SEARCH · PubMed Health

Results for “Extracellular Traps”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources

PubMed2003

AtBXL1, a novel higher plant (Arabidopsis thaliana) putative beta-xylosidase gene, is involved in secondary cell wall metabolism and plant development.

To investigate mechanisms involved in cell wall development, an Arabidopsis T-DNA insertion mutant collection was screened to identify mutants with beta-glucuronidase fusion gene expression in tissues undergoing secondary cell wall thickening. This promoter-trapping strategy allowed the isolation of a transformant containing the GUS coding sequence inserted 700 bp upstream of the ATG of a putative beta-xylosidase gene. The transformant has no phenotype as the expression of the gene was not disrupted by the insertion. The analysis of the predicted protein, AtBXL1, suggests its targeting to the extracellular matrix and its involvement in cell wall metabolism through a putative activity towards xylans. The 2-kb promoter sequence of AtBXL1 was fused to the GUS coding sequence and introduced into wild-type Arabidopsis thaliana. GUS expression was shown to be restricted to tissues undergoing secondary cell wall formation. Beta-xylosidase activity was associated with the cell wall-enriched fraction of different organs of wild-type plants. The level of activity correlates with transcript accumulation of AtBXL1 and other AtBXL1-related genes. Transgenic plants expressing the AtBXL1 cDNA in antisense orientation were generated. Lines exhibiting the highest decrease in AtBXL1 transcript accumulation and beta-xylosidase activity had phenotypic alterations. This newly identified gene is proposed to be involved in secondary cell wall hemicellulose metabolism and plant development.

Amino Acid Sequence↗

PubMed2001

Inhibition of cell growth and spreading by stomach cancer-associated protein-tyrosine phosphatase-1 (SAP-1) through dephosphorylation of p130cas.

SAP-1 (stomach cancer-associated protein-tyrosine phosphatase-1) is a transmembrane-type protein-tyrosine phosphatase that is abundant in the brain and certain cancer cell lines. With the use of a "substrate-trapping" approach, p130(cas), a major focal adhesion-associated phosphotyrosyl protein, has now been identified as a likely physiological substrate of SAP-1. Expression of recombinant SAP-1 induced the dephosphorylation of p130(cas) as well as that of two other components of the integrin-signaling pathway (focal adhesion kinase and p62(dok)) in intact cells. In contrast, expression of a substrate-trapping mutant of SAP-1 induced the hyperphosphorylation of these proteins, indicating a dominant negative effect of this mutant. Overexpression of SAP-1 induced disruption of the actin-based cytoskeleton as well as inhibited various cellular responses promoted by integrin-mediated cell adhesion, including cell spreading on fibronectin, growth factor-induced activation of extracellular signal-regulated kinase 2, and colony formation. Finally, the enzymatic activity of SAP-1, measured with an immunocomplex phosphatase assay, was substantially increased by cell-cell adhesion. These results suggest that SAP-1, by mediating the dephosphorylation of focal adhesion-associated substrates, negatively regulates integrin-promoted signaling processes and, thus, may contribute to contact inhibition of cell growth and motility.

Animals↗

PubMed2003

Sustained Ca2+ transfer across mitochondria is Essential for mitochondrial Ca2+ buffering, sore-operated Ca2+ entry, and Ca2+ store refilling.

