Body O2 Consumption Research Articles

O-289 Effects of Taxol on the developmental potency of human and mouse GV oocytes

Abstract Study question Is it possible to improve the quality of oocytes with delayed maturation or aging? Summary answer Yes, modification of oocyte microtubules at the germinal vesicle (GV) stage inhibits abnormal chromosome separation in in-vitro maturation and enhances early cleavage. What is known already Oocyte aging is characterized by an increase of aneuploidy and a decrease of the developmental potency with maternal ages, which will results in low frequencies of the blastocyte formation and implantation. In addition to the 1st meiotic division, it has become clear that the 2nd meiotic division also significantly contributes to aneuploidy production which is followed by pre-implantation embryo loss. However, no method for overcoming the oocyte aging has been established. Study design, size, duration Human GV oocytes with delayed maturation obtained from consented female patients were used. Mouse GV oocytes collected from 9-15 month old ICR mice were also used. After exposure to Taxol for 1hr, the oocytes were matured in vitro and examined cytogenetically and cytologically at the GV stage, the MII stage and pronuclear stage. Participants/materials, setting, methods RNA transcripts of the GV stage oocytes were compared before and after Taxol exposure with microarray in both species. Chromosome aberrations at the MII stage and blastocyst formation rate were examined in human IVM oocytes. Mouse IVM oocytes were evaluated on 2nd polar body (PB) extrusion and O2 consumption (CRAS3.0, Crino Co Inc.) at the pronuclear stage after parthenogenetic activation with electro-stimulation. Main results and the role of chance After Taxol treatment, premature chromosome separation was significantly reduced from 96% to 7% and the blastocyst formation rate increased from 3% to 16% in human. In mice, normal PB extrusion rate increased from 29% to 92%, and oxygen consumption was higher in some pronuclear oocytes. In human GV oocytes, taxol treatment altered gene expression only in a few factors related to chromosome attachment and segregation. On the other hand, in mouse GV oocytes, gene expression was significantly altered by oocyte aging and Taxol treatment. Limitations, reasons for caution The present results were obtained in human GV oocytes with delayed maturation which were collected after PMS and HCG administrations. It is not clear whether Taxol is effective on the GV oocytes collected before HCG administration. Wider implications of the findings Our results indicate that the combination of biochemical modification and IVM in the GV stage may be able to restore the aging of human oocytes. Trial registration number not applicable

Novel noninvasive estimation of mixed venous oxygen saturation by echocardiography and expired gas analysis.

Mixed venous oxygen (O2) saturation ([Formula: see text]) is an important measure for evaluating the sufficiency of cardiac output (CO) relative to whole body O2 consumption (V̇o2), while clinical use is limited to the required invasive catheterization. According to Fick's equation, V̇o2 (mL/min) = CO (L/min) × Hb (g/dL) × 1.36 (mL/g) × ([Formula: see text] - [Formula: see text])/10 (Hb = hemoglobin concentration, [Formula: see text] = arterial blood O2 saturation). Because V̇o2, CO, Hb, and [Formula: see text] can be measured noninvasively with expired gas analysis, echocardiography, a simple blood test, and percutaneous O2 saturation, respectively, [Formula: see text] can be calculated noninvasively. We hypothesized that noninvasively calculated [Formula: see text] shows a significant correlation and agrees well with invasively measured [Formula: see text]. In 47 patients (29 men; mean age, 70 ± 12 yr) who underwent right heart catheterization, [Formula: see text] was directly measured by sampling pulmonary artery blood. Noninvasively calculated [Formula: see text] was also obtained by the method described above. The calculated [Formula: see text] was significantly correlated with the measured [Formula: see text] (r = 0.79, P < 0.001) and was significantly smaller than the measured [Formula: see text] (70 ± 5.1 vs. 72.1 ± 4.9%, P < 0.001). Bias at [Formula: see text] was -2.2% (95% confidence interval, -3.2 to -1.1%) with limits of agreement from -9.5 to 5.2%, demonstrating acceptable agreement. The optimal cutoff value of calculated [Formula: see text] was 69% for reduced measured [Formula: see text] < 70% with an area under the curve of 0.94. Reduced calculated [Formula: see text] < 69% indicated a sensitivity of 92.9% and a specificity of 90.9% for reduced measured [Formula: see text] < 70%. Noninvasive [Formula: see text] calculated from echocardiography, expired gas analysis, percutaneous arterial blood O2 saturation, and hemoglobin level significantly correlated and agreed well with direct [Formula: see text] measured by catheterization. This novel method allows for practical evaluation of [Formula: see text] to assess the sufficiency of CO according to whole body metabolism.NEW & NOTEWORTHY Clinical use of mixed venous oxygen saturation ([Formula: see text]) is limited to the required invasive procedure. With Fick's equation, expired gas analysis, echocardiography, simple blood tests, and percutaneous oxygen saturation, [Formula: see text] can be calculated noninvasively. We hypothesized that noninvasively calculated [Formula: see text] shows a significant correlation and agrees well with invasively measured [Formula: see text]. The present study examined the relationship between measured [Formula: see text] and calculated [Formula: see text] in patients who underwent right heart catheterization and demonstrated acceptable agreement. This novel method can expand the indication of evaluating [Formula: see text].

