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R van Dijk

Publications and source records attributed to R van Dijk.

At least 19 recordsLinked to original sources
PubMed2001

Tagging Hansenula polymorpha genes by random integration of linear DNA fragments (RALF).

We have investigated the feasibility of using gene tagging by restriction enzyme-mediated integration (REMI) to isolate mutants in Hansenula polymorpha. A plasmid that cannot replicate in H. polymorpha and contains a dominant zeocin resistance cassette, pREMI-Z, was used as the integrative/mutagenic plasmid. We observed that high transformation efficiency was primarily dependent on the use of linearised pREMI-Z, and that the addition of restriction endonuclease to linearised pREMI-Z prior to transformation increased the transformation frequency only slightly. Integration of linearised pREMI-Z occurred at random in the H. polymorpha genome. Therefore, we termed this method Random integration of Linear DNA Fragments (RALF). To explore the potential of RALF in H. polymorpha, we screened a collection of pREMI-Z transformants for mutants affected in peroxisome biogenesis (pex) or selective peroxisome degradation (pdd). Many previously described PEX genes were obtained from the mutant collection, as well as a number of new genes, including H. polymorpha PEX12 and genes whose function in peroxisome biogenesis is still unclear. These results demonstrate that RALF is a powerful tool for tagging genes in H. polymorpha that should make it possible to carry out genome-wide mutagenesis screens.

Base Sequence↗
PubMed2000

Spinal arachnoiditis following subarachnoid haemorrhage: report of two cases and review of the literature.

Two patients with spinal arachnoiditis following subarachnoid haemorrhage are described. A complete spinal block was seen at the mid thoracic level with characteristics of spinal arachnoiditis. Only one patient had severe symptoms. Both patients were treated conservatively. Signs and symptoms diminished in time. A review of the literature is given and the aetiology is discussed.

Aged↗
PubMed1999

European multi-centre validation study of NucliSens Extractor in combination with HCV Amplicor 2.0 assay for HCV-NAT screening of plasma pools.

The NucliSens Extractor in combination with the 2.0 version of the Roche Cobas HCV Amplicor test has been validated by five European blood screening laboratories in a multi-centre study. For testing the performance characteristics of this HCV-NAT method, the European Pharmacopoeia validation guidelines were followed. The CLB VQC reference reagents were used for testing robustness and sensitivity. After a technical improvement in the extraction stations, the NucliSens Extractor appeared to be contamination-free as was proved by testing negative controls alternating with samples containing a high HCV-RNA concentration. The Pelicheck HCV-RNA genotype 1 dilution panel was tested 74 times in the five laboratories and an overall 95% detection limit of 80 genome equivalents (geq)/ml was found. In one laboratory the Pelicheck panel was tested in 25 runs and here a 95% detection limit of 32 geq/ml was achieved. In this laboratory the Pelispy HCV-RNA run control samples of 140 geq/ml were consistently picked up in all extractor stations. In addition the laboratories have tested a WHO HCV-RNA genotype 1 standard dilution series 39 times and a Pelicheck HCV-RNA genotype 3 reference panel in 32 test runs. The limiting dilution analysis enabled us to compare the detection efficiency of the NucliSens-Amplicor method for the genoype 1 and genotype 3 isolates and to calibrate the reference reagents against each other. The combined Nuclisens-Amplicor method was found to detect the genotype 3 isolate in the Pelicheck HCV-RNA panels with 2-3 fold lower efficiency than the genotype 1 standard (assuming that the historical calibration of the genotype 3 against the genotype 1 standard is correct). In this study of a single method 1 IU of the WHO HCV-RNA standard was found to be equivalent to 5.1 geq of the VQC HCV-RNA standard (95% confidence intervals 3.1-9.1 geq). To avoid confusion with the use of the CLB VQC reagents we accept the NIBSC collaborative study in which calibration by a variety of methods showed that the Pelispy 380 geq/ml run control is equivalent to 100 IU/ml of the WHO standard. This multi-centre validation study demonstrates that the 95% detection limit of the NucliSens HCV Amplicor method lies far below the detection limits required by the international regulatory bodies.

Europe↗
PubMed1999

The need for correct realistic geometry in the inverse EEG problem.

For accurate electroencephalogram-based localization of mesial temporal and frontal sources correct modeling of skull shape and thickness is required. In a simulation study in which results for matched sets of computed tomography and magnetic resonance (MR) images are compared, it is found that errors arising from skull models based on smooth and inflated segmented MR images of the cortex are of the order of 1 cm. These errors are comparable to those found when overestimating or underestimating skull conductivity by a factor of two.

