Serum cardiac troponin I concentration in dogs with ehrlichiosis

Background: Ehrlichiosis is a multisystemic disease with the potential to cause cardiomyocyte injury in naturally infected dogs. Hypothesis: Myocardial injury occurs in dogs infected with Ehrlichia canis. Animals: One-hundred and ninety-four dogs from Brazil with clinical and laboratory abnormalities indicative of ehrlichiosis. Sixteen healthy dogs served as controls. Methods: Electrocardiogram, echocardiogram, noninvasive blood pressure measurement, and serum cardiac troponin I (cTnI) concentrations were evaluated. Serologic assays and PCR determined the exposure and infection status for E. canis, Anaplasma spp., Babesia canis vogeli, Bartonella spp., Borrelia burgdorferi, Dirofilaria immitis, Ehrlichia chaffeensis, Ehrlichia ewingii, Leishmania chagasi, and spotted-fever group Rickettsia. Dogs were assigned to groups according to PCR status: E. canis infected, infected with other vector-borne organisms, sick dogs lacking PCR evidence for infection, and healthy controls. Results: E. canis-infected dogs had higher serum cTnI concentrations than controls (median: 0.04 ng/dL; range 0.04-9.12 ng/dL; control median: 0.04 ng/dL; range: 0.04-0.10 ng/dL; P = .012), and acute E. canis infection was associated with myocardial injury (odds ratio [OR]: 2.67, confidence interval [CI] 95%: 1.12-6.40, P = .027). Severity of anemia was correlated with increased risk of cardiomyocyte damage (r = 0.84, P < .001). Dogs with clinical signs of systemic inflammatory response syndrome (SIRS) were at higher risk for myocardial injury than were other sick dogs (OR: 2.55, CI 95%: 1.31-4.95, P = .005). Conclusions and Clinical Importance: Acute infection with E. canis is a risk factor for myocardial injury in naturally infected Brazilian dogs. Severity of anemia and SIRS might contribute to the pathophysiology of myocardial damage.

Intra-strain variations of baroreflex sensitivity in young Wistar-Kyoto rats

Purpose: To compare baroreflex sensitivity among conscious rats of the same strain. Methods: Male WKY rats (eight weeks old) were studied. Cannulas were inserted into the abdominal aortic artery through the right femoral artery to measure mean arterial pressure (MAP) and heart rate (HR). Baroreflex gain was calculated as the ratio between variation of HR in function of the MAP variation (Delta HR/Delta MAP) tested with a depressor dose of sodium nitroprusside (SNP, 50 mu g/kg, iv) and with a pressor dose of phenylephrine (PE, 8 mu g/kg, iv). We divided the rats into four groups: 1) Low bradycardic baroreflex (LB), BG between -1 and -2 bpm/mmHg tested with PE; 2) High bradycardic baroreflex (HB), BG < -2 bpm/mmHg tested with PE; 3) Low tachycardic baroreflex (LT), BG between -1 and -2 bpm/mmHg tested with SNP and; 4) High tachycardic baroreflex (HT), BG < -2 bpm/mmHg tested with SNP. Significant differences were considered for p<0.05. Results: Approximately 82% of the rats presented reduced bradycardic reflex while 22 showed attenuated tachycardic reflex. No alterations were noted regarding basal MAP and HR, tachycardic and bradycardic peak and HR range. Conclusions: There was alteration in baroreflex sensitivity among rats of the same strain. Care should be taken when interpreting studies employing WKY as a control for the SHR.

