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  • Ultrastructure  (74)
  • bioavailability  (28)
  • 42.55
  • Gas chromatography
  • seaweed
  • Springer  (133)
  • 1980-1984  (133)
  • 1983  (133)
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  • 1980-1984  (133)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    European journal of nutrition 22 (1983), S. 185-194 
    ISSN: 1436-6215
    Schlagwort(e): sugar substitutes ; D-glucose ; bioavailability ; D-glucitol (D-sorbitol) ; D-mannitol ; Palatinit® ; D-glucosyl-α(1→1)-D-mannitol ; D-glucosyl-α(1→6)-D-glucitol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Zur Vertiefung des Verständnisses vom Stoffwechsel des Zuckeraustauschstoffes Palatinit® wurden seine zwei Bestandteile D-Glucosyl-α(1→1)-D-mannit und D-Glucosyl-α(1→6)-D-glucit [D-Glucosyl-α(1→6)-D-sorbit] nach dem Verfahren von Karimzadegan et al. auf ihre Glucose-Bioverfügbarkeit an ketotischen Ratten untersucht. Bei Umwandlungsraten in Glucose von 6 bzw. 20 % für Mannit und Glucit (Sorbit) sowie von 39 bzw. 42% für Glucosylmannit und Glucosylglucit erhält demnach der metabolische Glucose-Pool nicht das volle Glucose-Äquivalent aus diesen Verbindungen. Von dem Anteil an präformierter Glucose in den Glucosylhexiten — theoretisches Maximum 50 % — sind nur 36 % aus Glucosylmannit bzw. 32 % aus Glucosylglucit bioverfügbar. Die im Vergleich zur Theorie verminderte Bioverfügbarkeit von Glucose aus Palatinit® wird auf partiellen mikrobiellen Abbau in unteren Darmabschnitten zurückgeführt. Die an Ratten erhaltenen Ergebnisse werden auch für alle anderen Spezies gelten, welche in Caecum und/oder Colon Kohlenhydrate vergären. Die Unterschiede zwischen D-Glucosyl-α(1→1)-D-mannit und D-Glucosyl-α(1→6)-D-glucit werden durch unterschiedliche Verzögerung der Glucoseresorption im Dünndarm, wo auch D-Glucit angreift, bedingt. Die Ermittlung der Glucose-Bioverfügbarkeit gewährt weitgehende Einblicke in das Schicksal von Kohlenhydraten einschließlich der Symbiose zwischen Säugetier und Mikroorganismen im Dickdarm. Da ein ziemlich vollständiger Überblick über die metabolischen Konsequenzen nach ihrer Zufuhr erhalten wird, sollte das Verfahren zur Messung der Bioverfügbarkeit von Glucose daher bei Abschätzungen der Lebensmittelsicherheit anderer Zuckeraustauschstoffe ebenfalls angewandt werden.
    Notizen: Summary For the sake of metabolic insight into the fate of the sugar substitute Palatinit®, its two components D-glucosyl-α(1→1)-D-mannitol and D-glucosyl-α(1→6)-D-glucitol [D-glucosyl-α-(1→6)-D-sorbitol] were assayed for glucose bioavailability by the procedure of Karimzadegan et al. using ketotic rats. With conversion rates into glucose of 6 and 20 %, respectively, for free mannitol and glucitol (sorbitol), 39 % for glucosylmannitol and 42 % for glucosylglucitol, the metabolic glucose pool of the rat does not receive the full carbohydrate complement of these compounds. The preformed glucose moiety of the glucosylhexitols is bioavailable by 36 and 32 %, respectively, from glucosylmannitol and glucosylglucitol, with 50 % as theoretical maximum. Less than theoretical bioavailability of glucose from Palatinit® is ascribed to microbial attack in the hindgut. The data on rats are held valid also for other species demonstrating carbohydrate fermentation in the caecum and/or colon. Differences between D-glucosyl-α(1→1)-D-mannitol and D-glucosyl-α(1→6)-D-glucitol are caused by a differential delay of glucose absorption in the small intestine, also exerted by D-glucitol. The deep metabolic insight offered by the glucose bioavailability assay into the fate of carbohydrates includes the mammal-microbial symbiosis in the large bowel. Since a rather complete survey of the metabolic consequences after their intake can be obtained, the assay system should be generally applied in assessments of food safety also of other sugar substitutes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 34 (1983), S. 20-26 
    ISSN: 1570-7458
    Schlagwort(e): Dioryctria abietella ; Cone pyralid ; Lepidoptera ; Pyralidae ; Sex pheromone, (Z,E)-9,11-tetradecadienyl acetate ; Single sensillum recordings ; Electroantennography ; Gas chromatography ; Mass spectrometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé L'analyse en chromatographie gazeuse associée à une détection électroantennographique a montré que l'acétate (Z,E)-9,11-tétradécadiényle (Z,E)-9,11–14:Ac est l'un des composants de la phéromone de Dioryctria abietella Schiff (Lepid.: Pyralidae). Couplage chromatographie en phase gazeuse spectrometrie de masse a montré la présence d'acétate tétradécadiényle avec un spectre de masse et un indice de rétention identiques au Z,E-9,11–14:Ac Un récepteur cellulaire sensible à la fois au Z,E-9,11–14:Ac et à un extrait de la femelle a été identifié sous l'antenne du mâle. Les analyses des antennogrammes et de la cellule isolée ont étayé la caractérisation du composant de la phéromone comme étant Z,E-9,11–14:Ac. Un récepteur cellulaire additionnel sensible à l'acétate (Z.)-9-tétradécadiényle et à l'acétate (Z.E.)-9,12-tétradécadiényle a été trouvé sur l'antenne du mâle, mais il n'était pas activé par l'extrait de la femelle. Sur le terrain Z,E-9,11–14:Ac, présenté seul, attirait des nombres importants de mâles de D. abietella. L'addition de l'acétate (Z)-9-tétradécényle a inhibé l'attraction des mâles par les pièges.
    Notizen: Summary Gas chromatographic analyses coupled with electro-antennographic detection indicated that (Z,E)-9,11-tetradecadienyl acetate (Z,E-9, 11–14:Ac) is a pheromone component of the cone pyralid Dioryctria abietella. Gas chromatographic-mass spectrometric analyses confirmed the presence of a tetradecadienyl acetate with mass spectrum and retention index identical to Z,E-9,11–14:Ac. A receptor cell sensitive to both Z,E-9,11–14:Ac and the female extract was identified on the male antenna. An additional receptor cell sensitive to (Z)-9-tetradecenyl acetate and (Z,E)-9,12-tetradecadienyl acetate was found on the male antenna but was not activated by the female extract. In the field Z,E-9,11–14:Ac presented alone attracted significant numbers of male D. abietella. Addition of (Z)-9-tetradecenyl acetate inhibited the attraction of males to traps.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 30 (1983), S. 1-4 
    ISSN: 1432-0649
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Twenty FIR laser lines with wavelengths between 146 and 2000 μm have been observed from deuterated formyl fluoride (DCOF) optically pumped with isotopic CO2 lasers. Tunable diode laser measurements on thev 4 band of DCOF were combined with earlier high precision spectroscopic data on thev 3 andv 4 bands, and enabled identification of the transitions responsible for 9 of the new FIR lines.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 30 (1983), S. 135-142 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An analysis of cw synchronously pumped dye lasers is presented. Under the assumption that the cavity (tuning element) bandwidth is much wider than the bandwidth of the transform limited pulses generated, the pulse forming dynamics is rigorously treated. It is shown that for a finite mismatch between the lengths of the dye and the pump lasers, a steady-state pulse develops in the dye laser cavity with a conserved pulseshape. The characteristics (energy, shape, peak power, duration) of these pulses of ultimate width are quantitatively determined as a function of cavity mismatch. An analytical solution for the pulse envelope is determined, which yieldsI(t)∝Sech2(t/t p ) to a good approximation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 32 (1983), S. 75-78 
    ISSN: 1432-0649
    Schlagwort(e): 33 ; 34 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Multiphoton absorption (MPA) of the CO2 laser 9 μmR(30) line (pulse width 60 ns, FWHM) by NH3 and NH3/N2 mixtures was studied as a function of gas composition, pressure and laser fluence (Φ). MPA occurs for Φ smaller than those that have been used for optically pumped NH3/N2 lasers; consequently a simple two-level absorption model will not adequately describe laser action in these systems. The photon energy deposited in NH3/N2 mixtures can be calculated from the MPA cross-section and the fluence dependence of the illumination geometry. An examination of the efficiency of conversion of this absorbed energy to the reported radiant energy of optically pumped NH3/N2 lasers shows an optimum value which depends on pressure, and gas composition.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 32 (1983), S. 105-111 
    ISSN: 1432-0649
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The effects of H2, He, and N2 buffer gases on the efficiency of the cw 12.08 μm NH3 Raman laser are studied experimentally. The laser output power is increased by nearly 60% with the addition of H2 or He, which we essentially attribute to the high thermal conductivity of these buffer gases. In the optimum conditions (NH3/H2:1/1 mixture with 0.35 Torr partial pressure of NH3) 3.3 W output power at 12.08 μm is obtained which corresponds to 11% power conversion efficiency.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 32 (1983), S. 127-135 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A cw uv copper hollow cathode laser is described, which could be operated for a longer time duration with an output power of 7 mW in the 260 nm region. A double-cathode configuration with a protection for the mirrors from metal-vapour deposition is presented. Characteristics of the laser output power, the spontaneous emission, and the ion densities in the negative glow were measured as depending on the discharge current, the neon gas pressure, and the size of the cathode slit. The observed saturation of the laser output power at high discharge current (1 A/cm2) and the optimum slot size are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 32 (1983), S. 83-84 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 33.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A population inversion between the 62 P 3/2 and 62 P 1/2 state of thallium has been achieved for the first time by incoherent photodissociation of TII. This is accomplished by using wall-ablating flashlamps of short risetime and appropriate light filtering. The inversion lasts about 4 μs and is terminated by quenching collisions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 32 (1983), S. 193-198 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 33 ; 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The vibrational relaxation time constant for theB v=0 vibrational level of XeCl* has been investigated by observing the coupling between theB v=1 andB v=0 vibrational levels under saturated lasing conditions. Based on this observation, estimates of the expected extraction efficiency from theB-state have been made.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 30 (1983), S. 29-33 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This report describes an experimental examination of the output characteristics of the continuous-wave (cw) carbon monoxide flame chemical laser (FCL) of the CS2/O2/N2O type in case of small CS2/O2 reactants ratios (tipically CS2/O2≦1/10). A linear burner which gives a homogeneous and stable flame was used during the experimental study. The measurements of temperature distribution in CS2/O2 as well as CS2/O2/N2O flames show maximum temperatures of 1040 and 890 K, respectively. The addition of nitrous oxide (N2O) leads to dramatically enhanced output laser power caused primarily by V−V transfer processes. A chemical efficiency, based on the reaction O+CS→CO*+S, of 3% was achieved. The spectral composition of the CO FCL of the CS2/O2/N2O type shows lasing in the region from 5.130 to 5.586 μm. Experimental results were obtained with a nondispersive optical cavity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 31 (1983), S. 5-8 
    ISSN: 1432-0649
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Short FIR laser pulses of high repetition rate are obtained by pumping NH3 with the pulses of a passively Q-switched IR laser. The two cascade laser transitions observed show coupled relaxation oscillations. The pulse shapes and delay times are qualitatively in agreement with a four-level rate-equation model.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 30 (1983), S. 57-77 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report detailed experimental data on the passive Q-switching operation in a CO2 laser with CH3I saturable absorber, and on the transient behaviour in the near-Q-switching situation. Under suitable operating conditions, we found bistability in the output power. In some cases, we observed the simultaneous presence of bistability and passive Q-switching. The theoretical part of the paper starts from the four-level model of laser with saturable absorber, as formulated by other authors. By adiabatically eliminating the variables of the resonant levels, we reduce the problem to a set of three differential equations, from which we derive explicit analytical conditions for the rise of passive Q-switching. These conditions turn out to be in good qualitative and partially quantitative agreement with our experimental findings as well as with other experimental data previously obtained by other authors. Finally we classify the possible combinations of passive Q-switching and bistability that one can find in this type of experiments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 30 (1983), S. 109-116 
    ISSN: 1432-0649
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The stability of polymethine dyes under XeCl laser excitation has been investigated. (For these dyes emitting in the ir the difference between absorbed and emitted photoenergy is 2 eV.) The stability was measured in an amplifier device operating in the saturated regime. While the influence on dye concentration is negligible, the fluence dependence shows the importance of two photon absorptions. A meausure for the stability is the number of photons which can be emitted per dye molecule before the dye solution has degraded to 50% of the initial value. This value is in the range of 150–280. The stability is clearly related to the formation of photoproducts absorbing at the pump and the laser wavelength. A model starting from the change in the dye solution absorption spectra is in very good agreement with the observed energy decays.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 30 (1983), S. 41-45 
    ISSN: 1432-0649
