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H Tabel

Publications and source records attributed to H Tabel.

At least 37 records · Page 2Linked to original sources
PubMed1990

Genetic polymorphism of complement factor H in cattle.

Bovine factor H was found to be polymorphic by the combined techniques of SDS-polyacrylamide electrophoresis of bovine plasma and immunoblotting. Three phenotypes (S, SF, F) were identified in a sample population of 149 cattle. Variant S and F differed by an apparent molecular weight of 5000 daltons. Family studies demonstrated Mendelian segregation of variants S and F. The data indicate that these genetic variants of bovine factor H are encoded by two codominant alleles at a single autosomal locus.

Alleles↗
PubMed1990

Sequence of the pckA gene of Escherichia coli K-12: relevance to genetic and allosteric regulation and homology of E. coli phosphoenolpyruvate carboxykinase with the enzymes from Trypanosoma brucei and Saccharomyces cerevisiae.

The sequence of the pckA gene coding for phosphoenolpyruvate carboxykinase in Escherichia coli K-12 and previous molecular weight determinations indicate that this allosteric enzyme is a monomer of Mr 51,316. The protein is homologous to ATP-dependent phosphoenolpyruvate carboxykinases from Trypanosoma brucei and Saccharomyces cerevisiae. A potential ATP binding site was conserved in all three sequences. A potential binding site for the allosteric activator, calcium, identified in the E. coli enzyme, was only partially conserved in T. brucei and S. cerevisiae, consistent with the observation that the enzymes from the latter organisms were not activated by calcium. The published sequence of the ompR and envZ genes from Salmonella typhimurium is followed by a partial sequence that is highly homologous to pckA from E. coli. The order of these genes and the direction of transcription of the presumptive S. typhimurium pckA gene are the same as those in E. coli. The potential calcium binding site of the E. coli enzyme is conserved in the partial predicted sequence of the S. typhimurium phosphoenolpyruvate carboxykinase, consistent with the observation that calcium activation of the S. typhimurium phosphoenolpyruvate carboxykinase is very similar to that observed for the E. coli enzyme. A pckA mRNA transcript was observed in stationary-phase cells but not in logarithmically growing cells. The mRNA start site was mapped relative to the sequence of the pckA structural gene.

Allosteric Regulation↗
PubMed1990

Bb fragment of bovine complement factor B: stimulation of the oxidative burst in bovine monocytes.

In a previous study, we reported that fragment Bb of bovine complement factor B activated bovine monocytes, as demonstrated by the uptake of 3H-deoxyglucose. In the present study, the effects of Bb on the production of superoxide anion and hydrogen peroxide by bovine monocytes was investigated. The production of superoxide was measured by the superoxide dismutase inhibitable reduction of cytochrome c. The change in absorbance was determined by a spectrophotometer at a wavelength of 550 nm. Hydrogen peroxide production was measured by the horse-radish peroxidase-dependent oxidation of phenol red. The resulting color change was measured by a spectrophotometer at a wavelength of 620 nm. Fragment Bb (20 micrograms/mL) induced the generation of 0.96 +/- 0.2 (mean +/- SEM) nanomoles of superoxide/2.5 x 10(5) monocytes at 5 min. The production of superoxide peaked at 15 min (1.24 +/- 0.3 nanomoles). The production of hydrogen peroxide was also rapid: 0.195 +/- 0.05 nanomoles/2.5 x 10(5) monocytes at 5 min with a peak at 15 min (0.250 +/- 0.04 nanomoles). These observations show that fragment Bb, which has serine protease activity, induces bovine monocytes to generate reactive oxygen intermediates such as superoxide and hydrogen peroxide.

Animals↗
PubMed1990

Fragment Bb of bovine complement factor B: stimulatory effect on the microbicidal activity of bovine monocytes.

We have previously shown that the Bb fragment of bovine complement factor B activates bovine monocytes and neutrophils. The activation was demonstrated by the enhanced uptake of 3H-deoxyglucose. To investigate the potential effect of fragment Bb on the microbicidal activity of bovine monocytes, a direct method was used. This method involves an initial ingestion period at 37 degrees C followed by repeated washing. The decrease in the total number of viable intracellular Staphylococcus aureus during the reincubation of the bacteria with bovine monocytes determines the intracellular killing. Maximal intracellular killing was seen when the monocytes containing the ingested S. aureus was incubated with fresh bovine serum (mean +/- SEM = 73.4 +/- 1.4%). On incubation of the monocytes, containing the ingested bacteria with heat-inactivated bovine serum, 32.5 +/- 0.7% of the intracellular bacteria were killed. When affinity-purified bovine factor Bb was added to the heat-inactivated serum, the intracellular killing capacity was almost restored (65.8 +/- 1.5%). When monocytes were incubated with medium alone, they killed 22.4% of the intracellular microorganisms. When fragment Bb (25 micrograms/mL) was added to the medium, the intracellular killing of S. aureus doubled (46 +/- 1.29%). We conclude that the Bb fragment of bovine complement factor B stimulates bovine monocytes in their microbicidal activity.

