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Biomedical subjects

A Tabib

Publications and source records attributed to A Tabib.

At least 37 records · Page 2Linked to original sources
PubMed1999

Thoracoscopic epicardial radiofrequency ablation for vagal atrial fibrillation in dogs.

Epicardial radiofrequency catheter ablation of the atria in the open-chest dog has been shown to reduce inducibility of atrial fibrillation. Video-assisted endoscopic techniques decrease the operative trauma in adult thoracic surgery. We report our results of video-assisted thoracoscopic radiofrequency catheter ablation of the atria for the prevention of atrial fibrillation induction in canines. In 12 consecutive anesthetized dogs, induction of sustained atrial fibrillation was reproducibly obtained by burst pacing and cervical vagal stimulation. In six dogs, biatrial ablation was performed through right and left minithoracotomies and guided by video-assisted endoscopic techniques. The remaining six dogs underwent a video-guided left atrial procedure. Long continuous and transmural lesions were produced using epicardial temperature controlled radiofrequency energy delivery according to a simplified maze approach. Transmural lesions were demonstrated at the end of the study by examination of the heart. Sustained atrial fibrillation was still inducible after the right atrial ablation but sustained atrial fibrillation could not be induced following left atrial ablation. In acute canine studies: (1) epicardial radiofrequency catheter ablation of the atria is feasible using video-assisted endoscopic techniques; (2) ablation extended or confined to the left atrium appears to be effective in preventing the inducibility of sustained vagal atrial fibrillation; and (3) ablation of the right atrium alone had no antiarrhythmic effect.

Animals↗
PubMed1998

Polyamines induce malignant transformation in cultured NIH 3T3 fibroblasts.

Previous studies have demonstrated that polyamines accumulate in cancer cells and that overproduction of ornithine decarboxylase (ODC), which catalyzes polyamine synthesis, elicits the acquisition of the transformed phenotype. However, it was not clear whether the overexpression of ODC and the accumulation of polyamines are only innocent by-products of the transformation process. In this study we demonstrate that polyamines as such, may play a crucial role in malignant transformation. The system used consisted of NIH 3T3 fibroblasts transfected with a construct (pATMras) in which Ha-ras was under the transcriptional control of the mouse mammary tumor virus long terminal repeat (MMTV-LTR) promoter (MMTVras cells). Dexamethasone, which activates the promoter, triggered phenotypic transformation. This was accompanied by an increase in ODC activity and polyamine accumulation. Cells, thus transformed, grew in soft agar and formed typical foci. alpha-Difluoromethylornithine (DFMO), which blocks polyamine synthesis, inhibited the dexamethasone-enhanced transformation. This inhibition was reversed by polyamines. Polyamines caused transformation of MMTVras cells in the absence of dexamethasone. Under these conditions, cells became anchorage independent. This phenomenon is not explained by the leakiness of ras, since normal, immortalized NIH 3T3 fibroblasts, also grew in soft agar in the presence of polyamines. Taken together, these observations suggest that polyamines may stimulate malignant transformation of immortalized cells, in cooperation with other factors, such as oncogenes or genetic defects.

3T3 Cells↗
PubMed1998

[Arrhythmogenic right ventricular dysplasia and Uhl disease. Anatomic study of 100 cases after sudden death].

Assessing 100 cases of arrhythmogenic right ventricular dysplasia causing unexpected sudden death, we stress two aspects of the disease, specially concerning pathologists: diagnosis value and limitations of endomyocardial biopsy and high frequency of the disease among unexpected sudden death in young adults. When the disease is identified genetic screening should be performed among patient's family members. The anterior right ventricular wall is very thin (partly or completely) and microscopic examination shows absence of muscle cells, replaced by normal fatty tissue. Associated lesions are often present: slight abnormalities of left ventricle, mucoid degeneration of auriculo-ventricular valves and recently described lesions of His conductive tissue. Apoptotic anomalies are now incriminated for agenesy or disappearing right ventricular muscle.

