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Biomedical subjects

F C Thomas

Publications and source records attributed to F C Thomas.

35 records · Page 2Linked to original sources
PubMed1982

Embryo transfer as a means of controlling the transmission of viral infections. I. The in vitro exposure of preimplantation bovine embryos to akabane, bluetongue and bovine viral diarrhea viruses.

As part of a program to study the feasibility of using embryo transfer to control disease, initial experiments were undertaken to determine the virus susceptibility of early embryos. Two hundred and ninety-three preimplantation bovine embryos (16-cell to blastocyst stage) were exposed to either akabane virus (AV), bluetongue virus (BTV) or bovine viral diarrhea virus (BVDV). Two hundred and thirty-seven of these embryos were then cultured for 24-48 hours in order to determine whether the virus had any effect on embryonic development and to allow viral replication to occur. No infectious virus was isolated from any of the embryos and the in vitro development of virus exposed embryos proceeded normally. In addition, twenty-nine eggs/embryos isolated from donors that were seropositive to BVDV were found to be uninfected with this virus.

Journal Article↗
PubMed1982

Embryo transfer as a means of controlling the transmission of viral infections. II. The in vitro exposure of preimplantation bovine embryos to infectious bovine rhinotracheitis virus.

Bovine embryos, at the 16-cell to the blastocyst stage of development, were exposed to infectious bovine rhinotracheitis virus (IBRV) for either one or 24 hours. These embryos were then washed and incubated for 24 or 48 hours before being assayed for IBRV. Under these conditions, infectious virus at the level of 0-10(2.2) TCID(50)/ml was isolated from 57-64% of the embryos exposed to IBRV. Trypsin and IBRV-antiserum were found to be capable of removing and/or inactivating the IBRV from exposed embryos. Both the low level of the virus isolated from these embryos and the susceptibility of this virus to trypsin and antiserum suggests that IBRV attaches to the zona pellucida of embryos and cannot penetrate this structure to gain access to the embryonic cells. IBRV was found to have no effect on embryonic development in vitro . In addition, thirty-one eggs/embryos isolated from donors that were seropositive to IBRV were found to be uninfected with this virus.

Journal Article↗
PubMed1982

Inactivation by gamma irradiation of animal viruses in simulated laboratory effluent.

Several animal viruses were treated with gamma radiation from a 60Co source under conditions which might be found in effluent from an animal disease laboratory. Swine vesicular disease virus, vesicular stomatitis virus, and blue-tongue virus were irradiated in tissues from experimentally infected animals. Pseudorabies virus, fowl plague virus, swine vesicular disease virus, and vesicular stomatitis virus were irradiated in liquid animal feces. All were tested in animals and in vitro. The D10 values, that is, the doses required to reduce infectivity by 1 log10, were not apparently different from those expected from predictions based on other data and theoretical considerations. The existence of the viruses in pieces of tissue or in liquid feces made no difference in the efficacy of the gamma radiation for inactivating them. Under the "worst case" conditions (most protective for virus) simulated in this study, no infectious agents would survive 4.0 Mrads.

Bluetongue virus↗
PubMed1982

Evidence for bluetongue virus in Canada: 1976-1979.

Since the identification of approximately 1 400 bovine serological reactors to bluetongue virus in the Okanagan Valley of British Columbia in 1976, there has been no evidence of virus establishment in Canada. No clinical signs suggestive of bluetongue were observed. It was not possible to demonstrate viral activity at the time the seropositive animals were detected and subsequent serological testing supports the hypothesis that the virus has not become endemic or indeed survived in Canadian cattle populations. This combined with the dramatic reduction in prevalence of serological reactors in the years following the initial slaughter suggests that viral activity occurred in the Okanagan Valley prior to 1976 and disappeared. There has been no evidence for transmissions different from that expected of a classical arbovirus; that is, no evidence of "vertical" transmission.

Animals↗
PubMed1981

Gamma ray inactivation of some animal viruses.

Twenty samples of animal viruses comprising 14 different viruses in 12 families were subjected to varying doses of gamma irradiation from a 60Co source in a Gamma Cell 220 (Atomic Energy of Canada Limited) to determine lethal dose levels. The dose responses appeared linear throughout inactivation. The D10 values, that is the dose necessary to reduce infectivity by one log10, ranged from less than 0.20 Megarads to approximately 0.55 Megarads. There was not a complete inverse correlation between the target size (virion core) and the D10 value.

Dose-Response Relationship, Radiation↗
PubMed1979

Comparisons of some bluetongue virus isolates by plaque neutralization and relatedness tests.

Seven North American bluetongue virus isolates, cloned by plaquing, and sera to five of them were reacted in a plaque neutralization test. Using a paired controls system, each virus-serum reaction was studied in terms of the regression of percent neutralization on log serum dilution. Antigen-antibody interaction terms in the analysis of effective dose estimates were used to assess the relatedness of the virus isolates. The degree of cross reactivity formed a spectrum from virtually no evidence of unrelatedness to clear antigenic differences.

Antigens, Viral↗
PubMed1979

A rapid plaque neutralization test for bluetongue virus.

