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Biomedical subjects

L G Adams

Publications and source records attributed to L G Adams.

At least 91 records · Page 5Linked to original sources
PubMed1990

Brucella abortus in captive bison. I. Serology, bacteriology, pathogenesis, and transmission to cattle.

Two groups of six, non-brucellosis vaccinated, brucellosis seronegative pregnant American bison (Bison bison) were individually challenged with 1 x 10(7) colony forming units (CFU) of Brucella abortus strain 2308. Three days after challenge, each bison group was placed in a common paddock with six non-vaccinated, brucellosis susceptible, pregnant domestic heifers. In a parallel study, two groups of six susceptible, pregnant cattle were simultaneously challenged with the identical dose as the bison and each group was placed with six susceptible cattle in order to compare bison to cattle transmission to that observed in cattle to cattle transmission. Blood samples were collected from bison and cattle weekly for at least 1 mo prior to exposure to B. abortus and for 180 days post-exposure (PE). Sera from the bison and cattle were evaluated by the Card, rivanol precipitation, standard plate agglutination, standard tube agglutination, cold complement fixation tube, warm complement fixation tube, buffered acidified plate antigen, rapid screening, bovine conjugated enzyme linked immunosorbent assay, bison or bovine conjugated enzyme linked immunosorbent assay, and the hemolysis-in-gel techniques for the presence of antibodies to Brucella spp. At the termination of pregnancy by abortion or birth of a live-calf, quarter milk samples, vaginal swabs, and placenta were collected from the dam. Rectal swabs were collected from live calves, and mediastinal lymph nodes, abomasal contents and lung were taken at necropsy from aborted fetuses for culture of Brucella spp. These tissues and swabs were cultured on restrictive media for the isolation and identification of Brucella spp. Pathogenesis of brucellosis in bison was studied in an additional group of six pregnant bison which were challenged with 1 x 10(7) CFU of B. abortus strain 2308. One animal was euthanatized each week PE. Tissues were collected at necropsy and later examined bacteriologically and histologically. Lesions of brucellosis in bison did not significantly differ grossly or histologically from those in cattle. There were six abortions and two nonviable calves in the bison group, as compared to nine abortions in the 12 similarly inoculated cattle. As determined by bacterial isolations, transmission of B. abortus from bison to cattle (five of 12 susceptible cattle became infected) did not differ statistically from cattle to cattle transmission (six of 12 susceptible cattle became infected) under identical conditions. No single serologic test was constantly reliable to diagnosing B. abortus infected bison for 8 wk PE.(ABSTRACT TRUNCATED AT 400 WORDS)

Agglutination Tests↗
PubMed1990

Bovine T-lymphocyte lines reactive with Brucella abortus.

Bovine T-cell lines reactive with Brucella abortus were established by repeated stimulation with B abortus and mitomycin C-treated autologous antigen-presenting cells. Representative results were obtained, using 33 cell lines from 14 cows. Cultures responded to the virulent laboratory strain 2308, the vaccine strain 19, and the rough mutant strain RB51 in thymidine-incorporation assays. The cells in these cultures required antigen-presenting cells for their response to B abortus. Autologous antigen-presenting cells were optimal for most lines tested, although some T-cell lines could respond to B abortus in the presence of some, but not all, allogeneic antigen-presenting cells. The cell lines expressed cell surface markers characteristics of activated bovine T cels. Of the cell lines tested for expression of cluster-determinant (CD) 4 and CD8 cell surface antigens, no cells in any cultures expressed the bovine CD8 equivalent, but all cultures included CD4+ cells in variable amounts. Some cell lines consisted of up to 50% CD2+CD4-CD8- cells. None of the cell lines tested expressed surface immunoglobulin or other bovine B-cell markers. Thus, these long-term cell lines appear to include 2 T-lymphocyte subsets: the helper/inducer subset and a second subset expressing a phenotype similar to major histocompatibility complex-unrestricted cytolytic cells in other species.

