[Dutch sign language and communication by and with deaf subjects].
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Communication↗
Biomedical subjects
E de Boer
Publications and source records attributed to E de Boer.
[Enterohemorrhagic Escherichia coli O157:H7, an underestimated food pathogen? A literature review].
Escherichia coli O157:H7 has recently been recognised as a human pathogen involved in outbreaks and sporadic cases of food-borne diseases in North America and Great Britain. At present, less is known about the significance of E. coli O157:H7 as a cause of food-borne diseases in the Netherlands. This article will review current literature about this serotype, which is a predominant representative of the enterohaemorrhagic E. coli (EHEC) group. Biochemical features, toxins, pathogenesis, clinical characteristics, epidemiology and methods of isolation will also be discussed.
Animals↗
Evaluation of the MPN, Anderson-Baird-Parker, Petrifilm E. coli and Fluorocult ECD method for enumeration of Escherichia coli in foods of animal origin.
Commercially available beta-D-glucuronidase (GUR) based methods, Petrifilm E. coli (PEC) and Fluorocult ECD (FECD), and ISO standard MPN and Anderson-Baird-Parker (ABP) procedures were evaluated for routine enumeration of E. coli in naturally contaminated foods of animal origin. The methods concerned were classifiable in a sequence of best qualities for: production, MPN > ABP = PEC = FECD; costs, FECD > ABP = PEC > MPN; time per measurement, ABP = PEC = FECD > MPN; practical use, PEC > FECD > ABP > MPN; detection at low contamination, MPN > ABP = PEC > FECD. The ABP and PEC method appeared useful for routine counting of E. coli in raw meat, poultry and meat products, whereas the MPN procedure turned out to be more sensitive, however, impractical and considerably more expensive. The FECD method was inexpensive although suitable for the enumeration of E. coli at higher contamination level (> 50 cfu/g). The indole and MUG indicators both applied to demonstrate E. coli with the ABP or FECD method proved to be equal in specificity.
Colony Count, Microbial↗
Isolation of Yersinia enterocolitica from foods.
Many selective enrichment and plating media for the isolation of Yersinia enterocolitica from foods are described. However, at present no single isolation procedure is available for the recovery of all pathogenic strains of Yersinia enterocolitica. Cold enrichment in phosphate-buffered saline plus 1% sorbitol and 0.15% bile salts (PBSSB) and two-step enrichment with tryptone soy broth (TSB) and bile oxalate sorbose (BOS) broth are very efficient methods for the recovery of a wide spectrum of serotypes of Y. enterocolitica. Enrichment in irgasan ticarcillin chlorate (ITC) broth was found to be the most efficient method for the recovery of strains of serotype 0:3, which is the most common clinical serotype of Y. enterocolitica in Europe. Post-enrichment alkali treatment often results in higher isolation rates. Cefsulodin irgasan novobiocin (CIN) agar and Salmonella-Shigella deoxycholate calcium chloride (SSDC) agar are the most commonly used plating media. For the recovery of serotype 0:8 strains, the common clinical isolates in North America, enrichment in BOS and plating on CIN seems the most efficient procedure. Selection of the proper enrichment procedure will depend on the bio/serotypes of Yersinia spp. sought and on the type of food to be examined. The use of more than one medium for both enrichment and plating will result in higher recovery rates of Yersinia spp. from foods. Parallel use of the following two isolation procedures is recommended. (1) Enrichment in ITC for 2 days at 24 degrees C; plating on SSDC agar (2 days at 30 degrees C). (2) Pre-enrichment in TSB for 1 day at 24 degrees C; enrichment in BOS for 5 days at 24 degrees C; alkali treatment (mixing 0.5 ml enriched broth with 4.5 ml of 0.5% KOH in 0.5% NaCl for 5 s); plating on CIN agar (2 days at 24 degrees C).
Culture Media↗
[Pork meat as a source of pathogenic Yersinia enterocolitica].
