Fused in sarcoma (FUS) inhibits milk production efficiency in mammals

Efficient milk production in mammals confers evolutionary advantages by facilitating the transmission of energy from mother to offspring. However, the regulatory mechanism responsible for the gradual establishment of milk production efficiency in mammals, from marsupials to eutherians, remains elusive. Here, we find that mammary gland of the marsupial sugar glider contained milk components during adolescence, and that mammary gland development is less dynamically cyclic compared to that in placental mammals. Furthermore, fused in sarcoma (FUS) is found to be partially responsible for this establishment of low efficiency. In mouse model, FUS inhibit mammary epithelial cell differentiation through the cyclin-dependent kinase inhibitor p57Kip2, leading to lactation failure and pup starvation. Clinically, FUS levels are negatively correlated with milk production in lactating women. Overall, our results shed light on FUS as a negative regulator of milk production, providing a potential mechanism for the establishment of milk production from marsupial to eutherian mammals.

Marsupials have monoallelic MEST expression with a conserved antisense lncRNA but MEST is not imprinted

The imprinted isoform of the Mest gene in mice is involved in key mammalian traits such as placental and fetal growth, maternal care and mammary gland maturation. The imprinted isoform has a distinct differentially methylated region (DMR) at its promoter in eutherian mammals but in marsupials, there are no differentially methylated CpG islands between the parental alleles. Here, we examined similarities and differences in the MEST gene locus across mammals using a marsupial, the tammar wallaby, a monotreme, the platypus, and a eutherian, the mouse, to investigate how imprinting of this gene evolved in mammals. By confirming the presence of the short isoform in all mammalian groups (which is imprinted in eutherians), this study suggests that an alternative promoter for the short isoform evolved at the MEST gene locus in the common ancestor of mammals. In the tammar, the short isoform of MEST shared the putative promoter CpG island with an antisense lncRNA previously identified in humans and an isoform of a neighbouring gene CEP41. The antisense lncRNA was expressed in tammar sperm, as seen in humans. This suggested that the conserved lncRNA might be important in the establishment of MEST imprinting in therian mammals, but it was not imprinted in the tammar. In contrast to previous studies, this study shows that MEST is not imprinted in marsupials. MEST imprinting in eutherians, therefore must have occurred after the marsupial-eutherian split with the acquisition of a key epigenetic imprinting control region, the differentially methylated CpG islands between the parental alleles.

The alternate pathway of androgen metabolism and window of sensitivity

Since the discovery in 1968 that dihydrotestosterone (DHT) is a major mediator of androgen action, a convincing body of evidence has accumulated to indicate that the major pathway of DHT formation is the 5α-reduction of circulating testosterone in androgen target tissues. However, we now know that DHT can also be formed in peripheral tissues by the oxidation of 5α-androstane-3α,17β-diol (adiol). This pathway is responsible for the formation of the male phenotype. We discuss the serendipitous discovery in the tammar wallaby of an alternate pathway by which adiol is formed in the testes, secreted into plasma and converted in peripheral tissues to DHT. This alternate pathway is responsible for virilisation of the urogenital system in this species and is present in the testes at the onset of male puberty of all mammals studied so far. This is the first clear-cut function for steroid 5α-reductase 1 in males. Unexpectedly, the discovery of this pathway in this Australian marsupial has had a major impact in understanding the pathophysiology of aberrant virilisation in female newborns. Overactivity of the alternate pathway appears to explain virilisation in congenital adrenal hyperplasia CAH, in X-linked 46,XY disorders of sex development. It also appears to be important in polycystic ovarian syndrome (PCOS) since PCOS ovaries have enhanced the expression of genes and proteins of the alternate pathway. It is now clear that normal male development in marsupials, rodents and humans requires the action of both the classic and the alternate (backdoor) pathways.

Hormonal and Molecular Regulation of Phallus Differentiation in a Marsupial Tammar Wallaby

Congenital anomalies in phalluses caused by endocrine disruptors have gained a great deal of attention due to its annual increasing rate in males. However, the endocrine-driven molecular regulatory mechanism of abnormal phallus development is complex and remains largely unknown. Here, we review the direct effect of androgen and oestrogen on molecular regulation in phalluses using the marsupial tammar wallaby, whose phallus differentiation occurs after birth. We summarize and discuss the molecular mechanisms underlying phallus differentiation mediated by sonic hedgehog (SHH) at day 50 pp and phallus elongation mediated by insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein 3 (IGFBP3), as well as multiple phallus-regulating genes expressed after day 50 pp. We also identify hormone-responsive long non-coding RNAs (lncRNAs) that are co-expressed with their neighboring coding genes. We show that the activation of SHH and IGF1, mediated by balanced androgen receptor (AR) and estrogen receptor 1 (ESR1) signalling, initiates a complex regulatory network in males to constrain the timing of phallus differentiation and to activate the downstream genes that maintain urethral closure and phallus elongation at later stages.

When less is more: a comparison of models to predict fluoride accumulation in free-ranging kangaroos

Vegetation contaminated by industrial fluoride emissions can cause disease in herbivorous mammals. Spatially explicit exposure models offer a quantitative approach for evaluating and managing the potentially toxic effects of chronic fluoride consumption on wildlife. We monitored eastern grey kangaroos (Macropus giganteus) inhabiting a high-fluoride environment in the buffer zone of an aluminium smelter in southeastern Australia between 2010 and 2013. We measured fluoride levels at 19 pasture sites and determined the foraging range of 37 individual kangaroos. A series of generalised linear models were developed to estimate bone fluoride accumulation as a function of pasture exposure. Model outputs were compared to identify the most appropriate predictive tool for kangaroo bone fluoride accumulation relative to exposure. Accounting for age there was a negative association between bone fluoride concentration and distance of the central emission point from both the mean centre of foraging range and the point of death. The mean foraging range centre was the best predictor, with point of death just as suitable (and simpler), whereas more complex parameters such as monthly and cumulative fluoride exposure were poor predictors of bone fluoride concentration. The more complex dietary fluoride exposure estimates did not improve predictive capability compared with the simple, spatial models. We conclude that in actively managed wildlife populations, simple, locally validated models can provide estimates of bone fluoride accumulation sufficient to support decision-making.

Marsupial tammar wallaby delivers milk bioactives to altricial pouch young to support lung development

Our research is exploiting the marsupial as a model to understand the signals required for lung development. Marsupials have a unique reproductive strategy, the mother gives birth to altricial neonate with an immature lung and the changes in milk composition during lactation in marsupials appears to provide bioactives that can regulate diverse aspects of lung development, including branching morphogenesis, cell proliferation and cell differentiation. These effects are seen with milk collected between 25 and 100days postpartum. To better understand the temporal effects of milk composition on postnatal lung development we used a cross-fostering technique to restrict the tammar pouch young to milk composition not extending beyond day 25 for 45days of its early postnatal life. These particular time points were selected as our previous study showed that milk protein collected prior to ~day 25 had no developmental effect on mouse embryonic lungs in culture. The comparative analysis of the foster group and control young at day 45 postpartum demonstrated that foster pouch young had significantly reduced lung size. The lungs in fostered young were comprised of large intermediate tissue, had a reduced size of airway lumen and a higher percentage of parenchymal tissue. In addition, expression of marker genes for lung development (BMP4, WNT11, AQP-4, HOPX and SPB) were significantly reduced in lungs from fostered young. Further, to identify the potential bioactive expressed by mammary gland that may have developmental effect on pouch young lungs, we performed proteomics analysis on tammar milk through mass-spectrometry and listed the potential bioactives (PDGF, IGFBP5, IGFBPL1 and EGFL6) secreted in milk that may be involved in regulating pouch young lung development. The data suggest that postnatal lung development in the tammar young is most likely regulated by maternal signalling factors supplied through milk.

Reconstructing temporal variation of fluoride uptake in eastern grey kangaroos (Macropus giganteus) from a high-fluoride area by analysis of fluoride distribution in dentine

Trace element profiling in the incrementally formed dentine of mammalian teeth can be applied to reconstruct temporal variation of incorporation of these elements into the tissue. Using an electron microprobe, this study analysed fluoride distribution in dentine of first and third mandibular molars of free-ranging eastern grey kangaroos inhabiting a high-fluoride area, to assess temporal variation in fluoride uptake of the animals. Fluoride content in the early-formed dentine of first molars was significantly lower than in the late-formed dentine of these teeth, and was also lower than in both, the early and the late-formed dentine of third molars. As early dentine formation in M1 takes place prior to weaning, this finding indicates a lower dentinal fluoride uptake during the pre-weaning compared to the post-weaning period. This is hypothetically attributed to the action of a partial barrier to fluoride transfer from blood to milk in lactating females and a low bioavailability of fluoride ingested together with milk. Another factor contributing to lower plasma fluoride levels in juveniles compared to adults is the rapid clearance of fluoride from blood plasma in the former due to their intense skeletal growth. The combined action of these mechanisms is considered to explain why in kangaroos from high-fluoride areas, the (early-formed) first molars are not affected by dental fluorosis while the (later-formed) third and fourth molars regularly exhibit marked to severe fluorotic lesions.

