Postnatal changes in vagal control of esophageal muscle contractions in rats

AimsReplacement of smooth muscles by striated muscles occurs in the esophagus during the early postnatal period. The aim of this study was to clarify postnatal changes in vagal control of esophageal muscle contractions in rats.Main methodsAn isolated segment of the neonatal rat esophagus was placed in an organ bath and the contractile responses were recorded using a force transducer.Key findingsElectrical stimulation of the vagus trunk evoked a biphasic contractile response in the neonatal esophageal segment. The first and second components of the contractions were inhibited by α-bungarotoxin and atropine, respectively. Ganglion blockers, hexamethonium and mecamylamine, did not affect vagally mediated contractions. The first component gradually enlarged with age in days, whereas the second component declined during the first week after birth. Application of d-tubocurarine or acetylcholine caused an apparent contraction in the esophageal striated muscle at postnatal day 0, but responses to these drugs were not observed at 1 week after birth. The neonatal esophagus expressed the γ-subunit of nicotinic acetylcholine receptors. In contrast, the ε-subunit was dominantly expressed in the adult esophagus.SignificanceThe vagus nerves directly innervate both the esophageal striated muscles and smooth muscles in the early neonatal period. During the process of muscle rearrangement, the property of the striated muscles is altered substantially. The specific features of striated muscles in the neonatal rat esophagus might compensate for immature formation of neuromuscular junctions. Unsuccessful conversion of the striated muscle property during postnatal muscle rearrangement would be related to disorders of esophageal motility.     

Morphohistochemical characteristics of structures of the esophageal cross-striated muscle tissue]

On the bases of histochemical enzymatic studies and morphometric investigations, some differences were revealed between cross-striated esophageal muscular tissue and other skeletal muscles of mammals. A peculiar feature of the esophageal musculature is prevalence of unitypical fibres with small diameter and possessing high activity of oxidating enzymes. According to these signs, esophageal myons can be ascribed to the first type of muscular fibres. Simultaneously, a high activity of myofibrillar ATPh is revealed in them. Thus, according to histochemical indices, cross-striated esophageal muscular fibres of mammals are quick and slowly fatiqued fibres.     

Electric activity of striated muscles of the cervical part of the rabbit esophagus under conditions of hunger, food intake and satiation

The experiments of free-moving rabbits have shown that the muscles of the proximal zone in the esophageal cervical part functions as the superior esophageal sphincter. In hunger stage the motor unit activity of the sphincter has regular low-amplitude discharge with monomodal distribution of interspike intervals. The process of food satisfaction leads to the appearance of burst-like unit activity with bimodal distribution of interspike intervals. During the food intake reorganization of the motor unit activity of the esophageal cervical part is manifested in characteristic patterns of interspike interval distribution.     

The role of the frontal ganglion in foregut movements of the moth,Manduca sexta

Two types of rhythmic foregut movements are described in fifth instar larvae of the moth, Manduca sexta. These consist of posteriorly-directed waves of peristalsis which move food toward the midgut, and synchronous constrictions of the esophageal region, which appear to retain food within the crop. We describe these movements and the muscles of the foregut that generate them.The firing patterns of a subset of these muscles, including a constrictor and dilator pair from both the esophageal and buccal regions of the foregut, are described for both types of foregut movement.The motor patterns for the foregut muscles require innervation by the frontal ganglion (FG), which lies anterior to the brain and contains about 35 neurons. Eliminating the ventral nerve cord, leaving the brain and FG intact, did not affect the muscle firing patterns in most cases. Eliminating both the brain and the ventral nerve cord, leaving only the FG to innervate the foregut, generally resulted in an increased period for both gut movements and muscle bursts. This manipulation also produced increases in burst durations for most muscles, and had variable effects on the phasing of muscle activity. Despite these changes, the foregut muscles still maintained a rhythmic firing pattern when innervated by the FG alone.Two nerves exit the FG to innervate the foregut musculature: the anteriorly-projecting frontal nerve, and the posteriorly-directed recurrent nerve. Cutting the frontal nerve immediately and irreversibly stopped all muscle activity in the buccal region, while cutting the recurrent nerve immediately stopped all muscle activity in the pharyngeal and esophageal regions. Recordings from the cut nerves leaving the FG showed that the ganglion was spontaneously active, with rhythmic activity continuing within the nerves. These observations indicate that all of the foregut muscle motoneurons are located within the FG, and the FG in isolation produces a rhythmic firing pattern in the motoneurons. We have identified several motoneurons within the FG, by cobalt backfills and/or simultaneous intracellular recordings and fills from putative motoneurons and their muscles.Abbreviations BC Buccal Constrictor - BC1 buccal constrictor motoneuron 1 - BC2 buccal constrictor motoneuron 2 - BD Buccal Dilator - BD1 buccal dilator motoneuron 1 - EC Esophageal Dilator - EC1 esophageal dilator motoneuron 1 - EC2 esophageal dilator motoneuron 2 - EC3 esophageal dilator motoneuron 3 - ejp excitatory junction potential - FG frontal ganglion - psp postsynaptic potential     

