1. The coenzyme preference of bovine liver glutamate dehydrogenase (GDH) was probed using dual wa... more 1. The coenzyme preference of bovine liver glutamate dehydrogenase (GDH) was probed using dual wavelength spectroscopy and pairing the thionicotinamide analogues, S-NAD or S-NADP (which have absorbance maxima at 400 nm), with the natural coenzymes, NADP or NAD. 2. S-NAD and S-NADP were found to be good alternate substrates for GDH: the apparent Km's for the thioderivatives were similar to those of the corresponding natural coenzymes, the apparent Km's for glutamate were unaltered by the substitution of the thioderivatives, and the effects of inhibitors and activators on S-NAD or S-NADP kinetics were qualitatively the same as those found for NAD or NADP, respectively. 3. Dual wavelength assays paired NAD and S-NADP or S-NAD and NADP to study the simultaneous reduction of the two coenzymes. Conditions of increasing glutamate concentrations produced differential effects on the rates of the NAD vs NADP reactions, the result, with either nucleotide pair, promoting the NADP linked...
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1974
1. Glycolytic enzyme levels for skeletal muscle of the Pacific white striped dolphin (Lagenorhyne... more 1. Glycolytic enzyme levels for skeletal muscle of the Pacific white striped dolphin (Lagenorhynehus obliquidens) were determined.
Comparative biochemistry and physiology. A, Comparative physiology, 1986
The ability to tolerate extracellular freezing as an adaptation for winter survival was tested in... more The ability to tolerate extracellular freezing as an adaptation for winter survival was tested in seven species of terrestrially-hibernating amphibians found in eastern Canada. All species had only moderate supercooling abilities, with whole animal supercooling points of -1.5 to -3 degrees C. Two salamander species, Plethodon cinereus and Ambystoma laterale, and the toad, Bufo americanus, were freezing intolerant and were killed when frozen for 24 hr at temperatures just below their supercooling points. The major winter strategy of these animals appears to behavioural avoidance of subzero temperatures. Four species of frogs Rana sylvatica, Hyla versicolor, Hyla crucifer and Pseudacris triseriata, survived extracellular freezing at moderate subzero temperatures (-2 to -4 degrees C) for periods of time ranging up to 2 weeks. All four frog species accumulated low molecular weight carbohydrates as cryoprotectants, glycerol being the major cryoprotectant in adult H. versicolor, while imm...
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1975
1. Acetylcholinesterase binding of substrate depends upon at least two contributions. One, the co... more 1. Acetylcholinesterase binding of substrate depends upon at least two contributions. One, the coulombic contribution, is favored by low temperature and high pressure; the other, the hydrophobic contribution, is disrupted by low temperature and high pressure.
Comparative biochemistry and physiology. B, Comparative biochemistry, 1979
1. The malate-aspartate cycle was demonstrable in subcellular preparations of hearts from Arapaim... more 1. The malate-aspartate cycle was demonstrable in subcellular preparations of hearts from Arapaima, Lepidosiren, and Synbranchus (obligate air breathers), Hoplerythriunus (facultative air breather), and Osteoglossum and Hoplias (obligate water breathers). 2. Although no respiratory evidence for significant alpha-glycerophosphate cycle participation could be shown in the air breathers, this cycle was demonstrable in hearts of water breathers. 3. In agreement with the O2 uptake studies, it was possible to reconstruct the malate-aspartate, but not the alpha-glycerophosphate cycle, in isolated mitochondria from air breathers, while both shuttles could be reconstructed with heart mitochondria in the case of water breathing fishes.
