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Biomedical subjects

S Demirel

Publications and source records attributed to S Demirel.

At least 19 recordsLinked to original sources
PubMed2006

Modeling the sensitivity to variability relationship in perimetry.

PURPOSE: Studies in glaucoma patients show that standard automated perimetry results increase in variability as sensitivity decreases. However, the reasons for this change are unclear. This study presents the principle of Divergent Dysfunction as a possible explanation for this change in variability, and incorporates it into a model that can be used to simulate perimetry. METHODS: A computer program was written to simulate visual field test results based on the model, using a Full Threshold testing strategy. The validity of the simulation was tested by comparing it with normal sensitivity values, and with test-retest data from 63 participants evaluated five times each over the course of 1 month. The effect on the simulated data of varying parameters of the model was investigated, such as changing the magnitude of variability and the percentages of false positive and negative responses. RESULTS: The correlation between subject and simulated test-retest data was 0.987. Several factors were found to affect the sensitivity-variability relationship for the simulated data, most notably the rate of sensitivity decline, the percentage of false positives, and the starting luminance of the test procedure. CONCLUSIONS: The principle of Divergent Dysfunction presented here provides a plausible explanation for the sensitivity-variability relationship for standard automated perimetry in glaucomatous eyes. The model and resultant simulation program aim to provide an intuitive demonstration of the principle, which can also be used to examine the effectiveness of different testing strategies. These findings have great implications for future clinical research.

Computer Simulation↗
PubMed2004

Does the endothelial function change in renal transplant patients with longer duration of exposure and with higher cumulative doses of cyclosporine?

OBJECTIVE: Administration of cyclosporine (CsA) is one potential cause of endothelial dysfunction in renal transplant patients. We sought to investigate endothelial functional changes with respect to the cumulative dose and duration of exposure to CsA. METHODS: Sixty-six renal recipients and 25 healthy controls were included in the study. The recipients were classified according to their time of CsA exposure: group 1 (0 to 36 months); group 2 (36 to 72 months); and group 3 (over 72 months). Endothelial function of the brachial artery was evaluated using high-resolution vascular ultrasound. Endothelium-dependent and -independent vasodilatation (EDD and EID, respectively) were assessed by assessing the responses to reactive hyperemia and using sublingual isosorbide dinitrate (ISDN), respectively. RESULTS: There were no statistically significant differences between the groups with regard to their demographic, clinical, and most biochemical characteristics. Baseline measurements of the diameter of the brachial artery were similar in all groups. The values of mean brachial artery EDD and EID responses in groups 1, 2, and 3 were less than those in the control group (P < .05, P < .05, and P < .05, respectively). Mean brachial artery EDD and EID in group 1 were significantly impaired compared to groups 2 and 3 (for EDD: P < .05 and P < .05, respectively; for EID: P < .05 and P < .05, respectively). In contrast there was no difference between groups 2 and 3 with respect to these parameters. There were mild to moderate positive correlations between the cumulative doses of CsA and EDD and EID (r = .26 and r = .52, P < .05, respectively). CONCLUSION: Endothelial dysfunction was more prominent in the first 36-month period than later despite the longer exposure to and higher cumulative doses of CsA. This finding may reflect an extended effect of the uremic state on endothelial function or more intense doses of CsA in early posttransplant period.

Adult↗
PubMed2002

Ischemic spinal cord injury after aortocoronary bypass operation. A case report.

Although spinal ischemia is a very well recognized complication after operation on the thoraco-abdominal and abdominal aorta, it is very rare following coronary artery bypass surgery. A case of a 56-year-old man, who had juxtarenal aortic occlusion and became paraplegic after internal mammary artery grafting for ischemic heart disease is reported. The complete paraplegia was thought to be due to interruption of critical collateral blood supply to the spinal cord.

Humans↗
PubMed2001

Micronucleus incidence and their chromosomal origin related to therapy in acute lymphoblastic leukemia (ALL) patients: detection by micronucleus and FISH techniques.

