RESUMO
The patterns of immunity conferred by host sex or age represent two sources of host heterogeneity that can potentially shape the evolutionary trajectory of disease. With each host sex or age encountered, a pathogen's optimal exploitative strategy may change, leading to considerable variation in expression of pathogen transmission and virulence. To date, these host characteristics have been studied in the context of host fitness alone, overlooking the effects of host sex and age on the fundamental virulence-transmission trade-off faced by pathogens. Here, we explicitly address the interaction of these characteristics and find that host sex and age at exposure to a pathogen affect age-specific patterns of mortality and the balance between pathogen transmission and virulence. When infecting age-structured male and female Daphnia magna with different genotypes of Pasteuria ramosa, we found that infection increased mortality rates across all age classes for females, whereas mortality only increased in the earliest age class for males. Female hosts allowed a variety of trade-offs between transmission and virulence to arise with each age and pathogen genotype. In contrast, this variation was dampened in males, with pathogens exhibiting declines in both virulence and transmission with increasing host age. Our results suggest that differences in exploitation potential of males and females to a pathogen can interact with host age to allow different virulence strategies to coexist, and illustrate the potential for these widespread sources of host heterogeneity to direct the evolution of disease in natural populations.
Assuntos
Evolução Biológica , Interações Hospedeiro-Patógeno/genética , Doenças Parasitárias/mortalidade , Pasteuria/patogenicidade , Fatores Etários , Animais , Daphnia , Feminino , Aptidão Genética , Masculino , Doenças Parasitárias/transmissão , Pasteuria/genética , Fatores Sexuais , VirulênciaRESUMO
Genetic sequence data from pathogens present a novel means to investigate the spread of infectious disease between infected hosts or infected premises, complementing traditional contact-tracing approaches, and much recent work has gone into developing methods for this purpose. The objective is to recover the epidemic transmission tree, which identifies who infected whom. This paper reviews the various approaches that have been taken. The first step is to define a measure of difference between sequences, which must be done while taking into account such factors as recombination and convergent evolution. Three broad categories of method exist, of increasing complexity: those that assume no withinhost genetic diversity or mutation, those that assume no within-host diversity but allow mutation, and those that allow both. Until recently, the assumption was usually made that every host in the epidemic could be identified, but this is now being relaxed, and some methods are intended for sparsely sampled data, concentrating on the identification of pairs of sequences that are likely to be the result of direct transmission rather than inferring the complete transmission tree. Many of the procedures described here are available to researchers as free software.
L'accès aux données sur les séquences génétiques des agents pathogènes ouvre de nouvelles perspectives pour étudier la manière dont les maladies infectieuses se propagent entre différents hôtes ou établissements infectés, en complément des méthodes traditionnelles d'évaluation de l'exposition ; de grands efforts ont donc été déployés pour mettre au point des techniques permettant d'arriver à cette fin. Leur objectif est de reconstituer l'arborescence de la transmission d'une épidémie, ce qui permet d'identifier chaque individu ayant infecté d'autres individus. Les auteurs passent en revue les différentes méthodes appliquées. La première étape consiste à définir les modalités de mesure des différences entre séquences, ainsi que les facteurs à prendre en compte, par exemple les phénomènes de recombinaison ou d'évolution convergente. Les méthodes disponibles se répartissent en trois catégories principales, par ordre de complexité croissante : celles qui présupposent qu'il ne peut y avoir de diversité ni de mutation génétiques chez l'hôte ; celles qui présupposent qu'il peut y avoir une diversité génétique mais pas de mutation ; enfin celles qui présupposent qu'il peut y avoir les deux. Jusqu'à une période récente, le présupposé le plus courant était que tous les hôtes intervenant dans un foyer pouvaient être identifiés ; cette exigence s'est considérablement assouplie et de nouvelles méthodes ont été conçues pour travailler à partir d'un échantillon de données plus clairsemé, ce qui permet de se concentrer sur l'identification de paires de séquences révélatrices d'une transmission directe au lieu de déduire l'intégralité de l'arbre de transmission. La plupart des procédures décrites par les auteurs existent sous forme de logiciels libres accessibles aux chercheurs.
