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.     

Tissue transglutaminase 2 promotes apoptosis of rat neonatal cardiomyocytes under oxidative stress

The role of tissue transglutaminase 2 (TG2) in cardiac myocyte apoptosis under oxidative stress induced by ischemic injury remains unclear. Here, we investigated the effects of TG2 on apoptosis of cardiomyocytes under oxidative stress. Ectopic expression of TG2 increased caspase-3 activity and calcium overload in cardiomyocytes. Expression levels of TG2 were significantly increased in H(2)O(2)-treated cardiomyocytes. Caspase-3 activity assay demonstrated its considerable correlation with TG2 expression, which supported that caspase-3 inhibitor inhibited the apoptosis induced by the ectopic overexpression of TG2. In addition, the other apoptotic signals, such as caspase-8, cytochrome c, and Bax, were increased dependent with TG2 expression in H(2)O(2)-treated cardiomyocytes. These results indicated that apoptotic signals had a positive correlation with TG2 expression. The decreased expression of phospholipase C (PLC)-δ1 and phospho-PKC in H(2)O(2)-treated cardiomyocytes were rescued by TG2 silencing. Together, our data strongly suggest that oxidative stress up-regulates TG2 expression in cardiomyocytes, leading to apoptosis.     

Tissue transglutaminase 2 promotes apoptosis of rat neonatal cardiomyocytes under oxidative stress

The role of tissue transglutaminase 2 (TG2) in cardiac myocyte apoptosis under oxidative stress induced by ischemic injury remains unclear. Here, we investigated the effects of TG2 on apoptosis of cardiomyocytes under oxidative stress. Ectopic expression of TG2 increased caspase-3 activity and calcium overload in cardiomyocytes. Expression levels of TG2 were significantly increased in H₂O₂-treated cardiomyocytes. Caspase-3 activity assay demonstrated its considerable correlation with TG2 expression, which supported that caspase-3 inhibitor inhibited the apoptosis induced by the ectopic overexpression of TG2. In addition, the other apoptotic signals, such as caspase-8, cytochrome c, and Bax, were increased dependent with TG2 expression in H₂O₂-treated cardiomyocytes. These results indicated that apoptotic signals had a positive correlation with TG2 expression. The decreased expression of phospholipase C (PLC)-δ1 and phospho-PKC in H₂O₂-treated cardiomyocytes were rescued by TG2 silencing. Together, our data strongly suggest that oxidative stress up-regulates TG2 expression in cardiomyocytes, leading to apoptosis.     

Functional state of adenylyl cyclase signaling system in rat testis and ovary under conditions of fasting

Sensitivity of the adenylyl cyclase signaling system (ACSS) to polypeptide hormones and biogenic amines is studied in testes and ovaries of rats after the 2- and 4-day fasting as compared with control animals. In tissues of the fasted rats there is shown a decrease in the basal activity of adenylyl cyclase (AC) and of the basal level of the GTP binding of heterotrimeric G proteins. An increase in duration of fasting from 2 to 4 days led to intensification of these changes. In the fasted rats, the AC-stimulating effects of chorionic gonadotropin, PACAP-38, and isoproterenol, realized via G protein of stimulatory type are enhanced, whereas the inhibitory effects of somatostatin on the AC activity realized via G protein of the inhibitory type are reduced. In testes of the fasted rats the stimulating effect of serotonin on AC via both types of G proteins increased, whereas the inhibitory effects of the hormone decreased. Thus, under conditions of fasting, in rat testes and ovaries the ACSS sensitivity to regulatory effects of hormones is changing: their stimulatory effects are increased, while its inhibitory effects, on the contrary, are decreased. We suggest that these changes are one of the key mechanisms of adaptation of organism to deficiency of nutritional resources to be aimed at intensifying the tissues catabolic processes, preferably lypolysis.     

Ultrastructure and metabolism of cardiomyocytes under experimental stress

Morphogenesis of adaptational, disadaptational, and alterative changes affected structure and function of all live-supporting systems (contractile elements, macroergic phosphate synthesis, intracellular regeneration, and electrolyte exchange control) was studied in cardiomyocytes under experimental chronic stress using ultrastructural and cytochemical methods.     

