RESUMO
The 3' noncoding region (3' NCR) of flaviviruses contains secondary and tertiary structures essential for virus replication. Previous studies of yellow fever virus (YFV) and dengue virus have found that modifications to the 3' NCR are sometimes associated with attenuation in vertebrate and/or mosquito hosts. The 3' NCRs of 117 isolates of South American YFV have been examined, and major deletions and/or duplications of conserved RNA structures have been identified in several wild-type isolates. Nineteen isolates (designated YF-XL isolates) from Brazil, Trinidad, and Venezuela, dating from 1973 to 2001, exhibited a 216-nucleotide (nt) duplication, yielding a tandem repeat of conserved hairpin, stem-loop, dumbbell, and pseudoknot structures. YF-XL isolates were found exclusively within one subclade of South American genotype I YFV. One Brazilian isolate exhibited, in addition to the 216-nt duplication, a deletion of a 40-nt repeated hairpin (RYF) motif (YF-XL-DeltaRYF). To investigate the biological significance of these 3' NCR rearrangements, YF-XL-DeltaRYF and YF-XL isolates, as well as other South American YFV isolates, were evaluated for three phenotypes: growth kinetics in cell culture, neuroinvasiveness in suckling mice, and ability to replicate and produce disseminated infections in Aedes aegypti mosquitoes. YF-XL-DeltaRYF and YF-XL isolates showed growth kinetics and neuroinvasive characteristics comparable to those of typical South American YFV isolates, and mosquito infectivity trials demonstrated that both types of 3' NCR variants were capable of replication and dissemination in a laboratory-adapted colony of A. aegypti.
Assuntos
Variação Genética , RNA não Traduzido/genética , RNA Viral/genética , Vírus da Febre Amarela/genética , Vírus da Febre Amarela/isolamento & purificação , Aedes/virologia , Animais , Sequência de Bases , Células Cultivadas , Modelos Animais de Doenças , Camundongos , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Filogenia , RNA não Traduzido/química , RNA não Traduzido/fisiologia , RNA Viral/química , RNA Viral/fisiologia , Sequências Repetitivas de Ácido Nucleico , Deleção de Sequência , América do Sul , Febre Amarela/virologia , Vírus da Febre Amarela/classificação , Vírus da Febre Amarela/crescimento & desenvolvimento , Vírus da Febre Amarela/patogenicidadeRESUMO
After sarcoplasmic reticulum (SR) Ca2+ depletion in intact ventricular myocytes, electrical activity promotes SR Ca2+ reloading and recovery of twitch amplitude. In ferret, recovery of twitch and caffeine-induced contracture required fewer twitches than in rabbit or rat. In rat, there was no difference in action potential duration at 90% repolarization (APD90) at steady state (SS) versus at the first post-depletion (PD) twitch. The SS APD90 was similar in ferret and rabbit (but longer than in rat). However, compared to SS, the PD APD90 was lengthened in ferret, but shortened in rabbit. When rabbit myocytes were subjected to AP-clamp patterns during SR Ca2+ reloading (ferret- or rabbit-type APs), reloading was much faster using the ferret AP templates. We conclude that the faster SR Ca2+ refilling in ferret is due to the increased Ca2+ influx during the longer PD AP. The PD versus SS APD90 difference was suppressed by thapsigargin in ferret (indicating Ca2+ dependence). In rabbit, the PD AP shortening depended on the preceding diastolic interval (rather than Ca2+), because rest produced the same AP shortening, and SS APD90 increased as a function of frequency (in contrast to ferret). Transient outward current (Ito) was larger and recovered from inactivation much faster in ferret than in rabbit. Moreover, slow Ito recovery (tau approximately 3 s) in rabbit was a much larger fraction of Ito. Our data and a computational model (including two Ito components) suggest that in rabbit the slowly recovering Ito is responsible for short post-rest and PD APs, for the unusual frequency dependence of APD90, and ultimately for the slower post-depletion SR Ca2+ reloading.
