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Biomedical subjects

R Busse

Publications and source records attributed to R Busse.

At least 271 records · Page 15Linked to original sources
PubMed1982

Mechanical properties of arteries.

UNLABELLED: For the description of the mechanical properties of the arterial wall, a number of different models and mathematical approaches of varying complexity have been used. Most investigations based on the elastomeric approach have been related to the elastic properties of arteries, while relatively little is known about the arterial wall viscosity (eta w) and its dependence on circumferential wall stress (sigma t) and smooth muscle tone. For this reason we have examined these relationships on segments of the abdominal aorta, the carotid artery, and the tail artery of normotensive rats in vitro under the condition of strong smooth muscle activation induced by norepinephrine (NE), and during smooth muscle relaxation induced by papaverine (PAP). RESULTS: 1. For the abdominal aorta, the quotient of the dynamic (Ed) and the quasistatic elastic modulus (ESt) increase from 1.5 to 2.1 under NE, and from 1.2 to 1.5 under PAP, for the carotid artery from 2.8 to 3.9 under NE, and from 1.3 to 1.4 under PAP, when sigma t increases from 10 to 120 kPa. For the tail artery, this quotient is 8.6 under NE and 1.9 under PAP in the low sigma t-range (5 to 60 kPa) and 12.1 under NE and 1.5 under PAP in the sigma t-range between 60 and 120 kPa. 2. For all three types of arteries, Ed and eta w increases with increasing sigma t. At a given sigma t, the values of Ed are virtually independent of frequency, while the values of eta w decrease markedly with increasing frequency. 3. The values of Ed and eta w, obtained under NE and PAP, are virtually identical for a given sigma t-range.

Animals↗
PubMed1982

[Effect of nitrates, nitrate-like substances, calcium antagonists and beta-adrenergic receptor blockers on peripheral circulation].

The effectiveness of organic nitrates in the therapy of angina pectoris can be explained from their direct relaxing action on vascular smooth muscle. At conventional dosage the most important action of nitrates is a pooling of blood in the large systemic venous capacitance vessels which leads to a decrease of central venous pressure and ventricular filling pressure. The resulting reduction in left ventricular volume lowers, at virtually constant arterial pressure, systolic wall tension and hence myocardial oxygen consumption. Only at higher dosage, is a distinct dilatation of systemic resistance vessels affected. The fundamental action of the "Ca antagonists", i.e. the inhibition of transmembrane calcium influx in the myocardium and the vascular smooth muscle, includes various beneficial effects for the treatment of angina pectoris. The lowering of myocardial oxygen consumption after application of calcium antagonist is mainly due 1. to the decrease in afterload of the left ventricle, caused by the relaxation of peripheral resistance vessels, 2. to the reduction in ventricular preload by a peripheral venodilation. By a direct inhibitory effect on the coronary vascular tone, coronary blood flow at rest in patients with angina pectoris increases. In addition, Ca antagonists are very efficacious in relieving angiospastic angina. The primary mode of action of beta-blocking drugs in angina pectoris affects, in contrast to the peripheral mechanisms of nitrates and Ca antagonists, is on the heart directly. By the reduction in the extent of exercise heart rate, the increase in cardiac output and, hence, the mean arterial pressure is also significantly lower during exercise under beta-blockade. Beta-blockers also depress the contractile state of myocardium. Therefore, the main factors of the myocardial oxygen consumption (mean arterial pressure, size of the left ventricle, contractility and heart rate) may be essentially influenced. By the decrease in heart rate and the longer diastolic period a better myocardial oxygen delivery results. Besides the immediate cardiac effects of beta-adrenergic blockade, a decline in peripheral resistance combined with a fall in blood pressure occur in hypertensive patients during long-term drug administration. Different hypotheses have been proposed in the last years to explain the antihypertensive mode of action of beta-blockers. Some possible mechanisms are discussed.

