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.     

Contribution of endothelin to pulmonary vascular tone under normoxic and hypoxic conditions

The contribution of endothelin to resting pulmonary vascular tone and hypoxic pulmonary vasoconstriction in humans is unknown. We studied the hemodynamic effects of BQ-123, an endothelin type A receptor antagonist, on healthy volunteers exposed to normoxia and hypoxia. Hemodynamics were measured at room air and after 15 min of exposure to hypoxia (arterial PO(2) 99.8 +/- 1.8 and 49.4 +/- 0.4 mmHg, respectively). Measurements were then repeated in the presence of BQ-123. BQ-123 decreased pulmonary vascular resistance (PVR) 26% and systemic vascular resistance (SVR) 21%, whereas it increased cardiac output (CO) 22% (all P < 0.05). Hypoxia raised CO 28% and PVR 95%, whereas it reduced SVR 23% (all P < 0.01). During BQ-123 infusion, hypoxia increased CO 29% and PVR 97% and decreased SVR 22% (all P < 0.01). The pulmonary vasoconstrictive response to hypoxia was similar in the absence and presence of BQ-123 [P = not significant (NS)]. In vehicle-treated control subjects, hypoxic pulmonary vasoconstriction did not change with repeated exposure to hypoxia (P = NS). Endothelin contributes to basal pulmonary and systemic vascular tone during normoxia, but does not mediate the additional pulmonary vasoconstriction induced by acute hypoxia.     

Efficacy of Second Generation Direct-Acting Antiviral Agents for Treatment Na?ve Hepatitis C Genotype 1: A Systematic Review and Network Meta-Analysis

Background

The treatment of hepatitis C (HCV) infections has significantly changed in the past few years due to the introduction of direct-acting antiviral agents (DAAs). DAAs could improve the sustained virological response compared to pegylated interferon with ribavirin (PR). However, there has been no evidence from randomized controlled trials (RCTs) that directly compare the efficacy among the different regimens of DAAs.

Aim

Therefore, we performed a systematic review and network meta-analysis aiming to compare the treatment efficacy between different DAA regimens for treatment naïve HCV genotype 1.

Methods

Medline and Scopus were searched up to 25^th May 2015. RCTs investigating the efficacy of second generation DAA regimens for treatment naïve HCV genotype 1 were eligible for the review. Due to the lower efficacy and more side effects of first generation DAAs, this review included only second generation DAAs approved by the US or EU Food and Drug Administration, that comprised of simeprevir (SMV), sofosbuvir (SOF), daclatasvir (DCV), ledipasvir (LDV), and paritaprevir/ritonavir/ombitasvir plus dasabuvir (PrOD). Primary outcomes were sustained virological response at weeks 12 (SVR12) and 24 (SVR24) after the end of treatment and adverse drug events (i.e. serious adverse events, anemia, and fatigue). Efficacy of all treatment regimens were compared by applying a multivariate random effect meta-analysis. Incidence rates of SVR12 and SVR24, and adverse drug events of each treatment regimen were pooled using ‘pmeta’ command in STATA program.

Results

Overall, 869 studies were reviewed and 16 studies were eligible for this study. Compared with the PR regimen, SOF plus PR, SMV plus PR, and DVC plus PR regimens yielded significantly higher probability of having SVR24 with pooled risk ratios (RR) of 1.98 (95% CI 1.24, 3.14), 1.46 (95% CI: 1.22, 1.75), and 1.68 (95% CI: 1.14, 2.46), respectively. Pooled incidence rates of SVR12 and SVR24 in all treatment regimens without PR, i.e. SOF plus LDV with/without ribavirin, SOF plus SMV with/without ribavirin, SOF plus DCV with/without ribavirin, and PrOD with/without ribavirin, (pooled incidence of SVR12 ranging from 93% to 100%, and pooled incidence of SVR24 ranging from 89% to 96%) were much higher than the pooled incidence rates of SVR12 (51%) and SVR24 (48%) in PR alone. In comparing SOF plus LDV with ribavirin and SOF plus LDV without ribavirin, the chance of having SVR12 was not significantly different between these two regimens, with the pooled RR of 0.99 (95% CI: 0.97, 1.01). Regarding adverse drug events, risk of serious adverse drug events, anemia and fatigue were relatively higher in treatment regimens with PR than the treatment regimens without PR. The main limitation of our study is that a subgroup analysis according to dosages and duration of treatment could not be performed. Therefore, the dose and duration of recommended treatment have been suggested in range and not in definite value.

