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C Julien

Publications and source records attributed to C Julien.

At least 55 records · Page 3Linked to original sources
PubMed1994

Pressure-dependent renin release and arterial pressure maintenance in conscious rats.

The relationship between pressure-dependent renin release and mean arterial pressure (MAP) level was assessed in normotensive intact (n = 10), sympathectomized (guanethidine at 1-13 wk of age; n = 8), and renal-denervated (1 wk before the study; n = 6) rats under normal-salt diet. MAP was recorded beat-to-beat for 2 h in conscious animals. Then plasma renin concentration (PRC) responses to graded reductions of MAP were determined using an aortic inflatable cuff. Neither sympathectomy nor renal denervation altered baseline MAP level and PRC. Lowering MAP below a threshold pressure induced large increases in PRC. Threshold pressure did not differ between intact (87 +/- 1 mmHg), sympathectomized (88 +/- 2 mmHg), and renal-denervated (83 +/- 2 mmHg) rats. MAP frequently fell below threshold pressure in sympathectomized but not in intact and renal-denervated rats. We conclude that in conscious normotensive quiet rats under normal-salt diet the pressure-dependent renin release is not activated spontaneously and is therefore unlikely to play a role in MAP maintenance. This regulatory mechanism develops and operates normally in the absence of sympathetic nerves.

Animals↗
PubMed1993

Role of vasoconstrictor tone in arterial pressure lability after chronic sympathectomy and sinoaortic denervation in rats.

In both chronically sympathectomized (SNX) and sinoaortic denervated (SAD) rats, removal of vasoconstrictor influences decreases mean arterial pressure (MAP) and its variability in parallel. This study examined if this decrease in arterial pressure lability is solely a result of decreasing vascular tone. In conscious 14-week-old male sympathectomized (guanethidine at 1-13 weeks of age) and sinoaortic denervated (2 weeks before study) rats, arterial pressure was recorded beat-to-beat during 30-min consecutive periods; control; ganglionic blockade in sinoaortic denervated rats and angiotensin converting enzyme inhibition plus vasopressin antagonism in sympathectomized rats; and restoration of the initial arterial pressure with continuous infusions of phenylephrine and angiotensin II. Sympathectomized and, even more, sinoaortic denervated rats had increased pressure variability. Neural or humoral blockade markedly reduced arterial pressure and its liability in both groups of rats and subsequent restoration of the arterial pressure with vasoconstrictor infusions returned lability to levels either slightly above (sympathectomy) or below (sinoaortic denervation) control values. In basal conditions, an increased frequency of occurrence of depressor episodes was evidenced in sympathectomized rats whereas a variable ratio of pressor to depressor events was observed in sinoaortic denervated rats. During vasoconstrictor infusions, blood pressure lability was mainly due to depressor events in both groups of rats. It is concluded that the background vascular tone provided by endogenous pressor systems is necessary for the expression of the depressor component of blood pressure lability in sinoaortic denervated and in sympathectomized rats. The study also suggests that in sympathectomized rats, humoral influences act to limit rather than enhance blood pressure lability, whereas in sinoaortic denervated rats, the sympathetic nervous system may directly generate part of the lability.

Angiotensin II↗
PubMed1993

Do thymic-neuroendocrine interactions play a role in the antihypertensive effect of neonatal thymectomy in Lyon hypertensive rats?

Previous studies showed that neonatal thymectomy prevented the spontaneous increase in blood pressure in genetically hypertensive rats (LH) of the Lyon strain, leaving untouched that of their normotensive controls (LN). As the thymus is connected to the neuroendocrine system through secretion of hormonal factors, we investigated the possible role played by these factors in hypertension of LH rats. To that end we studied, in sham-operated and neonatally thymectomized LH rats, the blood pressure effects of thymostimulin, a partially purified thymus extract and examined whether changes in major neuroendocrine factors of blood pressure regulation occurred in thymectomized LH rats. Thymostimulin (1 or 10 mg/kg/48 h) did not modify blood pressure in sham-operated LH rats and failed to consistently increase it in neonatally thymectomized animals. Urinary mineralocorticoids, catecholamines and their metabolites, and plasma renin levels were not altered by neonatal thymectomy. Plasma testosterone was decreased to a similar degree by neonatal thymectomy in LH and normotensive controls. These results do not favor a pressor role of thymic hormonal factors in LH rats and show that the antihypertensive effect of neonatal thymectomy is not secondary to a decreased secretion of catecholamines, renin, mineralocorticoids, and testosterone. They therefore suggest that the role of the thymus in genetically hypertensive LH rats is more likely mediated by cellular immune mechanisms than by hormonal processes.

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

Cardiovascular habituation to emotional stress in Lyon hypertensive rats.

1. Intra-aortic blood pressure was recorded continuously in freely moving genetically hypertensive (LH), normotensive (LN) and low blood pressure (LL) rats of the Lyon strain during two 11 h periods (08:00-19:00 h). During the first period (control), the animals were left undisturbed and during the second period (stress), a jet of air was applied for 20 min every hour. Urine was collected simultaneously and analysed for its content in norepinephrine and epinephrine. 2. The first exposure to the stressor induced larger increases in blood pressure and heart rate in LH than in LN and LL rats. However blood pressure and heart rate responses to the 10 following stressors decreased in LH rats while they remained stable in LN and LL animals. 3. Repeated stress exposure induced significant increases in epinephrine excretion in both LN and LL but not in LH rats. 4. It is concluded that LH rats exhibit marked cardiovascular habituation to repeated stress. Taken together with the lack of stress-induced sympathoadrenal activation, this suggests a reduced level of emotional responsiveness in Lyon hypertensive rats.

Adrenal Medulla↗
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

Trophoblast-like cells sorted from peripheral maternal blood using flow cytometry: a multiparametric study involving transmission electron microscopy and fetal DNA amplification.

Three monoclonal antibodies (MAbs) against trophoblast (GB17, GB21, and GB25) and flow cytometry were used to sort trophoblast-like cells (TLCs) from peripheral blood of pregnant women. Sorted TLCs were processed for electron microscopy and fetal DNA amplification of the Y-specific sequences from mothers carrying male fetuses. At the ultra-structural level, most of the nucleated cells had the morphology of leucocytes, suggesting maternal contaminants, and we did not find the characteristic features of the free intervillous trophoblast cells. Nevertheless, polymerase chain reaction (PCR) analysis showed an amplification of Y-specific sequences in two out of three samples of sorted TLCs. These results suggest that besides the maternal leucocytes, sufficient trophoblast nucleated fetal cells can be obtained using cell enrichment by sorting. This sensitive method holds promise for non-invasive prenatal diagnosis of fetal sex and if sufficient Y(positive) nuclei are found, for the diagnosis of selected numerical chromosome abnormalities.

Antibodies, Monoclonal↗
PubMed1991

Nonorgan-specific autoantibodies in individuals infected with type 1 human immunodeficiency virus.

Fifty-six human immunodeficiency virus-1-positive asymptomatic carriers were tested for the presence of a variety of nonorgan-specific autoantibodies. Antinuclear antibodies were detected in 34 sera, of which 27 were directed to the mitotic spindle apparatus and all were of the IgG isotype. Anti-Golgi complex, anti-centriole, and anti-vimentin antibodies were also present in 20.4, and 4 sera, respectively. Ten patients had less than 500 CD4-carrying T lymphocytes per cubic millimeter. Nine of them had more than one autoantibody. No correlation could be demonstrated between the number of autoantibodies and the level of serum immunoglobulins.

Adult↗