Assuntos
Potenciais de Ação/fisiologia , Cálcio/metabolismo , Miócitos Cardíacos/metabolismo , Retículo Sarcoplasmático/metabolismo , Animais , Cafeína/farmacologia , Furões , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Técnicas In Vitro , Masculino , Miócitos Cardíacos/efeitos dos fármacos , Coelhos , Ratos , Ratos Wistar , Retículo Sarcoplasmático/efeitos dos fármacos , Especificidade da EspécieAssuntos
Emigração e Imigração , Osteomalacia/etiologia , Dor/etiologia , Deficiência de Vitamina D/complicações , Deficiência de Vitamina D/etnologia , África Oriental/etnologia , Negro ou Afro-Americano/estatística & dados numéricos , Sudeste Asiático/etnologia , Criança , Humanos , Indígenas Norte-Americanos/estatística & dados numéricos , México/etnologia , Estados Unidos , População Branca/estatística & dados numéricosRESUMO
We have analyzed the effects of the endogenous redoxactive agents S-nitrosoglutathione and glutathione disulfide, and the NO donor NOR-3, on calcium release kinetics mediated by ryanodine receptor channels. Incubation of triad-enriched sarcoplasmic reticulum vesicles isolated from mammalian skeletal muscle with these three agents elicits different responses. Glutathione disulfide significantly reduces the inhibitory effect of Mg2+ without altering Ca2+ activation of release kinetics, whereas NOR-3 enhances Ca2+ activation of release kinetics without altering Mg2+ inhibition. Incubation with S-nitrosoglutathione produces both effects; it significantly enhances Ca2+ activation of release kinetics and diminishes the inhibitory effect of Mg2+ on this process. Triad incubation with [35S]nitrosoglutathione at pCa 5 promoted 35S incorporation into 2.5 cysteine residues per channel monomer; this incorporation decreased significantly at pCa 9. These findings indicate that S-nitrosoglutathione supports S-glutathionylation as well as the reported S-nitrosylation of ryanodine receptor channels (Sun, J., Xu, L., Eu, J. P., Stamler, J. S., and Meissner, G. (2003) J. Biol. Chem. 278, 8184-8189). The combined results suggest that S-glutathionylation of specific cysteine residues can modulate channel inhibition by Mg2+, whereas S-nitrosylation of different cysteines can modulate the activation of the channel by Ca2+. Possible physiological and pathological implications of the activation of skeletal Ca2+ release channels by endogenous redox species are discussed.
Assuntos
Cálcio/metabolismo , Glutationa/metabolismo , Magnésio/metabolismo , Nitrogênio/metabolismo , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , Animais , Western Blotting , Proteínas de Transporte/metabolismo , Dissulfetos/metabolismo , Relação Dose-Resposta a Droga , Eletroforese em Gel de Poliacrilamida , Cinética , Bicamadas Lipídicas , Proteínas Musculares/metabolismo , Músculo Esquelético/metabolismo , Oxirredução , Coelhos , Rianodina/metabolismo , Retículo Sarcoplasmático/metabolismo , Fatores de TempoRESUMO
We previously have identified a large kindred from Colombia in which Alzheimer's disease (AD) is caused by the E280A presenilin 1 (PS1) mutation. The objective of this study was to examine whether environmental and genetic factors are responsible for variation in the phenotypic expression of the E280A PS1 mutation. We genotyped coding and promoter polymorphisms of the APOE gene in carriers of the E280A PS1 mutation. Kaplan-Meier product-limit and Cox proportional hazard models were used in the statistical analyses. DNA was available from 114 carriers of the E280A PS1 mutation, including 52 subjects with AD. APOE epsilon 4 allele carriers were more likely to develop AD at an earlier age than subjects without the epsilon 4 allele (hazard ratio, 2.07; 95% confidence interval, 1.07-3.99; p = 0.030). Subjects with low education were more likely to develop AD later than those with higher education (hazard ratio, 0.476; 95% confidence interval, 0.26-0.87). Low educational level was associated with rural residence (p < 0.001). Promoter APOE variants did not influence either the onset or the duration of the disease. This study is the first to our knowledge to demonstrate that genetic and environmental factors influence age of onset in a kindred with a familial AD mutation.
