Optimal size of self-adhesive preapplied electrode pads in pediatric defibrillation.
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Child↗
Biomedical subjects
R A Samson
Publications and source records attributed to R A Samson.
Comparison of transesophageal and intracardiac electrophysiologic studies in characterization of supraventricular tachycardia in pediatric patients.
OBJECTIVES: This study sought to determine the accuracy of transesophageal electrophysiologic studies in diagnosing and characterizing various mechanisms of supraventricular tachycardia in pediatric patients. BACKGROUND: Transesophageal electrophysiologic studies are a relatively noninvasive means of characterizing supraventricular tachycardia. Although widely used, to our knowledge no data exist that directly compare information obtained from transesophageal electrophysiologic studies with that from intracardiac electrophysiologic studies. METHODS: We reviewed the records of 57 pediatric patients undergoing both transesophageal and intracardiac electrophysiologic studies at our institution. The results of these studies were compared with respect to mechanism of tachycardia, localization of accessory atrioventricular (AV) connections (if present) and characterization of anterograde accessory connection conduction properties. RESULTS: Tachycardia mechanisms were concordant in 56 of 57 patients: orthodromic reciprocating tachycardia in 43, antidromic reciprocating tachycardia in 1, both orthodromic and antidromic tachycardia in 2, AV node reentrant tachycardia in 5, atrial reentrant tachycardia in 4 and ectopic atrial tachycardia in 2. Of 29 patients with orthodromic reciprocating tachycardia using a concealed accessory connection, transesophageal study predicted the accessory connection site through changes induced by transient bundle branch block in 12. By the Bland-Altman method in 14 patients with pre-excitation, the anterograde accessory connection effective refractory period determined by transesophageal study compared favorably with that determined by intracardiac study (mean difference 5.0 ms, limits of agreement -55 and 65 ms). CONCLUSIONS: Transesophageal electrophysiologic studies are a highly accurate means of diagnosing and characterizing various mechanisms of supraventricular tachycardia in pediatric patients.
Adolescent↗
DNA markers for differentiating isolates of Paecilomyces lilacinus.
Paecilomyces lilacinus is an agent for the potential biological control of soil nematodes. Arbitrarily primed PCR was used to fingerprint the genomes of 28 isolates of this fungus. Most (72%) of the isolates originated from soil of different regions of Brazil. Fourteen 10-mer oligonucleotide primers of arbitrary sequence revealed 293 scorable binary characters. Distinct genotypes were obtained for each isolate. Cluster analysis showed a high level of variability among these genotypes. The similarity among pairwise comparisons of the isolates varied from 84.3% to 7.6%, with a mean of 63.5%. No clearly defined phenetic groups were identified by cluster or multivariate analyses. No correlation with geographical origin or host was detected. In addition, PCR with four pairs of consensus tRNA gene primers was performed on a subsample of 12 P. lilacinus isolates, three P. farinosus isolates, two P. fumosoroseus isolates, and one isolate of P. amoenoroseus. An inferred phylogeny based on 112 binary characters obtained by tRNA-PCR showed a monophyletic group which contained most of the P. lilacinus isolates. In contrast, three isolates of P. farinosus were not in a monophyletic group under the inferred phylogeny. These results suggest that tRNA fingerprinting could provide a valuable tool which could be used to develop the molecular taxonomy of Paecilomyces, as morphological characteristics of asexual structures cannot entirely resolve species.
Base Sequence↗
Electrophysiological effects of alpha 2-adrenergic stimulation in canine cardiac Purkinje fibers.
