SEARCH · PubMed Health

Results for “Convergence”

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 919 records · Page 51Linked to original sources

PubMed2006

Sodium channel genes and the evolution of diversity in communication signals of electric fishes: convergent molecular evolution.

We investigated whether the evolution of electric organs and electric signal diversity in two independently evolved lineages of electric fishes was accompanied by convergent changes on the molecular level. We found that a sodium channel gene (Na(v)1.4a) that is expressed in muscle in nonelectric fishes has lost its expression in muscle and is expressed instead in the evolutionarily novel electric organ in both lineages of electric fishes. This gene appears to be evolving under positive selection in both lineages, facilitated by its restricted expression in the electric organ. This view is reinforced by the lack of evidence for selection on this gene in one electric species in which expression of this gene is retained in muscle. Amino acid replacements occur convergently in domains that influence channel inactivation, a key trait for shaping electric communication signals. Some amino acid replacements occur at or adjacent to sites at which disease-causing mutations have been mapped in human sodium channel genes, emphasizing that these replacements occur in functionally important domains. Selection appears to have acted on the final step in channel inactivation, but complementarily on the inactivation "ball" in one lineage, and its receptor site in the other lineage. Thus, changes in the expression and sequence of the same gene are associated with the independent evolution of signal complexity.

Amino Acid Sequence↗

PubMed2006

Topoisomerase IIIalpha and Bloom's helicase can resolve a mobile double Holliday junction substrate through convergent branch migration.

It has long been suspected that a double Holliday junction (dHJ) could be resolved by a topoisomerase partnered with a helicase by convergent branch migration of the HJs. Genetic analysis of yeast TOP3 and SGS1 has lent considerable evidence to the notion that the protein products of these genes are involved in just such a process, although biochemical analysis of the metabolism of a dHJ has been hindered by the lack of a substrate that adequately replicates the endogenous structure. We have synthesized a dHJ substrate that recapitulates many of the features of an endogenous dHJ and represents a much earlier intermediate in the resolution pathway. Here, we show that Drosophila topoisomerase IIIalpha (Topo IIIalpha) and Blm (a homolog of Sgs1) are capable of resolving this substrate to non-cross-over products and that this activity is stimulated by replication protein A (RPA). We investigated the ability of other Drosophila topoisomerases to perform this reaction in concert with Blm and RPA and discovered that this resolution activity is unique to Topo IIIalpha. Examination of the mechanism of resolution reveals that Topo IIIalpha, Blm, and RPA resolve this substrate by convergent migration of the two HJs toward each other, collapsing the dHJ. This mechanism stands in contrast to classic resolvase activities that use a structure-specific endonuclease to cleave the HJs.

Animals↗

PubMed2002

Transcriptional collision between convergent genes in budding yeast.

Transcriptional interference between genes and the regulatory elements of simple eukaryotes such as Saccharomyces cerevisiae is an unavoidable consequence of their compressed genetic arrangement. We have shown previously that with the tandem arranged genes GAL10 and GAL7, inefficient transcriptional termination of the upstream gene inhibits initiation of transcription on the downstream gene. We now show that transcriptional interference can occur also with S. cerevisiae RNA polymerase II genes arranged convergently. We demonstrate that when the GAL10 and GAL7 genes are rearranged in a convergent orientation, transcriptional initiation occurs at full levels. However, as soon as the two transcripts begin to overlap, elongation is restricted, resulting in a severe reduction in steady-state mRNA accumulation. This effect is observed only in cis arrangement, arguing against RNA-interference effects acting on the potential generation of antisense transcripts. These data reinforce the necessity of separating adjacent RNA polymerase II transcription units by efficient termination signals.

Base Sequence↗

PubMed2024

TMPRSS2-mediated SARS-CoV-2 uptake boosts innate immune activation, enhances cytopathology, and drives convergent virus evolution.