HISTAMINE IN THE POSTERODORSAL MEDIAL AMYGDALA MODULATES CARDIOVASCULAR REFLEX RESPONSES IN AWAKE RATS

Centrally injected histamine (HA) affects heart rate (HR), arterial blood pressure (BP), and sympathetic activity in rats. The posterodorsal medial amygdala (MePD) has high levels of histidine decarboxylase, connections with brain areas involved with the modulation of cardiovascular responses, and is relevant for the pathogenesis of hypertension. However, there is no report demonstrating the role of the MePD histaminergic activity on the cardiovascular function in awake rats. The alms of the present work were: 1) to study the effects of two doses (10-100 nM) of HA microinjected in the MePD on basal cardiovascular recordings and on baroreflex- and chemoreflex-mediated responses; 2) to reveal whether cardiovascular reflex responses could be affected by MePD microinjections of (R)-alpha-methylhistamine (AH(3)), an agonist of the inhibitory autoreceptor H(3); and, 3) to carry out a power spectral analysis to evaluate the contribution of the sympathetic and parasympathetic components in the variability of the HR and BP recordings. When compared with the control group (microinjected with saline, 0.3 mu l), HA (10 nM) promoted an increase in the MAP(50), i.e. the mean value of BP at half of the HR range evoked by the baroreflex response. Histamine (100 nM) did not affect the baroreflex activity, but significantly decreased the parasympathetic component of the HR variability, increased the sympathetic/parasympathetic balance at basal conditions (these two latter evaluated by the power spectral analysis), and promoted an impairment in the chemoreflex bradycardic response. Microinjection of AH(3) (10 mu M) led to mixed results, which resembled the effects of both doses of HA employed here. Present data suggest that cardiovascular changes induced by baroreceptors and chemoreceptors involve the histaminergic activity in the MePD. This neural regulation of reflex cardiovascular responses can have important implications for homeostatic and allostatic conditions and possibly for the behavioral displays modulated by the rat MePD. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.

Baroreflex sensitivity and oxidative stress in the LDL receptor knockout mice

This study alms at observing the effect of low-density lipoprotein (LDL) receptor deficiency in cholesterol blood levels, baroreflex sensitivity (BRS), nitric oxide (NO) bioavailability, and oxidative stress. The lack of LDL receptors in mice significantly increased the cholesterol blood levels (179 +/- 35 vs. 109 +/- 13 mg/dL) in the knockout (KO) mice compared to control. There was no difference in basal mean arterial pressure and heart rate between the groups. However, in KO mice the BRS was significantly attenuated and the antioxidant enzyme activities, measured in erythrocytes and heart, were significantly decreased. On the other hand, the oxidative damage measured by chemiluminescence and carbonyls was increased, while total plasma nitrate levels were lower in KO mice, indicating a decrease in NO availability. In conclusion, these results indicate that the lack of LDL receptor increased cholesterol blood levels, induced oxidative stress and decreased BRS. (C) 2008 Elsevier GmbH. All rights reserved.

Systemic delivery of adult stem cells improves cardiac function in spontaneously hypertensive rats

Heart regeneration after myocardial infarction (MI) can occur after cell therapy, but the mechanisms, cell types and delivery methods responsible for this improvement are still under investigation. In the present study, we evaluated the impact of systemic delivery of bone marrow cells (BMC) and cultivated mesenchymal stem cells (MSC) on cardiac morphology, function and mortality in spontaneously hypertensive rats (SHR) submitted to coronary occlusion. Female syngeneic adult SHR, submitted or not (control group; C) to MI, were treated with intravenous injection of MSC (MI + MSC) or BMC (MI + BM) from male rats and evaluated after 1, 15 and 30 days by echocardiography. Systolic blood pressure (SBP), functional capacity, histology, mortality rate and polymerase chain reaction for the Y chromosome were also analysed. Myocardial infarction induced a decrease in SBP and BMC, but not MSC, prevented this decrease. An improvement in functional capacity and ejection fraction (38 +/- 4, 39 +/- 3 and 58 +/- 2% for MI, MI + MSC and MI + BM, respectively; P < 0.05), as well as a reduction of the left ventricle infarcted area, were observed in rats from the MI + BM group compared with the other three groups. Treated animals had a significantly reduced lesion tissue score. The mortality rate in the C, MI + BM, MI + MSC and MI groups was 0, 0, 16.7 and 44.4%, respectively (P < 0.05 for the MI + MSC and MI groups compared with the C and MI + BM groups). The results of the present study suggest that systemic administration of BMC can improve left ventricular function, functional capacity and, consequently, reduce mortality in an animal model of MI associated with hypertension. We speculate that the cells transiently home to the myocardium, releasing paracrine factors that recruit host cells to repair the lesion.

