Molecular cloning of natriuretic peptides from the heart of reptiles : loss of ANP in diapsid reptiles and birds

Atrial natriuretic peptide (ANP) and B-type NP (BNP) are hormones involved in homeostatic control of body fluid and cardiovascular regulation. Both ANP and BNP have been cloned from the heart of mammals, amphibians, and teleost fishes, while an additional cardiac peptide, ventricular NP, has been found in selected species of teleost fish. However, in chicken, BNP is the primary cardiac peptide identified thus far. In contrast, the types of NP/s present in the reptilian heart are unknown, representing a considerable gap in our understanding of NP evolution. In the present study, we cloned and sequenced a BNP cDNA from the atria of representative species of reptile, including crocodile, lizard, snake, and tortoise. In addition, we cloned BNP from the pigeon atria. The reptilian and pigeon BNP cDNAs had ATTTA repeats in the 3′ untranslated region, as observed in all vertebrate BNP mRNAs. A high sequence homology was evident when comparing reptile and pigeon preproBNP with the previously identified chicken preproBNP. In particular, the predicted mature BNP-29 was identical between crocodile, tortoise, and chicken, with pigeon having a single amino acid substitution; lizard and snake BNP had seven and nine substitutions, respectively. Furthermore, an ANP cDNA could only be cloned from the tortoise atria. Since ANP was not isolated from the heart of any non-chelonian reptile and appears to be absent in birds, we propose that the ANP gene has been lost after branching of the turtles in the amniote line. This data provides new avenues for research on NP function in reptiles.

The Heart of the South American Rattlesnake, Crotalus durissus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Remodelamento cardíaco: análise seriada e índices de detecção precoce de disfunção ventricular

FUNDAMENTO: A estenose aórtica supravalvar (EAo) é utilizada para o estudo da remodelação cardíaca (RC) por sobrecarga pressórica. Nesse modelo, não estão claramente estabelecidos o comportamento da RC desde a fase inicial, nem os melhores parâmetros para a identificação da disfunção ventricular. OBJETIVOS: 1) Caracterizar, precoce e evolutivamente, as modificações morfofuncionais durante a RC em ratos com EAo e 2) identificar o índice mais sensível para detecção do momento do aparecimento da disfunção diastólica e sistólica do ventrículo esquerdo (VE). MÉTODOS: Ratos Wistar foram divididos em dois grupos - controle (GC, n=13) e EAo (GEAo, n=24) - e estudados nas 3ª, 6ª, 12ª e 18ª semanas pós-cirurgia. Os corações foram analisados por meio de ecocardiograma (ECO). RESULTADOS: Ao final do experimento, as relações do VE, do ventrículo direito e dos átrios com o peso corporal final foram aumentadas no GEAo. O ECO mostrou que o átrio esquerdo sofreu uma remodelação significativa a partir da 6ª semana. No GEAo, a porcentagem de encurtamento endocárdico apresentou queda significativa a partir da 12ª semana e a porcentagem de encurtamento mesocárdico, na 18ª semana. A relação onda E e onda A (E/A) foi superior no GC em comparação ao GEAo em todos os momentos analisados. CONCLUSÕES: O ventrículo esquerdo dos ratos com EAo, durante o processo de remodelação, apresentou hipertrofia concêntrica, disfunção diastólica precoce e melhoria da função sistólica, com posterior deterioração do desempenho. Além disso, constatou-se que os índices ecocardiográficos mais sensíveis para a detecção da disfunção diastólica e sistólica são, respectivamente, a relação E/A e a porcentagem de encurtamento endocárdico.

Stress-induced subsensitivity to catecholamines depends on the estrous cycle

In this article we compare how sensitivity to the chronotropic effect of noradrenaline and adrenaline of right atria isolated from female rats is modified after repeated swimming or foot-shock stress, under the influence of the estrous cycle. Right atria from stressed female rats sacrificed at diestrus were subsensitive to both catecholamines, irrespective of the stressor agent. However, although subsensitivity to noradrenaline was of similar intensity, subsensitivity to adrenaline was more pronounced in right atria from foot shock stressed rats as opposed to swimming-stressed rats. Identical stress protocols did not induce any alteration in atrial sensitivity to catecholamines when the stressed female rats were sacrificed at estrus. We conclude that the stress reaction concerning the mediation of cardiac chronotropism by catecholamines is related to the severity of the stressor agent and is strongly influenced by the estrous cycle.

Modulation of coronary flow and cardiomyocyte size by sensory fibers

Cardiac tissue is densely innervated by sensory neurons that an believed to play important modulatory roles in cardiac functions. In this study, pretreatment of neonate mts with capsaicin was performed. In adult rats, cardiomyocyte size and amount of fibrous tissue in left ventricles as well as in vitro coronary flow were evaluated, the chronotropic and inotropic responses to beta-adrenoceptor agonists (norepinephrine and isoproterenol), muscarinic agonists (carbachol and pilocarpine), and calcitonin gene-related peptide (CGRP) were also investigated with the use of the isolated right atria preparation. Capsaicin pretreatment significantly (P<0.05) reduced both basal coronary flow (18% reduction) and cardiomyocyte size (34% reduction) without affecting the amount of fibrous tissues in the left ventricles. The positive inotropic and chronotropic effects in response to norepinephrine in the isolated rat heart did not significantly differ between control and capsaicin-treated rats, Similarly, the positive chronotropic effects in response to norepinephrine, isoproterenol, and CGRP as well as the negative chronotropic responses to carbachol and pilocarpine in the isolated light atria were not affected by capsaicin pretreatment, Our data are consistent with the suggestion that reductions of both basal coronary flow and cardiomyocyte size seen in hearts from capsaicin-pretreated rats may be consequences of CGRP depletion. The cardiomyocyte size reduction produced by capsaicin treatment may be related to a modulatory role of CGRP as a growth factor.