Mitochondria have been found to sequester and release Ca2+ during cell stimulation with inositol 1,4,5-triphosphate-generating agonists, thereby generating subplasmalemmal microdomains of low Ca2+ that sustain activity of capacitative Ca2+ entry (CCE). Procedures that prevent mitochondrial Ca2+ uptake inhibit local Ca2+ buffering and CCE, but it is not clear whether Ca2+ has to transit through or remains trapped in the mitochondria. Thus, we analyzed the contribution of mitochondrial Ca2+ efflux on the ability of mitochondria to buffer subplasmalemmal Ca2+, to maintain CCE, and to facilitate endoplasmic reticulum (ER) refilling in endothelial cells. Upon the addition of histamine, the initial mitochondrial Ca2+ transient, monitored with ratio-metric-pericam-mitochondria, was largely independent of extracellular Ca2+. However, subsequent removal of extracellular Ca2+ produced a reversible decrease in [Ca2+]mito, indicating that Ca2+ was continuously taken up and released by mitochondria, although [Ca2+]mito had returned to basal levels. Accordingly, inhibition of the mitochondrial Na+/Ca2+ exchanger with CGP 37157 increased [Ca2+]mito and abolished the ability of mitochondria to buffer subplasmalemmal Ca2+, resulting in an increased activity of BKCa channels and a decrease in CCE. Hence, CGP 37157 also reversibly inhibited ER refilling during cell stimulation. These effects of CGP 37157 were mimicked if mitochondrial Ca2+ uptake was prevented with oligomycin/antimycin A. Thus, during cell stimulation a continuous Ca2+ flux through mitochondria underlies the ability of mitochondria to generate subplasmalemmal microdomains of low Ca2+, to facilitate CCE, and to relay Ca2+ from the plasma membrane to the ER.

Biological Transport↗

PubMed2000

The cysteine-rich domain of the macrophage mannose receptor is a multispecific lectin that recognizes chondroitin sulfates A and B and sulfated oligosaccharides of blood group Lewis(a) and Lewis(x) types in addition to the sulfated N-glycans of lutropin.

The mannose receptor (MR) is an endocytic protein on macrophages and dendritic cells, as well as on hepatic endothelial, kidney mesangial, tracheal smooth muscle, and retinal pigment epithelial cells. The extracellular portion contains two types of carbohydrate-recognition domain (CRD): eight membrane-proximal C-type CRDs and a membrane-distal cysteine-rich domain (Cys-MR). The former bind mannose-, N-acetylglucosamine-, and fucose-terminating oligosaccharides, and may be important in innate immunity towards microbial pathogens, and in antigen trapping for processing and presentation in adaptive immunity. Cys-MR binds to the sulfated carbohydrate chains of pituitary hormones and may have a role in hormonal clearance. A second feature of Cys-MR is binding to macrophages in marginal zones of the spleen, and to B cell areas in germinal centers which may help direct MR-bearing cells toward germinal centers during the immune response. Here we describe two novel classes of carbohydrate ligand for Cys-MR: chondroitin-4 sulfate chains of the type found on proteoglycans produced by cells of the immune system, and sulfated blood group chains. We further demonstrate that Cys-MR interacts with cells in the spleen via the binding site for sulfated carbohydrates. Our data suggest that the three classes of sulfated carbohydrate ligands may variously regulate the trafficking and function of MR-bearing cells.

Acetylgalactosamine↗

PubMed1979

A kinetic analysis of the uptake of cytosine-beta-D-arabinoside by rat-B77 cells. Differentiation between transport and phosphorylation.

We present here a differentiation by kinetic methods of the tandem processes of transport and metabolic during uptake of cytosine-beta-D-arabinoside by intact rat fibroblasts. Transport across the cell membrane occurs by a carrier-mediated mechanism displaying a Km of approximately 500 microM and a V of approximately pmol x min-1 x (10(6) cells)-1. The subsequent metabolic trapping (phosphorylation) has a Km of approximately 15 microM and V of approximately 0.25 pmol x min-1 x (10(6) cells)-1. In this system, transport is rate-limiting for the first phase of the uptake process whereas phosphorylation becomes rate-limiting when internal concentration of radioactive labeled substrate exceeds that in the extracellular medium. The duration of the first phase depends on the substrate concentration.

Animals↗

PubMed1987

GRF elevates cytosolic free calcium concentration in rat anterior pituitary cells.

