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  • 1
    Electronic Resource
    Electronic Resource
    Nerve cell production in Hydra is deregulated by tumour-promoting phorbol ester (1991)
    Springer
    Development genes and evolution 200 (1991), S. 234-236 
    Details
    ISSN: 1432-041X
    Keywords: Hydra ; Nerve cells ; Differentiation ; Tumour-promoting phorbol esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The tumour-promoting phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) interfers with nerve cell production in Hydra when applied to the animals' culture medium. Precursor cells exposed to 0.2 nM TPA during the first half of their S-phase are prevented from differentiating into nerve cells. Precursor cells which start their S-phase following a treatment with TPA give rise to nerve cells. The frequency is higher than in untreated control animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00361343
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  • 2
    Electronic Resource
    Electronic Resource
    Necessity of protein synthesis for metamorphosis in the marine hydroidHydractinia echinata (1991)
    Springer
    Development genes and evolution 200 (1991), S. 336-341 
    Details
    ISSN: 1432-041X
    Keywords: Hydractinia echinata ; Metamorphosis ; Pattern formation ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the marine colonial hydroidHydractinia echinata metamorphosis from the larval to the adult (polyp) stage is induced by various agents, including CsCI and dioctanoylglycerol (diC8). Induction is prevented when the inhibitors of protein synthesis cycloheximide or ementine were applied simultaneously with the metamorphosis-inducing agents. With diC8 treatment, the inhibitors caused most animals to transform into mosaics consisting of larval and polyp body parts instead of normal shaped polyps. In contrast, treatment with cycloheximide or ementine just before or after incubation with the metamorphosis-inducing agents did not prevent larvae from metamorphosis. No substantial quantitative changes in protein synthesis occur during induction of metamorphosis, however, the protein pattern is changed upon induction. The most prominent new polypeptides (25 and 73 kD) were observed when CsCI was used to trigger metamorphosis. In addition, both in CsCl- and in diC8-treated larvae, the synthesis of a new 23 kD protein occurred, whilst synthesis of others ceased (41 and 44 kD).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665529
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  • 3
    Electronic Resource
    Electronic Resource
    Is homarine a morphogen in the marine hydroid Hydractinia? (1986)
    Springer
    Development genes and evolution 195 (1986), S. 33-38 
    Details
    ISSN: 1432-041X
    Keywords: Hydractinia ; Hydra ; Homarine ; Nicotinamide ; Pattern formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Homogenate of coelenterate tissue interferes with metamorphosis in Hydractinia and pattern formation in both Hydractinia, and Hydra. From the extracts two fractions comprising low-molecular-weight compounds with strong metamorphosis-inhibiting activity were separated. One of these contains, as the active compound, homarine (N-methyl picolinic acid). Homarine concentrations down to 10−6 mol/l stop or retard metamorphosis. High concentrations block the continuation of metamorphosis as long as they are maintained in the culture medium and treatment with homarine during metamorphosis influences the proportioning of the future polyp's body pattern. Most of the homarine found in Hydra tissue derives from Artemia given as food. It is not identical with inhibitor I, an activity partially purified from Hydra tissue, which prevents head and foot formation in Hydra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00444039
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  • 4
    Electronic Resource
    Electronic Resource
    Heat shock as inducer of metamorphosis in marine invertebrates (1992)
    Springer
    Development genes and evolution 201 (1992), S. 169-172 
    Details
    ISSN: 1432-041X
    Keywords: Heat-shock proteins ; Metamorphosis ; Invertebrates ; Hydractinia echinata ; Ciona intestinalis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In most sessile marine invertebrates, metamorphosis is dependent on environmental cues. Here we report that heat stress is capable of inducing metamorphosis in the hydroid Hydractinia echinata. The onset of heat-induced metamorphosis is correlated with the appearance of heat-shock proteins. Larvae treated with the metamorphosis-inducing agents Cs+ or NH4 + also synthesize heat-shock proteins. In heat-shocked larvae, the internal NH4 +-concentration increases. This fits the hypothesis that methylation plays a central role in control of metamorphosis. In the tunicate Ciona intestinalis, a heat shock is able to induce metamorphosis too.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188715
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  • 5
    Electronic Resource
