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Biomedical subjects

L Janský

Publications and source records attributed to L Janský.

At least 19 recordsLinked to original sources
PubMed2005

Thermal, cardiac and adrenergic responses to repeated local cooling.

The aim of this study was to ascertain whether repeated local cooling induces the same or different adaptational responses as repeated whole body cooling. Repeated cooling of the legs (immersion into 12 degrees C water up to the knees for 30 min, 20 times during 4 weeks = local cold adaptation - LCA) attenuated the initial increase in heart rate and blood pressure currently observed in control subjects immersed in cold water up to the knees. After LCA the initial skin temperature decrease tended to be lower, indicating reduced vasoconstriction. Heart rate and systolic blood pressure appeared to be generally lower during rest and during the time course of cooling in LCA humans, when compared to controls. All these changes seem to indicate attenuation of the sympathetic tone. In contrast, the sustained skin temperature in different areas of the body (finger, palm, forearm, thigh, chest) appeared to be generally lower in LCA subjects than in controls (except for temperatures on the forehead). Plasma levels of catecholamines (measured 20 and 40 min after the onset of cooling) were also not influenced by local cold adaptation. Locally cold adapted subjects, when exposed to whole body cold water immersion test, showed no change in the threshold temperature for induction of cold thermogenesis. This indicates that the hypothermic type of cold adaptation, typically occurring after systemic cold adaptation, does not appear after local cold adaptation of the intensity used. It is concluded that in humans the cold adaptation due to repeated local cooling of legs induces different physiological changes than systemic cold adaptation.

Adaptation, Physiological↗
PubMed2005

Steroids and thermogenesis.

Apart from thyroid hormones, as the main hormonal regulators of obligatory thermogenesis, and catecholamines, as major hormonal regulators of facultative thermogenesis, production of heat in homeotherms can also be influenced by steroids. Generally, hormones can influence heat production by regulating the activity of various enzymes of oxidative metabolism, by modulating membrane protein carriers and other membrane or nuclear protein factors. Proton carriers in the inner mitochondrial membrane, known as uncoupling proteins, play the key role in heat dissipation to the detriment of the formation of energy-rich phosphates. In this minireview we have focused on the effects of steroids and thyroid hormones on heat production in brown adipose tissues and in skeletal muscles, with particular respect to their effect on uncoupling protein expression. Apart from hormonal steroids, dehydroepiandrosterone, an important precursor in the metabolic pathway leading to hormonal steroids which possess many, mostly beneficial effects on human health, modulates metabolic pathways which may lead to increased heat production. Recent studies demonstrate that 7-oxo-dehydroepiandrosterone, one of its 7-oxygenated metabolites, is even more effective than dehydroepiandrosterone. Recent findings of various actions of these steroids support the view that they may also participate in modulating thermogenic effects.

Adrenal Cortex Hormones↗
PubMed2003

[Physiologic basis of human adaptation to cold].

Intermittent exposures to cold (15 head out immersions into 14 degrees C water, for 1 h, within 3 weeks) induce physiological changes leading to the restriction of heat loss from the body, due to hypothermia and vasoconstriction. These adaptational changes may save more than 25% of energy during 1 hour cold test. Insulative adaptation due to increased amount of the subcutaneous fat is less prominent. Winter swimmers show similar mechanisms of cold adaptationn as humans adapted by intermittent cold exposures in the laboratory. Additionally, winter swimmers exert a greater capacity of nonshivering thermogenesis than nonadapted controls. Thus, adaptation of humans to cold involves hypothermic, metabolic and insulative mechanisms. Time courses of development of individual mechanisms of adaptation differ. Intermittent local cold exposures (20 immersions of legs into 12 degrees C water, for 45 min, within 4 weeks lower sympathetic tone and induce redistribution of cardiac output, in order to ensure preferential warming of central parts of the body. Basal metabolism and cold induced thermogenesis are increased, but the threshold for induction of cold thermogenesis is not influenced. In contrast to changes induced by repeated whole body immersions, these changes may not ensure greater resistance to the cold stress.

