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PubMedDate not supplied

[Checking a model of cardiac segmentation of the left half of the heart].

The present work is aimed to study the distribution of the coronary arteries to the left ventricle; 120 fresh and prepared human hearts harvested from healthy individuals of both sexes aged 4 to 78 have been used. The denomination of the cardiac segments is the one used by Liberato, Didio & Rodrigues in 1983. Starting from this model, we sought for sustaining or invalidating arguments. We used special dissection techniques, radiographs of radioopaque substances injected hearts, and corroded after plastic substances injection organs. Each ventricular segment in the left ventricle is supplied by an arterial branch (called "segmental") of the coronary arteries (left coronary artery in most of cases). The anterior interventricular branch segment (I SV or SVIA) is the area of the heart supplied by the arterial branch with the same name, originating in the left coronary artery. Depending on its length, we found a small segment (the branch did not pass over the apex of the heart, thus supplying the sternocostal surface of the heart only) in 39 cases (32.5%), and a big segment (the artery ended on the diaphragmatic surface of the heart, in the posterior interventricular groove) in 81 cases (67.5%). The lateral branch segment (II SV or SVL) includes in most of cases (78%) a part of the pulmonary wall of he left ventricle, up to the apex (Liberato et al. found a percent of 66). In the rest of cases (22%) it additionally includes a part of the diaphragmatic wall of the left ventricle. The left marginal branch segment (III SV or SVM) is a big one when it includes parts of the pulmonary and diaphragmatic walls of the left ventricle and part of the diaphragmatic wall of the right ventricle; it is middle-sized when it includes parts of the left and diaphragmatic walls of the left ventricle; it is considered small when it extends over parts of the left and diaphragmatic walls of the left ventricle adjacent to the pulmonary surface (36%, 40% and 24% of cases, respectively). The posterior ventricular branch segment (IV SV or SVP) includes: a small part of the diaphragmatic wall of the left ventricle close to the pulmonary surface--52 cases (43.3%); the superior half of the diaphragmatic wall of the left ventricle up to the posterior interventricular septum--19% of cases; the superior third of the left ventricle, up to the septum--20% of cases; the superior part of the diaphragmatic wall of both ventricles and the superior part of the septum--13.6% of cases. The segments are separated by intersegmental planes whose position depends of the degree of development of each cardiac segment. No significant differences were observed in what concerns the extension of the cardiac segments and the position of intersegmental planes in relation to sex. The segments can be totally independent or slightly dependent to the blood supply of the neighbouring segments.

Adolescent↗
PubMed1998

Specific projections of sympathetic preganglionic neurons are not intrinsically determined by segmental origins of their cell bodies.

Sympathetic preganglionic projections of the chick are segmentally specific. Neurons from the 16th cervical (C16) and the first thoracic (T1) spinal cord segments project almost exclusively in the rostral direction, while those from the fifth thoracic (T5) to the first lumbar (L1) spinal segments project almost exclusively in the caudal direction. Neurons from the intervening spinal cord segments (T2-4) project in rostral and caudal directions. There is also a tendency for rostrally located neurons in each segment to project rostrally and caudally located neurons to project caudally. To investigate whether specific projections of preganglionic neurons are intrinsically determined by segmental origins of their cell bodies, neural tube segments were transplanted or rotated in embryos at stages 19-26; these stages include times during and after preganglionic cell birth and just prior to axon outgrowth. When the T1 neural tube segment was replaced with the T5 or T7 neural tube segment the transplanted T5 or T7 preganglionic neurons, now in the T1 position, projected rostrally. Conversely, when the T5 or T7 neural tube segment was replaced with the T1 neural tube, the transplanted T1 preganglionic neurons projected caudally. In addition, when individual T3 spinal cord segments were rotated 180 degrees along the A-P axis, neurons which were originally in the caudal part of the segment projected rostrally, whereas neurons originally from the rostral part of the segment projected caudally. These results show that specific projections of preganglionic neurons are not intrinsically determined by segmental origins of their cell bodies.

Animals↗
PubMedDate not supplied

Projection-neurons that send axons through the lumbar spinal cord of the chick embryo are not obviously distributed in a segmentally repetitive pattern.

