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Biomedical subjects

P Stiegler

Publications and source records attributed to P Stiegler.

At least 37 records · Page 2Linked to original sources
PubMed1997

Polyomavirus large T antigen-dependent DNA amplification.

DNA amplification is a readily measurable indicator for genome destabilization. Contrary to normal senescing cells, those of most immortal or transformed cell lines are karyotypically unstable and permissive for amplification. Permissivity for amplification can be generated by gene products of several DNA tumor viruses whereby their interaction with the tumorsuppressor protein p53 is important. p53 is the major protein involved in check point control of DNA damage. Polyomavirus large T antigen is also involved in immortalization and transformation of cells but it does not interact with p53. We, therefore, examined whether this protein could still make the non-permissive cell line REF52 permissive for gene amplification. To this end REF52 cell lines were constructed which conditionally expressed the wild type polyomavirus large T antigen or a mutant form unable to bind the retinoblastoma protein. Using the inhibitor of de novo pyrimidine biosynthesis, phosphonoacetyl-L-aspartate (PALA), as selective agent we found that PALA resistant cells arise with a frequency of about 5 x 10(-5) and that the interaction of polyomavirus large T protein with the retinoblastoma protein or another related pocket protein is important for this to occur. PALA resistant cells have an increased number of chromosomes and dicentric chromosomes which are considered as starting point for DNA structures characteristic for amplified DNA. Such structures were indeed found with the help of fluorescence in situ hybridization. PALA resistant cells appear normal with respect to p53. Our data indicate that PALA induces a G1 block which can be partially overcome by polyomavirus large T protein by its interaction with E2F-pocket protein complexes providing further evidence that these complexes are downstream targets of p53.

Animals↗
PubMed1997

Mojave rattlesnake envenomation in southern California: a review of suspected cases.

To clarify whether Mojave rattlesnake (Crotalus scutulatus scutulatus) envenomations occurring in California cause typical crotalid tissue effects, pain, edema, and ecchymosis, we reviewed charts of snakebite victims at a tertiary care teaching hospital and a moderate-size community hospital. Forty-two patients were bitten within the range of Mojave rattlesnakes. Eight snakes were identified as Mojave rattlesnakes (group 1); of these, four were confirmed by experts in snake identification (group 1a). Fifteen patients were reported bitten by other rattlesnake species (group 2), and in 19 envenomations the species was unknown (group 3). Seventy-five percent of patients in group 1 were reported to have local edema at the envenomation site compared with all of the patients in group 2. Ecchymosis was found in 25% of group 1 patients and 73% of group 2 patients. Pain was documented in only 12% of group 1 and 67% of group 2 victims. Neurotropic events, many severe, were found in 75% of group 1 patients compared with 7% of those in group 2. Although this study does not have the power to justify statistical evaluation, C. scutulatus envenomations do appear inclined to less tissue reaction. A disturbing trend toward severe neurotropic manifestations was also suggested in presumed Mojave rattlesnake envenomations.

Adolescent↗
PubMed1995

Whole-mount in situ hybridization reveals the expression of the Xl-Fli gene in several lineages of migrating cells in Xenopus embryos.

The expression of the Xl-Fli gene, which belongs to the ets family of transcription factors, was studied by whole-mount in situ hybridization during Xenopus embryogenesis. Digoxigenin-labeled antisense RNA probes were synthesized by in vitro transcription and used in the hybridization reaction. In addition to expression in territories invaded by neural crest cells reported earlier (Meyer et al., 1993), we observed Xl-Fli gene expression in a number of regions affected by important cellular migrations and/or epithelium<==>mesenchyme transitions: in the endothelial cells of the heart, in blood vessels, along the pronephric duct migration pathway and at the level of hypophysis. The possibility that the FLI protein is involved in the expression of guidance cues and/or modification of the cellular adhesion properties is discussed. A screening of a promoter library with a consensus sequence, bound by the FLI protein with a high affinity, revealed the presence of putative FLI response elements in a number of genes encoding adhesion molecules or components of the extra-cellular matrix.

Animals↗
PubMed1993

The c-ets-1 proto-oncogenes in Xenopus laevis: expression during oogenesis and embryogenesis.

We previously reported the cloning and sequencing of two cDNAs derived from the Xenopus laevis ets-1 gene (Stiegler et al., 1990). The Xl-ets-1a cDNA encodes a polypeptide highly homologous to known ets-1 proteins. The 3'-UTR contains two AATAAA polyadenylation signals together with three copies of the TTTTTAT sequence thought to confer a maturation-specific polyadenylation and implicated in the deadenylation of dormant mRNAs. Several transcripts with maternal characteristics were detected in oogenesis and early embryogenesis. A marked augmentation of the major transcript in the poly(A)+ fraction was detected at fertilization. Ets-1 transcripts were observed at constant levels during the cleavage stages but decreased abruptly at gastrulation, to reappear from neurulation to late embryogenesis. The possible contribution of 3'-UTR sequence elements to this behavior is discussed.

Adenosine↗
PubMed1993

Xl-fli, the Xenopus homologue of the fli-1 gene, is expressed during embryogenesis in a restricted pattern evocative of neural crest cell distribution.

