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Biomedical subjects

K Köhler

Publications and source records attributed to K Köhler.

At least 19 recordsLinked to original sources
PubMed1994

Polyethylene glycol-potassium phosphate aqueous two-phase systems. Insertion of short peptide units into a protein and its effects on partitioning.

Two different tetrapeptides, AlaTrpTrpPro and AlaIleIlePro, were inserted near the C-terminus of the protein ZZT0. The Trp-rich peptide unit strongly increased both the partitioning of ZZT0 into the polyethylene glycol (PEG)-rich phase in a PEG-potassium phosphate aqueous two-phase system and its retention on PEG and propyl hydrophobic interaction chromatographic columns with potassium phosphate as eluent. Both the partitioning and the retention increased with increasing number of Trp-rich peptide units inserted into ZZT0. Insertion of Ile-rich tetrapeptide units affected the partitioning and retention to a much lesser extent. Partition data also indicated a folding of inserted Trp tetrapeptides units, probably to minimize their water contact.

Amino Acid Sequence↗
PubMed1991

[Prognosis of local-regional recurrence in breast carcinoma].

992 primary breast cancers were treated at the Gynaecological Department of the University Hospital of Zürich between 1971 and 1988. Local recurrence (LR) has occurred in 131 patients up to now after a median follow-up of 5.1 years. 75% of the LR manifested the first three years after operation. Especially the locoregional (axillary) recurrences occurred early. The frequency of LR was independent of the menopausal status and the steroid receptors, but was dependent on the initial axillary nodal status and the tumor size. Patients with nodal involvement had recurrences significantly more often (74 of 372 = 20%) than those without (34 of 469 = 7%). LR of patients with tumors smaller than or equal to 2 cm occurred in 7%, in patients with tumors greater than 2 cm in 17%. The 5-year survival of all patients and the patients with a LR was 80% and 57% respectively. The longer the disease-free interval, the better the prognosis of survival. The findings suggest, that especially an early LR can not be looked at as merely a local problem but rather as a signal of a systemic manifestation of the disease.

Breast Neoplasms↗
PubMed1991

Partitioning of beta-galactosidase fusion proteins in PEG/potassium phosphate aqueous two-phase systems.

Four different beta-galactosidase fusion proteins have been partitioned in poly(ethylene glycol) (PEG) 4000/potassium phosphate aqueous two-phase systems. The partition coefficients (K) of staphylococcal protein A-beta-galactosidase (SpA beta gal) (K = 3.5) and staphylococcal protein A-streptococcal protein G-beta-galactosidase (AG beta gal) (K = 2.8) were compared with the partition coefficients of their constituent molecules, beta-galactosidase, SpA, and protein AG. It was found that by fusing beta-galactosidase to the smaller proteins SpA and protein AG, their partition coefficients were increased four to five times. Experimental data were fitted into, and found to agree with, the Albertsson partition model of interacting molecules. The compatibility with PEG and potassium phosphate of beta-galactosidase, SpA, and two different versions of the SpA beta gal protein, displayed as precipitation curves, showed a relationship to the protein partition coefficients in PEG/potassium phosphate systems. High solubility in one phase component was accompanied by preferential partitioning to the phase rich in the same component in the PEG/potassium phosphate system. Also, a changed linker region in SpA beta gal resulted in a more soluble protein. This, together with the improved K values of the target proteins by fusion, shows that it is possible to use beta-galactosidase as an affinity handle.

Cloning, Molecular↗
PubMed1991

The molecular basis of partitioning in aqueous two-phase systems.

Protein purification based on partition in aqueous two-phase systems has attracted interest for many years. This approach has been advocated as a primary-stage unit operation in downstream processing. In reality, application has been strictly limited through inadequate understanding of the complex molecular forces involved in partitioning processes.

Amino Acid Sequence↗
PubMed1991

Engineering proteins to enhance their partition coefficients in aqueous two-phase systems.

