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ABSTRACT: The microsomal NADH-dependent electron transport system consisting of cytochrome b5 reductase and cytochrome b5 participates in a number of physiologically important processes including lipid metabolism as well as is involved in the metabolism of various drug and xenobiotics. In the present study, we assessed the inhibitory effects of eight dietary flavonoids representing five distinct chemical classes on cytochrome b5 reduction by purified cytochrome b5 reductase. From the flavonoids tested, myricetin was the most potent in inhibiting cytochrome b5 reduction with an IC50 value of 0.35μM. Myricetin inhibited b5 reductase noncompetitively with a Ki of 0.21μM with respect to cofactor NADH, and exhibited a non-linear relationship indicating non-Michaelis-Menten kinetic binding with respect to cytochrome b5. In contrast to the potent inhibitory activity of myricetin, (+)-taxifolin was found to be a weak inhibitor (IC50=9.8μM). The remaining flavonoids were inactive within the concentration range tested (1-50μM). Analysis of structure-activity data suggested that simultaneous presence of three OH groups in ring B is a primary structural determinant for a potent enzyme inhibition. Our results suggest that inhibition of the activity of this system by myricetin or myricetin containing diets may influence the metabolism of therapeutic drugs as well as detoxification of xenobiotics.
Toxicology 04/2013; · 3.68 Impact Factor
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ABSTRACT: This study attempted to investigate the ability of microsomal NADH-cytochrome b5 reductase and cytochrome P450 2B4 to reductively activate idarubicin and mitomycin C. In vitro plasmid DNA damage experiments and assays using purified hepatic enzymes were employed to examine their respective roles in the metabolic activation of anticancer drugs. Mitomycin C was found to be not a good substrate for microsomal b5 reductase unlike P450 reductase. It produced low amounts of strand breaks in DNA when incubated with b5 reductase and its one-electron reduction by purified enzyme was found as negligible. Our findings revealed that P450 reductase-mediated metabolism of idarubicin resulted in a large increase in single-strand DNA breaks, whereas, b5 reductase neither catalyzed the reduction of idarubicin nor mediated the formation of DNA damage in the presence of idarubicin. The reconstitution studies, on the other hand, have identified rabbit liver CYP2B4 isozyme as being a potential candidate enzyme for reductive bioactivation of idarubicin and mitomycin C. Thus, the present novel findings strongly suggest that while b5 reductase could not play a key role in the cytotoxic and/or antitumor effects of idarubicin and mitomycin C, CYP2B4 could potentiate their activity in combination with P450 reductase.
Xenobiotica 08/2012; · 1.79 Impact Factor
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ABSTRACT: The aim of implantation of interspinous device is to unload the facet joints, restore foraminal height and provide stability in order to improve the clinical outcome of surgery.
After microsurgical decompression, Coflex™ device was applied. Patients were evaluated at a month after surgery and last follow-up using the visual analogue scale (VAS) and Oswestry Disability Index (ODI). Foraminal height and lumbar lordosis angle were recorded.
The mean preoperative VAS was 7.85 and fell to 1.7 a month after surgery (p < 0.0001). At the last follow-up the mean VAS score was 1.65 (p < 0.0001). The mean foraminal heights were measured 19.95 mm preoperatively and 25.05 mm a month after surgery (p < 0.0001). The mean foraminal height was 21.60 mm at the last follow-up (p=0.002). The mean lumbar lordosis were measured 32.05 and 34.3 degrees at preoperative and a month after surgery respectively (p=0.155). The mean lumbar lordosis was 32 (±5.99) degrees at the last follow-up (p=0.974).
Using the Coflex device is a minimal invasive, effective and safe procedure. Restoration of the foraminal height may not be a responsible factor for clinical improvement. We think microsurgical decompression looks responsible of the good clinical outcome and using interspinous device is unnecessary. Comparative clinical studies can be informative.
Turkish neurosurgery 01/2012; 22(1):50-4. · 0.62 Impact Factor
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ABSTRACT: In this study, the reverse polarization method is implemented using transmit and receive arrays to improve the visibility of the interventional devices. Linearly polarized signal sources--inductively and receptively coupled radiofrequency coils--are used in the experimental setups to demonstrate the ability of the method to separate these sources from a forward polarized anatomy signal. Two different applications of the reverse polarization method are presented here: (a) catheter tracking and (b) fiducial marker visualization, in both of which transmit and receive arrays are used. The performance of the reverse polarization method was further tested with phantom and volunteer studies, and the results proved the feasibility of this method with transmit and receive arrays.
