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Biomedical subjects

C Cerutti

Publications and source records attributed to C Cerutti.

At least 37 records · Page 2Linked to original sources
PubMed1995

Short report: hepatitis E infection in the Brazilian Amazon.

This is the first report of serologic evidence of hepatitis E infection in Brazil. During a community-based survey of healthy individuals, six of 97 gold miners in the Amazon region of Mato Grosso had antibody to the virus. The mining camps have poor sanitation with a great potential for fecal-oral transmission of disease. Since levels of hepatitis E antibodies may quickly wane, studies to directly measure the incidence of seroconversion are planned to determine the intensity of transmission in this area.

Adult↗
PubMed1995

[Comparison of three methods for the estimation of spontaneous cardiac baroreflex sensitivity in normotensive and hypertensive subjects].

This study aimed at comparing estimations of spontaneous cardiac baroreflex sensitivity (BRS) obtained with 3 different methods from continuous non-invasive blood pressure recordings in humans. A new method, allowing the quantification of the statistical dependence between values of 2 parameters (Z coefficient), was applied to beat-to-beat systolic blood pressure (SBP) and heart period (HP) values. SBP and HP values with positive Z coefficient and corresponding to baroreflex activity (SBP and HP values both lower or higher than the modal values) were submitted to a linear regression and the regression coefficient (Zgain) was taken as an index of BRS. Second, cross-spectral analysis of SBP and HP gave a BRS value (Csgain) computed as the average value of transfer function moduli for frequencies between 0.07 and 0.14 Hz, with coherence between SBP and HP greater than 0.5. The third method relies on the analysis of linear sequences (r > 0.97) containing at least 3 values of SBP and HP varying in the same direction. The average regression coefficient obtained from all selected SBP and HP sequences is the index of BRS (Seqgain). SBP and HR were recorded during 1 hour with a Finapres in 10 healthy male volunteers (NT), 23 to 32 year-old (SBP: 123 +/- 2 mmHg) and 10 recent and untreated hypertensive subjects (HT) (SBP: 152 +/- 6 mmHg). [table: see text] These results show that, in both groups, Zgain and Seqgain correlated with Csgain. No correlation was found between Zgain and Seqgain in healthy volunteers whereas the correlation was strong in hypertensives probably due to more heterogeneous SBP levels and BRS values in these subjects. This suggests that these methods are sensitive to different ways of response of the baroreflex.

Adult↗
PubMed1994

Baroreflex modulation of blood pressure and heart rate variabilities in rats: assessment by spectral analysis.

The role of the baroreflex in the spectral characteristics of mean arterial pressure (MAP) and heart rate (HR) was investigated in 12 control rats and 9 rats with chronic sinoaortic baroreceptor denervation (SAD) during 1) basal conditions and 2) ganglionic blockade with chlorisondamine and restoration of the basal MAP level. In SAD rats, power spectral density of MAP, estimated by a fast Fourier transform, was reduced in the low-frequency (LF, 0.27- to 0.74-Hz) band. Ganglionic blockade highly decreased LF power spectral density of MAP in control rats. No relationship was found between the MAP response to chlorisondamine, taken as an index of the sympathetic vasomotor tone, and the basal LF power spectral density. Transfer function analysis between MAP and HR showed that, in control rats, coherence was high for frequencies surrounding the LF and high-frequency peaks. In SAD rats, coherence was abolished in the LF band but maintained in the high-frequency band. In conclusion, approximately 80% of the LF power spectral density of MAP depends on the sympathetic nervous system activity, and the baroreflex accounts for one-half of this power and for the coherence between MAP and HR oscillations in the LF band.

Analysis of Variance↗
PubMed1994

Hemodynamic analysis of arterial pressure lability in sympathectomized rat.