Adolescent↗
PubMed1997

Ultrasound contrast agent in intravascular echography: an in vitro study.

The intravascular ultrasound image of the intraluminal contour depends on the difference between acoustic impedances of the media which create the endoluminal interface. There are several limitations to the visualization and detection of this interface. These limitations are due to artifacts encountered during image formation and to anatomical complexity. The purpose of this study is to obtain intraluminal contour enhancement using ultrasound contrast agent (UCA). Therefore, our objective was to address the feasibility of this technique by documenting the following: (i) the acoustic properties of UCA at 30 MHz; (ii) in vitro experimentation with tube or postnecrotic artery; and (iii) suitable digital processing. The images obtained with UCA (enhanced image quality) and subtracted from those without UCA provided, after simple digital processing, accurate visualization of the arterial lumen. The image obtained exhibits an even, high-contrast intraluminal edge. Such characteristics facilitate contour extraction by the automated contour detection procedures.

Contrast Media↗
PubMed1997

[Analysis of the diagnostic value of endovascular ultrasound with roc curves. Practical implications].

Intravascular ultrasound enables detection of the components of atherosclerotic plaques. The diagnostic value was assessed by ROC (receiver operating characteristic) curves on images acquired in vitro and correlated with the histological findings in 61 arteries. Five questions were asked of each operator; the reply was represented by a continuous variable in order to express all nuances of judgement. The area under the ROC curve, Az, was the criterion of performance (0.5 : chance response : 1.0 : all replies were accurate). Detection of plaque was satisfactory (Az = 0.89). The three layer appearance of muscular arteries was well recognised (Az = 0.94). The fibrous composition of a plaque was only just satisfactory (Az = 0.88) with 38.7% interindividual variability. The lipid composition of the plaque was poorly recognised (Az = 0.76) with large interindividual variability (52.8%) : hypoechogenicity was too ambiguous a sign from the acoustic point of view. A hypoechogenic zone must not be synonymous with a lipid plaque but a cellular zone. Calcium can almost always be detected (Az = 0.98) with a very low interindividual variability (10.7%), fibrohyaline progression of some plaques can be confusing. The authors present a more objective description of endovascular ultrasonographic images. They conclude that the diagnostic performance of 30 MHz intravascular ultrasound is satisfactory but several limitations are apparent in the interpretation of images, especially hypoechogenic zone and hyper-reflective zones with high attenuation.

Arteries↗
PubMed1997

[Large coronary artery aneurysms. A study of 20 clinical cases in the elderly].

The aim of this study was describe the anatomical features of coronary aneurysms and assess their role in causing death. Twenty clinico-pathological cases were recensed prospectively out of 8,920 autopsies (0.22%). The average age at death was 68 +/- 20 years (14 men and 6 women). Death was due to a cardiac cause in 90% of cases. The aneurysms were located on a single coronary artery in 14 cases, on 2 coronary arteries in 3 cases, and on all three arteries in 3 cases with a mean maximum diameter of 15 +/- 4.5 mm. Aneurysms of the right coronary artery were the most common (p < 0.01) and the largest (16.7 +/- 3.8 mm; p = 0.12) and circumflex arteries (12 +/- 3.1 mm, p = 0.03). The diameter of the coronary aneurysm was greater in the more elderly patients (r = 0.51 ; p = 0.022). The coronary aneurysms were diffuse in 10 subjects and localised in the other 10 (mainly fusiform and proximal). Only 3 aneurysms were directly associated with significant stenosis of the same artery. The aetiology was atherosclerosis in 18 cases, with associated extra-cardiac disease in 14 cases; the other 2 cases were dystrophic. The underlying anatomical abnormality constantly found was variable degrees of atrophy and destruction of the musculo-elastic elements of the media, a source of dilation. In 80% of cases, thrombosis of the aneurysm was directly or indirectly responsible for death. Coronary artery aneurysms are a rare finding and are frequently complicated by fatal thrombosis. Coronary angiographic detection of this condition characterised by the large size and absence of stenosis of the artery should lead to prophylactic antithrombotic therapy.

