Litterfall production in intact and selectively logged forests in southern of Amazonia as a function of basal area of vegetation and plant density

Nutrient recycling in the forest is linked to the production and decomposition of litter, which are essential processes for forest maintenance, especially in regions of nutritionally poor soils. Human interventions in forest such as selecttive logging may have strong impacts on these processes. The objectives of this study were to estimate litterfall production and evaluate the influence of environmental factors (basal area of vegetation, plant density, canopy cover, and soil physicochemical properties) and anthropogenic factors (post-management age and exploited basal area) on this production, in areas of intact and exploited forest in southern Amazonia, located in the northern parts of Mato Grosso state. This study was conducted at five locations and the average annual production of litterfall was 10.6 Mg ha-1 year-1, higher than the values for the Amazon rainforest. There were differences in litterfall productions between study locations. Effects of historical logging intensity on litterfall production were not significant. Effects of basal area of vegetation and tree density on litterfall production were observed, highlighting the importance of local vegetation characteristics in litterfall production. This study demonstrated areas of transition between the Amazonia-Cerrado tend to have a higher litterfall production than Cerrado and Amazonia regions, and this information is important for a better understanding of the dynamics of nutrient and carbon cycling in these transition regions.

Protective effect of left ventricular hypertrophy in right coronary artery occlusions

OBJECTIVE: To test the hypothesis that left ventricular hypertrophy (LVH) reduces the electrocardiographic and functional effects of right coronary artery occlusion. METHODS: We analysed 215 patients (166 males and 49 women,age of 58.9±10.6 years), with occlusion of the right coronary artery without other associated lesions. There was no significant difference (p>0.05) in age and gender distribution between the 78 patients with LVH (left ventricular mass >100g/m²) (Group A) when compared with the 137 patients without LVH (left ventricular mass <100g/m²) (Group B). RESULTS: The electrocardiographic finding of transmural necrosis was more often found in group B patients than in group A patients (56.9% and 30.8%, respectively; p<0.05). The left ventricular function parameters of group A were better than those of group B: the ratio end-diastolic pressure/systolic pressure (EDP/SP) (A: 0.108±0.036; B: 0.121±0.050; p<0.05); the end-diastolic volume index (A: 75.9±31.3ml/m²; B: 88.0±31.0ml/m²; p<0.01); the end-systolic volume index (A: 16.0±10.0ml/m²; B: 27.0 ±20.0ml/m²; p<0.001); the ejection fraction (A 78.6±10.8%; B 67.7±17.9%; p<0.001); the anteroinferior shortening (A: 43.9±10.3%; B: 35.1±12.8%; p<0.001). A higher degree of coronary tortuosity was observed in group A than in group B (78.2% and 24.1%; p<0.001) and also a more frequent absent or minimal diaphragmatic hypokinetic area (A: 80.8%; B: 54.0%; p<0.05). CONCLUSION: LVH reduces the effects of myocardial sequela and protects LV function when right coronary occlusion develops.

Effects of protein-calorie restriction on mechanical function of hypertrophied cardiac muscle

OBJECTIVE: To assess the effect of food restriction (FR) on hypertrophied cardiac muscle in spontaneously hypertensive rats (SHR). METHODS: Isolated papillary muscle preparations of the left ventricle (LV) of 60-day-old SHR and of normotensive Wistar-Kyoto (WKY) rats were studied. The rats were fed either an unrestricted diet or FR diet (50% of the intake of the control diet) for 30 days. The mechanical function of the muscles was evaluated through monitoring isometric and isotonic contractions. RESULTS: FR caused: 1) reduction in the body weight and LV weight of SHR and WKY rats; 2) increase in the time to peak shortening and the time to peak developed tension (DT) in the hypertrophied myocardium of the SHR; 3) diverging changes in the mechanical function of the normal cardiac muscles of WKY rats with reduction in maximum velocity of isotonic shortening and of the time for DT to decrease 50% of its maximum value, and increase of the resting tension and of the rate of tension decline. CONCLUSION: Short-term FR causes prolongation of the contraction time of hypertrophied muscles and paradoxal changes in mechanical performance of normal cardiac fibers, with worsening of the shortening indices and of the resting tension, and improvement of the isometric relaxation.

