Effects Of Carcinogenic Agents Research Articles

The underlying cause of cervical cancer in oral contraceptive users may be related to cervical mucus changes

Oral contraceptives (OCs) remain among the most effective reversible methods of birth control available today, providing almost 100% effectiveness with an impressively high margin of safety and other important health benefits. However, concerns have been raised about the role that the hormones in OCs might play in the pathogenesis of cervical cancer. Evidence shows that long-term use of OCs (five or more years) may be associated with an increased risk of cancer of the cervix. The mechanism of increased risk of cervical cancer in OCs users has long been debated, and remains uncertain. Our hypothesis is that scanty, thick, and highly viscous cervical mucus obtained in OCs users intimately involved in the pathogenesis of cervical cancer. Possibly, this architecture of cervical mucus may modulate and prolong the effect of carcinogenic agents, which have been carried by coitus and stored in posterior vaginal fornix, on squamocolumnar junction of cervix by not permitting them to be removed because of its highly viscous pattern. The role of cervical mucus changes by means of specific mucin protein changes on the pathophysiology of cervical cancer in OCs users should be investigated.

Effects of carcinogenic agents upon different mechanisms for intragenic recombination in mammalian cells.

A growing body of carcinogens are known to affect genetic recombination in mammalian cells and to thereby interfere with the process of carcinogenesis. In order to screen for recombinogenic effects of chemical and physical agents a variety of in vitro assay systems utilizing mammalian cells have been developed. However, the effects of potential carcinogens differ in these different systems. In order to investigate this phenomenon further, we have employed two different assay procedures, involving spontaneous duplication mutants in mammalian cells, which respond to homologous or non-homologous recombination. Four carcinogens were investigated, i.e. Aroclor 1221, benzene, methylmethanesulphonate (MMS) and thiourea, as were gamma- and UV-irradiation. With the exception of thiourea all of these factors resulted in elevated frequencies of homologous recombination. On the other hand, only UV-irradiation affected the rate of non-homologous recombination. These results indicate that substrate length and/or the recombination mechanism may influence the recombinogenic response of mammalian fibroblasts to carcinogenic factors. Thus, procedures for recombinogenic effects of carcinogens should consider the different pathways of recombination occurring in mammalian cells.

Carcinogenic mixtures.

Human populations are generally exposed simultaneously to a number of toxicants present in the environment, including complex mixtures of unknown and variable origin. While scientific methods for evaluating the potential carcinogenic risks of pure compounds are relatively well established, methods for assessing the risks of complex mixtures are somewhat less developed. This article provides a report of a recent workshop on carcinogenic mixtures sponsored by the Committee on Toxicology of the U.S. National Research Council, in which toxicological, epidemiological, and statistical approaches to carcinogenic risk assessment for mixtures were discussed. Complex mixtures, such as diesel emissions and tobacco smoke, have been shown to have carcinogenic potential. Bioassay-directed fractionation based on short-term screening test for genotoxicity has also been used in identifying carcinogenic components of mixtures. Both toxicological and epidemiological studies have identified clear interactions between chemical carcinogens, including synergistic effects at moderate to high doses. To date, laboratory studies have demonstrated over 900 interactions involving nearly 200 chemical carcinogens. At lower doses, theoretical arguments suggest that risks may be near additive. Thus, additivity at low doses has been invoked as as a working hypothesis by regulatory authorities in the absence of evidence to the contrary. Future studies of the joint effects of carcinogenic agents may serve to elucidate the mechanisms by which interactions occur at higher doses.

Effects of carcinogenic agents on aquatic animals: An environmental and experimental overview

(1985). Effects of carcinogenic agents on aquatic animals: An environmental and experimental overview. Journal of Environmental Science and Health. Part C: Environmental Carcinogenesis Reviews: Vol. 3, No. 1, pp. 63-105.

Teratogenic effects of carcinogenic agents on limb regeneration in the Japanese newt Cynops pyrrhogaster.

Normal regeneration of the amputated forelimb of the Japanese newt Cynops pyrrhogaster and regeneration after a single intraperitoneal injection of three potent mutagenic/carcinogenic agents was investigated. Three dose levels of each agent and controls were tested for teratogenicity in this newt model with the following chemicals: N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 4-nitro-quinoline-1-oxide, and 2-(2-furyl)-3-(5-nitrofuryl)acrylamide. These chemicals were administered at 10 days (late dedifferentiation stage), 20 days (late bud stage), and 30 days (early digits stage) after amputation at the midforelimb. A total of 628 newts, with 16-20 animals per group, were used. Normal forelimb regeneration in Cynops pyrrhogaster closely paralleled that reported for other species. A variety of deformities, including syndactyly, polydactyly, oligodactyly, brachydactyly, and digital branching, were occasionally observed in control regenerating forelimbs, with syndactyly occurring at highest incidence (17.5%). All three mutagens at all tested dose levels enhanced the incidence of teratogenic changes, though increases were not always statistically significant. MNNG, particularly when administered at the time of initial chondrogenesis (20 days, late bud stage), was especially teratogenic. The type of forelimb deformity was not mutagen-specific in this experiment. As Cynops pyrrhogaster is easily and inexpensively maintained and tolerates surgery well, this model with the regenerating forelimb should prove useful for further studies on teratogen screening. Also, studies directed toward mutagenic and epigenetic effects of exogenous agents on rapidly proliferating and differentiating tissues can be investigated with this model, which obviates transplacental excursion and metabolism of test compounds.

The Effect of Carcinogenic Agents on the Phosphorus Content of Hair Bulbs and Epidermis: The Effect of X-Rays on the Phosphorus Content of the Hair Bulbs

In a previous paper it has been demonstrated that a positive calcium phosphate reaction can be observed in the skin on the border surface between the epidermis and cutis as well as on the surface of the hair bulbs and the follicles. It was also shown that on the surface of hair bulbs removed by the action of X-rays and thallium, the calcium phosphate reaction fails to occur. On investigating the cause of this occurrence, it was found that because of the disappearance of the inorganic phosphate, the reaction becomes negative on the surface of the hair bulbs epilated by X-rays or by thallium.