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Biomedical subjects

W Burger

Publications and source records attributed to W Burger.

88 records · Page 5Linked to original sources
PubMed1985

The effect of ischemia and reperfusion on sarcolemmal function in perfused canine hearts.

The report deals with the effect of ischemia and reperfusion on purified sarcolemma obtained from canine myocardium of perfused supported heart preparations. Perfusion was carried out with a perfluorochemical (FC-43). Ischemia was produced by intermittent total clamping of inflow and outflow followed by release until the decrease in dP/dtmax had become stabile. Purity of sarcolemmal vesicles was ascertained with marker enzymes: succinate cytochrome c reductase (for mitochondria), K+-stimulated p-nitrophenylphosphate (K+-pNPPase), (Na+/K+)ATPase and adenylate cyclase (for SL). In addition Na+/Ca2+-exchange characteristics for SL were determined. Sidedness of vesicles was ascertained by means of adenylate cyclase activity using sarcolemmal preparations treated and untreated with alamethicin. Emphasis was placed on ATP-dependent Ca2+ uptake, phosphorylation of sarcolemmal vesicles and yield of SL proteins. Ischemia and reperfusion resulted in a significant reduction in adenylate cyclase activity. This decline was significant following ischemia and reperfusion. The yield of protein recovered from SL vesicles from ischemic-reperfused heart preparations was also significantly decreased. Both initial rate of ATP-dependent Ca2+ uptake and maximal Ca2+ uptake fell significantly following ischemia and reperfusion. The initial rate of phosphorylation also dropped significantly. These disturbances in SL Ca2+ transport following ischemia and reperfusion are probably a part of the general deficit in Ca2+ translocation.

4-Nitrophenylphosphatase↗
PubMed1985

Crystalloid and perfluorochemical perfusates in an isolated working rabbit heart preparation.

Krebs-Henseleit buffer (KH) and a perfluorochemical (FC-43) were compared as perfusates in an isolated working rabbit heart preparation. Both perfusates were oxygenated in an identical manner using an infant bubble oxygenator. After 60 min of perfusion, no difference could be detected in the ratio of wet to dry heart weight between KH- and FC-43-perfused hearts (KH, 6.25 +/- 0.3; FC-43, 5.99 +/- 0.20). Left ventricular systolic pressure, maximal rate of left ventricular pressure rise, mean aortic systolic pressure, cardiac output, aortic flow, left ventricular power, and myocardial O2 consumption (MVO2) were significantly higher in FC-43-perfused hearts throughout the time of perfusion. However, there were no differences in resistance to cardiac output and heart rate. In KH- and FC-43-perfused hearts, MVO2 and left ventricular power were closely correlated (KH, r = 0.793; FC-43, r = 0.831). Significantly higher coronary flow of KH-perfused hearts could be attributed to the lower viscosity of KH (1.05 Pa . s) compared with FC-43 (1.91 Pa . s). Increased O2 extraction during KH perfusion could not compensate for low O2-carrying capacity of KH buffer (345 compared with 705 nmol O2 X ml-1 in FC-43 emulsion). A postischemic increase of coronary flow was observed only in FC-43-perfused hearts (28%). These results demonstrate a different response of perfused heart preparations to FC-43 and KH buffer.

Animals↗
PubMed1985

A new method for the visualization of subepicardial coronary arteries in small isolated mammalian hearts.

A model is described which permits direct visualization of large coronary arteries in a supported modified perfused heart preparation, using a perfluorochemical (FC-43) as perfusate. Filling of a large coronary artery with Patent Blue Dye is recorded by gated photography (color arteriography). The technique is applicable to the study of reactivity (spasm) of coronary arteries in hearts of small and large animals (rats, rabbits, dogs). The technique has the following advantages: preservation of vascular endothelium, adequate oxygenation, avoidance of major surgical intervention to implant sensors for the detection of changes in coronary diameter, quantitative evaluation of time dependent changes in geometry of large coronary arteries and simultaneous measurement of large coronary vessel and total coronary vascular resistance.

Animals↗
PubMed1984

Effects of active and passive wall stress changes on the rhythmic mechanical activity of the pressurized rat tail artery.

