Browsing by Subject "Food"
Now showing 1 - 18 of 18
Results Per Page
Sort Options
Item Open Access A Farm-to-School Program Review and Implementation Guide for North Carolina Public School Parents Case Study: E.K. Powe Elementary School | Durham, North Carolina(2010-04-29T18:56:58Z) Shoecraft, KellynFarm to School is a phrase used to describe programs that connect locally-grown foods to schools (Farm to School, 2009). The medium that provides this connection varies, but it is typically made through school gardens, farm field trips, nutrition and culinary education, or serving local foods in the school meals program. Farm to School programs are implemented to provide students with a hands-on learning environment and experiential education, to increase the nutritional quality of food served to students and the amount of time students spend outdoors, and to teach students about the agricultural heritage of their region, among other features. Four approaches are typically utilized in North Carolina and other states to institute Farm to School program: (1)The North Carolina Farm to School Program; (2) Local purchasing through contracted produce vendors; (3) Individual school initiatives; (4) District-wide initiatives. The method that a school or school district uses to implement a Farm to School program depends heavily on stakeholder commitment, funding opportunities, and the support of the school community and the district’s Child Nutrition Services. In this project I have evaluated these four approaches to Farm to School programs, using examples in three North Carolina counties: Durham, Guilford and Wake, and one North Carolina City: Asheville. As a corollary case study, I documented my experiences working with stakeholders from E.K. Powe Elementary School in Durham, North Carolina as they worked to implement a Farm to School program during the 2009-2010 school year. In short, I evaluate Farm to School programs state-wide and determine the strengths, weaknesses, opportunities and threats of each program. Further, I describe a formative process in Durham and use this experience in conjunction with my research to create a Farm to School implementation guide geared to North Carolina public school parents.Item Open Access A Quantitative Analysis of Growth and Size Regulation in Manduca sexta: The Physiological Basis of Variation in Size and Age at Metamorphosis.(PLoS One, 2015) Grunert, Laura W; Clarke, Jameson W; Ahuja, Chaarushi; Eswaran, Harish; Nijhout, H FrederikBody size and development time are important life history traits because they are often highly correlated with fitness. Although the developmental mechanisms that control growth have been well studied, the mechanisms that control how a species-characteristic body size is achieved remain poorly understood. In insects adult body size is determined by the number of larval molts, the size increment at each molt, and the mechanism that determines during which instar larval growth will stop. Adult insects do not grow, so the size at which a larva stops growing determines adult body size. Here we develop a quantitative understanding of the kinetics of growth throughout larval life of Manduca sexta, under different conditions of nutrition and temperature, and for genetic strains with different adult body sizes. We show that the generally accepted view that the size increment at each molt is constant (Dyar's Rule) is systematically violated: there is actually a progressive increase in the size increment from instar to instar that is independent of temperature. In addition, the mass-specific growth rate declines throughout the growth phase in a temperature-dependent manner. We show that growth within an instar follows a truncated Gompertz trajectory. The critical weight, which determines when in an instar a molt will occur, and the threshold size, which determines which instar is the last, are different in genetic strains with different adult body sizes. Under nutrient and temperature stress Manduca has a variable number of larval instars and we show that this is due to the fact that more molts at smaller increments are taken before threshold size is reached. We test whether the new insight into the kinetics of growth and size determination are sufficient to explain body size and development time through a mathematical model that incorporates our quantitative findings.Item Restricted A switch in the control of growth of the wing imaginal disks of Manduca sexta.(PLoS One, 2010-05-19) Tobler, Alexandra; Nijhout, H FrederikBACKGROUND: Insulin and ecdysone are the key extrinsic regulators of growth for the wing imaginal disks of insects. In vitro tissue culture studies have shown that these two growth regulators act synergistically: either factor alone stimulates only limited growth, but together they stimulate disks to grow at a rate identical to that observed in situ. It is generally thought that insulin signaling links growth to nutrition, and that starvation stops growth because it inhibits insulin secretion. At the end of larval life feeding stops but the disks continue to grow, so at that time disk growth has become uncoupled from nutrition. We sought to determine at exactly what point in development this uncoupling occurs. METHODOLOGY: Growth and cell proliferation in the wing imaginal disks and hemolymph carbohydrate concentrations were measured at various stages in the last larval instar under experimental conditions of starvation, ligation, rescue, and hormone treatment. PRINCIPAL FINDINGS: Here we show that in the last larval instar of M. sexta, the uncoupling of nutrition and growth occurs as the larva passes