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Alternative Pathway (alternative + pathway)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	23%
Chemistry	19%
Humanities and Social Sciences	5%

Selected Abstracts

METAMORPHOSIS AND NEOTENY: ALTERNATIVE PATHWAYS IN AN EXTINCT AMPHIBIAN CLADE

EVOLUTION, Issue 7 2006
Rainer R. Schoch
Abstract The Branchiosauridae was a clade of small amphibians from the Permo-Carboniferous with an overall salamander-like appearance. The clade is distinguished by an extraordinary fossil record that comprises hundreds of well-preserved specimens, representing a wide range of ontogenetic stages. Branchiosaurids had external gills and weakly ossified skeletons, and due to this larval appearance their status as neotenic (perennibranchiate) froms has long been accepted. Despite their extensive fossil record large specimens with an adult morphology appeared to be lacking altogether, but recently two adult specimens were identified in a rich sample of Apateon gracilis collected in the 19th century from a locality near Dresden, Saxony. These specimens are unique among branchiosaurids in showing a high level of ossification, including bones that have never been reported in a branchiosaur. These highlight the successive formation of features believed to indicate terrestrial locomotion, as well as feeding on larger prey items. Moreover, these transformations occurred in a small time window (whereas the degree of size increase is used as a proxy of time) and the degree of concentration of developmental events in branchiosaurids is unique among tetrapods outside the lissamphibians. These specimens are compared with large adults of the neotenic branchiosaurid Apateon caducus from the Saar-Nahe Basin, which despite their largetr body size lack the features found in the adult. A. gracilis specimens. These specimens give new insight into patterns of metamorphosis (morphological transformation) in branchiosaurids that are believed to be correlated to a change of habitat, and clearly show that different life-history pathways comparable to those of modern salamanders were already estabilshed in this Paleozoic clade. [source]

ORIGINAL ARTICLE: Activation of the Alternative Pathway of Complement is a Feature of Pre-Term Parturition but not of Spontaneous Labor at Term

AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 4 2010
Edi Vaisbuch
Citation Vaisbuch E, Romero R, Erez O, Mazaki-Tovi S, Kusanovic JP, Soto E, Dong Z, Chaiworapongsa T, Kim SK, Ogge G, Pacora P, Yeo L, Hassan SS. Activation of the alternative pathway of complement is a feature of pre-term parturition but not of spontaneous labor at term. Am J Reprod Immunol 2010; 63: 318,330 Problem, Plasma concentrations of fragment Bb (FBb) are a marker for activation of the alternative pathway of the complement system. High concentrations of FBb in maternal blood, as early as the first trimester, are associated with subsequent spontaneous pre-term delivery <34 weeks of gestation. The aim of this study was to determine whether spontaneous pre-term labor (PTL) with intact membranes, intra-amniotic infection/inflammation (IAI) or labor at term are associated with alterations in circulating maternal FBb concentrations. Method of study, This cross-sectional study included women in the following groups: (i) non-pregnant (n = 40); (ii) normal pregnancy (gestational age range 20,36, 6/7 weeks, n = 63); (iii) women at term not in labor (n = 70); (iv) women at term in spontaneous labor (n = 59); (v) patients with an episode of PTL who delivered at term (n = 62); (vi) PTL without IAI who delivered pre-term (n = 30); and (vii) PTL with IAI who delivered pre-term (n = 67). Maternal plasma FBb concentrations were determined by ELISA. Results, (i) Among patients with PTL, those who had a pre-term delivery either with IAI (1.21 ,g/mL, IQR 0.77,2.16) or without IAI (1.13 ,g/mL, IQR 0.92,2.08) had a higher median maternal plasma FBb concentration than those who delivered at term (0.86 ,g/mL, IQR 0.64,1.57; P = 0.007 and P = 0.026, respectively); (ii) there was no difference in the median plasma FBb concentration between patients with and without IAI who delivered pre-term (P = 0.9); (iii) in contrast, spontaneous labor at term was not associated with a significant change in the maternal plasma FBb concentration (P = 0.8); (iv) maternal plasma concentration of FBb did not differ significantly between normal pregnant women and the non-pregnant controls (P = 0.8) and were not correlated with advancing gestational age (r = ,0.28, P = 0.8). Conclusion, (i) Pre-term parturition is associated with activation of the alternative complement pathway in maternal circulation; (ii) such activation is not detectable in spontaneous labor at term; (iii) IAI does not explain the activation of the alternative pathway of complement in PTL. Collectively, these observations suggest that pre-term and term labors have fundamental differences in the regulation of innate immunity. [source]

Alternative Pathways to Community and Economic Development: The Latrobe Valley Community Partnering Project

GEOGRAPHICAL RESEARCH, Issue 3 2005
JENNY CAMERON
Abstract Conventional approaches to development in areas that are experiencing economic decline invariably focus on business growth through interventions such as incentives, infrastructure development and job readiness training. This paper reports on a pilot project aimed at developing an alternative approach to community and economic development in the context of the Latrobe Valley, Victoria, a resource region that has experienced downsizing and privatisation of its major employer, the state-owned power industry. The project was shaped by a poststructuralist concern with the effects of representation. It sought to challenge familiar understandings of disadvantaged areas, the economy, community and the research process in order to open up new ways of addressing social and economic issues. The resulting four-stage research project was informed by the techniques of asset-based community development and action research, as well as by discourses of the diverse economy and communities of difference. During the two-year span of the project, four community enterprises were developed. The varying degrees of success they have met with in the four years since the project concluded highlight the critical role of local agencies such as the council in providing ongoing support for such endeavours. [source]

Up-regulation of leukocyte CXCR4 expression by sulfatide: An L-selectin-dependent pathway on CD4+ T cells