Assuntos
Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Apolipoproteínas E/genética , Proteínas de Membrana/genética , Adulto , Idade de Início , Idoso , Idoso de 80 Anos ou mais , Alelos , Apolipoproteína E4 , Colômbia , DNA/genética , Educação , Meio Ambiente , Feminino , Heterozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Mutação/genética , Mutação/fisiologia , Linhagem , Fenótipo , Polimorfismo Genético/genética , Presenilina-1 , Regiões Promotoras Genéticas/genética , População Rural , Análise de SobrevidaRESUMO
The Guaymas Basin (Gulf of California) is a hydrothermal vent site where thermal alteration of deposited planktonic and terrestrial organic matter forms petroliferous material which supports diverse sulfate-reducing bacteria. We explored the phylogenetic and functional diversity of the sulfate-reducing bacteria by characterizing PCR-amplified dissimilatory sulfite reductase (dsrAB) and 16S rRNA genes from the upper 4 cm of the Guaymas sediment. The dsrAB sequences revealed that there was a major clade closely related to the acetate-oxidizing delta-proteobacterial genus Desulfobacter and a clade of novel, deeply branching dsr sequences related to environmental dsr sequences from marine sediments in Aarhus Bay and Kysing Fjord (Denmark). Other dsr clones were affiliated with gram-positive thermophilic sulfate reducers (genus Desulfotomaculum) and the delta-proteobacterial species Desulforhabdus amnigena and Thermodesulforhabdus norvegica. Phylogenetic analysis of 16S rRNAs from the same environmental samples resulted in identification of four clones affiliated with Desulfobacterium niacini, a member of the acetate-oxidizing, nutritionally versatile genus Desulfobacterium, and one clone related to Desulfobacula toluolica and Desulfotignum balticum. Other bacterial 16S rRNA bacterial phylotypes were represented by non-sulfate reducers and uncultured lineages with unknown physiology, like OP9, OP8, as well as a group with no clear affiliation. In summary, analyses of both 16S rRNA and dsrAB clone libraries resulted in identification of members of the Desulfobacteriales in the Guaymas sediments. In addition, the dsrAB sequencing approach revealed a novel group of sulfate-reducing prokaryotes that could not be identified by 16S rRNA sequencing.
Assuntos
Deltaproteobacteria/genética , Deltaproteobacteria/metabolismo , Sedimentos Geológicos/microbiologia , Sulfatos/metabolismo , Sequência de Bases , Deltaproteobacteria/classificação , Deltaproteobacteria/isolamento & purificação , Genes Bacterianos , Variação Genética , Sulfito de Hidrogênio Redutase , México , Dados de Sequência Molecular , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/genética , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genéticaRESUMO
Subcutaneous mycoses include a heterogeneous group of fungal infections that develop at the site of transcutaneous trauma. Infection slowly evolves as the etiologic agent survives and adapts to the adverse host tissue environment. Diagnosis rests on clinical presentation, histopathology, and culture of the etiologic agents. This article considers sporotrichosis, chromoblastomycosis, and mycetoma.
