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Biomedical subjects

Eduardo Moacyr Krieger

Publications and source records attributed to Eduardo Moacyr Krieger.

13 recordsLinked to original sources
PubMed2006

Exercise training improves arterial baro- and chemoreflex in control and diabetic rats.

We investigated the effect of exercise training on blood pressure, heart rate, and arterial baro- and chemoreflex sensitivity in diabetic rats (streptozotocin, 50 mg/kg iv). Male Wistar rats (251+/-10 g) were divided into 4 groups (n=8, each group): sedentary normotensive (SC), sedentary diabetic (SD), trained normotensive (TC), and trained diabetic (TD). Trained groups underwent exercise training on a treadmill (10 weeks). Exercise training induced resting bradycardia (340+/-5 vs. 316+/-8 bpm) and improvement in baroreflex tachycardic response (3.4+/-0.31 vs. 2.7+/-0.06 bpm/mmHg in SC) and chemoreflex bradycardic (145+/-12 vs. 78+/-7 bpm in SC) and pressor (49+/-5 vs. 22+/-3 mmHg in SC) responses in control rats. Diabetic-induced hypotension (SC: 107+/-2 vs. SD: 93+/-2 mmHg) and bradycardia (SC: 340+/-5 vs. SD: 276+/-7 bpm) were reversed by exercise training. Baroreflex tachycardic and bradycardic responses impaired in SD rats (SD: 2.1+/-0.18 and 1.3+/-0.08 vs. SC: 2.7+/-0.06 and 1.3+/-0.08 bpm/mmHg) were enhanced in TD rats (2.5+/-0.1 and 1.7+/-0.06 bpm/mmHg). Chemoreflex bradycardic and pressor responses, attenuated in SD rats (23+/-9 bpm and 7+/-1 mmHg) in relation to SC rats, were improved by exercise (TD: 84+/-15 bpm and 32+/-5 mmHg). The improvement in arterial baro- and chemoreflex-mediated control of circulation in trained control and diabetic rats reinforces the role of exercise in the management of cardiovascular risk in healthy and diabetic individuals.

Animals↗
PubMed2006

Increased sympathetic nerve activity correlates with neurovascular compression at the rostral ventrolateral medulla.

We used microneurography to measure muscle sympathetic nerve activity (MSNA) in 25 hypertensive subjects and correlated these results with the presence or absence of signs of neurovascular compression (NVC) at the rostral ventrolateral (RVL) medulla on MRI. Subjects were divided into 3 groups based on MRI findings: NVC-, no MRI evidence of NVC (N=9); NVC+contact, image showing artery in contact but not compressing the RVL medulla (N=8); and NVC+compression, image showing arterial compression of the RVL medulla (N=8). The MSNA measurements were performed at rest, after a hypothermic stimulus, and during isometric exercise. The MSNA during rest in the NVC+compression group was significantly higher than that in the NVC+contact and NVC- groups (30.4+/-3.4 versus 17.5+/-1.1 and 21.4+/-3.2 spikes per minute, respectively). However, the blood pressure in the NVC+compression group was slightly but not significantly higher than that in the other 2 groups (183+/-7/115+/-8, 174+/-6/108+/-7, and 171+/-5/110+/-5 mm Hg, respectively). The increases in MSNA, blood pressure, and heart rate during the cold pressor and isometric exercise tests were similar. Our results show that, although resting MSNA is elevated in patients with true NVC of the RVL medulla, patients without NVC or with arterial contact but not overt compression of the RVL medulla have similar MSNA. These findings are important for identifying, among hypertensive patients with NVC, individuals who may have associated physiological repercussions, such as increased sympathetic activity.

Adult↗
PubMed2006

Effects of rat sinoaortic denervation on the vagal responsiveness and expression of muscarinic acetylcholine receptors.