Influence of the elevation of the left ventricular diastolic pressure on the values of the first temporal derivative of the ventricular pressure (dP/dt)

PURPOSE: To assess the effects of the elevation of the left ventricular end-diastolic pressure (LVEDP) on the value of the 1st temporal derivative of the ventricular pressure (dP/dt). METHODS: Nineteen anesthetized dogs were studied. The dogs were mechanically ventilated and underwent thoracotomy with parasympathetic nervous system block. The LVEDP was controlled with the use of a perfusion circuit connected to the left atrium and adjusted to the height of a reservoir. The elevation of the LVEDP was achieved by a sudden increase in the height of a reservoir filled with blood. Continuous recordings of the electrocardiogram, the aortic and ventricular pressures and the dP/dt were performed. RESULTS: Elevation of the LVEDP did not result in any variation of the heart rate (167±16.0bpm, before the procedure; 167±15.5bpm, after the procedure). All the other variables assessed, including systolic blood pressure (128±18.3mmHg and 150±21.5mmHg), diastolic blood pressure (98±16.9mmHg and 115±19.8mmHg), LVEDP (5.5±2.49 and 9.3±3.60mmHg), and dP/dt (4,855 ± 1,082 mmHg/s and 5,149±1,242mmHg/s) showed significant increases following the expansion of the ventricular cavity. Although the elevation of the dP/dt was statistically significant, 6 dogs curiously showed a decrease in the values of dP/dt. CONCLUSION: Sudden elevation of the LVEDP resulted in increased values of dP/dt; however, in some dogs, this response was not uniform.

Doppler echocardiographic study in adolescents and young adults with sickle cell anemia

OBJECTIVE: Anatomical and functional assessment of the heart through Doppler and echocardiography in patients with cell anemia (SCA). METHODS: Twenty-five patients with SCA and ages ranging from 14 to 45 years were prospectively studied in a comparison with 25 healthy volunteers. All of them underwent clinical and laboratory evaluation and Doppler echocardiography as well.The measurements were converted into body surface indices. RESULTS: There were increases in all chamber diameters and left ventricle (LV) mass of the SCA patients. It was characterised an eccentric hypertrophy of the left ventricle. The preload was increased (left ventricle end-diastolic volume) and the afterload was decreased (diastolic blood pressure, peripheral vascular resistance and end-systolic parietal stress ESPS). The cardiac index was increased due to the stroke volume. The ejection fraction and the percentage of the systolic shortening , as well as the systolic time intervals of the LV were equivalent. The isovolumetric contraction period of the LV was increased. The mitral E-septum distance and the end-systolic volume index (ESVi) were increased. The ESPS/ESVi ratio,a loading independent parameter, was decreased in SCA, suggesting systolic dysfunction. No significant differences in the diastolic function or in the pulmonary pressure occurred. CONCLUSION: Chamber dilations, eccentric hypertrophy and systolic dysfunction confirm the evidence of the literature in characterizing a sickle cell anemia cardiomyopathy.

End-systolic pressure-diameter relation of the left ventricle during transient and sustained elevations of blood pressure

OBJECTIVE: To assess the effect of transient and sustained variations in cardiac load on the values of the end-systolic pressure-diameter relation (ESPDR) of the left ventricle. METHODS: We studied 13 dogs under general anesthesia and autonomic blockade. Variations of cardiac loads were done by elevation of blood pressure by mechanical constriction of the aorta. Two protocols were used in each animal: gradual peaking and decreasing pressure variation, the "transient arterial hypertension protocol" (TAH), and a quick and 10 min sustained elevation, the "sustained arterial hypertension protocol"(SAH). Then, we compared the ESDR in these two situations. RESULTS: Acute elevation of arterial pressure, being it "transitory" or "sustained", did not alter the heart frequency and increased similarly the preload and after load. However, they acted differently in end systolic pressure-diameter relation. It was greater in the SAH than TAH protocol, 21.0±7.3mmHg/mm vs. 9.2±1.2mmHg/mm (p<0.05). CONCLUSION: The left ventricular ESPDR values determined during sustained pressure elevations were higher than those found during transient pressure elevations. The time-dependent activation of myocardial contractility associated with the Frank-Starling mechanism is the major factor in inotropic stimulation during sustained elevations of blood pressure, determining an increase in the ESPDR values.

