Publications

marsupial light chains: complexity and conservation of lambda in the opossum monodelphis domestica.	the ig lambda chains in the south american opossum, monodelphis domestica, were analyzed at the expressed cdna and genomic organization level, the first described for a nonplacental mammal. the v lambda segment repertoire in the opossum was found to be comprised of at least three diverse v lambda families. each of these families appears to be related to distinct v lambda families present in placental mammals, suggesting the divergence of these genes before the separation of metatherians and euth ...	1998	9862702
energetics of offspring production: a comparison of a marsupial (monodelphis domestica) and a eutherian (mesocricetus auratus).	this study compares the energetic cost of reproduction during gestation and lactation of a eutherian, the golden hamster (mesocricetus auratus), and a similar-sized (60,120 g) marsupial, the gray short-tailed opossum (monodelphis domestica). food consumption was monitored in 20 reproductively active (ra) opossums and 16 ra hamsters from conception to weaning at equivalent intervals in 19 non-reproductive (nr) opossums and 21 nr hamsters, all maintained within their zone of thermoneutrality (30 d ...	1999	10093907
the p53 tumor suppressor gene of the marsupial monodelphis domestica: cloning of exons 4-11 and mutations in exons 5-8 in ultraviolet radiation-induced corneal sarcomas.	inactivating p53 mutations are found in many ultraviolet radiation (uvr)-induced skin tumors. we examined 12 uvr-induced corneal tumors of the marsupial monodelphis domestica for mutations in exons 5-8 of p53 and compared their mutational spectrum with that of uvr-induced skin tumors of other species. first we cloned and characterized a cdna extending from the middle of exon 4 through exon 11 of the monodelphis p53 gene. based on the sequence information obtained, primers were designed to amplif ...	1999	10357774
development of motoneurons and primary sensory afferents in the thoracic and lumbar spinal cord of the south american opossum monodelphis domestica.	the postnatal development of the primary sensory afferent projection to the thoracic (t4) and lumbar (l4) spinal cord of the marsupial species monodelphis domestica was studied by using anterograde and retrograde neuronal tracers. large numbers of primary afferents and motoneurons were labelled by application of the carbocyanine dye dii into individual dorsal root ganglia (drg) afferents in short-term organ cultures. dorsal root axons had entered the cord at birth, but most primary afferent inne ...	1999	10531537
localization of the 5-ht1a receptors in the brain of opossum monodelphis domestica.	this paper describes the distribution of 5-ht1a receptors in the brain of opossum monodelphis domestica. they were visualized by immunohistological staining with an antibody against the amino acid sequence (170-186) of this receptor that was previously successfully used in the rat and monkey. as in eutherians, high levels of immunostaining were present in the septum, hippocampus, raphe nuclei and some other brain stem nuclei. neocortex, several thalamic nuclei and hypothalamus showed moderate de ...	1999	10574559
isolation and comparison of the igm heavy chain constant regions from australian (trichosurus vulpecula) and american (monodelphis domestica) marsupials.	cdnas encoding igm heavy chain constant region (cmu) were isolated from two metatherians (marsupials)--the australian common brushtail possum (trichosurus vulpecula) and the south american grey short-tailed opossum (monodelphis domestica). analysis of the sequences suggested that they correspond to the secreted form of cmu in both species. the domain size and structure of the marsupial cmu sequences were compared with other cmu sequences and a high degree of conservation throughout vertebrate ev ...	1999	10579393
injection of a boar sperm factor causes calcium oscillations in oocytes of the marsupial opossum, monodelphis domestica.	at fertilisation, the sperm triggers an abrupt and transient increase in intracellular calcium ([ca2+]i) in the oocyte cytoplasm. in eutherian mammals, oocytes exhibit multiple [ca2+]i transients which are necessary for egg activation. we investigated [ca2+]i in the marsupial opossum, monodelphis domestica. embryo development in this therian mammal is quite distinct from that in most eutheria. oestrus was induced in an adult female opossum by introduction of a male into her cage. injection of a ...	1999	10717944
distribution of unipolar brush cells and other calretinin immunoreactive components in the mammalian cerebellar cortex.	we have compared the distribution of unipolar brush cells (ubcs) in the cerebellum of brazilian opossum (monodelphis domestica), mouse, guinea pig, rabbit, cat, and rhesus monkey, using an antiserum to calretinin which is present in those cells. the morphology and calretinin staining intensity of the ubcs remains constant across species. as a general trend, in all species studied, ubcs are particularly enriched in the vestibulocerebellum. interspecies differences, however, were noted in the dist ...	1999	10590511
why does the central nervous system not regenerate after injury?	spinal cord injuries in humans and in other mammals are never followed by regrowth. in recent years, considerable progress has been made in analyzing mechanisms that promote and inhibit regeneration. the focus of this review is changes that occur in the transition period in development when the central nervous system (cns) changes from being able to regenerate to the adult state of failure. in our experiments we have used the neonatal opossum (monodelphis domestica), which corresponds to a 14-da ...	1999	10416756
organization of somatosensory cortex in three species of marsupials, dasyurus hallucatus, dactylopsila trivirgata, and monodelphis domestica: neural correlates of morphological specializations.	the organization of somatosensory neocortex was investigated in three species of marsupials, the northern quoll (dasyurus hallucatus), the striped possum (dactylopsila trivirgata), and the short-tailed opossum (monodelphis domestica). in these species, multiunit microelectrode mapping techniques were used to determine the detailed organization of the primary somatosensory area (si). in the striped possum and quoll, the topography of somatosensory regions rostral (r), and caudal (c) to si were de ...	1999	10075440
marsupial light chains: igk with four v families in the opossum monodelphis domestica.	a full-length and several partial cdnas encoding igk light chains from the marsupial south american opossum, monodelphis domestica, were isolated and characterized. using these clones as a starting point, the expressed igkv repertoire was sampled by anchored polymerase chain reaction using an igkc-specific primer. based on nucleotide sequences of twenty unique, expressed igkv-j combinations, there are at least four igkv families and two j segments. southern blot analysis revealed each igk-v fami ...	1999	10630297
differential projections from the anterior and posterior divisions of the accessory olfactory bulb to the medial amygdala in the opossum, monodelphis domestica.	the vomeronasal sensory epithelium of mammals contains apical and basal cell populations expressing different g proteins and putative pheromone receptors, which project, respectively, to the anterior and posterior divisions of the accessory olfactory bulb (aob). in order to analyse whether these segregated pathways are preserved in the connections between the aob and the amygdala, conjugated dextran-amines were iontophoretically injected into the anterior and posterior divisions of the aob. we f ...	1999	10583468
