Characteristics of responses of the sympatho-adrenal system to various types of cooling

Fast cooling involving the dynamic activity of the skin cold receptors seems to establish a condition for changes in catecholamine concentration at a lesser decrease of body temperature as compared with slow cooling.     

Aerobic fitness and sympatho-adrenal response to short-term psycho-emotional stress under field conditions

A possible relationship between aerobic fitness (AF), measured by maximal cycle ergometry (CE) and sympatho-adrenal response to acute, short lasting psycho-emotional stress was investigated by monitoring heart rate (f _c) and excretion of catecholamines. The activation of the sympatho-adrenal system was characterised by the noradrenaline : adrenaline ratio. A group of 11 healthy men [22.8 (SD 2.52) years] lived under identical environmental conditions; their mean maximal oxygen uptake ( ) was 47.1 (SD 3.9) ml · min^–1 · kg^–1. After the physiological and psychological laboratory tests had been completed thef _c of the subjects was monitored continuously during the guerilla slide and parachute jump by night, two emotionally stressful military tasks. Maximalf _c (f _{c, max}) attained during these events was 84.5% and 83% off _{c, max} during CE (f _{c, max, CE}), respectively. A significant relationship (r=–0.92,P<0.0002) betweenf _{c, max} reached during the stressful tasks and was found only for the guerilla slide, which was preceded by physical strain, sleep deprivation and energy deficit. One subject with some prior experience in parachuting showed the lowestf _c response and the lowest sympatho-adrenal activation in both events, independent of the degree of AF. In conclusion, AF was found to influence the sympatho-adrenal and fc response to acute, short-lasting emotional stress when the stressful event was aggravated by preceding physical strain, the magnitude of the stress response depending largely on individual experience and effective mechanisms for coping with specific stimuli.     

Dependence of response reaction of root voles to low-intensity irradiation on initial state of the tissue antioxidant system

There has been studied the response of antioxidant (AO) reaction of the tissue system of the root voles Microtus oeconomus Pall., whose parents belonged to the populations long inhabiting the Republic Komi regions with different degrees of radioactive contamination, on an additional irradiation at low doses. Differences have been revealed in the phospholipid content, activity of AO defense, intensity of processes of lipid peroxidation (LPO) in tissues of the offspring of voles caught in the control and contaminated regions. It has been revealed that direction and degree of changes in the offspring tissues after the additional action are determined by the parameter value in the non-irradiated animal group. Intensity of the LPO processes in liver and brain was leveled after the long low-intensity irradiation. The obtained data and analysis of literature indicate that at predicting effects of chronic action of low doses of a damaging factor both in experiment and in the natural habitation, it is necessary to take into account initial characteristics of biological objects.     

Dependence of response reaction of root voles to low-intensity irradiation on the initial state of the tissue antioxidant system

There has been studied the response of antioxidant (AO) reaction of the tissue system of the root voles Microtus oeconomus Pall. whose parents belonged to the populations long inhabiting the Republic Komi regions with different degrees of radioactive contamination on an additional radiation action at low doses. Differences have been revealed in the phospholipid content, activities of AO defense, intensities of processes of lipid peroxidation (LPO) in tissues of the vole offspring caught in the control and contaminated regions. It has been revealed that direction and degree of changes in the offspring tissues after the additional action are determined by the parameter value in the non-irradiated animal group. Intensity of the LPO processes in liver and brain was leveled after the long low-intensity irradiation. The obtained data and analysis of literature indicate that at predicting effects of chronic action of low doses of a damaging factor both in experiment and in the natural habitation, it is necessary to take into account initial characteristics of biological objects.     

