Collège de France

About: Collège de France is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Receptor. The organization has 6541 authors who have published 11983 publications receiving 648742 citations. The organization is also known as: College de France.

Activity-Dependent Neuronal Control of Gap-Junctional Communication in Astrocytes

Abstract: A typical feature of astrocytes is their high degree of intercellular communication through gap junction channels. Using different models of astrocyte cultures and astrocyte/neuron cocultures, we have demonstrated that neurons upregulate gap-junctional communication and the expression of connexin 43 (Cx43) in astrocytes. The propagation of intercellular calcium waves triggered in astrocytes by mechanical stimulation was also increased in cocultures. This facilitation depends on the age and number of neurons, indicating that the state of neuronal differentiation and neuron density constitute two crucial factors of this interaction. The effects of neurons on astrocytic communication and Cx43 expression were reversed completely after neurotoxic treatments. Moreover, the neuronal facilitation of glial coupling was suppressed, without change in Cx43 expression, after prolonged pharmacological treatments that prevented spontaneous synaptic activity. Altogether, these results demonstrate that neurons exert multiple and differential controls on astrocytic gap-junctional communication. Since astrocytes have been shown to facilitate synaptic efficacy, our findings suggest that neuronal and astrocytic networks interact actively through mutual setting of their respective modes of communication.

Estradiol Alters Nitric Oxide Production in the Mouse Aorta Through the α-, but not β-, Estrogen Receptor

Abstract: Although estradiol (E2) has been recognized to exert several vasculoprotective effects in several species, its effects in mouse vasomotion are unknown, and consequently, so is the estrogen receptor subtype mediating these effects. We investigated the effect of E2 (80 μg/kg/day for 15 days) on NO production in the thoracic aorta of ovariectomized C57Bl/6 mice compared with those given placebo. E2 increased basal NO production. In contrast, the relaxation in response to ATP, to the calcium ionophore A23187, and to sodium nitroprusside was unaltered by E2, whereas acetylcholine-elicited relaxation was decreased. The abundance of NO synthase I, II, and III immunoreactive proteins (using Western blot) in thoracic aorta homogenates was unchanged by E2. To determine the estrogen receptor (ER) subtype involved in these effects, transgenic mice in which either the ERα or ERβ has been disrupted were ovariectomized and treated, or not, with E2. Basal NO production was increased and the sensitivity to acetylcholine decreased in ERβ knockout mice in response to E2, whereas this effect was abolished in ERα knockout mice. Finally, these effects of E2 on vasomotion required long-term and/or in vivo exposure, as short-term incubation of aortic rings with 10 nmol/L E2 in the isolated organ chamber did not elicit any vasoactive effects. In conclusion, this study demonstrates that ERα, but not ERβ, mediates the beneficial effect of E2 on basal NO production.

Moving along the number line: operational momentum in nonsymbolic arithmetic.

Abstract: Can human adults perform arithmetic operations with large approximate numbers, and what effect, if any, does an internal spatial-numerical representation of numerical magnitude have on their responses? We conducted a psychophysical study in which subjects viewed several hundred short videos of sets of objects being added or subtracted from one another and judged whether the final numerosity was correct or incorrect. Over a wide range of possible outcomes, the subjects’ responses peaked at the approximate location of the true numerical outcome and gradually tapered off as a function of the ratio of the true and proposed outcomes (Weber’s law). Furthermore, an operational momentum effect was observed, whereby addition problems were overestimated and subtraction problems were underestimated. The results show that approximate arithmetic operates according to precise quantitative rules, perhaps analogous to those characterizing movement on an internal continuum.

The fate map of the cephalic neural primordium at the presomitic to the 3-somite stage in the avian embryo

Abstract: The fate map of the early neural plate and neural fold has been established at the cephalic level by using the quail–chick marker system (Le Douarin, 1969, 1973). The experimental design comprised the replacement of definite territories belonging to the neural plate and neural folds in the chick embryo by their counterparts from quail embryos at the same developmental stage. This technique is referred to as the isotopic and isochronic exchange of preneural tissues between these two species. The various types of experiments that were carried out are schematized in Fig. 2. The possibility of distinguishing quail from chick cells by the structure of their nuclei allowed the fate of the grafted territories to be recognized at later developmental stages ranging from 3 to 9 days of incubation (E3–E9). Fig. 1 illustrates the morphological changes in the anterior neural plate and neural ridges in the chick embryo at the early somitic stages.