L'effet de la vasoréactivité cérébrale (CVR) sur le pronostic fonctionnel après un AVC ischémique chez l'homme est mal connu. L'expérimentation animale suggère une rôle de la réorganisation vasculaire du parenchyme cérébral dans la neuroplasticité et la récupération fonctionnelle post-AVC (1,2). Notre objectif était d'explorer l'impact pronostique de la microvascularisation cérébrale estimée par des mesures de perfusion basale et de CVR en IRM au cours des 6 mois suivant un AVC ischémique sylvien. Cette étude longitudinale a exploré la récupération avec l'index de Barthel (BI), la perfusion basale en IRM, et la CVR à l'hypercapnie en IRMf BOLD chez 25 patients inclus dans l’étude ISIS-HERMES (3) pour un infarctus sylvien avec un suivi clinique et IRM à 1, 1,5 et 7 mois. L'analyse statistique a comporté l’étude des corrélations entre mesures du BI et de CVR, et la modélisation temporelle du BI en fonction des mesures de perfusion et de CVR avec un modèle linéaire mixte (LMM). Parmi les 25 patients, 14 avaient reçu un traitement par cellules souches et 9 une thrombolyse IV. Le NIHSS initial médian était de 15 (IQR = 13,0-18,5). L'AVC siégeait à gauche chez 16 patients, avec un volume lésionnel médian de 83,1 ml (IQR = 47,3-128,2). La perfusion et la CVR étaient altérées dans le territoire vasculaire (p<0,001) même à distance de l'infarctus comparativement à l'hémisphère sain, avec une évolution temporelle du CBV et du CBF uniquement au niveau de la péri-nécrose (respectivement p<0,001 et p=0,021). La CVR dans le territoire vasculaire sylvien périlésionnel à 1 mois de l'AVC était corrélée au BI à 6 mois (r=0,44 ; p=0,049) et prédisait le BI après ajustement au traitement, au MTT et au volume lésionnel (F=5,08 ; p=0,028). L'IRMf de laCVR présente un intérêt pronostique dans l'AVC.

Background and Purpose. - Severe intracranial atherosclerotic stenosis (SIAS) remains at risk of recurrent ischemic events despite intensive medical management. Exhausted cerebrovascular reserve seems to be associated with higher risk of recurrent stroke. Materials and Methods. - We used whole brain MRI to estimate basal perfusion using dynamic susceptibility contrast and cerebrovascular reactivity (CVR) to hypercapnic challenge (CO2 inhalation) using BOLD contrast, in 20 patients with symptomatic SIAS (> 70%) of the middle cerebral artery (MCA) or the distal internal carotid artery. We studied relationships between individual clinical, biological, radiological baseline characteristics, recurrent ischemic events, basal perfusion parameters (mean transit time, delay, time to peak, cerebral blood flow and volume), and CVR measured in MCA territories (CVRMCA), and reported using laterality indices (LI). Results. - Ten patients had an impaired CVR with (|LI| CVRMCA >= 0.08). During a mean follow-up of 3.3 years, all recurrent ipsilateral ischemic events occurred within the first year. They were more frequent in impaired CVRMCA group (n = 7/10 patients) than in normal CVRMCA group (n = 1/10), with different survival curves (log rank, P = 0.007). Conclusion. - Impaired CVR is associated with an increased rate of recurrent stroke in patients with symptomatic SIAS. CVR mapping should be used as a well tolerated method to select higher-risk patients in further therapeutic trials such as endovascular procedures. (C) 2020 Published by Elsevier Masson SAS.

The structural characterization of modular proteins containing long intrinsically disordered regions intercalated with folded domains is complicated by their conformational diversity and flexibility and requires the integration of multiple experimental approaches. Nipah virus (NiV) phosphoprotein, an essential component of the viral RNA transcription/replication machine and a component of the viral arsenal that hijacks cellular components and counteracts host immune responses, is a prototypical model for such modular proteins. Curiously, the phosphoprotein of NiV is significantly longer than the corresponding protein of other paramyxoviruses. Here, we combine multiple biophysical methods, including x-ray crystallography, NMR spectroscopy, and small angle x-ray scattering, to characterize the structure of this protein and provide an atomistic representation of the full-length protein in the form of a conformational ensemble. We show that full-length NiV phosphoprotein is tetrameric, and we solve the crystal structure of its tetramerization domain. Using NMR spectroscopy and small angle x-ray scattering, we show that the long N-terminal intrinsically disordered region and the linker connecting the tetramerization domain to the C-terminal X domain exchange between multiple conformations while containing short regions of residual secondary structure. Some of these transient helices are known to interact with partners, whereas others represent putative binding sites for yet unidentified proteins. Finally, using NMR spectroscopy and isothermal titration calorimetry, we map a region of the phosphoprotein, comprising residues between 110 and 140 and common to the V and W proteins, that binds with weak affinity to STAT1 and confirm the involvement of key amino acids of the viral protein in this interaction. This provides new, to our knowledge, insights into how the phosphoprotein and the nonstructural V and W proteins of NiV perform their multiple functions.