The extracellular matrix regulates MaeuCath1a gene expression

We have previously shown that the gene for MaeuCath1, a cathelicidin secreted in wallaby milk is alternately spliced into two variants, MaeuCath1a and MaeuCath1b which are temporally regulated in order to provide antimicrobial protection to the newborn and stimulate mammary growth, respectively. The current study investigated the extracellular matrix (ECM) for its regulatory role in MaeuCath1 gene expression. Reverse transcription qPCR using RNA isolated from mammary epithelial cells (WallMEC) cultured on ECM showed that ECM regulates MaeuCath1a gene expression in a lactation phase-dependent manner. Luciferase reporter-based assays and in silico analysis of deletion fragments of the 2245bp sequence upstream of the translation start site identified ECM-dependent positive regulatory activity in the -709 to -15 region and repressor activity in the -919 to -710 region. Electrophoretic Gel Mobility Shift Assays (EMSA) using nuclear extract from ECM-treated WallMEC showed differential band shift in the -839 to -710 region.

Maturation of the growth axis in marsupials occurs gradually during post-natal life and over an equivalent developmental stage relative to eutherian species

The separation of a nutrition-responsive insulin-like growth factor (IGF) system and a growth hormone (GH) responsive IGF system to control pre- and post-natal growth of developing mammals may originate from the constraints imposed by intra-uterine development. In eutherian species that deliver relatively precocial young, maturation of the GH regulatory system is coincident with the time of birth. We measured the hepatic expression of the four key growth axis genes GH-receptor, IGF-1 and -2, and IGFBBP-3, and plasma protein concentrations of IGF-1 from late fetal life through to adult stages of a marsupial, the tammar wallaby. The data clearly show that maturation of GH-regulated growth in marsupials occurs gradually over the course of post-natal life at an equivalent developmental stage to that of precocial eutherian mammals. This suggests that the timing of GH-regulated growth in marsupials is not related to parturition but instead to the relative developmental stage.

Bone fluoride concentrations of eastern grey kangaroos (Macropus giganteus) resident near an aluminium smelter in south-eastern Australia

Lesions of skeletal and dental fluorosis have been described recently in eastern grey kangaroos (Macropus giganteus). The present study further examined the epidemiology of skeletal fluorosis in this species. Bone fluoride concentrations were obtained from a range of skeletal sites of animals from a high (Portland Aluminium) and a low (Cape Bridgewater) fluoride environment in Victoria, Australia. Age, but not sex, affected the mean bone fluoride concentration of kangaroos. For a given age, bone fluoride concentrations were significantly higher in kangaroos from Portland than Cape Bridgewater. Concentrations varied between skeletal sites examined, with samples containing cancellous bone having higher fluoride concentrations than those containing only cortical bone.

Sub-cellular localisation of alkaline phosphatase activity in the cytoplasm of tammar wallaby (Macropus eugenii) neutrophils and eosinophils

Alkaline phosphatase (ALP) has been used in studies of neutrophil morphology and function as a marker for identifying different granule populations. In human neutrophils, ALP is found within secretory vesicles, a rapidly mobilisable vesicle population important for upregulating membrane receptors during early activation. Intra-cellular ALP activity in the heterophils of rabbits and guinea pigs, in contrast, is found only in secondary granules. The neutrophils and eosinophils of tammar wallabies (Macropus eugenii) have previously been reported to contain large amounts of ALP activity when stained using routine cytochemical techniques. To define the subcellular location of ALP in this species, cell suspensions were examined using cerium chloride cytochemistry and transmission electron microscopy (TEM). ALP was found in 2 distinct cytoplasmic compartments. One compartment displayed morphology consistent with a subpopulation of secondary granules while a second tubulo-vesicular population appeared similar to the secretory vesicles of human neutrophils. Thin tubular vesicles containing ALP were also identified within the cytoplasm of tammar wallaby eosinophils. Large numbers of ALP-containing vesicles have not been recognised previously in eosinophils and this may represent a novel cytoplasmic compartment. In both cell types, ALP-containing structures showed alteration in morphology following stimulation with N-formyl-Met-Leu-Phe (fMLP) and PMA.

Lens proteome map and alpha-crystallin profile of the catfish Rita rita

Crystallins are a diverse group of proteins that constitute nearly 90% of the total soluble proteins of the vertebrate eye lens and these tightly packed crystallins are responsible for transparency of the lens. These proteins have been studied in different model and non-model species for understanding the modifications they undergo with ageing that lead to cataract, a disease of protein aggregation. In the present investigation, we studied the lens crystallin profile of the tropical freshwater catfish Rita rita. Profiles of lens crystallins were analyzed and crystallin proteome maps of Rita rita were generated for the first time. alphaA-crystallins, member of the alpha-crystallin family, which are molecular chaperons and play crucial role in maintaining lens transparency were identified by 1- and 2-D immunoblot analysis with anti-alphaA-crystallin antibody. Two protein bands of 19-20 kDa were identified as alphaA-crystallins on 1-D immunoblots and these bands separated into 10 discrete spots on 2-D immunoblot. However, anti-alphaB-crystallin and antiphospho-alphaB-crystallin antibodies were not able to detect any immunoreactive bands on 1- and 2-D immunoblots, indicating alphaB-crystallin was either absent or present in extremely low concentration in Rita rita lens. Thus, Rita rita alpha-crystallins are more like that of the catfish Clarias batrachus and the mammal kangaroo in its alphaA- and alphaB-crystallin content (contain low amount from 5-9% of alphaB-crystallin) and unlike the dogfish, zebrafish, human, bovine and mouse alpha-crystallins (contain higher amount of alphaB-crystallin from 25% in mouse and bovine to 85% in dogfish). Results of the present study can be the baseline information for stimulating further investigation on Rita rita lens crystallins for comparative lens proteomics. Comparing and contrasting the alpha-crystallins of the dogfish and Rita rita may provide valuable information on the functional attributes of alphaA- and alphaB-isoforms, as they are at the two extremes in terms of alphaA-and alphaB-crystallin content.

Pulmonary cytochrome P450 enzymes belonging to the CYP4B subfamily from an Australian marsupial, the tammar wallaby (Macropus eugenii)

Cytochromes P450 (CYPs) are critically important in the oxidative metabolism of a diverse array of xenobiotics and endogenous substrates. We have previously reported the cloning and characterisation of the koala CYP4A15, the first reported member of the CYP4 family from marsupials, and have demonstrated important species differences in CYP4A activity and tissue expression. In the present study, the cloning of CYP4B1 in the wallaby (Macropus eugenii) and their expression across marsupials is described. Rabbit anti-mouse CYP4B1 antibody detected immunoreactive proteins in lung and liver microsomes from all test marsupials, with relative weak signal detected from the koala, suggesting a species-specific expression. Microsomal 2-aminofluorene bio-activation (a CYP4B1 marker) in wallaby lung was comparable to that of rabbit, with significant higher activities detected in wallaby liver and kidneys compared to rabbit. A 1548bp wallaby lung CYP4B complete cDNA, designated CYP4B1, which encodes a protein of 510 amino acids and shares 72% nucleotide and 69% amino acid sequence identity to human CYP4B1, was cloned by polymerase chain reaction approaches. The results demonstrate the presence of wallaby CYP4B1 that shares several common features with other published CYP4Bs; however the wallaby CYP4B1 cDNA contains four extra amino acid residues at the NH₂-terminal, a fundamentally conserved transmembrane anchor of all eukaryote CYPs.

Stress in an Island kangaroo? The Barrow Island euro, Macropus robustus isabellinus

Selected physiological parameters were monitored over a 4-year period in the Barrow Island euro, Macropus robustus isabellinus, in Western Australia in a study of this species' homeostatic capabilities in an extremely arid habitat where individuals are exposed to high environmental temperatures and a lack of free water for much of the year. Evidence was found of a significant change in the animal's milieu intérieur on only one occasion on Barrow Island: in November 1994, following a protracted 8-month drought. Euros had significantly elevated levels of plasma osmolality, cortisol, anti-diuretic hormone (lysine vasopressin - LVP), and a reduced eosinophil count. This suggests that these animals may have been dehydrated, despite the operation of appropriate physiological responses to water deprivation. Lower eosinophil counts also suggest that immune function may have been suppressed as a result of the elevated corticosteroid levels. Comparisons with the mainland sub-species of the euro revealed the presence of a non-generative normocytic hypochromic anaemia in Barrow Island euros that potentially compromises their aerobic capacity. Barrow Island is Australia's most important A Class Reserve, harbouring 8 species of marsupials, 4 of which are now extinct, or virtually so, on the adjacent mainland. This study reveals the remarkable effectiveness of the euro's homeostatic capacities, however, its future conservation depends on ensuring that potential stress due to declining water availability and environmental change is avoided.

