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  • Arthrobotrys oligospora  (4)
  • 21.60.Ev  (3)
  • Organic Chemistry  (3)
  • 1
    ISSN: 1434-601X
    Keywords: 21.60.Ev ; 23.60.+e ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The nuclei221Ra and217Rn have been investigated in the α-decay chain225Th→221Ra →217Rn through γ-ray and conversion-electron studies. The short-lived225Th nuclei (T 1/2=8min) were produced in the226Ra(α, 5n) reaction, and γ-rays and conversion electrons were measured — between the irradiation periods — in coincidence with αparticles. In221Ra the five lowest levels are interpreted as members of aK=5/2 paritydoublet with ΔEπ=104 keV. These levels, as well as a higher-lying Kπ=3/2+ band, are consistent with an octupole deformation of221Ra, as expected from theoretical considerations. In217Rn only three excited levels are observed, with a favoured α-decay to a 5/2+ excited level thus establishing positive parity for the ground state of221Ra.
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  • 2
    ISSN: 1434-601X
    Keywords: 21.60.Ev ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Positive and negative parity bands have been followed up to 10+ (possibly 12+) and 11− in224Ra and are compared to the corresponding bands in the isotone226Th. If a constant value of the intrinsic quadrupole moment is assumed for allE2 transitions in224Ra theE1/E2 branching ratios are consistent with an intrinsic dipole moment of ¦Q1¦=0.032(3)e·fm. This small value, as compared to ¦Q1¦=0.30(2)e·fm for226Th, can be explained by an almost complete cancellation of large positive liquid-drop and negative shell-model contributions.
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  • 3
    ISSN: 1572-9699
    Keywords: electron dense microbodies ; nematophagous fungus ; Arthrobotrys oligospora ; ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have studied the fate of electron dense microbodies in nematode-trapping organs (traps) of the fungus A. oligospora during the initial hours following nematode capture. The interaction studies were performed with isolated traps which had captured a nematode under conditions where the fungal cells had no access to external energy sources. Video enhanced contrast microscopy showed that under these conditions the number of dense bodies present in the trap cell that formed the penetration tube, rapidly decreased. During subsequent penetration and development of the infection bulb this decrease continued while at this time common cell organelles such as mitochondria and vacuoles were formed. This was confirmed by electron microscopy which also revealed that the dense bodies were degraded by means of an autophagic process. The organelles were degraded individually and finally turned into compartments which, based on ultrastructural criteria, were considered vacuoles. Fusion of such vacuoles into larger organelles frequently occurred. The degradation process was initiated early in the interaction since initial stages were already evident within 15 min after capture. Generally it took 1–2 h before the infection bulb had fully developed and trophic hyphae formation started. During this time the original trap cell, characterized by numerous dense bodies, was transformed into an active vegetative hyphal cell containing typical cell organelles such as nuclei, mitochondria, a strongly proliferated endoplasmic reticulum, vacuoles and “normal” microbodies but lacked dense bodies. This disappearance of dense bodies was confined to the cell that penetrated the nematode and—less frequently—its two neighbouring cells in the hyphal loop. In the other cells, constituting the trap, the dense bodies remained unaffected. As will be discussed, the present results support our current view that traps of A. oligospora contribute to the survival of the organism in its natural environment.
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  • 4
    ISSN: 1572-9699
    Keywords: nematophagous fungus ; Arthrobotrys oligospora ; digestion ; trophic hyphae ; microbodies ; β-oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper describes the results of an ultrastructural study on the subcellular events occurring in nematode-infecting (trophic) hyphae of the nematophagous fungus Arthrobotrys oligospora. In early stages of the infection process (30 min-4 h), the infection bulb and developing trophic hyphae are characterized by a highly proliferated endoplasmic reticulum (ER). Its membranes often appeared vesiculated and occur in close association with the cell membrane of the cells. Upon further invasion of the nematode, lipid droplets developed in the trophic hyphae; these droplets were first observed 4–5 h after the infection but were abundantly present after 24–36 h. Along with the formation of lipid droplets proliferation of microbodies was observed. These organeles were characterized by the presence of catalase and thiolase and were frequently observed in close association with the lipid droplets. Later on the lipid droplets disappeared. During this period new vegetative mycelium developed from the trap that had originally captured the nematode. Our results suggest that part of the nutrients released from the nematode are first converted into lipids by the fungus which in turn are degraded via the β-oxidation pathway and further metabolized to support growth of new vegetative hyphae.
