ABSTRACT
ABSTRACT PURPOSE: To evaluate the effects of levobupivacaine on neuromuscular transmission and neuromuscular blockade produced by pancuronium in vitro. METHODS: Thirty rats were distributed into groups (n = 5) according to the drug used alone or in combination: Group I - levobupivacaine (5 µg.mL-1); Group II - pancuronium (2 µg.mL-1); Group III - pancuronium (2 µg.mL-1) + levobupivacaine (5µg.mL-1). The following parameters were evaluated: 1) amplitude of diaphragmatic response to indirect stimulation, before and 60 minutes after the addition of levobupivacaine and pancuronium alone, and after the addition of levobupivacaine combined with pancuronium; 2) membrane potentials (MP) and miniature endplate potentials (MEPP). RESULTS: Levobupivacaine alone did not alter the amplitude of muscle response and MP. In preparations previoulsy exposed to levobupivacaine, the block with pancuronium was significantly denser (90.2 ± 15.2%), showing a significant difference (p=0.031) in comparison to the block produced by pancuronium alone (48.9% ± 9.8%). There was a decrease in the frequency and amplitude of MEPPs. CONCLUSION: Levobupivacaine potentiated the neuromuscular blockade produced by pancuronium, confirming a presynaptic action by a decrease in miniature endplate potentials.
Subject(s)
Animals , Male , Pancuronium/pharmacology , Bupivacaine/analogs & derivatives , Synaptic Transmission/drug effects , Neuromuscular Blockade , Neuromuscular Junction/drug effects , Bupivacaine/pharmacology , Diaphragm/drug effects , Diaphragm/innervation , Rats, Wistar , Neuromuscular Nondepolarizing Agents/pharmacology , Synaptic Transmission/physiology , Models, Animal , Drug Therapy, Combination , Electric Stimulation/methods , Anesthetics, Local/pharmacology , Membrane Potentials/drug effects , Membrane Potentials/physiology , Neuromuscular Junction/physiologyABSTRACT
O objetivo deste estudo foi identificar fatores associados à utilização dos serviços odontológicos, públicos (básicos e especializados) e privados. Foi realizado inquérito populacional de base domiciliar em dois municípios da Bahia, Brasil. Informantes-chave forneceram dados socioeconômicos e de utilização dos serviços odontológicos (desfecho). A organização do serviço público odontológico local foi classificada em pior/melhor. Realizou-se regressão logística politômica uni e múltipla. Do total de 1.290 indivíduos, 38,76% usaram o serviço privado, 33,80% atenção básica e 17,29% atenção básica e o Centro de Especialidades Odontológicas (CEO). Um perfil de vulnerabilidade social foi associado ao uso do serviço público, quando comparado ao privado. Menor escolaridade (OR = 1,47; IC95%: 1,03-2,10) e pior organização do serviço (OR = 1,74; IC95%: 1,22-2,48) foram associados ao menor uso da rede de serviços atenção básica e CEO em comparação ao uso exclusivo da atenção básica. A desigualdade na utilização dos serviços odontológicos foi observada mesmo quando comparados grupos mais homogêneos, como os usuários dos serviços públicos.
The aim of this study was to identify factors associated with the use of primary and specialized public dental health services and private services. A population-based household survey was conducted in two cities of Bahia State, Brazil. Key informants provided data on socioeconomic variables and use of dental health services. Organization of the local public dental health service was ranked as worse versus better. Univariate and multivariate polytomous logistic regression was performed. Of the total of 1,290 individuals, 38.76% used private services, 33.80% used public primary care, and 17.29% used both primary care and the Center for Dental Specialties. Less use of both primary care and specialized public services was associated with lower education (OR = 1.47; 95%CI: 1.03-2.10) and worse organization of services (OR = 1.74; 95%CI: 1.22-2.48), when compared to the exclusive use of primary care. The study showed inequality in the use of dental services, even when comparing more homogeneous groups, namely users of public services.
El objetivo de este estudio fue identificar los factores asociados al uso de los servicios odontológicos (primarios y especializados) públicos y privados. Se realizó una encuesta poblacional en dos ciudades de Bahía, Brasil. Los informantes clave contestaron cuestiones socioeconómicas y de utilización de los servicios odontológicos (resultado). La organización de los servicios odontológicos públicos locales fue clasificada en peor/mejor. Se realizó regresión simple y múltiple con variable politómica. Del total de 1.290 personas, un 38,76% utilizaron el servicio privado, un 33,80% la atención primaria y un 17,29% atención primaria y el Centro de Especialidades Dentales (CED). Una menor escolaridad (OR = 1,47; IC95%: 1.03-2.10) y una peor organización de servicio (OR = 1,74; IC95%: 1,22-2,48) se asociaron con un menor uso de la red de servicios de atención primaria y CED, en comparación con el uso exclusivo de la atención primaria. La desigualdad en el uso de los servicios dentales se observó incluso cuando se comparan grupos más homogéneos, como usuarios de servicios públicos.
