Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Segmentation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources
PubMedDate not supplied

Prognostic implication of ST-segment resolution following primary percutaneous transluminal coronary angioplasty for ST-elevation acute myocardial infarction.

BACKGROUND: ST-segment changes have been shown to correlate with myocardial tissue perfusion. Complete ST-segment resolution after thrombolysis in acute myocardial infarction is associated with lower mortality and better left ventricular function. Primary percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction restores better epicardial coronary flow to the infarct-related artery than thrombolysis. However, ST changes may persist and flow can remain poor despite a patent vessel. AIM: To examine the prognostic implication of ST-segment resolution immediately following primary and rescue PTCA for ST-elevation acute myocardial infarction (STEMI). METHODS: Records of 201 consecutive primary and rescue PTCA performed at Westmead Hospital for STEMI from January 2000 to December 2001 were reviewed. ST-segment elevation (taken 20 ms after the end of the QRS complex) was measured immediately before and after the procedure. ST-segment resolution of greater than 70% after the procedure was considered as -'complete' ST-segment resolution, whereas ST-segment resolution of less than 70% was considered as 'incomplete' ST-segment resolution. RESULTS: Of the 201 patients, 117 (58%) had complete ST-elevation resolution and 84 (42%) did not. There was a significant difference in survival free of major adverse cardiovascular events; 60% of those with complete ST-segment resolution were event-free at 2 years compared with 35% of those patients without complete ST-segment resolution. CONCLUSION: ST-segment resolution after primary and rescue PTCA for STEMI is associated with significantly higher event-free survival. The goal of primary angio-plasty should be the restoration of normal epicardial flow with normalization of ST-segments.

Angioplasty, Balloon, Coronary↗
PubMed1993

Axonal projections and synaptic connections of C5 segment expiratory interneurones in the cat.

1. Respiratory interneurones in the C4-C6 segments of the spinal cord have only recently been described; until now their projections and connections were not known. We investigated expiratory interneurones in the C5 spinal segment, using antidromic mapping to trace their projections and spike-triggered averaging to test their synaptic connections with phrenic motoneurones. 2. A total of seventy expiratory interneurones were recorded in nineteen cats anaesthetized with pentobarbitone, paralysed and ventilated. The interneurones were found scattered dorsomedial to the phrenic motor nucleus, with discharge patterns of a constant (66%), augmenting (24%) or decrementing (10%) type. 3. Interneurone axons were found in the ipsilateral ventrolateral funiculus using antidromic activation at thresholds < 20 microA. The axons of eighteen of thirty-three interneurones tested (55%) were found to extend to the rostral part of the C6 segment, seventeen of thirty-three (52%) to the caudal part of the C6 segment and ten of nineteen (53%) to the rostral part of the C7 segment. 4. Axon collaterals for thirteen of thirty-three interneurones (39%) were found in the ipsilateral half of the C6 segment, with their endings near the phrenic motor nucleus. In three cases two collaterals were found. None of the interneurones had projections in the contralateral halves of the C5 or C6 segments. 5. In a separate group of thirty-four expiratory interneurones, antidromic mapping was used to find an axon collateral in the C6 segment prior to spike-triggered averaging. Eleven of these interneurones had collaterals (32%) and were subsequently tested for synaptic connections to thirty-two phrenic motoneurones. In three separate instances (9%), inhibitory postsynaptic potentials were observed. Amplitudes, fall times and half-amplitude widths of the inhibitory postsynaptic potentials were 6.7, 10.4 and 10.6 microV; 0.3, 0.5 and 0.7 ms and 0.6, 1.6 and 3.3 ms respectively. 6. We conclude: (i) there is a population of expiratory interneurones in the C5 segment, located predominantly dorsomedial to the phrenic motor nucleus; (ii) at least one-half of these interneurones have ipsilateral intersegmental projections to the C6 segment and (iii) although synaptic connections from expiratory interneurones in the C5 segment to phrenic motoneurones in the C6 segment may be rare, the observed inhibitory postsynaptic potentials had fall times and latencies commensurate with monosynaptic connections.

Animals↗
PubMed2004

Relation between different methods for analysing ST segment deviation and infarct size as assessed by positron emission tomography.

