Optimizing Care for Military Women: The Value of the Dual-Certified Family and Women's Health Nurse Practitioner.

The number of women in the military has more than tripled over the past 50 years, increasing from 5% in the 1970s to 17% in 2023, making them essential for global health engagement and military operations. Provider competence and confidence are barriers to the consistent availability of preventive, gynecologic, and reproductive services for women across service locations and duty platforms. The Defense Health Board recommends standardizing services and improving the availability and scope of services for women at every point of care. In direct conflict with these recommendations, however, is a congressional call for a drawdown of medical forces, which creates a need for operationally trained clinicians with a broad skill set including comprehensive care for women. Advanced practice registered nurses, such as family and women's health nurse practitioners, are key assets to fill this gap on military medical health-care teams. At the request of the U.S. Air Force, the Graduate School of Nursing at the Uniformed Services University began offering a Women's Health Nurse Practitioner (WHNP) program in 2014. The WHNP curriculum was layered onto the existing Family Nurse Practitioner program so that Family Nurse Practitioner students receive enhanced education in women's health and WHNP students are prepared to meet the holistic, primary care needs of patients across the lifespan in addition to caring for women with obstetric and urogenital health concerns. This article highlights the value of dual-certified Family Nurse Practitioners and WHNPs in the military health-care system. These Uniformed Services University alumni are uniquely prepared to provide comprehensive primary and specialty care for female warfighters across the lifecycle from stable, well-resourced duty stations to austere, operational settings or deployment platforms.

Robotically quantifying finger and ankle proprioception: Role of range, speed, anticipatory errors, and learning.

Proprioception plays a key role in motor control and stroke recovery. Robotic devices are increasingly being used to improve proprioceptive assessments, but there is a lack of knowledge about how programmable factors such as testing range, speed, and prior exposure affect tests. From a physiological standpoint, such factors may regulate the sensitivity of limb proprioceptors, thereby influencing assessment results when not controlled for. To determine the relative influence of such factors, we studied the Crisscross proprioceptive assessment, a recently developed robotic assessment that requires participants to indicate when two joints pass by each other as they are moved passively by the robot. We implemented Crisscross with novel robots for the fingers and ankles and tested young unimpaired participants in single sessions (N = 16) and longitudinally (N = 5, across 15-30 sessions over 3-10 weeks). In single-session testing, we found that proprioceptive acuity was better for the fingers than the ankle (p < 0.01). For both limbs, acuity improved near the ends of the range of motion, which may be due to greater involvement of load and joint receptors. Acuity was poorer for slower movements due to greater anticipatory errors. These results show how the range and speed selected for a proprioceptive test affect proprioceptive acuity and highlight the heightened role of anticipatory errors at slow speeds. Improvements in proprioceptive acuity were not detectable in a single session, but acuity improved across multiple testing sessions (p < 0.01). This result shows that multiple prior exposure over at least several days can affect acuity.Clinical Relevance- Proprioceptive assessments should account for range and speed, which could be enabled by leveraging robotics technology. Proprioceptive acuity can be improved through repeated testing, an observation that is relevant to proprioceptive rehabilitation as well.

Temperature Sensitivity of Fitness Components across Life Cycles Drives Insect Responses to Climate Change.

AbstractThermal performance curves (TPCs) are increasingly used as a convenient approach to predict climate change impacts on ectotherms that accounts for organismal thermal sensitivity; however, directly applying TPCs to temperature data to estimate fitness has yielded contrasting predictions depending on assumptions regarding climate variability. We compare direct application of TPCs to an approach integrating TPCs for different fitness components (e.g., per capita birth rate, adult life span) across ectotherm life cycles into a population dynamic model, which we independently validated with census data and applied to hemipteran insect populations across latitude. The population model predicted that climate change will reduce insect fitness more at higher latitudes due to its effects on survival but will reduce net reproductive rate more at lower latitudes due to its effects on fecundity. Directly applying TPCs underestimated climate change impacts on fitness relative to incorporating the TPCs into the population model due to simplifying survival dynamics across the life cycle. The population model predicted that climate change will reduce mean insect density and increase population variability at higher latitudes via reduced survival, despite faster development and a longer activity period. Our study highlights the importance of considering how multiple fitness components respond to climate variability across the life cycle to better understand and anticipate the ecological consequence of climate change.

