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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 165 (1991), S. 51-63 
    ISSN: 1615-6102
    Schlagwort(e): Bivalent structure ; Meiosis ; Microtubules ; Mitochondria ; Nuclear envelope
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Using ultrathin sections and electron microscopy, the structure of prophase I spermatocytes is described in the mothEphestia kuehniella Z. Some stages were also examined using light microscopy and antitubulin immunofluorescence microscopy. Changes in the mitochondrial inventory, the endomembranes, and the nuclear content during the progression of meiosis from pachytene to diakinesis have a bearing on the structure of prometaphase and metaphase I spermatocytes. In late diplotene, a short-lived system of cytoplasmic microtubules forms independently of the flagellar bases. Possibly mediated by these microtubules, mitochondria gather in a portion of the cell and fusion of individual mitochondria occurs. The clustering of mitochondria, which persists until the meiotic spindle has developed, may be the prerequisite for the bipartition of the chondriome during cytokinesis. After late pachytene, the mass of perinuclear endoplasmic reticulum and the number and size of the Golgi stacks also increase. These endomembranes give rise to the multi-layered membraneous envelope around the meiotic spindle and probably to the intraspindle membrane system. After late pachytene, the number of nuclear pores also increases and material export from the nucleus is apparent. The exchange is interpreted as an indicator for transcriptional activity in the late prophase I nucleus when the chromatin is transiently decondensed (diffuse stage). In the course of chromatin recondensation, the bivalents assume a speckled appearance in ultrathin sections. Metaphase I bivalents possess lighter staining equatorial material. This material is not stained with a DNA-specific fluorescent dye or with acetic orcein, which preferentially binds to chromatin. It is hypothesized that less dense core material becomes interspersed with chromatin during the diffuse stage and is involved in the maintenance of bivalent structure until the onset of anaphase I.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1435-0130
    Schlagwort(e): Split vascularized fibula ; Vascularized periosteal flap ; Bone defects ; Reconstruction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A new principle in reconstructive surgery is presented: “The immediate reconstruction of a missing bone segment with a primary osteoperiosteal tube that will secondarily be transformed into a complete osseous tube. ” In 5 out of 7 baboons, a bone tube with an almost normal bone cavity was achieved after 16 to 28 weeks. In 2 cases, we failed to reconstruct the tube because of an intraoperative fault and postoperative plate fracture with subsequent destruction of the vascularized periosteal flap. On the basis of this study, we describe a new concept in reconstruction of segmental bone defects of the lower extremity. The osteoperiosteal tube is formed by the combination of two successful experimental and clinical techniques: the vascularized fibular transfer which is modified by splitting the bone graft longitudinally, and transfer of vascularized periosteum (“concept of the substitution of a missing bone segment by an organ-like tube”). In the most stressed marginal region of the bone defect, there is vascularized cortical bone from the longitudinally split fibular graft and an increasing amount of lamellar bone being produced under the vascularized periosteal flap. By splitting the graft, nutrition depends entirely on the periosteal blood supply. The “concept of the dual blood supply” was initially described by Berggren et al. and Papanastasiou et al. [4, 18]. The significance of the “concept of the vascularized periosteum transfer for reconstruction of a segmental bone defect” is well illustrated. Only in cases where the vascularized periosteal flap was intact and securely sutured to the fibulae graft and the two tibia stumps could a bone tube be reconstructed. The arrangement of both vascularized grafts as an osteoperiosteal tube exemplify the “concept of the given space” as described by Stock et al. [26]. Inside the osteoperiosteal tube, a “consolidation chamber” is created in which all the factors required for bone formation can be concentrated. Comparison of the results of successfully reconstructed bone tubes with the solid bone column in the defect of the baboon where no bone tube could be reconstructed underline the “concept of combination of different vascularized grafts for reconstruction of segmental bone defects in long bone defects of the lower extremity.”
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Langenbeck's archives of surgery 376 (1991), S. 257-263 
    ISSN: 1435-2451
    Schlagwort(e): Parenteral nutrition ; LCT-fat ; Yoshida sarcoma ; Tumor growth ; Nitrogen balance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung In einer experimentellen Untersuchung an Sprague-Dawley-Ratten wurden die Auswirkungen von parenteral zugeführten LCT-Fetten auf das Tumorwachstum des Yoshida-Sarkoms in seiner Aszites form überprüft. Dabei wurden 4 Gruppen mit je 10 tumortragenden (TTR) and 10 nicht tumortragenden Ratten (NTTR) gebildet, denen parenteral LCT-Fette in unterschiedlicher Dosierung (Gruppe 1–3) zugeführt, bzw. die enteral ad libitum ernährt wurden (Gruppe 4). Es zeigt sich, daß die tumortragenden Ratten (TTR) cine höhere Stickstoffretention aufwiesen, als die nicht tumortragenden Ratten (NTTR). Dabei fiel auf, daß die NTTR einen höheren Stickstoffgehalt in der Muskulatur hatten. Der Stickstoffanteil nahm dabei mit zunehmendem Fettanteil ab. Die Betrachtung des Sarkoms ergab, daß sich sowohl der Stickstoffgehalt des Aszites, wie auch die Menge and die Zellzahl des Tumors umgekehrt proportional zur Menge des parenteral zugeführten Fettes verhielt. Für den Wirt konnten wir zeigen, daß er die zugeführten Energiemengen nicht unmittelbar für sich verwerten konnte. Der Tumor wächst nicht proportional mit der ihm zugeführten Energie, sondern muß sich vom Katabolismus des Wirtes ernähren.
    Notizen: Summary In an experimental study with sprague-dawley-rats we tested the effect of parenteral substituted LCT-fats on tumor growth of the Yoshida sarcoma in its ascites form. Therefore we tested 4 groups with 10 tumor-bearing and 10 non-tumor-bearing rats. We added group 1–3 LCT-fats in different doses. Group 4 was fed enterally. We found that tumor-bearing rats had a higher nitrogen retention than non-tumor-bearing rats. Non-tumor-bearing rats showed a higher nitrogen concentration in the muscles. The portion of nitrogen increased with increasing portion of fat. The content of nitrogen in the ascites, the quantity and the number of tumor cells was reversed in proportion to the portion of fat. For the host we showed that he cannot make use of the energy directly. The tumor does not grow in proportion to the available energy but has to support itself from the catabolism of the host.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 18 (1991), S. 409-412 
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 35.80.+s
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The kinetics of cluster formation in supersonic jets is examined by numerical integration of the master equation system. Some general characteristics of cluster kinetics could be formulated. Excellent agreement between experimental curves of p-cresol (H2O)0, 1, 2, 3 formation as function of H2O pressure and the corresponding calculated curves were obtained assuming successive cluster formation. From the kinetic curves, an unambiguous assignment of cluster size was possible which agreed with mass-resolved REMPI measurements. The fit of the rate coefficients shows the formation of p-cresol (H2O)1 to be faster than p-cresol (H2O)2 and p-cresol (H2O)3.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 11 (1991), S. 467-477 
    ISSN: 0138-4988
    Schlagwort(e): Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The kinetics based on the MONOD conception of anaerobic, discontinuous, isothermal, isobaric fermentation producing a special protein in secondary metabolism is studied.The kinetic analysis results in a growth limitation by the primary product which shows a sigmoidal behaviour, a lineary correlation between the specific substrate degradation and the specific rate of formation lactic acid and a lineary correlation in a good approximation between the formation of proteins and substrate degradation.In this study a process model with coupled differential equations is provided. Kinetic and stoichiometric coefficients are determined.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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