Common Cavity Research Articles

Molecular genetic advances in semicircular canal abnormalities and sensorineural hearing loss: a report of 16 cases

Objectives The study goals were (1) to determine if the degree and pattern of semicircular canal dysmorphology and the presence or absence of a cochlea in patients with congenital sensorineural hearing loss predict audiologic outcome, severity, or the frequencies involved and (2) to review the recent advances in molecular genetics of the semicircular canals and correlate this information with audiologic and anatomic patterns seen in our series of patients Design and setting We conducted a retrospective study at a tertiary care center with a large otologic and cochlear implant service. Patients and methods The study population consisted of 16 patients with congenital sensorineural hearing loss in 28 congenitally malformed inner ears consisting of semicircular canal dysplasia or aplasia, with or without cochlear malformation. History, physical examination, computed tomography scans, and serial audiograms were reviewed. Factors analyzed included other phenotypic dysmorphology characteristic of syndromes, audiometric configuration, severity and type of hearing loss, and the presence of associated inner ear anomalies other than the vestibular system. An extensive review of the literature regarding molecular genetic factors in semicircular canal anomalies, with or without cochlear abnormalities, was performed. Results Sixteen patients (31 ears) were identified with profound sensorineural hearing loss and semicircular canal abnormalities. Only 3 patients had known syndromes, although 4 patients had other congenital anomalies. Most radiographic detectable abnormalities were bilateral. Audiograms of the patients demonstrated pure tone averages between 90 and 100 dB in the affected ears with few exceptions. No correlation was found between type and severity of malformation of either the cochlea or semicircular canals with the severity of hearing loss. There was no stepwise progression of hearing loss increasing malformation severity. Seven of the 16 patients received cochlear implants. Of these 7, 3 patients had cochlear hypoplasia and 1 patient had a common cavity deformity. Audiologic follow-up on all 7 patients revealed improvement in both speech assessment threshold and pure tone average. Presence or absence of the cochlea was not a factor in outcome after cochlear implantation. Conclusion We have assembled the largest series of patients with semicircular canal dysmorphology, with or without various cochlear abnormalities. Our study failed to correlate the type and severity of semicircular canal malformation with any specific audiologic outcome. The variation in hearing loss severity and pattern even in patients with similar bony radiographic findings must be explained by other non–radiologically detectable defects, likely abnormalities in membranous labyrinthine development. New molecular genetic discoveries have linked specific genes to the development of certain inner ear structures in mice studies. The independent development of the individual semicircular canals in relation to the cochlea and vestibule and the variability in hearing loss suggest a more complex embryologic process than merely an arrest in development as previously thought. As genetic studies are extended into humans, we will likely be able to stratify these patients by molecular defect and severity of hearing loss.

Molecular Genetic Advances in Semicircular Canal Abnormalities and Sensorineural Hearing Loss: A Report of 16 Cases

