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Biomedical subjects

A R Doster

Publications and source records attributed to A R Doster.

At least 19 recordsLinked to original sources
PubMed2005

Biological responses to porcine respiratory and reproductive syndrome virus in pigs of two genetic populations.

One hundred pigs from the NE Index Line (NEI) and 100 Hampshire-Duroc cross pigs (HD) were inoculated intranasally with porcine respiratory and reproductive syndrome virus (PRRSV 97-7895 strain) at 26 d of age to determine whether genetic variation in response to PRRSV exists. An uninfected littermate to each infected pig served as a control. Pigs were from 163 dams and 83 sires. Body weight and rectal temperature were recorded, and blood samples were drawn from each pig on d 0 before inoculation and on d 4, 7, and 14 after inoculation. Pigs were sacrificed on d 14. Lung and bronchial lymph nodes were collected, placed in optimal cutting temperature compound, and frozen at -80 degrees C. The presence of PRRSV in serum and in lung tissue and bronchial lymph nodes was determined by isolation in cell culture. The presence of antibodies in serum collected on d 14 was determined by a commercial ELISA test. Lung tissue was examined microscopically and scored for incidence and severity of lesions (score of 1 to 3; 1 = no or few lesions, and 3 = severe interstitial pneumonia). Data were analyzed with a mixed model that included random sire and dam effects. The interaction of line x treatment was significant (P < 0.001) for weight change and rectal temperature. Un-infected HD pigs gained 0.67 kg more from d 0 to 14 and averaged 0.32 degrees C higher rectal temperature than uninfected NEI pigs (P < 0.001), whereas infected NEI pigs gained 0.34 kg more and had -0.54 degrees C lower temperature than infected HD pigs (P < 0.001). Viremic titer (cell culture infectious dose 50%/mL) was greater (P < 0.05) in HD than NEI at d 4 (10(4.52) vs. 10(4.22)), 7 (10(4.47) vs. 10(3.99)), and 14 (10(3.49) vs. 10(3.23)). Viral titer loads in lung (P = 0.11) and bronchial lymph nodes tended (P = 0.07) to be greater in HD than NEI pigs. Antibody signal-to-positive (S/P) ELISA ratios in infected pigs ranged from 0.18 to 3.38, and 88% had levels > or = 0.40, which is the positive threshold for this ELISA. The S/P range in uninfected pigs was 0 to 1.11, and 99% had levels < or = 0.40. Mean S/P ratio for infected pigs was 0.23 units higher in HD than in NEI (P < 0.001). The HD pigs had a greater incidence of interstitial pneumonia and 0.65 higher mean lesion scores than NEI pigs (P < 0.001). In summary, responses of pigs of the two lines to infection with PRRSV differed, indicating that underlying genetic variation existed.

Animals↗
PubMed2003

Vesicular stomatitis virus infection and neuropathogenesis in the murine model are associated with apoptosis.

This study examines apoptosis and viral neuropathogenesis in a murine model infected with vesicular stomatitis virus (VSV). VSV induces apoptotic cell death in cultured cell lines, raising the possibility that apoptosis of infected neurons and other target cells may contribute to disease and mortality. To determine whether or not VSV induces apoptosis in neural tissues, mice were inoculated intranasally with VSV. At 24, 48, 72, 96, and 120 hours postinfection, brain tissues were assayed for the presence of viral RNA by in situ hybridization and viral antigen by immunohistochemistry. Apoptosis was identified by in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling and electron microscopy. Viral replication and lesions were observed predominantly in central nervous system neurons. Apoptotic cell death was restricted to the same regions of the brain in which infected cells and tissue injury were identified. Results suggest that VSV-induced apoptosis is a mechanism causing cell death, tissue injury, and mortality in VSV-infected mice.

Animals↗
PubMed2001

Evidence for the localization of porcine reproductive and respiratory syndrome virus (PRRSV) antigen and RNA in ovarian follicles in gilts.

