Publications

a pharmacological study of oesophageal muscularis mucosae from the cat, dog and american opossum (didelphis virginiana).	strips of muscularis mucosae from the oesophagi of cat, dog and opossum have been studied to determine their responses to drugs to electrical field stimulation. all tissues were contracted by acetylcholine, histamine and, with the exception of strips of muscularis mucosae from the opossum proximal oesophagus, noradrenaline. the effects of acetylcholine and histamine were competitively antagonized by atropine (50 nm) and mepyramine (50 nm) and were abolished by atropine (1 microm) and mepyramine ...	1984	6207883
initial experiments with cyproterone acetate and 1-amino-3-chloro-2-propanol hydrochloride in the male virginia opossum (didelphis virginiana).	cyproterone acetate (ca) was toxic for didelphis virginiana at a dose range of 22-28 mg/kg im. a loss of spermatozoal pairing int the cauda epididymidis did not occur until 2 wk after testicular degeneration caused by ca. the isomers of 1-amino-3-chloro-2-propanol hydrochloride (cl 88,236 and cl 88,237) were well tolerated by the opossum at doses up to 30 mg/kg im. after 8 days of cl 88,236 and cl 88,237 treatment there was no effect on spermatozoal pairing in the cauda epididymidis or on the se ...	2013	6220622
reticular and raphe projections to the spinal cord of the north american opossum. evidence for connectional heterogeneity.		1982	6296915
the purification and characterization of an antihemorrhagic factor in woodrat (neotoma micropus) serum.	a protein antihemorrhagic factor was purified from the serum of the southern plains woodrat (neotoma micropus) by gel filtration and ion exchange chromatography. the homogeneity of the purified factor was measured by disc electrophoresis in polyacrylamide gel. the factor had an isoelectric ph of 4.1, a molecular weight of 54,000, and migrated with alpha-globulins in disc electrophoresis. the factor failed to form a precipitate with crude western diamondback rattlesnake (crotalus atrox) venom and ...	1984	6372164
the neuronal types and the distribution of 5-hydroxytryptamine and enkephalin-like immunoreactive fibers in the dorsal cochlear nucleus of the north american opossum.	the opossum dorsal cochlear nucleus is divided into four layers distinguishable either on the basis of differential distribution of neuron types or by neuropil organization. we have used nissl, golgi and protargol stained preparations to examine these components. four types of neurons (excluding granule cells) are seen. the principal neurons have large cell bodies arranged in a sheet defining layer ii, their apical dendrites extend dorsally to form an elaborate arbor in layer i and their basal d ...	1984	6372948
metaphase synchronization and chromosome preparation from the ok opossum cell line having a potentially isolatable x chromosome.	as part of a study on x chromosomes, metaphase cell synchrony and chromosome isolation methods were developed for the opossum (didelphis virginiana) kidney epithelial cell line (ok). the cell synchrony yielded large amounts of metaphase cells using a relatively simple method in which a key feature was a calcium- and magnesium-free balanced salt wash. a neutral ph chromosome isolation method was developed for the kidney epithelial cells, because they were somewhat difficult to disrupt fully by ot ...	1984	6394469
studies on the energy metabolism of opossum (didelphis virginiana) erythrocytes. i. utilization of carbohydrates and purine nucleosides.	opossum erythrocytes filtered through cellulose columns were used to estimate their permeability to d-glucose and optimum inorganic phosphate requirement for d-glucose utilization at ph 7.4 and 8.1. d-glucose readily penetrated opossum red cells; there was no measurable difference whether plasma or electrolyte solution served as the suspending medium. optimum extracellular inorganic phosphate concentration for glucose utilization as indicated by red cell lactate production was ph-dependent, with ...	1984	6429161
description of sarcocystis falcatula stiles, 1893, a parasite of birds and opossums.	sarcocystis falcatula stiles, 1893 is re-described. intermediate hosts of the parasite which was earlier described as sarcocystis debonei vogelsang, 1929 are species of passeriform, psittaciform, and columbiform birds. in these birds, muscle zoites are 6.88 x 2.19 (4.8-8.4 x 1.2-3.6) micron and are enclosed in a cyst wall with regular protrusions, 1-5 micron long. the convoluted primary wall has multiple thin areas in the osmiophilic layer. microtubules originate in the ground substance and exte ...	1984	6439855
light- and electron-microscopic demonstration of immunoreactive opsin in the pinealocytes of various vertebrates.	an antibody to opsin isolated from rod outer segments of the frog retina was applied in light- and electron-microscopic immunocytochemical studies to the pineal organ of various vertebrates (cyprinus carpio, carassius auratus, rana esculenta, emys orbicularis, pseudemys scripta elegans, lacerta agilis and viridis. gallus domesticus, columba livia, melopsittacus undulatus, serinus canaria, taeniopyga punctata, didelphis virginiana, erinaceus roumanicus, myotis myotis, rabbit, rat, cat).	1981	6458362
two multigene families for marsupial neurohypophysial hormones? identification of oxytocin, mesotocin, lysipressin and arginine vasopressin in the north american opossum (didelphis virginiana).	oxytocin, mesotocin ([ile8]-oxytocin), lysipressin ([lys8]-vasopressin) and arginine vasopressin have been identified in the north american opossum (didelphis virginiana) by amino acid composition and high pressure liquid chromatography. the same peptides with the exception of mesotocin have previously been found in two south american opossums (didelphis marsupialis and philander opossum). although a dual heterozygocity could also explain the simultaneous presence of oxytocin/mesotocin on one ha ...	1984	6477584
developmental sequence in the origin of descending spinal pathways. studies using retrograde transport techniques in the north american opossum (didelphis virginiana).	the origin of descending pathways to thoracic and cervical levels of the spinal cord has been investigated with retrograde tracing techniques in a series of pouch young and adult opossums. the opossum was chosen because it is born in a very immature state, 12-13 days after conception, and has a protracted development in an external pouch. a few neurons in the pontine reticular formation and nucleus coeruleus were labeled by horseradish peroxidase (hrp) injections of the thoracic cord as early as ...	1984	6478250
cerebellar cortical efferent fibers in the north american opossum, didelphis virginiana. i. the anterior lobe.	the distribution of cerebellar corticonuclear and corticovestibular fibers from the anterior lobe of the north american opossum, didelphis virginiana, was studied using the fink and heimer ('67) technique. corticonuclear fibers from medial areas of anterior lobe project into the medial cerebellar nucleus (nm) in a topographically organized manner. fibers from lobules ii and iii enter rostral and rostrodorsal nm, while those from lobules iv and v terminate in progressively more caudal parts of th ...	1984	6480900
