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  • Analytical Chemistry and Spectroscopy  (145)
  • Life and Medical Sciences  (124)
  • MATERIALS, METALLIC
  • 1990-1994  (242)
  • 1980-1984
  • 1965-1969  (79)
  • 1991  (242)
  • 1969  (79)
Collection
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  • 1990-1994  (242)
  • 1980-1984
  • 1965-1969  (79)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Comparative kinetics of short and long sperm in sperm dimorphic Drosophila species (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 269-274 
    Details
    ISSN: 0886-1544
    Keywords: minor and major waves ; beat frequeney ; wave propagation velocity ; coiling diameter ; storage effect ; differential behaviour ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: All species of the Drosophila obscura group exhibit within-ejaculate sperm length dimorphism. The present work is a contribution to the understanding of sperm competition through a comparative study of sperm kinetic parameters in four of these species. Videomicrographic observations at 200 frames per second of sperm from males and females, out of the storage organ, prior or after storage were made. Drosophila sperm display both major and minor waves. The former is analysed by measuring coiling diameter (μm) and the latter by recording both beat frequency (s-1) and wave propagation velocity (μm·s-1). Results show that the ‘behaviour’ of short and long spermatozoa noticeably differ: short sperm kinetics remains unaltered after storage while both major and minor waves of long spermatozoa are markedly modified. Thus, evidence is provided here of a sort of “differential activation” which is assumed to result in different survival abilities of short and long sperm within the storage organ of females.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970190405
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation of spermatogenic cell populations at specific stages of differentiation in the human (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 30 (1991), S. 275-282 
    Details
    ISSN: 1040-452X
    Keywords: Human testis ; Cell separation ; Elutriation ; Spermatid ; Ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Studying biochemical events in human spermatogenesis requires separated populations of spermatogenic cells. Dissociation of these cells was performed by a Trypsin-DNAse method adapted from the technique used for rodents. Cell separation was performed by centrifugal elutriation. Seven populations were collected, one further purified by Percoll gradient centrifugation, giving nine different cell populations. The efficiency of the cell separation was evaluated by phase contrast microscopy, flow cytometric DNA analysis, and electron microscopy. Five populations were enriched in spermatids: two in round spermatids (87% and 73%), another in round (52%) and elongating (44%) spermatids, another constituted by 80% elongating spermatids, and the last by 90% elongated spermatids. Two of the four remaining populations were enrichied in primary spermatocytes (74% and 54%); another population was the upper part of the Percoll gradient and constituted cytoplasmic lobes and residual bodies (89%); the last population was made up of various cells, with no specific enrichment. Electron microscopic observations revealed good preservation of the separated cells; only the flagella from elongated spermatids were lost. Furthermore, an unusual pattern of nucleoplasm distribution during stages 2-4 of spermatid differentiation was observed and its signification is discussed with regard to the shape of the human spermatozoon.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080300316
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  • 3
    Electronic Resource
    Electronic Resource
    Developmental protein synthesis is required for the transcription of Dictyostelium prespore genes (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 12 (1991), S. 113-122 
    Details
    ISSN: 0192-253X
    Keywords: Dictyostelium discoideum ; cyclo heximide ; emetine ; protein synthesis ; mRNA accu mulation ; transcription ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: It has been established previ- ously that the maintenance of expression of pre-spore-specific genes of Dictyostelium discoideum is prevented by the translational inhibitor cyclohex- imide. The drug had no effect upon the level of transcripts of the other genes examined, prestalk-specific or cell type-nonspecific. However, the interpretation of this result is open to question, because of possible nonspecific effects of cyclo-heximide. We have now characterized the cellular specificity and temporal profiles of mRNA accumu- lation of additional Dictyostelium cDNA clones, and have examined other inhibitors of in vivo protein synthesis. Four structurally and mechanistically distinct translational inhibitors each prevented the reaccumulation of prespore transcripts in cyclic AMP-primed, disaggregated amoebae. These results establish the importance of developmental protein synthesis in the accumulation of prespore gene transcripts. Nuclear run-on transcription assays were used to learn whether protein synthesis is required primarily for mRNA synthesis or transcript stability. A transcriptional time course first demonstrated that the abundance of these cell-specific transcripts during development mirrors their rates of synthesis. Significantly, the protein synthesis requirement of the prespore genes examined also occurs at the level of mRNA transcription, implying the existence of one or more developmentally regulated transcriptional activators.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020120119
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  • 4
    Electronic Resource
    Electronic Resource
    Fourier transform Raman spectroscopy of superconducting YBa2Cu3O7-δ films on strontium titanate and magnesium oxide substrates (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 639-643 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin sputtered films of the high-Tc material YBa2Cu3O7-Δ were investigated using 180° back-scattering geometry with Fourier transform (FT) Raman spectroscopy. It is established that the main bands in the spectra of a YBa2Cu3O7-Δ film on strontium titanate substrate exhibit similarity with those obtained for oriented untwinned crystallites of the superconductor having their c-axis perpendicular to the surface of the substrate. No degradation or excessive heating of the film was observed with 1.064 μm excitation for low laser powers. The film on a magnesium oxide substrate gives unique evidence of the isolated strong, featureless, almost flat continuum, producing a broad maximum near the region of the antiphase axial bending O(2)—Cu(2)—O(3) motions of planar oxygens at very low excitation energy. This appears to be the first application of FT-Raman spectroscopy using near-infrared excitation (1.064 μm) to the field of high-temperature superconducting films and their detailed characterization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250221108
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  • 5
    Electronic Resource
    Electronic Resource