Earlier studies have shown that the formation of the segmentally repetitive pattern of spinal nerves in avian embryos depends upon the segmental arrangement of the somites and does not reflect an intrinsic pattern of the spinal cord. These studies could not, however, rule out the possibility that some elements of the central nervous system are intrinsically segmented. The question remained, for instance, whether projection-neurons are distributed in a segmentally repetitive pattern within the spinal cord. To address this question, horseradish peroxidase was injected into one or two segments of the lumbar spinal cord of chick embryos, thereby labeling projection-neurons that had ascending or descending axons passing through the injection site. In all stages examined, the number of labeled projection-neurons in the anterior and posterior halves of each segment did not differ significantly. In addition, segmentally repetitive peaks or troughs in the numbers of labeled projection-neurons were not detected in the center of each segment. Three subpopulations of projection-neurons, defined by their position along the dorsal-ventral axis of the spinal cord, were also not segmentally distributed by these criteria. While these results do not rule out the possibility that subpopulations of projection-neurons defined by dendritic morphology, functional class, or some other parameter are segmentally arranged or that there is a basic modular repetition of neural populations from segment to segment, they do show that projection-neurons as a class and subpopulations of these neurons defined by their dorsal-ventral position are not obviously distributed in a repetitive segmental pattern.

Animals↗
PubMed1993

Proportional analysis of the kidney arterial segments.

The proportional area of each renal arterial segment was analyzed in 49 polyester resin corrosion endocasts of the renal vasculature. We defined a segmental artery as a primary or secondary branch of the renal artery that could be isolated outside the hilum. We found kidneys with five arterial segments in 30 of 49 casts (61.2% of cases) and kidneys with four arterial segments in 19 of 49 casts (38.8%). To enable the evaluation of the proportional areas of the autonomous segments (by using the "point-counting planimetry method"), each arterial segmental branch was injected with different-colored resin. The superior segment (apical) was present in 36 of 49 casts (73.5% of cases) and had a median proportional area of 13.02%. The anterosuperior and anteroinferior segments were present in 30 of 40 casts (61.2% of cases) and had median proportional areas of 21.36% and 17.18%, respectively. The anterior segment was present in 19 of 49 casts (38.8% of cases; when the mid-kidney anterior surface received only one segmental artery) and had a median proportional area of 28.44%. The inferior segment was present in 100% of cases and had a median proportional area of 22.65%. The posterior segment was also present in 100% of cases and was the segment with the greatest median proportional area (33.76%).

Animals↗
PubMed1993

Quantitative angiographic follow-up studies on the development of coronary artery disease: which coronary segments should be analyzed? Experience from INTACT.

Angiographic follow-up studies on the evolution of coronary artery disease are of increasing relevance. It has still to be evaluated which coronary segments are predominantly involved in the process of atherosclerosis and, thus, should be preferably included in the analysis. Therefore, the correlation of progression and regression of coronary disease with the diameter and location (proximal, mid or distal) of coronary segments was investigated from the data of the INTACT-study, in which 25 different coronary segments were defined including anatomic variants of rather distal segments. In 348 patients with coronary artery disease, standardized coronary angiograms were repeated within 3 years and were quantitatively analyzed (CAAS). In 1063 coronary stenoses (% diameter stenosis > 20%) compared from both angiograms, progression and regression were not influenced by diameter nor location of arterial segments. In the follow-up angiograms, the number of new lesions (stenoses and occlusions) per coronary segment differed with regard to segment diameter (> 3 mm: 64/1125 (6%); 2-3 mm: 139/1967 (7%); < 2 mm: 44/1756 (2%); p < 0.001) and location of segments (proximal: 86/1285 (7%); mid: 84/1193 (7%); distal: 77/2370 (3%); p < 0.001). Out of 77 distal new lesions, only 25 (32%) were found in segments < 2 mm in diameter. Since the absolute number of new lesions was high in distal coronary segments, but low in segments with diameters < 2 mm, angiographic follow-up studies should analyze coronary segments at any location, but may neglect segments with diameters smaller than 2 mm.

Coronary Angiography↗
PubMed2004

Segmented attenuation correction for myocardial SPECT.