A Systematic Review of the Learning Dynamics of Proprioception Training: Specificity, Acquisition, Retention, and Transfer.

OBJECTIVE: We aimed to identify key aspects of the learning dynamics of proprioception training including: 1) specificity to the training type, 2) acquisition of proprioceptive skills, 3) retention of learning effects, and 4) transfer to different proprioceptive skills. METHODS: We performed a systematic literature search using the database (MEDLINE, EMBASE, Cochrane Library, and PEDro). The inclusion criteria required adult participants who underwent any training program that could enhance proprioceptive function, and at least 1 quantitative assessment of proprioception before and after the intervention. We analyzed within-group changes to quantify the effectiveness of an intervention. RESULTS: In total, 106 studies with 343 participant-outcome groups were included. Proprioception-specific training resulted in large effect sizes with a mean improvement of 23.4 to 42.6%, nonspecific training resulted in medium effect sizes with 12.3 to 22% improvement, and no training resulted in small effect sizes with 5.0 to 8.9% improvement. Single-session training exhibited significant proprioceptive improvement immediately (10 studies). For training interventions with a midway evaluation (4 studies), trained groups improved by approximately 70% of their final value at the midway point. Proprioceptive improvements were largely maintained at a delayed follow-up of at least 1 week (12 studies). Finally, improvements in 1 assessment were significantly correlated with improvements in another assessment (10 studies). CONCLUSIONS: Proprioceptive learning appears to exhibit several features similar to motor learning, including specificity to the training type, 2 time constant learning curves, good retention, and improvements that are correlated between different assessments, suggesting a possible, common mechanism for the transfer of training.

Exercise repetition rate measured with simple sensors at home can be used to estimate Upper Extremity Fugl-Meyer score after stroke.

Introduction: It would be valuable if home-based rehabilitation training technologies could automatically assess arm impairment after stroke. Here, we tested whether a simple measure-the repetition rate (or "rep rate") when performing specific exercises as measured with simple sensors-can be used to estimate Upper Extremity Fugl-Meyer (UEFM) score. Methods: 41 individuals with arm impairment after stroke performed 12 sensor-guided exercises under therapist supervision using a commercial sensor system comprised of two pucks that use force and motion sensing to measure the start and end of each exercise repetition. 14 of these participants then used the system at home for three weeks. Results: Using linear regression, UEFM score was well estimated using the rep rate of one forward-reaching exercise from the set of 12 exercises (r2 = 0.75); this exercise required participants to alternately tap pucks spaced about 20 cm apart (one proximal, one distal) on a table in front of them. UEFM score was even better predicted using an exponential model and forward-reaching rep rate (Leave One Out Cross Validation (LOOCV) r2 = 0.83). We also tested the ability of a nonlinear, multivariate model (a regression tree) to predict UEFM, but such a model did not improve prediction (LOOCV r2 = 0.72). However, the optimal decision tree also used the forward-reaching task along with a pinch grip task to subdivide more and less impaired patients in a way consistent with clinical intuition. At home, rep rate for the forward-reaching exercise well predicted UEFM score using an exponential model (LOOCV r2 = 0.69), but only after we re-estimated coefficients using the home data. Discussion: These results show how a simple measure-exercise rep rate measured with simple sensors-can be used to infer an arm impairment score and suggest that prediction models should be tuned separately for the clinic and home environments.

Competition for pollinators destabilizes plant coexistence.