    Schlagwort(e): 42.80 ; 42.10 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the propagation of radiation in a gas, the resonant frequency of which changes with time when affected by external electric and magnetic fields. It is shown that for an harmonic change of the resonant frequency under appreciable energy exchange between electromagnetic field and medium, deep amplitude modulation of radiation may be achieved. The analytical expressions obtained for a field in a gas allow rather accurate calculation of the space-time structure of the radiation penetrated through the medium layer. The numerical calculations are compared with the known experiment [4], good agreement is obtained. The transformation of radiation between dispersive branches with adiabatic stepwise variation of the resonant frequency has been also studied. Branch-tobranch transformation is investigated and the adiabatic invariant is found to be the total number of the high and low frequency radiation quanta corresponding to two dispersive branches.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 32 (1983), S. 79-81 
    ISSN: 1432-0649
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract 48 new resonant pumping schemes, by ir Stark tuning, have been performed on15NH3, with cw CO2 and N2O lasers. Among the 25 different fir wavelengths obtained, 15 correspond to new emissions, raising thus to 45 the total number of cw fir emissions from this gas, in the presence of electric field.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 192 (1983), S. 42-44 
    ISSN: 1432-041X
    Schlagwort(e): Chick embryo ; Gastrulation ; Adenylate cyclase ; cAMP phosphodiesterase ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ultrastructural localization of adenylate cyclase (E.C. 4.6.1.1.) and cAMP phosphodiesterase (PDE) (E.C. 3.1.4.17.) in the ectoderm of the developmental stage 4 chick embryo was studied. Adenylate cyclase was localized in the lateral surfaces of the ectodermal cells. In the primitive streak cells the enzymatic activity was observed on all the lateral surfaces, whereas in the periphery of the blastoderm the reaction product was localized in the apical parts of the lateral plasma membranes only. cAMP PDE localized in the apical cytoplasm of the ectodermal cells, with highest activity in the globular projections.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 192 (1983), S. 171-178 
    ISSN: 1432-041X
    Schlagwort(e): Differentiation ; Digestive tract ; Endoderm ; Organ culture ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The self-differentiation potency of the endoderm of the chick embryo was investigated mainly by transmission electron microscopy. Endodermal fragments isolated from 4- to 6-day stomach or small intestine were cultured in the absence of mesenchyme and were able to differentiate in vitro into organ-specific epithelia. Endodermal fragments isolated from the stomach region differentiated into a pseudo-stratified epithelium with periodic acid Schiff-positive mucous granules in the apical cytoplasm, while those from the small intestinal region differentiated into a simple columnar epithelium with a striated border which was positive in alkaline phosphatase activity. These features are comparable with those of the mucous secretory epithelium of the normal embryonic stomach and the absorptive epithelium of normal embryonic small intestine, respectively. Next, the self-differentiation potencies were investigated of the upper and lower layers of the blastoderms, at stages 1–5 of Hamburger and Hamilton (H. and H.). Both stomach-type and small-intestine-type epithelia developed only when fragments of the lower layer isolated from the blastoderms older than stage 3 of H. and H. were cultured, suggesting that cells possessing the potency to differentiate into the stomach- and small-intestine-type epithelia exist in the definitive endoderm at the beginning of its formation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 127-136 
    ISSN: 1432-1041
    Schlagwort(e): statistical analysis ; nonparametric statistical methods ; bioavailability ; confidence interval ; ANOVA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary For a two-way cross-over design, which appears to be the most common experimental design in bioavailability studies, 95%-confidence limits for expected bioavailability can be obtained by classical analysis of variance (ANOVA). If symmetry of the confidence interval is desired about zero (differences) or unity (ratios) rather than about the corresponding point estimator, Westlake's modification can be used. Two nonparametric methods and their adaptations to bioavailability ratios are reviewed, one based on Wilcoxon's signed rank test (Tukey), and the other on Pitman's permutation test. The necessary assumptions and the merits of these procedures are discussed. The methods are illustrated by an example of a comparative bioavailability study. A FORTRAN program facilitating the procedures is available from the authors upon request.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 791-796 
    ISSN: 1432-1041
    Schlagwort(e): furosemide ; bioavailability ; diuretic effect ; urine sodium ; urine potassium ; power of ANOVA ; tablet formulations ; urinary flow rate ; normal volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The relative bioavailability and diuretic effect of 2 commercially available tablet preparations of furosemide 40 mg was examined in 10 healthy male volunteers. A close linear relationship between the urinary excretion rate of furosemide and the rate of sodium ion excretion in urine and/or flow rate of urine was demonstrated. There were no significant differences in the urinary excretion of furosemide, sodium and potassium ions or urinary volume following the oral doses. The difference in drug content affected the urinary recovery of furosemide over 24 h but had no effect on the pharmacological response. The analytical power of ANOVA using the various parameters of the responses to furosemide was no lower than when the parameters of urinary excretion of furosemide were used.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 237-241 
    ISSN: 1432-1041
    Schlagwort(e): triamterene ; bioavailability ; pharmacokinetics ; metabolism ; hydroxy triamterene sulphate ; urinary excretion ; i.v. administration ; first-pass-effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary With a new formulation, which made intravenous infusion of triamterene (TA) possible, plasma levels and urinary excretion rates of TA and its main metabolite (OH-TA-ester) were measured in a randomized, cross-over trial in 6 healthy volunteers given triamterene 10 mg i.v. and 50 mg p.o. TA and OH-TA-ester were determined by densitometric measurement of native fluorescence after thin layer chromatography. Distribution volumes of the central compartment of TA and OH-TA-ester were 1.49 l/kg and 0.11 l/kg, respectively. Terminal half-lives were 255 min for TA and 188 min for OH-TA-ester after i.v. administration. For TA total plasma clearance was 4.5 l/min and renal plasma clearance 0.22 l/kg. The formation of OH-TA-ester was very rapid and the concentration of the metabolite exceeded that of TA at all times. After i.v. administration the urinary recovery of TA and OH-TA-ester was 4.4% and 50.9%, respectively. The bioavailability of TA was 52%, corresponding to absorption of 83%. TA is partly eliminated by a first-pass-effect. The main metabolite of TA is OH-TA-ester, which is pharmacologically active.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 449-453 
    ISSN: 1432-1041
    Schlagwort(e): canrenone ; pharmacokinetics ; plasma level ; bioavailability ; urinary excretion ; spironolactone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Five healthy male volunteers received canrenoate-K 200 mg (Sincomen® pro injectione) by intravenous injection and one week later spironolactone 200 mg (Sincomen®-100) orally. Plasma levels and urinary excretion of unchanged canrenone were determined up to 24 h by a specific HPLC method. Following intravenous administration, the maximum plasma level of 2066±876 ng/ml was found after 29±15 min and thereafter the concentration declined with a half-life of 3.7±1.2 h. Total clearance was 4.2±1.7 ml/min·kg. After oral ingestion, the maximum concentration of 177±33 ng/ml was observed at 4.4±0.9 h. The absolute bioavailability of canrenone was 25±9%. Within 24 h, respectively 0.4 and 0.6 mg, canrenone were excreted by the kidney after intravenous and oral administration. The half-life of elimination was 4.9±1.8 h (i.v.) and 3.9±1.2 h (p.o.).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 103-108 
    ISSN: 1432-1041
    Schlagwort(e): dexamethasone ; bioavailability ; pharmacokinetics ; ‘first-pass’ effect ; pre-systemic elimination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and oral biovailability of dexamethasone were studied in 6 patients with neurological disease being treated with high dosages of the drug. A specific high performance liquid chromatographic assay was used to measure dexamethasone concentrations. Unlike the previously published mean figure of 0.78 for the oral bioavailability of the drug given in single doses to healthy volunteers, the mean bioavailability of dexamethasone in the patients studied was 0.53±SD 0.40. It appeared more likely that this incomplete bioavailability was due to presystemic elimination than to poor absorption. The intravenous clearance of the drug was relatively high (0.4902±SD 2291 l kg−1, approximately 65% of expected hepatic plasma flow), the oral clearance higher (2.5804±SD 3.2181 l kg−1 h−1) while the absorption rate constant (4.8729±8.4998 h−1), suggested rapid absorption after oral administration. Prior phenytoin and possibly prior dexamethasone therapy is likely to have contributed to the higher clearance values of the drug in these patients than the values reported in healthy volunteers after single dose studies.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 353-356 
    ISSN: 1432-1041
    Schlagwort(e): oxmetidine ; pharmacokinetics ; bioavailability ; plasma half-life ; clearance ; oral dose ; i.v. dose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma concentration curves and urinary excretion of oxmetidine after administration of single i.v. (100 mg) and oral (200 mg) doses have been studied in 11 patients with peptic ulcer disease. The mean bioavailability of the drug was 70% (range 53–91%). After intravenous administration, the mean plasmat 1/2β was 3.0 h, the mean apparent volume of distribution 0.7 l/kg, the mean total plasma clearance 12.3 l/h and the mean plasma renal clearance was 0.7 l/h. Following intravenous and oral administration an average of 6% and 3%, respectively, of unchanged drug was found in the urine. The plasma concentration curve after oral administration in most patients exhibited two maxima, with peak concentrations appearing between 45 and 210 min after dosing.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 689-693 
    ISSN: 1432-1041
    Schlagwort(e): amiodarone ; bioavailability ; calculation ; linear pharmacokinetics ; absorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Methods for estimating the bioavailability of drugs with long elimination half-lives are examined. Provided both absorption and disposition are linear a simple linear regression method is developed which can be used to calculate bioavailability in situations where only an incomplete estimate of the area under the curve (AUC) is available. The regression method and the traditional method of comparing the AUC following an oral dose to the AUC following an i.v. dose were applied to simulated data. It was found that the AUC ratio method works well as long as absorption is complete within the time over which the AUC is computed. The regression method is less precise than the AUC ratio method but is more accurate for drugs with long absorption half-lives. When applied to published data on a beta blocker the two methods produced comparable results. The bioavailability of amiodarone in three human subjects was calculated to be 0.20, 0.44 and 0.98 using the regression method with similar results from the ratio method. It is not possible to estimate the clearance of amiodarone from single dose data.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 251-253 
    ISSN: 1432-1041
    Schlagwort(e): chlorambucil ; prednimustine ; plasma concentrations ; bioavailability ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of chlorambucil has been investigated in a cross over study after oral administration of the free drug (10 mg) and its prednisolone ester (prednimustine, 100 mg). The bioavailability of chlorambucil was about five times lower when given as prednimustine as compared to administration of the free drug. The peak plasma concentration was about twice as high and it was obtained more rapidly when the free drug was given. No intact prednimustine could be detected in plasma.
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 563-568 
    ISSN: 1432-1041
    Schlagwort(e): indomethacin ; multi-dose kinetics ; controlled release formulation ; capsule formulation ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetics of a controlled release (CR) formulation of indomethacin 75 mg (Indocid-Retard®) given once daily was compared with a conventional 25 mg indomethacin capsule (Indocid®) given 3 times daily for 7 days, to 14 healthy volunteers, using a randomized, cross-over, multiple-dose study design. The following differences in plasma indomethacin profiles after the 2 treatments were observed: average peak concentrations (Cmax) for the CR regimen were higher and the time to peak (Tmax) was significantly delayed. Trough (pre-morning dose) plasma concentrations (Cmin) on Days 2, 5, 6 and 7 were significantly lower after the CR-formulation. No statistically significant differences between preparations for area under the plasma concentration time curve (AUC0–24h) or for renal clearance were observed. Average steady-state plasma concentrations (C p ss ) on Day 7 of the multiple dose regimens averaged 0.477 and 0.427 µg/ml for the 75 mg CR once daily and the conventional 25 mg t.i.d. treatments, respectively. These results show that the bioavailability of the CR and conventional indomethacin formulations under these multiple-dose conditions was not significantly different.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 537-542 
    ISSN: 1432-1041
    Schlagwort(e): morphine ; analgesic activity ; tablets solution ; pharmacokinetics ; bioavailability ; pain score ; dose-response relationship ; chronic pain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The steady-state kinetics of morphine given as tablets and solution were compared in 7 cancer patients with chronic pain. There was no accumulation of morphine (20–40 mg) when repeatedly administered every 4 to 6 h. The mean steady-state concentration of morphine during the dose interval varied between 5.9 and 68.4 ng/ml (20.7–240 nmol/l), and was linearly related to the daily dose of morphine. There were no significant differences between the tablets and the solution of morphine with regard to relative oral bioavailability or peak concentration. The time-to-maximum plasma concentrations was significantly longer for the tablets. The pain score profile, assessed by a visual analogue scale during a dose interval, showed a similar pattern after the two oral formulations of morphine. No significant linear relationship between the scores and the plasma concentrations of morphine was observed.