cerebellar cortical efferent fibers in the north american opossum, didelphis virginiana. ii. the posterior vermis.	the projection pattern of corticonuclear and corticovestibular fibers from vermis lobules vi-x of the north american opossum, didelphis virginiana, was studied using a modification of the fink and heimer ('67) technique. the evidence suggests that corticovestibular projections in opossum are ipsilateral and exit the cerebellum via the juxtarestiform body. lobules vi and vii contribute few, if any, corticovestibular projections. corticovestibular fibers from lobule viii are sparse to moderate and ...	1984	6480901
motor units of the primary ankle extensor muscles of the opossum (didelphis virginiana): functional properties and fiber types.	motor units of the medial gastrocnemius (mg) and the single lateral gastrocnemius/soleus (lg/s) muscles of the opossum (didelphis virginiana) were found to have uniformly slow contraction times relative to homologous muscles of the cat. though a broad range of peak tetanic tensions was found among motor units from both muscles, most of the motor units were quite large relative to tension of the whole muscle. comparison of the relative sizes of motor units showed that those of lg/s are significan ...	1984	6481810
scanning electron microscopic observations on the 9-day opossum (didelphis virginiana) embryo.	all three germ layers are present in the opossum embryo by the 9th prenatal day. the embryo proper is part of, and continuous with, the remainder of the chorionic wall. the wall of the yolk sac-chorion away from the embryo consists only of an outer covering of ectoderm and an inner layer of endoderm. ectodermal cells covering the neural folds have dome-shaped apices and often show large, bleb-like expansions. microvilli are short and few in number. the apical surfaces of ectodermal cells that ov ...	1984	6516775
postnatal development of the thyroid gland in the opossum (didelphis virginiana).	thyroid lobes of the newborn opossum consist of small epithelial cords or plates, the constituent cells of which are joined by tight junctions and surround a minute lumen that courses throughout the length of each cord. occasional cells, not directly associated with the lumina of the cords, show central nuclei and clusters of small electron-dense granules: these may represent parafollicular cells at an early state of development. by the end of the 1st week after birth, parafollicular cells are w ...	1983	6624377
a golgi study of the opossum ventral basal complex.	the morphology of neurons in the ventral basal complex (vbc) of the adult opossum (didelphis virginiana) is described from thick coronal brain sections, using golgi-, horseradish peroxidase (hrp)-, and nissl-staining methods. soma cross-sectional area, dendritic field shape, and the number of appendages (spines) in a defined major branch zone (mbz) are quantified and statistically analyzed. results indicate that neurons in opossum vbc have relatively large cell bodies, dendrites which branch in ...	1983	6644824
ultrastructural observations on the shell membrane of the north american opossum (didelphis virginiana).	each developing opossum embryo is surrounded by a shell membrane which completely separates embryonic and maternal tissues. during the eighth and ninth prenatal days, the embryos together with their limiting shell membranes float freely within the uterine lumen, surrounded only by the secretions of the uterus. the shell membrane is transparent, nonelastic, tough, and capable of extreme deformation. it consists of a mat of interwoven fibers which vary in external diameter, are electron dense, and ...	1983	6650866
structure of the paws in didelphis virginiana.	the paws of didelphis virginiana show several unusual features. they possess dermatoglyphs on the foot pads, have opposable first digits and the pads show a peculiar vascular arrangement. the hallux lacks a claw. the degree of innervation and the number and size of pacinian corpuscles indicates that the paws of the opossum are finely sensitive to pressure and vibration.	1983	6660547
the auditory brainstem nuclei and some of their projections to the inferior colliculus in the north american opossum.	afferent projections to the inferior colliculus in the north american opossum have been examined using the retrograde transport of horseradish peroxidase. projections to primarily the contralateral inferior colliculus arise in the dorsal and ventral cochlear nuclei, the auditory nerve nucleus and the spinal trigeminal nucleus pars caudalis, while ipsilateral projections arise in the superior paraolivary nucleus, the ventral nucleus of the trapezoid body, the ventral nucleus of the lateral lemnis ...	1983	6664491
anatomical demonstration of the location and collateralization of rubral neurons which project to the spinal cord, lateral brainstem and inferior olive in the north american opossum.	rubral neurons innervating the spinal cord, the lateral brainstem and the inferior olivary nucleus have been identified in the north american opossum by the retrograde transport of horseradish peroxidase and fluorescent markers. neurons which project to the spinal cord are found mainly in caudal and rostroventral parts of the red nucleus. in contrast, rubral neurons which innervate the facial nucleus and lateral areas of the medulla are most numerous rostrodorsally. there is overlap in the locat ...	1983	6667372
life cycle and development of lagochilascaris sprenti (nematoda: ascarididae) from opossums (marsupialia: didelphidae) in louisiana.	the life cycle of lagochilascaris sprenti, a species which occurs in the stomach of opossums (didelphis virginiana) in louisiana, was determined. the larva in the egg developed to the infective stage after eggs from the feces of infected animals were in culture about 30 days. when eggs containing infective larvae were fed to mice, the larvae hatched, penetrated the intestinal mucosa, migrated through the liver and lungs, and eventually reached the skeletal muscles where they became encapsulated. ...	1983	6685179
lagochilascaris sprenti sp. n. (nematoda: ascarididae) from the opossum, didelphis virginiana (marsupialia: didelphidae).	sixty-eight specimens of lagochilascaris from the stomach of seven naturally-infected opossums from louisiana were described as lagochilascaris sprenti sp. n. observations were also made on adult worms of both sexes recovered from experimentally-infected opossums and mice. the new species differs from the four previously described species of lagochilascaris in the length of the spicules, number of pits on the circumference of the egg, and position of the vulva. the spicules are shorter in l. spr ...	1983	6685180
collateral innervation of the inferior colliculus in the north american opossum: a study using fluorescent markers in a double-labeling paradigm.	the innervation of the opossum inferior colliculus was investigated using the retrograde transport of fluorescent markers in a double-labeling paradigm. true blue was injected into one inferior colliculus while nuclear yellow was placed into the other. many single-labeled neurons were found in all of the brainstem and cortical areas previously labeled by comparable injections of hrp. when the two injections of fluorescent markers were bilaterally symmetrical within the inferior colliculi, double ...	1984	6733522
