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PubMed1981

Histology and histochemistry of the accessory reproductive glands in the male hairy-nosed wombat (Lasiorhinus latifrons).

The accessory male reproductive glands of the hairy-nosed wombat, Lasiorhinus latifrons, are a prostate and three pairs of Cowper's glands. Component units of all are branched tubular structures of varying epithelial makeup and secretory content. The prostate has the carrotlike shape and three consecutive regions commonly found in marsupials. The regions differ in their tubular histology and histochemistry: all contain secretory globules in glandular lumina. Cowper's glands A and B are histologically identical except for the absence of interstitial mast cells from gland G: gland C is characterized by narrower tubules and larger epithelial cells. Histochemical tests for protein, carbohydrate and iron indicate that glycogen is a major secretory product of the prostate (largely posterior region), iron is also secreted (mainly posterior region) and a small quantity of acid mucin is produced (mainly central region). Glycogen is a feature also of anterior prostatic glandular epithelium and of the capping cells of the urethral transitional epithelium. Cowper's gland A has considerable protein in its secretion, gland B a neutral glycoprotein and gland C a sialomucin: the latter two also exhibit cytoplasmic glycogen in their secretory cells.

Animals↗
PubMed1981

An autosomal gene assignment in a marsupial: the gene for LDH-A is on chromosome 5 of the red kangaroo, Macropus rufus.

A number of somatic cell hybrids between red kangaroo (Macropus rufus) and mouse cells, which lose marsupial chromosomes, were found to express the kangaroo form of LDH-A. Concordance between the expression of marsupial LDH-A and the presence of chromosome 5 in the hybrid cells and selected subclones enabled the gene for LDH-A to be assigned to this chromosome. This is the first autosomal gene assignment in a marsupial and should prove important for chromosome mapping in the red kangaroo and in many other species of marsupials.

Animals↗
PubMed1986

Genetic variation in natural and laboratory populations of the marsupial Sminthopsis crassicaudata.

Gel electrophoresis of blood proteins has detected allelic variation at five loci (TRF, PGD, SOD, ADA, GPI) in a laboratory colony of the dasyurid marsupial Sminthopsis crassicaudata. Family data show no significant departures from Mendelian expectations. Analysis of blood from wild-caught progenitors of the colony revealed significant differences in gene frequency between groups of animals captured from different parts of southern and central Australia and showed that there are two major population clusters. These interpopulation differences are particularly marked at the TRF locus and indicate that the river Murray is a barrier for this species.

Adenosine Deaminase↗
PubMed1987

Sarcocystis mucosa (Blanchard 1885) Labbé 1889 in unadorned rock wallabies (Petrogale assimilis) and Bennett's wallabies (Macropus rufogriseus).

Macroscopic cysts of a protozoan parasite were detected in the gastro-intestinal walls of two unadorned rock wallabies (Petrogale assimilis) and 20 Bennett's wallabies (Macropus rufogriseus). The cysts were located predominantly in the muscularis externa and the submucosa of the forestomach, small intestine and colon and sometimes in the muscularis externa of the oesophagus and caecum. All cysts exhibited similar morphological and ultrastructural characteristics. They were bounded by thick primary cyst walls (containing distinctive bulbous-like protrusions) and were surrounded by collagen fibres and host connective tissue cells (mainly fibrocytes). The cysts were divided by septae into internal compartments containing metrocytes and cystozoites. The cystozoites contained numerous organelles typical of apicomplexan protozoan parasites (including an apical complex, a micropore, rhoptries, micronemes, polysaccharide granules and 22 subpellicular microtubules) and they were observed to divide by the process of endodyogeny. Despite the unusual location of the cysts, they were classified on the basis of their ultrastructural characteristics as Sarcocystis mucosa (Blanchard 1885) Labbé 1889.

Animals↗
PubMed1991

Conservation genetics of the koala (Phascolarctos cinereus). II. Limited variability in minisatellite DNA sequences.

We have examined variability in TaqI and EcoRI restriction fragment sizes of DNA from the koala (Phascolarctos cinereus) using six HVR (hypervariable region) probes which reveal complex, individual-specific restriction patterns in humans and other species. Frequency of band-sharing among unrelated koalas was extremely high. This result is likely to be a consequence of the history of near-extinction and artificial recolonization of the populations we have studied, rather than a general marsupial or koala-wide phenomenon.