The role of taurine in adaptation of visceral systems under psycho-emotional stress in rats

In the recent years, an identification of regulatory mechanisms underlying the general adaptation syndrome as an organism’s response to drastic emotional stress-evoking environmental changes is gaining in its importance. The ability to control over visceral functions plays a crucial role in stress reactions due to a threat of neurodynamic imbalance in sympathetic-parasympathetic relationships with the heart as their most vulnerable element. Fast stress adaptation promotes restoration not only of the sympathetic-parasympathetic balance, but also of energy metabolism. Taurine is one of the major regulatory molecules that activate metabolic processes. The present work addresses the following issues: (1) the descending influence of the paraventricular nucleus (PVN) on neural reaction of the solitary tract nucleus (STN), which is the first link in the visceral sensitivity pathway, (2) the mechanisms of central control over visceral reactions as investigated by mathematical modelling and analysis of the heart rate variability (HRV), and (3) morphofunctional changes in brain structures, integrating and regulating the visceral sphere (hypothalamic PVN, amygdala), under psycho-emotional stress with and without intraperitoneal injection of taurine (50 mg/kg). Acute and semichronic experiments were conducted on white nonlinear rats under 5-h immobilization stress. An extremely strong centralization of the vegetative HRV parameters (HR, VBI, SSTI) was revealed, with these parameters normalized on days 7 and 14 post taurine injection. An interaction and interdependence of the central regulatory mechanisms of cardiovascular reactions as well as a considerable protective role of taurine, promoting fast restoration of adaptive properties of the central and peripheral visceral sensitivity components under the development of long-term psycho-emotional stress, were shown.     

Barley leaf antioxidant system under photooxidative stress induced by Rose Bengal

The effects of photooxidative stress induced in green barley (Hordeum vulgare L.) leaves by xanthene dye Rose Bengal (RB) on the content of low-molecular antioxidants and the activity of antioxidant enzymes were studied. During illumination (24 h, 160 mol quanta/(m² s)) of the leaves preincubated in darkness on 10 and 100 M RB, ROS accumulated, and their level increased along with RB concentration and duration of illumination. Under these conditions, the content of reduced ascorbate and reduced glutathione (GSH) increased, the level of -and -tocopherol decreased, and the activity of ascorbate peroxidase, the enzyme participating in H₂O₂ degradation, increased. At the same time, the activity of catalase, also participating in H₂O₂ detoxification, decreased, which may be due to the enzyme inhibition during the photochemical stress. In the illuminated treated leaves, superoxide dismutase (SOD), the enzyme destroying the superoxide anion radicals, was activated. The cytosolic SOD isoform was the first to be activated and chloroplastic isoforms followed. It is supposed that photodynamic processes induced by RB in barley leaves are initiated in the cytosol. The activity of glutathione reductase, participating in glutathione oxidized form reduction, did not change at first and grew only after continuous illumination. Thus, the increase in the GSH level, which we have revealed on the initial stage of photooxidative stress development, was due to its synthesis de novo. In addition, under photooxidative stress induced by the sensitizer RB, the level of tocopherol reduced, whereas the amount of other low-molecular antioxidants increased. The exhaustion of the tocopherol pool, in its turn, could limit the resistance of barley leaves to the photooxidative stress.     

Experimental hyperthyroidism-induced oxidative stress and impairment of antioxidant defence system in rat testis

Short-term hyperthyroidism, induced by daily administration of T3 (20 microg/100g body weight) for one, three, and five days consecutively, modulates oxidative stress and antioxidant defence parameters in mitochondrial and postmitochondrial fractions of testis in adult rats. Alteration in antioxidant defences along with oxidative stress parameters in testis by thyroid hormone was found to be associated with a decline in the number of sperms and disturbances in histoarchitecture of seminiferous tubules in the testes; the results indicated that induced hyperthyroid state altered testicular physiology by influencing antioxidant defence system of testes.     

Microcystin-LR regulates circadian clock and antioxidant gene expression in cultured rat cardiomyocytes

Background

Microcystins are waterborne environmental toxins that induce oxidative stress and cause injuries in the heart. On the other hand, many physiological processes, including antioxidant defense, are under precise control by the mammalian circadian clock.

