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Biomedical subjects

S M Collins

Publications and source records attributed to S M Collins.

At least 145 records · Page 8Linked to original sources
PubMed1988

The irritable bowel syndrome.

The irritable bowel syndrome (IBS) is an extremely common disorder. It is believed to occur usually after emotional stress and perhaps because of behavioural and dietary factors. There is definite evidence of disturbed gastrointestinal function associated with IBS; however, a diagnostic marker remains elusive. The current trend is to diagnose IBS on the basis of the patient's history and the findings at physical examination and after minimal investigation. The physician-patient relationship remains the most important factor in the management of IBS. Long-term benefit may be achieved with the use of dietary fibre supplements or stool-bulking agents. The evaluation of currently available drugs is difficult because of the placebo effect. Drug therapy should be aimed at specific symptoms and used mainly during the initial phase of treatment.

Colonic Diseases, Functional↗
PubMed1988

Influence of recording techniques on measurement of canine colonic motility.

The extent to which the established variability in colonic motility recordings is due to differences in recording techniques is not known. The aim of this study was to compare the ability of two intraluminal recording devices (perfused tube and tube mounted strain gauge) to record colonic motor activity against a reference device (serosal strain gauge). In six anesthetized dogs an intracolonic probe was positioned such that the component perfused tubes and tube mounted strain gauges were approximated to identical strain gauges mounted on the serosa. Contractions were induced by field stimulation and intraarterial injections of acetylcholine and carbachol. While both intraluminal devices demonstrated limitations in the detection of phasic and tonic motor events, perfused tubes detected a significantly greater proportion of tonic and phasic contractions than did strain gauges (P less than 0.001). Intraluminal strain gauges misrepresented 50% of tonic contractions (confirmed visually and by serosal strain gauges) as waveforms with negative polarity. This was not seen in recordings from perfused tubes. Perfused tubes represented tonic contractions as biphasic or bifid waveforms significantly less frequently than strain gauges (P less than 0.05). Radial asymmetry of colonic contractions is likely to account for these observed discrepancies. Recorded motility patterns are influenced by different recording techniques, and these differences are a source of variability in recorded patterns of colonic motor activity.

Acetylcholine↗
PubMed1988

Radiological appearance of migrating motor complex of the small intestine.

During fasting, a cyclical pattern of rhythmic peristaltic motor activity is known to occur in the small intestine. It is called the migrating motor complex (MMC), and periodically sweeps the small bowel of secretions. It is usually abolished by feeding. This report is the first description of an MMC observed during the fluoroscopic examination of a patient during a small bowel examination.

Fasting↗
PubMed1988

Sectional and segmental variability of left ventricular function: experimental and clinical studies using ultrafast computed tomography.

In this study, ultrafast computed tomography, a new high spatial and temporal resolution imaging system, was employed to define the range of sectional (tomographic) and segmental left ventricular function in 11 normal anesthetized dogs and 11 normal human volunteers. After intravenous infusion of contrast agent, multilevel tomographic images of the left ventricle (apex to base) were acquired at a rate of 17 frames/s. Analysis of these studies demonstrated substantial but predictable heterogeneity in left ventricular contraction from apex to base. In dogs and humans, for example, the average tomographic ejection fraction of the most basal level of the left ventricle was 40% less than that of the most apical level (p less than 0.05). In humans, circumferential segmental cavity contraction at the mid-papillary muscle level was relatively homogeneous (range 50 to 92% for 12 wedge-shaped segments around the tomographic circumference) if the reference system employed an endocardial centroid, but was less uniform if it used an epicardial centroid (range 22 to 98%). It is concluded that contraction of the normal left ventricle in dogs and humans is heterogeneous both between levels (apex to base) and within a single level (circumferential cavity contraction). However, the patterns of cavity contraction from apex to base and circumferential segmental cavity contraction within a given level as defined by ultrafast computed tomography are sufficiently narrow and predictable in normal individuals that these variables may be useful to define regional contraction abnormalities in pathologic conditions.

Adult↗
PubMed1988

Videodensitometric analysis of coronary stenoses. In vivo geometric and physiologic validation in humans.

