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Biomedical subjects

G Richter

Publications and source records attributed to G Richter.

At least 271 records · Page 15Linked to original sources
PubMed1978

Relation of cytolytic activity of an ether-deoxy lysophosphatidylcholine analog to available membrane surface. Comparison of normal and tumor cells from mice.

1-Hexadecylpropanediol-3-phosphorylcholine, an ether-deoxy analog of lysophosphatidylcholine, has been employed to study the sensitivity of various types of mouse cells with respect to changes in membrane permeability induced by lysophosphatidylcholine. Cells used included erythrocytes, thymocytes, spleen cells and macrophage, as well as 4 different tumors (2 lymphomas, 1 Ehrlich acites and 1 methylcholanthren-induced fibrosarcoma). The sensitivity to the lysophosphatide (on a per-cell basis) of the above cell types varied by a factor of 65. When lytic concentrations were related to available membrane surface, this variation was reduced to a factor of 2.5. No principal difference was observed between the sensitivity of normal versus tumor cell membranes with respect to lysophosphatidylcholine lysis. Membrane surface, available for lysophosphatidylcholine, has been estimated from binding equilibria of 14C-labelled deoxy-lysophosphatidylcholine to the cells under standardized conditions. This method is based on the finding that binding equilibria of lysophospholipids to cells are predominantly determined by the available membrane surface.

Animals↗
PubMed1978

Alternating polarity in rRNA genes.

Spread nucleolar material from A. exigua exhibits an unusual arrangement of rDNA cistrons. The cistrons form head-to-head "diamond-shaped" doublets with a short spacer separating the members of the doublet. Single cistrons are usually terminal and arrange tail-to-tail with the adjacent doublet, suggesting the possibility of a repeating unit with a tail-to-tail, "bow-tie" doublet configuration in which the cistrons (average length: 1.44 micron) could be explained by an extraordinary shrinking of the DNA strand during transcription. This suggestion is supported by the estimation of the molecular mass of an early, or the primary, transcription product (2.2 X 10(6)).

Acetabularia↗
PubMed1978

[Rehabilitation and gerontology (author's transl)].

The 9th congress of the GDR Society for Rehabilitation was organized jointly with the GDR Society for Gerontology and held from 4 to 6 January 1977. The article outlines observations made at and conclusions derived from this important scientific event. Three major problems were discussed: rehabilitation of chronically ill and handicapped persons of advanced age within the working process as a task for society as a whole; the combination between gerontology and rehabilitation as a result of the change in the age and morbidity structures of economically advanced countries; beginnings and first experience in the field of gerontology-oriented rehabilitation in the GDR and recommendations made by WHO on the planning and organization of geriatric services with special consideration for rehabilitation in advanced age.

Aged↗
PubMed1978

[Effect of temperature on formation of lysozyme in E. coli CRT 266 (dnaB ts) after infection with bacteriophage T3].

Lysozyme formation induced by bacteriophage T3 was studied in the ts-mutant E. coli CRT 266 (dnaBts) and in the wild-type E. coli CR 34--45 (dnaB+) at different temperatures. It was found that lysozyme was formed in E. coli CRT 266, however, no lysozyme synthesis took place at 41.5 degrees C. These results indicate that the expression of the lysozyme gene is disturbed in the ts-mutant at 41.5 degrees C.

Coliphages↗
PubMed1977

[Percutaneous puncture of the femoral vein for haemodialysis: report of 5000 punctures (author's transl)].

Using the Seldinger technique, a total of 5306 percutaneous femoral vein catheterisations were performed in the course of ten years. Two-catheter venovenous dialysis was performed 2357 times and single-needle technique 592 times. There were five important complications: severe retroperitoneal bleeding after perforation of the external iliac vein three times, fatal bleeding from the femoral artery once, and reversible damage to the femoral nerve once. The results indicate that for every 1000 percutaneous femoral-vein catheterisations one must expect one severe complication. However, by using the correct catheter technique, especially careful manipulation of the wire, complications can be largely avoided.

Adult↗
PubMed1977

Characterization of a protein factor stimulating RNA synthesis by DNA-dependent RNA polymerase II from plant cell cultures.

