Publications
| Title | Abstract | Year Filter | PMID(sorted ascending) Filter |
|---|
| development of early cell lineages in marsupial embryos: an overview. | all major embryonic and extra-embryonic cell lineages are established before implantation in marsupials. in reptiles, birds, monotremes and most marsupials, the zygote is polarized, sometimes markedly so, and the cleavage pattern in relation to the polarized state provides the mechanism for the generation of positional signals. these ensure that the embryonic cell lineages develop in the centre of the developing blastoderm or blastocyst epithelium and the extra-embryonic lineages at the peripher ... | 1994 | 7878224 |
| x-chromosome replication patterns in adult, newborn and prenatal opossums. | somatic cells from the opossums monodelphis domestica and didelphis virginiana were labelled with 5-bromodeoxyuridine (brdu), treated with colchicine, stained with acridine orange and examined using fluorescence microscopy. brdu-incorporated metaphase spreads from females of m. domestica at developmental stages from late bilaminar blastocysts to adults showed replication asynchrony of the two (acrocentric) x chromosomes. the long arm of one x chromosome was the latest replicating region in the e ... | 1994 | 7878226 |
| projection of visuotopically organized afferents to the dorsal thalamus in the opossum, monodelphis domestica. | retrogradely transported dyes, fluorogold and fast blue were injected into both sides of the dorsal thalamus in the monodelphis opossum. projection of the presumed primary visual cortical area, superior colliculus and parabigeminal nucleus to the dorsal lateral geniculate nucleus and the lateral posterior--lateral intermedius nuclear complex were described. they show close similarities to the homologous projections in the north american opossum, insectivores and some rodents. in comparison with ... | 1994 | 7887182 |
| early development of cerebellar afferent systems that contain corticotropin-releasing factor. | corticotropin-releasing factor (crf) and crf binding sites have been described in the cerebellum of several species, including the north american opossum (didelphis marsupialis virginiana), the species used in the present study. inotophoretic application of this peptide in the adult cerebellum enhances the spontaneous and amino acid-induced firing rate of purkinje cells and overcomes the gaba-induced suppression of purkinje cell activity. the present account provides immunohistochemical evidence ... | 1994 | 7890829 |
| timetable of in vivo embryonic development in the grey short-tailed opossum (monodelphis domestica). | the timing of development was examined in 496 embryos from female monodelphis domestica collected at known time intervals after video recorded mating. ovulation occurred approximately 20 hr (day 1) after mating, and fertilization was observed by 24 hr. transport through the oviducts was rapid, and pronuclear stage embryos were recovered from the uterus as early as 24 hr after mating. second cleavage had occurred by 55 hr after mating. three-celled embryos were among those collected on day 3 afte ... | 1994 | 7893485 |
| uroguanylin: structure and activity of a second endogenous peptide that stimulates intestinal guanylate cyclase. | the intestinal hormone guanylin and bacterial heat-stable enterotoxins (sts) are members of a peptide family that activates intestinal membrane guanylate cyclase. two different peptides that activate the human intestinal t84 cell guanylate cyclase have been purified from urine and intestinal mucosa of opossums (didelphis virginiana). the highly acidic peptide, qedcelcinvactgc, was named uroguanylin because it was isolated from urine and shares 53% identity with guanylin. a second peptide, shtcei ... | 1993 | 7902563 |
| hearing in primitive mammals: monodelphis domestica and marmosa elegans. | although opossums of the family didelphidae usually serve as a parsimonious starting point for tracing the otological and neurological evolution of modern mammals, audiological data for didelphid opossums is available only for the north american opossum (didelphis virginiana) which because of its large size, may be one of the least representative genera of the family. the present report extends the audiological data to two other species of didelphid opossums, monodelphis domestica, and marmosa e ... | 1994 | 7928716 |
| murine typhus: updated roles of multiple urban components and a second typhuslike rickettsia. | studies using serologic and polymerase chain reaction-(pcr) facilitated analysis of field samples from southern texas indicate the presence of rickettsia typhi and elb agent infected cat fleas, ctenocephalides felis (bouché), and the first observation of elb infected vertebrates (opossums). the elb agent is a recently described typhus-like rickettsia that is not distinguished from r. typhi or r. prowazekii by currently available serologic reagents. restriction digests of pcr products from 399 fl ... | 1994 | 7966170 |
| experimental ureteral obstruction in the fetal opossum: histologic assessment. | in the north american opossum, didelphis virginiana unilateral complete ureteral obstruction (eco) and partial unilateral (epo) ureteral obstruction were created during the early metanephric stage of kidney development in pups attached to the teat (approximately 4.5 cm. long, 20 days old). at 70 days of pouch life (full-term equivalent in the human) some completely obstructed ureters were unobstructed with reanastomosis in the bladder (reco). other pups underwent unilateral complete ureteral lig ... | 1994 | 7966702 |
| brain growth and neocortical development in the opossum. | general brain growth and differentiation of the neocortex have been studied in the marsupial, didelphis virginiana from the 10.5 day embryo through adulthood. didelphis is born after a short gestation period of about 12.5 days, at a time when the telencephalic wall consists only of two layers and is considered to be at an embryonic stage of development. the cortical plate does not appear until late in the first postnatal week, thus neocortical development is totally a postnatal phenomenon in did ... | 1994 | 7978336 |
| distribution of heat-stable enterotoxin/guanylin receptors in the intestinal tract of man and other mammals. | the human intestinal tract, as well as that of several eutherian and metatherian mammals, was examined for the distribution of heat-stable enterotoxin (st)/guanylin receptors. these receptors were confined to the intestinal epithelium lining the lumen and forming the intestinal glands throughout the length of both the small intestine and colon of all species examined. in man and most other mammalian species, there appeared to be a decrease in receptor density distally along the longitudinal axis ... | 1994 | 8014132 |
| the marsupial mitochondrial genome and the evolution of placental mammals. | the entire nucleotide sequence of the mitochondrial genome of the american opossum, didelphis virginiana, was determined. two major features distinguish this genome from those of other mammals. first, five trna genes around the origin of light strand replication are rearranged. second, the anticodon of trna(asp) is posttranscriptionally changed by an rna editing process such that its coding capacity is altered. when the complete protein-coding region of the mitochondrial genome is used as an out ... | 1994 | 8056314 |