Mounting concern over the global decline of pollinators has fuelled calls for investigating their role in maintaining plant diversity1,2. Theory predicts that competition for pollinators can stabilize interactions between plant species by providing opportunities for niche differentiation3, while at the same time can drive competitive imbalances that favour exclusion4. Here we empirically tested these contrasting effects by manipulating competition for pollinators in a way that predicts its long-term implications for plant coexistence. We subjected annual plant individuals situated across experimentally imposed gradients in neighbour density to either ambient insect pollination or a pollen supplementation treatment alleviating competition for pollinators. The vital rates of these individuals informed plant population dynamic models predicting the key theoretical metrics of species coexistence. Competition for pollinators generally destabilized the interactions between plant species, reducing the proportion of pairs expected to coexist. Interactions with pollinators also influenced the competitive imbalances between plant species, effects that are expected to strengthen with pollinator decline, potentially disrupting plant coexistence. Indeed, results from an experiment simulating pollinator decline showed that plant species experiencing greater reductions in floral visitation also suffered greater declines in population growth rate. Our results reveal that competition for pollinators may weaken plant coexistence by destabilizing interactions and contributing to competitive imbalances, information critical for interpreting the impacts of pollinator decline.

Coevolutionary transitions from antagonism to mutualism explained by the Co-Opted Antagonist Hypothesis.

There is now good evidence that many mutualisms evolved from antagonism; why or how, however, remains unclear. We advance the Co-Opted Antagonist (COA) Hypothesis as a general mechanism explaining evolutionary transitions from antagonism to mutualism. COA involves an eco-coevolutionary process whereby natural selection favors co-option of an antagonist to perform a beneficial function and the interacting species coevolve a suite of phenotypic traits that drive the interaction from antagonism to mutualism. To evaluate the COA hypothesis, we present a generalized eco-coevolutionary framework of evolutionary transitions from antagonism to mutualism and develop a data-based, fully ecologically-parameterized model of a small community in which a lepidopteran insect pollinates some of its larval host plant species. More generally, our theory helps to reconcile several major challenges concerning the mechanisms of mutualism evolution, such as how mutualisms evolve without extremely tight host fidelity (vertical transmission) and how ecological context influences evolutionary outcomes, and vice-versa.

Branched chain amino acids selectively promote cardiac growth at the end of the awake period.

Essentially all biological processes fluctuate over the course of the day, manifesting as time-of-day-dependent variations with regards to the way in which organ systems respond to normal behaviors. For example, basic, translational, and epidemiologic studies indicate that temporal partitioning of metabolic processes governs the fate of dietary nutrients, in a manner in which concentrating caloric intake towards the end of the day is detrimental to both cardiometabolic and cardiovascular parameters. Despite appreciation that branched chain amino acids impact risk for obesity, diabetes mellitus, and heart failure, it is currently unknown whether the time-of-day at which dietary BCAAs are consumed influence cardiometabolic/cardiovascular outcomes. Here, we report that feeding mice a BCAA-enriched meal at the end of the active period (i.e., last 4 h of the dark phase) rapidly increases cardiac protein synthesis and mass, as well as cardiomyocyte size; consumption of the same meal at the beginning of the active period (i.e., first 4 h of the dark phase) is without effect. This was associated with a greater BCAA-induced activation of mTOR signaling in the heart at the end of the active period; pharmacological inhibition of mTOR (through rapamycin) blocked BCAA-induced augmentation of cardiac mass and cardiomyocyte size. Moreover, genetic disruption of the cardiomyocyte circadian clock abolished time-of-day-dependent fluctuations in BCAA-responsiveness. Finally, we report that repetitive consumption of BCAA-enriched meals at the end of the active period accelerated adverse cardiac remodeling and contractile dysfunction in mice subjected to transverse aortic constriction. Thus, our data demonstrate that the timing of BCAA consumption has significant implications for cardiac health and disease.

How mutualisms influence the coexistence of competing species.

