Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cascade testing”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,513 records · Page 84Linked to original sources

Active site of C3a anaphylatoxin: contributions of the lipophilic and orienting residues.

Activation of the serum complement cascade generates C3a anaphylatoxin, a primary mediator of inflammation. The active-site pentapeptide from the COOH terminus of C3a, Leu-Gly-Leu-Ala-Arg (residues 73-77), exhibits the inflammatory activities and specificity of the native 77-residue polypeptide. Functionally important features of this active site were studied by testing the ability of 22 synthetic analogues of this pentapeptide to contract isolated muscle strips from guinea pig ileum and to desensitize this tissue to contraction induced by human C3a or C5a. The C3a receptors on mast cells and basophils probably contain lipophilic groups that interact with the lipophilic side chains of Leu-73 and Leu-75 and charged groups that interact with the carboxylate and guanidinium groups of Arg-77. The lipophilic contribution of Leu-73 is modest and sterically nonspecific while that of Leu-75 is substantial and sterically specific. Gly-74 and Ala-76 appear to position and orient the adjacent residues Leu-73, Leu-75, and Arg-77 for optimal receptor binding. The contribution of Gly-74 is neither conformationally nor sterically specific while that of Ala-76 is both conformationally and sterically specific. The cellular C3a receptors evidently interact most efficiently with peptides ending in -Leu-Ala-Arg-OH.

Anaphylatoxins↗

Complement fixation by model immune complexes free in solution and bound onto cell surfaces.

Immunoglobin (IgG) molecules with anti-2,4-dinitrophenyl activity were covalently cross-linked by using three cross-linking reagents. The resulting oligomers were separated into monomer, dimer, trimer, and heavy fractions. These stable assemblages of IgG molecules were capable of fixing dilute whole guinea pig complement in solution. When oligomers were further aggregated noncovalently into larger complexes, all were able to fix complement. Radioiodinated oligomers were attached to 2,4,6,-trinitrophenylsulfonic acid treated sheep red blood cells (N3ph-SRBC), and the number of bound molecules was determined from the cell-associated radioactivity. Complement-mediated lysis of N3ph-SRBC was then assayed over a range of levels of bound protein and at increasing concentrations of complement. The lytic efficiencies of all oligomers increased with the number of bound molecules, with complement concentration, with hapten density on N3ph-SRBC, and with oligomer size. The results suggest that two adjacent IgG molecules may not serve as a unit signal for triggering the complement cascade, but instead, initiation occurs with increasing efficiency as the size of cell-bound IgG clusters increases.

Animals↗

Detection of phospholipase Cgamma in sea urchin eggs.

Phosphorylation on tyrosine and turnover of polyphosphoinositide metabolism are rapidly stimulated after fertilization. However, the interconnection between these pathways remains to be determined. In the present paper it is demonstrated that eggs of two different sea urchin species contain tyrosine phosphorylated proteins with calcium-sensitive phospholipase C activity. We have investigated whether phospholipase Cgamma (PLCgamma), characteristic of tyrosine kinase receptors, could be responsible for this activity. Western blot and immunocytochemistry performed with antibodies directed against PLCgamma revealed the presence of this protein in cortical regions. It was also observed that PLCgamma displayed calcium-sensitive activity. The present results suggest that PLCgamma may be part of the cascade of events leading to the calcium signal responsible for egg activation at fertilization.

Animals↗

Eicosanoid activation of protein kinase C epsilon: involvement in growth cone repellent signaling.

Exposure of growing neurons to thrombin or semaphorin 3A stimulates a receptor-mediated signaling cascade that results in collapse of their growth cones. This collapse response necessitates eicosanoid production, as we have shown earlier. The present report investigates whether and which protein kinase C (PKC) isoforms may be activated by such eicosanoids. To examine these questions, we isolated growth cones from fetal rat brain and tested whether thrombin or the eicosanoid, 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), could activate endogenous growth cone PKC. We show that both thrombin and 12(S)-HETE stimulate the phosphorylation of the myristoylated alanine-rich protein kinase C substrate, an 87-kDa adhesion site protein. Furthermore, we show both with immunoprecipitated and with recombinant PKC that 12(S)-HETE activation is selective for the epsilon isoform and does not require accessory proteins. Last, we demonstrate that PKC activation is necessary for thrombin-induced growth cone collapse. These data indicate that eicosanoid-mediated repellent effects result from the direct and selective activation of PKCepsilon and suggest the involvement of myristoylated alanine-rich protein kinase C substrate phosphorylation in growth cone collapse.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

Blood-brain barrier damage induces release of alpha2-macroglobulin.

