Publications

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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
prostaglandin f in reproductive tissues collected during the luteal phase of the estrous cycle and at parturition in virginia opossums (didelphis virginiana ).	prostaglandin f(2alpha) (pgf(2alpha)) plays a role in the regression of the corpus luteum (cl) in a number of placental mammals. however, the mechanism of luteal regression has not been extensively studied in marsupials. the objectives of this study were to characterize changes in concentrations of pgf(2alpha) within utero-ovarian (uo) tissue/venous plasma during the luteal phase of the estrous cycle in virginia opossums, to correlate these changes with those of plasma progesterone (p(4)), and t ...	1989	16726728
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
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
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 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
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 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
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
mammary glands in male marsupials: i. primordia in neonatal opossums didelphis virginiana and monodelphis domestica.	neonates of the american didelphid marsupials didelphis virginiana and monodelphis domestica were sexed by karyotype and histologically examined on the day of birth. mammary anlagen were found in both sexes of both species, but the neonatal males had less than one-third of the full female complement of mammary glands. male neonates of both species also had paired scrotal bulges anterior to the genital tubercle but these were never present in females, once again raising the question of whether th ...	1990	2133544
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
development of catecholaminergic projections to the spinal cord in the north american opossum, didelphis virginiana.	the intent of our study was to determine when catecholaminergic axons grow into each of their adult targets in the spinal cord of the north american opossum (didelphis virginiana) and to identify the origin of catecholaminergic axons in the lumbosacral cord at different stages of development. tyrosine hydroxylase-like immunoreactive axons, presumed to be catecholaminergic, were demonstrated at different stages of development by the indirect antibody peroxidase-antiperoxidase technique of sternbe ...	1990	1971285
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
origins and terminations of bulbospinal axons that contain serotonin and either enkephalin or substance-p in the north american opossum.	we have shown previously that some enkephalin, substance-p, and serotoninergic neurons in the medullary raphe and adjacent reticular formation project to the spinal cord in the opossum. in the present study we have combined the retrograde transport of true blue and immunofluorescence histochemistry to determine whether methionine enkephalin or substance-p containing bulbospinal neurons are serotoninergic. furthermore, we have used the same immunofluorescence protocol to determine whether spinal ...	1990	1691216
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
characterization of the muscarinic cholinergic receptor in the opossum (didelphis virginiana, kerr) submandibular gland: differences in receptor density and subtype compared with higher mammalian species.	1. kinetic, saturation and inhibition radioligand binding experiments with [3h]-n-methylscopolamine and [3h]quinuclidinyl benzilate were used to characterize the muscarinic cholinergic receptor in opossum (didelphis virginiana, kerr) submandibular salivary gland membranes. 2. the receptor density in opossum submandibular gland was found to be more than 3-fold higher than in rat, and 22-fold higher than in human, submandibular glands. 3. inhibitor equilibrium dissociation constants for the antago ...	1990	1981346
autoradiographic demonstration of specific binding sites for e. coli enterotoxin in various epithelia of the north american opossum.	in the north american opossum, heat-stable specific binding sites for e. coli enterotoxin are observed (i) in epithelial cells lining the small intestine, colon, gall bladder, cystic duct, common bile duct and trachea, and (ii) in epithelial cells forming the duodenal (brunner's) glands, liver, kidneys (metanephros, mesonephros) and testis, as demonstrated by autoradiography. enterotoxin-specific binding sites in the intestinal tract are only found in intestinal epithelial cells with the highest ...	1990	2162736
aerobic bacteria cultured from the mouth of the american opossum (didelphis virginiana) with reference to bacteria associated with bite infections.	the american opossum inflicts bite injuries both when hunted for food and when accidentally provoked when handled in captivity. this study involved aerobically culturing organisms from the mouths of seven wild opossums (didelphis virginiana). isolates included streptococci, coagulase-positive and -negative staphylococci, aeromonas spp., citrobacter freundii, eikenella corrodens, and escherichia coli.	1990	2229365
