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Biomedical subjects

G London

Publications and source records attributed to G London.

At least 19 recordsLinked to original sources
PubMed1992

Response to vaccination against tetanus in chronic haemodialysed patients.

We studied the response to vaccination against tetanus and the changes in the antibody titers 6 months after this vaccination in 66 haemodialysed patients with chronic renal failure. We also investigated the factors that may affect the quality of this immune response. After the booster injection 96.5% of patients had antitetanus antibody titres considered to be protective (0.06 HU/ml). However, the titre of these antibodies rapidly declined and after 6 months, only 62% of the haemodialysed patients had a titre greater than 0.06 HU/ml. Among the different factors considered, only age significantly impaired or reduced the immune response. In addition, the acquisition of protection against tetanus was independent of the response to vaccination against hepatitis B in the same subjects. This study showed the efficacy and safety of vaccination against tetanus in hemodialysed patients, though the antibody titres should be assayed several months after vaccination to confirm the persistence of immunization.

Adolescent↗
PubMed1992

Increased systolic pressure in chronic uremia. Role of arterial wave reflections.

To assess the role of arterial wave reflections in the mechanism of systolic hypertension and altered pulsatile arterial dynamics in patients with end-stage renal disease (ESRD), 79 ESRD patients were compared with 73 age-matched control subjects with normal renal function and similar mean blood pressure. Wave reflections were investigated from the carotid pulse contour recorded by applanation tonometry using a Millar micromanometer-tipped probe. Wave reflections were quantified as the ratio (augmentation index, %) of the height of the late systolic peak to the total height of carotid pulse wave. Travel time of the reflected wave was timed from the foot of the pressure wave to the foot of the late systolic peak. Systolic and pulse pressure were increased in ESRD patients (p less than 0.001) and was not attributable to differences in left ventricular ejection pattern. The augmentation index was increased in ESRD patients (23.2 +/- 15.0 versus 9.8 +/- 15.6%; p less than 0.001) in association with a shorter travel time of reflected wave (109 +/- 24 versus 131 +/- 30 msec; p less than 0.001). Multiple regression analysis showed two principal factors associated (p less than 0.001) with the increase in augmentation index and shortened travel time of reflected wave: increased aortic pulse wave velocity and smaller stature with shorter body height in ESRD patients. The study points to the role of arterial wave reflections in the mechanisms producing alterations in pulsatile arterial dynamics in ESRD and is the first, through the mechanisms of early wave reflections, to show in humans that the increase in systolic and pulse pressures is associated with lesser body size.

Adult↗
PubMed1991

Establishing the relationship between complement activation and stimulation of phagocyte oxidative metabolism in hemodialyzed patients: a randomized prospective study.

The present prospective study was conducted in order to establish the relationship between complement activation and stimulation of phagocyte oxidative metabolism observed in long-term hemodialysis (HD) patients during the early phase of dialysis with cellulosic membranes. Two groups of 10 randomized (HD) patients treated with cellulosic (Cuprophan, CUP) or synthetic polyacrilonitrile (PAN AN-69) membranes were studied. Leukocyte counts, C3a antigen plasma concentration and whole blood basal and stimulated chemiluminescence (CL) production were determined in blood samples drawn from the fistula before dialysis (T0) and from both the afferent and efferent lines of the dialyser at 15 min (T15) and at the end (Tend) of the dialysis session. This study confirms that, coincident with the nadir of leukopenia observed at T15, dialysis with CUP but not PAN membranes induces a marked rise in C3a antigen levels and profound alterations in whole blood CL production consisting of a dramatic increase in basal CL and a significant loss in CL response capacity to stimulating agents. It further demonstrates that a direct relationship exists between the variations in C3a antigen plasma levels and whole blood CL production observed in the CUP group of patients from T0 to T15 (delta 15) of dialysis. This relationship is characterized by a positive correlation between delta 15 C3a and delta 15 basal CL levels in afferent and efferent lines, and a negative correlation between delta 15 C3a and delta 15 CL response capacity values in the efferent but not afferent line. In contrast, no significant correlation with the type of dialysis membrane could be demonstrated between the variations in polymorphonuclear neutrophil counts and C3a antigen levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed1991

[Evaluation of arterial compliance in renal insufficiency].

