Transcription profiling associated with life cycle of Anopheles gambiae.

Complex biological events occur during the developmental process of the mosquito Anopheles gambiae (Giles). Using cDNA expression microarrays, the expression patterns of 13,440 clones representing 8,664 unique transcripts were revealed from six different developmental stages: early larvae (late third instar/early fourth instar), late larvae (late fourth instar), early pupae (< 30 min after pupation), late pupae (after tanning), and adult female and male mosquitoes (24 h postemergence). After microarray analysis, 560 unique transcripts were identified to show at least a fourfold up- or down-regulation in at least one developmental stage. Based on the expression patterns, these gene products were clustered into 13 groups. In total, eight genes were analyzed by quantitative real-time polymerase chain reaction to validate microarray results. Among 560 unique transcripts, 446 contigs were assigned to respective genes from the An. gambiae genome. The expression patterns and annotations of the genes in the 13 groups are discussed in the context of development including metabolism, transport, protein synthesis and degradation, cellular processes, cellular communication, intra- or extra-cellular architecture maintenance, response to stress or immune-related defense, and spermatogenesis.

Pharyngeal dysphagia in postesophagectomy patients: correlation with deglutitive biomechanics.

BACKGROUND: Because of the transient nature of pharyngeal phase dysphagia, posttranshiatal esophagectomy patients provide a model for studying the correlation of dysphagic symptoms and aspiration with deglutitive biomechanics. METHODS: We studied 8 transhiatal esophagectomy patients (age range, 51 to 78 years) and 8 normal age-matched controls in upright position using lateral and anteroposterior (AP) projection videofluoroscopy during three 5 mL barium swallows. RESULTS: The maximum upper esophageal sphincter (UES) AP diameter and maximum anterior excursion of the hyoid bone in patients with transhiatal esophagectomy who experienced aspiration (6.2+/-0.6 and 9.0+/-2.0 mm, respectively) were significantly smaller than those of age-matched normal controls (9.4+/-0.7 and 17.0+/-1.0 mm, respectively). Resolution of aspiration was associated with a significant increase in AP diameter of the UES as well as anterior and superior excursion of the hyoid bone (p<0.05). CONCLUSIONS: Dysphagic symptoms and aspiration in posttranshiatal esophagectomy patients are associated with significant abnormalities of deglutitive biomechanics. Improvement in deglutitive biomechanics is associated with resolution of dysphagic symptoms as well as postdeglutitive aspiration in these patients.

Kinematic and dynamic characteristics of solid pellet movement during the pharyngeal phase of swallowing.

Information on solid particle movement through the pharynx, in addition to its physiologic importance, has relevance to the swallowing of medications in pill form. The purpose of this study was to determine the kinematics of a solid particle during the oral-pharyngeal phase of swallowing. We used a concurrent manometric-videofluoroscopic technique and identified two distinct zones of increasing bolus velocity, one at the tongue base and the other at the pharyngo-upper esophageal sphincter (UES) region. Velocity decreased significantly (p < .05), to 9.0 +/- 1.0 cm/s, while the bolus traversed the area located between the tip of the horizontal epiglottis and the pharyngeal wall. The velocity of the liquid barium bolus head was similar to that of the solid barium pellet. The average bolus tail velocity was relatively constant. The acceleration of the barium pellet was temporally associated with development of an incrementally decreasing pressure distal to the location of the pellet in the hypopharynx and across the UES. In conclusion, the kinematics of a solid particle are similar to those of the head of a liquid bolus, but both are different from bolus tail kinematics. During the pharyngeal phase of swallowing, the area located ahead of the bolus exhibits an incrementally decreasing pressure, caudally. This may facilitate bolus transport and contribute to airway protection.

Regional esophageal distribution and clearance of refluxed gastric acid.