Male Sprague-Dawley rats, treated with either saline (n = 14) or guanethidine (n = 12) from 1 to 13 wk of age, were instrumented for the measurement of mean arterial pressure (MAP) and indexes of regional blood flows (pulsed Doppler flow probes) in the subdiaphragmatic aorta, superior mesenteric artery, and distal aorta (hindquarters). Hemodynamic parameters were simultaneously recorded in the conscious rats on a beat-to-beat basis by a computer. Chronic sympathectomy did not change the MAP level but nearly doubled its spontaneous variability, mainly due to large decreases in MAP associated with regional vasodilations that were slightly delayed with respect to the onset of the decreases in pressure, especially in the aortic and mesenteric circulations. In the hindquarters vascular bed, the onset of vasodilations sometimes coincided with the onset of the decreases in MAP. During depressor episodes, blood flow varied little (aortic and mesenteric circulations) or even increased (hindquarters). This hemodynamic pattern was not affected by acute beta-adrenoceptor blockade. We conclude that chronic sympathectomy sensitizes the cardiovascular system to decreases in arterial pressure mainly by unmasking local autoregulatory responses of regional circulations. The sympathetic control of vascular tone overrides these responses and considerably limits the MAP variability.

Adrenergic beta-Antagonists↗
PubMed1993

High blood pressure maintenance in transgenic mRen-2 vs. Lyon genetically hypertensive rats.

The present work was aimed to assess the factors involved in the maintenance of hypertension in adult transgenic mRen-2 (TG) rats. Special attention was paid to the renal handling of sodium, the sympathetic, and the renin-angiotensin system (RAS) activity. TG rats were compared with age-matched Lyon genetically hypertensive rats (LH), as both are of Sprague-Dawley origin. Blood pressure (BP), heart rate, and renal sympathetic nerve activity (RSNA) were recorded in conscious freely moving animals. Kidneys were isolated and single-pass perfused at different pressure levels. It was observed that the peripheral sympathetic drive was identical in TG and LH rats as indicated by their similar 24-h urinary excretion of catecholamines and methoxylated metabolites, baseline RSNA and its control by the baroreflex, and hypotensive response to ganglion-blockade. On the contrary, TG rats differed from LH rats by a more rapid excretion of an oral isotonic sodium load, a greater hypotensive and natriuretic response to furosemide, and a more marked BP response to acute RAS blockade. The TG kidney responses to stepwise changes in renal perfusion pressure (RPP) differed from those of LH rats by significantly higher perfusate flow and glomerular filtration rate. However, the pressure natriuresis curve of TG kidneys did not differ from that of LH rats because of an elevated tubular sodium reabsorption rate. These results suggest that adult TG rats, compared with LH rats, exhibit a tendency toward sodium and water retention, which may explain that despite low renal and circulating renin levels, the RAS remains involved in the maintenance of high BP in that model.

Animals↗
PubMed1993

High blood pressure and metabolic disorders are associated in the Lyon hypertensive rat.

OBJECTIVE: A large population of F2 rats, obtained from a cross between male Lyon hypertensive (LH) rats and female Lyon normotensive (LN) rats, was studied in order to assess the relationship between increased body weight, hyperlipidaemia and high blood pressure which characterize LH rats. METHODS: Mean arterial pressure (MAP) was recorded in male, conscious, freely moving LH, LN, F1 and F2 rats aged 30 weeks. Plasma total cholesterol, high-density lipoprotein-, low-density lipoprotein- and very low-density lipoprotein-cholesterol, phospholipids, triglycerides, insulin and glucose were measured. RESULTS: In the F2 cohort it was observed that high MAP was a recessive trait that depends on several genes and was unrelated to body weight. The left ventricular weight, corrected for tibia length, was correlated with MAP. Plasma total and high-density lipoprotein-cholesterol and phospholipids concentrations were lower in the F1 rats than in the LN rats, suggesting an overdominance of the LN alleles. In the F2 rats MAP was related to total, high-density lipoprotein- and low-density lipoprotein-cholesterol. Plasma triglycerides, insulin and the insulin:glucose ratio, which were higher in the LH rats than in the LN rats, were also correlated with MAP in the F2 cohort. Using stepwise multiple regression analysis, MAP remained correlated with plasma total cholesterol, insulin and the insulin:glucose ratio, but not with triglycerides. CONCLUSIONS: Hypertension in LH rats is a recessive trait that is independent of body weight. In addition, the cosegregation of blood pressure with plasma cholesterol and, to a lesser degree, with insulin levels, which was observed in the present study provides the first direct evidence that these phenotypes are associated and are not due simply to genetic drift in the Lyon model.