The pathogenesis of porcine reproductive and respiratory syndrome virus (PRRSV) infection in ovary was studied in sexually mature, cycling, nonsynchronized gilts infected with the PRRSV 16244B, a virulent field strain. Previous studies have shown that PRRSV can be isolated from ovaries and is transplacentally passed from gilts to the fetuses. The cause of infertility following PRRSV infection is not known. In this study, we identified the tropism of PRRSV in ovarian tissue from experimentally infected gilts in samples collected between 7 and 21 days postinfection (DPI). Tissues were collected and examined by virus isolation, in situ hybridization (ISH), immunohistochemistry (IHC), and double labeling to identify PRRSV-infected cell types. PRRSV was isolated in ovarian follicles at 7 days DPI. The IHC and ISH indicated that PRRSV-positive cells in ovaries were predominantly macrophages, which were numerous in atretic follicles. No evidence of infection and/or perpetuation of PRRSV in ova was observed, indicating that the female gonad is an unlikely site of persistence. No alteration of the normal ovarian architecture that would support a possible role of PRRSV infection in porcine female infertility was observed.

Animals↗
PubMed2000

Porcine gastric ulcer.

Ulceration of the pars esophagea in swine develops from a complex interaction of dietary particle size, gastric fluidity, dietary carbohydrate content, and presence of certain species of commensal gastric organisms capable of fermenting dietary carbohydrates. Unlike in humans, the significance of the role of Helicobacter sp. in development of porcine gastric ulcers is yet undefined. Management practices that limit the incidence and severity of gastric ulceration without interfering with growth performance appear to be the best option for control.

Animals↗
PubMed1999

North American and European porcine reproductive and respiratory syndrome viruses differ in non-structural protein coding regions.

Although North American and European serotypes of porcine reproductive and respiratory syndrome virus (PRRSV) are recognized, only the genome of the European Lelystad strain (LV) has been sequenced completely. Here, the genome of the pathogenic North American PRRSV isolate 16244B has been sequenced and compared with LV. The genomic organization of 16244B was the same as LV but with only 63.4% nucleotide identity. The 189 nucleotide 5' non-coding region (NCR) of 16244B was distinct from the LV NCR, with good conservation (83%) only over a 43 base region immediately upstream of open reading frame (ORF) 1a. Major differences were found in the region encoding the non-structural part of the ORF1a polyprotein, which shared only 47% amino acid identity over 2503 residues of the six non-structural proteins (Nsps) encoded. Nsp2, thought to have a species-specific function, showed the greatest divergence, sharing only 32% amino acid identity with LV and containing 120 additional amino acids in the central region. Nsps encoded by the 5'-proximal and central regions of ORF1b had from 66 to 75% amino acid identity; however, the carboxy-terminal protein CP4 was distinct (42% identity). The ORF 1a-1b frameshift region of 16244B had 98% nucleotide identity with LV. Consistent with previous reports for North American isolates, the six structural proteins encoded were 58 to 79% identical to LV proteins. The 3' NCR (150 nucleotides) was 76% identical between isolates. These genomic differences confirm the presence of distinct North American and European PRRSV genotypes.

5' Untranslated Regions↗
PubMed1999

Characterization of antibody response to porcine reproductive and respiratory syndrome virus ORF5 product following infection and evaluation of its diagnostic use in pigs.

The sensitivity and specificity of recombinant open reading frame 5 products used in the Western blotting assay for confirmation of porcine reproductive and respiratory syndrome virus (PRRSV) serologic status were evaluated. The recombinant antigen-based assays were specifically compared with a commercial enzyme-linked immunosorbent assay (ELISA) for PRRSV antibodies using 1) PRRSV antibody-negative reference sera (n = 30), 2) naturally infected pig sera (n = 40), 3) sequential sera obtained from 24 experimentally infected pigs, and 4) sera submitted to 3 state diagnostic laboratories (n = 200). The recombinant antigen assay yielded an average increased sensitivity of 10% over the commercial PRRSV ELISA. The negative controls (group 1 sera) showed no difference between the 2 assays. This comparison confirmed that the recombinant antigen-specific assay was more sensitive than the commercial ELISA and is well suited for routine confirmation of the presence of PRRSV antibodies.

