Water Oxygen Partial Pressure Research Articles

Relationships between the peak hypoxic ventilatory response and critical O2 tension in larval and adult zebrafish (Danio rerio).

Fish increase ventilation during hypoxia, a reflex termed the hypoxic ventilatory response (HVR). The HVR is an effective mechanism to increase O2 uptake, but at a high metabolic cost. Therefore, when hypoxia becomes severe enough, ventilation declines, as its benefit is diminished. The water oxygen partial pressure (PwO2 ) at which this decline occurs is expected to be near the critical PwO2 (Pcrit), the PwO2 at which O2 consumption begins to decline. Our results indicate that in zebrafish (Danio rerio), the relationship between peak HVR and Pcrit is dependent on developmental stage. Peak ventilation occurred at PwO2 values higher than Pcrit in larvae, but at a PwO2 significantly lower than Pcrit in adults. Larval zebrafish use cutaneous respiration to a greater extent than branchial respiration and the cost of sustaining the HVR may outweigh the benefit, whereas adult zebrafish, which rely on branchial respiration, may benefit from using HVR at PwO2 below Pcrit.

Long‐time Performance of Bottles Made of PET Blended with Various Concentrations of Oxygen Scavenger Additive Stored at Different Temperatures

Blending of poly(ethylene terephthalate) (PET) with oxygen scavenger additives is a way to reduce ingress of oxygen into PET bottles made of these blends. The objective is to reduce oxidation of packaged beverages and oils. However, few studies were performed about the long‐time influence of temperature on PET bottles with oxygen scavenger additives. Such knowledge is relevant for the development of accelerated tests. In this study, the influence of temperature on oxygen permeation of PET bottles with the oxygen scavenger additives MXD6 or Oxyclear® was examined. PET bottles made of blends of PET with 2, 5 and 8 wt.−% MXD6, respectively, or with 2 wt.−% Oxyclear® were filled with deoxygenated water. The bottles were stored at 5, 23, 38 and 55 °C up to 5 years. Oxygen partial pressure of the water in the bottles was measured regularly. As expected, oxygen partial pressure increased earlier at higher temperature because of faster exhaustion of the oxygen scavenger. Oxygen partial pressure of water in PET bottles with 8 wt.−% MXD6 was below 10 mbar even after 5 years storage time at 5 and 23 °C. Oxygen absorption capacity of activated MXD6 was at least 76 mg/g. This study shows that PET bottles with oxygen scavengers are able to reduce the oxygen ingress for several years, even at elevated temperatures. Copyright © 2017 John Wiley & Sons, Ltd.

Mantle cavity water oxygen partial pressure (Po2) in marine molluscs aligns with lifestyle

Marine invertebrates with open circulatory system establish low and constant oxygen partial pressure (Po2) around their tissues. We hypothesized that as a first step towards maintenance of low haemolymph and tissue oxygenation, the Po2in molluscan mantle cavity water should be lowered against normoxic (21 kPa) seawater Po2, but balanced high enough to meet the energetic requirements in a given species. We recorded Po2in mantle cavity water of five molluscan species with different lifestyles, two pectinids ( Aequipecten opercularis , Pecten maximus ), two mud clams ( Arctica islandica , Mya arenaria ), and a limpet ( Patella vulgata ). All species maintain mantle cavity water oxygenation below normoxic Po2. Average mantle cavity water Po2correlates positively with standard metabolic rate (SMR): highest in scallops and lowest in mud clams. Scallops show typical Po2frequency distribution, with peaks between 3 and 10 kPa, whereas mud clams and limpets maintain mantle water Po2mostly <5 kPa. Only A. islandica and P. vulgata display distinguishable temporal patterns in Po2time series. Adjustment of mantle cavity Po2to lower than ambient levels through controlled pumping prevents high oxygen gradients between bivalve tissues and surrounding fluid, limiting oxygen flux across the body surface. The patterns of Po2in mantle cavity water correspond to molluscan ecotypes.

