Publications

distribution of cerebellar and somatic lemniscal projections in the ventral nuclear complex of the virginia opossum.		1973	4709264
convergent projection of three separate thalamic nuclei on to a single cortical area.	three distinct sensory-motor nuclei in the thalamus project to parietal cortex in the virginia opossum; the ventral posterior nucleus receives inputs from somatic sensory structures and projects to layers iv and iii, the ventral anterolateral nucleus receives inputs from motor structures and projects to layers iv and iii and inner i, and the central intralaminar nucleus receives inputs from sensory, motor, and other structures and projects to layers vi through outer i. the physiologically define ...	1973	4683125
the adrenergic control of lower esophageal sphincter function. an experimental model of denervation supersensitivity.	to evaluate the adrenergic regulation of lower esophageal sphincter (les) function, les pressure, les relaxation during swallowing, and blood pressure were measured in the anesthetized opossum, didelphis virginiana, during intravenous administration of alpha and beta adrenergic agonists and antagonists. studies were done in controls and animals adrenergically denervated with 6-hydroxydopamine. alpha adrenergic agonists (norepinephrine, phenylephrine) increased les pressure and blood pressure, wh ...	1973	4727458
diel temperature fluctuations of the virginia opossum (didelphis virginiana).		1973	4744938
cell cycle determination of phytohemagglutinin-stimulated lymphocytes from the opossum, didelphis virginiana.		1973	4708350
eimeria indianensis sp. n. and an isospora sp. from the opossum didelphis virginiana (kerr).		1974	4817974
effects of incubation temperature on the kinetics of cultured lymphocytes from the opossum, didelphis virginiana.		1974	4435132
the opossum (didelphis virginiana kerr) as a biomedical model. ii. breeding the opossum in captivity: facility design.		1974	4362894
the opposum (didelphis virginiana kerr) as a biomedical model. i. research perspective, husbandry, and laboratory technics.		1974	4362893
proceedings: control of steroidogenesis in adrenal tissue from the developing opossum, didelphis marsupialis virginiana.		1974	4374480
ovariectomy during gestation in the american opossum, didelphis marsupialis virginiana.		1974	4853513
the erythrocyte life span in the american opossum (didelphis marsupialis virginiana).		1974	4365338
pasteurella multocida infection in the opossum (didelphis virginiana).		1974	4374598
acquired immunity in opossum (didelphis virginiana) embryos.		1974	4133078
biosynthesis and secretion of testosterone by adrenal tissue from the north american opossum, didelphis virginiana, and the effects of tropic hormone stimulation.		1975	173619
frequency of sarcocystis spp in detroit, metropolitan area, michigan.	a survey of sarcocystis spp in feral animals and in domesticated animals slaughtered in detroit, mi, was undertaken during a 6-month period, april to september, 1973, using histologic and digestion diagnostic techniques. results indicated 75.3% of 789 sheep and 10.8% of 306 lambs were infected. infection in young and adult sheep was low in april (0% of 78 lambs and 6.7% of 62 adult sheep), but increased in july (24% of 90 lambs and 94.1% of 201 adult sheep). high frequency of sarcocystis in summ ...	1975	803806
vaccination of foxes against rabies using ingested baits.	a method for immunizing foxes against rabies was evaluated. fifteen of 36 red foxes (vulpes fulva) fed baits impregnated with modified live virus rabies vaccine developed serum rabies neutralizing antibody. the vaccine-bait proved unstable when held at 4 c or 25 c for 96 hours prior to feeding. for safety testing the vaccine virus was administered to opossums (didelphis virginiana), cotton rats (sigmodon hispidus), hamsters (mesocricetus auratus), and chickens (gallus domesticus) in either liqui ...	1975	1097743
the inferior olivary nucleus of the opossum (didelphis marsupialis virginiana), its organization and connections.	although the inferior olivary nucleus of the opossum is small, sections stained either for nissl substance, normal axons or cholinesterase activity reveal distinct medial, dorsal and principal nuclei. the medial nucleus contains three major subdivisions (labelled a, b, c after bowman and sladek, '73) and a group of neurons which is comparable to the cap of kooy. in contrast to the cat and monkey, the major portion of the "medial" nucleus (subgroup a) lies lateral to the principal nucleus in rost ...	1975	1123465
