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Biomedical subjects

P Brun

Publications and source records attributed to P Brun.

At least 55 records · Page 3Linked to original sources
PubMed1997

On the involvement of a tonic dopamine D2-autoinhibition in the regulation of pulse-to-pulse-evoked dopamine release in the rat striatum in vivo.

The dopamine overflow evoked by trains of electrical stimulation pulses applied to the ascending dopaminergic pathway was measured with continuous amperometry in the striatum of anesthetised rats. As previously observed in in vitro studies, a pulse by pulse analysis showed a fall in dopamine overflow evoked by pulses 2 to 6, compared to the response evoked by pulse 1. However, in contrast with in vitro findings, the present in vivo data showed that the dopamine receptor antagonist haloperidol i) completely reverses the fall in dopamine overflow between pulse 1 and subsequent pulses, ii) enhances the dopamine overflow elicited by pulse 1. These results suggest that in vivo, both basal and pulse-evoked dopamine overflow results in stimulation of dopamine D2-type autoreceptors and therefore in regulation of dopamine release.

Animals↗
PubMed1997

Value of Doppler ultrasound for the diagnosis of renal artery stenosis in children.

To evaluate the reliability of Doppler ultrasonography (US) in identifying children with renal artery stenosis (RAS) among those with hypertension, we compared Doppler US results in 22 hypertensive children (mean age 8.9 +/- 4.3 years), with (13 cases) and without RAS at angiography, and in 33 normotensive children (mean age 8.8 +/- 4.7 years). We observed 2 false-negatives and 2 false-positives with Doppler US. Of the 2 false-negative diagnoses, I had RAS on an accessory renal artery located behind a normal upper polar artery and the other was observed in a patient with bilateral multiple stenosis of the very distal segments of renal arteries. The 2 false-positive diagnoses were due to sinuous left renal artery and to technical reasons, respectively. In another patient, Doppler US showed a tight RAS, while arteriography was normal. RAS was subsequently confirmed by a second arteriography. Peak systolic velocity values of Doppler US were significantly higher in patients with proven angiographic RAS (3.44 +/- 0.66 m/s) than in hypertensive patients with normal renal arteries at angiography (0.99 +/- 0.35 m/s, P < 0.0001) and normotensive healthy children (1.04 +/- 0.23 m/s, P < 0.0001). With the use of multiple views, and the experience acquired with practice, false-negatives or false-positives due to the geometry of the renal artery can be avoided. Nevertheless, very distal stenosis can be missed by Doppler US.

Angiography↗
PubMed1997

Biocompatibility and enzymatic degradation studies on sulphated hyaluronic acid derivatives.

The biocompatibility and susceptibility to enzymatic degradation of new heparin-like polysaccharides obtained by hyaluronic acid sulphation (HyalSx) were evaluated. In particular, HyalSx cytotoxicity and cytocompatibility were assessed by the direct contact method using fibroblasts L929 and human endothelial cells. The results showed that hyaluronic acid derivatives are devoid of any cytotoxic effects on mouse fibroblasts and they are cytocompatible. The haemolysis test showed that the sulphated polysaccharides are not haemolytic. HyalSx susceptibility to enzymatic degradation was tested in the presence of both hyaluronidase and chondroitinase ABC. It was demonstrated that the introduction of sulphate groups along the hyaluronic acid chain makes the macromolecules resistant to enzymatic digestion.

Animals↗
PubMed1997

Alteration of left ventricular diastolic function during coronary angioplasty-induced ischemia: a color M-mode Doppler study.

