Biomedical subjects

Jörg Fuchs

Publications and source records attributed to Jörg Fuchs.

29 records · Page 2Linked to original sources

PubMed2003

Division of the nucleolus and its release of CDC14 during anaphase of meiosis I depends on separase, SPO12, and SLK19.

Disjunction of maternal and paternal centromeres during meiosis I requires crossing over between homologous chromatids, which creates chiasmata that hold homologs together. It also depends on a mechanism ensuring that maternal and paternal sister kinetochore pairs attach to oppositely oriented microtubules. Proteolytic cleavage of cohesin's Rec8 subunit by separase destroys cohesion between sister chromatid arms at anaphase I and thereby resolves chiasmata. The Spo12 and Slk19 proteins have been implicated in regulating meiosis I kinetochore orientation and/or in preventing cleavage of Rec8 at centromeres. We show here that the role of these proteins is instead to promote nucleolar segregation, including release of the Cdc14 phosphatase required for Cdk1 inactivation and disassembly of the anaphase I spindle. Separase is also required but surprisingly not its protease activity. It has two mechanistically different roles during meiosis I. Loss of the protease-independent function alone results in a second meiotic division occurring on anaphase I spindles in spo12delta and slk19delta mutants.

Anaphase↗

PubMed2003

Mesenterico-left portal vein bypass in children with congenital extrahepatic portal vein thrombosis: a unique curative approach.

OBJECTIVES: Current management of extrahepatic portal vein thrombosis (EPVT) comprises endoscopic eradication therapy of esophageal varices and conventional shunt surgery. The authors have used the novel technique of mesenterico-left portal bypass (Rex shunt) in seven children with symptomatic EPVT, and report their results here. METHODS: Median age of the children was 12 years (range, 2-16 years). All children had portal hypertension with hypersplenism and recurrent bleeding from esophageal varices. Furthermore, one patient suffered from a severe hepatopulmonary syndrome. Preoperative evaluation included liver function tests, liver biopsy, hepatic duplex ultrasonography, and radiologic evaluation of the intrahepatic and extrahepatic vascular anatomy. The internal jugular vein was used as vein graft in all patients. RESULTS: Median follow-up period was 15 months (range, 3-28 months). Ultrasound scans revealed sufficient perfusion in all shunts (median, 35 cm/s; range, 28-60 cm/s). The intrahepatic portal perfusion in segment 4 improved from a median of 6 cm/s before surgery to 18 cm/s postoperatively. The platelet count increased within 3 months from a mean of 50,625/microL to 137,750/microL. The clinical signs of hypoxemia in the child with hepatopulmonary syndrome disappeared within 6 months. CONCLUSIONS: In accordance with the limited experience published by others, the authors' data confirmed the mesenterico-portal Rex shunt as the therapy of choice for children with EPVT. Furthermore, this report is the first to show that a hepatopulmonary syndrome can be abolished by mesenterico-portal Rex shunt.

Adolescent↗

PubMed2003

Chromosome pairing does not contribute to nuclear architecture in vegetative yeast cells.

There are several reports of a closer-than-random colocalization of homologous chromosomes in the vegetative nuclei of diploid budding yeast. Here, we studied by fluorescence in situ hybridization (FISH) the nuclear distribution of chromosomes and found a slight tendency toward closer proximity between homologous (allelic) loci than between any nonhomologous chromosomal regions. We show that most of this preferential association is not due to vegetative (also known as somatic) pairing but is caused by the polar orientation of interphase chromosomes (Rabl orientation). We quantified the occasional loss of detectable fluorescence signals that is inherent to the FISH method. Signal loss leads to the occurrence of a single signal that may be misinterpreted as the close association of two homologous chromosomal sites. The nuclear distribution of homologous loci, when corrected for the influence of nuclear architecture and methodological faults, was not different or was only marginally different from a random relative positioning as predicted by computer simulation. We discuss here several possibilities for the residual homologous proximity that do not invoke homology-dependent vegetative pairing, and we conclude that, in diploid budding yeast, constitutive vegetative pairing is a negligible factor for the organization of the interphase nucleus.

Cell Nucleus↗

PubMed2002

The role of the MDR1 gene in the development of multidrug resistance in human hepatoblastoma: clinical course and in vivo model.

