1,721,035 research outputs found
The control of cell cycle in mouse primordial germ cells: old and new players
No full textThe cell cycle of primordial germ cells (PGCs), the embryonic precursors of gametes, is characterized by a mitotic phase common to both sexes and a mitotic-meiotic switch in the female. In the present work, we will review the results obtained in the last decade by studies aimed to clarify intrinsic and extrinsic regulatory signals of such processes, with particular reference to mouse PGCs. Besides providing a better understanding of how the gamete population is established in mammals, information about the players controlling the PGC cycle will be useful to clarify other intriguing aspects of germ cell biology such as the origin of germ cell tumours and the mechanisms allowing the maintenance of totipotency in the germ line
Estrogenic in vitro assay on mouse embryonic Leydig cells
Full text linkWe and others have reported that mouse embryonic testes contain a subpopulation of somatic cells expressing estrogen receptor alpha (ERalpha). In order to provide evidence for a possible direct estrogen effect on mammalian testes from the early stage of their differentiation, here we devised a method for the in vitro culture of the ERalpha-expressing cells from 12.5 days post coitum mouse testes and their transfection with plasmids containing the classical estrogen responsive element (ERE) or the alternative estrogen AP-1 responsive element upstream of the luciferase reporter gene (ERE-Luc and AP-1-Luc). StAR immunopositivity of the most part of the ERalpha+ cells grown in culture and subjected to the estrogenic assay, allowed their identification as embryonic Leydig cells. Maximum induction of the ERE-Luc activity was achieved with 10 nM 17-beta estradiol (E2), from 1.7 to 3-fold in such cells and from 2.3 to 5.7-fold in MCF-7 cells used for comparison; the anti-estrogen ICI 182.780 abolished such effects. AP-1-Luc was less sensitive to E2 in both cell types (10 nM E2, 1.2 to 2.7-fold increase in embryonic Leydig cells; about 3-fold in MCF-7 cells) and the effect was not ICI-dependent. Eventually, we stimulated the transfected cells with various xenoestrogens such as lindane, bisphenol A or mono-(2-ethylhexyl) pthalate and with the phytoestrogen zeralenone obtaining evidence for ERE-Luc, but not AP-1-Luc stimulation in embryonic Leydig cells. These results represent evidence of functional ERalpha-dependent genomic pathways in embryonic Leydig cells and describe an in vitro assay suitable for evaluating the activity of putative estrogenic compounds on such cells
Modulation of voltage-activated channels by calcitonini gene-related peptide in cultured rat neurones
No full text1. Whole-cell currents were recorded from cultures of dissociated neocortical neurones of the rat. Rat alpha-calcitonin gene-related peptide (CGRP; 1 nM-1-mu-M) caused significant dose-dependent decreases in the voltage-activated transient (A-current) and delayed rectifier K+ currents. Forskolin (10 nM-20-mu-M) mimicked this effect. Peak K+ currents were gradually decreased after loading neurones with cyclic AMP (100-mu-M) through patch pipettes. CGRP was ineffective in neurones loaded with cyclic AMP.
2. CGRP (0.5-2 mu-M) increased cytosolic cyclic AMP concentration and this effect was mimicked by forskolin (5-40 mu-M).
3. CGRP (0.1-1 mu-M) reduced high-threshold Ca2+ currents; as did forskolin (5-20 mu-M) and cyclic AMP loaded into the neurones. In contrast, low-threshold Ca2+ currents were not affected by any of these agents.
4. Voltage-activated Na+ currents were significantly reduced by both CGRP (0.1-1 mu-M) and forskolin (5-20 mu-M). A similar effect was observed when cells were loaded with cyclic AMP.