OBJECTIVE: To study the relation between resolution of ST segment deviation and infarct size using positron emission tomography. METHODS: 45 patients with ST segment elevation acute myocardial infarction treated with thrombolysis or percutaneous coronary intervention were studied prospectively. An ECG was taken before and at (mean (SD)) 100 (45) min after reperfusion therapy. ECGs were analysed by three methods. Residual ST segment deviation, obtained from the ECG immediately after completion of reperfusion therapy, was defined by summation for each of the three methods. Relative resolution of ST segment deviation was defined as the absolute resolution divided by the ST segment deviation score at baseline x 100 (%). After 29 (14) hours, myocardial blood flow was measured with 13NH3. For each patient, the regions with a myocardial blood flow < 80% of normally perfused myocardium ( = hypoperfusion) and < 50% ( = no reflow) were automatically delineated. RESULTS: Substantial differences were found between different ECG analysis methods. There were moderate correlations between the area with myocardial hypoperfusion and ST segment deviation scores at baseline and after reperfusion therapy. After reperfusion therapy, residual ST segment deviation in the single lead with maximum ST segment deviation was as good at discriminating between tertiles of myocardial damage as summed ST segment elevation. Relative ST segment resolution did not discriminate between different degrees of myocardial damage. CONCLUSIONS: In the individual patient, residual ST segment deviation after reperfusion in the single lead with maximum ST segment deviation is at least as good as summed ST elevation in predicting final myocardial damage.

Angioplasty, Balloon, Coronary↗
PubMed1983

Force-length relations in cardiac muscle segments.

Using a new technique that measures the length of a segment in the central region of isolated papillaries, we have determined the force-segment length relation for ferret papillary muscles at 27 degrees C. The muscles contracted under muscle length isometric (auxotonic) and segment isometric conditions in physiological solutions containing 9.0, 4.5, 2.25, and 1.125 mM Ca2+. Force-segment length relations obtained from auxotonic and segment isometric contractions were identical in a given Ca2+ concentration. Calcium variations, however, changed the position, shape, and segment length intercept of the force-segment length relation. Force, at a given segment length, increased with increasing Ca2+ up to 9.0 mM Ca2+. The force-segment length relation changed shape from linear, in 4.5 mM Ca2+, to concave in 1.125 mM Ca2+. The segment length intercept was found by extrapolation to be 68, 69, and 74% SLmax in 4.5, 2.25, and 1.125 mM Ca2+, respectively. Two passive force corrections were used to calculate the developed force-segment length relations. Assuming passive force to be related primarily to segment length yields curves that change shape with Ca2+ concentration, suggesting length-dependent activation. On the other hand, assuming passive force to be related to muscle length results in curves for different Ca2+ concentrations that are nearly vertically shifted versions of each other, suggesting the influence of internal loads.

Animals↗
PubMed1998

Association of kinesin with microtubules in diverse cytoskeletal systems in the outer segments of rods and cones.

The membranous outer segments of vertebrate photoreceptors are supported by cytoskeletons consisting of microtubules and associated proteins, which occur as the ciliary axoneme in rods and cones, and as a separate cytoskeletal system at the incisures of rod outer segments. We performed an immunocytochemical study of the cytoskeleton in photoreceptors isolated from amphibian retinas and found that immunoreactivity to the heavy chain of the motor protein kinesin was closely associated with the microtubules in each of these outer segment cytoskeletal systems. In the outer segments of cones, kinesin heavy chain immunoreactivity was confined to a streak at the axoneme that extended to the outer segment tip. In the outer segments of rods, kinesin heavy chain immunoreactivity was found as both a short streak at the axoneme and a series of long parallel lines that coincided with the microtubules at rod outer segment incisures. Our findings constitute the first report of kinesin in the axoneme of cones and at the incisures of rods. Closely associated with microtubules, kinesin in photoreceptor outer segment axonemes and at rod outer segment incisures can transport materials longitudinally along the microtubules and/or connect these with each other and/or with other components. Because these cytoskeletal systems differ in fundamental ways, kinesin can play different roles in each case, e.g., kinesin at rod outer segment incisures can have structural and functional roles that are unique to rods. These findings may have clinical relevance because similar cytoskeletal systems are expected to occur in the outer segments of human photoreceptors; thus, a disturbance involving kinesin in the cytoskeletal systems at photoreceptor axonemes and/or at rod outer segment incisures could interfere with the normal structure and function of photoreceptors and contribute to human photoreceptor degenerations.

