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Biomedical subjects

K Kühn

Publications and source records attributed to K Kühn.

At least 109 records · Page 6Linked to original sources
PubMed1985

Effects of muzolimine and of a combination of hydrochlorothiazide/triamterene in healthy subjects and in nephrotic patients.

The diuretic effects of 30 mg muzolimine and 25 mg hydrochlorothiazide/50 mg triamterene were comparable in healthy subjects and nephrotic patients (serum albumin less than 32 g/l, creatinine clearance greater than 50 ml/min/1.73 m2). A single daily dose of 30 mg muzolimine or 25 mg hydrochlorothiazide/50 mg triamterene was sufficient in the majority of the investigated nephrotic patients. The different diuretic effects which were observed in nephrotic patients were not related to the severity of hypalbuminemia, but rather to differences in preceding diuretic treatment. Plasma levels and urinary excretion of unchanged muzolimine were comparable in healthy subjects and nephrotic patients after one day of diuretic treatment; after seven days of treatment plasma levels of muzolimine were significantly lower and urinary excretion significantly higher in nephrotic patients than in control subjects.

Adolescent↗
PubMed1984

Complete amino acid sequence of the N-terminal extension of calf skin type III procollagen.

The N-terminal extension peptide of type III procollagen, isolated from foetal-calf skin, contains 130 amino acid residues. To determine its amino acid sequence, the peptide was reduced and carboxymethylated or aminoethylated and fragmented with trypsin, Staphylococcus aureus V8 proteinase and bacterial collagenase. Pyroglutamate aminopeptidase was used to deblock the N-terminal collagenase fragment to enable amino acid sequencing. The type III collagen extension peptide is homologous to that of the alpha 1 chain of type I procollagen with respect to a three-domain structure. The N-terminal 79 amino acids, which contain ten of the 12 cysteine residues, form a compact globular domain. The next 39 amino acids are in a collagenase triplet sequence (Gly- Xaa - Yaa )n with a high hydroxyproline content. Finally, another short non-collagenous domain of 12 amino acids ends at the cleavage site for procollagen aminopeptidase, which cleaves a proline-glutamine bond. In contrast with type I procollagen, the type III procollagen extension peptides contain interchain disulphide bridges located at the C-terminus of the triple-helical domain.

Amino Acid Sequence↗
PubMed1984

Localization of flexible sites in thread-like molecules from electron micrographs. Comparison of interstitial, basement membrane and intima collagens.

A computer method for detecting kinks and flexible sites in thread-like molecules was developed. The method is based on the determination of the local curvature along the digitized electron micrographs of the molecules. The root-mean-square curvature provided a measure for the local flexibility, which is related to the persistence length. The influence of various error sources was assessed using computer-simulated thread molecules. "Flexibility profiles" showing the variation of flexibility along molecules were calculated for interstitial, basement membrane and intima collagens. Approximately uniform stiffness corresponding to a persistence length of 60 nm was found for the triple helices of interstitial and monomeric intima collagen. A highly flexible site in interstitial collagen could be assigned to a non-triple helical segment in the sequence surrounding the linkage site of the N-terminal propeptide. A flexible site in the triple helix of collagen I corresponds to a segment of the sequence lacking proline residues. Flexibility varies strongly along the collagen IV molecule. This is consistent with the fact that a series of non-triple helical interruptions have already been found in the not yet completed amino acid sequence of basement membrane collagen. Most of the detected flexible sites allow random bending about the mean zero, but in one case, at the border of the 7S domain of polymeric collagen IV, a flexible site with a preferential angle of 40 degrees was found.

Animals↗
PubMed1984

Structural and functional domains of collagen: a comparison of the protein with its gene.

The covalent protein structures of the homologous chains alpha 1 (I), alpha 2 (I) and alpha 1 (III) are known. Recently the structure of the alpha 2 (I) gene, at least the number and size of its exons has been almost completely elucidated. About 60% of the pro alpha-chain amino acid sequence is involved in the formation of the collagen triple helix. In the protein a repeating D unit is present which is important for the self assembly of the molecules into fibrils. In the gene, no obvious relationship between the 54 base pairs long exons and the repeating D unit could be found. This led to the conclusion that the region of the pro alpha chains involved in triple helix formation evolved first by repeated tandem duplications of an ancestral 54 base pairs exon and that the D repeat in the protein evolved independently of the exon structure of the gene. However, in other important functional regions of the pro alpha-chains that are not involved in helix formation, there is a good correlation with the gene exon structure.

Amino Acid Sequence↗
PubMed1984

Monoclonal antibodies against chicken type IV and V collagens: electron microscopic mapping of the epitopes after rotary shadowing.

The location of the epitopes for monoclonal antibodies against chicken type IV and type V collagens were directly determined in the electron microscope after rotary shadowing of antibody/collagen mixtures. Three monoclonal antibodies against type IV collagen were examined, each one of which was previously demonstrated to be specific for only one of the three pepsin-resistant fragments of the molecule. The three native fragments were designated (F1)2F2, F3, and 7S, and the antibodies that specifically recognize each fragment were called, respectively, IA8 , IIB12 , and ID2 . By electron microscopy, monoclonal antibody IA8 recognized an epitope located in the center of fragment (F1)2F2 and in tetramers of type IV collagen at a distance of 288 nm from the 7S domain, the region of overlap of four type IV molecules. Monoclonal antibody IIB12 , in contrast, recognized an epitope located only 73 nm from the 7S domain. This result therefore provides direct visual evidence that the F3 fragment is located closest to the 7S domain and the order of the fragments must be 7S-F3-(F1)2F2. The epitope for antibody ID2 was located in the overlap region of the 7S domain, and often several antibody molecules were observed to binding to a single 7S domain. The high frequency with which antibody molecules were observed to bind to fragments of type IV collagen suggests that there is a single population of type IV molecules of chain organization [alpha 1(IV)]2 alpha 2(IV), and that four identical molecules must form a tetramer that is joined in an antiparallel manner at the 7S domain. The monoclonal antibodies against type V collagen, called AB12 and DH2 , were both found to recognize epitopes close to one another, the epitopes being located 45-48 nm from one end of the type V collagen molecule. The significance of this result still remains uncertain, but suggests that this site is probably highly immunoreactive. It may also be related to the specific cleavage site of type V collagen by selected metalloproteinases and by alpha-thrombin. This cleavage site is also known to be located close to one end of the type V molecule.

