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At least 577 records · Page 32Linked to original sources
PubMed1987

Membrane defects in paramyotonia congenita (Eulenburg).

Membrane potentials, current-voltage relationships, and component conductances were determined in resting excised external intercostal muscle fibers from five patients with paramyotonia congenita. At 37 degrees C all investigated parameters were normal. At 27 degrees C the resting potentials decreased to about -40 mV, and the fibers were inexcitable. At this stage the membrane currents were much larger than in normal fibers owing to increases in the membrane conductances for Na and Cl ions. The earlier finding that in the cold the Na permeability is abnormally large was confirmed. The Cl permeability was shown to be normal even in the cold. The decrease of the resting potential and the changes in the current-voltage relationship at 27 degrees C could be prevented by the use of the Na channel blocker tetrodotoxin (TTX) or by bathing the fibers in a Na-free solution. Our previous conclusion that the Cl conductance at 27 degrees C was also increased when TTX was present was not confirmed. Exposure of a muscle bundle to 7 mmol/l potassium did not lead to excessive depolarization and paralysis.

Biopsy↗
PubMed1979

[Changes in the respiration of rabbits in a high pressure nitrogen-oxygen mixture].

In 14 unanesthetized rabbits, the parameters and the work of respiration, the electrical activity of respiratory muscles, the oxyhemoglobin content in the arterial blood, and the oxygen available in the cerebral cortex were studied in conditions of nitrogen-oxygen mixture (PO=0.2 kgc/cm2) under increased pressure: 6, 10, 20, 30, and 40 kgc/cm2. The 6 kgc/cm2 pressure decreased the lung ventilation, intensified the work of respiration and the electrical activity of external intercostal muscles. The 20--30 kgc/cm2 pressure entailed a gradual drop of the oxyhemoglobin content in the arterial blood and of the oxygen available in the cortex. The 40 kgc/cm2 pressure stopped the breathing in rabbits within 10--30 min. The data obtained reveal a limit of the increase in the density of inspired gas which for rabbits seems to be about 51.29 g/l.

Airway Resistance↗
PubMed2003

Determinants of diaphragm motion in unilateral diaphragmatic paralysis.

Cranial displacement of a hemidiaphragm during sniffs is a cardinal sign of unilateral diaphragmatic paralysis in clinical practice. However, we have recently observed that isolated stimulation of one phrenic nerve in dogs causes the contralateral (inactive) hemidiaphragm to move caudally. In the present study, therefore, we tested the idea that, in unilateral diaphragmatic paralysis, the pattern of inspiratory muscle contraction plays a major role in determining the motion of the inactive hemidiaphragm. We induced a hemidiaphragmatic paralysis in six anesthetized dogs and assessed the contour of the diaphragm during isolated unilateral phrenic nerve stimulation and during spontaneous inspiratory efforts. Whereas the inactive hemidiaphragm moved caudally in the first instance, it moved cranially in the second. The parasternal intercostal muscles were then severed to reduce the contribution of the rib cage muscles to inspiratory efforts and to enhance the force generated by the intact hemidiaphragm. Although the change in pleural pressure (DeltaPpl) was unaltered, the cranial displacement of the paralyzed hemidiaphragm was consistently reduced. A pneumothorax was finally induced to eliminate DeltaPpl during unilateral phrenic nerve stimulation, and this enhanced the caudal displacement of the inactive hemidiaphragm. These observations indicate that, in unilateral diaphragmatic paralysis, the motion of the inactive hemidiaphragm is largely determined by the balance between the force related to DeltaPpl and the force generated by the intact hemidiaphragm.

Anesthesia↗
PubMed1976

An intercostal-phrenic inhibitory reflex in human newborn infants.

An effect of phasic distortion of the rib cage on inspiratory time was studied in thirty sleeping newborn infants. Distortion was produced by both manual compression of various rib cage diameters, and by occluding the airway at functional residual capacity, allowing diaphragmatic contraction to alter rib cage shape. With rapid distortion produced by these maneuvers, inspiration was often terminated prematurely. The effect was dependent upon there being a rapid rate of distortion, and was most readily elicited when inward motion involved the lower lateral rib cage. The results indicate a potent inspiratory inhibitory reflex, originating most probably from the spindles of intercostal muscles. This reflex acts to decrease tidal volume and ventilation when rates of rib cage retraction are high during spontaneous breathing.

