Studies on the effect of toxin T-514 on the integrity of peroxisomes in methylotrophic yeasts

Abstract We have studied the response of two methylotrophic yeasts ( Hansenula polymorpha and Candida boidinii ) to toxin T-514, a toxin lethal to man, extracted from the shrub Karwinska homboldtiana . Growth experiments indicated a dose-response effect; at enhanced concentrations (50 μg/ml) the different subcellular organelles rapidly disintegrated resulting in death of the cultures. At non-lethal concentrations (<2 μg / ml ) growth ceased initially, but resumed after a lag period of 4 h. At the subcellular level a specific effect was observed on peroxisomal integrity. Distinct holes appeared in the peroxisomal membranes, resulting in leakage of matrix proteins from these organelles. In addition, import of newly synthesized proteins appeared to be blocked since cytosolic aggregates of matrix proteins were formed. The peroxisomal damage was probably irreversible since affected organelles were degraded at later stages of incubation. Upon restoration of growth on methanol, new peroxisomes developed from those which had escaped degradation.     

Influence of <Emphasis Type="Italic">Daphnia</Emphasis> infochemicals on functional traits of <Emphasis Type="Italic">Microcystis</Emphasis> strains (Cyanobacteria)

We conducted a laboratory experiment to investigate the influence of Daphnia infochemicals on growth rate, microcystin production, colony formation and cell size of eight Microcystis strains isolated from two lakes. The strains were characterized genetically by their 16S-23S rDNA ITS sequence. The experiment was composed of four treatments: (1) a control using filtered WC medium, (2) addition of Scenedesmus obliquus culture medium filtrate, (3) addition of Daphnia magna culture medium filtrate and (4) addition of sodium octyl sulphate, a commercially available Daphnia infochemical. Our results showed that sympatric strains differed strongly for the measured functional traits, while no correlations between traits were found. Between-strain differences in growth rate, microcystin production, colony formation and cell size were generally larger than the differences in phenotypes observed between treatments. Despite this, several strains reacted to the infochemicals by changing functional trait values. Daphnia culture medium filtrate and, to a lesser extent, sodium octyl sulphate had a negative influence on the growth rate of half of the strains and stimulated microcystin production in one strain, but the latter effect was not Daphnia-specific as Scenedesmus culture medium filtrate had the same effect. Daphnia culture medium filtrate also induced colony formation in one strain. Our data suggest that Daphnia infochemicals generally have a weak influence on growth rate, microcystin production and colony formation of Microcystis strains as compared to the inter-strain variability, while existing inducible effects are highly strain-specific.     

The modified leukocytosis promoting factor (LPF)-test: A valuable supplement to the mouse weight gain (MWG)-test in toxicity control of whole cell pertussis vaccine

For the safety testing of pertussis vaccine, many in vivo assays have been developed, but none of these assays, except the Mouse Weight Gain (MWG)-test, are obligatory. Leukocytosis Promoting Factor (LPF) test, performed in mice, is one of the tests to examine the toxicity. However, due to lack of standardization, this test has not been implemented in the regular safety testing of the vaccine. Our investigations demonstrate that the LPF-test becomes more reproducible and sensitive if preparations are administered subcutaneously on day 0 and and counting of the leukocytes are done on day 6. Therefore, it is suggested to include the revised LPF-test in the quality control panel for the assessment of the toxicity of whole-cell pertussis vaccine.