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Biomedical subjects

S Laurent

Publications and source records attributed to S Laurent.

266 records · Page 15Linked to original sources
PubMedDate not supplied

Dynamic versus static compliance of the carotid artery in living Wistar-Kyoto rats.

Arteries, when they are subjected in vitro to cyclic loading and unloading, are reported to be stiffer than in static conditions and to be poorly influenced by changes in vasomotor tone. However, such parameters have never been studied in living animals. This study used very high resolution echotracking technics to evaluate pulsatile changes of carotid blood pressure and diameter and the resulting dynamic pressure-cross-sectional (CSA) curve in anesthetized Wistar-Kyoto rats before and following changes of arteriolar vasomotor tone produced by vasoconstrictive [phenylephrine, L-NG nitro-arginine (LNA)] or vasodilating (hydralazine, nitroprusside) agents. Phenylephrine and LNA caused a progressive upward shift of the pressure-CSA curve toward significantly higher values of mean blood pressure and diameter. Since the two vasoconstrictive agents produced exactly the same arterial hemodynamic pattern, their effects may be considered as 'passive', i.e. predominantly due to the mechanical effect of pressure distension. From this observation, a simple model was validated, permitting evaluation in vivo of the passive static properties of the pressure-CSA curve from the relationship between mean arterial diameter and mean arterial pressure at the various steady states produced by the two vasoconstrictive agents. This static relationship had a significantly steeper slope than the corresponding dynamic relationships determined for the same steady-state mean arterial pressures. With hydralazine, a downward shift of the pulsatile pressure-CSA curve was obtained, with exactly the same characteristics as for phenylephrine and LNA, but within lower ranges of blood pressure and with a corresponding decrease in arterial diameter. In contrast, nitroprusside shifted the pulsatile pressure diameter curve toward both lower values of blood pressure and higher values of arterial diameter, thus indicating an active change in arterial tone. At any given value of mean blood pressure and arterial diameter, operational pulsatile compliance was significantly higher with sodium nitroprusside than with hydralazine. This study provides evidence that in living rats (1) the described static carotid pressure-diameter curve has a significantly steeper slope than the corresponding dynamic curve for the same mean arterial pressure, (2) for the same mean arterial pressure and diameter, sodium nitroprusside has a significantly higher dynamic compliance than hydralazine, implicating the role of nonhemodynamic factors in the stiffness of changes, and (3) vasomotor tone influences markedly the dynamic pressure-diameter (or CSA) curve within intermediate and lower blood pressure ranges through active mechanisms involving the GMP cyclic pathway.

Animals↗
PubMedDate not supplied

The wall to lumen ratio of the radial artery in patients with Raynaud's phenomenon.

The pathophysiology of Raynaud's phenomenon (RP) remains an enigma. Whatever theories proposed, the final event leading to the clinical symptoms is the occlusion of digital vessels. However, the possibility that the upstream large arterial vessels contribute to vasopasm has never been investigated. We used a high resolution echo-tracking device to calculate lumen diameter, wall thickness, and circumferential wall stress upstream the digital arteries, i.e. at the site of the radial artery. Fifteen control women, 15 age-matched women with primary RP (PRP) and 15 women presenting with a secondary RP due to systemic sclerosis (SSc) were included in the study. All vasodilating agents were discontinued 72 h before the study session, which was conducted in a room with a stable ambient temperature of 22 degrees C. Radial artery internal diameter, intima-media wall thickness, and mean arterial pressure were measured simultaneously. Internal diameter of patients with RP was significantly decreased (p < 0.001 vs. controls) whereas intima-media wall thickness and mean arterial pressure were closely similar in the three groups, resulting in an increase in the wall to lumen ratio. Thus, circumferential wall stress was significantly smaller (p < 0.05 vs. controls) in patients with RP. In conclusion, this study demonstrates that in patients with RP, wall to lumen ratio is increased and circumferential wall stress is reduced at the level of the radial artery. It is suggested that the geometrical and mechanical changes of this artery may favor the downstream occlusive phenomena observed in patients with PRP and SSc.

Adult↗
PubMedDate not supplied

[Associations between viscoelastic properties of large arteries and their extracellular matrix composition in abdominal aortic aneurysms in humans].

The objective of the present study was to determine the viscoelastic properties of the common carotid artery in 35 patients with aortic aneurysm before surgery (AAA) (age 71 years, range 61-84), in comparison with 48 patients with essential hypertension (HT: 50 years, range 24-88) and 44 normotensive subjects (NT: 44 years, range 23-85). The second objective was to establish the relations between common carotid artery (CCA) viscoelastic properties and histologic lesions observed on AAA segments, obtained after surgery. CCA diameter was larger and distensibility smaller in AAA patients than in HT and NT. Distensibility of the aortic aneurysm was smaller than that of upstream 'normal' aorta, itself being smaller than control aortas. AAA wall lesions were extensive, associating adventitial and medial fibrosis, elastolysis, smooth muscle rarefaction, neovascularization, inflammation and plaques. The grade of these lesions was not correlated with the mechanical properties of the aorta and CCA; however, they could explain their qualitative alterations. AAA is characterized by severe stiffening and dilatation of large arteries distant from the aneurysm location. Whether this pattern of arterial phenotype is explained by the increase in stiff material (collagen) and the rarefaction of distensible material (smooth muscle and elastin) remains to be determined.