Insights into the mechanism of paradoxical low-flow, low-pressure gradient severe aortic stenosis: association with reduced O2 consumption by the whole body.

The mechanism of reduced stroke volume index (SVi) in paradoxical low-flow, low-pressure gradient (PLFLPG) aortic stenosis (AS) remains unclarified. Guyton et al. ( 21 ) demonstrated that SVi is determined by whole body O2 consumption (V̇o2) in many subjects, including patients with heart disease. We hypothesized that reduced SVi in PLFLPG AS is associated with reduced V̇o2 by the whole body. This study investigated the relationship between V̇o2, SVi, and AS severity in patients with AS to examine the association between reduced V̇o2 and PLFLPG AS. In 59 patients (24 men and 35 women, mean age: 78 ± 7 yr old) with severe AS, SVi, AS severity, and type were evaluated by echocardiography, and V̇o2 was measured by the fraction of O2 in expired gases. SVi and V̇o2 were significantly decreased in 20 patients with PLFLPG AS compared with 39 patients with non-PLFLPG AS (30 ± 4 vs. 41 ± 7 ml/m2 and 2.4 ± 0.5 vs. 3.0 ± 0.5 ml·min-1·kg-1, respectively, P < 0.01). The SVi-to-V̇o2 ratio was not different between the two groups (13.1 ± 2.6 vs. 13.6 ± 2.1, not significant). SVi was independently correlated with V̇o2 ( r = 0.74, P < 0.01) but not with the aortic valve area index. Categorized PLFLPG AS was also significantly associated with reduced V̇o2 ( P < 0.001). PLFLPG AS is associated with reduced V̇o2 by the whole body, which may offer insights into the mechanism of PLFLPG AS. NEW & NOTEWORTHY Paradoxical low-flow, low-pressure gradient severe aortic stenosis (PLFLPG AS) is an important and problematic subtype, and its central pathophysiology with reduced stroke volume is yet to be clarified. We hypothesized and subsequently clarified that reduced stroke volume in PLFLPG AS is associated with reduced O2 consumption by the whole body.This study suggests important insights into the mechanism of PLFLPG AS and may further promote studies to investigate further mechanisms and novel treatment.

Rho-Kinase Inhibition Ameliorates Metabolic Disorders through Activation of AMPK Pathway in Mice

BackgroundMetabolic disorders, caused by excessive calorie intake and low physical activity, are important cardiovascular risk factors. Rho-kinase, an effector protein of the small GTP-binding protein RhoA, is an important cardiovascular therapeutic target and its activity is increased in patients with metabolic syndrome. We aimed to examine whether Rho-kinase inhibition improves high-fat diet (HFD)-induced metabolic disorders, and if so, to elucidate the involvement of AMP-activated kinase (AMPK), a key molecule of metabolic conditions.Methods and ResultsMice were fed a high-fat diet, which induced metabolic phenotypes, such as obesity, hypercholesterolemia and glucose intolerance. These phenotypes are suppressed by treatment with selective Rho-kinase inhibitor, associated with increased whole body O2 consumption and AMPK activation in the skeletal muscle and liver. Moreover, Rho-kinase inhibition increased mRNA expression of the molecules linked to fatty acid oxidation, mitochondrial energy production and glucose metabolism, all of which are known as targets of AMPK in those tissues. In systemic overexpression of dominant-negative Rho-kinase mice, body weight, serum lipid levels and glucose metabolism were improved compared with littermate control mice. Furthermore, in AMPKα2-deficient mice, the beneficial effects of fasudil, a Rho-kinase inhibitor, on body weight, hypercholesterolemia, mRNA expression of the AMPK targets and increase of whole body O2 consumption were absent, whereas glucose metabolism was restored by fasudil to the level in wild-type mice. In cultured mouse myocytes, pharmacological and genetic inhibition of Rho-kinase increased AMPK activity through liver kinase b1 (LKB1), with up-regulation of its targets, which effects were abolished by an AMPK inhibitor, compound C.ConclusionsThese results indicate that Rho-kinase inhibition ameliorates metabolic disorders through activation of the LKB1/AMPK pathway, suggesting that Rho-kinase is also a novel therapeutic target of metabolic disorders.