OBJECTIVES: The aim of this study was to assess the effects of ischemia on diastolic function by analyzing flow propagation velocity with color M-mode Doppler echocardigraphy. BACKGROUND: Color M-mode Doppler echocardiography has been proposed as a method of assessing left ventricular filling. METHODS: Color M-mode Doppler echocardiography and measurement of hemodynamic data were performed simultaneously at baseline and during angioplasty-induced ischemia. Tau was compared with flow propagation velocity. Late diastolic indexes, left ventricular pressure and flow cessation time were also investigated. RESULTS: During ischemia, left ventricular relaxation rate (tau) increased, whereas flow propagation velocity decreased, from (mean +/- SD) 46.8 +/- 10 ms to 72.6 +/- 18.3 ms and from 59.8 +/- 15.8 cm/s to 30 +/- 8 cm/s, respectively (all p < 0.0001). The maximal slowing of flow propagation velocity was observed 20 to 30 s after the beginning of the inflation, coexisting with a notch on the ascending limb of the negative rate of rise of the left ventricular pressure (dP/dt) curve. Flow propagation velocity was correlated with tau both at baseline (r = 0.53, p < 0.05) and during inflation (r = 0.53, p < 0.03). Left ventricular end-diastolic pressure increased during ischemia from 13.5 +/- 8 mm Hg at baseline to 27.5 +/- 7 mm Hg, while a premature cessation of the entering flow occurred -13.8 +/- 23 ms before the next Q wave onset, compared with 4.5 +/- 19.6 ms after the Q wave onset at baseline (all p < 0.0001). CONCLUSIONS: The analysis of flow propagation velocity showed that early filling is highly dependent on left ventricular relaxation rate, particularly through the phenomenon of asynchrony. During ischemia, the premature cessation of late filling is associated with increased diastolic pressures.

Angioplasty, Balloon, Coronary↗
PubMed1997

[Renal stenosis in hypertensive children. Doppler/arteriographic correlation].

To evaluate the reliability of Doppler-ultrasonography in identifying children with renal artery stenosis among those with hypertension, we compared Doppler ultrasonography results in 29 hypertensive children (mean age: 8.3 +/- 4.7 years) with angiography. Doppler-ultrasonography and arteriography were performed within a period less than two months. First, we established normal values in 40 normotensive children (mean age: 8.4 +/- 4.5 years). The diagnosis of renal artery stenosis was settled when maximal systolic velocities where > or = to 1.70 m.s-1. Peak systolic velocities values of Doppler-ultrasonography were significantly higher in patients with proven angiographic renal artery stenosis (3.56 +/- 0.70 m.s-1) than in hypertensive patients with normal renal arteries at angiography (1.02 +/- 0.29 m.s-1, p < 0.0001), and than in normotensive healthy children (1.05 +/- 0.33 m.s-1, p < 0.0001). We observed 3 false negative and 2 false positive diagnoses with Doppler-ultrasonography. Of the 3 false negatives, one had a stenosis on a right and posterior segmental artery and the other had bilateral and multiply intra-renal artery stenosis with few hemodynamic significance. The 2 false positives were due to a sinuous main renal artery and to a technical mistake, respectively. In another patient, Doppler-ultrasonography revealed a tight main renal artery stenosis, not detected by arteriography. Renal artery stenosis was subsequently confirmed by a second arteriography. Our results showed a sensitivity of 88%, a specificity of 93%, a positive predictive value of 92% and a negative predictive value of 89%, demonstrating the reliability of Doppler-ultrasonography for the diagnosis of renal artery stenosis in hypertensive children. With the use of a rigorous methodology and the increasing experience of the operators, diagnostic errors of renal artery stenosis are currently avoidable. Nevertheless, it is not excluded that intra-renal artery stenosis with few hemodynamic significance might be missed by Doppler-ultrasonography.

Adolescent↗
PubMed1996

Evaluation of clinical and laboratory parameters during 2 years of growth hormone treatment in prepubertal children with chronic renal failure.

UNLABELLED: Twelve prepubertal children with chronic renal failure (CRF) were treated with human growth hormone (GH) (1.2 IU/kg/week) for 2 years. High doses of GH clearly increased growth velocity, from 3.8 +/- 1.3 to 9.6 +/- 1.5 (P = 0.0001) and 6.9 +/0 0.8 cm/year (P = 0.0001) after the 1st and 2nd year of treatment, respectively, leading to a mean height gain of 1.4 SD. During the 1st year of treatment the height increment, expressed in SDS, correlated negatively with chronological age (P = 0.003). Basal insulin-like growth factor 1 (IGF 1) levels were normal or elevated (7/12 patients) and correlated positively with the overnight integrated GH concentration (r = 0.68, P < 0.001). Basal insulin-like growth factor binding protein 3 (IGF-BP3) levels were elevated in 8/12 patients. GH induced a significant increase in IGF 1 and IGF-BP3 levels; IGF 1 peaked after 6 months (when growth velocity was optimal) and IGF-BP3 peaked after 12 months. The mean glomerula filtration rate, measured by inulin clearance and corrected for body surface area, fell after the 1st year of treatment, and significantly so at the end of the 2nd year (P = 0.02). CONCLUSION: Early initiation of GH therapy during CRF may prevent severe growth retardation and allow these children to attain normal height before dialysis and transplantation.