Results

In the present study, we evaluated the effect of microcystin-LR (MC-LR) on the rhythmic expression patterns of circadian and antioxidant genes in rat cardiomyocytes using the serum shock technique. We found that a non-toxic dose (10 μm) of MC-LR decreased the amplitudes of rhythmic patterns of clock genes, while it increased the expression levels of antioxidant genes.

Conclusions

Our results indicate an influence of MC-LR on the circadian clock system and clock-controlled antioxidant genes, which will shed some light on the explanation of heart toxicity induced by MC-LR from the viewpoint of chronobiology.

     

Regulation of PUMA induced by mechanical stress in rat cardiomyocytes

Background

PUMA (p53-up-regulated modulator of apoptosis), an apoptosis regulated gene, increased during endoplasmic reticulum stress. However, the expression of PUMA in cardiomyocytes under mechanical stress is little known. We aimed to investigate the regulation mechanism of PUMA expression and apoptosis induced by mechanical stress in cardiomyocytes.

Methods

Aorta-caval (AV) shunt was performed in adult Wistar rats to induce volume overload. Rat neonatal cardiomyocytes were stretched by vacuum to 20% of maximum elongation at 60 cycles/min.

Results

PUMA protein and mRNA were up-regulated in the shunt group as compared with sham group. The increased PUMA protein expression and apoptosis induced by shunt was reversed by treatment with atorvastatin at 30 mg/kg/ day orally for 7 days. TUNEL assay showed that treatment with atorvastatin inhibited the apoptosis induced by volume overload. Cyclic stretch significantly enhanced PUMA protein and gene expression. Addition of c-jun N-terminal kinase (JNK) inhibitor SP600125, JNK small interfering RNA (siRNA) and interferon-γ (INF-γ) antibody 30 min before stretch reduced the induction of PUMA protein. Gel shift assay demonstrated that stretch increased the DNA binding activity of interferon regulatory factor-1. Stretch increased, while PUMA-Mut plasmid, SP600125 and INF-γ antibody abolished the PUMA promoter activity induced by stretch. PUMA mediated apoptosis induced by stretch was reversed by PUMA siRNA and atorvastatin.

Conclusions

Mechanical stress enhanced apoptosis and PUMA expression in cardiomyocytes. Treatment with atorvastatin reversed both PUMA expression and apoptosis induced by mechanical stress in cardiomyocytes.     

Energy dissipation and antioxidant enzyme system protect photosystem II of sweet sorghum under drought stress

The effect of drought stress on energy dissipation and antioxidant enzyme system in two sweet sorghum inbred lines (M-81E and Roma) was investigated. Results showed that the germination indicator increased more in M-81E than that in Roma under rehydration. Under drought stress, both the maximal photochemical efficiency of PSII (F_v/F_m) and oxidoreductive activity (ΔI/I₀) of Roma decreased more than those in M-81E. Relative to Fv/Fm, the ΔI/I0 decreased markedly, which indicated that PSI was more sensitive to drought stress than PSII. Increases in the reduction state of Q_A (1–q_p), nonphotochemical quenching (NPQ) and minimal fluorescence yield of the dark-adapted state (F₀) were greater in Roma than those in M-81E; meanwhile, the H₂O₂ content was lower in M-81E than that in Roma. Our results suggested that the photoinhibition might be related to the accumulation of reactive oxygen species (ROS). The antioxidant enzyme system and energy dissipation of M-81E could respectively increase drought tolerance by eliminating ROS and excess energy more efficiently than that of Roma.     

