Biochemical and structural characterization of a beta-1,3-1,4-glucanase from Bacillus subtilis 168

beta-1,3-1,4-Glucanases (E.C. 3.2.1.73) hydrolyze linked beta-D-glucans, such as lichenan and barley beta-glucan. Recombinant beta-1,3-1,4-glucanase from Bacillus subtilis expressed in Escherichia coil and purified by Ni-NTA chromatography exhibited optimum activity at 50 degrees C and pH 6.0. The catalytic half-life at 60 degrees C decreased from 90 to 5 min when the enzyme was incubated in the presence and absence of Ca(2+) respectively. The kinetic parameters of lichenan hydrolysis were 2695, 3.1 and 1220 for V(max) (mu mol/min/mg), K(m) (mg mL(-1)) and K(cat) (s(-1)), respectively. Analysis by DLS, AUC and SAXS demonstrated the enzyme is monomeric in solution. Chemical denaturation monitored by ITFE and far-UV CD yielded Delta G(H2O) values of 9.6 and 9.1 kcal/mol, respectively, showing that the enzyme has intermediate stability when compared with other Bacillus beta-1,3-1,4-glucanases. The crystal structure shows the anti-parallel jelly-roll beta-sheet conserved in all GH16 beta-1,3-1,4-glucanases, with the amino acid differences between Bacillus sp. enzymes that are likely determinants of stability being distributed throughout the protein. (C) 2011 Elsevier Ltd. All rights reserved.

Wet deposition of major ions in a rural area impacted by biomass burning emissions

This work concerns the influence of industrialized agriculture in the tropics on precipitation chemistry. A total of 264 rain events were sampled using a wet-only collector in central Sao Paulo State, Brazil, between January 2003 and July 2007. Electroneutrality balance calculations (considering H(+), K(+), Na(+), NH(4)(+), Ca(2)(+), Mg(2)(+), Cl(-), NO(3)(-), SO(4)(2-), F(-), PO(4)(3-), H(3)CCOO(-), HCOO(-), C(2)O(4)(2-) and HCO(3)(-)) showed that there was an excess of cations (similar to 15%), which was attributed to the presence of unmeasured organic anion species originating from biomass burning and biogenic emissions. On average, the three ions NH(4)(+), NO(3)(-) and H(+) were responsible for >55% of the total ion concentrations in the rainwater samples. Concentrations (except of H(+)) were significantly higher (t-test; P = 0.05), by between two to six-fold depending on species, during the winter sugar cane harvest period, due to the practice of pre-harvest burning of the crop. Principal component analysis showed that three components could explain 88% of the variance for measurements made throughout the year: PC1 (52%, biomass burning and soil dust resuspension); PC2 (26%, secondary aerosols); PC3 (10%, road transport emissions). Differences between harvest and non-harvest periods appeared to be mainly due to an increased relative importance of road transport/industrial emissions during the summer (non-harvest) period. The volume-weighted mean (VWM) concentrations of ammonium (23.4 mu mol L(-1)) and nitrate (17.5 mu mol L(-1)) in rainwater samples collected during the harvest period were similar to those found in rainwater from Sao Paulo city, which emphasizes the importance of including rural agro-industrial emissions in regional-scale atmospheric chemistry and transport models. Since there was evidence of a biomass burning source throughout the year, it appears that rainwater composition will continue to be affected by vegetation fires, even after sugar cane burning is phased out as envisaged by recent Sao Paulo State legislation. (C) 2011 Elsevier Ltd. All rights reserved.

Intracellular free Ca2+ and basal Mn2+ influx in cultured aortic smooth muscle cells from spontaneously hypertensive and normotensive Wistar-Kyoto rats.