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  • 28
    ISSN: 1432-1041
    Schlagwort(e): metoprolol ; bioavailability ; young ; elderly ; metoclopramide ; probanthine ; gut motility
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The bioavailability of metoprolol was studied in eight healthy young and seven healthy elderly volunteers. Large interindividual differences in the bioavailability of metoprolol were observed in both groups. However, there was no significant difference in AUC, peak plasma concentration or elimination half-life between young and elderly, but time to peak concentration was significantly longer in the elderly. Pretreatment with metoclopramide had no effect on AUC but caused significant increases in peak concentration and decreases in time to peak concentration in both groups. Probanthine pretreatment (only to the young) resulted in a significant decrease in peak concentration of metoprolol and a significant increase in time to peak concentration but had no effect on the AUC. These results suggest that alterations in gastric emptying and gut motility due to ageing or other drugs have no effect on the overall availability of metoprolol to the systemic circulation but may have significant effects on the time to peak plasma concentration and peak concentration achieved after a single oral dose.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 419-424 
    ISSN: 1432-1041
    Schlagwort(e): dihydrocodeine ; pharmacokinetics ; acid metabolites ; radioimmunoassay ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Serum concentrations of dihydrocodeine and its acid metabolites have been determined in seven human volunteers (6 male) who received the drug orally (30 mg and 60 mg) and intravenously (30 mg) on separate occasions, and in twenty-four patients (12 male) receiving 25 mg or 50 mg of the drug intravenously. The concentrations were estimated by radioimmunoassay on reconstituted extracts from serum after an extraction process which effectively separates dihydrocodeine from its polar acidic metabolites. The intravenous data show that dihydrocodeine kinetics followed a two-compartment distribution model. The concentration curves after oral administration indicated relatively rapid absorption with mean peak concentrations at 1.6h–1.8h. The mean half-lives varied between 3.3h–4.5h. From the AUC, the mean bioavailability of orally administered drug was 21% (range 12–34%). The peak levels of the acidic metabolites occurred between 1.8h–2.0h after oral administration and 2.2h–2.5h after i.v. administration, and they were significantly greater after oral administration. The low bioavailability of dihydrocodeine, together with the earlier and higher plasma levels of the acid metabolites after oral administration is suggestive of substantial first-pass metabolism.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 467-473 
    ISSN: 1432-1041
    Schlagwort(e): hydralazine ; heart failure ; pharmacokinetics ; bioavailability ; metabolism ; hypertension ; dapsone ; acetylator phenotype
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of various disease states, other than hypertension, on the pharmacokinetic behaviour of hydralazine is not completely known. In the present study the pharmacokinetics of oral hydralazine has been evaluated in 7 patients with severe, chronic heart failure, using 8 compensated hypertensives as controls. The pharmacokinetics was evaluated by measuring the plasma concentrations of hydralazine (“apparent” and “real” hydralazine) and hydralazine pyruvate hydrazone, and by assessing acetylator phenotype after a small dose of dapsone. The AUC (area under the plasma concentration curve) following a single, oral 50 mg dose was significantly larger in patients with chronic heart failure NYHA Class III–IV than in patients with essential hypertension without cardiac decompensation. A decreased rate of hepatic elimination of hydralazine is suggested as a major contributory factor to this finding.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 553-556 
    ISSN: 1432-1041
    Schlagwort(e): Endralazine ; pharmacokinetic ; acetylator phenotype ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Endralazine (E), a new hydralazine-like antihypertensive was given intravenously (0.05 mg/kg) to 10 normal volunteers (5 slow and 5 fast acetylators). Plasma levels were fitted to a 3 compartment model and pharmacokinetic parameters (area under curve [AUC 0 ∞ ], clearance, volume of distribution, half-lives) obtained in the usual way. Bioavailabilities of 5 and 10 mg oral doses of E were determined from the AUC 0 ∞ generated in a previous study of oral E given to the same subjects. E had high system bioavailability (73.5–99.1%) suggesting that it was almost completely absorbed without undergoing appreciable first-pass metabolism. Furthermore, dose size and acetylator phenotype did not significantly affect the bioavailability of E. This behaviour contrasts with that of hydralazine where systemic bioavailability was 〈40%, and 2 to 3 times higher in slow acetylators than in fast acetylators. It is concluded that the bioavailability of E is high and not influenced by acetylator phenotype; these properties suggest some clinical advantages for the drug.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 667-672 
    ISSN: 1432-1041
    Schlagwort(e): theophylline ; asthma ; children ; sustained-release ; diurnal ; absorption ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The absolute oral bioavailability of a sustained release theophylline tablet (Nuelin-SR250), given 12 hourly was determined in 14 asthmatic children aged 5 to 13 years. In 4 of the patients, mean bioavailability of the fourth dose was 38.9±8.4% and that of the sixth dose was 67.9±25.9% (p〈0.05) in the other ten patients. This suggests steady-state had not been achieved after four doses. In the initial study with 9 patients, a significant diurnal variation in predose plasma theophylline concentrations was observed, as the mean morning predose concentrations were 2.9 fold greater than the mean evening predose concentrations (p〈0.005). Dual peak plasma concentrations occurred in 5 out of the 9 patients. The mechanism of this diurnal variation was investigated in a further 5 asthmatic children (10.8 years ±1.6). Morning and night steady-state plasma theophylline concentrations during a continuous intravenous infusion of aminophylline were not different (14.9±5.3 mg/l vs. 15.6±5.9 mg/l), demonstrating that there was no diurnal variation in the plasma clearance of theophylline. The diurnal variation in predose concentrations with Neulin-SR250 was confirmed with the morning concentrations again being 2.6 fold greater than those in the evening. However, bioavailability was not significantly different for day (09.00–21.00) and night (21.00–09.00) dosing intervals after doses 6 and 7 respectively of Nuelin-SR250. The plasma concentration versus time profiles suggested that the diurnal variation in predose concentrations was due to slower absorption of the evening dose.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 509-515 
    ISSN: 1432-1041
    Schlagwort(e): cibenzoline ; pharmacokinetics ; bioavailability ; urinary excretion ; antiarrhythmic drug ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetics of cibenzoline (UP 339.01), a new antiarrhythmic drug, was studied after i.v. and oral administration to 5 healthy subjects. Cibenzoline levels in plasma and urine cibenzoline were measured by a GLC method. After i.v. administration, the total clearance was 826 ml · min−1. The fraction of cibenzoline excreted unchanged in the urine was 0.602 and it was correlated with the creatinine clearance. After i.v. and oral administration, the renal clearances were 499 ml · min−1 and 439 ml · min−1, and the half-lives were 4 h 01 min and 3 h 24 min, respectively. The differences were not significant. Availability by the oral route was 0.92, the maximum plasma concentration being observed at 1 h 36 min. The results were compared with those for other antiarrhythmic drugs.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 281-283 
    ISSN: 1432-1041
    Schlagwort(e): dyphylline ; pharmacokinetics ; bioavailability ; drug levels
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and bioavailability of 3 oral dyphylline preparations, solution (S), regular (R) and sustained release (SR), were studied in 8 healthy subjects (mean age 25 years). A single dose of each preparation, 20 mg·kg−1, was given at one week intervals and multiple serum samples obtained over 24 h. Drug levels were measured by high performance liquid chromatography. No adverse effects were found. The dyphylline half-life for the solution was 2.16±0.18 h and for the tablet 2.59±0.56 h. The mean clearance rate for S was 13.6±1.7 h−1 and volume of distribution 43.0±3.91. Peak concentration (Cmax, µg·ml−1), time of peak (Tmax, h), area under the curve (AUC, µg·ml−1·h) and relative bioavailability (RB, %), were determined for three preparations: The data confirm the short half-life of dyphylline, demonstrate a lack of toxicity for the 20 mg·kg−1 dose and establish bioequivalence for the products studied.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 357-359 
    ISSN: 1432-1041
    Schlagwort(e): pindolol ; bioavailability ; fluorimetric assay ; GLC-ECD assay
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The absolute oral bioavailability of pindolol has been estimated by two analytical methods, fluorimetry and GLC-ECD. The study was carried out in six healthy subjects who received either i.v. or oral pindolol in random order. The results obtained by both methods were similar and confirm the high bioavailability (about 75%) of pindolol. The present findings are compared with previous publications and emphasize the importance of undertaking bioavailability studies in the same subjects.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 21-30 
    ISSN: 1432-1041
    Schlagwort(e): clonidine ; bioavailability ; blood pressure ; elimination half-life ; pharmacokinetics ; plasma catecholamines ; rebound phenomenon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Using considerably improved analytical methods, the kinetics and effects of clonidine were observed in healthy volunteers over periods of time more than 3 times longer than those previously reported. The high sensitivity and small work load of the newly developed method permitted the performance of low-dose and multipledose trials. 1. The complete bioavailability of clonidine and its elimination half-life (20 to 25.5 h) remained constant after single and multiple doses. 2. Approximately 62% of a given dose was excreted unchanged in the urine, independent of the quantity administered (0.075, 0.15, 0.2, 0.25 or 0.3 mg), the drug formulation (solution, tablet, Perlonget) or of the mode of administration (i.v., p.o.; single or multiple doses). 3. As the pharmacokinetics of the drug were affected by entero-hepatic circulation, it cannot be described by a conventional, open one or two compartment model. 4. The time courses of the plasma clonidine concentration and its drug effects ran asynchronously. 5. On cessation of chronic clonidine administration, blood pressure and plasma catecholamine levels increased to pretreatment levels without exhibiting any “overshoot” reaction.
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  • 37
    ISSN: 1432-1041
    Schlagwort(e): theophylline ; smoking ; sustained release formulation ; dosage forms ; multidose pharmacokinetics ; bioavailability ; circadian variation in kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and bioavailability of theophylline following 10 days of multiple doses of a plain uncoated (640 mg, q.i.d.) and a sustained-release tablet formulation (600 mg, b.i.d.) were related to habitual smoking in 11 healthy adult male volunteers, who had previously taken part in a single-dose study of an intravenous preparation of theophylline and of the same oral dosage form. There were significant differences (p〈0.05 to 0.01) in the steady-state mean and minimum theophylline concentration and AUC between the groups (6 smokers versus 5 nonsmokers), but not between other variables. A difference (p〈0.05) in peak time was also found between the dosage forms. The mean elimination t1/2 was significantly (p〈0.05) shorter in smokers than in nonsmokers. The intersubject variability in plasma theophylline concentration observed on the final trial day in the smoking group was larger and diverged more from simulation curves generated from the mean pharmacokinetic parameters of the single-dose study of the same formulations as compared to that of the nonsmoking group. There was no significant difference between the two groups in the mean accumulation ratio and absolute bioavailability of the two dosage forms. The mean morning (7 a.m.) trough theophylline concentrations after both formulations were significantly (p〈0.05 to 0.01) greater than the evening (7 p.m.) values within the same group. The average number of reported side-effects was significantly (p〈0.001) greater during the earlier period (Days 1 to 3) than the later period of the trial. A trend was observed suggesting that the incidence of side-effects was less in smokers than in nonsmokers. The results indicate that smoking is a determinant not only of enhanced elimination of theophylline but that it also produces more variability in the plasma level, irrespective of the dosage form administered or the dosing scheme employed. There may be circadian variation in theophylline kinetics.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 415-419 
    ISSN: 1432-1041
    Schlagwort(e): prednisolone ; bioavailability ; non-linear pharmacokinetics ; protein binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of prednisolone after oral and intravenous administration of 10 and 20 mg have been studied. Serum protein binding of prednisolone was also measured after the i.v. injections. The bioavailability after oral administration was 84.5% after 10 mg and 77.6% after 20 mg (p〉0.05). Dose dependent pharmacokinetics were found, the VDss and Clt being significantly larger (p〈0.01) after 20 mg i.v. than after 10 mg i.v. The protein binding of prednisolone in all subjects was non-linear, and is the most likely cause of the dose dependent pharmacokinetics, as there was no dose dependent variation in elimination half-time.
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  • 39
    ISSN: 1432-1041
    Schlagwort(e): ranitidine ; duodenal ulceration ; pharmacokinetics ; non-responders ; therapeutic response ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of orally administered ranitidine were studied in 17 male patients with chronic duodenal ulceration. The patients were divided into 2 groups, 10 responders and 7 nonresponders, on the basis of their endoscopic response to ranitidine treatment. The 10 responders were studied both after a single 150 mg dose (SD) and after multiple dosing (MD) with ranitidine 150 mg twice daily for 4 weeks. The area under the curve (AUC) and maximum concentration (Cmax) were significantly higher (p〈0.01 andp〈0.05, respectively) after MD than after SD, but the half-life (t1/2) and minimum concentration (Cmin) 12 h postdosing did not differ. The non-responders were studied after MD only and their pharmacokinetic characteristics were compared with those of responders. No differences between the 2 groups were found. However, 2 non-responders had particularly low plasma ranitidine levels and high acid output. Such patients may need larger doses of ranitidine for adequate suppression of gastric acid. Five patients (4 responders and 1 non-responder) received ranitidine 20 mg i.v. The drug followed a two-compartment model, with mean values for t1/2β, volume of distribution steady-state and total plasma clearance of 80 min, 701 and 680 ml/min, respectively. The oral bioavailability of ranitidine in these 5 patients showed wide variation (27–76%; mean 51%).