Los datos de la secuencia genética de patógenos ofrecen un medio novedoso para investigar la propagación de enfermedades infecciosas entre individuos o establecimientos infectados, medio que viene a complementar la fórmula tradicional consistente en rastrear los contactos. De ahí que últimamente se haya dedicado un ingente trabajo a definir métodos útiles para ese fin. El objetivo radica en desentrañar el árbol de transmisión epidémica, que permite determinar quién infectó a quién. Los autores pasan revista a los diferentes planteamientos adoptados. El primer paso consiste en definir una medida de la diferencia entre secuencias, para lo cual hay que tener en cuenta factores como la recombinación o la convergencia evolutiva. Existen tres grandes clases de métodos, que presentan un grado creciente de complejidad: aquellos que presuponen que no hay diversidad genética ni mutaciones dentro del individuo infectado; aquellos que presuponen que no hay diversidad, pero admiten la posibilidad de mutaciones; y aquellos que postulan que ambas cosas pueden producirse. Hasta hace poco, en general se partía de la premisa de que era posible identificar a todos los individuos infectados en una epidemia. Ahora, sin embargo, se está flexibilizando este postulado, y existen métodos que se aplican específicamente a datos obtenidos con muestreos dispersos, con los cuales se trata de determinar pares de secuencias que probablemente sean resultado de la transmisión directa, y no tanto de inferir el árbol de transmisión completo. Muchos de los procedimientos aquí descritos están a disposición de los investigadores en forma de programas informáticos gratuitos.
Assuntos
Busca de Comunicante/métodos , Surtos de Doenças , Genômica , Software , Animais , Variação Genética , Humanos , Epidemiologia MolecularRESUMO
The social environment has a strong effect on the strength and direction of sexual selection. Juveniles, however, often have social cues that signal the current competitive environment which may provide cues of future competitive challenges. Here we demonstrate that juvenile crickets (Teleogryllus commodus) use the calls of surrounding adult males as a cue of the quality and density of rivals/mates they are likely to encounter. We reared hatchling crickets in six acoustic environments that varied in the density and quality of calls and demonstrate that individuals modified their development rate, phenotype and behaviour at maturity. Males matured more rapidly at a smaller size and called more when reared in a low competition environment. In contrast, males delayed maturity to grow larger when faced with an increased density of high-quality males. Females matured more rapidly when reared in a high density of high-quality males and allocated proportionately more resources towards egg production. A second experiment limiting nutrient availability demonstrates sex-specific allocation shifts in the last stadium when cues are most reliable. Our results demonstrate that the social environment significantly affects allocation strategies and phenotypes, highlighting the importance of juvenile experience and competitive context when examining fitness and selection.
Assuntos
Comunicação Animal , Sinais (Psicologia) , Gryllidae/fisiologia , Comportamento Social , Estimulação Acústica , Fenômenos Fisiológicos da Nutrição Animal , Animais , Meio Ambiente , Feminino , Gryllidae/crescimento & desenvolvimento , Masculino , Fenótipo , Densidade Demográfica , Dinâmica Populacional , Maturidade Sexual , Fatores de TempoRESUMO
Male field crickets produce two acoustic signals for mating: advertisement calls and courtship calls. While the importance of advertisement calling in mate attraction is well understood, the function of courtship calling is less clear. Here, we tested if the courtship call of male crickets Teleogryllus commodus signals aspects of male quality by comparing the calls of inbred and outbred males. We examined the effect of one generation of full sibling mating on fine-scale call structure, along with several life history traits. Inbreeding reduced nymph survival but had no significant effect on weight or development time. Inbreeding resulted in a small but significant change in two of the six call parameters measured. We then tested if inbreeding affects call trait combinations that are important to females by using the results of a previous selection analysis to compare the multivariate attractiveness of the calls of inbred and outbred males. There was no difference. We conclude that the courtship call of T. commodus is not a reliable signal of aspects of male quality that are affected by inbreeding (which generally reduces fitness-enhancing traits). It might, however, signal components of male fitness that are not affected by changes in heterozygosity.
Assuntos
Comunicação Animal , Gryllidae/fisiologia , Endogamia , Preferência de Acasalamento Animal , Acústica , Animais , Peso Corporal , Feminino , Gryllidae/anatomia & histologia , Masculino , Ninfa/fisiologiaRESUMO
Theory predicts that lifespan will depend on the dietary intake of an individual, the allocation of resources towards reproduction and the costs imposed by the opposite sex. Although females typically bear the majority of the cost of offspring production, nuptial feeding invertebrates provide an ideal opportunity to examine the extent to which reproductive interactions through gift provisioning impose a cost on males. Here we use experimental evolution in an Australian ground cricket to assess how diet influences male lifespan and how the costs of mating evolve for males. Our findings show that males had significantly shorter lifespans in populations that adapted to a low-quality diet and that this divergence is driven by evolutionary change in how females interact with males over reproduction. This suggests that the extent of sexual conflict over nuptial feeding may be under-realized by focusing solely on the consequences of reproductive interactions from the female's perspective.