Animals↗
PubMed1998

Apoptosis induced in vivo during acute infection by porcine reproductive and respiratory syndrome virus.

We studied apoptosis caused by porcine reproductive and respiratory syndrome virus (PRRSV) in vivo, focusing on the tissues that constitute the main targets for infection: lung and lymphoid tissues. Previous investigators have shown that the PRRSV glycoprotein p25, encoded by PRRSV open reading frame 5, induces apoptosis when expressed in COS-1 cells. Results of studies conducted in our laboratory indicate the simultaneous occurrence of PRRSV-induced alterations of spermatogenesis and apoptotic death of germinal epithelial cells in the testicle. In this study, the goal was to determine whether virus-induced apoptosis is a direct mechanism of cell death caused by PRRSV in infected pigs. Eight 3-week-old pigs were intranasally inoculated with PRRSV 16244B, a highly virulent field strain. Lung, tonsil, bronchial lymph node, spleen, and heart were assessed histologically at 4 and 7 days postinfection. To characterize PRRSV-infected cells and apoptotic cell death, we used immunohistochemical methods for detection of viral antigen, DNA electrophoresis for detection of DNA fragmentation, the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-fluorescein nick end labeling method for in situ detection of DNA strand breaks, and electron microscopy for ultrastructural morphologic studies. PRRSV infection resulted in widespread apoptosis in the lungs and lymphoid tissues of infected pigs. Virus infection-induced apoptotic cells were more abundant than PRRSV-infected cells in all tissues. DNA laddering was detected in lung and lymphoid tissues. However, double-labeling experiments demonstrated that the majority of apoptotic cells did not colocalize with PRRSV-infected cells. Our findings suggest the presence of an indirect mechanism in the induction of apoptosis for PRRSV.

Acute Disease↗
PubMed1997

Porcine reproductive and respiratory syndrome virus replicates in testicular germ cells, alters spermatogenesis, and induces germ cell death by apoptosis.

Like other arteriviruses, porcine reproductive and respiratory syndrome virus (PRRSV) is shed in semen, a feature that is critical for the venereal transmission of this group of viruses. In spite of its epidemiological importance, little is known of the association of PRRSV or other arteriviruses with gonadal tissues. We experimentally infected a group of boars with PRRSV 12068-96, a virulent field strain. By combined use of in situ hybridization and immunohistochemistry, we detected infection by PRRSV in the testes of these boars. The PRRSV testicular replication in testis centers on two types of cells: (i) epithelial germ cells of the seminiferous tubules, primarily spermatids and spermatocytes, and (ii) macrophages, which are located in the interstitium of the testis. Histopathologically, hypospermatogenesis, formation of multinucleated giant cells (MGCs), and abundant germ cell depletion and death were observed. We obtained evidence that such germ cell death occurs by apoptosis, as determined by a characteristic histologic pattern and evidence of massive DNA fragmentation detected in situ (TUNEL [terminal deoxynucleotidyltransferase-mediated digoxigenin-UTP nick end labeling] assay). Simultaneously with these testicular alterations, we observed that there is a significant increase in the number of immature sperm cells (mainly MGCs, spermatids, and spermatocytes) in the ejaculates of the PRRSV-inoculated boars and that these cells are infected with PRRSV. Our results indicate that PRRSV may infect target cells other than macrophages, that these infected cells can be primarily responsible for the excretion of infectious PRRSV in semen, and that PRRSV induces apoptosis in these germ cells in vivo.

Animals↗
PubMed1997

Detection of canine parvovirus in naturally infected dogs with enteritis and myocarditis by in situ hybridization.