Assessment of the severity of coronary stenoses on arteriograms conventionally is based on subjective estimates of percent luminal diameter narrowing. However, in studies in patients with multivessel coronary artery disease, we have found a poor correlation between percent stenosis and the physiologic significance of an individual coronary obstruction. The purpose of this study was to determine whether computerized videodensitometry would allow estimation of coronary luminal area and therefore prediction of the physiologic significance of individual coronary stenoses in humans. Videodensitometry was used to define the minimal luminal area of 15 left anterior descending, 15 circumflex, and 15 right coronary artery segments in 43 patients. Computer-assisted quantitative coronary arteriography (method of Brown et al) was used to determine the minimal luminal cross-sectional area of these same segments. In each arterial segment, coronary vasodilator reserve was assessed using intraoperative (n = 18 segments) or intracoronary (n = 27 segments) Doppler measurements of coronary vasodilator reserve. Videodensitometric estimates of coronary luminal area correlated well with minimal luminal area defined using the independent geometric technique of quantitative coronary arteriography (r = 0.82, y = 0.97 X + 0.71, SEE = 1.83 mm2, n = 45) and with lesion physiologic significance as defined by studies of the peak-to-resting velocity ratio (r = 0.71, 0.92, and 0.74 for the left anterior descending, circumflex, and right coronary arteries, respectively). Thus, videodensitometry is a promising method that may supplement geometric approaches to quantitative analysis of coronary arteriograms in humans.

Absorptiometry, Photon↗
PubMed1988

Increased responsiveness of jejunal longitudinal muscle in Trichinella-infected rats.

We examined in vitro changes in contractility of jejunal longitudinal muscle strips in rats infected with the nematode parasite Trichinella spiralis. Length-passive tension relationships were unchanged. However, muscle from infected rats on days 5 and 6 postinfection (PI) generated maximal active tension induced by carbachol at significantly less stretch (39.9 +/- 1.0 and 34.3 +/- 6.3%, respectively) than control tissues (66.0 +/- 2.3%). In infected rats on day 5 PI, the maximum tension generated by carbachol (1.6 +/- 0.4 g/mm2) and by 5-hydroxytryptamine (5-HTP) (2.6 +/- 0.1 g/mm2) was significantly greater than in control tissue (0.5 +/- 0.2 g/mm2). On removal of calcium from the medium, responses of muscle from control and infected rats were reduced in a proportionate manner. The increased responsiveness to carbachol and 5-HTP was maximal by day 5 PI and was associated with a decrease in the ED50 value for 5-HTP but not for carbachol. All changes were reversed by 23 days PI. These results indicate that T. spiralis infection in the rat is associated with alterations in jejunal longitudinal smooth muscle function.

Animals↗
PubMed1988

Characterization of receptors for calcitonin gene-related peptide on gastric smooth muscle cells.

Rat calcitonin gene-related peptide (rat CGRP) and related peptides did not cause contraction of gastric smooth muscle cells; however, preincubation with rat CGRP or human CGRP inhibited smooth muscle contraction caused by carbachol. Rat CGRP and human CGRP were equipotent in opposing contraction with a half-maximal effect produced by 0.1 nM, but rat calcitonin-adjacent peptide (rat CAP) and human calcitonin had no effect. Rat CGRP caused an increase in cellular adenosine 3',5'-cyclic monophosphate (cAMP) of 60%, which was augmented to 155% with 1 mM isobutyl methylxanthine (IBMX). IBMX did not influence the sensitivity of the muscle cells to rat CGRP to increase cAMP, the half maximal effect being produced by 0.4 nM in the presence or absence of IBMX. Rat CGRP and human CGRP were equipotent for stimulating cAMP, but rat CAP and human calcitonin had no effect. Binding of 125I-CGRP was temperature dependent, saturable, reversible, and specific. Rat CGRP and human CGRP were equipotent at inhibiting binding of 125I-CGRP and rat CAP, and human calcitonin did not inhibit binding. For rat CGRP and human CGRP, the dose-response curves for binding of 125I-CGRP were broad, and both peptides accelerated the rate of dissociation of bound 125I-CGRP. Computer analysis of dose-response curves demonstrated two classes of binding sites for CGRP, one with a high affinity (Kd 3 nM) and another with low affinity (Kd 3,700 nM). Our results indicate that CGRP interacts with previously undescribed receptors on gastric smooth muscle cells to increase cellular cAMP and inhibit contraction.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Antigen-induced contraction of jejunal smooth muscle in the sensitized rat.

