Possible mechanism for the dynamic stabilization of protein structure.
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Peptide Chain Elongation, Translational↗
Biomedical subjects
I Simon
Publications and source records attributed to I Simon.
Chromosomal position and activation of retroviral genomes inserted into the germ line of mice.
The exogenous Moloney leukemia virus (M-MuLV) was inserted into the germ line of mice by exposing embryos to virus at different stages of embryogenesis. Mice derived from exposed embryos were mosaics with respect to integrated virus. Nine new substrains, designated Mov-5 to Mov-13, were derived, each of which carries a single M-MuLV genome at a different chromosomal position in its germ line. Four substrains, Mov-1 to Mov-4, were derived previously. Restriction enzyme analyses demonstrated that, with the exception of Mov-4 and Mov-6 mice, no major rearrangements or deletions have occurred in the integrated proviral genomes. Infectious virus is not activated in the majority of substrains (Mov-4 to Mov-8 and Mov-10 to Mov-12), whereas the other mice develop viremia. A detailed comparison between Mov-1 and Mov-13 mice demonstrated that the time of virus activation is different. Mov-13 mice activate infectious virus during embryogenesis, leading to a distinct pattern of virus expression in all tissues of the adult, but the viral genome in Mov-1 mice is activated only during the first two weeks after birth, leading to virus expression predominantly in lymphatic organs. Together with previous observations, at least four different phenotypes of virus expression-that is, early virus activation during embryogenesis, virus activation after birth, virus activation late in life and no expression of infectious virus at all-can be distinguished among the 13 substrains. Our results suggest that the chromosomal region at which a viral genome is integrated influences its expression during development and differentiation.
Animals↗
Effect of the membrane lipid environment on the properties of insulin receptors.
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Animals↗
Coenzyme induced changes in the interdimeric contact surface of D-glyceraldehyde-3-phosphate-dehydrogenase.
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Animals↗
[Evaluation of methods to determine the vitamin B6 status of humans. 1. alpha-EGOT: methods and validation].
A semiautomatic method to determine the activation coefficient of the glutamic-oxaloacetic-transaminase in the erythrocytes is described. This method is compared with other methods and possible sources of error are discussed. Colorimetric methods show considerable disadvantages, such as lack of precision or unspecific hydrazone formation. The kinetic tests avoid these problems. This is in part due to the fact that enzyme stimulation by excessive PLP-addition as used in our procedure bears practical and theoretical advantages. Nevertheless, comparison with published data on vitamin B6 status remains difficult because of insufficient standardization of the used methods. To validate our method we performed experiments testing the stability of the samples, short-term physiological changes and influence of the chelating agent EDTA on transamination. Heparinised blood samples can be stored only for one day with changing at 4 degrees C or room temperature. Storing of the erythrocytic suspension at deep-freezing temperature (-18 degrees C) leads to considerable changes of results. When kept under liquid nitrogen there is no change of the alpha-values for at least 45 days. The addition of EDTA to the samples is known to exclude the influences of cations, such as non enzymatic transamination of a direct alteration of the enzyme activity and therefore EDTA should be added to improve standardisation of the method. The described procedure is a fast, reliable and precise way to determine the alpha-EGOT.
Aspartate Aminotransferases↗
[Birth and development of otorhinolaryngology in the history of medicine].
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History, 15th Century↗
[Birth and development of otorhinolaryngology in the history of medicine].
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History, 15th Century↗
Subunit contact surface--an additional argument in favour of continuous folding during biosynthesis of proteins.
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Amino Acid Sequence↗
[Sodium or methyl glucamine salts as contrast media for urography (author's transl)].
A double blind trial was carried out comparing 15 g sodium amidotrizoate and 15.3 methyl glucamine amidotrizoate for urography. The sodium preparation resulted in significantly better visualisation of the urinary tract, both in normal patients and in those with renal insufficiency. For routine urography in the given dose there was no difference as regards demonstration of the parenchyma and filling of the urinary tract. Similarly, there was no difference in tolerance after the intravenous administration of the two substances. The sodium salt should be avoided in patients with cardiac failure, whereas these are better tolerated than methyl glucamine salts by asthmatics. Judging by our results, the sodium salts are to be preferred for routine urography in a dose of 50 ml., particularly for patients with mild to moderate renal insufficiency.