Animals↗
PubMed1990

Differential reactivity of bovine lymphocytes to species of Brucella.

The reactivity of bovine lymphocytes to 4 species of Brucella was tested in thymidine-uptake assays, using long-term cultured lymphocytes and freshly obtained blood mononuclear cells. Lymphocytes were taken from cows that had been challenge exposed with a virulent strain of B abortus at midgestation. The cows were classified retrospectively as being naturally resistant or susceptible to brucellosis. Lymphocytes taken from these cows had 3 patterns of reactivity with species of Brucella: pattern 1 was defined by reactivity with 4 species (B abortus, B canis, B suis, and B melitensis); pattern 2 was defined by reactivity with all these species, except B melitensis; pattern 3 was defined by reactivity with B abortus and B canis, but not with B suis or B melitensis. There was a statistically significant correlation between susceptibility to brucellosis and expression of lymphocyte cross-reactivity with B suis (P less than 0.01) and with B melitensis (P less than 0.001).

Animals↗
PubMed1990

Effect of dose of Brucella abortus strain 19 in yearling heifers on the relative risk of developing brucellosis from challenge exposure with strain 2308.

Yearling heifers were given SC injections of 10(8) (n = 40), 10(9) (n = 44), or 10(10) (n = 44) colony-forming units of Brucella abortus strain 19 (S19). The proportion of heifers with positive serologic test results at 1 month following vaccination increased as the dose of S19 increased. These proportions decreased with time, and all heifers had negative card, rivanol, and complement fixation test results within 4 months. Positive ELISA results persisted beyond 4 months in all three S19 dose groups; however, all heifers were ELISA-negative within 9 months after vaccination. Comparable lymphocyte transformation activity was stimulated by S19 dose of 10(9) or 10(10) and approximately half of the heifers in both groups had a positive stimulation index at 9 months. Immunity of the pregnant heifers was challenged 9 months after vaccination with 10(7) B abortus strain 2308 as follows: diluent controls (n = 69); 10(8) B abortus S19 (n = 40); 10(9) B abortus S19 (n = 39); and 10(10) B abortus S19 (n = 39). Tissue specimens from heifers were obtained at parturition and necropsy for culturing of B abortus. The proportion of heifers that developed brucellosis, ie, had positive culture results, increased as gestation days at challenge exposure increased. The effect of gestational age was controlled in the analysis using logistic regression. The relative risk of brucellosis was reduced to 0.38, 0.15, and 0.06 for B abortus S19 doses of 10(8), 10(9), and 10(10), respectively, compared with diluent controls at 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1989

Mixed acid-base disorders.

Mixed acid-base disturbances are combinations of two or more primary acid-base disturbances. Mixed acid-base disturbances may be suspected on the basis of findings obtained from the medical history, physical examination, serum electrolytes and chemistries, and anion gap. The history, physical examination, and serum biochemical profile may reveal disease processes commonly associated with acid-base disturbances. Changes in serum total CO2, serum potassium and chloride concentrations, or increased anion gap may provide clues to the existence of acid-base disorders. Blood gas analysis is usually required to confirm mixed acid-base disorders. To identify mixed acid-base disorders, blood gas analysis is used to identify primary acid-base disturbance and determine if an appropriate compensatory response has developed. Inappropriate compensatory responses (inadequate or excessive) are evidence of a mixed respiratory and metabolic disorder. The anion gap is also of value in detecting mixed acid-base disturbances. In high anion gap metabolic acidosis, the change in the anion gap should approximate the change in serum bicarbonate. Absence of this relationship should prompt consideration of a mixed metabolic acid-base disorder. Finding an elevated anion gap, regardless of serum bicarbonate concentration, suggests metabolic acidosis. In some instances, elevated anion gap is the only evidence of metabolic acidosis. In patients with hyperchloremic metabolic acidosis, increases in the serum chloride concentration should approximate the reduction in the serum bicarbonate concentration. Significant alterations from this relationship also indicate that a mixed metabolic disorder may be present. In treatment of mixed acid-base disorders, careful consideration should be given to the potential impact of therapeutically altering one acid-base disorder without correcting others.