Method of simultaneous registration of transpulmonary pressure and the electromyogram of the diaphragm

Standard esophageal ballon with silver electrodes implanted in it is suggested for simultaneous registration of the hysteresis loop and electromyogram of the diaphragm. The method provides qualitatively new information on the work of the respiratory muscles.     

Activity of respiratory muscles in upright and recumbent humans

It is established that during tidal breathing the rib cage expands more than the abdomen in the upright posture, whereas the reverse is usually true in the supine posture. To explore the reasons for this, we studied nine normal subjects in the supine, standing, and sitting postures, measuring thoracoabdominal movement with magnetometers and respiratory muscle activity via integrated electromyograms. In eight of the subjects, gastric and esophageal pressures and diaphragmatic electromyograms via esophageal electrodes were also measured. In the upright postures, there was generally more phasic and tonic activity in the scalene, sternocleidomastoid, and parasternal intercostal muscles. The diaphragm showed more phasic (but not more tonic) activity in the upright postures, and the abdominal oblique muscle showed more tonic (but not phasic) activity in the standing posture. Relative to the esophageal pressure change with inspiration, the inspiratory gastric pressure change was greater in the upright than in the supine posture. We conclude that the increased rib cage motion characteristic of the upright posture owes to a combination of increased activation of rib cage inspiratory muscles plus greater activation of the diaphragm that, together with a stiffened abdomen, acts to move the rib cage more effectively.     

Normal contractile algorithm of swallowing related muscles revealed by needle EMG and its comparison to videofluoroscopic swallowing study and high resolution manometry studies: A preliminary study

The purpose of this study was to investigate the function and importance of infrahyoid muscles with the suprahyoid muscles during swallowing, and to investigate swallowing sequences using kinematic analysis, high-resolution manometry (HRM) and electromyography (EMG). As a preliminary study, ten healthy subjects were prospectively enrolled. A needle EMG evaluated the onset latency, peak latency and duration of the suprahyoid and infrahyoid muscles. HRM measured the time intervals among the velopharynx, tongue base, and upper esophageal sphincter. We also evaluated hyoid motion using an automated kinematic analysis software® (AKAS). All of these parameters were synchronized with a tilting motion of the epiglottis. In the EMG analysis, the activations of the suprahyoid muscles developed about 300 ms earlier than that of the infrahyoid muscles. There was a significant relationship between the differences of suprahyoid and infrahyoid muscles’ latency and total duration of the hyoid motion (p < 0.05). The interval time of anterior hyoid motion has a significant correlation in the upper esophageal sphincter (UES) opening time. In conclusions, the functions of the infrahyoid muscles are also as important as that of the suprahyoid muscles for prolonged laryngeal elevation and UES opening. Moreover, kinematic analysis of videofluoroscopic swallowing study (VFSS) and HRM studies could reflect results of needle EMG study and replace EMG study.     

Anatomy of the extrinsic gut musculature of Gammarus minus (Crustacea: Amphipoda)

Inserting on the buccal and esophageal foregut of Gammarus minus are numerous pairs of serially arranged dorsal dilator muscles, a single pair of lateral muscles, and two pairs of posterior muscles. Muscles of the cardiac stomach include three dorsal sets, a single pair associated with the pterocardiac ossicles, and two pairs inserting on the ventral aspect. A single pair of muscles inserts on the lateral aspect of the pyloric stomach. The extrinsic muscles of the foregut originate from exoskeletal apodemes of the cephalothoracic cuticle, sockets of the mandible, and a maxillary bridge that lies just ventral to the cardiac stomach. The extrinsic musculature of the hindgut is restricted to the rectal region and consists of paired dorsal and ventral series in an X-configuration. A single unpaired muscle inserts on the ventral midline. Extrinsic muscles of the hindgut originate from the integument of the last pleonic segment. The general arrangement of extrinsic gut muscles in G. minus is similar but not identical to that of other amphipods studied. However, the pattern is quite different from that of other malacostracans.     