Comparative biochemistry and physiology. B, Comparative biochemistry, 1979
1. Using subcellular preparations of gills from Arapaima, an obligate air breather, and aruana, a... more 1. Using subcellular preparations of gills from Arapaima, an obligate air breather, and aruana, a related osteoglossid that is an obligate water breather, a comparison was made of the relative roles of the malate-aspartate cycle and the alpha-glycerophosphate (alpha-GP) cycle in transferring reducing equivalents from the cytosol to the mitochondria. 2. In aruana gill preparations, the alpha-GP cycle could be most clearly demonstrated by reconstructing it with purified isolated mitochondria, using the oxidation rate of exogenous NADH as a measure of the cycling activity. 3. Subcellular preparations of Arapaima gill, in contrast to the aruana gill, were not responsive to exogenous alpha-glycerophosphate, but a glutamate-malate stimulated O2 uptake was sensitive to aminooxyacetate, an aminotransferase inhibitor, a result that would be expected if the respiration were based on malate-aspartate cycling. 4. It was concluded that, compared to the alpha-glycerophosphate cycle, the malate-as...
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1975
1. Malic enzyme occurs in squid mantle muscle at low specific activity; it appears to function on... more 1. Malic enzyme occurs in squid mantle muscle at low specific activity; it appears to function only in the forward direction, displaying a neutral pH optimum for pyruvate formation.
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1975
1. The specific activities of alpha-glycero-P dehydrogenase (~-GPDH) from squid mantle muscle and... more 1. The specific activities of alpha-glycero-P dehydrogenase (~-GPDH) from squid mantle muscle and bee flight muscle are almost i00 times higher than in oyster adductor muscle.
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1975
1. Squid muscle fructose diphosphatase occurs at about 1/30th the activity level of phosphofructo... more 1. Squid muscle fructose diphosphatase occurs at about 1/30th the activity level of phosphofructokinase at 1 atmosphere and 25°C, but during deep diving the combined effects of temperature and pressure on this metabolic locus increase the ratio to about 1/5.
MicroRNAs (miRNAs) are small non-coding RNAs that are important in regulating metabolic stress. I... more MicroRNAs (miRNAs) are small non-coding RNAs that are important in regulating metabolic stress. In this study, we determined the expression and structural characteristics of 20 miRNAs in brown (BAT) and white adipose tissue (WAT) during torpor in thirteen-lined ground squirrels. Using a modified stem-loop technique, we found that during torpor, expression of six miRNAs including let-7a, let-7b, miR-107, miR-150, miR-222 and miR-31 was significantly downregulated in WAT (P<0.05), which was 16%-54% of euthermic non-torpid control squirrels, whereas expression of three miRNAs including miR-143, miR-200a and miR-519d was found to be upregulated by 1.32-2.34-fold. Similarly, expression of more miRNAs was downregulated in BAT during torpor. We detected reduced expression of 6 miRNAs including miR-103a, miR-107, miR-125b, miR-21, miR-221 and miR-31 (48%-70% of control), while only expression of miR-138 was significantly upregulated (2.91±0.8-fold of the control, P<0.05). Interestingl...
The intracellular distribution and maximal activities of some enzymes associated with lipogenesis... more The intracellular distribution and maximal activities of some enzymes associated with lipogenesis, gluconeogenesis and fatty acid oxidation have been determined in the fat body of the adult male cockroach Periplaneta americana. Of the enzymes of lipogenesis, acetyl-CoA synthase, acetyl-CoA carboxylase, glucose 6-phosphate dehydrogenase, and ATP citrate lyase are located entirely in the cytosol. Of the other enzymes of citrate metabolism studied, citrate synthase and NAD-dependent isocitrate dehydrogenase are almost exclusively mitochondrial, whereas NADP-dependent isocitrate dehydrogenase and aconitase are predominantly cytosolic although significant mitochondrial activity is also present. The latter subeellular distribution is also observed for 'malic enzyme' and NAD and NADP dependent malate dehydrogenase. The enzyme of fatty acid oxidation studied, 3-hydroxyacyl-CoA dehydrogenase is entirely mitochondrial. Of the enzymes possibly involved in glueoneogenesis, glucose 6-phosphate is microsomal, fructose 1,6-diphosphatase cytosolic, pyruvate carboxylase mitochondrial and phosphoenolpyruvate carboxykinase predominantly eytosolic. Of the enzymes of amino acid metabolism studied, glutamate dehydrogenase is NAD-dependent and located in the mitochondria whereas glutamate/oxalacetate and glutamate/pyruvate transaminases are predominantly cytosolic but with significant activity in the mitochondria. Glycerol kinase and sorbitol dehydrogenase are cytosolic and the glyoxylate cycle enzymes malate synthetase and isocitrate lyase are not detected in the fat body. The distribution and relative activities of the enzymes are discussed in relation to fat body biosynthesis and in comparison to mammalian liver and adipose tissue.
