Pub Date : 1978-04-01DOI: 10.1152/AJPRENAL.1979.236.6.F574-R
O. Candia, H. Schoen
Frog corneas were mounted in a modified Ussing chamber and short-circuit current (SCC) and unidirectional Cl fluxes were measured. Bumetanide, a loop diuretic, at concentrations as low as 10(-7) M, reduced the SCC 29%. At 10(-5) M, bumetanide reduced the SCC 96% and increased transcorneal electrical resistance 20-51%. The forward Cl flux declined from 0.71 +/- 0.04 to 0.20 +/- 0.03 mueq/h.cm2 (n, 7), while, in separate experiments, the backward Cl flux did not change significantly (from 0.22 +/- 0.03 to 0.23 +/- 0.04; n, 7). When corneas were mounted in Cl-free Ringer and the net Na transport was stimulated with amphotericin B, 10(-5) M bumetanide had no effect on the SCC. In separate experiments the effect of 10(-5) M bumetanide on the O2 consumption was measured in a stirrer bath assembly. Bumetanide decreased the O2 consumption from 352 +/- 14 to 297 +/- 19 microliter/h.cm2 (significantly different from sham-treated controls). This decrease was similar to that obtained with furosemide or when Cl was removed from the bathing medium. We infer from these results that bumetanide is a selective inhibitor of active Cl transport in the bullfrog cornea.
{"title":"Selective effects of bumetanide on chloride transport in bullfrog cornea.","authors":"O. Candia, H. Schoen","doi":"10.1152/AJPRENAL.1979.236.6.F574-R","DOIUrl":"https://doi.org/10.1152/AJPRENAL.1979.236.6.F574-R","url":null,"abstract":"Frog corneas were mounted in a modified Ussing chamber and short-circuit current (SCC) and unidirectional Cl fluxes were measured. Bumetanide, a loop diuretic, at concentrations as low as 10(-7) M, reduced the SCC 29%. At 10(-5) M, bumetanide reduced the SCC 96% and increased transcorneal electrical resistance 20-51%. The forward Cl flux declined from 0.71 +/- 0.04 to 0.20 +/- 0.03 mueq/h.cm2 (n, 7), while, in separate experiments, the backward Cl flux did not change significantly (from 0.22 +/- 0.03 to 0.23 +/- 0.04; n, 7). When corneas were mounted in Cl-free Ringer and the net Na transport was stimulated with amphotericin B, 10(-5) M bumetanide had no effect on the SCC. In separate experiments the effect of 10(-5) M bumetanide on the O2 consumption was measured in a stirrer bath assembly. Bumetanide decreased the O2 consumption from 352 +/- 14 to 297 +/- 19 microliter/h.cm2 (significantly different from sham-treated controls). This decrease was similar to that obtained with furosemide or when Cl was removed from the bathing medium. We infer from these results that bumetanide is a selective inhibitor of active Cl transport in the bullfrog cornea.","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"186 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1978-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121620594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1978-02-01DOI: 10.1016/0002-9149(78)90355-7
C. Limas
{"title":"Calcium transport ATPase of cardiac sarcoplasmic reticulum in experimental hyperthyroidism.","authors":"C. Limas","doi":"10.1016/0002-9149(78)90355-7","DOIUrl":"https://doi.org/10.1016/0002-9149(78)90355-7","url":null,"abstract":"","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1978-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128021468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1977-05-01DOI: 10.1152/AJPREGU.1977.233.5.R261-R
M. J. Achs, D. Garfinkel
An experiment where perfused rat hearts receiving no substrate are suddenly given glucose with insulin in the perfusate is simulated with a computer model of cardiac energy metabolism. Mitochondrial metabolism is quantitatively reorganized under cytoplasmic control, with fatty acid oxidation undergoing a two-step decrease. There is an unspanning of the Krebs cycle (different reactions going at different rates) due primarily to slowing of alpha-ketoglutarate dehydrogenase; this ends when cytoplasmic glucose reaches a new steady state. Mitochondria in vitro are known to have higher pH than their surroundings; it is found here that this also holds in situ. Under these conditions, glycolysis is coherently substrate controlled, as is phosphofructokinase, usually considered the typical example of an allosteric enzyme. Limitations on simple methods of analyzing metabolic data of this type, e.g., use of lactate/pyruvate ratios to calculate NADH/NAD ratios, are discussed. Here a large volume of enzyme and other biochemical information has been integrated into a physiologically meaningful system.
