白内障超声乳化囊膜破裂人工晶状体植入术后并发症

探讨了白内障超声乳化囊膜破裂行后房型人工晶状体植入术后并发症及视力结果．病例为解放军总医院眼科1999年1月至2002年12月因老年性白内障实施超声乳化及后房型人工晶状体植入术的患者．其中囊膜破裂64眼；囊膜完整164眼．结果表明视力在0．8或以上病例囊膜完整组明显多于囊膜破裂组．视网膜脱离、黄斑囊样水肿、眼压升高、人工晶状体偏位等并发症囊膜破裂组明显高于囊膜完整组．囊膜完整组视力明显好于囊膜破裂组．囊膜破裂组视网膜脱离、黄斑囊样水肿、眼压升高及人工晶状体脱位等并发症比较常见．因此，这些病例应该给予较长时间观察．     

改进法制备枯草杆菌膜囊及其电镜观察

使用改进膜囊制备法得到枯草杆菌膜囊.电镜观察表明,该膜囊是中空的,仅由质膜组成的囊状封闭结构,其中存在较大比例的内部膜囊,同时观察到多种膜囊形成的中间过程,据此提出了膜囊形成的两种机制.     

庆大霉素损伤条件下大肠杆菌内源过氧化氢对间体膜囊的作用

为了探讨细菌受到抗生素损伤后,内源过氧化氢(H_2O_2)对间体膜囊的影响,通过庆大霉素损伤大肠杆菌。以电导率和丙二醛(MDA)为损伤指标,采用组织化学染色法,通过透射电子显微镜,观察经庆大霉素损伤后大肠杆菌内源H_2O_2和间体膜囊的变化。研究结果表明:庆大霉素损伤可提高大肠杆菌的内源H_2O_2浓度、间体膜囊数量以及间体膜囊周围的H_2O_2浓度。在间体膜囊外排的过程中,使用Tris-HCl蔗糖高渗溶液进行处理之后,H_2O_2浓度显著提升,电导率大幅度降低。庆大霉素和过氧化氢酶处理后,间体膜囊中的MDA浓度升高,损伤加重。庆大霉素损伤导致大肠杆菌的间体膜囊外周聚集大量的H_2O_2,且这些H_2O_2对间体膜囊具有保护作用。     

人老化红细胞囊泡的分离及其特性研究

本文报道了人红细胞在体外老化(37℃。48h)过程中会自然形成并释放的囊泡为不均一的群体,经 Dextran-T70不连续密度梯度离心后可明显分成三种组分。囊泡主要集中在组分Ⅱ和Ⅲ中,而组分Ⅰ除了囊泡外还含有膜和膜碎片。这三种囊泡组分在流动性、封闭度等性质上有明显差异。值得引起注意的是,囊泡的荧光光谱与正常红细胞膜相比变化较大,红移22nm 左右,这提示了囊泡膜脂的结构和组分与红细胞有较大差异。     

氧化甾醇-磷脂脂质囊泡的制备及特性研究

 氧化甾醇3,19–二羟基-胆甾烷-24-酮（DHCO）和3β,5α,6β-胆甾烷三醇（Triol）替代胆甾醇与大豆磷脂形成脂质囊泡的性质研究。采用乙醇注入法制备脂质囊泡,通过测定脂溶性及水溶性荧光探针在脂质囊泡中的荧光强度变化,考察囊泡膜流动性及通透性;通过测定脂质囊泡中游离DHCO及结合DHCO的浓度考察DHCO与磷脂的结合率;考察DHCO/磷脂比例、超声条件对脂质囊泡粒径大小和分布的影响。结果表明,DHCO、Triol与磷脂形成的脂质囊泡与胆甾烷（CHOL）-磷脂脂质囊泡的膜流动性无明显差异,但膜通透性稍有增大。DHCO与磷脂的结合率为8258%。DHCO、Triol与大豆磷脂经简单工艺即可形成脂质囊泡。可通过调节DHCO/磷脂比例、超声条件获得具理想粒径和外观的脂质囊泡。氧化甾醇数量庞大,其作为脂质囊泡的新型“流动性缓冲剂”有巨大的发展潜力。     

