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Biomedical subjects

C D Johnson

Publications and source records attributed to C D Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1997

Computed tomographic colography and virtual colonoscopy.

CT colography (CTC) is a powerful new approach to imaging the colorectum and a promising screening tool for the detection of colorectal neoplasia. From data generated by a helical CT scan, CTC uses virtual reality technology to produce highly discriminant two- and three-dimensional images that permit a thorough and minimally invasive evaluation of the entire colorectum. A dynamic CTC display technique from the endoluminal perspective, called cf2virtual colonoscopy,cf1 simulates colonoscopy by "flying" through the three-dimensional colon image. CTC offers potential advantages in diagnostic performance, safety, and patient acceptance over current screening approaches. Although early data suggest excellent colorectal polyp detection rates, this nascent technology will require rigorous clinical investigation and further refinements to assess adequately its place in the endoscopist's armamentarium.

Barium Sulfate↗
PubMed1997

Intermittent claudication should not be treated by surgery.

This debate examines the proposition that surgery is unnecessary or obsolete in the management of intermittent claudication. The case for this argument is that many patients have stable disease or respond well to conservative measures, that claudication is an expression of a systemic cardiovascular illness and that surgery can be replaced by endovascular techniques with equal success, and less disadvantage in the event of treatment failure. The case against the motion is that claudication is associated with repeated cycles of ischaemia and reperfusion, and that these contribute to excess cardiovascular mortality states and, furthermore, that surgery is the only option to relieve symptoms for many patients, especially those with distal disease.

Angioplasty, Balloon↗
PubMed1996

On the dominant rhythm in the discharges of single postganglionic sympathetic neurones innervating the rat tail artery.

1. In anaesthetized rats, using a focal recording technique, activity was recorded from single sympathetic postganglionic neurones innervating the caudal ventral artery of the tail. The following hypotheses were tested: (i) that the frequency of the dominant rhythmic discharge of the neurones can be different from the frequency of the central respiratory rhythm (as indicated by rhythmic phrenic discharge); and (ii) that the dominant sympathetic rhythm is not reliant on afferent feedback carried in aortic, sinus and vagus nerves. 2. Four types of preparation were used: spontaneously breathing (group 1), artificially ventilated (group 2), artificially ventilated with vagi cut (group 3), and artificially ventilated with vagus and sino-aortic denervation (group 4). 3. The frequencies of the dominant sympathetic rhythm under control conditions were: group 1, 0.91 +/- 0.12 Hz (mean +/- S.E.M., n = 5); group 2, 0.81 +/- 0.04 Hz (n = 18); group 3, 0.83 +/- 0.03 Hz (n = 17); group 4, 0.95 +/- 0.06 Hz (n = 11). The frequency of the dominant sympathetic rhythm was different from that of the phrenic rhythm in thirty-five out of fifty-one cases. 4. The mean frequency of the dominant sympathetic rhythm was not influenced significantly by hypocapnic apnoea. 5. Hyperthermia increased the frequency of the phrenic rhythm whilst decreasing that of the dominant sympathetic rhythm. 6. In all cases the frequency of the dominant sympathetic rhythm was different from that of the artificial ventilation cycle. 7. It is concluded that the frequency of the dominant sympathetic rhythm can be different from that of central respiratory drive and that it is not "driven' by afferent feedback relayed via sinus, aortic and vagus nerves. 8. It is proposed that the dominant sympathetic rhythm is unlikely to be generated by a central respiratory oscillator.

Animals↗
PubMed1996

A genetic selection for Caenorhabditis elegans synaptic transmission mutants.

We have isolated 165 Caenorhabditis elegans mutants, representing 21 genes, that are resistant to inhibitors of cholinesterase (Ric mutants). Since mutations in 20 of the genes appear not to affect acetylcholine reception, we suggest that reduced acetylcholine release contributes to the Ric phenotype of most Ric mutants. Mutations in 15 of the genes lead to defects in a gamma-aminobutyric acid-dependent behavior; these genes are likely to encode proteins with general, rather than cholinergic-specific, roles in synaptic transmission. Ten of the genes have been cloned. Seven encode homologs of proteins that function in the synaptic vesicle cycle: two encode cholinergic-specific proteins, while five encode general presynaptic proteins. Two other Ric genes encode homologs of G-protein signaling molecules. Our assessment of synaptic function in Ric mutants, combined with the homologies of some Ric mutants to presynaptic proteins, suggests that the analysis of Ric genes will continue to yield insights into the regulation and functioning of synapses.

Acetylcholine↗
PubMed1996

Neuronal localization of serotonin in the nematode Ascaris suum.