Numerous studies investigating the possible role of altered Ca2+ homeostasis in hypertension have compared resting and agonist-stimulated intracellular free Ca2+ ([Ca2+](i)) in cultured aortic smooth muscle cells from spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. However, such studies have not given consistent results. Differences in the method used to load cells with the Ca2+-sensitive indicator fura-2 have been investigated here as a possible source of variability between studies. We also describe the adaptation of a fluorescence technique for the assessment of basal Ca2+ permeability in SHR and WKY through the measurement of Mn2+ influx. The results are consistent with the hypothesis that basal Ca2+ influx is elevated in cultured aortic smooth muscle cells from SHR compared to those from WKY. However, this was not reflected as a significant difference between the two strains in basal or angiotensin II (200 nmol/L)stimulated [Ca2+](i). Furthermore, this result was not dependent on the protocol used to load cells with fura-2. Hence, measurement of bulk [Ca2+](i) does not appear to be the most sensitive parameter for altered Ca2+ homeostasis in SHR. Other compartments of the cell may better reflect altered Ca2+ fluxes in hypertension and are discussed in this work.

Mouse Leydig cells express multiple P2X receptor subunits

ATP acts on cellular membranes by interacting with P2X (ionotropic) and P2Y (metabotropic) receptors. Seven homomeric P2X receptors (P2X(1)-P2X(7)) and seven heteromeric receptors (P2X(1/2), P2X(1/4), P2X(1/5), P2X(2/3), P2X(2/6), P2X(4/6), P2X(4/7)) have been described. ATP treatment of Leydig cells leads to an increase in [Ca(2+)](i) and testosterone secretion, supporting the hypothesis that Ca(2+) signaling through purinergic receptors contributes to the process of testosterone secretion in these cells. Mouse Leydig cells have P2X receptors with a pharmacological and biophysical profile resembling P2X(2). In this work, we describe the presence of several P2X receptor subunits in mouse Leydig cells. Western blot experiments showed the presence of P2X(2), P2X(4), P2X(6), and P2X(7) subunits. These results were confirmed by immunofluorescence. Functional results support the hypothesis that heteromeric receptors are present in these cells since 0.5 mu M ivermectin induced an increase (131.2 +/- 5.9%) and 3 mu M ivermectin a decrease (64.2 +/- 4.8%) in the whole-cell currents evoked by ATP. These results indicate the presence of functional P2X(4) subunits. P2X(7) receptors were also present, but they were non-functional under the present conditions because dye uptake experiments with Lucifer yellow and ethidium bromide were negative. We conclude that a heteromeric channel, possibly P2X(2/4/6), is present in Leydig cells, but with an electrophysiological and pharmacological phenotype characteristic of the P2X(2) subunit.

Luteinizing hormone (LH) acts through PKA and PKC to modulate T-type calcium currents and intracellular calcium transients in mice Leydig cells

LH increases the intracellular Ca(2+) concentration ([Ca(2+)](i)) in mice Leydig cells, in a process triggered by calcium influx through T-type Ca(2+) channels. Here we show that LH modulates both T-type Ca(2+) currents and [Ca(2+)]; transients through the effects of PKA and PKC. LH increases the peak calcium current (at -20 mV) by 40%. A similar effect is seen with PMA. The effect of LH is completely blocked by the PKA inhibitors H89 and a synthetic inhibitory peptide (IP-20), but only partially by chelerythrine (PKC inhibitor). LH and the blockers induced only minor changes in the voltage dependence of activation, inactivation or deactivation of the currents. Staurosporine (blocker of PKA and PKC) impaired the [Ca(2+)](i) changes induced by LH. A similar effect was seen with H89. Although PMA slowly increased the [Ca(2+)](i) the subsequent addition of LH still triggered the typical transients in [Ca(2+)](i). Chelerythrine also does not avoid the Ca(2+) transients, showing that blockage of PKC is not sufficient to inhibit the LH induced [Ca(2+)](i) rise. In summary, these two kinases are not only directly involved in promoting testosterone synthesis but also act on the overall calcium dynamics in Leydig cells, mostly through the activation of PKA by LH. (c) 2011 Elsevier Ltd. All rights reserved.