Regional differences in the esophageal distribution and clearance of refluxed gastric acid was studied in seven asymptomatic volunteers and seven patients with reflux esophagitis. Intraluminal pH was recorded for 3 postprandial hours from the distal, middle, and proximal esophagus on two separate occasions (with subjects in upright and supine positions). With the subjects in a supine position, about half of the acid reflux episodes reached the proximal esophagus in patients as well as in controls. This percentage decreased to 25% in patients and 29% in controls when they were upright. In both groups, the pH drops in the distal esophagus were significantly greater than in the proximal esophagus for both the supine and upright positions. In both patients and controls, a 4-5-fold greater acid exposure occurred in the distal esophagus, than in the proximal esophagus. In both patient and control groups, acid exposure time, as well as the number of reflux episodes in the distal esophagus, were significantly greater than that of the proximal esophagus (P less than 0.05). Spontaneous acid clearance time in the distal esophagus was significantly longer than that of the proximal esophagus in both positions (P less than 0.05) for both subject groups. In conclusion, regional differences exist in the exposure of the esophageal mucosa to refluxed gastric acid. These regional differences are more pronounced when subjects are upright than supine. Regional differences also exist in esophageal acid clearance, with clearance taking longer in the distal esophagus than in the proximal esophagus. The net effect of these phenomena is that acid exposure time in the distal esophagus is greater than that in the remainder of the esophagus.

Cerebral cortical representation of reflexive and volitional swallowing in humans.

The purpose of this study was to compare cerebral cortical representation of experimentally induced reflexive swallow with that of volitional swallow. Eight asymptomatic adults (24-27 yr) were studied by a single-trial functional magnetic resonance imaging technique. Reflexive swallowing showed bilateral activity concentrated to the primary sensory/motor regions. Volitional swallowing was represented bilaterally in the insula, prefrontal, cingulate, and parietooccipital regions in addition to the primary sensory/motor cortex. Intrasubject comparison showed that the total volume of activity during volitional swallowing was significantly larger than that activated during reflexive swallows in either hemisphere (P < 0.001). For volitional swallowing, the primary sensory/motor region contained the largest and the insular region the smallest volumes of activation in both hemispheres, and the total activated volume in the right hemisphere was significantly larger compared with the left (P < 0.05). Intersubject comparison showed significant variability in the volume of activity in each of the four volitional swallowing cortical regions. We conclude that reflexive swallow is represented in the primary sensory/motor cortex and that volitional swallow is represented in multiple regions, including the primary sensory/motor cortex, insular, prefrontal/cingulate gyrus, and cuneus and precuneus region. Non-sensory/motor regions activated during volitional swallow may represent swallow-related intent and planning and possibly urge.

The effect of high- vs low-density barium preparations on the quantitative features of swallowing.

We compared the effect of high-density and low-density barium preparations on the quantitative features of swallowing. The two barium preparations differed primarily in density but also differed somewhat in viscosity. Concurrent videofluoroscopic and manometric studies were done in nine healthy control subjects. Videofluoroscopy was recorded in the lateral projection at 30 frames/sec while concurrent manometry was done with five intraluminal transducers that straddled the pharynx and upper esophageal sphincter. Swallows of 5 and 10 ml of high- and low-density barium preparations were recorded. Analysis indicated that, compared with the low-density barium (1.4 g/cm3), the high-density barium (2.5 g/cm3) preparation had a slower oral and pharyngeal bolus transit time and caused significant quantitative differences in the function of the upper esophageal sphincter. Compared with low-density barium boluses, the high-density barium boluses were associated with later sphincter opening and closure, longer duration of sphincter opening and flow, lower flow rate, greater maximal anterior hyoid movement, greater sagittal sphincter diameter, and higher intrabolus pressure upstream of and within the sphincter. We conclude that the density as well as the viscosity of the barium preparation used in radiologic examination of the oral-pharyngeal phases of swallowing has an influence on bolus transit time through the mouth and pharynx, and on the quantitative features of upper esophageal sphincter opening. Although these quantitative differences cannot generally be recognized visually at fluoroscopy, they become important for the quantitative assessment of swallowing in patients with suspected disorders of oral-pharyngeal swallowing. Therefore, the basic barium preparations used to examine such patients should be either standardized or at least specified.

Viscosity measurements of barium sulfate mixtures for use in motility studies of the pharynx and esophagus.