PURPOSE: One of the main factors contributing to the accuracy of attenuation correction for SPECT imaging using transmission computed tomography (TCT) with an external gamma-ray source is the radionuclide count. To reduce deterioration of TCT images due to inadequate radionuclide counts, a correction method, segmented attenuation correction (SAC), in which TCT data are transformed into several components (segments) such as water, lungs and spine, providing a satisfactory attenuation correction map with less counts, has been developed. The purpose of this study was to examine the usefulness of SAC for myocardial SPECT with attenuation correction. METHODS: A myocardial phantom filled with Tc-99m was scanned with a triple headed SPECT system, equipped with one cardiac fan beam collimator for TCT and two parallel hole collimators for ECT. As an external gamma-ray source for TCT, 740 MBq of Tc-99m was also used. Since Tc-99m was also used for ECT, the TCT and ECT data were acquired separately. To make radionuclide counts, the TCT data were acquired in the sequential repetition mode, in which a 3-min-rotation was repeated 7 times followed by a 10-min-rotation 4 times (a total of 61 minutes). The TCT data were reconstructed by adding some of these rotations to make TCT maps with various radionuclide counts. Three types of SAC were used: (a) 1-segment SAC in which the body structure was regarded as water, (b) 2-segment SAC, in which the body structure was regarded as water and lungs, and (c) 3-segment SAC, in which the body structure was regarded as water, lungs and spine. We compared corrected images obtained with non-segmentation methods, and with 1- to 3-segment SACs. We also investigated the influence of radionuclide counts of TCT (3, 6, 9, 12, 15, 18, 21, 31, 41, 51, 61 min acquisition) on the accuracy of the attenuation correction. RESULTS: Either 1-segment or 2-segment SAC was sufficient to correct the attenuation. When non-segmentation TCT attenuation methods were used, rotations of at least 31 minutes were required to obtain sufficiently large counts for TCT. When the 3-segment SAC was used, the minimal acquisition time for a satisfactory TCT map was 7 min. CONCLUSION: The 3-segment SAC was effective for attenuation correction, requiring fewer counts (about 1/5 of the value for non-segmentation TCT), or less radiation for TCT.

Adult↗
PubMed1997

Segmentally distributed metamorphic changes in neural circuits controlling abdominal bending in the hawk moth Manduca sexta.

During the metamorphosis of Manduca sexta the larval nervous system is reorganized to allow the generation of behaviors that are specific to the pupal and adult stages. In some instances, metamorphic changes in neurons that persist from the larval stage are segment-specific and lead to expression of segment-specific behavior in later stages. At the larval-pupal transition, the larval abdominal bending behavior, which is distributed throughout the abdomen, changes to the pupal gin trap behavior which is restricted to three abdominal segments. This study suggests that the neural circuit that underlies larval bending undergoes segment specific modifications to produce the segmentally restricted gin trap behavior. We show, however, that non-gin trap segments go through a developmental change similar to that seen in gin trap segments. Pupal-specific motor patterns are produced by stimulation of sensory neurons in abdominal segments that do not have gin traps and cannot produce the gin trap behavior. In particular, sensory stimulation in non-gin trap pupal segments evokes a motor response that is faster than the larval response and that displays the triphasic contralateral-ipsilateral-contralateral activity pattern that is typical of the pupal gin trap behavior. Despite the alteration of reflex activity in all segments, developmental changes in sensory neuron morphology are restricted to those segments that form gin traps. In non-gin trap segments, persistent sensory neurons do not expand their terminal arbors, as do sensory neurons in gin trap segments, yet are capable of eliciting gin trap-like motor responses.

Abdomen↗
PubMed1995

Low-dose dobutamine echocardiography predicts the early response of dysfunctioning myocardial segments to coronary artery bypass grafting.

