Oxygen Utilization Ratio Research Articles

A Janus-gas diffusion electrode with suitable hydrophilicity and aerophilicity for highly efficient H2O2 electrosynthesis

Low solubility and slow oxygen transport in the electrolyte lead to poor hydrogen peroxide (H2O2) generation performance through oxygen reduction reactions (ORR) at traditional submerged cathodes. Herein, we fabricated a Janus-gas diffusion electrode with asymmetric wettability, high gas permeability, and abundant catalytic active sites using HNO3-modified graphite felt as the substrate, polytetrafluoroethylene (PTFE) as a hydrophobic gas diffusion layer (GDL), and polyvinylidene fluoride (PVDF)/acetylene black(AB) composite as a hydrophilic and aerophilic catalyst layer (CL). Using air as an oxygen supply and a working current density of 10.0 mA∙cm−2, the constructed Janus-gas diffusion electrode achieves an H2O2 yield of 39.0 mg∙L−1∙cm−2, a current efficiency of 97.8 %, and an oxygen utilization ratio of 3.5 % at 60 min, indicating excellent two-electron ORR performance. The enhanced performance is attributed to the superaerophilicity of the PTFE-based hydrophobic GDL, which provides sufficient oxygen mass transfer and supply. The hydrophilic PVDF-based CL remains good aerophilicity and contains abundant active functional groups due to the AB and graphite felt modified with nitric acid. AB increases the electrode’s specific surface area and gas permeability, allowing for more effective oxygen collection and transport. The electrode is stable for continuous use and indicates a promising application in in-situ H2O2 production.

Chemical looping gasification of waste plastics for syngas production using NiO/Al2O3 as dual functional material

This study investigates the chemical looping gasification (CLG) of typical waste plastic, polypropylene (PP), using NiO/Al2O3 as a dual functional material, i.e. oxygen carrier (OC) and catalyst. The whole PP-CLG process comprises PP gasification, coke steam oxidation, and OC air regeneration with the first one being the key step for syngas production. Four operation modes for PP gasification were studied and compared, which were distinguished by whether PP and OC were premixed, and whether the heating rate was fast or slow. Significant differences in the product distribution, PP conversion ratio, and the roles that NiO/Al2O3 played were observed under different modes. The highest syngas yield (64.7 mmol/g-PP), carbon conversion (64.9 %), and minimum coke deposition (19.3 %) during PP gasification were achieved through a combination of premixing and fast heating (Type A). Benefitting from its extensive lattice oxygen supply and the effective catalytic cracking capabilities of NiO/Al2O3, Type A accelerated volatile conversion, demonstrated elevated CO selectivity, and reduced tar content, thereby enhancing PP-syngas conversion efficiency. Direct CLG of PP was genuinely realized in Type A, which is different from the traditional pyrolysis-reforming scheme for syngas production. Characterizations further illustrated that the NiO/Al2O3 in Type A produced coke that was the easiest to remove, experienced less sintering, and exhibited the highest lattice oxygen utilization ratio. The findings are expected to provide practical guidance for the choice of a suitable reaction pathway maximizing the waste plastics to syngas conversion.

ESSENTIAL FATTY ACIDS IN DIET AND THEIR ROLE IN IMPROVING PHYSICAL PERFORMANCE OF SKI RACERS

Introduction: Associations between nutrition and physical performance among elite sportsmen have been extensively studied, although not all nutrients have been covered by these studies. For example, there is still lack of information on the levels of consumption of essential fatty acids (FAs) and their influence on the physical performance among high-performing ski racers. Aim: To study associations between consumption of essential fatty acids and indicators of physical performance Russian ski-racers. Methods: Thirty seven male members of the Komu republic team the Russian national team in cross-country ski aged 17- 33 years took part in this study. To assess physical performance, athletes underwent a test VO2 max, on the Oxycon-Pro ergospirometric system in the "breath-by-breath" mode. Indicators of oxygen consumption (VO2), oxygen utilization ratio, VO2 max, heart rate (HR), blood pressure (BP), anaerobic threshold (AnT), Watt/pulse were estimated. Consumption of different classes of FAs was assessed using the on-line service "Fatty acids in food items". Results: High variability in the consumption of difference classes of Fas was observed. Most ski racers reporten and higher consumption of n-6 linoleic acid and saturated fats compared to the recommended values. At the same time, consumption of n-3 eicosapentaenoic and docosahexaenoic acids was lower than recommended. Singificant correlations were observed between essential а-linolenic acid cnosumption and VO2 max and watt/pulse AnT in the studied sample. Conclusion: Our results suggest an association between the indicator of the efficiency of autonomic support for muscle work -the watt/pulse AnT and insufficient consumption of а-linolenic acid. The results of the study can be applied to optimize the diet and increase the functional reserves and physical performance in athletes.