The effect of human growth hormone-releasing factor (GRF) on intracellular free calcium concentration ([Ca2+]i) was examined in rat anterior pituitary cells. The [Ca2+]i was monitored directly by means of the intracellularly trapped fluorescent indicator, fura-2. GRF rapidly elevated [Ca2+]i, reaching a new plateau within approximately 30 s. The half-maximally effective concentration of GRF was approximately 130 pM. GRF produced a maximal increase in [Ca2+]i by approximately 120 nM. The GRF (2 nM)-induced elevation of [Ca2+]i was abolished by removal of extracellular calcium (Ca2+ omitted, 2 mM EGTA). The GRF (2 nM)-caused rise in [Ca2+]i was largely reduced in the presence of the calcium channel blockers Mg2+ (31.2 mM) or nifedipine (1 microM). An increase in [Ca2+]i by approximately 60 nM was elicited by the addition of prostaglandin E2 (1 microM), which can stimulate growth hormone secretion independent of GRF receptors. These data indicate that GRF elevates the [Ca2+]i, possibly in somatotrophs; this GRF-induced increase in [Ca2+]i may depend on an influx of extracellular Ca2+, largely through Mg2+- and nifedipine-sensitive calcium channels.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMedDate not supplied

The crystal structure of the L1 intermediate of halorhodopsin at 1.9 angstroms resolution.

The mutant T203V of the light driven chloride pump halorhodopsin from Halobacterium salinarum was crystallized and the X-ray structure was solved at 1.6 angstroms resolution. The T203V structure turned out to be nearly identical to the wild type protein with a root mean square deviation of 0.43 angstroms for the carbon alpha atoms of the protein backbone. Two chloride binding (CB) sites were demonstrated by a substitution of chloride with bromide and an analysis of anomalous difference Fourier maps. The CB1 site was found at the same position as in the wild type structure. In addition, a second chloride binding site CB2 was identified around Q105 due to higher resolution in the mutant crystal. As T203V showed a 10 times slower decay of its photocycle intermediate L, this intermediate could be trapped with an occupancy of 60% upon illumination at room temperature and subsequent cooling to 120 degrees K. Fourier transform infrared spectroscopy clearly identified the crystal to be trapped in the L1 intermediate state and the X-ray structure was solved to 1.9 angstroms resolution. In this intermediate, the chloride moved by 0.3 angstroms within binding site CB1 as indicated by peaks in difference Fourier density maps. The chloride in the second binding site CB2 remained unchanged. Thus, intraproteinous chloride translocation from the extracellular to the cytoplasmic part of the protein must occur in reaction steps following the L1 intermediate in the catalytic cycle of halorhodopsin.

Amino Acid Substitution↗

PubMed1994

Bactericidal potency of hydroxyl radical in physiological environments.

Rates of radiolytic inactivation of bacteria suspended in N2O-saturated solutions were dramatically increased over normal background levels when the media contained chloride or bicarbonate ions. The bacteria could be protected from this enhanced toxicity by the addition of free radical scavengers (ethanol, ascorbate, hydrogen peroxide, mannitol, glucose, EDTA, picolinic acid), indicating that the lethal reactions were extracellular in origin. Prior irradiation of chloride-containing solutions led to formation of hypochlorous acid, which was identified by detection of ring-chlorinated products when reacted with fluorescein. Prolonged irradiation of other solutions did not lead to accumulation of bactericidal agents; however, irradiation of bicarbonate-containing solutions in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) led to formation of the EPR-detectable DMPO.CO3- adduct. The results are interpreted in terms of formation of secondary radicals, among which the carbonate and chlorine radicals are uniquely toxic to bacteria. From rate comparisons of the solution components, it was concluded that the reactions involving chloride ion are unlikely to be expressed in biological environments, but that the CO3- radical could be an important intermediary oxidant in peroxide-inflicted cellular damage, particularly in spatially confined environments such as the leukocyte phagosome.

