Recent discovery of occult hepatitis C virus (HCV) infection persisting after spontaneous or antiviral therapy-induced resolution of hepatitis C was made possible by the introduction of nucleic acid amplification assa...Recent discovery of occult hepatitis C virus (HCV) infection persisting after spontaneous or antiviral therapy-induced resolution of hepatitis C was made possible by the introduction of nucleic acid amplification assays capable of detecting HCV RNA at sensitivities superseding those offered by clinical tests. Although individuals with this seemingly silent HCV infection are usually anti-HCV antibody reactive and have normal liver function tests, occult HCV infection has also been reported in anti-HCV-negative individuals with persistently elevated liver enzymes of unknown etiology. Studies have shown that HCV RNA can persist for years in serum, lymphomononuclear cells and liver in the absence of clinical symptoms, although histological evidence of a mild inflammatory liver injury can be occasionally encountered. Furthermore, while HCV RNA can be detected in circulating lymphoid cells in approximately 30% of cases, a short-term culture under stimulatory conditions augments HCV replication in these cells allowing detection of virus in otherwise HCV-negative cases. HCV infects different immune cell subsets, including CD4+ and CD8+ T lymphocytes, B cells and monocytes. Studies employing clonal sequencing and single-stranded conformational polymorphism analyses have revealed unique HCV variants residing in immune cells, further strengthening the notion of HCV lymphotropism. Overall, the data accumulated suggest that occult HCV infection is a common consequence of resolution of symptomatic hepatitis C and that examination of the cells of the immune system is an effective approach to diagnosis of HCV infection and its long-term persistence. Further work is required to fully realize pathogenic and epidemiological consequences of occult HCV persistence.展开更多
在福建省太姥山和浙江鹤顶山开展了GPS掩星观测实验并成功获取山基掩星观测数据,对掩星事件进行了分析和统计;阐述了利用山基掩星观测数据计算大气折射指数和电波弯曲角的原理和算法,基于山基反演数据与欧洲中期天气预报中心(European c...在福建省太姥山和浙江鹤顶山开展了GPS掩星观测实验并成功获取山基掩星观测数据,对掩星事件进行了分析和统计;阐述了利用山基掩星观测数据计算大气折射指数和电波弯曲角的原理和算法,基于山基反演数据与欧洲中期天气预报中心(European centre for medium-range weather forecasts,ECMWF)数据构建电波传播的直接折射模型和一次反射模型来计算任意两点之间的电波到达角.结果表明:山基反演数据计算的大气折射率剖面反演准确度在95%以上,在1km下的近距离计算中基于山基反演数据的直接折射模型优于一次反射模型,山基反演数据的电波到达角模型优于ECMWF数据模型,文中创建的两种电波到达角计算模型对模拟两点之间的电波传播路径和真实电波信号的调整接收具有重要指导意义.展开更多
文摘Recent discovery of occult hepatitis C virus (HCV) infection persisting after spontaneous or antiviral therapy-induced resolution of hepatitis C was made possible by the introduction of nucleic acid amplification assays capable of detecting HCV RNA at sensitivities superseding those offered by clinical tests. Although individuals with this seemingly silent HCV infection are usually anti-HCV antibody reactive and have normal liver function tests, occult HCV infection has also been reported in anti-HCV-negative individuals with persistently elevated liver enzymes of unknown etiology. Studies have shown that HCV RNA can persist for years in serum, lymphomononuclear cells and liver in the absence of clinical symptoms, although histological evidence of a mild inflammatory liver injury can be occasionally encountered. Furthermore, while HCV RNA can be detected in circulating lymphoid cells in approximately 30% of cases, a short-term culture under stimulatory conditions augments HCV replication in these cells allowing detection of virus in otherwise HCV-negative cases. HCV infects different immune cell subsets, including CD4+ and CD8+ T lymphocytes, B cells and monocytes. Studies employing clonal sequencing and single-stranded conformational polymorphism analyses have revealed unique HCV variants residing in immune cells, further strengthening the notion of HCV lymphotropism. Overall, the data accumulated suggest that occult HCV infection is a common consequence of resolution of symptomatic hepatitis C and that examination of the cells of the immune system is an effective approach to diagnosis of HCV infection and its long-term persistence. Further work is required to fully realize pathogenic and epidemiological consequences of occult HCV persistence.
文摘在福建省太姥山和浙江鹤顶山开展了GPS掩星观测实验并成功获取山基掩星观测数据,对掩星事件进行了分析和统计;阐述了利用山基掩星观测数据计算大气折射指数和电波弯曲角的原理和算法,基于山基反演数据与欧洲中期天气预报中心(European centre for medium-range weather forecasts,ECMWF)数据构建电波传播的直接折射模型和一次反射模型来计算任意两点之间的电波到达角.结果表明:山基反演数据计算的大气折射率剖面反演准确度在95%以上,在1km下的近距离计算中基于山基反演数据的直接折射模型优于一次反射模型,山基反演数据的电波到达角模型优于ECMWF数据模型,文中创建的两种电波到达角计算模型对模拟两点之间的电波传播路径和真实电波信号的调整接收具有重要指导意义.
