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Biomedical subjects

D Fink

Publications and source records attributed to D Fink.

At least 19 recordsLinked to original sources
PubMed2002

Photodynamic therapy of DNA mismatch repair-deficient and -proficient tumour cells.

Loss of DNA mismatch repair is a common finding in hereditary nonpolyposis colon cancer as well as in many types of sporadic human tumours. DNA mismatch repair-deficient cells have been reported to be resistant to many chemotherapeutic agents and to radiotherapy, and to have the potential of rapidly acquiring additional mutations leading to tumour progression. Photodynamic therapy is a new treatment modality using light to activate a photosensitiser that preferentially localises in tumour cells. An oxygen dependent photochemical reaction ensues, resulting in selective tumour necrosis. The effect of loss of DNA mismatch repair activity on the sensitivity to photodynamic therapy was tested using pairs of cell lines proficient or deficient in mismatch repair due to loss of either MLH1 or MSH2 protein function. Cells were incubated with the photosensitiser 5,10,15,20-meta-tetra(hydroxyphenyl)chlorin and exposed to laser light at 652 nm with various optical doses ranging from 0-1 J cm(-2). Cell survival was assessed using the clonogenic assay. Loss of MLH1 or MSH2 function was not associated with resistance to photodynamic therapy. MCF-7 cells repeatedly treated with photodynamic therapy expressed parental levels of MLH1, MSH2, MSH6, and PMS2. DNA mismatch repair-deficient and -proficient cells showed similar subcellular distributions of meta-tetra(hydroxyphenyl)chlorin as analysed by laser scanning and fluorescence microscopy. Therefore, repeated exposure of tumour cells to photodynamic therapy does not seem to result in loss of DNA mismatch repair, and loss of mismatch repair, in turn, does not seem to contribute to resistance to photodynamic therapy. Our results suggest recommending photodynamic therapy as a strategy for circumventing resistance due to loss of DNA mismatch repair.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Transmission of 3 keV Ne7+ ions through nanocapillaries etched in polymer foils: evidence for capillary guiding.

We report unprecedented transmission experiments of 3 keV Ne7+ ions through capillaries of 100 nm diameter and 10 microm length produced by etching ion tracks in a polymer foil. We studied foils tilted up to +/-20 degrees for which the incident ions are forced to interact with the capillary surface. Surprisingly, the majority of Ne7+ ions were found to survive the surface scattering events in their initial charge state. The angular distributions of the transmitted particles indicate propagation of the Ne7+ ions along the capillary axis. This capillary guiding of the Ne7+ ion provides evidence that the inner walls of the capillaries become charged and electron capture from the surface is suppressed in a self-organizing process.

Journal Article↗
PubMed2001

Resistance to topoisomerase poisons due to loss of DNA mismatch repair.

Sporadic breast carcinomas demonstrate microsatellite instability, reflecting the presence of DNA mismatch repair-deficient cells, in about one fourth of cases at the time of diagnosis. Loss of DNA mismatch repair has been reported to result in resistance not only to cisplatin and alkylating agents but also to the topoisomerase II poison doxorubicin, suggesting an association between DNA mismatch repair and topoisomerase II poison-induced cytotoxicity. Our study investigates the relationship between loss of MSH2 or MLH1 function and sensitivity to the topoisomerase I and II poisons, and to the taxanes, 2 classes of cytotoxic drugs commonly used in breast cancer. Two pairs of cell lines proficient and deficient in mismatch repair due to loss of either MSH2 or MLH1 function were used. Loss of either MSH2 or MLH1 function resulted in resistance to the topoisomerase II poisons doxorubicin, epirubicin and mitoxantrone, whereas only loss of MLH1 function was associated with low-level resistance to the topoisomerase I poisons camptothecin and topotecan. In contrast, there was no resistance to docetaxel and paclitaxel. Our data support the hypothesis that both MSH2 and MLH1 are involved in topoisomerase II poison-mediated cytotoxicity, whereas only MLH1 is involved in topoisomerase I poison-mediated cytotoxicity. Since our study shows that loss of DNA mismatch repair does not result in resistance to the taxanes, these drugs can be recommended for use in breast cancer deficient in mismatch repair.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Prognostic and predictive significance of ErbB-2 breast tumor levels measured by enzyme immunoassay.

