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  • 1
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1) In der Embryogenese vonSmittia wird die Entwicklung des Kopfendes durch cytoplasmatische Komponenten in der Vorderpolregion des Eies determiniert. Experimentelle Inaktiveirung oder Entfernung dieser Determinanten bewirkt die Entstehung des aberranten Segmentmusters “Doppelabdomen”. In diesem spiegelbildlich symmetrischen Segmentmuster sind Kopf, Thorax und vordere Abdominalsegmente durch ein zweites Abdominalende mit revertierter Polarität ersetzt. In Versuchen mit verschiedenen methodischen Ansätzen wurde geprüft, ob Mitochondrien als Determinanten des embryonalen Vorderpols fungieren. 2) Die folgenden Ergebnisse sind vereinbar mit der Vorstellung, daß mitochondriale Funktionen die Längsachsenpolarität imSmittia Ei determinieren: Mit größter Effizienz lassen sich Doppelabdomina durch Bestrahlung der vordersten Eiregion erzeugen; diese Region zeigt zugleich eine starke Anreicherung von Mitochondrien. Die UV-Bestrahlung verursacht sichtbare Schäden an Mitochondrien der exponierten Eiregion und eine signifikante Abnahme der Atmungsrate. 3) Die folgende Ergebnisse stehen im Widerspruch zur Annahme einer Determination der Längsachsenpolarität durch mitochondriale Funktionen: Photoreversion nach UV-Bestrahlung bewirkt keine signifikante Zunahme der Respirationsrate. Der ATP-Gehalt ganzer Eier und vorderer Eihälften wird durch Bestrahlung des vorderen Eiviertels signifikant erhöht. Durch Anstechen der Eier am Vorderpol und anschließende Inkubation in Dinitrophenol oder Ethidiumbromid lassen sich keine Doppelabdomina erzeugen; Bestrahlung mit intensivem Rotlicht nach Sensibilisierung mit Janus Grün B bewirkt ebenfalls keine Bildung von Doppelabdomina. 4) Nach UV-Bestrahlung in frühen Entwicklungsstadien kann die photorevertierende Belichtung um mehrere Stunden verzögert werden, ohne den Photoreversionseffekt signifikant zu beeinträchtigen. Die sensiblen Phasen für UV-Induktion und Photoreversionen dauern beide vollkommen übereinstimmend bis zur Blastodermbildung. Demnach scheinen die wirksamen Eikomponenten während dieser Zeit metabolisch inaktiv zu sein. 5) Nach diesen Ergebnissen wird es als äußerst unwahrscheinlich angesehen, daß die Vorn-Hinten-Polarität im Ei vonSmittia durch mitochondriale Funktionen determiniert wird.
    Notes: Summary 1) The development of the head end in the embryo ofSmittia is determined by cytoplasmic components in the anterior region of the egg. Experimental inactivation or removal of these determinants results in the formation of “double abdomens”. In embryos with this aberrant metameric pattern, head and anterior segments are replaced by an additional set of posterior segments joined in mirror image symmetry to the original abdomen. Several types of experiment were carried out to determine whether mitochondria act as determinants of the anterior pole in the embryo. 2) The following observations are compatible with a determinative rôle of mitochondria: mitochondria are more abundant in the anterior tip of theSmittia egg which responds most effectively in experiments inducing double abdomens by local UV irradiation. UV irradiation inflicts visible damage upon mitochondria in the irradiated egg region, and significantly decreases the oxygen consumption of the eggs. 3) The following data argue against a determinative rôle of mitochondria: photoreverting treatment after UV irradiation did not cause a significant increase of oxygen uptake. The ATP content of whole eggs and anterior egg halves was significantly increased after UV irradiation of the anterior egg quarter. Localized application of dinitrophenol and ethidium bromide via puncture of the anterior pole, as well as irradiation with intense red light after sensitization of mitochondria with Janus Green B, did not produce double abdomens. 4) After UV irradiation during intravitelline cleavage, photoreverting treatment can be delayed for several hours without diminishing its efficiency; the deadline for photoreversal coincides perfectly with the deadline for UV induction, i.e. with blastoderm formation. This result suggests that the effective targets are metabolically inactive from egg-laying until blastoderm-formation. 5) The results are considered as evidence that mitochondria and the determinants of anterior pole in theSmittia embryo are not identical despite their apparently similar cellular localization.
