Density distribution of 2′,3′-cyclic nucleotide 3′-phosphodiesterase and myelin proteins in particulate material from myelin deficient (mld) mutant and control brains

Total particulate material from control and myelin deficient (mld) brains was subjected to density centrifugation on a continuous sucrose gradient. Particles from control brains distributed in a bell-shaped mode with a peak density near 0.64 M-sucrose. In mld material only a slight elevation of optical density was observed near 0.8 M-sucrose. The highest specific activities of 2′,3′-cyclic nucleotide 3′-phosphodiesterase were observed at densities of 0.63 and 0.71 M-sucrose for mld and control brains, respectively. The peak of myelin basic protein in control fractions was near 0.60 M-sucrose. In mld fractions no peak was observed. Proteolipid and Wolfgram proteins had a maximum near 0.65 and 0.73 M-sucrose in control and mld fractions, respectively. The absence of myelin basic proteins in all the fractions makes it unlikely that, in mld mice, myelin basic proteins are synthesized but not incorporated into myelin.     

Common Properties of Fusion Peptides from Diverse Systems

Although membrane fusion occurs ubiquitously and continuously in alleukaroytic cells, little is known about the mechanism that governs lipidbilayer fusion associated with any intracellular fusion reactions. Recentstudies of the fusion of enveloped viruses with host cell membranes havehelped to define the fusion process. The identification and characterizationof key proteins involved in fusion reactions have mainly driven recent advancesin our understanding of membrane fusion. The most important denominator amongthe fusion proteins is the fusion peptide. In this review, work done in thelast few years on the molecular mechanism of viral membrane fusion will behighlighted, focusing in particular on the role of the fusion peptide and themodification of the lipid bilayer structure. Much of what is known regardingthe molecular mechanism of viral membrane fusion has been gained using liposomesas model systems in which the molecular components of the membrane and the environmentare strictly controlled. Many amphilphilic peptides have a high affinity forlipid bilayers, but only a few sequences are able to induce membrane fusion. Thepresence of -helical structure in at least part of the fusion peptideis strongly correlated with activity whereas, -structure tends to beless prevalent, associated with non-native experimental conditions, and morerelated to vesicle aggregation than fusion. The specific angle of insertionof the peptides into the membrane plane is also found to be an importantcharacteristic for the fusion process. A shallow penetration, extending onlyto the central aliphatic core region, is likely responsible for the destabilization ofthe lipids required for coalescence of the apposing membranes and fusion.     

Ornibactins—a new family of siderophores from Pseudomonas

Novel linear hydroxamate/hydroxycarboxylate siderophores from strains of Pseudomonas cepacia were isolated and named ornibactins. The ornibactins represent modified tetrapeptide siderophores, possessing the sequence l-Orn¹(N -OH, N -acyl)-d-threo-Asp(-OH)-l-Ser-l-Orn⁴(N -OH, N -formyl)-1,4-diaminobutane. The N -acyl groups of Orn¹(N -OH, N -acyl) may vary and represent the three acids 3-hydroxybutanoic acid, 3-hydroxyhexanoic acid and 3-hydroxyoctanoic acid, leading to a mixture of three different ornibactins, designated according to their acyl chain length as ornibactin-C4, ornibactin-C6 and ornibactin-C8. Each of the siderophores is accompanied by a small amount of a more hydrophilic component with a 16 a.m.u. higher mass. The structure elucidation was based on results from gas chromatography amino acid analysis, electrospray mass spectrometry, and one- and two-dimensional nuclear magnetic resonance techniques.     

