Biomedical subjects

T R Munro

Publications and source records attributed to T R Munro.

16 recordsLinked to original sources

PubMed1985

Relative density measurements in a simple lung phantom by Compton backscatter.

Compton backscatter of 60 keV gamma radiation from a simple lung phantom has been used to measure changes in "lung" density. It was shown how introduction of a small volume of air can increase as well as decrease the count. Radiation scattered from the "chest wall" was prevented from entering the detector by careful choice of geometry. The remaining count increased linearly with "lung" density. The relative increase of count rate with density was entirely independent of "chest wall" thickness. With our apparatus a change of 0.01 kg/L in "lung" density produced a change in count rate of 2.2%.

Humans↗

PubMed1979

The measurement of the depth of a point source of a radioisotope from gamma ray spectra.

The spectrum of the scattered radiation from a 'point' source of 99Tcm located within a slab of tissue-like material has been studied with a 19-phototube gamma camera, a 7.5 cm x 7.5 cm sodium iodide detector and a Ge(Li) counter. Both backscatter and forward scattered radiation contribute to the spectra observed; 'infinite' backscatter is achieved at a thickness of 8 cm. The scattered radiation can be used to estimate the thickness of the overlying material. The scatter from 133Xe and 51Cr was also measured. The depth of a source could usually be determined to within a few millimetres from the proportion of scatter in the spectrum; it was more accurate with the 51Cr (320 keV) than with the lower-energy photopeaks of the other two isotopes. The variation in the spectrum as the source moved across the field of the gamma camera was recorded.

Chromium Radioisotopes↗

PubMed1977

Competition for cytotoxic immune capacity against a 'syngeneic' mouse tumour distributed at two sites.

Normal C3H mice will develop fatal ascites after the intraperitoneal injection of as few as 100 BP8 cells. However, mice can be immunized so that they can specifically reject an intraperitoneal challenge of 10(7) of these C3H-derived tumour cells. This paper investigates a phenomenon in which the capacity of immunized mice to reject an intraperitoneal challenge of tumour cells is lost between two to seven days after tumour cells have been given subcutaneously. Investigation of this temporary loss of capacity to reject the intraperitoneal challenge of tumour suggests that this might be due to the attraction of cytotoxic immunity to the site of subcutaneous injection. The possibility that this phenomenon is due to blocking factors, tumour overload, suppressor cells or enhancing antibody has been investigated but experimental results are given which do not favour these explanations.

Animals↗

PubMed1977

Assessment of drug sensitivity of human leukaemic myeloblasts. I. Labelling human myeloblasts with 125IUdR for survival studies in mice.

The compound (125)IUdR can be incorporated in a stable form into the DNA of cells. The isotope is released if labelled cells or their progeny die. Consequently the rate of (125)I excretion from mice can be used to follow the fate of labelled cells in vivo. Using these principles we show:(1) Sufficient label can be incorporated in vitro into both fresh and cryopreserved human leukaemic myeloblasts, in non-toxic concentrations, to allow their survival in mice to be estimated by whole-body counting;(2) The release of isotope from labelled cells is sufficiently slow to offer reasonable expectation that this technique can be used for assessing the sensitivity of myeloblasts to cytotoxic agents in vivo (an application described in the second paper in this series, Sonis, Falcão and MacLennon, 1977);(3) The rate of (125)Iexcretion from mice injected with myeloblasts from different donors varies. This probably reflects different rates of spontaneous death of injected myeloblasts;(4) Active rejection of myeloblasts starts within 48 h of their injection into mice;(5) Indirect evidence that phagocytic cells may be active agents in myeloblast destruction in mice;(6) Various methods of immunologically depriving mice were assessed to see if they would result in a useful increase in survival of injected human myeloblasts. We conclude that there is little advantage and some limitations in using mice thus deprived;(7) One of the agents used for immunological deprivation-silica powder-markedly decreased the rate of (125)I loss from mice injected with labelled killed myeloblasts. This experience emphasizes the importance of including the killed-cell control in this assay.

Animals↗

PubMed1975