Tail Function Research Articles

Comparative sacral morphology and the reconstructed tail lengths of five extinct primates: Proconsul heseloni, Epipliopithecus vindobonensis, Archaeolemur edwardsi, Megaladapis grandidieri, and Palaeopropithecus kelyus

This study evaluated the relationship between the morphology of the sacrum—the sole bony link between the tail or coccyx and the rest of the body—and tail length (including presence/absence) and function using a comparative sample of extant mammals spanning six orders (Primates, Carnivora, Rodentia, Diprotodontia, Pilosa, Scandentia; N = 472). Phylogenetically-informed regression methods were used to assess how tail length varied with respect to 11 external and internal (i.e., trabecular) bony sacral variables with known or suspected biomechanical significance across all mammals, only primates, and only non-primates. Sacral variables were also evaluated for primates assigned to tail categories (‘tailless,’ ‘nonprehensile short-tailed,’ ‘nonprehensile long-tailed,’ and ‘prehensile-tailed’). Compared to primates with reduced tail lengths, primates with longer tails generally exhibited sacra having larger caudal neural openings than cranial neural openings, and last sacral vertebrae with more mediolaterally-expanded caudal articular surfaces than cranial articular surfaces, more laterally-expanded transverse processes, more dorsally-projecting spinous processes, and larger caudal articular surface areas. Observations were corroborated by the comparative sample, which showed that shorter-tailed (e.g., Lynx rufus [bobcat]) and longer-tailed (e.g., Acinonyx jubatus [cheetah]) non-primate mammals morphologically converge with shorter-tailed (e.g., Macaca nemestrina) and longer-tailed (e.g., Macaca fascicularis) primates, respectively. ‘Prehensile-tailed’ primates exhibited last sacral vertebrae with more laterally-expanded transverse processes and greater caudal articular surface areas than ‘nonprehensile long-tailed’ primates. Internal sacral variables performed poorly compared to external sacral variables in analyses of extant primates, and were thus deemed less useful for making inferences concerning tail length and function in extinct primates. The tails lengths of five extinct primates were reconstructed from the external sacral variables: Archaeolemur edwardsi had a ‘nonprehensile long tail,’ Megaladapis grandidieri, Palaeopropithecus kelyus, and Epipliopithecus vindobonensis probably had ‘nonprehensile short tails,’ and Proconsul heseloni was ‘tailless.’

Fast computation of large scale marginal extremes with multi-dimensional covariates

Safe and reliable design and operation of fixed and floating marine structures often located in remote and hostile environments is challenging. Rigorous extreme value analysis of meteorological and oceanographic data can greatly aid the design of such structures. Extreme value analysis is typically undertaken for single spatial locations or for small neighbourhoods; moreover, non-stationary effects of covariates on extreme values are typically accommodated in an ad-hoc manner. The objective of the work summarised here is to improve design practice by estimating environmental design conditions (such as return values for extreme waves, winds and currents) for a whole ocean basin, including additional covariate effects (such as storm direction) as necessary, in a consistent manner. Whole-basin non-stationary extreme value modelling is computationally complex, requiring inter-alia the estimation of tail functions, the parameters of which vary with respect to multi-dimensional covariates characterised by us using tensor products of penalised B-splines. We outline two technical contributions which make whole-basin non-stationary analysis feasible. Firstly, we adopt generalised linear array methods to reduce the computational burden of matrix manipulations. Secondly, using high-performance computing, we develop a parallel implementation of maximum likelihood estimation for the generalised Pareto distribution. Together, these innovations allow estimation of rigorous whole-basin extreme value models in reasonable time. We evaluate the new approach in application to marginal extreme value modelling of storm peak significant wave heights in two ocean basins, accommodating spatial and directional covariate effects.

Correlations of correlations: Secondary autocorrelations in finite harmonic systems.

