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1.
G. Wingsle 《Physiologia plantarum》1989,76(1):24-30
Changes in the excitability of the liverwort Conocephalum conicum L. caused by inhibitors of ionic channels and phosphorylation uncouplers, were examined. Action potentials were triggered by electrical and light stimuli. Tetraethylammonium chloride, an inhibitor of K+ channels, completely blocked the ability to generate action potentials. Excitability also disappeared under the influence of MnCl2 and LaCl3 , inhibitors of Ca2+ channels. The participation of Ca2+ and K+ in the electrogenesis of action potentials in C. conicum is discussed. Treatment with phosphorylation uncouplers induced a gradual disappearance of the metabolic component of the resting potential. It was accompanied by some series of excitations, numbering from several to over a dozen impulses characterized by decreasing amplitudes, after which the organism became totally unexcitable. Dicyclohexylcarbodiimide an inhibitor of H+ -ATPase, also caused depolarization of the transmembrane potential and disappearance of excitability. The results indicated the participation of a metabolic component in the generation of action potentials in C. conicum . 相似文献
2.
Oliver H. LeBlanc Jr. 《The Journal of membrane biology》1971,4(1):227-251
Summary Detailed experimental data for conductivity and membrane potentials are presented for lecithin/cholesterol/decane bilayers
in the presence of the uncoupler carbonylcyanidem-chlorophenylhydrazone (CCCP). These compare favorably with a theoretical model derived to explain the mechanism of action
of uncouplers on bilayers. The model assumes that the weak acid uncoupler HA and its anion A− are the sole species which permeate the membrane. Its key feature is the recognition of the existence of unstirred aqueous
layers on either side of the membrane. The model accounts for, among other things, a maximum in the transmembrane conductivity
at a pH to the alkaline side of the uncoupler pK
a
and saturating current-voltage characteristics at high pH, both phenomena being found for CCCP. From a quantitative fit of
model to data, values of 2.0×10−3 and 11 cm/sec are deduced for the permeability coefficients of the CCCP anion and the undissociated CCCP molecule, respectively. 相似文献
3.
In experiments on rats, we studied 4-aminopyridine (4-AP)-induced modifications of the excitability of peripheral nerve fibers in an efferent trunk, the ventral root (VR), and in a mixed trunk including both afferent and efferent fibers, the sciatic nerve (SN). For this purpose, we examined how 4-AP influenced the parameters of integral action potentials recorded from the VR and SN in three experimental modes. These were: (i) stimulation of the SN and recording of antidromic action potentials from the VR in vivo after systemic injections of 4-AP into the animal, (ii) stimulation of a preparation of the SN dissected from the animal after systemic injection of 4-AP and recording of action potentials from another segment of the same preparation in vitro, and (iii) stimulation of an SN preparation and recording of action potentials from another region of this preparation in vitro, but after direct application of the solution of 4-AP to this preparation. It was found that 4-AP significantly increased the threshold for generation of action potentials and enhanced their amplitude, decreased the duration of action potentials recorded from the VR, and shortened the refractory period following these responses. The drug also significantly increased the amplitude and decreased the duration of action potentials recorded from the SN in vitro after systemic injections of the agent, but the threshold for response generation in this preparation noticeably dropped; the post-response refractory period in this case showed no changes. Modifications of action potentials recorded from the SN in vitro after direct applications of 4-AP were in general similar to the described above. Other examined parameters of action potentials (chronaxia and dynamics of an increase in the amplitude related to intensification of stimulation) showed no significant changes under the influence of 4-AP. We conclude that 4-AP increases the excitability of nerve fibers in the nerve trunks under study, but not to the point where the electrical interaction between excited and nonexcited fibers in the fiber conductors under study (VR and SN) overcomes the threshold. 相似文献
4.