Sino-aortic denervation causes right atrial beta adrenoceptor down-regulation

Rat isolated right atria obtained 1 wk after sinoaortic denervation were less sensitive to the chronotropic actions of beta-agonists than were tissues obtained from animals that underwent sham surgery or no surgery at all. The potencies, but not the maximal responses for two high efficacy agonists, norepinephrine and isoproterenol, were reduced about 3- to 4-fold. Sinoaortic denervation (SAD) caused about a 3-fold decrease in potency and about a 60% decrease in maximal response for a low efficacy agonist, prenalterol. The changes in the actions of these agonists occurred in the absence of any changes in the subtype of beta receptor mediating the chronotropic response. The results of analyses of the data for prenalterol showed that SAD caused a decrease in the operational efficacy of this agonist without any changes in its K-D value for beta-1 adrenoceptors. SAD had no effect on the responses of the tissue to blockade of uptake 1 and uptake 2, suggesting no compensatory changes in the removal processes caused the decreased potency. The results of radioligand binding assays showed that SAD caused a decrease in the maximal binding of I-125-cyanopindolol without altering its K-D. Also, the results of competition binding assays confirmed the lack of effect of SAD on the K-D for prenalterol. The SAD-induced changes in the actions of agonists acting at right atrial beta-1 receptors were caused by a down-regulation of beta-1 adrenoceptors, which probably occurred in response to SAD-induced increases in sympathetic tone.

Influencia da elevacao sustentada da pressao arterial sobre a dP/dt do ventriculo esquerdo mantendo-se constante a pressao diastolica do ventriculo esquerdo

Purpose - To evaluate the influence of sustained elevations of arterial pressure on dP/dt values, which the left ventricular end diastolic pressure was kept constant. Methods - Thirteen anesthetized dogs, mechanically ventilated and submitted to thoracotomy and pharmacological autonomic block (atropine - 0.5 mg/kg IV + oxprenolol - 3 mg/kg IV) were studied. The arterial pressure elevation was obtained by mechanical constriction of the descending thoracic aorta. Analyses were made in control (C) situation and after two successives increments of arterial pressure, sustained for 10min, called hypertension 1 (H1) and hypertension 2 (H2), respectively. The end diastolic left ventricular pressure was kept constant by utilization of a perfusion system connected to the left atria. Results - Heart rate did not change (C: 125 ± 13.9bpm; H1: 125 ± 13.5bpm; H2: 123 ± 14.1bpm; p > 0.05); the LVSP increased (C: 119 ± 8.1mmHg; H1: 142 ± 7.9mmHg; H2: 166 ± 7.7mmHg; p < 0.01); the AoDP increased (C: 89 ± 11.6mmHg; H1: 99 ± 9.5mmHg; H2: 120 ± 11.8mmHg; p < 0.01); the LVEDP (C: 6.2 ± 2.48mmHg; H1: 6.3 ± 2.43mmHg; H2: 6.1 ± 2.51mmHg; p > 0.05) and the dP/dt (C: 3068 ± 1057.1mmHg/s; 3112 ± 995.7mmHg/s; H2: 3086 ± 979.5mmHg/s; p > 0.05) did not change. Conclusion - dP/dt values are not influenced by a sustained elevation of arterial pressure, when the end diastolic left ventricular pressure is kept constant.

Structural characteristics of the superior venae cavae wall at the intrapericardium segment in adults and aging individuals

The authors admit that the conjunctive-muscular constitution of the walls of the superior venae cavae throughout the length of the intrapericardium segment and the debouchement in the right atrium, associated with the presence of a myocardium sheath can be made up of a functional device of sphincter form able to act on the control of the blood flow to the interior of the arterial chamber as well as stopping blood flow during the arterial systole. The fixation of the venous wall to the deep chamber of the serous pericardium, contributes to growth in resistance during the elevation of venous pressure, making possible the preservation of integrity of the superior venae cavae. The expansion of fasciculi of nodal fibers in the right wall of the superior venae cavae permits that the unlocked impulse in the S-A node also reaches the vascular wall contributing to the shortening and diminution in caliber of the vein.

Estratificación y movilidad social en América Latina: transformaciones estructurales de un cuarto de siglo

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Estratificación y movilidad social en América Latina. Una agenda de trabajo

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Capital social y reducción de la pobreza en América Latina y el Caribe: en busca de un nuevo paradigma

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Capital social: concepto, dimensiones y estrategias para su desarrollo

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Estructura ocupacional, estructura social y clases sociales

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La dinámica del desarrollo del capital social: factores principales y su relación con movimientos sociales

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Heterogeneidad estructural urbana y poblacion en America Latina; version preliminar

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