title: Chorioallantoic placentation in Galea spixii (Rodentia, Caviomorpha, Caviidae).
abstract: BACKGROUND
  Placentas of guinea pig-related rodents are appropriate animal models for human placentation because of their striking similarities to those of humans. To optimize the pool of potential models in this context, it is essential to identify the occurrence of characters in close relatives.
  
  
  METHODS
  In this study we first analyzed chorioallantoic placentation in the prea, Galea spixii, as one of the guinea pig's closest relatives. Material was collected from a breeding group at the University of Mossoró, Brazil, including 18 individuals covering an ontogenetic sequence from initial pregnancy to term. Placentas were investigated by means of histology, electron microscopy, immunohistochemistry (vimentin, alpha-smooth muscle actin, cytokeration) and proliferation activity (PCNA).
  
  
  RESULTS
  Placentation in Galea is primarily characterized by an apparent regionalization into labyrinth, trophospongium and subplacenta. It also has associated growing processes with clusters of proliferating trophoblast cells at the placental margin, internally directed projections and a second centre of proliferation in the labyrinth. Finally, the subplacenta, which is temporarily supplied in parallel by the maternal and fetal blood systems, served as the center of origin for trophoblast invasion.
  
  
  CONCLUSIONS
  Placentation in Galea reveals major parallels to the guinea pig and other caviomorphs with respect to the regionalization of the placenta, the associated growing processes, as well as trophoblast invasion. A principal difference compared to the guinea pig occurred in the blood supply of the subplacenta. Characteristics of the invasion and expanding processes indicate that Galea may serve as an additional animal model that is much smaller than the guinea pig and where the subplacenta partly has access to both maternal and fetal blood systems.
authors.affiliation: Department of Surgery, Faculty of Veterinary Medicine, University of Sao Paulo, Cidade Universitária, São Paulo, Brazil. moacir@ufersa.edu.br
authors.forename: Moacir F
authors.initials: MF
authors.lastname: Oliveira
authors.forename: Andrea
authors.initials: A
authors.lastname: Mess
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Ambrósio
authors.forename: Carlos A G
authors.initials: CA
authors.lastname: Dantas
authors.forename: Phelipe O
authors.initials: PO
authors.lastname: Favaron
authors.forename: Maria A
authors.initials: MA
authors.lastname: Miglino
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D005260:Female; D007150:Immunohistochemistry; D007633:Keratins / Q000378:metabolism; D023421:Models, Animal; D010920:Placenta / Q000033:anatomy & histology* / Q000098:blood supply / Q000502:physiology* / Q000648:ultrastructure; D010929:Placentation; D011247:Pregnancy; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D012377:Rodentia / Q000502:physiology*; D014746:Vimentin / Q000378:metabolism
chemical_list: D000199:Actins; D018809:Proliferating Cell Nuclear Antigen; D014746:Vimentin; D007633:Keratins
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