Osman Akın | Bose Institute (original) (raw)

Papers by Osman Akın

Research paper thumbnail of Effects of Ellagic Acid on Copper, Zinc, and Biochemical Values in Serum and Liver of Experimental Cholestatic Rats

Biological Trace Element Research

Ellagic acid (EA) is a natural polyphenolic compound. Although, modulator effects of EA on copper... more Ellagic acid (EA) is a natural polyphenolic compound. Although, modulator effects of EA on copper (Cu) and zinc (Zn) levels in some liver diseases have been reported in experimental animals, its effects in obstructive jaundice (OJ) has not been clarified. We aimed to evaluate potential effects of EA on Cu and Zn levels in liver and serum of cholestatic rats. Forty Wistar albino rats were equally divided into four groups. First group was used as controls. Second group received EA (60 mg−1 kg−1 day−1) for 8 days. Third was OJ group, and fourth group was OJ plus EA group. After 8 days, blood and liver samples were obtained. Higher serum and liver Cu and lower serum and liver Zn levels were found in OJ group (p < 0.05) compared with other groups. However, these differences reached to significant levels for Cu in serum and for Zn in lever. Higher serum copper levels were decreased, and lower liver Zn levels were increased by EA treatment in cholestatic rats (p < 0.05). Also, higher Cu/Zn ratio in OJ group was decreased by EA treatment both in liver (p < 0.05) and in serum (p < 0.05). Significantly higher serum bilirubin, alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase values were found in OJ and OJ + EA groups compared with the control and EA groups (p < 0.05). In conclusion, result of the current study indicated that ellagic acid has modulator effects on Cu and Zn levels in liver and serum of cholestatic rats.

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Research paper thumbnail of Optimisation of the RF power density to obtain good quality hydrogenated amorphous silicon films in a home-made glow discharge system

Optical Materials, 2004

A set of hydrogenated amorphous silicon (a-Si:H) films were prepared in a home-made chemical vapo... more A set of hydrogenated amorphous silicon (a-Si:H) films were prepared in a home-made chemical vapour deposition (CVD) system by varying, 20 MHz RF power density from 20 to 130 mW/cm2 to find the optimised value of the RF power density. The other deposition parameters such as substrate temperature, Ts, total chamber pressure, P, silane (SiH4) gas flow rate and deposition time were kept constant at values 300 °C, 200 mTorr, 12 sccm and 4 h, respectively. Films were characterised by constant photocurrent method, darkconductivity, photoconductivity, and optical transmission measurements. The best film is deposited at the power density of 69 mW/cm2 and it has a deep defect density, Nd=2.3×1015 cm−3, an optical gap, EgTauc=1.69 eV, a thickness, d=3.49 μm, an Urbach parameter, E0=54 meV and a photocarrier mobility-lifetime product μτ=2.1×10−5 cm2/V. We have also studied the influence of deep defect density and structural disorder on the magnitude of steady-state photoconductivity.

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Research paper thumbnail of Temperature dependent photoluminescence of PECVD a-SiO x :H ( x<2

Journal of Luminescence, 2010

The temperature dependent visible photoluminescence (PL) property of a-SiOx:H (x<2) samples prepa... more The temperature dependent visible photoluminescence (PL) property of a-SiOx:H (x<2) samples prepared in a PECVD system by using SiH4+CO2 gas mixture is investigated at a temperature range of 20 K–400 K. One of the two explicitly distinguished PL bands, with varying peak photon energies between 1.70 and 2.05 eV, can be detected at only low temperatures below 200 K, which is attributed to tail-to-tail radiative recombination. Thermal quenching parameter (TL) of the tail-to-tail PL band is calculated as varying between 120 and 280 K as the atomic oxygen concentration ([O]at.%) of the samples increases. Stokes shift (ΔEStokes) of the tail-to-tail PL band is found to change from 85 meV to 420 meV due to band tail widening. The other PL band emerges at 2.1 eV and can be detected at higher temperatures with thermal activation behavior. The activation energies calculated about room temperature vary in the range of 8 meV–50 meV with oxygen concentration. Thermal activation of the 2.1 eV PL band is attributed to the behavior of thermally activated incoherent hopping migration of electrons. These electrons combine with self trapped holes (STHs) to form self trapped excitons (STEs). STEs are localized at intrinsic defects of SiO2 structure such as oxygen vacancies (E′ centers) and non-bridging oxygen hole centers (NBOHC).