Beta-adrenergic blocking agents in heart failure

Cardiac dysfunction in heart failure is widely recognized as a progressive process, regardless of the clinical signs and symptoms. An increase in cardiac sympathetic drive is one of the earliest neurohormonal responses occurring in patients with heart failure and may be one of the major causes of the progressive remodeling leading to the decline in myocardial function, and responsible for the poor prognosis of patients with heart failure. Therefore, recent data provided by several appropriately designed clinical trials clearly indicate the benefits of beta-adrenoceptor blocking agents, combined with diuretics, ACE inhibitors, and digoxin in chronic heart failure class II to IV due to systolic ventricular dysfunction. The benefits are related to symptoms, functional capacity, remodeling, and improvement in left ventricular function, reduction in cardiovascular hospitalization, a decrease in the overall and sudden cardiac death rate, and are similar in patients with ischemic or nonischemic cardiomyopathy, independent of age, gender, or functional class. In this review we describe the cardiovascular effects of the increase in sympathetic drive, the pharmacological properties of the beta-blockers most evaluated in heart failure therapy (metoprolol, bisoprolol, and carvedilol), the major clinical trials related to these agents in heart failure, the recommendations for their appropriate use in clinical practice, the precautions to be adopted, and how to handle the more common adverse reactions.

Acute Effects of Maternal Smoking on Fetal-Placental-Maternal System Hemodynamics

OBJECTIVE: To study acute hemodynamic alterations in the fetal-placental maternal system immediately after maternal exposure to nicotine. METHODS: This is a noncontrolled experimental study involving 21 pregnant smoking women, randomly selected, with uncomplicated pregnancies and without risk factors for fetal heart disease. Patients underwent ultrasound and fetal echocardiography before and after smoking a cigarette. They were asked to abstain from smoking for 12 hours before the study. The mean nicotine content of the cigarettes used in the study was 0.5mg of nicotine and 6mg of carbon monoxide. RESULTS: The average number of cigarettes smoked per a day prior to the study was 9.67. Gestational age ranged between 18 and 36 weeks. The mean maternal heart rate was elevated (P<0.001) as was the mean fetal heart rate (P=0.044). Maternal systolic blood pressure (P=0.004) and diastolic blood pressure (P=0.033) were also elevated after smoking. A decrease occurred in the systolic/diastolic ratio in the right uterine artery (P=0.014) and in the left uterine artery (P=0.039). The other hemodynamic variables remained unchanged. CONCLUSION: Cigarette smoking can cause changes in physiologic variables of fetal-placental circulation, but it does not change fetal cardiac function, in the dose of nicotine and its components used in this study. The decrease in systolic/diastolic ratio in the uterine arteries is probably related to a dose-dependent nicotine pattern.

Left Ventricular Diastolic Function in Essential Hypertensive Patients: Influence of Age and Left Ventricular Geometry

PURPOSE - To evaluate diastolic dysfunction (DD) in essential hypertension and the influence of age and cardiac geometry on this parameter. METHODS - Four hundred sixty essential hypertensive patients (HT) underwent Doppler echocardiography to obtain E/A wave ratio (E/A), atrial deceleration time (ADT), and isovolumetric relaxation time (IRT). All patients were grouped according to cardiac geometric patterns (NG - normal geometry; CR - concentric remodeling; CH- concentric hypertrophy; EH - eccentric hypertrophy) and to age (<40; 40 - 60; >60 years). One hundred six normotensives (NT) persons were also evaluated. RESULTS - A worsening of diastolic function in the HT compared with the NT, including HT with NG (E/A: NT - 1.38±0.03 vs HT - 1.27±0.02, p<0.01), was observed. A higher prevalence of DD occurred parallel to age and cardiac geometry also in the prehypertrophic groups (CR). Multiple regression analysis identified age as the most important predictor of DD (r²=0.30, p<0.01). CONCLUSION - DD was prevalent in this hypertensive population, being highly affected by age and less by heart structural parameters. DD is observed in incipient stages of hypertensive heart disease, and thus its early detection may help in the risk stratification of hypertensive patients.

