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Biomedical subjects

A Glück

Publications and source records attributed to A Glück.

18 recordsLinked to original sources
PubMed1999

Aneurysmal portosystemic venous shunt: a case report.

A case of an aneurysmal portosystemic venous shunt detected by colour Doppler ultrasound (CDUS) is presented. A young female patient complained of postprandial fatigue and had paroxysmal tachycardia. A direct vascular communication between right portal vein and right hepatic vein was found at CDUS and confirmed by direct portal angiogram. Using detachable coils a complete occlusion of the intrahepatic shunt was obtained. Reports from the literature regarding portovenous aneurysms are reviewed.

Adult↗
PubMed1996

Determination of the 28 S ribosomal RNA identity element (G4319) for alpha-sarcin and the relationship of recognition to the selection of the catalytic site.

Ricin A-chin and alpha-sarcin are ribotoxins that inactivate eukaryotic ribosomes by modifying 28 S rRNA; ricin A-chain is an RNA N-glycosidase that depurinates the adenosine at position 4324 and alpha-sarcin is a ribonuclease that cleaves the phosphodiester bond on the 3' side of the adjacent guanosine (at position 4325). In cartoons of the secondary structure these two residues are seen to be embedded in a 17 base single-stranded loop over a seven base-pair helix. However, NMR spectroscopy of an oligoribonucleotide, a 29-mer that mimics the sarcin/ricin domain, indicates that the RNA has a compact conformation in which the guanosine at the position analogous to 4319 in 28 S rRNA is bulged out of what otherwise is an extended A-form helix. Since similar structural irregularities are used by proteins to bind to RNA, we have tested the effect of mutations of the bulged guanosine on recognition and covalent modification of the RNA by ricin A-chain and by alpha-sacrin. For the test a synthetic oligoribonucletide, a 35-mer, was used; the mutations were the deletion, the transition to adenosine, and the transversion to cytidine and uridine of the guanosine that is the analog of G4319. Each of the four mutations abolished cleavage og the RNA by alpha-sacrin, where depurination by ricin A-chain was little affected. Thus G4319 is an identity element for alpha-sacrin recognition. Analysis of the effect of alpha-sacrin on variant oligoribonucleotides in which additional bases were inserted between the identity element guanosine and the site of catalysis suggest that on binding to the RNA the toxin uses the guanosine for orientation and then cleaves at a fixed distance and at a fixed position in space.

Base Sequence↗
PubMed1996

Dependence of depurination of oligoribonucleotides by ricin A-chain on divalent cations and chelating agents.

Ricin A-chain is a cytotoxic RNA N-glycosidase that inactivates eukaryotic ribosomes by depurinating the adenosine at position 4324 in 28S rRNA. The enzyme retains its specificity when a synthetic oligoribonucleotide (a 35-mer) that mimics the structure at the site of action is the substrate. However, covalent modification by ricin A-chain of the oligoribonucleotide but not of ribosomes, depends on the simultaneous presence of a divalent cation and a chelating agent.

Base Sequence↗
PubMed1994

A leucine zipper-like motif and a basic region-leucine zipper-like element in rat ribosomal protein L13a. Identification of the tum- transplantation antigen P198.

The amino acid sequence of the rat 60 S ribosomal subunit protein L13a was deduced from the sequence of nucleotides in two recombinant cDNAs. Mature ribosomal protein L13a has 202 amino acids (the NH2-terminal methionine is removed after translation of the mRNA) and a M(r) of 23,330. Hybridization of the L13a cDNA to digests of nuclear DNA suggests that there are 9-11 copies of the L13a gene. The mRNA for the protein is approximately 800 nucleotides in length. Rat L13a is related to the Saccharomyces cerevisiae ribosomal proteins that have been provisionally designated rp22 and rp23 and to the eubacterial and archaebacterial family of L13 ribosomal proteins. The mouse tum- transplantation antigen P198 is a mutant of the mouse homolog of rat ribosomal protein L13a. Rat ribosomal protein L7 has, at its NH2 terminus, five tandem repeats of a similar sequence of 12 amino acids (Lin, A., Chan, Y. L., McNally, J., Peleg, D., Meyuhas, O., and Wool, I. G. (1987) J. Biol. Chem. 262, 12665-12671); L13a has, in its carboxyl-terminal region, amino acid sequences with significant identity to L7 repeats 1, 3, and 5. L13a also has a number of short amino acid sequences that are repeated, a leucine zipper-like motif at its NH2 terminus, and a potential basic region-leucine zipper element in its carboxyl-terminal region.

