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Biomedical subjects

D Richter

Publications and source records attributed to D Richter.

At least 361 records · Page 20Linked to original sources
PubMed1981

The stringent response to unacylated tRNA, energy-and temperature-downshift in Bacillus stearothermophilus.

The response of the thermophile Bacillus stearothermophilus to inhibition of tRNA acylation, energy starvation and temperature downshift was characterized. We found that B. stearothermophilus, like other prokaryotic organisms, reacts with the so-called stringent response, which includes the accumulation of the unusual nucleotides guanosine 3',5' bis (diphosphate) [ppGpp] and guanosine 3'-diphosphate, 5'-tri-phosphate [pppGpp] and concomitantly the reduction of RNA synthesis and growth rate. The amount of (p)ppGpp formed depended on the cause of the stringent response: when tRNA acylation was inhibited (p)ppGpp synthesis was much higher than after energy starvation or temperature downshift whereas RNA synthesis was totally blocked in each case.

Energy Metabolism↗
PubMed1981

Immunological identification of a common precursor to arginine vasopressin and neurophysin II synthesized by in vitro translation of bovine hypothalamic mRNA.

mRNA from membrane-bound polysomes of bovine hypothalamus was translated in an mRNA-dependent cell-free system from reticulocyte lysate or wheat germ. The translation products were identified by immunoprecipitation with antibodies to either neurophysin II or arginine vasopressin followed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. An immunoreactive polypeptide was obtained with an apparent Mr of 21,000. Sequential immunoprecipitation studies indicated that the Mr 21,000 product is a common precursor to neurophysin II and arginine vasopressin. The specificity of the immunoprecipitation was demonstrated by competition with excess amounts of unlabeled neurophysin II or arginine vasopressin; little or no competition was observed with unlabeled neurophysin II or arginine vasopressin; little or no competition was observed with unlabeled neurophysin I or oxytocin. Processing experiments with microsomal membranes from dog pancreas or tunicamycin-treated ascites tumor cells showed that the Mr 21,000 polypeptide is the prepro form. It was converted to a pro form with Mr 19,000 suggesting a pre sequence of approximately 15 amino acids. The Mr 19,000 polypeptide was coreglycosylated to an apparent Mr of 23,000, indicating that the neurophysin II-arginine vasopressin precursor is a glycopolypeptide.

Animals↗
PubMed1981

Stringent response of Bacillus stearothermophilus: evidence for the existence of two distinct guanosine 3',5'-polyphosphate synthetases.

Bacillus stearothermophilus reacted to pseudomonic acid-induced inhibition of isoleucine-transfer ribonucleic acid (RNA) acylation and to energy downshift caused by alpha-methylglucoside addition with accumulation of guanosine 3',5'-polyphosphates [(p)ppGpp] and restriction of RNA synthesis. In vitro studies indicated that (p)ppGpp was synthesized by two different enzymes. One enzyme, (p)ppGpp synthetase I, was present in the ribosomal fraction, required the addition of a ribosome-messenger RNA-transfer RNA complex for activation, and was inhibited by tetracycline and thiostrepton. It is suggested that (p)ppGpp synthetase I is comparable to the relA gene product from Escherichia coli and is responsible for (p)ppGpp accumulation during amino acid starvation. The other enzyme, (p)ppGpp synthetase II, was found in the high-speed supernatant fraction (S100). It functioned independently of ribosomes, transfer RNA, and messenger RNA and was not inhibited by the above-mentioned antibiotics. (p)ppGpp synthetase II is thought to be responsible for (p)ppGpp accumulation during carbon source downshift. The two enzymes differ in their Km values for adenosine triphosphate (ATP):2mM ATP for synthetase I and 0.05 mM ATP for synthetase II. They also have different molecular weights: apparent Mr of 86,000 (+/- 5,000) for synthetase I and 74,000 (+/- 5,000) for synthetase II.

Geobacillus stearothermophilus↗
PubMed1981

Bovine hypothalamic poly(A)-rich RNA-directed synthesis of a common precursor to the nonapeptide arginine vasopressin and neurophysin II. Immunological identification and tryptic peptide mapping.