Adrenergic beta-Antagonists↗
PubMed1980

Photoelectric device for the recording of diameter changes of opaque and transparent blood vessels in vitro.

A new photoelectric device for measuring blood vessel diameters is described. The principle of this device consists in locating the vessel within a beam of parallel light at right angles to the beam direction, and eliminating all light striking the vessel. Thus only the light passing by the side of the vessel determines the signal strength of a photocell. The elimination of the light by the vessel due to reflection, refraction, diffraction, or scattering, is achieved with the aid of a lens and pinhole representing a spatial filter. This arrangement is effective irrespective of whether the vessel is opaque or transparent. The resolving power of the device in measuring changes of outside diameter is better than 0.5 micrometer for vessels up to 3 mm in diameter. The upper frequency limit is 300 Hz (--3 dB). The application of the method is demonstrated by two examples of measurements obtained on a small muscular artery.

Blood Pressure↗
PubMed1979

Separate determination of the pulsatile elastic and viscous forces developed in the arterial wall in vivo.

The viscoelastic behaviour of arteries in vivo is analyzed by separate representation of the purely elastic and the purely viscous properties, using natural pressure and diameter pulses of various dog arteries recorded under steady-state conditions. The circumferential wall stress (sigma) and the radius (r) of the mean wall layer are calculated as functions of time and the hysteresis of the sigma-r diagram is represented. The stress is regarded as the sum of an elastic stress (sigma el) which is a function of r, and a viscous stress (sigma vis) which is a function of dr/dt. Thus sigma el = sigma - sigma vis. Since the sigma el-r diagram must be free from hysteresis, the disappearance of the loop is the criterion that indicates that sigma el has been found. sigma vis is formulated as a second degree polynomial of dr/dt whose coefficients are determined using that criterion. The sigma el-r curve is always nonlinear and the elastic modulus increases with increasing radius. The sigma vis-dr/dt curve, too, is nonlinear. Its slope decreases with increasing dr/dt. The same applies to the wall viscosity (pseudoplastic behaviour). The nonlinear properties can be represented adequately by processing the experimental data in the time domain. Problems inherent in investigations based on the frequency domain, as reported in the literature, are pointed out.

Animals↗
PubMed1978

[Histotopography of chronic gastritis in localized processes of the gastric wall and in resected stomach (author's transl)].

The topography of gastritis was investigated by selective endoscopic biopsies from the antrum and body of the stomach in 231 patients with duodenal or gastric ulcers, 165 patients with gastric carcinoma, 83 patients with polyps of the gastric epithelium and 122 patients after gastric resection (Billroth II). The results of this study show that gastritis, even with localized gastric processes or lesions is not a general inflammation involving the whole of the gastric mucosa. Gastric epithelial polyps and gastric carcinoma are associated with a chronic atrophic gastritis in the affected gastric mucosal areas in less than or in about 50% of cases. A diffuse uniform gastritis was found in little more than 65% of gastric resections.

Biopsy↗
PubMed1977

Photoelectric device for contact-free recording of the diameters of exposed arteries in situ.

A photoelctric device is described which permits contact-free recording of the diameter of an in situ exposed artery. The light emitted by the filament of a bulb (6 W) is collimated by a projection lens (1:2.8, 50 mm) and directed onto the surface of a silicone photocell (12.6X6.2 mm) covered by a neutral light filter. The voltage drop caused by the photocell current flowing through an adjustable load resistor represents the signal voltage which is fed into the input of an instrumentation amplifer. The artery under investigation is positioned above the photocell parallel to its short axis. The signal voltage decreases linearly with increasing area of the shadow cast by the artery on the photocell and thus the output voltage of the amplifier is linearly proportional to the diameter of the artery. The combined frequency response of photocell and amplifier was examined by sinusoidally modulated light emitted by a luminescent diode. The amplitude ratio was constant up to 200 Hz and the time lag was about 0.2 ms. The device was used on the canine carotid and femoral arteries. An example is shown.