Adaptation, Physiological↗
PubMed2003

Dynamics of cytokine production in human peripheral blood mononuclear cells stimulated by LPS or infected by Borrelia.

To specify the role of individual cytokines in the immune response to pyrogens, isolated and cultivated human peripheral blood mononuclear cells (PBMC) were used for the experiments. Different pyrogens (lipopolysaccharide from Escherichia coli - LPS and live Borrelia afzelii) were applied and the time course of changes in concentrations of different cytokines in the medium was followed using the ELISA method. It was found that nonstimulated human PBMC proliferate under in vitro conditions and produce IL-6, TNF-alpha, IL-10 and finally also IL-1beta. Productions of IL-12 and INF-gamma are not changed. Proliferation of PBMC is potentiated after incubation with LPS or live Borrelia. PBMC stimulated by LPS increase the net production (stimulated minus unstimulated) of IL-1beta and TNF-alpha significantly, while production of IL-6 was smaller. A delayed increase in the production of IL-10 was also observed. Productions of IL-12 and INF-gamma were not influenced. In contrast to LPS, stimulation of PBMC with live Borrelia, increases also the production of IL-12 and IFN-gamma, besides IL-1beta, TNF-alpha, IL-6 and IL-10. Productions of IL-1beta, IL-6 and TNFalpha increased immediately after incubation with both LPS and Borrelia, while productions of IL-12 and INF-gamma begin to increase 8 hours and production of IL-10 12 hours after stimulation. Data indicate that stimulation with different pyrogens may activate the cells of the immune cascade in a different way. Stimulation of BPMC by LPS seems to activate the initial steps of the immune response (macrophages and granulocytes) only, while infection with live Borrelia also stimulates the later phase of the immune response, probably due to effect of initially produced cytokines.

Adult↗
PubMed2003

Dynamics of cytokine production in human peripheral blood mononuclear cells stimulated by LPS or infected by Borrelia.

To specify the role of individual cytokines in the immune response to pyrogens, isolated and cultivated human peripheral blood mononuclear cells (PBMC) were used for the experiments. Different pyrogens (lipopolysaccharide from Escherichia coli - LPS and live Borrelia afzelii) were applied and the time course of changes in concentrations of different cytokines in the medium was followed using the ELISA method. It was found that nonstimulated human PBMC proliferate under in vitro conditions and produce IL-6, TNF-alpha, IL-10 and finally also IL-1 beta. Productions of IL-12 and INF-gamma are not changed. Proliferation of PBMC is potentiated after incubation with LPS or live Borrelia. PBMC stimulated by LPS increase the net production (stimulated minus unstimulated) of IL-1 beta and TNF-alpha significantly, while production of IL-6 was smaller. A delayed increase in the production of IL-10 was also observed. Productions of IL-12 and INF-gamma were not influenced. In contrast to LPS, stimulation of PBMC with live Borrelia, increases also the production of IL-12 and IFN-gamma, besides IL-1 beta, TNF-alpha, IL-6 and IL-10. Productions of IL-1 beta, IL-6 and TNF alpha increased immediately after incubation with both LPS and Borrelia, while productions of IL-12 and INF-gamma begin to increase 8 hours and production of IL-10 12 hours after stimulation. Data indicate that stimulation with different pyrogens may activate the cells of the immune cascade in a different way. Stimulation of BPMC by LPS seems to activate the initial steps of the immune response (macrophages and granulocytes) only, while infection with live Borrelia also stimulates the later phase of the immune response, probably due to effect of initially produced cytokines.

Adult↗
PubMed2000

Role of beta adrenoceptors in metabolic and cardiovascular responses of cold exposed humans.