The momentum or velocity autocorrelation function C(t) for a tagged oscillator in a finite harmonic system decays like that of an infinite system for short times, but exhibits erratic behavior at longer time scales. We introduce the autocorrelation function of the long-time noisy tail of C(t) ("a correlation of the correlation"), which characterizes the distribution of recurrence times. Remarkably, for harmonic systems with same-mass particles this secondary correlation may coincide with the primary correlation C(t) (when both functions are normalized) either exactly, or over a significant initial time interval. When the tagged particle is heavier than the rest, the equality does not hold, correlations show nonrandom long-time scale pattern, and higher-order correlations converge to the lowest normal mode.

Iterated random functions and slowly varying tails

Consider a sequence of i.i.d. random Lipschitz functions {Ψn}n≥0. Using this sequence we can define a Markov chain via the recursive formula Rn+1=Ψn+1(Rn). It is a well known fact that under some mild moment assumptions this Markov chain has a unique stationary distribution. We are interested in the tail behaviour of this distribution in the case when Ψ0(t)≈A0t+B0. We will show that under subexponential assumptions on the random variable log+(A0∨B0) the tail asymptotic in question can be described using the integrated tail function of log+(A0∨B0). In particular we will obtain new results for the random difference equation Rn+1=An+1Rn+Bn+1.

Pycket: a tracing JIT for a functional language

We present Pycket, a high-performance tracing JIT compiler for Racket. Pycket supports a wide variety of the sophisticated features in Racket such as contracts, continuations, classes, structures, dynamic binding, and more. On average, over a standard suite of benchmarks, Pycket outperforms existing compilers, both Racket's JIT and other highly-optimizing Scheme compilers. Further, Pycket provides much better performance for Racket proxies than existing systems, dramatically reducing the overhead of contracts and gradual typing. We validate this claim with performance evaluation on multiple existing benchmark suites. The Pycket implementation is of independent interest as an application of the RPython meta-tracing framework (originally created for PyPy), which automatically generates tracing JIT compilers from interpreters. Prior work on meta-tracing focuses on bytecode interpreters, whereas Pycket is a high-level interpreter based on the CEK abstract machine and operates directly on abstract syntax trees. Pycket supports proper tail calls and first-class continuations. In the setting of a functional language, where recursion and higher-order functions are more prevalent than explicit loops, the most significant performance challenge for a tracing JIT is identifying which control flows constitute a loop---we discuss two strategies for identifying loops and measure their impact.

Loss and Gain of Natural Killer Cell Receptor Function in an African Hunter-Gatherer Population.

Modulating natural killer cell functions in human immunity and reproduction are diverse interactions between the killer cell immunoglobulin-like receptors (KIR) of Natural Killer (NK) cells and HLA class I ligands on the surface of tissue cells. Dominant interactions are between KIR2DL1 and the C2 epitope of HLA-C and between KIR2DL2/3 and the C1 epitope of HLA-C. KhoeSan hunter-gatherers of Southern Africa represent the earliest population divergence known and are the most genetically diverse indigenous people, qualities reflected in their KIR and HLA genes. Of the ten KhoeSan KIR2DL1 alleles, KIR2DL1*022 and KIR2DL1*026 likely originated in the KhoeSan, and later were transmitted at low frequency to the neighboring Zulus through gene flow. These alleles arose by point mutation from other KhoeSan KIR2DL1 alleles that are more widespread globally. Mutation of KIR2DL1*001 gave rise to KIR2DL1*022, causing loss of C2 recognition and gain of C1 recognition. This makes KIR2DL1*022 a more avid and specific C1 receptor than any KIR2DL2/3 allotype. Mutation of KIR2DL1*012 gave rise to KIR2DL1*026, causing premature termination of translation at the end of the transmembrane domain. This makes KIR2DL1*026 a membrane-associated receptor that lacks both a cytoplasmic tail and signaling function. At higher frequencies than their parental allotypes, the combined effect of the KhoeSan-specific KIR2DL1*022 and KIR2DL1*026 is to reduce the frequency of strong inhibitory C2 receptors and increase the frequency of strong inhibitory C1 receptors. Because interaction of KIR2DL1 with C2 is associated with risk of pregnancy disorder, these functional changes are potentially advantageous. Whereas all other KhoeSan KIR2DL1 alleles are present on a wide diversity of centromeric KIR haplotypes, KIR2DL1*026 is present on a single KIR haplotype and KIR2DL1*022 is present on two very similar haplotypes. The high linkage disequilibrium across their haplotypes is consistent with a recent emergence for these KIR2DL1 alleles that have distinctive functions.