Adrenergic innervation of pancreatic islets and modulation of insulin secretion by the sympatho-adrenal system

Summary Morphological changes in the adrenergic innervation of pancreatic islets after chemical sympathectomy by use of 6-hydroxydopamine and the influence of the sympatho-adrenal system on insulin secretion were investigated in the mouse and rat.Fluorescence histochemistry revealed a clear-cut reduction in the number of adrenergic nerve fibers in the pancreatic islets 2 days after administration of 6-hydroxydopamine; the reduction was more pronounced in the rat than in the mouse. In the rat, a partial regeneration was seen after 6 weeks. In the pancreas of the mouse, after administration of 6-hydroxydopamine, a severe damage of unmyelinated nerve fibers was revealed electron microscopically. However, no ultrastructural or immunohistochemical alterations could be demonstrated in the endocrine cells of the islets.6-Hydroxydopamine induced a depression of basal plasma insulin concentrations in mice and an elevation in rats. Adrenalectomy depressed basal plasma insulin levels in mice.The -adrenoceptor antagonist phentolamine enhanced insulin secretion in normal mice. The secretory response of insulin to phentolamine was diminished by chemical sympathectomy and almost abolished by adrenalectomy or the combination of chemical sympathectomy and adrenalectomy. Thus, the effect of phentolamine is probably mediated by liberated catecholamines.It is concluded that basal insulin secretion is partially regulated by the sympatho-adrenal system and that species differences exist in this respect. In addition, the results suggest that endogenous catecholamines have the ability to promote insulin secretion.     

The reaction of thymocytes to hypoxic stress

The reaction of thymocytes to hypoxic stress has been investigated according to indices of nucleic acid exchange. Acute and moderate, though long-term, hypoxia noticeably depresses DNA and RNA syntheses in rat thymocytes. Activation of nucleic acid repair synthesis during restoration of the organ takes place only if the hypoxic effect alternates with periods of normoxia. Under conditions of continuous prolonged hypoxia (high altitude), the adaptation is achieved by a decrease in thymocyte nucleic acid exchange. The role of thymocytes in the homeostasis-maintaining mechanisms, as the organism becomes adapted to hypoxia through different training conditions, is discussed.     

Effect of alpha-tocopherol on the adrenal reaction to cold stress

Adrenocortical function and the intensity of lipid peroxidation in the liver of animals fed the diet containing alpha-tocopherol (4 mg/day/rat for 7 days) and exposed to cold stress for 2, 5 and 20 hours were studied in vitro. It was established that alpha-tocopherol reduces the duration of the corticosterone secretion augmentation under cold stress but raises the sensitivity of the adrenals to ACTH. The action of the antioxidant correlated with its content in the tissues and inhibition of the cold-induced activation of lipid peroxidation.     

Activation of hypothalamic-pituitary-adrenocortical system as important gastroprotective component of stress reaction

The review is focused on the action of glucocorticoids released during activation of hypothalamic-pituitary-adrenocortical axis, on the susceptibility of gastric mucosa to injury. The data support the idea that glucocorticoids produced in response to acute stress or other ulcerogenic stimuli have a gastroprotective action but not ulcerogenic one as it has generally been considered for some decades. It has been shown that gastroprotective action of glucocorticoids may be mediated by multiple actions, including maintenance of glucose homeostasis, gastric mucosal blood flow, mucus production and attenuation of enhanced gastric motility and microvascular permeability. For maintenance of gastric mucosal integrity glucocorticoids may cooperate with other gastroprotective factors. Glucocorticoid hormones exert a pivotal role in the maintenance of gastric mucosal integrity in the case of impaired gastroprotective mechanisms provided by prostaglandins, nitric oxide and capsaicin-sensitive sensory neurons. These findings indicate that activation of hypothalamic-pituitary-adrenocortical system could be considered as a significant hormonal gastroprotective component of stress reaction and therefore glucocorticoid hormones are natural gastroprotective factors.     

Behavioral characteristics and stress reaction of the pituitary-adrenal system in prenatally stressed rats

Mothers' stress was shown to considerably diminish the orienting-studying activity of male rats in the dioestrus stage, as well as enhancement of anxiety. In prenatally stressed male rats, on the contraty, the anxiety diminished while their behaviour in the open field tests remained practically unaltered. The prenatal stress affected the stressor response of the hypophysis-adrenal systems in both sexes. The data obtained suggest that the mothers' stress affects both behaviour and stressor response in male as well as female rats.     