Acid-Base Equilibrium↗
PubMed1989

DNA sequence and expression of the 36-kilodalton outer membrane protein gene of Brucella abortus.

The cloning of the gene(s) encoding a 36-kilodalton (kDa) cell envelope protein of Brucella abortus has been previously described (T. A. Ficht, S. W. Bearden, B. A. Sowa, and L. G. Adams, Infect, Immun. 56:2036-2046, 1988). In an attempt to define the nature of the previously described duplication at this locus we have sequenced 3,500 base pairs of genomic DNA encompassing this region. The duplication represented two similar open reading frames which shared more than 85% homology at the nucleotide level but differed primarily because of the absence of 108 nucleotides from one of the two gene copies. These two genes were read from opposite strands and potentially encoded proteins which are 96% homologous. The predicted gene products were identical over the first 100 amino acids, including 22-amino-acid-long signal sequences. The amino acid composition of the predicted proteins was similar to that obtained for the Brucella porin isolated by Verstreate et al. (D. R. Verstreate, M. T. Creasy, N. T. Caveney, C. L. Baldwin, M. W. Blab, and A. J. Winter, Infect. Immun. 35:979-989, 1982) and presumably represented two copies of the porin gene, tentatively identified as omp 2a (silent) and omp 2b (expressed). The homology between the two genes extended to and included Shine-Dalgarno sequences 7 base pairs upstream from the ATG start codons. Homology at the 3' ends extended only as far as the termination codon, but both genes had putative rho-independent transcription termination sites. Localization of the promoters proved more difficult, since the canonical procaryotic sequences could not be identified in the region upstream of either gene. Promoter activity was demonstrated by ligation to a promoterless lacZ gene in pMC1871. However, only one active promoter could be identified by using this system. A 36-kDa protein was synthesized in E. coli with the promoter in the native orientation and was identical in size to the protein produced in laboratory-grown B. abortus. When the promoter-containing fragment was inverted, a 33-kDa protein was expressed. These results were consistent with the predicted sizes based on the nucleotide sequences of the open reading frames in omp 2b and omp 2a. Whether this locus contains one active and one silent or cryptic porin gene, or two active Brucella porin genes expressed under different environmental conditions, is discussed.

Amino Acid Sequence↗
PubMed1989

Capacity of passively administered antibody to prevent establishment of Brucella abortus infection in mice.

In contrast to immunity against some other facultative intracellular parasites, protective immunity against Brucella abortus is mediated in mice by antibodies as well as by cell-mediated immune responses. It was the purpose of this study to determine whether antibody alone would prevent infection with B. abortus. The majority (82%) of CD-1 outbred mice infected with 100 CFU of virulent B. abortus 2308 preincubated with graded quantities of an O polysaccharide-specific IgG2a monoclonal antibody (MAb) were free of infection 1. 2, 4, and 6 weeks later, based on detection limits of 13 brucellae per spleen and 39 per liver. Infection was present in 95% of control animals. Similar results were obtained with a challenge dose of 500 CFU, but with a challenge dose of 5,000 CFU, infection became established even with the highest concentration of MAb used (50 micrograms of MAb per 5,000 brucellae). Pretreatment with an O polysaccharide-specific IgG1 MAb or with convalescent-phase serum diminished but did not prevent establishment of infection by 100 CFU of B. abortus. A majority of culture-negative mice tested 6 weeks after infection were serologically negative, which could have signified either the absence of previous infection or the early elimination of infection. In an in vitro test system, all of the antibody preparations were efficient in opsonizing B. abortus. Effective killing of the organism by unelicited mouse peritoneal macrophages occurred in conventional but not in endotoxin-free medium, suggesting that activated macrophages were required for killing of opsonized B. abortus. These results emphasize the potential importance of antibodies in the immunoprophylaxis of brucellosis and suggest that the design of a successful vaccine will require the induction of antibodies not only of appropriate specificity but also of the optimal isotype for mediating protective functions.

