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  • Articles  (55)
  • Biology  (55)
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  • Articles  (55)
  • 1
    ISSN: 0304-4165
    Keywords: (Escherichia coli K-12) ; Enzyme IICB/enzyme IIA ; PEP-dependent mannitol ; Transport ; phosphotransferase system
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Zur quantitativen Bestimmung der Feulgen-DNS-Mengen wurden Leberzellkerne mit Acriflavin fluorochromiert. Durch fluoreszenzmikrospektrographische Untersuchung konnte gezeigt werden, daß die Meßergebnisse nicht durch Metachromasie beeinträchtigt werden. Bei der Photodekomposition kommt es zu keiner Verschiebung der relativen spektralen Intensitätsverteilung. Die Histogramme der Feulgen-DNS-Mengen von di- und tetraploiden Leberzellen zeigen die exakte Einhaltung der Ploidiestufen und eine geringe Streuung der Meßwerte.
    Notes: Summary For the purpose of quantitative determination of Feulgen-DNA liver nuclei had been stained with fluorescent Schiff-type dye Acriflavin according to Böhm and Sprenger (1968). Fluorescence microspectrophotometric investigations revealed that the quantitative measuring results are not falsified by metachromasia and that photofading does not cause a shift in the relative spectral distribution of fluorescence intensity. The Feulgen-DNA histograms of di- and tetraploid liver nuclei confirm the accuracy of quantitative measurements by exact reproduction of ploidy classes and low variation range in each class.
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  • 3
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Ausgehend vom Leitz-Mikrospektrographen wird gezeigt, wie dieses Gerät für mikrospektrofluorimetrische Untersuchungen und für die quantitative Fluoreszenzcytophotometrie ausgerüstet werden kann. Die im Zusammenhang mit der Anwendung des Gerätes auftretenden Fragen der Eichung und Korrektur der Spektralkurven werden erörtert.
    Notes: Summary The use and additional equipment of the Leitz-Mikrospectrograph for microspectrofluorometry and fluorescence cytophotometry are described in detail. Fluorescence excitation with incident light together with the use of dichromatic beam splitters for optimum separation of the excitation beam from emitted radiation are the characteristic features of this instrument. The fluorescence light is spectrally dispersed by a glass-prism (Special glass for visible light, quarz for UV). A motor driven oscillating mirror moves along the spectrum and reflects the light of continuously changing wavelength on to the photo-cathode of the multiplier, that transfers the optical impulse into an electrical signal. The wavelength dependend change of spectral intensity is registered by a light beam oscillograph fitted with four fixed potentiometers indicating the 400, 500, 600 and 700 nm wavelength position by crosspoints with an oblique line drawn by the wavelength potentiometer, while the sixth potentiometer records the spectral curve. Problems of spectral calibration and correction are discussed. When the prism and the oscillating mirror are removed the instrument may be used as fluorescence cytophotometer. For this purpose of quantitative fluorescence cytophotometry a digital measuring unit with a print-out instrument is presented.
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  • 4
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A cytofluorometric apparatus with incident illumination for fluorescence excitation is described here. Cytophotometric fluorescence measurements (UV- and blue excitation) of acriflavine-acridine yellow-, coriphosphine- and pararosaniline-Schiff stained di-, tetra- and octoploid liver nuclei, leucocytes and sperms (Feulgen reaction) were found to agree with the absorbance data obtained from the same slide by means of the integrating microdensitometer. The stoichiometry of the fluorescence emission is discussed in detail. It is emphasized that not a linear, but an exponential relationship exists between the emitted fluorescence intensity and the concentration of the fluorescent substance. Cytofluorometry of Feulgen-stained nuclei has proved to be as reliable and fast as the absorbance scanning measurements at the intergrating microdensitometer.
