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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of the reactions of hydroxyl radicals with aliphatic ethers studied under simulated atmospheric conditions (1989)
    Springer
    Journal of atmospheric chemistry 8 (1989), S. 87-94 
    Details
    ISSN: 1573-0662
    Keywords: Atmospheric photo-oxidation ; hydroxyl-radicals ; diethylether ; di-n-propylether ; di-n-butylether ; di-isobutylether ; ethyl n-butylether ; ethyl t-butylether ; smog chamber ; kinetic studies ; relative rate coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rate coefficients have been measured for the reactions of hydroxyl radicals with a range of aliphatic ethers by a competitive technique. Mixtures of synthetic air containing a few ppm of nitrous acid, isobutene and an ether were photolyzed in a Teflon-bag smog chamber. From the rates of depletion of the ether and of the isobutene, and based on the value of the rate coefficient k(OH+i-C4H8)=5.26×10-11 cm3 molecule-1 s-1, the following rate coefficients were obtained for the hydroxyl radical reactions at 750 Torr and at 294±2K in units of 10-12 cm3 molecule-1 s-1: diethylether = 12.0±1.1, di-n-propylether = 15.3±1.6, di-n-butylether=17.1±0.9, ethyl n-butylether = 13.5±0.4, ethyl t-butyl-ether = 5.6±0.5, and di-isobutylether = 26.1±1.6. The quoted error limits correspond to 2 standard deviations but do not include any contribution from k(OH+i-C4H8) for which the error limits are estimated to be about ±10%. The results are discussed in relation to the available literature data and considered in terms of the structure-activity relation for hydroxyl radical reactions with organic molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00053817
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics of the reactions of hydroxyl radicals with alkyl nitrates and with some oxygen-containing organic compounds studied under simulated atmospheric conditions (1986)
    Springer
    Journal of atmospheric chemistry 4 (1986), S. 253-262 
    Details
    ISSN: 1573-0662
    Keywords: Atmospheric photo-oxidation ; acetone ; ethanol ; isopropyl acetate ; n-propyl acetate ; methyl nitrate ; ethyl nitrate ; n-propyl nitrate ; hydroxyl radical ; smog chamber ; kinetic studies ; relative rate constants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rate constants have been measured for the reactions of hydroxyl radicals with alkyl nitrates and with some oxygen-containing organic compounds by a competitive technique. Mixtures of synthetic air containing a few ppm of nitrous acid, ethylene and the organic substrate were photolysed in a Teflon bag smog chamber. Based on the value k HO+C2H4}=8.1×10-12 cm3 molecule-1 s-1 the following rate constants were obtained for the hydroxyl radical reactions at 750 Torr and at 303 K in units of 10-12 cm3 molecule-1: CH3ONO2, 0.37±0.09; C2H5ONO2, 0.48±0.20; n-C3H7ONO2, 0.70±0.22; C2H5OH, 3.6±0.4; CH3COCH3, 0.26±0.08; CH3CO2 i-C3H7, 3.0±0.8; CH3CO2 n-C3H7, 2.4±0.2. The results are discussed in relation to the available literature data and the implications of the results are considered in terms of the ‘smog reactivity’ of these molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052004
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  • 3
    Electronic Resource
    Electronic Resource
    The photo-oxidations of propyl acetates in synthetic air-HONO-NO x mixtures: Product formation studies and proposed kinetic mechanisms (1986)
    Springer
    Journal of atmospheric chemistry 4 (1986), S. 263-276 
    Details
    ISSN: 1573-0662
    Keywords: Atmospheric photo-oxidation ; alkoxy radicals ; isopropyl acetate ; n-propyl acetate ; nitrous acid ; hydroxyl radical ; smog chamber ; reaction mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The formation of products following the hydroxyl radical initiated photo-oxidations of n-and isopropyl acetates has been studied. Mixtures of synthetic air containing a few ppm of nitrous acid, nitric oxide, nitrogen dioxide and one of the propyl acetates were irradiated with sunlamps in a Teflon bag smog chamber. The decay of reactants and the formation of products was monitored by chemiluminescent analysis or by gas chromatography. The major primary products from the photo-oxidation of n-propyl acetate are acetaldehyde and propionaldehyde while from isopropyl acetate they are acetone and methyl nitrate. It was not possible to analyse for formaldehyde, an expected primary product in these systems. The nature and distribution of products indicate that a significant fraction of primary products arise from decomposition reactions of the alkoxy-type radicals generated following the initial attack of hydroxyl radicals on the esters. The derived reaction stoichiometries (molecules of NO oxidised per molecule of ester reacted) are also consistent with the proposed mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052005
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  • 4
    Electronic Resource
    Electronic Resource
    Testosterone and FSH have independent, synergistic and stage-dependent effects upon spermatogenesis in the rat testis (1992)
    Springer
    Cell & tissue research 268 (1992), S. 179-189 
    Details
    ISSN: 1432-0878