Animals↗
PubMed1989

Macrophage function in mammary glands of Brucella abortus-infected cows and cows that resisted infection after inoculation of Brucella abortus.

Nonvaccinated pregnant cows were segregated retrospectively into 2 groups following inoculation with Brucella abortus strain 2308. One group resisted infection (resistant cows) and the other group developed active infections (susceptible cows) and subsequently aborted. Mammary gland macrophages collected from the 2 groups of cows were compared, using in vitro functional assays. In a chemiluminescence assay, mammary gland macrophages from resistant cows produced significantly (P = 0.014) higher oxidative burst activity than did macrophages from susceptible cows. Macrophages from resistant cows had significantly (P = 0.038) greater bacteriostatic activity against B abortus than did macrophages from susceptible cows. Differences in lysosomal enzymatic activity or Fc receptor expression were not observed for macrophages from the 2 groups of cows. Differences in macrophage function may be one factor responsible for natural resistance to Brucella infection in cattle.

Abortion, Veterinary↗
PubMed1989

DNA homology of Brucella abortus strains 19 and 2308.

The restriction endonuclease digestion DNA patterns from Brucella abortus strains 19 and 2308 were examined with 11 restriction enzymes (AvaI, BamHI, BglII, BstEII, DdeI, EcoRI, HindIII, KpnI, PstI, XbaI, and SalI). The DNA electrophoretic banding patterns between the 2 strains were highly similar, using this restriction enzyme analysis. Differences were not discernable between B abortus strains 19 and 2308 in any of the restriction banding patterns examined. Methylation at CCGG or GATC sites was not detectable on the basis of digestion with isoschizomers (HpaII and MspI, and DpnI, Sau3AI and MboI). Homology between B abortus strains 19 and 2308 was assessed, using solution-hybridization techniques followed by S1 nuclease assays. Results of these reassociation experiments indicated 98.6 to 99.3% homology between B abortus strains 19 and 2308 with 13.5 to 18.6% homology between B abortus (strains 19 and 2308) and the E coli HB101 control. We concluded that any DNA differences between the 2 B abortus strains are small and will require analysis at the DNA sequence level.

Animals↗
PubMed1988

Correlation of field strain exposure with new cases of brucellosis in six beef herds vaccinated with strain 19.

Three hundred sixty cattle at risk in 6 beef herds known to include cows infected with Brucella abortus field strains were vaccinated with 3 x 10(9) colony-forming units of strain 19. Field strain exposure after vaccination was estimated by the number of cows with brucellosis that calved or aborted in the herd. As the number of exposures increased, the number of cows developing brucellosis increased, and 19 exposures in the 6 herds resulted in 9 new cases. The ratio of exposures to new cases varied from 1.0 to 2.0 in the 4 herds with new cases, whereas 2 herds with 1 and 3 exposures, respectively, did not have new cases of brucellosis. The correlation coefficient between the number of exposures and the number of new cases was 0.85, and the coefficient of determination suggested that 73% of the variation in new cases could be explained by the number of exposures in strain 19-vaccinated herds.

Animals↗
PubMed1988

Failure to isolate Brucella abortus from embryos or ova from culture-positive superovulated cows.

Nine, Brucella abortus culture positive 2-yr-old cows were used to test the hypothesis that embryos and ova collected from such cows are not infected. Superovulation was induced at varying times postpartum or postabortion with intramuscular injections of follicle stimulating hormone (FSH). The cows were artificially inseminated with B. abortus-negative semen. Superovulations and nonsurgical embryo collections nonsurgical embryo collections were attempted twice for each cow. Jugular blood, udder secretions, cervical swabs, uterine collections, embryos and ova were cultured bacteriologically from the nine cows simultaneously at nonsurgical embryro collections, and B. abortus was isolated only from the udder secretions of seven cows. Brucella abortus was not isolated from 15 uterine collections, 21 embryos, or 18 ova from the culture-positive cows. It was concluded that B. abortus was not present at the detection limits of the culture method employed, which supports the finding or view that embryos and ova collected from donor cows at 100 days or greater post partum or post abortion are not likely to harbor Brucella.

