Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “mutualism”

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 73 records · Page 4Linked to original sources
PubMed2004

Mutual support groups in rheumatic diseases: Effects and participants' perceptions.

OBJECTIVE: To investigate in a randomized controlled trial the effects of mutual support groups in rheumatic diseases on social network size, social skills, loneliness, daily functioning, and life satisfaction as well as to identify patients' perceptions of the support group. METHODS: Participants were 112 patients with chronic rheumatic disorders affecting the joints. Data were collected with self-report questionnaires and group interviews. RESULTS: Effects have been found on social skills only. More specifically, mutual support groups at postintervention decreased distress in expressing negative feelings toward other people. This effect did not persist at the 6-month followup evaluation, but at that time an increase in frequency in making one's wishes known to others was found. In patients who attended at least 5 of all 10 sessions, an increase in expressing positive feelings toward others was found at followup. Mutual support groups were evaluated positively. CONCLUSION: Mutual support groups are recommended for patients experiencing difficulties in social interactions.

Adult↗
PubMed2002

Evolution of mutualism between globeflowers and their pollinating flies.

Plant/seed-eater pollinators mutualisms involve a plant pollinated by an insect whose larvae develop by eating a fraction of host-plant seeds. The outcome of the interaction therefore depends on the number of ovules fertilized by adult visits and the number of seeds destroyed by larvae. Among the very few cases of such mutualisms reported so far is the globeflower-globeflower flies mutualism, which is unique in that it involves several congeneric fly species (Chiastocheta genus) coexisting within a single host-plant species, Trollius europaeus. These species exhibit contrasted oviposition behaviors resulting in a more or less beneficial outcome for the plant. We designed an adaptive dynamics model to investigate how morphological traits of globeflower could affect the evolution of oviposition in its pollinating flies. Three fly traits (flower age at oviposition, clutch size and the level of avoidance of already parasitized flowers) and one plant trait (closed or open corolla) were examined. Whatever the shape of the flower, evolutionary branching occurs between early and late ovipositing flies, driven by strong competition among larvae within a fruit. Once this branching occurred, the closed shape of the corolla is likely to offer a better protection to eggs of early but not of late ovipositing flies. The difference in egg survival results in higher competition among early larvae and thus selects for decreased clutch size in early flies. This can be seen as a first step in the evolution of a mutualistic behavior. The prediction of our model fits field observations of fly behavior, giving theoretical support to the hypothesis of fly sympatric speciation within its host plant. Moreover, flower closed globe shape can be positively selected in globeflowers as it results in a reduction of parasitism strength. This last evolution therefore leads to a stable mutualism between globeflowers and globeflower flies.

Animals↗
PubMed1991

Charting uncharted terrain: a behavioral observation system for mutual help groups.

Describes the development of a behavioral observation system for mutual help meetings and presents evidence supporting its reliability, validity, and utility. The MHOS-BIC (Mutual Help Observation System-Behavioral Interaction Codes) was used by 10 observers to record the sequential flow of group interaction in 527 meetings. Psychometric analyses indicate that the system performed consistently with measurement objectives. Mean kappas for each of the 12 coding categories ranged from .62 to .87; the system demonstrated sensitivity to setting and time differences; and a predictable pattern of correlations was found among BIC categories and conceptually related participant and observer ratings. Studies using the BIC to address substantive questions about mutual help are reviewed, providing further evidence for its validity and utility. An empirical description of mutual help is presented using BIC data, and the promises and limitations of the system are discussed.

Affective Symptoms↗
PubMed2007

Effects of "dual focus" mutual aid on self-efficacy for recovery and quality of life.

