Multivesicular bodies and related structures of the syncytiotrophoblast of human term placenta

Abstract

Multivesicular bodies and related structures of the syncytiotrophoblast of human term placenta have been studied ultrastructurally and cytochemically. Circular profiles of vesicles termed pre-multivesicular bodies (premvb's) were observed often near Golgi complexes. Multivesicular bodies (mvb's with electron lucent matrices (L-mvb's), mvb's with electron dense matrices (D-mvb's), and dense bodies were also prevalent organelles of the syncytium. These organelles all exhibited dialyzed iron reactivity and staining characteristics suggesting that the organelles were related. Material within Golgi saccules, Golgi vesicles, vesicles of pre-mvb's, and vesicles of mvb's were all reactive with osmium zinc iodide (OZI). This OZI reactivity further indicated a relationship between the organelles. The matrix of the mvb's exhibited variable reactivity for acid phosphatase (AcPase) but such activity was not encountered in Golgi elements of syncytiotrophoblast. It is suggested that the mvb's of human term placental syncytium are likely formed by aggregation of vesicles of Golgi origin into pre-mvb's, that the pre-mvb's are then capable of transforming into L-mvbs, D-mvb's, and finally into dense (residual) bodies. It is also suggested that mvb's may function in the selective hydrolysis and transport of endocytosed proteins, including globulins. Additional bodies with intense acid phosphatase activity were designated elongate bodies. Other distinctive organelles designated dense cored spheroids were occasionally observed in the syncytioplasm.The placental syncytiotrophoblast functions as a barrier between the fetal and maternal vascular systems, as well as in the transport of nutrients and metabolic wastes (Grosser, '27; Hagerman and Villee, '60; Boyd and Hamilton, '70), and is apparently the site of synthesis and secretion of both protein and steroid hormones (Villee, '69; Wattenberg, '58; Benirschke and Driscoll, '67; Pierce and Midgley, '63; Dreskin, Spicer and Greene, '70). Thus, it is not surprising that the syncytioplasm is packed with a diverse population of inclusions and organelles. Among the numerous ultrastructural studies of the human pIacenta are investigations that have associated certain of the syncytioplasm organelles with a particular function (Tighe, Garrod and Curran, '67; Dreskin et al., '70; Burgos and Rodriguez, '66; Sato, '66). However, none has made a careful attempt to describe and classify the inclusions and organelles of the syncytiotrophoblast, a ANAT. REC., 175: 15-36. logical prerequisite to understanding their functional significance. This investigation is the beginning of an effort of this type and considers in detail the multivesicular bodies and related structures of the syncytium of human term placenta, particularly emphasizing morphologicaI and certain cytochemical characteristics of the multivesicular bodies (mvb's). MATERIALS AND METHODSTissue was excised as quickly as possible from full term placenta obtained postpartum or by Cesarian section. Some of the specimens were fixed in 1....

The fine structure of the midgut epithelium in Xerobiotus pseudohufelandi (Iharos, 1966) (Tardigrada, Eutardigrada, Macrobiotidae)

“…Also, no Golgi complexes were detected in the cytoplasm of digestive cells, which cannot participate in MVB formation, contrary to what is known in other taxa (Martin and Spicer, 1973;Büning et al, 2008). The role of MVBs can be multiple; they may participate in enzyme accumulation (Martin and Spicer, 1973), degradation of membrane proteins (Piper and Katzmann, 2007), growth factor receptor down-regulation (Futter et al, 1996), developmental signalling (Lai et al, 2001), and finally in protein sorting, recycling, transport and release (von Bartheld and Altick, 2011). Because MVBs in X. pseudohufelandi probably are formed with the participation of coated vesicles that originate from endocytosis, we may suppose that these structures take part in the accumulation of substances (e.g.…”

“…These organelles may be formed by small vesicles that originate from Golgi complexes or from endocytosis (Martin and Spicer, 1973;Piper and Katzmann, 2007;Büning et al, 2008). In the midgut digestive cells of X. pseudohufelandi we observed the fusion of a coated vesicle with a multivesicular body, which might suggest that endocytosis participates in MVB formation.…”

“…In the midgut digestive cells of X. pseudohufelandi we observed the fusion of a coated vesicle with a multivesicular body, which might suggest that endocytosis participates in MVB formation. Also, no Golgi complexes were detected in the cytoplasm of digestive cells, which cannot participate in MVB formation, contrary to what is known in other taxa (Martin and Spicer, 1973;Büning et al, 2008). The role of MVBs can be multiple; they may participate in enzyme accumulation (Martin and Spicer, 1973), degradation of membrane proteins (Piper and Katzmann, 2007), growth factor receptor down-regulation (Futter et al, 1996), developmental signalling (Lai et al, 2001), and finally in protein sorting, recycling, transport and release (von Bartheld and Altick, 2011).…”

Ultrastructural Studies in Fetal I-cell Disease

“…The inclusions were filled only with fine vesicles. and they appeared to be multivesicular bodies, one type of lysosome (3,8). The present ( x 1,000).…”

Scanning and Transmission Electron Microscopy of the Ependyma of the Fourth Ventricle in the Monkey Brain

“…Fie further reported that the presence of microvilli on an epithelial surface denoted a high degree of resorptive and/or secretory activity. Areas where cilia are completely absent and only a number of microvilli are seen, have been reported to perform an absorptive role by Martin and Spicer [1973]. Supraependymal cells have been reported to be both secretory [Coates, 1973c] and phagocytic [Bleier, 1975;Mestres and Breipohl, 1976] in nature.…”