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  • 1
    ISSN: 1432-0983
    Keywords: Key words Fungi ; gypsy-like LTR retrotransposon ; Solo-LTR ; Reverse transcriptase ; Repeat-induced point mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the filamentous ascomycete Podospora anserina a 6,935-bp retrotransposon, Yeti, has been identified and characterized. It is flanked by a 5-bp target site duplication and contains long terminal repeats (LTRs) 354 bp in length. The LTRs show a high degree of identity to the previously reported repetitive element repa, a sequence suggested to represent a solo-LTR element of an unknown transposon. In the investigated Podospora strains, the number of complete Yeti copies is significantly lower than the number of repa elements, with up to 25 copies. Yeti appears to be inactive: it is highly degenerate and no transcripts of the element have been detected even in Podospora cultures grown under elevated stress conditions. The amino acid sequences deduced from Yeti display significant homology, particularly in the reverse transcriptase region, to those of other fungal retrotransposons, indicating that it is a member of the gypsy family. As suggested by the unusual dinucleotide content, degeneration of Yeti appears to be the result of a molecular mechanism resembling repeat-induced point mutation in Neurospora crassa.
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  • 2
    ISSN: 1434-3932
    Keywords: Schlüsselwörter HIT Typ II ; Heparin-induzierte Thrombozytopenie ; White-clot-Syndrom ; Danaparoid ; Rekombinantes Hirudin ; Key words HIT type II ; Heparin-induced Thrombocyopenia ; White clot Syndrome ; Danaparoid ; Hirudin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract  The case of a 71-year-old patient is discussed in whom early occlusions of an implanted bypass and peripheral arteries developed after implantation of a femoropopliteal PTFE bypass and several reoperations. Heparin-induced thrombocytopenia (HIT) type II was suspected because of the intraoperative aspect of white clots and when platelet counts fell below 50% of initial levels. A platelet aggregation test confirmed the diagnosis. After discontinuing the heparin therapy and using danaparoid, the platelet count continued to fall, so cross-reactivity to this heparinoid was assumed and confirmed in a second laboratory test. We switched to an anticoagulation regimen with phenprocoumon and used hirudin for the perioperative prophylaxis when another reoperation was required. Problems confirming the diagnosis of HIT type II and difficulties in patients with cross-reactivity to other heparinoids are discussed.
    Notes: Zusammenfassung  Es wird über den Verlauf bei einer 71jährigen Patientin berichtet, bei der es nach Anlage eines femoropoplitealen Bypasses sowie mehrfachen Revisions-operationen zu frühen Bypassverschlüssen und peripheren Gefäßokklusionen kam. Ein zusätzli- cher Abfall der Thrombozytenwerte unter 50% der Ausgangswerte in Zusammenhang mit dem intraoperativem Befund ”weißer Thromben” lenkte den Verdacht auf’ein White-clot-Syndrom bei Heparin-induzierter Thrombozytopenie Typ II, welche sich im Heparin-induzierten Plättchenaggregationstest (HIPA) bestätigte. Nach Umsetzen der Heparin-Therapie auf Danaparoid-Na (Orgaran) kam es zu einem weiteren Abfall derThrombozyten. Der klini-sche Verdacht auf Kreuzreaktivität zu Danaparoid-Na wurde im HIPA-Test verifiziert. Im weiterem Verlauf erfolgte zunächst die Antikoagula- tion mit Phenprocoumon (Marcumar) und dann im Rahmen eines Revisionseingriffs mit rekombinantem Hirudin (Refludan, Fa. Hoechst). Die Probleme bezüglich rechtzeitiger Diagnosestellung und antikoagu-lativer Therapie bei Kreuzreaktivität mit Orgaran werden diskutiert.
