PubMed Health⌕ Search

Biomedical subjects

T B Constable

Publications and source records attributed to T B Constable.

15 recordsLinked to original sources
PubMed1979

The accuracy and spatial resolution of the measurement of tissue oxygen removal rate.

An analysis is presented of factors determining the accuracy and spatial resolution of a method for the estimation of oxygen removal rate in tissues using a multi-cathode electrode placed on the tissue surface. The effect of oxygen consumption by the cathodes is shown to be small for 25-micrometer diameter cathodes, but covering the tissue surface with a thin oxygen oxygen-permeable plastic film can introduce a systematic error into the estimate of removal rate, the size of which depends upon the oxygen diffusion coefficient and solubility in the plastic compared with those in the tissue. Spatial resolution is shown to be adequate for distinguishing changes in removal rate over distances of a few hundred microns, and the averaging of removal rate in the direction normal to the tissue surface is weighted heavily towards the superficial tissue layer.

Oxygen Consumption↗
PubMed1978

Comparison between the oxygen removal rate and the histological structure of normal and tumour tissues.

A technique has been used to measure distributions of oxygen removal rate, QR, in samples of recently excised tissue where QR is defined as the ratio of the oxygen uptake rate to the oxygen solubility. QR was measured at 91 sampling points across a cross section of tissue of diameter 5 mm. By placing markers in the tissue and using special procedures to obtain sections of the tissue samples it was possible to compare the distributions of QR with the histological structure of the tissues. The overall resolution of the system is about 1/2 mm so that structures of the order of a millimetre or more could be examined. There are considerable inhomogeneities in QR within some normal tissues, for example 4-19 mm Hg/s in rat kidney and 0.4-1.5 mm Hg/s in human cervix. Inhomogeneities in tumour tissues are also associated with the histological structure and examples for the Lewis lung mouse carcinoma show a correlation between QR and regions of viable or necrotic tissue. For a biopsy sample of human carcinoma of the cervix QR correlates with the degree of local infiltration by tumour cells.

Animals↗
PubMed1976

Independence of the radiobiological oxygen constant, K, and the respiration rate of mammalian cells.

The radiosensitivity, and the radiobiological oxygen-constant K for mouse Ehrlich ascites cells depend on the pre-irradiation growth conditions. Measurements of the oxygen-consumption rate of cells grown by different methods have been made to ascertain whether the differences in radiobiological properties could be associated with different rates of respiration. Inhibition of respiration by sodium amytal had no significant effect on either the radiosensitivity or the estimate of K.

Amobarbital↗
PubMed1975

A method for measuring the spatial distribution of tissue oxygen removal rates.

Distributions of oxygen removal rates are measured over cut surfaces of samples of recently excised tissue. The samples are initially equilibrated with a gas of known oxygen tension and the surface is occluded by bringing it into contact with the end of a glass rod which has a number of polarographic electrodes embedded in it. The oxygen removal rate in mm Hg/sec is calculated from the rate of fall of surface oxygen tension. 91 electrodes are arranged in an array with 0.5 mm separation and each gives an estimate of the oxygen removal rate with a spatial resolution of a few hundred microns. An artificial medium of uniform and controllable respiration rate was used to test the system. Spatial variations in oxygen removal rate were demonstrated in some transplantable rodent tumours.

Animals↗