Effects of Regular and Low-fluoride Dentifrices on Plaque Fluoride

Previous studies have indicated that the use of low-fluoride dentifrices could lead to proportionally higher plaque fluoride levels when compared with conventional dentifrices. This double-blind, randomized, crossover study determined the effects of placebo, low-fluoride, and conventional dentifrices on plaque fluoride concentrations ([F]) in children living in communities with 0.04, 0.72, and 3.36 ppm F in the drinking water. Children used the toothpastes twice daily, for 1 wk. Samples were collected 1 and 12 hrs after the last use of dentifrices and were analyzed for fluoride and calcium. Similar increases were found 1 hr after the children brushed with low-fluoride (ca. 1.9 mmol F/kg) and conventional (ca. 2.4 mmol F/kg) dentifrices in the 0.04- and 0.72-ppm-F communities. Despite the fact that the increases were less pronounced in the 3.36-ppm-F community, our results indicate that the use of a low-fluoride dentifrice promotes a proportionally higher increase in plaque [F] when compared with that achieved with a conventional dentifrice, based on dose-response considerations.

Solubility of Epiphany Endodontic Sealer Prepared with Resinous Solvent

Purpose: To evaluate in vitro the solubility of the Epiphany endodontic filling material Epiphany (Pentron Clinical Technologies, Wallingford, CT) prepared with its resinous solvent. Methods: The specimens were prepared in the following experimental conditions: (1) GI, epiphany without photoactivation; (2) GII, Epiphany prepared with resinous solvent without photoactivation; (3) Gill, Epiphany followed by photoactivation; and (4) GIV, Epiphany prepared with resinous solvent followed by photoactivation. Ten specimens of each group were obtained from Teflon molds with 80% reduction in volume of the specimen`s dimensions based on American National Standard Institute/American Dental Association (ANSI/ADA) Specification No. 57. The samples were weighted and immersed in distilled water for 7 days. After this period, they were removed, dried, and weighed again. Solubility was calculated by using samples weight loss (%). The immersion liquid was evaluated through atomic absorption spectrometry. Results: The sealers without photoactivation were statistically similar (p > 0.05) between themselves (GI = 6.93% and GII = 6.39%) and different from the uncured sealers, which were statistically different between themselves (p < 0.05) (GIII = 3.56% and GIV = 0.47%). Only the Epiphany sealer prepared with resinous solvent followed by photoactivation presented solubility values within ANSI/ADA requirements, liberating the following amounts of ions: 114.43 mu g of Ca(2+)/mL, 2.4 mu g of Mg(2+)/mL, 0.33 mu g of Fe(2+)/mL, 0.11 mu 4g of Zn(2+)/mL, 1.31 mu g of Ni(2+)/mL, and 7.1 mu g of Na(+)/mL. Conclusion: The association of resinous solvent to the Epiphany sealer followed by photoactivation resulted in a filling material with low solubility and expressive liberation of calcium ions. (J Endod 2009;35:715-718)

Valuing ecological functions of biodiversity in changbaishan mountain biosphere reserve in northeast china

Conservation of biodiversity can generate considerable indirect economic value and this is being increasingly recognized in China. For a forest ecosystem type of a nature reserve, the most important of its values are its ecological functions which provide human beings and other living things with beneficial environmental services. These services include water conservancy, soil protection, CO2 fixation and O-2 release, nutrient cycling, pollutant decomposition, and disease and pest control. Based on a case study in Changbaishan Mountain Biosphere Reserve in Northeast China, this paper provides a monetary valuation of these services by using opportunity cost and alternative cost methods. Using such an approach, this reserve is valued at 510.11 million yuan (USD 61.68 mill.) per year, 10 times higher than the opportunity cost (51.78 mill. yuan/ha.a) for regular timber production. While China has heeded United Nations Environmental Program (UNEP)'s call for economic evaluation of ecological functions, the assessment techniques used need to be improved in China and in the West for reasons mentioned.