Les patients avec des sténoses artérielles intracrâniennes sévères (SAIS) sont à haut risque d’infarctus cérébral. L’étude SAMMPRIS a montré l’absence de bénéfice du stenting intracrânien pour les SAIS athéromateuses symptomatiques comparé au traitement médical agressif seul dans la prévention du risque de récidive d’accident ischémique. L’altération de la réserve cérébrovasculaire (CVR) a été évoquée pour mieux sélectionner les patients à risque. Une IRM de la CVR, en contraste BOLD lors de stimuli hypercapniques (CO2 8 %) contrôlés par la pression expiratoire en CO2 (EtCO2), a été réalisée pour tous les patients qui présentaient une SAIS symptomatique entre 2011 et 2016. Des mesures de CVR, effectuées dans les régions d’intérêt localisées sur les territoires des artères cérébrales moyennes (ACM), ont exprimé par un index de latéralité IL = (CVR_ACMgauche – CVR_ACMdroite)/(CVR_ACMgauche + CVR_ACMdroite) et comparées à la normale (IC 95 % : |IL| < 0,08). Les caractéristiques cliniques des patients et la récidive d’AI dans le territoire de la SAIS ont été rétrospectivement analysés. Sur 75 patients examinés, 21 patients (16 hommes, 59,3 ans) étaient porteurs d’une SAIS athéromateuse unilatérale symptomatique de l’ACM (n = 16) ou de l’artère carotide interne (n = 5). Douze patients avaient un IL anormal et ipsilatéral à la SAIS. La récidive d’AI a été rapporté pour 5 patients avec un IL anormal et 3 patients avec un IL normal, sans différence significative. Les taux de cholestérol total et LDL étaient significativement plus élevés dans le groupe IL anormal. Notre série met en évidence une altération de la CVR dans 57 % des cas de SAIS athéromateuse intéressant la circulation antérieure, sans différence significative en terme de récidive ischémique.

Le débit sanguin cérébral (DSC) et la vasoréactivité cérébrale (VRC) déclinent naturellement avec l’âge. Ce déclin est connu pour être associé à des déficits cognitifs. De ce fait, le DSC et la VRC représentent d’éventuels marqueurs biologiques dans les pathologies neurodégénératives. Cette étude a pour objectif de caractériser l’association de ces paramètres hémodynamiques avec l’âge et les capacités cognitives dans le vieillissement sain, ainsi qu’au stade précoce du vieillissement pathologique. Trente-quatre participants (13 femmes) ont pris part à cette étude : 13 participants sains jeunes (44,08 ± 9,51 ans), 10 participants sains âgés (72,10 ± 5,70 ans) et 11 participants âgés présentant des plaintes mnésiques (73,36 ± 7,94 ans). Nous avons mesuré le DSC et la VRC en utilisant l’imagerie pCASL. Les participants ont également bénéficié d’un bilan neuropsychologique visant à évaluer le fonctionnement cognitif global, les fonctions frontales ainsi que le langage. L’évaluation neuropsychologique a montré des difficultés au niveau de l’attention, l’inhibition et la flexibilité mentale, chez les participants âgés. De plus, comparés aux scores des personnes âgées saines, les patients présentant des plaintes mnésiques avaient des scores significativement différents pour le fonctionnement cognitif global, les fonctions exécutives, la mémoire à court terme et la mémoire de travail. Nous avons retrouvé une diminution significative du DSC et de la VRC entre les participants jeunes et âgés. Cette diminution a été prédominante dans les régions postérieures (lobes occipitaux et pariétaux) chez les patients. Nous avons également retrouvé une corrélation significative entre la VRC et les scores neuropsychologiques au sein de plusieurs régions cérébrales. Le DSC global a présenté une corrélation significative avec l’âge uniquement. Le DSC semble décliner naturellement avec l’âge sans affecter les fonctions cognitives. En revanche, la VRC semble être spécifiquement associée aux capacités cognitives, qui déclinent précocement dans le vieillissement pathologique (stade préclinique).