Pregnancy and peripartum cardiomyopathy: a comparative and prospective study

OBJECTIVE: To assess pregnancy outcome in women with peripartum cardiomyopathy and to compare it with idiopathic cardiomyopathy. METHODS: Twenty-six pregnant women, aged 28.4±6.1 years, with dilated cardiomyopathy were followed. Eighteen patients had peripartum cardiomyopathy [11 with persistent left ventricular systolic dysfunction (EF=45.2±2) and 7 with recovered ventricular function (EF=62.3±3.6)]. The 8 remaining patients had idiopathic cardiomyopathy (EF= 43.5±4.1). During the prenatal period, limited physical activity and a low-sodium diet were recommended, and hospitalization was recommended when complications occurred. RESULTS: Of the 26 patients, 11 (42.3%) had a normal delivery; 9(35.5%) had cardiac complications, 6 (22.2%) had obstetric complications. Two patients (7.7%) died. Two preterm pregnancies occurred, with 26 health newborns (2 sets of twins). Two miscarriages took place. The cardiac complication rate during pregnancy was lower (p<0.009) in the peripartum cardiomyopathy group without ventricular dysfunction and greater (p=0.01) in the idiopathic group when compared with the peripartum group with ventricular dysfunction. Changes in left ventricular ejection fraction were not observed (p<0.05) in the postpartum period, when compared with that during pregnancy in the 3 groups. CONCLUSION: Pregnancy in patients with dilated cardiomyopathy is associated with maternal morbidity. Left ventricular function is a prognostic factor and must be the most parameter when counseling patients with peripartum cardiomyopathy about a new pregnancy.

Doppler Echocardiographic Assessment of Pregnant Women with Chronic Arterial Hypertension

OBJECTIVE: To assess structural and functional cardiac changes in asymptomatic pregnant women with chronic arterial hypertension (CAH). METHODS: One hundred pregnant women with CAH underwent conventional Doppler echocardiography. The Student t test was used to compare them with 29 normotensive pregnant women (NT) in their third gestational trimester. RESULTS: Systolic (SBP; mmHg) and diastolic (DBP; mmHg) blood pressure values were higher (p<0.001) in the CAH pregnant women (SBP: 139±19 and DBP: 92± 18) as compared with those of the NT group (SBP: 112±10 and DBP: 74±9). A significant enlargement of the left atrium (4.10±0.48 cm vs 3.6±0.3 cm; p<0.001) and of the left ventricular normalized mass (59.6±19.7 g/cm2,7 vs 41.9±3.4 g/cm2,7; p<0.001) was observed. Cardiac output (CO, L/min) and systolic volume (SV, mL) were significantly higher in the CAH group (CO: 6.0±1.54 vs 4.9±2.1, p<0.01; SV: 77.3±19.8 vs 56.5±25.8, p<0.001). CONCLUSION: Chronic hypertensive pregnant women have structural and functional cardiac changes that justify routine cardiologic assessment, even in the absence of cardiopulmonary symptoms.

Improvement in left ventricular dysfunction after surgical correction of mitral regurgitation

OBJECTIVE: To evaluate whether left ventricular end-systolic (ESD) diameters £ 51mm in patients (pt) with severe chronic mitral regurgitation (MR) are predictors of a poor prognosis after mitral valve surgery (MVS). METHODS: Eleven pt (aged 36±13 years) were studied in the preoperative period (pre), median of 36 days; in the early postoperative period (post1), median of 9 days; and in the late postoperative period (post2), mean of 38.5±37.6 months. Clinical and echocardiographic data were gathered from each pt with MR and systolic diameter ³51mm (mean = 57±4mm) to evaluate the result of MVS. Ten patients were in NYHA Class III/IV. RESULTS: All but 2 pt improved in functional class. Two pt died from heart failure and infectious endocarditis 14 and 11 months, respectively, after valve replacement. According to ejection fraction (EF) in post2, we identified 2 groups: group 1 (n=6), whose EF decreased in post1, but increased in post2 (p=0.01) and group 2 (n=5), whose EF decreased progressively from post1 to post2 (p=0.10). All pt with symptoms lasting £ 48 months had improvement in EF in post2 (p=0.01). CONCLUSION: ESD ³51mm are not always associated with a poor prognosis after MVS in patients with MR. Symptoms lasting up to 48 months are associated with improvement in left ventricular function.