Lifetime Overproduction of Circulating Angiotensin-(1-7) Attenuates Deoxycorticosterone Acetate-Salt Hypertension-Induced Cardiac Dysfunction and Remodeling

We evaluated the development of arterial hypertension, cardiac function, and collagen deposition, as well as the level of components of the renin-angiotensin system in the heart of transgenic rats that overexpress an angiotensin (Ang)-(1-7)-producing fusion protein, TGR(A1-7)3292 (TG), which induces a lifetime increase in circulating levels of this peptide. After 30 days of the induction of the deoxycorticosterone acetate (DOCA)-salt hypertension model, DOCA-TG rats were hypertensive but presented a lower systolic arterial pressure in comparison with DOCA-Sprague-Dawley (SD) rats. In contrast to DOCA-SD rats that presented left ventricle (LV) hypertrophy and diastolic dysfunction, DOCA-TG rats did not develop cardiac hypertrophy or changes in ventricular function. In addition, DOCA-TG rats showed attenuation in mRNA expression for collagen type I and III compared with the increased levels of DOCA-SD rats. Ang II plasma and LV levels were reduced in SD and TG hypertensive rats in comparison with normotensive animals. DOCA-TG rats presented a reduction in plasma Ang-(1-7) levels; however, there was a great increase in Ang-(1-7) (approximate to 3-fold) accompanied by a decrease in mRNA expression of both angiotensin-converting enzyme and angiotensin-converting enzyme 2 in the LV. The mRNA expression of Mas and Ang II type 1 receptors in the LV was not significantly changed in DOCA-SD or DOCA-TG rats. This study showed that TG rats with increased circulating levels of Ang-(1-7) are protected against cardiac dysfunction and fibrosis and also present an attenuated increase in blood pressure after DOCA-salt hypertension. In addition, DOCA-TG rats showed an important local increase in Ang-(1-7) levels in the LV, which might have contributed to the attenuation of cardiac dysfunction and prefibrotic lesions. (Hypertension. 2010;55:889-896.)

Ace gene dosage influences the development of renovascular hypertension

P>1. Clinical and experimental evidence highlights the importance of the renin-angiotensin system in renovascular hypertension. Furthermore, genetic factors affecting angiotensin-converting enzyme (ACE) could influence the development of renovascular hypertension. 2. To test the effect of small gene perturbations on the development of renovascular hypertension, mice harbouring two or three copies of the Ace gene were submitted to 4 weeks of two-kidney, one-clip (2K1C) hypertension. Blood pressure (BP), cardiac hypertrophy, baroreflex sensitivity and blood pressure and heart rate variability were assessed and compared between the different groups. 3. The increase in BP induced by 2K1C was higher in mice with three copies of the Ace gene compared with mice with only two copies (46 vs 23 mmHg, respectively). Moreover, there was a 3.8-fold increase in the slope of the left ventricle mass/BP relationship in mice with three copies of the Ace gene. Micewith three copies of the Ace gene exhibited greater increases in cardiac and serum ACE activity than mice with only two copies of the gene. Both baroreflex bradycardia and tachycardia were significantly depressed in mice with three copies of the Ace gene after induction of 2K1C hypertension. The variance in basal systolic BP was greater in mice with three copies of the Ace gene after 2K1C hypertension compared with those with only two copies of the gene (106 vs 54%, respectively). In addition, the low-frequency component of the pulse interval was higher mice with three copies of the Ace gene after 2K1C hypertension compared with those with only two (168 vs 86%, respectively). Finally, in mice with three copies of the Ace gene, renovascular hypertension induced a 6.1-fold increase in the sympathovagal balance compared with a 3.2-fold increase in mice with only two copies of the gene. 4. Collectively, these data provide direct evidence that small genetic disturbances in ACE levels per se have an influence on haemodynamic, cardiac mass and autonomic nervous system responses in mice under pathological perturbation.

