Thymocyte migration: an affair of multiple cellular interactions?

Cell migration is a crucial event in the general process of thymocyte differentiation. The cellular interactions involved in the control of this migration are beginning to be defined. At least chemokines and extracellular matrix proteins appear to be part of the game. Cells of the thymic microenvironment produce these two groups of molecules, whereas developing thymocytes express the corresponding receptors. Moreover, although chemokines and extracellular matrix can drive thymocyte migration per se, a combined role for these molecules appears to contribute to the resulting migration patterns of thymocytes in their various stages of differentiation. The dynamics of chemokine and extracellular matrix production and degradation is not yet well understood. However, matrix metalloproteinases are likely to play a role in the breakdown of intrathymic extracellular matrix contents. Thus, the physiological migration of thymocytes should be envisioned as a resulting vector of multiple, simultaneous and/or sequential stimuli involving chemokines, adhesive and de-adhesive extracellular matrix proteins, as well as matrix metalloproteinases. Accordingly, it is conceivable that any pathological change in any of these loops may result in the alteration of normal thymocyte migration. This seems to be the case in murine infection by the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas' disease. A better knowledge of the physiological mechanisms governing thymocyte migration will provide new clues for designing therapeutic strategies targeting developing T cells

Morphological action of tamoxifen in the endometrium of persistent estrous rats.

BACKGROUND: The aim of this study was to evaluate the action of tamoxifen on the endometrium in states of chronic anovulation. METHODS: Thirty-eight rats inducted to persistent estrous (testosterone propionate) confirmed by hormonal colpocytology were divided into a control and an experimental group; the latter received tamoxifen and had fragments of the uterine horns processed for morphological and morphometrical analysis. Data were analysed statistically by the Mann-Whitney and Student's t tests. RESULTS: Our findings revealed minor uterine weight, epithelial thickness; number of endometrial glands and low eosinophil counts in the group that received tamoxifen. These results were statistically significant. We often observed areas of metaplasic stratified squamous epithelium between cylindrical epithelial cells in both groups. CONCLUSIONS: Our results indicate that antiestrogenic effect of tamoxifen was only partial in persistent estrous, since there was no blocking against the squamous metaplasia of the endometrium.