PURPOSE: A retrospective analysis to assess the prognostic and predictive clinical value of breast tumor ErbB-2 receptor expression quantified by enzyme immunoassay (EIA), to compare levels measured by EIA with ErbB-2 status determined by immunohistochemistry (IHC), and to correlate receptor content with levels of phosphorylated (Y1248-P) ErbB-2, a measure of functional tyrosine kinase activity. MATERIALS AND METHODS: EIA quantification of ErbB-2 was performed on membrane extracts from 3,208 well-characterized primary breast cancers. Overall, relapse-free, distant disease-free, and local/regional-free patient survival data were available on 1,123 of these tumors. IHC scoring for ErbB-2 status (HercepTest; DAKO, Glostrup, Denmark) was performed on adjacent sections of 151 cases, and receptor functionality was measured in 230 tumors by an antibody specific for phosphorylated (Y1248-P) ErbB-2. RESULTS: Unlike nonmalignant breast tissues, breast tumors showed increased ErbB-2 levels in a bimodal distribution, with 12% constituting a distinct set of ErbB-2-overexpressing tumors. The intermodal threshold value for ErbB-2 overexpression distinguished tumors with reduced estrogen and progesterone receptor content, high IHC score for ErbB-2, and significantly increased levels of phosphorylated (Y1248-P) ErbB-2 receptor. By multivariate analysis, EIA-determined ErbB-2 overexpression predicted significantly reduced patient survival that was unaffected by tamoxifen or cyclophosphamide, methotrexate, and fluorouracil adjuvant therapy. CONCLUSION: Determination of ErbB-2 receptor expression by EIA offers a clinically valuable alternative to semiquantitative IHC assessment of breast tumor ErbB-2 overexpression and affords the opportunity to evaluate ErbB-2 phosphorylation, which may represent an important predictive parameter of receptor functionality.

Adult↗
PubMed2001

Skin protection for photosensitized patients.

BACKGROUND AND OBJECTIVE: The goal of this study was to evaluate various creams for their capability to protect photosensitized skin from visible light. STUDY DESIGN/MATERIALS AND METHODS: Two cover creams and creams containing various combinations of Vaseline with TiO(2), ZnO, and Fe(2)O(3) were used to measure the reduced light transmission and the light absorption spectrum. In vitro and in vivo tests were performed to assess the protection from light by above mentioned compounds. RESULTS: The cover creams and the 50% TiO(2) cream showed similar efficacy in reducing light transmission, while the sunscreen was less efficient by a factor of 5. Cell protection by 25% TiO(2)+25% ZnO, TiO(2), or the cover creams was more efficient than protection by the sunscreen or other compounds. In vivo, the dark cover cream protected the skin by a factor of 3.4 better than the sunscreen. CONCLUSION: The dark cover cream has acceptable properties to protect photosensitized skin.

Absorption↗
PubMed2001

Exercise hemodynamics of aortic prostheses: comparison between stentless bioprostheses and mechanical valves.

BACKGROUND: Nonstented bioprostheses have been associated with lower resting gradients than stented bioprostheses or mechanical valves. We compared the hemodynamic performance of nonstented bioprostheses and mechanical valves with normal native aortic valves at rest and exercise. METHODS: Dobutamine echocardiography was used to assess gradients and effective orifice area index at rest and exercise in patients with the Toronto stentless porcine valve (TSPV; n = 13; mean implant size 25.7 mm), Medtronic Freestyle (FR; n = 11; mean implant size 23.9 mm), Sorin Bicarbon (SOR; n = 11; mean implant size 24.5 mm), St. Jude Medical (SJM; n = 10; mean implant size 21.3 mm), and normal native aortic valves (NOR; n = 10). RESULTS: All groups demonstrated a major rise in cardiac output at maximal dobutamine infusion. At rest and exercise, respectively, mean gradients were 5.48 +/- 1.1 mm Hg and 5.83 +/- 0.9 mm Hg for TSPV, 5.68 +/- 1.2 mm Hg and 7.50 +/- 1.7 mm Hg for FR, 10.29 +/- 1.4 mm Hg and 20.78 +/- 2.7 mm Hg for SJM, 5.26 +/- 0.8 mm Hg and 11.1 +/- 1.8 mm Hg for SOR, and 1.54 +/- 0.4 mm Hg and 2.18 +/- 0.7 mm Hg for NOR. In comparison with normal valves, both stentless groups showed no change in mean gradient at exercise, whereas both mechanical groups showed an increase in gradient at exercise (p < 0.04). CONCLUSIONS: Stentless valves behave similarly to normal aortic valves in that there is almost no increase in gradient at exercise. Both mechanical valve groups showed increased gradients at exercise, suggesting that these valves obstruct blood flow. Our data add further evidence that stentless valves are hemodynamically superior to mechanical valves in the aortic position.

