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1.
Space Sci Rev ; 218(4): 22, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35502362

RESUMO

We present a review of Anomalous Cosmic Rays (ACRs), including the history of their discovery and recent insights into their acceleration and transport in the heliosphere. We focus on a few selected topics including a discussion of mechanisms of their acceleration, escape from the heliosphere, their effects on the dynamics of the heliosheath, transport in the inner heliosphere, and their solar cycle dependence. A discussion concerning their name is also presented towards the end of the review. We note that much is known about ACRs and perhaps the term Anomalous Cosmic Ray is not particularly descriptive to a non specialist. We suggest that the more-general term: "Heliospheric Energetic Particles", which is more descriptive, for which ACRs and other energetic particle species of heliospheric origin are subsets, might be more appropriate.

2.
Eur J Pharmacol ; 156(1): 55-62, 1988 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-2850211

RESUMO

The potency of (-)- and (+)-diprafenone to depress the Vmax of Na+-dependent action potentials and to block single cardiac Na+ channels was analyzed in microelectrode experiments with guinea pig papillary muscles and in patch clamp experiments with DPI-modified Na+ channels using neonatal cardiocytes. Within 20-30 min, both optical enantiomers caused a Vmax depression which occurred predominantly as a phasic blockade at a low dosage (10 mumol/l). (-)- and (+)-diprafenone were equally effective in evoking a tonic and phasic depression of Vmax. Exposing the cytoplasmic side of inside-out patches to 10 mumol/l of (-)- or (+)-diprafenone evoked a flicker block of DPI-modified Na+ channels within 1-2 s. Kinetic analysis of the latter revealed a KD value for the blocking action of 6.3 X 10(-5) mol for the (-) enantiomer and 7.1 X 10(-5) mol for the (+) enantiomer. Nevertheless, larger association and dissociation rate constants were obtained with (+)-diprafenone than with (-)-diprafenone. This indicates that there are stereoselective reaction kinetics in blocking open modified Na+ channels.


Assuntos
Antiarrítmicos/farmacologia , Coração/efeitos dos fármacos , Propafenona/análogos & derivados , Canais de Sódio/efeitos dos fármacos , Potenciais de Ação/efeitos dos fármacos , Animais , Cobaias , Coração/fisiologia , Técnicas In Vitro , Microeletrodos , Miocárdio/metabolismo , Músculos Papilares/efeitos dos fármacos , Propafenona/farmacologia , Estereoisomerismo
3.
Neuropsychology ; 17(3): 420-8, 2003 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-12959508

RESUMO

The effect of long-term heavy alcohol consumption on brain functions is still under debate. The authors investigated a sample of 17 Korsakoff amnesics, 23 alcoholics without Korsakoff's syndrome, and 21 controls with peripheral nerve diseases, matched for intelligence and education. Executive functions were examined for word fluency, the modified Wisconsin Card Sorting Test, an alternate response task, and an "n-back" working memory task. Korsakoff amnesics, but not alcoholics, showed a marked memory impairment. They also scored lower in each of the executive tasks-the alcoholics only in the alternate response task. This task also correlated with the years of the alcohol dependency. First, the authors conclude that Korsakoff's syndrome is associated not only with a memory impairment but also with a global executive deficit. Second, the decline in the ability to alternate between different responses argues for a restricted neurotoxic effect of alcohol on some frontal lobe areas.


Assuntos
Alcoolismo/psicologia , Lobo Frontal/fisiopatologia , Síndrome de Korsakoff/psicologia , Desempenho Psicomotor , Adulto , Idoso , Alcoolismo/fisiopatologia , Estudos de Casos e Controles , Feminino , Humanos , Síndrome de Korsakoff/fisiopatologia , Masculino , Transtornos da Memória/psicologia , Pessoa de Meia-Idade , Testes Neuropsicológicos , Aprendizagem Verbal
4.
Naunyn Schmiedebergs Arch Pharmacol ; 340(2): 210-8, 1989 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-2478894