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2007
Pascal Duchesneau
Abstract CXCR4 plays significant roles in immune and inflammatory responses and is important for selective recruitment of leukocytes. We previously showed that CXCR4 surface expression of human lymphocytes was affected by sulfatide, an in vivo ligand for L-selectin. Increased CXCR4 expression was shown to promote biologically relevant functions such as integrin-dependent adhesion and transmigration. Here, we show that sulfatide-induced CXCR4 up-regulation also occurs on other leukocyte subsets in humans and mice. B cells and CD4+CD25+ T cells had the highest CXCR4 up-regulation after sulfatide stimulation. Transfection of L-selectin was sufficient for K562 cells to acquire sulfatide-induced CXCR4 up-regulation, while analysis of L-selectin knockout mice revealed that this response was critically L-selectin dependent only for CD4+ T cells, suggesting an alternative pathway in CD8+ T cells and B cells. Sulfatide triggered several intracellular signaling events in CD4+ T cells, but only tyrosine kinase activation, including members of the Src family, were essential for L-selectin to CXCR4 signaling. CXCR4 up-regulation was rapid, enhanced CXCL12-induced signaling and increased chemotaxis toward CXCL12, and therefore has potentially important roles in vivo. Thus, the response to CXCL12 depends in part on tissue expression of sulfatide and, specifically in CD4+ T cells, also depends on the surface level of L-selectin. [source]

A crucial role for macrophages in the pathology of K/B,×,N serum-induced arthritis

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2005
Samuel Solomon
Abstract Autoantibodies in the form of immune complexes are known to be crucial mediators in initiating inflammation in a variety of autoimmune diseases. This has been well documented in the anti-collagen,II antibody-induced arthritis animal model for a long time now. Recently, in the K/B,×,N mouse model (the F1 of the TCR-transgenic KRN and the diabetic NOD mice), anti-glucose-6-phosphate isomerase (GPI) autoantibodies have been shown to induce arthritis. Experimental work in the K/B,×,N model demonstrated key roles of autoantigenic immune complexes activating the alternative pathway of complement, the subsequent association with C5aR and Fc,RIII-mediated cell activation and production of the inflammatory cytokines IL-1 and TNF-,, finally leading to joint destruction. The presence of high amounts of inflammatory cytokines and matrix-degrading proteases at sites of inflammation obviously put the cytokine-producing macrophages as the next target for investigation in this model. Here, we show that mice depleted of macrophages by clodronate liposome treatment are completely resistant to K/B,×,N serum-induced arthritis. Reconstituting clodronate liposome-treated mice with macrophages from naive animals could reverse this resistance. Also, we found that deficiencies in the Wiskott-Aldrich syndrome protein and CD40, which are both implicated in macrophage activation, chemotaxis and phagocytosis, are not essential in serum-induced arthritis. Mast cell degranulation was seen in arthritogenic serum-treated mice even in the absence of macrophages, possibly suggesting that mast cell degranulation/activation acts hierarchically before macrophages in the inflammatory cascade of anti-GPI antibody-induced arthritis. [source]

Observations on the Synthesis of Photochromic Naphthopyrans

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2003
Christopher D. Gabbutt
Abstract 1-Naphthol reacts with 1,1-diarylprop-2-yn-1-ols 5a,b, under alumina catalysis, by two pathways to give the photochromic naphtho[1,2- b]pyrans 6a,b, together with the propenylidenenaphthalenones 7a,b, representatives of a new class of merocyanine dyes. With 2-methyl-1-naphthol, formation of the photochrome is suppressed; the only products are merocyanines 7c,d. The cyclocondensation of 2-naphthol with 5a,b proceeds much more efficiently, to give the naphtho[2,1- b]pyrans 14a,b. Pyran formation is not suppressed from either 1-bromo- or 1-(4-methoxyphenyl)-2-naphthol; reaction with 5a,b merely results in expulsion of the C-1 substituent. An alternative pathway supervenes in the reaction of 1-methyl-2-naphthol with 5a to give the benz[e]indanone 17, the constitution of which was determined by X-ray crystallography. Reaction of the 1,3,3-triarylpropynols 19a,b with 1-naphthol affords the naphthopyrans 20 together with merocyanines 21, whilst the isomeric pyrans 23 are efficiently produced from 2-naphthol. The configuration of merocyanines 7a and 21a was unequivocally established by X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Metabolic fate of l -lactaldehyde derived from an alternative l -rhamnose pathway

FEBS JOURNAL, Issue 20 2008
Seiya Watanabe
Fungal Pichia stipitis and bacterial Azotobacter vinelandii possess an alternative pathway of l -rhamnose metabolism, which is different from the known bacterial pathway. In a previous study (Watanabe S, Saimura M & Makino K (2008) Eukaryotic and bacterial gene clusters related to an alternative pathway of non-phosphorylated l -rhamnose metabolism. J Biol Chem283, 20372,20382), we identified and characterized the gene clusters encoding the four metabolic enzymes [l -rhamnose 1-dehydrogenase (LRA1), l -rhamnono-,-lactonase (LRA2), l -rhamnonate dehydratase (LRA3) and l -2-keto-3-deoxyrhamnonate aldolase (LRA4)]. In the known and alternative l -rhamnose pathways, l -lactaldehyde is commonly produced from l -2-keto-3-deoxyrhamnonate and l -rhamnulose 1-phosphate by each specific aldolase, respectively. To estimate the metabolic fate of l -lactaldehyde in fungi, we purified l -lactaldehyde dehydrogenase (LADH) from P. stipitis cells l -rhamnose-grown to homogeneity, and identified the gene encoding this enzyme (PsLADH) by matrix-assisted laser desorption ionization-quadruple ion trap-time of flight mass spectrometry. In contrast, LADH of A. vinelandii (AvLADH) was clustered with the LRA1,4 gene on the genome. Physiological characterization using recombinant enzymes revealed that, of the tested aldehyde substrates, l -lactaldehyde is the best substrate for both PsLADH and AvLADH, and that PsLADH shows broad substrate specificity and relaxed coenzyme specificity compared with AvLADH. In the phylogenetic tree of the aldehyde dehydrogenase superfamily, PsLADH is poorly related to the known bacterial LADHs, including that of Escherichia coli (EcLADH). However, despite its involvement in different l -rhamnose metabolism, AvLADH belongs to the same subfamily as EcLADH. This suggests that the substrate specificities for l -lactaldehyde between fungal and bacterial LADHs have been acquired independently. [source]

