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Biomedical subjects

D Bakker

Publications and source records attributed to D Bakker.

At least 73 records · Page 4Linked to original sources
PubMed1990

Epitope analysis of the F4 (K88) fimbrial antigen complex of enterotoxigenic Escherichia coli by using monoclonal antibodies.

So far, three subtypes of the F4 (K88) fimbrial antigen of porcine enterotoxigenic Escherichia coli, F4ab, F4ac, and F4ad, have been distinguished by using polyclonal antisera in agglutination and precipitation tests. The a factor represents one or more common epitopes, whereas each of the b, c, and d factors represents one or more subtype-specific epitopes. We further characterized the F4 antigen complex by using a panel of 40 F4-specific monoclonal antibodies (MAbs). The specificity of all MAbs was proven by enzyme-linked immunosorbent assays, agglutination and radioimmunoprecipitation tests, and immunoelectron microscopy. The MAbs either reacted with all F4 subtypes, reacted with two subtypes, or were subtype specific. Epitope analysis by competition enzyme-linked immunosorbent assays revealed at least 11 epitope clusters on the F4 antigen complex, designated a1 to a7, b1, b2, c, and d. The following antigenic formulas were found for the F4 subtypes: F4ab, a1a2a3a4a5a6b1b2; F4ac, a1a2a3(a4)a5a6a7c; and F4ad, a1a2a3a4a7d. All MAbs were directed against conformational epitopes located on the 27,500-dalton major fimbrial subunits. Consequences for the replacement of polyclonal antisera by MAbs in diagnostic tests are discussed.

Antibodies, Bacterial↗
PubMed1989

Usefulness of the Henson Central Field Screener for the detection of visual field defects, especially in glaucoma.

The Henson Central Field Screener is a recently marketed, relatively inexpensive campimeter with semi-automated registration of responses. The strategy used is suprathreshold, eccentricity-compensated, multiple stimulus static perimetry. The clinical usefulness of this apparatus was tested in a number of glaucoma patients, glaucoma suspects and normals, as well as in subjects with other ocular disorders, for whom stable visual fields as tested with other perimeters were available. The results obtained with the Henson Screener are generally in agreement with the known defects. The apparatus has some drawbacks, however.

Adolescent↗
PubMed1989

The social experiences of cancer patients under treatment: a comparative study.

As part of a larger study on the quality of life of cancer patients under treatment, the positive and negative experiences in social interaction have been examined as compared to those of a control group (nonpatients, n = 201). Two patient groups were included: 109 patients who had recently undergone surgery and 108 patients receiving chemotherapy. The respondents returned a mailed questionnaire. Contrary to the assumptions based on a review from the literature, cancer patients appear to have more positive and fewer negative social experiences than a random sample from the 'normal' population. Even under more severe medical circumstances (a poor prognosis or heavy chemotherapy, a large number of chemotherapy cycles, poor progress after surgery) the poorer the patients, medically speaking, the more help and support they perceive. The results of this study do not support the idea of stigmatization. The personality characteristics, neuroticism and self-esteem are especially important for the having of positive and negative experiences in social interaction. Positive social experiences show a relationship with self-esteem and negative social experiences show a relationship with neuroticism.

Adolescent↗
PubMed1989

Detection and identification of FaeC as a minor component of K88 fibrillae of Escherichia coli.

A tribrid gene containing ompF, faeC, and lacZ sequences was constructed by subcloning a large central segment of the K88ab gene encoding the fibrillar subunit-like protein FaeC into the open reading frame expression vector pORF2. The resulting tribrid protein was isolated and used to raise antibodies against the FaeC protein. These antibodies were then used for the detection and subcellular localization of the FaeC protein in Escherichia coli harbouring the K88ab-encoding plasmid pFM205 or mutant derivatives. Immunoblotting of subcellular fractions and of purified fibrillae, and agglutination experiments using whole cells revealed that the FaeC protein is present in the periplasm and as a minor component in the K88ab fibrillae. FaeC was also detected in purified K88ac and K88ad fibrillae. Immunoelectron microscopy confirmed the presence of FaeC in K88ab fibrillae, particularly at the tips of the longer fibrillae.

