Specification of cell fate in the sea urchin embryo: summary and some proposed mechanisms

An early set of blastomere specifications occurs during cleavage in the sea urchin embryo, the result of both conditional and autonomous processes, as proposed in the model for this embryo set forth in 1989. Recant experimental results have greatly illuminated the mechanisms of specification in some early embryonic territories, though others remain obscure. We review the progressive process of specification within given lineage elements, and with reference to the early axial organization of the embryo. Evidence for the conditional specification of the veg(2) lineage subelement of the endoderm and other potential interblastomere signaling interactions in the cleavage-stage embryo are summarized. Definitive boundaries between mesoderm and endoderm territories of complex. the vegetal plate, and between endoderm and overlying ectoderm, are not established until later in development. These processes have been clarified by numerous observations on spatial expression of various genes, and by elegant lineage labeling studies. The early specification events depend on regional mobilization of regulatory factors resulting at once in the zygotic expression of genes encoding transcription factors, as well as downstream genes encoding proteins characteristic of the cell types that will much later arise from the progeny of the specified blastomeres. This embryo displays a maximal form of indirect development. The gene regulatory network underlying the embryonic development reflects the relative simplicity of the completed larva and of the processes required for its formation. The requirements for postembryonic adult body plan formation in the larval rudiment include engagement of a new level of genetic regulatory apparatus, exemplified by the Hox gene complex

Micromeres are required for normal vegetal plate specification in sea urchin embryos

Vegetal plate specification was assessed in S. purpuratus embryos after micromere deletions at the 4th, 5th and 6th cleavages, by assaying expression of the early vegetal plate marker Endo 16, using whole-mount in situ hybridization. After 4th cleavage micromere deletions, the embryos typically displayed weak Endo16 expression in relatively few cells of the lineages that normally constitute the vegetal plate, while after 5th and 6th cleavage micromere deletions the embryos exhibited strong Endo16 expression in larger fractions of cells belonging to those lineages. When all four micromeres were deleted, the embryos were severely delayed in initiating gastrulation and sometimes failed to complete gastrulation. However, if only one micromere was allowed to remain in situ throughout development, the embryos exhibited strong Endo16 expression and gastrulation occurred normally, on schedule with controls. Additional measurements showed that these microsurgical manipulations do not alter cleavage rates or generally disrupt embryo organization. These results constitute direct evidence that the micromeres provide signals required by the macromere lineages for initiation of vegetal plate specification. The specification of the vegetal plate is completed in a normal manner only if micromere signaling is allowed to continue at least to the 6th cleavage stage

Evidence of uneven selective pressure on different subsets of the conserved human genome : implications for the significance of intronic and intergenic DNA

Peer reviewedPublisher PD

Human Uniqueness: Standing Alone?

This is the author accepted manuscript. The final version is available from SAGE via http://dx.doi.org/10.1177/0014524615599101 Discussion of human uniqueness requires careful attention to what ‘uniqueness’ means. The word is commonly deployed as meaning both distinctiveness and superiority, which implies contrasting relations of continuity and distinction between what is ‘unique’ and what it is contrasted with. Human uniqueness has come into sharp focus in recent years because of discussions of ‘exobiology’: life beyond Earth. Intelligence has frequently been put forward as definitive of human uniqueness, but the ‘convergent evolution’ of intelligence suggests that intelligence would also evolve elsewhere, leaving human beings unique neither as to distinctiveness nor to excellence. However, while evolution might be convergent over basic characteristics such as intelligence, to how the body is structured seems to be more contingent, and we must take the role of the body’s role in thought (‘embodied cognition’) seriously. Basic bodily differences between putative life-forms might, therefore, lead to strong distinctions between the forms that intelligence takes. Human beings might not be ‘unique as superior’, but they would be unique as distinct, bodily speaking, and that distinction might be strongly determinative of the way in which intelligence is worked out. </jats:p

Safer recruitment? protecting children, improving practice in residential child care

In the wake of a number of high-profile cases of the abuse of children and young people in residential child care, there have been repeated calls for the improvement of recruitment and selection of residential child care staff. This paper describes the findings from a survey, undertaken in 2005, of operational and human resource managers who have responsibility for the recruitment and selection of residential child care staff in the voluntary and statutory sectors in Scotland. This research was commissioned by the Scottish Executive to identify which elements of safer recruitment procedures had been implemented following the countrywide launch of a Toolkit for Safer Recruitment Practice in 2001. Research findings show that although local authorities were more likely than voluntary organisations to have gone some way toward implementing safer recruitment procedures, the recruitment process lacked rigour and commitment to safer procedures in some organisations. The article discusses the current barriers to the introduction of safer recruitment methods and proposes some possible solutions for the future

Hindgut specification and cell-adhesion functions of Sphox11/13b in the endoderm of the sea urchin embryo