An improved method for the diagnosis of canine parvovirus using in situ hybridization in standard formalin-fixed, paraffin-embedded tissue sections was developed. A digoxigenin-labeled probe complementary to DNA sequences that code for the entire sequence of the capsid protein VP-1 and the middle part of the sequence of the capsid protein VP-2 was designed. Specific histologic localization of canine parvovirus-infected cells was demonstrated in small intestine, tonsil, lymph node, thymus, spleen, heart, liver, and kidney from dogs diagnosed at necropsy with canine parvovirus infection. The in situ hybridization accurately pinpointed the specific sites of viral infection. The detection of canine parvovirus in liver, kidney, and heart tissues together in the same pups could represent an enhanced virulence of this strain of canine parvovirus and suggests a broadened tissue tropism not seen before in Korean strains of canine parvovirus.

Animals↗
PubMed1996

In vivo detection of porcine reproductive and respiratory syndrome virus RNA by in situ hybridization at different times postinfection.

We studied the distribution of porcine reproductive and respiratory syndrome virus (PRRSV) RNA in tissues by in situ hybridization at different times postinfection (p.i.). The probe used for in situ hybridization was prepared by reverse transcription of PRRSV RNA, followed by PCR amplification of the cDNA. The sequence amplified corresponded to 433 bp from PRRSV open reading frame 7, which is contained in the nucleocapsid protein gene and which is highly conserved in both European and American strains (H. Mardassi, L. Wilson, S. Mounir, and S. Dea, J. Clin. Microbiol. 32:2197-2203, 1994). An immunohistochemical technique was used to detect PRRSV antigen in tissue from virus-infected animals by using a monoclonal antibody specific for the PRRSV nucleocapsid protein (E.A. Nelson, J. Christopher-Hennings, T. Drew, G. Wensvoort, J.E. Collins, and D.A. Benfield, J. Clin. Microbiol. 31:3184-3189, 1993). The detection of PRRSV RNA was conducted in tissues of 6-week-old pigs that had been infected with one of three different field PRRSV isolates and collected at times ranging from 4 to 42 days p.i. Hybridization signals specific for PRRSV RNA were detected in lung, lymphoid tissues, alveolar macrophages (obtained by lavage at the time of necropsy), Peyer's patches, and kidney. The PRRSV-positive cells in these tissues appeared to be predominantly macrophages. In lung tissue we also obtained evidence suggesting the involvement of type II pneumocytes in the replication of PRRSV. During the acute period of infection there was a close correlation between the detection of RNA and the detection of nucleocapsid protein in individual cells. At later times p.i. (28 and 42 days p.i.), instead, more cells containing only PRRSV RNA than those containing PRRSV RNA and also expressing PRRSV nucleocapsid protein were detected. These results suggest that PRRSV RNA might persist in the tissues of infected animals for a longer time than PRRSV antigen expression.

Animals↗
PubMed1995

Certain canine weakly beta-hemolytic intestinal spirochetes are phenotypically and genotypically related to spirochetes associated with human and porcine intestinal spirochetosis.

Four canine weakly beta-hemolytic intestinal spirochetes associated with intestinal spirochetosis (IS-associated WBHIS) were compared with IS-associated human and porcine WBHIS and the type species for Serpulina hyodysenteriae and S. innocens by using phenotypic and genotypic parameters. The IS-associated canine, human, and porcine WBHIS belonged to a phyletic group distinct from but related to previously described Serpulina type species.

Animals↗
PubMed1995

Porcine reproductive and respiratory syndrome: NEB-1 PRRSV infection did not potentiate bacterial pathogens.

