Biomedical subjects

L D Bacon

Publications and source records attributed to L D Bacon.

97 records · Page 6Linked to original sources

PubMedDate not supplied

Linkage of the major histocompatibility (B) complex and the nucleolar organizer in the chicken. Assignment to a microchromosome.

The linkage relationship and chromosomal locations of the major histocompatibility (B) complex and nucleolar organizers (18S + 28S ribosomal RNA genes) were studied in normal and aneuploid chickens. The Balloantigens were defined by hemagglutination, using monospecific alloantisera. A chicken having three B haplotypes was detected and used in test matings to normal disomic chickens. Additional cases of birds having three different haplotypes were generated in the progeny of such matings. Analysis of the segregation patterns of B haplotypes suggested that the chickens with an additional haplotype were trisomics. Chickens having three B haplotypes also displayed a maximum of three nucleoli in somatic cells instead of the normal two nucleoli of diploids. This indicated the presence of an additional nucleolus organizing region (NOR). Cytogenetic and cytochemical studies were performed on cells of normal and putative trisomic chickens. All chickens displayed a normal array of chromosomes for pairs 1 through 9. Silver staining differentiated Ag-NORs on the long arms of two and three microchromosomes in disomic and trisomic types, respectively. Viable tetrasomic chickens, produced from inter se matings of trisomics, displayed four nucleoli and four Ag-NORs in somatic cell preparations. These results indicate that the DNA sequences encoding the B histocompatibility antigens and the 18S + 28S ribosomal RNAs are linked on an acrocentric microchromosome in the domestic chicken.

Aneuploidy↗

PubMedDate not supplied

Progesterone receptor level as a predictor of response to megestrol acetate in advanced breast cancer: a retrospective study.

Megestrol acetate (160 mg/day) produced a response rate of 44% in a retrospective series of 39 evaluable patients with advanced breast cancer. The estrogen-receptor (ER) level was greater than 10 fmols/mg of protein in 28 patients, and the progesterone-receptor (PR) level was greater than 10 fmols/mg of protein in 26 patients. ER and PR levels, age, and disease-free interval were analyzed for their relationship to response. The PR was the single best predictor of response to megestrol acetate; the addition of ER added 2% to the predictive accuracy rate of PR alone.

Breast Neoplasms↗

PubMedDate not supplied

Mitogen-induced lymphocyte proliferation and interferon production following coccidia infection.

Concanavalin A-induced lymphocyte proliferation and interferon production were measured following infection with Eimeria acervulina in lines of chickens congenic at the major histocompatibility complex and in two unrelated lines. Similar proliferation responses were seen for splenic and peripheral blood lymphocytes following primary but not secondary infection. Greater differences in lymphocyte proliferation were found between the congenic lines and unrelated lines than among the congenic lines. The congenic lines had very low responses to Con A, in terms of both lymphocyte proliferation and interferon production. At some times after infection, background proliferation in all lines was higher for infected than uninfected chickens, which was probably an indication of activated lymphocytes in the circulation. Mitogen-induced lymphocyte proliferation and interferon production, although clearly affected by coccidial infection, were not reflective of severity of infection.

Animals↗

PubMedDate not supplied

Partial inhibition by turkey herpesvirus of serotype 2 Marek's disease virus plaque formation and in vivo infectivity.

The increased use of serotype 2 Marek's disease virus (MDV) and serotype 3 turkey herpesvirus (HVT) as components of effective bivalent vaccines against Marek's disease (MD) prompted studies on the possible interactions of these two viruses in vitro and in vivo. The replication of the SB-1 strain of MDV was compared with replication of the FC126/2 strain of HVT in chickens and cell cultures infected with one or both viruses. Replication of MDV was reduced in the presence of HVT in both in vitro and in vivo systems. MDV plaque counts in dually infected chicken embryo fibroblast cultures inoculated with tissue-culture-propagated viruses were reduced by up to 91%; however, no inhibition was noted when inocula consisted of virus-infected buffy-coat cells. Plaque formation by MDV in chicken embryo fibroblast cultures was inhibited by virus-free conditioned medium from HVT-infected cultures. This conditioned medium also inhibited growth of vesicular stomatitis virus in a standard interferon assay. In chickens inoculated with both MDV and HVT, MDV viremia titers were lower and the dose required to infect 50% of susceptible chickens was increased 13-fold compared with chickens inoculated with MDV alone. In spite of these findings, there was no evidence that high concentrations of HVT interfered with either the ability of MDV to induce protective synergism in vivo or the protective efficacy of bivalent vaccines. No reciprocal inhibitory effects of MDV on the replication of HVT in vivo or in vitro were noted.