The accessory protease transmembrane protease serine 2 (TMPRSS2) enhances severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uptake into ACE2-expressing cells, although how increased entry impacts downstream viral and host processes remains unclear. To investigate this in more detail, we performed infection assays in engineered cells promoting ACE2-mediated entry with and without TMPRSS2 coexpression. Electron microscopy and inhibitor experiments indicated TMPRSS2-mediated cell entry was associated with increased virion internalization into endosomes, and partially dependent upon clathrin-mediated endocytosis. TMPRSS2 increased panvariant uptake efficiency and enhanced early rates of virus replication, transcription, and secretion, with variant-specific profiles observed. On the host side, transcriptional profiling confirmed the magnitude of infection-induced antiviral and proinflammatory responses were linked to uptake efficiency, with TMPRSS2-assisted entry boosting early antiviral responses. In addition, TMPRSS2-enhanced infections increased rates of cytopathology, apoptosis, and necrosis and modulated virus secretion kinetics in a variant-specific manner. On the virus side, convergent signatures of cell-uptake-dependent innate immune induction were recorded in viral genomes, manifesting as switches in dominant coupled Nsp3 residues whose frequencies were correlated to the magnitude of the cellular response to infection. Experimentally, we demonstrated that selected Nsp3 mutations conferred enhanced interferon antagonism. More broadly, we show that TMPRSS2 orthologues from evolutionarily diverse mammals facilitate panvariant enhancement of cell uptake. In summary, our study uncovers previously unreported associations, linking cell entry efficiency to innate immune activation kinetics, cell death rates, virus secretion dynamics, and convergent selection of viral mutations. These data expand our understanding of TMPRSS2's role in the SARS-CoV-2 life cycle and confirm its broader significance in zoonotic reservoirs and animal models.

SARS-CoV-2↗

PubMed1972

Note on the convergence of sequences of rational functions of best approximation to a meromorphic function.

If the function f(z) is meromorphic at every finite point of the plane, analytic on C: [unk]z[unk] </= 1, there are results that can be established concerning the convergence of the sequence R(n)(z) of rational functions of each degree n of best approximation to f(z) on C. However, we need to assume certain additional conditions on the convergence of the sequence R(n)(z) itself. The results generalize to more general sets C and to more general functions.

Journal Article↗

PubMed1972

Airey's Converging Factor.

Asmptotic series for the calculation of functions, for values of the argument numerically >1, start off with terms whose numerical values decrease but, at a certain stage, the terms begin to increase in numerical value and must be ignored. At this stage, there may be two adjacent terms of equal numerical value; when the least term of the asymptotic series is spoken of, it is in reference to the first of these two terms. The sum of the initial terms of the asymptotic series up to, and including, the least term often furnishes a fair approximation to the desired value of the function being evaluated. It was early observed by computers that if the terms of the asymptotic series alternate in sign, this approximation was often improved by replacing the least term by its half. The factor by which the least term of the asymptotic series must be multiplied so that the true value of the function being evaluated is obtained by addition of this modified least term to the remaining initial terms of the asymptotic series is known as the converging factor for the asymptotic series. The converging factor for the asymptotic series involved in the calculation of the exponential integral, for large negative values of the argument, was given as a power series in the reciprocal of the argument by Airey; the first term of this series is (1/2). A method for the determination of the coefficients of this series is given.

Journal Article↗

PubMed1998

Preparation of MUC-1 oligomers using an improved convergent solid-phase peptide synthesis.

The sequentially repeating nature of the core mucin polypeptide chain MUC-1 on the surface of malignant cells makes it an excellent target for cancer immunotherapy. We describe a reliable and efficient method of synthesizing oligomers, up to five tandem repeats and oligomer heterotope derivatives with a 15-amino acid epitope from tetanus toxin using an improved convergent solid-phase peptide synthesis. The different oligomers were easily distinguishable by reverse-phase high pressure liquid chromatography, but they were poorly fixed and migrated with the same migration rate, irrespective of size, in electrophoretic studies. In contrast, the oligomer heterotopes exhibited size-dependent electrophoretic behavior but in high pressure liquid chromatography chromatograms the different heterotopes were eluted simultaneously in two peaks representing the L- and D-enantiomers of the derivatives. The oligomer heterotopes were recognized as antigens in Western blotting with a murine monoclonal antibody against the epitope APDTR. In enzyme immunoassay studies with the same antibody an increasing reactivity was observed against the larger oligomers and confirmed by inhibition assays as the MUC-1 pentamer was the most efficient inhibitor. These results support the suggestion that the pentamer attains a structure closer to the native conformation and is more immunogenic. In conclusion, large composite peptides can be reliably synthesized with the convergent solid-phase peptide strategy offering an attractive option to vaccine designing and development.

