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Membrane Components (membrane + component)
Kinds of Membrane Components Selected AbstractsOn reduced integration and locking of flat shell finite elements with drilling rotationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 2 2003Sannelie Geyer Abstract In recent times, a number of assumed stress membrane finite elements with drilling degrees of freedom have been presented. These highly accurate elements are natural candidates for the membrane component of geometrically simple, yet accurate, flat shell finite elements. Depending on a mixed formulation, these assumed stress membranes are normally integrated using full integration. However, this is not necessarily optimal. Reduced integration using modified quadratures decreases the effects of membrane-bending locking, while the accuracy and rank of the formulation is not impaired. Copyright ©2003 John Wiley & Sons, Ltd. [source] Citicoline: neuroprotective mechanisms in cerebral ischemiaJOURNAL OF NEUROCHEMISTRY, Issue 1 2002Rao Muralikrishna Adibhatla Abstract Cytidine-5,-diphosphocholine (citicoline or CDP-choline), an intermediate in the biosynthesis of phosphatidylcholine (PtdCho), has shown beneficial effects in a number of CNS injury models and pathological conditions of the brain. Citicoline improved the outcome in several phase-III clinical trials of stroke, but provided inconclusive results in recent clinical trials. The therapeutic action of citicoline is thought to be caused by stimulation of PtdCho synthesis in the injured brain, although the experimental evidence for this is limited. This review attempts to shed some light on the properties of,citicoline that are responsible for its effectiveness. Our studies in transient cerebral ischemia suggest that citicoline might enhance reconstruction (synthesis) of PtdCho and sphingomyelin, but could act by inhibiting the destructive processes (activation of phospholipases). Citicoline neuroprotection may,include: (i) preserving cardiolipin (an exclusive inner mitochondrial membrane component) and sphingomyelin; (ii),preserving the arachidonic acid content of PtdCho and phosphatidylethanolamine; (iii) partially restoring PtdCho levels; (iv) stimulating glutathione synthesis and glutathione reductase activity; (v) attenuating lipid peroxidation; and (vi),restoring Na+/K+ -ATPase activity. These observed effects,of citicoline could be explained by the attenuation of,phospholipase A2 activation. Based on these findings, a singular unifying,mechanism has been hypothesized. Citicoline also provides choline for synthesis of neurotransmitter acetylcholine, stimulation of tyrosine hydroxylase activity and dopamine release. [source] Gene Expression Profiles of Intracellular and Membrane Progesterone Receptor Isoforms in the Mediobasal Hypothalamus During Pro-OestrusJOURNAL OF NEUROENDOCRINOLOGY, Issue 12 2009B. Liu Progesterone action is mediated by its binding to specific receptors. Two progesterone receptor (PR) isoforms (PRA and PRB), three membrane progesterone receptor (mPR) subtypes (mPR,, mPR, and mPR,) and at least one progesterone membrane-binding protein [PR membrane component 1 (PRmc1)] have been identified in reproductive tissues and brain of various species. In the present study, we examined gene expression patterns for PR isoforms, mPR subtypes and PRmc1 in the rat mediobasal hypothalamus (MBH) during pro-oestrus. The mRNA level for each receptor subtype was quantified by a real-time reverse transcriptase-polymerase chain reaction (RT-PCR) at the time points: 13.00 h on dioestrous day 2; 09.00, 13.00, 17.00 and 22.00 h on pro-oestrus; and 13.00 h on oestrus. For PR, one primer set amplified PRA+PRB, whereas a second primer set amplified PRB. As expected, PRA+PRB mRNA expression was greater than PRB in MBH tissue. PRB mRNA levels increased throughout the day on pro-oestrus, with the highest levels being observed at 17.00 h. PRB mRNA levels in the MBH were increased by 2.4- and 3.0-fold at 13.00 and 17.00 h, respectively, on pro-oestrus compared to 13.00 h on dioestrous day 2. There were differential mRNA expression levels for mPRs and PRmc1 in the MBH, with the highest expression for PRmc1 and the lowest for mPR,. The mPR, mRNA contents at 13.00 and 17.00 h on pro-oestrus were increased by 1.5-fold compared to that at 13.00 h on dioestrous day 2. The mPR, mRNA levels at 13.00 and 17.00 h on pro-oestrus were 2.5- and 2.4-fold higher compared to that at 13.00 h on dioestrous day 2, respectively. PRA+PRB, mPR, and PRmc1 mRNA levels did not vary on pro-oestrus. These findings suggest that the higher