Action of polyethylene glycol on the fusion of human erythrocyte membranes

Summary Factors affecting the polyethylene glycol (PEG)-induced membrane fusion were examined. Human erythrocyte membrane ghosts, cytoskeleton-free vesicles budded from erythrocytes, mechanically disrupted erythrocyte vesicles, and recombinant vesicles from glycophorin and egg phosphatidylcholine were used as models. Fusion was monitored by darkfield light microscopy and by freeze-fracture electron microscopy. Osmotic swelling was found necessary for fusion between membrane ghosts following PEG treatment. The sample with the highest fusion percentage was sealed ghosts incubated in hypotonic media after at least 5 min of treatment in <25% PEG. At similar osmolarity, glycerol, dextran and PEG produced progressively more pronounced intramembranous particle (IMP) patching, correlating with their increasing fusion percentages. The patching of IMP preceded cell-cell contact, and occurred without direct PEG-protein interaction. The presence of cytoskeletal elements in small vesicles had no significant effect on fusion, nor on the aggregation of intramembranous particle (IMP) upon PEG treatment. Disrupting the membrane by lysolecithin, dimethylsulfoxide, retinol or mild sonication resulted in the fragmentation of ghosts without an increase in fusion percentage. The purity of the commercial PEG used had no apparent effect on fusion. We concluded that the key steps in PEG-induced fusion of cell membrane are the creation of IMP-free zones, and the osmotic swelling of cells after the formation of bilayer contacts during the PEG treatment. Cell cytoskeleton affects PEG-induced fusion only to the extent of affecting IMP patching.     

The biological relevance of HPLC-purified vasoactive intestinal polypeptide monoiodinated at tyrosine 10 or tyrosine 22

Three major forms of monoiodinated VIP (M125I-VIP) were isolated after chloramine-T iodination and HPLC purification. The iodinated tyrosine residue was located in each form of M125I-VIP using arginase C and trypsin digestion for obtaining defined fragments containing only one tyrosine residue. The HPLC isolated iodinated fragments thus obtained were used for HPLC comigration studies with iodinated synthetic C and N terminal VIP fragments and for amino acid analysis. The first two eluting peaks 1 and 2 are (M125I-Tyr10-VIP); peak 1 has an oxidized methionine; peak 3 is a (M125I-Tyr22-VIP) which also has an oxidized methionine. A reduced counterpart of peak 3 named peak 4 was isolated by further HPLC analysis. The ability of the different species of M125I-VIP to stimulate adenosine cyclic 3',5'-phosphate (cAMP) production in transformed colonic cells in culture (HT-29) was compared to that of native VIP. The mean potencies of the M125I-VIP species expressed as a percentage relative to the potency of native VIP were, peak (1): 0.98; (2): 0.84; (3): 1.38; (4): 1.48, in the range of concentrations tested (2-60 pM). The M125I-Tyr22-VIP are significantly more active than native VIP (P less than 0.01). Oxidation of methionine or iodination of tyrosine 10 does not significantly modify the biological activity of VIP. We conclude that iodination of Tyr-22 located in the apolar helical COOH-terminal of VIP increases the effectiveness of VIP interaction with its receptors. Thus the tyrosyl residue and the localized hydrophobic features of VIP are critically involved in the function of this neurotransmitter.     

蛙卵黄粒晶形区向非晶区过渡的电镜观察及伪彩色图象处理

用水溶性氨基树脂作为电镜标本包埋介质包埋早期卵裂时的黑龙江林蛙卵;用透射电镜观察了卵黄粒晶形体向非晶区转变的过程;一部分电镜照片用伪彩色图象处理技术转换成彩色照片以提高其清晰度。晶形体向非晶结构转化主要有两种形式:1.沿晶形体表面成排地脱落晶分子并在晶形体表面形成台阶样结构;2.晶分子参差不齐地成群脱离晶形体并在晶形区与非晶区之间形成一个似晶非晶的过渡区。脱离晶形体后的晶分子参加到非晶区,使深色亚区扩大并在其中酝酿成“微滴”样结构。若干“微滴”汇合并转变成微泡。伪彩色图象处理能较清楚地显示出卵脂蛋白半分子(一个亚单位)独立脱离晶形体的现象。讨论了引起晶分子脱离晶形体的可能??原因。     

脐鳞属地衣一个新种(英文)

本文描述了脐鳞属地衣一个新种:褐脐鳞。这个新种类似红脐鳞,但地衣体上表面为灰褐色并且不合松萝酸。本种与泡状脐鳞的区别是不含富马原岛衣酸及地理分布的差异。     

水蒸汽蒸馏巴柑檬叶和果皮精油化学成分的研究

巴柑檬是我们第一次从国外引种成功的一种名贵香料植物。用色谱-质谱-计算机联用技术、毛细管气相色谱保留指数法和标准品叠加法分析了水蒸汽蒸馏巴柑檬叶和果皮精油的化学成分。从叶和果皮精油分离出来的220个和200个成分中,分别鉴定出48个和57个成分。鉴定组分的含量分别占叶和果皮精油的99.80％和98.54％。叶精油与果皮精油在化学成分方面的主要区别是叶油中萜烃化合物含量较低,而萜醇类化合物含量较高。     

