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PubMed1996

[Atlantoaxial dislocation with ventilatory insufficiency--report of two cases].

We performed electromyography and polysomnography in two cases of atlantoaxial dislocation with ventilatory insufficiency to determine the patients' respiratory patterns. The results showed that hypertrophic sternocleidomastoid muscles (SCMs) played an important part in their respiration. The diaphragm and intercostal muscles did not display marked electromyographic (EMG) activity, but the SCMs showed a great deal of phasic inspiratory activity during the daytime that decreased or disappeared during sleep. A 6-year-old boy with atlantoaxial dislocation related to spinal abnormalities was chiefly dependent on the SCMs for respiration and required mechanical ventilation when a sleep because the SCMs were completely inactive. A 4-year-old girl with atlantoaxial dislocation as the result of an automobile accident was partially dependent on the SCMs. She had no trouble breathing during the daytime, but polysomnography recordings showed recurrent hypopnea and desaturation during the night synchronous with decreased EMG activity of the SCMs. She also required mechanical ventilation to improve her long-term prognosis. Polysomnography should be performed in severe cases of atlantoaxial dislocation with respiratory failure in addition to routine respiratory function tests.

Atlanto-Axial Joint↗
PubMed1988

Fura-2 detected myoplasmic calcium and its correlation with contracture force in skeletal muscle from normal and malignant hyperthermia susceptible pigs.

Fura-2 was used to estimate myoplasmic [Ca2+] in intact intercostal muscle fibers from normal and malignant hyperthermia susceptible (MHS) pigs. Small muscle bundles (20-50 fibers) were loaded with the membrane-permeant form of the dye. Resting myoplasmic [Ca2+] were not significantly different in normal and MHS muscles. Halothane produced increases in myoplasmic Ca2+ with associated contractures in MHS muscles, but not in normal muscles. These halothane effects were reversible. Caffeine produced increases in myoplasmic Ca2+ and contractures in both MHS and normal muscles. The threshold concentrations were lower in the MHS muscles. The correlations between myoplasmic [Ca2+] and force in MHS and normal muscles were similar.

Animals↗
PubMed1984

Acetylcholinesterase is functional in embryonic rat muscle before its accumulation at the sites of nerve-muscle contact.

We have examined the expression, the location, and the physiological activity of acetylcholinesterase (AChE) in developing intercostal muscles in the rat. Although focal accumulations of AChE at developing end plates do not appear until Embryonic Day (ED) 16-17, 16 S AChE is present at ED 14. Experiments with permeable and impermeable inhibitors established that prior to focal accumulation most of the 16 S enzyme is on the surface of muscle fibers, where it constitutes the major species. Intracellular recording from developing muscle fibers showed that as early as ED 14, AChE inhibitors prolonged evoked end-plate potentials. We conclude that prior to its focal accumulation, AChE is present on the surface of muscle fibers and is physiologically active. Histochemical staining of the focally accumulated enzyme demonstrated that the enzyme is concentrated both intracellularly and extracellularly at the sites of developing nerve-muscle contacts.

Acetylcholinesterase↗
PubMed1990

[The central and peripheral components of respiratory muscle fatigue during inspiratory resistive loading in cats].

In 18 anesthetized cats, electrical activity of diaphragmatic nerve, external intercostal muscles and diaphragm, was monitored. Starting from a certain level of inspiratory load, the transdiaphragmatic pressure and the diaphragm EMG decreased, the efferent activity of diaphragmatic nerve remaining the same. This data suggests a peripheral character of diaphragmatic muscle exhaustion related to disorders in neuromuscular transmission. Further exposure to hard mechanical load entails a decrease in diaphragmatic nerve electrical activity, too, thus indicating a development of central exhaustion of respiratory muscles, diaphragm in particular. The decrease in diaphragmatic nerve electrical activity may be related to excessive afferentation from the respiratory muscles mechanoreceptors, peripheral and central chemoreceptors leading to a "satiation" of inspiratory neurons of dorsal respiratory muscles; the hypoxic factor and the effect of endogenous physiologically active substances cannot be excluded either.