Micronucleus assay and dual color-fluorescence in situ hybridization (DC-FISH), using centromere-specific and whole chromosome-specific painting probes, are considered a useful screening test to determine the incidence of micronucleus, their origin and contents. The patients with acute lymphoblastic leukemia (ALL), who had undergone chemotherapy, were analysed before and after treatment with vincristine, methotrexate, daunomycin, prednisone, and asparaginase. The incidence of micronuclei after the antileukemic agent treatment was significantly higher than before the treatment. Application of DC-FISH using a combination of whole chromosome-specific painting probes and the same chromosome-specific alpha-satellite centromeric probe showed that there were no significant differences in the micronucleus incidence for any specific chromosome (chromosomes 7, 8, 11, 17, X, and Y). There were no significant differences between the incidence of centromere-positive micronuclei and the incidence of centromere-negative micronucleus. We concluded that antileukemic agents induced the somatic genetic damage but this damage is not related to any specific chromosome studied.

Antineoplastic Agents↗
PubMed2001

Incidence and prevalence of short wavelength automated perimetry deficits in ocular hypertensive patients.

PURPOSE: To determine the prevalence and incidence of short wavelength automated perimetry deficits in comparison to standard automated perimetry deficits in patients with ocular hypertension. METHODS: Five hundred eyes of 250 patients with ocular hypertension were recruited into a prospective, longitudinal study and tested with standard automated perimetry and short wavelength automated perimetry annually for 5 years. Both eyes of 60 normal subjects, 21 to 85 years of age, were used to establish normative data for short wavelength automated perimetry and standard automated perimetry. This allowed independent evaluation of left and right eyes of patients. All normal data were corrected for age, and short wavelength automated perimetry results were corrected for lens transmission. The lowest fifth and first percentiles for the normal observers were derived for the 10 glaucoma hemifield test zones for short wavelength automated perimetry and standard automated perimetry. Visual fields were considered outside normal limits if two glaucoma hemifield test zones were below the normal fifth percentile or one glaucoma hemifield test zone was below the normal first percentile. RESULTS: Baseline prevalence of short wavelength automated perimetry and standard automated perimetry deficits were 9.4% and 1.4%, respectively. During the study, incident rates of field loss were 6.2% (1.23% per year) for short wavelength automated perimetry and 5.9% (1.18% per year) for standard automated perimetry. Once abnormal, 80% of short wavelength automated perimetry fields remained abnormal on the next examination, whereas only 45% of abnormal standard automated perimetry fields remained abnormal. New short wavelength automated perimetry deficits in ocular hypertensives were more prominent and more persistent than new standard automated perimetry deficits. CONCLUSIONS: Our findings are consistent with the interpretation that short wavelength automated perimetry deficits occur before standard automated perimetry deficits in glaucoma. The similar incidence rates suggest that both standard automated perimetry and short wavelength automated perimetry are monitoring the same underlying glaucomatous disease process.

Adult↗
PubMed2001

Assessment of left atrial appendage function and its relationship to pulmonary venous flow pattern by transesophageal echocardiography.

We evaluated left atrial appendage function and its relationship to pulmonary venous flow in 53 patients divided into four groups. Group 1 consisted of 10 normal subjects. Group 2 included 15 patients with significant pure mitral stenosis in sinus rhythm. In group 3, there were 13 patients with pure significant mitral stenosis and atrial fibrillation. Group 4 consisted of 15 patients with normal mitral valve and atrial fibrilltion. We found significant decrease in left atrial appendage ejection fraction and maximum emptying flow velocity, velocity time integral of systolic pulmonary venous flow in Groups 2, 3 and 4 in comparison with normal subjects. Systolic pulmonary venous flow velocity was significantly decreased in Groups 3 and 4. There was significant correlation between left atrial appendage ejection fraction and peak emptying flow velocity (r = 0.62, P < 0,001). Systolic peak pulmonary venous flow velocity was significantly correlated with left atrial appendage ejection fraction and maximum emptying flow velocity (r = 0.67, P = 0,01; r = 0.58, P < 0,001, respectively). There was also significant correlation between systolic pulmonary venous flow velocity time integral and left atrial appendage ejection fraction (r = 0.66, P = 0.001). When normals were excluded from analysis, all the correlations were still significant. We concluded that left atrial appendage is a contractile structure, and that systolic pulmonary venous flow velocity is influenced by left atrial appendage dysfunction. Therefore left atrial appendage function needs to be considered when interpreting Doppler transmitral and systolic pulmonary venous flow patterns.

