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Biomedical subjects

S Weigert

Publications and source records attributed to S Weigert.

At least 19 recordsLinked to original sources
PubMed2001

Development of affinity microparticles for extracorporeal blood purification based on crystalline bacterial cell surface proteins.

In this article, the development of specific adsorbents for extracorporeal blood purification are described. Affinity microparticles were prepared by linking Protein A to crystalline cell surface layers (S-layers) from Thermoanaerobacter thermohydrosulfuricus 1111-69. S-layers were used in the form of cell wall fragments obtained by breaking whole cells by ultrasonification, resulting in cup-shaped structures (average size 0.5 x 1 microm) completely covered with S-layer protein. Protein A was covalently bound to carboxylic acid groups of the S-layer protein after activation with 1-ethyl-3,3'(dimethylamino)propylcarbodiimide. In batch adsorption experiments with fresh frozen human plasma, the resulting S-layer based affinity microparticles showed a high adsorption capacity for IgG (40 mg IgG were bound per g wet pellet of S-layer based affinity microparticles). Fractions eluted from the microparticles were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. They contained only IgG demonstrating that adsorption was specific. In biocompatibility tests, preparations of the S-layer microparticles showed no low-density lipoprotein-reactivity, no cytotoxicity, and no cytokine inducing activity.

Adsorption↗
PubMed2000

Quantum time evolution in terms of nonredundant probabilities

Each scheme of state reconstruction comes down to parametrize the state of a quantum system by expectation values or probabilities directly measurable in an experiment. It is argued that the time evolution of these quantities provides an unambiguous description of the quantal dynamics. This is shown explicitly for a single spin s, using a quorum of expectation values which contains no redundant information. The quantum mechanical time evolution of the system is rephrased in terms of a closed set of linear first-order differential equation coupling (2s+1)(2) expectation values. This new representation of the dynamical law refers neither to the wave function of the system nor to its statistical operator.

Journal Article↗
PubMed1997

Applications of S-layers.

The wealth of information existing on the general principle of S-layers has revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from many organisms are capable of recrystallizing as closed monolayers onto solid supports at the air-water interface, on lipid monolayers or onto the surface of liposomes. Particularly their repetitive physicochemical properties down to the subnanometer scale make S-layers unique structures for functionalization of surfaces and interfaces down to the ultimate resolution limit. The following review focuses on selected applications in biotechnology, diagnostics, vaccine development, biomimetic membranes, supramolecular engineering and nanotechnology. Despite progress in the characterization of S-layers and the exploitation of S-layers for the applications described in this chapter, it is clear that the field lags behind others (e.g. enzyme engineering) in applying recent advances in protein engineering. Genetic modification and targeted chemical modification would allow several possibilities including the manipulation of pore permeation properties, the introduction of switches to open and close the pores, and the covalent attachment to surfaces or other macromolecules through defined sites on the S-layer protein. The application of protein engineering to S-layers will require the development of straightforward expression systems, the development of simple assays for assembly and function that are suitable for the rapid screening of numerous mutants and the acquisition of structural information at atomic resolution. Attention should be given to these areas in the coming years.

Bacteria↗
PubMed1996

Do gonadotropins influence serum lipoprotein(a) concentrations? Observations on children, adolescents and adults.

Data from 7045 subjects were examined. The main groups consisted of the following in- and outpatients: 1414 neonates, 2554 children and adolescents (1336 males, 1218 females), 1209 women directly postpartum, 786 non-pregnant women and 1090 men aged between 18 and 100 years of age. Unless otherwise stated, persons were under medical observation or therapy. The results were obtained over a three-year period using an in-house immunoluminometric assay specific for apolipoprotein(a) using two polyclonal antibodies and single lot of reagents to allow for comparability of results. Girls aged between 10 and 12 years of age had significantly higher serum lipoprotein(a) (median 124 mg/l) levels than boys (median 88 mg/l) of the same age (p < 0.05-Mann-Whitney U-test). Post-pubertal lipoprotein(a) concentrations were not significantly different from pre-pubertal levels. Between the ages of 0-9 and 13-17 years there were no statistically significant sex-linked differences in serum lipoprotein(a). In adults, lipoprotein(a) serum levels were significantly higher in women (median 163 mg/l) aged between 50 and 59 years, when compared with men (median 128 mg/l) of the same age group (p = 0.05-Kruskal-Wallis one way ANOVA followed by the Nemenyi test). There was no significant difference in serum lipoprotein(a) concentrations between healthy women (median 91 mg/l), women direct postpartum (median 116 mg/l) and in-patient women (median 117 mg/l) aged between 18 and 41 years of age (p = 0.11-0.96). There was no correlation between maternal lipoprotein(a) and birth weight in mature newborns (r = -0.028-0.085). The results may indicate a direct influence of gonadotropins at puberty and during the menopause which cause an increase in serum lipoprotein(a) concentrations.

