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Rxivist combines preprints from bioRxiv with data from Twitter to help you find the papers being discussed in your field. Currently indexing 93,264 bioRxiv papers from 398,038 authors.

Most downloaded bioRxiv papers, since beginning of last month

91,433 results found. For more information, click each entry to expand.

89861: A Bimolecular Multicelular complementation system for the detection of syncytium formation: A new methodology for the identification of entry inhibitors
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Posted to bioRxiv 17 Jan 2019

A Bimolecular Multicelular complementation system for the detection of syncytium formation: A new methodology for the identification of entry inhibitors
2 downloads microbiology

María Jesús García-Murria, Neus Expósito-Domínguez, Ismael Mingarro, Luis Martinez-Gil

Fusion of viral and cellular membranes is a key step during the viral life cycle. Enveloped viruses trigger this process by means of specialized viral proteins expressed on their surface, the so called viral fusion proteins. There are multiple assays to analyze the viral entry including those that focus on the cell-cell fusion induced by some viral proteins. These methods often rely on the identification of multinucleated cells (syncytium) as a result of cell membrane fusions. In this manuscript, we describe a novel methodology for the study of cell-cell fusion. Our approach, named Bimolecular Multicelular Complementation (BiMuC), provides an adjustable platform to investigate qualitatively and quantitatively the formation of a syncytium. Furthermore, we demonstrated that our procedure meets the requirements of a drug discovery approach and performed a proof of concept small molecule high-throughput screening to identify compounds that could block the entry of the emerging Nipah virus.

89862: Serial dependence is absent at the time of perception but increases in visual working memory
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Posted to bioRxiv 12 Sep 2017

Serial dependence is absent at the time of perception but increases in visual working memory
2 downloads animal behavior and cognition

Daniel P. Bliss, Jerome J. Sun, Mark D’Esposito

Recent experiments have shown that visual cognition blends current visual input with that from the recent past to guide ongoing decision making. This serial dependence is tuned to the similarity between consecutive stimuli and appears to exploit the temporal autocorrelation normally present in visual scenes to promote perceptual stability. While these benefits have been assumed, evidence that serial dependence directly alters stimulus perception has been limited. In the present study, we parametrically vary the delay between stimulus and response in a spatial delayed response task to explore the trajectory of serial dependence from the moment of perception into post-perceptual visual working memory. We find that behavioral responses made immediately after viewing a stimulus show evidence of adaptation, but not attractive serial dependence. Only as the memory period lengthens is a blending of past and present information apparent in behavior, reaching its maximum with a memory delay of six seconds. These results dovetail with other recent findings to bolster the interpretation that serial dependence is a phenomenon of mnemonic rather than perceptual processes. We also demonstrate that when leading mathematical models of visual working memory are adjusted to account for this trial-history effect, their fit to behavioral data is substantially improved.

89863: Odor source localization in complex visual environments by fruit flies
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Posted to bioRxiv 23 Aug 2017

Odor source localization in complex visual environments by fruit flies
2 downloads animal behavior and cognition

Nitesh Saxena, Dinesh Natesan, Sanjay P. Sane

Flying insects routinely forage in complex and cluttered sensory environments. Their search for a food or a pheromone source typically begins with a whiff of odor, which triggers a flight response, eventually bringing the insect in the vicinity of the odor source. The precise localization of an odor source, however, requires the use of both visual and olfactory modalities, aided by air currents that trap odor molecules into turbulent plumes, which the insects track. Here, we investigated odor tracking behavior in fruit flies (Drosophila melanogaster) presented with low- or high contrast visual landmarks, which were either paired with or separate from an attractive odor cue. These experiments were conducted either in a gentle air stream which generated odor plumes, or in still air in which odor dissipates uniformly in all directions. The trajectories of the flies revealed several novel features of their odor-tracking behavior in addition to those that have been previously documented (e.g. cast and-surge maneuvers). First, in both moving and still air, odor-seeking flies rely on the co-occurrence of visual landmarks with olfactory cues to guide them to putative odorant objects in the decisive phase before landing. Second, flies abruptly decelerate when they encounter an odor plume, and thereafter steer towards nearby visual objects that had no inherent salience in the absence of odor. This indicates that the interception of an attractive odor increases their salience to nearby high-contrast visual landmarks. Third, flies adopt distinct odor tracking strategies during flight in moving vs. still air. Whereas they weave in and out of plumes towards an odor source when airflow is present, their approach is more gradual and incremental in still air. Both strategies are robust and flexible, and can ensure that the flies reliably find the odor source under diverse visual and airflow environments. Our experiments also indicate the possibility of an olfactory 'working memory' that enables flies to continue their search even when the olfactory feedback is reduced or absent. Together, these results provide insights into how flies determine the precise location of an odor source.

