Time filter

Source Type

Salisbury, Maine, United States

Armstrong L.E.,University of Connecticut | Casa D.J.,University of Connecticut | Emmanuel H.,University of Connecticut | Ganio M.S.,University of Arkansas | And 9 more authors.
Journal of Strength and Conditioning Research

Despite the rapid growth of mass participation road cycling, little is known about the dietary, metabolic, and behavioral responses of ultraendurance cyclists. This investigation describes physiological responses, perceptual ratings, energy balance, and macronutrient intake of 42 men (mean 6 SD; age, 38 ± 6 years; height, 179.7 ± 7.1 cm; body mass, 85.85 ± 14.79 kg) and 6 women (age, 41 ± 4 years; height, 168.0 ± 2.9 cm; body mass, 67.32 ± 7.21 kg) during a summer 164-km road cycling event. Measurements were recorded 1 day before, and on the Event Day (10.5 hours) at the start (0 km), at 2 aid stations (52 and 97 km), and at the finish line (164 km). The ambient temperature was >39.0° C during the final 2 hours of exercise. The mean finish times for men (9.1 ± 1.2 hours) and women (9.0 ± 0.2 hours) were similar, as were mean gastrointestinal temperature (TGI), 4 hydration biomarkers, and 5 perceptual (e.g., thermal, thirst, pain) ratings. Male cyclists consumed enough fluids on the Event Day (5.91 ± 2.38 L; 49% water) to maintain body mass within 0.76 kg, start to finish, despite a sweat loss of 1.13 ± 0.54 L.h -1 and calculated energy expenditure of 3,115 kcal.10.5.h -1. However, men voluntarily underconsumed food energy (deficit of 2,594 kcal, 10.9 MJ) and specific macronutrients (carbohydrates, 106 ± 48 g; protein, 8 ± 7 g; and sodium, 852 ± 531 mg) between 0530 and 1400 hours. Also, a few men exhibited extreme final values (i.e., urine specific gravity of 1.035-1.038, n = 5; body mass loss >4 kg, n = 2; T GI, 39.4 and 40.2°C). We concluded that these findings provide information regarding energy consumption, macronutrient intake, hydration status, and the physiological stresses that are unique to ultraendurance exercise in a hot environment. © 2012 National Strength and Conditioning Association. Source

Grim J.M.,Ohio University | Miles D.R.B.,Mt Desert Island Biological Laboratory | Crockett E.L.,Mt Desert Island Biological Laboratory
Journal of Experimental Biology

Cold acclimation of ectotherms results typically in enhanced oxidative capacities and lipid remodeling, changes that should increase the risk of lipid peroxidation (LPO). It is unclear whether activities of antioxidant enzymes may respond in a manner to mitigate the increased potential for LPO. The current study addresses these questions using killifish (Fundulus heteroclitus macrolepidotus) and bluegill (Lepomis macrochirus) acclimated to 5 and 25° C for 9days and 2 months, respectively. Because the effects of temperature acclimation on pro- and antioxidant metabolism may be confounded by variable activity levels among temperature groups, one species (killifish) was also subjected to a 9-day exercise acclimation. Oxidative capacity of glycolytic (skeletal) muscle (indicated by the activity of cytochrome c oxidase) was elevated by 1.5-fold in killifish, following cold acclimation, but was unchanged in cardiac muscle and also unaffected by exercise acclimation in either tissue. No changes in citrate synthase activity were detected in either tissue following temperature acclimation. Enzymatic antioxidants (catalase and superoxide dismutase) of either muscle type were unaltered by temperature or exercise acclimation. Mitochondria from glycolytic muscle of cold-acclimated killifish were enriched in highly oxidizable polyunsatured fatty acids (PUFA), including diacyl phospholipids (total carbons:total double bonds) 40:8 and 44:12. Increased oxidative capacity, coupled with elevated PUFA content in mitochondria from cold-acclimated animals did not, however, impact LPO susceptibility when measured with C11BODIPY. The apparent mismatch between oxidative capacity and enzymatic antioxidants following temperature acclimation will be addressed in future studies. ©2010. Published by The Company of Biologists Ltd. Source

Jung D.,Mt Desert Island Biological Laboratory | Sato J.D.,Mt Desert Island Biological Laboratory | Shaw J.R.,Mt Desert Island Biological Laboratory | Shaw J.R.,Indiana University Bloomington | Stanton B.A.,Mt Desert Island Biological Laboratory
Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology

Estuarine fish, such as the Atlantic killifish (Fundulus heteroclitus), are constantly and rapidly exposed to changes in salinity. Although ion transport in killifish gills during acclimation to increased salinity has been studied extensively, no studies have examined the role of aquaglyceroporin 3 (AQP3), a water, glycerol, urea, and ammonia transporter, during acclimation to increased salinity in this sentinel environmental model organism. The goal of this study was to test the hypothesis that transfer from freshwater to seawater decreases AQP3 gene and protein expression in the gill of killifish. Transfer from freshwater to seawater decreased AQP3 mRNA in the gill after 1. day, but had no effect on total gill AQP3 protein abundance as determined by western blot. Quantitative confocal immunocytochemistry confirmed western blot studies that transfer from freshwater to seawater did not change total AQP3 abundance in the gill; however, immunocytochemistry revealed that the amount of AQP3 in pillar cells of secondary lamellae decreased in seawater fish, whereas the amount of AQP3 in mitochondrion rich cells (MRC) in primary filaments of the gill increased in seawater fish. This response of AQP3 expression is unique to killifish compared to other teleosts. Although the role of AQP3 in the gill of killifish has not been completely elucidated, these results suggest that AQP3 may play an important role in the ability of killifish to acclimate to increased salinity. © 2011 Elsevier Inc. Source

Shaw J.R.,Indiana University Bloomington | Shaw J.R.,Mt Desert Island Biological Laboratory | VanderHeide J.,Mt Desert Island Biological Laboratory | LaCasse T.,Mt Desert Island Biological Laboratory | And 3 more authors.
Aquatic Toxicology

Seawater acclimation in killifish, Fundulus heteroclitus, is mediated in part by a rapid (1h) translocation of CFTR Cl- channels from an intracellular pool to the plasma membrane in gill and increased CFTR-mediated Cl- secretion. This effect is mediated by serum and glucocorticoid-inducible kinase 1 (SGK1), which is stimulated by plasma hypertonicity rather than cortisol. Since arsenic exposure prevents acclimation to seawater by decreasing CFTR protein levels we tested the hypothesis that arsenic (as sodium arsenite) blocks acclimation to seawater by down regulating SGK1 expression. Freshwater adapted killifish were exposed to arsenic (48h) and transferred to seawater containing arsenic, and SGK and CFTR expression were measured. Arsenic reduced the seawater induced increase in SGK1 mRNA and protein abundance, and reduced both the total amount of CFTR and the amount of CFTR in the plasma membrane. The decrease in membrane CFTR reduced Cl- secretion. Arsenic also increased the amount of ubiquitinated CFTR and its degradation by the lysosome. Thus, we propose a model whereby arsenic reduces the ability of killifish to acclimate to seawater by blocking the seawater induced increase in SGK1, which results in increased ubiquitination and degradation of CFTR. © 2010 Elsevier B.V. Source

Jung D.,Mt Desert Island Biological Laboratory | Adamo M.A.,Mt Desert Island Biological Laboratory | Lehman R.M.,Mt Desert Island Biological Laboratory | Jackson C.E.,Indiana University Bloomington | And 5 more authors.
Comparative Biochemistry and Physiology Part - C: Toxicology and Pharmacology

Killifish (Fundulus heteroclitus) are euryhaline teleosts that are widely used in environmental and toxicological studies, and they are tolerant to arsenic, in part due to very low assimilation of arsenic from the environment. The mechanism of arsenic uptake by the intestine, a major route of arsenic uptake in humans is unknown. Thus, the goal of this study was to determine if aquaglyceroporins (AQPs), which transport water and other small molecules including arsenite across cell membranes, are expressed in the killifish intestine, and whether AQP expression is affected by osmotic stress. Through RT-PCR and sequence analysis of PCR amplicons, we demonstrated that the intestine expresses kfAQP3a and kfAQP3b, two previously identified variants, and also identified a novel variant of killifish AQP3 (kfAQP3c) in the intestine. The variants likely represent alternate splice forms. A BLAST search of the F. heteroclitus reference genome revealed that the AQP3 gene resides on a single locus, while an alignment of the AQP3 sequence among 384 individuals from eight population ranging from Rhode Island to North Carolina revealed that its coding sequence was remarkably conserved with no fixed polymorphism residing in the region that distinguishes these variants. We further demonstrate that the novel variant transports arsenite into HEK293T cells. Whereas kfAQP3a, which does not transport arsenite, was expressed in both freshwater (FW) and saltwater (SW) acclimated fish, kfAQP3b, an arsenic transporter, was expressed only in FW acclimated fish, and kfAQP3c was expressed only in SW acclimated fish. Thus, we have identified a novel, putative splice variant of kfAQP3, kfAQP3c, which transports arsenic and is expressed only in SW acclimated fish. © 2015 Elsevier Inc. Source

Discover hidden collaborations