Complement Activation in Emergency Department Patients With Severe Sepsis

ACADEMIC EMERGENCY MEDICINE, Issue 4 2010
John G. Younger
Abstract Objectives:, This study assessed the extent and mechanism of complement activation in community-acquired sepsis at presentation to the emergency department (ED) and following 24 hours of quantitative resuscitation. Methods:, A prospective pilot study of patients with severe sepsis and healthy controls was conducted among individuals presenting to a tertiary care ED. Resuscitation, including antibiotics and therapies to normalize central venous and mean arterial pressure (MAP) and central venous oxygenation, was performed on all patients. Serum levels of Factor Bb (alternative pathway), C4d (classical and mannose-binding lectin [MBL] pathway), C3, C3a, and C5a were determined at presentation and 24 hours later among patients. Results:, Twenty patients and 10 healthy volunteer controls were enrolled. Compared to volunteers, all proteins measured were abnormally higher among septic patients (C4d 3.5-fold; Factor Bb 6.1-fold; C3 0.8-fold; C3a 11.6-fold; C5a 1.8-fold). Elevations in C5a were most strongly correlated with alternative pathway activation. Surprisingly, a slight but significant inverse relationship between illness severity (by sequential organ failure assessment [SOFA] score) and C5a levels at presentation was noted. Twenty-four hours of structured resuscitation did not, on average, affect any of the mediators studied. Conclusions:, Patients with community-acquired sepsis have extensive complement activation, particularly of the alternative pathway, at the time of presentation that was not significantly reversed by 24 hours of aggressive resuscitation. ACADEMIC EMERGENCY MEDICINE,2010; 17:353,359 © 2010 by the Society for Academic Emergency Medicine [source]

Lymphoid microenvironment in the gut for immunoglobulin A and inflammation

IMMUNOLOGICAL REVIEWS, Issue 1 2003
Robert Chin
Summary:, Signaling through lymphotoxin , receptor (LT,R) initiates the unfolding of a host of developmental programs ranging from the organogenesis of lymph nodes and Peyer's patches (PPs) to the coordination of splenic microarchitecture. While investigating an alternative pathway to immunoglobulin A (IgA) production, it was uncovered that LT,R signaling in the lamina propria (LP) stroma orchestrates the coordinated expression of key chemokines and adhesion molecules, creation of a cytokine milieu, and stroma development that facilitates robust IgA production independent of secondary lymphoid structures. Simultaneously, this same infrastructure can be commandeered by autoreactive T cells to organize both the acute destruction of the intestinal mucosa and chronic intestinal inflammation via the ligands for LT,R. The ability to modulate LT,R signaling may alternatively permit the suppression of autoimmune responses and augmentation of gut defenses. [source]

The ancestral complement system in sea urchins

IMMUNOLOGICAL REVIEWS, Issue 1 2001
L. Courtney Smith
Summary: The origin of adaptive immunity in the vertebrates can be traced to the appearance of the ancestral RAG genes in the ancestral jawed vertebrate; however, the innate immune system is more ancient. A central subsystem within innate immunity is the complement system, which has been identified throughout and seems to be restricted to the deuterostomes. The evolutionary history of complement can be traced from the sea urchins (members of the echinoderm phylum), which have a simplified system homologous to the alternative pathway, through the agnathans (hagfish and lamprey) and the elasmobranchs (sharks and rays) to the teleosts (bony fish) and tetrapods, with increases in the numbers of complement components and duplications in complement pathways. Increasing complexity in the complement system parallels increasing complexity in the deuterostome animals. This review focuses on the simplest of the complement systems that is present in the sea urchin. Two components have been identified that show significant homology to vertebrate C3 and factor B (Bf), called SpC3 and SpBf, respectively. Sequence analysis from both molecules reveals their ancestral characteristics. Immune challenge of sea urchins indicates that SpC3 is inducible and is present in coelomic fluid (the body fluids) in relatively high concentrations, while SpBf expression is constitutive and is present in much lower concentrations. Opsonization of foreign cells and particles followed by augmented uptake by phagocytic coelomocytes appears to be a central function for this simpler complement system and important for host defense in the sea urchin. These activities are similar to some of the functions of the homologous proteins in the vertebrate complement system. The selective advantage for the ancestral deuterostome may have been the amplification feedback loop that is still of central importance in the alternative pathway of complement in higher vertebrates. Feedback loop functions would quickly coat pathogens with complement leading to phagocytosis and removal of foreign cells, a system that would be significantly more effective than an opsonin that binds upon contact as a result of simple diffusion. An understanding of the immune response of the sea urchin, an animal that is a good estimator of what the ancestral deuterostome immune system was like, will aid us in understanding how adaptive immunity might have been selected for during the early evolution of the vertebrates and how it might have been integrated into the pre-existing innate immune system that was already in place in those animals. The authors are grateful to Drs Sham Nair and Paul Gross for their critique of the manuscript and helpful suggestions. This work was supported by the National Science Foundation (MCB 9603086). [source]

The delicate balance between male and female sex determining pathways: potential for disruption of early steps in sexual development