raphespinal projections in the north american opossum: evidence for connectional heterogeneity.	retrograde transport studies revealed that the nuclei pallidus, obscurus, and magnus raphae as well as the adjacent reticular formation innervate the spinal cord in the opposum. hrp-lesion experiments showed that a relatively large number of neurons within the nucleus obscurus raphae and closely adjacent areas of the nucleus reticularis gigantocellularis project through the ventrolateral white matter and that many cells within the nucleus magnus raphae, the nucleus reticularis gigantocellularis ...	1982	6749912
development of raphe-spinal connections in the north american opossum.	the falck-hillarp technique, serotonin (5-ht) immunohistochemistry and the retrograde transport of horseradish peroxidase (hrp) were utilized to investigate the development of raphe-spinal connections in the pouch-young opossum. the brainstem raphe and adjacent reticular formation contain 5-ht immunoreactive neurons in the newborn opossum (12 days after conception) and processes from these cells can be visualized in the marginal zone of the spinal cord. between eight and 15 days after birth 5-ht ...	2013	6756557
ultrastructure of sarcocystis sporocysts from passerine birds and opossums: comments on classification of the genus isospora.	sporocysts were obtained from the feces of opossums (didelphis virginiana) which had been fed muscles of passerine birds (molothrus ater and cassidix mexicanus) infected with sarcocystis. sporocysts were examined by phas microscopy and scanning and transmission electron microscopy. ridges on the surface of the sporocysts outlined four plates. thin sections of the sporocyst wall showed thickened regions and gaps interpreted as cross sections of the ridges. the sporocyst wall has four major layers ...	1980	6767835
small mammals and white-tailed deer as possible reservoir hosts of brucella abortus in texas.	four hundred sixty-eight wild mammals were collected from four ranches in texas where brucella-infected cattle herds are maintained, and examined as possible reservoir hosts for brucella abortus. seventy-one serums from five species were tested for brucella antibodies. liver and spleen from 453 mammals (14 species) were cultured for b. abortus. results of the serologic and bacteriologic examination of rodents, opossums (didelphis virginiana), raccoons (procyon lotor) and white-tailed deer (odoco ...	1980	6768900
sarcocystis of passerine birds: sexual stages in the opossum (didelphis virginiana).	sexual stages of a sarcocystis of passerine birds were demonstrated by feeding muscle cysts from cowbirds (molothrus ater) and grackles (cassidix mexicanus) to opossums (didelphis virginiana). opossums were examined at necropsy at 36 h, 13.5 days, and 29.5 days post-inoculation (pi). large numbers of macro- and microgamonts were present in the small intestine 36 h pi, while only sporocysts and oocysts were present 13 days or more pi. microgamonts in different stages of development were in the in ...	1980	6776294
organization of projections from the gracile, medial cuneate and lateral nuclei in the north american opossum. horseradish peroxidase study of the cells projecting to the cerebellum, thalamus and spinal cord.	using the horseradish peroxidase technique on the north american opossum, we were able to locate the neurons within the dorsal column and lateral cuneate nuclei which innervate the cerebellum and thalamus as well as those within the dorsal column nuclei which project spinalward. the medial and lateral cuneate nuclei supply axons to the anterior lobe, the paramedian lobule and the pyramis of the cerebellum and the lateral nucleus provides an additional projection to the uvula. the cerebellar proj ...	1981	6788345
experimental infection of opossums with brucella abortus.	thirteen opossums (didelphis virginiana) trapped in east central alabama were fed approximately 1.5 x 10(9) brucella abortus colony forming units. serologic responses to at least 1 of 3 tests developed in 8 of the 13 opossums. brucella abortus was recovered from 18 of 159 blood samples from 4 of the 13 opossums and from 7 of 159 fecal samples from 6 of them. all culture-positive feces had been excreted within 4 days after exposure. sixty-four urine, 123 saliva, and 78 vaginal samples were cultur ...	1981	6799466
sarcocystis spp. in white-tailed deer. i. definitive and intermediate host spectrum with a description of sarcocystis odocoileocanis n. sp.	sporocysts containing four sporozoites and measuring (avg.) 15.2 micrometers x 10.7 micrometers (n = 195) were shed in the feces of dogs (canis familiaris) 8 to 16 days (avg. 11.6 days) after the first feeding of venison infected with sarcocystis sp. sporocysts containing four sporozoites and measuring (avg.) 11.5 micrometers x 8.1 micrometers (n = 35) were shed by a cat (felis catus) 14 days after ingesting sarcocystis-infected venison. statistical (pooled t-test) comparison of the mean measure ...	1981	6802990
the intermediate host spectrum in a sarcocystis species of birds.	the life cycle of an avian sarcocystis has been completed in the laboratory, originating with naturally infected icterids and passing alternately between opossums (didelphis virginiana) and experimentally infected birds. to determine the intermediate host range, six avian species, including canaries (serinus canarius), zebra finches (poephila guttata), budgerigars (melopsittacus undulatus), pigeons (columba livia), chickens (gallus gallus), and guinea fowl (numida meleagris), were inoculated ora ...	1982	6811715
luteal and follicular populations in the ovary of the opossum (didelphis virginiana) after ovulation.	the maximum diameters of all luteal and antral follicular structures were measured in opossum ovaries on days 3, 7 and 11 after oestrus, and follicles were classed as developing or atretic. ovarian weights and luteal diameters were equivalent in comparisons of pregnant and non-pregnant animals on each day. the number of cl (range 45-85) per animal per cycle indicated a very high ovulation rate for a mammal. luteinized follicles (1-4 per ovary) were identified in all day-3 ovaries. ovarian weight ...	1983	6822974
retinal ganglion cell size groups projecting to the superior colliculus and the dorsal lateral geniculate nucleus in the north american opossum.	the retinal ganglion cells projecting to the superior colliculus (sc) and dorsal lateral geniculate nucleus (lgnd) of the north american opossum (didelphis virginiana) were studied by using the retrograde transport of horseradish peroxidase (hrp). the four ganglion cell size groups recognized previously were found to project in systematically different ways. after injections of hrp into the superior colliculus, labeled cells were seen in nasal retina contralateral to the injection and in tempora ...	1983	6826789
observations on the early development of ascending spinal pathways. studies using the north american opossum.	the development of ascending spinal pathways has been studied in the north american opossum using degeneration methods and the retrograde transport of horseradish peroxidase. axons from caudal thoracic and/or lumbosacral levels of the spinal cord reach the lateral reticular nucleus, the inferior olivary complex, the reticular formation of the medulla and pons as well as the cerebellum very early in development. innervation of the nucleus gracilis occurs somewhat later. spinal axons grow into mos ...	1983	6846856