We have used immunocytochemical techniques to investigate the distribution of serotonin-like immunoreactivity in the nematode Ascaris suum. Antisera raised against serotonin (5-hydroxytryptamine, 5-HT) conjugated to bovine serum albumin (BSA) labelled a pair of neurons in the pharynx of both sexes and five cells in the ventral cord of the male tail. The labelling was blocked by 5-HT or by 5-HT conjugated to BSA. The 5-HT-immunoreactive cells in the pharynx resemble neurosecretory cells and are probably homologous to the neurosecretory motor neurons (NSM) in Caenorhabditis elegans; the cells in the male tail appear to be motor neurons that are homologous to CP neurons in C. elegans. Other cells that stain with 5-HT antisera have been observed in C. elegans but are not seen in Ascaris.

Animals↗
PubMed1996

Effect of cisapride on gallbladder emptying and plasma CCK in normal and vagotomized human subjects.

Previous studies have provided conflicting results of cisapride on gallbladder emptying in response to a meal. We studied six volunteers and six patients after a truncal vagotomy in a double-blind, placebo-controlled, prospectively randomized study using 10 mg cisapride four times a day for three days. Gallbladder volume was quantitated using ultrasonography, and plasma CCK levels were measured with a sensitive and specific radioimmunoassay using the DINO antibody before and for 90 min after a fatty, mixed meal. Plasma effect was observed on the gallbladder either in normal subjects or vagotomized patients. Paradoxically, residual volume (RV) was increased in the vagotomized patients after treatment with cisapride: RV cisapride 7.1 (4.1-15.9) ml, RV placebo 5.1 (3.8-14) ml, P < 0.05. Further work is required to clarify the mechanisms of action of cisapride on the gallbladder and the sphincter of Oddi. The use of cisapride during litholytic therapy may impair gallbladder emptying and delay stone clearance.

Adult↗
PubMed1996

Detection of colorectal polyps by computed tomographic colography: feasibility of a novel technique.

BACKGROUND & AIMS: Computed tomographic colography (CTC) represents a novel technique for colorectal polyp detection. A prospective study was undertaken to determine the optimal CTC scanning parameters based on an artificial colon model and to assess the feasibility of CTC to detect clinically significant colorectal polyps. METHODS: A colon model was scanned by helical computed tomography at multiple parameters. Reformatted two-dimensional and three-dimensional images were then graded for polyp detection and image quality. Subsequently, 10 patients with known colon polyps underwent CTC immediately before colonoscopy. The number of polyps detected by two radiologists using CTC were compared with colonoscopy results that served as the gold standard. RESULTS: The optimal scanning parameters in the colon model were 5-mm collimation, 5 mm/s table speed, and 1-mm reconstruction interval. Ten patients had 30 polyps (range, 0.2-2.0 cm) by colonscopy, and all polyps > or = 0.5 cm were adenomas. Polyp detection by CTC for both observers was 100% (5 of 5) > or = 1 cm, 71% (5 of 7) between 0.5 and 0.9 cm, and 11%-28% (2-5 of 18) < 0.5 cm. CONCLUSIONS: Based on this small, unblinded pilot study, CTC is feasible for colorectal polyp detection > or = 0.5 cm in diameter.

Aged↗
PubMed1996

Standardization of a technique for BrIDA cholescintigraphy.

Calculation of ejection fraction by cholescintigraphy is a well-established technique to quantify motor function of the gallbladder. All previous cholescintigraphic studies of gallbladder emptying have exclusively used the anterior projection for gallbladder visualization. This may lead to inaccuracies because attenuation of gamma rays may vary depending on the state of gallbladder filling and body habitus. The use of geometric means may prevent these errors. In this study, 7 health volunteers were examined after the administration of 150 MBq 99Tcm-bromotrimethyl-IDA (99Tcm-BrIDA) without any stimulus and 9 volunteers ingested a maxied, fatty meal 35-40 min after BrIDA injection. Imaging was done using a dualheaded camera in a dynamic study of 140 one-minute frames. A plateau of activity was reached between 70 and 90 min post-injection of BrIDA and between 55-60% of maximal counts were achieved in the gallbladder region of interest (ROI) between 35 and 40 min. Significant emptying was seen in all nine subjects after the meal. No significant difference in ejection fraction was seen between the anterior projection and the geometric mean of the data from the anterier and posterior projections. The slope of the gallbladder filling curve from the anterior camera data was different from that obtained from the geometric mean, but the correlation coefficient was not significantly different. In conclusion, adequate counts are achieved in the gallbladder ROI 35-40 min after BrIDA injection, when the stimulus can be administered to study gallbladder emptying. There is no advantage to imaging in the anterior and posterior projections and data obtained from the anterior projection alone are adequate for gallbladder emptying studies.

Adult↗
PubMed1996

Cystic lymphangioma of the pancreas.

