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.

Proportion of fatigue-resistant motor units in hindlimb muscles of cat and their relation to axonal conduction velocity.

Abstract: 1. A study of motor units to hindlimb muscles of cat has been made, with as complete a sample as possible of the motor axons to an individual muscle. In single experiments as much as 95% of the motor supply to a muscle has been examined. 2. The following muscles have been studied: peroneus brevis, peroneus tertius, peroneus longus, plantaris, gastrocnemius medialis, soleus, tenuissimus and lumbricalis superficialis. 3. Units were identified as slow resistant (S), fast resistant (FR), fast fatigable (FF) and fast intermediate (FI). The proportion of various motor unit types differs from one muscle to another. There is also some variation in the proportions to a given muscle from one animal to another. With the exceptions of soleus, which is entirely slow resistant, and gastrocnemius, which has relatively fewer resistant units, most muscles contain 60% or more of resistant (S and FR) units. 4. The conduction velocity ranges of FF, FR and FI units overlapped. There was little overlap between the conduction velocity ranges of these F units and of S units. 5. In individual experiments there was a strong and significant positive correlation between the logarithm of maximal tetanic tension and axonal conduction velocity in S and in S+FR units. In terms of contractile response the total fatigue-resistant population appeared to be a continuum. The correlation coefficient between maximal tetanic tension and conduction velocity was also high in the totality of units of all types, although within the FF group there appeared to be little or no correlation. In pooled data there was much more scatter and these relations were less clear. This resulted largely from differences in the ranges of axonal conduction velocity for a given motor unit type from one animal to another. 6. There was a highly significant negative correlation between isometric twitch contraction time and axonal conduction velocity in individual experiments. This relationship could also be seen, but less clearly, in pooled data. 7. The possible bases for these relationships are discussed.

Functional segregation of cortical language areas by sentence repetition

Abstract: The functional organization of the perisylvian language network was examined using a functional MRI (fMRI) adaptation paradigm with spoken sentences. In Experiment 1, a given sentence was presented every 14.4 s and repeated two, three, or four times in a row. The study of the temporal properties of the BOLD response revealed a temporal gradient along the dorsal-ventral and rostral- caudal directions: From Heschl's gyrus, where the fastest responses were recorded, responses became increasingly slower toward the posterior part of the superior temporal gyrus and toward the temporal poles and the left inferior frontal gyrus, where the slowest responses were observed. Repetition induced a decrease in amplitude and a speeding up of the BOLD response in the superior temporal sulcus (STS), while the most superior temporal regions were not affected. In Experiment 2, small blocks of six sentences were presented in which either the speaker voice or the linguistic content of the sentence, or both, were repeated. Data analyses revealed a clear asymmetry: While two clusters in the left superior temporal sulcus showed identical repetition suppression whether the sentences were produced by the same speaker or different speakers, the homologous right regions were sensitive to sentence repetition only when the speaker voice remained constant. Thus, hemispheric left regions encode linguistic content while homologous right regions encode more details about extralinguistic features like speaker voice. The results demonstrate the feasibility of using sentence-level adaptation to probe the functional organization of cortical language areas. Hum Brain Mapp 27:360 -371, 2006. © 2006 Wiley-Liss, Inc.

Tyrosine hydroxylase activation in depolarized dopaminergic terminals—involvement of Ca2+ -dependent phosphorylation

Abstract: Tyrosine hydroxylase (tyrosine 3-monoxygenase, EC 1.14.16.2, TH) catalyses the rate limiting step of catecholamine biosynthesis, In vitro, TH from central dopaminergic1–4 as well as from central5,6 and peripheral6,7 noradrenergic neurones can be activated by a cyclic AMP-dependent phosphorylation process and several authors7–9 have proposed that this process can be responsible for the in vivo activation of TH resulting from the electrical stimulation of these neurones. However, this is unlikely to be the case for TH in central dopaminergic neurones because depolarization produces an enzyme activation which is additive with that due to the cyclic AMP-dependent phosphorylation process10–12. In the case of tryptophan hydroxylase in central serotoninergic neurones, recent evidence indicates that a Ca2+-dependent instead of a cyclic AMP-dependent phosphorylation process is responsible for the increased enzyme activity triggered by depolarization13. This finding led us to investigate whether a Ca2+-dependent phosphorylation process also accounts for the activation of TH inside depolarized dopaminergic terminals. We found that soluble TH from the rat striatum could be activated by a Ca2+-dependent process in optimal conditions for producing the phosphorylation of proteins. This activation corresponded exactly to that resulting from the incubation of striatal slices in K+-enriched medium and indeed TH activity from depolarized dopaminergic terminals could not be further stimulated by Ca2+-dependent phosphorylating conditions. In contrast, in situ TH activation by cyclic AMP-dependent phosphorylation (triggered by dibutyryl cyclic AMP or forskolin) did not prevent subsequent stimulation by Ca2+-dependent phosphorylation. These findings suggest that TH activation in depolarized dopaminergic terminals involves a Ca2+-dependent phosphorylation process similar to that controlling tryptophan hydroxylase activity in serotoninergic neurones.

The RXRalpha ligand-dependent activation function 2 (AF-2) is important for mouse development

Abstract: We have engineered a mouse mutation that specifically deletes the C-terminal 18 amino acid sequence of the RXRalpha protein. This deletion corresponds to the last helical alpha structure (H12) of the ligand-binding domain (LBD), and includes the core of the Activating Domain of the Activation Function 2 (AF-2 AD core) that is thought to be crucial in mediating ligand-dependent transactivation by RXRalpha. The homozygous mutants (RXRalpha af2(o)), which die during the late fetal period or at birth, exhibit a subset of the abnormalities previously observed in RXRalpha −/− mutants, often with incomplete penetrance. In marked contrast, RXRalpha af2(o)/RXRbeta −/− and RXRalpha af2(o)/RXRbeta −/− /RXRgamma −/− compound mutants display a large array of malformations, which nearly recapitulate the full spectrum of the defects that characterize the fetal vitamin A-deficiency (VAD) syndrome and were previously found in RAR single and compound mutants, as well as in RXRalpha/RAR(alpha, beta or gamma) compound mutants. Analysis of RXRalpha af2(o)/RAR(alpha, beta or gamma) compound mutants also revealed that they exhibit many of the defects observed in the corresponding RXR alpha/RAR compound mutants. Together, these results demonstrate the importance of the integrity of RXR AF-2 for the developmental functions mediated by RAR/RXR heterodimers, and hence suggest that RXR ligand-dependent transactivation is instrumental in retinoid signalling during development.

Modes and states in quantum optics

Abstract: Quantum states of light are at the same time endowed with two superposition principles: the one of the classical Maxwell waves and the one of the quantum states occupying these waves. This article reviews the interplay between these two aspects of quantum optics. A summary of the description of multimode quantum states is presented along with an example of the characterization of correlations and entanglement with applications in metrology and quantum computation.