Ednei Luiz Antonio

Determination of myocardial infarction size in rats by echocardiography and tetrazolium staining: correlation, agreements, and simplifications

Triphenyltetrazolium chloride (TTC) staining and echocardiography (ECHO) are methods used to determine experimental myocardial infarction (MI) size, whose practical applicability should be expanded. Our objectives were to analyze the accuracy of ECHO in determining infarction size in rats during the first days following coronary occlusion and to test whether a simplified single measurement by TTC correctly indicates MI size, as determined by the average value for multiple slices. Infarction was induced in female Wistar rats by coronary artery occlusion and MI size analysis was performed after the acute (7th day) and chronic periods (after 4 weeks) by ECHO matched with TTC. ECHO and TTC showed similar values of MI size (% of left ventricle perimeter) in acute (ECHO: 33 +/- 11, TTC: 35 +/- 14) and chronic (ECHO: 38 +/- 14, TTC: 39 +/- 13 periods), and also presented an excellent correlation (r = 0.92, P < 0.001). Although measurements from different heart planes showed discrepancies, a single measurement acquired from the mid-ventricular level by TTC was a good estimate of MI size calculated by the average of multiple planes, with minimal disagreement (Bland-Altman test with mean ratio bias of 0.99 +/- 0.07) and close to an ideal correlation (r = 0.99, P < 0.001). In the present study, ECHO was confirmed as a useful method for the determination of MI size even in the acute phase. Also, the single measure of a mid-ventricular section proposed as a simplification of the TTC method is a satisfactory prediction of average MI extension.

Increased NHE3 Abundance and Transport Activity in Renal Proximal Tubule of Rats with Heart Failure

Heart failure (HF) is associated with a reduced effective circulating volume that drives sodium and water retention and extracellular volume expansion. We therefore hypothesized that Na(+)/H(+) exchanger isoform 3 (NHE3), the major apical transcellular pathway for sodium reabsorption in the proximal tubule, is upregulated in an experimental model of HF. HF was induced in male rats by left ventricle radiofrequency ablation. Sham-operated rats (sham) were used as controls. At 6 wk after surgery, HF rats exhibited cardiac dysfunction with a dramatic increase in left ventricular end-diastolic pressure. By means of stationary in vivo microperfusion and pH-dependent sodium uptake, we demonstrated that NHE3 transport activity was significantly higher in the proximal tubule of HF compared with sham rats. Increased NHE3 activity was paralleled by increased renal cortical NHE3 expression at both protein and mRNA levels. In addition, the baseline PKA-dependent NHE3 phosphorylation at serine 552 was reduced in renal cortical membranes of rats with HF. Collectively, these results suggest that NHE3 is upregulated in the proximal tubule of HF rats by transcriptional, translational, and posttranslational mechanisms. Enhanced NHE3-mediated sodium reabsorption in the proximal tubule may contribute to extracellular volume expansion and edema, the hallmark feature of HF. Moreover, our study emphasizes the importance of undertaking a cardiorenal approach to contain progression of cardiac disease.

A função mecânica do miocárdio remanescente a um infarto do miocárdio é normal durante o período de cicatrização, embora exista insuficiência cardíaca

OBJECTIVE The temporal relation between ventricular dysfunction (VD) after myocardial infarction (MI) and remanent myocardium mechanics is not yet clear. The present work investigated--through Doppler echocardiography (ECHO)--ventricular function in rats with extensive MI, as well as the mechanical function of papillary muscles (PM) at the end of the healing period. METHODS ECHO and PM of 9 Wistar rats (MI) were studied against 9 controls (C) three weeks after LV myocardial infarction. The following were determined: developed tension (DT) and its first negative and positive derivative, time-to-peak tension (TPT), resting tension (RT), and relaxation time at 50% of DT at 0.5, 1.0, 1.5, 2.0 and 2.5 calcium concentrations (mM). Tetanic contractions were carried out after ryanodine administration at 1.5, 2.5 and 5.0 calcium concentrations. RESULTS VD was characterized by ECHO, with marked abnormality of diastolic volume and LV and ejection fraction in addition to clear restrictive pattern of blood flow through the mitral valve. No significant difference was found in myocardial mechanics data either for MI or for C rats. CONCLUSION The heart failure (HF) reported by MI rats with > 40% MI at the end of the healing period is not myocardial function dependent. Chamber structural changes and lower population of myocites should base VD and HF.

