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PubMed1963

CANINE NEOPLASIA. A PROTOTYPE FOR HUMAN CANCER STUDY.

The authors review current knowledge of spontaneous neoplasms in the dog. The prevalence of certain types of canine tumour has been studied, and comparisons have been made with the occurrence of similar neoplasms in man. Where there are appropriate analogies between the two species, the dog with spontaneous tumours can be used for studies that are not practicable in man.Nutritional and morphological studies have been done on cells cultured from canine tumours. Some consistency has been demonstrated in the morphology of cultures of different tumours of the same type. Nutritional studies with the transmissible venereal sarcoma of the dog have shown the cells to be subject to a growth-repressing effect by SH-containing amino-acids.Attempts to transmit tumours to other dogs or other species have generally been unsuccessful. A transplantable tumour developed in a mouse injected with non-cellular material from a canine thyroid carcinoma, but it is not certain that the tumour was induced. Cell-culture studies have shown that some tumours yield a factor that is cytopathogenic for normal cells, but none has been shown capable of inducing neoplasms in vivo.

Animals↗
PubMed1964

THE REPLICATION TIME AND PATTERN OF CARCINOGEN--INDUCED HEPATOMA CELLS.

The replication time and pattern have been investigated in hepatoma cells induced by feeding 3'Me-DAB to male rats for 5 months. With the use of tritiated thymidine as a DNA label along with autoradiography, mitotic nuclear labeling has been studied 0.5 to 72 hours after the administration of the label. The following time intervals have been estimated: replication time, 31 hours; DNA synthesis, 17 hours; G(2) plus Mitosis, 2 hours; G(1), 12 hours. Only about 8 per cent of the tumor cell (interphase) population is "flash" labeled, following a single dose of 50 microC of H(3)TDR. This group of cells has been followed through three cycles of division. The repeated rhythmic passage of tumor cells through cell division is similar to that previously reported for normal liver cells in the growing rat. However, tumor cells have longer replication and DNA synthesis times. In addition, the several time intervals studied vary more in the tumor cell population than they do in the growing normal cell population.

Autoradiography↗
PubMed1964

MURINE MAMMARY CARCINOMAS INDUCED BY INTRAVAGINAL APPLICATIONS OF METHYLCHOLANTHRENE IN MINIMAL DOSAGES.

Mammary cancer occurred in five of 80 ICR Swiss mice and two of 52 phenotypically normal pituitary dwarf strain mice following intravaginal applications of 20-methylcholanthrene in doses totalling 2.0 to 5.5 mg. Twenty-two of these 132 methylcholanthrene-treated mice had lower genital tract cancer. One acetone-treated Swiss mouse developed mammary cancer. No genital tract or mammary cancer occurred in mice receiving less than 2.0 mg. methylcholanthrene. The carcinogen was administered when mice were young; mammary cancers appeared between 65 and 167 days after methylcholanthrene application was begun. This study provides additional examples of carcinogenesis in organs remote from sites of carcinogen treatment with carcinogen doses close to threshold levels for treated tissues.

Adenocarcinoma↗
PubMed1964

SCHISTOSOMIASIS: AGE OF SNAILS AND SUSCEPTIBILITY TO X-IRRADIATION.

Studies on sensitivity of Australorbis glabratus to x-rays have defined the chronological and physiological age at which the snail is most sensitive to radiation damage. Results showed that the dose producing 50percent mortality at 30 days after irradiation increased with age but that at 90 days it was practically constant from 2 to 210 days of age. In view of the available data on recovery from radiation damage caused by doses from 6000 to 9000 roentgens it is suggested that doses above those causing 50 percent lethality at 60 days but below those causing 50 percent lethality for 30 days should be considered in setting up "radiation barriers" to control snails in water-distribution systems.

Animals↗