INTERNATIONAL JOURNAL OF ANDROLOGY, Issue 2 2010
P. Koopman
Summary Testes and ovaries develop from the same primordial structures, the genital ridges, in the mammalian foetus. Male development depends critically on the correct functioning of the Y-linked testis-determining gene, Sry. However, Sry is highly vulnerable to mutation, and so does not provide a very robust sex-determining mechanism. Both in testes and in ovaries, proper gonadal development involves co-ordinated regulation of the bipotential fates of a number of different cell lineages, and is dependent on intercellular signalling mechanisms. If either the testicular or ovarian pathway stalls in the early stages, mechanisms operate to engage the alternative pathway. For these reasons, the early steps in mammalian sexual development are vulnerable to genetic and environmental perturbation, and represent possible points of action of endocrine disrupting compounds. [source]

The Effect of Short Warm Breaks during Chilling on Photosynthesis and the Activity of Antioxidant Enzymes in Plants Sensitive to Chilling

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2000
G. Skrudlik
The effect of short warm breaks (from 15 min to 5 h) during chilling of three chilling-sensitive species (tomato, maize and soybean) was investigated. Injuries, intensity of net photosynthesis and antioxidant enzyme activity were measured. Throughout chilling treatment, plants were warmed by transferring them during the last few hours of the light phase from chilling temperature (5 °C for tomato and maize, 2 °C for soybean) to 20 °C. After warming, seedlings were moved back to chilling conditions. Warm breaks of 5 h almost entirely prevented the appearance of injuries, as measured by changes in leakage of electrolytes and tissue water content, during 12 days of chilling. Even a 15-min warm break ensured a significant decrease in injuries in chilled maize seedlings compared to continuously chilled seedlings. Inhibition of gas exchange and fluorescence in seedlings of two maize genotypes differing in chilling resistance was, to a small extent, prevented by 1-h warm breaks, while 4-h warm breaks reduced inhibition significantly. The length of the warm break (1 or 4 h) had no influence on changes in SOD activity compared to continuously chilled plants, but warm breaks of 4 h produced a significant increase in CAT activity. The possible influence of an alternative pathway in preventing injuries is discussed. Zusammenfassung Der Einfluß kurzer warmer Phasen (5 Std. bis 15 Min.) während der Kuühlephase auf drei kühleempfindliche Arten (Tomate, Mais und Sojabohne) wurden untersucht. Schäden, Intensität der Netto-Photosynthese und antioxidierender Enzymaktivität wurden gemessen. Während der Kühlebehandlung wurden die Pflanzen erwärmt, indem sie in den letzten Stunden der Belichtungsphase von den Kühletemperaturen (5 °C für Tomate und Mais, 2 °C für Sojabohnen) unter eine Temperatur von 20 °C verbracht wurden. Nach dem Aufwärmen der Sämlinge wurden sie unter die Kühlebedingungen zurückgebracht. 5 h Wärmeunterbrechungen vermieden nahezu vollständig das Auftreten von Beschädigungen, wie eine Messung der Änderungen im Austritt von Elektrolyten und dem Gewebewassergehalt während der 12 Stunden Kühle zeigten. Selbst 15-Min. Wärmeunterbrechung sicherten eine signifikante Abnahme der Schädigungen von gekühlten Maissämlingen im Vergleich zu ununterbrochen gekühlten Pflanzen. Der Gasaustausch und die Fluoreszensinhibierung von zwei Maisgenotypensämlingen mit unterschiedlicher Kühleresistenz waren in einem geringen Ausmaß vermindert bei 1 h Warmunterbrechung; lediglich 4 h Wärmunterbrechung erwies sich als günstig. Die Länge der Warmunterbrechungen (1 oder 4 h) hatte keinen Einfluß auf Änderungen in der SOD-Aktivität im Vergleich zu kontinuierlich gekühlten Pflanzen; Verlängerungen bis zuf vier Stunden Warmunterbrechungen führten zu einer signifikanten Zunahme der CAT-Aktivität. Eine mögliche Einwirkung alternativer Wege in der Verhinderung von Schäden wird diskutiert. [source]

The pivotal role of the alternative NF-,B pathway in maintenance of basal bone homeostasis and osteoclastogenesis,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2010
Niroshani S Soysa
Abstract The alternative NF-,B pathway consists predominantly of NF-,B-inducing kinase (NIK), I,B kinase , (IKK,), p100/p52, and RelB. The hallmark of the alternative NF-,B signaling is the processing of p100 into p52 through NIK, thus allowing the binding of p52 and RelB. The physiologic relevance of alternative NF-,B activation in bone biology, however, is not well understood. To elucidate the role of the alternative pathway in bone homeostasis, we first analyzed alymphoplasic (aly/aly) mice, which have a defective NIK and are unable to process p100, resulting in the absence of p52. We observed increased bone mineral density (BMD) and bone volume, indicating an osteopetrotic phenotype. These mice also have a significant defect in RANKL-induced osteoclastogenesis in vitro and in vivo. NF-,B DNA-binding assays revealed reduced activity of RelA, RelB, and p50 and no binding activity of p52 in aly/aly osteoclast nuclear extracts after RANKL stimulation. To determine the role of p100 itself without the influence of a concomitant lack of p52, we used p100,/, mice, which specifically lack the p100 inhibitor but still express p52. p100,/, mice have an osteopenic phenotype owing to the increased osteoclast and decreased osteoblast numbers that was rescued by the deletion of one allele of the relB gene. Deletion of both allele of relB resulted in a significantly increased bone mass owing to decreased osteoclast activity and increased osteoblast numbers compared with wild-type (WT) controls, revealing a hitherto unknown role for RelB in bone formation. Our data suggest a pivotal role of the alternative NF-,B pathway, especially of the inhibitory role of p100, in both basal and stimulated osteoclastogenesis and the importance of RelB in both bone formation and resorption. © 2010 American Society for Bone and Mineral Research [source]

