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Biomedical subjects

I Durak

Publications and source records attributed to I Durak.

106 records · Page 6Linked to original sources
PubMed1988

Analysis of magnesium and trace elements in urinary calculi by atomic absorption spectrophotometry.

Magnesium and trace element determinations in 29 urinary tract calculi were carried out using an atomic absorption spectrophotometric method. Of the calculi examined, 9 were pure calcium oxalate, 5 were mixed calcium oxalate/uric acid, 5 were mixed calcium oxalate/phosphate, 5 were magnesium ammonium phosphate and 5 were pure cystine. The measurement of magnesium and trace element levels has been considered useful in the elucidation of the mechanism of stone formation and the evaluation of factors leading to pathological consequences. In this study, the Mg, Zn, Cu, Fe, Cd and Pb content in all of the samples was determined and an attempt was made to compare the levels of these elements in calculi with the levels in normal hair.

Humans↗
PubMed1987

The effect of detergents on bovine cytochrome c oxidase: a kinetic approach.

(1) Investigation of the relationship between the detergent concentration and steady-state and pre-steady-state kinetics of cytochrome c oxidase proved to be a valid approach in the study of protein-detergent interaction. (2) Laurylmaltoside, sodium cholate and Triton X-100 influenced the kinetics of cytochrome c oxidase cooperatively at detergent concentrations near their critical micelle concentration. This mode of interaction reflects disaggregation of the oxidase as a result of cooperative binding of the detergent. (3) Addition of increasing concentrations of Tween-80 to the aggregated enzyme caused a more gradual decrease in aggregation of the oxidase, which did not result in a change in activity of the enzyme. This suggests that aggregation of cytochrome c oxidase occurs in a highly regular manner in which no catalytic sites are shielded off. (4) Oxidase aggregates present at detergent concentrations below the critical micelle concentration of laurylmaltoside and Triton X-100 showed considerable activity. Their kinetics were equal to those of the oxidase in Tween-80, suggesting that the protein molecules are aligned in a similar way in all oligomers. Aggregates present in low concentrations of sodium cholate showed turnover rates that were twice as low as those observed with other aggregates. (5) Solubilisation of the oxidase by sodium cholate or Triton X-100 resulted in almost complete inhibition of enzymic activity, whereas the association rate of ferrocytochrome c was almost equal to that found for monomeric oxidase in laurylmaltoside. These results are in agreement with a mixed-type inhibition.

Animals↗
PubMed1987

Bovine cytochrome c oxidases, purified from heart, skeletal muscle, liver and kidney, differ in the small subunits but show the same reaction kinetics with cytochrome c.

(1) Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate of purified cytochrome c oxidase preparations revealed that bovine kidney, skeletal muscle and heart contain different cytochrome c oxidase isoenzymes, which show differences in mobility of the subunits encoded by the nuclear genome. No differences in subunit pattern were observed between the oxidase preparations isolated from kidney and liver. (2) The kinetics of the steady-state reactions between bovine ferrocytochrome c and the four types of bovine cytochrome c oxidase preparation were compared under conditions of both high- and low-ionic strength. Also the pre-steady-state kinetics were studied. Only minor differences were observed in the electron-transfer activity of the isoenzymes. Thus, our experiments do not support the notion that the subunits encoded by the nuclear genome act as modulators conferring different activities to the isoenzymes of cytochrome c oxidase. (3) The cytochrome c oxidase preparation from bovine skeletal muscle was found to consist mainly of dimers, whereas the enzymes isolated from bovine kidney, liver and heart were monomeric.

Animals↗
PubMed1987

Human cytochrome c oxidase isoenzymes from heart and skeletal muscle; purification and properties.