Four million adults in the U.S. have co-occurring serious mental illness and a substance use disorder. Mutual aid can usefully complement treatment, but people with co-occurring disorders often encounter a lack of empathy and acceptance in traditional mutual aid groups. Double Trouble in Recovery (DTR) is a dual focus fellowship whose mission is to bring the benefits of mutual aid to persons with dual diagnoses. Three hundred and ten persons attending 24 DTR groups in New York City during 1998 were interviewed and followed-up for two years. A mediational model was specified and results across time were summarized with generalized estimating equations (GEE). Degree of DTR Affiliation (attendance and involvement) was significantly associated with Self-efficacy for Recovery and three quality of life measures: Leisure Time Activities, Feelings of Well-Being and Social Relationships. Self-efficacy fully mediated the effects of DTR Affiliation on Leisure Time and Feelings and partially mediated DTR's effect on Social Relationships. The association of DTR involvement with self-efficacy is consistent with the processes inherent in mutual aid, although the observational nature of these data preclude causal inference. To improve outcomes, clinicians should facilitate affiliation with dual focus groups among persons with dual diagnoses as part of a comprehensive treatment approach.

Adult↗
PubMed1994

A co-evolutionary model of mutualism from a commensal association on Lotka-Volterra dynamics.

This paper considers a Lotka-Volterra type of model of competition between a commensal pair of species and a mutualistic pair, presumed to have descended from a single ancestral pair of species. The species are behaviourally isolated but compete for resources. We have studied in detail the effects of the benefits of mutualism over commensalism. Specifically, it is shown that co-evolution of the mutalistic pair from the commensal association is not possible if (i) some of the interacting parameters coincide for the two pairs, or (ii) mutualists suffer more from competition, or (iii) mutualists produce a smaller competitive effect. If the costs of mutualism are density-independent, co-evolution of the mutualism is possible provided (i) the specific growth rate(s) of one or both of the mutualistic species is positive at the steady state of the commensal pair and (ii) the specific growth rate(s) of one or both of the commensal species is positive at the steady state of the mutualistic pair. Lastly, whenever the mutualists co-exist with the commensalists and the feasible interior equilibrium of the model is unstable, we have shown that the co-evolutionary model of mutualism collapses to the stable two-species mutualistic relationship, causing the ultimate extinction of both the species of the original commensal association.

Animals↗
PubMed2005

A competitive low-affinity binding model for determining the mutual and specific sites of two ligands on protein.

A competitive low-affinity binding model was proposed for determining the number of mutual (overlapped) and specific binding sites of two ligands (A, B) on a protein (P). To use the model, one needs to carry out a titration experiment by adding either ligand A or B into a three-component system (A-B-P), and to monitor the spectroscopic parameter changes. Fitting the titration curve to the proposed model, one can get the mutual and specific binding sites of the two ligands on the protein. The model was examined by using human serum albumin (HSA) as a receptor and tolmetin (TOL) and salicylic acid (SAL) as ligands. Proton longitudinal relaxation rates (R1) were measured on a 500-MHz NMR spectrometer during the titration and used to derive the mutual binding sites. It was found that among the binding sites of 32+/-4 for SAL and 28+/-2 for TOL on HSA, there were 17+/-5 mutual sites for the two ligands. This result indicates that, although HSA has large binding capacities for most ligands, there are still a reasonable amount of the low-affinity binding sites that are structure selective.

Algorithms↗
PubMed2005

The iterated continuous prisoner's dilemma game cannot explain the evolution of interspecific mutualism in unstructured populations.

The evolutionionary origin of inter- and intra-specific cooperation among non-related individuals has been a great challenge for biologists for decades. Recently, the continuous prisoner's dilemma game has been introduced to study this problem. In function of previous payoffs, individuals can change their cooperative investment iteratively in this model system. Killingback and Doebeli (Am. Nat. 160 (2002) 421-438) have shown analytically that intra-specific cooperation can emerge in this model system from originally non-cooperating individuals living in a non-structured population. However, it is also known from an earlier numerical work that inter-specific cooperation (mutualism) cannot evolve in a very similar model. The only difference here is that cooperation occurs among individuals of different species. Based on the model framework used by Killingback and Doebeli (2002), this Note proves analytically that mutualism indeed cannot emerge in this model system. Since numerical results have revealed that mutualism can evolve in this model system if individuals interact in a spatially structured manner, our work emphasizes indirectly the role of spatial structure of populations in the origin of mutualism.

Altruism↗
PubMed2006

Pathways to mutualism breakdown.

