PubMed Health⌕ Search

Biomedical subjects

F Iborra

Publications and source records attributed to F Iborra.

At least 19 recordsLinked to original sources
PubMed1992

[Cancer of the testis after Hodgkin's disease. Apropos of 2 cases].

We report about two cases of cancer of the testis occurring 2 and 7 years after Hodgkin's disease treated with combined chemotherapy and radiation therapy. From an etiopathogenic point of view, this association may, of course, be accidental, but it may also have an iatrogenic origin or be caused by contiguous carcinogenesis, or even by an immune deficiency. In addition to orchidectomy, the therapeutic history of these patients requires an adaptation of the treatment of their tumors of the testes.

Adult↗
PubMed1992

[Leiomyosarcoma of the inferior vena cava].

The authors report a case of leiomyosarcoma of the infrarenal inferior vena cava presenting as an abdominal mass. CT and MR imaging and immunotyping led to the diagnosis of retroperitoneal leiomyosarcoma whose origin in the inferior vena cava was only confirmed by histological examination of the resection specimen. Surgical resection was followed by radiotherapy (4,500 rads) with a favourable course after 12 months. The progress in medical imaging and histology has considerably simplified the diagnosis of these rare retroperitoneal tumours. In the absence of any truly effective adjuvant therapy, treatment essentially consists of surgery and the clinical course is characterised by a high incidence of local recurrences.

Humans↗
PubMed1991

[Prognostic factors of success in renal transplantation].

From January 1984 to January 1989, 139 kidneys were retrieved from 74 brain dead donors in our institution. The transplantation was performed either locally (79), or in an other French institution (40). The five year actuarial survival rate, for the 139 kidneys retrieved in Montpellier, was 65 percent. Many factors about the donor, the retrieval and the recipient, which may affect the graft survival, were entered in a Cox multivariate analysis. The minimal follow up duration was 18 months. The risk factors studied included: donor parameters (age, sex, cause of death, haemodynamic parameters and renal function); retrieval parameters (kidney alone or multiorgan harvesting, discoloration and renal perfusion quality); organ characteristics (multiple arteries and cold ischemia time); recipients parameters (age, sex, prior transplantation, local transplantation or not, and HLA matching). A first multivariate analysis included only pretransplant risk factors. The risk factors for graft loss, as identified by the Cox model, were in the order: donor's age (P = 0.03), arterial pressure (P = 0.01), prior transplantation of the recipient (P = 0.01) and kidney discoloration quality during the retrieval (P = 0.008). Early post transplant parameters were included within this Cox model (poor early renal function, need for dialysis, serum creatinine level at one week). The need for dialysis therefore was identified as the main predictive value (P = 0.002). The 4 other risk factors, selectioned in the first model, always remained significant.

Actuarial Analysis↗
PubMed1991

The MAT locus revisited within a 9.8 kb fragment of chromosome III containing BUD5 and two new open reading frames.

This paper reports the DNA sequence of a segment of 9.8 kb of the chromosome III. The sequenced DNA contains the MAT alpha locus. The new sequence of the MAT alpha locus differs from the previously reported sequence by six modifications in the W segment. We have found the same modifications in the HML locus. The corrected sequence contains, in HML, an open reading frame (ORF) of 190 codons which ends at the border between the W segment and the flanking DNA. In the MAT locus, this ORF extends in the flanking DNA up to 538 codons. This ORF corresponds to a gene independently identified as BUD5 (Chant et al., 1991). This gene presents homologies with the exchange factors SDC25 and CDC25. A large ORF of 1399 codons is found on the opposite side of MAT alpha (toward the telomere). This ORF corresponds to a new gene YCR724. Next to this gene is a small ORF, YCR725, of 127 codons. The localization of this fragment on chromosome III, originally supposed to be distal from the MAT locus based on genetic distance, illustrates variation in recombination frequency along the chromosome and suggests the existence of hot spots of recombination between MAT and the THR4 locus.

Base Sequence↗
PubMed1988

The promoter of the beta-glucosidase gene from Kluyveromyces fragilis contains sequences that act as upstream repressing sequences in Saccharomyces cerevisiae.

The relationship between the promoter length of the Kluyveromyces fragilis beta-glucosidase gene and the level of its expression in Saccharomyces cerevisiae was studied by gene fusion between deleted promoter fragments of various lengths and the promoterless beta-galactosidase gene of Escherichia coli. The removal of a region from position -425 to -232 led to a tenfold increase in the expression of the gene. The same results were obtained for the reconstructed beta-glucosidase gene with the same promoter length. It is likely that the deletion of this part of the promoter removes negative regulatory elements which are functional in Saccharomyces cerevisiae. This increase in activity is the main event which may explain the high increase in gene expression (60-fold) previously observed for an upstream deletion obtained during subcloning experiments of the beta-glucosidase gene. It is also shown that the expression of the gene greatly depends upon the nature of the recipient strain, the growth phase of the cell and that of the vector carrying it.

