The Relationship of Oxygen Consumption to Age and Weight During the Post-Embryonic Growth of Locusta Migratoria L

The effects of histamine and selected H1 and H2 histamine receptor antagonists on cardiac inotropic and chronotropic activity, coronary perfusate flow (CPF), and myocardial oxygen consumption (MVO2) were studied in isolated guinea pig hearts perfused at constant pressure. Data were collected at the end of a 3-min infusion period at steady state. Cardiac performance increased significantly whereas CPF decreased during histamine infusion. MVO2 remained constant owing to a significant increase in myocardial oxygen extraction. Diphenhydramine attenuated the coronary vasoconstriction but potentiated the positive inotropic response. Cimetidine attenuated the inotropic and chronotropic responses but had no effect on coronary vasoconstriction. In combination, the histamine antagonists attenuated the changes in heart rate, contractility, and CPF. The histamine-induced increase in myocardial oxygen extraction was accompanied by a significant increase in MVO2 in the presence of diphenhydramine. The ratio of the change in oxygen extraction to the change in oxygen consumption caused by histamine was significantly increased by diphenhydramine. This compensated for a histamine-induced decrement in the ratio of the change of CPF to the change in oxygen consumption. Cimetidine had no effect on the changes in coronary flow, oxygen consumption, or the above ratios. Thus, histamine causes direct coronary vasoconstriction via an H1 receptor mechanism, cardiac positive inotropy by an H2 receptor mechanism, and cardiac positive chronotropy by combined H1 and H2 mechanisms. In the presence of a histamine-induced decrease in myocardial oxygen supply, increments in oxygen demand are met by increased oxygen extraction.

To determine whether there are differences in hemodynamics, ventricular function, oxygen delivery, and oxygen consumption between septic and nonseptic patients who have the adult respiratory distress syndrome (ARDS). Cohort analytic study. Tertiary care medical and surgical intensive care unit, university hospital. Eighteen septic (survivors, n = 8; nonsurvivors, n = 10) and 14 nonseptic (survivors, n = 7; nonsurvivors, n = 7) patients studied within 24 hrs of the diagnosis of ARDS. Simultaneous hemodynamic, radionuclide cineangiographic, and oxygen delivery and consumption measurements. Cardiac index, right and left ventricular ejection fractions, end-diastolic volume indices, oxygen delivery, and oxygen consumption were measured. There were no differences in mean systemic and pulmonary arterial pressures, cardiac index, systemic vascular resistance, right and left ventricular ejection fractions, end-diastolic volumes, and oxygen delivery and consumption between septic and nonseptic patients. Early in the course of ARDS, there were no differences in hemodynamics, ventricular function, and oxygen delivery and consumption between septic and nonseptic patients. Sepsis does not account for the previously reported differences in hemodynamics, ventricular function, and oxygen delivery and oxygen consumption between survivors and non-survivors of ARDS. We speculate that both ARDS and sepsis cause release of mediators which cause similar changes in hemodynamics, ventricular function, and oxygen delivery and consumption.

Low level light/laser therapy (LLLT) is considered as a novel, non-invasive, and potential therapy in a variety of psychological and physical conditions, due to its effective intricate photobiomodulation. The mechanism of LLLT is that when cells are stimulated by photons, mitochondria produce a large quantity of ATP, which accelerates biochemical responses in the cell. It is of great significance to gain a clear insight into the change or interplay of various physiological parameters. In this study, we used functional near-infrared spectroscopy (fNIRS) and venous-occlusion plethysmography to measure the LLLT-induced changes in blood flow, oxygenation, and oxygen consumption in human forearms in vivo. Six healthy human participants (4 males and 2 females) were administered with 810-nm light emitted by LED array in ten minutes and blood flow, oxygenation and oxygen consumption were detected in the entire experiment. We found that LLLT induced an increase of blood flow and oxygen consumption on the treated site. Meanwhile, LLLT took a good role in promoting oxygenation of regional tissue, which was indicated by a significant increase of oxygenated hemoglobin concentration (Δ[HbO2]), a nearly invariable deoxygenated hemoglobin concentration (Δ[Hb]) and a increase of differential hemoglobin concentration (Δ[HbD] = Δ[HbO2] - Δ[Hb]). These results not only demonstrate enormous potential of LLLT, but help to figure out mechanisms of photobiomodulation.