Effect of a nonspecific beta adrenergic blocker - propranolol (40 mg per os) on thermoregulatory responses of cold water immersed (12.5 degrees C) humans was studied. Propranolol attenuates resting and cold induced thermogenesis, rectal temperature, heart rate and systolic blood pressure, but increases production of adrenaline and cortisol. Propranolol has no effect on the threshold body temperature for induction of cold thermogenesis and on central thermosensitivity. The following conclusions are drawn from consideration of the data presented: During the early phase of cooling (20 min after the start of cooling) the thermogenesis mediated by beta adrenergic receptors may cover about 80% of the total metabolic increase induced by cold. After about 30 min of cooling the relative proportion of beta adrenergic thermogenesis starts to decline, reaching 20% of the total cold thermogenesis at the end of cooling.It can be suggested from consideration of the data that, in man, the beta adrenergic receptors in the heart, blood vessels, adipocytes and muscles participate in mediating effect of cold on cardiovascular and thermoregulatory responses. Furthermore, these data imply that human adrenergic thermogenesis is produced outside of the brown adipose tissue. Thus, physiological mechanisms mediating adrenergic thermogenesis in humans appear to be different from those in small mammals.

Journal Article↗
PubMed2000

Human physiological responses to immersion into water of different temperatures.

To differentiate between the effect of cold and hydrostatic pressure on hormone and cardiovascular functions of man, a group of young men was examined during 1-h head-out immersions in water of different temperatures (32 degrees C, 20 degrees C and 14 degrees C). Immersion in water at 32 degrees C did not change rectal temperature and metabolic rate, but lowered heart rate (by 15%) and systolic and diastolic blood pressures (by 11 %, or 12%, respectively), compared to controls at ambient air temperature. Plasma renin activity, plasma cortisol and aldosterone concentrations were also lowered (by 46%, 34%, and 17%, respectively), while diuresis was increased by 107%. Immersion at 20 degrees C induced a similar decrease in plasma renin activity, heart rate and systolic and diastolic blood pressures as immersion at thermoneutrality, in spite of lowered rectal temperature and an increased metabolic rate by 93%. Plasma cortisol concentrations tended to decrease, while plasma aldosterone concentration was unchanged. Diuresis was increased by 89%. No significant differences in changes in diuresis, plasma renin activity and aldosterone concentration compared to subjects immersed to 32 degrees C were observed. Cold water immersion (14 degrees C) lowered rectal temperature and increased metabolic rate (by 350%), heart rate and systolic and diastolic blood pressure (by 5%, 7%, and 8%, respectively). Plasma noradrenaline and dopamine concentrations were increased by 530% and by 250% respectively, while diuresis increased by 163% (more than at 32 degrees C). Plasma aldosterone concentrations increased by 23%. Plasma renin activity was reduced as during immersion in water at the highest temperature. Cortisol concentrations tended to decrease. Plasma adrenaline concentrations remained unchanged. Changes in plasma renin activity were not related to changes in aldosterone concentrations. Immersion in water of different temperatures did not increase blood concentrations of cortisol. There was no correlation between changes in rectal temperature and changes in hormone production. Our data supported the hypothesis that physiological changes induced by water immersion are mediated by humoral control mechanisms, while responses induced by cold are mainly due to increased activity of the sympathetic nervous system.

Adult↗
PubMed1997

Hibernation triggers and cryogens: do they play a role in hibernation?

A survey of the literary evidence on cryogens and hibernation induction triggers is given and the results of experiments on the effect of hypothalamic or i.v. injections of opioids and plasma from hibernating European hamsters on body temperature control of rabbits are presented. Pharmacological doses of a delta opioid--DADLE (25 or 50 micrograms), when injected into the anterior hypothalamus, induce a small and short-lasting hypothermic effect in cold exposed rabbits, due to the downward shift of the temperature threshold for shivering. Lower doses (5 micrograms) are without effect, similarly as i.v. administrations (500 micrograms/kg) of this substance. Intrahypothalamic injections of met-enkephalin (0.1-1 microgram) induce a slight hyperthermia due to the shift of all thermoregulatory effectors to higher body temperatures. Intrahypothalamic injections of plasma from hibernating European hamsters do not influence the body temperature control in rabbits.

Animals↗
PubMed1996

Immune system of cold-exposed and cold-adapted humans.