Energy Metabolism and Thyroid Function of Mice with Deleted Wolframin (Wfs1) Gene

There is no data about the energy metabolism of patients with Wolfram syndrome caused by mutations in the wolframin (Wfs1) gene. The aim of this study was to investigate the role of Wfs1 in energy metabolism and thyroid function in Wfs1 deficient mice (Wfs1KO). 16 male (8 Wfs1KO, 8 wild type (wt)) and 16 female (8 Wfs1KO, 8wt) mice aged 11-13 weeks were studied alone in a specific metabolic cage for 48 h. Body weight, food, water and O2 consumption, motor activity, CO2 and heat production of mice were recorded. At the age of 14-20 weeks, plasma levels of thyroxine (T4), TSH and leptin were measured and histology of thyroid tissues examined. Mean CO2 and heat production was not different between the groups. Mean O2 consumption was higher in the Wfs1KO females compared to the Wfs1KO males (3 410.0±127.0 vs. 2 806.0±82.4 ml/kg/h; p<0.05), but not compared to the wt mice. The mean movement activity was not different between the groups except that the Wfs1KO females reared up more often than the wt females (199.8±63.46 vs. 39.26±24.71 cnts/48 h; p<0.05). Both male and female Wfs1KO mice had significantly lower body mass and food intake than wt mice. Male Wfs1KO mice also lost more weight in metabolic cage than wt males (20.43±0.41 vs. 16.07±0.86%; p<0.05) indicating more pronounced response to isolation. Male Wfs1KO mice had significantly lower levels of plasma leptin than wt male mice (3.37±0.40 vs. 5.82±0.71 ng/ml; p<0.01). Thyroid function measured by serum TSH and T4 levels was not different between Wfs1KO and wt groups, but both Wfs1KO and wt male mice had significantly higher mean T4 levels than female mice. The histology of thyroid tissue of Wfs1KO males showed a trend to a smaller mean number of epithelial cells per follicle than the wt male mice.Although Wfs1KO mice were smaller and lost more weight during the experiment, their energy metabolism was not different from wt mice except that the female Wfs1KO mice consumed more O2. As mice in this study were relatively young, longitudinal studies in older mice are necessary to clarify whether Wfs1 has a role in energy metabolism when the disease progresses further.

The choice of the intravenous fluid influences the tolerance of acute normovolemic anemia in anesthetized domestic pigs

IntroductionThe correction of hypovolemia with acellular fluids results in acute normovolemic anemia. Whether the choice of the infusion fluid has an impact on the maintenance of oxygen (O2) supply during acute normovolemic anemia has not been investigated so far.MethodsThirty-six anesthetized and mechanically ventilated pigs were hemodiluted to their physiological limit of anemia tolerance, reflected by the individual critical hemoglobin concentration (Hbcrit). Hbcrit was defined as the Hb-concentration corresponding with the onset of supply-dependency of total body O2-consumption (VO2). The hemodilution protocol was randomly performed with either tetrastarch (6% HES 130/0.4, TS-group, n = 9), gelatin (3.5% urea-crosslinked polygeline, GEL-group, n = 9), hetastarch (6% HES 450/0.7, HS-group, n = 9) or Ringer's solution (RS-group, n = 9). The primary endpoint was the dimension of Hbcrit, secondary endpoints were parameters of central hemodynamics, O2 transport and tissue oxygenation.ResultsIn each animal, normovolemia was maintained throughout the protocol. Hbcrit was met at 3.7 ± 0.6 g/dl (RS), 3.0 ± 0.6 g/dl (HS P < 0.05 vs. RS), 2.7 ± 0.6 g/dl (GEL, P < 0.05 vs. RS) and 2.1 ± 0.4 g/dl (TS, P < 0.05 vs. GEL, HS and RS). Hemodilution with RS resulted in a significant increase of extravascular lung water index (EVLWI) and a decrease of arterial oxygen partial pressure (paO2), and O2 extraction ratio was increased, when animals of the TS-, GEL- and HS-groups met their individual Hbcrit.ConclusionsThe choice of the intravenous fluid has an impact on the tolerance of acute normovolemic anemia induced by acellular volume replacement. Third-generation tetrastarch preparations (e.g., HES 130/0.4) appear most advantageous regarding maintenance of tissue oxygenation during progressive anemia. The underlying mechanism includes a lower degree of extravasation and favourable effects on microcirculatory function.

Abstract 4: Resuscitation with Adenocaine and Magnesium Reduces Fluid Requirement and Improves Cardiac Function Following 72% Blood Loss in the Pig

