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Biomedical subjects

M Hecker

Publications and source records attributed to M Hecker.

229 records · Page 13Linked to original sources
PubMed1981

[Synthesis of poly(A)-containing RNA in outgrowing spores of Bacillus subtilis].

The synthesis of poly(A)-containing RNA in outgrowing spores of Bacillus subtilis was studied. A significant amount of RNA puls-labelled with 3H-uridine is polyadenylated. With the beginning of RNA synthesis in outgrowing spores labelled poly(A)-containing RNA was detected. The amount of poly(A)-RNA during the outgrowth and first cell division remains constant. Besides poly(A)-RNA the synthesis of tRNA and rRNA occurs. These results indicate a simultaneous activation of synthesis of tRNA, rRNA as well as of poly(A)-containing RNA during outgrowth of B. subtilis spores.

Bacillus subtilis↗
PubMed1977

[Relationship between aminoacyl-tRNA synthetases (AAA) and cell division in temperature-sensitive filamentous mutants of Bacillus subtilis SB 19. III. Characterization of pre-incubation effect and effect of AAA-inhibitor produced by Agrostemma githago seedlings].

Further results on the correlations between the regulation of bacterial cell division and amino-acyl-tRNA synthetase are presented. Activity of aminoacyl-tRNA synthetases, extracted from a filamentous mutant of Bacillus subtilis SB 19, may be stimulated by preincubation of crude extracts. The mechanism of this stimulating effect has been studied by means of an inhibitor of amino-acyl-tRNA synthetases produced during the growth of Agrostemma githago-seedlings. According to preliminary results we suggest, this inhibitor can reduce the activity of subunits only, but not that of higher associates. Association of subunits to oligomers will be prevented by the inhibitor, too. Our results may be indicative of the assumption that the increase of enzyme activity during subunits with a low catalytic activity to functional oligomers. As to the verification of these hypotheses further work will still have to be done.

Amino Acyl-tRNA Synthetases↗
PubMed1977

[Effect of cordycepin on the activation of RNA and protein synthesis at the early inhibition stages of Agrostemma githago embryos].

In embryos of Agrostemma githago pre-rRNA, ribosomal, heterogeneous, and transfer RNA is transcribed at 0 to 3 hrs of inhibition. An essential amount of hnRNA/mRNA is polyadenylated and can be prepared by affinity chromatography on poly(U)-sepharose columns. At very low concentrations of cordycepin synthesis of poly(A)+-RNA is especially inhibited. At increasing concentration of cordycepin the synthesis of ribosomal RNA is inhibited too. According to these results cordycepin is a suitable inhibitor to study the function of post-transcriptional polyadenylation of mRNA at the regulation of early protein synthesis of imbibing Agrostemma embryos. Incorporation of [3H]-leucine into protein occurring from 0 to 3 hrs of inhibition is not remarkably inhibited by cordycepin. These results may indicate that neither synthesis of mRNA nor its polyadenylation nor the polyadenylation of stable mRNA is involved in the regulation of early protein synthesis.

Chromatography, Affinity↗
PubMedDate not supplied

Analysis of the expression and function of the sigmaB-dependent general stress regulon of Bacillus subtilis during slow growth.

Glucose-limited continuous cultures were used to analyze sigmaB activity at decreasing growth rates. Expression of the sigmaB-dependent genes gsiB and ctc started to increase at a growth rate of 0.2 h-1, and both genes were induced approximately fivefold at a growth rate of 0.1 h-1 as compared to expression at the maximal growth rate. However, maximal sigmaB activity was only reached when the growth stopped as a result of the exhaustion of the carbon and energy source glucose. During glucose-limited growth, increased expression of the general stress regulon at growth rates below 0.2 h-1 did not provide wild-type cells with a growth advantage over sigB mutants. Instead, expression of the stress regulon seems to constitute a significant burden during glucose-limited growth, resulting in a selective growth advantage of the sigB mutant as compared to the wild-type at a growth rate of 0.08 h-1.

Bacillus subtilis↗
PubMedDate not supplied

A novel polymorphism in the 5' promoter region of the human interleukin-4 receptor alpha-chain gene is associated with decreased soluble interleukin-4 receptor protein levels.

Interleukin (IL)-4 exerts its biological effects through binding to the IL-4 receptor (IL4R) complex, plays a central role in stimulating B-cell differentiation, and is crucial for the development of T helper 2 cells. Recently, a soluble form of the human IL4R alpha chain (sIL4R alpha), which is produced by alternate mRNA splicing of exon 8, was discovered. sIL4R is thought to play an important role in either enhancing or inhibiting IL-4 signalling. We analyzed the 5' promoter region of the human IL4R alpha-chain gene (IL4RA) of healthy volunteers by DNA sequencing and found three novel single-nucleotide polymorphisms (SNPs; T-890C, T-1914C, C-3223T) and one novel short tandem repeat [(CAAAA)(5-7)-3600]. The two common promoter region SNPs T-1914C and C-3223T as well as six known coding SNPs in the IL4RA gene were genotyped in healthy blood donors by PCR with sequence-specific primers; total sIL4R levels were measured by ELISA. Results revealed a highly significant association of the -3223T variant with lowered sIL4R levels (two-tailed t-test, P=0.0002). Results remained highly significant after Bonferroni adjustment for multiple comparisons (P=0.0017). Moreover, the C-3223T variant was found to be in strong linkage disequilibrium with the extracellular 150V variant (P<0.001), which was recently described to be associated with atopic asthma in a Japanese population. Since this novel IL4RA promoter region SNP is common (allele frequency 29.8%), we conclude that it may be of importance for the genetic regulation of the IL-4 signalling pathway.