Adolescent↗
Laboratory induced variations in a standardized Salmonella isolation method.
Four microbiologists from four European laboratories came together to a single laboratory for two weeks and during that period examined 100 samples of minced meat artificially contaminated with salmonellae and 100 naturally contaminated samples using a standardized technique. No significant differences were found between the results obtained by the different analysts with 92 to 97 of the artificially contaminated and 30 to 42 of the naturally contaminated samples being found positive. Over a further period of eight weeks, these analysts examined the same number of samples in their own laboratories again using an identical procedure. There were no significant containing approximately 100 salmonellae per gram but significant differences (43 to 93) were found in isolation rates from the artificially contaminated samples copntaining approximately 1 salmonella per gram. The differences in findings between the first and the second part of the experiments may have been caused fairly by variations in media preparation, temperature of incubators, storage conditions of media and thawing conditions of samples etc., and secondly by differences in working conditions such as performing only one task during two weeks in contrast to examining the samples as part of the daily routine. At high levels of contamination, these factors do not appear to have an important influence on the performance of a laboratory.
Animals↗
Investigation of protein folding: uneven distribution of point mutations along polypeptide chains.
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Animals↗
Differences in membrane unsaturated fatty acids and electron spin resonance in different types of myeloid leukemia cells.
The fatty acid composition and some physical properties of intact cells and isolated plasma membranes of two types of mouse myeloid leukemia cell clone grown in culture have been examined. One clone type, MGI+D+, can be induced by the macrophage and granulocyte-inducing protein (MGI) to differentiate into mature macrophages and granulocytes. The other clone type, MGI+D-, could not be induced to differentiate into mature cells. A two-fold increase in the ratio of saturated fatty acid to unsaturated fatty acid was found in the MGI+D- compared to the MGI+D+ clones. The MGI+D- clones produced an unusual polyunsaturated C20:5 fatty acid at 28 degrees C, whereas the MGI+D+ clones did not grow at this temperature. The cells and their isolated plasma membranes were studied by electron spin resonance. The motion of the 5-nitroxide stearate spin label was found to be higher in the intact cells and in the membranes of MGI+D- clones than of the MGI+D+ clones. The cells of MGI+D+ clones showed a similar freedom of motion to normal myeloblasts from the bone marrow. The results indicate that myeloid leukemia cells which differ in their competence to be induced to differentiate into mature cells have different physical properties of their plasma membranes and that this is correlated with their fatty acid acyl chain composition.
Animals↗
The correlation of routine cytology with the contents of carcinoembryonic antigen and alpha-fetoprotein in pleural and peritoneal effusions.
The levels of carcinoembryonic antigen (CEA) and of alpha-fetoprotein (AFP) were determined with radioimmunoassay in 63 samples of either pleural or peritoneal effusions. All samples were collected from 53 patients suspected for malignancy and were also studied with the routine cytological techniques. Elevated levels of CEA (above 20 ng/ml) were found in 14 out of 29 cytologically positive samples, in none of 6 cytologically suspected and of 14 cytologically negative samples. The highest levels of CEA (above 1,000 ng/ml) were found in samples from patients with gastrointestinal carcinomas, while negative results were most often found in lymphoreticular and ovarian malignancies. Elevated levels of AFP (above 5 ng/ml) were found in 9 samples (5 cytologically positive and 4 negative). Five of these exudates were negative for CEA. Positive results of AFP were most frequently found in samples derived from patients with secondary or primary liver tumours. The highest levels of AFP (6 and 30 ng/ml), were determined in samples of two hepatoma patients. The combined cytological and radioimmunological studies suggested malignancy in 52 out of 63 samples while cytology alone detected either neoplastic or suspected cells in 35 samples only.
Ascitic Fluid↗