Hay synthesis of cryptands and bismacrocycles starting from tripodands with cyanuric and isocyanuric cores is reported. The structure of the compounds is revealed by X-ray diffraction, NMR spectrometry and MS investigations. DNMR experiments carried out with bismacrocycles indicated the flipping of the rings and the free-energy barrier for the conformational process could be determined in one case.

The products of the reaction of d-glucuronic acid with various combinations of ammonia and volatile ammonium salts in water were studied by NMR and MS spectroscopy. For long reaction times (~24 h), the expected products β-d-glucopyranosylamine uronic acid and ammonium N-(β-d-glucopyranosyluronic acid)carbamate were obtained in good-to-high yield, whereas seven intermediate species were identified in samples taken at earlier reaction times. 1H–1H homonuclear and 1H–13C heteronuclear correlation experiments enabled a complete assignment of the 1H and 13C NMR spectra of the starting and final compounds, and a partial assignment of the peaks of intermediate species. Based on these results, a 1H NMR protocol for the quantification of the different compounds taking part in the reaction was developed, which was used to monitor the evolution of the composition of an early reaction sample redissolved in D2O. It was thus established that two of the observed intermediate species are actually the α anomer of the main products, whereas the others are precursors to the formation of α/β-d-glucopyranosylamine uronic acid and ammonium N-(α/β-d-glucopyranosyluronic acid)carbamate. The correct assignments for the 1H and 13C spectra of d-glucuronic acid in D2O are also reported.

Rheological and swelling properties of hydrogels based on pullulan crosslinked with sodium trimetaphosphate (STMP) are explained according to various polymer and crosslinking agent concentrations using 31P-nuclear magnetic resonance study. This method has allowed determining the amount of all the species present in the medium when varying both pullulan and STMP concentrations. We have clearly demonstrated with a good agreement by both 31P-NMR and rheology that a critical STMP concentration occurs which is function of pullulan concentration. This typical crosslinking agent concentration delimitates the maximum of gel structure together with the minimum of swelling.

Peptide E (a 25-amino acid peptide derived from proenkephalin A) and β-endorphin (a 31-amino acid peptide derived from proopiomelanocortin) bind with high affinity to opioid receptors and share structural similarities but induce analgesic effects of very different intensity. Indeed, whereas they possess the same N-terminus Met-enkephalin message sequence linked to a helix by a flexible spacer and a C-terminal part in random coil conformation, in contrast with peptide E, β-endorphin produces a profound analgesia. To determine the key structural elements explaining this very divergent opioid activity, we have compared the structural and pharmacological characteristics of several chimeric peptides derived from peptide E and β-endorphin. Structures were obtained under the same experimental conditions using circular dichroism, computational estimation of helical content and/or nuclear magnetic resonance spectroscopy (NMR) and NMR-restrained molecular modeling. The hot-plate and writhing tests were used in mice to evaluate the antinociceptive effects of the peptides. Our results indicate that neither the length nor the physicochemical profile of the spacer plays a fundamental role in analgesia. On the other hand, while the functional importance of the helix cannot be excluded, the last 5 residues in the C-terminal part seem to be crucial for the expression or absence of the analgesic activity of these peptides. These data raise the question of the true function of peptides E in opioidergic systems.