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 761-767 
    ISSN: 1432-1041
    Schlagwort(e): theophylline ; bioavailability ; sustained release tablet ; pharmacokinetics ; Theograd-250
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The bioavailability of theophylline after oral administration of a new sustained release tablet Theograd®-250 mg was studied in 7 healthy volunteers, under fasting and non-fasting conditions. Whilst fasting the bioavailability was moderate at 64±22% (mean±SD), whereas in the non-fasting state the relatively high bioavailability of 90±13% was found. The drug appeared to be significantly more slowly absorbed when a tablet was taken after a meal, than when it was ingested on an empty stomach. In the former case, the peak level was reached after 6.9±1.0 h, whereas in the fasting state the maximum serum concentration occurred 4.0±1.7 h after administration of the drug. Despite the slow absorption, the peak non-fasting level of 4.4±1.4 mg·l−1 was significantly higher than the 3.1±1.0 mg·l−1 observed in the fasting state. The profiles of the serum concentration-time curves showed that the concentration remained above 75% of Cmax for 8.7±1.3 h in the fasting and 9.0±1.1 h in the non-fasting state. It was concluded that to define the optimal dosage regime for sustained release oral dosage forms of theophylline, the influence of food on absorption from these preparations should be taken into account. Based on the present results, Theograd®-250 mg tablets have predictable absorption and a high (90%) bioavailability if taken after a meal.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 25 (1983), S. 69-72 
    ISSN: 1432-1041
    Schlagwort(e): levodopa ; intestinal absorption ; small intestine ; bioavailability ; benserazide ; presystemic clearance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In four healthy subjects the intestinal absorption of levodopa (l-dopa) was investigated by measuring the plasma concentration of the amino acid following the administration of l-dopa at three different sites in the small intestine. In order to minimize presystemic clearance of l-dopa, the subjects were pretreated with the peripheral decarboxylase inhibitor benserazide 3×50 mg every 8 h on the previous day and 1×50 mg 2 h prior to administration of the l-dopa. L-dopa 100 mg dissolved in 0.05 N HCl and 50 mg benserazide dissolved in 0.05 N HCl were coadministered. Under these conditions no difference in tmax, cmax or AUC of l-dopa was observed between administration of the drug into the proximal or the distal part of duodenum, or into the upper part of jejunum. The results indicate that in healthy subjects, during inhibition of peripheral decarboxylase, the rate and extent of l-dopa absorption does not differ at any site in the upper small intestine.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 134 (1983), S. 295-298 
    ISSN: 1432-072X
    Schlagwort(e): Actinomycetes ; Streptomyces thermoviolaceus ; Sporogenesis ; Spore ornamentation ; Cupular knobs ; Sheath ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The sporogenesis of aerial spores in Streptomyces thermoviolaceus corresponded to a common sporulation type in the genus. The sporulation septum was composed of an outer ring-shaped constriction wall and an inner interspace septum arising by the inwards growth of a double annulus. In mature spores the wall was composed of two layers, the outer one was part of the parent hyphal wall and septum material, the inner one was formed de novo. The spore chains were enclosed by the thin breakable sheath containing small rod-like elements. The ornamentation in the form of knobs, which were a characteristic feature of the species originated from the sheath. The knobs were hemispherical particles with an inner electron dense core and an outer electron transparent shell. The term “cupular knobs” was suggested for this type of tuberculate ornamentation. Frequently, the knobs became detached from the surface in which case the inner core separated easily from the shell.
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  • 43
    ISSN: 1432-072X
    Schlagwort(e): Cyanobacteria ; Ultrastructure ; Nitrogen fixation ; Water stress ; Taxonomy ; DNA ; Plasmids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two strains of desiccation-tolerant coccoid cyanobacteria, Chroococcus S24, a marine form, and Chroococcus N41, a cryptoendolith isolated from a hot-desert rock, have been characterized. The mol % DNA base compositions of the strains are 47.1 and 48.9% respectively. Plasmid DNA was not detected in either strain. The pigment contents and nutritional characteristics of the strains are identical. Both lack phycoerythrinoid pigments and, in culture, behave as slow-growing halotolerant marine forms with elevated requirements for Na+, Cl−, Mg2+ and Ca2+. Sucrose was the only carbon source of those tested that supported photoheterotrophic growth. Each strain synthesizes nitrogenase under anaerobic conditions but not in air. Morphologically the two strains are indistinguishable. They are considered to be independent isolates of the same cyanobacterial species. Chroococcus N41 was studied in detail with the electron microscope. When brought to equilibrium at matric water potentials of-168 MPa and lower (to-673 MPa=c0.12a w) the protoplast shrinks, but the cells maintain the same size and diameter as those at-2,156 kPa (MN medium; control); the sheath expands and remains attached to the cell wall outer membrane by fibrils. The cell wall, cell membrane, thylakoid membranes, cyanophycin granules and carboxysomes appeared intact in desiccated cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 234 (1983), S. 411-425 
    ISSN: 1432-0878
    Schlagwort(e): Intestines (chicken) ; Innervation ; Catecholamines ; Adrenergic fibres ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Axons in the duodenum, ileum and rectum of the domestic fowl were identified as catecholamine-containing (CA) on the basis of positive reactivity following chromaffin fixation for electron microscopy. CA-axons in association with blood vessels in all regions of the intestine and in non-vascular sites in the small intestine had a ‘ typical’ adrenergic appearance, in that they contained many small granular vesicles (SGV) and variable numbers of large granular vesicles (LGV). In the rectum the non-vascular CA-axon profiles were atypical, in that there were many elongated LGV and few SGV, and the chromaffin reactivity was weak. The nerve profiles in the rectum were dramatically reduced following 6-hydroxydopamine and reserpine treatment and were absent in rectum cultured in the absence of extrinsic ganglia. It was concluded that the profiles, in spite of their low chromaffin reactivity, truely represent CA-axons. The possibility was raised that the atypical morphology and reduced chromaffin reactivity is due to the presence of adrenaline.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 234 (1983), S. 427-437 
    ISSN: 1432-0878
    Schlagwort(e): Corticotropes ; Rat fetus ; Ultrastructure ; Immunocytochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Corticotropes of rat fetuses aged 16, 18 and 21 days were localized by the indirect antibody-enzyme method on semithin sections of the pituitary. The development of the ultrastructure of these cells was observed on consecutive ultrathin sections. In comparison with previous data our present results show that identification of a fetal cell type cannot be based entirely on morphological criteria. The structural peculiarities of corticotropes obtained from studies in vivo are compared with those observed in cells maintained in vitro.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 234 (1983), S. 679-689 
    ISSN: 1432-0878
    Schlagwort(e): Odontogenesis ; Rats ; Cyclophosphamide ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Cyclophosphamide-induced changes in rodent odontogenesis were investigated by light and electron microscopy in four-day-old Sprague Dawley rats given one injection of 40 mg/kg of body weight of cyclophosphamide and killed at intervals of one hour, one day, one week and two weeks. Incisor and molar teeth were dissected from the animals, fixed in 2.0% glutaraldehyde in 0.1 M sodium cacodylate with 3.4% sucrose, and subsequently some were incubated for alkaline phosphatase reaction, and embedded in Spurr's medium for sectioning at light- and electron-microscopic levels. From three days a cell-sparse zone was created in the pulp in the growing end of the tooth and progressive cellular changes were observed which became more severe in the one-week and two-week specimens. Subodontoblast and adjacent pulpal cells were the most affected showing nuclear changes, damage to, or loss of, organelles, and inclusion bodies. Odontogenic epithelium was less affected and odontoblasts appeared to be unaffected by the drug. A new irregular matrix was laid down in the defect area and seemed to be the product of depolarized odontoblasts. This new matrix showed alkaline phosphatase activity, as did the cells embedded in it, and later it became mineralized. It is speculated that the polarity of odontoblasts might be maintained by an intact subodontoblastic layer; when this is lost the odontoblasts become depolarized and capable of secreting matrix from both ends.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 232 (1983), S. 579-591 
    ISSN: 1432-0878
    Schlagwort(e): Cavernous bodies ; Endothelial cells ; Respiratory activity ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Work on endothelial cells has been limited by the availability of procedures for obtaining such cells in quantities adequate for direct in vitro analysis. The present paper describes a method for the isolation of endothelial cells from bovine cavernous bodies. A number of cells ranging from 2.5 to 4 × 108 per animal has been obtained. The cells were identified as follows 1) presence of the “Weibel and Palade” bodies in the isolated cells, 2) “cobblestone” appearance of cell cultures, and 3) presence of factor VIII, as demonstrated by immunofluorescence assays. The cell viability at the end of the purification procedure was tested 1) by dye-exclusion tests and 2) by metabolic assays. Features of this preparation are 1) the very high yield of viable endothelial cells, 2) the absence of contamination by fibroblasts and smooth muscle cells and a very low contamination by erythrocytes and 3) the fine dispersion of the isolated cells. These properties allow functional and subcellular fractionation studies on freshly isolated endothelial cells of microvascular origin.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 427-438 
    ISSN: 1432-0878
    Schlagwort(e): Myocardium ; Thunnus alalunga ; Ultrastructure ; Mitochondria ; Myofibrils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The common ventricle in the heart of the Thunnus alalunga was studied. The ventricular myocardium consists of an outer compact layer and a thick inner spongy layer. The compact layer has slightly larger cells (4–6 μm diameter) than the spongy layer (2.5–5 μm diameter). Ultrastructurally the myocardium displays normal arrangements of myofibrils and mitochondria. The sarcoplasmic reticulum is poorly developed. The intercalated discs are simple with the fascia adherens being the most frequent junctional type observed; occasionally a desmosome was seen. Nexus type junctions are present but are unassociated with the intercalated discs. There are no t-tubules evident but the plasmalemma exhibits numerous caveolae which rarely form couplings with the sarcoplasmic reticulum. A morphometric analysis of the volume percent of mitochondria and myofibrils showed that the myocardial cells in the spongy layer of the heart have a significantly greater volume percentage of mitochondria than the compact layer. No significant differences were found between myocardial regions when the volume percentages of myofibrils were compared. The physiological studies revealed that the albacore tuna has heart rates (120 bpm) and ventricular blood pressures (100 mmHg) that are among the highest reported for fish.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 523-537 
    ISSN: 1432-0878
    Schlagwort(e): Epididymis (rat) ; Myosin ; Actin ; Fibronectin ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The anatomical distribution of smooth muscle actin, myosin, fibronectin and basement membrane has been investigated immunohistochemically, using the indirect immunofluorescence technique, in the rat epididymis. The findings were correlated with the ultrastructural organization of the organ. Actin was found to be distributed in the stereociliary region of the epithelial principal cells and in the terminal web region. Actin was also visible along the base of the epithelium. Myosin was detected in the terminal web and in the terminal bar regions of the epithelium. The contractile cells showed a strong stain for both proteins. Basement membrane immunoreactivity was distributed along the epithelial basement membrane and around the contractile cells of the wall. In the cauda, between the epithelium and the contractile cell layers, the lamina propria, containing blood vessels and a thin layer of cells, was negative for all antigens investigated. Fibronectin showed a granular distribution around the contractile cells, mainly in the cauda. The ultrastructural study showed only thin (5–6 nm in diameter) filaments in the stereocilia and terminal web region. Thin filaments were also visible in the cytoplasm of the basal cells, thus suggesting a contractile function of this cell type. The heterogeneous appearance of the contractile cells of the wall seemed to support the different contractile pattern of the epididymal regions: caput, corpus and cauda. The cells present in the lamina propria showed cytoplasmic vesicles with dark granules resembling the “A” cell granules of the endocrine pancreas and gut mucosa cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 563-577 
    ISSN: 1432-0878