Insulin-like growth factor (IGF) binding protein-3 regulation of IGF-I is altered in an acidic extracellular environment

JOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2001
Kimberly E. Forsten
While extracellular acidification within solid tumors is well-documented, how reduced pH impacts regulation of insulin-like growth factor-I (IGF-I) has not been studied extensively. Because IGF-I receptor binding is affected by IGF binding proteins (IGFBPs), we examined how pH impacted IGFBP-3 regulation of IGF-I. IGF-I binding in the absence of IGFBP-3 was diminished at reduced pH. Addition of IGFBP-3 reduced IGF-I cell binding at pH 7.4 but increased surface association at pH 5.8. This increase in IGF-I binding at pH 5.8 corresponded with an increase in IGFBP-3 cell association. This, however, was not due to an increase in affinity of IGFBP-3 for heparin at reduced pH although both heparinase III treatment and heparin addition reduced IGFBP-3 enhancement of IGF-I binding. An increase in IGF-I binding to IGFBP-3, though, was seen at reduced pH using a cell-free assay. We hypothesize that the enhanced binding of IGF-I at pH 5.8 is facilitated by increased association of IGFBP-3 at this pH and that the resulting cell associated IGF-I is IGFBP-3 and not IGF-IR bound. Increased internalization and nuclear association of IGF-I at pH 5.8 in the presence of IGFBP-3 was evident, yet cell proliferation was reduced by IGFBP-3 at both pH 5.8 and 7.4 indicating that IGFBP-3-cell associated IGF-I does not signal the cell to proliferate and that the resulting transfer of bound IGF-I from IGF-IR to IGFBP-3 results in diminished proliferation. Solution binding of IGF-I by IGFBP-3 is one means by which IGF-I-induced proliferation is inhibited. Our work suggests that an alternative pathway exists by which IGF-I and IGFBP-3 both associate with the cell surface and that this association inhibits IGF-I-induced proliferation. © 2001 Wiley-Liss, Inc. [source]

Transient leukopenia and anaphylatoxin production during granulocyte apheresis as treatment for ulcerative colitis

JOURNAL OF CLINICAL APHERESIS, Issue 3 2002
Katsuhiko Yonemura
Abstract It is well known that transient leukopenia due to activation of the alternative pathway of the complement system accompanies hemodialysis when cellulose acetate dialyzers are used. However, it has not been evaluated whether leukopenia also occurs during granulocyte apheresis (GCAP) as treatment for ulcerative colitis, in which an extracorporeal column is filled with cellulose acetate beads in order to remove circulating leukocytes. The aim of the present study was to evaluate whether transient leukopenia and activation of the alternative pathway of the complement system were observed during GCAP. In 8 patients undergoing GCAP weekly for 10 weeks, circulating leukocyte counts and plasma concentrations of C3a, a product of the activated alternative pathway of the complement system, were determined. GCAP elicited a rapid decline in the number of circulating leukocytes to 61.8 ± 13.8% of the baseline value after 15 minutes of GCAP (P < 0.02). Thereafter, the number of circulating leukocytes returned to approximately baseline after 60 minutes. The baseline plasma C3a concentration was 123 ± 61 ng/mL, and a significant increase to 425 ± 123 ng/mL was observed after 15 minutes of GCAP (P < 0.02). The plasma C3a concentration reached 417 ± 96 ng/mL after 60 minutes (P < 0.02). It thus follows that GCAP activates the alternative pathway of the complement system, resulting in anaphylatoxin production. J. Clin. Apheresis 17:107,110, 2002. © 2002 Wiley-Liss, Inc. [source]

The efficiency of mitochondrial electron transport chain is increased in the long-lived mrg19 Saccharomyces cerevisiae

AGING CELL, Issue 6 2009
Nitish Mittal
Summary Integrity of mitochondrial functionality is a key determinant of longevity in several organisms. In particular, reduced mitochondrial ROS (mtROS) production leading to decreased mtDNA damage is believed to be a crucial aspect of longevity. The generation of low mtROS was thought to be due to low mitochondrial oxygen consumption. However, recent studies have shown that higher mitochondrial oxygen consumption could still result in low mtROS and contribute to longevity. This increased mitochondrial efficiency (i.e. low mtROS generated despite high oxygen consumption) was explained as a result of mitochondrial biogenesis, which provides more entry points for the electrons to the electron transport chain (ETC), thereby resulting in low mtROS production. In this study, we provide evidence for the existence of an alternative pathway to explain the observed higher mitochondrial efficiency in the long-lived mrg19 mutant of Saccharomyces cerevisiae. Although we observe similar amounts of mitochondria in mrg19 and wild-type (wt) yeast, we find that mrg19 mitochondria have higher expression of ETC components per mitochondria in comparison with the wt. These findings demonstrate that more efficient mitochondria because of increased ETC per mitochondria can also produce less mtROS. Taken together, our findings provide evidence for an alternative explanation for the involvement of higher mitochondrial activity in prolonging lifespan. We anticipate that similar mechanisms might also exist in eukaryotes including human. [source]

National survey of the prevalence and conditions of selection of HIV-1 reverse transcriptase K70E mutation,

