Role of LKB1 in migration and invasion of Cr(VI)-transformed human bronchial epithelial Beas-2B cells.

Hexavalent chromium [Cr(VI)] is a common human carcinogen associated with lung cancer and other pulmonary diseases as exposure to excessive Cr(VI) induces malignant transformation in human lung epithelial cells. The mechanism underlying its carcinogenicity is unclear in terms of how it facilitates metastases. Cr(VI) compounds are reported to briefly promote cell migration in a concentration-dependent manner and oncogene liver kinase B1 (LKB1) was reduced in Cr(VI)-transformed cells. Overexpression of LKB1 in Beas-2B-Cr [Cr(VI) malignantly transformed Beas-2B cells] suppressed cell migration and invasion and inactivated FAK, Src, MMP-2, GSK3ß, ß-catenin, and HEF1, which contribute to cell migration and invasion. Silencing LKB1 with siRNA promoted migration and invasion, and activated these downstream proteins. Long-term exposure to Cr(VI) enhanced the migration and invasiveness of Beas-2B cells and reduced the expression of LKB1, while activating these proteins as mentioned above. Data suggest that LKB1 may regulate downstream proteins such as FAK, Src, MMP-2, GSK3ß, ß-catenin, and HEF1, and affect the migration and invasiveness of Beas-2B-Cr cells.

Persistence of gentamicin residues in milk after the intramammary treatment of lactating cows for mastitis.

This study was designed to investigate persistence of gentamicin residues in milk after the intramammary treatment of lactating cows for mastitis. Milk samples were collected at a 1-d interval after the last administration from 34 individual cows that had received intramammary infusions of gentamicin. The doses and treatment times evaluated in this study represented those that have been applied by veterinarians in practice. The tetrazolium chloride assay was used to determine whether there were significant residues of the antibiotic in the samples. Persistence of detectable drug residues in milk from 33 cows (28 cows,