Publications
| Title | Abstract | Year Filter | PMID(sorted descending) Filter |
|---|
| early development and developmental plasticity of the fasciculus gracilis in the north american opossum (didelphis virginiana). | the first objective of the present study was to ask when axons of the fasciculus gracilis reach the nucleus gracilis in the north american opossum (didelphis virginiana). when fast blue (fb) was injected into the lumbar cord on postnatal day (pd) 1 and the pups were killed 2 days later, labeled axons were present within a distinct fasciculus gracilis at thoracic and cervical levels of the cord. when comparable injections were made at pd3 or 5 and the pups were allowed to survive for the same tim ... | 1997 | 9051256 |
| auditory quality cues are more effective than auditory location cues in a r--no r (go--no go) differentiation: the extension of the rule to primitive mammals (american opossum, didelphis virginiana). | discrimination learning of instrumental responses to auditory compound stimuli was investigated in opossums using the r-no r (go-no go) differentiation. each compound stimulus consisted of two factors: quality and location. each correct response performed to the conditioned positive, or "safe" stimulus, was rewarded by food and never punished. each incorrect response performed to the conditioned negative, or "warning" stimulus, was punished by an electric shock. in subsequent testing, each oposs ... | 1996 | 9033130 |
| ontogeny and limb bone scaling in two new world marsupials, monodelphis domestica and didelphis virginiana. | this study examines the growth of two species of marsupials who share common ancestry and are born at the same neonatal size of a little less than 1 g. despite this similarity at birth, adult size of these two species differs by about 50 times, with the smaller species believed to be the more ancestral. we quantified the growth in the limb bones (humerus, femur, ulna, tibia, metacarpal, and metatarsal) beginning around 40 days of age until adult size was reached. results indicate that the larger ... | 1997 | 8989872 |
| the organization of monoamine neurons within the brainstem of the north american opossum (didelphis virginiana). | 1978 | 8980724 | |
| the origin of brainstem-spinal pathways in the north american opossum (didelphis virginiana). studies using the horseradish peroxidase method. | 1978 | 8980723 | |
| methylation analysis of a marsupial x-linked cpg island by bisulfite genomic sequencing. | paternal x chromosome inactivation occurs in rodent extraembryonic membranes and in all tissues of marsupials. methylation of cpg islands occurs on the inactive x in eutherians and is considered to be a stabilizing mechanism. the only previous study of a marsupial x-linked cpg island was of the g6pd gene of the virginia opossum, in which the paternally derived allele is not completely repressed. we have cloned the 5' end of the g6pd gene from an australian marsupial, the common wallaroo, and seq ... | 1996 | 8919690 |
| ontogeny of suckling mechanisms in opossums (didelphis virginiana). | although adult mammals have several different mechanisms for drinking liquids, relatively little is known about the variation in mechanisms used by infants for suckling and how the mechanics of suckling change as a function of ontogeny. we examined suckling in infant opossums, animals that as adults use a lapping mechanism to drink. the youngest infants (45 days old) used a suction, pumping mechanism, based on dorsal/ventral tongue movements, similar to what has been documented in infant primate ... | 1996 | 8872320 |
| topography, architecture, and connections of somatosensory cortex in opossums: evidence for five somatosensory areas. | microelectrode maps of somatosensory inputs were related to cortical architecture and patterns of cortical connections to provide evidence for five subdivisions of the somatosensory or sensorimotor cortex in north american opossums (didelphis marsupialis). microelectrode recordings revealed three systematic representations of the body surface. a large mediolaterally oriented representation was identified as the primary somatosensory area (s1) by its relative position, somatotopy, architecture, a ... | 1996 | 8866849 |
| evidence for growth of supraspinal axons through the lesion after transection of the thoracic spinal cord in the developing opossum didelphis virginiana. | in the present study, we asked whether supraspinal axons grow through a complete transection of the spinal cord in the developing opossum didelphis virginiana. when the thoracic cord was transected at postnatal day (pd) 5 and bilateral injections of fast blue (fb) were made four segments caudal to the lesion 30-40 days later, fb-containing neurons were found in each of the supraspinal nuclei labeled by comparable injections in age-matched unlesioned controls. continuity between the cut ends of t ... | 1996 | 8835721 |