The PTEN Tumor Suppressor Forms Homodimers in Solution

As the phosphoinositol-3-kinase antagonist in the PI3K pathway, the PTEN tumor suppressor exerts phosphatase activity on diacylphosphatidylinositol triphosphate in the plasma membrane. Even partial loss of this activity enhances tumorigenesis, but a mechanistic basis for this aspect of PTEN physiology has not yet been established. It was recently proposed that PTEN mutations have dominant-negative effects in cancer via PTEN dimers. We show that PTEN forms homodimers in vitro, and determine a structural model of the complex from SAXS and Rosetta docking studies. Our findings shed new light on the cellular control mechanism of PTEN activity. Phosphorylation of the unstructured C-terminal tail of PTEN reduces PTEN activity, and this result was interpreted as a blockage of the PTEN membrane binding interface through this tail. The results presented here instead suggest that the C-terminal tail functions in stabilizing the homodimer, and that tail phosphorylation interferes with this stabilization.

Spinal Cord Injury in Rat – Therapeutic Effect of Pentadecapeptide BPC 157

BackgroundPreviously pentadecapeptide BPC 157 exhibited a strong healing effect on brain traumas and peripheral nerve injuries (Regul Pept. 2010;160(1‐3):26‐32; Regul Pept. 2010;160(1‐3):33‐41). Aim. To verify influence of BPC 157 on rat spinal cord injury. Materials and methods. Deeply anaesthetized Wistar Albino male rats, 350 g b.w., were subjected to surgery (all experimental procedures were approved by the local Ethics Committee): after laminectomy on level L2‐L3 (correspond to sacrocaudal spinal cord) 60 second compression with neurosurgical piston (60‐66 g) on exposed dural sac. One single medication (IP) (saline 5ml/kg; pentadekapeptide BPC 157 200µg/kg; 2 µg/kg) was 10 min post‐injury and sacrifice was at 1, 2, 4, 12, 26 and 52 weeks. Tail motor function (1 paralysis; 5 normal) and spasticity (1 normal; 5 maximum) was scored daily. Histology samples of spinal cord were taken from lesion site, and tail samples 10 mm distal from base. Results. Tail motor function. BPC 157 rats have significantly higher motor score in all investigated time. Tail spasticity. BPC 157 rats have significantly less spasticity starting from 4 weeks to the end of experiments. Histology of spinal cord. From 2 weeks to the end of follow up BPC 157 rats have less grey matter edema and less cyst and axonal necrosis in white matter. Histology of rat tail. All treatment groups show increased number of all and small axons starting from 4 weeks but without statistically difference between groups. Conclusions. Given after sacrocaudal spinal cord injury, BPC 157 recovered rat tail function with single treatment. Specifically, BPC 157 decreased secondary injury of spinal cord, and consequently, improved neurologic function recovery. Supported by Grant 108‐1083570‐3635, Croatia.

Alternative splicing modulates Kv channel clustering through a molecular ball and chain mechanism.

Ion channel clustering at the post-synaptic density serves a fundamental role in action potential generation and transmission. Here, we show that interaction between the Shaker Kv channel and the PSD-95 scaffold protein underlying channel clustering is modulated by the length of the intrinsically disordered C terminal channel tail. We further show that this tail functions as an entropic clock that times PSD-95 binding. We thus propose a 'ball and chain' mechanism to explain Kv channel binding to scaffold proteins, analogous to the mechanism describing channel fast inactivation. The physiological relevance of this mechanism is demonstrated in that alternative splicing of the Shaker channel gene to produce variants of distinct tail lengths resulted in differential channel cell surface expression levels and clustering metrics that correlate with differences in affinity of the variants for PSD-95. We suggest that modulating channel clustering by specific spatial-temporal spliced variant targeting serves a fundamental role in nervous system development and tuning.