Mutualisms are ubiquitous in nature and are thought to play important roles in the maintenance of biodiversity. For biodiversity to be maintained, however, species must coexist in the face of competitive exclusion. Chesson's coexistence theory provides a mechanistic framework for evaluating coexistence, yet mutualisms are conspicuously absent from coexistence theory and there are no comparable frameworks for evaluating how mutualisms affect the coexistence of competiting species. To address this conceptual gap, I develop theory predicting how multitrophic mutualisms mediate the coexistence of species competing for mutualistic commodities and other limiting resources using the niche and fitness difference concepts of coexistence theory. I demonstrate that failing to account for mutualisms can lead to erroneous conclusions. For example, species might appear to coexist on resources alone, when the simultaneous incorporation of mutualisms actually drives competitive exclusion, or competitive exclusion might occur under resource competition, when in fact, the incorporation of mutualisms generates coexistence. Existing coexistence theory cannot therefore be applied to mutualisms without explicitly considering the underlying biology of the interactions. By discussing how the metrics derived from coexistence theory can be quantified empirically, I show how this theory can be operationalized to evaluate the coexistence consequences of mutualism in natural communities.

Targeted Deletion of CXCR2 in Myeloid Cells Alters the Tumor Immune Environment to Improve Antitumor Immunity.

Recruitment of myeloid-derived suppressor cells (MDSC) into the tumor microenvironment (TME) contributes to cancer immune evasion. MDSCs express the chemokine receptor CXCR2, and inhibiting CXCR2 suppresses the recruitment of MDSCs into the tumor and the premetastatic niche. Here, we compared the growth and metastasis of melanoma and breast cancer xenografts in mice exhibiting or not exhibiting targeted deletion of Cxcr2 in myeloid cells (CXCR2myeΔ/Δ vs. CXCR2myeWT). Detailed analysis of leukocyte populations in peripheral blood and in tumors from CXCR2myeΔ/Δ mice revealed that loss of CXCR2 signaling in myeloid cells resulted in reduced intratumoral MDSCs and increased intratumoral CXCL11. The increase in intratumoral CXCL11 was derived in part from tumor-infiltrating B1b cells. The reduction in intratumoral MDSCs coupled with an increase in intratumoral B1b cells expressing CXCL11 resulted in enhanced infiltration and activation of effector CD8+ T cells in the TME of CXCR2myeΔ/Δ mice, accompanied by inhibition of tumor growth in CXCR2myeΔ/Δ mice compared with CXCR2myeWT littermates. Treatment of tumor-bearing mice with a CXCR2 antagonist (SX-682) also inhibited tumor growth, reduced intratumoral MDSCs, and increased intratumoral B1b cells expressing CXCL11, leading to an increase in activated CD8+ T cells in the tumor. Depletion of B220+ cells or depletion of CD8+ T cells reversed the tumor-inhibitory properties in CXCR2myeΔ/Δ mice. These data revealed a mechanism by which loss of CXCR2 signaling in myeloid cells modulates antitumor immunity through decreasing MDSCs and enriching CXCL11-producing B1b cells in the TME, which in turn increases CD8+ T-cell recruitment and activation in tumors.

Interactions among interactions: The dynamical consequences of antagonism between mutualists.

Species often interact with multiple mutualistic partners that provide functionally different benefits and/or that interact with different life-history stages. These functionally different partners, however, may also interact directly with one another in other ways, indirectly altering net outcomes and persistence of the mutualistic system as a whole. We present a population dynamical model of a three-species system involving antagonism between species sharing a mutualist partner species with two explicit life stages. We find that, regardless of whether the antagonism is predatory or non-consumptive, persistence of the shared mutualist is possible only under a restrictive set of conditions. As the rate of antagonism between the species sharing the mutualist increases, indirect rather than direct interactions increasingly determine species' densities and sometimes result in complex, oscillatory dynamics for all species. Surprisingly, persistence of the mutualistic system is particularly dependent upon the degree to which each of the two mutualistic interactions is specialized. Our work investigates a novel mechanism by which changing ecological conditions can lead to extinction of mutualist partners and provides testable predictions regarding the interactive roles of mutualism and antagonism in net outcomes for species' densities.

Asynchronous range shifts drive alpine plant-pollinator interactions and reduce plant fitness.