Adult↗
PubMed2001

Differential expression levels of Par-4 in melanoma.

The pro-apoptotic prostate apoptosis response-4 gene product Par-4 sensitizes prostate cells to the induction of programmed cell death. In this study we examined Par-4 expression in human melanoma cell lines and melanoma metastases. The heterogeneous expression detected prompted us to investigate the biological relevance of Par-4 in a human melanoma xenotransplantation model. Overexpression of Par-4 by transfection decreased tumour development in xenotransplanted A375-C6 melanoma cells in SCID mice and correlated to an increase in tumour cell apoptosis. These data suggest that high expression of the pro-apoptotic protein Par-4 could qualify as a prognostic marker in human melanoma.

Animals↗
PubMed2001

Elevated procaspase levels in human melanoma.

In this study procaspase expression levels were investigated by Western blotting in a panel of established melanoma cell lines, transformed melanocytic cell lines and normal primary melanocytes. Upstream caspases such as procaspase-8 that contain a death effector domain were found to be overexpressed in transformed melanocytes and melanoma cell lines compared with melanocytes. Heterogeneous levels of procaspase-8 were seen in melanoma cells, including one cell line that completely lacked procaspase-8 expression. Procaspase-10 is generally overexpressed in transformed melanocytes and melanoma cell lines. Expression of the downstream procaspases-3 and -7 was increased in melanoma cells compared with normal melanocytes. Procaspases containing caspase recruitment domains such as procaspase-2 were expressed at similar levels in nearly all the cell lines investigated. Reduced levels of procaspase-1 compared with normal melanocytes were detected in transformed melanocytes and melanoma cell lines. These data indicate that procaspase levels in general increase during the malignant transformation of melanocytic cells.

Blotting, Western↗
PubMed2000

Differential expression of p73 splice variants and protein in benign and malignant ovarian tumours.

The p73 gene encodes a protein with substantial structural and functional similarities to the tumour-suppressor p53. Alternative splicing of p73 mRNA leads to expression of 6 known RNA species and proteins (alpha, beta, gamma, delta, epsilon, zeta). We analysed the expression of these splice variants in ovarian adenocarcinoma by RT-PCR followed by detection of amplicons with the Southern technique and by immunoblot in 32 malignant and benign epithelial ovarian tumour specimens and 3 ovarian adenocarcinoma cell lines (A2780, 2008, OVCAR-3). p73alpha mRNA was expressed in all 17 ovarian cancer specimens, and 14 of 17 expressed at least 3 splice variants. In contrast, a different expression pattern was present in the ovarian adenomas: p73alpha was detected in 6 of 12 benign tumours, and only 1 adenoma expressed 3 splice variants. p73 protein was expressed in 9 of 16 ovarian cancer specimens, in all cell lines and in 1 of 3 borderline tumours. In contrast, none of 9 ovarian adenomas expressed detectable amounts of p73 protein. Expression of p73 mRNA and protein was not correlated with FIGO stage and histological grade, but we observed a significant correlation with over-expression of p53 protein. In summary, epithelial ovarian cancers express a more complex p73 isoform pattern and higher levels of p73 mRNA and protein than ovarian adenomas.