Early onset of ghrelin production in a marsupial

Ghrelin regulates appetite in mammals and can stimulate growth hormone (GH) release from the pituitary. In rats and humans, ghrelin cells appear in the stomach during late fetal life. Nevertheless, the role of ghrelin in early mammalian development is not well understood. Marsupials deliver highly altricial young that weigh less than 1g so they must feed and digest milk at a comparatively immature stage of development. Since they complete their growth and differentiation while in the pouch, they are accessible models in which to determine the time course of ghrelin production during development. We examined the distribution of gastric ghrelin cells, plasma ghrelin concentrations and pituitary expression of the ghrelin receptor (ghsr-1alpha) and GH in the tammar wallaby, Macropus eugenii. There were ghrelin immunopositive cells in the developing mesenchyme of the stomach from day 10 post partum (pp) to day 150pp. Subsequently ghrelin protein in the fore-stomach declined and was absent by day 250pp but remained in the gastric cells of the hind-stomach. Ghrelin was detected in the developing pancreas from day 10pp but was absent by day 150pp and in the adult. Pituitary ghsr-1alpha expression and plasma concentrations of ghrelin increased significantly up to day 70-120pp while GH expression was also elevated, declining with GH to reach adult levels by day 180pp. These results demonstrate an early onset of gastric ghrelin expression in the tammar in concert with a functional stomach at a relatively earlier stage than that of developmentally more mature eutherian young.

A longitudinal study of the protein components of marsupial milk from birth to weaning in the tammar wallaby (Macropus eugenii)

The major milk whey proteins of the tammar wallaby (Macropus eugenii) have been identified over the total period of lactation using proteomic analysis techniques comprising two-dimensional electrophoresis, comparative image analysis, matrix assisted laser desorption ionisation mass spectrometry (MALDI MS), de novo peptide sequencing and cross species protein matching. Samples were collected at the periods coinciding with major milestones of immunological development in the developing marsupial and in the four phases of milk production, specifically, Days 0, 5 (Phase 1); 27, 68 (Phase 2A); 137, 174 (Phase 2B) and 250 (Phase 3). Major changes in the protein content of marsupial milk whey correlated with the changing needs of the pouch young for stages in growth and development. We have shown that the levels of milk whey proteins vary with the developmental stage of the young animal, with a high number of proteins detected in early and late milk compared with the middle phases of lactation. Over 41 proteins were confidently identified, of which most had known roles in immunological protection. Proteins providing immunological protection across the lactation period included transferrin, beta2 microglobulin, haptoglobulin and a 78kDa glucose regulated protein. Immunoglobulin IgJ linker chain and a known antimicrobial cathelicidin, were only detected for the first 100-137 days, after which time Complement B factor was found to be present (Phase 2B). The changes which correlated with development and growth in the pouch young were reflected by the presence of proteins such as an alpha-fetoprotein like protein and clusterin found in early milk (Phase 1-2A) and two unknown proteins which were apparent in very early mammary gland secretions. This is the first comprehensive proteomic study of the major whey proteins of a marsupial across the entire period of lactation and provides fundamental data on proteins secreted by the mammary gland during key stages of immunological development of the young animal.

Comparative water metabolism of Barrow Island macropodid marsupials: hormonal versus behavioural-dependent mechanisms of body water conservation

Seasonal variations in rates of water turnover were measured over a 7-year period in four species of macropodid marsupials (Lagorchestes conspicillatus, Bettongia lesueur, Petrogale lateralis and Macropus robustus isabellinus), on Barrow Island off the arid Pilbara coast of Western Australia. These ranged from over 100 mL kg(-0.82) d(-1) in wet seasons to as low as 28.2 mL kg(-0.82) d(-1) in dry seasons in the Spectacled hare wallaby, L. conspicillatus. Plasma osmolality increased significantly in both Barrow Island euros (M. robustus isabellinus) and Spectacled hare wallabies in November 1994, in the driest year yet recorded on the island. In contrast, there was no change in plasma osmolality of the other two species (Black-footed rock wallaby, P. lateralis and Lesueur's burrowing bettong, B. lesueur) that exploit cool and humid thermal refugia such as caves and underground warrens to avoid diurnal temperature extremes. Plasma levels of the marsupial antidiuretic hormone (ADH), lysine vasopressin (LVP), were for the most part below the detectable limit of the assay of 0.41 pg mL(-1) in rock wallabies and bettongs, but reached high levels of 16.7+/-4.6 pg mL(-1) and 20.25+/-5.1 pg mL(-1) in euros and hare wallabies, respectively, in dry seasons. LVP levels were positively correlated with plasma osmolality in both euros and hare wallabies, and negatively correlated with total body water content in euros, supporting its rôle as an antidiuretic hormone in these two species. The study highlights the importance of environmental features, such as caves and underground warrens, which are critical for the long-term survival of endangered species such as the Black-footed rock wallaby and the Lesueur's bettong. These species appear to lack ADH-controlled renal systems for the conservation of body water and are thus dependent on behavioural strategies for the maintenance of fluid homeostasis in arid environments.

Clinical implications of androgen synthesis via 5alpha-reduced precursors

During embryogenesis, the male external genitalia are formed by the action of the potent androgen, dihydrotestosterone (DHT). DHT is produced in human genital skin and prostate from testosterone via the action of 5alpha-reductase type 2. The biological relevance of this pathway to DHT is evidenced by patients with mutations in the gene encoding 5alpha-reductase type 2, which causes severely undermasculinized external genitalia in genetic males. In contrast, this paradigm of androgen physiology does not explain some clinical observations, such as the differences noted in the virilization of females with various congenital adrenal hyperplasias. An alternate pathway to DHT was elucidated in the tammar wallaby pouch young, and studies in knockout mice showed that this pathway uses 5alpha-reductase type 1 to convert 17-hydroxyprogesterone to 5alpha-reduced androgen precursors. Flux via the alternate or 'backdoor' pathway has been implicated in human diseases such as P450 oxidoreductase deficiency, polycystic ovarian disease, and congenital adrenal hyperplasia. A better understanding of the 5alpha-reduced or 'backdoor'pathway to DHT in human disorders of androgen excess will provide pharmacotherapy opportunities to effectively treat androgen excess in females.

Characterization and expression of Peroxiredoxin 1 in the neonatal tammar wallaby (Macropus eugenii)

Peroxiredoxin 1 (PRDX1) is a ubiquitously expressed antioxidant with vital roles in basal metabolic functions. In addition PRDX1 is involved in cell differentiation and proliferation, apoptosis and innate immunity. In this study, we have characterized PRDX1 from the tammar wallaby (Macropus eugenii). Tammar PRDX1 has high conservation of functional residues and motifs, and demonstrates a close homology with eutherian and vertebrate orthologues. Stimulation of adult tammar leukocytes with lipopolysaccharide and lipoteichoic acid suggests a role for PRDX1 in innate immune defences. PRDX1 expression in the organs of tammar pouch young was mildly elevated early in life possibly reflecting its role in basal metabolic processes. Later increases in PRDX1 expression correlated with functional maturation of several immune organs or with preparation for increased oxidative stress of emergence. The findings of the study are reflections of the complex integrated roles that PRDX1 has in regulation of oxidative stress, apoptosis, cell differentiation and proliferation, and innate immunity.

Myosin isoforms and fibre types in limb muscles of Australian marsupials: adaptations to hopping and non-hopping locomotion

Using immunohistochemistry and SDS-PAGE, we studied the myosin heavy chain (MyHC) composition and fibre type distribution of hindlimb muscles of hopping and non-hopping Australian marsupials. We showed that hindlimb muscles of a bandicoot (Isoodon obesulus, order Peramelomorphia) and a small macropodoid, the brushtail bettong (Bettongia penicillata) expressed four MyHCs, slow, 2a, 2x and 2b, and had the corresponding fibre types as other macropods reported earlier. The fastest and most powerful 2b fibres predominated in most bettong hindlimb muscles, but were absent in the gastrocnemius and the flexor digitorum profundus, which are involved in elastic strain energy saving during hopping. The gastrocnemius of four large macropodids also showed little or no 2b MyHC, whereas this isoform was abundant in their tibialis anterior, which is not involved in elastic energy saving. In contrast, 2b MyHC predominated in the gastrocnemius of four non-hopping marsupials. These results suggest that absence of 2b fibres may be a general feature of macropodoid muscles involved in elastic energy saving. Large eutherians except llamas and pigs also have no 2b fibres. We hypothesize that 2x and 2a fibres perform better than 2b fibres in the storage and recovery of kinetic energy during locomotion in both marsupials and eutherians.