Homocysteine Thiolactone Induces Cardiac Dysfunction: Role of Oxidative Stress

This study investigates the cardiac functioning in male Wistar rats after treatments with methionine and homocysteine thiolactone (HcyT). The rats were distributed into 3 groups and treated for 8 weeks. Group I was the control (CO) group, given water, group II was treated with methionine, and group III with HcyT (100 mg/kg). Morphometric and functional cardiac parameters were evaluated by echocardiography. Superoxide dismutase (SOD), catalase, and glutathione S-transferase activities, chemiluminescence, thiobarbituric acid reactive substances, and immunocontent were measured in the myocardium. Hyperhomocysteinemia was observed in rats submitted to the both treatments. The results showed diastolic function was compromised in HcyT group, seen by the increase of E/A (peak velocity of early (E) and late (A) diastolic filling) ratio, decrease in deceleration time of E wave and left ventricular isovolumic relaxation time. Myocardial performance index was increased in HcyT group and was found associated with increased SOD immunocontent. HcyT group demonstrated an increase in SOD, catalase, and glutatione S-transferase activity, and chemiluminescence and thiobarbituric acid reactive substances. Overall, these results indicated that HcyT induces a cardiac dysfunction and could be associated with oxidative stress increase in the myocardium.

Research on Candida dubliniensis in a Brazilian yeast collection obtained from cardiac transplant, tuberculosis, and HIV-positive patients, and evaluation of phenotypic tests using agar screening methods

The aim of this study was to research Candida dubliniensis among isolates present in a Brazilian yeast collection and to evaluate the main phenotypic methods for discrimination between C. albicans and C. dubliniensis from oral cavity. A total of 200 isolates, presumptively identified as C. albicans or C. dubliniensis obtained from heart transplant patients under immunosuppressive therapy, tuberculosis patients under antibiotic therapy, HIV-positive patients under antiretroviral therapy, and healthy subjects, were analyzed using the following phenotypic tests: formation and structural arrangement of chlamydospores on corn meal agar, casein agar, tobacco agar, and sunflower seed agar; growth at 45 degrees C; and germ tube formation. All strains were analyzed by polymerase chain reaction (PCR). In a preliminary screen for C. dubliniensis, 48 of the 200 isolates on corn meal agar, 30 of the 200 on casein agar, 16 of the 200 on tobacco agar, and 15 of the 200 on sunflower seed agar produced chlamydoconidia; 27 of the 200 isolates showed no or poor growth at 45 degrees C. All isolates were positive for germ tube formation. These isolates were considered suggestive of C. dubliniensis. All of them were subjected to PCR analysis using C. dubliniensis-specific primers. C. dubliniensis isolates were not found. C. dubliniensis isolates were not recovered in this study done with immunocompromised patients. Sunflower seed agar was the medium with the smallest number of isolates of C. albicans suggestive of C. dubliniensis. None of the phenotypic methods was 100% effective for discrimination between C. albicans and C. dubliniensis. (C) 2011 Elsevier Inc. All rights reserved.

Reactive oxygen and nitrogen species balance in the determination of thyroid hormones-induced cardiac hypertrophy mediated by renin-angiotensin system

Role of reactive oxygen species (ROS)/nitric oxide (NO) balance and renin-angiotensin system in mediating cardiac hypertrophy in hyperthyroidism was evaluated in an in vivo and in vitro experimental model. Male Wistar rats were divided into four groups: control, thyroid hormone, vitamin E (or Trolox, its hydrosoluble analogue), thyroid hormone + vitamin E. Angiotensin II receptor (AT1/AT2) gene expression, immunocontent of AT1/AT2 receptors, angiotensinogen, NADPH oxidase (Nox2), and nitric oxide synthase isoforms, as well as ROS concentration (hydrogen peroxide and superoxide anion) were quantified in myocardium. Thyroid hormone increased ROS and NO metabolites, iNOS, nNOS and eNOS isoforms and it was accompanied by cardiac hypertrophy. AT1/AT2 expression and the immunocontent of angiotensinogen and Nox2 were enhanced by thyroid hormone. Antioxidants reduced ROS levels, Nox2, AT1/AT2, NOS isoforms and cardiac hypertrophy. In conclusion, ROS/NO balance may play a role in the control of thyroid hormone-induced cardiac hypertrophy mediated by renin-angiotensin system. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Blockage of Angiotensin II type 2 receptor prevents thyroxine-mediated cardiac hypertrophy by blocking Akt activation