89864: Tracking Borrelia afzelii from infected Ixodes ricinus nymphs to mice suggests a direct 'gut-to-mouth' route of Lyme disease transmission
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Posted to bioRxiv 08 May 2018

Tracking Borrelia afzelii from infected Ixodes ricinus nymphs to mice suggests a direct 'gut-to-mouth' route of Lyme disease transmission
2 downloads microbiology

Tereza Pospisilova, Veronika Urbanova, Ondrej Hes, Petr Kopacek, Ondrej Hajdusek, Radek Sima

Quantitative tracking of Borrelia afzelii has shown that its transmission cycle differs from the salivary route of B. burgdorferi transmission by Ixodes scapularis. Borrelia afzelii are abundant in the guts of unfed Ixodes ricinus nymphs and their numbers continuously decrease during feeding. In contrast, spirochetes are not present in the salivary glands. Borrelia afzelii transmission starts during the early stages of feeding, spirochetes could be detected in murine skin within 1 day of tick attachment. Tick saliva is not essential for B. afzelii infectivity, the main requirement for successful host colonization being a change in outer surface protein expression that occurs in the tick gut during feeding. Spirochetes in vertebrate mode are able to survive within the host even if the tick is not present. On the basis of our data we propose that a direct 'gut-to-mouth' route of infection appears to be the main route of B. afzelii transmission.

89865: DEET as a feeding deterrent
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Posted to bioRxiv 10 Aug 2017

DEET as a feeding deterrent
2 downloads animal behavior and cognition

WeiYu Lu, Justin Hwang, Fangfang Zeng, Walter S. Leal

The insect repellent N,N-diethyl-3-methylbenzamide (DEET), is a multimodal compound that acts as a spatial repellent as well as an irritant (contact repellent), thus being perceived by the insect's olfactory and gustatory systems as an odorant and a tastant, respectively. Soon after DEET was developed, almost 6 decades ago, it was reported that it reduced mosquito feeding on blood mixed with this repellent. It is now known that the mosquito proboscis senses contact repellents with the tips (labella) of the labium, which remain in direct contact with the outer layers of the skin, while the stylets, including the feeding deterrent sensor (labrum), penetrate the skin. We designed a behavioral assay that allowed us to tease apart contact repellency from feeding deterrence. First, we demonstrate here that when DEET was mixed with blood and covered by Parafilm layers, it did not leak to the outer surface. In our assays, the mean number of landings and duration of contacts with surfaces covering blood mixed with DEET or blood plus solvent (dimethyl sulfoxide) did not differ significantly. The feeding times, however, were significantly different. When blood was mixed either with 0.1 or 1% DEET, female southern house mosquitoes spent significantly less time feeding than the time spent feeding on blood mixed only with the solvent. By contrast, there were no significant differences in the mean times of feeding on blood containing 1% picaridin and blood plus solvent. Like DEET, the contact repellent and insecticide, permethrin, caused a significant reduction in feeding time. We, therefore, concluded, that in this context, DEET and permethrin act as feeding deterrents.

89866: Navigating infection risk during oviposition and larval foraging in a holometabolous insect
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Posted to bioRxiv 01 Aug 2017

Navigating infection risk during oviposition and larval foraging in a holometabolous insect
2 downloads animal behavior and cognition