Conclusions

Both DAA plus PR and dual DAA regimens should be included in the first line drug for treatment naïve HCV genotype 1 because of the significant clinical benefits over PR alone. However, due to high drug costs, an economic evaluation should be conducted in order to assess the value of the investment when making coverage decisions.     

The role of strong hypoxia in tumors after treatment in the outcome of bacteriochlorin-based photodynamic therapy

Blood flow and pO₂ changes after vascular-targeted photodynamic therapy (V-PDT) or cellular-targeted PDT (C-PDT) using 5,10,15,20-tetrakis(2,6-difluoro-3-N-methylsulfamoylphenyl) bacteriochlorin (F₂BMet) as photosensitizer were investigated in DBA/2 mice with S91 Cloudman mouse melanoma, and correlated with long-term tumor responses. F₂BMet generates both singlet oxygen and hydroxyl radicals under near-infrared radiation, which consume oxygen. Partial oxygen pressure was lowered in PDT-treated tumors and this was ascribed both to oxygen consumption during PDT and to fluctuations in oxygen transport after PDT. Similarly, microcirculatory blood flow changed as a result of the disruption of blood vessels by the treatment. A novel noninvasive approach combining electron paramagnetic resonance oximetry and laser Doppler blood perfusion measurements allowed longitudinal monitoring of hypoxia and vascular function changes in the same animals, after PDT. C-PDT induced parallel changes in tumor pO₂ and blood flow, i.e., an initial decrease immediately after treatment, followed by a slow increase. In contrast, V-PDT led to a strong and persistent depletion of pO₂, although the microcirculatory blood flow increased. Strong hypoxia after V-PDT led to a slight increase in VEGF level 24 h after treatment. C-PDT caused a ca. 5-day delay in tumor growth, whereas V-PDT was much more efficient and led to tumor growth inhibition in 90% of animals. The tumors of 44% of mice treated with V-PDT regressed completely and did not reappear for over 1 year. In conclusion, mild and transient hypoxia after C-PDT led to intense pO₂ compensatory effects and modest tumor inhibition, but strong and persistent local hypoxia after V-PDT caused tumor growth inhibition.     

Dynamic exercise training in foxhounds. I. Oxygen consumption and hemodynamic responses

Ten foxhounds were studied during maximal and submaximal exercise on a motor-driven treadmill before and after 8-12 wk of training. Training consisted of working at 80% of maximal heart rate 1 h/day, 5 days/wk. Maximal O2 consumption (VO2max) increased 28% from 113.7 +/- 5.5 to 146.1 +/- 5.4 ml O2 X min-1 X kg-1, pre- to posttraining. This increase in VO2max was due primarily to a 27% increase in maximal cardiac output, since maximal arteriovenous O2 difference increased only 4% above pretraining values. Mean arterial pressure during maximal exercise did not change from pre- to posttraining, with the result that calculated systemic vascular resistance (SVR) decreased 20%. There were no training-induced changes in O2 consumption, cardiac output, arteriovenous O2 difference, mean arterial pressure, or SVR at any level of submaximal exercise. However, if post- and pretraining values are compared, heart rate was lower and stroke volume was greater at any level of submaximal exercise. Venous lactate concentrations during a given level of submaximal exercise were significantly lower during posttraining compared with pretraining, but venous lactate concentrations during maximal exercise did not change as a result of exercise training. These results indicate that a program of endurance training will produce a significant increase in VO2max in the foxhound. This increase in VO2max is similar to that reported previously for humans and rats but is derived primarily from central (stroke volume) changes rather than a combination of central and peripheral (O2 extraction) changes.     

Vascular wall energetics in arterioles during nitric oxide-dependent and -independent vasodilation.