horizontal cell differentiation in the retina of the brazilian opossum, monodelphis domestica.	differentiation of many diverse neuronal phenotypes is an essential part of nervous system development. we have studied the differentiation of horizontal cells, one of the basic neuronal types in the vertebrate retina, in a small, easily maintained marsupial by immunocytochemistry using antineurofilament and antivimentin antibodies. at birth the retina consists of proliferating neural epithelial cells, with a few early ganglion cells. horizontal cells were first detected in 12-day-old pups; soma ...	1999	10452366
distribution of sensory receptors in joints of the upper cervical column in the laboratory marsupial monodelphis domestica.	in order to investigate the sensory innervation, the upper cervical spine of a small laboratory marsupial (monodelphis domestica) was examined with serial section light microscopy and re-embedding of selected sections for electron microscopy. large numbers of free nerve endings supplied by a delta- and c-fibres were found in the longitudinal ligaments and facet joint capsules. electron microscopically, areas of direct contact between axon and collagen fibres of the surrounding connective tissue ...	1999	10332524
developmental analysis of the peripheral olfactory organ of the opossum monodelphis domestica.	the gray, short-tailed opossum, monodelphis domestica, is born in a very immature state after a brief (14-day) gestation. as a result, the species provides a unique opportunity to examine very early periods of mammalian development. the present study provides the first detailed morphometric analysis of the development of the olfactory mucosa and the nasal cavity in monodelphis. the extent of the sensory mucosa increases dramatically across development, covering a growing nasal cavity and increas ...	1999	10209241
identification and sequence analysis of an mhc class ii b gene in a marsupial (monodelphis domestica).		1999	10199923
molecular cloning of the brushtail possum (trichosurus vulpecula) immunglobulin e heavy chain constant region.	the immunobiology of marsupial ige is poorly understood. as a first step towards the development of immunological reagents for marsupials and to obtain a further understanding of immunoglobulin evolution, a brushtail possum (trichosurus vulpecula) mesenteric lymph node cdna library was screened for the heavy chain constant region of ige (cepsilon), using a partial cepsilon probe from the american marsupial, monodelphis domestica. the cdna sequence for t. vulpecula cepsilon was determined and fou ...	1999	10684965
development of the facial and hypoglossal motor nuclei in the neonatal brazilian opossum brain.	the development of the facial and hypoglossal motor nuclei were examined in the neonatal brazilian opossum (monodelphis domestica), a marsupial in which postnatal central nervous system development has been well characterized. in this study, we utilized postnatal injection of the retrograde tracer cholera toxin subunit b (ctb) to characterize the formation of the facial and hypoglossal motor nuclei in the developing neonatal opossum brainstem. injections of ctb were made into the cheek/lip regio ...	1999	9878718
marsupial mhc class i: classical sequences from the opossum, monodelphis domestica.		1999	10541813
synaptogenesis in the brachial and lumbosacral enlargements of the spinal cord in the postnatal opossum, monodelphis domestica.	synaptic proteins were localized in light microscopy on sections of the brachial and lumbosacral enlargements of the spinal cord of postnatal opossums, monodelphis domestica, to determine whether their expression correlates with the development of major motor pathways and simple motor behaviors. the tissues were fixed, cryoprotected, frozen, cut in 15-micrometer sections, and processed immunohistochemically using antibodies against synaptophysin, synaptotagmin-i, or snap-25. immunolabeling was o ...	1999	10531545
three new species of eimeria from bolivian marsupials.	faecal samples collected from 300 bolivian marsupials (didelphimorphia: didelphidae) between 1984 and 1993 were examined for coccidian parasites. sporulated oocysts were present in the faeces of 50 (17%) marsupials representing 11 genera and 22 species. three new species of eimeria are described and named from six host species. one species occurred in marmosops dorothea, monodelphis domestica and thylamys venustus, another in micoureus constantiae constantiae and micoureus constantiae budini and ...	1999	10221628
the monodelphis melanoma model: initial report on large ultraviolet a exposures of suckling young.	the objective of this study was to determine whether exposure of early suckling young of the opossum monodelphis domestica to ultraviolet a (uva) radiation (320-400 nm) can lead to the development of melanocytic lesions similar to those induced after exposure to ultraviolet b (uvb) radiation (280-320 nm) to total doses as low as 380 j/m2. a total of 576 sucklings received nine exposures of 0.6, 2.6 or 15.5 kj/m2 per dose (total doses approximately 6, 23 and 140 kj/m2, respectively) from a blak r ...	2000	10857371
ionic permeability of the opossum sciatic nerve perineurium, examined using electrophysiological and electron microscopic techniques.	a parallel electrophysiological and electron microscopic study was used to assess the ionic permeability of the sciatic nerve perineurium of the opossum monodelphis domestica. the electrophysiological method was used to monitor permeability to k(+), followed by combined electron microscopy and x-ray probe analysis to monitor permeability to the electron-dense tracer lanthanum. isolated but intact nerves were mounted in a 'grease gap' chamber for extracellular measurement of dc potential and comp ...	2000	10837817
cross-matching marsupial proteins with eutherian mammal databases: proteome analysis of cells from uv-induced skin tumours of an opossum (monodelphis domestica).	the identification and characterisation of monodelphis proteins has required cross-species analysis. protein expression was investigated in normal, nonirradiated adult fibroblasts and also in fibroblastic cells from a benign cutaneous tumour after chronic ultraviolet (uvb) exposure and a metastatic cutaneous tumour after intermittent exposure. proteins were separated and visualised by two-dimensional gel electrophoresis (2-d page) and a peptide mass fingerprint (pmf) was obtained for protein spo ...	2000	11271499
the development of mammalian motor systems: the opossum monodelphis domestica as a model.	the opossum monodelphis domestica is a marsupial born considerably immature 14-15 days after conception. it is possible to study postnatally, in this species, almost the entire development of its motor behaviors as well as of the nerve centers involved in their control. the lumbosacral spinal cord of the newborn comprises a thick ventricular zone containing mitotic figures, an intermediate zone of small and undifferentiated cells, and a thin marginal zone. the hindlimbs are little more than embr ...	2000	11165797