菱异形叶光合特性的比较

比较分析了处于营养生长时期的水生植物－－菱（Trapa bispinosa R.）的异形叶在光合特性方面的差异。结果表明：沉水叶叶片的叶绿素含量、光合速率、呼吸速率及光呼吸速率明显低于浮水叶，其类囊体膜PSⅠ、PSⅡ电子传递活性相对较弱，分别为浮水叶的69．40％和72．51％；而二者的类囊体膜室温吸收光谱形状相似，但沉水叶类囊体膜在400－500nm的光吸收值要强于浮水叶；沉水叶类囊体膜680nm处有较强的荧光发射峰。浮水叶和沉水叶类囊体膜多肽组分也存在比较显著的差别。     

人老化红细胞囊泡的分离及其特性研究

本文报道了人红细胞在体外老化(37℃.48h)过程中会自然形成并释放的囊泡为不均一的群体,经Dextran-T70不连续密度梯度离心后可明显分成三种组分.囊泡主要集中在组分Ⅱ和Ⅲ中,而组分Ⅰ除了囊泡外还含有膜和膜碎片.这三种囊泡组分在流动性、封闭度等性质上有明显差异.值得引起注意的是,囊泡的荧光光谱与正常红细胞膜相比变化较大,红移22nm左右,这提示了囊泡膜脂的结构和组分与红细胞有较大差异.     

玉米根细胞正面向外和内翻外质膜囊泡的分离

利用水双相分配分离法从玉米根细胞提取原生质膜囊泡。其质膜成分特异的K~+,Mg~(2+)—ATP酶活性比膜粗提液高1.67倍。其他细胞器标记酶活性在质膜组分中很低或没有。特异染色电镜形态学定量统计表明质膜组分中90％以上是质膜囊泡。去污剂刺激ATP酶活性实验证明,约92％囊泡是正面向外的。应用此法也证明NAD(P)H—氧化酶可能是跨膜存在的,其催化Fe~(3+)还原的位点可能在膜的内侧。应用高盐冻—融法并结合水双相分配分离法处理正面向外囊泡,可获得内翻外质膜囊泡,实验证明它不仅纯度高而且封闭。     

Na:YAG激光晶体前囊膜切开在现代白内障手术中的应用

应用Na:YAG激光在现代白内障手术前做晶体前囊膜切开术394例417眼,其中老年性白内障365眼,外伤性白内障26眼,并发性白内障19眼,先天性白内障7眼。术中玻璃体脱出18眼占4.3％,前房出血12眼又占2.9％,瞳孔移位79眼占18.9％,全部病例术中瞳孔区透明无残余皮质,而且术后角膜内皮水肿轻、恢复快、矫正视力理想。与传统截囊方式比较:裁囊充分,简化手术程序,并发症少,并就激光晶体前囊膜切开术后眼压升高的机制进行探讨,提示在白内障术前1～2小时内做激光晶体前囊膜切开术较为适宜。     

华蟾素对晶状体上皮细胞超微结构的影响

目的:探讨华蟾素对兔晶状体上皮细胞超微结构的影响。方法:40只新西兰白兔随机分为4组,每组10只,均施行小切口晶状体摘除术,N组施行正常手术,a组、b组、c组分别在中央前囊膜截除后在周边前囊膜和皮质之间注入含0.1 mg·L-1、0.2 mg·L-1、0.3 mg·L-1华蟾素的平衡液0.2mL,5分钟后用不含药液的平衡液水分离。术后第90天,4组实验兔处死后周边前囊膜行透射电镜观察。结果:周边前囊膜电镜检查示N组表现出明显的细胞功能活跃状态;a、b、c组晶状体上皮细胞呈现凋亡改变。结论:通过囊袋内单剂量给药的方式,0.1 mg·L-1、0.2 mg·L-1、0.3 mg·L-1的华蟾素诱导兔晶状体上皮细胞凋亡,从而预防后发性白内障的发生。     

Human nectin-like 1, a novel membrane protein interacting with protein 4.1 R

Human nectin-like 1 (NECL1) full-length cDNA was cloned by bioinformatics method when searching for candidate membrane proteins interacting with members of protein 4.1 family. The cytoplasmic and extracellular regions of NECL1 were expressed in and purified from E. coli, and the polyclonal antibody was produced. Interaction between the cytoplasmic region of NECL1 and the 30 kD membrane binding domain of protein 4.1 on red blood cell (4. 1R) was demonstrated by IAsys-biosensor system and GST pull-down experiment. Results of biotin-labeled peptide ELISA further demonstrated the key amino acids for the binding. The interaction research of NECL1's cytoplasmic domain provides basis for further study of the functions of NECL1 in nervous system.     