Amino Acid Sequence↗
PubMed1994

The ribosomal RNA identity elements for ricin and for alpha-sarcin: mutations in the putative CG pair that closes a GAGA tetraloop.

alpha-Sarcin is a ribonuclease that cleaves the phosphodiester bond on the 3' side of G4325 in 28S rRNA; ricin A-chain is a RNA N-glycosidase that depurinates the 5' adjacent A4324. These single covalent modifications inactivate the ribosome. An oligoribonucleotide that reproduces the structure of the sarcin/ricin domain in 28S rRNA was synthesized and mutations were constructed in the 5' C and the 3' G that surround a GAGA tetrad that has the sites of toxin action. Covalent modification of the RNA by ricin, but not by alpha-sarcin, requires a Watson-Crick pair to shut off a putative GAGA tetraloop. Either the recognition elements for the two toxins are different despite their catalyzing covalent modification of adjacent nucleotides in 28S rRNA or there are transitions in the conformation of the alpha-sarcin/ricin domain in 28S rRNA and one conformer is recognized by alpha-sarcin and the other by ricin A-chain.

Base Sequence↗
PubMed1992

Ribosomal RNA identity elements for ricin A-chain recognition and catalysis. Analysis with tetraloop mutants.

Ricin is a cytotoxic protein that inactivates ribosomes by hydrolyzing the N-glycosidic bond between the base and the ribose of the adenosine at position 4324 in eukaryotic 28 S rRNA. Ricin A-chain will also catalyze depurination in naked prokaryotic 16 S rRNA; the adenosine is at position 1014 in a GAGA tetraloop. The rRNA identity elements for recognition by ricin A-chain and for the catalysis of cleavage were examined using synthetic GAGA tetraloop oligoribonucleotides. The RNA designated wild-type, an oligoribonucleotide (19-mer) that approximates the structure of the ricin-sensitive site in 16 S rRNA, and a number of mutants were transcribed in vitro from synthetic DNA templates with phage T7 RNA polymerase. With the wild-type tetraloop oligoribonucleotide the ricin A-chain-catalyzed reaction has a Km of 5.7 microM and a Kcat of 0.01 min-1. The toxin alpha-sarcin, which cleaves the phosphodiester bond on the 3' side of G4325 in 28 S rRNA, does not recognize the tetraloop RNA, although alpha-sarcin does affect a larger synthetic oligoribonucleotide that has a 17-nucleotide loop with a GAGA sequence; thus, there is a clear divergence in the identity elements for the two toxins. Mutants were constructed with all of the possible transitions and transversions of each nucleotide in the GAGA tetraloop; none was recognized by ricin A-chain. Thus, there is an absolute requirement for the integrity of the GAGA sequence in the tetraloop. The helical stem of the tetraloop oligoribonucleotide can be reduced to three base-pairs, indeed, to two base-pairs if the temperature is decreased, without affecting recognition; the nature of these base-pairs does not influence recognition or catalysis by ricin A-chain. If the tetraloop is opened so as to form a GAGA-containing hexaloop, recognition by ricin A-chain is lost. This suggests that during the elongation cycle, a GAGA tetraloop either exists or is formed in the putative 17-member single-stranded region of the ricin domain in 28 S rRNA and this bears on the mechanism of protein synthesis.

Base Sequence↗
PubMed1992

Ribotoxin recognition of ribosomal RNA and a proposal for the mechanism of translocation.