Adult↗
PubMed1997

[Sudden death and myocardial infarction caused by thrombosis of normal coronary arteries: an anatomic study of 3 cases].

The anatomic lesions of two cases of sudden death (one man and one 24 years old woman) and of one case of rapidly fatal myocardial infarction (51 years old woman) are described. The coronary lesions were exclusively thrombotic with no associated atherosclerosis or pre-existing arterial wall change. The thrombi were occlusive from the outset or were constituted in successive mural stages, the last being occlusive and giving rise to the clinical symptoms (sudden death and/or myocardial infarction). Several points are discussed. The concept of normal coronary artery must be confirmed by anatomic examination: coronary angiography is not sufficient for the diagnosis of dangerous atherosclerotic plaques which are not particularly stenotic, eccentric, lipidic and fragile. Thrombogenic factors are better understood and some may play a role in these cases of "primary thrombosis", by they of plasma or platelet origin. The trigger role of spasm cannot be ignored as some of the spastic and thrombotic factors are similar. The preferential coronary site of these thromboses may be explained by constitutional changes (arterial hypolasia with narrow lumen) or acquired lesions (repeated arterial trauma due to shearing by the movements of the underlying left ventricle transmitted to the epicardial coronary arteries).

Adult↗
PubMed1996

Effect of colchicine on circulating and myocardial neutrophils and on infarct size in a canine model of ischemia and reperfusion.

Myocardial injury after ischemia/reperfusion has been attributed in part to the effects of neutrophils. We examined whether colchicine, a potent and rapid inhibitor of neutrophils, may reduce inflammatory leukocytosis, prevent postischemic myocardial neutrophil accumulation, and reduce infarct size (IS). Twenty-four dogs were randomized to either a control (saline administration) or a colchicine (1 mg/kg intravenously, i.v.) group. Anesthetized open-chest dogs underwent 120-min coronary artery occlusion followed by 6-h reperfusion. Determinants of IS [area-at-risk (AAR) and collateral flow] and IS were measured in 22 dogs (11 in each group). We evaluated neutrophil toxicity by measuring ex vivo production of reactive oxygen species by chemiluminescence. Myocardial localization and accumulation of neutrophils were histologically evaluated by independent observers. The number of circulating neutrophils (p < 0.01), neutrophil cytotoxicity (p < 0.05), and neutrophil myocardial accumulation after 6-h reperfusion (p = 0.006) were reduced in treated dogs. Left ventricular (LV) peak rate of pressure increase was similar in both groups during ischemia /reperfusion. However, whereas collateral blood flow and AAR, the main determinants of IS, were similar in control and treated dogs, there was no reduction in IS: 37.1 +/- 7% of AAR in controls and 37.4 +/- 8% in treated dogs. Despite marked reduction of neutrophil toxicity and postischemic myocardial neutrophil accumulation, no myocardial protection could be detected in this dog model.

Animals↗
PubMed1996

A selenium supplement associated or not with vitamin E delays early renal lesions in experimental diabetes in rats.