The aim of this study was to investigate whether or not the human immune system can be activated by a noninfectious stimulus, thereby improving the physiological status of the individual. The effect of a single cold water immersion (14 degrees C for 1 h) on the immune system of athletic young men, monitored immediately after immersion, was minimal. With the continuation of the cold water immersions (three times a week for a duration of 6 weeks) a small, but significant, increase in the proportions of monocytes, lymphocytes with expressed IL2 receptors (CD25) and in plasma tumour necrosis factor alpha content was induced. An increase in the plasma concentrations of some acute phase proteins, such as haptoglobin and haemopexin, was also observed. After 6 weeks of repeated immersions a trend towards an increase in the plasma concentrations of IL6 and the amount of total T lymphocytes (CD3), T helper cells (CD4), T suppressor cells (CD8), activated T and B lymphocytes (HLA-DR) and a decrease in the plasma concentration of alpha 1-antitrypsin was observed. Concentrations of IL1 beta, neopterin, C-reactive protein, orosomucoid, ceruloplasmin, macroglobulin, immunoglobulins (IgG, IgM, IgA) and C3, C4 components of the complement, as well as the total number of erythrocytes, leucocytes, granulocytes and neutrophils showed no significant changes after the repeated cold water immersions. It was concluded that the stress-inducing noninfectious stimuli, such as repeated cold water immersions, which increased metabolic rate due to shivering the elevated blood concentrations of catecholamines, activated the immune system to a slight extent. The biological significance of the changes observed remains to be elucidated.

Adult↗
PubMed1996

Change in sympathetic activity, cardiovascular functions and plasma hormone concentrations due to cold water immersion in men.

The purpose of this study was to determine whether or not repeated short-term cold water immersions can induce a change in the activity of the sympathetic nervous system and, consequently, in cardiovascular functions in healthy young athletes. Changes in some plasma hormone concentrations were also followed. A single cold water immersion (head-out, at 14 degrees C, for 1 h) increased sympathetic nervous system activity, as evidenced by a four-fold increase (P < 0.05) in plasma noradrenaline concentration. Plasma adrenaline and dopamine concentrations were not increased significantly. Plasma renin-angiotensin activity was reduced by half (P < 0.05) during immersion but plasma aldosterone concentration was unchanged. Stimulation of the sympathetic nervous system during immersion did not induce significant changes in heart rate, but induced peripheral vasoconstriction (as judged from a decrease in skin temperature) and a small increase (by 10%) in systolic and diastolic blood pressures. No clear change in reactivity of the sympathetic nervous system was observed due to repeated cold water immersions (three times a week, for 6 weeks). Neither the plasma renin-angiotensin activity, aldosterone concentration nor cardiovascular parameters were significantly influenced by repeated cold water immersions. A lowered diastolic pressure and an increase in peripheral vasoconstriction were observed after cold acclimation, however. Evidently, the repeated cold stimuli were not sufficient to induce significant adaptational changes in sympathetic activity and hormone production.

Acclimatization↗
PubMed1996

Changes in thermal homeostasis in humans due to repeated cold water immersions.

The purpose of this study was to monitor changes in body and skin temperatures, heat production, subjective shivering, cold sensation and body fat content in humans after intermittent cold water immersion. Repeated exposures of young sportsmen to cold water (head out, 14 degrees C, 1 h, 3 times per week for 4-6 weeks) induced changes in regulation of thermal homeostasis. "Cold acclimated" subjects exhibited an hypothermic type of adaptation. Central and peripheral body temperatures at rest and during cold immersion were lowered. The metabolic response to cold was delayed and subjective shivering was attenuated. The observed hypothermia was due to the shift of the threshold for induction of cold thermogenesis to lower body temperatures. "Cold acclimated" subjects also showed a lowered cold sensation. Because of the observed physiological changes, about 20% of the total heat production was saved during one cold water immersion of "cold acclimated" subjects. Maximal aerobic and anaerobic performances were not altered. No change in the thermosensitivity of the body temperature controller, as assessed from the unchanged slope of the relation between the deep body temperature and total heat production, was observed. Changes in cold sensation and regulation of cold thermogenesis were noticed first after four cold water immersions and persisted for at least 2 weeks after termination of the adaptation procedure. A trend towards a small increase in the body fat content was also observed. This finding, as well as the increased vasoconstriction, evidenced by the lowered skin temperature, indicate that slight changes in body insulation may also occur after "cold acclimation" in humans.

