The impact of long-term confinement and exercise on central and peripheral stress markers

Long-term isolation has been reported to have impact on psycho-physiological performance in humans. As part of the 520 days isolation study (MARS500, n=6) from June 3rd 2010 to November 4th 2011, this study aimed to show that stress caused by isolation and confinement is mirrored in cortical activity and cortisol levels and that exercise is a valid countermeasure. Cortical activity was measured by electroencephalography (EEG) pre- and post-moderate exercise every two weeks, salivary cortisol was taken every 60 days. Data show a decrease of global cortical activity, in both alpha- and beta-activity (p<.05-p<.001), and an increase of salivary cortisol (p<.05-p<.001), during the isolation, indicating that isolation acts as a chronic stressor with impact on cortical activity and cortisol levels. Moderate exercise leads to an increase (p<.01) in cortical activity. Therefore, during long-term space missions the factor isolation must be kept in mind as the reduction of cortical activity and the heightened stress level could impair performance. However moderate exercise might be able to counteract this impairment.

Functional changes in neutrophils and psychoneuroendocrine responses during 105 days of confinement

The innate immune system as one key element of immunity and a prerequisite for an adequate host defense is of emerging interest in space research to ensure crew health and thus mission success. In ground-based studies, spaceflight-associated specifics such as confinement caused altered immune functions paralleled by changes in stress hormone levels. In this study, six men were confined for 105 days to a space module of ∼500 m3mimicking conditions of a long-term space mission. Psychic stress was surveyed by different questionnaires. Blood, saliva, and urine samples were taken before, during, and after confinement to determine quantitative and qualitative immune responses by analyzing enumerative assays and quantifying microbicide and phagocytic functions. Additionally, expression and shedding of L-selectin (CD62L) on granulocytes and different plasma cytokine levels were measured. Cortisol and catecholamine levels were analyzed in saliva and urine. Psychic stress or an activation of the psychoneuroendocrine system could not be testified. White blood cell counts were not significantly altered, but innate immune functions showed increased cytotoxic and reduced microbicide capabilities. Furthermore, a significantly enhanced shedding of CD62L might be a hint at increased migratory capabilities. However, this was observed in the absence of any acute inflammatory state, and no rise in plasma cytokine levels was detected. In summary, confinement for 105 days caused changes in innate immune functions. Whether these changes result from an alert immune state in preparation for further immune challenges or from a normal adaptive process during confinement remains to be clarified in future research.

Apigenin induces dermal collagen synthesis via smad2/3 signaling pathway

Decrease in fibroblast-produced collagen has been proven to be the pivotal cause of skin aging, but there is no satisfactory drug which directly increases dermal thickness and collage density. Here we found that a flavonoid natural product, apigenin, could significantly increase collagen synthesis. NIH/3T3 and primary human dermal fibroblasts (HDFs) were incubated with various concentrations of apigenin, with dimethyl sulfoxide (DMSO) serving as the negative control. Real-time reverse-transcription polymerase chain reaction (PCR), Western Blot, and Toluidine blue staining demonstrated that apigenin stimulated type-I and type-III collagen synthesis of fibroblasts on the mRNA and protein levels. Meanwhile, apigenin did not induce expression of alpha smooth muscle actin (α-SMA) in vitro and in vivo, a fibrotic marker in living tissues. Then the production of collagen was confirmed by Masson’s trichrome stain, Picrosirius red stain and immunohistochemistry in mouse models. We also clarified that this compound induced collagen synthesis by activating smad2/3 signaling pathway. Taken together, without obvious influence on fibroblasts’ apoptosis and viability, apigenin could promote the type-I and type-III collagen synthesis of dermal fibroblasts in vitro and in vivo, thus suggesting that apigenin may serve as a potential agent for esthetic and reconstructive skin rejuvenation.

A comparison of two common bile duct ligation methods to establish hepatopulmonary syndrome animal models

The major drawback of the current common bile duct ligation (CBDL)-induced hepatopulmonary syndrome (HPS) animal model is the extremely high mortality rate that hinders experimental studies. The purpose of this study was to investigate an improved method of CBDL with the goal of developing a simple and reproducible rat HPS model after a single CBDL treatment. Two groups of male Sprague–Dawley rats underwent separate methods of CBDL: (1) the upper common bile duct ligation (UCBDL) group ( n = 40), in which the first ligature was made near the junction of the hepatic ducts, and the second ligature was made above the entrance of the pancreatic duct; (2) the middle of the common bile duct ligation (MCBDL) group ( n = 40), in which the first ligature was made in the middle of the common bile duct, and the second ligature was made above the entrance of the pancreatic duct. The CBDL-induced HPS rats were evaluated by pulse oximeter, arterial blood analysis, histopathology, and cerebral uptake of intravenous technetium-99m-labeled albumin macroaggregates (which reflects intrapulmonary vascular dilation). The mortality rates of the UCBDL group and the MCBDL group were 42.5% and 77.5%, respectively ( P < 0.05). These results suggest that the UCBDL, a single improved procedure, provides a better method compared to the established HPS model, because of the relatively high success rate and the decreased risk of complications.

A novel method to optimize the mode spectrum of the dynamic resonant magnetic perturbation on the J-TEXT tokamak

The dynamic resonant magnetic perturbation (DRMP) system has been developed for the J-TEXT tokamak to study the interaction between the rotating perturbation magnetic field and the plasma. When the DRMP coils are energized by two phase sinusoidal currents with the same frequency, a 2/1 rotating resonant magnetic perturbation component will be generated. But at the same time, a small perturbation component rotating in the opposite direction is also produced because of the control error of the currents. This small component has bad influence on the experiment investigations. Actually, the mode spectrum of the generated DRMP can be optimized with an accurate control of phase difference between the two currents. In this paper, a new phase control method based on a novel all-digital phase-locked loop (ADPLL) is proposed. The proposed method features accurate phase control and flexible phase adjustment. Modeling and analysis of the proposed ADPLL is presented to guide the design of the parameters of the phase controller in order to obtain a better performance. Testing results verify the effectiveness of the ADPLL and validity of the method applying to the DRMP system.