| intrinsic factor-cobalamin receptor activity in a marsupial, the american opossum (didelphis virginiana). | 1. significant and specific binding of intrinsic factor-cobalamin occurred in proximal but not in the distal half of the intestine in an adult marsupial, the american opossum. 2. the purified opossum kidney receptor, like rat and canine kidney receptors, revealed a single band of m(r) approximately 230 on sds-page. however, unlike the rat and canine receptors, the opossum receptor was sensitive to both endoglycosidase h and peptide-n-glycosidase f. 3. the opossum intrinsic factor-cobalamin recep ... | 1993 | 8097983 |
| oxidation reactions of human, opossum (didelphis virginiana) and spot (leiostomus xanthurus) hemoglobins: a search for a correlation with some structural-functional properties. | 1. relative to human hba, opossum (didelphis virginiana) hemoglobin was found to be more susceptible to autoxidation. while the initial rate of autoxidation of spot (leiostomus xanthurus) hemoglobin is close to that of hba, complete oxidation occurs in 50 hr. 2. direct addition of hydrogen peroxide (h2o2) induced oxidation of hemoglobins in a definite order: spot hb > hba > opossum hb. excess h2o2 led to heme degradation and precipitation that occurred much faster for spot hb than the case with ... | 1993 | 8243064 |
| development of radial glia and astrocytes in the spinal cord of the north american opossum (didelphis virginiana): an immunohistochemical study using anti-vimentin and anti-glial fibrillary acidic protein. | we have shown previously that rubrospinal axons grow around a lesion of their pathway in developing opossums and that a critical period exists for that plasticity. as a first step toward addressing the possibility that glial maturation and/or the development of an astrocytic response to lesioning contribute to loss of rubrospinal plasticity, we have studied the normal development of radial glia and astrocytes in the spinal cord of the opossum by immunostaining for vimentin (vim) and glial fibril ... | 1993 | 8244526 |
| development of an astrocytic response to lesions of the spinal cord in the north american opossum: an immunohistochemical study using anti-glial fibrillary acidic protein. | we have shown previously that rubral axons grow around a lesion of their pathway in developing opossums and that a critical period exists for that plasticity. the critical period begins when rubral axons first reach the level of the lesion and ends sometime between postnatal days (pd) 26 and 30. the aim of the present study was to examine the development of an astrocytic response to lesioning the spinal cord to determine if there is a temporal correlation between the development of such a respon ... | 1993 | 8244527 |
| ixodes dammini (acari: ixodidae) infestation on medium-sized mammals and blue jays in northwestern illinois. | high prevalence of infestation of five species of medium-sized mammals and blue jays, cyanocitta cristata (l.), by immature ixodes dammini spielman, clifford, piesman and corwin was found in castle rock state park in northwestern illinois during may-august 1991. raccoons, procyon lotor l., and opossums, didelphis virginiana kerr, were infested with the highest larval densities and were trapped primarily in bottomland forest and ecotone habitats. all species had similar nymphal densities, except ... | 1993 | 8254647 |
| the effect of enzyme replacement on red cell adenine deoxyribonucleotides in adenosine deaminase-deficient erythrocytes of the opossum, didelphis virginiana. | 1. polyethyleneglycol-modified bovine adenosine deaminase was administered (10-20 u/kg/week) intramuscularly to two opossums for 15 weeks and changes in red cell adenine ribo- and deoxyribonucleotides quantitated by hplc. 2. only a moderate decline of erythrocyte daxp was observed at the end of the study when compared to results of enzyme replacement seen in human adenosine deaminase deficient patients. 3. opossum red cells salvage substantial amounts of deoxyadenosine provided in physiologic (5 ... | 1993 | 8281757 |
| 2'-deoxyadenosine metabolism in human and opossum didelphis virginiana erythrocytes in vitro. | 1. in erythrocytes of both species, deamination and phosphorylation of dado was completely inhibited by 5 microm 2'deoxycoformycin and 10 microm 5-itu respectively. 2. under physiologic conditions, provided with nanomolar concentrations of dado there was complete deamination of dado in human red cells. in opossum erythrocytes deamination and phosphorylation of the deoxynucleoside were nearly; additionally, 1-2% of the substrate was metabolized to axp. 3. with ada inhibited in intact red cells, a ... | 1993 | 8281758 |
| development of the eye in the north american opossum (didelphis virginiana). | marsupials are unique models for developmental biology-oriented research because of the immature state of their development at birth. the north american opossum (didelphis virginiana) has several advantages over other marsupials, including large litter size, short prenatal period (12.5 d), an extended postnatal period while accessible in the pouch, and its ability to reproduce reliably in captivity. studies of ocular development in this species have not been reported previously. the aim of the p ... | 1993 | 8300421 |
| maximum discharge rates of respiratory neurons during opossum development. | the observed low frequencies of action potentials observed in medullary respiratory neurons of immature opossums (didelphis virginiana) could occur because these cells are incapable of achieving higher sustained firing rates. nonsustainability of firing might also help explain why the inspired breath is brief (approximately 0.1 s) in the youngest opossums and rises very slowly during postnatal life. firing frequencies of medullary respiratory neurons were examined in spontaneously breathing thio ... | 1993 | 8307857 |
| characterization of mannose 6-phosphate receptors (mprs) from opossum liver: opossum cation-independent mpr binds insulin-like growth factor-ii. | bovine, human, and rat cation-independent mannose 6-phosphate receptors (ci-mprs) are capable of binding both mannose 6-phosphate and insulin-like growth factor-ii (igf-ii). however, the receptor isolated from either chicken or frog lacks the high affinity igf-ii-binding site. to determine whether ci-mprs isolated from a species that is closely related to placental mammals can bind igf-ii, the mprs were purified from a marsupial, the american opossum (didelphis virginiana), by phosphomannan-seph ... | 1993 | 8344189 |
| characterization of a marsupial sperm protamine gene and its transcripts from the north american opossum (didelphis marsupialis). | a synthetic oligonucleotide primer, designed from marsupial protamine protein-sequence data [balhorn, r., corzett, m., matrimas, j. a., cummins, j. & faden, b. (1989) analysis of protamines isolated from two marsupials, the ring-tailed wallaby and gray short-tailed opossum, j. cell. biol. 107] was used to amplify, via the polymerase chain reaction, protamine sequences from a north american opossum (didelphis marsupialis) cdna. using the amplified sequences as probes, several protamine cdna clone ... | 1993 | 8344286 |
| gestation and placentation in two new world opossums: didelphis virginiana and monodelphis domestica. | estrus, gestation, and placentation were studied in the virginia opossum (didelphis virginiana) and the gray short-tailed oppossum (monodelphis domestica), representatives of the prototypic, new world marsupial family didelphidae. didelphis is a large (3,000 g), pouched opossum that exhibits a 28-day estrous cycle, spontaneous estrus and ovulation, and a high ovulation rate (60 ova per cycle). monodelphis is a small (100 g), pouchless opossum with male-induced estrus and ovulation and a moderate ... | 1993 | 8371092 |
