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Biomedical subjects

H Hensel

Publications and source records attributed to H Hensel.

At least 37 records · Page 2Linked to original sources
PubMed1979

Parameters of the static burst discharge of lingual cold receptors in the cat.

Thermal stimuli were applied to the upper surface of the tongue of the cat. The stimuli ranged from 40 degrees C to 10 degrees C and were changed in cold steps of 5 degrees C, each temperature lasting 2 min. Afferent impulses of single specific cold fibers from the lingual nerve were analysed by a computer program. About 90% of the fibers showed bursts under static conditions. The bursts began as doublets at the temperature of maximal average frequency. This temperature varied from 40 degrees C to 15 degrees C in different fibers, the average being 30 degrees C. The parameters burst period, burst duration, pause duration, intraburst interval and spikes per burst increased monotonically from 30 degrees C to 15 degrees C. The possible physiological significance of the burst pattern is discussed.

Animals↗
PubMed1978

Autonomic thermoregulation after intermittent cooling of the spinal cord and cold exposure in the rat.

1. O2 consumption, rectal and several skin temperatures were studied, at various ambient temperatures, in unanaesthetized rats that had been thermally stressed for an average of 290 h either by prolonged and intermittent cooling of the spinal cord or by prolonged and intermittent exposure to an ambient temperature which induced the same increase in O2 consumption as did the thermal stimulation of the spinal cord. 2. At all the test ambient temperatures, both groups of thermally stressed animals maintained a metabolic level higher than that of the controls. In the animals previously exposed to cold the extent by which the metabolic rate was greater than that of the control animals was independent of ambient temperature; in those previously subjected to cooling of the spinal cord, however, it increased as the ambient temperature was lowered. Rectal and average skin temperatures were essentially unaffected by the treatments. 3. It is concluded that prolonged and intermittent cooling of the spinal cord increases the gain of the temperature control system, whereas prolonged and intermittent cold exposure has no effect on it, and that these forms of thermal stimulation are therefore not equivalent.

Animals↗
PubMed1978

The central control of shivering and non-shivering thermogenesis in the rat.

1. To test whether the preoptic area controls only non-shivering and the spinal cord only shivering thermogenesis, ten rats were chronically implanted with a preoptic and a spinal cord thermode each. The following were then studied: (a) the effect of propranolol (8 mg/kg.hr) on the metabolic response to cooling the preoptic area, and the spinal cord, (b) the effect of exogenous noradrenaline (0.5 mg/kg) on the metabolic response to cooling the preoptic area, and the spinal cord, and (c) the effect of warming the preoptic area on the metabolic response to cooling the spinal cord, and vice versa. 2. Administration of propranolol inhibited the metabolic response to cooling each of the thermosensitive areas, but the response to cooling the preoptic area was more strongly inhibited than that to cooling the spinal cord. 3. Administration of exogenous noradrenaline did not prevent the metabolic response to cooling either the preoptic area or the spinal cord. 4. Warming the spinal cord completely inhibited the metabolic response to cooling the preoptic area, and warming the preoptic area fully inhibited the metabolic response to cooling the spinal cord. 5. It is concluded that exogenous noradrenaline underestimates the capacity for non-shivering thermogenesis, and that both thermosensitive areas can control both forms of thermogenesis, but that the preoptic area threshold of non-shivering thermogenesis is probably lower than that of shivering, while the spinal cord threshold of shivering is probably lower than that of non-shivering thermogenesis.

Animals↗
PubMed1977

The dynamic response of warm units in human skin nerves.

Electrophysiological recordings were made from 12 specific warm receptors in the sensory nerves of human hairy skin. In all cases examined, single warm fibers were spontaneously active at normal skin temperature from about 32 degrees C upwards, while touch, stretching, vibration or pricking the skin did not elicit any response within the receptive fields of warm units. Moderate warming of the skin using linear temperature rates from 0.5 degrees C/s to 1.5 degrees C/s caused a transient overshoot in the frequency of discharge with peak frequencies depending on the rate of change of temperature (dT/dt), the magnitude of thermal increment (deltaT) and the adapting temperature (TA). Cooling the skin caused a transient inhibition of discharge.