Amplifiers, Electronic↗
PubMed1976

Comparison of the visco-elastic properties of the tail artery in spontaneously hypertensive and normotensive rats.

The quasistatic and dynamic elastic behaviour of the tail artery of male normotensive (NCR) and spontaneously hypertensive (SHR) rats was determined in vitro. The tone of the smooth muscle was enhanced by norepinephrine and diminished by papaverine. The circumferential wall stress was changed by varying the transmural pressure level. The experimental procedure was the same as that used in a previous investigation (Bauer and Pasch, 1971). The circumferential (tangential) elastic wall modulus Et was calculated from the mean internal and external radii determined at each pressure level and from dynamic pressure-volume recordings in the frequency range between 0.03 and 20 HZ. The calculation was based on a formula valid for thick-walled, longitudinally constrained vessels.

Animals↗
PubMed1975

[Endoscopic polypectomy of the upper gastro-intestinal tract: results and clinical features (author's transl)].

247 polyps were removed by electroresection through an endoscope (and 240 recovered) in 160 patients, aged 24-81 years. The histological substrate varied widely. Comparison of histological findings in the biopsy specimen with those of the entire polyp after polypectomy gave differing results in 41 of 87 gastric polyps. Complication rate of endoscopic polypectomy was 1.6%: postoperative bleeding occurred in three, which was treated conservatively, while in one patient ligation of a blood vessel by laparotomy became necessary. There were no perforation or lethal complications. Among three patients with hyperplasiogenic gastric polyps a "borderline lesion" was found in two (early carcinoma type I; adenocarcinoma). In 13 other patients with hyperplasiogenic polyps follow-up examination after one year revealed recurrence in three, absence of polyps in eight. In one patient a small gastric carcinoma (about 1 cm in diameter) was discovered four months later. It is possible that patients with hyperplasiogenic polyps are at a higher risk of cancer. Six-monthly endoscopic observation is, therefore, indicated.

Adenocarcinoma↗
PubMed1975

The genesis of the pulse contours of the distal leg arteries in man.

In order to clarify the genesis of the human pressure and flow pulse contours of the distal leg arteries, in particular the posterior tibial artery, pulse recordings were performed with transcutaneous techniques under normal conditions and in the state of strong vasodilatation (reactive hyperaemia) in the distal parts of the lower legs. From the experimental results it is concluded that the contour of the incident pressure wave arriving in the leg arteries is very similar to the pressure pulse contour of the abdominal aorta, while the resulting contour in the leg arteries is determined by this incident wave and superimposed reflected waves. The latter arise from positive reflection in the periphery of the lower legs. The travel in retrograde direction, are reflected negatively in proximal regions, particularly in the abdominal aorta, and appear again, with opposite sign, in the leg arteries. In addition, retrograde waves reflected positively at the aortic valve and then traveling in antegrade direction also influence the pulse contours. By considering this wave travel, the genesis of the characteristic contours of the pressure and flow pulses of the lower leg arteries is explained in a satisfactory way. This is demonstrated by a simplified graphical pulse construction as well as by the calculation of pulse contours on the basis of a theoretical tube model of the arterial system with the aid of a digital computer. The results of these calculations are discussed with respect to the findings of previous investigators who used analog and digital models of the arterial system.

Adolescent↗
PubMed1975

[Gastro-intestinal endoscopy - today and tomorrow (author's transl)].

Because of their optical and mechanical properties, glass fibers have fulfilled the requirements for a panendoscopy of the gastrointestinal tract. The upper digestive tract (as far as the lower knee of the duodenum) and the large intestine, including the terminal ileum can be examined routinely nowadays with minimal risk. Surgical diagnostic and therapeutic endoscopy open up new possibilities, i. e. polypectomy, endoscopic biopsy, extraction of foreign bodies, papillotomy etc. The development of gastrointestinal endoscopy demands reorientation in training and teaching, in practice and in hospital.

Biopsy↗