We studied heart rate (HR) responses to vagal electrical stimulation (VES) and the expression of muscarinic acetylcholine receptors (mAChRs) in the rat atria 1 day (SADa) and 20 days (SADc) after sinoaortic denervation (SAD). Arterial blood pressure (BP) was recorded in conscious, unrestrained rats and during vagal electrical stimulation of the vagus nerve. In the acute phase, SADa rats had hypertension, tachycardia, and increased blood pressure lability. In the chronic phase, heart rate and blood pressure in SADc rats returned to normal whereas blood pressure lability remained increased. VES produced a frequency-dependent bradycardia that was higher in SADa and SADc groups. Binding experiments with [H] N-methylscopolamine showed that in the chronic phase of SAD mAChRs density (SADc = 412.2 +/- 28.64, SADa = 273.38 +/- 48.37 and CTR = 241.5 +/- 25.35 fmol/mg of protein, P < 0.05) and affinity increased in SADc rats (reduced dissociation constant: SADc = 0.45 +/- 0.05, SADa = 1.01+/-0.26, and CTR = 0.98 +/- 0.12 mM, P < 0.05). Our study provides evidence that vagal hyperresponsiveness coexists with increased sympathetic activity in SADa rats without a concomitant increase in mAChRs density or affinity, suggesting that complex mechanisms might modulate the "accentuated antagonism" observed in the acute SAD phase. However, SADc rats had increased bradycardia to VES, increased affinity, and upregulation of mAChRs in the atria. Our results show that, 20 days after SAD in the rat, functional and cellular adaptations occur in the cardiac parasympathetic efferent pathway that may contribute to other regulatory mechanisms to compensate for cardiovascular changes provoked by baroreceptor arch disruption.

Animals↗
PubMed2005

The spectrum of magnetic resonance imaging findings in hypertension-related neurovascular compression.

Hypertension (HTN) has been controversially related to neurovascular compression (NVC) at the rostral ventrolateral (RVL) medulla in anatomical, surgical, and radiological reports. Our objective was to investigate the association between primary HTN and signs of NVC at the medulla oblongata on magnetic resonance imaging (MRI) and to explore a new classification based on image criteria. Subjects with (n=64) and without (n=29) HTN were studied. Three-millimeter slices, with 1-mm intervals in between, were performed on T2-weighted images in axial and coronal views. Attention was focused on the relationship between the upper medulla and the surrounding arteries. The findings were divided into three categories: 1) non-NVC: absence of signs of NVC, 2) NVC type I: an artery in contact with the RVL medulla but not compressing it, and 3) NVC type II: evident compression of the RVL medulla by an artery. Signs of NVC were observed in 65.7% (42/64) of the HTN group (type I: 39.1%, 25/42 patients; type II: 26.6%, 17/42 patients). Among the normotensive subjects, 27.6% (8/29) had signs of NVC; only one (3.3%) of these had NVC type II (evident compression), and the rest were NVC type I. We conclude that the presence of NVC at the RVL medulla on MRI is related to HTN. More importantly, the finding of frank compression (NVC type II) is present almost exclusively in hypertensive subjects; only one individual (3.3% of our normotensive population) had NVC type II.

Adult↗
PubMed2005

Autonomic control in rats with overactivity of tissue renin-angiotensin or kallikrein-kinin system.

UNLABELLED: The renin-angiotensin system (RAS) plays an important role in the regulation of the cardiovascular system and the kallikrein-kinin system (KKS) appears to counteract most of the RAS effects. In this study the vagal and the sympathetic influences on the heart rate and the baroreflex control of the heart rate were evaluated in transgenics rats with human tissue kallikrein gene expression [TGR(hKLK1)], and transgenics rats with tissue renin overexpression [TGR(mREN2)27]. Heart rate was similar in all groups but mean arterial pressure was higher in mREN2 rats than in kallikrein and control rats (149+/-4 vs. 114+/-3 vs. 113+/-3 mm Hg, respectively). The intrinsic heart rate was lower in mREN2 rats than in kallikrein and control rats (324+/-5 vs. 331+/-3 vs. 343+/-7 bpm). The HR response to atropine was similar but the response to propranolol was higher in kallikrein rats than control group (61+/-7 vs. 60+/-9 vs. 38+/-7 bpm, respectively). The vagal tonus was lower in mREN2 than in SD and hKAL rats (18+/-3 vs. 40+/-6 vs. 35+/-6 bpm) whereas the sympathetic tonus was higher in kallikrein rats (118+/-7 vs. 96+/-1 vs. 81+/-9 bpm in the mREN2 and SD rats), respectively. Baroreflex sensitivity to bradycardic responses was attenuated in mREN2 rats (0.37+/-0.05 vs. 1.34+/-0.08 vs. 1.34+/-0,13 bpm/mm Hg) while the tachycardic responses were unchanged. The bradycardic responses to electrical stimulation of the vagal nerve were depressed in both renin and kallikrein rats (129+/-47 vs. 129+/-22 vs. 193+/-25 bpm in control group in response to 32 Hz). IN CONCLUSION: 1.The rats with overexpression of renin showed decreased intrinsic heart rate and impairment of vagal function, characterized by decreased vagal tonus, reduced response of HR to electrical stimulation of vagus nerve, and depressed reflex bradycardia provoked by increases of blood pressure. 2. The rats with overexpression of kallikrein showed an increase of sympathetic activity that regulates the heart rate, characterized by increased HR response to propranolol and increased sympathetic tonus, accompanied by decreased bradycardic responses to electrical vagal stimulation.