Dobutamine echocardiography has recently been introduced for use in identification of viable myocardium in patients with acute myocardial infarction and prediction of the response of dysfunctioning myocardial segments to coronary angioplasty. The aim of this study was to evaluate whether this test may be used to predict the early response of dysfunctioning myocardial segments to surgical revascularization. We studied 30 patients with three-vessel disease and chronic, stable angina pectoris during coronary artery bypass grafting (CABG). Patients were monitored by intraoperative transesophageal echocardiography in the transgastric short-axis view at the papillary muscle level. The left ventricle was divided into eight segments; and 240 myocardial segments were analyzed. Percentage of systolic wall thickening (PSWT) was calculated in each segment at baseline (early after pericardiectomy), before bypass during dobutamine infusion (5 micrograms/kg/min), and after separation from cardiopulmonary bypass. Segments showing PSWT < 30% at baseline were considered dysfunctional. Segments showing an increase in PSWT > 10% during dobutamine infusion were considered responders. Segments showing an increase in PSWT < 10% during dobutamine infusion were considered nonresponders. At baseline, 161 (67%) of 240 segments had PSWT < 30% (dysfunctioning segments). During dobutamine, 98 (60%) of these segments increased PSWT > 10% (from 11.3% +/- 7.6% to 24.2% +/- 12.0%, p < 0.01; responder segments), and 63 (40%) increased PSWT < 10% (from 10.2% +/- 4.9% to 8.3% +/- 5.5%, p value not significant [NS]; nonresponder segments).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Evolution of reovirus genes: a comparison of serotype 1, 2, and 3 M2 genome segments, which encode the major structural capsid protein mu 1C.

The sequences of the M2 genome segments of reovirus serotypes 1 and 2 are presented and compared with that of the cognate genome segment of reovirus serotype 3. Genome segment M2 encodes protein mu 1, a cleavage product of which, mu 1C, is the major constituent of reovirus particles. The three M2 genome segments exhibit a serotype 1:3 relatedness pattern: the serotype 1 and 3, 1 and 2, and 2 and 3 genome segment pairs exhibit 15, 23, and 23% nucleotide mismatches, respectively. The vast majority of these mismatches (about 87%) occur in third base codon positions that do not cause amino acid changes; as a result the three mu 1 proteins are very highly related (about 97%). The mu 1 proteins are acidic proteins, low in cysteine, histidine, and methionine, and rich in proline; and they possess a rather low predicted alpha-helix content of 27%. The site where protein mu 1 is cleaved to mu 1C is predicted to be between residues 42 and 43 in a highly conserved portion of the molecule. The three M2 genome segments are related significantly more closely than the three S3 genome segments, and much more closely than the three S1 genome segments. We have analyzed the evolutionary divergence patterns of these three genome segments. The rate of mismatch accumulation in third base codon positions is roughly the same for all three genome segments, but the rates of mismatch accumulations in first, and particularly in second, base codon positions are quite different. For the S1 genome segments there is little difference between the rates of mismatch accumulations in all three codon positions, which indicates that retention of function is compatible with very extensive structural flexibility. By contrast, the rates of mismatch accumulations in first and second base codon positions are far less for the S3 genome segments, which encode the nonstructural protein sigma NS, and much lower still for the M2 genome segments, which suggests the existence of very stringent structural constraints for protein mu 1C, which might be expected of a protein that is a capsomer component.

Amino Acid Sequence↗
PubMed1996

Autonomic and antiarrhythmic drug modulation of ST segment elevation in patients with Brugada syndrome.