Preferential fatigue of the rib cage muscles during inspiratory resistive loaded ventilation

Because the inspiratory rib cage muscles are recruited during inspiratory resistive loaded breathing, we hypothesized that such loading would preferentially fatigue the rib cage muscles. We measured the pressure developed by the inspiratory rib cage muscles during maximal static inspiratory maneuvers (Pinsp) and the pressure developed by the diaphragm during maximal static open-glottis expulsive maneuvers (Pdimax) in four human subjects, both before and after fatigue induced by an inspiratory resistive loaded breathing task. Tasks consisted of maintaining a target esophageal pressure, breathing frequency, and duty cycle for 3-5 min, after which the subjects maintained the highest esophageal pressure possible for an additional 5 min. After loading, Pinsp decreased in all subjects [control, -128 +/- 14 (SD) cmH2O; with fatigue, -102 +/- 18 cmH2O; P less than 0.001, paired t test]. Pdimax was unchanged (control, -192 +/- 23 cmH2O; fatigue, -195 +/- 27 cmH2O). These data suggest that 1) inability to sustain the target during loading resulted from fatigue of the inspiratory rib cage muscles, not diaphragm, and 2) simultaneous measurement of Pinsp and Pdimax may be useful in partitioning muscle fatigue into rib cage and diaphragmatic components.     

Neuroanatomy of the sucking pump of the moth, Manduca sexta (Sphingidae, Lepidoptera)

Knowledge of the neuroanatomy of the sucking pump of Manduca sexta (Sphingidae) is valuable for studies of olfactory learning, pattern generators, and postembryonic modification of motor circuitry. The pump comprises a cibarial valve, a buccal pump, and an esophageal sphincter valve. Cibarial opener and closer muscles control the cibarial valve. Six pairs of dilator muscles and a compressor muscle operate the buccal pump. The cibarial opener and one pair of buccal dilator muscles are innervated by paired neurons in the tritocerebrum, and the cibarial opener has double, bilateral innervation. Their tritocerebral innervation indicates that these muscles evolved from labro-clypeal muscles. The remaining paired buccal dilator muscles each are innervated by an unpaired motor neuron in the frontal ganglion. These motor neurons project bilaterally through the frontal connectives to dendritic arborizations in the tritocerebrum. These projections also have a series of dendritic-like arborizations in the connectives. The cibarial closer and buccal compressor muscles are also innervated by motor neurons in the frontal ganglion, but only the closer muscle neuron projects bilaterally to the tritocerebrum. The innervation of the pump muscles indicates that they are associated with the stomodaeum, and, therefore, the buccal pump evolved from the anterior stomodaeum rather than from the cibarium.     

Pharynx, esophagus, and associated structures in the booklouse, Liposcelis divinatorius

Abstract. Ultrastructural features of the pharynx, esophagus, and associated intrinsic visceral muscular and nervous structures of the booklouse, Liposcelis divinatorius , were studied to determine whether the anatomical arrangements of these structures differed from the general pattern found in insects. The results are compared with previous light microscope studies of this tiny insect. Variations from the usual arrangement reported for intrinsic visceral muscles associated with the pharynx in insects are described. Intrinsic visceral muscles include a narrow band of circularly disposed fibers and both extra-circular and intra-circular longitudinally disposed fibers. This represents a departure from the slightly developed inner longitudinal and more prominent outer circular fibers seen in most insects. The outer surface of some circular muscle cells has apparently unique pouches packed with mitochondria, which contain many cristae. Numerous bacteroids appear in the esophageal epithelial cells and in the sub-esophageal ganglion. Nerve processes associated with the foregut contain neurotubules, synaptic vesicles, and electron-dense granules.     

Mechanics of vomiting: a minireview

In a cineradiographic analysis of the vomiting reflex in response to i.v. administration of an emetic drug (lanatoside C, 12 mg/kg) in cats, it was shown that the vomiting act is preceded by cyclic periods of abnormal peristaltic activity of the small bowel and inhibition of gastric peristalsis. It was further observed that massive antiperistalsis of the upper small bowel with reflux into the stomach is a common occurrence in the period immediately preceding vomiting. The emetic act itself is composed of phases of esophageal dilation, gastric emptying, gastric reflux, and esophageal collapse in cyclic repetition. The response of the esophagus and the stomach during emesis is passive, with external pressures and forces apparently providing the expulsive forces, the gastric bolus being contained by contraction of the pylorus and probably an upper esophageal or pharyngeal barrier. Earlier studies were conducted in cats in which observations were made on changes in thoracic venous pressure, abdominal venous pressure, and arterial blood pressure associated with vomiting induced by Veratrum alkaloids. Retching was characterized by a growing series of brief negative intrathoracic pressure pulses mirrored by positive pressure pulses in the abdomen. Expulsion then occurred and was followed with a sudden reversal of intrathoracic pressure from negative to positive. Expulsion involved a more sustained abdominal contraction, but both retching and expulsion were brought about by the same set of muscles, according to their EMG profiles. From results observed following phrenicotomy and spinal cord section at T5, it was concluded that the diaphragm, acting together with the inspiratory muscles against a closed glotis is responsible for the negative intrathoracic pressure that occurs in retching.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intramuscular and esophageal electrode recordings of posterior cricoarytenoid activity in normal subjects

