Development of the placenton in water buffalo (Bubalus bubalis bubalis Linnaeus, 1758) / Desenvolvimento do placentônio em búfalos (Bubalus bubalis bubalisLinnaeus, 1758)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

The ruminant placenta has an uniform gross structure based on specialized areas of feto-maternal membrane apposition and proliferation: the placentons. By exerting a fundamental role for the development of the pregnancy, these structures have been very well studied in several domestic species of commercial interest. Particularly in the buffalo, however, there is no consistent data with relationship the functional capabilities of this structure or even, the villus architeture in the individual placenton and their metabolic exchange efficacy that characterize the placentation process. One previous macroscopy study on the placenta of buffalo (Bubalus bubalis bubalis) has shown that the number of the placentons is 92 aproximately during pregnancy, but the fine morphology and development of such structures were not studied in all phases of pregnancy. So, in this work, the placentons of pregnant buffaloes on months 4-5, 7-8 and 9-10 were morphologically characterized. The specimens were sectioned and fixed by immersion in either a 4 % paraformaldehyde or in 2.5 % glutaraldehyde in 0.1 M phosphate buffer for light and electron microscopy, respectively. After 24 h, the placentons were cut and processed for embedding in paraplast, historesin or Spurrs resin. Sections were stained by HE, Toluidine Blue, Gomoris and Mallorys trichromes, Methilene Blue and Basic Fucsin and submitted to PAS reaction. In all periods of the pregnancy, we found placentons of different shapes and sizes, with a gross structure similar to the bovine placenton, but more flattened. Apparently, during the progress of the pregnancy, the placentons maintained the same gross morphology but with increased dimensions. At light microscopy, the interface between the trophoblast and the uterine epithelium is extremely irregular forming a fetal villous tree that indents the endometrium. The trophoblast consists of a simple layer of individual cells where binucleated cells are interposed into the remaining trophoblast cells. The axis of the villous tree is fundamentally formed by loose connective tissue, whereas the internal axis of the epithelial folds presented a connective tissue rich in collagen fibers. When compared to early phases of the pregnancy, the villus tree on months 9-10 is much more branched and the materno-fetal interface closely appositioned. Still, in the feto-maternal junction in late pregnancy were found regions of hematomes and erythrophagocytosis. Ultrastructurally, we also observed: the intense vascularization of the fetal villous, binucleated cells presenting a much developed GER (granular endoplasmic reticulum) and Golgi complex, indicating intense secretory activity. The trophoblastic cells showed junctions (desmossomes), euchromatic nuclei and 2 evident nucleoli. The trophoblast and the uterine epithelium were close associated by interdigitated microvilli.

ASSUNTO(S)

búfalos ruminants buffaloes microscopia microscopy anatomy anatomia ruminantes placenta placenta

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