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PubMed2003

[Implementation of mutual information based medical image registration methods].

Image registration methods based on mutual information, including mutual information and normalized mutual information, have been accepted as the most accurate and efficient methods. But there are many fluctuations in the registration functions that hinder the optimization procedure and lead to registration failure in intra-modal registration. We found that besides the interpolation artifacts, the uncertainty of the changing of entropy with the changing of overlap also contributes to the fluctuations. The effect of interpolation artifacts can be eliminated, but it is difficult to eliminate the effect of uncertainty of entropy. Luckily, this effect is not significant in normalized mutual information. Normalized mutual information is more stable and robust than standard mutual information and its better performance and wider application can be expected.

Algorithms↗
PubMed2004

A randomized controlled trial of a mutual support group for family caregivers of patients with schizophrenia.

This randomized controlled trial examined the effectiveness of a 12-session mutual support group conducted over 3-months for Chinese family caregivers of a relative with schizophrenia compared with routine family support services in Hong Kong. Forty-eight family caregivers from two psychiatric outpatient clinics were allocated randomly to an experimental (mutual support and usual outpatient care) group (n = 24) or a control (usual outpatient care only) group (n = 24). Data were collected prior to, 1 week and 3 months after the intervention. Families allocated to the mutual support group experienced decreased levels of family burden and increased family functioning and these changes were significantly greater than those of the controls at both post-intervention time points. The experimental group also showed a significant decrease in the duration of patient re-hospitalization (the total number of days of psychiatric hospitalization) at 3 months compared with the control group. This suggests that the mutual support group provided a more responsive service for patients than standard care. However, there was no significant difference in family service utilization between the two groups. The findings indicate that a mutual support group can provide benefits for family caregivers of people with schizophrenia that go beyond those provided by routine family support.

Adult↗
PubMed2005

Monolingual and bilingual children's use of mutual exclusivity in the naming of whole objects.

In two experiments, the use of mutual exclusivity in the naming of whole objects was examined in monolingual and bilingual 3- and 6-year-olds. Once an object has a known name, then via principles of mutual exclusivity it is often assumed that a new name given to the object must refer to some part, substance, or other property of the object. However, because bilingual children must suspend mutual exclusivity assumptions between languages, they may be more willing to accept two names for an object within a language. In the current research, the use of mutual exclusivity in the naming of whole objects was found across monolingual and bilingual children, although older bilingual children were significantly less inclined to use mutual exclusivity than were older monolingual children. These results are discussed in terms of differences in monolingual and bilingual children's word learning.

Child↗
PubMed1995

Cyclization-activated prodrugs: N-(substituted 2-hydroxyphenyl and 2-hydroxypropyl)carbamates based on ring-opened derivatives of active benzoxazolones and oxazolidinones as mutual prodrugs of acetaminophen.

N-(Substituted 2-hydroxyphenyl)- and N-(substituted 2-hydroxypropyl)carbamates based on masked active benzoxazolones (model A) and oxazolidinones (model B), respectively, were synthesized and evaluated as potential drug delivery systems. A series of alkyl and aryl N-(5-chloro-2-hydroxyphenyl)carbamates 1 related to model A was prepared. These are open drugs of the skeletal muscle relaxant chlorzoxazone. The corresponding 4-acetamidophenyl ester named chlorzacetamol is a mutual prodrug of chlorzoxazone and acetaminophen. Chlorzacetamol and two other mutual prodrugs of active benzoxazolones and acetaminophen were obtained in a two-step process via condensation of 4-acetamidophenyl 1,2,2,2-tetrachloroethyl carbonate with the appropriate anilines. Based on model B, two mutual prodrugs of acetaminophen and active oxazolidinones (metaxalone and mephenoxalone) were similarly obtained using the appropriate amines. All the carbamate prodrugs prepared were found to release the parent drugs in aqueous (pH 6-11) and plasma (pH 7.4) media. The detailed mechanistic study of prodrugs 1 carried out in aqueous medium at 37 degrees C shows a change in the Brönsted-type relationship log t1/2 vs pKa of the leaving groups ROH: log t1/2 = 0.46pKa-3.55 for aryl and trihalogenoethyl esters and log t1/2 = 1.46pKa-16.03 for alkyl esters. This change is consistent with a cyclization mechanism involving a change in the rate-limiting step from formation of a cyclic tetrahedral intermediate (step k1) to departure of the leaving group ROH (step k2) when the leaving group ability decreases. This mechanism occurs for all the prodrugs related to model A. Regeneration of the parent drugs from mutual prodrugs related to model B takes place by means of a rate-limiting elimination-addition reaction (E1cB mechanism). This affords acetaminophen and the corresponding 2-hydroxypropyl isocyanate intermediates which cyclize at any pH to the corresponding oxazolidinone drugs. As opposed to model A, the rates of hydrolysis of mutual prodrugs of model B clearly exhibit a catalytic role of the plasma. It is concluded from the plasma studies that the carbamate substrates can be enzymatically transformed into potent electrophiles, i.e., isocyanates. In the case of the present study, the prodrugs are 2-hydroxycarbamates for which the propinquity of the hydroxyl residue and the isocyanate group enforces a cyclization reaction. This mechanistic particularity precludes their potential toxicity in terms of potent electrophiles capable of modifying critical macromolecules.

