104 research outputs found
Hepatosomatic index & liver lipid composition of chondrichthyan fishes (compiled literature data) - Treberg & Speers-Roesch (2016) Does the physiology of chondrichthyan fishes constrain their distribution in the deep-sea? Journal of Experimental Biology
No full textSupplementary compiled literature data (Excel format) for: Jason R. Treberg and Ben Speers-Roesch (2016) Does the physiology of chondrichthyan fishes constrain their distribution in the deep-sea? <i>Journal of Experimental Biology. </i>doi:10.1242/jeb.12810
Supporting data Yancey et al 2018 deep-sea skate osmolytes PBZ
No full textSupporting raw data for Yancey, P.H., Speers-Roesch, B., Atchinson, S., Reist, J.D., Majewski, A.R., Treberg, J.R. 2018. Osmolyte Adjustments as a Pressure Adaptation in Deep-Sea Chondrichthyan Fishes: An Intraspecific Test in Arctic Skates (Amblyraja hyperborea) along a Depth Gradient. Physiological and Biochemical Zoology 91: 788-796. doi: 10.1086/69615
Life through a wider scope: Brook Trout (Salvelinus fontinalis) exhibit similar aerobic scope across a broad temperature range
No full textBrook Trout (Salvelinus fontinalis) have been widely introduced throughout the world and are often considered as direct competitors with native salmonid species. Metabolic rate is one metric we can examine to improve our understanding of how well fish perform in different habitats, including across temperature gradients, as metabolism can be directly influenced by environmental temperatures in ectotherms. We estimated the standard metabolic rate, maximum metabolic rate and aerobic scope of lab-reared juvenile Brook Trout (~1 year) using intermittent-flow respirometry across a range of temperatures (5-23°C) likely experienced in the wild. We included a diurnal temperature cycle of ± 1.5°C for each treatment temperature to simulate temporal variation observed in natural waterbodies. Standard metabolic rate and maximum metabolic rate both increased with acclimation temperature before appearing to plateau around 20°C, while mass specific aerobic scope was found to increase from 287.25±13.03 mg O2·kg-1·h-1 at 5°C to a mean of 384.85±13.31 mg O2·kg-1·h-1 at 15°C before dropping at higher temperatures. Although a slight peak was found at 15°C, the generally flat thermal performance curve for aerobic scope suggests Brook Trout are capable of adjusting to a relatively wide range of thermal regimes, appearing to be eurythermal, or a thermal generalist at least for salmonids. The ability of this population to maintain similar physiological performance across a wide range of temperatures may help explain why Brook Trout succeed in a variety of different thermal habitats.This work was supported by Fisheries and Oceans Canada Species at Risk Program and Strategic Program for Ecosystem Research; Dr. J. R. Treberg funding provided by NSERC grant #2018-06052
Characterization of 3 different types of aquaporins in Carcinus maenas and their potential role in osmoregulation
No full textIntertidal crustaceans like Carcinus maenas shift between an osmoconforming and osmoregulating state when inhabiting full-strength seawater and dilute environments, respectively. While the bodily fluids and environment of marine osmoconformers are approximately isosmotic, osmoregulating crabs inhabiting dilute environments maintain their bodily fluid osmolality above that of their environment by actively absorbing and retaining osmolytes (e.g., Na+, Cl-, urea) while eliminating excess water. Few studies have investigated the role of aquaporins (AQPs) in the osmoregulatory organs of crustaceans, especially within brachyuran species. In the current study, three different aquaporins were identified within a transcriptome of C. maenas, including a classical AQP (CmAQP1), an aquaglyceroporin (CmGLP1), and a big-brain protein (CmBIB1), all of which are expressed in the gills and the antennal glands. Functional expression of these aquaporins confirmed water transport capabilities for CmAQP1, CmGLP1, but not for CmBIB1, while CmGLP1 also transported urea. Higher relative CmAQP1 mRNA expression within tissues of osmoconforming crabs suggests the apical/sub-apically localized channel attenuates osmotic gradients created by non- osmoregulatory processes while its downregulation in dilute media reduces the water permeability of tissues to facilitate osmoregulation. Although hemolymph urea concentrations rose upon exposure to brackish water, urea was not detected in the final urine. Due to its urea- transport capabilities, CmGLP1 is hypothesized to be involved in a urea retention mechanism believed to be involved in the production of diluted urine. Overall, these results suggest that AQPs are involved in osmoregulation and provide a basis for future mechanistic studies investigating the role of AQPs in volume regulation in crustaceans.University of Manitoba Graduate Enhancement of Tri-agency Stipends GrantOctober 202
Evaluating the utility of a point of care device to assess physiological differences among wild boreal fishes
No full textWith the increasing risk of anthropogenic impacts in boreal ecosystems there is a
need for tools to rapidly assess impacts on organisms and properly inform resource
managers. Though well-researched, the i-STAT a portable Point-of-Care device has been
minimally validated in species and environments, especially those that represent
freshwater species in cold, boreal environments. To determine the accuracy of the i7 STAT, blood from Lake Trout (Salvelinus namaycush) and White Sucker
(Catostomus commersoni) was collected from the IISD Experimental Lakes Area (ELA)
and analyses compared between traditional lab methods and results of the i-STAT POCD.
