The embryoid development of Strigamia maritimaand its bearing on post-embryonic segmentation of geophilomorph centipedes

This is the final version. It was first published by BioMed Central at http://www.frontiersinzoology.com/content/11/1/58.Background Many arthropods add body segments post-embryonically, including most of the myriapods. However, geophilomorph and scolopendromorph centipedes are epimorphic, i.e. they form all their segments during embryonic time, although this has never been demonstrated directly. Understanding the similarity between embryonic and post-embryonic segmentation is pivotal to understand the possible evolution from anamorphosis to epimorphosis. We have previously demonstrated that in the geophilomorph centipede Strigamia maritima most segments are produced by an oscillatory mechanism operating through waves of expression at double segment periodicity, but that the last-forming (posteriormost) segments are patterned with a different system which might be more similar to post-embryonic segmentation. Results With a careful analysis of a large number of specimens, I show that the first (“embryoid”) phase of post-embryonic development is clearly distinct from the following ones. It is characterized by more moults than previously reported, allowing me to define and name new stages. I describe these embryoid stages and the first free-leaving stage in detail, providing data on their duration and useful identification characters. At hatching, the prospective last leg-bearing segment is limbless and the genital segments are added in the following stages, indicating a residual anamorphosis in Strigamia segmentation. I demonstrate directly for the first time that at least the leg-bearing segments are in general produced during embryonic life, although in some individuals the external delineation of the last leg-bearing segment may be delayed to post-embryonic time, a possible further residual of anamorphic development. Additionally, I show that the development of the poison claws during this post-embryonic phase may have some element of recapitulation. Conclusions The data presented in this paper show that the embryoid phase of post-embryonic development of geophilomorph centipedes may represent an extension of embryonic development, possibly in correlation with the evolution of epimorphic development from an anamorphic ancestor, accomplished without completely losing post-embryonic segmentation activity. This continuity in the segmentation process across the embryonic/postembryonic divide may concur to the evolvability of this developmental process

Studies on the Interaction and Organization of Bacterial Proteins on Membranes

Bacteria have developed various means of secreting proteins that can enter the host cell membrane. In this work I focus on two systems: cholesterol-dependent cytolysins and Type III Secretion. Cholesterol is a molecule that is critical for physiological processes and cell membrane function. Not only can improper regulation lead to disease, but also the role cholesterol plays in cell function indicates it is an important molecule to understand. In response to this need, probes have been developed that detect cholesterol molecules in membranes. However, it has been recently shown that there is a need for probes that only respond to cholesterol that is accessible at the membrane surface. Perfringolysin O (PFO) is a toxin secreted by Clostridium perfringens that has been developed into a probe capable of detecting accessible cholesterol. Recently, researchers have been expanding the capabilities of this probe by substituting residues, modifying residues, truncating the probe, or a combination of the three. However, lack of characterization of these new probes has led to controversial results. To understand the role of a conserved Cys residue, here we perform cholesterol binding assays and measure the pore formation activity of a Cys modified PFO derivative. The Type III Secretion (T3S) system is a syringe-like apparatus used by various pathogens to inject effector proteins into target cells. The apparatus spans both the inner and outer bacterial membrane, extending to make contact with the host cell where it forms a pore known as the translocon. In Pseudomonas aeruginosa, the translocon is made up of two proteins, PopB and PopD. While recent advances have been made on the structure of the needle and injectisome, information on the translocon remains sparse. In this work, the P. aeruginosa T3S translocon is analyzed using both in vivo and in vitro methods

The Effects of Proposition 8 in the LGBT Rights Movement in Orange County

Proposition 8 was a California ballot initiative that banned same-sex marriage in November of 2008. The issue of same-sex marriage is usually framed in the media as a political and cultural battle where the two opposing sides argue about the legal and cultural repercussions of the recognition of same-sex unions for same-sex relationships and society. Rather than focusing on the legal implications of the Proposition 8 campaign and its outcome, this paper addresses the campaign\u27s effects in the LGBT Rights Movement in Orange County. During the campaign many LGBTs became politically active for the first time in their lives, but it was after the passage of Proposition 8 when several LGBT rights organizations were founded and there were a greater number of people who became politically involved. I hypothesize that the Proposition 8 campaign was a socializing process that raised the LGBT community\u27s awareness of social stigma towards the LGBT identity. Political action was a coping mechanism for many LGBTs who saw their actions as means to better their social status. As a result, the campaign shaped the identity and the structure of the LGBT Rights Movement in Orange County

Stability of a class of action functionals depending on convex functions

We study the stability of a class of action functionals induced by gradients of convex functions with respect to Mosco convergence, under mild assumptions on the underlying space