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Biomedical subjects

P Stiegler

Publications and source records attributed to P Stiegler.

At least 19 recordsLinked to original sources
PubMed2006

Hyperbaric oxygen in tinnitus: influence of psychological factors on treatment results?

INTRODUCTION: The standard treatment of subjective tinnitus hardly reaches the level of placebo controls. Though the effectiveness of hyperbaric oxygenation (HBO) for subjective tinnitus has never been objectified, it is still advocated by some institutions. We analyzed the effectiveness of hyperbaric oxygen treatment in the context of accompanying factors. PATIENTS AND METHODS: We randomized 360 patients suffering from tinnitus into 2 HBO treatment protocols (group A: 2.2 bar for 60 min bottom time and group B: 2.5 bar for 60 min bottom time once a day for 15 days). All patients were asked to fill in a questionnaire (social and medical history, tinnitus characteristics, pre-HBO duration of tinnitus, prior therapy, pretreatment expectation, accompanying symptoms). A subjective assessment of the therapeutic effect was obtained. RESULTS: Twelve patients (3.3%) experienced complete remission of tinnitus, in 122 (33.9) the intensity lessened, and 44 (12.2%) had a subjectively agreeable change of noise characteristics. No change was found in 157 cases (43.6%) and 25 (6.9%) experienced deterioration. There was no statistically significant difference between groups A and B (p > 0.05). Out of 68 patients with a positive expectation of HBO effects, 60.3% stated that the tinnitus had improved whereas only 47.2 and 19%, respectively, out of patients who underwent therapy with an indifferent (n = 271) or negative expectation (n = 21) reported an improvement. The influence of subjective expectation on the outcome was statistically significant (p < 0.05). CONCLUSION: The therapeutic effects of HBO on subjective tinnitus may be substantially influenced by psychological mechanisms.

Major Depressive Disorder↗
PubMed2003

[Surgery of the saphenous-popliteal junction: a delicate procedures with potential risks].

UNLABELLED: The authors evaluate the results achieved in two groups of patients operated on for varicose veins in small saphenous vein (SSV) territory in 3 year interval. In the first group gathered from January to December 1998 (114 patients--36 men and 78 women, 123 procedures--118 primary and 5 re-do) the operative indication was based on the clinical examination and continual doppler evaluation. These patients were operated on in general, spinal or local and flash general anaesthesia. In the second group gathered in the same period of the year 2001 (72 patients--21 men and 51 women) 75 procedures were performed (3 patients with bilateral operation). In this group, 49 patients with 50 procedures were selected. The diagnosis was based not only on clinical and continuous doppler examination, but mainly on colour flow duplex mapping. The operation was performed on strictly ambulatory basis using pure local anaesthesia completed with small dose of sedation. Any patient needed complementary sclerotherapy one month after procedure. In mid-term follow-up complementary conservative treatment was necessary in 51 p.c. of the whole series. CONCLUSION: Use of colour coded duplex ultrasound in preoperative evaluation of varicose veins patients enabled us to precise preoperative diagnosis, to diminish the number of aggressive surgical procedures in favour of less traumatic operations and to perform this surgery on ambulatory basis. Nevertheless, small sahenous vein surgery still remains delicate and sometimes also hazardous.

Adolescent↗
PubMed2001

Identification of interaction partners for two closely-related members of the ETS protein family, FLI and ERG.

Fli and erg are two members of the ETS gene family that encodes transcription factors related to the c-ets-1 proto-oncogene. The products of the ETS genes act as transcriptional effectors in cell proliferation, differentiation, and oncogenic transformation. FLI and ERG, two closely-related proteins, bind, as do all the ETS proteins characterized so far, to DNA sequences with an invariable central GGA core flanked by preferred nucleotides. Nevertheless, promoter-specific responses to FLI or ERG may be driven by mechanisms involving multicomponent complexes. Using a yeast two-hybrid screen, we have identified several proteins that physically interact with either FLI or ERG proteins used as bait. The Xenopus developmentally implicated Xvent-2 and Xvent-2B proteins, and the Xenopus splicing factor RNP-C/U1C physically interact with Xl-FLI and Xl-ERG, both in the yeast two-hybrid system and in vitro. We also report the potential interaction of FLI and ERG with Sox-D, a stabilizing protein that may modulate their transcriptional activity. Furthermore, the possible involvement of the transcriptional effectors FLI and ERG in mRNA processing, hematopoiesis or in the control of angiogenesis is suggested through possible interactions with, respectively, RNA binding proteins and hnRNPs, a repressor of the hematopoietic pathway (SAP18), and the HAF protein.

