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PubMed1994

Down-regulation of parathyroid (PTH)/PTH-related peptide receptor immunoreactivity and PTH binding in opossum kidney cells by PTH and dexamethasone.

Recent data have shown that PTH down-regulation of its receptor on opossum kidney (OK) cells is not associated with any change in the steady state level of the PTH/PTH-related peptide (PTHrP) receptor messenger RNA. For analysis of down-regulation of the PTH/PTHrP receptor in OK cells, the present work uses a specific receptor anti-serum, SR-2, that is useful for detection and quantification of PTH/PTHrP receptor immunoreactivity on intact cells bearing the opossum PTH/PTHrP receptor. SR-2 specifically binds to COS-7 cells transiently expressing the opossum PTH/PTHrP receptor complementary DNA (OK-O), to LLCPK1 cells stably expressing the recombinant opossum PTH/PTHrP receptor (AOK cells), and to OK cells expressing endogenous PTH/PTHrP receptors, but not to mock-transfected COS-7 cells or untransfected LLCPK1 cells. SR-2 binding was also linearly correlated with PTH binding in COS-7 cells transfected with different amounts of OK-O plasmid DNA. Treatment with PTH (100 nM) for 4 and 6 h did not significantly down-regulate the PTH/PTHrP receptor immunoreactivity, although PTH binding was decreased to 51% and 49% of control, respectively, and PTH-stimulated cAMP accumulation was decreased to 27% and 28% of control, respectively. Treatment with PTH (100 nM) for 24 and 48 h significantly decreased PTH binding to 51% and 60% of control and decreased PTH/PTHrP receptor immunoreactivity to 68% and 58% of control, respectively. Incubation of OK cells with 0.1 nM to 1 microM PTH for 4 h did not down-regulate the PTH/PTHrP receptor immunoreactivity, although PTH binding was decreased dramatically. Scatchard blot analysis revealed that the binding affinity was decreased by 7-fold in OK cells treated with PTH for 4 h without change in receptor number. Conversely, treatment of OK cells with PTH for 24 h resulted in a parallel decrease in both receptor number and receptor immunoreactivity without any change in receptor binding affinity. Treatment of OK cells with dexamethasone (0.1 nM to 1 microM) had no effect on PTH binding or PTH/PTHrP receptor immunoreactivity. Incubation of OK cells with both dexamethasone (1 microM) and PTH (0.1 nM to 1 microM), however, caused a significantly greater down-regulation of both PTH binding and PTH/PTHrP receptor immunoreactivity than in cells treated with PTH alone. These data indicate that during the first 4 h of exposure of OK cells to PTH, PTH/PTHrP receptors remain on the cell surface but have lowered affinity to bind the ligand and that dexamethasone potentiates the effect of PTH on PTH/PTHrP receptor down-regulation in OK cells.

Animals↗
PubMed1994

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 VO2 in in undisturbed animals was 7.73 +/- 0.40 ml O2 kg-1 min-1 (5.67 +/- 0.20 ml O2 kg-1 min-1 during light and 9.84 +/- 0.81 ml O2 kg-1 min-1 during dark hours, mean +/- S.E.M., N = 6). Net cost of locomotion ranged between 6.16 and 8.99 J kg-1 s-1 as speed increased and was always higher than for an average mammal of equivalent mass. Net cost of transport decreased as speed increased and was 15-80% higher than for an average mammal. During aerobic locomotion, most of the energy was provided by carbohydrate oxidation, which accounted for 60-95% of VO2 as speed increased. Glycogen and triglyceride reserves were quantified in the major storage depots to estimate potential survival time and travelling distance. Enough metabolic fuel was stored to survive for at least 1 week without eating, and 95% of this energy was in adipose tissue triglycerides. However, maximal travelling distance was less than 2 km because opossum locomotion is mainly supported by carbohydrate reserves, which represented only 4% of the available energy. We conclude that aerobic, ground locomotion of Virginia opossums is associated with two major energetic handicaps because their particularly high cost of transport and the nature of the main oxidative fuel they consume are both incompatible with prolonged locomotion.

