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Biomedical subjects

D Hayoz

Publications and source records attributed to D Hayoz.

At least 91 records · Page 5Linked to original sources
PubMed1993

Endothelial function in congestive heart failure.

There is evidence that the endothelium plays an important role in the control of human vascular tone by releasing endothelium-derived nitric oxide and, therefore, a defective endothelial function could be involved in the increased peripheral vasoconstriction of patients with chronic congestive heart failure. To investigate endothelial function in humans in vivo, agents such as acetylcholine, a short-acting stimulator of the release of endothelium-derived nitric oxide, has been used. Conversely, N-mono-methyl-L-arginine, a specific inhibitor of nitric oxide synthesis from L-arginine, has recently been shown to decrease blood flow during infusion into the brachial artery of healthy volunteers (control subjects) by inhibiting the basal release of nitric oxide. Consistent with experimental studies, the blood flow response to acetylcholine is blunted in patients with chronic heart failure compared with healthy age-matched volunteers. In contrast, the decrease in blood flow induced by N-mono-methyl-L-arginine appears to be exaggerated in congestive heart failure. The blood flow response to nitroglycerin or sodium nitroprusside, endothelium-independent vasodilators, is usually preserved in patients with chronic, nonedematous heart failure, indicating a normal response of the vascular smooth muscle of resistance vessels to exogenous nitric oxide. In contrast, the dilator response of the radial artery diameter to nitroglycerin and flow-dependent dilation is impaired in patients with chronic heart failure, indicating that the abnormal flow-mediated relaxation of large arteries may be caused by both endothelial and structural abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Elastic behaviour of the carotid artery in intact spontaneously hypertensive rats.

Intact spontaneously hypertensive rats (SHR) were studied to assess the effect of prolonged antihypertensive treatment on the elastic behaviour of the external carotid artery. Thirty-week-old SHR received the ACE inhibitor captopril, the arteriolar dilator hydralazine or their vehicle for 6 weeks. These rats were compared to normotensive, vehicle treated WKY rats. The internal diameter of the carotid artery was measured continuously in halothane-anaesthetized rats using an echo-tracking device, and intra-arterial pressure was also monitored continuously, on the contralateral side. Captopril- and hydralazine-treated SHR as well as normotensive controls had similar blood pressure values. No significant shift in the distensibility-pressure curves was observed among vehicle-treated SHR and WKY rats or the SHR which had received captopril or hydralazine. Histological examination of the carotid artery fixed ex vivo with paraformaldehyde showed a significant increase in cross-sectional area in vehicle-treated SHR as compared to their normotensive counterparts. These results therefore suggest that the elastic behaviour of elastic arteries is not necessarily altered by the structural changes developing in response to hypertension.

Animals↗
PubMed1993

Isobaric compliance of the radial artery is increased in patients with essential hypertension.

OBJECTIVES: Hypertension is known to decrease arterial elasticity and systemic compliance. However, the arterial tree is not a homogeneous system, and whether a distal medium-sized artery such as the radial artery behaves like proximal arteries has not been determined. The aims of the present study were, first, to characterize non-invasively the mechanical properties of the radial artery through the determination of the pressure-diameter curve, the distensibility-pressure curve and the compliance-pressure curve, and, secondly, to compare untreated hypertensive patients with normotensive subjects. METHODS: A new high-precision echo-tracking device was developed which allows the diameter of peripheral arteries to be measured continuously. By relating the changes in internal diameter (cross-sectional changes) to those in blood pressure, the cross-sectional arterial compliance could be determined. PARTICIPANTS: Seventy-eight untreated mild or moderate essential hypertensive patients aged 24-78 years were compared with 44 normotensive subjects aged 22-81 years. In order to increase the database and provide independent assessments of the variables examined, the cross-sectional study was performed independently using a standardized procedure in three different research centres. RESULTS: The major finding was that diameter, distensibility and compliance of the radial artery of hypertensive patients were not significantly different from those of normotensive controls when the two populations were studied at their mean arterial pressure. Furthermore, when the two populations were compared for the same level of blood pressure, using distensibility--and compliance--pressure curves, it was clear that isobaric distensibility and compliance of hypertensives were not significantly lower than those of normotensives, being either unchanged or higher. CONCLUSIONS: These findings are in contrast with the well-known decrease in compliance of proximal large arteries due to hypertension. Whether such a difference between proximal large arteries and distal medium-sized arteries may be related to the structural vascular changes observed with long-standing hypertension is still difficult to analyse in humans, and requires further investigation.