A modeling tool for detector resolution and incomplete charge collection

The detector response function of X‐ray and gamma‐ray detectors is obtained from the convolution of the energy deposition spectrum with the detector resolution function. The energy deposition spectrum can be computed by using deterministic or Monte Carlo codes, while the energy resolution depends specifically on the detection mechanism, which is characteristic of the single detector. In a first approximation, the energy resolution can be modeled using a normalized Gaussian distribution having its full width at half maximum expressed in terms of specific semiempirical formulas for solid‐state detectors, scintillators, and gas proportional counters. However, this approach is not sufficient with some solid‐state detectors. It is frequent to find that the peaks show a deviation from the Gaussian shape: a long flat shelf structure from the peak centroid to the lower energies and an asymmetry that can be described with an exponential decay on the left side of the peak. These two effects have been introduced in the new tool RESOLUTION by adapting empirical models found in literature. RESOLUTION can be tailored to the specific detector by analyzing measured monochromatic peaks by means of the following strategies: (1) in a first approximation, a Gaussian shape is assumed in order to determine the full width at half maximum parameters, (2) if it is noted a flat background on the left side of the peak, then a shelf function is added, and (3) if a departure of the Gaussian is observed, then an exponential tail function is added. RESOLUTION gives a very precise description of the line shape. Copyright © 2015 John Wiley & Sons, Ltd.

The Atlastin C-terminal Tail Is an Amphipathic Helix That Perturbs the Bilayer Structure during Endoplasmic Reticulum Homotypic Fusion

Fusion of tubular membranes is required to form three-way junctions found in reticular subdomains of the endoplasmic reticulum. The large GTPase Atlastin has recently been shown to drive endoplasmic reticulum membrane fusion and three-way junction formation. The mechanism of Atlastin-mediated membrane fusion is distinct from SNARE-mediated membrane fusion, and many details remain unclear. In particular, the role of the amphipathic C-terminal tail of Atlastin is still unknown. We found that a peptide corresponding to the Atlastin C-terminal tail binds to membranes as a parallel α helix, induces bilayer thinning, and increases acyl chain disorder. The function of the C-terminal tail is conserved in human Atlastin. Mutations in the C-terminal tail decrease fusion activity in vitro, but not GTPase activity, and impair Atlastin function in vivo. In the context of unstable lipid bilayers, the requirement for the C-terminal tail is abrogated. These data suggest that the C-terminal tail of Atlastin locally destabilizes bilayers to facilitate membrane fusion.

Space-Efficient Manifest Contracts

The standard algorithm for higher-order contract checking can lead to unbounded space consumption and can destroy tail recursion, altering a program's asymptotic space complexity. While space efficiency for gradual types---contracts mediating untyped and typed code---is well studied, sound space efficiency for manifest contracts---contracts that check stronger properties than simple types, e.g., "is a natural'' instead of "is an integer''---remains an open problem. We show how to achieve sound space efficiency for manifest contracts with strong predicate contracts. The essential trick is breaking the contract checking down into coercions: structured, blame-annotated lists of checks. By carefully preventing duplicate coercions from appearing, we can restore space efficiency while keeping the same observable behavior.

Exposure to Fine Particles by Mine Tailing and Lung Function Effects in a Panel of Schoolchildren, Chañaral, Chile

There is much literature on the effects of fine particulate matter (PM2.5) on respiratory and cardiovascular health. However, few studies have evaluated the impact of PM2.5 on a population living in the vicinity of a massive deposit of mine tailings. A longitudinal panel study was performed to evaluate the association between exposure to PM2.5 and acute effects on lung function in schoolchildren from November 2012 to May 2013. Ambient levels of PM2.5 and its metal composition were measured. Lung function was evaluated using spirometric testing. Associations were quantified using GEE multilevel analysis controlling for confounders by using different lag time periods. The chemical characterization of PM2.5 had high levels of S > Na > Cl > Ca > Si > Fe > Al > Mg > K > Cu > Ti > and Zn, which would be associated with metals present in tailings. We found a negative association between the temporal variation of PM2.5 and changes in lung function specifically on forced vital capacity. Our results suggest that schoolchildren exposed to fine particulate matter from tailings deposited in the bay of Chanaral have their forced vital capacity decreased, which would affect their present and future lung development, increasing the risk of developing chronic respiratory diseases.

