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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 281 (1995), S. 249-259 
    ISSN: 1432-0878
    Keywords: Key words: Stem cells ; Testis ; PGP 9.5 ; Ultrastructure ; Tubular whole-mounts ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The spermatogonial stem cell line in prepubertal and adult bovine testis was studied by electron microscopy and protein gene product 9.5 immunohistochemistry. Three successive spermatogonia precursor cell configurations were observed. Small basal stem cells were found to possess a spherical shape and nuclei with two to three nucleoli. They were observed in prepubertal testes (25 and 30 weeks) and in low numbers during all the stages of the seminiferous epithelial cycle in the adult. Aggregated spermatogonia precursor cells are the dominating germ cell type in the 25-week-old and 30-week-old calf. In the adult seminiferous epithelium, they cause expansion of the basal tubular compartment as they form dense groups containing up to 15 cells. These groups are observed concomitantly with cycling A-spermatogonia and preleptotenes at the beginning of spermatocytogenesis. At the end of A-spermatogonia propagation, the aggregated spermatogonia precursor cells separate and intermingle with cycling A-spermatogonia. The spermatogonia precursor cells can later be found together with I-spermatogonia as members of an interconnected cellular network of medium-sized cells. When the I-spermatogonia divide to form the smaller B-spermatogonia, the precursor cells, which stay connected with the cycling spermatogonial population, pass through a growth phase. They can now be considered as committed spermatogonia precursor cells and are continuously being transformed into A1-spermatogonia to start a new round of spermatocytogenesis. Ultrastructurally, all members of the precursor cell line are similar. However, a number of features have been found to show a quantitative increase (endoplasmic reticulum, mitochondria) or to exhibit a rising degree of complexity (nucleolus) during the progression from basal stem cells to committed spermatogonia precursor cells.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 279 (1995), S. 277-289 
    ISSN: 1432-0878
    Keywords: Key words: Spermatogonia ; Protein gene product (PGP) 9.5 ; Immunohistochemistry ; Tubular whole-mounts ; Spermatogonial degeneration ; Testis ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The configuration and distribution of bovine spermatogonia, preleptotene primary spermatocytes and Sertoli cells in the basal seminiferous tubular compartment have been studied by means of whole-mount preparations, immunohistochemistry and quantitative morphology. Three types of spermatogonia (Sg) can be identified. Large A-spermatogonia are irregularly distributed in the tubular periphery. Following the period of propagation of the A-spermatogonia, an interconnected meshwork of medium-sized spermatogonia with different cytogenetic potency is observed. Although the majority of the medium-sized spermatogonia are kinetically of the I type and divide to produce small B-spermatogonia, some members of the medium-sized population are seen in a growth phase and differentiate into large A-spermatogonia. These mark the beginning of a new round of spermatocytogenesis. Only one generation of B-spermatogonia divides into preleptotene primary spermatocytes. The architectural arrangement of multiplying spermatogonia in circles or rows is primarily the result of the distribution of the Sertoli cells. Spermatogonial multiplication is not strictly coordinated with the stages of the seminiferous epithelial cycle. Spermatogonial degeneration amounts on average to 3.6% and has therefore no decisive impact on the yield of primary spermatocytes.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0878