expression of PRB, mPR, and mPR, in the MBH on pro-oestrous afternoon may influence both genomic and nongenomic mechanisms of progesterone action during the critical pre-ovulatory period. [source] Predictive toxicogenomics approaches reveal underlying molecular mechanisms of nongenotoxic carcinogenicityMOLECULAR CARCINOGENESIS, Issue 12 2006Alex Y. Nie Toxicogenomics technology defines toxicity gene expression signatures for early predictions and hypotheses generation for mechanistic studies, which are important approaches for evaluating toxicity of drug candidate compounds. A large gene expression database built using cDNA microarrays and liver samples treated with over one hundred paradigm compounds was mined to determine gene expression signatures for nongenotoxic carcinogens (NGTCs). Data were obtained from male rats treated for 24 h. Training/testing sets of 24 NGTCs and 28 noncarcinogens were used to select genes. A semiexhaustive, nonredundant gene selection algorithm yielded six genes (nuclear transport factor 2, NUTF2; progesterone receptor membrane component 1, Pgrmc1; liver uridine diphosphate glucuronyltransferase, phenobarbital-inducible form, UDPGTr2; metallothionein 1A, MT1A; suppressor of lin-12 homolog, Sel1h; and methionine adenosyltransferase 1, alpha, Mat1a), which identified NGTCs with 88.5% prediction accuracy estimated by cross-validation. This six genes signature set also predicted NGTCs with 84% accuracy when samples were hybridized to commercially available CodeLink oligo-based microarrays. To unveil molecular mechanisms of nongenotoxic carcinogenesis, 125 differentially expressed genes (P,<,0.01) were selected by Student's t -test. These genes appear biologically relevant, of 71 well-annotated genes from these 125 genes, 62 were overrepresented in five biochemical pathway networks (most linked to cancer), and all of these networks were linked by one gene, c - myc. Gene expression profiling at early time points accurately predicts NGTC potential of compounds, and the same data can be mined effectively for other toxicity signatures. Predictive genes confirm prior work and suggest pathways critical for early stages of carcinogenesis. © 2006 Wiley-Liss, Inc. [source] The role of lipopolysaccharides in induction of plant defence responsesMOLECULAR PLANT PATHOLOGY, Issue 5 2003Gitte Erbs SUMMARY Lipopolysaccharides (LPS) are ubiquitous, indispensable components of the cell surface of Gram-negative bacteria that apparently have diverse roles in bacterial pathogenesis of plants. As an outer membrane component, LPS may contribute to the exclusion of plant-derived antimicrobial compounds promoting the ability of a bacterial plant pathogen to infect plants. In contrast, LPS can be recognized by plants to directly trigger some plant defence-related responses. LPS also sensitize plant tissue to respond more rapidly or to a greater extent to subsequently inoculated phytopathogenic bacteria. Sensitization is manifested by an accelerated synthesis of antimicrobial hydroxycinnamoyl-tyramine conjugates, in the expression patterns of genes coding for some pathogenesis-related (PR) proteins, and prevention of the hypersensitive reaction caused by avirulent bacteria. The description at the molecular level of the various effects of LPS on plants is a necessary step towards an understanding of the signal transduction mechanisms through which LPS triggers these responses. A definition of these signal transduction pathways should allow an assessment of the contribution that LPS signalling makes to plant disease resistance in both natural infections and biocontrol. [source] Apolipoprotein E and apolipoprotein B genotypes and risk for spina bifidaBIRTH DEFECTS RESEARCH, Issue 5 2002Kelly A. Volcik Background Altered cholesterol metabolism and defects in cholesterol biosynthesis may influence abnormal central nervous system (CNS) development. During early stages of embryonic development, high levels of cholesterol are needed by rapidly proliferating cells that utilize cholesterol as a key cell membrane component. Alterations in cholesterol levels are influenced by variations in the apolipoprotein E (apoE) and apolipoprotein B (apoB) genes. The purpose of our study was to explore the possible association between infant genetic variations in the apoE and apoB genes and spina bifida (SB) risk. Methods Genomic DNA was extracted from newborn screening blood spots obtained from 26 infants with SB and 73 non-malformed control infants. ApoE and apoB genotypes were determined by restriction enzyme digestion of PCR amplification products. Results Genotype frequencies for the apoE and