| milk composition in the north american opossum (didelphis virginiana). | the composition of milk samples collected from captive opossums (didelphis virginiana) was determined at various intervals during lactation. the milk solids increased from 9% at week one to a maximum of 34% at 11 weeks post-partum. there were changes in the relative proportions of protein, lipid and carbohydrate at different stages of lactation. lipid represented the greatest fraction of the solids except for a period at mid-lactation when there was a peak in protein concentration. the concentra ... | 1996 | 8829811 |
| growth of dorsal spinocerebellar axons through a lesion of their spinal pathway during early development in the north american opossum, didelphis virginiana. | supraspinal axons grow around or through lesions of their spinal pathway during specific critical periods of mammalian development, but comparable plasticity has not been documented for axons which form ascending tracts. in the present study, we asked whether axons of the dorsal spinocerebellar tract (dsct) are capable of such growth. the spinal cord of the north american opossum, didelphis virginiana, was hemisected at mid-thoracic levels between postnatal day (pd) 5 and 68 and after varying su ... | 1996 | 8804690 |
| evolution of transthyretin gene expression in the liver of didelphis virginiana and other american marsupials. | the occurrence of the thyroid hormone-binding plasma protein transthyretin in the bloodstream was investigated for four american marsupial species. serum samples were analyzed by incubation with radioactive t4, followed by electrophoresis, then autoradiography, and western blotting. transthyretin was found in serum from monodelphis domestica, didelphis virginiana, caluromys lanatus, and dromiciops australis. for unambiguous identification, transthyretin from d, virginiana was purified from serum ... | 1996 | 8754780 |
| a molecular and evolutionary study of the beta-globin gene family of the australian marsupial sminthopsis crassicaudata. | beta-globin gene families in eutherians (placental mammals) consist of a set of four or more developmentally regulated genes which are closely linked and, in general, arranged in the order 5'-embryonic/fetal genes-adult genes-3'. this cluster of genes is proposed to have arisen by tandem duplication of ancestral beta-globin genes, with the first duplication occurring 200 to 155 mybp just prior to a period in mammalian evolution when eutherians and marsupials diverged from a common ancestor. in t ... | 1996 | 8752008 |
| ticks (acari: ixodidae) in bulloch county, georgia. | an 18-mo study was conducted in bulloch county, georgia, to determine tick species composition, seasonal activity of individual tick species, and host-tick associations. the following 7 methods of tick collection were included: (1) live trapping of potential host animals, (2) checking wild game, (3) drag sampling, (4) carbon dioxide attraction, (5) checking livestock, road kills, nests, and burrows, (6) samples submitted from veterinarians, and (7) ticks collected by local residents and submitte ... | 1996 | 8742526 |
| man and the chimaera. selective versus neutral oxytocin evolution. | the oxytocin/vasopressin superfamily encompasses vertebrate and invertebrate peptides and therefore the ancestral gene encoding the precursor protein antedates the divergence between the two groups, about 700 million years ago. the preserved nonapeptide pattern indicates that both the precursor structures and the processing enzymatic machinery were greatly conserved to ensure the building of a specific conformation. substitutions, which may be neutral or selective, occurred in precise positions. ... | 1995 | 8714026 |
| effects on breathing of medullary bicuculline microinjections in immature opossums. | the role of medullary gamma-aminobutyric acid a (gabaa)-receptor activation in the expression of breathing was studied in suckling opossums (didelphis virginiana) from 4 to 8 wk of age. animals were anesthetized with a thiobarbiturate, and the ventral medulla was exposed so that drugs could be microinjected into the medulla with a two-barrel glass micropipette. the gabaa antagonist bicuculline at approximately 1-3 pmol total dose was injected in volumes < 1 nl; injections of saline with pontamin ... | 1995 | 8594928 |
| perivitelline space of marsupial oocytes: extracellular matrix of the unfertilized oocyte and formation of a cortical granule envelope following the cortical reaction. | the purpose of this study was to characterize the structure of the vestments surrounding unfertilized and cortical granule-reacted oocytes from a marsupial, the grey short-tailed opossum monodelphis domestica and to determine if a cortical granule envelope (cge) forms in the perivitelline space (pvs) following the cortical reaction. unfertilized oocytes collected from mature ovarian follicles and oviducal oocytes that had undergone a cortical reaction were fixed for electron microscopy in the pr ... | 1995 | 8588937 |
| sarcocystis falcatula from passerine and psittacine birds: synonymy with sarcocystis neurona, agent of equine protozoal myeloencephalitis. | equine protozoal myeloencephalitis (epm) is a neurologic disease of horses caused by sarcocystis neurona. the horse is a dead-end host for s. neurona and the definitive and intermediate hosts have not previously been identified. we hypothesized that s. neurona is actually sarcocystis falcatula, a parasite that cycles in nature between virginia opossums (didelphis virginiana) and any of a variety of avian intermediate hosts. we extracted dna from s. falcatula sarcocysts in the muscle of a brown-h ... | 1995 | 8544067 |
