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Biomedical subjects

R Shaker

Publications and source records attributed to R Shaker.

At least 73 records · Page 4Linked to original sources
PubMed1999

Effect of pharyngeal stimulation on the motor function of the esophagus and its sphincters.

OBJECTIVE/HYPOTHESIS: Sensory impulses from the pharynx induce contraction of the upper esophageal sphincter (UES), relaxation of the lower esophageal sphincter (LES), and inhibition of peristalsis. To determine 1) the magnitude of UES contractile response to threshold volume of fluid that induces LES relaxation and 2) the effect of rapid pharyngeal air stimulation on LES resting pressure and its concurrent influence on the UES and progression of esophageal peristalsis. METHODS: Eleven healthy volunteers (age, 31 +/- 2 y) were studied by concurrent UES, esophagealbody, and LES manometry. RESULTS: At a threshold volume of 0.3 +/- 0.05 mL, injections of water into the pharynx directed posteriorly, resulted in complete LES relaxation. Duration of these relaxations averaged 19 +/- 1 seconds. In 10 of 11 subjects, these relaxations were accompanied by a simultaneous increase in UES resting tone that averaged 142% +/- 27% above preinjection values. Pharyngeal stimulation by rapid air injection resulted in complete LES relaxation in 8 of the 11 subjects (threshold volume, 14 +/- 6 mL). Five of 8 developed a concurrent mild increase in resting UES pressure (17% +/- 6% above preinjection values) (P < .05). Pharyngeal water injection inhibited the progression of the peristaltic pressure wave at all tested sites and in all subjects, but pharyngeal air injection in only 2 of the 11 studied subjects. CONCLUSIONS: The inhibitory effect of pharyngeal water injection on LES resting pressure is accompanied by a substantial contractile effect on the UES. Although stimulation of the pharynx by rapid air injection may induce LES relaxation, its inhibitory effect on esophageal peristalsis and stimulatory effect on UES pressure are negligible compared with that of water injection.

Adult↗
PubMed1999

Gastrointestinal motor and myoelectric correlates of motion sickness.

The objectives of this study were to characterize the digestive tract motor and myoelectric responses associated with motion sickness. Twenty-two cats (1.5-3.0 kg) were chronically implanted with force transducers and electrodes on the stomach and small intestine. Motion sickness was activated by vertical oscillation (VO) at +/-0.5 g and identified as salivation, licking, or vomiting. Vomiting was initiated chemically by UK-14304 (2.5-15 microg/kg iv) or CuSO4 (10-50 mg ig). We found that VO caused vomiting (45% of trials), a decrease in gastrointestinal (GI) motility (69% of trials), salivation or licking (59% of trials), bradygastria (39% of trials), retrograde giant contraction (RGC, 43% of trials), giant migrating contraction (GMC, 5% of trials), and defecation (18% of trials). The decrease in GI motility occurred with (62% of trials) or without (69% of trials) vomiting. Motion sickness was accompanied by bradygastria (52% of trials) and decreased GI motility (70% of trials). Similar events occurred after CuSO4 and UK-14304, but the incidences of responses after CuSO4 were less frequent, except for vomiting, RGC, and GMC. UK-14304 never caused GMCs or defecation. The magnitude and velocity of the RGC were the same during all emetic stimuli, and RGCs never occurred without subsequent vomiting. Supradiaphragmatic vagotomy (n = 1) or atropine (n = 2, 10 or 50 microg/kg iv) blocked the RGC, but not vomiting, due to VO. We concluded that 1) oculovestibular stimulation causes digestive tract responses similar to other types of emetic stimuli, 2) decreased GI motility and bradygastria may be physiological correlates of the motion sickness, and 3) motion sickness may not be dependent on any specific GI motor or myoelectric response.

Animals↗
PubMed1999

Comparison of upper esophageal sphincter opening in healthy asymptomatic young and elderly volunteers.

