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 181 records · Page 10Linked to original sources
PubMed1986

Does complete revascularization by the conventional method truly provide the best possible results? Analysis of results and comparison with revascularization of infarct-prone segments (systematic segmental myocardial revascularization): the Sheba Study.

Myocardial revascularization is usually considered "complete" if all stenosed major coronaries are bypassed. Attempts were made to compare the results of this method with an approach by which each of the following five left ventricular infarct-prone segments is revascularized if ischemic: anteroseptal, anterolateral, posterosuperior, posteroinferior, and diaphragmatic. Two subsets of patients were studied. A total of 366 patients (Group A) who underwent aortacoronary bypass operations from 1980 to 1982 were followed up for a mean of 16.3 (6 to 43) months and were retrospectively divided into two groups: Group A1 (120 patients) had incomplete segmental revascularization (mean of 3.4 grafts per patient) and Group A2 (246 patients) had complete segmental revascularization (4.0 grafts per patient) (p less than 0.0001). Groups A1 and A2 were identical in all clinical and angiographic parameters: unstable angina, 60%; previous myocardial infarction, 70%; left main stenosis, 10%; and ejection fraction less than 30%, 2%. Overall operative mortality was 2.3%. Results in Groups A1 and A2, respectively, were as follows: operative mortality, 5.8% versus 0.8% (p less than 0.005); perioperative myocardial infarction, 6.9% versus 0.8% (p less than 0.0005); 35 month survival rate, 93.3% versus 97.9% (p less than 0.02); total freedom from symptoms, 54.1% versus 68.3% (p less than 0.025). In addition, 151 patients operated on in 1984 (Group B) were studied prospectively with regard to operative mortality and perioperative myocardial infarction, and the results were identical to those in Group A. Compared to conventional complete revascularization, complete segmental revascularization provides better results.

Adult↗
PubMed1979

[Signs of anterior segment ischemia following segmental external buckling (author's transl)].

The symptoms of an acute anterior segment necrosis are described as they might occur as a postoperative complication due to encircling procedures. Report about a patient presenting postoperatively signs of ischemia in the anterior segment following segmental external buckling. In this case the cylinder of the explant was 5 mm in diameter and extended over 2 quadrants of the globe. Discussion of the factors most likely causing this rare complication due to segmental external buckling.

Aged↗
PubMed1983

[Experimental study of changes in the pressure of the posterior segment of the eye under general anesthesia. Consequences for surgery of the anterior segment].

Animal studies were conducted to compare variations in intraocular (IOP) and posterior segment pressure (PSP) during general anesthesia to assess the role of PSP in the development of anesthesia for ophthalmological procedures. Anesthetic agents appear to have a marked effect on IOP during operations involving opening of hypertonic globe or examinations of children under general anesthesia, but their action on IOP has no significance during procedures requiring opening of the anterior chamber because of alteration of aqueous humor physiology. The PSP, defined as pressure in the posterior segment when the anterior segment is at atmospheric pressure, is the main factor affecting surgical conditions, a rise in PSP possibly resulting in typical complications of cataract surgery but having beneficial effects in corneal grafts for example. Posterior segment pressure cannot be studied in humans and an experimental model using rabbits under artificial ventilation following tracheotomy after general anesthesia was developed. Pressure gauges recorded arterial and central venous pressures and were connected to needles inserted in both eyes to monitor IOP and PSP, the latter from a needle passed into the anterior chamber through the cornea, which was incised over the needle to enable permanent drainage of aqueous humor. All pressures were recorded simultaneously and no correlations were observed between IOP and PSP after pentobarbitone, neosynephrine, succinylcholine, or asphyxia (interruption of ventilation and curarization). These findings suggest that IOP is not a valid measurement for assessment of anesthetic techniques, whereas PSP provides a better guideline for development of ophthalmological anesthesia.

Anesthesia, General↗
PubMed1994

[Structure of segmental tuft lesions in childhood IgA nephropathy--three dimensional analysis indicates development of segmental lesions].