Acetaminophen↗
PubMed2000

Support, mutual aid and recovery from dual diagnosis.

Recovery from substance abuse and mental health disorders (dual-diagnosis) requires time, hard work and a broad array of coping skills. Empirical evidence has demonstrated the buffering role of social support in stressful situations. This paper investigates the associations among social support (including dual-recovery mutual aid), recovery status and personal well-being in dually-diagnosed individuals (N = 310) using cross-sectional self-report data. Persons with higher levels of support and greater participation in dual-recovery mutual aid reported less substance use and mental health distress and higher levels of well-being. Participation in mutual aid was indirectly associated with recovery through perceived levels of support. The association between mutual aid and recovery held for dual-recovery groups but not for traditional, single-focus self-help groups. The important role of specialized mutual aid groups in the dual recovery process is discussed.

Adult↗
PubMed2000

Parent-child mutuality in early childhood: two behavioral genetic studies.

Parent-child dyadic mutuality (shared positive affect, responsiveness, and cooperation) is an important component of family socialization processes. This study sought to extend previous research on mutuality by using a quantitative genetic design to examine between- and within-family variations (e.g., sibling differences) and gene-environment processes. The first study included 125 pairs of identical and same-sex fraternal 3-year-old twins. Observations of mutuality and parents' and observers' ratings of family environment and child behavior were gathered. Greater mutuality was associated with higher socioeconomic status. Moderate sibling similarity in parent-child mutuality was accounted for by child genetic similarity, suggesting evocative gene-environment correlation and nonshared environmental processes. These findings were replicated in a 2nd study of 102 pairs of adoptive and biological siblings.

Child, Preschool↗
PubMed2001

Consequences of a biological invasion reveal the importance of mutualism for plant communities.

Seed-dispersal mutualisms have a fundamental role in regenerating natural communities. Interest in the importance of seed dispersal to plant communities has been heightened by worldwide declines in animal dispersers. One view, the 'keystone mutualist hypothesis', predicts that these human-caused losses will trigger a cascade of linked extinctions throughout the community. Implicitly, this view holds that mutualisms, such as seed dispersal, are crucial ecological interactions that maintain the structure and diversity of natural communities. Although many studies suggest the importance of mutualism, empirical evidence for community-level impacts of mutualists has remained anecdotal, and the central role of mutualism, relative to other species interactions, has long been debated in the theoretical literature. Here I report the community-level consequences of a biological invasion that disrupts important seed-dispersal mutualisms. I show that invasion of South African shrublands by the Argentine ant (Linepithema humile) leads to a shift in composition of the plant community, owing to a disproportionate reduction in the densities of large-seeded plants. This study suggests that the preservation of mutualistic interactions may be essential for maintaining natural communities.

Africa, Southern↗
PubMed2004

The mutual diffusion coefficient for (meth)acrylate monomers as determined with a nuclear microprobe.