Cystic lymphangioma of the pancreas is a rare condition. A 14-year-old girl presented with a cystic abdominal mass and abdominal pain. She was initially treated by biopsy and cyst drainage, and subsequently with partial excision of the cystic mass. The mass, which was a cystic lymphangioma involving the pancreas, recurred after each operation. Persisting symptoms led to a pylorus-preserving pancreatectomy and hepaticojejunostomy. Total excision is the only effective method of treating this benign tumour. The patient remains symptom free 2 1/2 years after pancreatectomy.

Adolescent↗
PubMed1996

Colorectal polyp detection with CT colography: two- versus three-dimensional techniques. Work in progress.

PURPOSE: To compare detection of colorectal polyps with two-dimensional (2D) computed tomographic (CT) colography only, three-dimensional (3D) CT colography only, and a combination of 2D and 3D CT colography. MATERIALS AND METHODS: A total of 11 computer-simulated polyps (1-10 mm) were placed randomly in five identical CT data sets for images of a 72-year-old man's polyp-free, rectosigmoid colon. Fifteen CT colographic data sets were produced: five with 2D CT images only, five with 3D CT images only, and five with 2D and 3D CT images. Two radiologists randomly, blindly, and independently evaluated all 15 data sets to detect the simulated polyps. RESULTS: No polyps 2 mm or smaller were detected. No statistically significant differences in the detection of colorectal polyps were found between the three techniques. However, the combination of 2D and 3D CT colography resulted in polyp detection rates that were greater than or equal to those of 2D or 3D CT colography alone. Flat polyps were more difficult to detect than sessile polyps. Five false-positive findings occurred with 2D CT colography. CONCLUSION: A combined display of 2D and 3D CT images likely provides the greatest rate of detection of colorectal polyps.

Aged↗
PubMed1996

Preventing factitious gingival injury in an autistic patient.

A 34-year-old man with a history of autism developed a deep gingival cleft. During clinical evaluation, the patient repeatedly scraped the affected area with his fingernail. The lesion's clinical features were consistent with focal inflammatory hyperplasia, periodontal disease and factitious stomatitis. This article describes the case and discusses diagnostic and behavioral issues important in treating any patient whose mental age is impaired.

Adult↗
PubMed1996

Celiac disease: how common is jejunoileal fold pattern reversal found at small-bowel follow-through?

OBJECTIVE: Celiac disease, or nontropical sprue, is a cause of mucosal malabsorption. A decreased number of jejunal folds and an increased number of ileal folds (jejunoileal fold pattern reversal) found at small-bowel follow-through have been reported for patients with celiac disease. We asked three questions regarding jejunoileal fold pattern reversal found at small-bowel follow-through in patients with celiac disease. (1) How often is it present, either partially or completely? (2) How often is it associated with other findings of malabsorption? (3) How reliably can it be distinguished from the normal pattern? MATERIALS AND METHODS: Twenty-eight small-bowel follow-through examinations performed on 25 adult patients with celiac disease (confirmed by characteristic small-bowel biopsy and clinical response to a gluten-free diet) were reviewed retrospectively by two authors, who agreed by consensus on partial or complete jejunoileal fold pattern reversal and on other findings of malabsorption. Two methods were used to control for retrospective bias. (1) The prospective and retrospective readings of fold pattern reversal were compared for agreement. (2) The author who had not participated in the retrospective review was asked to distinguish, on the basis of the presence or absence of fold pattern reversal, 24 cases of celiac disease (all of which showed partial or complete fold pattern reversal on retrospective review) from 25 normal control cases (patients with diarrhea) (conformed by normal small-bowel biopsy). RESULTS: Partial or complete jejunoileal fold pattern reversal was identified retrospectively in 24 of the 28 small-bowel examinations (86%) performed on patients with celiac disease. One-half lacked other findings of malabsorption. The prospective and retrospective readings of fold pattern reversal agreed in 21 of the 28 examinations (75%). Forty-four of 49 examinations (90%) were correctly identified by the third author on the basis of fold pattern reversal. CONCLUSION: In patients with celiac disease, partial or complete jejunoileal fold pattern reversal discovered at small-bowel follow-through is common, is often not associated with other findings of malabsorption, and can be reliably distinguished from the normal pattern. Identification of jejunoileal fold pattern reversal found at small-bowel follow-through should prompt an appropriate clinical evaluation for celiac disease.

Adult↗
PubMed1996

Variability of consecutive in vivo MR flow measurements in the main portal vein.