Assuntos
Dermatomicoses , Antifúngicos/uso terapêutico , Cromoblastomicose/diagnóstico , Cromoblastomicose/tratamento farmacológico , Cromoblastomicose/patologia , Dermatomicoses/diagnóstico , Dermatomicoses/epidemiologia , Dermatomicoses/microbiologia , Fungos/patogenicidade , Humanos , Micetoma/diagnóstico , Micetoma/tratamento farmacológico , Micetoma/patologia , Infecções Oportunistas/epidemiologia , Esporotricose/diagnóstico , Esporotricose/tratamento farmacológico , Esporotricose/patologiaRESUMO
Molecular variants of GnRH were characterized by reverse-phase, high-performance liquid chromatography from brain extracts of fish in three different orders: Synbranchiformes (swamp eel [Synbranchus marmoratus]), Cyprinidontiformes (platyfish [Xiphophorus maculatus] and green swordtail [X. helleri]), and Atheriniformes (Patagonia pejerrey [Odontesthes hatchery]). Also, pituitary gland extracts from the pejerrey O. bonariensis (Atheriniformes) were characterized. Eluted fractions were tested in radioimmunoassays with antisera specific to GnRH, including both antisera that detected only one form of GnRH and those that detected several forms. The results show that brain extracts obtained from all species contained the same three molecular forms of GnRH, which were immunologically and chromatographically undistinguishable from chicken GnRH-II, pejerrey GnRH (pjGnRH), and salmon GnRH. This study supports the hypothesis that expression of these three forms is common in different fish orders and that pjGnRH is the main regulator of pituitary function in these fish.
Assuntos
Expressão Gênica , Hormônio Liberador de Gonadotropina/genética , Smegmamorpha/metabolismo , Animais , Química Encefálica , Cromatografia Líquida de Alta Pressão , Ciprinodontiformes/metabolismo , Feminino , Hormônio Liberador de Gonadotropina/isolamento & purificação , Masculino , Hipófise/química , Extratos de Tecidos/químicaRESUMO
Oxygen enrichment of room air has proved to be valuable for people who need to work at altitudes of 4000 m and above. In the present study the feasibility of using the same technique in ski and other mountain resorts at the lower altitudes of 2500 to 4000 m is considered. Although many people find these altitudes invigorating, some are distressed by the hypoxia, especially at night. The analysis shows that all resorts up to an altitude of 3250 m (10,600 ft) can have the equivalent altitude reduced to 1000 m (3280 ft) by oxygen enrichment without incurring a fire hazard. (The equivalent altitude is that which provides the same inspired P(O2) during air breathing.) Even resorts or laboratories as high as 4250 m can have the equivalent altitude safely reduced to 1500 m, that is, lower than the altitude of Denver, Colorado. This application of oxygen enrichment is likely to be most valuable for improving sleep and assisting in the initial acclimatization process.
Assuntos
Ar Condicionado/métodos , Doença da Altitude/prevenção & controle , Estâncias para Tratamento de Saúde , Oxigênio/administração & dosagem , Aclimatação , Ar/análise , Altitude , Bolívia , Incêndios/prevenção & controle , Humanos , Viagem , Estados UnidosRESUMO
We evaluated serotonergic hindbrain groups of cells for their involvement in the generation and inhibition of sodium appetite. For that purpose, we analyzed the number of Fos-immunoreactive (Fos-ir) cells and double-labeled Fos-serotonin (5-HT)-ir neurons within different nuclei of the hindbrain raphe system and the area postrema (AP). Sodium depletion and sodium appetite were induced by peritoneal dialysis. Twenty-four hours after peritoneal dialysis, a 2% NaCl solution intake test was given to peritoneal dialyzed animals [PD-with access (PD-A) group] and to control dialyzed animals [CD-with access (CD-A) group]. Two additional groups of animals received either peritoneal dialysis or control dialysis but were not given access to the 2% NaCl [CD-no access (CD-NA) group or PD-no access (PD-NA) group]. The number of Fos-ir neurons within different nuclei of the raphe system was increased in spontaneous and induced sodium ingestion of CD-A and PD-A groups compared with the CD-NA and PD-NA groups. The PD-NA group had significantly fewer double-labeled cells along the raphe system compared with the animals in near-normal sodium balance (CD-NA and CD-A) or in the process of restoring sodium balance by consuming NaCl (PD-A). The AP of the PD-A group showed a significant increase in the number of Fos-ir and Fos-5-HT-ir cells compared with the PD-NA and CD groups. Our results suggest that serotonergic pathways with cell bodies in the AP and the raphe system are involved in the control of sodium appetite.