Assuntos
Evolução Biológica , Dieta , Gryllidae/fisiologia , Longevidade/fisiologia , Comportamento Sexual Animal/fisiologia , Animais , Feminino , Masculino , Modelos BiológicosRESUMO
OBJECTIVES: The purpose of this study was to compare the albumin-bilirubin (ALBI) grade and model for end-stage liver disease (MELD) scores for predicting survival after transjugular intrahepatic portosystemic shunt (TIPS) creation. MATERIALS AND METHODS: A retrospective study of pre-procedure ALBI and MELD scores was performed in 197 patients who underwent TIPS from 2005 to 2012. There were 140 men and 57 women, with a mean age of 56±11 (SD) (range: 19-90years). The prognostic capability of ALBI and MELD scores were evaluated using competing risks survival analysis. Discriminatory ability was compared between models using the C-index derived from cause specific Cox proportional hazards models. RESULTS: TIPS were created for ascites or hydrothorax (128 patients), variceal hemorrhage (61 patients), or both (8 patients). Prior to TIPS, 5 patients were ALBI grade 1, 76 were grade 2, and 116 were grade 3. The average pre-TIPS MELD score was 14. Pre-TIPS ALBI score, ALBI grade, and MELD were each significant predictors of 30-day mortality from hepatic failure and overall survival (all P<0.05). Based on the C-index, the MELD score was a better predictor of both 30-day and overall survival (C-index=0.74 and 0.63) than either ALBI score (0.70 and 0.59) or ALBI grade (0.64 and 0.56). In multivariate models, after accounting for MELD score ALBI score provided no additional short- or long-term survival information. CONCLUSION: Although ALBI score and grade were statistically significantly associated with risk of death after TIPS, MELD remains the superior predictor.
Assuntos
Bilirrubina/sangue , Cirrose Hepática/mortalidade , Derivação Portossistêmica Transjugular Intra-Hepática , Albumina Sérica/análise , Índice de Gravidade de Doença , Adulto , Idoso , Idoso de 80 Anos ou mais , Ascite/terapia , Feminino , Hemorragia/terapia , Humanos , Hidrotórax/terapia , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Adulto JovemRESUMO
The structure of malate dehydrogenase from Escherichia coli complexed with the substrate analog, citrate and the cofactor NAD, has been determined by X-ray crystallography. A monoclinic crystal of the malate dehydrogenase, grown in citrate buffer, was soaked in 10 mM NAD solution and found to be isomorphous with the apo-form. The X-ray data extended to 1.9 A, nearly the same resolution limit as the apo-enzyme crystals. The ternary complex of malate dehydrogenase has very few conformational differences from that of the pseudo binary complex of enzyme with bound citrate. In addition, the NAD molecule has a very similar conformation to the NAD as found in the crystal structure of the cytosolic eukaryotic malate dehydrogenase. Similar hydrogen bond interactions are made by both enzymes from polar groups belonging to the NAD. Such interactions include hydrogen bonds from the ribose oxygens and the phosphate oxygens, to backbone amide and carbonyl atoms of the protein and to side-chains of a select few conserved hydrophilic residues. The only notable difference occurs in the active site region where the nicotinamide moiety is obstructed from further entering the active site by the C-6 carbonyl atoms of citrate. In this position there are no direct polar interactions between the protein and the nicotinamide moiety. Energy minimization of the structure with malate substituted for citrate in the active site shows that the nicotinamide moiety assumes the same position in the active site as the NAD in cytosolic malate dehydrogenase. The carboxamide atoms of the energy minimized model make significant hydrogen bond interactions with the catalytic residue, H177, and with the main-chain atoms of I117 and V146 in the vicinity of the active site, while the position of the rest of the cofactor remains unchanged.
Assuntos
Citratos/química , Malato Desidrogenase/ultraestrutura , NAD/química , Sítios de Ligação , Cristalografia , Escherichia coli/enzimologia , Ligação de Hidrogênio , Difração de Raios XRESUMO
The crystal structure of malate dehydrogenase from Escherichia coli has been determined with a resulting R-factor of 0.187 for X-ray data from 8.0 to 1.87 A. Molecular replacement, using the partially refined structure of porcine mitochondrial malate dehydrogenase as a probe, provided initial phases. The structure of this prokaryotic enzyme is closely homologous with the mitochondrial enzyme but somewhat less similar to cytosolic malate dehydrogenase from eukaryotes. However, all three enzymes are dimeric and form the subunit-subunit interface through similar surface regions. A citrate ion, found in the active site, helps define the residues involved in substrate binding and catalysis. Two arginine residues, R81 and R153, interacting with the citrate are believed to confer substrate specificity. The hydroxyl of the citrate is hydrogen-bonded to a histidine, H177, and similar interactions could be assigned to a bound malate or oxaloacetate. Histidine 177 is also hydrogen-bonded to an aspartate, D150, to form a classic His.Asp pair. Studies of the active site cavity indicate that the bound citrate would occupy part of the site needed for the coenzyme. In a model building study, the cofactor, NAD, was placed into the coenzyme site which exists when the citrate was converted to malate and crystallographic water molecules removed. This hypothetical model of a ternary complex was energy minimized for comparison with the structure of the binary complex of porcine cytosolic malate dehydrogenase. Many residues involved in cofactor binding in the minimized E. coli malate dehydrogenase structure are homologous to coenzyme binding residues in cytosolic malate dehydrogenase. In the energy minimized structure of the ternary complex, the C-4 atom of NAD is in van der Waals' contact with the C-3 atom of the malate. A catalytic cycle involves hydride transfer between these two atoms.