an alternative animal model for perinatal carcinogenesis.	the differences in developmental biology between marsupials and eutherian animals provide alternative approaches to major problems in perinatal carcinogenesis. the high susceptibility of the neonatal american marsupial, the opossum (didelphis virginiana), during early postnatal development to oral, chemical induction of dysontogenetic tumors with a close morphologic and biologic resemblance to those in the human suggests that the neonatal marsupial may offer unique opportunities for the study of ...	1983	6850030
origin and topography of thalamocaudate projections in the opossum.	the origins of the thalamocadaute projections in the north american opossum include the intralaminar nuclei (parafascicular complex, the paracentral, centralis and central lateral nuclei) and the intermedial dorsal, medial dorsal and interanterior dorsal nuclei. of these, portions of the intralaminar nuclei exhibit rudimentary elements of a topographically organized projection. however, it is obvious that the patterns observed here are much less specific than those reported in other mammalian sp ...	1983	6856198
morphological observations on the parathyroid of the opossum (didelphis virginiana).	parathyroid iii of the opossum, didelphis virginiana, lies on the medial surface of the internal carotid artery at its origin just above the bifurcation of the common carotid artery. it is limited externally by a capsule and is subdivided into lobule-like structures by connective tissue septae. the parenchyma consists solely of chief (principal) cells, arranged in irregular cords and clumps supported by a delicate vascular connective tissue. ultrastructurally, the chief cells are polyhedral in s ...	1983	6862174
cerebrospinal fluid-contacting neurons of the central canal and terminal ventricle in various vertebrates.	cerebrospinal fluid (csf)-contacting neurons were studied by means of electron microscopy in the spinal cord and/or terminal ventricle of the ray, raja clavata (elasmobranchii), the opossum, didelphis virginiana (marsupialia), the mouse, mus musculus, and the guinea pig, cavia cobaya (rodentia). dendrites of the csf-contacting neurons in the spinal cord of the ray penetrate the ependyma of the central canal and form terminals bearing stereocilia. axons apparently belonging to these neuronal peri ...	1983	6871973
neocortical projections of the suprageniculate and posterior thalamic nuclei in the marsupial brush-tailed possum, trichosurus vulpecula (phalangeridae), with a comparative commentary on the organization of the posterior thalamus in marsupial and placental mammals.	axonal transport methods were used to determine the extent and organisation of neocortical projections from the suprageniculate (sg) and posterior (po) thalamic nuclei in the brush-tailed possum. our findings show that sg projects extensively to the auditory cortex, overlapping the cortical projection field of the medial geniculate nucleus, and to the immediately neighbouring association cortex. though the input relationships of sg appear similar to those reported for other mammals, placental an ...	1983	6886058
opportunistic fungi in detroit's rats and opossum.	four norway rats (rattus norvegicus) and one opossum (didelphis virginiana) were surveyed for the presence of fungi. eighteen different fungi were isolated from rat samples and six from the opossum, including trichophyton mentagrophytes. hair and skin scrapings from laboratory raised norway rats, bedding and air from the room yielded only penicillium sp.	1980	6991950
the early development of corticobulbar and corticospinal systems. studies using the north american opossum.	the north american opossum is born 12 days after conception and is therefore available for experimental manipulation in an immature state. we have used the opossum to study the growth of cortical axons into the brainstem and spinal cord and have obtained evidence that such growth occurs in an orderly fashion. cortical axons reach the ventral mesencephalon 12 days after birth and some of them have grown into the caudal medulla where they decussate by 23 days. at the latter stage immature cortical ...	1980	7053121
separation of sperm pairs and sperm-egg interaction in the opossum, didelphis virginiana.		1982	7054492
acute hepatitis in an opossum (didelphis virginiana) infected with salmonella turnidorp.	salmonella turnidorp was isolated in pure culture from the liver of an opossum that died of acute hepatitis. microscopically, there were random foci of hepatic coagulation necrosis and gram negative bacteria within hepatocytes. the salmonella turnidorp isolate was aberrant in that it did not utilize citrate and did not agglutinate by a commercial salmonella polyvalent antiserum. additional salmonella serotypes, including salmonella mbandaka, salmonella rubislaw, and salmonella anatum were isolat ...	1982	7078089
phagosome movement and the diurnal pattern of phagocytosis in the tapetal retinal pigment epithelium of the opossum.	the diurnal pattern of phagocytosis and the movement of phagosomes was studied in the tapetal retinal pigment epithelium (rpe) of the opossum, didelphis virginiana. the opossum was chosen because of its rod-dominated retina and large tapetal rpe cells (up to 100 micrometers in height), which are packed with reflective granules and contain little melanin. thus phagosomes and their passage from apical to basal cell border were easily seen. opossums were maintained on a 12 hr light/12 hr dark cycle ...	1982	7107156
phagosome degradation in the tapetal retinal pigment epithelium of the opossum.	ultrastructural and cytochemical features of phagosome degradation were examined in the tapetal retinal pigment epithelium (rpe) of the opossum. didelphis virginiana. the tapetal rpe cells of the opossum measure as much as 100 micrometers in thickness, and the phagosomes traverse these cells so as to occupy a narrow region along the basal border. both ultrastructural and cytochemical observations showed that degradation of phagosomes by lysosomes occurs only in this basal region. acid phosphatas ...	1982	7107157
the notochord of the newborn opossum and its fate during postnatal development.	the notochord was examined by light, transmission and scanning electron microscopy, in 25 pouch young opossums (didelphis virginiana) ranging in age from 6 hr to 25 days post natum. in the newborn opossum, the notochord forms a thin cylinder within developing vertebral centra and presents diamond-shaped expansions in regions of the developing intervertebral discs. the opossum notochord differs from that of other species in that it appears to consist of a heterogeneous population of light and dar ...	1982	7125861