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  • 3
    ISSN: 1617-4623
    Keywords: Key words Filamentous fungi ; DNA transposon ; Fot1-like element ; Podospora anserina ; Repeat-induced point mutation (RIP)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A degenerate DNA transposon, Pat, was identified in the genomes of various wild-type strains of the filamentous fungus Podospora anserina. In these strains, the number (approximately 20–25 copies per genome) and location of Pat sequences appear to be conserved. Two copies of Pat, one complete and one partial, were cloned and characterized. The sequence of the complete element is 1856 bp long and contains imperfect inverted terminal repeats (ITRs) of 53 bp. The target site duplication comprises the sequence TA. The amino acid sequence derived from one reading frame of Pat shows significant homology to members of the Fot1 family of transposons. However, this reading frame is interrupted by numerous stop codons. Since no transcripts of Pat were identified in different P. anserina strains grown under standard conditions and under increased stress, we conclude that none of the copies of Pat is active in the strains analyzed, under the environmental conditions investigated. Comparison of the sequences of the two cloned Pat sequences revealed 89% (589/747 nucleotides) identity. Most of the differences (82%, 129/158) can be attributed to transitions preferentially at CpA:TpG and CpT:ApG dinucleotides. The dinucleotide ratios in Pat are similar to those in a Neurospora crassa transposon which was subject to repeat-induced mutation (RIP), but differ significantly from those found in single-copy genes of P. anserina and in fungal DNA transposons not modified by this mechanism. Molecular analysis of the progeny of a cross between the wild-type strain and a transgenic strain in which a nuclear gene was duplicated by transformation yielded the first clear evidence that a RIP-like process is active in P. anserina.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1953-1955 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work describes near-field investigations of luminescent nanosamples based on monitoring fluorescence due to the enhanced field around a laser-illuminated probe tip. These fluorescence effects are investigated as a function of probe-sample separation, which identify a strong, spatially localized ((approximate)7 nm) enhancement of the incident laser field in the vicinity of the probe tip. From a model fit to the fluorescence data, the localized enhancement of the electric field is estimated to be 〉tenfold, which predicts a significant increase in localized excitation intensity (〉100-fold) for fluorescence imaging of molecular size samples. © 2000 American Institute of Physics.
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  • 5
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Single molecule confocal microscopy is used to study fluorescence intermittency of individual ZnS overcoated CdSe quantum dots (QDs) excited at 488 nm. The confocal apparatus permits the distribution of "on" and "off" times (i.e., periods of sustained fluorescence emission and darkness) to be measured over an unprecedentedly large dynamic range (109) of probability densities, with nonexponential behavior in τoff over a 105 range in time scales. In dramatic contrast, these same τoff distributions in all QDs are described with remarkable simplicity over this 109-fold dynamic range by a simple inverse power law, i.e., P(τoff)∝1/τoff1+α. Such inverse power law behavior is a clear signature of distributed kinetics, such as predicted for (i) an exponential distribution of trap depths or (ii) a distribution of tunneling distances between QD core/interface states. This has important statistical implications for all previous studies of fluorescence intermittency in semiconductor QDs and may have broader implications for other systems such as single polymer molecules. © 2000 American Institute of Physics.
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  • 6
    ISSN: 1432-1424
    Keywords: Key words: Ion transport — Cotransport — Erythrocytes — Ionic strength — Intracellular pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The change of intracellular pH of erythrocytes under different experimental conditions was investigated using the pH-sensitive fluorescent dye BCECF and correlated with (ouabain + bumetanide + EGTA)-insensitive K+ efflux and Cl− loss. When human erythrocytes were suspended in a physiological NaCl solution (pH o = 7.4), the measured pH i was 7.19 ± 0.04 and remained constant for 30 min. When erythrocytes were transferred into a low ionic strength (LIS) solution, an immediate alkalinization increased the pH i to 7.70 ± 0.15, which was followed by a slower cell acidification. The alkalinization of cells in LIS media was ascribed to a band 3 mediated effect since a rapid loss of approximately 80% of intracellular Cl− content was observed, which was sensitive to known anion transport inhibitors. In the case of cellular acidification, a comparison of the calculated H+ influx with the measured unidirectional K+ efflux at different extracellular ionic strengths showed a correlation with a nearly 1:1 stoichiometry. Both fluxes were enhanced by decreasing the ionic strength of the solution resulting in a H+ influx and a K+ efflux in LIS solution of 108.2 ± 20.4 mmol (l cells hr)−1 and 98.7 ± 19.3 mmol (l cells hr)−1, respectively. For bovine and porcine erythrocytes, in LIS media, H+ influx and K+ efflux were of comparable magnitude, but only about 10% of the fluxes observed in human erythrocytes under LIS conditions. Quinacrine, a known inhibitor of the mitochondrial K+(Na+)/H+ exchanger, inhibited the K+ efflux in LIS solution by about 80%. Our results provide evidence for the existence of a K+(Na+)/H+ exchanger in the human erythrocyte membrane.
