Publications

the response of rubrospinal neurons to axotomy in the adult opossum, didelphis virginiana.	to provide endpoints for developmental studies of rubrospinal plasticity in the north american opossum, we have attempted to determine the degree to which rubrospinal neurons survive axotomy in the adult animal. bilateral or unilateral injections of the long-lasting fluorescent marker fast blue were made into the t-10 or the t-11 segment of the spinal cord to label rubrospinal neurons, and 7 days later, the rubrospinal tract was cut unilaterally four segments rostral to the injection(s). in case ...	1990	2318287
morphological organization of thalamocortical relay cells in the dorsal lateral geniculate nucleus of the north american opossum.	the morphology of relay cells in the dorsal lateral geniculate nucleus of the north american opossum was studied by using both golgi-cox material and cells stained from retrograde transport of horseradish peroxidase. in general, soma sizes were largest in the part of the nucleus representing the central retina and decreased from the middle third of the nucleus to the anterior to posterior poles. relay cells labeled with horseradish peroxidase were found to constitute approximately 90% of the dor ...	1990	2319015
studies on the energy metabolism of opossum (didelphis virginiana) erythrocytes: v. utilization of hypoxanthine for the synthesis of adenine and guanine nucleotides in vitro.	high pressure liquid radiochromatography was used to test the ability of opossum erythrocytes to incorporate tracer amounts of [g-3h] hypoxanthine (hy) into [3h] labelled triphosphates of adenine and guanine. in the presence of supraphysiologic (30 mm) phosphate which is optimal for prpp synthesis, both atp and gtp are extensively labelled. when physiologic (1 mm) medium phosphate is used, red cells incubated under an atmosphere of nitrogen accumulate [3h] atp in a linear fashion suggesting ongo ...	1990	2358475
opossum (didelphis virginiana) "little" and "big" gastrins.	1. "little" gastrins from most mammalian species are 17 amino acid peptides and the precursor "big" gastrins are 34 amino acid peptides. 2. "little" gastrins of the new world hystricomorphs, guinea-pig and chinchilla, are 16 amino acid peptides due to deletion of a glutamic acid in the region 6-9 from their nh2-terminus and the corresponding "big" gastrins are 33 amino acid peptides. 3. antral gastrins from the opossum, a new world marsupial, have a glutamic acid deletion in the same region as t ...	1990	2361360
experimental ureteral obstruction in the fetal opossum. i. renal functional assessment.	the north american opossum didelphis virginiana was used as a model for fetal urinary obstruction. in this animal the fetus develops on a teat in a pouch and, therefore, it is accessible to surgical intervention. unilateral ureteral obstruction was created at a mid trimester developmental equivalent in 8 pups, late ureteral obstruction was created in a similar fashion in 6 pups at a full-term equivalent and unobstruction of 9 pups was accomplished with a ureteroneocystostomy at a full-term equiv ...	2008	2374241
vascular and avascular retinae in mammals. a funduscopic and fluorescein angiographic study.	intraretinal blood vessels are present in some and absent in other vertebrate species, including the mammals. among the marsupials, both vascular and avascular retinae are seen. we determined the funduscopic appearance of the eye, investigated the functional aspects of ocular blood flow in both types of retina in marsupials and compared our results with known patterns in placental mammals. the australian polyprotodont marsupials, the tasmanian devil, sarcophilus harrisii, and the quoll, dasyurus ...	1990	2375974
ectoparasitic and phoretic arthropods of virginia opossums (didelphis virginiana) in central tennessee.	thirteen species of ectoparasitic (12) or phoretic (1) arthropods were collected from 26 adult virginia opossums, didelphis virginiana, live-trapped from april through september 1987 in davidson county, tennessee. the cat flea ctenocephalides felis and the american dog tick dermacentor variabilis were the predominant species with respect to mean intensity and prevalence. the macronyssid mite ornithonyssus wernecki and the atopomelid mite didelphilichus serrifer, both specific parasites of this h ...	1990	2380870
the role of medium-sized mammals as reservoirs of borrelia burgdorferi in southern new york.	the ability of raccoons (procyon lotor), striped skunks (mephitis mephitis) and opossums (didelphis virginiana) to serve as reservoirs of borrelia burgdorferi, the spirochetal agent of lyme disease, was compared with that of white-footed mice (peromyscus leucopus). twenty-eight (28) medium-sized mammals and 34 white-footed mice were captured in westchester county, new york (usa) in summer 1986. animals were caged over pans of water for 1 to 2 days to recover engorged tick larvae (ixodes dammini) ...	1990	2388356
a pharmacological study of oesophageal muscularis mucosae from the cat, dog and american opossum (didelphis virginiana). addendum.		1985	2411325
origin of mammalian thalamocortical projections. i. telencephalic projections of the medial geniculate body in the opossum (didelphis virginiana).	telencephalic projections from the medial geniculate nucleus (mg) in opossum were traced with tritiated leucine autoradiography and by horseradish peroxidase and fluorescent dye retrograde labeling techniques. the results show that the opossum's mg contains two separate populations of neurons-one in the anterior two-thirds of mg projecting to auditory neocortex, the other occupying the entire caudal one-third of mg and projecting mostly to lateral amygdala and putamen. because the subcortical pr ...	1986	2420841
development of projections from somatic motor-sensory areas of neocortex to the diencephalon and brainstem in the north american opossum.	the development of projections from somatic motor-sensory areas of neocortex to the diencephalon and brainstem was studied by using the orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (wga-hrp) in a series of pouch-young opossums. the opossum was chosen for study because it is born in a very immature state, 12 days after conception, and has a protracted postnatal development. cortical axons form a cerebral peduncle by at least postnatal day (pd) 10, a medullary ...	1986	2431011
development of the basilar pons in the north american opossum: dendrogenesis and maturation of afferent and efferent connections.	the present study provides data on temporal factors that may play a role in the development of precerebellar-cerebellar circuits in the north american opossum. in this study the basilar pons and cerebellum are analyzed from birth, 12-13 days after conception, to approximately postnatal day (pd) 80 at which time the brainstem and cerebellum have a mature histological appearance. in nissl preparations, the basilar pons was first seen at pd 7 as a small cluster of tightly packed cells. analysis of ...	1987	2441628