Animals↗
PubMed2005

Acute administration of 17beta-estradiol improves endothelium-dependent vasodilation in postmenopausal women.

OBJECTIVES: Estrogen's effect on endothelial function in postmenopausal women with mild hypertension but no other cardiovascular risk factors remains unclear. This study investigated the effect of an acutely administered therapeutic/low dose of 17beta-estradiol on vasodilation in this patient population. METHODS: Forearm blood flow (FBF) was measured in seven white, hypertensive (blood pressure 144 +/- 8/93 +/- 5 mmHg), postmenopausal (mean age: 54.4 +/- 5 years) women at baseline and during the intra-brachial infusion of increasing doses of acetylcholine (ACh; 0.75, 5, and 15 microg/100 mL tissue/min) and sodium nitroprusside (NP; 1, 2, and 4 microg/100 mL tissue/min). These measurements were obtained both before and after the sublingual administration of 17beta-estradiol. Eight normotensive women (blood pressure 115 +/- 8/76 +/- 5 mmHg) with otherwise similar characteristics served as controls (mean age: 55.8 +/- 5 years). Exclusion criteria included medications or any condition that could alter endothelial function. RESULTS: Before estradiol administration, FBF values at baseline and after all doses of ACh and NP were similar between groups. Acutely administered 17beta-estradiol significantly improved the FBF response to ACh in both the normotensive (maximal response: 17.6 +/- 5 versus 22.5 +/- 7 mL/min/100 mL) and hypertensive (11 +/- 4 versus 16 +/- 6; 12 +/- 4 versus 17 +/- 5 and 14 +/- 3 versus 20 +/- 7 mL/min/100 mL) groups. It also altered the NP dose-response curve in the both groups. CONCLUSION: 17beta-estradiol improved vasodilatory responses in mildly hypertensive postmenopausal women without other risk factors for cardiovascular disease.

Administration, Sublingual↗
PubMed2005

[Cardiovascular disease and risk factors in candidates for renal transplantation].

OBJECTIVE: To determine the prevalence of cardiovascular disease (CVD) and traditional risk factors in patients with chronic renal failure undergoing evaluation for inclusion on the renal transplantation list. METHODS: One hundred ninety-five patients with dialytic chronic renal failure underwent clinical evaluation and complementary tests and were compared with a group of 334 hypertensive patients paired for age. The Framingham equations were used for calculating the absolute risk (AR). The relative risk (RR) was calculated based on the absolute risk of the low-risk Framingham cohort. RESULTS: Thirty-seven percent of the patients had some sort of cardiovascular disease on the initial evaluation, peripheral vascular disease (23%) being the most prevalent. Patients with cardiovascular disease were excluded. Regarding traditional risk factors, a significant difference was observed in systolic blood pressure and total cholesterol (greater in the hypertensive group), and in the prevalence of men, diabetes, and smoking, which were greater in the chronic renal failure group. The latter had a greater degree of left ventricular hypertrophy, lower diastolic blood pressure, and a lower prevalence of familial history of cardiovascular disease and obesity. The relative risk for cardiovascular disease in patients with chronic renal failure was greater compared with that in the Framingham control population, but it did not differ from that observed in the group of hypertensive individuals. CONCLUSION: The prevalence of cardiovascular disease and traditional risk factors is high among candidates for renal transplantation; the Framingham equations do not adequately quantify the real cardiovascular risk, and other risk factors specific for that population should contribute for their greater cardiovascular risk.