Jonathon A Siva-Jothy, Katy M Monteith, Pedro F. Vale

Deciding where to eat and raise offspring carries important fitness consequences for all animals, especially if foraging, feeding and reproduction increase the risk of exposure to pathogens. In insects with complete metamorphosis, foraging occurs mainly during the larval stage, while oviposition decisions are taken by adult-stage females. Selection for infection avoidance behaviours may therefore be developmentally uncoupled. Using a combination of experimental infections and behavioural choice assays, here we tested if Drosophila melanogaster fruit flies avoid potentially infectious environments at distinct developmental stages. When given conspecific fly carcasses as a food source, larval-stage flies did not discriminate between carcasses that were clean or infected with the pathogenic Drosophila C Virus (DCV), even though scavenging was a viable route of DCV transmission. Adult females however, discriminated between different oviposition sites, laying more eggs near a clean rather than an infectious carcass if they were healthy; DCV-infected females did not discriminate between the two environments. While potentially risky, laying eggs near potentially infectious carcasses was always preferred to sites containing only fly medium. Our findings suggest that infection avoidance can play an important role in how mothers provision their offspring, and underline the need to consider infection avoidance behaviours at multiple life-stages.

89867: Consequences of measurement error in qPCR telomere data: A simulation study
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Posted to bioRxiv 10 Dec 2018

Consequences of measurement error in qPCR telomere data: A simulation study
2 downloads epidemiology

Daniel Nettle, Luise A. Seeker, Daniel H Nussey, Hannah Froy, Melissa Bateson

The qPCR method provides an inexpensive, rapid method for estimating relative average telomere length across a set of biological samples. Like all laboratory methods, it involves some degree of measurement error. The estimation of relative telomere length is done subjecting the actual measurements made (the Cq values for telomere and a control gene) to non-linear transformations and combining them into a ratio. Here, we use computer simulations, supported by mathematical analysis, to explore how errors in measurement affect qPCR estimates of relative telomere length, both in cross-sectional and longitudinal data. We show that errors introduced at the level of Cq values are magnified when the TS ratio is calculated. If the errors at the Cq level are normally distributed and independent of telomere length, those in the TS ratio are positively skewed and proportional to telomere length. The repeatability of the TS ratio declines abruptly with increasing error in measurement of the telomere sequence and/or the control gene. In simulated longitudinal data, measurement error alone can produce a pattern of low correlation between successive measures of telomere length, coupled with a strong dependency of the rate of change on initial telomere length. Our results illustrate the importance of control of measurement error: a small increase in error in Cq values can have large consequences for the power and interpretability of qPCR estimates of relative telomere length. They also illustrate the importance of characterising the measurement error that exists in each dataset (coefficients of variation are generally unhelpful, and researchers should report standard deviations of Cq values and/or repeatabilities of TS ratios) and allowing for the known effects of measurement error when interpreting patterns of TS ratio change over time.

89868: Improved detection of differentially represented DNA barcodes for high-throughput lineage phenomics
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Posted to bioRxiv 14 Aug 2019

Improved detection of differentially represented DNA barcodes for high-throughput lineage phenomics
2 downloads bioinformatics

Yevhen Akimov, Daria Bulanova, Sanna Timonen, Krister Wennerberg, Tero Aittokallio

Cellular DNA barcoding has become a popular approach to study heterogeneity of cell populations and to identify lineages with differential response to cellular stimuli. However, there is a lack of reliable methods for statistical inference of differentially responding lineages. Here, we used mixtures of DNA-barcoded cell pools to generate a realistic benchmark read count dataset for modelling a range of outcomes of lineage-tracing experiments. By accounting for the statistical properties intrinsic to the DNA barcode read count data, we implemented an improved algorithm that provides a significantly higher accuracy at detecting differentially responding lineages, compared to current RNA-seq data analysis algorithms. Building on the reliable statistical methodology, we illustrate how multidimensional phenotypic profiling (or high-throughput lineage phenomics) enables one to deconvolute phenotypically distinct cell subpopulations within a cancer cell line. The mixture control dataset and our analysis results provide a systematic foundation for benchmarking and improving algorithms for lineage-tracing experiments.

