High-intensity interval training improves acute plasma volume responses to exercise that is age dependent

Plasma volume (PV) is affected by several factors including age, physical training and, acutely, by exercise intensity. The purpose of this study was to investigate the effects of 6 weeks of high-intensity interval training (HIT) on PV and blood pressure (BP) changes among sedentary individuals. Thirty subjects aged between 18 and 71 years [body mass index=30.1(1.2) kg/m2] completed a 6-weeks HIT program. Anthropometric and fitness variables were obtained at pre- and post- HIT. PV variations during warm-up and after supramaximal cycling test (SCT) were calculated using two methods based on Hematocrit (Ht) and Hemoglobin (Hb) measures. After both the warm-up and SCT, PV decreased significantly among participants at pre- and at post-HIT (P < 0.01). However, PV decreases were significantly greater at pre-HIT compared with post-HIT during warm-up and after SCT (P < 0.01, respectively). In addition, at pre-HIT, a positive relationship was found between age and both PV variations at warm-up and after SCT (r2 = 0.55 and r2 = 0.46; P < 0.01 respectively). However, no relationship was found during the post-HIT period. After SCT and after both visits, only body weight predicted 22% of PV variations. In the current study, a significant relationship was found between systolic and diastolic BP improvements and PV variations in post-HIT (r2 = 0.54 and r2=0.56, P < 0.05, respectively). Our results suggest that HIT may improve PV values and reduce the effects of age on the decrease in PV. These interventions led to improvements in systolic and diastolic BP values among participants. © 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological SocietyThis work was supported by the Faculty of Superior Studies and Research of the Université de Moncton, New Brunswick, Canada.Scopu

Fatty acid content and enzymes of fatty acid metabolism in overwintering cold-hardy gall insects

Fatty acid content and enzymes of fatty acid metabolism were studied in overwintering larvae of two cold-hardy gall insects, the freeze-tolerant fly Eurosta solidaginis and the freeze-avoiding moth Epiblema scudderiana. Both species increased the proportion of unsaturated fatty acids during the winter. Whereas total lipid content did not change in Eurosta solidaginis, a decrease in total lipids over the winter in Epiblema scudderiana suggested the use of fat reserves to maintain basal metabolism. Changes in the activities of enzymes of fat oxidation correlated with these observations in Eurosta solidaginis: hydroxyacyl-CoA dehydrogenase, carnitine-palmitoyl transferase, and acetoacetyl-CoA thiolase activities all decreased during overwintering. In Epiblema scudderiana the same activities were constant, decreased, or increased. These activities were, however, higher in the fat-oxidizing, freeze-avoiding species than in the freeze-tolerant larvae. Lipid content in Epiblema scudderiana increased again by early spring, possibly indicating this pool as the fate of carbon derived from the spring clearance of the cryoprotectant glycerol pool. Decreased activities of malic enzyme and ATP-citrate lyase suggested decreased potential for fatty acid synthesis in both species over the winter, consistent with the cessation offeeding in the fall. The potential for ketone body metabolism, measured as the activity of P-hydroxybutyrate dehydrogenase, increased greatly in both species during overwintering; however, levels ofβ-hydroxybutyrate remained less than 0.35 μmol/g wet mass throughout the study period. These data indicate that changes to storage lipid profiles in order to maintain fluidity and to lipid-metabolizing enzyme activities may play important roles in insect cold hardiness

Oxidative damage and antioxidants in Rana sylvatica, the freeze-tolerant wood frog

Freeze-tolerant wood frogs (Rana sylvatica) must endure prolonged ischemia on freezing. Reperfusion on thawing brings with it the potential for oxidative damage due to reactive oxygen species formation, a well-known consequence of mammalian ischemia-reperfusion. To determine whether oxidative damage occurs during thawing and how frogs deal with this, we examined oxidative damage and antioxidant and prooxidant systems in tissues of Rana sylvatica and a nonfreezing relative, Rana pipiens. Glutathione status indicated little oxidative stress in tissues during freezing or thawing; an increase of the glutathione pool in the oxidized form was observed during freezing only in Rana sylvatica kidney (by 85%) and brain (by 33%). Oxidative damage to tissue lipids, measured as the levels of thiobarbituric acid- reactive substances and/or by an Fe(III)-xylenol orange assay, did not increase above control values over a freeze-thaw time course. Correlative data showing increased activities of some antioxidant enzymes during freezing, notably glutathione peroxidase (increasing 1.2- to 2.5-fold), as well as constitutively higher activities of antioxidant enzymes and higher levels of glutathione in the freeze-tolerant species compared with Rana pipiens, suggest that antioxidant defenses play a key role in amphibian freeze tolerance

Temperature acclimation and seasonal responses by enzymes in cold‐hardy gall insects

Changes in the activity of over 20 enzymes of intermediary metabolism in 15°C or −4°C acclimated goldenrod gall moth (Epiblema scudderiana) and gall fly (Eurosta solidaginis) larvae were measured. Increased activities of glyco‐genolytic and hexose monophosphate shunt enzymes in cold‐acclimated Epiblema scudderiana suggest a role for coarse control in the conversion of glycogen reserves into glycerol cryoprotectant synthesis. In Eurosta solidaginis, high glycogen phosphorylase activity with decreased activities of glycolytic enzymes may account in part for the temperature‐dependent switch from glycerol to sorbitol synthesis in these larvae upon cold acclimation. Isoelectric focusing analyses of five enzymes in overwintering Epiblema scudderiana revealed transient mid‐winter changes in the isoelectric points of phosphofructokinase and pyruvate kinase, suggesting seasonal changes in the phosphorylation state of these enzymes. A distinct developmental pattern of aldolase isozymes suggests a role for a new isozyme during overwintering or upon spring emergence. Regulation of metabolism by changes in enzyme activities is indicated for both larvae

Oxidative stress and antioxidants in overwintering larvae of cold-hardy goldenrod gall insects

Antioxidant and pro-oxidant systems were studied in overwintering larvae of two cold-hardy gall insect species, the freeze-tolerant fly Eurosta solidaginis and the freeze-avoiding ninth Epiblema scudderiana. An increase in the levels of the oxidized form of glutathione suggested slight oxidative stress in both species during the winter. Freeze-tolerant Eurosta solidaginis larvae generally had decreased activities of antioxidant enzymes in the winter, indicating that these larvae do not face increased challenge from oxidative stress during the numerous freeze-thaw events they experience. Instead, existing defences must be sufficient to prevent any damage. By contrast, increased winter activities of antioxidant enzymes in freeze- avoiding Epiblema scudderiana suggest that these larvae mast defend against the formation of reactive oxygen species. This may result from the oxidative nature of winter metabolism in these larvae, as well as a dependence on lipid oxidation as their fuel over this season. Xanthine dehydrogenase activity decreased dramatically in both species during the autumn, reducing the potential for the formation of the pro-oxidant xanthine oxidase. Indeed, xanthine oxidase activity fell to undetectable levels by winter in Epiblema scudderiana and was not detectable at any time in Eurosta solidaginis