Fate of N-15-labelled nitrate in a wet summer under different residue management regimes in young hoop pine plantations

A field study was conducted to investigate the fate of N-15-labelled nitrate applied at 20 kg N ha(-1) in a wet summer to microplots installed in areas under different residue management regimes in second-rotation hoop pine (Araucaria cunninghamii) plantations aged 1-3 years in south-east Queensland, Australia. PVC microplots of 235 mm diameter and 300 mm long were driven into 250 mm soil. There were three replications of each of eight treatments. These were areas just under and between 1-year-old windrows (ca. 2-3 m in width) of harvesting residues spaced 15 m apart, and with and without incorporated foliage residues (20 t DM ha(-1)); the areas just under and between 2- or 3-year-old windrows spaced 10 m apart. Only 7-29% of the added N-15 was recovered from the top 750 mm of the soil profile with the leaching loss estimated to be 70-86% over the 34-day period. The N-15 loss via denitrification was 3.7-6.3% by directly measuring the N-15 gases emitted. The microplots with the incorporated residues at the 1-year-old site had the highest N-15 loss (6.3%) as compared with the other treatments. The N-15 mass balance method together with the use of bromide (Br) tracer applied at 100 kg Br ha(-1) failed to obtain a reliable estimate of the denitrification loss. The microplots at the 1-year-old site had higher N-15 immobilisation rate (7.5-24.7%) compared with those at 2- and 3-year-old sites (2.1-3.6%). Incorporating the residues resulted in an increase in N-15 immobilisation rate (24.5-24.7%) compared with the control without the incorporated residues (8.4-14.3%). These findings suggest that climatic conditions played important roles in controlling the N-15 transformations in the wet summer season and that the residue management regimes could also significantly influence the N-15 transformations. Most of the N-15 loss occurred through leaching, but a considerable amount of the N-15 was lost through denitrification. Bromide proved to be an unsuitable tracer for monitoring the N-15 leaching and movement under the wet summer conditions. (C) 2002 Elsevier Science B.V. All rights reserved.

Composition and quality of harvest residues and soil organic matter under windrow residue management in young hoop pine plantations as revealed by solid-state C-13 NMR spectroscopy

Solid-state C-13 nuclear magnetic resonance (NMR) with cross-polarisation (CP) and magic-angle-spinning (MAS) was used to: (a) examine the changes in carbon (C) composition of windrowed harvest residues during the first 3 years of hoop pine plantations in subtropical Australia; (b) assess the impacts of windrowed harvest residues on soil organic matter (SOM) composition and quality in the 0-10 cm soil layer. Harvest residues were collected from 0-, 1-, 2- and 3-year-old windrows of ca. 2.5 m width (15 m apart for 0-, 1- and 2-year-old sites and 10 m apart for 3-year-old site). Soils from the 0 to 10 cm soil layer were collected from the 1-, 2- and 3-year-old sites. The 13C NMR spectra of the harvest residues indicated the presence of lignin in the hoop pine wood, foliage and newly incorporated organic matter (NIOM). Condensed tannin structures were found in the decay-resistant bark, small wood and foliage, but were absent in other residue components and SOM. The NMR spectra of small wood samples contained condensed tannin structures because the outer layer of bark was not removed. NIOM showed a shift from foliage-like structures (celluloses) to lignin-type structures, indicating an incorporation of woody residues from the decomposing harvest residues. Suberins were also present in the small wood, foliage and bark. The 13C CP NMR spectra of SOM indicated that in areas where windrows were present, SOM did not show compositional changes. However, an increase in SOM quality under the windrows in the second year after their formation as characterised by the alkyl C/O-alkyl C (A/O-A) ratio was mainly due to inputs from the decomposition of the labile, readily available components of the windrowed harvest residues. (C) 2002 Published by Elsevier Science B.V.