control of respiration in the isolated central nervous system of the neonatal opossum, monodelphis domestica.	respiration represents an unusual motor activity with respect to its development. as newly born mammals enter the world, their limb movements are not coordinated; time and experience are required for effective performance to be achieved. yet the rhythm of respiration is of necessity functionally perfected and unfailing at birth. inspiratory and expiratory motor neurons are already able to fire at appropriate rates, under the command of rhythmically active neurons in the medulla. in this review, ...	2000	11165796
the hormonal control of birth behavior in the gray short-tailed opossum (monodelphis domestica).	in all major groups of australian marsupials, prostaglandin f2alpha (pgf) or oxytocin injection initiates birth behavior in adult females, adult males and pouch young. because inhibitors of pgf synthesis block this initiation, oxytocin may activate birth behavior via the stimulation of pgf synthesis. in this study, the role of pgf and oxytocin in the activation of birth behavior was examined in an american marsupial, the gray short-tailed opossum (monodelphis domestica). adult male and female gr ...	2000	10753586
organization and connections of v1 in monodelphis domestica.	we examined the internal organization and connections of the primary visual area, v1, in the south american marsupial monodelphis domestica. multiunit electrophysiological recording techniques were used to record from neurons at multiple sites. receptive field location, size, progressions, and reversals were systematically examined to determine the visuotopic organization of v1 and its boundaries with adjacent visual areas. as in other mammals, a virtually complete representation of the visual h ...	2000	11064371
photoreactivation does not alter ras and p53 mutation spectra in ultraviolet radiation-induced corneal sarcomas of monodelphis domestica.	when chronically exposed to ultraviolet radiation (uv), opossums of the species monodelphis domestica develop corneal sarcomas at high frequency. post-uv exposure to photoreactivating light enhances repair of uv-induced pyrimidine dimers and suppresses, but does not abrogate, corneal tumor development. we compared mutation spectra in ras and p53 genes in 32 eye tumors from monodelphis exposed to uv alone and in 25 tumors from monodelphis exposed to uv followed by photoreactivation in order to id ...	2000	10657904
cell turnover in the vomeronasal epithelium: evidence for differential migration and maturation of subclasses of vomeronasal neurons in the adult opossum.	previous investigations of cell turnover in the mammalian vomeronasal sensory epithelium (vn-se) raised two issues. first, if, in addition to the already demonstrated vertical migration, horizontal migration from the edges of the vn-se participates in neuronal replacement. second, whether or not migration and maturation is differential in upper and lower populations of vomeronasal neurons, since these two cell populations are chemically, physiologically, functionally, and perhaps evolutionarily ...	2000	10756066
perinatal exposure to estradiol masculinizes aspects of sexually dimorphic behavior and morphology in gray short-tailed opossums (monodelphis domestica).	the effects on adult sexually dimorphic behavior of perinatal exposure to estrogen were examined by treating male and female gray opossums with estradiol (est), an estrogen receptor antagonist (tamoxifen:tx) or oil control (oil) during the first week of life, a time period corresponding in this marsupial to late gestation in rodent species. following gonadectomy and replacement therapy with testosterone in adulthood, males showed more scent-marking behavior than females and est animals showed mo ...	2000	10712860
metastatic melanoma in an adult opossum (monodelphis domestica) after short-term intermittent uvb exposure.		2000	11000291
spinal repair in immature animals: a novel approach using the south american opossum monodelphis domestica.	1. the adult mammalian central nervous system (cns) is unable to regenerate following injury and repair has only been seen when implants of peripheral nervous tissue, fetal tissue or schwann cells are used, or antibodies or trophic molecules applied. however, the immature mammalian cns has revealed a capacity to repair without extrinsic influence. 2. the marsupial mammal provides a unique opportunity to access the immature cns without invasive in utero surgery. in particular, the south american ...	2000	10874515
the organization of somatosensory cortex in the short-tailed opossum (monodelphis domestica).	the organization of neocortex in the short-tailed opossum (monodelphis domestica) was explored with multiunit microelectrode recordings from middle layers of cortex. microelectrode maps were subsequently related to the chemoarchitecture of flattened cortical preparations, sectioned parallel to the cortical surface and processed for either cytochrome oxidase (co) or nadph-diaphorase (nadphd) histochemistry. the recordings revealed the presence of at least two systematic representations of the con ...	2000	10833083
evidence for spontaneous postlactational estrus in gray short-tailed opossums (monodelphis domestica).	previous studies of the gray short-tailed opossum have shown that ovarian activity and estrus are induced by male pheromones, but we recently documented urogenital sinus (ugs) estrus in postlactational females despite their isolation from the male stimuli known to be associated with induced estrus. body weights and ugs smears were collected after removal of pups in midlactation (19-37 days postpartum), after weaning (55-61 days postpartum), or after pheromone exposure. estradiol was measured by ...	2000	10819788
somatosensory and motor representations in cerebral cortex of a primitive mammal (monodelphis domestica): a window into the early evolution of sensorimotor cortex.	to examine the potential early stages in the evolution of sensorimotor cortex, electrophysiological studies were conducted in the primitive south american marsupial opossum, monodelphis domestica. somatosensory maps derived from multiunit microelectrode recordings revealed a complete somatosensory representation of the contralateral body surface within a large region of midrostral cortex (primary somatosensory cortex, or s1). a large proportion ( approximately 51%) of s1 was devoted to represent ...	2000	10813771
photobiology of monodelphis domestica.	the gray, short-tailed opossum, monodelphis domestica, has been used for photobiologic studies since 1984. the presence of a light-activated dna repair pathway in the tissues of monodelphis has been used to identify pyrimidine dimers in dna as initiating events for a number of ultraviolet radiation (uvr)-induced pathologies of the skin and cornea. furthermore, monodelphis, unlike common laboratory rodents, is susceptible to the induction of melanoma by uvr alone.	2000	10785275
partner preference of intact and ovariectomized female gray short-tailed opossums (monodelphis domestica).	intact, ovariectomized and ovariectomized estradiol (e)-treated female gray short-tailed opossums were placed in a test situation in which they could choose between an intact and a castrated male. intact females chose to visit intact males first and visited them more frequently and spent more time with intact than with castrated males. ovariectomized (ovx) females did not show this preference for visiting intact males over castrates. when compared to ovx females with blank implants, ovx females ...	2000	11038293