Adult↗
PubMed1993

The renin-angiotensin system and arterial wall behavior.

To assess the behavior of the arterial wall in hypertensive patients, we developed a noninvasive ultrasonic device. Simultaneous recordings of internal diameter and blood pressure over the whole cardiac cycle are used to establish compliance-pressure curves. Blood pressure, which is a co-determinant of compliance, is thus taken into account. This method allows one to compare arteries from patients with different blood pressures. Arterial compliance and distensibility were first investigated in healthy young volunteers administered either lisinopril (20 mg), atenolol (100 mg) or nitrendipine (20 mg) once a day. After 8 days of treatment, only lisinopril was found to increase arterial compliance. Subsequently, we compared arterial diameter- and distensibility-pressure curves from newly diagnosed and untreated hypertensive patients with those of matched normotensive control patients. Diameter-pressure curves did not differ significantly between the groups and distensibility was not reduced. Similar findings were later obtained in an animal model, when mechanical properties of carotid arteries were compared between spontaneously hypertensive rats and normotensive counterparts (Wistar-Kyoto rats). These results, although interesting by providing noninvasive information on the elastic response of the wall, call for further development of the technique to be able to measure arterial wall thickness. Stress-strain relationship could ultimately be established to thoroughly characterize physical properties of blood vessel walls.

Animals↗
PubMed1993

Familial primary gastric lymphoma.

Familial lymphoma is uncommon and is usually associated with various forms of hereditary immunodeficiencies. Primary gastric lymphomas that occurred in three adults from the same family, who had no overt immunodeficiency or cancer of non-lymphomatous origin, are reported. Two sisters presented with a low grade lymphoma of the mucosa associated lymphoid tissue type. Their father presented with a high grade form of later onset. All lymphomas have been phenotypically characterised as being of B cell origin. Epstein-Bar virus DNA was detected by polymerase chain reaction in the biopsy specimen of the high grade lymphoma but bcl-2/JH protooncogene rearrangement, t (14:18), was not identified in either the low or high grade lymphoma specimens tested.

Aged↗
PubMed1993

Spontaneous diameter oscillations of the radial artery in humans.

In this study we investigated whether there exists a periodic contractile activity of the radial artery, and we evaluated the impact of such an oscillatory behavior on the mechanical properties of this medium-sized muscular vessel. The internal diameter of the right radial artery was measured noninvasively in six healthy male volunteers aged 18-42 yr using a high-precision ultrasonic echo-tracking device. Blood pressure was simultaneously recorded on the same side at the middle finger by photoplethysmography. The electrical activity of the heart was monitored during the entire experiment by electrocardiography. The frequency components of the arterial diameter, blood pressure, and heart rate were obtained using spectral analysis. Under resting conditions, the radial arterial diameter exhibited a spontaneous oscillation with a period ranging from 45 to 70 s and an amplitude of 80 +/- 14 microns (+/- SE). No very low-frequency mode (< or = 0.02 Hz) was identified in either heart rate or blood pressure. These diameter oscillations affected the distensibility-pressure curves acquired simultaneously. Thus the 3-4% oscillatory variation in arterial diameter was paralleled by a 1.5- to 2-fold change in distensibility. These low-frequency oscillations of large arteries seem to be mediated by an intrinsic vascular mechanism.

Adolescent↗
PubMed1992

Human carcinoembryonic antigen cDNA expressed in rat carcinoma cells can function as target antigen for tumor localization of antibodies in nude rats and as rejection antigen in syngeneic rats.

We have tried to develop a new model consisting of rats transplanted with syngeneic colon carcinoma PROb cells transfected with cDNA coding for the carcinoembryonic antigen (CEA), the human tumor marker most commonly used as target for MAbs. The antigenic density of the 4 CEA-expressing clones selected for a precise characterization ranged from 5 x 10(4) to 1 x 10(6) CEA molecules per cell. In all clones the CEA was shown to be attached to the membrane by a phosphatidylinositol (PI) anchor. Using a panel of radiolabeled MAbs directed against the 5 major epitopes described on the CEA molecule, we showed that all these CEA epitopes were expressed by the 4 transfectants. Southern-blot analysis showed that the entire CEA cDNA was present in the transfectants. Western-blot analysis, however, showed that the size of the CEA expressed by the 4 transfectants was slightly smaller than that of CEA produced by 2 reference human colon-carcinoma cell lines. Two clones, expressing 1 x 10(5) and 1 x 10(6) CEA molecules per cell, respectively, were grafted s.c. in nude mice and rats. Injection of radiolabeled anti-CEA F(ab')2 fragments into these animals showed specific tumor localization with the highest percentages of injected doses for the transfectants expressing the highest CEA level. When grafted into immunocompetent syngeneic BDIX rats, the CEA-expressing clones induced a strong antibody response against CEA and tumor rejections in a majority of the animals. Although the analysis of the immune response against the CEA-cDNA-transfected carcinoma cells is under investigation, the present results demonstrate that human CEA could function as a rejection antigen when transfected into rat carcinoma cells.

