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1.
The effects of laboratory synthesized octylguanidine are described. There is an early decease of the maximum rate of rise of the action potential with negligible reduction of the overshoot although the membrane resting potential is unchanged. Subsequently, there is a remarkable reduction of both membrane potential and overshoot, while the plateau is shortened. The former effects resemble those seen with tetrodotoxin, the latter ones, with metabolic poisons. 相似文献
2.
G Tonietti G Pecci G d'Acunto E Lioy M E Mercalli R Perricone L Fontana 《Experientia》1975,31(12):1464-1465
The ultrastructural comparison between E and EA rosettes showed that, in the former, the rosetting lymphocytes are mostly round in shape and their interaction with sheep erythrocytes only consists of limited areas of membrane contact, in the latter, rosetting lymphocytes are mostly in the shape of uropods and surrounding ox red cells show pseudopods protruding towards the lymphocyte and coming into contact with it. 相似文献
3.
Karina Weinhold Udo Krause-Buchholz Gerhard Rödel Michael Kasper Kathrin Barth 《Cellular and molecular life sciences : CMLS》2010,67(15):2631-2642
P2X4 and P2X7 receptors are ATP-gated ion channels that are co-expressed in alveolar epithelial type I cells. Both receptors
are localized to the plasma membrane and partly associated with lipid rafts. Here we report on our study in an alveolar epithelial
cell line of the molecular organization of P2X7R and P2X4R receptors and the effect of their knockdown. Native gel electrophoresis
reveals three P2X7R complexes of ~430, ~580 and ~760 kDa. The latter two correspond exactly in size to signals of Cav-1, the
structural protein of caveolae. Interestingly knockdown of P2rx7 affects protein levels, the intracellular distribution and the supramolecular organization of Cav-1 as well as of P2X4R,
which is mainly detected in a complex of ~430 kDa. Our data suggest upregulation of P2X4R as a compensatory mechanism of P2X7R
depletion. 相似文献
4.
Kubli E 《Cellular and molecular life sciences : CMLS》2003,60(8):1689-1704
Mating affects the reproductive behaviour of insect females: the egg-laying rate increases and courting males are rejected. These post-mating responses are induced mainly by seminal fluid. In Drosophila melanogaster, males transfer two peptides (sex-peptides, = Sps) that reduce receptivity and elicit increased egg laying in their mating partners. Similarities in the open reading frames of the genes suggest that they have arisen by gene duplication. In females, Sps bind to specific sites in the central and peripheral nervous system, and to the genital tract. The binding proteins of the nervous system and genital tract are membrane proteins, but they differ molecularly. The former protein is proposed to be a receptor located at the top of a signalling cascade leading to the two post-mating responses, whereas the latter is a carrier protein moving Sps from the genital tract into the haemolymph. Sps bind to sperm. Together with sperm they are responsible for the persistence of the two post-mating responses. But Sps are the molecular basis of the sperm effect; sperm is merely the carrier.Received 10 February 2003; received after revision 25 April 2003; accepted 1 May 2003This article is dedicated to the 85th birthday of the discover of the sex-peptide, Prof. Dr. Pei Shen Chen, Zoological Institute, University of Zürich, Switzerland. P. S. Chen has served on the Editorial Board of Experientia (now CMLS) from 1974 to 1988. 相似文献
5.
A. Tippe P. Greguss H. Müller-Mohnssen 《Cellular and molecular life sciences : CMLS》1978,34(3):365-366
Summary The influence of sound waves on the stationary membrane conductivity of the axon membrane in myelinated nerve was investigated. Sound fields with frequencies within the auditory limit shift the transition voltage Vtr and correspondingly the threshold voltage of the action potential in polarisation direction. The results indicate that these changes of the electrical membrane behavior are due to a direct mechanical interaction between low frequency sound fields and membrane structure. 相似文献
6.
Deponte M 《Cellular and molecular life sciences : CMLS》2012,69(7):1025-1033
Green fluorescent protein (GFP) is a powerful tool for studying gene expression, protein localization, protein–protein interactions,
calcium concentrations, and redox potentials owing to its intrinsic fluorescence. However, GFP not only contains a chromophore
but is also tightly folded in a temperature-dependent manner. The latter property of GFP has recently been exploited (1) to
characterize the translocase of the outer mitochondrial membrane and (2) to discriminate between protein transport across
and into biomembranes in vivo. I therefore suggest that GFP could be a valuable tool for the general analysis of protein transport
machineries and pathways in a variety of organisms. Moreover, results from such studies could be important for the interpretation
and optimization of classical experiments using GFP tagging. 相似文献
7.