Animals↗
PubMed1989

X-linked gene expression in metatherian fibroblasts: evidence from the Gpd and Pgk-A loci of the Virginia opossum and the red-necked wallaby.

Fibroblasts cultured from ear pinna biopsies of Virginia opossums (Didelphis virginiana) and red-necked wallabies (Macropus rufogriseus) were examined electrophoretically to determine the relative expression levels of the maternally and paternally derived alleles at X-linked, enzyme-coding loci. Only the maternally derived allele was expressed at the Pgk-A locus in fibroblasts of heterozygous D. virginiana (M. rufogriseus not examined), but fibroblasts of both species exhibited evidence of paternal allele expression at the Gpd locus. Furthermore, the heterozygous G6PD phenotypes in both species were skewed in favor of the maternal gene product, as expected if the paternal allele is only partially (incompletely) expressed. For M. rufogriseus this result is contrary to a previous finding which suggested equal expression of both Gpd alleles in cultured fibroblasts of this species. The present results suggest that X-linked genes in metatherian fibroblasts are subject to the same kind of determinate, paternal allele inactivation, incomplete at some loci, described previously for X-linked genes in adult tissues and that the pattern of paternal X-linked gene expression in these cells is independent of the patterns in the tissues from which the fibroblasts are derived.

Alleles↗
PubMed1992

Restriction fragment length variants in the marsupial Sminthopsis crassicaudata.

A fully pedigreed colony of the dasyurid marsupial Sminthopsis crassicaudata has provided material for establishing two panels of DNA samples: a broadbased test panel and a two-generation family panel. These have been used to search for genetic markers in the form of restriction fragment length variants. The molecular probes--pSG-2H, a region of the S. crassicaudata embryonic beta-globin gene; pB8.BS, a region of the human ubiquitin gene, and p3-21a1:1, a region of the processed pseudogene of phosphoglycerate kinase-1 of the macropodid marsupial Macropus robustus--were hybridized to Southern blots of EcoR1-digested DNA from the panels. Analysis of these blots when probed with pSG-2H provided evidence of two alleles segregating at a single EcoR1 site. Analysis of the same blots when probed with pB8.BS suggested allelic variation at two closely linked EcoR1 sites. Probing the blots with p3-21a1:1 produced a complex pattern of bands resembling DNA fingerprints. The presence of a 12.3-kb band was found to conform to a simple autosomal dominant mode of inheritance. Analysis of the family data, for each probe, revealed no significant departure from Mendelian inheritance. This work has provided additional genetic markers that will enhance the use of S. crassicaudata as a model marsupial species and has demonstrated that a high level of genetic variability has been maintained in the marsupial colony.

Animals↗
PubMed1990

Immunocytochemical study of the endocrine pancreas in the grey kangaroo (Macropus fuliginosus).

The endocrine pancreas of the grey kangaroo, Macropus fuliginosus, was investigated by means of immunocytochemistry using the PAP method on the same section at the light- and electron-microscopic levels. Semithin plastic sections were stained individually with primary antibodies for insulin, glucagon, somatostatin and pancreatic polypeptide (PP), and then photographed. Sections were osmicated, re-embedded in BEEM capsules, and ultrathin sections made and examined. The same labelled cells as in the semithin sections were localised in the thin sections, photographs taken and the morphology of secretory granules studied. The insulin cells were pleomorphic; their secretory granules displayed an electron-dense core surrounded by an empty halo. The glucagon cells possessed granules with an electron-dense core usually surrounded by a halo of less dense granular material. Somatostatin cells had larger, less dense secretory granules. The PP cells showed small, dense secretory granules. In order for an ultrastructural study to be considered reliable for the definite identification of endocrine cell types, it is essential that it be corroborated by correlated immunocytochemical data at the light- and electron-microscopic levels.

Animals↗
PubMed1987

Patterns of cytogenesis in the developing retina of the wallaby Setonix brachyurus.