Assuntos
Apetite/fisiologia , Neurônios/química , Proteínas Proto-Oncogênicas c-fos/análise , Serotonina/análise , Sódio na Dieta/farmacologia , Animais , Anticorpos , Quarto Ventrículo/química , Quarto Ventrículo/citologia , Imuno-Histoquímica , Masculino , Neurônios/fisiologia , Proteínas Proto-Oncogênicas c-fos/imunologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Núcleos da Rafe/química , Núcleos da Rafe/citologia , Ratos , Ratos Wistar , Serotonina/imunologia , Serotonina/metabolismoRESUMO
Salt appetite, a conditioning factor for hypertension and cardiovascular diseases, is produced when high doses of mineralocorticoids are given to experimental animals. A commonly used procedure to identify neuronal activation is to determine the number of Fos-immunoreactive cells. In rats with established salt appetite after 8 days of deoxycorticosterone acetate (DOCA) treatment, Fos-positive cells were studied in seven brain areas. Significant increases in Fos activity were recorded in the paraventricular (PVN) and supraoptic (SON) nuclei, median preoptic nucleus (MnPO), organum vasculosum of the lamina terminalis (OVLT), preoptic area (POA), bed nucleus of the stria terminalis (BNST) and amygdala (AMYG). In most of these areas, increased Fos expression was also observed early (2 h) after a single DOCA injection, well before salt appetite develops. Using a mineralocorticoid receptor (MR) antibody, we studied whether Fos-active regions also expressed MR. MR-positive cells were found in the OVLT, MnPO, AMYG and BNST, but not in the POA, PVN and SON. In the PVN and SON, nevertheless, prolonged or single DOCA treatment increased expression of mRNA for arginine vasopressin (AVP). The present demonstration of Fos activation, in conjunction with differential expression of MR and stimulation of AVP mRNA, suggests that a neuroanatomical pathway comprising the AMYG, osmosensitive brain regions and magnocellular nuclei becomes activated during DOCA effects on salt appetite. It is recognized, however, that DOCA effects may also depend on mechanisms and brain structures other than those considered in the present investigation. Since some Fos-positive regions were devoid of MR, a comprehensive view of DOCA-induced salt appetite should consider nongenomic pathways of steroid action, including the role of reduced DOC metabolites binding to GABAergic membrane receptors.
Assuntos
Apetite/fisiologia , Encéfalo/metabolismo , Desoxicorticosterona/farmacologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Cloreto de Sódio , Animais , Arginina Vasopressina/genética , Imuno-Histoquímica , Masculino , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Mineralocorticoides/metabolismo , Distribuição TecidualRESUMO
The present article is the adapted version of an electronic symposium organized by the Brazilian Society of Neuroscience and Behavior (SBNeC) which took place on June 14, 2000. The text is divided into three sections: I. The main issues, II. Chronodrugs, and III. Methods. The first section is dedicated to the perspectives of chronobiology for the next decade, with opinions about the trends of future research being emitted and discussed. The second section deals mostly with drugs acting or potentially acting on the organism's timing systems. In the third section there are considerations about relevant methodological issues concerning data analysis.