The intracellular distribution and maximal activities of phosphorylase, trehalase, all the enzyme... more The intracellular distribution and maximal activities of phosphorylase, trehalase, all the enzymes of glycolysis, NAD and FAD-linked glycerol 3-phosphate dehydrogenase, arginine kinase, and adenylate kinase have been determined in the fat body of the adult male cockroach Periplaneta americana. Phosphorylase activity is predominantly in the soluble form but some can be sedimented. Both forms of the enzyme exhibit large increases in activity due to the presence of AMP. Only low activities of trehalase are detected and the enzyme appears to exist in both active and inactive forms. FAD-linked glycerol 3-phosphate dehydrogenase is only found in the mitochondria whereas the NADlinked enzyme and the glycolytic enzymes are located entirely in the cytosol. Of the glycolytic enzymes, phosphoglucomutase, phosphofructokinase and aldolase exhibit unusually low activities. The results suggest that conversion of hexose to triosc phosphate may occur predominantly via the pentose phosphate pathway and not via glycolysis. Whereas considerable activities of both types of glycerol-3-phosphate dehydrogenase are present in the fat body only low activities of lactate dehydrogenase are detected in the tissue.
1. The coenzyme preference of bovine liver glutamate dehydrogenase (GDH) was probed using dual wa... more 1. The coenzyme preference of bovine liver glutamate dehydrogenase (GDH) was probed using dual wavelength spectroscopy and pairing the thionicotinamide analogues, S-NAD or S-NADP (which have absorbance maxima at 400 nm), with the natural coenzymes, NADP or NAD. 2. S-NAD and S-NADP were found to be good alternate substrates for GDH: the apparent Km's for the thioderivatives were similar to those of the corresponding natural coenzymes, the apparent Km's for glutamate were unaltered by the substitution of the thioderivatives, and the effects of inhibitors and activators on S-NAD or S-NADP kinetics were qualitatively the same as those found for NAD or NADP, respectively. 3. Dual wavelength assays paired NAD and S-NADP or S-NAD and NADP to study the simultaneous reduction of the two coenzymes. Conditions of increasing glutamate concentrations produced differential effects on the rates of the NAD vs NADP reactions, the result, with either nucleotide pair, promoting the NADP linked...
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1974
1. Glycolytic enzyme levels for skeletal muscle of the Pacific white striped dolphin (Lagenorhyne... more 1. Glycolytic enzyme levels for skeletal muscle of the Pacific white striped dolphin (Lagenorhynehus obliquidens) were determined.
Comparative biochemistry and physiology. A, Comparative physiology, 1986
The ability to tolerate extracellular freezing as an adaptation for winter survival was tested in... more The ability to tolerate extracellular freezing as an adaptation for winter survival was tested in seven species of terrestrially-hibernating amphibians found in eastern Canada. All species had only moderate supercooling abilities, with whole animal supercooling points of -1.5 to -3 degrees C. Two salamander species, Plethodon cinereus and Ambystoma laterale, and the toad, Bufo americanus, were freezing intolerant and were killed when frozen for 24 hr at temperatures just below their supercooling points. The major winter strategy of these animals appears to behavioural avoidance of subzero temperatures. Four species of frogs Rana sylvatica, Hyla versicolor, Hyla crucifer and Pseudacris triseriata, survived extracellular freezing at moderate subzero temperatures (-2 to -4 degrees C) for periods of time ranging up to 2 weeks. All four frog species accumulated low molecular weight carbohydrates as cryoprotectants, glycerol being the major cryoprotectant in adult H. versicolor, while imm...