The value of the mutual diffusion coefficient DV of two acrylic monomers is determined with nuclear microprobe measurements on a set of polymer films. These films have been prepared by allowing the monomers to diffuse into each other for a certain time and subsequently applying fast ultraviolet photo-polymerization, which freezes the concentration profile. The monomer diffusion profiles are studied with a scanning 2.1 MeV proton microprobe. Each monomer contains a marker element, e.g., Cl and Si, which are easily detected with proton induced x-ray emission. From the diffusion profiles, it is possible to determine the mutual diffusion coefficient. The mutual diffusion coefficient is dependent of concentration, which is concluded from the asymmetry in the Cl- and Si-profiles. A linear dependence of the mutual diffusion coefficient on the composition is used as a first order approximation. The best fits are obtained for a value of b=(0.38+/-0.15), which is the ratio of the diffusion coefficient of 1,3-bis(3-methacryloxypropyl)-1, 1,3,3-tetramethyldisiloxane in pure 2-chloroethyl acrylate and the diffusion coefficient of 2-chloroethyl acrylate in pure 1,3-bis(3-methacryloxypropyl)-1,1,3,3-tetramethyldisiloxane. Under the assumption of a linear dependence of the mutual diffusion coefficient DV on monomer composition, it follows that DV = (2.9+/-0.6)10(-10) m(2)/s at a 1:1 monomer ratio. With Flory-Huggins expressions for the monomer chemical potentials, one can derive approximate values for the individual monomer diffusion coefficients.

Journal Article↗
PubMed2005

Critical review of host specificity and its coevolutionary implications in the fig/fig-wasp mutualism.

Figs (Ficus spp., Moraceae) and their pollinating wasps (Agaonidae, Chalcidoidea) constitute perhaps the most tightly integrated pollination mutualism that is known. Figs are characterized by extraordinarily high global and local species diversity. It has been proposed that the diversification of this mutualism has occurred through strict-sense coadaptation and cospeciation between pairs of fig and wasp species that are associated in highly specific one-to-one relationships. However, existing studies cast doubt on the generality of this proposition. Here, we review our current knowledge of the evolutionary history of the fig/fig-wasp mutualism. We critically examine the idea that codivergence between figs and their pollinators has been dominated by strict-sense cospeciation. We present phylogenetic and population genetic data from neotropical fig and fig wasp species that suggest that a more accurate model for diversification in this mutualism is that of groups of genetically well defined wasp species coevolving with genetically less well defined (frequently hybridizing) groups of figs. Last, we use our results to assess previously proposed hypotheses on models of speciation in this mutualism.

Animals↗
PubMed1998

The evolution of interspecific mutualisms.

Interspecific mutualisms are widespread, but how they evolve is not clear. The Iterated Prisoner's Dilemma is the main theoretical tool to study cooperation, but this model ignores ecological differences between partners and assumes that amounts exchanged cannot themselves evolve. A more realistic model incorporating these features shows that strategies that succeed with fixed exchanges (e. g., Tit-for-Tat) cannot explain mutualism when exchanges vary because the amount exchanged evolves to 0. For mutualism to evolve, increased investments in a partner must yield increased returns, and spatial structure in competitive interactions is required. Under these biologically plausible assumptions, mutualism evolves with surprising ease. This suggests that, contrary to the basic premise of past theoretical analyses, overcoming a potential host's initial defenses may be a bigger obstacle for mutualism than the subsequent recurrence and spread of noncooperative mutants.

Biological Evolution↗
PubMed2003

Interacting guilds: moving beyond the pairwise perspective on mutualisms.