Developmental changes in ventricular myosin isoenzymes of the tammar wallaby

Ventricular myosin in eutherian mammals undergoes a perinatal change in response to a sharp rise in thyroid hormone levels during development. In this investigation, changes in ventricular myosin heavy chains (MyHCs) of the tammar wallaby (Macropus eugenii) from early pouch life to adulthood were analysed using native gel electrophoresis, SDS-PAGE and western blotting. Adult wallaby ventricle showed three myosin isoenzymes, V(1), V(2) and V(3); western blots using specific anti-alpha-MyHC and anti-beta-MyHC antibodies showed their MyHC compositions to be alphaalpha, alphabeta and betabeta, respectively. Ventricular muscle in early pouch joeys expressed predominantly beta-MyHC. Up to 200 days, the time of initial pouch exit, alpha-MyHC content was around 5%. Thereafter, there was a sharp increase of alpha-MyHC expression to 35% by 242 days of age, eventually falling back to 23% in the adult. These changes correlate with known surges in plasma levels of thyroid hormones around pouch exit. The results suggest that ventricular myosins in a marsupial mammal also undergo a developmental change, and that marsupial ventricular myosins are thyroid responsive as in eutherians. The increased alpha-MyHC expression empowers the heart to meet the enhanced cardiovascular demands of out-of-pouch activity and the thermogenic action of thyroid hormones.

Endogenous Nitrogen Excretion by Red Kangaroos (Macropus rufus): Effects of Animal Age and Forage Quality

Red kangaroos (Macropus rufus) are large (>20 kg) herbivorous marsupials common to arid and semiarid Australia. The population dynamics of red kangaroos are linked with environmental factors, operating largely through juvenile survival. A crucial period is the young-at-foot (YAF) stage, when juveniles have permanently left the mother's pouch but still take milk from a teat in the pouch. Forage quantity and quality have been implicated in drought-related mortalities of juvenile kangaroos. Here we compared how forage quality affected nitrogen (N) intake and excretion by YAF, weaned, and mature, nonlactating female red kangaroos. On high-quality forage (chopped lucerne hay, Medicago sativa) low in neutral-detergent fiber (43%+/-1%) and high in N (2.9%+/-0.1%), YAF and weaned kangaroos had ideal growth rates and retained 460-570 mg dietary N kg(-0.75) d(-1). But on poor-quality forage (chopped oaten hay, Avena sativa) high in neutral-detergent fiber (64%+/-1%) and low in N (0.9%+/-0.1%), YAF and weaned kangaroos could not sustain growth and were in negative N balance at -103+/-26 mg and -57+/-31 mg N kg(-0.75) d(-1), respectively. Notably, the YAF kangaroos excreted 64% of their truly digestible N intake from forage as nondietary fecal N (NDFN). By weaning age, the situation had improved, but the juveniles still lost 40% of their truly digestible N intake as NDFN compared with only 30% by the mature females. Our findings support field observations that forage quality, and not just quantity, is a major factor affecting the mortality of juvenile red kangaroos during drought.

Cyto- and chemoarchitecture of the monotreme olfactory tubercle

This study was undertaken to determine whether the olfactory tubercles of two monotremes (platypus and echidna) showed cyto- or chemoarchitectural differences from the tubercles of therian mammals. Nissl staining was applied in conjunction with enzyme reactivity for NADPH diaphorase and acetylcholinesterase, and immunoreactivity for calcium binding proteins (parvalbumin, calbindin and calretinin) and tyrosine hydroxylase (echidna only). Golgi impregnations of the tubercle were also available for the echidna. The olfactory tubercle is a poorly laminated structure in the echidna, despite the pronounced development of other components of the echidna olfactory system, and the dense cell layer of the olfactory tubercle was found to be discontinuous and irregular. Granule cell clusters (islands of Calleja) were present, but were small, poorly defined and did not show the intense NADPH diaphorase activity seen in marsupial and placental mammals. A putative small island of Calleja magna was seen in only one echidna out of four. In Golgi impregnations of the echidna olfactory tubercle, the most abundant neuron type was a medium-sized densely spined neuron similar to that seen in the olfactory tubercle of some therians. Large spine-poor neurons were also seen in the polymorphic layer. In the platypus, the olfactory tubercle was very small but showed more pronounced lamination than the echidna, although no granule cell clusters were seen. In both monotremes, the development of the olfactory tubercle was poor relative to other components of the olfactory system (bulb and piriform cortex). The small olfactory tubercle region in the platypus is consistent with poor olfaction in that aquatic mammal, but the tubercle in the echidna is more like that of a microsmatic mammal than other placentals occupying a similar niche (e.g., insectivores).

Postnatal development of orexin-A and orexin-B like immunoreactivities in the Eastern grey kangaroo (Macropus giganteus) hypothalamus

The Eastern grey kangaroo (Macropus giganteus) is a marsupial, which is born in an extremely undeveloped state and has a long suckling period in the mother's pouch. In the present study, we examined the immunoreactivities of orexin-A (OXA) and orexin-B (OXB) in the hypothalamus of the Eastern grey kangaroo during the preweaning period, postweaning period and adulthood. In the preweaning period, only a few OXA- and OXB-like immunoreactive (LI) neurons and fibers were present and the intensity of staining was very weak. In the postweaning period, there was a pronounced increase in the numbers of OXA- and OXB-LI neurons and fibers and the intensity of the immunoreactivity was considerably stronger in comparison to the preweaning period. In the adult, the numbers of OXA- and OXB-LI neurons and fibers appeared to be slightly increased and the intensity was slightly stronger in comparison to the postweaning period. At all time periods, the distributions of OXA- and OXB-LI neurons was similar. The postnatal development of hypothalamic orexin neurons may be associated with developmental changes, including feeding behavior.

Cyto- and Chemoarchitecture of the Cortex of the Tammar Wallaby (Macropuseugenii): Areal Organization

We have examined the cyto- and chemoarchitecture of the isocortex of a diprotodontid marsupial, the tammar wallaby (Macropus eugenii), using Nissl staining in combination with enzyme histochemical (acetylcholinesterase - AChE, NADPH-diaphorase - NADPHd, cytochrome oxidase) and immunohistochemical (non-phosphorylated neurofilament - SMI-32) markers. The primary sensory cortex showed distinctive patterns of reactivity in cytochrome oxidase, acetylcholinesterase and NADPH diaphorase. For example, in AChE material, S1 showed a heterogeneous appearance, with regions exhibiting a double layer of AChE activity (layers II and IV) adjacent to poorly reactive regions. In NADPHd preparations, activity in S1 was strongest in layers I to IV although, as in AChE material, there were consistent patches of reduced NADPHd activity which corresponded to poorly reactive regions in the AChE sections. Each of the primary sensory areas of the isocortex showed a different pattern of distribution of SMI-32+ neurons. In V1, SMI-32+ neurons were distributed in two layers (III and V) throughout the tangential extent of that region. In S1, SMI-32+ neurons were concentrated in layer V, but large and discrete patches within S1 had additional SMI-32+ neurons in layer III. In primary auditory cortex there was a dense band of SMI-32+ neurons in layer V, with only occasional labeled pyramidal neurons in layer III. In the secondary sensory areas (V2 and S2) SMI-32+ neurons were either distributed in layers III and V (V2) or solely within layer V (S2). The tangential and laminar distribution of Type I reactive NADPH diaphorase neurons in the tammar wallaby cortex was more like that seen in eutheria than in polyprotodontid metatheria.

Differential expression of mesotocin receptors in the uterus and ovary of the pregnant tammar wallaby

Mesotocin, an oxytocin-like peptide, is released in highest concentrations during parturition in macropodid marsupials. In late pregnant wallabies, uterine sensitivity to mesotocin increases markedly in the myometrium of the gravid uterus. This coincides with a significant increase in myometrial mesotocin receptor concentrations 3–4 days before term. To date, there is no information on mesotocin receptor gene expression in female wallaby reproductive tissues. This study aimed to examine mesotocin receptor gene expression in the uterus and ovaries of pregnant tammar wallabies, and to localise mesotocin receptors within the uterus. An RT-PCR strategy produced a consensus nucleotide sequence of 834 bp, which encoded 278 amino acids of transmembrane domains I to VI. This protein sequence has approximately 80% homology with the bovine and rat oxytocin receptor exon 2 region. Only one mesotocin receptor was detected in the tammar genome. The myometrium and mammary gland both expressed a 4.1 kb mesotocin receptor gene transcript. Myometrial mesotocin receptor gene expression increased on day 22 of the 26-day gestation and was significantly higher in the gravid than the non-gravid uterus in late pregnancy. This pattern of mesotocin receptor gene expression paralleled mesotocin receptor concentrations. Mesotocin binding sites were localised only to the myometrium, the highest densities being observed in the gravid uterus. Finally, this study showed high expression of mesotocin receptors in the corpus luteum. The pattern of luteal mesotocin receptor expression differed from the myometrium, with a decrease in mesotocin receptors occurring on the day of expected births.