Subject(s)
Animals , Rabbits , Action Potentials/physiology , Membrane Potentials/physiology , Myocytes, Cardiac/physiology , Potassium/metabolism , Tacrolimus Binding Proteins/metabolism , Ventricular Function, Left/drug effects , Action Potentials/drug effects , Cells, Cultured , Membrane Potentials/drug effects , Myocytes, Cardiac/drug effects , Up-Regulation/physiologyABSTRACT
Introduction: Tuberculosis is a common opportunistic infection in renal transplant patients. Objective: To obtain a clinical and laboratory description of transplant patients diagnosed with tuberculosis and their response to treatment during a period ranging from 2005 to 2013 at the Pablo Tobón Uribe Hospital. Methods: Retrospective and descriptive study. Results: In 641 renal transplants, tuberculosis was confirmed in 12 cases. Of these, 25% had a history of acute rejection, and 50% had creatinine levels greater than 1.5 mg/dl prior to infection. The disease typically presented as pulmonary (50%) and disseminated (33.3%). The first phase of treatment consisted of 3 months of HZRE (isoniazid, pyrazinamide, rifampicin and ethambutol) in 75% of the cases and HZME (isoniazid, pyrazinamide, moxifloxacin and ethambutol) in 25% of the cases. During the second phase of the treatment, 75% of the cases received isoniazid and rifampicin, and 25% of the cases received isoniazid and ethambutol. The length of treatment varied between 6 and 18 months. In 41.7% of patients, hepatotoxicity was associated with the beginning of anti-tuberculosis therapy. During a year-long follow-up, renal function remained stable, and the mortality rate was 16.7%. Conclusion: Tuberculosis in the renal transplant population studied caused diverse nonspecific symptoms. Pulmonary and disseminated tuberculosis were the most frequent forms and required prolonged treatment. Antituberculosis medications had a high toxicity and mortality. This infection must be considered when patients present with a febrile syndrome of unknown origin, especially during the first year after renal transplant. .
Introdução: A tuberculose é uma infecção oportunista comum em pacientes transplantados renais. Objetivo: Oferecer uma descrição clínica e laboratorial de pacientes transplantados com diagnóstico de tuberculose e sua resposta ao tratamento durante o período entre 2005 e 2013 no Hospital Pablo Tobón Uribe. Métodos: Estudo retrospectivo descritivo. Resultados: Em 641 transplantes renais, a tuberculose foi confirmada em 12 pacientes. Destes, 25% tinham histórico de rejeição aguda e 50% apresentaram níveis de creatinina superiores a 1,5 mg/dl antes da infecção. A patologia geralmente se apresentava como pulmonar (50%) e disseminada (33,3%). A primeira fase do tratamento consistiu de três meses de HZRE (isoniazida, pirazinamida, rifampicina e etambutol) em 75% dos casos e HZME (isoniazida, pirazinamida, moxifloxacina e etambutol) em 25% dos pacientes. Durante a segunda fase do tratamento, 75% dos pacientes receberam isoniazida e rifampicina e 25% isoniazida e etambutol. A duração do tratamento variou entre seis e 18 meses. Em 41,7% dos pacientes, hepatotoxicidade foi associada ao início do tratamento da tuberculose. Durante o seguimento de um ano a função renal manteve-se estável e a taxa de mortalidade foi de 16,7%. Conclusão: A tuberculose foi responsável por diversos sintomas inespecíficos na população de transplantados renais estudada. Tuberculose pulmonar e disseminada foram as formas mais frequentes de acometimento e necessitaram de tratamento prolongado. Medicamentos contra a tuberculose apresentaram alta toxicidade e mortalidade. Esta infecção deve ser considerada quando o paciente apresenta síndrome febril de origem desconhecida, especialmente durante o primeiro ano após o transplante renal. .
