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  • 1
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The interval after infection when bluetongue virus (BTV) was present in the blood of calves inoculated with BTV serotype 10 (BTV 10) was evaluated by virus isolation (VI) in embryonated chicken eggs (ECE), BTV-specific polymerase chain reaction (PCR), and in vitro blood feeding of vectorCulicoides variipennis (C.v.) sonorensis. BTV nucleic acid was detected by PCR in blood cells for 16 to 20 weeks after infection whereas infectious virus was detected by VI in ECE for 2 to 8 weeks. BTV was detected in calf blood by in vitro feeding ofC.v. sonorensis for only 0 to 2 weeks after inoculation of calves with BTV 10. Selected bloods which were positive by PCR analysis but not by VI in ECE were not infectious for sheep. The data are consistent with the hypothesis that prolonged viremia in BTV-infected cattle results from association of the virus with blood cells, especially erythrocytes. The fact that calf blood that contained viral nucleic acid as determined by PCR analysis, but not infectious virus as determined by VI in ECE, was not infectious for either the insect vector or sheep suggests that cattle whose blood contains BTV nucleic acid but not infectious virus are unimportant to the epidemiology of BTV infection.
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  • 2
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Some strains of bluetongue virus cause congenital brain damage in bovine and ovine fetuses, as well as in neonatal mice. Two strains of bluetongue virus serotype 11 (UC-2 and UC-8) which differ in neuroinvasiveness were used to determine the biological basis for this difference. UC-2 and UC-8 were inoculated subcutaneously into newborn mice and virus was titrated from blood, plasma and brain tissues over 14 days. For the invasive UC-8 strain, 50–175 plaque forming units of virus per ml was found associated with the blood cells and no virus was detected in the plasma. The virus was detected in the brain at day one post inoculation, and again at day 7, increasing to day 11. The results indicate that UC-8 was able to reach the brain soon after inoculation and to replicate and/or remain in the blood circulation better than UC-2. Immunohistochemical examination of frozen brain sections revealed a sudden, multifocal appearance of UC-8 at day 9, with more viral antigen seen at days 11 and 13, which was barely detected by day 15. Viral antigen was not associated with blood vessels in the brain, indicating that the viral invasion was not from infected vascular endothelium. No virus was detected in the mice infected with strain UC-2.
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  • 3
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary.  Neurotropism of bluetongue virus (BLU) has been demonstrated in the developing brain of fetal ruminants and neonatal mouse models. Two strains of BLU serotype 11, UC8 and UC2, differentiated by their electrophoretic characteristics and abilities to cause brain lesions in bovine fetuses and neonatal mice were investigated to determine differences in tissue distribution in new born mice following subcutaneous inoculation. Tissue analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) showed selective distribution of both BLU strains to the brain and spleen as early as 3 h post-inoculation (PI) but viral RNA was not detected in the blood or other tissues for the duration of the 15 day experiment. UC2 persisted within the brain and spleen until 9 h PI without development of CNS lesions. In contrast, UC8 persisted within the spleen for 24 h and in the brain through the end of the experiment. UC8 infected mice developed necrotizing lesions throughout the cerebrum and cerebellum that were most severe on PI days 11 and 13. Immunohistochemical staining for BLU identified infected cells within the brains of UC8 inoculated mice before inflammatory lesions were present and gave supportive evidence of the ability of UC2 to infect brain cells. Our results show that both UC8 and UC2 selectively target the brain and spleen in neonatal mice early after inoculation and suggest that the differences in neurovirulence between these strains are due to differences in replicative efficacy within host target cells.
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  • 4
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Partial cDNA clones representing 47%, 96%, and 98% of genome segments 7, 9, and 10, respectively, of a US bluetongue virus (BLU) 11 virulent strain were used to study, for the first time, the genetic relationships between Israeli BLU proto-serotypes and field isolates, and US BLU proto-serotypes. Their usefulness as group-specific identification probes was also determined. The viral nucleic acid was extracted from the infected cells and the purified dsRNA genome segments were fractionated by polyacrylamide gel electrophoresis, transferred to a nylon membrane and hybridized to the32P labeled DNA probes. The three probes recognized all the samples tested. Genome segment 7, that code for the mayor inner capsid protein VP7, showed the most variation in the hybridization signal with the US proto-serotypes and all the Israeli samples studied. The genome segments 9 and 10 that code for the minor inner capsid protein VP6 and the nonstructural protein NS3, respectively, were highly conserved in all the samples tested despite their distant geographical regions of origin. The last two mentioned clones showed to be good group-specific probes for the identification of BLU samples from Israel and United States. The obtained cloned genetic probes were also tested against US epizootic haemorrhagic disease virus (EHDV) serotype 1 and 2 viral dsRNA, a distantly related orbivirus. None of them hybridized with the viral dsRNA of these two viruses.
