Die Embryonalentwicklung der Paradiesschnecke ... - TOBIAS-lib

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Kapitel 3 Heat stress, but also heavy metal exposure and other kinds of proteotoxic stress, induce stress protein synthesis (reviewed in Gupta et al., 2010). However, constitutive levels of stress proteins are also important in stabilizing normal embryonic development (Rutherford and Lindquist, 1998; Queitsch et al., 2002) but apparently need to be elevated under proteotoxic condition to enable a proper embryogenesis. Gunter and Degnan (2008) exposed embryos of Haliotis asinina to slightly elevated temperatures and observed larvae with abnormally located tissues, although the tissues themselves kept their unique stress protein expression patterns. There are several examples showing that an induction of stress proteins during embryonic development can reduce the disrupting effect of teratogenic agents. In Drosophila melanogaster an elevated Hsp70 level either caused by a preceding heat shock or by genetic manipulation, mitigates the toxic effects of the mitotic poisons vinblastine and colchicine (Isaenko et al., 2002). Hsp70 and Hsp90, and probably other stress-induced proteins as well, are involved in the cell cycle and in proliferating cells higher Hsp levels can be detected than in cells at another stage of the cell cycle (reviewed in Helmbrecht et al., 2000). Hunter and Dix (2001) found that in mouse embryos stress-induced Hsp70 was able to decrease the incidence of neural-tube malformations induced by the metalloid arsenite. A further study on human cells by Barnes et al. (2002) revealed protection from arsenite-induced genotoxic effects by elevated Hsp70 levels. Osterauer et al. (2010a) investigated Hsp70-levels in juvenile platinum-exposed Marisa cornuarietis individuals. The highest concentration tested was 100 µg/L PtCl 2 , half of the concentration that was used in this study and, although histological investigations showed histopathological tissue alterations, the Hsp70 level was not significantly elevated. Also own preliminary studies on the induction of stress protein in platinum- and platinum-plus-heat-exposed Marisa embryos did not reveal a consistend induction pattern so far which could have been indicative for a protective role of chaperones in the context of shell gland and mantle edge outgrowth. Thus, for the moment, the role of Hsps in the signalling cascade triggering differential growth in Marisa embryos remains unclear. In Marisa, the evidently different phenotypes belong in fact to a con- 96
Kapitel 3 tinuum of gradual morphological variation and result from a more or less intense phenotypic expression of a single developmental trait: the formation and differential growth of an exterior mantle, and, consequently, an exterior shell. The further the exterior mantle is developed, the more “normal” is the development of the snail. This means, that, in this study, elevated temperatures, which are usually considered stressful, actually lead to a more normal development than lower temperatures when interacting with a developmental disruptor, platinum. Together with the observation that mortality in the platinum expositions was lower at higher temperatures than at 26 ◦ C this leads to the conclusion that the increase in temperature in this case was not posing additional stress but actually protected development to some extent. There is also another group of stress-induced proteins that should be discussed regarding their possible interaction with platinum: metallothioneins, proteins that are involved in metal trafficking and detoxification. Serafim et al. (2002) observed that heavy metal-induced metallothionein levels were higher at higher temperatures in Mytilus galloprovincialis, and Piano et al. (2004) even found a temperature-induced increase of metallothionein levels in the absence of heavy metal exposure in the oyster Ostrea edulis. Metallothioneins have also received attention as possible cytosolic sinks for platinum-containing anticancer drugs (Knipp, 2009). Possibly, heat-induced metallothioneins may scavenge platinum in Marisa and thus decrease the internal concentration of “active” platinum. It is, however, unlikely that solely a quantitative reduction of “free” platinum is responsible for the formation of various “partial” shells, because these phenotypes never occurred in exposure experiments with lower platinum concentrations in the medium (Osterauer et al., 2009). Internal shells have evolved in a number of gastropod and other molluscan clades independently from one another. So the question arises, whether there are any similarities between Marisa’s platinum-induced shell internalization and the formation of internal shells which have evolved in some molluscan taxa. In some groups (e.g. Naticidae), developing individuals start with an external shell which is then overgrown by extensions of the foot, the mantle, or both (Ponder et al., 2008). In Opisthobranchia, shell-internalization and 97
Page 1 and 2:
Die Embryonalentwicklung der Paradi
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Inhaltsverzeichnis Zusammenfassung
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Zusammenfassung Hintergrund und Zie
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Hintergrund und Zielsetzung der Arb
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Hintergrund und Zielsetzung der Arb
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Material und Methoden Marisa cornua
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Material und Methoden Hälterung Di
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Material und Methoden lindividuen a
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Ergebnisse lung von Marisa cornuari
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Ergebnisse Kapitel 3: Marschner, L.
