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  • Articles  (8)
  • Chemistry  (6)
  • Steroids  (2)
  • General Chemistry
  • Gonadotropin
  • Gonadotrops
  • Liquid chromatography
  • Magnetism
  • 2000-2004  (2)
  • 1980-1984  (6)
  • 1955-1959
  • 1940-1944
  • 1935-1939
  • 2000  (2)
  • 1983  (6)
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  • Articles  (8)
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  • 2000-2004  (2)
  • 1980-1984  (6)
  • 1955-1959
  • 1940-1944
  • 1935-1939
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 233 (1983), S. 377-388 
    ISSN: 1432-0878
    Keywords: Gonadotrops ; Gonadotropin secretion ; Steroids ; Brain-pituitary-gonadal axis ; Juvenile teleost
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In a cytophysiological study it was investigated whether in juvenile trout gonadal steroids stimulate the gonadotropic (GTH)-cells directly or indirectly via the brain. Pituitaries of donor animals were transplanted into the caudal musculature of testosterone-treated and non-testosterone-treated host fish. Testosterone treatment caused an increase in GTH-content in the in situ pituitaries and in the grafts. Accordingly, the gonadotrops displayed ultrastructural changes such as the appearance of well-developed Golgi systems and large globules. The stimulation of the morphological development of gonadotrops and of synthesis and storage of GTH in the allografted pituitaries indicates that testosterone affects the GTH-cells directly. In untreated juvenile trout the gonadotropin content of the pituitary and the gonadotropin concentration in the plasma vary with the time of year. This variation and the role of testosterone and gonadotropin-releasing hormone on the release of GTH are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0878
    Keywords: Pituitary, juvenile trout ; Gonadotropin ; Steroids ; LHRH ; Organ culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pituitary glands from 6-month-old sexually immature female rainbow trout, Salmo gairdneri, were kept in organ culture for 48 or 72 h. Certain groups of pituitaries were cultivated for 48 h on either control medium or medium with 17α-methyltestosterone (MT), or with estradiol-17β (E2) in concentrations of 8.5 × 10-7 M. Other groups of pituitaries were cultivated for 72 h on control medium, or for 48 h on either control medium or MT-medium or E2-medium, and subsequently for 24 h on medium with synthetic LHRH in concentrations of 8.5 × 10-7 M and 8.5 × 10-10 M. Gonadotropic (GTH) cells are identified by Alcian Blue-Periodic Acid Schiff-Orange G staining and the double-antibody immunoenzyme-cytochemical technique using anti-carp βGTH as the first antibody. A quantitative histological procedure was used to study the nuclear size of the GTH cells in response to the different hormones. Secretory activity was estimated by measuring the gonadotropin (GTH) content in extracts of pituitaries, plasma, and the culture media every 24 h by radioimmunoassay. Cultivation on MT- or E2-enriched medium results in an increase of the total amount of GTH in the pituitary and medium, an accumulation of GTH in GTH-cells (approximately 20 percentage points) and an increase in their nuclear size, indicating a stimulation of GTH synthesis. However, autonomous GTH-release is not affected by these steroids. Subsequent cultivation of the pituitaries for 24 h with LHRH causes stimulation of GTH synthesis (approximately 20 percentage points). Preincubation with steroids increases the GTH synthesis capacity of LHRH only when used in a concentration of 8.5 × 10-10 M. Moreover, 8.5 × 10-7 M LHRH causes a stimulation of GTH-release. Preincubation of the pituitaries with steroids increases the responsiveness of GTHcells to LHRH. It is concluded that GTH-production in pituitaries of immature female rainbow trout can be directly influenced by gonadal steroids and by a hypophysiotropic substance.
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  • 4
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional gas chromatography ; thermal desorption modulator ; temperature programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In comprehensive two-dimensional gas chromatography, two individual separations are coupled by means of a rotating thermal desorption modulator interface. The injection pulse introduced via the interface onto the second column should be as short as possible. Parameters affecting the modulator operation are studied. In the set-up used in this study, the temperature of the second column can be programmed independently from that of the first column. Optimization of the second-dimension separation to minimize peak broadening and maximize resolution is discussed and an elegant approach to determine second-dimension retention times using a non-constant modulation frequency is demonstrated. The high separation power of the comprehensive system is demonstrated by the analysis of technical and biota samples containing chlorinated biphenyls and toxaphene.
