Porous nanostructure controls kinetics, disposition and self-assembly structure of lipid digestion products

Combining ¹H NMR and sSAXS to discriminate the speciation and structure evolution of lipolysis products for submicron lipid droplets and lipid loaded in porous silica particles.

Interfacial processes that modulate the kinetics of lipase-mediated catalysis using porous silica host particles

Surface immobilised lipases are important bioactive materials that have a wide range of applications in the biotechnology, chemical and pharmaceutical industries.

QCM-D and ToF-SIMS Investigation to Deconvolute the Relationship between Lipid Adsorption and Orientation on Lipase Activity

Quartz crystal microbalance with dissipation (QCM-D) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to provide insights into the relationship between lipid adsorption kinetics and molecular behavior in porous silica particles of varying hydrophobicities on lipase activity. Lipase (an interfacial enzyme that cleaves ester bonds to break down lipids to fatty acids and monoglycerides) activity was controlled by loading triglycerides at different surface coverages in hydrophilic and hydrophobic porous silica particles. The rate of lipid adsorption increased 2-fold for the hydrophobic surface compared to the hydrophilic surface. However, for submonolayer lipid coverage, the hydrophilic surface enhanced lipase activity 4-fold, whereas the hydrophobic surface inhibited lipase activity 16-fold, compared to lipid droplets in water. A difference in lipid orientation for low surface coverage, evidenced by ToF-SIMS, indicated that lipid adsorbs to hydrophilic silica in a conformation promoting hydrolysis. Multilayer coverage on hydrophobic and hydrophilic surfaces was indistinguishable with ToF-SIMS analysis. Increased lipid adsorption for both substrates facilitated digestion kinetics comparable to a conventional emulsion. Improved understanding of the interfacial adsorption and orientation of lipid and its digestibility in porous silica has implications in improving the uptake of pharmaceuticals and nutrients from lipid-based delivery systems.

Bioactive Hybrid Particles from Poly(D,L-lactide-co-glycolide) Nanoparticle Stabilized Lipid Droplets

Biodegradable and bioactive hybrid particles composed of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles and medium-chain triglycerides were prepared by spray drying lipid-in-water emulsions stabilized by PLGA nanoparticles, to form PLGA-lipid hybrid (PLH) microparticles approximately 5 μm in mean diameter. The nanoparticle stabilizer was varied and mannitol was also incorporated during the preparation to investigate the effect of stabilizer charge and cryoprotectant content on the particle microstructure. An in vitro lipolysis model was used to demonstrate the particles' bioactivity by manipulating the digestion kinetics of encapsulated lipid by pancreatic lipase in simulated gastrointestinal fluid. Lipid digestion kinetics were enhanced in PLH and PLGA-lipid-mannitol hybrid (PLMH) microparticles for both stabilizers, compared to a coarse emulsion, in biorelevant media. An optimal digestion rate was observed for the negatively charged PLMH system, evidenced by a 2-fold increase in the pseudo-first-order rate constant compared to a coarse emulsion. Improved microparticle redispersion, probed by dual dye confocal fluorescence microscopy, increased the available surface area of lipid for lipase adsorption, enhancing digestion kinetics. Thereby, lipase action was controlled in hybrid microparticles by altering the surface charge and carbohydrate content. Our results demonstrate that bioactive microparticles composed of versatile and biodegradable polymeric particles and oil droplets have great potential for use in smart food and nutrient delivery, as well as safer and more efficacious oral delivery of drugs and drug combinations.

Inference for one-step beneficial mutations using next generation sequencing

Experimental evolution is an important research method that allows for the study of evolutionary processes occurring in microorganisms. Here we present a novel approach to experimental evolution that is based on application of next generation sequencing. Under this approach population level sequencing is applied to an evolving population in which multiple first-step beneficial mutations occur concurrently. As a result, frequencies of multiple beneficial mutations are observed in each replicate of an experiment. For this new type of data we develop methods of statistical inference. In particular, we propose a method for imputing selection coefficients of first-step beneficial mutations. The imputed selection coefficient are then used for testing the distribution of first-step beneficial mutations and for estimation of mean selection coefficient. In the case when selection coefficients are uniformly distributed, collected data may also be used to estimate the total number of available first-step beneficial mutations.