OBJECTIVE: The variability of consecutive cine phase-contrast MR flow measurements could significantly affect their use for clinical decisions, especially during provocative testing. The purposes of this study were to determine the normal variability of flow and consecutive flow measurements in the main portal vein on MR images and to determine how intraobserver variability, interobserver variability, and MR imager variability affect these measurements. SUBJECTS AND METHODS: MR flow measurements were acquired four consecutive times at the same location in the main portal vein of 12 subjects and three consecutive times at the same location in a nonpulsatile vessel model. All acquisitions were completed within 10 min. All main portal vein MR data sets were evaluated manually in a blinded review by two independent observers during three separate sessions spaced a mean of 4.5 weeks apart. Flow model data sets were evaluated during a single session by one observer. Variabilities were subsequently calculated by a components-of-variance analysis and by the coefficient of variation (SD/mean x 100). RESULTS: Of the total variance, 90% was due to flow variability among subjects (intersubject), 6% to flow variability within one subject (intrasubject), 2% to intraobserver variability, and 2% to interobserver variability. The coefficient of variation of consecutive MR portal vein flow measurements within a single subject was 11% +/- 5% (range, 3-23%). Intra- and interobserver variabilities were 5% +/- 2% (range, 1-11%) and 4% +/- 4% (range, 0-17%), respectively. MR imager variability was 1% +/- 1% (range, 0-2%). CONCLUSION: The mean variability of consecutive cine phase-contrast MR flow measurements in the main portal vein is 11% +/- 5% and could affect research and clinical protocols that employ this technique.

Adult↗
PubMed1996

Barium enema: detection of colonic lesions in a community population.

OBJECTIVE: The purposes of this study were to assess the prevalence of colonic lesions detected at barium enema in a community practice, to compare the findings at barium enema between patients who are asymptomatic and have no known risk factors for colorectal cancer (screening group) and patients who have symptoms of colonic disease or have known risk factors, and to determine if a questionnaire about symptoms and risk factors is an appropriate screening tool. SUBJECTS AND METHODS: A self-administered questionnaire about colorectal symptoms and risk factors was given to 1779 patients scheduled for barium enema examination. On the basis of their responses, patients were divided into three groups: screening group (asymptomatic, without risk factors), symptomatic, and asymptomatic with risk factors. Each patient underwent a fluoroscopic barium enema. We then compared the results (number, histologic type, size of lesion(s), location in the colon, and Patient's age) and risk factors among the three groups. RESULTS: At least one lesion within the colorectum was found in 166 (9%) of 1779 patients at combined proctosigmoidoscopy and barium enema. The prevalence of lesions in the 111 patients with at least one lesion above the rectum at barium enema was 4% (32 of 738) for the screening group, 8% (38 of 476) for asymptomatic patients with risk factors, and 7% (41 of 565) for symptomatic patients (p = .015 when comparing the prevalence in the screening group with the prevalences in the other two groups). Twenty-nine percent of all colonic lesions were found in the screening group. Among the asymptomatic patients, risk factors that included a history of colorectal polyps and advanced age were associated with a significantly higher prevalence of colonic polyps found at barium enema. In the symptomatic group, if patients with histories of polyps were excluded, we were unable to identify other risk factors that led to a significantly higher prevalence of polyps. CONCLUSION: Asymptomatic patients without known risk factors have a significantly lower prevalence of colonic polyps than either symptomatic patients or patients with risk factors alone. Despite this lower prevalence, 29% of all lesions in our series were in the screening group. Assessment of risk factors through a patient questionnaire was not helpful in identifying a group of patients with a higher prevalence of lesions--except for a history of polyps. Management decisions based on a patient questionnaire should be approached with caution. When low-risk patients are denied screening examinations, a significant number of lesions will be missed.

Aged↗
PubMed1996

Hepatic adenomatosis.

This case report describes a 41-year-old woman with hepatic adenomatosis (multiple hepatic adenomas) associated with acute hemorrhage. She had no history of oral contraceptive use or corticosteroid therapy. Ultrasonography showed multiple masses in the right lobe of the liver. The clinical associations and potential complications of hepatocellular adenomas are discussed, and the histologic characteristics are provided. Their typical appearance on computed tomography, ultrasonography, magnetic resonance imaging, and nuclear scintigraphy is described. The differential diagnosis of hepatic adenomatosis and multiple solid liver masses is discussed.

Adenoma, Liver Cell↗
PubMed1996

The lived experience of end-stage liver failure and liver transplantation.

This phenomenological study examined the lived experience of an individual who underwent end-stage liver failure and liver transplantation. The participant was asked to respond to the question, what was it like for you having experienced end-stage liver failure and liver transplantation? Permission was granted to tape-record the interview. Themes derived from the data analysis were identified, analyzed, and sorted. As a result, four categories were delineated: (1) uncertainty, (2) control, (3) social support, and (4) spirituality. Categories and themes contributing to a description of one individual's experience with end-stage liver failure and liver transplantation may provide direction for interventional studies designed to effect change in the lived experiences of those undergoing similar phenomena.

Fear↗