Assuntos
Encéfalo/fisiologia , Fenômenos Cronobiológicos/fisiologia , Pesquisa/tendências , Encéfalo/efeitos dos fármacos , Fenômenos Cronobiológicos/efeitos dos fármacos , Cronoterapia , Redes de Comunicação de Computadores , HumanosRESUMO
Serotonin [5-hydroxytryptamine (5-HT)] and CCK injected into the lateral parabrachial nucleus (LPBN) inhibit NaCl and water intake. In this study, we investigated interactions between 5-HT and CCK into the LPBN to control water and NaCl intake. Male Holtzman rats with cannulas implanted bilaterally in the LPBN were treated with furosemide + captopril to induce water and NaCl intake. Bilateral LPBN injections of high doses of the 5-HT antagonist methysergide (4 microg) or the CCK antagonist proglumide (50 microg), alone or combined, produced similar increases in water and 1.8% NaCl intake. Low doses of methysergide (0.5 microg) + proglumide (20 microg) produced greater increases in NaCl intake than when they were injected alone. The 5-HT(2a/2c) agonist 2,5-dimetoxy-4-iodoamphetamine hydrobromide (DOI; 5 microg) into the LPBN reduced water and NaCl intake. After proglumide (50 microg) + DOI treatment, the intake was not different from vehicle treatment. CCK-8 (1 microg) alone produced no effect. CCK-8 combined with methysergide (4 microg) reduced the effect of methysergide on NaCl intake. The data suggest that functional interactions between 5-HT and CCK in the LPBN may be important for exerting inhibitory control of NaCl intake.
Assuntos
Apetite/fisiologia , Núcleos Intralaminares do Tálamo/fisiologia , Serotonina/farmacologia , Sincalida/análogos & derivados , Sincalida/farmacologia , Sódio na Dieta , Anfetaminas/farmacologia , Animais , Apetite/efeitos dos fármacos , Interações Medicamentosas , Homeostase , Núcleos Intralaminares do Tálamo/efeitos dos fármacos , Masculino , Metisergida/administração & dosagem , Metisergida/farmacologia , Microinjeções , Modelos Neurológicos , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Proglumida/farmacologia , Ratos , Ratos Sprague-Dawley , Serotonina/administração & dosagem , Agonistas do Receptor de Serotonina/farmacologia , Sincalida/administração & dosagemRESUMO
Further studies have been carried out on the potential value of oxygen enrichment of room air for commuters to high altitude. Novel ways of providing oxygen-enriched spaces for working and sleeping are being tested at the California Institute of Technology where a radiotelescope is being designed for an altitude of 5,000 m in north Chile. The modules are containers such as those used on container ships, and they are fitted out in California and then sealed and transported to the telescope site in Chile. The result is a turnkey facility which shows promise for field studies. The oxygen is provided by oxygen concentrators, and different modules are used for sleeping, living, and laboratory quarters. Two extensive experiments on oxygen enrichment were carried out at the University of California White Mountain Research Station, altitude 3,800 m, in the summer of 1998. The first study was devoted to the mechanism for the increase in arterial oxygen saturation on the day after sleeping in an oxygen-enriched atmosphere compared with sleeping in ambient air (5). Possible mechanisms include less fluid accumulation in the lung associated with acute mountain sickness, or a change in the control of ventilation. A double blind study was therefore carried out of the effects of sleeping in oxygen enrichment on both the ventilatory response to hypoxia and to carbon dioxide. In a related study, subjects who had been at an altitude of 3,800 m for two days, and were therefore partially acclimatized, were studied at a simulated altitude of 5,000 both breathing ambient air and 27% oxygen. The studies were done at 3800 m altitude by enriching the atmosphere of the test room with appropriate amounts of nitrogen or oxygen. An extensive series of neuropsychological tests were carried out with the objective of determining which features of CNS function were improved by oxygen enrichment at an altitude of 5,000 m.