A bluetongue virus plaque neutralization test, done in small tissue culture wells (2.0 cm2) using minimal antibody-virus contact time, was found to be of comparable sensitivity to more classical methods involving preincubation. By using the cell culture plates as serum dilution wells and adding cells directly to the virus-antibody mixture, a considerable saving in time is realized. Because of the small size of the wells, reagent cost and incubator space requirements are reduced making the test much more attractive for wide scale use, either as a screening test or one that yields dose-response lines.

Animals↗
PubMed1977

Necrotizing encephalitis in skunks caused by Herpes simplex virus.

Herpes simplex virus was isolated from the brain of a wild skunk (Mephitis mephitis) which had clinical neurological disease. In the brain of this skunk and in brain of skunks inoculated intracerebrally, there were areas of necrosis in the grey matter of the cerebral cortex and to a lesser extent in the brain stem. Intranuclear inclusions occurred in neurons and glial cells with vascular cuffing by mononuclear cells and a few neutrophils. Skunks inoculated intravenously had extensive focal necrosis in the liver and adrenal glands.

Adrenal Glands↗
PubMed1976

Transmissible gastroenteritis virus: plaques and a plaque neutralization test.

A plaquing system and plaque neutralization test in porcine thyroid cells were used to study different transmissible gastroenteritis isolates and hemagglutinating encephalomyelitis virus. Among transmissible gastroenteritis virus isolates, plaque size varied considerably and mixed size ranges sometimes occurred. The most recently isolated viruses produced smaller plaques than the laboratory viruses or hemagglutinating encephalomyelitis virus. All transmissible gastroenteritis virus isolates reacted in the plaque neutralization test with a transmissible gastroenteritis virus antiserum which showed no activity against hemagglutinating encephalomyelitis virus. Plaque neutralization results both from experimentally infected pigs and following a field outbreak demonstrated the reliability of this test and its greater sensitivity than the conventional tube test.

Animals↗
PubMed1976

A comparison of some serological tests for bluetongue virus infection.

The plaque neutralization, complement fixation, and agar gel precipitin tests were compared by measuring bluetongue virus antibody in 137 serums from experimental animals (cattle and sheep) and suspected field reactors (cattle and deer). In general, the tests agreed well with each other. Plaque neutralization titers began earlier than the other two and went much higher than the complement fixation titers. Plaque neutralization titers usually peaked between two and three weeks after exposure and complement fixation titers from four to six weeks. The greater sensitivity of the plaque neutralization test allowed the detection of all complement fixation and agar gel precipitin reactors whereas occasionally the latter two tests failed to detect plaque neutralization reactors.

Agar↗
PubMed1974

Microculture plaque neutralization test for California group arboviruses.

A microculture plaque neutralization test is described for California-group arboviruses that is as precise and quantitative as the standard test conducted in 60-mm petri dishes. It was shown that there was no significant between-panel or between-day variation in determinations and that a single pipette could be used for all serum-dilution levels within a titration without inoculum carry-over effect. The experimental protocol and statistical methods used produce 50% neutralization end points that meet the assumptions of parametric statistics. This permits the power and versatility of the analysis of variance to be exploited in testing for treatment effects in serological and immunological studies with viruses.

Analysis of Variance↗
PubMed1971

A comparison of bluetongue virus and EHD virus: electronmicroscopy and serology.

Bluetongue virus, BT(8), and the virus of epizootic hemorrhagic disease (EHD) of deer, NJ-55, were plaque purified and compared electronmicroscopically and serologically. The latter included a plaque reduction neutralization test, the agar gel precipitin test, and the complement fixation test. The viruses were indistinguishable morphologically, but antigenically different. A plaquing technique was described for EHD virus.

Animals↗
PubMed1971

Bluetongue virus: some relationships among North American isolates and further comparisons with EHD virus.

Seven isolates of bluetongue virus with different isolation histories and one isolate of the virus of epizootic hemorrhagic disease of deer were cloned by three consecutive plaquings in L-929 cells. The isolates were categorized on plaque size and margin. Antisera to the bluetongue virus isolates were produced in calves and antiserum to epizootic hemorrhagic disease virus in deer. Plaque reduction neutralization tests were done using the eight isolates and antisera to six of these. The isolates could be partially categorized on plaque type. In the plaque reduction neutralization test, all of the bluetongue viruses cross reacted and although differences were frequently observed, no obvious antigenic classification was possible. Reactions between the bluetongue viruses and epizootic hemorrhagic disease virus were all within the limits of what is presently considered to be non-specific inhibition.

Animals↗
PubMed1970

Bluetongue virus: (1) in pregnant white-tailed deer (2) a plaque reduction neutralization test.

Six white-tailed deer (Odocoileus virginianus) were infected with bluetongue virus (BTs, vaccinal strain) approximately one-third of the way through their gestation period. One deer died of bluetongue 21 days after inoculation. Of the five surviving the infection, one had two mummified fetuses, and the others no fetuses upon euthanasia two weeks after term. Fetuses were present in two control deer and in the one which died of bluetongue. A plaque reduction neutralization test for bluetongue virus was developed and described for the first time and its sensitivity illustrated by high post inoculation titers which ranged from 1:3200 to greater than 1:16000.

Abortion, Veterinary↗