СЕЗОННЫЕ ИЗМЕНЕНИЯ ГАЗООБМЕНА У ГЕНДЕРНО СМЕШАННОГО ЭКИПАЖА В УСЛОВИЯХ 8-МЕСЯЧНОЙ ИЗОЛЯЦИИ В ГЕРМООБЪЕКТЕ С ИСКУССТВЕННОЙ ГАЗОВОЙ СРЕДОЙ

Changes in metabolic rates (oxygen consumption, ketogenesis, 14CO2 production from labelled fatty acids, glycolysis) following the addition of octanoate or oleate were studied in isolated livers from fed and starved rats perfused with Krebs-Henseleit bicarbonate buffer in a non-recirculating system. The following results were obtained. The infusion of fatty acids caused a large increase in the rate of oxygen consumption. The effect was greater with octanoate than with oleate and was half-maximal with fatty acid concentrations (free plus albumin bound) around 0.1 mM. The effects of oleate were only partially suppressed when the perfusate contained albumin concentrations near the physiological range. When fatty acids were oxidized at high rates, the glycolytic rate was diminished by 50%. The increase in oxygen consumption could not be explained fully by the increased ATP demand for fatty acid metabolism or by a compensation for the diminished extramitochondrial ATP generation. In the presence of phenylalkyl oxirane carboxylic acid, an inhibitor of the transport of long-chain acyl-CoA derivates into the mitochondria, ketogenesis and 14CO2 production from labelled oleate were strongly inhibited, whereas the increase in oxygen consumption was only slightly affected. In the presence of antimycin A, the increase in oxygen consumption due to fatty acids was totally abolished. Following pretreatment of rats with ciprofibrate (induction of enzymes for peroxisomal beta-oxidation of long-chain fatty acids), ketogenesis (but not 14CO2 production) from oleate was enhanced threefold. The increase in oxygen consumption, however, was not affected. In conclusion, the increase in hepatic oxygen consumption due to addition of fatty acids reflects a mitochondrial process; it is, in part, independent of the ATP demand of the cell. An uncoupling-like effect of fatty acids on the respiratory chain and its possible physiological significance in ketogenesis are discussed.

Aquatic and aerial respiration of the amphibious fishes Lipophrys pholis and Periophthalmus barbarus were examined using a newly designed flow‐through respirometer system. The system allowed long‐term measurements of oxygen consumption and carbon dioxide release during periods of aquatic and aerial respiration. The Mo 2 of L. pholis, measured at 15° C, was 2·1 μmol O2 g–1 h–1 during aquatic and 1·99 μmol O2 g–1 h–1 during aerial exposure. The corresponding values of the Mco2 were 1.67 and 1.59 μmol O2 g–1 h–1 respectively, giving an aquatic respiratory exchange ratio (RER) of 0·80 and an aerial RER of 0·79. The Mo2 of P. barbarus, measured at 28°C, was 4·05 μmol O2 g–1 h–1 during aquatic and 3·44 μmol O2 g–1 h–1 during aerial exposure. The corresponding values of the Mco2 were 3·29 μmol CO2 g–1 h–1 and 2·63 μmol CO2 g–1 h–1 respectively, giving an aquatic RER of 0·81 and an aerial RER of 0·77. While exposed to air for at least 10 h, both species showed no decrease in metabolic rate or carbon dioxide release. The RER of these fishes equalled their respiratory quotient. After re‐immersion an increased oxygen consumption, due to the payment of an oxygen debt, could not be detected.

Paranatal oxygen consumption and respiratory frequency in the Laysan Albatross.

Reduced TOR Signaling Extends Chronological Life Span via Increased Respiration and Upregulation of Mitochondrial Gene Expression

