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Biomedical subjects

D Atar

Publications and source records attributed to D Atar.

At least 55 records · Page 3Linked to original sources
PubMed1997

[Myocardial reperfusion: salvation or danger for the heart muscle? Stunning, hibernation and preconditioning: the states of endogenous cardiac protection against ischemia].

During most of our decade myocardial ischemia was regarded as an all-or-nothing phenomenon, either resulting in myocardial necrosis in case of severe and prolonged ischemia, or in negligible changes when ischemia was transient and mild. This view has been challenged in the wake of new discoveries during the last 15 years which indicate that depressed myocardial contractility with preserved viability may exist during or following ischemic insults. The clinical and pathophysiologic characteristics of these ischemic myocardial syndromes--stunning, hibernation and preconditioning--are discussed in the present overview.

Humans↗
PubMed1997

[Combined treatment for adhesive capsulitis of the shoulder].

Adhesive capsulitis is a problem for the orthopedic surgeon due to the difficulty of treatment. Although it is self-limited, few patients will wait for spontaneous resolutions while suffering pain and progressive loss of motion. Our aim was to modify the course of the disease and to shorten recovery time by combining intensive physiotherapy with intra-articular infiltration and gentle manipulation. 49 patients with 50 frozen shoulders were enrolled in the study. All patients were treated initially with physiotherapy for 4-8 weeks. If no improvement was noted the affected shoulder was infiltrated and gently manipulated. 27 of 49 patients (55%) improved dramatically with the initial physiotherapy regimen. They achieved full or nearly full range of motion, with significant relief of pain. 22 patients were infiltrated and manipulated. Elevation improved significantly from an average of 110.95 to 165.71 degrees (p < 0.001), external rotation from an average of 9.52 to 43.57 degrees (p < 0.001) and internal rotation also improved significantly (p < 0.001). Self assisted physiotherapy is the corner stone of treatment in adhesive capsulitis. When pain and limitation of passive range of motion persist, infiltration and gentle manipulation dramatically shortens the debilitating process.

Anesthetics, Local↗
PubMed1997

Bilateral dislocation of the hip during convulsions: a case report.

Simultaneous bilateral posterior dislocation of the hip is very uncommon and most cases are caused by road accidents. Simultaneous bilateral posterior dislocation of the hip due to convulsions is extremely rare. We report the case of a man who was diagnosed late and operated on 15 weeks after the injury. We discuss the treatment of chronic dislocation of the hip and review the literature.

Adult↗
PubMed1997

Role of troponin I proteolysis in the pathogenesis of stunned myocardium.

Myocardial stunning is characterized by decreased myofilament Ca2+ responsiveness. To investigate the molecular basis of stunned myocardium, we performed PAGE and Western immunoblot analysis of the contractile proteins. Isolated rat hearts were retrogradely perfused at 37 degrees C for either 50 minutes (control group) or for 10 minutes, followed by 20-minute global ischemia and 20-minute reperfusion (stunned group), or for 20-minute ischemia without reflow. Another group consisted of hearts subjected to 20-minute ischemia in which stunning was mitigated by 10-minute reperfusion with low Ca2+/low pH solution. Myocardial tissue samples subjected to PAGE revealed no obvious differences among groups. Western immunoblots for actin, tropomyosin, troponin C, troponin T, myosin light chain-1, and myosin light chain-2 showed highly selective recognition of the appropriate full-length molecular weight bands in all groups. Troponin I (TnI) Western blots revealed an additional band (approximately 26 kD, compared with 32 kD for the full-length protein) in stunned myocardial samples only. In parallel experiments, skinned trabeculae were treated with calpain I for 20 minutes; Western blots showed a TnI degradation pattern similar to that observed in stunned myocardium. Such TnI degradation was prevented by calpastatin, a naturally occurring calpain inhibitor. The results show that (1) TnI is partially and selectively degraded in stunned myocardium; (2) this degradation could be prevented by low Ca2+/low pH reperfusion, which also prevented the contractile dysfunction of stunning; and (3) calpain I could similarly degrade TnI, supporting the idea that Ca(2+)-dependent myofilament proteolysis underlies myocardial stunning.

Animals↗
PubMed1996

[Arthroscopic surgery of the knee with CO2 laser surgery of the knee].