The study goals were (1) to determine if the degree and pattern of semicircular canal dysmorphology and the presence or absence of a cochlea in patients with congenital sensorineural hearing loss predict audiologic outcome, severity, or the frequencies involved and (2) to review the recent advances in molecular genetics of the semicircular canals and correlate this information with audiologic and anatomic patterns seen in our series of patients. We conducted a retrospective study at a tertiary care center with a large otologic and cochlear implant service. The study population consisted of 16 patients with congenital sensorineural hearing loss in 28 congenitally malformed inner ears consisting of semicircular canal dysplasia or aplasia, with or without cochlear malformation. History, physical examination, computed tomography scans, and serial audiograms were reviewed. Factors analyzed included other phenotypic dysmorphology characteristic of syndromes, audiometric configuration, severity and type of hearing loss, and the presence of associated inner ear anomalies other than the vestibular system. An extensive review of the literature regarding molecular genetic factors in semicircular canal anomalies, with or without cochlear abnormalities, was performed. Sixteen patients (31 ears) were identified with profound sensorineural hearing loss and semicircular canal abnormalities. Only 3 patients had known syndromes, although 4 patients had other congenital anomalies. Most radiographic detectable abnormalities were bilateral. Audiograms of the patients demonstrated pure tone averages between 90 and 100 dB in the affected ears with few exceptions. No correlation was found between type and severity of malformation of either the cochlea or semicircular canals with the severity of hearing loss. There was no stepwise progression of hearing loss increasing malformation severity. Seven of the 16 patients received cochlear implants. Of these 7, 3 patients had cochlear hypoplasia and 1 patient had a common cavity deformity. Audiologic follow-up on all 7 patients revealed improvement in both speech assessment threshold and pure tone average. Presence or absence of the cochlea was not a factor in outcome after cochlear implantation. We have assembled the largest series of patients with semicircular canal dysmorphology, with or without various cochlear abnormalities. Our study failed to correlate the type and severity of semicircular canal malformation with any specific audiologic outcome. The variation in hearing loss severity and pattern even in patients with similar bony radiographic findings must be explained by other non-radiologically detectable defects, likely abnormalities in membranous labyrinthine development. New molecular genetic discoveries have linked specific genes to the development of certain inner ear structures in mice studies. The independent development of the individual semicircular canals in relation to the cochlea and vestibule and the variability in hearing loss suggest a more complex embryologic process than merely an arrest in development as previously thought. As genetic studies are extended into humans, we will likely be able to stratify these patients by molecular defect and severity of hearing loss.

Congenital Common Cavity Deformity of Frontal, Ethmoid, and Sphenoid Sinuses

To present a 17-year-old adolescent patient with lost right eye visual field and intermittent headache since the age of 14 years. The cranium was prominent at the right frontal region. The patient had no history of head trauma or infection and his past medical story was unremarkable. His mental status was normal. Computed tomography scanning revealed an abnormal occurrence of a common cavity deformity of the frontal, ethmoid, and sphenoid sinuses. No other lesions or deformities were present. Such common cavity deformity of these paranasal sinuses has not previously been reported in the English literature.

CW-measurements of Common Cavity Semiconductor Lasers

The output characteristics of a pair of identical antireflection-coated semiconductor lasers placed in a common cavity have been investigated. While in one propagating direction the usual power-current curves were measured, in the opposite one power saturation takes place. The experimental findings are in good agreement with a one-dimensional model for the longitudinal photon and carrier distributions.

Direct comparison of impedance, common cavity, and pH probe in detecting daytime GER's and their characteristics

Direct comparison of impedance, common cavity, and pH probe in detecting daytime GER's and their characteristics

Imaging of a congenital perilymphatic fistula

A 7-year-old boy with a history of purulent meningitis and watery rhinorrhea was studied using computed tomography (CT) and magnetic resonance imaging (MRI). He had a common cavity in the left inner ear. With high-resolution heavily T2-weighted MRI, leakage of the inner ear fluid into the middle ear at the oval window area through a congenital perilymphatic fistula could be visualized. Surgery to close the fistula showed a perforation in the stapes footplate.

A new classification for cochleovestibular malformations.

