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1.
PeerJ ; 12: e17324, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38784398

RESUMEN

Anthropogenic climate change and the associated increase in sea temperatures are projected to greatly impact marine ecosystems. Temperature variation can influence the interactions between species, leading to cascading effects on the abundance, diversity and composition of communities. Such changes in community structure can have consequences on ecosystem stability, processes and the services it provides. Therefore, it is important to better understand the role of species interactions in the development of communities and how they are influenced by environmental factors like temperature. The coexistence of closely related cryptic species, with significant biological and ecological differences, makes this even more complex. This study investigated the effect of temperature on species growth and both intra- and interspecific interactions of three species within the free-living nematode Litoditis marina complex. To achieve this, closed microcosm experiments were conducted on the L. marina species Pm I, Pm III and Pm IV in monoculture and combined cultures at two temperature treatments of 15 °C and 20 °C. A population model was constructed to elucidate and quantify the effects of intra- and interspecific interactions on nematode populations. The relative competitive abilities of the investigated species were quantified using the Modern Coexistence Theory (MCT) framework. Temperature had strong and disparate effects on the population growth of the distinct L. marina species. This indicates temperature could play an important role in the distribution of these cryptic species. Both competitive and facilitative interactions were observed in the experiments. Temperature affected both the type and the strength of the species interactions, suggesting a change in temperature could impact the coexistence of these closely related species, alter community dynamics and consequently affect ecosystem processes and services.


Asunto(s)
Cambio Climático , Temperatura , Animales , Ecosistema , Dinámica Poblacional , Nematodos/fisiología , Nematodos/crecimiento & desarrollo
2.
Ecol Lett ; 27(5): e14433, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38712704

RESUMEN

The negative diversity-invasion relationship observed in microbial invasion studies is commonly explained by competition between the invader and resident populations. However, whether this relationship is affected by invader-resident cooperative interactions is unknown. Using ecological and mathematical approaches, we examined the survival and functionality of Aminobacter niigataensis MSH1 to mineralize 2,6-dichlorobenzamide (BAM), a groundwater micropollutant affecting drinking water production, in sand microcosms when inoculated together with synthetic assemblies of resident bacteria. The assemblies varied in richness and in strains that interacted pairwise with MSH1, including cooperative and competitive interactions. While overall, the negative diversity-invasion relationship was retained, residents engaging in cooperative interactions with the invader had a positive impact on MSH1 survival and functionality, highlighting the dependency of invasion success on community composition. No correlation existed between community richness and the delay in BAM mineralization by MSH1. The findings suggest that the presence of cooperative residents can alleviate the negative diversity-invasion relationship.


Asunto(s)
Microbiota , Benzamidas , Interacciones Microbianas , Phyllobacteriaceae/fisiología , Agua Subterránea/microbiología , Biodiversidad
3.
Appetite ; 192: 107094, 2024 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-37866528

RESUMEN

Food choice decisions are challenging to conceptualise, and literature is lacking specific to adolescent food choice decisions. Understanding adolescent nutrition and food choice is becoming increasingly important. This research aims to understand what influences the food choices of Irish adolescents, and the mental negotiations occurring in food-based decisions. Additionally, it aims to develop a holistic conceptual model of food choice, specific to adolescents. A qualitative study was conducted in N = 47 Irish adolescents, via focus group discussions using vignettes to introduce discussion topics around food and eating habits. Data were analysed using reflexive thematic analysis, involving both semantic and latent analysis. Thirteen distinct factors related to adolescent food choices were discussed, forming one main theme and three inter-linking subthemes. The main theme relates to food choice being multi-factorial in nature, needing a balance of priorities through internal negotiations for food choice with the aim of reducing food guilt. This can change depending on the social setting. Social concerns and food guilt appear to play a strong role in adolescent food choice, with adolescents feeling guilty for eating unhealthy food, wasting food, or spending/wasting money on food. A conceptual model for food choice in adolescents was developed, named a "Food Choice Funnel", incorporating a specific "Food Guilt Matrix". While we should encourage healthy eating and a healthy lifestyle, it is important to understand the value placed on the social component to eating among adolescents, since they have increasing social interactions and occasions where choosing health-promoting foods may be more challenging. Healthy eating messages should be designed in a balanced manner to support healthy growth and development, while limiting the potential to induce feelings of guilt among adolescents.