Rhythmic mechanical activity was recorded in vitro in isolated rat tail arteries. Pressurized cylindrical segments of this artery, stretched to their in situ length, exhibit well-synchronized rhythmic contractions. Frequency and amplitude of the rhythmic activity can be modified by (1) passive stretch at a given constrictor agonist concentration, as well as by (2) active wall stress changes induced by varying doses of constrictor agonists. At a norepinephrine concentration of 0.5 microM, the frequency (f) of rhythmic contractions increases from 0.2 to 0.65 [sec-1], when the mean circumferential wall stress (sigma) is increased from 1 . 10(5) to 1 . 10(6) dyn/cm2. The relationship between f and sigma is, at a constant smooth muscle tone, virtually independent of the rate and also of the direction of the applied stress changes. Changes of the smooth muscle tone (i.e. changes of the actively developed wall stress), induced by vasoactive agents or other stimuli, lead to virtually parallel shifts of the sigma-f relationship, which is obtained by passive stretching. It is concluded that the actual stimulus for the stretch-sensing structure in the arterial smooth muscle is the change in wall stress rather than the change in strain. Since rhythmic contractions may still be observed 30-60 min after withdrawal of Ca++ from the bath solution, extracellular Ca++ seems not to be primarily involved in this rhythmicity.

Animals↗
PubMed1984

[Chloroquine and pyrimethamine/sulfadoxine resistant malaria tropica in a child with diabetes mellitus].

A 16-year old girl with insulin-dependent diabetes mellitus (8 years' duration) developed tropic malaria 7 weeks after her return from Kenya despite a longtime prophylaxis using pyrimethamine and sulfadoxine (Fansidar). The disease was detected during an episode of ketoacidosis which proved exceptionally difficult to manage. Adequate chloroquine therapy resulted in temporary recovery. A recurrence of malaria four weeks later was successfully treated with quinine and doxycycline. Intraleucocytary parasites were found during both these episodes. Already prior to antimalarial drug therapy the girls' preexisting retinopathy was found to have deteriorated.

Adolescent↗
PubMed1983

[Treatment of diabetic ketoacidosis in children and adolescents].

Despite low mortality rates, diabetic ketoacidosis in children and adolescents remains a potentially fatal condition. In this age group, cerebral edema, rapid decreases of serum potassium levels and severe hypoglycaemia seem to represent the most frequent complications of therapy which have to be avoided. This paper attempts to critically evaluate some greatly different treatment schedules previously published and presents our own experiences with a practicable therapeutic concept which has proved to be simple and safe and only slowly corrects the metabolic deviations. Insulin is administered by continuous intravenous infusion at a rate of 0.1 IU/kg bwt per hour following an initial bolus injection of 0.1 IU/kg. After reduction of blood glucose values to less than or equal to 250 mg/dl, the infusion rate can be reduced to half. For rehydration we use isotonic saline solution at a rate of 100-150 ml/kg body weight and per day, depending on age as far as basal fluid requirements are concerned, and the degree of dehydration, around one half during the first eight hours, the second half during the subsequent 16 hours. Potassium substitution begins after the onset of diuresis, supplying between 3 and 5 mmol/kg body weight during 24 hours. Bicarbonate substitution has proved to be hardly ever necessary and is only used in patients exhibiting the most severe clinical condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1977

Radioimmunoassay of the anti-hypertensive agent debrisoquin.

Antisera to debrisoquin, a widely used anti-hypertensive agent, have been obtained from rabbits following immunization with a conjugate of 4-[1,2,3,4-tetrahydroisoquinolin-2-yl)(imino)-methylamino] butanoic acid and bovine serum albumin. Employing tritium labelled debrisoquin as the radioligand for the antisera, a radioimmunoassay (RIA) was developed which allows for the specific determination of the drug directly in plasma. After logit transformation, a linear calibration line was obtained between 0.1 to 10 ng of unlabelled debrisoquin. The 4, 5, 6, 7 and 8-hydroxy derivatives of debrisoquion, known metabolites in man, showed less than 1.5% cross-reaction with the antisera. The specificity of the RIA was established when good agreement was obtained for the levels of debrisoquin in patients' plasma using the RIA and a specific GC/MS method. The simplicity of the RIA makes this method attractive for the routine clinical monitoring of the plasma levels and/or experimental protocols in which high sample throughput is required.

Animals↗
PubMedDate not supplied

Can retinopathy be prevented?

Clinical retinopathy eventually develops in the majority of insulin dependent diabetics during several decades of metabolic abnormality. Early structural lesions short of clinical significance may occasionally be detected in children much more frequently, however, after puberty. Major factors modulating the development of retinopathy are duration of diabetes, glycemic control and blood pressure.

Adolescent↗
PubMedDate not supplied

A novel ultrasonic resonance field device for the retention of animal cells.