Detecting resting-state brain activity using OEF-weighted imaging

Traditional resting-state functional magnetic resonance imaging (fMRI) is mainly based on the blood oxygenation level-dependent (BOLD) contrast. The oxygen extraction fraction (OEF) represents an important parameter of brain metabolism and is a key biomarker of tissue viability, detecting the ratio of oxygen utilization to oxygen delivery. Investigating spontaneous fluctuations in the OEF-weighted signal is crucial for understanding the underlying mechanism of brain activity because of the immense energy budget during the resting state. However, due to the poor temporal resolution of OEF mapping, no studies have reported using OEF contrast to assess resting-state brain activity. In this fMRI study, we recorded brain OEF-weighted fluctuations for 10 min in healthy volunteers across two scanning visits, using our recently developed pulse sequence that can acquire whole-brain voxel-wise OEF-weighted signals with a temporal resolution of 3 s. Using both group-independent component analysis and seed-based functional connectivity analysis, we robustly identified intrinsic brain networks, including the medial visual, lateral visual, auditory, default mode and bilateral executive control networks, using OEF contrast. Furthermore, we investigated the resting-state local characteristics of brain activity based on OEF-weighted signals using regional homogeneity (ReHo) and fractional amplitude of low-frequency fluctuations (fALFF). We demonstrated that the gray matter regions of the brain, especially those in the default mode network, showed higher ReHo and fALFF values with the OEF contrast. Moreover, voxel-wise test-retest reliability comparisons across the whole brain demonstrated that the reliability of resting-state brain activity based on the OEF contrast was moderate for the network indices and high for the local activity indices, especially for ReHo. Although the reliabilities of the OEF-based indices were generally lower than those based on BOLD, the reliability of OEF-ReHo was slightly higher than that of BOLD-ReHo, with a small effect size, which indicated that OEF-ReHo could be used as a reliable index for characterizing resting-state local brain activity as a complement to BOLD. In conclusion, OEF can be used as an effective contrast to study resting-state brain activity with a medium to high test-retest reliability.

Coordinated Optimization for the Descent Gradient of Technical Index in the Iron Removal Process.

In the iron removal process, which is composed of four cascaded reactors, outlet ferrous ion concentration (OFIC) is an important technical index for each reactor. The descent gradient of OFIC indicates the reduced degree of ferrous ions in each reactor. Finding the optimal descent gradient of OFIC is tightly close to the effective iron removal and the optimal operation of the process. This paper proposes a coordinated optimization strategy for setting the descent gradient of OFIC. First, an optimal setting module is established to determine the initial set-points of the descent gradient. The oxygen utilization ratio (OUR), an important parameter in this module, cannot be measured online. Therefore, a self-adjusting RBF (SARBF) neural network with an adaptive learning rate is developed to estimate the OUR. The convergence of the SARBF neural network is discussed. Then, a coordinated optimization strategy is proposed to adjust the set-points of the descent gradient when the measured OFICs drift away from their desired set-pints. If the final OFIC does not satisfy the process requirements, a compensation mechanism is developed to provide a compensation for the set-points of the descent gradient. Finally, industrial experiments in the largest zinc hydrometallurgy plant validate the effectiveness of the proposed coordinated optimization strategy. Our strategy improves the qualified ratio of the OFIC and the quality of the goethite precipitate. More profit is created to the iron removal process after our strategy is applied.

