Desarrollo de la Piel y sus Anexos en Vertebrados / Skin and Appendages Development in Vertebrates

La Piel y sus estructuras asociadas permiten a los seres vivos subsistir en los diferentes ambientes ecológicos. El desarrollo de la piel y sus anexos en diferentes especies repite patrones comunes. De suma importancia es la interacción epitelio-mesénquima como regulador inicial de este desarrollo. El evento crucial en la formación de anexos, es la aparición de una placoda ectodérmica, a la cual se le asocia una condensación de células dérmicas, expresándose proteínas como Sonic Hedgehog (SHH) y la proteína morfogenética del hueso (BMP) para luego dar forma al anexo de cada especie. En esta revisión describiremos las etapas sucesivas que transcurren en la formación de la dermis, epidermis y anexos, con énfasis en las proteínas que dirigen el proceso.

Skin and associated structures allow animals to survive in different ecological environments. The development of skin and appendages in different species has common patterns repeated. Of utmost importance is the epithelial-mesenchymal interaction as the initial controller development. The crucial event in the formation of appendages is the appearance of an ectodermal placode, which is associated with a condensation of dermal cells, expressing BMP and Sonic Hedgehog proteins and then give the way to each species appendages. In this review we describe the successive stages that take place in the formation of the dermis, epidermis and appendages, with emphasis on proteins that direct the process.

Changes in the corpora allata and epidermal proliferation along the fourth instar of the Chagas disease vector Triatoma infestans

Triatoma infestans, a blood-feeding insect, synchronises physiological mechanisms leading to moult with food intake. Since the corpora allata are important in moult and metamorphosis regulation, we have studied morphological changes in 4th instar nymphs (gland size, cell density, percent of animals showing mitoses and cell size). Changes were correlated with the effect of precocene II, epidermal proliferation, and with the extent of the [quot ]head critical period[quot ]. Based on morphological grounds, three stages can be defined in the gland along the 4th instar: Stage 1 (days 0-2 after feeding) showed small corpora allata, composed by a small number of cells, and in which mitoses were absent; Stage 2 (days 3-9) showed growing corpora allata, in which cell number was increasing and proliferation was apparent; and Stage 3 (days 10-13) showed no mitotic activity, and a sharply diminishing size of the gland, as a consequence of the diminishing size of their cells. The ability of precocene II to induce abnormal moulting disappeared during stage 2 correlating with the termination of the head critical period and suggesting that corpora allata are essential during days 3 to 5 to determine normal growth. Epidermal cell number was increasing as a consequence of more frequent mitotic activity, beginning after the finalization of the head critical period and after a first increment in the size of the gland.

Nkx-2.3 gene in mouse epidemial maturation

In higher vertebrates, from amphibians to humans, epidemial maturation is a conserved developmental process. Using adult epidemial tissue and an established keratinocyte cell line, the mouse Nkx-2.3 homeobox gene was demonstrated, for the first time, to be expressed in mouse epidermal keratinocytes. Under the normal culture condition, the spontaneous aggregation phenomenon, a common initiation step of ES cell differentiation, and the induction of mouse adult K1 keratin, a marker of mature epidermal keratinocytes, were both observed in vitro when the Xenopus Nkx-2.3 gene was stably transfected into a mouse pluripotent P19 EC cell line. The induction of mouse K1 keratin by using its Xenopus orthologous gene in the mouse P19 cell implies that Nkx-2.3 may play a conserved role in the epidermal maturation of the mouse, as it does in that of the frog (Ma, 2004). However, the CAT assay study on frog adult keratin promoter could not find the induction of adult keratin. This implies there might not be a direct activation of its promoter.

Histomorphometric study of skin in the sheep fetus

Histogenesis and histomorphometric studies of skin from regions of the face, neck, shoulder and fore-limb were carried out on 75 healthy sheep fetuses, which were collected from Urmia slaughter-house. After measurement of the crown-rump [CR] for determining the age of fetuses, tissue specimens were collected and fixed in 10% buffer formal saline, processed and sectioned into 5-7 micro m thick layers. The sections were stained with H and E method and observed by graduated objective lens. To study the reticular, elastic and collagen fibers and mast cells, appropriate staining methods such as PAS, Verhoeff, Van Gesson and toluidin blue were used, respectively. This study showed that the differentiation of epidermis begins from the end of the second month and rate of epidermal growth in the hind-limb was more than that in other regions studied. Melanocytes appeared in 61-65 days of fetal period in epidermis. The hair follicles were seen as cell accumulations in epidermis that protruded toward dermis in the first half of the third month. The hair follicles growth rate was found to be more in the hind-limb and less in shoulder than that in the other regions studied. Sebaceous and sweat glands appeared from the second half of the third month. They quickly increased in the first half of the fourth month in all studied regions. The sweat glands growth rate on the hind-limb was more than the other sites. The growth of sebaceous glands in shoulder continued till the fifth month. The relationship between thickness of epidermis and its cell layer numbers in all areas were significant [P<0.05] and their correlation coefficient [r = 0.78] in the hind-limb was more than that observed in other regions studied. Collagen fibers appeared during 65-75 days of fetal life, and their accumulation in deep regions of dermis [90-95 days] caused differentiation of dermis to papillary and reticular layers. Reticular and elastic fibers appeared during 55-60 and 70-75 days of fetal life, respectively. Mast cells were scattered in deep regions of dermis in fifth month of fetal period

Estudio de la clinica, patologia, estadios, evolucion del melenoma y marcadores pronosticos (PCNA y EGFR) / Study of the clinic, pathology, stadiamevolution from melanoma and prognosis makers

Se estudiaron 29 melanomas,en forma prospectiva en relacion a la exprecion del antigeno de proliferacion nuclear(PCNA)indicador de proliferacion celular y del receptor del factor de crecimiento epidermico(EGFR) responsable de estimular la hiperplasia.La PCNA mostro valores elevados y se correlaciono con los parametros habituales.El EGFR con bajo nivel de expresion,presento en el seguimiento un llamativo incremento en los niveles de invasion mas agresivos(nivel V)y en los casos del grupo de"fallecidos".