Evaluation of kynurenine pathway metabolism in Toxoplasma gondii-infected mice: implications for schizophrenia.

Toxoplasma gondii, an intracellular protozoan parasite, is a major cause of opportunistic infectious disease affecting the brain and has been linked to an increased incidence of schizophrenia. In murine hosts, infection with T. gondii stimulates tryptophan degradation along the kynurenine pathway (KP), which contains several neuroactive metabolites, including 3-hydroxykynurenine (3-HK), quinolinic acid (QUIN) and kynurenic acid (KYNA). As these endogenous compounds may provide a mechanistic connection between T. gondii and the pathophysiology of schizophrenia, we measured KP metabolites in both the brain and periphery of T. gondii-treated C57BL/6 mice 8 and 28 days post-infection. Infected mice showed early decreases in the levels of tryptophan in the brain and serum, but not in the liver. These reductions were associated with elevated levels of kynurenine, KYNA, 3-HK and QUIN in the brain. In quantitative terms, the most significant increases in these KP metabolites were observed in the brain at 28 days post-infection. Notably, the anti-parasitic drugs pyrimethamine and sulfadiazine, a standard treatment of toxoplasmosis, significantly reduced 3-HK and KYNA levels in the brain of infected mice when applied between 28 and 56 days post-infection. In summary, T. gondii infection, probably by activating microglia and astrocytes, enhances the production of KP metabolites in the brain. However, during the first two months after infection, the KP changes in these mice do not reliably duplicate abnormalities seen in the brain of individuals with schizophrenia.

64-slice computed tomography coronary angiography: diagnostic accuracy in the real world.

PURPOSE: This study was done to evaluate the diagnostic accuracy of 64-slice computed tomography coronary angiography (CTCA) for the detection of significant coronary artery stenosis in the real clinical world. MATERIALS AND METHOD: From the CTCA database of our institution, we enrolled 145 patients (92 men, 52 women, mean age 63.4 +/- 10.2 years) with suspected coronary artery disease. All patients presented with atypical or typical chest pain and underwent CTCA and conventional coronary angiography (CA). For the CTCA scan (Sensation 64, Siemens, Germany), we administered an IV bolus of 100 ml of iodinated contrast material (Iomeprol 400 mgI/ml, Bracco, Italy). The CTCA and CA reports used to evaluate diagnostic accuracy adopted > or =50% and > or =70%, respectively, as thresholds for significant stenosis. RESULT: Eleven patients were excluded from the analysis because of the nondiagnostic quality of CTCA. The prevalence of disease demonstrated at CA was 63% (84/134). Sensitivity, specificity and positive and negative predictive values for CTCA on a per-segment, per-vessel, and per-patient basis were 75.6%, 85.1%, 97.6%; 86.9%, 81.8%, 58.0%; 48.2%, 68.1%, 79.6%; and 95.7%, 92.3%, 93.5%, respectively. Only two out of 134 eligible patients were false negative. Heart rate did not significantly influence diagnostic accuracy, whereas the absence or minimal presence of coronary calcification improved diagnostic accuracy. The positive and negative likelihood ratios at the per-patient level were 2.32 and 0.041, respectively. CONCLUSION: CTCA in the real clinical world shows a diagnostic performance lower than reported in previous validation studies. The excellent negative predictive value and negative likelihood ratio make CTCA a noninvasive gold standard for exclusion of significant coronary artery disease.