topographical representation of the peripheral nerve branches of the facial nucleus of the opossum: a study utilizing horseradish peroxidase.	the main facial nucleus of a marsupial, the north american opossum (didelphis marsupialis virginiana), was subdivided into 6 portions by localizing hrp-positive neurons after injecting all muscles by each major peripheral motor branch of the facial nerve. in the medial lobe of this dumbbell-shaped nucleus the caudal auricular nerve, rostral auricular ramus and cervical ramus were represented dorsomedially, dorsolaterally and ventrally, respectively. the lateral lobe contained zygomatic ramus cel ...	1982	7127096
cytoarchitectural and dendritic patterns of the dorsal column nuclei of the opossum.	cytoarchitectural and dendritic patterns of dorsal column nuclei of the opossum, didelphis marsupialis virginiana, were studied with nissl and golgi preparations. two basic cell types, round cells and irregular cells, are found. round cells have a large, round cell body (20-30 mu) with a distinct nucleolus in the nucleus. the cytoplasm is fine, evenly dispersed nissl material with occasional tigroid bodies. irregular cells have triangular, multipolar or fusiform cell bodies (8-10 mu) with indist ...	1982	7130682
observations on turgida turgida (rudolphi, 1819) (nematoda: physalopteroidea) in the american opossum (didelphis virginiana).	turgida turgida is a common parasite of the stomach of the american opossum in florida. worms were usually found attached to the greater curvature of the corpus of the stomach. ulcers always occurred at the site of the attachment. large ulcers were associated with groups of adult parasites and were found in the oldest experimental infections. turgida turgida fed on food within the stomach of the opossum and attached to the stomach wall when not feeding. third-and fourth-stage larvae were found i ...	1982	7131652
husbandry of a small breeding colony of opossums (didelphis virginiana).	a small breeding colony of opossums was established in a semi-enclosed structure. minor modifications of pre-existing pens permitted efficient and productive management of the opossums. dry dog food was provided, and large amounts of shredded paper was used for nesting material. vaginal smears were taken from opossums that were restrained only by their tail, a procedure that allowed one person to obtain and interpret vaginal smears from 20 females in less than 2 hours per day. pregnancy resulted ...	1982	7144133
oxidation-reduction properties of the hemoglobin of the opossum, didelphis virginiana.		1982	7151402
cytosolic and membrane-bound methemoglobin reductases in erythrocytes of the opossum, didelphis virginiana.		1982	7151403
postnatal development of the spleen in didelphis virginiana.	the postnatal development of the spleen has been examined in 85 opossums ranging in age from newborn to adult. at birth the spleen consists of a well vascularized mass of mesenchymal tissue and lacks lymphatic tissue or any evidence of haemopoietic activity. haemopoiesis is evident at seven days, increases to a maximum at about two to three weeks and thereafter gradually declines. although production of granulocytes has disappeared by 60 days postnatum, a small degree of erythropoiesis and megak ...	1982	7153176
the development of descending spinal connections. studies using the north american opossum.		1982	7156395
quantitative analysis of the optic nerve of the north american opossum (didelphis virginiana): an electron microscopic study.	on the basis of an electron microscopic examination of the optic nerve of the north american opossum it was estimated that the nerve has approximately 100,000 axons, of which 98% are myelinated. the myelinated axons ranged from 0.3 to 6.7 micrometers in diamter (mean 1.6 micrometers), while unmyelinated axons were 0.2 to 1.6 micrometers in diameter (mean 0.6 micrometers). axoplasm and axon (axoplasm plus myelin) diameter spectrums were unimodal and positively skewed. the mean of the ratio of axo ...	1982	7174896
the pineal region in the opossum, didelphis virginiana. i. ultrastructural observations.	in the pineal region of the opossum, didelphis virginiana, two types of cells predominate: 1) pinealocytes, and 2) fibrous astrocytes. pinealocytes are characterized by the presence of prominent golgi bod'ies, numerous clear and dense-cored vesicles, sensory cilia (9+0), vesicle-crowned rods, and condensation of a maternial that was always associated with the rough endoplasmic reticulum. in addition, two other cell types are occasionally seen. these include 1) neuron-like cells, and 2) darker st ...	1980	7190067
induction of oestrus, recovery of gametes, and the timing of fertilization events in the opossum, didelphis virginiana.	of 14 lactating opossums maintained in laboratory conditions, 13 mated 4.7-8.5 days after removal of pouch young. the time between this removal and onset of receptive oestrus was negatively correlated with the age of the pouch young. mating generally occurred between 24:00 and 06:00 h, with ovulation following between 13:00 and 16:00 h. each animal ovulated a mean of 29.6 eggs (range 19-40), approximately equal numbers coming from both ovaries. spermatozoa were absent from the uterus and were pr ...	1982	7198686
changes in intramembranous particle distribution in the plasma membrane of didelphis virginiana spermatozoa during maturation in the epididymis.	structural specializations in the plasma membrane of opossum spermatozoa obtained from different levels of the epididymis have been analyzed in thin sections and freeze-fracture replicas. the maturation process was accompanied by a redistribution of intramembranous particles in the flagellar midpiece region. caput epididymal spermatozoa are immotile, and freeze-fracture replicas of the midpiece plasma membrane reveal a random arrangement of intramembranous particles. as spermatozoa transit the c ...	1980	7212298
estradiol and progesterone profiles indicate a lack of endocrine recognition of pregnancy in the opossum.	concentrations of estradiol and progesterone in blood collected during the 12.5-day gestation period of the virginia opossum were not significantly different from those during equivalent days of the estrous cycle. progesterone was correlated with an index of corpora luteral mass. ratio of estradiol to progesterone were highest 3 to 4 days before estrus and on the day of parturition.	1981	7233228
organization of thalamic projections to visual cortex in opossum.	projections from visual thalamus to posterior cortex of the virginia opossum revealed by retrograde transport of horseradish peroxidase show a specific and orderly pattern. the lateral geniculate nucleus projects only to cortical area 17, while a lateral sector of the lateral posterior nucleus sends afferents both to area 17 and 18. area 19 receives input from the lateral intermediate nucleus; the caudomedial sector of the lateral posterior nucleus projects to the anterior and posterolateral are ...	1981	7237104
the organization of thalamic projections to the parietal cortex of the virginia opossum.	the thalamic projections to somatic sensory-motor (ssm) cortex and adjacent cortical areas of the virginia opossum were studied using anterograde and retrograde axoplasmic transport techniques. large injections of horseradish peroxidase and/or tritiated amino acids were made in the parietal cortex to identify all of the thalamic nuclei that are interconnected with this large cortical area. very restricted injections were then made in physiologically identified subdivisions of ssm cortex, in the ...	1981	7240450