Upper Limb Evaluation and One-Year Follow Up of Non-Ambulant Patients with Spinal Muscular Atrophy: An Observational Multicenter Trial

Assessment of the upper limb strength in non-ambulant neuromuscular patients remains challenging. Although potential outcome measures have been reported, longitudinal data demonstrating sensitivity to clinical evolution in spinal muscular atrophy patients are critically lacking. Our study recruited 23 non-ambulant patients, 16 patients (males/females = 6/10; median age 15.4 years with a range from 10.7 to 31.1 years) with spinal muscular atrophy type II and 7 patients (males/females = 2/5; median age 19.9 years with a range from 8.3 to 29.9 years) with type III. The Brooke functional score was on median 3 with a range from 2 to 6. The average total vital capacity was 46%, and seven patients required non-invasive ventilation at night. Patients were assessed at baseline, 6 months, and 1 year using the Motor Function Measure and innovative devices MyoGrip, MyoPinch, and MoviPlate, which assess handgrip strength, key pinch strength, and hand/finger extension-flexion function, respectively. The study demonstrated the feasibility and reliability of these measures for all patients, and sensitivity to negative changes after the age of 14 years. The younger patients showed an increase of the distal force in the follow-up period. The distal force measurements and function were correlated to different functional scales. These data represent an important step in the process of validating these devices as potential outcome measures for future clinical trials.

Trial Registration

ClinicalTrials.gov NCT00993161     

Extracellular hemoglobin combined with an O2-generating material overcomes O2 limitation in the bioartificial pancreas

The bioartificial pancreas encapsulating pancreatic islets in immunoprotective hydrogel is a promising therapy for Type 1 diabetes. As pancreatic islets are highly metabolically active and exquisitely sensitive to hypoxia, maintaining O₂ supply after transplantation remains a major challenge. In this study, we address the O₂ limitation by combining silicone-encapsulated CaO₂ (silicone-CaO₂) to generate O₂ with an extracellular hemoglobin O₂-carrier coencapsulated with islets. We showed that the hemoglobin improved by 37% the O₂-diffusivity through an alginate hydrogel and displayed antioxidant properties neutralizing deleterious reactive O₂ species produced by silicone-CaO₂. While the hemoglobin alone failed to maintain alginate macroencapsulated neonate pig islets under hypoxia, silicone-CaO₂ alone or combined to the hemoglobin restored islet viability and insulin secretion and prevented proinflammatory metabolism (PTGS2 expression). Interestingly, the combination took the advantages of the two individual strategies, improved neonate pig islet viability and insulin secretion in normoxia, and VEGF secretion and PDK1 normalization in hypoxia. Moreover, we confirmed the specific benefits of the combination compared to silicone-CaO₂ alone on murine pseudo-islet viability in normoxia and hypoxia. For the first time, our results show the interest of combining an O₂ provider with hemoglobin as an effective strategy to overcome O₂ limitations in tissue engineering.     

Fluorescent (Au@SiO2)SiC Nanohybrids: Influence of Gold Nanoparticle Diameter and SiC Nanoparticle Surface Density

Gold@silica core–shell nanoparticles were prepared with various gold core diameters (ranging from 20 to 150 nm) and silica thicknesses (ranging from 10 to 30 nm). When the gold diameter is increased, the size dispersion became larger, leading to a broader plasmon band. Then, silicon carbide (SiC) nanoparticles were covalently immobilized onto silica to obtain hybrid (Au@SiO₂) SiC nanoparticles. The absorption properties of these hybrid nanoparticles showed that an excess of SiC nanoparticles in the dispersion can be identified by a strong absorption in the UV region. Compared to SiC reference samples, a blue shift of the fluorescence emission, from 582 to 523 nm, was observed, which was previously attributed to the strong surface modification of SiC when immobilized onto silica. Finally, the influence of several elaboration parameters (gold diameter, silica thickness, SiC concentration) on fluorescence enhancement was investigated. It showed that the highest enhancements were obtained with 10 nm silica thickness, low concentration of SiC nanoparticles, and surprisingly, with a 20-nm gold core diameter. This last result could be attributed to the broad plasmon band of big gold colloids. In this case, SiC emission strongly overlapped gold absorption, leading to possible quenching of SiC fluorescence by energy transfer.     

