The Experts below are selected from a list of 123 Experts worldwide ranked by ideXlab platform
Matti Vornanen - One of the best experts on this subject based on the ideXlab platform.
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Chapter 9 The Anoxia-Tolerant Crucian Carp (Carassius Carassius L.)
Fish Physiology, 2009Co-Authors: Matti Vornanen, Jonathan A. W. Stecyk, Göran E. NilssonAbstract:The crucian carp is probably the most anoxia-tolerant fish there is, surviving without oxygen for days to months depending on Temperature. The anoxia tolerance has evolved in response to over-wintering in ponds and small lakes that can become anoxic for months during the winter. The exceptional anoxia tolerance of the crucian carp is based on special physiological traits that are either constitutively expressed or seasonally primed. A key to its anoxia tolerance is its constitutive ability to produce ethanol as the major anaerobic end product. The ethanol production is supported by massive stores of glycogen in various tissues, and these stores are largest in the autumn before the onset of wintertime anoxia. Metabolic depression is less pronounced than in anoxia-tolerant turtles and there is no major down-regulation of membrane permeability in brain ("channel arrest"), possibly with the exception of reduced NMDA receptor function. Increased levels of the inhibitory neurotransmitter GABA and low levels of the excitatory transmitter glutamate together with a modest activation of glycolysis probably ensure energy balance to the anoxic brain and aid to maintain normal ion gradients across neuronal membranes. The heart has been found to sustain cardiac output in anoxia, possibly to allow for substrate transport and a sufficient rate of ethanol release to the water. Like the brain, the heart also shows few signs of reduced ion permeability in anoxia. However, a lack of compensatory Temperature Acclimatization suggests that it is utilizing the low winter Temperature to suppress its energy needs during anoxia.
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Does different thyroid state effect on the contractility of the cardiac muscle of eurythermal fish species, rainbow trout (Oncorhynchus mykiss, Walbaum)?
Journal of Thermal Biology, 2003Co-Authors: Virpi Tiitu, Matti VornanenAbstract:Abstract The effect of thyroid state on heart size and atrial contractility was examined in the rainbow trout (Oncorhynchus mykiss, Walbaum). Fish were randomly divided into four treatment groups: control (no treatment), sham (daily injections of drug vehicle), hyperthyroid (100 μg T3 kg−1 day−1) and hypothyroid (20 mg methimazole kg−1 day−1) fish. Hypothyroidism induced 6% and 8% increase in body mass (Mb) and 32% and 20% increase in relative ventricular mass (MV), compared to the values of control and sham, respectively. In hyperthyroid fish, Mb and MV did not change at all. In hypothyroid and hyperthyroid fish, heart rate was 40% and 21% higher than in control fish, respectively. Thyroid state did not effect the kinetics of isometric contractions or recovery of force from inactivation (restitution). Inhibitory effect of 10 μmol l−1 ryanodine on isometric force (30–40%) and rate of restitution were similar in all treatment groups, suggesting that thyroid state did not have any effect on the function of the sarcoplasmic reticulum. These findings indicate that hypothyroidism causes clear increases in heart rate and heart size in the rainbow trout, while the effects of hyperthyroidism on heart size and function are negligible. Although the increases in heart rate and heart size in hypothyroid trout are similar as the changes induced by cold acclimation, the absence of any changes in kinetics of contraction or ryanodine sensitivity of force development in hypothyroid trout heart suggest that thyroid state alone cannot be responsible for seasonal Temperature Acclimatization in trout.
Charlotte R Milling - One of the best experts on this subject based on the ideXlab platform.
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seasonal Temperature Acclimatization in a semi fossorial mammal and the role of burrows as thermal refuges
PeerJ, 2018Co-Authors: Charlotte R Milling, Janet L Rachlow, Mark A Chappell, Meghan J Camp, Timothy R Johnson, Lisa A Shipley, David R Paul, Jennifer S ForbeyAbstract:Small mammals in habitats with strong seasonal variation in the thermal environment often exhibit physiological and behavioral adaptations for coping with thermal extremes and reducing thermoregulatory costs. Burrows are especially important for providing thermal refuge when above-ground Temperatures require high regulatory costs (e.g., water or energy) or exceed the physiological tolerances of an organism. Our objective was to explore the role of burrows as thermal refuges for a small endotherm, the pygmy rabbit (Brachylagus idahoensis), during the summer and winter by quantifying energetic costs associated with resting above and below ground. We used indirect calorimetry to determine the relationship between energy expenditure and ambient Temperature over a range of Temperatures that pygmy rabbits experience in their natural habitat. We also measured the Temperature of above- and below-ground rest sites used by pygmy rabbits in eastern Idaho, USA, during summer and winter and estimated the seasonal thermoregulatory costs of resting in the two microsites. Although pygmy rabbits demonstrated seasonal physiological Acclimatization, the burrow was an important thermal refuge, especially in winter. Thermoregulatory costs were lower inside the burrow than in above-ground rest sites for more than 50% of the winter season. In contrast, thermal heterogeneity provided by above-ground rest sites during summer reduced the role of burrows as a thermal refuge during all but the hottest periods of the afternoon. Our findings contribute to an understanding of the ecology of small mammals in seasonal environments and demonstrate the importance of burrows as thermal refuge for pygmy rabbits.
Jennifer S Forbey - One of the best experts on this subject based on the ideXlab platform.