Mutualisms are ubiquitous in nature despite the widely held view that they are unstable interactions. Models predict that mutualists might often evolve into parasites, can abandon their partners to live autonomously and are also vulnerable to extinction. Yet a basic empirical question, whether mutualisms commonly break down, has been mostly overlooked. As we discuss here, recent progress in molecular systematics helps address this question. Newly constructed phylogenies reveal that parasites as well as autonomous (non-mutualist) taxa are nested within ancestrally mutualistic clades. Although models have focused on the propensity of mutualism to become parasitic, such shifts appear relatively rarely. By contrast, diverse systems exhibit reversions to autonomy, and this might be a common and unexplored endpoint to mutualism.

Animals↗
PubMed1989

Mutual diffusion of interacting membrane proteins.

The generalized Stokes-Einstein equation is used, together with the two-dimensional pressure equation, to analyze mutual diffusion in concentrated membrane systems. These equations can be used to investigate the role that both direct and hydrodynamic interactions play in determining diffusive behavior. Here only direct interactions are explicitly incorporated into the theory at high densities; however, both direct and hydrodynamic interactions are analyzed for some dilute solutions. We look at diffusion in the presence of weak attractions, soft repulsions, and hard-core repulsions. It is found that, at low densities, attractions retard mutual diffusion while repulsions enhance it. Mechanistically, attractions tend to tether particles together and oppose the dissipation of gradients or fluctuations in concentration, while repulsions provide a driving force that pushes particles apart. At higher concentrations, changes in the structure of the fluid enhance mutual diffusion even in the presence of attractions. It is shown that the theoretical description of postelectrophoresis relaxation and fluorescence correlation spectroscopy experiments must be modified if interacting systems are studied. The effects of interactions on mutual diffusion coefficients have probably already been seen in postelectrophoresis relaxation experiments.

Diffusion↗
PubMed2003

Comparison of an image registration technique based on normalized mutual information with a standard method utilizing implanted markers in the staged radiosurgical treatment of large arteriovenous malformations.

PURPOSE: To compare a noninvasive technique based on normalized mutual information for registering image sets associated with staged radiosurgical treatments of large arteriovenous malformations (AVMs), with a gold-standard method using radiographically evident markers implanted in the skull. METHODS: Nine patients receiving multistage treatment of large AVMs at the University of California at San Francisco (UCSF) gamma knife facility were included in this study. For each patient, the transformations of shot coordinates between a reference treatment stage and subsequent treatment stages were determined at UCSF, based on radiographically defined coordinates of implanted markers in each stereotactic space. A magnetic resonance (MR) image set was acquired for each treatment stage, and used for treatment planning. The two MR image sets for each treatment pair were sent to Yale for an unbiased, independent analysis of shot transformations. An image registration technique based on normalized mutual information was used to produce a single fused image study for each treatment pair. External copper sulfate fiducial markers for both image sets were evident on the fused images, allowing coordinates in both stereotactic systems to be defined. Coordinate transformation between the two systems was determined, based on digitized coordinates of seven common fiducial marker images. RESULTS: The average measured overall root-mean-square discrepancy between the Yale and UCSF transformed shot coordinates is 1.1 +/- 0.3 mm. The corresponding error in Yale transformed coordinates is 1.0 +/- 0.3 mm, assuming an inherent 0.5 mm error in the UCSF method. CONCLUSIONS: The normalized mutual information method can be used to obtain good image registration between successive sessions in staged treatments. Further improvements in the reported methodology are outlined. Because the mutual information method is less invasive than the implanted marker method, it may be preferable in many cases.

Algorithms↗
PubMed1997

Mutuality--an expression of nursing presence.

Nursing exists in the details of relationships. One crucial element of therapeutic nurse-patient/parent relationships is the attribute of mutuality. Mutuality not only embodies the philosophy of family-centered-care, it acknowledges and supports the evolution of parents and nurses toward greater competency in their role. Using concept analysis, this article explores the phenomenon of mutuality. The desired outcome is to provide a theoretical and operational definition of mutuality that will help guide practice and direct future research in the area of therapeutic nurse-parent relationships.