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Research paper thumbnail of The effects of plateletpheresis on donor platelet function and coagulation

Transfusion and Apheresis Science, 2007

Reviews in Gynaecological and Perinatal Practice, Volume 37, Issue 2, Pages 113-114, October 2007... more Reviews in Gynaecological and Perinatal Practice, Volume 37, Issue 2, Pages 113-114, October 2007, Authors:O. Meltem Akay; Enver Akın; Fezan Mutlu; Zafer Gulbas. Journal Home, Register or Login: Password: Auto-Login [Reminder]. ...

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Research paper thumbnail of Excitation power dependent photolu- minescence of PECVD a-SiO x :H (x<2) thin films

Physica Status Solidi (c), 2010

The excitation power dependent visible photoluminescence (PL) property of an a-SiOx:H (x < 2) sam... more The excitation power dependent visible photoluminescence (PL) property of an a-SiOx:H (x < 2) sample prepared in a PECVD system is studied within a temperature range of 12 K and 400 K. An explicit PL band was observed at the photon energy of 2.1 eV. It was observed that the PL intensity increased with a power of the excitation intensity (IPL∝Lγ) changed between 1.3 mWcm-2 and 25 mWcm-2. γ was calculated to change between 0.8-1.2 depending on the measurement temperature. The 2.1 eV PL band was found to show weak thermal activation energy around room temperature and calculated as about 1meV. The temperature dependence of PL for each excitation power was fitted to a function proposed due to the thermal activated radiative recombination and the defect related non-radiative recombination mechanism. As a result of the model the ratio of the average distance between a carrier and the non-radiative defect center to the decay length of the wave function of the defect was calculated to be varying between 21 and 33 with increased generation rate range of 1.75x1016 cm-3/s-3.5x1017 cm-3/s. The results were discussed in terms of the separation of phases and the behavior of thermally activated incoherent hopping migration of electrons to combine with self trapped holes (STH) to form self trapped excitons (STE). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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Research paper thumbnail of Deposition of highly photoconductive wide band gap a-SiO x :H thin films at a high temperature without H 2dilution

Solar Energy Materials and Solar Cells, 2005

Electrical and optical characterisation of hydrogenated amorphous silicon–oxygen alloy thin films... more Electrical and optical characterisation of hydrogenated amorphous silicon–oxygen alloy thin films (a-SiOx:H, x<2x<2) grown in a single chamber radio frequency plasma enhanced chemical vapour deposition (PECVD) system at a high substrate temperature of 300 °C is presented. The samples were investigated by Fourier transform infrared spectroscopy (FTIR), optical transmission, the constant photocurrent method (CPM), conductivity and steady-state photoconductivity measurements. With increasing oxygen concentration, the Tauc gap increases from 1.69 to 2.73 eV. The sample with an oxygen concentration of 26.2 at% and a reasonably high bandgap of 2.18 eV shows photoconductivity comparable to that of pure a-Si:H films. The Urbach parameter (E0E0) increases almost linearly with oxygen concentration whereas the dangling bond defect density is found to be saturating at a value of about 7.1×1016 cm−3. One of the highly alloyed samples with E0=123meV exhibited a detectable photosensitivity.