BACKGROUND: The P-glyprotein (P-gp), which is a membrane channel encoded by the MDR1 gene, represents a possible explanation for multidrug resistance in human hepatoblastoma (HB). P-gp shows up-regulation in tumor cells after chemotherapy; however, to date, its exact role in HB has not been described. The authors investigated the role of the MDR1 gene in the clinical course of patients with HB and in an in vivo model of HB. They also studied the effects of the MDR1 antagonizer PSC 833 on chemotherapy in mice xenotransplanted with HB. METHODS: Resected tumor specimens, including both primary tumors and recurrent tumors, from a child suffering from HB were investigated histologically. Cell suspensions from the originally removed tumor were incorporated subcutaneously into nude mice. Animals were treated with cisplatin (CDDP) plus PSC 833. MDR1 gene expression levels in the different resected tumors from the patient and in the xenotransplants after treatment were determined with polymerase chain reaction analysis. RESULTS: MDR1 gene expression was increased in the patient's tumors after every course of chemotherapy from 30% to > 190%. In the xenotransplants, MDR1 gene expression was enhanced significantly after chemotherapy (P(CDDP) = 0.008; P(CDDP+PSC) = 0.002). Tumor volumes (P < 0.001) and serum alpha-fetoprotein levels (P = 0.0002) were significantly lower in the animals that were treated with CDDP + PSC compared with the animals that were treated with CDDP alone. CONCLUSIONS: The current results suggest that MDR1 gene expression and P-gp are a potential mechanism of drug resistance in HB. The chemosensitizer PSC 833 significantly improved the effects of chemotherapy in animals xenotransplanted with HB. These data encourage further studies concerning the role of chemosensitizers in overcoming multidrug resistance in patients with HB.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2002

Spatial organisation and behaviour of the parental chromosome sets in the nuclei of Saccharomyces cerevisiae x S. paradoxus hybrids.

We demonstrate that the genomes of Saccharomyces cerevisiae and S. paradoxus are sufficiently divergent to allow their differential labeling by genomic in situ hybridisation (GISH). The cytological discrimination of the genomes allowed us to study the merging of the two genomes during hybrid mating. GISH revealed that in hybrid nuclei the two genomes are intermixed. In hybrid meiosis, extensive intraspectific nonhomologous pairing takes place. GISH on chromosome addition and substitution strains (with chromosomes of S. paradoxus added to or replacing the homoeologous chromosome of an otherwise S. cerevisiae background) was used to delineate individual chromosomes at interphase and to examine various aspects of chromosome structure and arrangement.

Cell Nucleus↗

PubMed2002

Pretreatment prognostic factors and treatment results in children with hepatoblastoma: a report from the German Cooperative Pediatric Liver Tumor Study HB 94.

BACKGROUND: In the past 20 years, a dramatic improvement in the prognosis of patients with hepatoblastoma (HB) has been achieved by combining surgery with chemotherapy in several national and international trials. A worldwide, unsolved problem remains the treatment of patients with advanced or metastatic HB. METHODS: The German Cooperative Pediatric Liver Tumor Study HB 94 was a prospective, multicenter, single-arm study. The study ran from January 1994 to December 1998. The protocol assessed the efficiency of chemotherapy consisting of cisplatin, ifosfamide, and doxorubicin (CDDP/IFO/DOXO) and/or etoposide and carboplatin (VP16/CARBO). The prognostic significance of the surgical strategy, pretreatment factors, and tumor characteristics for disease free survival (DFS) were analyzed. RESULTS: Sixty-nine children with HB were treated in the HB 94 study. The median follow-up of survivors was 58 months (range, 32-93 months). Fifty-three of 69 patients (77%) remained alive, and 16 of 69 patients (23%) died. Long-term DFS was as follows: 26 of 27 patients had Stage I HB, 3 of 3 patients had Stage II HB, 19 of 25 patients had Stage III HB, and 5 of 14 patients had Stage IV. A complete resection of the primary tumor was achieved in 54 of 63 patients (86%). Six children (8%) had no surgical treatment. Twenty-two tumors were resected primarily, and 41 children underwent surgery after initial chemotherapy. Two children underwent liver transplantation. There was no perioperative death. Forty-eight children received primary chemotherapy with CDDP/IFO/DOXO. Forty-one of 48 children achieved partial remission after CDDP/IFO/DOXO. Eighteen children with advanced or recurrent HB underwent VP16/CARBO chemotherapy, with a response achieved by 12 children. The relevant pretreatment prognostic factors were growth pattern of the liver tumor (P = 0.0135), vascular tumor invasion (P = 0.0039), occurrence of distant metastases (P = 0.0001), initial alpha-fetoprotein level (P = 0.0034), and surgical radicality (P < 0.0001). CONCLUSIONS: The current results underline the necessity of preoperative chemotherapy in all children with HB. Complete tumor resection is one of the main prognostic factors.