Gene Frequency↗
PubMedDate not supplied

Relaxation of isolated coronary arteries by angiotensin-converting enzyme inhibitors: role of endothelium-derived kinins.

In the presence of indomethacin (10 microM) and without previous exposure to bradykinin, two angiotensin-converting enzyme (ACE) inhibitors, moexiprilat and ramiprilat (0.1 microM), elicited distinct relaxation responses from preconstricted endothelium-intact but not from denuded bovine coronary artery rings, and enhanced the relaxation response to bradykinin (3 nM). All of these responses were strongly reduced by the selective B2-kinin receptor antagonist Hoe 140 (0.1 microM). Bradykinin (30 nM), moexiprilat or ramiprilat (0.3 microM) also significantly increased the cyclic GMP content of these coronary segments, an effect which was abolished by the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine (L-NNA; 30 microM) or by removal of the endothelium. L-NNA also strongly reduced the relaxation response to moexiprilat but only partially inhibited that to bradykinin, demonstrating that the ACE inhibitor-induced relaxation was predominantly mediated by endothelial NO release, whereas bradykinin acted in part through another endothelium-dependent mechanism. These findings suggest that ACE inhibitors induce endothelium-dependent relaxation presumably by facilitating the accumulation of endothelium-derived vasoactive kinins in or at the vessel wall. This local mechanism may significantly contribute to the dilator action of these compounds in vivo.

Angiotensin-Converting Enzyme Inhibitors↗
PubMedDate not supplied

Excretion into the culture medium of a Bacillus beta-glucanase after overproduction in Escherichia coli.

The beta-glucanase gene (bgl) from Bacillus amyloliquefaciens was expressed in E. coli CSH 55 under the control of the PR promoter of phage lambda that is repressed by the thermosensitive repressor C1857. Production of beta-glucanase was drastically stimulated by a temperature shift to 42 degrees C. This overexpression of the bgl gene (about 20% of the total cellular protein) led to an almost complete excretion of the otherwise periplasmic protein into the extracellular medium, beta-glucanase accounted for more than 50% of the extracellular proteins. Col E 1 related plasmid (pEG 1) are amplified in E. coli relA strains in response to an amino acid limitation leading to a 10-fold increase in the activity of plasmid encoded genes. In this work we intended to maximize the expression of the bgl gene by a concerted action of a plasmid amplification and temperature induction. Surprisingly we could not increase the beta-glucanase production above the level reached by plasmid amplification or temperature induction alone. The reasons for this unexpected result will be discussed. Under all conditions tested the expression of the bgl gene was much lower in the E. coli relA strain NF 162 than in E. coli CSH 55; the low beta-glucanase production was accompanied by a reduced excretion rate of the enzyme.

Bacillus↗
PubMedDate not supplied

[Replication of ColE 1-related plasmids at increased growth temperature depending on rom function].

The content of ColE 1-related plasmids increased about 4-6-fold after a temperature-shift from 30 to 42 degrees C (45 degrees C) if the rom-region of the plasmids was deleted. The copy number of rom(+)-plasmids did not change after the temperature shift. All rom(-)-plasmids tested in this study showed this plasmid amplification. The Rom-protein is capable of inhibiting plasmid replication by stabilization the initial reversible stage of the association of RNA I with the primer precursor RNA II. We suggest that the temperature-dependent enhancement of the copy number of rom(-)-plasmids is due to a destabilization of this initial phase of the RNA I-preprimer interaction at high temperatures which is suppressed by the Rom-protein in cells with rom(+)-plasmids.

Bacterial Proteins↗
PubMedDate not supplied

[Physiologic significance of "stringent control" in Escherichia coli under extreme starvation].

The viability of three isogenic relA+/relA strain pairs of Escherichia coli (CP78/CP79; NF161/NF162; CP107/CP143) was studied during prolonged starvation for amino acids, glucose or phosphate. After amino acid limitation we found a prolonged viability of all relA+ strains which synthesized ppGpp. We suggest that some ppGpp-mediated pleiotropic effects of the stringent response (e.g. glykogen accumulation, enhanced protein turnover) might be involved in this prolongation of survival. After glucose or phosphate starvation there was no difference in the relA+/relA strains either in the ppGpp content or in the survival.

Escherichia coli↗
PubMedDate not supplied

[Synthesis of heat shock proteins following amino acid or oxygen limitation in Bacillus subtilis relA+ and relA strains].

Some of the presumable heat shock proteins will be produced in Bacillus subtilis in response to different environmental conditions, e.g. heat shock, amino acid limitation or oxygen limitation. During amino acid limitation or during oxygen limitation the relA+ strain is able of synthesizing this set of proteins but the relA strain is not. We suggest that the accelerated rate of the synthesis of some heat shock proteins depends on the induction of the stringent response because the (p)ppGpp production does not occur in the relA strain during amino acid or oxygen limitation. On the other hand the relA strain can produce heat shock proteins under heat stress. Therefore different mechanisms must be responsible for the expression of this set of genes during heat and other stress stimuli. It can be supposed that in B. subtilis the (p)ppGpp-dependent stringent control is a central defense reaction against different adverse environmental conditions and furthermore, that the synthesis of "stress" proteins as an essential component of the stringent response is part of a general adaptation mechanism under non-growing conditions.

Amino Acids↗