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P van Dijck

Publications and source records attributed to P van Dijck.

10 recordsLinked to original sources
PubMed2006

Immunogold localization of trehalose-6-phosphate synthase in leaf segments of wild-type and transgenic tobacco plants expressing the AtTPS1 gene from Arabidopsis thaliana.

Following the establishment of a transgenic line of tobacco (B5H) expressing the trehalose-6-phosphate synthase (TPS) gene from Arabidopsis thaliana, a preliminary immunolocalization study was conducted using leaves of adequately watered B5H and wild-type plants. Immunocytochemical staining, followed by electron microscopy showed that the enzyme could be detected in both B5H and wild-type plants at two different levels. Quantification showed the signal to be two to three times higher in transgenic plants than in the wild type. This enzyme was markedly present in the vacuoles and the cell wall, and to a lesser extent in the cytosol. Moreover, a high profusion of gold particles was detected in adjacent cells and in the sieve elements. Occasional spots were also detected in chloroplasts and the nucleus, especially in the transgenic B5H line. No labeling signal was detected in mitochondria. Protein localization seems to confirm the important role of TPS in sugar metabolism and transport through the plant, which could explain its role in plant stress tolerance. Finally, it can be expected that TPS from tobacco has a relatively high similarity to the TPS of Arabidopsis thaliana.

Arabidopsis↗
PubMed2001

Analysis and modification of trehalose 6-phosphate levels in the yeast Saccharomyces cerevisiae with the use of Bacillus subtilis phosphotrehalase.

In the yeast Saccharomyces cerevisiae, trehalose is synthesized by the trehalose synthase complex in two steps. The Tps1 subunit catalyses the formation of trehalose 6-phosphate (Tre6P), which is dephosphorylated by the Tps2 subunit. Tps1 also controls sugar influx into glycolysis; a tps1 deletion strain is therefore unable to grow on glucose. It is unclear whether this regulatory function of Tps1 is mediated solely by Tre6P or also involves the Tps1 protein. We have developed a novel sensitive and specific assay method for Tre6P. It is based on the conversion of Tre6P into glucose and glucose 6-phosphate with purified phosphotrehalase from Bacillus subtilis. The glucose formed is measured with the glucose-oxidase/peroxidase method. The Tre6P assay is linear in the physiological concentration range. The detection limit, including the entire extraction procedure, is 15 nmol, corresponding to an intracellular concentration of 100 microM. To modify Tre6P levels in vivo, we expressed B. subtilis phosphotrehalase in yeast. The enzyme is functional because it rescues the temperature-sensitive growth defect of a tps2Delta strain and drastically lowers Tre6P levels in this strain. However, phosphotrehalase expression remains without effect on Tre6P levels in wild-type strains, as opposed to overexpression of Tps2. Because Tps2 is part of the Tre6P synthase (TPS) complex and because this complex is destabilized in tps2 deletion strains, these results can be explained if Tre6P is sequestered within the TPS complex in wild-type cells. The very low levels of Tre6P in cells overexpressing Tps2 have a limited effect on sugar phosphate accumulation and do not prevent growth on glucose. Taken together, our results support a model in which the regulatory function of Tps1 on sugar influx is mediated both by the Tps1 protein and by Tre6P.

Bacillus subtilis↗
PubMed1996

Genotyping of outbreak-related and sporadic isolates of Clostridium difficile belonging to serogroup C.

Serogroup C of Clostridium difficile is the serogroup most frequently related to outbreaks. Fifty-six toxigenic serogroup C isolates of C. difficile were genotyped by ribotyping PCR (ribo-PCR), random amplified polymorphic DNA (RAPD) assay, and pulsed-field gel electrophoresis (PFGE). Thirty-five of the 56 isolates were recovered from four unrelated outbreaks (Belgium, 1987, 1992, and 1995; France, 1992 to 1993) 7 derived from a spatiotemporal cluster in Cotonou, Benin (1992), and 14 were sporadic isolates. The serogroup C reference strain, also isolated during an outbreak (Belgium, 1983), was genotyped too. Ribo-PCR, the RAPD assay, and PFGE generated 2, 5, and 11 major genotypes, respectively. Combination of the three methods finally yielded 13 general types, although ribo-PCR did not play any role in enhancing resolution. Three general types were recovered from all the isolates from the five outbreaks and the cluster, with two types being predominant. The 14 sporadic serogroup C isolates were divided into 11 overall genotypes. These results indicate that genotyping methods, and more particularly the combination of the RAPD assay and PFGE, can resolve genetic diversity within toxigenic, serogroup C C. difficile strains. Also, this study suggests that outbreak-related serogroup C strains are limited to a few genetically stable and apparently very widely (internationally and intercontinentally) distributed genotypes.

Bacterial Typing Techniques↗
PubMed1995

Evaluation of pulsed-field gel electrophoresis and rep-PCR for the epidemiological analysis of Ochrobactrum anthropi strains.

Pulsed-field gel electrophoresis and polymerase chain reaction genome fingerprinting based on repetitive chromosomal sequences (rep-PCR) were used for typing 14 strains of Ochrobactrum anthropi. Six strains isolated during an outbreak of bacteraemia in patients who had received a contaminated rabbit anti-thymocyte globulin gave identical patterns by both techniques. Different patterns were found in sporadic and reference strains, except for one clinical isolate received from another hospital that showed the same pattern as the epidemic clone. This patient had also received rabbit anti-thymocyte globulin from the same source at the time of the outbreak. This study illustrates the advantages of genetic typing methods in terms of high typeability and discriminating power, even for rare pathogens. Furthermore, it highlights the need for interhospital communication for effective identification of common sources of outbreaks related to intrinsic drug contamination.