Aged↗
PubMed2005

The reproducibility of dipping status: beyond the cutoff points.

A limited reproducibility has been ascribed to 24-h ambulatory blood pressure monitoring, especially in relation to the dipper and nondipper phenomena. This study examined the reproducibility of 24-h ambulatory blood pressure monitoring in three recordings of pressure at intervals of 8-15 days in 101 study participants (73% treated hypertensive patients) residing in the city of Recife, Pernambuco, Brazil. SpaceLabs 90207 monitors were used, and the minimum number of valid measurements was 80. No significant differences were found between the mean systolic and diastolic pressures, between the second and third recordings when the normotensive and hypertensive patients were assessed jointly (P=0.44). Likewise, no significant differences were present when the normotensive patients were analyzed separately (P=0.96). In the hypertensive group, a significant difference existed between only the first and second ambulatory blood pressure readings (135.1 vs. 132.9 mmHg, respectively; P=0.0005). Regarding declines in pressure during sleep, no significant differences occurred when continuous percentage values were considered (P=0.27). The values obtained from 24-h ambulatory blood pressure monitoring are reproducible when tested at intervals of 8-15 days. Small differences, when significantly present, always involved the first ambulatory blood pressure monitoring. The reproducibility of the dipper and nondipper patterns is of greater complexity because it considers cutoff points rather than continuous ones to characterize these states.

Adult↗
PubMed2004

Acute reduction of ventricular volume decreases QT interval dispersion in elderly subjects with and without heart failure.

To evaluate the effects of acute reduction in ventricular volume (VV) on QT interval dispersion (QTd), 14 men with heart failure (HF; 74.5 +/- 2 yr of age) and 11 healthy male control subjects (68 +/- 2 yr of age) were studied. For 15 min, lower body negative pressure (LBNP) was applied at -15 and -40 mmHg to reduce venous return. At baseline and during LBNP application, QTd was measured with an 87-lead, body-surface-mapping device; chamber volumes were assessed by radioisotope ventriculography; blood pressure (BP) and heart rate (HR) were continuously monitored; and blood samples were obtained for assessment of norepinephrine (Nor) levels. At -15 mmHg, LNBP application induced a significant decrease in VV but did not change BP and HR in both groups. In addition, Nor levels increased significantly (P < or = 0.05) in the control group (from 286.7 +/- 31.5 to 388.8 +/- 41.2 pg/ml) and in HF patients (from 405.8 +/- 56 to 477.6 +/- 47 pg/ml), and QTd was significantly (P < or = 0.05) decreased in the control group (57.2 +/- 3.8 vs. 49.1 +/- 3.4 ms) and in HF patients (67.8 +/- 6 vs. 63.7 +/- 5.9 ms). No additional decreases in VV or QTd were produced by -40 mmHg LNBP, but Nor levels did increase in both groups and reach 475.5 +/- 34 and 586.5 +/- 60 pg/ml (P < 0.05) in the control and HF groups, respectively; BP did not change, but HR also increased in both groups. In conclusion, an acute LBNP-induced reduction in VV caused a decrease in the QTd of elderly men regardless of the existence of HF. Because increased sympathetic activity with more intense LBNP was not accompanied by additional changes in QTd, altered QTd may be better related to changes in VV than to autonomic nervous system activity.

Aged↗
PubMed2004

Frequent nurse visits decrease white coat effect in stage III hypertension.

