Limited Oxygen Consumption Research Articles

Marine redox and nutrient dynamics linked to the Cambrian radiation of animals

Abstract The early Cambrian witnessed an increase in metazoan ecosystem complexity, likely linked to enhanced oxygen and nutrient availability. However, while improved stratigraphic and geochemical records suggest that the Cambrian explosion occurred under highly dynamic redox conditions, mechanistic links to nutrient availability and early Cambrian evolutionary innovations are poorly constrained. Here, we report paleoredox and nutrient data for two drill cores documenting late Cambrian Stage 2 to Stage 3 (ca. 522–514 Ma) strata from the Yangtze block, South China. The development of water-column euxinia during Cambrian Stage 2 led to extensive recycling of P, fueling elevated primary production and hence an increase in atmospheric and shallow-marine oxygen concentrations. The resulting expansion of oxygenated shelf area promoted sedimentary P retention and, in combination with a diminished supply of P from upwelling, drove a transition to oligotrophic shallow-marine conditions during Cambrian Stage 3. Reduced primary production and limited water-column oxygen consumption allowed for the stabilization of oxygenated continental shelf habitats that supported a burgeoning biotic complexity.

Do freedivers and spearfishermen differ in local muscle oxygen saturation and anaerobic power?

Freediving is defined as an activity where athletes repetitively dive and are exposed to long efforts with limited oxygen consumption. Therefore, anaerobic features are expected to be an important facet of diving performance. This study aimed to investigate differences in anaerobic capacity and local muscle oxygenation in spearfisherman and freedivers. The sample of participants included 17 male athletes (nine freedivers, and eight spearfishermen), with an average age of 37.0±8.8 years, training experience of 10.6±9.5 years, body mass of 82.5±9.5 kg and height of 184.2±5.7 cm. Anthropometric characteristics included: body mass, body height, seated height, and body fat percentage. Wingate anaerobic test was conducted, during which local muscle oxygenation was measured with a NIRS device (Moxy monitor). Wingate power outputs were measured (peak power [W/kg] and average power [W/kg]), together with muscle oxygenation variables (baseline oxygen saturation [%], desaturation slope [%/s], minimum oxygen saturation [%], half time recovery [s], and maximum oxygen saturation [%]). The differences were not obtained between freedivers and spearfisherman in power outputs (peak power (9.24±2.08 spearfisherman; 10.68±1.04 freedivers; P=0.14); average power (6.85±0.95 spearfisherman; 7.44±0.60 freedivers; P=0.15) and muscle oxygenation parameters. However, analysis of effect size showed a moderate effect in training experience (0.71), PP (0.89), AP (0.75), Desat slope mVLR (0.66), half time recovery mVLR (0.90). The non-existence of differences between freedivers and spearfishermen indicates similar training adaptations to the anaerobic demands. However, the results show relatively low anaerobic capacities of our divers that could serve as an incentive for the further development of these mechanisms.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Sensorially important aldehyde production from amino acids in model wine systems: Impact of ascorbic acid, erythorbic acid, glutathione and sulphur dioxide

The efficiency of different white wine antioxidant systems in preventing aldehyde production from amino acids by oxidative processes is not well understood. The aim of this study was to assess the efficiency of sulphur dioxide alone and in combination with either glutathione, ascorbic acid or its stereoisomer erythorbic acid, in preventing formation of the sensorially important compounds methional and phenylacetaldehyde from methionine and phenylalanine in model white wine. UHPLC, GC–MS/MS, LC–MS/MS, flow injection analysis and luminescence sensors determined both compositional changes during storage, and sulphur dioxide–aldehyde apparent equilibrium constants. Depending on temperature (25 or 45°C) or extent of oxygen supply, sulphur dioxide was equally or more efficient in impeding the production of methional compared to the other antioxidant systems. For phenylacetaldehyde, erythorbic acid or glutathione with sulphur dioxide provided improved inhibition compared to sulphur dioxide alone, in conditions of limited oxygen consumption. The results also demonstrate the extent to which sulphur dioxide addition can lower the free aldehyde concentrations to below their aroma thresholds.

