PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “MARSUPIALIA”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effects of testosterone and cortisol on the renal morphology of male Antechinus stuartii (Marsupialia).

The life cycle of the marsupial Antechinus stuartii includes postmating mortality of all males. A previous study found that renal morphology changes during the yearly cycle when endogenous concentrations of testosterone and cortisol are elevated in males. The present study determined whether administration of testosterone only, cortisol only, or testosterone plus cortisol affects renal structure in males at a time of year when endogenous hormones are low (May). Saline administration was used as the control. Gross morphometrics of the kidney did not show significant differences between groups. However, some pathological changes were observed in distal tubules and collecting ducts from cortisol-treated groups, and in the glomeruli of testosterone-treated males. Hypertrophy of the proximal tubules, distal straight tubules, and the cells of the cortical collecting duct occurred with the administration of testosterone. Distension of the distal convoluted tubules, cortical collecting ducts, and outer medullary collecting ducts occurred with the administration of cortisol, and there was some interaction with testosterone. Glomerular volumes increased with cortisol administration, although cortisol interacted with testosterone in the superficial glomeruli. Many of these changes mimicked those seen in the seasonal study, with the kidneys of the testosterone plus cortisol group closely resembling those of males in August, just prior to male mortality. The present study demonstrates that testosterone administration causes hypertrophy of renal tissue, whereas cortisol administration can cause tubular disruption in male A. stuartii.

Animals↗
PubMed1993

Testicular and epididymal development in the brown marsupial mouse, Antechinus stuartii (Dasyuridae, Marsupialia).

Reproductive tissues were collected monthly from male Antechinus stuartii during the first 5 months of post-partum development, a period corresponding to the time between birth and the initial increase in plasma androgen above non-detectable levels. The gonad appeared undifferentiated at day 3 after birth, but the basic structure of the testis (tunica albuginea, sex cords, stroma) was well established at 1 month of age. At this stage the developing sex cords contained a single layer of pre-Sertoli cells which surrounded a central core of gonocytes. Mitotic division of cells within the cords was common. Intertubular fetal Leydig cells, often observed in clumps, and perivascular and peritubular fetal Leydig cells were common and readily identified. By 2 months of age there was an obvious increase in cord diameter and the abundance of pre-Sertoli cells, while a marked reduction in the density of connective tissue cells and fetal Leydig cells was observed in the interstitium. Fetal Leydig cells appeared to persist only in close association with the developing seminiferous cords. Testicular size and the diameter and convolutions of the seminiferous cords increased substantially (two fold increase in cord diameter) by 3 months of age. Gonocytes had begun to migrate toward the basal lamina of the cords, and connective tissue cells and Leydig cells appeared in large numbers throughout the interstitium. By 4 and 5 months of age, gonocytes were commonly seen in contact with the basement membrane, and the cords remained non-patent. Leydig cell number and density increased greatly during these months. The epididymal epithelium remained undifferentiated throughout the first 5 months of development. Epithelial cells characteristically contained a large nucleus which occupied most of the cell, very little cytoplasm and few organelles. The diameter of the epididymal duct was similar throughout for the first 3 months of the study. In months 4 and 5 the diameter of the duct in caput and corpus regions increased, ahead of that of the cauda, possibly in relation to variations in androgen exposure at different regions along the developing duct. Further histological and quantitative studies on the growth and development of Leydig cells within the Dasyuridae are needed for comparison with eutherian mammals, which together with knowledge of the changing levels of fetal androgens may provide a greater understanding of the role of the different populations of Leydig cells in the differentiation of the testis and male reproductive tract.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1982

Crystalloid inclusions in the Sertoli cell of the koala, Phascolarctos cinereus (Marsupialia).

Crystalloid inclusions are a common feature in the basal region of Sertoli cells in the koala, Phascolarctos cinereus. Generally located near the nucleus, they are non membrane-bounded, slender rectangular structures composed to tubules which are orientated at right angles to the long axis of the crystalloid and regularly arranged in rows parallel to this long axis. The tubules in adjacent rows are offset from one another at definite angles and extensively interconnected by filaments. Neither the composition nor function of the crystalloids has been determined, but their association with tonofilaments and the presence of ribosomes in the vicinity suggests that they are most likely proteinaceous.

Animals↗
PubMed1992

Digestive tract morphology and digestion in the wombats (Marsupialia: Vombatidae).