Arterial hypertension is a public health problem and patient adherence to treatment is challenging. This study tested whether frequent nurse visits provide additional benefits to antihypertensive treatment. Every 30 days, a pharmacist visited these patients to deliver antihypertensive drugs and perform a pill count. Nurses visited group A (48 patients) every 15 days and group B (52 patients) every 90 days. Ambulatory blood pressure (BP) monitoring was performed 15 and 180 days after randomization. At randomization, groups A and B had the same clinical systolic (191 +/- 5 v 186 +/- 3 mm Hg) and diastolic BP levels (122 +/- 3 v 117 +/- 4 mm Hg), respectively. After 90 days, BP declined more in group A than in group B (35 +/- 5/19 +/- 3 v 27 +/- 5/9 +/- 3 mm Hg). At 180 days, the difference increased because the reduction persisted in group A but decreased in group B (36 +/- 6/21 +/- 4 v 17 +/- 4/10 +/- 2 mm Hg). The mean ambulatory BP monitoring values were similar in both groups at 15 and 180 days. However, the attenuation of the clinic-daytime BP difference was larger in group A than in group B (systolic, -13 +/- 4 v -3 +/- 4 mm Hg; diastolic -11 +/- 3 v -4 +/- 3 mm Hg). The patients with clinic-daytime differences decreased more in group A (systolic, 16 to 10; diastolic, 20 to 14) than in group B (systolic, 19 and 20; diastolic, 22 and 22). These data indicate that frequent nurse visits significantly attenuate the white coat effect (clinic daytime BP difference).

Adrenergic beta-Antagonists↗
PubMed2003

Hypercholesterolemia blunts forearm vasorelaxation and enhances the pressor response during acute systemic hypoxia.

OBJECTIVE: During hypoxia, active substances released by the endothelium play a key role in the cardiovascular and respiratory responses elicited to optimize oxygen delivery. As hypercholesterolemia is a major cause of endothelial dysfunction, it may interfere with these responses. METHODS AND RESULTS: We studied cardiovascular and ventilatory responses to acute systemic hypoxia in 14 patients with hypercholesterolemia (HC) and 13 control (CO) subjects. Oxygen saturation decreased similarly in both groups. Diastolic blood pressure increased only in the HC group (P=0.0002) and, despite systolic blood pressure increases both in the HC group, 140+/-4 (95% confidence interval [CI],131 to 149 mm Hg) to 154+/-4 mm Hg (95% CI,145 to 164 mm Hg), and in the CO group, 133+/-3 (95% CI,126 to 140 mm Hg) to 140+/-4 mm Hg (95% CI,132 to 148 mm Hg), the HC group showed an enhanced pressor response (P=0.03, group comparison). Both groups had increased forearm blood flow, but the decrease in forearm vascular resistance in the CO group, 40+/-5 (95% CI, 30 to 51 UR) to 31+/-4 UR (95% CI,23 to 39 UR) (P=0.0001) was not seen in the HC group, 29+/-3 (95% CI, 22 to 37 UR) to 26+/-3 UR (95% CI, 20 to 33 UR), (P=0.03, group comparison). CONCLUSIONS: Hypercholesterolemic patients demonstrate a hyperreactive pressor response and absence of forearm vasodilation during acute systemic hypoxia.

Acute Disease↗
PubMedDate not supplied

Ineffective peripheral tissue perfusion: Clinical validation in patients with hypertensive cardiomiopathy.

PURPOSE: To validate defining characteristics of ineffective peripheral tissue perfusion using vasomotor function assessment. METHODS: Twenty-four patients with hypertensive cardiomiopathy were evaluated for 18 defining characteristics of ineffective peripheral tissue perfusion and underwent vasomotor function assessment with induction of reactive hyperemia, intra-arterial infusion of acetylcholine, and pulse wave velocity measurement. The Student's t test and Kruskall-Wallis test were used to assess the significance of relationships between defining characteristics and vasomotor function data. FINDINGS: Diminished lower extremity pulses were associated with diminished forearm blood flow during acetylcholine infusion; left ventricular overload, intermittent claudication, and diminished skin moisture were associated with elevated pulse wave velocity values. CONCLUSION: The defining characteristics of ineffective peripheral tissue perfusion were highly associated with vasomotor function data as "gold standards" for that diagnosis. PRACTICE IMPLICATIONS: Nurses should be able to accurately assess diminished lower extremity pulses, intermittent claudication, and diminished skin moisture as relevant characteristics of ineffective peripheral tissue perfusion in patients with hypertensive cardiomiopathy.

Acetylcholine↗