host-dependent differences in feeding and reproduction of ixodes dammini (acari: ixodidae).	the frequencies with which adult ixodes dammini spielman, clifford, piesman and corwin feed upon white-tailed deer (odocoileus virginianus), raccoons (procyon lotor), opossums (didelphis virginiana), and domestic cats were compared in a wooded site in northeastern united states. by combining estimates of the quantity of ticks feeding on each host species with host densities, we derived the relative contribution made by each kind of host to the feeding of the tick population. to compare engorgeme ...	1990	2280395
the lamina propria of vertebrate seminiferous tubules: a comparative light and electron microscopic investigation.	the lamina propria of the seminiferous tubules was compared by means of light and electron microscopy in specimens obtained from the following vertebrates: mute swan, northern mallard, blackbird, grey short-tailed opossum, north american opossum, european rabbit, mouse, rat, golden hamster, mini pig, bull, llama, roebuck, horse, coati, cat, dog, java monkey, orang utan. the lamina propria consists of basal lamina, ground substance, collagen fibers, fibroblasts and myofibroblasts. myofibroblasts ...	1990	2281881
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
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
pulmonary reflexes and breathing pattern during sleep in the opossum.	paradoxical sleep (ps) in the opossum (didelphis virginiana) and other mammals is typically accompanied by irregular breathing, while even breathing is usually found during slow wave sleep (sws). during ps certain brainstem reflexes are depressed, and it is possible that similar depression of pulmonary reflexes could contribute to the observed ventilatory uneveness. to test this possibility, we assessed pulmonary reflexes in the opossum during sws and during ps when breathing was irregular. prol ...	1990	184508
hypertrophic smooth muscle in the partially obstructed opossum esophagus. the model: histological and ultrastructural observations.	obstruction is a complication of many esophageal diseases, but the morphological changes occurring in the obstructed esophagus are poorly understood. we developed a model of esophageal obstruction in the american opossum, didelphis virginiana. a nonconstricting band around the gastroesophageal junction led to esophageal distention and tortuosity in the weeks following its placement. despite a marked increase of the esophageal circumference, the esophageal wall was not thinned, and the circular m ...	1991	2001825
lung lesions in an opossum (didelphis virginiana) associated with capillaria didelphis.	an opossum (didelphis virginiana) live-trapped on parramore island, virginia was infected with the lung parasite capillaria didelphis. lung lesions associated with this parasite were extensive and consisted of numerous areas with central necrosis deep within the parenchyma. necrotic foci were present around airways and consisted of a mixture of inflammatory cells and cellular debris, adult nematodes and many bipolar eggs. this parasite causes severe verminous pneumonia in the opossum.	1991	2023321
effects of hydrocortisone acetate treatment on the small intestine of the lactent marsupial didelphis albiventris.	when hydrocortisone acetate was administered subcutaneously to the lactent brazilian white belly opossum, it induced precocious intestinal maturation. histological features of the small intestine were reminiscent of those seen in human protein-caloric malnutrition. there were also indications that the glucocorticoid acted as an inducer of the differentiation of paneth, goblet and granulomucous cells within the small intestinal epithelium. in the lactent opossum the small intestine is lined by an ...	1991	2064018
organization of midbrain catecholamine-containing nuclei and their projections to the striatum in the north american opossum, didelphis virginiana.	presumptive catecholamine (ca) neurons in the opossum midbrain were identified by tyrosine hydroxylase immunohistochemistry. in the midline, small to moderate number of ca cells were present in the rostral third of the nucleus raphe dorsalis and throughout the nucleus linearis. ventrolaterally, such cells were observed in the deep tegmental reticular formation, in all subnuclei of the ventral tegmental area, and in the three subdivisions of the substantia nigra. the ca cells in these areas confo ...	1991	1677010