The report proposes a new classification system for inner ear malformations, based on radiological features of inner ear malformations reviewed in 23 patients. The investigation took the form of a retrospective review of computerized tomography findings relating to the temporal bone in 23 patients (13 male and 10 female patients) with inner ear malformations. The subjects were patients with profound bilateral sensorineural hearing loss who had all had high-resolution computed tomography (CT) with contiguous 1-mm-thick images obtained through the petrous bone in axial sections. The CT results were reviewed for malformations of bony otic capsule under the following subgroups: cochlear, vestibular, semicircular canal, internal auditory canal (IAC), and vestibular and cochlear aqueduct malformations. Cochlear malformations were classified as Michel deformity, common cavity deformity, cochlear aplasia, hypoplastic cochlea, incomplete partition types I (IP-I) and II (IP-II) (Mondini deformity). Incomplete partition type I (cystic cochleovestibular malformation) is defined as a malformation in which the cochlea lacks the entire modiolus and cribriform area, resulting in a cystic appearance, and there is an accompanying large cystic vestibule. In IP-II (the Mondini deformity), there is a cochlea consisting of 1.5 turns (in which the middle and apical turns coalesce to form a cystic apex) accompanied by a dilated vestibule and enlarged vestibular aqueduct. Four patients demonstrated anomalies involving only one inner ear component. All the remaining patients had diseases or conditions affecting more than one inner ear component. Eight ears had IP-I, and 10 patients had IP-II. Ears with IP-I had large cystic vestibules, whereas the amount of dilation was minimal in patients with IP-II. The majority of the semicircular canals (67%) were normal. Semicircular canal aplasia accompanied cases of Michel deformity, cochlear hypoplasia, and common cavity. In 14 ears, the IAC had a defective fundus at the lateral end. In two ears the IAC was absent. In all seven cases of common cavity malformations, there was a bony defect at the lateral end of the IAC. In five of them the IAC was enlarged, whereas in two the IAC was narrow. All patients with IP-I had an enlarged IAC, whereas in patients with type II disease, four had a normal IAC and 10 had an enlarged IAC. All cases of IP-II had an enlarged vestibular aqueduct, whereas this finding was not present in any of the cases of IP-I. In all cases, the vestibular aqueduct findings were symmetrical on both sides (simultaneously normal or enlarged). No patient demonstrated enlargement or any other abnormalities involving the cochlear aqueduct. Radiological findings of congenital malformations in the present study suggested two different types of incomplete partition. Cystic cochleovestibular malformation (IP-I) and the classic Mondini deformity (IP-II). The type I malformation is less differentiated than the type II malformation. Classic Mondini deformity has three components (a cystic apex, dilated vestibule, and large vestibular aqueduct), whereas type I malformation has an empty, cystic cochlea and vestibule without an enlarged vestibular aqueduct. Mondini deformity represents a later malformation, so the amount of dysplasia is much less than in type II. Therefore, it is more accurate and useful for clinical purposes to classify these malformations (in descending order of severity) as follows: Michel deformity, cochlear aplasia, common cavity, IP-I (cystic cochleovestibular malformation), cochlear hypoplasia, and IP-II (Mondini deformity). Only in this way can these complex malformations be grouped precisely and the results of cochlear implantation compared.

Composite resin restorations: a cross-sectional survey of placement and replacement in Jordan

To record the reasons for first time placement and replacement of composite resin restorations in Jordan, to determine the use of composite resin restorations in common cavity types and to collect data on the age of the replaced composite resin restorations. Dentists in Jordan (n = 241). Cross- sectional study using postal survey backed up with personal contact. Data were recorded for all restorations placed or replaced over a period of one month. Information was collected on 2,239 restorations from patients aged 12-65 years. Of all restorations, 61.6% were first time placements while 38.4% were replacement of old restorations. The major reason for the first time placement of restorations was primary caries while that for replacement was secondary caries 36.2%, followed by root canal therapy 22.2%, discolouration 14.4%, lost restorations 13.4%, composite fracture 11.3%, pain or sensitivity 2.4%. The main reason for first time placement of composite restorations is primary caries; the main reason for replacement is secondary caries.