Blood-brain barrier (BBB) failure occurs in many neurological diseases and is caused in part by activation of proinflammatory factors including matrix metalloproteinases. Counterbalancing, "BBB protective" cascades have recently been described, including NO-mediated interleukin 6 release by glia. Interleukin 6 has been shown to trigger production of matrix metalloproteinase inhibitors such as alpha2-macroglobulin (alpha2M). We hypothesized that BBB failure may result in increased alpha(2)M release by perivascular astrocytes. This was initially tested in patients undergoing iatrogenic BBB disruption by hyperosmotic mannitol for intra-arterial chemotherapy of brain tumors. Serum samples revealed significantly increased levels of alpha2M at 4 h after BBB disruption by hyperosmotic mannitol. In parallel in vitro experiments, we observed a similar increase of alpha2M release by astrocytes under conditions mimicking BBB failure and perivascular edema. For both experiments, protein analysis was initially performed by bidimensional gel electrophoresis and mass spectrometry followed by Western blotting immunodetection. We conclude that, in addition to proinflammatory changes, BBB failure may also trigger protective release of alpha2M by perivascular astrocytes as well as peripheral source.

Astrocytes↗

Sphingoid base signaling via Pkh kinases is required for endocytosis in yeast.

In yeast, sphingoid base synthesis is required for the internalization step of endocytosis and organization of the actin cytoskeleton. We show that overexpression of either one of the two kinases Pkh1p or Pkh2p, that are homologous to mammalian 3-phosphoinositide-dependent kinase-1 (PDK1), can specifically suppress the sphingoid base synthesis requirement for endocytosis. Pkh1p and Pkh2p have an overlapping function because only a mutant with impaired function of both kinases is defective for endocytosis. Pkh1/2p kinases are activated in vitro by nanomolar concentrations of sphingoid base. These results suggest that Pkh1/2p kinases are part of a sphingoid base-mediated signaling pathway that is required for the internalization step of endocytosis. The Pkc1p kinase that is phosphorylated by Pkh1/2p kinases and plays a role in endocytosis was identified as one of the downstream effectors of this signaling cascade.

3-Phosphoinositide-Dependent Protein Kinases↗

Computer-aided detection of lung nodules: false positive reduction using a 3D gradient field method and 3D ellipsoid fitting.

We are developing a computer-aided detection system to assist radiologists in the detection of lung nodules on thoracic computed tomography (CT) images. The purpose of this study was to improve the false-positive (FP) reduction stage of our algorithm by developing features that extract three-dimensional (3D) shape information from volumes of interest identified in the prescreening stage. We formulated 3D gradient field descriptors, and derived 19 gradient field features from their statistics. Six ellipsoid features were obtained by computing the lengths and the length ratios of the principal axes of an ellipsoid fitted to a segmented object. Both the gradient field features and the ellipsoid features were designed to distinguish spherical objects such as lung nodules from elongated objects such as vessels. The FP reduction performance in this new 25-dimensional feature space was compared to the performance in a 19-dimensional space that consisted of features extracted using previously developed methods. The performance in the 44-dimensional combined feature space was also evaluated. Linear discriminant analysis with stepwise feature selection was used for classification. The parameters used for feature selection were optimized using the simplex algorithm. Training and testing were performed using a leave-one-patient-out scheme. The FP reduction performances in different feature spaces were evaluated by using the area Az under the receiver operating characteristic curve and the number of FPs per CT section at a given sensitivity as accuracy measures. Our data set consisted of 82 CT scans (3551 axial sections) from 56 patients with section thickness ranging from 1.0 to 2.5 mm. Our prescreening algorithm detected 111 of the 116 solid nodules (nodule size: 3.0-30.6 mm) marked by experienced thoracic radiologists. The test Az values were 0.95 +/- 0.01, 0.88 +/- 0.02, and 0.94 +/- 0.01 in the new, previous, and combined feature spaces, respectively. The number of FPs per section at 80% sensitivity in these three feature spaces were 0.37, 1.61, and 0.34, respectively. The improvement in the test Az with the 25 new features was statistically significant (p<0.0001) compared to that with the previous 19 features alone.