Assuntos
Apoenzimas/química , Citratos/metabolismo , Escherichia coli/enzimologia , Malato Desidrogenase/química , Sequência de Aminoácidos , Animais , Apoenzimas/metabolismo , Sítios de Ligação , Malato Desidrogenase/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Miocárdio/enzimologia , Conformação Proteica , Homologia de Sequência do Ácido Nucleico , Suínos , Termodinâmica , Difração de Raios X/métodosRESUMO
The metalloenzyme catechol 1,2-dioxygenase from Pseudomonas arvilla C-1 consists of three isozymes formed by combinations of two non-identical subunits; alpha alpha, alpha beta and beta beta; with molecular masses of 59,000, 63,000 and 67,000 Da, respectively. The alpha alpha isozyme crystallizes in the orthorhombic space group C222(1) with unit cell dimensions a = 62.7 A, b = 71.5 A, c = 187.1 A. The rectangular plates diffract to 2.6 A resolution. This is the first dioxygenase to be crystallized that uses catechol as a substrate. Comparison of the structure of this enzyme with protocatechuate 3,4-dioxygenase will provide basic information about the mechanisms of subunit association, substrate selectivity, and the origins of metabolic diversity in enzymes.
Assuntos
Dioxigenases , Oxigenases/química , Pseudomonas/enzimologia , Catecol 1,2-Dioxigenase , Cristalização , Cristalografia por Raios X/métodos , Isoenzimas/química , Isoenzimas/isolamento & purificação , Oxigenases/isolamento & purificação , Conformação ProteicaRESUMO
Malate dehydrogenase from Escherichia coli has been crystallized with polyethylene glycol and citrate buffer at pH 5.7. The enzyme was obtained from an E. coli strain in which the chromosomal malate dehydrogenase gene was contained on a pBR322 vector. Two types of crystals have been observed; a monoclinic C2 form and an orthorhombic C222(1) form, which is found infrequently. Monoclinic crystals were used as seeds in several rounds of crystallization until large crystals suitable for diffraction analysis were available. A complete X-ray data set to 2.0 A has been collected.
Assuntos
Escherichia coli/enzimologia , Malato Desidrogenase/isolamento & purificação , Cromatografia por Troca Iônica , Cristalização , Escherichia coli/genética , Vetores Genéticos , Indicadores e Reagentes , Malato Desidrogenase/genética , Malato Desidrogenase/metabolismo , Plasmídeos , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Ultracentrifugação , Difração de Raios XRESUMO
The chemotherapeutic drug cisplatin is an important treatment for many types of solid tumours, in particular non-small cell lung cancer (NSCLC). Platinum(IV) complexes offer several advantages to cisplatin due to their requirement for reduction to the active platinum(II) form to elicit cytotoxicity. This should minimise non-specific effects and facilitate higher amounts of the active complexes reaching the target DNA. Hypoxia and a quiescent cell population are features of the tumour microenvironment known to lead to resistance to many chemotherapeutic agents. It is unclear how these microenvironmental factors will impact on the efficacy of novel platinum(IV) complexes. Consequently, the cytotoxicities of several platinum drugs were determined in monolayer and tumour spheroid cultures derived from NSCLC lines. Platinum(IV) reduction potential correlated well with cytotoxicity. The complex containing a chloro axial ligand demonstrated the greatest potency and the drug with the hydroxy ligand was the least effective. Although drug cytotoxicity was not enhanced under hypoxic conditions, both cisplatin and the platinum(IV) complexes retained full potency. In addition, all of the platinum drugs retained the ability to evoke apoptosis in quiescent cells. In summary, unlike many anticancer drugs, the platinum(IV) complexes retain cytotoxic potency under resistance-inducing tumour microenvironmental conditions and warrant further investigation as more selective alternatives to current platinum-based therapy for the treatment of solid tumours.