| identification of opossums (didelphis virginiana) as the putative definitive host of sarcocystis neurona. | sarcocystis neurona is an apicomplexan that causes equine protozoal myeloencephalitis (epm) in north and south america. horses appear to be an aberrant host, because the merozoites continually divide in the central nervous system, without encysting. the natural host species has not previously been identified. the small subunit ribosomal rna (ssurna) gene of s. neurona was compared to those of sarcocystis muris, sarcocystis cruzi, toxoplasma gondii, and cryptosporidium parvum to identify a unique ... | 1995 | 8544064 |
| morphological observations on the unique paired capillaries of the opossum retina. | light-microscopic and ultrastructural analysis of the ocular tissues of the north american opossum (didelphis virginiana) revealed that the arterial and venous segments of retinal vessels, including capillaries of the smallest calibre, occur in pairs. they do not form anastomotic networks, the common pattern in mammals with vascularised retinae, but instead the two segments of the pair join to form hairpin end loops. the paired vessels, with the arteriolar limb usually on the vitread aspect, pen ... | 1993 | 8472304 |
| parasitic arthropods of sympatric opossums, cotton rats, and cotton mice from merritt island, florida. | six species of parasitic arthropods were collected from 12 opossums (didelphis virginiana), 8 species were obtained from 28 cotton rats (sigmodon hispidus), and 4 species were collected from 10 cotton mice (peromyscus gossypinus) from merritt island, brevard county, florida. the flea polygenis gwyni was the only parasite that infested all 3 host species, and it was present in very high densities (mean intensity = 73.7) on the opossums. the american dog tick, dermacentor variabilis, and the tropi ... | 1993 | 8459341 |
| the origins of descending projections to the lumbar spinal cord at different stages of development in the north american opossum. | we have employed the retrograde transport of fast blue (fb) to identify the origins of descending projections to the lumbar cord of the opossum from postnatal day (pd)1, 12-13 days after conception, to maturity. when fb injections were made into the lumbar cord at pd1, supraspinal labeling was sparse and limited to the hypothalamus, the reticular formation, the coeruleus complex, the caudal raphe, and, in one case, the interstitial nucleus of the medial longitudinal fasciculus and the lateral ve ... | 1993 | 8457879 |
| release of nitric oxide by activation of nonadrenergic noncholinergic neurons of internal anal sphincter. | the purpose of the present study was to investigate the direct release of nitric oxide (no) in response to the stimulation of nonadrenergic noncholinergic (nanc) nerves. the studies were performed on isolated smooth muscle strips of the opossum (didelphis virginiana) internal anal sphincter (ias). electrical field stimulation (efs) using the appropriate parameters caused a frequency-dependent fall in the resting tone of the ias. the release of no was measured directly by the chemiluminescence me ... | 1993 | 8430806 |
| opossum serum alpha 1-proteinase inhibitor: purification, linear sequence, and resistance to inactivation by rattlesnake venom metalloproteinases. | opossum (didelphis virginiana) serum was fractionated with (nh4)2so4 and then chromatographed on deae-sepharose and phenyl-sepharose. affinity chromatography on a protein a-sepharose-antibody column removed traces of opossum serum metalloproteinase inhibitors, and resulted in a homogeneous preparation of opossum alpha 1-proteinase inhibitor (alpha 1-pi). the inhibitor is a single-chain glycoprotein (17.7% carbohydrate) with an estimated m(r) = 54,000. an opossum liver cdna library was immunoscre ... | 1993 | 8422360 |
| gestation and placentation in two new world opossums: didelphis virginiana and monodelphis domestica. | estrus, gestation, and placentation were studied in the virginia opossum (didelphis virginiana) and the gray short-tailed oppossum (monodelphis domestica), representatives of the prototypic, new world marsupial family didelphidae. didelphis is a large (3,000 g), pouched opossum that exhibits a 28-day estrous cycle, spontaneous estrus and ovulation, and a high ovulation rate (60 ova per cycle). monodelphis is a small (100 g), pouchless opossum with male-induced estrus and ovulation and a moderate ... | 1993 | 8371092 |
| characterization of a marsupial sperm protamine gene and its transcripts from the north american opossum (didelphis marsupialis). | a synthetic oligonucleotide primer, designed from marsupial protamine protein-sequence data [balhorn, r., corzett, m., matrimas, j. a., cummins, j. & faden, b. (1989) analysis of protamines isolated from two marsupials, the ring-tailed wallaby and gray short-tailed opossum, j. cell. biol. 107] was used to amplify, via the polymerase chain reaction, protamine sequences from a north american opossum (didelphis marsupialis) cdna. using the amplified sequences as probes, several protamine cdna clone ... | 1993 | 8344286 |