natural anti-snake venom proteins.	the resistance of several animals to snake venom has been reviewed. some general concepts are introduced to allow the comparative evaluation of the resistance of different animals studied by different investigators. the purification and properties of several factors isolated from the serum of different animals by some researchers are described: trimeresurus flavoviridis (omori-satoh et al., 1972); vipera palaestinae (ovadia et al., 1975, 1977); sigmodon hispidus (pichyangkul and perez, 1981); di ...	1991	1801313
salmonella infection of the biliary and intestinal tract of wild opossums.	bacteriologic cultures were taken from the mesenteric lymph nodes, biliary tract, blood, liver, spleen and pancreas of opossums (didelphis virginiana) obtained directly from the wild for use as research animals. the overall incidence of salmonellosis outside the intestinal tract was 61% among 18 opossums. salmonella was recovered from the gallbladder of six (33%) animals, indicating chronic biliary tract infection. among these six animals, translocation of salmonella to regional lymph nodes was ...	1991	1849588
deoxyadenosine triphosphate acting as an energy-transferring molecule in adenosine deaminase inhibited human erythrocytes.	deoxyadenosine triphosphate (datp) is present in adenosine deaminase (ada)-deficient or ada-inhibited human red cells and in the red cells of the opossum didelphis virginiana. in order to investigate the functions of datp in the red cell, red cells were treated with 2'-deoxycoformycin (dcf), a powerful inhibitor of ada, and incubated with phosphate, deoxyadenosine and glucose. these red cells in which atp was almost completely replaced by datp, had the same shape, lactate production, nucleotide ...	1991	1911876
the origins of supraspinal projections to lumbosacral and cervical levels of the spinal cord in the gray short-tailed brazilian opossum, monodelphis domestica.	retrograde tracing techniques were used to identify supraspinal neurons that project to sacral, lumbar and cervical levels of the spinal cord in the gray short-tailed brazilian opossum, monodelphis domestica. injections of fast blue, true blue or wheat germ agglutinin conjugated to horseradish peroxidase into the sacral or lumbar cord labeled neurons in hypothalamic and brainstem nuclei reported to innervate the same levels in other mammals. injections at cervical levels produced extensive label ...	1991	1684917
physiological interactions between enkephalin and excitatory amino acids in the cerebellar cortex of the opossum didelphis marsupialis virginiana.	the opiate peptide enkephalin has been immunohistochemically localized within specific populations of climbing fibers and mossy fibers in the opossum's cerebellum. the intention of the present study was to determine the physiological effects of this peptide on purkinje cell activity as well as to examine interactions between this peptide and the excitatory amino acids glutamate and aspartate. iontophoretic application of enkephalin onto purkinje cells in the posterior lobe vermis and adjacent he ...	1991	1682851
evidence for new growth and regeneration of cut axons in developmental plasticity of the rubrospinal tract in the north american opossum.	we have shown previously that rubral axons can grow around a lesion of their spinal pathway in the developing opossum and that a critical period exists for that plasticity (martin and xu, dev brain res 39:303, 1988). since most rubrospinal neurons degenerate after axotomy during the critical period, we have proposed that plasticity results primarily from growth of late arriving axons around the lesion rather than regeneration of cut axons (xu and martin, j comp neurol 279:368, 1989). in the pres ...	1991	1761748
the origin of serotoninergic projections to the lumbosacral spinal cord at different stages of development in the north american opossum.	we have employed immunohistochemistry and the retrograde transport of fast blue to study the origin of serotoninergic projections to the lumbosacral spinal cord at different stages of development in the north american opossum. a few serotoninergic axons are present in the lumbosacral cord at birth, 12 days after conception, and serotoninergic neurons are numerous in the brainstem where they are present in most, if not all, of the areas which contain them in the adult animals. a few neurons of th ...	1991	1851469
mammary glands in male marsupials. 2. development of teat primordia in didelphis virginiana and monodelphis domestica.	young and adults of both sexes of two didelphid marsupials, didelphis virginiana and monodelphis domestica, were examined externally for evidence of mammary gland development. female young possessed teat numbers typical of adult females (13-15 in d. virginiana; 11-13 in m. domestica). male young showed variable teat numbers which were always low compared with females, with the majority possessing 2-4 in anterior positions. teats were also present in adult males of both species, in similar number ...	1991	1947228
nad synthesis in ada deficient erythrocytes of the opossum didelphis virginiana.		1991	1781390