Assuntos
Antineoplásicos/farmacologia , Cisplatino/farmacologia , Compostos de Platina/farmacologia , Carcinoma Pulmonar de Células não Pequenas/patologia , Humanos , Neoplasias Pulmonares/patologiaRESUMO
CRF exerts a key neuroregulatory control on the function of the hypothalamic-pituitary-adrenal axis. These effects are thought to be mediated primarily through activation of Gs-coupled plasma membrane receptors. In the present study, we investigated the effects of activation of CRF receptors by sauvagine on signaling pathways that converge on phosphorylation of the transcription factor calcium/cAMP response element-binding protein (CREB). Studies were undertaken using CHO cell lines transfected with either rat CRF-1 or CRF-2alpha receptors. Signaling pathways were investigated using immunocytochemical, Western blot, and imaging techniques. Treatment with sauvagine increased phosphorylation of p42/p44, but not of p38 or stress-activated protein kinase (SAPK)/JUN N-terminal kinase (JNK) mitogen-activated protein (MAP) kinases correlating with increased p42/p44 MAP kinase activity. Mobilization of intracellular Ca2+ stores was observed in cells treated with high concentrations (100 nM, 1 microM) of sauvagine. A time- and dose-dependent increase in phosphorylation of the transcription factor CREB was observed in cultures treated with sauvagine. Phosphorylation of CREB occurred at lower concentrations of sauvagine than those required to mobilize intracellular calcium stores, and phosphorylation was not blocked by the mitogen-activated protein kinase kinase inhibitor PD98059 at a concentration (1 microM) that fully inhibited phosphorylation of MAP kinase. Cotreatment of cultures with the protein kinase A inhibitor H89 (10 microM) blocked fully the stimulatory actions of sauvagine (0.1 nM, 1 nM) on phosphorylation of CREB, but not those on phosphorylation of MAP kinase. Phosphorylation of MAP kinase was partially blocked by the phosphoinositide 3-kinase inhibitor LY294002 (5 microM) and by the phosphoinositide-phospholipase C inhibitor U73122 (10 microM). These data demonstrate that cAMP-, Ca2+-, and MAP kinase-dependent signaling pathways are activated by stimulation of CRF-1 and CRF-2alpha receptors. However, in these cells, only protein kinase A-dependent pathways contribute significantly to enhanced phosphorylation of CREB. These represent the first reported observations of CRF receptor-mediated phosphorylation of the transcription factor CREB and activation of MAP kinase signal transduction pathways.
Assuntos
Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Receptores de Hormônio Liberador da Corticotropina/fisiologia , Proteínas de Anfíbios , Animais , Western Blotting , Células CHO , Cálcio/metabolismo , Hormônio Liberador da Corticotropina/farmacologia , Cricetinae , Ativação Enzimática , Inibidores Enzimáticos/farmacologia , Flavonoides/farmacologia , Imuno-Histoquímica , Proteína Quinase 1 Ativada por Mitógeno/antagonistas & inibidores , Fragmentos de Peptídeos/farmacologia , Hormônios Peptídicos , Peptídeos/farmacologia , Fosforilação , Ratos , Receptores de Hormônio Liberador da Corticotropina/antagonistas & inibidores , Receptores de Hormônio Liberador da Corticotropina/genética , Transdução de SinaisRESUMO
Rats received L-DOPA (40 or 200 mg/kg, i.p.) for 14 days, followed by a 3 day withdrawal period. Spontaneous locomotor activity was not altered by repeated administration of L-DOPA. Rats treated with L-DOPA (200 mg/kg) showed identical locomotor hypoactivity in response to small doses of apomorphine when compared to saline-treated control animals. However, hyperactivity induced by large doses of apomorphine was reduced by prior treatment with L-DOPA (200 mg/kg). The smaller dose of L-DOPA (40 mg/kg) did not alter the locomotion induced by apomorphine. Stereotyped behaviour induced by apomorphine was enhanced by prior treatment with both 40 and 200 mg/kg of L-DOPA. The treatment regimes with L-DOPA had no effect on the concentrations of apomorphine in the striatum. Administration of L-DOPA (40 or 200 mg/kg) followed by withdrawal for 3 days, had no effect on the concentrations of dopamine, homovanillic acid (HVA) or 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum. The Bmax and KD for the binding of [3H]spiperone, [3H]N,n-propylnorapomorphine (NPA) and [3H] piflutixol in the striatum was not altered by drug treatment. Similarly, the formation of dopamine-stimulated cyclic AMP in homogenates of striatum was unaltered by repeated administration of L-DOPA. Repeated administration of L-DOPA for 14 days in the rat appears to result in altered behaviour mediated by dopamine in the absence of any apparent change in the function of dopamine receptors in the striatum.