We describe a novel method to partition recombinant proteins into the polymer-rich top phase in poly(ethylene glycol) (PEG)4000/potassium phosphate aqueous two-phase systems. The concept is based on fusion of a gene fragment encoding a short peptide sequence to the product gene of interest thereby changing the partitioning properties of the expressed product protein as a fusion to the peptide. The model protein in this study, ZZ, is a two domain molecule based on staphylococcal protein A (SPA) which distributes evenly in PEG/salt systems. A tetrapeptide sequence, AlaTrpTrpPro (designated the partitioning peptide), was designed by molecular modeling techniques to include exposed tryptophan residues and to have a coding DNA sequence which is possible to polymerize in an obligate head-to-tail fashion at the DNA level. Gene fragments encoding one and three partitioning peptides, respectively, were fused to the 3' end of the ZZ gene and the fusion proteins were produced intracellularly in Escherichia coli. The partition coefficients of ZZ proteins containing zero, one and three fused partitioning peptides were determined in three PEG 4000/potassium phosphate aqueous two-phase systems of different compositions. In all three phase systems, there were dramatic effects on the partition coefficient by the fused partitioning peptides. In the phase system with the largest effects, the partition coefficient was enhanced from 1.6 to 11.6 by fusing one tetrapeptide sequence to the 147 amino acid model ZZ protein. By the fusion of three partitioning peptides, the coefficient was increased to 96.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Embolization in the head and neck region.

With our results we want to demonstrate the usefulness of the presurgical embolization of tumours in areas where the operation of the highly vascularized tumours is very difficult or even impossible. In certain cases of angiomatous lesions, better results can be achieved by means of embolization than by surgery. For a safe and successful intravascular embolization an optimal technique with DSA, an experienced team and a cooperative patient are absolute prerequisites for interventional procedures in head and neck regions. CT in axial and coronal scans are important to outline the lesion, especially the bone destruction in the skull base. In juvenile nasopharyngeal angiofibroma we found the best results of devascularizing the tumour, if we first embolized the maxillary artery. According to Davis we performed a facial artery injection at the end of the embolization, in order to opacify the collateral of the maxillary artery, and thus control the completeness of maxillary artery embolization.

Embolization, Therapeutic↗
PubMed1991

[Conventional roentgen diagnosis of induratio penis plastica].

The therapeutic decision in the management of Peyronie's disease depends on the confirmation or exclusion of inflammatory activity. Plain films of the penis in mammographic technique demonstrate the presence of fibrotic or calcified areas, in which conservative treatment is not more effective. In twelve out of 32 patients, we found calcifications of various size.

Adult↗
PubMed1991

Prosomes (proteasomes) of higher plants.

From different plant tissues such as tobacco (Nicotiana rustica), potato (Solanum tuberosum), and mung bean (Phaseolus radiatus), ring- or cylinder-shaped particles called prosomes were isolated by either sucrose gradient centrifugation or fast protein liquid chromatography (FPLC). These particles have a diameter of 12 to 14 nm and a length of 16 to 18 nm. They migrate under conditions of nondenaturing gel electrophoresis as one distinct band. Sedimentation coefficient and buoyant density in Cs2SO4 of the plant prosomes were determined by analytical ultracentrifugation to be approximately 23S and 1.23 g/cm3, respectively. The total molecular mass was estimated by gel filtration to be 650 kDa. Plant prosomes are composed of 12 to 15 proteins with molecular masses in the range of 24 to 35 kDa with isoelectric points of pH 5 to 7 as revealed by two-dimensional gel electrophoresis. The protein patterns of prosomes from the three different plant species are very similar. Polyclonal antisera against potato prosomes reacted in Western blots with prosomal proteins of all three plant species. They also bind to some prosomal proteins of animal species. Antisera against animal prosomes react with some proteins of plant prosomes. As shown by lectin blotting, plant prosomes are glycosylated carrying glucosyl- or mannosyl, and N-acetylgalactosaminyl residues. Prosomal preparations contain non-stoichiometric amounts of small RNA of about 80 kDa. These results suggest that plant prosomes are structurally and functionally homologous to prosomes of other eukaryotic cells.

Cell Fractionation↗
PubMed1990

Selection of prosomes and prosomal RNA by immobilized viral RNAs.

