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  • 1
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary Ovarian function inPolistes is governed by three fundamental parameters:the delivery rate of the ovaries, the duration of oocyte development, andthe rythm of egg-laying. The first two, which act directly upon the ovaries (particularly the number of developing oocytes), are immediately influenced by the physical environment, especially the temperature. The third, on the other hand, is under behavioral control. It is emphasized that the late parameter rarely attains its maximum value: the female does not lay all her eggs, eliminating a variable proportion by ovosorption.
    Notes: Conclusions Cette étude du fonctionnement ovarien nous a notamment permis d'évaluer quantitativement les principales variables du phénomène, ce qui était, dans notre programme de travail, à résoudre en première urgence. Nous avons montré l'importance de l'ovosorption dont nous connaissions l'existence sans pouvoir lui attribuer une valeur quantitative. Nous noterons une différence avec le Dytique: la dégénérescence peut frapper les œufs mûrs. D'un point de vue plus général, nous mettons en évidence dans une même fonction, la dualité des caractères entre les phénomènes de comportement marqués par leur grande variabilité et leur discontinuité, et les phénomènes physiologiques qui expriment sans rupture l'action des facteurs externes. Le fait qu'une certaine proportion des œufs produits puisse ne pas être pondue, permet d'expliquer la diminution ou l'augmentationbrusque de la ponte sous l'action de stimulations d'origine sociale, dues soit à l'évolution normale du nid (cellules libres, couvain, etc.), soit, plus fréquemment dans nos conditions d'expérience, à l'effet de groupe.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Mushroom bodies, which are the main integrative centre for insect sensorial information, play a critical role in associative olfactory learning and memory. This paired brain structure contains interneurons grouped in a cortex, sending their axons into organized neuropiles. In the house cricket (Acheta domesticus) brain, persistent neuroblasts proliferate throughout adult life. Juvenile hormone (JH) has been shown to stimulate this proliferation [Cayre, M., Strambi, C. & Strambi, A. (1994) Nature, 368, 57–59]. In the present study, the effect of morphogenetic hormones on mushroom body cells maintained in primary culture was examined. Whereas JH did not significantly affect neurite growth, ecdysone significantly stimulated neurite elongation. Moreover, ecdysone also acted on neuroblast proliferation, as demonstrated by the reduced number of cells labelled with 5-bromodeoxyuridine following ecdysone application. Heterospecific antibodies raised against ecdysone receptor protein and ultraspiracle protein, the two heterodimers of ecdysteroid receptors, showed positive immunoreactivity in nervous tissue extracts and in nuclei of mushroom body cells, indicating the occurrence of putative ecdysteroid receptors in cricket mushroom body cells. These data indicate a dual role for ecdysone in adult cricket mushroom bodies: this hormone inhibits neuroblast proliferation and stimulates interneuron differentiation. These results suggest that a constant remodelling of mushroom body structure could result from physiological changes in hormone titres during adult life.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 20 (2004), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although neurogenesis in the adult is known to be regulated by various internal cues such as hormones, growth factors and cell-adherence molecules, downstream elements underlying their action at the cellular level still remain unclear. We previously showed in an insect model that polyamines (putrescine, spermidine and spermine) play specific roles in adult brain neurogenesis. Here, we demonstrate their involvement in the regulation of secondary neurogenesis in the rodent brain. Using neurosphere assays, we show that putrescine addition stimulates neural progenitor proliferation. Furthermore, in vivo depletion of putrescine by specific and irreversible inhibition of ornithine decarboxylase, the first key enzyme of the polyamine synthesis pathway, induces a consistent decrease in neural progenitor cell proliferation in the two neurogenic areas, the dentate gyrus and the subventricular zone. The present study reveals common mechanisms underlying birth of new neurons in vertebrate and invertebrate species.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 368 (1994), S. 57-59 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To determine whether neuroanatomical changes occur during adult life, we focused our study on the intrinsic neurons of the mushroom bodies of A. domesticus, as this paired structure rep-resents the main integrative centre of the insect brain15 18. Each mushroom body consists of a neuropile and a ...