Adenocarcinoma↗
PubMed1992

Endothelial function in chronic congestive heart failure.

There is evidence that the endothelium plays an important role in the control of human vascular tone by releasing endothelium-derived nitric oxide. The hypothesis that an impairment of this mechanism is involved in the increased peripheral vasoconstriction of patients with chronic congestive heart failure (CHF) was tested. Acetylcholine and N-monomethyl-L-arginine (L-NMMA), a specific inhibitor of nitric oxide synthesis from L-arginine, were infused in the brachial artery of healthy volunteer subjects (controls) and patients with severe CHF. The radial artery diameter was determined by a high-precision A-mode ultrasound device, using a 10 MHz probe. Forearm blood flow was calculated from vessel diameter and blood flow velocity measured simultaneously by Doppler. The blood flow response to acetylcholine was blunted in patients with CHF compared with that in control subjects. In contrast, the decrease in blood flow induced by L-NMMA was exaggerated in CHF, and the blood flow response to nitroglycerin was preserved. The changes in radial artery diameter induced by acetylcholine and L-NMMA were not significant in control subjects and CHF patients, but dilation of the radial artery by nitroglycerin was significantly reduced in CHF. The results demonstrate an impaired endothelium-dependent dilation of forearm resistance vessels in CHF, suggesting a reduced release of nitric oxide on stimulation. In contrast, the basal release of nitric oxide from endothelium of forearm resistance vessels is preserved or may even be enhanced, and may play an important compensatory role in chronic CHF by antagonizing neurohumoral vasoconstrictor forces in CHF.

Acetylcholine↗
PubMed1992

Conduit artery compliance and distensibility are not necessarily reduced in hypertension.

The goal of this study was to investigate whether the elastic behavior of conduit arteries of humans or rats is altered as a result of concomitant hypertension. Forearm arterial cross-sectional compliance-pressure curves were determined noninvasively by means of a high precision ultrasonic echo-tracking device coupled to a photoplethysmograph (Finapres system) allowing simultaneous arterial diameter and finger blood pressure monitoring. Seventeen newly diagnosed hypertensive patients with a humeral blood pressure of 163/103 +/- 4.4/2.2 mm Hg (mean +/- SEM) and 17 age- and sex-matched normotensive controls with a humeral blood pressure of 121/77 +/- 3.2/1.9 mm Hg were included in the study. Compliance-pressure curves were also established at the carotid artery of 16-week-old anesthetized spontaneously hypertensive rats (n = 14) as well as Wistar-Kyoto normotensive animals (n = 15) using the same echo-tracking device. In these animals, intra-arterial pressure was monitored in the contralateral carotid artery. Mean blood pressures averaged 197 +/- 4 and 140 +/- 3 mm Hg in the hypertensive and normotensive rats, respectively. Despite the considerable differences in blood pressure, the diameter-pressure and cross-sectional compliance-pressure and distensibility-pressure curves were not different when hypertensive patients or animals were compared with their respective controls. These results suggest that the elastic behavior of a medium size muscular artery (radial) in humans and of an elastic artery (carotid) in rats is not necessarily altered by an increase in blood pressure.

Animals↗
PubMed1992

Non-invasive determination of arterial diameter and distensibility by echo-tracking techniques in hypertension.