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Research paper thumbnail of Efficacy and safety of extended-release fluvastatin in Turkish patients with hypercholesterol­aemia: TULiPS (Turkish Lipid Study

Current Medical Research and Opinion, 2007

The efficacy and safety of extended-release fluvastatin (fluvastatin XL), 80 mg once daily, was a... more The efficacy and safety of extended-release fluvastatin (fluvastatin XL), 80 mg once daily, was assessed in Turkish patients with primary hypercholesterolaemia (low-density lipoprotein cholesterol (LDL-C) 3.37-5.70 mmol/l and triglyceride (TG) &amp;amp;lt; 4.52 mmol/l). In this open-label, prospective, multi-centre study, 154 patients were given fluvastatin XL 80 mg once daily and lipid levels were assessed after 2 and 12 weeks. Fluvastatin XL 80 mg once daily significantly reduced LDL-C levels by 38.8 and 38.1% at weeks 2 (n = 140) and 12 (n = 116), respectively (p &amp;amp;lt; 0.001 vs. baseline). Treatment with fluvastatin XL for 2 and 12 weeks significantly reduced total cholesterol levels by 30.2 and 27.4%, respectively (p &amp;amp;lt; 0.001 vs. baseline) and reduced TG levels by 14.9 and 7.5%, respectively (p &amp;amp;lt; 0.001 vs. baseline). Following stratification by risk factors for coronary heart disease (CHD) according to the National Cholesterol Education Program Adult Treatment Panel III guidelines, 87.3% of patients with &amp;amp;gt; or = 2 risk factors, and 67.4% of patients with existing CHD or CHD risk equivalents achieved target LDL-C levels (&amp;amp;lt; 3.37 mmol/l and &amp;amp;lt; 2.59 mmol/l, respectively) with fluvastatin XL. Fluvastatin XL reduced high-density lipoprotein cholesterol by 8.9 and 4.7% at weeks 2 and 12 weeks, respectively. fluvastatin XL 80 mg once daily was generally well-tolerated. This open-label study indicates fluvastatin XL 80 mg once daily is an effective and well-tolerated lipid-lowering therapy for the reduction of CHD risk in Turkish patients.

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Research paper thumbnail of Effect of Knitting Tightness on Mechanical Properties of Weft-knit Glass Fiber Reinforced Epoxy Composites

Journal of Reinforced Plastics and Composites, 2008

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Research paper thumbnail of Observation and enhancement of visible photoluminescence of PECVD a-SiOx:H (x < 2) thin films by microcavity effect

Physica Status Solidi (c), 2010

a-SiOx:H (x < 2) thin film samples prepared in a PECVD system by using SiH4+CO2 gas mixture show ... more a-SiOx:H (x < 2) thin film samples prepared in a PECVD system by using SiH4+CO2 gas mixture show strong room temperature visible photoluminescence (PL) at a photon energy of 2.1 eV. The PL spectrum of a single layer sample was observed to reshape due to the multiple reflection between two interfaces of the film. The orders of the resonance modes in the PL spectrum range of 1.5 eV-2.5 eV, were calculated to be within a range of m=8 to m=13. The peak energy of the most intense mode (m=11) was observed at 2.1 eV and the half width and the quality factor of the microcavity were calculated as Δν=20 THz and Q=20, respectively. Two multi-layered distributed Bragg reflectors (10 and 25 layer pairs) were fabricated with two different refractive indices (n1=3.2 and n2=2.4) of the layers with λ/4 (λ0=580nm) optical thickness. The PL intensity was detected increasing in intensity around the photon energy of 2 eV and the other modes were suppressed. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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Research paper thumbnail of Pulmonary artery hypertension as an initial manifestation of Takayasu's arteritis: A case report

Respiratory Medicine Cme, 2010

Takayasu's arteritis is a rare chronic vasculitis of unknown etiology. Symptomatic pulmonary arte... more Takayasu's arteritis is a rare chronic vasculitis of unknown etiology. Symptomatic pulmonary artery disease may be the first sign of Takayasu's arteritis. We describe a 51-year-old woman who presented with severe dyspnea. The initial evaluation and routine exams suggested the presence of pulmonary hypertension of unknown etiology. Absence of bilateral radial and brachial pulses in the physical examination led to an angiographic study, which confirmed the diagnosis of Takayasu's arteritis with severe pulmonary hypertension. During bosentan therapy, the patient's clinical symptoms and exercise capacity improved and her 6-min walking distance increased. We emphasize the importance of considering Takayasu's arteritis in the early diagnosis and therapy of pulmonary artery hypertension.