Acclimatization↗
PubMed1995

Production of systemic and hypothalamic cytokines during the early phase of endotoxin fever.

Changes in concentrations of cytokines in plasma and in hypothalamic push-pull perfusates of guinea pigs were measured within the 1st hour after intramuscular injections of bacterial lipopolysaccharide (LPS; Escherichia coli, 20 micrograms/kg) or solvent (0.9% saline). In control animals injected with solvent, interleukin (IL)-1 and tumor necrosis factor alpha (TNF-alpha) were not detectable in plasma. Only IL-6 was present in picogram quantities. Within 45 min after injection of LPS, the concentrations of IL-1, TNF-alpha, and IL-6 increased in the plasma: by several orders of magnitude for TNF-alpha and about tenfold for IL-G. Picogram amounts of biologically active IL-1 were detected in plasma after injection of LPS. No steady state levels of systemic cytokines were reached during the experimental period. In hypothalamic perfusates of animals injected with the solvent, no IL-1 was detectable. TNF-alpha could be detected at higher concentrations than IL-6. IL-6 was detectable at tenfold lower concentrations than in the plasma. In animals injected with LPS, the hypothalamic concentration of IL-6 started to increase during the period 15-30 min and the concentrations of TNF-alpha during the period 30-45 min after LPS injection. The concentrations of IL-6 increased by 300-400% and did not exceed picogram values. No progressive increase of hypothalamic levels of these cytokines was observed during the time course of the experiment. The method used did not detect any changes in the amount of biologically active IL-1 in hypothalamic perfusates of LPS-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Changes in body fluids and minerals after cold adaptation].

To characterize fluid and ion shifts during 5-weeks cold adaptation, 6 nonadapted volunteers underwent cold acclimation programme (CAP), consisted of 1 h head-out immersion in water 14 +/- 1 degrees C 3 times a week. Blood samples were analyzed before/after the immersion and in the first and in the last week of CAP. Urine was collected for 10 h before, during, and after immersion for 4 h. Plasma volume (PV) decreased during first immersion (-18%) and less after CAP (-12). Blood volume reduction was 8.5% before and 5.2% after the CAP. Mean corpuscular volume was not changed either after the cold exposition or after the cold adaptation. The concentration of serum proteins increased by 12.1% after first immersion and by 8.1% after the CAP. The changes in serum concentration of Na+, K+ and Cl- before and after the CAP were not significant. Urine flow increased by 102% after first immersion, and by 165% after CAP. Urinary excretion of Na+ increased by 167% and 283%, excretion of K+ by 222% and 362% during first immersion and after CAP, respectively. Serum concentration of aldosterone increased nonsignificantly (+30%) during immersion before CAP and it did not changed after CAP. After the cold adaptation we observed the reduction of PV decrease, and increased diuresis with higher excretions of cations.

Acclimatization↗
PubMed1992

A discrete mode of the antipyretic action of AVP, alpha-MSH and ACTH.

The antipyretic effect of AVP, alpha-MSH and ACTH consists in lowering the thermoregulatory threshold and in shortening the time span of the fever. Thus, neuropeptides influence activity of hypothalamic neurones regulating body temperature. This was confirmed by recent experiments of Moravec (this volume) which indicate that spontaneous activity and thermosensitivity of neurones in hypothalamic slices can be influenced, by AVP. Why neuropeptides of different chemical structure such as AVT, on one hand, and alpha-MSH and ACTH, on the other hand, induce the same effect on thermoregulation remains to be elucidated.

Adrenocorticotropic Hormone↗
PubMed1992

The effect of PGE2 on activity and thermosensitivity of hypothalamic neurones in rat brain slices.

Using brain slices the effect of prostaglandin E2 (PGE2) on neurones from different locations of the rat hypothalamus was analysed. PGE2 (150 ng), when injected into the perfusion chamber, influences all hypothalamic neurones studied. The pattern of firing rate changes after PGE2 is variable, but the depressive effect predominates--72% of neurones decrease their firing rate in long-term experiments. PGE2 also lowers the thermosensitivity of warm sensitive neurones and increases the thermosensitivity of temperature insensitive neurones.

Animals↗