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D O'Callaghan

Publications and source records attributed to D O'Callaghan.

81 records · Page 5Linked to original sources
PubMed1988

Characterization of aromatic- and purine-dependent Salmonella typhimurium: attention, persistence, and ability to induce protective immunity in BALB/c mice.

Stable transposon-generated auxotrophic mutations in aroA, purA, and purE or aroA and purA together were introduced into Salmonella typhimurium strains which were virulent in mice. Strains harboring any of these mutations were attenuated when tested in BALB/c mice. purE strains were less attenuated than aroA or purA strains. Both aroA and purA mutants persisted for several weeks in the livers and spleens of the mice after intravenous infection, although the numbers of viable cells detected at various times after infection differed. aroA strains persisted at a higher level than purA strains and were effective live vaccines given intravenously or orally. purA strains were ineffective as oral vaccines and were poor intravenous vaccines. Strains harboring both aroA and purA mutations together were ineffective vaccines when administered orally or intravenously even though they persisted in the livers and spleens of the mice for long periods after intravenous infection.

Administration, Oral↗
PubMed1987

Salmonella typhimurium aroA mutants as carriers of the Escherichia coli heat-labile enterotoxin B subunit to the murine secretory and systemic immune systems.

We investigated the ability of Salmonella typhimurium vaccines to deliver heterologous antigens to the systemic and secretory immune systems of the mouse, while retaining their immunogenicity against salmonellosis. S. typhimurium SL3261, an avirulent aroA mutant, or SL3261 carrying plasmid pBRD026, a pBR322 derivative encoding the gene for Escherichia coli LT-B were used to immunize BALB/c mice orally. Both immunizing strains invaded the mononuclear phagocyte system of the mice, grew slowly until approximately day 14 post-infection, and then were rapidly cleared. No salmonellae were detected in livers, spleens, mesenteric lymph nodes or Peyer's patches by day 42. Mice immunized with either strain and challenged orally with the virulent parent strain, SL1344, several weeks after clearing the immunizing organism, were protected against the lethal S. typhimurium infection. Mice infected with SL3261 (pBRD026) developed substantial levels of IgG and IgA anti-LT-B antibodies 14 days post-infection in both serum and gut samples. The sera neutralized the effects of LT in an in vitro Vero cell assay. Thus, aroA mutants of S. typhimurium can deliver a heterologous antigen from a different enteric pathogen to the murine systemic and secretory immune systems without altering their efficacy against salmonellosis.

Animals↗
PubMed1986

Effects of long acting and short acting oestradiol implants on growth rate and carcase weight of steers.

The effects of a number of steroid hormone treatments on growth were examined in a trial involving 204 Friesian-type steers which was carried out over an 11 month period from May to April. The animals were at pasture from May until October and were over-wintered indoors on grass silage and supplementary concentrates. Thirty-four animals were used as untreated controls, and there were four treatment groups: 43 steers were implanted with pellet-type implants containing 20 mg oestradiol benzoate and 200 mg progesterone on days 1, 105 and 187; 47 steers were implanted with a single silastic rubber implant containing 45 mg oestradiol-17 beta; 36 steers received treatment (1) and in addition were implanted on the same days with 300 mg trenbolone acetate; 44 steers received treatment (2) and were also implanted with 300 mg trenbolone acetate on days 1, 105 and 187. The mean liveweight gains (+/- sem) of the steers during the first 249 days of the trial were 201.7 kg for the controls and 236.8, 219.4, 254.4 and 247.8 (+/- 6.1) kg for the steers assigned to treatments 1, 2, 3 and 4, respectively. The corresponding values for the carcase weights (+/- sem) were 300.0 kg for the controls and 318.4, 312.0, 327.9 and 321.6 (+/- 3.5) kg for the treated groups. Although all the treatments increased the liveweight gains and carcase weights significantly compared with the controls, the responses to the silastic rubber implants were smaller owing primarily to an apparently high rate of loss of the implants.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

Oncogenic transformation of non-permissive murine cells by viable equine herpesvirus type 1 (EHV-1) and EHV-1 DNA.

