An Improved Capillary Microrespirometer

Abstract

Instruments for the measurement of tissue and cell respiration have steadily moved,, since the introduction of Warburg's convenient manometer, in the direction of smaller volume and greater sensitivity. Gerard and Hartlinel took advantage of the greater stability afforded by reducing the tissue chamber of a volumeter to capillary dimensions (0.5 to 1.2 mm diameter) and having this inside the relatively large "differential" chamber. Index drop movements, followed with an ocular micrometer, were consistent over 5-minute intervals, even when corresponding to volume changes of about 0.01 cmm. The diver technique, introduced by Linderstrom-Lang? ' is of the same order of sensitivity and consistency; and the electrical method4 gives promise of superior performance.We have further developed the capillary method so that it is convenient to follow the respiration of 10 tissue samples at once, and it is possible to measure absolute gas volume changes of 0.001 cmm, minute by minute, with an error of some 8% minute by minute, under 1% for longer intervals. The respiration even of bits of frog sciatic nerve weighing a fraction of a milligram can thus be followed at half -minute intervals.The tissue chamber, also containing filter paper bits soaked with acid or alkali and separated from each other and the tissue by dry paper guards, is a short length of capillary of 1.2-1.5 mm internal diameter. The "open" end of this, after the insertion of materials, is plugged with plasticine. Into the other end has been cemented a fine drawn capillary of about 0.2 mm diameter. At the close of the experiment, this capillary is broken off and its end diameters accurately measured by end on examination with an ocular micrometer. Several such units are mounted on a central rod extending from a glass stopper, which ultimately fits into a glass container to provide a completely closed system. This is then immersed in a thermostat with the capillaries horizontal, and the whole is rotated about its long axis so that one or another capillary is brought into

Techniques of Histo- and Cytochemistry: A Manual of Morphological and Quantitative Micromethods for Inorganic, Organic and Enzyme Constituents in Biological Materials

“…The index droplet consists of kerosene which has been treated for several days with concentrated sulfuric acid and then stored over pellets of sodium hydroxide in a closed vessel in order to remove unsaturated compounds which might lead to resin formation. [Tobias and Gerard, 1941, claim that isodecane (2,7-dimethyloctane) is the index fluid of choice for use in small capillaries. ]…”