Gastroesophageal reflux induced by white wine: the role of acid clearance and “rereflux”

OBJECTIVES: White wine has been demonstrated to induce gastroesophageal reflux (GER) in healthy people and GER patients. This GER is characterized by reflux episodes of prolonged duration. Our aim was to explore the pathogenesis of the prolonged reflux duration. METHODS: Twelve healthy volunteers received in a randomized order 300 ml of white wine and tap water together with a standardized meal. Esophageal pH and motility were continuously monitored by a glass pH electrode and a strain gauge manometry probe (four measuring points in the esophagus and one in the pharynx to register swallowing) for 90 min after ingestion. Blinded to the ingested beverage, we calculated the fraction of time esophageal pH was <4, the number of reflux episodes and their duration, the swallowing and contraction rate, the contraction amplitude, and the distribution of primary, secondary, simultaneous, and nonpropagated contractions. The motility analysis was separately performed for periods with and without GER. During GER, the time until occurrence of the first contraction, its type, the type of the contraction that raises pH to >4, and the number of peristaltic contractions necessary to raise pH to >4 were also determined. The percentage of GER episodes with simultaneous contractions and failed peristalsis (nontransmitted swallows and nonpropagated contractions) was calculated. The percentage of GER episodes with signs of “rereflux” (further pH drop, common cavity phenomenon in the motility trace) into the acidic esophagus was also determined. The mean reflux duration and the number of peristaltic contractions needed to raise pH to >4 were recalculated by taking the rereflux events into account. RESULTS: White wine significantly increased the fraction of time esophageal pH was <4, reflux frequency, and reflux duration compared to water. During periods without GER, no differences in the motility data were observed between wine and water. During GER, the contraction rate after white wine was significantly lower because of an increase in nontransmitted swallows. The time until occurrence of the first contraction after GER was significantly prolonged after white wine. Primary peristalsis was the main first and clearance contraction type. The percentage of GER episodes with simultaneous contractions and with failed peristalsis was significantly increased with wine. Similarly, the percentage of GER episodes with rereflux was significantly increased. The “corrected” mean reflux duration was still prolonged relative to water, but the difference was no longer significant. The numbers of peristaltic contractions necessary to raise pH to >4, which significantly differed for conventionally defined GER episodes between wine and water, were similar when counted only from onset of the latest rereflux event until pH rose to >4. CONCLUSIONS: The pathogenesis of white wine-induced GER episodes of long duration is 2-fold. First, white wine provokes a disturbed esophageal clearance due to an increase in simultaneous contractions and in failed peristalsis. The second mechanism is the occurrence of repeated reflux events into the esophagus when pH is still acidic from a previous reflux episode.

The shortened cochlea: its classification and histopathologic features

Introduction: The term ‘Mondini dysplasia’ has been used to describe virtually any congenital abnormality of the osseous labyrinth resulting in confusion and seemingly contradictory observations and conclusions about this type of deformity. The purpose of this study is to histopathologically classify and describe temporal bones whose cochleas have less than 2.5 turns. Methods: Of the 1800 temporal bones in our collection, 21 from 12 cases were found to have cochleas with less than 2.5 cochlear turns. Ages ranged from stillborn to 50 years. Temporal bones were harvested at autopsy, processed and embedded in celloidin. Sections were cut at a thickness of 20 μm and every 10th section stained with hematoxylin–eosin and examined using light microscopy. The number of turns, length of cochlea, integrity of cochlear base, length of modiolus, abnormalities of the semicircular canals and vestibule, enlargement of the vestibular aqueduct and middle ears were documented. Twenty-one temporal bones from age-matched patients without cochlear deformities were used as controls for modiolar length measurements. Results: Malformation of the shortened cochlea was histopathologically classified into three groups as follows: (1) Common cavity, cochlear dysplasia (one ear)—severe dysplasia of the cochlea without a complete basal turn; (2) Mondini dysplasia (11 ears)—1.5 cochlear turns, a complete basal turn, an incomplete or absent interscalar septum and a complete bone at the base of the modiolus; and (3) Mondini-like dysplasia type A (five ears)—2 turns to the cochlea including a complete basal turn and complete bone at the base of the modiolus; and type B (four ears)—1.5–2 turns to the cochlea, hypoplasia of or a missing bone at the base of the modiolus (either with or without a communication between the internal auditory canal and the cochlea) and a complete basal turn. Conclusion: The range of congenital malformations in short cochlea is highly variable. Fundamental to the accurate evaluation of a labyrinthine anomaly, malformations of the inner ear should be classified according to the findings in the labyrinth. We suggest the use of common cavity cochlear dysplasia, Mondini dysplasia and Mondini—like dysplasia to describe these variable anomalies.