Animals↗
PubMed1988

Arterial segmentation and subsegmentation in the human spleen.

The segmental nature of the arterial tree of the human spleen was analyzed in 181 subjects of both sexes, who had died of various accidental causes. Based on the observation of the pattern of the terminal and polar splenic branches, selective arteriographs and corrosion casts, and taking account of the ideas reported in the literature, we proposed that the spleen is divided in arterial segments and subsegments. Segments are the territories corresponding to both the primary branches of the splenic artery (primary segments) and the polar arteries (polar segments). In 92.82% of the cases there are two primary segments and in 7.18% three primary segments. Associated to these, in 29.28% there is a superior polar segment, in 44.75% an inferior polar segment, and in 10.49% both superior and inferior polar segments are present. Thus, the number of segments varies from two to five. Occasionally, two or three inferior polar segments can be present. Subsegments are the territories corresponding to the extrasplenic subdivisions of the primary branches and the polar arteries. According to the number of arterial subdivisions, the subsegments can be of second, third, fourth, fifth or sixth order. The last branches of the splenic artery (penetrating arteries) are all subsegmentary in nature and supply hilar or polar subsegments. Anastomoses between extrasplenic branches of the splenic artery were observed in 19.89% of the cases. Sometimes, thin anastomotic bridges could be observed between arterial splenic compartments.

Angiography↗
PubMed1982

Epicardial mapping of segmental myocardial function: an echocardiographic method applicable in man.

A technique for epicardial mapping of segmental myocardial function at multiple sites over both right and left ventricles was developed using a high-resolution, 7.5-MHz, short-focus, miniaturized, M-mode echocardiographic transducer worn on the fingertip. Myocardial function was determined from the extent and time course of systolic thickening and diastolic thinning at each site mapped. The technique was characterized in an open-chest canine model of myocardial ischemia. Ischemia was induced by transient or permanent coronary occlusion in 17 dogs. Acute occlusions produced reduced segmental thickening within 10-15 seconds and, often, overt systolic thinning of ischemic myocardium. Rhodamine fluorescence perfusion maps were compared with echocardiographic maps in nine dogs. Segmental thickening was reduced in perfused segments adjacent to, but not involved by, ischemia, as well as ischemic segments. Reproducibility appeared satisfactory for quantitative analysis of grouped data on multiple segments, and qualitative analysis in individual segments. Initial human studies performed during coronary bypass surgery in 11 subjects showed echocardiographic abnormalities in the six patients with ventriculographic abnormalities and in four with normal ventriculograms. Transmural infarctions were akinetic, showing no change in thickness throughout the cardiac cycle. Hypokinetic segments distal to high-grade coronary stenosis were common, although most segments distal to stenosis contracted normally. Reversal of segmental contraction abnormalities by coronary bypass grafting was shown in three subjects, while worsening of function was seen in previously abnormal segments in two and in a previously normal segment in one subject. Epicardial echocardiographic mapping is a practical method for intraoperative assessment of myocardial function during coronary surgery in man that may enhance our understanding of the pathophysiology of coronary disease and the effects of coronary surgery.

Animals↗
PubMed1979

Functional characterization of left ventricular segmental responses during the initial 24 h and 1 wk after experimental canine myocardial infarction.

