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PubMed1987

Voluntary hyperventilation changes recruitment order of parasternal intercostal motor units.

The order of recruitment of single-motor units in parasternal intercostal muscles during inspiration was studied in normal human subjects during quiet breathing and voluntary hyperventilation. Electromyograms were recorded from the second and third intercostal spaces by means of bipolar fine wire electrodes. Flow at the mouth, volume, end-expired CO2, and rib cage and abdominal anterior-posterior diameters were monitored. Single-motor units were identified using criteria of amplitude and shape, and the time of first appearance of each unit in each inspiration was noted. Hyperventilation was performed with visual feedback of the display of rib cage and abdomen excursions, keeping the ratio of rib cage to abdominal expansion. Subjects were normocapnic in quiet breathing and developed hypocapnia during hyperventilation. Recruitment order was stable in quiet breathing, but in some cases was altered during voluntary hyperventilation. Some low threshold units that fired early in the breath in quiet breathing fired earlier at the beginning of a period of voluntary hyperventilation but progressively later in the breath as hyperventilation went on, whereas later firing units moved progressively toward the early part of inspiration. This suggests that different groups of motoneurons in the pool supplying parasternal intercostal muscles receive different patterns of synaptic input.

Action Potentials↗

PubMed1996

Rib motion modulates inspiratory intercostal activity in dogs.

1. A test was performed of the hypothesis that the motion of the ribs during inspiration modulates, via changes in spindle afferent activity, the activation of the inspiratory intercostal muscles. The electrical activity of the parasternal intercostal, external intercostal, and levator costae muscles in anaesthetized spontaneously breathing dogs was thus recorded during manipulation of the inspiratory displacement of the ribs over a wide range of rib motion. 2. In agreement with the hypothesis, the external intercostal and levator costae muscles lengthened and showed increased inspiratory activities when the normal inspiratory cranial motion of the lower rib was reduced or reversed into an inspiratory caudal motion. Conversely, the inspiratory activities decreased when the inspiratory cranial motion of the rib and the inspiratory shortening of the muscles was augmented. The inspiratory activity of the parasternal intercostal remained unchanged throughout. 3. However, when the two ribs making up the interspace were linked together so that the external intercostal muscle was constant in length, the relationship of muscle activity to rib motion was maintained. 4. In addition, when the upper rather than the lower rib of the interspace was manipulated, the relationship between the change in muscle length and inspiratory activity was reversed, so that activity decreased when the muscle was lengthened and increased when the muscle was shortened. The relationship of muscle activity to lower rib motion, however, was still maintained. 5. These observations thus indicate that rib motion triggers proprioceptive reflexes which, regardless of the changes in length of the individual muscles, make the external intercostal inspiratory activity exquisitely sensitive to the direction of rib displacement.

Animals↗

PubMed1997

Pulmonary afferents are not necessary for the reflex inhibition of human inspiratory muscles produced by airway occlusion.

In contrast to limb muscles, the usual response of human inspiratory muscles to sudden loading consists of an initial marked reduction of electromyographic activity (EMG) followed by a subsequent increase in EMG. To determine definitively whether pulmonary receptors are necessary for this short-latency reflex inhibition produced by airway occlusion, we studied five subjects with complete pulmonary denervation due to bilateral transplantation of the lungs and five matched control subjects. Subjects with pulmonary denervation were studied between 10 and 50 days after transplantation (median 21 days). Brief airway occlusion during inspiration (i.e., loading; duration 250 ms) produced short-latency reduction in EMG in the inspiratory muscles of all subjects with acute pulmonary denervation (scalenes and parasternal intercostal muscles; mean onset of inhibition 27 and 29 ms, respectively). The ongoing EMG was reduced by an average of 50% in scalenes and 36% in parasternal intercostal muscles. The size and the magnitude of the initial response did not differ significantly from those in control subjects. After the occlusion (i.e., unloading), activity of the inspiratory muscles was transiently reduced in control subjects and patients after bilateral lung transplantation. Given that the initial responses to airway loading and unloading were preserved after bilateral lung transplantation, we conclude that these reflex responses are not critically dependent on the discharge of intrapulmonary receptors. The results support the view that the short-latency inspiratory responses to loading and unloading can be mediated by inspiratory muscle afferents. They suggest a functionally different organization of the reflex pathways for inspiratory compared with limb muscles.

Adolescent↗

PubMed1969

The fine structure of motor endplate morphogenesis.