Picosecond kinetics of the initial photochemical electron-transfer reaction in bacterial photosynthetic reaction centers

The absorption changes that occur in reaction centers of the photosynthetic bacterium Rhodopseudomonas sphaeroides during the initial photochemical electron-transfer reaction have been examined. Measurements were made between 740 and 1300 nm at 295 and 80 K by using a pulse-probe technique with 610-nm, 0.8-ps flashes. An excited singlet state of the bacteriochlorophyll dimer P* was found to give rise to stimulated emission with a spectrum similar to that determined previously for fluorescence from reaction centers. The stimulated emission was used to follow the decay of P*; its lifetime was 4.1 +/- 0.2 ps at 295 K and 2.2 +/- 0.1 ps at 80 K. Within the experimental uncertainty, the absorption changes associated with the formation of a bacteriopheophytin anion, Bph-, develop in concert with the decay of P* at both temperatures, as does the absorption increase near 1250 nm due to the formation of the cation of P, P+. No evidence was found for the formation of a bacteriochlorophyll anion, Bchl-, prior to the formation of Bph-. This is surprising, because in the crystal structure of the Rhodopseudomonas viridis reaction center [Deisenhofer, J., Epp, O., Miki, K., Huber, R., & Michel, H. (1984) J. Mol. Biol. 180, 385-398] a Bchl is located approximately in between P and the Bph. It is possible that Bchl- (or Bchl+) is formed but, due to kinetic or thermodynamic constraints, is never present at a sufficient concentration for us to observe. Alternatively, a virtual charge-transfer state, such as P+Bchl-Bph or PBchl+Bph-, could serve to lower the energy barrier for direct electron transfer between P* and the Bph.     

Enzymes of adenosine metabolism in lymphocytes and the functional state of the sympatho-adrenal system in tumor processes

A correlation between reactions of the sympathoadrenal system and the activity of adenosine transformation enzymes in lymphocytes is demonstrated in the dynamics of metastatic Lewis carcinoma development in C57Bl mice. In the period when metastases arise a decrease in the adenosine deaminase activity in lymphoid cells of the thymus and spleen is accompanied by drop in the content of DOPA, noradrenalin and adrenalin in adrenals. At the late stages of the tumour process a decrease in the amount of these compounds in adrenals is accompanied by the diminution of the adenosine deaminase activity and by an increase in the 5'-nucleotidase activity in the thymus. Contrary changes are observed in spleen lymphocytes. The revealed disturbances may stimulate to a considerable extent the appearance and growth of metastases.     

ER stress is the initial response to polyglutamine toxicity in PC12 cells

Persistent endoplasmic reticulum (ER) stress and impairment of the ubiquitin-proteasome system (UPS) cause neuronal cell death. However, the relationship between these two phenomena remains controversial. In our current study, we have utilized an expanded polyglutamine fusion protein (polyQ81) expression system in PC12 cells to further examine the involvement of ER stress and UPS impairment in cell death. The expression of polyQ81-induced ER stress and cell death. PolyQ81 also induced the activation of c-Jun N-terminal kinase (JNK) and caspase-3 and an increase in polyubiquitin immunoreactivity, suggesting UPS impairment. ER stress was induced prior to the accumulation of polyubiquitinated proteins. Low doses of lactacystin had almost similar effects on cell viability and on the activation of JNK and caspase-3 between normal cells and polyQ81-expressing cells. These results suggest that ER stress mediates polyglutamine toxicity prior to UPS impairment during the initial stages of these toxic effects.     

Influence of the incubation temperature on the reaction of oligotrophic bacteria to stress

Representatives of five genera of psychroactive oligotrophic bacteria, Arcocella, Renobacter, Spirosoma, Caulobacter, and Methylobacterium, were for the first time shown to be capable of growing at a negative temperature (–2°C). Long-term cultivation (for 116 days) at a low temperature under limitation by the carbon source is stressful for oligotrophic bacteria and leads to the death of a part of the cell population. The number of viable cells of Caulobacter crescentus decreased by two to three orders of magnitude. Over the studied period of time, Renobacter vacuolatum cells retained viability at a low temperature, whereas, at room temperature, the titer of colony-forming cells decreased by two orders of magnitude under starvation stress.Translated from Mikrobiologiya, Vol. 73, No. 6, 2004, pp. 758–762.Original Russian Text Copyright © 2004 by Slabova, Nikitin.