Faecal corticosteroid levels as an indicator of well-being in the tammar wallaby, Macropus eugenii

Faecal corticosteroid levels were measured in five female tammar wallabies, Macropus eugenii, at Macquarie University, NSW, Australia, to assess their reliability as indicators of well-being in this species. Animals were challenged with a change in conditions over the course of approximately 1 week, comprising movement from group yards to isolation in individual yards, in order to impose a disturbance to homeostasis ("stress"). Faecal samples were collected in 24-h intervals during the study period and analysed for corticosteroid concentration. The use of enzyme immunoassay for the measurement of corticosteroids in marsupial faecal pellets was validated. We observed a significant increase in faecal corticosteroids upon isolation and movement. Faecal corticosteroids remained above initial levels in all five animals throughout the study period, suggesting that faecal corticosteroid concentrations may be a useful indicator of a change in animal well-being. Faecal corticosteroid levels did not correlate with serum cortisol levels, implying that the use of noninvasive methods in a representative marsupial, the tammar wallaby, has the potential to provide information that is not readily apparent using blood-based protocols. Faecal corticosteroid analysis therefore has the potential for application in monitoring the well-being of captive and managed marsupial populations, as part of an integrated system of measures of animal health and well-being.

CD15 immunoreactivity in the developing brain of a marsupial, the tammar wallaby ( Macropus eugenii)

We have studied the distribution of the CD15 epitope in the developing brain of an Australian diprotodontid metatherian mammal, the tammar wallaby ( Macropus eugenii), using immunohistochemistry in conjunction with hematoxylin and eosin staining. At the time of birth (28 days after conception), CD15 immunoreactivity labeled somata in the primordial plexiform layer of the parietal cortex in a similar position to that seen in the early fetal eutherian brain. CD15 immunoreactivity in the brain of the developing pouch-young wallaby was found to be localized on the surface of radial glia at boundaries between developmentally significant forebrain compartments in a similar distribution to that seen in developing eutherian brain. These were best seen in the developing diencephalon, delineating epithalamus, ventral and dorsal thalamus and hypothalamic anlage, and in the striatum. Immunoreactivity for CD15 identified radial glia marking the lateral migratory stream at the striatopallial boundary, peaking in intensity at P19 to P25. From P37 to P54, CD15 immunoreactivity also demarcated patch compartments in the developing striatum. In contrast, CD15 immunoreactivity in hindbrain structures showed some differences from the temporospatial pattern seen in eutherian brain. These may reflect the relatively early brainstem maturation required for the newborn wallaby to be able to traverse the distance from the maternal genital tract to the pouch. The wallaby provides a convenient model for testing hypotheses concerning the role of CD15 in forebrain development because all events in which CD15 may play a critical role in forebrain morphogenesis occur during pouch life, when the young wallaby is accessible to experimental manipulation.

Comparative analysis of ATRX, a chromatin remodeling protein

The ATRX protein, associated with X-linked alpha-thalassaemia, mental retardation and developmental abnormalities including genital dysgenesis, has been proposed to function as a global transcriptional regulator within a multi-protein complex. However, an understanding of the composition and mechanics of this machinery has remained elusive. We applied inter-specific comparative analysis to identify conserved elements which may be involved in regulating the conformation of chromatin. As part of this study, we cloned and sequenced the entire translatable coding region (7.4 kb) of the ATRX gene from a model marsupial (tammar wallaby, Macropus eugenii). We identify an ATRX ancestral core, conserved between plants, fish and mammals, comprising the cysteine-rich and SWI2/SNF2 helicase-like regions and protein interaction domains. Our data are consistent with the model of the cysteine-rich region as a DNA-binding zinc finger adjacent to a protein-binding (plant homeodomain-like) domain. Alignment of vertebrate ATRX sequences highlights other conserved elements, including a negatively charged mammalian sequence which we propose to be involved in binding of positively charged histone tails.

Steroid-independent regulation of uterine oxytocin receptors

The oxytocin receptor is an important contractile-associated protein, up-regulated at term in the myometrium in many mammalian species. We conducted studies in a novel animal model to challenge the general view that gonadal steroids are a major regulatory factor of uterine oxytocin receptors. Female marsupials have separate uteri and, in monovular species such as the tammar wallaby, the conceptus is present in one uterus whereas the contralateral uterus is empty. A marked increase in myometrial oxytocin receptors occurs only in the gravid uterus. Fetectomy experiments demonstrated that local embryo-derived factors stimulate this gravid uterus-specific increase in oxytocin receptors, and that uterine distension is probably not a key component in this regulatory pathway. Unilateral ovariectomy has no significant effect on uterine oxytocin receptors, emphasizing the impact of the conceptus on oxytocin receptor regulation and the minimal influence of gonadal steroids on parturition in this species. Our data highlight that regulation of uterine oxytocin receptor expression is multifactorial, and does not necessarily rely on gonadal steroids.

Cyclic AMP-dependent tyrosine phosphorylation in tammar wallaby (Macropus eugenii) spermatozoa

Despite considerable advances in our understanding of the molecular mechanisms regulating eutherian sperm function, there is a paucity of such knowledge for the Metatheria. In eutherian spermatozoa, the attainment of functional competence is associated with a redox-regulated, cAMP-mediated tyrosine phosphorylation cascade, activated during capacitation. In this report we investigate whether tammar wallaby (Macropus eugenii) spermatozoa possess a similar signal transduction pathway. Western blot analysis of phosphotyrosine expression in caudal and ejaculated populations of tammar spermatozoa revealed that elevation of intracellular cAMP levels, but not exposure to oxidants or NADPH, induced a dramatic increase in the overall level of tyrosine phosphorylation. Washed, ejaculated spermatozoa exhibited more pronounced increases in tyrosine phosphorylation than unwashed sperm populations. Localisation of tyrosine phosphorylation by immunocytochemistry showed that phosphotyrosine residues were principally located along the tammar sperm flagellum, and occasionally at a small region of the sperm head, adjacent to the acrosome. Associated with the tyrosine phosphorylation of tammar spermatozoa, was a change in sperm head conformation to a T-shaped orientation, further implying the importance of these pathways to normal tammar sperm function. Redox activity, as detected by lucigenin-dependent chemiluminescence, was stimulated by NADPH in caudal sperm preparations but not ejaculated spermatozoa. However, neither sperm population responded to treatment with NADPH with changes in intracellular cAMP or tyrosine phosphorylation. In conclusion, tammar spermatozoa possess the same cAMP-mediated, tyrosine phosphorylation-dependent signal transduction cascade that has been associated with capacitation in eutherian spermatozoa. However in Metatherian spermatozoa we could find no evidence that this pathway was redox regulated.

Comparison of glucose metabolism in in vivo- and in vitro-matured tammar wallaby oocytes and its relationship to developmental potential following intracytoplasmic sperm injection

Although marsupial oocytes undergo nuclear maturation in vitro, there is, at present, no indication of their developmental potential, largely owing to the lack of in vitro fertilisation and related technologies for marsupials. Glucose metabolism has proven a useful indicator of oocyte cytoplasmic maturation and developmental potential in several eutherian species. Therefore, the aims of the present study were to compare: (1) the rates of glycolysis and glucose oxidation in immature, in vitro-matured and in vivo-matured tammar wallaby oocytes; and (2) the metabolic rate of individual oocytes with their ability to form pronuclei after intracytoplasmic sperm injection. The rates of glycolysis measured in immature (2.18 pmol oocyte–1 h–1), in vitro-matured (0.93 pmol oocyte–1 h–1) and in vivo-matured tammar wallaby oocytes (0.54 pmol oocyte–1 h–1) were within a similar range to values obtained in eutherian species. However, unlike the trend observed in eutherian oocytes, the glycolytic rate was significantly higher in immature oocytes compared with either in vivo- or in vitro-matured oocytes (P < 0.001) and significantly higher in in vitro-matured oocytes compared with in vivo-matured oocytes (P < 0.001). No relationship was identified between glucose metabolism and the developmental capacity of oocytes after intracytoplasmic sperm injection when assessed after 17–19 h. Oocytes that became fertilised (two pronuclei) or activated (one or more pronucleus) were not distinguished from others by their metabolic rates. Longer culture after intracytoplasmic sperm injection (e.g. blastocyst stage) may show oocyte glucose metabolism to be predictive of developmental potential; however, culture to the single-cell stage did not reveal any significant differences in normally developing embryos.