The mechanisms responsible for the formation and development of segmental lesions of IgA nephropathy in children were studied by analysis of three dimensional reconstruction. Forty-eight segmental lesions from 15 cases (diffuse proliferative glomerulonephritis (DPGN) in 13 cases, focal glomerulonephritis (FGN) in 2 cases) were examined by light microscopy by analysis of serial sections (in average 26 sections/glomerulus). In tuft, three types of tuft lesions were defined by their chronisity: 1) endocapillary proliferation including exudative changes, 2) mesangial hypercellularity, 3) deposition of mesangial matrix with sclerosis. Extra-capillary lesions, namely crescent were also defined by their chronisity: 1) cellular, 2) fibrocellular, 3) fibrous. The structural relation in each tuft and endocapillary lesions were observed. Endocapillary proliferative lesions of tufts were closely associated with cellular crescent of extra-capillary lesions. In fibrocellular and fibrous crescents, the frequency of endocapillary proliferation in tufts were reduced, while the association of mesangial proliferation and sclerosis were increased. Nevertheless, endocapillary proliferation of tufts were still observed in 33% of fibrous crescent. We concluded that segmental lesions were originated by endocapillary tuft lesions leading to cellular crescents. The multifocal and repeated attack of endocapillary proliferative lesions within segmental sclerosis promotes further development of glomerular sclerosis in IgA nephropathy in children.

Adolescent↗
PubMed1993

[A case of bilateral synchronous renal cell carcinoma treated with partial nephrectomy with temporary occlusion of the segmental renal artery (segmental nephrectomy)].

We present a case of bilateral synchronous renal cell carcinoma. A 57-year-old man visited our hospital with a complaint of fever up. On ultrasonography and computerized tomography scan, a round tumor about 2.5 cm in diameter in the posterior portion of the right kidney and another tumor about 7 cm in diameter arising from the upper pole of the left kidney. Selective renal arteriogram showed that the inferior branch of the posterior segmental artery supplied blood to the right renal tumor. Left partial nephrectomy with temporary occlusion of the main renal artery and posterior segmental nephrectomy of the right kidney were performed at the same time. In patients with cancer confined to the posterior segment of the kidney, segmental nephrectomy can be performed while allowing unimpaired perfusion to the remainder of the kidney from the main renal artery.

Carcinoma, Renal Cell↗
PubMed1998

12-lead ST-segment monitoring vs single-lead maximum ST-segment monitoring for detecting ongoing ischemia in patients with unstable coronary syndromes.

BACKGROUND: 12-lead ECG monitoring of the ST segment is more sensitive than patients' symptoms for detecting ischemia after thrombolytic therapy or catheter-based interventions, but it is unclear whether monitoring of the single lead showing maximum ST deviation would be as efficacious. OBJECTIVE: To determine whether monitoring all 12 ECG leads for changes in the ST segment is necessary to detect ongoing ischemia in patients with unstable coronary syndromes. METHODS: Continuous 12-lead ST segment monitoring was performed in 422 patients from the onset of myocardial infarction or during balloon inflation in catheter-based interventions until the patient's discharge from the cardiac care unit. Computer-assisted techniques were used to determine (1) which lead showed the maximum ST deviation at the onset of myocardial infarction or during balloon inflation and (2) what proportion of later ischemic events were associated with ST deviation in this lead. RESULTS: The lead with the maximum ST deviation could be determined in 312 patients (74%). The remaining 110 (26%) had non-Q wave infarction without ST deviation or no ST changes during balloon inflation. During 18,394 hours of 12-lead ST monitoring, 118 (28%) of the 312 patients had a total of 463 ischemic events, 80% of which were silent. Of 377 ischemic events in which a maximum ST lead was detected, 159 (42%) did not show ST deviation in this lead (sensitivity, 58%; 95% CI, 53%-63%). Routine monitoring of leads V1 and II showed ST deviation in only 152 of the 463 events (sensitivity, 33%; 95% CI, 29%-37%). CONCLUSIONS: Monitoring of all 12 ECG leads for changes in the ST segment is necessary to detect ongoing ischemia in patients with unstable coronary syndromes.

Aged↗
PubMed1997

Anterior segment prosthesis development: retinal function following anterior segment removal.