the critical weight. Before this time, starvation causes a decline in hemolymph glucose and trehalose and a cessation of wing imaginal disks growth, which can be rescued by injections of trehalose. After the critical weight the trehalose response to starvation disappears, and the expression of insulin becomes decoupled from nutrition. After the critical weight the wing disks loose their sensitivity to repression by juvenile hormone, and factors from the abdomen, but not the brain, are required to drive continued growth. CONCLUSIONS: During the last larval instar imaginal disk growth becomes decoupled from somatic growth at the time that the endocrine events of metamorphosis are initiated. These regulatory changes ensure that disk growth continues uninterrupted when the nutritive and endocrine signals undergo the drastic changes associated with metamorphosis.Item Open Access Agricultural Drivers of Children’s Nutrition and Food Security in Mvomero, Tanzania(2017-04-26) Lamy, JenniferThe main research question assessed in this paper is: What land use and agricultural practices most significantly influence nutritional and food security outcomes? In particular, are there specific crop growing or selling or irrigation practices that, when performed by a household, help to reduce the risk that children under five years old in that household are stunted or anemic or help to increase perceived food security by the household head? I use data collected in 2011 and 2013 in the Mvomero district of Tanzania in order to answer these questions. Using a combination of data at the household level on land use practices and on the individual level for health measures, I perform logit and linear regression analysis to identify any consistent significant associations between the two groups. My results are varied: some agricultural practices are associated with stunting or anemia, while others are more strongly associated with measures of food security. The number of children in a household is negatively associated with both food security measures, implying that larger households in the region have difficulty keeping up with food demands. My findings point to the fact that there is no silver bullet in the quest to improve childhood nutrition and food security in Mvomero, Tanzania and worldwide.Item Open Access Assessment of Smallholder Training Programs in Food Sector Climate Strategies(2022-04-21) Grigg, MarjorieThe future outcomes of climate change, the food sector, and supplier land management are codependent. The food sector is responsible for 37% of global greenhouse gas emissions—predominantly due to land use practices—while also facing decreased productivity as climate change worsens. As food companies and suppliers seek to increase yields, they run the risk of exacerbating this dynamic by intensifying and expanding production. Smallholder farmers (SHF) will play a key role in determining the trajectory of the sector’s land use, as they are particularly vulnerable to climate change and the need to boost food production for household income and consumption. Reducing emissions and mitigating climate risk in the food sector is therefore contingent upon strategic engagements that incentivize and support farmers—particularly SHFs—to transition to land use practices that boost productivity and reduce emissions across supply chains. Encouragingly, food companies are increasingly setting targets to reduce their emissions and establishing climate strategies to address supply risk. Many companies also have long-standing training programs to support SHFs, typically through philanthropic and Corporate Social Responsibility initiatives. However, even where companies are both taking climate action and engaging with small farmers, it is unclear how or if these initiatives are integrated within corporate climate strategy. Alignment across these efforts could accelerate progress by leveraging ongoing programming, and maximize investments and results by identifying synergies across these interconnected objectives. Failing to integrate these initiatives could lead to ineffective investment of limited funding; duplication or counteraction of efforts; and ultimately failure to optimize outcomes across these vital interventions for the sector. In sustainable business strategy, “embedded” initiatives (in which sustainability concerns are integrated into a company’s core strategy) are recognized as more effective than “bolt on” strategies, which tout “green initiatives and social philanthropy,” but are separate from the company’s core strategy. Beyond business strategy, it will be important for companies already investing in initiatives with smallholders to understand how these programs are “embedded into” or “bolted onto” their broader climate action if they are to optimize their efforts to bolster supply, reduce emissions, and support livelihoods. Given the importance of small farmers in creating a sustainable and viable trajectory for global food production and climate action, this study assesses the degree to which companies’ smallholder training programs are embedded within their corporate aims to reduce emissions and mitigate supply risk. Any learnings or areas for improvement will not only inform Corporate Sustainability Officers looking to scale their impact, but will also provide an important road map for companies newly investing in these types of interventions within their supply chains. To improve the level of comparability within this sample, I limited the study area to food companies with 1) emissions targets verified by the Science-based Targets Initiative; 2) climate strategies