Surface nucleolin participates in both the binding and endocytosis of lactoferrin in target cells.

Lactoferrin (Lf), a multifunctional molecule present in mammalian secretions and blood, plays important roles in host defense and cancer. Indeed, Lf has been reported to inhibit the proliferation of cancerous mammary gland epithelial cells and manifest a potent antiviral activity against human immunodeficiency virus and human cytomegalovirus. The Lf-binding sites on the cell surface appear to be proteoglycans and other as yet undefined protein(s). Here, we isolated a Lf-binding 105 kDa molecular mass protein from cell extracts and identified it as human nucleolin. Medium-affinity interactions ( approximately 240 nm) between Lf and purified nucleolin were further illustrated by surface plasmon resonance assays. The interaction of Lf with the cell surface-expressed nucleolin was then demonstrated through competitive binding studies between Lf and the anti-human immunodeficiency virus pseudopeptide, HB-19, which binds specifically surface-expressed nucleolin independently of proteoglycans. Interestingly, binding competition studies between HB-19 and various Lf derivatives in proteoglycan-deficient hamster cells suggested that the nucleolin-binding site is located in both the N- and C-terminal lobes of Lf, whereas the basic N-terminal region is dispensable. On intact cells, Lf co-localizes with surface nucleolin and together they become internalized through vesicles of the recycling/degradation pathway by an active process. Morever, a small proportion of Lf appears to translocate in the nucleus of cells. Finally, the observations that endocytosis of Lf is inhibited by the HB-19 pseudopeptide, and the lack of Lf endocytosis in proteoglycan-deficient cells despite Lf binding, point out that both nucleolin and proteoglycans are implicated in the mechanism of Lf endocytosis.     

Xylem development and cell wall changes of soybean seedlings grown in space

BACKGROUND AND AIMS: Plants growing in altered gravity conditions encounter changes in vascular development and cell wall deposition. The aim of this study was to investigate xylem anatomy and arrangement of cellulose microfibrils in vessel walls of different organs of soybean seedlings grown in Space. METHODS: Seeds germinated and seedlings grew for 5 d in Space during the Foton-M2 mission. The environmental conditions, other than gravity, of the ground control repeated those experienced in orbit. The seedlings developed in space were compared with those of the control test on the basis of numerous anatomical and ultrastructural parameters such as number of veins, size and shape of vessel lumens, thickness of cell walls and deposition of cellulose microfibrils. KEY RESULTS: Observations made with light, fluorescence and transmission electron microscopy, together with the quantification of the structural features through digital image analysis, showed that the alterations due to microgravity do not occur at the same level in the various organs of soybean seedlings. The modifications induced by microgravity or by the indirect effect of space-flight conditions, became conspicuous only in developing vessels at the ultrastructural level. The results suggested that the orientation of microfibrils and their assembly in developing vessels are perturbed by microgravity at the beginning of wall deposition, while they are still able to orient and arrange in thicker and ordered structures at later stages of secondary wall deposition. CONCLUSIONS: The process of proper cell-wall building, although not prevented, is perturbed in Space at the early stage of development. This would explain the almost unaltered anatomy of mature structures, accompanied by a slower growth observed in seedlings grown in Space than on Earth.     

Biosurfactants,an help in the biodegradation of hexadecane? The case of <Emphasis Type="Italic">Rhodococcus</Emphasis> and <Emphasis Type="Italic">Pseudomonas</Emphasis> strains

The roles of the extracellular biosurfactants produced by two bacterial strains, Pseudomonas aeruginosa GL1 and Rhodococcus equi Ou2, in hexadecane uptake and biodegradation were compared. For this purpose, cell hydrophobicity and production of glycolipidic biosurfactants were evaluated during bacterial growth on hexadecane, as well the effects of these biosurfactants on culture supernatants properties i.e., surface and interfacial tensions, and emulsification and pseudosolubilization capacities. The results showed that the role of biosurfactants was different in these two strains and was directly related to the hydrophobicity of the bacterial cells concerned. Extracellular biosurfactants produced by strain R. equi Ou2 had only a minor role in hexadecane degradation. Direct interfacial accession appeared to be the main mechanism for hexadecane uptake by the hydrophobic cells of strain R. equi Ou2. On the contrary, the biosurfactants produced by P. aeruginosa GL1 were required for growth on hexadecane, and their pseudosolubilization capacity rather than their emulsification capacity was involved in substrate degradation, allowing uptake from hexadecane micelles by the hydrophilic cells of this bacterium. The roles of biosurfactants thus differ widely among bacteria degrading hydrophobic compounds. J.-P. Vandecasteele—in retirement     

Are the IKKs and IKK-related kinases TBK1 and IKK-epsilon similarly activated?