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  • 7
    ISSN: 1432-2013
    Keywords: Electron microscopy Intracellular pH Monocarboxylate transport Pigment epithelium of eye Proton–lactate cotransport Retinal metabolism Sodium/proton exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Monolayer cultures of human fetal retinal pigment epithelial (RPE) cells were examined for ultrastructural characteristics and junctional integrity by means of electron microscopy. Intracellular pH (pHi) and cell volume changes were measured using the fluorescent dye BCECF. The EM studies indicate that the RPE cells preserve in vivo morphology before and after loading with BCECF. Monolayer cultures were placed in a perfusion chamber in which the solution facing the retinal cell membrane could be changed rapidly. Removal of Na+ or the addition of amiloride caused intracellular acidifications. pHi recovery from an NH4 +-induced acid load was blocked by sodium removal or amiloride addition. These results suggest the presence of a Na+–H+ exchange mechanism in the retinal cell membrane. When Cl- was replaced isotonically by lactate or pyruvate the cells acidified. The intracellular acidifications were saturable, reversibly reduced with the inhibitor probenecid (2 mM), and the lactate-induced acidifications were reversibly inhibited by equimolar concentrations of pyruvate. These results indicate the presence of a H+–lactate cotransport mechanism in the retinal membrane. When Cl– was replaced by lactate the cells not only acidified, they also swelled. The data are compatible with water transport induced by the H+–lactate cotransporter.
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  • 8
    ISSN: 1432-2013
    Keywords: Exocytosis Membrane potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. This study aimed to assess the relevance of specific potassium channels, such as inwardly or outwardly rectifying and calcium-regulated potassium channels, to the control of renin secretion. For this purpose we examined the effects of the K+ channel blockers 4-aminopyridine (1 mmol/l), barium (100 µmol/l), tetraethylammonium (2 mmol/l) and apamin (200 nmol/l) on basal renin secretion, on renin secretion stimulated by isoproterenol (10 nmol/l) and on the inhibition of renin secretion by angiotensin II (100–300 pmol/l) in the isolated rat kidney perfused at constant pressure. Whilst all four K+ channel blockers increased renal vascular resistance, only 4-aminopyridine and barium attenuated isoproterenol-stimulated renin secretion in an additive fashion and augmented the inhibitory effect of angiotensin II. These effects of K+ channel blockers were not changed by the L-type calcium channel blocker amlodipine (5 µmol/l), indicating that their effects on renin secretion are not due to voltage-operated calcium influx. Our data, moreover, suggest that potassium efflux from renal juxtaglomerular cells is not important for the inhibitory action of angiotensin II on renin secretion. As a consequence it appears that the membrane potential of renal juxtaglomerular cells per se is relevant to renin secretion such that membrane depolarization inhibits the exocytosis of renin whilst hyperpolarization favors renin secretion. By their activity, potassium channels can contribute to membrane hyperpolarization and thus facilitate renin secretion.
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  • 9
    ISSN: 1439-099X
    Keywords: Schlüsselwörter: Strahlentherapie ; Diarrhö ; Prophylaxe ; Smektit ; Key Words: Radiotherapy ; Diarrhea ; Prophylaxis ; Smectite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Purpose: Diarrhea and abdominal pain are well-known side effects abdominal or pelvic of radiation therapy that may lead to interruption of treatment in serious cases. In recent trials the silicate smectite has proven a promising drug in the prophylaxis if these adverse events. The presented trial aimed at the verification of earlier studies and the evaluation of a dose-effect relationship. Patients and Methods: Between April 1994 and May 1995, a total of 176 patients obtaining radiotherapy of the pelvis or the abdomen were evaluated in a double-blind, randomized placebo-controlled investigation regarding the prophylactic effect of smectite (= Colina®) against radiotherapy-induced diarrhea. During the whole period of radiotherapy 85 patients obtained 2 × 6 g smectite daily and 91 patients received 2 × 6 g placebo. The primary end point of the analysis was the time to the first appearance of diarrhea (≥ 3 pappy stools). Results: All 176 patients were evaluated according to an intent-to-treat analysis. There was no significant difference between the prophylactic effects of smectite and placebo. For an explorative post-hoc analysis the total study group was split up into 2 subgroups, one with an irradiated small bowel volume ≤ 837.5 ml, the other with a small bowel volume 〉 837,5 ml (median); the analysis indicated that the first subgroup showed a benefit for the smectite-treated patients in contrast to the placebo treatment (32 vs. 18 calendar days to the first appearance of diarrhea). This benefit was statistically not significant. Conclusion: Prophylactic application of smectite during irradiation of the pelvis and the abdomen can delay the development of radiotherapy-induced diarrhea, a statistical significance could not be verified neither in the total study group nor in the post-hoc subgroup analysis.