Contribui����o para o estudo da anexina V na apoptose celular em concentrados de eritr��citos

A hemoterapia moderna baseia-se na utiliza����o correcta dos diversos componentes sangu��neos, associados a um maior controle de qualidade do sangue, o que a torna mais segura e, actualmente, muitos doentes sao beneficiados pois, a transfus��o de componentes sanguineos, em situa��oes v��rias, est�� na linha da frente na manuten����o da vida e em casos extremos, o ��ltimo recurso que salva vidas. A qualidade e a seguran��a nas transfus��es de sangue s��o grandes preocupa����es da ��rea m��dica, autoridades de sa��de e doente1. O sangue obtido pelos Centros de Sangue provem de dadores volunt��rios, dotados de uma enorme sensibilidade social, que periodicamente assumem uma postura benevola e altruista e consequentemente mant��m os bancos de sangue providos de um produto imprescindivel no tratamento de diversas patologias. O produto final dispon��vel ��� concentrado de eritr��citos (CE��s), plasma e concentrado plaquet��rio ��� tem de assumir um car��cter seguro e vi��vel de modo a que os riscos para o doente sejam diminutos2. O controlo de qualidade aplicado a todo o sangue doado realiza provas de conformidade nas unidades com especifica����es previamente definidas, sendo a h��molise um dos par��metros importantes na avalia����o da qualidade dos concentrados de eritr��citos, pois, pode ocasionar implica����es clinicas para o receptor. Para al��m disso a avalia����o da concentra����o de hemoglobina (Hg) no sangue doado mostra-se um controlo imprescindivel que salvaguarda a qualidade e seguran��a do componente a transfundir3;4.At�� se obter um CE h�� todo um processo moroso e de responsabilidade vital. Todo o sangue obtido passa por v��rias etapas fundamentais at�� �� obten����o do componente pretendido (analise, produ����o e armazenamento). Os CE���s obtidos quando armazenados, num ambiente de refrigera����o, t��m uma vida ��til de 42 dias. Ap��s este per��odo, o sangue deve ser inutilizado por se verificar altera����es bioqu��micas, biomec��nicas, e imunol��gicas nos CE���s e por consequ��ncia a sua instabilidade vital no que ao tratamento de patologias, para as quais este componente est�� indicado, diz respeito5. Foi realizado um estudo experimental com o objetivo de avaliar a contribui����o da Anexina V na apoptose celular nos concentrados de eritr��citos, constatando a degrada����o dos mesmos ao longo de todo o per��odo de armazenamento e validar o paradigma que a ci��ncia preconiza: ���Os CE���s ap��s os 42 dias armazenados, em condi����es espec��ficas (2 a 6�� cent��grados), s��o inviaveis para transfundir���6;7. A avalia����o dos n��veis de apoptose por citometria de fluxo �� geralmente realizada por m��todos que utilizam Anexina V como marcador vital, que se associa aos res��duos de fosfatidilserina, externalizados no in��cio do processo apopt��tico. A Anexina V �� uma prote��na humana end��gena dependente do i��o Ca+2, amplamente distribu��da intracelularmente em altas concentra����es na placenta e em concentra����es mais baixas nos eritr��citos, plaquetas e mon��citos. Apresenta como principal caracter��stica a capacidade de se ligar �� fosfatidilserina, um fosfolip��do presente na camada interna da bicamada lip��dica, que durante a apoptose celular �� translocada para a camada externa da membrana celular. A determina����o da Anexina V �� normalmente utilizada para verificar se as c��lulas s��o vi��veis, apopt��ticas ou necr��ticas por meio de diferen��as na integridade da membrana plasm��tica. Assim, ao conjugar a Anexina V ao FITC (Isotiocianato de fluoresce��na) �� poss��vel identificar e quantificar as c��lulas apopt��ticas por citometria de fluxo7. Numa amostra de 15 CE���s, a qual foi induzida a hem��lise, verificou-se, por citometria de fluxo, que a viabilidade deste componente se desvanesce ao longo do tempo, confirmando assim que o tratamento, manuseamento e armazenamento do sangue compromete a vitalidade terapeutica deste insubstituivel produto vital.