Subject(s)
Animals , Female , Male , Mice , Locus Coeruleus/drug effects , Narcotics/pharmacology , Neural Inhibition/drug effects , Neurons/drug effects , Potassium Channels/metabolism , Barium/pharmacology , Calcium/metabolism , Enkephalin, Methionine/pharmacology , G Protein-Coupled Inwardly-Rectifying Potassium Channels , GTP-Binding Proteins/metabolism , Heterozygote , Homozygote , Ion Channel Gating/drug effects , Ion Channel Gating/physiology , Locus Coeruleus/cytology , Locus Coeruleus/physiology , Mice, Knockout , Membrane Potentials/drug effects , Membrane Potentials/physiology , Neural Inhibition/physiology , Neurons/physiology , Patch-Clamp Techniques , Protein Subunits , Potassium Channel Blockers/pharmacology , Potassium Channels, Inwardly Rectifying/antagonists & inhibitors , Potassium Channels, Inwardly Rectifying/deficiency , Potassium Channels, Inwardly Rectifying/genetics , Potassium Channels, Inwardly Rectifying/metabolism , Potassium Channels/deficiency , Potassium Channels/geneticsABSTRACT
Sialic acid is responsible for the negative charge of the erythrocyte. The decrease of sialic acid has hemodynamical and hemorheological importance. The aim was to study the effect of A. lumbricoides on the erythrocyte superficial charge using the Partition Method in aqueous two-phase system in order to indirectly evaluate the alteration of sialic acid in the red cells. We worked with five parasite extracts (AE) and larvae concentrate (LC). Erythrocyte superficial charge was studied by working with non-treated (Controls) and treated erythrocytes. The treatment consisted of incubating the erythrocytes with AE or LC for 30 minutes at 4 ºC, 20 ºC and 37 ºC. The red cells were separated in a sensitive charge two-phase system (Dx/ PEG). The partition coefficient (P) of treated and untreated erythrocytes were calculated. The results showed a P decrease at the three temperatures for red cells treated with four of the AE. The remaining extract did change P values at any of the temperatures studied. The erythrocytes treated with LC showed a decrease in the P value at 37 ºC and 4 ºC but no change was observed at 25 ºC. Statistical analysis concluded that P values were significantly lower in treated erythrocytes than in their corresponding untreated ones (p < 0.05). The Partition Method showed that this parasite alters the erythrocyte superficial charge which may indicate that it can catch sialic acid.
La disminución de ácido sialico, responsable de la carga negativa del eritrocito, tiene importancia hemodinámica y hemorreológica. El objetivo fue estudiar el efecto de A. lumbricoides sobre la carga superficial eritrocitaria aplicando el método de partición en sistemas bifásicos acuosos, a los fines de evaluar de manera indirecta la alteración de acido sialico de los eritrocitos. Se trabajó con 5 extractos del parásito adulto (EA) y con un concentrado de larvas (500-600 larvas/mL) (CL). Se estudió la carga superficial eritrocitaria, trabajando con eritrocitos no tratados y tratados. El tratamiento consistió en la incubación de los eritrocitos con EA o CL durante 30 minutos a 4 ºC, 25 ºC y 37 ºC. Los eritrocitos fueron sometidos a la separación en un sistema bifásico carga sensible constituido por Dx / PEG. Se calculó el coeficiente de reparto (P), de los eritrocitos sin tratar y tratados. Los resultados mostraron disminución de P a las 3 temperaturas, en hematíes tratados con 4 de los EA. El EA restante no modificó los valores de P a ninguna de las temperaturas estudiadas. CL produjo la disminución de P a 37 ºC y 4 ºC, pero no se observó modificación a 25 ºC. Los análisis estadísticos concluyeron que los valores de P son significativamente menores en los eritrocitos tratados que en los respectivos eritrocitos sin tratar (p < 0.05). El método de partición demostró que A. lumbricoides altera la carga superficial eritrocitaria lo que indicaría que el parásito, tanto en su estado adulto como en sus fases larvales, puede captar acido sialico.
Subject(s)
Animals , Ascaris lumbricoides/chemistry , Erythrocyte Membrane/chemistry , Erythrocytes/chemistry , Membrane Potentials/physiology , N-Acetylneuraminic Acid/analysis , Cell Separation/methods , Erythrocyte Membrane/physiology , Erythrocytes/physiology , Models, Biological , Osmolar ConcentrationABSTRACT
The isolated chick retina provides an in vitro tissue model, in which two protocols were developed to verify the efficacy of a peptide in the excitability control of the central gray matter. In the first, extra-cellular potassium homeostasis is challenged at long intervals and in the second, a wave is trapped in a ring of tissue causing the system to be under self-sustained challenge. Within the neuropil, the extra-cellular potassium transient observed in the first protocol was affected from the initial rising phase to the final concentration at the end of the five-minute pulse. There was no change in the concomitants of excitation waves elicited by the extra-cellular rise of potassium. However, there was an increase on the elicited waves latency and/or a rise in the threshold potassium concentration for these waves to appear. In the second protocol, the wave concomitants and the propagation velocity were affected by the peptide. The results suggest a synergetic action of the peptide on glial and synaptic membranes: by accelerating the glial Na/KATPase and changing the kinetics of the glial potassium channels, with glia tending to accumulate KCl. At the same time, there is an increase in potassium currents through nerve terminals.
