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Biomedical subjects

H Heumann

Publications and source records attributed to H Heumann.

At least 73 records · Page 4Linked to original sources
PubMed1987

[Cholesteatoma in childhood. Surgical treatment and results].

261 children with 281 cholesteatoma operations performed between 1970 and 1982 in the ENT-Clinic of the University of Tübingen were followed-up. In 77 ears an open technique (attico-antrotomy with removal of the posterior canal wall) was employed. In 103 ears a combined approach with posterior tympanotomy and preservation of the posterior canal wall was performed. In 47 ears an atticotomy with reconstruction of the lateral attix wall defect with tragal cartilage and perichondrium was done. The cholesteatoma was limited to the middle ear in 54 patients; treatment consisted of a transcanal tympanoplasty. 36.3% of the children had a residual or a recurrent cholesteatoma, 19.5% after open technique, 61.2% after a combined approach operation, 17% after atticoantrotomy and reconstruction of the scutum and 29.6% after a transcanal tympanoplasty. We therefore conclude that a second look operation is necessary especially after closed technique surgery.

Adolescent↗
PubMed1986

Solution structure of a short DNA fragment studied by neutron scattering.

The solution structure of a DNA fragment of 130 base pairs and known sequence has been investigated by neutron small-angle scattering. In 0.1 M NaCl, the overall structure of the DNA fragment which contains the strong promoter A1 of the Escherichia coli phage T7 agrees with that expected for B-DNA. The neutron scattering curve is well fitted by that of a rigid rod with a length of 44 nm and a diameter of 2 nm. The results were confirmed by quasi-elastic light scattering and analytical centrifugation. The neutron measurements in H2O and D2O buffer reveal a cross-sectional inhomogeneity not detected by X-ray small-angle scattering. This inhomogeneity is caused by the hydration layer around the DNA core and not by the helical structure. The primary solvent shell has a density increased by at least 4-9% compared to bulk water.

Base Composition↗
PubMed1986

Visualization of intermediary transcription states in the complex between Escherichia coli DNA-dependent RNA polymerases and a promoter-carrying DNA fragment using the gel retardation method.

DNA-dependent RNA polymerase in complex with a DNA fragment was analyzed by electrophoresis in non-denaturing gels as core enzyme, holoenzyme, during initiation and elongation. The DNA fragment carried the promoter A1 of the phage T7. The stoichiometry between holoenzyme and promoter and between sigma and core enzyme in complex with DNA was determined. Holoenzyme bound as a monomer to the DNA, whereas core enzyme formed aggregates before binding to the DNA. If the molar ratio of holoenzyme to DNA exceeded 0.5:1 a second holoenzyme molecule interacted with the DNA fragment with diminished affinity. A large difference in the frictional coefficient of the holoenzyme-promoter and the core enzyme-DNA complex indicated a drastic conformational difference between the two types of complexes. The stability of the holoenzyme-promoter complex decreased with decreasing temperature, accompanied by at least partial dissociation of holoenzyme into core enzyme and sigma factor. Addition of nucleoside triphosphates did not change the electrophoretic mobility of the complex if abortive transcription only was allowed, but increased it after addition of all four nucleoside triphosphates owing to release of the sigma factor.

DNA, Bacterial↗
PubMed1986

Deuterium incorporation into Escherichia coli proteins. A neutron-scattering study of DNA-dependent RNA polymerase.

Neutron small-angle scattering studies of single protein subunits in a protein-DNA complex require the adjustment of the neutron scattering-length densities of protein and DNA, which is attainable by specific deuteration of the protein. The neutron scattering densities of unlabelled DNA and DNA-dependent RNA polymerase of Escherichia coli match when RNA polymerase is isolated from cells grown in a medium containing 46% D2O and unlabelled glucose as carbon source. Their contrasts vanish simultaneously in a dialysis buffer containing 65% D2O. An expression was evaluated which allows the calculation of the degree of deuteration and match point of any E. coli protein from the D2O content of the growth medium, taking the 2H incorporation into RNA polymerase amino acids to be representative for all amino acids in E. coli proteins. The small-angle scattering results, on which the calculation of the degree of deuteration is based, were confirmed by mass spectrometric measurements.

DNA-Directed RNA Polymerases↗
PubMed1985

The formation of ultrastructural epithelial and subepithelial connective tissue changes in experimentally induced cholesteatomas in guinea pigs.

Histoacryl-induced cholesteatomas were produced in guinea pigs at the posterosuperior part of the external ear canal adjacent to the tympanic membrane. Semithin and ultrathin tissue sections were used to study primary formation of the cholesteatoma as well as the influence of the altered epithelium upon the bordering zone of connective tissue. Quantitative and qualitative tissue changes were analyzed by electron microscopy and showed degradation and new formation of collagen and activation of fibroblasts. Our findings are similar to those previously reported on human cholesteatomas and indicate that the bordering subepithelial tissue seems to be influenced through the basilar membrane.

Animals↗
PubMed1982

1H n.m.r. of the DNA-dependent RNA polymerase from Escherichia coli.

The (1)H n.m.r. study of the DNA-dependent RNA polymerase from Escherichia coli has revealed that the holoenzyme (betabeta'alpha(2)sigma) displays two mobile regions: one, observable also in the core enzyme (betabeta'alpha(2)), is characterized by basic amino acids and its appearance and form depend on ionic strength; the other, specific to the holoenzyme, is characterized by threonine residues and its appearance does not depend on ionic strength.

Apoenzymes↗
PubMed1982

[A clinical and experimental study on precious metal ventilation tubes (author's transl)].

Incompatibility reactions which lead to a profuse aural discharge and often necessitate the removal of the ventilation tube occur in approximately 10% of patients if ventilation tubes made of synthetic materials are used. We have used golden and other precious metal alloy grommets in patients after extensive bacteriological and animal experiments. The most important advantage is the oligodynamic action which gives the surface of the ventilation tube repellent properties against bacteria. The drainage function is excellent due to the smooth surface structure and no incompatibility reactions were seen.

Drainage↗
PubMed1982

[A light and electron microscopic study of the squamous epithelium of the external canal and drum in experimentally induced cholesteatoma in guinea pigs].

The skin of the postero-superior part of the meatus and drum of guinea pigs was treated with enbucrylate and examined via light microscope and electron microscope after three weeks. The squamous epithelium was thickened with extensive rete pegs in the subepithelial space. The epithelial cells were loosely arranged and their nuclei pathologically changed. In the oedematous perimatrix small finger-like epithelial proliferations and activated mesenchymal cells could be seen.

Animals↗