Brain↗
PubMed1998

The local neutron flux at low Earth-orbiting altitudes.

The COMPTEL instrument onboard the Compton Gamma Ray Observatory (CGRO) has been used to measure the variation of the atmospheric neutron flux below 5 MeV as a function of vertical cutoff rigidity and spacecraft orientation at an altitude of 450 km. The instrumental 2.2 MeV background line, resulting from thermal neutron capture on hydrogen, was used for the measurement. The dependence of the 2.2 MeV rate on rigidity and geocentre zenith can be described by an analytic function: the line rate decreases linearly with geocentre zenith, and decreases exponentially with the vertical cutoff rigidity. The flux varies on average by about a factor of 3.7 between the extremes in rigidity, and by a factor of 1.7 between the extremes of spacecraft orientation with respect to the Earth. We believe that mass shielding is more important in attenuating the atmospheric albedo than as a source of secondary neutrons. The COMPTEL instrument is well suited for a long-duration study of the dependence of the neutron flux on the vertical cutoff rigidity and the solar cycle.

Altitude↗
PubMed1997

Cloning, sequencing, disruption and phenotypic analysis of uvsC, an Aspergillus nidulans homologue of yeast RAD51.

We have cloned the uvsC gene of Aspergillus nidulans by complementation of the A. nidulans uvsC114 mutant. The predicted protein UVSC shows 67.4% sequence identity to the Saccharomyces cerevisiae Rad51 protein and 27.4% sequence identity to the Escherichia coli RecA protein. Transcription of uvsC is induced by methyl-methane sulphonate (MMS), as is transcription of RAD51 of yeast. Similar levels of uvsC transcription were observed after MMS induction in a uvsC+ strain and the uvsC114 mutant. The coding sequence of the uvsC114 allele has a deletion of 6 bp, which results in deletion of two amino acids and replacement of one amino acid in the translation product. In order to gain more insight into the biological function of the uvsC gene, a uvsC null mutant was constructed, in which the entire uvsC coding sequence was replaced by a selectable marker gene. Meiotic and mitotic phenotypes of a uvsC+ strain, the uvsC114 mutant and the uvsC null mutant were compared. The uvsC null mutant was more sensitive to both UV and MMS than the uvsC114 mutant. The uvsC114 mutant arrested in meiotic prophase-I. The uvsC null mutant arrested at an earlier stage, before the onset of meiosis. One possible interpretation of these meiotic phenotypes is that the A. nidulans homologue of Rad51 of yeast has a role both in the specialized processes preceding meiosis and in meiotic prophase I.

Amino Acid Sequence↗
PubMed1997

Maintaining efficiency in a satellite radiology department.

In this paper the organisation of a radiology satellite department is described. In the satellite department only bucky examinations are performed, thus avoiding the need for the duplication of sophisticated material and specialized staff. The satellite department maintains as efficient a service as the main radiology department. For this purpose a digital radiology system was chosen for the satellite department. This system permits digital data to be sent to the main location. This results in a maximisation of the advantages of a two-location system as well as avoiding the need for patients' files to be moved between different locations.

Efficiency, Organizational↗
PubMed1995

A comparison of hirudin with heparin in the prevention of restenosis after coronary angioplasty. Helvetica Investigators.

BACKGROUND: The likelihood of restenosis is a major limitation of coronary angioplasty. We studied whether hirudin, a highly selective inhibitor of thrombin with irreversible effects, would prevent restenosis after angioplasty. We compared two regimens of recombinant hirudin with heparin. METHODS: We randomly assigned 1141 patients with unstable angina who were scheduled for angioplasty to receive one of three treatments: (1) a bolus dose of 10,000 IU of heparin followed by an intravenous infusion of heparin for 24 hours and subcutaneous placebo twice daily for three days (382 patients), (2) a bolus dose of 40 mg of hirudin followed by an intravenous infusion of hirudin for 24 hours and subcutaneous placebo twice daily for three days (381 patients), or (3) the same hirudin regimen except that 40 mg of hirudin was given subcutaneously instead of placebo twice daily for three days (378 patients). The primary end point was event-free survival at seven months. Other end points were early cardiac events (within 96 hours), bleeding and other complications of the study treatment, and angiographic measurements of coronary diameter at six months of follow-up. RESULTS: At seven months, event-free survival was 67.3 percent in the group receiving heparin, 63.5 percent in the group receiving intravenous hirudin, and 68.0 percent in the group receiving both intravenous and subcutaneous hirudin (P = 0.61). However, the administration of hirudin was associated with a significant reduction in early cardiac events, which occurred in 11.0, 7.9, and 5.6 percent of patients in the respective groups (combined relative risk with hirudin, 0.61; 95 percent confidence interval, 0.41 to 0.90; P = 0.023). The mean minimal luminal diameters in the respective groups on follow-up angiography at six months were 1.54, 1.47, and 1.56 mm (P = 0.08). CONCLUSIONS: Although significantly fewer early cardiac events occurred with hirudin than with heparin, hirudin had no apparent benefit with longer-term follow-up.