Replacement of the entire anterior segment of the eye is a very ambitious and complex endeavor and it is not known whether the retina remains functional when the anterior structures have been removed. We used routine histo-pathologic evaluation and electroretinographic measurements to determine the structural and functional status of rabbit retinas following surgical removal of the internal anterior structures (iris, ciliary body, and lens) and replacement of the vitreous with silicone oil. In some cases, we were able to record both a scotopic and a photopic electroretinographic response as long as 15 weeks after complete removal of the internal anterior segment structures. Although many hurdles remain and more efficacious surgical techniques and biomaterials need to be developed, our results suggest that, in the rabbit, the retina may continue to function in the absence of critical anterior segment structures.

Animals↗
PubMed1986

Segmental differentiation in the leech nervous system: the genesis of cell number in the segmental ganglia of Haemopis marmorata.

In hirudinid leeches, the segmental ganglia associated with the sexual organs contain several hundred more neurons than other midbody ganglia. To determine whether this difference arises by differential cell addition or by differential cell death, cell counts were made in several segmental ganglia during the course of embryonic and postembryonic development. The results show that all ganglia behave equally in early development. In each case, at least 10-20% more cells than will make up the adult complement of about 400 neurons is generated, and by about 20 days of embryonic development cell loss brings the number down to about 400 cells. By about 30 days, when animals emerge from their cocoons, additional cells have begun to appear in the sex ganglia. The number of extra cells continue to increase gradually over the next several months, until the adult number of 600-700 neurons is attained. These observations indicate that at least some segmental differences in the size of neuronal populations are due to differential cell proliferation and that these differences can arise quite late in the maturation of an animal.

Animals↗
PubMed1991

Segmental differentiation in the leech central nervous system: proposed segmental homologs of the heart accessory neurons.

As part of an on-going study of segmental differentiation in the central nervous system (CNS) of the leech Hirudo medicinalis, a search was made for putative segmental homologs of the heart accessory (HA) neurons, which exist exclusively as a bilateral pair in the ganglia of the fifth and sixth body segments. As it is not yet feasible to obtain adequate cell lineage information in H. medicinalis, potential homologs of the HA neurons were determined using morphological, immunohistochemical, and electrophysiological criteria. Among cells in other body ganglia with somata in the same locations as HA neurons, a pair was found having extensive morphological and physiological similarities to HA neurons. These we have called HA-like (HAL) neurons. Adult HA and HAL neurons have closely related patterns of primary branching, in terms of shape, intraganglionic pathways taken, and extraganglionic projections. The number, location, and relative thickness of branches are also similar among these cells. In embryos 10 to 11 days old, HA and HAL neurons have virtually identical branching patterns, with primary and secondary branches of nearly uniform caliber. Differences in branch thickness develop gradually; by embryonic day 20, they resemble those found in adult neurons. Two features found to differ between HA and HAL neurons were the cell body diameter (larger for the HA cells) and the expression of antigens recognized by the monoclonal antibody Laz1-1 (absent at a detectable level in the HA neurons). At a physiological level, the HA and HAL neurons showed action potentials of similar size and shape, as well as inhibitory synaptic inputs from a common source, the heart interneurons (HN). The observations presented here suggest that there is a common developmental origin for the HA and HAL neurons, and hence that their fates are positionally determined by as yet unknown factors.

Aging↗
PubMed2002

Nerve root sleeve diameters at normal segments and at segments with proximate disc disease: MRI evaluation.

OBJECTIVE: To compare MR morphologic parameters of spinal nerve roots and their range of variability in normal and abnormal spinal segments. DESIGN AND PATIENTS: Ninety-six consecutive lumbar spine MRI examinations were segregated into three groups: group 1 was composed of 30 patients with disc bulge, protrusion or extrusion at the L5-S1 segment measuring 3 mm or more; group 2 consisted of 31 patients with no disc pathology; and group 3 was composed of 35 patients with no disc abnormality at the L5-S1 level but with coexisting spine pathology at other segments. Measurements of 192 S1 nerve root sleeves were performed at three consecutive levels on T1-weighted images. Differences between right and left nerve root sleeve diameters (delta value) at three slice levels were calculated in each group. Data were analyzed by ANOVA. RESULTS: No significant differences between the mean values of traversing S1 nerve root sleeve diameter on three corresponding consecutive slices were found among groups ( P=0.733, P=0.824, P=0.365 respectively), nor were significant differences in delta values between groups found ( P=0.639, P=0.113, P=0.722). CONCLUSIONS: S1 nerve root sleeve diameter and the differences between right and left in the abnormal group were not significantly different from normal and therefore can not be used as an objective criterion of nerve root pathology.

