Publications

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
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
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
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
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
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
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
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
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
comparative aspects of methemoglobin formation and reduction in opossum (didelphis virginiana) and human erythrocytes.	glucose-depleted, nitrite-treated opossum erythrocytes effectively reduce methemoglobin in an environment of physiological saline and added glucose does not accelerate the rate of reduction. in autologous plasma or 25 mm phosphate-buffered saline ph 7.4, added glucose significantly accelerates methemoglobin reduction in glucose-depleted, nitrite-treated opossum erythrocytes. human red cells require added glucose to carry out reduction of methemoglobin and increased phosphate concentration or aut ...	1983	6137318
the functional anatomy of the shoulder of the savannah monitor lizard (varanus exanthematicus).	the excursions of the scapulocoracoid and forelimb and the activity of 18 shoulder muscles were studied by simultaneous cineradiography and electromyography in savannah monitor lizards (varanus exanthematicus) walking on a treadmill at speeds of 0.7-1.1 km/hour. during the propulsive phase, the humerus moves anteroposteriorly 40-55° and rotates a total of 30-40°. simultaneously, the coracoid translates posteriorly along the tongue-and-groove coracosternal joint by a distance equivalent to about ...	1983	30068057
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
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
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
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
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
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
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
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
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
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
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
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
the development of descending spinal connections. studies using the north american opossum.		1982	7156395
cytosolic and membrane-bound methemoglobin reductases in erythrocytes of the opossum, didelphis virginiana.		1982	7151403
oxidation-reduction properties of the hemoglobin of the opossum, didelphis virginiana.		1982	7151402
separation of sperm pairs and sperm-egg interaction in the opossum, didelphis virginiana.		1982	7054492
reticular and raphe projections to the spinal cord of the north american opossum. evidence for connectional heterogeneity.		1982	6296915
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
conduction of velocity groups in the optic nerve of the north american opossum (didelphis virginiana): retinal origins and central projections.	the axonal conduction velocity groups in the optic nerve of the north american opossum were analyzed electrophysiologically and related to soma size groups of ganglion cells in terms of their retinal origin and laterality of projection. on the basis of analysis of field potentials and single unit responses recorded at the optic disc, three velocity groups were identified (d1, d2, and d3) and estimated to have average conduction velocities of 12, 8, and 5 meters/second. from recordings of the fie ...	1981	6168667
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
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
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
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
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
evidence for a lack of distinct rubrospinal somatotopy in the north american opossum and for collateral innervation of the cervical and lumbar enlargements by single rubral neurons.	studies using axonal transport techniques on the north american opossum show that rubral neurons innervating the cervical cord are not distinctly separated from those which project to lumbar levels. the absence of clear rubrospinal somatotopy contrasts with that described for the placental mammals studied to date. use of fluorescent markers in double-labeling experiments shows that most rubral neurons in the opossum still innervate either the cervical or lumbar enlargement alone, but that some s ...	1981	6169748
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 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
evidence for collateral innervation of the cervical and lumbar enlargements of the spinal cord by single reticular and raphe neurons. studies using fluorescent markers in double-labeling experiments on the north american opossum.	the use of fluorescent markers in double-labeling experiments reveals the presence of reticular and raphe neurons in the opossum's brainstem which innervate both the cervical and lumbar enlargements of the spinal cord by way of axonal collaterals. such neurons were mixed with those innervating either the cervical or lumber enlargement alone and were found within the nuclei reticularis medullae oblongatae dorsalis and ventralis, the nucleus reticularis gigantocellularis, the nucleus reticularis g ...	1981	6167916
