Statistical treatment of oxygenation-related data in muscle tissue.

Muscle oxygenation is determined not only by the flow and oxygen content of the supplying blood but also by the density of the capillary network, the heterogeneity of the distribution of the capillaries and the properties and distribution of the muscle fibres. The distribution of the capillaries is adequately analysed by the method of capillary domains, which also allows to link capillaries to individual fibres. Thus, capillarisation can be linked to cell properties like fibre cross-sectional surface area and perimeter, and oxygen consumption of the individual muscle fibres.

Region-specific adaptations in determinants of rat skeletal muscle oxygenation to chronic hypoxia.

Chronic exposure to hypoxia is associated with muscle atrophy (i.e., a reduction in muscle fiber cross-sectional area), reduced oxidative capacity, and capillary growth.

The influence of flow redistribution on working rat muscle oxygenation.

We applied a theoretical model of muscle tissue O2 transport to investigate the effects of flow redistribution on rat soleus muscle oxygenation. The situation chosen was the anaerobic threshold where redistribution of flow is expected to have the largest impact. In the basic situation all capillaries received an equal proportion of the total flow through the tissue, resulting in 4.

Maintenance of heterogeneity of capillary spacing is essential for adequate oxygenation in the soleus muscle of the growing rat.

Objectives: Normal muscle growth is accompanied by capillary proliferation, which usually lags behind the increase in muscle size, causing a decline in mean capillary density (CD). It is not known, however, how the capillary distribution is affected and what impact it has on the oxygenation of the muscle.

Methods: The capillarization of soleus muscles of rats (64-425 g) was determined with the method of capillary domains.

Calbindin-D28K dynamically controls TRPV5-mediated Ca2+ transport.

In Ca(2+)-transporting epithelia, calbindin-D(28K) (CaBP(28K)) facilitates Ca(2+) diffusion from the luminal Ca(2+) entry side of the cell to the basolateral side, where Ca(2+) is extruded into the extracellular compartment. Simultaneously, CaBP(28K) provides protection against toxic high Ca(2+) levels by buffering the cytosolic Ca(2+) concentration ([Ca(2+)](i)) during high Ca(2+) influx. CaBP(28K) consistently colocalizes with the epithelial Ca(2+) channel TRPV5, which constitutes the apical entry step in renal Ca(2+)-transporting epithelial cells.

A modeling investigation to the possible role of myoglobin in human muscle in near infrared spectroscopy (NIRS) measurements.

Near Infrared Spectroscopy (NIRS) analyzes infrared light having traveled through tissue, for its oxygenation status. The main chromophore analyzed is hemoglobin (Hb), but in muscle tissue also myoglobin (Mb) is present. Since NIRS cannot discern between these two species experimentally, we did model calculation studies using general data for human muscle.

Oxygen diffusion coefficient and oxygen permeability of metmyoglobin solutions determined in a diffusion chamber using a non-steady state method.

Non-steady state measurements of oxygen diffusion through various model layers can be performed using a diffusion chamber that was described earlier [1, 2]. A closer analysis of these measurements showed that they not only yield the oxygen diffusion coefficient (DO2) of the diffusion layer, but also the oxygen permeability (PO2). In this study DO2 and PO2 have been determined in solutions of metmyoglobin (metMb) with concentrations varying between 5 and 40 g/dL at 25 degrees C.

Peripheral oxygen transport in skeletal muscle of Antarctic and sub-Antarctic notothenioid fish.

Transcellular oxygen flux was modelled mathematically in the aerobic skeletal muscles of perciform fish species living at widely different temperatures (Antarctica, sub-Antarctica and the Mediterranean Sea). Using structural data derived from stereological analysis of electron micrographs, mean fibre P(O(2)) was calculated on the basis of temperature-corrected rates of mitochondrial respiration and oxygen diffusion. The mean muscle fibre diameter (MFD) among Antarctic notothenioids was in the range 17-61 microm and mitochondrial volume density, Vv(mit,f), was 0.

Reaction rates of oxygen with hemoglobin measured by non-equilibrium facilitated oxygen diffusion through hemoglobin solutions.