Adolescent↗
PubMed2004

Segmental duplication associated with the human-specific inversion of chromosome 18: a further example of the impact of segmental duplications on karyotype and genome evolution in primates.

The human-specific pericentric inversion of chromosome 18 was analysed using breakpoint-spanning BACs from the chimpanzee and human genome. Sequence and FISH analyses disclosed that the breakpoints map to an inverted segmental duplication of 19-kb, which most likely mediated the inversion by intrachromosomal homologous recombination. The 19-kb duplication encompasses the 3' end of the ROCK1 gene and occurred in the human lineage. Only one copy of this segment is found in the chimpanzee. Due to the inversion, the genomic context of the ROCK1 and USP14 genes is altered. ROCK1 flanks USP14 in the long arm of the chimpanzee chromosome 17, which is homologous to human chromosome 18. This order is interrupted by the inversion in humans. ROCK1 is localized close to the pericentromeric region in 18q11 and USP14 is inverted to distal 18p11.3 in direct neighbourhood to LSAU-satellites, beta-satellites and telomere-associated repeats. Our findings essentially confirm the analysis of Dennehey et al. (2004). Intriguingly, USP14 is differentially expressed in human and chimpanzee cortex as well as fibroblast cell lines determined previously by the analysis of oligonucleotide arrays. Either position effects mediated by the proximity to the telomeric region or nucleotide divergence in regulatory regions might account for the differential expression of USP14. The assignment of the breakpoint region to a segmental duplication underlines the significance of the genomic architecture in the context of genome and karyotype evolution in hominoids.

Animals↗
PubMed1975

Anterior segment ischemia after segmental episcleral buckling and cryopexy.

A 63-year-old man with a one-quadrant retinal detachment developed anterior segment ischemia after an operation that included the use of cryopexy, release of subretinal fluid, and segmental episcleral buckling without detachment of the extraocular muscles. A compromised cardiovascular condition of long duration and an episode of transient hypotension immediately preceding operation were factors in the pathogenesis of the ischemia. Although the anterior segment changes were moderately severe, recovery of vision ultimately was excellent.

Cardiovascular Diseases↗
PubMed1988

Rift Valley fever virus M segment: cellular localization of M segment-encoded proteins.

The Phlebovirus Rift Valley fever virus (RVFV), like other members of the Bunyaviridae family, matures intracellularly at the smooth-surfaced vesicles in the Golgi region of infected cells. Here we show that in cultured cells the RVFV glycoproteins G2 and G1 accumulate and are retained at this site. To investigate the parameters governing this subcellular localization, we have engineered portions of the cloned RVFV M segment (which encodes a 14- and a 78-kDa protein, in addition to glycoproteins G2 and G1) into vaccinia virus. Immunofluorescent analysis of cells infected with a vaccinia virus recombinant containing the entire open reading frame of the RVFV M segment revealed Golgi localization for glycoproteins G2, G1, the 78-kDa protein, and Golgi as well as some reticular distribution for the 14-kDa protein. These distributions paralleled those seen in authentic RVFV-infected cells. RVFV-vaccinia virus recombinants possessing progressive deletions within the 152 amino acid preglycoprotein sequence of the M segment were analyzed for possible effects on the cellular distribution of G2 and G1. Removal of the first 130 amino acids of the open reading frame amino-terminal to the mature glycoprotein coding sequences, while abolishing production of the 78- and 14-kDa proteins, did not alter the Golgi location of G2 and G1. The data suggest that Golgi-specific signals reside within the G2 and/or G1 glycoprotein sequences. The use of vaccinia virus recombinants provides a genetically manipulable expression system with which to further investigate the sequences involved in the intracellular localization of these Phlebovirus proteins.

Animals↗
PubMed1990

cDNA cloning of each genomic segment of the group B rotavirus ADRV: molecular characterization of the 11th RNA segment.