Asunto(s)
Preferencias Alimentarias , Negociación , Humanos , Adolescente , Conducta Alimentaria , Alimentos , Culpa
4.
Appetite ; 189: 106981, 2023 10 01.
Artículo en Inglés | MEDLINE | ID: mdl-37499761

RESUMEN

During adolescence, teens start making their own food choices. While health and nutrition are important, practical and social concerns are also influential. This study aims to determine factors that motivate the food choices of Irish teens (using Food Choice Questionnaire), using data from the National Teens' Food Survey II (N = 428, 50% male, 13-18 years), and to identify how these motivations relate to dietary intakes (4-day semi-weighed food diaries). Data analysis used PCA to determine the food choice motivation subscales, and correlation and comparative statistical tests (t-test, ANOVA). Eight motivating factors were identified for Irish teens: Sensory Appeal, Price & Availability, Health & Natural Content, Familiarity, Ease of Preparation, Mood, Weight Control, and Ethical Concerns. Health and practical aspects to food choice (Price, Availability, Ease of Preparation) are important for teens, but taste (Sensory Appeal) remains a key influence. Food choice motivations vary by sex and by age, BMI status and weight perception, where girls were more motivated by health, weight control, mood and ethical concerns, and older teens were more influenced by mood and ease of preparation. Both those classified as overweight and those who perceived they were overweight were motivated more by weight control and mood for their food choices, whereas those who perceived their weight to be correct placed more importance on health and natural content. Those motivated by weight control had lower energy and higher protein intakes, and those motivated by health and natural content had more health promoting behaviours, with higher physical activity, lower screen time, and higher protein intakes. Understanding the motivations of teens' food choice can help understand why they struggle to meet dietary recommendations, and help to develop more effective health promotion messages by capitalising on the key motivations in the population.


Asunto(s)
Motivación , Sobrepeso , Femenino , Humanos , Masculino , Adolescente , Preferencias Alimentarias , Encuestas y Cuestionarios , Ingestión de Alimentos
5.
Eur J Nutr ; 62(4): 1755-1765, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-36820883

RESUMEN

PURPOSE: Studies show that dairy fat consumed in the form of cheese reduce LDL-cholesterol concentration (LDL-c) compared to butter and mechanistic suggestions include the calcium content of cheese leading to enhanced faecal fat excretion. The aim of this study was to test the effect of varying the calcium content within a cheese, on faecal fat excretion as a primary outcome, and blood lipid markers, fasting glucose and calcium excretion as secondary outcomes. METHODS: 7 healthy males (BMI 18-25) participated in this randomized, cross-over control intervention, of 3 × 2 week periods. Diets contained 240 g/day cheese; a High Calcium Cheese (HCC) diet, a Reduced Calcium Cheese (RCC) diet, and a control arm: Reduced Calcium Cheese + CaCO3 Supplement (RCC + Supp) diet. Diets differed in calcium content and form but were otherwise controlled for energy and key macronutrients. Blood and 5-day faecal samples were collected. RESULTS: There was no significant difference in faecal fat excretion (g/day) between the diets (P = 0.066). Percent fat of faecel excretion was higher after RCC + Supp (P = 0.016). None of the individual fatty acids were different. Fasting LDL-c was significantly lower following the HCC diet vs. the other arms (P = 0.002). Faecal Ca was different across all diets (P = 0.001), lowest after RCC, and greatest after RCC + Supp. No differences were observed for fasting blood parameters or changes in anthropometry. CONCLUSION: Varying the calcium content within a cheese matrix significantly affected fasting LDL-c values. Results did not support higher faecal fat excretion as an underlying mechanism, but the high attrition rate was a limitation. Trial registerer Trial Registered at ISRCTN.org, registration number ISRCTN11663659 on 12.07.2022. Retrospectively registered.