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seasonal Temperature Acclimatization in a semi fossorial mammal and the role of burrows as thermal refuges
PeerJ, 2018Co-Authors: Charlotte R Milling, Janet L Rachlow, Mark A Chappell, Meghan J Camp, Timothy R Johnson, Lisa A Shipley, David R Paul, Jennifer S ForbeyAbstract:Small mammals in habitats with strong seasonal variation in the thermal environment often exhibit physiological and behavioral adaptations for coping with thermal extremes and reducing thermoregulatory costs. Burrows are especially important for providing thermal refuge when above-ground Temperatures require high regulatory costs (e.g., water or energy) or exceed the physiological tolerances of an organism. Our objective was to explore the role of burrows as thermal refuges for a small endotherm, the pygmy rabbit (Brachylagus idahoensis), during the summer and winter by quantifying energetic costs associated with resting above and below ground. We used indirect calorimetry to determine the relationship between energy expenditure and ambient Temperature over a range of Temperatures that pygmy rabbits experience in their natural habitat. We also measured the Temperature of above- and below-ground rest sites used by pygmy rabbits in eastern Idaho, USA, during summer and winter and estimated the seasonal thermoregulatory costs of resting in the two microsites. Although pygmy rabbits demonstrated seasonal physiological Acclimatization, the burrow was an important thermal refuge, especially in winter. Thermoregulatory costs were lower inside the burrow than in above-ground rest sites for more than 50% of the winter season. In contrast, thermal heterogeneity provided by above-ground rest sites during summer reduced the role of burrows as a thermal refuge during all but the hottest periods of the afternoon. Our findings contribute to an understanding of the ecology of small mammals in seasonal environments and demonstrate the importance of burrows as thermal refuge for pygmy rabbits.
Alain S Comtois - One of the best experts on this subject based on the ideXlab platform.
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Digitized infrared segmental thermometry: time requirements for stable recordings.
Journal of Manipulative and Physiological Therapeutics, 2006Co-Authors: Richard A Roy, Jean P Boucher, Alain S ComtoisAbstract:Abstract Objectives Digitized infrared segmental thermometry (DIST) is a method for measuring and recording skin surface body Temperatures. The project evaluated the required length of time for patients to acclimatize their core body Temperature to ambient conditions to obtain stable DIST readings. Methods Seventeen subjects were allowed a 20-minute acclimatizing period in a Temperature-controlled room. The bilateral DIST Temperature was measured with thermistors in combination with infrared cameras (IRCs) at the C4 and L4 levels. All IRC Temperatures were recorded after a 20-minute stabilization period. The room Temperature and relative humidity were recorded throughout all trials. The Acclimatization trend was computed from the 20- to 24-minute period for the IRCs, and the Acclimatization trend was computed continuously for a total of 30 minutes (at 2-minute intervals) for 5 days. Results We discovered a stabilization trend in the early trial stages, with the thermistor recordings between 8 and 16 minutes. The IRC trend was also conclusive for the core Temperature requirements. Conclusions This study determined a core body Temperature Acclimatization trend tested among patients using thermistor recordings in a controlled environment. Based on these findings, we recommend Acclimatization in a Temperature- and humidity-controlled environment for a minimum 8-minute period, followed by an 8-minute maximum recording period with the patient in a prone position to obtain accurate DIST recordings.
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Digitized infrared segmental thermometry: time requirements for stable recordings.
Journal of manipulative and physiological therapeutics, 2006Co-Authors: Richard A Roy, Jean P Boucher, Alain S ComtoisAbstract:Digitized infrared segmental thermometry (DIST) is a method for measuring and recording skin surface body Temperatures. The project evaluated the required length of time for patients to acclimatize their core body Temperature to ambient conditions to obtain stable DIST readings. Seventeen subjects were allowed a 20-minute acclimatizing period in a Temperature-controlled room. The bilateral DIST Temperature was measured with thermistors in combination with infrared cameras (IRCs) at the C4 and L4 levels. All IRC Temperatures were recorded after a 20-minute stabilization period. The room Temperature and relative humidity were recorded throughout all trials. The Acclimatization trend was computed from the 20- to 24-minute period for the IRCs, and the Acclimatization trend was computed continuously for a total of 30 minutes (at 2-minute intervals) for 5 days. We discovered a stabilization trend in the early trial stages, with the thermistor recordings between 8 and 16 minutes. The IRC trend was also conclusive for the core Temperature requirements. This study determined a core body Temperature Acclimatization trend tested among patients using thermistor recordings in a controlled environment. Based on these findings, we recommend Acclimatization in a Temperature- and humidity-controlled environment for a minimum 8-minute period, followed by an 8-minute maximum recording period with the patient in a prone position to obtain accurate DIST recordings.
S. Egginton - One of the best experts on this subject based on the ideXlab platform.
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Effects of seasonal Temperature Acclimatization on muscle metabolism in rainbow trout, Oncorhynchus mykiss
Fish Physiology and Biochemistry, 1997Co-Authors: S. Cordiner, S. EggintonAbstract:Maximal enzyme activities in cardiac and swimming muscles of rainbow trout (Oncorhynchus mykiss) were estimated during the natural progression of environmental Temperature, between seasonal extremes of 4 and 18°C. Specific activity of marker enzymes were measured at a common Temperature of 11°C to determine the potential for metabolic Acclimatization. The results confirm an increased oxidative capacity in the cold, with little or no expansion in glycolytic capacity of slow muscle: citrate synthase (CS) activity was 23, 15 and 3 µmoles min^-1 g wet wt^-1 and pyruvate kinase (PK) 15, 23 and 17 µmoles min^-1 g wet wt^-1 from 4, 11 and 18°C acclimatized groups, respectively. Expansion of lipid metabolism was limited, with increased carnitine palmitoleoyltrasferase (CPT) seen only in the coldest group. Cardiac and fast muscle showed a similar response for CS but not PK or CPT which were greatest at 11 and 18°C, respectively. When compared with previous laboratory acclimation studies, these data suggest that environmental factors other than Temperature are likely to influence the nature of metabolic Acclimatization.