The effects of alpha 2-adrenergic stimulation on action potentials were measured in isolated canine Purkinje fibers. Action potential durations at 50 and 90% of repolarization (APD50 and APD90) were significantly prolonged by 0.25 microM l-norepinephrine + 0.5 microM dl-propranolol (NE+P) from baseline values of 166 +/- 7 and 249 +/- 9 (SE) ms (n = 7) to 174 +/- 7 and 265 +/- 9 ms, respectively (P < 0.05 for both). Selective alpha 2-blockade with 0.01 microM yohimbine (YO) reduced this prolongation by NE+P in APD50 and APD90 to 169 +/- 7 and 256 +/- 8 ms, respectively (P < 0.05 compared with NE+P). Additional selective alpha 1-blockade with 0.01 microM prazosin (PZ) completely blocked the effects of NE+P, returning APD50 and APD90 to 163 +/- 7 and 250 +/- 9 ms (not different from baseline). After incubation of isolated Purkinje fibers with pertussis toxin (1 microgram/ml), which reduced the availability of a 41-kDa membrane protein for ADP ribosylation by 70 +/- 7% (n = 4, P < 0.05), YO failed to reverse the prolongation in action potential durations brought on by NE+P, but the effects of PZ were intact. The effects of alpha 2-stimulation on beta-adrenergic-induced delayed afterdepolarizations (DADs) were studied by burst pacing of Purkinje fibers in Tyrode solution containing 7.5 mM Ca2+. The DADs induced in the presence of NE+PZ (beta- + alpha 2-stimulation) were significantly smaller in amplitude and required a shorter pacing cycle length to reach threshold than those induced in the presence of NE+PZ+YO (unopposed beta-adrenergic stimulation). Furthermore sustained triggered activity, seen in five of eight preparations under beta-stimulation, could no longer be elicited in the presence of beta- + alpha 2-stimulation. These results suggest that the postjunctional alpha 2-adrenergic receptors in canine Purkinje fibers are coupled to a pertussis toxin-sensitive G protein and that stimulation of these receptors leads to action potential prolongation and suppression of DADs induced by beta-adrenergic stimulation.
Action Potentials↗
Secondary metabolites of Penicillium bilaii strain PB-50.
A phosphate-solubilizing strain of Penicillium bilaii was tested for the production of gliotoxin and other toxic compounds. The strain was fermented under five different conditions to allow the expression of various metabolites, including gliotoxin. These included Czapek-yeast extract medium under both shaken and still conditions as well as Czapek-yeast extract/malt extract/peptone medium and sucrose/glycerol medium in shake flasks. In addition, culture filtrate from an industrial fermentation of the fungus was examined. No gliotoxin was produced in any of the media. No other expected P. bilaii metabolites were found. Three compounds were identified in all samples: dibutyl phthalate, 1-(4-hydroxy-phenyl)ethanone and 4-hydroxy-3,6-dimethyl-2H-pyran-2-one. The production of other metabolites was dependent on the culture conditions. Two hyalodendrin derivatives were found in some fermentations and two related compounds were tentatively identified. None of the compounds found have been reported as toxic. The identity of the culture was confirmed by comparison with the ex-type culture of P. bilaii.
Acetophenones↗
Fungal propagules in house dust. I. Comparison of analytic methods and their value as estimators of potential exposure.
The presence of viable mold propagules in house dust was investigated by 10 different analytic methods, in order to determine to what extent different results are obtained when different analytic methods are used. Moreover, the value of this measurement as an estimator of the potential exposure to fungi in epidemiologic studies was assessed. Floor and mattress dust was sampled in 60 homes in The Netherlands during autumn 1990. For investigation of the variability in time, sampling was repeated in 20 homes after 6 weeks. Each analytic method is characterized by a unique combination of culture medium, suspension medium, and dilution step. The highest mean number of colony-forming units (CFU)/g dust was obtained by suspension of at least 100 mg dust in a peptone or sucrose solution in a ratio of 1:50 (w/w), followed by 10-fold dilution and plating on DG18 agar (geometric mean (GM) approximately 60,000 CFU/g dust). The lowest mean number of CFU/g dust was obtained by direct plating of 30 mg dust on V8 agar (GM approximately 5300 CFU/g dust). The mean coefficient of variation of duplicate analyses varied from 11%, for suspension in sucrose and plating on DG18 agar, to 27%, for suspension and dilution in sucrose in combination with V8 agar. The highest mean number of species isolated was obtained by direct plating of 30 mg dust on DG18 agar (mean number of species: 17). Suspension and dilution on DG18 or V8 agars yielded an average of approximately six species. In duplicate analyses, the mean percentage of agreement for the species isolated varied from approximately 35%, for suspension and dilution, to 60%, for direct plating.(ABSTRACT TRUNCATED AT 250 WORDS)
Colony Count, Microbial↗
Fungal propagules in house dust. II. Relation with residential characteristics and respiratory symptoms.
