Articoli di riviste: "Marsupials Molecular genetics"

1

McKenzie, LM, e DW Cooper. "Low MHC class II variability in a marsupial". Reproduction, Fertility and Development 6, n. 6 (1994): 721. http://dx.doi.org/10.1071/rd9940721.

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The major histocompatibility complex (MHC) loci have been shown to be highly polymorphic in most eutherian ('placental') species studied. Several hypotheses have been advanced for the maintenance of this exceptional level of genetic variation, one of which suggests that it is necessary for successful eutherian reproduction. Marsupials (metatherians) and eutherians are the only two groups of viviparous mammals, but their modes of reproduction are quite distinct. Although marsupials have placentae, they are generally shorter lived and less invasive than in eutherians. Other investigations have shown that genetic variation at marsupial MHC class I loci is probably high. Weak or non-existent mixed lymphocyte culture responses previously reported in several marsupial species have suggested a lack of class II variation. Data have therefore been collected on the level of restriction fragment length polymorphism at MHC class II beta-chain encoding loci of a marsupial, Macropus eugenii (the tammar wallaby). This level is shown to be low, between the level of MHC variation found in cheetahs and a population of lions with a restricted genetic base. Attention is drawn to the need to collect more data on the level of class II variability in both eutherians and marsupials, and to the potential of marsupials for understanding the relation, if any, between mode of reproduction and MHC variability.

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2

Renfree, Marilyn B. "Society for Reproductive Biology Founders' Lecture 2006 Life in the pouch: womb with a view". Reproduction, Fertility and Development 18, n. 7 (2006): 721. http://dx.doi.org/10.1071/rd06072.

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Marsupials give birth to an undeveloped altricial young after a relatively short gestation period, but have a long and sophisticated lactation with the young usually developing in a pouch. Their viviparous mode of reproduction trades placentation for lactation, exchanging the umbilical cord for the teat. The special adaptations that marsupials have developed provide us with unique insights into the evolution of all mammalian reproduction. Marsupials hold many mammalian reproductive ‘records’, for example they have the shortest known gestation but the longest embryonic diapause, the smallest neonate but the longest sperm. They have contributed to our knowledge of many mammalian reproductive events including embryonic diapause and development, birth behaviour, sex determination, sexual differentiation, lactation and seasonal breeding. Because marsupials have been genetically isolated from eutherian mammals for over 125 million years, sequencing of the genome of two marsupial species has made comparative genomic biology an exciting and important new area of investigation. This review will show how the study of marsupials has widened our understanding of mammalian reproduction and development, highlighting some mechanisms that are so fundamental that they are shared by all today’s marsupial and eutherian mammals.

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3

Cowan, PE. "Changes in milk composition during lactation in the common brushtail possum, Trichosurus vulpecula (Marsupialia: Phalangeridae)". Reproduction, Fertility and Development 1, n. 4 (1989): 325. http://dx.doi.org/10.1071/rd9890325.

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The milk constituents of Trichosurus vulpecula, a folivorous marsupial, showed marked quantitative and qualitative changes during the course of lactation. The milk produced in the early stages of lactation was dilute, with about 9-13% (w/w) solids during the first 3 weeks, comprising mostly carbohydrate and protein (35-40%). At 20 weeks, about three-quarters of the way through lactation, the milk was much more concentrated, about 28% solids, with lipid the predominant fraction (30-35%), after a marked decline in carbohydrate content (20-25%). Concentrations of the electrolytes sodium and potassium also underwent marked changes. The changes in milk composition of T. vulpecula during the first three-quarters of lactation were similar to those described for a range of herbivorous, insectivorous and carnivorous marsupials. In the last quarter of lactation, however, brushtail possum milk maintained a relatively stable composition, with higher levels of carbohydrate and lower levels of lipid than for other marsupials. There appears to be a uniform pattern of changes in milk composition throughout the Marsupialia over most of lactation, with family differences evident only in the latter stages.

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4

Moore, HD. "Gamete biology of the new world marsupial, the grey short-tailed opossum, Monodelphis domestica". Reproduction, Fertility and Development 8, n. 4 (1996): 605. http://dx.doi.org/10.1071/rd9960605.

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Mammalian gametes undergo a series of functional and developmental changes that culminate in fertilization. In order to appreciate the necessity for such complex processes as sperm maturation, capacitation and the intimate sperm-egg interactions leading to gamete fusion, it is important to understand how gametes may have evolved. In this respect, marsupials are particularly relevant since they exhibit features reminiscent of both non-mammalian vertebrates and eutherian mammals. The grey short-tailed opossum, Monodelphis domestica, is a New World marsupial from Brazil. It breeds well under laboratory conditions and is an excellent animal model to investigate marsupial gamete biology. As in other American marsupials, the spermatozoa of the opossum form pairs in the epididymis. Here, a number of studies carried out in this laboratory, related to sperm maturation, capacitation and fertilization in M. domestica, are reviewed and the gamete biology in this species is compared with what is known in other marsupials and eutherian mammals.

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5

Price, Gilbert J., Kyle J. Ferguson, Gregory E. Webb, Yue-xing Feng, Pennilyn Higgins, Ai Duc Nguyen, Jian-xin Zhao, Renaud Joannes-Boyau e Julien Louys. "Seasonal migration of marsupial megafauna in Pleistocene Sahul (Australia–New Guinea)". Proceedings of the Royal Society B: Biological Sciences 284, n. 1863 (27 settembre 2017): 20170785. http://dx.doi.org/10.1098/rspb.2017.0785.

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Seasonal two-way migration is an ecological phenomenon observed in a wide range of large-bodied placental mammals, but is conspicuously absent in all modern marsupials. Most extant marsupials are typically smaller in body size in comparison to their migratory placental cousins, possibly limiting their potential to undertake long-distance seasonal migrations. But what about earlier, now-extinct giant marsupial megafauna? Here we present new geochemical analyses which show that the largest of the extinct marsupial herbivores, the enormous wombat-like Diprotodon optatum , undertook seasonal, two-way latitudinal migration in eastern Sahul (Pleistocene Australia–New Guinea). Our data infer that this giant marsupial had the potential to perform round-trip journeys of as much as 200 km annually, which is reminiscent of modern East African mammal migrations. These findings provide, to our knowledge, the first evidence for repetitive seasonal migration in any metatherian (including marsupials), living or extinct, and point to an ecological phenomenon absent from the continent since the Late Pleistocene.

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6

Renfree, M. B., S. R. Frankenberg e C. Freyer. "054. TROPHOBLAST, PLACENTA AND EARLY EMBRYO: HOW THE MARSUPIAL DEVELOPS". Reproduction, Fertility and Development 22, n. 9 (2010): 15. http://dx.doi.org/10.1071/srb10abs054.

