The in vitro radiosensitivity of human head and neck cancers

A study was made of the intrinsic radiosensitivity of 140 biopsy and surgical specimens of malignant head and neck tumours of different histologies. Using a soft-agar clonogenic assay, the material was assessed for the ability to grow in culture (colony-forming efficiency; CFE) and inherent tumour radiosensitivity (surviving fraction at 2 Gy, SF2). The success rate for obtaining growth was 74% (104/140) with a mean CFE of 0.093% (median 0.031) and a range of 0.002-1.3%. SF2 was obtained for 88 of 140 specimens, representing a success rate of 63% with a mean SF2 of 0.48 (median 0.43) and a range of 0.10-1.00. There were no significant differences in radiosensitivity between different sites of the head and neck region. There were no significant relationships between SF2 and disease stage, nodal status, tumour grade, patient age, primary tumour growth pattern and CFE. The results were compared with those for other tumour types previously analysed with the same assay. The distribution of the SF2 values for the head and neck tumours was similar to that for 145 cervix carcinomas and there was no significant difference in mean radiosensitivity between the two tumour types. Also, there was no significant difference in radiosensitivity between head and neck tumours and either breast or colorectal cancers. However, a group of eight lymphomas was significantly more radiosensitive. These results confirm the feasibility of carrying out radiosensitivity measurements using a soft-agar clonogenic assay on head and neck tumours. In addition, the work has shown that radiosensitivity is independent of many clinical parameters and that the mean value is similar to that reported for cervix carcinomas.     

Breathing at low lung volumes and chest strapping: a comparison of lung mechanics

In six normal subjects forced expiratory flow rates increased progressively with increasing degrees of chest strapping. In nine normal subjects forced expiratory flow rates increased with the time spent breathing with expiratory reserve volume 0.5 liters above residual volume, the increase being significant by 30 s (P less than 0.01), and flow rates were still increasing at 2 min, the longest time the subjects could breathe at this lung volume. The increase in flow after low lung volume breathing (LLVB) was similar to that produced by strapping. The effect of LLVB was diminished by the inhalation of the atropinelike drug ipratropium. Quasistatic recoil pressures were higher following strapping and LLVB than on partial or maximal expiration, but the rise in recoil pressure was insufficient to account for all the observed increased in maximum flow. We suggest that the effects of chest strapping are due to LLVB and that both cause bronchodilatation.     

The role of the beta-adrnergic receptor in the secretion of gastrin: studies in normal subjects and in patients with duodenal ulcers

Intravenous infusion of isoproterenol, a beta-adrenergic receptor stimulatory agent, increased serum gastrin concentration significantly more in patients with a duodenal ulcer than in healthy subjects. The rise in pulse rate, blood glucose concentration and in serum insulin was the same in both groups of subjects. Gastrin secretion was also increased significantly more in the patients than in the control subjects after a beef-meal. Basal serum gastrin concentrations were higher in the patients than in the control subjects and correlated to the rise in serum gastrin during both tests in the patients with a duodenal ulcer. Isoproterenol and meal stimulated gastrin secretion, expressed as percent of the basal value, were twice as higher in the patients as in the control subjects. The combined administration of isoproterenol and the meal had an additive effect on the rise in serum gastrin. Isoproterenol stimulated gastrin secretion was completely suppressed by propranolol, a beta-adrenergic receptor blocking agent, which had no effect on meal stimulated gastrin secretion. It is concluded that the mechanism of the hypersecretion of gastrin in patients with a duodenal ulcer did not involve a specific abnormality of the beta-adrenergic receptor or the receptor which recognized proteins and their digested products. There is no established role of beta-adrenergic receptor activity in the hypersecretion of gastrin in patients with duodenal ulcers. It is suggested that the beta-adrenergic receptor may have some yet unknown function unrelated to the acute secretory response of gastrin.