Exercise Attenuates Renal Dysfunction with Preservation of Myocardial Function in Chronic Kidney Disease

Previous studies have suggested that exercise improves renal and cardiac functions in patients with chronic kidney disease. The aim of this study was to evaluate the effects of long-term aerobic swimming exercise with overload on renal and cardiac function in rats with 5/6 nefrectomy (5/6Nx). Eight Wistar rats were placed into 4 groups: Control (C), Control+Exercise (E), Sedentary 5/6Nx (NxS) and 5/6Nx+Exercise (NxE). The rats were subjected to swimming exercise sessions with overload for 30 min five days per week for five weeks. Exercise reduced the effect of 5/6Nx on creatinine clearance compared to the NxS group. In addition, exercise minimized the increase in mean proteinuria compared to the NxS group (96.9±10.0 vs. 51.4±9.9 mg/24 h; p<0.05). Blood pressure was higher in the NxS and NxE groups compared to the C and E groups (216±4 and 178±3 vs. 123±2 and 124±2 mm Hg, p<0.05). In the 200 glomeruli that were evaluated, the NxS group had a higher sclerosis index than did the NxE group (16% vs. 2%, p<0.05). Echocardiography demonstrated a higher anterior wall of the left ventricle (LV) in diastole in the NxS group compared with the C, E and NxE groups. The NxS group also had a higher LV posterior wall in diastole and systole compared with the E group. The developed isometric tension in Lmax of the heart papillary muscle was lower in the NxS group compared with the C, E and NxE groups. These results suggested that exercise in 5/6Nx animals might reduce the progression of renal disease and lessen the cardiovascular impact of a reduction in renal mass.

Myocardial remodeling after large infarcts in rat converts post rest-potentiation in force decay

Miocárdio Remodelado después de Grandes Infartos en Ratas Convierte Potenciación Post-pausa en Disminucion de la Fuerza Danilo Sales Bocalini1, Leonardo dos-Santos4, Ednei Luiz Antonio1, Alexandra Alberta dos Santos1, Ana Paula Davel3, Luciana Venturini Rossoni2, Dalton Valentim Vassallo5, Paulo José Ferreira Tucci1 Departamento de Medicina Divisão de Cardiologia Universidade Federal de São Paulo1; Departamento de Fisiologia e Biofísica Instituto de Ciências Biomédicas Universidade de São Paulo2, São Paulo, SP; Departamento de Biologia Estrutural e Funcional Instituto de Biologia Universidade Estadual de Campinas3, Campinas, SP; Departamento de Ciências Fisiológicas Universidade Federal do Espírito Santo4; Departamento de Ciências Morfofuncionais Escola Superior de Ciências da Santa Casa de Misericórdia5, Vitória, ES, BrasilBACKGROUND Post-rest contraction (PRC) of cardiac muscle provides indirect information about the intracellular calcium handling. OBJECTIVE Our aim was to study the behavior of PRC, and its underlying mechanisms, in rats with myocardial infarction. METHODS Six weeks after coronary occlusion, the contractility of papillary muscles (PM) obtained from sham-operated (C, n=17), moderate infarcted (MMI, n=10) and large infarcted (LMI, n=14) rats was evaluated, following rest intervals of 10 to 60 seconds before and after incubation with lithium chloride (Li(+)) substituting sodium chloride or ryanodine (Ry). Protein expression of SR Ca(2+)-ATPase (SERCA2), Na(+)/Ca(2+) exchanger (NCX), phospholamban (PLB) and phospho-Ser(16)-PLB were analyzed by Western blotting. RESULTS MMI exhibited reduced PRC potentiation when compared to C. Opposing the normal potentiation for C, post-rest decays of force were observed in LMI muscles. In addition, Ry blocked PRC decay or potentiation observed in LMI and C; Li(+) inhibited NCX and converted PRC decay to potentiation in LMI. Although MMI and LMI presented decreased SERCA2 (72±7% and 47±9% of Control, respectively) and phospho-Ser(16)-PLB (75±5% and 46±11%, respectively) protein expression, overexpression of NCX (175±20%) was only observed in LMI muscles. CONCLUSION Our results showed, for the first time ever, that myocardial remodeling after MI in rats may change the regular potentiation to post-rest decay by affecting myocyte Ca(2+) handling proteins.FUNDAMENTO: La Contraccion pos pausa (CPP) del musculo cardiaco provee informaciones indirectas sobre la manejo del calcio intracelular. OBJETIVO: Nuestro objetivo fue estudiar el comportamiento de la CPP y sus mecanismos subyacentes en Ratas con infarto de miocardio. METODOS: Seis semanas despues de la oclusion coronaria, la contractilidad de los Musculos Papilares (MP) obtenidos a partir de Ratas sometidos a falsa cirurgia (C, n = 17), con infarto moderado (MMI, n = 10) y gran infarto (LMI, n = 14), fue evaluada despues de pausas de estimulos de 10 a 60 segundos antes y despues de la incubacion con cloruro de litio (Li+) en substitucion del cloruro de sodio o rianodina (Ry). La expresion proteica de SR Ca(2+)-ATPasa (SERCA2), intercambiador Na+/Ca2+ (NCX), fosfolamban (PLB) y fosfo-Ser (16)-PLB fue analizada por Western blotting. RESULTADOS: Los Ratas MMI presentaron potenciacion de CPP reducida en comparacion a los Ratas C. En oposicion a la potenciacion normal para Ratas C, fueron observadas decaimientos de fuerza post-reposo en los musculos de Ratas LMI. Ademas de eso, la Ry bloqueo la decaimiento o potenciacion de PRC observada en Ratas LMI y C; el Li+ inhibio el NCX y convirtio la decaimiento en potenciacion de CPP en Ratas LMI. Aunque los Ratas MMI y LMI hayan presentado disminucion en el SERCA2 (72 ± 7% y 47 ± 9% de Ratas control, respectivamente) y expresion proteica de fosfo-Ser16-PLB (75 ± 5% y 46 ± 11%, respectivamente), la superexpresion del NCX (175 ± 20%) solo fue observada en los musculos de Ratas LMI. CONCLUSION: Nuestros resultados mostraron, por primera vez, que el remodelado miocardico post-IAM en Ratas puede cambiar la potenciacion regular para decaimiento post-reposo, afectando las proteinas de manejo del Ca(2+) en miocitos.