Seventy rats were separated into five groups: one group of 12 was used as a control and received a purified diet, and four groups of streptozotocin-induced diabetic rats, totalling 58, were fed the same diet without or with selenium (Se) supplementation. Of the noncontrol rats, 14 were without supplementation (Group D), 14 were fed a Se-rich yeast diet (i.e., selenion) (Group DSel), 14 received selenomethionine (Group DSm), and 16 received selenomethionine + tocopherol acetate (Group DSmE). Supplementation with Se in all groups was 0.99 micromole/100g of diet and with tocopherol acetate was 0.145 micromole/100 g. All diabetic rats were mildly balanced by insulin. After 24 weeks of diet, plasma glucose tended to decrease in diabetic Se-supplemented groups DSmE > DSm > DSel versus Group D. In DSm and DSmE groups, plasma lipid peroxides also decreased compared with Group D, but this decrease reached significance only for DSmE (P < 0.01 for both TBARS and conjugated dienes). Plasma triglycerides also decreased in DSm and DSmE groups versus Group D (P < 0.01; P < 0.05, respectively). At the same time, Se increased significantly in kidneys of Groups DSel and DSm versus D and more weakly in Group DSmE, but in this case was associated with a large increase of vitamin E. These beneficial effects of selenium supplement and more so of selenium combined with vitamin E were associated with a protection of kidneys in diabetic rats which found expression in a significant correction of renal hyperfiltration (P < 0.05) and in a diminution of the number and severity of glomerular lesions (P < 0.0005).

Animals↗
PubMed1996

[Unexpected sudden cardiac death. An evaluation of 1000 autopsies].

The aim of this study was to search for a cardiac cause of death after an otherwise negative medico-legal autopsy in 1,000 adults under 65 years of age with no previous history, who suffered a sudden death. Four hundred and seven coronary causes were established with 152 negative autopsies and 441 other cardiac lesions. These 441 cases comprised 193 cardiomyopathies, 106 His bundle lesions, 50 partial forms of Uhl's anomaly (or arrhythmogenic right ventricular dysplasia), 14 isolated mitral valve prolapses, 22 chronic valvular lesions, 8 myocarditis, 16 pulmonary embolisms, 11 chronic cor pulmonale, 11 aortic dissections and 10 atrophic fibrous plaques of the left ventricle, sequellae of thoracic trauma. His bundle lesions (isolated and associated) were observed 299 times out of 1,000 cases and mitral valve prolapse 125 times. Age and gender, circumstances of sudden death, the weight of the heart, are reported for each group of conditions. The frequency of associations, especially of His bundle lesions, suggests that they may have a potentialising effect on the genesis of the fatal arrhythmia.

Adult↗
PubMed1994

Activation of the proto-oncogene c-myc and c-fos by c-ras: involvement of polyamines.

Rat kidney cells infected with a temperature-sensitive mutant of Kirsten sarcoma virus (Ki-MSV ts 371) expressed Ki-Ras at 37 degrees C but not at 42 degrees C. This expression of the oncogene was accompanied by an increase in the activity of ornithine decarboxylase (ODC) and the accumulation of putrescine. Elevation of cellular polyamine content triggered the transcription of c-myc and c-fos. alpha-Difluoromethylornithine, a specific inhibitor of ODC, prevented the transcription of c-myc in cells grown at 37 degrees C. Putrescine, at physiological concentrations, triggered the transcription of c-myc and c-fos in cells grown at 42 degrees C, when Ki-ras was not expressed. It has been suggested that polyamines participate in a cascade of events leading to the communication between membrane-bound and nuclear oncogene products. These findings may attribute a new function to the naturally occurring polyamines.

Animals↗
PubMed1994

[Malignant mesothelioma of the pericardium. An anatomo-clinical study of 10 cases].

Ten pericardial mesotheliomas (8 of which had associated unilateral pleural involvement) were observed over a 22 year period in subjects over 50 years of age. The diagnosis was only confirmed several months after the presenting symptoms (shortness of breath, chest pain), usually by histological studies of pericardial biopsies performed during construction of a pleuro-pericardial window because of tamponade or of pleural biopsy in cases of pleuro-pericardial disease. There is no specific diagnostic feature and even modern imaging methods are unable to distinguish mesothelioma from pericardial tuberculosis. In 7 cases, there were large haemorrhagic pericardial effusions. At present, there is no effective treatment for mesothelioma and the physician's goal is to make the patient's short survival time as comfortable as possible with respect to the severe pain and recurrent pleuro-pericardial effusions. The pericardial mesothelioma is rare (less than 1% compared with 96% pleural and 3% peritoneal localisations) and possibly related to exposure to asbestos, at least in those cases with associated pleural involvement. The authors underline the utility of histological analysis of the utility of histological analysis of the pericardium if only to establish the diagnosis of mesothelioma and to enable administration of curative treatment of other pathologies (tuberculosis, malignant lymphoma) with identical clinical presentations.