reported to the same environmental disclosure platform, the Carbon Disclosure Project (CDP); and 3) SHF training programs in Latin America with the same implementing NGO, TechnoServe. I begin by examining companies’ publicly facing sustainability communications, such as Corporate Impact Reports. I examine these publications using the four capitals of environmental economics (natural capital, produced capital, and human and social capitals) to assess companies’ expressed priorities and concerns when communicating to stakeholders about sustainability efforts within their supply chains. I then draw on the principles of materiality and sustainable business strategy to track how supply chain concerns flow throughout companies’ climate strategies, as reported through their CDP “Climate Change Surveys.” I examine how those supply chain concerns translate (or fail to translate) into concrete targets, and then compare these targets with the metrics for success defined in their training programs. I use this alignment as a metric to evaluate the embeddedness of those programs into broader corporate climate action, and posit initial considerations to better integrate smallholders into more effective corporate climate strategies. Findings within this sample indicate that companies emphasizing broad social outcomes for their farmers—rather than explicit land use outcomes within their value chains—are motivated by “social philanthropy” rather than “embedded sustainability,” and, because of this, fail to leverage their investments to drive progress against corporate climate action. While the limited scope of this study does not allow for generalizable conclusions, it highlights initial trends and considerations that can be used by Corporate Sustainability Officers and implementers such as TechnoServe with the power to better align these climate initiatives and optimize their impact. Companies with “embedded” training programs distinguished themselves by training their direct suppliers, aligning training outcomes with internal supply standards, including specific land use concerns within these standards and public sustainability communications, and addressing challenges farmers may face in complying with those standards (for example facilitating access to credit). All “embedded” programs acted within a value chain that accounts for at least 30% of the companies’ revenues. Based on these findings, it will be important for Corporate Sustainability Officers managing “bolt on” farmer engagement programs to identify an achievable, initial set of sourcing standards that can bridge the gap between their farmer training activities and their supply-chain and climate interventions. Third-party certifications and implementing partners could facilitate this transition by providing verification standards and adapting ongoing training curricula to meet these standards, respectively. Because many of these programs are already promoting best practices similar to embedded programs’ sustainable sourcing criteria, a key challenge for corporate sustainability teams will be to measure uptake of those practices in relation to emissions outcomes, and to concentrate training within their companies’ sourcing channels. It will therefore be essential for these teams to understand and mitigate the barriers their sourcing counterparts may face in making direct investments with local suppliers. Conversely, companies with “embedded” training programs could leverage their land use outcomes to establish more rigorous emissions targets. For implementers working with both types of companies, it will be vital to understand their role in making the above transitions feasible and desirable for food companies in order to optimize results for the climate, food production, and the producers who depend on both.Item Open Access Food Advertising on Television Targeting Children in Honduras(2012) Gunderson, Matthew DonaldAbstract
Background: Rates of childhood overweight and obesity have increased dramatically across Latin America in recent years. In Honduras, the problem is more common among children of upper and middle socio-economic status (SES). Evidence suggests that television advertising of high-energy-density (HED) foods may be associated with increased rates of childhood overweight and obesity.
Objective: The purpose of this study was to characterize the advertising of foods during television programming that targets school-age children in Honduras.
Methods: Content analysis was performed on four different television stations accessible to children in Honduras, including one broadcast station and three cable networks. Programming for each station was observed and recorded for one complete week, during after-school hours (defined as 1:30 pm to 5:30 pm, Monday through Friday). Eighty hours of programming were recorded and analyzed. Foods were categorized as being high in energy density or not (HED or non-HED).
Results: A total of 2271 advertisements aired during the observation period; roughly half of these (49.3 percent) were product advertisements. Of the 1120 product advertisements, 397 marketed food-related products. Of these, 69.8 percent promoted HED foods. Children were targeted in the vast majority of advertisements for HED foods (92.1 percent). All of these foods were advertised on cable networks; none of the advertisements for HED foods were aired on broadcast television.
Conclusion: Cable television during after-school hours in Honduras included a high percentage of advertisements for HED foods. This may promote consumption of these foods by children, putting them at greater risk for overweight and obesity.