| characterization of mannose 6-phosphate receptors (mprs) from opossum liver: opossum cation-independent mpr binds insulin-like growth factor-ii. | bovine, human, and rat cation-independent mannose 6-phosphate receptors (ci-mprs) are capable of binding both mannose 6-phosphate and insulin-like growth factor-ii (igf-ii). however, the receptor isolated from either chicken or frog lacks the high affinity igf-ii-binding site. to determine whether ci-mprs isolated from a species that is closely related to placental mammals can bind igf-ii, the mprs were purified from a marsupial, the american opossum (didelphis virginiana), by phosphomannan-seph ... | 1993 | 8344189 |
| maximum discharge rates of respiratory neurons during opossum development. | the observed low frequencies of action potentials observed in medullary respiratory neurons of immature opossums (didelphis virginiana) could occur because these cells are incapable of achieving higher sustained firing rates. nonsustainability of firing might also help explain why the inspired breath is brief (approximately 0.1 s) in the youngest opossums and rises very slowly during postnatal life. firing frequencies of medullary respiratory neurons were examined in spontaneously breathing thio ... | 1993 | 8307857 |
| development of the eye in the north american opossum (didelphis virginiana). | marsupials are unique models for developmental biology-oriented research because of the immature state of their development at birth. the north american opossum (didelphis virginiana) has several advantages over other marsupials, including large litter size, short prenatal period (12.5 d), an extended postnatal period while accessible in the pouch, and its ability to reproduce reliably in captivity. studies of ocular development in this species have not been reported previously. the aim of the p ... | 1993 | 8300421 |
| 2'-deoxyadenosine metabolism in human and opossum didelphis virginiana erythrocytes in vitro. | 1. in erythrocytes of both species, deamination and phosphorylation of dado was completely inhibited by 5 microm 2'deoxycoformycin and 10 microm 5-itu respectively. 2. under physiologic conditions, provided with nanomolar concentrations of dado there was complete deamination of dado in human red cells. in opossum erythrocytes deamination and phosphorylation of the deoxynucleoside were nearly; additionally, 1-2% of the substrate was metabolized to axp. 3. with ada inhibited in intact red cells, a ... | 1993 | 8281758 |
| the effect of enzyme replacement on red cell adenine deoxyribonucleotides in adenosine deaminase-deficient erythrocytes of the opossum, didelphis virginiana. | 1. polyethyleneglycol-modified bovine adenosine deaminase was administered (10-20 u/kg/week) intramuscularly to two opossums for 15 weeks and changes in red cell adenine ribo- and deoxyribonucleotides quantitated by hplc. 2. only a moderate decline of erythrocyte daxp was observed at the end of the study when compared to results of enzyme replacement seen in human adenosine deaminase deficient patients. 3. opossum red cells salvage substantial amounts of deoxyadenosine provided in physiologic (5 ... | 1993 | 8281757 |
| ixodes dammini (acari: ixodidae) infestation on medium-sized mammals and blue jays in northwestern illinois. | high prevalence of infestation of five species of medium-sized mammals and blue jays, cyanocitta cristata (l.), by immature ixodes dammini spielman, clifford, piesman and corwin was found in castle rock state park in northwestern illinois during may-august 1991. raccoons, procyon lotor l., and opossums, didelphis virginiana kerr, were infested with the highest larval densities and were trapped primarily in bottomland forest and ecotone habitats. all species had similar nymphal densities, except ... | 1993 | 8254647 |
| development of an astrocytic response to lesions of the spinal cord in the north american opossum: an immunohistochemical study using anti-glial fibrillary acidic protein. | we have shown previously that rubral axons grow around a lesion of their pathway in developing opossums and that a critical period exists for that plasticity. the critical period begins when rubral axons first reach the level of the lesion and ends sometime between postnatal days (pd) 26 and 30. the aim of the present study was to examine the development of an astrocytic response to lesioning the spinal cord to determine if there is a temporal correlation between the development of such a respon ... | 1993 | 8244527 |
| development of radial glia and astrocytes in the spinal cord of the north american opossum (didelphis virginiana): an immunohistochemical study using anti-vimentin and anti-glial fibrillary acidic protein. | we have shown previously that rubrospinal axons grow around a lesion of their pathway in developing opossums and that a critical period exists for that plasticity. as a first step toward addressing the possibility that glial maturation and/or the development of an astrocytic response to lesioning contribute to loss of rubrospinal plasticity, we have studied the normal development of radial glia and astrocytes in the spinal cord of the opossum by immunostaining for vimentin (vim) and glial fibril ... | 1993 | 8244526 |