Anti-Bacterial Agents↗

PubMed1997

Sonodynamic toxicity of gallium-porphyrin analogue ATX-70 in human leukemia cells.

Low concentrations (> or = 1 microM) of the gallium-porphyrin analogue ATX-70 significantly enhanced cellular toxicity in human leukemia HL-525 cells exposed to 50 kHz ultrasound. The mechanism of this ATX-70-dependent sonosensitization is unknown, but we have established the requirement of extracellular localization of ATX-70 molecules for sonosensitization. Short-lived toxic intermediates produced from ATX-70 by ultrasound are implicated in the mechanism, since no cytotoxicity was found when medium containing ATX-70 was sonicated and subsequently added to the cells. However, we were unable to demonstrate the existence of radical intermediates by EPR spin trapping with the nitroso spin trap, DBNBS, and ATX-70-dependent sonotoxicity could not be ameliorated by the addition of up to 70 mM POBN and DMPO spin traps during ultrasound exposure.

Cell Death↗

PubMed1995

Barriers for lateral diffusion of transferrin receptor in the plasma membrane as characterized by receptor dragging by laser tweezers: fence versus tether.

Our previous results indicated that the plasma membrane of cultured normal rat kidney fibroblastic cell is compartmentalized for diffusion of receptor molecules, and that long-range diffusion is the result of successive intercompartmental jumps (Sako, Y. and Kusumi, A. 1994. J. Cell Biol. 125:1251-1264). In the present study, we characterized the properties of intercompartmental boundaries by tagging transferrin receptor (TR) with either 210-nm-phi latex or 40-nm-phi colloidal gold particles, and by dragging the particle-TR complexes laterally along the plasma membrane using laser tweezers. Approximately 90% of the TR-particle complexes showed confined-type diffusion with a microscopic diffusion coefficient (Dmicro) of approximately 10(-9) cm2/s and could be dragged past the intercompartmental boundaries in their path by laser tweezers at a trapping force of 0.25 pN for gold-tagged TR and 0.8 pN for latex-tagged TR. At lower dragging forces between 0.05 and 0.1 pN, particle-TR complexes tended to escape from the laser trap at the boundaries, and such escape occurred in both the forward and backward directions of dragging. The average distance dragged was half of the confined distance of TR, which further indicates that particle-TR complexes escape at the compartment boundaries. Since variation in the particle size (40 and 210 nm, the particles are on the extracellular surface of the plasma membrane) hardly affects the diffusion rate and behavior of the particle-TR complexes at the compartment boundaries, and since treatment with cytochalasin D or vinblastin affects the movements of TR (Sako and Kusumi as cited above), argument has been advanced that the boundaries are present in the cytoplasmic domain. Rebound of the particle-TR complexes when they escape from the laser tweezers at the compartment boundaries suggests that the boundaries are elastic structures. These results are consistent with the proposal that the compartment boundaries consist of membrane skeleton or a membrane-associated part of the cytoskeleton (membrane skeleton fence model). Approximately 10% of TR exhibited slower diffusion (Dmicro approximately 10(-10)-10(-11) cm2/s) and binding to elastic structures.

Animals↗

PubMed2004

Localization of the NO-cGMP signaling pathway molecules, NOS III-phosphorylation sites, ERK1/2, and Akt/PKB in osteoclasts.

