PubMed Health⌕ Search

Biomedical subjects

W C Hare

Publications and source records attributed to W C Hare.

At least 37 records · Page 2Linked to original sources
PubMed1982

Transfer of embryos from bovine leukaemia virus-infected cattle to uninfected recipients: preliminary results.

One hundred and fifty-one, day 6 or 7, embryos collected from cattle infected with bovine leukaemia virus (BLV) were transferred to uninfected recipients. Thirty-two pregnancies resulted. Two animals aborted at seven months. Three sets of twins and one single calf were still-born. The remaining 26 pregnancies produced 27 live calves which were raised to six months of age. All of the recipients, pregnant and non-pregnant, and all of the calves remained serologically negative for antibodies to BLV-glycoprotein antigen.

Animals↗
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

Attempts to isolate bovine leukemia and bovine syncytial viruses from blood, uterine flush fluid, unfertilized ova and embryos from infected donor cattle.

Blood leucocytes, sediments of uterine flush fluid (UFF), eggs and embryos from 25 BLV-positive donor cows were tested for bovine leukemia (BLV) and bovine syncytial (BSV) viruses by cocultivation with fetal lamb spleen cells and by applying syncytium induction and immunofluorescence tests. BLV was diagnosed in 11/15 (73.3%) leucocyte and 4/25 (16.0%) UFF-sediment specimens as compared to BSV in 14/15 (93.3%) and 21/25 (84.0%) of the similar specimens and neither BLV or BSV were found in 26 eggs and 60 embryos collected from 20 of the 25 cows. Detection of BLV antigens by immunofluorescence was hampered by the competitive replication of both BLV and BSV and competitive growth in indicator cells and uterine cells. As BLV has not been observed in cells of UFF sediments, it was probably isolated from leucocytes present in the lumen of uterus or from blood seeping out from inapparent vessel damage during flushing. Isolation of BLV in UFF sediments gives additional evidence to the concept of a transplacental transmission by a not yet elucidated mechanism. The high rate of BSV recovery from cells of UFF sediments indicated that this virus is more wide-spread than previously shown and that it may play a role in causing disorders of the reproductive tract.

Animals↗
PubMed1980

Chromosomal analysis of 159 bovine embryos collected 12 to 18 days after estrus.

One hundred and fifty-nine embryos were analysed in conjunction with embryo transfer studies. Chromosome preparations were made from small biopsy fragments of trophoblast, from large portions of trophoblast and the inner cell mass, or from the entire embryo. Results obtained from fragments were similar to those obtained from large portions of trophoblast and inner cell mass. No structural chromosomal abnormalities were observed. Single triploid, diploid-triploid and diploid-hexaploid and 66 diploid-tetraploid embryos were found. The 41.5% incidence of diploid-tetraploid embryos was relatively high, and appeared to be associated with a donor factor. The transfer of 49 biopsied and analysed embryos to recipients resulted in 15 pregnancies, seven with diploid-tetraploid embryos having up to 25% of polyploid cells. The diploid-triploid and diploid-hexaploid embryos were among the transfers that did not result in pregnancy. The low incidence of embryos with chromosomal abnormalities, excluding the diploid-tetraploid embryos, may have been due to the embryos being analysed at 12 to 18 days of age rather than at an earlier age before death or degeneration could have occurred.

Animals↗
PubMed1977

Genetic resistance to lymphoid tumor transplants.

Day-old chicks of Ottawa strains 4 and 5 and Cornell strains K and S, with or without maternal antibody against antigens related to Marek's disease (MD), were challenged with serial dilutions of MD tumor transplants (JMV-L or JMV-H) or transmissible lymphoid tumor (TLT) of Olson in three consecutive experiments. Thirty chicks were tested in most combinations of strain, dilution and antibody status for a total of approximately 2000 chicks per experiment. Two subsequent experiments, with a total of more than 1900 chickens, investigated the influence of age at challenge on the resistance of strains 4, K and S to JMV-L and the objective of the sixth experiment was to determine the chromosomal sex of the tumor cells. In terms of mortality up to 16 or 17 days after inoculation, the response to challenge of day-old chicks with JMV-L did not appear to be influenced by the presence of antibody against MD related antigens but differed among strains of chickens. The estimated dose (LD50) that would kill 50% of a challenged population of Strain 4 was approximately 10,000 live JMV-L cells, while the corresponding estimates for strains 5 and K were approximately 600 cells and for strain S it was 50 cells. JMV-H and TLT were highly lethal to all four strains and all estimates of LD50 at 16 or 17 days post challenge were less than 10 cells. Resistance to JMV-L increased rapidly with age at challenge. Strains 4 and K were approaching complete resistance by 7 days of age and the susceptible strain S, when challenged at 14 days, was more resistant than day-old chicks of strains 4 and K. The chromosomal sex of the JMV-L, JMV-H and TLT tumor cells was female and this marker was used to confirm their transplantability.

Age Factors↗
PubMed1977

Bovine lymphosarcoma in twin calves.

Lymphosarcoma in twin female calves, apparently the first to be observed in Canada, is reported here. Peripheral blood and cultured mononuclear cells of one of the calves showed aneuploidy of the chromosomes. No hematological or serological evidence of bovine leukemia virus infection was observed in the other members of the herd. Bovine leukemia virus infection of the leukemic cells could not be detected by electron microscopy or by tissue culture procedures. There is a need to clarify the relationship of the calf form of the disease to the adult form of enzootic bovine leukosis.

Animals↗
PubMed1976

Congenital retroflexion of the penis and inguinal cryptorchidism in a presumptive bovine twin with a 60,XY/60,XX/61,XX,+cen chromosome constitution.

Studies were carried out on a yearling Holstein with external genitalia resembling those of a freemartin whose birth and developmental history was unknown. Dissection following slaughter showed testes close to the external inguinal rings, an underdeveloped penis coiled up subcutaneously in the perineum and terminating in a deep fossa at the level of the ischial arch and no evidence of a female genital tract. Chromosome analyses showed 60,XY cells in the blood and 60,XX and 61,XX,+cen cells in other tissues. It is postulated that the animal had a basic 60,XX/61,XX+cen mixoploid chromosome constitution, that the centric fragment functioned as a Y chromosome or as an autosomal modifier of the X chromosome in sex determination which accounted for the animal's Klinefelter syndrome-like abnormalities, and that animal was also twin to a bull which accounted for the presence of 60,XY cells in the blood.

Animals↗
PubMed1975

Cytogenetic, cytological, and virological characteristics of a bovine fibrosarcoma.

The features of a bovine tumor with typical histopathological characteristics of a malignant fibrosarcoma are described. Direct karyotype preparations from the tumor tissue showed two populations of cells with bizarre karyotypes. An in vitro cell culture, designated BS-2, derived from the tumor had a normal diploid karyotype. This culture formed syncytia and produced a virus morphologically indistinguishable from the ubiquitous bovine syncytial virus. BS-2 cells reacted strongly in immunofluorescent tests with both bovine syncytial virus reference serum and serum from the tumorous cow. The virus was also demonstrated by immunofluorescence and mixed culture techniques in the buffy coat cells of the same cow.

Animals↗