Assuntos
Comportamento Animal/efeitos dos fármacos , Química Encefálica/efeitos dos fármacos , Levodopa/farmacologia , Receptores Dopaminérgicos/efeitos dos fármacos , Ácido 3,4-Di-Hidroxifenilacético/metabolismo , Adenilil Ciclases/metabolismo , Animais , Apomorfina/farmacologia , Peso Corporal/efeitos dos fármacos , Corpo Estriado/metabolismo , Dopamina/metabolismo , Feminino , Ácido Homovanílico/metabolismo , Humanos , Atividade Motora/efeitos dos fármacos , Ratos , Ratos Endogâmicos , Comportamento Estereotipado/efeitos dos fármacosRESUMO
Administration of cis-flupenthixol (0.8-1.2 mg/kg per day) for 18 months enhanced stereotyped behaviour induced by apomorphine, bromocriptine and lergotrile, but not that induced by amphetamine or lisuride. Catalepsy induced by acute administration of haloperidol, trifluoperazine or cis-flupenthixol was reduced by continuous chronic intake of cis-flupenthixol. The number (Bmax) and dissociation constant (KD) of specific [3H]spiperone binding sites on striatal membranes was increased by chronic administration of cis-flupenthixol, but not trans-flupenthixol. In contrast, the Bmax and KD for specific binding of [3H]N,n-propylnorapomorphine were decreased by administration of cis-flupenthixol compared to the effect of the trans-isomer. Specific binding of [3H]piflutixol was unaffected by chronic administration of cis- or trans-flupenthixol, but chronic administration of cis-flupenthixol enhanced stimulation by dopamine of the activity of striatal adenylate cyclase. As a result of chronic continuous administration of cis-flupenthixol dopamine receptors in the striatum appeared to be supersensitive to most dopamine agonists but sub-sensitive to dopamine antagonists. This was reflected by increased numbers of D-2 antagonist receptor sites of decreased affinity, but by a decreased number of agonist sites of higher affinity. The D-1 recognition sites appeared to be unaltered, but activity of adenylate cyclase stimulated by dopamine was enhanced, suggesting post-junctional changes. The D-2 receptors appear to be primarily concerned with altered function of dopamine receptors.
Assuntos
Corpo Estriado/efeitos dos fármacos , Flupentixol/farmacologia , Receptores Dopaminérgicos/efeitos dos fármacos , Tioxantenos/farmacologia , Adenilil Ciclases/análise , Animais , Apomorfina/farmacologia , Peso Corporal/efeitos dos fármacos , Catalepsia/induzido quimicamente , Corpo Estriado/análise , Humanos , Masculino , Ratos , Ratos Endogâmicos , Receptores Dopaminérgicos/análise , Espiperona/metabolismo , Estereoisomerismo , Comportamento Estereotipado/efeitos dos fármacosRESUMO
We have used the whole cell patch clamp method and fura-2 fluorescence imaging to study the actions of gabapentin (1-(aminoethyl) cyclohexane acetic acid) on voltage-activated Ca(2+) entry into neonatal cultured dorsal root ganglion (DRG) neurones and differentiated F-11 (embryonic rat DRG x neuroblastoma hybrid) cells. Gabapentin (2.5 microM) in contrast to GABA (10 microM) did not influence resting membrane potential or input resistance. In current clamp mode gabapentin failed to influence the properties of evoked single action potentials but did reduce the duration of action potentials prolonged by Ba(2+). Gabapentin attenuated high voltage-activated Ca(2+) channel currents in a dose- and voltage- dependent manner in DRG neurones and reduced Ca(2+) influx evoked by K(+) depolarisation in differentiated F-11 cells loaded with fura-2. The sensitivity of DRG neurones to gabapentin was not changed by the GABA(B) receptor antagonist saclofen but pertussis toxin pre-treatment reduced the inhibitory effects of gabapentin. Experiments following pre-treatment of DRG neurones with a PKA-activator and a PKA-inhibitor implicated change in phosphorylation state as a mechanism, which influenced gabapentin action. Sp- and Rp-analogues of cAMP significantly increased or decreased gabapentin-mediated inhibition of voltage-activated Ca(2+) channel currents. Culture conditions used to maintain DRG neurones and passage number of differentiated F-11 cells also influenced the sensitivity of Ca(2+) channels to gabapentin. We analysed the Ca(2+) channel subunits expressed in populations of DRG neurones and F-11 cells that responded to gabapentin had low sensitivity to gabapentin or were insensitive to gabapentin, by Quantitative TaqMan PCR. The data obtained from this analysis suggested that the relative abundance of the Ca(2+) channel beta(2) and alpha(2)delta subunit expressed was a key determinant of gabapentin sensitivity of both cultured DRG neurones and differentiated F-11 cells. In conclusion, gabapentin inhibited part of the high voltage-activated Ca(2+) current in neonatal rat cultured DRG neurones via a mechanism that was independent of GABA receptor activation, but was sensitive to pertussis toxin. Gabapentin responses identified in this study implicated Ca(2+) channel beta(2) subunit type as critically important to drug sensitivity and interactions with alpha(1) and alpha(2)delta subunits may be implicated in antihyperalgesic therapeutic action for this compound.
