Polydactylous limbs in Strong's Luxoid mice result from ectopic polarizing activity

Strong's Luxoid (1st^D) is a semidominant mouse mutation in which heterozygotes show preaxial hindlimb polydactyly, and homozygotes show fore- and hindlimb polydactyly. The digit patterns of these polydactylous limbs resemble those caused by polarizing grafts, since additional digits with posterior character are present at the anterior side of the limb. Such observations suggest that 1st^D limb buds might contain a genetically determined ectopic region of polarizing activity. Accordingly, we show that mutant embryos ectopically express the pattern-determining genes fibroblast growth factor 4 (fgf-4), sonic hedgehog (shh), and Hoxd-12 in the anterior region of the limb. Further, we show that anterior mesoderm from mutant limbs exhibits polarizing activity when grafted into host chicken limbs. In contrast to an experimentally derived polydactylous transgenic mouse, forelimbs of homozygotes show a normal pattern of Hoxb-8 expression, indicating that the duplication of polarizing tissue here occurs downstream or independently of Hoxb-8. We suggest that the 1st gene product is involved in anteroposterior axis formation during normal limb development

Conflits Armes Et Representativite Ethnique Au Nord-Kivu En Republique Democratique Du Congo

The goal pursued in the present reflection is to analyze and explain the relationship of cause and effect between the persistence of armed conflicts and the issue of ethnic representation in political institutions in North-Kivu in Democratic Republic of Congo. Since the 1990s, is observed a systematic use of ethnicity in the calculations of political, economic and social actors active in the province. In addition to the question of nationality of immigrants, access to land and overpopulation, the question of representation of ethnic groups arises with acuity and remains at the center of the attitudes and behaviour of political and security actors on the ground. The elections held in the country in 2006, leading to the no representativeness of the tutsi ethnic group, have reconfigured the dominant positions available since the advent of rebellions in the country. An attempt to maintain or regain their status as, gun violence has been used by stakeholders, leading to the reactivation of the other ethnic dormant for the construction of bands armed self-defence groups. The persistence of the conflict in North Kivu in recent years would be also linked to the violent struggle triggered by members of the tutsi ethnic group in order to ensure their representation in provincial institutions of North Kivu, central Government or even in other strategic positions in the country. This gives political and security logically motivated other ethnic local to replenish the armed groups in order to address the threat of domination that tries to impose the tutsi ethnic group in North-Kivu

From the Dollhouse to the Schoolhouse: The Changing Experience of Women Principals in British Columbia, 1980 to 1990

This study sought to determine if and how the experiences of recently appointed women principals differ from those of earlier appointees in the Lower Mainland of British Columbia. Interviews revealed both differences and similarities. Although recent women principals continue to face sex-role stereotyping from outsiders, they are now accepted and supported by their male peers. They demonstrate greater career initiative than their earlier counterparts and have a wider range of experience in both teaching and adminis- tration. Both groups are well-educated, expert teachers. They focus on learning for themselves, developing collegial relationships with teachers and caring relationships with children, who are their priority. They are career-oriented women whether mothers and wives or not. They perceive themselves as women principals whose leadership is characterized by their gender and accentuated by their feminine qualities. They are redefining the world of educational administration to include the woman’s voice. La recherche menée par les auteurs visait à déterminer si les expériences de directrices d’école nommées récemment diffèrent de celles de directrices nommées antérieurement dans le Lower Mainland de la Colombie-Britannique. Des entrevues ont permis de révéler à la fois des différences et des similitudes. Bien que les directrices en poste depuis plus récemment continuent à faire face à des stéréotypes reliés au sexe et au rôle de la part de personnes extérieures, elles sont maintenant acceptées et appuyées par leurs pairs de sexe masculin. Elles font preuve d’une plus grande initiative vis-à-vis de leur carrière que leurs homologues précédentes et ont une plus vaste expérience de l’enseignement et de l’administration. Les deux groupes sont constitués d’enseignantes chevronnées. Ces dernières mettent l’accent sur l’auto-apprentissage et l’établissement de relations collégiales avec les enseignants et de liens chaleureux avec les enfants, qui sont leur priorité. Il s’agit de femmes pour qui la carrière revêt une grande importance, qu’elles soient ou non mères ou épouses. Elles se perçoivent comme des femmes dont le leadership est caractérisé par leur sexe et accentué par leurs qualités féminines. Elles sont en train de redéfinir le monde de l’administration scolaire afin de donner aux femmes une voix au chapitre.

