Search PubMed⌕ Search

Biomedical subjects

M Schweiger

Publications and source records attributed to M Schweiger.

226 records · Page 13Linked to original sources
PubMed1969

Specificity and evolutionary divergence of the antigenic structure of the polypeptide chain elongation factors.

Antisera have been prepared against two electrophoretically homogeneous "polypeptide chain elongation factors," T and G, from Escherichia coli. Inactivation and precipitation tests showed that these two fractions were antigenically distinct with no cross-reaction. The immune inactivation curve of G factor from E. coli was distinguishable from that of G factor from Pseudomonas fluorescens. Mammalian factors were not inhibited by antibody directed against the E. coli T and G factors. By Ouchterlony diffusion tests, the antisera also detected significant antigenic variability among different bacterial species. It is concluded that the factors have undergone considerable evolutionary divergence in their antigenic structure.

Antigens↗
PubMedDate not supplied

The impact of overweight on the development of diabetes after heart transplantation.

BACKGROUND: Overweight is defined with a body mass index (BMI) >25. A BMI >25 is known as an independent risk factor for increased morbidity and mortality. The influence of an increased BMI on the development of diabetes and on survival after heart transplantation (HTX) was investigated. METHODS: A total of 137 patients (116 men, 21 women), who underwent HTX at our Department from 1986 to 2002, were included in the study. For group stratification, the pre-operative BMI values were taken (group I: BMI 25). Groups were compared for primary disease, age and sex, development of renal failure, development of diabetes, and survival. The probability of survival and the freedom-from-diabetes interval were calculated by the use of Kaplan-Meier method. RESULTS: No significant differences between groups I and II were found concerning primary disease, age and sex, and occurrence of renal failure. There was a tendency towards increased survival (p = 0.18) in group I. Patients of group II developed diabetes after HTX more frequently than those of group I (p < 0.001). Cox regression revealed that pre-operative BMI >25 is a highly significant independent risk factor for post-operative development of diabetes mellitus (DM) (p < 0.001). CONCLUSION: Overweight prior to HTX appears to negatively influence long-term survival after HTX, although this difference did not reach statistical significance. Pre-operative overweight is a significant and independent risk factor for the development of post-transplant diabetes.

Adult↗
PubMedDate not supplied

A finite element approach for modeling photon transport in tissue.

The use of optical radiation in medical physics is important in several fields for both treatment and diagnosis. In all cases an analytic and computable model of the propagation of radiation in tissue is essential for a meaningful interpretation of the procedures. A finite element method (FEM) for deriving photon density inside an object, and photon flux at its boundary, assuming that the photon transport model is the diffusion approximation to the radiative transfer equation, is introduced herein. Results from the model for a particular case are given: the calculation of the boundary flux as a function of time resulting from a delta-function input to a two-dimensional circle (equivalent to a line source in an infinite cylinder) with homogeneous scattering and absorption properties. This models the temporal point spread function of interest in near infrared spectroscopy and imaging. The convergence of the FEM results are demonstrated, as the resolution of the mesh is increased, to the analytical expression for the Green's function for this system. The diffusion approximation is very commonly adopted as appropriate for cases which are scattering dominated, i.e., where mu s >> mu a, and results from other workers have compared it to alternative models. In this article a high degree of agreement with a Monte Carlo method is demonstrated. The principle advantage of the FE method is its speed. It is in all ways as flexible as Monte Carlo methods and in addition can produce photon density everywhere, as well as flux on the boundary. One disadvantage is that there is no means of deriving individual photon histories.

Health Physics↗
PubMedDate not supplied

Werner syndrome: characterization of mutations in the WRN gene in an affected family.

Affected and unaffected members of a Caucasian family with Werner syndrome were analyzed for mutations in the recently described Werner syndrome (WRN) gene and for their relevance to phenotypic expression of chromosomal instability and x-ray hypersensitivity. Two distinct molecular alterations were documented in the family. Analysis of the genomic DNA revealed a single-base exchange from A to T at an intron-exon boundary in the otherwise strongly conserved 5' donor splice site. Consequently, exon 30 is spliced together with the intron. The ensuing structure could be confirmed by the presence and calculated size of the resulting RNA fragments. The patients, all compound heterozygotes, had a 1-bp deletion in the first third of the coding sequence in the other allele. The genotypes of the family members for these mutations were determined and consequences for the cellular phenotype of the otherwise unaffected heterozygotes are documented.

Adult↗
PubMedDate not supplied

Escherichia coli bacteriophage T1 DNA methyltransferase appears to interact with Escherichia coli enolase.

Infection of Escherichia coli cells with bacteriophage T1 induces synthesis of a bacteriophage-specific DNA methyltransferase (M.EcoT1, EC No: 2.1.1.72) with a specificity for adenine residues in the sequence 5'-GATC-3'. Purification of M.EcoT1 allowed the determination of the coding sequence of the gene (Schneider-Scherzer et al., 1990). The peptide of the entire coding sequence was over-expressed as a histidine-hexapeptide tagged protein in E. coli. Affinity purification using a Ni2+ chelating (Ni-NTA) resin yielded a recombinant enzyme with almost the same enzymatic properties as the protein purified from T1 infected E. coli cells. Interestingly, in both purification procedures, a protein with a molecular weight of 50000 was found to copurify with M.EcoT1. The N-terminal amino acid sequence identified these proteins in both cases as E. coli enolase (EC No: 4.2.1.11).

DNA↗