Detailed viscosity measurements have been made of barium sulfate mixtures over a wide range of viscosities for use in radiography of the esophagus, stomach, and duodenum. A new methodology was developed for more accurate estimation of viscosity in non-Newtonian fluids in conventional cylinder-type viscometers. As base cases, the variation of viscosity with shear rate was measured for standard commercial mixes of e.z.hd (250% w/v) and a diluted mixture of liquid e.z.paque (40% w/v). These suspensions are strongly shear thinning at low shear rates. Above about 3s-1 the viscosity is nearly constant, but relatively low. To increase the viscosity of the barium sulfate mixture, Knott's strawberry syrup was mixed to different proportions with e.z.hd powder. In this way viscosity was systematically increased to values 130,000 times that of water. For these mixtures the variation of viscosity with temperature, and the change in mixture density with powder-syrup ratio are documented. From least-square fits through the data, simple mathematical formulas are derived for approximate calculation of viscosity as a function of mixture ratio and temperature. These empirical formulas should be useful in the design of "test kits" for systematic study for pharyngeal and esophageal motility, and clinical analysis of motility disorders as they relate to bolus consistency.

Gender differences in cortical representation of rectal distension in healthy humans.

Cerebral cortical processing of information relayed via visceral afferents is poorly understood. We determined and compared cortical activity caused by various levels of rectal distension in healthy male and female subjects. Twenty-eight healthy, young (20-44 yr) volunteer subjects (13 male, 15 female) were studied with a paradigm-driven functional magnetic resonance imaging (fMRI) technique during barostat-controlled rectal distension at perception threshold and 10 mmHg below and above perception threshold. Male subjects showed localized clusters of fMRI activity primarily in the sensory and parietooccipital regions, whereas female subjects also showed activity in the anterior cingulate and insular regions. A progressive increase in maximum percent fMRI signal change and total volume of cortical activity was associated with the intensity of rectal distension pressure in both genders. Regions of cortical activity for below-threshold stimuli showed less substantial signal intensity and volume than responses for threshold and above-threshold stimuli. Volume of cortical activity during rectal distension in women was significantly higher than that for men for all distensions. We conclude that 1) there are substantial differences in female cortical activation topography during rectal distension compared with males; 2) intensity and volume of registered cortical activity due to rectal stimulation are directly related to stimulus strength; and 3) rectal stimulation below perception level is registered in the cerebral cortex.

Self-treatment of malaria in a rural area of western Kenya.

Reported are the results of a study of residents' knowledge about malaria and antimalarial drugs and of their treatment-seeking behaviour in a rural area of western Kenya. The study subjects were generally well-informed about the symptoms of the disease. Malaria was perceived as a relatively mild illness, much less severe than acquired immunodeficiency syndrome (AIDS), measles, difficulty in breathing, and diarrhoea. Self-treatment was extremely common: of 138 episodes of febrile illness, 60% were treated at home with herbal remedies or medicines purchased at local shops, and only 18% received treatment at a health centre or hospital; no treatment was sought by the remainder. Commercially available chloroquine preparations were perceived as more effective than either antipyretics or herbal remedies for the treatment of malaria, and injections were regarded as more effective than oral medications. 4-Amino-quinolines were used to treat 58% of febrile illnesses but in only 12% of the cases was a curative dose of > or = 25 mg/kg body weight employed. Even attendance at a health centre did not ensure adequate treatment because of the common practice of sharing medication among family members. Greatly increased attention should be paid to the role of home treatment of malaria when policies are being developed for the management of febrile illnesses in sub-Saharan Africa.

PIP: The results of a study of residents' knowledge about malaria and antimalarial drugs and of their treatment-seeking behavior in a rural area of western Kenya are reported. The investigation was conducted in 2 villages where malaria is holoendemic. Samples of 20-25 women were interviewed to discover their views about the main causes, symptoms, and treatments of malaria as well as measles, difficulty in breathing, and diarrhea. The study subjects were generally well-informed about the symptoms of the disease. Malaria was perceived as a relatively mild illness, much less severe than acquired immunodeficiency syndrome, measles, difficulty in breathing, and diarrhea. A total of 23 families completed an 8-week follow-up period, during which 230 separate illness episodes were reported. Only 23.1% of the patients who sought treatment did so at a health center, the remaining were treated at home. Most illnesses for which they sought treatment at a health center were self-diagnosed as malaria (82% vs. 60%; p 0.05). Self-treatment was extremely common: of 138 episodes of febrile illness, 60% were treated at home with herbal remedies or medicines purchased at local shops, and only 18% received treatment at a health center or hospital; no treatment was sought by the remainder. Commercially available chloroquine preparations were perceived as more effective than either antipyretics or herbal remedies for the treatment of malaria, and injections were regarded as more effective than oral medications. 4-aminoquinolines were used to treat 58% of febrile illnesses, but in only 12% of the cases was a curative dose of or= 25 mg/kg body weight employed. Even attendance at a health center did not ensure adequate treatment because of the common practice of sharing medication among family members. Increased attention should be paid to the role of home treatment of malaria when policies are being developed for the management of febrile illnesses in Sub-Saharan Africa.