Asunto(s)
Carcinoma de Células Renales , Queso , Neoplasias Renales , Humanos , Masculino , Glucemia , Calcio , Calcio de la Dieta , HDL-Colesterol , LDL-Colesterol , Estudios Cruzados , Grasas de la Dieta
6.
Crit Rev Food Sci Nutr ; 63(25): 7837-7851, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-35297716

RESUMEN

Dietary diversity is an established public health principle, and its measurement is essential for studies of diet quality and food security. However, conventional between food group scores fail to capture the nutritional variability and ecosystem services delivered by dietary richness and dissimilarity within food groups, or the relative distribution (i.e., evenness or moderation) of e.g., species or varieties across whole diets. Summarizing food biodiversity in an all-encompassing index is problematic. Therefore, various diversity indices have been proposed in ecology, yet these require methodological adaption for integration in dietary assessments. In this narrative review, we summarize the key conceptual issues underlying the measurement of food biodiversity at an edible species level, assess the ecological diversity indices previously applied to food consumption and food supply data, discuss their relative suitability, and potential amendments for use in (quantitative) dietary intake studies. Ecological diversity indices are often used without justification through the lens of nutrition. To illustrate: (i) dietary species richness fails to account for the distribution of foods across the diet or their functional traits; (ii) evenness indices, such as the Gini-Simpson index, require widely accepted relative abundance units (e.g., kcal, g, cups) and evidence-based moderation weighting factors; and (iii) functional dissimilarity indices are constructed based on an arbitrary selection of distance measures, cutoff criteria, and number of phylogenetic, nutritional, and morphological traits. Disregard for these limitations can lead to counterintuitive results and ambiguous or incorrect conclusions about the food biodiversity within diets or food systems. To ensure comparability and robustness of future research, we advocate food biodiversity indices that: (i) satisfy key axioms; (ii) can be extended to account for disparity between edible species; and (iii) are used in combination, rather than in isolation.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2022.2051163 .


Asunto(s)
Biodiversidad , Dieta , Humanos , Ingestión de Alimentos , Filogenia
7.
Environ Sci Technol ; 56(2): 1352-1364, 2022 01 18.
Artículo en Inglés | MEDLINE | ID: mdl-34982540

RESUMEN

Bioaugmentation often involves an invasion process requiring the establishment and activity of a foreign microbe in the resident community of the target environment. Interactions with resident micro-organisms, either antagonistic or cooperative, are believed to impact invasion. However, few studies have examined the variability of interactions between an invader and resident species of its target environment, and none of them considered a bioremediation context. Aminobacter sp. MSH1 mineralizing the groundwater micropollutant 2,6-dichlorobenzamide (BAM), is proposed for bioaugmentation of sand filters used in drinking water production to avert BAM contamination. We examined the nature of the interactions between MSH1 and 13 sand filter resident bacteria in dual and triple species assemblies in sand microcosms. The residents affected MSH1-mediated BAM mineralization without always impacting MSH1 cell densities, indicating effects on cell physiology rather than on cell number. Exploitative competition explained most of the effects (70%), but indications of interference competition were also found. Two residents improved BAM mineralization in dual species assemblies, apparently in a mutual cooperation, and overruled negative effects by others in triple species systems. The results suggest that sand filter communities contain species that increase MSH1 fitness. This opens doors for assisting bioaugmentation through co-inoculation with "helper" bacteria originating from and adapted to the target environment.


