Showing 481 - 490 of 733 Items
Multiple transcriptome mining coupled with tissue specific molecular cloning and mass spectrometry provide insights into agatoxin-like peptide conservation in decapod crustaceans
Date: 2020-12-01
Creator: Andrew E. Christie, Cindy D. Rivera, Catherine M. Call, Patsy S. Dickinson, Elizabeth A., Stemmler, J. Joe Hull
Access: Open access
- Over the past decade, in silico genome and transcriptome mining has led to the identification of many new crustacean peptide families, including the agatoxin-like peptides (ALPs), a group named for their structural similarity to agatoxin, a spider venom component. Here, analysis of publicly accessible transcriptomes was used to expand our understanding of crustacean ALPs. Specifically, transcriptome mining was used to investigate the phylogenetic/structural conservation, tissue localization, and putative functions of ALPs in decapod species. Transcripts encoding putative ALP precursors were identified from one or more members of the Penaeoidea (penaeid shrimp), Sergestoidea (sergestid shrimps), Caridea (caridean shrimp), Astacidea (clawed lobsters and freshwater crayfish), Achelata (spiny/slipper lobsters), and Brachyura (true crabs), suggesting a broad, and perhaps ubiquitous, conservation of ALPs in decapods. Comparison of the predicted mature structures of decapod ALPs revealed high levels of amino acid conservation, including eight identically conserved cysteine residues that presumably allow for the formation of four identically positioned disulfide bridges. All decapod ALPs are predicted to have amidated carboxyl-terminals. Two isoforms of ALP appear to be present in most decapod species, one 44 amino acids long and the other 42 amino acids in length, both likely generated by alternative splicing of a single gene. In carideans, a gene or terminal exon duplication appears to have occurred, with alternative splicing producing four ALPs, two 44 and two 42 amino acid isoforms. The identification of ALP precursor-encoding transcripts in nervous system-specific transcriptomes (e.g., Homarus americanus brain, eyestalk ganglia, and cardiac ganglion assemblies, finding confirmed using RT-PCR) suggests that members of this peptide family may serve as locally-released and/or hormonally-delivered neuromodulators in decapods. Their detection in testis- and hepatopancreas-specific transcriptomes suggests that members of the ALP family may also play roles in male reproduction and innate immunity/detoxification.
SIFamide peptides modulate cardiac activity differently in two species of Cancer crab
Date: 2019-10-01
Creator: Patsy S. Dickinson, Heidi M. Samuel, Elizabeth A. Stemmler, Andrew E. Christie
Access: Open access
- The SIFamides are a broadly conserved arthropod peptide family characterized by the C-terminal motif –SIFamide. In decapod crustaceans, two isoforms of SIFamide are known, GYRKPPFNGSIFamide (Gly1-SIFamide), which is nearly ubiquitously conserved in the order, and VYRKPPFNGSIFamide (Val1-SIFamide), known only from members of the astacidean genus Homarus. While much work has focused on the identification of SIFamide isoforms in decapods, there are few direct demonstrations of physiological function for members of the peptide family in this taxon. Here, we assessed the effects of Gly1- and Val1-SIFamide on the cardiac neuromuscular system of two closely related species of Cancer crab, Cancer borealis and Cancer irroratus. In each species, both peptides were cardioactive, with identical, dose-dependent effects elicited by both isoforms in a given species. Threshold concentrations for bioactivity are in the range typically associated with hormonal delivery, i.e., 10−9 to 10−8 M. Interestingly, and quite surprisingly, while the predicted effects of SIFamide on cardiac output are similar in both C. borealis and C. irroratus, frequency effects predominate in C. borealis, while amplitude effects predominate in C. irroratus. These findings suggest that, while SIFamide is likely to increase cardiac output in both crabs, the mechanism through which this is achieved is different in the two species. Immunohistochemical/mass spectrometric data suggest that SIFamide is delivered to the heart hormonally rather than locally, with the source of hormonal release being midgut epithelial endocrine cells in both Cancer species. If so, midgut-derived SIFamide may function as a regulator of cardiac output during the process of digestion.
