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排序方式: 共有198条查询结果,搜索用时 46 毫秒
1.
Steven J. Tucker David McClelland Kristina Sep?i? Roderick H. Scott 《生物化学与生物物理学报:生物膜》2003,1614(2):171-181
The ability of two alkyl pyridinium sponge toxin preparations (poly-APS and halitoxin) to form transient pores/lesions in cell membranes and allow transfection of plasmid cDNA have been investigated using HEK 293 cells. Poly-APS and halitoxin preparations caused a collapse in membrane potential, reductions in input resistance and increased Ca2+ permeability. At least partial recovery was observed after poly-APS application but recovery was more rarely seen with halitoxin. The transfection with plasmid cDNAs for an enhanced green fluorescent protein (EGFP) and human tumour necrosis factor receptor 2 (TNFR2) was assessed for both toxin preparations and compared with lipofectamine. Stable transfection was achieved with poly-APS although it was less efficient than lipofectamine. These results show that viable cells transfected with alien cDNA can be obtained using novel transient pore-forming alkyl pyridinium sponge toxins and a simple pre-incubation protocol. This provides the first proof of principle that pore-forming alkyl pyridinium compounds can be used to deliver cDNA to the intracellular environment without permanently compromising the plasma membrane. 相似文献
2.
Structure and Functions of Channel-Forming Peptides: Magainins,Cecropins, Melittin and Alamethicin 总被引:26,自引:0,他引:26
B. Bechinger 《The Journal of membrane biology》1997,156(3):197-211
3.
haemolysin of Escherichia coli: Comparison of pore-forming properties between chromosome and plasmid-encoded haemolysins 总被引:3,自引:0,他引:3
Roland Benz reas Döbereiner Albrecht Ludwig Werner Goebel 《FEMS microbiology letters》1992,105(1-3):55-62
Abstract Lipid bilayer experiments were performed with chromosome-encoded haemolysin of Escherichia coli . The addition of the toxin to the aqueous phase bathing lipid bilayer membranes of asolectin resulted in the formation of transient ion-permeable channels with two states at small transmembrane voltages. One is prestate (single-channel conductance 40 pS in 0.15 M KCl) of the open state, which had a single-channel conductance of 420 pS in 0.15 M KCl and a mean lifetime of 30 s. Membranes formed of pure lipids were rather inactive targets for this haemolysin. Experiments with different salts suggested that the haemolysin channel was highly cation-selective at neutral pH. The mobility sequence of the cations in the channel was similar if not identical to their mobility sequence in the aqueous phase. The single-channel data were consistent with a wide, water-filled channel with an estimated minimal diameter of about 1 nm. The pore-forming properties of chromosome-encoded haemolysin were compared with those of plasmid-encoded haemolysin. Both toxins share common features, oligomerize probably to form pores in lipid bilayer membranes. Both types of haemolysin channels have similar properties but different lifetimes. 相似文献
4.
Gianfranco Menestrina 《生物化学与生物物理学报:生物膜》1983,735(2):297-301
Megathura crenulata hemocyanin forms ionic channels in planar lipid bilayer membranes. It was found that hemocyanin is more potent as a channel former if TbCl3 is added to the bathing solution. Furthermore membranes separating symmetrical TbCl3 solutions show a pore formation rate which depends exponentially on the applied voltage, positive potentials favouring the insertion of new channels. The slope of this voltage dependence, which gives a measure of the effective charge displaced during the incorporation of one channel, increases and saturates with TbCl3 concentration. The dose response curve indicates that binding of Tb3+ to the phosphatidylcholine bilayer is involved in creating the effective charge. 相似文献
5.
G. Menestrina C. Pederzolli M. Dalla Serra M. Bregante F. Gambale 《The Journal of membrane biology》1996,149(2):113-121
Escherichia coli hemolysin is known to cause hemolysis of red blood cells by forming hydrophilic pores in their cell membrane. Hemolysin-induced
pores have been directly visualized in model systems such as planar lipid membranes and unilamellar vesicles. However this
hemolysin, like all the members of a related family of toxins called Repeat Toxins, is a potent leukotoxin. To investigate
whether the formation of channels is involved also in its leukotoxic activity, we used patch-clamped human macrophages as
targets. Indeed, when exposed to the hemolysin, these cells developed additional pores into their membrane. Such exogenous
pores had properties very different from the endogenous channels already present in the cell membrane (primarily K+ channels), but very similar to the pores formed by the toxin in purely lipidic model membranes. Observed properties were:
large single channel conductance, cation over anion selectivity but weak discrimination among different cations, quasilinear
current-voltage characteristic and the existence of a flickering pre-open state of small conductance. The selectivity properties
of the toxin channels appearing in phospholipid vesicles were also investigated, using a specially adapted polarization/depolarization
assay, and were found to be completely consistent with that of the current fluctuations observed in excised macrophage patches.
Received: 14 August 1995/Revised: 2 October 1995 相似文献
6.
Ursula Meindl 《Protoplasma》1982,112(1-2):138-141
Summary During the stage of pore formation developing cells ofMicrasterias denticulata show a patterned distribution of fluorescent dots on the plasma membrane after treatment with chlorotetracycline. The center-to-center spacing of these dots corresponds with the distances between the individual cell wall pores ofMicrasterias. Therefore it is supposed that the patterned distribution of pores and their formation which is mediated by special pore vesicles are related to local accumulations of membrane-associated Ca2+. Membrane-associated Ca2+ seems not only to be functional in tip growth but to be a general mediator for recognition and fusion processes between various vesicles and the plasma membrane. 相似文献
7.