Retinas de pinto isoladas proporcionam um modelo de tecidos in vitro, para o qual dois protocolos foram desenvolvidos para verificar a eficácia de um peptídeo no controle da excitabilidade da matéria cinzenta central. No primeiro, a homeostase do potássio extra-celular é desafiada por intervalos longos (1 hora) e no segundo, uma onda é capturada em um anel de tecido, de tal maneira que o sistema permaneça em estado de desafio auto-sustentado. Dentro da neuropil, o transiente de potássio extra-celular observado no primeiro protocolo foi afetado da fase de início de aumento à concentração final, ao final do pulso de cinco minutos. Não há mudanças nos parâmetros concomitantes das ondas de excitação geradas pelo aumento do potássio extra-celular. Entretanto, houve um aumento da latência das ondas geradas e/ou um aumento no nível de concentração de potássio necessário para gerar a onda. No segundo protocolo, os parâmetros concomitantes da onda e sua velocidade de propagação foram afetados pelo peptídeo. Os resultados sugerem uma ação sinergética do peptídeo nas membranas gliais e sinápticas: acelerando o Na/KATPase glial e mudando a cinética dos canais de potássio gliais, com a glia tendendo a acumular KCl. Nesse período, não há aumento nas correntes de potássio nas terminações nervosas.
Subject(s)
Animals , Membrane Potentials/physiology , Neurons/physiology , Periaqueductal Gray/physiology , Potassium/metabolism , Retina/physiology , Somatostatin/pharmacology , Chickens , Electric Stimulation , Membrane Potentials/drug effects , Periaqueductal Gray/drug effects , Retina/drug effectsABSTRACT
Antecedentes. Los canales iónicos ASIC (del inglés Acid Sensing Ion Channel) son canales iónicos activados por reducciones transitorias en el pH extracelular. Pese a no conocerse con exactitud su mecanismo, la activación ocurre por medio de la unión de protones al dominio extracelular del canal y es modulada por iones calcio y zinc. Objetivo. El hecho de que los cationes divalentes modifiquen el funcionamiento del canal nos llevó a preguntar si el plomo, otro catión divalente, sería capaz de alterar el funcionamiento de los ASIC. Métodos y resultados. Mediante el uso de la técnica de fijación de voltaje en configuración de célula completa en las neuronas de los ganglios de la raíz dorsal de la rata, encontramos que el plomo inhibe la corriente ASIC en forma dependiente de la concentración. Conclusiones. Estos resultados contribuyen a definir los mecanismos de activación de los canales ASIC y a explicar algunos de los mecanismos tóxicos del plomo en el organismo.
BACKGROUND: Acid sensing ion channels (ASIC) are ionic channels activated by transient pH reductions in the ext raceilularenvi ronment. Although the activation mechanism is not fully elucidated, it is clear that the channel is activated by proton binding to its extraceilular domain, a process that is modulated by calcium and zinc. OBJECTIVE: The fact that divalent cations are able to modify ASIC operation, lead us to consider if lead, anotherdivalent cation and widely distributed neurotoxicant, is also capable to affect ASIC function. METHODS: For this purpose, we recordedASiC currents in rat dorsal root ganglion neurons using the whole cell patch-clamp technique. RESULTS: The results indicated that lead inhibits ASIC currents in a concentration -dependent fashion. CONCLUSIONS: These results contribute to the understanding of the activation mechanism of ASIC and to explain some of the toxic mechanisms of lead in the organism.