Animals↗
PubMed1992

Arterial baroreflex control of heart period is not related to blood pressure variability in conscious hypertensive and normotensive rats.

1. The short-term (within 30 min periods) and the long-term (among 30 min periods) variabilities, expressed as variation coefficients, of blood pressure (BP) and heart period (HP) were studied using a computer analysis of BP recordings in freely moving genetically hypertensive (LH), normotensive (LN) and low BP (LL) rats of Lyon strains at ages 5, 9, 21 and 40 weeks. The baroreflex control of HP was estimated with the slope of the linear relationship between systolic BP (SBP) and HP (SBP-HP slope) computed after phenylephrine and nitroglycerin injections. 2. Short-term variability of BP increased between 5 and 9 weeks of age and then remained stable. Hypertension was accompanied by an increase in both short- and long-term variabilities of diastolic BP in adult rats. 3. A sharp increase in SBP-HP slope was observed between 5 and 9 weeks of age in LN rats. SBP-HP slope of LH rats increased slightly up to 21 weeks but remained lower than that of normotensive controls. 4. The weak inverse correlation existing between SBP-HP slope and BP variability appeared to be mediated by the BP level. In addition, atropine which is known to abolish almost completely the SBP-HP slope, did not increase BP variability. It is concluded that SBP-HP slope is not linearly associated with BP variability in conscious rats.

Aging↗
PubMed1992

Influence of anaesthesia on the cardiovascular effects of rilmenidine and clonidine in spontaneously hypertensive rats.

1. The acute cardiovascular effects of two alpha 2-adrenoceptor agonists, rilmenidine and clonidine, were studied in 15-week-old male spontaneously hypertensive rats (SHRs). The effects of these drugs were compared with intravenous (i.v.) and intracerebroventricular (i.c.v.) administration in conscious and pentobarbitone-anaesthetized SHRs, in which aortic blood pressure (BP) was continuously recorded. 2. In conscious SHRs, i.v. doses of either rilmenidine (30, 100, 300 micrograms kg-1) or clonidine (3, 10, 30 micrograms kg-1) induced dose-dependent short-lasting increases in BP followed by moderate decreases associated with bradycardia, while the same three doses of both drugs given i.c.v. were devoid of BP and heart rate (HR) effects. 3. Pentobarbitone-anaesthesia increased the sympathetic control of BP and suppressed the cardiac baroreflex sensitivity. 4. In anaesthetized SHRs, i.v. injections of the same 3 doses of rilmenidine and clonidine induced a slight increase in BP, rapidly followed by profound and long-lasting BP and HR decreases. Surprisingly, when given i.c.v., these 3 doses lowered BP and HR to the same extent but in a more progressive manner. 5. The lack of efficacy of both drugs in conscious SHRs after the i.c.v. administration of i.v. active doses and the lack of more marked and rapid effects in anaesthetized SHRs, after i.c.v. than after i.v. injections, question the involvement of a major central site of action for these antihypertensive alpha 2-adrenoceptor agonists. Moreover, these results show that the cardiovascular effects of these drugs are profoundly influenced by baseline sympathetic nervous system activity which is enhanced by pentobarbitone-anaesthesia.

Adrenergic alpha-Agonists↗
PubMed1992

[Role of sympathetic nerve fibers in hemodynamic responses to stress in rats].