METHODOLOGY: A new non-invasive ultrasonic device was developed to characterize the biomechanical properties of medium and large peripheral arteries. Simultaneous recordings of internal diameter and blood pressure over the whole cardiac cycle are used to establish compliance-pressure curves. Since blood pressure, which is an inherent co-determinant of arterial compliance, is taken into account, the comparison of arteries from patients with markedly different blood pressures has become possible. In a first study, the effects of three different antihypertensive drugs (20 mg lisinopril, 100 mg atenolol, 20 mg nitrendipine administered once a day) on arterial compliance and distensibility were investigated in young healthy volunteers. RESULTS: After 8 days of treatment, lisinopril induced a significant increase in arterial compliance. Subsequently, we compared the mechanical behaviour of arteries from newly diagnosed hypertensive patients (radial artery) or the carotid artery from spontaneously hypertensive rats (SHR) with that of corresponding arteries in normotensive counterparts. No decrease in arterial distensibility was found in the hypertensive groups over the measured blood pressure range. This result is not totally consistent with previous in vitro or in situ localized studies. Methodological differences, the absence of blood flow and/or denervation may partly explain these contradictory results. Finally, we tested the effects of hydralazine (5 mg/day) and captopril (25 mg/day), administered for 6 weeks in drinking water, on the behaviour of the carotid arteries of 16-week-old SHR. The two drugs effectively reduced blood pressure while shifting the distensibility-pressure curves upward in comparison to the placebo-treated animals, suggesting an improvement in arterial compliance. CONCLUSIONS: While hypertension does not itself appear to alter the elastic behaviour of large peripheral arteries, antihypertensive treatment may increase the compliance of these blood vessels.

Adult↗
PubMed1992

Dynamic non-invasive measurements of arterial diameter and wall thickness.

AIM: Non-invasive measurements of arterial diameter and wall thickness are critical in characterizing the onset and development of vascular disease. A precise dynamic method was proposed and tested for this purpose. DESIGN: A non-invasive method of measuring the variations in diameter and thickness of human arteries throughout the cardiac cycle was developed, using a high-precision ultrasonic echo-tracking system. An adaptive filtering technique was used to suppress artefacts caused by the layered tissue structure of the vessel wall. RESULTS: Based on decorrelation of microstructure noise, this technique improved the detectability of the wall interfaces, which allowed a determination of thickness and diameter. The accuracy and reproducibility of the method were tested by measurements of plastic films with known thicknesses. The discrepancies between standard micrometer and pulse-echo measurement were consistently less than 5 microns for film thicknesses ranging from 220 to 800 microns. The difference between two successive measurements was less than 2 microns. The identity of the measured vascular interfaces was checked in two ways. First, experiments on fixed bovine carotid arteries showed that the identified echogenic interfaces corresponded to the actual anatomical structure, as obtained by acoustic microscopy. Second, the radial artery thickness and diameter were extrapolated to obtain the change in wall volume over one cardiac cycle. The volume was found to be nearly constant, indicating incompressibility. CONCLUSION: This method will make it possible to obtain new information on atherogenesis and other vascular diseases.

Acoustics↗
PubMed1992

Non-invasive method for the assessment of non-linear elastic properties and stress of forearm arteries in vivo.

AIM: To propose a method for obtaining non-invasive highly accurate measurements of arterial diameter, thickness and pressure at a single location on a peripheral arm artery, and use this data to estimate the status of the arterial wall. METHODS: Diameter and thickness were measured with an A-mode ultrasonic echo-tracking device, with a precision of close to 1 micron. Pressure was measured with a photoplethysmograph at the finger level. A simple hemodynamic model was used to estimate, from the measured pressure pulse, the pressure waveform at the diameter-measuring site. RESULTS: The collected data made it possible to assess (1) the elastic response of the artery, through the compliance and distensibility, (2) the loading conditions, through the average stress-diameter curve and (3) the elastic properties of the wall material, through the incremental modulus of elasticity. CONCLUSION: This information can be used to assess the overall status of the arterial wall.

Blood Pressure↗
PubMed1992

Effect of mental stress on the tone of a medium-sized muscular artery.

AIM: We studied the effects of mental stress on the tone of the radial artery, a medium-sized muscular artery. METHODS: Using an A-mode echo-tracking device coupled to a photoplethysmograph, we took continuous measurements of the radial artery diameter, heart rate and finger arterial pressure in six healthy young volunteers. RESULTS: Under mental stress, the heart rate increased from 63 +/- 4 to 74 +/- 4 beats/min (mean +/- SEM, P < 0.01) and systolic pressure from 123 +/- 5 to 140 +/- 6 mmHg (P < 0.05). No consistent modification in the arterial diameter was observed at this time. CONCLUSION: The activation of sympathetic nerve activity induced by mental stress does not cause a significant contraction in the radial artery.

Adolescent↗
PubMed1992

Arterial dilatory reserve in congestive heart failure.