Adolescent↗
PubMed1996

2-D protein crystals as an immobilization matrix for producing reaction zones in dipstick-style immunoassays.

In the present study, the applicability of crystalline bacterial cell-surface layers (S-layers) as novel immobilization matrices and reaction zones for dipstick-style immunoassays was investigated. For this purpose, S-layer-carrying cell-wall fragments from Bacillus sphaericus CCM 2120 were deposited on a microporous support, and the S-layer protein was cross-linked with glutaraldehyde. For developing appropriate test systems, either human IgG was directly linked to the carboxylic acid groups from the S-layer protein or it was immobilized using Protein A or, after biotinylation, using streptavidin. A clear correlation was obtained between the amount of anti-human IgG applied and the absorbance values in the immunoassays. S-layers with covalently bound recombinant major birch pollen allergen were used for quantitative and semiquantitative determination of an antibody raised against it. Using S-layers as an immobilization matrix in comparison to amorphous polymers has advantages in that the closed monolayers of functional macromolecules on their outermost surface allows for strong signals in immunoassays, almost completely eliminates background and prevents diffusion.

Antibodies, Monoclonal↗
PubMed1995

(Apo)lipoprotein(a) concentrations at birth and in the first days and months of life--studies on the distribution of serum levels and the predictive value of measurements made at this time.

This study was carried out on 625 newborns delivered between July 1993 and December 1994 and 221 children visiting the clinic in the first year of life using an immunoluminometric assay specific for apolipoprotein(a), but calibrated with lipoprotein(a), hence the use of the term (apo)lipoprotein(a) for neonatal values. (Apo)lipoprotein(a) concentrations were measured in 278 neonates over the first 12 days of life (median observation time 6 days). A further 64 children were followed up over a period of 1-10 months (median observation time 5 months). The median (apo)lipoprotein(a) concentration at birth was 14.7 mg/l (males 14.6, females 14.7 mg/l). The range of concentrations measured was between 1 and 433 mg/l. The correlation coefficient between maternal and neonatal lipoprotein(a) at birth was 0.509 for 483 data pairs. The behaviour of serum concentrations of (apo)lipoprotein(a) during the first days of life varied greatly and was independent of the birth level. Eighty-four babies showed a decrease, 107 an increase and 87 no change in (apo)lipoprotein(a) levels; over the first months of life was more unified with 50 children showing an increase in serum lipoprotein(a), a decrease in 4 cases and no change in 10 cases. In these 64 children the median increase in serum (apo)lipoprotein(a) was from 15.8 mg/l at birth (range 1 to 364 mg/l) to 38.5 mg/l at 6 months. The median lipoprotein(a) concentrations in the children under 1 year (median age 6 months) was 37.0 mg/l (males 37.1, females 37.0 mg/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Lipoprotein(a) concentrations in cord and capillary blood from newborns and in serum from in-patient children, adolescents and adults.

Investigations have been made upon the distribution of lipoprotein(a) concentrations in cord and capillary blood from newborns and in serum from in-patient children and adults. Full-term neonates (n = 123), children aged 1 month to 16 years (n = 331) and adults aged between 17 and 88 years (n = 252) of age were included in the study. Lipoprotein(a) was determined using an immunoluminometric assay and a single lot of reagents. The assay had an effective measuring range of 1-800 mg/l. Lipoprotein(a) could be measured either in cord or capillary blood in the majority of cases. Problems arose in isolated cases, in each of which there was a large concentration difference in lipoprotein(a) between mother and child. The correlation data was: r = 0.897, n = 37, log (capillary blood) = 0.874 log (cord blood) + 0.165. The median lipoprotein(a) concentrations in cord and capillary blood were 13.9 and 10.2 mg/l respectively. Median lipoprotein(a) concentrations increased from birth up until the 6th decade (159 mg/l), decreasing to 95 mg/l during the 9th decade of life. In mature newborns, the median lipoprotein(a) concentrations correlated with gestational age. The distribution of lipoprotein(a) concentrations in serum is skewed throughout life, the ratio mean/median being 2.07 at birth, 2.71 in children and 2.72 in adults. The percentage of children with lipoprotein(a) concentrations above 250 mg/l was 23.0 (male) and 23.8 (female). The corresponding figures for adults was 38.2 for males and 28.2 for females respectively. In the group of newborns 27.7 percent had concentrations above 25 mg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