89869: Mkk4 and Mkk7 are important for retinal development and axonal injury-induced retinal ganglion cell death
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Posted to bioRxiv 09 Apr 2018

Mkk4 and Mkk7 are important for retinal development and axonal injury-induced retinal ganglion cell death
2 downloads neuroscience

Rebecca L Rausch, Stephanie B. Syc-Mazurek, Kimberly A. Fernandes, Michael P Wilson, Richard T. Libby

The mitogen activated protein kinase (MAPK) pathway has been shown to be involved in both neurodevelopment and neurodegeneration. c-Jun N-terminal kinase (JNK), a MAPK shown to be important in retinal development and after optic nerve crush injury, is regulated by two upstream kinases: MKK4 and MKK7. The specific requirements of MKK4 and MKK7 in retinal development and retinal ganglion cell (RGC) death after axonal injury, however, are currently undefined. Optic nerve injury is an important insult in many neurologic conditions including traumatic, ischemic, inflammatory, and glaucomatous optic neuropathies. Mice deficient in Mkk4, Mkk7, and both Mkk4 and Mkk7 were generated. Immunohistochemistry was used to study the distribution and structure of retinal cell types and to assess RGC survival after optic nerve injury (mechanical controlled optic nerve crush; CONC). Adult Mkk4 and Mkk7 deficient retinas had all retinal cell types. With the exception of small areas of lamination defects with photoreceptors in Mkk4 deficient mice, the retinas of both mutants were grossly normal. Deficiency of Mkk4 or Mkk7 reduced JNK signaling after axonal injury in RGCs. Mkk4 and Mkk7 deficient retinas had a significantly greater percentage of surviving RGCs 35 days after CONC as compared to wildtype controls (Mkk4: 51.5%, Mkk7: 29.1% WT: 15.2%; p<0.001). Combined deficiency of Mkk4 and Mkk7 caused failure of optic nerve formation, irregular retinal axonal trajectories, disruption of retinal lamination, clumping of RGC cell bodies, and dendritic fasciculation of dopaminergic amacrine cells. These results suggest that MKK4 and MKK7 may serve redundant and unique roles in molecular signaling important for retinal development and injury response following axonal insult.

89870: Risks to pollinators from different land-use transitions: bee species' responses to agricultural expansion show strong phylogenetic signal
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Posted to bioRxiv 18 Jan 2019

Risks to pollinators from different land-use transitions: bee species' responses to agricultural expansion show strong phylogenetic signal
2 downloads ecology

Adriana De Palma, Michael Kuhlmann, William D. Pearse, Emma Flynn, Stuart P.M. Roberts, Simon G. Potts, Andy Purvis

Bee species worldwide are facing a future of further land-use change and intensification. Populations of closely-related species with similar ecological characteristics are likely to respond similarly to such pressures. Such phylogenetic signal in species' responses could undermine the stability of pollination services in agricultural and natural systems. We use abundance data from a global compilation of bee assemblages in different land uses to assess the sensitivity of 573 bee species to agricultural expansion, intensification and urbanization; and combine the results with the Bee Tree of Life to assess phylogenetic signal. In addition, we assess whether variation in species' sensitivity to land-use change is better explained by phylogenetic or available functional trait differences. Bee species show strong phylogenetic signal in sensitivity to agricultural land expansion but only a weak signal in sensitivity to agricultural intensification and urbanisation. Sensitivities were usually best explained by a combination of functional and phylogenetic distances. This finding suggests that the commonly-recorded traits, despite being meaningful as functional response traits, do not capture all important determinants of bee species' vulnerability or resistance. However, it also suggests that model-based predictions of the sensitivity of poorly known species may be sufficient to help guide conservation efforts.

89871: Born to be asocial: newly-hatched tortoises spontaneously avoid unfamiliar individuals
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Posted to bioRxiv 20 Jun 2017

Born to be asocial: newly-hatched tortoises spontaneously avoid unfamiliar individuals
2 downloads animal behavior and cognition

Elisabetta Versace, Silvia Damini, Matteo Caffini, Gionata Stancher

Individual recognition is important for modulating social interactions but it is not clear to what extent this ability depends on experience gained through repeated interactions with different individuals. In wild tortoises, evidence of social interactions is limited to behaviours performed years after hatching, in the context of mating. To investigate the presence of abilities of individual recognition at the onset of life in tortoises, we used hatchlings of two species (Testudo marginata, Testudo graeca) reared with a single conspecific as unique social experience. When located in a novel environment together with the familiar conspecific, tortoises reached the average distance expected by random trajectories. On the contrary, tortoises tested with an unfamiliar conspecific first explored the mate, then actively kept a distance significantly larger than expected by chance. These results show spontaneous abilities of individual recognition in a non-social species at the onset of life, and active avoidance of unfamiliar conspecifics. We suggest that this predisposed behaviour might be adaptive for young tortoises' dispersal.

