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71.
Abstract: 5-Hydroxytryptamine3 (5-HT3 ) receptors are the only known monoamine receptors mediating fast excitatory responses in mammalian neurons. Their primary structure as well as their electrophysiological and pharmacological properties show a phylogenetic relation to nicotinic acetylcholine, GABAA , and glycine receptors. As a prototypical member of this gene superfamily, we investigated the membrane topology of functional homomeric 5-HT3 receptors by using epitope tagging of the channel subunits expressed in heterologous systems. Visualization of 5-HT3 receptors in transfected COS-7 cells, either in western blot (molecular mass 61.2 ± 0.8 kDa) or in situ, was performed with previously characterized antibodies recognizing artificial epitopes as well as with anti-fusion protein antibodies directed against a wild-type receptor intracellular domain. The extracellular location of the distal C-terminal tagged domain demonstrates the presence of a fourth transmembrane domain in 5-HT3 serotonin-gated channels. In this region, the significant homology between members of this class of neurotransmitter-gated channels suggests strongly that they have a common transmembrane organization basically different from glutamate-gated and ATP-gated channels. 相似文献
72.
†Daniel Guillaume Philippe Bertrand Doris Dea ‡Jean Davignon †§ Judes Poirier 《Journal of neurochemistry》1996,66(6):2410-2418
Abstract: Apolipoprotein (apo) E is likely involved in redistributing cholesterol and phospholipids during compensatory synaptogenesis in the injured CNS. Three common isoforms of apoE exist in human (E2, E3, and E4). The apoE4 allele frequency is markedly increased in both late-onset sporadic and familial Alzheimer's disease (AD). ApoE concentration in the brain of AD subjects follows a gradient: ApoE levels decrease as a function of E2 > E3 ? E4. It has been proposed that the poor reinnervation capacity reported in AD may be caused by impairment of the apoE/low-density lipoprotein (LDL) receptor activity. To understand further the role of this particular axis in lipid homeostasis in the CNS, we have characterized binding, internalization, and degradation of human 125I-LDL to primary cultures of rat astrocytes. Specific binding was saturable, with a KD of 1.8 nM and a Bmax of 0.14 pmol/mg of proteins. Excess unlabeled human LDL or very LDL (VLDL) displaced 70% of total binding. Studies at 37°C confirmed that astrocytes bind, internalize, and degrade 125I-LDL by a specific, saturable mechanism. Reconstituted apoE (E2, E3, and E4)-liposomes were labeled with 125I and incubated with primary cultures of rat astrocytes and hippocampal neurons to examine specific binding. Human LDL and VLDL displaced binding and internalization of all apoE isoforms similarly in both astrocytes and neurons. 125I-ApoE2 binding was significantly lower than that of the other 125I-apoE isoforms in both cell types. 125I-ApoE4 binding was similar to that of 125I-apoE3 in both astrocytes and neurons. On the other hand, 125I-apoE3 binding was significantly higher in neurons than in astrocytes. These isoform-specific alterations in apoE-lipoprotein pathway could explain some of the differences reported in the pathophysiology of AD subjects carrying different apoE alleles. 相似文献
73.
Caterina Crescimanno Jean-Michel Foidart Agns Noël Myriam Polette Erik Maquoi Philippe Birembaut Eugenia Baramova Peter Kaufmann Mario Castellucci 《Experimental cell research》1996,227(2):240
Implantation and placental development are dependent upon trophoblast invasion of the endometrium. While the villous trophoblast does not display invasive behavior, the extravillous cytotrophoblast is highly invasive. By cloning BeWo choriocarcinoma cells, we have isolated two distinct clones that share similarities with villous and extravillous cytotrophoblasts. When cultured at the surface of a type I collagen gel, BeWo MC-1 cells were not invasive, whereas BeWo MC-2 cells rapidly invaded this matrix. When injected subcutaneously in nude mice, BeWo MC-1 cells developed a localized tumor and BeWo MC-2 cells developed larger tumors with micrometastases. Gelatinase A expression and minute amounts of gelatinase B were detected in the parental cell line and in both clones. However, the parental and the BeWo MC-2 cells secreted 5- to 10-fold more gelatinase A than the BeWo MC-1 cells. Laminin and matrigel stimulated the production of gelatinase A in BeWo MC-2 cells. Type I collagen promoted the conversion of the 72-kDa progelatinase A in an active enzyme only in parental BeWo and in BeWo MC-2 cells. These clones provide an interesting model for studying the complex mechanisms regulating implantation as well as the controlled invasiveness during implantation compared to tumor invasion. 相似文献
74.