RESUMO

Cell-attached patch clamp recording of elementary Na+ currents were performed at 19 degrees C in neonatal cultured rat heart cells to study Na+ channel properties in the presence of dihydropyridines. Bath application of racemic CGP 28392, at 5 mumol/l, activated Na+ channels. By increasing the open probability, P0, and/or the number of functioning Na+ channels, peak INa in reconstructed macroscopic Na+ currents rose without changes in the decay kinetics. This was accompanied by a prolongation of open time. (-)-Bay K 8644 (1-10 mumol/l) had the same effect. In the presence of either agonist, Na+ channels retained an uniform open state and, as estimated from the mean number of openings per sequence, their initial tendency to reopen. Rarely appearing ultralong opening sequences are unlikely to be drug-induced as Na+ channels can likewise switch into this particular activity mode under drug-free conditions. Racemic CGP 28392, at 50 mumol/l, blocked Na+ channels in an all-or-none fashion suggesting that one enantiomer acts as agonist and the other enantiomer as blocker. A quite different response consisting of the occurrence of a second open state with a several-fold increased life time and a significantly increased reopening was observed with (-)-Bay K 8644 in damaged cardiocytes with hyperpermeable membranes and after patch excision into drug-containing solution. Evidence was obtained from control inside-out patches that this increased reopening is most probably caused by the solvent, ethanol.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Éster Metílico do Ácido 3-Piridinacarboxílico, 1,4-Di-Hidro-2,6-Dimetil-5-Nitro-4-(2-(Trifluormetil)fenil)/farmacologia , Animais Recém-Nascidos/metabolismo , Agonistas dos Canais de Cálcio/farmacologia , Piridinas/farmacologia , Canais de Sódio/metabolismo , Animais , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Citoplasma/efeitos dos fármacos , Citoplasma/metabolismo , Di-Hidropiridinas/farmacologia , Etanol/farmacologia , Coração/efeitos dos fármacos , Técnicas In Vitro , Masculino , Miocárdio/citologia , Miocárdio/metabolismo , Ratos , Canais de Sódio/efeitos dos fármacos
5.
Int J Rehabil Res ; 22(2): 119-22, 1999 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10448623

RESUMO

Young persons tied to wheelchairs increasingly report fears and inhibitions in romantic attachments, irrespective of whether they are paraplegic or not. More frequently they complain about being gaped at and being pitied by healthy persons more than they would like. Being tied to the wheelchair had a significant relation to these results, but not gender, age and illness variables. A high demand for psychosocial counselling during rehabilitation is deduced from these results, in particular also for young people without paraplegia.


Assuntos
Pessoas com Deficiência/psicologia , Relações Interpessoais , Aconselhamento Sexual , Cadeiras de Rodas , Adaptação Psicológica , Adulto , Análise de Variância , Pessoas com Deficiência/reabilitação , Humanos , Paraplegia/psicologia , Reprodutibilidade dos Testes , Autoavaliação (Psicologia) , Sexualidade , Inquéritos e Questionários
8.
Science ; 326(5955): 966-8, 2009 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-19833915

RESUMO

Simulations of energetic neutral atom (ENA) maps predict flux magnitudes that are, in some cases, similar to those observed by the Interstellar Boundary Explorer (IBEX) spacecraft, but they miss the ribbon. Our model of the heliosphere indicates that the local interstellar medium (LISM) magnetic field (B(LISM)) is transverse to the line of sight (LOS) along the ribbon, suggesting that the ribbon may carry its imprint. The force-per-unit area on the heliopause from field line draping and the LISM ram pressure is comparable with the ribbon pressure if the LOS approximately 30 to 60 astronomical units and B(LISM) approximately 2.5 microgauss. Although various models have advantages in accounting for some of the observations, no model can explain all the dominant features, which probably requires a substantial change in our understanding of the processes that shape our heliosphere.

9.
Science ; 326(5955): 959-62, 2009 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-19833923

RESUMO

The Sun moves through the local interstellar medium, continuously emitting ionized, supersonic solar wind plasma and carving out a cavity in interstellar space called the heliosphere. The recently launched Interstellar Boundary Explorer (IBEX) spacecraft has completed its first all-sky maps of the interstellar interaction at the edge of the heliosphere by imaging energetic neutral atoms (ENAs) emanating from this region. We found a bright ribbon of ENA emission, unpredicted by prior models or theories, that may be ordered by the local interstellar magnetic field interacting with the heliosphere. This ribbon is superposed on globally distributed flux variations ordered by both the solar wind structure and the direction of motion through the interstellar medium. Our results indicate that the external galactic environment strongly imprints the heliosphere.