the development of rubrospinal, cerebellorubral, and corticorubral connections in the north american opossum. evidence for asynchronism.	we have employed axonal transport and degeneration techniques to study the development of major rubral connections in the north american opossum. opposums were chosen for study because they are born 12 d after conception and have a protracted postnatal development. our results suggest that: the red nucleus innervates the spinal cord early in development, well before the somatic motor-sensory cortex (cabana and martin, 1984); the red nucleus projects to the spinal cord before it receives substant ...	2008	2442682
organization of forebrain projections from the medullary reticular formation in the north american opossum. evidence for connectional heterogeneity.	we have employed axonal transport techniques to study the organization of projections from the medullary reticular formation (rf) to the forebrain of the north american opossum. the results of retrograde transport studies using large injections of horseradish peroxidase (hrp), wheat germ agglutinin conjugated to hrp (wga-hrp), and fluorescent markers suggest that all nuclei of the medullary rf project to the forebrain although the parvocellular reticular nucleus makes only a very small contribut ...	1988	2450621
the early development of subcortical projections to presumptive somatic sensory-motor areas of neocortex in the north american opossum.	we have studied the early development of subcortical projections to presumptive somatic sensory-motor areas of neocortex in the north american opossum didelphis virginiana. the opossum is born in a very immature state, 12-13 days after conception, and climbs into an external pouch where it is available for experimental manipulation. using the retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase, we have obtained evidence that axons from the dorsal raphe and superior ...	1988	2459990
a cytoarchitectonic atlas of the medial geniculate body of the opossum, didelphys virginiana, with a comment on the posterior intralaminar nuclei of the thalamus.	the organization of the medial geniculate body and adjacent posterior thalamus of the virginia opossum was studied in nissl-, golgi-, reduced silver, and myelin-stained preparations. our chief goals were to define the cytoarchitectonic subdivisions and boundaries in nissl preparations and to reconcile these with those observed with the golgi method and in experimental material, to present these results in an atlas of nissl-stained sections, and to compare the chief nuclear groups in the opossum ...	1988	2464620
developmental plasticity of the rubrospinal tract in the north american opossum.	we have shown previously that rubral axons can grow caudal to a lesion of their pathway at thoracic levels of the spinal cord in the developing opossum, didelphis virginiana. in the present report we expand on that observation and present evidence which suggests that the critical period for plasticity of the rubrospinal tract ends earlier at cervical than at thoracic levels. in addition, we show that most rubrospinal neurons die as a result of axotomy during early stages of the critical period. ...	1989	2465321
the early development of major projections to the dorsal striatum in the north american opossum.	we have employed immunocytochemical and axonal transport techniques to study the development of major projections to the dorsal striatum of the north american opossum. the opossum is born in a very immature state, 12-13 days after conception, and climbs into an external pouch where it remains attached to a nipple for several months. its immaturity at birth and its protracted postnatal development make the opossum a good model for developmental studies. although tyrosine hydroxylase-like immunore ...	1989	2472908
the brainstem origin of enkephalin- and substance-p-like immunoreactive axons in the spinal cord of the north american opossum.	we have used the retrograde transport of true blue (tb) in conjunction with immunofluorescence to determine if any of the enkephalin (enk)- or substance p (sp)-immunoreactive axons in the spinal cord of the north american opossum originate within the brainstem. neurons containing enk-like immunoreactivity and tb after injections of the latter into the second or third cervical segment of the spinal cord were found within the locus coeruleus proper, the locus coeruleus pars alpha, the raphe magnus ...	1989	2480173
characterization of serotonin-1b receptors negatively coupled to adenylate cyclase in ok cells, a renal epithelial cell line from the opossum.	we have previously reported the presence of a 5-ht1 (serotonin)-like receptor coupled in an inhibitory manner to adenylate cyclase in the opossum kidney cell line, which is derived from the kidney of a north american opossum. pharmacological data from binding and cyclic amp production studies indicate that this receptor does not have characteristics of a 5-ht1a, 5-ht1c or 5-ht1d receptor, but is similar to 5-ht1b receptors found in rodent tissues. many serotonergic drugs, including 5-methoxy-3-( ...	1989	2542534
opossum kidney contains a functional receptor for the escherichia coli heat-stable enterotoxin.	the escherichia coli heat-stable enterotoxin (st1 or sta) binds to specific receptors on mammalian intestinal brush border membranes, and stimulates guanylate cyclase in those membranes. we have found a similar signal transduction system in brush border membranes prepared from kidney cortex of the american opossum (didelphis virginiana, and in a cell line (ok cell) derived from that tissue. activation of guanylate cyclase by st1 is therefore not limited to intestinal cells. furthermore, since it ...	1989	2564275
comparative biochemistry of hepatic arylsulfatases from north and south american opossums.	1. the virginia opossum (didelphis virginiana) possessed an arylsulfatase which had a relative molecular weight of 130 +/- 12 kda, displayed anomalous kinetics, hydrolysed aa2s, and exhibited other properties of arylsulfatase a. no arylsulfatase b was found. 2. the arylsulfatase present in the gray short-tailed opossum (monodelphis domestica) had a relative molecular weight of 56 +/- 4 kda, exhibited linear kinetics, was inhibited by chloride, and possessed other characteristics of arylsulfatase ...	1989	2574650
the cardiac, oxyntic and pyloric glands in the developing opossum (didelphis virginiana).	in the opossum the fundic area of the gastric mucosa develops first, and oxyntic glands show early division into gastric pits and glandular components which then grow simultaneously. at 40 d postnatum the oxyntic glands are longer than the gastric pits but in the pyloric glands the pits still are longer than the glands and it is not until the 73rd postnatal day, that pyloric glands are longer than their pits. development of the cardiac glands is delayed even more and the length of the gland does ...	1989	2610381