Summary The fine structure of the pore cells in pre- and post-hatched Deroceras reticulatum is described. The cells have been divided into three main types on morphological grounds, one type being particularly rich in glycogen. Certain pore cells contain haemocyanin granules in grooves below cytoplasmic tongues, and in characteristic double-membrane-bounded vesicles within dilated cisternae of rough endoplasmic reticulum, as well as in other identified areas. All types of pore cells show fine fibres reminiscent of collagen associated with the basal lamina and pore complexes.In addition to acid phosphatase activity in lysosomes and Golgi elements, intra- and extracisternal activity has been demonstrated in association with the rough endoplasmic reticulum. The intracisternal activity is in close proximity to the Golgi apparatus and may represent enzyme that is about to enter the GERL system. Extracisternal activity may be associated with cellular lysis and death, or may represent local areas of degradation leading to cytodifferentiation. Remnants of lysed pore cells appear to be taken up by connective tissue amoebocytes.The authors wish to acknowledge the financial support of the Agricultural Research Council (G.B.) Grant No. AG 72/21, the photographic assistance of Mr. Nigel Green, and some technical assistance from Miss Jane Morgans 相似文献
8.
Fang Liu Wei Wei Jianhua Fang Yuanyuan Wu Qifei Zhang Cunxin Wang Lihong Ye Min Liu 《Saudi Journal of Biological Sciences》2019,26(2)
Purpose
To explore how the use of a laser needle-knife affects vertebroarterial morphology and protein expression of PI-3K, AKT and VEGF in the carotid artery of a rabbit model of cervical spondylotic arteriopathy (CSA), and to determine its primary treatment mechanism.Methods
The CSA rabbit model consisted of 30 rabbits with CSA that were randomly divided into a model group (n?=?10), an acupuncture group (n?=?10) and a laser needle-knife group (n?=?10) plus a further 10 wild type rabbits placed into a normal group. Rabbits in the acupuncture group were treated by needling the Fengchi (GB 20) and Jiaji (EX-B2) acupoints, while those in the laser needle-knife group were treated with a laser needle-knife on the Jiaji (EX-B2) near the spinous process of the fifth cervical vertebra, the rabbit in both groups immobilized during treatment. Rabbits in the other two groups received no treatment, but were immobilized for a similar duration. The morphology of the right vertebral artery and the distribution of pore size before and after treatment were compared using BET and SEM, and the protein expression of PI-3K, AKT and VEGF in the carotid artery of the four groups measured using Western blot analysis.Results
The pore diameter and specific surface area of the right vertebral artery increased after treatment, as did the number of micropores. Compared with the normal group, the protein expression of PI-3K, AKT and VEGF in the carotid artery of the model group was significantly lower (P?<?0.05), while that of the laser needle-knife group was significantly higher (P?<?0.05 and P?<?0.01). In addition, rabbits from the acupuncture and laser needle-knife groups demonstrated significantly higher levels of protein expression of PI-3K and VEGF in the carotid artery compared with the model group (P?<?0.05 and P?<?0.01).Conclusions
By promoting micrangium hyperplasia within the vertebral artery of rabbits with CSA, treatment with a laser needle-knife modified the protein expression of PI-3K, AKT and VEGF, suggesting that laser needle-knife therapy possibly treats CSA though these signaling pathways. 相似文献9.
The purinergic receptor P2X(7) is part of a complex signaling mechanism participating in a variety of physiological and pathological processes. Depending on the activation scheme, P2X(7) receptors in vivo are non-selective cation channels or form large pores that can mediate apoptotic cell death. Expression of P2X(7)R in Xenopus oocytes results exclusively in formation of a non-selective cation channel. However, here we show that co-expression of P2X(7)R with pannexin1 in oocytes leads to the complex response seen in many mammalian cells, including cell death with prolonged ATP application. While the cation channel activity is resistant to carbenoxolone treatment, this gap junction and hemichannel blocking drug suppressed the currents induced by ATP in pannexin1/P2X(7)R co-expressing cells. Thus, pannexin1 appears to be the molecular substrate for the permeabilization pore (or death receptor channel) recruited into the P2X(7)R signaling complex. 相似文献
10.
Vié V Van Mau N Pomarède P Dance C Schwartz JL Laprade R Frutos R Rang C Masson L Heitz F Le Grimellec C 《The Journal of membrane biology》2001,180(3):195-203
After activation, Bacillus thuringiensis (Bt) insecticidal toxin forms pores in larval midgut epithelial cell membranes, leading to host death. Although the crystal
structure of the soluble form of Cry1Aa has been determined, the conformation of the pores and the mechanism of toxin interaction
with and insertion into membranes are still not clear. Here we show that Cry1Aa spontaneously inserts into lipid mono- and
bilayer membranes of appropriate compositions. Fourier Transform InfraRed spectroscopy (FTIR) indicates that insertion is
accompanied by conformational changes characterized mainly by an unfolding of the β-sheet domains. Moreover, Atomic Force
Microscopy (AFM) imaging strongly suggests that the pores are composed of four subunits surrounding a 1.5 nm diameter central
depression.
Received: 14 July 2000/Revised: 28 December 2000 相似文献