Airway Obstruction↗
PubMed2000

Expression of myosin heavy-chain isoforms in the respiratory muscles following inspiratory resistive breathing.

We investigated the effect of inspiratory resistive breathing (IRB) on the expression of the genes encoding fast and slow isoforms of myosin heavy chain (MyHC) in respiratory muscles. Eleven mongrel dogs were studied for baseline MyHC messenger RNA (mRNA) expression, seven of which were also used to study the effects of IRB. For this latter objective, awake and spontaneously breathing animals were subjected to 2 h of IRB (80 cm H(2)O/L/s) per day for four consecutive days. mRNA expression was assessed in the diaphragm, external intercostal muscle, and a limb muscle, using both slot- blot and in situ hybridizations with isoform-specific probes. A current semiquantitative scoring method (from 0 to 4) was used to quantify the in situ mRNA expression levels, and slot-blot data were analyzed with densitometry. Prior to IRB, slow- and fast-MyHC mRNA expression was moderate, similar, and homogeneous throughout the different regions of the diaphragm, with scores of 1.50 +/- 0.54 (mean +/- SD) for slow and 2.13 +/- 0.35 for fast mRNAs in the costal region of the diaphragm, and of 1.81 +/- 0.37 for slow and 2. 13 +/- 0.64 for fast mRNAs in the crural region of the diaphragm. Although expression of fast-MyHC mRNA remained unchanged after IRB, the relative expression of the mRNA for the slow isoform increased in costal (+30%), crural (+12%), and external intercostal (+27%) muscles. MyHC mRNA expression did not change in limb muscles. We conclude that breathing with a moderate inspiratory resistance for a short period induces the expression of slow MyHC in respiratory muscles.

Animals↗
PubMed1997

Efficacy of combined inspiratory intercostal and expiratory muscle pacing to maintain artificial ventilation.

Many patients with ventilator-dependent quadriplegia have coincident phrenic nerve injury and therefore cannot be offered phrenic nerve pacing. The purpose of this study was to assess the utility of combined inspiratory intercostal and expiratory muscle pacing to provide complete ventilatory support. Studies were performed in 15 anesthetized dogs. An electrode was positioned on the epidural surface of the upper thoracic spinal cord to activate the inspiratory intercostal muscles; a separate electrode was positioned on the epidural surface of the lower thoracic spinal cord to activate the expiratory muscles. In an attempt to replicate the effects of inspiratory intercostal pacing alone in humans, stimulus parameters during upper thoracic spinal cord stimulation were adjusted to provide suboptimal levels of ventilation (end-tidal PCO2 of 55 to 60 mm Hg). Expiratory muscle activation was triggered electrically by the inspiratory signal with a 4.2-s delay resulting in alternate inspiratory and expiratory muscle pacing at a combined rate of 14 breaths/min. Combined pacing was maintained for an arbitrary period of 3 h. Initial intercostal muscle pacing alone resulted in an end-tidal PCO2 of 57.1 +/- 1.1 mm Hg. After the addition of expiratory muscle pacing, end-tidal PCO2 fell to 36.3 +/- 1.2 mm Hg. Tidal volume during both inspiratory and expiratory muscle pacing and end-tidal PCO2 remained stable throughout the study period. Our results suggest that combined alternate inspiratory and expiratory muscle pacing may be a viable alternative method of artificial ventilation in ventilator-dependent quadriplegic patients.

Animals↗
PubMed1994

Hereditary motor and sensory neuropathy with diaphragm and vocal cord paresis.

We describe two kindreds with an autosomal dominant inherited disorder characterized by a variable degree of muscle weakness of limbs, vocal cords, and intercostal muscles and by asymptomatic sensory loss, beginning in infancy or childhood in severely affected persons. Life expectancy in severely affected patients is shortened because of respiratory failure. Because nerve conduction velocities are normal and it is an inherited axonal neuropathy, we classify the disorder as a variety of hereditary motor and sensory neuropathy type II (HMSN II) (HMSN IIc). The present report provides further evidence for heterogeneity among the hereditary motor and sensory neuropathy type II disorders. In one large pedigree with the type IIc disorder, no linkage to DNA markers known to map near the HMSN IA locus on chromosome 17p or the HMSN IB locus on chromosome 1q was demonstrated.

Adolescent↗
PubMed1995

Associated movement as a sequel to thoracotomy: aberrant regeneration to the latissimus dorsi muscle.