The objective of this study was to evaluate whether the nitric oxide (NO) released from vascular endothelial cells would decrease vessel wall oxygen consumption by decreasing the energy expenditure of mechanical work by vascular smooth muscle. The oxygen consumption rate of arteriolar walls in rat cremaster muscle was determined in vivo during NO-dependent and -independent vasodilation on the basis of the intra- and perivascular oxygen tension (Po2) measured by phosphorescence quenching laser microscopy. NO-dependent vasodilation was induced by increased NO production due to increased blood flow, whereas NO-independent vasodilation was induced by topical administration of papaverine. The energy efficiency of vessel walls was evaluated by the variable ratio of circumferential wall stress (amount of mechanical work) to vessel wall oxygen consumption rate (energy cost) in the arteriole between normal and vasodilated conditions. NO-dependent and -independent dilation increased arteriolar diameters by 13 and 17%, respectively, relative to the values under normal condition. Vessel wall oxygen consumption decreased significantly during both NO-dependent and -independent vasodilation compared with that under normal condition. However, vessel wall oxygen consumption during NO-independent vasodilation was significantly lower than that during NO-dependent vasodilation. On the other hand, there was no significant difference between the energy efficiency of vessel walls during NO-dependent and -independent vasodilation, suggesting the decrease in vessel wall oxygen consumption produced by NO to be related to reduced mechanical work of vascular smooth muscle.     

EPR study of the sea anemone cytolysin,equinatoxin II,cytotoxicity on V-79 cells

Electron paramagnetic resonance (EPR) was used to study the effect of equinatoxin II (EqT II), a cytolytic protein isolated from the sea anemone Actinia equina L., on membrane fluidity and cell metabolism of V-79 cells; the reduction of the spin probe incorporated into the cell membranes as well as the oxygen consumption in the cell suspension were measured. The results were compared with the results obtained by the cell viability study. Under the influence of EqT II (less than 37.5 μg/10⁶ cells) no significant changes in cell membrane fluidity were observed, while reduction kinetics of the spin probe and the oxygen consumption decreased when the cells were kept in Tris buffer solution. However, in the presence of 10% fetal calf serum, which prevented cell lysis, the effects of EqT II were diminished. The oxygen consumption corresponds to the cell viability changes but the reduction kinetics alterations indicate that some oxidation-reduction processes other than cell respiration are affected by EqT II in the absence of serum. The effect seems to be indirect, probably due to the formation of pores which are associated with changed permeability of plasmalemma for metabolites and ions.     

Lack of phosphatidylethanolamine N-methyltransferase in mice does not promote fatty acid oxidation in skeletal muscle

Phosphatidylethanolamine N-methyltransferase (PEMT) converts phosphatidylethanolamine (PE) to phosphatidylcholine (PC) in the liver. Mice lacking PEMT are protected from high-fat diet-induced obesity and insulin resistance, and exhibit increased whole-body energy expenditure and oxygen consumption. Since skeletal muscle is a major site of fatty acid oxidation and energy utilization, we determined if rates of fatty acid oxidation/oxygen consumption in muscle are higher in Pemt^−/− mice than in Pemt^+/+ mice. Although PEMT is abundant in the liver, PEMT protein and activity were undetectable in four types of skeletal muscle. Moreover, amounts of PC and PE in the skeletal muscle were not altered by PEMT deficiency. Thus, we concluded that any influence of PEMT deficiency on skeletal muscle would be an indirect consequence of lack of PEMT in liver. Neither the in vivo rate of fatty acid uptake by muscle nor the rate of fatty acid oxidation in muscle explants and cultured myocytes depended upon Pemt genotype. Nor did PEMT deficiency increase oxygen consumption or respiratory function in skeletal muscle mitochondria. Thus, the increased whole body oxygen consumption in Pemt^−/− mice, and resistance of these mice to diet-induced weight gain, are not primarily due to increased capacity of skeletal muscle for utilization of fatty acids as an energy source.     

Effect of cryostorage on oxygen uptake and autograft viability of rat skin

The pre- and post-thawing oxygen uptake of rat skin treated with either 0.9% NaCl or 10% DMSO was compared with the gross survival of skin autografts. Little change was observed in the average oxygen consumption of freshly excised samples taken 28 days apart. Soaking for 2 hr in 10% DMSO decreased oxygen consumption about 29% and freeze-thawing caused a further decrease in oxygen uptake. DMSO soaked, frozen and thawed grafts (studied 28 days after grafting) had a 12% higher oxygen utilization than freshly excised skin. Only 5 of 19 autografts soaked in 0.9% NaCl became functional, but 21 of 38 skin samples soaked in 10% DMSO became functional autografts. The oxygen consumption of the 21 takes was not significantly different from the non-takes. An analysis of variance showed that oxygen utilization of skin subsamples could not reliably predict autograft viability after freeze-storage.     