    Schlagwort(e): Nematocysts ; Structure ; Ultrastructure ; Function ; Cubozoa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Microbasic p-mastigophores, euryteles of two size groups, holotrichous isorhizas and atrichous isorhizas, comprise the cnidom of Chironex fleckeri, a cubozoan that has been responsible for several human fatalities. In its undischarged state each microbasic mastigophore of C. fleckeri consists of a capsule containing matrix and an inverted tube possessing a smooth-walled butt which is loosely coiled helically and which narrows to form a thread that is tightly coiled helically and markedly pleated. Both butt and thread carry three helices of spines and contain a granular matrix. During discharge, the proximal butt spines form initially a piercing stylet. Granular material from the butt and thread is released prior to the release of capsular material. Each eurytele possesses a tube with a butt composed of three bulbs, the middle bulb bearing long spines. Each holotrichous isorhiza possesses a coiled tube bearing small spines along its length. Each atrichous isorhiza exhibits a tube that is devoid of spines and loosely folded in the undischarged condition. The probable role of each type of nematocyst is inferred from its structure and features that enable the ready separation of the nematocysts of C. fleckeri from those of scyphozoan jellyfish are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 629-638 
    ISSN: 1432-0878
    Schlagwort(e): Ciliary process ; Cultured explant ; Epithelial cells ; Ultrastructure ; Bovine and rabbit eyes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructural characteristics of ciliary epithelium from bovine, pigmented rabbit, and fetal albino rabbit were studied in cultured explants. The tips of ciliary processes were cultured in plastic dishes with Dulbecco Modified Eagle Medium (DMEM) containing 5% fetal bovine serum. More than half of the expiants adhered to the plastic culture dish, and epithelial cells spread as monolayers within a few days. Initially the explant contains two layers, the outer (nonpigmented cells) and the inner (pigmented cells). Later the explant exhibits three layers: 1) outermost lightly pigmented flattened cells, 2) an outer layer of nonpigmented cells, and 3) an inner layer of densely pigmented cuboidal cells. The cells of the outermost layer are continuous with the cells of the inner layer. A narrow space lies between the outermost layer and the outer layer. The columnar cells in the outer layer contain well developed organelles but no pigment granules; they possess a basement membrane, lateral interdigitations, and junctional complexes near their apices. Numerous focal junctions and some ciliary channel-like structures were detected between the columnar cells of the outer layer and the cuboidal cells of the inner layer. The cuboidal cells of the inner layer are filled with pigment granules. These observations suggest that the columnar cells of the outer layer are nonpigmented epithelium, the cuboidal cells of the inner layer are pigmented epithelium, and the flatened cells in the outermost layer are derived from pigmented epithelium.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 693-698 
    ISSN: 1432-0878
    Schlagwort(e): Thyroid gland ; Human fetus ; Follicles ; Ultrastructure ; Differentiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Thyroid glands from 40 human fetuses ranging from 30 to 175 mm in length were examined by electron microscopy. At the 30 mm stage, the cells are arranged in cords or clusters and contain numerous free ribosomes. The rough-surfaced endoplasmic reticulum (RER) is poorly developed and the Golgi complex consists of saccules, smooth and coated vesicles. Mitochondria, microfilaments, glycogen particles, occasional lysosome-like structures, and single cilia are observed. At sites of incipient follicle formation, intercellular clefts containing interdigitating microvilli, delimited by junctional complexes, are evident. In addition, the apical region of some cells contains vacuoles. At the 50-mm stage, intercellular clefts are more apparent, some of them organized into small follicles through the enlargement of the lumen, the incorporation of additional cells, and the formation of a basal lamina. With increasing gestational age, more follicles are established. The lumina vary from round to clover-leaf shaped and have an electron-dense content. Cisternae of RER are dilated and contain flocculent material. The Golgi complex is more extensive, and lysosome-like structures are more numerous. By the 100-mm stage, the follicular cells appear morphologically well differentiated. The results demonstrate an extracellular origin of the follicular lumen in the human fetal thyroid.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 53
    ISSN: 1432-0878
    Schlagwort(e): Fibronectin ; Lung ; Development ; Ultrastructure ; Immunocytochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In a previous study changes in the macrodistribution of fibronectin during rat-lung development were examined. Using the peroxidase-antiperoxidase immunocytochemical technique, we have demonstrated the presence of fibronectin in embryonic, neonatal, and adult rat lung at the ultrastructural level. In the embryo, fibronectin is found both in an intra-and extracellular association with isolated pneumoblasts, and in a periodic distribution along the basal lamina. The neonate displays fibronectin in an intracellular association with early type-I cells and on their basal and luminal surfaces, but not in association with type-II cells. Neonatal basal lamina is diffusely labeled by anti-fibronectin antiserum. Fibronectin in adult tissue is found both intracellularly and on the basal and luminal surfaces of type-I cells but not in type-II cells. The basal lamina and interstitial connective tissue are slightly or non-reactive. These observations confirm and extend our initial suggestion that fibronectin is involved in rat-lung development.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 54
    ISSN: 1432-0878
    Schlagwort(e): Sea star ; Development ; Cuticle ; Extracellular materials ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The fine structure of conspicuous extracellular materials during the life history of a sea star (Patiria miniata) is described. The outer surface of the developing sea star is covered by two morphologically different cuticles that appear sequentially during ontogeny. The primary cuticle, which is about 120 nm thick and two-layered, is present from mid-blastula through the end of the larval stage. The secondary cuticle, which is about 1 μm thick and three-layered, first appears on the epidermis of the rudiment region of the larva and, after metamorphosis, covers the entire epidermis of the juvenile and adult stages. During ontogeny, there are only two conspicuous gut cuticles: the first lines the newly invaginated archenteron at the start of the gastrula stage, and the second lines the esophagus during the larval stage. A blastocoelic basal lamina first appears at mid-blastula and persists as subectodermal and subendodermal basal laminae. Ruthenium red-positive granules are detectable between the lateral surfaces of adjacent ectodermal cells during part of the gastrula stage; this transient intercellular material may possibly aid in lateral adhesion between cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 114 (1983), S. 85-92 
    ISSN: 1615-6102
    Schlagwort(e): Chloroplasts ; Iron stress ; Sugar beet ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary When grown in iron-free media, the youngest leaves of healthy green sugar beet plants became completely yellow after 6 to 8 days. This chlorosis was quickly reversed by resupplying iron. A study of the ultrastructure of the iron -stressed leaves revealed apparently normal subcellular organization except for the plastids which were small and undeveloped, contained a rudimentary, disorganized grana-fretwork and clusters of vesicles in the periphery. Twelve to 16 hours after resupply of iron, aggregates of phytoferritin were observed in the stroma, and the granal fretwork underwent further development. There was an increased orientation of the membranes along the long axis of the plastids and an increase in the length of the individual grana stacks. By 48 hours, leaf chlorophyll content was about 40% of the control. At the ultrastructural level, parallel alignment of membrane orientation was complete and the grana stacks began to increase in the number of thylakoids per stack.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 115 (1983), S. 1-10 
    ISSN: 1615-6102
    Schlagwort(e): Brassica napus ; Nucleolus ; Pisum sativum ; Ultrastructure ; Zea mays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The karyosome is a spherical body up to 1 μm in diameter that lies on the nucleolus of certain plant species, particularly those with a relatively low nuclear DNA content and an areticulate nuclear structure. It can be seen in the light microscope after impregnation with silver; in the electron microscope its structure consists of fibrillo-granular material. Nucleoli of cells in root apices may bear 0, 1, or 2 karyosomes. The frequency with which these numbers of karyosomes are observed depends on the location of the cells within the apex. In roots ofPisum sativum andZea mays the nucleoli of both slowly-dividing and young differentiating cells bear karyosomes more frequently than the nucleoli of rapidly-dividing cells. The karyosome seems to adopt a preferred location on the nucleolus, lying most frequently on the nucleolar surfaces directed towards the apex or base of the root. The origin and functional significance of the karyosome are discussed. Morphological evidence suggests that it may be material that formerly was part of a fibrillar centre.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 1-13 
    ISSN: 1615-6102
    Schlagwort(e): Cuticle ; Peristomatal transpiration ; Stomata ; Ultrastructure ; Funaria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cuticle and pore development in the guard cells ofFunaria were investigated with the electron microscope. Pore cuticle formation is simultaneous with the creation of the pore itself. The morphology of the pore cuticle is unlike that of any cuticle described in the literature. It has many lamellae which are penetrated by electron dense fibrils. Three different cuticular morphologies exist from the pore to the subsidiary cell walls. The cuticles on the pore and outer walls contain fibrils that sometimes reach to the surface. The subsidiary cell cuticle lacks fibrils altogether. It is hypothesized that (1) cuticularization of the middle lamella contributes to ventral wall separation and (2) differences in extent of cuticular fibrils are related to greater water loss from stomata than from subsidiary cells (peristomatal transpiration).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 115-124 
    ISSN: 1615-6102
    Schlagwort(e): Microtubules ; Moss ; MTOC ; Sporogenesis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Microtubule systems appear sequentially at the distal and proximal poles of tetrad members during mid-sporogenesis in the mossTetraphis pellucida Hedw. The distal microtubule system emanates from a microtubule organizing center (MTOC) located between the single plastid and the nucleus. The distal MTOC and associated microtubules, which appear immediately after cytokinesis, are ephemeral and do not appear to be associated with the deposition of exine occuring at the same time. The proximal microtubule system, which appears slightly later than the distal system, is a more stable component of mid-sporogenesis. The proximal MTOC is an irregularly lobed, patelliform aggregation of electron-dense granules located beneath the plasma membrane at the proximal spore pole. Several bundles of microtubules radiate from the proximal MTOC and traverse the cell, enclosing the nucleus in an cone of microtubules. The proximal microtubule system is thought to function in aperture development and organelle migration. The relatively large nucleus migrates a short distance in the small spore early in the tetrad stage and maintains its acentric position at the proximal pole throughout later stages of sporogenesis. The plastid migrates later in the tetrad stage from its meiotic position parallel to the distal surface to a position perpendicular to the distal surface with one tip in close proximity to the proximal MTOC. The proximal microtubule system reaches its maximum development by the end of the tetrad stage and all micrographic evidence of it is lost in the maturation stages of late sporogenesis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 99-114 
    ISSN: 1615-6102
    Schlagwort(e): Sphaerostilbe repens ; Ultrastructure ; Differentiation ; Coremia ; Rhizomorphs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The differentiating stages of coremia and rhizomorphs inSphaerostilbe repens were studied by transmission electron microscopy. Vegetative mycelium is characterized by highly cytoplasmic cells rich in ribosomes and mitochondria and with few vacuoles as well as endoplasmic reticulum. Cell walls are thin attaining a maximum thickness of 0.10 μm. During the aggregating phase a prosenchymatous mass of randomly oriented cells is produced by localized elongation and branching of the filaments. The hyphae in this region have the appearance of actively metabolising cells. In the course of the differentiating phase, numerous hyphae of the median zone of the aggregate grow upward and downward to give rise to coremium and rhizomorph primordia respectively. The individual hyphal tips lay parallel to each other and cells of the growing apices retain their meristematic characteristics. At the periphery of the aggregate and to a lesser extent in the subapical rhizomorphic zone, cells reduce their cytoplasmic density as a consequence of a decrease in the number of ribosomes. These cells also increase in size and become isodiametric and vacuolated. During cellular differentiation walls increase steadily in thickness and at the elongating phase they reach 0.30 μm in the rhizomorphic cortex. Mucilaginous material is progressively deposited around hyphae and in the most differentiated zones, coalesce to fill interhyphal spaces. This extracellular matrix seems to play a role in maintaining cohesiveness of the aggregated organs. The tissue in the process of differentiation is scattered with cells highly enriched in mitochondria and with cells virtually undifferentiated. Accumulation of microfilaments takes place in the differentiating zone localized behind the immersed meristematic apex. These structures might be involved in wall synthesis. Glycogen rosettes accumulate in the vegetative mycelium surrounding the aggregating centers, suggesting the possibility of supplying energy during the differentiating processes. The vacuolar system, represented by autophagic vacuoles which are present until the differentiation phase, presumably may also participate in the biochemical changes that occur during aggregation. Coremial cells are characterized by an increase in wall thickness, a highly sinuous plasma-membrane as well as large amounts of mucilaginous compounds accumulated between hyphae, but in all other respects they resemble the cells of actively growing vegetative hyphae.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 125-135 