The pulse wave velocity (PWV) of the aorta, of the arm, of the leg, was measured in 90 normal subjects (N) and 92 dialysis patients (D) of the same age and blood pressure status. All patients underwent blood biochemistry, especially serum liquid concentrations, and aortic ultra-sonography. Aortic calcifications were diagnosed by echo and radiologic examination. Aortic PWV was significantly higher in D (1,113 +/- 319 cm/s) than in N (965 +/- 216 cm/s) (p = 0.0016). The aortic diameters were greater in D both at the aortic root and at the bifurcation. The pulse pressure was higher in D (76.6 +/- 23.7 vs 63.9 +/- 2 mmHg, p = 0.007). In both populations, the PWV increased with age and blood pressure but aortic calcification was only weakly correlated with this increase. These results indicate that the compliance of the aortic wall is reduced in D and leads to an increase in the pulsatile component of the blood pressure and thereby to an increase in left ventricular afterload.

Adult↗
PubMed1990

[Methods for studying vasodilator agents in arterial hypertension].

The concept of vasodilatation has evolved with regards to the treatment of hypertension. Large multicentre trials have shown that decreasing mean arterial pressure alone does not reduce coronary morbidity and mortality related to hypertension. The authors suggest that the haemodynamic abnormalities related to hypertensive disease were not totally reversed by the antihypertensive agents used in these trials. Regression of structural arterial changes, regression of LVH without altering systolic function, reduction of the variability of blood pressure and maintenance of regional blood flow should all be objectives of any antihypertensive vasodilator therapy. Methods of studying vasodilators are described and the effects of the main classes of antihypertensive drugs on these parameters are analysed.

Antihypertensive Agents↗
PubMed1989

Deferoxamine test and bone disease in dialysis patients with mild aluminum accumulation.

Aluminum bone disease is a frequent complication of dialysis patients. The deferoxamine (DFO) test has been advocated as a noninvasive procedure for the diagnosis of AI bone lesion. However most of these studies have been performed in symptomatic patients with significant AI bone disease. Whether this test may provide similar data at an earlier stage of AI toxicity is not known. The present study evaluates prospectively 28 patients with mild AI load. Patients studied ranged in age from 21 to 65 years; duration of dialysis was 5.6 +/- 3.2 years; deferoxamine, 40 mg/kg body weight, was infused at the end of dialysis. Serum AI was measured before DFO administration and before the next dialysis treatment. Bone biopsies were performed in all patients. Cortical bone AI was determined biochemically; trabecular and cortical bone AI were also determined histochemically. Mean basal serum AI (43.2 +/- 30.8 micrograms/L) and cortical bone AI (25.7 +/- 35.2 micrograms/g) were moderately increased. Basal serum AI correlated (r = 0.77) with the increment in serum AI after DFO infusion. After DFO, stainable trabecular and cortical bone AI correlated in a similar manner with both basal serum AI and increment in serum AI. Only biochemically determined cortical bone AI was not significantly related to basal serum AI. Nineteen of the 28 patients had evidence of osteitis fibrosa on bone biopsy. Stained AI surfaces but not trabecular AI were different in patients with low and patients with high bone formation rates. The bone findings, assessed as bone formation rates and resorption surfaces, did not correlate with biochemically or histochemically determined bone AI.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1989

Effects of twenty-four hours of bed rest with head-down tilt on cardiopulmonary baroreflex control: preliminary study.