A 2-phase study was conducted to evaluate the ability of the NEB-1 strain of porcine reproductive and respiratory syndrome virus (PRRSV) to potentiate common bacterial pathogens of swine. In phase I, 25 of 50 4-5-week-old specific-pathogen-free (SPF) pigs were exposed to NEB-1 PRRSV (day 0). Seven days after virus inoculation, 8 groups received 1 of 4 bacterial pathogens: Haemophilus parasuis, Streptococcus suis, Salmonella cholerasuis, and Pasteurella multocida. The ability of NEB-1 PRRSV to produce clinical disease, viremia, neutralizing antibody, gross and microscopic lesions and to potentiate bacterial pathogens was assessed. Response to NEB-1 PRRSV was similar among inoculated pigs; prolonged hyperthermia, lethargy, mild to moderate dyspnea, and cutaneous erythema were consistent clinical signs. No clinical differences were observed in groups after bacterial challenge. Virus was isolated from serum at weekly intervals through the end of the study, and all PRRSV-inoculated pigs had seroconverted by study termination. Two of 5 pigs died in non-PRRSV-inoculated groups challenged with H. parasuis and Streptococcus suis. Mortality in PRRSV-infected pigs was limited to 1 of 5 pigs from the Salmonella cholerasuis-challenged group. Gross lesions were seen in pigs dying after inoculation in H. parasuis- and Streptococcus suis-inoculated groups, in Salmonella cholerasuis- and P. multocida-challenged pigs, and in 1 non-PRRSV-inoculated control pig. Microscopic lesions consisted of mild to moderate proliferative interstitial pneumonia, nonsuppurative myocarditis, lymphoid hyperplasia, and nonsuppurative encephalitis in PRRSV-inoculated pigs. Findings in phase I indicated that NEB-1 PRRSV does not potentiate bacterial disease while inducing consistent clinical signs, viremia, seroconversion, and microscopic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Laboratory findings associated with abomasal ulcers/tympany in range calves.

The etiology of abomasal ulcers/tympany was investigated in 48 animals from 36 ranches in Wyoming and Nebraska. Results indicate that subclinical trace mineral deficiencies of copper and/or selenium exist in the range cattle in west central Nebraska and Wyoming. Etiological agents most frequently incriminated by bacteriologic cultures and/or histopathic examination were Clostridium perfringens and Campylobacter species. Histopathologic evaluation of abomasums revealed 31 of 38 cases contained abundant gram-positive bacteria associated with the damaged abomasal mucosa. Campylobacter-like organisms were demonstrated in 9 of 38 cases using the modified Dieterle stain. Clostridium perfringens was isolated in 14 of 38 cases, and Campylobacter jejuni was recovered from 5 of 38 cases.

Abomasum↗
PubMed1990

Comparative pathogenicity of selected bovine viral diarrhea virus isolates in gnotobiotic lambs.

The infectivity and pathogenicity of selected bovine viral diarrhea virus (BVDV) isolates were determined in gnotobiotic, colostrum-deprived neonatal lambs. Five-day-old cesarean-derived gnotobiotic lambs were exposed to 1 of 10 BVDV isolates via aerosol suspension. These isolates were from tissues or secretions of calves or lambs affected with respiratory tract disease, weak neonatal calves, aborted bovine fetuses, or reference Singer or Draper BVDV. The pathogenicity of each isolate, relative to the others, was evaluated in lambs by measurement of the neutralizing antibody response, virus isolation from nasal secretions or tissues, and postmortem lesions. The BVDV isolates varied in their infectivity and pathogenicity. Singer, the cytopathic reference strain, was the most lymphotrophic isolate and stimulated the greatest neutralizing antibody response. Encephalitis was the most consistent lesion observed and was used as the final determinant of relative pathogenicity of the viruses. The most neuropathogenic isolates were the 2 viruses originating from lambs affected with respiratory tract disease, the 2 weak neonatal calf isolates, and 1 isolate from an aborted bovine fetus. The least pathogenic isolates were the 2 reference isolates, Draper and Singer; the 2 mucosal disease isolates; and 1 isolate originating from an aborted bovine fetus.

Animals↗
PubMed1989

Seminoma and parathyroid adenoma in a snow leopard (Panthera unica).

A seminoma and parathyroid adenoma were diagnosed in an aged snow leopard. The ultrastructural appearance of the seminoma was similar to that described in the dog and in man. The lack of significant amounts of rough endoplasmic reticulum, Golgi complexes and free ribosomes in the parathyroid adenoma suggested that it was non-functional. Parathyroid adenoma has not been previously described in a large wild feline.

Adenoma↗