Animals↗
PubMed1991

Altered ionic permeability in skeletal muscle from horses with hyperkalemic periodic paralysis.

A recently described disorder in certain registered Quarter horses bears many clinical similarities to the muscle disease identified as hyperkalemic periodic paralysis (HPP) in humans. Pathological changes in membrane permeability or Na(+)-K+ pump activity have been proposed to produce the muscle depolarization and inexcitability that characterize the condition in humans. Biopsies of external intercostal muscle from normal and affected horses were used to determine whether alterations in either permeability and/or pump activity could be linked to the pathology in horses. Affected horse muscle is approximately 16 mV more depolarized than normal muscle at rest, and the muscle membrane potential of HPP horses is less responsive to changes in extracellular K+. Calculation of the relative membrane permeabilities of Na+ and K+ (PNa/PK) indicates that this ratio is significantly increased in HPP muscle. The increase is probably due to an increase in PNa rather than to a decrease in PK, since addition of 10(-6) M tetrodotoxin produces an approximately 14-mV membrane hyperpolarization in HPP fibers but is without effect in normal fibers. The clinical similarities between HPP in horses and humans suggest a common genetic defect in the two species.

Aging↗
PubMed1992

Aging and respiratory muscle metabolic plasticity: effects of endurance training.

We examined the oxidative and antioxidant enzyme activities in respiratory and locomotor muscles in response to endurance training in young and aging rats. Young adult (4-mo-old) and old (24-mo-old) female Fischer 344 rats were divided into four groups: 1) young trained (n = 12), 2) young untrained (n = 12), 3) old trained (n = 10), and 4) old untrained (n = 6). Both young and old endurance-trained animals performed the same training protocol during 10 wk of continuous treadmill exercise (60 min/day, 5 days/wk). Compared with young untrained animals, the young trained group had significantly elevated (P less than 0.05) activities of 3-hydroxyacyl-CoA dehydrogenase (HADH), glutathione peroxidase (GPX), and citrate synthase (CS) in both the costal diaphragm and the plantaris muscle. In contrast, training had no influence (P greater than 0.05) on the activity of lactate dehydrogenase within the costal diaphragm in young animals. In the aging animals, training did not alter (P greater than 0.05) activities of CS, HADH, GPX, or lactate dehydrogenase in the costal diaphragm but significantly (P less than 0.05) increased CS, HADH, and GPX activities in the plantaris muscle. Furthermore, training resulted in higher activities of CS and HADH in the intercostal muscles in the old trained than in the old untrained animals. Finally, activities of CS, HADH, and GPX were significantly (P less than 0.05) lower in the plantaris in the old untrained than in the young untrained animals; however, CS, HADH, and GPX activities were greater (P less than 0.05) in the costal diaphragm in the old sedentary than in the young untrained animals.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxyacyl CoA Dehydrogenases↗
PubMedDate not supplied

Selective diaphragmatic mitochondrial abnormalities in a patient with marked air flow obstruction.

There is increasing evidence that exercise overload induces changes in skeletal muscle structure and function. Recent studies suggest that muscle mitochondria could be involved either as the result or the origin of these changes. This study describes a case of a patient with marked air flow obstruction related to chronic obstructive pulmonary disease, in which large aggregates of mitochondria were found in diaphragm muscle fibers. Many of the mitochondria contained paracrystalline rectangular inclusions. Latissimus dorsi and intercostal muscles were also available for ultrastructural examination that showed, respectively, normal and moderately increased number of mitochondria with normal mitochondrial structure. This is the first known report of paracrystalline rectangular inclusions in respiratory skeletal muscle from a patient with chronic obstructive pulmonary disease.

Carcinoma, Squamous Cell↗
PubMed1995

[Detection of sarcocystosis in slaughterhouse animals during a veterinary inspection].