89872: The reconstitution of body mass index in HIV positive subjects under antiretroviral treatment in Kinshasa
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Posted to bioRxiv 18 Jan 2019

The reconstitution of body mass index in HIV positive subjects under antiretroviral treatment in Kinshasa
2 downloads microbiology

Guyguy Kabundi Tshima, Paul Madishala Mulumba

Objective: We aimed to evaluate BMI changes in HIV adults subjects in the first year of ART in malaria-endemic areas. Methods: We used linear regression analysis showing that the change in weight at 12 months (y) in a malaria-endemic area is related to malaria infection at admission and its different episodes as illustrated by equation: y = a + bxi + c; where x is malaria on admission, i refers to episodes of clinical malaria infection during the year, b is the slope, a is a constant and c are confounding factors such as tuberculosis or poor eating habits. Results: We found a positive value for b (b = 0.697), and this shows that weight loss at 12 months is correlated with the diagnosis of severe malaria at admission. In other words, severe malaria eliminates the weight gained under ART. Conclusions: 1. Malaria is the leading cause of weight loss under ART; 2. An important recommendation for future: This study suggests nutritional education based on local foods containing antioxidants to fight the oxidative stress generated by HIV and stimulated by Plasmodium falciparum during febrile episodes. Oxidative stress is blocked by NADPHase which is a metalloenzyme based on selenium. Thus, to prevent a weight loss or the occurrence of the protein-energy malnutrition among people living with HIV, it is necessary to use the nutritional education.

89873: Fast and efficient QTL mapper for thousands of molecular phenotypes
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Posted to bioRxiv 07 Aug 2015

Fast and efficient QTL mapper for thousands of molecular phenotypes
2 downloads bioinformatics

Halit Ongen, Alfonso Buil, Andrew Anand Brown, Emmanouil T. Dermitzakis, Olivier Delaneau

Motivation: In order to discover quantitative trait loci (QTLs), multi-dimensional genomic data sets combining DNA-seq and ChiP-/RNA-seq require methods that rapidly correlate tens of thousands of molecular phenotypes with millions of genetic variants while appropriately controlling for multiple testing. Results: We have developed FastQTL, a method that implements a popular cis-QTL mapping strategy in a user- and cluster-friendly tool. FastQTL also proposes an efficient permutation procedure to control for multiple testing. The outcome of permutations is modeled using beta distributions trained from a few permutations and from which adjusted p-values can be estimated at any level of significance with little computational cost. The Geuvadis & GTEx pilot data sets can be now easily analyzed an order of magnitude faster than previous approaches. Availability: Source code, binaries and comprehensive documentation of FastQTL are freely available to download at http://fastqtl.sourceforge.net/

89874: Population-scale organization of cerebellar granule neuron signaling during a visuomotor behavior
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Posted to bioRxiv 10 Oct 2017

Population-scale organization of cerebellar granule neuron signaling during a visuomotor behavior
2 downloads neuroscience

Sherika J.G. Sylvester, Melanie M. Lee, Alexandro Ramirez, Sukbin Lim, Mark S Goldman, Emre R.F. Aksay

Granule cells at the input layer of the cerebellum comprise over half the neurons in the human brain and are thought to be critical for learning. However, little is known about granule neuron signaling at the population scale during behavior. We used calcium imaging in awake zebrafish during optokinetic behavior to record transgenically identified granule neurons throughout a cerebellar population. A significant fraction of the population was responsive at any given time. In contrast to core precerebellar populations, granule neuron responses were relatively heterogeneous, with variation in the degree of rectification and the balance of excitation versus inhibition. Functional correlations were strongest for nearby cells, with weak spatial gradients in the degree of rectification and excitation. These data open a new window upon cerebellar function and suggest granule layer signals represent elementary building blocks underrepresented in core sensorimotor pathways, thereby enabling the construction of novel patterns of activity for learning.