the laminar distribution and ultrastructure of fibers projecting from three thalamic nuclei to the somatic sensory-motor cortex of the opossum.	the projections of the ventrobasal complex (vb), the ventrolateral complex (vl), and the central intralaminar nucleus (cin) to the somatic sensory-motor (ssm) cortex of the virginia opossum were studied with light and electron microscopic autoradiographic methods. vb, vl, and cin have overlapping projections to ssm cortex and each one also projects to an additional cortical area. unit responses to somatic sensory stimulation and the areal and laminar distribution of axons in cortex is different ...	1981	7240451
natural la crosse virus infection in the red fox (vulpes fulva), gray fox (urocyon cinereoargenteus), raccoon (procyon lotor), and opossum (didelphis virginiana).	natural infection of sentinel red foxes (vulpes fulva) and free-ranging red foxes, gray foxes (urocyon cinereoargenteus) and raccoons (procyon lotor) with la crosse (lac) virus was demonstrated. one isolate of lac virus was obtained from a sentinel red fox in an enzootic area. the viremia titer of the lac virus-infected red fox was above the threshold of infection for aedes triseriatus mosquitoes. antibody responses were measured by the microneutralization test employing four california group vi ...	1981	7258486
laminar organization of efferent cells in the parietal cortex of the virginia opossum.	the size, shape and laminar position of efferent neurons in the parietal cortex of the virginia opossum were identified using the method of retrograde transport of horseradish peroxidase (hrp). injection of hrp into the spinal cord, dorsal column nuclei or pontine nuclei leads to labeling of cells in layer v and occasionally in layer vi, while a large injection of hrp in the dorsal thalamus labels many cells in layer vi, with fewer cells in layer v. hrp injections in the ssm cortex label cells i ...	1981	7262228
the origin of brain stem-spinal projections at different stages of development in the north american opossum.	the origin of brain stem neurons giving rise to axons innervating the thoracic cord has been determined in a developmental series of pouch-young opossums. the first spinal axons identified (17 days after conception, postnatal day 5) arise from the medullary and pontine reticular formation, certain raphe nuclei, the vestibular nuclei and the coeruleus complex. the contribution of the red nucleus before postnatal day 10 is not certain. the brain stem sensory relay nuclei and the hypothalamus do no ...	1981	7272768
uterine histology and reproductive cycles in pregnant and non-pregnant opossums, didelphis virginiana.	uteri (n = 18) were collected on days 3, 7, and 11 of the oestrous cycle or gestation. reproductive cycles were monitored by vaginal cytology in captive opossums. there was no difference in length of cycles between reproductive states (29.2 +/- 1.0 (s.e.m.) days). all uteri on day 3 or day 7 were similar in total volume, endometrial width, and glandular abundance. however, on day 11 endometrial widths were significantly less in pregnant animals and stroma appeared diffuse and flocculent in the n ...	1981	7277320
the purification and characterization of an antihemorrhagic factor in opossum (didelphis virginiana) serum.		1981	7302953
neurons of the basolateral amygdala: a golgi study in the opossum (didelphis virginiana).	the cytoarchitecture of the opossum basolateral amygdala was studied using golgi techniques. the neuronal morphology was similar in all nuclei of the basolateral complex, an three distinct cell classes were recognized. class i neurons, which vary in size in different nuclei, have spiny dendrites and long, projection axons. axon hillocks and initial axonal segments often have spinous protrusions, while more distal portions of the axon give off several beaded collaterals that arborize primarily in ...	1981	7325125
a description of the dorsal thalamus of the marsupial native cat, dasyurus viverrinus (dasyuridae).	the nuclear architecture of the dorsal thalamus in the marsupial native cat, dasyurus viverrinus, is described. the nine midline and intralaminar nuclei comprise a large and prominent part of the thalamus. the lateroposterior nucleus is clearly divided into medial and lateral divisions. a ventroanterior nucleus is distinguished from the ventrolateral nucleus, and the ventroposterior complex is divided into cytoarchitecturally distinctive medial and lateral divisions. there is a large posterior n ...	1981	7326574
an analysis of some thalamic projections to parietofrontal neocortex in the marsupial native cat, dasyurus viverrinus (dasyuridae).	thalamocortical projections to parietofrontal neocortex in the marsupial native cat, dasyurus viverrinus, were examined using the retrograde transport of horseradish peroxidase. the results show that the organisation in dasyurus is similar to that reported in another australian marsupial, the brush-tailed possum, trichosurus vulpecula, and is different to that found in the primitive american form, didelphis virginiana. in daysurus, as in trichosurus, the areas of neocortex receiving projections ...	1981	7326576
anatomy of the cerebral ganglion in oligacanthorhynchus tortuosa (acanthocephala) from the opossum (didelphis virginiana).	the anatomy of the cerebral ganglion from oligacanthorhynchus tortuosa (acanthocephala) resembles that previously described for large acanthocepalans from mammals. the cell population was equally distributed between each half of the ganglion, there were 38 cells on each side with seven cells centrally located. the core of the ganglion or neuropile occupied the central part of the ganglion and was the site for the crossover for many cell processes. many of the axons from these cells exited from t ...	1981	7328460
projections from the brain stem reticular formation to laminae i and ii of the spinal cord. studies using light and electron microscopic techniques in the north american opossum.	the horseradish peroxidase and autoradiographic methods show that laminae i and outer ii are innervated by the nucleus reticularis gigantocellularis pars ventralis, and the nucleus reticularis pontis pars ventralis. both areas contain neurons of the indolamine type and probably account for the indolamine-like varicosities which are present within laminae i and ii. degeneration materiom the above nuclei end on small dendritic shafts and spines as well as on vesicle-filled proflies. the terminals ...	1980	7370781
radiation esophagitis in the opossum: radioprotection with indomethacin.	twenty-five opossums (didelphis virginiana) were evaluated before irradiation by fiberoptic endoscopy and air-contrast barium esophagram examination. all animals received 2250 rad 60co-irradiation in a single exposure to the entire esophagus and lower exophageal sphincter. animals received treatment with indomethacin before and daily for 1 wk postirradiation of 16, 16-dimethylprostaglandin e2 before irradiation and every 4 hr for 24 hr postirradiation. control animals received only injection veh ...	1980	7380194