The IkappaB kinases (IKKs) IKK-alpha and IKK-beta, and the IKK-related kinases TBK1 and IKK-epsilon, have essential roles in innate immunity through signal-induced activation of NF-kappaB, IRF3 and IRF7, respectively. Although the signaling events within these pathways have been extensively studied, the mechanisms of IKK and IKK-related complex assembly and activation remain poorly defined. Recent data provide insight into the requirement for scaffold proteins in complex assembly; NF-kappaB essential modulator coordinates some IKK complexes, whereas TANK, NF-kappaB-activating kinase-associated protein 1 (NAP1) or similar to NAP1 TBK1 adaptor (SINTBAD) assemble TBK1 and IKK-epsilon complexes. The different scaffold proteins undergo similar post-translational modifications, including phosphorylation and non-degradative polyubiquitylation. Moreover, increasing evidence indicates that distinct scaffold proteins assemble IKK, and potentially TBK1 and IKK-epsilon subcomplexes, in a stimulus-specific manner, which might be a mechanism to achieve specificity.     

Denture contamination by yeasts in the elderly

Objectives: The aim of this study was to investigate yeast carriage in healthy denture wearers by swabbing and to evaluate the effect of denture hygiene habits. Materials and methods: Denture wearers (n = 87) without evidence of denture stomatitis or any other oral disease were investigated by separately swabbing the fitting surface of the upper denture and the corresponding palatal mucosa in contact with the appliance. In a group of volunteers, a gel without any active compound was spread on the palatal side of the denture once in every morning for 2 weeks. Results: Screening showed Candida colonisation of upper prosthesis in 75.9% of individuals. The most frequent species isolated were Candida albicans (77.9% of the positive cultures), Candida glabrata (44.1%) and Candida tropicalis (19.1%). Carriage of more than one yeast species was found in 48.5% of the contaminated dentures. There was a statistically significant association between denture contamination and palatal mucosa colonisation (chi‐squared test: p < 0.0001). Repeated swabbings after 1 week as well as during a weekly follow‐up for 1 month confirmed the denture contamination and its degree of severity. A daily gel application produced a yeast‐count decrease to 10% of the initial value after 2 weeks (chi‐squared test: p = 0.0134 and p = 0.2841 for prosthesis and palatal mucosa, respectively). Conclusion: This study documented the reliability of oral swabbing when investigating yeast carriage in healthy denture wearers. Moreover, just a diagnostic tool, sampling upper dentures for Candida could be the opportunity to verify the patient’s compliance to hygiene advice.     

Ostracodes de la Formation de Bhanness,Kimméridgien (Jurassique supérieur) du Liban central : taxonomie,paléoécologie et paléobiogéographie

A microfauna composed of 11 species of ostracodes belonging to 11 genera have been recovered from the Bhanness Formation of Kimmeridgian age, in Central Lebanon. Four species are new and are described herein: Ektyphocythere dahressawanensis nov. sp., Dicrorygma (Orthorygma) libanensis nov. sp., Citrella? elongata nov. sp. and Procytherura inflata nov. sp. From a palaeobiogeographical standpoint, this fauna characterizes the North Gondwana province which differs from the South Gondwana province, particularly by the presence of the genus Schuleridea and the absence of the genus Majungaella.     

Elucidation of Rab27 recruitment by its effectors: structure of Rab27a bound to Exophilin4/Slp2-a

Rab GTPases coordinate vesicular trafficking within eukaryotic cells by collaborating with a set of effector proteins. Rab27a regulates numerous exocytotic pathways, and its dysfunction causes the Griscelli syndrome human immunodeficiency. Exophilin4/Slp2-a localizes on phosphatidylserine-enriched plasma membrane, and its N-terminal Rab27-binding domain (RBD27) specifically recognizes Rab27 on the surfaces of melanosomes and secretory granules prior to docking and fusion. To characterize the selective binding of Rab27 to 11 various effectors, we have determined the 1.8 A resolution structure of Rab27a in complex with Exophilin4 RBD27. The effector packs against the switch and interswitch elements of Rab27a, and specific affinity toward Rab27a is modulated by a shift in the orientation of the effector structural motif (S/T)(G/L)xW(F/Y)(2). The observed structural complementation between the interacting surfaces of Rab27a and Exophilin4 sheds light on the disparities among the Rab27 effectors and outlines a general mechanism for their recruitment.     