The oxygen consumption of the grass shrimp, Palaemonetes pugio, was determined at different stages of the molt cycle. At each stage of the molt cycle, the oxygen consumption varied in relation to periods of activity. In order to minimize the errors in establishing basal (control) rates of oxygen consumption, measurements were made over extended periods (18 to 24 hours). In contrast to the previous reports of progressive increases in oxygen consumption during proecdysial stages in other crustaceans, we noted significant increases in oxygen consumption just prior to and during the actual shedding of exoskeleton (ecdysis) in grass shrimp. The effects of sodium pentachlorophenate (Na-PCP) on oxygen consumption varied depending on the stage of the molt cycle, concentration of Na-PCP and extent of pre-exposure of shrimp to Na-PCP. At concentrations of 1.5 and 5.0 ppm, Na-PCP did not alter the oxygen consumption of shrimp in intermolt and proecdysial stages of the molt cycle. Late proecdysial shrimp exposed to 5.0 ppm Na-PCP exhibited an increase in oxygen consumption in relation to ecdysis to the same level as that of control shrimp. However, following ecdysis, the shrimp exposed to 5.0 ppm Na-PCP exhibited a dramatic decline in oxygen consumption and died within three hours. This increased sensitivity during the early postecdysial period appeared to be related to an increase in the uptake of Na-PCP at this stage compared to intermolt and proecdysial stages. A decline in oxygen consumption as noted above could be induced in intermolt shrimp by using higher concentrations of Na-PCP. Exposure of shrimp to 10 or 20 ppm Na-PCP, or to 5 ppm followed by 20 ppm Na-PCP caused an initial increase in oxygen consumption and a subsequent decline leading to death. The survival time of intermolt shrimp pretreated with 5 ppm Na-PCP was longer than that of shrimp exposed directly to 10 or 20 ppm Na-PCP. Although 20 ppm 2,4-dinitrophenol (DNP) caused an initial increase in oxygen consumption in intermolt shrimp, this was not followed by any decline in oxygen consumption or death during a 24-hour exposure.

Background. When administered early after an overdose of acetaminophen, intravenous acetylcysteine prevents hepatic necrosis by replenishing reduced stores of glutathione. How acetylcysteine improves the survival of patients with established liver damage induced by acetaminophen, however, is unknown. This study was undertaken to determine whether the beneficial effect of acetylcysteine under such circumstances could be due to enhancement of oxygen delivery and consumption. Methods. We studied the effect of acetylcysteine on systemic hemodynamics and oxygen transport in 12 patients with acetaminophen-induced fulminant hepatic failure and 8 patients with acute liver failure from other causes. The acetylcysteine was given in a dose of 150 mg per kilogram of body weight in 250 ml of 5 percent dextrose over a period of 15 minutes and then in a dose of 50 mg per kilogram in 500 ml of 5 percent dextrose over a period of 4 hours; measurements were made before treatment began and after 30 minutes of the regimen. Results. In the patients with acetaminophen-induced liver failure, the infusion of acetylcysteine resulted in an increase in mean oxygen delivery from 856 to 975 ml per minute per square meter of body-surface area (P = 0.0036), due to an increase in the cardiac index from 5.6 to 6.7 liters per minute per square meter (P = 0.0021). Mean arterial pressure rose from 88 to 95 mm Hg (P = 0.0054) despite a decrease in systemic vascular resistance from 1296 to 1113 dyn · sec · cm−6 per square meter (P = 0.027). There was an increase in oxygen consumption from 127 to 184 ml per minute per square meter (P = 0.0007) associated with an increase in the oxygen-extraction ratio from 16 to 21 percent (P = 0.022). The effects in the patients with acute liver failure from other causes were similar. Conclusions. The increase in oxygen delivery and consumption in response to acetylcysteine may account for its beneficial effect on survival in patients with fulminant hepatic failure induced by acetaminophen.

A simple and reliable method of constructing an intracellular pH microelectrode is described. Antimony is used as the pH sensor. Antimony electrodes have been used in biological systems as early as 1927 (1). Since then several investigators have used different kinds of Sb electrodes. Roos and Boton (3) describe the latest methods of construction and application of pH sensitive micro-electrodes. In most cases the pH electrodes were fabricated by pulling glass capillaries filled with molten antimony and in a few cases by coating glass with antimony. The electrodes were of the open type.

Background Previous investigators have proposed that postoperative shivering may be poorly tolerated by patients with cardiopulmonary disease because of the associated significant increase in total-body oxygen consumption. However, the often-quoted 300-400% increase in oxygen consumption with shivering was derived from relatively few studies performed in a small number of younger persons specifically selected on the basis of clinically recognizable shivering. We hypothesized that the average elderly postoperative patient has a shivering response that is associated with a relatively small increase in total-body oxygen consumption. Methods One hundred eleven elderly patients (age > 60 yr) undergoing surgery were studied to assess the determinants of shivering and total-body oxygen consumption in the early postoperative period. Anesthetic technique, postoperative analgesia, and thermal management were controlled by protocol. The clinical variables associated with shivering and increased total-body oxygen consumption were determined by univariate and multivariate analyses. Results Mean total-body oxygen consumption in shivering patients was 38% greater than in nonshivering patients. Regardless of whether data from shivering patients were included in the analysis, oxygen consumption was directly proportional to mean body temperature. Despite similar core temperatures, men had a greater incidence of clinically recognizable shivering and greater total-body oxygen consumption than did women. Conclusions The metabolic demands associated with postoperative shivering in elderly patients are less than those reported previously in younger persons. These findings suggest that if hypothermia predisposes to cardiovascular complications in the postoperative period, these complications are not likely to be mediated by shivering and increased metabolism.