Developmental expression and subcellular localization of wallaby gonadotropin-releasing hormone receptor and its splice variants

The developmental expression of gonadotropin-releasing hormone receptor (GnRH-R) and its splice variants was examined in the gonads of tammar wallaby pouch young in order to elucidate the functional role of GnRH-R in the developing testis and ovary. Wallaby GnRH-R, like eutherian GnRH-Rs, contains three exons and two introns. In the present study, the transcripts of two splice variants (GnRH-R Delta 1 and GnRH-R Delta 2) were cloned from the pituitary. GnRH-R Delta 1 contained a 291 bp deletion from nucleotide positions 232 to 522 within exon 1. This transcript appears to be distinctive in the wallaby and has not been reported in other species. GnRH-R Delta 2 contained a 220 bp deletion from nucleotide positions 523 to 742, corresponding to exon 2. We examined the subcellular localization of the wild type GnRH-R and its splice variants with confocal microscopy, showing that both the wild type receptor and the splice variants were membrane-associated molecules. The different pattern of expression of the wild type receptor and the variants transcripts found in adult and neonatal tissues suggests a specific developmental regulation of the GnRH-R Delta 2 transcript. In addition, the developmental expression of the GnRH-R and GnRH-R Delta 1 transcripts showed a possible association with key physiological events during gonadal development in the wallaby pouch young, suggesting that GnRH-R may be involved in the regulation of early development in the testis and ovary.

A survey of type I interferons from a marsupial and monotreme: implications for the evolution of the type I interferon gene family in mammals

Sequence data for type I interferons (IFNs) have previously only been available for birds and eutherian ('placental') mammals, but not for the other two groups of extant mammals, the marsupials and monotremes. This has left a large gap in our knowledge of the evolutionary and functional relationships of what is a complex gene family in eutherians. In this study, a PCR-based survey of type I IFN genes from a marsupial, the tammar wallaby (Macropus eugenii), and a monotreme, the short-beaked echidna (Tachyglossus aculeatus), was conducted. Along with Southern blot and phylogenetic analysis, this revealed a large number of type I IFN genes for the wallaby, rivalling that of eutherians, but relatively few type I IFN genes in the echidna. The wallaby genes include both IFNA and IFNB orthologues, indicating that the gene duplication leading to these subtypes occurred prior to the divergence of marsupials and eutherians some 130 million years ago. Results from this study support the idea that the expansion of type I IFN gene complexity in mammals coincides with a concomitant expansion in the functionality of these molecules. For example, this expansion in complexity may have, at least partially, facilitated the evolution of viviparity in marsupials and eutherians. Other evolutionary aspects of these sequences are also discussed.

5alpha-androstane-3alpha,17beta-diol is formed in tammar wallaby pouch young testes by a pathway involving 5alpha-pregnane-3alpha,17alpha-diol-20-one as a key intermediate

The synthetic pathway by which 5alpha-androstane-3alpha,17beta-diol (5alpha-adiol) is formed in the testes of tammar wallaby pouch young was investigated by incubating testes from d 20-40 males with various radioactive precursors and analyzing the metabolites by thin-layer chromatography and HPLC. [(3)H]Progesterone was converted to 17-hydroxyprogesterone, which was converted to 5alpha-adiol by two pathways: One involves the formation of testosterone and dihydrotestosterone as intermediates, and the other involves formation of 5alpha-pregnane-3alpha,17alpha-diol-20-one (5alpha-pdiol) and androsterone as intermediates. Formation of 5alpha-adiol from both [(3)H]testosterone and [(3)H]progesterone was blocked by the 5alpha-reductase inhibitor 4MA. The addition of nonradioactive 5alpha-pdiol blocked the conversion of [(3)H]progesterone to 5alpha-adiol, and [(3)H]5alpha-pdiol was efficiently converted to androsterone and 5alpha-adiol. We conclude that expression of steroid 5alpha-reductase in the developing wallaby testes allows formation of 5alpha-reduced androgens by a pathway that does not involve testosterone as an intermediate.

Enhanced repair of cyclobutane pyrimidine dimers and improved UV resistance in photolyase transgenic mice

During evolution, placental mammals appear to have lost cyclobutane pyrimidine dimer (CPD) photolyase, an enzyme that efficiently removes UV-induced CPDs from DNA in a light-dependent manner. As a consequence, they have to rely solely on the more complex, and for this lesion less efficient, nucleotide excision repair pathway. To assess the contribution of poor repair of CPDs to various biological effects of UV, we generated mice expressing a marsupial CPD photolyase transgene. Expression from the ubiquitous beta-actin promoter allowed rapid repair of CPDs in epidermis and dermis. UV-exposed cultured dermal fibroblasts from these mice displayed superior survival when treated with photoreactivating light. Moreover, photoreactivation of CPDs in intact skin dramatically reduced acute UV effects like erythema (sunburn), hyperplasia and apoptosis. Mice expressing the photolyase from keratin 14 promoter photo reactivate CPDs in basal and early differentiating keratinocytes only. Strikingly, in these animals, the anti-apoptotic effect appears to extend to other skin compartments, suggesting the presence of intercellular apoptotic signals. Thus, providing mice with CPD photolyase significantly improves repair and uncovers the biological effects of CPD lesions.

The development of the gubernaculum and inguinal closure in the marsupial Macropus eugenii

This study reports the developmental anatomy of testicular descent and inguinal closure of the tammar wallaby (Macropus eugenii) from birth to maturity. In females the ovary migrated caudally between days 10 and 20 after birth. The gubernaculum differentiates into the round ligament in the abdomen and extra-abdominally as the ilio-marsupialis muscle of the mammary glands. In males the testes migrated to the internal inguinal ring by day 20 post partum (pp), coinciding with the enlargement of the gubernaculum, and from the internal inguinal ring to the scrotum between days 20 and 65 pp. During descent there was an increase in the hyaluronic acid concentration in cells of the gubernaculum and scrotum. Development of the cremaster muscle began by day 10 pp on the periphery of the gubernaculum and its basic structure was completed by day 60 pp. After descent the inguinal canal closed between days 50 and 60 pp, but a small irregular lumen persisted, somewhat similar to that seen in the congenital scrotal hydrocoele of humans. Tammars have a hopping mode of locomotion and, like humans, are essentially bipedal. We suggest that inguinal closure evolved in these two species because their upright posture may otherwise lead to a high incidence of inguinal hernias.

Up-regulation of mesotocin receptors in the tammar wallaby myometrium is pregnancy-specific and independent of estrogen

The oxytocin-like peptide of most Australian marsupials is mesotocin, which stimulates uterine contractions and is important for normal birth in the tammar wallaby. Female marsupials have two uteri and, in monovular species such as the tammar, one uterus is gravid with a single fetus, whereas the contralateral uterus is nongravid. A significant increase in myometrial mesotocin receptor concentrations occurs only in the gravid uterus on Day 23 of the 26-day gestation. This study examined whether or not mesotocin receptors are present in the myometrium and are up-regulated at the equivalent stage of the luteal phase in unmated tammars. In contrast to the marked increase in mesotocin receptor mRNA and protein concentrations in the myometrium of the gravid uterus during pregnancy, receptors did not increase in the unmated animals. There were also no significant differences between the two uteri, except on Day 27. Plasma profiles of peripheral estradiol-17beta and progesterone did not differ significantly between pregnant and nonpregnant cycles. However, progesterone concentrations were significantly lower on Day 1 postpartum compared with Day 27 of the nonpregnant cycle. In pregnant tammars, the molar ratio of circulating estradiol-17beta to progesterone increased significantly between Day 25 of gestation and 1 day postpartum, but was not correlated with an increase in mesotocin receptor concentrations in either uterus. The data confirm that a local fetal influence is more important than systemic factors, such as estrogen, in the regulation of uterine mesotocin receptors in the tammar wallaby.

Comparison of the positive and negative ion electrospray mass spectra of some small peptides containing pyroglutamate

The positive ion electrospray mass spectra of [M+H](+) and the negative ion electrospray mass spectra of [M-H](-) ions of selected pyroglutamate containing peptides both provide sequencing data. The negative ion spectra show the normal alpha and beta backbone cleavages in addition to delta and gamma backbone cleavages initiated by the side chains of Glu and Phe residues. For example, the [M-H](-) ion of pGlu Pro Gln Val Phe Val-NH(2) shows delta and gamma peaks at m/z 224 (delta, Gln3), 244 (gamma, Phe4), 451 (delta, Phe4), 471 (gamma, Gln3). Some of the negative ion spectra show unusual grandaughter peaks that originate by alpha and beta, or delta and gamma backbone cleavages of a beta(1) cleavage ion.

