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Biomedical subjects

J Werner

Publications and source records attributed to J Werner.

At least 163 records · Page 9Linked to original sources
PubMed1986

Thermoregulatory responses to cold during a 7-week acclimatization process in rabbits.

A group of six rabbits reared at +20 degrees C ambient temperature was adapted to moderate cold by housing for seven weeks at +10 degrees C. Rectal and skin temperatures, metabolic heat production and respiratory evaporative heat loss were recorded continuously over 1 h for each animal on 3 days per week in the climatic chamber. There was no significant change either of rectal or of ear skin temperature during the acclimatization process. On the other hand, metabolic heat production was progressively reduced (20% in the 7th week). Slight changes of mean skin temperature and respiratory evaporative heat loss could not account for compensation. Therefore it must be concluded that both adaptive improvement of peripheral insulation and reduction of heat production were achieved during the acclimatization process. Both processes together ensure that deviations of core temperature are minimal. The possible origin of the functional adaptive effects is discussed. The results are in full agreement both with former neurophysiological results and with system-theoretical considerations of adaptive processes.

Acclimatization↗
PubMed1986

Dynamics of endotoxin fever in the rabbit.

To analyze the dynamic properties of body temperature and effector mechanisms during endotoxin fever, both experimental and mathematical procedures were applied. Experiments were carried out on rabbits in a climatic chamber at various ambient temperatures. Salmonella typhosa endotoxin (0.1 microgram/kg) was injected into an ear vein. A biphasic core temperature increase evoked by different effector mechanisms depending on ambient temperature was observed. A mathematical model based on experimental results with nonfebrile rabbits predicts the effector behavior at all ambient temperatures. From a comparison of experimental results with the model prediction, it is concluded that the increase of core temperature during fever is essentially caused by a dynamic shift of the controller characteristics. The effect of the pyrogen may be simulated by a resultant fever-controlling signal that is biphasic but increases more steeply than does core temperature. The analysis suggests that the three possible fever-driving effectors, metabolism, ear blood flow, and respiratory evaporative heat loss, should be controlled by the same resultant signal, although the time courses of the effectors and of core temperature vary distinctly at different air temperatures. The model uses an additive controller structure.

Animals↗
PubMed1985

Heat balance of the human body: influence of variations of locally distributed parameters.

Human body temperature control is characterized by a local dependence of system variables and parameters. Essential properties regarding inhomogeneity of the passive system have been investigated using mathematical methods. The general diffusion-equation has been solved using implicit finite difference methods with nonlinear boundary conditions. In order to allow comparison with experimental results, a simple ideal controller has been defined. On the basis of an inhomogeneous cylinder model with four concentric layers, influences of variations due to differences between tissues and individuals or measurements of parameters such as basal metabolism and conductivity have been studied. Stationary temperature profiles calculated for homogeneous and inhomogeneous conditions have been compared. Finally, the influence of blood flow has been discussed, as well as the stationary behaviour of profiles due to blood flow and blood flow control. The change of sign of curvature of temperature profile is possible only if blood flow mechanisms and the local distribution of metabolism are taken into account.

Air↗
PubMed1985

Effects of medial midbrain lesions on thermoresponsive neurons in the thalamus of the rat.

This study is concerned with midbrain influences on the transmission of thermal information from the rat's scrotal skin to the specific thalamus. Single unit recordings were made from neurons in the ventrobasal thalamus which responded to scrotal warming. After a thermoresponsive neuron had been identified, a small area of the medial midbrain was electrolytically lesioned and the thermal response of the unit was tested again. Lesioning the midbrain raphe nuclei, centralis or dorsalis, or parts of the central grey matter was always followed by a complete loss of thermal responsivity. Lesions which destroyed the rostral end of the nucleus raphe centralis together with parts of the adjacent reticular formation had no effect on thalamic discharge rates. It is concluded that the midbrain raphe nuclei and the central grey matter form an essential part of the extralemniscal pathways which transmit peripheral thermal information to the rat's thalamus.