Antireflux stents in tumors of the cardia

Self-expanding metal esophageal stents (SMES) are highly effective in relieving dysphagia in patients with esophageal carcinoma. As the incidence of cancer at the lower esophagus/cardia continues to increase, SMES also are being deployed across the gastroesophageal junction (GEJ). However, use of SMES in this location makes the stomach and the esophagus, in effect, a common cavity, which predisposes patients to gastroesophageal reflux (GER) and aspiration. Reflux may result from an increase in intra-abdominal pressure or it may occur passively when the patient is recumbent. Acid-suppression medications do not protect against regurgitation and aspiration. We developed a modified antireflux SMES and evaluated its efficacy in vitro, in dogs, and in 11 patients with distal esophageal/GEJ carcinoma. The modification involved extending the polyurethane coating of the stent to 8 cm below the lower edge. In dogs, significantly more reflux episodes occurred with the regular stent (mean, 197 episodes) than with the modified stent (mean, 16 episodes; P = 0.03). In patients who received the modified stent, dysphagia scores were significantly reduced (mean baseline score, 3.4; mean end point score, 1.1; P <0.001). The modified stent prevented GER while allowing belching and vomiting.

Tunic cells in pyrosomes (Thaliacea, Urochordata): cell morphology, distribution, and motility

Abstract. Cellular components of the tunic were histologically examined in 3 pyrosome species representing all 3 genera of the order: Pyrosoma atlanticum, Pyrosomella verticillata, and Pyrostremma spinosum. Three cell types are distributed in the tunic. Tunic amebocytes, irregularly shaped and motile, often contain granules and/or phagosomes. Spherical tunic cells contain many round vesicles with eosinophilic and acidic materials. Tunic net cells form a cellular network in which their long filopodia connect with one another. The net cells are densely distributed just beneath the tunic surface lining the common cloacal cavity and may produce tension to maintain the colony shape. The presence of net cells suggests a phylogenetic relationship between pyrosomes and some aplousobranch ascidians. Test fibers are multicellular cords that run in the tunic and connect the zooids. In P. atlanticum, they are attached to they are attached to the epidermal cells of the zooids, and transverse cloacal muscles are attached to the other (proximal) side of the epidermal cells. The test fibers may mediate coordination of the zooids and control muscle contraction.

Extraction characteristics of a cw double-hexagonal Talbot cavity with stochastic propagation phase

We solve the coupled cw electric field differential equations for an hexagonal array of fiber gain elements all sharing a common monolithic Talbot cavity mirror. A threshold analysis shows that the lowest gains are nearly equal, within 10% of one another, and that one of these corresponds to an in-phase supermode. Above threshold we study the extraction characteristics as a function of the Talbot cavity length, and we also determine the optimum outcoupling reflectivity. These simulations show that the lasing mode is an in-phase solution. Lastly, we study extraction when random linear propagation phases are present by using Monte Carlo techniques. This shows that the coherence function decreases as $\exp(-\sigma;2)$, and that the near-field intensity decreases faster as the rms phase $\sigma;2$ increases. All of the above behaviors are strongly influenced by the hexagonal array rotational symmetry.

Vestibular stimulation after cochlear implantation in common cavity deformity

Vestibular stimulation after cochlear implantation in common cavity deformity

Esophageal longitudinal muscle contraction: Another component of transient lower esophageal sphincter relaxation (tLESR)?