Amino Acid Sequence↗

PubMed2000

Targeting of PYK2 to focal adhesions as a cellular mechanism for convergence between integrins and G protein-coupled receptor signaling cascades.

The non-receptor tyrosine kinase PYK2 appears to function at a point of convergence of integrins and certain G protein-coupled receptor (GPCR) signaling cascades. In this study, we provide evidence that translocation of PYK2 to focal adhesions is triggered both by cell adhesion to extracellular matrix proteins and by activation of the histamine GPCR. By using different mutants of PYK2 as green fluorescent fusion proteins, we show that the translocation of PYK2 to focal adhesions is not dependent on its catalytic activity but rather is mediated by its carboxyl-terminal domain. Translocation of PYK2 to focal adhesions was attributed to enhanced tyrosine phosphorylation of PYK2 and its association with the focal adhesion proteins paxillin and p130(Cas). Translocation of PYK2 to focal adhesions, as well as its tyrosine phosphorylation in response to histamine treatment, was abolished in the presence of protein kinase C inhibitors or cytochalasin D treatment, whereas activation of protein kinase C by phorbol ester resulted in focal adhesion targeting of PYK2 and its tyrosine phosphorylation in an integrin-clustering dependent manner. Overexpression of a wild-type PYK2 enhanced ERK activation in response to histamine, whereas a kinase-deficient mutant substantially inhibited this response. Furthermore, inhibition of PYK2 translocation to focal adhesions abolished ERK activation in response to histamine treatment. These results suggest that PYK2 apparently links between GPCRs and focal adhesion-dependent ERK activation and can provide the molecular basis underlying PYK2 function at a point of convergence between signaling pathways triggered by extracellular matrix proteins and certain GPCR agonists.

Cell Line↗

PubMed2000

Fas- and tumor necrosis factor-mediated apoptosis uses the same binding surface of FADD to trigger signal transduction. A typical model for convergent signal transduction.

FADD is known to function as a common signaling conduit in Fas- and tumor necrosis factor (TNF)-mediated apoptosis. The convergent death signals from the Fas receptor and TNF receptor 1 are transferred to FADD by death domain interactions triggering the same cellular event, caspase-8 activation. In this work, we investigated whether the same binding surface of FADD is used for both signaling pathways by using FADD death domain mutants. Mutations in helices alpha2 and alpha3 of the FADD death domain, the interacting surface with the Fas death domain, affected TNF-mediated apoptosis to various extents. This indicated that TNF-mediated apoptosis uses the same binding surface of the FADD death domain as Fas-mediated apoptosis. The binding specificity is not the same, however. Some mutations affected the binding affinity of the Fas death domain for the FADD death domain, but did not influence TNF-mediated apoptosis and vice versa. Interestingly, all mutants tested that affected TNF-mediated apoptosis have structural perturbations, implying that the structural integrity, involving helices alpha2 and alpha3 in particular, is critical in TNF-mediated apoptosis. Our results suggest that different signaling molecules use a similar structural interaction to trigger the same cellular event, such as caspase-8 recruitment, which could be typical in convergent signal transduction.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Risk and panic in late modernity: implications of the converging sites of social anxiety.

Comparing moral panic with the potential catastrophes of the risk society, Sheldon Ungar contends that new sites of social anxiety emerging around nuclear, medical, environmental and chemical threats have thrown into relief many of the questions motivating moral panic research agendas. He argues that shifting sites of social anxiety necessitate a rethinking of theoretical, methodological and conceptual issues related to processes of social control, claims making and general perceptions of public safety. This paper charts an alternative trajectory, asserting that analytic priority rests not with an understanding of the implications of changing but converging sites of social anxiety. Concentrating on the converging sites of social anxiety in late modernity, the analysis forecasts a proliferation of moral panics as an exaggerated symptom of the heightened sense of uncertainty purported to accompany the ascendency of the risk society.

Anxiety↗

PubMed1998

Task analysis for the investigation of human error in safety-critical software design: a convergent methods approach.