The cardiopulmonary baroreflex response was studied before and after 24 h bed rest with head-down tilt (-5 degrees) in six normal male subjects, through lower body negative pressure (-5, -10, -15 mmHg) and passive leg raising. The reflex response was assessed (using plethysmography) by changes in forearm vascular resistance. During the lower body negative pressure and leg raising, forearm vasoconstriction and vasodilation were similar before and after head-down tilt. The study shows that orthostatic intolerance following head-down tilt is not explained by an abnormality in the response of low pressure baroreceptors.

Adult↗
PubMed1989

Arterial compliance in uraemia.

Aortic and brachial pulse wave velocity were measured in 26 haemodialysis patients in order to assess the effect of uraemic waste-product retention on arterial compliance. Dialysis with a 'low-calcium' dialysate (1.50 mmol/l) did not change the pulse wave velocity, but dialysis with a 'high-calcium' dialysate (1.75 mmol/l) induced a significant increase in both aortic and brachial pulse wave velocity. The results indicate that (1) waste-product retention is not responsible for the increased arterial pulse wave velocity observed in uraemic patients and (2) the increase in serum ionized calcium decreases arterial compliance.

Arteries↗
PubMed1989

Increased vasodilator response during stimulation of cardiopulmonary baroreceptors in borderline hypertensives.

1. The effects of passive leg elevation on the forearm circulation were compared in 14 borderline hypertensive and 16 normotensive men. 2. In the supine position, mean arterial pressure (MAP), heart rate (HR) and forearm blood flow (FBF) were significantly greater in borderline hypertensives. 3. With leg raising, MAP and HR did not change significantly from basal values. FBF increased by +0.6 +/- 0.2 (s.e.m.) mL/min/100 mL (P less than 0.02) in normotensives and by + 1.3 +/- 0.2 mL/min/100 mL (P less than 0.001) in hypertensives (P for difference between groups less than 0.05).

Adolescent↗
PubMed1989

[Increased vasodilation response to the stimulation of low pressure mechanoreceptors in borderline hypertension].

Passive lifting of the lower limbs (antitilt) is a simple manoeuvre which stimulates low-pressure mechanoreceptors. Patients with borderline hypertension have an alteration of the arterial baroreflex modulated by an increased inhibitory effect of cardiopulmonary mechanoreceptors on vasomotor centres. The repercussions of antitilt on mean arterial pressure (MAP), heart rate (HR) and blood flow rate in the forearm (FRFA) were studied in 30 male subjects aged 18 to 25 years: 14 with untreated borderline hypertension ("patients") and 16 controls. FRFA was measured with a plethysmograph by means of a mercury constraint gauge. MAP was recorded during exploration with a DINAMAP instrument. The parameters were measured in recumbent position, then within minutes of the antitilt manoeuvre. In recumbent position the differences between patients and controls were: MAP 94.7 +/- 6 vs 84.7 +/- 7 mmHg (p less than 0.001); HR 76 +/- 13 vs 63 +/- 9 beats/min (p less than 0.01); FRFA 4.6 +/- 1.5 vs 3.5 +/- 1.4 ml/min/100 ml (p less than 0.05). Following antitilt, MAP and HR remained unchanged in the two groups, but there was a significant increase of FRFA in both controls (+ 0.6 +/- 0.2 ml/min/100 ml; p less than 0.02) and patients (+ 1.3 +/- 0.2 ml/min/100 ml; p less than 0.001). This increase was significantly greater in patients than in controls (p less than 0.05). This study shows that antitilt produces an increase of blood flow rate in the forearm that is more pronounced in patients with borderline hypertension than in controls. The stability of MAP and HR is in favour of non-actuation of the high-pressure arterial baroreflex.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Venous tone of the limbs. Methods and comparison of 2 areas].

