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Biomedical subjects

A Bozkurt

Publications and source records attributed to A Bozkurt.

At least 19 recordsLinked to original sources
PubMed2006

Simultaneous determination of equivalent dose to organs and tissues of the patient and of the physician in interventional radiology using the Monte Carlo method.

This study presents the results of computations of organ equivalent doses and effective doses for the patient and the primary physician during an interventional cardiological examination. The simulations were carried out for seven x-ray spectra (between 60 kVp and 120 kVp) using the Monte Carlo code MCNP. The voxel-based whole-body model VIP-Man was employed to represent both the patient and the physician, the former lying on the operation table while the latter standing 15 cm from the patient at about waist level behind a lead apron. The x-rays, which were generated by a point source positioned around the table and were directed with a conical distribution, irradiated the patient's heart under five major projections used in a coronary angiography examination. The mean effective doses under LAO45, PA, RAO30, LAO45/CAUD30 and LLAT irradiation conditions were calculated as 0.092, 0.163, 0.161, 0.133 and 0.118 mSv/(Gy cm2) for the patient and 1.153, 0.159, 0.145, 0.164 and 0.027 microSv/(Gy cm2) for the shielded physician. The effective doses for the patient determined in this study were usually lower than the literature data obtained through measurements and/or calculations and the discrepancies could be attributed to the fact that this study computes the effective doses specific to the VIP-Man body model, which lacks an ovarian contribution to the gonadal equivalent dose. The effective doses for the physician agreed reasonably well with the literature data.

Adult↗
PubMed2006

Penetration of second-, third-, and fourth-generation topical fluoroquinolone into aqueous and vitreous humour in a rabbit endophthalmitis model.

AIMS: This study was designed to investigate the penetration of second-, third- and fourth-generation topical fluoroquinolone into aqueous and vitreous humour in a rabbit endophthalmitis model. METHODS: Thirty New Zealand white rabbits were divided into six groups. Left eye was infected with an intravitreal inoculum of Staphylococcus aureus. Groups 1, 2, 3, 4, and 5 received topical ofloxacin, ciprofloxacin, lomefloxacin, levofloxacin, or moxifloxacin treatment 24 h after the inoculation, respectively. No treatment was given to group 6 as the control group (n=5). Aqueous and vitreous samples were obtained 30 min after the last drop. High-performance liquid chromatography was used to determine the fluoroquinolone concentration. RESULTS: In the normal and inflamed eyes, mean aqueous concentrations of ofloxacin were 1.90 and 2.69 mug/ml, ciprofloxacin were 2.16 and 3.65 mug/ml, lomefloxacin were 3.54 and 1.19 mug/ml, levofloxacin were 2.89 and 9.41 mug/ml, and moxifloxacin were 4.92 and 43.33 mug/ml, respectively. Mean vitreous concentrations of ofloxacin were 0.25 and 0.07 mug/ml, ciprofloxacin were 0.08 and 0.32 mug/ml, lomefloxacin were 0.001 and 0.03 mug/ml, levofloxacin were 0.03 and 0.09 mug/ml, and moxifloxacin were 0.28 and 2.68 mug/ml, in normal and inflamed eyes, respectively. Moxifloxacin achieved a significantly higher concentration in aqueous and vitreous humour of infected eyes compared with ofloxacin (P<0.01), ciprofloxacin (P<0.05), lomefloxacin (P<0.01), and levofloxacin (P<0.05). CONCLUSION: This study demonstrated that fourth-generation fluoroquinolone, moxifloxacin, seems to have better penetration to inflamed ocular tissues in rabbit.

Animals↗
PubMed2006

Tamoxifen inhibits cytochrome P450 2C9 activity in breast cancer patients.

