Search results for "Oxygen transport"
showing 10 items of 63 documents
Diffusion of Oxygen through Cork Stopper: Is It a Knudsen or a Fickian Mechanism?
2014
International audience; The aim of this work is to identify which law governs oxygen transfer through cork: Knudsen or Fickian mechanism. This is important to better understand wine oxidation during post-bottling aging. Oxygen transfer through cork wafers is measured at 298 K using a manometric permeation technique. Depending on the mechanism, we can extract the transport coefficients. Increasing the initial pressure of oxygen from 50 to 800 hPa leads to a change in the values of the transport coefficients. This implies that oxygen transport through cork does not obey the Knudsen law. From these results, we conclude that the limiting step of oxygen transport through cork occurs in the cell …
Geometric Considerations in Modeling Oxygen Transport Processes in Tissue
1973
Numerical solution of partial differential equations describing transport processes in capillaries and tissue is used for calculation of oxygen transport to brain tissue. Calculation is based on a three-dimensional network model which covers inhomogeneities in capillary blood flow in a relation of 27:1, This study was performed in order to obtain information about the influence of the main physiological parameters on oxygen tension frequency distribution pattern. Following results were obtained: a)Increase (or decrease) of the oxygen consumption rate in tissue to about twice (or half) of the normal case for cerebral grey matter causes an extreme left (or right) shift of the oxygen tension f…
Die Veränderung der Sauerstofftransportfunktion und des Säure-Basenstatus von unterschiedlich stabilisiertem Konservenblut
1967
Unter Verwendung des Mikroverfahrens vonNiesel u.Thews (1961) wurde die Lage der O2-Bindungskurve in Blutkonserven wahrend einer Lagerungszeit von 3–6 Wochen untersucht. Ein Teil der Konserven enthielt ACD-, die ubrigen (ACD + IAG)-Stabilisatoren. Gleichzeitig wurden die extra- und intracellularen pH-Werte gemessen, um die Abhangigkeit der O2-Bindungskurve von der H+-Ionenkonzentration zu prufen. Die Untersuchung fuhrte zu folgenden Ergebnissen: 1. Die O2-Bindungskurve des ACD-Blutes erfahrt, bezogen auf einen CO2-Druck von 40 Torr, eine mit der Zeit zunehmende Rechtsverlagerung, d. h. die O2-Affinitat des Blutes ist herabgesetzt. Extracellulares und intracellulares pH des ACD-Konservenblut…
Facilitated Oxygen Transport
2010
The amount of dioxygen an organism needs for aerobic metabolism depends on many factors, size and activity being the most important. However, as an approximate figure, we may say that a typical higher eukaryote will utilize about 3.5 ml dioxygen kg−1 body weight per minute. This must reach the tissues where active metabolism is occurring and be maintained there at a steady-state pressure of approximately 2 Torr. This will assure a sufficient rate of delivery to mitochondria and allow continued utilization therein for oxidative reactions (see Chap. 4). The problem faced by the organism is how to assure sufficient delivery to all the tissues, even those buried deep in the body, sometimes whil…
Diffusion and reactions of interstitial oxygen species in amorphous SiO2: A review
2008
This article briefly summarizes the diffusion and reactions of interstitial oxygen species in amorphous SiO 2 (a-SiO 2 ). The most common form of interstitial oxygen species is oxygen molecule (O 2 ), which is sensitively detectable via its characteristic infrared photoluminescence (PL) at 1272 nm. The PL observation of interstitial 0 2 provides key data to verify various processes related to interstitial oxygen species: the dominant role of interstitial O 2 in long-range oxygen transport in a-SiO 2 ; formation of the Frenkel defect pair (Si-Si bond and interstitial oxygen atom, 0°) by dense electronic excitation; efficient photolysis of interstitial O 2 into O° with F 2 laser light (λ= 157…
Influence of Temperature, Hypercapnia, and Development on the Relative Expression of Different Hemocyanin Isoforms in the Common CuttlefishSepia offi…
2012
The cuttlefish Sepia officinalis expresses several hemocyanin isoforms with potentially different pH optima, indicating their reliance on efficient pH regulation in the blood. Ongoing ocean warming and acidification could influence the oxygen-binding properties of respiratory pigments in ectothermic marine invertebrates. This study examined whether S. officinalis differentially expresses individual hemocyanin isoforms to maintain optimal oxygen transport during development and acclimation to elevated seawater pCO2 and temperature. Using quantitative PCR, we measured relative mRNA expression levels of three different hemocyanin isoforms in several ontogenetic stages (embryos, hatchlings, juv…
Putative phenoloxidases in the tunicate Ciona intestinalis and the origin of the arthropod hemocyanin superfamily.
2003
In addition to the respiratory copper-containing proteins for which it is named, the arthropod hemocyanin superfamily also includes phenoloxidases and various copperless storage proteins (pseudo-hemocyanins, hexamerins and hexamerin receptors). It had long been assumed that these proteins are restricted to the arthropod phylum. However, in their analysis of the predicted genes in the Ciona intestinalis (Urochordata:Tunicata) genome, Dehal et al. (Science 298:2157–2167) proposed that the sea squirt lacks hemoglobin but uses hemocyanin for oxygen transport. While there are, nevertheless, four hemoglobin genes present in Ciona, we have identified and cloned two cDNA sequences from Ciona that i…
Microcirculatory dysfunction in sepsis: a pathogenetic basis for therapy?
2000
Sepsis is a frequent complication of multiple organ dysfunction syndrome and remains a major problem of intensive care medicine. It is also a common factor in the final cause of death in hospital populations. Clinical observations, assisted by invasive monitoring techniques as well as pathological-anatomical studies, clearly indicate that microcirculatory dysfunction lies at the centre of sepsis pathogenesis. Numerous animal models, from rodents to primates, many of which employ bacteria or their toxins, especially endotoxins, have helped to shed light on the pathomechanisms leading to this dysregulation in the peripheral circulation. Among these are activation of humoral and cellular infla…
Ventilation-Perfusion Ratio in Perflubron During Partial Liquid Ventilation
2010
BACKGROUND: Functional magnetic resonance imaging (fMRI) of fluorine-19 allows for the mapping of oxygen partial pressure within perfluorocarbons in the alveolar space (Pao(2)). Theoretically, fMRI-detected Pao(2) can be combined with the Fick principle approach, i.e., a mass balance of oxygen uptake by ventilation and delivery by perfusion, to quantify the ventilation-perfusion ratio (Va/Q) of a lung region: The mixed venous blood and the inspiratory oxygen fraction, which are equal for all lung regions, are measured. In addition, the local expiratory oxygen fraction and the end capillary oxygen content, both of which may differ between the lung regions, are calculated using the fMRI-detec…
Oxygen-carrying v. non-oxygen-carrying colloidal blood substitutes in schock
1982
Loss of more than 10-15 per cent of the circulating blood causes a corresponding fall in filling pressure and a marked reduction in minute volume. In order to combat a fall in the minute volume, catecholamines are liberated, the stimulating components of these cause a rise in vessel tone. In spite of the blood volume being reduced by blood loss, filling pressure and minute volume are restored by compensating mechanisms as long as the volume lost is not enough to exceed the autoregulative capacity. Even with a blood loss of 10-15 per cent, full compensation is not achieved without replenishing the blood volume unless the fluid lost from the vascular bed is less than I0 per cent of the total.…