We examined contractility of longitudinal muscle strips of jejunum from control rats and rats infected 34-85 days previously with Trichinella spiralis. Antigen prepared from T. spiralis larvae contracted muscle from previously infected but not control rats. Contraction was specific for the sensitizing agent because antigen from Nippostrongylus brasiliensis did not induce contraction. Contraction was resistant to atropine or tetrodotoxin but was inhibited by the 5-hydroxytryptamine (5-HT) antagonist cyproheptadine and by 5-HT desensitization. Neither histamine antagonists, diphenhydramine (H1-receptor antagonist) or ranitidine (H2-receptor antagonist), nor indomethacin, a prostaglandin synthase inhibitor, influenced the antigen response. In Trichinella-infected rats there was a significant increase in mast cell number in the muscle layers, and the contraction induced by T. spiralis antigen was inhibited by the mast cell stabilizer doxantrazole. In addition, anti-rat immunoglobulin E serum, compound 48/80, and concanavalin A each contracted muscles from rats previously infected with T. spiralis. These results are consistent with the hypothesis that T. spiralis infection leads to mast cell proliferation in the muscle layers and that subsequent exposure to antigen results in mast cell degranulation, 5-HT release, and contraction of smooth muscle.

Animals↗
PubMed1988

A comparison of cholecystokinin-induced changes in gastric emptying and feeding in rats.

We have compared the abilities of the cholecystokinin octapeptide (CCK-8) to delay gastric emptying and to influence feeding under similar experimental conditions in the rat. The effect of CCK-8 on gastric emptying was assessed in 6-h-deprived rats receiving 10-ml intragastric test loads of 0.15 M saline or 15% (wt/vol) sucrose. Analysis of half-emptying times indicated that intraperitoneal administration of CCK-8 in doses of 1.4-22.4 micrograms/kg produced a dose-dependent retardation of emptying of both saline and nutrient. Lower doses of CCK-8, 0.01 and 0.1 micrograms/kg, had no effect on gastric emptying. The effect of CCK-8 on feeding was assessed in normally feeding rats tested under the same experimental conditions used in the gastric emptying studies. Doses of CCK-8 capable of retarding gastric emptying also suppressed eating in a dose-dependent manner. These findings provide necessary correlational support for the hypothesis that the satiety produced by CCK-8 may be mediated by inhibition of gastric emptying. However, a further quantitative analysis of the correspondence of the gastric emptying and feeding effects of CCK-8 suggest that retardation of emptying cannot account entirely for the satiety effect of the peptide.

Analysis of Variance↗
PubMed1988

Videodensitometric analysis of human coronary stenoses: validation in vivo by intraoperative high-frequency epicardial echocardiography.

Videodensitometry is a nongeometric method of coronary angiographic analysis that can be used to provide an index of coronary luminal area. However, there are few direct studies in vivo of the relationship of videodensitometric data to independent measures of luminal area in humans. Although videodensitometry is theoretically independent of angiographic projection and luminal shape, validation of these assumptions in vivo is also limited. We therefore used intraoperative high-frequency epicardial echocardiography, a technique that can directly determine human coronary luminal area and shape in vivo, to further validate videodensitometry. A total of 36 arterial segments in the left anterior descending and right coronary arteries were studied by videodensitometry and high-frequency echocardiography. Videodensitometry was performed on angiograms in which the arterial segment of interest was not markedly foreshortened and was uniformly filled with contrast. In 22 discrete lesions (13 with circular lumens and nine with oval or complex lumens), videodensitometric and echocardiographic measures of luminal area correlated well (r = .86). In 33 coronary arterial segments, the effect of angiographic projection on videodensitometry was determined by comparison of the results of videodensitometry performed on left anterior oblique vs right anterior oblique angiograms of the segments. Here too, the correlation was good (r = .94, y = 1.04x + 0.002). The good correlation of left anterior oblique with right anterior oblique videodensitometric results held true for lesions with circular and oval or complex lumens. This study further validates the ability of videodensitometry to provide an index of coronary luminal area and confirms in vivo previous assumptions that the results of videodensitometric analysis are independent of angiographic projection and luminal shape.

Adult↗
PubMed1988

Small bowel and colonic permeability to 51Cr-EDTA in patients with active inflammatory bowel disease.

51Cr-EDTA was administered both orally and per rectum via a catheter to controls and to patients with inflammatory bowel disease. The patients were divided into two groups, either with active inflammation of the small bowel or with active inflammation of the colon. Fifteen patients with Crohn's disease of the small bowel and 19 patients with either Crohn's disease of the colon or ulcerative colitis were investigated. After oral administration of the probe, controls showed a median excretion of 1.17%/24 h of the dose compared to 3.47%/24 h by patients with small bowel disease and 6.07%/24 h by patients with colonic disease. After rectal administration, controls showed a median excretion of 0.74%/24 h of the dose compared to 0.93%/24 h by patients with small bowel disease and 5.73%/24 h by patients with colonic disease. The rectal test differentiated small bowel disease from colonic disease with an accuracy of 85%. The results confirmed the inflamed colon as a site of increased intestinal permeation.

Adult↗
PubMed1987

Quantitation in echocardiography.