Assuntos
Altitude , Oxigenoterapia , Viagem , California , Chile , Humanos , Oxigenoterapia/instrumentação , VentilaçãoAssuntos
Aclimatação/fisiologia , Altitude , Encéfalo/fisiologia , Circulação Cerebrovascular/fisiologia , Montanhismo/fisiologia , Pressão Sanguínea , Bolívia , Encéfalo/irrigação sanguínea , Dióxido de Carbono/sangue , Feminino , Homeostase , Humanos , Masculino , Oxigênio/sangue , Respiração , VasodilataçãoRESUMO
To determine the role of intracellular Ca2+ in compaction, the first morphogenetic event in embryogenesis, we analyzed preimplantation mouse embryos under several decompacting conditions, including depletion of extracellular Ca2+, blocking of Ca2+ channels, and inhibition of microfilaments, calmodulin, and intracellular Ca2+ release. Those treatments induced decompaction of mouse morulae and simultaneously induced changes in cytosolic free Ca2+ concentration and deregionalization of E-cadherin and fodrin. When morulae were allowed to recompact, the location of both proteins recovered. In contrast, actin did not change its cortical location with compaction nor with decompaction-recompaction. Calmodulin localized in areas opposite to cell-cell contacts in eight-cell stage embryos before and after compaction. Inhibition of calmodulin with trifluoperazine induced its delocalization while morulae decompacted. A nonspecific rise of intracellular free Ca2+ provoked by ionomycin did not affect the compacted shape. Moreover, the same decompacting treatments when applied to uncompacted embryos did not produce any change in intracellular Ca2+. Our results demonstrate that in preimplantation mouse embryos experimentally induced stage-specific changes of cell shape are accompanied by changes of intracellular free Ca2+ and redistribution of the cytoskeleton-related proteins E-cadherin, fodrin, and calmodulin. We conclude that intracellular Ca2+ specifically is involved in compaction and probably regulates the function and localization of cytoskeleton elements.
Assuntos
Blastocisto/fisiologia , Caderinas/fisiologia , Cálcio/metabolismo , Morfogênese/fisiologia , Mórula/fisiologia , Animais , Blastocisto/citologia , Blastocisto/efeitos dos fármacos , Calmodulina/metabolismo , Proteínas de Transporte/fisiologia , Tamanho Celular/efeitos dos fármacos , Tamanho Celular/fisiologia , Gonadotropina Coriônica/fisiologia , Citocalasina D/farmacologia , Citosol/metabolismo , Ácido Egtázico/farmacologia , Desenvolvimento Embrionário e Fetal , Feminino , Masculino , Proteínas de Membrana/fisiologia , Camundongos , Camundongos Endogâmicos ICR , Proteínas dos Microfilamentos/fisiologia , Microscopia Confocal , Mórula/citologia , Mórula/efeitos dos fármacos , Trifluoperazina/farmacologia , Verapamil/farmacologia , Zona Pelúcida/fisiologiaRESUMO
We have compared the effect of calcium channel blockers on the potassium-evoked release of tritium-labeled acetylcholine and on preganglionic spike-evoked synaptic transmission in the rat superior cervical ganglion. Transmitter release at the nerve terminals is mediated by the influx of calcium through voltage-gated calcium channels. While four types of voltage-gated calcium channels (T, L, N and P) have been identified in neurons, it is not clear which may actually be involved in excitation-secretion coupling. Release of tritiated acetylcholine evoked by sustained depolarization in high (40 mM) extracellular potassium decreased markedly in the absence of calcium or the presence of cadmium. High potassium-evoked release was substantially inhibited by the P-type channel blockers, purified from funnel-web spider toxin, and omega-agatoxin-IVA, and by the N-type channel blocker omega-conotoxin-GVIA, but was unaffected by the L-type channel blocker nitrendipine. In contrast, postganglionic compound action potentials synaptically triggered by preganglionic stimulation were strongly blocked by funnel-web spider toxin and slightly blocked by a high concentration of omega-agatoxin-IVA, but were unaffected by either omega-conotoxin-GVIA, nitrendipine or a low concentration of omega-agatoxin-IVA. Thus, at the superior cervical ganglion, funnel-web spider toxin-sensitive calcium channels play a dominant role in transmitter release evoked by transient, spike-mediated depolarization, but other types of voltage-gated calcium channels in addition to the funnel-web spider toxin-sensitive channel mediate the transmitter release that is evoked by sustained high potassium depolarization.