Tamoxifen has been reported to potentiate the anticoagulant effect of warfarin and also to increase the plasma level of phenytoin, which are mainly metabolized by CYP2C9. The aim of this study was to determine the influence of tamoxifen on CYP2C9 activity in vivo in humans. Thirteen breast cancer patients who would start tamoxifen following cytotoxic chemotherapy were enrolled in the study. A single oral dose of 25 mg losartan was given to the patients 2 days before and 2 weeks after starting tamoxifen therapy. Losartan and E3174 in 8-hour urine samples were measured by HPLC. Tamoxifen significantly increased the average urinary losartan/E3174 ratio from 0.73 (CI 95% = 0.15 - 2.30) to 1.66 (CI 95% = 0.68 - 5.20), after 2 weeks of treatment (p = 0.002). Tamoxifen inhibited CYP2C9 activity in breast cancer patients within two weeks of its administration. The inhibition of CYP2C9 activity may be a possible explanation for the drug-drug interaction of tamoxifen with CYP2C9 substrates.

Adult↗
PubMed2006

Variant alleles and genotypes of alcohol dehydrogenase 3 in a Turkish population.

Alcohol dehydrogenase (ADH) is a genetically polymorphic dimeric enzyme that is responsible for the metabolism of alcohol. ADH3 gene encodes for the gamma subunit of dimeric ADH and has an important role in the function of the enzyme. The aim of this study was to determine the frequencies of ADH3 alleles and genotypes in a healthy Turkish population sample. Genotypic assay was carried out in 102 unrelated volunteers. DNA samples were genotyped for the ADH3*2 allele. The ADH3*1 and ADH3*2 allele frequencies were determined as 0.66 (95% confidence interval [CI] = 0.57-0.75) and 0.34 (95% CI = 0.25-0.43), respectively. The genotype frequencies of ADH3*1/*1, *1/*2, and *2/*2 were 39% (95% CI = 30-49), 54% (95% CI = 44-64), and 7% (95% CI = 2-12), respectively. According to our results, the frequencies of variant ADH3 alleles and genotypes are similar to that in the other Caucasian populations.

Adult↗
PubMed2005

Comparison of effective doses from various monoenergetic particles based on the stylised and the VIP-Man tomographic models.

This study compares the effective doses from a MIRD-type stylised model with those derived from the scaled-down version of the tomographic VIP-Man model for photon, electron, neutron and proton beams. The effective dose results from these two models show that they differ from each other within approximately 10% for common high-energy photon beams, within approximately 16% for neutrons, and within approximately 4% for high-energy proton beams. However, for low-energy protons and common electron beams, the effective doses can be different in >100%. It is concluded that the use of a single tomographic models will not improve the operational radiation protection dosimetry involving external beam exposures.

Adult↗
PubMed2004

Fluence-to-dose conversion coefficients for monoenergetic proton beams based on the VIP-Man anatomical model.

A new set of fluence-to-absorbed dose and fluence-to-effective dose conversion coefficients has been calculated for high-energy protons using the whole-body anatomical model VIP-Man, which was developed from the high-resolution transverse colour photographic images of the National Library of Medicine's Visible Human Project. For 10 monoenergetic proton beams between 20 and 10,000 MeV, organ dose calculations were performed using the Monte Carlo code MCNPX under six different irradiation geometries: anterior-posterior, posterior-anterior, left lateral, right lateral, isotropic and rotational. The absorbed dose results for 24 major organs of VIP-Man are presented and compared with those based on mathematical phantoms reported in the literature. The discrepancies (generally within 40%) in organ dose and effective dose estimates are attributed to the use of different transport models employed by different Monte Carlo codes.

Adult↗
PubMed2001

Advanced database methodology for the Collation of Connectivity data on the Macaque brain (CoCoMac).