Managing the difficult airway in children

The small diameter of a child's airway makes it more susceptible to obstruction, and the limited respiratory reserve and high oxygen consumption lead to rapid desaturation. Try to predict problems by careful assessment. Check for syndromes and diseases associated with airway problems, and any history suggestive of airway narrowing. Look in particular for mandibular abnormalities and signs of increased work of breathing. Prepare equipment, experienced assistance, the anaesthetic plan, and the child and parents for the mode of induction. Management is generally gas induction with sevoflurane or halothane in oxygen deepening anaesthesia until laryngoscopy is possible. Maintain spontaneous ventilation until the airway is secured. Simple airway manoeuvres or adjuncts may be needed to maintain a good airway. The laryngeal mask airway (LMA) is often very useful in difficult situations. If oxygenation is easy, a range of intubating techniques can be used. There is a well described technique for fibreoptic intubation via the LMA, which maintains oxygenation and allows small infants to be intubated using an adult-size fibreoptic scope. In the situation of ‘can't intubate, can't ventilate’ with worsening hypoxia and bradycardia, a transtracheal airway is the only option. For children aged more than 8 years, adult equipment can be used, but in young children a cannula cricothyroidotomy is recommended. A 14 or 16G cannula is inserted through the cricothyroid membrane, and jet ventilation delivered from a high pressure source. There are numerous complications of cricothyroidotomy and jet ventilation.

Intracellular kinetics of ATX-S10⋅Na(II) and its correlation with photochemical reaction dynamics during a pulsed photosensitization process: effect of pulse repetition rate

Although photodynamic therapy with pulsed light excitation has interesting characteristics, its photosensitization mechanism has not been fully elucidated. In this study, we showed that the intracellular kinetics of ATX-S10.Na(II), a lysosomal sensitizer, was closely related to photochemical reaction dynamics during photodynamic treatment of A549 cells with nanosecond pulsed light. Fluorescence microscopy revealed that at high frequencies of 10 and 30 Hz the sensitizer initially localized mainly in lysosomes but that it started to be redistributed to the cytosol in certain ranges of radiant exposures. These ranges were found to coincide with a regime of fluorescence degradation with limited oxygen consumption. On the other hand, at 5 Hz, there was no such a discontinuous behavior in the sensitizer redistribution characteristics throughout the period of irradiation; this was consistent with the fact that no reaction switching was observed. Two possible reasons for the appearance of the regime with limited oxygen consumption are discussed: participation of an oxygen-independent reaction and change in the microenvironment for the sensitizer caused by lysosomal photodamage. The pulse frequency-dependent intracellular kinetics of the sensitizer also explains our previous results showing higher cytotoxicity at 5 Hz than at 10 and 30 Hz.

Effect of inhibiting nitric oxide production on mouse preimplantation embryo development and metabolism.

Nitric oxide (NO) is a free radical that functions as a cell signaling molecule but at high concentrations can be toxic. It is formed from arginine, which is consumed by the mouse blastocyst, but its effect on early embryo development has been little studied. In this study, the role of NO in mouse preimplantation development has been examined in terms of developmental rate and oxidative metabolism. Zygotes were cultured in one of four media; potassium simplex optimization medium (KSOM), KSOM with amino acids (KSOMaa), KSOM without glutamine (KSOM-glut), or KSOM with 0.5 mM arginine (KSOMarg) +/- l-NAME (a specific inhibitor of NO production). End points were Day 4 blastocyst rates, cell counts determined using bisbenzimide and oxygen consumption. In KSOM and KSOM-glut, the blastocyst rate was decreased by 1 mM l-NAME from 50.2% +/- 3.1% and 37.4% +/- 4.5% to 6% +/- 3% and 0%, respectively. In KSOMaa, cavitation rates were unaltered but the blastocysts contained fewer cells (P < 0.001). Blastocysts cultured in KSOM and KSOM-glut consumed significantly more oxygen than those cultured in KSOMaa (P < 0.001 and P < 0.05, respectively). However, the addition of 0.1 mM or 1 mM l-NAME to KSOMaa significantly increased the amount of oxygen consumed (P < 0.05 and P < 0.001, respectively). The data suggest a physiological role for NO in mouse preimplantation metabolism and development. One possibility is that NO may limit oxygen consumption at the blastocyst stage at the level of mitochondrial cytochrome c oxidase.

Role of Oxygen in Limiting Respiration in theIn SituMyocardium

1H NMR has now detected the proximal histidyl NδH myoglobin (Mb) signal from the myocardiumin situ. Upon ligation of the left anterior descending coronary artery in the rat myocardium, the deoxy Mb signal appears at 78 ppm During dopamine infusion at up to 80 μg/kg/min, the heart rate pressure product (RPP) increases by a factor of 2, the phosphocreatine (PCr) decreases by 17%, and the ratio of the change in inorganic phosphate over PCr (ΔPi/PCr) increases by 0.2. However, no deoxy myoglobin signal is detected. Oxygen availability does not appear to limit oxygen consumption nor oxidative phosphorylation under dopamine enhanced work state in myocardium.