Adult↗
PubMed2001

Risk factors for coronary heart disease in patients with spinal cord injury in Turkey.

OBJECTIVE: To compare the standard risk factors for coronary heart disease (CHD), defined in National Cholesterol Education Program II (NCEP II) of Turkish spinal cord injury (SCI) patients with healthy controls, discuss the results according to the findings in Turkish population, and SCI patients in the literature. DESIGN: We assessed 52 age and sex matched healthy control subjects, and 69 SCI patients (16 females, 53 males with the mean age of 33.9+/-11.37 years) with time since injury of 12.8+/-13.45 months. The study consisted of 45 paraplegics, and 24 tetraplegics with 54% incomplete, and 46% complete injury. RESULTS: Risk factors for CHD according to NCEP II were; age and sex in 16%, positive family history in 0%, cigarette smoking in 54%, hypertension (HT) in 0%, high total cholesterol (TC) in 32%, high low-density lipoprotein cholesterol (LDL) in 41%, low high-density lipoprotein cholesterol (HDL) in 52%, and diabetes mellitus (DM) in 7% of our SCI patients, respectively. Compared to controls DM, high TC, LDL, and low HDL were statistically more frequent in SCI patients. We found a negative correlation between serum HDL and time since injury. TC (186+/-32 vs 205+/-36; P=0.025), TC/HDL (5.34+/-1.17 vs 6.26+/-1.5; P=0.005), and LDL/HDL (3.57+/-0.9 vs 4.16+/-1.3; P=0.027) were significantly increased in patients with time since injury of more than 1 year, while HDL levels (35.8+/-6.36 vs 33.86+/-6.47; P=0.213) decreased without reaching statistical significance. The lipid profiles did not show any correlation with the neurological level, and completeness of lesions. CONCLUSIONS: SCI confers additional CHD risk over that present inherently in the parent population due to enforced sedentary lifestyle and this increases with time since injury. The preliminary study consisting of 26 patients was accepted for poster presentation in Copenhagen, Denmark (18-20 June 1999) at the 38th Annual Scientific Meeting of IMSOP in association with the Nordic Medical Society of Paraplegia.

Adult↗
PubMed2000

Effect of Valsalva maneuver on surface electrocardiographic P-wave dispersion in paroxysmal atrial fibrillation.

The purpose of this study was to investigate the effect of the Valsalva maneuver on P-wave durations and dispersion. After the Valsalva maneuver, we found that maximum P-wave duration increased, minimum P-wave duration decreased, and P-wave dispersion increased in controls, whereas the opposite was true for unselected patients with paroxysmal AF. It was concluded that patients with paroxysmal AF performing the Valsalva maneuver normalized their P-wave dispersion, thereby correcting the inhomogeneous intra-atrial conduction.

Anti-Arrhythmia Agents↗
PubMed2000

Isolation of short-wavelength sensitive mechanisms in normal and glaucomatous visual field regions.

PURPOSE: To determine whether "isolation" of short wavelength sensitive mechanisms (i.e., exclusive detection of a threshold stimulus by a short wavelength sensitive mechanism) is maintained in areas of glaucomatous visual field damage as measured with short-wavelength automated perimetry (SWAP). METHODS: Data from conventional automated perimetry and SWAP were analyzed for both eyes of 60 normal control subjects, 38 patients with ocular hypertension, and 22 patients with early to moderate glaucomatous field damage (mean defect better than -12 dB). Comparisons of results of SWAP and conventional perimetry were performed by determining the deviation from the mean normal sensitivity for the two procedures. Locations with sensitivity <3 dB for either procedure were rejected, as 3 dB is near the maximum stimulus luminance and may have introduced a bias by underestimating defects. The interval between deviation from normal (the isolation interval) on conventional perimetry and SWAP was examined to determine the likelihood of short wavelength mechanism isolation loss for different levels of glaucomatous visual field damage. RESULTS: Using normal isolation estimates of 13 dB and 10 dB as bases for determining the likelihood that isolation of short wavelength sensitive mechanisms may have been lost, it was found that this was an infrequent possibility, as low as 0.39 to 1.63% for normal control subjects and 2.53 to 10.44% for patients with glaucoma. CONCLUSION: Analyses indicate that isolation of short wavelength sensitive mechanisms is mostly maintained for SWAP, even in areas of moderate glaucomatous field damage. One limitation of SWAP for evaluating extensive glaucomatous damage is its dynamic range. This could be overcome by using a more intense stimulus light source.

