Rate of oxygen loss from arterioles is an order of magnitude higher than expected

1989 ◽  
Vol 256 (3) ◽  
pp. H921-H924 ◽  
Author(s):  
A. S. Popel ◽  
R. N. Pittman ◽  
M. L. Ellsworth
Keyword(s):  
Experimental Data ◽  
Oxygen Flux ◽  
Cheek Pouch ◽  
Retractor Muscle ◽  
Hamster Cheek Pouch ◽  
Oxygen Loss ◽  
Order Of Magnitude ◽  
Solubility Coefficients ◽  
Tissue Permeability

The experimental data on oxygen flux from arterioles in the hamster cheek pouch retractor muscle [L. Kuo and R. N. Pittman, Am. J. Physiol. 254 (Heart Circ. Physiol. 23): H331-H339, 1988] were analyzed under the assumption that the permeability to oxygen is the same in both perfused and unperfused tissue; permeability is defined as the product of the diffusion and solubility coefficients. However, our analysis indicated that the observed oxygen flux was inconsistent with this assumption and that permeability to oxygen of a blood-perfused tissue may be an order of magnitude higher than previously assumed.

Measurement of hemoglobin oxygen saturation in capillaries

1987 ◽  
Vol 252 (5) ◽  
pp. H1031-H1040 ◽  
Author(s):  
M. L. Ellsworth ◽  
R. N. Pittman ◽  
C. G. Ellis
Keyword(s):  
Light Intensity ◽  
Oxygen Saturation ◽  
Red Blood Cells ◽  
Optical Density ◽  
Blood Cells ◽  
Striated Muscle ◽  
Cheek Pouch ◽  
Retractor Muscle ◽  
Hamster Cheek Pouch

We present a computer-aided videodensitometric method for the determination of oxygen saturation in red blood cells flowing through capillaries of the hamster cheek pouch retractor muscle. The optical density (OD) of red blood cells is determined at two wavelengths. At the first, 431 nm, there is a maximum difference between absorption by oxygen deoxyhemoglobin. At the second, 420 nm, absorption is equal for the two absorbing species (isosbestic wavelength). In capillaries of the retractor muscle a relationship between oxygen saturation (S) and the following OD ratio was obtained as S = -1.71 (OD431/OD420) + 2.20. The error (95% confidence interval) in oxygen saturation associated with a determination of the OD ratio is estimated to be +/- 4.8%. The computerization of the method employs a frame-by-frame analysis of the light intensity over a selected capillary segment. The light intensity waveform along the segment is digitized and the minimum (I) and maximum (I0) light intensities are used to compute an optical density (OD = log10 [I0/I]). These minimum and maximum intensities correspond to the presence and absence of a red blood cell, respectively. The method permits the off-line analysis of videotaped scenes and provides a means of assessing the extent of temporal and spatial heterogeneity of oxygen saturation in selected capillary networks. The method has been developed for use in capillaries in transilluminated striated muscle but should be generally applicable to the measurement of capillary oxygen saturation in other tissues.

Analysis of oxygen diffusion from arteriolar networks

1979 ◽  
Vol 237 (6) ◽  
pp. H681-H689 ◽  
Author(s):  
A. S. Popel ◽  
J. F. Gross
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Blood Flow ◽  
Oxygen Diffusion ◽  
Blood Flow Rate ◽  
Cheek Pouch ◽  
Oxygen Distribution ◽  
Hamster Cheek Pouch ◽  
Longitudinal Gradients ◽  
Po2 Gradients

A mathematical model of oxygen transport in the precapillary microcirculation is presented. The theory is then used to simulate oxygen distribution in the arteriolar network of the hamster cheek pouch. Theoretical prediction of transmural and longitudinal oxygen tension (PO2) gradients is in qualitative agreement with available experimental data. The effect of the variation of inlet network PO2, blood flow rate, blood hematocrit, and other parameters on the transport characteristics is studied. The calculations predict that the luminal PO2 in small arterioles is practically independent of the inlet network PO2 leve if the latter is sufficiently high; when this inlet PO2 level is low, then the longitudinal gradients of luminal PO2 vanish. It is further shown that retardation of blood flow may cause a significant increase in precapillary oxygen losses.

