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Biomedical subjects

S Butz

Publications and source records attributed to S Butz.

26 records · Page 2Linked to original sources
PubMed1994

Forearm BMD as measured by peripheral quantitative computed tomography (pQCT) in a German reference population.

Low bone mass as estimated by decreased bone mineral density (BMD) is an established predictor of osteoporotic fractures. One of the latest developments in bone densitometry is peripheral quantitative computed tomography (pQCT) of the forearm. In Germany, the CT bone scanner XCT 900 has already been widely used; however, interpretation of measurements with respect to osteoporosis risk assessment can be improved by better defined and validated reference data. In the present study, this device was used to measure BMD at the distal radius in a well-defined healthy population of 179 German adults (91 men, 88 women) aged 20-79 years. In vivo precision was 1.67% for trabecular and 0.81% for total BMD measurements. Peak values of trabecular and total BMD were observed at the ages 40-50 years in women and 30-40 years in men. Beyond these ages, both trabecular and total BMD showed a linear decline with age, decreasing by 0.85% and 1.08% per year in women and by 0.59% and 0.54% in men, respectively. Measures of BMD were not influenced by weight, height or body mass index (BMI). In both sexes, trabecular and total radial BMD showed a positive and significant correlation with femoral BMD measures obtained by dual X-ray absorptiometry (DXA). Weaker correlations were observed with DXA measures of the lumbar spine. Compared with the 95% reference range provided by the manufacturer, the distribution of age- and sex-specific values of trabecular BMD of the distal radius was shifted to lower values by up to 1 standard deviation.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1994

Cadherins and cadherin-associated molecules in the developing and maturing rat testis.

The calcium-dependent class of cell adhesion molecules known as cadherins mediate homotypic cell interactions in most epithelia. We have now investigated the expression and distribution of cadherins and cadherin-associated molecules in the developing and maturing rat testis. E-Cadherin was not detected in the seminiferous tubule at any time in development or in the adult. In contrast, Leydig cells expressed E-cadherin between day 15 of gestation and postnatal day 3. alpha- and beta-catenins were expressed throughout the developing testis, but were particularly prominent in Leydig cells. In the maturing testis, alpha-catenin and plakoglobin became progressively more restricted to the basal part of the seminiferous epithelium and by 23 days exhibited a pattern characteristic of the Sertoli cell junctional complex. beta-Catenin recruitment to the Sertoli cell junctional complex was not complete until 60 days. alpha-Catenin and plakoglobin were not present at sites of Sertoli cell-germ cell contacts. Northern blot analysis of testicular RNA showed three mRNA species hybridizing with N-cadherin cDNA. A pan-cadherin antibody specific for a region of the highly conserved C-terminal of all cadherins stained sites of Sertoli-spermatocyte and Sertoli-round spermatid contact in the adult rat seminiferous epithelium, but did not stain the Sertoli cell tight junctional complex. Western blots of testicular extracts indicated that the molecule(s) recognized by these antibodies had an approximate molecular mass of 120 kilodalton, typical of members of the cadherin family. Therefore, although Sertoli cells do not express E-cadherin, another member(s) of the cadherin family is present in the testis, but may not be directly involved in tight junction dynamics as in other cells. Instead, cadherin-mediated adhesion is likely to be involved in Sertoli cell-germ cell interactions. As catenins are not present at these sites, our results suggest a catenin-independent role of cadherins in germ cell adhesion to Sertoli cells.

Aging↗
PubMed1994

Assembly of the cadherin-catenin complex in vitro with recombinant proteins.

The cytoplasmic domain of classical cadherins is tightly associated with three proteins termed alpha-, beta- and gamma-catenin. These accessory proteins are of central importance for the adhesive properties of this class of cell adhesion molecules. In order to examine the molecular architecture of the cadherin-catenin complex in more detail we have expressed the catenins and the cytoplasmic domain of E-cadherin as fusion proteins in Escherichia coli, and analyzed the interaction of purified recombinant cadherin and catenins in combinatorial protein-protein interaction experiments. The cytoplasmic domain of E-cadherin cannot directly associate with alpha-catenin but interacts with high affinity with beta-catenin, whereas the binding of gamma-catenin (plakoglobin) to E-cadherin is less efficient. alpha- and beta-catenin assemble into a 1:1 heterodimeric complex. The analysis of various truncated beta-catenins revealed that an alpha-catenin binding site in beta-catenin is localized between amino acid positions 120 and 151. The central role of beta-catenin for the assembly of the heterotrimeric E-cadherin/alpha-catenin/beta-catenin complex in mixing experiments with all components was demonstrated. The reconstitution in vitro of the cadherin-catenin complex should allow the study of the interaction with signalling molecules and with the actin-based cytoskeleton.

Base Sequence↗
PubMed1993

Catenins in Xenopus embryogenesis and their relation to the cadherin-mediated cell-cell adhesion system.

In the course of an analysis of cell-cell adhesion in the Xenopus embryo, antibodies directed against alpha- and beta-catenin were applied to investigate their relation to the cadherins occurring early in this system. The results demonstrate that alpha- and beta-catenin are provided maternally and increase in amount throughout embryogenesis. Immunoprecipitations indicate that both of the catenins are complexed to U-cadherin in the early phase of embryogenesis and to E-cadherin, when it appears during gastrulation. An excess of alpha-catenin occurs in free form in the early embryo, whereas all of the beta-catenin seems to be complexed to cadherin. Synthesis of the two components throughout early embryogenesis and their binding to newly synthesized cadherins were demonstrated by metabolic labelling. The spatial distribution of alpha-catenin was analysed by immunohistology. During cleavage alpha-catenin is deposited evenly along the plasma membranes within the embryo, while the cell peripheries at the surface of the embryo remain devoid of alpha-catenin. At later stages, the pattern of alpha-catenin distribution becomes more complex. Quantitative differences in the intensity of staining along the plasma membranes in the different regions of the embryo can be distinguished. Particularly the appearance of E-cadherin in the gastrula ectoderm is accompanied by conspicuous depositions of alpha-catenin along the respective plasma membranes in this layer. All cells in the later embryo, apart from the neural crest cells, carry alpha-catenin on their plasma membranes indicating the universal character of cadherin-mediated cell-cell adhesion in the Xenopus embryo.

Animals↗
PubMedDate not supplied

Immunization and affinity purification of antibodies using resin-immobilized lysine-branched synthetic peptides.

A new method has been developed to raise antibodies against synthetic peptides. A multiple antigenic peptide system (MAP) containing a branched oligolysine was synthesized on a beaded polystyrene polyoxyethylene graft copolymer resin, which acts as a synthetic hapten carrier for use in immunization. The peptides, already attached to the carrier, can be used directly after final deprotection without any further purification steps. The utility of this peptide-carrier conjugate is highlighted by its additional application for affinity purification of antibodies generated.

Amino Acid Sequence↗