    Keywords: Key words: Testis ; Seminiferous epithelium ; Proliferating cell nuclear antigen (PCNA) ; Ki-67 protein ; MIB-1 antibody ; Immunohistochemistry ; Tubular whole-mounts ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The distribution pattern of proliferating cell nuclear antigen (PCNA) and Ki-67 protein was studied in adult bovine seminiferous epithelium by means of immunohistochemistry using monoclonal antibodies. Tailoring the methodological protocol for each of the two proliferation markers was a necessary prerequisite for obtaining optimal results in tubular sections and whole-mounts. A-, I- and B-spermatogonia displayed PCNA-positive nuclei, except during meta-, ana- and telophases of mitosis. PCNA-negative nuclei in the basal tubular compartment, excluding those from non-cycling Sertoli cells, belonged to the spermatogonia precursor cell line. However, only about 30%, 45% and 47% of the respective A-, I-, B-spermatogonia had positive nuclei after exposure to the MIB-1 antibody directed against the Ki-67 protein. Spermatogonia with MIB-1-negative nuclei represented cells in the G1-phase. Both antibodies reacted intensely with the nuclei of preleptotene primary spermatocytes. PCNA reactivity was also present during leptotene through pachytene. Ki-67 protein expression was absent during leptotene and zygotene but was again encountered during pachytene and meiosis I and II. Anti-PCNA/anti-protein gene product 9.5 double-labelling indicated that the transition from spermatogonia precursor cells into A1-spermatogonia is not strictly synchronized in a given tubular segment, a possible reason for the flexibility in A-spermatogonial propagation seen in bovine seminiferous tubules.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 37 (1954), S. 553-565 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aus dem Calebassen-alkaloid Fluorocurin C20H25O2N2⊕, einem Indoxylderivat, wurde durch Reduktion mit NaBH4 Hydro-fluorocurin C20H27O2N2⊕ erhalten, welches durch Säuren sehr leicht in das Indolderivat Mavacurin C20H25ON2⊕ übergeht. Mavacurin, ein Calebassen-alkaloid, haben wir auch in Rinde von Strychnos toxifera gefunden. Die Überführung von Fluorocurin in Mavacurin gelang auch direkt durch Reduktion ersterer Verbindung mit Zink und Schwefelsäure. Durch thermische Spaltung wurde Fluorocurin in Norfluorocurin C19H22O2N2 übergeführt; letzteres lässt sich durch Reduktion mit NaBH4 oder LiAlH4 in Norhydro-fluorocurin C19H24O2N2 verwandeln, das seinerseits durch Methylierung in Hydro-fluorocurin C20H27O2N2⊕ und durch H-Ionen in Normavacurin C19H22ON2 übergeht. Methylierung des Normavacurins liefert Mavacurin.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α-Phenyl-a-piperidyl-(2)-essigsäure-methylester oder Ritalin wird nach Gaben an Ratten hydrolytisch gespalten und grösstenteils als Phenyl-piperidyl-essigsäure im Harn ausgeschieden. Es liess sich eine Halbwertszeit von 6-7 Std. berechnen. Schon nach 15 Std. sind in den Organen und im Carcass nur noch sehr geringfügige Aktivitäten nachweisbar.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 43 (1960), S. 2129-2138 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ferrioxamine B, the main sideramine type growth factor isolated from cultures of Streptomyces pilosus ETTLINGER et al., is a racemic trihydroxamate-iron(III) complex of the compound IV. The possible configurations for the iron(III) complex are Va-e.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 45 (1962), S. 1396-1405 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acumycin, a new antibiotic, could be isolated in crystalline form from cultures of a new strain, ETH 23112, of Streptomyces griseoflavus. On acid hydrolysis the dimethylamino-sugar mycaminose is obtained. From this and other evidence it is concluded that acumycin belongs to the group of the macrolide antibiotics.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 51 (1968), S. 1108-1119 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 7-Aminocephalosporanic acid or esters thereof are prepared either by intramolecular aminolysis of esters of the antibiotic cephalosporin C or vïa imino-ethers derived from the latter.A simple procedure for the preparation of 7-aminocephalosporanic acid in high yield is described.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 2044-2054 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Benzhydrylic esters of 3-unsubstituted cephem-4-carboxylic acids of types 9 and 10 (Scheme 2) are prepared by decarbonylation of esters of 3-formylcephem compounds of type 2 with tris-triphenylphosphine-rhodium chloride. The preparation of the starting materials 2 and 5, as well as of the nucleus 13 is described.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 43 (1960), S. 457-458 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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