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Biomedical subjects

Z Popovic

Publications and source records attributed to Z Popovic.

At least 19 recordsLinked to original sources
PubMed2001

Resolution, separation of retinal ganglion cells, and cortical magnification in humans.

We present direct comparisons of resolution thresholds and quantitative estimates of retinal ganglion cell separation in humans with reported functional magnetic resonance imaging estimates of the human linear cortical magnification factor. Measurements of resolution thresholds (MAR), retinal ganglion cell (GC) densities, and linear cortical magnification factor (M) values were taken from the literature. Our objective was to analyse the apparent overrepresentation of human central vision in the visual cortex and to determine whether the cause of this is an effect of the uneven distribution of GC in the retina and/or that central GC have more devoted cortical area per cell. The reserved amount of cortical distance per retinal unit, i.e. the product of M on the one hand and effective GC separation, MAR, and GC receptive field separation on the other, indicates an overrepresentation of the fovea and immediately surrounding retina in the human striate cortex due to an increase in devoted cortical distance per central GC or resolution unit. This cannot be explained by lateral displacement of foveal ganglion cells nor by peripheral scaling, but rather by an additional magnification in the retino-cortical pathway.

Ganglia, Sensory↗
PubMed2000

Cooperative jahn-teller coupling in the manganites

The cooperative Jahn-Teller coupling between the Mn e(g) electrons and the oxygen octahedral distortions in LaMnO3 is studied using ab initio density-functional calculations and tight-binding models. The linear and quadratic vibronic coupling parameters are calculated using density-functional methods. It is shown that the cooperative Jahn-Teller coupling, primarily due to the interoctahedral electron hopping (band structure term), leads to the ordering of the octahedral distortion and simultaneously to orbital ordering. The coupling results in a two-minima adiabatic potential surface in the solid, instead of the three-minima "Mexican-hat" surface for the isolated octahedron.

Journal Article↗
PubMed2000

Partial left ventriculectomy: which patients can be expected to benefit?

BACKGROUND: Although some patients with end-stage heart disease will benefit from a partial left ventriculectomy, no criteria have been found for identifying this group preoperatively. Our experience with partial left ventriculectomy at two institutions-the Texas Heart Institute in Houston, TX, USA, and Dedinje Cardiovascular Institute in Belgrade, Yugoslavia-showed a higher survival rate and better postoperative myocardial function in the Yugoslavian patients. METHODS: We reviewed data from 42 patients (21 at each center) who had idiopathic cardiomyopathy, a left ventricular end-diastolic dimension of more than 70 mm, wall thickness of 1 cm or greater, and New York Heart Association class III or IV symptoms. The only significant difference in preoperative status between the two groups was duration of symptoms. Histologic specimens, blinded as to origin, were graded with regard to myocyte hypertrophy, cytoplasmic vacuolation, and fibrosis. Computer-assisted myocyte and nuclear morphometry was also performed. RESULTS: Immediately postoperatively, there were no significant intergroup differences in the reduction in cardiac dimension or in corrections of mitral regurgitation. During 6-month follow-up, however, the Texas Heart Institute patients had a lower cardiac index (1.8 versus 3.0 L x min(-1) x m(-2); p = 0.001) and left ventricular ejection fraction (24% versus 34%; p = 0.006) than the Dedinje Cardiovascular Institute patients. The Texas Heart Institute patients differed from the Dedinje Cardiovascular Institute patients in the degree of severe or moderate changes in myocyte hypertrophy (90% versus 29%; p = 0.0003) and fibrosis (71% versus 29%; p = 0.006), as well as in the measurements of median myocyte diameter (35 +/- 7 microm versus 27 +/- 4 microm; p = 0.0002) and median nuclear size (15 +/- 4 microm versus 12 +/- 2 microm; p = 0.0029). CONCLUSIONS: In the Texas Heart Institute patients, the significant intergroup difference in clinical outcome may have been related to increased myocyte hypertrophy and fibrosis. Further studies should be performed to determine the usefulness of these criteria in selecting patients for partial left ventriculectomy.

Adult↗
PubMed1999

Morphometric study of the displacement of retinal ganglion cells subserving cones within the human fovea.

BACKGROUND: A study was carried out to measure the displacement of retinal ganglion cells subserving the cones within the human fovea. METHODS: Four human retinas were examined along the nasal or vertical hemi-meridians. Total displacement was estimated by adding the displacement due to fibres of Henle and bipolar cells, measured as the lateral extension of the Henle fibres and of the obliquely running fibre bundles within the inner nuclear layer, respectively. RESULTS: At the foveal border (0.5-0.8 mm or 1.8-2.9 deg eccentricity) the mean offset due to fibres of Henle and mean total lateral displacement was at a maximum of 0.32 +/- 0.03 mm and 0.37 +/- 0.03 mm, respectively. A steep decrease of displacement was found outside the foveal border out to an eccentricity of 2.0-2.5 mm. We were able to plot displacement along the vertical meridian in relation to eccentricity with good correlation between three eyes. The data were used to establish different mathematical functions describing the relation between eccentricity and displacement. These functions were applied to previously presented data on densities of retinal ganglion cells and cones. CONCLUSIONS: The present estimates of displacement within the human central fovea offer the possibility of analysis of quantitative relations between cones and retinal ganglion cells. Our data provide predictive guidance by establishing that vitreo-retinal procedures causing damage to retinal ganglion cells up to 1 mm from the foveal centre could have implications for loss of information generated within the fovea.