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Research paper thumbnail of Effects of Ellagic Acid on Copper, Zinc, and Biochemical Values in Serum and Liver of Experimental Cholestatic Rats

Biological Trace Element Research

Ellagic acid (EA) is a natural polyphenolic compound. Although, modulator effects of EA on copper... more Ellagic acid (EA) is a natural polyphenolic compound. Although, modulator effects of EA on copper (Cu) and zinc (Zn) levels in some liver diseases have been reported in experimental animals, its effects in obstructive jaundice (OJ) has not been clarified. We aimed to evaluate potential effects of EA on Cu and Zn levels in liver and serum of cholestatic rats. Forty Wistar albino rats were equally divided into four groups. First group was used as controls. Second group received EA (60 mg−1 kg−1 day−1) for 8 days. Third was OJ group, and fourth group was OJ plus EA group. After 8 days, blood and liver samples were obtained. Higher serum and liver Cu and lower serum and liver Zn levels were found in OJ group (p < 0.05) compared with other groups. However, these differences reached to significant levels for Cu in serum and for Zn in lever. Higher serum copper levels were decreased, and lower liver Zn levels were increased by EA treatment in cholestatic rats (p < 0.05). Also, higher Cu/Zn ratio in OJ group was decreased by EA treatment both in liver (p < 0.05) and in serum (p < 0.05). Significantly higher serum bilirubin, alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase values were found in OJ and OJ + EA groups compared with the control and EA groups (p < 0.05). In conclusion, result of the current study indicated that ellagic acid has modulator effects on Cu and Zn levels in liver and serum of cholestatic rats.

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Research paper thumbnail of Optimisation of the RF power density to obtain good quality hydrogenated amorphous silicon films in a home-made glow discharge system

Optical Materials, 2004

A set of hydrogenated amorphous silicon (a-Si:H) films were prepared in a home-made chemical vapo... more A set of hydrogenated amorphous silicon (a-Si:H) films were prepared in a home-made chemical vapour deposition (CVD) system by varying, 20 MHz RF power density from 20 to 130 mW/cm2 to find the optimised value of the RF power density. The other deposition parameters such as substrate temperature, Ts, total chamber pressure, P, silane (SiH4) gas flow rate and deposition time were kept constant at values 300 °C, 200 mTorr, 12 sccm and 4 h, respectively. Films were characterised by constant photocurrent method, darkconductivity, photoconductivity, and optical transmission measurements. The best film is deposited at the power density of 69 mW/cm2 and it has a deep defect density, Nd=2.3×1015 cm−3, an optical gap, EgTauc=1.69 eV, a thickness, d=3.49 μm, an Urbach parameter, E0=54 meV and a photocarrier mobility-lifetime product μτ=2.1×10−5 cm2/V. We have also studied the influence of deep defect density and structural disorder on the magnitude of steady-state photoconductivity.

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Research paper thumbnail of Temperature dependent photoluminescence of PECVD a-SiO x :H ( x<2

Journal of Luminescence, 2010

The temperature dependent visible photoluminescence (PL) property of a-SiOx:H (x<2) samples prepa... more The temperature dependent visible photoluminescence (PL) property of a-SiOx:H (x<2) samples prepared in a PECVD system by using SiH4+CO2 gas mixture is investigated at a temperature range of 20 K–400 K. One of the two explicitly distinguished PL bands, with varying peak photon energies between 1.70 and 2.05 eV, can be detected at only low temperatures below 200 K, which is attributed to tail-to-tail radiative recombination. Thermal quenching parameter (TL) of the tail-to-tail PL band is calculated as varying between 120 and 280 K as the atomic oxygen concentration ([O]at.%) of the samples increases. Stokes shift (ΔEStokes) of the tail-to-tail PL band is found to change from 85 meV to 420 meV due to band tail widening. The other PL band emerges at 2.1 eV and can be detected at higher temperatures with thermal activation behavior. The activation energies calculated about room temperature vary in the range of 8 meV–50 meV with oxygen concentration. Thermal activation of the 2.1 eV PL band is attributed to the behavior of thermally activated incoherent hopping migration of electrons. These electrons combine with self trapped holes (STHs) to form self trapped excitons (STEs). STEs are localized at intrinsic defects of SiO2 structure such as oxygen vacancies (E′ centers) and non-bridging oxygen hole centers (NBOHC).