U. Mallik 《Cellular and molecular life sciences : CMLS》1976,32(11):1399-1400
Summary A strain ofParamaecium multimicronucleatum was exposed to a medium containingl-lysine; the concentrations of the amino acid were 0.1%, 0.5% and 1.0% for different sets of experiments. In these two latter concentrations, the macronucleus of the ciliate broke down into innumerable small fragments, the microspheres. The micronuclei remained inert. The microspheres left the body of paramaecium as cell-free, self-duplicating entities constituted of DNA and RNA and enveloped by a protein coat. They had no nuclear membrane and they resembled the prokaryotes. Grown in culture medium with 0.1% horse serum, the microspheres transformed into small amoebae having typical eukaryotic features. These amoebae maintained a typical cyst-trophic cycle during the successive sub-cultures; they had no similarity with the paramaecia. 相似文献
8.
Robert Renthal 《Cellular and molecular life sciences : CMLS》2010,67(7):1077-1088
Polytopic α-helical membrane proteins cannot spontaneously insert into lipid bilayers without assistance from polytopic α-helical
membrane proteins that already reside in the membrane. This raises the question of how these proteins evolved. Our current
knowledge of the insertion of α-helices into natural and model membranes is reviewed with the goal of gaining insight into
the evolution of membrane proteins. Topics include: translocon-dependent membrane protein insertion, antibiotic peptides and
proteins, in vitro insertion of membrane proteins, chaperone-mediated insertion of transmembrane helices, and C-terminal tail-anchored
(TA) proteins. Analysis of the E. coli genome reveals several predicted C-terminal TA proteins that may be descendents of proteins involved in pre-cellular membrane
protein insertion. Mechanisms of pre-translocon polytopic α-helical membrane protein insertion are discussed. 相似文献
9.
Sporulation and δ-endotoxin synthesis by Bacillus thuringiensis 总被引:4,自引:0,他引:4
Aronson A 《Cellular and molecular life sciences : CMLS》2002,59(3):417-425
Bacillus thuringiensis is distinguished from the very closely related Bacillus cereus and Bacillus anthracis by the presence of several plasmid-encoded δ-endotoxin genes. These δ-endotoxins, synthesized as protoxins, are produced
in large quantities during sporulation and are packaged into intracellular inclusions. Ingestion of the inclusions by insect
larvae leads to protoxin solubilization and conversion to toxins each specific for one of several orders of insects. The toxins
form cation-selective channels in the membrane of cells lining the larval midgut with subsequent lethality. In most cases,
δ-endotoxin synthesis and sporulation are closely coupled. The latter process in B. thuringiensis is probably virtually identical to that in Bacillus subtilis with the additional use of mother cell sporulation forms of RNA polymerase for the synthesis of the δ-endotoxins. There are
other more subtle plasmid-encoded functions or plasmid interactions related to regulating protoxin synthesis. Consideration
of both plasmid and chromosomal genes is thus critical for defining this organism. 相似文献
10.
Nitrate and nitrite transport in bacteria 总被引:7,自引:0,他引:7
The topological arrangements of nitrate and nitrite reductases in bacteria necessitate the synthesis of transporter proteins
that carry the nitrogen oxyanions across the cytoplasmic membrane. For assimilation of nitrate (and nitrite) there are two
types of uptake system known: ABC transporters that are driven by ATP hydrolysis, and secondary transporters reliant on a
proton motive force. Proteins homologous to the latter type of transporter are also involved in nitrate and nitrite transport
in dissimilatory processes such as denitrification. These proteins belong to the NarK family, which is a branch of the Major
Facilitator Superfamily. The mechanism and substrate specificity of transport via these proteins is unknown, but is discussed
in the light of sequence analysis of members of the NarK family. A hypothesis for nitrate and nitrite transport is proposed
based on the finding that there are two distinct types of NarK. 相似文献
11.
J. Dreysel O. W. Thiele D. Hermann 《Cellular and molecular life sciences : CMLS》1970,26(12):1304-1306
Summary The ability to accumulate lipids was investigated in two strains of hydrogen oxidizing bacteria (Hydrogenomonas H 16 and strain 11/x). Along with the deposition of poly--hydroxybutyrate the amount of other lipids is shown to increase 1.8 times in strain H 16. It is suggested that the increase of the latter lipids is due to the formation of membrane lipids that are needed for the formation of membranes around the intracellular globules of poly--hydroxybutyrate. In strain 11/x the amount of lipids increases 7 times along with the storage of carbohydrates. In this case, the majority of lipids consists of triglycerides. It is suggested that there is a true storage of neutral fat in strain 11/x. 相似文献
12.