Area Under Curve↗
PubMed1996

[Vitamin A poisoning revealed by hypercalcemia in a child with kidney failure].

BACKGROUND: Patients with chronic renal failure are at risk of vitamin A intoxication, a risk that must be evoked when unexplained hypercalcemia occurs. CASE REPORT: An 8 year-old boy with Alagille syndrome and chronic renal failure was admitted because of general deterioration, and bone pain. Severe hypercalcemia (3.9 mmol/L) was present. Serum phosphate, parathyroid hormone and 25 OH D3 levels were normal; 1-25 (OH)2 D3 levels were undetectable. Hypercalcemia was attributed to vitamin A intoxication, due to the administration of a mean daily dose of 12000 IU of vitamin A for at least 2 years. The diagnosis was confirmed by high plasma levels of retinol (1475 micrograms/L). Hypercalcemia only partially responded to treatment with bisphosphonates, calcitonin and dialysis with low calcium dialysate. Serum vitamin A levels remained elevated one month after vitamin A withdrawal. The boy died two months after admission from atrioventricular block. CONCLUSION: Vitamin A administration induces a high risk of intoxication in patients with chronic renal failure. Serum vitamin A concentrations are elevated in these patients, because of decreased renal metabolism of retinol, and vitamin A supplements must be avoided.

Alagille Syndrome↗
PubMed1996

Antioxidant effects of hyaluronan and its alpha-methyl-prednisolone derivative in chondrocyte and cartilage cultures.

OBJECTIVE: To compare hyaluronan and its alpha-methyl prednisolone derivative (HYC-141) with respect to their potential to directly cause tissue damage and to protect tissues from attack by reactive oxygen species. METHODS: Cartilage samples and chondrocytes were isolated from 15-day chick embryos and were exposed to enzyme-based and activated inflammatory cell-free radical generating systems in the presence of varying concentrations of alpha-methyl prednisolone, hyaluronan, and HYC-141. Tissue and cell vitality was measured by determining the incorporation of radioactive sulphate into newly synthesized glycosaminoglycans. RESULTS: Only alpha-methyl prednisolone caused a significant decrease in biosynthetic activity. All the tested substances were capable, to some extent, of protecting tissues and cells from damage by reactive oxygen species; HYC-141 demonstrated the greatest protective effect. CONCLUSION: These data suggest that HYC-141 may possess certain advantages over the individual component molecules in the local treatment of arthropathies.

Animals↗
PubMed1996

[Treatment of urinary tract infection in children].

The management of urinary tract infection in children must take into account several factors, namely the type of bacteria, the localization of the infection, the presence of an uropathy and the age of the patient. In acute pyelonephritis, the risk of renal scarring justifies a first line treatment with two antibiotics to be administrated intravenously in newborns and infants. Treatment must be maintained for at least 10 days: double antibiotherapy for 4-5 days, followed by oral monotherapy according to the antibiogram. Cystitis requires an oral monotherapy for 3-7 days. In any case it is important to search for a cause to the infection.

Age Factors↗
PubMed1996

Alteration of lung diffusion capacity in IgA nephropathy.