Algorithms↗

Golf: an olfactory neuron specific-G protein involved in odorant signal transduction.

Biochemical and electrophysiological studies suggest that odorants induce responses in olfactory sensory neurons via an adenylate cyclase cascade mediated by a G protein. An olfactory-specific guanosine triphosphate (GTP)-binding protein alpha subunit has now been characterized and evidence is presented suggesting that this G protein, termed Golf, mediates olfaction. Messenger RNA that encodes Golf alpha is expressed in olfactory neuroephithelium but not in six other tissues tested. Moreover, within the olfactory epithelium, Golf alpha appears to be expressed only by the sensory neurons. Specific antisera were used to localize Golf alpha protein to the sensory apparatus of the receptor neurons. Golf alpha shares extensive amino acid identity (88 percent) with the stimulatory G protein, Gs alpha. The expression of Golf alpha in S49 cyc- kin- cells, a line deficient in endogenous stimulatory G proteins, demonstrates its capacity to stimulate adenylate cyclase in a heterologous system.

Adenylyl Cyclases↗

Transcription program of red sea bream iridovirus as revealed by DNA microarrays.

Red sea bream iridovirus (RSIV) has been identified as the causative agent of a serious disease in red sea bream and at least 30 other marine fish species. We developed a viral DNA microarray containing 92 putative open reading frames of RSIV to monitor the viral gene transcription program over the time course of an in vitro infection and to classify RSIV transcripts into temporal kinetic expression classes. The microarray analysis showed that viral genes commenced expression as early as 3 h postinfection (p.i.) and this was followed by a rapid escalation of gene expression from 8 h p.i. onwards. Based on the expression of some enzymes associated with viral DNA replication, the DNA replication of RSIV appeared to begin at around 8 h p.i. in infected cells in vitro. Using a de novo protein synthesis inhibitor (cycloheximide) and a viral DNA replication inhibitor (phosphonoacetic acid), 87 RSIV transcripts could be classified into three temporal kinetic classes: nine immediate-early (IE), 40 early (E), and 38 late (L) transcripts. The gene expression of RSIV occurred in a temporal kinetic cascade with three stages (IE, E, and L). Although the three classes of transcripts were distributed throughout the RSIV genome, E transcripts appeared to cluster in at least six discrete regions and L transcripts appeared to originate from seven discrete regions. The microarray data were statistically confirmed by using a t test, and were also clustered into groups based on similarity in the gene expression patterns by using a cluster program.

DNA, Viral↗

Mechanism of VEGF-induced uterine venous hyperpermeability.

BACKGROUND: Transfer of molecular signals from veins to adjacent arteries is an established mechanism of vascular communication in the uterine circulation, which ultimately depends on venous permeability. This study tests the hypotheses that: (1) uterine veins are permeable to intravenous solutes, using a 3-kDa dextran tracer and (2) this permeability is enhanced in response to vascular endothelial growth factor (VEGF). Additionally, the involvement of nitric oxide (NO), calcium, and the phospholipase C-protein kinase C (PLC-PKC) cascade in VEGF-enhanced permeability were investigated, and the impact of pregnancy-induced uterine vascular remodeling on permeability was evaluated. METHODS: Studies utilized fluorimetry to quantitate solute flux in isolated segments of rat uterine vein as a function of endothelial surface area and time under basal and VEGF-stimulated conditions. VEGF signaling was probed using NO synthase inhibition (L-NNA), calcium channel blockade (lanthanum chloride) and withdrawal (calcium-free solution), and inhibitors of the PLC-PKC cascade (U-73122 and chelerythrine chloride, respectively). Gestational effects were assessed using vessels from late pregnant (day 20) rats. RESULTS: Basal flux (control) in nonpregnant animals was 26 +/- 2.5 molecules/microm2/min x 1,000 and was increased significantly by VEGF in a concentration-dependent manner (1 nM approximately 3.3-fold, 10 nM approximately 4.6-fold). Inhibition of PLC, PKC, and calcium signaling, but not NO, attenuated the response to VEGF. Gestation significantly increased flux (78 +/- 9.3 molecules/microm2/min x 1,000), and maintained responsiveness to VEGF. CONCLUSIONS: These results demonstrate uterine venous permeability to intermediate-sized solutes through a VEGF-sensitive pathway involving calcium and PLC-PKC, but not NO, and further substantiate a role for veno-arterial communication in uterine blood flow regulation during pregnancy.

