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Biomedical subjects

E Brinkman

Publications and source records attributed to E Brinkman.

8 recordsLinked to original sources
PubMed1998

Maternal corticotropin-releasing hormone is increased with impending preterm birth.

The objective of this study was to test the hypothesis that maternal CRH concentrations are elevated in women experiencing threatened preterm labor who subsequently give birth within 24 h compared to those in women who do not. We also characterized the changes in maternal plasma cortisol, ACTH, corticosteroid binding capacity (CBC), and CRH concentrations in 28 healthy pregnant women between 20-38 weeks gestation. Overall, maternal plasma CRH concentrations were significantly greater (P < 0.05) in those women giving birth within 24 h (1343.3 +/- 143.9 pg/mL; n = 81) compared to those in women who did not (714.5 +/- 64.8 pg/mL; n = 144) or those in normal subjects. This difference was present between 28-36 weeks, but not 24-28 weeks gestation. The ratio of maternal cortisol to CBC was also significantly greater (P < 0.05; 0.65 +/- 0.04; n = 82) in women giving birth within 24 h than in those who did not (0.55 +/- 0.02; n = 136). This difference was significant at all gestational ages studied. Elevated CRH concentrations and bioavailability of free cortisol may both be implicated in the pathogenesis of preterm labor in some women. Further prospective clinical trials are warranted to determine the positive and negative predictive values of maternal CRH concentrations and/or the ratio of cortisol/CBC for identifying women with threatened preterm labor destined to give birth within 24 h.

Adrenal Cortex Hormones↗
PubMed1994

Molecular characterization of enterobacterial pldA genes encoding outer membrane phospholipase A.

The pldA gene of Escherichia coli encodes an outer membrane phospholipase A. A strain carrying the most commonly used mutant pldA allele appeared to express a correctly assembled PldA protein in the outer membrane. Nucleotide sequence analysis revealed that the only difference between the wild type and the mutant is the replacement of the serine residue in position 152 by phenylalanine. Since mutants that lack the pldA gene were normally viable under laboratory conditions and had no apparent phenotype except for the lack of outer membrane phospholipase activity, the exact role of the enzyme remains unknown. Nevertheless, the enzyme seems to be important for the bacteria, since Western blotting (immunoblotting) and enzyme assays showed that it is widely spread among species of the family Enterobacteriaceae. To characterize the PldA protein further, the pldA genes of Salmonella typhimurium, Klebsiella pneumoniae, and Proteus vulgaris were cloned and sequenced. The cloned genes were expressed in E. coli, and their gene products were enzymatically active. Comparison of the predicted PldA primary structures with that of E. coli PldA revealed a high degree of homology, with 79% of the amino acid residues being identical in all four proteins. Implications of the sequence comparison for the structure and the structure-function relationship of PldA protein are discussed.

Amino Acid Sequence↗
PubMed1991

Poly(vinyl alcohol)-heparin hydrogels as sensor catheter membranes.

Poly(vinyl alcohol)-heparin hydrogels with varying water content were synthesized for use as sensor catheter membranes. Films were cast from aqueous mixtures of poly(vinyl alcohol) (PVA), a photosensitive cross-linker p-diazonium diphenyl amine polymer (PA), glutaraldehyde (GA) and heparin. After drying, the films were cross-linked by successive UV irradiation and heat treatment. To get an indication about the cross-linking density of the networks, the water content of the hydrogels was measured after equilibration in water. Hydrogels from PVA, PA, GA and heparin, with a water content of 35-95%, could be obtained if the components were dissolved in saline instead of water. The release of heparin from PVA-heparin or PVA-PA-heparin hydrogels was studied using different receiving phases. The cumulative amount of released heparin appeared to be dependent on the initial water content of the hydrogels and the composition of the receiving phase. For the PVA-PA-heparin hydrogels as well as the PVA-heparin hydrogels the cumulative amount of released heparin in water was about six times higher than in a Tris buffer. Using Tris buffer as receiving phase PVA-PA-heparin hydrogels with water contents of 53, 61 or 71% released heparin for at least 3 wk. The cumulative amount of released heparin increased with initial water content of these hydrogels. Recalcification times (RCT) of plasma exposed to PVA-PA-heparin hydrogels (water content 53%), which released heparin at a low rate (2 micrograms/cm2 per day), were markedly prolonged compared with the RCT values for PVA-PA hydrogels without heparin.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMed1991

Enzyme-linked immunoassays for the detection of Salmonella spp.: a comparison with other methods.

The first enzyme immunoassay for Salmonella was reported in 1977 and since that time several enzyme-linked immuno assays (ELISAs) have been developed, using either polyclonal or monoclonal antibodies that will detect most Salmonella serotypes. Two of these kits have been declared official first status by the Association of Official Analytical Chemists (AOAC). In comparison with a culture method used in collaborative studies, the total assay time is reduced by 2 days and statistical analysis of the data indicated no significant difference. The main problem related to all methods other than traditional culture methods is the occurrence of false-positive and/or false-negative results. False-positive ELISA results can be eliminated by using (combinations of) highly specific monoclonal antibodies. Good enrichment procedures are very important to be sure that the detection limit of approx. 10(5) cells/ml will be reached. In the future even better limits of detection may be achieved by using enzyme amplification or chemiluminescence to decrease the number of false-negative results.

Enzyme-Linked Immunosorbent Assay↗
PubMed1990

Platelet deposition studies on copolyether urethanes modified with poly(ethylene oxide).

Pellethane 2363 80A films and tubings were chemically modified and the effect of these modifications on platelet deposition was studied. Grafting of high molecular weight poly(ethylene oxide) and graft polymerization of methoxy poly(ethylene glycol) 400 methacrylate resulted in surfaces with a good water wettability. The increased hydrophilicity of these modified surfaces could be demonstrated by contact angle measurements. The platelet deposition was investigated with tubings in a capillary flow system, using different types of perfusates. Platelet deposition from a buffer-containing perfusate on surfaces modified with either high molecular weight poly(ethylene oxide) or methoxy poly(ethylene glycol) 400 methacrylate was almost absent and less than on Pellethane 2363 80A. Using a citrated plasma-containing perfusate the amount of deposited platelets on Pellethane 2363 80A modified with high molecular weight poly(ethylene oxide) was low and about the same as on unmodified surfaces. However, a marked reduced platelet deposition compared to unmodified Pellethane 2363 80A was found when the platelets were activated by Ca2+ ionophore. The improved blood compatibility of the modified Pellethane 2363 80A tubings obviously indicates the favourable effect of the presence of grafted PEO on the surface.

Biocompatible Materials↗
PubMed1989

Surface modification of copolyether-urethane catheters with poly(ethylene oxide).

Pellethane 2363 80A catheters were modified with poly(ethylene oxide) in order to improve their blood compatibility. Contact angle measurements showed that Pellethane 2363 80A surfaces had increased wettability after this modification. The results of in vitro blood compatibility tests showed that surface modification with poly(ethylene oxide) resulted in a five-fold reduction of platelet deposition. Activation of coagulation was not affected.

Biocompatible Materials↗
PubMed1984

Preferential adsorption of high density lipoprotein from blood plasma onto biomaterial surfaces.

In the present study a two step enzyme immuno assay (EIA) was used for the investigation of the adsorption of proteins and lipoproteins from solutions and from blood plasma onto polymer surfaces. It was found that only a small adsorption of the major blood proteins occurred from plasma. Evidence is presented that the reason for this adsorption behaviour is a preferential adsorption of high density lipoprotein (HDL).

Adsorption↗