Rapid Methods for Lipoxygenase Assay in Sweet Corn
Potential methods for rapid assay of sweet corn lipoxygenase (LPO) were evaluated and compared by visual inspection. Both model system (partially purified) and vegetable (LPO extract) system studies were carried out. Model system studies indicated that LPO had maximum activity at pH 6.0 and 2.0 mM linoleic acid. Methylene blue bleaching (MBB), carotene bleaching (CB), and potassium iodide-starch (KI-S) methods were evaluated both spectrophotometrically and visually. Both MBB and KI-S methods were effective for the model system. For the vegetable LPO extract systems (sweet corn and green beans), the MBB method indicated positive results for both, the CB method was not effective for either, and the KI-S method was very effective for green beans but not for sweet corn.
Partial Purification and Characterization of Asparagus Lipoxygenase
Lipoxygenase (LOX) from fresh asparagus was partially purified by extraction of acetone-washed asparagus powder with pH 4.5 potassium phosphate, ammonium sulfate fractionation and carboxymethyl-cellulose (CMC) chromatography. Asparagus LOX purified by ammonium sulfate fractionation had a pH activity optimum of 5.5–6.0 and was stable at pH 4.5–8.0 when stored at 2°C. Asparagus LOX was active on monolinolein as well as linoleic acid, but activity was very low on di- or tri-linolein. The CMC fractions with greatest LOX activity were nearly free of peroxidase activity while the protein fractions which did not bind with CMC at pH 5 were peroxidase active. The LOX activity in the purified asparagus extract was 90% inhibited by 1 mM cyanide when preincubated for 30 min at 25°C.
Genotypic diversity in field isolates of Babesia bovis from cattle with babesiosis after vaccination.
OBJECTIVE
To determine whether particular genotypes of Babesia bovis were common to field isolates obtained from cattle properties in Queensland where the B bovis vaccine had apparently failed.


DESIGN
A comparative study of polymerase chain reaction genotypes in different populations of B bovis.


PROCEDURE
Two polymerase chain reaction assays were applied to analyse DNA extracts of B bovis vaccine (K, T and Dixie strains) and 27 field isolates from 24 properties where disease outbreaks had occurred despite the use of the vaccine. To evaluate the stability of the genotypes identified, 11 of the field isolates were inoculated into experimental cattle that had either been previously vaccinated with T strain or not vaccinated.


RESULTS
No particular genotype of B bovis was responsible for the problems observed in previously vaccinated herds. None of the isolates had genotypes identical to the vaccine strains used. No geographic trends among the genotypes were observed. Isolates that originated from the same property also had different genotypes. Blood passage of the 11 field isolates in either previously vaccinated or nonvaccinated cattle did not alter the original genotype.


CONCLUSION
No particular genotypes identified by the Bv80 and BvVA1 polymerase chain reaction assays could be associated with vaccine failures.