Adenocarcinoma↗
PubMed2000

Identification of domains of the HPV11 E1 protein required for DNA replication in vitro.

The HPV E1 and E2 proteins along with cellular factors, are required for replication of the viral genome. In this study we show that in vitro synthesized HPV11 E1 can support DNA replication in a cell-free system and is able to cooperate with E2 to recruit the host polymerase alpha primase to the HPV origin in vitro. Deletion analysis revealed that the N-terminal 166 amino acids of E1, which encompass a nuclear localization signal and a cyclin E-binding motif, are dispensable for E1-dependent DNA replication and for recruitment of pol alpha primase to the origin in vitro. A shorter E1 protein lacking the N-terminal 190 amino acids supported cell-free DNA replication at less than 25% the efficiency of wild-type E1 and was active in the pol alpha primase recruitment assay. An even shorter E1 protein lacking a functional DNA-binding domain due to a truncation of the N-terminal 352 amino acids was inactive in both assays despite the fact that it retains the ability to associate with E2 or pol alpha primase in the absence of ori DNA. We provide additional functional evidence that E1 interacts with pol alpha primase through the p70 subunit of the complex by showing that p70 can be recruited to the HPV origin by E1 and E2 in vitro, that the domain of E1 (amino acids 353-649) that binds to pol alpha primase in vitro is the same as that needed for interaction with p70 in the yeast two-hybrid system, and that exogenously added p70 competes with the interaction between E1 and pol alpha primase and inhibits E1-dependent cell-free DNA replication. On the basis of these results and the observation that pol alpha primase competes with the interaction between E1 and E2 in solution, we propose that these three proteins assemble at the origin in a stepwise process during which E1, following its interaction with E2, must bind to DNA prior to interacting with pol alpha primase.

Animals↗
PubMed2000

Prognostic significance of CA 125 and TPS levels after 3 chemotherapy courses in ovarian cancer patients.

OBJECTIVE: To evaluate the prognostic significance of and predictive value for survival of CA 125 and TPS levels after three chemotherapy courses in ovarian cancer patients. METHODS: We analyzed in a prospective multicenter study the 1- and 2-year overall survival (OS) in ovarian carcinoma patients. The prognostic significance of CA 125 and TPS levels above the discrimination value (25 kU/L and 100 U/L, respectively) was examined by univariate and multivariate analyses. RESULTS: Of the 213 cases included, 64 patients were staged as FIGO I + II and 149 patients were staged as FIGO III + IV. Tumor marker levels in stage I + II were not correlated with survival. However, stage III and IV patients with elevated levels of CA 125 or TPS after three chemotherapy courses had a worse 2-year OS (69% vs 26%, P < 0.0001 and 57% vs 20%, P < 0.0001, respectively) than patients with normal levels of the markers. In univariate analysis the result of operation (staging laparatomy and partial debulking) and advanced FIGO stage (IV) were also adverse prognostic factors. Independent factors predictive of low 2-year OS by multivariate analysis were staging laparotomy, TPS elevated, and CA 125 elevated. The only factors predictive of low 1-year OS were TPS elevated and staging laparotomy. CONCLUSIONS: Ovarian cancer patients with elevated CA 125 levels after three chemotherapy courses have a poor prognosis. However, the prognostic accuracy can be significantly increased by the parallel determination of serum TPS.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2000

Transcriptional analysis of the gene for glutamine synthetase II and two upstream genes in Streptomyces coelicolor A3(2).

