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Biomedical subjects

R A Samson

Publications and source records attributed to R A Samson.

At least 55 records · Page 3Linked to original sources
PubMed1990

Avian penicilliosis caused by Penicillium griseofulvum in a captive toucanet.

A sudden fatal illness developed in a group of New World toucanets held captive in Finland. Necropsy studies on one of the birds revealed the presence of invasive, hyaline, septate, branched mycelium in the lungs, air sacs, liver and other tissues. In addition, conidiophores and conidial chains, typical of members of the genus Penicillium were present in the lungs and air sacs. Cultures yielded a mould which was subsequently identified as Penicillium griseofulvum. A critical review of the literature revealed that only seven other species of Penicillium have been convincingly documented as agents of penicilliosis on the basis of histologic and cultural findings.

Animals↗
PubMed1989

Paecilotoxin production in clinical or terrestrial isolates of Paecilomyces lilacinus strains.

The production of paecilotoxin from various isolates of Paecilomyces lilacinus was studied using three different media and high performance liquid chromatography (HPLC). Alkaline medium was found to be suitable for the production of the toxins. Among 20 strains tested, 19 including four clinical isolates were found to produce the toxins. Production patterns of paecilotoxins were very similar in each strain and the main toxins were A and B.

Amino Acid Sequence↗
PubMed1985

Occurrence of moulds in modern living and working environments.

The occurrence of saprophytic moulds in indoor environments and their potential hazards to human health are discussed. In addition to mesophilic species, xerophilic moulds appear to be common, often developing together with mites. Allergic and non-allergic symptoms are reported when patients are exposed to moulds in homes, schools and working places. Air-conditioning systems are consistently involved with mould development. Complaints of eye-, nose- and throat-irritation as well as fatigue seem to be correlated with unpleasant odours produced by abundant mould growth, but the relationship between the symptoms and the odours is not understood. The role of air-borne mycotoxins is discussed. Methods to detect moulds in indoor environments are described. Because no single method or cultivation medium is sufficient to detect all the various indoor moulds, a combination of air sampling, direct microscopic examination and cultivation on both standard and low water activity media is recommended.

Air Conditioning↗
PubMed1984

The taxonomic situation in the hyphomycete genera Penicillium, Aspergillus and Fusarium.

Classification of species in the three genera Penicillium, Aspergillus and Fusarium is in a state of change. Criteria used are reviewed; possible stabilization of nomenclature is envisaged. Proper typification of recognized species is necessary. In Penicillium and Aspergillus some species known mainly from fermented food are considered as domesticated versions of other, wild species. In Penicillium a further standardization of conditions of cultivation and careful description of micromorphology are necessary, before the species concepts of different laboratories can be reconciled. Secondary metabolites (mycotoxins, pigments) prove to support taxonomic conclusions reached by morphological work. In Aspergillus the taxonomic situation is simpler than in Penicillium, but typification is not yet sufficiently settled. For some well-known species older names were recently unearthed. In Fusarium the taxonomic views of different laboratories are becoming more similar, but much work on type specimens and neotypification of other species is still required. More genetic evidence is necessary to decide about specific or varietal rank in critical cases.

Aspergillus↗
PubMed1983

On the taxonomy of the entomogenous fungus Filobasidiella arachnophila.

The taxonomic status of Filobasidiella arachnophila Malloch et al. was investigated. The carbohydrate profile of two strains revealed basidiomycetous affinities. However, the vast majority of the mycelial cells are monokaryotic, demonstrating that F. arachnophila is not a typical basidiomycete. The morphological resemblance to the two teleomorph species of Filobasidiella is noteworthy and therefore the accommodation in Filobasidiella is maintained. F. arachnophila proved to be identical with Aspergillus depauperatus Petch and the new combination Filobasidiella arachnophila (Petch) Samson et al. is made.

Basidiomycota↗
PubMed1983

Microscopic studies of Candida albicans and Torulopsis glabrata after in vitro treatment with bifonazole. Light and scanning electron microscopy.

1-[(4-Biphenylyl)-phenylmethyl]-1H-imidazole (bifonazole, Bay h 4502, Mycospor) preferentially inhibited yeast-hypha conversion in the dimorphic fungus Candida albicans. As observed by phase-contrast and scanning electron microscopy the morphology of C. albicans yeast cells and Torulopsis glabrata cells markedly altered after treatment with bifonazole. Whereas control cells were mostly occurring singly, the bifonazole-treated cells did not separate, resulting in the formation of chains and clusters of interconnected cells. Furthermore, in contrast with control cells bifonazole-treated cells of C. albicans and T. glabrata were almost spherical in shape. Evidence is presented by means of fluorescence microscopy that bifonazole-treated yeast cells of C. albicans frequently lacked septa and often contained irregular deposition of chitin.

Antifungal Agents↗
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↗
PubMedDate not supplied

Normal values for corrected sinus node recovery time in adolescents.

Sinus node recovery times have been used to evaluate sinus node function in adults and children. Normal values for corrected sinus node recovery time (CSNRT) are generally accepted as 275 and 500-550 msec in young children and adults, respectively. However, normal CSNRT values have not been determined for adolescent patients. Therefore, we mesured CSNRT in 29 consecutive patients, ages 12-17 years, who underwent electrophysiology testing as part of radiofrequency ablation. CSNRTs were performed by rapid atrial pacing for 30 seconds. Pacing cycle lengths were then shortened in 50-msec decrements to a minimum of 300 msec CSNRTs were determined by subtracting the patients' resting sinus cycle length from the maximal SNRT measured. The mean CSNRT was 323 +/- 61 msec (mean +/- SD, range 186-422 msec). A significant positive correlation between CSNRT and age was found. We conclude that the CSNRT value for the upper limit of normal in adolescents lies between the normal values previously determined for children and adults and is approximately 445 msec (mean + 2 SD). Because sinus node dysfunction is a well-recognized, long-term complication following surgical repair for complex congenital heart disease, this value becomes especially relevant as more children with congenital heart disease survive into adolescence.

Adolescent↗
PubMedDate not supplied

Phylogenetic relationships of five species of Aspergillus and related taxa as deduced by comparison of sequences of small subunit ribosomal RNA.

The nucleotide sequences of the genes encoding the 18S rRNA of Aspergillus flavus, A. nidulans, A. terreus and A. niger were elucidated and aligned to the sequences of A. fumigatus. In addition, the 18S rRNA sequences of the V4-V9 region of morphologically similar filamentous fungi, e.g. Penicillium chrysogenum, P. marneffei and Paecilomyces variotii, were elucidated. Phylogenetic analysis and comparison showed a very close intergeneric relationship of the genus Aspergillus to species of the genera Paecilomyces and Penicillium. However, the sequenced Aspergillus species also showed a very close relationship to Eurotium rubrum and Monascus purpureus. Phylogenetic analysis of fungal 18S rRNA sequences divided the general Aspergillus, Penicillium and Paecilomyces into two coherent clusters and showed a close intergeneric relationship which is in keeping with the existing morphological and taxonomic classification.

Aspergillus↗