| opossum serum alpha 1-proteinase inhibitor: purification, linear sequence, and resistance to inactivation by rattlesnake venom metalloproteinases. | opossum (didelphis virginiana) serum was fractionated with (nh4)2so4 and then chromatographed on deae-sepharose and phenyl-sepharose. affinity chromatography on a protein a-sepharose-antibody column removed traces of opossum serum metalloproteinase inhibitors, and resulted in a homogeneous preparation of opossum alpha 1-proteinase inhibitor (alpha 1-pi). the inhibitor is a single-chain glycoprotein (17.7% carbohydrate) with an estimated m(r) = 54,000. an opossum liver cdna library was immunoscre ... | 1993 | 8422360 |
| release of nitric oxide by activation of nonadrenergic noncholinergic neurons of internal anal sphincter. | the purpose of the present study was to investigate the direct release of nitric oxide (no) in response to the stimulation of nonadrenergic noncholinergic (nanc) nerves. the studies were performed on isolated smooth muscle strips of the opossum (didelphis virginiana) internal anal sphincter (ias). electrical field stimulation (efs) using the appropriate parameters caused a frequency-dependent fall in the resting tone of the ias. the release of no was measured directly by the chemiluminescence me ... | 1993 | 8430806 |
| the origins of descending projections to the lumbar spinal cord at different stages of development in the north american opossum. | we have employed the retrograde transport of fast blue (fb) to identify the origins of descending projections to the lumbar cord of the opossum from postnatal day (pd)1, 12-13 days after conception, to maturity. when fb injections were made into the lumbar cord at pd1, supraspinal labeling was sparse and limited to the hypothalamus, the reticular formation, the coeruleus complex, the caudal raphe, and, in one case, the interstitial nucleus of the medial longitudinal fasciculus and the lateral ve ... | 1993 | 8457879 |
| parasitic arthropods of sympatric opossums, cotton rats, and cotton mice from merritt island, florida. | six species of parasitic arthropods were collected from 12 opossums (didelphis virginiana), 8 species were obtained from 28 cotton rats (sigmodon hispidus), and 4 species were collected from 10 cotton mice (peromyscus gossypinus) from merritt island, brevard county, florida. the flea polygenis gwyni was the only parasite that infested all 3 host species, and it was present in very high densities (mean intensity = 73.7) on the opossums. the american dog tick, dermacentor variabilis, and the tropi ... | 1993 | 8459341 |
| morphological observations on the unique paired capillaries of the opossum retina. | light-microscopic and ultrastructural analysis of the ocular tissues of the north american opossum (didelphis virginiana) revealed that the arterial and venous segments of retinal vessels, including capillaries of the smallest calibre, occur in pairs. they do not form anastomotic networks, the common pattern in mammals with vascularised retinae, but instead the two segments of the pair join to form hairpin end loops. the paired vessels, with the arteriolar limb usually on the vitread aspect, pen ... | 1993 | 8472304 |
| identification of opossums (didelphis virginiana) as the putative definitive host of sarcocystis neurona. | sarcocystis neurona is an apicomplexan that causes equine protozoal myeloencephalitis (epm) in north and south america. horses appear to be an aberrant host, because the merozoites continually divide in the central nervous system, without encysting. the natural host species has not previously been identified. the small subunit ribosomal rna (ssurna) gene of s. neurona was compared to those of sarcocystis muris, sarcocystis cruzi, toxoplasma gondii, and cryptosporidium parvum to identify a unique ... | 1995 | 8544064 |
| sarcocystis falcatula from passerine and psittacine birds: synonymy with sarcocystis neurona, agent of equine protozoal myeloencephalitis. | equine protozoal myeloencephalitis (epm) is a neurologic disease of horses caused by sarcocystis neurona. the horse is a dead-end host for s. neurona and the definitive and intermediate hosts have not previously been identified. we hypothesized that s. neurona is actually sarcocystis falcatula, a parasite that cycles in nature between virginia opossums (didelphis virginiana) and any of a variety of avian intermediate hosts. we extracted dna from s. falcatula sarcocysts in the muscle of a brown-h ... | 1995 | 8544067 |
| perivitelline space of marsupial oocytes: extracellular matrix of the unfertilized oocyte and formation of a cortical granule envelope following the cortical reaction. | the purpose of this study was to characterize the structure of the vestments surrounding unfertilized and cortical granule-reacted oocytes from a marsupial, the grey short-tailed opossum monodelphis domestica and to determine if a cortical granule envelope (cge) forms in the perivitelline space (pvs) following the cortical reaction. unfertilized oocytes collected from mature ovarian follicles and oviducal oocytes that had undergone a cortical reaction were fixed for electron microscopy in the pr ... | 1995 | 8588937 |
| effects on breathing of medullary bicuculline microinjections in immature opossums. | the role of medullary gamma-aminobutyric acid a (gabaa)-receptor activation in the expression of breathing was studied in suckling opossums (didelphis virginiana) from 4 to 8 wk of age. animals were anesthetized with a thiobarbiturate, and the ventral medulla was exposed so that drugs could be microinjected into the medulla with a two-barrel glass micropipette. the gabaa antagonist bicuculline at approximately 1-3 pmol total dose was injected in volumes < 1 nl; injections of saline with pontamin ... | 1995 | 8594928 |
| man and the chimaera. selective versus neutral oxytocin evolution. | the oxytocin/vasopressin superfamily encompasses vertebrate and invertebrate peptides and therefore the ancestral gene encoding the precursor protein antedates the divergence between the two groups, about 700 million years ago. the preserved nonapeptide pattern indicates that both the precursor structures and the processing enzymatic machinery were greatly conserved to ensure the building of a specific conformation. substitutions, which may be neutral or selective, occurred in precise positions. ... | 1995 | 8714026 |
| ticks (acari: ixodidae) in bulloch county, georgia. | an 18-mo study was conducted in bulloch county, georgia, to determine tick species composition, seasonal activity of individual tick species, and host-tick associations. the following 7 methods of tick collection were included: (1) live trapping of potential host animals, (2) checking wild game, (3) drag sampling, (4) carbon dioxide attraction, (5) checking livestock, road kills, nests, and burrows, (6) samples submitted from veterinarians, and (7) ticks collected by local residents and submitte ... | 1996 | 8742526 |
| a molecular and evolutionary study of the beta-globin gene family of the australian marsupial sminthopsis crassicaudata. | beta-globin gene families in eutherians (placental mammals) consist of a set of four or more developmentally regulated genes which are closely linked and, in general, arranged in the order 5'-embryonic/fetal genes-adult genes-3'. this cluster of genes is proposed to have arisen by tandem duplication of ancestral beta-globin genes, with the first duplication occurring 200 to 155 mybp just prior to a period in mammalian evolution when eutherians and marsupials diverged from a common ancestor. in t ... | 1996 | 8752008 |