therapeutics of companion exotic marsupials.	exotic marsupials are becoming popular companion pets, yet little pharmacologic information is available to the practitioner. species include sugar gliders (petarus breviceps), south american (brazilian) short-tailed opossums (monodelphis domestica), brushtail possum or "phalanger" (trichosurus vulpecula), and wallabies: bennett's (macropus rufogriseus rufogriseus) and tammar or dama (macropus eugenii). guidelines for logical choices of medications based on allometric scaling, gastrointestinal t ...	2000	11228826
allelic expression of igf2 in marsupials and birds.	genomic imprinting, the parent-of-origin- specific expression of genes, has been observed in a variety of eutherian mammals. one gene that has been shown to be imprinted in all eutherians examined is the igf2 gene. this gene encodes a potent fetal-specific growth factor that is expressed almost exclusively from the paternal chromosome. several other imprinted genes in the igf2 pathway are imprinted as well, suggesting that igf2 is a focal point for the selective pressure leading to imprinted gen ...	2000	10603082
attempted eradication of salmonellosis from a colony of short-tail grey opossums (monodelphis domestica).	prior to re-housing a colony of laboratory short-tail grey opossums, the animals were found to harbour salmonella. this paper describes an unsuccessful attempt to eradicate the infection from the colony by means of antibiotic treatment and hygienic measures. a pilot treatment of five animals which received enrofloxacin 10 mg/kg for 5 days appeared to be successful in that no salmonellae were recovered from faeces or organs sampled after treatment. the process was repeated on the whole colony pri ...	2000	10817463
spontaneous behavior of the gray short-tailed opossum (monodelphis domestica) in the elevated plus-maze: comparison with long-evans rats.	we observed the spontaneous behavior of a laboratory marsupial--the gray short-tailed opossum (monodelphis domestica)--in the elevated plus-maze (epm) during six consecutive sessions and compared it with the behavior of long-evans rats. during the first exposure to the maze both species spent most of the time in the enclosed arms but opossums showed much higher frequency of entries into the open arms and stayed there longer. on the third and subsequent days opossums reduced their entries into th ...	2000	11200175
evidence for extended action of gonadal hormones on the organization of sexually dimorphic behavior and morphology in gray short-tailed opossums (monodelphis domestica).	male and female gray short-tailed opossums were gonadectomized (gdx), or treated with the estrogen receptor antagonist tamoxifen citrate (tx), or corn oil (oil) (control) during the 5th postnatal week, a time period equivalent to the 3rd postnatal week in rats and associated with high levels of circulating gonadal hormones and neural aromatase activity in this marsupial species. in adulthood following gonadectomy (for animals not previously gonadectomized) and replacement therapy with estradiol ...	2001	11243739
characterisation of the kappa light chain of the brushtail possum (trichosurus vulpecula).	two full length cdna sequences encoding the kappa light chain of the australian marsupial, trichosurus vulpecula, the brushtail possum, were isolated from a mesenteric lymph node cdna library. the constant regions (ckappa) of the two light chains were identical, but the variable (vkappa) and joining (jkappa) regions were different. at the amino acid level, possum ckappa was most similar to ckappa of an american marsupial, monodelphis domestica (75%), with similarity to eutherian ckappa ranging f ...	2001	11292532
topography of muscle spindles and golgi tendon organs in shoulder muscles of "monodelphis domestica".	the topography of muscle spindles and golgi tendon organs in the rotator cuff and surrounding shoulder muscles of a small laboratory marsupial (monodelphis domestica) were studied using light microscopy of serial sections. the shoulder joint of monodelphis has a large degree of freedom of movement allowing this animal to use the upper extremities for a wide range of activities like climbing and manipulating food. thus, similar to the situation in man the shoulder joint is mainly secured by muscl ...	2001	11396793
karyotype relationships between distantly related marsupials from south america and australia.	reciprocal chromosome painting and g-banding were used to compare the karyotypes of three australian marsupials (sminthopsis crassicaudata, macropus eugenii, trichosurus vulpecula) and one south american marsupial (monodelphis domestica). the results revealed only a limited number of rearrangements between these species and that the four karyotypes can be described as different combinations of fifteen conserved segments. five chromosomes are totally conserved between m. domestica (pairs 1, 2, 5, ...	2001	11419794
early development of the neural plate, neural crest and facial region of marsupials.	marsupial mammals have a distinctive reproductive strategy. the young are born after an exceptionally short period of organogenesis and are consequently extremely altricial. yet because they must be functionally independent in an essentially embryonic condition, the marsupial neonate exhibits a unique suite of adaptations. in particular, certain bones of the facial region, most cranial musculature and a few additional structures are accelerated in their development. in contrast, central nervous ...	2001	11523813
permeability and route of entry for lipid-insoluble molecules across brain barriers in developing monodelphis domestica.	1. we have studied the permeability of blood-brain barriers to small molecules such as [(14)c]sucrose, [(3)h]inulin, [(14)c]l-glucose and [(3)h]glycerol from early stages of development (postnatal day 6, p6) in south american opossums (monodelphis domestica), using a litter-based method for estimating steady-state cerebrospinal fluid (csf)/plasma and brain/plasma ratios of markers that were injected i.p. 2. steady-state ratios for l-glucose, sucrose and inulin all showed progressive decreases du ...	2001	11691876
differential localization of snare complex proteins snap-25, syntaxin, and vamp during development of the mammalian retina.	snare complex proteins have critical functions during regulated vesicular release of neurotransmitter. in addition, they play critical roles during neurite outgrowth and synaptogenesis. although it is clear that the function of any one snare complex protein during release of neurotransmitter is dependent on its association with other members of the complex, it is less certain whether their function during development and differentiation is dependent on interaction with one another. previously, w ...	2001	11169469
topography of corpuscular mechanoreceptors in the shoulder joint region of monodelphis domestica.	the topography and structure of corpuscular mechanoreceptors in the shoulder joint capsule and periarticular connective tissue of a small laboratory marsupial (monodelphis domestica) were studied using light and electron microscopy. this animal is known to use its upper extremities for a wide range of activities like climbing and manipulating food. thus, the shoulder joint of this animal species has a similar wide range of movement as the human shoulder joint, but is small enough for serial sect ...	2001	11331969
cloning of the mhc class ii drb cdna from the brushtail possum (trichosurus vulpecula).	the cell-surface glycoproteins encoded by the major histocompatibility complex (mhc) bind to processed foreign antigens and present them to t lymphocytes. two classes of mhc molecules and their corresponding gene sequences have been extensively studied in eutherian mammals and birds, but data on the marsupial mhc are limited. marsupials split from eutherian mammals about 125 million years ago and represent a distinct branch in mammalian evolution. here the cdna cloning of mhc class ii genes of t ...	2001	11222910