spinal projections from the medullary reticular formation of the north american opossum: heterogeneity.	retrograde and orthograde transport techniques show that the nucleus reticularis gigantocellularis pars ventralis and the nucleus reticularis gigantocellularis project the entire length of the spinal cord. double-labelling methods show that some of the neurons in each area innervate both cervical and lumbar levels. there is evidence, however, that neurons in the lateral part of the nucleus reticularis gigantocellularis pars ventralis and the dorsal extreme of the nucleus reticularis gigantocellu ...	1981	6110678
the purification and characterization of an antihemorrhagic factor in opossum (didelphis virginiana) serum.		1981	7302953
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
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
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
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
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
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
immunohistochemical localization of substance-p, somatostatin, and methionine-enkephalin in the spinal cord and dorsal root ganglia of the north american opossum, didelphis virginiana.	the occurrence and distribution of substance-p (sp), somatostatin (som), and enkephalin (enk) were studied in the north american opossum, a generalized marsupial. substance-p immunoreactivity was present in the tract of lissauer as well as within lamina i, the outer part of lamina ii, the lateral portion of laminae iii through vii, and lamina x at all spinal levels. although present, it was very spare in the ventral horn. substance-p was also localized within autonomic areas of the thoracolumbar ...	1981	6165743
the distribution of ganglion cells in the retina of the north american opossum (didelphis virginiana).	the distribution of ganglion cells in the retina of the opossum was determined from whole-mounted retinae stained with cresyl violet. isodensity lines were approximately circular with a peak density of 2,000 to 2,700 cells/mm2 in superior temporal retina (area centralis). the total number of retinal ganglion cells was estimated to be 72,000 to 135,000 (mean 101,026) in retinae ranging from 125 to 187 mm2 in total area. three groups of ganglion cells were distinguished on the basis of soma size a ...	1981	6168666
comparative limb myology of two opossums, didelphis and chironectes.	a comparative study of limb morphology indicates that the osteological and myological differences between didelphis virginiana, the virginia opossum, and chironectes minimus, the water opossum, may be associated in chironectes with decreased resistance to water and increased mechanical advantage of its muscles for increased force. limb myology is described and a synonymy of terms is applied to the musculature of these two opossums.	1981	30111008
substance p immunoreactivity in the median eminence of the north american opossum and domestic fowl.		1980	6154507
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
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
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 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
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
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
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
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 development of major projections to the inferior olivary nucleus. experimental studies using the north american opossum.		1980	7457915
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
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 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
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
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
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
morphological observations on the metanephros in the postnatal opossum, didelphis virginiana.	the metanephros of the newborn opossum is very immature, consisting only of collecting tubules and a few immature nephrons. development during the postnatal period can be divided into two distinct phases. the initial phase occurs during the first 60 days of postnatal life and is concerned with nephronogenesis and the differentiation of nephrons that have formed during this period. the second phase lasts through the remainder of the postnatal period and is concerned with further differentiation a ...	1979	541236
response to cryptorchidism of the testis and epididymis of the opossum (didelphis virginiana).	adult male opossums, didelphis virginiana, were rendered hemicryptorchid for 35 days. the cyrptorchid testis exhibited a significant reduction in weight, while the contralateral testis had a compensatory weight gain compared with testes of untreated animals. histological changes in the cryptorchid testis included fibrosis of the tunica propria, involution of the seminiferous tubules and an apparent increase in the interstitial tissue. many seminiferous tubules were empty and germinal cells were ...	1979	41944
the development of monoaminergic brainstem-spinal systems in the north american opossum.	evidence is presented for an early appearance of monoaminergic neurites within the spinal cord of the developing opossum. they are present within the marginal zone before hindlimb movements begin (stage i) and they start to grow into the intermediate zone by the time hindlimb movements are first observed (stage ii). monoaminergic neurites grow first into the dorsolateral intermediate zone and the intermediolateral cell column where they can be found by the beginning of stage ii. shortly thereaft ...	1979	475000
evidence for direct bulbospinal projections to laminae ix, x and the intermediolateral cell column. studies using axonal transport techniques in the north american opossum.		1979	88996