BACKGROUND: Nitric oxide (NO) mediates different cellular functions by activating soluble guanylate cyclase (sGC) that converts guanosine-5'-triphosphate (GTP) to cyclic guanosine-3',5'-monophosphate (cGMP). Membrane-bound GCs produce cGMP in response to natriuretic peptides in osteoblasts, but neither the NO-target enzyme sGC, nor the phosphorylation sites of NOS III, nor their regulation by extracellular signal-regulated kinases 1 and 2 (ERK1/2) and Akt/protein kinase B (Akt/PKB) in osteoclasts have been established. METHODS: Rat molars with periodontium were perfusion- and post-fixed, decalcified, and frozen-sectioned. Free-floating sections were stained using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) and tartrate-resistant acid phosphatase (TRAP) histochemical techniques and immunoreacted with antisera against NO-synthase (NOS) I-III, NOS III phoshorylated at Thr495, NOS III phoshorylated at Serine1177 (Ser1177), ERK1/2, phosphorylated ERK1/2, Akt/PKB, phosphorylated Akt/PKB, sGC (alpha2/beta1), and cGMP. RESULTS: NADPH-d staining and immunostaining of NOS I-III, NOS III phosphorylated at Ser1177, ERK1/2, Akt/PKB, phosphorylated Akt/PKB, sGC (alpha2 and beta1-subunits), and cGMP were detected in osteoclasts. Immunohistochemical reaction products for NOS III phosphorylated at threonine495 (Thr495) and phosphorylated ERK1/2 could not be identified in osteoclasts. Comparison of TRAP activity and immunostaining for sGC beta1-subunit revealed that sGC beta1-subunit is only expressed in a sub-population of osteoclasts. CONCLUSIONS: NO is likely to be generated by NOS I and NOS III in osteoclasts. The inconstant expression of NOS II in some osteoclasts may be explained with inducible expression of NOS II upon physiological cell activation. Localization of the sGC alpha2- and beta1-subunits and cGMP in osteoclasts is compatible with an involvement of NO-sGC signaling in the homeostasis of osteoclasts. The phosphorylation site of NOS III at Ser1177 and phosphorylated Akt/PKB are involved in regulation of NO production by NOS III in osteoclasts under basal conditions.

Alveolar Process↗

PubMed1992

Perivitelline space of mammalian oocytes: extracellular matrix of unfertilized oocytes and formation of a cortical granule envelope following fertilization.

Extracellular matrices (ECM) present around unfertilized and fertilized mammalian oocytes were studied ultrastructurally in samples prepared in the presence of ruthenium red to facilitate stabilization of extracellular materials. Unfertilized mouse, hamster, and human oocytes have an ECM comprising granules and filaments in their perivitelline spaces (PVS). This matrix is more abundant in the human than in hamsters and mice. The granule/filament matrix appears identical to the matrix seen between cumulus and corona radiata cells following ruthenium red processing and previously shown to comprise protein and hyaluronic acid. By including ruthenium red during fixation, it is possible to demonstrate the existence of cortical granule exudate in the PVS of fertilized oocytes from hamsters, mice, and humans. Much of the cortical granule exudate is trapped in the PVS and forms a new coat around the fertilized oocyte. This material is particulate when stained with ruthenium red and appears to be uniformly dispersed around the entire oocyte surface. We refer to this new coat as the cortical granule envelope. This envelope is observed in the PVS of all developmental stages up to and including blastocysts in all three species. Following hatching of mouse and hamster blastocysts, the cortical granule envelope is no longer present. Possible functions of this envelope are discussed.

Animals↗

PubMed1989

Adenosine triphosphate, bradykinin, and thyrotropin-releasing hormone regulate the intracellular Ca2+ concentration and the 45Ca2+ efflux of human thyrocytes in primary culture.