Capsiate Supplementation Reduces Oxidative Cost of Contraction in Exercising Mouse Skeletal Muscle In Vivo

Chronic administration of capsiate is known to accelerate whole-body basal energy metabolism, but the consequences in exercising skeletal muscle remain very poorly documented. In order to clarify this issue, the effect of 2-week daily administration of either vehicle (control) or purified capsiate (at 10- or 100-mg/kg body weight) on skeletal muscle function and energetics were investigated throughout a multidisciplinary approach combining in vivo and in vitro measurements in mice. Mechanical performance and energy metabolism were assessed strictly non-invasively in contracting gastrocnemius muscle using magnetic resonance (MR) imaging and 31-phosphorus MR spectroscopy (³¹P-MRS). Regardless of the dose, capsiate treatments markedly disturbed basal bioenergetics in vivo including intracellular pH alkalosis and decreased phosphocreatine content. Besides, capsiate administration did affect neither mitochondrial uncoupling protein-3 gene expression nor both basal and maximal oxygen consumption in isolated saponin-permeabilized fibers, but decreased by about twofold the K _m of mitochondrial respiration for ADP. During a standardized in vivo fatiguing protocol (6-min of repeated maximal isometric contractions electrically induced at a frequency of 1.7 Hz), both capsiate treatments reduced oxidative cost of contraction by 30-40%, whereas force-generating capacity and fatigability were not changed. Moreover, the rate of phosphocreatine resynthesis during the post-electrostimulation recovery period remained unaffected by capsiate. Both capsiate treatments further promoted muscle mass gain, and the higher dose also reduced body weight gain and abdominal fat content. These findings demonstrate that, in addition to its anti-obesity effect, capsiate supplementation improves oxidative metabolism in exercising muscle, which strengthen this compound as a natural compound for improving health.     

The role of prostacyclin (PGI2) in metabolic hyperemia

We explored the possibility that prostacyclin might be the dilator metabolite of postprandial hyperemia. In canine free-flow preparations, effects of prostacyclin were compared with effects of actively absorbed nutrients on hemodynamic and metabolic parameters in the small intestine. Prostacyclin was infused directly into the superior mesenteric artery for 10 minutes at 1.0 nanograms/kg-min. In absorptive study an isosmotic solution of glucose (1.0 g/l) dissolved in 0.9% NaCl was perfused through the gut lumen for 20 minutes. Prostacyclin increased total blood flow to the intestinal segment and decreased oxygen extraction, while not significantly changing either oxygen consumption or PS-product. Active cotransport of glucose and sodium increased total blood flow, oxygen extraction, oxygen consumption and PS-product.In constant flow canine gut preparations, intraarterial prostacyclin infusion decreased arterial pressure, oxygen extraction, oxygen consumption and mesenteric vascular resistance but increased venous pressure. Absorption of glucose and sodium increased oxygen extraction but decreased mesenteric vascular resistance while not affecting other parameters significantly.Since responses to prostacyclin did not coincide with responses to metabolically dependent transport of glucose and sodium, we conclude that the dilator metabolite of postprandial hyperemia is probably not prostacyclin.     

Systemic vascular reactivity during high-altitude pregnancy

There is an increased incidence of preeclampsia at high compared with low altitude. Increased vasoreactivity, possibly due to a deficiency of vasodilator prostaglandins, is thought to contribute to the etiology of preeclampsia. We sought to determine whether high-altitude exposure increased systemic vascular reactivity during pregnancy. We measured systemic vascular reactivity and contractile sensitivity of isolated aortic rings from pregnant and nonpregnant guinea pigs kept for 6 wk at either simulated high altitude (3,900 m) or low altitude (1,600 m). We found that pregnancy at high compared with low altitude increased baseline systemic vascular resistance (SVR) but not the SVR response to angiotensin II in awake unstressed guinea pigs. Contractile sensitivity to norepinephrine was also increased in aortic rings isolated from high-altitude compared with low-altitude pregnant animals. Meclofenamate, a prostaglandin synthesis inhibitor, did not equalize vasoreactivity in the high- and low-altitude pregnant guinea pigs or in their isolated aortic rings. We concluded that pregnancy at high compared with low altitude increased base-line SVR and aortic contractile sensitivity but that mechanisms other than decreased vasodilator prostaglandin production were responsible.     