OBJECTIVES: We examined the modulatory effects of autonomic nervous system and antiarrhythmic drugs on the ST segment in patients with Brugada syndrome to gain an insight into the mechanism of ST segment elevation. BACKGROUND: Right bundle branch block, ST segment elevation and ventricular tachyarrhythmias define a distinct clinical and electrocardiographic (ECG) syndrome (Brugada syndrome). However, the mechanism of ST segment elevation and the causes of this syndrome are unknown. METHODS: The study included four patients in whom structural heart or coronary artery disease was excluded by noninvasive and invasive tests. High take-off ST segment elevation of either the coved or saddle-back type in precordial leads V1, V2 and V3 was seen in all patients. Three patients experienced recurrent episodes of syncope or aborted sudden cardiac death, and the remaining patient had palpitation. Autonomic receptor stimulation and blockade and intravenous administration of antiarrhythmic drugs were performed during sinus rhythm while the 12-lead ECG was recorded. Metaiodobenzylguanidine (MIBG) scanning and Holter monitoring were also performed. RESULTS: Beta-adrenoceptor stimulation by intravenous isoproterenol consistently reduced (> or = 0.1 mV) ST segment elevation at or 80 ms after the J point in all four patients. Selective alpha-adrenoceptor stimulation by intravenous norepinephrine in the presence of propranolol or by intravenous methoxamine consistently augmented, whereas alpha-adrenoceptor blockade reduced, ST segment elevation in three patients. Intracoronary acetylcholine or intravenous edrophonium or neostigmine augmented ST segment elevation without inducing coronary spasm in three of four patients. Class IA antiarrhythmic drugs also consistently augmented (three patients), whereas class IB drugs had no effect on (two patients) ST segment elevation. No abnormality was found on MIBG imaging or heart rate variability in three patients, suggesting that autonomic dysfunction is not a primary disease process. Class IA drugs had no effect on ST segment in three control patients, suggesting that the ST segment elevation seen in patients with Brugada syndrome in response to the drugs is not a nonspecific response. CONCLUSIONS: ST segment elevation in patients with Brugada syndrome was augmented by selective stimulation of alpha-adrenoceptors or muscarinic receptors or by class IA drugs but was mitigated by beta-adrenoceptor stimulation or alpha-adrenoceptor blockade. These responses might be explained by postulating the presence of an area of early repolarization or a local "depolarized" area in the ventricle causing ST segment elevation in this syndrome. Because only a small number of patients were studied, these possibilities need further evaluation.

Adult↗
PubMed1995

A new segmentation method of electroencephalograms by use of Akaike's information criterion.

Non-stationary EEGs, whose statistical properties change with time, were segmented into stationary segments to closely track the behavior of EEG characteristics. We have developed a new segmentation method of optimizing segmentation parameters by using AIC (Akaike's information criterion) as an objective criterion. We applied the segmentation method to EEGs. The instantaneous power spectra of EEGs estimated with wavelet transform were compared with the segmented EEGs. EEGs were recorded from F3, F4, C3, C4, P3, P4, 01 and 02 in 13 normal subjects. Artifact-free 15-s epochs were taken at each electrode location. Each epoch was divided into stationary segments, consisting of several fixed intervals, by optimizing 2 segmentation parameters (interval length and starting point) so that the sum of AICs for several sequences of segments could be the smallest. The EEG segmentation could represent differences in the power spectra between segments. The average length of segments during relaxed wakefulness was 6.0 +/- 3.8 s. The EEG segmentation during mental arithmetic could detect the start of mental arithmetic.

Adolescent↗
PubMed2006

Classification and segmentation of intracardiac masses in cardiac tumor echocardiograms.

This paper describes an automatic method for classification and segmentation of different intracardiac masses in tumor echocardiograms. Identification of mass type is highly desirable, since to different treatment options for cardiac tumors (surgical resection) and thrombi (effective anticoagulant treatment) are possible. Correct diagnosis of the character of intracardiac mass in a living patient is a true challenge for a cardiologist; therefore, an objective image analysis method may be useful in heart diseases diagnosis. Image texture analysis is used to distinguish various types of masses. The presented methods assume that image texture encodes important histological features of masses and, therefore, texture numerical parameters enable the discrimination and segmentation of a mass. The recently developed technique based on the network of synchronized oscillators is proposed for the image segmentation. This technique is based on a 'temporary correlation' theory, which attempts to explain scene recognition as it would be performed by a human brain. This theory assumes that different groups of neural cells encode different properties of homogeneous image regions (e.g. shape, color, texture). Monitoring of temporal activity of cell groups leads to scene segmentation. A network of synchronized oscillators was successfully used for segmentation of Brodatz textures and medical textured images. The advantage of this network is its ability to detect texture boundaries. It can be also manufactured as a VLSI chip, for a very fast image segmentation. The accuracy of locating of analyzed tissues in the image should be assessed to evaluate a segmentation technique. The new evaluation method based on measurement of physical textured test objects was proposed. Firstly, a series of object images was obtained by the use of different devices (scanner, digital camera and TV camera). Secondly, the images were segmented using oscillator network and feedforward artificial neural network. Thirdly, geometrical test object parameters were estimated and compared to its true values. The experiment was repeated also for ultrasound images, which represented rectangular cross-section of synthetic sponge submerged in water. In addition, classification and segmentation of selected benign tumor echocardiograms were performed. Oscillator network was used with network weights defined for both whole texture region and texture boundary detection for the tumor segmentation. The latter method provides much faster segmentation with the similar accuracy. The obtained segmentation results were discussed and compared to the artificial neural network classifier. Finally, it was demonstrated that the network of synchronized oscillators is a reliable tool for the segmentation of the selected intracardiac masses, since it gives a relatively accurate location of analyzed tissues. The advantage of the proposed method is its resistance to changes of the visual information in the analyzed image and to noise and artifacts, often present in echocardiograms.