Breathlessness in microvascular angina

In patients with microvascular angina (MA), there is some evidence from studies of plethysmography, that there are widespread microvascular abnormalities. In addition to exertional chest pain, all these patients complain of breathlessness, with no evidence of airways obstruction or resting left ventricular dysfunction. Progressive exercise testing was performed in 12 age and sex matched controls and 12 patients (three males), in whom the diagnosis of MA was established on the basis of exertional chest pain, abnormal thallium scans, and an attenuated myocardial flow response to a vasodilator challenge, with angiographically entirely normal epicardial vessels. Symptom limited exercise was performed with on line ventilation and expired gas analysis, measuring minute ventilation, oxygen consumption and carbon dioxide production and arterial blood gas values using a transcutaneous system. Anaerobic threshold was calculated by curve fitting a plot of oxygen consumption against carbon dioxide production. Compared to controls (49.7 +/- 7.3 SD% predicted maximum VO2) in patients with MA, the anaerobic threshold was reduced (41.6 +/- 5.82; P < 0.02) although still within accepted normal limits. Maximal (symptom limited) oxygen consumption, as a percentage of predicted, was reduced 60.73 +/- 16.51 compared to 87.21 +/- 5.2 (P < 0.003). The ventilatory response (VE/VCO2 l l-1 CO2 output) was significantly increased in the MA patients compared to controls (35.9 +/- 8.01 and 27.5 +/- 3.08, respectively; P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Factors regulating plankton community respiration in Chesapeake Bay

Rates of plankton community respiration were measured in surface and bottom waters during spring, summer and autumn in the mesohaline region of Chesapeake Bay, USA. Seasonal patterns of plankton respiration generally followed the annual temperature cycle, with peak rates in July and August of 40 to 70 pg 0,l-I h-', which are among the highest values reported in the literature. In addition, strong diel variations in surface water community respiration, with mid-day maxima, were coherent with cycles of irradiance and photosynthesis, suggesting the dependence of community respiration on recently produced organic matter. The range of diel variations in respiration during summer was almost half the annual range in mean rates. Size-fractionated incubations demonstrated the importance of picoplankton (< 3 pm) respiration compared to total rates On average, picoplankton accounted for most of community respiration in surface waters (56%) and dominated total rates in the summer pycnocline (89%). This size fraction was less important in the bottom waters during spring (23 %). Temperature per se as a control on plankton respiration was investigated by comparing rates at in situ temperatures against those measured in temperature-manipulated experiments in spnng and summer. Strong relations between respiration and temperature were observed in all cases; least-squares regresslons (exponential and linear) for experimental data were not significantly different between seasons, nor between the experin~ents and the seasonal rates measured at in s ~ t u temperatures. These results suggest the absence of significant physiological adaptation and/or selection for temperature optima over the annual cycle. Respiration by bacterioplankton (< 1 p) exhibited no oxygen dependence down to concentrations of 0.16 mg O2 l? ' ; however, rates for whole water (unfiltered) declined with decreasing oxygen below 0.8 mg O2 l-'. Evidently, diffusion limited oxygen consumption by protoand metazoans as well as bacteria associated with detrital particles and organic flocs.

Depression of Aerobic Metabolism and Intracellular pH by Hypercapnia in Land Snails,Otala Lactea

ABSTRACTThe pulmonate land snail Otala lactea undergoes simultaneous hypercapnia, hypoxia, extracellular acidosis and metabolic depression during dormancy. We tested the effects of ambient hypercapnia and hypoxia on oxygen consumption and on extracellular and intracellular pH of active (i.e. non-dormant) individuals. Active snails reduced by 50% within 1h when exposed to 65 mmHg (1 mmHg = 133·3 Pa) ambient and by 63% in 98 mmHg. These levels of CO2 are within the range that occurs naturally in the lung and blood during dormancy. of hypercapnic snails remained below that of controls for the duration of exposure (up to 9 h) and returned to control levels within 1 h when CO2 was removed. Both pHe and whole-body pHi (measured using [14C]DMO) fell with increasing haemolymph by approximately 0·71og. Critical ( -limiting) ambient of active snails was 90 mmHg in the absence of CO2 and dropped to 50 mmHg when was reduced 45% by exposure to CO2. Estimated critical at the lower typical of dormancy is well below the typical lung of dormant Otala, suggesting that in the lung does not normally limit oxygen consumption during dormancy. These results support the hypothesis that hypercapnia or resulting respiratory acidosis depresses metabolic rate during dormancy, and argue against a limitation of by hypoxia.

Anemia blunts the thermogenic response to environmental cold stress in newborn piglets.