We present a preliminary report of our experience with the CO2 laser in arthroscopic surgery of the knee. Between August '94 and February '95 a total of 27 knee arthroscopies were done with the Sarplan 1030 30-watt CO2 laser for various knee problems, mostly degenerative arthritis. Complications such as subcutaneous emphysema and reactive effusion were noted, but no other significant problems. Although the arthroscopies were performed in a CO2 medium, which created some technical difficulties, the CO2 laser was very effective in neatly shaving the degenerative, articular cartilage, and in meniscal debridement. With the laser probe, some areas of the knee joint previously not accessible, can be reached and treated. Our impression is that with proper indications, laser arthroscopy has some advantages over traditional arthroscopy. Further technical improvement is needed before it is introduced for routine use.

Adolescent↗
PubMed1995

Excitation-transcription coupling mediated by zinc influx through voltage-dependent calcium channels.

Electrical activity initiates a program of selective gene expression in excitable cells. Although such transcriptional activation is commonly attributed to depolarization-induced changes in intracellular Ca2+, zinc represents a viable alternative given its prominent role as a cofactor in DNA-binding proteins coupled with evidence that Zn2+ can enter excitable cells in a voltage-dependent manner. Here it is shown that Zn2+ entry into heart cells depends upon electrical stimulation and occurs via dihydropyridine-sensitive Ca2+ channels. The addition of extracellular Zn2+ to spontaneously depolarizing GH3 pituitary tumor cells induced the expression of a reporter gene driven by the metallothionein promoter, an effect that was prevented by exposure to dihydropyridine Ca2+ channel blockers. Thus, Zn2+ influx through L-type Ca2+ channels can mediate voltage-dependent gene expression.

Animals↗
PubMed1995

The diagnostic value of exercise echocardiography in ischemic heart disease in relation to quantitative coronary arteriography.

The aim of the study was to assess the diagnostic value of bicycle exercise echocardiography using quantitative coronary arteriography as a reference. Exercise echocardiography was performed in 70 consecutive patients referred for coronary angiography. Digital loops were obtained at rest, peak, and immediately after exercise in the standard views (parasternal long and short axis, apical two and four chamber views). Wall motion analysis was made on the basis of the 16 segment model, scoring each segment from 3 (hyperkinesia) to -1 (hypokinesia). Exercise echocardiography was considered positive when wall motion in at least one segment decreased at least one score from rest to peak or post exercise. Cinefilms were evaluated using automated quantitative coronary arteriography software. Transstenotic pressure gradients were calculated based on flow assumptions at the maximal stenosis flow reserve. Pressure losses > 30 mmHg and quantitatively measured percent diameter stenosis of > 50% were considered clinically significant. Stenoses in the equivocal range of 40-69% were subjected to separate analysis. Exercise echocardiography was superior to exercise-induced ST-segment depression in the diagnosis of coronary artery disease. In the overall sample of 70 patients, the sensitivity of exercise echocardiography against percent diameter stenosis was 84%, against pressure gradient 86%. The specificity against these two parameters was 86% and 84%, respectively. When analysing the subgroup of 40-69% stenoses (N = 14), sensitivity of exercise echocardiography against percent diameter stenosis was 67%, against pressure gradient 88%. The specificity against these two parameters was 100% and 84%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Alterations of excitation-contraction coupling in stunned myocardium and in failing myocardium.

Although both myocardial stunning and chronic heart failure are characterized by contractile dysfunction, there are profound differences in their underlying mechanisms. Changes in cardiac contractile force can be effected by modulation of intracellular [Ca2+] or by alteration of the contractile protein response to intracellular Ca2+. New evidence suggests that the principal lesion in the stunned myocardium resides at the level of the contractile proteins, which may be injured by proteases activated early during reperfusion. In contrast, failing myocardium is known to display abnormal intracellular Ca2+ handling, indicative of dysfunction of the sarcoplasmic reticulum. Alterations of gene expression and isoform switching of the myofilaments also occur in failing myocardium, consistent with an observed shift of the kinetics of crossbridge cycling. In conclusion, changes in both intracellular Ca2+ homeostasis and myofilament function occur in failing myocardium, while stunned myocardium primarily reflects an uncoupling between Ca2+ and contractile force.

Animals↗
PubMed1995

Bilateral hypoplastic lateral meniscus.

Among other anomalies of the menisci, a hypoplastic medial meniscus is extremely rare, with only four cases being described in the English literature. We were unable to find a description of this anomaly in the lateral knee compartment. A case report of a young patient with an arthroscopic diagnosis of bilateral hypoplastic lateral menisci is presented. We believe the arthroscopist should be familiar with this rare entity, even though it might be an incidental finding.

Adolescent↗
PubMed1995

Relationship between intracellular calcium and contractile force in stunned myocardium. Direct evidence for decreased myofilament Ca2+ responsiveness and altered diastolic function in intact ventricular muscle.