Emiss��o de fluxos foliares, flora����o e ciclagem de nutrientes em clones de copa de Hevea pauciflora

A fenologia foliar tem sido utilizada como uma caracter��stica importante na sele����o dos clones de Hevea spp., enquanto o teor de nutrientes na serapilheira �� um bom indicador da ciclagem de nutrientes. O objetivo deste trabalho foi verificar o efeito da periodicidade de emiss��o de fluxos foliares na flora����o de copa de Hevea pauciflora, estado nutricional e qualidade da serapilheira. Foram avaliadas 15 plantas de 10 anos de idade dos clones de copa CNS G 112, CNS G 124 e CBA 2. Nas condi����es edafoclim��ticas da Amaz��nia tropical ��mida, a emiss��o de folhas e de flora����o de H. pauciflora ocorre com maior intensidade no segundo semestre (in��cio do per��odo chuvoso). A H. pauciflora apresenta maior ac��mulo de serapilheira que a floresta prim��ria e os teores foliares de 22,18 g kg-1 de N, 1,47 g kg-1 de P, 5,77 g kg-1 de K, 3,79 g kg-1 de Ca, 2,09 g kg-1 de Mg, 16,15 mg kg-1 de B, 6,14 mg kg-1 de Cu, 53,87 mg kg-1 de Fe, 66,20 mg kg-1 de Mn e 48,44 mg kg-1 de Zn podem ser utilizados como refer��ncia para essa esp��cie de seringueira.

Levosimendana em pacientes com insufici��ncia card��aca descompensada: efic��cia em uma coorte brasileira. Resultados do estudo BELIEF

FUNDAMENTO: A levosimendana �� um novo agente inodilatador que aumenta a contratilidade card��aca pela sensibiliza����o ao Ca(2+) e induz vasodilata����o por meio da ativa����o dos canais KATP/BKCa. OBJETIVO: Estudar a efic��cia e seguran��a da levosimendana em uma coorte brasileira portadora de insufici��ncia card��aca descompensada e em pacientes resistentes a agonistas b-adren��rgicos. M��TODOS: O BELIEF (Brazilian Evaluation of Levosimendan Infusion Efficacy) foi um estudo aberto, prospectivo, multic��ntrico e observacional realizado com 182 portadores de ICD de alto risco, todos tratados com levosimendana. O desfecho prim��rio do estudo era alta hospitalar sem terapia inotr��pica adicional (pacientes que responderam ao tratamento). Os desfechos secund��rios eram altera����es nos par��metros cl��nicos e hemodin��micos e nos n��veis de pept��deo natriur��tico cerebral (BNP). RESULTADOS: A taxa de mortalidade foi de 14,8%, e 139 dos 182 pacientes responderam ao tratamento. Entre os que n��o responderam, a taxa de mortalidade foi de 62,8%. A press��o arterial sist��lica foi um preditor de resposta ao tratamento. No grupo resistente aos agonistas b-adren��rgicos, 55,8% responderam ao tratamento. Ao todo, 54 pacientes tiveram pelo menos um evento adverso, a maioria dos quais desapareceu espontaneamente ou ap��s redu����o da dose da levosimendana. Houve uma melhora significativa na qualidade de vida entre 2 e 6 meses do acompanhamento (p < 0,0001). CONCLUS��O: Nossos resultados indicam que a infus��o de levosimendana �� uma terapia alternativa de curto prazo para tratamento de pacientes com ICD. A gravidade da insufici��ncia card��aca pode influenciar a resposta ao tratamento com levosimendana. S��o necess��rios estudos prospectivos com uma coorte brasileira que inclua tamb��m pacientes com doen��a de Chagas.