Introduction: Fluid therapy following severe hemorrhagic shock triggers ischemia-reperfusion (I/R) injury and multi-organ dysfunction. The combination of adenocaine (adenosine and lidocaine), and Mg2+ (ALM) has been shown to stabilize cardiac function and hemodynamics after myocardial I/R. Hypothesis: ALM in 7.5%NaCl at resuscitation: 1) reduces fluid requirements during permissive hypotension and 2) improves post-resuscitation cardiac function. Methods: Pigs (38kg) were randomized to: Sham (n=5), Sham + ALM (n=5), hemorrhage (n=11), and hemorrhage + ALM (n=9). Animals were subjected to pressure controlled hemorrhage at a target MAP of 35mmHg. After 90 min Ringers acetate and 20ml 7.5% NaCl ± ALM (Adenosine 0.23 mg/kg; Lidocaine 0.64 mg/kg; Mg2+ 0.4 mg/kg) was infused to maintain a target MAP of 50 mmHg (permissive hypotension). After 30min 75% of the shed blood was re-infused ± ALM (Adenosine 0.82 mg/kg; Lidocaine 1.66 mg/kg) and the pigs were observed for 6 hrs. Cardiac function was evaluated by pressure-volume (P-V) analysis. Results: In the ALM group 40% less fluid was required to maintain a MAP of 50mmHg for 30min (hemorrhage: 41.5ml/kg CI: 27.7-61.8 vs. ALM: 24.7ml/kg CI:19.4-31.5*). During permissive hypotension 7.5% NaCl ALM significantly increased end-systolic pressure by 27% (hemorrhage: 70 mmHg ± 3 vs. ALM: 89 mmHg ± 9*) and cardiac contractility by 64% (dP/dtmax) (hemorrhage: 2622 mmHg/sec ± 331 vs. ALM: 4301 mmHg/sec ± 262*). Treatment with ALM at blood infusion reduced whole body O2 consumption by 27% lasting 30 min into infusion (group difference p&lt;0.05). In addition, systolic function after blood reinfusion, evaluated by the end-systolic P-V relationship and preload recruitable stroke work, was significantly improved in ALM vs. hemorrhage. Furthermore, ALM enhanced relaxation (dP/dtmin) during reperfusion (hemorrhage: -1578 mmHg/sec ± 103 vs. ALM -2178 mmHg/sec ± 189*). Conclusion: 7.5% NaCl ALM reduced fluid requirements by 40% during permissive hypotension, improved cardiac function and reduced total body O2 consumption following severe hemorrhage. Administration of ALM is effective in minimizing fluid requirements and I/R injury following hemorrhage. (* p&lt;0.05)

Altered glucose metabolism and preserved energy charge and neuronal structures in the brain of mouse intermittently exposed to hypoxia

The key for an animal to survive prolonged hypoxia is to avoid rapid decline in ATP levels in vital organs such as the brain. This can be well achieved by a very few of hypoxia-tolerant animals such as freshwater turtles and newborn animals, since these animals can substantially suppress their metabolic levels by coordinated regulation of ATP-producing and ATP-demanding pathways. However, most animals, especially adult mammals, can only tolerate a short period of hypoxia since they are unable to maintain constant ATP levels and energy charge in vital organs during prolonged hypoxic exposure. Here, we described a special mouse model, in which a hypoxia intolerant adult mouse gradually built up an ability to survive prolonged hypoxia after intermittent hypoxic exposures. This increased ability was accompanied by reductions in body temperature and O2 consumption as well as transient variations in blood pCO2, pO2 and pH. The glucose and energy metabolism in the brain of the mouse altered similarly to those reported in the brain of hypoxic turtles. Activities of phosphofructokinase and pyruvate kinase, the two rate-limiting enzymes controlling the rate of glycolysis decreased to baseline levels after a short period of increase. In contrast, the activity of complex I, the major enzyme complex controlling oxidative phosphorylation, was kept inhibited. These alterations in the ATP-producing pathway suggest the occurrence of reverse Pasteur effect, indicating that the animal had entered a hypometabolic state favoring maintenance of ATP level and energy charge in hypoxic conditions. In supporting this idea, the ATP levels and energy charge as well as neuronal structures in the brain were well preserved. This study provides evidence for a possibility that a hypoxic intolerant animal can build up an ability to survive prolonged hypoxia through regulation of its glucose and energy metabolism after an appropriate hypoxic training, which deserves further investigation.

Altered ventilatory and thermoregulatory control in male and female adult Pet-1 null mice

The integrity of the serotonin (5-HT) system is essential to normal respiratory and thermoregulatory control. Male and female transgenic mice lacking central 5-HT neurons (Lmx1b(f/f/p) mice) show a 50% reduction in the hypercapnic ventilatory response and insufficient heat generation when cooled (Hodges and Richerson, 2008a; Hodges et al., 2008b). Lmx1b(f/f/p) mice also show reduced body temperatures (T(body)) and O(2) consumption [Formula: see text] , and breathe less at rest and during hypoxia and hypercapnia when measured below thermoneutrality (24 °C), suggesting a role for 5-HT neurons in integrating ventilatory, thermal and metabolic control. Here, the hypothesis that Pet-1 null mice, which retain 30% of central 5-HT neurons, will demonstrate similar deficits in temperature and ventilatory control was tested. Pet-1 null mice had fewer medullary tryptophan hydroxylase-immunoreactive (TPH(+)) neurons compared to wild type (WT) mice, particularly in the midline raphé. Female (but not male) Pet-1 null mice had lower baseline ventilation (V(E)), breathing frequency (f), [Formula: see text] and T(body) relative to female WT mice (P < 0.05). In addition, V(E) and [Formula: see text] were decreased in male and female Pet-1 null mice during hypoxia and hypercapnia (P < 0.05), but only male Pet-1 null mice showed a significant deficit in the hypercapnic ventilatory response when expressed as % of control (P < 0.05). Finally, male and female Pet-1 null mice showed significant decreases in T(body) when externally cooled to 4 °C. These data demonstrate that a moderate loss of 5-HT neurons leads to a modest attenuation of mechanisms defending body temperature, and that there are gender differences in the contributions of 5-HT neurons to ventilatory and thermoregulatory control.