| evolution of transthyretin gene expression in the liver of didelphis virginiana and other american marsupials. | the occurrence of the thyroid hormone-binding plasma protein transthyretin in the bloodstream was investigated for four american marsupial species. serum samples were analyzed by incubation with radioactive t4, followed by electrophoresis, then autoradiography, and western blotting. transthyretin was found in serum from monodelphis domestica, didelphis virginiana, caluromys lanatus, and dromiciops australis. for unambiguous identification, transthyretin from d, virginiana was purified from serum ... | 1996 | 8754780 |
| growth of dorsal spinocerebellar axons through a lesion of their spinal pathway during early development in the north american opossum, didelphis virginiana. | supraspinal axons grow around or through lesions of their spinal pathway during specific critical periods of mammalian development, but comparable plasticity has not been documented for axons which form ascending tracts. in the present study, we asked whether axons of the dorsal spinocerebellar tract (dsct) are capable of such growth. the spinal cord of the north american opossum, didelphis virginiana, was hemisected at mid-thoracic levels between postnatal day (pd) 5 and 68 and after varying su ... | 1996 | 8804690 |
| milk composition in the north american opossum (didelphis virginiana). | the composition of milk samples collected from captive opossums (didelphis virginiana) was determined at various intervals during lactation. the milk solids increased from 9% at week one to a maximum of 34% at 11 weeks post-partum. there were changes in the relative proportions of protein, lipid and carbohydrate at different stages of lactation. lipid represented the greatest fraction of the solids except for a period at mid-lactation when there was a peak in protein concentration. the concentra ... | 1996 | 8829811 |
| evidence for growth of supraspinal axons through the lesion after transection of the thoracic spinal cord in the developing opossum didelphis virginiana. | in the present study, we asked whether supraspinal axons grow through a complete transection of the spinal cord in the developing opossum didelphis virginiana. when the thoracic cord was transected at postnatal day (pd) 5 and bilateral injections of fast blue (fb) were made four segments caudal to the lesion 30-40 days later, fb-containing neurons were found in each of the supraspinal nuclei labeled by comparable injections in age-matched unlesioned controls. continuity between the cut ends of t ... | 1996 | 8835721 |
| topography, architecture, and connections of somatosensory cortex in opossums: evidence for five somatosensory areas. | microelectrode maps of somatosensory inputs were related to cortical architecture and patterns of cortical connections to provide evidence for five subdivisions of the somatosensory or sensorimotor cortex in north american opossums (didelphis marsupialis). microelectrode recordings revealed three systematic representations of the body surface. a large mediolaterally oriented representation was identified as the primary somatosensory area (s1) by its relative position, somatotopy, architecture, a ... | 1996 | 8866849 |
| ontogeny of suckling mechanisms in opossums (didelphis virginiana). | although adult mammals have several different mechanisms for drinking liquids, relatively little is known about the variation in mechanisms used by infants for suckling and how the mechanics of suckling change as a function of ontogeny. we examined suckling in infant opossums, animals that as adults use a lapping mechanism to drink. the youngest infants (45 days old) used a suction, pumping mechanism, based on dorsal/ventral tongue movements, similar to what has been documented in infant primate ... | 1996 | 8872320 |
| methylation analysis of a marsupial x-linked cpg island by bisulfite genomic sequencing. | paternal x chromosome inactivation occurs in rodent extraembryonic membranes and in all tissues of marsupials. methylation of cpg islands occurs on the inactive x in eutherians and is considered to be a stabilizing mechanism. the only previous study of a marsupial x-linked cpg island was of the g6pd gene of the virginia opossum, in which the paternally derived allele is not completely repressed. we have cloned the 5' end of the g6pd gene from an australian marsupial, the common wallaroo, and seq ... | 1996 | 8919690 |
| the origin of brainstem-spinal pathways in the north american opossum (didelphis virginiana). studies using the horseradish peroxidase method. | 1978 | 8980723 | |
| the organization of monoamine neurons within the brainstem of the north american opossum (didelphis virginiana). | 1978 | 8980724 | |
| ontogeny and limb bone scaling in two new world marsupials, monodelphis domestica and didelphis virginiana. | this study examines the growth of two species of marsupials who share common ancestry and are born at the same neonatal size of a little less than 1 g. despite this similarity at birth, adult size of these two species differs by about 50 times, with the smaller species believed to be the more ancestral. we quantified the growth in the limb bones (humerus, femur, ulna, tibia, metacarpal, and metatarsal) beginning around 40 days of age until adult size was reached. results indicate that the larger ... | 1997 | 8989872 |
| auditory quality cues are more effective than auditory location cues in a r--no r (go--no go) differentiation: the extension of the rule to primitive mammals (american opossum, didelphis virginiana). | discrimination learning of instrumental responses to auditory compound stimuli was investigated in opossums using the r-no r (go-no go) differentiation. each compound stimulus consisted of two factors: quality and location. each correct response performed to the conditioned positive, or "safe" stimulus, was rewarded by food and never punished. each incorrect response performed to the conditioned negative, or "warning" stimulus, was punished by an electric shock. in subsequent testing, each oposs ... | 1996 | 9033130 |
| early development and developmental plasticity of the fasciculus gracilis in the north american opossum (didelphis virginiana). | the first objective of the present study was to ask when axons of the fasciculus gracilis reach the nucleus gracilis in the north american opossum (didelphis virginiana). when fast blue (fb) was injected into the lumbar cord on postnatal day (pd) 1 and the pups were killed 2 days later, labeled axons were present within a distinct fasciculus gracilis at thoracic and cervical levels of the cord. when comparable injections were made at pd3 or 5 and the pups were allowed to survive for the same tim ... | 1997 | 9051256 |
| experimental induction of equine protozoal myeloencephalitis in horses using sarcocystis sp. sporocysts from the opossum (didelphis virginiana). | sarcocystis sp. sporocysts isolated from eight feral opossums (didelphis virginiana) were pooled and fed to 18 commercially reared budgerigars (melopsittacus undulatus), 14 wild-caught sparrows (passer domesticus), one wild-caught slate-colored junco (junco hyemalis) and five weanling horses (equus caballus). all budgerigars died within 5 weeks post inoculation (wpi). histologic examination revealed meronts within the pulmonary epithelia and typical sarcocystis falcatula sarcocysts developing in ... | 1997 | 9066066 |