During purification of DNA-dependent RNA polymerase II (or B) from cell cultures of parsley a protein fraction was separated by phosphocellulose chromatography which enhanced RNA synthesis in the presence of native homologous DNA. This 'stimulatory factor' was characterized in respect to some effects on the reaction catalyzed by RNA polymerase II. In the presence of the factor the metal ion requirements as well as the ionic strength for optimal RNA synthesis were markedly changed; addition of the factor to RNA polymerase II purified by cellulose chromatography restored those enzyme properties which had apparently changed upon this purification step. The chain length of the RNA product synthesized is favouring the view that the factor acts mainly by stabilizing the elongation step during transcription. The stimulatory factor was further purified by several steps of column chromatography. As derived from the results of gel electrophoresis under denaturing conditions the factor consists of several small polypeptides. Those of Mr = 26000, 25000 and 14000 apparently have counterparts among the smaller subunits of highly purified RNA polymerase II from parsley cells. Another polypeptide of the factor, with Mr = 30000, was only found in those preparations of RNA polymerase II which had not been subjected to phosphocellulose chromatography.

DNA-Directed RNA Polymerases↗
PubMed1977

[Effect of temperature on the transcription of T3 DNA b y T3-specific RNA polymerase in cell-free extracts of Escherichia coli CRT266].

Cell free extracts were prepared from E. coli CRT266 9 min after infection with T3 phages. RNA synthesis in these extracts is almost entirely due to T3 RNA polymerase. The inactivation of T3 RNA polymerase in these extracts proceeds rapidly at 42 degrees C. 90% of the activity is lost within 10 min at this temperature. Under conditions where the formation of a stable initiation complex with T3 DNA is possible, i.e., in the presence of GPT, APT, and UTP the T3 RNA polymerase becomes protected against heat inactivation losing only )0% of its activity during an exposure to 42 degrees C for 10 min. Studies on the time course of RNA synthesis have shown that reinitiation is still possible at 37 degrees C and 42 degrees C. At 44 degrees C, however, RNA synthesis stops abruptly after 3 min indicating that reinitiation does no longer take place. The elongation of already initiated T3 RNA chains is rather resistant to heat. At 44 degrees C the same elongation rates are observed as at 37 degrees C and 42 degrees C, respectively.

Cell-Free System↗
PubMed1977

[Protein and amino acid metabolism in laying hens receiving N-15 labeled casein. 6. Patterns of N-15 incorporation into the N fraction and amino acids of the follicles and residual ovaries].

4 experimental hens were fed labelled casein as sole protein source for a period of 6 days. The dietary nitrogen contained a 15N excess of 0.69 atom%. Hens 1 and 2 were slaughtered 2 days and hens 3 and 4 four days after receiving the last 15N' dose. 10 follicles with diameters more than 6 mm were investigated for their content of N, for the TCE-soluble portion of N (TCE=trichloracetic acid) and for the content of different amino acids in protein. The corresponding 15N' data were established and the same analyses were carried out with the residual ovaries. The mean proportion of the TCE soluble N fraction in the total amount of N was 90% in the follicles and 88% in the residual ovaries. The content of certain kinds of amino acids in follicular protein depends on the degree of maturity of the follicles. There were differences in the percentage composition of amino acids between the follicles and residual ovaries. The mean percentage of lysine contained in follicular protein was 7,2%, that in the residual ovaries 7,9%. Corresponding data for arginine were 6,9% and 7,9%, those for glutamic acid 11,5% and 13,8%, for glycine 3,1% and 5,7%, for alanine 5,0% and 6,1%, for methionine 2,8% and 1,7% and for cystine 3,7% and 2,4%. Less than half of the 15N' atom % and less than half of the percentage of 15N' in the total amount of N and of the amount of amino acids in both the follicles and the residual ovaries were found in the hens killed 144 hrs after the last 15N dose than in the hens slaughtered 48 hrs after the last 15N intake. The atom % of 15N' in the N contained in the amino acids serine, threonine, glutamic acid, proline and leucine decreased with the process of ageing of the follicles. On an average, 88% of the total quantity of 15N' contained in the follicle samples were found as amino acid N, while in the residual ovaries 90% were found.

Amino Acids↗
PubMed1977

[Protein and amino acid metabolism in laying hens receiving N-15 labeled casein. 7. Incorporation and distribution of labeled nitrogen into egg fractions].

