Reading the unique DNA methylation landscape of the brain: Non-CpG methylation,hydroxymethylation, and MeCP2

DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system.     

Dynamic LVOT Obstruction and Aortic Stenosis in the Same Patient: A Case of Challenging Doppler Hemodynamics

We present a patient with both dynamic left ventricular outflow tract obstruction and valvular aortic stenosis. The aortic valve was calcified, and velocities and gradients measured by continuous‐wave Doppler met standard criteria for severe aortic stenosis. The increased subvalvular velocities invalidated assumptions of the simplified Bernoulli equation; correction using the longer form of the Bernoulli equation suggested a lower but still significant gradient. The complex shape of the subvalvular spectral Doppler envelope indicated supranormal systolic function and dynamic left ventricular outflow obstruction. Left heart catheterization with an end‐hole catheter was required to determine the subvalvular and valvular components of the obstruction.     

试论异常毒性作为药品质量控制指标的合理性

异常毒性最初是一种确保复杂成分制剂生产工艺一致性及安全性的辅助检测手段，后来成为针对外源性毒性污染物的通用安全性检测项，曾在世界范围内被各国药典收载。由于该检测与药品质量、安全性之间的关联性受到质疑，各国药典逐渐在各论及通则中删除该检测项，目前仅《中国药典》保留异常毒性。由于该检测存在设定限值难以统一、给药体积及给药剂量不合理、结果易受干扰且缺乏明确的判定标准等试验原理及设计上的缺陷，导致其试验结果没有实际参考意义。基于对历史数据的回顾分析，国际监管机构及卫生组织对异常毒性有了更为科学的认知，并已逐渐形成统一的监管共识：严格的生产控制措施和有效的质量检测手段，比异常毒性检测更为重要；异常毒性检测结果或与产品质量及污染不具相关性；在异常毒性检查中使用大量动物不符合动物福利和“3R”原则。本文从科学角度试论异常毒性作为药品质量控制指标的合理性，并总结异常毒性修订的科学原则，希望能为我国监管机构、制药行业修订异常毒性相关内容提供思考角度。