{"title":"Computer simulation of rat heart metabolism after adding glucose to the perfusate.","authors":"M. J. Achs, D. Garfinkel","doi":"10.1152/AJPREGU.1977.233.5.R261-R","DOIUrl":"https://doi.org/10.1152/AJPREGU.1977.233.5.R261-R","url":null,"abstract":"An experiment where perfused rat hearts receiving no substrate are suddenly given glucose with insulin in the perfusate is simulated with a computer model of cardiac energy metabolism. Mitochondrial metabolism is quantitatively reorganized under cytoplasmic control, with fatty acid oxidation undergoing a two-step decrease. There is an unspanning of the Krebs cycle (different reactions going at different rates) due primarily to slowing of alpha-ketoglutarate dehydrogenase; this ends when cytoplasmic glucose reaches a new steady state. Mitochondria in vitro are known to have higher pH than their surroundings; it is found here that this also holds in situ. Under these conditions, glycolysis is coherently substrate controlled, as is phosphofructokinase, usually considered the typical example of an allosteric enzyme. Limitations on simple methods of analyzing metabolic data of this type, e.g., use of lactate/pyruvate ratios to calculate NADH/NAD ratios, are discussed. Here a large volume of enzyme and other biochemical information has been integrated into a physiologically meaningful system.","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131456159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper examined some of the relations between thyroid function and the hypothermia of the obese mouse after exposure to the cold. The fall in body temperature of obese mice treated with T3 was less rapid than in untreated obese mice. In the lean mouse, the induction of hypothyroidism by pretreatment with PTU enhanced the rate of fall of body temperature of these mice while in the cold. Circulating levels of TSH were the same in lean and obese mice at 28 t and after exposure to 24°C, TSH in obese mouse was increased more than in lean mouse, but maximal response of TSH to cold at 4°C was same between lean and obese mouse.The TSH response to TRH was significantly less in the obese mice. The thyroidal 125I-uptake was also lower in the obese mouse. The lowered uptake was, however, accompanied by a higher turnover rate as indicated by the more rapid appearance of radioactivity in BEI. Pretreatment with TSH increased the size of the thyroid gland, the uptake of radioactive iodine, the concentration of T4 and T3 in the serum, but did not alter the rapid decline in body temperature of the obese mouse after exposure to the cold. The possibility of an impaired response to exogenous T3 was examined by rendering lean and obese mice hypothyroid with injections of methimazole and then giving T3. The level of plasma T3 in obese mouse was higher than in lean mouse on daily supprement of T3 15mg and and the level of plasma TSH in obese mouse was lower on daily supprement of T3 50ng. However, not even the highest dose of T3 in the obese mice prevented completely the fall in body temperature. These studies suggest that peripheral unresponsiveness to the actions of triiodothyronine may be a major reason for the hypometabolism and hypothermia in these animals.
{"title":"Studies on hypothermia and thyroid function in the obese (ob/ob) mouse.","authors":"M. Ohtake, G. Bray, M. Azukizawa","doi":"10.2974/KMJ1951.26.431","DOIUrl":"https://doi.org/10.2974/KMJ1951.26.431","url":null,"abstract":"This paper examined some of the relations between thyroid function and the hypothermia of the obese mouse after exposure to the cold. The fall in body temperature of obese mice treated with T3 was less rapid than in untreated obese mice. In the lean mouse, the induction of hypothyroidism by pretreatment with PTU enhanced the rate of fall of body temperature of these mice while in the cold. Circulating levels of TSH were the same in lean and obese mice at 28 t and after exposure to 24°C, TSH in obese mouse was increased more than in lean mouse, but maximal response of TSH to cold at 4°C was same between lean and obese mouse.The TSH response to TRH was significantly less in the obese mice. The thyroidal 125I-uptake was also lower in the obese mouse. The lowered uptake was, however, accompanied by a higher turnover rate as indicated by the more rapid appearance of radioactivity in BEI. Pretreatment with TSH increased the size of the thyroid gland, the uptake of radioactive iodine, the concentration of T4 and T3 in the serum, but did not alter the rapid decline in body temperature of the obese mouse after exposure to the cold. The possibility of an impaired response to exogenous T3 was examined by rendering lean and obese mice hypothyroid