JOURNAL OF MEDICAL VIROLOGY, Issue 5 2008
C. Delaugerre
Abstract Tenofovir disoproxil fumarate (TDF) has become an important component of HIV combination therapy because of its potency and once-daily dosing. Key mutation associated with resistance to TDF is a K65R in the reverse transcriptase (RT) gene. According to occurrence of K70E mutation after failure to TDF regimen, this mutation was recently reported as a mutation associated with TDF resistance in most resistance genotypic algorithms. The aim of this study was to analyze, retrospectively, the prevalence and conditions of selection of HIV-1 RT K70E mutation from a national clinical survey. Absence of selection of K70E in 850 HIV-1-infected naive patients suggests its role in NRTI drug resistance. Prevalence of K70E RT was low (99/41601, 0.24%) in patients treated between 1999 and 2005. Conversely with K65R mutation, thymidine analog mutations (TAMs) can be concomitantly observed with K70E mutation but its frequency decreased as the number of TAM increases. Concomitant association of K65R and K70E was possible but infrequent (11%). At the time of K70E selection, 60% of patients had received or received TDF-containing regimen and one-third received exclusive NRTI regimen. In conclusion, the K70E mutation could be an alternative pathway of TDF resistance, but as the K65R mutation, other NRTI as ABC, ddI, and 3TC could be also associated with the K70E selection. J. Med. Virol. 80:762,765, 2008. © 2008 Wiley-Liss, Inc. [source]

Release of the type I secreted ,-haemolysin via outer membrane vesicles from Escherichia coli

MOLECULAR MICROBIOLOGY, Issue 1 2006
Carlos Balsalobre
Summary The ,-haemolysin is an important virulence factor commonly expressed by extraintestinal pathogenic Escherichia coli. The secretion of the ,-haemolysin is mediated by the type I secretion system and the toxin reaches the extracellular space without the formation of periplasmic intermediates presumably in a soluble form. Surprisingly, we found that a fraction of this type I secreted protein is located within outer membrane vesicles (OMVs) that are released by the bacteria. The ,-haemolysin appeared very tightly associated with the OMVs as judged by dissociation assays and proteinase susceptibility tests. The ,-haemolysin in OMVs was cytotoxically active and caused lysis of red blood cells. The OMVs containing the ,-haemolysin were distinct from the OMVs not containing ,-haemolysin, showing a lower density. Furthermore, they differed in protein composition and one component of the type I secretion system, the TolC protein, was found in the lower density vesicles. Studies of natural isolates of E. coli demonstrated that the localization of ,-haemolysin in OMVs is a common feature among haemolytic strains. We propose an alternative pathway for the transport of the type I secreted ,-haemolysin from the bacteria to the host cells during bacterial infections. [source]

Consequences of RNase E scarcity in Escherichia coli

MOLECULAR MICROBIOLOGY, Issue 4 2002
Chaitanya Jain
Summary The endoribonuclease RNase E plays an important role in RNA processing and degradation in Escherichia coli. The construction of an E. coli strain in which the cellular concentration of RNase E can be precisely controlled has made it possible to examine and quantify the effect of RNase E scarcity on RNA decay, gene regulation and cell growth. These studies show that RNase E participates in a step in the degradation of its RNA substrates that is partially or fully rate-determining. Our data also indicate that E. coli growth requires a cellular RNase E concentration at least 10,20% of normal and that the feedback mecha-nism that limits overproduction of RNase E is also able to increase its synthesis when its concentration drops below normal. The magnitude of the in-crease in RNA longevity under conditions of RNase E scarcity may be limited by an alternative pathway for RNA degradation. Additional experiments show that RNase E is a stable protein in E. coli. No other E. coli gene product, when either mutated or cloned on a multicopy plasmid, seems to be capable of compensating for an inadequate supply of this essential protein. [source]

The expression, function and regulation of mitochondrial alternative oxidase under biotic stresses

MOLECULAR PLANT PATHOLOGY, Issue 3 2010
FENG HANQING
SUMMARY To survive, plants possess elaborate defence mechanisms to protect themselves against virus or pathogen invasion. Recent studies have suggested that plant mitochondria may play an important role in host defence responses to biotic stresses. In contrast with animal mitochondria, plant mitochondria possess a unique respiratory pathway, the cyanide-insensitive alternative pathway, which is catalysed by the alternative oxidase (AOX). Much work has revealed that the genes encoding AOX, AOX protein and the alternative respiratory pathway are frequently induced during plant,pathogen (or virus) interaction. This raises the possibility that AOX is involved in host defence responses to biotic stresses. Thus, a key to the understanding of the role of mitochondrial respiration under biotic stresses is to learn the function and regulation of AOX. In this article, we focus on the theoretical and experimental progress made in the current understanding of the function and regulation of AOX under biotic stresses. We also address some speculative aspects to aid further research in this area. [source]

Neuroinvasion in sheep transmissible spongiform encephalopathies: the role of the haematogenous route

NEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 3 2009
S. Sisó
Background: It is generally believed that after oral exposure to transmissible spongiform encephalopathy (TSE) agents, neuroinvasion occurs via the enteric nervous system (ENS) and the autonomic nervous system. As a result, the dorsal motor nucleus of the vagus nerve is the initial point of disease-associated prion protein (PrPd) accumulation in the brain. Hypothesis and aim: If direct ENS invasion following oral infection results in an early and specific brain targeting for PrPd accumulation, such topographical distribution could be different when other routes of infection were used, highlighting distinct routes for neuroinvasion. Methods: An immunohistochemical study has been conducted on the brain of 67 preclinically infected sheep exposed to natural scrapie or to experimental TSE infection by various routes. Results: Initial PrPd accumulation consistently occurred in the dorsal motor nucleus of the vagus nerve followed by the hypothalamus, regardless of the breed of sheep, PrP genotype, TSE source and, notably, route of infection; these factors did not appear to affect the topographical progression of PrPd deposition in the brain either. Moreover, the early and consistent appearance of PrPd aggregates in the circumventricular organs, where the blood,brain barrier is absent, suggests that these organs can provide a portal for entry of prions when infectivity is present in blood. Conclusions: The haematogenous route, therefore, can represent a parallel or alternative pathway of neuroinvasion to ascending infection via the ENS/autonomic nervous system. [source]

Nitrogen-assimilating enzymes in land plants and algae: phylogenic and physiological perspectives