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  • 5
    ISSN: 1572-9699
    Keywords: anastomosis ; Arthrobotrys oligospora ; Nematophagous fungus ; trap formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hyphal fusion during initial stages of trap formation by Arthrobotrys oligospora was studied by video-enhanced contrast and electron microscopy. Trap initials grew perpendicularly to the parent hypha, then curved around and anastomosed with a peg that developed on the hypha. Trap initials usually developed 40–140 μm apart while the anastomosis occurred 20–25 μm from the initial. Vigorous cytoplasmic movements in trap initials and developed traps corresponded to intense staining with fluorescein diacetate (FDA) of these cells. In addition, bundles of microfilaments were seen in developing loops of traps. On fusion organelle migration took place from the tip cell of the trap into the peg. Later on a septum was formed at the site of fusion.
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  • 6
    ISSN: 1572-9699
    Keywords: nematode/fungal interactions ; Arthrobotrys oligospora ; nematode digestion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method is presented that enables studies to be made of single nematode-fungal interactions under conditions where fungal growth at the expense of external nutrients is prevented. The nematophagous fungus Arthrobotrys ologospora was used as a model organism in these studies. The method is based on removal of the traps from the vegetative mycelium, immediately after a nematode was captured and transfer of the trap with the captured nematode into a droplet of sterile distilled water placed in a moisture chamber. In the absence of external nutrients, such isolated traps of A. oligospora were fully effective in penetrating and subsequently digesting the captured nematode. Solely vegetative mycelium was formed at the expense of the digested nematode; this developed from the trap that originally had captured the nematode. One advantage of the present method is that studies on various stages of the nematode-fungal interaction can now be performed under conditions that exclude major influences of external nutrients which otherwise could be communicated to the trap cells by way of the vegetative mycelium.
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  • 7
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 8
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Cyanide Ions with α,β-Unsaturated Esters, IV1,2,3). - Reactions to CarbocyclesSodium cyanide reacts with diethyl 2-methylenealkanedioates 1a-c and 8a-h to give simple or alkylated ethyl 2-cyano-3-oxo-1-cycloalkanecarboxylates 5a-c and 9a-h, respectively. From these the 3-oxo-1-cycloalkanecarboxylic acids 6a-c and 10a-h, respectively, and the methyl esters 11a-h are obtained. Analogously α,β-unsaturated dicarboxylates such as 12a, b lead to ethyl 2-cyano-2-methyl-5-oxo-1-cyclopentanecarboxylate (13a) and ethyl 2-cyano-2-methyl-6-oxo-1-cyclohexanecarboxylate (13b), respectively.
    Notes: Einwirkung von Natriumcyanid auf 2-Methylenalkandisäure-diethylester 1a-c und 8a-h führt zu einfachen bzw. alkylierten 2-Cyan-3-oxo-1-cycloalkancarbonsäure-ethylestern 5a-c und 9a-h. Daraus erhält man die 3-Oxo-1-cycloalkancarbonsäuren 6a-c und 10a-h sowie die Methylester 11a-h. Analog reagieren α,β-ungesättigte Dicarbonsäureester wie 12a, b zum 2-Cyan-2-methyl-5-oxo-1-cyclopentancarbonsäure-ethylester (13a) bzw. 2-Cyan-2-methyl-6-oxo-1-cyclo-hexancarbonsäure-ethylester (13b).
    Additional Material: 5 Tab.
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  • 9
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Cyanide Ions with α,β-Unsaturated Esters, V1). - Reactions Leading to Affiliation of CarbocyclesSodium cyanide reacts with the unsaturated diesters 4-6 under aprotic conditions (DMSO) to give the bicycles 7-9. These are easily transformed into the acids 10-12 and the methyl esters 13-15. Reaction with unsaturated esters like 16, 18 leads to the bicyclic compounds with bridged atoms 17, 19.
    Notes: Natriumcyanid reagiert mit den ungesättigten Di-Estern 4-6 unter aprotischen Bedingungen (DMSO) zu den Bicyclen 7-9. Diese lassen sich leicht in die Säuren 10-12 sowie in die Ester 13-15 überführen. Bei Verwendung von ungesättigten Estern des Typs 16, 18 entstehen bicyclische Verbindungen mit Brückenkohlenstoffatomen 17, 19.
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  • 10
    ISSN: 1434-601X
    Keywords: 21.60.Ev ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract TheK π=0− bands in even uranium nuclei were studied in the compound reactions231Pa(p, 2n)230U,230, 232Th(α,2n)232, 234U and236U(d, pn)236U. In-beamγ-rays were measured in coincidence with conversion-electrons, which were detected with an iron-free orange spectrometer. The negative-parity levels are observed up to intermediate spins (I〈13−). In addition, the 1− and 3− levels in230U were confirmed by a decay study with an isotope separated230Pa source. For the heavier isotopes (A≥232) the properties of theK π=0− bands (energies andγ-branchings) are consistent with a vibrational character of these bands. For230U theK π=0− band lies at rather low energy (E(1−)=367 keV), and the level spacings within this band are very similar to those of the isotones228Th and226Ra, which might indicate the onset of a stable octupole deformation.
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