The fine structure of the developing neuromuscular junction of rat intercostal muscle has been studied from 16 days in utero to 10 days postpartum. At 16 days, neuromuscular relations consist of close membrane apposition between clusters of axons and groups of myotubes. Focal electron-opaque membrane specializations more intimately connect axon and myotube membranes to each other. What relation these focal contacts bear to future motor endplates is undetermined. The presence of a group of axons lying within a depression in a myotube wall and local thickening of myotube membranes with some overlying basal lamina indicates primitive motor endplate differentiation. At 18 days, large myotubes surrounded by new generations of small muscle cells occur in groups. Clusters of terminal axon sprouts mutually innervate large myotubes and adjacent small muscle cells within the groups. Nerve is separated from muscle plasma membranes by synaptic gaps partially filled by basal lamina. The plasma membranes of large myotubes, where innervated, simulate postsynaptic membranes. At birth, intercostal muscle is composed of separate myofibers. Soleplate nuclei arise coincident with the peripheral migration of myofiber nuclei. A possible source of soleplate nuclei from lateral fusion of small cells' neighboring areas of innervation is suspected but not proven. Adjacent large and small myofibers are mutually innervated by terminal axon networks contained within single Schwann cells. Primary and secondary synaptic clefts are rudimentary. By 10 days, some differentiating motor endplates simulate endplates of mature muscle. Processes of Schwann cells cover primary synaptic clefts. Axon sprouts lie within the primary clefts and are separated from each other. Specific neural control over individual myofibers may occur after neural processes are segregated in this manner.

Animals↗

PubMed1987

Activity of lower intercostal and abdominal muscle after upper abdominal surgery.

The decrease in end-expiratory lung volume after upper abdominal surgery has been attributed, in part, to reflex spasm of the abdominal muscles. To examine the influence of abdominal surgery on abdominal muscle tone, electromyographic (EMG) activity of abdominal and lower intercostal muscle was compared before operation with that at 3 hr and at 24 hr after operation in 18 healthy patients undergoing elective gastric or biliary surgery. After operation, EMG activity increased markedly and showed a phasic pattern of activity associated with respiration in most patients. This was characterized by a progressive increase in EMG activity during expiration with an abrupt decrease at the onset of inspiration. We conclude that increased expiratory activity in abdominal and lower intercostal muscle may be responsible for the decrease in lung volumes that occurs after upper abdominal surgery.

Abdomen↗

PubMed2003

Reproducibility and responsiveness of a noninvasive EMG technique of the respiratory muscles in COPD patients and in healthy subjects.

In the present study, we assessed the reproducibility and responsiveness of transcutaneous electromyography (EMG) of the respiratory muscles in patients with chronic obstructive pulmonary disease (COPD) and healthy subjects during breathing against an inspiratory load. In seven healthy subjects and seven COPD patients, EMG signals of the frontal and dorsal diaphragm, intercostal muscles, abdominal muscles, and scalene muscles were derived on 2 different days, both during breathing at rest and during breathing through an inspiratory threshold device of 7, 14, and 21 cm H2O. For analysis, we used the logarithm of the ratio of the inspiratory activity during the subsequent loads and the activity at baseline [log EMG activity ratio (EMGAR)]. Reproducibility of the EMG was assessed by comparing the log EMGAR values measured at test days 1 and 2 in both groups. Responsiveness (sensitivity to change) of the EMG was assessed by comparing the log EMGAR values of the COPD patients to those of the healthy subjects at each load. During days 1 and 2, log EMGAR values of the diaphragm and the intercostal muscles correlated significantly. For the scalene muscles, significant correlations were found for the COPD patients. Although inspiratory muscle activity increased significantly during the subsequent loads in all participants, the COPD patients displayed a significantly greater increase in intercostal and left scalene muscle activity compared with the healthy subjects. In conclusion, the present study showed that the EMG technique is a reproducible and sensitive technique to assess breathing patterns in COPD patients and healthy subjects.

Aged↗

PubMed2002

On the respiratory function of the ribs.

To assess the respiratory function of the ribs, we measured the changes in airway opening pressure (Pao) induced by stimulation of the parasternal and external intercostal muscles in anesthetized dogs, first before and then after the bony ribs were removed from both sides of the chest. Stimulating either set of muscles with the rib cage intact elicited a fall in Pao in all animals. After removal of the ribs, however, the fall in Pao produced by the parasternal intercostals was reduced by 60% and the fall produced by the external intercostals was eliminated. The normal outward curvature of the rib cage was also abolished in this condition, and when the curvature was restored by a small inflation, external intercostal stimulation consistently elicited a rise rather than a fall in Pao. These findings thus confirm that the ribs play a critical role in the act of breathing by converting intercostal muscle shortening into lung volume expansion. In addition, they carry the compression that is required to balance the pressure difference across the chest wall.