To determine the relative contribution of splanchnic and leg tissues to postprandial thermogenesis, systemic and regional oxygen consumption rates were measured in nine women and eight men before and for 6 h after the consumption of a mixed meal that provided one-third of the daily energy needs. In women, the increase in splanchnic oxygen uptake accounted for 63 +/- 12% of the postprandial increase in oxygen consumption, whereas in men it accounted for 35 +/- 14% (P = not significant between women and men). Leg oxygen uptake accounted for 11 +/- 4 and 10 +/- 3% of the increase in postprandial oxygen consumption in women and men, respectively. The combined data suggest that approximately 48% of postprandial thermogenesis over 6 h occurs in splanchnic tissues, whereas 30-35% occurs in skeletal muscle. Thus the increase in oxygen consumption after a mixed meal is primarily localized to splanchnic tissues, and major reductions in postprandial thermogenesis are unlikely to be attributable solely to abnormalities of skeletal muscle metabolism.

The uncoupling-like effect of fatty acids [ Scholz , R., Schwabe , U., and Soboll , S. (1984) Eur. J. Biochem. 141, 223-230] was further substantiated in experiments with perfused rat livers by two ways: firstly the kinetics of changes in metabolic rates (oxygen consumption, ketogenesis, fatty acid oxidation) were analysed; secondly subcellular contents of adenine nucleotides and pH gradients across the mitochondrial membrane were determined following fractionation of freeze-fixed and dried tissues in non-aqueous solvents. The following results were obtained. The relaxation kinetics of the increase in oxygen consumption following fatty acid infusion revealed two components, a rapid one with a half-time around 10 s and a slow one with a half-time of more than 100 s. The rapid component was similar to the kinetics of fatty acid oxidation (ketogenesis and 14CO2 production from labelled fatty acids) whereas the half-time of the slow component was in the range of half-times observed with the increase in oxygen consumption following addition of carbonylcyanide p-trifluoromethoxyphenylhydrazone. In the presence of fatty acids, the cytosolic ATP concentrations and ATP/ADP ratios decreased, whereas the corresponding parameters for the mitochondrial space were either increased (oleate) or decreased (octanoate). The effects of oleate were dependent on the albumin concentrations in the perfusate. The normally large difference between cytosolic and mitochondrial ATP/ADP ratios became smaller. Similar observations were obtained with uncoupling agents. The pH gradient across the mitochondrial membrane as calculated from the subcellular distribution of 5,5 dimethyl[2-14C]oxazolidine-2,4-dione was inversed following the addition of both carbonylcyanide p-trifluoromethoxyphenylhydrazone and fatty acids, i.e. the mitochondrial matrix became more acidic than the cytosol. The pH gradient was not affected when oleate was added in the presence of high albumin concentrations. The data support the hypothesis that the increase in hepatic oxygen consumption due to octanoate or oleate is, in part, caused by a mechanism similar to uncoupling of oxidative phosphorylation. This mechanism seems not to be an artifact of isolated systems; it may be of physiological importance for processes in which reducing equivalents are removed independently of the ATP demand of the hepatocyte.

Previous investigators have proposed that postoperative shivering may be poorly tolerated by patients with cardiopulmonary disease because of the associated significant increase in total-body oxygen consumption. However, the often-quoted 300-400% increase in oxygen consumption with shivering was derived from relatively few studies performed in a small number of younger persons specifically selected on the basis of clinically recognizable shivering. We hypothesized that the average elderly postoperative patient has a shivering response that is associated with a relatively small increase in total-body oxygen consumption. One hundred eleven elderly patients (age > 60 yr) undergoing surgery were studied to assess the determinants of shivering and total-body oxygen consumption in the early postoperative period. Anesthetic technique, postoperative analgesia, and thermal management were controlled by protocol. The clinical variables associated with shivering and increased total-body oxygen consumption were determined by univariate and multivariate analyses. Mean total-body oxygen consumption in shivering patients was 38% greater than in nonshivering patients. Regardless of whether data from shivering patients were included in the analysis, oxygen consumption was directly proportional to mean body temperature. Despite similar core temperatures, men had a greater incidence of clinically recognizable shivering and greater total-body oxygen consumption than did women. The metabolic demands associated with postoperative shivering in elderly patients are less than those reported previously in younger persons. These findings suggest that if hypothermia predisposes to cardiovascular complications in the postoperative period, these complications are not likely to be mediated by shivering and increased metabolism.

