The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Thomas A Mckean - One of the best experts on this subject based on the ideXlab platform.
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calcium transport mechanisms in Muskrat and rat hearts
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2001Co-Authors: Thomas A MckeanAbstract:Abstract Mammalian hearts experience calcium overload during extreme and prolonged hypoxia and the calcium overload may lead to enzyme activation and cell death. Several calcium transport systems were examined in Muskrat hearts and compared to those found in rat hearts to determine if there is a species difference that might be related to the Muskrats’ superior ability to survive hypoxia. Radiolabeled nitredendipine binding was determined in rat and Muskrat hearts to estimate the density of voltage gated calcium channels in surface membranes. There were no species differences. Calcium release channel density in the sarcoplasmic reticulum was estimated by the determination of radiolabeled ryanodine binding in Muskrat and rat heart SR membranes. No differences were revealed between species. The SR uptake of calcium was measured in SR membranes from the hearts of the two species. No differences were found in the B max values, however, the Muskrat SR membranes did have a slightly lower K m value. There were large species differences in Na + /Ca 2+ exchange in SL membranes with the Muskrat heart having approximately 3.5 times the transport capacity of rat SL membranes. During hypoxic conditions in which there is extensive ATP depletion leading to [Na + ] i accumulation and discharge of cellular membrane potential, the Na + /Ca 2+ exchanger may operate in the reverse mode and import calcium into the cell and accelerate hypoxic damage. Prior to reaching this state a robust Na + /Ca 2+ exchange would facilitate the maintenance of normal diastolic calcium levels and calcium cycling. Muskrats hearts are hypoxia tolerant by virtue of their ability to reduce metabolic demand and generate ATP anaerobically thus, maintaining a favorable ATP balance. Therefore, the relative overexpression of Na + /Ca 2+ exchangers in Muskrat hearts may be beneficial in the preservation of contractile function and calcium homeostasis in this freshwater diving mammal.
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calcium uptake by mitochondria isolated from Muskrat and guinea pig hearts
The Journal of Experimental Biology, 1991Co-Authors: Thomas A MckeanAbstract:Subsarcolemmal and interfibrillar mitochondria were isolated from the hearts of the diving Muskrat and non-diving guinea pig and direct and indirect measurements of calcium uptake were examined in vitro. The calcium-stimulated respiration rate and 45Ca uptake were measured and found to be greater in Muskrat than in guinea pig mitochondria. Muskrat mitochondria were able to endure a greater external calcium concentration than guinea pig mitochondria before exhibiting indications of inner membrane damage. Calcium uptake by Muskrat heart mitochondria was inhibited more by 1 mmoll-1 MgCl2 than was uptake by guinea pig mitochondria. No differences were detected between the interfibrillar and subsarcolemmal populations of mitochondria within species. An increased ability to sequester calcium by mitochondria without causing them damage may aid an animal during recovery from hypoxia, ischemia or acidosis.
Mark S Boyce - One of the best experts on this subject based on the ideXlab platform.
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Mink Prey Diversity Correlates with Mink–Muskrat Dynamics
Journal of Mammalogy, 2009Co-Authors: C J Shier, Mark S BoyceAbstract:Historic fur returns from Hudson’s Bay Company posts in northwestern Canada reveal periodic oscillations in mink (Neovision vision) harvests lagging 2–3 years behind oscillations in Muskrat (Ondatra zibethicus) harvests, as would be expected in a predator–prey interaction. Toward central and eastern Canada, the strength of the interaction between time series of harvests of minks and Muskrats weakens and the lag between fluctuations of these 2 species decreases to 1 and 0 years, respectively. We tested the hypothesis that this gradient in mink– Muskrat interactions is the result of decreased dependency of minks on Muskrats in areas where minks have access to more alternate prey. We tested 2 predictions: species richness of mink prey is greatest in eastern Canada and decreases to the west, and percent Muskrats in the diets of minks decreases as species richness of mink prey increases. Contrary to the 1st prediction, we found that species richness of mink prey in Canada is highest in southcentral Canada. Consistent with the 2nd prediction, percent occurrence of Muskrats in the diets of minks was much lower in areas with greater species richness of mink prey. Local species richness of mink prey therefore could influence the degree of specialization of minks on Muskrats, but may be insufficient to explain the geographic pattern in the lag between Muskrat and mink harvests in eastern Canada.