Deglutitive upper esophageal sphincter opening (UES) in the elderly has been incompletely studied. Our aim was to determine in the elderly the temporal and dimensional characteristics of deglutitive UES opening; anterior and superior hyoid and laryngeal excursions as measures of distracting forces imparted on the UES; and hypopharyngeal intrabolus pressure (IBP). Fourteen healthy elderly and 14 healthy young volunteers were studied by concurrent videofluoroscopy and hypopharyngeal manometry during swallowing of 5- and 10-mL barium boluses. The anteroposterior UES diameter, as well as the anterior hyoid bone and laryngeal excursion, was significantly smaller in the elderly compared to the young (p < .05) for 5-mL barium boluses, but not for 10-mL boluses. The lateral diameter of UES opening was similar between groups for all boluses. The IBP for 5- and 10-mL swallows in the elderly was significantly higher than that in the young (p < .05). We conclude that anteroposterior deglutitive UES opening and hyoid bone and thyroid cartilage anterior excursion are reduced in the elderly. These changes are associated with increased IBP, suggesting a higher pharyngeal outflow resistance in the elderly compared to the young.

Adult↗
PubMed1999

Event-related fMRI of tasks involving brief motion.

The assessment of brain function by blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) for tasks involving motion near the field of view is compromised by artifacts arising from the motion. The aim of this study is to demonstrate that these artifacts can be reduced by acquiring the average response from a brief stimulus (a "single-trial," or "event-related," paradigm) as opposed to alternating blocks of repeated task with rest (a "block-trial" paradigm). The basis of this technique is that the NMR signal changes from neuronal activation are delayed relative to the motion due to a slow hemodynamic response. By acquiring the average response from a brief stimulus, motion-induced signal changes occur prior to neuronal activation-induced signal changes, and the two can thus be distinguished. This technique is applied to the tasks of speaking out loud, swallowing, jaw clenching, and tongue movement. Functional activation maps derived from the single-trial paradigm contain significantly less artifact than functional activation maps derived from a more traditional block-trial paradigm.

Artifacts↗
PubMed1998

Magnetic field changes in the human brain due to swallowing or speaking.

Variations in the magnetic field in the human brain caused by the processes of swallowing or speaking are measured. In both processes, motion of the pharyngeal muscles, especially the tongue and jaw, alter the susceptibility-induced magnetic field distribution at the brain slice being imaged. This leads to image warping, compromising the analysis of a time series of images, such as in functional magnetic resonance imaging (fMRI). These dynamic changes are assessed by acquiring a time series of images using a gradient-echo asymmetric-spin-echo sequence (GREASE), a technique in which two images are acquired for each excitation--one during the gradient echo, and one during the latter part of the spin echo. The NMR phase difference between the two images is a measure of the magnetic field distribution. A series of brain images, acquired with this sequence while the subject either swallows or speaks, indicated negative magnetic field changes of up to 0.087 ppm in the inferior region of the brain for both speaking and swallowing, and in some speech, additional positive changes of up to 0.056 ppm in the frontal region of the brain were indicated.

Brain↗
PubMed1998

Identification and characterization of cerebral cortical response to esophageal mucosal acid exposure and distention.

BACKGROUND & AIMS: Esophageal acid exposure is a common occurrence in healthy individuals and patients with esophagitis. Clinically, perception of this exposure ranges from no perception to severe heartburn and chest pain. Cerebral cortical response to esophageal mucosal contact to acid has not been systematically studied. The aim of this study was to elucidate cerebral cortical response to esophageal acid exposure in normal individuals by functional magnetic resonance imaging (FMRI). METHODS: We studied 10 normal healthy volunteers. Cortical FMRI response to 10 minutes of intraesophageal perfusion of 0.1N HCl (1 mL/min) was determined, and the results were compared with those of saline infusion and balloon distention. RESULTS: Acid perfusion did not induce heartburn or chest pain but increased FMRI signal intensity by 6.7% +/- 2.0% over the preperfusion values. No increase was detected for saline infusion. FMRI signal intensity to balloon distention was similar to that of acid perfusion. Activation latency, activation to peak, and the deactivation periods for response to acid perfusion were significantly longer than those of balloon distention (P < 0.05). CONCLUSIONS: Contact of esophageal mucosa with acid, before inducing heartburn, evokes a cerebral cortical response detectable by FMRI. Temporal characteristics of this response are significantly different from those induced by esophageal balloon distention.

Adult↗
PubMed1998

Discrete ulcers in Barrett's esophagus: relationship to acute gastrointestinal bleeding.