10.
Z Orthop Ihre Grenzgeb ; 115(2): 243-8, 1977 Apr.
Artigo em Alemão | MEDLINE | ID: mdl-857465

RESUMO

For more than 100 years in different sectors the attempt has been made to define rehabilitation and to make it significant in the practice of rehabilitation. If you watch especially the past 70 years in Germany, then the legislature concerning the protection of health, the provident measures, the case of invalidity is so progressive and from year to year becoming more extensive, that there is actually always an area, in which there is a legal way to help the disabled. Nevertheless there are always gaps within a measure of rehabilitation which are necessary to be filled in common efforts. In the Federal Republic of Germany there is a legal clain of rehabilitative measures in a comprehensive way indeed, in which we think of the necessity of a federal rehabilitation law, since certain methods in the arrangement and exhausting of previous legislature for the disabled is often too difficult. In spite of best legal conditions, however, it has to be considered, and the dynamics in the accomplishment not only of the particular functions, but also of the special aims always will be significant for the understanding of a society. Legal claim of integration should therefore never be in doubt.


Assuntos
Legislação Médica , Reabilitação Vocacional , Alemanha Ocidental
11.
Rehabilitation (Stuttg) ; 24(3): 113-5, 1985 Aug.
Artigo em Alemão | MEDLINE | ID: mdl-2931780

RESUMO

Starting out from describing an orthopaedic institute with an orthopaedic-rehabilitative approach, established in 1780 by Venel in the Suisse canton of Waadt, a historical retrospective is given of the field of rehabilitation of the physically disabled, going back for some notable industrial and social medicine aspects to Graeco-Roman times. Reference is in particular made to the peculiarities of 19th century private, residential care, and the development of modern-day facilities for persons with a physical disability is outlined.


Assuntos
Pessoas com Deficiência/história , Reabilitação/história , História do Século XVIII , História do Século XIX , História do Século XX , História Antiga , História Medieval , Humanos , Ortopedia/história
12.
Gesundheitswesen ; 54(10): 552-8, 1992 Oct.
Artigo em Alemão | MEDLINE | ID: mdl-1450539

RESUMO

The development of common education of handicapped and non-disabled children in kindergartens and schools has removed all doubt that disabled children are encouraged and helped to a considerable degree whereas non-disabled children acquire more social aptitude. In no case need one fear that their learning performance is negatively affected by integrated education. This is of course conditional on the availability of suitable conditions under which such integrated education takes place. The medical profession as a whole did not participate in the development and testing of integrative models and test projects. The main reasons for this are difficulties in communication between physicians and educationists, which require to be discussed. The article describes the need for cooperation by physicians in further development of integrative measures, their possibilities of influencing the development, and their special task in cooperating with educational experts, from a paedogical aspects; finally, the sociopolitical and medicopolitical tasks of the medical profession in Public Health services are pointed out.


Assuntos
Pessoas com Deficiência , Educação Inclusiva , Inclusão Escolar , Equipe de Assistência ao Paciente , Reabilitação/métodos , Socialização , Criança , Pré-Escolar , Terapia Combinada , Alemanha , Humanos , Lactente
13.
J Membr Biol ; 102(2): 105-19, 1988 May.
Artigo em Inglês | MEDLINE | ID: mdl-2458471

RESUMO

Cell-attached patch-clamp experiments were performed in cultured cardiocytes of neonatal rats at 19 degrees C to analyze elementary currents through single Na+ channels under control conditions and in the presence of the class 1 antiarrhythmic drugs amiodarone, propafenone, and diprafenone. As observed in a cell-attached patch with only one functioning Na+ channel, repetitive stepping of the membrane at 0.4 Hz triggered periodically channel openings except during a silent period of about 1.5 min. The latter began and ceased abruptly and did not fit the monoexponential distribution of the run length of sweeps without activity (blank sweeps). Treating the cardiocytes with amiodarone, propafenone or diprafenone (10 to 20 mumol/liter) led rapidly to a blockage and reduced the likelihood that membrane depolarization triggers the opening of Na+ channels. The number of blank sweeps increased at the expense of the number of sweeps with activity. The fraction of activity sweeps with superpositions, indicating the simultaneous activation of two or more Na+ channels, also declined. As tested with amiodarone, the run length of blank sweeps is voltage- and time-dependent, analogous to the intensity of the block of macroscopic Na+ currents. Open time, open-time distribution, unitary current size and the tendency to reopen did not differ in unblocked cardiac Na+ channels (i.e. that channel fraction capable of opening in the presence of amiodarone or propafenone) from the respective control values obtained before superfusing the cardiocytes with these drugs. Apart from its blocking action, the propafenone derivative diprafenone exerted additionally a modifying effect and reduced mean open time by up to 45%. In contrast to the block, this reduction in conducting state proved insensitive to changes in holding potential, at least between -130 and -150 mV, the range tested. This means that block was attenuated on hyperpolarization whereas the reduction in open time persisted. It is concluded that, in the presence of these drugs, unblocked cardiac Na+ channels share a number of properties with normal Na+ channels in the absence of these drugs. Shortening of channel lifetime by diprafenone may be indicative of a channel modification brought about possibly by a receptor-mediated facilitation of the transition from the open to the inactivated state.