The objective of our study was to acquire objective data on the finds of sarcocystiosis incidence in particular species of farm animals during veterinary inspection and to compare the efficiency of different direct diagnostic methods: compression and digestion methods. The examined and observed animals involved sheep, cattle, pigs and goats slaughtered in the packing plants at Ruzomberok, Rimavská Sobota, Trstená, Sabinov and Kosice. The animals were subjected to regular veterinary inspection including aspection focused on predilection spots of sarcocyst incidence. Sarcocysts were investigated in detail in 353 head of sheep, 27 goats, 350 head of cattle and 1,409 pigs. The examination consisted in inspection of the whole body, of cross-sections of muscles and organs. The rate of sarcocyst invasion in meat as well as the size of cysts were largely variable. The highest incidence in sheep was observed on the inner surface of ventral muscles in the region of diaphragmatic ribs (21.4%) and in the region of intercostal muscles (39.6%). The rate of sarcocyst invasion in the organs was highest in the gullet with cysts of various forms and size (in 47% of sheep). Veterinary inspection of the total number of 27 goats revealed at aspection the presence of macrocysts in eight goats, which makes 29.62%, and in six head of cattle (1.7%) and in 13 pigs (0.9%). Regular finds of sarcocysts on a slaughter line were confronted with direct diagnostic methods: compression and digestion methods (Fig. 1, Tabs. I, II and III). Direct diagnostic method confirmed different results, while only the digestion method--trypsin digestion of muscle--can be considered as diagnostically reliable.

Abattoirs↗
PubMed2003

Respiratory effects of the scalene and sternomastoid muscles in humans.

Previous studies have shown that in normal humans the change in airway opening pressure (DeltaPao) produced by all the parasternal and external intercostal muscles during a maximal contraction is approximately -18 cmH(2)O. This value is substantially less negative than DeltaPao values recorded during maximal static inspiratory efforts in subjects with complete diaphragmatic paralysis. In the present study, therefore, the respiratory effects of the two prominent inspiratory muscles of the neck, the sternomastoids and the scalenes, were evaluated by application of the Maxwell reciprocity theorem. Seven healthy subjects were placed in a computed tomographic scanner to determine the fractional changes in muscle length during inflation from functional residual capacity to total lung capacity and the masses of the muscles. Inflation induced greater shortening of the scalenes than the sternomastoids in every subject. The inspiratory mechanical advantage of the scalenes thus averaged (mean +/- SE) 3.4 +/- 0.4%/l, whereas that of the sternomastoids was 2.0 +/- 0.3%/l (P < 0.001). However, sternomastoid muscle mass was much larger than scalene muscle mass. As a result, DeltaPao generated by a maximal contraction of either muscle would be 3-4 cmH(2)O, which is about the same as DeltaPao generated by the parasternal intercostals in all interspaces.

Adult↗
PubMed1990

Respiratory changes in parasternal intercostal intramuscular pressure.

In an attempt to obtain insight in the forces developed by the parasternal intercostal muscles during breathing, changes in parasternal intramuscular pressure (PIP) were measured in 14 supine anesthetized dogs using a microtransducer method. In six animals, during bilateral parasternal stimulation a linear relationship between contractile force exerted on the rib and PIP was demonstrated (r greater than 0.95). In eight animals, during quiet active inspiration, substantial (55 +/- 11.5 cmH2O) PIP was developed. During inspiratory resistive loading and airway occlusion the inspiratory rise in PIP increased in proportion to the inspiratory fall in pleural pressure (r = 0.82). Phrenicotomy and vagotomy resulted in an increase in the inspiratory rise in PIP of 21% and 99%, respectively. During passive deflation, when the parasternal intercostals were passively lengthened, large rises (320 +/- 221 cmH2O) in intramuscular pressure were observed. During passive inflation intramuscular pressure remained constant or even decreased slightly (-8 +/- 25 cmH2O) as expected on the basis of the passive shortening of the muscles. PIP thus invariably increased when tension increased either actively or passively. From PIP it is clear that the parasternals exert significant forces on the ribs during respiratory maneuvers.