Deep homology in the age of next-generation sequencing

The principle of homology is central to conceptualizing the comparative aspects of morphological evolution. The distinctions between homologous or non-homologous structures have become blurred, however, as modern evolutionary developmental biology (evo-devo) has shown that novel features often result from modification of pre-existing developmental modules, rather than arising completely de novo. With this realization in mind, the term 'deep homology' was coined, in recognition of the remarkably conserved gene expression during the development of certain animal structures that would not be considered homologous by previous strict definitions. At its core, it can help to formulate an understanding of deeper layers of ontogenetic conservation for anatomical features that lack any clear phylogenetic continuity. Here, we review deep homology and related concepts in the context of a gene expression-based homology discussion. We then focus on how these conceptual frameworks have profited from the recent rise of high-throughput next-generation sequencing. These techniques have greatly expanded the range of organisms amenable to such studies. Moreover, they helped to elevate the traditional gene-by-gene comparison to a transcriptome-wide level. We will end with an outlook on the next challenges in the field and how technological advances might provide exciting new strategies to tackle these questions.This article is part of the themed issue 'Evo-devo in the genomics era, and the origins of morphological diversity'

Bmp2 instructs cardiac progenitors to form the heart-valve-inducing field

AbstractA hallmark of heart-valve development is the swelling and deposition of extracellular matrix in the heart-valve region. Only myocardium overlying this region can signal to underlying endothelium and cause it to lose cell–cell contacts, delaminate, and invade the extracellular space abutting myocardium and endocardium to form endocardial cushions (EC) in a process known as epithelial to mesenchymal transformation (EMT). The heart-valve myocardium expresses bone morphogenetic protein-2 (Bmp2) coincident with development of valve mesenchyme. BMPs belong to the transforming growth factor beta superfamily (TGF-β) and play a wide variety of roles during development. We show that conditional ablation of Bmp2 in cardiac progenitors results in cell fate changes in which the heart-valve region adopts the identity of differentiated chamber myocardium. Moreover, Bmp2-deficient hearts fail to induce production and deposition of matrix at the heart-valve-forming region, resulting in the inability of the endothelium to swell and impairing the development of ECs. Furthermore, in collagen invasion assays, Bmp2 mutant endothelium is incapable of undergoing EMT, and addition of BMP2 protein to mutant heart explants rescues this phenotype. Our results demonstrate that Bmp2 is both necessary and sufficient to specify a field of cardiac progenitor cells as the heart-valve-inducing region amid developing atria and ventricles

Morphological studies and development of Ex-situ protocol for rehabilitation of threatened Rheum species under nursery conditions

Rheum is a strong vigorous plant and can live long even in tough conditions. The Rheum species have been domesticated as medicinal plants for human consumption. Rheum species are perennial stout herbs. Rhubarb is a common English name of the genus Rheum. Rhubarb is a plant name for the many different species of Rheum, distributed in the temperate and sub tropical regions of Himalaya from Kashmir to Sikkim and growing wild in the mountains of the Western and North-western provinces of China and adjoining Tibetan territory. It is cultivated much in Europe and the United States. In Kashmir Himalaya, it ranges from an altitude of 1700 - 5500m. It is famous for its medicinal uses. Roots are long and stout. Stem is erect, hollow, sulcate, glabrous or strigose. It is native to Asia-Temperate to Asia – Tropical, from China to India, Nepal and Pakistan. In India, its found in Himachal Pradesh Jammu & Kashmir and Uttar Pradesh. In Jammu and Kashmir, it grows on open slopes and shrubberies in Kashmir, Leh and Zanaskar valley between 3000-5000 m, where R.webbianum is found. The Rheum spiciforme is also one of most known medicinal plant and is  found on high altitudes of Gurez valley(3000m 5000m). Rheum also prefers a full sunny location and thrives in a moist, fertile soil. Most Rheum species can handle heavier clay soils better than many other herbs and makes a striking addition to the spring landscape. Rhubarb is propagated from seeds, seedlings, or pieces of rhizome.Â

Limb regeneration revisited

The investigation of vertebrate limb regeneration, a favorite topic of early developmental biologists, is enjoying a renaissance thanks to recently developed molecular and genetic tools, as indicated in recent papers in BMC Biology and BMC Developmental Biology. Classical experiments provide a rich context for interpreting modern functional studies

Regeneration review reprise

There have been notable advances in the scientific understanding of regeneration within the past year alone, including two recently published in BMC Biology. Increasingly, progress in the regeneration field is being inspired by comparisons with stem cell biology and enabled by newly developed techniques that allow simultaneous examination of thousands of genes and proteins