the pontocerebellar system in the opossum, didelphis virginiana. a horseradish peroxidase study.	the method of retrograde axonal transport of horseradish peroxidase was employed to demonstrate certain organizational features of the pontocerebellar system in adult opossums. the spinal cerebellum (anterior lobe, pyramis and paramedian lobule) receives input from neurons situated in ventral and lateral regions throughout the rostro-caudal extent of the pons. the projection to the anterior lobe and pyramis was primarily contralateral, whereas the projection to the paramedian lobule included a s ...	1980	7388596
asynaptic behavior of x and y chromosomes in the virginia oppossum and the southern pygmy mouse.	the meiotic behavior of silver-stained x and y chromosomes of the virginia opossum, didelphis virginiana, and the southern pygmy mouse, baiomys musculus, was studied by light microscopy. while the sex chromosomes of these two species differ in both size and morphology, their meiotic behavior is very similar. in both species a typical sex vesicle is formed during pachytene, but unlike most other mammalian species thus far studied, a synaptonemal complex does not form between the x and y chromosom ...	1980	7389409
the site of the dipsogenic action of angiotensin ii in the north american opossum.	adult north american opossums (didelphis virginiana), predominantly nocturnal water drinkers, were found to respond by drinking to water deprivation, cellular dehydration produced by intravenous infusion of hypertonic saline, and to both intravenous and intracerebroventricular administration of angiotensin ii (aii). by taking advantage of the absence of the corpus callosum, an anatomical characteristic of the marsupial, we removed the subfornical organ and implanted a cannula into the anterior t ...	1980	7407596
postnatal differentiation of ventricular myocardial cells of the opossum (didelphis virginiana kerr) and t-tubule formation.	cardiac muscle cells in the right ventricle of the postnatal opposum were studied ultrastructurally, with particular attention to the developmental stage of t-tubule formation. animals ranging from 5.5 cm (day 29 of postnatal life) to 41 cm (young adult) in body length were used. typical t-tubules were first recognized in a few myocardial cells of the 7.5 cm (day 43) opossum. t-tubules increased in number as cardiac muscle cells continued to differentiate until 22 cm in body length (about 105 da ...	1980	7407865
the ontogenesis of sleep states, thermogenesis, and thermoregulation in the virginia opossum.	polygraphic recordings of sleep and wakefulness were obtained over 4-hr periods from infant opossums, aged 48-79 days, while they were in the mothers' pouches. concurrent body temperature measurements were obtained from littermates held at ambient temperatures of 25 and 30 degrees c. the ontogenesis of sleep was similar to that of placental mammals: quiet sleep increased from 13% sleep time at 48 days to 55% at 79 days; conversely, active sleep decreased from 87% to 45%, respectively. the amplit ...	1980	7409325
morphology of differentiating epithelial cells in the respiratory tract of the postnatal opossum (didelphis virginiana).	correlative microscopy of the developing respiratory epithelium during mucous cell differentiation reveals a decrease in the concentration of ciliated cells concomitant with proliferation of mucous cells and formation of an inner layer of the mucous blanket. nonciliated cells increase in concentration between 40 and 80 days postnatal and provide the major surface area of the tracheal epithelium. nonciliated cells change from isolated small patches with flat, finely-corrugated surfaces to larger, ...	1980	7414271
the development of major projections to the inferior olivary nucleus. experimental studies using the north american opossum.		1980	7457915
sperm maturation and the formation of sperm pairs in the epididymis of the opossum, didelphis virginiana.	didelphis spermatozoa released from different levels of the epididymis exhibit a series of changes that reflect events involved in the process of their maturation. their progression through the duct is accompanied by a rotation of the sperm head on the axis of the tail, by an eccentric movement of the cytoplasmic droplet to the anterior region of the midpiece from where it is discarded, by appearance in the posterior midpiece of regular submembranous electron-dense ridges, and by visible condens ...	1980	7462982
aspermatogenesis in a paralyzed opossum (didelphis virginiana).		1980	7464014
nucleotide sequence of a marsupial line-1 element and the evolution of placental mammals.	l1 (line-1) elements, previously described in several placental species, were shown to exist in several thousands of copies dispersed in the genome of a marsupial (the north american opossum, didelphis virginiana). a restriction fragment containing the partial nucleotide sequence of the reverse transcriptase gene (orf-2) from the marsupial l1 element was cloned and sequenced. the element was shown to evolve in concert within the marsupial when compared to placental mammals. when the marsupial l1 ...	1995	7476141
colocalization of nadph-diaphorase activity and certain neuropeptides in the esophagus of opossum (didelphis virginiana).	nitric oxide and various neuropeptides in the myenteric plexus regulate esophageal motility. we sought colocalization of nitric oxide synthase and neuropeptides in frozen sections of mid-portion of smooth-muscled opossum esophagus using nadph-diaphorase activity to mark the synthase and immunoreactivity to detect peptides. the peptides, all with demonstrated physiological activity in this organ, were calcitonin gene-related peptide, galanin, neuropeptide y, substance p, and vasoactive intestinal ...	1994	7531620
adenosine deaminase isoenzymes of the opossum didelphis virginiana: initial chromatographic and kinetic studies.	extracts of liver and spleen were used to isolate opossum adenosine deaminase isoenzymes (ada1 and ada2) and to determine their activities with adenosine and 2'-deoxyadenosine as substrates. km values (microm) for adenosine and 2'-deoxyadenosine, respectively, as substrates for partially purified opossum liver adenosine deaminase isoenzymes were ada1: 57 +/- 7 vs. 26 +/- 4 and ada2: 285 +/- 25 vs. 580 +/- 92. in crude spleen extract, ada2 activity was stable at 56 degrees c during 40 min of incu ...	1995	7599990
cytoarchitecture of the substantia nigra pars lateralis in the opossum (didelphis virginiana): a correlated light and electron microscopic study.	the substantia nigra has been divided into three subdivisions. however, the cytoarchitecture of one of these subdivisions, the pars lateralis (snl), has not been previously examined in detail at the light and electron microscopic levels in any species. in the adult opossum, the three nigral subdivisions can be easily distinguished as distinct, rostrocaudally oriented cell groups separated by neuron-free zones. thus it was possible to determine the boundaries of the snl unambiguously. this report ...	1995	7604970
