American journal of physiology. Regulatory, integrative and comparative physiology
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Mar 2009
Reactive oxygen species-dependent endothelin signaling is required for augmented hypoxic sensory response of the neonatal carotid body by intermittent hypoxia.
We previously reported that intermittent hypoxia (IH) augments hypoxic sensory response (HSR) and increases the number of glomus cells in neonatal carotid bodies. In the present study, we tested the hypothesis that recruitment of endothelin-1 (ET-1) signaling by reactive oxygen species (ROS) plays a critical role in IH-evoked changes in neonatal carotid bodies. Experiments were performed on neonatal rats exposed either to 10 days of IH (P0-P10; 8 h/day) or to normoxia. ⋯ Systemic administration of manganese (III) tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride (MnTMPyP; 5 mg/kg ip), a scavenger of O(2)(*-), prevented IH-induced elevation of ROS, basal release of ET-1, upregulation of ET(A) mRNA, and augmented HSR. In striking contrast, MnTMPyP treatment had no significant effect on IH-induced hyperplasia of glomus cells. These results demonstrate that IH-evoked increase in HSR involve a ROS-mediated increase in basal ET-1 release and upregulation of ET(A) receptor mRNA.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Mar 2009
Expression of intracellular cytokines, HSP72, and apoptosis in monocyte subsets during exertional heat stress in trained and untrained individuals.
This study examined intracellular cytokine, heat shock protein (HSP) 72, and cellular apoptosis in classic and inflammatory CD14(+) monocyte subsets during exertional heat stress (EHS). Subjects were divided into endurance-trained [TR; n = 12, peak aerobic power (Vo(2peak)) = 70 +/- 2 ml.kg lean body mass (LBM)(-1).min(-1)] and sedentary-untrained (UT; n = 11, Vo(2peak) = 50 +/- 1 ml.kg LBM(-1).min(-1)) groups before walking at 4.5 km/h with 2% elevation in a climatic chamber (40 degrees C, 30% relative humidity) wearing protective clothing until exhaustion (Exh). Venous blood samples at baseline and 0.5 degrees C rectal temperature increments (38.0, 38.5, 39.0, 39.5, and 40.0 degrees C/Exh) were analyzed for cytokines (TNF-alpha, IL-1beta, IL-6, IL-1ra, and IL-10) in CD14(++)CD16(-)/CD14(+)CD16(+) and HSP72/apoptosis in CD14(Bri)/CD14(Dim) subsets. ⋯ Induced HSP in vitro was not uniform across CD14(+) subsets. Findings suggest that circulating CD14(+)CD16(+), but not CD14(++)CD16(-) monocytes, contribute to the proinflammatory cytokine profiles observed during EHS. In addition, the enhanced HSP72 response in endurance-trained individuals may confer improved heat tolerance through both anti-inflammatory and anti-apoptotic mechanisms.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Mar 2009
Nonlinear properties of vagal and sympathetic modulations of heart rate variability in ovine fetus near term.
Fetal heart rate (FHR) monitoring is commonly used although clinical studies questioned its diagnostic value. Sophisticated FHR variability (fHRV) measures such as fHRV complexity may improve the sensitivity and specificity of FHR monitoring. A more detailed understanding of the physiology underlying fHRV complexity is essential to harness its use for monitoring fetal health. ⋯ With propranolol, the nonlinear part of fHRV complexity decreased on the short-term time scale (P < 0.05), suggesting that sympathetic influences on fHRV can be detected by the nonlinear part of fHRV complexity. Thus the complex interplay of vagal and sympathetic modulations of fHRV is reflected differently and specifically in the linear and nonlinear properties of fHRV complexity, and on different time scales. Analysis of linear and nonlinear properties of fHRV may improve sensitivity and specificity of FHR monitoring.
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Am. J. Physiol. Regul. Integr. Comp. Physiol. · Mar 2009
Cerebral adaptations to chronic anemia in a model of erythropoietin-deficient mice exposed to hypoxia.
Anemia and hypoxia in rats result in an increase in factors potentially involved in cerebral angiogenesis. Therefore, the aim of this study was to assess the effect of chronic anemia and/or chronic hypoxia on cerebral cellular responses and angiogenesis in wild-type and anemic transgenic mice. These studies were done in erythropoietin-deficient mice (Epo-TAg(h)) in normoxia and following acute (one day) and chronic (14 days, barometric pressure = 420 mmHg) hypoxia. ⋯ In acute hypoxia, WT mice up-regulated all of the studied factors, including cerebral NO. Polycythemia and angiogenesis occurred with acclimatization to chronic hypoxia only in WT mice. In Epo-TAg(h), the decrease in HIF-1alpha, VEGF proteins, and phospho-STAT-5 ratio in chronic hypoxia suggest that neuroprotective and angiogenesis pathways are altered.