This article describes two types of flow-through cell retention devices based on the concept of layered piezoelectric resonators. A single-chamber device is compared to a novel optimized steam-sterilizable prototype ultrasonic cell separator with improved acoustic design and an integrated cooling circuit, eliminating the problem of local temperature increase caused by the high amplitudes necessary to achieve the separation of animal cells with low acoustic contrast. This setup yields highly reproducible results and is ideal for studying the long-term effects of ultrasonic sound fields and separation efficiency. The novel two-chamber system has the potential for scaleability due to the reduction in thermal and acoustic flow, increased field stability, and separation efficiency. Finally, the effect of power input on separation and cell viability is reported. Such flow-through cell retention systems could be used as systems to retain biomass within the fermentor or as a substitute for centrifugation, with the major advantage of eliminating high-speed rotational motion.

Animals↗
PubMedDate not supplied

Selective retention of viable cells in ultrasonic resonance field devices.

A double-chamber ultrasonic resonance field device was used for the separation and retention of animal cells. By controlling operational parameters such as flow and power input, the device can retain viable cells more efficiently, allowing for selective removal of nonviable cells and cell debris. A simple model describing the forces acting on spherical particles in a sound field (primary radiation force, Bernoulli force, secondary radiation force) is presented. Field stability increases with decreasing average flow rates and increasing power input. At very high field stability, as achieved with low flow rates and high power input, the selectivity for viable cells is reduced, due to the efficient retention of all types of particles. At high flow rates and resulting low field stability, selectivity is also reduced, due to poor separation efficiency, resulting in equally low retention of viable cells, nonviable cells, and cell debris.

Animals↗
PubMedDate not supplied

Endothelium-dependent and endothelium-independent flow regulation in coronary vascular regions supplied by arterial and venous bypass grafts.

The endothelium-dependent and endothelium-independent vasodilation of arterial and venous coronary bypass grafts and of epicardial conduit vessels and microcirculatory coronary vessels supplied by these grafts was investigated. Vasodilatory response and flow regulation were tested with cumulative intracoronary doses of acetylcholine (25 and 50 micrograms i.c.), nitroglycerin (0.3 mg i.c.), and papaverine (10 mg i.c.) in 10 patients (age 60 +/- 2.3 years) with arterial grafts and in 16 patients (age 57.7 +/- 1.5 years) with venous grafts. The effect of acetylcholine on arterial and venous bypass grafts and on large conduit arteries was evaluated by quantitative coronary angiography. Coronary blood flow velocity changes as a parameter of microcirculatory function were measured by intraluminal Doppler ultrasound. Indices for coronary flow and coronary resistance were calculated from the mean Doppler flow velocity and the computed cross-sectional vascular area. The coronary resistance decreased endothelium dependent after 25 and 50 micrograms of acetylcholine by 16 +/- 30% (p < 0.05 vs. control) and 22 +/- 25% (p < 0.05 vs. control), respectively, in regions supplied by venous grafts and by 48 +/- 20% (p < 0.05 vs. control and vs. venous graft) and 41 +/- 32% (p < 0.05 vs. control), respectively, in regions supplied by arterial grafts. The coronary resistance decreased endothelium independent after 0.3 mg nitroglycerin and 10 mg papaverine by 18 +/- 56% (p < 0.05 vs. control) and 39 +/- 29% (p < 0.05 vs. control), respectively in regions supplied by venous grafts and by 45 +/- 45% (p < 0.05 vs. control) and 70 +/- 12% (p < 0.05 vs. control and vs. venous graft), respectively in regions supplied by arterial grafts. In conclusion, during the long-term course after coronary artery bypass grafting, vascular regions supplied by arterial grafts have a better preserved endothelium-dependent and endothelium-independent flow reserve as compared with vascular regions supplied by venous grafts.

Acetylcholine↗
PubMedDate not supplied

A phase II trial of vindesine in hepatocellular cancer.

Sixteen patients with histologically confirmed inoperable hepatocellular carcinoma were treated with vindesine 3 mg/m2 i.v. weekly. Anemia, leukopenia and neuritis were documented but no severe or life-threatening toxicity was seen. There were no objective responses among the 14 evaluable patients. Eight had a no change status (median duration of 16 weeks, range 6-33), while the remaining 6 had progressive disease as their best evaluation. The median survival time was 20 weeks. Vindesine does not have a therapeutic effect in patients with advanced hepatocellular carcinoma.

Adolescent↗