Asunto(s)
Agua Subterránea , Phyllobacteriaceae , Purificación del Agua , Bacterias , Benzamidas , Biodegradación Ambiental , Purificación del Agua/métodos
8.
Proc Nutr Soc ; 81(1): 75-86, 2022 03.
Artículo en Inglés | MEDLINE | ID: mdl-35039094

RESUMEN

The aim of this review is to summarise the common barriers and motivations for healthy food choice among adolescents, with a specific focus on the Irish context where available. It will also discuss other concerns adolescents have, which may influence their food choices and eating habits. Adolescence represents a period of rapid physical, mental and social development, and many health-related habits developed during adolescence tend to persist into adulthood, making the teenage years an optimal time to encourage healthy eating and health-promoting behaviours. Adolescents are concerned about the health impact of their diet, but their understanding of health is often seen in the context of their physical appearance or body image. Body image concerns are prevalent in adolescents, and this can affect their food choices. Taste, price and convenience are commonly noted factors influencing adolescents' food choices, and as they grow, their level of independence increases and spending more time with their peers means that social desirability and social norms about food become increasingly important factors in adolescent food choice. However, their limited autonomy means their supporting food environment also plays an important role. When developing more targeted interventions in adolescent populations, information on adolescent nutrition needs, their concerns for health and body image, and the barriers and motivations for healthy eating and food choice should be considered. Such a holistic approach should help support healthy eating and the prevention of overweight and obesity in the population, whilst also supporting a healthy relationship with food and their bodies.


Asunto(s)
Conducta Alimentaria , Preferencias Alimentarias , Adolescente , Fenómenos Fisiológicos Nutricionales de los Adolescentes , Adulto , Dieta , Dieta Saludable , Humanos
9.
Ir J Med Sci ; 190(4): 1429-1433, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-33409842

RESUMEN

BACKGROUND: This study examines Irish undergraduate students' behaviours and motives regarding alcohol consumption. The study explores both levels and patterns of consumption. METHOD: A cross-sectional design using a convenience sample of (n = 213) students from a selection of different courses in Health Sciences at Trinity College Dublin was used to obtain this data. The study used a peer-led approach to design and data collection. Peer-led research is emerging as a robust methodology. Evidence supports it as an effective approach, particularly with sensitive questions, which may be shared with more ease between persons with common interests and experiences. RESULTS: In terms of alcohol consumption levels and patterns, of those who drank almost three quarters (149/71%) met the threshold for binge drinking (i.e. six of more consecutive drinks in one session). Males (n = 36/73.4%) were more likely than females (n = 113/69.7%) to binge drink. Moreover, one in 5 males (n = 10/20.4%) said that they drank ten or more drinks in one session. Males were more likely to drink for conformity reasons. Despite this, a significant proportion (69.2%) of participants reported alcohol-related problems. The Drinking Motives Questionnaire-Revised (DMQR) results showed that overall students were more likely to drink for social and enhancement reasons rather than coping or conformity reasons, consistent with other studies. Nonetheless, males in the current study were more likely to drink for conformity reasons. CONCLUSION: Given the high rates of hazardous drinking, the development of an alcohol intervention may be justified, given the high response rates to peer-screening, a peer-led intervention for alcohol-related harms may yield positive results.


Asunto(s)
Consumo de Bebidas Alcohólicas , Motivación , Adaptación Psicológica , Consumo de Bebidas Alcohólicas/epidemiología , Estudios Transversales , Femenino , Humanos , Masculino , Estudiantes , Encuestas y Cuestionarios , Universidades
10.
Public Health Nutr ; 24(8): 2144-2152, 2021 06.
Artículo en Inglés | MEDLINE | ID: mdl-32883405