The ribotoxins alpha-sarcin and ricin catalyse covalent modifications in adjacent nucleotides in 28S rRNA, yet the elements of nucleic acid structure that they recognize are not only different but incompatible. This suggests that this ribosomal domain (which in two dimensions is a seven-base-pair helical stem and a 17-member single-stranded loop) has alternate conformers. Since the domain is involved in binding of aminoacyl-tRNA and GTP hydrolysis, we propose that the switch between the two configurations, perhaps initiated by the binding of elongation factors, plays a role in translocation.

Animals↗
PubMed1991

Ribosomal RNA identity elements for ricin A-chain recognition and catalysis.

Ricin is a cytotoxic protein that inactivates ribosomes by hydrolyzing the N-glycosidic bond between the base and the ribose at position A4324 in eukaryotic 28 S rRNA. The requirements for the recognition by ricin A-chain of this nucleotide and for the catalysis of cleavage were examined using a synthetic oligoribonucleotide that reproduces the sequence and the secondary structure of the RNA domain (a helical stem, a bulged nucleotide, and a 17-member single-stranded loop). The wild-type RNA (35mer) and a number of mutants were transcribed in vitro from synthetic DNA templates with phage T7 RNA polymerase. With the wild-type oligoribonucleotide the ricin A-chain catalyzed reaction has a Km of 13.55 microM and a Kcat of 0.023 min-1. Recognition and catalysis by ricin A-chain has an absolute requirement for A at the position that corresponds to 4324. The helical stem is also essential; however, the number of base-pairs can be reduced from the seven found in 28 S rRNA to three without loss of identity. The nature of these base-pairs can affect catalysis. A change of the second set from one canonical (G.C) to another (U.A) reduces sensitivity to ricin A-chain; whereas, a change of the third pair (U.A----G.C) produces supersensitivity. The bulged nucleotide does not contribute to identification. Hydrolysis is affected by altering the nucleotides in the universal sequence surrounding A4324 or by changing the position in the loop of the tetranucleotide GA(ricin)GA: all of these mutants have a null phenotype. If ribosomes are treated first with alpha-sarcin to cleave the phosphodiester bond at G4325 ricin can still catalyze depurination at A4324. This implies that cleavage by alpha-sarcin at the center of what has been presumed to be a 17 nucleotide single-stranded loop in 28 S rRNA produces ends that are constrained in some way. On the other hand, hydrolysis by alpha-sarcin of the corresponding position in the synthetic oligoribonucleotide prevents recognition by ricin A-chain. The results suggest that the loop has a complex structure, affected by ribosomal proteins, and this bears on the function in protein synthesis of the alpha-sarcin/ricin rRNA domain.

Adenosine↗
PubMed1990

RNA-protein interaction. An analysis with RNA oligonucleotides of the recognition by alpha-sarcin of a ribosomal domain critical for function.

alpha-Sarcin is a cytotoxic protein that inactivates ribosomes by hydrolyzing a single phosphodiester bond on the 3' side of G-4325 in eukaryotic 28 S rRNA. We have examined the requirements for the recognition by alpha-sarcin of this domain using a synthetic oligoribonucleotide (35-mer) that reproduces the sequence and, we presume, the secondary structure (a stem, a bulged nucleotide, and a loop) at the site of modification. The wild type structure and a large number of variants were transcribed in vitro from synthetic DNA templates with phage T7 RNA polymerase. Recognition of the substrate is strongly favored by a G at the position that corresponds to 4325. There is an absolute requirement for a helical stem; however, it can be reduced from the 7 base pairs in the natural structure to 3 without loss of specificity. The nature of the base pairs in the stem modifies but does not abolish recognition; whereas, the bulged nucleotide does not contribute to identification. Cleavage is materially affected by altering the nucleotides in the universal sequence surrounding G-4325 and changing the position in the loop of the tetranucleotide GAG(sarcin)A leads to loss of recognition by the toxin. We propose that the alpha-sarcin domain RNA participates in elongation factor catalyzed binding of aminoacyl-tRNA and of translocation; that translocation is driven by transitions in the structure of the alpha-sarcin domain RNA initiated by the binding of the factors, or the hydrolysis of GTP, or both; and that to toxin inactivates the ribosomes by preventing this transition.

