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Biomedical subjects

M Niederberger

Publications and source records attributed to M Niederberger.

At least 37 records · Page 2Linked to original sources
PubMed1994

Paradoxes of body fluid volume regulation in health and disease. A unifying hypothesis.

The body's normal homeostasis is maintained by the integrity of the excretory capacity of the kidneys. In advanced cardiac failure, however, the avidity of the renal sodium and water retention contributes to the occurrence of pulmonary congestion and peripheral edema. In patients with advanced cirrhosis, the kidneys again fail to excrete the amounts of sodium and water ingested, thus leading to ascites and peripheral edema. The signals for this renal retention of sodium and water in a patient with cirrhosis must be extrarenal because when the same kidneys are transplanted into persons with normal liver function, renal sodium and water retention no longer occurs; rather, the kidneys maintain normal fluid and electrolyte balance. Excessive sodium and water retention by the kidneys also occurs during pregnancy despite a 30% to 50% increase in plasma volume, cardiac output, and glomerular filtration rate. What are the afferent and efferent signals whereby normal kidneys retain sodium and water so that total extracellular, interstitial, and intravascular volumes expand far beyond those limits observed in normal subjects? These dilemmas are the subject of this review, in which a "unifying hypothesis of body fluid volume regulation" is presented.

Body Fluids↗
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↗
PubMed1992

[Practical consequences blood pressure variability].

Arterial pressure varies over the course of the day depending on activities. It increases frequently in the presence of the physician. Long term blood pressure recording makes available a multitude of measurements taken during usual activities of the patient. These measurements permit identification of hypertensive patients at high risk i.e. patients with high blood pressure not only when facing their physician.

Blood Pressure↗
PubMed1992

[The treatment of arterial hypertension: which drug for which patient?].

Hypertension is a multifactorial disease. Various antihypertensive drugs can lower arterial pressure in a given patient in a more or less efficient way. The sequential testing of several drugs is most promising for lowering blood pressure by monotherapy. If necessary a drug combination is preferable to dose adjustments of a single substance because of the risk for side effects growing with the dose.

Algorithms↗
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

Pathogenesis of sodium and water retention in liver disease.

The "Peripheral Arterial Vasodilation" hypothesis most completely explains the clinical spectrum of cirrhosis ranging from compensated to decompensated to the hepatorenal syndrome (Figure 15-1). As the systemic peripheral vasodilation increases, the neurohumoral responses to arterial underfilling are stimulated with resultant renal vasoconstriction, sodium and water retention. Hypoalbuminemia and portal hypertension, as well as local effects of vasodilation at the capillary level, also contribute to ascites formation and peripheral edema. The suppressed plasma renin activity and aldosterone concentrations and exaggerated natriuresis, which are observed in some patients with early cirrhosis during HWI and the supine position, probably indicate greater central translocation of splanchnic fluid in these volume expanded cirrhotic patients when compared with normal subjects. This interpretation is supported by the greater increases in ANF during HWI in these patients when compared with controls. The neurohumoral responses to arterial vasodilation in cirrhosis combine to decrease distal sodium and water delivery, an event which impairs escape from the sodium retaining effects of aldosterone and causes resistance to the distal tubular effect of ANF (Figure 15-3). As discussed, the peripheral arterial vasodilation of cirrhosis is no doubt multifactorial in nature and the resultant arterial underfilling may be worsened by events that could impair the cardiac response to afterload reduction, including bile salt accumulation, alcoholic cardiomyopathy, and tense ascites decreasing cardiac preload. This pathogenetic schema of cirrhosis is compatible with the unifying body fluid volume hypothesis (Figure 15-3), which we have recently proposed.

Body Water↗
PubMed1991

Ambulatory blood pressure monitoring in children, adolescents and elderly people.