Adipose Tissue↗
PubMedDate not supplied

Isolation of Salmonella enterica and serologic reactivity to Leptospira interrogans in opossums (Didelphis virginiana) from Yucatán, México.

The presence of Salmonella enterica and serologic evidence of infection by Leptospira interrogans, were detected in the opossum Didelphis virginiana in a semi-urban locality of the Yucatán State, México. Ninety-one opossums were captured during the period April 1996 and May 1998. From a total of 17 feces samples, four Salmonella enterica subsp. enterica serotypes (Sandiego, Newport, Anatum, and Minnesota), and one Salmonella enterica subsp. arizonae serovar O44:Z4,Z23:- were isolated. Some opossums presented mixed infections. From 81 sera samples, four (4.9%) were positive to antibodies to Leptospira serovars pomona and wolfii. Both animals infected with Salmonella enterica and those serologically positive to Leptospira interrogans were captured in peridomestic habitat. Opossums infected with Salmonella enterica, were captured in dry season, and those seropositive to Leptospira interrogans during the rainy season. The implications of infection and reactivity of these zoonotic pathogens in D. virginiana in the Yucatan state are briefly discussed.

Animals↗
PubMedDate not supplied

[Natural infection of the anal glands of the opossum (Didelphis albiventris) by Trypanosoma cruzi in the municipality of Bambuí--MG, Brazil].

Out of 87 opossums, Didelphis albiventris, captured in the Bambuí area (Minas Gerais State), 32 (36.7%) were found infected by Trypanosoma cruzi; the rates varied according to whether the specimens originated from sylvan, rural peridomiciliar or urban surroundings, being 34.9, 81.8 and 7.7 respectively. From 20 of the infected opossums the anal glands were repeatedly examined and found positive in only one (5%) specimen (GA 9), with 7 positive examinations out of 17 performed through an 18-months periods. Material from these glands produced patent parasitemia in opossums and sub-patent infections in mice. Isolates from the opossum GA 9, obtained through xenodiagnoses and hemocultures and from cultures of the infected anal glands fitted into zymodeme Z1.

Anal Sacs↗
PubMed2002

Prevalence of agglutinating antibodies to Sarcocystis neurona in skunks (Mephitis Mephitis), raccoons (Procyon lotor), and opossums (Didelphis Virginiana) from Connecticut.

Equine protozoal myeloencephalitis is the most important protozoan disease of horses in North America and is usually caused by Sarcocystis neurona. Natural cases of encephalitis caused by S. neurona have been reported in skunks (Mephitis mephitis) and raccoons (Procyon lotor). Opossums (Didelphis spp.) are the only known definitive host. Sera from 24 striped skunks, 12 raccoons, and 7 opossums (D. virginiana) from Connecticut were examined for agglutinating antibodies to S. neurona using the S. neurona agglutination test (SAT) employing formalin-fixed merozoites as antigen. The SAT was validated for skunk sera using pre- and postinfection serum samples from 2 experimentally infected skunks. Of the 24 (46%) skunks 11 were positive, and all 12 raccoons were positive for S. neurona antibodies. None of the 7 opossums was positive for antibodies to S. neurona. These results suggest that exposure to sporocysts of S. neurona by intermediate hosts is high in Connecticut. The absence of antibodies in opossums collected from the same areas is most likely because of the absence of systemic infection in the definitive host.

Agglutination Tests↗
PubMed2003

Seroprevalence of Neospora caninum and Toxoplasma gondii antibodies in the South American opossum (Didelphis marsupialis) from the city of São Paulo, Brazil.