As part of a case-control study on the relation between home dampness and respiratory symptoms of children, house-dust samples were collected from bedroom floors and mattresses in 60 homes in The Netherlands. The house-dust samples were analyzed for the presence of fungal propagules by plating 30 mg of dust directly onto DG18 agar. A checklist and questionnaire were used to obtain information on the home characteristics and occupant behavior that may have an effect on the presence of fungal propagules in house dust. The geometric mean (GM) numbers of colony-forming units (CFU)/g dust collected from the floors was 8990. The number of CFU/g dust was significantly higher in dust from carpeted floors than in dust from smooth floors (GM, respectively, 12,880 CFU/g dust and 3530 CFU/g dust). The GM number of CFU/g dust collected from mattresses was 6760. Overall, the mean numbers of CFU/g dust collected from floors and mattresses were higher in bedrooms where damp spots mold growth, or both were observed. However, these differences were not statistically significant. The relation between home characteristics and the number of CFU/g dust of the most frequently isolated mold species (n = 17), including Alternaria alternata, Cladosporium cladosporioides, Penicillium brevicompactum, and Scopulariopsis brevicaulis, was also investigated. Only the type of flooring had a significant and consistent effect on the number of CFU/g floor dust of the different mold species.(ABSTRACT TRUNCATED AT 250 WORDS)
Analysis of Variance↗
Ecology of Thermophilic Fungi in Mushroom Compost, with Emphasis on Scytalidium thermophilum and Growth Stimulation of Agaricus bisporus Mycelium.
Twenty-two species of thermophilic fungi were isolated from mushroom compost. Scytalidium thermophilum was present in the compost ingredients, fresh straw, horse droppings, and drainage from compost and dominated the fungal biota of compost after preparation. Of 34 species of thermophilic fungi tested, 9 promoted mycelial growth of Agaricus bisporus on sterilized compost: Chaetomium thermophilum, an unidentified Chaetomium sp., Malbranchea sulfurea, Myriococcum thermophilum, S. thermophilum, Stilbella thermophila, Thielavia terrestris, and two unidentified basidiomycetes. These species will be considered for future experiments on inoculation and more controlled preparation of compost.
Journal Article↗
Delayed afterdepolarizations and triggered arrhythmias in hypertrophic cardiomyopathic hearts.
Hypertrophic cardiomyopathy is known to be associated with increased risk of sudden cardiac death. The mechanism is unknown but ventricular tachyarrhythmia is believed to be a major contributing cause. Using standard microelectrode techniques, we examined the propensity of delayed afterdepolarizations (DADs) and triggered activity development in isolated ventricular myocardium from Syrian hamsters with hereditary hypertrophic cardiomyopathy (BIO 14.6) and control hamsters (BIO RB). Induction of DAD was facilitated by burst pacing (15-beat trains with decremental cycle lengths) and with isoproterenol (2 x 10(-7) mol/L). Under baseline conditions with Tyrode's solution containing 2.0 mmol/L CaCl2, no DADs were inducible in eight preparations of myocardium from normal hamsters by burst pacing with or without isoproterenol. In contrast, 2 out of 6 preparations of ventricular myocardium from BIO 14.6 hamsters had inducible DADs by burst pacing alone, and 5 out of 6 preparations had inducible DADs or triggered activity in the presence of isoproterenol (p < 0.05 compared with control). Increasing the extracellular Ca++ to 4.0 mmol/L resulted in enhancement of inducible DADs: in 2 out of 8 preparations with pacing alone, in an additional 2 preparations with isoproterenol in control myocardium, and in 5 out of 6 preparations of BIO 14.6 by burst pacing alone (p < 0.05 compared with control). Exposure to the protein kinase C (PKC)-activating phorbol ester phorbol 12-myristate 13-acetate resulted in suppression of the beta-adrenergic-induced triggered activity in hypertrophic cardiomyopathic preparations.(ABSTRACT TRUNCATED AT 250 WORDS)
Action Potentials↗
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↗
Mycotoxins: a mycologist's perspective.