Influence of transsphincteric fluid flow on spike burst rate of the opossum sphincter of Oddi.

In this study, we evaluated the effect of transsphincteric fluid flow on the rate of spike bursts in the opossum sphincter of Oddi (SO). For chronic studies in awake animals, bipolar electrodes were implanted on the SO, gastric antrum, duodenum, and jejunum. In group 1 animals, surgery was limited to electrode implantation. Subsequently, these animals underwent a cholecystectomy. Group 2 animals had electrode implantation without further surgery. In group 3 animals, bile flow was diverted around the SO, whereas in group 4 animals, pancreatic juice as well as bile was diverted around the SO. Multiple myoelectric recordings were obtained in each animal during fasting and after feeding. In fasted control animals, the rate of SO spike bursts showed cyclic increases synchronous with phase III of the duodenal migratory myoelectric complex. Feeding increased the rate of SO spike bursts. Cholecystectomy had no effect on SO spike bursts in fasted animals. Diversion of bile or bile and pancreatic juice around the SO did not alter the fasting pattern of SO spike bursts. However, flow diversion in the group 3 and group 4 animals did cause a modest decrease of SO spike bursts, from approximately 2/min to about 1/min, during phase I of the duodenal migrating myoelectric complex (p less than 0.05). Sphincter of Oddi spike-burst rate was not affected during the remainder of the migrating myoelectric complex cycle. Neither cholecystectomy nor flow diversion caused any change in the normal SO responses to feeding. Excitatory SO responses caused by motilin or by cholecystokinin-octapeptide were shown to be independent of changes in transsphincteric flow. We conclude that variations in transsphincteric flow cause only minimal alteration of the rate of spike bursts in the opossum SO during fasting. Therefore, factors other than transsphincteric flow, such as hormonal or neural influences, appear to be the major mechanism(s) that regulate the rate of SO contractions in awake opossums.

Biomechanics of cricopharyngeal bars.

Patients with a prominent cricopharyngeal bar visible on radiography are generally considered to have spasm of the cricopharyngeus, which is the major muscle component of the upper esophageal sphincter. This condition has been termed "cricopharyngeal achalasia." The aim of this study was to determine the pathogenesis of cricopharyngeal bars. Concurrent videofluoroscopic and manometric examinations of the pharynx and upper esophageal sphincter were performed in a cohort of six patients with prominent cricopharyngeal bars and in eight control volunteers. In each subject, swallows of 2-30-mL barium boluses were recorded. The patients with cricopharyngeal bars showed (a) normal peristaltic contraction in the pharynx, (b) normal axial upper esophageal sphincter pressure and relaxation, (c) normal flow rate across the upper esophageal sphincter, and (d) normal duration of upper esophageal sphincter opening for different bolus volumes. The major abnormalities in the patients with cricopharyngeal bars were (a) reduced maximal dimensions of the upper esophageal sphincter during the transsphincteric flow of barium and (b) increased intrabolus pressure upstream to the upper esophageal sphincter. Thus, the increase in intrabolus pressure preserved normal transsphincteric flow rates even though the upper esophageal sphincter did not open normally. Overall, the constellation of findings in the patients studied suggests that the underlying pathogenesis of their cricopharyngeal bar was reduced muscle compliance wherein the relaxed cricopharyngeus did not distend normally during swallowing.

Influence of bolus volume on swallow-induced hyoid movement in normal subjects.

Swallowing normally elicits a superior-anterior excursion of the hyoid that contributes to elevation of the larynx and opening of the upper esophageal sphincter. The magnitude of hyoid movements, however, has not been quantitated with respect to the volume of the swallowed bolus. In this study, we determined the magnitude of superior and anterior movements of the hyoid associated with swallows of barium of different volumes. Lateral videoradiographic images of 2- to 20-ml boluses of barium were obtained in 15 subjects who had no pharyngoesophageal symptoms and had normal pharyngoesophageal motor function. Analysis indicated that a significant direct correlation existed between the volume of the swallowed bolus and the magnitude of the superior and anterior movements of the hyoid. For example, the mean values for these respective movements were 13.0 +/- 5 mm and 13.5 +/- 6 mm for a 2-ml bolus, compared with 14.8 +/- 5 mm and 16.7 +/- 5 mm for a 10-ml bolus. The findings indicate that values of deglutitive movement of the hyoid need to be indexed to the volume of the swallowed bolus. The results imply that the neural program in the brainstem that generates the oral and pharyngeal phases of swallowing is not completely stereotyped, but rather is modulated by volume-dependent sensory feedback.