Jaromír Plášek David Babuka Milan Hoefer 《Journal of bioenergetics and biomembranes》2017,49(5):391-397
According to the common view, weak acid uncouplers increase proton conductance of biological (and phospholipid bilayer) membranes, thus effecting H+ fluxes driven by their electrochemical gradients. Under certain conditions, however, uncouplers can induce unexpected effects opposite to the dissipation of H+ gradients. Results are presented here demonstrating CCCP-induced proton influx into Saccharomyces cerevisiae cytosol driven by the electrochemical potentials of CCCP and its CCCP? anions, independent of electrochemical H+-gradient. Another view of week acid uncouplers’ action is proposed that is logically consistent with these observations. 相似文献
5.
John A. Macdonald Malcolm S. Brodwick 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1973,87(4):293-316
Summary Single fibers of the bullfrog glossopharyngeal nerve give rise to several peripheral branches, each innervating separate fungiform papillae on the dorsal surface of the tongue. Extracellular electrodes were used to stimulate and record simultaneously from several papillae and from the central branch.Minor changes in centrally recorded neural output were caused by collision of action potentials originating in separate branches of a common fiber.Following an antidromic or orthodromic action potential in any branch, a series of excitability changes occured in that branch. Normal excitability was regained within 5 msec of an action potential, but was followed by a secondary decrease in excitability, which reached a minimum approximately 50 msec after the spike, and returned to normal within 200–400 msec after the spike. Subthreshold stimuli caused no depression, while doubling the stimulus strength above threshold did not enhance depression. After several spikes, both amplitude and duration of depression increased. Depression could be evoked even after the gustatory receptors were surgically removed.Post-stimulus depression in fiber branches is suggested as one source of gustatory adaptation, and may also contribute to interference between stimulating substances.The authors are particularly grateful for assistance and advice from Dr. Douglas Junge, of the School of Dentistry and Department of Physiology at the University of California, Los Angeles. The reported work was supported by NIDR Contract No. 69-2227 to Dr. Junge, and was carried out while one of the authors (JAM) held a PHS postdoctoral traineeship with the Department of Zoology, U.C.L.A., and the other (MSB) held a NIH predoctoral traineeship with the Department of Anatomy, U.C.L.A. Draughts of the paper have been read and criticized by Dr. Junge and Dr. J. P. Leader, of Auckland University. 相似文献
6.
A marked increase in electrical excitability and process formation occurs in the N-18 clone of mouse neuroblastoma as these cells go from the logarithmic phase of growth to the stationary state in confluent cultures. Even more excitable cells can be selected by growth in culture medium containing 10−5 M aminopterin which kills about 90% of the cells. Clone 1A-103 does not develop significant processes or exhibit marked electrical excitability under any of the culture conditions studied. Thus, our results show that one or more of the steps required for generation of the action potential is sensitive to regulation in cultured cells. Methods are presented for obtaining populations of either electrically passive cells or electrically excitable cells which can easily be maintained for several weeks. Clones differ markedly in their capacity to extend processes and their ability to generate action potentials. 相似文献
7.
The effects of anoxia on cardiac action potentials were studied at different stages of development of embryonic chick heart. The plateau phase of the action potential was markedly depressed by anoxia in old (15–16 days old) embryonic hearts without any significant change in other configurations of the action potential. Raising the concentration of glucose in the external fluid prevented the shortening of the action potential plateau by anoxia, and, conversely, a further reduction was observed in glucose-free media. In young (3–4 days old) embryonic hearts, the shortening of the action potential plateau was not produced by anoxia, but was produced by a combination of anoxia and glucose deprivation. When the action potential was shortened by anoxia in old hearts and by anoxia plus glucose deprivation in young hearts, isoproterenol (10?5M), dibutyryl cyclic 3′,5′-adenosine monophosphate (dBcAMP: 1 mM) plus aminophylline (1 mM), and calcium ion (3–6 mM), partially reversed the shortened action potential in old hearts, but did not produce any prolongation in the young hearts. Therefore, the cation channels responsible for the action potential plateau in young hearts may be pharmacologically different from those in old hearts. The differences in action potential plateau between young and old hearts were discussed in relation to dependence upon energy. 相似文献
8.
