Mesure des durées de vie des premiers niveaux excités du molybdène 93

Les durées de vie des six premiers niveaux excités du 93Mo ont été mesurées en utilisant l'effet Doppler associé à la réaction 93Nb(p, nγ)93Mo. Deux nouvelles durées de vie ont été obtenues et la précision des quatre autres a été améliorée

Influence of phyllosilicate mineral assemblages, fabrics, and fluids on the behavior of the Punchbowl fault, southern California

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95206/1/jgrb13457.pd

Compensatory remodeling of a septo-hippocampal GABAergic network in the triple transgenic Alzheimer’s mouse model

Abstract Background Alzheimer’s disease (AD) is characterized by a progressive loss of memory that cannot be efficiently managed by currently available AD therapeutics. So far, most treatments for AD that have the potential to improve memory target neural circuits to protect their integrity. However, the vulnerable neural circuits and their dynamic remodeling during AD progression remain largely undefined. Methods Circuit-based approaches, including anterograde and retrograde tracing, slice electrophysiology, and fiber photometry, were used to investigate the dynamic structural and functional remodeling of a GABAergic circuit projected from the medial septum (MS) to the dentate gyrus (DG) in 3xTg-AD mice during AD progression. Results We identified a long-distance GABAergic circuit that couples highly connected MS and DG GABAergic neurons during spatial memory encoding. Furthermore, we found hyperactivity of DG interneurons during early AD, which persisted into late AD stages. Interestingly, MS GABAergic projections developed a series of adaptive strategies to combat DG interneuron hyperactivity. During early-stage AD, MS-DG GABAergic projections exhibit increased inhibitory synaptic strength onto DG interneurons to inhibit their activities. During late-stage AD, MS-DG GABAergic projections form higher anatomical connectivity with DG interneurons and exhibit aberrant outgrowth to increase the inhibition onto DG interneurons. Conclusion We report the structural and functional remodeling of the MS-DG GABAergic circuit during disease progression in 3xTg-AD mice. Dynamic MS-DG GABAergic circuit remodeling represents a compensatory mechanism to combat DG interneuron hyperactivity induced by reduced GABA transmission

Biophysical Basis for Three Distinct Dynamical Mechanisms of Action Potential Initiation

Transduction of graded synaptic input into trains of all-or-none action potentials (spikes) is a crucial step in neural coding. Hodgkin identified three classes of neurons with qualitatively different analog-to-digital transduction properties. Despite widespread use of this classification scheme, a generalizable explanation of its biophysical basis has not been described. We recorded from spinal sensory neurons representing each class and reproduced their transduction properties in a minimal model. With phase plane and bifurcation analysis, each class of excitability was shown to derive from distinct spike initiating dynamics. Excitability could be converted between all three classes by varying single parameters; moreover, several parameters, when varied one at a time, had functionally equivalent effects on excitability. From this, we conclude that the spike-initiating dynamics associated with each of Hodgkin's classes represent different outcomes in a nonlinear competition between oppositely directed, kinetically mismatched currents. Class 1 excitability occurs through a saddle node on invariant circle bifurcation when net current at perithreshold potentials is inward (depolarizing) at steady state. Class 2 excitability occurs through a Hopf bifurcation when, despite net current being outward (hyperpolarizing) at steady state, spike initiation occurs because inward current activates faster than outward current. Class 3 excitability occurs through a quasi-separatrix crossing when fast-activating inward current overpowers slow-activating outward current during a stimulus transient, although slow-activating outward current dominates during constant stimulation. Experiments confirmed that different classes of spinal lamina I neurons express the subthreshold currents predicted by our simulations and, further, that those currents are necessary for the excitability in each cell class. Thus, our results demonstrate that all three classes of excitability arise from a continuum in the direction and magnitude of subthreshold currents. Through detailed analysis of the spike-initiating process, we have explained a fundamental link between biophysical properties and qualitative differences in how neurons encode sensory input

Perception of Thermal Pain and the Thermal Grill Illusion Is Associated with Polymorphisms in the Serotonin Transporter Gene