The glutamine synthetase II (GSII, encoded by glnII) activity detectable in crude extracts from Streptomyces coelicolor is low compared to the activity of glutamine synthetase I (GSI, encoded by glnA) and to that of GSII from S. viridochromogenes. We have identified and sequenced a 3.9-kb BglII-BamHI fragment carrying the glutamine synthetase II gene (glnII) from S. coelicolor. Besides glnII, this region contains four ORFs (orf1-orf4). While homologues of orf1 and orf2 were also found in the glnII region of the S. viridochromogenes chromosome, this was not the case for orf3 and orf4, which encode a putative hydrolase and a transcriptional regulator (Ptr) of the MarR family, respectively. High-resolution S1 nuclease mapping showed that the S. coelicolor glnII gene is expressed from two overlapping promoters. The first comprises a vegetative promoter sequence and the second contains sequence elements that are recognized by Esigma31. Similar promoter structures were found upstream of the S. viridochromogenes glnII gene. The involvement of ptr in glnII regulation was studied by gel retardation assays. Recombinant Ptr interacted with the upstream region of ptr, but not with the promoter region of glnII. A ptr gene replacement mutant (S. coelicolor IP) was also constructed. RT-PCR analysis of RNA from wild-type S. coelicolor and the IP mutant demonstrated that expression of orf3 depends on Ptr. Thus, the difference in gene organization between S. coelicolor and S. viridochromogenes is not responsible for the difference in GSII activity.

Bacterial Proteins↗
PubMed2000

Accelerator mass spectrometry analyses of environmental radionuclides: sensitivity, precision and standardisation

Accelerator Mass Spectrometry (AMS) is the analytical technique of choice for the detection of long-lived radionuclides which cannot be practically analysed with decay counting or conventional mass spectrometry. AMS allows an isotopic sensitivity as low as one part in 10(15) for 14C (5.73 ka), 10Be (1.6 Ma), 26Al (720 ka), 36Cl (301 ka), 41Ca (104 ka), 129I (16 Ma) and other long-lived radionuclides occurring in nature at ultra-trace levels. These radionuclides can be used as tracers and chronometers in many disciplines: geology, archaeology, astrophysics, biomedicine and materials science. Low-level decay counting techniques have been developed in the last 40-50 years to detect the concentration of cosmogenic, radiogenic and anthropogenic radionuclides in a variety of specimens. Radioactivity measurements for long-lived radionuclides are made difficult by low counting rates and in some cases the need for complicated radiochemistry procedures and efficient detectors of soft beta-particles and low energy x-rays. The sensitivity of AMS is unaffected by the half-life of the isotope being measured, since the atoms not the radiations that result from their decay, are counted directly. Hence, the efficiency of AMS in the detection of long-lived radionuclides is 10(6)-10(9) times higher than decay counting and the size of the sample required for analysis is reduced accordingly. For example, 14C is being analysed in samples containing as little as 20 microg carbon. There is also a world-wide effort to use AMS for the analysis of rare nuclides of heavy mass, such as actinides, with important applications in safeguards and nuclear waste disposal. Finally, AMS microprobes are being developed for the in-situ analysis of stable isotopes in geological samples, semiconductors and other materials. Unfortunately, the use of AMS is limited by the expensive accelerator technology required, but there are several attempts to develop compact AMS spectrometers at low (< or = 0.5 MV) terminal voltages. Recent advances in AMS will be reviewed with highlights from the scientific programs at Lucas Heights and other AMS centres.

Journal Article↗
PubMed2000

Isolation and expression in Escherichia coli of cslA and cslB, genes coding for the chondroitin sulfate-degrading enzymes chondroitinase AC and chondroitinase B, respectively, from Flavobacterium heparinum.

In medium supplemented with chondroitin sulfate, Flavobacterium heparinum synthesizes and exports two chondroitinases, chondroitinase AC (chondroitin AC lyase; EC 4.2.2.5) and chondroitinase B (chondroitin B lyase; no EC number), into its periplasmic space. Chondroitinase AC preferentially depolymerizes chondroitin sulfates A and C, whereas chondroitinase B degrades only dermatan sulfate (chondroitin sulfate B). The genes coding for both enzymes were isolated from F. heparinum and designated cslA (chondroitinase AC) and cslB (chondroitinase B). They were found to be separated by 5.5 kb on the chromosome of F. heparinum, transcribed in the same orientation, but not linked to any of the heparinase genes. In addition, the synthesis of both enzymes appeared to be coregulated. The cslA and cslB DNA sequences revealed open reading frames of 2,103 and 1,521 bp coding for peptides of 700 and 506 amino acid residues, respectively. Chondroitinase AC has a signal sequence of 22 residues, while chondroitinase B is composed of 25 residues. The mature forms of chondroitinases AC and B are comprised of 678 and 481 amino acid residues and have calculated molecular masses of 77,169 and 53,563 Da, respectively. Truncated cslA and cslB genes have been used to produce active, mature chondroitinases in the cytoplasm of Escherichia coli. Partially purified recombinant chondroitinases AC and B exhibit specific activities similar to those of chondroitinases AC and B from F. heparinum.