Most textbook treatments imply, and almost all theoretical analyses assume, that mutualistic interactions take place between a single pair of interacting partner species. A major goal of this symposium is to broaden and shift this pairwise perspective and make it concordant with the emerging view that locally exclusive mutualisms between just two species are the exception and that many communities include guilds of mutualistic species on one or both sides of the interaction. Many pollination and seed-dispersal mutualisms have long been recognized as diffuse, but recent molecular analyses are revealing unrecognized partner diversity in mutualistic interactions previously thought to be locally species specific. Co-occurring species within a mutualist guild are unlikely to be ecologically equivalent in the way they locate, compete for, and/or reward partners, and so intraguild interactions have the potential to influence population dynamics and patterns of selection in species on both sides of the mutualistic interaction. To illustrate some of these potential complexities for population dynamics, I use simple path analytic models to show that positive pairwise interactions between mutualists do not necessarily translate into positive net interactions within a mutualism involving more than two species. For example, when there is intraguild competition for partners, or even for resources external to the mutualism, the presence of a lower-quality mutualist can negatively affect the partner population by reducing associations it can form with better mutualists. Variation in quality among potential partners is likely to place a premium on traits or behaviors that enhance association with better mutualists. More investigations are needed to determine how variation among interacting mutualists, with respect to characteristics such as longevity, dispersal capability, and competitive ability, influence population dynamics and selection in multispecies mutualisms.

Ecosystem↗
PubMed2004

Gene clustering based on clusterwide mutual information.

Cluster analysis of gene-wide expression data from DNA microarray hybridization studies has proved to be a useful tool for identifying biologically relevant groupings of genes and constructing gene regulatory networks. The motivation for considering mutual information is its capacity to measure a general dependence among gene random variables. We propose a novel clustering strategy based on minimizing mutual information among gene clusters. Simulated annealing is employed to solve the optimization problem. Bootstrap techniques are employed to get more accurate estimates of mutual information when the data sample size is small. Moreover, we propose to combine the mutual information criterion and traditional distance criteria such as the Euclidean distance and the fuzzy membership metric in designing the clustering algorithm. The performances of the new clustering methods are compared with those of some existing methods, using both synthesized data and experimental data. It is seen that the clustering algorithm based on a combined metric of mutual information and fuzzy membership achieves the best performance. The supplemental material is available at www.gspsnap.tamu.edu/gspweb/zxb/glioma_zxb.

Algorithms↗
PubMed2004

Cooperative nest defence in red-winged blackbirds: reciprocal altruism, kinship or by-product mutualism?

Male red-winged blackbirds (Agelaius phoeniceus) often cooperate with their neighbours in defending nests against predators. Some studies have suggested that this is an example of by-product mutualism, whereas others have suggested the possibility of reciprocal altruism. No study has addressed the possibility of kin-selected cooperation in nest defence in this species. Reciprocal altruism, kin selection and by-product mutualism are not mutually exclusive alternatives, but few studies of territorial neighbours have tested for multiple mechanisms simultaneously. We test for these three possibilities in a population of red-winged blackbirds. We used simulated defections to test for reciprocal altruism. We used analysis of microsatellite loci to test for kin selection between adult male neighbours. We also used microsatellite loci to test for by-product mutualism resulting from nest defence of offspring sired on neighbouring territories. We found that male red-winged blackbirds cooperate in nest defence primarily as a form of reciprocal altruism. Experimental males reduced their level of nest defence relative to controls following simulated defection by a neighbour. In contrast to some earlier studies, we found no evidence for by-product mutualism: males did not defend nests where they had sired extra-pair offspring. We also found no evidence for kin selection: males were no more cooperative with more closely related neighbours. Considered alongside the results from other studies, our study suggests that mechanisms stabilizing cooperation in red-winged blackbirds may vary among populations.

Animals↗
PubMed2005

Limiting cheaters in mutualism: evidence from hybridization between mutualist and cheater yucca moths.

Mutualisms are balanced antagonistic interactions where both species gain a net benefit. Because mutualisms generate resources, they can be exploited by individuals that reap the benefits of the interaction without paying any cost. The presence of such 'cheaters' may have important consequences, yet we are only beginning to understand how cheaters evolve from mutualists and how their evolution may be curtailed within mutualistic lineages. The yucca-yucca moth pollination mutualism is an excellent model in this context as there have been two origins of cheating from within the yucca moth lineage. We used nuclear and mitochondrial DNA markers to examine genetic structure in a moth population where a cheater species is parapatric with a resident pollinator. The results revealed extensive hybridization between pollinators and cheaters. Hybrids were genetically intermediate to parental populations, even though all individuals in this population had a pollinator phenotype. The results suggest that mutualisms can be stable in the face of introgression of cheater genes and that the ability of cheaters to invade a given mutualism may be more limited than previously appreciated.

