Incidence Of Tumor Formation Research Articles

Laser effect on DMBA-induced dyskeratoses of the hamster cheek pouch.

Results of 21 months of experimental investigation of 120 Syrian hamsters with 9, 10 dimethylbenz (a) anthracene-induced dyskeratoses and subsequent papillomas and squamous-cell carcinomas, and the reaction to treatment of pulsed ruby laser are presented. In addition, tentative results of experiments with continuous argon-ion laser radiation are presented and histopathology of the lesions is reported. Conclusions are given involving statistical analysis of the data which strongly support the hypothesis that pulsed laser radiation has an inhibitory effect on tumor growth, reducing the rate of cell division. On the basis of this work, it is postulated that an approximately eightfold reduction in mitotic rate in hamster oral tumor growth occurs, along with a decrease of incidence of tumor formation to approximately one half of control results.

Effects of mercaptoethanol on tumor induction in a Nicotiana amphiploid

Young seedlings of the amphiploid Nicotiana glauca × N. langsdorffii, grown aseptically on nutrient medium, were treated with solutions containing 2-mercaptoethanol, and the incidence of tumor formation was scored for 30 days subsequent to exposure. Mercaptoethanol caused a marked acceleration in the rate of tumorigenesis when the pH of the test solution was in the alkaline range. The effectiveness of the compound was reduced by lowering the pH of the treatment solution.

Experimental Production of Midgut Tumours in Periplaneta Americana L

ABSTRACT Sub-oesophageal ganglia taken from Periplaneta americana L. which had been kept in reversed conditions of light and darkness have been implanted into the abdomens of cockroaches living in normal light: dark conditions. When implantation was continued for 4 days transplantable tumours appeared by the eighteenth day in the midgut of the majority of cockroaches. No tumours appeared in the guts of cockroaches when the implanted sub-oesophageal ganglia had been taken from animals kept in normal conditions of fight and darkness, nor when brains or corpora allata were implanted. Injection of an extract of five sub-oesophageal ganglia in 0·05 ml. Ringer solution produced tumours only when injection took place during the inactive phase of the 24 hr. locomotory rhythm.

Hormonal treatment of thyroid cancer.

THERE is considerable evidence that there may be two factors in the induction of malignant neoplasm (1) Certain stimuli (initiating factor) which alone are incapable of inciting tumor formation may so alter the cellular physiology and biologic potential that a sequential stimulus of a different sort (promoting factor) may be followed by neoplastic growth. Experimentally, carcinoma of the thyroid fits closely into this scheme (2). A carcinogen alone (such as dibenzanthracine or 2-acetyl-aminofluorene) may induce very few thyroid tumors. If, however, this carcinogen is followed by a promoting factor (goitrogen) the incidence of tumor formation is strikingly high and much greater than when the goitrogen alone is administered. Most of these tumors remain dependent, but a few attain complete autonomy (3–5). Since in some instances these carcinomas appear to be under the influence of thyrotropic hormone, as long ago as 1947 Purves and Griesbach (6) suggested that, “It might be possible to influence the course o...

Incidence of epidermal methylcholanthrene tumors in mice after administration of cortisone.

Summary1. Under the conditions of our experiments; the administration of cortisone to mice given external applications of methyl-cholanthrene in benzene or in carbowax 1500 was followed by some reduction of the early inflammatory response and by an increase in the incidence of epidermal tumor formation per number of animals, as compared with the results in the control experiments without cortisone injections. 2. Biopsy excisions performed in the methylcholanthrene-exposed skin areas appeared to increase still further the incidence of tumor formation in the mice treated with cortisone.

The Local Influence of Zinc on the Development of Thymomas in Marsh-Buffalo Mice

The carcinogenic action of zinc injected intratesticularly in cockerels is well established (1, 2). In an effort to determine whether the action of zinc is specific for the testes of cockerels or whether its action is more general in nature, the study has been extended to the mouse, and to other endocrine glands and parts of the body. The injection of zinc into the mammary gland tissues of female mice has been found to have an inhibiting instead of an enhancing effect upon the development of the adenocarcinoma of the breast (3). The present report is concerned with the influence of injecting zinc into the thymus. As in our mammary gland studies, mice of the Marsh-Buffalo strain have been used, as they show a tendency to develop tumors of the thymus. A study of the incidence of tumor formation in the first twenty months of life for 270 female mice of the Marsh-Buffalo strain which had been subjected to various experimental procedures in our laboratory and for 229 control female litter mates showed that 2 per cent of the controls and 5 2 per cent of the treated mice developed lymphosarcomas of the thymus; 2 per cent of each group had lymphosarcoma in the thymus and in the lymph nodes.