Climate change is driving species' range shifts, which are in turn disrupting species interactions due to species-specific differences in their abilities to migrate in response to climate. We evaluated the consequences of asynchronous range shifts in an alpine plant-pollinator community by transplanting replicated alpine meadow turfs downslope along an elevational gradient thereby introducing them to warmer climates and novel plant and pollinator communities. We asked how these novel plant-pollinator interactions affect plant reproduction. We found that pollinator communities differed substantially across the elevation/temperature gradient, suggesting that these plants will likely interact with different pollinator communities with warming climate. Contrary to the expectation that floral visitation would increase monotonically with warmer temperatures at lower elevations, visitation rate to the transplanted communities peaked under intermediate warming at midelevation sites. In contrast, visitation rate generally increased with temperature for the local, lower elevation plant communities surrounding the experimental alpine turfs. For two of three focal plant species in the transplanted high-elevation community, reproduction declined at warmer sites. For these species, reproduction appears to be dependent on pollinator identity such that reduced reproduction may be attributable to decreased visitation from key pollinator species, such as bumble bees, at warmer sites. Reproduction in the third focal species appears to be primarily driven by overall pollinator visitation rate, regardless of pollinator identity. Taken together, the results suggest climate warming can indirectly affect plant reproduction via changes in plant-pollinator interactions. More broadly, the experiment provides a case study for predicting the outcome of novel species interactions formed under changing climates.

Multimodal Multiplexed Immunoimaging with Nanostars to Detect Multiple Immunomarkers and Monitor Response to Immunotherapies.

The overexpression of immunomarker programmed cell death protein 1 (PD-1) and engagement of PD-1 to its ligand, PD-L1, are involved in the functional impairment of cluster of differentiation 8+ (CD8+) T cells, contributing to cancer progression. However, heterogeneities in PD-L1 expression and variabilities in biopsy-based assays render current approaches inaccurate in predicting PD-L1 status. Therefore, PD-L1 screening alone is not predictive of patient response to treatment, which motivates us to simultaneously detect multiple immunomarkers engaged in immune modulation. Here, we have developed multimodal probes, immunoactive gold nanostars (IGNs), that accurately detect PD-L1+ tumor cells and CD8+ T cells simultaneously in vivo, surpassing the limitations of current immunoimaging techniques. IGNs integrate the whole-body imaging of positron emission tomography with high sensitivity and multiplexing of Raman spectroscopy, enabling the dynamic tracking of both immunomarkers. IGNs also monitor response to immunotherapies in mice treated with combinatorial PD-L1 and CD137 agonists and distinguish responders from those nonresponsive to treatment. Our results showed a multifunctional nanoscale probe with capabilities that cannot be achieved with either modality alone, allowing multiplexed immunologic tumor profiling critical for predicting early response to immunotherapies.

Muscle fiber hypertrophy in response to 6 weeks of high-volume resistance training in trained young men is largely attributed to sarcoplasmic hypertrophy.

Cellular adaptations that occur during skeletal muscle hypertrophy in response to high-volume resistance training are not well-characterized. Therefore, we sought to explore how actin, myosin, sarcoplasmic protein, mitochondrial, and glycogen concentrations were altered in individuals that exhibited mean skeletal muscle fiber cross-sectional area (fCSA) hypertrophy following 6 weeks of high-volume resistance training. Thirty previously resistance-trained, college-aged males (mean ± standard deviation: 21±2 years, 5±3 training years) had vastus lateralis (VL) muscle biopsies obtained prior to training (PRE), at week 3 (W3), and at week 6 (W6). Muscle tissue from 15 subjects exhibiting PRE to W6 VL mean fCSA increases ranging from 320-1600 µm2 was further interrogated using various biochemical and histological assays as well as proteomic analysis. Seven of these individuals donated a VL biopsy after refraining from training 8 days following the last training session (W7) to determine how deloading affected biomarkers. The 15 fCSA hypertrophic responders experienced a +23% increase in mean fCSA from PRE to W6 (p<0.001) and, while muscle glycogen concentrations remained unaltered, citrate synthase activity levels decreased by 24% (p<0.001) suggesting mitochondrial volume decreased. Interestingly, repeated measures ANOVAs indicated that p-values approached statistical significance for both myosin and actin (p = 0.052 and p = 0.055, respectively), and forced post hoc tests indicated concentrations for both proteins decreased ~30% from PRE to W6 (p<0.05 for each target). Phalloidin-actin staining similarly revealed actin concentrations per fiber decreased from PRE to W6. Proteomic analysis of the sarcoplasmic fraction from PRE to W6 indicated 40 proteins were up-regulated (p<0.05), KEGG analysis indicated that the glycolysis/gluconeogenesis pathway was upregulated (FDR sig. <0.001), and DAVID indicated that the following functionally-annotated pathways were upregulated (FDR value <0.05): a) glycolysis (8 proteins), b) acetylation (23 proteins), c) gluconeogenesis (5 proteins) and d) cytoplasm (20 proteins). At W7, sarcoplasmic protein concentrations remained higher than PRE (+66%, p<0.05), and both actin and myosin concentrations remained lower than PRE (~-50%, p<0.05). These data suggest that short-term high-volume resistance training may: a) reduce muscle fiber actin and myosin protein concentrations in spite of increasing fCSA, and b) promote sarcoplasmic expansion coincident with a coordinated up-regulation of sarcoplasmic proteins involved in glycolysis and other metabolic processes related to ATP generation. Interestingly, these effects seem to persist up to 8 days following training.