Greater Absolute Deoxygenation In Deep Versus Superficial Quadriceps Muscles At Vo2max During Cycle Ergometry

Skeletal muscle deoxygenation ([HHb]) during exercise is dependent on the ratio of oxygen utilization (Vo2) to oxygen delivery (Qo2). Assessment of regional muscle deoxygenation by near infrared spectroscopy (NIRS) has previously been limited technically to superficial muscles. PURPOSE: To use a new high-power Time Resolved (TR) NIRS to investigate deep and superficial muscle deoxygenation during exercise. Because deep muscle has a greater oxidative fiber expression and Qo2/Vo2, we hypothesized that deep quadriceps muscle would deoxygenate less during exercise than superficial muscle. METHODS: Deep and superficial [HHb] was measured by TR NIRS in eight men during incremental cycle ergometry in: superficial vastus lateralis (VL), superficial vastus medialis (VM), and superficial (RF-s) and deep rectus femoris (RF-d). Pulmonary Vo2 was measured breath-by-breath. RESULTS: Vo2max was 2.6±0.4 L/min. On average, for all muscle regions, [HHb] increased from 55±7 μM at baseline to 80±20 μM at peak exercise. [HHb] was less (P<0.05) in RF-d than superficial VL at 70% and 80% peak power, but greater (88±33 μM; P<0.05) than superficial VM (75±20 μM) and VL (77±18 μM) at peak power (Fig.). CONCLUSION: Compared with the superficial muscles, [HHb] was significantly less in deep muscles at submaximal high-intensity work rates: Likely reflecting better maintenance of Qo2/Vo2 in oxidative deep muscle fibers. At peak exercise however, greater [HHb] in deep muscle reveals a greater absolute capacity for O2 extraction compared to more glycolytic superficial muscles. High power NIRS has substantial potential to address important questions regarding vascular and muscle function during exercise. Supported by BBSRC UK, BB/I024798/1, JSPS-24247046

Predicted structural change in erythropoietin of plateau zokors — Adaptation to high altitude

Erythropoietin (EPO) is a glycoprotein hormone, expressed mainly in fetus liver and adult kidneys. EPO plays an important role in enhancing red blood cell formation in bone marrow under hypoxia. Plateau zokor (Myospalax baileyi), an subterranean burrowing endemic rodent inhabiting areas of 2 800–4 200m above sea level on Qinghai–Tibet Plateau, is a typical high hypoxia tolerant mammal with high ratio of oxygen utilization in adaptation to the harsh plateau environment. To investigate the possible mechanisms of adaptation of plateau zokor EPO to high altitude, the complete cDNA and amino acid sequences of plateau zokor EPO have been described. Phylogenetic tree of Epo showed the convergence of the Spalax and Myospalax, indicating that, the convergent evolution was driven by similar hypoxic ecological niches. Our results showed that some common sites under positive selection in zokor (116M and 144A) and Spalax (102R, 116M, 144A and 152P) are the important sites for Epo biological activity. This study thus reports a gene level observation which may be involved in adaptation to underground life at high altitude.

CDNA cloning and expression of erythropoietin in the plateau zokor (Myospalax baileyi) from the Qinghai-Tibet Plateau

All organisms respond to variation in their environments and manage environmental stress through metabolic adjustments. The plateau zokor (Myospalax baileyi) is an endemic and keystone subterranean rodent species that inhabits the Qinghai-Tibet Plateau between 2800 and 4200 m above sea level. It is a hypoxic-tolerant mammal with a high ratio of oxygen utilization that enables it to cope with its harsh surroundings. To explore the molecular mechanism of altitude acclimatization of the plateau zokor, we cloned the zokor erythropoietin (Epo) gene and used real-time PCR to compare Epo mRNA levels in zokors inhabiting 16 different altitudes. The full-length zokor Epo open reading frame was 579 bp that encoded a precursor peptide of 192 amino acids with a signal peptide of 26 residues. The Epo gene of the plateau zokor was 81%-95% homologous to that of human, mouse, rat, root vole and the Golan Heights blind mole rat, with the highest homology (95%) to species of the genus Spalax. Epo mRNA was detected mainly in the zokor kidney and spleen among 8 selected tissues. The level of Epo mRNA increased in the liver and kidney with increases in altitude. The increase in the kidney was 5 times that in the liver. Remarkably, expression of Epo mRNA in the kidney of zokors living at the highest altitude (4268 m) was 12-fold higher than that of zokors living at the lowest (2492 m) altitude. These findings provide essential information for understanding the possible role of Epo in adaptation to hypoxia in the plateau zokor.