The need to integrate massively increasing amounts of data on the mammalian brain has driven several ambitious neuroscientific database projects that were started during the last decade. Databasing the brain's anatomical connectivity as delivered by tracing studies is of particular importance as these data characterize fundamental structural constraints of the complex and poorly understood functional interactions between the components of real neural systems. Previous connectivity databases have been crucial for analysing anatomical brain circuitry in various species and have opened exciting new ways to interpret functional data, both from electrophysiological and from functional imaging studies. The eventual impact and success of connectivity databases, however, will require the resolution of several methodological problems that currently limit their use. These problems comprise four main points: (i) objective representation of coordinate-free, parcellation-based data, (ii) assessment of the reliability and precision of individual data, especially in the presence of contradictory reports, (iii) data mining and integration of large sets of partially redundant and contradictory data, and (iv) automatic and reproducible transformation of data between incongruent brain maps. Here, we present the specific implementation of the 'collation of connectivity data on the macaque brain' (CoCoMac) database (http://www.cocomac.org). The design of this database addresses the methodological challenges listed above, and focuses on experimental and computational neuroscientists' needs to flexibly analyse and process the large amount of published experimental data from tracing studies. In this article, we explain step-by-step the conceptual rationale and methodology of CoCoMac and demonstrate its practical use by an analysis of connectivity in the prefrontal cortex.

Animals↗
PubMed2001

Inflammatory response to cold injury in remote organs is reduced by corticotropin-releasing factor.

Current experimental evidence concerning the potential activity of corticotropin releasing factor (CRF) in inflammatory processes still remains controversial. To determine whether CRF has protective effects on three remote organs (liver, lung and stomach) affected by cold injury and to characterize the role of neutrophils in cold-induced inflammation, dorsums of anesthetized rats were exposed for 5 min to a 22% NaCl solution maintained at -20+/-0.5 degrees C and the rats were sacrificed at 24 h after the cold injury. The results indicate that cold-exposure-induced edema in the liver, lung and stomach was blocked by subcutaneous (s.c.; 1.2 and 12 nmol/kg; 30 min before cold trauma) CRF pretreatment, while the central administration of CRF (intracisternally (i.c.); 0.30 and 1.5 nmol/rat; 15 min before cold) had the similar effect at the higher dose. Histological assessment and the tissue myeloperoxidase activities also revealed that CRF given peripherally has a protective role in damage generation. Moreover, CRF had a facilitatory effect in the recovery of the body temperature following cold exposure. In conclusion, CRF is likely to act on its peripheral receptors in the inflamed remote organs, suppressing the edematogenic effects of inflammatory mediators, some of which are neutrophil-derived.

Animals↗
PubMed2001

Estrogens ameliorate remote organ inflammation induced by burn injury in rats.

OBJECTIVE AND DESIGN: The present study was designed to investigate the role of sex steroids in burn-induced remote organ injury. MATERIAL OR SUBJECTS: Male Wistar albino rats were given burn trauma (n=39), and underwent castration or sham operation at 2 h following the burn injury. TREATMENT: Rats were injected sc with either 17beta estradiol benzoate (E2, 10 mg/kg) or an androgen receptor blocker cyproterone acetate (CPA, 25 mg/kg) or vehicle, immediately after burn and at 12 h. METHODS: At 24 h of burn insult, rats were decapitated. Blood samples for RIA of testosterone, estradiol and tumor necrosis factor (TNF)-alpha and the tissue samples for myeloperoxidase activitiy (MPO) were taken. ANOVA student's t test was used for statistical analysis. RESULTS: Castration, antiandrogen and E2 treatments increased plasma estradiol levels and depressed burn-induced elevation in serum TNF-alpha levels. In the liver and lung, burn-induced increase in MPO was reduced by E2 and castration, while CPA was effective in reducing neutrophil infiltration only in the liver. CONCLUSION: We propose that treatment with estrogens or antiandrogens might be applicable in clinical situations to ameliorate systemic inflammation induced by burn.

Animals↗
PubMed2001

N-acetyltransferase polymorphism in patients with Behçet's disease.