Animals↗

Absence of association between polymorphisms in the hemostatic factor pathway genes and carotid intimal medial thickness: the Framingham Heart Study.

BACKGROUND AND PURPOSE: Fibrinogen, plasminogen activator inhibitor-1, and other key proteins in the coagulation cascade have been implicated in the origin of cardiovascular disease. Polymorphisms in genes encoding these proteins have been associated with variability in plasma levels of these proteins. Carotid intimal medial thickness (IMT) is a heritable, quantitative measure of atherosclerosis that is predictive of subsequent myocardial infarction and stroke. We sought to test whether carotid IMT is associated with polymorphisms in several well-characterized genes in the hemostatic factor pathways. METHODS: Here, 867 men and 911 women (mean age, 57 years) in the Framingham offspring cohort underwent B-mode carotid ultrasonography to determine the mean internal (ICA) and common carotid artery (CCA) IMT. Age-, sex-, and multivariable-adjusted linear regression was used to estimate the association of the following variants with log-transformed CCA and ICA IMT: factor V Leiden, factor VII Arg/Gln, fibrinogen HindIII beta-148, plasminogen activator inhibitor-1 4G/5G, and the glycoprotein IIIa Pl(A2) polymorphism. RESULTS: Mean ICA IMT was 0.58 mm; mean CCA IMT was 0.60 mm. There were no differences in ICA or CCA IMT by genotype for any of the candidate genes in unadjusted, age- or sex-adjusted, and multivariable-adjusted models. CONCLUSIONS: There is no evidence for an association between well-studied polymorphisms in the hemostatic factor genes and carotid IMT. Whether other common genetic variants in hemostatic factor genes are associated with subclinical atherosclerosis remains to be determined.

Blood Coagulation Factors↗

Regulation of Msx genes by a Bmp gradient is essential for neural crest specification.

There is evidence in Xenopus and zebrafish embryos that the neural crest/neural folds are specified at the border of the neural plate by a precise threshold concentration of a Bmp gradient. In order to understand the molecular mechanism by which a gradient of Bmp is able to specify the neural crest, we analyzed how the expression of Bmp targets, the Msx genes, is regulated and the role that Msx genes has in neural crest specification. As Msx genes are directly downstream of Bmp, we analyzed Msx gene expression after experimental modification in the level of Bmp activity by grafting a bead soaked with noggin into Xenopus embryos, by expressing in the ectoderm a dominant-negative Bmp4 or Bmp receptor in Xenopus and zebrafish embryos, and also through Bmp pathway component mutants in the zebrafish. All the results show that a reduction in the level of Bmp activity leads to an increase in the expression of Msx genes in the neural plate border. Interestingly, by reaching different levels of Bmp activity in animal cap ectoderm, we show that a specific concentration of Bmp induces msx1 expression to a level similar to that required to induce neural crest. Our results indicate that an intermediate level of Bmp activity specifies the expression of Msx genes in the neural fold region. In addition, we have analyzed the role that msx1 plays on neural crest specification. As msx1 has a role in dorsoventral pattering, we have carried out conditional gain- and loss-of-function experiments using different msx1 constructs fused to a glucocorticoid receptor element to avoid an early effect of this factor. We show that msx1 expression is able to induce all other early neural crest markers tested (snail, slug, foxd3) at the time of neural crest specification. Furthermore, the expression of a dominant negative of Msx genes leads to the inhibition of all the neural crest markers analyzed. It has been previously shown that snail is one of the earliest genes acting in the neural crest genetic cascade. In order to study the hierarchical relationship between msx1 and snail/slug we performed several rescue experiments using dominant negatives for these genes. The rescuing activity by snail and slug on neural crest development of the msx1 dominant negative, together with the inability of msx1 to rescue the dominant negatives of slug and snail strongly argue that msx1 is upstream of snail and slug in the genetic cascade that specifies the neural crest in the ectoderm. We propose a model where a gradient of Bmp activity specifies the expression of Msx genes in the neural folds, and that this expression is essential for the early specification of the neural crest.

