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Biomedical subjects

A Seeger

Publications and source records attributed to A Seeger.

13 recordsLinked to original sources
PubMed2000

Placement of the preparation line and periodontal health--a prospective 2-year clinical study.

The aim of this prospective clinical 2-year study was to determine whether the placement of the proximal margins of crowns within the zone of the biologic width results in periodontal alterations. In 41 patients, 116 prepared teeth as well as 82 unrestored, healthy contralateral teeth were examined. The following indices were determined before as well as 3, 6, 12, and 24 months after preparation: hygiene index, papillary bleeding index (PBI), and probing depth. After preparation, the distance between the restoration margins and the alveolar crest was measured with a modified periodontal probe on both proximal aspects of each tooth. These values were classified into 3 groups: I = < or = 1 mm between crown margin and alveolar crest, II = 1 to 2 mm, and III = > 2 mm. In addition, radiographs were taken directly after cementation of each restoration and after 12 and 24 months. The hygiene index did not significantly vary during the investigation, but PBI increased in all groups. The highest PBI increase was found in group I; in this group, the most significant increase was found between 3 and 6 months after preparation. The mean probing depth only increased in group I during the first 3 months after preparation on the mesial aspects. Only minor changes were found on the distal aspects of the teeth in group I and on all aspects in groups II and III. No alterations of the bone levels were diagnosed on the radiographs. These results indicate that the location of the restoration margins within the zone of the biologic width may impair the periodontal health of restored teeth.

Adult↗
PubMed1996

Two-step chromatographic procedure for purification of basic fibroblast growth factor from recombinant Escherichia coli and characterization of the equilibrium parameters of adsorption.

A two-step chromatographic procedure for purification of basic fibroblast growth factor (bFGF) from high-cell-density cultures of recombinant E. coli is described. Heparin-Sepharose as a material which shows a high affinity to endothelial growth factors was used as sorbent for purification of bFGF from the soluble cell fraction. A one-step affinity chromatographic procedure resulted in very pure bFGF. However, this one-step affinity isolation of bFGF caused the loss of around 60% of the recombinant protein. A combination of ion-exchange chromatography with heparin-Sepharose affinity chromatography was favored for bFGF purification. A first cation-exchange chromatographic step resulted in a solution of bFGF with a purity of around 70%. The weak cation exchanger CM Sepharose C50 was preferred in comparison to the strong cation exchanger S-Sepharose because of the higher recovery of bFGF. With the ion-exchange chromatographic step prior to the heparin-Sepharose affinity chromatography, the total yield of recovery of bFGF increased to 56% compared to 40% using the one-step purification procedure with heparin-Sepharose. To characterize the equilibrium parameters of adsorption, batch experiments for the calculation of maximum capacities and dissociation constants for CM-Sepharose C50 and heparin-Sepharose were carried out. The equilibrium experiments revealed that adsorption of bFGF to the ion-exchange sorbent followed single-site interaction according to the Langmuir model of adsorption. The adsorption of bFGF to heparin-Sepharose was described by a double Langmuir approach of two independent binding sites with different maximum capacities and dissociation constants. The purified bFGF showed a high biological activity and circular dichroic spectra of a proper folded molecule. The analysis of the N-terminal amino acid sequence revealed a mixture of two fractions of bFGF, which both are characterized by the cleavage of the first amino acid methionine. In addition, half of the bFGF molecules lacked the second amino acid alanine.

Chromatography, Affinity↗
PubMed1996

A complement factor B-like cDNA clone from the zebrafish (Brachydanio rerio).

An important molecule in the activation of the complement system in vertebrates is factor B, a serine protease with a molecular mass of 95,000. Factor B and the complement component C2 are thought to have arisen by gene duplication. In mammals and in Xenopus the factor B gene is linked to the major histocompatibility complex (MHC), whereas in domestic fowl it segregates independently of the MHC. Here we describe the isolation of a cDNA clone coding for factor B in the zebrafish, Brachydanio rerio. The deduced protein sequence exhibits a characteristic mosaic structure consisting of the short consensus repeat (SCR), the von Willebrand factor, and the serine protease domains. The estimated time of factor B and C2 divergence (approximately 350 million years ago), combined with the fact that C2 has thus far been found only in mammals, suggest that the factor B-C2 gene duplication occurred after the divergence of mammal-like reptiles from other reptiles and hence also birds. After the duplication, the C2 component evolved significantly faster than factor B.

Amino Acid Sequence↗
PubMed1995

Entry of Escherichia coli into stationary phase is indicated by endogenous and exogenous accumulation of nucleobases.

Endogenous and exogenous accumulation of nucleobases was observed when Escherichia coli entered the stationary phase. The onset of the stationary phase was accompanied by excretion of uracil and xanthine. Except for uracil and xanthine, other nucleobases (except for minor amounts of hypoxanthine), nucleosides, and nucleotides (except for cyclic AMP) were not detected in significant amounts in the culture medium. In addition to exogenous accumulation of nucleobases, stationary-phase cells increased the endogenous concentrations of free nucleobases. In contrast to extracellular nucleobases, hypoxanthine was the dominating intracellular nucleobase and xanthine was present only in minor concentrations inside the cells. Excretion of nucleobases was always connected to declining growth rates. It was observed in response to entry into the stationary phase independent of the initial cause of the cessation of cell growth (e.g., starvation for essential nutrients). In addition, transient accumulation of exogenous nucleobases was observed during perturbations of balanced growth conditions such as energy source downshifts. The nucleobases uracil and xanthine are the final breakdown products of pyrimidine (uracil and cytosine) and purine (adenine and guanine) bases, respectively. Hypoxanthine is the primary degradation product of adenine, which is further oxidized to xanthine. The endogenous and exogenous accumulation of these nucleobases in response to entry into the stationary phase is attributed to degradation of rRNA.

Cell Cycle↗
PubMed1986

[Structure elucidation of gestodene].

The structure of 17 alpha-ethinyl-17 beta-hydroxy-18-methyl-4,15-estradien-3-one (gestodene) was elucidated by the spectrometric methods UV, IR, NMR, MS.

Contraceptives, Oral↗
PubMed1977

Isolation and identification of 15-beta-hydroxy cyproterone acetate as a new metabolite of cyproterone acetate in dog, monkey and man.

15-beta-hydroxy cyproterone acetate could be identified by thin layer chromatography, mass spectrum, NMR and IR spectrum as a major unconjugated metabolite of cyproterone acetate in plasma and urine of dog, monkey and man. This metabolite has been found to interferein the Mattingly method for the determination of 11-hydroxy-corticosteroids which suggests, that this method is inadequate in controling the adrenal function of subjects treated with cyproterone acetate.

Animals↗