    ISSN: 1615-6102
    Schlagwort(e): Ciliated protozoan ; Sorogenesis ; Extracellular matrix ; Secretion ; Extrusive organelles ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Sorogena stoianovitchae Bradbury andOlive is an unusual kinetophragminophoran ciliate characterized by the aggregation of individual trophic cells to form a multicellular sorogen that rises aerially from the medium surface to produce a sorocarp. A light and electron microscope study of sorogenesis revealed how the sorogenic cells produce the stalk. The feeding ciliates contain numerous subpellicular expansions of rough endoplasmic reticulum cisternae that are only one element of the secretory system necessary for stalk formation. Upon aggregation, the stalk secretory system develops further, initially with the proliferation of the subpellicular expansions. Then, during later aggregation and early sorogenesis, other secretory elements appear: stalk material vesicles, dense granule vesicles, and electron lucent vacuoles. These are all derived from the rough endoplasmic reticulum. Only the subpellicular expansions and stalk material vesicles appear to add to the stalk matrix. The dense granule vesicles could be precursors of the stalk material vesicles; the electron lucent vacuoles, which can be demonstrated to contain fibrillar material, are perhaps by-products of the secretory process. Sorogenesis inSorogena occurs by a mechanism unique among the stalk-producing protists that have been studied.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 136-144 
    ISSN: 1615-6102
    Schlagwort(e): Stalk ; Ciliated protozoan ; Sorogenesis ; Extracellularmatrix ; Ultrastructure ; Secretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The sorogenic cells of the haptorid ciliateSorogena stoianovitchae Bradbury andOlive secrete a hydrated, fibrillar matrix that becomes organized to form a stalk. This light and electron microscope study examines the role of the secreted stalk matrix in the development of the sorocarp. The stalk material is secreted as a compact clump or clumps of material that expands as it hydrates. The expanded stalk material is initially viscous, but soon, through dehydration or cross-linking, solidifies to form a sheath. The sheath is the outside layer of the stalk, provides structural support, and controls the expansion of the newly secreted stalk material. The sorogenic cells continue to secrete stalk material that expands once it is outside of the cell. The resulting expansion force is directed upward by the sheath, thereby moving the cells further above the surface. The continued dehydration of the sheath material provides an inwardly directed force that also contributes to the upward movement of the sorogen.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 62
    ISSN: 1615-6102
    Schlagwort(e): Cytochrome oxidase ; Cytochemistry ; Ultrastructure ; Neurospora ; Heat treatment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cytochrome oxidase (EC 1.9.3.1) activity of conidia of wild-typeNeurospora crassa was detected cytochemically at the ultrastructural level by 3,′-diaminobenzidine (DAB) reaction during heat treatment at 46 °C and after shift down to 25 °C. At 46 °C the decrease in the enzyme activity was shown to be time-dependent (0–10 hours) in the progressively overswelling conidia. Gradual recovery of the DAB reaction occurred in mitochondria of conidia outgrowing conidiogenous germ tubes (microcycle conidiation) when shifted down to 25 °C. Inactivation of cytochrome oxidase was efficiently prevented during heat treatment in the presence of Tween 20. Such conidia no longer overswelled but still required shift down to 25 °C to produce germ tubes with delayed conidiogenous ability.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 117 (1983), S. 7-16 
    ISSN: 1615-6102
    Schlagwort(e): Beta vulgaris ; Chloroplast ; Ultrastructure ; Ultraviolet radiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The effect of UV-C (254 nm) and UV-B (290–320 nm) radiation on leaves ofBeta vulgaris L. at the ultrastructural level was investigated. Although the damage caused by UV-C radiation was more striking than that resulting from UV-B radiation, several structural changes were seen in the UV-B treated material. Generally the effects of UV-B and UV-C radiation were different, suggesting different mechanisms of action, discernible even at the ultrastructural level.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 117 (1983), S. 116-129 
    ISSN: 1615-6102
    Schlagwort(e): Pollen ; Amoeboid tapetum ; Arum italicum ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A tapetum is found around all higher plant meiocytes and is thought to nourish them. It may, in turn, be influenced by their development. The mature tapetal membrane in amoeboid (or periplasmodial) tapeta, of whichArum italicum is an example, fits closely around the developing meiocyte. This description of tapetal ultrastructure starts from the meiotic prophase when the tapetum is still cellular and comprises two rows of cells on the inside of the tetrasporangiate anther. The radial walls of the still cellular tapetum start to dissolve during leptotene of the first meiosis. The lysis begins in the middle lamella in those areas penetrated by the most plasmodesmata. The walls in contact with the meiocytes on the other hand do not disappear until after the first meiosis. At telophase the now fused cytoplasmic tapetal mass begins to extend its joint plasmamembrane, amoeboid fashion, into the loculus. A cluster of microtubules can be seen at the apex of this intrusion apparently initiating or maintaining the shape of the invading plasmamembrane front. The tapetum now adheres closely to the microspores. The tapetal zone closest to the spores has a prominent population of microtubules and just a little ER, whereas the outer zone away from the spores contains all the other organelles. The inner zone, in a squash preparation, is not readily separated from the spores. The microtubules, at the middle microspore stage, are no longer to be seen in a circle around the microspores, but spread out with some lying orthogonal to the now-forming exine surface. In places the tapetal plasmamembrane begins to retract from the exine leaving roughly cone-shaped zones (spines) which become filled with fibrillar material. This material begins to be deposited on the exine surface. These “spines” are both PAS. and Coomassie-blue positive and susceptible to acetolysis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 65
    ISSN: 1615-6102
    Schlagwort(e): Histochemistry ; Sclerotia ; Sclerotial germination ; Sclerotinia ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cytoplasmic reserves and extracellular substances were progressively broken down and utilized during carpogenic germination of sclerotia ofSclerotinia minor. Glycogen, wall polysaccharides and polyphosphate granules were removed first from regions of the sclerotium distant from developing apothecia, while protein bodies near the base of apothecial stipes were hydrolysed before those further away. The number of profiles of mitochondria and endoplasmic reticulum in cortical and medullary hyphae increased at the onset of germination, indicating increased metabolism in the hyphae. In contrast to developing sclerotia, simple pores with Woronin bodies were frequent in walls and septa during germination. Hyphae that appeared to converge towards the base of apothecial initials retained their cytoplasm and organelles until late in germination and hydrolysis of their reserves was delayed; these are interpreted as translocatory hyphae, although further work is required to determine their role unequivocally. When apothecia were fully developed, hyphae throughout the sclerotium were empty and the walls and extracellular matrix of cortical and medullary hyphae had almost completely broken down.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 118 (1983), S. 56-70 
    ISSN: 1615-6102
    Schlagwort(e): Carposporophyte ; Cell division ; Mitosis ; Rhodophyta ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Mitotic ultrastructure was observed in meristematic cells of carposporophyte generations of the freshwater red algaBatrachospermum ectocarpum. Prior to nuclear division, cell elongation occurs resulting in the nucleus being located at the proximal end of the cell and separated by a large central vacuole from a distal “empty region” which the daughter nucleus eventually occupies. In late prophase, nuclear envelope-attached polar rings are situated adjacent to shallow nuclear invaginations. At prometaphase the nuclear invaginations extend deeply into the nucleus forming continuous cytoplasmic channels containing microtubules. Perinuclear ER and a typical equatorial chromosomal plate are formed by metaphase at which time the nuclear envelope lining the cytoplasmic channels has dispersed. Chromosomal and non-chromosomal microtubules converge at the poles where a single, large gap is seen in the otherwise intact nuclear envelope. Polar rings were not detected in the few mitotic cells observed beyond prometaphase but are thought to be present. During anaphase an interzonal midpiece is formed and the distal-most incipient daughter nucleus moves laterally past the central vacuole into the apical “empty region”. Features of mitosis inBatrachospermum are believed to be intermediate between those exhibited by the lower and higher orders of red algae, this being consistent with the taxonomic placement of the genus in theNemaliales, the least advanced order of the classFlorideophyceae.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 118 (1983), S. 95-103 
    ISSN: 1615-6102
    Schlagwort(e): Nuclear bodies ; Nucleolus ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Nuclear bodies are found in interphase nuclei of root apices of a number of plant species. They often show differences in structure and position relative to the nucleolus and this has led to an attempt to define two classes of body. However, in some species their separation into two classes on structural grounds alone breaks down, indicating that although they may occupy different positions within the nucleus they may in these particular cases be only different forms of the same body. The two extremes of the range of bodies examined represent what have been called “nucleolus-associated body” (karyosome) and “dense body”. The nucleolus-associated body is typically attached to, or adjacent to, the nucleolus. It is composed of fibrils 4–8 nm wide and often has an open structure showing compound threads or fibrils separated from each other by electron-lucent spaces. The dense body is more compact in structure and typically lies free in the nucleoplasm. Both types of body have an affinity for silver ions which, together with their staining reaction following treatment with EDTA, indicates that they consist of ribonucleoprotein. The characteristics of nuclear bodies found in different plant species have some relationship with the structure and DNA content of the interphase nucleus. Nucleolus-associated bodies are characteristic of species with an areticulate nuclear structure (2 C DNA content 〈6 pg), while dense bodies are common in species with a reticulate nuclear structure (2 C DNA content 〉6 pg). The possible functions of the two forms of nuclear body are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 68
    ISSN: 1615-6102
    Schlagwort(e): Calcification ; Coccolithophorids ; Polysaccharide localization ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Emiliania huxleyi is a marine coccolithophorid which produces coccoliths,i.e., particles consisting of calcite and macromolecular organic material. The coccoliths are formed intracellulary in specialized organelles which comprise a coccolith vesicle (CV) and a reticular body (RB), together forming the CV/RB system or calcifying system. After termination of calcification, the coccolith is extruded and incorporated into the coccosphere,i.e., one or several layers of extracellular coccoliths surrounding the cell. Apart from the coccolith-producing cells (C cells) ofE. huxleyi, there are naked cells (N cells) which seem to have lost the capacity to produce coccoliths but are very similar to the C cells in other morphological respects. Biochemical studies have revealed that polysaccharides may play a regulatory role in calcification. The aim of the present study was to determine the localization of polysaccharides in both C and N cells electron microscopically. For this purpose, a cytochemical staining technique according toThiéry (1967) was applied. The CV/RB system of C cells was conspicuously stained. Due to the excellent stainability of this system, a putative succession of morphological stages during coccolithogenesis could be described. The staining pattern of the N cells closely resembled that of the C cells. It was found, however, that the “calcifying” system of N and C cells differed in both morphology and position. It is suggested that the divergent morphology of the “calcifying” system of N cells accounts for its failure to produce coccoliths.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 269-284 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid chromatography ; Phenols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Gas and high-performance liquid chromatographic methods in the analysis of phenols are reviewed. Among the great number of phenolic compounds analyzed, alkylphenols, chlorophenols, dihydroxy- and trihydroxybenzenes and biphenols are chiefly considered. The advantages and drawbacks of the methods are discussed, quoting the most important work. Relationships between the structural characteristics of phenols, the stationary phase structure, the mobile phase composition and the retention data are treated. Typical examples of the conditions for GC and HPLC analysis are summarized in tables. The literature comprises over 270 references, most of them recent.