leptospirosis in wildlife in brazil: isolation of a new serotype in the pyrogenes group.	a new leptospiral serotype in the serogroup pyrogenes is described. the strain was isolated from one gray "four-eyed" opossum (philander opossum). it is proposed that the serotype be designated guaratuba, strain an-7705. the isolations of serotypes ballum from the south american field mouse (akodon arviculoides), szwajizak and icterohaemorrhagiae from the north american opossum (didelphis marsupialis), and grippotyphosa from many other wild animal species as well as domesticated animals are also ...	1975	1163877
corticobulbar fibres in the north american opossum (didelphis marsupialis virginiana) with notes on the tasmanian brust-tailed possum (trichosurus vulpecula) and other marsupials.	corticobulbar projections have been studied in the american opossum by both degeneration and autoradiographic methods and, for the most part, the results confirm our earlier observations (martin & west, 1967; martin, 1968). however, we have obtained evidence for certain connexions not previously described and have delineated the origin(s) of several connexions more precisely by paying particular attention to the degeneration present at thalamic levels in all cases and by the use of autoradiograp ...	1975	1213949
uterine proteins in the marsupial, didelphis marsupialis virginiana, during gestation.		1975	1110467
cortical and brain stem projections to the spinal cord of the american opossum, didelphis marsupialis virginiana.	the present report describes the results of experiments designed to study supraspinal systems in the american opossum by several techniques. the data indicate that although spinal fibers from the opossum motor-sensory cortex are small and limited in their distribution, those from the brain stem are comparable in their origin, course, caudal extent and distribution to those described for placental mammals. such results support the use of the opossum as an experimental animal for nervous system re ...	1975	1225466
primary afferent fiber distribution at brachial and lumbosacral spinal cord levels in the opossum (didelphis marsupialis virigniana).	this paper describes the spinal cord distribution of primary afferent fibers from forelimb and hindlimb in the north american opossum. fibers entering the cord distribute to all ipsilateral laminae (i-ix) within their segment of entry, often have a small crossed projection to the contralateral dorsal horn, and extend as well into adjacent segments of lumboseacral and cervical enlargements. segmentally derived afferents have a longitudinal extent of up to 10 segments into laminae vi and vii, of 5 ...	1975	1225464
pre- and postnatal development of lactate and malate dehydrogenases in the marsupial didelphis marsupialis virginiana.		1975	1237386
the primary structure of the myoglobin of didelphis marsupialis (virginia opossum).		1975	1164514
methods for obtaining neonates of known age from the virginia opossum (didelphis marsupialis virginiana).	postlactational estrus occurred in the opossum 6-17 da (mean 10.08 +/- 3.2da) after sucklings were removed from the pouch 1-60 da postpartum. this estrus occurred somewhat earlier in females whose young were removed later than 24 hr postpartum, rather than within the first 24 hr. thirteen litters (37% conception) resulted from 35 initial attempts at breeding during postlactational estrus. three of 5 females conceived when litters were removed twice in succession. the tendency forindividual femal ...	1975	1152417
megakaryocytopoiesis in the liver of the developing opossum (didelphis virginiana).	the development of hepatic megakaryocytes has been examined in the livers of 35 young opossums at four different stages of postnatal development. megakaryocytopoiesis is carried out within the sinusoidals and there appears to be a close relationship between the young megakaryocytes and the sinusoid lining cells. megakaryocytes in the opossum are relatively small and lack the degree of nuclear complexity seen in other species. both the nucleus and the cytoplasm undergo sequential maturational cha ...	1975	1201961
the postnatal development of the liver in a marsupial, didelphis virginiana. 2. electron microscopy.	the postnatal development of the liver has been examined with the electron microscope in 15 groups of young opossums. at birth, hepatic cells show little organization and large islands of haemopoietic elements occur between clusters of hepatic cells. hepatocytes appear small and contain an abundance of granular endoplasmic reticulum. the cytoplasm is also characterized by scattered lipid droplets of varying sizes. canaliculi occasionally are found between hepatocytes. only a few scattered lining ...	1975	1184456
a field study of anatrichosoma infections in the opossum, didelphis virginiana.		1975	1165567
spectrophotometric measurement of hemoglobin oxygen saturation in the opossum didelphis virginiana.		1975	234330