Characterization of the temporal evolution of resting segmental function and inotropic reserve after coronary occlusion may be important in evaluating attempts to salvage ischemic but non-necrotic myocardium. Accordingly, we chronically implanted up to six pairs of pulse-transit piezoelectric crystals in the left ventricular myocardium of dogs to measure segmental wall thickness. Segments were separated into groups according to the loss of net systolic thickening (NET) at 5 min postocclusion of the left anterior descending coronary artery in awake, unsedated dogs. Group 1 included segments with NET values of 67--100+ (percent control); group 2 between 67 and 0; and group 3 less than 0 (paradoxical motion). 5 min after coronary occlusion, group 1 NET was 92 +/- 5% (SEM) although significant decreases occurred in NET in group 2 (36 +/- 4%) and group 3 segments (-33 +/- 5%). Between 5 min and 24 h after coronary occlusion, no further significant changes occurred in NET in groups 1, 2, and 3 crystals. Some segments underwent further functional deterioration between 24 h and 1 wk after left anterior descending coronary artery occlusion, although no overall change occurred in segments with mild to moderate ischemic dysfunction. Segments with NET less than 0 at 24 h, on the other hand, exhibited a reduction in aneurysmal bulging between 24 h and 1 wk from -41 +/- 10 to -23 +/- 11% (n = 12, P = 0.02). Inotropic reserve was assessed with postextrasystolic potentiation (PESP) in 14 dogs, and with infusions of dopamine (11 dogs), and isoproterenol (13 dogs). PESP was the most potent intervention and produced a significant augmentation in NET in group 2 crystals at 1, 2, 4, 6,8, and 24 h after coronary occlusion but only at 1 and 2 h in NET in group 3 crystals. Thus, following experimental coronary occlusion, the evolution of ischemic segmental dysfunction is dynamic and variable. A significant degree of inotropic reserve, as assessed by PESP, dopamine, and isoproterenol, exists in segments with moderate ischemic dysfunction for 24 h but for only 2 h after coronary occlusion in those segments with the most severe ischemic dysfunction. In addition, at least some segmental sites with mild to moderate ischemic dysfunction at 24 h deteriorate further between 24 h and 1 wk after experimental coronary occlusion.

Animals↗
PubMed2003

Development of the Drosophila genital disc requires interactions between its segmental primordia.

In both sexes, the Drosophila genital disc comprises three segmental primordia: the female genital primordium derived from segment A8, the male genital primordium derived from segment A9 and the anal primordium derived from segments A10-11. Each segmental primordium has an anterior (A) and a posterior (P) compartment, the P cells of the three segments being contiguous at the lateral edges of the disc. We show that Hedgehog (Hh) expressed in the P compartment differentially signals A cells at the AP compartment border and A cells at the segmental border. As in the wing imaginal disc, cell lineage restriction of the AP compartment border is defined by Hh signalling. There is also a lineage restriction barrier at the segmental borders, even though the P compartment cells of the three segments converge in the lateral areas of the disc. Lineage restriction between segments A9 and A10-11 depends on factors other than the Hh, En and Hox genes. The segmental borders, however, can be permeable to some morphogenetic signals. Furthermore, cell ablation experiments show that the presence of all primordia (either the anal or the genital primordium) during development are required for normal development of genital disc. Collectively, these findings suggest that interaction between segmental primordia is required for the normal development of the genital disc.

Animals↗
PubMed1993

Mismatched vascular defects. An easy alternative to mismatched segmental equivalent defects for the interpretation of ventilation/perfusion lung scans in pulmonary embolism.

The purpose of this investigation was to test the hypothesis that ventilation/perfusion (V/Q) lung scans in patients with suspected acute pulmonary embolism (PE) can be evaluated on the basis of the total number of mismatched vascular defects, irrespective of whether such defects are moderate or large size segmental defects. Lung scan data from the national collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) were assessed in 383 patients with acute PE and 681 patients in whom suspected PE was excluded. The predictive value of the cumulative number of mismatched moderate size segmental defects (irrespective of the number of mismatched large segmental defects) was nearly the same as that of mismatched large segmental defects (irrespective of the number of mismatched moderate size segmental defects). This suggests that the diagnostic value of mismatched moderate size segmental defects is the same as mismatched large segmental defects. Lung scans evaluated on the basis of the number of mismatched vascular defects (moderate and/or large segmental defects) were compared with V/Q scans evaluated on the basis of the number of mismatched segmental equivalents. The maximum likelihood estimates of the areas under the receiver operating characteristic (ROC) curves for the number of mismatched vascular defects and for mismatched segmental equivalents were similar (0.8512 vs 0.8530) (NS). Stratification according to the presence or absence of prior cardiopulmonary disease permitted a more accurate assessment of both clinical groups. Evaluation of V/Q scans by vascular defects and by segmental equivalents showed similar areas under the ROC curves. In conclusion, the number of mismatched vascular defects is as powerful for the assessment of V/Q scans as the number of mismatched segmental equivalents. The number of mismatched vascular defects, however, is easier to interpret, and permits a more objective evaluation.