Antibodies to Neospora caninum and Toxoplasma gondii were assayed in sera of 396 opossums (Didelphis marsupialis) from the city of São Paulo, Brazil. Antibodies to N. caninum were assayed using the indirect immunofluorescent antibody test (IFAT). Antibodies (IFAT, approximately 1:25) to N. caninum were found in 84 opossums (D. marsupialis) in titers of 1:25 in 46, 1:50 in 20, 1:100 in 17, and 1:400 in 1. Antibodies to T. gondii were assayed with the modified agglutination test (MAT) and the IFAT. Antibodies to T. gondii (MAT, approximately 1:25) were found in 82 (20.4%) of the 396 opossums, in titers of 1:25 in 24, 1:50 in 26, 1:100 in 18, 1:200 in 13, and 1:800 in 1. The IFAT antibodies to T. gondii were found in 148 of 396 opossums, in titers of 1:16 in 41, 1:32 in 23, 1:64 in 13, 1:128 in 6, 1:256 in 20, 1:512 in 17, 1:1,024 in 10, 1:2,048 in 10, 1:4,096 in 7, and 1:8,192 in 1. This is the first report of N. caninum and T. gondii infections in D. marsupialis.

Agglutination Tests↗
PubMed1982

The notochord of the newborn opossum and its fate during postnatal development.

The notochord was examined by light, transmission and scanning electron microscopy, in 25 pouch young opossums (Didelphis virginiana) ranging in age from 6 hr to 25 days post natum. In the newborn opossum, the notochord forms a thin cylinder within developing vertebral centra and presents diamond-shaped expansions in regions of the developing intervertebral discs. The opossum notochord differs from that of other species in that it appears to consist of a heterogeneous population of light and dark cells, and also in the thinness of the notochordal sheath which never attains the degree of development seen in other animals. The sheath is made up of thin cytoplasmic processes which arise both from the light and dark cells. The processes cross a mucopolysaccharide-filled space and then expand to form a thin cytoplasmic sheath that forms the external boundary of the space. The matrix of the cartilage immediately adjacent to the cytoplasmic sheath shows an increased concentration of microfilaments as compared to the cartilage further from the notochord. During postnatal development the notochordal tissue in the centra of the vertebral bodies decreases, while in the regions of the developing discs, there is a corresponding increase. At the end of the first week, notochordal tissue in the vertebral centra is represented only by a thin cylinder of mucopolysaccharide which contains cell fragments. In subsequent weeks, as ossification of the centra occurs, both the cartilage and notochordal tissue are replaced by bone. Notochordal tissue in the intervertebral regions contributes to the formation of the nucleus pulposus of the intervertebral discs. Despite its short gestation period of only 12 1/2 days, the basic structure and fate of the notochord in the opossum is similar to that of other mammals.

Aging↗
PubMed2002

Experimental inoculation of North American opossums (Didelphis virginiana) with Mycobacterium bovis.

Eight North American opossums (Didelphis virginiana) were inoculated with 1 x 10(5) colony forming units of Mycobacterium bovis to investigate their potential as reservoir hosts for bovine tuberculosis in Michigan. Four animals received this dose orally and four were inoculated intramuscularly (i.m.). In each group, two animals were euthanized 1 mo postinoculation (PI) and two at 2 mo PI. Four control animals were housed separately and sacrificed in the same manner as those inoculated. One of four orally inoculated opossums and three of four i.m.-inoculated opossums were positive for M. bovis by culture of tissues obtained at necropsy. The oral recipient had positive cultures from intestine and pooled lymphoid samples. Pooled lymphoid samples were positive in three i.m.-inoculated animals and two of these also had positive liver and lung cultures. One animal with gross and histologic lesions compatible with tuberculosis had negative tissue cultures. The findings suggest that opossums are susceptible to M. bovis infection by multiple routes, although their relative susceptibility compared to true reservoir hosts appears to be low.

Animals↗
PubMed2002

Normal conjunctival flora in the North American opossum (Didelphis virginiana) and raccoon (Procyon lotor).