Animals↗
PubMed2001

RB2/p130 gene-enhanced expression down-regulates vascular endothelial growth factor expression and inhibits angiogenesis in vivo.

Angiogenesis is an essential step in the progression of tumor formation and development. The switch to an angiogenetic phenotype can occur as a distinct step before progression to a neoplastic phenotype and is linked to genetic changes such as mutations in key cell cycle regulatory genes. The pathogenesis of the angiogenetic phenotype may involve the inactivation of tumor suppressor genes such as the "guardian of the genome," p53, and the cyclin-dependent kinase inhibitor p16. Retinoblastoma family member RB2/p130 encodes a cell cycle regulatory protein and has been found mutated in different tumor types. Overexpression of RB2/p130 not only suppresses tumor formation in nude mice but also causes regression of established tumor grafts, suggesting that RB2/p130 may modulate the angiogenetic balance. We found that induction of RB2/p130 expression using a tetracycline-regulated gene expression system as well as retroviral and adenoviral-mediated gene delivery inhibited angiogenesis in vivo. This correlated with pRb2/p130-mediated down-regulation of vascular endothelial growth factor protein expression both in vitro and in vivo.

Animals↗
PubMed2001

pRb2/p130 and p107 control cell growth by multiple strategies and in association with different compartments within the nucleus.

It has been recently reported that retinoblastoma family proteins suppress cell growth by regulating not only E2F-dependent mRNA transcription but also rRNA and tRNA transcription and, through HDAC1 recruitment, chromatin packaging. In the present study we report data showing that these various control strategies are correlated, at least in part, with nuclear compartmentalization of retinoblastoma proteins. In a first series of experiments, we showed that pRb2/p130 and p107 are not evenly distributed within the nucleus and that cell cycle-dependent binding with E2F4 changes also as a function of their subnuclear localization. Namely, in the nucleoplasm pRb2/p130-E2F4 complexes are more numerous during G0/G1 while in the nucleolus they increase in S phase. Partially different functions for p107 are suggested since p107-E2F4 complexes in the nucleoplasm are more numerous is S phase with respect to G0/G1 and no cell cycle change is observed in the nucleolus. In a second series of experiments we showed that pRb2/p130, p107, E2F4, and pRb2/p130-HDAC1 complexes are all inner nuclear matrix-associated proteins and localize to sites different from pRb/p105 ones. We provide further evidence of multiple and partially distinct retinoblastoma protein family functional roles during cell cycle. Moreover, our data support emerging evidence for functional interrelationships between nuclear structure and gene expression.

Cell Compartmentation↗
PubMed2001

Class I histone deacetylases sequentially interact with MyoD and pRb during skeletal myogenesis.

We describe a functional and biochemical link between the myogenic activator MyoD, the deacetylase HDAC1, and the tumor suppressor pRb. Interaction of MyoD with HDAC1 in undifferentiated myoblasts mediates repression of muscle-specific gene expression. Prodifferentiation cues, mimicked by serum removal, induce both downregulation of HDAC1 protein and pRb hypophosphorylation. Dephosphorylation of pRb promotes the formation of pRb-HDAC1 complex in differentiated myotubes. pRb-HDAC1 association coincides with disassembling of MyoD-HDAC1 complex, transcriptional activation of muscle-restricted genes, and cellular differentiation of skeletal myoblasts. A single point mutation introduced in the HDAC1 binding domain of pRb compromises its ability to disrupt MyoD-HDAC1 interaction and to promote muscle gene expression. These results suggest that reduced expression of HDAC1 accompanied by its redistribution in alternative nuclear protein complexes is critical for terminal differentiation of skeletal muscle cells.