Child↗

PubMed2002

Chromosome associations in budding yeast caused by integrated tandemly repeated transgenes.

The binding of GFP-tagged tetracycline repressor (TetR) molecules to chromosomally integrated tetracycline operator (tetO) sequence repeats has been used as a system to study chromosome behaviour microscopically in vivo. We found that these integrated transgenes influence the architecture of yeast interphase nuclei, as chromosomal loci with tandem repeats of exogenous tetO sequences are frequently associated. These associations occur only if TetR molecules are present. tetO tandem repeats associate regardless of their chromosomal context. When they are present at a proximal and a distal chromosomal position, they perturb the normal polarized Rabl-arrangement of chromosome arms by recruiting chromosome ends to the centromeric pole of the nucleus. Associations are established at G1 and are reduced during S-phase and mitosis. This system may serve as a model for the role of DNA sequence-specific binding proteins in imposing nonrandom distribution of chromosomes within the nucleus.

Bacterial Proteins↗

PubMed2002

Prognostic impact of molecular genetic alterations in hepatoblastoma.

BACKGROUND: During recent years, we identified characteristic genetic alterations in sporadic hepatoblastoma (HB). These include loss of heterozygosity (LOH) at the chromosomal region 11p15.5, LOH on chromosome arms 1p and 1q, activating mutations in exon 3 of the beta-catenin gene, as well as overexpression of the c-met oncogene, which encodes the hepatocyte growth factor receptor. We now wanted to evaluate the prognostic relevance of these abnormalities concerning the outcome in a large group of patients. PROCEDURE: All but 7 of 56 patients with HB were treated either with primary resection for small tumors, or neo-adjuvant chemotherapy with ifosfamide, cisplatin and doxorubicin (IPA) before delayed surgery in case of extended disease and additional adjuvant IPA therapy in all cases. Seven tumors were primarily resected and adjuvantly treated with different cytotoxic drugs. LOH 11p15.5, LOH 1p, and LOH 1q were detected in tumor tissue in comparison to normal liver and/or peripheral blood leukocytes by PCR based microsatellite analysis. Beta-catenin mutations were analysed with SSCP, deletion screening and direct sequencing. RT-PCR was used for identification of c-met mRNA overexpression. The results were correlated with the tumors' stage, histological type and epithelial differentiation, as well as with the patients' outcome. RESULTS: Overall disease-free survival after median follow-up of 5 years was 43/56 patients (77%). LOH 11p15.5 was found in 15/56, LOH1p in 11/53, LOH1q in 7/53 and beta-catenin mutations in 25/55 HB. 13/23 HB had a c-met overexpression. LOH 11p15.5 and LOH 1p were significantly more often found in embryonal HB, while there was no correlation of other genetic alterations with histological type or differentiation. Furthermore, statistical analysis revealed no correlation of any of these disorders with initial tumor stage, nor with the patients' outcome. CONCLUSION: None of the investigated molecular genetic alterations are suited to serve as a prognostic indicator in HB. Further investigations, especially genetic screening of tumor tissue may reveal prognostic markers for this neoplasm.

Child↗

PubMed2002

MDR1 modulators improve the chemotherapy response of human hepatoblastoma to doxorubicin in vitro.