Assuntos
Acetatos/farmacologia , Aminas , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/fisiologia , Ácidos Cicloexanocarboxílicos , Ativação do Canal Iônico/efeitos dos fármacos , Inibição Neural/efeitos dos fármacos , Neurônios Aferentes/efeitos dos fármacos , Animais , Anticonvulsivantes/farmacologia , Canais de Cálcio/biossíntese , Canais de Cálcio/genética , Células Cultivadas , Técnicas de Cocultura , Gabapentina , Ativação do Canal Iônico/fisiologia , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Inibição Neural/fisiologia , Neurônios Aferentes/fisiologia , Técnicas de Patch-Clamp , Ratos , Ratos Wistar , Ácido gama-Aminobutírico/farmacologiaRESUMO
Models of the hydrophobicity of platinum drugs based on exposed surface areas of polar and nonpolar atoms are presented. For a total of 24 log P(oct) data, the best model resulted in a standard deviation of 0.35 over a range of more than 4 log units, with regression coefficients in broad agreement with previous models of log P(oct) for organic molecules. This model is used to compare log P(oct) to cell uptake for five platinum drugs and hence to establish an exponential relation between these parameters.
Assuntos
Antineoplásicos/química , Compostos Organoplatínicos/química , Modelos Químicos , Teoria Quântica , Análise de Regressão , SolubilidadeRESUMO
A combination of autoradiographical techniques and computerized image analysis has been used to study the distribution and density of cholecystokinin receptors in the paraventricular and supraoptic nuclei of animals in which the magnocellular-posterior pituitary axis is activated, namely, in salt-loaded (2% sodium chloride) and homozygous Brattleboro rats. [125I]cholecystokinin octapeptide binding was greatly elevated in the paraventricular, supraoptic and accessory nuclei of salt-loaded and homozygous Brattleboro rats, compared to the respective control animals. Furthermore, under these conditions [125I]cholecystokinin octapeptide binding in the paraventricular nucleus was localized almost exclusively to magnocellular subdivisions, and especially to those containing predominantly oxytocin neurons. Autoradiographical competition studies revealed that the increase in [125I]cholecystokinin octapeptide binding in magnocellular nuclei reflected an increase in receptor number (Bmax) rather than affinity (Kd). These results suggest that cholecystokinin receptor density in the paraventricular, supraoptic and accessory magnocellular nuclei is closely linked to magnocellular neurosecretory activity and raises the possibility that cholecystokinin receptors may be involved in oxytocin and vasopressin release processes.
Assuntos
Núcleo Hipotalâmico Paraventricular/metabolismo , Ratos Brattleboro/metabolismo , Ratos Mutantes/metabolismo , Receptores da Colecistocinina/metabolismo , Sincalida/metabolismo , Núcleo Supraóptico/metabolismo , Núcleos Vestibulares/fisiologia , Animais , Processamento de Imagem Assistida por Computador , Masculino , Núcleo Hipotalâmico Paraventricular/fisiologia , Ratos , Ratos Endogâmicos , Núcleo Supraóptico/fisiologiaRESUMO
1-Methyl-4-phenylpyridinium ion (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, has been chronically infused (10 micrograms/24 h for 7 days) via osmotic minipumps into the left median forebrain bundle of the rat in order to determine whether it can induce permanent damage to the nigrostriatal dopamine system. Its effects were assessed over a period of 6 months post lesion. Four to 5 days following minipump implantation, all MPP+-treated animals displayed spontaneous ipsilateral postural bias indicating a marked imbalance in striatal dopamine and degeneration of the ipsilateral nigrostriatal dopamine pathway. After 3-5 weeks, MPP+-infused animals showed dose-related ipsilateral and contralateral circling in response to methamphetamine (1-5 mg/kg i.p.) and apomorphine (0.05-0.25 mg/kg s.c.) respectively. In vivo, using bilateral monitoring of striatal dopamine in MPP+-infused animals at 2 and 4 months by push-pull perfusion, both basal and methamphetamine- (2.5 mg/kg i.p.) stimulated release of dopamine was undetectable in the ipsilateral striatum, indicating a complete loss of dopamine terminals. In contrast, in the contralateral striatum of these animals and in striata of saline-infused animals, there were 4-5-fold increases in dopamine release in response to methamphetamine. Six months after lesion, animals infused with MPP+ continue to exhibit robust rotational behaviour in response to methamphetamine and apomorphine. In the ipsilateral striatum of the MPP+-infused animals the tissue concentrations of dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, were all undetectable; however, the levels of noradrenaline, serotonin and its metabolite, 5-hydroxyindoleacetic acid, were not significantly different from control values. In contrast to the striatum, MPP+ had no significant effect on the levels of dopamine and its metabolites in the ipsilateral nucleus accumbens; in addition, the levels of noradrenaline and serotonin and its metabolite were comparable to control levels. Histological examination revealed a marked loss of cells and severe gliosis in the substantia nigra pars compacta of MPP+-infused animals. The present results provide evidence that direct infusion of MPP+ into the medial forebrain bundle of the rat can lead to a complete loss of dopamine neurons in the pars compacta of the substantia nigra with ensuing behavioural, neurochemical and biochemical changes characteristic of the lesion.(ABSTRACT TRUNCATED AT 400 WORDS)