蒋国昌 《世界科技研究与发展》2005,27(2):29-33
21世纪中冶金学及材料制备学的发展在于两个方向。其一是信息论冶金学和材料制备学;其二是在若干外加物理场综合作用下的7台金和材料制备过程。前者意在创建冶金学及材料制备学的一个新的高度。所以,由基础研究到过程控制有5个平台包含在此概念之中。关于第二个方向,本文讨论了超强磁场、脉冲电磁场、脉冲电流、超声波、等离子体以及离子选择性高效透过膜的应用可能性。对企业的发展提出了一个建议:应懂得技术储备的重要。 相似文献
13.
Katarzyna Kwiatkowska 《Cellular and molecular life sciences : CMLS》2010,67(23):3927-3946
Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is a minor lipid of the inner leaflet of the plasma membrane that controls the activity of numerous proteins and serves
as a source of second messengers. This multifunctionality of PI(4,5)P2 relies on mechanisms ensuring transient appearance of PI(4,5)P2 clusters in the plasma membrane. One such mechanism involves phosphorylation of PI(4)P to PI(4,5)P2 by the type I phosphatidylinositol-4-phosphate 5-kinases (PIP5KI) at discrete membrane locations coupled with PI(4)P delivery/synthesis
at the plasma membrane. Simultaneously, both PI(4)P and PI(4,5)P2 participate in anchoring PIP5KI at the plasma membrane via electrostatic bonds. PIP5KI isoforms are also selectively recruited
and activated at the plasma membrane by Rac1, talin, or AP-2 to generate PI(4,5)P2 in ruffles and lamellipodia, focal contacts, and clathrin-coated pits. In addition, PI(4,5)P2 can accumulate at sphingolipid/cholesterol-based rafts following activation of distinct membrane receptors or be sequestered
in a reversible manner due to electrostatic constrains posed by proteins like MARCKS. 相似文献
14.
Bocchinfuso G Bobone S Mazzuca C Palleschi A Stella L 《Cellular and molecular life sciences : CMLS》2011,68(13):2281-2301
Since their initial discovery, 30 years ago, antimicrobial peptides (AMPs) have been intensely investigated as a possible
solution to the increasing problem of drug-resistant bacteria. The interaction of antimicrobial peptides with the cellular
membrane of bacteria is the key step of their mechanism of action. Fluorescence spectroscopy can provide several structural
details on peptide–membrane systems, such as partition free energy, aggregation state, peptide position and orientation in
the bilayer, and the effects of the peptides on the membrane order. However, these “low-resolution” structural data are hardly
sufficient to define the structural requirements for the pore formation process. Molecular dynamics simulations, on the other
hand, provide atomic-level information on the structure and dynamics of the peptide–membrane system, but they need to be validated
experimentally. In this review we summarize the information that can be obtained by both approaches, highlighting their versatility
and complementarity, suggesting that their synergistic application could lead to a new level of insight into the mechanism
of membrane destabilization by AMPs. 相似文献
15.
This paper examines the information available through leading indicators for modelling and forecasting the UK quarterly index of production. Both linear and non‐linear specifications are examined, with the latter being of the Markov‐switching type as used in many recent business cycle applications. The Markov‐switching models perform relatively poorly in forecasting the 1990s production recession, but a three‐indicator linear specification does well. The leading indicator variables in this latter model include a short‐term interest rate, the stock market dividend yield and the optimism balance from the quarterly CBI survey. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
16.
Summary In the guinea pig taenia coli, when glycogen is depleted by repeating Ca-induced contracture in excess K solution containing no glucose, the tension cannot be maintained. The decrease in tension is accompanied by reduction of high energy phosphate compounds and oxygen consumption. When substrate is readmitted to the glycogendepleted preparation in the presence of 2.4 mM Ca and 20 mM K, the first response is hyperpolarization of the membrane and relaxation, and this is followed by depolarization and development of contracture. The latter response is blocked by verapamil, suggesting that energy supply increases the Ca conductance of the plasma membrane. The early response is considered to be due to activation of electrogenic Ca pump, since this is not affected by ouabain as well as removal of Na and K. ATP produced by substrate readmission is probably preferentially utilized for Ca pump activation to reduce the intracellular. Ca. The recovery of tension is likely to be brought about by ATP supply not only to the contractile machinery but also to the plasma membrane to remove inactivation of Ca conductance. It is postulated that as the energy source is depleted, energy consumption is automatically limited by suppressing Ca influx, as a selfdefence mechanism. Since HB is as effective as glucose in the recovery of these processes, and also in the activation of electrogenic Na pump, the matabolic pathway of oxidative phosphorylation alone can support these functions without a contribution of the glycolytic pathway. 相似文献
17.
