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.     

Uptake of free amino acids by the diatom,Melosira mediocris

Individual ¹⁴C-labelled amino acids are rapidly removed from dilute solution in artificial sea water (0.2 mol 1^–1) by suspensions of Meliosira medocris. The rate of disappearance of radioactivity corresponds closely to removal of primary amines as determined by measurement of the rate of decrease of fluorescamine-positive material. Net removal of naturally occurring free amino acids from the sea water habitat from which the alga was isolated is demonstrated using high performance liquid chromatography. Removal of amino acids from natural sources makes a significant contribution to the carbon requirements of the alga as well as supplying significant amounts of amino nitrogen.     

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.     

Isolation of complement-fragment-iC3b-binding proteins by affinity chromatography. The identification of p150,95 as an iC3b-binding protein.

The proteins from labelled human spleen membranes and polymorphonuclear leucocytes which bind to the iC3b fragment of complement component C3 were prepared by iC3b-Sepharose chromatography in the presence of bivalent cations. Complement receptor type 3(CR3) was eluted from iC3b-Sepharose by removal of bivalent cations. Complement receptors type 1 and 2 (present in spleen but not in polymorphonuclear leucocytes) were sequentially eluted by an NaCl gradient. An additional protein of Mr 135 000 was eluted from iC3b-Sepharose under the same conditions as those used to elute CR3. Preabsorption of the starting material on an anti-(CR3 beta-subunit) antibody column before iC3b-Sepharose chromatography removed the alpha- and beta-chains of CR3 and the 135 000-Mr protein. Preabsorption with iC3b-Sepharose before the anti-(CR3 beta-subunit) antibody column showed that iC3b binds CR3 and p150,95, the smallest member of the group of three homologous proteins that share the same beta-subunit.     

Population structure and dynamics of Pinus massoniana Lamb. on mount Jinyun,Sichuan, China

Masson Pine (Pinus massoniana Lamb.) is a pioneer in forest succession in the subtropics of East Asia. However, the species persits, though with decreasing abundance, throughout the various successional phases. Agestructure, spatial pattern, density, population biomass, and their dynamics are described for a population in Sichuan, China, on the basis of a census of all individuals in the population while substituting space with time. In the course of succession, the population density increases and its rate of growth decreases until self-thinning starts; during the phase of self-thinning density decrease and continues to decrease even afterwards, but the rate of growth increase markedly after self-thinning has stopped. The development of population biomass (Bp) during the early succession from shrub-grassland to the early stages of mixed pine and broad-leaved forest can be described by a logistic equation. Later, Bp decrease rapidly. These changes are governed partly by inherent biological features of P. massoniana and partly by the invasion, establishment and development of shade-tolerant evergreen broad-leaved trees. Both self- and alien-thinning occur. Soil conditions affect the rates of these processes.     

The groin flap in reparative surgery of the hand

The historical literature of the use of axial vascular pattern flaps from the hypogastric and iliofemoral regions in reparative surgery of the hand is concisely reviewed. Thirty-six iliofemoral (groin) flaps were utilized for delayed primary resurfacing and secondary reconstruction of defects of the hand and forearm. Two flaps (6 percent) were complicated by partial necrosis. We caution against the immediate resurfacing (within 24 hours of injury) of acute crushed hand wounds by distant flaps. The immediate application of a healthy flap on a soiled or crushed wound invites complications of local tissue necrosis, infection, and subsequent loss of the flap. When distant flaps are indicated for coverage of acute hand wounds, delayed primary coverage following complete removal of all nonviable tissue is a safe and reliable regimen. It is advantageous to design the serviceable portion of the flap on the distal area of the vascular territory of the groin flap. Thoughtful yet "radical" defatting can be performed on the lateral portion of the groin flap territory. Constructed in this way, the long medial base of the groin flap allows freedom for movement at the wrist and metacarpophalangeal and interphalangeal joints, thus decreasing edema and stiffness. In the management of soft-tissue defects in the hand requiring distant flap coverage, we choose to utilize the conventional groin flap in preference to the microvascular free flap when both techniques will deliver equal results.     

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。     

Interferon affects intracellular calmodulin levels

Interferon lowers calmodulin levels in two cell lines sensitive to its antiproliferative effect. Further, in synchronized cells, interferon strongly inhibits the increase in calmodulin observed when control cells enter the S phase, and concomitantly inhibits DNA synthesis. Calmodulin has been implicated in the control of cell proliferation and an increase in this protein seems to be necessary for the progression of cells into the S phase of the cell cycle. Therefore, the effect of interferon on calmodulin content might constitute part of the molecular mechanism by which interferon inhibits DNA synthesis.     

Gastrointestinal absorption of estrone sulfate in germfree and conventional rats

Steroids are extensively excreted in the bile of rats. There was no significant difference in biliary excretion of steroid following administration of [3H]-estrone sulfate into the proximal small intestine (PSI) of conventional (CVL; 17.8 +/- 62%; mean +/- SD) or germfree (GF; 28.2 +/- 5.3) rats. A similar finding resulted from administration into the distal small intestine (DSI)-CVL, 22.3 +/- 11.8%; GF, 11.4 +/- 3.7%. However, when the drug was given into the caecum, excretion in the bile of CVL rats after 5 h was 59.1% whereas in GF rats it was only 1.7%. When estrone was injected into the PSI and DSI of CVL and GF rats, absorption (as judged by excretion in bile) was more rapid than that seen with estrone sulfate. Five hours after injection into the PSI, biliary excretion was, in CVL 88.2% and in GF 81.7% and after injection into the DSI excretion was, in CVL 84.7% and in GF 83.6%. Absorption of estrone from the caeca of GF rats was apparently reduced (49.0% and 25.3% excreted in the bile of CVL and GF rats respectively). There was no significant difference in bile flow rate between CVL and GF rats. These results give unequivocal evidence of intact absorption of estrone sulfate from the small intestine of the rat. The rate of absorption is however very much reduced compared to the non-sulphated steroid. Estrone sulfate is not absorbed intact in the caecum but is hydrolysed by the gut microflora prior to absorption.