Exerc��cio e restri����o alimentar aumentam o RNAm de prote��nas do tr��nsito de Ca2+ mioc��rdico em ratos

FUNDAMENTO: Treinamento f��sico (TF) aumenta a sensibilidade dos horm��nios tireoidianos (HT) e a express��o g��nica de estruturas moleculares envolvidas no movimento intracelular de c��lcio do mioc��rdio, enquanto a restri����o alimentar (RIA) promove efeitos contr��rios ao TF. OBJETIVO: Avaliar os efeitos da associa����o TF e RIA sobre os n��veis plasm��ticos dos HT e a produ����o de mRNA dos receptores HT e estruturas moleculares do movimento de c��lcio do mioc��rdio de ratos. M��TODOS: Utilizaram-se ratos Wistar Kyoto divididos em: controle (C, n = 7), RIA (R50, n = 7), exerc��cio f��sico (EX, n = 7) e exerc��cio f��sico + RIA (EX50, n = 7). A RIA foi de 50% e o TF foi nata����o (1 hora/dia, cinco sess��es/semana, 12 semanas consecutivas). Avaliaram-se as concentra����es s��ricas de triiodotironina (T3), tiroxina (T4) e horm��nio tireotr��fico (TSH). O mRNA da bomba de c��lcio do ret��culo sarcoplasm��tico (SERCA2a), fosfolamban (PLB), trocador Na+/Ca+2 (NCX), canal lento de c��lcio (canal-L), rianodina (RYR), calsequestrina (CQS) e receptor de HT (TR&#945;1 e TR&#946;1) do mioc��rdio foram avaliados por rea����o em cadeia da polimerase (PCR) em tempo real. RESULTADOS: RIA reduziu o T4, TSH e mRNA do TR&#945;1 e aumentou a express��o da PLB, NCX e canal-L. TF aumentou a express��o do TR&#946;1, canal-L e NCX. A associa����o TF e RIA reduziu T4 e TSH e aumentou o mRNA do TR&#946;1, SERCA2a, NCX, PLB e correla����o do TR&#946;1 com a CQS e NCX. CONCLUS��O: Associa����o TF e RIA aumentou o mRNA das estruturas moleculares c��lcio transiente, por��m o eixo HT-receptor n��o parece participar da transcri����o g��nica dessas estruturas.

Disfun����o mioc��rdica e altera����es no tr��nsito de c��lcio intracelular em ratos obesos

FUNDAMENTO: V��rios mecanismos t��m sido propostos contribuir para a disfun����o card��aca em modelos de obesidade, tais como altera����es nas prote��nas do tr��nsito de c��lcio (Ca+2) e nos receptores beta-adren��rgicos. Todavia, o papel desses fatores no desenvolvimento da disfun����o mioc��rdica induzida pela obesidade ainda n��o est�� claro. OBJETIVO: Este estudo pretende investigar se a obesidade induzida por um ciclo de dieta hipercal��ricas resulta em disfun����o card��aca. Al��m disso, foi avaliado se essa altera����o funcional em ratos obesos est�� relacionada com o preju��zo do tr��nsito de Ca+2 e do sistema beta-adren��rgico. M��TODOS: Ratos Wistar machos, 30 dias de idade, foram alimentados com ra����o padr��o (C) e um ciclo de cinco dietas hipercal��ricas (Ob) por 15 semanas. A obesidade foi definida pelo aumento da porcentagem de gordura corporal dos ratos. A fun����o card��aca foi avaliada mediante an��lise isolada do m��sculo papilar do ventr��culo esquerdo em condi����es basais e ap��s manobras inotr��picas e lusitr��picas. RESULTADOS: Em compara����o com o grupo controle, os ratos obesos apresentaram aumento da gordura corporal e intoler��ncia a glicose. Os m��sculos dos ratos obesos desenvolveram valores basais semelhantes; entretanto, as respostas mioc��rdicas ao potencial p��s-pausa e aumento de Ca+2 extracelular foram comprometidas. N��o houve altera����es na fun����o card��aca entre os grupos ap��s a estimula����o beta-adren��rgica. CONCLUS��O: A obesidade promove disfun����o card��aca relacionada com altera����es no tr��nsito de Ca+2 intracelular. Esse preju��zo funcional �� provavelmente ocasionado pela redu����o da atividade da bomba de Ca+2 do ret��culo sarcoplasm��tico (SERCA2a) via Ca+2 calmodulina-quinase.