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In marsupials, the blastocyst forms as a single cell layer of cells. The marsupial blastocyst has no inner cell mass, so the 80–100 cell tammar embryo remains in diapause as a unilaminar blastocyst. All marsupials have a unilaminar stage, but what is unusual is that in the tammar the total cessation of cell division and cell metabolism lasts for 11 months each year. Marsupials are placental mammals. The yolk sac forms the definitive placenta up to birth. Only very few marsupials, such as the bandicoot, have a chorio-allantoic placenta, which supplements the placental functions of the yolk sac. However, the understanding how the unilaminar layer of trophoblast cells of the diapausing blastocyst become specified into placental and embryonic tissues has been an ongoing puzzle. To identify genes that do become differentially expressed in tammar development, we targeted the stage of the earliest appearance of the embryonic disc, at which the remainder of the blastocyst is then defined as trophoblast, as well as early cleavage stages. Intriguingly, we found no evidence for early differential expression of the canonical pluripotency genes POU5F1, SOX2 and NANOG, or of CDX2. By contrast, we found overt differential expression of GATA3, the closely related gene GATA2, and FGF4. This expression profile suggests that in the tammar, mechanisms regulating trophoblast- and pluriblast-specific expression of POU5F1, SOX2, NANOG and CDX2 are temporally secondary to those regulating GATA2 & -3 and FGF4 expression. Together, our results may signify the evolution of alternative mechanisms of early lineage specification in marsupials, or alternatively reveal a general hierarchy of signalling mechanisms that are masked in the relatively rapid and ‘compressed’ development of mice. The results of our ongoing study have important implications for understanding not only marsupial stem cells but the early development of all therian mammals.

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7

Robinson, ES, MB Renfree, RV Short e JL VandeBerg. "Mammary glands in male marsupials. 2. Development of teat primordia in Didelphis virginiana and Monodelphis domestica". Reproduction, Fertility and Development 3, n. 3 (1991): 295. http://dx.doi.org/10.1071/rd9910295.

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Young and adults of both sexes of two didelphid marsupials, Didelphis virginiana and Monodelphis domestica, were examined externally for evidence of mammary gland development. Female young possessed teat numbers typical of adult females (13-15 in D. virginiana; 11-13 in M. domestica). Male young showed variable teat numbers which were always low compared with females, with the majority possessing 2-4 in anterior positions. Teats were also present in adult males of both species, in similar numbers and locations to those of young males. There are no previous reports of the presence of teats in any adult male marsupials. No mammary primordia in males have been recorded at any stage of development in the most thoroughly studied Australian marsupials. Our findings strengthen the view that there is a dichotomy between the two marsupial lineages in the regulation of male mammary gland expression.

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8

Deakin, Janine E., e Sally Potter. "Marsupial chromosomics: bridging the gap between genomes and chromosomes". Reproduction, Fertility and Development 31, n. 7 (2019): 1189. http://dx.doi.org/10.1071/rd18201.

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Marsupials have unique features that make them particularly interesting to study, and sequencing of marsupial genomes is helping to understand their evolution. A decade ago, it was a huge feat to sequence the first marsupial genome. Now, the advances in sequencing technology have made the sequencing of many more marsupial genomes possible. However, the DNA sequence is only one component of the structures it is packaged into: chromosomes. Knowing the arrangement of the DNA sequence on each chromosome is essential for a genome assembly to be used to its full potential. The importance of combining sequence information with cytogenetics has previously been demonstrated for rapidly evolving regions of the genome, such as the sex chromosomes, as well as for reconstructing the ancestral marsupial karyotype and understanding the chromosome rearrangements involved in the Tasmanian devil facial tumour disease. Despite the recent advances in sequencing technology assisting in genome assembly, physical anchoring of the sequence to chromosomes is required to achieve a chromosome-level assembly. Once chromosome-level assemblies are achieved for more marsupials, we will be able to investigate changes in the packaging and interactions between chromosomes to gain an understanding of the role genome architecture has played during marsupial evolution.

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9

Rodger, JC. "Prefertilization gamete maturation events in marsupials". Reproduction, Fertility and Development 6, n. 4 (1994): 473. http://dx.doi.org/10.1071/rd9940473.

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Despite many fundamental similarities between the gametes of marsupials and placental mammals, the regulation and timing of prefertilization gamete maturation are quite different. The marsupial acrosome is remarkably stable and an acrosome reaction (AR) is not induced by reagent effective for the sperm of placental mammals. The ultrastructure of the marsupial sperm AR is essentially similar to that of placental mammals, however, whether an equatorial segment (ES) persists to serve as the site of sperm-egg membrane fusion is unclear. Diacylglycerol induction of the AR suggests that the sperm of Australian species lack an ES, yet an ES-like region appears to be involved in fertilization in the opossum Monodelphis. The marsupial oocyte, unlike those of placentals, continues to grow throughout follicular life and major cytoplasmic maturation events occur late in oocyte development. Cortical granules only become evident shortly before ovulation and mature dark granules may only appear after ovulation. Further, the zona pellucida (ZP) changes in character and function during the peri-ovulatory period. In vitro fertilization has been achieved for an opossum but not for any Australian marsupial, owing to failure of sperm-ZP binding. Requirement for a sperm maturation process is likely, but capacitation treatments used for placental sperm in vitro have been ineffective. Since it is now feasible to experimentally manipulate marsupial gametes in vitro major advances in our understanding of their function can be expected.

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10

Frankenberg, S., A. J. Pask e M. B. Renfree. "259. Pluripotency genes in a marsupial, the tammar wallaby". Reproduction, Fertility and Development 20, n. 9 (2008): 59. http://dx.doi.org/10.1071/srb08abs259.

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Markers of pluripotency and early differentiation in the early embryo have been extensively characterised in eutherian species, most notably the mouse. By comparison, mechanisms controlling pluripotency and early lineage specification have received surprisingly little attention in marsupials, which represent the second major infraclass of mammals. Early marsupial embryogenesis exhibits overt morphological differences to that of eutherians, however the underlying developmental mechanisms may be conserved. In order to characterise early marsupial development at the molecular level, we have identified, cloned and analysed expression of orthologueues of several eutherian genes encoding transcription factors and signalling molecules involved in regulating pluripotency and early lineage specification. These genes include POU5F1 (OCT4), SOX2, NANOG, FGF4, FGFR2, CDX2, EOMES, TEAD4, GATA6 and KITL and are all expressed at early stages of development in the tammar. In addition, we have identified and cloned tammar POU2, which has orthologueues in non-mammalian vertebrates. POU2 is a paralogue of POU5F1 – a master regulator of pluripotency in eutherians. Genomic analysis indicates that POU5F1 arose via gene duplication of POU2 before the monotreme-therian divergence. Both genes have persisted in marsupials and monotremes, while POU2 was lost early during eutherian evolution. Similar expression profiles of tammar POU5F1 and POU2 in early embryos and gonadal tissues suggest possible overlapping roles in the maintenance of pluripotency.

