The transepidermal oxygen flux from the environment is in balance with the capillary oxygen supply.

It has been known since the nineteenth century that oxygen is taken up by the human skin. With a newly developed sensor it became possible to examine the influence of the vascular supply on the oxygen flux into the skin, tcJ(O2). tcJ(O2) was measured optically by determining the oxygen partial pressure difference, DeltapO2 across a diffusion test membrane, which itself was brought into close contact to the skin surface. Under these conditions DeltapO2 is proportional to the tcJ(O2). The skin perfusion was varied by the application of a hyperemizing ointment on the abdomen of 12 volunteers and by suprasystolic occlusion at the thigh of 20 volunteers. The tcJ(O2) was measured at a temperature of 33 degrees C of the humid skin. It was compared with the skin perfusion monitored by laser Doppler flow, and the capillary oxygen supply measured by transcutaneous partial pressure of oxygen, tcpO2, at an electrode temperature of 37 degrees C. The transcutaneous O2 flux produced a distinct DeltapO2 of 81.8 +/- 8.2 Torr (abdomen) and 72.8 +/- 12.3 Torr (ankle). In hyperemic skin on the abdomen the O2 flux was reduced (DeltapO2 = 57.7 +/- 10.6 Torr). The tcpO2 increased from 8.7 +/- 10.7 to 35.1 +/- 16.9 Torr. During suprasystolic occlusion, DeltapO2 increased by 6.4 +/- 2.3 Torr, whereas laser Doppler flow and tcpO2 decreased significantly. These results indicate that the total oxygen supply of the epidermis and the upper dermis is guaranteed even if the perfusion varies.

Applicability of the Kubelka-Munk theory for the evaluation of reflectance spectra demonstrated for haemoglobin-free perfused heart tissue.

Reflectance spectrometry is a useful tool for studying in vivo kinetic changes in the oxygen saturation of haemoglobin and myoglobin as well as the redox state of cytochromes. A method is given which allows the quantification of tissue reflectance spectra using multicomponent analysis. This method utilizes the Kubelka-Munk theory for modelling the measured tissue spectra. To test this approach, reflectance spectra of a haemoglobin-free perfused guinea pig heart were measured by a fast scanning spectrophotometer (100 spectra/s, spectral resolution 1.0 nm) and evaluated using the component absorbance spectra measured separately. A relative mean spectral residual error of 0.15% was achieved by least-squares fitting. Using statistical error propagation, oxygenation of myoglobin is obtained within a relative precision of 1%, and the redox state of cytochromes aa3 and c are determined simultaneously within a margin of 3%; the results for the redox-state of cytochrome b, however, are less precise. Special component error functions are presented to provide a reliability measure for the concentration prediction using this multicomponent assay. The consistency of the theory and the component absorptivity data is tested by regressing the actual concentrations obtained for each of the redox pair components during the various states of tissue oxygenation. A method is described for the recognition and reduction of systematic errors.

A cooling chain for studies of cryofixed biological specimens by scanning transmission electron microscopy and X-ray microanalysis.

A cooling chain is described which enables the transfer of frozen hydrated biological specimens (ultrathin cryosections as well as about 1 micrometer thick cultured cells) from a cryoultramicrotome into a scanning transmission electron microscope with a field emission gun. Transfer is done at 118 K, specimen temperature in the microscope is 165 K. Sublimation processes are controlled visually and by mass spectrometry. Electron micrographs and X-ray microanalytical spectra of cryofixed unstained tissue culture cells and rat liver tissue sections are described and discussed. Contamination of the specimen is much reduced by use of the cold stage.

Electrochromic dyes, enzyme reactions and hormone-protein interactions in fluorescence optic sensor (optode) technology.

The analytical potential of fluorescence-based optochemical sensors (optodes) has been expanded by use of (1) electrochromic dyes incorporated in thin polymeric multilayers by means of Langmuir-Blodgett film techniques, (2) enzyme-catalysed biochemical reactions and (3) antibody-linked immunological reactions. Fluorescence optical biosensors have been developed for the determination of electrical potentials (e.g., those produced by ion-selective membranes) and of hormones (e.g., thyroxine) and metabolites (e.g., lactate, glucose, xanthine and ethanol).

Correlation of field potentials with redox-states of cytochromes recorded from the olfactory cortical slice of guinea pig.

Field potentials and the reflection spectra of cytochromes were continuously recorded from the olfactory cortical slice of a guinea pig which was incubated under the normoxic and anoxic conditions. The reduction of the oxidated spectra of the cytochromes occurred before the decrease of field potential heights and the oxidation of the reduced spectra occurred before their recovery. In a 3 min anoxic experiment, a 90% recovery of the cytochromes aa3, b, and c, and the field potential amplitudes took place in this order after the restoration of oxygen.