Three-dimensional structure of the bacterial protein-translocation complex SecYEG

Transport and membrane integration of polypeptides is carried out by specific protein complexes in the membranes of all living cells. The Sec transport path provides an essential and ubiquitous route for protein translocation. In the bacterial cytoplasmic membrane, the channel is formed by oligomers of a heterotrimeric membrane protein complex consisting of subunits SecY, SecE and SecG. In the endoplasmic reticulum membrane, the channel is formed from the related Sec61 complex. Here we report the structure of the Escherichia coli SecYEG assembly at an in-plane resolution of 8 A. The three-dimensional map, calculated from two-dimensional SecYEG crystals, reveals a sandwich of two membranes interacting through the extensive cytoplasmic domains. Each membrane is composed of dimers of SecYEG. The monomeric complex contains 15 transmembrane helices. In the centre of the dimer we observe a 16 x 25 A cavity closed on the periplasmic side by two highly tilted transmembrane helices. This may represent the closed state of the protein-conducting channel.     

A signal sequence is not sufficient to lead beta-galactosidase out of the cytoplasm

Escherichia coli strains have been constructed in which lacZ, the gene for the cytoplasmic enzyme beta-galactosidase, is fused to lamB, the gene for an outer membrane protein. One such strain produces a beta-galactosidase which remains cytoplasmic even though it possesses the complete signal sequence of the lamB protein precursor at the amino-terminal end.     

Immunoreactive forms of human erythrocyte ankyrin are present in diverse cells and tissues.

Ankyrin is a polypeptide of molecular weight (MW) 200,000 which is tightly bound to the cytoplasmic surface of the human erythrocyte membrane and has been identified as the high-affinity membrane attachment protein for spectrin. This protein has also been shown to be associated with band 3 (ref. 4), the major transmembrane protein which links a cytoplasmic structural protein to an integral membrane protein. A water-soluble, 72,000-MW, proteolytic fragment of ankyrin has been purified which retains the ability to bind to spectrin, and competitively inhibits reassociation of spectrin with membranes. Monospecific antibodies directed against this fragment have been prepared and demonstrated to cross-react only with ankyrin among the erythrocyte membrane proteins. The present study reports the use of these antibodies to develop a radioimmunoassay capable of detecting femtomolar quantities of ankyrin, and demonstrates the presence of small but significant amounts of immunoreactivity in a variety of types of cells and tissues.     

Ankyrin binding to (Na+ + K+)ATPase and implications for the organization of membrane domains in polarized cells

The interaction between membrane proteins and cytoplasmic structural proteins is thought to be one mechanism for maintaining the spatial order of proteins within functional domains on the plasma membrane. Such interactions have been characterized extensively in the human erythrocyte, where a dense, cytoplasmic matrix of proteins comprised mainly of spectrin and actin, is attached through a linker protein, ankyrin, to the anion transporter (Band 3). In several nonerythroid cell types, including neurons, exocrine cells and polarized epithelial cells homologues of ankyrin and spectrin (fodrin) are localized in specific membrane domains. Although these results suggest a functional linkage between ankyrin and fodrin and integral membrane proteins in the maintenance of membrane domains in nonerythroid cells, there has been little direct evidence of specific molecular interactions. Using a direct biological and chemical approach, we show here that ankyrin binds to the ubiquitous (Na+ + K+)ATPase, which has an asymmetrical distribution in polarized cells.     

Investigation of structural change of purple membrane in storage by transmission electron microscope and atomic force microscope

The structural change of purple membrane during storage has been investigated by means of transmis sion electron microscope and atomic force microscope. It is found that many liposomes have spontaneously evolved from the purple membrane sheets isolated three years ago. The membrane proteins on the liposomes, bacteriorhodopsin, are still presented as trimers in 2-D hexagonal structure, which is the same as that in natural cell membrane. However, the cytoplasmic surface of purple membrane faced outside on the liposomes.     

