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The aim of the study was to compare the effectiveness of calves infected with bovine leukaemia virus with that gained after the administration of FLK-BLV cells and lymphocytes of a leukaemic cow. The experiment was carried out on two groups of animals aged from 6 to 8 months. Each group of the cows was infected intravenously with the same dose of 1.2 x 105 FLK cells or lymphocytes. The third group involving two animals served as the control one. The sera of calves were tested at 2, 4, 6 weeks and 2, 3, 4 and 5 months after infection. The geometric mean titer of FLK infected calves was 3.9; 50.8; 101.6; 80.0; 64.0; 63.5 and 51.2 and in the group infected with lymphocytes - 0.0.; 511.6; 776.0; 2051.0; 1559.0; and 504.1, respectively. Serological examinations by means of the ELISA test revealed specific antibodies at two weeks after infection in the FLK group and at four weeks in the lymphocyte treated group. The highest titers were observed at six weeks in the sera of calves of the first group and at two months in case of the second group. It was found that the highest titer of antibodeis in the calves infected with lymphocytes was 20-fold higher than that of FLK cells infected animals.
The influence of non-cytopathic and cytopathic strains of M-PI₃ parainfluenza virus on bovine leukaemia virus (BLV) replication was assessed. It was found that enzymatic activity of BLV revertase from FLK cells was 21 471 cpm, 23 127 cpm, 12 406 cpm and 2506 cpm after 24, 48, 72 and 96 hours, respectively. In FLK cells infected additionally with the cytopathic strain M-PI₃ the number of cpm was lower than in that of control cells (FLK uninfected with M-PI₃) and was 16 367, 17 329, 20 987 and 4637 after 24, 48, 72 and 96 hours, respectively. The highest activity of BLV revertase from FLK cells infected also with the non-cytopathic strain of M-PI₃ was obtained after 24 and 48 h; the findings were: 26 451 cpm and 28 319 cpm, respectively. This activity after 72 h was 18 952 cpm and after 96 h 3421 cpm. The yield of BLV from FLK cells infected additionally with the non-cytopathic strain M-PI₃ was higher by 37,9 per cent after 24 h p.i. and by 38,8 per cent after 48 h p.i. than in that received from FLK control cels. The results have indicated the synergetic activity of BLV and non-cytopathic M-PI₃ viruses cultivated in FLK cells.
The protein antigens of BLV were detected in the lysates of bovine lymphocytes stimulated in vitro using the Western blot method. Specific antibodies against BLV were detected in the sera of animals by the ELISA test. Protein bands of the molecular weight 72, 51, 35 and 24 kD were detected by the rabbit antiserum against BLV in the blots from infected lymphocytes and FLK cells. Thе proteins mentioned above were not detected in the lysates of lymphocytes of uninfected animals. Densitometry analysis of immunoblots from FLK cells indicated that a minimal amount of 100 ug of gp51 viral protein can be discovered. The presence of BLV antigens and specific antibodies were detected in 18 of 25 animals. The antibodies were also found in four cows of the remaining seven animals whose lymphocytes were free from BLV proteins.
Using the PCR method the proviral sequence of the bovine leukaemia virus was detected in the peripheral blood leukocytes of cattle from an infected herd. BLV antibodies were determined by the ELISA and AGID tests. PCR amplification was performed with one set of 20-mer oli- gonucleotyde primers that should produce a 364 bp fragment of BLV-DNA located in the gag gene region. The reaction products were analyzed in 1 A°/< agarose, blatted to Hybond-N filter by the Southern method and probed with an 8.3 kb Sac I fragment of BLV, labelled with di- goxigenin -dVTP. In 23 animals examined by PCR the presence of proviral DNA was found in all serologically positive animals and also in three serologically negative animals. BLV-DNA was not detected in only one seropositive individual. The presented findings indicate that the determination of the proviral DNA of BLV using the PCR method is more sensitive than serological tests and it should be beneficial for the diagnosis of cattle infection with BLV.
The aim of the studies was to determine the usefulness >f the ELISA test to detect antibodies against EBB virus n the milk of cows from the Wroclaw voivodship, where he test is to be used for the routine examination of milk. The results of this test were compared with blood sera ;xaminations by the ID test. The studies were done on 29 nilk samples including 17 bulk milk samples. A kit of ,Leukotest” acc. to Bommeli was used. Except for 4 cases, he results of both tests were identical. Positive results in he ELISA test obtained with milk samples negative in he ID test point to a high sensitivity of ELISA. The results obtained confirmed the usefulness of the ID :est with blood sera to detect and control EBB. On the 'arms where the program of EBB eradication has been ntroduced, the latest negative results in the ID test have jeen in most cases confirmed by ELISA. ELISA, as one )f the serological diagnostic methods, can be used to :xamine bulk milk in large farms free of EBB.
Infection of calves with parainfluenza virus (PI₃) and bovine leukemia virus (BLV) induced a clear immunologic response. A high titre of HI type antibodies (1:1280-1:2560) 2 weeks after the injection (p.i.) of PI₃ has been determined. The antibodies persisted at the level of 1:1280-1:2560 for one month and then steadily decreased. The Geometric Mean Titre (GMT) of antibodies for PI₃ virus in this group of calves after 2, 4 and 6 weeks and after 2, 3 and 4 months p.i. was 2250, 1810, 2560, 905, 240 and 323.8, respectively. In calves infected exclusively with PI₃ virus the positive HI titres were 1:80-1:160 two weeks p.i., but the highest titres (1:320-1:1280) were noted at 4 and 6 weeks after infection. Titres 1:20-1:80 were noted at the 4th month after infection. The GMT of antibodies in these calves was 95.1, 678, 1280, 269, 170 and 33.6, respectively. The level of antibodies for calves infected with PI₃ virus and BLV was two- or threefold higher than that in animals infected with PI₃ virus only. The HI titres were 23-fold higher in these animals at 2 weeks p.i. The simultaneous infection of calves with PI₃ virus and BLV significantly enhances immune response and the level of HI type antibodies for PI₃ virus.
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