Background. Longitudinal muscle contraction is an integral part of primary peristalsis (PP). This study aimed to characterize longitudinal muscle contraction during tLESR. Method. 8 healthy subjects (4 males, 26_+1 yrs) had metal clips endoscopically affixed at O, +3, and + 8 cm relative to the squamocolumnar junction (SCJ), defining two distal esophageal segments. Axial clip movement was assessed by concurrent manometry and fluoroscopy during LES relaxation with PP, secondary peristalsis (SP) induced by esophageal air injection, and tLESR induced by gastric distension with 800ml of air through the manometric catheter. Segment lengths were measured at 0.5 s intervals during relaxation and the percentage change relative to the initial length was calculated. If a tLESR ended with PP or SP, only the earlier period was used. Maximal SCJ upward movement was measured at end expiration. Results (Table). Although significant shortening was evident in both segments with all three types of LES relaxation, the magnitude of distal segment shortening was least with tLESR and greatest with PP. On the other hand, the maximal degree of overall esophageal shortening durin 0 tLESR, evident by the SCJ excursion, was similar to that during PP suggesting a global effect on the esophagus. In three instances, the moment of LES opening and gas reflux was optimally imaged and SCJ excursion was 0.3-+0.1 cm prior to LES opening and 1.4-+0.7 cm immediately after the occurrence of an esophageal common cavity. Conclusions. Although the segmental pattern appears to be distinct from that seen during PP or SP, esophageal shortening (likely attributable to longitudinal muscle contraction) occurs during tLESR. However, elevation of the LES did not precede LES opening during tLESR suggesting that this is nut part of the opening mechanism, but rather a consequence of the esophageal distension induced by gas reflux.

Reasons for placement and replacement of amalgam restorations in Jordan

To record the reasons for placement and replacement of amalgam restorations in Jordan, to determine the use of amalgam restorations in common cavity types and to collect data on the age of the replaced amalgam restorations. Dentists in Jordan (n=241). Cross-sectional study using postal survey backed up with personal contact. Data was recorded for all restorations placed or replaced over a period of one month. Information was collected on 3,166 restorations from patients aged 9 to 66 years. Of all restorations, 54.8% were first time placements while 45.2% were replacements of old restorations. The major reason for the first time restorations was primary caries, while that for replacement was secondary caries (28.5%) followed by broken and lost restorations (20.4%), root canal therapy (17%), tooth fracture (12%), pain or sensitivity (8.8%), poor margins (8.5%). In Jordan, the main reason for first placement of amalgam restoration is primary caries, the main reason for replacement is secondary caries.

Evidence for a Common Binding Cavity for Three General Anesthetics within the GABAAReceptor

The GABA(A) receptor is an important target for a variety of general anesthetics (Franks and Lieb, 1994) and for benzodiazepines such as diazepam. Specific point mutations in the GABA(A) receptor selectively abolish regulation by benzodiazepines (Rudolph et al., 1999; McKernan et al., 2000) and by anesthetic ethers (Mihic et al., 1997; Krasowski et al., 1998; Koltchine et al., 1999), suggesting the existence of discrete binding sites on the GABA(A) receptor for these drugs. Using anesthetics of different molecular size (isoflurane > halothane > chloroform) together with complementary mutagenesis of specific amino acid side chains, we estimate the volume of a proposed anesthetic binding site as between 250 and 370 A(3). The results of the "cutoff" analysis suggest a common site of action for the anesthetics isoflurane, halothane, and chloroform on the GABA(A) receptor. Moreover, the data support a crucial role for Leu232, Ser270, and Ala291 in the alpha subunit in defining the boundaries of an amphipathic cavity, which can accommodate a variety of small general anesthetic molecules.

Clinical course of pediatric congenital inner ear malformations.