Animals↗
PubMed1990

Activation of bovine monocytes and neutrophils by the Bb fragment of complement factor B: demonstration by the uptake of 3H-deoxyglucose.

The Bb fragment is the enzymatically active split product of bovine complement factor B. The Bb fragment was obtained after zymosan treatment of fresh bovine serum and fractionation of the treated serum, first over diethylaminoethyl-Sephacel and then over an affinity column made up of monoclonal antibody to bovine Bb, coupled to cyanogen-bromide-activated Sepharose. Purified Bb has a molecular weight of 64,000, as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The ability of purified Bb to activate phagocytes was assessed. The activation assay was based on the principle that the primary source of energy for the phagocytes is obtained from glucose. 3H-deoxyglucose, a nonmetabolizable analogue of glucose, was used to obtain the quantitative measurement of the activation process. The activation by Bb was shown by the uptake of the labelled deoxyglucose in the phagocytic cells and was comparable to the activation caused by phorbol myristate acetate and N-formyl-L-methionyl-L-leucyl-L-phenylalanine, run in parallel. These data showed that fragment Bb activates bovine monocytes and neutrophils and also suggested that, when generated after complement activation, Bb may stimulate monocytes and neutrophils for enhanced phagocytosis.

Animals↗
PubMed1990

Immunohistochemical demonstration of Trypanosoma evansi in tissues of experimentally infected rats and a naturally infected water buffalo (Bubalus bubalis).

Trypanosoma evansi was demonstrated by an immunohistochemical technique in formalin-fixed paraffin-embedded tissues of experimentally infected rats. Trypanosoma evansi was visible readily, nuclei were stained darkly, the cytoplasm was stained moderately, and the cell membranes were delineated clearly. The parasites were present in small- to large-sized blood vessels of all organs, in extravascular spaces of ventricles and neuropil of the brain, and in interstitial tissues of the lung and testes. This method also stained nuclei but not cytoplasm or cell membranes of Trypanosoma congolense, and did not stain Trypanosoma theileri. In a water buffalo (Bubalus bubalis) with nonsuppurative meningoencephalitis, the presence of T. evansi could not be demonstrated by conventional histological stains. However, the trypanosomes were recognized readily in the Virchow-Robin spaces and neuropil of the brain by the immunohistochemical method.

Animals↗
PubMed1987

Enhanced resistance of highly susceptible Balb/c mice to infection with Trypanosoma congolense after infection and cure.

Balb/c and C57Bl/6 mice were cured with Berenil after infection with cloned organisms of Trypanosoma congolense and challenged with homologous or heterologous variants. The mice were fully protected against infection with 10(3) but not 10(5) organisms of the homologous variant. Normal Balb/c mice infected with 10(5) organisms developed uncontrolled parasitemia and had a mean survival time of 8.4 days. Challenge of drug-cured Balb/c mice with 10(5) organisms of the homologous variant established an infection associated with prolonged prepatent period, control of the first peak of parasitemia, and prolonged survival time (36 days). Indirect immunofluorescent and agglutination tests on live trypanosomes revealed that the "delayed" population of the first peak of parasitemia consisted of variants other than that used for challenge. No protection of drug-cured Balb/c mice was obtained following challenge with 10(1)-10(5) organisms of a heterologous variant. Passive transfer of variant-specific antiserum protected mice against infection with 10(3) organisms. Against infection with 10(5) organisms, it resulted in a prolonged prepatent period but had no effect on severity of parasitemia or duration of survival. There was no evidence for persistence of Berenil, which potentially could affect resistance. It was concluded that enhanced immunity in drug-cured Balb/c mice was due to (a) antibody to the variant surface glycoprotein and (b) another, yet unidentified, synergistically acting immune response to the parasite. Possible mechanisms are discussed.

Agglutination Tests↗
PubMed1986

The alternative pathway of complement in sheep during the course of infection with Trypanosoma congolense and after Berenil treatment.

Experimental T. congolense infections in sheep resulted in a striking decrease in parameters of the alternative complement pathway (ACP), ie. factor B, C3 and haemolytic complement activity (HA) initiated via the ACP. The levels of factor B, C3 and HA declined before, during and after the first wave of parasitemia which reached a peak at day 8. Levels of 20 to 25% of normal values (factor B) and 20% (C3, HA) persisted throughout the course of the infection. After Berenil treatment, when no parasites were detected in blood, their serum levels remained low. The returned to normal values about 8 (factor B) to 20 days (C3, HA) after trypanocidal treatment. Serum concentrations of factor B were significantly elevated in some, but not all sheep 6 days after infection with T. congolense. The sheep were tested for their potential state of immuno-modulation by immunization with Brucella abortus 4 days after trypanocidal treatment. In contrast to other sheep, the sheep which had shown early elevated serum factor B levels were found to express immune enhancement. It is suggested that there might be a positive correlation between the degree of enhanced serum levels of factor B at the early stage of infection and enhanced immune responsiveness.