| evidence for gap-43 within descending spinal axons in the north american opossum, didelphis virginiana. | we have shown previously that gap-43, a growth associated protein characteristically present in growing and regenerating axons, is relatively abundant in the spinal cord of adult opossums. in the present study, we combined the orthograde transport of the fluorescent marker fluoro-ruby with immunofluorescence for gap-43 to determine if any of it is present within descending spinal axons. when fluoro-ruby was injected into the red nucleus and midbrain tegmentum, the medial pontine or medullary ret ... | 1996 | 9156783 |
| didelphid behavior. | there are approximately 75 species of american opossums (didelphids). systematic behavioral research has been reported for only a small number of species, namely, monodelphis domestica and didelphis virginiana. observational studies and field reports on several other didelphid species have also been published. the current review covers behavioral studies on didelphids including research on territoriality, reproductive behaviors, parturition, maternal behaviors, nest-building, vocalizations, scen ... | 1997 | 9168270 |
| development of the lymphoid tissues of the tammar wallaby macropus eugenii. | a study has been made of the development of four lymphoid tissues from birth to maturity in the tammar wallaby macropus eugenii--the cervical and thoracic thymus, lymph nodes and gut-associated lymphoid tissue (galt). the development of these tissues in the tammar wallaby is similar to that in two other marsupials, the quokka setonix brachyurus and the virginian opossum didelphis virginiana. lymphocytes were first detected in the cervical thymus of the tammar at day 2 post partum and in the thor ... | 1997 | 9208435 |
| l-arginine deficiency causes suppression of nonadrenergic noncholinergic nerve-mediated smooth muscle relaxation: role of l-citrulline recycling. | studies were performed on the internal anal sphincter (ias) smooth muscle strips obtained from opossums (didelphis virginiana). isometric tension and l-arginine levels of the tissues were measured under basal conditions, in the presence of electrical field stimulation (efs) and after treatment with different concentrations of arginase. for the nonadrenergic noncholinergic nerve stimulation, short trains (4 sec) as well as continuous efs were used. during continuous efs, after the initial ias rel ... | 1997 | 9223577 |
| developmental plasticity of selected spinocerebellar axons. studies using the north american opossum, didelphis virginiana. | when the thoracic spinal cord of the opossum is hemisected at postnatal day 5 or 8, but not at day 12 or later ages, spinocerebellar axons which originate from spinal border cells, the sacral/coccygeal ventrolateral nucleus, and stilling's nucleus grow through the lesion and reach the cerebellum. the critical period for such growth is comparable to that reported previously for spinocerebellar axons originating within clarke's nucleus and for axons of the fasciculus gracilis, but shorter than tha ... | 1997 | 9352116 |
| north american opossum didelphis virginiana as a fetal nephrotoxicity model: histologic and ultrastructural assessment of uranyl nitrate (un)-induced damage. | we have used our opossum model of fetal nephrotoxicity to investigate uranyl nitrate-induced morphologic changes in the developing kidney. the present study establishes a renal dose response curve for the uranyl nitrate (un). we find that pups treated with nonlethal doses of un do not demonstrate growth retardation compared to saline-treated controls. the kidneys of un-treated pups are heavier than the control animals, an effect less apparent the longer the pups are followed. a low dose of 60 mg ... | 1997 | 9372500 |
| glucose kinetics of the virginia opossum: possible implications for predicting glucose turnover in mammals. | primed continuous infusions of 6-3h-glucose, respirometry and measurements of nitrogen excretion were carried out in adult virginia opossums (didelphis virginiana). our goals were to determine resting glucose turnover rate, to establish the relative importance of this oxidative fuel in the energy budget of this species, to assess whether metabolic rate is a better predictor of glucose turnover rate than body mass and to demonstrate that glucose kinetics can be measured in the opossum for future ... | 1997 | 9406445 |
| adult opossums (didelphis virginiana) demonstrate near normal locomotion after spinal cord transection as neonates. | when the thoracic spinal cord of the north american opossum (didelphis virginiana) is transected on postnatal day (pd) 5, the site of injury becomes bridged by histologically recognizable spinal cord and axons which form major long tracts grow through the lesion. in the present study we asked whether opossums lesioned on pd5 have normal use of the hindlimbs as adults and, if so, whether that use is dependent upon axons which grow through the lesion site. the thoracic spinal cord was transected o ... | 1998 | 9582254 |
| regeneration of supraspinal axons after transection of the thoracic spinal cord in the developing opossum, didelphis virginiana. | when the thoracic spinal cord of the north american opossum is transected early in development, supraspinal axons grow through the lesion. in the experiments reported here, we asked whether regeneration of cut axons contributes to such growth. fast blue (fb) was injected into the lumbar cord on postnatal day (pd)5, 8, 15, or 20. five days later, fb was removed by gentle suction, and the spinal cord was transected at thoracic levels. fourteen days later, rhodamine b dextran was injected between t ... | 1998 | 9703028 |
| mycobacterium bovis in coyotes from michigan. | during a survey for tuberculosis in wild carnivores and omnivores, mycobacterium bovis was cultured from pooled lymph nodes of three adult female coyotes (canis latrans) harvested by hunters in michigan (usa). no gross or histologic lesions suggestive of tuberculosis were seen in these animals. one coyote was taken from montmorency county and two coyotes from alcona county located in the north-eastern portion of michigan's lower peninsula where free-ranging white-tailed deer (odocoileus virginia ... | 1998 | 9706576 |
| origin, course, and laterality of spinocerebellar axons in the north american opossum, didelphis virginiana. | spinocerebellar axons have been studied extensively in placental mammals, but there have been no full reports on their origin, laterality, or spinal course in any marsupial. we have used the north american opossum (didelphis virginiana) to obtain such information and to ask whether any spinocerebellar neurons innervate both the anterior and posterior lobes of the cerebellum through axonal collaterals. to identify spinal neurons that project to the cerebellum, we employed the retrograde transport ... | 1998 | 9713988 |
| the detection of hemorrhagic proteins in snake venoms using monoclonal antibodies against virginia opossum (didelphis virginiana) serum. | most snakes and a few warm-blooded animals have a resistance to snake venoms because of naturally occurring antihemorrhagins found in their sera. the antihemorrhagins in serum of virginia opossum (didelphis virginiana) neutralize hemorrhagic activity by binding to hemorrhagins in snake venoms. the binding characteristic of antihemorrhagins in d. virginiana serum was used to develop a five-step western blot. the detection of hemorrhagic proteins were measured indirectly with antihemorrhagins in v ... | 1998 | 9723843 |