Adult↗
PubMedDate not supplied

[Methods for exploring arteries in humans: application to the study of estrogens].

In recent years, two concepts--endothelial dysfunction and arterial remodelling--have emerged as keys to the understanding of the pathophysiology of the arterial system. The clinical investigation of endothelial dysfunction and arterial remodelling became a requisite for understanding the effects of any drug acting on the arterial wall, such as oestrogens during oestrogen replacement therapy. In this paper, we describe the various non-invasive methods for studying the geometry and the function of large and small arteries. Recent technological and methodological improvements allow this investigation to be carried out with satisfactory repeatability, and to be applied to clinical pharmacology. We also discuss the few studies which have applied these methods to the study of the effect of oestrogens on the arterial system and we suggest a physiological schema for an integrative mechanism of action.

Arteries↗
PubMedDate not supplied

Development of adenocarcinoma in chronic fistula in Crohn's disease.

The authors report the case of a 55 yr-old woman suffering from Crohn's disease since 31 years with stricture and fistulas developed in the ileocolic junction and anorectal portion. Long-standing anorectal fistulas and stricture led to adenocarcinoma and finally fistulisation in the vagina. Diagnosis was made by perineal examination with biopsies under general anaesthesia. Treatment was first posterior pelvectomy with resection of the anterior wall of vagina. Secondarily, radiochemotherapy was administrated. The authors discuss the incidence and risk factors of carcinoma in Crohn's disease with chronic fistulas.

Adenocarcinoma↗
PubMedDate not supplied

Report on the Belgian consensus meeting on colorectal cancer screening.

Screening and prevention of colorectal cancer must be a public health priority. It is the most frequent malignancy in Europe, the second leading cause of cancer death, including Belgium where more than 6000 new cases occur per year. Various screening modalities, from non invasive to invasive are available and currently in use and they are all cost-effective in comparison with no screening. The decision as to which screening test to use should be made by the patient and clinician. Consensus documents prepared by the Belgian scientific community appear in this issue of Acta Gastroenterologica Belgica, summarizing the scientific evidence in favour as well as the limitations of fecal occult blood tests, flexible sigmoidoscopy, videocolonoscopy and virtual colonoscopy.

Belgium↗
PubMedDate not supplied

A patient who survived total colonic ulcerative colitis surinfected by cytomegalovirus complicated by toxic megacolon and disseminated intravascular coagulation.

The authors report the case of a patient aged 60-year-old who survived ulcerative colitis complicated by toxic megacolon and disseminated intravascular coagulation. This patient was not known for this ulcerative colitis and was first hospitalised for a suspicion of diverticulitis. The admission symptoms were fever, abdominal pain and bloody diarrhoea. The evolution was defavorable under antibiotics and sulfasalazine. The patient was readmitted 5 days after he left hospital, and the diagnosis of UC was based on colon biopsy made during the first hospitalisation. A treatment with methylprednisolone was started and the patient worsened day by day with apparition of toxic megacolon and disseminated intravascular coagulation. Subtotal colectomy was performed for degradation of general status and coagulation factors. Pathological findings confirmed ulcerative colitis with toxic megacolon. Cytomegalovirus inclusions were demonstrated on the colonic specimen and confirmed by PCR. In this report the authors discuss the etiology of toxic megacolon and disseminated intravascular coagulation in ulcerative colitis surinfected by cytomegalovirus. Mortality of these pathologies is high necessitating rapid diagnosis of cytomegalovirus infection by sigmoid biopsy. Management requires immunosupression interruption and ganciclovir therapy, or surgery in unsuccessful medical treatment.

Biopsy, Needle↗
PubMedDate not supplied

[Antihypertensive efficacy of the combination of captopril 50mg and hydrochlorothiazide 25mg evaluated by ambulatory blood pressure measurement].

The anti-hypertensive effects of the captopril-hydrochlorothiazide combination administered during three months as one single morning dose were evaluated in 51 patients with moderate essential hypertension by means of ambulatory blood pressure recording. At the end of the study, the mean values of arterial blood pressure recorded over 24 hours were significantly lowered: systolic pressure was reduced from 145 +/- 11 to 131 +/- 10 mmHg (P less than 0.001), and diastolic pressure from 88 +/- 5 mmHg to 81 +/- 4 mmHg (P less than 0.001). The same results were recorded during the day (07.00 to 22.00 hours) and during the night (23.00 to 06.00 hours). No change in heart rate was observed.

Adult↗
PubMedDate not supplied

Relative negative inotropic potencies of nine calcium channel blockers in cultured heart cells.