the vestibular apparatus of the opossum (didelphis virginiana) prior to and immediately after birth.	the vestibular apparatus of the opossum was examined shortly before and immediately after birth. a band of about 20 sensory cells was observed within the forming utricle by 24 h prior to birth. stereocilia projecting from the apices of the sensory cells appeared intimately associated with a well-defined population of overlying otoliths. these morphological observations suggest that a functional utricle may be present at the time of birth and together with other senses (tactile, olfaction) may ai ...	1991	1781240
fetal nephrotoxicity.	investigation of fetal nephrotoxicity by maternally administered nephrotoxins is hampered by many constraints, including the maternal effects of the nephrotoxin, the ability of the nephrotoxin to cross the placenta and the difficulties associated with direct fetal intervention. in the pouch young of the north american opossum, didelphis virginiana, we describe the toxic effects of a heavy metal on the immature metanephric kidneys. varying doses of uranyl nitrate, a heavy metal salt, were adminis ...	1992	1640562
morphological observations on the harderian gland of the north american opossum (didelphis virginiana).	the harderian gland of the north american opossum (didelphis virginiana) is large and well developed, despite the absence of a nictitating membrane in the adult of this species. the elongate glands are surrounded by a delicate connective tissue capsule from which thin septae extend, subdividing the gland into numerous lobules. the secretory units of the opossum harderian gland are drained by a well defined but not extensive intralobular and interlobular duct system. most of the secretory end pie ...	1992	1510244
development of the digestive system in the north american opossum (didelphis virginiana).		1992	1632285
the response of rubrospinal neurons to axotomy at different stages of development in the north american opossum.	rubral axons can grow around a lesion of their pathway in the thoracic spinal cord of developing opossums and a critical period exists for that plasticity. the critical period probably begins when rubral axons first grow into the thoracic cord, and it extends until approximately postnatal day 30. we previously noted that most rubrospinal neurons die after transection of their axon during the critical period, suggesting that plasticity results primarily from growth of axons not damaged by the les ...	1992	1383556
a light-microscopic immunocytochemical study of the endocrine pancreas in the australian brush-tailed possum (trichosurus vulpecula).	the endocrine pancreas of the australian brush-tailed possum (trichosurus vulpecula) was investigated by means of immunocytochemistry using the avidin-biotin-peroxidase technique. this was a light microscopic study using this established technique. serial paraffin sections were stained individually with primary antibodies for glucagon, insulin, somatostatin, and pancreatic polypeptide (pp), showing the same islet. cells immunoreactive to glucagon, insulin, somatostatin and pp were found in endoc ...	1992	1380858
the functional morphology of xenarthrous vertebrae in the armadillo dasypus novemcinctus (mammalia, xenarthra).	in order to assess the mechanical properties of xenarthrous vertebrae, and to evaluate the role of xenarthrae as fossorial adaptations, in vitro bending tests were performed on posterior thoracic and lumbar vertebral segments excised from specimens of the armadillo dasypus novemcinctus and the opossum didelphis virginiana, the latter being used to represent the primitive mammalian condition. the columns of the two species were subjected to dorsal, ventral, and lateral bending, as well as torsion ...	1992	1433308
isolation from opossum serum of a metalloproteinase inhibitor homologous to human alpha 1b-glycoprotein.	fractionation of opossum (didelphis virginiana) serum with (nh4)2so4, followed by chromatography on deae-sepharose, phenyl-sepharose, and mono q hr 5/5, has resulted in the isolation in homogeneous condition of a metalloproteinase inhibitor designated oprin (opossum proteinase inhibitor). oprin is a single-chain glycoprotein (26% carbohydrate) with an estimated mr = 52,000, pi = 3.5, and e(1%/1 cm) = 11. oprin inhibited snake venom metalloproteinases, but showed no activity on venom serine prote ...	1992	1731898
immunohistochemical localization of relaxin in the reproductive system of the female opossum (didelphis virginiana).	relaxin-immunoreactivity was demonstrated in the cytoplasm in the luteal cells from pregnant and lactating opossums. immunoreactivity for relaxin was not demonstrated elsewhere in the ovary, in the reproductive tract or in the placenta. the corpus luteum is thought to be the primary source of relaxin in didelphis and in this regard is similar to several eutherian mammals including man.	1992	1416066
