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    Biocatalytic Properties of Lipase from Walnut Seed (Juglans regia L.)
    (Wiley, 2010) Yesiloglu, Yesim; Demirkan, Bora
    Lipase (E.C. 3.1.1.3) from walnut seed was purified 28.6-fold with 31% yield using Sephadex G-100 gel chromatography. Olive oil served as good substrate for the enzyme. The optimum pH and temperature were 9.0 and 70 A degrees C, respectively. The lipase was stable between 30 and 80 A degrees C for 5 min. K (m) and V (max) values were determined as 48 mM and 23.06 x 10(-3) U/min mg for triolein as substrate. Lipase activity was slightly reduced by Cu2+, Ca2+, Hg2+, Mn2+, and Ni2+ ions, while Mg2+ and Zn2+ had no effects. Anionic surfactant sodium dodecyl sulfate stimulated lipase activity while non-ionic surfactants Tween-80 and Triton X-100 had negligible effects on enzymatic activity. The enzyme activity was not affected by 50 mM urea and thioacetamide. Potassium ferricyanide, n-bromosuccinamide and potassium cyanide reduced the enzyme activity. The enzyme showed a good stability in organic solvents, the best result being in n-hexane (113% residual activity). The activity of dialysate was maintained approximately 80% for 1 year at -20 A degrees C.
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    The Effects of Spironolactone on Nephron Function in Patients with Diabetic Nephropathy
    (Taylor & Francis Ltd, 2008) Ustundag, Ayten; Tugrul, Armagan; Ustundag, Sedat; Sut, Necdet; Demirkan, Bora
    Increasing evidence suggests that circulating aldosterone per se contributes directly to renal and cardiovascular diseases. We sought to evaluate the effects of a three-month treatment with 25 mg spironolactone, an aldosterone receptor antagonist, on nephron function in 20 type II diabetic patients with persistent microalbuminuria, despite at least six months' use of an ACEi or ARB (combination group), and in eleven type II diabetic patients with persistent microalbuminuria who have never used an ACEi or an ARB (spironolactone group). In the combination group, urinary protein excretion (UPE, p = 0.015), urinary albumin excretion (UAE, p = 0.010), and the urinary albumin to creatinine ratio (ACR, p = 0.007) decreased, and serum potassium (sK+, p = 0.004) was significantly elevated. ACR (p = 0.016) decreased significantly in the spironolactone group. In 31 patients given spironolactone (all patients group), UPE (p = 0.019), UAE (p = 0.002), and ACR (p = 0.011) decreased, and serum creatinine (sCr, p = 0.025) and sK+ (p = 0.002) were significantly elevated. Changes in albuminuria showed a positive correlation with changes in GFR (p = 0.002) and a negative correlation with changes in sCr (p = 0.007), and changes in ACR showed a negative correlation with changes in sCr (p = 0.004) in all patient groups. In our study, we observed that spironolactone, both alone and in combination with ACEi/ARB treatment, was well tolerated, and that it slowed down the progression of diabetic nephropathy with a marked antialbuminuric effect. Our results showed that the antialbuminuric effect developed by the decrease of intraglomerular pressure, particularly in patients with persistent microalbuminuria despite long-term ACEi/ARB treatment; adding aldosterone blockers to treatment was beneficial.
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    The effects of vitamin C alone or in combination with L-Carnitine in experimental myoglobinuric acute renal failure (MARF)
    (Oxford Univ Press, 2006) Ustundag, Sedat; Sen, Saniye; Yalcin, Omer; Cukur, Ziya; Demirkan, Bora
    [Abstract Not Available]
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    Experimental myoglobinuric acute renal failure: The effect of vitamin C
    (Taylor & Francis Ltd, 2008) Ustundag, Sedat; Yalcin, Omer; Sen, Saniye; Cukur, Ziya; Ciftci, Senturk; Demirkan, Bora
    During times of war and natural disasters, rhabdomyolysis-induced myoglobinuric acute renal failure (ARF) can assume epidemic proportions. Free radicals play an important role in the pathogenesis of myoglobinuric ARF. Vitamin C is a major antioxidant, scavenging free radicals. We have not found any studies on the effect of vitamin C on myoglobinuric ARF. Thus, we aimed to investigate the effects of vitamin C on the myoglobinuric ARF formed by glycerol in rats. Three groups of rats were employed in this study. Group 1 served as control, group 2 was given 50% glycerol (10 mL/kg, i.m.), and group 3 was given glycerol plus vitamin C (20 mg/kg, i.p. for four days). Ninety-six hours after glycerol injections, blood samples and kidney tissues were taken from the anesthetized rats. Urea and creatinine levels in plasma; N-acetyl-beta-D-glucosaminidase activity in urine; malondialdehyde levels, superoxide dismutase and catalase enzyme activity in kidney tissue were determined. Histopathological changes and iron accumulation in the kidney tissue were evaluated. In this study, glycerol administration led to marked renal oxidative stress and severe renal functional and morphological deterioration. The treatment of animals with vitamin C partially corrected the renal dysfunction and morphological impairment. In this respect, vitamin C appears to be a promising candidate for the prevention of rhabdomyolysis-induced ARF. Higher dosages of vitamin C than in 20 mg/kg may be beneficial for better functional and morphological recovery in this model ARF.
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    Hypertension and salt: Intake or sensitivity?
    (Oxford Univ Press, 2006) Sen, Saniye; Ustundag, Sedat; Altun, Gulay Durmus; Okten, Omur; Sipahi, Tammam; Demirkan, Bora
    [Abstract Not Available]
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    L-Carnitine Ameliorates Glycerol-Induced Myoglobinuric Acute Renal Failure in Rats
    (Taylor & Francis Ltd, 2009) Ustundag, Sedat; Sen, Saniye; Yalcin, Omer; Ciftci, Senturk; Demirkan, Bora; Ture, Mevlut
    There is increasing evidence indicating that oxidative stress plays an important role in the pathogenesis of rhabdomyolysis-induced myoglobinuric acute renal failure (ARF). During times of war and natural disasters, myoglobinuric ARF can assume epidemic proportions. Thus, early and effective renoprotective treatments are of utmost importance. It has been shown that L-carnitine, used as a safe and effective nutritional supplement for more than three decades, is effective in preventing renal injury in many renal injury models involving oxidative stress. The present study was performed to investigate the effects of L-carnitine in an experimental model of myoglobinuric ARF. Four groups of rats were employed in this study: group 1 served as a control; group 2 was given glycerol (10 mL/kg, i.m.); group 3 was given glycerol plus L-carnitine (100 mg/kg, i.p.), starting at the same time as the glycerol injection; group 4 was given glycerol plus L-carnitine (100 mg/kg, i.p.), starting 48h before the glycerol injection. After glycerol injections, the i.p. injections of L-carnitine were repeated every 24h for four days. Ninety-six hours after glycerol injections, blood samples and kidney tissues were taken from the anesthetized rats. Urea and creatinine levels in plasma, N-acetyl-beta-D-glucosaminidase activity in urine, and malondialdehyde levels and catalase enzyme activity in kidney tissue were determined. Histopathological changes and iron accumulation in the kidney tissue were evaluated. In this study, glycerol administration led to marked renal oxidative stress, as well as severe functional and morphological renal deterioration. L-carnitine, possibly via its antioxidant properties, ameliorates glycerol-induced myoglobinuric kidney injury.