Mean Induction Time Research Articles

Tumor frequency and characteristics after a single dose of dimethylnitrosamine or diethylnitrosamine in partially hepatectomized rats

Two groups of 75 rats were injected intraperitoneally with one single dose of 9 mg/kg DMNA and 120 mg/kg DENA, respectively, 28 h after partial hepatectomy. Control groups of non-hepatectomized rats received one single injection of DMNA or DENA at doses of 20 mg/kg and 200 mg/kg, respectively, which were found to be equitoxic to the doses administered to partially hepatectomized rats. One control group of partially hepatectomized rats was injected with saline. Tumors developed in the partially hepatectomized rats injected with nitrosamines with the following frequency: for DMNA: 13% in the liver, 13% in kidney, 4% in lung, 4% at the surgical scar, 9% in hematopoietic tissue and 13% in other organs; for DENA: 11% in liver, 27% in the kidney, 2% at the surgical scar, 2% in hematopoietic tissue, and 11% in other organs. The histological characteristics of these tumors are described. Statistical analysis of the results shows that no significant difference exists in the overall tumor incidence induced by DMNA and DENA and that the difference between liver and kidney tumors induced by DENA is significant, whereas the difference between DMNA- and DENA-induced kidney tumors is less significant. When analyzed by t-test, our results show that death from tumors occurred at an earlier time after DENA than after DMNA treatment and that liver tumors appeared at a significantly earlier time after DENA than after DMNA treatment. Tumors appearing in the same experimental group display similar mean induction times.

Effect of dietary fats on the incidence of 7,12-dimethylbenz(a)-anthracene-induced tumors in rats.

Female rats have been fed high fat diets containing either polyunsaturated or saturated fat. After being fed either of the diets for 4 weeks, some of the animals received an intragastric dose of 7,12-dimethylbenz(a)anthracene (DMBA). At this point, the diets of half of the animals were interchanged so that animals previously fed the polyunsaturated fat diet were fed the saturated fat diet and vice versa. The cumulative incidence of tumor-bearing rats among DMBA-dosed rats was greater when the polyunsaturated fat diet was fed. The mean induction time of tumors decreased and the proportion of tumor-bearing rats which developed malignant tumors increased when the polyunsaturated fat diet was fed. This promotional effect of the polyunsaturated fat diet was exerted only when the diet was fed after DMBA administration.

A comparative study of induction and recovery characteristics of propofol and midazolam

Propofol and midazolam were compared in 40 adult patients in A.S.A. 1 or 2 presenting for short surgical procedures (< 70 minutes) with respect to induction time, pain on injection, apnoea, heart rates, blood pressure, oxygen saturation, time to eye opening on command. The first group was induced with midazolam (0.15-0.20 mg/kg) while the second was induced with propofol (2-2.5 mg/kg) intravenously. In all other respects except for the surgery that patients had the same treatment. The mean induction time was 55.25 + 26.66 and 69.75 + 24.72 for propofol and midazolam groups respectively. In the midazolam group apnoea occurred in 10% of patients compared to 80% of patients in the propofol group. Local reaction (phlebitis) was absent in the midazolam compared with 20% incident rate observed in the midazolam group. Propofol lowered blood pressure more than midazolam after three minutes of induction at a statistically significant level (P < 0.05). Recovery was significantly more rapid following propofol (P < 0.05).

INDIRECT TRANSFER OF RADIOGENIC LYMPHOMA.

SummaryAn incidence of generalised lymphoma of twenty‐two per cent has been seen in mice surviving neonatal inoculation with cell‐free extracts of radiation‐induced lymphomas. The median time to lymphoma induction was 600 days, compared with a mean induction time of some 200 days in the propositi following a leukaemogenic schedule of irradiation. Chromosome abnormalities which were seen in high frequency in radiogenic lymphoma were also observed in the lymphomas which followed inoculation with cell‐free extracts.

INFLUENCE OF ESTRADIOL-17-BETA, PROGESTERONE AND HYDROCORTISONE ON 3-METHYLCHOLANTHRENE-INDUCED MAMMARY CANCER IN INTACT AND OVARIECTOMIZED SPRAGUE-DAWLEY RATS.

Intact, ovariectomized and ovariectomized-adrenalectomized Sprague- Dawley rats, at the age of 50 days, were fed 10 mg of 3-methylcholanthrene (3-MC) by gastric tube 3 or 6 times each week for 7 weeks. Steroids were administered concurrently by the subcutaneous or intramuscular route. Mammary adenocarcinoma was observed in all intact rats. Mean tumor induction time was 52.7 ± 3.9 days for the group injected with sesame oil, 44.1 ± 1.5 for the group injected with progesterone (4 mg) and 47.5 ± 3.9 for the group injected with estradiol-17β (0.01 βg). In rats ovariectomized at 42 days of age, one week prior to treatment with 3-MC and steroids, breast cancer occurred in 63 % of the group injected with sesame oil, in 67 % of the group injected with progesterone, in 12% of the group injected with estradiol-17β and in 81 % of the groups injected with progesterone (4 mg) in combination with estradiol-17β (0.01 or 0.1 βg)- Mean tumor induction time was significantly prolonged in all ovariectomized groups. In rats ...

Influence of Repeated Doses of 3-Methylcholanthrene at Fixed Intervals on Breast Cancer in Sprague-Dawley Female Rats.

Summary3-Methylcholanthrene, 0.66 mg/g rat, was administered by gastric tube to female Sprague-Dawley rats, age 50 days. This dose was repeated at 10-day intervals 1, 2, 3, or 4 times. Mammary cancer was observed in 77.3% of rats 90 days after a single dose and in 100% of the animals given 2 or more doses of carcinogen. Maximal acceleration of mean tumor induction time was achieved with 3 doses. The number of tumors observed correlated directly with the number of doses administered, a response which appears to be quantitatively additive.