Animals↗
PubMed1984

Alternative pathway of bovine complement: concentration of factor B, hemolytic activity and heritability.

Concentrations of bovine factor B (Bbov) were determined by radial immunodiffusion in sera of 46 Holstein cows and heifers aged one to nine years. Mean values were 34.2 +/- 5.3 mg/100 ml. A hemolytic diffusion plate assay in agarose gel in presence of 10 mM EGTA and 5 mM Mg accurately measured concentrations of purified Bbov but gave higher mean values, i.e. 47.8 +/- 10.2 mg/100 ml, for concentrations of Bbov in whole sera. Hemolytic values obtained by the hemolytic diffusion plate assay, however, weakly correlated (r = .4539, p less than 0.01) with the serum concentration of Bbov measured by radial immunodiffusion. It was concluded that the hemolytic diffusion plate assay was not an accurate technique for the quantitative measurement of Bbov but a good assay for quantitation of the total hemolytic activity mediated via activation of the alternative complement pathway. It is suggested that the difference between the values obtained by the two tests for one particular serum is, to some degree, an expression of the ratio of amplification and restriction of the alternative pathway activity. No significant heritability (offspring and one parent) was detected for the hemolytic activity of serum. A heritability of 0.93 at a significance level of p less than 0.1 was determined for the serum concentration of Bbov.

Animals↗
PubMed1983

Induction of parturition in mares: effect on passive transfer of immunity to foals.

Parturition was induced in 11 mares, using a synthetic prostaglandin. Eight mares, not treated, were used as controls. There was no significant difference between the serum immunoglobulin G (IgG) concentrations of the treated and control mares. The concentration of IgG in the colostrum of treated mares compared favorably with that reported for naturally foaling mares. Four foals from treated mares died or were euthanatized because of weakness during the 1st 24 hours after birth. The mean IgG concentration in the surviving foals from treated mares at 24 to 36 hours of age was 1,561 mg/100 ml, which was significantly (P less than 0.01) lower than the mean concentration of 2,731 mg/100 ml in foals from control mares. The mean serum IgG concentration in foals from control mares was significantly (P less than 0.01) greater than that of their dams, whereas the mean serum IgG concentration of the foals from treated mares was significantly (P less than 0.01) lower than that of their dams.

Animals↗
PubMed1983

Immune depression in bovine trypanosomiasis: effects of acute and chronic Trypanosoma congolense and chronic Trypanosoma vivax infections on antibody response to Brucella abortus vaccine.

Cattle were vaccinated with Brucella abortus (S19) vaccine during acute (25 days) and chronic (25 weeks) Trypanosoma congolense and chronic Trypanosoma vivax (25 weeks) infections in order to determine the effect of such infections on the antibody response to the vaccine. It was found that the specific antibody responses of IgG1 and IgG2 sub-classes were profoundly depressed (80%) in both the acute and chronic infections with T. congolense. Whereas IgM antibody response was also profoundly depressed (90%) in cattle with the acute infection, it was only 50% depressed in those with chronic infection. There was no depression of IgG1, IgG2, or IgM in cattle infected with T. vivax. These animals, however, had no detectable parasitaemia at the time of vaccination and thereafter. These results suggest that during acute infection with T. congolense depressive mechanisms could be acting on the afferent arm of the immune response, namely, antigen recognition and/or processing.

Acute Disease↗
PubMed1982

A comparative study of the disease in cattle caused by Theileria parva or T. lawrencei: II. Hematology, clinical chemistry, coagulation studies and complement.

Theileria lawrencei tick-derived stabilate infection of 8 cattle resulted in the development of panleukopenia and hypoproteinemia. In addition to these changes, T. parva infection caused mild normocytic, normochromic, non-responsive anemia at either of two dose rates. Disseminated intravascular coagulation, as indicate by positive protamine paracoagulation tests, prolonged prothrombin and partial thromboplastin times, and thrombocytopenia, developed in cattle infected with either of the Theileria spp., and was probably an important intermediary mechanism leading to death. Infection of calves with a high dose of T. parva stabilate resulted in more rapid onset of clinico-pathologic changes than did the low dose infection. Theileria lawrencei infection produced a severe, acute syndrome, the clinico-pathologic alterations of which varied in time of onset and severity between those of the T. parva high dose and low dose groups.

Animals↗
PubMed1982

Activation of the alternative pathway of bovine complement by Trypanosoma congolense.