RESUMEN

OBJECTIVES: To describe the eating behaviour styles of Irish teens and to explore the relationships between demographic factors, BMI and dietary intake and these eating behaviour styles. DESIGN: Cross-sectional data from the Irish National Teens' Food Survey (2005-2006). The Dutch Eating Behaviour Questionnaire assessed three eating behaviour styles in teens: restrained, emotional and external eating. Data were stratified by sex and age groups. SETTING: The Republic of Ireland. PARTICIPANTS: Nationally representative sample of teens aged 13-17 years (n 441). RESULTS: The highest scoring eating behaviour style was external eating (2·83 external v. 1·79 restraint and 1·84 emotional). Girls scored higher than boys on all three scales (Restraint: 2·04 v. 1·56, P < 0·001, Emotional: 2·15 v. 1·55, P < 0·001 and External: 2·91 v. 2·76, P = 0·03), and older teens scored higher than younger teens on the Emotional (1·97 v. 1·67, P < 0·001) and External scales (2·91 v. 2·72, P = 0·01). Teens classified as overweight/obese scored higher than those classified as normal weight on the Restraint scale (2·15 v. 1·71, P < 0·001) and lower on the External scale (2·67 v. 2·87, P < 0·03). Daily energy intake was negatively correlated with the Restraint (r -0·343, P < 0·001) and Emotional scales (r -0·137, P = 0·004) and positively correlated with the External scale (r 0·110, P = 0·02). CONCLUSIONS: External eating is the predominant eating behaviour style among Irish teens, but sex, age, BMI and dietary differences exist for each eating behaviour style. Including measures of eating behaviour styles into future dietary research could help understand both how and why as well as what people eat.


Asunto(s)
Ingestión de Alimentos , Conducta Alimentaria , Adolescente , Estudios Transversales , Dieta , Emociones , Femenino , Humanos , Masculino , Obesidad , Encuestas y Cuestionarios
11.
World J Orthop ; 11(3): 197-205, 2020 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-32280609

RESUMEN

BACKGROUND: Bone lesions can present the multi-displinary team with a challenge by way of diagnosis as some lesions share many radiological and histological characteristics. Giant cell tumours of the bone (GCTB) are relatively common, benign bone tumours. Aneurysmal bone cysts (ABC) are less common benign osteolytic lesions that are histologically similar to GCTBs but produce blood filled cavities. Both GCTBs and ABCs are locally aggressive and are typically found on meta-epiphyseal regions of long bones with pelvic tumours being less common. CASE SUMMARY: A 17-year old female presented with atraumatic right groin pain and was initially diagnosed with a GCTB on the right superior pubic ramus of the pelvis. The patient was treated successfully with a wide excision, curettage and bone graft and underwent open reduction and internal fixation of the right hemi-pelvis. Following further intra-operative histological investigations, the lesion was diagnosed as an ABC. CONCLUSION: This patient has had an uncomplicated post-operative course, has returned to comfortable weight bearing and will be reviewed for minimum 5 yr in the out-patient setting to monitor for reoccurrence.

12.
Environ Sci Technol ; 53(24): 14459-14469, 2019 12 17.
Artículo en Inglés | MEDLINE | ID: mdl-31682110

RESUMEN

Many disciplines rely on testing combinations of compounds, materials, proteins, or bacterial species to drive scientific discovery. It is time-consuming and expensive to determine experimentally, via trial-and-error or random selection approaches, which of the many possible combinations will lead to desirable outcomes. Hence, there is a pressing need for more rational and efficient experimental design approaches to reduce experimental effort. In this work, we demonstrate the potential of machine learning methods for the in silico selection of promising co-culture combinations in the application of bioaugmentation. We use the example of pollutant removal in drinking water treatment plants, which can be achieved using co-cultures of a specialized pollutant degrader with combinations of bacterial isolates. To reduce the experimental effort needed to discover high-performing combinations, we propose a data-driven experimental design. Based on a dataset of mineralization performance for all pairs of 13 bacterial species co-cultured with MSH1, we built a Gaussian process regression model to predict the Gompertz mineralization parameters of the co-cultures of two and three species, based on the single-strain parameters. We subsequently used this model in a Bayesian optimization scheme to suggest potentially high-performing combinations of bacteria. We achieved good performance with this approach, both for predicting mineralization parameters and for selecting effective co-cultures, despite the limited dataset. As a novel application of Bayesian optimization in bioremediation, this experimental design approach has promising applications for highlighting co-culture combinations for in vitro testing in various settings, to lessen the experimental burden and perform more targeted screenings.