with injections of methimazole and then giving T3. The level of plasma T3 in obese mouse was higher than in lean mouse on daily supprement of T3 15mg and and the level of plasma TSH in obese mouse was lower on daily supprement of T3 50ng. However, not even the highest dose of T3 in the obese mice prevented completely the fall in body temperature. These studies suggest that peripheral unresponsiveness to the actions of triiodothyronine may be a major reason for the hypometabolism and hypothermia in these animals.","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1976-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129631747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1976-01-21DOI: 10.1249/00005768-197621000-00128
J. McGarr, L. B. Oscai, J. Borensztajn
Hormone-sensitive lipase activity was measured in adipocytes of rats subjected to a 12-wk program of treadmill running. Enzyme activity in the runners sacrificed immediately after exercise increased 2.5-fold (P less than 0.001) in tissue exposed to epinephrine and threefold (P less than 0.001) in tissue not exposed to epinephrine, when the results were expressed per gram of adipose tissue. Increases of almost the same magnitude were observed in runners sacrificed 24 h after their last bout of work. These significant increases in enzyme activity, however, were the result of a significant reduction in the size of cells in the epididymal fat pads of the exercisers compared with those of the freely eating sedentary animals (68.7 +/- 2.7 mum vs. 82.0 +/- 2.7 mum; P less than 0.01). When the results were expressed on a per-cell basis, therefore, hormone-sensitive lipase activity, assayed in the presence or absence of epinephrine, was unaffected by the exercise program. These results provide evidence that the lipolytic capacity of adipocytes of normal, untrained rats is sufficiently large to meet the increased demand for free fatty acids imposed by the exercise program without the need for an adaptive increase in enzyme activity.
{"title":"Effect of exercise on hormone-sensitive lipase activity in rat adipocytes.","authors":"J. McGarr, L. B. Oscai, J. Borensztajn","doi":"10.1249/00005768-197621000-00128","DOIUrl":"https://doi.org/10.1249/00005768-197621000-00128","url":null,"abstract":"Hormone-sensitive lipase activity was measured in adipocytes of rats subjected to a 12-wk program of treadmill running. Enzyme activity in the runners sacrificed immediately after exercise increased 2.5-fold (P less than 0.001) in tissue exposed to epinephrine and threefold (P less than 0.001) in tissue not exposed to epinephrine, when the results were expressed per gram of adipose tissue. Increases of almost the same magnitude were observed in runners sacrificed 24 h after their last bout of work. These significant increases in enzyme activity, however, were the result of a significant reduction in the size of cells in the epididymal fat pads of the exercisers compared with those of the freely eating sedentary animals (68.7 +/- 2.7 mum vs. 82.0 +/- 2.7 mum; P less than 0.01). When the results were expressed on a per-cell basis, therefore, hormone-sensitive lipase activity, assayed in the presence or absence of epinephrine, was unaffected by the exercise program. These results provide evidence that the lipolytic capacity of adipocytes of normal, untrained rats is sufficiently large to meet the increased demand for free fatty acids imposed by the exercise program without the need for an adaptive increase in enzyme activity.","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1976-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131536585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1975-06-01DOI: 10.1152/AJPLEGACY.1975.228.6.1893
P. Guth, E. Smith
Escape of splanchic resistance vessels from vasconstriction due to adrenergic stimulation has been attributed to increasing submucosal blood flow due to dilation of submucosal arteriovenous anastomes (shunts). This postulate, as applied to the rat gastric microcirculation, was studied by in vivo microscopy. Using an image-splittingTV microscope recording system, response of gastric submucosal arterioles (13-33 mum)to 3 min of left splanchnic nerve stimulation, norepinephrine superfision, and vasopressin superfission was measured. All stimuli produced initial vasoconstriction. Escape occurred in all rats with nerve stimulation and norepinephrine, but in onlyone of five with vasopressin. No shunts were seen. The study demonstrates that thegastric submucosal arterioles exhibit an escape phenomenon, suggesting that "autoregulatory escape" in other splanchic beds also may be due to relaxation of constricted vessels and not to opening of shunts.