Oxygen saturation and blood volume analysis by photoacoustic imaging to identify pre and post-PDT vascular changes

In this study, the blood volume and oxygen saturation of tumors were measured after photoacoustic imaging (PAI) under conditions of pre-photodynamic therapy (PDT), post-PDT, and 4 hrs, and 24 hrs post-PDT. PDTs with aminolevulinic acid (ALA) and low and high doses of benzoporphyrin derivative (BPD) were conducted to observe oxygen saturation changes, and the rapid oxygen consumption in the blood detected due to the action of BPD at the vascular level resulted in the recovery of PDT completion. Likewise, blood volume changes followed by ALA-PDT and BPD-PDT at low and high doses depicted a fast expansion of the blood volume after treatment. The tumor subjected to a high dose of ALA-PDT showed a partial alteration of Hb-pO₂ in the first 24 hrs, as did the tumors treated with two ALA- and BPD-mediated PDTs. The Hb-pO₂ started reducing immediately post-PDT and was less than 30% after 4 hrs until 24 hrs post-PDT. Reduced vascular demand was possibly due to tumor necrosis, as shown by the permanent damage in the cancer cells' bioluminescence signal. The ALA-mediated PDT-subjected tumor showed a 50% drop in BV at 24 hrs post-PDT, which is suggestive of vascular pruning. The studied data of blood volume against BLI showed the blood volume and oxygenation variations validating the cells' metabolic activity, including cell death.     

Reactive oxygen species derived from NAD(P)H oxidase play a role on ethanol-induced hypertension and endothelial dysfunction in rat resistance arteries

Chronic ethanol consumption is a risk factor for cardiovascular diseases. We studied whether NAD(P)H oxidase-derived reactive oxygen species (ROS) play a role in ethanol-induced hypertension, vascular dysfunction, and protein expression in resistance arteries. Male Wistar rats were treated with ethanol (20 %?v/v) for 6 weeks. Ethanol treatment increased blood pressure and decreased acetylcholine-induced relaxation in the rat mesenteric arterial bed (MAB). These responses were attenuated by apocynin (30 mg/kg/day; p.o. gavage). Ethanol consumption increased superoxide anion (O₂ ^?) generation and decreased nitrate/nitrite (NO _x ) concentration in the rat MAB and apocynin prevented these responses. Conversely, ethanol did not affect the concentration of hydrogen peroxide (H₂O₂) and reduced glutathione (GSH) or the activity of superoxide dismutase (SOD) and catalase (CAT) in the rat MAB. Ethanol increased interleukin (IL)-10 levels in the rat MAB but did not affect the levels of tumor necrosis factor (TNF)-α, IL-6, or IL-1β. Ethanol increased the expression of Nox2 and the phosphorylation of SAPK/JNK, but reduced eNOS expression in the rat MAB. Apocynin prevented these responses. However, ethanol treatment did not affect the expression of Nox1, Nox4, p38MAPK, ERK1/2, or SAPK/JNK in the rat MAB. Ethanol increased plasma levels of TBARS, TNF-α, IL-6, IL-1β, and IL-10, whereas it decreased NO _x levels. The major finding of our study is that NAD(P)H oxidase-derived ROS play a role on ethanol-induced hypertension and endothelial dysfunction in resistance arteries. Moreover, ethanol consumption affects the expression and phosphorylation of proteins that regulate vascular function and NAD(P)H oxidase-derived ROS play a role in such responses.     

Differential effects of prostaglandins and arachidonic acid on gastric circulation and oxygen consumption