A large-scale, rapid public health response to rabies in an organ recipient and the previously undiagnosed organ donor

This article describes and contrasts the public health response to two human rabies cases: one organ recipient diagnosed within days of symptom onset and the transplant donor who was diagnosed 18 months post-symptom onset. In response to an organ-transplant-related rabies case diagnosed in 2013, organ donor and recipient investigations were conducted by multiple public health agencies. Persons with potential exposure to infectious patient materials were assessed for rabies virus exposure. An exposure investigation was conducted to determine the source of the organ donor's infection. Over 100 persons from more than 20 agencies spent over 2700 h conducting contact investigations in healthcare, military and community settings. The 564 persons assessed include 417 healthcare workers [5.8% recommended for post-exposure prophylaxis (PEP)], 96 community contacts (15.6% recommended for PEP), 30 autopsy personnel (50% recommended for PEP), and 21 other persons (4.8% recommended for PEP). Donor contacts represented 188 assessed with 20.2% recommended for PEP, compared with 5.6% of 306 recipient contacts recommended for PEP. Human rabies cases result in substantial use of public health and medical resources, especially when diagnosis is delayed. Although rare, clinicians should consider rabies in cases of encephalitis of unexplained aetiology, particularly for cases that may result in organ donation.

The role of porous nanostructure in controlling lipase-mediated digestion of lipid loaded into silica particles

The rate and extent of lipolysis, the breakdown of fat into molecules that can be absorbed into the bloodstream, depend on the interfacial composition and structure of lipid (fat) particles. A novel method for controlling the interfacial properties is to load the lipid into porous colloidal particles. We report on the role of pore nanostructure and surface coverage in controlling the digestion kinetics of medium-chain and long-chain triglycerides loaded into porous silica powders of different particle size, porosity, and hydrophobicity/hydrophilicity. An in vitro lipolysis model was used to measure digestion kinetics of lipid by pancreatic lipase, a digestive enzyme. The rate and extent of lipid digestion were significantly enhanced when a partial monolayer of lipid was loaded in porous hydrophilic silica particles compared to a submicrometer lipid-in-water emulsion or a coarse emulsion. The inhibitory effect of digestion products was clearly evident for digestion from a submicrometer emulsion and coarse emulsion. This effect was minimal, however, in the two silica-lipid systems. Lipase action was inhibited for lipid loaded in the hydrophobic silica and considered due to the orientation of lipase adsorption on the methylated silica surface. Thus, hydrophilic silica promotes enhanced digestion kinetics, whereas hydrophobic silica exerts an inhibitory effect on hydrolysis. Evaluation of digestion kinetics enabled the mechanism for enhanced rate of lipolysis in silica-lipid systems to be derived and detailed. These investigations provide valuable insights for the optimization of smart food microparticles and lipid-based drug delivery systems based on lipid excipients and porous nanoparticles.

As it happens: current directions in experimental evolution

Recent decades have seen a significant rise in studies in which evolution is observed and analysed directly-as it happens-under replicated, controlled conditions. Such 'experimental evolution' approaches offer a degree of resolution of evolutionary processes and their underlying genetics that is difficult or even impossible to achieve in more traditional comparative and retrospective analyses. In principle, experimental populations can be monitored for phenotypic and genetic changes with any desired level of replication and measurement precision, facilitating progress on fundamental and previously unresolved questions in evolutionary biology. Here, we summarize 10 invited papers in which experimental evolution is making significant progress on a variety of fundamental questions. We conclude by briefly considering future directions in this very active field of research, emphasizing the importance of quantitative tests of theories and the emerging role of genome-wide re-sequencing.

Efficient simulation and likelihood methods for non-neutral multi-allele models

Throughout the 1980s, Simon Tavaré made numerous significant contributions to population genetics theory. As genetic data, in particular DNA sequence, became more readily available, a need to connect population-genetic models to data became the central issue. The seminal work of Griffiths and Tavaré (1994a , 1994b , 1994c) was among the first to develop a likelihood method to estimate the population-genetic parameters using full DNA sequences. Now, we are in the genomics era where methods need to scale-up to handle massive data sets, and Tavaré has led the way to new approaches. However, performing statistical inference under non-neutral models has proved elusive. In tribute to Simon Tavaré, we present an article in spirit of his work that provides a computationally tractable method for simulating and analyzing data under a class of non-neutral population-genetic models. Computational methods for approximating likelihood functions and generating samples under a class of allele-frequency based non-neutral parent-independent mutation models were proposed by Donnelly, Nordborg, and Joyce (DNJ) (Donnelly et al., 2001). DNJ (2001) simulated samples of allele frequencies from non-neutral models using neutral models as auxiliary distribution in a rejection algorithm. However, patterns of allele frequencies produced by neutral models are dissimilar to patterns of allele frequencies produced by non-neutral models, making the rejection method inefficient. For example, in some cases the methods in DNJ (2001) require 10(9) rejections before a sample from the non-neutral model is accepted. Our method simulates samples directly from the distribution of non-neutral models, making simulation methods a practical tool to study the behavior of the likelihood and to perform inference on the strength of selection.