We documented the normal conjunctival bacterial flora from 17 opossums (Didelphis virginiana) and 10 raccoons (Procyon lotor) trapped in Manhattan, Kansas (USA) from November 1999 to January 2000. Both raccoons and opossums were free of apparent ocular disease. The inferior conjunctival sacs of each animal were swabbed for aerobic bacterial and Mycoplasma culture and polymerase chain reaction (PCR) for Mycoplasma and Chlamydia detection. All conjunctival samples were positive for one or more species of aerobic bacteria. The most common isolate from opossums was Staphylococcus spp. Other isolates included Streptococcus spp., Bacillus spp., Corynebacterium spp., and Enterococcus faecalis. The most common isolates in raccoons was Bacillus spp. Other isolates included Streptococcus spp., Staphylococcus spp., non-hemolytic Escherichia coli, and Enterococcus faecalis. Mycoplasma culture was negative in samples from opossums and raccoons. Evidence of Mycoplasma and Chlamydia presence was detected by PCR.

Animals↗
PubMed1991

Characterization of the alpha-2C adrenergic receptor subtype in the opossum kidney and in the OK cell line.

The alpha-2 adrenergic receptors have been subdivided into two pharmacological subtypes known as alpha-2A and alpha-2B. The OK cell, a cell line derived from an opossum kidney, expresses an alpha-2 adrenergic receptor which has pharmacological characteristics different from both the alpha-2A and alpha-2B subtypes, and thus may be a third subtype. To test this hypothesis, we compared the affinities (Ki values from radioligand binding) of 49 drugs in the OK cell with their affinity for the alpha-2A (HT-29 cells) and alpha-2B (neonatal rat lung) adrenergic receptor subtypes. Eight drugs (spiroxarine, prazosin, WY 27127, L-657,743, ARC 239, akuammigine, rauwolscine and oxymetazoline) were identified whose Ki differed by 10-fold or more between the OK cells and HT29 cells. Five drugs (BAM 1303, raubasine, WB 4101, akuammigine and rauwolscine) differentiated, by at least 10-fold, between OK cells and neonatal rat lung. Correlations of pKi values between the OK cell and tissues or cell lines expressing either the alpha-2A or alpha-2B subtypes were poor, confirming that the OK cell receptor could not be classified as either alpha-2A or alpha-2B. In contradistinction, there was a good correlation between pKi values for the OK cell line and opossum kidney showing that they express the same subtype. In addition, ratios of subtype-selective drug Ki values were similar for the OK cell and opossum kidney, but different from other tissues or cell lines expressing either the alpha-2A or alpha-2B subtypes. We conclude that the OK cell line and opossum kidney express a novel subtype of alpha-2 adrenergic receptor which we term the alpha-2C subtype.

Animals↗
PubMed1989

Cyclic GMP: a potential mediator of neurally- and drug-induced relaxation of opossum lower esophageal sphincter.

Electrical field stimulation (EFS) of isolated strips of opossum lower esophageal sphincter (LES) produced a relaxation that was accompanied by an elevation of intracellular cyclic GMP content. In order to compare the time dependence of the EFS-induced relaxation with that of the elevation of cyclic GMP, the ability of EFS to produce relaxation and increase cyclic GMP was measured. The results of these experiments showed that cyclic GMP content increased before the onset of relaxation. Cumulative addition of atriopeptin II, an activator of particulate guanylate cyclase, produced a concentration-dependent relaxation of this tissue and increased cyclic GMP content. In other experiments, zaprinast, an inhibitor of a cyclic GMP selective-phosphodiesterase, produced a concentration-related relaxation of opossum LES and increased cyclic GMP content. However, pretreatment with zaprinast (3 microM) did not potentiate the EFS-induced relaxation or the increase in cyclic GMP content. At this concentration, however, zaprinast increased the basal content of cyclic GMP. Finally, 8-Br-cyclic GMP, a membrane-permeable analog of cyclic GMP, produced a concentration-dependent relaxation of isolated strips of opossum LES. In conclusion, these data extend the initial findings that an elevation in cyclic GMP content is associated with relaxation and suggest that cyclic GMP is a potential intracellular messenger of neurally- and drug-induced relaxation of opossum LES.

Animals↗
PubMed1989

Antigenic relationship among antihemorrhagic factors from snake and opossum plasmas.