Non-invasive ambulatory blood pressure monitoring is increasingly being used in the diagnosis and the treatment of adult hypertensive patients. In children, the most obvious clinical use for intermittent blood pressure recordings is in the evaluation of borderline hypertension and the assessment of the efficacy of antihypertensive therapy. Adolescents who are hypertensive in the presence of the doctor are more often normotensive outside the physician's office than adult and elderly patients. Many elderly patients with isolated systolic hypertension have normal ambulatory systolic readings. Elderly patients with high blood pressures only in the physician's presence generally do not show a fall in ambulatory blood pressures when antihypertensive therapy is initiated or intensified. Thus, ambulatory blood pressure monitoring may be useful in detecting truly hypertensive patients among children and adolescents and in elderly people. This technique should make it possible to better define the cardiovascular risk, to avoid overtreatment and to individualize antihypertensive therapy.

Adolescent↗
PubMed1991

[Non invasive measurement of arterial compliance].

Pulse pressure waves are damped by the elastic properties of the blood vessels. This damping capacity can be evaluated by measuring vascular compliance a parameter which expresses changes of volume with respect to changes of pressure. Arterial compliance varies continuously with respect to intravascular pressure. Our group has developed an ultrasonograph which functions in the A mode capable of measuring the diameter of peripheral arteries during the cardiac cycle. This system is coupled to a photoplethysmograph which records non-invasively and continuously finger blood pressure. This enables construction of pressure-diameter graphs and the determination of arterial compliance and distensibility at each pressure value.

Arteries↗
PubMed1990

Hemodynamic effects of a kinin antagonist.

The present study was undertaken to assess in unanesthetized rats the effect of a kinin antagonist (D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Phe-Thi-Arg-trifluoroacetic acid) on blood pressure, heart rate, and splanchnic nerve activity. The antagonist infused intra-arterially (50 micrograms/min) for 10 min had no blood pressure effect in control rats. It did, however, cause a significant increase in blood pressure in animals preinfused with a nonpressor dose of angiotensin II (1 ng/min i.v.) for 70 min. The antagonist-induced blood pressure rise was not associated with an increase in splanchnic nerve activity. Acute angiotensin-converting enzyme (ACE) inhibition with captopril (2.5 mg i.v.) had no influence on the pressor response to the kinin antagonist in angiotensin II-treated rats. These results obtained in conscious normotensive rats suggest that endogenous kinins participate in the control of blood pressure by attenuating the vasoconstrictor effect of angiotensin II. The involvement of kinin does not seem to be enhanced by acute ACE inhibition.

Amino Acid Sequence↗
PubMed1988

Differences between subcutaneous and intraperitoneal forms of three human testicular teratocarcinomas in nude mice.

Three human testicular teratocarcinomas were serially passaged following subcutaneous transplantation into nude mice. Tumor cell suspensions from selected passages were injected intraperitoneally. The subcutaneous transplants of each tumor conserved the morphological characteristics of one component of the primary tumor, namely an embryonal carcinoma in one case and a yolk sac tumor in two. The latter maintained the capacity to synthesize alpha-fetoprotein (AFP). After intraperitoneal injection of cell suspensions, tumors, either attached to or even invading abdominal organs or in the form of free-floating tumor spheroids, were observed. AFP could be localized within the attached growths but not in the spheroids. A critical tumor volume and/or vascularization seemed to be necessary for AFP production in tumor cells. In spheroids from one tumor, cytogenetic analysis revealed both human and murine cells. Thus, these spheroids, apparently composed of tumor cells in the center and murine cells at the periphery, can not be considered to be embryoid bodies.

Animals↗
PubMed1987

[The "Medical-Psychologic Questionnaire for Heart Patients": a study of the assessment of the validity of a study instrument for psychological health of patients following myocardial infarct].