Mass spectrometric identification of pEGFYSQRYamide: A crustacean peptide hormone possessing a vertebrate neuropeptide Y (NPY)-like carboxy-terminus
Date: 2007-05-15
Creator: Elizabeth A. Stemmler, Emily A. Bruns, Noah P. Gardner, Patsy S. Dickinson, Andrew E., Christie
Access: Open access
- In invertebrates, peptides possessing the carboxy (C)-terminal motif -RXRFamide have been proposed as the homologs of vertebrate neuropeptide Y (NPY). Using matrix assisted laser desorption/ionization mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation and chemical and enzymatic reactions, we have identified the peptide pEGFYSQRYamide from the neuroendocrine pericardial organ (PO) of the crab Pugettia producta. This peptide is likely the same as that previously reported, but misidentified, as PAFYSQRYamide in several earlier reports (e.g. [Li, L., Kelley, W.P., Billimoria, C.P., Christie, A.E., Pulver, S.R., Sweedler, J.V., Marder, E. 2003. Mass spectrometric investigation of the neuropeptide complement and release in the pericardial organs of the crab, Cancer borealis. J. Neurochem. 87, 642-656; Fu, Q., Kutz, K.K., Schmidt, J.J., Hsu, Y.W., Messinger, D.I., Cain, S.D., de la Iglesia, H.O., Christie, A.E., Li, L. 2005. Hormone complement of the Cancer productus sinus gland and pericardial organ: an anatomical and mass spectrometric investigation. J. Comp. Neurol. 493, 607-626.]). The -QRYamide motif contained in pEGFYSQRYamide is identical to that present in many vertebrate members of the NPY superfamily. Mass spectrometric analysis conducted on the POs of several other decapods showed that pEGFYSQRYamide is present in three other brachyurans (Cancer borealis, Cancer irroratus and Cancer productus) as well as in one species from another decapod infraorder (Lithodes maja, an anomuran). Thus, our findings show that at least some invertebrates possess NPY-like peptides in addition to those exhibiting an -RXRFamide C-terminus, and raise the question as to whether the invertebrate -QRYamides are functionally and/or evolutionarily related to the NPY superfamily. © 2007 Elsevier Inc. All rights reserved.
APPSSAT: Approximate probabilistic planning using stochastic satisfiability
Date: 2007-07-01
Creator: Stephen M. Majercik
Access: Open access
- We describe appssat, an anytime probabilistic contingent planner based on zander, a probabilistic contingent planner that operates by converting the planning problem to a stochastic satisfiability (Ssat) problem and solving that problem instead [S.M. Majercik, M.L. Littman, Contingent planning under uncertainty via stochastic satisfiability, Artificial Intelligence 147 (2003) 119-162]. The values of some of the variables in an Ssat instance are probabilistically determined; appssat considers the most likely instantiations of these variables (the most probable situations facing the agent) and attempts to construct an approximation of the optimal plan that succeeds under those circumstances, improving that plan as time permits. Given more time, less likely instantiations/situations are considered and the plan is revised as necessary. In some cases, a plan constructed to address a relatively low percentage of possible situations will succeed for situations not explicitly considered as well, and may return an optimal or near-optimal plan. We describe experimental results showing that appssat can find suboptimal plans in cases in which zander is unable to find the optimal (or any) plan. Although the test problems are small, the anytime quality of appssat means that it has the potential to efficiently derive suboptimal plans in larger, time-critical domains in which zander might not have sufficient time to calculate any plan. We also suggest further work needed to bring appssat closer to attacking real-world problems. © 2006 Elsevier Inc. All rights reserved.
The Rubble of Culture: Debris of an Extinct Thought
Date: 2023-01-01
Creator: David A. Collings
Access: Open access
- Humanity now faces the possibility that it will become extinct over the next few decades or so. This is not simply a reality about the biological fate of the species; it also raises the prospect of thought’s own extinction. But what does it mean for thought that it, too, might disappear? Thought’s possible disappearance shatters the assumption, at work across all the institutions and disciplines of the West, that one version or another of thought is enduring and will survive. As it turns out, no familiar practice rests on a secure ground; under the sign of the terminus - the prospect of humanity’s extinction - each one is shattered and undone. The cultural legacy becomes a field of rubble. In dozens of short essays, this book moves through this field. It takes up a host of specific inheritances and traces how each is shattered and transformed by an extinct thought. It engages with religion, philosophy, history, literature, ethics, studies of political power and resistance, and depictions of humanity’s place in the nonhuman world. It reconsiders the emergence of capitalism and of biopower, the science of climate change, the import of mediation and technology, and philosophies of temporality. Moreover, it contends with many innovative waves of thought over the past two centuries, from German idealism to deconstruction, from psychoanalysis to queer theory, from decolonizing theory to Afropessimism, and from the critique of ideology to speculative realism. It concludes by assessing what it is like for thought, having confronted its extinction, to live on in this debris, to dance with its own oblivion.
