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A “marginally deficient” essential fatty acid state was produced in male Sprague‐Dawley rats by dietary supplementation with Ω3 fatty acids. Animals fed diets containing the highest amounts of these fatty acids (10% menhaden fish oil) demonstrated a 70% maximum decrease in the linoleic and arachidonic acid content of articular cartilage, a 30–40% decrease in cartilage hexosamine content, with little effect on hydroxyproline levels, and a 32% inhibition of proteoglycan synthesis. Histologic analysis revealed an occasional surface irregularity and localized depletion of Safranin O and toluidine blue staining of articular cartilage on the femoral heads from animals taking the higher doses. Electron microscopic analysis revealed a marked decrease in “dark‐staining” chondrocytes relative to “light‐staining” cells in all animals fed menhaden fish oil. The cartilaginous changes noted in this study reflect a causal relationship between chondrocyte metabolism and an altered unsaturated fatty acid content. The observed responses of chondrocytes to Ω3 fatty acids may be similar to those commonly associated with the development of early osteoarthrosis. It is not known whether similar changes are induced in other species, including humans, but these observations suggest that some caution must be taken in the long‐term adminitration of menhaden fish oil or other Ω3 fatty acid‐containing preparations in rheumatoid arthritis patients.

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Our experiments were designed to identify initial biochemical and biological changes that occur during pancreatic carcinogenesis. TAKA‐1, an immortal hamster pancreatic ductal cell line, was treated in vitro for up to 11 weeks with the pancreatic carcinogen N‐nitorosobis(2‐oxopropyl)amine (BOP). These treated cells were designated TAKA‐1 + BOP. The growth of TAKA‐1 and TAKA‐1 + BOP cell lines was investigated in soft agar and in hamsters intradermally. The resulting tumor from TAKA‐1 + BOP was re‐cultured in vitro and designated TAKA‐1 + BOP‐T. Mutation of c‐K‐ras and p53 oncogenes, chromosomal changes, expression of transforming growth factor alpha (TGF‐α) and epidermal growth factor (EGF) receptor and several biochemical markers were examined in all cell lines. TAKA‐1 + BOP but not TAKA‐1 cells grew in soft agar and produced an invasive tumor in vivo. However, there were no differences in cell growth rate, DNA flow cytometry, or immunohistochemical findings between the non‐transformed and transformed cells. TAKA‐1, TAKA‐1 + BOP and TAKA‐1 + BOP‐T cells all expressed mRNA of TGF‐α and EGF receptor in a comparable pattern. DNA sequence analysis following polymerase chain reaction showed that neither TAKA‐1 nor TAKA‐1 + BOP cells has a mutation of c‐K‐ras or p53. Karyotype analysis demonstrated that TAKA‐1 + BOP cells had more chromosomal abnormalities compared with TAKA‐1 cells. Mutation of c‐K‐ras and p53 was not essential for carcinogenesis in hamster pancreatic ductal cells in vitro. In conclusion, immortality of the TAKA‐1 cells caused expression of TGF‐α to the same extent as in malignant cells. Chromosomal and ultrastructural patterns were the only differences detected between the non‐transformed and BOP‐transformed cells. Int. J. Cancer 72:1095–1103, 1997. © 1997 Wiley‐Liss, Inc.