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Animals↗
Environmental mycology and its importance to public health.
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Air Microbiology↗
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↗
Current taxonomic schemes of the genus Aspergillus and its teleomorphs.
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Aspergillus↗
Problems caused by new approaches in fungal taxonomy.
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Fungi↗
Chemotaxonomy of the genus Talaromyces.
Species of the ascomycetous genus Talaromyces have been examined for profiles of secondary metabolites on TLC. The greatest number of specific metabolites were produced on oatmeal-, malt extract- and yeast-extract sucrose agars. Profiles of intracellular secondary metabolites produced on oatmeal agar were specific for each species and provided a means of simple differentiation of the taxa. Examination of the most important species using high performence liquid chromatography (HPLC) allowed to solve some taxonomic problems. Known mycotoxins are produced by T. stipitatus (duclauxin, talaromycins, botryodiploidin), T. stipitatus chemotype II (emodin), T. panasenkoi (spiculisporic acid), T. trachyspermus (spiculisporic acid), T. macrosporus (duclauxin) and T. wortmannii (rugulosin). Wortmannin is produced by an atypical strain of T. flavus but not T. wortmannii. Several other secondary metabolites were discovered for the first time in the following species: Glauconic acid is produced by T. panasenkoi, T. ohiensis and T. trachyspermus; vermiculine by T. ohiensis; duclauxin by T. flavus var. macrosporus and the mitorubrins by T. flavus and T. udagawae. The profiles of secondary metabolites support the established taxonomy of the species based on morphology, showing the genetic stability of profiles of secondary metabolites in Talaromyces. Two new taxa are proposed: T. macrosporus comb. nov. (stat. anam. Penicillium macrosporum stat. nov.), and Penicillium vonarxii, sp. nov. for the anamorph of T. luteus.
Ascomycota↗
Enumeration and identification of airborne viable mould propagules in houses. A field comparison of selected techniques.
A number of techniques for the enumeration and identification of viable mould propagules in the indoor air of houses were evaluated in order to document to what extent different results are obtained when different methods are used. A comparison was made between the results obtained with five commercially available air sampling devices (Slit-to agar sampler, N6-Andersen sampler, Surface Air System sampler, Reuter Centrifugal Air sampler, Gelatine Filter sampler) and a non-volumetric sampler (the Open Petri Dish), in combination with four culture media (malt extract agar, dichloran glycerol-18 agar, oxytetracycline glucose yeast extract agar and dichloran rose bengal chloramphenicol agar). The coefficients of variation were high (generally greater than 20%) for all combinations. Statistical analysis showed that the Slit sampler and the N6-Andersen sampler in combination with DG18 and MEA gave the best precision and the highest yield in terms of colony forming units per square cubic meter of air (CFU/m3) and number of species isolated.
Air Microbiology↗
Presence of viable mould propagules in the indoor air of houses.
The aim of the first part of this study was to select the optimal technique for the enumeration and identification of viable mould propagules in the indoor air of houses. A comparison was made between the results obtained with six commercially available air sampling devices in combination with four culture media. The optimal technique was defined as the technique with the best precision and the highest yield. The coefficients of variation were high (generally greater than 20%) for all combinations. Statistical analysis showed that the Slit sampler and the N6-Andersen sampler in combination with DG18 and MEA gave the best precision and the highest yield in terms of CFU/m3 and number of species isolated. In the second part of this study the presence of viable mould propagules in the indoor air of 46 houses in relation to the dampness of these houses was investigated, using the N6-Andersen sampler in combination with DG18. To assess the variability in time, the measurements were repeated after five weeks. Overall, between the two periods no difference was found between the average number of CFU/m3 in the investigated homes. However, the variation between homes was much smaller than the variation within homes. The mean number of CFU/m3 was somewhat higher in "damp" houses than in "dry" houses. However, this difference was not significant. Furthermore, there were no demonstrable differences in the presence of specific mould species in "damp" and "dry" houses.
Air Microbiology↗