BACKGROUND AND STUDY AIMS: Although discrete ulcers are a recognized complication of Barrett's esophagus, it is not clear how common discrete ulceration is in Barrett's mucosa. Furthermore, the relationship of gastrointestinal hemorrhage to Barrett's ulceration is unknown. These issues were investigated in this paper. METHODS: Seventy-eight patients with histologically confirmed Barrett's esophagus were monitored by endoscopic surveillance over 1 to 11 years (mean 3.3 years). The incidence of a Barrett's ulcer was noted and its site recorded. The frequency of gastrointestinal hemorrhage at diagnosis or on follow-up was documented and the source of the bleeding was identified. RESULTS: Discrete ulcers were identified in 36 of 78 patients (46%) at some time over the period of follow-up. Eight patients had two or more ulcers. Most of ulcers were in the distal esophagus; 86% of these were within 3 cm of the anatomic gastroesophageal junction. Nineteen patients (24%) either presented with active gastrointestinal bleeding or had bleeding at follow-up. In 15 of the 19 patients with bleeding (79%) a discrete Barrett's ulcer was the source of the hemorrhage. CONCLUSIONS: Ulceration is a common complication of Barrett's esophagus. These ulcers are usually located close the gastroesophageal junction and have a high incidence of bleeding.

Adult↗
PubMed1998

Pharyngeal acid reflux events in patients with vocal cord nodules.

OBJECTIVE: Gastroesophageal reflux has been implicated in the pathogenesis of vocal cord nodules. However, a cause-and-effect relationship has not been established. Because documentation of pharyngeal acid reflux events makes this correlation more plausible, the aim of the present study was to determine the frequency of pharyngeal acid reflux events in patients with vocal cord nodules. METHODS: Eleven patients with vocal cord nodules (mean age, 42 +/- 6 years) and eleven healthy volunteers (mean age, 45 +/- 6 years) were studied. Patients underwent barium esophagram and ambulatory 24-hour simultaneous three-site pharyngoesophageal pH monitoring. Controls only had ambulatory 24-hour simultaneous three-site pH monitoring. In the ambulatory pH monitoring studies, pH was recorded from the manometrically determined sites of pharynx (2 cm above upper esophageal sphincter), proximal esophagus (10 cm distal to pharyngeal site), and distal esophagus (5 cm above the lower esophageal sphincter). Pharyngeal acid reflux event was deemed acceptable if all three sites recorded a decrease in pH below 4 which was not related to meal or drinking. RESULTS: Pharyngeal acid reflux events occurred in seven of 11 patients with vocal cord nodules (1-4 episodes) and two of 11 controls (1-2 episodes) (P < .05). In both groups all pharyngeal acid reflux events occurred in upright position and were not associated with belching or coughing. Barium studies documented hiatal hernia in two patients and gastroesophageal reflux in five of 11 patients. However, none of the esophageal reflux events reached the pharynx on barium esophagram. CONCLUSIONS: Prevalence of pharyngeal acid reflux events is significantly higher in patients with vocal cord nodules compared with normal controls and suggests a contributory role for gastroesophagopharyngeal acid reflux in the pathogenesis of some vocal cord nodules.

Adolescent↗
PubMed1998

Pharyngo-UES contractile reflex in patients with posterior laryngitis.

BACKGROUND: Earlier studies have shown that stimulation of the human pharynx by injection of minute amounts of water stimulates the pharyngo-UES contractile reflex. It has been suggested that this reflex may be activated during pharyngeal reflux of gastric and/or esophageal content, thus increasing the UES pressure and possibly preventing further entry of the refluxate into the pharynx. However, the integrity of this reflex in patients with posterior laryngitis has not been studied. AIM: Evaluate the pharyngo-UES contractile reflex in a group of patients with objective findings of posterior laryngitis. METHODS: Fourteen consecutive patients with posterior laryngitis (mean age, 48+/-6 y) and 13 healthy volunteers (mean age, 53+/-6 y) were studied by concurrent pharyngeal water stimulation and UES manometry. RESULTS: The threshold volume required to evoke the pharyngo-UES contractile reflex in the laryngitis group (0.4+/-0.05 mL) was significantly higher than that of the control (0.2+/-0.04 mL) (P < .05). Following stimulation of the pharyngo-UES contractile reflex, the maximum postinjection pressure in patients (75+/-6 mm Hg) was similar to that of the controls (78+/-6 mm Hg). The percent increase in UES pressure following stimulation of the reflex in the laryngitis group (99%+/-15%) was significantly higher than that of controls (55%+/-11%) (P < .05). CONCLUSIONS: Compared with normal controls, a significantly larger volume of liquid is required to trigger this reflex in patients with posterior laryngitis. When triggered, the maximum UES pressure induced by the pharyngo-UES contractile reflex is similar between the two groups. These findings suggest an altered afferent sensory limb of this reflex in patients with posterior laryngitis.