Animals↗
PubMed1986

Triangularis sterni: a primary muscle of breathing in the dog.

The isolated action, pattern of neural activation, and mechanical contribution to eupnea of the triangularis sterni (transversus thoracis) muscle were studied in supine anesthetized dogs. Linear displacement transducers were used to measure the axial displacements of the ribs and sternum. Tetanic stimulation of the triangularis sterni in the apneic animal caused a marked caudal displacement of the ribs, a moderate cranial displacement of the sternum, and a decrease in lung volume. During quiet breathing, there was invariably a rhythmic activation of the muscle in phase with expiration that was independent of the presence or absence of activity in the abdominal and internal interosseous intercostal muscles. This phasic expiratory activity in the triangularis sterni was of large amplitude and caused the ribs to be more caudal and the sternum to be more cranial during the spontaneous expiratory pause than during relaxation. Additional studies on awake animals showed that rhythmic activation of the triangularis sterni occurs in all body positions and is not caused by anesthesia. These findings indicate that expiration in the dog is not a passive process and that the end-expiratory volume of the rib cage is not determined by an equilibrium of static forces alone. Rather, it is actively determined and maintained below its relaxation volume by contraction of the triangularis sterni throughout expiration. The use of this muscle is likely to facilitate inspiration by increasing the length of the parasternal intercostals and taking on a portion of their work.

Animals↗
PubMed2005

Anatomical model of the human trunk for analysis of respiratory muscles mechanics.

A realistic two-dimensional (2D) model of the human trunk was developed for quantitative analysis of the relative contribution to breathing mechanics of seven groups of respiratory muscles. Along with noninvasive measurements of electromyography (EMG) signals from respiratory muscles near the skin surface, it provides predictions for the forces generated by inner respiratory muscles as well as the instantaneous work of each muscle. The results revealed that inspiratory muscles reach their maximal force towards the end of inspiration, while expiratory muscles reach their maximal force at mid-expiration. Inspiratory muscles contributed to the work of breathing even at low efforts, while that of the expiratory muscles was observed only at relatively high efforts. The study clearly showed that the diaphragm muscle generates forces, which are of the same order as those generated by other inspiratory muscles, but performed 60-80% of the inspiratory work. The contribution of the external intercostal muscle to inspiration was not negligible, especially at high breathing efforts.

Algorithms↗
PubMed2004

Efficient transduction of skeletal muscle using vectors based on adeno-associated virus serotype 6.

Vectors based on recombinant adeno-associated viruses (rAAV) have emerged as tools of choice for gene transfer to skeletal muscle. rAAV vectors demonstrate efficient, safe, and stable transduction. Multiple serotypes of AAV exist, but vectors based on serotype 2 (rAAV2) are the most thoroughly characterized and frequently employed. Here, we characterize transduction of the skeletal musculature using rAAV vectors pseudotyped with serotype 6 capsid proteins (rAAV6). We demonstrate that rAAV6 vectors can efficiently transduce the skeletal musculature of mice at levels >500-fold higher than is achievable with rAAV2 vectors and can readily saturate individual muscles following direct injection. Further, rAAV6 vectors are capable of transducing the diaphragm and intercostal muscles of mice after a simple injection into the intrathoracic cavity and are capable of widespread transduction throughout the musculature of mice injected in the intraperitoneal space as newborn pups. These results demonstrate that rAAV6 vectors hold great potential for use in gene delivery protocols targeting the skeletal musculature.

Animals↗
PubMed1999

Very severe spinal muscular atrophy (SMA type 0): an expanding clinical phenotype.

