BAI1 is an engulfment receptor for apoptotic cells upstream of the ELMO/Dock180/Rac module

Engulfment and subsequent degradation of apoptotic cells is an essential step that occurs throughout life in all multicellular organisms. ELMO/Dock180/Rac proteins are a conserved signalling module for promoting the internalization of apoptotic cell corpses; ELMO and Dock180 function together as a guanine nucleotide exchange factor (GEF) for the small GTPase Rac, and thereby regulate the phagocyte actin cytoskeleton during engulfment. However, the receptor(s) upstream of the ELMO/Dock180/Rac module are still unknown. Here we identify brain-specific angiogenesis inhibitor 1 (BAI1) as a receptor upstream of ELMO and as a receptor that can bind phosphatidylserine on apoptotic cells. BAI1 is a seven-transmembrane protein belonging to the adhesion-type G-protein-coupled receptor family, with an extended extracellular region and no known ligands. We show that BAI1 functions as an engulfment receptor in both the recognition and subsequent internalization of apoptotic cells. Through multiple lines of investigation, we identify phosphatidylserine, a key 'eat-me' signal exposed on apoptotic cells, as a ligand for BAI1. The thrombospondin type 1 repeats within the extracellular region of BAI1 mediate direct binding to phosphatidylserine. As with intracellular signalling, BAI1 forms a trimeric complex with ELMO and Dock180, and functional studies suggest that BAI1 cooperates with ELMO/Dock180/Rac to promote maximal engulfment of apoptotic cells. Last, decreased BAI1 expression or interference with BAI1 function inhibits the engulfment of apoptotic targets ex vivo and in vivo. Thus, BAI1 is a phosphatidylserine recognition receptor that can directly recruit a Rac-GEF complex to mediate the uptake of apoptotic cells.     

Improving enzymes by using them in organic solvents

The technological utility of enzymes can be enhanced greatly by using them in organic solvents rather than their natural aqueous reaction media. Studies over the past 15 years have revealed not only that this change in solvent is feasible, but also that in such seemingly hostile environments enzymes can catalyse reactions impossible in water, become more stable, and exhibit new behaviour such as 'molecular memory'. Of particular importance has been the discovery that enzymatic selectivity, including substrate, stereo-, regio- and chemoselectivity, can be markedly affected, and sometimes even inverted, by the solvent. Enzyme-catalysed reactions in organic solvents, and even in supercritical fluids and the gas phase, have found numerous potential applications, some of which are already commercialized.     

上海市百岁老人的谱系及其分析

本文调查了上海市百岁老人的性别、职业和谱系,并绘制了57个完整的寿命谱系图,其中男性10名(占总数的17.5%),女性47名(占82.5%).男性中脑力劳动者4名(占男性总数的40%),体力劳动者6名(占60%);女性中脑力劳动者1人(占女性总数的2.1%),体力劳动者3人(占6.4%),操持家务者43人(占91.5%).有长寿家族史者40人(占寿命家族史清楚者的70.2%),无长寿家族史者17人(占29.8%).百岁老人配偶寿长≥70岁者,其已故子女的平均寿命高于配偶<70岁的.作者认为长寿是遗传的,并着重从遗传和环境两方面分析了女寿星数明显多于男寿星数的原因.     

协方差矩阵的MINQUE和简单估计的比较

在二次损失函数下,作者研究了多元线性模型协方差矩阵的MINQUE估计和简单估计的比较问题,其中多元线性模型的设计矩阵和离散矩阵可以不满秩,得到了一个充分和必要条件。     

心肌宁冲剂对抗垂体后叶素所致大鼠急性心肌缺血实验研究

心肌宁冲剂按1.75g/kg,0.875g/kg剂量,每天早晚分两次灌胃给药,连续7天,均能明显对抗垂体后叶素所诱发的大鼠急性心肌缺血的心电图改变。     

宇航员头部冲击的模拟创伤实验研究

该文通过３４只罗猴头颈实验研究，从中决定罗猴的颅脑损伤容限．当颅脑受到冲击时，颅壳发生局部变形瞬间，大脑亦发生变形，致使颅内压升高．利用这些结果来确定它的损伤机制，以模拟宇航员在冲击载荷下的创伤分析模型，将有助于进行临床创伤治疗和宇航弹射时的防护．