    Electronic Resource
    Dicapryloylglycerol and ammonium ions induce metamorphosis of ascidian larvae (1990)
    Springer
    Development genes and evolution 198 (1990), S. 430-432 
    Details
    ISSN: 1432-041X
    Keywords: Ascidia ; Metamorphosis ; Ammonium ions ; Diacylglycerol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Larvae of the tunicate Ciona start metamorphosis between some hours and a few days after hatching. Several substances were found to reduce this time span, such as vital dyes [Cloney (1961) Am Zool 1:67–87; Hirani (1961) Bull Mar Biol Stn Asamushi 11:121–125], heavy-metal ions including copper [see review by Lynch (1961) Am Zool 1:59–66] and the hormone thyroxine [Patricolo et al. (1981) Cell Tissue Res 214:289–301]. This study shows that low concentrations of ammonium ions as well as the second messenger dicapryloylglycerol induce metamorphosis immediately after hatching. On the other hand, when the follicle cells are removed newly hatched Ciona remain larvae for days. Follicle cells are possibly degraded by bacteria, which thereby produce ammonia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376162
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  • 6
    Electronic Resource
    Electronic Resource
    The orientation of the dorsal/ventral axis of zebrafish is influenced by gravitation (1994)
    Springer
    Development genes and evolution 203 (1994), S. 281-283 
    Details
    ISSN: 1432-041X
    Keywords: Zebrafish ; Axis orientation ; Gravitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Following fertilization of eggs of Brachydanio rerio a blastodisc is formed which, by cleavage divisions and epibolic movements, gives rise to a cell cap covering the yolk. When about half of the yolk is covered by the cells, a thickening appears at the progressing margin, the embryonic shield, which gives rise to the axial organs of the future embryo. Thereby, the dorsal/ventral axis can be recognized. Our experiments show that the blastodisc is formed at the position of the micropyle, the only site where the sperm can enter the egg and oocyte. Later the head appears at this position. We show that the position of the embryonic shield on the circumference of the cell cap is influenced by gravitation. We also demonstrate that there is no correlation between the orientation of the first or second cleavage plane and the position of the embryonic shield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00360523
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  • 7
    Electronic Resource
    Electronic Resource
    Lithium ions interfere with pattern control in Hydra vulgaris (1990)
    Springer
    Development genes and evolution 198 (1990), S. 382-388 
    Details
    ISSN: 1432-041X
    Keywords: Hydra vulgaris ; Pattern control ; Lithium ; Foot formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary LiCl in concentrations exceeding 0.5 mM affects morphogenesis in Hydra vulgaris (formerly named H. attenuata) by interfering with the foot-forming system(s). Pulse treatment of Hydra bearing small buds or of animals that develop a bud within 14 h after the end of treatment prevented foot formation at the bud's base in a concentration-dependent manner. With increasing concentrations of Li+ or length of treatment in increasing percentage of the buds remained permanently connected to the parent by a bridge of tissue thus forming a stable secondary axis. Instead of the normal ring-shaped foot a patch of basal disc tissue developed or the bud failed to differentiate foot tissue at all. Long-term culture of animals in 1 mM LiCl inhibited budding from the second day of treatment onwards and detachment of existing buds was delayed. After 4 days of treatment 15%–30% of budless or bud-bearing animals developed up to three patch-like basal discs at various positions along the body axis; these usually grew out one above the other on the same side of the animal but never at the same transverse level. Besides these patch feet broad belts of foot tissue were observed in the lower gastric region. After 1 week of treatment half of the animals developed a constriction located usually in the lower two-thirds of the body axis. The tissue adjacent to this constriction and particularly above it differentiated into mucus-secreting foot tissue. Subsequent separation into two morphologically intact polyps occurred occasionally. When treatment was stopped, budding restarted within the next 3 days at several positions along the body axis whether or not secondary feet or a constriction existed. Buds grew out in different budding zones, which persisted for several days. This burst of budding led to up to 7 buds per animal within 3 days. After about 1 week the animals regulated to normality or became epithelial, i.e. they lost their stem cells during and after treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376156
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  • 8
    Electronic Resource
    Electronic Resource
    Protein kinase modulators interfere with bud formation in Hydra vulgaris (1994)