Six normal human subjects were studied to compare intramuscular and esophageal electrode recordings of posterior cricoarytenoid (PCA) muscle activity. A new electromyographic technique was developed to implant hooked wire electrodes into the PCA via a nasopharyngoscope. The esophageal electrode was similar to that used by other investigators to record PCA activity (P. C. Kosch et al. J. Appl. Physiol. 64: 1968-1978, 1988). Simultaneous recordings from the intramuscular and esophageal electrodes were obtained during wakefulness and sleep. Changes in esophageal electrode activity were compared with changes in intramuscular electrode activity under four conditions: 1) voluntary maneuvers, 2) differences in state, 3) nasal airway occlusion during non-rapid-eye-movement sleep, and 4) spontaneous variations in respiratory efforts during non-rapid-eye-movement or rapid-eye-movement sleep. Although similar results were obtained from the esophageal and intramuscular electrodes, differences were present between the two recordings during both wakefulness and sleep. The esophageal electrode recorded activity from surrounding muscles during voluntary maneuvers, vocalization, and quiet breathing in wakefulness. Discrepancies between the two electrode recordings during sleep occurred under conditions of increased and decreased respiratory motor output. The data suggest that the esophageal electrode may not give an accurate assessment of PCA activity during many conditions in wakefulness and sleep.     

Sternomastoid, rib cage, and expiratory muscle activity during weaning failure.

We hypothesized that patients who fail weaning from mechanical ventilation recruit their inspiratory rib cage muscles sooner than they recruit their expiratory muscles, and that rib cage muscle recruitment is accompanied by recruitment of sternomastoid muscles. Accordingly, we measured sternomastoid electrical activity and changes in esophageal (DeltaPes) and gastric pressure (DeltaPga) in 11 weaning-failure and 8 weaning-success patients. At the start of trial, failure patients exhibited a higher DeltaPga-to-DeltaPes ratio than did success patients (P = 0.05), whereas expiratory rise in Pga was equivalent in the two groups. Between the start and end of the trial, failure patients developed additional increases in DeltaPga-to-DeltaPes ratio (P < 0.0014) and the expiratory rise in Pga also increased (P < 0.004). At the start of trial, sternomastoid activity was present in 8 of 11 failure patients contrasted with 1 of 8 success patients. Over the course of the trial, sternomastoid activity increased by 53.0 +/- 9.3% in the failure patients (P = 0.0005), whereas it did not change in the success patients. Failure patients recruited their respiratory muscles in a sequential manner. The sequence began with activity of diaphragm and greater-than-normal activity of inspiratory rib cage muscles; recruitment of sternomastoids and rib cage muscles approached near maximum within 4 min of trial commencement; expiratory muscles were recruited slowest of all. In conclusion, not only is activity of the inspiratory rib cage muscles increased during a failed weaning trial, but respiratory centers also recruit sternomastoid and expiratory muscles. Extradiaphragmatic muscle recruitment may be a mechanism for offsetting the effects of increased load on a weak diaphragm.     

Differences in calmodulin and calmodulin-binding proteins in phasic and tonic smooth muscles

To determine whether densities ofcalmodulin (CaM) and CaM-binding proteins are related to phasic andtonic behavior of smooth muscles, we quantified these proteins in theopossum esophageal body (EB) and lower esophageal sphincter (LES),which represent phasic and tonic smooth muscles, respectively. Gelelectrophoresis, immunoprecipitation, Western blot, and hemagglutininepitope-tagged CaM (HA-CaM) overlay assay with quantitative scanningdensitometry and phosphorylation measurements were used. Total proteincontent in the two smooth muscles was similar (~30 mg protein/gfrozen tissue). Total tissue concentration of CaM was significantly(25%) higher in EB than in LES (P < 0.05).HA-CaM-binding proteins were qualitatively similar in LES and EBextracts. Myosin, myristoylated alanine-rich C kinase substrateprotein, Ca²⁺/CaM kinase II, and calponin contents werealso similar in the two muscles. However, content and total activity ofmyosin light chain kinase (MLCK) and content of caldesmon (CaD) werethree- to fourfold higher in EB than in LES. Increased CaM and MLCKcontent may allow for a wide range of contractile force varying fromcomplete relaxation in the basal state to a large-amplitude,high-velocity contraction in EB phasic muscle. Increased content ofCaD, which provides a braking mechanism on contraction, may furthercontribute to the phasic contractile behavior. In contrast, low CaM,MLCK, and CaD content may be responsible for a small range ofcontractile force seen in tonic muscle of LES.