Animals↗

PubMedDate not supplied

Serotype specificity of B-haplotype influence on the relative efficacy of Marek's disease vaccines.

B-haplotype genes in the chicken were previously shown to differentially influence vaccine efficacy against challenge with very virulent Marek's disease virus according to the type of Marek's disease (MD) vaccine used. To determine whether MD vaccines of the same serotype gave comparable levels of protection against MD in chickens of the same haplotype challenged with MD virus strain Md5, two serotype 1 and two serotype 2 vaccines were compared with one serotype 3 vaccine using chickens of 15-B-congenic lines. There was a strong correlation in development of MD lesions among chickens of the different lines receiving the two serotype 2 vaccines (r = 0.94) as well as among chickens receiving the two serotype 1 vaccines (r = 0.76). The serotype 1 vaccines were preferable for B2, B13, B15, and B21, but serotype 2 vaccines were more protective for B5 chickens. The two serotype 2 vaccines gave equivalent protection; however, of the serotype 1 vaccines, CVI988/Rispens provided more protection than Md11/75c/R2/23. We conclude that the B-haplotype influence on MD vaccine efficacy is dependent on the serotype of the vaccine.

Animals↗

PubMedDate not supplied

Influence of B-haplotype on the relative efficacy of Marek's disease vaccines of different serotypes.

To determine if B-haplotype differentially influences vaccinal immunity to very virulent Marek's disease (MD) virus challenge, chickens of five 15.B-congenic lines were vaccinated with vaccines representing serotypes 1, 2, and 3. B-haplotype differentially influenced vaccinal immunity to very virulent MD virus challenge using vaccines of all three serotypes, and different MD vaccines were optimal for some B-haplotypes. Regarding specific haplotypes, the 15.B-congenic chickens with B2 and B13 developed less protection against MD than chickens with B15 following vaccination with all three serotypes of MD vaccine, whereas the chickens with B5 and B21 developed variable protection with different MD vaccines. Thus, for induction of maximum MD resistance, it may be necessary to select a vaccine appropriate for the predominant B-haplotypes of the chicken flock.

Animals↗

PubMedDate not supplied

Effect of serotype 2 and 3 Marek's disease vaccines on the development of avian leukosis virus-induced pre-neoplastic bursal follicles.

The effect of serotype 2 and 3 Marek's disease virus (MDV) vaccines on the development of pre-neoplastic bursal lesions induced by two strains of subgroup A avian leukosis virus (ALV) was studied. Chickens of line 15I5 x 7(1) susceptible to ALV-induced lymphoma were inoculated at hatch with Rous-associated virus-1 (RAV-1) or strain RPL-40 of subgroup A ALV. All chickens, except for negative controls, were also inoculated at hatch with strain 301B/1 of serotype 2 MDV or strain FC126 of turkey herpesvirus (HVT), a serotype 3 MDV. At 11 and 14 weeks of age, serial sections of bursal tissues from chickens in various treatment groups were stained with methyl green pyronin and examined for ALV-induced pre-neoplastic bursal lesions, also known as hyperplastic follicles. At 6 days and at 11 and 14 weeks of age, bursal tissues from groups of chickens inoculated with serotype 2 MDV and ALV at hatch were also examined for the presence of MDV genome by in situ hybridization. The number of ALV-induced hyperplastic follicles was significantly higher in chickens inoculated with serotype 2 MDV than in unvaccinated chickens or in chickens vaccinated with HVT. In contrast, the lowest number of hyperplastic follicles was noted in chickens vaccinated with HVT, regardless of strain of ALV used. These results suggest that enhancement of lymphoid leukosis may result from an increase in the number of ALV-induced hyperplastic follicles caused by the MDV and also that the enhancing effect of MDV on ALV-induced lymphomagenesis may occur at the stage of formation of hyperplastic follicles in the bursa.

Animals↗