The limb venous tone, index of local venous compliance, was studied with mercury strain gauge plethysmography on 28 male normal subjects (40 +/- 17 years, +/- SD) simultaneously on upper and lower limbs. Measurements were done after 20 mn rest in supine position. Venous tone (VT) equals the slope of the pressure-volume curve established by simultaneous recording of the forearm and calf relative volumes for successive steps of pressure lower than or equal to 30 mmHg. Limb venous capacitance was expressed by means of the maximal limb relative volume (V30) reached for a pressure of 30 mmHg applied through cuffs in standardized conditions. The upper limb venous tone was greater than the lower limb venous tone: 24.3 +/- 8.2 mmHg/ml/100 vs 17.5 +/- 7.9 mmHg/ml/100, p = 0.001. V30 was greater in lower limb than in upper limb: 1.5 +/- 0.5 ml/100 vs 1.1 +/- 0.4 ml/100, p = 0.001. In conclusion, it appears that upper and lower limbs venous distensibility and capacitance are different. They are greater in the lower limb in baseline conditions. Thus simultaneous studies of both these limb venous systems seems important for physiological experiments because of their baseline differences.

Adult↗
PubMed1988

Non-invasive ultrasonic study of maximal aortic blood acceleration in patients with borderline and sustained essential hypertension.

Using a pulsed Doppler method to evaluate the aortic velocity curve transcutaneously, the maximal aortic blood acceleration was evaluated in normal subjects and in age-matched patients with borderline and sustained essential hypertension. Maximal aortic blood acceleration was significantly elevated in patients with borderline hypertension and remained within the normal range in patients with sustained hypertension. Since maximal aortic blood acceleration is relatively insensitive to preload and afterload, these findings might give indirect information on the contractile state of the myocardium in patients with hypertension.

Adult↗
PubMed1988

Hemodynamics of the carotid artery after vasodilation in essential hypertension.

We performed simultaneous noninvasive measurements of common carotid artery and brachial artery hemodynamics in nine normal subjects and 10 subjects with sustained essential hypertension. In hypertensive subjects, brachial artery blood flow and forearm vascular resistance were in the normal range while carotid artery blood flow and carotid artery resistance were decreased and increased, respectively. The most important findings were the changes in the internal caliber of large arteries. Although the brachial and carotid artery diameters of hypertensive subjects were measured for the same level of mean arterial pressure, brachial artery diameter was significantly increased and carotid artery diameter was strictly normal as compared with values found in normal subjects. To assess whether carotid artery circulation could influence the baroreceptor reflex response to arteriolar vasodilation, carotid artery and brachial artery hemodynamics were measured in immediate succession in normotensive and hypertensive subjects before and after oral administration of cadralazine, a dihydralazine derivative. After cadralazine treatment, carotid artery tangential tension decreased in hypertensive subjects, and the changes were significantly correlated to the increase in heart rate. A similar correlation was found in normal subjects, but it was reset toward higher heart rates. These results indicate that the carotid artery does not behave like the brachial artery in response to a chronic increase in blood pressure. This behavior indicates intrinsic alterations of the arterial wall and might be involved in the resetting of the carotid baroreceptor reflex. Carotid artery circulation could play a role in hypertension by modulating the carotid baroreceptor mechanisms involved in the response to drug-induced arteriolar vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

[Regional hemodynamics of the forearm. Comparison between obese and non-obese hypertensive patients].

Forearm hemodynamics using pulsed Doppler flowmetry were studied in 83 men: 15 non-obese and 8 obese normotensive subjects; and 30 non-obese and 30 obese hypertensive patients. Mean ages were similar in the four subgroups. The blood pressure of normotensives and hypertensives was identical in obese and non-obese subjects. Blood flow expressed in ml/mn was significantly higher in obese subjects whether normotensive or hypertensive. However, when blood flow was expressed per unit liter of forearm volume, it was similar in the four subgroups. Forearm vascular resistance, whether expressed as absolute of normalized values, was significantly higher (p less than 0.001) in non-obese hypertensives. When obese and non-obese hypertensives were compared, the former were characterized by higher values of blood velocity and blood flow, and lower values of vascular resistance, whether absolute or normalized values were used. The present study shows that: (i) forearm vascular resistance in hypertensives is increased exclusively in non-obese subjects, and (ii) obese hypertensives, when compared with non-obese hypertensives, are characterized by a hyperkinetic forearm circulation.