| oxidation reactions of human, opossum (didelphis virginiana) and spot (leiostomus xanthurus) hemoglobins: a search for a correlation with some structural-functional properties. | 1. relative to human hba, opossum (didelphis virginiana) hemoglobin was found to be more susceptible to autoxidation. while the initial rate of autoxidation of spot (leiostomus xanthurus) hemoglobin is close to that of hba, complete oxidation occurs in 50 hr. 2. direct addition of hydrogen peroxide (h2o2) induced oxidation of hemoglobins in a definite order: spot hb > hba > opossum hb. excess h2o2 led to heme degradation and precipitation that occurred much faster for spot hb than the case with ... | 1993 | 8243064 |
| intrinsic factor-cobalamin receptor activity in a marsupial, the american opossum (didelphis virginiana). | 1. significant and specific binding of intrinsic factor-cobalamin occurred in proximal but not in the distal half of the intestine in an adult marsupial, the american opossum. 2. the purified opossum kidney receptor, like rat and canine kidney receptors, revealed a single band of m(r) approximately 230 on sds-page. however, unlike the rat and canine receptors, the opossum receptor was sensitive to both endoglycosidase h and peptide-n-glycosidase f. 3. the opossum intrinsic factor-cobalamin recep ... | 1993 | 8097983 |
| the marsupial mitochondrial genome and the evolution of placental mammals. | the entire nucleotide sequence of the mitochondrial genome of the american opossum, didelphis virginiana, was determined. two major features distinguish this genome from those of other mammals. first, five trna genes around the origin of light strand replication are rearranged. second, the anticodon of trna(asp) is posttranscriptionally changed by an rna editing process such that its coding capacity is altered. when the complete protein-coding region of the mitochondrial genome is used as an out ... | 1994 | 8056314 |
| distribution of heat-stable enterotoxin/guanylin receptors in the intestinal tract of man and other mammals. | the human intestinal tract, as well as that of several eutherian and metatherian mammals, was examined for the distribution of heat-stable enterotoxin (st)/guanylin receptors. these receptors were confined to the intestinal epithelium lining the lumen and forming the intestinal glands throughout the length of both the small intestine and colon of all species examined. in man and most other mammalian species, there appeared to be a decrease in receptor density distally along the longitudinal axis ... | 1994 | 8014132 |
| brain growth and neocortical development in the opossum. | general brain growth and differentiation of the neocortex have been studied in the marsupial, didelphis virginiana from the 10.5 day embryo through adulthood. didelphis is born after a short gestation period of about 12.5 days, at a time when the telencephalic wall consists only of two layers and is considered to be at an embryonic stage of development. the cortical plate does not appear until late in the first postnatal week, thus neocortical development is totally a postnatal phenomenon in did ... | 1994 | 7978336 |
| experimental ureteral obstruction in the fetal opossum: histologic assessment. | in the north american opossum, didelphis virginiana unilateral complete ureteral obstruction (eco) and partial unilateral (epo) ureteral obstruction were created during the early metanephric stage of kidney development in pups attached to the teat (approximately 4.5 cm. long, 20 days old). at 70 days of pouch life (full-term equivalent in the human) some completely obstructed ureters were unobstructed with reanastomosis in the bladder (reco). other pups underwent unilateral complete ureteral lig ... | 1994 | 7966702 |
| murine typhus: updated roles of multiple urban components and a second typhuslike rickettsia. | studies using serologic and polymerase chain reaction-(pcr) facilitated analysis of field samples from southern texas indicate the presence of rickettsia typhi and elb agent infected cat fleas, ctenocephalides felis (bouché), and the first observation of elb infected vertebrates (opossums). the elb agent is a recently described typhus-like rickettsia that is not distinguished from r. typhi or r. prowazekii by currently available serologic reagents. restriction digests of pcr products from 399 fl ... | 1994 | 7966170 |
| hearing in primitive mammals: monodelphis domestica and marmosa elegans. | although opossums of the family didelphidae usually serve as a parsimonious starting point for tracing the otological and neurological evolution of modern mammals, audiological data for didelphid opossums is available only for the north american opossum (didelphis virginiana) which because of its large size, may be one of the least representative genera of the family. the present report extends the audiological data to two other species of didelphid opossums, monodelphis domestica, and marmosa e ... | 1994 | 7928716 |