Animals↗
PubMed2001

The family of retinoblastoma proteins.

Our understanding of how the retinoblastoma family members, pRB/p105, pRB2/p130, and pRBL1/p107, regulate cellular properties has progressed significantly. Mechanisms have been described regarding how these proteins utilize properties of additional factors, such as histone deacetylases, to negatively regulate transcription. More importantly, the retinoblastoma proteins have been integrated within multiple cellular pathways, and a complex view has emerged on how the individual members respond to various external and internal stimuli. pRB/p105 is best described in its biochemical properties as well as in the resulting cellular functions. Less is known about pRB2/p130 and pRBL1/p107, but an improved map of their individual as well as redundant functions has been drawn over the last years. In this review we describe general aspects of the properties and functions of the three retinoblastoma family members and their protein-binding partners in cellular growth control.

Amino Acid Motifs↗
PubMed2000

Inducible pRb2/p130 expression and growth-suppressive mechanisms: evidence of a pRb2/p130, p27Kip1, and cyclin E negative feedback regulatory loop.

The retinoblastoma family of proteins, pRb/p105, p107, and pRb2/ p130, cooperate to regulate cell cycle progression through the G1 phase of the cell cycle. Each of the family members realize their common goal of G1-S checkpoint regulation through overlapping and unique growth regulatory pathways. We took advantage of a tetracycline-regulated gene expression system to control the expression of RB2/p130 in JC virus-induced hamster brain tumor cells to study in vivo the molecular mechanisms used by pRb2/p130 to elicit its growth-suppressive function. We have previously used this system to demonstrate that induction of pRb/ p130 expression suppresses tumor growth in vivo by overcoming neoplastic transformation mediated by the large T-antigen oncoprotein of JCV (JCV TAg). Here we found that induction of pRb2/p130 in vivo specifically inhibits cyclin A- and cyclin E-associated kinase activity and by doing so induces p27Kip1 levels presumably by inhibiting p27Kip1-targeted proteolysis by cyclin E-Cdk2 phosphorylation of p27Kip1. RB2/p130 induction also decreased cyclin A and the transcription factor E2F-1 while increasing cyclin E at both the transcriptional and protein levels of expression. The growth inhibitory activity of pRb2/p130 also correlated with its E2F-binding capacity. Furthermore, p27Kip1 and pRb2/p130 were found to be targets of the JCV TAg oncoprotein and to interact in vivo with each other independently from the presence of TAg. Interestingly, pRb2/p130 expression negatively modulated the binding of p27Kip1 to JCV TAg. These data suggest that pRb2/p130 and p27Kip1 may cooperate in regulating cellular proliferation, and both may be involved in a negative feedback regulatory loop with cyclin E.

Animals↗
PubMed2000

International conference on basic and clinical aspects of cell-cycle control.

Scientists of numerous medical and life science disciplines met in Siena, Italy to discuss the latest proceedings in basic and clinical research. General models of interconnected linear and back-feeding cell-cycle control pathways provide a basis for applied molecular research. Cell-cycle determining factors essential for the control of cellular homeostasis either become markers to determine characteristics of a disease and/or become therapeutic targets. Apart from animal and tissue culture models, molecular theories finally have to stand proof in clinical application and evaluation. Therefore, the clinical feedback to the basic scientist's bench is essential for necessary adjustments of their models to improve future approaches to research challenges. A select group of speakers provided the audience with such an interdisciplinary dialogue at the first International Conference on Basic and Clinical Aspects of Cell-Cycle Control from May 29 to 31, 2000 in Siena, Italy.

Animals↗
PubMed2000

Genomic organization, promoter analysis, and chromosomal mapping of the mouse gene encoding Cdk9.