The process of change in psychotherapy for depression: helping clients to reformulate the problem

There is increasing interest in mental health nurses delivering structured short-term evidence-based psychotherapies such as cognitive behavioural therapy (CBT) and interpersonal psychotherapy (IPT); however, while there is evidence of the efficacy of psychotherapy for depression, there is limited understanding of the treatment processes. Data were drawn from audio tapes of CBT and IPT sessions for treatment of depression. The transcripts of the initial, middle and final psychotherapy sessions of 40 clients were analysed. A thematic analysis was conducted to identify what was occurring in the sessions, how the client was describing psychotherapy and how the client was describing improvement or lack of improvement in depressive symptoms. There were differences in descriptions of therapy and the experience of depression between clients who responded and those who did not respond to therapy that were related to improvement in symptoms but not to the specific therapy. These differences were in the client's engagement with the language of therapy, sense of optimism about the particular model of psychotherapy, ability to examine their own role in the problem and desire to engage with new ways of being in their lives. Clients who responded to CBT or IPT had flexibility to develop new ways of thinking and acting, the ability to accept responsibility for their role in the identified problem and were willing to risk change.

Estimating the number of one-step beneficial mutations

Mutations that confer a selective advantage to an organism are the raw material upon which natural selection acts. The number of such mutations that are available is a central quantity of interest for understanding the tempo and trajectory of adaptive evolution. While this quantity is typically unknown, it can be estimated with varying levels of accuracy based on data obtained experimentally. We propose a method for estimating the number of beneficial mutations that accounts for the evolutionary forces that generate the data. Our model-based parametric approach is compared to an adjusted nonparametric abundance-based coverage estimator. We show that, in general, our estimator performs better. When the number of mutations is small, however, the performances of the two estimators are similar.

Nurse-led delivery of specialist supportive care for bipolar disorder: a randomized controlled trial

The aim of the study is (1) to assess the feasibility of delivering nurse-led specialist supportive care as an adjunct to usual care in the clinical setting; (2) to examine the relationship between the delivery of specialist supportive care and improved self-efficacy and functioning and reduced depressive symptoms. A randomized controlled trial of the clinical effectiveness of specialist supportive care as an adjunct to usual care was conducted in community mental health services at one site. Participants were randomized to either usual care or usual care and the adjunctive intervention. Self-report measures of depression, general functioning and self-efficacy were completed by participants in both groups at baseline and 9 months. The intervention was delivered parallel to usual treatment arrangements. While recruitment numbers were sufficient, a low rate of engagement meant we were unable to show significant differences in depressive symptoms or self-efficacy between the usual care group and the specialist supportive care plus usual care group. This study demonstrated that it was difficult to engage patients with bipolar disorder in specialist supportive care when they were currently in a mood episode and under the care of community mental health services.

Feeling out of control: a qualitative analysis of the impact of bipolar disorder

Bipolar disorder is a chronic and recurrent disorder with fluctuating symptoms. Few patients with bipolar disorder experience a simple trajectory of clear-cut episodes, with recovery typically occurring slowly over time. The chronic and disabling course of the disorder has a marked impact on the person's functioning and relationships with others. The objectives of this study were to investigate the impact of bipolar disorder on the lives of people diagnosed with this disorder. The method used was a general inductive qualitative approach. Twenty-one participants were interviewed between 2008 and 2009 about how they had experienced the impact of bipolar disorder. The interviews were audio-taped and transcribed. The core theme that emerged was the participants were feeling out of control. Their own reactions and the reactions of others to the symptoms of bipolar disorder contributed to this core theme. The core theme was constituted by feeling overwhelmed, a loss of autonomy and felling flawed. Mental health nurses can help facilitate a sense of personal control for people with bipolar disorder by exploring what the symptoms mean for that person and implementing strategies to manage the symptoms, address social stigma and facilitate active involvement in treatment.

