Optimization of the Photometric Enzyme Activity Assay For Evaluating Real Activity of Prolidase

Prolidase cleaves the bonds of dipeptides containing proline (X-Pro) and an importantenzyme in collagen metabolism. Prolidase activity is generally determinedby photometric methods based on the measurement of proline levels produced byprolidase. We aimed to investigate the measured prolidase activity is suitable forthe assessment of its physiological activity. Effects of manganese on the enzymeactivation, protein precipitation and reading steps of the photometric method, andinhibitory effect of proline on the enzyme were analyzed. The intra- and inter-assayCVs % were higher than 10 % for photometric method and turnaround timewas 6-8 hours/test. The activation reagent containing manganese was not stableand its concentration was not optimal for enzyme activation. Thus we modifiedthe photometric method by changing manganese concentrations and pH of activatingsolution, eliminating protein-precipitating step, arranging the pH of colorreagent to the pH optimum for ninhidrin reaction and shortened incubation timewith substrate. The inhibitory effect of proline on the prolidase activity even in thephysiological and produced proline concentrations during enzymatic analysis maylimit the analytical performance of prolidase assays. In conclusion, the modifiedphotometric method presented in this study seems to be more reliable than the classicalphotometric method and measured prolidase activity may not reflect the truephysiological activity of enzyme due to proline inhibition

Relationship between renal tubulointerstitial fibrosis and serum prolidase enzyme activity

Objectives: The severity of interstitial fibrosis/tubular atrophy (IFTA) is the most important determinant of the irreversible progression of chronic kidney disease (CKD). Prolidase is the key enzyme in collagen turnover and is associated with an extracellular matrix increase. We aimed to evaluate the relationship between the presence and degree of IFTA and serum prolidase enzyme activity (SPEA) in patients undergoing a renal biopsy

A new method for computer-assisted detection, definition and differentiation of the urinary calculi

Purpose: Urinary stones are common and can be diagnosed with computed tomography (CT) easily. In this study, we aimed to specify the opacity characteristics of various types of calcified foci that develop through the urinary system by using an image analysis program. With this method, we try to differentiate the calculi from the non-calculous opacities and also we aimed to present how to identify the characteristic features of renal and ureteral calcules. Materials and methods: We obtained the CT studies of the subjects (n = 48, mean age = 41 years) by using a dual source CT imaging system. We grouped the calculi detected in the dual-energy CT sections as renal (n = 40) or ureteric (n = 45) based on their locations. Other radio-opaque structures that were identified outside but within close proximity of the urinary tract were recorded as calculi "mimickers". We used ImageJ program for morphological analysis. All the acquired data were analyzed statistically. Results: According to thorough morphological parameters, there were statistically significant differences in the angle and Feret angle values between calculi and mimickers (p < 0.001). Multivariate logistical regression analysis showed that Minor Axis and Feret angle parameters can be used to distinguish between ureteric (p = 0.003) and kidney (p = 0.001) stones. Conclusions: Computer-based morphologic parameters can be used simply to differentiate between calcular and noncalcular densities on CT and also between renal and ureteric stones

Relation of Serum ADMA, Apelin-13 and LOX-1 Levels with Inflammatory and Echocardiographic Parameters in Hemodialysis Patients

Cardiovascular diseases are the leading causes of mortality in patients with chronic kidney disease. Nitric oxide has a critical role in both endothelial dysfunction and the atherosclerosis process. We aimed to investigate the relationships between serum asymmetric dimethyl arginine (ADMA), LOX-1, and Apelin-13 levels, which are known to act over nitric oxide with endothelial dysfunction and cardiac morphology as well as with each other in hemodialysis patients. The study comprised a total of 120 patients (53females and 67males) receiving hemodialysis three times a week for at least 6months and an age-gender matched control group (55 females and 58 males). Serum ADMA, LOX-1, and Apelin-13 levels were measured using the ELISA technique. Echocardiography, 24-h blood pressure monitoring by the Holter and carotid artery intima-media thickness (CIMT) measurement was performed on all of the included subjects. The associations between serum ADMA, LOX-1, and Apelin-13 levels with CIMT, echocardiographic parameters [left ventricular mass (LVM) and left ventricular mass index (LVMI)], and inflammatory markers [high sensitive C-reactive protein (hsCRP) and neutrophil lymphocyte ratio (NLR)] were evaluated by correlation analysis. Serum ADMA, Apelin-13, and LOX-1 levels were significantly higher in the hemodialysis group than the controls (P<0.001, P<0.001, and P<0.001, respectively). CIMT, hsCRP, and NLR levels were also significantly higher in the hemodialysis group (P<0.05, P<0.001, P<0.001, respectively). Significant correlations were observed among the serum ADMA, Apelin-13, and LOX-1 levels. Moreover, notably positive correlations were found between these three biochemical markers and LVM, LVMI, hsCRP, and CIMT. Serum ADMA, Apelin-13, and LOX-1 levels can be indicators not only for the inflammatory process but also for the pathogenesis of cardiovascular diseases in hemodialysis patients