An investigation was conducted into sources of error within a safety-critical software design task. A number of convergent methods of task- and error-analysis were systematically applied: hierarchical task analysis (HTA), error log audit, error observation, work sample and laboratory experiment. HTA, which provided the framework for the deployment of subsequent methods, revealed possible weaknesses in the areas of task automation and job organization. Application of other methods within this more circumscribed context focused on the impact of task and job design issues. The use of a convergent methods approach draws attention to the benefits and shortcomings of individual analysis methods, and illustrates the advantages of combining techniques to analyse complex problems. The features that these techniques should possess are highlighted.

Ergonomics↗

PubMed1998

An Analysis and Comparison of Convergence and Uniqueness of Time-Independent Bone Adaptation Models.

Several stimuli are proposed in the bone remodeling theory. It is not clear, if a unique solution exists and if the result is convergent using a certain stimulus. In this study, the strain stimulus, strain energy stimulus and the von Mises stress stimulus for bone remodeling are compared and applied to a square plate model using the finite element method. In the plane stress state, the remodeling equilibrium equations are transformed into functions of only the principal strains and the graphs of these functions are drawn in a diagram using the principal strains as the variables of two coordinate axes. The equation of the sum of principal strain squared equal to a constant is a circle in the diagram. The remodeling equilibrium equation of the strain stimulus is a quadrangle fitting into the circle, the remodeling equilibrium equation of the strain energy stimulus is an ellipse and the remodeling equilibrium equation of the von Mises stress stimulus is also an ellipse close to the principal strains circle when we take the same constants in the above equations. Using the finite element method, two models are performed with the uniform initial elastic properties and with the semi-random initial distribution of the elastic properties. The principal strains as the final finite element results converge within 2% of the objective constant for all the different stimuli. The obtained Young's moduli of two models as the adaptation object are different but in equilibrium, i.e. the equilibrium solution of adaptation model is not unique. The principal strains can not be used to examine the uniqueness of solution, since two different solutions can have the same results of principal strains. Using a certain stimulus, certain initial properties and a certain iterative equation, the solution is unique in equilibrium. The results using the model in this study show also that the same results can be obtained using any of the three stimuli when a proper constant in each remodeling equilibrium equation is chosen.

Journal Article↗

PubMed2006

The convergent and discriminant validity of burnout measures in sport: a multi-trait/multi-method analysis.

Athlete burnout research has been hampered by the lack of an adequate measurement tool. The Athlete Burnout Questionnaire (ABQ) and the Maslach Burnout Inventory General Survey (MBI-GS) are two recently developed self-report instruments designed to assess burnout. The convergent and discriminant validity of the ABQ and MBI-GS were assessed through multi-trait/multi-method analysis with a sporting population. Overall, the ABQ and the MBI-GS displayed acceptable convergent validity with matching subscales highly correlated, and satisfactory internal discriminant validity with lower correlations between non-matching subscales. Both scales also indicated an adequate discrimination between the concepts of burnout and depression. These findings add support to previous findings in non-sporting populations that depression and burnout are separate constructs. Based on the psychometric results, construct validity analysis and practical considerations, the results support the use of the ABQ to assess athlete burnout.

Adolescent↗

PubMed2005

Convergent validity of self-awareness measures and their association with employment outcome in adults following acquired brain injury.

PRIMARY OBJECTIVE: To examine the convergent validity of three measures of self-awareness and their correlation with employment status in 38 adults with acquired brain injury. RESEARCH DESIGN: A cross-sectional study examining correlations between standardized measures of self-awareness and employment outcome. METHODS AND PROCEDURES: Self-awareness was assessed using the Self-Awareness of Deficits Interview (SADI), the Self-Regulation Skills Interview (SRSI) and the Awareness Questionnaire (AQ). Employment outcome was classified using a five-point work status rating scale and work items from the Sydney Psychosocial Reintegration Scale (SPRS). MAIN OUTCOMES AND RESULTS: Significant correlations were found between the SADI total score and the AQ discrepancy score and between the total SADI score and the SRSI indices. The work status rating scale was significantly correlated with the SADI and SRSI scores but not the AQ. CONCLUSIONS: The findings support the convergent validity of the three measures of self-awareness and highlight the need to address self-awareness deficits in vocational rehabilitation.