Generation of the action potentials (AP) necessary to activate skeletal muscle fibers requires that inward membrane currents exceed outward currents and thereby depolarize the fibers to the voltage threshold for AP generation. Excitability therefore depends on both excitatory Na+ currents and inhibitory K+ and Cl- currents. During intensive exercise, active muscle loses K+ and extracellular K+ ([K+]o) increases. Since high [K+]o leads to depolarization and ensuing inactivation of voltage-gated Na+ channels and loss of excitability in isolated muscles, exercise-induced loss of K+ is likely to reduce muscle excitability and thereby contribute to muscle fatigue in vivo. Intensive exercise, however, also leads to muscle acidification, which recently was shown to recover excitability in isolated K(+)-depressed muscles of the rat. Here we show that in rat soleus muscles at 11 mM K+, the almost complete recovery of compound action potentials and force with muscle acidification (CO2 changed from 5 to 24%) was associated with reduced chloride conductance (1731 +/- 151 to 938 +/- 64 microS/cm2, P < 0.01) but not with changes in potassium conductance (405 +/- 20 to 455 +/- 30 microS/cm2, P < 0.16). Furthermore, acidification reduced the rheobase current by 26% at 4 mM K+ and increased the number of excitable fibers at elevated [K+]o. At 11 mM K+ and normal pH, a recovery of excitability and force similar to the observations with muscle acidification could be induced by reducing extracellular Cl- or by blocking the major muscle Cl- channel, ClC-1, with 30 microM 9-AC. It is concluded that recovery of excitability in K(+)-depressed muscles induced by muscle acidification is related to reduction in the inhibitory Cl- currents, possibly through inhibition of ClC-1 channels, and acidosis thereby reduces the Na+ current needed to generate and propagate an AP. Thus short term regulation of Cl- channels is important for maintenance of excitability in working muscle. 相似文献
9.
Summary Carbonyl cyanide m-chlorophenylhydrazone (CCCP) and pentachlorophenol (PCP), two powerful uncouplers of phosphorylation, specifically inhibit the assimilation of nitrite in the course of nitrate reduction. These results support our former conclusion that high-energy phosphate is involved in the metabolism of nitrite. 相似文献
10.
Respiration and Mitochondrial Membrane Potential Are not Required for Apoptosis and Anti-apoptotic Action of Bcl-2 in HeLa Cells 总被引:3,自引:0,他引:3
The release of cytochrome c from intermembrane space of mitochondria into cytosol is one of the critical events in apoptotic cell death. The important anti-apoptotic oncoprotein Bcl-2 inhibits this process. In the present study it was shown that apoptosis and release of cytochrome c induced by staurosporine or by tumor necrosis factor- in HeLa cells were not affected by inhibitors of respiration (rotenone, myxothiazol, antimycin A) or by uncouplers (CCCP, DNP) that decrease the membrane potential at the inner mitochondrial membrane. The inhibitors of respiration and the uncouplers did not affect also the anti-apoptotic activity of Bcl-2. 相似文献
11.
Tom Piek Bernard Hue Marcel Pelhate Jonathan A. David Willem Spanjer Robin D. Veldsema-Currie 《Archives of insect biochemistry and physiology》1983,1(3):297-306
This paper provides answers to the questions which of the toxins present in the venom of the wasp Philanthus triangulum may be responsible for the previously reported blockage of transmission through the sixth abdominal ganglion of the cockroach, and whether this may occur by block of synaptic transmission or by affecting axonal exitability. In current clamp experiments the crude venom induces a slight depolarization of the membrane of the giant axon from the sixth abdominal ganglion of the cockroach and a small and irreversible decrease in the amplitude of the action potential. These marginal effects are not seen with relatively high concentrations of the philanthotoxins β-PTX and δ-PTX. It appears that neither the crude venom nor the toxins significantly affect the excitability of the cockroach giant axon. At a concentration of 20 μg ml?1 δ-PTX causes a slowly reversible block of synaptic transmission from the cercal nerve XI to a giant interneuron without any change in resting membrane potential, whereas β-PTX is inactive. Iontophoretically evoked acetylcholine potentials of the giant neuron are more sensitive to δ-PTX than excitatory postsynaptic potentials. This suggests that the toxin acts on the postsynaptic membrane. 相似文献
12.
