Oxygen tension measurements in bone marrow fleck cultures.

Cultures-Marrow fluid was aspirated from the sternum, ilium or vertebral spine and placed in a tube containing 1 mg. of heparin dissolved in 1 ml. of normal serum. After pouring it into a petri dish, the separated flecks of marrow w’re cultured as described dl’ Fifty marrow flecks from 7 individuals were cultured, and measurements of oxygen tension in the fluid medium were taken at intervals. Cytologically the niarrows were within normal limits. Method of measuring oxygen tension-Oxygen tension measurements were made by an (‘lectrochemical method based on that described by Cater, Silver and Wilson2 using flushc’nded electrodes in conjunction with a transistor amplifier. The oxygen-cathode electrodes were made from platinum wire ( 0.33 mm. diameter ) , insulated with 8 coats of “araldite 985e” resin ( kindly supplied by Aero Research Ltd., I)uxford, Cambridge, England). The reference electrode of silver/silver chloride was in electrical contact with the culturt’ fluid through an agar bridge. The bridge was made from thin glass tubing pulled to a capillary of about 1 mm. bore at on end and bent through 90 degrees to facilitate the accommodation of the chambers in the incubator. Both the platinum electrodes and the bridge were inserted through guide holes in the rubber gaskets of the Rose chambers ( fig. 1 ), until they protruded several millimeters into the interior. A molten 2 per cent agar in balanced salt solution was then introduced into the bridge and the end plugged with drawn-out polythene rod. The culture fluid used was 20 per cent normal serum and 80 per cent medium 199; after equilibration with air containing 5 per cent carbon dioxide it was introduced into the chambers by means of a syringe. The gasket holes were oversealed on the outside with high vacuum grease to prevent any diffusion of air into the chamber. The platinum electrode was left sealed into the chamber for the duration of each experiment, but for ease of handling the reference electrode was inserted into the agar only when required for reading. A potential of 600 mV was placed across the electrodes and the current passing was measured in terms of amps. x 10-s using a transistor amplifier. Correlation of oxygen tension and electrical rexistance.-Cater and colleagues3 found an approximately linear relationship between current and oxygen tension over the range 7.2 to 143 mm. of mercury with their earlier apparatus and a similar relationship with the apparatus used here.2 \Ve have confirmed this using our own tissue culture fluid over a range from 0 to 680 mm.