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  • 5
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Ausgehend vom Leitz-Mikroskopphotometer MPV mit Auflicht-Anregung wird ein Durchflußfluorescenzcytophotometer beschrieben, das es gestattet, die relativen Feulgen-DNS-Mengen von bis zu 1000 Zellen pro Sekunde zu bestimmen. Die Meßwerte werden in einem Impulshöhenanalysator klassifiziert und gespeichert. Auf Abruf wird der Speicherinhalt analog als Histogramm ausgeschrieben oder digital als Zahlenfolge ausgedruckt. Das Vorgehen bei der Zellsuspensionsherstellung, Fixierung, Hydrolyse und Färbung mit dem Feulgen-Farbstoff Akriflavin wird dargelegt. Anwendungsbeispiele werden besprochen.
    Notes: Summary A flow-through cytophotometer based upon the Leitz-microscope photometer (MPV) is described. The light source is a high pressure Xenon arc HBO 100 in an arrangement for epiillumination. The flow system is designed in such a way that each cell, after previous Feulgenstaining in aqueous suspension, has to pass through the focal plane of the objective. This is achieved by a self-constructed flow channel with a vertical fluid stram carrying the stained cells along the optical axis of the microscope at a flow rate of 100 to 1000 cells per sec. After passage through the focal plane with simultanneous registration of the highest fluorescence reading the cells are flushed off by a horizontal water current. The fluorescence light impulses emitted by the cells are classified and stored by an impulse height discriminator, from which they may be recalled either analogically as a histogram (DNA distribution pattern) or digitally as a series of numbers. In addition, the fluorescence impulses can be visualized at the screen of an oscillograph. The flow rate of the fluorochromized cells is determined by means of a counter unit. The steps of preparation of the cell suspension as well as fixation, hydrolysis and Feulgen-staining with acriflavine-Schiff of the suspended tissue cells is described in detail. The possibilities of application of the instrument as a cyto-morphometric approach to cytology and cytochemistry automation are discussed.
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  • 6
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Die Akriflavin-Feulgen-Färbung (Böhm und Sprenger, 1968) und die Ethidiumbromid-Fluorochromierung nach vorausgehender Pepsinbehandlung (Göhde et al., 1971) ergeben an Leberzellausstrich-Präparaten weitgehend gleichartige DNS-Häufigkeitsverteilungen. Bei der zeitlich aufwendigen (220 min) Akriflavin-Färbung ist eine optimale Darstellung der Zellmorphologie und eine jahrelange Archivierung der Ausstrichpräparate möglich. Die rasch durchführbare Ethidiumbromid-Färbung (70 min) bietet nur nach schwerer Alteration der Zellmorphologie durch die vorausgehende Pepsinbehandlung eine selektive Darstellung der DNS. Eine Archivierung von Ausstrichpräparaten ist nur für 2 Tage möglich. Die schwere Alteration der Zellmorphologie ist besonders bei durchflußphotometrischen Prescreeninguntersuchungen in der gynäkologischen Krebsvorsorge nachteilig. Zellpopulationen, die zu einer zytophotometrischen Verdachtsdiagnose geführt haben, sind durch Verlust des Zytoplasmas und der Kernstruktur einer konventionellen morphologischen Diagnostik nicht mehr zugängig.
    Notes: Summary Acriflavine-Feulgen (Böhm und Sprenger, 1968) and ethidiumbromide fluorescence after previous pepsin digestion (Göhde et al., 1971) yield corresponding DNA distribution patterns when applied to liver smears. With the time-consuming acriflavine staining (220 min) the cellular morphology is best preserved and the stained specimen may be stored for long periods. The rapidly obtainable ethidiumbromide staining (70 min) results in a selective fluorescence of DNA only after heavy alteration of the cellular morphology by pepsin digestion. Storage of the material is only possible for two days. The heavily altered cellular morphology, however, is rather unfavorable for prescreening in automated cytology. Specimens that were found to be suspicious are no longer suitable for conventional cytological diagnosis, because they have lost their cytoplasm and nuclear chromatin structure.