AIM: The purpose of this study was to determine whether there are abnormalities in flow-mediated large vessel relaxation in patients with congestive heart failure (CHF). METHODS: The radial arterial diameter and flow responses upon the release of 10 min of forearm arterial occlusion (reactive hyperemia) were measured with ultrasound and Doppler devices. RESULTS: In patients with CHF there was a 26% reduction in peak blood flow (P = 0.09) compared to age-matched controls. However, the increase in arterial diameter that followed the peak blood flow was reduced by 49% in CHF (P < 0.01). CONCLUSIONS: The causes of the abnormal flow-mediated large artery relaxation in CHF are unclear; both structural and endothelial abnormalities may contribute.

Blood Flow Velocity↗
PubMed1992

Arterial compliance and distensibility in spontaneously hypertensive rats.

AIM: These studies were undertaken in intact spontaneously hypertensive rats (SHR) to assess whether the elastic behavior of conduit arteries changes as a function of age. METHODS: We studied 16-week-old (n = 10) and 36-week-old (n = 10) SHR under fluothane anesthesia. Diameter-, compliance-, and distensibility-pressure curves were established non-invasively for the carotid artery by means of a high-precision ultrasonic echo-tracking device. Intra-arterial pressure was monitored simultaneously in the contralateral carotid artery. RESULTS: Mean blood pressure was 197 +/- 6 and 185 +/- 3 mmHg (mean +/- SEM) in the younger and older SHR, respectively. No significant difference was observed between the two groups of rats in the diameter-, compliance- and distensibility-pressure curves. CONCLUSIONS: These results suggest that the elastic behavior of elastic arteries is not necessarily altered with aging in rats with genetic hypertension.

Age Factors↗
PubMed1991

Frequent detection of Epstein-Barr virus DNA by the polymerase chain reaction in lymph node biopsies from patients with Hodgkin's disease without genomic evidence of B- or T-cell clonality.

This study of 52 Swiss patients with Hodgkin's disease (HD), including 17 cases with a high content of Sternberg-Reed (SR) and Hodgkin (H) cells, was performed to determine the percentage of cases harboring Epstein-Barr virus (EBV) DNA and/or clonal rearrangements of Ig and T-cell antigen receptor (TcR) genes in diagnostic lymph node biopsies. Special attention was drawn to the heavily infiltrated cases to detect a possible relationship between clonality and EBV DNA identification. EBV DNA was detected by the polymerase chain reaction (PCR) using three different sets of specific primers. The viral origin of the amplification products was confirmed by hybridization with a radiolabeled internal probe or demonstration of a specific Sma I restriction site. Genomic rearrangement of Ig and TcR genes was studied by Southern blot analysis. EBV DNA was identified by PCR in 38 of 48 cases (79%). Clonal rearrangements were identified in only 4 of 52 cases (Ig genes) and were independent of the degree of infiltration by SR cells and the presence of EBV DNA. The absence of EBV DNA in three cases with numerous SR cells (only one of them showed clonal rearrangement) and the presence of only a few viral copies in four further cases with numerous SR cells (semiquantitative analysis of viral DNA by PCR was performed in 26 EBV-positive cases) suggests that this virus is modulating rather than an etiologic agent in a considerable proportion of HD cases.

B-Lymphocytes↗
PubMed1991

Evaluation of arterial compliance-pressure curves. Effect of antihypertensive drugs.

A new high-precision ultrasonic device was developed to determine noninvasively arterial compliance as a function of blood pressure. Because of the nonlinear elastic properties of arterial walls, measurements of compliance can be appropriately compared only if obtained over a range of pressures. This apparatus was used to evaluate in a double-blind, parallel fashion the effect of three different antihypertensive drugs and of a placebo on radial artery compliance. Thirty-two normotensive volunteers were randomly allocated to an 8-day, once-a-day oral treatment with either a placebo, 100 mg atenolol, 20 mg nitrendipine, or 20 mg lisinopril. Blood pressure, heart rate, radial artery diameter, and arterial compliance were measured immediately before as well as 6 hours after dosing on the first and last days of the study. On the eighth day of administration, within 6 hours after dosing, lisinopril induced an acute increase in radial artery diameter, from 2.99 +/- 0.06 to 3.28 +/- 0.09 mm (mean +/- SEM, p less than 0.01). The compliance-pressure curve was shifted upward on day 1 (p less than 0.01) as well as on day 8 (p less than 0.05). None of the other drugs induced any significant modification of these parameters. Arterial compliance has a strong nonlinear dependency on intra-arterial pressure and therefore has to be defined as a function of pressure. Antihypertensive drugs acting by different mechanisms may have different effects on the mechanical properties of large arteries.

Adrenergic beta-Antagonists↗