Abstract:Estudou-se a resistência à infecção pelo S. mansoni em moluscos B. tenagophila inoculados com vários tipos de hemolinfa provenientes de moluscos infectados por S. mansoni da linhagem SJ ou por outros trematódeos avaliando-se, nestas circunstâncias, o comportamento dos amebócitos. Concluiu-se que dois tipos de mecanismos teriam agido provocando resistência à infecção pelo S. mansoni: celular e humoral. A reação do tipo celular ocorreu quando os moluscos eram inoculados com hemolinfa de moluscos infectados por S… Show more
“…Pan (1996) suggested that, under appropriate conditions, B. glabrata hyalinocytes can become granulocytes. Reis et al (1995) noted a direct correlation between the resistance to infection by Schistosoma mansoni and sporocyst death; this observation suggested that hemocytes were an important factor in fighting infections. Kassim and Richards (1979), Sullivan and Richards (1981), and Guaraldo et al (1981) confirmed that sporocyst development in susceptible mollusks was slow, whereas in non-susceptible mollusks the sporocysts were surrounded by defense cells and were quickly killed.…”
“…Pan (1996) suggested that, under appropriate conditions, B. glabrata hyalinocytes can become granulocytes. Reis et al (1995) noted a direct correlation between the resistance to infection by Schistosoma mansoni and sporocyst death; this observation suggested that hemocytes were an important factor in fighting infections. Kassim and Richards (1979), Sullivan and Richards (1981), and Guaraldo et al (1981) confirmed that sporocyst development in susceptible mollusks was slow, whereas in non-susceptible mollusks the sporocysts were surrounded by defense cells and were quickly killed.…”
“…However, the data collected thus far have not supported this hypothesis. In addition, other researchers have failed to demonstrate a consistent finding between the tissue response and its effect on cells from the haemolymph (Reis et al 1995, Borges 2005). In addition, as first noted by Jeong et al (1983), our ultrastructural findings demonstrated that the APO is a complex structure that is composed of juxtaposed cells with epithelial characteristics, such as microvilli, on its free surface.…”
In molluscs, internal defence against microorganisms is performed by a single cell type, i.e., the haemocyte or amoebocyte. The origin of these cells in Biomphalaria glabrata was initially thought to be localised within the vasculo-connective tissue. More recently, origin from a single organ, termed the amoebocyte-producing organ (APO), has been postulated based on the occurrence of hyperplasia and mitoses during Schistosoma mansoni infection. The present investigation represents a histological, immuno-histochemical and ultra-structural study of the B. glabrata APO, whereby histological identification was facilitated by means of collecting epithelial basophilic cells. These cells were comprised of single-cell layers that cover a portion of the stroma, which contains many small, round cells and haemolymph sinuses, as well as a small area of the pericardial surface of the reno-pericardial region. On occasion, this epithelial component vaguely resembled the vertebrate juxtaglomerular apparatus, which reinforces its presumed relationship to the kidney. Both in normal and infected molluscs, mitoses were only occasionally found. The present quantitative studies failed to demonstrate the presence of APO cellular hyperplasia, either in normal or schistosome-infected B. glabrata. Conversely, several structural details from the APO region in B. glabrata were found to be consistent with the hypothesis that the APO is a filtration organ, i.e., it is more closely related to the kidney rather than the bone marrow, as has been suggested in the literature.
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