Animals↗

Pseudorabies virus propagated in rabbit kidney-derived RK13 cells is neutralized by natural IgM antibodies in normal swine serum which specifically lyse host cells.

Pseudorabies virus (PRV) propagated in rabbit kidney-derived RK-13 cells (PRV-RK) was neutralized by serum obtained from specific pathogen-free pigs through the activation of complement. The virus-neutralizing activity of swine serum was lost after treatment with ethylene glycol-bis-aminoethylether-N,N,N',N'-tetraacetic acid (EGTA) or ethylenediaminetetraacetic acid (EDTA). Anti-C1q and anti-IgM antibodies also inhibited virus-neutralizing activity. Though IgG-depleted swine serum neutralized PRV, IgM and IgG-free swine serum lost virus-neutralizing activity. Pre-incubation of swine serum with RK-13 cells, but not with swine kidney-derived CPK cells, at 4 degrees C eliminated the virus-neutralizing activity to PRV-RK. Results indicated that swine serum contained natural IgM against an antigen(s) on the RK-13 cell surface and that this surface antigen was integrated into the PRV envelope during the budding process. Thus the natural IgM in swine serum reacted with the RK-13 antigen on the viral envelope, activated the complement cascade and neutralized the PRV-RK.

Animals↗

Current and future therapeutic strategies to target inflammation in stroke.

Experimentally and clinically, stroke is followed by both acute and prolonged inflammatory responses characterized by the production of inflammatory cytokines and leukocyte infiltration into the brain. A debate on whether inflammation after stroke is neurotoxic or participates in brain repair remains unresolved. However, the need to pharmacologically control inflammatory amplification has been commonly acknowledged. The principal challenge of devising successful anti-inflammatory strategies for stroke is to understand molecular and temporal interplay of inflammatory and cell-death-inducing processes triggered by cerebral ischemia in both parenchymal and vascular brain cells. This article will review a number of experimental and clinically tested approaches to reduce brain inflammation and damage after stroke (e.g., anti-neutrophil, anti-ICAM-1, anti-cytokine strategies) and will suggest potential pathways where novel therapeutic targets may emerge, including transcriptional regulators of inflammatory gene expression (e.g., NF-kappaB, proteasome) and signaling pathways (e.g., ICE-cascade, MAPK/MKK/ERK cascade) linked to both inflammation and neuronal cell death. Finally, we will discuss applications of functional genomics technologies in the discovery of stroke diagnostics and therapies.

Animals↗

Effect of the new spacer-device on the deposition of the inhaled metered dose aerosol.

The effect of the new spacer-device on the in vitro and in vivo deposition of inhaled drug particles was studied. The in vitro deposition of beclomethasone dipropionate 250 micrograms/dose aerosol administered either through the conventional aerosol actuator with the short plastic mouthpiece or through the new pear-shaped spacer-device was evaluated with the modified cascade impactor method. For the in vivo study the disodium cromoglycate particles were labelled with a pure gamma-radiator 99mTc using a coprecipitation technique based on spray drying. The deposition of the inhaled disodium cromoglycate particles in the human respiratory tract after administration of the drug doses from the devices tested was determined by means of a gamma camera. The new spacer-device increased both in the in vitro and in vivo tests the fraction of the drug dose deposited into the therapeutically significant regions of the respiratory tract. In addition, the therapeutically insignificant fraction deposited in the upper airways and mouth clearly decreased. Thus using the new spacer-device evaluated in this study the local side effects would be decreased.

Aerosols↗

Reduced activation of immunomodulatory transcription factors during positive end-expiratory pressure adjustment based on volume-dependent compliance in isolated perfused rabbit lungs.