Effect of GH on human skeletal muscle lipid metabolism in GH deficiency

Adult-onset growth hormone (GH) deficiency (GHD) is associated with insulin resistance and decreased exercise capacity. Intramyocellular lipids (IMCL) depend on training status, diet, and insulin sensitivity. Using magnetic resonance spectroscopy, we studied IMCL content following physical activity (IMCL-depleted) and high-fat diet (IMCL-repleted) in 15 patients with GHD before and after 4 mo of GH replacement therapy (GHRT) and in 11 healthy control subjects. Measurements of insulin resistance and exercise capacity were performed and skeletal muscle biopsies were carried out to assess expression of mRNA of key enzymes involved in skeletal muscle lipid metabolism by real-time PCR and ultrastructure by electron microscopy. Compared with control subjects, patients with GHD showed significantly higher difference between IMCL-depleted and IMCL-repleted. GHRT resulted in an increase in skeletal muscle mRNA expression of IGF-I, hormone-sensitive lipase, and a tendency for an increase in fatty acid binding protein-3. Electron microscopy examination did not reveal significant differences after GHRT. In conclusion, variation of IMCL may be increased in patients with GHD compared with healthy control subjects. Qualitative changes within the skeletal muscle (i.e., an increase in free fatty acids availability from systemic and/or local sources) may contribute to the increase in insulin resistance and possibly to the improvement of exercise capacity after GHRT. The upregulation of IGF-I mRNA suggests a paracrine/autocrine role of IGF-I on skeletal muscle.     

Hydroxycinnamic acids are ester-linked directly to glucosyl moieties within the lignan macromolecule from flaxseed hulls

In flaxseed hulls, lignans are present in an oligomeric structure. Secoisolariciresinol diglucoside (SDG), ester-linked to hydroxy-methyl-glutaric acid (HMGA), forms the backbone of this lignan macromolecule. The hydroxycinnamic acids p-coumaric acid glucoside (CouAG) and ferulic acid glucoside (FeAG) are also part of the lignan macromolecule. However, their position and type of linkage are still unknown. The aim of this study was to investigate how CouAG and FeAG are linked within the lignan macromolecule from flaxseed hulls. Fragments of the lignan macromolecule were obtained by partial saponification. After isolation of the fragments by preparative RP-HPLC, several key structures were identified by MS and NMR. Within the lignan macromolecule, CouAG is attached to the C-6 position of a glucosyl moiety of SDG. FeA is linked to the C-2 position of a glucosyl moiety of SDG. FeAG is ester-linked within the lignan macromolecule with its carboxyl group, but it remains unclear whether FeAG links to the C-2 or C-6 position of SDG. Attachment of HMGA to the glucosyl moiety of CouAG or FeAG was not observed. The results clearly show that within the lignan macromolecule, the hydroxycinnamic acids are linked directly via an ester bond to the glucosyl moiety of SDG.     

Aspergillus conidia activate the complement by the mannan-binding lectin C2 bypass mechanism

Innate immunity is the major host defense against invasive aspergillosis. To determine whether the collectin mannan-binding lectin (MBL) is involved in the initial protective immunity through complement activation against opportunistic fungal infections caused by Aspergillus, we performed in vitro studies on 29 different strains of Aspergillus conidia from five different species. Incubation of Aspergillus conidia in human normal serum leads to activation of the alternative pathway, whereas neither the classical nor the lectin pathways through C4 and C2 cleavage are activated. Complement response to conidia was investigated using a MBL-deficient serum and reconstitution experiments were conducted with MBL/MASPs complexes. We found that MBL can directly support C3 activation by a C2 bypass mechanism. Finally, a stronger activation of the alternative pathway was observed for the clinical strains isolated from patients with invasive aspergillosis, compared with the environmental strains.