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Biomedical subjects

R Howells

Publications and source records attributed to R Howells.

25 records · Page 2Linked to original sources
PubMed1979

Altered growth and development of lower teeth in children receiving mantle therapy.

The improvement in survival and local control rates in children with neoplasms in the head and neck region can be expected to demonstrate increased iatrogenic adverse effects of treatment. The authors report on mandibular growth and developmental abnormalities in 3 children with Hodgkin disease treated by external beam megavoltage therapy. Radiations to the mandible during mantle field therapy were measured and found to be significant. Possible methods of dose reduction are discussed.

Adolescent↗
PubMed1979

Treatment of P388 leukemia in vivo with perfluoroctylbromide and radiation: a preliminary study.

Perfluorinated hydrocarbon compounds (PFHC) possess unique physical properties suggesting possible usefulness in man. Their low surface tension allows free flow into tiny folds and crevices, facilitating dispersion along peritoneal surfaces affected by a tumor. These substances are also oxygen solvents. BDF1 female mice injected intraperitoneally (IP) with 10(6) P388 mouse leukemia cells were studied following treatment with preoxygenated compound 1913 and increasing doses of radiation. Preliminary results suggest increased life span compared to radiation treatment alone. Radioenhancement at high sublethal doses of whole-body radiation cannot be excluded.

Animals↗
PubMed1977

A simple isodose plotter using a rectilinear radioisotope scanner.

An inexpensive isodose plotter is described which uses major items already present in most radiology departments. A rectilinear scanner provides scanning motions and plotting table and two electrometers are used to measure the currents from silicon diodes used as reference adn probe detectors. A simple box of electronics, incorporating an integrated ratio circuit and 13 integrated circuit comparators, interfaces the electrometers to the scanner's printing mechanism. The device worked very satisfactorily and took between 30 and 60 minutes for each plot.

Humans↗
PubMed1977

On determining the levels of treatment to optimize the probability of a favorable response.

This paper presents a statistical method for analyzing the dose response surface associated with treatments resulting from combinations of any number of cytotoxic agents. The results of such an analysis are the dosages of each agent in the combination which will maximize the probability of a favorable response. An example utilizing a combination of hexamethylmelamine and ICRF-159 is presented. The predictive ability of the model is verified by a kappa 2 goodness of fit test. The advantages of such a method relate to its potential applicability to more complex experimental situations where multiple drugs are used in combination and/or where variations in timing of drug administration exist.

Altretamine↗
PubMedDate not supplied

Stimulation of iodine organification in porcine thyroid cells by thyroid stimulators.

Several Graves' sera were simultaneously assessed in a bioassay based on the ability of porcine thyroid cells to organify 125I and in a radioreceptor assay for TSH receptor binding activity. Both assay systems were sensitive to 1 mcU/ml (final concentration) of unlabelled bovine TSH. Six Graves' sera were studied in detail over a wide (0-1.0 mcl sera) dose response range in repeat determinations. Two sera exhibited parallel binding and stimulating. However, two sera revealed significant inhibition of 125I-TSH binding prior to the demonstration of stimulation and the other two sera showed stimulatory capabilities before significant binding was evident. IgG was prepared from one serum by ammonium sulphate precipitation and chromatography on Sepharose 6B and then subjected to preparative isoelectric focusing. The isoelectric distribution of the two activities were found to be identical with major peaks of activity at pl=9.5 and pl=8.5. In summary: 1) each Graves' sera exhibits different dose-response curves with respect to binding and stimulation, 2) at certain concentrations of sera, only binding or stimulation were evident, 3) neither assay was consistently more sensitive for the presence of Graves' immunoglobulins, 4) for one Graves' sera, binding and stimulation could not be separated by isoelectric focusing. These studies would suggest each Graves' immunoglobulin has inherently different characteristics in its interaction with the TSH receptor.

Animals↗