The Xenopus laevis fli cDNA, belonging to the ets family of transcription factors, was isolated from a library prepared from unfertilized eggs. It encodes a polypeptide with extensive homology to murine and human Fli proteins. The long 3'-untranslated region contains five nuclear polyadenylation signals and three cytoplasmic polyadenylation elements, as well as many A/T rich elements. Two polyadenylated transcripts appear at the early neurula and accumulate up to the tadpole stage. In situ hybridization reveals an expression in territories invaded by neural crest cells. In the head region, fli is expressed in the peri-ocular zone, in the branchial buds and at the level of the brain floor. In the trunk, a metamerized expression is detected in the dorsum. At a lower level, the tailbud and the peri-cardiac region also appear positive.

Animals↗
PubMed1992

Nucleotide sequence of the mitochondrial 5S rRNA gene from lupine (Lupinus luteus).

A lupine mitochondrial clone containing 5S rRNA gene is characterized. The gene is located on the same strand as 18S rRNA and separated from it by 190 nucleotides. The intergenic region in different plants shows high degree of homology. In the case of lupine and soybean 43 nucleotides upstream of 5S rRNA gene exhibits 100% of homology. Comparisons of lupine 5S rRNA gene sequence with other plant mitochondrial 5S rRNA genes displays high degree of homology (from 89.8% to 95.8%).

Animals↗
PubMed1991

Cloning, sequencing, and expression of two Xenopus laevis c-ets-2 protooncogenes.

In a general approach to identify genes important in the control of genetic expression during development of Xenopus laevis, two complementary DNAs corresponding to two different c-ets-2 genes were cloned and sequenced. One of these complementary DNAs appears to be almost full length. The two variant genes differ in their overlapping sequences by 87 nucleotide substitutions, leading to 17 amino acid modifications in the proteins, 8 of them being conservative. All but one of these changes map outside of the 142 COOH-terminal residues, a region critical for nuclear localization and DNA binding in the ets proteins. Features potentially important for the biological activity of the gene products are conserved. Two transcripts (3.2 and 1.7 kilobases) with maternal characteristics are detected at a constant level from stages II/III of oogenesis to stage 10 of embryogenesis. They later decline to hardly detectable levels at stages 30-40. Variable amounts of the same transcripts are observed in many adult tissues. All of these characteristics support the idea that the ets-2 gene products play an important role during embryogenesis, as well as in adult life. Indeed, they act as ubiquitous transcriptional activators, as recently demonstrated by several investigators (C. V. Gunther, J. A. Nye, R. S. Bryner, and B. J. Graves, Genes & Dev., 4: 667-679, 1990; R. Bosselut, J.F. Duvall, A. Gegonne, M. Bailly, A. Hemar, J. Brady, and J. Ghysdael, EMBO J., 9: 3137-3144, 1990; R. Wasylyk, C. Wasylyk, P. Florès, A. Bègue, D. Leprince, and D. Stéhelin, Nature (Lond.), 346: 191-193, 1990).

Amino Acid Sequence↗
PubMed1990

[Do we amputate too much or too little? A retrospective analysis of the situation in the East Bohemian Region].

A retrospective analysis of 1146 amputations of the lower extremities in five departments of the East Bohemin a region revealed that the number of amputations in the thigh is higher and less frequently preceded by angiographic examination and reconstruction operations of the arteries as compared with distinguished departments abroad. The mortality after amputations was 12.5%. The results call for more intensive training of vascular surgeons and the establishment of vascular surgical departments where it would be possible by early reconstruction operations made in time to prevent amputations or at least shift the height of the amputation in the most distal direction possible.

Amputation, Surgical↗
PubMed1987

Antigenic regions of ribosomal protein S1 as defined by monoclonal antibodies.

Analysis of the antigenic structure of the E. coli ribosomal protein S1 was undertaken using a set of 13 monoclonal antibodies (MAbs) directed against the isolated S1. The location of the epitopes was mapped using a series of large fragments and truncated forms of S1. Most of the epitopes were localized in the C-terminal half of the molecule, while only one antibody bound to the N-terminal region. Two MAbs were able to bind to more than one region of S1, suggesting the presence of repeated epitopes related to internal sequence homologies. Six distinct antigenic domains were identified by competitive binding assays. Competition between some antibodies suggested that the C-terminal region of S1 might be in spatial proximity with the N-terminal domain in the tertiary structure of the protein. The binding of a few MAbs induced conformational changes in the protein which resulted in the complete inhibition of antibody binding at non-adjacent sites. All the MAbs reacted with the isolated form of S1 or with the protein bound to the small ribosomal subunit. This indicated that the same epitopes were expressed in the two forms of the antigen and that they were accessible to antibody binding when S1 was part of the ribosomal subunit.

Animals↗
PubMed1986

Rapid separation of Escherichia coli 30S ribosomal proteins by fast protein liquid chromatography (FPLC).

The proteins of the 30S ribosomal subunit from Escherichia coli have been separated by reverse-phase high-performance liquid chromatography on a short alkyl chain (C1/C8)-coated phase. The reverse-phase column was connected to a fast protein liquid chromatography (FPLC) system. The 21 proteins of the 30S ribosomal subunit were resolved into 16 peaks. Eleven proteins were isolated in purified form in a single chromatographic run as shown by polyacrylamide gel electrophoresis and amino acid analysis. Interestingly, the retention times of some proteins differed from the retention times observed on other reversed-phase support materials. The results show the speed and resolution of reverse-phase FPLC for both analytical and semi-preparative separations of 30S ribosomal proteins.

Amino Acids↗