Item Open Access Food Sovereignty and Conservation(2023-04-28) Drici, AdamThis Master's Project examines the intersections between food sovereignty and conservation. Interviews and focus groups with community members and experts inform the recommendations. Equitable access to food, land, funding, and markets were the most pressing challenges detailed by community members. Several recommendations regarding policy, program, and approach were offered to the client, including equitable government conservation funding access policy reform and the development of a nationwide system of Indigenous protected areas based upon Indigenous traditional food and medicine species ranges. Conservation organizations must center community priorities in efforts to protect wild places to build resilient, inclusive strategies.Item Open Access Food, Eating, and the Anxiety of Belonging in Seventeenth-Century Spanish Literature and Art(2012) Bacarreza, Leonardo MauricioIn my dissertation I propose that the detailed representation of food and eating in seventeenth-century Spanish art and literature has a double purpose: to reaffirm a state of well-being in Spain, and to show a critical position, because artistic creations emphasize those subjects who, because of social status or cultural background, do not share such benefits. This double purpose explains why literature and painting stress the distance between foodstuffs and consumers, turning food into a commodity that cannot be consumed directly, but through its representation and value. Cervantes's writing is invoked because, especially in Don Quixote, readers can see how the protagonist rejects food for the sake of achieving higher chivalric values, while his companion, Sancho Panza, faces the opposite problem: having food at hand and not being able to enjoy it, especially when he achieves his dream of ruling an island. The principle is similar in genre painting: food is consumed out of the picture in still lifes, or out of the hands of the represented characters in kitchen scenes, for they are depicted cooking for others. Because of the distance between product and consumer, foodstuffs indicate how precedence and authority are established and reproduced in society. In artistic representations, these apparently unchangeable principles are mimicked by the lower classes and used to establish parallel systems of authority such as the guild of thieves who are presented around a table in a scene of Cervantes's exemplary novel "Rinconete and Cortadillo." Another problem to which the representation of foodstuffs responds is the inclusion of New Christians from different origins. In a counterpoint with the scenes in which precedence is discussed, and frequently through similar aesthetic structures, Cervantes and his contemporaries create scenes where the Christian principle of sharing food and drinking wine together is the model of inclusion that dissolves distinctions between Old and New Christians. I argue that this alternative project of community can be related to the expulsion of the Moriscos from Spain, decreed in 1609, because this event made many subjects interrogate themselves about their own status and inclusion. An artistic model of response to these interrogations about belonging is the figure of the roadside meal, which appears as the main motif of a meal shared by Sancho and a self-proclaimed Christian Morisco in the second part of Don Quixote, and reappears in a painting by Diego de Velázquez, which presents in the foreground a dark-skinned servant working in a kitchen, and in the background another roadside meal: the Supper at Emmaus. Both in literature and painting the way of preparing meals, eating and drinking creates ties, establishes a different principle of belonging, and promotes unity. In this alternative model characters are recognized as subjects of the kingdom as long as they eat and drink the way Christians do. Even though this model still leads to a single Christian kingdom, paintings and writings suggest a different form of cohesion, in which subjects are considered equal and recognize each other because of their participation.
Item Open Access Food, Justice, and the Church: How Local Churches Can Better Serve Black Communities Through Food Pantries—and Why They Should(2022) Jackson, CynthiaThis thesis seeks to examine how churches might better practice Jesus's command to “love your neighbor” (Matt. 22:37) through food pantries that primarily serve Black communities. Although churches believe they exemplify Jesus’s command to love through their food pantry ministry, they are too often offering cheap love—love that is artificial, inauthentic, and unhealthy. Many churches, in my experience, have a transactional approach in their food pantries—they collect and distribute foods that are cheap, processed, and high in sodium and sugar. However, this practice is possibly causing long-term effects that are physically harmful to Black people who regularly receive and consume these kinds of goods. This thesis will examine food insecurity and health disparities that significantly affect the Black community. Second, this thesis will review literature that has contributed to the food justice movement. Third, in conjunction with Matthew 22 and Daniel 1 and ministry examples, this thesis will encourage churches to adopt a relational approach that will lead them to love and empower their patrons and lean into Christianity’s surprise. Fourth, this thesis will offer curriculum to help church leaders enhance their love for God and others. By learning to love more and in new ways, churches can adopt a more relational approach in the food pantry ministry. Last, this research will offer creative models of how churches and organizations have been able to connect their community to agriculture. When churches embody the expansive nature of this love through their food pantry ministry, their fight against the hunger crisis will be more holistic as they will understand the critical correlation between healthy relationships and healthy food distribution. If churches are going to commit to providing food for Black communities, they must integrate equality and justice in their food ministry mission. It is critical for churches to be more thoughtful about how their actions and the ways they give can be rooted more in love and justice. This type of food ministry will require churches to rethink the kinds of food they provide to other people and their methods to collect and distribute foods. This thesis posits that if churches want to better serve Black communities through food pantry ministries, they should consider possible health risks of Black people and how the act of food distribution can reflect the church’s love for God and the hungry.