Leptin cDNA cloning and its mRNA expression in plateau pikas ( Ochotona curzoniae) from different altitudes on Qinghai-Tibet Plateau

Leptin, an adipocyte-derived hormone, plays an important role in body energy homeostasis. Plateau pika ( Ochotona curzoniae), an endemic and keystone species living only at 3000–5000 m above sea level on Qinghai-Tibet Plateau, is a typically high hypoxia and low temperature tolerant mammal with high resting metabolic rate (RMR), non-shivering thermogenesis (NST), and high ratio of oxygen utilization to cope with harsh plateau environment. To explore the molecular mechanism of ecological acclimation in plateau pika, we first cloned pika leptin cDNA and compared its mRNA expression in different altitudes (3200 and 3900 m) using real-time RT-PCR (Taqman probe) technology. The full-length pika leptin cDNA was 3015 with 504 bp open-reading frame encoding the precursor peptide of 167 amino acids including 21 residues of signal peptide. Pika leptin was 70–72% homologous to that of other species and was of similarly structural characteristics with other species. The pika-specific genetic diversity in leptin sequence occurred at twenty sites. With the increase in altitude, there were larger fat store and high level of ob gene expression in plateau pika. Our results indicated that leptin is sensitive to cold and hypoxia plateau environment and may play one of important roles in pika’s ecological adaptation to harsh plateau environment.

The cardiovascular effects of dexmedetomidine given by continuous infusion during isoflurane anesthesia in dogs

In a previous study we showed that the MAC of isoflurane was decreased by 18 ± 12% and 59 ± 7% by constant rate infusions of dexmedetomidine at 0.5 and 3 μg kg–1 hour–1. The purpose of this study was to document the cardiovascular changes associated with these infusions of dexmedetomidine at 1.3 MAC isoflurane/ dexmedetomidine. Dogs were anesthetized with isoflurane in oxygen given by mask. A cephalic venous catheter, a dorsal pedal arterial catheter and a balloon tipped, Swan–Ganz, pulmonary arterial catheter were placed percutaneously. After instrumentation the dogs were maintained at 1.3 MAC isoflurane for 60 minutes. At this time a set of measurements was made including, heart rate, respiratory rate, core body temperature, pulmonary and systemic arterial blood pressures (SAP, MAP, DAP, CVP, SPAP, MPAP, DPAP and PAOP), cardiac output and arterial and mixed venous blood samples were collected for the measurement of blood gases, pH, hemoglobin concentration, PCV and total protein. Calculated variables included base excess (BE), (HCO3−), cardiac index, systemic and pulmonary vascular resistance indices, oxygen delivery, oxygen consumption, oxygen utilization ratio and shunt fraction. After these measurements to dogs were randomly assigned to receive a loading dose of 0.5 or 3 μg kg–1 of dexmedetomidine given over 6 minutes followed by an infusion of 0.5 (LD) or 3 μg kg–1 hour–1 (HD), respectively. The concentration of isoflurane was reduced by the above percentages, respectively, to maintain 1.3 MAC. Full sets of measurements were repeated at 10, 30, 60, 90, 120, 150 and 180 minutes after the start of the loading dose. Measured and calculated variables were compared with baseline using an anovaand a post-hoc Tukey's test. Significance was set at p = 0.05 and results are given as mean ± SD. The initial concentration of isoflurane was 1.73 ± 0.02% and was reduced to 1.41 ± 0.02 and 0.72 ± 0.09% for the LD and HD, respectively. Heart rate decreased with both doses but no other parameter changed significantly with the LD. With the HD there were significant changes in SAP, MAP, DAP, CVP, MPAP, PAOP, CI, SVRI, PCV, DO2 and shunt fraction. The LD appeared to have minimal effect on the cardiopulmonary values measured, whereas the HD caused typical changes expected with an alpha-2 agonist.