    Additional Material: 7 Ill.
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  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Time-resolved fluorescence depolarization was applied to investigate the dynamics of low-molecular-weight polyethylene glycols (MW 150, 400, 1000, 4000) labeled by fluorescein-isothiocyanate. The analysis of measurements revealed considerable flexibility of the polymer chain. To interpret the observed dependence of the relaxation time of polarization anisotropy on the molecular weight of the polymer, a simple freely-hinged dumbbell model was developed. The properties of the model were investigated by computer experiments. The model was found to account well for the measured data.
    Additional Material: 7 Ill.
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  • 6
    ISSN: 0935-6304
    Keywords: μLC ; FID ; LC-FID ; carbohydrates ; amino acids ; alcohols ; phosphonic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The potential of the on-line coupling of microcolumn liquid chromatography (μLC) using aqueous eluents with a flame ionization detector (FID) was evaluated. An eluent-jet interface was modified to allow the efficient introduction of the eluent into the FID. The potential of the method is demonstrated by the μLC-FID determination of lower alcohols and bis(2-hydroxyethylthio)alkanes on porous and non-porous stationary phases, respectively. Flow injection analysis (FIA)-FID experiments with highly polar, thermolabile, semi-volatile and non-volatile compounds like amino acids, organic acids, alkylphosphonic acids, and carbohydrates showed the developed configuration to be a promising approach for the detection of a wide range of analytes. Compared with a nebulization interface, the eluent-jet interface showed 4-10 times higher peaks for citric acid. Detection limits by FIA for all compounds were in the range of 0.2-5 ng injected. With ribose as test compound, plots of peak height vs. amount injected showed good linearity (r2 〉 0.999) in the range of 75-12,000 μg/mL. The repeatability showed relative standard deviations of less than 5%.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Plant/Operations Progress 2 (1983), S. 137-140 
    ISSN: 0278-4513
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 498 (1983), S. 153-160 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions on the Thermal Behaviour of Sulfates. VI. On the Chemical Transport of CuSO4, Cu2OSO4, and CuOA powder of anhydrous CuSO4 can be prepared by heating CuSO4 · 5 H2O in air or in an argon atmosphere. In the same way it is possible to get a powder of Cu2OSO4. But up to now, it was difficult to get crystals of CuSO4 and there was no method known to synthesize crystals of Cu2OSO4. Investigations concerning chemical transport reactions of anhydrous heavy metal sulfates showed, that it is possible to get well formed crystals of CuSO4 and Cu2OSO4 by deposition from a vapour phase. As transport agents for CuSO4, Cl2 and HgCl2 are especially suitable. Less appropriate are HCl, NH4Cl, and I2.The chemical vapor deposition of Cu2OSO4 proceeds well with HgCl2. In course of these investigations we recognized, that for CuO in addition to the well approved transport agents also Cl2, HgCl2 or I2 (NH4Cl less suitable) can successfully be used.
    Notes: Wasserfreies CuSO4 ist in Pulverform durch thermischen Abbau der Hydrate leicht zugänglich, pulverförmiges Cu2OSO4 läßt sich dementsprechend aus CuSO4 darstellen. Kristalle waren dagegen bisher von CuSO4 nur sehr schwierig und von Cu2OSO4 noch nicht synthetisch zu gewinnen. Wie sich im Rahmen einer Untersuchung zum chemischen Transport wasserfreier Schwermetallsulfate zeigte, sind gut ausgebildete Kristalle von CuSO4 und Cu2OSO4 durch Abscheidung aus der Gasphase zugänglich. Als Transportmittel für CuSO4 sind besonders Cl2 und HgCl2 geeignet, weniger brauchbar sind HCl, NH4Cl oder I2. Das Oxidsulfat ist mit HgCl2 und NH4Cl, weniger gut mit I2 zu transportieren. Dabei fanden wir, daß für CuO außer den dafür bereits erprobten Transportmitteln auch Cl2, HgCl2 und I2 (NH4Cl weniger gut) verwendbar sind.
    Additional Material: 2 Ill.
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