12 resultados para Ciona-intestinalis Metamorphosis
em QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast
Resumo:
The allatostatins are a family of peptides isolated originally from the cockroach, Diploptera punctata. Related peptides have been identified in Periplaneta americana and the blowfly, Calliphora vomitoria. These peptides have been shown to be potent inhibitors of juvenile hormone synthesis in these species. A peptide inhibitor of juvenile hormone biosynthesis has also been isolated from the moth, Manduca sexta; however, this peptide has no structural homology with the D. punctata-type allatostatins. Investigations of the phylogeny of the D. punctata allatostatin peptide family have been started by examining a number of nonarthropod invertebrates for the presence of allatostatin-like molecules using immunocytochemistry with antisera directed against the conserved C-terminal region of this family. Allatostatin-like immunoreactivity (ALIR) was demonstrated in the nervous systems of Hydra oligactis (Hydrozoa), Moniezia expansa (Cestoda), Schistosoma mansoni (Trematoda), Artioposthia triangulata (Turbellaria), Ascaris suum (Nematoda), Lumbricus terrestris (Oligochaeta), Limax pseudoflavus (Gastropoda), and Eledone cirrhosa (Cephalopoda). ALIR could not be demonstrated in Ciona intestinalis (Ascidiacea). These results suggest that molecules related to the allatostatins may play an important role in nervous system function in many invertebrates as well as in insects and that they also have an ancient evolutionary lineage. (C) 1994 Wiley-Liss, Inc.
Resumo:
This chapter, in a prize-winnng volume, examines Milton's bilingual practices in relation to his translation of Horace, Odes 1, 5 and the 1645 volume as a whole. Drawing upon seventeenth-century pedagogical practice and methodology it examines the potential importance of his schooling and university exercises to the methodology of Paradise Lost.
Resumo:
Macroalgal blooms are a growing environmental problem in eutrophicated coastal ecosystems. Members of the green algal genus Ulva are significant contributors to blooms, which are typically dominated by only one of several co-occurring opportunistic species. Our understanding of bloom dynamics, such as the importance of clonality, is limited because previously used genetic markers such as internal transcribed spacer sequences have shown very little resolution. Microsatellites are the marker of choice for such studies, but to date, only five primer pairs have been developed for a single member of this genus, Ulva intestinalis. We have now developed four new microsatellite markers for U. intestinalis using genome screening and restriction-ligation and tested them on individuals from six populations in the Gulf of Finland, Finland. All new markers exhibited polymorphism in U. intestinalis, with the numbers of alleles ranging from 6 to 10. On the basis of assignment tests, F-ST estimates and analysis of molecular variance, there was genetic differentiation among populations. Where significantly different, expected heterozygosity (HE) was higher than observed heterozygosity (Ho), indicating a trend toward heterozygote deficiency. This may indicate that although Ulva spores can disperse relatively efficiently, asexual reproduction can result in genetic differentiation among populations. We also tested the cross-species amplification of our primers and the five primer pairs reported previously on seven species of Ulva, Ulvaria obscura and Unbraulva olivascens (all members of the Ulvaceae). In each species, from five to nine of the loci produced an amplification product, and one to four alleles were discovered at each locus. These markers therefore have great potential for testing hypotheses about the formation and maintenance of multispecies macroalgal blooms.
Resumo:
The only supernovae (SNe) to show gamma-ray bursts ( GRBs) or early x-ray emission thus far are overenergetic, broad- lined type Ic SNe ( hypernovae, HNe). Recently, SN 2008D has shown several unusual features: (i) weak x-ray flash (XRF), (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SN Ic HNe, and (iv) development of helium lines as in SNe Ib. Detailed analysis shows that SN 2008D was not a normal supernova: Its explosion energy (E approximate to 6 x 10(51) erg) and ejected mass [similar to 7 times the mass of the Sun ( M.)] are intermediate between normal SNe Ibc and HNe. We conclude that SN 2008D was originally a similar to 30 M. star. When it collapsed, a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes.
Resumo:
This chapter seeks to identify cultural and generic trends and authorial methodologies that may serve to unify or to differentiate between the histories of neo-Latin literature in England, Scotland, Wales and Ireland. It considers ways in which Latin served to bridge horizontal spaces (both physical and metaphorical) between four British regions, between neo-Latin writers in Britain and their continental predecessors and peers, and between Latin and the respective vernacular(s). It also examines vertical spaces (both chronological and cultural) between the neo-Latin and the classical Latin text, and between the linear demarcations of ‘early modern’, ‘Augustan’ and ‘Romantic’. An assessment of links between nationhood and the neo-Latin text as evinced by anthologies, antiquarian and quasi-historical writing, is followed by examples of generic continuity and metamorphosis in the British neo-Latin pastoral, ode and epigram. The concluding sections offer two generic case-studies (neo-Latin epic and didactic) both of which, it is argued, engendered the birth of specifically British versions of the mock-heroic and mock-didactic.
Resumo:
The majority of bacteria in the natural environment live within the confines of a biofilm. The Gram-positive bacterium Bacillus subtilis forms biofilms that exhibit a characteristic wrinkled morphology and a highly hydrophobic surface. A critical component in generating these properties is the protein BslA, which forms a coat across the surface of the sessile community. We recently reported the structure of BslA, and noted the presence of a large surface-exposed hydrophobic patch. Such surface patches are also observed in the class of surface-active proteins known as hydrophobins, and are thought to mediate their interfacial activity. However, although functionally related to the hydrophobins, BslA shares no sequence nor structural similarity, and here we show that the mechanism of action is also distinct. Specifically, our results suggest that the amino acids making up the large, surface-exposed hydrophobic cap in the crystal structure are shielded in aqueous solution by adopting a random coil conformation, enabling the protein to be soluble and monomeric. At an interface, these cap residues refold, inserting the hydrophobic side chains into the air or oil phase and forming a three-stranded β-sheet. This form then self-assembles into a well-ordered 2D rectangular lattice that stabilizes the interface. By replacing a hydrophobic leucine in the center of the cap with a positively charged lysine, we changed the energetics of adsorption and disrupted the formation of the 2D lattice. This limited structural metamorphosis represents a previously unidentified environmentally responsive mechanism for interfacial stabilization by proteins.
Resumo:
Detailed studies of larval development of Octolasmis angulata and Octolasmis cor are pivotal in understanding the larval morphological evolution as well as enhancing the functional ecology. Six planktotrophic naupliar stages and one non-feeding cyprid stage are documented in details for the first time for the two species of Octolasmis. Morphologically, the larvae of O. angulata and O. cor are similar in body size, setation patterns on the naupliar appendages, labrum, dorsal setae-pores, frontal horns, cyprid carapace, fronto-lateral gland pores, and lattice organs. Numbers of peculiarities were observed on the gnathobases of the antennae and mandible throughout the naupliar life-cycle. The setation pattern on the naupliar appendages are classified based on the segmentation on the naupliar appendages. The nauplius VI of both species undergoes a conspicuous change before metamorphosis into cyprid stage. The cyprid structures begin to form and modify beneath the naupliar body towards the end of stage VI. This study emphasises the importance of the pedunculate barnacle larval developmental studies not only to comprehend the larval morphological evolution but also to fill in the gaps in understanding the modification of the naupliar structures to adapt into the cyprid life-style.