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Biomedical subjects

J Werner

Publications and source records attributed to J Werner.

At least 127 records · Page 7Linked to original sources
PubMed1995

Control of liquid cooling garments: subjective versus technical control of thermal comfort.

Liquid cooled garments (LCG) are a powerful tool for alleviating heat strain during work in hot conditions. However, the potential advantage of an LCG depends on a more or less proper control of the cooling liquid's temperature. To gain more knowledge on this subject two experimental studies concerning manual control by the wearer were carried out. In both studies the subjects had to exercise in a warm environment. In the first study the subjects (n = 5) were asked to control the temperature directly. They used different strategies, ranging from gradual changes to oscillations of the suit temperature. This was accompanied by large differences of the chosen inlet temperature and the comfort level attained, although by repetition of the experiment it was possible to increase the subjective thermal comfort. In the second study a technical 'comfort' controller changed the inlet temperature of the LCG in the appropriate direction whenever the personal assessment of thermal sensation differed from the neutral state. The subjects (n = 6) had no information about the control mode. The experiments showed that it was possible to maintain a comfortably neutral thermal sensation throughout nearly the whole experiment. This result, however, was partly in contrast to the objective thermal state of the subjects. Two of them had problems with their heat balance, expressed by the fact that their rectal temperature did not reach a steady state. The results of both studies indicate that manual or subjective control is not optimal and should therefore be replaced by an objective control of the thermal state.

Body Temperature↗
PubMed1994

Estimation of the thermal effect of blood flow in a branching countercurrent network using a three-dimensional vascular model.

A three-dimensional thermal model is presented in which convective heat transfer is defined in terms of the physical details of the vascular system. The convective heat exchange between prearteriole and postvenule vessels and the tissue across the vessel walls is calculated explicitly without using shape factors. Conduction in x-, y-, and z-direction is considered. This vascular model is applied to a human extremity. The spatial variations in the arterial, venous and tissue temperatures under basal conditions, hyperthermic conditions and in a cold environment are computed. Conclusions are drawn as to the validity of bioheat approaches.

Basal Metabolism↗
PubMed1994

Efficiency function: improvement of classical bioheat approach.

In view of the complex vascular architecture and the intricate physical heat transfer processes in the human body, convective heat transfer via the blood is generally described by simple substitutional processes ("non-vascular models"). The classical "bioheat" approach of Pennes (J. Appl. Physiol. 1: 93-122, 1948), defining the heat flow to or from the tissue as being proportional to the product of perfusion rate and the difference of arterial and tissue temperature, has been seriously questioned after having been used for > 40 yr in many applications. In our laboratory, we have at our disposal a complex three-dimensional vascular model for the special case of tissue in a human extremity. This was used to test the performance of simple nonvascular models. It turned out that the Pennes approach may deliver acceptable results if the body is in the thermoneutral zone or if heat stress acts uniformly on the whole body. However, when cold stress or local hyperthermia is present, unreliable results must be expected. As the vascular model is not generally practicable because of its extreme complexity, we offer the efficiency function concept as a simple way of correcting the classical bioheat approach by factor multiplication. Efficiency function is determined as a function of perfusion rate and tissue depth in a way that compensates for the deficiencies of the Pennes bioheat term. The results are reasonable compared with those of the vascular model and experimental results.

Blood Physiological Phenomena↗
PubMed1994

[The pre-positioned intracutaneous suture--a method for treatment of soft tissue defects after fascia splitting in acute compartment syndrome].

In the treatment of the acute compartment syndrome open fasciotomy gives rise to a wide soft tissue opening. The persistence of this opening prevents a timely change to internal osteosynthesis in case of additional fractures usually treated by a fixateur externe. Closure of the skin defect itself requires additional surgery. The cosmetical results particular in cases of a mesh-grafting are unsatisfactory. After open fasciotomy the prepositioned intracutaneous suture is a simple operation technique leading to early wound closure with a good cosmetical result.