89875: Speed tuning in the macaque posterior parietal cortex
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Posted to bioRxiv 18 Oct 2017

Speed tuning in the macaque posterior parietal cortex
2 downloads neuroscience

Eric Avila, Kaushik J Lakshminarasimhan, Gregory C. DeAngelis, Dora E. Angelaki

Neurons in the macaque posterior parietal cortex are known to encode the direction of self-motion. But do they also encode one's speed? To test this, we performed neural recordings from area 7a while monkeys were passively translated or rotated at various speeds. Visual stimuli were delivered as optic flow fields and vestibular stimuli were generated by a motion platform. Under both conditions, the responses of a fraction of neurons scaled linearly with self-motion speed, and speed-selective neurons were not localized to specific layers or columns. We analyzed ensembles of simultaneously recorded neurons and found that the precision of speed representation was sufficient to support path integration over modest distances. Our findings describe a multisensory neural code for linear and angular self-motion speed in the posterior parietal cortex of the macaque brain, and suggest a potential role for this representation.

89876: Stochastic model of BKPy Virus replication and assembly
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Posted to bioRxiv 24 Aug 2019

Stochastic model of BKPy Virus replication and assembly
2 downloads bioinformatics

Suzy M Stiegelmeyer, Liesl K Jeffers-Francis, Morgan C Giddings, Jennifer Webster-Cyriaque

BK Polyomavirus (BKPyV), belongs to the same family as SV40 and JC Virus and has recently been associated with both Sjogrens Syndrome and HIV associated Salivary Gland Disease. BKPyV was previously only known for causing the rejection of kidney transplants. As such, BKPyV infection of salivary gland cells implicates oral transmission of the virus. BKPyV replicates slowly in salivary gland cells, producing infectious virus after 72-96 hours. However, it remains unclear how this virus infects or replicates within salivary gland cells, blocking the development of therapeutic strategies to inhibit the virus. Thus, an intracellular, computational model using agent-based modeling was developed to model BKPyV replication within a salivary gland cell. In addition to viral proteins, we modeled host cell machinery that aids transcription, translation and replication of BKPyV. The model has separate cytosolic and nuclear compartments, and represents all large molecules such as proteins, RNAs, and DNA as individual computer "agents" that move and interact within the simulated salivary gland cell environment. An application of the Boids algorithm was implemented to simulate molecular binding and formation of BKPyV virions and BKPyV virus-like particles (VLPs). This approach enables the direct study of spatially complex processes such as BKPyV virus self-assembly, transcription, and translation. This model reinforces experimental results implicating the processes that result in the slow accumulation of viral proteins. It revealed that the slow BKPyV replication rate in salivary gland cells might be explained by capsid subunit accumulation rates. BKPyV particles may only form after large concentrations of capsid subunits have accumulated. In addition, salivary gland specific transcription factors may enable early region transcription of BKPyV.

89877: Control of Systemic Iron Homeostasis by the 3' Iron-Responsive Element of Divalent Metal Transporter 1 in Mice.
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Posted to bioRxiv 20 Feb 2020

Control of Systemic Iron Homeostasis by the 3' Iron-Responsive Element of Divalent Metal Transporter 1 in Mice.
2 downloads molecular biology

Elisabeth Tybl, Hiromi Gunshin, Sanjay Gupta, Tomasa Barrientos, Michael Bonadonna, Ferran Celma Nos, Gael Palais, Zoubida Karim, Mayka Sanchez, Nancy C Andrews, Bruno Galy

Divalent metal transporter 1 (DMT1) is essential for dietary iron assimilation and erythroid iron acquisition. The 3' untranslated region of the murine DMT1 mRNA contains an iron responsive element (IRE) that is conserved in humans but whose functional role remains unclear. We generated and analyzed mice with targeted disruption of the DMT1 3'IRE. These animals display hypoferremia during the suckling period, associated with a reduction of DMT1 mRNA and protein in the intestine. In contrast, adult mice exhibit hyperferremia, accompanied by enlargement of hepatic and splenic iron stores. Intriguingly, disruption of the DMT1 3'IRE in adult animals augments intestinal DMT1 expression, in part due to increased mRNA translation. Hence, during postnatal growth, the DMT1 3'IRE promotes intestinal DMT1 expression and secures iron sufficiency; in adulthood, it suppresses DMT1 and prevents systemic iron loading. This work demonstrates that the 3'IRE of DMT1 plays a role in the control of DMT1 expression and systemic iron homeostasis, and reveals an age-dependent switch in its activity.