| snake envenomation and protective natural endogenous proteins: a mini review of the recent developments (1991-1997). | the properties of several factors--antihaemorrhagic, antineurotoxic, antimyotoxic--isolated from the blood serum or plasma of different animals are described with more emphasis placed on the structural differences and similarities among the factors of the snake (trimeresurus flavoviridis) and mammals (didelphis marsupials and herpestes edwardsii). classification of antihaemorrhagic factors of snake and mammals according to structural homologies, and their effectiveness in neutralizing venom haem ... | 1998 | 9792161 |
| seroprevalence of antibodies against toxoplasma gondii in free-ranging mammals in iowa. | serum samples from raccoons (procyon lotor), striped skunks (mephitis mephitis), virginia opossums (didelphis virginiana), and free-ranging house cats trapped in iowa between 1984 and 1988 were tested for antibodies against toxoplasma gondii using the modified direct agglutination test (mat). antibody titers > or = 1:32 were considered indicative of infection. prevalence rates by species were estimated for raccoons at 134/885 (15%), skunks at 38/81 (47%), opossums at 12/53 (23%), and cats at 16/ ... | 1998 | 9813854 |
| a review of histogenesis/organogenesis in the developing north american opossum (didelphis virginiana). | 1998 | 9816723 | |
| a review of histogenesis/organogenesis in the developing north american opossum (didelphis virginiana). | 1998 | 9816726 | |
| isolation of a third species of sarcocystis in immunodeficient mice fed feces from opossums (didelphis virginiana) and its differentiation from sarcocystis falcatula and sarcocystis neurona. | opossums (didelphis virginiana) were found to be hosts for 3 species of sarcocystis: sarcocystis falcatula with an avian intermediate host, s. neurona with an undetermined intermediate host, and a third, unnamed, species. sporocysts from the intestines of 2 opossums (nos. 26 and 47) were fed to budgerigars (melopsittacus undulatus), nude mice, and gamma-interferon knockout (ko) mice. sporocysts of s. falcatula were not infective to nude or ko mice. sporocysts of s. neurona induced encephalitis i ... | 1998 | 9920306 |
| isolation in immunodeficient mice of sarcocystis neurona from opossum (didelphis virginiana) faeces, and its differentiation from sarcocystis falcatula. | sarcocystis neurona was isolated in nude mice and gamma-interferon knockout mice fed sporocysts from faeces of naturally infected opossums (didelphis virginiana). mice fed sporocysts became lethargic and developed encephalitis. protozoa were first found in the brain starting 21 days post-inoculation. sarcocystis neurona was recovered in cell culture from the homogenate of liver, spleen and brain of a nude mouse 11 days after feeding sporocysts. the protozoa in mouse brain and in cell culture mul ... | 1998 | 9925260 |
| developmental plasticity of ascending spinal axons studies using the north american opossum, didelphis virginiana. | the objectives of the present study were to determine if axons of all ascending tracts grow through the lesion after transection of the thoracic spinal cord during development in the north american opossum, and if so, whether they reach regions of the brain they normally innervate. opossum pups were subjected to transection of the mid-thoracic cord at pd5, pd8, pd12, pd20, or pd26 and injections of fast blue (fb) into the lower thoracic or upper lumbar cord 30-40 days or 6 months later. in the p ... | 1999 | 9974160 |
| field immobilization and euthanasia of american opossum. | seventeen recently trapped opossum, didelphis virginiana, (median weight 2.45 kg; range = 1.6-5.0 kg; quartiles = 1.8-3.3 kg) were immobilized with either telazol (15 or 30 mg/kg) or a mixture of medetomidine (100 micrograms/kg), butorphanol (0.2 mg/kg), and ketamine hcl (10 mg/kg) based on estimated weights. anesthetized animals were subjected to cardiac puncture for blood withdrawal and toe pinch. euthanasia was accomplished by intracardiac administration of 1 ml of concentrated pentobarbital ... | 1999 | 10073367 |
| site selection by intestinal helminths of the virginia opossum (didelphis virginiana). | digestive tract helminths of the virginia opossum (didelphis virginiana) were examined for site specificity and interspecific interactions. thirty opossums were live-trapped at 2 localities in georgia, killed, and their digestive tracts removed and divided into the following sections; esophagus, stomach, small intestine (20 equal sections), cecum, and large intestine (5 equal sections). helminths present in each section were identified and counted. three trematode, 1 cestode, 2 acanthocephala, a ... | 1999 | 10207354 |
| multiple dna markers differentiate sarcocystis neurona and sarcocystis falcatula. | studies designed to investigate the causative agent of equine protozoal myeloencephalitis and its life cycle have been hampered by the marked similarity of sarcocystis neurona to other sarcocystis spp. present in the same definitive host. random-amplified polymorphic dna techniques were used to amplify dna from isolates of s. neurona and sarcocystis falcatula. dna sequence analysis of polymerase chain reaction (pcr) products was then used to design pcr primers to amplify specific sarcocystis spp ... | 1999 | 10219299 |
| are sarcocystis neurona and sarcocystis falcatula synonymous? a horse infection challenge. | equine protozoal myeloencephalitis (epm) is a debilitating neurologic disease of the horse. the causative agent. sarcocystis neurona, has been suggested to be synonymous with sarcocystis falcatula, implying a role for birds as intermediate hosts. to test this hypothesis, opossums (didelphis virginiana) were fed muscles containing s. falcatula sarcocysts from naturally infected brown-headed cowbirds (molothrus ater). ten horses were tested extensively to ensure no previous exposure to s. neurona ... | 1999 | 10219313 |
| patterns of infestation by adult dermacentor variabilis (acari: ixodidae) in a mark-recapture study of raccoons (mammalia: carnivora) and virginia opossums (mammalia: didelphimorphia) in tennessee. | a mark-recapture study of raccoons (procyon lotor l.) and virginia opossums (didelphis virginiana kerr) was conducted from february 1991 through april 1994 to determine host interactions with adult dermacentor variabilis say. we captured 1,293 raccoons and virginia opossums during the 3-yr study (140 individual raccoons and 160 individual virginia opossums) with 1,895 adult d. variabilis collected. raccoons had a significantly higher mean intensity and higher prevalence of adult ticks than virgi ... | 1999 | 10337094 |
| implications of raccoon latrines in the epizootiology of baylisascariasis. | raccoons (procyon lotor) frequently establish defecation sites, termed latrines, on large logs, stumps, rocks, and other horizontally oriented structures/surfaces. these latrines are important foci of infective eggs of baylisascaris procyonis, a nematode parasite of raccoons which is pathogenic to numerous species of mammals and birds. to examine the role of raccoon latrines in this animal-parasite interaction, we documented animal visitations to raccoon latrines in two large forested tracts and ... | 1999 | 10479081 |
| characterization of metastatic intestinal adenocarcinoma with differentiation into multiple morphologic cell types in a virginia opossum. | a captively maintained mature male opossum (didelphis virginiana) utilized in a research protocol was presented with clinical signs of chronic diarrhea and severe muscle wasting. at necropsy, there was multifocal mural gastric, intestinal, and urinary bladder thickening, concurrent bilateral hydroureter and hydronephrosis, and extensive fibrous abdominal adhesions. histologic evaluation revealed intestinal adenocarcinoma with coelomic metastasis to the stomach and urinary bladder. the adenocarci ... | 1999 | 10490217 |
