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  • Key words Chemical carcinogens  (1)
  • Tumour growth  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cancer research and clinical oncology 110 (1985), S. 11-16 
    ISSN: 1432-1335
    Keywords: Tumour growth ; Cell kinetics ; Melanoma ; Nude mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A human malignant melanoma was grown in nude mice. The tumour showed an exponential growth for several weeks which gradually slowed down, until following week 8 the tumour growth ceased. The reasons for this growth pattern were examined by labelling techniques (PLM, LI). The tumour cell production as quantified by the growth fraction, showed only a moderate reduction which, taken alone, could not explain the growth cessation. The important mechanism seems to be an increased loss of tumour cells during the intermitotic interval. While the loss of cells/h remains constant the total intermitotic cell loss is increased because the cell cycle times are prolonged by 50% from the exponential phase (45 h in week 3) to the plateau phase (66 h in week 8).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1335
    Keywords: Key words Chemical carcinogens ; List of MAK and BAT values ; Cancer risk ; carcinogen classification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Carcinogenic chemicals in the work area were previously classified into three categories in section III of the German List of MAK and BAT values (the list of values on maximum workplace concentrations and bio‐logical tolerance for occupational exposures). This classification was based on qualitative criteria and reflected essentially the weight of evidence available for judging the carcinogenic potential of the chemicals. In the new classification scheme the former sections IIIA1, IIIA2, and IIIB are retained as categories 1, 2, and 3, to correspond with European Union regulations. On the basis of our advancing knowledge of reaction mechanisms and the potency of carcinogens, these three categories are supplemented with two additional categories. The essential feature of substances classified in the new categories is that exposure to these chemicals does not contribute significantly to the risk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed. Chemicals known to act typically by non-genotoxic mechanisms, and for which information is available that allows evaluation of the effects of low-dose exposures, are classified in category 4. Genotoxic chemicals for which low carcinogenic potency can be expected on the basis of dose/response relationships and toxicokinetics and for which risk at low doses can be assessed are classified in category 5. The basis for a better differentiation of carcinogens is discussed, the new categories are defined, and possible criteria for classification are described. Examples for category 4 (1,4-dioxane) and category 5 (styrene) are presented.
    Type of Medium: Electronic Resource
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