Animals↗

PubMed1987

Blood flow in respiratory muscles during maximal exertion in ponies with laryngeal hemiplegia.

Laryngeal hemiplegia increases the respiratory effort required during exercise. By use of 15-micron-diam radionuclide-labeled microspheres, respiratory muscle blood flows were studied at rest, submaximal exercise (SE), maximal exercise (ME), and ME + adenosine (3 mumol X kg-1 X min-1) in nine healthy laryngeal hemiplegic (LH) ponies to ascertain whether vasodilator reserve in these tissues may be exhausted during SE, which caused maximal respiratory frequency (f) to be reached. Blood flows were also studied in the limb muscles, and data were compared with normal ponies (M. Manohar, J. Appl. Physiol. 60: 1571-1577, 1986). The heart rate, f, and change in pleural pressure in LH ponies during SE were 205 +/- 5 beats/min, 91 +/- 10 breaths/min, and 61.2 +/- 8.7 cmH2O. Corresponding values for ME were 223 +/- 2 beats/min, 90 +/- 7 breaths/min, and 75.1 +/- 5.2 cmH2O. The treadmill speed for SE was set at 75% of that for ME. Mean aortic pressure (161 +/- 9 mmHg), diaphragmatic (206 +/- 27 ml X min-1 X 100 g-1), and intercostal muscle (124 +/- 12 ml X min-1 X 100 g-1) blood flows in LH ponies increased markedly with SE and these values were not different from ME (170 +/- 5 mmHg, 293 +/- 40 ml X min-1 X 100 g-1, 167 +/- 15 ml X min-1 X 100 g-1, respectively). This suggested that maximal vasodilation in the respiratory muscles was achieved during SE. Vascular resistance in the diaphragm and intercostal muscles of LH ponies also remained similar for SE, ME, and ME + adenosine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗

PubMed1961

Observations on the fine structure and cytochemistry of mouse and human intercostal neuromuscular junctions.

The fine structure of the mouse and human intercostal muscle neuromuscular junction was studied after brief fixation in a new formol-sucrose fixative. This primary formalin fixation was followed by brief postosmication in buffered 1 per cent osmium tetroxide. Muscle blocks were embedded in methacrylate or Epon 812 epoxy resin. Marked similarities between mouse and human motor end-plates were observed. Neuromuscular junctions from both mouse and human intercostal muscle showed synaptic vesicles, primary and secondary synaptic clefts, and layered differentiation of the amorphous surface material (ASM) present on the surface of the Schwann cell plasma membrane and on the muscle surface membrane in the region of the neuromuscular junction. An attempt to stain the ASM with lead was unsuccessful. Observations on thick and thin plastic-embedded sections stained by PAS after diastase digestion showed that the ASM within the subneural apparatus is PAS positive. Alcian blue stained the endoneurium and perineurium of peripheral nerve bundles and portions of the end-plates. The similarity of the PAS-positive ASM to other basement membranes described in other sites is discussed and its possible physiologic significance within the subsynaptic apparatus is considered.

Animals↗

PubMed1993

[An operative case of empyema necessitatis].

A case of empyema necessitatis presenting a mass in the retroperitoneal space is reported. Computer tomography preoperatively revealed the transdiaphragmatic abscess with calcified capsule. The operation was performed by means of resection of the abscess together with overlying ribs. Dead space after resection of the lesion was filled up with intercostal muscles. Empyema necessitatis is rare after introduction of antituberculous drugs. However, recognition of this disease is necessary for an appropriate surgical management. Total resection of the abscess followed by filling of the dead space with the intercostal muscles should be considered as a useful alternative method.

Aged↗

PubMed1982

Sodium currents in human skeletal muscle fibers.

Sodium currents from human external intercostal muscle fibers were recorded using the Hille-Campbell voltage clamp method. Sodium currents are analyzed in terms of the m and h parameters of the Hodgkin-Huxley model. The results indicate that the kinetics and voltage dependence of sodium currents in human skeletal muscle fibers are very similar to those reported in rat fibers.

Humans↗

PubMed1988

Changes in intracellular ion activities induced by adrenaline in human and rat skeletal muscle.