Echocardiography↗
PubMed2005

Semi-automated brain tumor and edema segmentation using MRI.

PURPOSE: Manual segmentation of brain tumors from magnetic resonance images is a challenging and time-consuming task. A semi-automated method has been developed for brain tumor and edema segmentation that will provide objective, reproducible segmentations that are close to the manual results. Additionally, the method segments non-enhancing brain tumor and edema from healthy tissues in magnetic resonance images. METHODS AND MATERIALS: In this study, a semi-automated method was developed for brain tumor and edema segmentation and volume measurement using magnetic resonance imaging (MRI). Some novel algorithms for tumor segmentation from MRI were integrated in this medical diagnosis system. We exploit a hybrid level set (HLS) segmentation method driven by region and boundary information simultaneously, region information serves as a propagation force which is robust and boundary information serves as a stopping functional which is accurate. Ten different patients with brain tumors of different size, shape and location were selected, a total of 246 axial tumor-containing slices obtained from 10 patients were used to evaluate the effectiveness of segmentation methods. RESULTS: This method was applied to 10 non-enhancing brain tumors and satisfactory results were achieved. Two quantitative measures for tumor segmentation quality estimation, namely, correspondence ratio (CR) and percent matching (PM), were performed. For the segmentation of brain tumor, the volume total PM varies from 79.12 to 93.25% with the mean of 85.67+/-4.38% while the volume total CR varies from 0.74 to 0.91 with the mean of 0.84+/-0.07. For the segmentation of edema, the volume total PM varies from 72.86 to 87.29% with the mean of 79.54+/-4.18% while the volume total CR varies from 0.69 to 0.85 with the mean of 0.79+/-0.08. The HLS segmentation method perform better than the classical level sets (LS) segmentation method in PM and CR. CONCLUSIONS: The results of this research may have potential applications, both as a staging procedure and a method of evaluating tumor response during treatment, this method can be used as a clinical image analysis tool for doctors or radiologists.

Algorithms↗
PubMed2005

A parametric imaging approach for the segmentation of ultrasound data.

When an ultrasonic examination is performed, a segmentation tool would often be very useful, either for the detection of pathologies, the early diagnosis of cancer or the follow-up of the lesions. Such a tool must be both reliable and accurate. However, because of the relatively reduced quality of ultrasound images due to the speckled texture, the segmentation of ultrasound data is a difficult task. We have previously proposed to tackle the problem using a multiresolution Bayesian region-based algorithm. For computation time purposes, a multiresolution version has been implemented. In order to improve the quality of the segmentation, we propose to perform the segmentation not only from the envelope image but to combine more information about the properties of the tissues in the segmentation process. Several acoustical parameters have thus been computed, either directly from the images or from the radio-frequency (RF) signal. In a previous study, two parametric images were involved in the segmentation process. The parameter represented the integrated backscatter (IBS) and the mean central frequency (MCF), which is a measurement related to the attenuation of ultrasound waves in the media. In this study, parameters representative of the scattering conditions in the tissue are evaluated in the multiparametric segmentation process. They are extracted from the K-distribution (alpha,b) and the Nakagami distribution (m,Omega) and are related to the local density of scatterers (alpha,m), the size of the scatterers (b) and the backscattering properties of the medium (Omega). The acoustical features are calculated locally on a sliding window. This procedure allows to built parametric mapping representing the particular characteristics of the medium. To test the influence of the acoustical parameters in the segmentation process, a set of numerical phantoms has been computed using the Field software developed by J.A. Jensen. Each phantom consists in two regions with two different acoustical properties: the density of scatterers and the scattering amplitude. From both the simulated RF signals and envelope images, the parameters have been computed; their relevance to represent a particular characteristic of the medium is evaluated. The segmentation has been processed for each phantom. The ability of each parameter to improve the segmentation results is validated. A agar-gel phantom has also been created, in order to test the accuracy of the parameters in conditions closer to the in vivo ultrasound imaging. This phantom contains four inclusions with different concentrations of silica. A B&K ultrasound device provides the RF data. The quantification of the segmentation quality is based on the rate of correctly classified pixels and it has been computed for all the parameters either from the field images or the phantom images. The large improvement in the segmentation results obtained reveals that the multiparametric segmentation scheme proposed in this study can be a reliable tool for the processing of noisy ultrasound data.

