Search results for "quiescence"

Hippo pathway regulates neural stem cell quiescence.

2016

Neural Stem Cell Regulation by Adhesion Molecules Within the Subependymal Niche

2019

In the mammalian adult brain, neural stem cells persist in neurogenic niches. The subependymal zone is the most prolific neurogenic niche in adult rodents, where residing stem cells generate large numbers of immature neurons that migrate into the olfactory bulb, where they differentiate into different types of interneurons. Subependymal neural stem cells derive from embryonic radial glia and retain some of their features like apico-basal polarity, with apical processes piercing the ependymal layer, and a basal process contacting blood vessels, constituting an epithelial niche. Conservation of the cytoarchitecture of the niche is of crucial importance for the maintenance of stem cells and fo…

Unique Organization of the Nuclear Envelope in the Post-natal Quiescent Neural Stem Cells

2017

Summary Neural stem cells (B1 astrocytes; NSCs) in the adult ventricular-subventricular-zone (V-SVZ) originate in the embryo. Surprisingly, recent work has shown that B1 cells remain largely quiescent. They are reactivated postnatally to function as primary progenitors for neurons destined for the olfactory bulb and some corpus callosum oligodendrocytes. The cellular and molecular properties of quiescent B1 cells remain unknown. Here we found that a subpopulation of B1 cells has a unique nuclear envelope invagination specialization similar to envelope-limited chromatin sheets (ELCS), reported in certain lymphocytes and some cancer cells. Using molecular markers, [3H]thymidine birth-dating, …

Estrogen Regulates the Satellite Cell Compartment in Females

2019

SUMMARY Skeletal muscle mass, strength, and regenerative capacity decline with age, with many measures showing a greater deterioration in females around the time estrogen levels decrease at menopause. Here, we show that estrogen deficiency severely compromises the maintenance of muscle stem cells (i.e., satellite cells) as well as impairs self-renewal and differentiation into muscle fibers. Mechanistically, by hormone replacement, use of a selective estrogen-receptor modulator (bazedoxifene), and conditional estrogen receptor knockout, we implicate 17β-estradiol and satellite cell expression of estrogen receptor α and show that estrogen signaling through this receptor is necessary to preven…

STRIPAK Members Orchestrate Hippo and Insulin Receptor Signaling to Promote Neural Stem Cell Reactivation

2019

Summary Adult stem cells reactivate from quiescence to maintain tissue homeostasis and in response to injury. How the underlying regulatory signals are integrated is largely unknown. Drosophila neural stem cells (NSCs) also leave quiescence to generate adult neurons and glia, a process that is dependent on Hippo signaling inhibition and activation of the insulin-like receptor (InR)/PI3K/Akt cascade. We performed a transcriptome analysis of individual quiescent and reactivating NSCs harvested directly from Drosophila brains and identified the conserved STRIPAK complex members mob4, cka, and PP2A (microtubule star, mts). We show that PP2A/Mts phosphatase, with its regulatory subunit Widerbors…

¿El Estado de Derecho en peligro? El juez constitucional contra la Constitución y a favor de la reelección presidencial indefinida : caso Bolivia

2021

In Bolivia, the third term and the habilitation of former President Evo Morales to the 2019 presidential elections was allowed with the acquiescence of the Plurinational Constitutional Court. Despite the fact that the Constitution prohibited it and there was a referendum that rejected indefinite presidential re-election. This occurred through the judicialization of politics that produced a non-formal reform of the Constitution producing a case of abusive constitutionalism and the destabilization of the rule of law.

A Post-contentious Turning Point for the Contentious French? Crisis Without Protest in France

2018

International audience; This chapter shows that the ‘contentious French’ may not be that contentious anymore. The economic crisis provides a unique chance to argue that a post-contentious turning point is emerging in spite of a long-standing tradition of protesting. Yet the chapter suggests that this post-contentious turning point is not bringing about acquiescence but opens space for new forms of political participation, especially in connection with resources acquired through employment and educational track. In this case, we find a more extensive engagement in online activism and non-institutional forms of political participation, that is, the two forms of political participation that ar…

Hematopoietic Stem Cells Reversibly Switch from Dormancy to Self-Renewal during Homeostasis and Repair

2008

Bone marrow hematopoietic stem cells (HSCs) are crucial to maintain lifelong production of all blood cells. Although HSCs divide infrequently, it is thought that the entire HSC pool turns over every few weeks, suggesting that HSCs regularly enter and exit cell cycle. Here, we combine flow cytometry with label-retaining assays (BrdU and histone H2B-GFP) to identify a population of dormant mouse HSCs (d-HSCs) within the lin(-)Sca1(+)cKit(+)CD150(+)CD48(-)CD34(-) population. Computational modeling suggests that d-HSCs divide about every 145 days, or five times per lifetime. d-HSCs harbor the vast majority of multilineage long-term self-renewal activity. While they form a silent reservoir of th…

Three-dimensional cell culture induces novel proliferative and metabolic alterations associated with oncogenic transformation

1996

To date, cell biological characteristics of oncogene-transfected cells have been investigated either in relatively homogeneous monolayer cultures or in heterogeneous tumors in vivo. To evaluate the emergence of cellular heterogeneity during tumor formation, we have established a multicellular spheroid system from an oncogene-dependent, genetically determined 2-stage carcinogenesis model for 3-dimensional growth under well-defined conditions. The effect of T24Ha-ras transfection on cellular growth, proliferation, cell viability and oxygenation was investigated using spontaneously immortalized (Rat1) and c-myc-transfected (M1) Fisher 344 rat embryo fibroblasts and a tumorigenic T24Ha-ras-tran…

Some Remarks on the Concept of Toleration

1997

The paper contains a conceptual analysis of “act of toleration” and the property of “being tolerant”. Being tolerant is understood as a dispositional property of persons manifested in what the author calls the “circumstances of toleration”. The main circumstances distinguished are: a tendency to prohibit a certain behaviour and the competence to determine the deontic status of the behaviour in question. An act of toleration, then, consists in not prohibiting (or cancelling the prohibition of) that behaviour. It is argued that this requires the existence of two different normative systems, the “basic system”, and the “justifying system”. Acts of toleration must be based on reasons coming fro…