Wombats consume grasses and sedges which are often highly fibrous. The morphology of the digestive tract and the sequence of digestion were studied in two species of wombats from contrasting habitats: Vombatus ursinus from mesic habitats and Lasiorhinus latifrons from xeric regions. Studies were performed on wild wombats consuming their natural winter diets, and on captive wombats fed a high-fibre pelleted straw diet. Vombatus had a shorter digestive tract (9.2 vs 12.5 times body length) of greater capacity (wet contents 17.9 vs 13.7% body weight) than Lasiorhinus. The most capacious region of the digestive tract was the proximal colon (62-79% of contents). The proportional length and surface area of the proximal colon were greater in Vombatus, but those of the distal colon were greater in Lasiorhinus. These digestive morphologies may reflect adaptations for greater capacity and longer retention of digesta in Vombatus, but greater absorption and lower faecal water loss in Lasiorhinus. Apparent digestion along the digestive tract was estimated by reference to lignin. The proximal colon was the principal site of fibre and dry matter digestion, whereas nitrogen was mainly digested in the small intestine. Depot fats in captive wombats were highly unsaturated and reflected those in the diet. Therefore, lipids, proteins and soluble carbohydrates in the plant cell contents were digested and absorbed in the stomach and small intestine. Conversely, dietary fibre was probably retained and digested by microbial fermentation along the proximal colon.

Animal Nutritional Physiological Phenomena↗
PubMed1981

Verification of the structure of the complex sex chromosome system in Lagorchestes conspicillatus Gould (Marsupialia: Mammalia).

The complex sex chromosome system of Lagorchestes conspicillatus has been reinvestigated using G-banding, Hoechst 33258 sensitivity, and Ag staining. These investigations demonstrate that, as proposed, three exchanges have been involved in the evolution of this system. An autosome was translocated to the original X and the homologue of that autosome was translocated to the original Y. An additional autosome has been translocated to the Y. There is no sex vesicle at meiosis in the male, and no association between the original X and Y elements of the compound chromosomes. The inadequacies of the present terminology for complex sex chromosomes are considered and an alternative system suggested.

Animals↗
PubMed1988

Energy expenditure and protein turnover in three species of wallabies (Marsupialia: Macropodidae).

Relationships between basal and fed metabolic rates and whole-body protein turnover rates were examined in three species of wallabies, the red-necked pademelon (Thylogale thetis), parma wallaby (Macropus parma) and tammar wallaby (M. eugenii). There were no significant differences among wallaby species in basal metabolic rate (BMR) which was 30% below eutherian mammals. However, the fed metabolic rate of the tammar was lower than that of the other two species (P less than 0.05), as was the protein turnover rate (P less than 0.01) which is consistent with its lower voluntary feed intake and with its lower maintenance nitrogen requirement. Protein turnover rates in the wallabies were 23-47% lower than in eutherian mammals. Similarly, protein synthesis made a lower contribution to fed metabolic rates in the wallabies (7-8%) than in eutherians (17-25%). Thus, compared with several eutherian species, macropodid marsupials have low rates of both energy and protein metabolism, but within the macropodids there is not necessarily a close link between basal metabolic rate and whole-body protein turnover.

Animals↗
PubMed1979

Position of the nucleolus within the nuclei of pachytene spermatocytes of Dromiciops australis and Marmosa elegans (Didelphoidea-Marsupialia).

The location of the nucleoli within the nuclei of pachytene spermatocytes, and their relation with the position of the nucleolar organizer region (NOR) was studied. It appears that a terminal NOR determines a peripheral location of the nucleolus, due to the position of the NOR over the synaptonemal complex and to the attachment of the nucleolar chromosome telomeres at the nuclear membrane.

Animals↗
PubMed1990

DNA/DNA hybridization studies of the carnivorous marsupials. I: The intergeneric relationships of bandicoots (Marsupialia: Perameloidea).