immunohistochemical study of the developing endocrine pancreas of the opossum (didelphis virginiana).	cells immunoreactive for insulin, glucagon, somatostatin, bovine pancreatic polypeptide and 5-hydroxytryptamine are found in the pancreas of the newborn opossum and of all later stages examined. all immunoreactive cell types are present in primary and secondary islets and within elements of the exocrine pancreas. cells immunoreactive for glucagon, bovine pancreatic polypeptide, somatostatin and 5-hydroxytryptamine generally are confined to the periphery of secondary (intralobular) islets, wherea ...	1989	2665414
comparative enzymatic study of hplc-fractionated crotalus venoms.	1. ten venoms of the genus crotalus (crotalus adamanteus, crotalus atrox, crotalus durissus durissus, crotalus horridus horridus, crotalus lepidus, crotalus polystictus, crotalus molossus molossus, crotalus pusillus, crotalus scutulatus scutulatus, venom b, and crotalus viridis lutosus) were fractionated using hplc anion and cation exchange chromatography. 2. hplc venom fractions were tested for hemorrhagic, hemolytic, and proteolytic activities. 3. crude virginia opossum (didelphis virginiana) ...	1989	2680253
fatal lungworm infection in an opossum.	a 3-mo-old male, feral opossum (didelphis virginiana) was presented to the university of tennessee college of veterinary medicine (usa) for evaluation of prolonged dyspnea. the animal died shortly after examination and a necropsy was performed. the cause of death was attributed to a verminous pneumonia, associated with numerous intrabronchial and intrabronchiolar nematodes, subsequently identified as didelphostrongylus hayesi.	1989	2716108
vasoactive intestinal polypeptide and non-adrenergic, non-cholinergic inhibition in lower oesophageal sphincter of opossum.	1. field stimulation or vasoactive intestinal polypeptide (vip) relaxed lower oesophageal sphincter (los) from north american opossum. pretreatment with carbachol in cl-ion-containing or cl-ion-free krebs solution or with 10(-3) m 9-aminoacridine abolished or markedly reduced relaxation due to vip applied exogenously but not that elicited by field stimulation of non-adrenergic, non-cholinergic nerves. 2. inhibitory junction potentials (7.5 +/- 1.2 mv, n = 5) could be recorded in los strips with ...	1989	2720302
host associations of ticks (acari: ixodidae) parasitizing medium-sized mammals in a lyme disease endemic area of southern new york.	ticks of eight medium-sized mammal species were studied in an area of endemic lyme disease in westchester county, n.y., from 1 april 1984 to 31 march 1985. most (81%) of the 266 total mammal captures were raccoon, procyon lotor (l.) (47%), opossum, didelphis virginiana (kerr) (19%), and striped skunk, mephitis mephitis schreber (15%); these host species accounted for 91% of the 1,519 ticks collected. although the total number of ticks was rather evenly distributed among these mammals, species co ...	1989	2724317
laminar and non-laminar patterns of acetylcholinesterase activity in the marsupial lateral geniculate nucleus.	acetylcholinesterase (ache) distribution in the dorsal lateral geniculate nucleus (lgd) of 3 polyprotodont and 3 diprotodont marsupials has been compared with the cytoarchitecture and, as appropriate, with retinal terminal bands (rtbs) as demonstrated by tracers injected into the vitreous body. in this series those polyprotodont marsupials showing only partial segregation of retinal input (virginia opossum and tasmanian devil), display the least cell laminar differentiation. in them ache stainin ...	1989	2731033
a cyto-architectonic description of the thalamus of the tammar wallaby, macropus eugenii.	very few studies are available on the cyto-architectural features of the thalamus of metatherian mammals. most of these studies describe the thalamus of a polyprotodont metatherian, the north american opossum, didelphis virginiana. studies on diprotodont metatherians are fewer still. there are two descriptions of the thalamus of the australian possum trichosurus vulpecula. the only part of the thalamus that has been described in the wallabies is the lateral geniculate nucleus. hence, there was a ...	1989	2765853
studies on the energy metabolism of opossum didelphis virginiana erythrocytes--iv. red cells have low adenosine deaminase activity and high levels of deoxyadenosine nucleotides.	alkaline extracts of adult opossum red cells were used to determine triphosphates of adenosine, deoxyadenosine and guanosine by anion exchange hplc. mean (nm/g hg) atp content of erythrocytes was 3713 and that of datp 1913 (n = 12). sonicates of red cells deaminated adenosine (ado) at a rate of 1.55 nm/mg hg/h and deoxyadenosine (dado) at 1.82 nm/mg hg/h. datp synthesis from provided dado was one order of magnitude greater in opossum than in human erythrocytes at both low and high dado and pi co ...	1989	2784528
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 pater ...	1989	2803226
comparison of the muscle mechanics of the forelimb of three climbers.	the climbing behavior, muscle mechanics, and functional properties of selected forelimb muscles were examined to ascertain how three distantly related mammals may be adapted for climbing. to determine if features of the fox squirrel (stalheim-smith: j. morphol. 180:55-68, '84) are general or unique features for a climber, two distantly related climbers, the raccoon (procyon lotor) and the opossum (didelphis virginiana), were studied. muscle mechanics varied: the elbow flexors of the fox squirrel ...	2008	2810372
oral vaccination of raccoons (procyon lotor) with an attenuated (sad-b19) rabies virus vaccine.	unlike previous reports to the contrary, raccoons (procyon lotor) were successfully vaccinated against rabies with a liquid sad-b19 attenuated virus vaccine administered per os and given in vaccine-laden baits. there was neither evidence of vaccine-induced rabies in raccoons nor in a limited safety trial with opossums (didelphis virginiana) given sad-b19. protection from lethal street rabies virus infection was not absolute: only three of nine raccoons given 1 x 10(6.0) tcid/ml were protected ve ...	1989	2810555
molecular studies of marsupial x chromosomes reveal limited sequence homology of mammalian x-linked genes.	to explore the extent to which the x chromosome has been conserved during mammalian evolution, we compared six loci that are x-linked in the human genome with the corresponding genes of the north american marsupial, the virginia opossum (didelphis virginiana). our analysis shows that in the opossum genome there are sequences highly homologous to those of human cdnas for housekeeping genes, glucose-6-phosphoribosyltransferase (hprt), phosphoglycerate kinase a (pgk1), and alpha-galactosidase a (gl ...	1987	2822568