To study the stimulating effect of adrenaline (ADR) on active Na+/K+ transport we used double-barrelled ion-sensitive micro-electrodes to measure the activities of extracellular K+ (aKe) and intracellular Na+ (aNai) in isolated preparations of rat soleus muscle, normal human intercostal muscle and in one case of hyperkalemic periodic paralysis (h.p.p.). In these preparations, bath-application of ADR (10(-6) M) resulted in a membrane hyperpolarization and transient decreases aKe and aNai which could be blocked by ouabain (3 x 10(-4) M). In the h.p.p. muscle a continuous rise of aNai induced by elevation of aKe to 5.2 mM could be stopped by ADR. In addition, the intracellular K+ activity (aKi), the free intracellular Ca2+ concentration (pCai) and intracellular pH (pHi) were monitored in rat soleus muscle. During ADR aKi increased, pHi remained constant and intracellular Ca2+ apparently decreased. In conclusion, our data show that ADR primarily stimulates the Na+/K+ pump in mammalian skeletal muscle. This stimulating action is not impaired in the h.p.p. muscle.

Animals↗

PubMed1990

Phrenic afferents and ventilatory control.

It has been understood since the late 1800s that the diaphragm has significant sensory innervation. The role of phrenic afferents in the control of breathing, however, has been obscure. The phrenic nerve has been shown to contain a full array of afferent fibers. However, proprioceptive (group 1 fibers) afferents are few compared to postural muscles or the intercostals. The diaphragm, unlike the inspiratory intercostal muscles, has a small complement of spindle afferents and not all of these spindles are supplied with fusorial fibers. Reduced spindle afferents under gamma control help to explain previous studies of the diaphragm that have failed to reveal autogenic facilitation, that is, a reflex-mediated increase in drive during inspiratory loading. Nevertheless, some clinical studies have revealed increased activation of the diaphragm when its length is reduced. Group 1 fibers, which are predominantly tendon organ afferents in the diaphragm, have been shown to have a phasic inhibitory function. A reduction in this inhibition brought about by a reduction in diaphragmatic length during lung inflation may explain the increased diaphragmatic activation reported in clinical studies. Phrenic afferents have been shown to have multiple spinal and supraspinal projections. Recent studies have explored the ventilatory effects of thin fiber afferents (group III and IV fibers) in the phrenic nerve. Stimulation of these afferents has been shown both to inhibit and excite ventilation. These afferents arise from polymodal receptors that respond to both mechanical and chemical stimulation. Activation of these receptors may occur in a variety of conditions and the ventilatory response may be determined by the specific receptor activated.

Animals↗

PubMed2000

Pitfalls of intramuscular electromyographic recordings from the human costal diaphragm.

OBJECTIVE: Techniques for intramuscular recordings from the costal diaphragm have been described. This report describes procedures to assist with precise placement of these electrodes using ultrasound imaging and describes several sources of error that must be excluded when interpreting recordings made with intramuscular electrodes. METHODS: Fine-wire electrodes were inserted into the left costal diaphragm under the guidance of ultrasound imaging in 17 healthy volunteers. Various respiratory maneuvers were performed to confirm the accuracy of the electromyographic (EMG) recordings and the electrode placement was confirmed with intercostal nerve blocks in one subject. RESULTS: EMG recordings can be made from the costal diaphragm. However, despite precise electrode placement and use of intramuscular electrodes with small receptive areas, the EMG recording could be contaminated by cross-talk (discrete motor unit activity) from the adjacent internal intercostal muscle and from movement of the electrode relative to the muscle fibers during breathing. Furthermore, it is necessary to distinguish between expiratory intercostal muscle activity and units in the diaphragm that discharge tonically throughout expiration. CONCLUSIONS: While ultrasound guidance of intramuscular electrode insertion can assist with accurate electrode placement in the diaphragm, confirmation of the stability of the recording and absence of cross-talk is critical to avoid misinterpretation of diaphragm function.

Diaphragm↗

PubMed2003

Myasthenic syndrome caused by mutation of the SCN4A sodium channel.

