Biomedical subjects
Publications and source records attributed to M Dekker.
This research focuses on determining the concentration and antioxidant activity of flavonoids in apples and apple products as a function of storage and processing. The results will be used to optimise apple products with respect to both flavonoid content and antioxidant activity.
An HPLC method with gradient elution for the quantification of catechins ((-)-epigallocatechin (EGC), (+)-catechin (C), (-)-epicatechin (EC), (-)-epigallocatechingallate (EGCg) and (-)-epicatechingallate (ECg)) in tea was developed. The method was used to determine catechins in black tea, green tea and oolong tea. Sample preparation was simple because only filtration and adjustment of pH was required. The levels of catechins in different teas varied between <5 and 287 (EGC), 17 and 94 (EC), 18 and 408 (EGCg), and 8 and 85 mg/l (ECg). (+)-Catechin was not present in any of these teas.
Glucosinolates constitute a well-defined group of secondary plant metabolites in cruciferous plants. They occur especially in brassica vegetables, which represent a major part of the human diet. Glucosinolates undergo hydrolysis, catalysed by an endogenous plant enzyme, known as myrosinase, into a range of biological active compounds. Some compounds, for example isothiocyanates, show an anticarcinogenic action by inducing phase II biotransformation enzyme activity (Jongen, Proc. Nutr. Soc. 1996; 55: 433-446). Processing of brassica vegetables influences glucosinolate degradation and therefore the biological activity. We investigate the effects of processing conditions on glucosinolates and their breakdown products. Besides measurement of concentrations also the biological activity of these compounds will be analysed.
Myotonic dystrophy (DM) is commonly associated with CTG repeat expansions within the gene for DM-protein kinase (DMPK). The effect of altered expression levels of DMPK, which is ubiquitously expressed in all muscle cell lineages during development, was examined by disrupting the endogenous Dmpk gene and overexpressing a normal human DMPK transgene in mice. Nullizygous (-/-) mice showed only inconsistent and minor size changes in head and neck muscle fibres at older age, animals with the highest DMPK transgene expression showed hypertrophic cardiomyopathy and enhanced neonatal mortality. However, both models lack other frequent DM symptoms including the fibre-type dependent atrophy, myotonia, cataract and male-infertility. These results strengthen the contention that simple loss- or gain-of-expression of DMPK is not the only crucial requirement for development of the disease.
To investigate the role of the presumed DNA mismatch repair (MMR) gene Msh2 in genome stability and tumorigenesis, we have generated cells and mice that are deficient for the gene. Msh2-deficient cells have lost mismatch binding and have acquired microsatellite instability, a mutator phenotype, and tolerance to methylating agents. Moreover, in these cells, homologous recombination has lost dependence on complete identity between interacting DNA sequences, suggesting that Msh2 is involved in safeguarding the genome from promiscuous recombination. Msh2-deficient mice display no major abnormalities, but a significant fraction develops lymphomas at an early age. Thus, Msh2 is involved in MMR, controlling several aspects of genome stability; loss of MMR-controlled genome stability predisposes to cancer.
Fourteen young adolescents with specific reading disabilities received short term neuropsychological treatment--specifically left hemisphere (LH) or right hemisphere (RH) stimulation--in a clinical pilot project. The effects on single-word and passage reading were evaluated when the language of treatment was either Dutch (mother tongue) or English (foreign language). Transfer effects across the two languages were also studied. In general, the results indicate that these short term interventions may prove successful for the treated language and with the additional transfer to a second (not treated) language.
A retrospective study was performed of patients who had undergone an open knee procedure treated as day cases at the Regional Hospital of Zevenaar. An analysis was made of the rate of complications, whether complications were treated adequately, and how patients experienced an arthrotomy of the knee as a day-case procedure. Eighty-seven healthy patients aged 15 to 50 years underwent an arthrotomy of one knee as a day-case procedure, secondary to a diagnostic arthroscopy. The mean follow-up period was 8 months. Patients were reviewed by questionnaire, after which the knee was examined. The number of complications (6) was comparable with those reported in the literature. Complications within a few days after operation were reported to the GPs, who either treated themselves, or referred patients to the hospital. Of the patients 76% preferred this procedure to an operation in a clinical setting. The amount of pain suffered appears to be of great influence on the preference of the patient. The results of this study demonstrate that an arthrotomy of the knee is feasible as a day-care procedure, although extensive pre- and postoperative instructions to the patients may be improved.
