Borrelia-like spirochetes recovered from ticks and small mammals collected in the Atlantic Forest Reserve, Cotia county, State of Sao Paulo, Brazil.
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Forty-four marsupials, 77 rodents and 161 ticks were captured in an Atlantic Forest Reserve in Cotia county, State of Sao Paulo, where human cases of Lyme disease (LD) simile were reported. Twenty-one borrelia-like spirochete isolates were recovered from the mammals' blood and rodent livers or spleens, and triturated ticks inoculated into BSK II medium. Our results suggest that the reservoirs and ticks collected may harbor borrelia-like spirochetes, some of which have an antigenic similarity with the unknown causative agent of LD simile in Brazil, and/or with North American Borrelia burgdorferi s. s. (+info)
A staging scheme for assessing development in vitro of organogenesis stage embryos of the stripe-faced dunnart, Sminthopsis macroura (Marsupialia: dasyuridae).
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The inaccessibility of mammalian organogenesis stage embryos has precluded their widespread use in embryological and teratological studies. As organogenesis occurs during the last 1.5 days of the 10. 7 days of gestation in the stripe-faced dunnart (Sminthopsis macroura), the aim of the present study was to investigate whether day 9 and day 10 embryos and fetuses could be grown to term in vitro. High glucose Dulbecco's modified Eagle's medium with 10% fetal calf serum (FCS) supported embryonic growth for various periods of time, some to within 5 h of the predicted time of parturition. A roller culture system maintained at 35 degrees C was used to incubate organogenesis stage embryos (n = 43). Nine unincubated (control) embryos were either fixed for microscopic analysis or frozen for microprotein determination. The results of the present study indicate that with some optimization of the culture conditions (increasing oxygen in the gas phase in the culture tubes, replacing FCS with rat serum), it might be possible for organogenesis stage S. macroura embryos to be grown to term. A scoring scheme for assessing morphological development was devised for use as a standard in staging organogenesis stage embryos. This scheme reflects the highly compressed schedule of developmental events that occurs mainly during day 9 of gestation in S. macroura embryos. In comparison, during embryogenesis in Didelphis virginiana these developmental events occur from day 8 to day 10.5 of gestation, and birth occurs on day 13. (+info)
An orphaned mammalian beta-globin gene of ancient evolutionary origin.
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Mammals possess multiple, closely linked beta-globin genes that differ in the timing of their expression during development. These genes have been thought to be derived from a single ancestral gene, by duplication events that occurred after the separation of the mammals and birds. We report the isolation and characterization of an atypical beta-like globin gene (omega-globin) in marsupials that appears to be more closely related to avian beta-globin genes than to other mammalian beta-globin genes, including those previously identified in marsupials. Phylogenetic analyses indicate that omega-globin evolved from an ancient gene duplication event that occurred before the divergence of mammals and birds. Furthermore, we show that omega-globin is unlinked to the previously characterized beta-globin gene cluster of marsupials, making this the first report of an orphaned beta-like globin gene expressed in a vertebrate. (+info)
Endogenous type D retrovirus in a marsupial, the common brushtail possum (Trichosurus vulpecula).
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We have sequenced and characterized an endogenous type D retrovirus, which we have named TvERV(D), from the genome of an Australian marsupial, the common brushtail possum (Trichosurus vulpecula). Intact TvERV(D) gag, pro, pol, and env open reading frames were detected in the possum genome. TvERV(D) was classified as a type D retrovirus, most closely related to those of Old World monkeys, New World monkeys, and mice, based on phylogenetic analyses and genetic organization. Approximately 30 TvERV(D) proviruses are present in the genomes of possums, as detected by Southern hybridization. However, variability in fragment patterns between possums was observed and suggests recent (or ongoing) retrotranspositional activity. (+info)
The development and mature organisation of the end-artery retinal vasculature in a marsupial, the dunnart Sminthopsis crassicaudata.