BACKGROUND: Repeated alveolar collapse and cyclic alveolar overdistension with associated activation of inflammatory signalling cascades contribute to ventilator-induced lung injury (VILI). The appropriate positive end-expiratory pressure (PEEP) which prevents or ameliorates VILI is unknown. In the isolated perfused lung, repeated adjustments of PEEP based on the continuously analysed intratidal compliance-volume curve have previously been shown to result in full end-expiratory alveolar recruitment and low risk of cyclic alveolar overdistension. Accordingly, we tested the hypothesis that such ventilatory management reduces intrapulmonary activation of the immunomodulatory transcription factors nuclear factor kappaB (NF-kappaB), activator protein 1 (AP-1) and cAMP-responsive element binding protein (CREB) which induce the expression of various chemokines and cytokines. METHODS: Isolated perfused rabbit lungs were randomly allocated to one of three groups: zero end-expiratory pressure (ZEEP) to induce repeated alveolar collapse (n=6), high PEEP to induce cyclic alveolar overdistension (n=6) and repeated PEEP adjustments based on intratidal compliance-volume curve analysis by the slice method to minimize repeated alveolar collapse and overdistension (n=9). All lungs were ventilated with a tidal volume of 6 ml kg(-1) bodyweight for 120 min. Thereafter, activation of transcription factors NF-kappaB, AP-1 and CREB in lung tissue was analysed by electrophoretic mobility shift assay. RESULTS: High PEEP was associated with the highest activation of NF-kappaB and AP-1 and repeated PEEP adjustments with the lowest activation when compared with the other two study groups (P<0.001). In contrast, activation of CREB did not differ between groups. Activated NF-kappaB and AP-1 protein complexes consisted mainly of the transactivators p50/p65 and c-Fos/Jun, respectively. CONCLUSIONS: In isolated perfused rabbit lungs, repeated adjustments of PEEP based on the continuously analysed intratidal compliance-volume curve were associated with less activation of early steps of inflammatory signalling cascades than ventilation with ZEEP or high PEEP.

Animals↗

Apoptogenic ganglioside GD3 directly induces the mitochondrial permeability transition.

Early events in apoptotic cascades initiated by ceramides or by activation of the surface receptor CD95 (Fas/APO-1) include the formation of ganglioside GD3. GD3 appears to be both necessary and sufficient to propagate this lipid-mediated apoptotic pathway. Later events common to many apoptotic pathways include induction of the mitochondrial permeability transition (PT) and cytochrome c release, which in turn triggers downstream caspases and cell death. The links between GD3 formation and downstream stages of apoptosis are unknown. We report that ganglioside GD3 directly induces the PT in isolated rat liver mitochondria at 30-100 microM in the presence of exogenous substrate (succinate) and at approximately 3 microM in the absence of exogenous substrate. In contrast, other gangliosides tested (e.g. GM1) have only weak stimulatory effects in the presence of succinate and protect against PT induction in the absence of respiratory substrates. GD3-mediated induction of PT was antagonized by known PT inhibitors, namely cyclosporin A, ADP, trifluoperazine, and Mg(2+). GD3 induced PT even in the presence of submicromolar Ca(2+); GD3 is therefore the first biological PT inducer identified that does not require elevated Ca(2+). Exposure to GD3 also led to mitochondrial cytochrome c release. In contrast, C(2)-ceramide, which can initiate the lipid-mediated apoptotic cascade in susceptible cells, failed to either induce PT or release cytochrome c. These observations suggest that GD3 propagates apoptosis by inducing the PT and cytochrome c release. This model provides a mechanistic link between the earlier and later stages of CD95-induced/ceramide-mediated apoptosis.

Adenosine Diphosphate↗

[The complement system--a fascinating biological cascade. 2--clinical aspects].

Knowledge about the complement system has increased considerably the recent years. Research in the field of activation and regulation of the system has contributed to a more dynamic conception of how the system functions under physiological and pathophysiological conditions. In the first paper, the author considered some important physiological mechanisms. In this paper, he discusses some clinical aspects of complement deficiencies and pathological complement activation. He briefly reviews relevant laboratory tests for clinical evaluation of complement, with particular emphasis on interpretation of the results.

Autoimmune Diseases↗