Monotone tail and moment ratio properties of Student’s family of distributions

Let Gp denote the tail function of Student’s distribution with p degrees of freedom. It is shown that the ratio Gq(x)/Gp(x) is decreasing in x > 0 for any p and q such that 0 0. Corollaries on the monotonicity of (generalized) moments and ratios thereof are also given.

Decoding the function of the N-terminal tail of the cellular prion protein to inspire novel therapeutic avenues for neurodegenerative diseases

The cellular prion protein (PrPC), a cell surface glycoprotein involved in prion disorders, has been shown to mediate the toxicity of several pathological aggregates, including its own misfolded state and some oligomeric assemblies of the amyloid β peptide, which are thought to be primarily responsible for the synaptic dysfunction characterizing Alzheimer's disease. Thus, elucidating the physiological function of PrPC, and how it could be corrupted by the interaction with misfolded proteins, may provide important insights to understand the pathological processes of prion and Alzheimer's diseases, and possibly other neurodegenerative disorders. In this manuscript, we review the data supporting a role for PrPC at the intersection of different neurodegenerative diseases, discuss potential mechanisms by which this protein could mediate neurotoxic signals, and examine therapeutic approaches that may arise from the identification of PrPC-directed compounds.

The fear of unseen predators: ground squirrel tail flagging in the absence of snakes signals vigilance

Rather than fleeing from predators, many animals exhibit conspicuous displays that are thought to deter attacks by advertising quality (physical capabilities), or awareness of the predator. However, prey commonly exhibit the same antipredator display when predators are absent. Signaling in this context could either dishonestly indicate predator detection, or honestly indicate vigilance, but no study has tested these hypotheses experimentally. We tested the vigilance advertisement function of tail flagging, a signal given by California ground squirrels (Otospermophilus beecheyi) to rattlesnakes (Crotalus oreganus), by simulating snake strikes and quantifying strike avoidance behaviors in signaling and non-signaling squirrels. We removed the effect of snake presence on signaling by simulating strikes 1) in the presence of a rattlesnake, 2) with no snake present, or 3) in an area where squirrels had recently encountered a snake that was no longer present. Squirrels tail flagged most when interacting with a snake. Squirrels also signaled in areas of recent snake encounters, and in this context, they responded faster to simulated strikes and were more likely to leap vertically or horizontally away from the attack. Tail flagging rate was also related to squirrels’ body displacement time and flee modality. Squirrels rarely signaled or exhibited evasive leaping with no snake present. These results indicate that displays in the absence of predators can honestly signal vigilance, or the readiness to avoid an attack, even if predators are undetected. Such antipredator displays may be widespread as many species could benefit from advertising alertness when uncertain of the location of predators.

Histone H3.3 Is Required to Maintain Replication Fork Progression after UV Damage

SummaryUnlike histone H3, which is present only in S phase, the variant histone H3.3 is expressed throughout the cell cycle [1] and is incorporated into chromatin independent of replication [2]. Recently, H3.3 has been implicated in the cellular response to ultraviolet (UV) light [3]. Here, we show that chicken DT40 cells completely lacking H3.3 are hypersensitive to UV light, a defect that epistasis analysis suggests may result from less-effective nucleotide excision repair. Unexpectedly, H3.3-deficient cells also exhibit a substantial defect in maintaining replication fork progression on UV-damaged DNA, which is independent of nucleotide excision repair, demonstrating a clear requirement for H3.3 during S phase. Both the UV hypersensitivity and replication fork slowing are reversed by expression of H3.3 and require the specific residues in the α2 helix that are responsible for H3.3 binding its dedicated chaperones. However, expression of an H3.3 mutant in which serine 31 is replaced with alanine, the equivalent residue in H3.2, restores normal fork progression but not UV resistance, suggesting that H3.3[S31A] may be incorporated at UV-damaged forks but is unable to help cells tolerate UV lesions. Similar behavior was observed with expression of H3.3 carrying mutations at K27 and G34, which have been reported in pediatric brain cancers. We speculate that incorporation of H3.3 during replication may mark sites of lesion bypass and, possibly through an as-yet-unidentified function of the N-terminal tail, facilitate subsequent processing of the damage.