Assuntos
Antiarrítmicos/farmacologia , Canais Iônicos/efeitos dos fármacos , Miocárdio/metabolismo , Sódio/metabolismo , Amiodarona/farmacologia , Animais , Células Cultivadas , Canais Iônicos/metabolismo , Cinética , Miocárdio/citologia , Propafenona/análogos & derivados , Propafenona/metabolismo , Propafenona/farmacologia , Ratos
14.
J Membr Biol ; 103(3): 283-91, 1988 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-2846849

RESUMO

Elementary Na+ currents through single cardiac Na+ channels were recorded at -50 mV in cell-attached patches from neonatal rat cardiocytes kept at holding potentials between -100 and -120 mV. Na+ channel activity may occur as burst-like, closely-timed repetitive openings with shut times close to 0.5-0.6 msec, indicating that an individual Na+ channel may reopen several times during step depolarization. A systematic quantitative analysis in 19 cell-attached patches showed that reopening may be quite differently pronounced. The majority, namely 16 patches, contained Na+ channels with a low tendency to reopen. This was evidenced from the average value for the mean number of openings per sequence, 2.5. Strikingly different results were obtained in a second group of three patches. Here, a mean number of openings per sequence of 3.42, 3.72, and 5.68 was found. Ensemble averages from the latter group of patches revealed macroscopic Na+ currents with a biexponential decay phase. Reconstructed Na+ currents from patches with poorly reopening Na+ channels were devoid of a slow decay component. This strongly suggests that reopening may be causally related to slow Na+ inactivation. Poorly pronounced reopening and, consequently, the lack of slow Na+ inactivation could be characteristic features of neonatal cardiac Na+ channels.


Assuntos
Miocárdio/metabolismo , Canais de Sódio/metabolismo , Sódio/metabolismo , Animais , Animais Recém-Nascidos , Células Cultivadas , Cinética , Miocárdio/citologia , Ratos
15.
Eur Biophys J ; 15(5): 289-92, 1988.
Artigo em Inglês | MEDLINE | ID: mdl-2452729

RESUMO

Patch clamp recordings from neonatal cardiac Na+ channels treated with N-bromoacetamide (NBA, 5-50 X 10- mol/l) showed modified Na+ channel activity. By chemical removal of inactivation, repetitive openings with an increased life time and burst-like activity occurred. NBA-modified Na+ channels differ in life time and may attain either a slightly (mean open time 3.1 +/- 0.2 ms) or a strongly (mean open time 15.2 +/- 1.4 ms) prolonged open state. This strongly suggests a heterogeneous population of NBA-modified Na+ channels in newborn rat cardiocytes.


Assuntos
Acetamidas/farmacologia , Canais Iônicos/efeitos dos fármacos , Miocárdio/metabolismo , Animais , Células Cultivadas , Técnicas In Vitro , Potenciais da Membrana , Ratos
16.
FASEB J ; 3(8): 1963-7, 1989 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-2542113

RESUMO

Elementary Na+ currents through single cardiac Na+ channels were recorded at 19 degrees C in patch clamp experiments with cultured neonatal rat cardiocytes. The metabolites of the glycolytic pathway, 2,3-diphosphoglycerate and glyceraldehyde phosphate, were identified as a novel class of modulators of Na+ channel activity. In micromolar concentrations (1-10 mumol/liter), their presence at the cytoplasmic membrane face increased the number of sequential openings during depolarization and prolonged the conductive channel state. As found after ensemble averaging, the decay kinetics of reconstructed macroscopic Na+ currents became retarded and slow Na+ inactivation may have been evoked. Both metabolites attenuated the rundown of channel activity that regularly develops after patch excision in the inside-out patch configuration. It is tempting to assume that interference with Na+ inactivation is the mode of action underlying the increase in single-channel activity.