Cdk9, previously known as PITALRE, belongs to the Cdc2 family of protein kinases. We report the isolation and characterization of the complete gene coding for the murine Cdk9 protein. The gene contains seven exons spanning over 6 kb of genomic DNA, and the exon/intron boundaries conformed to the GT/AG rule. The Cdk9 gene mapped on mouse chromosome 2, which is consistent with the known region of synteny with human chromosome 9q34.1. The length of the individual exons ranged from 82 to 850 bp, and introns ranged from 452 to 1,465 bp. The further 5' flanking region of the gene showed features of a housekeeping promoter, such as the lack of a canonical TATA box and the presence of a CCAAT box as well as several GC boxes, which are potential binding sites for numerous transcription factors. Additionally, we performed a basic analysis of the transcriptional activity of the promoter and found that the 364 bp of Cdk9 5' flanking region were able to elicit high transcriptional levels of a luciferase reporter gene in NIH3T3 cells. This study provides the molecular basis for understanding the transcriptional control of the Cdk9 gene, and could serve to facilitate the molecular genetic investigation of Cdk9 function during mouse embryonal development.

3T3 Cells↗
PubMed1999

From cell cycle regulation to angiogenesis: dialogue between the basic and clinical sciences.

Basic research in biological and medical disciplines has revealed fundamental aspects of the differentiation of single cells as well as the development of multicellular organisms. The combination of knowledge of intracellular and intercellular pathways controlling development and homeostasis in higher organisms is the key to understanding certain diseases that are associated with abnormalities in these pathways and developing strategies for fighting them. Today's high scientific output in a rapidly growing number of scientific journals requires great effort to keep up with the latest developments outside one's specialization. The tenth international conference of the International Society of Differentiation (ISD) therefore was a great opportunity for scientists of diverse fields of biological and medical research to learn about the latest developments in even remotely related branches of research and opening new perspectives. The authors have tried to conserve this spirit in reviewing main aspects of research presented at the conference.

Apoptosis↗
PubMed1999

Role of pRB2/p130 in cellular growth regulation.

Cellular growth control in multicellular organisms has been shown to be essential to maintaining homeostasis. The retinoblastoma family of tumor suppressor proteins, pRB, p107 and pRB2/p130, encode proteins that act as transcriptional repressors of cell cycle-regulating and -promoting genes. The three proteins share similar and overlapping, yet distinctive, structural and functional features. Obvious differences are time and regulation of expression and the regulation of the functionality of pRb, p107 and pRB2/p130 by phosphorylation. PRB2/p130 is unique in that it is preferentially expressed and active in differentiated and silenced cells. This review discusses retinoblastoma family protein functions and the role of pRB2/p130 in cellular regulation.

Cell Cycle↗
PubMed1998

The COOH-terminal region of pRb2/p130 binds to histone deacetylase 1 (HDAC1), enhancing transcriptional repression of the E2F-dependent cyclin A promoter.

The tumor suppressor retinoblastoma protein family members pRb, p107, and pRb2/p130 are potent negative transcriptional regulators. The best understood target is the transcription factor E2F, which activates cell cycle-dependent transcription of genes controlling and promoting the cell division cycle (e.g., cyclin A). pRb2/p130 is known to be important in implementing cell cycle exit into G0 due to serum deprivation or various differentiation programs. Several recent studies demonstrated the effect histone acetylases and histone deacetylases (HDACs) have on fine-tuning transcriptional regulation of eucaryotic cells. In this study, we demonstrate that pRb2/p130 binds to HDAC1. This interaction increases the ability of pRb2/p130 to inhibit transcription of the E2F-dependent cyclin A promoter in vivo. We also identify the COOH-terminal 35aa as being necessary for stable interaction between HDAC1 and pRb2/p130.

3T3 Cells↗
PubMed1998

Pacing-induced heart failure in dogs enhances the expression of p53 and p53-dependent genes in ventricular myocytes.