In a myasthenic syndrome associated with fatigable generalized weakness and recurrent attacks of respiratory and bulbar paralysis since birth, nerve stimulation at physiologic rates rapidly decremented the compound muscle action potential. Intercostal muscle studies revealed no abnormality of the resting membrane potential, evoked quantal release, synaptic potentials, acetylcholine receptor channel kinetics, or endplate ultrastructure, but endplate potentials depolarizing the resting potential to -40 mV failed to excite action potentials. Pursuing this clue, we sequenced SCN4A encoding the skeletal muscle sodium channel (Nav1.4) and detected two heteroallelic mutations involving conserved residues not present in 400 normal alleles: S246L in the S4/S5 cytoplasmic linker in domain I, and V1442E in the S3/S4 extracellular linker in domain IV. The genetically engineered V1442E-Na channel expressed in HEK cells shows marked enhancement of fast inactivation close to the resting potential, and enhanced use-dependent inactivation on high-frequency stimulation; S246L is likely a benign polymorphism. The V1442E mutation in SCN4A defines a novel disease mechanism and a novel phenotype with myasthenic features.

Adult↗

PubMed1981

Dependence of membrane potential on extracellular ionic concentrations in myotonic goats and rats.

Intracellular potassium concentration([K]i) and the resting sodium-to-potassium permeability ratio (alpha = PNa/PK) were determined by recording resting potentials at 25 degrees C in six solutions with variable potassium concentrations, constant [K+] + [Na+], and constant [K+] X [Cl-] product and fitting the results by nonlinear least squares to the Goldman-Hodgkin-Katz equation. Fits to models including chloride permeability terms suggest that chloride is in Donnan equilibrium in the muscles studied. External intercostal muscle was biopsied from anesthetized normal goats and goats with hereditary myotonia. In normal goat muscle, alpha was 0.012 +/- 0.001 (mean +/- SE, n = 11), and [K]i was 133 +/- 6 mM (n = 9); myotonic goat muscle did not differ from this. Extensor digitorum longus (EDL) muscle was removed from anesthetized male Wistar rats and from like rats pretreated with a single large dose of 20,25-diazacholesterol (DAC). In normal rat EDL, alpha was 0.019 +/- 0.002 (n = 12), and [K]i was 142 +/- 4 mM (n = 12). In the 16-day DAC-treated rats, alpha was significantly reduced (P < 0.002) to 0.010 +/- 0.002 (n = 8), and [K]i was slightly reduced by DAC. It is concluded that DAC reduced PNa in rat fibers. Tetrodotoxin at 5 microM did not affect either parameter in the rats.

Animals↗

PubMed1994

[Surgery of bilateral pulmonary aspergilloma].

A 60-year-old man with cough and fever was admitted to our hospital. Chest radiography revealed multiple bullae and fungus balls in both lungs. He was treated with MCZ and FCZ for about 2 months, but the chest radiograph shadows did not improve and the fever continued. A two-stage operation was performed. The bullae were incised and the fungus balls were removed, then a muscle flap plombage was made with a pectoralis major muscle, a latissimus dorsi muscle and an intercostal muscle. The postoperative course was uneventful and respiratory function was preserved.

Aspergillosis↗

PubMed1993

[Propriospinal myoclonus--a case report].

Propriospinal myoclonus is one type of myoclonus that is proposed to originate in the spinal cord and spread up and down via propriospinal tract. There are a few reports describing the detailed electrophysiological findings of this myoclonus. In this communication, we present the results of electrophysiological analysis of a patient with propriospinal myoclonus. A 23-year-old woman suddenly noticed abdominal pain, which spontaneously faded in a few hours. Irregular involuntary flexion jerks of the trunk appeared spontaneously without pain or hiccups after this episode. It involved the bilateral axial muscles; sternocleidomastoid muscles (SCM), paravertebral muscles (PVM), abdominal muscles (ABD), and intercostal muscles (ICM), but not the limb muscles. It was worsened by the mental stress, but not by her posture or position. While she slept, the jerks were not observed. Routine laboratory examinations were all normal. Magnetic resonance imaging of the spinal cord revealed no abnormalities. The electrophysiological studies done on this patient are polymyography, back-averaging of the EEG activity preceding spontaneous jerks (jerk-locked averaging (JLA), and movement related cerebral potential (MRCP) preceding the involuntary jerks and voluntary abdominal movements. No EEG activities preceding the myoclonus were demonstrated by JLA or MRCP. No MRCP recorded preceding the myoclonus suggests that the jerk is not a self-initiated or externally triggered voluntary movement. Polymyography revealed that the jerks involved the bilateral axial muscles including SCM, PVM, ICM, and ABD, but not the limb muscles. Homologous muscles were activated synchronously. The duration of EMG bursts was variable ranging 50 to 250 ms in these muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