Bronchopulmonary Dysplasia↗
PubMed2002

Mutual information and phase dependencies: measures of reduced nonlinear cardiorespiratory interactions after myocardial infarction.

The heart rate variability (HRV) is related to several mechanisms of the complex autonomic functioning such as respiratory heart rate modulation and phase dependencies between heart beat cycles and breathing cycles. The underlying processes are basically nonlinear. In order to understand and quantitatively assess those physiological interactions an adequate coupling analysis is necessary. We hypothesized that nonlinear measures of HRV and cardiorespiratory interdependencies are superior to the standard HRV measures in classifying patients after acute myocardial infarction. We introduced mutual information measures which provide access to nonlinear interdependencies as counterpart to the classically linear correlation analysis. The nonlinear statistical autodependencies of HRV were quantified by auto mutual information, the respiratory heart rate modulation by cardiorespiratory cross mutual information, respectively. The phase interdependencies between heart beat cycles and breathing cycles were assessed basing on the histograms of the frequency ratios of the instantaneous heart beat and respiratory cycles. Furthermore, the relative duration of phase synchronized intervals was acquired. We investigated 39 patients after acute myocardial infarction versus 24 controls. The discrimination of these groups was improved by cardiorespiratory cross mutual information measures and phase interdependencies measures in comparison to the linear standard HRV measures. This result was statistically confirmed by means of logistic regression models of particular variable subsets and their receiver operating characteristics.

Aged↗
PubMed1999

Rigid point feature registration using mutual information.

We have developed a new mutual information-based registration method for matching unlabeled point features. In contrast to earlier mutual information-based registration methods, which estimate the mutual information using image intensity information, our approach uses the point feature location information. A novel aspect of our approach is the emergence of correspondence (between the two sets of features) as a natural by-product of joint density estimation. We have applied this algorithm to the problem of geometric alignment of primate autoradiographs. We also present preliminary results on three-dimensional robust matching of sulci derived from anatomical magnetic resonance images. Finally, we present an experimental comparison between the mutual information approach and other recent approaches which explicitly parameterize feature correspondence.

Algorithms↗
PubMedDate not supplied

Mutually exclusive expression of the L and M pigment genes in the human retinoblastoma cell line WERI: Resetting by cell division.

The key steps in the evolution of full trichromatic color vision in primates include duplication of the ancestral pigment gene to form the L and M pigment gene array on the X chromosome, mutually exclusive expression of the L and M pigment genes in cone photoreceptors, and formation of a retinal mosaic with randomly distributed L and M cones. Previous work using transgenic mice has indicated that a locus control region adjacent to this array of genes plays an important role in their mutually exclusive expression in respective cone cells (Smallwood et al., 2002). However, the mechanism by which this is accomplished is unknown. We searched for a cellular model system to investigate the mechanism of this mutually exclusive expression. We previously showed that the undifferentiated human retinoblastoma cell line WERI expresses L and M cone opsin but not rod opsin genes. We now show that WERI cells express the L and M pigment genes in a mutually exclusive manner, in that either L or M pigment mRNA is expressed in a single cell. Importantly, clonal analysis showed that single WERI cells that express either L or M generate, upon cell division produce, a mixed population of L- or M-expressing cells. These results indicate, first, that cell division resets L or M pigment gene expression, most likely due to disassembly and reassembly of LCR-promoter DNA-protein complexes during cell division. Second, a retinal mosaic with near-random distribution of L and M cones may have been generated automatically after duplication of the ancestral gene to form the L and M pigment genes. Third, determination of L and M cone identity may not require external molecular cues during differentiation, and is consistent with the idea that L and M cones are not intrinsically different.

Blotting, Northern↗
PubMed2000

Mutual help groups, perceived status benefits, and well-being: a test with adult children of alcoholics with personal substance abuse problems.

