Angioarchitecture and morphology of temporomandibular joint of Monodelphis domestica.

The opossum Monodelphis domestica presents movement of the temporomandibular joint (TMJ) reflecting adaptation to eating habits similar to movement in humans, but the structure of the TMJ is not yet known. Thus, nine young M. domestica, of both sexes were weighed, anesthetized with xylazine (10 mg kg(-1) ), and ketamine (70 mg kg(-1) ) and processed for: 1. The analyses of the macroscopic angioarchitecture after latex injection, as well as the topography of the TMJ; 2. The analysis of microvascularization after injection of Mercox resin and corrosion of soft tissue with NaOH using scanning electron microscopy and; 3. The histological evaluation of the TMJ with an optical microscope. Macroscopic analysis of the latex injected vessels revealed the distribution of the arteries from the common carotid artery, receiving branches of the superficial temporal and maxillary arteries. The mandibular condyle has the long axis in the lateral-lateral direction, and is convex in the anterior-posterior direction. Its topography was determined in relation to the eye and external acoustic meatus. With scanning electron microscopy, microvascularization consists of arterioles of varying diameter (85-15 µm) of the meandering capillary network in the retrodiscal region, and a network of straight capillaries in the TMJ anterior region. Via light microscopy the TMJ has similar histological features to those of humans. These macroscopic, microscopic and ultrastructural data from TMJ of the M. domestica could be a suitable model for TMJ physiology and pathophysiology studies for then speculate on possible human studies. Microsc. Res. Tech. 79:806-813, 2016. © 2016 Wiley Periodicals, Inc.

The second known specimen of Monodelphis unistriata (Wagner) (Mammalia: Didelphimorphia), with redescription of the species and phylogenetic analysis.

Very little information exists relevant to the species grouping and phylogenetic relationships of the opossum genus Monodelphis Burnett. Of the clearly distinct named species, the least information is available for M. unistriata (Wagner), one of the world's most poorly known species of mammals. Extant specimens consist of the Brazilian holotype of a skin now without a skull and dating from almost 200 years ago, and a second specimen with skin and incomplete skull dating from over a hundred years ago and from Argentina. The most recent published notes on the holotype date from well over half a century ago and, all told, such notes, the earliest dating from 1842, add up to a highly fragmentary and contradictory picture. No observations whatsoever have ever been published for the second and more complete specimen. Also, no hypotheses have ever been made concerning the intrageneric affinities of M. unistriata and such affinities have also been obscure throughout the genus. Herein, we provide a detailed redescription of M. unistriata, the first published images of specimens, and the first account, beyond the previous few most vague and incomplete remarks, of the morphology of the skull. In an effort to ascertain the phylogenetic affinities of M. unistriata, we performed a combined molecular (cytochrome b) and nonmolecular (postcranial, cranial, integument, and karyotypic characters) parsimony analysis incorporating 27 species of didelphids, including 11 of Monodelphis. Our results strongly support the monophyly of Monodelphis, and place M. unistriata as sister group to M. iheringi, among the included species.

Cell birth and death in the developing retina of the Brazilian opossum, Monodelphis domestica.

The purpose of this study was to characterize cytogenesis and apoptosis in the developing retina of the Brazilian opossum, Monodelphis domestica. Monodelphis is a small pouchless marsupial whose young undergo a protracted period of postnatal development. Moreover, the Monodelphis retina represents a unique in vivo compartment for investigating cellular interactions that occur during early neural development and is an important system to study plasticity of neural stem cells following transplantation. Using bromodeoxyuridine (BrdU) labeling of newly generated cells, double-labeling immunohistochemistry and TUNEL labeling of apoptotic cells we have performed a detailed analysis of cell birth and death in the Monodelphis retina from fetal development through early postnatal life. Pregnant opossums or pups received a single injection of BrdU between gestational day 12 and postnatal day 35 (35PN), eyes were collected two hours after injection or on day 15, 30, or 60 of postnatal life. BrdU-labeled cells were visualized immunohistochemically. Cells were classified according to their morphology, location and immunoreactivity for cell-type specific antibodies. Cell genesis in the opossum retina begins at E13 and was near completion by 25PN. Apoptotic retinal cells were identified using the TUNEL technique for labeling of fragmented DNA. Apoptosis covered a relatively broad period of postnatal development, beginning around 10PN, peaking at 30PN, and concluding before 60PN. These results demonstrate that the retina of Monodelphis, a polyprotodont marsupial, is generated in a similar pattern to the wallaby, a diprotodont marsupial, and to eutherian species.

Distribution of the parvalbumin, calbindin-D28K and calretinin immunoreactivity in globus pallidus of the Brazilian short-tailed opossum (Monodelphis domestica).

This study describes the topography, borders and divisions of the globus pallidus in the Brazilian short-tailed opossum (Monodelphis domestica) and distribution of the three calcium binding proteins, parvalbumin (PV), calbindin D-28k (CB) and calretinin (CR) in that nucleus. The globus pallidus of the opossum consists of medial and lateral parts that are visible with Nissl or Timm's staining and also in PV and CR immunostained sections. Neurons of the globus pallidus expressing these proteins were classified into three types on the basis of size and shape of their soma and dendritic tree. Type 1 neurons had medium-sized fusiform soma with dendrites sprouting from the opposite poles. Neurons of the type 2 had medium-to-large, multipolar soma with scarce, thin dendrites. Cell bodies of type 3 neurons were small and either ovoid or round. Immunostaining showed that the most numerous were neurons expressing PV that belonged to all three types. Density of the PV-immunopositive fibers and puncta correlated with the density of the PV-labeled neurons. Labeling for CB resulted mainly in the light staining of neuropil in both parts of the nucleus, while the CB-expressing cells (mainly of the type 2) were scarce and placed only along the border of the globus pallidus and putamen. Staining for calretinin resulted in labeling almost exclusively the immunoreactive puncta and fibers that were distributed with medium-to-high density throughout the nucleus. Close to the border of globus pallidus with the putamen these fibers (probably dendrites) were long, thin and varicous, while more medially bundles of thick, short and smooth fibers predominated. Single CR-ir neurons (all of the type 3) were scattered through the globus pallidus. Colocalization of two calcium binding proteins in one neuron was. never observed. The CB-ir puncta (probably terminals of axons projecting to the nucleus) frequently formed basket-like structures around the PV-ir neurons. Therefore, the globus pallidus in the opossum, much as that in the rat, consists of a heterogeneous population of neurons, probably playing diversified functions.