Subject(s)
Animals , Rats , Sodium Channels/drug effects , Organometallic Compounds/toxicity , Ganglia, Spinal/drug effects , Membrane Proteins/drug effects , Nerve Tissue Proteins/drug effects , Sodium Channels/physiology , Ganglia, Spinal/physiopathology , Membrane Potentials/drug effects , Membrane Potentials/physiology , Membrane Proteins/physiology , Nerve Tissue Proteins/physiology , Rats, WistarSubject(s)
Animals , Humans , Rabbits , Calcium Channels/metabolism , Heart Rate/physiology , Sinoatrial Node/physiology , Sodium Channels/metabolism , Action Potentials , Angina Pectoris/drug therapy , Benzazepines/therapeutic use , Calcium Channels/drug effects , Cyclic Nucleotide-Gated Cation Channels/therapeutic use , Electric Conductivity , Heart Rate/drug effects , Membrane Potentials/drug effects , Membrane Potentials/physiology , Sinoatrial Node/cytology , Sinoatrial Node/metabolism , Sodium Channels/drug effectsABSTRACT
Amygdala plays a very important role in the mediation of pain. In the present study the behaviour of the amygdalar neurons in response to various peripheral noxious stimuli was observed. Noxious mechanical, thermal, electrical, chemical and the non-noxious stimuli (touch) were applied individually to the animal and then the neuronal responses to these stimuli were recorded. Our results showed that the majority of amygdalar units recorded from medial, lateral and basolateral nuclei, responded to different peripheral noxious (thermal, electrical, chemical mechanical) and non-noxious stimuli by excitation. However few neurons decreased their activity on stimulation. Some of these neurons also exhibited after discharge following application of higher intensity of noxious stimuli.
Subject(s)
Action Potentials , Amygdala/physiology , Animals , Female , Membrane Potentials/physiology , Nociceptors/physiology , Rats , Rats, Wistar , Signal Transduction/physiologyABSTRACT
Large conductance Ca2+-activated K+ (BK) channels belong to the S4 superfamily of K+ channels that include voltage-dependent K+ (Kv) channels characterized by having six (S1-S6) transmembrane domains and a positively charged S4 domain. As Kv channels, BK channels contain a S4 domain, but they have an extra (S0) transmembrane domain that leads to an external NH2-terminus. The BK channel is activated by internal Ca2+, and using chimeric channels and mutagenesis, three distinct Ca2+-dependent regulatory mechanisms with different divalent cation selectivity have been identified in its large COOH-terminus. Two of these putative Ca2+-binding domains activate the BK channel when cytoplasmic Ca2+ reaches micromolar concentrations, and a low Ca2+ affinity mechanism may be involved in the physiological regulation by Mg2+. The presence in the BK channel of multiple Ca2+-binding sites explains the huge Ca2+ concentration range (0.1 ìM-100 ìM) in which the divalent cation influences channel gating. BK channels are also voltage-dependent, and all the experimental evidence points toward the S4 domain as the domain in charge of sensing the voltage. Calcium can open BK channels when all the voltage sensors are in their resting configuration, and voltage is able to activate channels in the complete absence of Ca2+. Therefore, Ca2+ and voltage act independently to enhance channel opening, and this behavior can be explained using a two-tiered allosteric gating mechanism.
Subject(s)
Animals , Calcium Channels/physiology , Large-Conductance Calcium-Activated Potassium Channels/physiology , Allosteric Regulation/physiology , Ion Channel Gating/physiology , Membrane Potentials/physiologyABSTRACT
The Maxi-chloride channel was the first ion channel described by electrophysiological methods in placenta. Because it is difficult to access a complex epithelium such as the placenta for electrophysiological procedures, the studies of ion channels from placental membranes have been performed only very recently. It was only in 1993 that a direct demonstration of a high-conductance chloride channel in apical membranes of intact trophoblastic epithelium was mentioned, and two years later, the description of this channel was reported from purified placental apical membranes reconstituted into artificial lipid membranes suitable for patch-clamp recordings. This brief review comments on the work done with regard to the electrophysiological characterization and regulation of the large-conductance or "Maxi" chloride channel and its contribution to the development of a cellular model for syncytiotrophoblast ion transport.
Subject(s)
Female , Humans , Pregnancy , Chloride Channels/metabolism , Membrane Potentials/physiology , Placenta/metabolism , Trophoblasts/metabolism , Electrophysiology , Ion Transport , Patch-Clamp Techniques , Placenta/physiologyABSTRACT
We used the single-microelectrode voltage-clamp technique to record ionic currents from pancreatic â-cells within intact mouse islets of Langerhans at 37C, the typical preparation for studies of glucose-induced "bursting" electrical activity. Cells were impaled with intracellular microelectrodes, and voltage pulses were applied in the presence of tetraethylammonium. Under these conditions, a voltage-dependent Ca2+ current (I Cav), containing L-type and non-L-type components, was observed. The current measured in situ was larger than that measured in single cells with whole-cell patch clamping, particularly at membrane potentials corresponding to the action potentials of â-cell electrical activity. The temperature dependence of I Cav was not sufficient to account for the difference in size of the currents recorded with the two methods. During prolonged pulses, the voltage-dependent Ca2+ current measured in situ displayed both rapid and slow components of inactivation. The rapid component was Ca2+-dependent and was inhibited by the membrane-permeable Ca2+ chelator, BAPTA-AM. The effect of BAPTA-AM on â-cell electrical activity then demonstrated that Ca2+-dependent inactivation of I Cav contributes to action potential repolarization and to control of burst frequency. Our results demonstrate the utility of voltage clamping â-cells in situ for determining the roles of ion channels in electrical activity and insulin secretion.