89878: Optimal Response Vigor and Choice Under Non-stationary Outcome Values
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Posted to bioRxiv 07 Feb 2017

Optimal Response Vigor and Choice Under Non-stationary Outcome Values
2 downloads animal behavior and cognition

Amir Dezfouli, Bernard W. Balleine, Richard Nock

Within a rational framework a decision-maker selects actions based on the reward-maximisation principle which stipulates they acquire outcomes with the highest values at the lowest cost. Action selection can be divided into two dimensions: selecting an action from several alternatives, and choosing its vigor, i.e., how fast the selected action should be executed. Both of these dimensions depend on the values of the outcomes, and these values are often affected as more outcomes are consumed, and so are the actions. Despite this, previous works have addressed the computational substrates of optimal actions only in the specific condition that the values of outcomes are constant, and it is still unknown what the optimal actions are when the values of outcomes are non-stationary. Here, based on an optimal control framework, we derive a computational model for optimal actions under non-stationary outcome values. The results imply that even when the values of outcomes are changing, the optimal response rate is constant rather than decreasing. This finding shows that, in contrast to previous theories, the commonly observed changes in the actions cannot be purely attributed to the changes in the outcome values. We then prove that this observation can be explained based on the uncertainty about temporal horizons; e.g., in the case of experimental protocols, the session duration. We further show that when multiple outcomes are available, the model explains probability matching as well as maximisation choice strategies. The model provides, therefore, a quantitative analysis of optimal actions and explicit predictions for future testing.

89879: B-1 cell-mediated modulation of M1-macrophage profile can ameliorate microbicidal functions and disrupt the evasion mechanisms of Encephalitozoon cuniculi
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Posted to bioRxiv 04 Mar 2019

B-1 cell-mediated modulation of M1-macrophage profile can ameliorate microbicidal functions and disrupt the evasion mechanisms of Encephalitozoon cuniculi
2 downloads microbiology

Adriano Pereira, Anuska Marcelino Alvares-Saraiva, Fabiana Toshie de Camargo Konno, Diva Denelle Spadacci-Morena, Elizabeth Cristina Perez, Mario Mariano, Maria Anete Lallo

Here, we have investigated the possible effect of B-1 cells on the activity of peritoneal macrophages in E. cuniculi infection. In the presence of B-1 cells, peritoneal macrophages had an M1 profile with showed increased phagocytic capacity and index, associated with the intense microbicidal activity, increased proinflammatory cytokines production and a higher percentage of apoptotic death. The absence of B-1 cells was associated with a predominance of the M2 macrophages, indicating reduced phagocytic capacity and index, microbicidal activity, proinflammatory cytokine production, and apoptotic death, but equal death rate. In addition, in the M2 macrophages, spores of phagocytic E. cuniculi with polar tubular extrusion were observed, which is an important mechanism of evasion of the immune response. The results showed the importance of B-1 cells in the modulation of macrophage function against E. cuniculi infection, increasing microbicidal activity, and reducing the fungal mechanisms involved in the evasion of the immune response.

89880: Reduced foraging investment as an adaptation to patchy food sources: a phasic army ant simulation
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Posted to bioRxiv 20 Jan 2017

Reduced foraging investment as an adaptation to patchy food sources: a phasic army ant simulation
2 downloads animal behavior and cognition

Serafino Teseo, Francesco Delloro

Colonies of several ant species within the subfamily Dorylinae alternate stereotypical discrete phases of foraging and reproduction. Such phasic cycles are thought to be adaptive because they minimize the amount of foraging and the related costs, and at the same time enhance the colony-level ability to rely on patchily distributed food sources. In order to investigate these hypotheses, we use here a simple computational approach to study the population dynamics of two species of virtual ant colonies that differ quantitatively in their foraging investment. One species, which we refer to as 'phasic', forages only half of the time, mirroring the phasic activity of some army ants; the other 'non-phasic' species forages instead all the time. We show that, when foraging costs are relatively high, populations of phasic colonies grow on average faster than non-phasic populations, outcompeting them in mixed populations. Interestingly, such tendency becomes more consistent as food becomes more difficult to find but locally abundant. According to our results, reducing the foraging investment, for example by adopting a phasic lifestyle, can result in a reproductive advantage, but only in specific conditions. We thus suggest phasic colony cycles to have emerged together with the doryline specialization in feeding on the brood of other eusocial insects, a resource that is hard to obtain but highly abundant if available.

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