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N Mihailovich

Publications and source records attributed to N Mihailovich.

7 recordsLinked to original sources
PubMed1979

Neoplastic response of mouse tissues during perinatal age periods and its significance in chemical carcinogenesis.

A series of studies pertaining to perinatal carcinogenesis have been reviewed. Their main objective was development and definition of a sensitivity biologic model for carcinogenicity screening. Data were summarized on factors modifying the carcinogenic response of various tissues following transplacental, neonatal-infant, or adult exposure of (B57BL/6J X C3HeB/FeJ)F1 mice to a single administration of ENU. In addition, tumor response of mice treated during specific perinatal age periods with DEN, BP, aflatoxin B1, benzidine . 2HCl, DDT, dieldrin, and safrole were analyzed. The results revealed that the age of the animals at the time of carcinogenic exposure has been the most effective modulator of carcinogenesis in liver, lung, stomach, ovary, and lymphoreticular tissues. Infancy proved to be the most susceptible period to carcinogenesis as demonstrated by a great variety of tissues that responded to treatment and the incidence of tumors which developed. Depending on the nature of carcinogen, variation in organ sites undergoing carcinogenesis was considerable, apparently due to difference in their enzymatic competence to activate and metabolize the agent. Thus a single treatment with ENU, a spontaneously activated type of procarcinogen, induced 59 primary types of tumors in 22 tissues. In contrast, treatment of infants by procarcinogens requiring enzymatic activation led to development of tumors only at a limited number of tissue sites. However, regardless of the type of carcinogen used, the liver consistently responded with development of tumors. Detailed morphologic and biologic evaluations of the induced liver tumors demonstrated in addition to the benign neoplastic variety, the presence of the frank malignant tumors. The character of tumors was dependent not only on carcinogenicity of the agent used but also on the age of mice at the time of carcinogenic treatment. Perinatally induced primary liver tumors showed greater tendency to metastasize and were more readily transplantable into an isogeneic host than those induced at later age periods. Data showed the advantage of prenatal and/or postnatal treatment in combination of life-long exposures to test agents as a more sensitive bioassay system in comparison with solely postweaning treatment. Because the early age period is the most sensitivity life phase to carcinogenesis, it appears to be a good model for prescreening various potential carcinogens, especially when only small amounts of test substances are available. The importance of the proper relationship of such bioassay to the other test systems regarding assessment of potential human risk has been emphasized.

Animals↗
PubMed1978

Morphology and metastatic nature of induced hepatic nodular lesions in C57BL x C3H F1 mice.

The metastatic capabilities of well-defined nodular hepatic lesions induced by benzo(a)pyrene, ethylnitrosourea, benzidine.2HCl, and diethylnitrosamine were evaluated. Coded liver and lung tissues from 1264 treated C57BL/6J x C3HeB/FeJ F1 mice were assessed independently for the presence of primary nodular lesions and metastases, respectively. Primary lesions were classified according to their size, cell morphology, and growth patterns into hyperplastic, adenomatous, and trabecular nodules. None of the 126 mice bearing hyperplastic nodules had pulmonary metastases. Four of 291 (1.4%) mice with adenomatous nodular lesions showed metastases. In contrast, of the 733 mice bearing the trabecular type of nodular lesions alone or in combination with other lesions 266 (36%) showed pulmonary metastases. The pulmonary metastases were first detected in mice dying between 51 and 60 weeks of age (5%). This rate increased as a function of age at death, reaching an incidence of 51% in mice surviving more than 81 weeks. It was concluded that nodules showing trabecular and the more anaplastic solid sheet type of growths represented bona fide hepatocellular carcinomas in the mouse.

Animals↗
PubMed1977

Prenatal multicarcinogenesis by ethylnitrosourea in mice.

The Role of prenatal age, sex, and the maternal background upon the incidence, multiplicity, and spectrum of tumors induced by ethylnitrosourea has been studied in the offspring of reciprocal hybrids of the same genotype. The first generation (F1) offspring of C57BL/6J X C3HeB/FeJ and the reciprocal hybrids were observed throughout their life-span for tumor development following single i.p. injections of ethylnitrosourea (60 microng/g) given to pregnant mothers at 12, 14, 16, or 18 days of gestation. Animals exposed to ethylnitrosourea survived on the average for only 90 weeks. They developed by that age tumors in lungs, livers, ovaries, nervous system, and forestomach. Control mice killed at 90 weeks were essentially free of tumors. The fetal age at the time of administration of the carcinogen was one of the most significant modulators of tumor development in lung, liver, ovaries, and nervous system. The sex of the animals influenced the rate of development of liver tumors, whereas maternal background affected the multiplicity of lung tumors.

Animals↗
PubMed1975

Factors influencing augmentation and/or acceleration of lymphoreticular tumors in mice by benzo(a)pyrene treatment.