The purpose of this study was to verify the concept of non-equilibrium facilitated oxygen diffusion. This work succeeds our previous study, where facilitated oxygen diffusion by hemoglobin was measured at conditions of chemical equilibrium, and which yielded diffusion coefficients of hemoglobin and of oxygen. In the present work chemical non-equilibrium was induced using very thin diffusion layers.

Non-steady-state O(2) diffusion in metmyoglobin solutions studied in a diffusion chamber.

In this study, we studied the "passive" diffusion through myoglobin solutions by determining the oxygen diffusion coefficient (DO(2)) and the oxygen permeability (permeability O(2)) of metmyoglobin (metMb) solutions (3-33 g. 100 mL(-1)) at 25 degrees C. These oxygen diffusion parameters were determined in a diffusion chamber using a non-steady-state method and were also determined of albumin solutions (4-32 g.

Effect of carbogen breathing on the physiological profile of human glioma xenografts.

The aim of this study was to evaluate the effect of carbogen breathing on the physiological profile of human glioma xenografts. Near infrared spectroscopy was used to investigate changes in oxy- and deoxyhemoglobin concentrations in tumor blood. Oxygen tension changes in tumor tissue were evaluated by (19)F-MR relaxometry, using perfluoro-15-crown-5-ether, and modifications of tumor blood perfusion (TBP) were analyzed by fast dynamic (1)H-MR imaging of Gd-DTPA uptake.

Global HDO uptake in human glioma xenografts is related to the perfused capillary distribution.

The aim of this study is to evaluate the existence of a possible relationship between global deuterium-labeled water (HDO) uptake rates and the diffusion geometry of human glioma xenografts in nude mice. HDO diffusion times in the whole extravascular tumor volume were estimated by combining quantitative (1)H-MR diffusion imaging and morphometric analysis of intercapillary distances in two tumor lines with a different perfused vascular architecture. HDO uptake was measured independently using (2)H-magnetic resonance spectroscopy.

Muscle O(2) consumption by NIRS: a theoretical model.

In the past, the measurement of O(2) consumption ((2)) by the muscle could be carried out noninvasively by near-infrared spectroscopy from oxyhemoglobin and/or deoxyhemoglobin measurements only at rest or during steady isometric contractions. In the present study, a mathematical model is developed allowing calculation, together with steady-state levels of (2), of the kinetics of (2) readjustment in the muscle from the onset of ischemic but aerobic constant-load isotonic exercises. The model, which is based on the known sequence of exoergonic metabolic pathways involved in muscle energetics, allows simultaneous fitting of batched data obtained during exercises performed at different workloads.

Diffusion coefficients of oxygen and hemoglobin measured by facilitated oxygen diffusion through hemoglobin solutions.

Diffusion coefficients of oxygen (DO2) and hemoglobin (DHb) were obtained from measuring the oxygen flux through thin layers of hemoglobin solutions at 20 degrees C. The liquid layers were supported by a membrane and not soaked in any filter material. Oxygen fluxes were measured from the changes in oxygen partial pressure in the gas phases at both sides of the layer.

The possible role of intracellular lipid in determining oxygen delivery to fish skeletal muscle.

Transcellular oxygen flux in skeletal muscle fibres was modelled mathematically. In eels at the same environmental temperature (15 degrees C), changes in muscle structure associated with increased levels of activity elevated mean fibre Po2 by 30% to 5.2 kPa, despite greater fibre radius and Vo2, due to more capillaries and intracellular lipid.

The effect of separate red blood cells on capillary tissue oxygenation calculated with a numerical model.

In simplified models that describe large quantities of capillaries the capillary content is considered to be homogeneous for oxygen transport; but, in reality, the capillaries contain discrete red blood cells (RBCs), and this discreteness will affect oxygen transport from the capillary to the tissue. This was previously investigated with an analytical model, where RBCs were modelled as point-like sources. A numerical approach is used in this investigation, and the results are compared with the analytical model.

Reconsidering the effect of local plasma convection in a classical model of oxygen transport in capillaries.

In 1970, Aroesty and Gross investigated the influence of local plasma convection in between two successive red blood cells (RBC) in a capillary on the local oxygen transfer into tissue by combining convectional and diffusional oxygen transport. They concluded that the effect of local plasma convection on oxygen transport in the capillaries was insignificant. Here it is shown that this result was due to their choice of flat oxygen concentration profiles as boundary conditions.