Rats with high left ventricular end-diastolic pressure can be identified by Doppler echocardiography one week after myocardial infarction

The severity of left ventricular (LV) dysfunction in rats with myocardial infarction (MI) varies widely. Because homogeneity in baseline parameters is essential for experimental investigations, a study was conducted to establish whether Doppler echocardiography (DE) could accurately identify animals with high LV end-diastolic pressure as a marker of LV dysfunction soon after MI. Direct measurements of LV end-diastolic pressure were made and DE was performed simultaneously 1 week after surgically induced MI (N = 16) or sham-operation (N = 17) in female Wistar rats (200 to 250 g). The ratio of peak early (E) to late (A) diastolic LV filling velocities and the ratio of E velocity to peak early (Em) diastolic myocardial velocity were the best predictors of high LV end-diastolic pressure (>12 mmHg) soon after MI. Cut-off values of 1.77 for the E/A ratio (P = 0.001) identified rats with elevated LV end-diastolic pressure with 90% sensitivity and 80% specificity. Cut-off values of 20.4 for the E/Em ratio (P = 0.0001) identified rats with elevated LV end-diastolic pressure with 81.8% sensitivity and 80% specificity. Moreover, E/A and E/Em ratios were the only echocardiographic parameters independently associated with LV end-diastolic pressure in multiple linear regression analysis. Therefore, DE identifies rats with high LV end-diastolic pressure soon after MI. These findings have implications for using serial DE in animal selection and in the assessment of their response to experimental therapies.

Gender-Based Differences in Cardiac Remodeling and ILK Expression after Myocardial Infarction

Background Gender can influence post-infarction cardiac remodeling. Objective To evaluate whether gender influences left ventricular (LV) remodeling and integrin-linked kinase (ILK) after myocardial infarction (MI). Methods Female and male Wistar rats were assigned to one of three groups: sham, moderate MI (size: 20-39% of LV area), and large MI (size: ≥40% of LV area). MI was induced by coronary occlusion, and echocardiographic analysis was performed after six weeks to evaluate MI size as well as LV morphology and function. Real-time RT-PCR and Western blot were used to quantify ILK in the myocardium. Results MI size was similar between genders. MI resulted in systolic dysfunction and enlargement of end-diastolic as well as end-systolic dimension of LV as a function of necrotic area size in both genders. Female rats with large MI showed a lower diastolic and systolic dilatation than the respective male rats; however, LV dysfunction was similar between genders. Gene and protein levels of ILK were increased in female rats with moderate and large infarctions, but only male rats with large infarctions showed an altered ILK mRNA level. A negative linear correlation was evident between LV dimensions and ILK expression in female rats with large MI. Conclusions Post-MI ILK expression is altered in a gender-specific manner, and higher ILK levels found in females may be sufficient to improve LV geometry but not LV function.

