Background: The mechanisms of drug resistance of cancer have not been yet elucidated in details. Recently, the role of mast cells (MCs) in the development of drug resistance has been brought in the limelight. The aim of the study was to examine the morphological features of doxorubicin (DOX)-resistant Walker 256 carcinosarcoma and to assess the response of MCs and histamine content in these cells in relation to the development of resistance to DOX as well as in DOX-resistant tumors. Materials and Methods: The DOX resistance was induced by serial passages of Walker 256 carcinosarcoma in rats in the setting of DOX treatment in vivo. MCs in tumors were detected in the sections by staining with Toluidine Blue O. Histamine content in MCs stained with solution of Water Blue-Orcein was assessed by Astaldi semiquantitative method taking into account different staining intensity. Results: Formation of DOX resistance in the course of serial passages of Walker 256 carcinosarcoma was accompanied by the increase in the number of MCs in tumors and histamine content. Nevertheless, in tumors with phenotype of complete DOX resistance the number of histamine-containing MCs decreased to the same level as in tumors of the original strain that are DOX-sensitive. Conclusion: MCs are involved in formation of DOX resistance in Walker 256 carcinosarcoma.

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The object of the investigation reported in this paper was to study, from the point of view of statistical and geometric theory of pattern recognition, the DNA optical density distribution peculiarities in the interphase nuclei of buccal epithelium present in the pathology of the thyroid and mammary glands. Two new indices to characterize this distribution (ratio of modal class volumes and relief index) are proposed. It is shown that in malignant neoplasms of the thyroid and mammary glands the changes in the nuclei of buccal epithelium are characterized by an increase in the optical density of DNA over a range from 0.15 to 0.30 in conventional units of measure, as compared with its values in benign pathological processes. The sensitivity of the proposed criterion for diseases of the thyroid gland is equal to 76.2% and the specificity is equal to 85.8%. For diseases of the mammary gland (excluding IDLC) we have discovered that the sensitivity of the method is equal to 94.29% and its specificity equal to 90.91%. In diseases of the mammary gland (including IDLC) we have discovered that the sensitivity of the method is equal to 71.42% and its specificity is equal to 90.91%.

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