Dr. Benjamin J. Cook John P. Reinecke 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1973,84(1):95-118
Summary The hindgut of the Madeira cockroach contains an intricate network of longitudinal and circular muscles that are distinctive for each region. In the rectum, the longitudinal muscles are symmetrically arranged in 6 distinct bands, while the circular muscles appear as a uniform layer over the rectal pads. In the colon, the muscle fibers are arranged in an irregular lattice with the longitudinal fibers generally superimposed on the circular ones but with an evident weaving between the layers. In addition to these muscle layers, a delicate, superficial network of muscle-like fibers covers many portions of the colon and rectum.In spite of the bewilderingly complex motile activity of deganglionated hindguts, all activity could be classified under 4 basic types after cinematographic analysis: segmentation, compression, peristalsis, or reverse peristalsis or a combination thereof. Although much of the activity that occurred was seemingly random, there was an evident rhythmicity that spontaneously arose and ended in several types of motility during the course of observations. The defined modes of activity seemed to be completely myogenic in nature, as all 4 categories were readily observed in hindguts 30 min after treatment with tetrodotoxin (10–6 g/ml). Each region of the hindgut seemed to have its own particular rhythm.Action potentials were recorded both intracellularly and extracellularly from all regions of the hindgut; amplitude usually ranged between 10 and 20 mV for intracellular recordings, and such spike potentials were often preceded by a slow depolarizing pre-potential. Generally, however, the depolarization was abrupt. Transmembrane potentials from the visceral muscle fibers were never truly at rest. Slow, continuous fluctuations (3–8 mV) were common. At times, plateau-type action potentials were recorded, but generally the repolarization contour was almost linear with time. Contractions were evoked by action potentials but not by the slow, rhythmic fluctuations in the membrane potential.No particular region or structure in the hindgut showed an exclusive pacemaker function. However, there was an evident gradient of increased excitability progressing in an caudal direction from the ileum.In a sodium-free saline, the amplitude of action potentials was remarkable enhanced from 5 to 10 min after the initial change. Even after a 20 min exposure, action potentials were still often present although their frequency and amplitude dropped. Tetrodotoxin (10–6g/ml) had no. pronounced effect on frequency or amplitude of action potentials. However, spike potentials ceased within 1.5 min after exposure to a sodium and calcium-free saline. When such preparations were re-exposed to a sodium-free saline containing normal calcium, the action potentials reappeared, suggesting that calcium might be a current-carrying ion. Although action potentials in a calcium-free medium showed variability, we generally saw a marked reduction in amplitude of potentials within 5 min. We further observed that 2 mM manganous ion completely abolished action potentials within 2 min. Thus, it seems likely that sodium is not the sole current-carrying ion in cockroach hindgut muscle.The authors express their indebtedness to Ms. Susan Swann, Mr. Gerald Holt, Mr. David Owens, and Ms. Mary Strand for their competent technical assistance. 相似文献
13.