receptors and cgmp signalling mechanism for e. coli enterotoxin in opossum kidney.	receptors for the heat-stable enterotoxin produced by escherichia coli were found in the kidney and intestine of the north american opossum and in cultured renal cell lines. the enterotoxin markedly increased guanosine 3',5'-cyclic monophosphate (cgmp) production in slices of kidney cortex and medulla, in suspensions of intestinal mucosa, and in the opossum kidney (ok) and rat kangaroo kidney (ptk-2) cell lines. in contrast, atrial natriuretic factor elicited much smaller increases in cgmp level ...	1988	2847547
studies on the energy metabolism of opossum didelphis virginiana erythrocytes--ii. comparative aspects of 2-deoxy-d-glucose catabolism in opossum and human red cells in vitro.	1. g-6-p, f-6-p, f-1, 6-p, dhap and ga-3-p in opossum erythrocytes were found at levels above those reported in human red cells. 2. about 1% of the radioactivity provided as [1-14c] dog to red cells of both species was recovered as 14co2 in 1 hr. 3. unlike [1-14c] dog, radiochromatography of extracts of cells incubated dog revealed two diffusible radiolabelled compounds in the supernatant of cell suspensions. 4. the catabolism of dog was quantitatively and qualitatively similar in opossum and hu ...	1988	2896089
studies on the energy metabolism of opossum didelphis virginiana erythrocytes--iii. metabolic depletion with 2-deoxyglucose markedly accelerates methemoglobin reduction in opossum but not in human erythrocytes.	1. glucose-depleted, nitrite-treated erythrocytes reduce ferriheme in vitro in an environment 100 mm to 2-deoxy-d-glucose at a rate of 2.4 microm/ml cells/hr (opossum) and 0.37 microm/ml cells/hr (human). 2. during the process of methemoglobin reduction the breakdown of adenine ribonucleotides is more rapid in opossum (0.9 microm/g hg/hr) than in human (0.36 microm/g hg/hr) erythrocytes. 3. radiolabelled ribose from [u-14c] atp is catabolized exclusively to [14c] lactate in opossum, and to [14c] ...	1988	2896090
seasonal energetics of opossums (didelphis virginiana) in ohio.	1. female opossums acclimatized to each of the four seasons were not significantly different (p greater than 0.05) in oxygen consumption at a ta of 0 degrees c; the overall average was 0.66 +/- 0.1 ml o2/g-hr. 2. body weight decreased by 27% from autumn to spring; pelage density increased in winter, but thermal conductance changed very little between seasons. 3. respirometry revealed no evidence of thermoregulatory adjustments in opossums acclimatized to winter in ohio.	1988	2901314
catecholaminergic innervation of the spinal cord in the north american opossum, didelphis virginiana.	axons presumed to contain catecholamines were visualized in the spinal cord of the spinal cord of the north american opossum using antibodies to tyrosine hydroxylase (th) by an indirect antibody peroxidase-antiperoxidase (pap) technique. axons showing th-like immunoreactivity (th-ir) coursed primarily in the dorsal part of the lateral funiculus, although they were also present more ventrally. an occasional th-ir axon was seen in the dorsal funiculus. within the gray matter, th-ir axons were dist ...	1988	2906810
sex determination in marsupials: evidence for a marsupial-eutherian dichotomy.	in this paper, we review briefly the current state of knowledge about sexual differentiation in eutherian mammals, and then describe the situation in detail in two marsupial species: the north american opossum and the tammar wallaby. the conventional explanation for the genesis of all male somatic sexual dimorphisms in mammals is that they are a consequence of the systemic action of testicular hormones. in the absence of testes, the embryo will develop a female phenotype. we present evidence for ...	1988	2907802
distribution of fibre types in thirty-seven muscles of didelphis virginiana.	the proportions of type i and ii fibers were determined in 37 muscles of didelphis virginiana, representing 9 body regions. there was a distinct cranial/caudal gradation in the distribution of type ii fibers throughout the trunk musculature. muscles of the fore- and hind-limbs showed a gradation of type ii fiber across the width of the muscle, being more prominent at the surface. the type ii fibers in the tip of the tail showed peculiar staining properties in which the core of each fiber stained ...	1987	2960253
development of brainstem and cerebellar projections to the diencephalon with notes on thalamocortical projections: studies in the north american opossum.	the north american opossum is born in a very immature state, 12 days after conception, and climbs into an external pouch where it remains attached to a nipple for an extended period of time. we have taken advantage of the opossum's embryology to study the development of brainstem and cerebellar projections to the diencephalon as well as the timing of diencephalic projections to somatosensory motor areas of neocortex. the techniques employed included immunocytochemistry for serotonin, the retrogr ...	1987	3038968
proteolytic, hemorrhagic and hemolytic activities of snake venoms.	proteolytic, hemorrhagic and hemolytic activities were tested on 47 different venoms from the crotalidae, viperidae, elapidae, and hydrophiidae families. antihemorrhagic activity of crude opossum (didelphis virginiana) and woodrat (neotoma micropus) serum was tested against the venoms that presented hemorrhagic activity. all venoms showed proteolytic activity when non-specific substrates such as hide powder and collagen were used. members of the crotalidae family had the highest hide powder, chy ...	1988	3059584
receptive field properties and latencies of cells in the lateral geniculate nucleus of the north american opossum (didelphis virginiana).	relay cells in the lateral geniculate nucleus (lgn) of the north american opossum were classified as types 1, 2, and 3 on the basis of their receptive field properties and afferent latencies to optic nerve (on) and optic chiasm (ox) stimulation and antidromic latencies to stimulation of cortex. type 1 and type 3 cells gave transient responses and type 2 cells gave sustained responses to appropriate standing contrast in the receptive field center. the differences in response pattern were quantifi ...	1986	3097274
pathogenesis of sarcocystis falcatula in the budgerigar. i. early pulmonary schizogony.	sarcocystis falcatula is a protozoan parasite which obligatorily alternates its definitive host, the opossum (didelphis virginiana), and a uniquely wide range of avian intermediate hosts. the disease produced by this coccidian parasite in intermediate hosts was studied in the budgerigar bird (melopsittacus undulatus). the ultrastructure of pulmonary sporozoites, meronts and merozoites of this sarcocystis species is described. early schizogony occurs progressively in pulmonary capillary and in ve ...	1987	3099083
pathogenesis of sarcocystis falcatula in the budgerigar. ii. pulmonary pathology.	sarcocystis falcatula is a protozoan parasite which obligatorily alternates its definitive host, the opossum (didelphis virginiana), and a uniquely wide range of avian intermediate hosts. the disease produced by this coccidian parasite in intermediate hosts was studied in the budgerigar bird (melopsittacus undulatus). early schizogony occurs in pulmonary endothelial cells, resulting in endothelial cell hypertrophy, capillary obstruction preceding endothelial lysis, acute endophlebitis, and chron ...	1987	3099084