Adult↗

PubMed1993

On the intrinsic force of convergence to stability.

"Observed populations differ greatly in the speed with which they approach the stable form, but what determines rates of convergence is not fully understood.... Here we examine the trajectory to stability, derive a mathematical expression for the force of convergence, and provide an approximate relationship in terms of the mean and variance of the stable net maternity function." Trajectories for Japan, Togo, and the United States are used as illustrations. (SUMMARY IN FRE)

Africa↗

PubMed1997

The autophagic and endocytic pathways converge at the nascent autophagic vacuoles.

We used an improved cryosectioning technique in combination with immunogold cytochemistry and morphometric analysis to study the convergence of the autophagic and endocytic pathways in isolated rat hepatocytes. The endocytic pathway was traced by continuous uptake of gold tracer for various time periods, up to 45 min, while the cells were incubated in serum-free medium to induce autophagy. Endocytic structures involved in fusion with autophagic vacuoles (AV) were categorized into multivesicular endosomes (MVE) and vesicular endosomes (VE). Three types of AV--initial (AVi), intermediate (AVi/d), and degradative (AVd)--were defined by morphological criteria and immunogold labeling characteristics of marker enzymes. The entry of tracer into AV, manifested as either tracer-containing AV profiles (AV+) or fusion profiles (FP+) between AV and tracer-positive endosomal vesicles/vacuoles, was detected as early as 10 min after endocytosis. The number of AV+ exhibited an exponential increase with time. FP+ between MVE or VE and all three types of AV were observed. Among the 112 FP+ scored, 36% involved VE. Of the AV types, AVi and AVi/d were found five to six times more likely to be involved in fusions than AVd. These fusion patterns did not significantly change during the period of endocytosis (15-45 min). We conclude that the autophagic and endocytic pathways converge in a multistage fashion starting within 10 min of endocytosis. The nascent AV is the most upstream and preferred fusion partner for endosomes.

Animals↗

PubMed2004

STAT3 noncell-autonomously controls planar cell polarity during zebrafish convergence and extension.

Zebrafish signal transducer and activator of transcription 3 (STAT3) controls the cell movements during gastrulation. Here, we show that noncell-autonomous activity of STAT3 signaling in gastrula organizer cells controls the polarity of neighboring cells through Dishevelled-RhoA signaling in the Wnt-planar cell polarity (Wnt-PCP) pathway. In STAT3-depleted embryos, although all the known molecules in the Wnt-PCP pathway were expressed normally, the RhoA activity in lateral mesendodermal cells was down-regulated, resulting in severe cell polarization defects in convergence and extension movements identical to Strabismus-depleted embryos. Cell-autonomous activation of Wnt-PCP signaling by DeltaN-dishevelled rescued the defect in cell elongation, but not the orientation of lateral mesendodermal cells in STAT3-depleted embryos. The defect in the orientation could be rescued by transplantation of shield cells having noncell-autonomous activity of STAT3 signaling. These results suggest that the cells undergoing convergence and extension movement may sense the gradient of signaling molecules, which are expressed in gastrula organizer by STAT3 and noncell-autonomously activate PCP signaling in neighboring cells during zebrafish gastrulation.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Essential roles of G{alpha}12/13 signaling in distinct cell behaviors driving zebrafish convergence and extension gastrulation movements.

Galpha(12/13) have been implicated in numerous cellular processes, however, their roles in vertebrate gastrulation are largely unknown. Here, we show that during zebrafish gastrulation, suppression of both Galpha(12) and Galpha(13) signaling by overexpressing dominant negative proteins and application of antisense morpholino-modified oligonucleotide translation interference disrupted convergence and extension without changing embryonic patterning. Analyses of mesodermal cell behaviors revealed that Galpha(12/13) are required for cell elongation and efficient dorsalward migration during convergence independent of noncanonical Wnt signaling. Furthermore, Galpha(12/13) function cell-autonomously to mediate mediolateral cell elongation underlying intercalation during notochord extension, likely acting in parallel to noncanonical Wnt signaling. These findings provide the first evidence that Galpha(12) and Galpha(13) have overlapping and essential roles in distinct cell behaviors that drive vertebrate gastrulation.

Animals↗