Experiments were carried out on anesthetized dogs to compare the effects of prostaglandin E₂ (PGE₂), prostacyclin (PGI₂) and arachidonic acid (AA) administered intraarterially on gastric blood flow and oxygen consumption during constant arterial pressure perfusion and constant flow perfusion of the stomach. Both PGE₂ and PGI₂ increased total blood flow and oxygen consumption both in the resting stomach and following histamine stimulation although the effects of PGE₂ on the oxygen consumption in stimulated stomach were not statistically significant. On the contrary, AA decreased both gastric blood flow and oxygen consumption in the histamine stimulated stomach. To determine if these compounds can influence gastric oxygen consumption independently of their effects on blood flow, the experiments with constant flow perfusion were performed. Both PGE₂ and PGI₂ decreased both the perfusion pressure and oxygen consumption in the resting as well as in the histamine-stimulated stomach whereas AA increased perfusion pressure and decreased oxygen consumption during histamine administration. Effects of AA were blocked by indomethacin suggesting that not AA itself but some of its metabolites, most likely thromboxanes were responsible for the hemodynamic and metabolic changes resulting from the contraction of gastric arterioles and precapillary sphincters. On the contrary, both PGE₂ and PGI₂ caused gastric hyperemia and an increase in oxygen consumption in the resting stomach, but decreased the latter parameter in the stimulated stomach, most probably as a result of secretory inhibition overcoming direct vascular effects of these compounds.     

Suppression of pulmonary and systemic vascular histamine H2-receptors in allergic sheep

We have previously demonstrated a depression of airway H2-receptor function in sheep allergic to Ascaris suum antigen. To investigate whether this is a generalized defect, we studied the H1- and H2- histamine receptor functions in the pulmonary and systemic circulations of allergic and nonallergic sheep. Pulmonary arterial pressure, and cardiac output were measured for calculation of pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) before and immediately after a rapid intrapulmonary infusion of histamine (10 micrograms/kg), with and without pretreatment with H1- (chlorpheniramine) and H2- (metiamide) antagonists. Histamine alone increased mean PVR to 435 and 401% of base line and decreased mean SVR by 51 and 54% in the nonallergic and allergic sheep, respectively (P less than 0.001). In the nonallergic sheep following pretreatment with chlorpheniramine (selective H2 stimulation) or metiamide (selective H1 stimulation), histamine decreased SVR by 18 and 36%, respectively, suggesting that approximately two-thirds of the vasodepressor response was mediated by H1-receptors and one-third by H2-receptors. Combined H1- and H2-antagonists completely blocked the histamine response. In allergic sheep the histamine-induced decrease in SVR was primarily mediated by H1-receptors, because the response was blocked by H1-antagonist, chlorpheniramine, and the H2-antagonist, metiamide, had no effect. In the pulmonary circulation selective H1-stimulation caused a similar increase in PVR in allergic (365%) and nonallergic sheep (424%), whereas selective H2-stimulation caused a significant decrease in PVR in the nonallergic group (14%) but not in the allergic group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nitric oxide regulation of microvascular oxygen exchange during hypoxia and hyperoxia.

The objective of this work was to test the hypothesis that the limitation of nitric oxide (NO) availability accentuates microvascular reactivity to oxygen. The awake hamster chamber window model was rendered hypoxic and hyperoxic by ventilation with 10 and 100% oxygen. Systemic and microvascular parameters were determined in the two conditions and compared with normoxia in a group receiving the NO scavenger nitronyl nitroxide and a control group receiving only the vehicle (saline). Mean arterial blood pressure did not change with different gas mixtures during infusion of the vehicle, but it increased significantly in the NO-depleted group. NO scavenging increased the reactivity of microvessels to the changed oxygen supply, causing the arteriolar wall to significantly increase oxygen consumption. Tissue Po2 was correspondingly significantly reduced during NO scavenger infusion. The present findings support the hypothesis that microvascular oxygen consumption is proportional to oxygen-induced vasoconstriction. The effect of oxygen on vascular tone is modulated by NO. As a consequence, NO acts as a regulator of the vessel wall oxygen consumption. The vessel wall consumes oxygen in proportion to the local Po2, and an impairment of NO availability renders the circulation more sensitive to changes in the oxygen supply.     

Respiratory and osmoregulatory responses of the hermit crab, Clibanarius vittatus (Bosc), to salinity changes