development of the neonate opossum (didelphis virginiana).	this study describes the postnatal growth and development of the opossum (didelphis virginiana). measurements were made weekly on 6 young opossums between 50 and 189 days following birth. these measurements included: total length, length of ear and tail, and length of front and rear appendages. body weight measurements were extended to 233 days. the mean body weight at 50 days was 14.1 g, which increased rapidly to 2,560 g at 233 days.	1975	1182241
cellular mechanisms involved in cyclic stromal renewal of the uterus. i. the opossum, didelphis virginiana.	at the close of a uterine cycle, the remodelling of the endometrial stroma of the north american opossum involves removal of extracellular material by macrophages. this study provides cytochemical and ultrastructural evidence which indicates that the laden macrophages are eliminated from the endometrium through emigration across the glandular and luminal epithelia. during diestrus or the early postpartum period, the abundant uterine glands relinguish their secretory function to acquire a transie ...	1976	1252015
high tolerance to snake venom by the virginia opossum, didelphis virginiana.		1976	960117
retinofugal pathways in two marsupials.	autoradiographic and anterograde degeneration tracing methods were used to study and compare the organization of retinofugal pathways in two marsupial opossums, didelphis virginiana and marmosa mitis. seven identical retinal targets were demonstrated for each opossum. these include: (1) the suprachiasmatic nucleus of the hypothalamus, (2) the dorsal and (3) ventral lateral geniculate nuclei, (4) the lateral posterior nucleus, (5) the pretectal complex, (6) the superior colliculus and (7) the acc ...	1976	993375
fine structure of the retinal epithelium and tapetum lucidum of the opossum (didelphis virginiana).	the fine structure of the retinal epithelium has been studied by electron microscopy in the opossum (didelphis virginiana). the retinal epithelium, over most of the retina, is typical of that in other vertebrates and consists of a single layer of heavily pigmented, cuboidal cells. these cells display extensive basal (scleral) infoldings and numerous apical (vitreal) processes which enclose photoreceptor outer segments. a semicircular area of the retinal epithelium in the superior fundus is furth ...	1976	966288
hemoglobins of the opossum (didelphis virginiana kerr). i. developmental changes from yolk sac to definitive erythropoiesis.	in 5- to 7-da old opossum pouch young, hemoglobins were observed. the "primitive" species i, ii, and iv were shown to be electrophoretically distinct from the adult hemoglobin iii. hemoglobin i was detectable until the 7th postnatal da. hemoglobins i, ii, and iv were detected only during the period when yolk sac-derived primitive erythroblasts were seen in circulation, ei, until the 13th postnatal da, but in decreased amounts from the 6th to 13th da. the electrophoretic pattern of hemoglobin of ...	1976	1271732
laterality and topography of cerebellar cortical efferents in the opossum (didelphis marsupialis virginiana).		1976	1268704
opossum somatic sensory cortex: a microelectrode mapping study.	organization of opossum somatic sensory cortex has been investigated utilizing closely spaced microelectrode penetrations (0.25-0.5 mm apart) and delicate mechanical stimulation of body surfaces including the facial vibrissae. results may be summarized as follows: (1) the general organization of somatic sensory cortex, as originally defined by lende ('63a) has been confirmed; (2) a double representation of the contralateral mystacial vibrissae and rhinarium, implicit in lende's original data, wa ...	1976	1245614
cerebello-olivary fibers: their origin, course and distribution in the north american opossum.	although degeneration techniques suggest that cerebello-olivary fibers are limited in their origin and distribution, horseradish peroxidase and autoradiographic experiments make it clear that they arise within all cerebellar nuclei and project to most, if not all, areas of the contralateral inferior olive. autoradiographic preparations show that cerebello-olivary fibers are highly ordered and suggest that the dentate nucleus projects primarily to the principal olive, the interpositus anterior re ...	1976	1253856
the amino-acid sequence of the alpha-crystallin a chains of red kangaroo and virginia opossum.	the amino acid sequence of the a chain of the eye lens protein alpha-crystallin from the red kangaroo (macropus rufus) was completely determined by manual edman degradation of tryptic, thermolytic and cyanogen bromide peptides. the sequence of the alpha-crystallin a chain from the virginia opossum (didelphis marsupialis) was deduced from amino acid analyses and partial edman degradation of peptides. the 173-residue a chains of kangaroo and opossum differ in six positions, whereas comparison with ...	1976	964255