The hormonal stimulation of phospholipase C and the consequent activation of the Ca2+-phosphatidylinositol cascade in eukaryotic cells is associated with modifications of the [Ca2+]i (intracellular Ca2+ concentration) which modulates cellular functions. In this study, these modifications were investigated in primary cultures of human thyroid cells. The mean apparent basal [Ca2+]i of human thyrocytes measured using the intracellularly trapped fluorescent indicator Quin-2 was found to be 89 +/- 16 nM (n = 49). ATP and, to a lesser extent, ADP, but not AMP or adenosine, elicited a concentration-dependent biphasic rise in human thyrocytes [Ca2+]i and increased their 45Ca2+ efflux. The first transient phase of the [Ca2+]i rise induced by ATP was resistant to extracellular Ca2+ depletion, whereas the second sustained phase was abolished in these conditions. This suggests that although the first phase of this response involves a release of Ca2+ from intracellular stores, the second phase requires extracellular Ca2+ influx. The response of human thyrocytes to analogs of ATP is compatible with a P2-purinergic effect of ATP on these cells. Bradykinin and TRH affected the human thyrocyte [Ca2+]i and 45Ca2+ efflux similarly to ATP. The human thyrocyte [Ca2+]i and the 45Ca2+ efflux were not modified by carbachol, a nonhydrolyzable analog of acetylcholine. The present results suggest the presence of P2-purinergic receptors to ATP and of receptors to TRH and bradykinin on human follicular thyroid cells. They also confirm that the Ca2+-phosphatidylinositol cascade is present in these cells and suggest that this cascade is modulated by ATP, TRH, and bradykinin. As this cascade is involved in the regulation of protein iodination, and therefore of thyroid hormones synthesis, these agents might have an important role in the regulation of the thyroid function.

Adenine Nucleotides↗

PubMed2002

Water secretion associated with exocytosis in endocrine cells revealed by micro forcemetry and evanescent wave microscopy.

It has been a long belief that release of substances from the cell to the extracellular milieu by exocytosis is completed by diffusion of the substances from secretory vesicles through the fusion pore. Involvement of any mechanical force that may be superposed on the diffusion to enhance the releasing process has not been elucidated to date. We tackled this problem in cultured bovine chromaffin cells using direct and sensitive methods: the laser-trap forcemetry and the evanescent-wave fluorescence microscopy. With a laser beam, we trapped a micro bead in the vicinity of a cell (with 1 microm of separation) and observed movements of the bead optically. Electrical stimulation of the cell induced many of rapid and transient movements of the bead in a direction away from the cell surface. Upon the same stimulation, secretory vesicles stained with a fluorescent probe, acridine orange, and excited under the evanescent field illumination, showed a flash-like response: a transient increase in fluorescence intensity associated with a diffuse cloud of brightness, followed by a complete disappearance. These mechanical and fluorescence transients indicate a directional flow of substances. Blockers of the Cl(-) channel suppressed the rates of both responses in a characteristic way but not exocytotic fusion itself. Immunocytochemical studies revealed the presence of Cl(-) and K(+) channels on the vesicle membranes. These results suggest that the externalization of hormones or transmitters upon exocytosis of vesicles is augmented by secretion of water from the vesicle membrane through the widened fusion pore, possibly modulating the rate and reach of the hormone or transmitter release and facilitating transport of the signal molecules in intercellular spaces.

Acridine Orange↗

PubMed2004

Structural characterization of a type III secretion system filament protein in complex with its chaperone.

The type III secretion system (TTSS) mediates the specific translocation of bacterial proteins into the cytoplasm of eukaryotic cells, a process essential for the virulence of many Gram-negative pathogens. The enteropathogenic Escherichia coli TTSS protein EspA forms a hollow extracellular filament believed to be a molecular conduit for type III protein translocation. Structural analysis of EspA has been hampered by its polymeric nature. We show that EspA alone is sufficient to form filamentous structures in the absence of other pathogenicity island-encoded proteins. CesA is the recently proposed chaperone of EspA, and we demonstrate that CesA traps EspA in a monomeric state and inhibits its polymerization. Crystallographic analysis of the heterodimeric CesA-EspA complex at a resolution of 2.8 A reveals that EspA contains two long a-helices, which are involved in extensive coiled-coil interactions with CesA.

Circular Dichroism↗

PubMed1999

Isolation and characterization of CA XIV, a novel membrane-bound carbonic anhydrase from mouse kidney.