Developmental profile of thyroid hormone distributor proteins in a marsupial, the tammar wallaby Macropus eugenii

The ontogeny of thyroxine distributor proteins in serum of the marsupial Macropus eugenii (tammar wallaby) was investigated from day 3 after birth until adulthood. The thyroxine distributor proteins in the serum of adult M. eugenii are transthyretin and albumin. Northern analysis of RNA prepared from liver showed that transthyretin mRNA levels were initially high (about adult levels at the earliest ages tested), reduced to about 60% adult levels (between days 50 and 150), and then steadily increased to adult levels (by days 200 to 250). Albumin mRNA levels were initially about 50% of adult levels (day 3) and steadily rose to 90% of adult levels by days 175 to 220. A globulin, "wallaby thyroxine-binding protein" (W-TBP), bound [(125)I]thyroxine from day 3 until about day 200. Of the protein-bound thyroxine, the proportion bound by transthyretin had a similar pattern to the transthyretin mRNA levels. From day 26 onward, about half of the protein-bound thyroxine was bound to albumin. On day 3, less than 10% was bound to W-TBP and the proportion steadily increased to a maximum of about 46% by about day 120 and then reduced to undetectable levels by around day 250. The developmentally regulated W-TBP was present throughout pouch life, when the pouch young is dependent on obtaining thyroxine required for normal growth and development from the mother. After the young tammar wallaby leaves its mother's pouch, a time when it has reached a level of physiological development approximately equivalent to that at the time of birth in precocious eutherian mammals such as cattle and sheep, W-TBP was no longer detected as a thyroxine distributor protein in serum.

Salivary secretion during selective beta-adrenoreceptor stimulation and blockade in the parotid gland of red kangaroos, Macropus rufus

Intracarotid infusions of noradrenaline (0.3 nmol.kg(-1) x min(-1)) stimulated salivary fluid secretion and caused increases in salivary concentrations of protein, potassium. magnesium. chloride and phosphate, and decreases in bicarbonate. These effects of intracarotid noradrenaline were not reduced by simultaneous intracarotid infusion of phentolamine (3.0 nmol.kg(-1) x min(-1)) but were significantly greater than the responses accompanying intravenous noradrenaline infusion. Concomitant administration of the beta-antagonist, CGP20712A, were much more effective in blocking the noradrenaline-induced changes in salivary composition than equimolar infusions of the beta2-antagonist, ICI118551, thereby confirming the presence of beta1-adrenoreceptors. Intracarotid infusion of salbutamol at 0.6 nmol x kg(-1) x min(-1) and 6.0 nmol x kg(-1) x min(-1) caused increasing but qualitatively similar changes in salivary composition to intracarotid noradrenaline but was less effective than noradrenaline in augmenting salivary protein release. Equimolar intravenous infusions of salbutamol and noradrenaline were equally potent in altering salivary electrolyte concentrations but salbutamol by this route had less effect on protein release and fluid secretion. Concurrent intravenous and intracarotid infusions of beta1-(CGP) and beta2-(ICI) antagonists with intracarotid salbutamol showed that the beta2-antagonist was more potent than the beta1-antagonist by the intracarotid route thereby demonstrating the presence of glandular beta2-receptors and eliminating the possibility that the response to salbutamol was due totally by reflex increases in general sympathetic tone triggered by lowered blood pressure. It was concluded that the kangaroo parotid has functional beta1- and beta2-adrenoreceptor subtypes in endpieces whereas the data provide little support for either adrenoreceptor subtype being present in the excurrent duct system.

Histology and immunohistochemistry of the gut-associated lymphoid tissue of the eastern grey kangaroo, Macropus giganteus

Mesenteric lymph nodes and gut-associated lymphoid tissue (GALT) from juvenile eastern grey kangaroos were investigated. The mesenteric nodes had a similar structure to that described for eutherian mammals. They contained distinct regions of medulla and cortex, with prominent follicles and germinal centres. Gut associated lymphoid tissue consisted of areas of submucosal follicles. These varied from areas of densely packed lymphocytes with darkly staining, prominent coronas to areas with no defined follicles. The distribution of T cells in these tissues was documented by use of species-crossreactive antibodies to the surface markers CD3 and CD5; B cells were identified by antibodies to CD79b. Within the lymph nodes T cells were located mainly in the paracortex and cortex, with limited numbers observed in the follicles; B cells were located on the marginal zone of the follicles. In GALT, T cells were located in the peripheral regions of the germinal centres of secondary follicles, while B cells were abundant in primary follicles. These observations are consistent with those made in a range of other marsupials (metatherian) and eutherian mammals and are indicative of the capacity to respond to antigens entering via the mouth.

Convection requirement is established by total metabolic rate in the newborn tammar wallaby

Ventilation (VE) and metabolic rate, determined from both pulmonary and cutaneous gas exchange, were measured in 39 newborn tammar wallabies, Macropus eugenii, aged between 0 and 3 days. In 1-day-old animals both total metabolic rate (skin+lung exchange) and ventilation were approximately 50% of the values predicted for eutherian newborns of equivalent body mass. Hence, the convection requirement (VE/total metabolic rate) of the newborn tammar is close to predicted values for newborns and adult mammals in general. Metabolic rate in the newborn tammar is supported to some extent by cutaneous gas exchange, approximately 30% of the total in the 1-day-old animal. This ratio diminishes with increasing age as the lung takes on an increasingly more important role for respiratory exchange. The early establishment of the convection requirement in the newborn tammar, despite significant cutaneous gas exchange, provides supporting evidence that metabolic rate per se is important in establishing the level of ventilation.

Free-ranging heart rate, body temperature and energy metabolism in eastern grey kangaroos (Macropus giganteus) and red kangaroos (Macropus rufus) in the arid regions of South East Australia

Eastern grey kangaroos (Macropus giganteus) are generally regarded as mesic inhabitants. Even though access to drinking water in permanent stock watering troughs is commonly available, these animals are still found in only low densities in arid pastoral areas. We hypothesised that the differential success of red and grey kangaroos in the arid zone may be due to higher energy requirements of M. giganteus with a concomitant need for increased food, rather than limitations imposed by inadequate water access. We set out to test this by indirectly measuring energy expenditure through the monitoring of heart rate by radio telemetry in semi-free-ranging eastern grey and red kangaroos (Macropus rufus). Radio telemetry measurements of heart rate were calibrated against oxygen consumption and were used in the assessment of energy expenditure of animals maintained in an 8-ha enclosure in the arid zone of southeast Australia. Heart rate provided a reliable estimate of oxygen consumption. This well-correlated relationship was curvilinear and was established for each individual. Behavioural observations revealed that both kangaroo species spent most of the day in low energy demanding activities. M. rufus were more active at night whilst M. giganteus were more active in the early mornings and late afternoons. Like other marsupials, both species had low field metabolic rates (FMRs). However, M. giganteus in keeping with their mesic history had higher FMRs than the more arid-adapted M. rufus, particularly during water restriction. Body temperature telemeters revealed a further species difference in that under hot conditions when water is freely available, M. rufus exhibits a higher and more labile daytime body temperature than M. giganteus. During the hottest part of the day M. giganteus maintain body temperature, relying upon increased evaporative cooling mechanisms, such as licking. Indeed, only when access to drinking water was restricted was thermolability evident in M. giganteus. Differences in behaviour and concomitant energy expenditure may thus contribute substantially to the divergent distribution and abundance of these two kangaroo species.

Graded expression of EphA3 in the retina and ephrin-A2 in the superior colliculus during initial development of coarse topography in the wallaby retinocollicular projection

We describe the expression of EphA3 and EphA7 receptors and ephrin-A2 ligand in the retina and the superior colliculus during the development of the retinocollicular projection in the marsupial wallaby (Macropus eugenii), using immunoblotting and immunohistochemistry. EphA3 in the retina was in a striking, low central to high peripheral gradient, superimposed on which was a high temporal to low nasal level of expression. This distribution was evident from postnatal day 30, when axons are growing into the colliculus and forming a coarsely organized topographic projection, to postnatal day 65, when axons have arborized in their correct retinotopic positions. EphA7 showed a shallow centroperipheral gradient with no nasotemporal differences in expression. In the superior colliculus no rostrocaudal differences in distribution were detected for either of these receptors. Ephrin-A2 was distributed in a gradient increasing from the rostral to the caudal pole in the superficial layers of the superior colliculus only up to postnatal day 30. Ephrin-A2 was evenly distributed in the retina throughout development of the projection. Expression of EphA3 in the retina increased, while the expression of ephrin-A2 in the colliculus was downregulated over time. The graded expression of EphA3 and ephrin-A2 early in the development of the projection suggests that they play a role in establishment of coarse topography of retinal axons along the rostrocaudal axis of the superior colliculus. However, the gradients were not complementary, meaning that EphA3 alone cannot mediate the repulsive interactions with ephrin-A2 that have been postulated to underlie formation of the topographic map.