Subject(s)
Animals , Mice , Calcium Channels/physiology , Insulin-Secreting Cells/physiology , Membrane Potentials/physiology , Electrophysiology , Insulin-Secreting Cells/drug effects , Microelectrodes , Patch-Clamp Techniques , Tetraethylammonium/pharmacologyABSTRACT
Based on indirect evidence, a role for synaptically released copper and zinc as modulators of neuronal activity has been proposed. To test this proposal directly, we studied the effect of copper, zinc, and other divalent cations on voltage-dependent currents in dissociated toad olfactory neurons and on their firing rate induced by small depolarizing currents. Divalent cations in the nanomolar range sped up the activation kinetics and increased the amplitude of the inward sodium current. In the micromolar range, they caused a dose dependent inhibition of the inward Na+ and Ca2+ currents (INa and ICa) and reduced de amplitude of the Ca2+-dependent K+ outward current (ICa-K). On the other hand, the firing rate of olfactory neurons increased when exposed to nanomolar concentration of divalent cations and decreased when exposed to micromolar concentrations. This biphasic effect of divalent cations on neuronal excitability may be explained by the interaction of these ions with high and low affinity sites in voltage-gated channels. Our results support the idea that these ions are normal modulators of neuronal excitability.
Subject(s)
Animals , Copper/pharmacology , Olfactory Receptor Neurons/drug effects , Zinc/pharmacology , Anura , Action Potentials/drug effects , Action Potentials/physiology , Cell Membrane , Cations, Divalent/pharmacology , Electric Stimulation , Membrane Potentials/drug effects , Membrane Potentials/physiology , Olfactory Receptor Neurons/physiology , Signal Transduction/physiologyABSTRACT
A change in pH can alter the intracellular concentration of electrolytes such as intracellular Ca2+ and Na+ ([Na+]i) that are important for the cardiac function. For the determination of the role of pH in the cardiac magnesium homeostasis, the intracellular Mg2+ concentration ([Mg2+]i), membrane potential and contraction in the papillary muscle of guinea pigs using ion-selective electrodes changing extracellular pH ([pH]o) or intracellular pH ([pH]i) were measured in this study. A high CO2-induced low [pH]o causes a significant increase in the [Mg2+]i and [Na+]i, which was accompanied by a decrease in the membrane potential and twitch force. The high [pH]o had the opposite effect. These effects were reversible in both the beating and quiescent muscles. The low [pH]o-induced increase in [Mg2+]i occurred in the absence of [Mg2+]o. The [Mg2+]i was increased by the low [pH]i induced by propionate. The [Mg2+]i was increased by the low [pH]i induced by NH4Cl-prepulse and decreased by the recovery of [pH]i induced by the removal of NH4Cl. These results suggest that the pH can modulate [Mg2+]i with a reverse relationship in heart, probably by affecting the intracellular Mg2+ homeostasis, but not by Mg2+ transport across the sarcolemma.
Subject(s)
Animals , Female , Male , Cations, Divalent , Guinea Pigs , Heart Ventricles/metabolism , Hydrogen-Ion Concentration , Ion Transport/physiology , Ion-Selective Electrodes/veterinary , Magnesium/metabolism , Membrane Potentials/physiology , Papillary Muscles/metabolism , Propionates/pharmacology , Sodium/metabolismABSTRACT
RACIONAL: A atividade respiratória das mitocôndrias está associada à lesão por isquemia e reperfusão do fígado. OBJETIVO: Investigar in vitro se há obrigatoriedade de impedimento da respiração mitocondrial para que a lesão por isquemia e reperfusão do fígado possa ser detectada. MATERIAIS E MÉTODOS: Vinte e quatro cães de ambos os gêneros foram divididos nos seguintes grupos: controle, cães operados sem sofrer isquemia ou reperfusão hepática; I60, cães submetidos a 60 minutos de isquemia do fígado; I30/R60, cães submetidos a 30 minutos de isquemia e 60 minutos de reperfusão do fígado e I45/R120, cães submetidos a 45 minutos de isquemia e 120 de reperfusão do fígado. Amostras de fígado foram obtidas para dosagem de malondialdeído, para estudo da respiração mitocondrial por meio de traços polarográficos e para avaliação do potencial de membrana mitocondrial. Sangue foi obtido para dosagem de transaminases e desidrogenase lática. RESULTADOS: O grupo I45/R120 apresentou evidente aumento dos valores de transaminases, desidrogenase lática, aumento dos valores de malondialdeído e tendência à diminuição da respiração mitocondrial estimulada por adenosina difosfato, sem haver prejuízo irreversível para a fosforilação oxidativa ou para o potencial de membrana mitocondrial. CONCLUSÃO: A lesão por isquemia e reperfusão do fígado do cão pode ser documentada sem que haja prejuízo demonstrável para a função mitocondrial. Dados referentes à respiração mitocondrial podem não mostrar diferenças significativas em relação aos controles, mesmo em situações de evidente lesão tecidual por isquemia e reperfusão do fígado.