Adult↗
PubMed2000

No association between deletion-type angiotensin-converting enzyme gene polymorphism and left-ventricular hypertrophy in hemodialysis patients.

Left-ventricular hypertrophy (LVH), a bad prognostic sign, is a common finding in hemodialysis patients. The aim of the study was to analyze factors, including angiotensin-converting enzyme (ACE) genotype that may have an effect on the development of LVH in hemodialysis patients. Seventy-nine hemodialysis patients (42 males, 37 females, mean age 37.7 +/- 13.1 years) and 82 age- and sex-matched normotensive healthy controls (40 males, 42 females, mean age 35.6 +/- 5.7 years) were included. Left-ventricular mass index (LVMI) was higher in the hemodialysis group compared to controls (170.1 +/- 69.3 versus 84.9 +/- 15.7 g/m(2), p < 0.001). Fourty-three hypertensive patients in the hemodialysis group had an increased LVMI compared to 36 normotensive hemodialysis patients (194.2 +/- 75.5 versus 141.2 +/- 48.0 g/m(2), p < 0.001). On univariate analysis, LVMI was found to be correlated with blood pressure (r = 0.38, p < 0.001), time spent on dialysis (r = 0.22, p = 0.02) and hemoglobin levels (r = -0.21, p = 0.03). No correlation was found between LVMI and age (r = 0.09, p = 0.22), predialytic creatinine (r = 0.09, p = 0.21) and albumin (r = -0.10, p = 0.18). On multivariate analysis for the predictors of LVMI, blood pressure, time spent on dialysis and hemoglobin levels were also found to be significant. LVMI in DD, ID and II genotypes were 155.0 +/- 71.2, 181.6 +/- 60.6, and 163.6 +/- 83.4 g/m(2), respectively (p > 0.05). No association between LVMI and DD genotype was found. ACE genotype distribution was similar in hemodialysis patients and healthy controls. It was concluded that LVH in hemodialysis patients was mainly related to hypertension, anemia and time spent on dialysis and the DD genotype had no effect on LVMI in hemodialysis patients.

Adult↗
PubMed2000

Chromosomal abnormalities in mentally retarded children in the Konya region--Turkey.

Etiology of mental retardation is diverse. 120 Students from 11 special training, education, and rehabilitation subclasses were investigated cytogenetically for determining the contribution of chromosomal abnormalities to mild mental retardation. 23 of the 120 children (19%) had chromosomal abnormalities: thirteen cases a classical trisomy 21 (the male:female ratio was 9:4), three a balanced autosomal reciprocal translocation, one a pericentric inversion of chromosome 9, and six fragile-X syndrome (The male:female ratio was 5:1).

Adolescent↗
PubMed2000

Echocardiographic findings in professional league soccer players. Effect of the position of the players on the echocardiographic parameters.

BACKGROUND: The purpose of the study was to compare the echocardiographic parameters of soccer players to healthy controls and to assess the effect of the position of the soccer players on the echocardiographic findings. METHODS: M Mode 2D and Doppler echocardiographic examination were carried out on 83 professional league soccer players and 52 healthy controls. RESULTS: Soccer players had increased interventricular septum (1.14+/-0.13 cm vs 0.99+/-0.17 cm, p<0.001) left ventricular posterior wall (1.08+/-0.16 cm vs 0.91+/-0.13 cm, p<0.001) thickness, increased left ventricular diastolic diameter (5.24+/-0.40 cm vs 4.88+/-0.43 cm, p<0.001), volume (133+/-23 ml vs 113+/-22 ml, p<0.001) and increased left ventricular mass index (142+/-28 g/m2 vs 103+/-23 g/m2, p<0.001) compared to controls. Soccer players had greater mitral E wave to A wave ratio (2.08+/-0.53 vs 1.65+/-0.43, p<0.001) compared to controls. Soccer players were subgrouped according to their position in the play as goal keepers, defensive, midfielder, and offensive players. Comparison among defensive, midfield and offensive players revealed subtle differences between defensive and midfield players. Right ventricular dimensions were higher in goal keepers compared to midfielders due to the greater body surface area of the goal keepers (2.8+/-0.4 cm vs 2.4+/-0.5 cm, p<0.05). Left ventricle end diastolic dimension were similar between groups but when these dimensions were corrected for the greater height of the defensive players the difference between midfields and defensive players became significant (3.05+/-0.18 vs 2.89+/-0.22, p=0.05). On Doppler flow parameters the ratio of peak E wave to A wave velocity (2.27+/-0.55 vs 1.84+/-0.36, p<0.05) was increased in midfield players compared to defensive players. CONCLUSIONS: It was concluded that soccer players had greater left ventricular wall thickness, volume and mass compared to controls. But the effect of the position of the players on the measured cardiac dimensions were minimal. These subtle findings were explained by the leveling effect of the playing system and training, and lack of physical training during the previous month.