Journal Article↗
PubMed1988

A 36-kilodalton Brucella abortus cell envelope protein is encoded by repeated sequences closely linked in the genomic DNA.

Recombinant bacteriophage expressing Brucella abortus antigens have been isolated from a lambda gt11 expression library by using antibody raised against a sodium dodecyl sulfate-polyacrylamide gel electrophoresis-purified cell envelope protein of 36 kilodaltons. Fusion products expressed by these recombinants vary in apparent molecular mass by sodium dodecyl sulfate-polyacrylamide gel electrophoresis but only slightly exceed the size of beta-galactosidase. Western blot (immunoblot) analysis of crude lysates derived from lambda gt11 lysogens indicates that the fusion products react specifically with the original antisera used for recombinant selection and selectively bind antibody directed against the 36-kilodalton cell envelope protein. Analysis of the DNA inserts from 11 independently selected recombinants reveals similar-size EcoRI fragments which range in size from 150 to 300 base pairs (bp), all of which cross-hybridize via Southern blot analysis. Three independently selected EcoRI inserts ranging in size from 200 to 270 bp have been subcloned into M13mp18 and sequenced; all three contain a common region of about 200 bp. Southern blot analysis of B. abortus genomic DNAs digested with EcoRI, PstI, or DdeI indicates the presence of two fragments which hybridize to these DNA probes while single BamHI and HindIII fragments hybridize. The absence of these sites from the internal DNA sequence of the cloned probes suggests the presence of more than one copy of these sequences within the B. abortus genome. The same DNA probes have been used to select genomic clones of approximately 20 kbp from a lambda 2001 library. The lambda 2001 recombinants contain single BamHI fragments and two PstI fragments which hybridize to these oligonucleotide probe constructed on the basis of the amino-terminal sequence of the mature gene product hybridizes to the same BamHI and PstI fragments as the lambda gt11-derived DNA probe. Although the relative positions of the oligonucleotide sequences and the lambda gt11 insert within the genes is not known, the two sequences flank a region which corresponds to at least 40% of the size of the predicted gene. Additional experimentation must be performed to determine whether these sequences represent either two complete structural genes encoding major cell envelope proteins or repetitive sequences within a single structural gene.

Amino Acid Sequence↗
PubMed1988

Interspecific transmission of Brucella abortus from experimentally infected coyotes (Canis latrans) to parturient cattle.

In four separate trials, 10 coyotes (Canis latrans) which had been individually fed mascerated bovine placental tissue experimentally inoculated with Brucella abortus strain 2308 were placed in a 1 ha isolation area with six parturient, non-B. abortus vaccinated, Brucella spp. seronegative Hereford heifers. During the second trial, three of the heifers became Brucella spp. seroreactive (as determined by the card, standard agglutination tube, rivanol, complement fixation, and enzyme labeled immunosorbent assay tests) 14 days after exposure to the B. abortus infected coyotes. Five of 10 coyotes in the second trial seroconverted to Brucella spp. positive by day 14 postexposure (PE) and by day 27 PE seven of the 10 coyotes were Brucella spp. reactive. The three Brucella spp. seroreactive heifers subsequently aborted on days 35, 64 and 66 PE and B. abortus strain 2308 was isolated from vaginal swabs, milk, and placental and fetal tissues. There was no serologic or bacteriologic evidence of transmission from B. abortus infected coyotes to the susceptible cattle recorded in the other three trials.

Animal Feed↗
PubMed1988

Relationship of days in gestation at exposure and development of brucellosis in strain 19-vaccinated heifers.