Adult↗
PubMed1999

Quantitative estimations of foveal and extra-foveal retinal circuitry in humans.

For an understanding of the basis for psychophysical measurement of visual resolution, quantitative morphological studies of retinal neuronal architecture are needed. Here we report on cell densities and retinal ganglion cell:cone ratio (RGC:C) from the foveal border to the peripheral retina (34 degrees eccentricity). Quantitative estimates of RGC and C densities were made using a modified disector method in three vertically sectioned human retinae and were adjusted for RGC displacement. In agreement with our previous data on humans, we found an RGC:C ratio close to 3 at 2-3 degrees eccentricity. Outside the foveal border, the ratio declined to 1.0 at 7.5 degrees eccentricity and to 0.5 at eccentricities larger than 19 degrees. Center-to-center separation of C and RGC in addition to center-to-center separation of estimated 'receptive fields' was calculated at corresponding locations along the superior and inferior hemimeridians. The center-to-center separation of estimated 'receptive fields' was found to be more closely related to resolution thresholds from the fovea to 19 degrees eccentricity than was the separation of RGC and C. On the basis of these quantitative estimates, models for neural circuitry involved in central and peripheral spatial vision can be discussed.

Cell Count↗
PubMed1999

The occurrence of congenital cataract in western Sweden.

PURPOSE: To estimate the occurrence of congenital cataract in a Nordic country. METHODS: In 1980, we constructed a database in the Department of Ophthalmology, Göteborg University, containing basic data from all cases in western Sweden diagnosed with congenital cataract. By collecting and processing these data from 1980 onwards, we hoped to improve the management of congenital cataract treatment and to optimize the outcome of the treatment. RESULTS: In this study, the incidence of congenital cataract in the four western counties of Sweden was evaluated. The occurrence rate of all cases with congenital cataract during the study period was 36 cases per 100,000. The occurrence rate for dense bilateral and all unilateral cases were both 14 per 10,0000 each. CONCLUSION: There were no time-related changes in incidence of congenital cataract from 1980 until today, although there was a large variation in the yearly incidence.

Cataract↗
PubMed1999

Age-related progressive brachial artery endothelial dysfunction precedes the changed carotid and left ventricular geometry in healthy humans.

In this study the authors evaluated correlation between aging and brachial endothelial and vascular smooth muscle dysfunction, changes in carotid geometry, and left ventricular remodeling. Vasomotor influences of brachial endothelium and brachial smooth muscle function to reactive hyperemia and nitroglycerin (400 microg, sublingual spray) were assessed by noninvasive ultrasound in 66 healthy subjects of different ages (20-82 years). Carotid intima-media thickness and left ventricular mass index were also assessed by ultrasound and compared with brachial hemodynamic parameters. All results were analyzed by linear regression analysis. The response of brachial artery diastolic diameter to reactive hyperemia decreased with aging (p<0.0001). Also, the response of brachial artery diastolic diameter to nitroglycerin increased relative to aging (p<0.004). Age-related correlations between increased carotid intima-media thickness and brachial artery diastolic diameter response to reactive hyperemia (p<0.01) as well as between increased carotid intima-media thickness and increased left ventricular mass index (p<0.001) were found. However, there was no correlation between brachial artery diastolic diameter response to reactive hyperemia and increased left ventricular mass index (p>0.05). The study showed that aging influences not only brachial endothelial vasomotor properties but also vascular and cardiac geometry. The authors believe that modern therapeutic approach should take these results into consideration to establish new vasculo-protective and cardioprotective strategies.

Adult↗
PubMed1999

Ventricular performance following valve replacement for chronic mitral regurgitation: importance of chordal preservation.

OBJECTIVE: To assess immediate and late changes in left ventricular performance after mitral valve replacement (MVR) for mitral regurgitation with or without preservation of chordae tendineae. EXPERIMENTAL DESIGN: a prospective, one year follow-up, study. SETTING: university cardiosurgical hospital. PATIENTS: Fourteen patients with symptomatic chronic mitral regurgitation were divided into Group A (n = 7), which underwent MVR with chordal preservation, and Group B (n = 7) which underwent MVR with chordal transection. METHODS: Transesophageal echocardiography, obtained simultaneously with radial artery and pulmonary capillary wedge pressures over a range of loading conditions, was used to estimate left ventricular elastance (Eps), calculated as the slope of peak systolic pressure/end-systolic volume relation, and preload recruitable stroke work (PRSW). Measurements were taken intraoperatively before and after cardiopulmonary bypass, 6 hours later and 10 days later. Transthoracic echocardiography follow-up data were obtained after 3 months and one year. RESULTS: Eps significantly decreased immediately after MVR (p = 0.018), with no difference among 2 groups. Eps gradually increased to preoperative levels 10 days after surgery. PRSW also significantly decreased after MVR (p = 0.01). The decrease was significantly larger in Group B (p = 0.038). During follow-up, Group A showed a significantly better ejection fraction (p = 0.008), and a smaller end-systolic volume index (p = 0.01) and left ventricular mass index (p = 0.04), than Group B. CONCLUSIONS: These data support the hypothesis that chordal preservation during MVR has beneficial effects on left ventricular performance.

