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Biomedical subjects

A Yaman

Publications and source records attributed to A Yaman.

At least 19 recordsLinked to original sources
PubMed2005

Inhibition of vascular endothelial growth factor-induced retinal neovascularization by retinoic acid in experimental retinopathy of prematurity.

Vascular endothelial growth factor (VEGF) has an important role in the pathogenesis of retinopathy of prematurity (ROP) and inhibition of VEGF expression in the neovascular phase might prevent destructive neovascularization in ROP. It is suggested that retinoids exert a highly potent antiangiogenic activity by inhibiting VEGF expression. The aim of this study was to demonstrate the preventive effect of retinoic acid (RA) on the VEGF-induced retinal neovascularization in a rat model of ROP. Wistar albino rats were placed into incubators at birth and exposed to an atmosphere alternating between 50 % and 10 % O(2) every 24 hours. After 14 days, the animals were removed to room air and received either an intraperitoneal injection of RA (5 mg/kg/day) (n=9) or saline (n=4) daily for six days, and sacrificed at 21 days. Other rats (n=4) were raised in room air and served as age-matched controls. The globe of each eye was cut through the cornea and embedded in paraffin. Serial sections were stained with hematoxylin-eosin for quantification of neovascular nuclei. The avidin-biotin peroxidase method was performed for evaluation of VEGF expression. The average number of neovascular nuclei was significantly lower in the control group compared to that in the ROP groups. In addition, it significantly decreased in the RA-treated ROP group compared to that of the saline-administrated ROP group. VEGF immunostaining was overall negative in room air-exposed rats. The VEGF immunostaining score significantly decreased in the RA-treated ROP group compared to that in the saline-administered ROP group. RA treatment might be beneficial in preventing neovascularization resulting from oxygen-induced retinopathy by downregulation of VEGF expression.

Animals↗
PubMed2005

Antithymocyte globulin for the prevention of graft-versus-host disease after unrelated hematopoietic stem cell transplantation for acute myeloid leukemia: results from the multicenter German cooperative study group.

A total of 155 patients with acute myeloid leukemia (AML) received hematopoietic stem cell transplants from unrelated donors after standard conditioning. Clinical outcome after the use of two different antithymocyte globulins for the prevention of graft-versus-host disease (GvHD) was analyzed in a retrospective study as follows: rabbit ATG (Thymoglobulin Sangstat/Genzyme, n=49, median age 42 years, 53% in CR, further ATG-S); rabbit ATG (ATG-Fresenius, n=38, median age 42 years, 58% in CR, further ATG-F) or no ATG (n=68, median age 36 years, 55% in CR). The groups were comparable regarding disease status at transplant, age, CMV status and cytogenetics. Grade III-IV acute GvHD was found in 15% in the ATG and 27% in the no ATG group (P=0.44). The most important independent risk factors for chronic GvHD (cGvHD) were the use of ATG, disease status at transplant and conditioning. cGvHD developed significantly more frequently in no ATG group. With the median follow-up of 34 months, the 5-year survival is 42% for those transplanted in CR. To conclude, these data demonstrate that the transplants performed in CR, with ATG, are associated with a good outcome, low incidence of cGvHD and no increase of relapse.

Adolescent↗
PubMed2003

Ocular myasthenia gravis coincident with thyroid ophthalmopathy.

Graves' disease and myasthenia gravis are both auto-immune diseases and the coexistence of these two diseases is well recognized. Myasthenia gravis is more frequent in patients with thyroid disease. Here we present a case of thyroid ophthalmopathy and ocular myasthenia.

Adult↗
PubMed2002

Surveillance of antimicrobial resistance in gram-negative isolates from intensive care units in Turkey: analysis of data from the last 5 years.

A multicenter antimicrobial surveillance program was established in Turkey in 1995 to monitor the predominant Gram-negative pathogens from intensive care units (ICUs) and antimicrobial resistance patterns of these isolates. Sixteen hospitals participated in the study and a total of 1479 isolates from 1,100 patients were collected. The isolates were tested for their susceptibility against 13 antibiotics by E-test method. Minimum inhibitory concentrations (MICs) for each isolate were determined for imipenem, ceftazidime, ceftazidime-clavulanate, cefoperazone-sulbactam, ceftriaxone, cefepime, cefuroxime, piperacillin-tazobactam, ticarcillin-clavulanate, gentamicin, amikacin and ciprofloxacin. The most common isolates were Pseudomonas spp. (28.2%), Escherichia coli (19.2%) and Klebsiella spp. (19.1%). We found very high resistance rates to all major antibiotics that are used to treat serious infections. Although imipenem is the most active agent, it had an overall susceptibility rate of 68%. Half of the tested Klebsiella spp. strains were found to produce ESBL. This is a very high rate when compared with the literature. Cross-resistance among species was also investigated. 52% of ciprofloxacin-resistant strains were also resistant to imipenem, 80% to ceftazidime, 97% to ceftriaxone, 86% to amikacin and 19% of imipenem-resistant strains were susceptible to ceftazidime and 18% to amikacin. When susceptibilities of the years 1995 and 1999 were compared, the most interesting finding was the decrease in resistance to 3rd generation cephalosporins. In conclusion, this national clinical isolate database shows that resistance rates are high, the change over years is not predictable and continuous surveillance is necessary to monitor antimicrobial resistance and to guide antibacterial therapy.