During a period of eight months, samples of carcasses, tonsils, tongues and rectal swabs were taken in four pig slaughter halls. Porcine head meat was sampled in a meat products factory and samples of minced pork were taken in butcher's shops. Pathogenic strains of Yersinia enterocolitica (serological groups O:3, O:9 and O:5.27) were isolated from 36 (42 per cent) of 86 porcine tonsils, 8 (20 per cent) of 40 tongues, 17 (17 per cent) of 100 rectal swabs and from 4 (1 per cent) of 400 pork samples. Pathogenic strains of Yersinia were not isolated from samples of 210 pig carcasses and from 20 samples of porcine head meat. These results confirm that pigs are an important reservoir of pathogenic Y. enterocolitica. However, contamination of carcasses during the process of slaughter with Yersinia from either faecal material or from the tonsillary region does not seem to occur frequently, which may also explain the low rate of contamination with pathogenic Y. enterocolitica observed in pork. As pork is rarely contaminated with pathogenic Y. enterocolitica, the possibilities for growth of these organisms in raw pork are limited, the minimum infective dose is probably high and pork is usually not eaten raw, it is not likely that pork is an important source of yersiniosis in the Netherlands.
Animals↗
Recovery of Listeria monocytogenes on selective agar media in a collaborative study using reference samples.
Sixteen laboratories compared counts of Listeria monocytogenes in reference samples using Blood agar, Palcam(y) agar and Oxford agar. Significant differences were found between laboratories. The mean counts on Blood agar were significantly higher than on Palcam(y) or Oxford agar. The mean counts on Palcamy agar were somewhat higher than on Oxford agar (only after 48 h incubation), but no significant difference was found. Addition of egg yolk to Palcam agar seems to be beneficial for the recovery of sublethally injured cells. Recovery of L. monocytogenes was higher after 48 h incubation for all media tested.
Agar↗
Slaughter pigs and pork as a source of human pathogenic Yersinia enterocolitica.
Pathogenic Yersinia enterocolitica strains (serogroups 0:3;0:9 and 0:5.27) were isolated from 36 (42%) of 86 porcine tonsils, 8 (20%) of 40 tongues, 17 (17%) of 100 rectal swabs and from 4 (1%) of 400 pork samples. Pathogenic Yersinia strains were not isolated from samples of 210 pig carcasses and from 20 samples of porcine head meat. These results confirm that pigs are an important reservoir of pathogenic Y. enterocolitica. However, contamination of carcasses during the slaughtering process with Yersinia from either faecal material or from the tonsillary region does not seem to occur frequently and this may also explain the low contamination rate of pathogenic Y. enterocolitica found for pork. For the isolation of pathogenic Y. enterocolitica strains from foods, enrichment in irgasan-ticarcillin-chlorate broth (ITC) and isolation on SS-deoxycholate-calcium agar (SSDC) is recommended.
Animals↗
On ringing limits of the auditory periphery.
In classical hearing theory frequency and time have been treated as nearly independent acoustical dimensions. In this paper the interaction between temporal and spectral aspects is studied. An important determinant in this respect is the filtering of auditory stimuli in the cochlea. A view of auditory filtering that is balanced in frequency and time is obtained from the 'reverse-correlation function', abbreviated: revcor function. This function is derived from the response of an auditory-nerve fibre to a white-noise sound stimulus. It is a useful descriptor of peripheral filtering for a wide class of stimuli in which effects of nonlinear distortion are of minor importance. Measured revcor functions can be approximated by a standard mathematical function of which the parameters have a clear meaning. For these functions the spread in time and in frequency are uniquely related to one another. This relation is carried over to the case of cochlear filtering and applied to two important cases: stimulation by signals with small and with large amplitude variations. The results turn out to be markedly different in these two cases. In the final section the relevance of the results to various other fields of auditory research is discussed.
Acoustic Stimulation↗
Can shape deformations of the organ of Corti influence the travelling wave in the cochlea?
Via their motile reactions outer hair cells may produce oscillatory power or amplify the fluid waves in the cochlea. When the cells move or change their lengths, the organ of Corti (OC) will change its shape. This paper describes the consequences of such shape changes for the physics of cochlear waves. The assertions posed are based on a mathematical derivation but the major conclusions can be grasped without following the mathematics in detail. There are two basic types of OC deformations. In the first type the net cross-sectional area of the OC is periodically varying, in the second type--the central subject of this paper--is is not. It is shown that for the latter type of OC shape deformation there is no interaction with the cochlear fluids, at least for long waves. Hence, in this case the outer hair cells cannot amplify cochlear waves. The other type of OC deformation has a better coupling with the cochlear waves. However, much of the pressure developed by oscillating hair cells is spent in the 'wrong' way, namely, by squeezing fluid lengthwise through the narrow channel of the OC. Therefore, in this mode power transfer from cochlear hair cells to cochlear fluids (and from there to the basilar membrane) would be very inefficient.