First-step mutations for adaptation at elevated temperature increase capsid stability in a virus

The relationship between mutation, protein stability and protein function plays a central role in molecular evolution. Mutations tend to be destabilizing, including those that would confer novel functions such as host-switching or antibiotic resistance. Elevated temperature may play an important role in preadapting a protein for such novel functions by selecting for stabilizing mutations. In this study, we test the stability change conferred by single mutations that arise in a G4-like bacteriophage adapting to elevated temperature. The vast majority of these mutations map to interfaces between viral coat proteins, suggesting they affect protein-protein interactions. We assess their effects by estimating thermodynamic stability using molecular dynamic simulations and measuring kinetic stability using experimental decay assays. The results indicate that most, though not all, of the observed mutations are stabilizing.

The onion model, a simple neutral model for the evolution of diversity in bacterial biofilms

Bacterial biofilms are particularly resistant to a wide variety of antimicrobial compounds. Their persistence in the face of antibiotic therapies causes significant problems in the treatment of infectious diseases. Seldom have evolutionary processes like genetic drift and mutation been invoked to explain how resistance to antibiotics emerges in biofilms, and we lack a simple and tractable model for the genetic and phenotypic diversification that occurs in bacterial biofilms. Here, we introduce the 'onion model', a simple neutral evolutionary model for phenotypic diversification in biofilms. We explore its properties and show that the model produces patterns of diversity that are qualitatively similar to observed patterns of phenotypic diversity in biofilms. We suggest that models like our onion model, which explicitly invoke evolutionary process, are key to understanding biofilm resistance to bactericidal and bacteriostatic agents. Elevated phenotypic variance provides an insurance effect that increases the likelihood that some proportion of the population will be resistant to imposed selective agents and may thus enhance persistence of the biofilm. Accounting for evolutionary change in biofilms will improve our ability to understand and counter diseases that are caused by biofilm persistence.

A novel comparative method for identifying shifts in the rate of character evolution on trees

Evolutionary biologists since Darwin have been fascinated by differences in the rate of trait-evolutionary change across lineages. Despite this continued interest, we still lack methods for identifying shifts in evolutionary rates on the growing tree of life while accommodating uncertainty in the evolutionary process. Here we introduce a Bayesian approach for identifying complex patterns in the evolution of continuous traits. The method (auteur) uses reversible-jump Markov chain Monte Carlo sampling to more fully characterize the complexity of trait evolution, considering models that range in complexity from those with a single global rate to potentially ones in which each branch in the tree has its own independent rate. This newly introduced approach performs well in recovering simulated rate shifts and simulated rates for datasets nearing the size typical for comparative phylogenetic study (i.e., ≥64 tips). Analysis of two large empirical datasets of vertebrate body size reveal overwhelming support for multiple-rate models of evolution, and we observe exceptionally high rates of body-size evolution in a group of emydid turtles relative to their evolutionary background. auteur will facilitate identification of exceptional evolutionary dynamics, essential to the study of both adaptive radiation and stasis.

Epistasis between beneficial mutations and the phenotype-to-fitness Map for a ssDNA virus

Epistatic interactions between genes and individual mutations are major determinants of the evolutionary properties of genetic systems and have therefore been well documented, but few quantitative data exist on epistatic interactions between beneficial mutations, presumably because such mutations are so much rarer than deleterious ones. We explored epistasis for beneficial mutations by constructing genotypes with pairs of mutations that had been previously identified as beneficial to the ssDNA bacteriophage ID11 and by measuring the effects of these mutations alone and in combination. We constructed 18 of the 36 possible double mutants for the nine available beneficial mutations. We found that epistatic interactions between beneficial mutations were all antagonistic—the effects of the double mutations were less than the sums of the effects of their component single mutations. We found a number of cases of decompensatory interactions, an extreme form of antagonistic epistasis in which the second mutation is actually deleterious in the presence of the first. In the vast majority of cases, recombination uniting two beneficial mutations into the same genome would not be favored by selection, as the recombinant could not outcompete its constituent single mutations. In an attempt to understand these results, we developed a simple model in which the phenotypic effects of mutations are completely additive and epistatic interactions arise as a result of the form of the phenotype-to-fitness mapping. We found that a model with an intermediate phenotypic optimum and additive phenotypic effects provided a good explanation for our data and the observed patterns of epistatic interactions.