Winning and losing with microbes: how microbially mediated fitness differences influence plant diversity.

Interactions between plants and soil microbes can strongly influence plant diversity and community dynamics. Soil microbes may promote plant diversity by driving negative frequency-dependent plant population dynamics, or may favor species exclusion by providing one species an average fitness advantage over others. However, past empirical research has focused overwhelmingly on the consequences of frequency-dependent feedbacks for plant species coexistence and has generally neglected the consequences of microbially mediated average fitness differences. Here we use theory to develop metrics that quantify microbially mediated plant fitness differences, and show that accounting for these effects can profoundly change our understanding of how microbes influence plant diversity. We show that soil microbes can generate fitness differences that favour plant species exclusion when they disproportionately harm (or favour) one plant species over another, but these fitness differences may also favor coexistence if they trade off with competition for other resources or generate intransitive dominance hierarchies among plants. We also show how the metrics we present can quantify microbially mediated fitness differences in empirical studies, and explore how microbial control over coexistence varies along productivity gradients. In all, our analysis provides a more complete theoretical foundation for understanding how plant-microbe interactions influence plant diversity.

Coexistence and competitive exclusion in mutualism.

The competitive exclusion principle is fundamental to understanding coexistence. Well-established theories predict the conditions for coexistence in consumer-resource interactions. Given that species often compete for commodities offered by mutualists, competitive exclusion theory should also be critical to understanding how mutualisms function. We explicitly apply the competitive exclusion principle to mutualism and derive a rule analogous to Tilman's R* rule for exploitative competition. Coexistence is impossible when competitors compete solely for a shared partner-provided commodity because superior competitors deplete that commodity sufficiently to exclude inferior competitors. We then investigate how competition between two guild members for a partner-provided commodity and a resource external to the mutualism affects competitor coexistence. There are three key results. First, coexistence is possible via partitioning of a partner-provided commodity and another resource. Second, unlike in classic R* Theory, competitive outcomes are influenced both by species' abilities to obtain commodities and their mutualisms with the shared commodity-providing partner, which can indirectly alleviate competitors' commodity limitation. Third, the outcome of competition has important consequences for the commodity-providing partner, which depend on the type of mutualism and the competitive abilities of competing mutualists. This theory provides a novel framework for investigating how competitors for mutualistic commodities coexist in nature.

Altered eicosanoid production and phospholipid remodeling during cell culture.