Subject(s)
Animals , Dogs , Female , Male , Ischemia/physiopathology , Liver/blood supply , Mitochondria, Liver/physiology , Reperfusion Injury/physiopathology , Alanine Transaminase/blood , Aspartate Aminotransferases/blood , Ischemia/diagnosis , L-Lactate Dehydrogenase/blood , Liver/metabolism , Membrane Potentials/physiology , Oxygen Consumption/physiology , Random Allocation , Reperfusion Injury/diagnosisABSTRACT
Mitochondrial ion transport, oxidative phosphorylation, redox balance, and physical integrity are key factors in tissue survival following potentially damaging conditions such as ischemia/reperfusion. Recent research has demonstrated that pharmacologically activated inner mitochondrial membrane ATP-sensitive K+ channels (mitoK ATP) are strongly cardioprotective under these conditions. Furthermore, mitoK ATP are physiologically activated during ischemic preconditioning, a procedure which protects against ischemic damage. In this review, we discuss mechanisms by which mitoK ATP may be activated during preconditioning and the mitochondrial and cellular consequences of this activation, focusing on end-effects which may promote ischemic protection. These effects include decreased loss of tissue ATP through reverse activity of ATP synthase due to increased mitochondrial matrix volumes and lower transport of adenine nucleotides into the matrix. MitoK ATP also decreases the release of mitochondrial reactive oxygen species by promoting mild uncoupling in concert with K+/H+ exchange. Finally, mitoK ATP activity may inhibit mitochondrial Ca2+ uptake during ischemia, which, together with decreased reactive oxygen release, can prevent mitochondrial permeability transition, loss of organelle function, and loss of physical integrity. We discuss how mitochondrial redox status, K+ transport, Ca2+ transport, and permeability transitions are interrelated during ischemia/reperfusion and are determinant factors regarding the extent of tissue damage.
Subject(s)
Humans , Mitochondria, Heart/metabolism , Myocardial Reperfusion Injury/metabolism , Potassium Channels/physiology , Biological Transport , Ischemic Preconditioning, Myocardial , Membrane Potentials/physiology , Myocardial Ischemia/metabolism , Oxidative Stress , Phosphorylation , Potassium Channels/metabolism , Potassium/metabolismABSTRACT
The nucleus tractus solitarius (NTS) plays an important role in the control of autonomic reflex functions. Glutamate, acting on N-methyl-D-aspartate (NMDA) and non-NMDA ionotropic receptors, is the major neurotransmitter in this nucleus, and the relative contribution of each receptor to signal transmission is unclear. We have examined NMDA excitatory postsynaptic currents (NMDA-EPSCs) in the subpostremal NTS using the whole cell patch clamp technique on a transverse brainstem slice preparation. The NMDA-EPSCs were evoked by stimulation of the solitary tract over a range of membrane potentials. The NMDA-EPSCs, isolated pharmacologically, presented the characteristic outward rectification and were completely blocked by 50 æM DL-2-amino-5-phosphonopentanoic acid. The I-V relationship of the NMDA response shows that current, with a mean (± SEM) amplitude of -41.2 ± 5.5 pA, is present even at a holding potential of -60 mV, suggesting that the NMDA receptors are weakly blocked by extracellular Mg2+ at near resting membrane potentials. This weak block can also be inferred from the value of 0.67 ± 0.17 for parameter delta obtained from a fit of the Woodhull equation to the I-V relationship. The maximal inward current measured on the I-V relationship was at -38.7 ± 4.2 mV. The decay phase of the NMDA currents was fitted with one exponential function with a decay time constant of 239 ± 51 and 418 ± 80 ms at a holding potential of -60 and +50 mV, respectively, which became slower with depolarization (e-fold per 145 mV). The biophysical properties of the NMDA receptors observed in the present study suggest that these receptors in the NTS contain NR2C subunits and may contribute to the synaptic signal integration.