Patterns of mitosis were examined during development from embryonic day (E) 19, 9 days before birth, for retinae of the wallaby Setonix brachyurus, using cresyl violet stained material. For neural retina, mitosis took place at the ventricular surface from the earliest stage of eye formation until postnatal day (P) 100. Numbers of mitotic figures reached a peak of approximately 12,000 by P43. Average densities ranged between 300/mm2 and 600/mm2 up to P12 and then fell to below 50/mm2 by P25 before reaching a second peak of over 400/mm2 at P43. Up to P50, mitoses were present across the entire retina. By P60, a 'cold spot' lacking mitotic activity had formed in temporal retina and progressively extended to reach peripheral regions by P100; no mitoses were seen at P150. The timing and location of the 'cold spot' coincided with our previous description of the appearance of an area centralis in the ganglion cell layer (Dunlop and Beazley 1985). Inner and outer plexiform layers (IPL and OPL) formed between P24-40 and P50-100 respectively and were seen first in temporal retina. Furthermore, the extent of the OPL matched the mitotic 'cold spot'. By contrast to neural retina, mitosis in the pigment epithelium was panretinal and was largely complete by P3. The data suggest that cell addition to the inner or outer nuclear layers contribute to differential retinal expansion and the establishment of cell density gradients in the ganglion cell layer.

Age Factors↗
PubMed1983

Regional differences in electrolyte, short-chain fatty acid and water absorption in the hindgut of two species of arboreal marsupials.

Short-chain fatty acid, electrolyte and water absorption from the hindgut of two arboreal marsupial species, the greater glider (Petauroides volans) and the brush-tail possum (Trichosurus vulpecula) were studied in vivo using a single perfusion technique. Qualitative and quantitative differences in the net movement of sodium, potassium and chloride were found between the different hindgut segments and between the two species. ALl transport processes exhibited active characteristics. Net Na+ transport in all segments was concentration-dependent in the range of 45-135 mmol . 1(-1) Na+. The proximal colon of the greater glider showed a net Na+, Cl- and water secretion and K+ absorption, all electrolyte movements being against the electrochemical gradient. Water followed passively the osmotic gradient generated mainly by the net movement of Na+. Short-chain fatty acids were absorbed according to their chain length in a constant ratio of 1.0:1.2:1.3 for acetate, propionate and butyrate, respectively. Our data indicate that absorptive and secretory processes in the hindgut of these marsupials are basically similar to those of eutherians, even in epithelia differing significantly in the direction of net solute transport.

Animals↗
PubMed1985

An allometric comparison of the mitochondria of mammalian and reptilian tissues: the implications for the evolution of endothermy.

The effects of body size and phylogeny on metabolic capacities were examined by comparing the mitochondrial capacities of 6 mammalian and 4 reptilian species representing 100-fold body weight ranges. The mammals examined included 3 eutherian, 2 marsupial and a monotreme species and the reptiles 2 saurian, 1 crocodilian and 1 testudine species. The tissues examined were liver, kidney, brain, heart, lung and skeletal muscle. Allometric equations were derived for tissue weights, mitochondrial volume densities, internal mitochondrial membrane surface area densities, tissue mitochondrial membrane surface areas both per gram and per total tissue and summated tissue mitochondrial membrane surface areas. For the mammals and reptiles studied a 100% increase in body size resulted in average increases of 68% in internal organ size and 107% in skeletal muscle mass. Similarly, total organ mitochondrial membrane surface areas increase in mammals and reptiles by an average 54% and for skeletal muscle by an average 96%. These values are similar to increases in standard (54 and 71%) and maximum (73 and 77%) organismal metabolism values found by other authors for mammals and reptiles respectively. Although the allometric exponents (or rates of change with increasing body size) of the mitochondrial parameters in mammals and reptiles are statistically the same, in general the total amount of mitochondrial membrane surface area in the mammalian tissues are four times greater than found in the reptilian tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Alligators and Crocodiles↗
PubMed1989

Characteristics of cardiac action potentials in marsupials.

