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PubMed2004

Paraxial protocadherin coordinates cell polarity during convergent extension via Rho A and JNK.

Convergent extension movements occur ubiquitously in animal development. This special type of cell movement is controlled by the Wnt/planar cell polarity (PCP) pathway. Here we show that Xenopus paraxial protocadherin (XPAPC) functionally interacts with the Wnt/PCP pathway in the control of convergence and extension (CE) movements in Xenopus laevis. XPAPC functions as a signalling molecule that coordinates cell polarity of the involuting mesoderm in mediolateral orientation and thus selectively promotes convergence in CE movements. XPAPC signals through the small GTPases Rho A and Rac 1 and c-jun N-terminal kinase (JNK). Loss of XPAPC function blocks Rho A-mediated JNK activation. Despite common downstream components, XPAPC and Wnt/PCP signalling are not redundant, and the activity of both, XPAPC and PCP signalling, is required to coordinate CE movements.

Animals↗

PubMed2003

Acute influences of estrogen and testosterone on divergent and convergent thinking in postmenopausal women.

Previous studies indicated an enhanced capability of divergent creative thinking in young women during the ovulatory phase, which expressed itself also by an increased dimensional complexity of ongoing electroencephalographic (EEG) activity. Considering the enhanced plasma levels of estrogen and testosterone characterizing the ovulatory phase, we tested whether short-term administration of estrogen or testosterone in postmenopausal women with constantly low levels of gonadal steroids induces similar changes in divergent thinking. In two placebo-controlled cross-over studies, healthy postmenopausal women (n=12, in each study, mean age 58 years, range 47-65 years) were treated transdermally over 3 days with estrogen and testosterone, respectively, at doses inducing plasma hormone concentrations comparable with those observed in young women around ovulation. Capabilities of divergent thought and convergent analytical thought, performance on motor perseveration, and verbal memory were examined. EEG activity was recorded while subjects performed on tasks of thinking and during mental relaxation. Estrogen impaired divergent thinking (p <0.01) and enhanced convergent thinking, motor perseveration, and memory for the initial word list (p <0.05 for all tests). In parallel, EEG dimensional complexity was reduced (p <0.05). Overall, these changes indicate an estrogen-induced shift from a "divergent" towards a more "convergent" mode of processing. However, overall less consistent, effects of testosterone were opposite to those of estrogen. It increased performance on some of the divergent thinking tasks (p <0.05), and tended to increase EEG dimensional complexity during divergent thinking. Data indicate a differential sensitivity of modes of thinking to short-term treatment with estrogen and testosterone in postmenopausal women.

Aged↗

PubMed2002

Convergence of parvocellular and magnocellular information channels in the primary visual cortex of the macaque.

We investigated whether responses of single cells in the striate cortex of anaesthetized macaque monkeys exhibit signatures of both parvocellular (P) and magnocellular (M) inputs from the dorsal lateral geniculate nucleus (dLGN). We used a palette of 128 isoluminant hues at four different saturation levels to test responses to chromatic stimuli against a white background. Spectral selectivity with these isoluminant stimuli was taken as an indication of P inputs. The presence of magnocellular inputs to a given cortical cell was deduced from its responses to a battery of tests, including assessment of achromatic contrast sensitivity, relative strengths of chromatic and luminance borders in driving the cell at different velocities and conduction velocity of their retino-geniculo-cortical afferents. At least a quarter of the cells in our cortical sample appear to receive convergent P and M inputs. We cannot however, exclude the possibility that some of these cells could be receiving a convergent input from the third parallel channel from the dLGN, namely the koniocellular (K) rather than the P channel. The neurons with convergent P and M inputs were recorded not only from supragranular and infragranular layers but also from the principal geniculate input recipient layer 4. Thus, our results challenge classical ideas of strict parallelism between different information streams at the level of the primate striate cortex.

Afferent Pathways↗

PubMed1995

Convergence of afferents from superior sagittal sinus and tooth pulp on cells in the thalamus of the cat.

We have previously shown convergence of craniovascular and tooth pulp afferents in the cervical spinal cord of cats. This study looked for similar convergence in the thalamus. Fifty-four thalamic cells with input from tooth pulp, superior sagittal sinus, or both, were identified. Twenty-nine cells with tooth pulp and superior sagittal sinus input were located in the ventrobasal complex of the intralaminar nuclei. Most of these 29 cells were also excited by cooling the contralateral tooth pulp, and 21 had receptive fields on the contralateral face or forelimb. Twenty cells excited by stimulation of superior sagittal sinus, and not tooth pulp, were found in several nuclei. The 5 cells excited by stimulation of tooth pulp, but not sagittal sinus, were restricted to the ventrobasal complex. The data confirm convergence from sagittal sinus, tooth pulp, and skin in the thalamus of anaesthetized cats.