| subretinal macrophages in the developing eye of eutherian mammals and marsupials. | blood-borne mononuclear cells invade the developing retina via the hyaloid vasculature at the optic nerve head. following removal of apoptotic cell debris they give rise to the network of resident microglia. the population of cells recently described in the peripheral subretinal space of developing human eyes may represent a further population of macrophages destined to become microglia. the aim of the present study was to confirm the presence of subretinal macrophages in the developing eye in o ... | 1999 | 10526023 |
| ticks and antibodies to borrelia burgdorferi from mammals at cape hatteras, nc and assateague island, md and va. | results of a survey for ixodid ticks and/or serum antibodies to borrelia burgdorferi from 14 species of small to large mammals from eastern coastal areas of the united states are presented. most samples were obtained from july 1987 through june 1989 (excluding december-march) at 3 locales: assateague is. national seashore, worcester co., md., and accomack co., va. (approximately 38 degrees 05' n 75 degrees 10' w), and cape hatteras national seashore, dare co., nc (approximately 35 degrees 30' n ... | 1999 | 10534951 |
| oral rabies vaccine contact by raccoons and nontarget species in a field trial in florida. | rabies is enzootic in raccoons (procyon lotor) in the eastern united states. oral vaccination of free-ranging raccoons against rabies has the potential to control the disease in a principal reservoir and reduce the risk of rabies exposure among domestic animals and humans. free-ranging animal contact with baits containing a vaccinia virus recombinant vaccine expressing the rabies glycoprotein gene (v-rg) was monitored in pinellas county (florida, usa) from february through may 1997. bait contact ... | 1999 | 10574527 |
| sarcocystis speeri n. sp. (protozoa: sarcocystidae) from the opossum (didelphis virginiana). | the north american opossum (didelphis virginiana) is host to at least 3 species of sarcocystis: sarcocystisfalcatula, sarcocystis neurona, and a recently recognized sarcocystis sp. a new name, sarcocystis speeri, is proposed for the third unnamed sarcocystis. immunodeficient mice are an experimental intermediate host for s. speeri. sarcocystis speeri sporocysts are 12-15 x 8-10 microm in size, and its schizonts are found in many organs of mice. sarcocysts of s. speeri are found in skeletal muscl ... | 1999 | 10577729 |
| screening for fibrinolytic activity in eight viperid venoms. | snake venoms contain direct-acting fibrinolytic metalloproteinases (mmp) that could have important applications in medicine. fibrinolytic enzymes isolated from venom can induce in vitro clot lysis by directly acting on a fibrin clot. the most ideal fibrinolytic enzyme would have high affinity for clots, dissolve clots directly without causing hemorrhage, and would not be neutralized in vivo by endogenous metalloproteinase inhibitors. the purpose of this study was to compare deae/hplc venom profi ... | 1999 | 10579653 |
| rescue of axotomized rubrospinal neurons by brain-derived neurotrophic factor (bdnf) in the developing opossum, didelphis virginiana. | many rubrospinal neurons die in developing opossums when their axon is cut at thoracic levels of the spinal cord and in the present study we asked whether they can be rescued by brain-derived neurotrophic factor (bdnf). bilateral injections of fast blue (fb) were made into the rostral lumbar cord to prelabel rubrospinal neurons and 5 days later the rubrospinal tract was cut unilaterally by hemisecting the thoracic cord. immediately after hemisection, bdnf-soaked gelfoam was placed into the lesio ... | 1999 | 10611517 |
| a simple technique for blood collection in the opossum (didelphis virginiana). | the left and right brachiocephalic veins were used for rapid collection of 5-10 ml blood samples in adult opossums. these vessels were also used to collect 0.5-1 ml blood samples in 120-day-old opossums. the animals were anaesthetized with 30 mg/kg of ketamine hydrochloride given intramuscularly prior to blood collection. | 1984 | 10628788 |
| isolation of sarcocystis speeri dubey and lindsay, 1999 parasite from the south american opossum (didelphis albiventris) from argentina. | sarcocystis sporocysts from the intestines of 2 opossums (didelphis albiventris) from argentina were fed to gamma-interferon knockout (ko) and nude mice. protozoal schizonts were seen in brain, liver, spleen, and adrenal glands of mice examined 33-64 days after feeding sporocysts. sarcocysts were seen in skeletal muscles of ko mice 34-71 days after feeding sporocysts. schizonts and sarcocysts were structurally similar to sarcocystis speeri dubey and lindsay, 1999 seen in mice fed sporocysts from ... | 2000 | 10701583 |
| energy metabolism of the virginia opossum during fasting and exercise. | rates of oxygen consumption and co(2) production were measured in virginia opossums (didelphis virginiana) during fasting and prolonged exercise to quantify changes in total energy expenditure and oxidative fuel selection. we hypothesized that fasting would cause metabolic depression and a progressive shift towards lipid utilization to spare alternative substrates. it was also predicted that prolonged exercise would cause the same relative changes in fuel preference as fasting, but on a compress ... | 2000 | 10729284 |
| streptococcus didelphis sp. nov., a streptococcus with marked catalase activity isolated from opossums (didelphis virginiana) with suppurative dermatitis and liver fibrosis. | beta-haemolytic, catalase-positive, gram-positive cocci that formed chains in broth media but did not react with lancefield group antisera were isolated from skin lesions, spleen, liver and lungs of nine opossums, including eight from a research colony and one from a wildlife rehabilitation organization. the isolates had vigorous catalase activity that was retained on initial passage on non-blood-containing media, but this activity was lost in subsequent passages. the use of standard phenotypic ... | 2000 | 10758886 |
| isolation and characterization of dm40 and dm43, two snake venom metalloproteinase inhibitors from didelphis marsupialis serum. | from didelphis marsupialis serum, two antihemorrhagic proteins were isolated by deae-sephacel, phenyl-sepharose and superdex 200 and characterized. their masses by mass spectrometry were 40318 amu for dm40 and 42373 and 43010 amu for dm43, indicating the presence of isoforms for the last. molecular masses of 44.8 and 47.3 were obtained by sds-page, respectively for dm40 and dm43. both inhibitors showed isoelectric points lower than 3.5 and glycosylation percentages varying from 20.5 to 29.0%, as ... | 2000 | 10779682 |
| experimental transmission of sarcocystis speeri dubey and lindsay, 1999 from the south american opossum (didelphis albiventris) to the north american opossum (didelphis virginiana). | sarcocystis speeri dubey and lindsay, 1999 from the south american opossum didelphis albiventris was successfully transmitted to the north american opossum didelphis virginiana. sporocysts from a naturally infected d. albiventris from argentina were fed to 2 gamma-interferon knockout (ko) mice. the mice were killed 64 and 71 days after sporocyst feeding (daf). muscles containing sarcocysts from the ko mouse killed 71 daf were fed to a captive d. virginiana; this opossum shed sporocysts 11 days a ... | 2000 | 10864267 |