Variable Effects of Caloric Restriction on Metabolic and Breathing Regulation Between Two Inbred Mouse Strains

The World Health Organization reports that ~800 million people worldwide are undernourished, corresponding to a daily mortality rate of 25,000 people. While altered metabolic and breathing characteristics occur with severe caloric restriction (CR), the mechanisms are unclear. We hypothesize that a robust genetic difference between C3H/HeJ (C3) and C57BL/6 (B6) mice lead to variation in metabolic and breathing regulation with CR. C3 and B6 mice (n = 8 per strain) were fed a diet equal to 33% of the daily food intake for 21 days. Using plethysmography, breathing characteristics were measured weekly on room air, and following acute hypercapnic (5% CO2) and hypoxic (10% O2) challenges. While the decline in body weight through 21 days of CR was similar in C3 vs. B6 strains (~40%), reductions in body temperature (10.0±1.8 vs. 2.8±1.0°C) and O2 consumption (1.36±0.32 vs. ‐0.04±0.16 ml/hr/g) were significantly (P &lt; 0.01) lower in C3 relative to B6 mice. Minute ventilation (VE) on room air remained unchanged with CR in both strains, but hypercapnic and hypoxic VE were depressed incrementally though 14 days. By day 21 of CR, hypercapnic and hypoxic VE recovered in B6 but not in C3 mice. In conclusion, genetic factors determine variation in metabolic and breathing regulation during CR, allowing B6 mice to maintain indices of homeostasis closer to control values than C3 mice.

Skeletal muscle gene transcript changes in type 1 diabetic patients following insulin deprivation

Insulin resistance is associated with skeletal muscle mitochondrial (mito) dysfunction in many conditions including type 2 diabetes (T2D). Poor glycemic control in T2D is associated with muscle mito gene transcript alterations. It is unknown whether muscle mito changes are related to reduced insulin action or vice versa. We obtained vastus lateralis muscle biopsies from 7 type 1 diabetic patients (T1D) following 8–12 hrs of insulin deprivation (I−) and replacement (I+) and measured skeletal muscle mito ATP production (MATP) and gene transcripts. I− and I+ changed glucose and glucagon levels (glucose=291±15mg/dl in I− vs 97±3 in I+ and glucagon=79.8±15.3 pg/mL in I− vs 47.3±5.9 in I+, p<0.04). Whole body O2 consumption increased during I− by 15% (p<0.05) but maximal MATP decreased by 21.3–27.9% (p<0.05). Gene transcript profiling in skeletal muscle analyzed using Affymetrix GeneChip arrays showed alterations in 2355 transcripts. Pathway analysis showed down-regulation of oxidative phosphorylation and arachidonic acid metabolism, and up-regulation of VEGF and actin cytoskeleton signaling in I−. We conclude that the reduced insulin action that occurred during I− in T1D resulted in substantial changes in gene transcript levels of muscle mito genes and reduced maximal MATP, supporting that insulin is key regulator of muscle mito function by exerting its effect at various levels. Supported by NIHRO1DK41973.

Apelin, an APJ Receptor Ligand, Regulates Body Adiposity and Favors the Messenger Ribonucleic Acid Expression of Uncoupling Proteins in Mice

Apelin, the endogenous ligand of the APJ receptor, has been identified in a variety of tissues, including stomach, heart, skeletal muscle, and white adipose tissue. We sought to clarify the effects of apelin on body adiposity and the expression of uncoupling proteins (UCPs) in C57BL/6 mice. Treatment with ip apelin at a dose of 0.1 mumol/kg.d for 14 d decreased the weight of white adipose tissue and serum levels of insulin and triglycerides, compared with controls, without influencing food intake. Apelin treatment also decreased body adiposity and serum levels of insulin and triglycerides in obese mice fed a high-fat diet. Apelin increased the serum adiponectin level and decreased that of leptin. Additionally, apelin treatment increased mRNA expression of UCP1, a marker of peripheral energy expenditure, in brown adipose tissue (BAT) and of UCP3, a regulator of fatty acid export, in skeletal muscle. In addition, immunoblot bands and relative densities of UCP1 content in BAT were also higher in the apelin group than controls. Furthermore, apelin treatment increased body temperature and O(2) consumption and decreased the respiratory quotient. In conclusion, apelin appears to regulate adiposity and lipid metabolism in both lean and obese mice. In addition, apelin regulates insulin resistance by influencing the circulating adiponectin level, the expression of BAT UCP1, and energy expenditure in mice.