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  • 5
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Although the simultaneous infection of individual animals with more than one serotype of bluetongue (BLU) virus has been documented, the humoral immune responses elicited by viral reassortants recovered from the host has not been reported. This study characterized the serologic responses of a bull infected with BLU serotypes 11 and 17. Genome reassortants isolated from this bull over the course of 34 days were used. The genomic profiles of the reassortants were characterized by polyacrylamide gel electrophoresis of viral double stranded RNA under reducing conditions using two concentrations of acrylamide. This approach permitted the detection of three novel genome segments among the isolates. Selected reassortants were tested in plaque neutralization assays, using serum samples collected from the bull at different times during the infection. To better define the role of BLU virus outer capsid proteins in viral antigenicity, the neutralizing antibody titer curves of viral isolates that contained reassorted VP2 and VP5 were compared to those of the parental strains and of other reassortants. The present study reports the heterotypic pattern of neutralization of the bull sera against different reassortants recovered from this animal.
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  • 6
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The diagnostic potential of the polymerase chain reaction (PCR) for specific identification of epizootic hemorrhagic disease virus serotype 1 (EHDV-1) in cell culture and clinical specimens was evaluated. Using oligonucleotide primers, selected from genome segment 2 of EHDV-1 (New Jersey strain), the PCR-based assay resulted in a 862 base pair (bp) PCR product. EHDV-1 RNA from United States prototype serotype 1 and a number of EHDV-1 field isolates, propagated in cell cultures, were detected by this PCR based assay. The specific 862 bp PCR products were visualized on ethidium bromide-stained agarose gel. Identity of the PCR product was confirmed by chemiluminescent hybridization with non radiolabelled internal probe. Using chemiluminescent hybridization, the sensitivity of the PCR assay was 1.0 fg of virus RNA (equivalent to 60 virus particles). Amplification product was not detected when the PCR-based assay was applied to RNA from EHDV serotype 2 (EHDV-2); the United States bluetongue virus (BLU) prototypes serotypes 2, 10, 11, 13, and 17; total nucleic acid extracts from uninfected BHK-21 cell; or blood cells from calves and deer that were EHDV-seronegative and virus isolation negative. Application of this EHDV-1 PCR-based assay to clinical samples resulted in detection of EHDV-1 RNA from blood samples, collected from a calf experimentally infected with EHDV-1. The described PCR-based assay provides a simple, rapid, sensitive, specific and inexpensive method for specific identification of EHDV-1 infection in susceptible ruminants.
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  • 7
    ISSN: 1573-7446
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This short reveiw considers some of the more widely accepted biological actions of bacterial endotoxin. Early sections concern endotoxin chemical composition, assay techniques, and species variation in toxigenicity. Individual specific actions and classical endotoxin-induced phenomena are presented under headings of pyrogenic effect, hemodynamic effects, disseminated intravascular coagulation, complement system effects, induction of the generalized Shwartzman reaction, effects upon cellular constituents of blood, metabolic and endocrinologic effects, immunologic effects, nervous system effects, hepatic effects, and abortifacient action. The relationship of these effects to clinical manifestations is discussed where warranted.
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  • 8
    ISSN: 1573-7446
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Subpopulations of leukocytes have been characterized by using cell surface membrane markers, and attempts have been made to correlate membrane receptors with cellular function. Histamine receptors on cell membranes have been identified in the mouse, man and rhesus monkey by numerous methods. In this study, an immunofluorescent technique was used to identify and enumerate histamine-receptor leukocytes in the peripheral blood of cattle. This report appears to be the first documenting these cells in the bovine.
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  • 9
    ISSN: 1573-7446
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A mixed breed flock of lambs, consisting of Suffolks, Hampshires, Columbias and Finnish breeds, were vaccinated with binary ethylenimine inactivated bluetongue virus (BTV) serotypes 11, 17 and a mixture of 11 and 17 in aluminum hydroxide. Agar gel precipitin antibodies were used as an indicator of immunity. Sero-conversion of Hampshires and Suffolk lambs was poor at 43% as compared to 84% in the Columbia and Finn lambs. These results indicate a breed difference in immunological response to inactivated BTV vaccine.
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  • 10
    ISSN: 0145-305X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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