Immunological relationships among antihemorrhagic factors (AHF) present in the plasma of different snakes and a mammal (opossum) were studied. Antibodies were prepared against purified Bothrops jararaca and Didelphis marsupialis aurita (opossum) AHF. The antigen-antibody reaction was determined by direct ELISA and by the competition of homologous antigen-antibody reaction with a heterologous competitor antigen. Plasmas from several snakes and from opossum were used as antigens. Anti-AHF (B. jararaca) reacted only with snake plasmas. Antibody against opossum AHF was detectable only when the homologous antigen was used. Differences in the reactivity of snake plasmas with antibodies against B. jararaca were demonstrable only when a competition assay was used: B. alternatus showed a reaction pattern similar to that of B. jararaca while Crotalus durissus terrificus and the nonvenomous snake, Wanglerophis merremii, presented reduced reactivity.

Animals↗
PubMed1986

Enteroendocrine cells in the developing opossum stomach.

The distribution of enteroendocrine cells showing immunoreactivities to four peptides and one amine was examined in the gastric mucosa of the opossum during postnatal development using specific immunocytochemical methods. Gastrin-, BPP-, glucagon-, somatostatin- and 5-HT-immunoreactive cells were identified in the gastric mucosa of the newborn opossum. Gastrin-immunoreactive cells were restricted to the epithelial lining of the pylorus; glucagon-immunoreactive cells were seen only in the epithelium of the fundus. Somatostatin- and 5-HT-immunoreactive cells were found in the epithelium of both fundic and pyloric regions. BPP-immunoreactive cells were the most numerous endocrine cell type seen in the gastric epithelium of the newborn opossum and although found mainly at the confluence of the fundic and pyloric regions, were confined primarily to the fundus in the one week old opossum and all older animals. A marked increase in all five immunoreactive cell types was seen by the end of the first postnatal week. Gastrin-immunoreactive cells were the most numerous at this time and exceeded adult numbers. Both glucagon- and BPP-immunoreactive cells were confined to the fundic glands of older animals and showed the same pattern of decline with age. Somatostatin- and 5-HT-immunoreactive cells showed a shift in population from the fundus to the pylorus with age and together with gastrin-immunoreactive cells were restricted to a narrow zone at the bottoms of the gastric pits and the upper parts of the pyloric glands.

Animals↗
PubMed1988

Valvular endocarditis associated with experimental Erysipelothrix rhusiopathiae infection in the opossum (Didelphis virginiana).

Intravenous inoculation of a wild type isolate of Erysipelothrix rhusiopathiae in opossums resulted in valvular endocarditis in all infected animals. Opossums were inoculated once a week for 3 weeks. Lesions became visible with cardiac ultrasound by week four post-inoculation. Opossums remained clinically normal throughout the experiment, and preinfection body weight was maintained. Other lesions of chronic erysipelas including skin necrosis and arthritis were not found in infected opossums.

Animals↗
PubMed1984

The effect of 16, 16-dimethyl prostaglandin E2 on experimental bile reflux pancreatitis in the opossum.

Pharmacological attempts to alter the course of experimental pancreatitis in the opossum were made using synthetic 16, 16-dimethyl prostaglandin E2 (16, 16-dm PGE2). Anatomically, the opossum has an elongated ampulla resulting in a supraduodenal pancreatic duct-common bile duct junction allowing for bile reflux pancreatitis to be produced by ligating the distal common bile duct. Preliminary evaluation demonstrated that at 72 hours common bile duct ligation distal to the pancreatic duct orifice produced pancreatitis comparable in severity to that produced by a Pfeffer loop. When the oppossum distal common bile duct was ligated, serum amylase concentrations progressively increased from control values of 182 +/- 43 to 742 +/- 62 Somogyi units/dl at 5 hours. Administration of 0.2 microgram-kg-1-min-1 16, 16-dm PGE2 significantly decreased the hyperamylasemia associated with bile reflux pancreatitis and, in addition, decreased the pancreatic gland weights when compared to control values. Subsequent evaluation of the administration of 75 micrograms-kg-1 16, 16-dm PGE2 every 12 hours for 72 hours to opossums with distal common bile duct ligation demonstrated no significant differences in serum amylase concentrations when compared to control values. Histologic evaluation of the pancreas glands at 72 hours demonstrated increased glandular integrity when the pancreas glands from the opossums receiving 16,16-dm PGE2 were compared to the glands subjected to distal common bile duct ligation alone. This report identifies several favorable characteristics in the course of experimental pancreatitis associated with the administration of a synthesis PGE analog at the onset of the inflammatory process.(ABSTRACT TRUNCATED AT 250 WORDS)