Humans↗
PubMed2003

Dobutamine-induced ST-segment elevation associated with a biphasic response of wall motion in patients with a recent myocardial infarction is caused by myocardial ischaemia and is abolished by revascularization of the infarct-related artery.

OBJECTIVE: ST-segment elevation is frequently induced by dobutamine in patients with a recent myocardial infarction and may represent dyskinesia of the infarcted region or myocardial viability and ischaemia. Revascularization of the infarct-related artery may abolish myocardial ischaemia, and thus represents a useful tool to verify the significance of this finding. The aim of this study was to assess the relation between ST-segment elevation and wall motion response during dobutamine echo stress test and to evaluate the effect of coronary revascularization with percutaneous coronary angioplasty of the infarct-related artery on stress test results. METHODS AND RESULTS: Twenty-two patients (17 men; mean age 58+/-12 years) with a first acute myocardial infarction (5 anterior (23%) and 17 (77%) inferior) who showed ST-segment elevation during a dobutamine echo stress test performed early (7+/-5 days) after the acute event where included in the analysis. All patients underwent coronary arteriography followed by percutaneous revascularization with coronary angioplasty or atherectomy with or without stenting of the culprit lesion and a second dobutamine echo stress test at a mean of 40+/-20 days after revascularization. The minimal lumen diameter increased from 0.63+/-0.36 to 3+/-0.44 mm and % diameter stenosis decreased from 80+/-11 to 12+/-7 after revascularization. At baseline evaluation there were 62 normal moving segments (34%), 57 (32%) akinetic and 62 (34%) hypokinetic segments within the area at risk. Maximal ST-segment shift changed from a basal mean value of 0.41+/-0.6 to a peak value of 2.15+/-0.9 mm; angina developed in 6/22 patients (22%). A biphasic response to dobutamine indicative of myocardial ischaemia within the infarcted area was observed in 20/22 patients (91%) and in 54/74 (73%) segments showing wall motion abnormalities. After revascularization of the infarct-related artery 78 (43%) segments were considered to be normal, 46 (25%) akinetic and 57 (32%) hypokinetic. Dobutamine-induced ST-segment elevation in 6/22 cases (27%), but the amount of ST-segment shift at peak stress was significantly reduced (from 2.15+/-0.9 to 0.30+/-0.5 mm) and angina was present in 1 patient only (5%) despite a significant increase of double product compared to the pre-revascularization test (from 17,348+/-3536 to 21,005+/-4105, p < 0.003). At echocardiographic analysis, ischaemia involved only 4 segments (2%), 3 of them showing the persistence of a biphasic response to dobutamine. CONCLUSIONS: In patients with a recent myocardial infarction and no baseline dyskinesia dobutamine-induced ST-segment elevation in the infarct-related leads is usually associated with a biphasic response of wall motion within the infarcted region and may be considered an ancillary sign of myocardial ischaemia because it is abolished in the great majority of cases by successful revascularization of the infarct-related artery.

Adrenergic beta-Agonists↗
PubMed2004

Accelerated spondylotic changes adjacent to the fused segment following central cervical corpectomy: magnetic resonance imaging study evidence.

OBJECT: The authors studied whether cervical spine motion segments adjacent to a fused segment exhibit accelerated degenerative changes on short-term follow-up magnetic resonance (MR) imaging. METHODS: Preoperative and short-term follow-up (mean duration 17.5 months, range 10-48 months) cervical MR images obtained in 44 patients who had undergone one- or two-level corpectomy for cervical spondylotic myelopathy were evaluated qualitatively and quantitatively. The motion segment adjacent to the fused segment and a segment remote from the fused segment were evaluated for indentation of the thecal sac, disc height, and sagittal functional diameter of the spinal canal on midsagittal T2-weighted MR images. Thecal sac indentations were classified as mild, moderate, and severe. New indentations of the thecal sac of varying severity (mild in 17 patients [38.6%], moderate in 10 [22.7%], and severe in six [13.6%]) had developed at the adjacent segments in 33 (75%) of 44 patients. The degenerative changes were seen at the superior level in 11 patients, inferior level in 10 patients, and at both levels in 12 patients and resulted from both anterior and posterior element degeneration in the majority (23 [69.6%]) of patients. The remote segments showed mild thecal sac indentations in seven patients and moderate indentations in two patients (nine [20.5%] of 44). Compared with the changes at the remote segment, the canal size was significantly decreased at the superior adjacent segment by 0.9 mm (p = 0.007). No patient sustained a new neurological deficit due to adjacent-segment changes. CONCLUSIONS: On short-term follow-up MR imaging, levels adjacent to the fused segment exhibited more pronounced degenerative changes (compared with remote levels) in 75% of patients who had undergone one- or two-level central corpectomy.