Intracellular energy metabolism in avian intrapulmonary chemoreceptors

Intrapulmonary chemoreceptors (IPC) are CO2-sensitive sensory neurons that innervate the lungs of birds. Although IPC neurons are present near the interface between air and blood, several lines of evidence suggests that they rely primarily on glycolysis and not on oxidative phosphorylation for ATP generation (Burger et al., 1974).The goal of the present study was to test this topic further by examining IPC discharge using pharmacological inhibitors of both glycolysis and oxidative phophorylation. We recorded the response of 12 single unit IPC from 12 adult Anas platyrhynchos to step changes in CO2 before and after intravenous administration of up to 70 mg/kg (0.38 mmole/kg) of the glycolytic inhibitor Na-iodoacetate (IAA; n=6) and 2 mg/kg of the oxidative phosphorylation inhibitor rotenone (n=6). In addition, we tested possible the acid-base affects of IAA on IPC discharge with up to 0.38 mmole/kg of Na-acetate (n=3). Results indicate that IAA cause > 70% reduction of IPC discharge at 70 mg/kg (P < 0.05) independent of acid-base disturbances. Similarly, 2 mg/kg rotenone also caused > 80% reduction in IPC discharge and CO2 sensitivity as well as > 50% reduction in whole body O2 consumption (P < 0.05). We conclude that IPC are dependent on glucose for ATP production, and that oxidative phosphorylation is also required for proper IPC function. These results suggest that glucose is completely oxidized to CO2 and H2O by aerobic metabolism within IPC. Support: NSF IBN-0217815

Vasopressin maintains tissue oxygenation in a piglet model of septic shock

Vasopressin (VP) can acutely reverse hypotension in catecholamine-resistant septic shock, yet there is concern that its potent vasoconstriction may increase tissue ischemia. Thus, we compared the effects of VP (100 ng/kg/min; n=10) on O2 utilization and tissue perfusion in endotoxin (ETX; 10–30 μg/kg iv)-induced shock, to that of no treatment (UNTX; n=9) or first line drugs dopamine (DA; 50 μg/kg/min; n=7) or norepinephrine (NE; 1 μg/kg/min; n=8). ETX caused a 45% decrease in mean arterial pressure (MAP), 30% drop in cardiac output, 40% decrease in O2 delivery, and 3-fold increase in the pulmonary to systemic vascular resistance ratio (PVR/SVR). VP restored MAP whereas NE and DA did not. VP reversed the PVR/SVR increase which helped maintain PaO2 and prevented escalating pulmonary hypertension. Whole body O2 consumption was maintained in UNTX, VP- and NE-treated groups via reduced shunt fraction QS/QT and more efficient % O2 extracted whereas O2 consumption decreased with DA. VP preserved flow to the brain, heart, and kidneys, which revealed no pathologic tissue changes suggestive of ischemia. In comparison, NE and DA preserved flow to the heart, but not to the brain, and DA further decreased flow to the kidneys. Although DA increased flow to the small bowel, VP and NE shunted flow away from the gastrointestinal tract in favor of vital organs, with no further small bowel ischemic damage. Results indicate that VP promotes better whole body O2 utilization in hypotensive conditions of septic shock by sparing pulmonary vasoconstriction, and causing preferential vital organ perfusion. (Supported by USAMRAA grant DAMD 170310072)

OXYGENT™ AS A TOP LOAD TO COLLOID AND HYPEROXIA IS MORE EFFECTIVE IN RESUSCITATION FROM HEMORRHAGIC SHOCK THAN COLLOID AND HYPEROXIA ALONE

