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J Köhler

Publications and source records attributed to J Köhler.

At least 73 records · Page 4Linked to original sources
PubMed1991

Cytogenetic and molecular characterization of a small ring chromosome in the complex karyotype of a girl with Turner syndrome.

Blood samples of an 8-year-old girl with Turner syndrome were examined using cytogenetic and molecular methods. Chromosomal analyses revealed a mosaic karyotype consisting of 25% 47,X,der(X), +r(X) and 75% 46,X,der(X) cells. Southern blot hybridizations with Y-specific DNA probes excluded a Y chromosomal origin of the small ring chromosome. In situ hybridization using DNA probe pXBR showed it to be X-derived. Examination of C-, Q-, and R-banding patterns indicated that the der(X) chromosome probably arose by a translocation event.

Blotting, Southern↗
PubMed1991

Cinematics and sticking of heart valves in pulsatile flow test.

The aim of the project was to develop laboratory test devices for studies of the cinematics and sticking behaviour of technical valve protheses. The second step includes testing technical valves of different types and sizes under static and dynamic conditions. A force-deflection balance was developed in order to load valve rims by static radial forces until sticking or loss of a disc (sticking- and clamping-mould point) with computer-controlled force deflection curves. A second deflection device was developed and used for prosthetic valves in the aortic position of a pulsatile mock circulation loop with simultaneous video-cinematography. The stiffness of technical valve rims varied between 0.20 (St. Jude) and about 1.0 N/micron (metal rim valves). The stiffness decreased significantly with increasing valve size. Sticking under pulsatile flow conditions was in good agreement with the static deflection measurements. Hence, valve sticking with increasing danger of thrombus formation is more likely with a less stiff valve rim. In the case of forces acting perpendicularly to the pendulum axis, the clamping mould-point of the valve can be reached, followed by disc dislodgement.

Heart Valve Prosthesis↗
PubMed1991

[Doppler echocardiographic determination of the effective orifice area of mechanical heart valve prostheses in a flow model].

In a flow model the effective orifice areas (Ae) of 17 mechanical heart valve prostheses were determined. We measured the Ae-values of several sizes of three types of mechanical prostheses (Medtronic-Hall, St. Jude Medical, and Omnicarbon) under quasi-steady flow conditions using the continuity equation: Ae = flow/maximal transprosthetic velocity. The flow through the model could be determined exactly by directly measuring the decreasing fluid level within the feed tank, while the maximal velocities were calculated from CW-Doppler echocardiographic spectra. It was found that 1) over a range of 200-800 cm3/s Ae was constant for all prostheses and 2) in small aortic prostheses the Ae could be determined with only little scattering of the obtained values, while in large mitral prostheses there was a considerable variation within the results of repeated investigations. For example, in the 21- and 31-Omnicarbon-valves mean values of Ae were calculated as 1.41 and 4.03 cm2, respectively, with standard deviations of 0.05 and 0.49 cm2 as a result of about 70 single calculations in each valve. 3) The absolute values of Ae were smaller than those of comparable in vitro studies based on the Gorlin formula. We conclude that the effective orifice areas of prosthetic heart valves can be easily determined in a flow model by the combination of flow and Doppler echocardiographic measurements. As determinations are based on the same principle, the obtained values should clinically be referred to patients where the corresponding continuity equation for pulsatile flow is used as Ae = stroke volume/time integral of the maximal transvalvular velocity.

Aortic Valve↗
PubMed1990

The minor-groove binding DNA-ligands netropsin, distamycin A and berenil cause polyploidisation via impairment of the G2 phase of the cell cycle.

Distamycin A, netropsin and berenil are known to cause undercondensation of heterochromatic regions of metaphase chromosomes. These ligands interfere with DNA curvature by binding to the minor groove of the DNA. Whereas the effects of these ligands upon chromatin structure are well established, little is known about their possible interference with cell cycle progression. We show that the presence of these DNA-ligands causes protracted cell growth consisting of a prolongation of the G1 phase of the cell cycle along with arrest in the G2 compartment. Concomitant with these cell kinetic disturbances the DNA ligands cause increased polyploidisation. These observations suggest that the DNA-minor groove may play an important role in progression through the G2 phase and proper mitotic transit.

Amidines↗
PubMed1989

[Resection of the superior vena cava in tumor occlusion].

Report about three cases of resection of the superior vena cava for tumor stenosis or occlusion. In one patient no reconstruction was performed while in the other two interposition of an armored PTFE-prosthesis between right brachio-cephalic vein and vena cava superior was carried out. In agreement with other authors it is concluded that best results can be obtained by reconstruction with a PTFE-prosthesis or autologous vein graft.

Adult↗
PubMed1988

Characterization of a newly established human urinary bladder cancer cell line (BT-1).