OBJECTIVE: To establish whether changes of lung transfer for carbon monoxide (TLCO) are related to the phase of IgA nephropathy. METHODS: Respiratory function was tested in 12 children with IgA nephropathy assessed by percutaneous renal biopsy. This was done during acute exacerbations or haematuria-free phases of the disease. RESULTS: TLCO was low in 12/13 measurements made in the haematuric phase of IgA nephropathy or during the month following gross haematuria (mean TLCO 64% of expected values). Lung volumes and blood gas values were normal and only minor radiological signs of interstial lung involvement were observed in 11/12 patients. When respiratory tests were performed more than three months after gross haematuria, TLCO was low in 4/9 patients, with no relation to the significance of residual proteinuria or severity of findings at renal biopsy. There was a significant difference between tests performed when haematuria was present or recent and those performed more than three months after an episode of gross haematuria (p < 0.01). CONCLUSIONS: The decrease of TLCO in the acute phases of the disease is probably related to alterations of the lung alveolarcapillary membrane by immune complexes containing IgA. This non-invasive technique, easy to perform and repeat, could be of value in the diagnosis of IgA nephropathy in haematuric children.

Acute Disease↗
PubMed1996

[Treatment of keloid with intralesional bleomycin].

INTRODUCTION: Treatment of keloids is often disappointing and sometime quite difficult to manage. In addition to unpleasant esthetic effects, treatment may also produce functional impairment due to pruritus and contraction of the scar tissue. PATIENTS AND METHODS: We proposed a new treatment scheme using intralesional infiltrations of bleomycin. RESULTS: We treated 31 keloids and 5 hypertrophic scars with 3 to 5 infiltrations with a 1-month period. Total regression was obtained in 25 keloids and hypertrophic scars. Important regression was obtained in 6 keloids (86% good results). Treatment was effective in all cases within the first 2 infiltrations evidenced by a reduction in the volume of the keloid and clear reduction of functional impairment in most patients. CONCLUSION: Effective well-tolerated treatment without pain was achieved with infiltration suggesting that this treatment should be used as first line therapy for keloids.

Adolescent↗
PubMed1995

Improvement of subendocardial myocardial perfusion after percutaneous transluminal coronary angioplasty. A myocardial contrast echocardiography study with correlation between myocardial contrast reserve and Doppler coronary reserve.

BACKGROUND: After angioplasty coronary reserve improves but does not normalize in most patients. The purpose of this study was to examine before and after angioplasty coronary reserve and transmural myocardial blood flow distribution using myocardial contrast echocardiography. METHODS AND RESULTS: Twelve patients with left anterior descending coronary artery stenosis were investigated before and immediately after angioplasty. A Doppler catheter was placed in the proximal segment. Myocardial contrast echocardiography was performed by imaging the septum in M mode in a parasternal view using a 3.0-mL bolus of sonicated amidotrizoate sodium meglumine through the guiding catheter. The gray level before injection was subtracted from the gray level after injection to maximize contrast time-intensity curves. The area under the curve was used as an indicator of myocardial blood flow, and subendocardial/subepicardial ratios were measured. After baseline measurements were obtained, Doppler and echographic data were recorded after a bolus infusion of papaverine into the left main coronary artery. The same protocol was performed in patients after angioplasty and in five control subjects with normal coronary arteries. Before angioplasty, echocardiographic and Doppler coronary reserve were 2.57 +/- 0.48 and 2.54 +/- 0.57, respectively. Both increased after angioplasty to 3.65 +/- 0.57 and 3.36 +/- 0.70, respectively (P < .05). Coronary reserve values obtained in patients with these two methods under the different conditions and in control subjects were correlated (r = .81; P = .0001). Before angioplasty, subendocardial/subepicardial septal ratios decreased from 0.80 +/- 0.48 to 0.60 +/- 0.27 after papaverine (P < .05). However, after angioplasty, these ratios tended to increase, from 0.72 +/- 0.27 to 0.92 +/- 0.45 after papaverine, but they did not change in control subjects (1.11 +/- 0.23 to 0.92 +/- 0.11). CONCLUSIONS: These results show that myocardial contrast echocardiography yields flow reserve values that correlate with values obtained using intracoronary Doppler. This technique may be considered as an accurate tool to assess coronary reserve in humans.

Angioplasty, Balloon, Coronary↗
PubMed1995

Neurochemical and behavioural effects of neurotensin vs [D-Tyr11]neurotensin on mesolimbic dopaminergic function.