Asunto(s)
Purificación del Agua , Teorema de Bayes , Biodegradación Ambiental , Técnicas de Cocultivo , Simulación por Computador
13.
Chaos ; 28(12): 123124, 2018 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-30599525

RESUMEN

Theoretical and experimental research studies have shown that ecosystems governed by non-transitive competition networks tend to maintain high levels of biodiversity. The theoretical body of work, however, has mainly focused on competition networks in which the outcomes of competition events are predetermined and hence deterministic, and where all species are identical up to their competitive relationships, an assumption that may limit the applicability of theoretical results to real-life situations. In this paper, we aim to probe the robustness of the link between biodiversity and non-transitive competition by introducing a three-dimensional winning probability parameter space, making the outcomes of competition events in a three-species in silico ecosystem uncertain. While two degenerate points in this parameter space have been the subject of previous studies, we investigate the remaining settings, which equip the species with distinct competitive abilities. We find that the impact of this modification depends on the spatial dimension of the system. When the system is well mixed, it collapses to monoculture, as is also the case in the non-transitive deterministic setting. In one dimension, chaotic patterns emerge, which tend to maintain biodiversity, and a power law relates the time that species manage to coexist to the degree of uncertainty regarding competition event outcomes. In two dimensions, the formation of spiral wave patterns ensures that biodiversity is maintained for moderate degrees of uncertainty, while considerable deviations from the non-transitive deterministic setting have strong negative effects on species coexistence. It can hence be concluded that non-transitive competition can still produce coexistence when the assumption of deterministic competition is abandoned. When the system collapses to monoculture, one observes a "survival of the strongest" law, as the species that has the highest probability of defeating its competitors has the best odds to become the sole survivor.

14.
Pain Med ; 18(2): 252-264, 2017 02 01.
Artículo en Inglés | MEDLINE | ID: mdl-28204691

RESUMEN

Objective: The purpose of this study was to examine the effectiveness of acceptance and commitment therapy (ACT) for older adults with chronic pain. Secondarily, we examined the associations between changes on processes of psychological flexibility and treatment outcome variables. Subjects: Participants were 60 adults with chronic pain age 65 and older selected from a larger consecutive sample of 928 adults of any age. All participants had longstanding pain that was associated with significant distress and disability. Methods: Participants completed measures of pain, functioning, and depression, and processes of psychological flexibility at baseline, immediately post-treatment, and at a 9-month follow-up. Treatment consisted of a 2- or 4-week residential program based on principles of ACT delivered by an interdisciplinary team. Treatment was designed to increase daily functioning by enhancing key processes of psychological flexibility, including openness, awareness, and committed action. Results: Participants showed significant improvements in functioning and mental health at posttreatment. Participants also showed significant increases in pain acceptance and committed action from pre- to post-treatment. Small effect sizes were observed for most treatment outcome and process variables in the pre-treatment to follow-up intervals; however, these improvements were not statistically significant. In secondary analyses, changes in facets of psychological flexibility were significantly associated with improvements in social functioning and mental health. Conclusion: This study supports the potential effectiveness of ACT for chronic pain among older adults. Future research is needed to determine how to maximize the impact of this treatment, particularly through greater impact on psychological flexibility.


Asunto(s)
Terapia de Aceptación y Compromiso/métodos , Dolor Crónico/terapia , Manejo del Dolor/métodos , Anciano , Femenino , Humanos , Masculino , Resultado del Tratamiento
15.
Phys Rev E ; 93: 042414, 2016 04.
Artículo en Inglés | MEDLINE | ID: mdl-27176336

RESUMEN

The critical role that biodiversity plays in ecosystem functioning has motivated many studies of the mechanisms that sustain biodiversity, a notable example being cyclic competition. We extend existing models of communities with cyclic competition by incorporating variable community evenness and resource dependence in demographic processes, two features that have generally been neglected. In this way, we align previous approaches more closely with real-world microbial ecosystems. We demonstrate the existence of a trade-off between increasing biomass production and maintaining biodiversity. This supports experimental observations of a net negative biodiversity effect on biomass productivity, due to competition effects suffered by highly productive species in diverse communities. Our results also support the important role assigned by microbial ecologists to evenness in maintaining ecosystem stability, thus far largely overlooked in in silico approaches.