    Springer
    Development genes and evolution 203 (1994), S. 284-289 
    Details
    ISSN: 1432-041X
    Keywords: Hydra ; Protein kinase C ; Budding ; Pattern formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fresh water polyp Hydra can reproduce asexually by forming buds. These buds separate from the parent animal due to the development of foot tissue in a belt-like region and the formation of a constriction basal to that region. A single pulse treatment with activators of protein kinase C, including 1,2-dioctanoyl-rac-glycerol and 12-o-tetradecanoylphorbol-13-acetate, and inhibitors of various protein kinases, including staurosporine, H-7 and genistein, interfered with foot and constriction formation. The buds did not separate. Therewith, branched animals were formed, some of which bore a lateral foot patch. Simultaneous treatments with an activator and inhibitor led to a higher amount of branched animals than treatments with one of these agents alone. Based on the different specificities of the activators and inhibitors used we propose that activation of a protein kinase C and/or inhibition of a probably non-C-type protein kinase interfere with the decrease of positional value at the bud's base, a process necessary to initiate the pattern forming system leading to foot formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00360524
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  • 9
    Electronic Resource
    Electronic Resource
    Analysis of head and foot formation inHydra by means of an endogenous inhibitor (1979)
    Springer
    Development genes and evolution 186 (1979), S. 189-210 
    Details
    ISSN: 1432-041X
    Keywords: Hydra ; Morphogenesis ; Regeneration ; Inhibitor ; Model for Patterning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In tissue regenerating the head, the ability to initiate head formation in a host increases with the time allowed for regeneration before grafting, while the foot-initiating ability decreases concomitantly. The reverse was found for tissue about to regenerate a foot. The early divergent changes thus indicated are counteracted in both head and foot regeneration by treatment with an inhibitor (Berking, 1977) in low concentrations. The inhibitor also interferes with processes which determine wether or not hypostome and tentacles are formed, and how many tentacles (if any) appear. The circumferential spacing of the tentacles was regular whether their number was normal or below normal. Secondary axes caused by implanted tissue either detach after having formed a head and a foot (i.e. behave like buds) or do not detach, having only formed a head. This alternative depends on the origin and amount of the implanted tissue and on the position of the implant within the host. The following model based on these findings is proposed: Head and foot formation start with pre-patterns which cause a continuously increasing change of the tissue's ability to initiate a head or a foot. Along the body axis this ability is determined by a graded distribution of “sources”. As development progresses, the high source density which accumulates in the head region causes the formation of a hypostome and tentacles; the angular spacing of tentacles is also dependent on source density. At a certain low source density foot-formation is initiated. The inhibitor counteracts the increase of source density in head-forming tissue as well as the decrease of source density in foot-forming tissue. It thus appears to be part of the mechanism which controls morphogenesis in hydra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848589
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  • 10
    Electronic Resource
    Electronic Resource
    The fractionation of aHydra-derived inhibitor into head and foot inhibitors may be an artefact (1983)
    Springer
    Development genes and evolution 192 (1983), S. 327-332 
    Details
    ISSN: 1432-041X
    Keywords: Hydra ; Morphogen ; Inhibitor I ; Head inhibitor ; Foot inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A fraction has been purified from crude extracts ofHydra, termed inhibitor I, which inhibits budding as well as head and foot regeneration. This fraction has been proposed by others to contain (at least) two substances, a head inhibitor (HI) and a foot inhibitor (FI), which preferentially inhibit head and foot regeneration respectively. The present study indicates that the reported fractionation is an artefact produced by the chromatographic procedure used. Substances can be eluted from virgin Dowex 50 which preferentially inhibit head regeneration. These substances are formed in the resin if left standing in its hydrogen form. Further, we have not been able to confirm that the extract from heads preferentially inhibits head regeneration and the extract from feet preferentially inhibits foot regeneration. Rather it appears that the inhibitor I is contained both in the head and in the foot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848812
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