We tested the hypothesis that isovolemic anemia blunts the thermogenic response to environmental cold stress in 3 to 4-day-old newborn piglets. Eight animals were studied in both thermoneutral (31.6-32.8 degrees C) and cold (19.6-20.2 degrees C) environments, before and after an isovolemic, partial volume exchange transfusion which reduced the hematocrit from 26 to 15%. In the nonanemic phase of study, deep rectal temperatures declined but had plateaued by 30 minutes after onset of cold stress and remained within normal limits for newborn piglets. In the anemic phase of study, deep rectal temperature declined continuously throughout cold stress with true body core hypothermia (less than 38 degrees C) observed at all measurement points beyond 15 min of cold stress. Baseline oxygen consumption did not differ between the two study phases (17.6 +/- 1.8 versus 16.7 +/- 2.1 ml/kg-1/min-1, mean +/- SEM). However, during environmental cold stress, oxygen consumption increased by 64% over baseline in the nonanemic phase of study (p less than 0.05) whereas 21% increase over baseline was observed in the anemic phase (p NS). We conclude that isovolemic anemia limited oxygen consumption and heat production during environmental cold stress, resulting in body core hypothermia.

Effect of Temperature and Body Size on Oxygen Consumption of Two Species of Eubranchipus (Crustacea: Anostraca)

Oxygen consumption of Eubranchzpus vernalis and E. holmani was measured between 4 C and 20 C on a Gilson Differential Respirometer. Qjo values and the relationship between weight-specific oxygen consumption and temperature indicated that individuals of E. holmani and juveniles of E. vernalis were more tolerant to temperature change than adults of E. vernalis. Oxygen consumption rates of E. holmani were proportional to surface area, while those of E. vernalis were a function of volume. Both species are metabolically well-adapted to the thermal conditions in their respective habitats. INTRODUCTION Information on oxygen consumption in the Anostraca, an order of crustaceans, is derived primarily from work on Artemia salina, a species adapted to salt water (Gilchrist, 1956, 1959) and provides little insight into the metabolism and respiration of freshwater anostracans. Data on oxygen consumption of freshwater groups are scarce. Daborn (1975) studied oxygen consumption in an arctic species. Limited oxygen consumption information on several other freshwater species is available in Knight et al. (1975) and Wycliffe (1979). Eubranchipus vernalis and E. holmani are common anostracans inhabiting temporary freshwater ponds in the temperate latitudes of North America. Their life cycles were described by Weaver (1943), Dexter and Kuehnle (1951), Moore (1959) and Modlin (1982). During the autumn-winter season of 1978-1979 these species were present in two temporary ponds in the same watershed in Madison Co., Alabama. Specimens of E. vernalis were collected in S & J Pond (RIW T3S Sect. 28), which is 0.4 km S of WEUP Pond (RIW T3S Sect. 21), the pond inhabited by E. holmani. This research emphasizes the influence of body size and the acute effects of temperature change on oxygen consumption by these freshwater anostracans. MATERIALS AND METHODS Specimens were collected with a D-ring dip net and transported to the laboratory in an ice chest partially filled with pond water to insure that they did not experience a drastic temperature change. In the laboratory anostracans were held in unfiltered habitat water maintained at 10 C which was near the ambient water temperature of the ponds at the time collections were made. Aquaria were illuminated with a light intensity comparable to that measured at the ponds when specimens were collected. Lights were timed to a winter photoperiod, 11 L 13D. The anostracans were assumed to be fed prior to oxygen consumption analysis because their guts were filled with Aufwuchs. The interval between specimen collection and use in oxygen consumption measurements never exceeded 48 hr. Oxygen consumption was measured at 4.0, 6.0, 8.0, 10.0, 12.0, 14.0, 16.0, 18.0 and 20.0 C on a 20-reaction-vessel Gilson Differential Respirometer. Ten to 18 reaction vessels were used as experimentals and two as controls. Each experimental vessel contained one anostracan in 5.0 ml filtered pond water and a CO2 trap. Control vessels contained 5.0 ml filtered pond water and the CO2 trap. Since the anostracans were acclimatized to their habitat temperature, no further acclimation was performed. The rationale was to maintain the organisms in as near ambient conditions as possible. Acclimation to a temperature higher or lower than ambient would mask any acute

Oxygen consumption in carbon dioxide anesthetized house flies, Musca domestica linn. (Diptera: Muscidae)

1. 1. Carbon dioxide in concentrations (33 per cent) producing knockdown in house flies does not limit oxygen consumption when oxygen is maintained at normal atmospheric tension. 2. 2. Analyses were performed on a gas chromatograph employing a thermal conductivity detector, nitrogen carrier gas and Porapak Q (80–100 mesh) columns. 3. 3. A previous hypothesis ascribing the site of action to a site near the cytochromes is contradicted by these findings.