To determine whether oxygen consumption during submaximal running increases in proportion to years of accumulated training and racing in masters runners after a bout of downhill running. University of Cape Town, Sports Science Institute of South Africa. Seventeen male masters distance runners (45-55 years) with a range of training (3,536 km to 79,320 km) and racing (205 km to 12,218 km) experience. A 40-minute continuous treadmill run, at 70% of peak treadmill running speed, consisting of two horizontal runs of 10 minutes each, separated by a 20-minute downhill (-10%) run. Heart rate and oxygen consumption were measured continuously during the run. Data were analyzed to identify correlations between the end of the first horizontal section (minute 10) and the first minute of the second horizontal run (minute 31). Delta values were related to current training mileage (km/wk), total accumulated racing distance (km), and total accumulated training distance (km). There were significant changes in both heart rate (p < 0.001) and oxygen consumption (p < 0.001) over time during the 40-minute run. There were no significant relationships between the change in oxygen consumption (delta) between minute 10 and minute 31 and total accumulated training mileage, total accumulated racing mileage, and current training. The results of this study suggest either that submaximal oxygen consumption is not a sensitive marker of changes in neuromuscular activity or that the downhill protocol did not impose a sufficient eccentric stress for the subjects.

Using ventriculography, we assessed the relationship between performance, blood flow, and oxygen consumption of the left ventricle in seven anesthetized dogs. Ventricular loading was varied between increased and decreased afterload by intraaortic infusion of angiotensin and acetylcholine. Intact ventricular performance was measured by computer-based analysis of biplane left ventriculograms. Myocardial blood and flow distribution was determined by radioactive microspheres, and oxygen consumption was measured by coronary arteriovenous oxygen difference times blood flow. When left ventricular systolic pressure rose, tension-time index, stress-time index, stroke work, and minute work derived from the ventriculogram increased significantly; end diastolic volume increased; and ejection fraction decreased. Inverse responses occurred to a smaller degree when left ventricular pressure was reduced. With increased pressure, myocardial blood flow and oxygen consumption changed proportionately to minute work. Correlation coefficients between oxygen consumption and stroke work (0.782), oxygen consumption and minute work (0.769), oxygen consumption and tension-time index (0.792), and between oxygen consumption and stress-time index (0.740) all indicate that performance measures obtained from ventriculograms can be used to estimate changes in oxygen consumption during acute afterload changes. These measurements can be applied to data obtained from clinical catheterization studies in man and suggest that changes in myocardial performance and oxygen consumption can be estimated from ventriculographic data.

It was reported that an application of high-K (isotonic, 40 mM) caused an increase in oxygen consumption accompanied by an increase in tension change in guinea pig taenia coli (1) and that these changes were reversibly abolished by a depletion of Ca from the high-K medium and Sr could replace Ca only for oxygen consumption (2). These results suggest that Ca entering smooth muscle treated with high-K probably increases oxygen consumption, independent of an increase in muscle tension. In a previous paper (3), effects of factors inhibiting tension development on oxygen consumption of the muscle in high-K medium were reported. Glucose removal from the high-K medium abolished the already developed tension corresponded with a decrease in the elevated oxygen consumption rate. Addition of DNP (1×10-4M) to high-K medium further increased or maintained the increased oxygen consumption although it abolished the already developed tension, and the change in oxygen consumption was not modified by Ca removal. On the other hand ouabain (2.5×10-6 M) maintained the increased oxygen consumption in high-K medium, but almost abolished the developed tension. The increase in oxygen consumption was dependent on external calcium. In the present paper, effects of factors inhibiting high-K induced tension and/or oxygen consumption on Ca distribution in taenia coli are studied and this throws some light on a participation of Ca distribution in changes in tension and oxygen consumption of the muscle in high-K medium. A study on ouabain and DNP with high-K on Ca exchange in taenia coli has been reported by Pfaffman and Holland (4), which is incompatible with the present data.