BACKGROUND: Rapid ventricular pacing in dogs is characterized by a dilated myopathy in which myocyte cell death by apoptosis may play a significant role in the impairment of cardiac pump function. However, the molecular mechanisms implicated in the modulation of programmed cell death under this setting remain to be identified. Moreover, questions have been raised on the specificity and sensitivity of the histochemical detection of DNA strand breaks in nuclei by the terminal deoxynucleotidyl transferase (TdT) reaction. METHODS AND RESULTS: Changes in the expression of Bcl-2 and Bax and their transcriptional regulator, p53, were determined by Western blot analysis in myocytes isolated from dogs affected by pacing-induced heart failure. A mobility shift assay for p53 binding activity was also performed. In addition, apoptosis was measured by confocal microscopy, which allowed the simultaneous detection of chromatin alterations and DNA damage. p53 DNA binding activity to the bax promoter was increased in nuclear extracts from myocytes obtained from failing hearts, and this response was associated with enhanced expression of Bax protein, 52%, and attenuation of Bcl-2, -92%. Immunolabeling of p53 in myocyte nuclei, measured by confocal microscopy, was 100% higher in cells from paced hearts. The combination of the TdT assay and confocal microscopy demonstrated that 20 myocyte nuclei per 10(6) were undergoing apoptosis in control myocardium and 4000 per l0(6) after pacing. Moreover, DNA laddering was shown in myocytes by agarose gel electrophoresis of DNA fragments. CONCLUSIONS: The activation of p53 and p53-dependent genes may be critical in the modulation of myocyte apoptosis in pacing-induced heart failure.

Animals↗
PubMed1998

The avian fli gene is specifically expressed during embryogenesis in a subset of neural crest cells giving rise to mesenchyme.

The ets-family of transcription factors is involved in the development of endothelial and hematopoietic cells. Among these genes, fliwas shown to be responsible for erythroblastomas and Ewing's sarcomas. Its involvement in Ewing's sarcoma, a putative neurectodermal tumor, as well as the in situ hybridization studies performed in mice and Xenopus suggested a role in neural crest development. We cloned quail fli cDNA in order to analyze in more detail its expression in neural crest cells, which have been extensively studied in avian species. Fli gene maps on chicken chromosome 1 to band q31->q33. Two RNAs are transcribed, most likely arising from two different promoters. The analysis of its expression in neural crest cells reveals that it is expressed rather late, when the neural crest cells reach their target. Among the various lineages derived from the crest, it is restricted to the mesenchymal one. It is maintained at later stages in the cartilage of neural crest but also of mesodermal origin. In addition, fli is expressed in several mesoderm-derived cells: endothelial cells as well as intermediate and splanchnopleural mesoderm.

Amino Acid Sequence↗
PubMed1998

The RB family of cell cycle regulatory factors.

The intense investigation of the retinoblastoma "tumor suppressor family" members, pRb, pRb2/p130, and p107, has revealed impressive mechanisms evolved to safeguard development and homeostasis in higher eukaryotes. Members of the retinoblastoma family are involved in implementing and controlling three major aspects of cellular life: (1) proliferative growth, (2) differentiation, and (3) apoptosis. The activities of these proteins are highly regulated, enabling them to precisely establish control. The pRb protein is well understood in its regulatory abilities and is considered a classical tumor suppressor. The role of pRb2/p130 protein in growth suppression and its potential as a tumor suppressor have been established during the last few years. The p107 protein, structurally and functionally similar to, but yet distinctive from, pRb2/p130, is characterized at a more rudimentary level. In this report, we review the latest data on the retinoblastoma protein family and its web of regulatory mechanisms.

Animals↗
PubMed1997

Mouse thymidine kinase stability in vivo and after in vitro translation.

Using a combination of centrifugal elutriation and recultivation of synchronised cell populations we could show that murine thymidine kinase (TK) is rapidly degraded during mitosis in polyoma virus-transformed mouse fibroblasts, in parallel to the time-course for loss of cyclin A. Transformation is no prerequisite for the instability phenotype since artificial overexpression of TK under the control of a constitutive promoter in normal mouse fibroblasts also resulted in rapid turnover of TK during mitosis. The decay of TK protein could be partially mimicked in vitro with enzymatically active protein translated in a rabbit reticulocyte lysate: full length polypeptide was lost slightly more rapidly in the presence of G2/M cytosolic extracts than with G1/S preparations. In addition, an enzymatically active C-terminal truncation of 37 amino acids at Gln-196 was completely stable under the conditions tested, confining the instability domain between residues 196 to 233. These experiments also indicated the border for intact TK since translation products up to Tyr-189 or less were completely inactive. This was also confirmed by a mutant TK protein from mouse F9tk- teratocarcinoma cells which harboured a similar deletion.

Animals↗