5. We conclude that, in neocortical neurones, CGRP attenuates voltage-activated currents by stimulating the intracellular cyclic AMP signalling system
Effects of calcitonin gene-related peptide on synaptic acetylcholine receptor-channels in rat muscle fibres
No full textCultured myotubes and freshly dissociated muscle fibres from adult rats were exposed to calcitonin gene-related peptide (CGRP) and studied by patch-clamp recording during the peptide-induced maximal accumulation of cellular cyclic AMP (cAMP). Acetylcholine receptor- (AChR-) channel properties in myotubes were not modified by the presence of CGRP (10(-7) M). The peptide, applied to the non-patched membrane, significantly increased the variance of the AChR-channel amplitude distribution at the synaptic region of muscle fibres, and three classes of AChR-channels were resolved immediately after peptide application. AChR-channels at extrasynaptic regions of fibres from denervated muscles were unaffected by CGRP. It is suggested that CGRP may regulate the synaptic AChR-channel conductance through second messenger systems
Adhesion molecules for mouse primordial germ cells
No full textIn the present article we will focus on the adhesion molecules expressed by mouse primordial germ cells (PGCs) and will discuss the role that they play, or are believed to play, in two crucial processes of PGC development, namely cell lineage specification and migration into the gonadal ridges. Recent findings indicate that the adhesion-dependent allocation of the PGC precursors to a niche within the epiblast and the forming extraembryonic mesoderm during the pre-gastrulation period is crucial for their commitment. Subsequently, PGC migration and homing within the gonadal ridges require integrated signals involving contact of PGCs with extracellular matrix molecules and cellular substrates or repulsion from them, adhesion among PGCs themselves and attraction by the developing gonads. A number of adhesion, or putative adhesion molecules, have been identified in mammalian PGCs, mainly in the mouse. These molecules belong to three adhesion molecule families such as cadherins (E-P- and N-cadherins), integrins and the IgG superfamily (PECAM-1). Moreover oligosaccarides (LewisX) and growth factor receptors (c-Kit) can also play adhesive roles in some stages of PGC development. An understanding of how genes encoding adhesive molecules are regulated in PGCs and the molecular pathways associated with the functions of adhesion receptors is crucial in furthering our knowledge of PGC biology. Adhesion molecules might once again turn out to be crucial in controlling not only the germ cell lineage and PGC migration but also the PGC differentiation fate itself
Impaired meiotic competence in putative primordial germ cells produced from mouse embryonic stem cells
Full text linkABSTRACT There are still several unanswered questions and problems about the recently claimed possibility of producing functional germ cells in vitro from pluripotent embryonic stem cells (ESCs). In the present paper, we compared by single-cell analysis the capability of putative primordial germ cells (PGCs), produced in vitro from ESCs, and that of endogenous PGCs isolated from embryos, to enter and progress through meiotic prophase I. Using a protocol previously reported to be suitable to produce female germ cells from mouse ESC monolayers, we first identified putative PGCs by analysing the expression pattern of several markers such as SSEA1, APase, OCT4, NANOG, MVH and SCP3 of pre-and post migratory PGCs. Next, after isolation of such cells from culture, we tested their meiotic capability. The evaluation at 2-5 days of culture of the number of cells showing meiotic nuclear SCP3 staining in cytospreads showed that it remained nearly constant in the putative PGCs, whereas it increased markedly in endogenous PGCs. Moreover, we observed that in putative PGCs, the nuclear distribution or expression of SCP3 and other meiotic markers such as DMC1, gH2AX and SCP1 were always highly abnormal in comparison to that observed in endogenous cultured PGCs. We conclude that although the formation of cells showing characteristics of PGCs can occur efficiently from ESCs in vitro, these cells possess impaired capability to enter and progress through meiotic prophase I
Modulation of voltage-activated channels by calcitonin gene-related peptide in cultured rat neurones
No full text1. Whole-cell currents were recorded from cultures of dissociated neocortical neurones of the rat. Rat alpha-calcitonin gene-related peptide (CGRP; 1 nM-1 microM) caused significant dose-dependent decreases in the voltage-activated transient (A-current) and delayed rectifier K+ currents. Forskolin (10 nM-20 microM) mimicked this effect. Peak K+ currents were gradually decreased after loading neurones with cyclic AMP (100 microM) through patch pipettes. CGRP was ineffective in neurones loaded with cyclic AMP. 2. CGRP (0.5-2 microM) increased cytosolic cyclic AMP concentration and this effect was mimicked by forskolin (5-40 microM). 3. CGRP (0.1-1 microM) reduced high-threshold Ca2+ currents; as did forskolin (5-20 microM) and cyclic AMP loaded into the neurones. In contrast, low-threshold Ca2+ currents were not affected by any of these agents. 4. Voltage-activated Na+ currents were significantly reduced by both CGRP (0.1-1 microM) and forskolin (5-20 microM). A similar effect was observed when cells were loaded with cyclic AMP. 5. We conclude that, in neocortical neurones, CGRP attenuates voltage-activated currents by stimulating the intracellular cyclic AMP signalling system
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