Assuntos
Ácidos Difosfoglicéricos/metabolismo , Gliceraldeído 3-Fosfato/metabolismo , Gliceraldeído/análogos & derivados , Miocárdio/metabolismo , Canais de Sódio/metabolismo , 2,3-Difosfoglicerato , Animais , Animais Recém-Nascidos , Células Cultivadas , Glicólise , Cinética , Ratos
17.
J Membr Biol ; 112(1): 67-78, 1989 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-2556581

RESUMO

Elementary Na+ currents were recorded at 19 degrees C during 220-msec lasting step depolarizations in cell-attached and inside-out patches from cultured neonatal rat cardiocytes in order to study the modifying influence of iodate, bromate and glutaraldehyde on single cardiac Na+ channels. Iodate (10 mmol/liter) removed Na+ inactivation and caused repetitive, burst-like channel activity after treating the cytoplasmic channel surface. In contrast to normal Na+ channels under control conditions, iodate-modified Na+ channels attain two conducting states, a short-lasting one with a voltage-independent lifetime close to 1 msec and, likewise tested between -50 and +10 mV, a long-lasting one being apparently exponentially dependent on voltage. Channel modification by bromate (10 mmol/liter) and glutaraldehyde (0.5 mmol/liter) also included the occurrence of two open states. Also, burst duration depended apparently exponentially on voltage and increased when shifting the membrane in the positive direction, but there was no evidence for two bursting states. Chemically modified Na+ channels retain an apparently normal unitary conductance (12.8 +/- 0.5 pS). Of the two substates observed, one of them is remarkable in that it is mostly attained from full-state openings and is very short living in nature; the voltage-independent lifetime was close to 2 msec. Despite removal of inactivation, open probability progressively declined during membrane depolarization. The underlying deactivation process is strongly voltage sensitive but, in contrast to slow Na+ inactivation, responds to a voltage shift in the positive direction with a retardation in kinetics. Chemically modified Na+ channels exhibit a characteristic bursting state much shorter than in DPI-modified Na+ channels, a difference not consistent with the hypothesis of common kinetic properties in noninactivating Na+ channels.


Assuntos
Coração/efeitos dos fármacos , Iodatos/farmacologia , Iodo/farmacologia , Ativação do Canal Iônico/efeitos dos fármacos , Canais de Sódio/efeitos dos fármacos , Animais , Bromatos/farmacologia , Glutaral/farmacologia , Técnicas In Vitro , Cinética , Piperazinas/farmacologia , Ratos
18.
J Membr Biol ; 98(2): 125-33, 1987.
Artigo em Inglês | MEDLINE | ID: mdl-2444709

RESUMO

In cultured bovine aortic endothelial cells, elementary K+ currents were studied in cell-attached and inside-out patches using the standard patch-clamp technique. Two different cationic channels were found, a large channel with a mean unitary conductance of 150 +/- 10 pS and a small channel with a mean unitary conductance of 12.5 +/- 1.1 pS. The 150-pS channel proved to be voltage- and Ca2+-activatable and seems to be a K+ channel. Its open probability increased on membrane depolarization and, at a given membrane potential, was greatly enhanced by elevating the Ca2+ concentration at the cytoplasmic side of the membrane from 10(-7) to 10(-4) M. 150-pS channels were not influenced by the patch configuration in that patch excision neither induced run-down nor evoked channel activity in silent cell-attached patches. However, they were only seen in two out of 55 patches. The 12-pS channel was predominant, a nonselective cationic channel with almost the same permeability for K+ and Na+ whose open probability was minimal near -60 mV but increased on membrane hyperpolarization. An increase in internal Ca2+ from 10(-7) to 10(-4) M left the open probability unchanged. Although the K+ selectivity of the 150-pS channels remains to be elucidated, it is concluded that they may be involved in controlling Ca2+-dependent cellular functions. Under physiological conditions, 12-pS nonselective channels may provide an inward cationic pathway for Na+.