Viral messengers were used to select and purify prosomes and prosomal RNA from subribosomal fractions of HeLa cells and mouse erythroblasts. Adenovirus mRNA immobilized on oligo(dT)-cellulose and tobacco mosaic virus RNA (TMV) sedimenting in sucrose gradients associated strongly with prosomes at high salt conditions forming intermolecular RNA-RNA hybrids between prosomal RNA and viral RNA. Hybrid selection of small cytoplasmic RNAs with immobilized TMV-RNA revealed a RNA species migrating at the same position as prosomal RNA. The possible existence of a box-like sequence involved in hybridization will be discussed.

Adenoviruses, Human↗
PubMed1990

Impact of genetic engineering on downstream processing of proteins produced in E. coli.

Genetic engineering can be used to give a protein properties that are advantageous for downstream processing. Many heterologous proteins are degraded at high rates by proteases. Depending on which type of proteolytic degradation is encountered the strategy may be different: induction of inclusion bodies, change of the amino acid sequence in the sensitive site of the product, or protection by fusion of the product with other proteins. The number of unit operations needed to purify a protein may be reduced by addition of other polypeptides or amino acids to the product. Affinity chromatography, immobilized metal ion affinity chromatography, and extraction in aqueous two-phase systems are unit operations which can be made more versatile by the fusion technique.

Amino Acid Sequence↗
PubMed1990

Combined use of extraction and genetic engineering for protein purification: recovery of beta-galactosidase fused proteins.

Partitioning of beta-galactosidase in aqueous two-phase systems of poly(ethylene glycol) and potassium phosphate is reviewed. The affinity of Escherichia coli beta-galactosidase for the PEG-rich phase dominates also in beta-galactosidase fusion proteins and the concept of using beta-galactosidase as an affinity handle for extraction of other proteins, after fusion, is discussed. A hypothesis is presented, assuming that tryptophan residues at the surface of beta-galactosidase is responsible for its partitioning to the PEG rich phase, and the concept of poly-tryptophan handles fused to the target protein for extraction is introduced.

Genetic Engineering↗
PubMed1990

[The problem of mammography in patients with breast cancer following organ-preserving surgery and irradiation].

In our study therapy induced early and late effects on the breast were investigated with mammography. All patients with breast carcinoma were treated with conserving surgery and then irradiated. Criterium for the evaluation of the changes was a postoperative mammogram for comparison with the found changes. Severe limitations for the diagnosis of tumour recurrence did not result for this form of therapy.

Breast Neoplasms↗
PubMed1990

[Vein of Galen malformation in a newborn infant with clinical symptoms of a cardiologic emergency].

We report on the management of one term newborn infant with a malformation of the Vena Galeni. The baby suffered from cyanosis and intractable congestive heart failure without evidence of congenital heart malformation at his second day of life. The diagnosis was established by two-dimensional sonography and Doppler examination. However, we thought it necessary additionally to perform an angiography of the intracerebral vessels before surgical intervention. We conclude that a real time two-dimensional imaging system and a range-gated pulsed Doppler velocimeter should be available in newborn intensive care units. Otherwise neonatologists are forced to transport these infants to pediatric heart centers because of inability to detect such an extracardiac origin of heart and circulatory failure.

Cerebral Veins↗
PubMed1989

Cellular localization of induced human interferon-beta mRNA by non-radioactive in situ hybridization.

Induced interferon-beta (IFN-beta) mRNA was localized in human FS-4 fibroblasts by in situ hybridization using biotinylated probes. The hybridization sites were detected by incubation with a nick-translated genomic DNA probe (1.8 kb) via streptavidin-colloidal gold followed by silver contrast enhancement. The positive signals were observed by reflection-contrast light microscopy. IFN-beta mRNA was transiently induced by poly r(I): r(C) in fibroblasts 2-4 h after induction. Induction in the presence of cycloheximide and actinomycin D (superinduction conditions) exhibited an enhanced level of IFN-beta mRNA with a maximum at 4-8 h. The kinetics of the IFN-beta mRNA expression in the cytoplasm as revealed by in situ hybridization proved to be compatible with the results of Northern blotting experiments of total cellular RNA.

Cells, Cultured↗