Assessment of cell wall porosity in Arabidopsis thaliana by NMR spectroscopy

The impact of homogalacturonans deficiency on the cell wall porosity of Arabidopsis thaliana QUA1 mutant was investigated using NMR measurements of protons mobility interpreted in terms of pore size variations at nanometer and micrometer scales. Isolation and purification of wild type and mutant stems and calli cell walls permitted to exacerbate the putative impact of the mutation on cellulose-hemicelluloses assembly in highly and poorly organised cell walls, respectively. NMR relaxation measurements of water and exchangeable biopolymer protons and self-diffusion processes of polyethylene glycol in walls informed about the porosity network density and heterogeneity. The role of pectins and proteins as well as the growth status of the cells on the wall porosity regulation are discussed.     

Umbelliprenin from Ferula szowitsiana inhibits the growth of human M4Beu metastatic pigmented malignant melanoma cells through cell-cycle arrest in G1 and induction of caspase-dependent apoptosis.

Metastatic malignant melanoma have a bad prognosis (median survival: 6-8 months) mainly due to the development of lung, hepatic and brain metastases. In this study we have used the resazurin reduction test and FACS analysis to assess the cytostatic and cytotoxic effect of umbelliprenin from Ferula szowitsiana (Apiaceae) on human solid cancer cells and human primary fibroblasts. We have observed that the cell susceptibility to umbelliprenin decreases in the order M4Beu (metastatic pigmented malignant melanoma)>A549 (nonsmall cell lung carcinoma) approximately PC3 (androgen-resistant prostate carcinoma)>PA1 (ovary teratocarcinoma)>human primary fibroblasts approximately MCF7 (breast adenocarcinoma)>DLD1 (colon adenocarcinoma). M4Beu cell-proliferation is inhibited through cell-cycle arrest in G1 and induction of caspase-dependent apoptosis. The finding that the cytotoxic effect of umbelliprenin is markedly more pronounced in M4Beu cells than in primary fibroblasts, suggests a therapeutic margin. As M4Beu cell proliferation is more potently inhibited by umbelliprenin (IC50 12.3 microM) than by the citrus coumarin auraptene (7-geranyloxycoumarin, IC50 17.1 microM) previously reported capable of inhibiting the prevalence of lung metastasis in mice bearing B16BL6 murine melanoma, our data suggest that umbelliprenin orally administered and foods and folk medicines containing this coumarin, may afford protection against the development and early recurrence of malignant melanoma. In vivo investigations are needed to test these hypotheses.     

The acetate recovery factor to correct tracer-derived dietary fat oxidation in humans

When using (13)C tracer to measure plasma fat oxidation, an acetate recovery factor should be determined in every subject to correct for label sequestration. Less is known regarding the acetate recovery factor for dietary fatty acid oxidation. We compiled data from six studies to investigate the determinants of the dietary acetate recovery factor (dARF) at rest and after physical activity interventions and compared the effects of different methods of dARF calculation on both the fat oxidation and its variability. In healthy lean subjects, dARF was 50.6 +/- 5.4% dose (n = 56) with an interindividual coefficient of variation of 10.6% at rest and 9.2% after physical activity modifications. The physical activity interventions did not impact dARF, and the intraindividual coefficient of variation was 4.6%. No major anthropological or physiological determinants were detected except for resting metabolic rate, which explains 7.4% of the dARF variability. Applying an individual or an average group dARF did not affect the mean and the variability of the derived dietary lipid oxidation at rest or after physical activity interventions. Using a mean dARF for a group leads to over- or underestimation of fat oxidation of less than 10% in individual subjects. Moreover, the use of a group or individual correction did not affect the significant relationship found between fasting respiratory exchange ratio and dietary fat oxidation. These data indicate that an average dARF can be applied for longitudinal and cross-sectional studies investigating dietary lipid metabolism.     

Vitamin D signaling in immune-mediated disorders: Evolving insights and therapeutic opportunities

1,25(OH)(2)D(3), the active form of vitamin D, is a central player in calcium and bone metabolism. More recently, important immunomodulatory effects have been attributed to this hormone. The widespread presence of the vitamin D receptor (VDR) in the immune system and the expression of the enzymes responsible for the synthesis of the active 1,25(OH)(2)D(3) regulated by specific immune signals, even suggest a paracrine immunomodulatory role for 1,25(OH)(2)D(3). Additionally, the different molecular mechanisms used by 1,25(OH)(2)D(3) to exert its immunomodulatory effects prove of a broad action radius for this compound. Both, the effects of vitamin D deficiency and/or absence of the VDR as well as intervention with pharmacological doses of 1,25(OH)(2)D(3) or one of its less-calcemic analogs, affects immune system behavior in different animal models of immune-mediated disorders, such as type 1 diabetes. This review aims to summarize the data as they stand at the present time on the role of vitamin D in the pathogenesis of immune-mediated disorders, with special focus on type 1 diabetes, and on the therapeutic opportunities for vitamin D in the prevention and treatment of this autoimmune disease in mouse models and humans.     