Adolescent↗
PubMed1993

Ultrastructural localization of lectin-binding sites in different basement membranes.

In the present work we localized binding sites for the lectins WGA, RCA I, con A and SBA at the ultrastructural levels in morphologically different basement membranes. These different basement membranes included (a) thin ones, for example, tubular basement membrane of the mouse kidney which separates epithelial cell layers from mesenchymal cells and glomerular basement membrane which separates epithelial cells from other epithelial cells, (b) thick multilayered ones, for example. Reichert's membrane which is built up during the embryonic development of rodents and as an example of a pathologically thickened basement membrane, the basement membrane of the Engelbreth-Holm-Swarm (EHS) sarcoma. We were able to show that, in contrast to the thick multilayered basement membranes, the thin ones showed a strong positive SBA-binding pattern. Thick basement membranes otherwise revealed very strong labelling with the lectins WGA and RCA I. Our findings lead us to conclude that thin and thick basement membranes differ markedly in the quality and quantity of the carbohydrates which they contain.

Animals↗
PubMed1993

A six-cylinder model of human thermoregulation for general use on personal computers.

The paper describes the basics of a six-cylinder model of human thermoregulation, written in MS-FORTRAN for use on personal computers. The heat balance equations with respect to the radial coordinate, the initial and boundary conditions, and the controller equations are explained. A complete set of parameter values is given. Emphasis is laid on the problems and status of validation. Therefore conditions and methods, on which a standard set of experimental results (dynamics of 29 core, muscle, subcutaneous and skin temperatures) is based, are explained as well as possible deficiencies both of the experimental and the simulation results. It turned out that within the environmental conditions tested (15-45 degrees C), the model, although simplifying the complex geometry of the human body to six cylinders, gives reliable results, both for steady state and dynamics of body temperature topography.

Body Temperature Regulation↗
PubMed1993

Computer supported analysis of cardiovascular parameters by impedance cardiography and plethysmography.

A fully automated system for computer supported analysis of cardiovascular parameters on the basis of impedance technique, which is confined to the analysis of relative changes of stroke volume and cardiac output, has been developed and tested. The evaluation showed good agreement between automatic and manual calculation. As the whole computational procedure is done by software, which is written in a common language (BASIC), a maximum of flexibility and portability is guaranteed. Estimation of relative changes of stroke volume and cardiac output as well as peripheral blood flow is possible without any manual interaction. Extension from physiological measurement of healthy individuals to clinical application has been started.

Cardiac Output↗
PubMed1993

[New methods of veterinary care for swine herds].

In hybrid breeding schemes it is important to make sure that no diseases are transferred from the multiplier farms to the piglet producers. In the German Federal Hybrid Scheme (BHZP) are 280 multiplier farms working with Personal Computers with the same software. The software helps the veterinarians in analysing health problems in the herds. Some data-evaluations of piglet losses, herd performance-traits and causes of sow-losses are shown. Because of the identical software in all farms is it possible to work with the same vaccine strategy in the whole breeding scheme. The results of the data-evaluations are the main basis for the farmer, veterinarian and adviser.

Animal Husbandry↗
PubMed1992

Thermographic studies on patterns of skin temperature after exercise.

In six subjects thermograms of the thighs and the forearms were taken before, during and after 10 min ergometer exercise at 100 W at an ambient temperature of 23 degrees C. During exercise, an intra-individually constant and reproducible skin temperature pattern with local temperature differences exceeding 3 degrees C evolved. Reactions after external local cooling or after occlusion of blood flow and measurements with a laser Doppler-flowmeter showed dispersed convective heat transport to be the source of this irregular pattern. Temperature differences of 3.6 degrees C and deviations of blood flow in the skin microcirculation of 300% within a distance of a few centimetres reduce the value of single-spot measurements of skin temperature with reference to the whole extremity.

Adult↗
PubMed1991

[Animal nutrition for the veterinarian--recent cases. Unsatisfactory development of piglets after disintegration of a piglet breeding feed].