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11

Rodger, John C. "Likely targets for immunocontraception in marsupials". Reproduction, Fertility and Development 9, n. 1 (1997): 131. http://dx.doi.org/10.1071/r96073.

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There is a growing need to manage marsupial populations as a means to mitigate economic and environmental damage and resolve animal welfare problems. In Australia, the problems of population management are highly specific and localized. In contrast, in New Zealand the problem is the control of the many millions of widely-distributed brushtail possums which are the country’s major vertebrate pest. The needs of the two countries are thus very different but immunocontraception may provide an effective and humane alternative to current lethal control strategies. This paper discusses the features of marsupial reproduction and development that offer potential as targets for immunocontraceptive interference, including: (1) sperm production and maturation in the male; (2) sperm transport and maturation in the female; and (3) sperm and egg antigens and the early embryo. Some of these antigen targets are shared with eutherian mammals but others are likely to be unique to marsupials.

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12

Breed, WG. "Egg maturation and fertilization in marsupials". Reproduction, Fertility and Development 8, n. 4 (1996): 617. http://dx.doi.org/10.1071/rd9960617.

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This brief review summarizes our knowledge of the morphological events that are associated with oocyte maturation and fertilization in marsupials in which it has been suggested that there are marked differences from eutherians in both the developmental timetable of oocyte maturation and in some of the processes associated with sperm-egg interaction. Most of the data have been obtained from studies on four species: Monodelphis domestica, Sminthopsis crassicaudata, Sminthopsis macroura, and Trichosurus vulpecula. Differences between the species have been described for: (1) the arrangement of 'yolk' in the oocyte cytoplasm; (2) the time of formation of cortical granules: (3) the mode of sperm penetration through the zone pellucida: (4) the sperm membrane involved in sperm-egg fusion: (5) the fate of inner acrosomal and sperm plasma membranes: and (6) the rapidity of sperm chromatin decondensation in the ooplasm. Such differences suggest considerable variation in these processes between different marsupial species although some of the variation described may be due to technical differences in the obtaining of the data. Thus, whether there are fundamental differences between the two major extant infraclasses of mammals, marsupials and eutherians, in some of the processes associated with fertilization is conjectural at the present time. The interspecific variation in the results obtained cautions one in extrapolating from observations on one or two 'model' species to the infraclass as a whole: a conclusion that might not, on reflection, be too surprising bearing in mind the long and separate evolutionary history of the major extant marsupial lineages.

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13

Marín-Gual, Laia, Laura González-Rodelas, Gala Pujol, Covadonga Vara, Marta Martín-Ruiz, Soledad Berríos, Raúl Fernández-Donoso et al. "Strategies for meiotic sex chromosome dynamics and telomeric elongation in Marsupials". PLOS Genetics 18, n. 2 (7 febbraio 2022): e1010040. http://dx.doi.org/10.1371/journal.pgen.1010040.

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During meiotic prophase I, homologous chromosomes pair, synapse and recombine in a tightly regulated process that ensures the generation of genetically variable haploid gametes. Although the mechanisms underlying meiotic cell division have been well studied in model species, our understanding of the dynamics of meiotic prophase I in non-traditional model mammals remains in its infancy. Here, we reveal key meiotic features in previously uncharacterised marsupial species (the tammar wallaby and the fat-tailed dunnart), plus the fat-tailed mouse opossum, with a focus on sex chromosome pairing strategies, recombination and meiotic telomere homeostasis. We uncovered differences between phylogroups with important functional and evolutionary implications. First, sex chromosomes, which lack a pseudo-autosomal region in marsupials, had species specific pairing and silencing strategies, with implications for sex chromosome evolution. Second, we detected two waves of γH2AX accumulation during prophase I. The first wave was accompanied by low γH2AX levels on autosomes, which correlated with the low recombination rates that distinguish marsupials from eutherian mammals. In the second wave, γH2AX was restricted to sex chromosomes in all three species, which correlated with transcription from the X in tammar wallaby. This suggests non-canonical functions of γH2AX on meiotic sex chromosomes. Finally, we uncover evidence for telomere elongation in primary spermatocytes of the fat-tailed dunnart, a unique strategy within mammals. Our results provide new insights into meiotic progression and telomere homeostasis in marsupials, highlighting the importance of capturing the diversity of meiotic strategies within mammals.

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14

Renfree, MB. "Monotreme and marsupial reproduction". Reproduction, Fertility and Development 7, n. 5 (1995): 1003. http://dx.doi.org/10.1071/rd9951003.

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Marsupials were regarded as curiosities by their early European discoverers, animals to be wondered at. Monotremes were even more surprising; the platypus was such an amalgam of characters that it was thought to be a hoax. They were recognized very early as mammals that could make a major contribution to our understanding of reproductive processes, and work on marsupials at the turn of the century was much in evidence. It is, however, only in the past two decades, and especially in the past few years that marsupial research has regained this position. There is no doubt that future research will strengthen this contribution, but we are faced with serious conservation questions that must be solved if we are to maintain these wonderful animals as a resource for future generations.

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Polymeropoulos, E. T., G. Heldmaier, P. B. Frappell, B. M. McAllan, K. W. Withers, M. Klingenspor, C. R. White e M. Jastroch. "Phylogenetic differences of mammalian basal metabolic rate are not explained by mitochondrial basal proton leak". Proceedings of the Royal Society B: Biological Sciences 279, n. 1726 (giugno 2011): 185–93. http://dx.doi.org/10.1098/rspb.2011.0881.

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Metabolic rates of mammals presumably increased during the evolution of endothermy, but molecular and cellular mechanisms underlying basal metabolic rate (BMR) are still not understood. It has been established that mitochondrial basal proton leak contributes significantly to BMR. Comparative studies among a diversity of eutherian mammals showed that BMR correlates with body mass and proton leak. Here, we studied BMR and mitochondrial basal proton leak in liver of various marsupial species. Surprisingly, we found that the mitochondrial proton leak was greater in marsupials than in eutherians, although marsupials have lower BMRs. To verify our finding, we kept similar-sized individuals of a marsupial opossum ( Monodelphis domestica ) and a eutherian rodent ( Mesocricetus auratus ) species under identical conditions, and directly compared BMR and basal proton leak. We confirmed an approximately 40 per cent lower mass specific BMR in the opossum although its proton leak was significantly higher (approx. 60%). We demonstrate that the increase in BMR during eutherian evolution is not based on a general increase in the mitochondrial proton leak, although there is a similar allometric relationship of proton leak and BMR within mammalian groups. The difference in proton leak between endothermic groups may assist in elucidating distinct metabolic and habitat requirements that have evolved during mammalian divergence.