1. Simultaneous measurements of oxygen consumption and mechanical activity have been made in isolated preparations of guinea-pig taenia coli, rabbit abdominal aorta and the longitudinal muscle of rabbit duodenum.2. Mean resting oxygen consumption was greater in mechanically-active preparations (taenia coli and duodenum) than in the aorta which showed no spontaneous activity.3. The relaxation produced by isoprenaline in guinea-pig taenia coli and rabbit duodenum was accompanied by a dose-dependent fall in oxygen consumption.4. The relaxation produced by phenylephrine in guinea-pig taenia coli was accompanied by a dose-dependent fall in oxygen consumption whereas, in the rabbit duodenum, the transient fall in tension was not accompanied by any significant change in oxygen consumption.5. The increase in tension produced by phenylephrine in rabbit abdominal aorta was accompanied by an increase in oxygen consumption.6. Changes in mechanical activity and oxygen consumption produced by isoprenaline and phenylephrine were antagonized by propranolol and phentolamine respectively.7. It is concluded that the variations in oxygen consumption associated with spontaneous or drug-induced mechanical changes are simple reflections of altered mechanical activity. The possibility of additional direct metabolic actions of isoprenaline and phenylephrine is discussed.

NADH fluorescence, [K +] 0 and oxygen consumption in cat cerebral cortex during direct cortical stimulation

In a porcine model of endotoxemia we have studied the effects of nitric oxide (NO) on hepatic oxygen delivery and consumption. After 3 h of endotoxemia, NO biosynthesis was modulated by a bolus dose of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME). Fifteen minutes thereafter a continuous infusion of the NO donor sodium nitroprusside (SNP) was started. Endotoxin significantly reduced hepatic oxygen delivery from 3.4 +/- 0.6 to 2.2 +/- 0.3 ml/kg/min at 3 h. Due to an increased extraction ratio (ER), oxygen consumption was nearly unaffected. L-NAME further diminished oxygen delivery to 1.0 +/- 0.2 ml/kg/min within 15 min (p < 0.05), but despite an increase in ER from 47 to 68% (p < 0.05), oxygen consumption tended to decrease (from 1.0 to 0.7 ml/ kg/min, nonsignificant). A similar tendency was observed in a control group of 9 pigs which was treated in the same way as the study group, except for the SNP infusion. SNP induced an almost selective increase in hepatic arterial flow, with a corresponding increase in oxygen delivery to 1.8 +/- 0.3 ml/kg/min (p < 0.05). At the same time ER was reduced from 68 to 42% (p < 0.05). Oxygen consumption remained unaltered. The control group exhibited no change in either oxygen delivery or consumption. The study shows that nonselective inhibition of NO synthesis is detrimental to hepatic perfusion and oxygen transport. The NO donor SNP increased oxygen delivery via a selective increase in hepatic arterial flow, but failed to influence oxygen consumption. This was probably mainly due to a massive shutdown of sinusoids, which did not reopen when flow was increased. A functioning microcirculation thus seems to be a prerequisite for the stimulation of organ blood flow to be effective.

Comparison between the antioxidant status of terrestrial and diving mammals

Oxygen tension (PO2) was measured with microelectrodes within the retina of anesthetized cats during normoxia and hypoxemia (i.e., systemic hypoxia), and photoreceptor oxygen consumption was determined by fitting PO2 measurements to a model of steady-state oxygen diffusion and consumption. Choroidal PO2 fell linearly during hypoxemia, about 0.64 mmHg/mmHg decrease in arterial PO2 (PaO2). The choroidal circulation provided approximately 91% of the photoreceptors' oxygen supply under dark-adapted conditions during both normoxia and hypoxemia. In light adaptation the choroid supplied all of the oxygen during normoxia, but at PaO2's less than 60 mmHg the retinal circulation supplied approximately 10% of the oxygen. In the dark- adapted retina the decrease in choroidal PO2 caused a large decrease in photoreceptor oxygen consumption, from approximately 5.1 ml O2/100 g.min during normoxia to 2.6 ml O2/100 g.min at a PaO2 of 50 mmHg. When the retina was adapted to a rod saturating background, normoxic oxygen consumption was approximately 33% of the dark-adapted value, and hypoxemia caused almost no change in oxygen consumption. This difference in metabolic effects of hypoxemia in light and dark explains why the standing potential of the eye and retinal extracellular potassium concentration were previously found to be more affected by hypoxemia in darkness. Frequency histograms of intraretinal PO2 were used to characterize the oxygenation of the vascularized inner half of the retina, where the oxygen distribution is heterogeneous and simple diffusion models cannot be used. Inner retinal PO2 during normoxia was relatively low: 18 +/- 12 mmHg (mean and SD; n = 8,328 values from 36 profiles) in dark adaptation, and significantly lower, 13 +/- 6 mmHg (n = 4,349 values from 19 profiles) in light adaptation. Even in the dark- adapted retina, 30% of the values were less than 10 mmHg. The mean PO2 in the inner (i.e., proximal) half of the retina was well regulated during hypoxemia. In dark adaptation it was significantly reduced only at PaO2's less than 45 mmHg, and it was reduced less at these PaO2's in light adaptation.