Magnetic Resonance in Medicine 06/2011; 67(2):446-56. · 2.96 Impact Factor
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ABSTRACT: Idarubicin is a synthetic anthracycline anticancer drug widely used in the treatment of some hematological malignancies. The studies in our laboratory have clearly demonstrated that idarubicin can undergo reductive bioactivation by NADPH-cytochrome P450 reductase to free radicals with resulting formation of DNA strand breaks, which can potentially contribute to its genotoxic effects [Celik, H., Arinç, E., Bioreduction of idarubicin and formation of ROS responsible for DNA cleavage by NADPH-cytochrome P450 reductase and its potential role in the antitumor effect. J Pharm Pharm Sci, 11(4):68-82, 2008]. In the current study, our aim was to investigate the possible protective effects of several phenolic antioxidants, quercetin, rutin, naringenin, resveratrol and trolox, against the DNA-damaging effect of idarubicin originating from its P450 reductase-catalyzed bioactivation.
DNA damage was measured by detecting single-strand breaks in plasmid pBR322 DNA using a cell-free agarose gel method.
Our results indicated that, among the compounds tested, quercetin was the most potent antioxidant in preventing DNA damage. Quercetin significantly decreased the extent of DNA strand breaks in a dose-dependent manner; 100 microM of quercetin almost completely inhibited the DNA strand breakage. Unlike quercetin, its glycosidated conjugate rutin, failed to provide any significant protection against idarubicin-induced DNA strand breaks except at the highest concentration tested (2 mM). The protective effects of other antioxidants were significantly less than that of quercetin even at high concentrations. Quercetin was found to be also an effective protector against DNA damage induced by mitomycin C.
We conclude that quercetin, one of the most abundant flavonoids in the human diet, is highly effective in reducing the DNA damage caused by the antitumor agents, idarubicin and mitomycin C, following bioactivation by P450 reductase.
Journal of pharmacy & pharmaceutical sciences: a publication of the Canadian Society for Pharmaceutical Sciences, Societe canadienne des sciences pharmaceutiques 01/2010; 13(2):231-41. · 1.65 Impact Factor
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ABSTRACT: The operative treatment of lumbar disc disease has long challenged spine surgeons. In this study, we aimed to show that recruits with lumbar disc herniation managed by the interlaminar approach could return to work after 6 weeks. Forty male recruits were included in this study and interlaminar discectomy was adequate in 40 cases. Early postoperative rehabilitation had a positive effect on early return to work. We believe that interlaminar lumbar discectomy is an effective technique for treating patients with herniated lumbar discs; with early postoperative rehabilitation, recruits can return to work 6 weeks after surgery.
Military medicine 10/2008; 173(9):924-6. · 0.92 Impact Factor
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ABSTRACT: Idarubicin is a clinically effective synthetic anthracycline analog used in the treatment of several human neoplasms. Anthracyclines have the potential to undergo bioactivation by flavoenzymes to free radicals and thus exert their cytotoxic actions. In this study, our main objective was to investigate the possible involvement of NADPH-cytochrome P450 reductase in the bioreductive activation of idarubicin to DNA-damaging species.
A pBR322 plasmid DNA damage assay was used as a sensitive method for detecting strand breaks in DNA exposed to idarubicin in the presence of P450 reductase and cofactor NADPH under various incubation conditions. In addition, the rates of idarubicin reduction by P450 reductases purified from phenobarbital-treated rabbit liver, beef liver and sheep lung microsomes were determined by measuring NADPH oxidation at 340 nm.
The plasmid DNA experiments demonstrated that idarubicin could undergo bioreduction by P450 reductase with the resulting formation of DNA strand breaks. The antioxidant enzymes SOD and catalase, and hydroxyl radical scavengers, DMSO and thiourea, afforded significant levels of protection against idarubicin-induced DNA strand breaks. These findings suggested that DNA damage by idarubicin occurs through a mechanism which involves its redox cycling with P450 reductase to generate reactive oxygen species (ROS). The extent of DNA damage by idarubicin was found to increase with increasing concentrations of drug or enzyme as well as with increasing incubation time. The capacity of idarubicin to induce DNA damage under above incubation conditions was compared with that of a model compound, mitomycin C. Finally, enzyme assays carried out with purified P450 reductases revealed that idarubicin exhibited about two-fold higher rate of reduction than mitomycin C.