Imaging of the heart is the predominant approach to cardiovascular diagnosis in current practice. Of the wide variety of cardiac imaging techniques available, echocardiography is one of the most widely used. Standard methods of quantitation of M-mode and two-dimensional echocardiograms yield reproducible, accurate measurements of cardiac chamber, wall, and great vessel dimensions. Qualitative analysis of valvular appearance and motion permits the diagnosis of a wide variety of valvular disorders. Doppler echocardiography yields information on blood flow velocity and pattern in the heart and great vessels. Evolving methods of quantitation in echocardiography include computerized image enhancement, computer-assisted border detection, analysis of regional left ventricular contraction, three-dimensional reconstruction, contrast-enhanced echocardiography, ultrasound myocardial tissue characterization, and intraoperative echocardiography. Echocardiography is a dynamic, evolving discipline with the potential of defining cardiac structure, function, blood flow dynamics, myocardial perfusion, and tissue characteristics. Thus, ultrasonography will continue to be of major importance in the diagnosis of cardiac disease.

Coronary Disease↗
PubMed1987

Patients with irritable bowel syndrome have greater pain tolerance than normal subjects.

A low tolerance for pain has been postulated as a factor in the expression of symptoms in patients with irritable bowel syndrome. This has been based on previous work demonstrating reduced intestinal thresholds for rectal pain induced by balloon distention in patients with irritable bowel syndrome. As the disease may alter the rectal response to distention, inferences regarding pain perception and reporting behavior cannot be drawn from these data. In this study, using electrocutaneous stimulation, we found that patients with irritable bowel syndrome had pain reporting behavior comparable to patients with Crohn's disease. Both patient groups were less likely than normals to report a noxious stimulus as painful. This suggests that pain perception and reporting is attenuated in patients with chronic abdominal pain and, accordingly, a generalized reduction in the threshold for reporting pain is not a factor in the expression of symptoms in the irritable bowel syndrome.

Abdomen↗
PubMed1987

Measurement of upper esophageal sphincter pressure. Effect of acute emotional stress.

Recent studies suggest that resting upper esophageal sphincter pressure is more labile than previously thought, being augmented during rapid manometric pull-through and markedly decreased during sleep and anesthesia. The effect of acute emotional stress on resting upper esophageal sphincter pressure was evaluated in 13 normal subjects with a manometric sleeve assembly. Manometric sideholes were positioned in the pharynx and cervical and thoracic esophagus while the sleeve sensor straddled the upper esophageal sphincter. Subjects were stressed intermittently by 14-min periods of a dichotic listening task. As incentive, a financial reward was offered and made commensurate with performance. Alterations of heart rate, blood pressure, and skin conductance confirmed the effectiveness of the stressor. The overall mean upper esophageal sphincter pressure during control periods was 46.5 mmHg (SEM = 4.7). During stress there was a significant mean increase (11.8 +/- 2.9 mmHg; p = 0.002) in upper esophageal sphincter pressure from control levels, and the pressure increase during the first 2-min epoch of stress was 20.8 +/- 3.9 mmHg (p = 0.0003). Emotional stress causes significant elevation of upper esophageal pressure in normal subjects. This effect is likely to influence resting sphincter pressure measurements, particularly if measurement conditions are stressful to the subject.

Acute Disease↗
PubMed1987

A procedure for within-trial repeated measurement of gastric emptying in the rat.

A double sampling procedure, developed originally for investigation of liquid phase gastric emptying in humans, is adapted for use in the rat. The double sampling technique permits repeated measurement of gastric volume, allowing a determination of a time course of emptying in a single experimental session. Further, the method allows determination of the amount of gastric secretion, volume emptied into the intestines, and amount of initial gastric load remaining in the stomach. Experiments are presented which: demonstrate the utility of the technique; validate its accuracy in determining gastric volume; indicate the stability of measurements obtained with this procedure; and indicate a procedure for quantitative evaluation of data obtained with this technique. The limitations of the double sampling method are also discussed.

Animals↗
PubMed1987

Computers in cardiac imaging.

Imaging has become a widely used technique for the evaluation of cardiac disease. Computer technology and techniques have had an enormous impact on many of the available cardiac imaging methods. These methods include echocardiography, digital angiography, radionuclide imaging, X-ray computed tomography and nuclear magnetic resonance imaging. Computers have performed a number of functions in these cardiac imaging methods, including image acquisition, formation, management, display, enhancement and analysis. This article describes each of these roles that computer technology and techniques currently play in cardiac imaging and concludes with an assessment of the impact that computers have had on the various cardiac imaging methods.

Cardiology↗