apoB polymorphisms were not statistically different between case and control infants. For each apoB polymorphism, however, the frequency of the wild-type allele was higher in SB infants as compared to controls. Additionally, the apoE genotype E2/E3 was observed more frequently in the controls than in SB infants [15% in controls compared to 4% in cases; OR = 0.2 (0,1.6)]. Conclusions Results from this study suggest that genetic variations in the apoE and apoB genes, known to regulate cholesterol metabolism, do not substantially contribute to the risk of SB in infants. Teratology 66:257,259, 2002. © 2002 Wiley-Liss, Inc. [source] Novel MRI and fluorescent probes responsive to the Factor XIII transglutaminase activityCONTRAST MEDIA & MOLECULAR IMAGING, Issue 4 2010Lorenzo Tei Abstract Transglutaminases, including factor XIII and tissue transglutaminase, participate in multiple extracellular processes associated with remodeling of the extracellular matrix during wound repair, blood clotting, tumor progression and fibrosis of ischemic injuries. The aim of this work was to evaluate a novel substrate analog for transglutaminase optimized by molecular modeling calculations (DCCP16), which can serve for molecular imaging of transglutaminase activity by magnetic resonance imaging and by near-infrared imaging. Experimental data showed covalent binding of Gd,DCCP16 and DCCP16-IRIS Blue to human clots, to basement membrane components and to casein in purified systems as well as in three-dimensional multicellular spheroids. In vivo, DCCP16 showed enhancement with a prolonged retention in clots and tumors, demonstrating the ability to detect both factor XIII and tissue transglutaminase mediated covalent binding of the contrast material. Copyright © 2010 John Wiley & Sons, Ltd. [source] Deposition of chromatin-IgG complexes in skin of nephritic MRL-lpr/lpr mice is associated with increased local matrix metalloprotease activitiesEXPERIMENTAL DERMATOLOGY, Issue 8 2010Annica Hedberg Please cite this paper as: Deposition of chromatin-IgG complexes in skin of nephritic MRL-lpr/lpr mice is associated with increased local matrix metalloprotease activities. Experimental Dermatology 2010; 19: e265,e274. Abstract:, Chromatin-IgG complexes appear as electron dense structures (EDS) in glomerular basement membranes in lupus nephritis. Here, we present results of comparative analyses of the composition of EDS in murine lupus dermatitis and nephritis. One focus was to perform an analytical approach to understand why such complex structures bind skin basement membrane components. Transcription of skin membrane-encoding genes was analysed to see if expression of such genes was increased, eventually indicating that binding capacity of immune complexes increased when dermatitis developed. Variations in matrix metalloprotease 2 (MMP2), MMP9 and Dnase1 mRNA levels and enzymatic activities were correlated with circulatory chromatin-IgG complexes and deposition in skin. We also examined if glomerular deposits of EDS predicted similar deposits in skin of (NZB × NZW)F1 or MRL-lpr/lpr mice, as we observed chromatin-IgG complexes in capillary lumina in skin and glomeruli in both strains. EDS consisting of chromatin fragments and IgG were found sub-epidermally in skin with LE-like lesions of end-stage nephritic MRL-lpr/lpr mice. Dermal MMP-encoding genes were up-regulated during disease progression, and gelatinolytic activity was increased in affected skin. Dnase1 mRNA level and total nuclease activity remained stable in skin during the disease, in contrast to progressive loss of renal Dnase1 mRNA and total renal nuclease activity during development of nephritis. Loss of renal Dnase1 may explain release of chromatin fragments, while increased MMP activity may disrupt membranes making them accessible for chromatin fragment-IgG complexes. Circulatory chromatin-IgG complexes, and up-regulated intradermal MMP activity may be crucial for deposition of immune complexes in skin of lupus-prone mice. [source] Molecular determinants of UV-induced immunosuppressionEXPERIMENTAL DERMATOLOGY, Issue 2002Agatha Schwarz Abstract: It is almost three decades ago that it was discovered that ultraviolet radiation (UV) can compromise the immune system. UV suppresses immune responses in several ways. It inhibits the function of antigen-presenting cells, induces T cells with suppressor activity and induces the release of immunosuppressive cytokines. The latter phenomenon is mainly responsible for systemic immunosuppression. Although UV can also target cytoplasmic and cell membrane components, UV-induced DNA damage has been recognized