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Ergebnisse Wachstum des Columellamu
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Diskussion Naticidae) entwickelt si
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Diskussion engrailed und dpp-BMP2/4
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Diskussion Abb. 4: Vergleich der mi
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Schlussfolgerung perimentell zu unt
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Literatur Engelhardt, W. (2008). Wa
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Literatur Ponder, W. F. und Lindber
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Kapitel 1:Turning snails into slugs
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Kapitel 1 dae). Their ontogeny also
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Kapitel 1 Exposure experiments Test
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Kapitel 1 et al. (2001, 2003) or wi
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Kapitel 1 for 4 × 5 min with PTw (
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Kapitel 1 treatment 29.9 ± 32.78%
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Kapitel 1 Fig. 2 3 : Images of M. c
Page 49 and 50: Kapitel 1 Fig. 4 4 : Location of th
Page 51 and 52: Kapitel 1 internal solid circular s
Page 53 and 54: Kapitel 1 ietis as it was shown for
Page 55 and 56: Kapitel 1 Burnett, L.E., Woodson, P
Page 57 and 58: Kapitel 1 Page, L.R., 2002. Ontogen
Page 59 and 60: Kapitel 2: Arresting mantle formati
Page 61 and 62: Kapitel 2 tropods (Crofts, 1937, su
Page 63 and 64: Kapitel 2 Scanning electron microsc
Page 65 and 66: Kapitel 2 called “mantle anlage
Page 67 and 68: Kapitel 2 Fig. 2: M. cornuarietis,
Page 69 and 70: Kapitel 2 and the visceral sac rema
Page 71 and 72: Kapitel 2 Seven-day-old embryos At
Page 73 and 74: Kapitel 2 Fig. 7: M. cornuarietis,
Page 75 and 76: Kapitel 2 gation of internal shells
Page 77 and 78: Kapitel 2 first tended to invaginat
Page 79 and 80: Kapitel 2 side of the visceral sac
Page 81 and 82: Kapitel 2 cornuarietis (Mesogastrop
Page 83 and 84: Kapitel 3: External and internal sh
Page 85 and 86: Kapitel 3 during embryonic developm
Page 87 and 88: Kapitel 3 Differential growth of ma
Page 89 and 90: Kapitel 3 sac, facing away from the
Page 91 and 92: Kapitel 3 Fig. 4 9 : SEM-images of
Page 93 and 94: Kapitel 3 Fig. 6: Histological sect
Page 95 and 96: Kapitel 3 side of the visceral sac
Page 97 and 98: Kapitel 3 different mechanism that
Page 99: Kapitel 3 whether the inhibition of
Page 103 and 104: Kapitel 3 served one. However, ther
Page 105 and 106: Kapitel 3 hand and modified in Inks
Page 107 and 108: Kapitel 3 ticipated in designing th
Page 109 and 110: Kapitel 3 Demian, E. S. and Yousif,
Page 111 and 112: Kapitel 3 Page, L. R. (2003). Gastr
Page 113 and 114: Kapitel 4 Herewith, we were able to
Page 115 and 116: Kapitel 4 Histology and 3D reconstr
Page 117 and 118: Kapitel 4 72 or 96 hours at 6 ◦ C
Page 119 and 120: Kapitel 4 tioned on the ventral sid
Page 121 and 122: Kapitel 4 P2 does not curve backwar
Page 123 and 124: Kapitel 4 which this nerve is attac
Page 125 and 126: Kapitel 4 Fig. 5 13 : 3D reconstruc
Page 127 and 128: Kapitel 4 system in which the right
Page 129 and 130: Kapitel 4 ready present during tors
Page 131 and 132: Kapitel 4 Haydon, P. G., McCobb, D.
Page 133 and 134: Kapitel 5: Quantifikation der Hsp70
Page 135 and 136: Kapitel 5 Die Gesamtproteinmenge wu
Page 137 and 138: Kapitel 5 steigt mit steigendem pro
Page 139 and 140: Kapitel 5 Piano, A., Valbonesi, P.,
Page 141 and 142: Publikationsliste • Marschner, L.
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