Adenosine↗
PubMed1990

A new assay to measure RNA N-glycosidase activity.

We have developed a convenient procedure to measure the activity of Ricin A-chain and other enzymes with RNA N-glycosidase activity. The method is based on the use of a tritiated oligoribonucleotide as a substrate. The enzymatic activity is directly determined by measuring the release of adenine from the substrate. This method should prove useful in the study of the molecular mechanism of action of Ricin A and other RNA N-glycosidases.

Animals↗
PubMed1989

The primary structure of rat ribosomal protein S10.

The amino acid sequence of rat ribosomal protein S10 was deduced from the sequence of nucleotides in a recombinant cDNA and confirmed from the NH2-terminal amino acid sequence of the protein. Ribosomal protein S10 contains 165 amino acids and has a molecular mass of 18917 Da. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 17-20 copies of the S10 gene. The mRNA for the protein is about 750 nucleotides in length. Ribosomal protein S10 has several possible internal duplications; one is a tandem repeat of ten residues that is basic and contains two or three prolines.

Amino Acid Sequence↗
PubMed1981

Impedance cardiography in normal children.

Cardiac output, cardiac index (cardiac output/body surface) and stroke volume were investigated in 20 normal children by means of impedance cardiography. Significant differences were found in the mean values of cardiac output and cardiac index between both sexes, as well as in means of cardiac index between younger and older children. The obtained data generally agreed with the results of other investigators performing the examination by using the same technique and other methods.

Adolescent↗
PubMed1981

Estimation of the correlation between the transcutaneous aortic flow velocity curve and impedance cardiogram in normal children.

83 measurements of stroke volume from an impedance cardiogram and of the corresponding area under the systolic complex of the aortic flow velocity curve obtained by means of the transcutaneous ultrasound Doppler device were carried out in 15 normal children. Between the "ideal" complexes and those requiring a little reconstruction (below 10% of maximal height of the given complex) and corresponding stroke volumes, significant correlation and regression coefficients were found. It has been suggested that the aortic flow velocity curve obtained by means of the transcutaneous ultrasound nondirectional Doppler device would be helpful in approximately estimating the stroke volume in normal children.

Adolescent↗
PubMedDate not supplied

The primary structure of rat ribosomal proteins P0, P1, and P2 and a proposal for a uniform nomenclature for mammalian and yeast ribosomal proteins.

The covalent structures of rat ribosomal proteins P0, P1, and P2 were deduced from the sequences of nucleotides in recombinant cDNAs. P0 contains 316 amino acids and has a molecular weight of 34,178; P1 has 114 residues and a molecular weight of 11,490: and P2 has 115 amino acids and a molecular weight of 11,684. The rat P-proteins have a near identical (16 of 17 residues) sequence of amino acids at their carboxyl termini and are related to analogous proteins in other eukaryotic species. A proposal is made for a uniform nomenclature for rat and yeast ribosomal proteins.

Amino Acid Sequence↗
PubMedDate not supplied

Structure and evolution of mammalian ribosomal proteins.

Mammalian (rat) ribosomes have 80 proteins; the sequence of amino acids in 75 have been determined. What has been learned of the structure of the rat ribosomal proteins is reviewed with particular attention to their evolution and to amino acid sequence motifs. The latter include: clusters of basic or acidic residues; sequence repeats or shared sequences; zinc finger domains; bZIP elements; and nuclear localization signals. The occurrence and the possible significance of phosphorylated residues and of ubiquitin extensions is noted. The characteristics of the mRNAs that encode the proteins are summarized. The relationship of the rat ribosomal proteins to the proteins in ribosomes from humans, yeast, archaebacteria, and Escherichia coli is collated.

Amino Acid Sequence↗