Arterioles supply oxygen to capillaries by diffusion as well as by convection

1990 ◽  
Vol 258 (4) ◽  
pp. H1240-H1243 ◽  
Author(s):  
M. L. Ellsworth ◽  
R. N. Pittman
Keyword(s):  
Oxygen Saturation ◽  
Red Blood Cells ◽  
Oxygen Transport ◽  
Blood Cells ◽  
Oxygen Exchange ◽  
Cheek Pouch ◽  
Retractor Muscle ◽  
Hamster Cheek Pouch ◽  
Local Oxygen

In the early part of this century, August Krogh proposed a model of oxygen transport in capillaries that assumes that all oxygen is delivered to the capillaries by convection from small terminal arterioles and lost from these capillaries by diffusion. This model and its consequences have been used extensively to interpret whole organ oxygen transport data in terms of diffusion between capillaries and tissues and to relate changes in microvascular hemodynamics to alterations in oxygen transport. We evaluated the appropriateness of such extrapolation by measuring oxygen saturation at discrete locations along the lengths of individual capillaries in the hamster cheek pouch retractor muscle. Our results indicate that the amount of oxygen lost from individual capillaries can be markedly affected by the presence of larger microvessels that frequently cross the capillary path. These larger vessels act either as a diffusive supply of oxygen for the red blood cells within the capillary or as an additional sink for the oxygen depending on the direction of the oxygen tension gradient. This transfer of oxygen between larger microvessels and capillaries attenuates the importance of capillary hemodynamics in oxygen exchange. Therefore, conclusions about local oxygen exchange that utilize only hemodynamic data from whole organ or microvascular experiments and the Krogh model will generally be invalid and should be viewed with caution.

Simulation of O2 transport in skeletal muscle: diffusive exchange between arterioles and capillaries

1994 ◽  
Vol 267 (3) ◽  
pp. H1214-H1221 ◽  
Author(s):  
T. W. Secomb ◽  
R. Hsu
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Transport ◽  
Metabolic Regulation ◽  
Three Dimensional ◽  
Cheek Pouch ◽  
Retractor Muscle ◽  
Hamster Cheek Pouch ◽  
Consumption Rates ◽  
Three Dimensional Configuration ◽  
Diffusive Exchange

Theoretical simulations of oxygen transport in skeletal muscle are used to study the role of arterioles in oxygen delivery. A three-dimensional configuration of capillaries and arterioles in a cuboidal tissue region is simulated, based on observations of hamster cheek pouch retractor muscle. Equations describing convective and diffusive oxygen transport are solved using a Green's function method. In resting muscle, predicted oxygen saturation of capillary blood increases as it flows toward arterioles, and adjacent capillaries flowing in opposite directions show very similar variations in saturation. Diffusive oxygen loss from arterioles equals about 85% of consumption. Capillaries absorb much of this oxygen (equal to approximately 45% of consumption) and deliver it at downstream locations. Thus diffusive exchange between arterioles and capillaries plays an important part in distributing oxygen throughout the tissue. At higher flow and consumption rates, the relative amounts of oxygen diffusing out of arterioles and into capillaries decrease. The results are consistent with the hypothesis that oxygen content of arteriolar blood participates in metabolic regulation of blood flow.

A new preparation for microcirculatory studies of the hamster cheek pouch

1985 ◽  
Vol 248 (1) ◽  
pp. H143-H146
Author(s):  
M. J. Davis ◽  
R. W. Gore
Keyword(s):  
Optical Resolution ◽  
Vascular Supply ◽  
Cheek Pouch ◽  
Retractor Muscle ◽  
Surgical Trauma ◽  
Hamster Cheek Pouch ◽  
Thin Glass ◽  
Support Plate ◽  
Made In ◽  
Glass Support

Existing methods of preparing the hamster cheek pouch for observation under an intravital microscope have several disadvantages. The everted method, described by Duling (Microvasc. Res. 5: 423-429, 1973), appears to restrict blood flow by placing unnatural tension on the retractor muscle and by requiring an incision in the tip of the pouch. The method of Yamaki et al. (Microvasc. Res. 21: 299-301, 1981) requires an incision in the tip of the pouch and complete disconnection of the retractor muscle. The chamber method of Greenblatt et al. (Microvasc. Res. 1: 420-432, 1969) has a limited optical resolution because the tissue cannot easily be transilluminated with properly condensed light. We have devised a less traumatic method of preparing the pouch, which eliminates these disadvantages. The hamster is anesthetized, and a thin, glass support plate is inserted into the left cheek pouch. The plate is constructed and positioned so that it does not restrict flow to any part of the pouch. The free end of the plate is secured to the animal stage. An incision is made in the skin to expose the cheek pouch, and the loose, avascular connective tissue investing the pouch and the retractor muscle is removed. The pouch is positioned at an angle of 20 degrees from the hamster's body in a temperature-controlled chamber over a standard microscope condensor system. Throughout both surgical and experimental procedures, the pouch is superfused with Ringer-bicarbonate solution at 37.5 degrees C. This preparation minimizes surgical trauma and allows the entire vascular supply to the cheek pouch to be studied.