    Mass spectrometry in stereochemical problems. 6  -  The case of mono and di-substituted norbornanes (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 977-984 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectrometric behaviour of pairs of stereoisomeric mono- and di-substituted norbornanes, namely bicyclo[2.2.1]heptane-2-endo- and -exo-carboxylic acid, methyl bicyclo[2.2.1]heptane-2-endo- and -exo-carboxylate, 2-exo-acetamidobicyclo[2.2.1]heptane-2-endo- and 2-endo-acetamidobicyclo[2.2.1]heptane-2-exo-carboxylic acid and methyl 2-exo-acetamidobicyclo[2.2.1]heptane-2-endo- and 2-endo-acetamido-bicyclo[2.2.1]heptane-2-exo-carboxylate was studied in detail with particular emphasis on characterization of the stereoisomers. The fragmentation patterns, studied with the aid of mass-analysed ion kinetic energy spectrometry, were supported by semi-empirical MO-SFC calculations, performed using the AM1 method included in the AMPAC program.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210261112
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  • 6
    Electronic Resource
    Electronic Resource
    Association of vanadate-sensitive Mg2+-ATPase and shape change in intact red blood cells (1991)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 46 (1991), S. 284-290 
    Details
    ISSN: 0730-2312
    Keywords: erythrocytes ; magnesium ; echinocyte ; calcium ; plasma membrane ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Intact human erythrocytes, initially depleted of Mg2+ by EDTA incubation in the presence of A23187, exhibit Mg2+-dependent phosphate production of around 1.5 mmol per liter cells · h, half-maximally activated at around 0.4 mM added free Mg2+. This appears to correspond to Mg2+-stimulated adenosine triphosphatase (Mg2+-ATPase) activity found in isolated membranes, which is known to have a similar activity and affinity for Mg2+. Vanadate (up to 100 μM) inhibited Mg2+-dependent phosphate production and ATP breakdown in intact cells. Over a similar concentration range vanadate (3-100 μM) transformed intact cells from normal discocytes to echinocytes within 4-8 h at 37°C, and more rapidly in Mg2+-depleted cells. The rate of Ca2+-induced echinocytosis was also enhanced in Mg2+-depleted cells. These results support previous studies in erythrocyte ghosts suggesting that vanadate-induced shape change is associated with inhibition of Mg2+-ATPase activity localized in the plasma membrane of the red blood cell.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240460403
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  • 7
    Electronic Resource
    Electronic Resource
    Investigation of products arising from enzymatic digestion of advanced glycated albumin by high-performance liquid chromatography/mass spectrometry (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 624-628 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The structural investigation of the products arising from 28 days incubation of albumin with high glucose concentration and further enzymatic hydrolysis has been carried out by means of high-performance liquid chromatography/mass spectrometry (HPLC/MS) under plasmaspray conditions. By this approach many different compounds have been detected, and for most of them, possible structures have been proposed on the basis of literature data and molecular weight assignments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290051212
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  • 8
    Electronic Resource
    Electronic Resource
    Formation and decay of doubly charged ions from polycyclic aromatic hydrocarbons and related compounds (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 512-517 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Coincidence techniques have been used to investigate double photoionization and subsequent decay of a series of polycyclic aromatic hydrocarbons (PAHs) from benzene to perylene. At fixed photon energy (40.8eV) the total yield of double ionization relative to single photoionization for both PAHs and for aliphatic compounds increases asthe same function of the excess energy above the double ionization energy. The ratio of double to single ionization for a given compound at different photon energies varies linearly with the excess energy. The fraction of dissociative double photoionization falls with increasing size in the PAH series; the ejection of characteristic neutral species (H·, H2 and C2H2) is the main dissociation pathway in the larger PAHs while charge separation is important for smaller species. Partial hydrogenation or aliphatic substitution results in decreasing stability of the doubly charged ions and increasing dissociation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290051106
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  • 9
    Electronic Resource
    Electronic Resource
    A gas chromatographic/mass spectrometric approach for isomer-specific environmental monitoring of the 1700 bromo-, chloro-, and bromochloro-dibenzo-p-dioxins (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1991), S. 329-337 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A combined approach using gas chromatographic retention indices and mass spectrometric characteristics has been elaborated for the isomer-specific identification of the 1700 bromo-, chloro- and bromochloro-dioxins which may be found in the environment. Over 100 dioxins were synthesized to develop this approach. This environmental monitoring strategy allows qualitative and quantitative monitoring of the 2,3,7,8-substituted isomers, which are considered to be more toxic, and many of which have assigned toxicity equivalency factors.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200200515
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  • 10
    Electronic Resource
    Electronic Resource
    The analysis of trenbolone and the human urinary metabolites of trenbolone acetate by gas chromatography/mass spectrometry and gas chromatography/tandem mass spectrometry (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1991), S. 459-466 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact mass spectrometric properties of trimethylsilyl ether and fluoroacyl ester derivatives of trenbolone, combined or not combined with a methoxime group, are presented. Some derivatization problems were observed and were due to the formation of enol derivatives at the 3C-position in several tautomeric forms, which in their turn were not stable and lost two or four hydrogens under the conditions studied. The enolization could be minimized by carefully selecting the reaction conditions or could be prevented by the introduction of a methoxime group at the 3C-position. The limits of detection and identification of the methoxime heptafluorobutyryl ester and the methoxime trimethylsilyl ether derivative of trenbolone were determined using a mass selective detector in the electron impact mode and a triple-stage quadrupole in the methane positive chemical ionization mode. Selected reaction monitoring in tandem mass spectrometry did not improve the limit of detection, but because of the gain in selectivity did improve the limit of identification. The glucuronides of trenbolone and epitrenbolone could be identified in three urine specimens out of 200 samples in routine doping control.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200200805
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