Relationship between a metabolic rhythm and emergence rhythm in Drosophila melanogaster

IMPORTANCE:Lower oxygen consumption is associated with worse survival in septic shock and in other forms of critical illness. No treatment that increases oxygen extraction, a key determinant of oxygen consumption, has been found. Thiamine is required for aerobic metabolism, and deficiency is common in the critically ill.OBJECTIVES:We evaluated the effect of thiamine on oxygen consumption in patients requiring mechanical ventilation for an acute illness.DESIGN:Phase II, randomized, double-blind, and placebo-controlled trial.SETTING AND PARTICIPANTS:ICUs in a tertiary care hospital in the United States. Patients admitted to the ICU and requiring mechanical ventilation were screened for enrollment.INTERVENTIONS:After enrollment, baseline measurement of oxygen consumption and baseline laboratories including lactate, central venous oxygen saturation, and pyruvate dehydrogenase, a single dose of 200 mg IV thiamine or placebo was administered. Oxygen consumption was then monitored for 6 additional hours and repeat laboratories were drawn at the end of the protocol.MAIN OUTCOMES AND MEASURES:The primary outcome was the change in oxygen consumption. Analysis was done using linear regression with a first-order autoregressive variance-covariance structure to account for repeated measures within subjects. Secondary outcomes included change in lactate, central venous oxygen saturation, and pyruvate dehydrogenase quantity and activity.RESULTS:Sixty-seven patients were enrolled. After excluding 11 patients due to inadequate quantity or quality of oxygen consumption data, 56 patients were included. There was no difference in change in oxygen consumption in the 6 hours after study drug. Results for secondary outcomes were similarly negative. In the prespecified subgroup of 18 thiamine deficient patients, there was a difference in the two oxygen consumption curves (p = 0.006), although no difference in median oxygen consumption or area under the curve.CONCLUSIONS AND RELEVANCE:A single dose of IV thiamine did not alter oxygen consumption in patients requiring mechanical ventilation for acute illness.

Changes in whole body oxygen consumption due to bolus infusions of fentanyl and thiopentone given during "balanced anaesthesia" have been examined in 17 patients. It has been shown that fentanyl causes an average decrease in oxygen consumption of 4.9, 8.4, and 5.2 per cent at 5, 10 and 15 minutes after its infusion. Thiopentone causes an average decrease of 7.0, 8.8, and 1.9 per cent at 5, 10 and 15 minutes after infusion. It is believed that the effects of fentanyl and thiopentone on oxygen consumption are caused mainly by decreases in cerebral and myocardial oxygen consumption.

To examine the relation of oxygen delivery to uptake in normals, we have measured cardiac index, oxygen delivery and oxygen consumption directly and indirectly in two human volunteers before and during a prostacyclin (PGI2) infusion (5 ng/kg/min). We have also investigated the relation of direct and indirect measurements of delivery to consumption in two critically ill patients over a more prolonged study period of 24 hours. Overall, there were close correlations between both cardiac index measured by thermodilution with that calculated from the Fick equation (r = 0.97 p less than 0.001) and oxygen consumption measured directly by analysis of inspired gases (V O2) with that calculated by the reverse Fick method (OUI) (r = 0.95 p less than 0.001). Nevertheless, the limits of agreement between the two methods were wide (1.6 L/min.m2 for the cardiac index and 70.5 ml 02/min.m2 for oxygen consumption, 95% confidence limits). In the two human volunteers, PGI2 produced substantial increases in oxygen delivery but there was no change in oxygen consumption measured directly or indirectly; V O2 and OUI were unrelated and independent of oxygen delivery. However, in the two patients studied over 24 hours, there were close correlations between delivery and both V O2 (r = 0.93 p less than 0.001) and OUI (r = 0.94 p less than 0.001). These results suggest that the derivation of oxygen consumption by the reverse Fick method (OUI) is a reasonable substitute for direct measurements of V O2 but occasionally the absolute values so obtained may be somewhat different.(ABSTRACT TRUNCATED AT 250 WORDS)