Hemodynamic responses to acute stress exposure were studied in normotensive control (C) and chronically sympathectomized (S) rats. Male Sprague-Dawley rats received daily sc injections of either saline (C) or guanethidine (S) from 1 to 13 weeks of age. Doppler flow probes were then implanted for the measurement of blood velocity in the sub-diaphragmatic aorta, superior mesenteric artery and distal aorta (hindquarters). After 10 days of recovery and 24 hours before the study, the caudal artery was cannulated. In the conscious freely moving rats, mean arterial pressure (MAP), heart rate (HR) and indices of regional blood flows and vascular conductances (G as blood flow/MAP ratio) were recorded beat to beat, before and during emotional stress (jet of air for 2 min). In basal conditions, mean values of MAP and HR were similar in C (107 +/- 2 mmHg; 399 +/- 8 bpm, n = 9) and S (106 +/- 3 mmHg; 384 +/- 12 bpm, n = 7) rats. The effects of stress on MAP, HR, aortic (AoG), mesenteric (MeG) and hindquarters (HqG) vascular conductances are expressed as percentage changes from baseline (delta): [table: see text] These results highlight the role of vascular sympathetic nerves in pressor responses and systemic and mesenteric vasoconstrictions induced by stress in the rat. They also indicate that vasodilatation in the hindquarters vascular bed is not secondary to withdrawal of sympathetic vasoconstrictor tone but rather to active phenomena which do not involve the stimulation of vascular beta 2-adrenoceptors by neuronal catecholamines nor the release of vasodilator cotransmitters from the sympathetic nerve endings.

Adrenergic Fibers↗
PubMed1991

Autonomic nervous system and cardiovascular variability in rats: a spectral analysis approach.

Mechanisms underlying systolic (SBP) and diastolic (DBP) blood pressure and heart rate (HR) beat-to-beat variability were investigated using spectral analysis in conscious genetically normotensive (LN) and hypertensive (LH) adult rats from the Lyon strains. In LN rats, basal SBP, DBP, and HR spectra exhibited peaks in low (LF: 0.38-0.45 Hz) and high (HF: 1.04-1.13 Hz) frequencies. The LF peak of SBP, and even more of DBP, could be attributed to the influence of the sympathetic nervous system as it disappeared after destruction of the sympathetic nerves or a combined alpha- and beta-adrenoceptor blockade, whereas it was higher after blockade of the parasympathetic system. The HF peak of HR, linked to the respiratory rate, was abolished by the parasympathetic system blockade, whereas those of SBP and DBP were enhanced. In LH rats, which exhibit a lower sympathetic activity, the LF peaks of SBP and DBP were less distinct compared with LN controls. We conclude that the LF peak of DBP and the HF peak of HR are likely to represent useful estimates of the sympathetic vascular control and of the parasympathetic cardiac control, respectively.

Angiotensin Receptor Antagonists↗
PubMed1991

Blood pressure maintenance in hypertensive sympathectomized rats. I. Adrenal medullary catecholamines.

To assess the role of the sympathetic nervous system in the development of genetic hypertension, blood pressure (BP) was recorded in conscious adult Lyon hypertensive (LH) and normotensive (LN) rats that had received daily injections of saline or guanethidine at 1-13 wk of age. Guanethidine abolished the pressor response to tyramine, decreased plasma norepinephrine by greater than 70% and plasma 3,4-dihydroxyphenylglycol by approximately 90%, and did not change plasma epinephrine. Bilateral adrenalectomy further reduced plasma norepinephrine to 8 and 5% of control levels in LH and LN rats, respectively. BP was lowered (-7%) in sympathectomized rats, but the mean absolute BP difference between LH and LN rats was unaltered. Despite marked supersensitivity to alpha-adrenoreceptor stimulation, phentolamine induced only a small transient depressor response, which was abolished by adrenalectomy in sympathectomized rats. It is concluded that the sympathetic nervous system is not necessary for the development of hypertension in LH rats. After sympathectomy, circulating catecholamines, which mostly derive from the adrenal medulla, play only a minor role in BP maintenance.

