Immunohistochemistry of phosphotyrosine residues: identification of distinct intracellular patterns in epithelial and steroidogenic tissues.

Tyrosine kinases are thought to play a major role in the control of cell growth and differentiation. Most of the work on the phosphorylated product was performed, however, on isolated proteins or cultured cell lines. To assess the overall involvement of tyrosine phosphorylation in vivo, a monoclonal antibody (MAb) against phosphotyrosine was applied to conventional histological sections of various tissues. With the immunoperoxidase staining method, two unique patterns of intracellular distribution of phosphotyrosine were identified among a large variety of normal tissues. (a) In many of the epithelia examined, a peripheral staining was observed, either at the apical aspect alone or at the entire contact region between neighboring cells. This pattern of staining seems to coincide with the distribution of a subset of cytoskeletal elements and requires pre-treatment with proteinase K. (b) In most steroidogenic tissues examined, vesicular cytoplasmic staining was evident, which seems to represent steroid-containing granules. In this case, proteolytic pretreatment is not essential and can be harmful. An extensive survey of human ovarian carcinoma biopsies failed to reveal any consistent staining pattern. These findings might indicate the involvement of tyrosine phosphorylation in basic cellular activities such as the assembly of the specialized cytoskeletal components.

Periovulatory multifocal mesothelial proliferation: a possible association with malignant transformation.

This study was aimed at the identification of the site and characterization of the kinetics of tissue renewal during the repair of the ovarian surface epithelium (OSE) surrounding ovulation. Prepubescent C57BL female mice were induced hormonally either by intraperitoneal (ip) injection of pregnant mare serum gonadotropin (PMSG, 5 IU) +/- human chorionic gonadotropin (HCG, 5 IU) 46 h later, or subcutaneous (sc) diethylsilbesterol (DES) 0.1 mg or 1.0 mg in 0.5 ml corn oil, in addition to saline-injected controls. The animals were killed after various time intervals. Autoradiography was carried out on formaldehyde-fixed paraffin sections of genital organs with subsequent hematoxylin & eosin staining. The preparations were examined for nuclear [3H]thymidine incorporation (0.5 &mgr;Ci injected 1 h before killing) in the OSE, as well as the surrounding and more distal mesothelium. Surprisingly, a significant proliferative response was observed in the extra-ovarian mesothelium surrounding the uterine horns, tubes and nearby peritoneum, while the OSE proliferation rate was less than half of it. In contrast to the common notion, it seems that the expansion and repair of the OSE, associated with ovulation, is contributed mainly by its extra-ovarian mesothelial continuum. This observation may provide additional support to the multifocal theory suggested in the pathogenesis of ovarian cancer. Therefore, any search for cellular or molecular events related to malignant transformation should include the proximal and distal mesothelium in addition to the OSE.