Sphox11/13b is one of the two hox genes of Strongylocentrotus purpuratus expressed in the embryo. Its dynamic pattern of expression begins during gastrulation, when the transcripts are transiently located in a ring of cells at the edge of the blastopore. After gastrulation, expression is restricted to the anus–hindgut region at the boundary between the ectoderm and the endoderm. The phenotype that results when translation of Sphox11/13b mRNA is knocked down by treatment with morpholino antisense oligonucleotides (MASO) suggests that this gene may be indirectly involved in cell adhesion functions as well as in the proper differentiation of the midgut–hindgut and midgut–foregut sphincters. The MASO experiments also reveal that Sphox11/13b negatively regulates several downstream endomesoderm genes. For some of these genes, Sphox11/13b function is required to restrict expression to the midgut by preventing ectopic expression in the hindgut. The evolutionary conservation of these functions indicates the general roles of posterior Hox genes in regulating cell-adhesion, as well as in spatial control of gene regulatory network subcircuits in the regionalizing gut

Spatial expression of Hox cluster genes in the ontogeny of a sea urchin

The Hox cluster of the sea urchin Strongylocentrous purpuratus contains ten genes in a 500 kb span of the genome. Only two of these genes are expressed during embryogenesis, while all of eight genes tested are expressed during development of the adult body plan in the larval stage. We report the spatial expression during larval development of the five 'posterior' genes of the cluster: SpHox7, SpHox8, SpHox9/10, SpHox11/13a and SpHox11/13b. The five genes exhibit a dynamic, largely mesodermal program of expression. Only SpHox7 displays extensive expression within the pentameral rudiment itself. A spatially sequential and colinear arrangement of expression domains is found in the somatocoels, the paired posterior mesodermal structures that will become the adult perivisceral coeloms. No such sequential expression pattern is observed in endodermal, epidermal or neural tissues of either the larva or the presumptive juvenile sea urchin. The spatial expression patterns of the Hox genes illuminate the evolutionary process by which the pentameral echinoderm body plan emerged from a bilateral ancestor

A Study of Dark Matter and QCD-Charged Mediators in the Quasi-Degenerate Regime

We study a scenario in which the only light new particles are a Majorana fermion dark matter candidate and one or more QCD-charged scalars, which couple to light quarks. This scenario has several interesting phenomenological features if the new particles are nearly degenerate in mass. In particular, LHC searches for the light scalars have reduced sensitivity, since the visible and invisible products tend to be softer. Moreover, dark matter-scalar co-annihilation can allow even relatively heavy dark matter candidates to be consistent thermal relics. Finally, the dark matter nucleon scattering cross section is enhanced in the quasi-degenerate limit, allowing direct detection experiments to use both spin-independent and spin-dependent scattering to probe regions of parameter space beyond those probed by the LHC. Although this scenario has broad application, we phrase this study in terms of the MSSM, in the limit where the only light sparticles are a bino-like dark matter candidate and light-flavored squarks.Comment: 24 pages, 5 figures; as published in PRD with significant revision

Effect of Shoulder Angle on the Activation Pattern of the Elbow Extensors During a Submaximal Isometric Fatiguing Contraction

PURPOSE: The aim of the current study was to examine the effect of shoulder angle on the electromyographic (EMG) activation pattern of the elbow extensors during a fatiguing contraction. METHODS: Ten young men (23.5 ± 1.7) were tested on two occasions with the shoulder at either 0° or 90° of flexion. Baseline isometric maximum voluntary contraction torque and the EMG-torque relationship were determined prior to a sustained isometric contraction at 20% of MVC. RESULTS: EMG activity of the long head during the final 10% o f the fatiguing contraction exhibited a significantly greater increase when at 90° versus 0° with no effect of shoulder angle on any other portion of the elbow extensors. CONCLUSION: Measures from one muscle portion of the elbow extensors are not representative of the whole group under isometric fatiguing contractions, and at longer length the activation o f the long head was greater than at the short length

Inclusive Just War Theory: Confucian and Mohist contributions

2016 Spring.Includes bibliographical references.Warfare has permeated humanity across cultures and through time. It is a human activity that often carries with it large-scale consequences. However, even if it does not, human lives are always lost, and the effects of war are devastating. Because of this, thinkers from around the globe have given accounts regarding the ethics of war. Can war ever be justified? If so, how? What entity has the authority to declare war? What actions are permissible in a justified war? These are only a few of the questions that are often raised, and the answers to them are perhaps as numerous as their developers. This project serves to explain and examine some of these theories. I begin by describing three major positions as they have developed in the West: realism, pacifism, and Just War Theory. Using the categories and conceptions described here, I look to classical Chinese approaches to war from the Confucian and Mohist traditions. Ren xing, “human nature”, is important to Confucian thoughts on the ruler. I use this account to craft a more robust notion of Just War Theory’s “legitimate authority” condition. Jian ai, “impartial care”, is a Mohist concept that I argue informs a type of pacifism and may also play into thoughts on justification for going to war, especially in cases of humanitarian intervention. The latter part of this project applies these theories and new formulations to specific examples of warfare, hoping to show their relevance. Upon this examination, and overall, I hope to increase our understanding of the ethics of war by looking to forgotten or less popular approaches to thinking about the conducting of military affairs