A complete suite of comparisons among six bandicoot species and one outgroup marsupial was generated using the hydroxyapatite chromatography method of DNA/DNA hybridization; heterologous comparisons were also made with three other bandicoot taxa. Matrices of delta Tm's, delta modes, and delta T50Hs were generated and corrected for nonreciprocity, homoplasy, and, in the case of delta Tm's, normalized percent hybridization; these matrices were analyzed using the FITCH algorithm in Felsenstein's PHYLIP (version 3.1). Uncorrected and nonreciprocity-corrected matrices were also jackknifed and analyzed with FITCH to test for consistency. Finally, sample scores for delta Tm, delta mode, and delta T50H matrices were bootstrapped and then subjected to phylogenetic analysis. These manipulations were carried out, in part, to address criticisms of the statistics used to summarize DNA/DNA hybridization (especially T50H) and the method itself. However, with the exception of an unresolved trichotomy among the two Echymipera species and Peroryctes longicauda, all trees showed the same branchpoints. Except in the case of the tree generated from reciprocal-corrected delta Tm data, nodes were stable under jackknifing; and, again excepting the above-mentioned trichotomy, all nodes were supported by 95% or more of the bootstrapped trees. These results suggest that, despite arguments to the contrary, all three summary statistics can be valid for DNA/DNA hybridization data. Of taxonomic interest is the placement of Echymipera spp. and Peroryctes longicauda together and separate from the more distant Peroryctes raffrayanus; the genus Peroryctes is thus at least paraphyletic. The trees further grouped Echymipera-plus-Peroryctes as the sister group of Isoodon-plus-Perameles. Limited hybridizations with Macrotis lagotis suggest that its current position as representative of an entirely distinct family of perameloids is correct.

Animals↗
PubMed2006

Effects of long-term captivity on thermoregulation, metabolism and ventilation of the southern brown bandicoot (Marsupialia: Peramelidae).

Thermoneutral metabolic and ventilatory parameters were measured every 3 months over 2 years for southern brown bandicoots held in captivity, and from a nearby reserve. Captive bandicoots were 130 g (9.9%) heavier than wild bandicoots. Long-term captivity had no effect on body temperature, basal metabolic rate (oxygen consumption), thermal conductance or respiratory ventilation, but there was an effect on carbon dioxide production, respiratory exchange ratio and total evaporative water loss (values were between 15 and 25% higher for captive than for wild bandicoots). Diet may be influencing these aspects of captive bandicoot physiology; the diet of captive bandicoots would be considerably different to that of wild bandicoots. Water availability seems to have a minimal effect. This study has important implications regarding physiological measurement for captive and wild mammals. For bandicoots at least, captive animals are equivalent to wild animals for some physiological parameters at thermoneutrality (body temperature, resting metabolic rate and thermal conductance), but not others.

Animal Feed↗
PubMed2000

Digestive performance and digesta passage in the omnivorous greater bilby, Macrotis lagotis (Marsupialia: Peramelidae).

Omnivores such as the greater bilby (Macrotis lagotis) consume a variety of dietary items and often are faced with large changes in the nutrient composition of their food. This paper explores the basis for the dietary flexibility of the bilby by comparing digestive performance and digesta retention patterns of captive bilbies fed either an insect diet (mealworm larvae) or a plant diet (mixed seeds). Mean retention times (MRTs) of particle and solute markers in the gastrointestinal tract did not differ significantly between the two diets, but MRT of the particle marker was significantly longer than that of the solute marker on both the mealworm (particle: 23.5 h; solute: 17.9 h) and mixed seed (particle 33.0 h; solute: 30.2 h) diets. Lack of selective retention of solutes and small particles in the bilby gastrointestinal tract probably restricts them to relatively low-fibre diets, such as those based on seeds rather than leaves and stems of plants. It was observed radiographically that the major sites of digesta retention were the caecum, proximal colon and distal colon, and thus the hindgut is probably the principal site of microbial fermentation. The mealworms were more digestible than the mixed seeds, but digestible energy intake (mealworm: 939 kJ x kg(-0.75) x d(-1); mixed seed: 629 kJ x kg(-0.75) x d(-1)) was high enough for maintenance of body mass and positive nitrogen balance on both diets. Thus, although bilbies may be limited in their ability to utilize high-fibre diets by a lack of selective retention of solutes and small particles in their hindgut, their digestive strategy is flexible enough to accommodate at least some diets of both animal and plant origin. Such a strategy should benefit an animal inhabiting environments in which food resources are unpredictable in their relative abundance.

Animal Nutritional Physiological Phenomena↗
PubMed1998

Seasonal changes in glomerular filtration rate in Antechinus stuartii (Marsupialia: Dasyuridae).