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mink prey diversity correlates with mink Muskrat dynamics
Journal of Mammalogy, 2009Co-Authors: C J Shier, Mark S BoyceAbstract:Historic fur returns from Hudson’s Bay Company posts in northwestern Canada reveal periodic oscillations in mink (Neovision vision) harvests lagging 2–3 years behind oscillations in Muskrat (Ondatra zibethicus) harvests, as would be expected in a predator–prey interaction. Toward central and eastern Canada, the strength of the interaction between time series of harvests of minks and Muskrats weakens and the lag between fluctuations of these 2 species decreases to 1 and 0 years, respectively. We tested the hypothesis that this gradient in mink– Muskrat interactions is the result of decreased dependency of minks on Muskrats in areas where minks have access to more alternate prey. We tested 2 predictions: species richness of mink prey is greatest in eastern Canada and decreases to the west, and percent Muskrats in the diets of minks decreases as species richness of mink prey increases. Contrary to the 1st prediction, we found that species richness of mink prey in Canada is highest in southcentral Canada. Consistent with the 2nd prediction, percent occurrence of Muskrats in the diets of minks was much lower in areas with greater species richness of mink prey. Local species richness of mink prey therefore could influence the degree of specialization of minks on Muskrats, but may be insufficient to explain the geographic pattern in the lag between Muskrat and mink harvests in eastern Canada.
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predator prey coupling interaction between mink mustela vison and Muskrat ondatra zibethicus across canada
Oikos, 2009Co-Authors: Nina Holmengen, Mark S Boyce, Knut L Seip, Nils Chr StensethAbstract:In this paper we explore variation in the predator-prey interaction between mink Mustela vison and Muskrat Ondatra zibethicus across Canada based on 25 years of mink (predator) and Muskrat (prey) data from the Hudson's Bay Company. We show that predator-prey interactions have stronger signatures in the west of Canada than in the east. In particular, we show that the observed phase plot trajectories of mink and Muskrat rotate significantly clock-wise, consistent with predator-prey theory. We also investigate four phases of the mink Muskrat interaction sequence (predator crash phase, prey recovery phase, etc.) and show that they are all consistent with a strong coupling in the west, whereas the presence of generalist predators and alternative preys can explain deviations from this pattern in the east.
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spatial variation in mink and Muskrat interactions in canada
Oikos, 2001Co-Authors: Mark S Boyce, Nils Chr StensethAbstract:We investigated the spatial attributes of mink (Mustela vison) and Muskrat (Ondatra zibethicus) interactions in Canada using 160 geographically paired historic time series of mink (n = 80) and Muskrat (n = 80) harvest data obtained from Hudson's Bay Co. Archives. All series were 25 years in length (1925-1949) and were distributed primarily throughout five ecozones. We used autoregressive models and cross-correlation analysis to characterize the interactions between mink and Muskrat. Model selection results did not differ among ecozones, and indicated that a predator-prey autoregressive model incorporating a delayed density-dependent term best described both the mink and Muskrat harvest time series. Subsequent analysis of autoregressive coefficients and estimated lags indicated that mink and Muskrat interactions vary throughout Canada. In western Canada, the trophic interactions appear to be strong, and mink population cycles lag behind Muskrats 2-3 years. In central Canada, mink harvests lagged behind Muskrats 1 year, and mink and Muskrat interactions in central Canada, with the exception of the Hudson Plains ecozone, were intermediate. In eastern Canada, the trophic interactions appeared weakest, and there were no distinct time lags between mink and Muskrat. Stronger interactions in western Canada may be a result of decreased prey diversity, forcing mink to specialize more on Muskrats, whereas comparatively stronger perturbations stemming from other trophic interactions may alter the estimated interaction between mink and Muskrat in eastern Canada.