Item Open Access Glycosylation of KEAP1 links nutrient sensing to redox stress signaling.(The EMBO journal, 2017-08) Chen, Po-Han; Smith, Timothy J; Wu, Jianli; Siesser, Priscila F; Bisnett, Brittany J; Khan, Farhan; Hogue, Maxwell; Soderblom, Erik; Tang, Flora; Marks, Jeffrey R; Major, Michael B; Swarts, Benjamin M; Boyce, Michael; Chi, Jen-TsanO-GlcNAcylation is an essential, nutrient-sensitive post-translational modification, but its biochemical and phenotypic effects remain incompletely understood. To address this question, we investigated the global transcriptional response to perturbations in O-GlcNAcylation. Unexpectedly, many transcriptional effects of O-GlcNAc transferase (OGT) inhibition were due to the activation of NRF2, the master regulator of redox stress tolerance. Moreover, we found that a signature of low OGT activity strongly correlates with NRF2 activation in multiple tumor expression datasets. Guided by this information, we identified KEAP1 (also known as KLHL19), the primary negative regulator of NRF2, as a direct substrate of OGT We show that O-GlcNAcylation of KEAP1 at serine 104 is required for the efficient ubiquitination and degradation of NRF2. Interestingly, O-GlcNAc levels and NRF2 activation co-vary in response to glucose fluctuations, indicating that KEAP1 O-GlcNAcylation links nutrient sensing to downstream stress resistance. Our results reveal a novel regulatory connection between nutrient-sensitive glycosylation and NRF2 signaling and provide a blueprint for future approaches to discover functionally important O-GlcNAcylation events on other KLHL family proteins in various experimental and disease contexts.Item Open Access Identification of late larval stage developmental checkpoints in Caenorhabditis elegans regulated by insulin/IGF and steroid hormone signaling pathways.(PLoS Genet, 2014-06) Schindler, Adam J; Baugh, L Ryan; Sherwood, David ROrganisms in the wild develop with varying food availability. During periods of nutritional scarcity, development may slow or arrest until conditions improve. The ability to modulate developmental programs in response to poor nutritional conditions requires a means of sensing the changing nutritional environment and limiting tissue growth. The mechanisms by which organisms accomplish this adaptation are not well understood. We sought to study this question by examining the effects of nutrient deprivation on Caenorhabditis elegans development during the late larval stages, L3 and L4, a period of extensive tissue growth and morphogenesis. By removing animals from food at different times, we show here that specific checkpoints exist in the early L3 and early L4 stages that systemically arrest the development of diverse tissues and cellular processes. These checkpoints occur once in each larval stage after molting and prior to initiation of the subsequent molting cycle. DAF-2, the insulin/insulin-like growth factor receptor, regulates passage through the L3 and L4 checkpoints in response to nutrition. The FOXO transcription factor DAF-16, a major target of insulin-like signaling, functions cell-nonautonomously in the hypodermis (skin) to arrest developmental upon nutrient removal. The effects of DAF-16 on progression through the L3 and L4 stages are mediated by DAF-9, a cytochrome P450 ortholog involved in the production of C. elegans steroid hormones. Our results identify a novel mode of C. elegans growth in which development progresses from one checkpoint to the next. At each checkpoint, nutritional conditions determine whether animals remain arrested or continue development to the next checkpoint.Item Open Access Long-term effects of chronic intermittent ethanol exposure in adolescent and adult rats: radial-arm maze performance and operant food reinforced responding.(PloS one, 2013-01) Risher, Mary-Louise; Fleming, Rebekah L; Boutros, Nathalie; Semenova, Svetlana; Wilson, Wilkie A; Levin, Edward D; Markou, Athina; Swartzwelder, H Scott; Acheson, Shawn KBackground
Adolescence is not only a critical period of late-stage neurological development in humans, but is also a period in which ethanol consumption is often at its highest. Given the prevalence of ethanol use during this vulnerable developmental period we assessed the long-term effects of chronic intermittent ethanol (CIE) exposure during adolescence, compared to adulthood, on performance in the radial-arm maze (RAM) and operant food-reinforced responding in male rats.Methodology/principal findings