Adult↗
PubMed1977

Thermoregulatory behaviour after repetitive cooling of the preoptic area and of the spinal cord in the rat.

The thermoregulatory behaviour of 6 rats was studied during exposure to cold and warm ambient temperatures after either the preoptic area or the cervical spinal cord had been intermittently cooled for an average of 130 h. The precooled animals worked more for heat in cold environments and for cool air in a warm environment than the control animals. This behaviour, probably due to a decreased ability of the precooled animals to retain heat, suggested that the precooled animals were not fully adapted to cold. 1974) will learn to press a lever to modify their thermal environment, and this paper describes the thermoregulatory behaviour of rats after prolonged cooling of the preoptic area, and of the spinal cord. The thermoregulatory behaviour of cold exposed and cold adapted animals has already been studied in several species (Carlton and Marks, 1958; Laties and Weiss, 1960; Revusky, 1966; balwin and Ingram, 1967).

Adaptation, Physiological↗
PubMed1977

Response of rapidly and slowly adapting mechanoreceptors and vibratory sensitivity in human hairy skin.

Single unit activity was recorded percutaneously with microelectrodes from 38 rapidly adapting (RA) mechanoreceptors of the dorsal surface of the hand in 49 awake human subjects. Tuning characteristics were determined for 28 RA-fibers at various frequencies between 5 and 100 cps of sinusoidal mechanical stimulation. In separate experiments human thresholds of vibration perception were studied under comparable conditions. Several RA-mechanoreceptive fibers were broadly tuned, showing no clearly defined best frequency in the range between 5 and 20 cps. Other RA-fibers had a minimum of sensitivity between 20 and 40 cps. For either lower or higher frequencies, stronger stimuli were required to elicit one nerve impulse per stimulus cycle. These RA-receptors may be related to the perception of low frequency oscillation (flutter). They cannot account for human vibration sensitivity in the higher frequency range, since tuning of the receptors required considerably higher amplitudes than perception. Sixteen slowly adapting (SA) mechanoreceptors of Type I and II showed a frequency modulation in phase with low frequency mechanical oscillations of stimulus amplitudes far below human thresholds for perception of movement.

Action Potentials↗
PubMed1977

6-Plate element for recording of cutaneous blood flow.

A 6-plate element for isocaloric recording of cutaneous blood flow is described. Co-heating, penetrating depth and influence of a larger vessel simulated in a model were examined. The 6-plate element is less influenced by inhomogenous and anisotropic blood flow than the conventional 2-plate element and thus particularly suitable for routine measurements and repeated applications.

Humans↗
PubMed1977

The control of shivering and non-shivering thermogenesis in the rat.

1. The effect of intraperitoneal administration of propranolol (4, 8 and 12 mg/kg) on colonic temperature was studied in twelve rats during exposure to ambient temperatures of 30, 15 and 5 degrees C. 2. At 30 degrees C, propranolol had no effect on colonic temperature; at 15 and 5 degrees C, however, 4 mg propanolol/kg induced a fall in colonic temperature of about 0-8 degrees C, whereas 8 and 12 mg propanolol/kg induced a fall of about 1-5-2-0 degrees C. 3. Assuming that the temperature regulations system of the rat has a proportional controller and that the effect of propranolol was due to the blockade of non-shivering thermogenesis, the results are interpreted as showing that shivering is activated only when heat loss exceeds the capacity for non-shivering thermogenesis.

Animals↗
PubMed1977

[Reaction of local myocardial blood flow in non-anesthetized dogs and anesthetized cats to the oral and parenteral administration of a Crateagus fraction (oligomere procyanidines)].