The common precursor to arginine vasopressin (AVP) and neurophysin II (NpII) has been synthesized in a reticulocyte lysate system directed by bovine hypothalamic poly(A)-rich RNA. The precursor, identified with antibodies raised against neurophysin II and arginine vasopressin, has an apparent Mr of 21 000 (21 k). The specificity of the immune reaction has been shown by competition experiments using excess amounts of a variety of unlabeled peptides. With anti Np II, but not with anti AVP, a second neurophysin precursor with an apparent Mr of 18 000 (18 k) has been identified. Comparison of the tryptic maps obtained from the 21 k and 18 k precursors shows that both products give rise to the four [35S]cysteine-labeled neurophysin II-peptide fragments; however, only the 21 k yields an AVP-like tryptic peptide, identified with antibodies raised against AVP. The possible implications of the two precursors, one consisting of AVP and Np II, the other of Np II only, are discussed.

Animals↗
PubMed1980

Uncharged tRNA inhibits guanosine 3',5'-bis (diphosphate) 3'-pyrophosphohydrolase [ppGppase], the spoT gene product, from Escherichia coli.

The spot gene product from Escherichia coli, the guanosine 3',5'-bis(diphosphate) 3'-pyrophos phohydrolase [ppGppase] catalyzes the specific release of pyrophosphate from the 3'-position of guanosine 3',5'-bis(diphosphate) [ppGpp]; this reaction is significantly inhibited in the presence of uncharged tRNAPhe yeast. Little or no inhibition is observed with Phe-tRNAPhe, tRNAPhe-CpCpAoxi-red or ribosomal RNA (16S and 23S).

Depression, Chemical↗
PubMed1980

In vitro degradation of guanosine 3',5'-bis(diphosphate) [ppGpp] by the spoT gene product [ppGppase] from auxotrophic strains of Escherichia coli: effects of various antibiotics and drugs.

The enzyme specifically hydrolyzing guanosine 3',5'-bis(diphosphate) [ppGpp] has been isolated from the ribosomal fraction of Escherichia coli; it released pyrophosphate from the 3'-position of ppGpp. The effects of various drugs and antibiotics known to interfere with protein and/or RNA synthesis were investigated in the ppGpp degrading reaction. It was determined that tetracycline, chlorotetracycline, and thiostrepton strongly inhibited the reaction, whereas levallorphan gave a moderate inhibition. Only the tetracycline-mediated inhibition could be reversed by manganese ions. Oxytetracycline, rifampicin, fusidic acid, kirromycin, streptomycin, puromycin, chloramphenicol, and morphine did not inhibit the decay reaction.

Anti-Bacterial Agents↗
PubMed1980

[Unruptured tubal pregnancy at full term with survival of mother and child (author's transl)].

A clinically intact child was delivered from breech presentation in the 40th week of pregnancy. The amniotic sac was removed by salpingectomy. Basiotrophic implantation, the absence of chorion frondosum reduction, and the presence of amniotic fluid appeared to have been major prerequisites for unimpaired development. Diagnostic possibilities and symptoms of complete tubal pregnancies are discussed.

Adult↗
PubMed1979

In vivo studies on the incorporation of microinjected acidic proteins of the large ribosomal subunit from Escherichia coli and artermia salina into oocyte ribosomes from Xenopus laevis.

Tritium-labeled acidic proteins from the large ribosomal subunit of Artermia salina or Escherichia coli were microinjected into the cytoplasm of stage IV/V oocytes from Xenopus laevis. eL12 from the large ribosomal subunit of A. salina but not L7/L12 or L7/L12--L10 from E. coli is specifically incorporated into 60S ribosomal subunits of oocytes. This incorporation is not significantly inhibited by actinomycin D. Incorporation of eL12 into the 60S subunits occurs in enucleated oocytes, suggesting that active ribosomal ribonucleic acid synthesis and ribosome assembly as well are not prerequired for this reaction. Apparently the incorporation proceeds via an exchange reaction between a free cytoplasmic pool of eL12 and ribosomal eL12.

Animals↗