Male Sprague Dawley rats were exposed to CIE (or saline) and then allowed to recover. Animals were then trained in either the RAM task or an operant task using fixed- and progressive- ratio schedules. After baseline testing was completed all animals received an acute ethanol challenge while blood ethanol levels (BECs) were monitored in a subset of animals. CIE exposure during adolescence, but not adulthood decreased the amount of time that animals spent in the open portions of the RAM arms (reminiscent of deficits in risk-reward integration) and rendered animals more susceptible to the acute effects of an ethanol challenge on working memory tasks. The operant food reinforced task showed that these effects were not due to altered food motivation or to differential sensitivity to the nonspecific performance-disrupting effects of ethanol. However, CIE pre-treated animals had lower BEC levels than controls during the acute ethanol challenges indicating persistent pharmacokinetic tolerance to ethanol after the CIE treatment. There was little evidence of enduring effects of CIE alone on traditional measures of spatial and working memory.Conclusions/significance
These effects indicate that adolescence is a time of selective vulnerability to the long-term effects of repeated ethanol exposure on neurobehavioral function and acute ethanol sensitivity. The positive and negative findings reported here help to further define the nature and extent of the impairments observed after adolescent CIE and provide direction for future research.Item Open Access Mine or yours? Development of sharing in toddlers in relation to ownership understanding.(Child Dev, 2013-05) Brownell, Celia A; Iesue, Stephanie S; Nichols, Sara R; Svetlova, MargaritaTo examine early developments in other-oriented resource sharing, fifty-one 18- and 24-month-old children were administered 6 tasks with toys or food that could be shared with an adult playmate who had none. On each task the playmate communicated her desire for the items in a series of progressively more explicit cues. Twenty-four-month-olds shared frequently and spontaneously. Eighteen-month-olds shared when given multiple opportunities and when the partner provided enough communicative support. Younger children engaged in self-focused and hypothesis-testing behavior in lieu of sharing more often than did older children. Ownership understanding, separately assessed, was positively associated with sharing and negatively associated with non-sharing behavior, independent of age and language ability.Item Open Access Plant species' origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands.(Nat Commun, 2015-07-15) Seabloom, Eric W; Borer, Elizabeth T; Buckley, Yvonne M; Cleland, Elsa E; Davies, Kendi F; Firn, Jennifer; Harpole, W Stanley; Hautier, Yann; Lind, Eric M; MacDougall, Andrew S; Orrock, John L; Prober, Suzanne M; Adler, Peter B; Anderson, T Michael; Bakker, Jonathan D; Biederman, Lori A; Blumenthal, Dana M; Brown, Cynthia S; Brudvig, Lars A; Cadotte, Marc; Chu, Chengjin; Cottingham, Kathryn L; Crawley, Michael J; Damschen, Ellen I; Dantonio, Carla M; DeCrappeo, Nicole M; Du, Guozhen; Fay, Philip A; Frater, Paul; Gruner, Daniel S; Hagenah, Nicole; Hector, Andy; Hillebrand, Helmut; Hofmockel, Kirsten S; Humphries, Hope C; Jin, Virginia L; Kay, Adam; Kirkman, Kevin P; Klein, Julia A; Knops, Johannes MH; La Pierre, Kimberly J; Ladwig, Laura; Lambrinos, John G; Li, Qi; Li, Wei; Marushia, Robin; McCulley, Rebecca L; Melbourne, Brett A; Mitchell, Charles E; Moore, Joslin L; Morgan, John; Mortensen, Brent; O'Halloran, Lydia R; Pyke, David A; Risch, Anita C; Sankaran, Mahesh; Schuetz, Martin; Simonsen, Anna; Smith, Melinda D; Stevens, Carly J; Sullivan, Lauren; Wolkovich, Elizabeth; Wragg, Peter D; Wright, Justin; Yang, LouieExotic species dominate many communities; however the functional significance of species' biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.Item Open Access Rapid, accurate time estimation in zebrafish (Danio rerio).(Behav Processes, 2013-10) Cerutti, Daniel T; Jozefowiez, J; Staddon, John ERZebrafish were tested in an appetitive Pavlovian delayed conditioning task. After an intertrial interval of k*T s (k=11.25; T=8, 16 or 32 s), a small, translucent vertical pole was illuminated (CS) for T s. Food was presented at T/2 s. Pole-biting response latencies from CS onset were a linear function of the food delay T/2, with slope approximating unity (proportional timing), and standard deviation proportional to latency (scalar timing). Response latencies tracked changes in food delays even when they changed every other day. These findings are significant because the zebrafish genome has recently been sequenced, opening the door to studies in the genetics of interval timing.Item Open Access Rapid, accurate time estimation in zebrafish (Danio rerio).