Search results for "Romer"
showing 10 items of 86 documents
A Systematic Nomenclature for the <i>Drosophila</i> Ventral Nervous System
2020
The fruit fly, Drosophila melanogaster, is an established and powerful model system for neuroscience research with wide relevance in biology and medicine. Until recently, research on the Drosophila brain was hindered by the lack of a complete and uniform nomenclature. Recognising this problem, the Insect Brain Name Working Group produced an authoritative hierarchical nomenclature system for the adult insect brain, using Drosophila melanogaster as the reference framework, with other taxa considered to ensure greater consistency and expandability (Ito et al., 2014). Here, we extend this nomenclature system to the sub-gnathal regions of the adult Drosophila nervous system, thus providing a sys…
The columnar gene vnd is required for tritocerebral neuromere formation during embryonic brain development of Drosophila.
2006
International audience; In Drosophila, evolutionarily conserved transcription factors are required for the specification of neural lineages along the anteroposterior and dorsoventral axes, such as Hox genes for anteroposterior and columnar genes for dorsoventral patterning. In this report, we analyse the role of the columnar patterning gene ventral nervous system defective (vnd) in embryonic brain development. Expression of vnd is observed in specific subsets of cells in all brain neuromeres. Loss-of-function analysis focussed on the tritocerebrum shows that inactivation of vnd results in regionalized axonal patterning defects, which are comparable with the brain phenotype caused by mutatio…
Normal Function of the mushroom body defect Gene of Drosophila Is Required for the Regulation of the Number and Proliferation of Neuroblasts
1994
In the developing central nervous system of Drosophila, proliferation follows a reproducible and well-described spatial and temporal pattern. This pattern involves a defined number and distribution of neural stem cells (neuroblasts), as well as a precisely regulated time course of division of these neuroblasts. We show that mutations in the mushroom body defect (mud) gene interfere with the regulation of this pattern in a rather specific manner. In the abdominal neuromeres a subset of neuroblasts prolongs the period of proliferation. Additional daughter cells persist into the imago. Similar defects are expressed in the anterior ventral nerve cord and in the lateral central brain region. In …
Neuroblast formation and patterning during early brain development in Drosophila.
2004
The Drosophila embryo provides a useful model system to study the mechanisms that lead to pattern and cell diversity in the central nervous system (CNS). The Drosophila CNS, which encompasses the brain and the ventral nerve cord, develops from a bilaterally symmetrical neuroectoderm, which gives rise to neural stem cells, called neuroblasts. The structure of the embryonic ventral nerve cord is relatively simple, consisting of a sequence of repeated segmental units (neuromeres), and the mechanisms controlling the formation and specification of the neuroblasts that form these neuromeres are quite well understood. Owing to the much higher complexity and hidden segmental organization of the bra…
Acanthochaetetidae (Hadromerida, Demospongiae) fromthe Coniacian of Vera de Bidasoa (basque pyrénées, Northern Spain)
1986
Abstract Acanthochaetetes specimens from the Coniacian brecciated limestones near Vera de Bidasoa (Northern Spain) are described. It is the first report of acanthochaetetids from Coniacian strata. The specimens are very small and probably lived in fissures and crevices in fore-reef breccias and deep water mud mounds. The family Acanthochaetetidae Fischer is placed in the order Hadromerida (Tetractinomorpha, Demospongiae). The order Tabulospongida Hartman & Goreau was abandoned.
Neoclassical Convergence Versus Technological Catch-Up : A Contribution for Reaching a Consensus.
2004
http://www.businessperspectives.org/files/ppm/PPM_EN_2004_03pp15_42.pdf; International audience; New macro empirical evidence is provided to assess the relative importance of object andidea gaps in explaining the world income distribution dynamics over a benchmark period of 1960-1985. Results are then extended through 1995. Formal statistical hypothesis tests allow us to discriminatebetween two competing growth models: (i) the standard neoclassical growth model similarto that employed by Mankiw, Romer, and Weil (1992), and (ii) an endogenous growth modelclosely related to the Nelson and Phelps' approach (1966) that emphasizes the importance of technologytransfer in addition to factor accumu…
Centromeric heterochromatin and satellite DNA in the Chironomus plumosus species group
1994
Species of the Chironomus plumosus group display significant differences in their amount of centromeric heterochromatin. A tandem-repetitive satellite-like DNA has been isolated from C. plumosus. This DNA accounts for a major part of the centromeric heterochromatin. The DNA element has a Sau3AI restriction site ("Sau elements") and a monomer length of 165 or 166 bp. It is A-T rich (73%) and reveals a moderate DNA curvature, as shown by gel migration and computer analysis. The chromosomal localization and genomic organization of Sau elements were studied in 24 Chironomus species by in situ hybridization and (or) Southern analysis. The DNA is predominantly located in the centromeric regions …
Existence of competitive equilibrium in a non-optimal one-sector economy without conditions on the distorted marginal product of capital
2012
Abstract This paper develops a method for proving the existence of competitive equilibrium in a distorted/non-optimal one-sector economy–a discrete time variant of the Romer model–without conditions on the equilibrium value of the marginal product of capital. Existence is obtained under weaker conditions than in Le Van et al. (2002) . Moreover, we provide an existence result for an economy with a regressive tax studied in Santos (2002) . The proofs rely on ideas of Becker and Boyd (1997) .
Prokaryotic symbiotic consortia and the origin of nucleated cells: A critical review of Lynn Margulis hypothesis.
2021
The publication in the late 1960s of Lynn Margulis endosymbiotic proposal is a scientific milestone that brought to the fore of evolutionary discussions the issue of the origin of nucleated cells. Although it is true that the times were ripe, the timely publication of Lynn Margulis' original paper was the product of an intellectually bold 29-years old scientist, who based on the critical analysis of the available scientific information produced an all-encompassing, sophisticated narrative scheme on the origin of eukaryotic cells as a result of the evolution of prokaryotic consortia and, in bold intellectual stroke, put it all in the context of planetary evolution. A critical historical reas…
<p><strong>A new type designation of <em>Thymus microphyllus</em>, basionym of <em>Micromeria</em> <em>micr…
2020
Micromeria Bentham (1829: sub t. 1282) (Lamiaceae) is a monophyletic and taxonomically intricate genus, represented by nearly 70 species. These are distributed from the Macaronesian-Mediterranean region to southern Africa, India, and China (Morales 1991b, Govaerts 1999, Harley et al. 2004, Bräuchler et al. 2005, 2008; Puppo & Meimberg 2015, Puppo et al. 2014, 2015).