Human cytochrome c oxidase was isolated in an active form from heart and from skeletal muscle by a fast, small-scale isolation method. The procedure involves differential solubilisation of the oxidase from mitochondrial fragments by laurylmaltoside and KCl, followed by size-exclusion high-performance liquid chromatography. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate showed differences between the subunit VI region of cytochrome c oxidases from human heart and skeletal muscle, suggesting different isoenzyme forms in the two organs. This finding might be of importance in explaining mitochondrial myopathy which shows a deficiency of cytochrome c oxidase in skeletal muscle only. In SDS polyacrylamide gel electrophoresis most human cytochrome c oxidase subunits migrated differently from their bovine counterparts. However, the position of subunits III and IV was the same in the human and in the bovine enzymes. The much higher mobility of human cytochrome c oxidase subunit II is explained by a greater hydrophobicity of this polypeptide than of that of the subunit II of the bovine enzyme.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Choroidal folds associated with a sellar mass.

We report a case with progressive visual loss whose ophthalmic examination revealed bilateral optic atrophy and choroidal folds in the left eye. Neuroimaging demonstrated a sellar mass compressing the optic chiasm and the left optic nerve was to be stretched. We assume the traction created on the optic nerve by the mass stretched the optic nerve and caused the choroidal folds.

Aged↗
PubMedDate not supplied

Calcification at the posterior pole in scleritis. A case report.

We report a case with unilateral recurrent anterior scleritis which developed sclerochoroidal calcification at the posterior pole without any overt sign of posterior scleritis during the follow-up period of nine years. We believe that subtle posterior scleral inflammation might lead to sclerochoroidal calcification which might be dystrophic in nature.

Adult↗
PubMedDate not supplied

Oxidant status in maternal and cord plasma and placental tissue in gestational diabetes.

The aim of this study was to measure oxidant/antioxidant status in maternal and cord plasma and in placental tissue in gestational diabetes and to correlate the results with the quality of glycemic control of the mother. To achieve this, blood and placental tissue samples have been obtained from pregnant women with gestational diabetes mellitus (GDM) and from the umbilical cord of their fetuses. The same samples have been collected from pregnant women without GDM. In all the samples, oxidant and antioxidant parameters have been studied. It has been observed that the antioxidant defense system was impaired; xanthine oxidase, which is the main free radical-producing enzyme (XO) in the living cells, was activated; and oxidation reactions were accelerated in the samples obtained from patients with GDM. Results suggest presence of oxidant stress in the gestational diabetes, the reason probably being impaired antioxidant defense mechanism and increased free radical production through XO activation.

Adult↗
PubMedDate not supplied

Colour Doppler assessment of blood flow in eyes with central retinal vein occlusion.

PURPOSE: To assess the blood flow changes in eyes with central retinal vein occlusion (CRVO) and compare these values with values of fellow eyes and eyes of normal subjects. METHODS: 25 eyes of 25 consecutive newly diagnosed patients with CRVO comprised the study group. Their fellow eyes and those of 25 healthy subjects were the control group. All patients underwent a complete ophthalmological examination. Eyes with CRVO were classified into two groups as non-ischaemic and ischaemic by fundus fluorescein angiography. Colour Doppler imaging was performed with a Toshiba Sonolayer SSH-140A and 7.5-MHz linear array probe. Maximum systolic velocity (V(max)), end-diastolic velocity (V(min)) and resistive index (R(i)) values were noted for each of the central retinal artery (CRA), central retinal vein (CRV) and ophthalmic artery (OA). These parameters were compared with those of the fellow eyes and both eyes of the control group. RESULTS: Mean ages were 63.55 and 61.45 years in the CRVO and control groups, respectively. Age and sex distributions were statistically identical in both groups. When we compared the eyes with CRVO to the control group, no statistically significant difference existed between the two groups with regard to the V(min) and R(i )values of the CRA and CRV. However, V(max ) values of the CRA and CRV were significantly lower in CRVO eyes when compared to the control group. The CRVO group and control group had similar V(max), V(min ) and R(i) values for the OA. Only the V(max) was significantly lower in the CRV in eyes with CRVO when compared to the unaffected fellow eyes. No statistically significant difference could be detected between any of the parameters of CRA, CRV and OA of the ischaemic and non-ischaemic CRVO groups. CONCLUSIONS: More data on broader series need to be obtained in order to decide on the practical use of colour Doppler imaging in the differentiation of ischaemic eyes from non-ischaemic eyes in CRVO.