抗菌肽作用机制的研究进展

综述近年来有关抗菌肽抗细菌、肿瘤、病毒作用机制的研究进展。抗菌肽是广泛存在于多种生物中的一类带正电荷的小分子多肽，具有广谱抗菌活性，也具有抗真菌、肿瘤、病毒的活性。已有的研究普遍认为抗菌肽的杀菌机理涉及抗菌肽与细胞膜的相互作用，迄今大部分相关研究都集中在抗菌肽与细胞膜之间的相互作用上，抗菌肽还可以通过抑制细胞内生物大分子的合成来抑制细菌生长。     

Control of Ca2+ in rod outer segment disks by light and cyclic GMP

Photons absorbed in vertebrate rods and cones probably cause electrochemical changes at the photoreceptor plasma membrane by changing the cytoplasmic concentration of a diffusible transmitter substance, reducing the Na+ current flowing into the outer segment of the cell in the dark, to produce the observed membrane hyperpolarization that is the initial excitatory response. Cyclic GMP has been proposed as the transmitter because a light-activated cyclic GMP phosphodiesterase (PDE) has been found in rod disk membranes and because intracellularly injected cyclic GMP reduces rod membrane potentials. Free Ca2+ has also been proposed because increasing external [Ca2+] quickly and reversibly reduces the dark current and divalent cationophores increase the Ca2+ sensitivity. Ca2+ efflux from rod outer segments (ROS) of intact retinas occurs simultaneously with light responses. Vesicles prepared from ROS disk membranes become more permeable on illumination, releasing trapped ions or molecules, but intact outer segment disks have not previously been found to store sufficient Ca2+ in darkness and to release enough in light to meet the theoretical requirements for control of the dark current by varying cytoplasmic Ca2+ (refs 14-18). We now report experiments that show the required Ca2+ storage and release from rod disk membranes suspended in media containing high-energy phosphate esters and electrolytes approximating the cytoplasmic composition of live rod cells. Cyclic GMP stimulates Ca2+ uptake by ROS disks in such media.     

Topology of signal recognition particle receptor in endoplasmic reticulum membrane

The signal recognition particle (SRP) receptor is an integral membrane protein of the endoplasmic reticulum which, in conjunction with SRP, ensures the correct targeting of nascent secretory proteins to this membrane system. From the complementary DNA sequence we have deduced the complete primary structure of the SRP receptor and established that its amino-terminal region is anchored in the membrane. The anchor fragment and the cytoplasmic fragment contribute jointly to a functionally important region which is highly charged and may function in nucleic acid binding.     

Translocation of lipid-linked oligosaccharides across the ER membrane requires Rft1 protein.

N-linked glycosylation of proteins in eukaryotic cells follows a highly conserved pathway. The tetradecasaccharide substrate (Glc3Man9GlcNAc2) is first assembled at the membrane of the endoplasmic reticulum (ER) as a dolichylpyrophosphate (Dol-PP)-linked intermediate, and then transferred to nascent polypeptide chains in the lumen of the ER. The assembly of the oligosaccharide starts on the cytoplasmic side of the ER membrane with the synthesis of a Man5GlcNAc2-PP-Dol intermediate. This lipid-linked intermediate is then translocated across the membrane so that the oligosaccharides face the lumen of the ER, where the biosynthesis of Glc3Man9GlcNAc2-PP-Dol continues to completion. The fully assembled oligosaccharide is transferred to selected asparagine residues of target proteins. The transmembrane movement of lipid-linked Man5GlcNAc2 oligosaccharide is of fundamental importance in this biosynthetic pathway, and similar processes involving phospholipids and glycolipids are essential in all types of cells. The process is predicted to be catalysed by proteins, termed flippases, which to date have remained elusive. Here we provide evidence that yeast RFT1 encodes an evolutionarily conserved protein required for the translocation of Man5GlcNAc2-PP-Dol from the cytoplasmic to the lumenal leaflet of the ER membrane.