Animals↗
PubMed1983

A conserved nucleotide sequence, coding for a segment of the C-propeptide, is found at the same location in different collagen genes.

The nucleotide sequence of a segment of the chick alpha 1 type III collagen gene which codes for the C-propeptide was determined and compared with the corresponding sequence in the alpha 1 type I and alpha 2 type I collagen genes. As in the alpha 2 type I gene the coding information for the C-propeptide of the type III collagen gene is subdivided in four exons. Similarly, the amino proximal exon contains sequences for both the carboxy terminal end of the alpha-helical segment of collagen and for the beginning of the C-propeptide in both genes. Therefore, this organization of exons must have been established before these two collagen genes arose by duplication of a common ancestor. In several subsegments the deduced amino acid sequence for the C-propeptide of type III collagen shows a strong homology with the corresponding amino acid sequence in alpha 1 and alpha 2 type I. For one of these homologous amino acid sequences, however, the nucleotide sequence is much better conserved than for the others. It is possible that a mechanism of gene conversion has maintained the homogeneity of this nucleotide sequence among the interstitial collagen genes. Alternatively, the conserved nucleotide sequence may represent a regulatory signal which could function either in the DNA or in the RNA.

Amino Acid Sequence↗
PubMed1983

Rectal and oral cimetidine for prophylaxis of aspiration pneumonitis in paediatric anaesthesia.

In a prospective randomized study, 60 children between 1 and 8 years of age in three groups received no premedication, 10 mg kg-1 cimetidine orally or 40 mg kg-1 cimetidine rectally for prophylaxis of acid aspiration syndrome 120-180 min before induction of anaesthesia. The pH of the stomach contents was above 2.5 in both cimetidine groups. The aspirated gastric volume was significantly reduced with rectal cimetidine compared to the other groups. Rectal cimetidine proved to be the more effective drug for prophylaxis of acid aspiration syndrome in paediatric anaesthesia.

Administration, Oral↗
PubMed1983

[Preoperative phase of limited normovolemic hemodilution].

In 35 cases, the attempt is made to present hemodilution as an appropriate means of hepatitis prophylaxis and blood sparing in patients having to undergo selective orthopedic or oral surgery. Especially in hospitals which cannot afford the expensive methods of autotransfusion, this method which is easy to perform from the technical and practical point of view offers a possibility of markedly reducing the transfusion rate of whole blood. Taking into account possible contraindications, this method is to be considered in all patients undergoing selective surgery where the general condition of the patient is sufficient and a blood loss of 1000-1500 ml is not exceeded.

Adolescent↗
PubMed1982

Characterization of a highly soluble collagenous molecule isolated from chicken hyaline cartilage.

Recently, we have isolated a new collagenous molecule from chicken hyaline cartilage after limited pepsin digestion. This molecule, which contains interchain disulfide bonds, has been called the high molecular weight fraction or HMW [Reese, C. A., & Mayne, R. (1981) Biochemistry 20, 5443-5448]. We now present a detailed model for the structure of HMW, the model being derived from analyses both of components of HMW obtained after denaturation either with or without reduction and from electron microscopic observation of replicas of HMW obtained after rotary shadowing. We propose that HMW is a typical, triple-helical collagen molecule of length 134 nm, in which one of the chains has been cleaved at a distance of 96 nm from one end of the triple helix, while the other two chains remain uncleaved. The result of this cleavage is the appearance of a recognizable kink in molecules of HMW when visualized after rotary shadowing.

Amino Acids↗
PubMed1982

Shape and assembly of type IV procollagen obtained from cell culture.

Type IV procollagen was isolated from the culture medium of the teratocarcinoma cell line PYS-2 by affinity chromatography on heparin-Sepharose. Immunological studies showed that type IV procollagen is composed of pro-alpha 1(IV) and pro-alpha 2(IV) chains and contains two potential cross-linking sites which are located in the short triple-helical 7S domain and the globular domain NC1 . The 7S domain was also identified as the heparin binding site. Rotary shadowing visualized type IV procollagen as a single triple-helical rod (length 388 nm) with a globule at one end. Some of the procollagen in the medium, however, had formed aggregates by alignment of 2-4 molecules along their 7S domains. After deposition in the cell matrix, non-reducible cross-links between the 7S domains are formed while the globules of two procollagen molecules connect to each other. The latter may require a slight proteolytic processing of the globular domains NC1 . The shape of type IV procollagen and the initial steps in its assembly are compatible with a recently proposed network of type IV collagen molecules in basement membranes. Since both type IV collagen and laminin bind to heparin, the formation of higher ordered structures by interaction of both proteins with heparan-sulfate proteoglycan may occur in situ.

Animals↗