as the most important molecular structure in mediating UV-induced immunosuppression. Recently, it was observed that interleukin-12 (IL-12), which antagonizes UV-induced immunosuppression, can accelerate the removal of UV-induced DNA lesions, probably via inducing DNA repair. Hence, it is tempting to speculate that the activity of IL-12 to reduce UV-induced immunosuppression may be due at least partially to this new biological activity of IL-12. [source] Rafts in oligodendrocytes: Evidence and structure,function relationshipGLIA, Issue 6 2006Ellen Gielen Abstract The plasma membrane of eukaryotic cells exhibits lateral inhomogeneities, mainly containing cholesterol and sphingomyelin, which provide liquid-ordered microdomains (lipid "rafts") that segregate membrane components. Rafts are thought to modulate the biological functions of molecules that become associated with them, and as such, they appear to be involved in a variety of processes, including signal transduction, membrane sorting, cell adhesion and pathogen entry. Although still a matter of ongoing debate, evidence in favor of the presence of these microdomains is gradually accumulating but a consensus on issues like their size, lifetime, composition, and biological significance has yet to be reached. Here, we provide an overview of the evidence supporting the presence of rafts in oligodendrocytes, the myelin-producing cells of the central nervous system, and discuss their functional significance. The myelin membrane differs fundamentally from the plasma membrane, both in lipid and protein composition. Moreover, since myelin membranes are unusually enriched in glycosphingolipids, questions concerning the biogenesis and functional relevance of microdomains thus appear of special interest in oligodendrocytes. The current picture of rafts in oligodendrocytes is mainly based on detergent methods. The robustness of such data is discussed and alternative methods that may provide complementary data are indicated. © 2006 Wiley-Liss, Inc. [source] Relationship between fascicle size and perineurial collagen IV content in diabetic and control human peripheral nerveHISTOPATHOLOGY, Issue 6 2000P E Williams Aim: The relationship between perineurial collagen IV content and fascicle size was determined in diabetic and control human peripheral nerve. Methods and results Age-matched diabetic and control sural nerve samples were immunostained using antibodies to collagen IV. The number of cell layers and the perimeter of the fascicle were measured and the collagen IV content of the perineurium determined. Using this method, a comparison could be made of collagen IV content in the perineuria of fascicles of different size. A positive linear relationship was found between fascicle size and the amount of collagen IV per unit of perineurium. The number of perineurial cell layers and the collagen IV content of the diabetic nerve did not differ from control values. Conclusions The linear relationship between fascicle size and perineurial collagen IV content per unit of perineurium underlines the importance of taking fascicle size into account when determining changes in basement membrane components associated with neuropathy. The results indicate that increased deposition of collagen IV is not involved in the early changes in the perineurial cell basement membrane and is thus not the primary factor involved in altered nerve function associated with diabetic neuropathy. [source] Antibody response to influenza infection of mice: different patterns for glycoprotein and nucleocapsid antigensIMMUNOLOGY, Issue 4 2003Robert Sealy Summary Our previous studies of C57BL/6 mice intranasally infected with influenza virus (A/PR8) revealed a spike of virus-specific immunoglobulin A (IgA)-secreting antibody-forming cells (AFC) in the mediastinal lymph node (MLN) 7 days post-infection. Here we show that these AFC are directed only against viral glycoprotein, and not nucleocapsid antigens. The early IgA spike associates with a decline in glycoprotein-specific AFC during week 2 post-infection. In contrast to the glycoprotein-specific AFC, nucleocapsid-specific, IgA-secreting AFC develop gradually in the MLN and persist for more than 3 weeks post-infection. As peripheral lymph node reactions wane, the nucleocapsid-specific AFC appear as long-sustained populations in the bone marrow. Microanatomical examination of the respiratory tract in infected mice shows foci of infection established in the lung 2 days post-infection, from which virus spreads to infect the entire lining of the trachea by day 3. At this time, viral haemagglutinin can be seen within