A field experiment was conducted to examine the potential effects of mutual help group participation on perceived status benefits, depression, and substance use among adult children of alcoholics (ACOAs) with personal substance abuse problems. Participants were randomly assigned to attend either ACOA-specific mutual help group meetings or substance abuse education classes during the initial month that they were enrolled in a residential treatment program for low-income substance abusers. Analyses were based on assessments made at baseline, a 1-month posttest, and a 6-month follow-up. Results indicated that participation in the mutual help group promoted perceived status benefits, which in turn led to reductions in depression and substance use. These findings have clear implications for consumers of ACOA groups and can inform research on the social psychological underpinnings of different types of mutual help groups.

Adult↗
PubMed1997

Synchronous bursting can arise from mutual excitation, even when individual cells are not endogenous bursters.

Mutual excitation between two neurons is generally thought to raise the excitation level of each neuron or, if they are both bursty, to act to synchronize their bursts. If only one is bursty, it can induce synchronized bursts in the other cell. Here we show that two nonbursty cells can be induced to burst in synchrony by mutual excitatory synaptic connections, provided the presynaptic threshold for graded synaptic transmission at each synapse is at a different level. This mechanism may operate in a recently discovered network in the lobster Homarus gammarus. By a duality between presynaptic threshold and injected current, we also show that two identical, nonbursty, mutual excitatory cells could be induced to burst in synchrony by injecting differing amounts of current in the two cells. Finally we show that differential oscillations between two mutual excitatory cells could be stopped by a slow-tailed hyperpolarizing current pulse into one cell or a slow-tailed depolarizing pulse into the other.

Animals↗
PubMed2003

Mutual interactions of boar seminal plasma proteins studied by immunological and chromatographic methods.

PROBLEM: Boar seminal plasma contains various types of proteins. Most of them belong to spermadhesins and some of them contain fibronectin type II domain. Almost all of these proteins are present under physiological conditions in aggregated forms differing in their relative molecular mass, composition, and binding properties. The study of mutual specific interactions between proteins of boar seminal plasma that could be involved in the formation of aggregated forms and most probably of sperm coating layers is the subject of our present communication. METHODS OF STUDY: Aggregated forms of boar seminal plasma proteins separated by size exclusion chromatography were analysed by Reversed-phase High-performance Liquid Chromatography (RP HPLC), SDS-PAGE and immunochemical methods (ELISA and immunoblotting). Mutual interactions between proteins were investigated by size exclusion chromatography of a mixture of separated monomer proteins and affinity chromatography of boar seminal plasma on immobilized spermadhesins. RESULTS: Composition of proteins that are adsorbed from boar seminal plasma to immobilized spermadhesins corresponds to that of aggregated forms found in seminal plasma. Mutual interactions between monomer forms observed by size exclusion chromatography are in good agreement with results of affinity chromatography. An existence of interactions between spermadhesins of the AQN and AWN families and the DQH sperm surface protein, as well as between proteins involved in the formation of heterodimer porcine seminal plasma I (PSP I)/PSP II was proved. CONCLUSION: Mutual specific interactions between protein components of boar seminal plasma were shown. These interactions participate in the formation of aggregated forms of proteins in seminal plasma and probably also in the arrangement and remodelling of protein coating layers of sperm. Aggregation of seminal plasma proteins is probably an important phenomenon in the fertilization process.

Animals↗
PubMed2005

Molecular dynamics simulation of self- and mutual diffusion coefficients for confined mixtures.

The self- and mutual diffusion coefficients for binary mixtures of Ar-Kr both in the bulk and in the nanopores were studied by molecular dynamics simulations. The composition dependences and the relationships between the self- and the mutual diffusion coefficients both in the bulk and in the nanopores were further discussed. It was found that the simulation results (D(c.m.)) are close to the calculated ones (D(s)) for the Ar-Kr system. Both self- and mutual diffusion coefficients in nanopores are much lower than that of the bulk, and they ever decrease as the pore width decreases. Nevertheless, the self- and mutual diffusion coefficients increase as the mole fraction of Ar increases, and as expected, increase as the temperature increases. The self-diffusion coefficients of mixtures both in the bulk and in the nanopores are predicted by the Carman model and by the molecular cluster model.

Journal Article↗