The direct inhibitory effects on contractility and beating rate of the calcium channel blockers diltiazem, verapamil and dihydropyridine derivatives nicardipine, nifedipine, nitrendipine, PY 108-068, (+/- ) PN 200-110 and its 2 stereoisomers, were compared in cultured chick embryo ventricular cells. In spontaneously beating cells, the negative inotropic and chronotropic potencies of nicardipine, nifedipine, nitrendipine and PY 108-068 were not significantly different. The inhibitory effects of verapamil, nifedipine and nicardipine were studied in cells electrically driven at a frequency close to their spontaneous beating rate: verapamil, nifedipine and nicardipine had similar negative chronotropic potencies; when the rate of stimulation was increased 1.5 and 2-fold, a frequency-dependent inhibitory effect on contraction was shown for verapamil, but not for nifedipine and nicardipine. Therefore, in our model, where the effects of beating rate on the amplitude of contraction were taken into account, no significant difference in the direct negative inotropic potenties of nifedipine and nicardipine was shown.

Animals↗
PubMedDate not supplied

[Arterial wall: a new pharmacological and therapeutic target?].

In recent years, endothelial dysfunction and arterial remodelling in various cardiovascular diseases have emerged as two key concepts, with numerous interrelationships. Both endothelial dysfunction and arterial remodelling occur in various pathologies including heart failure, atherosclerosis, restenosis after angioplasty, and pulmonary hypertension, and have modified the therapeutic approach by offering new pharmacological targets: specific receptors not only at the site of the vascular smooth muscle cells but also on the endothelial cells, growth factors that stimulate proliferation of smooth muscle, and receptors and enzymes of the extracellular matrix. Among the various substances under research, the present review will discuss angiotensin II receptor antagonists, endothelin receptor antagonists, nitrates-NO donors, potassium channel activators, and substances interfering with proteoglycans and other components of the extracellular matrix.

Animals↗
PubMedDate not supplied

[Calcium antagonists and arterial hypertension].

The pharmacological class of calcium channel antagonists (CCA) is, with beta-adrenergic antagonists, diuretics, converting enzyme inhibitors and alpha-adrenergic antagonists, one of the first line monotherapies of essential hypertension, according to the recommendations of the "Fifth Joint National Committee on Detection, Evaluation and Treatment of Hypertension". CCA have several advantages for the treatment of hypertension: the blood pressure lowering effect is due to a reduction of total peripheral vascular resistance, which are primarily abnormally increased in hypertension; the antihypertensive efficacy of CCA is comparable to that of other commonly used antihypertensive drugs; CCA induce a significant regression of left ventricular hypertrophy, a factor of morbidity and mortality which is considered to be independent of the level of mean arterial pressure; CCA have vasodilating properties on the coronary circulation; CCA are generally well tolerated, from both clinical and biological points of view. The challenge for CCA concerns three domains related to the morbidity/mortality of hypertension (coronary and cerebrovascular events) a better antihypertensive efficacy for the whole period of 24 hours, a better prevention of cerebrovascular events and an effect on the development of atherosclerosis.

Antihypertensive Agents↗
PubMedDate not supplied

[Comparison between the effects of angiotensin-converting enzyme inhibitors and angiotensin II antagonists].

The renin-angiotensin-aldosterone system (RAAS) plays an important role in blood pressure regulation and fluid and electrolyte homeostasis. Angiotensin converting enzyme inhibitors (ACEI) were the first of the RAAS blocking agents to be widely used in the treatment of hypertension and congestive heart failure. Angiotensin II receptor antagonists, another class of pharmacological blockers of the RAAS, have more recently been shown to be safe and useful in hypertension and perhaps also in heart failure. This review deals with the similarities and differences between these two classes of drugs with particular emphasis on the effects of the drugs on the heart, the blood vessels, the kidney (role of the drugs as nephroprotective), the brain, the hormonal profile and finally the potential adverse effects. The place of angiotensin II antagonists in congestive heart failure remains to be more precisely defined.

Angiotensin II↗
PubMedDate not supplied

[Cell adhesion molecules and pharmacologic applications. Round Table No 3 at Giens XIII].

This workshop intended to perform a "state-of-the art" of current research on adhesion molecules in various pathophysiologies, and to determine pharmacological targets. Indeed, recent important progress concerning the cellular and molecular physiology of adhesion molecules led to the development of various integrin antagonists in several domains, like cardiovascular disease, inflammation and cancer. Integrins play a major role in numerous process like embryonic development, tumor growth and metastasis, apoptosis, hemostasis, leucocyte recruitment and activation, and bone resorption. The development of integrin antagonists is well advanced in the cardiovascular domain, since the first marketed drug (abciximax, Reopro) is an antibody directed against the GPIIb/IIIa complex (integrin alpha IIb/beta 3) involved in the final pathway of platelet aggregation. Another active domain of research in pharmacology is 'cardioprotection', i.e. the prevention of cardiac damages induced by the reperfusion of the coronary bed after an ischemia secondary to thrombolysis, angioplasty, of coronary bypass. The pharmacological targets of these antagonists are integrins involved in various process like leucocyte and platelet adhesion and endothelial function. Other potential indications in the cardiovascular field are restenosis after angioplasty, and atherosclerosis.

Cardiovascular Diseases↗