Surgery performed during general anaesthesia has been shown to induce an increase in oxygen consumption. It is postulated that this response might be influenced by the surgical procedure performed. Metabolic gas exchange was continuously measured by indirect calorimetry for 30 min in 45 patients undergoing four different surgical procedures during general anaesthesia with propofol/fentanyl/vecuronium as follows: elective laparotomy (n = 13); emergency laparotomy (n = 10); elective knee joint arthroscopy (n = 10); gynaecological laparoscopy (n = 12). A significant increase in oxygen consumption occurred in all the groups within 5 min of skin incision. The greatest increase was seen in those undergoing elective laparotomy (+13%, p < 0.001 at 15 min), with similar smaller increases in the other three groups (+6 to +7%, p < 0.05). Surgery induced an increase in systolic blood pressure in all four groups, being most pronounced in the elective laparotomy group (+47% 15 min after skin incision, p < 0.001). These patients also experienced a significant rise in heart rate (+14%, p < 0.01 at 15 min). Carbon dioxide production increased both in the laparoscopy patients (+9%, p < 0.05) and, transiently, in the elective laparotomy group (+6% at 15 min, p < 0.01), but decreased in the other two groups (-7 to -15%, p < 0.05). Surgery induced a parallel increase in both oxygen consumption and systolic blood pressure in all types of operations, although the magnitude varied. Continuous measurement of metabolic gas exchange may provide an additional method of evaluating the metabolic response to different types of surgery.

Physiology and biochemistry of the pseudobranch: an unanswered question?

Oxygen uptake and carbon dioxide release by rainbow trout (Oncorhynchus mykiss Walb.) embryos exposed to constant magnetic fields of 5 and 10 mT (oxygen uptake and carbon dioxide release) and 50, 150, and 300 mT (oxygen uptake) were measured. The data were compared with those recorded in embryos developing under natural magnetic field (control). The magnetic fields tested were found to stimulate respiratory processes in the rainbow trout embryos as shown by a significantly increased oxygen consumption, particularly during periods of intensified morphogenesis. Exposure to 5 and 10 mT magnetic fields resulted in a slightly higher carbon dioxide release, the oxygen consumption being observed to increase as well. The respiratory quotient of the embryos exposed to magnetic fields was slightly higher than that in the control.

Increases in neural activity evoke increases in the delivery and consumption of oxygen. Beyond observations of cerebral tissue and blood oxygen, the role and properties of cerebral oxygen delivery and consumption during changes in brain function are not well understood. This work overviews the current knowledge of functional oxygen delivery and consumption and introduces recent and preliminary findings to explore the mechanisms by which oxygen is delivered to tissue as well as the temporal dynamics of oxygen metabolism. Vascular oxygen tension measurements have shown that a relatively large amount of oxygen exits pial arterioles prior to capillaries. Additionally, increases in cerebral blood flow (CBF) induced by evoked neural activation are accompanied by arterial vasodilation and also by increases in arteriolar oxygenation. This increase contributes not only to the down-stream delivery of oxygen to tissue, but also to delivery of additional oxygen to extra-vascular spaces surrounding the arterioles. On the other hand, the changes in tissue oxygen tension due to functional increases in oxygen consumption have been investigated using a method to suppress the evoked CBF response. The functional decreases in tissue oxygen tension induced by increases in oxygen consumption are slow to evoked changes in CBF under control conditions. Preliminary findings obtained using flavoprotein autofluorescence imaging suggest cellular oxidative metabolism changes at a faster rate than the average changes in tissue oxygen. These issues are important in the determination of the dynamic changes in tissue oxygen metabolism from hemoglobin-based imaging techniques such as blood oxygenation-level dependent functional magnetic resonance imaging (fMRI).