Heifers injected with 10(8) (n = 40), 10(9) (n = 39), or 10(10) (n = 39) colony-forming units of Brucella abortus strain 19 were conjunctivally exposed to 10(7) colony-forming units of strain 2308 during gestation. At parturition, milk from each quarter of the udder, a piece of placenta, and 2 swab specimens of the uterus from the dam plus a swab specimen of the rectum from each calf were cultured for Brucella. If the calf was dead or died, additional specimens of lung, stomach contents, and a mediastinal lymph node also were cultured. Days in gestation was determined for each heifer, using data from rectal palpation after breeding and crown-rump length and weight of calf at parturition, with the median value used for data analysis. In each vaccine dosage group, the proportion (%) of heifers developing brucellosis increased as days in gestation at exposure increased. Strain 2308 was isolated from 3 (11%) of 26, 16 (25%) of 64, and 18 (64%) of 28 heifers that were grouped as less than 121, 121 to 150, and greater than 150 days in gestation at time of exposure, respectively. Thirty-two (86%) of the 37 infected heifers were less than 260 days in gestation at parturition, and calves were premature. Heifers with premature calves were more likely to be infected, and tissues were more likely to yield multiple isolations of strain 2308, regardless of days in gestation at exposure or of days after exposure to parturition. Days after exposure to premature parturition of infected heifers ranged from 35 to 110.

Animals↗
PubMed1988

Survival of rough and smooth strains of Brucella abortus in bovine mammary gland macrophages.

Chronic bovine brucellosis is characterized by persistent infection of the mammary gland. The interaction of live Brucella abortus with bovine mammary gland macrophages was studied in vitro. Opsonization of smooth B abortus strain 2308 and rough strain 45/20 was required for phagocytosis by mammary gland macrophages. When opsonized with specific antiserum, strains 2308 and 45/20 stimulated a considerable oxidative burst when phagocytized by mammary gland macrophages. Intracellular survival rates for strain 2308 were significantly higher than those for strain 45/20. After being phagocytized, B abortus localized in phagosomes and phagolysosomes of mammary gland macrophages.

Animals↗
PubMed1987

Aplastic anemia associated with trimethoprim-sulfadiazine and fenbendazole administration in a dog.

A dog that was treated with trimethoprim-sulfadiazine and fenbendazole developed transient aplastic anemia. The onset of bone marrow aplasia at 14 days after initiation of treatment and remission of it after cessation of treatment suggested that the aplasia was drug-induced. A hematologically normal dog treated with the same drug combination failed to develop hematologic dyscrasia. Because of the potential toxic effects of trimethoprim-sulfadiazine and/or fenbendazole, animals under treatment with this combination should be monitored by use of periodic CBC.

Anemia, Aplastic↗
PubMed1987

Influence of interferon in natural resistance of mice to Sendai virus pneumonia.

The influence of interferon (IFN) on the natural resistance to Sendai virus was investigated in resistant (C57BL/6NCr) and susceptible (DBA/2NCr) mouse strains. After inoculation with strain 52 Sendai virus, the pulmonary titers of Sendai virus were similar in both mice strains, indicating that the quantity of virus in the lungs may not be a major factor in determination of resistance. The pulmonary IFN titers were higher in DBA/2 mice, indicating that increased susceptibility of DBA/2 mice is not a result of inadequate production of IFN. Treatment of both strains with exogenous IFN before and during viral infection induced an increased survival time in C57BL/6 mice, but eventual mortality was the same in both mouse strains. Administration of anti-IFN antibodies to both mouse strains during Sendai infection decreased mortality equally in both strains, compared with mortality in control mice. Seemingly, the difference in resistance to Sendai virus in DBA/2 and C57BL/6 mice was probably not a result of the beneficial effects of IFN. On the contrary, administration of anti-IFN antibodies decreased the susceptibility of both mouse strains.

Animals↗