Base Sequence↗
PubMed1985

Elongation factor 1 alpha from Saccharomyces cerevisiae. Rapid large-scale purification and molecular characterization.

Cytoplasmic elongation factor 1 alpha (EF-1 alpha) was purified to homogeneity from the yeast Saccharomyces cerevisiae using a large-scale procedure. The three steps of purification used were batch adsorption on phosphocellulose, phosphocellulose chromatography and, as the last step, GDP-Sepharose or Biorex column chromatography. The protein is very basic (pI = 9.2) and has an apparent molecular mass of 49 kDa, as determined by polyacrylamide gel electrophoresis using denaturing conditions. It is one of the most abundant proteins in yeast (about 5% of total soluble protein), as shown by two-dimensional gel electrophoresis and by immunological titration. A strong immunological and structural homology was found between yeast EF-1 alpha and elongation factors from other sources. Common immunological features were found between yeast and wheat germ EF-1 alpha. Tryptic hydrolysis of yeast EF-1 alpha in the presence of 25% glycerol generated a large trypsin-resistant polypeptide (Mr = 43,000) which had the same NH2-terminal sequence as the proteolyzed product from rabbit reticulocyte, Artemia salina EF-1 alpha and Escherichia coli EF-Tu. Completed DNA sequence determination of one structural gene for yeast EF-1 alpha confirmed a remarkable conservation of several protein sequence domains in yeast and animal EF-1 alpha (Cottrelle, P., Thiele, D., Price, V., Memet, S., Micouin, J.Y., Marck, C., Buhler, J.M. Sentenac, A., and Fromageot, P. (1985) J. Biol. Chem. 260, 3090-3096).

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

Localization of the upstream regulatory sites of yeast iso2-cytochrome c gene.

In order to study the regulation of expression of the iso2-cytochrome c gene, we have constructed a fused gene between the 5'flanking region of the gene coding for the yeast iso2-cytochrome c and the coding region of the E. coli beta-galactosidase lacZ gene. When introduced in yeast cells this hybrid gene is expressed and regulated like the production of iso2-cytochrome c: it is under the control of the general catabolic repression and of the unlinked trans-acting CYP1 gene whose CYP1-18 allele causes an overproduction of iso2-cytochrome c. The expression of hybrid genes whose upstream region has been progressively shortened or altered by internal deletions was studied either in wild-type CYP1+ cells or in cells carrying the CYP1-18 allele grown either on glucose or on glycerol. It appears that the expression and the regulation of the iso2-cytochrome c gene is controlled by an upstream regulatory site composed of a positive and a negative element. This site is the target of regulation by the CYP1 gene product and, directly or through this gene, of the control by the general catabolic repression.

Base Sequence↗
PubMed1979

Identification of two different RNase H activities associated with yeast RNA polymerase A.

Two ribonuclease H activities have been found in yeast RNA polymerase A. The nuclease activities comigrated with subunits A49 (Mr = 49,000) and A40 (Mr = 40,000), after electrophoresis in a sodium dodecyl sulfate polyacrylamide gel containing [32P](rG)n . (dC)n as substrate. Both activities were also found, among other nucleases, in a high salt chromatin extract. Several lines of evidence suggest that the chromatin RNase H of 49,000 daltons (RNase H49) is the same protein as subunit A49. They co-migrate on sodium dodecyl sulfate-gel electrophoresis, have the same chromatographic properties, and dissociate simultaneously from RNA polymerase A. Fractions containing RNase H49 stimulate RNA synthesis by RNA polymerase A* lacking A49 and A34.5 subunits. Finally, limited proteolysis of the protein band having RNase H49 activity yields the characteristic fingerprint of the A49 subunit. This subunit, therefore, exists in two states: bound to chromatin and associated with RNA polymerase A. On the other hand, it is not yet clear whether the RNase H activity of 40,000 daltons, associated with RNA polymerase A, is due to the A40 subunit or whether it represents a trace contamination by a very active nuclease tightly bound to the enzyme.

Chromatin↗
PubMed1976

Structural studies on yeast RNA polymerases. Existence of common subunits in RNA polymerases A(I) and B(II).