the MLN, probably on projections from infected dendritic cells. This feature disappears within a day, though viral antigen expression continues to spread throughout the respiratory tract. Total IgA- and IgG-secreting AFC appear histologically in large numbers during the first week post-infection, significantly preceding the appearance of germinal centres (revealed by peanut agglutinin staining in week 2). To explain these results, we suggest that the initial immunogenic encounter of B cells with viral antigens occurs about 3 days post-infection in the MLN, with antigens transported by dendritic cells from airway mucosa, the only site of viral replication. Viral glycoproteins expressed as integral membrane components on the surface of infected dendritic cells [probably in the absence of cognate T helper (Th) cells] promote members of expanding relevant B-cell clones to undergo an IgA switch and terminal local plasmacytoid differentiation. Anti-glycoprotein specificities are thus selectively depleted from progeny of activated B-cell clones which are channelled to participate in germinal centre formation (perhaps by cognate T helper cells when they become sufficiently frequent). One product of the germinal centre reaction is the long-sustained, bone marrow-resident population, which is accordingly rich in anti-nucleoprotein, but not anti-glycoprotein specificities. Of note, we find that AFC responses toward influenza virus and Sendai virus differ, even though viral replication is limited to the airway mucosa in each case. The response towards Sendai virus exhibits neither the early appearance of anti-glycoprotein AFC expressing IgA in draining lymph nodes, nor the subsequent relative deficit of this specificity from bone marrow AFC populations. [source] Virus-Vector Cell Interactions Regulating Transmission Specificity of Soybean Dwarf LuteovirusesJOURNAL OF PHYTOPATHOLOGY, Issue 6 2000F. E. Gildow Abstract Transmission of soybean dwarf viruses (SbDV) indigenous to Japan (SbDV-D) and to the eastern United States (SbDV-Va19) were compared in vector and nonvector aphid species. Absolute vector-specificity was maintained when Aulacorthum solani, Acyrthosiphon pisum, and Myzus persicae were allowed to feed on solutions of either virus (100 ,g/ml) through Parafil© membranes. SbDVD was transmitted only by A. solani, and SbDV-Va19 was transmitted only by A. pisum and M. persicae. Similar results were obtained when individual aphids were micro-injected with 2 ng virus and subsequently allowed to feed on healthy plants. Ultrastructural studies of A. solani and M. persicae indicated that both SbDV-D and SbDV-Va20 were acquired specifically through the aphid hindgut. No difference in hindgut acquisition specificity was observed, and both A. solani and M. persicae were able to transport SbDV-D and SbDV-Va20 into the haemocoel by endocytotic/exocytotic pathways. When injected, SbDV was shown to be associated with only the accessory salivary glands (ASG) in aphids, indicating a high level of tissue specificity. Two different interactions with the ASG were observed for SbDV-D and SbDV-Va20 in A. solani and M. persicae. SbDV-D penetrated the ASG basal lamina of A. solani, but was never observed in the basal lamina of M. persicae. The ASG basal lamina was a barrier to SbDV-D transmission by M. persicae. SbDV-Va19 penetrated the ASG basal lamina of both A. solani and M. persicae. However, SbDV-Va20 was not observed in the ASG cytoplasm in A. solani, indicating that the basal plasmalemma functioned as the transmission barrier. Observations indicated that capsid protein structure, aphid basal lamina composition and cell membrane components influenced virus-aphid interactions regulating SbDV transmission. Zusammenfassung Die Übertragung von Verzwergungsviren der Sojabohne (SbDV), die aus Japan (SbDV-D) bzw. dem Osten der USA (SbDV-Va20) stammten, wurde in Vektor und Nichtvektor-Blattlausarten geprüft. Eine absolute Vektorspezifität wurde stets festgestellt, wenn Aulacorthum solani, Acyrthosiphon pisum und Myzus persicae Lösungen mit einem der Viren (100 ,gml -1) durch Parafilm© Membranen aufnehmen konnten. SbDV-D wurde nur von A. solaniübertragen, SbDV-Va20 nur von A. pisum und M. persicae.