Qiang Weng - One of the best experts on this subject based on the ideXlab platform.
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seasonal expression of prolactin receptor in the scented gland of male Muskrat ondatra zibethicus
Scientific Reports, 2015Co-Authors: Liang Wang, Xia Sheng, Shuo Zhang, Lu Lu, Zhengrong Yuan, Qiang WengAbstract:Prolactin (PRL) has numerous actions in mammalian biological systems including mammary development and biological processes. The aim of this study was to investigate the seasonal changes of prolactin receptor (PRLR) expression in the scented gland of Muskrat during the breeding and nonbreeding seasons. Histologically, glandular cells, interstitial cells and excretory tubules were identified in the scented glands in both seasons, whereas epithelial cells were sparse in the nonbreeding season. PRLR was observed in glandular cells of scented glands during the breeding and nonbreeding seasons with stronger immunostaining during the breeding season. Consistent with the immunohistochemical results, both the mean of protein and mRNA levels of PRLR were higher in the scented glands of the breeding season, and relatively lower level in the nonbreeding season. In addition, differential seasonal changes were also detected in the expression profile of microRNAs (miRNAs) in the scented gland of Muskrat. Besides, plasma PRL concentration was remarkably higher in the breeding season than that in the nonbreeding season. These results suggested that Muskrat scented gland was the direct target organ of PRL, and stronger expression of PRLR in scented glands during the breeding season indicated that PRL may directly regulate scented glandular function of the Muskrats.
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seasonal expression of androgen receptor in scented gland of Muskrat ondatra zibethicus
General and Comparative Endocrinology, 2014Co-Authors: Lu Lu, Xia Sheng, Qinglin Li, Shiyang Huang, Gen Watanabe, Kazuyoshi Taya, Qiang WengAbstract:Abstract Muskrat is a seasonal breeder, males of which secret musk from paired perineal scented glands found beneath the skin at the ventral base of the tail for attracting female during the breeding season. The aim of this study was to investigate the seasonal changes of expression of androgen receptor (AR) in the scented gland of Muskrat during the breeding and nonbreeding seasons. Histologically, glandular cells, interstitial cells and excretory tubules were identified in scented glands in both seasons, whereas epithelial cells were sparse in the nonbreeding season. AR was observed in glandular cells of scented glands during the breeding and nonbreeding seasons with stronger immunostaining during the breeding season compared to the nonbreeding season. Consistent with the immunohistochemical results, AR protein level was higher in the scented glands of the breeding season, and then decreased to a relatively low level in the nonbreeding season. The mean mRNA level of Ar was significantly higher in the breeding season than in the nonbreeding season. In addition, plasma gonadotropins and testosterone concentrations were remarkably higher in the breeding season than those in the nonbreeding season. These results suggested that Muskrat scented gland was the direct target organ of androgen, and stronger expression of AR in scented glands during the breeding season suggested that androgens may directly influence scented glandular function of the Muskrats and also courtship behavior as we inferred.
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Immunolocalization of inhibin/activin subunit proteins during the breeding season in testes and scented glands of Muskrats (Ondatra zibethicus).
Journal of Veterinary Medical Science, 2011Co-Authors: Xiaoting Ma, Haolin Zhang, Jiaju Weng, Xia Sheng, Li-zhi Lu, Xiao Hu, Meiyu Xu, Qiang Weng, WatanabeAbstract:The objective of this study was to investigate the cellular immunolocalization of inhibin a and inhibin/activin (βA and βB) subunits in the Muskrat testes and scented glands during the breeding season. Inhibin α and inhibin/activin (βA and βB) subunits were expressed in Sertoli cells and Leydig cells of testes and glandular cells of scented glands, respectively. Also, positive signals of inhibin α and inhibin/activin (βA and βB) subunits by Western blotting were both observed in testicular and scented glandular tissues. These results suggested that the testes and scented glands of the Muskrats had the ability to synthesize inhibins and activins and that activins and inhibins might play an important role in testicular and scented glandular function in Muskrats.