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  • 5
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The contribution of ovaries and ovarian ecdysteroids to dominance and nest initiation was tested in foundresses of Polistes gallicus at the end of hibernation. Removal of the ovaries resulted in a significant decrease of the ecdysteroid titre in haemolymph. Dominance in ovariectomized foundresses was found to be closely correlated to the size of corpora allata. The operated wasps started nest building, but they did not show any egg-laying behaviour. We conclude that both juvenile hormone and ovarian ecdysteroids contribute to degree of dominance, and that factors other than ovary development may stimulate building.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Laboratory studies on overwintered foundresses of Polistes gallicus show that differences in the endocrine activity are mainly responsible for achieving the dominance rank. Females that became dominant had either larger corpora allata or more developed ovaries than subordinate females. Body size did not contribute to dominance rank. Since a correlation exists between the length of terminal oocytes and the ecdysteroid titre in haemolymph as well as between the volume of corpora allata and the synthesis of juvenile hormone, dominant behaviour is thought to depend upon an elevated hormone titre in haemolymph. Injections of juvenile hormone (JHI) and 20-hydroxyecdysone, separately and simultaneously, significantly increased the probability that the treated female would be the dominant female of a test pair. After a hierarchy has been established, endocrine activity in subordinate foundresses is inhibited by the dominant foundress that then monopolizes reproduction.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 24 (1993), S. 203-217 
    ISSN: 0739-4462
    Keywords: Acheta domesticus ; polyamines ; neural tissue ; fat body ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The three major polyamines - putrescine, spermidine, and spermine - were studied and changes of their levels were examined in extracts of cerebral ganglia and fat body from adult Acheta domesticus. In nervous tissue, only spermidine and spermine were present and spermine was two- to three-fold more abundant than spermidine. The polyamine levels were high up to day 3, decreased on day 4, and then remained relatively unchanged up to day 10. The spermidine/spermine ratios decreased during the imaginal life. Higher spermidine titres were observed in the neural tissue of egg-laying females compared to virgin females. In the fat body, putrescine was detected together with spermidine and spermine. Spermidine and spermine levels were two-fold higher than putrescine. Fat body of virgin females contained two times more polyamines than male fat body. Low at emergence, spermidine and spermine concentrations peaked on days 2-3 only in females, and egg-laying was characterized by an increase of putrescine and spermidine titres. Starvation did not change polyamine contents, implying homeostatic regulation of the intracellular polyamine metabolism. These data showing tissue specific changes in polyamine levels during the imaginal life of Acheta domesticus point to the physiological importance of polyamines as possible intracellular regulators during adult insect development. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 23 (1993), S. 147-152 
    ISSN: 0739-4462
    Keywords: honey bee ; Apis mellifera ; juvenile hormone ; radioimmunoassay ; hemolymph ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Juvenile hormone from the hemolymph of adult worker honey bees of known age and behavioral status was extracted and analyzed by two different radioimmunoassays in two independent laboratoies. The assays are different in hapten attachment, radiolabeled tracer, and the method by which bound and unbound hormone are separated. Despite these differences in the methods, hormone determinations were in excellent agreement at lower levels (0-50 ng/ml) but diverged as the hormone concentrations increased (〉 50 ng/ml). The relative changes are in good agreement, with a correlation coefficient of 0.97. © 1993 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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  • 9
    ISSN: 0739-4462
    Keywords: Acheta domesticus ; ornithine decarboxylase ; S-adenosylmethionine decarboxylase ; neural tissue ; fat body ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase, two key enzymes in polyamine metabolism, were determined during the first 10 days of imaginal life in the nervous tissue and the fat body of the adult cricket Acheta domesticus. The kinetic constants of the two enzymes were also determined in both tissues. Both decarboxylases presented a higher activity in fat body than in nervous tissue. In nervous tissue, the activity of the two enzymes peaked at 16 h postemergence, then slowly decreased up to day 3-4. By contrast, the enzymatic activities in fat body, low at emergence, strongly increased on day 2. Thereafter, whereas ornithine decarboxylase activity remained rather high. S-adenosyl-methionine decarboxylase activity dropped back to emergence levels by day 10. These results, examined in light of the temporal alterations of polyamine levels observed in the two tissues, demonstrate synchronous variations between polyamine contents and the enzymes involved in their biosynthesis. © 1993 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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