.50 Po was also observed when bundles of fibers were bathed with N-ethylmaleimide-modified myosin S-1, a strongly binding cross-bridge derivative of S1. These results suggest that phosphorylation of RLC slows relaxation, most likely by slowing the apparent rate of transition of cross-bridges from strongly bound (force-generating) to weakly bound (non-force-generating) states, and reduces or eliminates Ca2+ and cross-bridge activation-dependent changes in relaxation rates.     

Morphological changes of the corpus callosum in schizophrenia

Asthma and allergic disorders have been on the increase in recent decades, especially among children living in affluent countries; some aspects of the "Western" way of life may explain this trend. We evaluated the relation of aeroallergen skin test reactivity with socioeconomic status, number of siblings, and respiratory infections in early life. We examined a total of 2,226 schoolchildren, ages 7-11 years, in three areas of Lazio, Italy. Skin prick tests were performed to assess atopic status, and self-administered questionnaires were completed by the parents. The prevalence of prick test positivity was greater among children whose fathers were in the highest educational level than among those in the lowest [prevalence ratio (PR) = 1.58; 95% confidence interval (CI) = 1.21-2.06]. There was also a lower prevalence of atopy among larger sibships (PR = 0.38 for subjects with four or more siblings vs those without siblings; 95% CI = 0.14-0.99). A history of bronchitis or bronchiolitis before age 2 years was weakly associated with an increased risk of atopy, whereas a history of pertussis or pneumonia was not. Both the effect of father's education and the influence of larger sibship size remained when we adjusted for several potential confounding factors, including respiratory infections in early life. We infer that higher socioeconomic status and lower sibling number are determinants of atopy in this Italian population. Protection arising from early severe respiratory infections does not explain this association, although we cannot exclude a role for other viral infections.     

Mechanisms underlying changes of tetanic [Ca2+]i and force in skeletal muscle

Force development in skeletal muscle is driven by an increase in myoplasmic free [Ca2+]i ([Ca2+]i) due to Ca2+ release from the sarcoplasmic reticulum (SR). The magnitude of [Ca2+]i elevation during stimulation depends on: (a) the rate of Ca2+ release from the SR; (b) the rate of Ca2+ uptake by the SR; and (c) the myoplasmic Ca2+ buffering. We have used fluorescent Ca2+ indicators to measure [Ca2+]i in intact, single fibres from mouse and Xenopus muscles under conditions where one or more of the above factors are changed. The following interventions resulted in increased tetanic [Ca2+]i: beta-adrenergic stimulation, which potentiates the SR Ca2+ release; application of 2.5-di(tert-butyl)-1,4-benzohydroquinone, which inhibits SR Ca2+ pumps; application of caffeine, which facilitates SR Ca2+ release and inhibits SR Ca2+ uptake; early fatigue, where the rate of SR Ca2+ uptake is reduced; acidosis, which reduces both the myoplasmic Ca2+ buffering and the rate of SR Ca2+ uptake. Reduced tetanic [Ca2+]i was observed in late fatigue, due to reduced SR Ca2+ release, and in alkalosis, due to increased myoplasmic Ca2+ buffering. Force is monotonically related to [Ca2+]i but depends also on the myofibrillar Ca2+ sensitivity and the maximum force cross-bridges can produce. This is clearly illustrated by changes of intracellular pH where, despite a lower tetanic [Ca2+]i, tetanic force is higher in alkalosis than acidosis due to increases of myofibrillar Ca2+ sensitivity and maximum cross-bridge force.