Hemodynamic effects of sevoflurane in spontaneously breathing cats

Sevoflurane has recently been introduced in feline anesthesia. However, its cardiovascular effects have not, to our knowledge, been reported in this species. Six healthy cats, aged 1.81 ± 0.31 years (mean ± SEM) and weighing 3.47 ± 0.11 kg, were studied. Anesthesia was induced and maintained with sevoflurane in oxygen. Body temperature was maintained between 38.5 and 39.55 °C. After instrumentation, end-tidal sevoflurane concentration was randomly set at 1.25, 1.5, and 1.75 times the individual minimum alveolar concentration (MAC), determined in a previous study, according to a Latin Square Design. Thirty minutes of stabilization was allowed after each change of concentration. ECG and heart rate, systemic and pulmonary arterial pressures, central venous pressure (CVP), and core body temperature were continuously monitored and recorded. Inspired and end-tidal oxygen, carbon dioxide, and sevoflurane concentrations were measured using a Raman spectrometer, calibrated every 80 minutes with three calibration gases of known sevoflurane concentration (1, 2, and 5%). Moreover, at selected times, pulmonary artery occlusion pressure and cardiac output (thermodilution) were measured, and arterial and mixed venous blood samples were collected for pH and blood gas analysis, hemoglobin concentration, hemoglobin oxygen saturation, packed cell volume (PCV) and total protein determination, and lactate concentration measurement. Cardiac index (CI), stroke index (SI), systemic and pulmonary vascular resistance indices, rate-pressure product, left and right ventricular stroke work indices (LVSWI and RVSWI, respectively), arterial and mixed venous oxygen contents, oxygen delivery, oxygen consumption, and oxygen utilization ratio were calculated. Data were analyzed by a Repeated Measure Latin Square Design followed by a Tukey's test for 2 × 2 comparisons. Arterial pH significantly decreased from 7.40 ± 0.05 to 7.29 ± 0.07 with the administration of increasing concentrations of sevoflurane. Similarly, LVSWI decreased from 3.72 ± 0.60 to 2.60 ± 0.46 g m−2. Mean arterial pressure, PaO2, mixed venous pH, CI, SI, and oxygen delivery tended to decrease dose-dependently, whereas CVP, PaCO2, PvCO2, PCV, and arterial and mixed venous hemoglobin concentrations tended to increase dose-dependently with the administration of sevoflurane. However, these trends did not reach statistical significance, possibly because of the limited number of animals studied. Sevoflurane seemed to induce dose-dependent cardiovascular depression in cats.

Cardiovascular and respiratory effects of propofol administration in hypovolemic dogs

Summary Cardiopulmonary effects of propofol were studied in hypovolemic dogs from completion of, until 1 hour after administration. Hypovolemia was induced by withdrawal of blood from dogs until mean arterial pressure of 60 mm of Hg was achieved. After stabilization at this pressure for 1 hour, 6 mg of propofol/kg of body weight was administered iv to 7 dogs, and cardiopulmonary effects were measured. After blood withdrawal and prior to propofol administration, oxygen utilization ratio increased, whereas mean arterial pressure, mean pulmonary arterial pressure, central venous pressure, pulmonary capillary wedge pressure, cardiac index, oxygen delivery, mixed venous oxygen tension, and mixed venous oxygen content decreased from baseline. Three minutes after propofol administration, mean pulmonary arterial pressure, pulmonary vascular resistance, oxygen utilization ratio, venous admixture, and arterial and mixed venous carbon dioxide tensions increased, whereas mean arterial pressure, arterial oxygen tension, mixed venous oxygen content, arterial and mixed venous pH decreased from values measured prior to propofol administration. Fifteen minutes after propofol administration, mixed venous carbon dioxide tension was still increased; however by 30 minutes after propofol administration, all measurements had returned to values similar to those measured prior to propofol administration.