Unusual intracellular trafficking of Salmonella typhimurium in human melanoma cells

Salmonella spp. are enterobacteria capable of invading and replicating in both professional and non‐professional phagocytes. Here, we investigate the fate of S. typhimurium in human melanoma MelJuSo cells. The bacterium entered MelJuSo cells by a trigger mechanism and resided within a unique organelle, the Salmonella‐containing vacuole (SCV). The SCV acquired early endosomal markers transiently and then underwent a series of membrane modifications. In HeLa cells, vacuole maturation is characterized by the simultaneous acquisition of the lysosomal membrane glycoproteins (Lgps) Lamp1, CD63 and vacuolar (v)‐ATPase; in MelJuSo cells, however, acquisition of CD63 and v‐ATPase preceded that of Lamp1. A very striking event in MelJuSo cells was the arrest of bacterial septation starting from 8 h after infection. Bacteria nevertheless continued to elongate, remained morphologically intact and viable and were eventually exocytosed. This original feature was observed in several skin‐related cells including melanocytes, suggesting that it may provide the basis for an efficient host defence mechanism against Salmonella infection.     

Effects of long-term spaceflight on mechanical properties of muscles in humans

The effects of long-term spaceflight(90-180 days) on the contractile and elastic characteristics ofthe human plantarflexor muscles were studied in 14 cosmonauts beforeand 2-3 days after landing. Despite countermeasures practicedaboard, spaceflight was found to induce a decrease in maximal isometrictorque (17%), whereas an index of maximal shortening velocity wasfound to increase (31%). In addition, maximal muscle activationevaluated during isokinetic tests decreased by 39%. Changes inmusculotendinous stiffness and whole joint stiffness were characterizedby means of quick-release movements and sinusoidal perturbations.Musculotendinous stiffness was found to be increased by 25%. Wholejoint stiffness decreased under passive conditions (21%), whereaswhole joint stiffness under active conditions remained unchanged afterspaceflight (1%). This invariance suggests an adaptive mechanism tocounterbalance the decrease in stiffness of passive structures by anincreased active stiffness. Changes in neural drive could participatein this equilibrium.

     

Synthesis and potential anti-inflammatory activity of some tetrahydrophthalazinones

A solid-phase route for the preparation of 4a,5,8,8a-tetrahydrophthalazinon-1-ones employing the Diels-Alder reaction has been developed. Some of the new compounds have been tested for inhibition of LPS-stimulated TNF-alpha production in human whole blood from patients with chronic obstructive pulmonary disease (COPD). This evaluation revealed two compounds 17 and 18 of interest, incorporating an arylpiperazine moiety, which were found to inhibit LPS-induced TNF-alpha release like the well known anti-inflammatory PDE4 inhibitors, rolipram and roflumilast.     

Heme as an optical probe of a conformational transition of ovine recPrP

The prion protein occurs as a globular domain and a leading fragment whose structure is not well-defined. For the ovine species, all of the tryptophan residues are in the initial fragment, while the globular domain is rich in tyrosine residues. Using heme as a spectroscopic probe, we have studied the recombinant prion protein before and after a temperature-induced conformational change. As for most heme proteins, the absorption spectrum of heme-CO displays a red shift upon binding to the protein, and both the Y and W fluorescence are highly quenched. Flash photolysis kinetics of the PrP-heme-CO complex shows a low yield for the bimolecular phase, indicating a pocket around the hemes. By comparing the holoprotein and the truncated sequence corresponding to the globular domain, the stoichiometry was determined to be five hemes for the globular domain and two hemes for the leading fragment. At high temperature, the hemes are released; upon cooling, only two hemes bind, and only the tryptophan fluorescence is quenched; this would indicate that the globular domain has formed a more compact structure, which is inert with respect to the hydrophobic probe. The final state of polymerization is perturbed if the synthetic peptide "N3" (PrP residues 142-166, which include the first helix) is added to the prion protein solution; the temperature cycle no longer reduces the number of heme binding sites. This would indicate that the peptide may alter or inhibit the polymer formation.     

Acritarches ordoviciens des Zekkara (Maroc oriental)

Ordovician Acritarchs (Arenigian-Llanvirnian) werefound in the blacks of the Zekkara (Morocco). A well preserved assemblage proves this age, which was unknown and often indicated as Silurian or Tournaisian-Visean age. In this association, which is especially typical of the Middle Ordovician, about one hundred and twenty taxa have been recognized; some morphologic characteristics of a certain number of them are indicated here.     

Retinal ganglion cell-derived sonic hedgehog signaling is required for optic disc and stalk neuroepithelial cell development

The development of optic stalk neuroepithelial cells depends on Hedgehog (Hh) signaling, yet the source(s) of Hh protein in the optic stalk is unknown. We provide genetic evidence that sonic hedgehog (Shh) from retinal ganglion cells (RGCs) promotes the development of optic disc and stalk neuroepithelial cells. We demonstrate that RGCs express Shh soon after differentiation, and cells at the optic disc in close proximity to the Shh-expressing RGCs upregulate Hh target genes, which suggests they are responding to RGC-derived Shh signaling. Conditional ablation of Shh in RGCs caused a complete loss of optic disc astrocyte precursor cells, resulting in defective axon guidance in the retina, as well as conversion of the neuroepithelial cells in the optic stalk to pigmented cells. We further show that Shh signaling modulates the size of the Pax2(+) astrocyte precursor cell population at the optic disc in vitro. Together, these data provide a novel insight into the source of Hh that promotes neuroepithelial cell development in the mammalian optic disc and stalk.