tissue differentiation and susceptibility to embryonal tumor induction by ethylnitrosourea in the opossum.	opossums (didelphis virginiana kerr) exposed to 100 mg enu/kg in single or incremental doses early in postnatal life developed a spectrum of epithelial and mesenchymal neoplasms including several types of embryonal neoplasms not previously induced in laboratory animals. a correlation was apparent to a varying degree between susceptibility to tumor induction and the state of morphologic maturation of the presumed target tissues at the light microscopic level for embryonal tumors of the eye, kidne ...	1979	225667
pairing of spermatozoa in the epididymis of the opossum (didelphis virginiana): a scanning electron microscopic study.	spermatozoa of the opossum, didelphis virginiana, were taken from three different regions of the epididymis and examined by scanning electron microscopy, phase-contrast and dark-field microscopy. it has been demonstrated that marked morphological changes occur in spermatozoa during their passage through the epididymis. in the first segment or head of the epididymis, spermatozoa are non-motile and the long axis of their nuclei is perpendicular to that of the tail. the nucleus is v-shaped with a t ...	1979	464751
prostaglandins and myogenic control of tension in lower esophageal sphincter in vitro.	active tension is produced by the lower esophageal sphincter (les) of north american opossum in vitro by a myogenic mechanism. strips of les, but not those from the esophageal body, contracted to prostaglandin (pg)f2 alpha, stable expoxymethano derivatives of pgh2 and to thromboxane b2. stable endoperoxides were more than 500 times more potent than pgf2 alpha. pgi2 and 6-keto pgf1 alpha were weak relaxants of les strips. les strips transformed arachidonic acid into contractile substances. this t ...	1979	379920
structure of the esophagus in the adult opossum, didelphis virginiana.	the structure of the esophagus has been studied in the adult opossum, didelphis virginiana. a thickening of both layers of the muscularis externa occurs at the origin of the esophagus and may represent the upper esophageal sphincter; a massive expansion of the muscularis mucosae occurs in the region of the lower esophageal sphincter. the distribution of striated, mixed and smooth muscle in the muscularis externa differs in the inner and outer layers and elements of the myenteric plexus are found ...	1979	474990
spinal projections from the mesencephalic and pontine reticular formation in the north american opossum: a study using axonal transport techniques.	the results from several experimental approaches lead to the following conclusions. the nucleus cuneiformis projects to at least lumbar levels of the spinal cord. its axons course through the ipsilateral sulcomarginal and ventral funiculi to distribute within lamina viii and adjacent portions of lamina vii. neurons within the nucleus reticularis pontis (rp), particularly within more medial parts of the nucleus, project through comparable routes to the same laminae. in addition, however, neurons ...	1979	489785
dipetalonema (acanthocheilonema) didelphis sp. n. (nematoda: filarioidea) from opossums, with a redescription of d. (a.) pricei (vaz and pereira 1934).	dipetalonema (acanthocheilonema) didelphis sp. n. recovered from the subcutaneous and periesophageal connective tissues of didelphis virginiana from several localities in the united states and of d. marsupialis from colombia is described. dipetalonema didelphis sp. n. resembles d reconditum and d. mansonbahri in size, in lacking a two-segmented buccal capsule, and in the female having a long, digitiform tail. dipetalonema reconditum, however, has a much longer glandular esophagus and d. mansonba ...	1979	575550
the organization of olivo-cerebellar projections in the opossum, didelphis virginiana, as revealed by the retrograde transport of horseradish peroxidase.	the retrograde transport of horseradish peroxidase was utilized to map olivo-cerebellar projections in the virginia opossum. the spinal cerebellum (anterior lobe, paramedian lobule and pyramis) receives input from several separate regions in the dorsal accessory nucleus, the medial accessory nucleus and portions of the principal nucleus. evidence is present for a topographical organization whereby specific regions of the olive project to restricted longitudinal zones. the visual-auditory region ...	1978	641222
experimental transmission of sarcocystis from icterid birds to sparrows and canaries by sporocysts from the opossum.	cowbirds (molothrus ater) and grackles (cassidix mexicanus) infected with muscle cysts of sarcocystis were fed to opposums (didelphis virginiana) and fecal sporocysts from the latter were given to sparrows (passer domesticus, family ploceidae), canaries (serinus canarius, family fringillidae) and ducks (anas platyrhynchos, family anatidae). asexual parasites were found in the endothelium of sparrows and canaries but not in ducks. when birds were kept 10 weeks or more after infection, muscle cyst ...	1978	98622
the opossum (didelphis virginiana) as a host for sarcocystis debonei from cowbirds (molothrus ater) and grackles (cassidix mexicanus, quiscalus quiscula).	sarcocystis-infected muscles from ducks, cowbirds, and grackles were fed to cats, opossums, rats, and a dog. only the opossum (didelphis virginiana) was a suitable definitive host. all opossums that were fed sarcocystis-infected cowbirds (molothrus ater) and grackles (cassidix mexicanus and quiscalus quiscula) passed sporocysts in their feces. opossums that ate the cowbirds had prepatent periods of 5 and 10 days and remained patent for at least 105 days. opossums that ate the grackles became pat ...	1978	417165
the organization of monoamine neurons within the brainstem of the north american opossum (didelphis virginiana).		1978	8980724
