Histology and histopathology Vol.12, nº 4 (1997)
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- PublicationOpen AccessBronchial epithelium associated to lymphoid tissue does not selectively express vimentin(Murcia : F. Hernández, 1997) Alonso, L.M.; Cortés, A.; Barrutia, M.G.; Romo, T.; Varas, A.; Zapata, A.G.The existence of a lymphoepithelium containing M cells in the bronchus-assmiated lymphoid tissue (BALT) of severa1 species has repeatedly been questioned. In previous electron microscopical studies we failed to ultrastmcturally identify these cells in the epithelium covering bronchial lymphoid tissue of adult rats. In the present study, we analyze immunohistochemically the expression of vimentin, an intermediate filament, reported to be a sensitive marker for rabbit M cells, in both BALT and Peyer's patches. Our results demonstrate, however, the absence of vimentin expression in the epithelium covering the bronchial lymphoid aggregates as well as in the lymphoepithelium of the Peyer's patches. On the contrary, both epithelia are strongly cytokeratin positive. Furthermore, numerous vimentin-positive lymphocytes appear in both lymphoid organs. Results are discussed from a view of the possible relationship between BALT and the so-called mucosaeassociated lymphoid tissue (MALT).
- PublicationOpen AccessSystemic mast cell disease (mastocytosis). General aspects and histopathological diagnosis(Murcia : F. Hernández, 1997) Horny, H.P.; Ruck, P.; Krober, S.; Kaiserling, E.Systemic mast cell disease/mastocytosis (SMCD) is best defined as a multitopic proliferation of cytologically andlor functionally abnormal tissue mast cells (TMC). SMCD preferentially involves the bone marrow, skin, spleen, liver, and lymph nodes. The histopathological diagnosis of SMCD may be very difficult to make, and the disease is often not considered in the differential diagnosis of lymphoreticular neoplasia. In suspected cases of SMCD, basic dyes such as Giemsa and toluidine blue are useful to demonstrate the specific metachromatic granules of TMC. The naphthol AS-D chloroacetate esterase reaction has also proved to be very reliable for enzyme-histochemical identification of TMC. Major diagnostic problems may arise in cases of malignant or «aggressive» SMCD exhibiting tissue infiltrates consisting predominantly of highly atypical, non-metachromatic TMC, which are usually also only weakly reactive for chloroacetate esterase. Immunostaining with antibodies against the mast cell-specific proteases tryptase and chymase has proved to be of great value for establishing the correct diagnosis in such cases. Anti-tryptase antibodies have major diagnostic significance due to their extremely high sensitivity and specificity. The classification of SMCD is controversial, but there is increasing support for the differentiation of at least two major subtypes that differ in prognosis: (i) a benign or «indolent» variant in which skin involvement (urticaria pigmentosa-like skin lesions) is usual, but associated malignant hematological disorders are rare; and (ii) a malignant or «aggressive» variant where skin involvement is usually absent but concomitant malignant hematological disorders (myelodysplastic and myeloproliferative syndromes and acute non-lymphocytic leukemias) are very common. Preliminary molecular biological studies of a few cases of malignant SMCD using the recently developed HUMARA assay have yielded evidence that the disease is monoclonal.
- PublicationOpen AccessAlteration of cell cycle-related genes in hepatocarcinogenesis(Murcia : F. Hernández, 1997) Nishida, N.; Fukuda, Y.; Ishizaki, K.; Nakao, K.The mammalian cell cycle is controlled by regulators of the G1 to S transition such as tumor suppressor proteins, p53 and retinoblastoma (RB); cyclin D1 and cyclin-dependent kinase 4; and inhibitor of cyclin dependent kinase, Recently, aberrations of these cell cycle-related genes have been reported to contribute to the formation and development of cancer. In human hepatocellular carcinoma (HCC), high frequencies of aberration have been detected in the p53 and RB genes. Loss of heterozygosity (LOH) of chromosome 13q was detected in 35% of HCC and LOH on chromosome 17p was detected in 49%. Mutation of the p53 gene was also detected in 32%. The aberrations of these genes were observed more frequently in poorly differentiated and in advanced HCCs. On the other hand, genetic alterations of the cyclin DI and p161NK4A genes were not so frequent, but appeared to be associated with the aggressive behavior of the tumor, which suggests that disruption of the cell cycle-related genes results in the progression of HCC. Further study with a substantial number of cases is required to determine the actual frequency of the aberrations of the G1 controlling genes in hepatocarcinogenesis.
- PublicationOpen AccessProhormone and proneuropeptide synthesis and secretion(Murcia : F. Hernández, 1997) Perone, M.J.; Castro, M.G.Hormones and neuropeptides in eukaryotic cells, are synthesised as large precursor molecules in the rough endoplasmic reticulum (RER), from where they are translocated to the Golgi apparatus. The sorting of proteins destined for the regulated secretory pathway from those which will be released constitutively takes place in the trans-Golgi network (TGN). In both these pathways, vesicles need to be transported to the plasma membrane before their contents can be released by exocytosis. Hormones and neuropeptides need to be secreted from the cells in which are synthesised to exert their biological actions, although they can also play paracrine and autocrine actions. Prohormones and proneuropeptides must undergo post-translational modifications which occur in determined subcellular compartments within eukaryotic cells and are carried out in a strict succession of intracellular events, which give rise to biologically active products. The biosynthesis of prohormones/proneuropeptides is mediated by the action of endoproteolytic enzymes and other post-translational modifying enzymes within the secretory pathway. The major focus of this review will be the biosynthetic pathway, sorting and intracellular trafficking of prohormone and proneuropeptide precursors within the secretory pathway of eukaryotic cells.
- PublicationOpen AccessWhen intracellular pathogens invade the frontiers of cell biology and immunology(Murcia : F. Hernández, 1997) Pizarro-Cerdá, J.; Moreno, E.; Desjardins, M.; Gorvel, J.P.Cellular microbiology has recently been described as a new discipline emerging at the interface between cell biology and rnicrobiology (Cossart et al., 1996). Many microbial pathogens can enter eukaryotic cells and live intracellularly either inside vacuoles or in the cytoplasm. The different steps during the invasion process are on the way of being dissected at the molecular leve1 revealing new insights in basic cellular functions. Indeed, bacterial pathogenesis can help us to better understand the dynamics of cell cytoskeleton, intracellular membrane traffic and signal transduction events. The recent advancements in the field of microbial pathogenesis are creating a new cross-taik between cell biologists, microbiologists and immuno-logists. In this review, the different strategies used by several pathogens are presented and the mechanisms elaborated by host cells from the immune system to eliminate the parasites discussed.