Calcineurin suppresses AMPK-dependent cytoprotective autophagy in cardiomyocytes under oxidative stress

Calcineurin signalling plays a critical role in the pathogenesis of many cardiovascular diseases. Calcineurin has been proven to affect a series of signalling pathways and to exert a proapoptotic effect in cardiomyocytes. However, whether it is able to regulate autophagy remains largely unknown. Here, we report that prolonged oxidative stress-induced activation of calcineurin contributes to the attenuation of adaptive AMP-activated protein kinase (AMPK) signalling and inhibits autophagy in cardiomyocytes. Primary cardiomyocytes exhibited rapid formation of autophagosomes, microtubule-associated protein 1 light chain 3 (LC3) expression and phosphorylation of AMPK in response to hydrogen peroxide (H₂O₂) treatment. However, prolonged (12 h) H₂O₂ treatment attenuated these effects and was accompanied by a significant increase in calcineurin activity and apoptosis. Inhibition of calcineurin by FK506 restored AMPK function and LC3 expression, and decreased the extent of apoptosis caused by prolonged oxidative stress. In contrast, overexpression of the constitutively active form of calcineurin markedly attenuated the increase in LC3 induced by short-term (3 h) H₂O₂ treatment and sensitised cells to apoptosis. In addition, FK506 failed to induce autophagy and alleviate apoptosis in cardiomyocytes expressing a kinase-dead K45R AMPK mutant. Furthermore, inhibition of autophagy by 3-methylanine (3-MA) or by knockdown of the essential autophagy-related gene ATG7 abrogated the protective effect of FK506. These findings suggest a novel role of calcineurin in suppressing adaptive autophagy during oxidative stress by downregulating the AMPK signalling pathway. The results also provide insight into how altered calcineurin and autophagic signalling is integrated to control cell survival during oxidative stress and may guide strategies to prevent cardiac oxidative damage.     

Oxidative stress enhances phosphorylation of p53 in neonatal rat cardiomyocytes

p53 is an important regulator of cell growth and apoptosis and its activity is regulated by phosphorylation. Accordingly, in neonatal rat cardiomyocytes we examined the involvement of p53 in H₂O₂-induced apoptosis. Treatment with 50–100 μM H₂O₂ markedly induced apoptosis in cardiomyocytes, as assessed by gel electrophoresis of genomic DNA. To examine whether H₂O₂ increases p53 phosphorylation in cardiomyocytes, we utilized an antibody that specifically recognizes phosphorylated p53 at serine-15. The level of phosphorylated p53 was markedly increased by 100 μM H₂O₂ at 30 and 60 min. Using specific protein kinase inhibitors we examined the involvement of protein kinases in p53 phosphorylation in response to H₂O₂ treatment. However, staurosporine, a broad spectrum inhibitor of protein kinases, SB202190, a specific p38 kinase inhibitor, PD98059, a MAP kinase inhibitor, wortmannin, an inhibitor of DNA-PK and PI3 kinase, SP600125, a JNK inhibitor and caffeine,an inhibitor of ATM and ATR, failed to prevent the H₂O₂-induced phosphorylation of p53. cDNA microarray revealed that H₂O₂ markedly increased expression of several p53 upstream modifiers such as the p300 coactivator protein and several downstream effectors such as gadd45, but decreased the expression of MDM2, a negative regulator of p53. Our results suggest that phosphorylation of p53 at serine-15 may be an important signaling event in the H₂O₂-mediated apoptotic process.     

Influence of thioacetamide-provoked liver injury on female rat blood and alveolar bone under stress

Experimental liver injury with different stages was induced to adult female test rats with daily injection of thioacetamide (ThAA). The doses administered intraperitoneally were 50 mg/kg body weight. In the liver sections progressive changes of damage, regeneration and fat substitution were noticed. Kidney sections revealed enhanced glomerular atrophy, particularly in the cortical tubules, provoked in the 3-week traumatization period. The influence of ThAA on female rat blood was assayed using standard biochemical methods. The analyses done were: the percentage of blood obtainable and the serum/blood ratio; the serum alanine transferase; serum alkaline phosphatase; serum creatinine; serum hydroxyproline and serum beta-glucuronidase activity in the acute, subacute, chronic and highly chronic stage of liver injury. The biochemical findings show continuously progressing damages when traumatization proceeds. In the 3-week test period the histological findings processed showed an increase in osteoclastic resorption in the alveolar bone around the occlusally stressed tooth simultaneously with a horizontal bone loss. Some indications of recovering incidents were seen, too. Only in the histological findings was no difference seen in the deterioration between both sexes, contrarily to the biochemical results also discussed in this study.     