an electron microscopic study of rubrospinal projections to the lumbar spinal cord of the opossum.	the rubrospinal system is a major suprasegmental input to the important interneuronal pool at the base of the lumbar dorsal horn in the north american opossum. after appropriate lesions, rubral axons and their synaptic terminals were found in electron micrographs of lamina iv, v and vi as well as within the dorsal extreme of lamina vii. degenerating terminals contact small diameter dendrites in the lateral terminal zone and large dendritic profiles in the medial terminal zone. correlating these ...	1978	630404
respiratory characteristics of opossum (didelphis virginiana) blood during chronic anemia.	in five adult opossums (didelphis virginiana), blood hemoglobin concentration was lowered from 12.3g% to 6.4g% by daily bleeding. blood p50 rose significantly (p is less than 0.05) from 44.5 mm hg to 47.4 mm hg and the concentration of 2, 3-diphosphoglycerate (dpg) increased from 14.17 mumol/g hb to 20.90 mumol/g hb. the observed shift in blood oxygen affinity was of similar magnitude to that recorded in humans with a similar degree of anemia, but the concomitant rise in dpg concentration was gr ...	1978	26945
postnatal development of the epidermis in a marsupial, didelphis virginiana.	at birth the epidermis of the opossum is 43 micron thick and consists of a basal layer of columnar cells, an intermediate layer of fusiform cells, a layer of incompletely cornified cells and a single surface layer of cells (the periderm). the latter shows central nuclei and distinct cell boundaries. adjacent surface cells. are contiguous and show extensive interdigitations of the lateral cell membranes. the periderm is lost during the first week of postnatal development. the epidermis attains it ...	1978	632218
development of the external muscle coats in the digestive tract of the opossum, didelphis virginiana.	development of the external musculature of the gastrointestinal tract has been studied in the stomach, small intestine and colon of the postnatal opossum. the muscle support is thin and poorly developed at birth, especially in the stomach and small intestine where only the inner layer is completely formed. the outer layer is discontinuous and formed by scattered myoblasts. the muscularis externa of the colon at birth is considerably thicker and both layers are present. subsequent development of ...	1978	567924
general observations on the growth and development of the young pouch opossum, didelphis virginiana.	a 3-year study of general growth and development revealed a uniform increase in body length of young pouch opossums during the first 10 weeks of life. throughout this period, growth was linear and constant for all animals regardless of sex, litter size, or whether animals were obtained from first, second or third litters. body weights were somewhat more variable, but there were no significant sex differences. various aspects of external gross morphology are presented and discussed as they relate ...	1978	567497
age ratios, weights, and reproduction of the virginia opossum in north louisiana.		1978	750645
an autoradiographic study of midbrain-diencephalic projections to the inferior olivary nucleus in the opossum (didelphis virginiana).	techniques of intra-axonal transport were utlizied to elucidate the organization of diencephalic and midbrain projections to the inferior olivary nucleus of the virginia opossum. retrograde transport of horseradish peroxidase injected into the olive suggests that terminals within it arise from the subparafascicular nucleus of the caudal thalamus, the nucleus of darkschewitsch, the fields of forel, the interstitial nucleus of cajal, the periaqueductal grey, the caudal pretectal nucleus, the tegme ...	1978	641221
the origin of brainstem-spinal pathways in the north american opossum (didelphis virginiana). studies using the horseradish peroxidase method.		1978	8980723
the north american opossum (didelphis marsupialis) is an excellent model for the study of hemoglobin ontogeny.		1978	721616
the nucleus corporis pontobulbaris of the north american opossum.	the nucleus of the pontobulbar body (pbu) in the north american opossum is located, for the most part, adjacent to the motor root of the trigeminal nerve. material prepared by degeneration and autoradiographic methods shows that the pbu receives projections from the facial motor-sensory cortex, red nucleus, spinal cord and cerebellum. the latter fibers probably take origin within the fastigial nucleus. each of the afferent connections ends in a restricuted part of the pbu, but there is considera ...	1977	903428
the second somatic sensory area (smii) of opossum neocortex.	organization of the neocortical second somatic sensory area (smii) of anesthetized virginia opossums has been examined utilizing micro-electrode recording techniques. smii is situated between the first somatic sensory area (smi) medially, and the rhinal fissure laterally. the head representation is located anteromedially within smii, and the hindlimb representation posterolaterally, with the forelimb representation in between. approximately 49% of smii is devoted to representation of the head, 3 ...	1977	864034
the organization of reticulo-olivo-cerebellar circuits in the north american opossum.	by employing the autoradiographic method we have determined that the inferior olivary nucleus receives input from the reticular formation of the midbrain, pons and, probably, the medulla. the remarkable thing about such connections is that they are not diffuse, but targeted in large part on restricted portions of the caudal acessory nuclei. from our previous studies it is clear that some of the olivary regions receiving reticular input also receive projections from the cerebral cortex, the spina ...	1977	589453