Adrenergic control of venous capacitance during moderate hypoxia in the rainbow trout (Oncorhynchus mykiss): role of neural and circulating catecholamines

Central venous blood pressure (P(ven)) increases in response to hypoxia in rainbow trout (Oncorhynchus mykiss), but details on the control mechanisms of the venous vasculature during hypoxia have not been studied in fish. Basic cardiovascular variables including P(ven), dorsal aortic blood pressure, cardiac output, and heart rate were monitored in vivo during normoxia and moderate hypoxia (P(W)O(2) = approximately 9 kPa), where P(W)O(2) is water oxygen partial pressure. Venous capacitance curves for normoxia and hypoxia were constructed at 80-100, 90-110, and 100-120% of total blood volume by transiently (8 s) occluding the ventral aorta and measure P(ven) during circulatory arrest to estimate the mean circulatory filling pressure (MCFP). This allowed for estimates of hypoxia-induced changes in unstressed blood volume (USBV) and venous compliance. MCFP increased due to a decreased USBV at all blood volumes during hypoxia. These venous responses were blocked by alpha-adrenoceptor blockade with prazosin (1 mg/kg body mass). MCFP still increased during hypoxia after pretreatment with the adrenergic nerve-blocking agent bretylium (10 mg/kg body mass), but the decrease in USBV only persisted at 80-100% blood volume, whereas vascular capacitance decreased significantly at 90-110% blood volume. In all treatments, hypoxia typically reduced heart rate while cardiac output was maintained through a compensatory increase in stroke volume. Despite the markedly reduced response in venous capacitance after adrenergic blockade, P(ven) always increased in response to hypoxia. This study reveals that venous capacitance in rainbow trout is actively modulated in response to hypoxia by an alpha-adrenergic mechanism with both humoral and neural components.

저산소환경이 방어(Seriola quinqueradiata) 순환계의 산소운반 기능에 미치는 영향

We studied the cardio-respiratory properties in the Japanese amberjack (Seriola quinqueradiata) during acute hypoxia exposure. Fish were exposed to three levels of hypoxia (80, 60 or 50 mmHg) for 60 min at <TEX>$25^{\circ}C$</TEX>. Cardiovascular parameters (cardiac output; Q, heart rate; HR, stroke volume; SV, blood pressure; <TEX>$P_{DA}$</TEX>) changed little from pre-exposure values during both 80 and 60 mmHg of hypoxia. During 50 mmHg of hypoxia, the fish showed a bradycardia which significantly affected Q, whereas no change in SV. <TEX>$P_{DA}$</TEX> increased transiently. Arterial oxygen partial pressure (<TEX>$PaO_2$</TEX>) immediately reduced along with a decrease of the water oxygen partial pressure (<TEX>$P_WO_2$</TEX>). Arterial <TEX>$O_2$</TEX> content (<TEX>$CaO_2$</TEX>) decreased significantly only after 60 min of 50 mmHg of hypoxia. Arterial pH (pHa) and hematocrit value (Hct) did not change significantly. Comparing the effects of different levels of hypoxia, oxygen delivery to the tissues (<TEX>$Q\;{\times}\;CaO_2$</TEX>) should be maintained a constant over a broad range of <TEX>$P_WO_2$</TEX>, however, severely depressed below 50 mmHg of hypoxia.

Temperature-controlled enhancement of oxygen uptake from water using oxygen carrier solution

Development of an artificial gill, for the uptake of oxygen from water to air, requires an increase in oxygen transfer rate. In the present study, oxygen transfer rate was enhanced using a washed red blood cell suspension as a thermo-responsive oxygen carrier solution, which changes oxygen affinity with temperature. Oxygen dissolved in water first combined with the oxygen carrier solution at a low temperature using a membrane module. The oxygen carrier solution was then heated to release oxygen into the air using a second membrane module. The water flow rate required to sustain a human being at rest was greatly reduced by heating the oxygen carrier solution due to increase in the limit of the oxygen partial pressure of water of which can be transferred, compared with when oxygen was transferred directly from water. The required membrane surface area is 225 m 2, sufficient for the development of a compact artificial gill.