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Behringer, Richard R., Guy S. Eakin e Marilyn B. Renfree. "Mammalian diversity: gametes, embryos and reproduction". Reproduction, Fertility and Development 18, n. 2 (2006): 99. http://dx.doi.org/10.1071/rd05137.

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The class Mammalia is composed of approximately 4800 extant species. These mammalian species are divided into three subclasses that include the monotremes, marsupials and eutherians. Monotremes are remarkable because these mammals are born from eggs laid outside of the mother’s body. Marsupial mammals have relatively short gestation periods and give birth to highly altricial young that continue a significant amount of ‘fetal’ development after birth, supported by a highly sophisticated lactation. Less than 10% of mammalian species are monotremes or marsupials, so the great majority of mammals are grouped into the subclass Eutheria, including mouse and human. Mammals exhibit great variety in morphology, physiology and reproduction. In the present article, we highlight some of this remarkable diversity relative to the mouse, one of the most widely used mammalian model organisms, and human. This diversity creates challenges and opportunities for gamete and embryo collection, culture and transfer technologies.

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Dobrovic, A., e Marshall Graves. "Gene mapping in marsupials and monotremes". Cytogenetic and Genome Research 41, n. 1 (1986): 9–13. http://dx.doi.org/10.1159/000132189.

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18

Dawson, G. W., e Marshall Graves. "Gene mapping in marsupials and monotremes". Cytogenetic and Genome Research 42, n. 1-2 (1986): 80–84. http://dx.doi.org/10.1159/000132256.

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Dawson, G. W., P. G. Johnston e Marshall Graves. "Gene mapping in marsupials and monotremes". Cytogenetic and Genome Research 45, n. 1 (1987): 1–4. http://dx.doi.org/10.1159/000132415.

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Graves, Jennifer A. Marshall, e Marilyn B. Renfree. "Marsupials in the Age of Genomics". Annual Review of Genomics and Human Genetics 14, n. 1 (31 agosto 2013): 393–420. http://dx.doi.org/10.1146/annurev-genom-091212-153452.

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21

Westerman, M., S. Loke e M. S. Springer. "Molecular phylogenetic relationships of two extinct potoroid marsupials, Potorous platyops and Caloprymnus campestris (Potoroinae: Marsupialia)". Molecular Phylogenetics and Evolution 31, n. 2 (maggio 2004): 476–85. http://dx.doi.org/10.1016/j.ympev.2003.08.006.

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Denyer, Alice L., Sophie Regnault e John R. Hutchinson. "Evolution of the patella and patelloid in marsupial mammals". PeerJ 8 (19 agosto 2020): e9760. http://dx.doi.org/10.7717/peerj.9760.

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Abstract (sommario):

The musculoskeletal system of marsupial mammals has numerous unusual features beyond the pouch and epipubic bones. One example is the widespread absence or reduction (to a fibrous “patelloid”) of the patella (“kneecap”) sesamoid bone, but prior studies with coarse sampling indicated complex patterns of evolution of this absence or reduction. Here, we conducted an in-depth investigation into the form of the patella of extant marsupial species and used the assembled dataset to reconstruct the likely pattern of evolution of the marsupial patella. Critical assessment of the available literature was followed by examination and imaging of museum specimens, as well as CT scanning and histological examination of dissected wet specimens. Our results, from sampling about 19% of extant marsupial species-level diversity, include new images and descriptions of the fibrocartilaginous patelloid in Thylacinus cynocephalus (the thylacine or “marsupial wolf”) and other marsupials as well as the ossified patella in Notoryctes ‘marsupial moles’, Caenolestes shrew opossums, bandicoots and bilbies. We found novel evidence of an ossified patella in one specimen of Macropus rufogriseus (Bennett’s wallaby), with hints of similar variation in other species. It remains uncertain whether such ossifications are ontogenetic variation, unusual individual variation, pathological or otherwise, but future studies must continue to be conscious of variation in metatherian patellar sesamoid morphology. Our evolutionary reconstructions using our assembled data vary, too, depending on the reconstruction algorithm used. A maximum likelihood algorithm favours ancestral fibrocartilaginous “patelloid” for crown clade Marsupialia and independent origins of ossified patellae in extinct sparassodonts, peramelids, notoryctids and caenolestids. A maximum parsimony algorithm favours ancestral ossified patella for the clade [Marsupialia + sparassodonts] and subsequent reductions into fibrocartilage in didelphids, dasyuromorphs and diprotodonts; but this result changed to agree more with the maximum likelihood results if the character state reconstructions were ordered. Thus, there is substantial homoplasy in marsupial patellae regardless of the evolutionary algorithm adopted. We contend that the most plausible inference, however, is that metatherians independently ossified their patellae at least three times in their evolution. Furthermore, the variability of the patellar state we observed, even within single species (e.g. M. rufogriseus), is fascinating and warrants further investigation, especially as it hints at developmental plasticity that might have been harnessed in marsupial evolution to drive the complex patterns inferred here.

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Svartman, Marta. "American marsupials chromosomes: why study them?" Genetics and Molecular Biology 32, n. 4 (23 ottobre 2009): 675–87. http://dx.doi.org/10.1590/s1415-47572009005000084.

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Fidler, Andrew E., Andrea H. Western, Nicole Griffith, Lynne Selwood, Vicki Stent e Kenneth P. McNatty. "Production of a biologically active recombinant marsupial growth factor using the methylotrophic yeast Pichia pastoris". Reproduction, Fertility and Development 14, n. 6 (2002): 327. http://dx.doi.org/10.1071/rd02040.

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The cytokine stem cell factor (SCF) and its interaction with its receptor c-kit plays an important role in the development of germ cells in eutherians. To investigate the putative roles of the SCF/c-kit system in marsupials, recombinant Australian brushtail possum (Trichosurus vulpecula) SCF was purified after secretion by the methylotrophic yeast Pichia pastoris. The purification procedure utilized Ni2+ affinity chromatography with a poly-histidine tag engineered onto the C-terminus of the recombinant SCF. The recombinant possum SCF had a molecular weight of 48 kDa, as determined by sodium dodecyl sulphate–polyacrylamide gel electrophoresis, and was biologically active with respect to its ability to maintain and induce proliferation of marsupial primordial germ cells in vitro. Furthermore, the recombinant possum SCF stimulated proliferation of the cell line TF1 and this bioactivity could be inhibited using an antibody directed against recombinant mouse SCF. This source of biologically active marsupial SCF may prove useful in future studies of marsupial development.