the epidemiology of toxoplasmosis on iowa swine farms with an emphasis on the roles of free-living mammals.	multiparous sows from 19 central iowa swine farms were tested for antibodies against toxoplasma gondii by the modified direct agglutination test. antibody titers of 1:32 or greater were considered positive. rodents, domestic cats, opossums (didelphis virginiana), raccoons (procyon lotor) and striped skunks (mephitis mephitis) were live-trapped on each farm and similarly tested for antibodies. the overall prevalence of t. gondii antibodies in the species tested was 39/273 (14.3%) swine, 31/74 (41 ...	1992	1496780
retinal topography in the koala (phascolarctos cinereus).	nissl-stained retinal wholemounts were used to investigate the topographical organization of the ganglion cell layer of the koala (phascolarctos cinereus); the visual resolution limit of this animal was subsequently estimated from retinal ganglion cell density data. two types of cells could be differentiated on the basis of their size and staining characteristics: a subpopulation of presumed ganglion cells, consisting of medium to large cells with nissl substance in the cytoplasm and pale unifor ...	1992	1537048
bacterial flora of the gastrointestinal tract of opossums.	the bacterial flora of the stomach, small intestine, cecum and bile from 20 healthy opossums (didelphis virginiana) captured from the wild was studied. results showed that their gastrointestinal flora was similar to that found in other small mammals but, in addition, opossums are heavily colonized by salmonella spp., which might adversely affect their adequacy as laboratory animals for some experimental protocols.	1992	1557901
electrocardiographic and echocardiographic features of trypanosomiasis in dogs inoculated with north american trypanosoma cruzi isolates.	purebred beagles were inoculated with trypanosoma cruzi isolates from a north american opossum or armadillo (tc-w), and dog (tc-d). although tc-d established infection in dogs, the dogs did not develop cardiac abnormalities. dogs inoculated with tc-w developed acute myocarditis associated with increases in p-r interval, atrioventricular block, depression of r wave amplitude and shifts in mean electrical axis. echocardiograms were normal during this stage. three tc-w-inoculated dogs died during t ...	1992	1586022
serologic response of the opossum didelphis virginiana to a temperature-sensitive mutant (ts-4) of toxoplasma gondii.	a study was designed to measure the toxoplasma gondii-specific igm and igg antibody responses of opossums inoculated with tachyzoites of the temperature-sensitive mutant of t. gondii, ts-4, and to examine its persistence in the tissues. four young opossums seronegative for anti-toxoplasma gondii igm and igg antibodies immediately after capture and 4 wk later were injected subcutaneously with 1.8 x 10(6) ts-4 tachyzoites; a fifth opossum (also seronegative) received an injection of saline only. s ...	1992	1635036
a serosurvey of swine and free-living species on iowa farms for antibodies against encephalomyocarditis virus.	swine and free-living nonporcine species from 20 iowa swine farms were surveyed for antibodies against encephalomyocarditis virus (emcv). the microtitration serum neutralization test was used, and antibody titers >/= 1:8 were considered positive. the overall prevalence in 267 sows in various groups was 37.8% (range 20-86%). the prevalence in sows maintained in total confinement was significantly lower than in sows not maintained in total confinement (p = 0.01). prevalence in sows was not associa ...	1992	17424088
odors as cues for orientation to mothers by weanling virginia opossums.	three experiments were conducted to investigate whether wholebody and pouch odors facilitate social cohesion between young virginia opossums and their mothers just prior to weaning. in experiment 1, young oriented toward plastic buckets containing their mothers, directing significantly higher levels of investigative behavior and more distress vocalizations toward them than toward buckets containing unrelated lactating females. in experiment 2, young oriented toward and investigated empty buckets ...	1992	24254869
anatomy of the bilioduodenal junction of the opossum.	prevention of reflux is a major function of the terminal biliary duct system at its junction with the duodenum. we examined this area via scanning electron microscopy and light microscopy to explore anatomic features that might play such a role in the virginia opossum, a species with a highly developed sphincter of oddi (so). the terminal apparatus, most of which consists of a dilated extramural ampulla, has a lumen with abundant folds. mucus is produced by the lining epithelium and by a plethor ...	1992	1554107
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
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
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