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1975
1. Acetylcholinesterase binding of substrate depends upon at least two contributions. One, the co... more 1. Acetylcholinesterase binding of substrate depends upon at least two contributions. One, the coulombic contribution, is favored by low temperature and high pressure; the other, the hydrophobic contribution, is disrupted by low temperature and high pressure.
Comparative biochemistry and physiology. B, Comparative biochemistry, 1979
1. The malate-aspartate cycle was demonstrable in subcellular preparations of hearts from Arapaim... more 1. The malate-aspartate cycle was demonstrable in subcellular preparations of hearts from Arapaima, Lepidosiren, and Synbranchus (obligate air breathers), Hoplerythriunus (facultative air breather), and Osteoglossum and Hoplias (obligate water breathers). 2. Although no respiratory evidence for significant alpha-glycerophosphate cycle participation could be shown in the air breathers, this cycle was demonstrable in hearts of water breathers. 3. In agreement with the O2 uptake studies, it was possible to reconstruct the malate-aspartate, but not the alpha-glycerophosphate cycle, in isolated mitochondria from air breathers, while both shuttles could be reconstructed with heart mitochondria in the case of water breathing fishes.
Comparative biochemistry and physiology. B, Comparative biochemistry, 1979
1. Using subcellular preparations of gills from Arapaima, an obligate air breather, and aruana, a... more 1. Using subcellular preparations of gills from Arapaima, an obligate air breather, and aruana, a related osteoglossid that is an obligate water breather, a comparison was made of the relative roles of the malate-aspartate cycle and the alpha-glycerophosphate (alpha-GP) cycle in transferring reducing equivalents from the cytosol to the mitochondria. 2. In aruana gill preparations, the alpha-GP cycle could be most clearly demonstrated by reconstructing it with purified isolated mitochondria, using the oxidation rate of exogenous NADH as a measure of the cycling activity. 3. Subcellular preparations of Arapaima gill, in contrast to the aruana gill, were not responsive to exogenous alpha-glycerophosphate, but a glutamate-malate stimulated O2 uptake was sensitive to aminooxyacetate, an aminotransferase inhibitor, a result that would be expected if the respiration were based on malate-aspartate cycling. 4. It was concluded that, compared to the alpha-glycerophosphate cycle, the malate-as...
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1975
1. Malic enzyme occurs in squid mantle muscle at low specific activity; it appears to function on... more 1. Malic enzyme occurs in squid mantle muscle at low specific activity; it appears to function only in the forward direction, displaying a neutral pH optimum for pyruvate formation.
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1975
1. The specific activities of alpha-glycero-P dehydrogenase (~-GPDH) from squid mantle muscle and... more 1. The specific activities of alpha-glycero-P dehydrogenase (~-GPDH) from squid mantle muscle and bee flight muscle are almost i00 times higher than in oyster adductor muscle.
Comparative biochemistry and physiology. B, Comparative biochemistry, Jan 15, 1975
1. Squid muscle fructose diphosphatase occurs at about 1/30th the activity level of phosphofructo... more 1. Squid muscle fructose diphosphatase occurs at about 1/30th the activity level of phosphofructokinase at 1 atmosphere and 25°C, but during deep diving the combined effects of temperature and pressure on this metabolic locus increase the ratio to about 1/5.