Four colostomated hybrid laying hens were fed, for 6 days, a semisynthetic ration containing 15N labelled casein as sole protein source. Within this period, the hens laid 13 eggs which were fractionated into egg yolk, egg white and egg shell. The N content of these egg fractions was established. A TCE soluble and TCE precipitable fraction (TCE=trichloroacetic acid) were obtained from the fractions of egg yolk and egg white. Additionally, an analysis was made of the set of amino acids contained in the crude protein of the egg yolk, egg white and egg membrane (lysine, histidine and arginine only). The excess 15N atom% (15N') was established in the crude protein, in the nitrogen from the TCE soluble and TCE precipitable fractions and in the N from 17 amino acids of the egg yold and egg white. In the egg membrane fraction the 15N' atom% was determined as percentage of the total amount of N and of the amount of N contained in the basic amino acids. Essential differences between the 3 egg fractions were noticed with regard to the process of initial incorporation of labelled N and the intensity of this process after the onset of 15N application. 15N' was detected in the egg shell as early as 4 hrs after administration of the 15N' dose. Heavy nitrogen was found to be contained in the egg white of eggs that were laid on the 2nd day of experiment. The level of 15N' atom% in the egg white increased essentially during the following days of experiment; the 15N'quantities in the egg white were considerably higher than those in the egg yolk. Similar results were obtained for the process of 15N incorporation into the 17 amino acids. It is assumed that differences between the 3 fractions as observed in the level of labelling and in the pattern of 15N' incorporation are accounted for by the different sites and different times of protein synthesis for the different egg proteins.

Amino Acids↗
PubMed1977

[Studies on the protein and amino-acid metabolism of laying hens using 15N-labelled casein. 15N-incorporation into N-fractions and amino acids of various parts of the body].

Four colostomized Leghorn hens were fed, during 6 days, 15N-labelled casein as sole protein source. Two animals were slaughtered 48 hours, the other two 144 hours after the last 15N-application. The share of TCE-soluble N in total N averaged 16% for the body parts analysed, i.e. meat, bone, liver, kidneys, oviducts, residual viscera and other. The variation of the lysine, histidine and arginine levels in the body parts ranged from 3.6 to 7.9 g, 1.1. to 3.7 g and 6.4 to 7.4 g in 16.7 g hydrolysate N, respectively. Except for feathers, the analysed body parts contained and excess amount of heavy nitrogen. The degree of labelling was found to depend on the time of slaughtering after the tracer application. In the liver and in the oviduct being metabolically active organs, the 15N-excess in the total N fraction decreased by 45% between the 2nd and the 6th days after 15N-feeding, whilst in the meat it went down by 20%. The decline of the 15N-concentration in the TCE-soluble N compounds was faster than in the total N-fraction. Out of the body samples analysed, the lysine of the liver having 0.26 atom % 15N-excess was found to be more strongly labelled in hens 1 and 2. The amino acid arginine reached about the same level of labelling, the 15N-frequency of histidine being the lowest.

Amino Acids↗
PubMed1977

[Studies on the protein and amino acid metabolism of laying hens receiving 15N-labelled casein. 5. 15N incorporation into different blood fractions and into the amino acids lysine, histidine and arginine contained in these fractions].

4 colostomizted laying hens were fed 15N labelled casein as a sole source of protein for a period of 6 days. The birds were slaughtered 2 or 6 days after receiving 15N dose. The blood was separated into corpuscular blood components and blood plasma. Then, the amount and content of nitrogen in the blood, the blood fractions and in the amino acids lysine, histidine and arginine and the excess of 15N atom% (15N') were estimated. The average N concentrationin the blood was 3.8%. The crude protein in the blood corpuscles contained 8.7% lysine, 7.1% histidine and 6.4% arginine; the corresponding values for crude plasma protein were 6.3%, 2.2% and 5.7%. The 15N atom% in blood nitrogen was found to be lower in the hens slaughtered 144 hrs after receiving the last 15N dose than in the birds already slaughtered after 48 hrs. The same trend was found for the plasma proteins. The level of excess 15N atom% in the blood corpuscles increased with the length of time elapsing after the withdrawal of 15N casein (over the period of time investigated); a decrease of excess 15N atom% in plasma lysine was noted, however, for the investigated period of time after the last 15N dose. In the corpuscular blood components a higher level of 15N atom% was usually found in histidine relative to that in lysine and arginine; it was higher in the hens slaughtered 6 days after receiving the final 15N dose than in the hens killed 2 days after administration of the last 15N dose.

Amino Acids↗