The interstitial cells of Cajal and a gastroenteric pacemaker system.
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In spite of a claim by Kobayashi (1990) that they do not correspond to the cells originally depicted by CAJAL, a particular category of fibroblast-like cells have been identified in the gut by electron microscopy (Faussone-Pellegrini, 1977; Thuneberg, 1980) and by immunohistochemistry for Kit protein (Maeda et al., 1992) under the term of the "interstitial cells of Cajal (ICC)". Generating electrical slow waves, the ICC are intercalated between the intramural neurons and the effector smooth muscular cells, to form a gastroenteric pacemaker system. ICC at the level of the myenteric plexus (IC-MY) are multipolar cells forming a reticular network. The network of IC-MY which is believed to be the origin of electrical slow waves is morphologically independent from but associated with the myenteric plexus. On the other hand, intramuscular ICC (IC-IM) usually have spindle-shaped contours arranged in parallel with the bulk smooth muscle cells. Associated with nerve bundles and blood vessels, the IC-IM possess receptors for neurotransmitters and such circulating hormones as cholecystokinin, suggesting their roles in neuromuscular and hormone-muscular transmissions. In addition, gap junctions connect the IC-MY and IC-IM, thereby realizing the electrically synchronized integrity of ICC as a pacemaker system in the gut. The smooth muscle cells are also coupled with ICC via gap junctions, and the functional unit thus formed enables rhythmically synchronized contractions and relaxations. It has recently been found that a lack of Kit-expressing cells may induce hyper-contractility of the tunica muscularis in vitro, whereas a decrease in Kit expression within the muscle wall causes dysmotility-like symptoms in vivo. The pacemaker system in the gut thus seems to play a critical role in the maintenance of both moderate and normal motility of the digestive tract. A loss of Kit positive cells has been detected in several diseases with an impaired motor activity, including diabetic gastroenteropathy. Pathogenesis of these diseases is thought to be accounted for by impaired slow waves and neuromuscular transmissions; a pacemaker disorder may possibly induce a dysmotility-like symptom called 'gastroenteric arrhythmia'. A knowledge of the structure and function of the ICC and the pacemaker system provides a basis for clarifying the normal mechanism and the pathophysiology of motility in the digestive tract. (+info)
Exploring issues of quality of service in a Next Generation Internet testbed: a case study using PathMaster.
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This case study describes a project that explores issues of quality of service (QoS) relevant to the next-generation Internet (NGI), using the PathMaster application in a testbed environment. PathMaster is a prototype computer system that analyzes digitized cell images from cytology specimens and compares those images against an image database, returning a ranked set of "similar" cell images from the database. To perform NGI testbed evaluations, we used a cluster of nine parallel computation workstations configured as three subclusters using Cisco routers. This architecture provides a local "simulated Internet" in which we explored the following QoS strategies: (1) first-in-first-out queuing, (2) priority queuing, (3) weighted fair queuing, (4) weighted random early detection, and (5) traffic shaping. The study describes the results of using these strategies with a distributed version of the PathMaster system in the presence of different amounts of competing network traffic and discusses certain of the issues that arise. The goal of the study is to help introduce NGI QoS issues to the Medical Informatics community and to use the PathMaster NGI testbed to illustrate concretely certain of the QoS issues that arise. (+info)
Undergraduate basic science preparation for dental school.
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In the Institute of Medicines report Dental Education at the Crossroads, it was suggested that dental schools across the country move toward integrated basic science education for dental and medical students in their curricula. To do so, dental school admission requirements and recommendations must be closely reviewed to ensure that students are adequately prepared for this coursework. The purpose of our study was twofold: 1) to identify student dentists' perceptions of their predental preparation as it relates to course content, and 2) to track student dentists' undergraduate basic science course preparation and relate that to DAT performance, basic science course performance in dental school, and Part I and Part II National Board performance. In the first part of the research, a total of ninety student dentists (forty-five from each class) from the entering classes of 1996 and 1997 were asked to respond to a survey. The survey instrument was distributed to each class of students after each completed the largest basic science class given in their second-year curriculum. The survey investigated the area of undergraduate major, a checklist of courses completed in their undergraduate preparation, the relevance of the undergraduate classes to the block basic science courses, and the strength of requiring or recommending the listed undergraduate courses as a part of admission to dental school. Results of the survey, using frequency analysis, indicate that students felt that the following classes should be required, not recommended, for admission to dental school: Microbiology 70 percent, Biochemistry 54.4 percent, Immunology 57.78 percent, Anatomy 50 percent, Physiology 58.89 percent, and Cell Biology 50 percent. The second part of the research involved anonymously tracking undergraduate basic science preparation of the same students with DAT scores, the grade received in a representative large basic science course, and Part I and Part II National Board performance. Using T-test analysis correlations, results indicate that having completed multiple undergraduate basic science courses (as reported by AADSAS BCP hours) did not significantly (p < .05) enhance student performance in any of these parameters. Based on these results, we conclude that student dentists with undergraduate preparation in science and nonscience majors can successfully negotiate the dental school curriculum, even though the students themselves would increase admission requirements to include more basic science courses than commonly required. Basically, the students' recommendations for required undergraduate basic science courses would replicate the standard basic science coursework found in most dental schools: anatomy, histology, biochemistry, microbiology, physiology, and immunology plus the universal foundation course of biology. (+info)
Application of laser capture microdissection to cytologic specimens for the detection of immunoglobulin heavy chain gene rearrangement in patients with malignant lymphoma.
