Action Of Carcinogenic Agents Research Articles

Chronic diseases, precancer, and cancer of the lung, which are associated with pathology of the club cells of respiratory and terminal bronchioles

The review of the literature deals with the participation of Clara cells now called club cells (CCs) of the epithelium in the respiratory and terminal bronchioles in the pathogenesis and morphogenesis of chronic inflammatory diseases, precancer, and cancer of the lung, which develop in the respiratory segments. The review summarizes data on the histophysiology of CCs and their participation in the pathogenesis and morphogenesis of chronic interstitial lung diseases, pneumoconiosis, chronic obstructive diseases, adenomatosis, and adenocarcinoma of the lung. In this area, there is a bronchioloalveolar junction area (BAJA), one of the most important stem cell niches. CCs are located in the BAJA; they are progenitor tissue stem cells and play an important role in the regeneration of the epithelium of the respiratory bronchioles and alveoli. Pathology of CCs in the BAJA leads to the maintenance of chronic inflammation, to the destruction of the lung elastic frame, and to impaired epithelial regeneration, interstitial fibrosis, and adenomatosis. In this case, decompensated inflammation, pathological regeneration, and fibrosis develop, which, along with the action of carcinogenic agents, can contribute to the accumulation of mutations and epigenetic rearrangements in the CCs, which subsequently results in atypical adenomatous hyperplasia and adenocarcinoma of the lung.

Surgical Resection of the Rat Colon: Effects on Carcinogenesis by 1,2-Dimethylhydrazine<xref ref-type="fn" rid="fn2">2</xref>, <xref ref-type="fn" rid="fn3">3</xref>

Following a 3-month treatment with 1,2-dimethylhydrazine (DMH) given weekly (sc), outbred Sprague-Dawley rats were subjected to partial resection of the transverse colon. After surgery, DMH treatment was continued for 6 months, after which the rats were killed. At autopsy, 63% of the tumors were found in the transverse colon. By contrast, only 29% of the tumors found in the "sham-operated" control animals occurred in the transverse colon. Surgical trauma in the colon mucosa subjected to the action of carcinogenic agents appeared to promote the conditions suitable for the development of tumors in that organ.

The Action of Carcinogenic Agents and Radiations. Some Implications of New Ideas of the Structure of DNA

The Action of Carcinogenic Agents and Radiations. Some Implications of New Ideas of the Structure of DNA

The Action of Carcinogenic Agents and Radiations. Some Implications of New Ideas of the Structure of DNA

The Action of Carcinogenic Agents and Radiations. Some Implications of New Ideas of the Structure of DNA

On the Aetiology of Cancer of the Mamma in the Mouse and in Man

Carcinogenic Factors for the Skin of the Mouse The experimental production of mammary cancer has opened a new chapter in the investigation of cancer by revealing differences, previously not recognised, in the aetiological factors determining the development of malignancy in the two tissues—skin and mamma. In the term “carcinogenic factors” I include with the carcinogenic agents proper those factors which make their action effective. Until recently, the action of carcinogenic agents has been studied almost exclusively in the skin and the connective tissue. The carcinogenic agents for the skin are very varied: they may be physical agencies, such as radium or light; chemical substances; or gross parasites. All of these agencies have this in common: when they are applied to the skin their action is strictly localized: they require a long period of time to induce cancer, and the development of malignancy is preceded by localized pathological changes—a hyperplasia—in the area of tissue on which they act, the precancerous condition. There is, therefore, a great variety in the nature of the carcinogenic agents; there is even a great variety, if we restrict our attention to the one group, of pure chemical substances. We know now that their carcinogenic power is not restricted to organic hydrocarbons having a phenanthrene nucleus, but that this carcinogenic power is possessed also by substances differing widely in their chemical constitution. One and the same carcinogenic agent is not equally effective for the skin of different mice kept under the same conditions. Some animals react readily with the development of malignancy; some take a longer time; and some individuals fail altogether to react. Such differences are due to intrinsic factors which are designated by the vague term “susceptibility.”