云南叶螨属一新种(蜱螨目:叶螨科)

在鉴定云南叶螨标本时,发现叶螨属一新种,现记述如下。模式标本保存于上海农学院。本文量度单位均为微米。 食禾叶螨Tetranychus graminivorus新种(图1—14) 雌螨 体长(包括喙)454,宽298。椭圆形。浅黄绿色。须肢端感器圆柱形,长6.8,     

Proteases from human immunodeficiency virus and avian myeloblastosis virus show distinct specificities in hydrolysis of multidomain protein substrates.

The virally encoded proteases from human immunodeficiency virus (HIV) and avian myeloblastosis virus (AMV) have been compared relative to their ability to hydrolyze a variant of the three-domain Pseudomonas exotoxin, PE66. This exotoxin derivative, missing domain I and referred to as LysPE40, is made up of a 13-kilodalton NH2-terminal translocation domain II connected by a segment of 40 amino acids to enzyme domain III of the toxin, a 23-kilodalton ADP-ribosyltransferase. HIV protease hydrolyzes two peptide bonds in LysPE40, a Leu-Leu bond in the interdomain region and a Leu-Ala bond in a nonstructured region three residues in from the NH2-terminus. Neither of these sites is cleaved by the AMV enzyme; hydrolysis occurs, instead, at an Asp-Val bond in another part of the interdomain segment and at a Leu-Thr bond in the NH2-terminal region of domain II. Synthetic peptides corresponding to these cleavage sites are hydrolyzed by the individual proteases with the same specificity displayed toward the protein substrate. Peptide substrates for one protease are neither substrates nor competitive inhibitors for the other. A potent inhibitor of HIV type 1 protease was more than 3 orders of magnitude less active toward the AMV enzyme. These results suggest that although the crystallographic models of Rous sarcoma virus protease (an enzyme nearly identical to the AMV enzyme) and HIV type 1 protease show a high degree of similarity, there exist structural differences between these retroviral proteases that are clearly reflected by their kinetic properties.     

Concerted generation of Ig isotype diversity in human fetal bone marrow

The human fetal bone marrow B cell compartment of 14- to 21-wk gestational age was examined phenotypically and with respect to Ig H chain commitment and diversity. A dramatic expansion of fetal marrow B cell pools at 16- to 18-wk gestational age characterizes a rapid and concerted chain of differentiation events. Transiently up to 1/4 of nucleated marrow cells are CD20+/CD21+ cells which begin to express surface Ig other than IgM. Limiting dilution analysis of EBV-infected marrow cells delineated a virtually exclusive commitment to IgM production until 15 wk and the absolute and relative number of these cells were small (approximately 5% of comparable adult values). In parallel to the rapid increase in total B cell pools size, cells committed and able to secrete any of the five Ig isotypes are generated by 16-wk gestational age and by 18 wk the frequencies of these cells rapidly reach levels typical for adult peripheral tissue such as blood or lymph node. Fetal L chain diversity always anticipated that observed in adult serum. In addition to rising pool sizes and diverse IgH expression, EBV transformability is a major variable during this period of B cell development with up to 2/3 of B lineage cells transformable, about half of which are pre-B cells. By 21-wk gestational age transformable pre-B cells have disappeared and (as in adult tissue) approximately 10 to 20% of CD20+ cells are transformable. The rapid, concerted expression of full H chain diversity during a narrow period in fetal development is unique to marrow and implies a lymphopoietic process in a privileged site rather than an immunologic differentiation event. During this event, the relative proportions between the different IgH classes expressed, resembled that found in adult tissue, perhaps suggesting that B cell inherent programming rather than only antigenic forces determine heavy chain choice. The staggered expression, early in postnatal life, of IgH regions 3' of the C mu locus may reflect regulatory functions rather than inherent immaturity of the B lineage.     

夜蛾复眼转化速度与光暗适应的时间关系

夜行蛾类的复眼,随光、暗适应时间而逐步转化,这种转化是可逆的.以屏蔽色素分布范围的大小为指标来判断复眼的转化速度得以下结果:1.从亮眼到暗眼:亮眼进入暗适应后其屏蔽色素随暗适应时间的增加而逐步向远心端方向集中.屏蔽色素的移动是减速进行的.暗适应开始后的前3分钟,每分钟移动百分率为10.7,当暗到10—15分钟时每分钟移动百分率为4.6,再暗到60—150分钟时每分钟移动百分率为0.7.屏蔽色素移动的速度个体间差异较大,完成全过程大多数个体需150分钟,少数个体只需60分钟,另有个别个体经过270分钟暗适应仍尚未完成全过程.2.从暗眼到亮眼:暗眼受光后,其屏蔽色素随光适应时间的增加而向近心端方向扩散,色素移动速度随时间的增加而减缓.转化全过程约需60分钟.