Spatial and temporal contribution of somitic myoblasts to avian hind limb muscles

Skeletal muscles of the avian limb are derived from mononucleated myogenic precursor cells (myoblasts) that migrate into the somatopleural mesoderm of the developing limb bud from the ventrolateral dermomyotome of limb adjacent somites. In the present study, we utilized replication-deficient lacZ-encoding retroviruses to elucidate the source of myoblasts for all hind limb muscles in the chick and define the distinct patterns of myoblast distribution within the limb. We also examined, using the same marker, whether the time of migration from the somites into the limb dictates the spatial contribution the myoblasts make to the developing musculature, particularly in relation to the proximodistal and dorsovental axes. Finally, we used these investigations to examine whether the precursors of both primary and secondary myotubes are derived from somitic mesoderm, a presumption, which up until now, has not been demonstrated in vivo. Overall, the results of our studies demonstrate that individual somites have a selective spatial pattern of participation in the development of the avian hind limb musculature and contribute to both primary and secondary myotubes. We also show that both early and later migrating myoblasts can contribute fully to the formation of the appendicular muscles.     

Why do fish have so few roundworm (nematode) parasites?

Synopsis Although they are the oldest and most diverse members of the subphylum, the fishes have relatively few nematode parasites in comparison with other vertebrate classes. It is hypothesized that this paucity of parasite species has occurred because nematode parasites first evolved in terrestrial hosts and only a few lines of these parasites were able to transfer to fish after the appearance of heteroxeny (use of intermediate hosts) and paratenesis (use of transport hosts). The inability of nematodes to initiate parasitism in aquatic ecosystems restricted fish parasites mainly to forms first adapted to terrestrial vertebrates and at the same time deprived large groups of aquatic invertebrates such as the crustaceans, annelids and molluscs of a nematode parasite fauna.Invited editorial     

Genetic distance: probing the origin of a Papua New Guinea isolate

In an attempt to elucidate the origin of an isolated peripheral Highland, Papua New Guinea population (the Karimui), HLA, blood group and serum protein markers were investigated. Due to the paucity of published HLA marker data, genetic distances using non-HLA markers were constructed between populations surrounding the Karimui and compared in 3-dimensions by multidimensional scaling analysis. Genetically, the Karimui is most closely associated with Highland populations to the east and northeast. In a attempt to develop a more global view of relationships, distances constructed from HLA marker data between 2 close Highland populations, 2 Coastal Papua New Guinea populations and 4 Australian aborigine populations were compared. The Karimui associated most closely with the Highland populations and equidistantly and at opposite poles from both the Coastal Papuan and aborigine populations. A paradigm of the composition of the founder group and the early population dynamics is developed from genetic, linguistic and anthropologic data.     

A case for the extreme antiquity of recombination

Recombination is usually assumed to be a mode of reproduction that evolved long after asexual reproduction in response to specific genetic and environmental circumstances. Here the argument is made that recombination was an evolutionary development as ancient as the origins of life. To support this proposition four lines of evidence are given, in particular, the need for primordial genomes to acquire substantial length and to escape from Mullers Ratchet.     

De l’origine des anthropoïdes à l’émergence de la famille humaine

The human lineage has a very ancient origin, as most of the mammals. Its oldest representatives, anthropoid primates, have been described from Asia some 45 million years ago. During this long evolutionary story, two critical stages have appeared as especially important, their beginning in Asia and the emergence of hominids in Africa, some seven million years ago. These two stages are discussed hereby with new data relative to their Asian origins and their dispersal into Africa between 45 and 40 million years ago. Following this dispersal event, these primates evolved in Africa and gave rise to the early hominids. These appeared around seven million years ago and have three distinct representatives. Among them, Toumaï appears as the oldest and the closest to our ancestry, a point that is evidenced here.     

Overview on the recent study of antimicrobial peptides: Origins, functions, relative mechanisms and application

Antimicrobial peptides (AMPs), which are produced by several species including insects, other animals, micro-organisms and synthesis, are a critical component of the natural defense system. With the growing problem of pathogenic organisms resistant to conventional antibiotics, especially with the emergence of NDM-1, there is increased interest in the pharmacological application of AMPs. They can protect against a broad array of infectious agents, such as bacteria, fungi, parasite, virus and cancer cells. AMPs have a very good future in the application in pharmaceuticals industry and food additive. This review focuses on the AMPs from different origins in these recent years, and discusses their various functions and relative mechanisms of action. It will provide some detailed files for clinical research of pharmaceuticals industry and food additive in application.     

Ser-His catalyses the formation of peptides and PNAs

The dipeptide seryl-histidine (Ser-His) catalyses the condensation of esters of amino acids, peptide fragments, and peptide nucleic acid (PNA) building blocks, bringing to the formation of peptide bonds. Di-, tri- or tetra-peptides can be formed with yields that vary from 0.5% to 60% depending on the nature of the substrate and on the conditions. Other simpler peptides as Gly-Gly, or Gly-Gly-Gly are also effective, although less efficiently. We discuss the results from the viewpoint of primitive chemistry and the origin of long macromolecules by stepwise fragment condensations.     

Lipid domain boundaries as prebiotic catalysts of peptide bond formation

To address central problems in the origin of life such as the formation of linear polymers composed of only a small number of types of molecules, we have modeled the distribution of peptides in lipid monolayers. We show that short peptides and amino acids accumulate at the boundary between lipid domains, and that the concentration towards the boundary is higher the longer the peptide. We invoke a constraint on diffusion to one dimension as well as on orientation to suggest that polymerization of peptides is more likely to occur at the domain boundary than within domains or in the bulk phase. In a simple model, in which polymerization is taken to occur only at the boundary, we show that the equilibrium distribution of polymer lengths is shifted towards longer peptides. Since the reaction is occurring in a partially non-aqueous environment, hydrolysis is reduced and condensation increased to yield a significant polymerization. We show also that the free energy change from the redistribution of peptides within domains is sufficient to drive the formation of the peptide bond.     

Recent Advances in the Identification of Replication Origins Based on the Z-curve Method

Precise DNA replication is critical for the maintenance of genetic integrity in all organisms. In all three domains of life, DNA replication starts at a specialized locus, termed as the replication origin, oriC or ORI, and its identification is vital to understanding the complex replication process. In bacteria and eukaryotes, replication initiates from single and multiple origins, respectively, while archaea can adopt either of the two modes. The Z-curve method has been successfully used to identify replication origins in genomes of various species, including multiple oriCs in some archaea. Based on the Z-curve method and comparative genomics analysis, we have developed a web-based system, Ori-Finder, for finding oriCs in bacterial genomes with high accuracy. Predicted oriC regions in bacterial genomes are organized into an online database, DoriC. Recently, archaeal oriC regions identified by both in vivo and in silico methods have also been included in the database. Here, we summarize the recent advances of in silico prediction of oriCs in bacterial and archaeal genomes using the Z-curve based method.