Epistasis, the extent to which the effects of a mutation depend on its genetic context, can have profound effects on the evolutionary process and strongly affects our understanding of the prevalence of sexual reproduction. It has been investigated in a diverse array of organisms but almost exclusively for deleterious mutations. Interactions between beneficial mutations can impede adaptation, and we therefore investigated epistasis between beneficial mutations by constructing 18 bacteriophage genomes, each with two mutations that had been previously identified as beneficial, and measuring their fitnesses. We found universal evidence for epistasis—every pair of mutations conferred fitness lower than that expected from the single mutations alone. In many cases, a beneficial mutation became deleterious when in combination with another, and in fact, only one pair out of 18 could be shown to confer significantly greater fitness than its constituent mutations alone. To explain these results, we developed a model of the relationship between phenotype and fitness that posits an intermediate phenotypic optimum and assumes no epistasis at the phenotypic level. This model fit our data well and showed that the patterns we observed could result because mutants have phenotypes that overshoot the optimum.

Was it something I did wrong? A qualitative analysis of parental perspectives of their child's bipolar disorder

The aims of this study were to examine parental views on the onset of symptoms, impact on functioning and meanings attributed to their child's bipolar disorder. Early onset bipolar disorder impacts on development and functioning across multiple domains. Psychosocial disability fluctuates in parallel with changes in affective symptoms and may significantly affect family members. This study utilized descriptive statistical data and qualitative data from parental self-reports of 85 participants in a trial of psychotherapy for young people (15-34 years) with bipolar disorder. A content analysis was conducted on the written self-reports. Most parents identified the onset of depressive symptoms in their child by early adolescence, but it was not until late adolescence, or later, that parents noted symptoms of mania. The onset of symptoms during a crucial period of development had a considerable impact on social and occupational functioning. Without prompting, the parents took the opportunity to attempt to make sense of the diagnosis by attributing its onset to childhood adversity, parenting or substance misuse. Parents often blame themselves for the development of bipolar disorder in their child. Nursing care for clients with bipolar disorder could include interventions for the family to help them understand and manage the disorder. Such interventions could include: psycho-education, communication enhancement and problem-solving skills training.

Inference on the strength of balancing selection for epistatically interacting loci

Existing inference methods for estimating the strength of balancing selection in multi-locus genotypes rely on the assumption that there are no epistatic interactions between loci. Complex systems in which balancing selection is prevalent, such as sets of human immune system genes, are known to contain components that interact epistatically. Therefore, current methods may not produce reliable inference on the strength of selection at these loci. In this paper, we address this problem by presenting statistical methods that can account for epistatic interactions in making inference about balancing selection. A theoretical result due to Fearnhead (2006) is used to build a multi-locus Wright-Fisher model of balancing selection, allowing for epistatic interactions among loci. Antagonistic and synergistic types of interactions are examined. The joint posterior distribution of the selection and mutation parameters is sampled by Markov chain Monte Carlo methods, and the plausibility of models is assessed via Bayes factors. As a component of the inference process, an algorithm to generate multi-locus allele frequencies under balancing selection models with epistasis is also presented. Recent evidence on interactions among a set of human immune system genes is introduced as a motivating biological system for the epistatic model, and data on these genes are used to demonstrate the methods.

Two sides of the same coin: caring for a person with bipolar disorder

The aim of this paper was to gain an in-depth understanding of the way the lives of individuals supporting someone diagnosed with bipolar disorder. Bipolar disorder is a severe, recurrent and chronic mental disorder that has a significant impact on the lives of those who experience it and the people supporting them. It is often the subsyndromal symptoms that cause major impairment in functioning and can have financial, social, interpersonal and health impacts for carers. A qualitative thematic analysis was chosen to enable an in-depth exploration of participants' experiences. Twelve participants were interviewed using a semi-structured interview and the data were analysed to identify the themes that represented the participants' experiences. The predominant theme that emerged, two sides of the same coin, described the positive and negative aspects of being an informal carer for a person with bipolar disorder. This theme is constituted by two sub-themes: (1) 'I am a much more compassionate person'; and (2) 'It's tough and it's a sacrifice'. Mental health nurses could support informal caregivers more by providing care that demonstrates an understanding of the complexities associated with bipolar disorder and utilizes a collaborative approach to care that actively involves informal caregivers.