urokinase activity in corneal fibroblasts may be modulated by dna damage and secreted proteins.	proteases like urokinase-type plasminogen activator (upa) play an important role in tumor invasion. cells derived from ultraviolet radiation (uvr)-induced corneal sarcomas of monodelphis domestica produce relatively high levels of upa compared to the untransformed keratocytes suggesting a mechanism for their invasiveness. because uvr is known to stimulate upa production in many cell types, uvr exposure may further increase upa expression in corneal tumor cells, thus enhancing their ability to in ...	2001	11281030
dose response for ultraviolet radiation a-induced focal melanocytic hyperplasia and nonmelanoma skin tumors in monodelphis domestica.	four groups of 30 dorsally shaved opossums (monodelphis domestica) were exposed to graded doses of ultraviolet radiation a (uva) (320-400 nm) three times per week for 90 weeks. animals were monitored for the appearance of focal melanocytic hyperplasia (fmh) and nonmelanoma skin tumors (nmst) during the course of the exposures and for an additional 20 weeks following termination of exposures. fmh is the putative precursor for melanoma in the opossum. the lowest dose of uva (2.5 x 10(3) j/m2) used ...	2001	11202361
reorganization of the corticotectal projections introduced by neonatal monocular enucleation in the monodelphis opossum and the influence of serotoninergic depletion.	the influence of neonatal serotoninergic lesion (performed with s.c. injection of 5,7-dihydroxytryptamine) on the plasticity of the developing corticotectal projection was studied in the gray short-tailed opossum (monodelphis domestica). as a first step, the placement and density of neurons projecting from the visual cortical areas to the superior colliculus was established in the adult opossum. injections of retrogradely transported fluorescent dyes into the superior colliculus of intact three- ...	2001	11182253
photoreactivation of ultraviolet radiation-induced basic fibroblast growth factor (bfgf) and the role of bfgf in corneal lesion formation in monodelphis domestica.	chronic ultraviolet radiation (uvr) exposure to the eyes of monodelphis domestica causes corneal opacification, neovascularization, and fibrosarcoma induction. by immunohistochemistry and western blotting, we have shown that one to four exposures of the eyes of this opossum to uvr enhances basic fibroblast growth factor (bfgf) expression by the corneal epithelium. treatment with photoreactivating light, which selectively removes uvr-induced pyrimidine dimers, suppresses bfgf induction, indicatin ...	2001	11746752
ultraviolet b-induced melanoma in monodelphis domestica occurs in the absence of alterations in the structure or expression of the p53 gene.	monodelphis domestica, a south american opossum, has been established as a mammalian model for sporadic ultraviolet radiation (uvr)-induced melanoma. using this model system, we investigated the role of changes in the p53 gene in the development of cutaneous melanocyte-derived lesions. cutaneous melanocytic hyperplasias, benign melanomas and metastatic primary melanomas, plus affected lymph nodes and visceral organs, were screened for mutations in the monodelphis p53 gene by single-strand confor ...	2001	11468512
the development of articular cartilage: evidence for an appositional growth mechanism.	it is well-established that cartilage grows by a combination of matrix secretion, cell hypertrophy and cell proliferation. the extent to which this growth is by appositional, as opposed to interstitial mechanisms, however, remains unclear. using the knee joints of the marsupial monodelphis domestica to study cartilage growth, we have combined an immunohistochemical study of the tgf-beta family of cartilage growth and differentiation factors between 30 days postpartum to 8 months, together with a ...	2001	11453164
the development of vesicular acetylcholine transporter immunoreactivity in the hindlimbs of the opossum monodelphis domestica.	vesicular acetylcholine transporter (vacht) was revealed immunohistochemically in light microscopy on hindlimb sections of developing opossums, monodelphis domestica. in the immobile hindlimbs of the newborn, which comprise cartilaginous bones and loose, unstriated myofibers, scant immunolabeled nerve segments and small spherical terminals, presumably growth cones or immature neuromuscular junctions, are found in the muscle tissue of the thigh, leg and proximal foot, decreasing in number and siz ...	2001	11412906
characterization of the cdkn2a and arf genes in uv-induced melanocytic hyperplasias and melanomas of an opossum (monodelphis domestica).	we examined the involvement of the cyclin-dependent kinase inhibitor 2a (cdkn2a) locus in the pathogenesis of ultraviolet (uv) radiation-induced melanomas in an opossum (monodelphis domestica) melanoma model in which suckling young were exposed to uvb to produce melanocytic lesions. monodelphis cdkn2a and alternated reading frame (arf) cdnas were cloned and sequenced, and the expression patterns of these genes were determined by reverse transcription-polymerase chain reaction in normal tissues, ...	2001	11398194
absence of ras gene mutations in uv-induced malignant melanomas correlates with a dermal origin of melanocytes in monodelphis domestica.	the south american opossum, monodelphis domestica, has been used as a model system to study ultraviolet (uv)-induced genetic alterations that lead to the development of melanoma. suckling young of monodelphis exposed to multiple doses of uvb radiation can develop benign or malignant melanomas later as adults. point mutations predominantly at codon 61 of the n-ras gene have been found in melanomas from sun-exposed body sites in humans. to determine if similar mutations are associated with uv-indu ...	2002	12104050
ultrastructural changes in the cervical epithelium during the estrous cycle of the marsupial monodelphis domestica (grey short-tailed opossum).	ultrastructural changes in the cervical epithelium related to the estrous cycle have been studied in the south american marsupial monodelphis domestica. the two cervices protrude with prominent papillae into the sinus vaginalis. at times of simple columnar at others of more pseudostratified character consists of two types of cells, ciliated and secretory cells. the mucosal epithelium is uniform in its entire length and shows no division into an endo- and ectocervix. the mucosa of the cervix diff ...	2002	12097839
axotomy of single fluorescent nerve fibers in developing mammalian spinal cord by photoconversion of diaminobenzidine.	a technique has been developed for cutting single nerve fibers in mammalian spinal cord. in the presence of diaminobenzidine (dab), a laser microbeam was applied to carbocyanine (dil) stained sensory fibers in cultured spinal cords of the newly born opossum monodelphis domestica. digital images of fluorescent fibers were acquired with an intensified video ccd-camera coupled to an image processor. laser illumination of two spots on a fiber in the presence of 3 mg/ml dab cut it, so that following ...	2002	12084566