PURPOSE: P-glycoprotein, a membrane efflux pump encoded by the MDR1 gene, plays an important role in the development of multidrug resistance in human hepatoblastoma (HB). Chemosensitizers antagonize the efflux action of P-glycoprotein. This study investigates the effects of 3 chemosensitizers (the cyclosporin analogue SDZ PSC 833 (PSC 833), the acridone carboxamide derivative GG 918, and verapamil) on the chemotherapy of HB in vitro. METHODS: The doxorubicin (DOXO) concentration that produces 50% growth inhibition (IC50) in a HB cell line was determined and additional effects of PSC 833, GG 918, and verapamil were investigated in a cytotoxicity assay. The MDR1 gene expression after treatment was determined in a semiquantitative reverse transcription polymerase chain reaction approach. RESULTS: The IC50 of DOXO is 2.5 microg/mL, 0.61 microg/mL for DOXO + PSC 833, 1.17 microg/mL for DOXO + verapamil, and 1.47 microg/mL for DOXO + GG 918. In combination with DOXO, cell growth was inhibited 4.1-fold by PSC 833, 2.1-fold by verapamil, and 1.9-fold by GG 918. The MDR1 gene expression was enhanced significantly in all treated cells, with and without modulator. CONCLUSIONS: MDR1 modulators significantly improve the response of HB to DOXO in vitro. The combination of anticancer agents and MDR1 modulators might be a possible contribution to overcome multidrug resistance in HB.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

Effects of P-glycoprotein modulation on the chemotherapy of xenotransplanted human hepatoblastoma.

Multidrug resistance (MDR) contributes to limited treatment results in human hepatoblastoma (HB). The MDR1 gene and its product P-glycoprotein (P-gP) has been identified as important factor in this development. In other tumors, P-gP modulation leads to a restored chemosensitivity of the cells. The aim of this study was to analyze the P-gP-modulating effects of PSC 833, a cyclosporine derivate, and verapamil on the chemotherapy of HB in vivo. HB from 2 patients were transplanted subcutaneously into nude mice NMRI (nu/nu). Animals were divided into 7 groups: Group 1 (Control); Group 2 (CDDP); Group 3 (DOXO); Group 4 (DOXO + verapamil); Group 5 (DOXO + PSC 833); Group 6 (CDDP + verapamil); and Group 7 (CDDP + PSC 833). If DOXO was administered (regardless of the combination), the dose was two times 60 mg/m2. If CDDP was administered, the dose was two times 27 mg/m2. When the chemosensitizers were administered, the doses for PSC 833 and for verapamil were four times 5 mg/kg body-weight. In the combined treatment groups the chemosensitizers were given ten minutes prior to CDDP and DOXO. Tumor volume developments and a-fetoprotein (AFP) alterations were assessed. Relative expression levels of the MDR1 gene after treatment were determined using a semiquantitative rT-PCR approach. In a mixed HB, both chemosensitizers combined with DOXO or CDDP produced a significant reduction of tumor growth (p = .0001-.00063) and AFP levels (p = .0006-.0128) compared to tumors treated with DOXO or CDDP only. Treatment results were identical to those in a less differentiated pure embryonal HB, but only in one case (DOXO + PSC 833, p = .031) significant. The chemosensitizers had no influence on the MDR1 gene expression. MDR1 modulators improve the efficiency of DOXO and CDDP treatment in xenotransplanted HB. They do not induce a further increase of drug resistance in the tumors. The data provide evidence that chemosensitizers might improve treatment results in patients with advanced or relapsed HB.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

P-glycoprotein modulation improves in vitro chemosensitivity in malignant pediatric liver tumors.

BACKGROUND: Multidrug resistance (MDR) is a major reason for the poor outcome of advanced pediatric liver malignancies. The P-glycoprotein (P-gP), which contributes to this phenomenon, has been potently antagonized in other tumors. Our aim was to investigate the influence of P-gP antagonizers on the chemotherapy of pediatric liver malignancies in vitro. MATERIALS AND METHODS: One hepatocellular carcinoma (HCC) and three hepatoblastoma (HB) cell lines were incubated with doxorubicin or cisplatin. Additional effects of three P-gP-modulators were determined in a cytotoxicity assay. Expression levels of the MDR1 gene were determined using rT-PCR. RESULTS: Modulation of P-gP improved chemotherapy results in all HB cell lines, more effectively in the more highly differentiated tumors. Combined treatment of the HCC cell line was only more efficient using doxorubicin and PSC 833. CONCLUSION: Modulation of P-gP can overcome MDR in HCC and HB in vitro. Our data encourage further studies analyzing this effect under in vivo conditions.

ATP Binding Cassette Transporter, Subfamily B, Mem↗