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The end-artery retinal vasculature of a marsupial, the fat-tailed dunnart, was defined by India ink injection and studied in wholemounts. In the adult, the vitreal vasculature supplying the ganglion-cell layer has major paired-vessels in a horizontal H shape. These vessels skirt the area centralis and visual streak that are supplied by fine end-loops. A second vascular layer of uniformly distributed endloops arises from the superficial vessels and lies at the inner nuclear/outer plexiform border. During development, vessels enter the eye via the optic nerve head to form the upper vasculature, assuming an essentially mature arrangement prior to the formation of the area centralis and visual streak. Vessels then descend to form the lower bed. Unlike the cat, the dunnart has retinal vessels that are patent throughout development, their growth is interstitial and reductive remodelling is not seen. A retinal end-artery system may have evolved in marsupials because their precocity requires a vasculature that is functional from early stages of development. (+info)
Identification of an extracellular segment of the oxytocin receptor providing agonist-specific binding epitopes.
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The effects of the peptide hormone oxytocin are mediated by oxytocin receptors (OTRs) expressed by the target tissue. The OTR is a member of the large family of G-protein-coupled receptors. Defining differences between the interaction of agonists and antagonists with the OTR at the molecular level is of fundamental importance, and is addressed in this study. Using truncated and chimaeric receptor constructs, we establish that a small 12-residue segment in the distal portion of the N-terminus of the human OTR provides important epitopes which are required for agonist binding. In contrast, this segment does not contribute to the binding site for antagonists, whether peptide or non-peptide. It does, however, have a role in agonist-induced OTR signalling. Oxytocin is also an agonist at the vasopressin V(1a) receptor (V(1a)R). A chimaeric receptor (V(1a)R(N)-OTR) was engineered in which the N-terminus of the OTR was substituted by the corresponding, but unrelated, sequence from the N-terminus of the V(1a)R. We show that the V(1a)R N-terminus present in V(1a)R(N)-OTR fully restored both agonist binding and intracellular signalling to a dysfunctional truncated OTR construct. The N-terminal segment does not, however, contribute to receptor-selective agonism between the OTR and the V(1a)R. Our data establish a key role for the distal N-terminus of the OTR in providing agonist-specific binding epitopes. (+info)
The structural organisation of sperm head components of the wombat and koala (suborder: Vombatiformes): an enigma amongst marsupials.
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The sperm head structural organisation of the koala and hairy-nosed wombat, and the effects of varying concentrations of the ionic detergent, Triton X-100, on its component parts, were determined by electron microscopy. Although alike in form between the 2 species, the sperm nucleus of the former, but not the latter, had nuclear vacuoles and appeared to be more easily dispersed by the Triton X-100. The structure of the acrosome of the spermatozoon was similar between the 2 species and, in both, previously undescribed thin posterior and lateral segments were found to be present. It is suggested that this thin segment may facilitate sperm-zona and/or sperm-oolemma binding and fusion. (+info)
Semelparity in a large marsupial.
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Complete mortality of males after mating is known in several small dasyurid and didelphid species (up to 300g) and has previously been suggested to be a consequence of their small size and their inability to sequester sufficient fat reserves for an intense rut in the winter. Males of these species use increased corticosteroid levels to allow protein catabolism, enabling them to support their mating effort with other body reserves. However, increased corticosteroid levels have negative consequences such as anaemia, gastrointestinal ulceration, immune suppression and disease. The Australian dasyurid Dasyurus hallucatus shows complete male die off after mating in tropical savannah, yet males of this species may weigh as much as 1120 g and continue to eat during the rut. Die off in D. hallucatus shows many similarities to that in the smaller species including weight loss, fur loss, parasite infestation, increased testosterone levels and anaemia. However, in contrast to smaller species, there is no evidence of elevated corticosteroid levels or gastrointestinal ulceration. Consequently, the phenomenon of male die off after mating lacks a universal explanation. (+info)