A glycine-leucine-rich peptide was isolated from norepinephrine-stimulated skin secretions of the Sante Fe frog Leptodactylus laticeps (Leptodactylidae) whose primary structure (Gly-Leu-Val-Asn-Gly-Leu-Leu-Ser-Ser-Val-Leu-Gly-Gly-Gly-Gln-Gly-Gly-Gly-Gly-Leu-Leu-Gly-Gly-Ile-Leu) contains the (GXXXG)(3) motif found in the plasticins, previously identified only in phyllomedusid frogs (Hylidae). Circular dichroism studies showed that the secondary structure of the peptide, termed plasticin-L1, was markedly solvent-dependent displaying a random coil conformation in water, a beta-sheet structure in methanol, and an alpha-helical conformation in 50% trifluoroethanol-water. A synthetic replicate of the peptide did not inhibit the growth of Escherichia coli or Staphylococcus aureus or lyse human erythrocytes at concentrations up to 500 microM. At relatively high concentrations (>or=1 microM), the peptide produced a significant (P<0.05), although modest (139% of basal rate at 3 microM), increase in the rate of glucose-induced release of insulin from rat clonal BRIN-BD11 beta cells without increasing the rate of release of lactate dehydrogenase. A peptide, termed ocellatin-L2 was also identified in the skin secretion that was identical to the previously described ocellatin-L1 except for the substitution Asn(23)-->Asp. Ocellatin-L2 was devoid of antimicrobial and hemolytic activity but also showed significant activity in stimulating insulin release from BRIN-BD11 cells (181% of basal rate at 3 microM).

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Brevinin‐2 related peptide (B2RP; GIWDTIKSMG10KVFAGKILQN20L.NH2), first isolated from skin secretions of the mink frog Lithobates septentrionalis, shows broad‐spectrum antimicrobial activity but its therapeutic potential is limited by moderate hemolytic activity. The peptide adopts an α‐helical conformation in a membrane‐mimetic solvent but amphipathicity is low. Increasing amphipathicity together with hydrophobicity by the substitutions Lys16→Leu and Lys16→Ala increased hemolytic activity approximately fivefold without increasing antimicrobial potency. The substitution Leu18→Lys increased both cationicity and amphipathicity but produced decreases in both antimicrobial potency and hemolytic activity. In contrast, increasing cationicity of B2RP without changing amphipathicity by the substitution Asp4→Lys resulted in a fourfold increase in potency against Escherichia coli [minimal inhibitory concentration (MIC) = 6 μm) and twofold increases in potency against Staphylococcus aureus (MIC = 12.5 μm) and Candida albicans (MIC = 6 μm) without changing significantly hemolytic activity against human erythrocytes (LC50 = 95 μm). The emergence of antibiotic‐resistant strains of the Gram‐negative bacterium Acinetobacter baumannii constitutes a serious risk to public health. B2RP (MIC = 3–6 μm) and [Lys4]B2RP (MIC = 1.5–3 μm) potently inhibited the growth of nosocomial isolates of multidrug‐resistant Acinetobacter baumannii. Although the analogs [Lys4, Lys18]B2RP and [Lys4, Ala16, Lys18]B2RP showed reduced potency against Staphylococcus aureus, they retained activity against Acinetobacter baumannii (MIC = 3–6 μm) and had very low hemolytic activity (LC50 > 200 μm).

The synthesis, the X-ray, NMR and molecular modeling structure determination of a new orthopara[4.4]cyclophane are reported. The similarity of the π(CO)–π(Ar) driven conformational equilibrium of this compound to the work of an amusement ride machinery is also revealed.

The frog skin peptides, ascaphin-8 (GFKDLLKGAAKALVKTVLF.NH2) and XT-7 (GLLGPLLKIAAKVGSNLL.NH2), show broad-spectrum antimicrobial activity but their therapeutic potential is limited by toxicity against mammalian cells. Circular dichroism spectra demonstrate that the peptides adopt an amphipathic alpha-helical conformation in a membrane-mimetic solvent. This study has investigated the cytolytic properties of analogs containing selected amino acid substitutions that increase cationicity while maintaining amphipathicity. Substitutions at Ala(10), Val(14), and Leu(18) in ascaphin-8 by either L-Lys or D-Lys produced peptides that retained antimicrobial activity against the bacteria Escherichia coli and Staphylococcus aureus and the opportunistic yeast pathogen, Candida albicans but showed appreciably reduced toxicities (> 10-fold) against human erythrocytes, HepG2 hepatoma-derived cells, and L929 fibroblasts. The improved therapeutic index of the L-Lys(18) and D-Lys(18) analogs correlated with a decrease in % helicity and in effective hydrophobicity. Substitution of Gly(4) by L-Lys in XT-7 produced an analog with high potency against micro-organisms (MIC <= 25 mu M) but low cytolytic activity against erythrocytes (LD50 > 500 mu M) and this increase in therapeutic index also correlated with decreased helicity and hydrophobicity. Analogs of XT-7 with increased cationicity, containing multiple substitutions by L-Lys, not only displayed increased antimicrobial potencies, particularly against Candida albicans (MIC <= 6 mu M), but also increased hemolytic activities.