| granulomatous pneumonia in the opossum (didelphis virginiana) associated with an intracellular fungal agent. | two of nine female opossums (didelphis virginiana) in a closed breeding colony were submitted for necropsy due to a history of poor reproductive performance in the absence of overt clinical disease. on histologic examination, marked granulomatous to pyogranulomatous pneumonia was identified in these animals. | 2000 | 10894501 |
| why fuse the mandibular symphysis? a comparative analysis. | fused symphyses, which evolved independently in several mammalian taxa, including anthropoids, are stiffer and stronger than unfused symphyses. this paper tests the hypothesis that orientations of tooth movements during occlusion are the primary basis for variations in symphyseal fusion. mammals whose teeth have primarily dorsally oriented occlusal trajectories and/or rotate their mandibles during occlusion will not benefit from symphyseal fusion because it prevents independent mandibular moveme ... | 2000 | 10918127 |
| prevalence of sarcocystis species sporocysts in wild-caught opossums (didelphis virginiana). | sarcocystis sporocysts were found in intestinal scrapings from 24 (54.5%) of 44 opossums (didelphis virginiana). the number of sporocysts varied from a few (< 10,000) to 245 million. sporocysts from 23 of 24 opossums were fed to captive budgerigars (melopsittacus undulatas), and the inocula from 21 opossums were infective, indicating the presence of sarcocystis falcatula. sporocysts from 24 opossums were fed to gamma-interferon-knockout (ko) or nude mice; inocula from 14 opossums were infective ... | 2000 | 10958444 |
| light and electron microscopic features of eperythrozoon-like parasites in a north american opossum (didelphis virginiana). | epierythrocytic parasites associated with a severe anemic episode have not been previously reported in the opossum. a wright-giemsa-stained peripheral blood smear from an anemic north american opossum (didelphis virginiana) revealed numerous organisms attached to red blood cells either singularly or in chains. ring forms of the organism were common and could be found free in the plasma. electron microscopy revealed that these organisms were attached to the intact plasma membrane in depressions o ... | 2000 | 10982141 |
| a staging scheme for assessing development in vitro of organogenesis stage embryos of the stripe-faced dunnart, sminthopsis macroura (marsupialia: dasyuridae). | 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 gr ... | 2000 | 11006151 |
| the seroprevalence of antibodies to sarcocystis neurona in michigan equids. | a cross-sectional study of serum antibodies to sarcocystis neurona (the etiologic agent of equine protozoal myeloencephalitis, epm) was performed on michigan equids. our objectives were to determine the seroprevalence of antibodies to s. neurona in michigan equids and to identify specific risk factors for seropositivity. a random, weighted sample of michigan horse farms (stratified by the state's opossum (didelphis virginiana) population and the number of equids on each operation) was selected. ... | 2001 | 11154784 |
| the south american opossum, didelphis marsupialis, from brazil as another definitive host for sarcocystis speeri dubey and lindsay, 1999. | the north american opossum, didelphis virginiana, is a definitive host for at least 3 species of sarcocvstis: s. falcatula stiles 1983, s. neurona dubey, davis, speer, bowman, de lahunta, granstrom, topper, hamir, cummings, suter 1991, and s. speeri dubey and lindsay 1999. in order to identify species of sarcocystis in the south american opossum, d. inarsupialis, sarcocystis sporocysts from the intestines of a naturally infected opossum (d. marsupialis) from brazil were fed to 4 gamma-interferon ... | 2000 | 11155929 |
| regeneration of descending spinal axons after transection of the thoracic spinal cord during early development in the north american opossum, didelphis virginiana. | opossums are born in an immature, fetal-like state, making it possible to lesion their spinal cord early in development without intrauterine surgery. when the thoracic spinal cord of the north american opossum, didelphis virginiana, is transected on postnatal day 5, and injections of fast blue (fb) are made caudal to the lesion site 30-40 days or 6 months later, neurons are labeled in all of the spinal and supraspinal areas that are labeled after comparable injections in age-matched, unlesioned ... | 2000 | 11165803 |
| repair of the transected spinal cord at different stages of development in the north american opossum, didelphis virginiana. | when the thoracic spinal cord is transected on postnatal day (pd) 5 in the north american opossum, descending and ascending axons grow through the lesion site. when the lesion is made on pd20, comparable growth is limited to a subset of descending axons. to better understand the mechanisms underlying these differences, we analyzed the transection site at different times after lesioning at both ages. axons which crossed the lesion site could be identified using silver impregnation and immunostain ... | 2000 | 11179852 |
| completion of the life cycle of sarcocystis neurona. | sarcocystis neurona is the most important cause of a neurologic disease in horses, equine protozoal myeloencephalitis (epm). the complete life cycle of s. neurona, including the description of sarcocysts and intermediate hosts, has not been completed until now. opossums (didelphis spp.) are definitive hosts, and horses and other mammals are aberrant hosts. in the present study, laboratory-raised domestic cats (felis domesticus) were fed sporocysts from the intestine of a naturally infected oposs ... | 2000 | 11191904 |
| host utilization and seasonal occurrence of dermacentor species (acari:ixodidae) in missouri, usa. | a total of 3,235 dermacentor variabilis (say) specimens were collected from birds, mammals, and by dragging vegetation, and 2,683 d. albipictus (packard) ticks were collected from deer from 1993 to 1996. peak seasonal occurrence of adult d. variabilis was from may through july with a precipitous decrease in august. nymphal d. variabilis populations peaked in june. peak activity of larvae was bimodal, with one activity peak during late summer (september) and a second peak in winter or early sprin ... | 2000 | 11201355 |
| a review of sarcocystis neurona and equine protozoal myeloencephalitis (epm). | equine protozoal myeloencephalitis (epm) is a serious neurological disease of horses in the americas. the protozoan most commonly associated with epm is sarcocystis neurona. the complete life cycle of s. neurona is unknown, including its natural intermediate host that harbors its sarcocyst. opossums (didelphis virginiana, didelphis albiventris) are its definitive hosts. horses are considered its aberrant hosts because only schizonts and merozoites (no sarcocysts) are found in horses. epm-like di ... | 2001 | 11223193 |
| immunoconversion against sarcocystis neurona in normal and dexamethasone-treated horses challenged with s. neurona sporocysts. | equine protozoal myeloencephalitis is a common neurologic disease of horses in the americas usually caused by sarcocystis neurona. to date, the disease has not been induced in horses using characterized sporocysts from didelphis virginiana, the definitive host. s. neurona sporocysts from 15 naturally infected opossums were fed to horses seronegative for antibodies against s. neurona. eight horses were given 5x10(5) sporocysts daily for 7 days. horses were examined for abnormal clinical signs, an ... | 2001 | 11223200 |