Afferent Pathways↗

PubMed2005

Basis set convergence studies of Hartree-Fock calculations of molecular properties within the resolution of the identity approximation.

Within the resolution of the identity (RI) method, the convergence of the Hartree-Fock (HF) total molecular energy and the multipole moments in the course of the combined regular expansion of the molecular and auxiliary (RI) basis sets is studied. Dunning's cc-pVXZ series is used for both the molecular and the RI basis sets. The results show the calculated quantities converge to the HF limit when both the molecular and the RI basis sets are expanded from correlation-consistent polarized valence double zeta to correlation-consistent polarized valence sextuple zeta. Combinations of molecular/RI basis sets sufficient for convergence of the total energy and of the multipole moments at various accuracy levels have been determined. A measure of the RI basis set incompleteness is suggested and discussed. As it is significantly faster than the standard HF algorithm for small and midsize molecules, the RI-HF method, together with appropriate expanding series of both molecular and RI basis sets, provide an efficient tool to estimate and control the error of the Hartree-Fock calculations due to the finite basis set.

Journal Article↗

PubMed2006

Spectral convergence of the quadrature discretization method in the solution of the Schrodinger and Fokker-Planck equations: comparison with sinc methods.

Spectral methods based on nonclassical polynomials and Fourier basis functions or sinc interpolation techniques are compared for several eigenvalue problems for the Fokker-Planck and Schrodinger equations. A very rapid spectral convergence of the eigenvalues versus the number of quadrature points is obtained with the quadrature discretization method (QDM) and the appropriate choice of the weight function. The QDM is a pseudospectral method and the rate of convergence is compared with the sinc method reported by Wei [J. Chem. Phys., 110, 8930 (1999)]. In general, sinc methods based on Fourier basis functions with a uniform grid provide a much slower convergence. The paper considers Fokker-Planck equations (and analogous Schrodinger equations) for the thermalization of electrons in atomic moderators and for a quartic potential employed to model chemical reactions. The solution of the Schrodinger equation for the vibrational states of I2 with a Morse potential is also considered.

Journal Article↗

PubMed1977

Binocular convergence as a determinant of reaching behavior in infancy.

Reaching behavior in eighteen- to thirty-two-week-old infants was studied as a function of binocular convergence. The infant looked at the object to be reached for through prism arrangements which changed convergence only. The reaches obtained were nearly always directed at the virtual object defined by convergence. Corrections of the reaches, if any, were made rather late and often not before the hand arrived at the place of the virtual object.

Age Factors↗

PubMed1998

Test of a convergence model for color transparency perception.

Models of color transparency suggest that a region in which colors of surfaces converge in color space will appear transparent. The convergence is described by a transparency parameter alpha and a target of convergence. To test such models psychophysically, observers were presented a display with four colored areas. The colors of three of the areas were chosen in advance by the experimenter. The task of the observer was to choose the color of the fourth area to make a central region appear transparent. Settings for the fourth color were collected for a total of twenty-four color combinations chosen from three planes in color space. Observers' settings agreed well with the model, which predicts that choices for the fourth color lie along a line segment in color space that is parameterized by alpha. The results suggest further that color discriminability and color opponency also influence transparency judgment.

Color Perception↗

PubMed1979

Local convergence theorems for adaptive stochastic approximation schemes.

For the regression model y = M(x) + epsilon, adaptive stochastic approximation schemes of the form x(n+1) = x(n) - y(n)/(nb(n)) for choosing the levels x(1),x(2),... at which y(1),y(2),... are observed converge with probability 1 to the unknown root theta of the regression function M(x). Certain local convergence theorems that relate the convergence rate of x(n) - theta to the limiting behavior of the random variables b(n) are established.

Journal Article↗

PubMed1992

On the origin of the enthalpy and entropy convergence temperatures in protein folding.

Temperature dependence of the thermodynamics of folding/unfolding for cytochrome c has been determined as a function of moderate [0-10% (vol/vol)] concentrations of methanol. Heat capacity change (delta Cp) for unfolding decreases with increased concentrations of methanol, consistent with a higher solvent hydrophobicity. For a given transition temperature, this effect results in higher experimental enthalpy (delta H) and entropy (delta S) changes with increased methanol concentrations. When the enthalpy or entropy data sets obtained at different methanol concentrations are plotted as a function of temperature, they are seen to converge and assume common values around 100 degrees C for delta H and 112 degrees C for delta S. These convergence temperatures are similar to those obtained for different proteins in aqueous solution when delta H and delta S are normalized with respect to number of residues. It has been previously hypothesized that these convergence temperatures correspond to the temperatures at which the hydrophobic contributions to delta H and delta S are zero; the results presented here agree with this viewpoint.

Calorimetry, Differential Scanning↗

PubMed2001

DNA array studies demonstrate convergent regulation of virulence factors by Cph1, Cph2, and Efg1 in Candida albicans.