Reversible inhibition of the human xenobiotic-metabolizing enzyme arylamine N-acetyltransferase 1 by S-nitrosothiols

Human arylamine N-acetyltransferase 1 (NAT1) is a polymorphic phase II xenobiotic-metabolizing enzyme which catalyzes the biotransformation of primary aromatic amines, hydrazine drugs, and carcinogens. Structural and functional studies have shown that the NAT1 and factor XIII transglutaminase catalytic pockets are structurally related with the existence of a conserved catalytic triad (Cys-His-Asp). In addition, it has been reported that factor XIII transglutaminase activity could be regulated by nitric oxide (NO), in particular S-nitrosothiols (RSNO). We thus tested whether NAT1 could be a target of S-nitrosothiols. We show here that human NAT1 is reversibly inactivated by S-nitrosothiols such as SNAP (S-nitroso-N-acetyl-DL-penicillamine). A second-order rate constant for the inactivation of NAT1 by SNAP was determined (k(inact)=270M(-1)min(-1)) and shown to be in the same range of values reported for other enzymes. The inhibition of NAT1 by S-nitrosothiols was reversed by dithiothreitol and reduced glutathione, but not by ascorbate. As reported for some reactive cysteine-containing enzymes, our results suggest that inactivation of NAT1 by S-nitrosothiols is due to direct attack of the highly reactive cysteine residue in the enzyme active site on the sulfur of S-nitrosothiols to form a mixed disulfide between these NO-derived oxidants and NAT1. Finally, our findings suggest that, in addition to the polymorphic-dependent variation of NAT1 activity, NO-derived oxidants, in particular S-nitrosothiols, could also regulate NAT1 activity.     

Climate change impacts on tree ranges: model intercomparison facilitates understanding and quantification of uncertainty

Model-based projections of shifts in tree species range due to climate change are becoming an important decision support tool for forest management. However, poorly evaluated sources of uncertainty require more scrutiny before relying heavily on models for decision-making. We evaluated uncertainty arising from differences in model formulations of tree response to climate change based on a rigorous intercomparison of projections of tree distributions in France. We compared eight models ranging from niche-based to process-based models. On average, models project large range contractions of temperate tree species in lowlands due to climate change. There was substantial disagreement between models for temperate broadleaf deciduous tree species, but differences in the capacity of models to account for rising CO(2) impacts explained much of the disagreement. There was good quantitative agreement among models concerning the range contractions for Scots pine. For the dominant Mediterranean tree species, Holm oak, all models foresee substantial range expansion.     

CAF01 potentiates immune responses and efficacy of an inactivated influenza vaccine in ferrets

Trivalent inactivated vaccines (TIV) against influenza are given to 350 million people every year. Most of these are non-adjuvanted vaccines whose immunogenicity and protective efficacy are considered suboptimal. Commercially available non-adjuvanted TIV are known to elicit mainly a humoral immune response, whereas the induction of cell-mediated immune responses is negligible. Recently, a cationic liposomal adjuvant (dimethyldioctadecylammonium/trehalose 6,6'-dibehenate, CAF01) was developed. CAF01 has proven to enhance both humoral and cell-mediated immune responses to a number of different experimental vaccine candidates. In this study, we compared the immune responses in ferrets to a commercially available TIV with the responses to the same vaccine mixed with the CAF01 adjuvant. Two recently circulating H1N1 viruses were used as challenge to test the vaccine efficacy. CAF01 improved the immunogenicity of the vaccine, with increased influenza-specific IgA and IgG levels. Additionally, CAF01 promoted cellular-mediated immunity as indicated by interferon-gamma expressing lymphocytes, measured by flow cytometry. CAF01 also enhanced the protection conferred by the vaccine by reducing the viral load measured in nasal washes by RT-PCR. Finally, CAF01 allowed for dose-reduction and led to higher levels of protection compared to TIV adjuvanted with a squalene emulsion. The data obtained in this human-relevant challenge model supports the potential of CAF01 in future influenza vaccines.