Ähnliche Ergebnisse wurden erhalten, wenn einzelne Blattläuse Mikroinjektionen mit 2 ng Virus erhielten und anschließend an gesunden Pflanzen saugen konnten. Feinstrukturelle Untersuchungen von A. solani und M. persicae ergaben, daß SbDV-D und SbDV-Va20 spezifisch durch den Enddarm der Blattläuse aufgenommen wurden. Bei der Aufnahme durch den Enddarm wurde keine unterschiedliche Spezifität festgestellt; A. solani und M. persicae konnten SbDV-D und SbDV-Va20 durch Endo-/Exocytose in die Leibeshöhle aufnehmen. Nach Injektion wurde SbDV bei Blattläusen nur in Assoziation mit den akzessorischen Speicheldrüsen (ASG) beobachtet, was auf eine hohe Gewebsspezifität hindeutet. SbDV-D und SbDV-Va20 zeigten in A. solani und M. persicae zwei unterschiedliche Reaktionen mit den ASG. SbDV-D penetrierte die Basalmembran der ASG von A. solani, wurde in der Basalmembran von M. persicae jedoch in keinem Fall gefunden. Die Basalmembran der ASG fungierte bei M. persicae als Hindernis für eine Übertragung von SbDV-D. SbDV-Va20 penetrierte die Basalmembranen von A. solani und von M. persicae. SbDV-Va20 wurde im ASG-Cytoplasma von A. solani jedoch nicht festgestellt, was darauf hindeutet, daß das Basalplasmalemma als Übertragungshindernis fungierte. Unsere Beobachtungen zeigen, daß die Struktur des Hüllproteins, die Zusammensetzung der Basalmembranen der Blattläuse und die Zellwandbestandteile die Interaktionen zwischen Viren und Blattläusen beeinflussen, welche die SbDV-Übertragung regulieren. [source] Markers for the lymphatic endothelium: In search of the holy grail?MICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2001Jonathan P. Sleeman Abstract The ability to discriminate reliably at the histological level between blood and lymphatic microcapillaries would greatly assist the study of a number of biological and pathological questions and may also be of clinical utility. A structure,function comparison of these types of microcapillary suggests that differences which could function as markers to allow discrimination between blood and lymphatic endothelium should exist. Indeed, to date a variety of such markers have been proposed, including basement membrane components, constituents of junctional complexes such as desmoplakin and enzymes such as 5,-nucleotidase. Additionally, a variety of cell surface molecules are thought to be differentially expressed, including PAL-E, VEGFR-3, podoplanin, and LYVE-1. Several of the lymphatic markers proposed in the literature require further characterization to demonstrate fully their lymphatic specificity and some have proven not to be reliable. The relative merits and drawbacks of each of the proposed markers is discussed. Microsc. Res. Tech. 55:61,69, 2001. © 2001 Wiley-Liss, Inc. [source] Expression of basement membrane components in odontogenic cystsORAL DISEASES, Issue 3 2006S Poomsawat Objective:, To compare the expression of basement membrane components (BMCs), including laminins 1 and 5, collagen type IV, and fibronectin in odontogenic keratocysts (OKCs) with dentigerous cysts (DCs) and radicular cysts (RCs). Materials and methods:, Basement membrane components were analysed in 20 OKCs, 20 DCs and 20 RCs using an immunohistochemical technique. Results:, Odontogenic keratocysts, DCs and RCs showed positive reaction to all BMCs studied, with different distributions and intensity. OKCs showed continuous linear deposits for laminins 1 and 5 but two staining patterns (continuous and discontinuous) for collagen type IV and fibronectin. DCs exhibited continuous linear deposits for laminins 1 and 5 and collagen type IV but a discontinuous linear deposit for fibronectin. RCs displayed similar results to DCs for laminin 1, collagen type IV and fibronectin. Laminin 5 in RCs had two staining patterns. Constant results in all cysts were strong intensity for laminin 1 and moderate intensity for laminin 5. Conclusions:, Substantial differences in the expression of BMCs among studied cysts were not observed, suggesting that the separation of the epithelial lining in OKCs is not associated with the existence of these proteins. [source] Hg2+ Reacts with Different Components of the NADPH: Protochlorophyllide Oxidoreductase MacrodomainsPLANT BIOLOGY, Issue 3 2004K. Solymosi Abstract: The molecular background of Hg2+ -induced inhibition of protochlorophyllide (Pchlide) photoreduction was investigated in homogenates of dark-grown wheat leaves. Our earlier work showed that 15 min incubation with 10 -2 M Hg2+ completely inhibits the activity of NADPH: Pchlide oxidoreductase. Detailed analysis of spectra recorded at 10 K indicated the appearance of emission bands at 638 and 650 nm, which are characteristic for NADP+ -Pchlide complexes. Fluorescence emission spectra recorded with different excitation wavelengths, fluorescence lifetime measurements and the analysis of acetone extractions revealed that Hg2+ can also react directly with Pchlide, resulting in protopheophorbide formation. At 10 -3 M Hg2+, the phototransformation was complete but the blue shift of the