Anti-Bacterial Agents↗
PubMed2001

Alternative methods of terminal sterilization for biologically active macromolecules.

The traditional perception within the pharmaceutical industry of the manufacture of injectable drug products is that active pharmaceutical ingredients (API) that are peptides, proteins or biopolymers, such as poly(DL-lactide) (PLA) and poly(DL-lactideco-glycolide) (PLGA), cannot be terminally sterilized. This perception exists largely because terminal sterilization is assumed by many to be only carried out by steam sterilization in a standard autoclave. Thus, it is understood that these API candidates must be manufactured by aseptic techniques. With the current technological advances in the area of protein and peptide sterilization, which has largely come from the food industry and has in recent years been developed for pharmaceutical use, techniques have been developed for the terminal sterilization of thermally sensitive APIs and biopolymers. In this review, the focus will be on the four major types of sterilization that are presented in the literature: (i) gamma-irradiation; (ii) e-Beam; (iii) natural light; and (iv) microwave. Each of these sterilization techniques present advantages and disadvantages for use in large-scale terminal sterilization of bioactive macromolecules.

Biopolymers↗
PubMed2000

STAT6 and the regulation of CD23 expression in B-chronic lymphocytic leukemia.

High CD23 expression is a hallmark of B-CLL cells. It is lost during in vitro culture and can be reinduced by IL-4, albeit to a lower extent than in normal B cells. To elucidate the events controlling CD23 expression in B-CLL cells, the IL-4 mediated induction of STAT6 was investigated. Western-blot analysis demonstrated that B-CLL cells contain comparable amounts of STAT6. Electrophoretic mobility shift assays (EMSA) showed no constitutive nuclear translocation of STAT6. IL-4 induced the translocation of STAT6 in B-CLL cells from all 22 patients investigated. The increase was transient, dose and time dependent without a distinct difference between B-CLL cells and non-malignant B cells. However, in contrast to normal B lymphocytes no strict correlation between CD23 expression and STAT6 activation was detected in B-CLL. Therefore further signalling pathways and transcription factors in addition to STAT6 have to be activated to explain the high expression of CD23 in B-CLL cells. For example, STAT1 which is induced by IFN-gamma and binds to the classical STAT6 site. It might be involved in the strong induction of CD23 on B-CLL cells after cotreatment with IL-4 and IFN-gamma, while in non-malignant B lymphocytes IFN-gamma leads to a reduction of IL-4 mediated CD23 expression.

Biological Transport↗
PubMed2000

Electronic absorption and Raman resonance scattering of spectroscopically pure SiO2.

An ultraviolet absorption, as well as Stokes and anti-Stokes Raman resonance scattering of spectroscopically pure SiO2 was investigated by flash photolysis technique. The whole spectrum of 'absorption and scattered bands' was recorded photographically in ultraviolet. A resonance absorption line was observed at 288.2 nm, without structure, while scattered lines were observed at 285-288.2 and 288.2-290 nm.

Silicon Dioxide↗
PubMed2000

Photophysical properties of 5H-dibenzo(a,d)cyclohepten-5-one in different solutions.

A number of photophysical properties of 5H-dibenzo(a,d)cyclohepten-5-one have been measured for the first time including the prompt and P-type delayed fluorescence, and triplet-triplet absorption. Decay parameters, for the triplet-state of this molecule, have also been measured in different quenching conditions. The results are discussed and compared for those of similar molecules.

Cycloheptanes↗
PubMed2000

The effects of J modulation on spin-echo acquisition and calculation of spin-spin relaxation time (T2) from the J-suppressed data set.

The effects of J modulation on localized 1H NMR spectra were observed on metabolites with both a short T2 relaxation time like glutamate and a comparatively long T2 relaxation time like N-acetyl-L-aspartic acid (NAA). All examinations were performed by either the double spin-echo (PRESS) sequence or J-suppressed PRESS (JPRESS) sequence. Both of the sequences allow spectral editing and relaxation time studies of J coupled spins. Water-suppressed proton spectra were obtained at 1.5 T (GE Signa) from a 6-8 ml volume of interest. T1 and T2 relaxation times of some of the major brain metabolites were obtained by varying the repetition time and echo time of the JPRESS sequence.