primary isolation of mycobacterium avium complex-serotype 6 on blood agar.	mycobacterium avium complex-serotype 6 was isolated in pure culture on blood agar plates from inocula taken from the heart blood, lungs, liver, kidneys, and spleen of a naturally infected captive female opossum (didelphis marsupialis virginiana). repeat cultures from stored tissues and transfer of colonies from original blood agar plates revealed that the mycobacterium grew on tryptose, brilliant green, eosin-methylene blue. sabouraud glucose, and mycobiotic agar plates and in fletcher leptospir ...	1976	972192
observations on the involvement of wildlife in an epornitic of chlamydiosis in domestic turkeys.	in an investigation of potential wildlife reservoirs of chlamydia psittaci at the site of an acute, highly fatal epornitic of chlamydiosis in domestic turkeys in texas, various species of wild birds and rodents were captured and tested for chlamydial serum antibodies and chlamydiae in their tissues. thirteen (65%) of 20 blackbirds (agelaius sp), 4 (44%) of 9 killdeer (oxyechus vociferus), 3 (27%) of 11 sparrows (passer sp) and 1 of 4 mourning doves (zenaidura macroura) were seropositive, but chl ...	1976	988009
the vestibular complex of the american opossum, didelphis virginiana. i. conformation, cytoarchitecture and primary vestibular input.	degeneration experiments reveal that the vestibular nerve of the adult opossum distributes to an extensive and diverse area of the brainstem and, as in placental mammals, the traditionally named nuclei do not receive a uniform distribution of primary afferent fibers. nevertheless, such nuclei as well as other nearby cell groups have been considered as vestibular since they share other mutual connections. except for subgroups "l", "g" and the nucleus supravestibularis all of the vestibular subdiv ...	1977	838884
the vestibular complex of the american opossum didelphis virginiana. ii. afferent and efferent connections.	we have demonstrated the connectivity of the opossum's vestibular nuclei using degeneration, autoradiographic and horseradish peroxidase techniques and have found it to be generally comparable to that reported for the cat. apart from the primary input described in part i of our study, the cerebellum provides the major source of afferent connections to the vestibular complex. axons from the cerebellar cortex distribute mainly to vestibular areas which receive no primary afferent projections, e.g. ...	1977	65367
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
ventilatory effects accompanying spontaneous movement in the suckling opossum.	to determine whether spontaneous movement was associated with an organized respiratory response during early stages of mammalian development, we studied immature suckling opossums (didelphis virginiana) between 30 and 60 days of age. rate and depth of breathing were measured using pressure plethysmography and movement was assessed using electromyography of neck muscles. during air-breathing as well as during ventilatory chemostimulation with hypoxic, hypercapnic, and asphyxiant test gases, the o ...	1977	597380
the lateral reticular nucleus of the opossum (didelphis virginiana). ii. connections.		1977	864033
the lateral reticular nucleus of the opossum (didelphis virginiana). i. conformation, cytology and synaptology.		1977	864031
resistance of the opossum (didelphis virginiana) to envenomation by snakes of the family crotalidae.		1977	841589
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
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
age ratios, weights, and reproduction of the virginia opossum in north louisiana.		1978	750645
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
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
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
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 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
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
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
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
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
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
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
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
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
substance p immunoreactivity in the median eminence of the north american opossum and domestic fowl.		1980	6154507
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
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
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
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 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
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
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
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
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