Standard microelectrode techniques were used to record action potentials from single atrial, ventricular and Purkinje fibers of hearts taken from three species of marsupial (Macropus rufus, Macropus robustus and Macropus eugenii) and from dogs, sheep and guinea-pigs. The major electrophysiological parameters of marsupial potentials were qualitatively similar to the values for placental mammals. The grouped data for ventricular action potentials from studies on 6 adult male red kangaroos (Macropus rufus) were (mean +/- SD): Resting potential -69.5 +/- 5.0 mV; action potential amplitude 92.7 +/- 5.7 mV; action potential duration (to 90% repolarization): 182.5 +/- 17.5 ms; maximum rate of depolarization: 196.5 +/- 80.1 V/s. The major point of difference was the short duration of the red kangaroo ventricular action potential compared to those of the placental mammals, and compared to atrial cells from the kangaroos. It is suggested that this explains the short QT interval reported by others for kangaroo electrocardiograms, and that it may also be implicated in the high frequency of sudden death previously noted in these animals.

Action Potentials↗
PubMed1986

Physiological and metabolic changes associated with weaning in the tammar wallaby, Macropus eugenii.

The tammar wallaby (Macropus eugenii) is a small macropodid marsupial in which the major part of weaning occupies the period between 28 and 36 weeks of pouch life. Before weaning the diet of the tammar is high in carbohydrate and low in lipid/volatile fatty acid whereas the reverse applies after weaning. The adult tammar is a forestomach fermenter. The aim of this study was to elucidate some of the physiological and metabolic changes associated with this major change in the diet. Hepatic glycogen content increased gradually early in development to a maximum of 7% of liver weight at 28-30 weeks of pouch life. It then fell precipitously to less than 1% of liver weight at 36 weeks before recovering to the adult level of about 3% liver weight. Plasma glucose levels were maintained at about 10 mM until 36 weeks, after which they fell gradually to adult values of about 4 mM. Hepatic hexokinase activity increased several-fold between 18 and 30 weeks of pouch life, remained high until 42 weeks, and then fell to the adult level. The hepatic activities of fructose-bisphosphatase and particulate phosphoenolpyruvate carboxykinase (PEPCK) were unchanged during development but soluble hepatic PEPCK activity, which was low until 28 weeks of pouch life, increased 3-4 fold between 30 and 36 weeks and then fell slightly to the adult level. Hepatic pyruvate kinase increased in activity up to 28 weeks and then fell to about half peak values at 36 weeks and 20% of peak activity in the adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1989

Secretion by the mandibular gland of the red kangaroo (Macropus rufus) during isoprenaline infusion.

Intracarotid infusion of isoprenaline, either alone or in combination with acetylcholine infusion was used to stimulate salivation by the mandibular glands of anaesthetized red kangaroos. Isoprenaline alone (0.20-1.25 eta mol.kg-1.min-1) elicited flow rates ranging from 0.014 to 0.239 ml.min-1 (1.21-28.1 microliters.g gland-1.min-1). Salivary concentrations of sodium, chloride, phosphate and urea were negatively correlated with flow, whereas potassium, calcium, magnesium, hydrogen ion, bi-carbonate, protein, and osmolality were poorly correlated with flow. Relative to cholinergic saliva produced at equivalent flow rates, isoprenaline-evoked saliva had higher osmolality, saliva/plasma urea ratios and concentrations of protein, potassium, magnesium, bicarbonate, and phosphate, but lower sodium, chloride and hydrogen ion levels. At a steady salivary flow (0.5 ml.min-1), superim-position of isoprenaline infusion (0.15 eta mol.kg-1.min-1) on a pre-existing acetylcholine infusion reduced the rate of acetylcholine administration necessary to maintain flow, increased osmolality and the concentrations of protein, urea, potassium, calcium, magnesium, bicarbonate and phosphate and decreased sodium, chloride and hydrogen ion in the saliva. Salivary amylase activity was low and highly variable and the amylase activity/protein ratio fell substantially during isoprenaline stimulation. These results support the conclusion that the enzyme is of extrinsic origin. The response of the kangaroo mandibular gland to isoprenaline stimulation was very similar to that reported for rat mandibular gland, suggesting that the same ion transport phenomena underlie mandibular secretion in both species and probably in therian mammals generally.

Acetylcholine↗