Primary cultures of BALB/c mouse embryo fibroblasts infected with as much as 100 PFU per cell of EHV-1 do not exhibit cytopathology or synthesize detectable amounts of EHV-1 specific RNA, DNA, or infectious virus. Addition of 1--2 microgram of non-fragmented EHV-1 DNA as a co-precipitate with calcium phosphate to monolayers of such non-permissive mouse cells resulted in the appearance, after 4--6 weeks, of foci of piled-up, morphologically altered cells. Cell lines established from such transformed foci exhibited a greatly increased growth rate, unlimited growth potential, aneuploid karyotype, and grew with colony formation in soft agar. Inoculation of 10(6) transformed cells into newborn syngeneic mice resulted in the formation of serially transplantable tumours (undifferentiated fibrosarcomas) with a 100% incidence within eight weeks. Infectious virus could not be rescued from the EHV-1 transformed or tumour-derived cell lines by growth in the presence of IUDR, by cocultivation with permissive horse cells, or by attempts to transfect permissive cells with transformed or tumour cell DNA. However, EHV-1 specific membrane antigens were detected in the transformed cells by immunofluorescence with hyperimmune anti-EHV-1 mouse serum, and the presence of a fragment of the EHV-1 genome was demonstrated in both the transformed and tumour cells. These results indicate that cells nonpermissive for replication of EHV-1 remain susceptible to neoplastic transformation by the EHV-1 genome.

Animals↗
PubMedDate not supplied

Immunogenicity of foreign peptide epitopes expressed in bacterial envelope proteins.

We have used two bacterial proteins from Escherichia coli to express heterologous peptides. Both proteins are situated in the E. coli cell envelope but have different properties: LamB is an integral outer membrane protein, and MalE a soluble periplasmic protein. The peptides were expressed as genetic inserts within "permissive sites" of these recipient proteins, i.e. sites which allow the insertion of foreign peptides without affecting the biological properties of the host protein. In this paper, we summarize preliminary rules governing the immunogenicity of resulting LamB and MalE hybrid proteins when expressed in E. coli. We focus on two model epitopes: either peptide 132-145 from the preS(2) region of hepatitis B virus or peptide 93-103 from poliovirus VP1 capsid protein. We also present first results obtained when the same hybrid proteins were expressed in attenuated Salmonella typhimurium. Plasmids encoding the hybrid proteins were transferred to aroA S.typhimurium by electroporation. In vitro, the hybrid proteins could be expressed at high levels by S. typhimurium. Mice were immunized by parenteral and oral routes. The effect of the carrier protein and the level of its expression on the in vivo behaviour of the immunizing bacteria and on the immune response induced will be discussed.

Animals↗
PubMedDate not supplied

Factors associated with delay to treatment for acute myocardial infarction in Ireland.

Irish data from the ISIS-2 multi-centre study of thrombolytic therapy has indicated longer delays to treatment for acute myocardial infarction (AMI) than in other countries (7.9 vs 6.9 hours, p < 0.001). Further examination of this database (n = 831 patients) found no influence of age and sex of patient on delay times. Distance from hospital was not associated with delay while previous experience of MI was marginally associated with decreased delay (previous MI: 7.1 vs no previous MI: 8 hours, p = 0.06). These relatively lengthy Irish delays require further investigation to inform management strategies aimed at reducing delay.

Humans↗
PubMedDate not supplied

[A genetic and molecular biological study of the pathogenicity factors in Brucella].

The use of gene engineering techniques made it possible to obtain strain GSE830, capable of a higher level of expression of the gene of 38-kD protein in immunoblotting with sheep and rabbit antibrucellar sera in comparison with the expression of this gene of other Escherichia coli strains, containing recombinant plasmids with this gene. Due to the presence of the gene of 38-kD protein, recombinant E.coli strains were capable of survival in macrophage-like cell line U937 3.6-6.3 times more effectively. The model of interaction of Brucella pathogenic and nonpathogenic species with HeLa cells was studied. The bank of insertion mutants of B.suis virulent strain 1330 was studied with the use of transposon TnblaM. Out of 380 insertion mutants, 7 clones expressing beta-lactamase and having decreased capacity for multiplication in HeLa cells 48 hours after inoculation were selected. Detailed analysis revealed that 3 of them had lower adhesive capacity, 1 of them had lower invasive capacity and 3 other mutants were less capable of intracellular multiplication in HeLa cells than the initial B.suis strain 1330. All these 7 mutants had different sites of TnblaM insertion into the chromosome of B.suis strain 1330.

Brucella↗