an immunohistochemical survey of gastric proteinase (pepsinogen and prochymosin)-containing cells in the stomach of the developing opossum (didelphis virginiana).	cells immunoreactive to antisera of bovine pepsinogen and prochymosin are seen in the oxyntic glands but not the pyloric or cardiac glands of the opossum. immunoreactivities to pepsinogen and prochymosin occur within the same cell and are restricted to an undifferentiated cell type prior to weaning. the undifferentiated cells producing these gastric proteinases decrease in number until just prior to weaning and disappear with the appearance of chief cells. thereafter, immunoreactivities to both ...	1987	3128513
structure, processing and evolution of the neurohypophysial hormone-neurophysin precursors.	neurohypophysial hormones and neurophysins are derived from common precursors processed during the axonal transport from the hypothalamus to the neurohypophysis. two neurohormones, an oxytocin-like and a vasopressin-like, on one hand, two neurophysins, termed vldv-and msel-neurophysins according to residues in positions 2, 3, 6 and 7, on the other, are usually found in vertebrate species. in contrast to placental mammals that have oxytocin and arginine vasopressin, marsupials have undergone a pe ...	1988	3147712
trichinella spiralis in an agricultural ecosystem. iii. epidemiological investigations of trichinella spiralis in resident wild and feral animals.	as part of a larger epidemiological study examining the transmission of trichinella spiralis in an agricultural ecosystem, resident wild and feral animals were trapped to determine the extent of their involvement in the natural, on-farm cycling of the parasite among swine. during a 21-mo-study, seven of 15 skunks (mephitis mephitis), one of three opossums (didelphis virginiana), two of two feral domestic cats and a raccoon (procyon lotor) were found to be infected, while five shrews (blarina bre ...	1988	3193554
differential distribution of the p1 and p2 protamine gene sequences in eutherian and marsupial mammals and a monotreme.	at the protein level, the p1 protamine is the predominant form of mammalian protamine, present in all mammalian spermatozoa analyzed to date. an additional variant, the p2 protamine, has been detected only in spermatozoa of the mouse, hamster and human. southern blot analysis of a group of restriction enzyme-digested mammalian dnas has revealed the presence of sequences homologous to the p1 and p2 mouse protamine genes in diverse species. in agreement with protein studies, nucleotide sequences h ...	1988	3209180
development of the optic nerve of the opossum (didelphis virginiana).	the development of the optic nerve of a marsupial, the north american opossum, was examined in 24 animals from postnatal days 5 to 78 (p5-p78): gestation is 13 days. the estimated number of axons increased from 24,000 at p5, to 267,000 at p27, approximately 2.7 times the mean number in the adult. following p27, axon numbers decreased rapidly to 140,000 at p40, then decreased more slowly, attaining adult values between p50 and p59. thus, the opossum is similar to placental mammals examined in evi ...	1988	3233732
induced renal dysplasia in the young pouch opossum.	using the north american opossum, didelphis virginiana, we have developed a new model for studying the effects of early fetal urinary obstruction on subsequent renal development. we have successfully induced renal dysplasia in the marsupial that has a typically mammalian kidney.	2011	3236178
localization of g6pd and hprt to different arms of the x chromosome of the north american marsupial (didelphis virginiana) by in situ hybridization and deletion mapping: evolutionary significance.	we have mapped hprt and g6pd loci on the x chromosome in the american opossum, didelphis virginiana, by in situ hybridization to cells derived from two females by using genomic opossum dna as probes. the localizations (g6pd to xp13 and hprt to xq21), indicating that the two genes are separated by the centromere, were confirmed by results of hybridization to x chromosomes with deletions that include the hprt locus and opossum-mouse cell hybrids containing the relevant fragment of the opossum x ch ...	1988	3243545
experimental cryptosporidium parvum infections in opossums (didelphis virginiana).	five nursing opossums (didelphis virginiana) were each inoculated with 5 x 10(6) cryptosporidium parvum oocysts of calf origin. following inoculation, endogenous stages of c. parvum were observed in the ileum, cecum, and colon of these opossums. two of three noninoculated pouch mates acquired infections during the study based on examinations of feces and tissue sections of all eight opossums. mild diarrhea was observed in four of seven opossums harboring c. parvum, although none died as a result ...	1988	3352085
endogenous lipid pneumonia in opossums from louisiana.	endogenous lipid pneumonia was present in 19 of 27 opossums (didelphis virginiana) trapped in the vicinity of baton rouge, louisiana. the severity of lesions varied from small pleural and subpleural aggregates of foamy macrophages with minimal disruption of pulmonary architecture to large nodular accumulations of foam cells with cholesterol clefts and localized emphysema. the cause of the lipid pneumonia may be related to pulmonary nematode parasite infections, which were evident in 13 of the af ...	2012	3373627
valvular endocarditis associated with experimental erysipelothrix rhusiopathiae infection in the opossum (didelphis virginiana).	intravenous inoculation of a wild type isolate of erysipelothrix rhusiopathiae in opossums resulted in valvular endocarditis in all infected animals. opossums were inoculated once a week for 3 weeks. lesions became visible with cardiac ultrasound by week four post-inoculation. opossums remained clinically normal throughout the experiment, and preinfection body weight was maintained. other lesions of chronic erysipelas including skin necrosis and arthritis were not found in infected opossums.	1988	3374091
evolutionary and developmental aspects of two hemoglobin beta-chain genes (epsilon m and beta m) of opossum.	a series of gene duplications that began in a stem species of mammalia and led to five developmentally regulated hemoglobin beta-chain loci (epsilon, gamma, eta, delta, and beta) in a common ancestor of eutherian orders artiodactyla, rodentia, lagomorpha, and primates had important consequences in mammalian evolution. findings reported here indicate that two progenitors of the five linked genes existed by the time of the eutherian (placental mammal)-metatherian (marsupial mammal) split and that ...	1988	3375246
