Search results for "Metamorphosis"
showing 10 items of 93 documents
The regulation of expression of insect cuticle protein genes
2010
International audience; The exoskeleton of insects (cuticle) is an assembly of chitin and cuticle proteins. Its physical properties are determined largely by the proteins it contains, and vary widely with developmental stages and body regions. The genes encoding cuticle proteins are therefore good models to study the molecular mechanisms of signalling by ecdysteroids and juvenile hormones, which regulate molting and metamorphosis in insects. This review summarizes the studies of hormonal regulation of insect cuticle protein genes, and the recent progress in the analysis of the regulatory sequences and transcription factors important for their expression.
A novel putative insect chitinase with multiple catalytic domains: hormonal regulation during metamorphosis
2002
0264-6021 (Print) Journal Article Research Support, Non-U.S. Gov't; We have used differential display to identify genes that are regulated by juvenile hormone in the epidermis of the beetle Tenebrio molitor. One of the genes encodes T. molitor chitinase 5 (TmChit5), a chitinase possessing an unusual structure. Sequence analysis of TmChit5 identified five 'chitinase units' of approx. 480 amino acids with similarity to chitinase family 18. These units are separated by less conserved regions containing putative PEST (rich in proline, glutamic acid, serine and threonine) sequences, putative chitin-binding domains and mucin domains. Northern-blot analysis identified a single transcript of approx…
Ligands and receptors: common theme in insect storage protein transport.
1999
The passage of macromolecules through biological membranes is an essential process for all multicellular organisms. Insects have developed a mechanism different from that known for all other eukaryotes investigated so far. This review discusses the function and evolution of this mechanism. Insect pupae do not feed during metamorphosis. Therefore they depend on material that has been accumulated during the larval life. At the end of this period, shortly before pupariation, a rise in titer of ecdysteroid hormones induces the incorporation of a large fraction of storage proteins (hexamerins) from the body fluid into the fat body cells. The transport of hexamerins across the cell-membrane is me…
Has innate immunity evolved through different routes?
2010
Invertebrate self/non-self recognition, defense responses, mating and development share innate immune surveillance and functions challenged by competition and linked to fitness. Independent evolutionary branches of immune responses may use conserved gene traits. On the other hand immunity genes may be conserved due to their role in development. Finally, upregulation of innate immunity genes during ascidian metamorphosis supports the danger hypothesis.
Cuticular protein genes in Tenebrio molitor (Coleoptera: Tenebrionidae)
1995
1210-5759; We have previously isolated from the beetle Tenebrio molitor, cDNAs coding for two glycine-rich cuticular proteins named ACP-20, ACP-22 and ACP-17 and an alanin-rich cuticular protein named LPCP-22. The ACP-20, ACP-22, ACP-17 mRNAs are detected by Northern blot and In situ hybridization analysis only in epidermal regions secreting heavily sclerotized cuticle during the pharate adult stage.The LPCP-22 mRNA is detected in most epidermal regions during the secretion of larval and pupal cuticles. Then, its presence is restricted to the epidermal zones secreting intersegmental soft cuticle in the newly ecdysed pupa. The stage- and tissue-specific gene system seems to be convenient mod…
Cuticle: Formation, Moulting and Control
1984
The relative rigidity of the arthropod exoskeleton makes it impossible for body size to increase continuously during the postembryonic development of these animals. Once they have hatched from the egg, they grow in steps, passing through a variable number of (larval) stages (Fig. 1 a). Apart from a few exceptions, there are between 3 and 10 such stages in the arachnids, 3–20 in the crustaceans, and 3–10 in the insects. In many cases a metamorphosis stage intervenes (some crustaceans; holometabolous insects) (Fig. 9b, c).
Organometallic complexes with biological molecules: XVI. Endocrine disruption effects of tributyltin(IV)chloride on metamorphosis of the ascidian lar…
2001
The effects of tributyltin(IV)chloride (TBT) on the metamorphosis of ascidian larvae of Ciona intestinalis, 2 h after hatching, were investigated. Ascidians are protochordates that lack thyroid follicles and possess thyroid hormones (THs) and their precursors, 3-monoiodo-tyrosine (MIT) and 3,5-diiodo-tyrosine (DIT), in their endostyle. According to recent findings, these hormones are also present at larval stages, localize in mesenchymal cells and their function seems to be mainly related to larval transformations. Here, we investigate the effects of TBT on thyroxine (T4) content and localization by exposing larvae of C. intestinalis for different times to TBT concentrations known to block …
Suspension feeding of anuran larvae at low concentrations of Chlorella algae (Amphibia, Anura).
1990
Ingestion and filtering rates in larval Xenopus laevis, Bufo calamita, Rana temporia and Bufo bufo fed suspensions of Chlorella fusca were investigated. Concentrations were measured with a Coulter Counter. (1) For all species, filtration occurred at concentrations far below those reported by other authors for Rana sylvatica feeding on Chlorella pyrenoidosa. For Bufo bufo, only larvae near metamorphosis showed ingestion at low particle concentrations. Since buccopharyngeal ventilation continues even in the absence of food particles, this threshold feeding behaviour in the younger larvae must be due to different mechanisms to those found in Daphnia and Calanus studied by other authors: probab…
Cytotoxic Activity of Tunicate Hemocytes
1996
Tunicates (protochordates) are filter-feeding marine invertebrates with a worldwide distribution. In their larval form, they exhibit many of the features characteristic of the vertebrates. The larva, with a tail, notochord, and dorsal neural tube, upon settlement undergoes a remarkable metamorphosis in which it loses most of its chordate characteristics and becomes a sessile invertebrate adult. Thus, due to these characteristics, tunicates are considered to be the most primitive members of the phylum Chordata. Owing to their position in the phylogenetic line leading to the vertebrates, they have attained importance as experimental organisms and have been examined by researchers from a varie…
Inflamed adult pharynx tissues and swimming larva of Ciona intestinalis share CiTNFalpha-producing cells.
2010
In situ hybridisation and immunohistochemistry analyses have shown that the Ciona intestinalis tumour necrosis factor alpha gene (CiTNFalpha), which has been previously cloned and sequenced, is expressed either during the inflammatory pharynx response to lipopolysaccharide (LPS) or during the swimming larval phase of development. Granulocytes with large granules and compartment/morula cells are CiTNFalpha-producing cells in both inflamed pharynx and larvae. Pharynx vessel endothelium also takes part in the inflammatory response. Haemocyte nodules in the vessel lumen or associated with the endothelium suggest the involvement of CiTNFalpha in recruiting lymphocyte-like cells and promoting the…