Adolescent↗
PubMed1998

Effect of chronic and acute cigarette smoking on the pharyngo-upper oesophageal sphincter contractile reflex and reflexive pharyngeal swallow.

BACKGROUND: Cigarette smoking is known to affect adversely the defence mechanisms against gastro-oesophageal reflux. The effect of smoking on the supraoesophageal reflexes that prevent aspiration of gastric contents has not been previously studied. AIMS: To elucidate the effect of cigarette smoking on two of the supraoesophageal reflexes: the pharyngo-upper oesophageal sphincter (UOS) contractile reflex; and the reflexive pharyngeal swallow. METHODS: Ten chronic smokers and 10 non-smokers were studied, before and 10 minutes after real or simulated smoking, respectively. UOS pressure and threshold volume for the reflexes were determined using a UOS sleeve assembly. Two modes of fluid delivery into the pharynx were tested: rapid injection and slow injection. RESULTS: For both rapid and slow injections, the threshold volume for triggering the pharyngo-UOS contractile reflex was significantly higher in smokers than in non-smokers (rapid: smokers 0.42 (SE 0.07) ml, non-smokers 0.16 (0. 04) ml; slow: smokers 0.86 (0.06) ml, non-smokers 0.38 (0.1) ml; p<0. 05). During rapid injection, the threshold volume for reflexive pharyngeal swallow was higher in smokers (smokers 0.94 (0.09) ml, non-smokers 0.46 (0.05) ml; p<0.05). Acute smoking further increased the threshold volume for the pharyngo-UOS contractile reflex and reflexive pharyngeal swallow during rapid injection. CONCLUSIONS: Smoking adversely affects stimulation of the pharyngo-UOS contractile reflex and pharyngeal reflexive swallow. These findings may have implications in the development of reflux related respiratory complications among smokers.

Adult↗
PubMed1998

Pharyngoglottal closure reflex: identification and characterization in a feline model.

Earlier studies in humans have shown that pharyngeal stimulation by water at a threshold volume induces a brief vocal cord adduction, i. e., pharyngoglottal closure reflex. The present study was undertaken to 1) develop a suitable animal model for physiological studies of this reflex and 2) delineate its neural pathway and effector organs. Studies were done in cats by concurrent videoendoscopy and manometry followed by electromyographic studies. At a threshold volume (0.3 +/- 0.06 ml), injection of water into the pharynx resulted in a brief closure of the vocal folds, closing the introitus to the trachea. Duration of this closure averaged 1.1 +/- 0.1 s. Bilateral transection of the glossopharyngeal nerve completely abolished this reflex but not swallows induced by pharyngeal water stimulation. The pharyngoglottal closure reflex is present in the cats. The glossopharyngeal nerve is the afferent pathway of this reflex, and the interarytenoid and lateral cricoarytenoid muscles are among its target organs.

Animals↗
PubMed1998

Characterization and mechanisms of the pharyngoesophageal inhibitory reflex.