OBJECTIVES: The objective of our study was to investigate the possible role of human arylamine N-acetyltransferase 2 (NAT2) polymorphism in susceptibility to Behçet's disease. METHODS: Eighty-five patients with Behçet's disease gave their written informed consent to participate in the study. Seven point mutations (G191A, C282T, T341C, C481T, A803G, G590A, G857A) in the NAT2 gene were analysed using polymerase chain reaction/restriction fragment length polymorphism techniques. In addition, each patient received 100 mg dapsone orally to determine their NAT2 phenotype. Dapsone and its metabolite monoacetyl-dapsone were measured in 3-h plasma samples using high-performance liquid chromatography. Subjects with an acetylation ratio (monoacetyl-dapsone/dapsone) less than 0.4 were defined as slow acetylators. RESULTS: Of 85 patients with Behçet's disease, 54 (63.5%) were identified as genotypically slow acetylators. However, 60% (51 of 85) of patients were diagnosed as slow acetylators according to monoacetyl-dapsone/dapsone ratio. Thus, a low incidence of genotype/phenotype discrepancy (3.5%) was observed in Turkish patients with Behcet's disease. When we compared our results with previous phenotyping and genotyping studies in the Turkish population, frequencies of slow and rapid acetylators were not statistically different in patients with Behçet's disease. The frequency of the *5B allele was found to be slightly higher in patients with Behçet's disease than historic controls (44.7 vs 35.6%, P = 0.039). However, there was no significant difference in the frequency of the overall genotypes and alleles of NAT2 between patients and controls. CONCLUSION: Although the frequency of the NAT2*5B allele, responsible for slow acetylation, was slightly higher in patients than historic controls, our results failed to show an association between NAT2-acetylator status and risk for developing Behçet's disease.

Acetylation↗
PubMed2001

Comparison of subretinal fluid levels of two 0.3% ciprofloxacin-containing eye drops.

PURPOSE: Two ophthalmic solutions of 0.3% ciprofloxacin eye drops are available in Turkey: Ciloxan and Siprogut. A previous study by the same authors was the first to report vitreous penetration of ciprofloxacin-containing eye drops. The aim of the present study was to compare the levels of drug found in the subretinal fluid by the two products following local administration. METHODS: Forty-three patients undergoing conventional retinal detachment surgery received either Ciloxan (22 patients) or Siprogut (21 patients). Beginning 6 h before surgery, two drops of solution were instilled onto the operative eye every 30 min for the first 3 h and then hourly for the next 3 h. Subretinal fluid samples were collected 30 min after administration of the last dose and were assayed for ciprofloxacin levels using a method involving high-performance liquid chromatography with fluorometric detection. RESULTS: The minimum and maximum subretinal fluid concentrations measured were 0.11 microg/mL and 0.65 microg/mL, respectively, with Ciloxan, and 0.08 microg/mL and 0.62 microg/mL, respectively wth Siprogut. There was no statistical difference between the subretinal fluid ciprofloxacin levels of the two products. The subretinal fluid drug evels attained by both products were below the minimum inhibitory concentrations of common ocular pathogens. CONCLUSIONS: Ciloxan and Siprogut can penetrate subretinal fluid. The ocular bioavailability of ciprofloxacin after local administration is equivalent for both pharmaceutical products.

Absorption↗
PubMed2001

Conversion coefficients based on the VIP-Man anatomical model and EGS4.

A new set of conversion coefficients from kerma free-in-air to absorbed dose and kerma free-in-air to "effective VIP-Man dose" has been calculated for external monoenergetic photon beams from 10 keV to 10 MeV using an image-based whole-body anatomical model. This model, called VIP-Man, was recently developed at Rensselaer from the high-resolution color images of the National Library of Medicine's Visible Human Project. An EGS4-based Monte Carlo user code, named EGS4-VLSI, was developed to efficiently process the extremely large image data in VIP-Man. Irradiation conditions include anterior-posterior, posterior-anterior, right lateral, left lateral, rotational, and isotropic geometries. Conversion coefficients from this study are compared with those obtained from two mathematical models, ADAM and EVA. "Effective VIP-Man doses" differ from the previously reported effective dose results by 10%-50% for photons between 100 keV and 10 MeV. Discrepancies are more significant at lower energies and for individual organ doses. Since VIP-Man is a realistic model that contains several tissues that were not previously defined well (or not available) in other models, the reported results offer an opportunity to improve the existing dosimetric data and the mathematical models.