Cardiopulmonary effects of etomidate in hypovolemic dogs

Summary Cardiopulmonary effects of etomidate administration were studied in hypovolemic dogs. Baseline cardiopulmonary data were recorded from conscious dogs after instrumentation. Hypovolemia was induced by withdrawal of blood from dogs until mean arterial pressure of 60 mm of Hg was achieved. Blood pressure was maintained at 60 mm of Hg for 1 hour, by further removal or replacement of blood. One milligram of etomidate/kg of body weight was then administered iv to 7 dogs, and the cardiopulmonary effects were measured 3, 15, 30, and 60 minutes later. After blood withdrawal and prior to etomidate administration, heart rate, arterial oxygen tension, and oxygen utilization ratio increased. Compared with baseline values, the following variables were decreased: mean arterial pressure, mean pulmonary arterial pressure, central venous pressure, pulmonary wedge pressure, cardiac index, oxygen delivery, mixed venous oxygen tension, mixed venous oxygen content, and arterial carbon dioxide tension. Three minutes after etomidate administration, central venous pressure, mixed venous and arterial carbon dioxide tension, and venous admixture increased, and heart rate, arterial and venous pH, and arterial oxygen tension decreased, compared with values measured immediately prior to etomidate administration. Fifteen minutes after etomidate injection, arterial pH and heart rate remained decreased. At 30 minutes, only heart rate was decreased, and at 60 minutes, mean arterial pressure was increased, compared with values measured before etomidate administration. Results of this study indicate that etomidate induces minimal changes in cardiopulmonary function when administered to hypovolemic dogs.

Cardiovascular and respiratory effects of thiopental administration in hypovolemic dogs

SUMMARY The cardiopulmonary effects of thiopental sodium were studied in hypovolemic dogs from completion of until 1 hour after administration of the drug. Hypovolemia was induced by withdrawal of blood from dogs until mean arterial pressure of 60 mm of Hg was achieved. After stabilization at this pressure for 1 hour, 8 mg of thiopental/kg of body weight was administered iv to 7 dogs, and cardiopulmonary effects were measured. After blood withdrawal and prior to thiopental administration, heart rate and oxygen utilization ratio increased, whereas mean arterial pressure, mean pulmonary arterial pressure, central venous pressure, pulmonary wedge pressure, cardiac index, oxygen delivery, mixed venous oxygen tension, and mixed venous oxygen content decreased from baseline. Three minutes after thiopental administration, heart rate, mean arterial pressure, mean pulmonary arterial pressure, pulmonary vascular resistance, and mixed venous oxygen tension increased, whereas oxygen utilization ratio and arterial and mixed venous pH decreased from values measured prior to thiopental administration. Fifteen minutes after thiopental administration, heart rate was still increased; however by 60 minutes after thiopental administration, all measurements had returned to values similar to those obtained prior to thiopental administration.

Continuous monitoring of mixed venous oxygen saturation in infants after cardiac surgery

Continuous mixed venous oxygen saturation (SvO2c) was measured in 16 infants immediately after cardiac surgery. A polyurethane 4F, dual channel catheter (Opticath, Modell U440, Oximetrix) with fiberoptic filaments was introduced into the pulmonary artery during cardiothoracic surgery. The catheters were left in place for an average of 67.5 h (range 27 h -125 h) and there were no catheter-related complications. Correlation between continuous in vivo SvO2 values and in vitro values was satisfactory (r = 0.85), whereas a correlation between SvO2c and arterial oxygen saturation (SaO2) was not found (r = 0.07). The sampled arterial lactate values were inversely correlated to the simultaneously measured SvO2c, but the correlation coefficient was only r = -0.4. There was an inverse correlation between SvO2c and arteriovenous oxygen content difference (Ca-vDO2) (r = -0.82), and a marked inverse correlation to the calculated oxygen utilization ratio (r = -0.97). Therefore SvO2c continuously reflects the overall balance between oxygen consumption and delivery, but the use of SvO2 as a predictor of blood lactate levels is unreliable. A further purpose of the present study was to demonstrate the clinical applications and to show the usefulness of SvO2c-monitoring; particularly as a surveillance and early warning system, as a guide for assessing therapy and its relevance in interpreting other monitored parameters. In our opinion continuous SvO2 measurement is a reliable and valuable indicator of cardiopulmonary function in the immediate post-operative period, even in infants with complicated repair of cardiac malformations.