Agglutination↗
PubMed1988

Biocompatibility of six elastomers in vitro.

The biocompatibility of two silicone rubbers, Silastic and Dow Corning Elastomer, and of a polyether and a polyester urethane, a polyether polyester copolymer, and polypropylene oxide was assessed in vitro. These elastomers were selected for assessment as a possible alloplastic tympanic membrane. For these studies use was made of rat middle ear mucosa explants and serially cultured epithelium. The quantitative results were based on epithelial growth curves, the morphological picture was based on the findings in epithelium, and the aging of a biomaterial was simulated. Epithelium morphology was investigated by scanning and transmission electron microscopy and x-ray microanalysis. Quantitative results showed that on Dow Corning Elastomer and polypropylene oxide, cell proliferation was significantly lower compared to normal growth curves. The morphological findings were negative for polypropylene oxide, and did not discriminate between the other biomaterials under study. The simulation results indicated better biocompatibility for the polyurethanes and the polyether polyester copolymer compared with that of polypropylene oxide and both silicone rubbers. Under the simulation conditions, cells exposed to Silastic showed silicon-containing inclusions. These in vitro results suggest that the biocompatibility of the polyurethanes and the polyether polyester copolymer is better than that of both silicone rubbers and polypropylene oxide.

Animals↗
PubMed1988

Effect of implantation site on phagocyte/polymer interaction and fibrous capsule formation.

Implants of Silastic, Estane, polypropylene oxide and an HPOE/PBT segmented polyether polyester copolymer were qualitatively and quantitatively evaluated, with respect to interaction with mononuclear and multinucleated phagocytes as well as fibrous capsule formation, after implantation at three sites in the rat middle ear. The volume of the phagocyte exudate surrounding the implants, the degree of implant degradation and fragmentation and the thickness of the fibrous capsules were found to be correlated with the implantation site. From these findings, it can be concluded that it is important to assess the biological performance of a biomaterial at carefully chosen implantation sites.

Animals↗
PubMed1986

Regulation and structure of an Escherichia coli gene coding for an outer membrane protein involved in export of K88ab fimbrial subunits.

The nucleotide sequence of the faeD gene of Escherichia coli and the amino acid sequence of its product is presented. The faeD product is an outer membrane protein required for transport of K88ab fimbrial subunits across the outer membrane. The protein is synthesized as a precursor containing a signal peptide, and the tentative mature protein comprises 777 amino acid residues. The distribution of amino acids in the faeD protein is similar to that of other outer membrane proteins; showing a fairly even distribution of charged residues and the absence of extensive hydrophobic stretches. Secondary structure predictions revealed a region of 250 amino acid residues which might be embedded in the outer membrane. The 5'-end of faeD is located within a region showing dyad symmetry. This region serves to couple translation of faeD to the translation of the gene preceding it (faeC). The 3'-end of faeD shows an overlap of 5 bases with the next gene (faeE).

Amino Acid Sequence↗
PubMed1986

The biological performance of calcium phosphate ceramics in an infected implantation site: II. Biological evaluation of hydroxyapatite during short-term infection.

Macroporous hydroxyapatite was implanted submucosally in the rat middle ear and studied after intratympanic injection of a Staphylococcus aureus suspension. The middle ear infection was induced 1 week after the implantation, and the effects of infection on the middle ear and the implant material were evaluated after 1, 3, 7, and 14 days by light and electron microscopy. The findings in the infected middle ear with an implant corresponded well with those described for the infected middle ear cavity without an implant. The reactions of the tissue over the implant were similar to those of the original mucosa of the middle ear. Bone was deposited on the implant and in its pores in relatively large quantities. Biodegradation, due at least partially to phagocytic activity of macrophages and multinucleated cells, was more prominent than previously found. This higher degree of biodegradation may be attributed to the use of the mucosal implantation technique, because this was the only point of divergence with respect to material or methods from earlier work reported by our group. The present results, together with those published earlier, suggest that this material has promising features for use as a bone substitute in reconstructive middle ear surgery. Definitive conclusions on biological performance and biofunctionality will, however, have to await long term clinical trials.