Simulations of plasma obeying Coulomb's law and the formation of suprathermal ion tails in the solar wind

AbstractWe present a model for the velocity distribution function (VDF) of the suprathermal ion tail in the solar wind and its commonly observed spectrum, a power law in velocity of index −5. The mechanism for our model is acceleration from extremely small scale electric fields caused by the finite number of particles in the solar wind (or any plasma). The simulations produce a VDF with a broken power law at short times and a type of κ distribution VDF at later times. The simulation uses very few assumptions as it is based solely on Coulomb's law, and the results are robust to a range of parameters that, although outside the range of the solar wind at 1 AU, are close to those in the lower solar atmosphere. Furthermore, we provide predictions based on the following mechanism: the probability distribution function for the electric field (the electric field distribution function or EDF) dictates the final state of the plasma, which means that the VDF at any time is a convolution of the initial VDF and the EDF. We have also shown that by varying the power law index of the electrostatic force law, the relationship between the two is such that the EDF power law index is exactly 5 for Coulomb's law, harder for shorter‐range forces, and softer for longer‐range forces, converging to a power law of index 3 in the former limit and to a Maxwellian in the latter.

Cover Image

AbstractPrehensile tails are defined as having the ability to grasp objects and are commonly used as a fifth appendage during arboreal locomotion. Despite the independent evolution of tail prehensility in numerous mammalian genera, data relating muscle structure, physiology, and function of prehensile tails are largely incomplete. Didelphid marsupials make an excellent model to relate myosin heavy chain (MHC) isoform fiber type with structure/function of caudal muscles, as all opossums have a prehensile tail and tail use varies between arboreal and terrestrial forms. Expanding on our previous work in the Virginia opossum, this study tests the hypothesis that arboreal and terrestrial opossums differentially express faster versus slower MHC isoforms, respectively. MHC isoform expression and percent fiber type distribution were determined in the flexor caudae longus (FCL) muscle of Caluromys derbianus (arboreal) and Monodelphis domestica (terrestrial), using a combination of gel electrophoresis and immunohistochemistry analyses. C. derbianus expresses three MHC isoforms (1, 2A, 2X) that are distributed (mean percentage) as 8.2% MHC‐1, 2.6% 1/2A, and 89.2% 2A/X hybrid fibers. M. domestica also expresses MHC‐1, 2A, and 2X, in addition to the 2B isoform, distributed as 17.0% MHC‐1, 1.3% 1/2A, 9.0% 2A, 75.2% 2A/X, and 0.3% 2X/B hybrid fibers. The distribution of similar isoform fiber types differed significantly between species (P < 0.001). Although not statistically significant, C. derbianus was observed to have larger cross‐sectional area (CSA) for each corresponding fiber type along with a greater amount of extra‐cellular matrix. An overall faster fiber type composition (and larger fibers) in the tail of an arboreal specialist supports our hypothesis, and correlates with higher muscle force required for tail hanging and arboreal maneuvering on terminal substrates. Conversely, a broader distribution of highly oxidative fibers in the caudal musculature is well suited for tail nest building/remodeling behaviors of terrestrial opossums. Anat Rec, 297:1364–1376, 2014. © 2014 Wiley Periodicals, Inc.

Research of Propagation Behavior on Tibetan Network Public Sentiment

In the past some of the social and economic system of the study, often simplified to a single person's behavior can be described using the Poisson process stationary random process. However, since 2005, and reply by email, mail Propagations, human behavior, the actual statistics of time intervals, it was found there with the above assumptions these acts very different characteristics: a long period of silence and short-term high-frequency The outbreak, while present in these human behavior, the time interval distribution also satisfy the inverse power function of the fat tail, that is, during the occurrence of these acts can not be described by Poisson process. In order to study public sentiment of the Tibetan language network generation, transmission and disappearance of the law, it is necessary in the public sentiment research networks in the spread of the main roles. In this paper, the network user behavior patterns in Tibetan, Tibetan text of automatic segmentation, user behavior of the subject property and the main information dissemination and other aspects of behavior modeling are discussed.