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  • 70
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Average molecular polarizability ; Retention index ; Polycyclic aromatic hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The Kováts retention indices of 10 polycyclic aromatic hydrocarbons were determined on SE-30, OV-101, SE-52, OV-7 and OV-17 stationary phases. A significant correlation has been found between the retention indices and the average molecular polarizabilities of the analyzed substances. Equations were derived for the direct determination of the average molecular polarizabilities from the retention index values. The influence of the temperature on this relationship is also indicated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 493-500 
    ISSN: 1612-1112
    Schlagwort(e): Esterification in aqueous solution ; iso butyl esters of C1–C20 fatty acids ; Gas chromatography ; Fatty acid analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary C1–C20 carboxylic acids have been esterified in aqueous solutions with i-butanol. Gas chromatographic analyses have been performed from a single chromatogram. It has been established that esterification in the concentration range of [H2O]/[i-BuOH]=0.01–10.3 can be utilized for the quantitative determination of these carboxylic acids. The presence of water does not interfere in the range of [H2O]/[i-BuOH]=0.01–1.03. In the cases of [H2O]/[i-BuOH]〉1.03, anhydrous sodium sulfate has been used for binding the water, in an amount of [Na2SO4]anh./[H2O]≥0.2.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 561-576 
    ISSN: 1573-8744
    Schlagwort(e): methylprednisolone ; bioavailability ; pharmacokinetics ; oral and parenteral administration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This study was conducted to evaluate the influence of route of administration upon the bioavailability and pharmacokinetics of methylprednisolone sodium succinate. Fourteen healthy adult male volunteers received 40 mg doses of methylprednisolone as the following treatments after an overnight fast in a 4-way crossover design: (a) as a 1 ml i.v. bolus;(b) as a 1 ml i.m. injection;(c) administered as an oral solution;and (d) as 5×8 mg oral tablets. Both the ester and free methylprednisolone were determined in plasma and urine. Study results indicate that the ester is rapidly and extensively converted to free methylprednisolone after all routes. The extent of methylprednisolone absorption was equivalent after i.v. and i.m. administration. Both orally administered treatments resulted in a lower extent of absorption attributed to a first-pass effect. Although a slightly lower extent of absorption was demonstrated following the oral administration of the methylprednisolone sodium succinate solution relative to the methylprednisolone oral tablets, this average difference of 9% would probably be of minimal therapeutic importance.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 205-214 
    ISSN: 1573-8744
    Schlagwort(e): bioavailability ; clearance ; V area ; V ss
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The limitations of using estimates of extent of bioavailability (F) based on the assumption that either clearance (CL) or Varea remain, constant are discussed in relation to the situation where CL changes between doses. When estimates of F assume CL to remain constant, the entent of the error is the same for all drugs where the percentage change in CL is the same. Assuming Varea to remain constant, the error in F will vary between drugs for similar percentage changes in CL and is related to the extent to which the kinetics of the disposition process deviate from a one compartment body model. A noncompartmental method is described where, provided the reference dose is given intravenously, F can be estimated based on the assumption that Vss remains constant between doses. This method is more accurate than those based on the assumption that either CL or Varea remain, constant when CL changes between doses, but is subject to error when the terminal loglinear slope of Cp vs. time better reflects the process of absorption rather than elimination.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 529-545 
    ISSN: 1573-8744
    Schlagwort(e): bioavailability ; nitrofurantoin ; capacity-limited elimination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The influence of route of administration on the absolute bioavailability and GI tract absorption of nitrofurantoin was investigated in rabbits. The disposition of nitrofurantoin was described by a one-compartment model with simultaneous first-order and Michaelis-Menten type elimination kinetics, and bioavailability was estimated by nonlinear assessment. The plasma levels following oral administration were significantly lower than those after intravenous administration, and absolute Fvalues for oral administration were approximately 0.3. However, Fvalues following intraduodenal administration and portal vein infusion were nearly unity, and it was concluded that the reduction of bioavailability following oral administration could not be attributed to metabolism by intestinal microflora or to the hepatic first-pass effect. Thus, reduction of Fvalues following oral administration is probably due to gastric degradation of the drug. The effects of factors influencing bioavailability, such as water volume taken with the drug, change of gastric emptying rate and effect of particle size, were also investigated. Increase of volume of water administered tended to improve the bioavailability, and a particle size dependency was also observed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 71 (1983), S. 147-153 
    ISSN: 1573-5036
    Schlagwort(e): Cortex ; Endodermis ; Picea sitchensis ; Tilia cordata ; Transfer cells ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The endodermis of bothTilia cordata andPicae citchensis progressess through 3 characteristic phases of development. These developments are delayed somewhat in the xylem pole endodermis ofT. cordata, while inP. sitchensis 3–5 passage cells are found. The cortex ofT. cordata is characterised by very thick walls, while that ofP. sitchensis is characterised by a thick walled layer just outside the endodermis and by 2–3 outer layers of transfer cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 228 (1983), S. 205-218 
    ISSN: 1432-0878
    Schlagwort(e): Spermatozoa ; Ultrastructure ; Deep-freezing ; Sperm manipulation ; Trout
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Trout spermatozoa taken from the testis, vas deferens and ejaculate are described at the ultrastructural level. The morphology of the spermatozoa head, changes in the middle-piece structure, and the relationship between the centrioles and the flagellum were studied under consideration of their role in the reproduction of this species. Morphological changes observed after dilution of the spermatozoa in freshwater or saline and subsequent freezing deserve attention in connection with certain manipulations used in fish farms and laboratories.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 228 (1983), S. 231-244 
    ISSN: 1432-0878
    Schlagwort(e): Pineal gland ; Circadian rhythm ; Synaptic ribbon ; Ultrastructure ; Chinese hamster (Cricetulus griseus)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Circadian morphological variations of pinealocytes in the superficial pineal of the Chinese hamster (Cricetulus griseus) were studied using quantitative electron-microscopic techniques. The volume of the nucleus and cytoplasm of pinealocytes exhibited similar circadian variations, with the maximum around the middle of the light period and the minimum during the first half of the dark period. Synaptic ribbons in pinealocytes were classified into three groups, type-1, −2 and −3 synaptic ribbons, which appeared as rods, round or irregular bodies and ring-shaped structures, respectively; a synaptic ribbon index was determined for the respective types. The synaptic ribbon index was expressed as the number of synaptic ribbons in the pinealocyte profile representing the cell size. The type-1 synaptic ribbon index, which was smallest during the second half of the light period, was increased during the dark period. The length of straight or slightly curved rods showed a 24-h change similar to that of the type-1 synaptic ribbon index; the length of the rods was maximal during the first half of the dark period and minimal at the end of the light period. There was no apparent circadian variation in the type-2 synaptic ribbon index. The type-3 synaptic ribbon index was higher during the light period than during the dark period; the index attained zero 3h after the onset of darkness and, thereafter, increased gradually.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 228 (1983), S. 265-276 
    ISSN: 1432-0878
    Schlagwort(e): Met- and leu-enkephalin ; Immunocytochemistry ; Ultrastructure ; Lateral septum ; Guinea-pig brain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary By the use of antisera to met-enkephalin and leu-enkephalin, enkephalin-containing structures were visualized in the lateral septum of the guinea-pig brain. The present results do not reveal immunoreactive perikarya in this area. The immunostaining is exclusively located in numerous nerve fibers and endings mostly encompassing neuronal perikarya, which accounts for the fact that at the light-microscopic level cellular somata appear to be immunostained. The immunoreactive terminals and fibers contain granules approximately 110nm in diameter and synaptic vesicles. The origin and the functional role of these numerous enkephalin terminals remain to be established. This work was supported by a grant from INSERM N∘ 804012
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 228 (1983), S. 323-335 
    ISSN: 1432-0878
    Schlagwort(e): Ultrastructure ; Colonic epithelium ; Colchicine ; Vesicles ; Glycoproteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In murine colonic epithelial cells, cell-coat glycoproteins are transported to the cell surface in vesicles that originate at the Golgi apparatus. To determine the role of microtubules in the movement of these vesicles the antimicrotubule agent colchicine was injected into mice at several time intervals prior to sacrifice. In the mice that were treated with colchicine for 4.5 h it was observed that the polarity of the cells was disturbed. The Golgi apparatus and nucleus often appeared interchanged in their positions. The glycoprotein-containing vesicles, normally located apically, were sparse in that location, but abundant near the lateral plasma membranes of the cells at the level of the nucleus and Golgi apparatus. Staining by the periodic acid-chromic acid-silver methenamine technique for glycoproteins clearly revealed the reduction of vesicles apically and accumulation of vesicles laterally. The mechanism responsible for the movement of the vesicles to this location is unclear. It is suggested that the accumulation of vesicles in the lateral region may reflect some hindrance in the fusion of the vesicles with the lateral cell membranes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 80
    ISSN: 1432-0878
    Schlagwort(e): Lymph nodes ; Postnatal development ; Fibroblastic reticulum cells ; Interdigitating cells ; Deep cortex units ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary This study describes the postnatal development of the nonlymphoid cells with special reference to the fibroblastic reticulum cells (FRCs) and interdigitating cells (IDCs). The first lymphocytes of the neonatal lymph nodes are located in the developing deep cortex units (DCUs) identified by the Gomori's technique for reticulin fibres. Ultrastructural studies demonstrate that FRCs form the stroma of the DCUs. By light and electron microscopy, it is demonstrated that FRCs occupy the outer cortex in the following stages of development of the lymph nodes. Thus, FRCs form the stroma of the primary follicles and, later, are transformed in follicular dendritic cells (FDCs) of the germinal centres. Immature or pro-IDCs appear as migrating elements in the deep cortex of lymph nodes of the neonatal rats. The ultrastructure of the pro-IDCs resembles that of the mature IDCs but not that of the phagocytic cells. Pro-IDCs are transformed into mature IDCs whose cytoplasmic expansions contact lymphocytes via tight junctions. Some of these lymphocytes are likely apposed to FRCs of the DCUs. No cells containing Birbeck granules were found in the parenchyma of the lymph nodes during the postnatal development. The role of these nonlymphoid cells is discussed with respect to the immunologic function of mammalian lymph nodes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 229 (1983), S. 281-297 
    ISSN: 1432-0878
    Schlagwort(e): Paraventricular nucleus ; Hypothalamus ; Development ; Golgi study ; Ultrastructure ; Chick embryo
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The developmental changes in the cytoarchitecture of the hypothalamic paraventricular nucleus of the chick embryo were studied with particular emphasis on the differentiation of the magnocellular neurons. These cells can be distinguished from the parvocellular elements starting from stages 34–35 (Hamburger and Hamilton 1951) in Golgi-impregnated specimens. At the same stages, electron microscopy reveals dense-core granules, resembling the characteristic elementary granules of the neurosecretory material in the cytoplasm of the larger neurons. In addition, a few immature synapses were observed on these magnocellular perikarya. The present observations suggest that the early onset of neurosecretion in this area may be neurally regulated during early phases of development.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 231 (1983), S. 663-674 
    ISSN: 1432-0878
    Schlagwort(e): Ciliary tuft ; Pallil tentacles ; Patella vulgata ; Sensory ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The structure and ultrastructure of ciliary tufts on the pallil tentacles of the limpet Patella vulgata (L.) are described. The tip of each tentacle is covered by a dense crown of tufts and additional tufts can be seen scattered evenly across the surface of each tentacle. The cilia are nonmotile and nerve fibres run from the base of the ciliated cells suggesting a sensory function. Comparisons are made with ciliary tufts found in a Pacific species of limpet, Acmaea scutum, and other molluscan sensory structures.
    Materialart: Digitale Medien
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  • 83
    ISSN: 1432-0878
    Schlagwort(e): Pregnancy ; Adrenal zona glomerulosa ; Juxtaglomerular apparatus ; Ultrastructure ; Sheep
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructural changes in the adrenal zona glomerulosa and renal juxtaglomerular apparatus have been examined during normal pregnancy in sheep. As pregnancy progressed, increasing numbers of cells in the adrenal zona glomerulosa displayed mitochondria with straight tubular “rod-like” structures replacing their normal lamelliform cristae; groups of cells showing these mitochondrial changes were predominantly located in the middle and superficial regions of the zona glomerulosa, but at all stages remained interspersed with cells with apparently normal mitochondria. In the same animals, the renal juxtaglomerular index was raised, reflecting an increase in renin storage, and juxtaglomerular myoepithelioid cells showed increased numbers of cytoplasmic granules, but no apparent increase in granular endoplasmic reticulum and Golgi profiles; there were no distinguishing morphological changes in juxtaglomerular peripolar cells. These findings provide morphologic evidence of stimulation of the adrenal zona glomerulosa in association with increased juxtaglomerular renin storage during pregnancy. The mitochondrial changes observed in an increasing proportion of cells in the zona glomerulosa closely resemble those seen in sodium-depleted animals, and may reflect the altered steroidogenic capacity of the adrenal gland in pregnant sheep. The finding of groups of cells displaying altered mitochondria lying next to cells with normal mitochondria suggests the presence of cells with different sensitivities to stimuli for aldosterone production or may indicate the presence of different cell types in the zona glomerulosa responding to different stimuli.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 234 (1983), S. 365-376 
    ISSN: 1432-0878
    Schlagwort(e): Oesophageal striated muscle ; Ultrastructure ; Guinea-pig, marmoset
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructural characteristics of oesophageal striated muscle from guinea-pig and marmoset have been examined using transmission electron microscopy and compared with ultrastructural features of skeletal muscle. The findings show that, although similar to skeletal muscle, oesophageal striated muscle exhibits important differences in the arrangement of its muscle fibres and their motor innervation. It was also found impossible to classify oesophageal striated muscle according to the usual ultrastructural criteria since its motor endplates bore a greater resemblance to those of intrafusal skeletal muscle fibres. The consideration of these differences in conjunction with characteristics revealed elsewhere by other techniques confirms the unique nature of oesophageal striated muscle.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 229 (1983), S. 155-174 
    ISSN: 1432-0878
    Schlagwort(e): Pituitary ; Tammar wallaby ; Marsupialia ; Ultrastructure ; Immunohistochemistry ; Cell types
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary An immunohistochemical, light- and electron-microscopial study was made of the pars distalis in adult tammar wallabies (Macropus eugenii). The pars distalis of this marsupial mammal was divided into three regions, based on the distribution of cell types within the gland. Somatotropic, mammotropic, luteotropic, folliculotropic, corticotropic and thyrotropic cells were identified on the basis of their immunohistochemistry, cytology and ultrastructure. Non-granulated (folliculo-stellate) cells, identified in electron micrographs, were found throughout the pars distalis. Somatotropic cells were predominant in the posterior pars distalis in all animals examined. In the single male specimen and in the non-lactating females examined, small numbers of apparently inactive mammotropic cells were scattered throughout the pars distalis; the same cell type was apparently active and present in considerable numbers in lactating females. Only one morphological type of gonadotropic cell was evident; these cells were scattered throughout the pars distalis, but in largest numbers in the median region. Small numbers of thyrotropic cells were found, most commonly in the anterior pars distalis. Corticotrops were also observed in moderate numbers, predominantly in the anterior regions of the pars distalis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 228 (1983), S. 313-322 