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Research paper thumbnail of The effects of plateletpheresis on donor platelet function and coagulation

Transfusion and Apheresis Science, 2007

Reviews in Gynaecological and Perinatal Practice, Volume 37, Issue 2, Pages 113-114, October 2007... more Reviews in Gynaecological and Perinatal Practice, Volume 37, Issue 2, Pages 113-114, October 2007, Authors:O. Meltem Akay; Enver Akın; Fezan Mutlu; Zafer Gulbas. Journal Home, Register or Login: Password: Auto-Login [Reminder]. ...

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Research paper thumbnail of Excitation power dependent photolu- minescence of PECVD a-SiO x :H (x<2) thin films

Physica Status Solidi (c), 2010

The excitation power dependent visible photoluminescence (PL) property of an a-SiOx:H (x < 2) sam... more The excitation power dependent visible photoluminescence (PL) property of an a-SiOx:H (x < 2) sample prepared in a PECVD system is studied within a temperature range of 12 K and 400 K. An explicit PL band was observed at the photon energy of 2.1 eV. It was observed that the PL intensity increased with a power of the excitation intensity (IPL∝Lγ) changed between 1.3 mWcm-2 and 25 mWcm-2. γ was calculated to change between 0.8-1.2 depending on the measurement temperature. The 2.1 eV PL band was found to show weak thermal activation energy around room temperature and calculated as about 1meV. The temperature dependence of PL for each excitation power was fitted to a function proposed due to the thermal activated radiative recombination and the defect related non-radiative recombination mechanism. As a result of the model the ratio of the average distance between a carrier and the non-radiative defect center to the decay length of the wave function of the defect was calculated to be varying between 21 and 33 with increased generation rate range of 1.75x1016 cm-3/s-3.5x1017 cm-3/s. The results were discussed in terms of the separation of phases and the behavior of thermally activated incoherent hopping migration of electrons to combine with self trapped holes (STH) to form self trapped excitons (STE). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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Research paper thumbnail of Deposition of highly photoconductive wide band gap a-SiO x :H thin films at a high temperature without H 2dilution

Solar Energy Materials and Solar Cells, 2005

Electrical and optical characterisation of hydrogenated amorphous silicon–oxygen alloy thin films... more Electrical and optical characterisation of hydrogenated amorphous silicon–oxygen alloy thin films (a-SiOx:H, x<2x<2) grown in a single chamber radio frequency plasma enhanced chemical vapour deposition (PECVD) system at a high substrate temperature of 300 °C is presented. The samples were investigated by Fourier transform infrared spectroscopy (FTIR), optical transmission, the constant photocurrent method (CPM), conductivity and steady-state photoconductivity measurements. With increasing oxygen concentration, the Tauc gap increases from 1.69 to 2.73 eV. The sample with an oxygen concentration of 26.2 at% and a reasonably high bandgap of 2.18 eV shows photoconductivity comparable to that of pure a-Si:H films. The Urbach parameter (E0E0) increases almost linearly with oxygen concentration whereas the dangling bond defect density is found to be saturating at a value of about 7.1×1016 cm−3. One of the highly alloyed samples with E0=123meV exhibited a detectable photosensitivity.