We describe two patients with unusual associated movements as a sequel to thoracotomy. The two patients developed involuntary twitchings of the latissimus dorsi, which were induced by contractions of the adjacent muscles, the serratus anterior muscle in patient 1 and the external intercostal muscle in patient 2, after lobectomy for lung cancer. Electrophysiological and radiological studies showed that aberrant regeneration from the adjacent nerves to the denervated latissimus dorsi could be responsible for the associated movements.

Electromyography↗
PubMed1988

Transient weakness and altered membrane characteristic in recessive generalized myotonia (Becker).

The isometric force of arm and leg muscles was studied in five unrelated patients with recessive generalized myotonia (Becker). The symptom of myotonia was present mainly in the legs, whereas transient weakness was the prominent symptom in the arms. Tocainide improved both symptoms, although it improved the stiffness more than the weakness. A specimen of intact muscle fibers was excised from the external intercostal muscle of one of the patients. The resting potential of the fibers was normal, but on injection of depolarizing current the fibers responded with repetitive action potentials. In normal interstitial fluid the current-voltage relationship was N-shaped, with a region of negative slope between -70 and -55 mV. Replacement of chloride by an impermeant anion changed this relationship very little, suggesting an abnormally small chloride conductance. The potassium current through the inward-going rectifier was larger than normal. The force of tetanic contractions of a rested bundle was not sustained but fell quickly to a plateau that increased with repeated stimulation. The relaxation of a rested tetanus was slow and accompanied by spontaneous electrical activity. In subsequent contractions the relaxation became faster and electrical after-activity decreased. However at 23 degrees C the speed of relaxation was always high despite a large amount of electrical after-activity. The electrical instability of the membrane and the transient weakness can be explained on the basis of the N-shaped membrane characteristic.

Action Potentials↗
PubMed1989

The in vitro determination of susceptibility to malignant hyperthermia.

To evaluate the reliability of the in vitro contracture test for susceptibility to malignant hyperthermia, we studied muscles from normal pigs and those susceptible to malignant hyperthermia. We performed the contracture test with various muscles from the same animal. Trapezius and intercostal muscles gave similar results, whereas the extensor digiti II muscle had lower sensitivities to both caffeine and halothane. Thus, the muscle chosen to determine susceptibility to malignant hyperthermia is important. In several animals, a false negative diagnosis would have resulted if only the distal muscle had been studied, and this was true even if weak contractures (less than 200 mg) were considered significant. In addition, we compared the response to caffeine or halothane of cut and intact muscle fibers. Although the cut fibers were depolarized, the sensitivity to these drugs was unchanged. Hence, results of the in vitro contracture test are independent of the resting membrane potential.

Animals↗
PubMed1991

Ca-, Sr-tension relationships and contraction velocities of human muscle fibers.

Muscle fibers from the lateral gastrocnemius or intercostal muscles of 7 normal adult males were chemically skinned (sarcolemma disrupted) and isolated fibers were divided into two parts for histochemical determination of fiber type and physiologic studies. The Ca- and Sr-induced tension relationships and maximum contraction velocities were measured. Slow twitch fibers developed tension at lower concentrations of Ca or Sr than fast twitch fibers. The difference between fast and slow twitch fibers was greatest when Sr was the activating cation. Fast and slow twitch fibers was greatest when Sr was the activating cation. Fast and slow twitch fibers generated similar maximum tensions. The contraction velocities of fast twitch fibers were more than two-fold greater than slow twitch fibers. Fast-oxidative-glycolytic (FOG, type IIA) and fast-glycolytic (FG, type IIB) fibers had similar Ca- and Sr-tension relationships and contraction velocities.

Adult↗
PubMed1991

Effect of resistive loads on pattern of respiratory muscle recruitment during exercise.