Although most of effects of Angiotensin II (Ang II) related to cardiac remodelling can be attributed to type 1 Ang II receptor (AT(1)R), the type 2 receptor (AT(2)R) has been shown to be involved in the development of some cardiac hypertrophy models. In the present study, we investigated whether the thyroid hormone (TH) action leading to cardiac hypertrophy is also mediated by increased Ang II levels or by change on AT(1)R and AT(2)R expression, which could contribute to this effect. In addition, we also evaluated the possible contribution of AT(2)R in the activation of Akt and in the development of TH-induced cardiac hypertrophy. To address these questions, Wistar rats were treated with thyroxine (T(4), 0.1 mg/kg BW/day, i.p.), with or without AT(2)R blocker (PD123319), for 14 days. Cardiac hypertrophy was identified based on heart/body weight ratio and confirmed by analysis of atrial natriuretic factor mRNA expression. Cardiomyocyte cultures were used to exclude the influence of TH-related hemodynamic effects. Our results demonstrate that the cardiac Ang II levels were significantly increased (80%, P < 0.001) as well as the AT(2)R expression (50%, P < 0.05) in TH-induced cardiac hypertrophy. The critical involvement of AT(2)R to the development of this cardiac hypertrophy in vivo was evidenced after administration of AT(2) blocker, which was able to prevent in 40% (P < 0.01) the cardiac mass gain and the Akt activation induced by TH. The role of AT(2)R to the TH-induced cardiomyocyte hypertrophy was also confirmed after using PD123319 in the in vitro studies. These findings improve understanding of the cardiac hypertrophy observed in hyperthyroidism and provide new insights into the generation of future therapeutic strategies.

Exercise changes the size of cardiac neurons and protects them from age-related neurodegeneration

Aging leads to changes in cardiac structure and function. Evidence suggests that the practice of regular exercise may prevent disturbances in the cardiovascular system during aging. We studied the effects of aging on the morphology and morphometry of cardiac neurons in Wistar rats and investigated whether a lifelong moderate exercise program could exert a protective effect toward some deleterious effects of aging. Aging caused a significant decline (28%) in the number of NADH-diaphorase-stained cardiac Animals submitted to a daily session of 60 min, 5 day/week, at 1.1 km/h of running in treadmill over the entire life span exhibited a reversion of the observed decline in the number of cardiac neurons. However, most interesting was that the introduction of this lifelong exercise protocol dramatically altered the sizes of cardiac neurons. There was a notable increase in the percentage of small neurons in the rats of the exercise group compared to the sedentary animals. This is the first time that a protective effect of lifelong regular aerobic exercise has been demonstrated on the deleterious effects of aging in cardiac neurons. (C) 2009 Elsevier GmbH. All rights reserved.

AMP hydrolysis in soluble and microsomal rat cardiac cell fractions: kinetic characterization and molecular identification of 5 `-nucleotidase

The present study describes the enzymatic properties and molecular identification of 5`-nucleotidase in soluble and microsomal fractions from rat cardiac ventricles. Using AMP as a substrate, the results showed that the cation and the concentration required for maximal activity in the two fractions was magnesium at a final concentration of 1 mM. The pH optimum for both fractions was 9.5. The apparent K-m (Michaelis constant) values calculated from the Eadie-Hofstee plot were 59.7 +/- 10.4 mu M and 134.8 +/- 32.1 mu M, with V-max values of 6.7 +/- 0.4 and 143.8 +/- 23.8 nmol P-i/min/mg of protein (means +/- S.D., n = 4) from soluble and microsomal fractions respectively. Western blotting analysis of ecto-5`-nucleotidase revealed a 70 kDa protein in both fractions, with the major proportion present in the microsomal fraction. The presence of these enzymes in the heart probably has a physiological function in adenosine signalling. Furthermore, the presence of ecto-5`-nucleotidase in the microsomal fraction could have a role in the modulation of the excitation-contraction-coupling process through involvement of the Ca2+ influx into the sarcoplasmic reticulum. The measurement of maximal enzyme activities in the two fractions highlights the potential capacity of the different pathways of purine metabolism in the heart.