Perfluorocarbon (PFC) emulsions are intravascular oxygen therapeutics that temporarily enhance tissue oxygenation in dilutional anemia. However, PFC emulsions are not resuscitation fluids because PFCs only work optimally in the presence of high O2 partial pressure (hyperoxia); moreover, because they have no oncotic potential, dosing limitations prevent their use to permanently replace large hemorrhage volumes. Our objective was to clarify whether in the presence of hyperoxia a conventional colloid therapy supplemented by PFC is more efficacious than colloid alone. To answer this question, 22 anesthetized, ventilated dogs were hemorrhaged to a mean arterial pressure of 45 mmHg and were kept at this level until a metabolic O2 debt of 120 mL kg(-1) body weight had evolved. Hyperoxia was established and dogs were randomly allocated to receive colloid (6% HES, Hydroxy Ethyl Starch shed blood volume) or colloid together with Oxygent (perflubron emulsion, 60%, w/v; Alliance Pharmaceutical Corp., San Diego, CA; single dose, 4.5 mL kg(-1); i.e., 2.7 g PFC kg body weight) in a blinded fashion. Hemodynamic and O2 transport parameters, intestinal mucosal blood flow (microspheres), and O2 partial pressure (MDO-Electrode; Eschweiler, Kiel, Germany) were measured at baseline, in shock, and during 3 h post-therapy. In the presence of hyperoxia, Oxygent improved the amount of physically dissolved O2 in plasma and increased the contribution of physically dissolved O2 to global O2 delivery (P < 0.05) and thus whole body O2 consumption when compared with colloid alone (P < 0.05). As a result, Oxygent reduced intestinal mucosal hypoxia and global O2 debt within the first hour post-therapy (P < 0.05). We conclude that under hyperoxic conditions, fluid resuscitation supplemented by Oxygent was more efficacious than colloid and hyperoxia alone. PFC temporarily enhanced intestinal mucosal tissue oxygenation during resuscitation.

Digitalis therapy for patients in clinical heart failure.

The most commonly used preparation of digitalis is digoxin, which is obtained from the leaves of Digitalis lanata , a common flowering plant called “foxglove.” The words digitalis and digoxin in this article are used interchangeably. An exhaustive review published in 19961 cited a large number of references and had detailed data and descriptions of a large number of studies and all early trials. The present article summarizes those data but focuses on and emphasizes data collected since that time. These have been described in detail previously1 and are briefly summarized. ### Inotropic Effects The inotropic effects have been documented in the isolated papillary muscles and in the normal hearts of animals and humans. The inotropic action occurs in both ventricles and in both atria. In the normal heart and in those with coronary artery disease and normal left ventricular (LV) systolic function, with digitalis the LV function curve is moved upward and to the left.1 As a result, LV end-diastolic pressure and LV end-diastolic and end-systolic volumes are reduced, and there is an increase of LV ejection fraction (LVEF).1 ### Patients With Heart Failure In patients with heart failure (HF), digoxin slows the ventricular rate (1) in sinus rhythm because of an improvement in HF and withdrawal of sympathetic stimulation and (2) in atrial fibrillation by increasing parasympathetic tone. The combination of digoxin and carvedilol is superior to digoxin or carvedilol alone.2 ### Peripheral Vessels In normal subjects given intravenous ouabain, there is arterial and venous vasocontriction.3 The vasoconstriction is obviated by administering digoxin slowly over a period of 15 to 20 minutes1; moreover, the vasoconstriction lasts up to 30 minutes. The seminal study of Mason and Braunwald3 showed that in HF, the effects are different. Digitalis produces an increase of blood flow, a decrease of vascular resistance, venodilation, and a …

Ascorbate dynamics and oxygen consumption during arousal from hibernation in Arctic ground squirrels.

During hibernation in Arctic ground squirrels (Spermophilus parryii), O(2) consumption and plasma leukocyte counts decrease by >90%, whereas plasma concentrations of the antioxidant ascorbate increase fourfold. During rewarming, O(2) consumption increases profoundly and plasma ascorbate and leukocyte counts return to normal. Here we investigated the dynamic interrelationships among these changes. Plasma ascorbate and uric acid (urate) concentrations were determined by HPLC from blood samples collected at approximately 15-min intervals via arterial catheter; leukocyte count and hematocrit were also determined. Body temperature, O(2) consumption, and electromyographic activity were recorded continuously. Ascorbate, urate, and glutathione contents in body and brain samples were determined during hibernation and after arousal. During rewarming, the maximum rate of plasma ascorbate decrease occurred at the time of peak O(2) consumption and peak plasma urate production. The ascorbate decrease did not correlate with mouth or abdominal temperature; uptake into leukocytes could account for only a small percentage. By contrast, liver and spleen ascorbate levels increased significantly after arousal, which could more than account for ascorbate clearance from plasma. Brain ascorbate levels remained constant. These data suggest that elevated concentrations of ascorbate [(Asc)] in plasma [(Asc)(p)] provide an antioxidant source that is redistributed to tissues during the metabolic stress that accompanies arousal.

Role of K(ATP)(+) channels in regulation of systemic, pulmonary, and coronary vasomotor tone in exercising swine.