Microinjection of neurotensin(1-13) or neurotensin(8-13) into the ventral tegmental area (VTA) of anaesthetized rats produced dose-dependent (1-100 pg) dopamine release in the nucleus accumbens as measured by differential pulse amperometry (DPA). Higher doses (100 pg-10 ng) of [D-Tyr11]neurotensin were required to produce an identical effect. In addition, the 3 peptides enhanced the K(+)-evoked [3H]DA release from nucleus accumbens slices. The stimulatory actions produced by 10(-8) M neurotensin(1-13) and neurotensin(8-13) were respectively of 96% and 72% while the effect of [D-Tyr11]neurotensin was only of 79% at 10(-6) M. Unilateral application of the 3 peptides in the VTA of cannulated rats produced contralateral circling. [D-Tyr11]neurotensin was effective in a dose-dependent manner, between 40 and 320 ng. Similar effects were observed with 80 ng of neurotensin(1-13) and neurotensin(8-13) in presence of the protease inhibitor thiorphan. In view of the higher potency of neurotensin(1-13) and neurotensin(8-13) versus [D-Tyr11]neurotensin to stimulate DA release both in vivo and in vitro and the higher efficacy of [D-Tyr11]neurotensin to induce circling, this study further strengthens the concept of neurotensin receptor heterogeneity.

Animals↗
PubMed1995

Blockade of neurotensin receptor by SR 48692 potentiates the facilitatory effect of haloperidol on the evoked in vivo dopamine release in the rat nucleus accumbens.

The present experiments assessed the effects of SR 48692, a selective nonpeptide antagonist of neurotensin receptors, on mesolimbic dopaminergic neurotransmission. Dopamine release evoked by the electrical stimulation of the median forebrain bundle (20 Hz, 10 s) was measured in the nucleus accumbens of urethane-anesthetized rats using differential pulse amperometry combined with carbon fiber electrodes. SR 48692 (0.1 mg/kg, i.p.) alone did not affect this release, whereas it dose-dependently (0.03-1 mg/kg, i.p.) enhanced the haloperidol (50 micrograms/kg, i.p.)-induced facilitation of the electrically evoked DA release. The increase induced by haloperidol (92 +/- 26% above control values 30 min after injection) was potentiated by SR 48692 (264 +/- 75% at 0.03 mg/kg, 428 +/- 113% at 0.1 mg/kg, and 480 +/- 135% at 1 mg/kg). Effects identical to those of SR 48692 were obtained with SR 48527, a chemically related compound with a high affinity for neurotensin receptors, but not with SR 49711, its low-affinity antipode. The potentiating effects of SR 48692 were positively related to the stimulation frequency (from 6 to 20 Hz) and to the dose of haloperidol (from 12.5 to 50 micrograms/kg) and were abolished after prior kainic acid lesion (1 microgram/1 microliter) of the nucleus accumbens. Thus, the effects of SR 48692 required the integrity of postsynaptic elements of the nucleus accumbens and occurred under the combination of two, at least partly, interdependent conditions: strong D2 autoreceptor blockade and high-intensity stimulation likely to release neurotensin. It is interesting that these potentiating effects of SR 48692 did not appear in the striatum. In conclusion, these findings suggest that endogenous neurotensin may attenuate the facilitation of D2 receptor blockade on mesolimbic but not nigrostriatal dopamine transmission.

Animals↗
PubMed1995

Changing heat and moisture exchangers every 48 hours rather than 24 hours does not affect their efficacy and the incidence of nosocomial pneumonia.