Adult↗
PubMedDate not supplied

Staining of intraocular lenses with various dyes: a study of digital image analysis.

PURPOSE: To evaluate the interaction of various intraocular lens (IOL) materials with commonly used dyes. MATERIALS AND METHODS: One IOL of each of the five groups (polymethylmethacrylate, silicone, three-piece hydrophobic acrylic, single-piece hydrophobic acrylic and single-piece hydrophilic acrylic) was bathed in trypan blue 0.1%, fluorescein sodium 2% and indocyanine green (ICG) 0.5% for 15 min. Digital photographs of the IOLs were obtained prior to bathing and after the 15-min bath in each dye. The same IOLs were immersed in the same dye for another 15 min and digital images were reobtained to depict the 30-min dye uptake. New IOLs from the group that exhibited visible colour change after the 15-min bath were then bathed in twofold dilution and if there was still visible dye uptake, fourfold dilution was performed, repeating the 15-min bath and digital photography. The images were then processed using Adobe Photoshop 5.1 to get mean luminosity and red-green-blue values. These values were compared between the groups and the undyed control. Also, dye washout was observed in serum-containing vials. RESULTS: None of the polymethylmethacrylate, silicone and hydrophobic acrylic IOLs were stained with the dyes used. The only IOL material that changed colour was hydrophilic acrylic and did so with all dyes. The most marked colour change was with fluorescein sodium 2%, the least was with trypan blue 0.05%. Twofold dilution of trypan blue and fourfold dilutions of fluorescein sodium and ICG still stained the hydrophilic acrylic IOL; however, fourfold dilution of trypan blue did not cause a significant colour change. Trypan blue washed out within 6 h, while the IOL stained with ICG remained stained for longer than 24 h. COMMENT: Hydrophilic acrylic IOLs should be used with caution together with dyes since this material demonstrates marked dye uptake and washout may also take some time.

Coloring Agents↗
PubMedDate not supplied

Analysis of the pterygium size inducing marked refractive astigmatism.

PURPOSE: Astigmatic changes induced by the pterygium and their relation to its size and morphology were analysed to establish the critical size for surgery before significant astigmatism occurs. MATERIALS AND METHODS: We evaluated the refraction in 148 eyes of 108 adult patients with primary pterygia. We grouped the astigmatic values according to the keratometric results correlating with the maximal length, width and the approximate total area of the pterigium encroaching on the corneal surface. RESULTS: Pterygia with length or width > or = 3.00 mm were related to significantly higher astigmatism than other groups (p<0.01). The effect of the pterygium morphology on corneal astigmatism was not significant. CONCLUSIONS: Pterygia exceeding 3.00 mm of length or width should be considered within the limits of surgery.

Adult↗
PubMedDate not supplied

Comparison of sedation requirements for cataract surgery under topical anesthesia or retrobulbar block.

PURPOSE: Topical anesthesia is increasingly being used for cataract surgery. However, it is believed that topical anesthesia causes an increased risk of intraoperative complications from unrestricted eye movement and insufficient pain control and more need for sedation. It is difficult to compare pain and anxiety experienced by individual patients; therefore, the authors used the method of patient-controlled sedation to determine whether there is a difference in sedation requirements under topical or retrobulbar anesthesia. METHODS: In this prospective study, patients received either topical anesthesia (n=87) or retrobulbar block (n=104) and self-administered a mixture of midazolam (0.5 mg) and fentanyl (25 microg) in increments using a patient controlled analgesia infuser to achieve sedation. At the end of surgery, patients rated their pain on a 10-point numerical rating scale and their comfort on a 5-point scale. The number of demands and deliveries were noted from the patient controlled analgesia infuser display. RESULTS: Pain scores were between 0 and 2 in 95.4% in the topical and in 94.2% in the retrobulbar group (p>0.05). Patient comfort was equal in both groups with 2.94+/-0.92 in the topical group and 2.92+/-0.99 in the retrobulbar group (p>0.05). Mean sedation requirements were similar in both groups: 26.4% of patients in the topical group and 19.2% in the retrobulbar group did not request any sedation (not significant, p>0.05). CONCLUSIONS: Sedation requirements were similar for cataract surgery under topical and retrobulbar anesthesia.