Adult↗
PubMed2001

Time-domain analysis of exercise-induced ST-segment elevation in Q-wave myocardial infarction: a useful tool for the screening of myocardial viability.

BACKGROUND: Exercise-induced ST-segment elevation in Q-wave leads has been traditionally associated with passive stretching of the infarct wall, perinecrotic ischemia and, according to recent scintigraphic studies, with myocardial viability. At present, however, no definitive conclusions are available. We evaluated the potential role of a time-domain analysis of exercise-induced ST-segment elevation for the identification of viable myocardium and residual ischemia in patients with previous Q-wave myocardial infarction. METHODS: Sixty patients with a previous Q-wave myocardial infarction underwent a bicycle exercise stress test, dobutamine stress echocardiography, coronary arteriography and left ventriculography. RESULTS: Patients with exercise-induced ST-segment elevation in Q-wave leads (n = 36) showed more severe impairment of resting left ventricular function, when evaluated in terms of wall motion score index at echocardiography (1.62 +/- 0.33 vs 1.41 +/- 0.22, p < 0.01) and in terms of wall motion score at ventriculography (5.9 +/- 1.6 vs 4.1 +/- 1.5, p < 0.03), compared to patients without ST-segment shift (n = 24). No differences between the two groups were seen in the severity and extension of coronary artery disease. The two groups of patients did not differ in the overall incidence of viability (50% in patients with vs 62% in those without ST-segment elevation, p = NS) and homozonal ischemia (39 vs 26%, p = NS), when evaluated with dobutamine echocardiography. However, a time-domain analysis of the ST-segment changes during exercise showed that the duration of exercise up to 0.1 mV ST-segment elevation was significantly lower in patients with viability (6.2 +/- 3.3 min) than in those without (10.2 +/- 2.2 min) (p < 0.001). Accordingly, ST-segment elevation occurred within 3 and 6 min of exercise in 7/18 and in 12/18 patients with viability respectively, but in only 0/18 (p < 0.01) and in 1/18 (p < 0.01) patients without viability. Thus, ST-segment elevation occurring within the first two stages of the exercise test was, respectively, 39 and 67% sensitive and 100 and 94% specific for viability. Early onset ST-segment elevation (within 3 and 6 min) was also more frequent in patients with high-dose dobutamine-induced homozonal ischemia than in those without (sensitivity for ischemia 50 and 67%; specificity 95 and 74%, respectively). CONCLUSIONS: After myocardial infarction, ST-segment elevation in Q-wave leads at the peak of exercise is associated with severe resting left ventricular dysfunction but fails to identify patients with a viable myocardium or residual ischemia. Instead, ST-segment elevation occurring in the early phases of exercise is a highly specific, although not very sensitive marker of dobutamine-assessed viability in the infarct area and may be indicative of residual ischemia.

Dobutamine↗
PubMed2003

Segmentation: mono- or polyphyletic?

Understanding the evolutionary origins of segmented body plans in the metazoa has been a long-standing fascination for scientists. Competing hypotheses explaining the presence of distinct segmented taxa range from the suggestion that all segmentation in the metazoa is homologous to the proposal that segmentation arose independently many times, even within an individual clade or species. A major new source of information regarding the extent of homology vs. homoplasy of segmentation in recent years has been an examination of the extent to which molecular mechanisms underlying the segmentation process are conserved, the rationale being that a shared history will be apparent by the presence of common molecular components of a developmental program that give rise to a segmented body plan. There has been substantial progress recently in understanding the molecular mechanisms underlying the segmentation process in many groups, specifically within the three overtly segmented phyla: Annelida, Arthropoda and Chordata. This review will discuss what we currently know about the segmentation process in each group and how our understanding of the development of segmented structures in distinct taxa have influenced the hypotheses explaining the presence of a segmented body plan in the metazoa.