Carbonic anhydrase (CA) is involved in various physiological processes such as acid-base balance and transport of carbon dioxide and ions. In this study, we have succeeded in the isolation of a novel CA from the mouse kidney by use of the signal sequence trap method. It is a 337-amino acid polypeptide with a calculated molecular mass of 37.5 kDa, consisting of a putative amino-terminal signal sequence, a CA domain, a transmembrane domain, and a short hydrophilic carboxyl terminus, which we designated CA XIV. The CA domain of CA XIV is highly homologous with those of known CAs, especially extracellular CAs including CA XII, IX, VI, and IV. The expression study of an epitope-tagged protein has suggested that CA XIV is located on the plasma membrane. When expressed in COS-7 cells, CA XIV exhibits CA activity that is predominantly associated with the membrane fraction. By Northern blot analysis, the gene expression of CA XIV is most abundant in the kidney and heart, followed by the skeletal muscle, brain, lung, and liver. In situ hybridization has revealed that, in the kidney, the gene is expressed intensely in the proximal convoluted tubule, which is the major segment for bicarbonate reabsorption and also in the outer border of the inner stripe of the outer medulla. In conclusion, we have cloned a functional cDNA encoding a novel membrane-bound CA. This study will bring new insights into our understanding of carbon dioxide metabolism and acid-base balance.

Amino Acid Sequence↗

PubMed1994

Dorsal midline fate in Drosophila embryos requires twisted gastrulation, a gene encoding a secreted protein related to human connective tissue growth factor.

The twisted gastrulation (tsg) gene is one of seven known zygotic genes that specify the fate of dorsal cells in Drosophila embryos. Mutations in these genes cause at least some of the cells on the dorsal half of the embryo to adopt more ventral cell fates leading to the proposal that most of these genes participate in establishing, maintaining, or modulating a gradient of a single signaling molecule DECAPENTAPLEGIC (DPP). We have examined the effects of tsg mutations on the development of cuticule elements, expression of a region specific enhancer trap, and patterns of mitotic domains. Mutations of tsg only affect the fate of a narrow strip of dorsal midline cells and do not affect dorsal ectoderm cells. However, the pattern of tsg expression is not coincident with the territories affected by tsg mutations. Structural analysis of the tsg gene reveals features of a secreted protein suggesting an extracellular site of action. The TSG protein bears a weak resemblance to human connective tissue growth factor (CTGF), a TGF-beta-induced protein. We propose that dorsal midline cell fate is specified by the combination of both a TSG and a DPP signal to which the dorsal midline cells are uniquely competent to respond.

Algorithms↗

PubMed1988

Neutralization of adenoviruses: kinetics, stoichiometry, and mechanisms.

Kinetic curves for neutralization of adenovirus type 2 with anti-hexon serum revealed no lag periods even when the serum was highly diluted or when the temperature was lowered to 4 degrees C, thus indicating a single-hit mechanism. Multiplicity curves determined with anti-hexon serum displayed a linear correlation between the degree of neutralization and dilution of antiserum. Neutralization values experimentally obtained under steady-state conditions fully fitted a single-hit model based on Poisson calculations. Quantitation of the amount of 125I-labeled type-specific anti-hexon antibodies needed for full neutralization of adenovirus showed that 1.4 antibodies were attached per virion under such conditions. Virions already attached to HeLa cells at 4 degrees C were, to a large extent, neutralizable by anti-hexon serum, whereas anti-fiber and anti-penton base antisera were negative. It is suggested that adenovirus may be neutralized by two pathways: aggregation of the virions (extracellular neutralization) as performed by anti-fiber antibodies and blocking of virion entrance from the acidic endosomes into the cytoplasm (intracellular neutralization). The latter effect could be obtained by (i) covering of the penton bases, as performed by anti-penton base antibodies, thereby preventing interaction between the penton bases and the endosomal membrane, which results in trapping of virions within endosomes, and (ii) inhibition of the low-pH-induced conformational change of the viral capsid, which seems to occur in the endosomes and is necessary for proper exposure of the penton bases, as performed by anti-hexon antibodies.

Adenoviridae↗