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  • 2
    ISSN: 1432-041X
    Keywords: Insect embryogenesis ; 3H-uridine precursor conversion ; Polyadenylated RNA ; Maternal RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung In der Oogenese und frühen Embryogenese markierte Nukleinsäuren wurden aus Eiern der ZikadeEuscelis plebejus isoliert. Poly(A)-haltige RNS wird in frühen Oogenesestadien in die Oocyte eingebaut. Im frisch abgelegten Ei beträgt ihr Anteil am RNS-Gehalt etwa 2,7%. Im Molekulargewicht ist diese Fraktion (15–32 S) deutlich verschieden von poly(A)-haltiger RNS aus dem embryonalen Markierungszeitraum zwischen früher Furchung und Vorkeimanlagenstadium (4–20 S). Am vorderen Eiende injiziertes3H-Uridin war innerhalb von 3 h gleichmäßig über den Eiraum verteilt. Als3H-Uridin im frühen Furchungsstadium injizierte Markierung fand sich in späteren Stadien (nach 10–10 h) in hohem Umfang in DNS eingebaut (25–35%); markierte RNS konnte erst im zellulären Blastodermstadium nachgewiesen werden. Bei getrennter Aufarbeitung von Dotter-Endoplasma und Blastodermzellen war nur in den letzteren eine embryonale RNS-Synthese erkennbar. Von der im Embryo markierten RNS lagen im frühen Blastodermstadium etwa 10% als poly(A)-haltige RNS vor, im frühen Keimanlagenstadium nur etwa 3%. Anteriore und posteriore Eihälften im frühen Keimanlagenstadium zeigten keine Unterschiede der Molekulargewichte ihrer poly(A)-haltigen RNS.
    Notes: Summary RNA labelled during oogenesis or early embryogenesis was isolated from eggs of the leaf hopperEuscelis plebejus. The polyadenylated RNA fraction deposited during early oogenesis accounted for approximately 2.7% of the total RNA content of the newly laid egg. This fraction differed significantly in molecular weight (15–32 S) from poly(A)-containing RNA synthesised between early cleavage and early germ anlage stages (4–20S). Locally injected3H-uridine spread through the egg within approximately 3 h. A considerable fraction (25–35%) of label injected as3H-uridine during early cleavage was recovered in DNA at subsequent stages (10–20 h later); labelled RNA was not found prior to the cellular blastoderm stage. When the yolk-endoplasm was separated from the blastoderm cells, only the latter contained demonstrable amounts of RNA synthesised by the embryo. Of the precursor incorporated into embryonic RNA, approximately 10% was found in the polyadenylated fraction at the early blastoderm stage, but only 3% at the early germ anlage stage. No differences in size distribution of polyadenylated RNA were evident between anterior and posterior halves of the early germ anlage stage.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0365-9496
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0365-9496
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0365-9496
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0739-4462
    Keywords: Ephestia kühniella ; Venturia canescens ; hemocyte adhesion ; immune suppression ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Insect endoparasitoids are able to circumvent the defense reactions of their habitual hosts. In the ichneumonid wasp Venturia canescens, viruslike particles found on the egg surface are responsible for the protection of the parasitoid against the encapsulation reaction of the host. Some of the particle proteins are structurally and probably functionally related to a protein in the host caterpillar Ephestia kühniella. The host protein is synthesized in hemocytes and fat body in low amounts and can be induced together with other proteins to higher levels of protein synthesis after bacterial infection. Hemocytes that show an increased expression of protein(s) are less likely to attach to a glass surface and are not involved in spreading.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 0739-4462
    Keywords: VLP-protein ; Venturia canescens ; hybridization ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Virus-like particles (VLPs) that are bound to the egg surface of a parasitic wasp Venturia canescens are void of nucleic acid and unable to infect host tissue but instead provide a passive protection against the host's immune recognition. To investigate evolutionary and functional properties of Venturia particles, we isolated cDNAs coding for a VLP-protein by screening an expression library of the wasp, using antibodies against purified VLPs. The corresponding coding DNA is present in the wasp genome as a single-copy gene. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0365-9496
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0365-9496
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0365-9496
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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