Asunto(s)
Biodiversidad , Simulación por Computador , Microbiología , Biomasa
16.
Chaos ; 26(12): 123121, 2016 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-28039986

RESUMEN

Biodiversity has a critical impact on ecosystem functionality and stability, and thus the current biodiversity crisis has motivated many studies of the mechanisms that sustain biodiversity, a notable example being non-transitive or cyclic competition. We therefore extend existing microscopic models of communities with cyclic competition by incorporating resource dependence in demographic processes, characteristics of natural systems often oversimplified or overlooked by modellers. The spatially explicit nature of our individual-based model of three interacting species results in the formation of stable spatial structures, which have significant effects on community functioning, in agreement with experimental observations of pattern formation in microbial communities.


Asunto(s)
Dinámica Poblacional , Biodiversidad , Simulación por Computador , Ecosistema , Modelos Biológicos
17.
J Theor Biol ; 387: 189-205, 2015 Dec 21.
Artículo en Inglés | MEDLINE | ID: mdl-26458785

RESUMEN

Initial community evenness has been shown to be a key factor in preserving the functional stability of an ecosystem, but has not been accounted for in previous modelling studies. We formulate a model that allows the initial evenness of the community to be varied in order to investigate the consequent impact on system diversity. We consider a community of four interacting bacterial species, and present a stochastic, spatial individual-based model simulating the ecosystem dynamics. Interactions take place on a two-dimensional lattice. The model incorporates three processes: reproduction, competition and mobility. In addition to variable initial evenness, multiple competition schemes are implemented, modelling various possible communities, which results in diverse coexistence and extinction scenarios. Simulations show that long-term system behaviour is strongly dependent on initial evenness and competition structure. The system is generally unstable; higher initial evenness has a small stabilizing effect on ecosystem dynamics by extending the time until the first extinction.


Asunto(s)
Bacterias/metabolismo , Biodiversidad , Simulación por Computador , Evolución Biológica , Probabilidad , Especificidad de la Especie , Factores de Tiempo
18.
Oral Oncol ; 44(7): 646-51, 2008 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-17996483

RESUMEN

Invasion and metastasis of oral squamous cell carcinoma (OSCC) is dependent on signals received from stromal fibroblasts present in the surrounding connective tissue. The aim of this study was to investigate the regulation of expression of two important signaling molecules--HGF and SDF-1--by both stromal fibroblasts and their 'activated' form, myofibroblasts, and to determine the role of these two factors in stimulating OSCC cell invasion in vitro. Fibroblasts and myofibroblasts produced similar levels of HGF and SDF-1. IL-1alpha and OSCC cell conditioned medium both stimulated HGF and SDF-1 expression, while TGF-beta(1) inhibited production of each factor. Myofibroblast-derived conditioned medium stimulated OSCC cell invasion through matrigel. Blocking antibodies to both HGF and SDF-1 reduced the level of invasion. In fibroblast-free organotypic raft cultures, addition of HGF and SDF-1 stimulated OSCC cell invasion into the underlying collagen gel, although the pattern of invasion differed from that induced by fibroblasts. Fibroblast-derived HGF and SDF-1 appear to play central roles in the reciprocal interactions between OSCC cells and underlying stromal fibroblasts leading to the local invasion of oral cancer.


Asunto(s)
Carcinoma de Células Escamosas/metabolismo , Quimiocina CXCL12/metabolismo , Factor de Crecimiento de Hepatocito/metabolismo , Neoplasias de la Boca/metabolismo , Proteínas de Neoplasias/metabolismo , Factor de Crecimiento Transformador beta1/metabolismo , Animales , Carcinoma de Células Escamosas/patología , Fibroblastos/metabolismo , Regulación de la Expresión Génica , Humanos , Interleucina-1alfa/metabolismo , Neoplasias de la Boca/patología , Invasividad Neoplásica , Fragmentos de Péptidos/metabolismo , Células del Estroma/patología
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