Comparison of arsenazo III optical signals in intact and cut frog twitch fibers 总被引:13,自引:6,他引:7
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The Ca indicator arsenazo III was introduced into cut frog twitch fibers by diffusion from end-pool segments rendered permeable by saponin. After 2-3 h, the arsenazo III concentration at the optical recording site in the center of a fiber reached two to three times that in the end-pool solutions. Thus, arsenazo III was bound to or taken up by intracellular constituents. The time course of indicator appearance was fitted by equations for diffusion plus linear reversible binding; on average, 0.73 of the indicator was bound and the free diffusion constant was 0.86 x 10(-6) cm2/s at 18 degrees C. When the indicator was removed from the end pools, it failed to diffuse away from the optical site as rapidly as it had diffused in. The wavelength dependence of resting arsenazo III absorbance was the same in cut fibers and injected intact fibers. After action potential stimulation, the active Ca and dichroic signals were similar in the two preparations, which indicates that arsenazo III undergoes the same changes in absorbance and orientation in both cut and intact fibers. Ca transients in freshly prepared cut fibers appeared to be similar to those in intact fibers. As a cut fiber experiment progressed, however, the Ca signal changed. With action potential stimulation, the half-width of the signal gradually increased, regardless of whether the indicator concentration was increasing or decreasing. This increase was usually not accompanied by any change in the amplitude of the Ca signal at a given indicator concentration or by any obvious deterioration in the electrical condition of the fiber. In voltage-clamp experiments near threshold, the relation between peak [Ca] and voltage usually became less steep with time and shifted to more negative potentials. All these changes were also observed in cut fibers containing antipyrylazo III (Maylie, J., M. Irving, N. L. Sizto, and W. K. Chandler. 1987. Journal of General Physiology. 89:83-143). They are considered to represent a progressive change in the physiological state of a cut fiber during the time course of an experiment. 相似文献
14.
V. D. Gerasimov 《Neurophysiology》1969,1(3):240-246
We conducted a comparative investigation of the restorative action of different sodium ion concentrations on generation of action potentials by apple snail neurons of the central nervous system kept for a prolonged period in a solution in which such ions were lacking. Of the 180 neurons investigated, 60% of the cells had lost all excitability, while 40% retained the ability to generate action potentials of normal amplitude. In neurons that ceased under these conditions to generate action potentials both independently and as the result of direct stimulation, amplitude of the action potentials and of the "overshoot" was restored after adding only 2.5–10 mM of sodium to the solution. Analogous concentrations of lithium ions did not exert a similar restorative action. They repressed the capacity of a neuron to regain excitability in the presence of small amounts of sodium ions. Increasing the external concentration of sodium after restoration of the action potentials led to a proportional decline of their amplitude. Keeping neurons in a sodium-containing solution for periods of 25 min and more caused restoration of the neuron's ability to increase linearly the amplitude of action potentials upon raising the external concentration of sodium ions.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 3, pp. 315–322, November–December, 1969. 相似文献
15.
《生物化学与生物物理学报:生物膜》2018,1860(5):1000-1007
The formerly widely used broad-spectrum biocide triclosan (TCS) has now become a subject of special concern due to its accumulation in the environment and emerging diverse toxicity. Despite the common opinion that TCS is an uncoupler of oxidative phosphorylation in mitochondria, there have been so far no studies of protonophoric activity of this biocide on artificial bilayer lipid membranes (BLM). Yet only few works have indicated the relationship between TCS impacts on mitochondria and nerve cell functioning. Here, we for the first time report data on a high protonophoric activity of TCS on planar BLM. TCS proved to be a more effective protonophore on planar BLM, than classical uncouplers. Correlation between a strong depolarizing effect of TCS on bacterial membranes and its bactericidal action on Bacillus subtilis might imply substantial contribution of TCS protonophoric activity to its antimicrobial efficacy. Protonophoric activity of TCS, monitored by proton-dependent mitochondrial swelling, resulted in Ca2+ efflux from mitochondria. A comparison of TCS effects on molluscan neurons with those of conventional mitochondrial uncouplers allowed us to ascribe the TCS-induced neuronal depolarization and suppression of excitability to the consequences of mitochondrial deenergization. Also similar to the action of common uncouplers, TCS caused a pronounced increase in frequency of miniature end-plate potentials at neuromuscular junctions. Thus, the TCS-induced mitochondrial uncoupling could alter neuronal function through distortion of Ca2+ homeostasis. 相似文献
16.
