Biomedical subjects

S Reeh

Publications and source records attributed to S Reeh.

9 recordsLinked to original sources

PubMed1994

[Predicting load bearing of the hip joint. Computerized analysis with a 3-D multibody model of the human].

Multibody analysis was applied to construct an advanced model of the human body, where the large joints and complete mass and inertial properties were implemented. The model represents the 50th-percentile rank of a male adult. The hip joint is controlled by three muscle forces. The muscle coordinates were taken from a data source, previously collected by our group. The model enables one to analyze 3D hip joint forces with respect to various joint angles and represents conceptually an improvement of the classical method of graphical statics, which was established by Pauwels [15]. A hip joint load of three times body weight was found in the single leg stance. A load of 3.7 times body weight was calculated when simulating a knee flexion angle of 90 degrees, and a ventral inclination of the resultant hip joint force was seen. A constant amount of gluteus medius muscle force was observed during flexion. An increasing flecting moment at the hip joint, however, had to be balanced by a significantly increased gluteus maximus muscle force. As a consequence, torsional forces can be studied by the system presented here and should also be considered when testing stems of hip prostheses. External muscle and joint forces are provided and can be used as input data for stress analyses.

Adult↗

PubMed1979

Post-translational modification of Escherichia coli ribosomal protein S6.

Escherichia coli has multiple forms of ribosomal protein S6, differing in number of glutamyl resideus at the C-terminal end. Three forms are revealed when crude cell extracts are fractionated by a two-dimensional gel electrophoresis technique. Pulse-chase experiments show that the shortest and most alkaline form of S6 is the first to appear. In about one doubling time this form reaches equilibrium with the two other forms of S6, implicating the existence of an enzyme, which adds glutamic acid residues to S6. We show that the relative levels of these three S6 forms are not affected by the growth rate of the culture.

Amino Acid Sequence↗

PubMed1978

Functional mRNA half lives in E. coli.

Analysis of the synthetic rate of individual protein species at various times after complete inhibition of transcription with either streptolygidin or rifampicin was carried out by two-dimensional polyacrylamide electrophoresis of total Escherichia coli cell extracts. The decay rate of the potential to synthesize different proteins was assumed to be equal to the functional decay rate of the corresponding mRNA. We conclude the following: (a) The tufA and tufB messengers have different half lives (3.0 and 2.4 min, respectively). (b) Different genes within the same transcriptional unit can have different half lies (S7, EGF and EFTuA--2.5, 3.8 and 3.0 min, respectively). (c) There is at least a twenty-fold variation in individual mRNA half lives in E. coli; ribosomal protein S1 mRNA was observed to have the shortest half life in the cell (40 sec), while the longest observed half life was approximately 20 min (all values at 30 degrees C). (d) Addition of rifampicin increases the absolute rate of RNA polymerase subunit alpha and beta synthesis two-fold. (e) The induction of the synthesis of alpha subunit of RNA polymerase takes place without a concomitant induction of ribosomal protein S4 and L17, which are reported to be on either side of alpha in the same transcriptional unit.

Aminoglycosides↗

PubMed1978

Patterns of protein synthesis in E. coli: a catalog of the amount of 140 individual proteins at different growth rates.

The amount of 140 individual proteins of E. coli B/r was measured during balanced growth in five different media. The abundance of each protein was determined from its absolute amount in 14C-glucose-minimal medium and a measurement of its relative amount at each growth rate using a double labeling technique. Separation of the proteins was carried out by two-dimensional gel electrophoresis. This catalog of proteins, combined with 50 additional ribosomal proteins already studied, comprises about 5% of the coding capacity of the genome, but accounts for two thirds of the cell's protein mass. The behavior of most of these proteins could be described by a relatively small number of patterns. 102 of the 140 proteins exhibited nearly linear variations with growth rate. The remaining 38 proteins exhibited levels which seemed to depend more on the chemical nature of the medium than on growth rate. Proteins, including the ribosomal proteins, that increase in amount with increasing growth rate account for 20% of total cell protein by weight during growth on acetate, 32% on glucose-minimal medium and 55% on glucose-rich medium. Proteins with invariant levels in the various media comprise about 4% of the cell's total protein.

Bacterial Proteins↗

PubMed1977

Chemical measurement of steady-state levels of ten aminoacyl-transfer ribonucleic acid synthetases in Escherichia coli.

Polypeptide chains of 10 aminoacyl-transfer ribonucleic acid synthetases (those for arginine, glutamine, glutamic acid, glycine, isoleucine, leucine, lysine, phenylalanine, threonine, and valine) have been identified in lysates of Escherichia coli resolved by the O'Farrell two-dimensional gel system. By labeling cells uniformly with [14C]glucose and by measuring the total amounts of these polypeptides by their radioactivity, estimations of the steady-state, molecular amounts of these enzymes were made and compared to the number of ribosomes and elongation factors in these cells. Portions of a reference culture grown on glucose and labeled with [14C]leucine or [35S]sulfate were mixed with four cultures grown in widely different media containing [3H]leucine or [3H]leucine plus [3H]isoleucine. From the isotope ratios of the total protein and of the spots containing the synthetase chains, the chemical amount of each synthetase relative to that of the reference culture was determined. The results, where comparable, show reasonable agreement with enzyme activity measurements. In general, these synthetases each exhibit a positive correlation with growth rate in unrestricted media, indicating a strong tendency for the levels of transfer ribonucleic acid, synthetases, elongation factors, and ribosomes to remain approximately, though not exactly, in balance at different growth rates.

