Induction of bulbing of tulip shoots in vitro

Bulbing has been induced in adventitious shoots from floral stem explants of Tulipa ‘Merry Widow’. Incubation of 1-mm thick explants at 20°C on a medium containing 1 mg l⁻¹ NAA and BAP for 14–18 weeks, followed by 4°C for 8 weeks, produced a consistent bulbing response in shoots after transfer back to 20°C. Bulbing was further enhanced by transfer to 25°C and by raising the concentration of sucrose in the medium. Microscopy indicated the presence of developing meristematic centres in shoots 12 weeks of age. Shoots over 16 weeks of age containing meristematic centres gave a variable bulbing response with applied gibberellins and cold incubation, depending on whether gibberellins were supplied continuously in the medium or via a brief soak in sterile gibberellin solutions before sub-culturing. A GA₃ “soak” of 1.0 mg l⁻¹ was optimum for bulb production. The possible mechanisms of cold and gibberellin effects are discussed.     

Antibody Development in Pigs Inoculated with Live or Killed Cultures of Brucella Abortus

As shown by density gradient ultracentrifugation and column chromatography, pigs formed IgM antibodies during the first week following vaccination with Brucella abortus, strain 19. At this time their sera reacted in both plate and tube agglutination but not in complement-fixation tests. A few days later, when IgG antibodies had developed, agglutination titers were still high and some activity was recorded in hemolytic complement-fixation tests. A similar sequence was observed in pigs repeatedly inoculated with phenol-killed suspensions of B. abortus. As the proportion of IgM to IgG antibodies decreased, agglutinin titers fell in relation to complement-fixing titers. In some animals the conglutinating complement absorption test became positive earlier than the plate agglutination.     

Studies of Johne's Disease in Canada: XII. Electrophoretic Analysis of Changes in Serum Proteins in Infected Cattle and Sheep

Electrophoretic examinations were made on sera collected monthly for a period of eleven months from ten cattle naturally or experimentally infected with Johne''s bacilli and from ten contact sheep. With one exception, the percentage estimates for the four major classes of serum proteins, albumin, alpha₁-, alpha₂-, beta- and gamma-globulins did not differ significantly in sera from infected and non-infected, presumably healthy cattle. One cow with a persistently high complement-fixing titre with Johne''s bacillus antigen, showed an exceptionally high proportion of gamma-globulin in its serum. The percentage of gamma-globulin tended to be higher in sera of contact sheep than in that of normal sheep sera but the monthly variation in the relative proportion of these and other globulins showed no evident relationship to the fluctuations observed in the specific complement-fixing and anti-complementary properties of these sera.     

The Effect of Unheated Normal Bovine Serum on the Complement-Fixing Activity of Heat Inactivated Bovine Antiserum with Homologous Antigen: III. Immunodiffusion Studies

Examination by immuno-diffusion methods in agar gel plates demonstrated that the supplementing fraction precipitated from normal bovine serum by dialysis against dilute buffer, pH 5.0 to 6.6, contains at least three main antigens, and a weaker fourth. Two of these antigens or antigen determinants appeared to be present in globulin fractions prepared by dilution with distilled water or differential precipitation with ammonium or sodium sulphate.     

Comparison of inoculation regimes for the experimental production of swine erysipelas arthritis: II Serological findings in a gel diffusion precipitin test and enzyme-linked immunosorbent assay

The serological response of pigs to Erysipelothrix rhusiopathiae inoculation was monitored by a gel diffusion precipitin test (GDPT) using a crude, serotype-specific, autoclaved antigen and an enzyme-linked immunosorbent assay (ELISA) using a heat-extracted, alcohol precipitated and molecular seived antigen previously shown to react with serum from pigs infected with serotypes 1 or 2. All pigs receiving 3 or 5 weekly intravenous inoculations of either a highly virulent (VRS 229) or a lowly virulent isolate (VRS 252) produced GDPT-reactive antibody within 3 weeks, but only 44% were still reactive at 8 to 9.5 weeks. The ELISA response was significantly higher in pigs inoculated with the highly virulent strain, and was similar in pigs receiving 3 or 5 doses of either strain. In a dose-response trial, after 3 doses of VRS 229, GDPT reactivity occurred earlier and was stronger in pigs given higher doses of E. rhusiopathiae, but the response peaked 3 to 5 weeks after the start of challenge and was short lived. GDPT reactivity correlated with dose, but not with the severity of arthritis. The ELISA demonstrated specific IgG antibody was present by 2 weeks, and persisted to at least 11 weeks. The ELISA reactivity was significantly higher in pigs with arthritis than in pigs that received low doses and were not arthritic. Within groups of pigs with arthritis a significant, dose dependent, linear ELISA response developed but did not correlate with the presence or degree of arthritis at slaughter. Non-arthritic pigs had similar low ELISA responses to uninoculated controls.