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S Iskander

Publications and source records attributed to S Iskander.

12 recordsLinked to original sources
PubMed2001

Real-time assessment of myocardial perfusion and wall motion during bicycle and treadmill exercise echocardiography: comparison with single photon emission computed tomography.

OBJECTIVES: We sought to determine the feasibility and accuracy of real-time imaging of myocardial contrast echocardiography (MCE) in detecting myocardial perfusion defects during exercise echocardiography compared with radionuclide tomography. BACKGROUND: Ultrasound imaging at a low mechanical index and frame rate (10 to 20 Hz) after intravenous injections of perfluorocarbon containing microbubbles has the potential to evaluate myocardial perfusion and wall motion (WVM) simultaneously and in real time. METHODS: One hundred consecutive patients with intermediate-to-high probability of coronary artery disease underwent treadmill (n = 50) or supine bicycle (n = 50) exercise echocardiography. Segmental perfusion with MCE and WM w ere assessed in real time before and at peak exercise using low mechanical index (0.3) and frame rates of 10 to 20 Hz after 0.3 ml bolus injections of intravenous Optison (Mallinckrodt Inc., San Diego, California). All patients had a dual isotope (rest thallium-201, stress sestamibi) study performed during the same exercise session, and 44 patients had subsequent quantitative coronary angiography. RESULTS: In the 100 patients, agreement between MCE and single photon emission computed tomography (SPECT) was 76%, while it was 88% between MCE and WM assessment. Compared with quantitative angiography, sensitivity of MCE, SPECT and WM was comparable (75%), with a specificity ranging from 81% to 100%. The combination of MCE and WM had the best balance between sensitivity and specificity (86% and 88%,respectively) with the highest accuracy (86%). CONCLUSIONS: The real-time assessment of myocardial perfusion during exercise stress echocardiography can be achieved with imaging at low mechanical index and frame rates. The combination of WM and MCE correlates well with SPECT and is a promising important addition to conventional stress echocardiography.

Adult↗
PubMed2001

Nestin expression in cortical dysplasia.

OBJECT: It is recognized that cortical dysplasia (CD) is associated with an increased incidence of glioneuronal neoplasms. Among hypothetical considerations, there is the possibility that CD and other neuronal migration abnormalities harbor dysmature cells with the potential to give rise to glioneuronal neoplasms. Such cells, if present, would be reasonably expected to display immature features. The goal of the present study was to characterize the expression of nestin, a neuroepithelial precursor/stem cell antigen, in CD, along with other pathological and clinical features of this entity. METHODS: Clinical and surgical features of 10 recent cases meeting the histological criteria for CD were reviewed. Expressions of nestin, MAP2, neurofilament, and glial fibrillary acidic protein (GFAP) were assessed using immunohistochemical analysis and confocal scanning laser microscopy. Immunoreactivity for both glial and neuronal antigens as well as nestin was found in a select group of cells within regions of CD. Immunohistochemical and confocal microscopic findings demonstrated that these cells with neuronal or ambiguous features are a mixed population, some of which are dysmature neurons (positive for nestin and MAP2), whereas others are astrocytic (positive for nestin and GFAP). CONCLUSIONS: Further insight into the nature of nestin-positive neurons may shed light on the cause and pathogenesis of the associated glioneuronal tumors and the accompanying chronic seizures.

Adolescent↗
PubMed2000

Metallothionein induction in human CNS in vitro: neuroprotection from ionizing radiation.

PURPOSE: There have been extensive studies on the regulation of metallothionein (MT) synthesis, and its biological role in liver and kidney. Although there are few reports on brain MT, there is a growing interest in the role of MT in brain. There have been no publications to date on MT synthesis in the human central nervous system (CNS) following exposure to ionizing radiation. In the present study, primary human CNS cultures were used to examine the effect of ionizing radiation on MT mRNA and protein synthesis. In the same cultures, the neuroprotective effects of zinc (Zn) and cadmium (Cd)-induced MT synthesis from high-dose radiation were also examined. MATERIALS AND METHODS: Primary, serum-free, human CNS cultures were exposed to 30 or 60 Gy gamma-rays. The total MT protein was then measured by a Cd-heme assay, and mRNA for MT-II and MT-III was detected by reverse transcription polymerase chain reaction (RT-PCR). Cytotoxicity was measured by LDH release and apoptotic cell death by DNA fragmentation analysis. Sublethal neuroglial injury was assessed morphologically using specific astrocytic (glial fibrillary acidic protein--GFAP) and neuronal (microtubule-associated protein 2--MAP2) immunohistochemical markers. RESULTS: The total MT protein content was increased 12h after exposure to 30Gy. The increase in MT content in response to 60Gy was not statistically significant. MT-II mRNA levels increased at 3 and 6h after exposure to 30Gy gamma-rays, with a maximum expression at 12-24 h. MT-III mRNA was not significantly affected. Exposure to 60 Gy, but not 30 Gy, caused a marked increase in LDH release. Cells exposed to 30 Gy or less showed some apoptotic cell death by DNA fragmentation analysis, while exposure to 60 Gy resulted in a DNA smear confirmed by LDH assays. Preinduction of MT by 5 microM Cd or 100 microM Zn resulted in a significant reduction in radiation-induced LDH release. Morphological evaluations revealed that Cd or Zn preincubation led to relative preservation of MAP2 staining and GFAP. CONCLUSION: Both MT protein and MT-II mRNA can be induced in human CNS cells by ionizing radiation. Furthermore, induction of MT synthesis with Zn and Cd can protect human CNS cells from radiation-induced cytocidal and sublethal injuries. Both findings have implications in the development of strategies to protect human CNS tissue from damage during radiotherapy.