The role of ATP-sensitive K(+) (K(ATP)(+)) channels in vasomotor tone regulation during metabolic stimulation is incompletely understood. Consequently, we studied the contribution of K(ATP)(+) channels to vasomotor tone regulation in the systemic, pulmonary, and coronary vascular bed in nine treadmill-exercising swine. Exercise up to 85% of maximum heart rate increased body O(2) consumption fourfold, accommodated by a doubling of both cardiac output and body O(2) extraction. Mean aortic pressure was unchanged, implying that systemic vascular conductance (SVC) also doubled, whereas pulmonary artery pressure increased almost in parallel with cardiac output, so that pulmonary vascular conductance (PVC) increased only 25 +/- 9% (both P < 0.05). Myocardial O(2) consumption tripled during exercise, which was paralleled by an equivalent increase in O(2) supply so that coronary venous PO(2) was maintained. Selective K(ATP)(+) channel blockade with glibenclamide (3 mg/kg iv), decreased SVC by 29 +/- 4% at rest and by 10 +/- 2% at 5 km/h (both P < 0.05), whereas PVC was unchanged. Glibenclamide decreased coronary vascular conductance and hence myocardial O(2) delivery, necessitating an increase in O(2) extraction from 76 +/- 2% to 86 +/- 2% at rest and from 79 +/- 2% to 83 +/- 1% at 5 km/h. Consequently, coronary venous PO(2) decreased from 25 +/- 1 to 17 +/- 1 mmHg at rest and from 23 +/- 1 to 20 +/- 1 mmHg at 5 km/h (all values are P < 0.05). In conclusion, K(ATP)(+) channels dilate the systemic and coronary, but not the pulmonary, resistance vessels at rest and during exercise in swine. However, opening of K(ATP)(+) channels is not mandatory for the exercise-induced systemic and coronary vasodilation.

Nitric oxide does not modulate whole body oxygen consumption in anesthetized dogs.

The effects of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) and the NO donor sodium nitroprusside (SNP) on whole body O2 consumption (VO2) were assessed in 16 dogs anesthetized with fentanyl or isoflurane. Cardiac output (CO) and mean arterial pressure (MAP) were measured with standard methods and were used to calculate VO2 and systemic vascular resistance (SVR). Data were obtained in each dog under the following conditions: 1) Control 1, 2) SNP (30 microg. kg-1. min-1 iv) 3) Control 2, 4) L-NAME (10 mg/kg iv), and 5) SNP and adenosine (30 and 600 microg. kg-1. min-1 iv, respectively) after L-NAME. SNP reduced MAP by 29 +/- 3% and SVR by 47 +/- 3%, while it increased CO by 39 +/- 9%. L-NAME had opposite effects; it increased MAP and SVR by 24 +/- 4% and 103 +/- 11%, respectively, and it decreased CO by 37 +/- 3%. Neither agent changed VO2 from the baseline value of 4.3 +/- 0.2 ml. min-1. kg-1, since the changes in CO were offset by changes in the arteriovenous O2 difference. Both SNP and adenosine returned CO to pre-L-NAME values, but VO2 was unaffected. We conclude that 1) basally released endogenous NO had a tonic systemic vasodilator effect, but it had no influence on VO2; 2) SNP did not alter VO2 before or after inhibition of endogenous NO production; 3) the inability of L-NAME to increase VO2 was not because CO, i.e., O2 supply, was reduced below the critical level.

Autonomic control of cardiovascular performance and whole body O2 delivery and utilization in swine during treadmill exercise.

The present study determined the role of the autonomic nervous system (ANS) in the regulation of systemic and pulmonary circulation and of O2 delivery and utilization in swine at rest and during graded treadmill exercise. Instrumented swine (n = 12) were subjected to treadmill exercise (1-5 km/h) under control conditions and in the presence of single and combined beta-adrenergic, alpha-adrenergic and muscarinic (M) receptor blockade. Exercise produced a four-fold increase in body O2 consumption, due to a doubling of both cardiac output and the arterio-mixed-venous O2 content difference. The latter resulted from an increase in O2 extraction, from 45 +/- 1% at rest to 74 +/- 1% at 5 km/h, as the O2 carrying capacity [haemoglobin concentration (Hb)] increased by only approximately 10%. The increase in cardiac output resulted from a doubling of the heart rate and a small (< 10%) increase in stroke volume. The mean aortic pressure (MAP) was unchanged, implying a 50% decrease in systemic vascular resistance (P < or = 0.05). In contrast, exercise had no significant effect on pulmonary vascular resistance. The sympathetic division of the ANS controlled O2 delivery via beta-adrenoceptors (heart rate and contractility) and Hb concentration via alpha-adrenoceptor-mediated splenic contraction. In addition, the sympathetic division modulated systemic vascular tone via alpha- and beta-adrenoceptors, but also exerted a vasodilator influence on the pulmonary circulation via beta-adrenoceptors. The parasympathetic division controlled O2 delivery in part directly (heart rate) and in part indirectly via inhibition of beta-adrenoceptor activity (heart rate and contractility), even during heavy exercise. In addition, the parasympathetic division exerted a direct vasodilator influence on the pulmonary, but not on the systemic, circulation. Thus, in swine, in a manner similar to that in humans, both the sympathetic and parasympathetic division of the ANS contribute to cardiovascular homeostasis during exercise up to levels of high intensity.