腐植酸浸种对盐碱胁迫下小麦幼苗抗氧化系统的影响

对龙麦26和克旱16两种不同基因型春小麦品种进行腐植酸浸种处理,研究了腐植酸对盐(NaCl)、碱(Na CO3)两种胁迫下小麦幼苗抗氧化系统的影响.结果表明:盐碱胁迫下小麦幼苗叶片脯氨酸含量增加,膜透性增强,地上部鲜质量降低;盐胁迫下,过氧化氢酶(CAT)活性升高,过氧化物酶(POD)活性降低,超氧化物歧化酶(SOD)活性先升后降,而碱胁迫下CAT和POD活性均升高,SOD活性降低;碱胁迫处理的小麦幼苗叶片抗氧化酶系统活性高于同浓度的盐胁迫处理;腐植酸浸种提高了小麦叶片谷胱甘肽含量,提高了SOD和CAT活性,有效缓解了盐碱胁迫对幼苗生长的影响.不同基因型小麦品种在抵御盐碱胁迫的能力和机制上存在一定差异,且与盐离子组成、浓度间存在一定互作,并受浸种方式调控.     

Changes of leaf antioxidant system, photosynthesis and ultrastructure in tea plant under the stress of fluorine

Seedlings of Camellia sinensis were grown hydroponically for 30 d in order to study the effect of fluorine (F) on growth parameters, antioxidant defence system, photosynthesis and leaf ultrastructure. Fresh and dry mass, chlorophyll (Chl) content and net photosynthetic rate (P_N) decreased with increasing F concentration. Superoxide dismutase (SOD) activity decreased significantly, catalase (CAT) and guaiacol peroxidase (GPX) activities reached maximun under 0.21 and 0.32 mM F, respectively. Proline, malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) contents increased significantly. These results suggested, that antioxidant defence system of leaves did not sufficiently scavenge excessive reactive oxygen species. The cell ultrastructure was not changed under 0.11–0.21 mM F, however, it was destroyed at 0.32–0.53 mM F. So tea plants tolerated F in concentration less than 0.32 mM.     

Changes in alpha-actinin localization and myofibrillogenesis in rat cardiomyocytes under cultivation

By indirect immunofluorescence with monoclonal anti-alpha-actinin antibodies the localization of this contractile protein was studied in ventricular cardiac myocytes from newborn 2-4-day old rats in the course of their cultivation. In freshly isolated heart muscle cells a predominant longitudinal orientation of myofibrils was observed; in some cells on the periphery of cytoplasm the contours of Z-lines are indistinct. During cell spreading, in the areas of intercalated discs, growing processes were observed mostly containing no contractile structures at earlier stages of cultivation. On days 3 to 14, the cytoplasmic processes and ruffles are filled with developing myofibrils. The cultures are heterogeneous in the morphology of contractile apparatus of individual cells. In most cardiomyocytes mature myofibrils are well-developed in the central part of the cytoplasm, whereas in its peripheral areas non-myofibrillar stress-fiber-like structures and bundles with continuous distribution of alpha-actinin frequently connected to myofibrils are more typical. In the areas of active myofibrillogenesis, located mainly on the cell periphery, numerous alpha-actinin dots are observed; most of them are arranged linearly and periodically at a distance of 0.3-1.5 microns and seem to be structural precursors of Z-lines. The data obtained show that the cultures of mammalian cardiac cells may be a convenient object for studying myofibrillogenesis in the course of cardiomyogenic differentiation.     

Functional state of rat liver RNA polymerase IA and IB

Phosphocellulose chromatography has been employed to characterize RNA polymerase I present in two different functional states in rat liver cells. The actively transcribing enzyme solubilized from nuclei appears to belong both to the IA and IB classes, whereas the non-transcribing enzyme present in the cytoplasmic fraction has been found to belong only to the IA class. Indirect and direct evidence indicates, however, that in isolated nuclei only the IB form is to be regarded as the physiological form of the enzyme, the IA form arising as a procedural artefact during the extraction process. It may, therefore, be concluded that rat liver IA and IB RNA polymerase are to be strictly regarded as the non-transcribing and transcribing form of the enzyme, respectively.