Experimental physiology
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Experimental physiology · Apr 2015
Interleukin-10 limits intense acute swimming-induced muscle mechanical hyperalgesia in mice.
What is the central question of this study? This study investigated the role of the endogenous anti-inflammatory cytokine interleukin-10 in intense acute swimming-induced muscle mechanical hyperalgesia in mice. What is the main finding and its importance? Endogenous interleukin-10 has a key role in limiting exercise-induced muscle pain in a model presenting similarities to delayed-onset muscle soreness in mice. Interleukin-10 reduced muscle pain by diminishing leucocyte recruitment, hyperalgesic cytokine production, oxidative stress and myocyte damage. ⋯ There was no statistical difference in the levels of the antihyperalgesic cytokines interleukin-4, interleukin-5, interleukin-13 and transforming growth factor-β between wild-type and IL-10(-/-) mice (P ˃ 0.05). Interleukin-10 deficiency also resulted in increased myeloperoxidase activity, greater depletion of reduced glutathione levels, increased superoxide anion production and the maintenance of high plasma concentrations of creatine kinase (until 24 h after the swimming session) in soleus muscle (P ˂ 0.05). These results demonstrate that endogenous IL-10 controls intense acute swimming-induced muscle mechanical hyperalgesia by limiting oxidative stress and cytokine production.
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Experimental physiology · Mar 2015
Exogenous interleukin-10 attenuates hyperoxia-induced acute lung injury in mice.
What is the central question of this study? It is not known whether treatment with interleukin-10 (IL-10) attenuates hyperoxia-induced acute lung injury in mice. What is the main finding and its importance? Our results showed that exogenous IL-10 treatment alleviated hyperoxia-induced acute lung injury in mice, possibly by regulating neutrophil recruitment and the subsequent generation of cytokines, nitric oxide and matrix metalloproteinases. Lung injury caused by breathing air enriched with oxygen continues to be a major problem in clinical medicine. ⋯ Furthermore, absence of IL-10 aggravated hyperoxia-induced acute lung injury and reduced the duration of survival of mice during oxygen exposure, which was attenuated by treatment with IL-10. In conclusion, our results show that exogenous IL-10 treatment alleviates hyperoxia-induced acute lung injury in mice, possibly by regulating neutrophil recruitment and the subsequent generation of cytokines, nitric oxide and matrix metalloproteinases. This suggests that IL-10 treatment may be a promising therapeutic strategy to reduce lung injury in patients exposed to hyperoxia.
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Experimental physiology · Feb 2015
Refinement of analgesia following thoracotomy and experimental myocardial infarction using the Mouse Grimace Scale.
What is the central question of this study? There is an ethical imperative to optimize analgesia protocols for laboratory animals, but this is impeded by our inability to recognize pain reliably. We examined whether the Mouse Grimace Scale (MGS) provides benefits over a standard welfare scoring system for identifying a low level of pain in the frequently used murine surgical model of myocardial infarction. What is the main finding and its importance? Low-level pain, responsive to analgesia, was detected by MGS but not standard methods. ⋯ Pain attributable to the myocardial injury, as opposed to thoracotomy, persisted at 24 h only in mice with large infarcts >40%. In conclusion, the use of a multi-observer, post hoc version of the MGS is a sensitive tool to assess the efficacy of postsurgical analgesic protocols. Following surgical induction of myocardial infarction, we identified a significant proportion of mice that were in low-level pain at 24 h that were not identified by other assessment methods.
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Experimental physiology · Nov 2014
Randomized Controlled TrialCerebral vasomotor reactivity: steady-state versus transient changes in carbon dioxide tension.
Cerebral vasomotor reactivity (CVMR) to changes in arterial carbon dioxide tension (P aCO 2) is assessed during steady-state or transient changes in P aCO 2. This study tested the following two hypotheses: (i) that CVMR during steady-state changes differs from that during transient changes in P aCO 2; and (ii) that CVMR during rebreathing-induced hypercapnia would be blunted when preceded by a period of hyperventilation. For each hypothesis, end-tidal carbon dioxide tension (P ET , CO 2) middle cerebral artery blood velocity (CBFV), cerebrovascular conductance index (CVCI; CBFV/mean arterial pressure) and CVMR (slope of the linear regression between changes in CBFV and CVCI versus P ET , CO 2) were assessed in eight individuals. ⋯ To address the second hypothesis, the same measurements were made during the following two conditions (randomized): (i) immediately following a brief period of hypocapnia induced by hyperventilation for 1 min followed by rebreathing; and (ii) during rebreathing only. The slope of the linear regression for CBFV versus P ET , CO 2 (P < 0.01) and CVCI versus P ET , CO 2 (P < 0.01) was reduced during hyperventilation plus rebreathing relative to rebreathing only. These results indicate that cerebral vasomotor reactivity to changes in P aCO 2 is similar regardless of the employed methodology to induce changes in P aCO 2 and that hyperventilation-induced hypocapnia attenuates the cerebral vasodilatory responses during a subsequent period of rebreathing-induced hypercapnia.
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Experimental physiology · Oct 2014
Respiratory pump contributes to increased physiological reserve for compensation during simulated haemorrhage.
Intrathoracic pressure regulation (IPR) represents a therapy for increasing systemic circulation through the creation of negative intrathoracic pressure. We hypothesized that using this 'respiratory pump' effect would slow the diminution of the physiological reserve to compensate during progressive reductions in central blood volume. The compensatory reserve index (CRI) algorithm was used to measure the proportion (from 100 to 0%) of reserve capacity that remained to compensate for central volume loss before the onset of cardiovascular decompensation. ⋯ The CRI at the onset of presyncope during active IPR (0.08 ± 0.01) was similar to the CRI at presyncope with placebo. Kaplan-Meier and log rank tests indicated that CRI survival curves were shifted to the right by active IPR. Optimizing the respiratory pump contributed a small but significant effect of increasing tolerance to progressive reductions in central blood volume by extending the compensatory reserve.