The small marsupial Antechinus stuartii experiences a synchronised life cycle that culminates in complete male mortality (within 3 weeks) following the 1 week mating period in mid-August (late winter). There are pronounced physiological changes in male A. stuartii over the life cycle and renal function was assessed for correlation with these changes. Glomerular filtration rate and urine and plasma electrolytes were determined in male and female A. stuartii in February, May, July and August. Females showed little change in glomerular filtration rate, except for pre-mating values in August which decreased. In contrast, glomerular filtration rate of males decreased significantly in July and August. Plasma sodium and chloride levels were higher in males than females and were higher in animals in July and August than in February and May. Plasma potassium levels dropped in both males and females in July and August. Plasma osmolality was higher in animals in February compared to animals from May and August. However, there were no significant sex or seasonal differences in urine electrolytes, although urea concentration was higher in females than males. Urine osmolality was higher in both sexes in July and August. There were no significant differences in total excretory rates of sodium, potassium or chloride between sexes or between seasons. Many of the alterations in renal function are correlated with known physiological and hormonal profiles in A. stuartii. This is the first observation of seasonal changes in glomerular filtration rate that are unrelated to dietary and water stresses.

Animals↗
PubMed1998

The effects of cortisol and testosterone on renal function in male Antechinus stuartii (Marsupialia).

Seasonal changes in the physiology of Antechinus stuartii result in complete male mortality after mating. The most important endocrine changes in males are large rises in plasma testosterone and cortisol concentrations. Glomerular filtration rate (GFR) in males declines coincident with high plasma testosterone and cortisol. In the present study GFRs were measured in males captured in May (when endogenous plasma testosterone and cortisol levels are low) and given depot injections of either saline, testosterone-only, cortisol-only or testosterone plus cortisol at doses designed to mimic plasma levels during the mating period. GFR decreased significantly with testosterone injection, independent of cortisol treatment. Urinary concentrations of sodium and chloride, and osmolality decreased significantly with cortisol treatment, although the addition of testosterone reversed the effect. Total urinary excretion of electrolytes was similar between groups. Plasma potassium levels significantly increased in testosterone plus cortisol treated males. Plasma sodium levels significantly increased and plasma chloride significantly decreased in all groups treated with cortisol. Water consumption significantly increased in all cortisol-treated males and food consumption significantly increased in all testosterone-treated males. The seasonal renal functional changes observed in A. stuartii were mimicked by testosterone administration.

Animals↗
PubMed2003

The field energetics and water fluxes of free-living wombats (Marsupialia: Vombatidae).

Wombats are large, fossorial, herbivorous marsupials exhibiting physical and behavioural characteristics indicative of extreme energy conservation. Previous energetics studies have been limited to their basal metabolism under laboratory conditions; little is known of the energetics of free-living wombats. We measured seasonal field metabolic rates (FMR) and water fluxes in the three species of free-living wombat using the doubly labelled water technique, to further investigate the extent of energy conservation in the Vombatidae. Measurements were taken during the wet and dry annual extremes of their characteristically harsh environments, which corresponded to seasonal extremes of food and water availability. Seasonal FMRs for all wombat species were lower than that recorded for other marsupials and well below that predicted for herbivorous mammals. Dry-season FMR of Lasiorhinus kreftii was 40% of that predicted for a mammal. Wombats maintained energy balance during the poor season by reducing FMR to about half that of the good season. Water flux rates during the dry season for the arid-adapted Lasiorhinus are amongst the lowest recorded for mammals, being only 25% of that predicted for a similarly sized herbivorous mammal. These low water flux rates enable wombats in semi-arid areas to maintain water balance without drinking. Estimated food and nitrogen intake rates were also low. We conclude that the energetically frugal lifestyle of the Vombatidae is amongst the most extreme for mammals.

Animals↗
PubMed2006

Morphological and molecular characteristics of a species of Hepatozoon Miller, 1908 (Apicomplexa: Adeleorina) from the blood of Isoodon obesulus (Marsupialia: Peramelidae) in Western Australia.

Examination of blood films as part of a study to assess the health status of the southern brown bandicoot Isoodon obesulus (Shaw) in Western Australia revealed the gamonts of a haemogregarine parasite in some samples, the first to be recognised in a bandicoot in this state. Light microscope morphological characteristics and partial sequence of the 18S rRNA gene were used to describe these organisms. Morphological characters did not differentiate the organism in the current study from previously reported Hepatozoon peramelis (Welsh & Dalyell, 1909). Phylogenetic analysis has not previously been reported for any species of Hepatozoon from Australian marsupials and consequently could not be used to confirm the identity of the organism in the current study as that described in the 1900s. If this organism is H. peramelis, then it has a wide distribution, being found in three species of bandicoot, in western and eastern Australia and the in island state of Tasmania.

Animals↗