In healthy subjects, we compared the effects of an expiratory (ERL) and an inspiratory (IRL) resistive load (6 cmH2O.l-1.s) with no added resistive load on the pattern of respiratory muscle recruitment during exercise. Fifteen male subjects performed three exercise tests at 40% of maximum O2 uptake: 1) with no-added-resistive load (control), 2) with ERL, and 3) with IRL. In all subjects, we measured breathing pattern and mouth occlusion pressure (P0.1) from the 3rd min of exercise, in 10 subjects O2 uptake (VO2), CO2 output (VCO2), and respiratory exchange ratio (R), and in 5 subjects we measured gastric (Pga), pleural (Ppl), and transdiaphragmatic (Pdi) pressures. Both ERL and IRL induced a high increase of P0.1 and a decrease of minute ventilation. ERL induced a prolongation of expiratory time with a reduction of inspiratory time (TI), mean expiratory flow, and ratio of inspiratory to total time of the respiratory cycle (TI/TT). IRL induced a prolongation of TI with a decrease of mean inspiratory flow and an increase of tidal volume and TI/TT. With ERL, in two subjects, Pga increased and Ppl decreased more during inspiration than during control suggesting that the diaphragm was the most active muscle. In one subject, the increases of Ppl and Pga were weak; thus Pdi increased very little. In the two other subjects, Ppl decreased more during inspiration but Pga also decreased, leading to a decrease of Pdi. This suggests a recruitment of abdominal muscles during expiration and of accessory and intercostal muscles during inspiration. With IRL, in all subjects, Ppl again decreased more, Pga began to decrease until 40% of TI and then increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1980

On some properties of a new steroid curare-like compound pipecurium bromide.

In experiments on cats it has been shown that 2 beta, 16 beta-bis (4'-dimethyl-1'-piperazino)-3 alpha, 17 beta-diacetoxy-5 alpha-androstane dibromide (pipecurium bromide, RGH-1106, Arduan), is a non-depolarizing muscular blocker. The order of myorelaxation evoked by this agent is characteristic: first the chewing and limb muscles, then abdominal muscles and diaphragm and at the end intercostal muscles are relaxed. Pipercurium bromide has no cardiotropic, atropine-like, or ganglion-blocking activity. It fails to influence the coronary blood-supply or myocardial oxygen consumption. No acetylcholinesterase inhibiting action of the compound was seen. It does not affect the central nervous system.

Androstane-3,17-diol↗
PubMed1993

Radioautographic study on 3H-thymidine incorporation at different stages of muscle development in aging mice.

The DNA synthesis of mouse intercostal muscle from the 13th prenatal day through postnatal 24 months has been studied by light microscopic radioautography after the injection of 3H-thymidine. Chronological changes of labeling indices showed the highest value at E13, decreased gradually and reached almost 0% at 3 months after birth. We classified the embryonic muscle development into five stages, and the LI at stage I was the highest, the LI at stage II was significantly lower than that at stage I, the LI at stage IV was significantly higher than that at stage II, and the LI at stage V was significantly lower than that at stage IV. These changes accorded well with the primary and secondary myotube formation.

Aging↗
PubMed1980

Induction of fetal breathing by metabolic acidemia and its effect on blood flow to the respiratory muscles.

Sustained and vigorous fetal breathing activity was produced in a chronic fetal lamb preparation by infusion into the fetus of either NH4Cl or HCl. Over a 2 to 3 hour period, 20 to 25 mEq/kg were infused. All of the fetuses tolerated blood pH values of 6.7 to 6.8 and survived. The breathing activity began after the completion of the infusion, and consisted of regular 30 to 50 torr inspirations at a rate of 60 to 120 breaths/min. This activity was continuous for as much as 8 hours, and persisted with pauses and decreased amplitude for 24 to 36 hours. During fetal breathing, blood flow to the diaphragm and intercostal muscles increased approximately 12- and sixfold, respectively.

Ammonium Chloride↗
PubMed1994

Rib-muscle pedicle flap for the repair of congenital tracheal stenosis.

Congenital tracheal stenosis (CTS) is an uncommon congenital anomaly that presents early in life with symptoms of biphasic stridor. Most cases require surgical correction. Techniques have included dilation, resection of the involved segment, and tracheoplasty. Today pericardium and costal cartilage are the most frequently used materials for tracheoplasty, but patients still often encounter problems with the graft, with the procedure, or with late complications. This preliminary study was undertaken to determine the feasibility of a rib-intercostal muscle pedicle flap for the treatment of CTS. Tracheoplasties were performed on seven 3.5- to 5.5-kg piglets with a pedicled segment of the right fourth rib via a lateral thoracotomy incision. The method was found to be technically feasible, and pedicles of greater than 2.5 cm were easily developed. The repair provided good structural support and an airtight seal at high ventilator pressures. Histologic examination after 2 weeks showed the flap to be incorporating into the native trachea and to be without degenerative changes. This "vital" composite flap has several real and theoretic advantages over current methods of repair and may prove to be valuable in the treatment of CTS. The clinical application of this myo-osseous pedicle graft in the treatment of patients with stenoses not amenable to surgical resection and primary anastomosis should be explored.

Animals↗