Aged↗
PubMedDate not supplied

Antioxidant status of erythrocytes from patients with cirrhosis.

BACKGROUND/AIMS: The aim of the present study was to investigate possible involvement of oxidant stress in the anemia of cirrhotic patients and to assess blood antioxidant status of these patients. METHODOLOGY: Superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) enzyme activities were measured in the erythroctes from patients with liver cirrhosis and from controls. Levels of thiobarbituric acid reagent substance were also measured in the erythrocyte (TBARSe) and plasma (TBARSp) samples of the groups. RESULTS: Lower activities of SOD and GSH-Px were established in the erythrocytes from patients compared with control subjects. No differences were found between erythrocyte TBARS levels of control and patient groups. Plasma TBARS levels were, however, found to be significantly higher in the patient groups compared with controls. CONCLUSIONS: Results suggest that although enzymatic antioxidant defense system is significantly reduced in the erythrocytes from cirrhotic patients, this does not lead to further peroxidative reactions in the erythrocytes, possible due to preoxidation of some cellular structures sensitive to peroxidative attacks. There was, however, an important indication of accelerated peroxidative reactions in the plasma of the cirrhotic patients, which possibly resulted from extracellular oxidant stress in these patients.

Adult↗
PubMedDate not supplied

Mucosal antioxidant defense is not impaired in ulcerative colitis.

BACKGROUND/AIMS: In this study, mucosal antioxidant defense was investigated in the biopsy samples from 12 patients with active ulcerative colitis and from 13 patients under remission. METHODOLOGY: Biopsy samples obtained from healthy colon parts of the same subjects were used as control. RESULTS: No changes were observed between superoxide dismutase, glutathione peroxidase and catalase enzyme activities of control or inflamed biopsy samples. However, antioxidant potential values were found to be higher and malondialdehyde levels lower in inflamed samples compared with controls. CONCLUSIONS: Our results show that in contrast to previous suggestions, mucosal antioxidant defense is not impaired in ulcerative colitis.

Antioxidants↗
PubMedDate not supplied

Long-term results of various anterior capsulotomies and radial tears on intraocular lens centration.

BACKGROUND AND OBJECTIVE: To evaluate the long-term effects of various anterior capsulotomies and radial tears on intraocular lens (IOL) centration. MATERIALS AND METHODS: Ninety-five eyes of 87 senile cataract patients operated with extracapsular technique were evaluated in IOL tilt and decentration with a new method of measurement. According to the type of anterior capsulotomy and number of radial tears, five groups were constituted as, can opener, envelope, continous curvilinear capsulorrhexis (CCC), CCC with one radial tear (relaxing incision at quadrant 12), and CCC with two relaxing incisions (relaxing incisions at quadrants 6 and 12), respectively. RESULTS: Early decentration and tilt in groups CCC and CCC with one radial tear were significantly lower than the other groups (P < 0.05). Late decentration and tilt in the CCC group were significantly lower than the other groups (P < 0.01). Highest values of tilt and decentration were determined in envelope capsulotomy. Additional symmetric relaxing incision at quadrant 6 revealed no effect on the prevention of decentration and tilt compared to one relaxing incision. CONCLUSION: CCC with one radial tear is not ideal but sufficient for IOL centration. All other anterior capsulotomy techniques, other than intact CCC, do not guarantee the IOL centration.

Aged↗