Assuntos
Corpo Estriado/fisiopatologia , Dopamina/fisiologia , Doença de Parkinson Secundária/fisiopatologia , Compostos de Piridínio/toxicidade , Comportamento Estereotipado/fisiologia , Substância Negra/fisiopatologia , 1-Metil-4-fenilpiridínio , Animais , Apomorfina/farmacologia , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/metabolismo , Dopamina/metabolismo , Relação Dose-Resposta a Droga , Feminino , Lateralidade Funcional , Metanfetamina/farmacologia , Doença de Parkinson Secundária/induzido quimicamente , Doença de Parkinson Secundária/metabolismo , Postura , Ratos , Ratos Endogâmicos , Comportamento Estereotipado/efeitos dos fármacos , Substância Negra/efeitos dos fármacos , Substância Negra/metabolismoRESUMO
The autoradiographical localization of dopamine D1, D2 and cholecystokinin receptors has been investigated in rat brain 6 months following unilateral infusion of 1-methyl-4-phenyl pyridinium ion (MPP+) (10 micrograms/day for 7 days) into the nigrostriatal dopamine pathway. Treatment with 1-methyl-4-phenyl pyridinium ion produced a marked depletion of dopamine cell bodies in the substantia nigra together with greater than 95% loss of tyrosine hydroxylase immunoreactivity in the striatum. Measurement of specific [3H]spiperone binding to D2 receptors indicated a 38% increase (P less than 0.01) in the maximal binding capacity of [3H]spiperone to striatal membrane homogenates and a 13% increase (P less than 0.05) in specific [3H]spiperone binding to striatal tissue sections, verifying striatal D2 receptor denervation supersensitivity. In contrast, MPP+ lesion of the nigrostriatal tract had no effect on the autoradiographical localization of striatal D1 or cholecystokinin receptors. In addition, there was a 38% loss (P less than 0.05) of D2 receptor binding sites in the substantia nigra pars compacta, whilst D1 receptors remained unchanged. Similar changes in dopamine and cholecystokinin receptor number were found following 6-hydroxydopamine lesion of the nigrostriatal dopamine pathway. These results provide further evidence that 1-methyl-4-phenyl pyridinium ion treatment in rats produces extensive destruction of the dopaminergic nigrostriatal tract and supports the differential anatomical localization of striatal and nigral D1, D2 and cholecystokinin receptors.
Assuntos
Benzazepinas , Benzazepinas/análogos & derivados , Corpo Estriado/metabolismo , Doença de Parkinson Secundária/metabolismo , Compostos de Piridínio/toxicidade , Receptores da Colecistocinina/metabolismo , Receptores Dopaminérgicos/metabolismo , Substância Negra/metabolismo , 1-Metil-4-fenilpiridínio , Animais , Autorradiografia , Benzazepinas/metabolismo , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/fisiopatologia , Lateralidade Funcional , Processamento de Imagem Assistida por Computador , Masculino , Doença de Parkinson Secundária/induzido quimicamente , Doença de Parkinson Secundária/fisiopatologia , Ratos , Ratos Endogâmicos , Sincalida/metabolismo , Espiperona/metabolismo , Substância Negra/efeitos dos fármacos , Substância Negra/fisiopatologiaRESUMO
Specific [3H]-spiperone and [3H]-N,n-propylnorapomorphine (NPA) binding was measured in striatum and substantia nigra of the rat following unilateral 6-hydroxydopamine (6-OHDA) lesions of the medial forebrain bundle, kainic acid lesions of the substantia nigra or striatum, and following decortication. Binding sites labelled by [3H]-spiperone in striatum were found to lie on striatal cell bodies and on the terminals of cortico-striate glutamate fibres, but not on presynaptic dopamine terminals. In contrast, binding sites labelled by [3H]-NPA were demonstrated on striatal cell bodies and on the terminals of nigro-striata dopamine fibres, but not on cortical afferents. In substantia nigra, specific [3H]-spiperone binding sites were found only on non-dopamine cell bodies. No clear evidence was found for their existence on dopamine cell bodies, the terminals of strio-nigral fibres or the terminals of cortico-nigral fibres. In contrast, specific binding sites for [3H]-NPA were found on dopamine cell bodies and the terminals of strio-nigral fibres. Localization on non-dopamine cell bodies or on cortico-nigral fibres was not demonstrated. These studies support the concept of differential localization of agonist and antagonist binding sites.