evidence for developmental plasticity of the rubrospinal tract. studies using the north american opossum.	using axonal tracing techniques we have shown that rubral axons are capable of growing around lesions of the rubrospinal tract during early stages of development in the north american opossum and that a critical period for such growth exists. the opossum was employed for study because it is born in a very immature state 12-13 days after conception and the entire development of its rubrospinal tract occurs postnatally.	1988	3378179
the development of selected rubral connections in the north american opossum.	we have employed axonal transport and degeneration techniques to study the development of selected rubral connections in the north american opossum. opossums were chosen for study because they are born in an immature state, 12 days after conception, and have a lengthy postnatal development. the results of our studies suggest that: (1) the red nucleus innervates the spinal cord early in development, but not as early as some areas of the brainstem; (2) rubrospinal development occurs postnatally in ...	2007	3382514
the origin of projections from the medullary reticular formation to the spinal cord, the diencephalon and the cerebellum at different stages of development in the north american opossum: studies using single and double labeling techniques.	we have employed the retrograde transport of horseradish peroxidase alone or conjugated to wheat germ agglutinin, to label neurons within the medullary reticular formation which project to the spinal cord, the diencephalon and the cerebellum at different stages of development in the north american opossum. at selected ages, the fluorescent markers fast blue and diamidino yellow were also used in double-labeling experiments to determine if single neurons innervate both the spinal cord and diencep ...	1988	3393288
dual duplication of neurohypophysial hormones in an australian marsupial: mesotocin, oxytocin, lysine vasopressin and arginine vasopressin in a single gland of the northern bandicoot (isoodon macrourus).	neurohypophysial hormones of an australian marsupial, the northern bandicoot (isoodon macrourus), have been identified by their retention times in high-pressure reverse-phase liquid chromatography using two solvent systems and by their molar pressor or uterotonic activities. two pressor peptides, arginine vasopressin and lysipressin, and two uterotonic peptides, mesotocin and oxytocin, have been characterized. because mesotocin and arginine vasopressin have been identified in three other austral ...	1988	3395337
characterization of erysipelothrix rhusiopathiae isolated from an opossum (didelphis virginiana) with septicemia.	erysipelothrix rhusiopathiae was isolated from a wild-caught opossum (didelphis virginiana). the opossum was quarantined in isolation and removed from contact with other animals. after a 2-mo period it was found dead in its cage, and presented for postmortem examination. pure cultures of erysipelothrix rhusiopathiae (slu isolate) were recovered from heart blood, liver, spleen and lungs. to compare pathogenicity, an experimental infection was attempted in cf1 mice with a single dose of 1.5 x 10(7 ...	1988	3411715
dna methylation stabilizes x chromosome inactivation in eutherians but not in marsupials: evidence for multistep maintenance of mammalian x dosage compensation.	in marsupials and eutherian mammals, x chromosome dosage compensation is achieved by inactivating one x chromosome in female cells; however, in marsupials, the inactive x chromosomes is always paternal, and some genes on the chromosome are partially expressed. to define the role of dna methylation in maintenance of x chromosome inactivity, we examined loci for glucose-6-phosphate dehydrogenase and hypoxanthine phosphoribosyltransferase in a north american marsupial, the opossum didelphis virgini ...	1987	3476942
x-linked gene expression in the virginia opossum: differences between the paternally derived gpd and pgk-a loci.	expression of x-linked glucose-6-phosphate dehydrogenase (g6pd) and phosphoglycerate kinase-a (pgk-a) in the virginia opossum (didelphis virginiana) was studied electrophoretically in animals from natural populations and those produced through controlled laboratory crosses. blood from most of the wild animals exhibited a common single-banded phenotype for both enzymes. rare variant animals, regardless of sex, exhibited single-banded phenotypes different in mobility from the common mobility class ...	1987	3557111
lyme disease ecology in wisconsin: distribution and host preferences of ixodes dammini, and prevalence of antibody to borrelia burgdorferi in small mammals.	lyme disease recently has been recognized in wisconsin. trapping studies were conducted at four geographically separate and ecologically distinct regions in wisconsin to elucidate the distribution and host preferences of ixodes dammini on small and medium sized mammals, and the occurrence of antibodies to borrelia burgdorferi in these wild mammals. peak i. dammini larval activity occurred from june-september. nymphs were most active from may-august. white-footed mice (peromyscus leucopus) and ch ...	1987	3605501
unique regional distribution of delta 4-3-ketosteroid-5 alpha-oxidoreductase and associated epididymal morphology in the marsupial, didelphis virginiana.	the epididymal epithelial ultrastructure has been described in the adult male north american opossum, didelphis virginiana. morphological results have suggested that absorptive activity is prominent in the proximal epididymal region by virtue of numerous microvilli, an endocytotic complex, dense granules, and multivesicular bodies in the apical cytoplasm. in contrast, the middle and distal epididymal regions exhibit ultrastructural features indicative of protein synthesis such as large invaginat ...	2013	3676395
the development and migration of large multipolar neurons into the cochlear nucleus of the north american opossum.	we have studied the maturation of the inferior colliculus and cochlear nuclei of the north american opossum with particular emphasis on the large multipolar neurons of the cochlear nucleus. these neurons include the principal and giant cells of the dorsal cochlear nucleus (dcn) and the large neurons of the ventral cochlear nucleus (vcn), all of which can be labelled by horseradish peroxidase (hrp) injections into the contralateral inferior colliculus (ic). the size of these neurons, their charac ...	1986	3722450
mechanical factors in the evolution of the mammalian secondary palate: a theoretical analysis.	the secondary palate of mammals is a bony shelf that closes the ventral aspect of the rostrum. the rostrum, therefore, approximates to a tapered semicylindrical tube that is theoretically a mechanically efficient structure for resisting the forces of biting, including the more prolonged bouts of mastication typical of mammals. certain mammal-like reptiles illustrate stages in the development of the palate in which the shelves projecting medially from each premaxilla and maxilla do not meet in th ...	1986	3746918