The subunits of yeast RNA polymerases A(I) and B(II) were characterized using several techniques. The present studies demonstrate that the A and B enzymes possess three subunits, which are indistinguishable on the basis of molecular weight, isoelectric point, and fingerprint pattern. The three common subunits belong to the small molecular weight components of the enzymes. By polyacrylamide gel electrophoresis with sodium dodecyl sulfate they migrate with apparent molecular weights of 27,000, 23,000, and 14,500, respectively. A two-dimensional subunit mapping technique on polyacrylamide gel was used to separate the subunits according to isoelectric point and molecular weight. The common polypeptides co-migrated on three spots corresponding to isoelectric points of 9.2 (27,000), 4.5 (23,000), and 4.6 (14,500). The fingerprints of the 35S-labeled tryptic peptides of the presumptive common subunits were found to be essentially identical. Finally, the presence of common subunits was supported by the fact that antibodies against pure RNA polymerase A cross-react with and inhibit RNA polymerase B. Except for the common subunits, it is likely that RNA polymerases A and B are primarily made of distinct gene products for the following reasons. A total of 13 polypeptide chains are present in enzyme A, whereas 10 polypeptides are found in enzyme B. The molecular weight, isoelectric point, and sulfur content of the majority of these polypeptide chains are different in the two enzymes. No similarity was found in the 35S-peptide fingerprint from a number of A and B subunits of slightly different molecular weight. Finally, antibodies against the largest subunit from RNA polymerase A do not cross-react with or inhibit RNA polymerase B. The data are discussed in terms of structural organization of eukaryotic RNA polymerases.

DNA-Directed RNA Polymerases↗
PubMed1976

Further characterization of yeast RNA polymerases. Effect of subunits removal.

Two forms of yeast RNA polymerase A are resolved by phosphocellulose chromatography. One of these, called RNA polymerase A, is lacking two polypeptide chains of 48,000 and 37,000 daltons. The properties of the two enzymes are compared in the present paper. RNA polymerase A transcribes d(A-T)n with a similar efficiency as the complete enzyme, but it is comparatively much less active with native DNA. The two enzymes can also be differentiated on the basis of their ionic strength and divalent cation requirements. RNA polymerase A has a particularly low activity at high salt and low Mg2+ concentrations. Thermal inactivation curves of the two enzymes are different when residual activity is assayed with native DNA. In contrast with d(A-T)n as template the apparent inactivation curves of the two enzymes are identical. The data suggest that the two dissociable polypeptide chains play an important role in transcription. The template specificity of yeast RNA polymerase B was further investigated using SV40 DNA-FI as template. RNA polymerase B is able to retain [3H]SV40 DNA-FI on nitrocellulose filters but the enzyme-DNA complex is very unstable. The observation that RNA polymerase B can transcribe to some extent a supercoiled DNA but not a linear double stranded template supports the hypothesis that the enzyme needs some unpaired DNA structure to initiate transcription.

Cations, Divalent↗
PubMed1975

Structure-activity relationships in tryptophanyl transfer ribonucleic acid synthetase from beef pancreas. Influence of the alkylation of the sulfhydryl groups on the dimer-monomer equilibrium.

Upon reaction with N-ethylmaleimide, tryptophanyl-tRNA synthetase from beef pancreas dissociates into subunits. At pH7, the rate of the dissociation is close to both the reaction rate of the buried--SH groups and the rate of inactivation (Iborra, F., Mourgeon, G., Labouesse B., and Labouesse, J. (1973) Eur. J. Biochem. 39, 547-556). The pH and enzyme concnetration dependences of the reaction rate of the 16 cysteinyl residues of the enzyme as well as that of its inactivation support the idea that inactivation by alkylation of the--SH groups is due essentially to the dissociation of the protein into inactive subunits and not to the chemical blocking of a catalytic residue. This is confirmed by the independence on N-ethylmaleimide concentration of the reaction of the buried--SH groups and of the inactivation of the enzyme at high N-ethylmaleimide concentration. The dissociation becomes in this case the rate-limiting step of the chemical reaction. The monomeric structure is stabilized by the blocking of the--SH groups exposed during the dissociation. The dissociation constant of the dimeric enzyme is progressively increased during the alkylation. The tightness of the associated structure depends on the protonation of groups titrating between pH 7 and pH 9.

Amino Acyl-tRNA Synthetases↗
PubMed1975

Molecular aspects of the inactivation of tryptophanyl transfer ribonucleic acid synthetase by N-ethylmaleimide.

The tryptic maps of tryptophanyl-tRNA synthetase from beef pancreas show that the 8 cysteinyl residues of the enzyme subunit are located, 2 by 2, on four different peptides. The kinetics of the incorporation of radioactivity from N-[ethyl-14C]ethylmaleimide into these peptides are compared in this paper with the kinetics of the changes of the catalytic properties of the enzyme occurring during alkylation. This comparison allows the identification of (a) the peptide carrying the cysteinyl residues located on the surface of the molecule, (b) the peptide carrying the deeply buried residues unmasked by the dissociation of the subunits, and (c) the peptide carrying the --SH group located in the vicinity of the binding site of tryptophan. The fourth peptide is shown to have a great sensitivity to pH with respect to the reactivity of its cysteinyl residues toward N-ethylmaleimide. The same unusual pH dependence is found for the rate of quenching of the intrinsic fluorescence of the protein during the alkylation, suggesting a strong sensitivity of the conformation of tryptophanyl-tRNA synthetase to pH in the range of 7 to 9.

Amino Acid Sequence↗