Insufficient performance and health problems of reared piglets in individual boxes gave rise to sent 2 samples of the diet to the institute. Due to a demixing process on the transport (winding) the composition of the diet changed markedly. The crude ash content increased (62.7 g----96.2 g/kg feed), on the other hand the protein content decreased significantly (181----126 g/kg feed). Obviously the variable mineral content in the diet impaired the palatability and consequently the performance of reared piglets due to increased disposition for diarrhea.

Animal Feed↗
PubMed1990

Loss and restoration of preoptic thermoreactiveness after lesions of the rostral raphe nuclei.

Preoptic neurons, extracellularly recorded in the rat's brain, were tested for their responses to thermal stimulation of the scrotal and abdominal skin before and after electrolytic lesions of about 1 mm3 in the area of the rostral raphe nuclei, nucleus raphe dorsalis and centralis (NRD/NRC). All analyzed neurons were of the switching type, i.e. they changed their firing rates to a higher or lower level when a threshold of the peripheral stimulation temperature was exceeded. When major parts of NRD or NRC were destroyed, the preoptic neurons no longer changed their firing rates after thermal stimulation, whereas transmission of noxious information in most cases was not impeded. Smaller lesions in NRD or NRC did not abolish the responses, but brought about essentially modified responses compared to those before the lesions. Lesions lateral to NRD or NRC had no effect. If the lesions were effective and the neurons could be observed for a longer period after the lesions, the response was restored in many cases. As the noxious response had often not been abolished and the lateral lesions were without any effect, it might be that the lesion effects and the restoration of responses involve short-term plasticity. However, temporary block of input to the neurons by unspecific effects cannot be excluded.

Action Potentials↗
PubMed1990

Consequences of partial body warming and cooling for the drives to local sweat rates.

Climatic chamber experiments were carried out on young, healthy male students. The ambient temperature was 36 degrees C, while local warming of one extremity was compensated for by heatflow-equivalent cooling of the ipsilateral extremity by on-line calculation of the heat balance. When warming the arm and cooling the leg (type 1 experiments), a slight, but not statistically significant increase of local sweat rates at these extremities was recorded. However, when cooling the arm and warming the leg (type 2 experiments), both corresponding local sweat rates declined. The divergent results are interpreted in terms of previously reported different central weighting factors for skin temperatures as determined: (1) by the weighting for the area, or (2) by the weighting for the area and the sensitivity of the local sweat rate to warming and cooling. This means that the central processing of the mean skin temperature may be different for cooling and warming and that in both cases values can be different from recorded (area weighted) skin temperature. Calculating this modified mean skin temperature, we conclude that type 1 experiments may be interpreted by the hypothesis that the central regulator has a status very near an overall heat-balance, whereas type 2 experiments, although also carried out at heat-balance, may be centrally evaluated as predominant cooling. In these experiments again the central drives representing the whole body thermal state seem to override both the direct and centrally mediated local drives.

Adult↗
PubMed1990

[Does induced Heinz body formation lead to the liberation of IgG receptors on the erythrocyte membrane?].

Immunofluorescence microscopical and biochemical studies led other authors to the conclusion that the formation of membrane-bound Heinz bodies at these parts of the plasmalemma of erythrocytes leads to clustering of band 3-protein and increased binding of IgG. We failed to detect immunocytochemically an increased IgG binding over phenylhydrazine induced membrane-bound Heinz bodies in otherwise intact erythrocytes using transmission electronmicroscopy and we also did not notice any clustering of intramembraneous particles over the numerous Heinz bodies by means of freeze etching. Especially at higher phenylhydrazine concentrations the erythrocytes show formation of vesicles and hemolysis accompanied by increased IgG binding and clustering of the intramembraneous particles. Photographs of such cells obtained by immunofluorescence microscopy are very similar to the pictures known from the literature.

Anion Exchange Protein 1, Erythrocyte↗