The objectives of this study were to identify and to characterize the pharyngoesophageal inhibitory reflex (PEIR) in an animal model. Thirty-one cats (2.4-5.0 kg) were anesthetized using alpha-chloralose (45 mg/kg ip), and esophageal peristalsis was recorded manometrically. Secondary peristalsis was activated by rapid air injection (8-20 ml) at midesophagus or slow infusion of water through the manometric catheters. Neither stimulus activated primary peristalsis. The PEIR was activated by rapid water injection or focal mechanical stimulation of the pharynx. Rapid air injection activated secondary peristalsis in 92% of the trials, and slow water infusion activated 1 secondary peristalsis every 3.2 min. Pharyngeal stimulation by 0.3, 0.5, 0.8, or 1.0 ml of water inhibited or blocked ongoing secondary peristalsis in 67, 82, 97, or 93% of trials, respectively. Mechanical stimulation of the posterior wall of the pharynx with 11-20 g pressure attenuated secondary peristalsis in 96% of the trials or blocked secondary peristalsis in 41% of the trials. Centripetal electrical stimulation at 30 Hz, 0.2 ms, 2 V for 4 s of the superior laryngeal (SLN) or glossopharyngeal (GPN) nerves blocked or inhibited secondary peristalsis in 100% of the trials. Bilateral transection of the GPN (n = 8), but not the SLN (n = 6), blocked the PEIR. Anesthetization of the pharyngeal mucosa using lidocaine (2%) blocked the PEIR (n = 3). We concluded that 1) the PEIR exists in the cat, 2) mechanical stimulation of the pharynx more strongly activates the PEIR than water, 3) activation of either SLN or GPN afferents attenuates ongoing secondary peristalsis, 4) the receptors mediating the PEIR are located in the pharyngeal mucosa, and 5) both SLN and GPN contribute to the PEIR, but the GPN is the major afferent limb of this reflex.

Animals↗
PubMed1998

Evaluation of gastroesophageal reflux in patients with laryngotracheal stenosis.

To report the incidence of pharyngeal acid reflux events in patients with laryngotracheal stenosis (LTS), we studied 12 patients with LTS and 34 healthy volunteers. All patients and controls underwent ambulatory 24-hour 3-site pH monitoring. In ambulatory pH monitoring, pH was recorded at manometrically determined sites of the pharynx, proximal esophagus, and distal esophagus. For all 3 sites, a pH value below 4 that was not related to the time of oral intake or belching was considered an acid reflux event. Eight of the 12 LTS patients exhibited pharyngeal acid reflux events. In the control group, pharyngeal acid reflux events were documented in 7 subjects. In between-group comparison, the number of reflux episodes and the percent acid exposure time in the pharynx were greater in LTS patients than in controls. Reflux parameters of the proximal and distal esophagus in LTS patients were similar to those of controls. The incidence of pharyngeal acid reflux events in LTS patients was higher than that in controls. It is suggested that identification and treatment of gastroesophageal reflux in patients will significantly simplify and improve the results of treatment for LTS.

Adult↗
PubMed1997

Anatomy and physiology of the upper esophageal sphincter.

The upper esophageal sphincter (UES) is composed of the cricopharyngeus (CP), thyropharyngeus (TP; inferior pharyngeal constrictor [IPC] in humans), and cranial cervical esophagus. All 3 muscles may at times function to maintain tone in the UES, but only the CP contracts and relaxes in all physiologic states consistent with the UES. The CP is a striated muscle composed of variable-sized small (25-35 microm) muscle fibers that are primarily type I (slow twitch), highly oxidative, and contain abundant (40%) endomysial elastic connective tissue. The fibers may attach to the connective tissue framework, forming a muscular net. In humans and rats, but not other animals, the CP has no median raphe. The optimum length of the CP for development of active tension is about 1.7 times resting length; therefore, in some respects the CP acts more like cardiac than striated muscle. A passive tone in the CP is present and increases through all degrees of stretch. The high compliance of the CP allows it to be opened by distraction of other muscles (e.g., geniohyoideus) or increased intraluminal pressure. The CP is innervated by branches of the vagus nerves: pharyngoesophageal (PE), superior laryngeal (SLN), and recurrent laryngeal (RLN); glossopharyngeal (GPN); and cervical sympathetics. Only the PE and SLN provide motor fibers to the CP. The GLN may be sensory; the sympathetics may innervate the mucosa, blood vessels, and glands; but no functional innervation by the RLN has been identified. Parasympathetic ganglia and various peptides (galanin, cGRP, VIP, neuropeptide Y, substance P, tyrosine hydroxylase) have been found in the CP, but their role in control of the CP is unknown. The motoneurons of the CP are found in the nucleus ambiguus, and the innervation is ipsilateral for animal species in which the CP has a median raphe. These motoneurons are topographically organized with other pharyngeal and laryngeal muscles and the striated muscle esophagus. Pharyngeal motoneurons often have a respiratory rhythm, but not a spontaneous background discharge. Therefore, the CP motoneurons may not generate CP tone. Various reflexes control the tone of the CP. Distension of the esophagus causes contraction of the CP and UES, which is mediated by a vago-vagal reflex. Pressure on the pharyngeal mucosa contracts the CP and UES and is mediated by a glossopharyngo-vagal reflex. Inflation of the lungs causes contraction of the CP and UES, which is mediated by a vago-vagal reflex. The pharyngo-UES and pulmonary-UES reflexes may generate the respiratory rhythm often observed on UES pressure or electromyographic activity. The UES or CP also contracts with arousal or with changes in posture. All of these reflexes and responses and the passive elastic properties of the CP may contribute to the generation of tone in the CP and UES.