The stability of i-STAT-based whole blood parameters was also evaluated over 3-4 hours
for both ELA and captive Lake Trout. Finally, the i-STAT was tested in ambient
conditions that are outside of its recommended usage (<16°C) to assess changes in
physiological status in spawning Lake Trout across various capture and handling methods
from five ELA lakes in October 2020. The time between capture method and blood
sampling was also assessed for spawning Lake Trout. [...
Using isolated mitochondria to investigate mitochondrial hydrogen peroxide metabolism
No full textMitochondria are recognized as centrally important to cellular reactive oxygen species (ROS), both as a potential source and due to their substantial antioxidant capacity. While much of the initial ROS formed by mitochondria is superoxide, this is rapidly converted to hydrogen peroxide (H2O2) which more readily crosses membranes making H2O2 important in both redox signalling mechanisms and conditions of oxidative stress. Here I outline our studies on mitochondrial H2O2 metabolism with a focus on some of the challenges and strategies involved with developing an integrated model of mitochondria being intrinsic regulators of H2O2. This view of mitochondria as regulators of H2O2 goes beyond the simpler contention of them being net producers or consumers. Moreover, the integration of both consumption and production can then be tied to a putative mechanism linking energy sensing at the level of the mitochondrial protonmotive force. This mechanism would provide a means of mitochondria communicating their energetic status the extramitochondrial compartment via local H2O2 concentrations. I conclude by explaining how these concepts developed using rodent muscle as a model have high relevance and applicability to comparative studies
The role of the cAMP/PKA and cGMP/PKG pathways in the regulation of the transbranchial ammonia excretion in the green shore crab, Carcinus maenas
No full textAs a toxic nitrogenous waste, ammonia causes ionoregulatory and neuronal dysfunction in aquatic animals. Without mechanisms to convert ammonia into less toxic molecules such as urea and uric acid, ammonotelic animals excrete ammonia directly into the surrounding environment. In order to deal with conditions causing possible elevated hemolymph ammonia levels, such as feeding, an efficient ammonia excretion process must be in place to keep the hemolymph ammonia levels within a tolerable range. While the excretory mechanisms of ammonia have been investigated in detail in fish and crustaceans, the intracellular regulation of these processes is basically unknown. To investigate the involvement of two key pathways, the cAMP/PKA and cGMP/PKG pathway, in the ammonia excretion process, gills from osmoregulating green shore crabs, Carcinus maenas, were isolated and perfused with hemolymph-like solutions containing either 200 µmol L-1 or 500 µmol L-1 NH4Cl, mimicking the hemolymph ammonia levels in the resting state and after feeding, respectively. Basolateral application of the adenylyl cyclase activator or membrane-permeable 8-Bromo-cAMP, caused a significant decrease in the ammonia excretion rate. In addition, after PKA activation by 8-Bromo-cAMP, metabolically generated ammonia increased and the majority was now transported towards the hemolymph and not, as seen under control conditions, into the environment. Together, this suggests that the cAMP/PKA pathway promotes an ammonia retention mechanism. In contrast, activating the cGMP/PKG pathway by the application of membrane-permeable 8-Bromo-cGMP, resulted in an increase of the transbranchial ammonia excretion rate, which could be blocked by the PKG inhibitor KT5823. In addition, participation of nitric oxide synthase (NOS) in the cGMP synthesis via the soluble guanylyl cyclase is suggested due to the observed inhibitory effect on the branchial ammonia excretion after basolateral application of the NOS inhibitor L-NAME.