isolation of antihemorrhagic factors in opossum (didelphis virginiana) serum using a monoclonal antibody immunoadsorbent.	the antihemorrhagic factor in opossum (didelphis virginiana) serum isolated by sephadex g-200 gel filtration and deae a-50 ion exchange chromatography was used as antigen to immunize balb/c mice. hybrid cell lines secreting monoclonal antibodies against antihemorrhagic factor were produced by fusion of sp2/0 myeloma cells with spleen cells of the immunized mice. the ascites fluid was produced in balb/c mice. the monoclonal antibody in the ascites fluid was partially purified by deae a-50 ion exc ...	1986	3750345
efferent projections of the basolateral amygdala in the opossum, didelphis virginiana.	the autoradiographic anterograde axonal transport technique was used to study efferent projections of the opossum basolateral amygdala. all nuclei of the basolateral amygdala send topographically organized fibers to the bed nucleus of the stria terminalis (bst) via the stria terminalis (st). injections into rostrolateral portions of the basal nuclei label fibers that surround the commissural bundle of the st, cross the midline by passing along the outer aspect of the anterior commissure, and ter ...	2011	3768738
a plastic cage for restraint of the opossum (didelphis virginiana).		1986	3773475
the adult organization and development of the rubrospinal tract. an experimental study using the orthograde transport of wga-hrp in the north-american opossum.	we have employed the orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase to study the organization of rubrospinal connections in adult and pouch young opossums. our results suggest that: in the adult opossum rubrospinal axons are distributed more widely than suggested by previous studies; rubrospinal projections are formed postnatally in the opossum, but much earlier than corticospinal connections; rubrospinal axons do not grow synchronously, as a massive bundle fo ...	1986	3779426
the nonmammalian-mammalian transition through neurohypophysial peptides.	neurohypophysial hormones are particularly proper evolutionary tracers. whereas eutherian mammals have oxytocin and virtually always arginine vasopressin, nonmammalian tetrapods possess instead mesotocin and vasotocin. the transitions of mesotocin-oxytocin and vasotocin-vasopressin involved in the passage of reptiles-mammals seem to have occurred independently. australian marsupials are endowed with mesotocin but american marsupials have either oxytocin (south-american opossums) or both oxytocin ...	1985	3831965
the development of commissural connections of somatic motor-sensory areas of neocortex in the north american opossum.	the north american opossum does not have a corpus callosum; neocortical commissural axons are contained entirely within the anterior commissure. we have used axonal transport techniques to study the origin and distribution of commissural axons from somatic motor-sensory cortex in developing and adult opossums. neocortical axons grow into the anterior commissure by postnatal day (pnd) 12, the contralateral external capsule by approximately pnd 19, the area deep to the contralateral homotypic cort ...	1985	3838629
cortical projections to superficial laminae of the dorsal horn and to the ventral horn of the spinal cord in the north american opossum. studies using the orthograde transport of wga-hrp.	the orthograde transport of horseradish peroxidase conjugated to wheat germ agglutinin (wga-hrp) has been used to study the distribution of corticospinal axons in adult and pouch-young opossums. as predicted from the results of degeneration and autoradiographic experiments, injections of wga-hrp into limb areas of somatic motor-sensory cortex labeled axons in the dorsal and lateral funiculi of the cervical and upper thoracic spinal cord which could be traced to dense terminal zones in laminae ii ...	1985	3839153
tactile cutaneous representation in cerebellar granule cell layer of the opossum, didelphis virginiana.	recent studies of the albino rat revealed extensive cutaneous somatosensory projections to the granule cell (gc) layer of the cerebellar hemispheres and the caudal vermis. these projections are organized asomatotopically in patchy mosaics. to determine whether similar projections exist in a marsupial, we explored the gc layer of the cerebellar cortex of anesthetized virginia opossums using in-depth microelectrode micromapping and juxtathreshold cutaneous natural stimulation techniques. we found: ...	1985	3843070
the sensory innervation of the nasal glabrous skin in the short-nosed bandicoot (isoodon macrourus) and the opossum (didelphis virginiana).	the glabrous skin at the anterior end of the snout of the short-nosed bandicoot and the american opossum was investigated by electron microscopy. in both species of animals, this region was lined by skin with broad epidermal pegs, innervated by three types of intraepidermal nerves. these were intraepidermal nerves which penetrated the epidermis up to the level of the stratum spinosum or the stratum granulosum, intraepidermal nerves in the basal layer of the epidermis partially surrounded by schw ...	1985	3870723
serotonergic innervation of the forebrain in the north american opossum.	the forebrain distribution of axons showing serotonin-like immunoreactivity was studied in the north american opossum. serotonergic innervation of the hypothalamus was extensive, particularly within the ventromedial nucleus, the periventricular nucleus and the rostral supraoptic nucleus. serotonergic axons were also present within the fields of forel and zona incerta, but they tended to avoid parts of the subthalamic nucleus. in the thalamus serotonergic innervation was dense within the midline ...	1985	3910165
beta-like ganglion cells in the retina of the north american opossum.	injection of horseradish peroxidase into the severed optic tract or nerve of the opossum retrogradely filled retinal ganglion cells. an abundance of well-labeled ganglion cells had dendritic morphology closely resembling that of beta-type ganglion cells in the cat retina. this finding suggests that an x-like functional class of ganglion cells is prominent in the retina of the opossum.	1985	3921195
brucella abortus in wildlife on selected cattle farms in alabama.	two studies of brucellosis in wildlife on farms where the brucellosis infection prevalence in cattle was known are reported. on a research farm, 233 feral animals of 22 mammalian species and 12 of seven avian species were trapped during three time periods. sixty were studied before cattle were introduced, 128 were studied while 501 cattle infected with brucella abortus were calving and aborting, and 60 specimens were collected 20 mo after the last infected cow calved. selected tissues from 229 w ...	1985	3923213