To determine any factors that could improve the early detection and management of congenital inner ear malformations. A retrospective review was performed of all patients with a diagnosis of inner ear malformation at Loyola University Medical Center (LUMC) and the Hospital for Sick Children (HSC) between 1987 and 1995. Clinical records and audiometric data were accumulated. One neuroradiologist reviewed every temporal bone computed tomography (CT) scan. Forty-six pediatric patients with congenital inner ear anomalies evaluated at two tertiary care hospitals. The average patient age at initial assessment was 25.7 months. A family history of hearing loss was noted in only five patients (12.8%). A major nonotological deformity was seen in 41% of patients. The average hearing threshold was 88 dB. All three patients with sudden hearing loss had vestibular aqueduct enlargement. Two of the three patients with common cavity anomalies had a history of recurrent meningitis. Twenty-seven patients had a vestibular aqueduct deformity, the most frequent radiographic abnormality in the series. Because inner ear malformation was diagnosed after 24 months of age in a significant percentage of patients, we recommend increased parental education and vigilance by primary care practitioners. Universal newborn screening may be the key to earlier detection of these infants. For children with idiopathic sensorineural hearing loss, we recommend a temporal bone CT scan. Patients with vestibular aqueduct enlargement must be counseled about the risk of progressive sensorineural hearing loss, meningitis, and the need to avoid contact sports. Patients with common cavity abnormalities should be considered for exploratory tympanotomy and also educated about the risk for meningitis.

Belching and bloating: facts and fantasy after antireflux surgery.

Fundoplication is commonly complicated by belching difficulty and abdominal bloating. Postoperative belching ability, however, is difficult to assess; subjective patient reporting is often used but may be unreliable. Manometric measurement of the gastro-oesophageal 'common cavity' is an objective marker of gastro-oesophageal gas reflux. Twenty patients who had undergone Nissen fundoplication and 11 healthy controls underwent oesophageal manometry at rest and during gastric distension for 10 min with 750 ml of gas. Half of the patients reported an inability to belch; the other half reported varying degrees of belching difficulty, most of whom were rarely able to relieve bloating by belching. During gastric distension, none of the patients had transient lower oesophageal sphincter relaxation, while the controls had a median of 1 (range 0-1). Patients had fewer common cavities than controls; however, none of the belch urges experienced during gastric distension in patients was associated with a common cavity, compared with 48 per cent in controls. After fundoplication, patients do not belch as a result of gastro-oesophageal gas reflux; rather it may be due to oesophagopharyngeal reflux of swallowed air. Subjective reporting of belching ability is inaccurate and manometric measurement of common cavities provides a better means of assessment.

Relative contributions of "pressure pump" and "peristaltic pump" to gastric emptying.

The relative contributions to gastric emptying from common cavity antroduodenal pressure difference ("pressure pump") vs. propagating high-pressure waves in the distal antrum ("peristaltic pump") were analyzed in humans by high-resolution manometry concurrently with time-resolved three-dimensional magnetic resonance imaging during intraduodenal nutrient infusion at 2 kcal/min. Gastric volume, space-time pressure, and contraction wave histories in the antropyloroduodenal region were measured in seven healthy subjects. The subjects fell into two distinct groups with an order of magnitude difference in levels of antral pressure activity. However, there was no significant difference in average rate of gastric emptying between the two groups. Antral pressure history was separated into "propagating high-pressure events" (HPE), "nonpropagating HPEs," and "quiescent periods." Quiescent periods dominated, and average pressure during quiescent periods remained unchanged with decreasing gastric volume, suggesting that common cavity pressure levels were maintained by increasing wall muscle tone with decreasing volume. When propagating HPEs moved to within 2-3 cm of the pylorus, pyloric resistance was found statistically to increase with decreasing distance between peristaltic waves and the pylorus. We conclude that transpyloric flow tends to be blocked when antral contraction waves are within a "zone of influence" proximal to the pylorus, suggesting physiological coordination between pyloric and antral contractile activity. We further conclude that gastric emptying of nutrient liquids is primarily through the "pressure pump" mechanism controlled by pyloric opening during periods of relative quiescence in antral contractile wave activity.