Alanine-tRNA Ligase↗

PubMed1977

Transient rates of synthesis of five amionacyl-transfer ribonucleic acid synthetases during a shift-up of Escherichia coli.

The steady-state levels of a number of aminoacyl-transfer ribonucleic acid synthetases are known to be positively correlated with growth rate in Escherichia coli. To describe the regulation of these enzymes during a nutritional shift-up, use was made of the recent identification of polypeptide chains of several synthetases in whole cell lysates resolved by the O'Farrell two-dimensional gel system. A culture growing in acetate minimal medium was shifted to glucose-rich medium and pulse labeled with [3H]leucine and [3H]isoleucine for 30- or 6-s intervals during the 20 min after the shift. After mixing with a uniformly [35S]sulfate-labeled reference culture, the samples were subjected to two-dimensional gel electrophoresis. The 3H/35S ratio in the resolved synthetase polypeptides provided an accurate estimation of their transient rates of synthesis. Five aminoacyl-transfer ribonucleic acid synthetases (those for argnine, glycine, isoleucine, phenylalanine, and valine) exhibited an increase in formation within 30 to 90 s after the shift-up. The magnitude of the increases corresponded to the final steady-state values and were reached within 2 to 3 min. The addition to rifampin revealed that the increase in the differential rate of valyl-transfer ribonucleic acid synthetase formation was the result of increased messenger ribonucleic acid transcription and not of a relaxation of some translation restriction.

Acetates↗

PubMed1976

Biosynthetic regulation of individual proteins in relA+ and relA strains of Escherichia coli during amino acid starvation.

An isogenic pair of Escherichia coli mutants (relA+ tufB valSts and relA1 tufB valSts) has been cultured at several temperatures to establish various degrees of limitation for valyl-tRNA synthetase. The biosynthetic rate of 16 identifiable proteins, most of which are components of the transcription and translation apparatus, was measured by pulse-labelling with [35S]-methionine, followed by protein separation using two-dimensional gel electrophoresis (O'Farrell, 1975). No single pattern of response to amino acid starvation of biosynthetic rate was observed. EF-Ts, L12 and S6 were found to be under strong stringent and relaxed regulation; EF-G, EF-Tu-A and S1 are under strong stringent, but weak relaxed regulation; EF-Tu-B, alpha, VRS, IRS and ARS are under week stringent and weak relaxed regulation; beta is under weak stringent regulation and does not respond at all to relaxed conditions; the biosynthetic rate of a protein called stringent starvation protein is strongly stimulated, relative to other proteins, in the starved stringent strain.

Amino Acids↗

PubMed1976

A mutant of Escherichia coli with an altered elongation factor Tu.

A previously isolated mutant of E. coli K12 HAK 88 [Kuwano, M., Endo, h & yamamoto, M. (1972) J. Bacteriol, 112, 1150-1156], contains a new protein that in two-dimensional gel electropherorgrams has the same molecular weight as normal elongation factor Tu, but whose isoelectric point is altered approximately 0.1 pH unit in the acidic direction. Peptide mapping, purification properties and the ratio of leucyl plus isoleucyl to methionyl plus cysteinyl residues of the normal elongation factor Tu protein and the new protein show a close similarity between the two. The mutation causing the altered electrophoretic mobility is located between argH and rif (79 min on the E. coli genetic map). These biochemical and genetic data indicate that strain HAK 88 has a mutationally altered tufB gene.

Chromosome Mapping↗

PubMed1976

Regulation of transcription factor rho and the alpha subunit of RNA polymerase in Escherichia coli B/r.

Transcriptional termination factor rho, the alpha subunit of RNA polymerase (RNA nucleotidyltransferase nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.7.6), and ribosomal protein S6 were resolved from whole-cell extracts of E. coli B/r by a high-resolution, two-dimensional polyacrylamide gel electrophoretic technique, and were identified through coelectrophoresis with the purified proteins. The regulation of rho, alpha, and S6 was studied, in steady-state cultures of E. coli B/r growing at rates ranging from 0.6 to 2.1 generations per hr, through the use of this gel technique and a double radioisotope labeling procedure. The regulatory patterns of rho and alpha are distinct from, but similar to, one another. Neither rho nor alpha shows the sharply increasing levels with increasing growth rate shown by the ribosomal proteins was exemplified by S6. The difference between the levels of rho and alpha, on the one hand, and S6, on the other, is most pronounced during rapid growth. The regulatory pattern of alpha is interesting, given the recent suggestion that the gene coding for alpha is contranscribed with genes coding for ribosomal proteins.

Bacterial Proteins↗