    ISSN: 1432-0878
    Schlagwort(e): Olfactory ; Sensilla ; Ultrastructure ; Insects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Scanning- and transmission electron-microscope studies of the sensilla of the pedicel of Nilaparvata lugens have revealed an elaborate plaque organ and three structurally different types of trichoid hairs. Each plaque organ is innervated by 120–150 neurons arranged in groups. The porous sensory cuticle is folded into finger-like projections and is surrounded by protective non-sensory denticles. Trichoid sensilla differ in number of neurons, appearance of dendrites and arrangement of pores. Type I, innervated by 2 neurons, has pores along its length and is probably olfactory in function. Types II and III are innervated by one and five neurons, respectively, and the absence of pores along the hair shaft indicates a possible gustatory role. The importance of these sensilla is discussed with reference to the behaviour of this important insect pest.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 228 (1983), S. 389-403 
    ISSN: 1432-0878
    Schlagwort(e): Lymph node, avian ; Ultrastructure ; Macrophages ; Phagocytic capacity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The structure of the avian lymph node (ALN) is characterized by a thin capsule, thin lymphoreticular cords, and an absence of trabeculae. It is not possible to subdivide the ALN into cortex, paracortex and medulla, or to subdivide the system of sinuses into marginal, trabecular and medullary divisions. The lymphoreticular cords contain avian germinal centers (AGC) with B-lymphocytes and the area of T-lymphocytes. Postcapillary venules are responsible for the recirculation of lymphocytes. Sinus reticular cells do not exist in the ALN, but free macrophages are present. The phagocytic capacity of the macrophages was determined by injection of vital dyes (India ink, Berlin blue) and inoculation with Candida cells. Macrophages filled with markers migrate from the lymph sinuses into the lymphoreticular cords and further into the AGC. The mobility of the macrophages is remarkably lower after phagocytosis of Candida cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 229 (1983), S. 299-308 
    ISSN: 1432-0878
    Schlagwort(e): Adrenal chromaffin cells ; Plasticity ; Transplants ; Kidney capsule ; Ultrastructure ; Catecholamine biochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Histochemical, ultrastructural and biochemical studies (quantitative determinations of catecholamines (CA) and phenylethanolamine N-methyltransferase (PNMT) activity) were carried out on autologous transplants of adult guinea-pig adrenal medulla under the kidney capsule, in order to investigate the specific influences of a virtually nerve-free environment in comparison to those mediated by a densely innervated one such as in the iris (cf. Unsicker et al. 1981). Three weeks after transplantation chromaffin cells survived well, most cells maintaining their morphological identity in terms of adrenaline (A) storage, although biochemically measured A and PNMT had dramatically decreased. Chromaffin cells in transplants extended neurite-like processes in an identical fashion as seen in transplants to the anterior chamber of the eye and in culture. Chromaffin cells were frequently connected by synaptoid contacts, but did not receive cholinergic synapses as observed in transplants to the iris. It may be concluded that the growth factor(s) eliciting neurite outgrowth from transplanted chromaffin cells are rather ubiquitously present, independent of whether the transplantation site is sparsely or richly innervated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 89
    ISSN: 1432-0878
    Schlagwort(e): Adrenal zona glomerulosa ; Ultrastructure ; Sodium depletion ; Sodium loading ; Sheep
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effects of alterations in sodium status upon the morphology of the adrenal zona glomerulosa in sheep have been examined qualitatively and quantitatively, using lightand electron microscopy, and correlated with functionally related biochemical data. With severe sodium depletion induced by parotid-cannula drainage, there was mitotic activity throughout the zona glomerulosa, and glandular cells showed striking ultrastructural changes. These changes particularly affected mitochondria, which were enlarged, rounded and showed replacement of their normal lamelliform cristae by thin elongated cristal elements and bundles of tubular “rod-like” structures. Quantitative morphometric studies showed an increase in the volumes of zona glomerulosa cells, nuclei, mitochondria, smooth and granular endoplasmic reticulum, and Golgi profiles. In contrast, with dietary sodium loading, zona glomerulosa cells appeared shrunken and showed cytoplasmic lipid accumulation; mitochondria and other organelles were not significantly altered. The correlation of the ultrastructural cytological alterations in zona glomerulosa cells in sodium-depleted sheep with raised blood aldosterone levels suggests that such morphologic changes reflect a heightened capacity of these cells for aldosterone biosynthesis and secretion. These changes may also account for the increased sensitivity of the zona glomerulosa to aldosterone-producing stimuli during sodium deficiency.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 229 (1983), S. 611-625 
    ISSN: 1432-0878
    Schlagwort(e): Spermatozoa ; Ultrastructure ; Pseudomys (Muridae, Rodentia)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Sperm morphology among the various members of the genus Pseudomys showed great interspecific variation. In P. apodemoides, P. desertor, P. fumeus, P. gracilicaudatus, P. hermannsburgensis, P. higginsi and P. nanus the sperm head was bilaterally flattened and possessed three hooks, the length of which varied somewhat between species. The top hook contained nuclear, subacrosomal and acrosomal material, whereas the two lower ventral hooks displayed largely only an extension of the subacrosomal material. Four other species of Pseudomys had no ventral hooks in their sperm head. In P. novaehollandiae there was a single long top hook, whereas in P. pilligaensis it was almost nonexistent. Neither the sperm head of P. delicatulus, nor that of P. shortridgei possessed any hooks; the former became narrower towards the tip, whereas the latter was spatulate in shape. The acrosome covered about two thirds of the nucleus and varied considerably in shape between species. Insertion of the connecting piece of the tail occurred on the lower ventral side of the sperm head in all species with a long top hook but was nearly basal in P. delicatulus and midbasal in P. shortridgei. The ultrastructure of mid and principal pieces was similar among species, but the number of gyres of mitochondria ranged from about 64 to 100.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 230 (1983), S. 353-366 
    ISSN: 1432-0878
    Schlagwort(e): Homoptera ; Labium ; Sensilla ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructure of the sensory receptors located on the labium of the rice brown planthopper is described; possible functions of individual receptors are suggested on morphological grounds. Uniporous chemosensilla which may or may not possess a mechanoreceptive dendrite, domed multiporous chemosensilla, and mechanoreceptive pegs are present on the flattened labial tip. Mechanoreceptive pegs are distributed over the labium. The fine structure of a multilobed sensillum located on either side of the labium is also described.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 59-67 
    ISSN: 1432-0878
    Schlagwort(e): Pineal gland ; Synaptic ribbon ; Melatonin ; Ultrastructure ; Chinese hamster (Cricetulus griseus)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effects of melatonin on synaptic ribbons (SR) in pinealocytes of the Chinese hamster (Cricetulus griseus) were examined. SR were classified into types 1, 2 and 3, which appear as rods, round or irregular bodies and ring-shaped structures, respectively; a synaptic ribbon index (SR index) was determined for the three types. Administration of two doses of 1.5 mg/kg melatonin at noon and 3 p.m. causes an increase in the type-1 and type-2 SR indices 3 h after the second injection in hamsters kept under alternating light and dark conditions (lights on from 7 a.m. to 7 p.m.). Likewise, in animals that are exposed to extended light for 6 h and receive two doses of melatonin at 7 p.m. and 10 p.m., an increase in the type-1 and type-2 SR indices occurs 3 h after the second injection. The increase in the type-2 SR index induced by melatonin administration to hamsters exposed to extended light is greater than the increase in the type-1 SR index under the same experimental conditions. Type-2 SR index, but not type-1 SR index, increases following bilateral superior cervical ganglionectomy. An increase in type-1 and type-2 SR indices occurs at 6 p.m. in ganglionectomized animals administered two doses of melatonin 6 h (noon) and 3 h (3 p.m.) before the time of sacrifice. No significant change is observed in type-3 SR index in animals subjected to any of the above treatments. The results indicate that exogenous melatonin may act directly on pinealocytes of the Chinese hamster to cause an increase in size and/or number of the type-1 and type-2 SR. Type 3-SR may have a role different from that of type-1 and type-2 SR; type-1 and type-2 SR may be functionally related.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 227-231 
    ISSN: 1432-0878
    Schlagwort(e): Muscle-tendon junction ; Ultrastructure ; Myofibrillar pattern ; M. flexor digitorum longus ; Mouse
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The muscle-tendon junctions of adult mice show a special arrangement of myofibrils. Essentially, the myofibrils are oriented in an anchor-like manner in the large finger-shaped processes of the muscle fiber, which contain “mitochondrial sacks” (Demmel et al. 1979) in a subsarcolemmal position. Furthermore, the single myofibril frequently branches out into smaller fibrils. It is suggested that due to the three-dimensional arrangement, these processes gain a high rigidity during contraction, thus maintaining their shape and preserving the “mitochondrial sacks”.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 265-284 
    ISSN: 1432-0878
    Schlagwort(e): Spermiogenesis ; Rainbow trout ; Ultrastructure ; Spermatids ; Chromatin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In an ultrastructural study on the spermiogenesis of the rainbow trout (Salmo gairdneri R.) four spermatogenetic stages were identified. In young round spermatids, the nuclear chromatin was first heterogeneous (euchromatin and heterochromatin). Subsequently, it became more homogeneous and started to condense in the form of coarse granules and fibers and then into fibrils associated in ribbon-like elements which eventually partly fused together. During early spermiogenesis, a juxtanuclear vacuole appeared in the area where the nuclear envelope was specialized due to condensation of material between the two envelopes and a slight accumulation of nuclear material. This area was finally located in the anterior part of spermatids and spermatozoa; it probably plays a role during fertilization. A flagellar rootlet appeared early in spermiogenesis; it may play a role in the attachment of the flagellum to the nucleus since it persisted until the centriolar complex was definitively fixed in the implantation fossa. The flagellum did not display a plasma membrane and was first located in the cytoplasm, but when it was later extruded from the cell, it acquired a membrane. The cytoplasm was rich in ribosomes (free or in small groups) but poor in membranous organelles. The few mitochondria polarized around the centriolar complex were finally organized into an annular mid-piece. The spermatids remained connected by intercellular bridges until the end of spermiogenesis. The complexity of trout spermiogenesis is intermediate between that in poecilids and that in carp and pike, which have very simple spermatozoa. The role of the material from the nucleus and the cytoplasm reaching the Sertoli cell in the control of spermatogenesis has been discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 232 (1983), S. 445-455 
    ISSN: 1432-0878
    Schlagwort(e): Avian thymus ; Intrathymic erythropoiesis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Although previously described in other avian species, intrathymic erythropoiesis is a remarkable feature of the thymus of Sturnus unicolor. In discrete stages of the life cycle of this species, erythroblasts and mature erythrocytes occupy large areas of the thymic cortex and cortico-medullary border. Simultaneously, degenerated thymocytes and epithelial-reticular cells occur in the same areas. The relationship between intrathymic erythropoiesis, degeneration of cortical lymphocytes and epithelial-reticular cells, and macrophage activity is discussed and related to a possible functional role of sex hormones in this phenomenon.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    ISSN: 1432-0878
    Schlagwort(e): Fetal macrophages ; Subepidermal mesenchyme (dermal tissue) ; Rat fetus ; Ontogeny ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary After about 12 days of gestation, fetal macrophages begin to appear in the subepidermal mesenchyme of rat fetuses. The macrophages are ultrastructurally characterized by cytoplasmic vacuoles, abundant polyribosomes and long filopodia. Immunocytologically, they possess Fc and complement (C3) receptors on the cell surface and are capable of immune phagocytosis, Latex or carbon phagocytosis, and glass adherence. From 15 days of gestation, lysosomal granules and miropinocytic vesicles gradually develop, together with an enlargement of Golgi complexes, whereas the number of polysomes and the number and size of cytoplasmic vacuoles are gradually reduced when gestation ends. Finally, the macrophages become amoeboid. Non-specific esterase and endogenous peroxidase activities are always absent in these macrophages. In culture experiments with cell suspensions prepared from the mesenchyme, fetal macrophages show a similar maturation process. Autoradiography with 3H-thymidine demonstrates a high proliferative capacity of the macrophages, particularly during the fetal stage.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    ISSN: 1432-0878
    Schlagwort(e): Ecdysteroids ; Epidermis ; In vitro differentiation ; Tenebrio ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In order to study the pupal-adult metamorphosis of Tenebrio in vitro, pupal sternites of different ages were cultured in Landureau's medium and their development systematically observed by electron microscopy. In hormone-free medium, explants taken from young pupae do not secrete pupal postecdysial cuticle in vitro, and the epidermis spontaneously detaches from the pupal cuticle. On the contrary, explants taken from pharate adults continue to secrete adult preecdysial cuticle in vitro, and the epidermis never detaches from the cuticle. Ecdysterone in physiological concentrations (0.2 to 4 μg/ml) induces the secretion of a new cuticle in explants from young pupae but the epidermis remains undifferentiated. Ecdysone is necessary for the induction of some adult differentiation. Moreover, the quality of the cuticle secreted in vitro is increased by the addition of 2% foetal calf serum; the best results have thus far been obtained in a medium containing 0.2 μg/ml ecdysone, 1 μg/ml ecdysterone, and 2% foetal calf serum.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    ISSN: 1432-0878
    Schlagwort(e): Skin ; Operculum ; Fenestration ; Ultrastructure ; Anura ; Metamorphosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The process of histolysis and fenestration of the skin of the prospective opercular perforation region of Rana japonica after extirpation of the right forelimb was observed during metamorphosis by transmission and scanning electron microscopy. Epidermal cells of the belly of the tadpole, including the operculum, are extremely similar in their ultrastructure. Epidermal cells of the prospective opercular perforation region during metamorphosis become thin and vacuolated especially around the nucleus perhaps by autolysis, associated with lysosomal activity. The histolysis and formation of the perforation of the operculum occurs in the complete absence of forelimb. Macrophages containing phagosomes and lymphocytes or other blood cells are almost always found in the intercellular epidermis. Necrotic epidermal cells progressively separate by cleft formation and slough off without cornification.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 33-36 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Preparative scale chromatography ; Capacity ; Dual-step separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The capacity of dual-step preparative chromatographic separation systems is considered. It is shown that dualstep separation makes it possible to enhance the capacity of preparative installations as compared with single- and dual-stage purification of the compounds.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 44-46 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Natural gas analysis ; Poropak N
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A simple gas chromatographic method is described for the rapid analysis of natural gas using thermal conductivity detectors and programmed-temperature operation of a single Poropak N column. The method permits the determination of nitrogen, carbon dioxide and hydrocarbons containing one to seven carbon atoms.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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