Animals↗
PubMed2004

A semantic approach to segmentation of overlapping objects.

OBJECTIVES: This paper aims at introducing a novel approach for segmentation of overlapping objects and at demonstrating its applicability to medical images. METHODS: This work details a novel approach enhancing the known theory of full-segmentation of an image into regions by lifting it to a semantic segmentation into objects. Our theory allows the formal description of partitioning an image into regions on the first level and allowing the occurrence of overlaps and occlusions of objects on a second, semantic level. Possible applications for the use of this 'semantical segmentation' are the analysis of radiographs and micrographs. We demonstrate our approach by the example of segmentation and separation of overlapping cervical cells and cell clusters on a set of 787 image pairs of registered PAP- and DAPI-stained micrographs. The semantical cell segmentation yielding areas of cell plasmas and nuclei are compared to a manual segmentation of the same images, where 2212 cells have been labeled. A direct comparison of over and under-segmentation between the two segmentation sets yields a mean difference value of 10.15% for the nuclei and 10.80% for the plasma. RESULTS: Using the proposed theory of semantical segmentation of images in combination with adequate models of the image contents, our approach allows identifying, separating and distinguishing several overlapping, occluding objects in medical images. Applying the proposed theory to the application of cervical cell segmentation from overlapping cell clusters and aggregates, it can be seen that it is possible to formally describe the complex image contents. CONCLUSIONS: The proposed method of semantical segmentation is a mighty tool and under the assumption of the subtractive transparency model can be used in different medical image processing applications such as radiology and microscopy. By using alternative models to solve the ambiguities attached to overlaps and occlusions, further fields of application can be addressed.

Algorithms↗
PubMed1989

Comparative effects of cholera toxin, Salmonella typhimurium culture lysate, and viable Salmonella typhimurium in isolated colon segments in ponies.

Isolated segments of left dorsal colon and a side-to-side colocolostomy (between the left ventral colon and left dorsal colon) were surgically created in 6 adult ponies. Four segments, each separated by an empty segment, were inoculated (20 ml) with 1 of the following 4 solutions: phosphate buffered saline solution (PBSS)/1% polyethylene glycol (PEG); purified cholera toxin in PBSS/1% PEG (5 micrograms cholera toxin/ml of PBSS/1% PEG); lyophilized Salmonella typhimurium UCD 1755 culture lysate, reconstituted in PBSS/1% PEG; and viable S typhimurium UCD 1755 (10(8) organisms/ml of PBSS/1% PEG). Twenty hours following inoculation of the treatment solutions into the isolated colon segments, the ponies were reanesthetized. Fluid accumulation in the isolated segments was measured, and tissue samples from isolated segments were taken for examination by light microscopy and electron microscopy, and for measurement of mucosal cyclic adenosine monophosphate levels. There was fluid accumulation in segments inoculated with cholera toxin in 4 ponies (29.5 +/- 12.7 ml), and in segments inoculated with S typhimurium UCD 1755 culture lysate in 3 ponies (14.0 +/- 8.7 ml). There was no fluid accumulation in segments inoculated with either the control solution (PBSS/1% PEG) or viable S typhimurium UCD 1755. There was significantly (P less than 0.05) less cyclic adenosine monophosphate in segments inoculated with cholera toxin, Salmonella lysate, and viable Salmonella, compared with control segments. Histologically, there were minimal changes in control segments, consisting of mild to moderate submucosal edema and capillary congestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

[The courses and the segmental origins of the cutaneous branches of the thoracic dorsal rami].