Adult↗
PubMed1997

Ductus diverticulum aneurysm associated with bicuspid aortic valve and dilatation of ascending aorta.

Saccular aortic aneurysm arising in the ductal region, known as ductus diverticulum aneurysm, is a rare anomaly. Due to potentially malignant evolution, recognition of radiological signs associated with this anomaly during the asymptomatic phase may be important in order to plan surgical intervention in time. We report an unusual case of ductus diverticulum aneurysm combined with bicuspid aortic valve, dilatation of ascending aorta, and coronary artery disease.

Aorta↗
PubMed1996

Chordal preservation improves postoperative ventricular performance following valve replacement for chronic mitral regurgitation.

Worsening of left ventricular performance had been recognized after mitral valve replacement for mitral regurgitation. The effects of chordal preservation on ventricular performance after mitral valve replacement have been assessed. Twelve patients with mitral regurgitation were allocated to group A (undergoing mitral valve replacement with chordal preservation), or to group B (undergoing mitral valve replacement with chordal excision). Transoesophageal echocardiography was recorded simultaneously with radial artery and pulmonary capillary wedge pressures. Load was varied by withdrawal of blood from a venous line of cardiopulmonary bypass and/or nitroglycerine bolus. Ventricular performance was assessed by the slope of peak systolic pressure-end-systolic volume relation (Eps), and by the slope of the left ventricular stroke work-end-diastolic volume relationship. Eps significantly decreased immediately after mitral valve replacement (P < 0.02), with no difference among two groups. Eps gradually increased to preoperative levels 10 days after surgery. Pre-load recruitable stroke work also significantly decreased after mitral valve replacement (P = 0.01). The decrease was significantly larger in group B (P < 0.04). These data support the hypothesis that chordal preservation during mitral valve replacement has beneficial effects on left ventricular performance.

Adult↗
PubMed1995

Subaortic left ventricular pseudoaneurysm of obscure origin.

Subaortic pseudoaneurysms of the left ventricle are rare acquired cardiac defects. They are usually associated with previous valve surgery, trauma, or aortic valve endocarditis. We describe the appearance of subaortic pseudoaneurysm 10 years after left heart catheterization in a patient with both aortic stenosis and regurgitation. The differential diagnosis of such lesions is presented.

Aneurysm, False↗
PubMed1995

"Kissing-balloon" technique for abdominal aorta angioplasty. Initial results and long term outcome.

We evaluated results after angioplasty of the distal abdominal aorta using "kissing-balloon" technique. MATERIALS AND METHODS. From 1981 through 1993, 14 patients (12 women and 2 men, average age 52.4 years), underwent balloon angioplasty of the distal segment of the abdominal aorta. In 8 patients stenosis involved one or both iliac arteries as well. In all cases double balloon technique was used. Follow-up was based on clinical, angiographical and duplex scanning examinations. RESULTS. The initial success rate was 85% (12/14). In one case there was residual stenosis of 20% (redilated successfully 1 month later), and in one case there was acute thrombosis of the right iliac artery (successfully relieved surgically). Long-term follow-up (6-143 months) showed good patency of the dilated segment in all patients (including patients that initially failed). At follow-up, all patients were asymptomatic. CONCLUSION. Dilatation of the distal abdominal aorta using "kissing-balloon" technique is a safe and efficient modality of treatment, with acceptable initial and excellent long-term results.

Adult↗
PubMed1994

The disbalance of alpha- and beta-globins in anemic Belgrade rat red blood cells.

The Belgrade Laboratory (b/b) rat has an autosomal mutation which in homozygous state induces severe anemia. This study was based on solubilization of total rat globin chains and their separation into alpha- and beta-globins using a 20% SDS polyacrylamide gel. These analyses demonstrated that the disbalance of alpha/beta globins in b/b red blood cells (RBC) is due to decreased level of alpha-globins. Iron-dextran administration corrected the level and globin ratio in b/b RBC thus confirming that the iron deficiency is the primary defect in b/b rats.

Anemia↗
PubMed1993

Constitutive interferon expression from retroviral vector.

A genomic fragment with the human beta-interferon gene was cloned into a pL3-4, a defective Moloney murine leukemia virus (M-MuLV) vector. Here we show that clones selected after viral infection of mouse NIH 3T3 cells constitutively produced 128 IU/ml of human beta-interferon. Constitutive synthesis of retroviral RNA was confirmed by dot blot hybridization of RNA isolated from two of the selected clones. Poly(I) x poly(C) and cycloheximide induction resulted in an increased RNA level, but this was not reflected in an increased production of biologically active interferon.

3T3 Cells↗