(Behav Processes, 2013-10) Cerutti, DT; Jozefowiez, J; Staddon, JERZebrafish were tested in an appetitive Pavlovian delayed conditioning task. After an intertrial interval of k*T s (k=11.25; T=8, 16 or 32 s), a small, translucent vertical pole was illuminated (CS) for T s. Food was presented at T/2 s. Pole-biting response latencies from CS onset were a linear function of the food delay T/2, with slope approximating unity (proportional timing), and standard deviation proportional to latency (scalar timing). Response latencies tracked changes in food delays even when they changed every other day. These findings are significant because the zebrafish genome has recently been sequenced, opening the door to studies in the genetics of interval timing.Item Open Access Rapid, accurate time estimation in zebrafish (Danio rerio).(Behav Processes, 2013-10) Cerutti, Daniel T; Jozefowiez, J; Staddon, John ERZebrafish were tested in an appetitive Pavlovian delayed conditioning task. After an intertrial interval of k*T s (k=11.25; T=8, 16 or 32 s), a small, translucent vertical pole was illuminated (CS) for T s. Food was presented at T/2 s. Pole-biting response latencies from CS onset were a linear function of the food delay T/2, with slope approximating unity (proportional timing), and standard deviation proportional to latency (scalar timing). Response latencies tracked changes in food delays even when they changed every other day. These findings are significant because the zebrafish genome has recently been sequenced, opening the door to studies in the genetics of interval timing.Item Open Access Serotonin synthesis, release and reuptake in terminals: a mathematical model.(Theor Biol Med Model, 2010-08-19) Best, Janet; Nijhout, H Frederik; Reed, MichaelBACKGROUND: Serotonin is a neurotransmitter that has been linked to a wide variety of behaviors including feeding and body-weight regulation, social hierarchies, aggression and suicidality, obsessive compulsive disorder, alcoholism, anxiety, and affective disorders. Full understanding of serotonergic systems in the central nervous system involves genomics, neurochemistry, electrophysiology, and behavior. Though associations have been found between functions at these different levels, in most cases the causal mechanisms are unknown. The scientific issues are daunting but important for human health because of the use of selective serotonin reuptake inhibitors and other pharmacological agents to treat disorders in the serotonergic signaling system. METHODS: We construct a mathematical model of serotonin synthesis, release, and reuptake in a single serotonergic neuron terminal. The model includes the effects of autoreceptors, the transport of tryptophan into the terminal, and the metabolism of serotonin, as well as the dependence of release on the firing rate. The model is based on real physiology determined experimentally and is compared to experimental data. RESULTS: We compare the variations in serotonin and dopamine synthesis due to meals and find that dopamine synthesis is insensitive to the availability of tyrosine but serotonin synthesis is sensitive to the availability of tryptophan. We conduct in silico experiments on the clearance of extracellular serotonin, normally and in the presence of fluoxetine, and compare to experimental data. We study the effects of various polymorphisms in the genes for the serotonin transporter and for tryptophan hydroxylase on synthesis, release, and reuptake. We find that, because of the homeostatic feedback mechanisms of the autoreceptors, the polymorphisms have smaller effects than one expects. We compute the expected steady concentrations of serotonin transporter knockout mice and compare to experimental data. Finally, we study how the properties of the the serotonin transporter and the autoreceptors give rise to the time courses of extracellular serotonin in various projection regions after a dose of fluoxetine. CONCLUSIONS: Serotonergic systems must respond robustly to important biological signals, while at the same time maintaining homeostasis in the face of normal biological fluctuations in inputs, expression levels, and firing rates. This is accomplished through the cooperative effect of many different homeostatic mechanisms including special properties of the serotonin transporters and the serotonin autoreceptors. Many difficult questions remain in order to fully understand how serotonin biochemistry affects serotonin electrophysiology and vice versa, and how both are changed in the presence of selective serotonin reuptake inhibitors. Mathematical models are useful tools for investigating some of these questions.