Important GABAergic mechanism within the NTS and the control of sympathetic baroreflex in SHR

Inhibitory neurotransmission has an important role in the processing of sensory afferent signals in the nucleus of the solitary tract (NTS), particularly in spontaneously hypertensive rats (SHR). In the present study, we tested the hypothesis that gamma-aminobutyric acid (GABA) mediated neurotransmission within the NTS produces an inhibition of the baroreflex response of splanchnic sympathetic nerve discharge (sSND). In urethane-anesthetized, artificially ventilated and vagotomized male SHR and Wistar Kyoto (WKY) rats we compared baroreflex-response curves evoked after bilateral injections into the NTS of the GABA-A antagonist bicuculline (25 pmol/50 nl) or the GABA-B antagonist CGP 35348 (5 nmol/50 nl). Baseline MAP in SHR was higher than the WKY rats (SHR: 153+/-5, vs. WKY: 112+/-6 mm Hg, p<0.05). Bilateral injection of bicuculline or CGP 35348 into the NTS induced a transient (5 min) reduction in MAP (Delta = -26+/-4 and -41+/-6 mm Hg, respectively vs. saline Delta = +4+/-3 mm Hg, p<0.05) and sSND (Delta = -21+/-13 and -78+/-7%, respectively vs. saline: Delta = +6+/-4% p<0.05). Analysis of the baroreceptor curve revealed a decrease in the lower plateau (43+/-11 and 15+/-5%, respectively vs. saline: 78+/-6%, p<0.05) and an increase in the sympathetic gain of baroreflex (6.3+/-0.3, 7.2+/-0.8% respectively vs. saline: 4.2+/-0.4%, p<0.05). Bicuculline or CGP35348 into the NTS in WKY rats did not change MAP, sSND and sympathetic baroreflex gain. These data indicate that GABAergic mechanisms within the NTS act tonically reducing sympathetic baroreflex gain in SHR. Crown Copyright (C) 2010 Published by Elsevier By. All rights reserved.

Exercise Training Reduces Insulin Resistance and Upregulates the mTOR/p70S6k Pathway in Cardiac Muscle of Diet-Induced Obesity Rats

Obesity and insulin resistance are rapidly expanding public health problems. These disturbances are related to many diseases, including heart pathology. Acting through the Akt/mTOR pathway, insulin has numerous and important physiological functions, such as the induction of growth and survival of many cell types and cardiac hypertrophy. However, obesity and insulin resistance can alter mTOR/p70S6k. Exercise training is known to induce this pathway, but never in the heart of diet-induced obesity subjects. To evaluate the effect of exercise training on mTOR/p70S6k in the heart of obese Wistar rats, we analyzed the effects of 12 weeks of swimming on obese rats, induced by a high-fat diet. Exercise training reduced epididymal fat, fasting serum insulin and plasma glucose disappearance. Western blot analyses showed that exercise training increased the ability of insulin to phosphorylate intracellular molecules such as Akt (2.3-fold) and Foxo1 (1.7-fold). Moreover, reduced activities and expressions of proteins, induced by the high-fat diet in rats, such as phospho-JNK (1.9-fold), NF-kB (1.6-fold) and PTP-1B (1.5-fold), were observed. Finally, exercise training increased the activities of the transduction pathways of insulin-dependent protein synthesis, as shown by increases in Raptor phosphorylation (1.7-fold), p70S6k phosphorylation (1.9-fold), and 4E-BP1 phosphorylation (1.4-fold) and a reduction in atrogin-1 expression (2.1-fold). Results demonstrate a pivotal regulatory role of exercise training on the Akt/ mTOR pathway, in turn, promoting protein synthesis and antagonizing protein degradation. J. Cell. Physiol. 226: 666-674, 2011. (C) 2010 Wiley-Liss, Inc.