A routine electrocardiogram cannot be used to determine the size of myocardial infarction in the rat

Nine lead electrocardiograms of non-infarcted (N = 61) and infarcted (N = 71) female Wistar rats (200-250 g) were analyzed in order to distinguish left ventricle myocardial infarction (MI) larger than 40% (LMI) from MI smaller than 40% (SMI). MI larger than 40% clearly caused a deviation of AQRS and AT from normal values of 270-360 degrees to 90-270 degrees. Infarcted rats showed Q wave in D1 larger than 1 mm with 94% sensitivity and 100% specificity. The sum of QRS positivity in V1, V2 and V6 lower than 10 mm identified MI with 82% sensitivity and 100% specificity. The data showed that MI can be easily and reliably diagnosed by electrocardiogram in the rat. However, contradicting what is frequently believed, when specificity and sensitivity were analyzed focusing on MI size, none of these current electrocardiographic indices of MI size adequately discriminates LMI from SMI.

Cardiac implications after myocardial infarction in rats previously undergoing physical exercise.

BACKGROUND Few studies have analyzed the cardiac effects of exercise prior to coronary occlusion. OBJECTIVE To evaluate the effects of myocardial infarction in rats undergoing physical exercise. METHODS Female rats underwent swimming exercise or were kept sedentary for eight weeks and were randomized to coronary occlusion or sham surgery, in one of the following four groups: Sedentary (S), exercise (E), Sedentary myocardial infarction (SMI) and Exercise myocardial infarction (EMI). After six weeks, their biometrics, Doppler echocardiography, hemodynamics and myocardial mechanics were analyzed. RESULTS No cardioprotection was observed in EMI animals and there was no difference in infarct size (%LV) between EMI (38.50 ± 4.60%) and SMI (36.58 ± 4.11%). Water content of the lung (%) of SMI (80 ± 0.59) and EMI (80 ± 0.57) was higher than that of S (78 ± 0.15) and E (78 ± 0.57) groups. Left ventricular systolic pressure (mmHg) (S: 130 ± 5, E: 118 ± 8; SMI: 91 ± 3; EMI: 98 ± 3) and the first positive time derivative (mmHg) positive pressure (S: 8216 ± 385; E: 8437 ± 572; SMI: 4674 ± 455; EMI: 5080 ± 412) of S and E were higher than those of SMI and EMI. The transverse fractional shortening (%) of SMI (27 ± 2) and EMI (25 ± 2) were similar and lower than that of E (65 ± 2) and S (69 ± 2). The E/A ratio was higher in SMI (5.14 ± 0.61) and EMI (4.73 ± 0.57) compared to S (2.96 ± 0.24) and E (2.83 ± 0 21). In studies of isolated papillary muscle, depression of the contractile capacity observed was similar to that of SMI and EMI, and there was no change in myocardial stiffness. CONCLUSION Previous training by swimming did not attenuate cardiac implications due to myocardial infarction.

Nível de atividade física em professores da rede estadual de ensino

OBJECTIVE To assess the level of physical activity in public school teachers. METHODS Cross-sectional study conducted with 1,681 teachers from the city of São Paulo, southeastern Brazil, in 2009. The International Physical Activity Questionnaire short version was applied and the level of physical activity was categorized as low, moderate or high. The study sample was stratified by age, gender and area of the city (south and east). The chi-square test was used for comparisons at a 5% level of significance. RESULTS The prevalence of low, moderate and high levels of physical activity was 46.3%, 42.7% and 11%, respectively. Low physical activity was more prevalent among those aged 31 to 42 years (19.5%) and less prevalent among those aged 55 to 66 (5.7%). Moderate and high levels of physical activity were less prevalent among older teachers. A greater proportion of teachers showed low and high levels of physical activity in the east compared to the south of the city (50.5% vs. 48.6%; 11.4% vs. 8.1%, respectively). The proportion of teachers reporting moderate physical activity was significantly lower in the east (38.1%) compared to the south of the city (43.3%). Low and high levels of physical activity were significantly higher in men than women (53% vs. 42.9%; 14.1% vs. 9.4%, respectively). The prevalence of moderate level of physical activity was significantly lower in men (32.9%) than women (47.7%). CONCLUSIONS The prevalence of low physical activity was strikingly high. Variables such as age, gender and city area should be taken into account while planning and targeting campaigns aimed at promoting increased physical activity in this population.