Search

We studied the profiles of 3,5,3'-l-triiodothyronine (T3), thyroxine (T4), and thyroid hormone receptors (TRs) in Pacific bluefin tuna (Thunnus orientalis) during embryonic and post-embryonic development. Both T3 and T4 were detected in embryos just before hatching, and it was found that the levels of both were increased in postflexion fish. The thyroid follicles were increased in both size and number in postflexion fish compared with preflexion fish. A TRbeta cDNA clone was generated by RACE. Two TRalpha cDNA clones were also partially identified and analyzed by real-time RT-PCR in this study. The TR mRNA levels in embryos were determined, and these were found to be lower than those in preflexion fish. Therefore, we considered that thyroid hormones function during early post-embryonic development as well as during embryonic development. Moreover, there was a peak in the TR mRNA level during postflexion stages, as seen during metamorphosis in Japanese flounder and Japanese conger eel. It is possible that thyroid hormones control the early development of scombrid fish through TRs, as they do for Pluronectiformes and Anguilliformes.

Cytopathic effects of adenovirus-infected human cells consist of rounding and detachment from the substrate at late times postinfection. It is not known, however, whether any changes in cell adhesion are induced by adenoviruses before cytopathic effects become evident. We show here that attachment and spreading of human adenovirus type 2 (Ad2)-infected KB cells on fibronectin (FN) are, unexpectedly, promoted at intermediate times postinfection. The promotion of spreading by Ad2 is not only on fibronectin but also on laminin and vitronectin. In contrast, Ad2 or Ad5 mutants defective in the E1b 19-kDa function did not lead to a promotion in cell attachment but they led to a promotion in cell spreading. Inhibition of spreading of Ad2-infected KB cells on FN by the peptide Gly-Arg-Gly-Asp-Ser-Pro is partial, although it is complete in uninfected KB cells. We found, however, that Ad2 infection does not significantly change the levels of expression of beta 1 integrin mRNA and FN receptor polypeptides. Our results thus suggest that adenovirus infection leads to a promotion in adhesion through influencing integrin molecules without altering the quantity and/or through activation in the cytoskeleton or some other pathway.