    Notes: Hintergrund und Ziel: Strahlentherapieinduzierte Diarrhöen und Schmerzen sind bekannte Nebenwirkungen der Becken- und Abdominalbestrahlung und können in schwerwiegenden Fällen zur Unterbrechung der Strahlenbehandlung führen. Das Schichtsilikat Smektit hat sich in den ersten Anwendungsstudien als ein vielversprechendes Therapeutikum zur Prophylaxe dieser Nebenwirkungen erwiesen. Die vorliegende Untersuchung diente der Verifizierung bekannter Studienresultate und der Erarbeitung einer Dosis-Wirkungs-Beziehung. Patienten und Methoden: Zwischen April 1994 und Mai 1995 wurde bei 176 Patienten mit Becken- bzw. Abdominalbestrahlung die prophylaktische Wirkung von Smektit (Handelsname: Colina®) bezüglich radiogener Diarrhöen in einer doppelblinden, randomisierten und plazebokontrollierten Studie untersucht. Während des gesamten Zeitraums der Strahlentherapie erhielten 85 Patienten täglich 2mal 6 g Smektit und 91 Patienten täglich 2mal 6 g von identisch aussehender Plazebosubstanz. Das Hauptzielkriterium der Auswertung war der Zeitraum bis zum Auftreten einer bestrahlungsinduzierten Diarrhö (definiert als ≥ 3 breiige Stühle). Ergebnisse: Alle 176 Patienten wurden in der Intent-to-treat-Analyse ausgewertet. In der Gesamtgruppe zeigten sich keine signifikanten Unterschiede zwischen der prophylaktischen Wirkung von Smektit und Plazebo. Eine explorative Post-hoc-Analyse mit Teilung des Gesamtkollektivs in Subgruppen mit einem bestrahlten Dünndarmvolumen ≤ 837,5 ml bzw. 〉 837,5 ml (Median) deutet im Kollektiv ≤ 837,5 ml an, dass bei gegebener Dosierung ein Vorteil für Smektit gegenüber Plazebo (32 versus 18 Kalendertage bis zum ersten Auftreten einer Diarrhö) besteht; dieser Vorteil ist jedoch statistisch nicht signifikant. Schlussfolgerung: Durch den prophylaktischen Einsatz eines Smektitpräparates als Antidiarrhoikum während einer Bestrahlung des Becken- und Abdominalbereiches kann die Entstehung einer bestrahlungsinduzierten Diarrhö verzögert werden, eine statistische Signifikanz konnte jedoch sowohl im Gesamtkollektiv als auch in einer Post-hoc-Subgruppenanalyse nicht nachgewiesen werden.
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  • 10
    ISSN: 1573-7217
    Keywords: BRCA1 mutation ; breast cancer ; disease-free survival ; overall survival ; pathology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Reports from different countries have been inconclusive in attempting to relate the BRCA1 mutation status to the survival of breast cancer patients. The purpose of this study was to investigate overall and disease-free survival for German hereditary breast cancer patients. Data on clinical outcome and data on age at diagnosis of breast cancer, histology, tumor size, lymph node status, histological grade, and laterality of 36 breast cancer patients from 12 families with a BRCA1 mutation and from one family with strong evidence for linkage to BRCA1 were compared with those of 49 hereditary breast cancer patients from 23 families that did not harbor a BRCA1 mutation. Overall and disease-free survival was estimated for both groups. BRCA1 mutation carriers had a significantly earlier age of diagnosis than non-carriers (p = 0.0001) and more frequently developed contralateral breast cancer (p = 0.04). Also, BRCA1-associated tumors more frequently were of larger size (p = 0.041) and higher grade of malignancy (p = 0.005) than non-BRCA1-associated tumors. Whereas no difference in overall survival was seen, disease-free survival at 10 years differed significantly with 53.3% for BRCA1 mutation carriers and 76% for non- carriers (p = 0.02). However, after stratification for age and in multivariate analysis for mutation status, age, and bilaterality, it was shown that the worse prognosis for BRCA1 mutation carriers disappeared. Our results suggest that the worse prognosis of BRCA1 mutation carriers in terms of disease-free survival may in large part be due to the age of onset of breast cancer in this population. Thus, BRCA1 mutation status does not appear to be an independent prognostic factor.
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