Animals↗
PubMed1997

Coordination of deglutitive glottal function and pharyngeal bolus transit during normal eating.

BACKGROUND & AIMS: Deglutitive glottal function during the preparatory phase of swallowing and its coordination with bolus transit during normal eating are important for airway protection. The aim of this study was to examine this coordination during consumption of a normal meal. METHODS: Fifteen healthy volunteers were studied using a videoendoscopic and videofluoroscopic technique. RESULTS: A total of 207 liquid and 470 solid bolus swallows were analyzed. In 60% of liquid and 76% of solid food swallows, the bolus was seen in the pharynx before a swallow was initiated. Entry of boluses into the pharynx was associated with brief partial adduction of the vocal cords. Solid food entered and traversed the pharynx at the midline, whereas liquid bolus was split around the larynx and rejoined in the hypopharynx. Swallowing was initiated significantly earlier when bolus made contact with the upper third of the epiglottis compared with vallecula or pyriform sinuses. CONCLUSIONS: In more than half of the instances, during normal eating, food enters the pharynx during the preparatory phase before a swallow is initiated, the path of pharyngeal transit of solid bolus is different from that of liquid bolus, and the epiglottal edge appears to be the most sensitive trigger zone for swallowing.

Adult↗
PubMed1997

Frequency of gastroesophageal reflux events induced by pharyngeal water stimulation in young and elderly subjects.

Earlier studies have shown that isolated complete lower esophageal sphincter (LES) relaxation occurs as a result of pharyngeal water stimulation. Association of these relaxations with gastroesophageal reflux has not been studied systematically. Our aim was to determine this association in young and elderly subjects during precibal and postprandial periods. We studied 8 young subjects and 10 elderly subjects for 1 h before and 2 h after a 1,000-cal meal. In both groups, during the precibal period, negligible LES relaxation induced by pharyngeal water stimulation resulted in gastroesophageal reflux. In the postprandial period, gastroesophageal reflux events occurred after 16% of pharyngeal water injections in young subjects and after 44% in elderly subjects (P < 0.05). Intraabdominal length of the LES in elderly subjects was significantly shorter compared with younger subjects (P < 0.05). We conclude that gastroesophageal reflux events induced by pharyngeal water stimulation in the postprandial period are significantly increased compared with those of the precibal period and are significantly more prevalent in the elderly compared with the young. These differences seem to be associated with a significantly shorter intra-abdominal segment of the LES in the elderly.

Adult↗
PubMed1997

Effect of pharyngeal water stimulation on esophageal peristalsis and bolus transport.

Sensory stimuli originating from the pharynx inhibit esophageal peristalsis induced by a dry swallow. Our aims were to determine the effect of these stimuli on esophageal bolus transport and esophageal peristalsis induced by swallowing different volumes of liquid and semisolid boluses. We studied nine healthy volunteers age 35 +/- 4 yr in the supine position by intraluminal esophageal manometry as well as concurrent videofluoroscopy and manometry. In all subjects progression of peristalsis induced by swallowing of different volumes of water and mashed potato boluses was inhibited at all sites by pharyngeal water injection. Threshold volume for inhibition of the peristalsis induced by swallows of 5 and 10 ml of water was similar but significantly higher compared with dry swallows (P < 0.05). Pharyngeal water injection invariably halted transit of the barium boluses through the esophagus. Sensory impulses originating from the pharynx 1) inhibit esophageal bolus transit and 2) are capable of overcoming the facilitating effect of a liquid bolus on the swallowing apparatus. This phenomenon may explain the mechanism of some of the failed esophageal peristalsis observed in clinical practice.

Adult↗