Air Pollutants, Radioactive↗
PubMed2001

Fluence-to-dose conversion coefficients based on the VIP-Man anatomical model and MCNPX code for monoenergetic neutrons above 20 MeV.

A new set of fluence-to-absorbed dose and fluence-to-effective dose conversion coefficients has been calculated for high-energy neutrons using a whole-body anatomical model, VIP-Man, developed from the high-resolution transversal color photographic images of the National Library of Medicine's Visible Human Project. Organ dose calculations were performed using the Monte Carlo code MCNPX for 20 monoenergetic neutron beams between 20 MeV and 10,000 MeV under 6 different irradiation geometries: anterior-posterior, posterior-anterior, left lateral, right lateral, isotropic, and rotational. For neutron Monte Carlo calculations, results based on an image-based whole-body model were not available in the literature. The absorbed dose results for 24 major organs of VIP-Man are presented in the form of tables and selected figures that compare with those based on simplified mathematical phantoms reported in the literature. VIP-Man yields up to 40% larger values of effective dose and many organ doses, thus suggesting that the results reported in the past may not be conservative.

Humans↗
PubMed2001

Organ dose conversion coefficients for 0.1-10 MeV electrons calculated for the VIP-Man tomographic model.

A whole-body tomographic model, called VIP-Man, was recently developed at Rensselaer Polytechnic Institute from the high-resolution color photographic images of the National Library of Medicine's Visible Human Project. An EGS4-based Monte Carlo user code, named EGS4-VLSI, was developed to efficiently transport electrons using the large image data set for VIP-Man. VIP-Man has been used to calculate doses for neutrons and photons. This paper presents a new set of fluence-to-absorbed-dose conversion coefficients for monoenergetic electron beams between 100 keV and 10 MeV for VIP-Man. Irradiation conditions include anterior-posterior, posterior-anterior, right lateral, left lateral, rotational, and isotropic source geometries. Comparisons between organ doses from VIP-Man, which is taller and heavier than the Reference Man, and existing data from mathematical models show significant discrepancies. It appears that even slight differences between body models can cause dramatic dosimetric deviations for low penetrating electron irradiation. This suggests that a single standard body model may poorly represent a large population and may not be acceptable for electron dosimetry.

Electrons↗
PubMed2001

Lymphocyte subsets in patients with idiopathic dilated cardiomyopathy.

OBJECTIVE: Although chronic myocardial inflammatory process mediated by viral and autoimmune factors has been postulated in the pathogenesis of idiopathic dilated cardiomyopathy (IDC), the role of autoimmune mechanisms still remains unclear. The aim of the present study was to investigate the rates of various T cell subsets and natural killer (NK) cells in peripheral blood in order to see whether they had a role in the immunoregulation of IDC. METHODS: The surface markers of peripheral T and B lymphocytes were detected and percentages of pan T and B cells as well as helper (CD4+) and suppressor (CD8+) T lymphocytes subsets in the peripheral blood and their ratio (CD4+/CD8+) were determined in 27 patients with IDC and in 20 healthy controls. NK cell percentage was also studied. RESULTS: There were no significant differences between IDC and control groups with respect to T and B cell percentages. The percentages of CD4+ T cell subsets were similar in both groups (48.7 +/- 8.7% vs. 43.5 +/- 9.7% respectively; p = 0.107). CD8+ T cell percentage was significantly decreased in patients with IDC than in controls (22.6 +/- 7.7% vs. 28.2 +/- 8.2%, respectively; p = 0.044). CD4+/CD8+ ratio was markedly higher in patients with IDC than controls (2.6 +/- 1.8 vs. 1.6 +/- 0.6, respectively; p = 0.006). There was no significant difference in the NK cell percentage between groups. CONCLUSION: Decreased CD8+ T cell subset is the cause of increased CD4+/CD8+ ratio, which may imply decreased self-tolerance and an immunoregulatory defect in the pathogenesis of IDC.

Adult↗