Vitaly D. Samuilov Gernot Renger Vladimir Z. Paschenko Alexander V. Oleskin Michail V. Gusev Olga N. Gubanova Sergei S. Vasil'ev Eugene L. Barsky 《Photosynthesis research》1995,46(3):455-465
The protonophoric uncouplers carbonyl cyanide m-chlorophenylhydrazone (CCCP), 2,3,4,5,6-pentachlorophenol (PCP) and 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole (TTFB) inhibited the Hill reaction with K3[Fe(CN)6] (but not with SiMo) in chloroplast and cyanobacterial membranes (the I50 values were approx. 1–2, 4–6 and 0.04–0.10 M, respectively). The inhibition is due to oxidation of the uncouplers on the Photosystem II donor side (ADRY effect) and their subsequent reduction on the acceptor side, ie. to the formation of a cyclic electron transfer chain around Photosystem II involving the uncouplers as redox carriers. The relative amplitude of nanosecond chlorophyll fluorescence in chloroplasts was increased by DCMU or HQNO and did not change upon addition of uncouplers, DBMIB or DNP-INT; the HQNO effect was not removed by the uncouplers. The uncouplers did not inhibit the electron transfer from reduced TMPD or duroquinol to methylviologen which is driven by Photosystem I. These data show that CCCP, PCP and TTFB oxidized on the Photosystem II donor side are reduced by the membrane pool of plastoquinone (Qp) which is also the electron donor for K3 [Fe(CN)6] in the Hill reaction as deduced from the data obtained in the presence of inhibitors. Inhibition of the Hill reaction by the uncouplers was maximum at the pH values corresponding to the pK of these compounds. It is suggested that the tested uncouplers serve as proton donors, and not merely as electron donors on the oxidizing side of Photosystem II.Abbreviations ADRY-
acceleration of the deactivation reactions of the water-splitting enzyme system Y
- ANT2p-
2-(3-chloro-4-trifluoromethyl) anilino-3,5-dinitrothiophene
- CCCP-
carbonyl cyanide m-chlorophenylhydrazone
- DBMIB-
2,5-dibromo-3-methyl 6-isopropyl-p-benzoquinone
- DCMU-
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DNP-INT-
2-iodo-6-isopropyl-3-methyl 2,4,4-trinitrodiphenyl ether
- DPC-
1,5-diphenylcarbazide
- DPIP-
2,6-dichlorophenolindophenol
- FCCP-
carbonyl cyanide p-trifuoromethoxyphenylhydrazone
- FeCy-
potassium ferricyanide
- HQNO-
2-n-heptyl-4-hydroxyquinoline N-oxide
- (MN)4-
the tetranuclear Mn cluster of water oxidizing complex
- P680-
photoactive Chl of the reaction center of Photosystem II
- PCP-
2,3,4,5,6-pentachlorophenol
- PS-
photosystem
- QA and QB-
primary and secondary plastoquinones of PS II
- QC and QZ-
plastoquinone binding sites in the cytochrome blf complex
- Qp-
membrane pool of plastoquinone
- SiMo-
sodium silicomolybdate
- TMPD-
N,N,N-tetramethyl-p-phenylenediamine
- TTFB-
4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole
- WOC-
water oxidixing complex
- YZ-
tyrosine-161 of the Photosystem II D1 polypeptide 相似文献
17.