| uroguanylin: structure and activity of a second endogenous peptide that stimulates intestinal guanylate cyclase. | the intestinal hormone guanylin and bacterial heat-stable enterotoxins (sts) are members of a peptide family that activates intestinal membrane guanylate cyclase. two different peptides that activate the human intestinal t84 cell guanylate cyclase have been purified from urine and intestinal mucosa of opossums (didelphis virginiana). the highly acidic peptide, qedcelcinvactgc, was named uroguanylin because it was isolated from urine and shares 53% identity with guanylin. a second peptide, shtcei ... | 1993 | 7902563 |
| timetable of in vivo embryonic development in the grey short-tailed opossum (monodelphis domestica). | the timing of development was examined in 496 embryos from female monodelphis domestica collected at known time intervals after video recorded mating. ovulation occurred approximately 20 hr (day 1) after mating, and fertilization was observed by 24 hr. transport through the oviducts was rapid, and pronuclear stage embryos were recovered from the uterus as early as 24 hr after mating. second cleavage had occurred by 55 hr after mating. three-celled embryos were among those collected on day 3 afte ... | 1994 | 7893485 |
| early development of cerebellar afferent systems that contain corticotropin-releasing factor. | corticotropin-releasing factor (crf) and crf binding sites have been described in the cerebellum of several species, including the north american opossum (didelphis marsupialis virginiana), the species used in the present study. inotophoretic application of this peptide in the adult cerebellum enhances the spontaneous and amino acid-induced firing rate of purkinje cells and overcomes the gaba-induced suppression of purkinje cell activity. the present account provides immunohistochemical evidence ... | 1994 | 7890829 |
| projection of visuotopically organized afferents to the dorsal thalamus in the opossum, monodelphis domestica. | retrogradely transported dyes, fluorogold and fast blue were injected into both sides of the dorsal thalamus in the monodelphis opossum. projection of the presumed primary visual cortical area, superior colliculus and parabigeminal nucleus to the dorsal lateral geniculate nucleus and the lateral posterior--lateral intermedius nuclear complex were described. they show close similarities to the homologous projections in the north american opossum, insectivores and some rodents. in comparison with ... | 1994 | 7887182 |
| x-chromosome replication patterns in adult, newborn and prenatal opossums. | somatic cells from the opossums monodelphis domestica and didelphis virginiana were labelled with 5-bromodeoxyuridine (brdu), treated with colchicine, stained with acridine orange and examined using fluorescence microscopy. brdu-incorporated metaphase spreads from females of m. domestica at developmental stages from late bilaminar blastocysts to adults showed replication asynchrony of the two (acrocentric) x chromosomes. the long arm of one x chromosome was the latest replicating region in the e ... | 1994 | 7878226 |
| development of early cell lineages in marsupial embryos: an overview. | all major embryonic and extra-embryonic cell lineages are established before implantation in marsupials. in reptiles, birds, monotremes and most marsupials, the zygote is polarized, sometimes markedly so, and the cleavage pattern in relation to the polarized state provides the mechanism for the generation of positional signals. these ensure that the embryonic cell lineages develop in the centre of the developing blastoderm or blastocyst epithelium and the extra-embryonic lineages at the peripher ... | 1994 | 7878224 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 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 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| aspermatogenesis in a paralyzed opossum (didelphis virginiana). | 1980 | 7464014 | |
| 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 |
| 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 |
| 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 |
| 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 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 |
| 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 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| the purification and characterization of an antihemorrhagic factor in opossum (didelphis virginiana) serum. | 1981 | 7302953 | |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 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 |
| 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 development of descending spinal connections. studies using the north american opossum. | 1982 | 7156395 | |
| 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 |
| 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 | |
| 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 |
| 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 |
| 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 |
| 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 |