Heterogeneity of Vascular Innervation in Hamster Cheek Pouch and Retractor Muscle

1999 ◽  
Vol 36 (6) ◽  
pp. 465-476 ◽  
Author(s):  
Dallas J. Grasby ◽  
Judy L. Morris ◽  
Steven S. Segal
Keyword(s):  
Cheek Pouch ◽  
Retractor Muscle ◽  
Hamster Cheek Pouch ◽  
Vascular Innervation

Diagnostics of metal samples using the results of experimental and theoretical study of positively charged microparticles formed upon sample destruction

2018 ◽  
Vol 84 (10) ◽  
pp. 23-28
Author(s):  
D. A. Golentsov ◽  
A. G. Gulin ◽  
Vladimir A. Likhter ◽  
K. E. Ulybyshev
Keyword(s):  
Experimental Data ◽  
Early Stage ◽  
Experimental Studies ◽  
Material Model ◽  
Total Charge ◽  
Cross Sectional ◽  
Practical Applications ◽  
Mechanical And Electrical Properties ◽  
Order Of Magnitude ◽  
Using Data

Destruction of bodies is accompanied by formation of both large and microscopic fragments. Numerous experiments on the rupture of different samples show that those fragments carry a positive electric charge. his phenomenon is of interest from the viewpoint of its potential application to contactless diagnostics of the early stage of destruction of the elements in various technical devices. However, the lack of understanding the nature of this phenomenon restricts the possibility of its practical applications. Experimental studies were carried out using an apparatus that allowed direct measurements of the total charge of the microparticles formed upon sample rupture and determination of their size and quantity. The results of rupture tests of duralumin and electrical steel showed that the size of microparticles is several tens of microns, the particle charge per particle is on the order of 10–14 C, and their amount can be estimated as the ratio of the cross-sectional area of the sample at the point of discontinuity to the square of the microparticle size. A model of charge formation on the microparticles is developed proceeding from the experimental data and current concept of the electron gas in metals. The model makes it possible to determine the charge of the microparticle using data on the particle size and mechanical and electrical properties of the material. Model estimates of the total charge of particles show order-of-magnitude agreement with the experimental data.

scholarly journals Perchloric acid-soluble proteins from goat liver inhibit chemical carcinogenesis of Syrian hamster cheek-pouch carcinoma

1998 ◽  
Vol 79 (1) ◽  
pp. 54-58 ◽  
Author(s):  
F Ghezzo ◽  
G N Berta ◽  
B Bussolati ◽  
A Bosio ◽  
G Corvetti ◽  
...  
Keyword(s):  
Perchloric Acid ◽  
Syrian Hamster ◽  
Chemical Carcinogenesis ◽  
Soluble Proteins ◽  
Cheek Pouch ◽  
Hamster Cheek Pouch

Comparison of soot models for reacting sprays in diesel engine-like conditions

2021 ◽  
pp. 095440702110154
Author(s):  
Pavan Prakash Duvvuri ◽  
Rajesh Kumar Shrivastava ◽  
Sheshadri Sreedhara
Keyword(s):  
Experimental Data ◽  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Modeling Framework ◽  
Aerosol Dynamics ◽  
Significant Difference ◽  
Polycyclic Aromatic ◽  
Order Of Magnitude ◽  
Detailed Kinetics ◽  
Soot Model

Stringent emission legislations and growing health concerns have contributed to the evolution of soot modeling in diesel engines from simple empirical relations to methods involving detailed kinetics and complex aerosol dynamics. In this paper, four different soot models have been evaluated for the high temperature, high pressure combusting dodecane spray cases of engine combustion network (ECN) spray A which mimics engine-relevant conditions. The soot models considered include an empirical, a multistep, a method of moments based, and a discrete sectional method soot model. Two experimental cases with ambient oxygen volume of 21% and 15% have been modeled. A good agreement between simulations and experiments for vapor penetration and heat release rate has been obtained. Quasi-steady soot volume fraction contours for the four soot models have been compared with experiments. Contours of the species and source terms involved in soot modeling have also been compared for a better understanding of soot processes. The empirical soot model results in higher magnitude and spread of soot due to a lack of modeling framework for oxidation through OH species. Among the four models studied, the multistep soot model has been observed to provide the most promising agreement with the experimental data in terms of distribution of soot and location of peak soot volume fraction. Due to a two-way coupling of soot models, the detailed models predict an upstream location for soot as compared to the multi-step soot model which is one way coupled. A significant difference (of an order of magnitude) in the concentration of PAH (polycyclic aromatic hydrocarbons) precursor between multistep and detailed soot models has been observed because of precursor consumption due to the coupling of detailed soot models with chemical kinetics. It is recommended that kinetic schemes, especially those concerning PAH, be validated with experimental data with a kinetics-coupled soot model.

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