The fair or good yield synthesis of new [(4.4)(n)]cyclophanes (n = 1-5), starting from 1,4-bis(2-hydroxymethyl-5,5-dimethyl-1,3-dioxan-2-yl)benzene and several diacid-dichlorides, based on monomer and oligomer formation reactions (from 1 + 1 to 5 + 5), is reported. The structure and the complex architectures of the lattices for these cyclophanes are revealed by the X-ray molecular structure for five compounds, NMR investigations, and mass spectrometry measurements. Intramolecular and intermolecular CH-pi, p-pi, and pi-pi interactions are observed, both in solid state and solution.

The configurational and conformational behavior of some new 3,3,9,9-tetrasubstituted-2,4,8,10-tetraoxaspiro[5.5]undecane derivatives with axial chirality was investigated by conformational analysis and variable temperature NMR experiments.

The synthesis of new spiro and trispiro compounds with 2,4,8,10-tetrathiaspiro[5.5]undecane and 7,11,18,21-tetrathia[5.2.2.5.2.2]heneicosane units is reported. The structural analysis was carried out by NMR investigations and the X-ray single crystal molecular structure determined for one of the compounds. The barriers for the flipping of the 1,3-dithiane units are determined by variable temperature NMR experiments.

The synthesis of some new [4.4]cyclophane diketals, monoketones, and diketones in good yields is reported along with the unusually low reactivity towards hydrolysis of the spiro-1,3-dioxane rings connected to the cyclophane bridges. The structural analysis carried out by X-ray diffraction, NMR spectroscopy, and mass spectrometry shows significant intra- and intermolecular pi-pi and C-H-pi interactions. The rotation of the aromatic rings and the flipping of the bridges have been investigated by molecular modeling and variable-temperature NMR experiments. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).

Temporin-1DRa (HFLGTLVNLAKKIL.NH2), first isolated from the skin of the California red-legged frog Rana draytonii, shows broad-spectrum antimicrobial activity but its therapeutic potential is limited by its toxicity against mammalian cells. The cytolytic properties of cationic α-helical peptides are determined by a complex interaction between cationicity, hydrophobicity, conformation, and amphipathicity. This study has investigated the cytolytic properties of conformationally constrained analogs of temporin-1DRa containing α-aminoisobutyric acid (Aib) substitutions. Cytolytic activity was determined against the bacteria Escherichia coli and Staphylococcus aureus, the opportunistic yeast pathogen, Candida albicans, human erythrocytes, HepG2 hepatoma-derived cells, and L929 fibroblasts. Aib substitutions at Gly4, Asn8, and Ala10 increased both % helicity, determined in methanol solution, and hydrophobicity resulting in increases in both antimicrobial potencies and toxicities against the mammalian cells. Substitution at Leu6 resulted in an appreciable decrease in cytolytic activity against all cells whereas the substitutions at His1, Phe2, Leu3, Thr5, and Val7 had only minor effects on activity. Substitutions at Leu9, Ile13, Leu14 produced analogs with decreased helicity and hydrophobicity that retained activity against microorganisms but showed appreciably lower cytolytic activities against mammalian cells. In particular, the fourfold increase in therapeutic index [ratio of LC50 against erythrocytes to minimum inhibitory concentration (MIC) against microorganisms] of [Aib13]temporin-1DRa identifies it as a compound with potential for development as a therapeutically valuable anti-infective agent.

An NMR spectroscopy study (P-31, H-1, C-13) of the postulated crosslinking mechanism of sodium trimetaphosphate (STMP) on polysaccharides is reported using methyl alpha-D-glucopyranoside as a model. In a first step, reaction of STMP with Glc-OMe gives grafted sodium tripolyphosphate (STPPg). On the one hand, STTPg can react with a second alcohol functionality to give a crosslinked monophosphate. On the other hand, a monophosphate (grafted phosphate) could be obtained by alkaline degradation of STPPg. NMR spectroscopy allows to detect the various species formed and to obtain the crosslinking density of STMP-polysaccharides hydrogels. (c) 2007 Elsevier Ltd. All rights reserved.