Sonographic measurement of gallbladder volume.

Sonographic images of the gallbladder enable satisfactory approximation of gallbladder volume using the sum-of-cylinders method. The sum-of-cylinder measurements, however, are moderately cumbersome and time consuming to perform. In this investigation, in vitro and in vivo testing was done to determine that a simple ellipsoid method applied to sonographic gallbladder images yields reasonable volume approximations that are comparable to the volumes calculated by the sum-of-cylinders method. Findings from a water-bath experiment showed that measurement of gallbladder volume by the ellipsoid method closely approximated the true volume with a mean difference of about 1.0 ml. The results of in vivo studies in five volunteers demonstrated that the gallbladder contracted substantially after a fatty meal and that volumes calculated by the ellipsoid and sum-of-cylinders methods were nearly identical. Thus, a simple ellipsoid method, requiring negligible time, may be used to approximate satisfactory gallbladder volume for clinical or investigative studies.

Fasting and postprandial hepatic bile flow in unanesthetized opossums.

In conscious opossums, we evaluated the relationship between hepatic bile flow and the intestinal motor function during fasting as well as after feeding. In six opossums, bipolar electrodes were implanted from the gastric antrum to the terminal ileum. After cholecystectomy, the common duct was ligated, and a catheter was tied into the proximal common duct for collecting hepatic bile. During subsequent studies, hepatic bile flow was measured, and bile was returned to the duodenum through an externalized duodenal catheter. Cyclic increases in bile flow during fasting did not show a close correlate with the duodenal migratory motor complex (MMC) cycle. Rather, bile flow showed peak values [0.11 +/- 0.02 (SE) ml/min] when phase III MMC activity reached the midileum. Hepatic bile flow correlated closely with the amount of bile acid secreted by the liver. When the bile acid pool was depleted by diverting bile from the intestine, hepatic secretion of bile fell to uniformly low values of approximately 0.04 ml/min that did not show cyclic variation. Hepatic bile flow after feeding increased to a maximal value of 0.12 +/- 0.01 ml/min at 90 min. We conclude that increases in hepatic bile flow during fasting and after meals are determined mainly by variations in intestinal motor activity that alter small bowel transit and thereby affect the enterohepatic circulation of bile acids.

Tipper and dipper types of oral swallows.

We characterized the normal patterns relating to the onset of the oral-swallowing phase in patients with normal oral motor function. The main pattern of swallowing was of the tipper type, in which swallowing is initiated with the tip of the tongue against the incisors and the bolus is in a supralingual position. However, a second pattern of a dipper-type swallow occurred, in which part of the bolus initially is positioned beneath the anterior part of the tongue. This circumstance requires that the tongue dip beneath the bolus in order to elevate the bolus above the tongue. Dipper swallows occurred in all age groups, but were more prevalent in subjects 60 years or older. Recognition of this component in normal swallowing patterns is essential for optimal evaluation of normal subjects and patients with an abnormal oral phase of swallowing.

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.

Effect of swallowed bolus variables on oral and pharyngeal phases of swallowing.

In this investigation, we studied the effects of bolus volume and viscosity on the quantitative features of the oral and pharyngeal phases of swallowing. Concurrent videofluoroscopic and manometric studies were done in 10 healthy volunteers who were imaged in lateral projection. Videofluorography was done at 30 frames/s while concurrent manometry was done with 5 intraluminal transducers that straddled the pharynx and upper esophageal sphincter (UES). Submental electromyography was recorded also. Swallows of 2-20 ml were recorded for low-viscosity liquid barium and high-viscosity paste barium. Analysis indicated that the major effect of increases in bolus volume was an earlier onset of anterior tongue base movement, superior palatal movement, anterior laryngeal movement, and UES opening. These events provide receptive adaptation for receiving a swallowed bolus. Earlier UES opening was associated with an increase in the duration of sphincter opening and sphincter diameter. The major effects of high bolus viscosity, unrelated to bolus volume, were to delay oral and pharyngeal bolus transit, increase the duration of pharyngeal peristaltic waves, and prolong and increase UES opening. Thus the specific effect of bolus viscosity per se differs substantially from that of bolus volume. We conclude that 1) specific variables of swallowing are affected significantly by the variables of the swallowed bolus, such as volume and viscosity; 2) overall, bolus volume and viscosity affect swallowing in a different manner; and 3) the study findings have implications about the neural control mechanisms that govern swallowing as well as about the diagnosis and treatment of patients with abnormal oral-pharyngeal swallowing.