The response of lymphoreticular tissues to a single i.p. injection of benzo(a)pyrene was studied in the first generation of C57BL/6J X C3HeB/FeJ F1 and C3HeB/FeJ X A/J F1 mice. Groups of 1-, 15-, and 42-day-old animals of both sexes received 75 or 150 mug of the carcinogen per g body weight. After a period of approximately 90 weeks, a high incidence (up to 43%) of reticulum cell sarcomas was observed in C57BL/6J X C3HeB/FeJ F1 mice treated with benzo(a)pyrene at 40 days of age. Animals treated with carcinogen at younger ages had a lower incidence of reticulum cell sarcomas. These sarcomas showed marked cellular pleomorphism and were classified into histiocytic, epitheloid-nodular, reticulocytic, and fibrocytic forms according to the predominant cell type. Lymphomas of thymic and extrathymic lymphoid origin and leukemia of granulocytic type were seen in a descending order of frequency. Control animals of either strain that were killed at 90 weeks of age were basically free of lymphoreticular tumors, while those kept under observation up to 170 weeks developed these tumors in 24% (C57BL X C3H F1) and 10% (C3H X A/J F1), respectively. Studies revealed that the augmentation and/or acceleration of development of the lymphoreticular neoplasms and specifically reticulum cell sarcomas by benzo(a)pyrene was dependent upon the strain and sex of mice used and the age at which the animals were exposed to carcinogen.

Age Factors↗
PubMed1975

Factors modulating benzidine carcinogenicity bioassay.

An integrated series of studies was presented in which several factors were assessed as to their capability to influence the outcome of carcinogenicity of benzidine dihydrochloride in mice. In all studies C57BL/6J X C3HeB/FeJ F1 mice of both sexes were utilized. Animals were either 6 or 1 week of age at the beginning of carcinogenic treatment. Six-week-old mice were exposed to p.o. administration of carcinogen delivered either in food (50 or 100 ppm daily) or by stomach intubation at equivalent dose levels at twice-weekly intervals. In addition, a 150-ppm dose level in food was administered for 39, 54, or 84 weeks. A limited 3-week, daily intubation of benzidine (30 or 100 mug/mouse) was also explored in 1- and 6-week-old mice. Animals were killed in all studies at 90 weeks of age, at which time their tumor incidence was evaluated. Depending upon experimental conditions, benzidine treatment effected development of liver tumors, lung adenomas. Harderian gland cystadenomas, and lymphoreticular neoplasms. Continuous feeding of adult mice for 84 weeks at three dose levels of benzidine resulted in development of liver tumors with a positive dose-response relationship in both sexes. The analysis of data revealed a greater susceptibility of females than of males (94% versus 44% at 150 ppm). Twice-weekly administration of benzidine by stomach intubation was shown to be less hepatocarcinogenic than continuous feeding of equivalent amounts. In the series in which male mice were fed food containing 150 ppm of benzidine for only 34 or 54 weeks, in contrast to the above 84-week schedule, a negative relationship was observed between the incidence of liver tumors and the duration of treatment. Daily administration of 30 mug of benzidine to infants by stomach intubation for a 3-week period significantly enhanced development of liver tumors only in males (66%). Introduction of 150 ppm of benzidine into food offered to mother and offspring from delivery to weaning led to development of liver tumors in 95% of male mice and in 5% of females. No liver tumors developed following similar 3-week treatment of 6-week-old adults.

Administration, Oral↗
PubMed1975

Conditions modifying development of tumors in mice at various sites by benzo(a)pyrene.

The modifying roles of age, sex, and strain of mice on the incidence, multiplicity, and spectrum of tumors induced by benzo(a)pyrene have been investigated. The first-generation (F1) hybrids of C57BL/6J X C3HeB/FeJ and C3HEB/Fej X A/J mice of both sexes were given single i.p. injections (75 or 150 mug/g) of benzo(a)pyrene at 1, 15, or 42 days of age. Experimental animals were allowed to live their life-spans, while animals in control groups were killed at 52, 90, 142, or 170 weeks of age. Animals treated with benzo(a)pyrene died, in general, by the 100th week of age due to development of liver, lung, stomach and lymphoreticular tumors. Few of the control animals died during that same observational period. The age of mice at the time of exposure to the carcinogen modified development of tumors at all the sites. The sex of animals influenced the development of liver and lymphoreticular tumors. The C3HeB/FeJ X A/J F1 hybrids developed lung tumors more readily than did the C57BL/6J X C3HeB/FeJ F1 mice, which had significantly more liver tumors and neoplasms of the lymphoreticular system than the former strain. No strain difference was observed in regard to tumors at other sites. Higher doses of benzo(a)pyrene were more effective in inducing lung, liver, and stomach tumors. In addition, 5 cases of pancreatic ductal adenoma and adenocarcinoma were observed in carcinogen-treated mice.

Age Factors↗