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BACKGROUND: The demonstration of the monoclonality of immunoglobulin heavy chain (IgH) gene rearrangement is an indispensable method for the diagnosis of B-cell lymphoma as well as histocytochemical analysis. For the detection of IgH gene rearrangement, the extraction of DNA from a homogenous cell population is necessary. Recently, the laser capture microdissection (LCM) technique was shown to isolate specific cells from histopathologic specimens for molecular analysis. However, to the authors' knowledge the applicability of LCM to cytologic specimens has not yet been well established. METHODS: Using LCM, a homogenous population of B-cell lymphoma cells as both histologic sections and cytologic specimens was captured, and genomic DNA was extracted from the captured cells. IgH gene rearrangement was analyzed by the polymerase chain reaction (PCR)-based single-strand conformational polymorphism (SSCP) method. RESULTS: Genomic DNAs were extracted successfully from ethanol-fixed cytologic specimens, but cells were not captured from air-dried specimens. Using PCR-SSCP analysis, the monoclonality of the IgH gene rearrangement was detected in five cases of tissue sections among nine analyzed cases of malignant lymphoma diagnosed immunohistochemically. However, analysis of the cytologic specimens with LCM demonstrated the monoclonality of the IgH gene rearrangement in seven cases of lymphoma. CONCLUSIONS: The results of the current study suggest that the novel application of LCM to cytologic specimens occasionally exhibits high sensitivity for the detection of IgH gene rearrangement monoclonality compared with the use of histologic sections. (+info)
Comparison of ThinPrep and conventional smears in detecting carcinoma in bile duct brushings.
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BACKGROUND: Bile duct brushing cytology is a common procedure for the exclusion of adenocarcinoma in the bile duct. The authors evaluated the use of ThinPrep (TP) to determine whether the information obtained is equivalent to that found with conventional smear cytology (CS). METHODS: Thirty-eight prospectively collected endoscope retrograde cholangiopancreatography-guided bile duct brushing samples were split in the following manner. First, two to four CS were prepared and immediately spray-fixed or wet-fixed. Second, the remaining sample was rinsed in PreservCyt (Cytyc Corp., Boxborough, MA). In the laboratory, one TP slide was prepared from each sample. TP and CS were stained by routine Papanicolaou stain. For the current study, TP and CS were reviewed independently by two cytopathologists. The diagnoses made by the two methods were compared with the final histology. RESULTS: The cytologic diagnoses for both TP and CS were categorized into five main groups: 1) unsatisfactory, 2) negative, 3) reactive, 4) suspicious for malignancy, and 5) malignant. The diagnoses on the 38 TP bile duct brushings and CS were categorized as follows: 1) unsatisfactory-2, 4; 2) negative-7, 4; 3) reactive-10, 14; 4) suspicious for malignancy-9, 9; and 5) malignant-10, 7, respectively. Histologic follow-up was available in 14 cases (reactive-4, suspicious for malignancy-1, and malignant-9). The sensitivity was 77% for TP and 66% for CS. The specificity was 100% for both methods. CONCLUSIONS: The two methods described in the current study detected equivalent disease on bile duct brushings. TP was found to provide better preservation and cytologic detail. However, the diagnostic criteria may require modification. (+info)
Some effects of the microtome knife and electron beam on methacrylate-embedded thin sections.
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A technique for the examination of specimens at low electron beam intensity has been presented. Sections micrographed with this technique showed numerous knife scratches and frequently contained bands running parallel to the knife edge. Banding with an average spacing of 0.2 micro appeared to result from periodic distortion produced by impact of the knife. At the beam intensities customarily employed, differential sublimation and probably flow of the methacrylate resulted in obliteration of the bands and all but the deepest knife scratches. In addition, changes in the size, shape, and orientation of certain structures were noted. Artifacts resulting from incineration or sublimation of tissue components fixed in formalin were illustrated, and the suggestion was made that such instability to the electron beam accounted in part for the differences observed in osmium- and formalin-fixed tissues. The deformation revealed in serial sections was discussed, and it was pointed out that shortening in the axis perpendicular to the knife edge was associated with elongation in the axis parallel to the cutting edge, the elongation usually occurring locally without change in the width of the section. It was noted that the material causing contamination of the surface of sections during examination exhibited no structure but caused progressive loss of contrast. (+info)
The isolation of a cell membrane fraction from rat liver.
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A procedure is described for isolating cell membranes from rat liver homogenates. 20 gm. of rat liver was homogenized in a Dounce homogenizer in ice cold water buffered to pH 7.5 with NaHCO(3), rupturing all of the cells and most nuclei. The diluted homogenate was filtered through cheesecloth to remove precipitated nucleoprotein and centrifuged at 1500 g, 10 minutes, to sediment a crude membrane fraction. The membrane containing sediment was recentrifuged 3 times in conical tubes (1220 g, 10 minutes), the top layer of the 2-layered sediment being retained. Flotation in a sucrose solution d = 1.22 freed the preparation from contaminating cell fragments and nuclear membranes not previously disintegrated. The floating material approximately 0.4 ml. was quite homogeneous and consisted of thin amorphous membranes. Electron micrographs revealed numerous double profiles similar in shape and dimensions to apposed liver cell membranes in intact tissue. (+info)
Phase contrast observations of the endoplasmic reticulum in living tissue cultures.
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Cells from three human sources (two malignant and one fetal) were observed through phase contrast microscopy to contain unusual cytoplasmic images. These were photographed and are discussed as representing the endoplasmic reticulum in the living cell. (+info)