Homogenates of Trypanosoma congolense and particulate and supernatant fractions thereof were, by two different techniques, shown to activate bovine complement via the alternative pathway. (1) All three preparations converted complement factor Bbov to its split product B gamma 2 as demonstrated (a) qualitatively by immunoelectrophoresis and (b) quantitatively by radial immunodiffusion. (2) Lysis of guinea-pig erythrocytes by bovine complement via the alternative pathway was inhibited by whole homogenates and particulate fractions of T. congolense organisms.

Animals↗
PubMed1981

Alternative pathway fof bovine complement Immunochemical studies on factor B-like serum protein and its conversion product B gamma 2.

Rabbits produced antibodies to a factor B-like serum protein (factor Bbov), its conversion product B gamma 2 and some other bovine serum proteins after repeated immunization with zymosan which previously had been incubated with fresh bovine serum. Such antisera were used to monitor purification of B gamma 2 from fresh bovine sera incubated with zxymosan. Subsequently, antisera specific for factor Bbov and B gamma 2 were produced. Antiserum produced against B gamma 2 cross-reacted with factor Bbov. Functional assays for factor Bbov were carried out in a hemolytic system with guinea pig erythrocytes in EGTA buffer. Heat inactivation (56 degrees C/5 min) of bovine serum destroyed the antigenicity of factor Bbov but not that of B gamma 2. Factor Bbov had an apparent molecular weight of 95,000 and B gamma 2 a molecular weight of 40,000 daltons. Conversion of factor Bbov to B gamma 2 was determined qualitatively by immunoelectrophoresis and quantitatively by radial immunodiffusion. Conversion of factor Bbov to B gamma 2 in bovine serum, in the presence of zymosan or cobra venom factor (CoVF) required Mg++ but not Ca++, did not occur in heat inactivated (56 degrees C/5 min) serum and was maximal, but not complete, when fresh bovine serum was incubated with zymosan (20 mg/mL) at 37 for two hours.

Animals↗
PubMed1981

Subclinical infectious bursal disease in commercial broiler flocks in Saskatchewan.

Five commercial broiler flocks, not vaccinated for infectious bursal disease virus, derived from infectious bursal disease virus-vaccinated breeder flocks were surveyed for evidence of bursal damage and infectious bursal disease virus infection. They were compared with two groups of birds raised in isolation. Serum samples from one day old chicks contained maternal anti-infectious bursal disease virus antibodies which declined to undetectable levels by four weeks of age. Serum antibody levels remained undetectable in both control groups and one commercial flock, whereas four of the five commercial flocks had actively produced anti-infectious bursal disease virus antibodies by slaughter age. The weight of bursae from infectious bursal disease virus-positive flocks declined as compared to controls after four weeks of age. The decline in weight correlated with the appearance of histopathological lesions. Infectious bursal disease virus antigen was demonstrated in selected infected bursae and infectious bursal disease bursae and infectious bursal disease virus was isolated from some of these damaged bursae. Clinical infectious bursal disease was not observed in any of the commercial flocks. The importance of subclinical bursal damage and immunosuppression is discussed.

Animals↗
PubMed1981

Experimental bovine trypanosomiasis (Trypanosoma vivax and T. congolense). III. Serum levels of immunoglobulins, heterophile antibodies, and antibodies to T. vivax.

Twenty-five steers were infected with T. vivax (EATRO 1721), 25 steers with T. congolense (EATRO 1800) and 25 steers kept as controls. Serum levels of immunoglobulins (IgG1, IgG2, IgM), natural antibodies to erythrocytes of chicken and sheep, and complement-fixing antibodies to T. vivax were measured. A significant decrease of serum IgM and natural antibodies to chicken erythrocytes occurred in the T. vivax group at day 9, i.e. at the decline of the first parasitemic wave. This was followed by a transient moderate increase of IgM accompanied by a transient decrease of IgG2. The T. congolense group had moderate decreases (less than 30%) of the mean IgG1 levels and moderate increases (less than or equal to 50%) of the mean IgG2, levels. It was concluded that there was little evidence for polyclonal activation of lymphocytes and that the decreased IgG1 levels in the T. congolense group might have been a reflection of immunosuppression. The complement-fixation test proved to be a sensitive tool for monitoring the antibody response to T. vivax.

Animals↗
PubMed1981

Experimental Bovine Trypanosomiasis (Trypanosoma congolense). Lack of relation of the level of Parasitemia to the J blood group.

Twenty-five Holstein-Friesian steers were experimentally infected with Trypanosoma congolense EATRO 1721. They were tested for their J blood group status. Twelve steers were found to belong to Ja blood group and thirteen steers were either Js or Jcs. The level of parasitemia did not significantly differ between these two groups of cattle. It was concluded that the level of parasitemia is not influenced by J blood group antigens.

Animals↗