PHYSIOLOGIA PLANTARUM, Issue 1 2002
Ritsuko Inokuchi
An important biochemical feature of autotrophs, land plants and algae, is their incorporation of inorganic nitrogen, nitrate and ammonium, into the carbon skeleton. Nitrate and ammonium are converted into glutamine and glutamate to produce organic nitrogen compounds, for example proteins and nucleic acids. Ammonium is not only a preferred nitrogen source but also a key metabolite, situated at the junction between carbon metabolism and nitrogen assimilation, because nitrogen compounds can choose an alternative pathway according to the stages of their growth and environmental conditions. The enzymes involved in the reactions are nitrate reductase (EC 1.6.6.1-2), nitrite reductase (EC 1.7.7.1), glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.1.13-14, 1.4.7.1), glutamate dehydrogenase (EC 1.4.1.2-4), aspartate aminotransferase (EC 2.6.1.1), asparagine synthase (EC 6.3.5.4), and phosphoenolpyruvate carboxylase (EC 4.1.1.31). Many of these enzymes exist in multiple forms in different subcellular compartments within different organs and tissues, and play sometimes overlapping and sometimes distinctive roles. Here, we summarize the biochemical characteristics and the physiological roles of these enzymes. We also analyse the molecular evolution of glutamine synthetase, glutamate synthase and glutamate dehydrogenase, and discuss the evolutionary relationships of these three enzymes. [source]

Biological activity, membrane-targeting modification, and crystallization of soluble human decay accelerating factor expressed in E. coli

PROTEIN SCIENCE, Issue 9 2004
Jennifer White
CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate; GPI, glycophosphatidyl inositol; PpDAF, human DAF1,4 expressed in Pichia pastoris, N glycosylated and with an oligohistidine tag; EcDAF, nonglycosylated human DAF 1,4 expressed in Escherichia coli; nDAF, human native glycosylated (GPI-anchored) DAF from erythrocytes; EcDAF-MP, soluble E. coli human DAF linked through a C-terminal cysteine to the myristoylated peptide APT542; PCR, polymerase chain reaction; SCR, short consensus repeat; TCEP, Tris- (2-carboxyethyl) phosphine Abstract Decay-accelerating factor (DAF, CD55) is a glycophosphatidyl inositol-anchored glycoprotein that regulates the activity of C3 and C5 convertases. In addition to understanding the mechanism of complement inhibition by DAF through structural studies, there is also an interest in the possible therapeutic potential of the molecule. In this report we describe the cloning, expression in Escherichia coli, isolation and membrane-targeting modification of the four short consensus repeat domains of soluble human DAF with an additional C-terminal cysteine residue to permit site-specific modification. The purified refolded recombinant protein was active against both classical and alternative pathway assays of complement activation and had similar biological activity to soluble human DAF expressed in Pichia pastoris. Modification with a membrane-localizing peptide restored cell binding and gave a large increase in antihemolytic potency. These data suggested that the recombinant DAF was correctly folded and suitable for structural studies as well as being the basis for a DAF-derived therapeutic. Crystals of the E. coli -derived protein were obtained and diffracted to 2.2 Å, thus permitting the first detailed X-ray crystallography studies on a functionally active human complement regulator protein with direct therapeutic potential. [source]

The role of phosphoinositide 3-kinase and phosphatidic acid in the regulation of mammalian target of rapamycin following eccentric contractions

THE JOURNAL OF PHYSIOLOGY, Issue 14 2009
T. K. O'Neil
Resistance exercise induces a hypertrophic response in skeletal muscle and recent studies have begun to shed light on the molecular mechanisms involved in this process. For example, several studies indicate that signalling by the mammalian target of rapamycin (mTOR) is necessary for a hypertrophic response. Furthermore, resistance exercise has been proposed to activate mTOR signalling through an upstream pathway involving the phosphoinositide 3-kinase (PI3K) and protein kinase B (PKB); however, this hypothesis has not been thoroughly tested. To test this hypothesis, we first evaluated the temporal pattern of signalling through PI3K,PKB and mTOR following a bout of resistance exercise with eccentric contractions (EC). Our results indicated that the activation of signalling through PI3K,PKB is a transient event (<15 min), while the activation of mTOR is sustained for a long duration (>12 h). Furthermore, inhibition of PI3K,PKB activity did not prevent the activation of mTOR signalling by ECs, indicating that PI3K,PKB is not part of the upstream regulatory pathway. These observations led us to investigate an alternative pathway for the activation of mTOR signalling involving the synthesis of phosphatidic acid (PA) by phospholipase D (PLD). Our results demonstrate that ECs induce a sustained elevation in [PA] and inhibiting the synthesis of PA by PLD prevented the activation of mTOR. Furthermore, we determined that similar to ECs, PA activates mTOR signalling through a PI3K,PKB-independent mechanism. Combined, the results of this study indicate that the activation of mTOR following eccentric contractions occurs through a PI3K,PKB-independent mechanism that requires PLD and PA. [source]

ORIGINAL ARTICLE: Activation of the Alternative Pathway of Complement is a Feature of Pre-Term Parturition but not of Spontaneous Labor at Term

Anti,cyclic citrullinated peptide antibodies from rheumatoid arthritis patients activate complement via both the classical and alternative pathways