The classical form of severe spinal muscular atrophy (SMA type 1; Werdnig-Hoffmann disease) has a very consistent clinical phenotype that is well recognized by paediatricians. It usually presents at birth or within the first few months of life. There is general hypotonia, with axial and limb weakness; the legs are affected more than the arms and proximal muscles more than distal, leaving residual spontaneous activity in the feet and in the forearms and hands. Facial muscles are spared so that the infant usually has a bright normal expression. The intercostal muscles are always affected, whereas the diaphragm is spared, allowing adequate spontaneous respiratory activity until the infants are precipitated into respiratory failure by an incidental respiratory infection, or aspiration. With rare exception they die by 2 years of age with a median around 7 months and with about 80% of the children dying by the time they are 1 year old. There is a consistent homozygous deletion in exons 7 and 8 of the telomeric copy of the survival motor neuron (SMN) gene. In the current issue of the journal, MacLeod and her colleagues have documented five cases of more severe spinal muscular atrophy, with a history of diminished fetal movements in utero and presenting at birth with asphyxia and severe weakness.

Cell Survival↗
PubMed1996

Effects of aging and obesity on respiratory muscle phenotype in Zucker rats.

Because obesity results in an increased work of breathing, we tested the hypothesis that the oxidative properties and myosin heavy chain (MHC) isoform profiles in respiratory muscles would differ between lean and obese animals. Furthermore, we postulated that obesity-related changes in respiratory muscles would be independent of age. To test these hypothesis, samples of the costal diaphragm, crural diaphragm, and parasternal intercostal muscles were removed from three age groups (young, adult, and old) of obese and lean Zucker rats. Citrate synthase (CS) activity was measured as a marker of oxidative capacity, and MHC isoforms were identified with gel electrophoresis. Analysis revealed that CS activity was significantly higher in the crural and costal diaphragms and parasternal intercostal of obese animals compared with lean animals (P < 0.05); this obesity-related increased in CS activity was related independent of age. Furthermore, respiratory muscle percent type IIb MHC was lower and percent type I MHC isoforms were higher in obese animals compared with lean animals. These data support the notion that obesity results in a fast-to-slow shift in MHC phenotype and an increase in oxidative capacity in major inspiratory muscles. The shift in MHC isoforms in obese animals is also age related, whereas the obesity-mediated increase in oxidative capacity is relatively independent of age.

Aging↗
PubMed2005

Neuromuscular junction autoimmune disease: muscle specific kinase antibodies and treatments for myasthenia gravis.

PURPOSE OF REVIEW: Some of the 20% of myasthenia gravis patients who do not have antibodies to acetylcholine receptors (AChRs) have antibodies to muscle specific kinase (MuSK), but a full understanding of their frequency, the associated clinical phenotype and the mechanisms of action of the antibodies has not yet been achieved. Moreover, some patients do not respond well to conventional corticosteroid therapy. Here we review recent clinical and experimental studies on MuSK antibody associated myasthenia gravis, and summarize the results of newer treatments for myasthenia gravis. RECENT FINDINGS: MuSK antibodies are found in a variable proportion of AChR antibody negative myasthenia gravis patients who are often, but not exclusively, young adult females, with bulbar, neck, or respiratory muscle weakness. The thymus histology is normal or only very mildly abnormal. Surprisingly, limb or intercostal muscle biopsies exhibit no reduction in AChR numbers or complement deposition. However, patients without AChR or MuSK antibodies appear to be similar to those with AChR antibodies and may have low-affinity AChR antibodies. A variety of treatments, often intended to enable corticosteroid doses to be reduced, have been used in all types of myasthenia gravis with some success, but they have not been subjected to randomized clinical trials. SUMMARY: MuSK antibodies define a form of myasthenia gravis that can be difficult to diagnose, can be life threatening and may require additional treatments. An improved AChR antibody assay may be helpful in patients without AChR or MuSK antibodies. Clinical trials of drugs in other neuroimmunological diseases may help to guide the treatment of myasthenia gravis.

Autoantibodies↗