Candida albicans, normally a human commensal, can cause fatal systemic infections under certain circumstances. Its unique ability to switch from yeast to hyphal growth in response to various environmental signals is inherent to its pathogenicity. Filamentation is regulated by multiple pathways including a Cph1-mediated mitogen-activated protein kinase pathway, an Efg1-mediated cAMP/PKA pathway, and a Cph2 pathway. To gain a general picture of how these various signaling pathways regulate differential gene expression during filamentation, we have constructed a partial C. albicans DNA array of 7,000 genes and used it to study the gene expression profiles using various mutants and growth conditions. By combining this novel technology with a new liquid medium in which cph1/cph1 is defective in filamentation, previously identified differentially expressed genes (ECE1, HWP1, HYR1, RBT1, SAPs5-6, and RBT4) are found to be regulated by all three pathways. In addition, two novel genes, DDR48 and YPL184, have been found to be differentially regulated during hyphal development and by all three pathways. This suggests that distinct filamentation signaling pathways converge to regulate a common set of differentially expressed genes. As one of the mechanisms for the observed convergence, we find that the transcription of a key regulator, TEC1, is regulated by Efg1 and Cph2. Importantly, most of the genes regulated by multiple filamentation pathways encode known virulence factors. Perhaps, C. albicans utilizes converging pathways to regulate its vital virulence factors to ensure its survival and pathogenicity in various host environments.

Basic Helix-Loop-Helix Proteins↗

PubMed2003

Convergence of peroxisome proliferator-activated receptor gamma and Foxo1 signaling pathways.

The forkhead factor Foxo1 (or FKHR) was identified in a yeast two-hybrid screen as a peroxisome proliferator-activated receptor (PPAR) gamma-interacting protein. Foxo1 antagonized PPARgamma activity and vice versa indicating that these transcription factors functionally interact in a reciprocal antagonistic manner. One mechanism by which Foxo1 antagonizes PPARgamma activity is through disruption of DNA binding as Foxo1 inhibited the DNA binding activity of a PPARgamma/retinoid X receptor alpha heterodimeric complex. The Caenorhabditis elegans nuclear hormone receptor, DAF-12, interacted with the C. elegans forkhead factor, DAF-16, paralleling the interaction between PPARgamma and Foxo1. daf-12 and daf-16 have been implicated in C. elegans insulin-like signaling pathways, and PPARgamma and Foxo1 likewise have been linked to mammalian insulin signaling pathways. These results suggest a convergence of PPARgamma and Foxo1 signaling that may play a role in insulin action and the insulinomimetic properties of PPARgamma ligands. A more general convergence of nuclear hormone receptor and forkhead factor pathways may be important for multiple biological processes and this convergence may be evolutionarily conserved.

3T3-L1 Cells↗

PubMed2001

Eating patterns--temporal distribution, converging and diverging foods, meals eaten inside and outside of the home--implications for developing FBDG.

OBJECTIVE: A consideration of eating patterns in the general population is necessary when deriving food-based dietary guidelines (FBDG) as promoting the intake of one food may indirectly result in the increased consumption of another, which may not always be desirable. A number of issues that influence meal patterns such as temporal distribution of food intake (using data from the Netherlands), converging and diverging foods (using data from Ireland) and meals eaten inside and outside of the home (using data from the UK) are examined and discussed in the context of developing FBDG. SETTING: Food intake databases from three EU countries: The Netherlands, Ireland and the UK. RESULTS: The hot meal (dinner) was found to be the main contributor to the intake of energy and macro-nutrients in the Dutch population. It was also the main contributor to the intake of all micro-nutrients with the exception of calcium where the bread meal contributed a similar proportion as the hot meal to the intake of this micronutrient. Furthermore, fruit intake showed a very different temporal distribution to vegetable intake. Exploring the convergence of certain foods in the Irish population also revealed differences between fruit and vegetables. A low correlation was shown for consumers of fruit and vegetables indicating that being a high fruit consumer did not suggest being also a high vegetable consumer. An examination of where meals were consumed among British adults showed that 71% of all meals were consumed inside the home while 29% were consumed outside. 27% of food energy and 45% of alcohol energy was consumed out of home by the total population. In addition, those eating less of their foods out of home obtained a lower proportion of their food energy from fat and protein and a higher proportion from carbohydrate. A different demographic profile was associated with eating out compared to eating in, comprising more males and younger individuals. CONCLUSIONS: Information on patterns of food intake and food habits, specifically temporal distribution, the convergence and divergence of foods and foods consumed inside and outside of the home, give a culturally specific picture of food consumption practices within a population. This should enable the development of more culturally acceptable and realistic FBDG.

Adolescent↗

PubMed1997

Convergence in understanding hypnosis? Perhaps, but perhaps not quite so fast.