Alcaligenes↗
PubMed1993

A Fos-Jun element in the first intron of an alpha 2u-globulin gene.

The hepatic expression of the alpha-2u-globulin gene family is controlled by a variety of hormones including steroids, growth hormone and insulin. The mechanisms by which these hormones affect alpha 2u-globulin expression are only partially understood. Recently we isolated and characterized clone RAP 01, an alpha 2u-globulin gene expressed in the liver. In preliminary experiments we noted that partial hepatectomy, a procedure which results in a sharp rise in the level of the oncoproteins c-Fos and c-Jun, also causes a transient induction of the messenger RNA corresponding to clone RAP 01. Using the DNAseI footprinting technique we were able to show that this clone contains a TPA (phorbol 12-myristate 13-acetate)-responsive element (TRE) in its first intron. This element (denoted as element X) is identical to the consensus AP-1 binding site (TGACTCAG) and is protected by rat liver nuclear extracts as well as by purified c-Jun. Gel retardation experiments show that an oligonucleotide containing the TRE consensus sequence competes for binding of liver nuclear proteins to element X and that antibodies directed against the M2 peptide of the mouse Fos protein or the PEP-2 peptide of Jun prevent the formation of specific complexes with the same element. Moreover, element X functions as a TRE in transfected BWTG3 hepatoma cells treated with TPA. Co-transfection with fos and jun expression vectors mimics the effects of TPA suggesting that AP-1 is in fact the mediator of the observed response. It is concluded that the first intron of RAP 01 contains a functional Fos-Jun element.

Alpha-Globulins↗
PubMed1987

Comparison of the 5' upstream putative regulatory sequences of three members of the alpha 2u-globulin gene family.

We have isolated and characterized seven members of the alpha 2u-globulin gene family from a rat genomic library. The 5' upstream region (up to 1250 base pairs starting from the EcoRI site in exon 2) of three clones was sequenced. The major transcriptional start points were located 25 base pairs downstream from the 'TATA' box. A very high degree of homology was observed over the entire studied region. Two of the examined genes displayed structural features which suggest that their expression may be impeded. A high degree of homology was observed between the promotor regions of alpha 2u-globulin and those of the major urinary protein (MUP) multigene family of the mouse. A remarkable feature is the variable length of an A-rich region between the putative 'CAAT' and the 'TATA' consensus sequences. The size of this region differs markedly between MUP and alpha 2u-globulin and between different members of the alpha 2u-globulin gene family. Comparison of the alpha 2u-globulin promotor with the corresponding region of other androgen-dependent genes (the C1, C2 and C3 subunits of prostatic steroid binding protein) reveals the presence of an A-rich region of homology located approximately 378 base pairs upstream from the cap site in the alpha 2u-globulin genes. This region compares well with a sequence of putative enhancer function previously demonstrated in the alpha-fetoprotein promotor and in the immunoglobulin heavy chain promoter.

Alpha-Globulins↗
PubMed1987

Influence of the growth characteristics of Candida albicans on disinfectant testing.

In order to standardize antifungal disinfectant testing using Candida albicans as a test organism, the morphology of four type strains of C. albicans DSM 1836, ATCC 10231, CNCM 1180-79 and CBS 562, grown on sixteen different media was determined. The incubation was carried out at 28 degrees C and 37 degrees C. The yeast phase was obtained predominantly on TSA medium with all strains. Mixed phases, i. e. true mycelium and yeast cells, were easily obtained in TSB in shaking flasks for three type strains but not for CBS 562. True mycelium was formed on corn meal media (CMA) for all strains, but the growth was very poor. The morphology of the growth was determined more by the type of strain than by the nutritive medium. Therefore C. albicans ATCC 10231 grown on either TSA or CMA was used as a test organism. Its resistance was determined towards four disinfectant standards: benzalkonium chloride, mercuric chloride, phenol and o-phenylphenol. No difference in sensitivity was found for the former disinfectant, but yeast cells grown on TSA were more resistant than C. albicans cultures on CMA in case of mercuric chloride, phenol and o-phenylphenol.

Antifungal Agents↗
PubMed1984

The choice of fungi as test organisms in disinfectant testing.

In order to find out whether more than one test organism is needed for the determination of the activity of disinfectants towards mycelium-forming fungi and yeasts, eight different species of fungi and one yeast-like fungus were submitted to seven different disinfectants in varying concentrations. As Candida albicans was found to be the most resistant, the authors propose that only Candida albicans should be used.

Bacteriological Techniques↗
PubMed1977

Factors affecting pyrogen testing in rabbits.

A response of rabbits to toxins causing fever and originating from microorganisms may be related to different factors. In this respect the race and the age of the animals were examined as variables. Three rabbit strains of local origin were used: New Zealand White, White of Dendermonde and Holland race. As pyrogen preparations sterile surface water and preparations of E. coli strains were used. A bacterial count, as for ordinary drinking water examination, was carried out in order to evaluate the presence of bacteria to pyrogenicity. An attempt was made to remove the pyrogens by absorption on charcoal and by filtration through asbestos filters. A decrease of pyrogenicity was obtained but the fever toxins did not completely disappear with the simple procedure. The stability of the toxins found in surface waters was examined over a short range of preservation. Only a slow decrease in pyrogenic activity was seen. Pyrogens of E. coli were prepared in vitro, but used unpurified. A slight difference in the strains was observed, but all E. coli's were pyrogenic.

Age Factors↗