Correlations between scales and items of the "MPFH", and physical performance of MI-patients, lead us to conclude that the self-perception of decreased physical performance after MI is often generalized and thus leads to a decrease in self-esteem, often connected with feelings of social isolation. This pattern of reaction can in itself be a new risk factor during rehabilitation. Psychological rehabilitation must therefore focus on both: 1. trying to find a meaningful balance between moderate increase in physical performance and psychological adaptation to the reduction in performance, and 2. trying to reduce the feeling of social isolation which comes along with decreased physical performance.

Adaptation, Psychological↗
PubMed1984

Effects in elderly people 67-76 years of age of three-month endurance training on a bicycle ergometer.

Eight women and 4 men, mean age 71.1 years, examined by a clinical check-up participated in a bicycle ergometer training program (12 weeks with 3 training sessions per week). Symptom limited ergometric bicycle tests were performed before and after the training period. The training work load was continuously controlled by maintaining the training heart rate according to 60% of the maximum work load of the first test. To hold the training heart rate (HR) on a constant level the work load had to be increased systematically during the whole training period up to 180% of the level at the beginning. The working time in each training session was increased from 2 X 10 mm at the beginning up to 2 X 20 min after the sixth week. The maximum work load (+ 16%) and the maximum oxygen uptake (+ 11%) increased significantly. The submaximal HR decreased significantly. In contrast there was no significant difference in maximum HR and maximal change of base excess between the initial exercise test and the control study at the end of the training program. This indicates that the increased exercise capacity represents a real endurance training effect and not only an increase in the degree of exhaustion. We conclude that also in healthy people between 67-76 years a significant endurance effect is possible when the training work load and training time is increased systematically according to the rules of training sciences.

Aged↗
PubMed1984

Diagnostic value of exercise testing versus long-term ECG in evaluation of arrhythmias in old age.

The usefulness of exercise testing (ET) in old age is so far undefined particularly for detection of arrhythmias. We compared the diagnostic value of ET with 24-h long-term ECG recording (LT-ECG) in patients older than 70 years that were evaluated because of symptoms possibly related to arrhythmias. In 37 patients (age 72.8 +/- 2.7 years) the incidence of ventricular arrhythmias (LOWN greater than or equal to 1) was greater during ET (67%) than during 24-h LT-ECG recording (48%, P less than 0.01). Complex ventricular arrhythmias were detected in 6/37 patients (16%) by ET, in 9/37 patients (24%) by LT-ECG, in one patient (3%) by both tests and in 14/37 patients (37%) by one of the two tests, while 23/37 patients (63%) had no significant complex arrhythmias recorded by either test. During ET 12 patients (32%) showed signs of myocardial ischaemia with ST-depression greater than or equal to 0.2 mV and/or increasing angina pectoris. In 42% of these patients complex ventricular arrhythmias LOWN greater than or equal to 3 occurred during ET. Thus both ET and LT-ECG are useful methods to uncover arrhythmias in symptomatic patients older than 70 years and have to be considered as complementary tools.

Aged↗
PubMed1984

[Results of 3 months' endurance training on a bicycle ergometer in people between 67 and 76].

8 healthy women and 4 men, examined by a clinical check-up, mean age 71.1 years, took part in a bicycle ergometer training, 3 times a week, for 12 weeks. Symptom limited ergometric bicycle tests were done before and after the training period. The training work load was continuously controlled by maintaining the training heart rate according to 60% of the maximum work load of the first test. In order to hold the training heart rate (HR) on a constant level the work load had to be increased systematically during the whole training period up to 180% of the level at the beginning. The working time in each training session was increased from 2 X 10 minutes in the beginning up to 2 X 20 minutes from the 7. week on. The maximum work load (+ 15%) and the maximum oxygen uptake (+ 14%) increased significantly. The submaximal HR decreased significantly. In maximum HR and maximum decrease of the base excess were no significant changes, indicating a real endurance training effect and not only an increase in the degree of exhaustion. We conclude that also in healthy people between 67-76 years a significant endurance effect is possible when the training is systematically increased in work load and working time, according to the rules of training science.

Aged↗