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Mitchell, Kieren J., Renae C. Pratt, Laura N. Watson, Gillian C. Gibb, Bastien Llamas, Marta Kasper, Janette Edson et al. "Molecular Phylogeny, Biogeography, and Habitat Preference Evolution of Marsupials". Molecular Biology and Evolution 31, n. 9 (30 maggio 2014): 2322–30. http://dx.doi.org/10.1093/molbev/msu176.

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Witt, R. R., L. A. Hinds e J. C. Rodger. "93 Oestrous Synchronisation Studies in a Marsupial". Reproduction, Fertility and Development 30, n. 1 (2018): 186. http://dx.doi.org/10.1071/rdv30n1ab93.

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Abstract (sommario):

There is no strategy to precisely synchronise and predict oestrus and ovulation in marsupials. This is the major limitation in applying assisted reproduction to marsupial conservation. Routine methods of female synchronization that target the ovary (effective in eutherians) are ineffective in marsupials because they do not disrupt the corpus luteum. Gondaotropin-releasing hormone (GnRH) agonists have been used to suppress female cycling in several marsupials and work by targeting GnRH action in the pituitary. After the GnRH agonist reaches its active endpoint, female cycling returns. This study investigated whether Lucrin Depot (Abbott Laboratories, Lake Bluff, IL, USA), a tailored 1-month microsphere GnRH agonist preparation, has the potential to first suppress female cycling, and then facilitate a synchronous return to female cycling in a model marsupial, the tammar wallaby (Macropus eugenii). Preliminary studies indicated that Lucrin could be used to regulate ovarian activity, but a dose >0.20 mg kg−1 was required. In this study, nonpregnant tammars (n = 18, 6 per group) had their pouch young removed (RPY) on Day 0; RPY suspends lactation and reactivates cycling, allowing for controlled assessment of oestrus and mating in treated and untreated females. On Day 0, an intramuscular (IM) injection of water (Control) or 1 mg kg−1 of Lucrin Depot (group A) was given after RPY. Group B also received 1 mg kg−1 of Lucrin Depot but this was not injected until Day 10 after RPY (a strategy to assess whether timing of Lucrin yields different results). Females were placed in breeding pens of 1 male to 3 females. Reproductive suppression and synchrony of return to female cycling was assessed by pouch and urogenital opening checks to detect newborn young and copulatory plugs. All data (time of mating/conception) were analysed using ANOVA (significance, P < 0.05). There was a significant difference between the first mating response in the Control compared with Groups A and B (P = 0.0003), but the time from Lucrin injection to mating, Day 0 or Day 10, was not significant (P = 0.1431). All control females mated before Day 32 RPY, whereas all Lucrin-treated females mated from Day 33 to 66. All Lucrin-treated females conceived as evidenced by pouch young. Further analysis revealed 2 Lucrin-injection to mating response intervals, those females delayed by ~10 days that conceived between 33 and 50 days (n = 7: 41 ± 2.1 days; mean ± SEM), and those females delayed by ~30 days that conceived between 61 and 66 days (n = 5: 62 ± 1.0 days; mean ± SEM) following injection. Thus, an IM injection of 1 mg kg−1 of Lucrin Depot is sufficient to delay oestrus in breeding tammar wallabies whether given at the time of RPY or 10 days later. This study confirmed that Lucrin Depot can be used to regulate ovarian activity in macropod marsupials, and has potential to form the basis of a GnRH agonist-based synchronisation strategy for use in assisted breeding for marsupial conservation. This research was supported by Holsworth Wildlife Research Endowment.

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Watson, C. M., P. G. Johnston, K. A. Rodger, L. M. McKenzie, R. J. Waugh O'Neill, D. W. Cooper e D. W. Cooper. "SRY and karyotypic status of one abnormal and two intersexual marsupials". Reproduction, Fertility and Development 9, n. 2 (1997): 233. http://dx.doi.org/10.1071/r96107.

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Abstract (sommario):

An intersexual agile wallaby (Macropus agilis) with a penis, a pouch and four teats had a sex-chromosome constitution of XXY in lymphocytes and cultured fibroblasts; the sex-determining region Y (SRY) gene was present, consistent with the presence of a testis. An intersexual eastern grey kangaroo (Macropus giganteus) with a small empty scrotum and no penis, and an abnormal red kangaroo (Macropus rufus) with no penis, pouch or teats, both had XX sex-chromosome complements; the SRY gene was not present, consistent with testis absence. The agile wallaby and grey kangaroo described here provide further evidence that scrotal development in marsupials is independent of the Y chromosome. The cause of the abnormalities in the XX individuals cannot be determined until candidate genes are identified. These animals provide a basis for further genetic studies into marsupial intersexuality and sex differentiation.

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28

O'Neill, R. J., M. D. B. Eldridge e C. J. Metcalfe. "Centromere Dynamics and Chromosome Evolution in Marsupials". Journal of Heredity 95, n. 5 (1 settembre 2004): 375–81. http://dx.doi.org/10.1093/jhered/esh063.

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29

Ralston, GB. "Proteins of Marsupial Erythrocyte Membranes". Australian Journal of Biological Sciences 38, n. 1 (1985): 121. http://dx.doi.org/10.1071/bi9850121.

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Abstract (sommario):

The proteins of erythrocyte membranes from the red kangaroo, western grey kangaroo, eastern grey wallaroo (euro), red-necked wallaby, Tammar wallaby, and brush-tail possum have been fractionated on acrylamide gels in the presence of sodium dodecyl sulfate. The pattern of proteins was remarkably similar between the different marsupial species. The pattern of Coomassie blue-staining proteins in the membranes of these species was also very similar to that of the human erythrocyte membrane. However, the glycoproteins in the marsupial erythrocyte membranes were markedly less conspicuous than those of the human erythrocyte membrane. Furthermore, the mobilities of the glycoproteins from the marsupials were different from those of the human erythrocyte membrane.

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30

Potter, Sally, e Janine E. Deakin. "Cytogenetics: an important inclusion in the conservation genetics toolbox". Pacific Conservation Biology 24, n. 3 (2018): 280. http://dx.doi.org/10.1071/pc18016.

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Abstract (sommario):

Conservation uses information from genetics to assist in management decisions. However, conservation genetics typically assesses genetic diversity at the DNA level but this alone does not address all the risks associated with managing wild and captive populations. DNA is packaged into chromosomes. Differences in the number and morphology of chromosomes between species or even between populations of the same species can have important implications for management programs for threatened species. Cytogenetics, analysis of the higher molecular chromosome structure, can provide invaluable insight for the management of threatened species, where DNA alone could not address all genetic risks and threats to populations. Here we outline the important and valuable role of cytogenetics in conservation, highlighting two case studies based on threatened Australian marsupials: rock-wallabies and the Tasmanian devil. In conclusion, we summarise how cytogenetics should be better linked to conservation genetics and integrated into our management of threatened species, to ensure they have the best platform from which to persist and adapt into the future.