Animals↗
What type of force does the cochlear amplifier produce?
Recent experimental measurements suggest that the mechanical displacement of the basilar membrane (BM) near threshold in a viable mammalian cochlea is greater than 10(-8) cm, for a stimulus sound-pressure level at the eardrum of 20 microPa. The associated response peak is very sensitive to the physiological condition of the cochlea. In the formulation of all recent cochlear models, it has been explicitly assumed that this peak is produced by the cochlear amplifier injecting a large amount of energy into the cochlea, thereby altering the real component of the BM impedance. In this paper, a new cochlear model is described which produces a realistic response by assuming that the cochlear amplifier force acts at a phase such that the main effect is to reduce the imaginary component of the BM impedance. In this new model, the magnitude of the cochlear amplifier force required to produce a realistic response is much smaller than in the previous models. It is suggested that future experimental investigations should attempt to determine both the magnitude and the phase of the forces associated with the cochlear amplifier.
Acoustic Impedance Tests↗
Vanadium K-edge X-ray absorption spectroscopy of bromoperoxidase from Ascophyllum nodosum.
Bromoperoxidase from Ascophyllum nodusum was the first vanadium-containing enzyme to be isolated. X-ray absorption spectra have now been collected in order to investigate the coordination of vanadium in the native, native plus bromide, native plus hydrogen peroxide, and dithionite-reduced forms of the enzyme. The edge and X-ray absorption near-edge structures show that, in the four samples studied, it is only on reduction of the native enzyme that the metal site is substantially altered. In addition, these data are consistent with the presence of vanadium(IV) in the reduced enzyme and vanadium(V) in the other samples. Extended X-ray absorption fine structure data confirm that there are structural changes at the metal site on reduction of the native enzyme, notably a lengthening of the average inner-shell distance, and the presence of terminal oxygen together with histidine and oxygen-donating residues.
Eukaryota↗
Determination of 3-methylhistidine in urine by high-performance liquid chromatography using pre-column derivatization with 9-fluorenylmethyl chloroformate.
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Adult↗
Realistic mechanical tuning in a micromechanical cochlear model.
Two assumptions were made in the formulation of a recent cochlear model [P.J. Kolston, J. Acoust. Soc. Am. 83, 1481-1487 (1988)]: (1) The basilar membrane has two radial modes of vibration, corresponding to division into its arcuate and pectinate zones; and (2) the impedance of the outer hair cells (OHCs) greatly modifies the mechanics of the arcuate zone. Both of these assumptions are strongly supported by cochlear anatomy. This paper presents a revised version of the outer hair cell, arcuate-pectinate (OHCAP) model, which is an improvement over the original model in two important ways: First, a model for the OHCs is included so that the OHC impedance is no longer prescribed functionally; and, second, the presence of the OHCs enhances the basilar membrane motion, so that the model is now consistent with observed response changes resulting from trauma. The OHCAP model utilizes the unusual spatial arrangement of the OHCs, the Deiters cells, their phalangeal processes, and the pillars of Corti. The OHCs do not add energy to the cochlear partition and hence the OHCAP model is passive. In spite of the absence of active processes, the model exhibits mechanical tuning very similar to those measured by Sellick et al. [Hear. Res. 10, 93-100 (1983)] in the guinea pig cochlea and by Robles et al. [J. Acoust. Soc. Am. 80, 1364-1374 (1986)] in the chinchilla cochlea. Therefore, it appears that mechanical response tuning and response changes resulting from trauma should not be used as justifications for the hypothesis of active processes in the real cochlea.
Animals↗
Autotransfusion in a ruptured ectopic pregnancy.
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Adult↗
The reaction mechanism of the novel vanadium-bromoperoxidase. A steady-state kinetic analysis.
