Salisbury, Maine, United States
Salisbury, Maine, United States

Time filter

Source Type

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 | Year: 2012

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.


Bomberger J.M.,University of Pittsburgh | Sato J.D.,Mt Desert Island Biological Laboratory | Chapline M.C.,Mt Desert Island Biological Laboratory | Stanton B.A.,Mt Desert Island Biological Laboratory
PLoS ONE | Year: 2014

Background: Chloride (Cl) secretion by the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) located in the apical membrane of respiratory epithelial cells plays a critical role in maintenance of the airway surface liquid and mucociliary clearance of pathogens. Previously, we and others have shown that the serum and glucocorticoid-inducible kinase-1 (SGK1) increases wild type CFTR (wt-CFTR) mediated Cl transport in Xenopus oocytes by increasing the amount of wt-CFTR protein in the plasma membrane. However, the effect of SGK1 on the membrane abundance of wt-CFTR in airway epithelial cells has not been examined, and the mechanism whereby SGK1 increases membrane wt-CFTR has also not been examined. Thus, the goal of this study was to elucidate the mechanism whereby SGK1 regulates the membrane abundance of wt-CFTR in human airway epithelial cells. Methods and Results: We report that elevated levels of SGK1, induced by dexamethasone, increase plasma membrane abundance of wt-CFTR. Reduction of SGK1 expression by siRNA (siSGK1) and inhibition of SGK1 activity by the SGK inhibitor GSK 650394 abrogated the ability of dexamethasone to increase plasma membrane wt-CFTR. Overexpression of a constitutively active SGK1 (SGK1-S422D) increased plasma membrane abundance of wt-CFTR. To understand the mechanism whereby SGK1 increased plasma membrane wt-CFTR, we examined the effects of siSGK1 and SGK1-S442D on the endocytic retrieval of wt-CFTR. While siSGK1 increased wt-CFTR endocytosis, SGK1-S442D inhibited CFTR endocytosis. Neither siSGK1 nor SGK1-S442D altered the recycling of endocytosed wt-CFTR back to the plasma membrane. By contrast, SGK1 increased the endocytosis of the epidermal growth factor receptor (EGFR). Conclusion: This study demonstrates for the first time that SGK1 selectively increases wt-CFTR in the plasma membrane of human airway epithelia cells by inhibiting its endocytic retrieval from the membrane. © 2014 Bomberger et al.


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 | Year: 2010

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.


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 | Year: 2015

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.


PubMed | Mt Desert Island Biological Laboratory, Dartmouth College and Indiana University Bloomington
Type: | Journal: Comparative biochemistry and physiology. Toxicology & pharmacology : CBP | Year: 2015

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.


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 | Year: 2012

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.


Jillette N.,University of Maine at Machias | Jillette N.,Auburn University | Cammack L.,Auburn University | Cammack L.,Mt Desert Island Biological Laboratory | And 4 more authors.
Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology | Year: 2011

The euryhaline green crab, Carcinus maenas, undergoes an annual cycle of salinity exposure, having to adapt to low salinity during its annual spring migration into estuaries, and then having to re-adapt to high salinity when it moves off-shore at the end of summer. Most studies have focused on low salinity acclimation, the activation of osmoregulatory mechanisms, and the induction of transport protein and transport-related enzyme activity and gene expression. In this study we followed the changes in hemolymph osmolality, carbonic anhydrase activity, and mRNA expression of three proteins through a complete cycle of low (15. ppt) and high (32. ppt) salinity acclimation. One week of low salinity acclimation resulted in hemolymph osmoregulation and a four-fold induction of branchial carbonic anhydrase activity. Relative mRNA expression increased for two CA isoforms (CAc 100-fold, and CAg 7-fold) and the α-subunit of the Na/K-ATPase (8-fold). Upon re-exposure to high salinity, hemolymph osmolality increased to 32. ppt acclimated levels by 6. h, and mRNA levels returned to high salinity, baseline levels within 1. week. However, CA activity remained unchanged in response to high salinity exposure for the first week and then gradually declined to baseline levels over 4. weeks. The relative timing of these changes suggests that while whole-organism physiological adaptations and regulation at the gene level can be very rapid, changes at the level of protein expression and turnover are much slower. It is possible that the high metabolic cost of protein synthesis and/or processing could be the underlying reason for long biological life spans of physiologically important proteins. © 2010.


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 | Year: 2010

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.

Loading Mt Desert Island Biological Laboratory collaborators
Loading Mt Desert Island Biological Laboratory collaborators