chlorophyllide emission band speeded up remarkably. This indicates oxidation of the NADPH molecules that have a structural role in keeping together the etioplast inner membrane components. We suggest a complex model for the Hg2+ effect: depending on concentration it can react with any components of the NADPH: Pchlide oxidoreductase macrodomains. [source] An Antimicrobial Peptide Modulates Epithelial Responses to Bacterial ProductsTHE LARYNGOSCOPE, Issue 5 2008Marcel J. Vonk BSc Abstract Introduction: Changes in the respiratory epithelium and chronic and recurrent infections are thought to play a central role in the pathogenesis of otitis media and sinusitis. The airway epithelium is the primary defense system of the respiratory tract. Bacterial cell membrane components like lipopolysaccharide (LPS) and lipoteichoic acid (LTA) can affect the mucociliary clearance function of the respiratory epithelium. P60.4-Ac is a synthetic antimicrobial peptide based on the structure of the cathelicidin LL-37 that neutralizes the pro-inflammatory activity of LPS and LTA. Materials and Methods: Normal respiratory sinus epithelium was cultured at the air liquid interface. The cells were incubated with LPS or LTA in the presence or absence of P60.4-Ac. Results: P60.4-Ac neutralized the LPS- and LTA- induced effect on air-liquid interface cultured epithelial cells. P60.4-Ac significantly inhibited the increase in the epithelial layer caused by LPS or LTA. Conclusion: These data demonstrate that P60.4-Ac might be of clinical benefit in the management of otitis media with effusion and sinusitis. [source] Effects of impurities on membrane-protein crystallization in different systemsACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2009Christopher A. Kors When starting a protein-crystallization project, scientists are faced with several unknowns. Amongst them are these questions: (i) is the purity of the starting material sufficient? and (ii) which type of crystallization experiment is the most promising to conduct? The difficulty in purifying active membrane-protein samples for crystallization trials and the high costs associated with producing such samples require an extremely pragmatic approach. Additionally, practical guidelines are needed to increase the efficiency of membrane-protein crystallization. In order to address these conundrums, the effects of commonly encountered impurities on various membrane-protein crystallization regimes have been investigated and it was found that the lipidic cubic phase (LCP) based crystallization methodology is more robust than crystallization in detergent environments using vapor diffusion or microbatch approaches in its ability to tolerate contamination in the forms of protein, lipid or other general membrane components. LCP-based crystallizations produced crystals of the photosynthetic reaction center (RC) of Rhodobacter sphaeroides from samples with substantial levels of residual impurities. Crystals were obtained with protein contamination levels of up to 50% and the addition of lipid material and membrane fragments to pure samples of RC had little effect on the number or on the quality of crystals obtained in LCP-based crystallization screens. If generally applicable, this tolerance for impurities may avoid the need for samples of ultrahigh purity when undertaking initial crystallization screening trials to determine preliminary crystallization conditions that can be optimized for a given target protein. [source] Structural studies of MIP synthaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2000Adam J. Stein The conversion of glucose 6-phosphate to 1- l - myo -inositol 1-phosphate (MIP) by 1- l - myo -inositol 1-phosphate synthase (MIP synthase) is the first committed and rate-limiting step in the de novo biosynthesis of inositol in all eukaryotes. The importance of inositol-containing molecules both as membrane components and as critical second messenger signal-transduction species make the function and regulation of this enzyme important for a host of biologically important cellular functions including proliferation, neurostimulation, secretion and contraction. MIP synthase has been overexpressed in Esherichia coli and purified to homogeneity by chromatographic methods. Two crystal forms of MIP synthase were obtained by the hanging-drop vapor-diffusion method. Native data sets for both crystal forms were collected in-house on a Rigaku R-AXIS IIC imaging-plate detector. Crystal form I belongs to space group C2, with unit-cell parameters a = 153.0, b = 96.6, c = 122.6,Å, , = 126.4°, and diffracts to 2.5,Å resolution. Crystal form II