Assuntos
Cálcio/farmacologia , Endotélio Vascular/fisiologia , Canais Iônicos/fisiologia , Potássio/metabolismo , Animais , Aorta Torácica/fisiologia , Bovinos , Células Cultivadas , Canais Iônicos/efeitos dos fármacos , Cinética , Potenciais da Membrana/efeitos dos fármacos , Potássio/farmacologia
19.
Rehabilitation (Stuttg) ; 34(1): 8-15, 1995 Feb.
Artigo em Alemão | MEDLINE | ID: mdl-7716341

RESUMO

Between June 1991 and June 1992, a total of 39 rehabilitees aged 16 to 25 years were examined, i.e., 21 patients suffering from spina bifida and 18 patients suffering from traumatic paraplegia. Diagnostic instruments used were the Freiburg questionnaire on coping with illness (FKV 102), Goldberg et al's questionnaire for the evaluation of subjective wellbeing regarding health, and a self-constructed questionnaire for evaluating satisfaction with rehabilitation. Medical interviews on the present state of health and the present situation were held with each patient. The level of paralysis was taken as an indicator of the motor handicap present. The patients examined showed distinctly less confidence in doctors than adults do. From a subjective point of view, however, the confidence in doctors was good: among the coping strategies chosen, the compliance strategies ranked first and second, respectively, in the two groups. The coping strategy of "cognitive avoidance and dissimilation" is distinctly less common among spina bifida patients than among patients with traumatic paraplegia. They are less inclined to hope for a miracle, and take their handicap much more seriously than adolescents suffering from traumatic paraplegia. The higher the level of paraplegia, the more use is made of the coping strategy of "emotional control and social withdrawal". Regressive tendencies and depressive modes of coping were equally present in both groups. When investigating satisfaction with rehabilitation and with the own person, both groups showed very high satisfaction with the physical independence achieved and the possibilities of acting independently.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Adaptação Psicológica , Pessoas com Deficiência/psicologia , Paraplegia/psicologia , Papel do Doente , Traumatismos da Medula Espinal/psicologia , Disrafismo Espinal/psicologia , Adolescente , Adulto , Mecanismos de Defesa , Feminino , Humanos , Masculino , Paraplegia/reabilitação , Inventário de Personalidade , Relações Médico-Paciente , Traumatismos da Medula Espinal/reabilitação , Disrafismo Espinal/reabilitação
20.
Circ Res ; 64(5): 867-81, 1989 May.
Artigo em Inglês | MEDLINE | ID: mdl-2539922

RESUMO

In patch-clamped membranes from neonatal rat cardiocytes, elementary Na+ currents were recorded at 19 degrees C for study of the inhibitory influence of several antiarrhythmic drugs including lidocaine, diprafenone, propafenone, and prajmalium on DPI-modified cardiac Na+ channels. Diprafenone (20 mumol/l) and lidocaine (300 mumol/l) induced a voltage- and time-dependent block of reconstructed macroscopic sodium current (INa). The drugs depressed the sustained, noninactivating INa component (which reflects the number and open probability of DPI-modified Na+ channels) effectively, in a voltage- and time-dependent fashion. Once opened, DPI-modified Na+ channels are highly drug-sensitive. Antiarrhythmic drugs (propafenone, diprafenone, and, to a lesser extent, lidocaine) provoke a flicker block, that is, the long-lasting openings are chopped into a large number of short and grouped openings. This indicates rapid transitions between a drug-associated, blocked state and a drug-free, conducting state. The latter has a unitary conductance of 12 pS, very similar to the control value in the absence of antiarrhythmic drugs. The decrease in open time of drug-treated DPI-modified Na+ channels is concentration-dependent. Hill coefficients for propafenone of about 1.0 and for prajmalium of about 0.7 were calculated. A blocking rate constant of 6.1 x 10(7) mol-1sec-1 for propafenone, but of 1.5 x 10(7) mol-1sec-1 for prajmalium was obtained at -30 mV. The unblocking rate constant for propafenone was, also at -30 mV, about twice as large as the unblocking rate constant for prajmalium. The open channel block kinetics are essentially voltage-dependent. The affinity of the channel-associated drug receptor increases on membrane depolarization. The blocking rate constant was inversely related to the number of Na+ ions moving through the open channel. It is concluded that the manifestation of this voltage- and Na+-dependent flicker block is intimately related to removal of fast Na+ inactivation.


Assuntos
Antiarrítmicos/farmacologia , Catecolaminas/farmacologia , Imidazolinas , Miocárdio/citologia , Canais de Sódio/efeitos dos fármacos , Sódio/metabolismo , Animais , Células Cultivadas , Lidocaína/farmacologia , Miocárdio/metabolismo , Prajmalina/farmacologia , Propafenona/análogos & derivados , Propafenona/farmacologia , Ratos , Sódio/fisiologia
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