Adult↗
PubMed1987

[Index of arterial and venous compliance and echocardiographic parameters in essential permanent arterial hypertension].

Forearm venous tone (FVT), carotido-femoral pulse wave velocity (PWV), and left ventricular end diastolic diameter (LVD), left ventricular posterior wall thickness (LVPWT), myocardiac mass (MM), measured by echography were evaluated on 25 subjects with sustained essential hypertension and 30 normotensive subjects with same age and same sex. For the overall population, FVT is positively correlated with LVD (r = 0.45, p less than 0.001), with LVPWT (r = 0.37, p less than 0.01) and with MM (r = 0.55, p less than 0.001). PWV is not correlated with LVD but is positively correlated with LVPWT (r = 0.48, p less than 0.001) and with MM (r = 0.40, p less than 0.01). Stroke volume is positively correlated with FVT (r = 0.42, p less than 0.01), but not with PWV. This study shows that in a population of normals and sustained essential hypertensive subjects: i) indexes of venous compliance are correlated with myocardial thickness, myocardiac mass, left ventricular diameter and stroke volume, while ii) indexes of arterial compliance are only correlated with myocardial thickness. Thus, the modifications of arterial and venous compliance observed in sustained essential hypertension influence cardiac structure and function.

Adult↗
PubMed1987

[Hyperreactivity of the humeral artery to noradrenaline in essential hypertension patients].

The hyperresponsiveness of small arteries to norepinephrine is well documented in essential hypertensive patients. Our objective was to investigate in situ the reactivity to norepinephrine of the diameter of large arteries which are involved in the arterial disease of hypertension as well as small arteries. Brachial artery diameter, blood flow velocity, local volumic blood flow and local vascular resistances were determined non invasively using a pulsed Doppler system in 19 patients with essential hypertension and 9 normotensive subjects, before and after placebo (glucose) or increasing doses of norepinephrine (10, 20 and 40 ng/kg/min; i.v.) given in a single blind fashion. In hypertensive patients, norepinephrine (40 ng/kg/min) induced (i) a significant decrease in brachial artery diameter, local blood velocity, volumic flow and conductance and (ii) a small increase in mean arterial pressure. These hemodynamic changes did not occurred in the placebo group and were significantly greater in hypertensive patients than in normotensive subjects although plasma norepinephrine increased to the same extent in both groups. We conclude that in hypertensive patients, the increase in vascular reactivity to norepinephrine involves not only the resistive vessels, but also the large arteries thus decreasing their conducting and buffering function.

Adult↗
PubMed1986

[Non-invasive study of the role of carotid distension in the baroreflex response to the arteriolar vasodilator cadralazine in essential hypertension].

Using pulsed Doppler methods, hemodynamics of the common carotid and the brachial arteries were measured in 10 patients with essential hypertension. After vasodilatation due to Cadralazine, a Dihydralazine-like substance, mean arterial pressure significantly decreased and heart rate increased. Change in PRA was significantly and positively correlated with the change in heart rate. In the brachial artery circulation, diameter and vascular resistance decreased while blood flow velocity and volumic blood flow did not increase significantly. In the common carotid artery circulation, diameter, mean blood flow did not change. However, vascular resistance and tangential tension decreased slightly. The increase in heart rate was strongly and negatively correlated (r = 0.82 p less than 0.01) with the change in the carotid artery tangential tension (measured as the product between mean arterial pressure and arterial radius) while no comparable correlation was observed with the change in blood pressure or arterial radius alone. The study suggested that in essential hypertensives, modifications in the carotid artery tangential tension secondary to arteriolar vasodilatation contribute actively to the baroreflex response.

Adult↗