Angina, Unstable↗
PubMed1993

Work-up and management of incidentally found hypoechoic lesions of the testis.

This study reviews our experience with the presentation of occult echo-poor lesions of the testis in patients who were seen with problems such as infertility, prostatitis or orchialgia. A range of pathologic problems revealed by scrotal ultrasonography in these patients is presented, and we compared surgical and pathological findings to those of preoperative scrotal ultrasonography. Scrotal ultrasound appears to be a highly sensitive but nonspecific diagnostic technique.

Adult↗
PubMed1993

Extradural cyst.

Explore the source record for details and available documents.

Cysts↗
PubMedDate not supplied

Ultrasonography versus clinical examination in evaluation of testicular tumors.

The diagnostic results of clinical examination and gray-scale ultrasonography for scrotal pathology were compared in 411 patients. Sensitivity and specificity of the clinical diagnosis of a testis tumor improved significantly with the use of ultrasonography. Criteria for the ultrasonographic diagnosis of a testicular tumor were evaluated. We had no false-negative ultrasonographic diagnoses, and they have rarely been reported in the literature. With ultrasonography, the number of false-positive clinical diagnoses was reduced from 11 to 5.

Follow-Up Studies↗
PubMedDate not supplied

Determination of nitrate in vegetables by continuous flow: interlaboratory study.

A collaborative study for the determination of nitrate in leafy vegetables, such as endive, lettuce, spinach, and beetroot, by continuous flow (CF) was conducted by the Project Group on Collaborative Studies of the Inspectorate for Health Protection, Food Inspection Service, in The Netherlands. After extraction with water and filtration, samples were cleaned up by dialysis in the CF system. Extracted nitrates were reduced to nitrite in the system by metallic cadmium, and then the nitrite was reacted with sulfanilamide and N-1-naphthylethylenediamine to form a reddish-purple azo dye. This dye was measured colorimetrically at 530 nm. Fourteen vegetable samples (including 7 blind duplicates) containing nitrate at ca 900 to 5200 mg/kg were analyzed singly by the proposed procedure by 13 laboratories. The data were analyzed by the International Union for Pure and Applied Chemistry (IUPAC)-International Organization for Standardization (ISO)-AOAC protocol for statistics. One collaborator was identified as an outlier for all results. For all samples analyzed, the repeatability relative standard deviation values varied from 1.7 to 5.5%, whereas the reproducibility relative standard deviation values ranged from 3.3 to 5.9%.

Chromatography↗
PubMedDate not supplied

Determination of polymerized triglycerides in frying fats and oils by gel permeation chromatography: interlaboratory study.

An interlaboratory study of the gel permeation chromatographic (GPC) determination of polymerized triglycerides (PTG) in frying fats and oils was conducted by the Project Group on Collaborative Studies (PCS) of the Inspectorate for Health Protection, Food Inspection Service, The Netherlands. Thirteen laboratories participated in this study, which was focused on thermally abused oil and fat samples containing dimerized and polymerized triglycerides at levels just below and far above the Dutch regulatory limit of 16% (m/m). Samples were dissolved in tetrahydrofuran (THF) and analyzed on a GPC system, using THF as the mobile phase. Refractive index (RI) detection was used to determine PTG. Six heat-processed fat samples containing from 14 to 28% (m/m) PTG at 3 different levels (3 pairs of split level samples) were single analyzed according to the proposed procedure. Data analysis was performed according to the International Union of Pure and Applied Chemistry/International Organization for Standardization/AOAC protocols for statistics. The results of 2 collaborators were identified as outliers at the 20% (m/m) PTG level by applying the paired Grubbs test at the 1% level of significance. The repeatability relative standard deviation (RSDr) values ranged from 0.48 to 2.25%, whereas the reproducibility relative standard deviation (RSDR) values ranged from 1.34 to 4.57%.

Chromatography, Gel↗