16,16-Dimethylprostaglandin E2↗
PubMed1982

Effect of gastrointestinal hormones on the biliary sphincter of the opossum.

The smooth muscle sphincter enveloping the terminal portion of the common bile duct in the opossum exhibits spontaneous electrical activity and simultaneous rhythmic contractions. The aim of our study was to define the influence of four gastrointestinal hormones on biliary sphincter electrical and mechanical activity. An array of five monopolar extracellular electrodes was placed along the opossum choledochal sphincteric smooth muscle and contiguous duodenum. A catheter in continuity with a pressure transducer, drop counter, and saline reservoir was placed in the common duct for simultaneous measurement of ductal pressure and flow. The cystic and distal common hepatic ducts were then ligated to isolate the common bile duct from the gallbladder and liver. In each opossum, biliary sphincteric and duodenal myoelectric activity, common bile duct and gallbladder pressure, and common duct flow were recorded simultaneously before and after the intravenous administration of five different doses of an enteric hormone. Ten animals were given 0.1-10.0 international dog units per kilogram body wt of cholecystokinin, 10 received 0.01-1.00 microgram/kg body wt of cholecystokinin-octapeptide, 10 were given 0.1-10.0 micrograms/kg body wt of secretin, and 5 were given 0.1-10.0 micrograms/kg body wt of pentagastrin. Cholecystokinin, cholecystokinin-octapeptide, and pentagastrin all effected a significant increase in sphincter electrical spike activity and common duct pressure with a decrease in common duct flow. This contractile response was consistent at a wide range of hormonal levels. Secretin had little effect on biliary pressure, flow, and myoelectric activity. The data lend support to the concept that cholecystokinin and gastrin contract the biliary sphincter, metering bile flow at the time of gallbladder emptying in the opossum.

Action Potentials↗
PubMedDate not supplied

Natural resistance of opossum (Didelphis marsupialis) to the mapanare (Bothrops lanceolatus) snake venom.

The inactivation of local and general effects of the Mapanare (Bothrops lanceolatus) venom by Opossum's (Didelphis marsupialis) serum fractions was tested using an in vivo assay and an in vitro preincubation experiment. A serum fraction of the Opossum serum has been obtained by immunochemical purification. It is only present in opossum's protective opossum serum fraction (F-0.1).

Animals↗
PubMed1995

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 region suitable for a species-specific amplification primer. The S. neurona SSURNA primer was used in a polymerase chain reaction (PCR) assay for the purpose of identifying this organism in feces and intestinal digest of wildlife specimens. Sporocysts were isolated from 4 raccoons (Procyon lotor), 2 opossums (Didelphis virginiana), 7 skunks (Mephitis mephitis), 6 cats (Felis catus), 1 hawk (Accipiter sp.), and 1 coyote (Canis latrans). The S. neurona SSURNA PCR assay and a control PCR assay using protist-specific primers were applied to all sporocyst DNA samples. All sporocyst DNA samples tested positive on the control assay. The SSURNA PCR assay yielded a 484-bp product only when applied to opossum samples. The SSURNA gene of both opossum sporocyst samples was sequenced to determine its relationship to the S. neurona SSURNA gene. The sequence had 99.89% similarity with S. neurona. This suggests that opossums are the definitive host of S. neurona.

Animals↗