Yuri N. Antonenko Ljudmila S. Khailova Dmitry A. Knorre Olga V. Markova Tatyana I. Rokitskaya Tatyana M. Ilyasova Inna I. Severina Elena A. Kotova Yulia E. Karavaeva Anastasia S. Prikhodko Fedor F. Severin Vladimir P. Skulachev 《PloS one》2013,8(4)
Protonophorous uncouplers causing a partial decrease in mitochondrial membrane potential are promising candidates for therapeutic applications. Here we showed that hydrophobic penetrating cations specifically targeted to mitochondria in a membrane potential-driven fashion increased proton-translocating activity of the anionic uncouplers 2,4-dinitrophenol (DNP) and carbonylcyanide-p-trifluorophenylhydrazone (FCCP). In planar bilayer lipid membranes (BLM) separating two compartments with different pH values, DNP-mediated diffusion potential of H+ ions was enhanced in the presence of dodecyltriphenylphosphonium cation (C12TPP). The mitochondria-targeted penetrating cations strongly increased DNP- and carbonylcyanide m-chlorophenylhydrazone (CCCP)-mediated steady-state current through BLM when a transmembrane electrical potential difference was applied. Carboxyfluorescein efflux from liposomes initiated by the plastoquinone-containing penetrating cation SkQ1 was inhibited by both DNP and FCCP. Formation of complexes between the cation and CCCP was observed spectophotometrically. In contrast to the less hydrophobic tetraphenylphosphonium cation (TPP), SkQ1 and C12TPP promoted the uncoupling action of DNP and FCCP on isolated mitochondria. C12TPP and FCCP exhibited a synergistic effect decreasing the membrane potential of mitochondria in yeast cells. The stimulating action of penetrating cations on the protonophore-mediated uncoupling is assumed to be useful for medical applications of low (non-toxic) concentrations of protonophores. 相似文献
18.
《BBA》1987,891(3):293-299
Uncoupling activity with rat liver mitochondria and protonophoric activity across the lecithin liposomal membranes were measured for a series of non-classical uncouplers related to the most potent uncoupler known until now, SF6847 (2,6-di-t-butyl-4-(2′,2′-dicyanovinyl)phenol). The correlation between uncoupling and protonophoric activities for a number of uncouplers, both non-classical and classical (simply substituted phenols), was examined quantitatively. Correlation was excellent when such factors as the stability of anionic species in the membrane phase and the difference in the pH conditions of the extramembranous aqueous phase were taken into account. Carbonylcyanide m-chlorophenylhydrazone (CCCP) and carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), which are structurally different, were correlated in a way that resembled the correlation of phenolic compounds, so we think that the mode of action of weakly acidic uncouplers was the same regardless of the structural type. Our findings were evidence for the shuttle-type mechanism of uncoupling action. 相似文献
19.
It has been shown experimentally that the crustacean motor axon is supernormally excitable following a train of action potentials (Zucker 1974). Such a phenomenon can lead to recruitment of terminals which are unexcited at low rates of stimulation. Although currents underlying the crustacean motor axon have been characterized (Connor et al. 1977), it is not known whether this membrane model accounts for a supernormal period, what might cause superexcitablity in this model, or how excitability might change during repetitive stimulation. In present study, it is demonstrated that the crustacean motor axon model does predict a supernormal period, that the supernormal period results from slow recovery from inactivation of the transient potassium, or A, current, and that supernormal excitability is enhanced by repetitive stimulation. 相似文献
20.
Quantitative relationship between protonophoric and uncoupling activities of analogs of SF6847 (2,6-di-t-butyl-4-(2',2'-dicyanovinyl)phenol) 总被引:3,自引:0,他引:3
Uncoupling activity with rat liver mitochondria and protonophoric activity across the lecithin liposomal membranes were measured for a series of non-classical uncouplers related to the most potent uncoupler known until now, SF6847 (2,6-di-t-butyl-4-(2',2'-dicyanovinyl)phenol). The correlation between uncoupling and protonophoric activities for a number of uncouplers, both non-classical and classical (simply substituted phenols), was examined quantitatively. Correlation was excellent when such factors as the stability of anionic species in the membrane phase and the difference in the pH conditions of the extramembranous aqueous phase were taken into account. Carbonylcyanide m-chlorophenylhydrazone (CCCP) and carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), which are structurally different, were correlated in a way that resembled the correlation of phenolic compounds, so we think that the mode of action of weakly acidic uncouplers was the same regardless of the structural type. Our findings were evidence for the shuttle-type mechanism of uncoupling action. 相似文献