Heat and moisture exchangers (HME) (Dar-Hygrobac II, Peters) can safely be used every 24 h for long-term mechanical ventilation and provide a cost-saving alternative to heated humidifiers. We have prospectively determined whether changing HMEs every 48 h only affects their clinical and bacteriological efficiency in a series of consecutive nonselected ICU patients requiring long-term mechanical ventilation. Two consecutive periods were compared. During period 1, HMEs were replaced every day; during period 2, they were changed every 48 h. Patients from the two periods were similar in terms of age and indication for and overall duration of MV (10 +/- 8.6 versus 10 +/- 9 d, p = 0.9). Minute ventilation and maximum values for peak airway pressure were identical during the two periods. These values were also identical after 1 and 2 d of HME use during period 2, indicating that HME resistance was not increased by prolonged use. Obstruction of the tracheal tube occurred only once in a period 1 patient. The results of quantitative cultures indicate that the maximum and mean levels of bacterial colonization during the two periods were similar for the pharynx, trachea, Y-connector, patient, and ventilator side of the HME. More importantly, the incidence of nosocomial pneumonia was similar during the two periods (6/61 versus 8/68, p = 0.7). Thus, prolonged HME use is safe and provides a substantial reduction in the cost of mechanical ventilation.

Adult↗
PubMed1995

[Doppler echocardiographic evaluation of left ventricular wall stress in aortic stenosis].

The measurement of wall stress allows study of morphological adaptation of the left ventricle, especially in conditions associated with symmetric hypertrophy (hypertension, aortic stenosis). The calculation is performed in hypertensive heart disease but not in aortic stenosis because of the ventriculo-aortic pressure gradient. In a preliminary study, the authors validated the peak systolic left ventricular pressure calculated by adding the systolic brachial artery pressure to the maximal transvalvular pressure gradient by comparing the value with that obtained by catheterization in 21 patients with aortic stenosis. The second phase of the study was to measure meridian and circumferential wall stress prospectively in 35 patients with aortic stenosis (29 symptomatic, 6 asymptomatic) and to compare the results with those observed in 21 normal subjects. In the latter group, the values were 151 +/- 22 and 311 +/- 37 10(3) dynes/cm2 respectively, whereas in asymptomatic aortic stenosis the stresses were 136 +/- 28 and 303 +/- 41 10(3) dynes/cm2 respectively (NS) and in symptomatic aortic stenosis 210 +/- 55 and 437 +/- 94 10(3) dynes/cm2 respectively (p < 0.0001). None of the cases of asymptomatic aortic stenosis had raised wall stress values whereas only 6 symptomatic aortic stenosis patients had normal wall stress. The values of wall stress obtained using the method proposed were comparable to those reported by other authors with invasive investigations. Non-invasive measurement of wall stress by Doppler echocardiography may be proposed as a method of evaluation of left ventricular adaptation, especially in severe stenosis and in patients with a patent geometric abnormality (abnormal dilatation or even an inadequately hypertrophied wall).

Adult↗
PubMed1995

[Adaptation to effort in patients with chronic cardiac insufficiency; study by post-exercise Doppler echocardiography, comparative results with a control population].

Adaptation to exercise was studied by post-exercise Doppler echocardiography in patients with chronic cardiac failure and an apparently healthy control population matched for age. This post-exercise Doppler echocardiographic method initially introduced for the detection of myocardial ischaemia has already been validated in normal subjects for the analysis of haemodynamic changes caused by exercise providing the data is recorded in the first 5 minutes following recovery in the recumbent position. Eleven patients with chronic cardiac failure in NYHA classes II or III with a mean age of 54 +/- 11 years and 6 controls (mean age: 46 +/- 9 years) were investigated. The patients had been stabilised for at least 3 months with a vasodilator and diuretic therapy: the control subjects had no medication. After bicycle ergometry performed to 70% of maximum capacity, the subjects were positioned in the left lateral recumbent position. Doppler echocardiography was then performed in the immediate recovery phase. When compared to the control population, the patients with cardiac failure had a reduced chronotropic reserve, a smaller increase in the parameters of myocardial contractility (maximal aortic velocity, maximal aortic acceleration and left ventricular fractional shortening) without an increase in left ventricular end diastolic dimensions in subjects with severe dilatation under basal conditions (left ventricular end diastolic dimension 69 +/- 3 mm). This result suggests the absence of a Frank-Starling effect. The lack of adaptation of the peripheral vascular system was demonstrated by the lack of reduction of left ventricular end systolic stress, already greatly increased at rest (176 vs 77 +/- 10 g/cm2 for patients, compared with controls; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