Mathematics↗
PubMed2005

Cooperative function of deltaC and her7 in anterior segment formation.

Segmentation of paraxial mesoderm in vertebrates is regulated by a genetic oscillator that manifests as a series of wavelike or cyclic gene expression domains in the embryo. In zebrafish, this oscillator involves members of the Delta/Notch intercellular signaling pathway, and its down-stream targets, the Her family of transcriptional repressors. Loss of function of any one of the genes of this system, such as her7, gives rise to segmentation defects in the posterior trunk and tail, concomitant with a disruption of cyclic expression domains, indicating that the oscillator is required for posterior segmentation. Control of segmentation in the anterior trunk, and its relationship to that of the posterior is, however, not yet well understood. A combined loss of the cyclic Her genes her1 and her7 disrupts segmentation of both anterior and posterior paraxial mesoderm, indicating that her genes function redundantly in anterior segmentation. To test whether this anterior redundancy is specific to the her gene family, or alternatively is a more global feature of the segmentation oscillator, we looked at anterior segmentation after morpholino knock down of the cyclic cell-surface Notch ligand deltaC (dlc), either alone or in combination with her7, or other Delta/Notch pathway genes. We find that dlc is required for coherence of wavelike expression domains of cyclic genes her1 and her7 and maintenance of their expression levels, as well as for cyclic transcription of dlc itself, confirming that dlc is a component of the segmentation oscillator. Dose dependent, posteriorly-restricted segmentation defects were seen in the dlc knock down, and in combination with the deltaD or notch1a mutants. However, combined reduction of function of dlc and her7 results in defective segmentation of both anterior and posterior paraxial mesoderm, and a failure of cyclic expression domains to initiate, similar to loss of both her genes. Thus, anterior segmentation requires the functions of both her and delta family members in a parallel manner, suggesting that the segmentation oscillator operates in paraxial mesoderm along the entire vertebrate axis.

Animals↗
PubMed2000

Control of ion and fluid transport by putative second messengers in different segments of the Malpighian tubules of the black field cricket Teleogryllus oceanicus.

The differences in second messenger control of secretion were investigated in the distal and main segments of the Malpighian tubules of the black field cricket Teleogryllus oceanicus. Secretion by the main segment was considerably increased by corpora cardiaca extract and db-cAMP. Corpora cardiaca had no effect on secreted fluid composition or intracellular elemental composition but db-cAMP increased Na(+) and Cl(-) transport, as measured by x-ray microanalysis of secreted fluids and cells. Secretion by the main segment was considerably increased by forskolin and by Sp-cAMP. Secretion in the distal segment was abolished by corpora cardiaca extract but was unaffected by db-cAMP and only slightly reduced by 8-bromo-cAMP. However, Sp-cAMP increased secretion but forskolin reduced secretion. The responses of the distal segment suggest the possibility of a multiplicity of controls through different protein kinases and adenylyl cyclases. Secretion rate in the main segment was also increased by cGMP but distal segment secretion was unaffected. Secretion from both segments was increased by 5-HT. In the main segment secretion rate was increased by Ca-ionophore and thapsigargin and decreased by verapamil. This suggests a role for Ca(2+) as a controlling second messenger. In the distal segment only Ca-ionophore had an effect on secretion rate, which was reduced. Secretion rates in both segments were decreased in Ca-free saline. In saline in which Sr(2+) replaced Ca(2+), secretion rate in the main segment was greatly increased whilst that of the distal segment was decreased, suggesting that Sr(2+) could substitute for Ca(2+) as a second messenger.