Blotting, Southern↗
PubMed2000

[Neurofibromatosis of the breast in a patient with Morbus von Recklinghausen].

Neurofibromatosis is a rare autosomal dominant disorder with several subtypes. Common is the appearance of specific skin alterations. Neurofibromas occurring in the breast are very rare, and in such cases they are most common in the areolar area. A case of a 46-year-old woman with von Recklinghausen's disease of the breast is reported, and the literature will be discussed.

Breast Neoplasms↗
PubMed2000

Analysis of MLH1 and MSH2 expression in ovarian cancer before and after platinum drug-based chemotherapy.

Preclinical studies have demonstrated a relationship between DNA mismatch repair (MMR) status and sensitivity to cisplatin and carboplatin. MMR-deficient cells are resistant to both drugs, and selection for cisplatin resistance in vitro is sometimes accompanied by loss of MMR protein expression. We used immunohistochemical staining techniques to investigate hMLH1 and hMSH2 expression in paired ovarian tumor sections from 54 ovarian cancer patients before and after platinum-based therapy. We sought associations between hMLH1 and hMSH2 protein expression and clinical parameters known to be of prognostic significance as well as response to treatment and overall survival. hMLH1 and hMSH2 staining decreased significantly after platinum-based therapy. The percent of malignant cells that stained positive correlated with the intensity of nuclear staining for both proteins; staining for hMLH1 correlated well with staining for hMSH2. Unexpectedly, expression of nuclear hMLH1 correlated negatively with response to treatment. Expression of nuclear hMLH1 and hMSH2 was positively correlated with pretreatment CA125 level, and expression of nuclear hMSH2 was positively correlated with change in CA125 level after treatment. Tumor stage was associated with expression of nuclear hMSH2, and tumor histological subtype was associated with both hMLH1 and hMSH2 staining. No association was found between expression of either protein and overall survival. These results indicate that the tumor is biologically altered after chemotherapy consistent with treatment-induced selection for cells expressing lower hMLH1 and hMSH2 levels. However, immunohistochemical staining for either hMLH1 or hMSH2 was not highly predictive of drug sensitivity as measured by response or survival.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Primary carcinoma of the fallopian tube. A report of 19 cases with literature review.

Primary carcinoma of the fallopian tube is the rarest cancer of the female genital tract with an incidence of 0.5% of all gynecologic tumors. Since the first report in 1847 about 1,500 cases have been published. Due to similarity of the clinical presentation the staging and therapeutic management have been adapted to that of ovarian cancer. We retrospectively evaluated all the 19 patients who had been diagnosed with primary carcinoma of the fallopian tube at the Department of Obstetrics and Gynecology of the University of Zurich between 1977 and 1998. All lesions were staged according to the rules of FIGO adopted in 1991. At the time of diagnosis the median age was 62 (46-87) years. Twelve (63%) women revealed FIGO stage III-IV, whereas four (21%) and three (16%) patients were diagnosed in stage I and stage II, respectively. Eight (42%) women were nullipara. Histology showed serous-papillary carcinoma, in ten (53%) cases. The 5-year survival rate was 22% for all FIGO stages and 80% for stage I. None of the patients with stage III and IV survived 5 years. Ovarian cancer and primary carcinoma of the fallopian tube are similar in many aspects. Both carcinomas have a similar age distribution, show an increase among nulliparous women, are often of serous papillary histology, have a poor prognosis with stage and residual tumor size as important prognostic factors, and respond initially well to platinum-based chemotherapy. Nevertheless, there appears to be a difference between the two diseases: primary carcinoma of the fallopian tube is more often diagnosed in an earlier stage. This many be due to lower abdominal pain resulting from tubal dilatation and to abnormal bloody-watery discharge.

Adult↗