Progesterone and oestrogen receptors in the female genital tract throughout pregnancy in tammar wallabies

The tammar, Macropus eugenii, is a monovular macropodid marsupial which has a post-partum oestrus and an 11 month embryonic diapause. Progesterone and oestradiol cytosol receptors were measured by Scatchard analyses and single point analysis in the lateral vagina, endometrium and myometrium of the gravid and contralateral non-gravid uterus throughout pregnancy, immediately after parturition and during seasonal reproductive quiescence. In endometrial tissues, both progesterone and oestradiol receptors doubled in concentration in both gravid and non-gravid uteri between day 0 and day 5 of pregnancy, coinciding with previously described peak values in peripheral plasma progesterone and oestrogen. Receptor concentrations in endometrial tissue during seasonal quiescence were not significantly different from those immediately after reactivation. After day 12 of pregnancy, downregulation of both progesterone and oestradiol cytosolic receptors occurred concomitant with the increase in progesterone in the peripheral plasma. However, there was a unilateral increase in oestradiol receptor concentrations in endometrium obtained from the non-gravid uterus between day 25 of the 26.5 day gestation and immediately after parturition. Myometrial receptor concentrations mirrored those of the endometrium but were lower. Concentrations of progesterone receptor in the lateral vaginae were at the lower limit of detection, while the oestradiol cytosol receptor concentrations were even lower in this tissue. Thus, the steroid receptor concentrations provide another example of local unilateral endocrine responses in the reproductive tract of the tammar. These results also indicate that the downregulation of progesterone and oestradiol receptors that occurs in both uteri in mid- and late-pregnancy is selectively and locally reversed before parturition in the non-gravid endometrium in response to the local effects of follicular oestradiol from the ipsilateral ovary.

Effect of beta-antagonists on isoprenaline-induced secretion of fluid, amylase and protein by the parotid gland of the red kangaroo, Macropus rufus

Selective and non-selective beta-adrenoceptor antagonists were used to block the increases in fluid, protein and amylase secretion caused by sympathomimetic stimulation of the parotid gland of red kangaroos during intracarotid infusion of isoprenaline. ICI118551 at antagonist/agonist ratios up to 300:1 caused increasing but incomplete blockade of fluid secretion, and protein/amylase release. Atenolol at antagonist/agonist ratios up to 300:1 was only marginally more potent than ICI118551 at blocking the fluid, protein and amylase responses. Propranolol at antagonist/agonist ratios of 30:1 was as effective at blocking fluid and protein secretion as the highest ratios of either atenolol or ICI118551. Simultaneous administration of atenolol (30:1) with ICI118551 (30:1) was not as potent as propranolol (30:1). Thus, the beta-adrenoceptor/s in the acini of the kangaroo parotid gland appear to have antagonist-binding affinities atypical of those found for eutherian tissues. The data are consistent with the gland possessing either a single anomalous beta-adrenoceptor or functional beta(2)-receptors in addition to the beta(1)-receptors which are characteristic of eutherian salivary glands.

Kangaroo IGF-II is structurally and functionally similar to the human [Ser29]-IGF-II variant

Kangaroo IGF-II has been purified from western grey kangaroo (Macropus fuliginosus) serum and characterised in a number of in vitro assays. In addition, the complete cDNA sequence of mature IGF-II has been obtained by reverse-transcription polymerase chain reaction. Comparison of the kangaroo IGF-II cDNA sequence with known IGF-II sequences from other species revealed that it is very similar to the human variant, [Ser29]-hIGF-II. Both the variant and kangaroo IGF-II contain an insert of nine nucleotides that encode the amino acids Leu-Pro-Gly at the junction of the B and C domains of the mature protein. The deduced kangaroo IGF-II protein sequence also contains three other amino acid changes that are not observed in human IGF-II. These amino acid differences share similarities with the changes described in many of the IGF-IIs reported for non-mammalian species. Characterisation of human IGF-II, kangaroo IGF-II, chicken IGF-II and [Ser29]-hIGF-II in a number of in vitro assays revealed that all four proteins are functionally very similar. No significant differences were observed in the ability of the IGF-IIs to bind to the bovine IGF-II/cation-independent mannose 6-phosphate receptor or to stimulate protein synthesis in rat L6 myoblasts. However, differences were observed in their abilities to bind to IGF-binding proteins (IGFBPs) present in human serum. Kangaroo, chicken and [Ser29]-hIGF-II had lower apparent affinities for human IGFBPs than did human IGF-II. Thus, it appears that the major circulating form of IGF-II in the kangaroo and a minor form of IGF-II found in human serum are structurally and functionally very similar. This suggests that the splice site that generates both the variant and major form of human IGF-II must have evolved after the divergence of marsupials from placental mammals.

Hepatic microsomal enzyme activity in the koala and tammar wallaby: high 17beta-hydroxysteroid oxidoreductase activity in koala liver microsomes

We have studied the hepatic microsomal xenobiotic metabolising capacity of koala (Phascolarctos cinereus) and tammar wallaby (Macropus eugenii). Total cytochrome P450 content in hepatic microsomes from koala (0.87 +/- 0.18 nmol/mg protein, n = 4, mean (S.D.) and rat were comparable while tammar wallaby displayed reduced P450 content (0.24 +/- 0.04 nmol/mg protein). Associated microsomal activities (NADPH cytochrome P450 reductase, aminopyrine N-demethylation, aniline hydroxylation, and androstenedione 6beta- and 16alpha-hydroxylation) in koala liver were similar to or reduced relative to rat. Hepatic microsomal NADPH-supported 17beta-hydroxysteroid oxidoreductase (17beta-HSOR) activity was significantly higher in koala (9.99+/-3.08 nmol/mg protein/min) than in tammar wallaby liver (0.86 +/- 0.16 nmol/mg protein/min). However, when NADH was utilised as cofactor the activity was similar in both marsupial species (koala, 1.44 +/- 0.84 nmol/mg protein/min; tammar wallaby, 1.52 +/- 0.44 nmol/mg protein/min). Michaelis-Menten parameters for the kinetics of 17beta-HSOR androstenedione reduction by NADPH and NADH were determined in the koala. The Km for androstenedione was of the order of 1.9-4 microM (n = 4) irrespective of the cofactor used, whilst the Km for NADPH was 0.04-0.05 microM (n = 2) and for NADH was 134-430 microM (n = 2). Potential inhibitors were evaluated for their effects on NADPH-mediated 17beta-HSOR activity with menadione and, to lesser extents, menthone, benzaldehyde and metyrapone eliciting significant inhibition. From detailed kinetic studies menthone was found to be an uncompetitive inhibitor of the activity in koala liver (Ki 220 microM).

Cortisol in fetal fluids and the fetal adrenal at parturition in the tammar wallaby (Macropus eugenii)

Glucocorticoid hormones may play a critical role in initiating parturition in tammar wallabies. In this study, we investigated the concentration of cortisol in fetal fluids and cortisol production by fetal adrenals over the last 3 days of the 26-day pregnancy and within 24 h postpartum. The fetal adrenals almost doubled in size between Days 24 and 26 of pregnancy, and their cortisol content increased over 10-fold during this period, from 10 pg to over 100 pg per adrenal pair. After birth, neonatal adrenals continued to grow, but cortisol content fell dramatically to 20 pg. The prepartum increase in adrenal cortisol was reflected by a substantial rise in cortisol concentrations in yolk sac fluid, allantoic fluid, and fetal blood, which were below 10 ng/ml on Day 24 and rose to over 40 ng/ml by Day 26. Cortisol concentrations in neonatal blood decreased postpartum, mirroring decreased cortisol content in neonatal adrenals. Cortisol production by the fetal adrenal was stimulated in vitro by ACTH and prostaglandin E2, suggesting that the in vivo increase may be stimulated by release of ACTH from the fetal hypothalamic-pituitary axis and prostaglandin E2 from the placenta. These results indicate that increasing cortisol production by the fetal adrenal is a characteristic of late pregnancy in the tammar wallaby and support the suggestion that fetal cortisol may trigger the initiation of parturition in this marsupial species.