A new human transitonal cell carcinoma cell line has been established in long term tissue culture. The BT-1 cells were derived from a poorly differentiated human bladder cancer. The tumor cell line produces tumors in nude mice. BT-1 has been characterized by cytogenetic and flow cytometric analysis and by isoenzyme typing. As in direct preparations of human bladder tumors, an isochromosome 5p is a consistent marker of the newly established line. The BT-1 cells produce transforming growth factors but do not respond to exogeneous EGF.

Animals↗
PubMed1987

[Avoidable risks in the drug treatment of very old patients].

Among 196 patients with a mean age of 80 years there were, at the time of hospitalization, 12.2% who had been prescribed wrong or partly even high-risk medication drugs, some of which carried a high risk. Among 694 prescriptions 4.2% were faulty. The faults consisted of failure to take account of impaired renal function, contraindications, accompanying illnesses, and misinterpretation of side-effects. 80% of these prescriptions were for diuretics, psychoactive and antiarrhythmic drugs, digitalis and hypnotics. The number of faulty prescriptions on discharge was 1.4%. In all, the average number of prescribed drugs had decreased from 3.5 on admission to 2.9 on discharge. This retrospective study demonstrates that the manner of prescribing for elderly patients needs to be handled more critically and rationally.

Age Factors↗
PubMed1987

Effect of column degradation on the reversed-phase high-performance liquid chromatographic separation of peptides and proteins.

Many reversed-phase separations of proteins and peptides are currently performed in acidic mobile phases, e.g., 0.1% trifluoroacteic acid in water (pH 2) with organic modifiers. Such conditions are known to promote the cleavage of the silane from the silica in bonded-phase columns, especially for monomeric stationary phases. The stability of some columns commonly used for proteins and peptides has been examined, and it has been shown by both chromatographic and elemental analysis that degradation occurs very rapidly with fresh, "totally covered" column materials. Despite the loss of over half of the bonded phase in some cases, certain columns still exhibit adequate chromatographic performance, although reproducibility can be affected. The implications of these results with respect to both bonded-phase synthesis and mechanistic interpretation of chromatographic data is discussed.

Chromatography, High Pressure Liquid↗
PubMed1987

Interphase cell flow cytometry as a means of monitoring genomic size in normal and neoplastoid cell cultures.

The DNA specific fluorescence of mass cultures and clones derived from human skin and bladder tumor tissue was assayed by flow cytometry. In order to detect and quantitate small fluorescence intensity changes, cytogenetically defined triploid or diploid human fibroblast strains were cocultivated, harvested, and stained with the cell strain of unknown karyotype. The triploid standard (derived from human abortus tissue) proved chromosomally unstable at high passage level. Fifteen male, female, and 45,X strains displayed target-to-standard cell fluorescence ratios commensurate with their respective chromosome constitutions. Interstrain variation was highest among the 45,X strains, although mosaicism could not be detected by conventional cytogenetics. Interclonal fluorescence variation was two- to ten-fold higher among the tumor-derived clones tested. Chromosome counts and subcloning experiments indicate that this increased fluorescence variation is due to genome size variation. The clonal evolution of genome size differences was observed in subclones of chromosomally divergent parental clones. These observations suggest that well controlled flow cytometry can adequately resolve subtle degrees of genome size variation in cultivated human cells. The technique is especially suited for monitoring genome size changes in cultivated tumor cells.

Cell Separation↗
PubMed1986

The fragile site (16) (q22). I. Induction by AT-specific DNA-ligands and population frequency.

The rare fragile site at 16q22 was experimentally induced in lymphocyte cultures with various AT-specific, non-intercalating DNA-ligands. The optimum conditions for the induction of fra(16)(q22) were determined. The best expression of fra(16)(q22) was found with the aromatic diamidine berenil which is recommended for further studies on this fragile site. The results indicate that fra(16)(q22) is a region with AT-rich, late replicating DNA. The simultaneous treatment of lymphocytes with berenil and aphidicolin (inhibitor of DNA polymerase alpha) induces both the rare fra(16)(q22) and the common fra(16)(q23) within the same chromosome. A population study on 350 unselected individuals showed that fra(16)(q22) is the most common of all rare autosomal fragile sites in man. The frequency of individuals heterozygous for fra(16)(q22) is 5.1%, no homozygosity for fra(16)(q22) was detected. Statistical analysis indicates that the population is in Hardy-Weinberg equilibrium with respect to the fragile and non-fragile chromosomes 16.

Base Sequence↗
PubMed1985

Familial paracentric inversion inv(2)(q31q36).

A paracentric inversion of chromosome 2 is described for the first time. The breakpoints were localized in the bands q31 and q36. The paracentric inversion was initially identified in a female with repeated abortions and thereafter detected in eight other family members over three generations. The meiotic consequences and the risk for liveborn unbalanced chromosomal recombinants is discussed.

Abortion, Habitual↗