Adrenal Medulla↗
PubMed1991

[Role of sympathetic nervous system on blood pressure and heart rate variabilities in the rat: spectral analysis].

The role of the sympathetic nervous system (SNS) in the genesis of the beat-to-beat variability of blood pressure (BP) and heart rate (HR) was studied using spectral analysis. The SNS activity of genetically normotensive rats of the Lyon strain (LN) was abolished in 2 ways: 1) adrenergic blockade with administrations of phentolamine (PHE, 5 mg/kg i.v.) or propranolol (PRO, 5 mg/kg i.v.) or both drugs (PHEPRO) or 2) destruction of the sympathetic fibers with an early chronic treatment with guanethidine (LNSx). HR and systolic (SBP) and diastolic (DBP) BP spectra were computed using 50 to 100 stationary sequences from 1 h beat-to-beat recordings and covered the 0.015-3.85 Hz frequency band. In LN rats, spectra obtained in baseline conditions exhibited a high-frequency peak (HF, 1.04-1.13 Hz) related to the respiratory frequency and a mid-frequency peak (MF, 0.38-0.45 Hz). Concerning BP, the alterations of the SNS induced significant decreases of the total modulus (mmHg/Hz1/2) of the MF band (0.27-0.74 Hz): [formula: see text] In addition, the MF peak of SBP and DBP spectra was abolished in LNSx and PHEPRO rats. Concerning HR spectra, the moduli of all the frequency components were decreased in PHEPRO rats only. In conclusion, the similarity of the results observed in LNSx and PHEPRO rats shows that the MF oscillations of BP depend in a large extent (65%) on the action of the sympathetic fibers and involve the activation of both alpha- and beta-adrenoceptors. Concerning DBP, this effect is especially mediated by the activation of alpha-adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Heterogeneous computer network for real-time hemodynamic signal processing.

A computer network is described that allows real-time processing, graphical monitoring and off-line analysis of blood pressure, nervous activity and Doppler signals recorded in conscious rats. Real-time processing is performed by an acquisition station using a powerful microprocessor, allowing extraction and storage of several characteristic parameters from each cardiac cycle and real-time graphical monitoring. The experimenter can thereby follow the time evolution of the hemodynamic parameters. Experimental data are sent through the local network to a workstation that ensures off-line processing such as chronograms, histograms and statistical analyses.

Animals↗
PubMed1990

Effects of sympathectomy on blood pressure and its variability in conscious rats.

To further assess the role of the sympathetic nervous system (SNS) in the control of blood pressure (BP), continuous recordings of BP were performed in conscious freely moving rats that had received daily injections of guanethidine or saline from 7 to 90 days of age. Guanethidine extensively destroyed the peripheral sympathetic fibers as indicated by marked decreases in the norepinephrine content of the heart and kidneys and the absence of pressor response to tyramine injection. Such a chronic sympathectomy did not alter the BP and heart rate (HR) levels but markedly enhanced the BP variability while the HR variability and the sensitivity of the cardiac baroreceptor reflex were not altered. Angiotensin-converting enzyme inhibition with perindopril induced a rapid fall in BP and normalized the BP variability in sympathectomized animals. It is concluded that in rats, the SNS is not necessary for the full development of the BP level but is essential to buffer the spontaneous variability of BP. After sympathectomy, BP is maintained at nearly normal levels mainly through activation of the renin angiotensin system.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1990

Antirenin immunization versus angiotensin converting enzyme inhibition in rats.