To elucidate the abnormalities of excitation-contraction coupling in stunned myocardium, we measured [Ca2+]i and force in thin fura 2-loaded ventricular trabeculae from control or stunned (20 minutes ischemia followed by 20 minutes reflow at 37 degrees C) rat hearts. At any given [Ca2+]o, force development was significantly lower in the stunned trabeculae than in control trabeculae. In contrast, there was no difference in the amplitude of Ca2+ transients between the two groups. The steady state force-[Ca2+]i relationship, assessed by tetanization in the presence of ryanodine, revealed both a decrease in maximal Ca(2+)-activated force and an increase in the [Ca2+]i required for 50% activation in stunned trabeculae. Postischemic myocardium also exhibited an accelerated rate of diastolic relaxation that was not due to changes in the rate of Ca2+ transient decay. Destabilization of attached cross-bridges in a quantitative model of cardiac myofibrils accurately reproduced the salient systolic and diastolic features of the stunned phenotype, suggesting an abnormality of the thin filaments. In response to supraphysiological increases in [Ca2+]o, diastolic [Ca2+]i and diastolic tone increased much more in stunned trabeculae than in controls, with the frequent occurrence of aftercontractions. This novel experimental model lends further support to the hypothesis that the primary lesion of excitation-contraction coupling resides at the level of the contractile proteins. The finding of enhanced susceptibility to calcium overload helps to rationalize the functional deterioration of stunned myocardium during intense inotropic stimulation and additionally suggests that stunned myocardium may represent a favorable substrate for triggered arrhythmias.

Actin Cytoskeleton↗
PubMed1995

Highlights of talipes equinovarus deformity.

Talipes equinovarus deformity has been extensively reported; however, controversy still exists regarding the cause, mechanism of the deformity, and treatment. This paper highlights these controversies to enhance understanding of this deformity.

Child, Preschool↗
PubMed1995

Reactivity of coronary arteries in relation to serum magnesium levels in patients with ischaemic heart disease--a quantitative coronary angiographic study.

The aim of the present study was to evaluate the relationship between coronary vascular tone and serum magnesium concentration in patients with ischaemic heart disease. Thirty-seven patients were subjected to intracoronary injection of 200 micrograms nitroglycerine after discontinuation of anti-anginal medication for 24 h (group I, n = 23), except if they received calcium channel blockers (group II, n = 14). Coronary angiographic images were acquired before and 2 min after the nitroglycerine injection. Using quantitative coronary arteriography, the luminal diameter of one middle-sized non-stenotic coronary artery segment in each patient was measured before and after nitroglycerine injection, and the percentual increase was computed. In group I, coronary artery diameter changed from 3.0 +/- 0.7 to 3.5 +/- 0.6 mm (mean +/- SD), representing a 16.3 per cent increase. As expected, a more blunted response was observed in group II (from 3.5 +/- 0.8 to 3.7 +/- 1.0 mm, 6.5 per cent increase). However, neither of the groups displayed significant correlation between serum magnesium levels and the measured response to intracoronary nitroglycerine. In conclusion, this study fails to provide any correlation between serum magnesium levels within the normal physiological range and coronary vascular reactivity in patients with ischaemic heart disease.

Adult↗
PubMed1995

Combined hip surgery in cerebral palsy patients.

Seventeen cases of dislocated/subluxated hips in 14 cerebral palsy patients that were relocated by the combined hip procedure were reviewed. The combined hip procedure includes varus derotation osteotomy, open reduction, innominate bone osteotomy, adductor releases, and iliopsoas recession, all done at one stage. Eleven patients were spastic quadriplegic, 1 was spastic diplegic; and 2 were spastic hemiplegic. Average age at operation was 10 years. Average follow-up was 3 years. A total of 16 hips (94%) remained stable at follow-up with almost no change in center edge angle and the migration percentage, although the neck shaft angle remodeled over time. We conclude that the combined hip procedure is effective in maintaining hip reduction in cerebral palsy patients.

Adolescent↗
PubMed1995

Femoral varus derotational osteotomy in cerebral palsy.

The records concerning 64 hips in 36 cerebral palsy patients treated with varus derotational osteotomy (VDO) alone (2 hips), VDO with muscle releases (adductors, iliopsoas, hamstrings; 46 hips), and VDO, soft-tissue release, and innominate bone osteotomy (16 hips) were reviewed. There were 23 quadriplegic and 13 diplegic patients. Average age at surgery was 7 years. Average follow-up period was 3.8 years. All hips that had VDO, soft-tissue release, and innominate osteotomy were stable at follow-up. Nine hips of the 44 treated with VDO and muscle release alone dislocated, and required second osteotomies.

Adolescent↗