ARTHRITIS & RHEUMATISM, Issue 7 2009
L. A. Trouw
Objective It has been suggested that anti,citrullinated protein antibodies (ACPAs) play an important role in the pathogenesis of rheumatoid arthritis (RA). To exert their pathologic effects, ACPAs must recruit immune effector mechanisms such as activation of the complement system. Mouse models of RA have shown that, surprisingly, arthritogenic antibodies activate the alternative pathway of complement rather than the expected classical pathway. This study was undertaken to investigate whether human anti,cyclic citrullinated peptide (anti-CCP) antibodies activate the complement system in vitro and, if so, which pathways of complement activation are used. Methods We set up novel assays to analyze complement activation by anti-CCP antibodies, using cyclic citrullinated peptide,coated plates, specific buffers, and normal and complement-deficient sera as a source of complement. Results Anti-CCP antibodies activated complement in a dose-dependent manner via the classical pathway of complement, and, surprisingly, via the alternative pathway of complement. The lectin pathway was not activated by anti-CCP antibodies. Complement activation proceeded in vitro up to the formation of the membrane attack complex, indicating that all activation steps, including the release of C5a, took place. Conclusion Our findings indicate that anti-CCP antibodies activate the complement system in vitro via the classical and alternative pathways but not via the lectin pathway. These findings are relevant for the design of interventions aimed at inhibition of complement-mediated damage in RA. [source]

Crystallization of human complement component C3b in the presence of a staphylococcal complement-inhibitor protein (SCIN)

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2009
Brandon L. Garcia
Staphylococcus aureus secretes a number of small proteins that effectively attenuate the human innate immune response. Among these, the staphylococcal complement-inhibitor protein (SCIN) disrupts the function of the complement component 3 (C3) convertase that is initiated through either the classical or the alternative pathway and thereby prevents amplification of the complement response on the bacterial surface. Recent studies have shown that SCIN may affect the activities of the C3 convertase by binding in an equimolar fashion to C3b, which is itself an integral although non-enzymatic component of the convertase. In order to better understand the nature of the C3b,SCIN interaction, the hanging-drop vapor-diffusion technique was used to crystallize human C3b in the presence of a recombinant form of SCIN. These crystals diffracted synchrotron X-rays to approximately 6,Å Bragg spacing and grew in a primitive tetragonal space group (P41212 or P43212; unit-cell parameters a = b = 128.03, c = 468.59,Å). Cell-content analysis of these crystals was consistent with the presence of either two 1:1 complexes or a single 2:2 assembly in the asymmetric unit, both of which correspond to a solvent content of 51.9%. By making use of these crystals, solution of the C3b,SCIN structure should further our understanding of complement inhibition and immune evasion by this pathogen. [source]

Bacterial Cell Penetration by ,3 -Oligohomoarginines: Indications for Passive Transfer through the Lipid Bilayer

CHEMBIOCHEM, Issue 6 2005
Birgit Geueke Dr.
Uptake of fluorescently labeled ,-oligohomoarginines amides by bacteria was examined with confocal laser scanning microscopy and fluorescence quenching assays. The results indicate that microorganisms, which have no endocytotic mechanisms for transmembrane transport, internalize the peptides through an unidentified alternative pathway (see micrograph). [source]

The AMD-associated complement factor H (CFH) polymorphism Y402H results in decreased CFH localisation to Bruch's membrane

ACTA OPHTHALMOLOGICA, Issue 2009
PN BISHOP
Purpose CFH down-regulates the alternative pathway of the complement system by binding to polyanionic structures on host cells/tissues and inactivating surface associated C3b. Recently, the Y402H polymorphism in CFH has been shown to be a major risk factor for AMD. Here we investigated the functional consequences of the Y402H polymorphism by testing the hypothesis that the resultant amino acid substitution alters CFH binding to macular tissue Methods The 402H and 402Y forms of full-length CFH and recombinant CFH fragments (composed of CCP6-8) were labelled with different fluorophores (402Y with AlexFluor-488 and 402H with AlexaFluor-594). These were simultaneously incubated with frozen sections of human macular tissue from donor eyes and the relative binding of the two forms was investigated. In some experiments the tissue sections were digested with glycosidic enzymes prior to incubation with the fluorescently-labelled proteins. Results Whilst the 402H and 402Y variants showed similar levels of binding to the RPE, there was a marked reduction in binding of the 402H form to Bruch's membrane. The binding of both forms to Bruch's membrane was dependent upon interactions with heparan sulfates, and to a lesser extent dermatan sulfates. Conclusion Complement mediated damage is important in the pathogenesis of AMD and the relative failure of the 402H form of CFH to localise to Bruch's membrane may result in over activation of the complement system at the retinal pigment epithelium/Bruch's membrane interface. [source]

Inflammation in AMD pathology

ACTA OPHTHALMOLOGICA, Issue 2008
JZ NOWAK
Age-related macular degeneration (AMD) is a progressive retinal disease that leads to substantial irreversible vision loss in elderly patients. Two clinical categories of AMD are distinguished: the "dry" atrophic form and the exudative neovascular or "wet" form. There is neither a preventive therapy nor a cure for both forms, although recent efforts succeeded in a more effective treatment of the wet AMD with PDT and anti-VEGF drugs. AMD is a multifactorial pathology which involves complex interaction of metabolic, genetic and environmental factors, with major biochemical-clinical abnormalities seen in four functionally interrelated tissues: photoreceptors, retinal pigment epithelium, Bruch's membrane and choriocapilaries. Four processes specifically contribute to the development of AMD pathology: lipofuscinogenesis (in RPE cells), drusogenesis (with drusen located between RPE and Bruch's membrane), inflammation (local) and choroidal neovascularization (in wet form). Although the role of immune system and inflammation has been implicated in AMD pathogenesis for many years, an impetus to intensify the research in this direction gave a recent discovery of polymorphisms in genes that encode for elements of the complement system, including factor H (CFH; Y402H), factor B, and complement component 2. An increased activity of the complement alternative pathway due to the lack of or insufficient control by CFH appears to contribute to AMD progression via immunologic mechanism which drives inflammatory response. An arising question is whether blockade of overactive complement system will be a therapeutic strategy safe for patients and effective to prevent or slowing down the macula-devastating and vision-threatening disease. Supported by grant no. 503-1023-1 from Medical University of Lodz. [source]