Adult↗
PubMed1999

The oculomotor gap effect without a foveal fixation point.

Turning off a fixation point prior to or coincident with the appearance of a visual target reduces the latency of saccades to that target. We investigated this 'gap effect' when subjects fixated a central point or the center of a square formed by four points that were 4, 2 or 1 degree eccentric from the square's center. The fixation anchor vanished 200 ms prior to the appearance of a saccadic target in a Gap condition, coincident with the target's appearance in a 0-Gap condition, or remained on in an Overlap condition. Saccadic reaction time was reduced in the Gap relative to 0-Gap condition irrespective of the type of fixation anchor. However, saccadic reaction time was not reduced in the 0-Gap relative to Overlap condition when the points forming the square had eccentricities of 2 or 4 degrees. Results are interpreted in terms of a partial mediation of the gap effect by fixation cells in the rostral pole of the superior colliculus.

Analysis of Variance↗
PubMed1999

Surgical treatment of Peyronie's disease with incision and venous patch technique.

Peyronie's patients are candidates for surgical treatment when the acute phase has resolved. The choice of surgical treatment modality, either reconstructive procedure or implantation of penile prosthesis, largely depends on the type and degree of the deformity and the penile vascular status of the patient. We present the results of ou1Effects of inhibitors and rmTNF-alpha on FMLP-induced O2 production by mouse leukocytesr experience with incision and venous patch technique in Peyronie's disease. Incision and venous patch technique was performed in 20 patients with a mean duration of the disease of 26.1 +/- 19.8 months. Complete straightening was achieved in 15 (75%) patients after a mean followup of 13.2 +/- 9.4 (3-27) months. Postoperative residual curvature (< 20 degrees) was observed in 4 (20%) patients. Bulging at the graft site was noted in 1 (5%) patient. Potency was preserved in all patients except one. Incision and venous patch technique, with its satisfactory results, should be considered in Peyronie's patients having an adequate penile vascular system during chronic stable phase of the disease.

Adult↗
PubMed1998

Autonomic dysfunction in vitamin B12 deficiency: a heart rate variability study.

This study was arranged to examine whether vitamin B12 deficiency may cause autonomic dysfunction. Time-domain and long-term frequency-domain heart rate variability parameters from 12 patients with pernicious anemia were compared to 12 age and sex matched controls. In B12 deficient patient group time-domain parameters; SDNN (100.4 +/- 37.86 vs. 131.91 +/- 26.94, P = 0.05), SDANN (87.00 +/- 37.77 vs. 118.83 +/- 26.22, P = 0.05) SD (39.41 +/- 13.32 vs. 53.41 +/- 15.39, P = 0.0221), rMSSD (21.41 +/- 10.00 vs. 28.5 +/- 8.42, P = 0.046) were significantly lower when compared to controls. Difference in pNN50 between groups were not statistically significant. In B12 deficient patients frequency-domain parameters; total power (23.08 +/- 9.89 vs. 34.75 +/- 9.56, P = 0.0078), low frequency power (13.5 +/- 6.57 vs. 22.75 +/- 7.25, P = 0.0069) and high frequency power (7.58 +/- 4.25 vs. 11.58 +/- 3.80, P = 0.0175) were significantly lower when compared to controls. It was concluded that B12 deficiency may cause autonomic dysfunction.

Adult↗