The remodeling of PUFAs by the Lands cycle is responsible for the diversity of phospholipid molecular species found in cells. There have not been detailed studies of the alteration of phospholipid molecular species as a result of serum starvation or depletion of PUFAs that typically occurs during tissue culture. The time-dependent effect of cell culture on phospholipid molecular species in RAW 264.7 cells cultured for 24, 48, or 72 h was examined by lipidomic strategies. These cells were then stimulated to produce arachidonate metabolites derived from the cyclooxygenase pathway, thromboxane B2, PGE2, and PGD2, and the 5-lipoxygenase pathway, leukotriene (LT)B4, LTC4, and 5-HETE, which decreased with increasing time in culture. However, the 5-lipoxygenase metabolites of a 20:3 fatty acid, LTB3, all trans-LTB3, LTC3, and 5-hydroxyeicosatrienoic acid, time-dependently increased. Molecular species of arachidonate containing phospholipids were drastically remodeled during cell culture, with a new 20:3 acyl group being populated into phospholipids to replace increasingly scarce arachidonate. In addition, the amount of TNFα induced by lipopolysaccharide stimulation was significantly increased in the cells cultured for 72 h compared with 24 h, suggesting that the remodeling of PUFAs enhanced inflammatory response. These studies supported the rapid operation of the Lands cycle to maintain cell growth and viability by populating PUFA species; however, without sufficient n-6 fatty acids, 20:3 n-9 accumulated, resulting in altered lipid mediator biosynthesis and inflammatory response.

Determination of Double Bond Positions in Polyunsaturated Fatty Acids Using the Photochemical Paternò-Büchi Reaction with Acetone and Tandem Mass Spectrometry.

The positions of double bonds along the carbon chain of methylene interrupted polyunsaturated fatty acids are unique identifiers of specific fatty acids derived from biochemical reactions that occur in cells. It is possible to obtain direct structural information as to these double bond positions using tandem mass spectrometry after collisional activation of the carboxylate anions of an acetone adduct at each of the double bond positions formed by the photochemical Paternò-Büchi reaction with acetone. This reaction can be carried out by exposing a small portion of an inline fused silica capillary to UV photons from a mercury vapor lamp as the sample is infused into the electrospray ion source of a mass spectrometer. Collisional activation of [M - H]- yields a series of reverse Paternò-Büchi reaction product ions that essentially are derived from cleavage of the original carbon-carbon double bonds that yield an isopropenyl carboxylate anion corresponding to each double bond location. Aldehydic reverse Paternò-Büchi product ions are much less abundant as the carbon chain length and number of double bonds increase. The use of a mixture of D0/D6-acetone facilitates identification of these double bonds indicating product ions as shown for arachidonic acid. If oxygen is present in the solvent stream undergoing UV photoactivation, ozone cleavage ions are also observed without prior collisional activation. This reaction was used to determine the double bond positions in a 20:3 fatty acid that accumulated in phospholipids of RAW 264.7 cells cultured for 3 days.

Effects of temperature and resource variation on insect population dynamics: the bordered plant bug as a case study.

In species with complex life cycles, population dynamics result from a combination of intrinsic cycles arising from delays in the operation of negative density-dependent processes (e.g., intraspecific competition) and extrinsic fluctuations arising from seasonal variation in the abiotic environment. Abiotic variation can affect species directly through their life history traits and indirectly by modulating the species' interactions with resources or natural enemies.We investigate how the interplay between density-dependent dynamics and abiotic variability affects population dynamics of the bordered plant bug (Largus californicus), a Hemipteran herbivore inhabiting the California coastal sage scrub community. Field data show a striking pattern in abundance: adults are extremely abundant or nearly absent during certain periods of the year, leading us to predict that seasonal forcing plays a role in driving observed dynamics.We develop a stage-structured population model with variable developmental delays, in which fecundity is affected by both intra-specific competition and temporal variation in resource availability and all life history traits (reproduction, development, mortality) are temperature-dependent. We parameterize the model with experimental data on temperature-responses of life history and competitive traits and validate the model with independent field census data.We find that intra-specific competition is strongest at temperatures optimal for reproduction, which theory predicts leads to more complex population dynamics. Our model predicts that while temperature or resource variability interact with development-induced delays in self-limitation to generate population fluctuations, it is the interplay between all three factors that drive the observed dynamics. Considering how multiple abiotic factors interact with density-dependent processes is important both for understanding how species persist in variable environments and predicting species' responses to perturbations in their typical environment.