Brain↗
PubMed1999

Prognostic utility of myocardial viability assessment.

Myocardial viability assessment is useful in patients with severe coronary artery disease and severe left ventricular dysfunction. Whereas most studies have focused on recovery of regional function, there are emerging data on patient outcome. Review of these data suggests that patients with chronic ischemia, cardiomyopathy, and viable myocardium who are treated medically have a worse, outcome than those treated with coronary revascularization. However, there are no prospective randomized trials. We present perspectives for future studies.

Cardiomyopathies↗
PubMed1998

Risk assessment using single-photon emission computed tomographic technetium-99m sestamibi imaging.

OBJECTIVES: This review summarizes the results of single-photon emission computed tomographic (SPECT) technetium-99m (Tc-99m) tracer imaging in patients with stable symptoms, patients with acute coronary syndromes, patients undergoing major non-cardiac surgery and patients with chest pain in the emergency department. BACKGROUND: Previous studies have examined the prognostic value of stress thallium imaging in several subsets of patients with ischemic heart disease. At present, >50% of myocardial perfusion studies are performed with technetium-labeled tracers in the United States. Furthermore, there is a shift from diagnostic to the prognostic utility of stress testing. There are important differences between technetium-labeled tracers and thallium-201. It is therefore important to review the prognostic value of technetium-labeled tracers. METHODS: We analyzed published reports in English on risk assessment using Tc-99m perfusion tracers. Results. The largest experience is in patients with stable symptoms, comprising >12,000 patients in 14 studies. In these patients, normal stress SPECT sestamibi images were associated with an average annual hard event rate of 0.6% (death or nonfatal myocardial infarction [MI]). In contrast, patients with abnormal images had a 12-fold higher event rate (7.4% annually). Both fixed and reversible defects are prognostically important, and quantitative analysis shows increased risk in relation to the severity of the abnormality. These results are similar to those obtained with thallium-201. CONCLUSIONS: Patients with stable chest pain syndromes and normal stress SPECT sestamibi images have a very low risk of death or nonfatal MI. It is highly unlikely that coronary revascularization can improve survival in such patients. Patients with abnormal images have an intermediate to high risk for future cardiac events, depending on the degree of the abnormality. Further prospective studies comparing aggressive medical therapy with coronary revascularization in these patients are warranted.

Cause of Death↗
PubMedDate not supplied

MAP2 and nestin co-expression in dysembryoplastic neuroepithelial tumors.

BACKGROUND: The ontogeny and maturity of neurons and oligodendroglia-like cells (OLC) found in dysembryoplastic neuroepithelial tumors (DNT) remains controversial. A developmental origin has been proposed based on the close association to cortical dysplasia and the benign microscopic and clinical course. Our goal was to characterize the expression of nestin, a neuroepithelial precursor/stem cell antigen in DNT, along with other pathological and clinical features of this entity. METHODS: The clinical and operative features of 13 surgical specimens meeting the histological criteria for DNT were reviewed. Nestin, microtubule-associated protein 2 (MAP2), neurofilament (NF) and glial fibrillary acidic protein (GFAP) were examined by immunohistochemistry and confocal scanning laser microscopy. RESULTS: Select neuronal cells in all cases demonstrated strong MAP2 immunoreactivity. Nestin-positive cells of neuronal morphology were found in 6 cases. OLC demonstrated frequent selective staining for MAP2, GFAP and nestin. Confocal microscopy demonstrated numerous examples of cells co-expressing nestin and MAP2. CONCLUSIONS: Our study suggests that OLCs represent a united population of immature neuronal (nestin + MAP2) and glial (GFAP) phenotypes. Larger, morphologically recognizable neurons also showed occasional co-expression of nestin and MAP2, suggesting a degree of dysmaturity in common with their OLC counterparts. The apparent mixed lineage of OLCs lends support to theories suggesting that DNTs arise from pluripotent neuroepithelial cells.

Adolescent↗