Animals↗
PubMed1985

Plasmid-mediated degradation of dibenzothiophene by Pseudomonas species.

The microbial transformation of dibenzothiophene (DBT) is of interest in the potential desulfurization of oil. We isolated three soil Pseudomonas species which oxidized DBT to characteristic water-soluble, sulfur-containing products. Two of our isolates harbored a 55-megadalton plasmid; growth in the presence of novobiocin resulted in both loss of the plasmid and loss of the ability to oxidize DBT. Reintroduction of the plasmid restored the ability to oxidize DBT to water-soluble products. The products resulting from the oxidation of DBT were characterized and included 3-hydroxy-2-formyl benzothiophene, 3-oxo-[3'-hydroxy-thionaphthenyl-(2)-methylene]-dihydrothionaph thene, and the hemiacetal and trans forms of 4-[2-(3-hydroxy)-thianaphthenyl]-2-oxo-3-butenoic acid. The products of DBT oxidation were inhibitory to cell growth and further DBT oxidation. DBT oxidation in our soil isolates was induced by naphthalene or salicylate and to a much lesser extent by DBT and was repressed by succinate.

Biotransformation↗
PubMed1985

Plasmid-borne Tn5 insertion mutation resulting in accumulation of gentisate from salicylate.

Plasmid-borne Tn5 insertion mutants of a Pseudomonas species which accumulated 2,5-dihydroxybenzoate (gentisate) following growth on 2-hydroxybenzoate (salicylate) were obtained from a pool of mutants that were unable to grow on naphthalene. One such mutant was characterized further. The ability of this mutant to oxidize gentisate was 100-fold less than the ability of a Nah+ Sal+ strain harboring the unmutagenized plasmid, although both strains oxidized and grew on salicylate. These bacteria were presumably able to metabolize salicylate via catechol, since they possessed an inducible, plasmid-encoded catechol 2,3-dioxygenase. Our results suggest that there is an alternate, plasmid-encoded route of salicylate degradation via gentisate and that some plasmid-associated relationship between this pathway and naphthalene oxidation exists.

Catechol 2,3-Dioxygenase↗
PubMed1984

Dichotic listening ear asymmetry: patterns of longitudinal development.

Dichotic listening research with children has continued to be prevalent although numerous authors have described both theoretical and methodological limitations with traditional dichotic listening free-recall paradigms. The present research adds to this growing skepticism by reanalyzing two major longitudinal studies of children's ear asymmetries. These two studies, based in different countries (United States, Holland), utilized highly similar paradigms (free-recall digits), subjects (males), and age levels (kindergarten and second and fifth grade). The questions of ear advantage development, patterns of ear advantages, and the relationship between dichotic listening performance and reading skills are addressed from the multiple statistical methodologies represented in the literature. From these analyses, support for all of the major hypotheses regarding the developmental patterns of dichotic listening performances could be obtained from the same data samples. The use of traditional free-recall dichotic listening paradigms are not recommended for use with children. The implications for future research are discussed.

Child↗
PubMed1982

The competer automatic campimeter II. Clinical experience.

The Competer automatic campimeter was tested in 98 patients. The results of 31 visual fields with glaucomatous defects and 11 (para) central defects due to maculopathies are reported. The examination with the Competer will miss a certain amount of early glaucomatous visual field defects. The percentage depends on the selection of the visual fields. Any substantial glaucomatous visual field defect will be detected. The indication of typical configuration is not ideal. The examination with the Competer is not suitable for the detection of small (para) central defects, due to lack of stimulus-positions in the (para) central visual field. The Competer's meridional static perimetry device was not used in this study. The Competer has a large dynamic range and a good detection strategy. The stimulus distribution over the visual field could be improved.

Computers↗
PubMed1982

Clinical evaluation of the Scoperimeter, an experimental automatic perimeter.