ultrastructural changes in the uterine luminal and glandular epithelium during the oestrous cycle of the marsupial monodelphis domestica (grey short-tailed opossum).	ultrastructural changes in the endometrium associated with the oestrous cycle were studied in the south american marsupial monodelphis domestica. the most conspicuous changes include the height and the differentiation of the uterine luminal and glandular epithelium, which consists of ciliated and non-ciliated cells. the glandular epithelium attains its maximum development during oestrus, the luminal epithelium at postoestrus. a distinct increase in the number of ciliated cells can be observed du ...	2002	11731700
11 postnatal development of the fore and hindlimbs in the grey short-tailed opossum, monodelphis domestica.		2002	17103755
changes in the epithelium of the vaginal complex during the estrous cycle of the marsupial monodelphis domestica. 1. transmission electron microscopy study.	the vaginal complex of marsupials differs from that of eutherians. cervices open separately in a sinus vaginalis or cul-de-sac. two lateral vaginae adjoin the sinus vaginalis and fuse at the level of the urethra opening and form the sinus urogenitalis. during the estrous cycle the vaginal epithelium undergoes a number of specified morphological changes. this paper is the first to describe these changes on an ultrastructural level in a marsupial. investigations in monodelphis vagina reveal that a ...	2002	12566630
the cerebellum at birth in therian mammals, with special reference to rodents.	the stage of cerebellar development at birth was assessed in 23 species of placental mammals. serial histological sections were examined and five stages in the differentiation of the cerebellar cortical layers were defined. a wide diversity of conditions at birth was found. the available evidence (after parsimony reconstruction) suggests that the last common ancestor of placentals was born with an altricial cerebellum in which the molecular layer was just present between the external granular la ...	2002	12119530
mapping the distribution of the interstitial telomeric (ttaggg)n sequences in eight species of brazilian marsupials (didelphidae) by fish and the correlation with constitutive heterochromatin. do its represent evidence for fusion events in american marsupials?	the c-band pattern and the distribution of the (ttaggg)(n) sequence after fluorescence in situ hybridization (fish), were studied in eight species of didelphidae marsupials: four species with 2n = 14 (marmosops parvidens, marmosops incanus, marmosa murina and metachirus nudicaudatus), two species with 2n = 18 (monodelphis domestica and m. americana), and two with 2n = 22 (didelphis marsupialis and lutreolina crassicaudata). the hybridization signals were observed at both termini telomeres of all ...	2002	12826754
animal models of ultraviolet radiation (uvr)-induced cutaneous melanoma.	the incidence of cutaneous melanoma continues to increase in many parts of the world including the united states. the american cancer society predicts that there will be approximately 53,600 new cases of melanoma in the united states during 2002 and that there will be 7,400 deaths from melanoma during the same time period. increased understanding of the underlying mechanisms and risk factors involved in the induction of this deadly disease will require the use of suitable animal models of melano ...	2002	12045011
ultrastructure of the placenta of the tammar wallaby, macropus eugenii: comparison with the grey short-tailed opossum, monodelphis domestica.	the ultrastructure of the tammar placenta was studied throughout pregnancy. the uterine epithelium grows from a columnar to an enlarged, undulating epithelium between early gestation and mid-gestation when the shell coat that surrounds the marsupial conceptus ruptures. trophectoderm and uterine epithelium do not form syncytia, nor does invasion of the endometrium occur at any stage of pregnancy. uterine secretion is provided to both the bilaminar and the trilaminar side of the yolk sac placenta ...	2002	12220120
ontogenetic and phylogenetic transformations of the ear ossicles in marsupial mammals.	this study is based on the examination of histological sections of specimens of different ages and of adult ossicles from macerated skulls representing a wide range of taxa and aims at addressing several issues concerning the evolution of the ear ossicles in marsupials. three-dimensional reconstructions of the ear ossicles based on histological series were done for one or more stages of monodelphis domestica, caluromys philander, sminthopsis virginiae, trichosurus vulpecula, and macropus rufogri ...	2002	11835361
retinofugal projections in the short-tailed opossum (monodelphis domestica).	in the current investigation, retinofugal projections to midbrain and thalamic nuclei of monodelphis domestica were investigated using wheat-germ agglutinin conjugated to horseradish peroxidase (wga-hrp). large intraocular injections of wga-hrp were placed into the eye, and patterns of labeled axon terminals were related to nuclear boundaries in tissue that was stained for nissl or reacted for cytochrome oxidase (co). our results demonstrate that the major projection from the retina is to the co ...	2002	11977115
carpal ontogeny in monodelphis domestica and caluromys philander (marsupialia).	carpal bones have experienced numerous changes during marsupial evolution, even though their diversity and development remain poorly studied. the aim of this work was to document adult form and the pattern of mesenchymal tissue condensation and formation of chondrification and ossification centers in the hand of two marsupials. two fundamental questions were asked: whether the loss of embryonic precursors was associated with the loss of adult elements, or whether there were developmental signs o ...	2003	16351892
ontogenesis of the scapula in marsupial mammals, with special emphasis on perinatal stages of didelphids and remarks on the origin of the therian scapula.	the development of the scapula was studied in embryonic and postnatal specimens of monodelphis domestica and perinatal specimens of philander opossum, caluromys philander, and sminthopsis virginiae using histological sections and 3d reconstructions. additionally, macerated skeletons of postnatal m. domestica were examined. this study focused on the detachment of the scapulocoracoid from the sternum and on the acquisition of a supraspinous fossa, a supraspinatus muscle, and a scapular spine, all ...	2003	14518007
incorporation of murine brain progenitor cells into the developing mammalian retina.	to investigate the influence of a developing host environment on the survival, differentiation, and morphologic integration of murine brain progenitor cells (mbpcs) transplanted into the mammalian retina.	2003	12506105
behavior of the gray short-tailed opossum (monodelphis domestica) in the open field and in response to a new object, in comparison with the rat.	we compared the behavior of the gray short-tailed opossums (monodelphis domestica) and long-evans rats during repeated exposures to the open-field (of) test. animals were videotaped for 10 min on four consecutive days. a new object was placed in the center of the field on the third day and it was present there again on the fourth day. the rate of locomotor activity in the opossum was always higher than that in the rat. on the first exposure to the open field, both species showed strong thigmotax ...	2003	12842293