Cardiorespiratory responses of skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares), and bigeye tuna (Thunnus obesus) to acute reductions of ambient oxygen

Cardiorespiratory responses to acute reductions of ambient oxygen were measured in skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares), and bigeye tuna (Thunnus obesus). Prevented from swimming by a spinal injection of lidocaine, fish were placed in seawater flowing at a velocity equivalent to their normal swimming speed. Ventilation volume [Formula: see text], heart rate, cardiac output, mouth gape, and inspired water and exhalant water oxygen partial pressures ([Formula: see text] and [Formula: see text], respectively) were simultaneously measured during periods of full oxygen saturation (normoxia) and brief (ca. 3–4 min) periods of reduced oxygen (hypoxia). During hypoxia, [Formula: see text] ranged from 140 to 50 mmHg. [Formula: see text] during normoxia was significantly different in skipjack, yellowfin, and bigeye tunas (6.7, 3.9, and 1.5 L∙min−1∙kg−1, respectively) and paralleled differences in oxygen consumption (740, 455, and 322 mg O2∙kg−1∙h−1). All three species were sensitive to [Formula: see text], and mild hypoxia [Formula: see text] elicited significant cardiorespiratory adjustments, including increased mouth gape and [Formula: see text] and reduced heart rate. Cardiac output was maintained until [Formula: see text] reached 95 mmHg, but at lower oxygen levels it too began to decrease. Therefore, the three tuna species studied appear as sensitive to hypoxia as other marine teleosts and show cardiorespiratory adjustments at [Formula: see text] values well above those eliciting swimming speed changes.

Metabolic adjustments of an air‐breathing teleost, Channa maculata, to acute and prolonged exposure to hypoxic water

Plasma and tissue metabolite levels were measured in the air‐breathing Channa maculata during acute and prolonged exposure to normoxic and hypoxic water. Exposure of the fish to hypoxic water (water oxygen partial pressure, PwO2= 50 mmHg) for 1 h caused increases in plasma glucose and lactate, liver and brain lactate, liver a‐amino acid, heart and brain alanine and brain succinate levels. The metabolic changes in heart, brain and muscle could only be detected when PwO2 was 30 or 10 mmHg. Heart glycogen and liver lipid decreased during acute exposure. Prolonged exposure to hypoxic water (PwO2= 30 mmHg) for 3 days caused an increase in plasma glycerol and liver lactate dehydrogenase activity, and a depletion of glycogen store in all tissues investigated. However, metabolite levels which had been elevated during acute hypoxic exposure were observed to return to their normoxic values after prolonged exposure. It was concluded that anaerobic metabolism was triggered by acute exposure to hypoxic water. Prolonged exposure to hypoxic water induced a metabolic readjustment involving mobilisation of lipid and glycogen stores, which is probably a reflection of the high metabolic load of aerial respiration imposed on the fish during exposure to hypoxic water.

Oxygen and carbon dioxide in the marine intertidal environment: Diurnal and tidal changes in rockpools

Water oxygen partial pressure (P O 2 ), pH, titration alkalinity (TA), temperature and salinity were measured hourly in rockpools during emersion periods occuring at various times of the diurnal cycle. Measurements allowed calculation of oxygen concentration (C O 2 ), CO 2 partial pressure (P CO 2 ) and concentrations of bicarbonate and total CO 2(C CO 2 ). During night emersion periods, water P O 2 decreased to almost zero in a few hours, pH fell, TA rose and P CO 2 increased up to 1–3 Torr. During day emersion periods, water P O 2 rose to 400–600 Torr, pH increased to more than 10, TA decreased substantially and P CO 2 fell as low as 10 −4 Torr. The direction of the observed changes essentially on the illumination, indicating that respiratory and photosynthetic activities were the main processes involved. The large variations of the components of the carbonate system imply considerable changes of the CO 2 capacitance coefficient in water, mainly during the day-time emersion. These changes are discussed in relation to the respiratory and acid-base physiology of the animals living in these biotopes.

Blood oxygen transport and metabolism of the confined lugworm Arenicola marina (L.).

Oxygen consumption (MO2), haemoglobin oxygen saturation level (SVO2) and pH (pHv) in prebranchial blood were measured in lugworms experimentally confined in sea water at 15 degrees C. Total blood flow through the gills (Vb) was estimated. For sea water oxygen partial pressure (PwO2) between 120 and 150 Torr MO2, SVO2 and Vb were high and nearly constant. For PwO2 less than 120 Torr, Vb fell quickly, MO2 progressively dropped, and metabolism remained aerobic at the expense of the prebrancial blood oxygen store. For PwO2 less than 50 Torr, Vb and SvO2 values were extremely low, and the low pHv and the modified buffer power of the surrounding sea water showed that anaerobic metabolism was occurring. Changes in respiratory gas exchanges and metabolism during the tidal cycle are deduced from the comparison of these results with data obtained in the field.