Afferent Pathways↗
PubMed1985

The significance of nucleus raphe dorsalis and centralis for thermoafferent signal transmission to the preoptic area of the rat.

Neuronal spike-trains were recorded extracellularly within the preoptic area, which is generally considered the center of information processing for thermoregulation. The neuronal responses were tested by thermal stimulation of the scrotal and abdominal skin of the rat. After a neuron had been identified as warm responsive, electrical stimulation and/or lesion were applied in medial midbrain to test the influence on the preoptic neurons. Post-stimulus-histograms were determined by using 600 single shocks. Furthermore a small area of the medial midbrain was electrolytically lesioned and the thermal response of the neuron was tested again. All lesion, stimulation and recording sites were examined histologically. Electrical stimulation of either nucleus raphe dorsalis or centralis influenced the responsiveness of the recorded preoptic neurons. The post-stimulus-histograms predominantly reveal polysynaptic ascending pathways. Lesion of either nucleus raphe dorsalis or centralis abolished the responsiveness of the recorded preoptic neurons. Lesions lateral to these nuclei were ineffective. By this it is concluded that both nucleus raphe dorsalis and centralis are essentially involved in the thermal signal transmission to the preoptic area.

Afferent Pathways↗
PubMed1985

Dynamics and topography of human temperature regulation in response to thermal and work load.

Climatic chamber experiments were carried out with male subjects who were submitted to various rapid temperature changes. All experiments were performed first with the subjects at rest and later at work on a bicycle ergometer. The aims of the study were to obtain quantitative data enabling to determine effects of abrupt thermal load, abrupt work load, and combined load on the topography and the dynamics of temperatures and effectors, and to answer the question whether the effects of combined load may be computed by a linear superposition of pure thermal plus pure work load. Skin temperatures generally respond more directly to abrupt changes of thermal than of work load. This is in contrast to the dynamic behaviour of central temperatures which moreover exhibit the interesting effect of a transient paradoxical response both to the onset of work and of thermal load. Time constants of the dynamics of metabolic heat production are high in response to changes of thermal load as compared to the time constants at the onset and end of work. Generally the time constants of skin temperatures are shorter at rest than at work. Temperature topography changes only to a small extent in exercising subjects. The central temperature increase to combined thermal and work load is not significantly different from the added amount of temperature increases due to pure thermal and to pure work load. This suggests a quasi-linear superposition of both thermal effects and confirms, in accordance with further evidence of this and former studies, the hypothesis that work load does not interfere non-linearly with the regulatory processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Differential heating of trunk and extremities. Effects on thermoregulation mechanisms.

Experiments in which the whole human body was heated or cooled are compared with others in which one extremity (arm or leg) was simultaneously cooled or heated. With a warm load on the rest of the body resulting in general sweating, a cold load on one extremity did not evoke local shivering; with general body cooling, heating one limb did not stop the shivering. Skin temperatures of the other parts of the body were not influenced by warming or cooling one extremity. Evaporative heat loss was influenced by local, mean skin and core temperature, whereas shivering did not depend on local temperature, and vasomotor control seemed to be controlled predominantly by central temperatures. A cold load on an extremity during whole body heating in most cases induced an oscillatory behaviour of core temperature and of the evaporative heat loss from the body and the extremity. It is assumed that local, mean skin and core temperatures influence the three autonomous effector systems to very different degree.

Biomechanical Phenomena↗
PubMed1984

Properties of central control of body temperature in the rabbit.

The structure of the central temperature controller in rabbits has been analysed. On the one hand, experiments were carried out to obtain the necessary data for system analysis; on the other hand, a mathematical model of the passive system was developed which describes the thermal characteristics of the body in accordance with the experimental results. In applying the model, different controller equations for the effector mechanisms involved were tested to fit the experimental data best. They are compared with already existing models of metabolic control. In addition, mechanisms of the effector coordination are discussed. It is shown that the three effectors make use of a similar controller structure that feeds core temperature as well as skin temperature back into the controller. The system is insensitive to variations of the controller gains, whereas a slight change in the controller reference temperature causes significant changes of the controlled core temperature. Furthermore it is shown that any mutual effector blockings are dispensible.