Steven M Gorelick - One of the best experts on this subject based on the ideXlab platform.
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drying drives decline in Muskrat population in the peace athabasca delta canada
Environmental Research Letters, 2018Co-Authors: Ellen M Ward, Steven M GorelickAbstract:Empirical and anecdotal reports suggest that Muskrat are in decline across North America, including in the Peace-Athabasca Delta ("Delta"), Canada, one of the largest inland deltas in the world and part of a World Heritage Site with "in Danger" status pending. Muskrat are a key ecological indicator in the Delta. We investigate whether the largescale loss of critical habitat over the past half-century could be driving a decline in Muskrat abundance in the Delta. To do this, we use the Landsat record (1972-2017) to construct a 46-year record of inundation, and compare changes in the extent of critical habitat to the survey record for Muskrat (1970-2016) over this 5500 km2 region. Results show that the declines in critical habitat and Muskrat numbers in the Delta are synchronous: ~1450 km2 of temporarily inundated regions that support critical habitat have diminished by ~10 km2/year over the past 46 years, while the Muskrat population density (houses/km2) has also declined and is significantly related to critical habitat area (km2) (R2 =0.60, P=0.0001). These findings have implications for the Delta, a Ramsar Wetland of International Importance in part for its role as habitat for nearly 200 species of birds, many of which rely on the aquatic habitat considered here. Our results further suggest that the loss of wetland habitat is a primary driver of the decline of Muskrat across the species' native range.
Nils Chr Stenseth - One of the best experts on this subject based on the ideXlab platform.
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predator prey coupling interaction between mink mustela vison and Muskrat ondatra zibethicus across canada
Oikos, 2009Co-Authors: Nina Holmengen, Mark S Boyce, Knut L Seip, Nils Chr StensethAbstract:In this paper we explore variation in the predator-prey interaction between mink Mustela vison and Muskrat Ondatra zibethicus across Canada based on 25 years of mink (predator) and Muskrat (prey) data from the Hudson's Bay Company. We show that predator-prey interactions have stronger signatures in the west of Canada than in the east. In particular, we show that the observed phase plot trajectories of mink and Muskrat rotate significantly clock-wise, consistent with predator-prey theory. We also investigate four phases of the mink Muskrat interaction sequence (predator crash phase, prey recovery phase, etc.) and show that they are all consistent with a strong coupling in the west, whereas the presence of generalist predators and alternative preys can explain deviations from this pattern in the east.
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spatial variation in mink and Muskrat interactions in canada
Oikos, 2001Co-Authors: Mark S Boyce, Nils Chr StensethAbstract:We investigated the spatial attributes of mink (Mustela vison) and Muskrat (Ondatra zibethicus) interactions in Canada using 160 geographically paired historic time series of mink (n = 80) and Muskrat (n = 80) harvest data obtained from Hudson's Bay Co. Archives. All series were 25 years in length (1925-1949) and were distributed primarily throughout five ecozones. We used autoregressive models and cross-correlation analysis to characterize the interactions between mink and Muskrat. Model selection results did not differ among ecozones, and indicated that a predator-prey autoregressive model incorporating a delayed density-dependent term best described both the mink and Muskrat harvest time series. Subsequent analysis of autoregressive coefficients and estimated lags indicated that mink and Muskrat interactions vary throughout Canada. In western Canada, the trophic interactions appear to be strong, and mink population cycles lag behind Muskrats 2-3 years. In central Canada, mink harvests lagged behind Muskrats 1 year, and mink and Muskrat interactions in central Canada, with the exception of the Hudson Plains ecozone, were intermediate. In eastern Canada, the trophic interactions appeared weakest, and there were no distinct time lags between mink and Muskrat. Stronger interactions in western Canada may be a result of decreased prey diversity, forcing mink to specialize more on Muskrats, whereas comparatively stronger perturbations stemming from other trophic interactions may alter the estimated interaction between mink and Muskrat in eastern Canada.