It is described in many textbooks that the medial cutaneous branches (RCM) from the medial branches of the upper six thoracic dorsal rami supply the upper half of the back of the body, the lateral cutaneous branches (RCL) from the lateral branches of the lower six thoracic dorsal rami supply the lower half of it, and the area supplied by both branches is limited to a few segments. Unlike those descriptions, we had frequently observed RCL from the second or the third thoracic dorsal ramus penetrating the rhomboideus muscle during previous research concerning the double innervation of the superficial muscles of the back by both the ventral and the dorsal rami (Kumaki et al., 1984). To make clear the origin of the discrepancy between the description in the textbooks and our observations, we examined the segmental origins, the courses, and the distributions of both the medial and the lateral branches of the thoracic dorsal rami on 20 sides of 11 bodies dissected in the years 1986 and 1989. Consequently, RCL from the second thoracic dorsal ramus (Th 2) was observed in 25% of the cases and RCL from Th 3 and Th 4 were observed in 50% and in 70%, respectively. The highest segment of RCL was Th 2 in 25%, Th 3 in 25%, Th 4 in 35%, Th 6 in 10%, or Th 8 in 5%, and the mean was Th 3.65 +/- 1.53. On the other hand, the lowest segment of RCM was Th 6 (15%), Th 7 (35%), Th 8 (25%), Th 9 (15%), or Th 10 (10%), and the mean was Th 7.70 +/- 1.19. The mean number of the segments at which the dorsal ramus of the thoracic nerve sent both RCM and RCL was 4.55 +/- 1.50 (Max: 9 segments). Thus, we made clear that RCL from the upper thoracic nerves were commonly observed and that the number of segments sending both RCM and RCL was larger than hitherto described. The course of the upper RCL was bent at the points where the RCL penetrated the superficial muscles of the back forming a "Z"-shape, i.e., RCL changed its course from an infero-lateral to an infero-medial direction at the point of penetrating the rhomboid muscle and from an infero-medial to a lateral direction at the point of penetrating the trapezius muscle or the latissimus dorsi muscle. These directions might be associated with the development of the muscles. Sometimes RCL was sharply pulled in a medial direction by the trapezius muscle to penetrate the muscle near the median plane and appeared as RCM. Therefore, we supposed that the main reason why the upper RCL had been overlooked was because the complicated zigzag course of the RCL was damaged by the inadequate dissection or RCL was mistaken for the RCM. While the points where the cutaneous branches penetrated the superficial muscles were variable, the points where they penetrated the thoraco-lumbar fascia were relatively stable. This point of the RCM was generally near the tip of the spinal process of the same segmental number of the nerve, and the same point of RCL was generally at the gap between the longissimus and the iliocostal muscles in the intercostal space one segment lower than the segment of the RCL. The RCL from the last thoracic to the third lumbar dorsal rami communicated with one another to form a nerve plexus under the lumbo-dorsal aponeurosis, then penetrated that aponeurosis forming several nerve bundles, crossed over the iliac crest and supplied the hip skin as the superior cluneal nerves. Therefore, each bundle was not equivalent to each segment, but was composed of two or more segments.

Humans↗
PubMed1994

Transport of phosphatidylcholine to Xenopus photoreceptor rod outer segments in the presence of tunicamycin.

Study of the dynamics of membrane protein and phospholipid transport from the inner to the outer segment of vertebrate photoreceptors has shown an interesting dissociation of the two components under a number of experimental treatments which inhibit protein synthesis or transport. Under conditions which block the addition of opsin to outer segments, various lipids continue to be synthesized and transported to the outer segment in the presence of monensin, puromycin, brefeldin A, tunicamycin and several general metabolic inhibitors. In the current study, isolated retinas from adult Xenopus laevis were incubated with or without 20 micrograms mg-1 of tunicamycin in total darkness or light for 2-12 h in the presence of [3H]choline to study the dependence of phosphatidylcholine synthesis and transport on protein transport to the outer segment. Phosphatidylcholine is a major bulk lipid of outer segments, comprising close to one half of the phospholipid of outer segment phospholipids, and blocking choline uptake in retinas is known to cause photoreceptor degeneration. Biochemical analysis demonstrates that tunicamycin does not block the synthesis of phosphatidylcholine in photoreceptor inner segments or transport of radiolabelled phosphatidylcholine to outer segments during 6 h incubations with [3H]choline in light or total darkness. Light and electron microscopic autoradiography and morphometric analysis show that [3H]choline radiolabelled phospholipid does not accumulate in a band of newly formed basal discs in the outer segment or in the tubulo-vesicular structures which accumulate in the intersegmental space of tunicamycin-treated retinas. We conclude that transport of phosphatidylcholine can occur independently of opsin transport to the outer segment but whether this represents two separable components of a single pathway or involves two distinct routes of transport to the outer segment is still unresolved.

Animals↗