MicroRNAs (miRNAs) are small non-coding RNAs that are important in regulating metabolic stress. I... more MicroRNAs (miRNAs) are small non-coding RNAs that are important in regulating metabolic stress. In this study, we determined the expression and structural characteristics of 20 miRNAs in brown (BAT) and white adipose tissue (WAT) during torpor in thirteen-lined ground squirrels. Using a modified stem-loop technique, we found that during torpor, expression of six miRNAs including let-7a, let-7b, miR-107, miR-150, miR-222 and miR-31 was significantly downregulated in WAT (P<0.05), which was 16%-54% of euthermic non-torpid control squirrels, whereas expression of three miRNAs including miR-143, miR-200a and miR-519d was found to be upregulated by 1.32-2.34-fold. Similarly, expression of more miRNAs was downregulated in BAT during torpor. We detected reduced expression of 6 miRNAs including miR-103a, miR-107, miR-125b, miR-21, miR-221 and miR-31 (48%-70% of control), while only expression of miR-138 was significantly upregulated (2.91±0.8-fold of the control, P<0.05). Interestingl...
The intracellular distribution and maximal activities of some enzymes associated with lipogenesis... more The intracellular distribution and maximal activities of some enzymes associated with lipogenesis, gluconeogenesis and fatty acid oxidation have been determined in the fat body of the adult male cockroach Periplaneta americana. Of the enzymes of lipogenesis, acetyl-CoA synthase, acetyl-CoA carboxylase, glucose 6-phosphate dehydrogenase, and ATP citrate lyase are located entirely in the cytosol. Of the other enzymes of citrate metabolism studied, citrate synthase and NAD-dependent isocitrate dehydrogenase are almost exclusively mitochondrial, whereas NADP-dependent isocitrate dehydrogenase and aconitase are predominantly cytosolic although significant mitochondrial activity is also present. The latter subeellular distribution is also observed for 'malic enzyme' and NAD and NADP dependent malate dehydrogenase. The enzyme of fatty acid oxidation studied, 3-hydroxyacyl-CoA dehydrogenase is entirely mitochondrial. Of the enzymes possibly involved in glueoneogenesis, glucose 6-phosphate is microsomal, fructose 1,6-diphosphatase cytosolic, pyruvate carboxylase mitochondrial and phosphoenolpyruvate carboxykinase predominantly eytosolic. Of the enzymes of amino acid metabolism studied, glutamate dehydrogenase is NAD-dependent and located in the mitochondria whereas glutamate/oxalacetate and glutamate/pyruvate transaminases are predominantly cytosolic but with significant activity in the mitochondria. Glycerol kinase and sorbitol dehydrogenase are cytosolic and the glyoxylate cycle enzymes malate synthetase and isocitrate lyase are not detected in the fat body. The distribution and relative activities of the enzymes are discussed in relation to fat body biosynthesis and in comparison to mammalian liver and adipose tissue.
The intracellular distribution and maximal activities of phosphorylase, trehalase, all the enzyme... more The intracellular distribution and maximal activities of phosphorylase, trehalase, all the enzymes of glycolysis, NAD and FAD-linked glycerol 3-phosphate dehydrogenase, arginine kinase, and adenylate kinase have been determined in the fat body of the adult male cockroach Periplaneta americana. Phosphorylase activity is predominantly in the soluble form but some can be sedimented. Both forms of the enzyme exhibit large increases in activity due to the presence of AMP. Only low activities of trehalase are detected and the enzyme appears to exist in both active and inactive forms. FAD-linked glycerol 3-phosphate dehydrogenase is only found in the mitochondria whereas the NADlinked enzyme and the glycolytic enzymes are located entirely in the cytosol. Of the glycolytic enzymes, phosphoglucomutase, phosphofructokinase and aldolase exhibit unusually low activities. The results suggest that conversion of hexose to triosc phosphate may occur predominantly via the pentose phosphate pathway and not via glycolysis. Whereas considerable activities of both types of glycerol-3-phosphate dehydrogenase are present in the fat body only low activities of lactate dehydrogenase are detected in the tissue.
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