Transcutaneous measurements of skin O2 supply and blood gases.

The data of the O2 exchange through the surface of the skin show that a part of the normal upper skin can be supplied with O2 from the surrounding atmosphere. This may be important in pathological situations although probably simultaneous disturbances of the substrate supply may be more serious. The noninvasive continuous registration of skin surface pO2 (and pCO2) allows to monitor skin oxygen supply under different conditions. The new optical sensing of pssO2 and of the local O2 flux into the skin opens up new promising possibilities for quantification of the skin oxygen supply.

The microphotometric determination of the variability of oxygen saturation of erythrocytes lying within rouleaux.

It was found that by using nonlinear multicomponent analysis with the spectra of oxygenated and deoxygenated haemoglobin as basic spectra the mean O2 saturation of 2 to 3 red cells lying in a rouleau could be determined with an accuracy of 0.5 - 1.0%. At the same PO2 and PCO2 distinct differences in O2 saturation were found in different red cells; for 50% of the saturation values the differences were in the range +/- 1.5%, for 30% of the values, the differences were in the range of +/- 3% and 15% lay in the range of +/- 4.5%. Only 5% of saturation differences were larger than 4.6%. These differences are so large that they have to be considered in calculations of the PO2 from O2 saturation measurements.

Quantitative analysis of reflection spectra of the surface of the guinea pig brain.

For a nearly constant light scattering coefficient a method is presented which allows the quantitative analysis of reflection spectra of the brain using a nonlinear multicomponent analysis ( NLMCA ).

Oxygen profiles and structure of Penicillium chrysogenum pellets.

Oxygen profiles were measured polarographically with micro-needle electrodes in single fixed pellets of Penicillium chrysogenum. The oxygen concentration, the grade of turbulence and the flow conditions of the outer medium were varied. Pellets were then histologically investigated. Under our experimental conditions the pellets were found to contain a 200 micrometers thick active outer zone with intact cells. In this zone, the oxygen partial pressure decreased from the initial values to zero. The results show that the Po2 profile within the pellet is strongly influenced by the Po2 of the outer medium. Apart from molecular diffusion, surface turbulence as well as a convective flow through the pellets are of importance for the oxygen transport.

Oxygen transfer from gas bubble into liquid.

Oxygen transfer from a gas bubble into the surrounding liquid is examined by measuring oxygen pressure with Po2-needle electrodes at different distances from the bubble. From there, the mass transfer coefficient can be calculated. First measurements yielded results in the range to be expected.

Effect of prostaglandins F2alpha and E1 on local tissue Po2 and microflow of the brain cortex (cat).

The effects of prostaglandin F2 alpha (PGF2 alpha) and E1 (PGE1) on local tissue Po2 and microflow in the cat's brain surface were studied. Local tissue Po2 was polarographically measured with a multiwire surface electrode, and microflow measured by local hydrogen clearance method. The PGs were investigated by intracarotid (i.c.) infusions, single i.c. and intravenous (i.v.) injections. The i.c. infusions were made with dose of 3, 10 and 30 microgram/kg/min of PGF2 alpha and 0.1, 0.4 and 1.0 microgram/kg/min of PGE1. The i.c. application of PGF2 alpha led to a decrease in local tissue Po2 and tissue microflow. With the use of comparatively low doses (3 and 10 microgram) the effect appeared to be more specific, since SAP did not change significantly. Systemic (i.v.) injections of PGF2 alpha caused a significant drop in arterial pressure and decrease in tissue Po2. Studies with PGE1 always demonstrated a decrease in local tissue Po2 and microflow associated with a significant decrease in the SAP. No evidence for a specific effect was found. Suggestions for possible mechanism of action for these PGs are made.

[Regulation of local tissue PO2 in the cerebral cortex of the cat]. / Reguliatsiia mestnogo tkanevogo PO2 v kore mozga koshki

Local PO2 was measured in the cat cortex on adjacent sites with a platinum multiwire surface electrode both during steady state conditions and with varying arterial oxygen supply. Concomitantly, PO2 in the sinus sagittalis was recorded continuously through the vascular wall. Under normoxia and steady state conditions local tissue PO2 values varied between O Torr and almost arterial levels of 85 Torr in accordance with theoretical calculations. With increased arterial oxygen supply local tissue PO2 as measured on agjacent sites was found to react fairly differently. Linear increases in local tissue PO2 as compared with arterial PO2, as well as constant levels, or only very small increases, were recorded. The constancy of local PO2 (="local PO2 autoregulation") was caused by local vasoconstriction. With reduced supply of arterial oxygen, however, tissue PO2 dropped in all studied sites down to hypoxia and anoxia. PO2 autoregulation during a decrease in arterial PO2, as described by Bicher (1973) could not be found.