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31

Czarny, N. A., K. E. Mate e J. C. Rodger. "Acrosome stability in the spermatozoa of dasyurid marsupials". Reproduction, Fertility and Development 20, n. 2 (2008): 295. http://dx.doi.org/10.1071/rd07178.

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Abstract (sommario):

The spermatozoa of most marsupials lack nuclear stabilising disulfide-bonded protamines found in eutherian mammals. However, disulfide stabilisation has been observed in the acrosome of macropodid (Macropus eugenii) and phalangerid (Trichosurus vulpecula) marsupials. As a result this organelle, which is normally fragile in eutherian mammals, is robust and able to withstand physical and chemical challenge in these marsupials. The present study examined acrosomal characteristics of the spermatozoa of three dasyurid marsupials; the fat-tailed dunnart (Sminthopsis crassicaudata), eastern quoll (Dasyurus viverrinus) and northern quoll (Dasyurus hallucatus). In all species examined Bryan’s staining demonstrated that significant acrosomal loss occurred following physical challenge with osmotic stress, cryopreservation without cryoprotectant and exposure to detergent (Triton-X). Bromobimane staining indicated that the acrosomes of dasyurids lacked stabilising disulfide bonds. As reported for the wallaby and possum, calcium ionophore (A23187) did not induce the acrosome reaction-like exocytosis in dasyurid spermatozoa but treatment with diacylglycerol (DiC8) caused significant acrosome loss at concentrations similar to those effective for other marsupials. The present study found that the spermatozoa of dasyurids are more sensitive to physical challenge than the previously-studied marsupials and we suggest that this is due to the absence of acrosomal stabilising disulfide bonds.

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32

Sinclair, A. R. E. "Fertility control of mammal pests and the conservation of endangered marsupials". Reproduction, Fertility and Development 9, n. 1 (1997): 1. http://dx.doi.org/10.1071/r96057.

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Abstract (sommario):

Populations are bounded by negative feedbacks operating through fertility or mortality, termedpopulation regulation. If fertility is artificially reduced, the average size of the population is also reduced, but only under certain conditions. If (i) juvenile survival or (ii) adult survival improve due to lower fertility, or (iii) territoriality limits populations, the effects of lower birth rate will not change population size unless such reduction exceeds the effects of these processes. Published data on population trends and birth rates have allowed a comparison among species of instantaneous rates of change. The intrinsic rate of increase, rm, and population variability are both related to body size, because birth rates and survivorship are also related to body size. These rates are trade-offs as adaptations. Populations of species in exotic habitats may fluctuate more than when they are in their indigenous habitats. Fertility control could reduce such fluctations. Marsupials have lower birth rates than eutherians, and so rely more on survivorship, perhaps as an adaptation to unpredictable environments. Compromising survival by either habitat change or increased predation will affect marsupials more than eutherians. This explains why many marsupial populations are declining towards extinction.

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33

O'Neill, RJ Waugh, MDB Eldridge, R. Toder, MA Ferguson-Smith, P. C. O'Brien e JAM Graves. "Chromosome evolution in kangaroos (Marsupialia: Macropodidae): Cross species chromosome painting between the tammar wallaby and rock wallaby spp. with the 2n = 22 ancestral macropodid karyotype". Genome 42, n. 3 (1 giugno 1999): 525–30. http://dx.doi.org/10.1139/g98-159.

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Abstract (sommario):

Marsupial mammals show extraordinary karyotype stability, with 2n = 14 considered ancestral. However, macropodid marsupials (kangaroos and wallabies) exhibit a considerable variety of karyotypes, with a hypothesised ancestral karyotype of 2n = 22. Speciation and karyotypic diversity in rock wallabies (Petrogale) is exceptional. We used cross species chromosome painting to examine the chromosome evolution between the tammar wallaby (2n = 16) and three 2n = 22 rock wallaby species groups with the putative ancestral karyotype. Hybridization of chromosome paints prepared from flow sorted chromosomes of the tammar wallaby to Petrogale spp., showed that this ancestral karyotype is largely conserved among 2n = 22 rock wallaby species, and confirmed the identity of ancestral chromosomes which fused to produce the bi-armed chromosomes of the 2n = 16 tammar wallaby. These results illustrate the fission-fusion process of karyotype evolution characteristic of the kangaroo group.

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34

Belov, Katherine, Gavan A. Harrison e Desmond W. Cooper. "Short Communication: Cloning of the red kangaroo (Macropus rufus) follicle stimulating hormone beta subunit". Reproduction, Fertility and Development 10, n. 3 (1998): 289. http://dx.doi.org/10.1071/r98067.

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Abstract (sommario):

The cDNA encoding the follicle stimulating hormone beta subunit (FSH-β) was isolated from a red kangaroo pituitary cDNA library by using a porcine probe and the nucleotide sequence for the coding region was determined. The highest degree of deduced amino acid sequence identity (91%) was observed between the red kangaroo and another marsupial, the brushtail possum (Trichosurus vulpecula), followed by eutherian species (76%, 75% and 74%, respectively, for pig, mouse and sheep). Based on the deduced red kangaroo FSH-β amino acid sequence, putative antigenic sites have been identified that may prove useful for studying the hormonal control of reproduction in marsupials.

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35

Kress, A. "A comparison of oocyte organelles in Monodelphis domestica with those of other marsupials and eutherians". Reproduction, Fertility and Development 8, n. 4 (1996): 521. http://dx.doi.org/10.1071/rd9960521.

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Abstract (sommario):

This paper reviews the current knowledge of oocyte cytology in marsupials, particularly Monodelphis domestica, and eutherian mammals. Some of the conspicuous features will be described and their function discussed. Despite many fundamental similarities between the oocytes of eutherian mammals and marsupials, some aspects are different (e.g. growth pattern, final size, timetable of cytoplasmic maturation and utilization of storage material during early cleavage stages), when most of the vesicles are extruded into the perivitelline space in marsupials.

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36

Samollow, P. B., e J. A. M. Graves. "Gene Maps of Marsupials". ILAR Journal 39, n. 2-3 (1 gennaio 1998): 203–24. http://dx.doi.org/10.1093/ilar.39.2-3.203.

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37

Toder, R., R. J. W. O'Neill e J. A. M. Graves. "Chromosome Painting in Marsupials". ILAR Journal 39, n. 2-3 (1 gennaio 1998): 92–95. http://dx.doi.org/10.1093/ilar.39.2-3.92.