    Keywords: Testis ; Spermatogenesis ; FSH ; Testosterone ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Adult rats were hypophysectomized and treated with ethane dimethanesulphonate (EDS) selectively to eliminate the Leydig cells in the testis. By removing the source of endogenous gonadotrophins and androgens, the subsequent effects on the seminiferous epithelium were studied after 20 days of treatment with vehicle, or FSH (2x50 μg/day) or a low dose of testosterone (0.6 mg testosterone esters every 3rd day) alone or in combination. Compared to vehicle-treated hypophysectomized rats with Leydig cells, testis weight in saline-treated hypophysectomized rats treated with EDS declined by 50%, spermatogenesis was disrupted severely and only 18% of the tubules contained spermatids, these being confined to stages I–VI of the spermatogenic cycle. Treatment with either FSH or testosterone esters alone significantly (P〈0.01) increased testis weight compared to vehicle-treated hypophysectomized rats treated with EDS and 40% of tubules contained spermatids either at stages I–VI after FSH, or at all stages I–XIV after testosterone treatment. Treatment with FSH and testosterone esters together maintained testis weights approximately 20% above vehicle-treated hypophysectomized controls; over 70% of the seminiferous tubules contained spermatids and there was a marked stimulation of spermatogenesis at all stages of the spermatogenic cycle. The results suggest, that in the absence of the pituitary gland and the Leydig cells, FSH alone partially supports spermatogenesis up to the development of round spermatids whereas testosterone is capable of maintaining spermatid development at all 14 stages of the cycle. When FSH and testosterone were administered in combination, the effects upon spermatogenesis were far greater than the response expected if their individual effects were simply additive. It is therefore concluded that FSH may play a role in normal spermatogenesis and that this role is essentially that of augmenting the response of the testis to testosterone. The biochemical mechanisms via which this might occur are discussed and hypophysectomized rats treated with EDS used in the present studies should provide a useful approach for their identification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338067
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  • 5
    Electronic Resource
    Electronic Resource
    Focal disruption of spermatogenesis in the testis of adult rats after a single administration of human chorionic gonadotrophin (1989)
    Springer
    Cell & tissue research 257 (1989), S. 163-169 
    Details
    ISSN: 1432-0878
    Keywords: Testis ; Human chorionic gonadotrophin ; Inflammatory response ; Spermatogenic disruption ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of a single injection of 100 i.u. human chorionic gonadotrophin (hCG) upon the morphology of the rat testis was studied by light and electron-microscopy from 12–48 h after treatment. Twelve hours after injection of hCG, emigration of leukocytes occurred across the intertubular blood vessels and, both at this time and at 24 h, infiltrations of leukocytes were observed within the extracellular tissue spaces. Furthermore, 12 h after hCG, the seminiferous epithelium showed focal disruption of spermatogenesis involving germ cell degeneration and pyknosis. Focal damage to the seminiferous epithelium persisted at 24 h and 48 h after injection of hCG, the affected seminiferous tubules showing failure of spermiation, accumulation of extracellular vacuoles and degeneration or partial loss of spermatogonia and primary spermatocytes. The observations show that, after stimulation of the Leydig cells with hCG, the intertubular tissue exhibits an inflammatory-type response and this is associated with focal tissue destruction in the seminiferous tubules. It is concluded that a high dose of hCG exerts anti-spermatogenic effects upon the testis and raises the possibility of unexpected interference with tests of normal Leydig cell function in both laboratory and clinical investigations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221647
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  • 6
    Electronic Resource
    Electronic Resource
    Response of the seminiferous epithelium of the rat testis to withdrawal of androgen: evidence for direct effect upon intercellular spaces associated with Sertoli cell junctional complexes (1993)
    Springer
    Cell & tissue research 274 (1993), S. 153-161 
    Details
    ISSN: 1432-0878
    Keywords: Testis ; Sertoli cells ; Testosterone ; Hypophysectomy ; Ethane dimethanesulphonate ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The morphological response of the Sertoli cells to partial or complete withdrawal of testosterone was studied in adult rats following hypophysectomy or administration of ethane dimethanesulphonate (EDS), a toxicant known to destroy selectively the Leydig cells of the testis. To assess the role of germ cells in effecting changes to Sertoli cells following withdrawal of testosterone, germ cell-deficient rats with Sertoli-cell-only testes (SCO) were treated with EDS to remove the source of testosterone. At 6 days after hypophysectomy or 4,6 and 8 days after EDS treatment, stage VII and VIII seminiferous tubules showed degenerating germ cells and numerous basally-located vacuoles approximately 1–15 μm in diameter. Ultrastructural analysis indicated that most of the vacuoles were multiple focal dilations of the intercellular space associated with Sertoli cell junctional complexes. In SCO rats, treatment with EDS resulted in a significant (P〈0.05) increase in the formation of many vacuoles particularly in the base but also in the trunk of the Sertoli cells and again electron microscopic analysis showed multiple, localized expansions of the intercellular space associated with Sertoli cell junctional complexes. The appearance of intercellular spaces in SCO testes following androgen withdrawal cannot be attributed to shrinkage of degenerating germ cells since the seminiferous tubules did not contain germ cells. It is concluded that withdrawal of androgen induces early morphological alterations of the Sertoli cell junctional complexes in which the sites of membrane fusions representing tight junctions remain intact whereas the intercellular spaces exhibit major focal dilations. The results are discussed in relation to the fluid secretion by the seminiferous tubules which is regulated by the Sertoli cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327996
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