The study of hypnosis has been plagued by conflict. Although a more recent trend has been the search for convergence among disparate points of view, two highly salient issues remain contentious: the question of whether hypnosis involves alterations in consciousness, and the nature and correlates of individual differences in hypnotic response. Theoretical convergence is a laudable goal, but not at the expense of obscuring the complexity of hypnosis as a state of altered consciousness, a cognitive skill, and a social interaction. Perhaps the best prescription for convergence in hypnosis is the cautious conviction advocated by Kenneth S. Bowers and so clearly exemplified in his own research.

Awareness↗

PubMed1987

Convergent validity of observational and self-report measures of marital interaction.

Previous research findings have challenged the validity of couple's self-reports of their communication effectiveness. In the present study, observational ratings of couples' communication and spouses' self-reports on a multidimensional measure of marital interaction were obtained for a sample of 30 clinic and 12 nonclinic couples. The convergent validity of these two approaches to marital assessment was evaluated by identifying significant correlations for the total sample and for clinic and nonclinic couples, separately. In contrast to previous investigations of this nature, substantial convergence was obtained between the Couples Interaction Scoring System (CISS) and the Marital Satisfaction Inventory (MSI). In general, convergence of the two approaches was stronger for couples in marital therapy. Implications of these findings for clinical assessment and research with nonclinic populations are discussed.

Adaptation, Psychological↗

PubMed2006

The Marijuana Screening Inventory (MSI-X): concurrent, convergent and discriminant validity with multiple measures.

This study evaluates the concurrent, convergent and discriminant validity between the MSI-X and five other instruments completed by 107 adults. Pearson correlation analysis with follow-up t-tests found concurrent validity between the MSI-X, Drug Abuse Screening Test (DAST-20), five Substance Abuse Subtle Screening Inventory (SASSI-3) subscales, a Diagnostic Statistical Manual (DSM) IV-TR Guided Marijuana Inventory, and two Addiction Severity Index variables. As evidence of MSI-X discriminant validity, no correlations were found with three alcohol measures. Convergent validity, determined by t-test associations between MSI-X total problems with SASSI-3 substance dependence scores, supported the MSI-X > or =6 scoring cutoff. Overall, the findings support MSI-X concurrent, convergent and discriminant validity.

Adolescent↗

PubMed2001

Investigating Gender Convergence in Alcohol Consumption in Finland, Germany, The Netherlands, and Switzerland: A Repeated Survey Analysis.

Since the 1970s there has been concern that women may have started to adopt the drinking behaviors of men, a process seen as the result of emancipation in which women increasingly move into professions and/or lifestyles similar to those of men. This is called the convergence hypothesis. The present analysis investigated a possible closing of the gender gap and includes four countries that had national survey data for at least two time points: Finland (1984, 1992), Germany (1984, 1990), The Netherlands (1981, 1989), and Switzerland (1987, 1992). Significant convergence could be found only in Finland, which consisted of a greater increase of Finnish women becoming current drinkers and of a greater relative increase in the women's mean consumption. The fact that gender convergence was found only for Finland could be due not only to the longer observation period, but also to the egalitarian position of women and the changing drinking culture of the country.

Journal Article↗

PubMed2006

Searching for convergence in phylogenetic Markov chain Monte Carlo.

Markov chain Monte Carlo (MCMC) is a methodology that is gaining widespread use in the phylogenetics community and is central to phylogenetic software packages such as MrBayes. An important issue for users of MCMC methods is how to select appropriate values for adjustable parameters such as the length of the Markov chain or chains, the sampling density, the proposal mechanism, and, if Metropolis-coupled MCMC is being used, the number of heated chains and their temperatures. Although some parameter settings have been examined in detail in the literature, others are frequently chosen with more regard to computational time or personal experience with other data sets. Such choices may lead to inadequate sampling of tree space or an inefficient use of computational resources. We performed a detailed study of convergence and mixing for 70 randomly selected, putatively orthologous protein sets with different sizes and taxonomic compositions. Replicated runs from multiple random starting points permit a more rigorous assessment of convergence, and we developed two novel statistics, delta and epsilon, for this purpose. Although likelihood values invariably stabilized quickly, adequate sampling of the posterior distribution of tree topologies took considerably longer. Our results suggest that multimodality is common for data sets with 30 or more taxa and that this results in slow convergence and mixing. However, we also found that the pragmatic approach of combining data from several short, replicated runs into a "metachain" to estimate bipartition posterior probabilities provided good approximations, and that such estimates were no worse in approximating a reference posterior distribution than those obtained using a single long run of the same length as the metachain. Precision appears to be best when heated Markov chains have low temperatures, whereas chains with high temperatures appear to sample trees with high posterior probabilities only rarely.

Bayes Theorem↗