520-d Isolation and confinement simulating a flight to Mars reveals heightened immune responses and alterations of leukocyte phenotype

During interplanetary exploration, chronic stress caused by long term isolation and confinement in the spacecraft is one of the major concerns of physical and psychological health of space travelers. And for human on Earth, more and more people live in an isolated condition, which has become a common social problem in modern western society. Collective evidences have indicated prolonged chronic stress could bring big influence to human immune function, which may lead to a variety of health problems. However, to what extent long-term isolation can affect the immune system still remains largely unknow. A simulated 520-d Mars mission provided an extraordinary chance to study the effect of prolonged isolation. Six healthy males participated in this mission and their active neuroendocrine and immune conditions were studied with saliva and blood samples from all participants on chosen time points during the isolation period. As a typical neuroendocrine parameter, stress hormone cortisol was measured in the morning saliva samples. Immune phenotype changes were monitored through peripheral leukocyte phenotype analysis. Using an ex vivo viral infection simulation assay we assessed the immune response changes characterized by the ability to produce representative endogenous pro-inflammatory cytokines. The results of this study revealed elevated cortisol levels, increased lymphocyte amount and heightened immune responses, suggesting that prolonged isolation acting as chronic stressors are able to trigger leukocyte phenotype changes and poorly controlled immune responses.

mTOR pathway is involved in ADP-evoked astrocyte activation and ATP release in the spinal dorsal horn in a rat neuropathic pain model

BACKGROUND

ATP/ADP-evoked spinal astrocyte activation plays a vital role in the development of neuropathic pain. We aim to investigate the role of mammalian target of rapamycin (mTOR) pathway on the spinal astrocyte activation in the neuropathic pain development in rats.

METHODS

Sprague Dawley (SD) rats were subjected to chronic constriction of the sciatic nerve (CCI). Rapamycin or ADP was intrathecally injected daily to explore their effects on spinal astrocyte activation and pain development. Expression of glial fibrillary acidic protein (GFAP) and mTOR in the spinal dorsal horn was assessed by immunohistochemistry. Von Frey hairs and Hargreaves paw withdrawal test were conducted to evaluate mechanical allodynia and thermal sensitivity, respectively. Firefly luciferase ATP assay was used to assess the change of ATP level in cerebrospinal fluid (CSF) and medium of cultured astrocytes.

RESULTS

GFAP expression was enhanced in the ipsilateral spinal dorsal horn from day 3 after surgery. GFAP and mTOR expression in the rat spinal dorsal horn on post-surgical day 14 was enhanced by daily intrathecal injection of ADP, which was inhibited by rapamycin. Rapamycin decreased lower mechanical pain threshold and the thermal withdrawal latency. Intrathecal injection of ADP enhanced the ATP release, which was partially inhibited by rapamycin. Study of cultured astrocytes indicated that ATP could be released from astrocytes.

CONCLUSION

Our data demonstrated that ADP enhanced neuropathic pain in CCI rats, which was inhibited by rapamycin. This study indicates that targeting mTOR pathway could serve as a novel therapeutic strategy in neuropathic pain management.

Analytical compensation of axisymmetric equilibrium fluxes picked up by locked mode detectors in tokamaks

In the detection of locked modes using saddle loops, the problem of how to remove the axisymmetric equilibrium flux picked up by the loops has still to be solved. The problem becomes more difficult when there are conductive structures located near the saddle loops. In this paper, we present an analytical model based on lumped eddy current circuits and use it to interpret the measured equilibrium flux and the corresponding eddy current fluxes. Using this model, precise compensation for fluxes induced by the horizontal field coils and the toroidal field coils, with relative errors of less than 1%, has been realized for the saddle loops in the Joint Texas Experimental Tokamak. This paper also presents a new method to compensate for the detection of equilibrium flux by the locked mode detector.

A corticoid-sensitive cytokine release assay for monitoring stress-mediated immune modulation

The human immune system is orchestrated in a complex manner and protects the host against invading organisms and controls adequate immune responses to different antigen challenges in an endo-, auto- and paracrine-regulated fashion. The variety and intensity of immune responses are known to be dependent on stress-sensitive neural, humoral and metabolic pathways. The delayed-type hypersensitivity (DTH) skin test was a validated and standardized measure applied in clinical studies to monitor the integral function of cellular immune responses in vivo. The DTH skin test was, however, phased out in 2002. To obtain insight into the mechanisms of stress-sensitive immune reactions, we have developed an alternative in-vitro assay which allows the evaluation of antigen-dependent cellular immune responses triggered by T lymphocytes. The change in the concentration of proinflammatory cytokines in supernatant of the blood-antigen mixture is of particular interest to mirror the degree and adequacy of cellular immune responses. In this study we report that the proinflammatory cytokines interleukin (IL)-2, interferon (IFN)-γ and tumour necrosis factor (TNF)-α show a time-dependent increase upon ex-vivo bacterial, viral and fungal antigen stimulations. Furthermore, evidence is provided that this assay is sensitive to mirror stress hormone-mediated immune modulation in humans as shown either after hydrocortisone injection or after acute stress exposure during free fall in parabolic flight. This in-vitro test appears to be a suitable assay to sensitively mirror stress hormone-dependent inhibition of cellular immune responses in the human. Because of its standardization and relatively simple technical handling, it may also serve as an appropriate research tool in the field of psychoneuroendocrinology in clinical as in field studies.