Animals↗
PubMed1984

Thermoafferent signal processing in rats: an electrophysiological analysis of midbrain influences on thermoresponsive neurons in the ventrobasal thalamus.

The influence of electrical midbrain stimulation on thalamic cells which respond to scrotal skin warming with steep increases in firing rate was studied in anaesthetized rats. Square-wave stimuli of 200 microseconds duration and 30-250 microA intensity at 15 Hz were applied in trains lasting about 1 min. At low scrotal temperatures stimulation of the nucleus raphe dorsalis, the adjacent central grey or the median raphe nucleus was nearly always followed by a rise in thalamic activity. Inhibition occurred only in 4 of 75 experiments. Often midbrain stimulation caused neuronal responses similar to those following scrotal warming. Single stimulation experiments and the combination of electrical stimulation and electrolytic lesions indicated local interactions between excitatory and inhibitory neuronal networks in midbrain. Poststimulus latencies revealed polysynaptic midbrain/thalamic connections. Direct projections with no more than a few synaptic interruptions were seen in about 10% of the experiments. It is concluded that medial midbrain neurons influence the transmission of peripheral thermal information to the specific thalamus and contribute to the typical switching form of thalamic responses to scrotal warming.

Afferent Pathways↗
PubMed1984

[The quadrate pronator muscle--a morphological and functional analysis].

Based upon the findings of dissections and of histological investigations, the m. pronator quadratus was found to be composed of 2 heads. In the majority of the cases an oblique superficial head entirely covered a deep head, whose fasciculi were oblique from the ulnar origin to the distal volar surface of the radius. The fibers of both heads were arranged obliquely to the axis of rotation. From this both heads by contraction will develop a rotatory and a shunt force, the shunt components acting antagonistically. The superficial head is the rotator for pronation, whereas the deep head is well located for maintenance of transverse forces at the distal radioulnar joint. Moreover, the two heads insert into the capsule of the articulatio radioulnaris distalis.

Adult↗
PubMed1983

Correlation between immunogenetic markers and "in vivo" response to the german hepatitis B vaccine.

The antibody response to the German HB-vaccine in 100 volunteers was investigated with respect to the individual immunogenetic markers. After 3 doses of vaccine at days 0, 28 and 140, 7 serum samples were collected at days 0, 28, 56, 98, 140, 154, 168 and anti-HBs concentrations determined. Seroconversion was 96% after the 3rd injection with a mean antibody concentration of 947 mIU/ml. On the basis of antibody values on day 154 four groups of responders could be observed. Nonresponders, late and low responders, early and high responders and mixed type high responders with an early peak (IgM) between days 28 and 42. Assigning immunogenetic markers of the HLA-system and immunoglobulin G-allotype system to the different groups yielded evidence that HLA-DR3 is associated with higher antibody production towards HBsAg.

Adolescent↗
PubMed1982

[The performance of ECG telemetry in the analysis of rhythm disorders].

630 outpatients and inpatients under rest as well as under conditions of physical loads and psychic stress were examined with the help of a radiobiotelemetry device of own construction, which corresponds to a combination of traditional radiotelemetry and tape storage. In 81.4% of the patients with hitherto unclarified disturbances of the cardiac rhythm telemetry obtained their qualitative clarification. In 50% of all cases with classical angina pectoris symptomatology the ischaemic heart disease was verified by determination of the usual criterias of ECG at the telemetry stripe. Of these 50% only 7 patients had no arrhythmia. In 57.5% of all examined patients with pacemakers of permanent frequency we could prove a considerable parasystoly in load by telemetry. 9 patients with R-demand-pacemakers became evident by triggering defects in load. During the psychoanalytic examination we registered extrasystoles in 25%, apart from this once developed a pancardiac asystolism. The radiobiotelemetry is a valuable completion of the well-known methods of load.

Arrhythmias, Cardiac↗