The group B noncultivatable rotavirus, ADRV, was purified from infected stool specimens. Double-stranded RNA was extracted, polyadenylated, reverse transcribed into cDNA, and cloned into plasmid vector pAT153. Each cDNA clone hybridized to a single ADRV RNA segment and cDNA clones of each genomic RNA segment were identified. Sequencing of genomic RNA and a full-length cDNA clone (AD63) determined that ADRV RNA segment 11 is 631 bases in length and contains a single open reading frame of 170 amino acids with a calculated molecular weight of 19.9 kDa and a pl of 6.2. The RNA 5'- and 3'-termini contain untranslated regions of 58 and 63 bases, respectively, and are complementary to each other. A comparison of encoded ADRV gene 11 amino acids with the NS26 protein of group A rotaviruses demonstrates a distant similarity between the two proteins. Further analysis and use of these ADRV clones should aid in determining the gene coding assignments for group B proteins as well as for diagnostic detection of group B or ADRV-specific nucleic acids in specimens.

Amino Acid Sequence↗
PubMed1990

Coding strategy of rice stripe virus: major nonstructural protein is encoded in viral RNA segment 4 and coat protein in RNA complementary to segment 3.

The two major proteins found in plants infected with rice stripe virus (RSV), coat protein and a major nonstructural protein (major NS), were purified and their partial amino acid sequences were determined. Oligonucleotides were synthesized according to the amino acid sequence information, and used as probes for Northern blot analyses of four single-stranded RNA species (segments 1-4) and four double-stranded RNA species of RSV. The results indicated that the coding strategy of RSV was similar to those of ambisense viruses: Segment 3 coded for the coat protein in the (-) sense while segment 4 coded for the major NS protein in the (+) sense.

Amino Acid Sequence↗
PubMed1991

Interactions between segment polarity genes and the generation of the segmental pattern in Drosophila.

Although mutations in the segment polarity genes wingless, engrailed, hedgehog, gooseberry and cubitus-interruptusD all affect the region of naked cuticle within each segment of the Drosophila larva, subtle phenotypic differences suggest that these genes play different roles in segmental patterning. In this paper, the regulative interactions between these genes are analysed. They have revealed that the products of most of these genes accomplish more than one function during embryogenesis. Whereas early on a positive feed-back loop involving wg, en and hh maintains the expression of wg and en in the extremes of each parasegment, later on wg and en become independent from each other. en appears to regulate the expression of hh and ptc, while wg depends on gsb and ciD.

Animals↗
PubMed2005

Impact of ST-segment depression resolution on mortality after successful mechanical reperfusion in patients with ST-segment elevation acute myocardial infarction.

The aim of the present study was to evaluate the additional prognostic effect of ST-depression resolution in 610 patients who had ST-elevation myocardial infarction and underwent successful primary angioplasty (postprocedural Thrombolysis In Myocardial Infarction 3 flow and complete resolution of ST-segment elevation). Incomplete resolution of ST-segment depression (<70%) was observed in 50 patients (8.2%). These patients were older, had a higher Killip's class at presentation, had larger infarcts, and had an increased 1-year mortality (10% vs 2%, p = 0.0004). At multivariate analysis, incomplete resolution of ST-segment depression was an independent predictor of 1-year mortality (p = 0.028).

Aged↗
PubMed2005

Impact of mediolateral segmentation on a multi-segment foot model.

MacWilliams et al. report their progress on a multi-segment foot model, including mediolateral segmentation, from which they calculate kinematics and kinetics [MacWilliams BA, Cowley M, Nicholson DE. Foot kinematics and kinetics during adolescent gait. Gait Posture 2003;17:214-24]. Their methods are generally well described, and in concept, lead us to new insights regarding foot biomechanics during gait, including kinetics of several joints within the foot itself. However, forces and moments (i.e., force systems) between mediolaterally adjacent segments were ignored in their inverse dynamics calculations. We show theoretically that these omitted force systems instead corrupt the calculated proximal force systems. We also show empirically that physiologically reasonable moment-arms (10-20 mm) and omitted forces (one to four bodyweights) could change both the shape and magnitude of the calculated proximal force systems. In this regard, we demonstrate that these kinetic data need to be viewed with caution. Finally, we extend the concept used in our analysis to general biomechanical modeling.

Acceleration↗