Correcting in situ chlorophyll fluorescence time-series observations for nonphotochemical quenching and tidal variability reveals nonconservative phytoplankton variability in coastal waters
Date: 2019-08-01
Creator: Luke Carberry, Collin Roesler, Susan Drapeau
Access: Open access
- Chlorophyll fluorometry is one of the most commonly implemented approaches for estimating phytoplankton biomass in situ, despite documented sources of natural variability and instrumental uncertainty in the relationship between in vivo fluorescence and chlorophyll concentration. A number of strategies are employed to minimize errors and quantify natural variability in this relationship in the open ocean. However, the assumptions underlying these approaches are unsupported in coastal waters due to the short temporal and small spatial scales of variability, as well as the optical complexity. The largest source of variability in the in situ chlorophyll fluorometric signal is nonphotochemical quenching (NPQ). Typically, unquenched nighttime observations are interpolated over the quenched daytime interval, but this assumes a spatial homogeneity not found in tidally impacted coastal waters. Here, we present a model that provides a tidally resolved correction for NPQ in moored chlorophyll fluorescence measurements. The output of the model is a time series of unquenched chlorophyll fluorescence in tidal endmembers (high and low tide extremes), and thus a time series of phytoplankton biomass growth and loss in these endmember populations. Comparison between modeled and measured unquenched time series yields quantification of nonconservative variations in phytoplankton biomass. Tidally modeled interpolation between these endmember time series yields a highly resolved time series of unquenched daytime chlorophyll fluorescence values at the location of the moored sensor. Such data sets provide a critical opportunity for validating the satellite remotely sensed ocean color chlorophyll concentration data product in coastal waters.
An architecture for emotional decision-making agents
Date: 2002-01-01
Creator: Eric Chown, Randolph M. Jones, Amy E. Henninger
Access: Open access
- Our research focuses on complex agents that are capable of interacting with their environments in ways that are increasingly similar to individual humans. In this article we describe a cognitive architecture for an interactive decision-making agent with emotions. The primary goal of this work is to make the decision-making process of complex agents more realistic with regard to the behavior moderators, including emotional factors that affect humans. Instead of uniform agents that rely entirely on a deterministic body of expertise to make their decisions, the decision making process of our agents will vary according to select emotional factors affecting the agent as well as the agent's parameterized emotional profile. The premise of this model is that emotions serve as a kind of automatic assessment system that can guide or otherwise influence the more deliberative decision making process. The primary components of this emotional system are pleasure/pain and clarity/confusion subsystems that differentiate between positive and negative states. These, in turn, feed into an arousal system that interfaces with the decision-making system. We are testing our model using synthetic special-forces agents in a reconnaissance simulation.
RoboGrams: A lightweight message passing architecture for RoboCup soccer
Date: 2015-01-01
Creator: Elizabeth Mamantov, William Silver, William Dawson, Eric Chown
Access: Open access
- RoboGrams is a lightweight and efficient message passing architecture that we designed for the RoboCup domain and that has been successfully used by the Northern Bites SPL team. This unique architecture provides a framework for separating code into strongly decoupled modules, which are combined into configurable dataflow graphs. We present several different architecture types and preexisting message passing implementations, but among all of these, we contend that Robo-Grams' features make it particularly well suited for use in RoboCup. As a success story, we describe the Northern Bites' use of RoboGrams and the benefits it has provided to a single team, but we also suggest that it could help SPL teams collaborate in the future.
Lankapura: The Legacy of the Ramayana in Sri Lanka
Date: 2019-01-01
Creator: Justin W. Henry, Sree Padma
Access: Open access
- The five articles which make up this special issue of South Asia explore the role of the Ramayana in Sri Lankan art, literature, religious ritual and political discourse in shaping Sinhala Buddhist and Tamil Saiva perceptions of the island’s distant past. Contributors work to answer the question as to when and how Sri Lanka came to be equated with the mythic ‘Lankapura’ of Valmiki’s epic, exploring both positive and negative portrayals of Ravana (ruler of Lanka antagonist of the Ramayana) in Sinhala and Tamil literature from the late medieval period to the present day. Authors work to account for the politicisation and historicisation of the Ramayana in twenty-first century Sri Lanka (including similarities to and differences from the contemporary Indian situation), along with the appropriation of Ravana as a Sinhala Buddhist cultural hero, and the incorporation of Vibhishana as a ‘guardian deity’ in the Sinhala Buddhist pantheon.
Local adaptation of a parasite to solar radiation impacts disease transmission potential, spore yield, and host fecundity*
Date: 2020-08-24
Creator: Mary Alta Rogalski, Meghan A. Duffy
Access: Open access