Environmental arsenic content is influenced by natural condition, microorganism and human activity.Certain natural conditions favor arsenic mobilization to the environment.Some microorganisms adapt in high arsenic environment, which is an important factor for arsenic biotransformation and mobilization in the environment.Moreover, human activities can intensify arsenic accumulation in the environment.The environmental arsenic accumulates rapidly through the food chain and enters human bodies to be detoxicated through methylation.Water arsenic pollution is one of very serious public health problems, which not only causes acute and chronic toxicosis, but also increases human susceptivity to many kinds of diseases.

Objective To understand the quality and test ability of syphilis serological tests among the laboratories of seconda-ry and higher medical institutions in Shaanxi province,in order to reinforce the quality control and the management of vene-real laboratory and improve the technical capability of them.Methods Five quality control samples,QC manual and reports were delivered,and detected for treponemal qualitative tests and non-treponemal qualitative and quantitative tests,respective-ly.Syphilis laboratories were requested to provide feedback on the test results and other information within the specified time for a final statistical analysis.Results 341 laboratories participated in this assessment,the total qualification rates was 70. 97%.The coincidence rate of non-treponemal qualitative and quantitative tests were 97.69% and 76.16%,respectively.The coincidence rate of treponemal qualitative test was 9 9.9 1%.Conclusion The syphilis serological testing capacity of laborato-ries in Shaanxi province should be improved,the coincidence rate of non-treponemal quantitative tests was low.A program of improving external quality assessment of syphilis serological testing among different laboratories should be established and the professional training and the management system should be strengthened.

Objective To investigate the characteristic MRI appearance of neuromyelitis optics (NMO) and muhip]e sclerosis (MS) in the spinal cord.Methods Twenty cases of MS and 23 cases of NMO were examined by MRL All image appearances were analyzed.Results The characteristic MRI appearance of NMO patients in the spinal cord was linear medullary lesion (LML), linear medullospinal lesion (LMSL), linear spinal lesion (LSL) and longitudinally extensive transverse myelitis (LETM), and spinal cord MRI with contiguous T2-weighted signal abnormality extending over 3 or more vertebral segments (23 cases), while in MS, spinal cord MRI with contiguous T2-weighted signal abnormality often extended less than 3 vertebral segments (only 12 cases, χ2 = 19.142, P < 0.01), and the distribution of spinal lesion usually was eccentric (17 cases, compared with NMO group, χ2 = 25.256, P < 0.01).Conclusions NMO is distinct from MS.In MRI, spinal lesion in NMO usually conforms to the distribution of aquaporin 4, while spinal lesion in MS always conforms to the demyelination.NMO has neuroimaging features that move it ever closer to distinct disease status.