the role of androgens in development of the scrotum of the grey short-tailed brazilian opossum ( monodelphis domestica).	in eutherian mammals, sex differentiation is initiated by expression of the testis-determining gene on the y chromosome. subsequent phenotypic development of the reproductive tract and genitalia depends on the production of hormones by the differentiated testis. in marsupials the mechanisms of phenotypic development may vary from this pattern, as differentiation of the scrotal primordia has been shown to occur before that of the gonad. thus, the development of the scrotum in the marsupial has be ...	2003	12698362
conservation of dnmt1o cytosine methyltransferase in the marsupial monodelphis domestica.	imprinted genes have been identified in both eutherian mammals and in marsupials. in eutherian species, there is a conservation of the imprinting process, both in terms of the genes imprinted and the epigenetic inheritance mechanism. in the mouse, the inheritance of gametic methylation patterns depends on an oocyte-derived isoform of the dnmt1 (cytosine-5)-methyltransferase protein, dnmt1o, which functions during preimplantation development to maintain methylation patterns on imprinted alleles. ...	2003	12929092
species differences in the ovarian distribution of 3beta-hydroxysteroid dehydrogenase/delta5-->4 isomerase (3beta-hsd) in two marsupials: the brushtail possum trichosurus vulpecula and the grey, short-tailed opossum monodelphis domestica.	the ovarian distribution of the steroidogenic enzyme 3beta-hydroxysteroid dehydrogenase/delta(5-->4) isomerase (3beta-hsd) was investigated by immunocytochemistry in two marsupial species throughout the reproductive cycle, using a rabbit polyclonal antibody raised against human placental 3beta-hsd. in the polyoestrous and polyovular south american opossum monodelphis domestica, immunostaining was positive for 3beta-hsd in the adrenal cortex, the ovarian interstitial tissue, the corpus luteum and ...	2003	12622697
regeneration of supraspinal axons after complete transection of the thoracic spinal cord in neonatal opossums (monodelphis domestica).	these studies define the time table and origin of supraspinal axons regenerating across a complete spinal transection in postnatal monodelphis domestica. after lumbar (l1) spinal cord injection of fluorophore-dextran amine conjugate on postnatal (p) day 4, a consistent number of neurons could be labeled. the numbers of labeled neurons remained stable for several weeks, but subsequently declined by p60 in control animals and by p35 in animals with complete spinal transection (t4-t6) performed at ...	2003	14556298
in vivo opossum xenograft model for cancer research.	the inadequacies of athymic mice for research with grafted tumors are well known. monodelphis domestica, the laboratory opossum, has the potential to complement the rodent model because of the immunoincompetent window period during early marsupial development. we injected pups of different ages with mouse melanoma cells and human melanoma, colon, and prostate cancer cells. the results showed that the xenogeneic tumors can grow and metastasize. we also obtained positive results by heterotopically ...	2003	14559788
conservation of chromosomal location of nucleolus organizer in american marsupials (didelphidae).	the distribution and expression of nucleolus organizer regions (nors) were analyzed in seven species of marsupials representative of the three karyotypes (2n = 14, 18 and 22) found in the american family didelphidae. analyses comprised silver-staining of nors and fluorescence in situ hybridization with an rdna probe. in addition to confirming the variability in number and distribution of nors in didelphidae, we demonstrated the conserved location of nors on one autosome pair in the three karyoty ...	2003	12733660
ontogeny of feeding function in the gray short-tailed opossum monodelphis domestica: empirical support for the constrained model of jaw biomechanics.	the constrained model of masticatory function enables specific predictions of bite force potentials in skulls of differing craniodental configurations. in this study, empirical support for the constrained model is provided using maximum voluntary bite force data along region i and ii of the jaws of gray short-tailed opossums monodelphis domestica. then, growth series of m. domestica are used to assess how bite force potential changes with growth by evaluating craniodental changes using longitudi ...	2003	12547947
comparative analysis of alphaglobin and carbonic anhydrase i-cdnas of the opossum monodelphis domestica with related vertebrate sequences.	alphaglobin and carbonic anhydrase i coding sequences and part of their flanking untranslated regions were isolated from a cdna library of the opossum monodelphis domestica. this paper describes their characteristics and presents a brief phylogenetic analysis of these sequences and related ones.	2003	14686651
conspecific odor investigation by gray short-tailed opossums (monodelphis domestica).	gray short-tailed opossums (monodelphis domestica) are small marsupials, which have recently become the subjects of numerous laboratory investigations. while these opossums have well-developed olfactory systems and complex scent-marking behaviors, the significance of their use of odors in conspecific communication is still poorly understood. investigation of body odors by male and female opossums was examined in the present study. males investigated flank and urine odors of nonestrous adult fema ...	2003	14637220
chronic cold exposure increases liver oxidative capacity in the marsupial monodelphis domestica.	marsupials lack brown adipose tissue, and therefore rely exclusively on other tissues for thermogenesis. to determine the magnitude of phenotypic plasticity of the liver in response to changing metabolic demand, gray short-tailed opossums (m. domestica) were exposed to thermoneutral (28 degrees c) or cold (9-12 degrees c) conditions continuously for 6 weeks. half of each group was also endurance trained with a treadmill program during their respective temperature exposure. mass specific summit m ...	2003	14613790
survival anesthetic and injection procedures for neonatal opossums.	the laboratory opossum, monodelphis domestica, differs from most other marsupial species in that females lack a pouch, and neonates are exposed. this characteristic has fostered the use of this species for research on normal developmental processes early in life and on experimental perturbations of those processes. however, in vivo experiments on neonates younger than 5 days old have been hampered by lack of a protocol that is efficient in anesthetizing the mother without causing loss of the lit ...	2003	14510524
differentiation and morphological integration of neural progenitor cells transplanted into the developing mammalian eye.	transplantation of neural stem/progenitor cells has been proposed as a novel approach for the replacement and repair of damaged cns tissues. we have evaluated the influence of the host cellular microenvironment upon the survival, differentiation, and integration of neural progenitor cells transplanted into the cns. using this approach, we have investigated the fate of neural progenitor cells in vivo following transplantation into the developing mammalian eye. murine brain progenitor cells (mbpcs ...	2003	12814945
structural characteristics and barrier properties of the choroid plexuses in developing brain of the opossum (monodelphis domestica).	the structural and functional development of the choroid plexuses, the site of the blood-cerebrospinal fluid (csf) barrier, in an opossum (monodelphis domestica) was studied. marsupial species are extremely immature at birth compared with more conventional eutherian species. choroid plexus tissue of each brain ventricle, from early stages of development, was collected for light and electron microscopy. during development, the choroidal epithelium changes from a pseudostratified to a cuboidal lay ...	2003	12717706