In conclusion, cGMP/PKG pathway, not the cAMP/PKA pathway promotes transbranchial ammonia excretion across the gill epithelium in C. maenas. The cAMP/PKA pathway is involved in a so far undescribed ammonia retention mechanism. The provided data will offer a basis for new venues investigating epithelial ammonia transport processes in general.May 202
The pH sensitivity of H2O2 metabolism in skeletal muscle mitochondria
No full textAbstractMitochondria have the capacity to produce and consume H2O2. We examined H2O2 metabolism in isolated rat skeletal muscle mitochondria and found that the substrate-dependent capacity to consume extramitochondrial H2O2 was markedly higher than the observed rate of H2O2 efflux from mitochondria under the same conditions. The substrate-dependent capacity to consume H2O2 was sensitive to the pH of the medium and we propose that pH related differences in H2O2 consumption pathways may explain inconsistencies we observed between H2O2 efflux rate and the reduction state of the matrix NADH pool
The accumulation and metabolism of methylamine organic osmolytes in elasmobranch fishes
No full textIt is widely accepted that marine elasmobranch fishes accumulate the methylamine compounds trimethylamine oxide (TMAO), glycine-betaine (betaine) and sarcosine as osmolytes. The metabolism and accumulation of these compounds has received relatively little study in elasmobranchs, and as such the purpose of this thesis was to investigate aspects of methylamine metabolism, retention and accumulation. Experimental approaches range from multispecies comparisons to directed study of a single species (the winter skate, Leucoraja ocellata ) at different levels of organization from the whole animal down to subcellular components. -- Marine elasmobranchs and a euryhaline species in freshwater accumulate methylamines as the predominant intracellular non-urea organic osmolytes in muscle, whereas, freshwater species preferentially accumulated the β-amino acid taurine. All elasmobranch species examined in this thesis had measurable enzymatic capacity for betaine synthesis in the liver and strong correlation between hepatic betaine synthesizing enzymes and muscle betaine content was found. Only one species of the seven examined had measurable TMAO synthetic capacity and a phylogenetic explanation is proposed for the distribution of TMAO synthesis in elasmobranch fishes. -- In a detailed study of TMAO metabolism in the winter skate, it was concluded that the presence of flavin-containing monoxygenase activity does not indicate the capacity for the synthesis of TMAO. Winter skates lack measurable endogenous TMAO synthesis, apparently obtaining this compound in the diet, and maintain levels without feeding as a result of very low whole animal TMAO losses (<1% day -1 ). Betaine synthesis was also examined in detail in the winter skate, where the liver and kidney are the likely sites of synthesis. The enzymes of betaine synthesis from choline, choline dehydrogenase and betaine aldehyde dehydrogenase, are localized in the mitochondria, as is the case in other animals. Winter skates do not activate betaine synthetic capacity in response to food deprivation or accumulate betaine in the muscle when exposed to a hyperosmotic challenge; however, muscle betaine content increases when they are fed a high betaine diet, suggesting exogenous methylamine supply may be a key determinant in muscle methylamine accumulation in elasmobranchs.Includes bibliographical references
Exploring the role of ammonia transporters (AMTs) in the branchial tissue of the horseshoe crab, Limulus polyphemus
No full textAll organisms must manage ammonia as it is highly toxic and a product of many essential biochemical processes. One group of proteins that facilitates the movement of ammonia across cell membranes is the Ammonia Transport Protein family which are generally sorted into three groups—ammonia transporters (AMTs), Rhesus glycoproteins (Rh proteins), and methylamine permeases (MEPs)—expressed in plants, animals, and fungi, respectively. Recently, transcripts of AMTs have also been found in invertebrates, where experimental evidence suggest that they play a role in both ammonia excretion and ammonia sensing. The American horseshoe crab, Limulus polyphemus, expresses at least two AMT and two Rh proteins within the epithelia of their book gills which is the primary surface for ammonia excretion. Each gill lamellae have a ventral ammonia permeable side and a dorsal ammonia impermeable side. mRNA transcripts for both proteins LpAMT-1 and LpAMT-3 were found on the dorsal and ventral surfaces, bringing into question their function in direct ammonia excretion. In oocyte expression trials both AMTs failed to mediate the transport of radiolabeled methylamine, while transport was detected for both a coral and a human Rh protein. Direct evidence of ammonia transport by invertebrate AMTs has not been previously found and further research should be conducted into the function of these proteins in invertebrates
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