Proteins are spontaneously transferred from an aqueous solution into reversed micelles, provided the aqueous phase has the proper composition. Besides the composition of the aqueous phase, the composition of the organic phase and the properties of the proteins also play a role. We studied uptake profiles of 19 proteins as a function of pH of the aqueous solution. The organic phase consisted of trioctylmethylammonium chloride and nonylphenol pentaethoxylate (Rewopal HV5) as surfactant, octanol as cosurfactant and isooctane as continuous phase. In all cases, except for rubredoxin, proteins were transferred at pH values above their isoelectric point. The pH where maximal solubilization takes place can be described by the relationship: pHoptimum = isoelectric point +0.11 x 10(-3) Mr -0.97. So, the larger the protein, the more charge is needed to provide the energy required for the adaptation of the micellar size to the protein size. For protein transfer into sodium di-(2-ethylhexyl)sulphosuccinate (AOT) reversed micelles a similar relationship was found. The percentage of protein transferred could be related to the symmetry of charge distribution over the protein. This symmetry was expressed as the % of random electric moments on a protein that is larger than the effective electric moment of the protein (% S) [Barlow, D. J. and Thornton, J. M. (1986) Biopolymers 25, 1717]. The larger the value of % S, the more homogeneously the charges are distributed and the lower the percentage transfer.
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We have discovered that chromophoric sulfonyl chlorides and affinity ligand-containing sulfonyl chlorides prepared based upon fluorinated carbon skeletons are excellent activating agents for agarose. The primary basis for development of such reagents has been pentafluorobenzenesulfonyl chloride and tresyl chloride, both of which are excellent activating agents. Activation using the sulfonyl chlorides whose synthesis is described here has yielded matrices that are very reactive to nucleophilic displacement by amines and thiols and, thus, should be excellent agents for the immobilization of affinity ligands, enzymes, cells, etc. The resulting material is based on covalent coupling and, thus, is more stable than affinity ligands or enzymes immobilized by other methods.
Evidence will be presented in this review article that the application of hydrogenase has large biotechnological possibilities. Our investigations show: Fast reaction of hydrogenase at an electrode surface to reduce H+; Photochemical production of H2 by hydrogenase by photosensitized Ru-complexes dissolved in reversed micellar membranes and vectorial H+ transport through the membrane to the water phase; The production of fine chemicals in reversed micelles by a system containing specific enzymes, hydrogenase and H2. The rules to obtain maximal conversion rates with this system will be presented.
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During the period from January 1968 to June 1974, 21 patients were subjected to surgical repair of a ruptured Achilles tendon in the Eindhoven Deaconess Hospital. In 19 of them, the plantaris tendon was used as autogenous suturing material. Followup examination revealed 'excellent' or 'good' results in 19 cases. In one case, the result was classified as 'bad' because of a fistula still present at the time of the follow-up, although functionally the patient was not handicapped. In view of the above, we regard the technique with use of the plantaris tendon for reconstruction of the ruptured Achilles tendon as reliable and worthy of recommendation.
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OBJECTIVE: Strategies are available to reduce maternal-fetal transmission of HIV and depend on adequate prenatal screening. At present, a significant proportion of Canadian pregnant women remain unscreened. We reviewed our screening practices before and after the implementation of a departmental policy on universal counselling for HIV screening and the distribution of a patient educational brochure developed at our centre (interventions). METHODS: Charts of all new antenatal patients seen during February-April in 1996 (n = 186) and 1998 (n = 212) were reviewed. Maternal demographics and evidence of HIV counselling and screening were collected and analyzed. RESULTS: Following our interventions, HIV counselling and screening rates increased from 13% to 72%. Patient acceptance of testing was high. The majority of missed opportunities for HIV testing were patients transferred urgently from other institutions. CONCLUSION: HIV counselling and screening can be improved by implementation of local strategies. We have demonstrated the feasibility of this approach in a tertiary care unit.