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Research paper thumbnail of Efficacy and safety of extended-release fluvastatin in Turkish patients with hypercholesterol­aemia: TULiPS (Turkish Lipid Study

Current Medical Research and Opinion, 2007

The efficacy and safety of extended-release fluvastatin (fluvastatin XL), 80 mg once daily, was a... more The efficacy and safety of extended-release fluvastatin (fluvastatin XL), 80 mg once daily, was assessed in Turkish patients with primary hypercholesterolaemia (low-density lipoprotein cholesterol (LDL-C) 3.37-5.70 mmol/l and triglyceride (TG) &amp;amp;lt; 4.52 mmol/l). In this open-label, prospective, multi-centre study, 154 patients were given fluvastatin XL 80 mg once daily and lipid levels were assessed after 2 and 12 weeks. Fluvastatin XL 80 mg once daily significantly reduced LDL-C levels by 38.8 and 38.1% at weeks 2 (n = 140) and 12 (n = 116), respectively (p &amp;amp;lt; 0.001 vs. baseline). Treatment with fluvastatin XL for 2 and 12 weeks significantly reduced total cholesterol levels by 30.2 and 27.4%, respectively (p &amp;amp;lt; 0.001 vs. baseline) and reduced TG levels by 14.9 and 7.5%, respectively (p &amp;amp;lt; 0.001 vs. baseline). Following stratification by risk factors for coronary heart disease (CHD) according to the National Cholesterol Education Program Adult Treatment Panel III guidelines, 87.3% of patients with &amp;amp;gt; or = 2 risk factors, and 67.4% of patients with existing CHD or CHD risk equivalents achieved target LDL-C levels (&amp;amp;lt; 3.37 mmol/l and &amp;amp;lt; 2.59 mmol/l, respectively) with fluvastatin XL. Fluvastatin XL reduced high-density lipoprotein cholesterol by 8.9 and 4.7% at weeks 2 and 12 weeks, respectively. fluvastatin XL 80 mg once daily was generally well-tolerated. This open-label study indicates fluvastatin XL 80 mg once daily is an effective and well-tolerated lipid-lowering therapy for the reduction of CHD risk in Turkish patients.

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Research paper thumbnail of Effect of Knitting Tightness on Mechanical Properties of Weft-knit Glass Fiber Reinforced Epoxy Composites

Journal of Reinforced Plastics and Composites, 2008

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Research paper thumbnail of Observation and enhancement of visible photoluminescence of PECVD a-SiOx:H (x < 2) thin films by microcavity effect

Physica Status Solidi (c), 2010

a-SiOx:H (x < 2) thin film samples prepared in a PECVD system by using SiH4+CO2 gas mixture show ... more a-SiOx:H (x < 2) thin film samples prepared in a PECVD system by using SiH4+CO2 gas mixture show strong room temperature visible photoluminescence (PL) at a photon energy of 2.1 eV. The PL spectrum of a single layer sample was observed to reshape due to the multiple reflection between two interfaces of the film. The orders of the resonance modes in the PL spectrum range of 1.5 eV-2.5 eV, were calculated to be within a range of m=8 to m=13. The peak energy of the most intense mode (m=11) was observed at 2.1 eV and the half width and the quality factor of the microcavity were calculated as Δν=20 THz and Q=20, respectively. Two multi-layered distributed Bragg reflectors (10 and 25 layer pairs) were fabricated with two different refractive indices (n1=3.2 and n2=2.4) of the layers with λ/4 (λ0=580nm) optical thickness. The PL intensity was detected increasing in intensity around the photon energy of 2 eV and the other modes were suppressed. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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Research paper thumbnail of Pulmonary artery hypertension as an initial manifestation of Takayasu's arteritis: A case report

Respiratory Medicine Cme, 2010

Takayasu's arteritis is a rare chronic vasculitis of unknown etiology. Symptomatic pulmonary arte... more Takayasu's arteritis is a rare chronic vasculitis of unknown etiology. Symptomatic pulmonary artery disease may be the first sign of Takayasu's arteritis. We describe a 51-year-old woman who presented with severe dyspnea. The initial evaluation and routine exams suggested the presence of pulmonary hypertension of unknown etiology. Absence of bilateral radial and brachial pulses in the physical examination led to an angiographic study, which confirmed the diagnosis of Takayasu's arteritis with severe pulmonary hypertension. During bosentan therapy, the patient's clinical symptoms and exercise capacity improved and her 6-min walking distance increased. We emphasize the importance of considering Takayasu's arteritis in the early diagnosis and therapy of pulmonary artery hypertension.

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