Local blood flow in the myocardium of the left ventricle in unanesthetized dogs was measured by chronically implanted heat-conduction probes. Oral administration of a fraction of Crataegus (oligomere procyanidines) led to a significant rise in blood flow for several hours depending on the dose, the highest increase reaching an average value of about + 70% of the resting flow. In dogs regularly fed with this substance for a longer period of time, a rising tendency of the matutinal resting values of myocardial blood flow towards a maximum was seen. Intravenous application of oligomere procyanidines in anesthetized cats led to a dose-dependent increase in myocardial blood flow for several minutes and a slight decrease in arterial blood pressure.

Administration, Oral↗
PubMed1976

Differential thermosensitivity and electric prepolarization of the ampullae of Lorenzini.

In a single-fibre preparations the afferent discharges from prepolarized ampullae of Lorenzini responding to graded temperature steps were investigated in the dogfish (Scyliorhinus canicula). The transformation characteristics of the ampullary receptors, especially their differential thermosensitivity interfering with electrosensitivity, were analyzed. Prepolarization significantly influenced the dynamic component of differential thermosensitivity, while the static component remained practically unchanged. Hyperpolarization reduced positive and negative dynamic thermal responses; depolarization amplified them. Biological consequences of this bimodal interference for receptor transformation of superimposed thermal and electric stimuli and for decoding afferent ampullary impulse patterns are discussed.

Animals↗
PubMed1976

The interaction between cutaneous and spinal therman inputs in the control of oxygen consumption in the rat.

1. The effect of thermal stimulation of the spinal cord on the rate of oxygen consumption was studied in five unanaesthetized rats during exposure to various ambient temperatures. 2. In a warm environment, cooling the spinal cord had no effect on the rate of oxygen consumption but in thermoneutral and cold environments the rate of oxygen consumption increased proportionally to the intensity of spinal cooling. Heating the spinal cord decreased the level of oxygen consumption and, if intense enough, suppressed the thermoregulatory increase in metabolic rate. 3. It is concluded that, in the control of oxygen consumption in the rat, the afferent signals from thermal sensors in the spinal cord and skin are added.

Animals↗
PubMed1976

Nonshivering thermogenesis induced by repetitive hypothalamic cooling in the rat.

The effect of prolonged and repetitive cooling of the preoptic/anterior hypothalamic area on the sensitivity to the metabolic effect of noradrenaline and on the resistance to cold exposure was studied in the white rat. The preoptic area of 18 unanesthetized animals was cooled 9 h/day 5 days/wk, for a total of 80-150 h. One hour after a noradrenaline test injection (0.4 mg/kg), the experimental animals in which the preoptic area had been cooled to about 24 degrees C increased oxygen uptake by 81%, whereas those in which the preoptic area had been cooled to about 28 degrees C increased oxygen uptake by 48% (the control animals by only 37%). Despite their increased capacity for nonshivering thermogenesis, the experimental animals did not tolerate cold exposure (-10 degrees C) better than the controls. This development of nonshivering thermogenesis is thought to have been mediated by the hypothalamic temperature-sensitive neurons, and the possibility that it could explain the shift from shivering to nonshivering thermogenesis seen during adaptation to cold is discussed.

Animals↗
PubMed1976

Nonshivering thermogenesis induced by repetitive cooling of spinal cord in the rat.

The effect of prolonged and repetitive cooling of the spinal cord on the sensitivity to the metabolic effect of exogenous noradrenaline and on the resistance to cold exposure was studied in the white male rat. The spinal cord of 10 animals was cooled for an average of 90 h-9 h/day 5 days/wk - to a level that induced an increase in oxygen uptake of almost 70%. Oxygen consumption was then measured at 30 degrees C before and 1 h after a subcutaneous injection of noradrenaline (0.4 mg/kg). Following the noradrenaline injection, the experimental animals increased oxygen uptake by 71%, while the control ones increased it by only 33% (P less than 0.01). During exposure to -20 degrees C, the experimental animals, despite their increased capacity for nonshivering thermogenesis, did not maintain rectal temperature longer than the control ones, thus showing that other factors also play a significant role in cold adaptation in the rat.

Animals↗