The effects of specific active immunization against renin were compared with those of chronic angiotensin converting enzyme (ACE) inhibition. Male spontaneously hypertensive rats (SHR) were immunized (SHR-I) (n = 10) against pure murine renin (four injections of 30 micrograms/kg s.c.) or received (SHR-P) (n = 11) a converting enzyme inhibitor (perindopril, 2 mg/kg/day per os for 4 weeks). Sham-immunized SHR (SHR-S) (n = 12) and normotensive Wistar-Kyoto (WKY-S) (n = 12) rats served as controls. At 15 weeks of age, 24-hour average blood pressure was obtained in freely moving rats using intra-aortic pressure recording with computer analysis. Antirenin immunization induced high circulating titers of antibodies, a fall in plasma renin activity (-95%), and urinary excretion of mineralocorticoids. Perindopril abolished the pressor response to angiotensin I, whereas plasma ACE was only partly (-56%) decreased. It also increased plasma renin activity and did not alter the urinary excretion of steroids. Both immunization and perindopril allowed the blood pressure of SHR to return to the level of WKY-S rats and reduced the left ventricular weight. These decreases were associated with an elevated sympathetic nervous system activity as indicated by increases in the urinary excretion of catecholamines and their metabolites. It is conclude that, apart from an unaltered steroid synthesis, most of the cardiovascular effects of chronic ACE inhibition are similar to those of antirenin immunization, thus indicating that blockade of the circulating and renal renin-angiotensin system accounts for most of the effects of ACE inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1989

Cardiovascular effects of rilmenidine, a new alpha 2-adrenoceptor agonist, and clonidine in conscious spontaneously hypertensive rats.

1. The acute and chronic effects of rilmenidine, a partial agonist of alpha 1- and alpha 2-adrenoceptors with antihypertensive properties, were compared to those of clonidine on blood pressure (BP), heart rate (HR) and the urinary excretion of catecholamines, which was used as an index of sympathetic activity. 2. As these drugs are known to interfere centrally and peripherally with the sympathetic nervous system, long-term arterial blood pressure recordings in freely moving unstressed adult spontaneously hypertensive rats (SHR) were used. 3. Acute i.v. administrations of rilmenidine (0.3 mg/kg at 1200 h, 1.2 mg/kg at 1700 and 2200 h) and clonidine (12 micrograms/kg at 1200 h, 50 micrograms/kg at 1700 and 2200 h) induced short-lasting increases in BP associated with a decrease in HR, which were followed by prolonged, dose-dependent decreases in BP without bradycardia. The pressor effect was less marked and the associated bradycardia was more marked in active SHR with physiologically high sympathetic activity than in resting SHR. 4. A 12-day oral treatment with rilmenidine (6.0 mg/kg daily) or clonidine (150 micrograms/kg daily) induced moderate decreases in BP without change in HR. Rilmenidine but not clonidine decreased normetanephrine (NMN) excretion in active but not in resting SHR. 5. Finally, during the 24 h following the cessation of the treatments, BP returned to normal, without significantly exceeding that of untreated controls. However, upswings in BP or HR were observed, more markedly and frequently after clonidine than after rilmenidine. 6. In conclusion the effects of alpha 2-adrenoceptor agonists appear to be influenced by the pre-existing sympathetic tone. The general agreement between these data and those observed in patients demonstrates that the use of conscious unstressed animals is of value to determine the cardiovascular effects of drugs which act on the sympathetic nervous system.

Administration, Oral↗
PubMed1989

Evolution with age of baroreflex sensitivity and its autonomic nervous components in conscious hypertensive rats of the Lyon strain.

1. Cardiac baroreflex sensitivity (BRS) and its sympathetic and vagal components were studied after atropine and propranolol administrations in conscious genetically hypertensive (LH), normotensive (LN) and low blood pressure (LL) rats of the Lyon strain at 5, 9, 13 and 70 weeks of age. 2. LH rats older than 9 weeks exhibit a lower BRS than age-matched LN and LL controls. 3. The vagal component of cardiac baroreflex is predominant. In LN rats, this component increases up to 9 weeks of age. 4. The sympathetic component of cardiac baroreflex is small and identical in the three strains and does not alter with age. 5. Thus, in normotensive rats, the increase in BRS during maturation reflects mainly the vagal component. The development of hypertension prevents this physiological increase in the sensitivity of the vagal component of cardiac baroreflex leading to a reduced BRS.

Aging↗