the synthesis and metabolism of gonadal steroids in pouch young of the opossum, didelphis virginiana.	we have measured steroid hormone biosynthesis from pregnenolone in ovaries and testes, aromatization of testosterone in gonads and peripheral tissues, and 5 alpha-reduction of testosterone in peripheral tissues of developing opossum pouch young. sex of the newborn opossums is discernible grossly with development of the pouch in females and the scrotum in males approximately 10 days after birth. differentiated endocrine function of ovaries and testes was demonstrable as soon as development of the ...	1985	3971901
electrical properties of smooth muscle cell membrane of opossum esophagus.	the electrical properties of the circular smooth muscle layer from the north american opossum esophagus (body) were studied in vitro by microelectrode recording techniques, both at rest and during stimulation of intramural inhibitory nerves. all observations were made at 37 degrees c in an abe-tomita partitioned bath on muscle strips dissected 2 cm orad of the lower esophageal sphincter. at rest, the potential of the smooth muscle cell membrane was -49 +/- 4 mv (mean +/- se); the length constant ...	1985	3976893
the allantois of the north american opossum (didelphis virginiana) with preliminary observations on the yolk sac endoderm and trophectoderm.	during the middle of prenatal day 10, the opossum allantois forms as a ventral outgrowth of the hindgut. by day 11 it appears as a large, fluid filled sac and by the middle of day 12 (just prior to birth) it reaches its maximal development. the simple squamous epithelium lining the allantois consists of only one cell type that often contains numerous filaments in the apical cytoplasm. at the luminal surface, the apices of the cells are united by junctional complexes and desmosomes are present be ...	1985	3977085
experimental studies of st. louis encephalitis virus in vertebrates.	serologically negative birds and mammals of species, known from other studies to be exposed naturally to st. louis encephalitis (sle) virus in memphis, tennessee, and other selected species were inoculated experimentally with strains of sle virus to determine their potential as natural hosts. mosquitoes (culex sp.) were allowed to feed on some of the inoculated vertebrate species, held for 14 days, and tested for sle infection. the cardinals (richmondena cardinalis), robins (turdus migratorius), ...	1985	3999258
experimental la crosse virus infection of red fox (vulpes fulva), raccoon (procyon lotor), opossum (didelphis virginiana), and woodchuck (marmota monax).	susceptibility to infection, resulting viremia and antibody responses, and potential to provide infectious blood meals for aedes triseriatus were determined and compared for the red fox (vulpes fulva), raccoon (procyon lotor), and opossum (didelphis virginiana) exposed to la crosse (lac) virus transmitted by mosquitoes, ae. triseriatus. woodchucks (marmota monax) were infected with lac virus by needle and syringe. all 5 red foxes became viremic following the bite of a single lac virus-infected f ...	1985	4003669
responses of opossum and rat hippocampal ca1 cells to paired stimulus volleys.	short-term synaptic plasticity was studied in the in vitro hippocampus of the north american opossum (didelphis virginiana) and rat (rattus norvegicus). conditioning and test stimulus pulses were delivered to fibers in stratum radiatum, and intracellular and extracellular recordings were obtained from area ca1 pyramidal cells. in rat, the amplitude of the population spike in response to the second (test) of two stimulus impulses is suppressed at short inter-pulse-intervals (ipi's). in opossum, t ...	1985	4052826
placentation in the opossum, didelphis virginiana.	for the first 9 days of gestation, opossum embryos float in uterine secretions, separated from maternal tissues by a shell membrane. each embryo is part of the wall of its hollow embryonic sphere. by the 10th day of development, the embryo becomes enveloped by both the amnion and yolk-sac. the yolk-sac consists of vascular and non-vascular portions and, together with the surrounding trophectoderm (trophoblast), forms the yolk-sac placenta of the opossum: the allantois does not contribute to form ...	1985	4061035
the distribution of photoreceptors, dopaminergic amacrine cells and ganglion cells in the retina of the north american opossum (didelphis virginiana).	quantitative light microscopic techniques have been applied to photoreceptors, ganglion cells and dopaminergic amacrine cells in the retina of the north american opossum didelphis virginiana. this marsupial has a retina with a central areal specialization where ganglion cells reach a maximum density of 2900/mm2 and cone photoreceptors are concentrated. however, the retina is very much rod dominated and there is a ring of peak rod density approximately 2 mm around the area centralis (a.c.). at th ...	1985	4072000
corticospinal development in the north-american opossum: evidence for a sequence in the growth of cortical axons in the spinal cord and for transient projections.	the course and distribution of corticospinal axons have been traced in a series of pouch young and adult opossums using wheat germ agglutinin conjugated to horseradish peroxidase (wga-hrp). cortical axons enter the spinal cord approx. 28 days after birth (40 days after conception) and, at that time, are limited to those portions of the dorsal and lateral funiculi which contain them in the adult animal. shortly thereafter, cortical axons are also found in regions of presumptive white matter where ...	1985	4075107
quantitative distribution of enteroendocrine cells in the gastrointestinal tract of the adult opossum, didelphis virginiana.	the distribution and quantification of enteroendocrine cells exhibiting immunoreactivities to nine peptides and one amine were examined in the gastrointestinal mucosa of the adult opossum using specific immunocytochemical methods. in the stomach, 90% of the enteroendocrine cells are confined to the pyloric glands and this region contained 73% of the gastrin-containing cells, 60% of the somatostatin-containing cells and 9% of cells reactive for 5-ht. enteroendocrine cells showing immunoreactiviti ...	1985	4077699
reticulospinal fibers of the opossum, didelphis virginiana. i. origin.		1971	4101679
reticulospinal fibers of the opossum, didelphis virginiana. ii. course, caudal extent and distribution.		1971	4101680
thalmocortical projections from the mediodorsal nucleus in the virginia opossum.		1973	4121726
acquired immunity in opossum (didelphis virginiana) embryos.		1974	4133078
hematologic parameters of the opossum (didelphis virginiana).		2014	4145239
the immunologic responses of the north american opossum (didelphys virginiana).		1968	4177528
the basilar pontine gray of the opossum (didelphis virginiana). i. morphology.		1968	4185130
blood chemical and hematological studies in the laboratory-confined, unanesthetized opossum, didelphis virginiana.		1969	4240125
the opossum, didelphis virginiana, as a laboratory animal.		1969	4240729