     

Rib cage and abdominal expiratory muscle responses to CO2 and esophageal distension

The present study compared the responses of rib cage and abdominal expiratory muscles to chemical and mechanical stimuli. In pentobarbital-anesthetized spontaneously breathing dogs, electromyograms (EMG) were recorded from the triangularis sterni (TS) and transverse abdominis (TA) muscles using bipolar intramuscular wire electrodes. During resting oxygen breathing, both muscles were electrically active during expiration. Progressive hyperoxic hypercapnia significantly augmented the expiratory activity of both the TA and the TS. However, the mean percent increases in electrical activity in response to CO2 were substantially greater for the TA than for the TS at all PCO2 levels greater than 50 Torr (P less than 0.01). Occlusion of the airway at end inspiration significantly delayed the onset of TS EMG (from 0.35 +/- 0.07 to 3.35 +/- 0.67 sec; P less than 0.002) and decreased TS EMG rate of rise (P less than 0.002), but did not significantly alter these parameters for the TA. Esophageal distension increased TS EMG in all dogs (by mean of 220 +/- 64%; P less than 0.01), but in contrast decreased TA EMG in all dogs (by a mean of 63 +/- 12%; P less than 0.001). The response to esophageal distention occurred in a graded manner and appeared to be mediated predominantly via vagal afferents. We concluded that expiratory muscles of the rib cage and abdomen manifest substantial differences in their electrical responses to chemoreceptor, pulmonary stretch receptor, and esophageal mechanoreceptor stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)     

金丝猴食管和胃连接部的组织学研究

本文研究了金丝猴食管和胃连接处的组织结构。金丝猴的食管粘膜为典型的复民鳞状上皮,食管末端含有粘膜腺,粘膜表面有轻微的角质化。管壁外纵肌层有少量的横纹肌。与胃粘膜的连接均位于胃的贲门部以内,两种上皮的连接是突然的,不存在过渡。 贲门腺为少量的分枝管状腺,短而直,由粘膜细胞构成,对PAS染色呈阳性反应。     

Mandible position and activation of submental and masseter muscles during sleep.

Movement of the mandible could influence pharyngeal airway caliber because the mandible is attached to the tongue and to muscles that insert on the hyoid bone. In normal subjects and patients with obstructive sleep apnea (OSA) we measured jaw position during sleep with strain gauges, as well as masseter and submental electromyograms, airflow, esophageal pressure, oximetry, electroencephalograms, and electrooculograms. Jaws of patients with OSA were open more than those of normal subjects at end expiration and opened further at end inspiration, particularly at the termination of apneas when the masseter and submental muscles contracted. Masseter activation occurred only in patients with OSA and in a pattern similar to that of submental muscles. Jaw opening at end expiration could narrow the upper airway, whereas opening at end inspiration could reflect efforts to expand the airway with tracheal tug and with submental muscle activation and efforts to open the mouth to allow mouth breathing. Masseter contraction does not close the jaw but may serve to stabilize it.     

Alae nasi electromyographic activity and timing in obstructive sleep apnea

The alae nasi is an accessible dilator muscle of the upper airway located in the nose. We measured electromyograms (EMG) of the alae nasi to determine the relationship between their activity and timing to contraction of the rib cage muscles and diaphragm during obstructive apnea in nine patients. Alae nasi EMG were measured with surface electrodes and processed to obtain a moving time average. Contraction of the rib cage and diaphragm during apneas was detected with esophageal pressure. During non-rapid-eye-movement (NREM) sleep, there was a significant correlation in each patient between alae nasi EMG activity and the change in esophageal pressure. During rapid-eye-movement (REM) sleep, correlations were significantly lower than during NREM sleep. As the duration of each apnea increased, the activation of alae nasi EMG occurred progressively earlier than the change in esophageal pressure. We conclude that during obstructive apneas in NREM sleep, activity of the alae nasi increases when diaphragm and rib cage muscle force increases and the activation occurs earlier as each apneic episode progresses.