Harry Adams Neil A. Bailey Philippe Bertrand Simon R. Collinson David E. Fenton Simon J. Kitchen 《Inorganica chimica acta》1996,250(1-2):139-148
The cyclocondensation of 2,5-diformylthiophene and the amines N,N-bis-(2-aminoethyl)-2-phenylethylamine, N,N-bis-(2aminoethyl)-t-butyl-amine and N,N-bis-(2-aminoethyl)-t-butyl-amine in the presence of silver(I) salts yields homodinuclear bibracchial tetraimine Schiff base macrocyclic complexes. The structures of two such complexes are also reported. The complex Ag2L4(NO3)(PF6) (2) crystallises in the triclinic space group
, No. 2) and has unit-cell dimensions a = 12.834(6), B = 13.183(6), C = 14.588(7) Å, = 64.86(4), β = 79.77(4), γ = 69.44(3)° with Z = 2; there is a monodentate and singly bridging nitrate anion present and the Ag---Ag separation is 4.161 Å. The complex Ag2L4(CH3CN)2(BF4)2·CH3CN (9) crystallises in the triclinic space group
, No. 2) and has unit-cell dimensions a = 9.297(4), B = 12.985(3), C = 21.770(5) Å, = 91.570(10), β = 92.33(3), γ = 97.92(3) ° with Z = 2; there is a strongly bonded acetonitrile molecule coordinated to each silver atom and the Ag---Ag separation is 4.920 Å. 相似文献
75.
Regeneration of fertile transgenic indica (group 1) rice plants following microprojectile transformation of embryogenic suspension culture cells 总被引:8,自引:0,他引:8
Shiping Zhang Lili Chen Rongda Qu Philippe Marmey Roger Beachy Claude Fauquet 《Plant cell reports》1996,15(7):465-469
Regenerable embryogenic suspensions of elite Indica (group 1) rice varieties IR24, IR64, IR72 and an advanced Indica rice breeding line IR57311-95-2-3 were established within 6–8 weeks from 3–4 week old calli derived from mature seeds. Transgenic rice plants were obtained by introducing a plasmid carrying genes encoding hygromycin phosphotransferase (hph, conferring resistance to hygromycin B) and ß-glucuronidase (uidA), both driven by the CaMV 35S promoter, via particle bombardment of embryogenic suspensions. The effect of osmotic conditioning on transformation was evaluated. Regenerated plants were resistant to hygromycin B and expressed the uidA (GUS) gene. The growth of mother plants (R0) was normal and seeds were produced. Southern blot analysis of R0 and R1 plants showed that hygromycin resistant plants contained intact hph genes that were inherited in a Mendelian fashion. A protocol for a simple, efficient, repeatable, genotype- and environment-independent Indica rice transformation system is described.Abbreviations 2,4-D
2,4-dichlorophenoxy acetic acid
- NAA
-naphthalene acetic acid
- kb
kilobase
- GUS
ß-glucuronidase
- hph
hygromycin B phosphotransferase 相似文献
76.
The presence of galanin was examined in the cat gut and related autonomic nervous structures using radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). In the gut wall, the concentration of galanin-like immunoreactivity (GAL-LI) was assayed separately in the muscular layers with the nervous plexuses and in the mucosa and ranged from 0.35 to 0.55 pmol/g wet tissue. In the autonomic nervous structures, GAL-LI concentrations ranged from 0.22 (thoracic spinal ganglia) to 0.81 (inferior mesenteric ganglion) pmol/g wet tissue. The presence of galanin was checked by HPLC in the antrum, intestine, and colon. HPLC of extractable material revealed a major peak coeluting with the synthetic porcine peptide and minor earlier peaks representing likely different molecular forms of galanin. Our study strengthens the notion that galanin acts in nervous control of the cat gut functions. 相似文献
77.
78.
79.
80.
We demonstrate that complete sea urchin male pronuclear development in vitro is a two-step process involving membrane-independent chromatin decondensation and nuclear envelope-dependent pronuclear swelling. In the absence of cytoplasmic membrane vesicles (MVs), permeabilized sperm chromatin decondenses into a spherical nucleus of ≈4 μm in diameter. Pronuclear swelling to ≈7 μm requires an intact nuclear envelope, and the degree of swelling is limited by the amount of MVs assembled on the chromatin. Furthermore, after a nuclear envelope is formed, swelling can occur in the absence of additional cytoplasmic MVs. Nuclear swelling also requires ATP hydrolysis, Ca2+ and cytosolic factors, some of which are sensitive to heat and to the sulfhy-dryl alkylating agent, N-ethylmaleimide. The requirement for a nuclear envelope and the rate of pronuclear swelling are consistent with previous in vivo observations. © 1995 wiley-Liss, Inc. 相似文献