Algorithms↗
PubMed1998

The effect of pre-induction clonidine on platelet aggregation during minor surgery.

OBJECTIVE: This paper reports the results of a prospective randomized double-blind trial on the effects of pre-operative clonidine on platelet aggregation. METHODS: Thirty adult (ASA I-II) patients undergoing elective minor orthopaedic surgery were randomly allocated into three groups of ten patients each. In group I clonidine 2 microg x kg(-1), in group II clonidine 4 microg x kg(-1) and in group III saline placebo was administered intravenously before the induction of anaesthesia. Anaesthesia was induced with propofol and vecuronium and maintained with halothane-nitrous oxide. Platelet counts and aggregation tests were performed before (t0) and 1 h (t1) and 24 h (t24) after administration of the study drug. RESULTS: Changes in platelet counts among the groups and values over time were not significant. Both maximum rate and intensity of collagen-induced aggregation in both clonidine groups and maximum intensity of adenosine 5'-diphosphate (ADP)-induced aggregation in the high-dose clonidine group increased significantly at t1. However, all these increases in aggregation were within the normal ranges. CONCLUSION: The effects of both low and high doses of clonidine on platelet aggregation appeared to be minor, and we did not observe any increases above the normal ranges.

Adult↗
PubMed1997

Serum tumor necrosis factor-alpha in neonatal sepsis.

Tumor necrosis factor-alpha (TNF-alpha) is thought to be an important mediator in the pathogenesis of neonatal septicemia. To assess the role of TNF-alpha in neonatal sepsis, serum levels of TNF-alpha were measured in a group of neonates with septicemia and compared with the levels of gestational-postnatal, age-matched healthy controls. The relationships between severity of infection, the nature of causative microorganisms, and TNF-alpha levels were also investigated in this prospective study. A total of 49 infants (25 full-term, 24 preterm) with proven sepsis and 40 healthy infants (20 full-term, 20 preterm) were included. Serum TNF-alpha levels were measured using the TNF-alpha immunoradiometric assay. The median level of TNF-alpha was found to be significantly higher in infants suffering from sepsis (154 pg/mL) particularly in those with septic shock (242.5 pg/mL) as compared to healthy controls (61.5 pg/mL) (p < 0.001). No correlation was found between TNF-alpha and postnatal ages, gestational ages or birth weights of the infants. TNF-alpha levels were not different in surviving and terminal neonates. Although serum, TNF-alpha levels were found to be slightly higher in gram-negative septicemia, the difference was not significant. These findings suggest that TNF-alpha plays an important role in the pathophysiology of neonatal septicemia, but its importance as a prognostic factor is not yet clear.

Bacteremia↗
PubMed1997

Widespread detection of PER-1-type extended-spectrum beta-lactamases among nosocomial Acinetobacter and Pseudomonas aeruginosa isolates in Turkey: a nationwide multicenter study.

We studied the prevalence and molecular epidemiology of PER-1-type beta-lactamases among Acinetobacter, Klebsiella, and Pseudomonas aeruginosa strains isolated over a 3-month period in eight university hospitals from distinct regions of Turkey. A total of 72, 92, and 367 Acinetobacter, Klebsiella, and P. aeruginosa isolates were studied, respectively. The presence of blaPER was determined by the colony hybridization method and later confirmed by isoelectric focusing. We detected PER-1-type beta-lactamases in 46% (33/72) of Acinetobacter strains and in 11% (40/367) of P. aeruginosa strains but not in Klebsiella strains. PER-1-type enzyme producers were highly resistant to ceftazidime and gentamicin, intermediately resistant to amikacin, and susceptible or moderately susceptible to imipenem and meropenem. Among PER-1-type-beta-lactamase-positive isolates, five Acinetobacter isolates and six P. aeruginosa isolates from different hospitals were selected for ribosomal DNA fingerprinting with EcoRI and SalI. The EcoRI-digested DNAs were later hybridized with a digoxigenin-labelled PER-1 probe. The ribotypes and the lengths of blaPER-carrying fragments were identical in four Acinetobacter strains. A single isolate (Ac3) harbored a PER gene on a different fragment (approximately 4.2 kbp) than the others (approximately 3.4 kbp) and showed a clearly distinguishable ribotype. Ribotypes of P. aeruginosa strains obtained with EcoRI showed three patterns. Similarly, in Pseudomonas strains two different EcoRI fragments harbored blaPER (approximately 4.2 kbp in five isolates and 3.4 kbp in one isolate). PER-1-type beta-lactamases appear to be restricted to Turkey. However, their clonal diversity and high prevalence indicate a high spreading potential.