Intertidal hermit crabs were stepwise acclimated to 10, 20, and 30‰ salinity (S) and 21 ± 1 °C. Hemolymph osmolality, sodium, chloride, and magnesium were isosmotic (isoionic) to ambient sea water at 30‰ and hyperosmotic (hyperionic) at 20 and 10‰ S, while hemolymph potassium was significantly hyperionic in all acclimation salinities. Total body water did not differ significantly at any acclimation salinity. Oxygen uptake rates were higher in summer-than winter-adapted crabs. No salinity effect on oxygen consumption occurred in winter-adapted individuals. Summer-adapted, 30‰ acclimated crabs had a significantly lower oxygen consumption rate than those acclimated 10 and 20‰ S. Crabs exposed to 30 10 30‰ and 10 30 10‰ semidiurnal (12 h) and diurnal (24.8 h) fluctuating salinity regimes showed variable osmoregulatory and respiratory responses. Hemolymph osmolality followed the osmolality of the fluctuating ambient sea water in all cases, but was regulated hyperosmotically. Hemolymph sodium, chloride, and magnesium concentrations were similar to hemolymph osmolality changes. Sodium levels fluctuated the least. Hemolymph potassium was regulated hyperionically during all fluctuation patters, but corresponded to sea water potassium only under diurnal conditions. The osmoregulatory ability of Clibanarius vittatus (Bosc) resembles that reported for several euryhaline brachyuran species. The time course of normalized oxygen consumption rate changed inversely with salinity under semidiurnal and diurnal 10 30 10‰ S fluctuations. Patterns of 30 10 30‰ S cycles had no effect on oxygen consumption rate time course changes. The average hourly oxygen consumption rates during both semidiurnal fluctuations were significantly lower than respective control rates, but no statistical difference was observed under diurnal conditions.     

N-acetylcysteine effects on a murine model of chronic critical limb ischemia

During chronic limb ischemia, oxidative damage and inflammation are described. Besides oxidative damage, the decrease of tissue oxygen levels is followed by several adaptive responses. The purpose of this study was to determine whether supplementation with N-acetylcysteine (NAC) is effective in an animal model of chronic limb ischemia. Chronic limb ischemia was induced and animals were treated once a day for 30 consecutive days with NAC (30 mg/kg). After this time clinical scores were recorded and soleus muscle was isolated and lactate levels, oxidative damage and inflammatory parameters were determined. In addition, several mechanisms associated with hypoxia adaptation were measured (vascular endothelial growth factor - VEGF and hypoxia inducible factor - HIF levels, ex vivo oxygen consumption, markers of autophagy/mitophagy, and mitochondrial biogenesis). The adaptation to chronic ischemia in this model included an increase in muscle VEGF and HIF levels, and NAC was able to decrease VEGF, but not HIF levels. In addition, ex vivo oxygen consumption under hypoxia was increased in muscle from ischemic animals, and NAC was able to decrease this parameter. This effect was not mediated by a direct effect of NAC on oxygen consumption. Ischemia was followed by a significant increase in muscle myeloperoxidase activity, as well as interleukin-6 and thiobarbituric acid reactive substances species levels. Supplementation with NAC was able to attenuate inflammatory and oxidative damage parameters, and improve clinical scores. In conclusion, NAC treatment decreases oxidative damage and inflammation, and modulates oxygen consumption under hypoxic conditions in a model of chronic limb ischemia.     

Oxygen Consumption Rates and Oxygen Concentration in Molt-4 Cells and Their mtDNA Depleted (ρ0) Mutants

Respiratory deficient cell lines are being increasingly used to elucidate the role of mitochondria and to understand the pathophysiology of mitochondrial genetic disease. We have investigated the oxygen consumption rates and oxygen concentration in wild-type (WT) and mitochondrial DNA (mtDNA) depleted (ρ⁰) Molt-4 cells. Wild-type Molt-4 cells have moderate oxygen consumption rates, which were significantly reduced in the ρ⁰ cells. PCMB (p-chloromercurobenzoate) inhibited the oxygen consumption rates in both WT and ρ⁰ cells, whereas potassium cyanide decreased the oxygen consumption rates only in WT Molt-4 cells. Menadione sodium bisulfite (MSB) increased the oxygen consumption rates in both cell lines, whereas CCCP (carbonyl cyanide m-chlorophenylhydrazone) stimulated the oxygen consumption rates only in WT Molt-4 cells. Superoxide radical adducts were observed in both WT and ρ⁰ cells when stimulated with MSB. The formation of this adduct was inhibited by PCMB but not by potassium cyanide. These results suggest that the reactive oxygen species (ROS) induced by MSB were at least in part produced via a mitochondrial independent pathway. An oxygen gradient between the extra- and intracellular compartments was observed in WT Molt-4 cells, which further increased when cells were stimulated by CCCP and MSB. The results are consistent with our earlier findings suggesting that such oxygen gradients may be a general phenomenon found in most or all cell systems under appropriate conditions.