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  • 7
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Beim Vergleich des Feulgen-Farbgehaltes verschiedener Zellkerne (Leberzellen, Lymphozyten, Granulozyten und Spermien) traten nach Alkoholfixierung Abweichungen der gemessenen Feulgen-Werte von den nach dem Gesetz von der DNS- Konstanz zu erwartenden DNS-Gehalt dieser Kerne auf. Verglichen mit den Feulgen-Werten der diploiden Leberzellkerne ergaben Lympho- und Granulozyten bei allen Hydrolysezeiten zu niedrige (bis zu minus 20%), haploide Spermien im postmaximalen Hydrolysebereich zu hohe Feulgen-Werte (z. T. sogar höhere Werte als die diploiden Zellkerne). Innerhalb desselben Zelltypes wurden dagegen, auch beim Vergleich der verschiedenen Ploidiestufen der Leberkerne, keine Differenzen festgestellt. Da die an Leukozyten und Spermien beobachteten Abweichungen nach Methanol-Formalin-Eisessig-Fixierung nicht mehr auftraten und auch durch UV-absorptionscytophotometrische Messungen nicht bestätigt werden konnten, muß man annehmen, daß es sich um Proportionalitätsfehler handelt, die auf Hydrolyseunterschieden beruhen. Für die quantitative Feulgen-Cytophotometrie scheint daher die Methanol-Formalin-Eisessig-Fixierung besser geeignet zu sein als die Alkoholfixierung, bei deren Verwendung es leicht zu Proportionalitätsfehlern während der Feulgen-Hydrolyse kommen kann.
    Notes: Summary Comparing the Feulgen dye-content of different nuclei (liver cells, lymphocytes, granulocytes and sperms) after alcohol-fixation deviations were found between the measured Feulgen values and the DNA-content to be expected from the DNA-constancy law. The Feulgen values of lymphocytes and granulocytes proved to be lower (up to minus 20%) than those of diploid liver nuclei at all hydrolysis times, while in the postmaximal range of hydrolysis the values of the haploid sperms were too high (even higher than those of the diploid nuclei). Such differences did not appear when nuclei of the same cell type in different DNA- ploidy classes (liver nuclei) were compared. Those deviations of leucocytes and sperms were no longer found after fixation in methanol-formalin-glacial acetic acid and, in addition, could not be confirmed by UV-absorption measurements. For that reason we suppose them to be due to proportionality errors caused by variations in the hydrolytic behaviour of the different nucleoproteins. Thus fixation in methanol-formalin-glacial acetic acid seems to be more suitable for quantitative Feulgen measurements than alcohol-fixation, which may easily give rise to proportionality errors during Feulgen hydrolysis. Moreover, to avoid any false interpretation of Feulgen data we should suggest controll measurements using another independent method (f. e. UV-absorption), or — if this is impossible — to check the Feulgen values after different fixations and variant hydrolysis times (premaximal, maximal, postmaximal).
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  • 8
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A sensitive test is described for proof of even illumination of the light field as well as a steady surface response of the photocathode in fluorescence cytophotometry using a GG 21 uranyl glass platelet as fluorescence standard.
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  • 9
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The film-submerged reactor (FSR) is a modified “Gorbach fermenter” (Gorbach 1969). Using this reactor at low rotation speed, good yeast growth was reached on n-alkanes. The biomass yield by Candida oleophila was more than 7 g/l from 1% alkanes in 48 h. Low aeration resulted in slow growth but high biomass yield, high aeration resulted in quick growth but lower yield. The optimal rotation frequency at tested conditions was 32 rpm. Alkane concentrations greater than 1% decreased the growth of C. oleophila. The influence of pH-regulation was not important, whereas the age of inoculum cultures showed significant influence on growth velocity.
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  • 10
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Grown anaerobically on d-xylose, Klebsiella planticola ATCC 33531 produced acetate, formate, lactate, CO2 and ethanol as major end-products. A Mu-insertion mutant which lacked pyruvate-formate-lyase showed among its fermentation products more than 70% d-lactate with residual acetate, 2,3-butanediol, and traces of ethanol, formate, and CO2. After the introduction of a plasmid carrying the gene for the enzyme pyruvate decarboxylase from Zymomonas mobilis, this Klebsiella mutant became an efficient ethanol producer. The recombinant strain produced 387 mM ethanol from 275 mM xylose in 80 h, about 83% of the theoretical maximal yield. Furthermore, this mutant consumed more than double the amount of xylose (41 g/l) compared to the wild-type, due to reduced production of inhibiting acids during growth.
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