Inhibitory effect of asymmetric dimethylarginine and NG-Monomethyl-L-arginine methyl ester on nitric oxide synthase activity

Background and Objective: Nitric oxide synthase (NOS) paly a role in nitric oxide (NO) generation. Despite the beneficial effects of NO on different body systems its overproduction of produce reactive nitrogen species (RNS) and nitrosilation of proteins. This study was done to evaluate the effect of asymmetric dimethylarginine (ADMA) and NG-Monomethyl-L-arginine methyl ester (L-NMMA) on inhibition of nitric oxide synthase activity. Materials and Methods: In this laboratory study, Nitric oxide synthase was extracted from 500 grams of sheep kidney by homogenization, ammonium sulphate precipitation and column chromatography on DEAE-32 Cellulose and 2', 5'-ADP-agarose. During purification, protein content was measured according to the Bradford and enzyme activity was assayed using the Griess reactions the inhibitory effects of 25 μΜ concentrations of ADMA and L-NMMA on purified enzyme were determined. Results: Specific activity and yield of NOS were 0.6 units/mg protein and 0.9%, respectively. Molecular weight of purified enzyme was 54 KD with SDS-PAGE. ADMA and L-NMMA in 25 μΜ concentrations reduced enzyme activity by 76 and 61.2%, respectively. Km values for NOS in absence and in presence of ADMA and L-NMMA were 5.32 μM, 31.25 μM (P<0.05) and 14.29 μM (P<0.05), respectively. Vmax for NOS in absence and presence of inhibitors was not changed. Conclusion: ADMA and L-NMMA have competitive inhibitory effect on NOS activity and ADMA have higher inhibitory effect than L-NMMA

The comparison of Friedwald formula and direct measurement to determine the serum levels of LDL-C

Background and Objective: The risk of coronary heart disease (CHD) is proportional to the LDL-C lipoprotein. Due to frequent use of Friedwald formula in estimation of LDL-C in most laboratories, this study was done to compare the Friedwald formula and direct measurement to determine the serum levels of LDL-C Materials and Methods: This descriptive study was conducted on of 598 patients 226 male and 372 female whome referred to Imam Ali hospital Andimeshk cityin Khozestan province of Iran for health check up during 2009. 5 ml of the venous blood was drown. Total cholesterol (TC) (mg/dl), Triglyceride (TG) (mg/dl), HDL-C (mg/dl) and LDL-C (mg/dl) of serum are measured with Pars azmun company kits. The Friedwald formula was used for estimation of LDL-C. The K=3, 3.5 and 5 were used to stimate the lipid by Friedwald formula. Data were analyzed using SPSS-18, Pearson correlation coefficient and ANOVA tests. Results: A total of 598 serum samples collected 37.8% were men and 62.2% women. The mean age of participants was 38.8±10.77 years. Minimum age 21 years and maximum age was 77 years. Mean deviation for TG≤150, 201-300 and 301-400 in Friedwald formula (k=5) were -13.01±8.79, -17.11±13.17 and -18.63±18.54, respectively and with k=3 are -.39±12.04, -0.078±18.55 and 0.04±25.55 and for TG between 151-200 is -9.72±10.54 and with k=3.5 is equal to 0.82±13.70. Pearson correlation test showed that direct measurment and calculated from the equation Friedwald, for triglycerides in the area equal to or less than 150, 151-200, 201-300 and 301-400 mg/dl, with correlated to Pearson correlation coefficient were 0.982, 0.991, 0.991 and 0.975, respectively. Conclusion: This study showed that the direct measurement method is superior to the Friedwald equation, otherwise, equation Friedwald formula with K=3 is recommended

Alteration of the level of salivary cortisol under psychological stress and its relationship with rumination and personality traits

Background and Objective: Gender differences in biobehavioral responses to environmental stressors and experience of psychological stress should be identified. This study was done to evaluate the changes of the level of salivary cortisol under psychological stress and its relationship with rumination and personality traits. Methods: In this case-control study, for 45 medical students, The NEO Personality Inventory-Short Form and emotional control questionnaire (ECQ) were filed two months before the final examination. Saliva samples were taken from students in the non-stress (control) and examination stress conditions. Salivary cortisol levels were measured by ELISA method. Results: Gender differences were not observed in the level of salivary cortisol under psychological stress. Significant difference was observed between the mean of salivary cortisol in the non-stress and under examination stress conditions. Positive correlation was found between traits of neuroticism (P<0.05) and rumination (P<0.05) with salivary cortisol as well as negative correlation between the traits openness to experience (P<0.05) and angery control (P<0.05) with salivary cortisol. Neuroticism, rumination and angery control may predict a substantial variance (32%) of salivary cortisol under exam stress. Conclusion: Psychological stress leads to increase in the secretion of salivary cortisol unrelated to gender. Subjects with different personality traits are prone to cortisol responses to stress based on their particular character