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38

Renfree, Marilyn B., Timothy A. Hore, Geoffrey Shaw, Jennifer A. Marshall Graves e Andrew J. Pask. "Evolution of Genomic Imprinting: Insights from Marsupials and Monotremes". Annual Review of Genomics and Human Genetics 10, n. 1 (settembre 2009): 241–62. http://dx.doi.org/10.1146/annurev-genom-082908-150026.

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39

Mitchinson, Ben, Robyn A. Grant, Kendra Arkley, Vladan Rankov, Igor Perkon e Tony J. Prescott. "Active vibrissal sensing in rodents and marsupials". Philosophical Transactions of the Royal Society B: Biological Sciences 366, n. 1581 (12 novembre 2011): 3037–48. http://dx.doi.org/10.1098/rstb.2011.0156.

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Abstract (sommario):

In rats, the long facial whiskers (mystacial macrovibrissae) are repetitively and rapidly swept back and forth during exploration in a behaviour known as ‘whisking’. In this paper, we summarize previous evidence from rats, and present new data for rat, mouse and the marsupial grey short-tailed opossum ( Monodelphis domestica ) showing that whisking in all three species is actively controlled both with respect to movement of the animal's body and relative to environmental structure. Using automatic whisker tracking, and Fourier analysis, we first show that the whisking motion of the mystacial vibrissae, in the horizontal plane, can be approximated as a blend of two sinusoids at the fundamental frequency (mean 8.5, 11.3 and 7.3 Hz in rat, mouse and opossum, respectively) and its second harmonic. The oscillation at the second harmonic is particularly strong in mouse (around 22 Hz) consistent with previous reports of fast whisking in that species. In all three species, we found evidence of asymmetric whisking during head turning and following unilateral object contacts consistent with active control of whisker movement. We propose that the presence of active vibrissal touch in both rodents and marsupials suggests that this behavioural capacity emerged at an early stage in the evolution of therian mammals.

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40

Carvalho-Silva, Denise R., Rachel J. W. O’Neill, Judith D. Brown, Kim Huynh, Paul D. Waters, Andrew J. Pask, Margaret L. Delbridge e Jennifer A. Marshall Graves. "Molecular characterization and evolution of X and Y-borne ATRX homologues in American marsupials". Chromosome Research 12, n. 8 (dicembre 2004): 795–804. http://dx.doi.org/10.1007/s10577-005-5376-5.

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41

McFarlane, James R., Carl D. Rudd, Lynda M. Foulds, Terry P. Fletcher e Marilyn B. Renfree. "Isolation and partial characterization of tammar wallaby luteinizing hormone and development of a radioimmunoassay". Reproduction, Fertility and Development 9, n. 4 (1997): 475. http://dx.doi.org/10.1071/r96089.

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Abstract (sommario):

Tammar wallaby (Macropus eugenii) luteinizing hormone (LH) was purified from pituitaries collected from wild and captive populations by salt sequential precipitation, ion exchange chromatography and gel filtration. Pituitary tissue (5 g) yielded 1·8 mg of purified wallaby luteinizing hormone (ME-14B), as verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). A heterologous radioimmunoassay has been developed for measurement of LH in plasma of marsupials using a monoclonal antibody raised against bovine LH (518B7). This assay system was able to measure basal LH concentrations in male and female tammars and detected a significant rise in plasma LH in response to oestradiol benzoate in female tammars and luteinizing hormone-releasing hormone (LHRH) in males. Parallel dose–response curves were also obtained from pituitary extracts from four other species of marsupial (brushtail possum, Trichosurus vulpecula; brown antechinus,Antechinus stuartii; kowari, Dasyuroides byrnei; and Eastern pygmy possum,Cercartetus nanus) in this assay, which suggests its usefulness in the measurement of LH in other marsupial species.

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42

Kullander, Klas, Barbro Carlson e Finn Hallböök. "Molecular Phylogeny and Evolution of the Neurotrophins from Monotremes and Marsupials". Journal of Molecular Evolution 45, n. 3 (settembre 1997): 311–21. http://dx.doi.org/10.1007/pl00006235.

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43

Kirsch, John A. W., e Gregory C. Mayer. "The platypus is not a rodent: DNA hybridization, amniote phylogeny and the palimpsest theory". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 353, n. 1372 (29 luglio 1998): 1221–37. http://dx.doi.org/10.1098/rstb.1998.0278.

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Abstract (sommario):

We present DNA–hybridization data on 21 amniotes and two anurans showing that discrimination is obtained among most of these at the class and lower levels. Trees generated from these data largely agree with conventional views, for example in not associating birds and mammals. However, the sister relationships found here of the monotremes to marsupials, and of turtles to the alligator, are surprising results which are nonetheless consistent with the results of some other studies. The Marsupionta hypothesis of Gregory is reviewed, as are opinions about the placement of chelonians. Anatomical and reproductive data considered by Gregory do not unequivocally preclude a marsupial–monotreme special relationship, and there is other recent evidence for placing turtles within the Diapsida. We conclude that the evidential meaning of the molecular data is as shown in the trees, but that the topologies may be influenced by a base–compositional bias producing a seemingly slow evolutionary rate in monotremes, or by algorithmic artefacts (in the case of turtles as well).

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44

Schmid, M., W. Feichtinger, C. Steinlein, T. Haaf, R. Visbal García e A. Fernández Badillo. "X chromosomes of American marsupials contain minimal amounts of euchromatin". Cytogenetic and Genome Research 99, n. 1-4 (2002): 315–22. http://dx.doi.org/10.1159/000071610.

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45

Stannard, Hayley J., Robert D. Miller e Julie M. Old. "Marsupial and monotreme milk—a review of its nutrient and immune properties". PeerJ 8 (23 giugno 2020): e9335. http://dx.doi.org/10.7717/peerj.9335.

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Abstract (sommario):

All mammals are characterized by the ability of females to produce milk. Marsupial (metatherian) and monotreme (prototherian) young are born in a highly altricial state and rely on their mother’s milk for the first part of their life. Here we review the role and importance of milk in marsupial and monotreme development. Milk is the primary source of sustenance for young marsupials and monotremes and its composition varies at different stages of development. We applied nutritional geometry techniques to a limited number of species with values available to analyze changes in macronutrient composition of milk at different stages. Macronutrient energy composition of marsupial milk varies between species and changes concentration during the course of lactation. As well as nourishment, marsupial and monotreme milk supplies growth and immune factors. Neonates are unable to mount a specific immune response shortly after birth and therefore rely on immunoglobulins, immunological cells and other immunologically important molecules transferred through milk. Milk is also essential to the development of the maternal-young bond and is achieved through feedback systems and odor preferences in eutherian mammals. However, we have much to learn about the role of milk in marsupial and monotreme mother-young bonding. Further research is warranted in gaining a better understanding of the role of milk as a source of nutrition, developmental factors and immunity, in a broader range of marsupial species, and monotremes.