AIM: The main aim of this study was to assess if the perception of thermal pain thresholds is associated with genetically inferred levels of expression of the 5-HT transporter (5-HTT). Additionally, the perception of the so-called thermal grill illusion (TGI) was assessed. Forty-four healthy individuals (27 females, 17 males) were selected a-priori based on their 5-HTTLPR/rs25531 ('tri-allelic 5-HTTLPR') genotype, with inferred high or low 5-HTT expression. Thresholds for heat- and cold-pain were determined along with the sensory and affective dimensions of the TGI. RESULTS: Thresholds to heat- and cold-pain correlated strongly (rho  = -0.58, p<0.001). Individuals in the low 5-HTT-expressing group were significantly less sensitive to heat-pain (p = 0.02) and cold-pain (p = 0.03), compared to the high-expressing group. A significant gender-by-genotype interaction also emerged for cold-pain perception (p = 0.02); low 5-HTT-expressing females were less sensitive. The TGI was rated as significantly more unpleasant (affective-motivational dimension) than painful (sensory-discriminatory dimension), (p<0.001). Females in the low 5-HTT expressing group rated the TGI as significantly less unpleasant than high 5-HTT expressing females (p<0.05), with no such differences among men. CONCLUSION/SIGNIFICANCE: We demonstrate an association between inferred low 5-HTT expression and elevated thresholds to thermal pain in healthy non-depressed individuals. Despite the fact that reduced 5-HTT expression is a risk factor for chronic pain we found it to be related to hypoalgesia for threshold thermal pain. Low 5-HTT expression is, however, also a risk factor for depression where thermal insensitivity is often seen. Our results may thus contribute to a better understanding of the molecular underpinnings of such paradoxical hypoalgesia. The results point to a differential regulation of thermoafferent-information along the neuraxis on the basis of 5-HTT expression and gender. The TGI, suggested to rely on the central integration of thermoafferent-information, may prove a valuable tool in probing the affective-motivational dimension of these putative mechanisms

Publisher Correction: A PRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients

The original version of this Article contained an error in the title, which was incorrectly given as 'APRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients'. This has now been corrected in both the PDF and HTML versions of the Article to read 'A PRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients'

Contribution à l'étude du schéma nucléaire du samarium 151

Study by scintillation counters of β and γ radiation of transition 151Pm → 151Sm give following results : — The γ spectra décomposition indicates components of 65, 100, 170, 205, 240, 275, 340, 440, 650 and 715 keV. — The β spectra is built up of five components of maxima energy 1 300, 115, 960, 860, 485 keV. — The study of βγ and γγ coïncidences leads to the following results for excited levels of 151Sm. 65, 100, 165, 340, 440, 750 and 815 keV. — The lifetime of levels at 65 keV and 100 keV is τ65 keV ≤ 5 × 10—10 s. τ100 keV ≤ 10—9 s. — The angular correlation coefficients of the following sequences are : 275— 65 keV : A2 = 0.090 ± 0.011 A4 = — 0.078 ± 0.011 240 — 100 keV : A2 = 0.080 ± 0.017 A4 = 0.062 ± 0.018 175 —165 keV: A2 = 0.180 ± 0.080 A4 = —0.057 ± 0.081 Finally, for levels 0, 65, 100, 165, 340 keV of samarium 151, the spins proposed are 7/2, 9/2, 9/2, 7/2, 7/2.L'étude par la technique des compteurs à scintillations des rayonnements β et γ émis lors de la transition 151Pm → 151Sm conduit aux résultats suivants : — La décomposition du spectre γ fait apparaître-des composantes à 65,100,170, 205, 240, 27,5, 340, 440, 650 et 775 keV. — Le spectre β est complexe avec 5 composantes d'énergie maximum 1 300, 1 115, 960, 860, 485 keV. — L'étude des coïncidences βγ et γγ conduit à situer les niveaux excités du 151Sm à 65, 100, 165, 340, 440, 750 et 815 keV. — La mesure de vie moyenne des niveaux 65 et 100 keV donne τ65 keV ≤ 5 .10—10 s. τ100 keV ≤ 10—9 s. — La mesure des corrélations angulaires directionnelles donne, pour les séquences suivantes : 275 — 65 keV : A2 = 0,090 ± 0,011 A4 = - 0,078 ± 0,011 240 — 100 keV : A2 = 0,080 ± 0,017 A4 = 0,062 ± 0,018 175—165 keV: A2 = 0,180 ± 0,080 A4 = — 0,057 ± 0,081 En conséquence, les spins 7/2, 9/2,9/2, 7/2, 7/2 sont proposés pour les niveaux 0,65, 100, 165, 340 keV du Samarium 151