Our findings implicated bioreduction of idarubicin by P450 reductase and subsequent redox cycling under aerobic conditions as being one mode of idarubicin action potentially contributing to its antitumor effect.
Journal of pharmacy & pharmaceutical sciences: a publication of the Canadian Society for Pharmaceutical Sciences, Societe canadienne des sciences pharmaceutiques 02/2008; 11(4):68-82. · 1.65 Impact Factor
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ABSTRACT: To conduct interventional procedures in MRI, reliable visualization of interventional devices such as catheters is necessary. For this purpose, the use of inductively-coupled radio frequency (ICRF) coils has been proposed. Without a wired connection, the signal around the ICRF coil is amplified, enabling catheters to be visualized. The wireless connection allows easy handling of catheters, in some pulse sequences, however, it might be difficult to differentiate the catheters from anatomical background information. In this work, a novel ICRF coil visualization method, which allows separation of the catheter and the anatomical information by using the reverse and forward polarization modes of a coil, is proposed. This method allows images of the anatomy and the catheter to be combined into a color-coded image. First, an ICRF coil with decoupling diodes was constructed; we call this a receive-coupled RF (RCRF) coil. The RF safety profile of the RCRF coil is shown to be better than the ICRF coil. Second, to demonstrate the feasibility of this method, a receive-only birdcage coil without a hybrid coupler was constructed and then connected to a scanner as a two-channel phased-array coil. MR signals acquired from two channels were added after phase adjustments to create the reverse and forward polarization mode images. The reverse polarization mode image contained signal only from the RCRF coil, but the forward polarization mode displayed both anatomical information and the RCRF coil. The performance of this novel tracking method was tested in phantom and animal experiments. Color-coded images demonstrate the feasibility of the method to track catheters using RCRF coils.
Magnetic Resonance in Medicine 01/2008; 58(6):1224-31. · 2.96 Impact Factor
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ABSTRACT: The upper bounds of the signal-to-noise ratio (also known as the "ultimate intrinsic signal-to-noise ratio" (UISNR)) for internal and external coils were calculated. In the calculation, the body was modeled as a dielectric cylinder with a small coaxial cylindrical cavity in which internal coils could be placed. The calculated UISNR values can be used as reference solutions to evaluate the performance of internal MRI coils. As examples, we evaluated the performance of a loopless antenna and an endourethral coil design by comparing their ISNR with the UISNR.
Magnetic Resonance in Medicine 10/2004; 52(3):640-9. · 2.96 Impact Factor
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ABSTRACT: NADPH-cytochrome P450 reductase, an obligatory component of the cytochrome P450 dependent monooxygenase system, was purified to electrophoretic homogeneity from beef liver microsomes. The purification procedure involved the ion exchange chromatography of the detergent-solubilized microsomes on first and second DEAE-cellulose columns, followed by 2',5'-ADP Sepharose affinity chromatography. Further concentration of the enzyme and removal of Emulgen 913 and 2'-AMP were accomplished on the final hydroxylapatite column. The enzyme was purified 239-fold and the yield was 13.5%. Monomer molecular weight of the enzyme was estimated to be 76000 +/- 3000 (N = 5) by SDS-PAGE. The absolute absorption spectrum of beef reductase showed two peaks at 455 and 378 nm, with a shoulder at 478 nm, characteristics of flavoproteins. The effects of cytochrome c concentration, pH, and ionic strength on enzyme activity were studied. Reduction of cytochrome c with the enzyme followed Michaelis-Menten kinetics, and the apparent K(m) of the purified enzyme was found to be 47.7 microM for cytochrome c when the enzyme activity was measured in 0.3 M potassium phosphate buffer (pH 7.7). Stability of cytochrome c reductase activity was examined at 25 and 37 degrees C in the presence and absence of 20% glycerol. The presence of glycerol enhanced the stability of cytochrome c reductase activity at both temperatures. Sheep lung microsomal cytochrome P4502B and NADPH-cytochrome P450 reductase were also purified by the already existing methods developed in our laboratory. Both beef liver and sheep lung reductases were found to be effective in supporting benzphetamine and cocaine N-demethylation reactions in the reconstituted systems containing purified sheep lung cytochrome P4502B and synthetic lipid, phosphatidylcholine dilauroyl.
Journal of Biochemical and Molecular Toxicology 02/2002; 16(6):286-97. · 1.38 Impact Factor