Cerebral metabolic changes during treatment of subacute cerebral infarction by alpha and beta adrenergic blockade with phenoxybenzamine and propranolol.

Cerebral hemispheric blood flow (HBF) and metabolism were measured in 30 patients with acute and subacute cerebral infarction before and after intracarotid infusion of the alpha adrenergic blocking agent phenoxybenzamine (PBZ) or the beta adrenergic blocker propranolol (PPL) dissolved in saline. Following intracarotid injection of 7 µg per kilogram per minute PBZ, HBF showed no change but cerebral hemispheric oxygen consumption (HMIO 2 ) and carbon dioxide production (HMICO 2 ) decreased. Glucose consumption (HMIGl) was unchanged but the glucose to oxygen utilization ratio (HG:O) increased. Intracarotid injection of 1.45 µg per kilogram per minute PPL caused reduction of HBF, HMIO 2 , HMICO 2 , HMIGl and HG:O. After PBZ infusion, mean systemic arterial blood pressure (MABP) decreased slightly, intracranial venous pressure (ICVP) and CSF pressure (CSFP) increased, and central venous pressure (CVP) remained unchanged. PPL infusion had no effect on intracranial dynamics. Possible mechanisms whereby PBZ and PPL influence cerebral metabolism and function were discussed. Inhibition of uncoupling of oxidative phosphorylation appeared to be the most likely explanation for the improvement in brain function and metabolic change associated with each of the drugs. These data support the concept that catecholamines released into brain tissue are a possible cause of uncoupled oxidative phosphorylation. Presently available evidence suggests that adrenergic blocking agents warrant clinical evaluation in the treatment of acute cerebral ischemia, infarction, hemorrhage, and anoxia.

Cerebral metabolic effects of glycerol infusion in diabetics with stroke

Measurement of cerebral blood flow and metabolism before and after intravenous infusion of 10% glycerol was investigated in 22 patients with acute cerebral ischemia, 10 of whom had diabetes mellitus and 12 of whom did not. In diabetic patients, resulting increases of hemispheric blood flow and reduction of oxygen consumption and CO 2 production were not significant whereas these changes in the non-diabetic group were significant. In diabetics cerebral glucose consumption and glucose:oxygen utilization ratio increased significantly but remained unchanged in non-diabetics. Following glycerol infusion, release of free fatty acids and inorganic phosphate from the infarcted hemisphere was diminished or reversed in both groups. It is postulated that the differences in cerebral metabolic responses to glycerol among an acute stroke population with diabetes compared to a similar group with acute stroke but without diabetes may be accounted for by the depressed cerebral glucose consumption in diabetics resulting from elevated blood levels of β-hydroxybutyrate, which tends to be reversed by the antiketogenic effect of glycerol and/or by the greater rise in blood glucose in diabetics following glycerol administration. Hence glycerol would not reduce cerebral oxygen consumption and CO 2 production in the diabetics as much as in the non-diabetics although the release of cerebral free fatty acids and inorganic phosphate from the infarcted brain would be reduced or reversed in both groups. It is concluded that intravenous glycerol infusion may improve uncoupled cerebral oxidative phosphorylation or provide the brain with an additional source of high energy phosphate bonds (ATP production) such as glycerol phosphate.

Étude Séméiologique de la Dilatation de L’Arc Moyen du Cœur

SummaryAuthor emphasizes the importance of the bulged pulmonary artery for the diagnostic of some heart diseases.He shortly describes the different heart diseases which show this roentgenologic abnormality and notices their most pathognomonic symptoms. Some investigations as catheterisation of the heart cavities, angiocardiography, rebreathing test and ratio of oxygen utilization (Bing’s test) are specially valuable for diagnosis.At last, a practical classification of the heart diseases with bulged pulmonary artery is proposed.