Journal Article↗
PubMed1998

Inappropriate microvascular constriction produced transient ST-segment elevation in patients with syndrome X.

OBJECTIVES: The aim of this project was to study the responsible site(s) and underlying cardiac disease(s) of patients with transient ST-segment elevation and normal coronary angiograms. BACKGROUND: Transient ST-segment elevation has been demonstrated in patients with variant angina or unstable angina. In those patients, epicardial coronary arteries, not microvessels, are always the responsible site for the transient ST-segment elevation. METHODS: This study consisted of three cases with a transient ST-segment elevation and normal coronary angiograms. Treadmill testings were performed before coronary angiography in all cases. Coronary angiography was undertaken during the control state and during ST-segment elevation and, when possible, a Doppler guide wire was positioned in the left anterior descending artery (LAD). Coronary responses to vasodilators were observed. Finally, cardiac biopsy was performed and pathologic observation was conducted. RESULTS: All three cases had significant ST-segment depression during treadmill testing in II, III, aVF and V4-6 leads; however, no angiographic coronary stenosis was demonstrated and vasospasm was not provoked. A transient ST-segment elevation associated with chest pain was observed in V1-5 leads, but normal coronary angiograms during ST-segment elevation were observed in every case. Coronary blood flow (CBF) velocity profile remained normal during ST-segment elevation. In one case, vasodilator responses to the LAD during ST-segment elevation were also measured. A 0.5 mg intracoronary injection of nitroglycerin increased CBF velocity (220%), but ST-segment elevation was not normalized and chest pain persisted. A 10 mg intracoronary injection of papaverine (PVN) further increased CBF velocity up to 340%, and this normalized ST-segment elevation and relieved chest pain quickly. Either endothelium-dependent coronary flow reserve (CFR) measured with a 100 microg intracoronary infusion of acetylcholine, or flow-dependent CFR by a 10 mg intracoronary injection of PVN was reduced in one of two cases measured. Pathologic findings supported syndrome X as the underlying cardiac disease in all cases. CONCLUSIONS: These findings suggested a new clinical implication involving transient ST-segment elevation mimicking variant angina and normal coronary angiograms in patients with syndrome X. The major responsible site for this phenomenon was suggested to be coronary arterioles of less than 200 microm in diameter.

Acetylcholine↗
PubMed1997

Muscles in the Drosophila second thoracic segment are patterned independently of autonomous homeotic gene function.

BACKGROUND: In Drosophila, segment-specific muscle pattern is thought to be determined by the autonomous function of homeotic selector genes in the mesoderm in combination with inductive cues from the developing epidermis and nervous system. Here, we have examined the roles of homeotic genes in the patterning of the somatic muscles of the thoracic segments of Drosophila. RESULTS: We determined the expression patterns of homeoproteins in the mesoderm of the thoracic segments during embryonic and adult development. We found that, unlike the mesoderm of the first and third thoracic segments which express Sex combs reduced and Antennapedia (Antp), respectively, the mesoderm of the second thoracic segment does not express any known homeotic selector gene of the Antp or bithorax complex. In animals homozygous for Antp null mutations, the muscles of the second thoracic segment were affected in the embryo, probably as an indirect consequence of its requirement in the ectoderm. Animals that specifically lacked Antp function in the mesoderm, but expressed the gene in the epidermis, developed with a normal muscle pattern in the second thoracic segment. Furthermore, specific ectopic expression of Antp and other homeotic selector genes in the mesoderm of the second thoracic segment respecified its muscle pattern, indicating that these genes are not required autonomously during muscle development in this segment. Finally, we showed that Antp continues to be expressed in the mesoderm of the homeotically transformed third thoracic segment in the 'four-winged fly', and suggest that this is a likely reason for the failure of flight muscle development in the transformed segment. CONCLUSIONS: We present a model for muscle development in the second thoracic segment whereby mesodermal properties are specified entirely by induction, in contrast to muscle development in other segments, where autonomous function for homeotic selector genes is also required.

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