The evolution of anural larvae in molgulid ascidians

Ascidians are urochordates, marine invertebrates with non-feeding motile chordate tadpole larvae, except in the family Molgulidae. Urodele, or tailed, Molgulids have typical ascidian chordate tadpole larvae possessing tails with muscle cells, a notochord, and a dorsal hollow nerve cord. In contrast, anural (or tail-less) Molgulids lack a tail and defining chordate features. Molecular phylogenies generated with 18S and 28S ribosomal sequences indicate that Molgulid species fall into at least four distinct clades, three of which have multiple anural members. This refined and expanded phylogeny allows careful examination of the factors that may have influenced the evolution of tail-less ascidians.     

Human immunodeficiency virus seroconversion presenting with acute inflammatory demyelinating polyneuropathy: a case report

Introduction

Electrocardiogram (ECG) abnormalities in patients with blunt chest trauma are diverse and non-specific, but may be indicative of potentially life-threatening conditions.

Case presentation

We report a rare case of pneumopericardium with extreme ECG abnormalities after blunt chest trauma in a 22-year-old male. The diagnosis was confirmed using computed tomography (CT) scanning. The case is discussed, together with its differential diagnosis and the aetiology of pneumopericardium and tension pneumopericardium.

Conclusion

Pneumopericardium should be distinguished from other pathologies such as myocardial contusion and myocardial infarction because of the possible development of tension pneumopericardium. Early CT scanning is important in the evaluation of blunt chest trauma.     

Two distinct classes of prechondrogenic cell types in the embryonic limb bud

Differences are demonstrated in the chondrogenic potential of cells derived from the distal and proximal halves of chick wing buds from as early as stage 23, prior to the appearance of overt cartilage differentiation. In high cell density cultures, cells obtained from the distal portions of stage 23 or 24 limb buds are spontaneously chondrogenic in micromass cultures. Cells obtained from the proximal portions, however, become blocked in their differentiation as protodifferentiated cartilage cels, since these cells in micromass cultures make detectable type II collagen, but fail to synthesize significant levels of cartilage proteoglycan or to accumulate an extracellular matrix that will stain for sulfated glycosaminoglycans. Such cultures of proximal limb bud cells can be stimulated to form alcian blue staining nodules by the addition of 1 mM dbcAMP or 50 micrograms/ml ascorbate, or by mixing proximal cells with small numbers of distal cells (1 distal cell to 10 proximal cells). These results demonstrate the existence of two distinct stages among prechondrogenic mesenchyme cells. The earlier stage appears to be able to provide a chondrogenic stimulus to proximal cells.     

Interspecific hybridization between an anural and urodele ascidian: differential expression of urodele features suggests multiple mechanisms control anural development

Anural development in the ascidian Molgula occulta was examined using tissue-specific markers and interspecific hybridization. Unlike most ascidians, which develop into a swimming tadpole larva (urodele development), M. occulta eggs develop into a tailless slug-like larva (anural development) which metamorphoses into an adult. M. occulta embryos show conventional early cleavage patterns, gastrulation, and neurulation, but then diverge from the urodele developmental mode during larval morphogenesis. M. occulta larvae do not contain a pigmented sensory cell in their brain or form a tail with differentiated notochord and muscle cells. As shown by in situ hybridization with cloned probes and analysis of in vitro translation products, M. occulta embryos do not accumulate high levels of alpha actin or myosin heavy chain mRNA. In contrast, acetylcholinesterase is expressed in muscle lineage cells, indicating that various muscle cell features are differentially suppressed. M. occulta embryos also lack tyrosinase activity, suggesting that suppression of brain pigment cell differentiation occurs at an early step in development. M. occulta eggs fertilized with sperm from Molgula oculata (a closely related urodele species) develop into hybrid larvae exhibiting some of the missing urodele features. Some hybrid embryos develop tyrosinase activity and differentiate a brain pigment cell and a short row of notochord cells, and form a short tail. These urodele features appeared together or separately in different hybrid embryos suggesting that they develop by independent mechanisms. In contrast, alpha actin and myosin heavy chain mRNA accumulation was not enhanced in hybrid embryos. These results suggest that multiple mechanisms control anural development.     

Global diversity of Ascidiacea

The class Ascidiacea presents fundamental opportunities for research in the fields of development, evolution, ecology, natural products and more. This review provides a comprehensive overview of the current knowledge regarding the global biodiversity of the class Ascidiacea, focusing in their taxonomy, main regions of biodiversity, and distribution patterns. Based on analysis of the literature and the species registered in the online World Register of Marine Species, we assembled a list of 2815 described species. The highest number of species and families is found in the order Aplousobranchia. Didemnidae and Styelidae families have the highest number of species with more than 500 within each group. Sixty percent of described species are colonial. Species richness is highest in tropical regions, where colonial species predominate. In higher latitudes solitary species gradually contribute more to the total species richness. We emphasize the strong association between species richness and sampling efforts, and discuss the risks of invasive species. Our inventory is certainly incomplete as the ascidian fauna in many areas around the world is relatively poorly known, and many new species continue to be discovered and described each year.     

The Arctic Warbler Phylloscopus borealis– three anciently separated cryptic species revealed

The Arctic Warbler Phylloscopus borealis breeds across the northern Palaearctic and northwestern‐most Nearctic, from northern Scandinavia to Alaska, extending south to southern Japan, and winters in Southeast Asia, the Philippines and Indonesia. Several subspecies have been described based on subtle morphological characteristics, although the taxonomy varies considerably among different authors. A recent study (T. Saitoh et al. (2010) BMC Evol. Biol. 10 : 35) identified three main mitochondrial DNA clades, corresponding to: (1) continental Eurasia and Alaska, (2) south Kamchatka, Sakhalin and northeast Hokkaido, and (3) most of Japan (Honshu, Shikoku, Kyushu). These three clades were estimated to have diverged during the late Pliocene to early Pleistocene (border at c. 2.6 million years ago). Differences in morphometrics have also been reported among members of the three clades (T. Saitoh et al. (2008) Ornithol. Sci. 7 : 135–142). Here we analyse songs and calls from throughout the range of the Arctic Warbler, and conclude that these differ markedly and consistently among the populations representing the three mitochondrial clades. Kurile populations, for which no sequence data are available, are shown to belong to the second clade. To determine the correct application of available scientific names, mitochondrial DNA was sequenced from three name‐bearing type specimens collected on migration or in the winter quarters. Based on the congruent variation in mitochondrial DNA, morphology and vocalizations, we propose that three species be recognized: Arctic Warbler Phylloscopus borealis (sensu stricto) (continental Eurasia and Alaska), Kamchatka Leaf Warbler Phylloscopus examinandus (Kamchatka (at least the southern part), Sakhalin, Hokkaido and Kurile Islands), and Japanese Leaf Warbler Phylloscopus xanthodryas (Japan except Hokkaido).     

Investigation of the diurnal variation in bone resorption for optimal drug delivery and efficacy in osteoporosis with oral calcitonin

Background  

Bone resorption displays marked diurnal variation. Reversible inhibition of bone resorption may result in best possible efficacy when bone resorption peaks. The aim of the study was to assess the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of 0.8 mg of oral salmon calcitonin (sCT) and the effect of timing of drug intake.