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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 49 (2000), S. 48-56 
    ISSN: 1432-0762
    Keywords: Keywords Antipredator behavior ; Phylogenetic inertia ; Conflicting selection pressures ; Evolution ; Salamanders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The streamside salamander, Ambystoma barbouri, exhibits ineffective antipredator behavior (high emergence rate from refuge, and high activity while out of refuge) and thus suffers heavy predation in stream pools with sunfish. A. barbouri evolved relatively recently from an ancestor that closely resembled a sister species, A. texanum, which breeds in fishless, ephemeral ponds. Sunfish thus represent a relatively new selection pressure for A. barbouri. Phylogenetic inertia predicts that (1) A. texanum should be very poor at coping with fish and (2) because it has only recently been exposed to fish, A. barbouri should still be poor at avoiding fish, but due to its recent exposure to fish, A. barbouri should be better than A. texanum at coping with sunfish. Experimental results provided mixed support for these predictions. As predicted, A. texanum suffered heavy sunfish predation. Compared to A. texanum, A. barbouri showed a greater tendency to initiate alarm moves that enhanced escape success from fish. However, in both the presence and absence of fish, A. barbouri showed higher emergence rates from refuge and higher movement while out of refuge than A. texanum. These behaviors tend to increase exposure to sunfish, i.e., for these key behaviors, A. barbouri apparently evolved in the wrong direction as far as fish predation is concerned. Due to these offsetting effects (increased exposure to fish, increased escape success), A. barbouri is no better at surviving with sunfish than A. texanum. A possible explanation for the high activity of A. barbouri is its use of highly ephemeral habitats (relative to A. texanum) that favor the evolution of higher activity, feeding, and developmental rates for A. barbouri relative to A. texanum.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1420
    Keywords: Key words Cholesteatoma ; epidermoid ; infratertorial ; intracranial ; fungal pneumonia ; mechanical ventilation ; intracranial hypertension ; Schlüsselwörter Cholesteatom ; Epidermoidzyste ; Infratentorell ; Intrakraniell ; Pilzpneumonie ; Respiratortherapie ; Hirndrucksteigerung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Cholesteatome sind prinzipiell gutartige ektodermale Tumore, die aus epidermalen verhornenden Plattenepithelzellen stammen und eine typische histologische Charakteristik aufweisen. Die Lokalisation ist ubiquitär möglich, es besteht eine Tendenz zu einem gehäuften Auftreten im Kopf-Hals-Bereich und hier wiederum in häufiger Assoziation zum Mittelohr, aber auch in lateraler oder medianer Lokalisation innerhalb der Schädelkalotte vor allem im Kleinhirnbrückenwinkel, im suprasellären Bereich, im 4. Ventrikel, im Bereich der Zirbeldrüse oder in den Großhirnhämisphären. Primär intrakraniell wachsende Cholesteatome verursachen Symptome aufgrund lokaler Beeinträchtigung der umgebenden Strukturen bzw. raumfordernder Wirkung. Aufgrund des langsamen Wachstums ist die Symptomatik über lange Zeit häufig nur geringfügig und unspezifisch. Wegen der Potenz zur Induktion einer intrakraniellen Drucksteigerung kann vor allem bei Koinzidenz mit anderen Erkrankungen ein primär oligo- oder asymptomatisches Cholesteatom einen fatalen Verlauf nehmen. Wir berichten über einen 42-jährigen Patienten, der wegen Dyspnoe und linksthorakaler Schmerzen sowie chronischer Kopfschmerzen hospitalisiert wurde. Aufgrund einer progredienten Pilzpneumonie wurde eine Respiratortherapie erforderlich. Unter dieser Behandlung entwickelte der Patient die Zeichen einer intrakraniellen Drucksteigerung die letztlich therapierefraktär war, der Patient verstarb schließlich unter dem klinischen Bild einer zerebralen Einklemmung. Letztlich als Ursache dafür konnte computertomographisch ein präexistentes Cholesteatom der hinteren Schädelgrube mit konsekutiver Hirndrucksteigerung und partieller Liquorzirkulationsstörung unter der begleitenden respiratorpflichtigen Lungenerkrankung anzuschuldigen.
    Notes: Summary Cholesteatomas are benign tumors resulting from inclusion of ectodermal tissue at the time of closure of the neuronal groove and soon thereafter. The tumors are composed from epithelial squamous cells with a typical histopathological pattern, are slowly growing, and often afflict young adults, occuring at multiple locations but commonly in the middle ear and in lateral or midline location within the skull especially the cerebellopontine angle, the suprasellar region, the fourth ventricle, the pineal region, and over the hemispheres. Symptoms from cholesteatomas with primary intracranial growth vary according to the location of these tumors, the general pattern being slow evolution of defects attributable to the specific area. Partial blockade of cerebrospinal fluid circulation with elevation of intracranial pressure can adversly affect the natural course of intracranial cholesteatomas. We report on a 42-year old male suffering from cephalea for a few months before admission to hospital because of severe dyspnea and left-sided chest pain. Further diagnostic procedures revealed fungal pneumonia. Hypoxemic respiratory failure required endotracheal intubation and mechanical ventilatory support. Clinical signs of intracranial hypertension were present after a few days of mechanical ventilation. Computed tomography of the cerebrum revealed diffuse cerebral edema and a large-sized cholesteatoma in the posterior fossa. The patient died due to herniation of cerebellar tonsils into the foramen magnum as a consequence of diffuse intracerebral hypertension.
    Type of Medium: Electronic Resource
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