Subject(s)
Animals , Male , Female , Rats , Neurons/chemistry , Receptors, N-Methyl-D-Aspartate/analysis , Solitary Nucleus/cytology , Synapses/physiology , Synaptic Transmission/physiology , Electrophysiology , Membrane Potentials/physiology , Neurons/physiology , Patch-Clamp Techniques , Rats, Wistar , Solitary Nucleus/physiologyABSTRACT
T84 is an established cell line expressing an enterocyte phenotype whose permeability properties have been widely explored. Osmotic permeability (P OSM), hydraulic permeability (P HYDR) and transport-associated net water fluxes (J W-transp), as well as short-circuit current (I SC), transepithelial resistance (R T), and potential difference (deltaV T) were measured in T84 monolayers with the following results: P OSM 1.3 ± 0.1 cm.s-1 x 10-3; P HYDR 0.27 ± 0.02 cm.s-1; R T 2426 ± 109 omega.cm², and deltaV T 1.31 ± 0.38 mV. The effect of 50 æM 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (DCEBIO), a "net Cl- secretory agent", on T84 cells was also studied. We confirm the reported important increase in I SC induced by DCEBIO which was associated here with a modest secretory deltaJ W-transp. The present results were compared with those reported using the same experimental approach applied to established cell lines originating from intestinal and renal epithelial cells (Caco-2, LLC-PK1 and RCCD-1). No clear association between P HYDR and R T could be demonstrated and high P HYDR values were observed in an electrically tight epithelium, supporting the view that a "water leaky" barrier is not necessarily an "electrically leaky" one. Furthermore, the modest secretory deltaJ W-transp was not consistent with previous results obtained with RCCD-1 cells stimulated with vasopressin (absorptive fluxes) or with T84 cells secreting water under the action of Escherichia coli heat stable enterotoxin. We conclude that, while the presence of aquaporins is necessary to dissipate an external osmotic gradient, coupling between water and ion transport cannot be explained by a simple and common underlying mechanism.
Subject(s)
Humans , Epithelial Cells/metabolism , Hydrostatic Pressure , Osmosis/physiology , Water/metabolism , Cell Line/metabolism , Electrophysiology , Epithelial Cells/physiology , Membrane Potentials/physiology , Osmolar Concentration , PermeabilityABSTRACT
Here we compare excitation-contraction coupling in single muscle cells of frogs and rats. Because amphibians have isoform 3 (or b) of the ryanodine receptor/Ca2+ release channel, in addition to 1 (a), which is also present in the mammal, any extra feature present in the frog may in principle be attributed to isoform 3. Ca2+ release under voltage clamp depolarization has a peak and a steady phase in both taxonomic classes, but the peak is more marked in the frog, where the ratio of amplitudes of the two phases is voltage-dependent. This dependence is a hallmark of CICR. Confocal imaging identified Ca2+ sparks in the frog, but not in the voltage-clamped rat cells. Because Ca2+ sparks involve CICR both observations indicate that the contribution of CICR is minor or null in the mammal. The "couplon" model well accounts for observations in the frog, but assumes a structure that we now know to be valid only for the rat. A revised model is proposed, whereby the isoform 3 channels, located parajunctionally, are activated by CICR and contribute its characteristic global and local features. Several issues regarding the roles of different channels remain open to further study.
Subject(s)
Animals , Rats , Calcium/metabolism , Ryanodine Receptor Calcium Release Channel/physiology , Ryanodine Receptor Calcium Release Channel/metabolism , Muscle Contraction/physiology , Sarcoplasmic Reticulum/physiology , Anura , Protein Isoforms/physiology , Models, Biological , Membrane Potentials/physiology , Species Specificity , Calcium Signaling/physiologyABSTRACT
The pancreatic acinar unit is a classical example of a polarized tissue. Even in isolation, these cells retain their polarity, and this has made them particularly useful for Ca2+ signaling studies. In 1990, we discovered that this cell has the capability of producing both local cytosolic and global Ca2+ signals. The mechanisms underlying this signal generation have now been established. Furthermore, it has become clear that the local signals are sufficient for the control of both fluid and enzyme secretion, whereas prolonged global signals are dangerous and give rise to acute pancreatitis, a disease where the pancreas digests itself.