{"title":"Escape from vasoconstriction in the gastric microcirculation.","authors":"P. Guth, E. Smith","doi":"10.1152/AJPLEGACY.1975.228.6.1893","DOIUrl":"https://doi.org/10.1152/AJPLEGACY.1975.228.6.1893","url":null,"abstract":"Escape of splanchic resistance vessels from vasconstriction due to adrenergic stimulation has been attributed to increasing submucosal blood flow due to dilation of submucosal arteriovenous anastomes (shunts). This postulate, as applied to the rat gastric microcirculation, was studied by in vivo microscopy. Using an image-splittingTV microscope recording system, response of gastric submucosal arterioles (13-33 mum)to 3 min of left splanchnic nerve stimulation, norepinephrine superfision, and vasopressin superfission was measured. All stimuli produced initial vasoconstriction. Escape occurred in all rats with nerve stimulation and norepinephrine, but in onlyone of five with vasopressin. No shunts were seen. The study demonstrates that thegastric submucosal arterioles exhibit an escape phenomenon, suggesting that \"autoregulatory escape\" in other splanchic beds also may be due to relaxation of constricted vessels and not to opening of shunts.","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1975-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123755785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1975-02-01DOI: 10.1016/0002-9149(73)90970-3
W. Parmley, L. Chuck, L. Yeatman
{"title":"Comparative evaluation of the specificity and sensitivity of isometric indices of contractility.","authors":"W. Parmley, L. Chuck, L. Yeatman","doi":"10.1016/0002-9149(73)90970-3","DOIUrl":"https://doi.org/10.1016/0002-9149(73)90970-3","url":null,"abstract":"","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1975-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116157582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1975-01-21DOI: 10.1249/00005768-197500710-00117
W. Stainsby
Oxygen uptake for negative work, stretching twitch contractions by in situ gastrocnemius-plantaris muscle was calculated from measurements of venous outflow and arterial and venous blood oxygen contents. Contractions were produced by valving air at high pressure into the pneumatic lever 10-50 ms before stimulation of the muscle. The loads produced were up to about 2.5 times isometric. Muscle length was always below optimal isometric length. Oxygen uptake for shortening contractions increased with increasing load up to isometric load. Oxygen uptake for stretching contractions decreased with increasing loads above isometric load. Velocity of shortening decreased with increasing loads up to isometric load whereas velocity of stretching increased with increasing loads above isometric. In shortening contractions external work done by the muscle was greatest at intermediate loads, but in stretching contractions the work done on the muscle increased with increasing loads. In stretching contractions the ratio of the energy equivalent of the work absorbed by the muscle reached 8.0 times the energy equivalent of the oxygen uptake. Since this ratio cannot exceed 1.0 for an engine, muscles must act as brakes during stretching contractions.
{"title":"Oxygen uptake for negative work, stretching contractions by in situ dog skeletal muscle.","authors":"W. Stainsby","doi":"10.1249/00005768-197500710-00117","DOIUrl":"https://doi.org/10.1249/00005768-197500710-00117","url":null,"abstract":"Oxygen uptake for negative work, stretching twitch contractions by in situ gastrocnemius-plantaris muscle was calculated from measurements of venous outflow and arterial and venous blood oxygen contents. Contractions were produced by valving air at high pressure into the pneumatic lever 10-50 ms before stimulation of the muscle. The loads produced were up to about 2.5 times isometric. Muscle length was always below optimal isometric length. Oxygen uptake for shortening contractions increased with increasing load up to isometric load. Oxygen uptake for stretching contractions decreased with increasing loads above isometric load. Velocity of shortening decreased with increasing loads up to isometric load whereas velocity of stretching increased with increasing loads above isometric. In shortening contractions external work done by the muscle was greatest at intermediate loads, but in stretching contractions the work done on the muscle increased with increasing loads. In stretching contractions the ratio of the energy equivalent of the work absorbed by the muscle reached 8.0 times the energy equivalent of the oxygen uptake. Since this ratio cannot exceed 1.0 for an engine, muscles must act as brakes during stretching contractions.","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"9 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1975-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114129700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1974-09-01DOI: 10.1007/978-1-4684-0940-6_12
W. Aoi, M. Wade, D. Rosner, M. Weinberger
{"title":"Renin release by rat kidney slices in vitro: effects of cations and catecholamines.","authors":"W. Aoi, M. Wade, D. Rosner, M. Weinberger","doi":"10.1007/978-1-4684-0940-6_12","DOIUrl":"https://doi.org/10.1007/978-1-4684-0940-6_12","url":null,"abstract":"","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1974-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127109496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1974-05-01DOI: 10.1097/00132586-197504000-00007
K. Pavek, J. Carey
{"title":"Hemodynamics and oxygen availability during isovolemic hemodilution.","authors":"K. Pavek, J. Carey","doi":"10.1097/00132586-197504000-00007","DOIUrl":"https://doi.org/10.1097/00132586-197504000-00007","url":null,"abstract":"","PeriodicalId":125752,"journal":{"name":"The American journal of physiology","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1974-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121057073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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