The reaction of vanadium-bromoperoxidase from the brown alga Ascophyllum nodosum with hydrogen peroxide, bromide, and 2-chlorodimedone has been subjected to an extensive steady-state kinetic analysis. Systematic variation of pH and the concentrations of these three components demonstrate that the reaction model includes four enzyme species: native bromoperoxidase, a bromoperoxidase-bromide inhibitory complex, a bromoperoxidase-hydrogen peroxide intermediate, and a bromoperoxidase-HOBr species. This latter intermediate did not display any direct interaction with the nucleophilic reagent as oxidized bromine species (Br-3, Br2, and/or HOBr) were the primary reaction products. The generation of oxidized bromine species was as fast as the bromination of 2-chlorodimedone. The enzyme did not show any specificity with regard to bromination of various organic compounds. Formation of the bromoperoxidase-bromide inhibitory complex was competitive with the reaction between hydrogen peroxide and enzyme. From the steady-state kinetic data lower limits for the second-order rate constants at various pH values were calculated for individual steps in the catalytic cycle. This pH study showed that native enzyme must be unprotonated prior to binding of hydrogen peroxide (second-order association rate constant of 2.5.10(6) M-1.s-1 at pH greater than 6). The pKa for the functional group controlling the binding of hydrogen peroxide was 5.7 and is ascribed to a histidine residue. The reaction rate between bromide and enzyme-hydrogen peroxide intermediate also depended on pH (second-order association rate constant of 1.7.10(5) M-1.s-1 at pH 4.0).
Barbital↗
The reaction of nitric oxide with copper proteins and the photodissociation of copper-NO complexes.
The reactivity with nitric oxide was investigated for a number of type-1, type-2 and type-3 copper proteins azurin from Pseudomonas aeruginosa (type-1 copper); bovine superoxide dismutase, diamine oxidase from pig kidney and galactose oxidase from Dactylium dendroides (type-2 copper); haemocyanin from Helix pomatia (type-3 copper); the blue oxidases ceruloplasmin from pig serum, and ascorbate oxidase from Cucurbita pepo medullosa. Type-1 copper formed complexes with NO in the oxidised state, which complexes were only fully formed at low temperatures and could be photodissociated at 77K. Complex formation led to the disappearance of the EPR signal of type-1 copper and of the optical absorbance band in the 600 nm region. In azurin, photodissociation caused the reappearance of the original 625 nm absorbance band, but in the blue oxidases, a new band with lower intensity was found at 595 nm instead of the original absorbance band at 610 nm. In all cases, the EPR signal of type-1 copper did not return. These results are best explained by the formation of a photolabile type-1 Cu1+-NO+ complex. They also indicate that in the complex formed, the type-1 copper structure is probably not disrupted, and that after illumination, the nitric oxide molecule is still in the near vicinity of the copper atom. Type-2 copper did not react at all with nitric oxide, and type-3 copper formed complexes with nitric oxide in both the oxidised and the reduced state, but photodissociation of these complexes could not be demonstrated.
Amine Oxidase (Copper-Containing)↗
[The microbiological status of dry sausage in East Netherlands].
Dry fermented sausage (dfs) was the food most suspected in a number of outbreaks of salmonellosis and staphylococcal enterotoxaemia. Data on formulation and processing showed that over 75 per cent of 76 producers still manufactured dfs in a traditional manner: fermentation and drying at ambient temperature for ten days on an average, green room facilities not present. 'Modern' processes were characterised by fermentation in green rooms at elevated temperatures, thus limiting production time to six days on an average. However, precautions to prevent luxurious growth of S. aureus under these conditions were not adopted to any appreciable extent. Consequently, high S. aureus levels (greater than 10(4) cfu/g) were detected precisely in dfs from five manufacturers using rapid processes. Colony counts of Enterobacteriaceae were low in dfs (81 per cent of 151 samples less than 10(3) cfu/g), associated with relatively low pH and aw levels and a high concentration of salt. However, Salmonella was detected in 16 (11%) of the samples, both from 'traditional' and 'modern' producers. Improvement of manufacturing practices in the manufacture of dfs should be stimulated to guarantee wholesome and safe products.
Enterobacteriaceae↗
Matching impedance of a nonuniform transmission line: application to cochlear modeling.
A generalization of the concept of characteristic impedance to nonuniform transmission lines leads to an impedance having a local character. This matching impedance depends on the solution of the transmission line equations, and cannot generally be obtained in analytical form. However, when the propagation properties of the line vary only slowly (as is the case in cochlear macromechanics), a convenient analytical approximation of the matching impedance can be derived by means of the Liouville-Green method.
Acoustic Impedance Tests↗