Adaptation, Biological↗
PubMed2003

Mutual-information-based registration of medical images: a survey.

An overview is presented of the medical image processing literature on mutual-information-based registration. The aim of the survey is threefold: an introduction for those new to the field, an overview for those working in the field, and a reference for those searching for literature on a specific application. Methods are classified according to the different aspects of mutual-information-based registration. The main division is in aspects of the methodology and of the application. The part on methodology describes choices made on facets such as preprocessing of images, gray value interpolation, optimization, adaptations to the mutual information measure, and different types of geometrical transformations. The part on applications is a reference of the literature available on different modalities, on interpatient registration and on different anatomical objects. Comparison studies including mutual information are also considered. The paper starts with a description of entropy and mutual information and it closes with a discussion on past achievements and some future challenges.

Algorithms↗
PubMed2006

Effects of a mutual support group for families of Chinese people with schizophrenia: 18-month follow-up.

BACKGROUND: Family intervention in schizophrenia can reduce patient relapse and improve medication adherence, but few studies on this have involved a Chinese population. AIMS: To examine the effects of a mutual support group for Chinese families of people with schizophrenia, compared with psychoeducation and standard care. METHOD: Randomised controlled trial in Hong Kong with 96 families of out-patients with schizophrenia, of whom 32 received mutual support, 33 psychoeducation and 31 standard care. The psychoeducation group included patients in all the sessions, the mutual support group did not. Intervention was provided over 6 months, and patient- and family-related psychosocial outcomes were compared over an 18-month follow-up. RESULTS: Mutual support consistently produced greater improvement in patient and family functioning and caregiver burden over the intervention and follow-up periods, compared with the other two conditions. The number of readmissions did not decrease significantly, but their duration did. CONCLUSIONS: Mutual support for families of Chinese people with schizophrenia can substantially benefit family and patient functioning and caregiver burden.

Adaptation, Psychological↗
PubMed2002

Psychiatric comorbidity, continuing care and mutual help as predictors of five-year remission from substance use disorders.

OBJECTIVE: In a cohort of 2,595 male patients in VA intensive treatment programs for substance use disorders (SUD), we tested whether psychiatric comorbidity, outpatient care and mutual help group attendance during the first two follow-up years predicted remission status at Year 5, controlling for covariates. METHOD: Logistic regression modeling of longitudinal data was used to test the hypotheses. RESULTS: Dual diagnosis patients were less likely to be in remission at Year 5 than SUD-only patients. Outpatient care was at best only weakly related to Year 5 remission status. By contrast, mutual help involvement substantially improved the chances of substance use remission at Year 5 for both SUD-only and dual diagnosis patients. Mutual help involvement did not, however, offset the poorer prognosis for dual diagnosis patients. CONCLUSIONS: Because mutual help groups specifically targeted to individuals with comorbid substance use and psychiatric disorders are currently rare, further research is recommended to investigate whether they are more effective than standard SUD mutual help groups in facilitating the recovery of persons with dual diagnoses.

Adult↗
PubMed2005

[Mutual evaluation as a method of quality assurance in hospital units].

BACKGROUND: Mutual visit schemes have been used in quality assurance of general practice. We have examined the effect of mutual evaluation in the quality assurance of patient care in hospital units. MATERIAL AND METHODS: Four university hospital units for medical gastroenterology received and performed one visit each. The visits were performed by one doctor and two nurses and lasted two days. The visit resulted in written reports that were first discussed locally and subsequently jointly in connection with a seminar. The evaluation was based on reported experiences, proposed improvements and surveys of patient satisfaction before and after the mutual evaluation process. A method was developed for surveying patient satisfaction with outpatient endoscopy. RESULTS AND INTERPRETATION: The mutual evaluation created enthusiasm, increased understanding and generated many proposals for improvement. Some improvement was observed in patients' satisfaction with the information given. The study suggests that mutual evaluation is a suitable method for quality assurance of patient care in hospital units.

Endoscopy, Gastrointestinal↗