Acinetobacter↗
PubMed1997

Macular hole formation in Bietti's crystalline retinopathy. A case report.

Three years after the initial diagnosis, a 21-year-old healthy man with Bietti's crystalline retinopathy developed unilateral stage 4 macular hole with surrounding macular detachment. The mechanism of macular hole formation, which may or may not be a feature of Bietti's crystalline dystrophy, is not clear.

Adult↗
PubMed1996

Effect of defibrotide on platelet function.

Defibrotide, a polydeoxyribonucleotide, has been found to modulate endothelial cell function, causing an increase in tissue plasminogen activator (t-PA) levels, a decrease in plasminogen activator inhibitor (PAI) levels, and an increase in prostaglandin I2 (PGI2) formation in humans. Defibrotide has no direct anticoagulant effect but has a synergistic action with heparin. A strong antithrombotic effect has been observed in animal models. Thus, defibrotide has a beneficial effect in cases of deep venous thrombosis (DVT), peripheral obliterative vascular disorder (POVD), stroke, vasculitis, and thromboembolism. Defibrotide also inhibits platelet function and activation. A significant decrease in platelet aggregate formation on the suture line in microarterial anastomosis in rats is one way defibrotide can inhibit platelet function and activation. In humans, a slight prolongation' of the lag period in collagen-induced aggregation has been observed. In addition, a slight decrease in the maximum amplitude of the secondary wave of ADP and adrenalin-induced aggregations was also found. Platelet adhesion is diminished, the platelet differential count on formvar membrane is altered, and platelet aggregate formation is significantly inhibited. With an increase in platelet cyclic AMP (cAMP) content and a decrease in malonyl dialdehyde (MDA) and thromboxane B2 (TXB2) formation, the levels of platelet secretion products such as PF-4 and beta-thromboglobulin (beta-TG) in plasma decreased progressively. It was also demonstrated that the 14C-glucose transport defect of the platelet membrane of atherosclerotic patients was partially corrected with defibrotide treatment.

Animals↗
PubMed1995

Homonuclear J-refocused spectral editing technique for quantification of glutamine and glutamate by 1H NMR spectroscopy.

Quantification of the excitatory amino acid of glutamine and glutamate is extremely important partly because, when in excessive amounts, they can produce neuronal damage. However, quantification of such metabolites seems to be not straightforward owing to a large number of metabolic signals, particularly between the 2.0- and 3.0-ppm chemical shift range. The authors investigated a quantification method by using a homonuclear J-refocused spectral editing technique, namely the J-refocused PRESS (JPRESS), using both 1.5- and 4-T whole body NMR systems. At first, the J-coupling modulation of each metabolite at different TE values using the PRESS and JPRESS pulse sequences was compared. The suppression of J modulations with the JPRESS is well demonstrated on condition that TE values are less than 1/4J. Then, the accuracy of glutamate quantification after subtracting the two spectra obtained at two different echo times and integrating the difference spectral area at different concentrations was evaluated. The results exhibit an excellent linear relationship between the actual concentration versus the difference spectral peak area at both 1.5 and 4 T. The achievable minimum voxel size was also considered and a 1-ml voxel size seems to be possible at the typical glutamate concentration in vivo at a field strength of 4 T.

Algorithms↗
PubMedDate not supplied

Etiology of childhood blindness in Izmir, Turkey.

PURPOSE: To identify the anatomic sites and the etiology of childhood blindness and to discern treatable and preventable causes. METHODS: The records of 998 patients seen in the authors' pediatric ophthalmology unit between June 1998 and May 2002 were examined retrospectively. A total of 148 patients who had visual impairment and blindness according to World Health Organization criteria were included in the study. They are classified according to the etiology based on time of insult and the anatomic site of visual loss. RESULTS: The most common anatomic site of visual loss was retina, with a rate of 25.0%. The etiology according to the time of insult was unknown in 45.2% of the patients, of whom 20.2% had cataract. Genetic disorders were responsible in 25.0% of the patients. In 69.6% of the patients, the causes of visual impairment were considered either preventable or treatable, including cataract, retinopathy of prematurity, genetic disorders, and refractive errors. CONCLUSIONS: A high percentage of our patients had avoidable causes of childhood blindness. Genetic counseling services, as well as national screening programs for amblyopia, red fundus reflex, and retinopathy of prematurity, should be established.

Adolescent↗