Effect of oscillatory breathing on the variability of the RR Intervals and its prognostic importance in individuals with left ventricular global systolic dysfunction

OBJECTIVE: To assess the effect of the oscillatory breathing on the variability of RR intervals (VRR) and on prognostic significance after one year follow-up in subjects with left ventricular global systolic dysfunction. METHODS: We studied 76 subjects, whose age ranged from 40 to 80 years, paired for age and gender, divided into two groups: group I - 34 healthy subjects; group II - 42 subjects with left ventricular global systolic dysfunction (ejection fraction < 0.40). The ECG signals were acquired during 600s in supine position, and analyzed the variation of the thoracic amplitude and the VRR. Clinical and V-RR variables were applied into a logistic multivariate model to foretell survival after one year follow-up. RESULTS: Oscillatory breathing was detected in 35.7% of subjects in vigil state of group II, with a concentration of the spectral power in the very low frequency band, and was independent of the presence of diabetes, functional class, ejection fraction, cause of ventricular dysfunction and survival after one year follow-up. In the logistic regression model, ejection fraction was the only independent variable to predict survival. CONCLUSION: 1) Oscillatory breathing pattern is frequent during wakefulness in the left ventricular global systolic dysfunction and concentrates spectral power in the very low band of V-RR; 2) it does not relate to severity and cause of left ventricular dysfunction; 3) ejection fraction is the only independent predictive variable for survival in this group of subjects.

Effects of high glucose concentrations on the endothelial function of the renal microcirculation of rabbits

OBJECTIVE: To assess the acute effects of high glucose concentrations on vascular reactivity in the isolated non diabetic rabbit kidney. METHODS: Rabbits were anaesthetized for isolation of the kidneys. Renal arteries and veins were cannulated for perfusion with Krebs-Henselleit solution and measurement of perfusion pressure. After 3 hours of perfusion with glucose 5,5 mM (control ) and 15 mM, the circulation was submitted to sub maximal precontraction (80% of maximal response) trough continuous infusion of noradrenaline 10 mM. Vascular reactivity was then assessed trough dose-responses curves with endothelium-dependent (acetylcholine) and independent (sodium nitroprusside) vasodilators. The influence of hyperosmolarity was analyzed with perfusion with mannitol 15mM. RESULTS: A significant reduction in the endothelium-dependent vasodilation in glucose 15mM group was observed compared to that in control, but there was no difference in endothelium-independent vasodilation. After perfusion with mannitol 15 mM, a less expressive reduction in endothelium-dependent vasodilation was observed, only reaching significance in regard to the greatest dose of acetylcholine. CONCLUSION: High levels of glucose similar to those found in diabetic patients in the postprandial period can cause significant acute changes in renal vascular reactivity rabbits. In diabetic patients these effects may also occur and contribute to diabetes vascular disease.

Follow-up study of morphology and cardiac function in rats undergoing induction of supravalvular aortic stenosis

OBJECTIVE: To characterize the follow-up of an experimental model of left ventricular hypertrophy (LVH) induced by supravalvular ascending aortic stenosis in young rats. METHODS: Wistar rats were submitted to thoracotomy and aortic stenosis was created by placing a clip on the ascending aorta (AoS group, n=12). Age-matched control animals underwent a sham operation (C group, n=12). Cardiac function was analysed by echocardiograms performed 6, 12, and 21 weeks after aortic banding. Myocardial morphological features and myocardial hydroxyproline concentration (HOP) were evaluated 2, 6, 12, and 21 weeks after surgery in additional animals. RESULTS: Aortic banding promoted early concentric LVH and a progressive increase in HOP. Under light microscopy, we observed myocyte hypertrophy and wall thickening of the intramural branches of the coronary arteries due to medial hypertrophy. Cardiac function was supranormal after 6 weeks (percentage of fractional shortening - EAo6: 70.3±10.8; C6: 61.3±5.4; p<0.05), and depressed in the last period. Diastolic dysfunction was detected after 12 weeks (ratio of early-to-late filling velocity - EAo12: 4.20±3.25; C12: 1.61±0.16; p<0.05). CONCLUSION: Ascending aortic stenosis promotes concentric LVH with myocardial fibrosis and minimal histological changes. According to the period of evaluation, cardiac function may be improved, normal, or depressed. The model is suitable and useful for studies on pathophysiology and treatment of the different phases of cardiac hypertrophy.