Free radicals are implicated in many diseases including atherosclerosis, cancer and also in rheumatoid arthritis. Reaction of uric acid with free radicals, such as hydroxyl radical and hypochlorous acid (HOCl) results in allantoin production. In this study, we measured the serum allantoin levels, oxidation products of uric acid, as a marker of free radical generation in rheumatoid arthritis. Fasting blood samples were obtained from 21 rheumatoid patients and 15 healthy controls. In this study, the serum allantoin and uric acid levels were measured by a gas chromatography-mass spectrometry method and the ratios were calculated. The mean allantoin and uric acid levels and ratios in the patient group were 22.1 +/- 11.3, 280.5 +/- 65.0 and 8.0 +/- 3.7 microM, while in the control group they were 13.6 +/- 6.3, 278.3 +/- 53.6 and 4.9 +/- 2.1 microM, respectively. The effects of gender, age, menopausal status, duration of disease and medications on serum allantoin and uric acid levels of the patient and control groups were studied. Our results suggest that uric acid acts as a free radical scavenger and thus is converted to allantoin. Increased allantoin levels suggest the possible involvement of free radicals in rheumatoid arthritis.

The increased production of reactive oxygen species (ROS) from activated neutrophils in Behçet's disease (BD) and recurrent aphthous stomatitis (RAS) may result in increased oxidative stress. Uric acid can react rapidly with neutrophil-derived ROS to form allantoin. The purpose of the study was to evaluate the serum levels of allantoin as a new marker of oxidative stress in BD compared with malondialdehyde (MDA) levels as a well-known marker. Blood samples were obtained from 23 BD patients, 22 RAS patients as positive controls, and 21 healthy controls. When compared to the healthy controls, we found higher allantoin and MDA levels in the BD patients and higher MDA levels in the RAS patients. Serum ascorbic acid levels in the BD patients were significantly lower than in the controls. Increased allantoin and MDA levels suggest the possible involvement of free radicals in BD. As allantoin is only a product of uric acid oxidation by reactive oxygen and nitrogen species, it may also be used as a marker of oxidative stress in BD.

Inflammation is one of the pathophysiological pathways suggested for the development of cardiovascular disease in obstructive sleep apnea (OSA). The recurrent nocturnal episodes of hypoxia/reoxygenation observed in patients with OSA appear to be partly responsible for the systemic inflammatory response. The aim of this study was to investigate the role of inflammation by measuring the C-reactive protein (CRP) and fibrinogen levels, and erythrocyte sedimentation rate (ESR) in the OSA according to gender. This study included 139 apparently healthy subjects with newly diagnosed OSA and 27 control subjects who underwent overnight polysomnography and routine blood tests. Levels of inflammatory markers (CRP, fibrinogen, and ESR) were determined from the blood samples taken in the morning. The levels of CRP and fibrinogen were significantly higher in patients than in controls (p<0.0001 and p=0.001, respectively). Fibrinogen and ESR were significantly higher in the female patients than in the male patients (p<0.0001). In female patients, CRP and ESR correlated with time spent at oxygen saturation (T%SaO₂)<90 (R=0.327, p=0.029 and R=0.301, p=0.05, respectively), T%SaO₂<85 (R=0.482, p=0.001 and R=0.409, p=0.006, respectively), oxygen desaturation index (ODI) (R=0.298, p=0.047 and R=0.340, p=0.026, respectively), lowest oxygen saturation (SaO₂) (R=-0.293, p=0.051 and R=-0.374, p=0.013, respectively), mean SaO₂ (R=-0.408, p=0.005 and R=-0.385, p=0.011, respectively). In male patients, CRP correlated with T%SaO₂<90 (R=0.267, p=0.009), T%SaO₂<85 (R=0.279, p=0.006), mean SaO₂ (R=-0.284, p=0.006) and fibrinogen correlated with T%SaO₂<90 (R=0.282, p=0.028), and mean SaO₂ (R=-0.252, p=0.05). In conclusion, increased values of systemic inflammatory markers and their correlations with sleep data observed in our study support other studies suggesting the possible involvement of inflammation in OSA. As this correlation is more apparent in female patients then the males, it suggests that there may be a stronger relation between OSA development and inflammation in females. Higher levels of CRP, fibrinogen, and ESR may result from the combined interactions of obesity, metabolic syndrome (MetS) and nocturnal hypoxia.

Reactive oxygen species produced either endogenously or exogenously can attack lipids, proteins and DNA in human cells and cause potentially deleterious consequences. In recent years, their role in the pathogenesis of lung cancer and the preventive effect of antioxidants have been studied extensively. In this study, our aim was to investigate the levels of 8-hydroxy-2'-deoxyguanosine (8OHdG) and malondialdehyde as a marker for the effects of reactive oxygen species on DNA and lipids, the levels of antioxidant vitamins and the correlations between these oxidative stress markers and antioxidants in lung cancer. Serum malondialdehyde, beta-carotene, retinol, and vitamins C and E were measured by high-performance liquid chromatography methods in fasting blood samples and 8OHdG was measured by gas chromatography-mass spectrometry in 24-h urine samples of patients with lung cancer (n=39) and healthy controls (n=31). The levels of 8OHdG and malondialdehyde were significantly higher (p<0.05 and p<0.005, respectively) and beta-carotene, retinol, and vitamins C and E (p<0.0001, p<0.0001, p<0.0001, and p<0.05, respectively) were significantly lower in patients than in controls. There was a significantly positive correlation between 8OHdG and malondialdehyde (r=0.463, p=0.01) and a negative correlation between the levels of 8OHdG and retinol (r=-0.419, p=0.021) in the patient group. Our results demonstrate that the oxidant/antioxidant balance was spoiled in favor of lipid peroxidation and DNA damage in lung cancer patients. Significant increases in the levels of malondialdehyde and 8OHdG and decreases in the levels of antioxidants suggest the possible involvement of oxidative stress in lung cancer.

Gamma-glutamyltransferase,glutathione,molecular subgroups of breast cancer