Aged↗
PubMed1994

[Artefacts and intravascular ultrasonography. Analysis and implications for a better reliability in the interpretation of images and measurements].

Intravascular ultrasound catheters provide cross-sectional images of vessel walls and surrounding tissues with rotating transducers, and the behavior of ultrasound in heterogeneous media both cause degradation of image quality. Qualitative and quantitative analyses of in vivo studies are operator-dependent and limited by artifacts. We investigated these limitations by an in vitro study on plexiglass phantoms and segments of fresh arteries. We observed, analyzed and interpreted the most specific reasons for image artifacts: geometric distortions, the point spread function of the imaging system and the near field effects. Various practical implications have resulted from this study. Knowledge of the most obvious pitfalls will enable the user to obtain maximum benefits from intravascular ultrasound imaging, and to appreciate its limitations.

Arterial Occlusive Diseases↗
PubMed1994

[Pericardium and heart transplantation].

The authors emphasise the role of the pericardium in the post-operative complications of cardiac transplantation: its role is as important as it is underestimated in its frequency, severity and the pathogenic discussions that it induces. This study, based on a retrospective analysis of 191 anatomo-clinical cases (156 autopsies and 35 retransplantations) of patients undergoing cardiac transplantation before the 1/03/1993 including macroscopic and histopathologic analysis of the pericardial lesions, histochemical analysis of the lymphocytic populations, and analysis of associated coronary and myocardial lesions. The results were classified as early or late (after the 75th postoperative day) complications. Early complications included 27 suppurating mediastino-pericarditis (13 aspergillosis and 14 bacterial), 16 autonomous non-infective pericardial complications (6 haemopericardiums, 6 organised compressive haematomas, 4 early constrictive pericarditis) and 9 lymphocytic epicarditis associated with acute myocardial rejection. Late complications included one common constrictive symphysis and 14 reactivated epicarditis associated with transplantation coronary disease (chronic rejection) with associated lymphoplasmocytic nodules and a myocardial vasculitis. These observations suggest two important conclusions: 1) the need for active diagnostic measures to detect pericardial complications in cases of cardiac transplant dysfunction in the early postoperative period with no signs of acute rejection on myocardial biopsy: the presence of epicardial lesions on biopsy should be taken into account and not just assumed to be a postoperative epiphenomenon; 2) the presence of epicarditis due to reactivated epicarditis may cause inextensible hardening of the epicardium which adds to the effects of restrictive cardiomyopathy of chronic rejection.

Adult↗
PubMed1993

Artifacts in intravascular ultrasound imaging: analyses and implications.

The ability of an intravascular ultrasound catheter to give cross-sectional images of vessel walls and surrounding tissues, and the behavior of ultrasound in heterogeneous media, are at the origin of degradation of image quality. Qualitative and quantitative analyses of in vivo studies are then operator-dependent and are limited by artifacts. We investigated these limitations by an in vitro study on plexiglass phantoms and segments of fresh arteries. We used a 20 MHz transducer mounted on the tip of a 4.8 F catheter and an interventional ultrasound system. The ultrasound beam is reflected onto the rotating transducer at 600 rotations per minute (RPM), creating 360 degrees real-time images (10 images/second). We then observed, analyzed and interpreted the most specific reasons for image artifacts: geometric distortions, multiple echoes, the point spread function (PSF) of the imaging system, near-field effects, "petal-shaped" effect, and ultrasound speckle. Various practical implications have resulted from this study. Only a thorough knowledge of how to avoid some of the most obvious pitfalls will enable the user to obtain maximum benefits from intravascular ultrasound imaging, and to appreciate its limitations.

Arteries↗