The Scoperimeter is an experimental automatic campimeter based on an oscilloscope connected with a microcomputer and a printer-plotter. The instrument has 60 stimuli in the 25 degrees visual field and uses a suprathreshold gradient-adapted threshold related strategy (1). The report describes the results of a comparative examination of the threshold related gradient-adapted suprathreshold detection and limited assessment programme in 20 eyes with normal visual fields, 24 eyes of patients with glaucomatous defects and 10 eyes of patients with (para) central defects due to maculopathies. The Scoperimeter detected all larger defects. The Scoperimeter detected 60% of very early glaucomatous defects. The remaining 40% was detected by high resolution (1 degree) manual meridional static perimetry. The configuration of defects was demonstrated satisfactorily only for homogeneous defects of considerable size. The strategy is quite satisfactory for the detection of glaucomatous defects provided the resolution is increased and the peripheral field can be examined. A high resolution threshold strategy serving as a data base for follow-up examination is under investigation. The Scoperimeter's low resolution grid and suprathreshold strategy are not suitable for the detection and assessment of small relative (para) central defects.

Glaucoma↗
PubMed1982

The Peritest, a new automatic and semi-automatic perimeter.

The Peritest is a new automatic and semi-automatic (manual) perimeter for detection and limited assessment of visual field defects. It uses either multiple or single stimulus static perimetry. The lightsources are LED's. A total of 206 positions can be examined including the center; 151 positions inside 25 degrees-eccentricity. The programmes use a threshold-related gradient adapted suprathreshold (0.6) strategy. The results are printed on a special chart using non-interpolated grey scales for indicating local reduction of sensitivity. General and local reduction of sensitivity are separated. The progress of the examination can be followed on a LED-monitor. The reliability of the patient is measured. 70% of small early glaucomatous defects (that are only found by high resolution meridional static perimetry) were detected. Such defects are not usually detected by routine kinetic perimetry. More peripheral defects were detected (greater than 25 degrees) than by kinetic perimetry. Due to the relatively high number of stimuli the typical configuration of defects was satisfactorily demonstrated for defects of moderate size and larger. The duration of the examination varies from less than 4 min. for a semi-automatic examination of normal eyes to 10-20 min. for automatic examination of eyes with defects of moderate size (average 15 minutes for 206 positions).

Glaucoma↗
PubMed1982

Argon laser treatment of pigment epithelial detachments and of subretinal neovascular membranes in Junius-Kuhnt's senile disciform macular degeneration. A prospective, randomized study.

Results of argon laser treatment of pigment epithelial detachments and of subretinal neovascular membranes in Junius-Kuhnt's senile disciform macular degeneration have been compared in a prospective, randomized investigation with the natural course of these affections. Of several hundred cases 26 eyes met our criteria for treatment. In control periods ranging from 1 to 3 years, six eyes with pigment epithelial detachments received laser treatment and seven served as controls; seven eyes with subretinal neovascular membranes received laser treatment and six served as controls. The results indicate that impairment of vision progresses more rapidly after argon laser treatment than when no such treatment is given.

Adult↗
PubMed1981

Organization and expression of genes involved in the production of the K88ab antigen.

Escherichia coli K-12 minicells were used to study the expression of the genes located on plasmid pFM205, which contains the genetic determinant of the K88ab antigen. Plasmid pFM205 is composed of a 4,3-megadalton large deoxyribonucleic acid fragment derived from the wild-type K88ab plasmid pRI8801 (51 megadaltons) and the cloning vehicle pBR322. The K88ab deoxyribonucleic acid of pFM205 appeared to express six polypeptides with apparent molecular masses of 81, 30, 29, 27, 26, and 17 kilodaltons, respectively. These polypeptides account for approximately 85% of the coding capacity of the cloned deoxyribonucleic acid. The 26-kilodalton polypeptide was found to react with specific anti-K88ab antibodies and therefore represents the K88ab subunit. The K88ab subunit and at least two other polypeptides (81 and 17 kilodaltons) were translated into precursors which were about 2 kilodaltons larger than the mature proteins. Plasmid pFM205 was used to construct deletion mutants. By analyzing these mutants in minicells the genes of the six polypeptides could be located on the physical map of pFM205. It appeared that deletion of the gene of the 81-kilodalton polypeptide resulted in an altered conformation of the K88ab antigen.

Antigens, Bacterial↗