postnatal development of the fore- and hindlimbs in the grey short-tailed opossum, monodelphis domestica.	marsupials are good experimental animals for developmental studies as their offspring are born at a stage comparable to embryonic stages of eutherian species. the south american opossum, monodelphis domestica, is particularly useful because of its small size and easy maintenance. this study was carried out to compare development of opossum fore- and hindlimbs during postnatal life, using light microscopy and whole mount alizarin staining. at birth, well-developed mobile forelimbs show cartilage ...	2003	12587929
loss of melanogenic response to dna damage correlates with the metastatic phenotype of a melanoma cell line from monodelphis domestica.		2003	12690292
male pheromone stimulates ovarian follicular development and body growth in juvenile female opossums (monodelphis domestica).	female opossums are induced into estrus by direct exposure to a non-volatile pheromone in male scentmarks. juvenile females develop this responsiveness by 150 days of age (days), and earlier (130 days) if exposed to male pheromone beginning at 90 days. the goal of this study was to examine the effect of male pheromone on body growth and ovarian follicular development in young opossums. females (n = 28) were weaned at 56 days and caged individually with ad libitum food and water from 84 days. bod ...	2003	12646055
whole-body mechanics and gaits in the gray short-tailed opossum monodelphis domestica: integrating patterns of locomotion in a semi-erect mammal.	gaits (footfall patterns) and external mechanical energy patterns of the center of mass were quantified in a generalized, semi-erect mammal in order to address three general questions. first, do semi-erect mammals exhibit the walk/run gait transitions that have been proposed as the primitive condition for tetrapods? second, do small, semi-erect mammals employ the energy-saving pendular and spring-based mechanics used by erect mammals? third, how well do mechanical locomotor patterns of the cente ...	2003	12624172
characterization of the brainstem auditory evoked potential (baep) in the grey short-tailed opossum (monodelphis domestica).	brainstem auditory evoked potentials (baep) have been measured and characterized in the marsupial monodelphis domestica in response to toneburst stimulation. five peaks are usually identified. the baep occurs within a time window of 5 ms starting 1.2 ms after onset of stimulation. latencies decrease with increasing stimulus level at a rate of about -11 microsecond/db. at high stimulus frequencies latencies are shorter than with lower frequencies and shorten at a rate of about -0.2 ms/octave. the ...	2003	8879448
analysis of a marsupial mhc region containing two recently duplicated class i loci.	a 37-kb cosmid containing two complete major histocompatibility complex (mhc) class i alpha chain loci from the opossum monodelphis domestica was isolated, fully sequenced, and characterized. this sequence represents the largest contiguous genomic sequence reported for the mhc region of a nonplacental mammal. based on particular conserved amino acid residues, and limited expression analyses, the two mhc-i loci, designated modoub and modouc, appear to encode functional mhc-i molecules. the two co ...	2004	15520888
the biodynamics of arboreal locomotion: the effects of substrate diameter on locomotor kinetics in the gray short-tailed opossum (monodelphis domestica).	effects of substrate diameter on locomotor biodynamics were studied in the gray short-tailed opossum (monodelphis domestica). two horizontal substrates were used: a flat 'terrestrial' trackway with a force platform integrated into the surface and a cylindrical 'arboreal' trackway (20.3 mm diameter) with a force-transducer instrumented region. on both terrestrial and arboreal substrates, fore limbs exhibited higher vertical impulse and peak vertical force than hind limbs. although vertical limb i ...	2004	15531652
changes in the epithelium of the vaginal complex during the estrous cycle of the marsupial monodelphis domestica. 2. scanning electron microscopy study.	the four stages of the estrous cycle in monodelphis domestica, namely proestrus, estrus, postestrus and the transitional metestrus, were analyzed with the scanning electron microscope and compared with the results of the previously published transmission electron-microscopic paper [cells tissues organs 2002;172:276-296]. during the estrous cycle the vaginal epithelium undergoes dramatic changes from a nonkeratinized to a highly keratinized epithelium. the predominant feature of proestrus with th ...	2004	15550759
transplantation of neural progenitor cells into the developing retina of the brazilian opossum: an in vivo system for studying stem/progenitor cell plasticity.	in developing cell transplant strategies to repair the diseased or injured retina is essential to consider host-graft interactions and how they may influence the outcome of the transplants. in the present study we evaluated the influence of the host microenvironment upon neural progenitor cells (npcs) transplanted into the developing and mature retina of the brazilian opossum, monodelphis domestica. monodelphis pups are born in an extremely immature state and the neonatal pups provide a fetal-li ...	2004	15855762
effect of lead exposure on spatial learning and running speed in the short-tailed opossum, monodelphis domestica (didelphidae).	studies were conducted to assess the spatial learning ability in adult males of the short-tailed opossum, monodelphis domestica using a t-maze, complex maze and elevated radial 8-arm maze. this is the first study of maze learning in opossums. in the t-maze, the performance of these animals improved over an 8-day training period. eighty percent of the subjects initially trained to turn to the right for food reinforcement reached criterion (80% correct responses) by day 3 and all reached criterion ...	2004	15303699
effect of dietary cholesterol with or without saturated fat on plasma lipoprotein cholesterol levels in the laboratory opossum (monodelphis domestica) model for diet-induced hyperlipidaemia.	laboratory opossums (monodelphis domestica) show extreme genetic variability in their responsiveness to dietary lipids; a great proportion of the genetic variability in responsiveness is due to a single major gene. to determine whether the major gene for dietary response detected by genetic analysis in opossums is responsive to dietary cholesterol or dietary saturated fat, or a combination of both, we used males and females of susceptible and resistant lines of laboratory opossums that were 5 to ...	2004	15230988
postnatal development of the reproductive system in the grey short-tailed opossum, monodelphis domestica.	postnatal phenotypic sex differentiation has been investigated in a laboratory marsupial, monodelphis domestica, as part of a larger study to resolve apparent discrepancies between eutherian and marsupial mammals. these include the formation of sex-specific structures in marsupials prior to gonadal differentiation and the retention in both sexes of structures which are sex-specific in eutherians. the time-course and nature of differentiation was investigated in 131 specimens ranging in age from ...	2004	15118913