insulin-like growth factor improves renal architecture of fetal kidneys with complete ureteral obstruction.	others have previously demonstrated that the administration of insulin-like growth factor-i accelerates recovery from ischemic acute tubular necrosis in the rat kidney. we investigated the effect of insulin-like growth factor-i on the histology of unilaterally obstructed kidneys in the pouch young of the north american opossum, didelphis virginiana. in this model complete unilateral ureteral obstruction reliably induces statistically significant degrees of caliceal dilatation, tubular cystic cha ...	1995	7609156
developmental progression of gpd expression from the inactive x chromosome of the virginia opossum.	metatherian (marsupial) mammals possess a non-random form of x-chromosome inactivation in which the paternally-derived x is always the one inactivated. to examine the progression of x-linked gene expression during metatherian development, we compared relative levels of the maternally and paternally encoded gpd gene products in heterozygous female virginia opossums (didelphis virginiana) across a major portion of the developmental period. panels of tissues obtained from fetuses, newborns, and pou ...	1995	7641417
molecular anatomy of an endodermal gland: investigations on mucus glycoproteins and cell turnover in brunner's glands of didelphis virginiana using lectins and pcna immunoreactivity.	brunner's glands are located in the submucosa of the proximal duodenum and are unique to mammalian species. the north american opossum (didelphis virginiana) is generally regarded as a prototype marsupial that closely resembles fossil didelphids which can be placed at the beginning of mammalian evolution. the current investigation provided an opportunity for the analysis of secretory products from these glands in a species thought to be more closely related to earlier evolutionary forms. extract ...	1995	7642723
the development of myelin in the spinal cord of the north american opossum and its possible role in loss of rubrospinal plasticity. a study using myelin basic protein and galactocerebroside immuno-histochemistry.	the aims of this study were to observe the timing and sequence of myelin formation in the opossum's spinal cord by using myelin basic protein (mbp) immuno-histochemistry and to determine whether the onset of myelination, as demonstrated by the presence of mbp or galactocerebroside (galc)-like immuno-reactivity (li), correlates temporally with the end of the critical period for rubrospinal plasticity. rubral axons grow around a lesion of their pathway during early development but they do not do s ...	1993	7680969
distribution of corticotropin-releasing factor (crf) binding sites in the opossum cerebellum.	corticotropin-releasing factor (crf) has been demonstrated in the hypothalamic-pituitary-adrenal axis and studied in extrahypothalamic sites throughout the brain. localization of crf immunoreactivity, crf mrna, and crf receptors within specific brain areas supports an extrahypothalamic function for crf. previous reports have revealed the localization of several peptides, including crf, in the cerebellar cortex and nuclei of the north american opossum (didelphis marsupialis virginiana); climbing ...	1995	7746352
the distribution of gap-43 immunoreactivity in the central nervous system of adult opossums (didelphis virginiana) with notes on their development.	the distribution of the growth associated protein gap-43 has been described in the brain and spinal cord of rats and other placental mammals but not marsupials. in order to provide such information, we employed a monoclonal antibody to immunostain for gap-43 in the central nervous system of adult and developing opossums, didelphis virginiana. the gap-43 immunoreactivity was widely distributed in the brain of adult opossums, but it was particularly dense within specific layers of the olfactory bu ...	1995	7749727
distribution of cholecystokinin binding sites in the north american opossum cerebellum.	previous studies in our laboratory have reported on the differential distribution of several neuropeptides, including the octapeptide cholecystokinin (cck8), in the cerebellar cortex and nuclei of the north american opossum (didelphis marsupialis virginiana). the present account reports on the distribution of cck8 binding sites as determined from serial autoradiographic images of the cerebellum which were labelled by using [125i]bolton hunter sulfated cck8. evidence for the limited presence of c ...	1994	7802965
heavy metals in the hair of opossum from palo verde, costa rica.	levels of lead, cadmium, mercury, chromium, and manganese were measured in the hair of opossum (didelphis virginiana) from palo verde, guanacaste, costa rica. this area has some agriculture, but is slated for extensive water development that will increase ecosystem exposure to a variety of agricultural chemicals. metal levels were generally not intercorrelated except for chromium and lead, chromium and cadmium, and cadmium and lead. there were significant gender differences only for lead and chr ...	1994	7811107
ectoparasites of opossums and raccoons in southeastern georgia.	twelve species of ectoparasites (four fleas, three ticks, three chiggers, one macronyssid mite, and one atopomelid mite) were recovered from 42 opossums, didelphis virginiana kerr, live-trapped from september 1992 through april 1994 in southeastern georgia. the fleas, ctenocephalides felis (bouché) (prevalence = 19%) and polygenis gwyni (c. fox) (36%); the ticks, dermacentor variabilis (say) (40%) and ixodes scapularis say (19%); and the macronyssid mite, ornithonyssus wernecki (fonseca) (21%), ...	1994	7815408
locomotory energetics and metabolic fuel reserves of the virginia opossum.	marsupials have lower resting metabolic rates than placental mammals, but it is not clear whether particular species can extend this energetic advantage to locomotion. some active marsupials have a low cost of locomotion, but other more sedentary species, such as the virginia opossum, appear to run very inefficiently. steady-state rates of o2 consumption (vo2) and co2 production (vco2) were measured at rest and during horizontal treadmill exercise in wild-caught, trained opossums. average daily ...	1994	7852899
developmental plasticity of reticulospinal and vestibulospinal axons in the north american opossum, didelphis virginiana.	we have shown previously that rubral axons grow around a lesion of their spinal pathway in the north american opossum if it is made at early stages of development. in the present experiments, we have asked whether reticular and vestibular axons have the same ability. the spinal cord was hemisected at postnatal day 20, 12, or 5, well within the critical period for rubrospinal plasticity, and, approximately 30 days later, bilateral injections of fast blue were made about four segments caudal to th ...	1994	7860784
effect of deer exclusion on the abundance of immature ixodes scapularis (acari: ixodidae) parasitizing small and medium-sized mammals.	effects of deer exclusion on abundance of immature ixodes scapularis say parasitizing small and medium-sized mammals, and the role mammals have in introducing ticks to exclosure areas, were examined at two sites in westchester county, new york. in total, 686 mammal captures representing nine species were obtained, with white-footed mice, peromyscus leucopus rafinesque, composing > 80% of all captures, followed by raccoons, procyon lotor (l.); opossums, didelphis virginiana (kerr); and striped sk ...	1995	7869342