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46

Selwood, L. "Development of early cell lineages in marsupial embryos: an overview". Reproduction, Fertility and Development 6, n. 4 (1994): 507. http://dx.doi.org/10.1071/rd9940507.

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Abstract (sommario):

All major embryonic and extra-embryonic cell lineages are established before implantation in marsupials. In reptiles, birds, monotremes and most marsupials, the zygote is polarized, sometimes markedly so, and the cleavage pattern in relation to the polarized state provides the mechanism for the generation of positional signals. These ensure that the embryonic cell lineages develop in the centre of the developing blastoderm or blastocyst epithelium and the extra-embryonic lineages at the periphery. The evolution of the vertebrate yolky egg was accompanied by a decreasing dependence on maternal determinants and increasing dependence on positional signals to determine cell fate. It is proposed that when a less yolky egg evolved, the mechanisms for determination of cell fate in a developing epithelium were retained. It is proposed that in marsupials, positional signals are involved in the determination of cell fate of embryonic and trophectoderm cells but do so in a two-dimensional epithelium not a three-dimensional morula. The next lineage formed is the primary endoderm which separates off from the primitive ectoderm in the embryoblast and eventually lines the blastocyst cavity. Positional signals are responsible for the determination of primary endoderm in eutherian mammals, birds and probably also marsupials. Order of cell division during cleavage provides a mechanism whereby some cells in the embryoblast of marsupials have earlier and greater contact with their neighbouring cells. The mechanism for determination of primary endoderm cells in the blastocyst epithelium is examined in the Virginia opossum and the stripe-faced dunnart.

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47

Kirsch, John A. W., Mark S. Springer, Carey Krajewski, Michael Archer, Ken Aplin e Allan W. Dickerman. "DNA/DNA hybridization studies of the carnivorous marsupials. I: The intergeneric relationships of bandicoots (Marsupialia: Perameloidea)". Journal of Molecular Evolution 30, n. 5 (maggio 1990): 434–48. http://dx.doi.org/10.1007/bf02101115.

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48

Mate, KE. "Cytoplasmic maturation of the marsupial oocyte during the periovulatory period". Reproduction, Fertility and Development 8, n. 4 (1996): 509. http://dx.doi.org/10.1071/rd9960509.

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Abstract (sommario):

During the period immediately before ovulation, the oocytes of most eutherian and marsupial mammals complete the first meiotic maturation division and extrude the first polar body. In marsupials, this phase of nuclear maturation is accompanied by an increase in size of the egg and maturation of cytoplasmic components. Oocytes from at least four marsupial species, Trichosurus vulpecula, Macropus eugenii, Bettongia penicillata and Monodelphis domestica, continue to grow after formation of the follicular antrum and, although the rate of growth slows in larger follicles, it continues into the period immediately before ovulation. The basis of this growth is unknown but may include accumulation of fluid and/or yolk-like material. Maturational changes within the cytoplasm of the oocyte also occur during the periovulatory period, including the accumulation of cortical granules. Differences in the structure of the zona pellucida are also evident between follicular and ovulated eggs; these differences are suggestive of compression of the zona pellucida, but may involve the addition of extra material. These findings suggest that the marsupial oocyte may not achieve complete cytoplasmic maturity until after ovulation; however, their relevance to fertilization and embryonic development require further investigation. Like those of eutherian mammals, marsupial oocytes undergo spontaneous nuclear maturation once removed from the follicular environment, suggesting a basically similar control system. It is not known whether the preovulatory cytoplasmic changes seen in marsupial oocytes matured in vivo also occur during maturation in vitro.

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49

Pharo, Elizabeth A. "Marsupial milk: a fluid source of nutrition and immune factors for the developing pouch young". Reproduction, Fertility and Development 31, n. 7 (2019): 1252. http://dx.doi.org/10.1071/rd18197.

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Abstract (sommario):

Marsupials have a very different reproductive strategy to eutherians. An Australian marsupial, the tammar wallaby (Macropus eugenii) has a very short pregnancy of about 26.5 days, with a comparatively long lactation of 300–350 days. The tammar mother gives birth to an altricial, approximately 400 mg young that spends the first 200 days postpartum (p.p.) in its mother’s pouch, permanently (0–100 days p.p.; Phase 2A) and then intermittently (100–200 days p.p.; Phase 2B) attached to the teat. The beginning of Phase 3 marks the first exit from the pouch (akin to the birth of a precocious eutherian neonate) and the supplementation of milk with herbage. The marsupial mother progressively alters milk composition (proteins, fats and carbohydrates) and individual milk constituents throughout the lactation cycle to provide nutrients and immunological factors that are appropriate for the considerable physiological development and growth of her pouch young. This review explores the changes in tammar milk components that occur during the lactation cycle in conjunction with the development of the young.

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50

Hickford, D., A. Pask, G. Shaw e M. B. Renfree. "264. Primordial germ cell specification in a marsupial, the tammar wallaby". Reproduction, Fertility and Development 20, n. 9 (2008): 64. http://dx.doi.org/10.1071/srb08abs264.

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Abstract (sommario):

Primordial germ cells (PGCs) are the precursors of the gametes. In the mouse, PGCs are specified within the proximal epiblast in response to signals from the extraembryonic membranes during early gastrulation. Epiblast cells competent to form PGCs express Ifitm3. A subset of these cells then express Blimp1, a marker of PGC precursors. Once lineage-restricted, PGCs express Stella. Germ cells entering the gonads express VASA protein, which is a component of the germ plasm in animals in which germ cells are specified by the inheritance of maternal determinatives. Almost all of the research on mammalian PGC specification has used the mouse as a model and it is tacitly assumed that findings in the mouse will apply to mammals in general. We are using the tammar wallaby as a marsupial model for PGC specification. Eutherians and marsupials diverged 125–148 million years ago, so comparisons between the two will provide insights into the evolution of the control of mammalian PGC specification. There are IFITM clusters in both the human (chromosome 11) and mouse (chromosome 7). In the mouse, IFITM1, 2 and 3 are expressed in PGCs, whereas IFITM4 and 5 are not (1). Only one IFITM member, IFITM5, is annotated in the opossum Ensemble database. We have cloned one tammar IFITM member and identified at least one other putative member in the tammar trace archive database. We have also cloned tammar BLIMP1 and VASA, both of which show high sequence conservation with other mammals. RT–PCR profiles for both genes during tammar gastrulation are similar to those for the mouse. In contrast, no marsupial STELLA orthologueue has been identified in either the opossum or tammar genomes. These findings suggest that some but not all of the signals and mechanisms involved in eutherian PGC specification are also applicable to marsupials. (1) Lange UC, Saitou M, Western P, Barton SC and Surani MA (2003) BMC Dev. Biol. Epub 2003 Mar 19

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