belongs to space group P21, with unit-cell parameters a = 94.5, b = 186.2, c = 86.5,Å, , = 110.5°, and diffracts to 2.9,Å resolution. [source] Emerging mechanisms in morphogen-mediated axon guidanceBIOESSAYS, Issue 10 2009Cristina Sánchez-Camacho Abstract Early in animal development, gradients of secreted morphogenic molecules, such as Sonic hedgehog (Shh), Wnt and TGF,/Bmp family members, regulate cell proliferation and determine the fate and phenotype of the target cells by activating well-characterized signalling pathways, which ultimately control gene transcription. Shh, Wnt and TGF,/Bmp signalling also play an important and evolutionary conserved role in neural circuit assembly. They regulate neuronal polarization, axon and dendrite development and synaptogenesis, processes that require rapid and local changes in cytoskeletal organization and plasma membrane components. A key question then is whether morphogen signalling at the growth cone uses similar mechanisms and intracellular pathway components to those described for morphogen-mediated cell specification. This review discusses recent advances towards the understanding of this problem, showing how Shh, Wnt and TGF,/Bmp have adapted their ,classical' signalling pathways or adopted alternative and novel molecular mechanisms to influence different aspects of neuronal circuit formation. [source] Channel-like crystal structure of cinchoninium L - O -phosphoserine salt dihydrateCHIRALITY, Issue 6 2010Aleksandra Wese, ucha-Birczy Abstract Studies on the interactions between L - O - phosphoserine, as one of the simplest fragments of membrane components, and the Cinchona alkaloid cinchonine, in the crystalline state were performed. Cinchoninium L - O -phosposerine salt dihydrate (PhSerCin) crystallizes in a monoclinic crystal system, space group P21, with unit cell parameters: a = 8.45400(10) Å, b = 7.17100(10) Å, c = 20.7760(4) Å, , = 90°, , = 98.7830(10)°, , = 90°, Z = 2. The asymmetric unit consists of the cinchoninium cation linked by hydrogen bonds to a phosphoserine anion and two water molecules. Intermolecular hydrogen bonds connecting phosphoserine anions via water molecules form chains extended along the b axis. Two such chains symmetrically related by twofold screw axis create a "channel." On both sides of this channel cinchonine cations are attached by hydrogen bonds in which the atoms N1, O12, and water molecules participate. This arrangement mimics the system of bilayer biological membrane. Chirality 2010. © 2009 Wiley-Liss, Inc. [source] Suppressive activity of fexofenadine hydrochloride on metalloproteinase production from nasal fibroblasts in vitroCLINICAL & EXPERIMENTAL ALLERGY, Issue 12 2004K. Asano Summary Background Allergic rhinitis (AR) is an inflammatory disease characterized by nasal wall remodelling with intense infiltration of eosinophils and mast cells/basophils. Matrix metalloproteinases (MMPs), MMP-2 and MMP-9, are the major proteolytic enzymes that induce airway remodelling. These enzymes are also important in the migration of inflammatory cells through basement membrane components. Objective We evaluated whether fexofenadine hydrochloride (FEX), the carboxylic acid metabolite of terfenadine with selective H1 -receptor antagonist activity, could inhibit MMP production from nasal fibroblasts (NFs) in response to TNF-, stimulation in vitro. Methods NFs were established from nasal polyp-derived fibroblasts (PFs) taken from patients with AR. Nasal mucosal fibroblasts (MFs) were also induced from nasal mucosal tissues from septal deformity patients without allergy. PF and MF (2 × 105 cells/mL, each) were stimulated with TNF-, in the presence of various concentrations of FEX. After 24 h, culture supernatants were obtained and assayed for MMP-2, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 levels by ELISA. The influence of FEX on mRNA expression of MMPs and TIMPs in 4 h-cultured cells was also evaluated by real-time RT-PCR. Furthermore, nuclear factor-,B (NF-,B) activation in fibroblasts treated with FEX for 4 h was examined by ELISA. Results FEX at more than 350 ng/mL inhibited the production of MMP-2 and MMP-9 from both PF and MF in response to TNF-, stimulation, whereas TIMP-1 and TIMP-2 production was scarcely affected by FEX. FEX also inhibited MMP mRNA expression and NF-,B activation in PF and MF after TNF-, stimulation. Conclusion The present data suggest that the attenuating effect of FEX on MMP-2 and -9 production from NFs induced by inflammatory stimulation may underlie the therapeutic mode of action of the agent on allergic diseases, including AR. [source] | ||||||||||||||||