Cheung NS Choy MS Halliwell B Teo TS Bay BH Lee AY Qi RZ Koh VH Whiteman M Koay ES Chiu LL Zhu HJ Wong KP Beart PM Cheng HC 《Cellular and molecular life sciences : CMLS》2004,61(15):1926-1934
The tumor suppressor function of PTEN is attributed to its phospholipid phosphatase activity that
dephosphorylates the plasma membrane phosphatidylinositol-(3,4,5)-triphosphate
[PtdIns(3,4,5)P3]. Implicit in this notion is that PTEN needs to be targeted to the plasma
membrane to dephosphorylate PtdIns(3,4,5)P3. However, the recruitment of PTEN to the plasma
membrane is not fully understood. Here, we demonstrate PTEN accumulation in the detergent-insoluble fraction of
neuronal cells in response to treatment by the proteasome inhibitor lactacystin. First, lactacystin induces
apoptosis and the activation of caspase-3 in cultured cortical neurons. Second, PTEN undergoes proteolysis to
form a truncated 50-kDa form that lacks parts of its C-terminal tail. Third, the truncated PTEN is stably
associated with the detergent-insoluble fraction in which the plasma membrane marker protein flotillin-1 resides.
Taken together, our results suggest that truncation and accumulation of PTEN to the detergent-insoluble membrane
fraction are two events associated with the apoptotic signals of the proteasome inhibitor in cortical neurons.Received 24 March 2004; received after revision 26 May 2004; accepted 5 June 2004 相似文献
18.
Summary Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial functions. The former induce a catalytic exchange with K+ in valinomycon-treated, respiratory-inhibited mitochondria, and act as uncouplers in respiring mitochondria. The latter induce a stoicheometric exchange with K+ and are actively taken up by respiring mitochondria. 相似文献
19.
The functional significance of the lipid-protein interface in photosynthetic membranes, mainly in thylakoids, is reviewed with emphasis on membrane structure and dynamics. The lipid-protein interface is identified primarily by the restricted molecular dynamics of its lipids as compared with the dynamics in the bulk lipid phase of the membrane. In a broad sense, lipid-protein interfaces comprise solvation shell lipids that are weakly associated with the hydrophobic surface of transmembrane proteins but also include lipids that are strongly and specifically bound to membrane proteins or protein assemblies. The relation between protein-associated lipids and the overall fluidity of the thylakoid membrane is discussed. Spin label electron paramagnetic resonance spectroscopy has been identified as the technique of choice to characterize the protein solvation shell in its highly dynamic nature; biochemical and direct structural methods have revealed an increasing number of protein-bound lipids. The structural and functional roles of these protein-bound lipids are mustered, but in most cases they remain to be determined. As suggested by recent data, the interaction of the non-bilayer-forming lipid, monogalactosyldyacilglycerol (MGDG), with the main light-harvesting chlorophyll a/b-binding protein complexes of photosystem-II (LHCII), the most abundant lipid and membrane protein components on earth, play multiple structural and functional roles in developing and mature thylakoid membranes. A brief outlook to future directions concludes this review. 相似文献
20.
Amanda J. Wilson Roman Schoenauer Elisabeth Ehler Irina Agarkova Pauline M. Bennett 《Cellular and molecular life sciences : CMLS》2014,71(1):165-181
Cardiomyocytes grow during heart maturation or disease-related cardiac remodeling. We present evidence that the intercalated disc (ID) is integral to both longitudinal and lateral growth: increases in width are accommodated by lateral extension of the plicate tread regions and increases in length by sarcomere insertion within the ID. At the margin between myofibril and the folded membrane of the ID lies a transitional junction through which the thin filaments from the last sarcomere run to the ID membrane and it has been suggested that this junction acts as a proto Z-disc for sarcomere addition. In support of this hypothesis, we have investigated the ultrastructure of the ID in mouse hearts from control and dilated cardiomyopathy (DCM) models, the MLP-null and a cardiac-specific β-catenin mutant, cΔex3, as well as in human left ventricle from normal and DCM samples. We find that the ID amplitude can vary tenfold from 0.2 μm up to a maximum of ~2 μm allowing gradual expansion during heart growth. At the greatest amplitude, equivalent to a sarcomere length, A-bands and thick filaments are found within the ID membrane loops together with a Z-disc, which develops at the transitional junction position. Here, also, the tops of the membrane folds, which are rich in αII spectrin, become enlarged and associated with junctional sarcoplasmic reticulum. Systematically larger ID amplitudes are found in DCM samples. Other morphological differences between mouse DCM and normal hearts suggest that sarcomere inclusion is compromised in the diseased hearts. 相似文献