Sonographic evaluation of resting gallbladder volume and postprandial emptying in patients with gallstones.

We investigated fasting gallbladder volume and gallbladder emptying in response to a fatty meal in 20 patients with asymptomatic gallstones and compared the results with findings from healthy controls. Compared with control subjects without gallstones, the majority of patients with gallstones exhibited a higher resting gallbladder volume, less fractional emptying after a fatty meal, and a higher postmeal residual volume. These abnormalities all appeared to stem from an abnormally high resting gallbladder volume. Whether the increased gallbladder volume and decreased postprandial fractional emptying in the gallstone patients represents a primary or secondary abnormality remains to be determined. The results suggest that in some patients decreased gallbladder contractility may contribute to gallstone development or proliferation.

Coordination of deglutition and phases of respiration: effect of aging, tachypnea, bolus volume, and chronic obstructive pulmonary disease.

The effects of aging, tachypnea, bolus volume, and chronic obstructive pulmonary disease on the coordination of swallowing with the phases of respiration were studied by concurrent respirography and submental surface electromyography. Study findings showed that in young healthy volunteers, during rest, there is preferential coupling of subconscious swallowing with the expiratory phase of continuous respiration. This preferential coupling of swallowing with expiration was found to increase relative to other phases of respiration during water swallows and tachypnea (P < 0.05). Respiratory phase occurrence of swallowing and postdeglutitive resumption of respiration during exacerbation of chronic obstructive pulmonary disease was found to be significantly different compared with the basal state (P < 0.05). Respiratory phase occurrence of subconscious swallowing in the elderly was found to be different from the young (P < 0.05). Position had no significant effect on the coordination of swallowing and phases of respiration. We concluded that in resting young volunteers the majority of deglutitions are coupled with the expiratory phase of swallowing. This coupling is increased in frequency by the presence of a liquid bolus and tachypnea. And finally, age and chronic obstructive pulmonary disease alter this coordination significantly.

Contraction pattern of opossum gallbladder during fasting and after feeding.

Our major aims in this study were to determine in unanesthetized opossums the gallbladder volume, pressure, and tone during fasting as well as after feeding, model the kinetics of changes in gallbladder volume, and correlate gallbladder contractility with concurrent spike burst activity in the upper gastrointestinal tract and sphincter of Oddi (SO). In 10 animals, we implanted electrodes on the gastric antrum, duodenum, SO, and jejunum. An indwelling catheter monitored gallbladder pressure and volume. In two animals, a force transducer sutured to the gallbladder wall monitored gallbladder tone. In each animal, fasting migrating myoelectric complexes (MMCs) were recorded in the stomach and small bowel. Cyclic changes in SO spike bursts occurred in synchrony with the MMCs. During fasting, gallbladder pressure, tone, and volume showed cyclic variations. During the second half of the duodenal MMC cycle, the gallbladder exhibited phasic as well as tonic contractions associated with net gallbladder emptying, whereas during the first half of the cycle the gallbladder relaxed and refilled. Minimal gallbladder volume during the MMC cycle averaged 4.8 +/- 0.7 (SE) ml compared with a maximal volume of 7.0 +/- 0.9 ml. Decreases in gallbladder volume occurred as an exponential function, whereas increases in gallbladder were linear. After feeding, the gallbladder underwent a sustained tonic contraction, without superimposed phasic contractions. Decreases in gallbladder volume occurred exponentially to a residual volume of 2.0 +/- 0.5 ml. Net postprandial gallbladder emptying was maximal by 40 min; then the volume remained unchanged for 2-3 h.(ABSTRACT TRUNCATED AT 250 WORDS)