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Biomedical subjects

R A Samson

Publications and source records attributed to R A Samson.

13 recordsLinked to original sources
PubMed1992

Mycological condition of maize products.

Maize and maize-related products were investigated in a collaborative study for viable moulds and antigenic extracellular polysaccharides (EPS) produced by Aspergillus and Penicillium species. In addition, the samples were tested for the presence of aflatoxin B1. All maize products, with the exception of the heat processed products, contained viable moulds on an average of (log10 values) 3.3 +/- 0.7 colony-forming units per gram. In most samples a mixed mould flora was present. Species of the genus Fusarium were dominant, followed by Aspergillus, Eurotium and Penicillium. The mould colony count correlated positively with the presence of antigenic extracellular polysaccharides produced by species of Aspergillus and Penicillium. Gamma irradiation did not affect the detection of antigenic extracellular polysaccharides. Aflatoxin B1 was detected in two out of 35 samples; these contained 0.6 and 0.8 microgram/kg. From one of these aflatoxin B1-containing samples, Aspergillus flavus was isolated.

Aflatoxin B1↗
PubMed1992

Presence of viable mould propagules in indoor air in relation to house damp and outdoor air.

The presence of viable mould propagules in indoor air was investigated using the N6-Andersen sampler in combination with DG18-agar, in relation to house damp (characterized with a checklist) and in relation to the presence of moulds in outdoor air. The first part of the study was conducted in 46 houses in the autumn of 1987, the second part in 84 houses in May 1989. Further, in the second part, the results obtained with settlement plates (OPD) were compared with those obtained with the N6-Andersen sampler. The number of CFU/m3 in the indoor and outdoor air varied widely. A large variety of mould genera and species was isolated. Species of Cladosporium, Penicillium and Wallemia predominated. The variability in time was high and the reproducibility of the measurements in terms of CFU/m3 and of species isolated was only moderate. The low predictive value of these measurements limits their use in epidemiological studies of the relationship between exposure to moulds and respiratory symptoms. Overall, the geometric mean concentration was somewhat higher outdoors than indoors. However, the clear differences found between the number of CFU/m3 belonging to different mould species in in- and outdoor air show that the presence of viable mould propagules in indoor air is not simply a reflection of the presence of moulds in outdoor air. The presence of moulds in indoor air was only weakly related to house damp as characterized by the checklist. High, statistically significant correlations were found between the CFU yield obtained with the OPD and the CFU/m3 yield obtained with the N6-Andersen sampler.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants↗
PubMed1979

Scanning electron microscopy of Acholeplasma colonies on agar.

The colony formation and morphology of Acholeplasma laidlawii and of an Acholeplasma species was studied by scanning electron microscopy. In the colonies of both Acholeplasma spp. large irregularly shaped cells, spherical cells, chains of beads, and long filaments with small bulbous distensions were seen. The membrane of some of the large cells seemed to be perforated, giving the cell a pitted appearance.

Acholeplasma↗
PubMed1979

A simplified technique to prepare fungal specimens for scanning electron microscopy.

A simplified technique to prepare fungal specimens for scanning electron microscopy is described and discussed. Fixation in either 6% glutaraldehyde or 2% Os04 (both unbuffered aqueous solutions), yielded good results. The minimum fixation time in OSO4 was 2 h, in glutaraldehyde 4 to 5 h. Chemical dehydration with 2-methoxyethanol or 2,2-dimethoxypropane proved to be useful since it considerably reduced the preparation time. Because of the relatively few changes of reagent solutions during the whole process, the fungal specimens were less disturbed without much loss of material. The preparation technique described has been applied to specimens of various fungal groups with good results.

Fixatives↗
PubMed1978

Studies on the PR toxin of Penicillium roqueforti.

A mycotoxin, confirmed by chemical, physical and spectroscopic data as the PR toxin described by Ru-Dong Wei and coll. (15) has been isolated from culture filtrates of Penicillium roqueforti Thom. Factors affecting the toxin and mycelium production, acute and chronic toxicity in experimental animals and the frequency of toxinogenesis of 21 isolates of P. roqueforti (including a brown mutant) isolated from different materials, foods especially, were also studied. An hypothesis on the absence of PR toxin in cheeses fermented with P. roqueforti is also advanced.

Animals↗
PubMed1978

Aspergillus penicilloides and Eurotium halophilicum in association with house-dust mites.

Aspergillus penicilloides Speg., Eurotium halophilicum Christensen et al. and other xerophilic fungi were isolated from house dust. The isolates of E. halophilicum are described and compared with the type strain of this species. A. penicilloides appeared to be rather common. The species concept of this species is broadened to accomodate some variable forms with different colony characters and conidophore structures. The role of both species is discussed in connection with house-dust mites, house-dust allergy and skin diseases.

Air Microbiology↗
PubMed1977

A taxonomic study of the Penicillium chrysogenum series.

The taxonomy of the Penicillium chrysogenum series is reconsidered. On account of the observations of the available type strains and numerous isolates mainly obtained from food products, Penicillium notatum Westling, P. meleagrinum Biourge and P. cyaneofulyum Biourge are placed in synonymy with P. chrysogenum Thom. Synonymy and variability of the species are discussed.

Mutation↗
PubMed1977

The taxonomy of Penicillium species from fermented cheeses.

The taxonomy of the Penicillium camberti and P. roqueforti series is re-investigated. P. caseicolum Bainier is regarded as a synonym of P. camemberti Thom on the basis of morphological characters. P. casei Staub is considered to be identical with P. verrucosm Dierckx var. cyclopium (Westling) Samson, Stolk et Hadlok. Descriptions and illustrations of P. camemberti and P. roqueforti Thom are given. The occurrence and mycotoxin production of both species are shortly discussed.

Cheese↗