Acute TNFα levels predict cognitive impairment 6-9 months after COVID-19 infection.

A neurocognitive phenotype of post-COVID-19 infection has recently been described that is characterized by a lack of awareness of memory impairment (i.e., anosognosia), altered functional connectivity in the brain's default mode and limbic networks, and an elevated monocyte count. However, the relationship between these cognitive and brain functional connectivity alterations in the chronic phase with the level of cytokines during the acute phase has yet to be identified. Determine whether acute cytokine type and levels is associated with anosognosia and functional patterns of brain connectivity 6-9 months after infection. We analyzed the predictive value of the concentration of acute cytokines (IL-1RA, IL-1β, IL-6, IL-8, IFNγ, G-CSF, GM-CSF) (cytokine panel by multiplex immunoassay) in the plasma of 39 patients (mean age 59 yrs, 38-78) in relation to their anosognosia scores for memory deficits via stepwise linear regression. Then, associations between the different cytokines and brain functional connectivity patterns were analyzed by MRI and multivariate partial least squares correlations for the whole group. Stepwise regression modeling allowed us to show that acute TNFα levels predicted (R <sup>2</sup> = 0.145; β = -0.38; p = .017) and were associated (r = -0.587; p < .001) with scores of anosognosia for memory deficits observed 6-9 months post-infection. Finally, high TNFα levels were associated with hippocampal, temporal pole, accumbens nucleus, amygdala, and cerebellum connectivity. Increased plasma TNFα levels in the acute phase of COVID-19 predict the presence of long-term anosognosia scores and changes in limbic system functional connectivity

Brain functional connectivity alterations associated with neuropsychological performance 6-9 months following SARS-CoV-2 infection.

Neuropsychological deficits and brain damage following SARS-CoV-2 infection are not well understood. Then, 116 patients, with either severe, moderate, or mild disease in the acute phase underwent neuropsychological and olfactory tests, as well as completed psychiatric and respiratory questionnaires at 223 ± 42 days postinfection. Additionally, a subgroup of 50 patients underwent functional magnetic resonance imaging. Patients in the severe group displayed poorer verbal episodic memory performances, and moderate patients had reduced mental flexibility. Neuroimaging revealed patterns of hypofunctional and hyperfunctional connectivities in severe patients, while only hyperconnectivity patterns were observed for moderate. The default mode, somatosensory, dorsal attention, subcortical, and cerebellar networks were implicated. Partial least squares correlations analysis confirmed specific association between memory, executive functions performances and brain functional connectivity. The severity of the infection in the acute phase is a predictor of neuropsychological performance 6-9 months following SARS-CoV-2 infection. SARS-CoV-2 infection causes long-term memory and executive dysfunctions, related to large-scale functional brain connectivity alterations

Measurement of melatonin in body fluids: Standards, protocols and procedures

Abstract: The circadian rhythm of melatonin in saliva or plasma, or of the melatonin metabolite 6‐ sulphatoxymelatonin in urine, is a defining feature of suprachiasmatic nucleus function, the endogenous oscillatory pacemaker. These measurements are useful to evaluate problems related to the onset or offset of sleep and for assessing phase delays or advances of rhythms in entrained individuals. Additionally, they have become an important tool for psychiatric diagnosis, its use being recommended for phase typing in patients suffering from sleep and mood disorders. Thus, the development of sensitive and selective methods for the precise detection of melatonin in tissues and fluids of animals emerges as necessary. Due to its low concentration and the co‐existence of many other endogenous compounds in blood, the determination of melatonin has been an analytical challenge. This review discusses current methodologies employed for detection and quantification of melatonin in biological fluids and tissues

INFLUENCE D'UN ATOME D'IMPURETÉ SUR LES MODES DE VIBRATIONS D'UNE CHAINE ATOMIQUE

L'atome d'impureté modifie les distributions des masses et des constantes de force le long de la chaîne. Le défaut ainsi introduit est analysé en fonctions harmoniques sur le réseau ; l'amplitude du déplacement de chaque atome est analysée de la même façon et le problème revient à calculer les composantes du développement correspondant. On en déduit les valeurs des fréquences de vibrations et on les compare à celles du réseau parfait. On exprime simplement les déplacements atomiques dans le cas d'ondes stationnaires. Les modes localisés déjà obtenus à partir des fonctions de Green par d'autres auteurs ont été retrouvés.The distributions of masses and force constants are changed by the impurity atom. The defect which is so introduced is expressed in terms of harmonic functions in the lattice ; the same method is applied for analysing the amplitude of displacement, thus the problem is to calculate the components of corresponding development. Atomic displacements are easily expressed in the case of stationnary waves. This method, in particular, gives the same localized modes as obtained by other authors using Green's functions

Application de la topographie par diffraction des rayons X à l'étude des métaux

On rappelle le principe des différentes méthodes de topographie par diffraction des rayons X : méthode de Berg-Barrett par réflexion ; méthode de Lang et méthode de Borrmann par transmission. Dans le cas des métaux, ces techniques ont permis d'étudier la microstructure des monocristaux, les configurations des dislocations, les déplacements des dislocations, les fautes d'empilement, les macles et les parois des domaines ferromagnétiques. Elles présentent certains avantages par rapport aux autres méthodes d'observation des dislocations : elles sont non destructives, elles explorent des volumes importants du cristal, elles utilisent des échantillons épais et les effets des surfaces sont éliminés ; elles se trouvent cependant limitées en résolution et elles ne s'appliquent qu'à des échantillons à faible densité de dislocations ( N ≤ 105 disl. cm-2). Les principaux résultats obtenus jusqu'à ce jour sont regroupés par métaux. On indique les améliorations à apporter dans le cadre de l'appareillage : tubes à rayons X plus puissants, intensificateurs d'image, porte-échantillon à haute et à basse température, dispositifs de déformation sur la chambre. On pourra utiliser ces techniques pour différentes études : mécanismes d'interaction entre dislocations, vitesse de déplacement des dislocations en fonction de la température et de la contrainte, origine et multiplication des dislocations, rôles respectifs des dislocations fraîches et des dislocations originelles, microdéformation plastique, transformation de phases, diffusion, précipitation... ; ces études supposent que l'on dispose d'échantillons ayant une densité de dislocations assez faible et une épaisseur convenable

Configurations de dislocations dans un cristal d'aluminium en fonction de la température

X-ray topography shows the appearance of rows of dislocation loops in aluminium crystals, initially dislocation free, cooled from 345°C to different temperatures. Thèse loops seem to be emitted from Bardeen-Herring sources. They grow by the elimination of the vacancies retained under supersaturation during the cooling ; then they develop into a random dislocation configuration.La topographie aux rayons X montre l'apparition d'alignements de boucles de dislocations dans les cristaux d'aluminium, initialement sans dislocation, refroidis depuis 345°C à différentes températures. Il semble que ces boucles sont émises par des sources de Bardeen-Herring. Elles croissent par élimination des lacunes retenues en sursaturation au cours du refroidissement ; elles évoluent ensuite vers une configuration de dislocations réparties au hasard