Tail Function Research Articles

Flexibility of Heterocercal Tails: What Can the Functional Morphology of Shark Tails Tell Us about Ichthyosaur Swimming?

SynopsisThe similarities between ichthyosaurs and sharks are a text-book example of convergence, and similarities in tail morphology have led many to theorize that they had similar swimming styles. The variation of ichthyosaur tail shapes is encompassed within the diversity of shark families. In particular early ichthyosaurs have asymmetrical tails like the heterocercal tails of carcharhinid sharks, while later occurring ichthyosaurs have lunate tails similar to those of lamnid sharks. Because it is not possible to measure ichthyosaur tail function, the goal of this study is to measure and compare the flexibility and stiffness of lunate and heterocercal shark tails, and to measure skeletal and connective tissue features that may affect tail flexibility. We measured flexibility in 10 species and focused on five species in particular, for dissection: one pelagic and one bottom-associated individual from each order, plus the common thresher shark (Alopias vulpinus), a tail-slapping specialist. As expected, lunate tails were overall less flexible than heterocercal tails and had greater flexural stiffness. Our results suggest that the cross-sectional profile of the skeletally supported dorsal lobe dictates flexural stiffness, but that changing tissue composition dictates flexural stiffness in the ventral lobe. We also found structural differences that may enable the tail slapping behavior of the common thresher shark. Finally, we discuss how our morphological measurements compare to ichthyosaur measurements from the literature; noting that similarities in functional morphology suggest sharks may be a good analog for understanding ichthyosaur swimming biomechanics.

Small time convergence of subordinators with regularly or slowly varying canonical measure

We consider subordinators Xα=(Xα(t))t≥0 in the domain of attraction at 0 of a stable subordinator (Sα(t))t≥0 (where α∈(0,1)); thus, with the property that Π¯α, the tail function of the canonical measure of Xα, is regularly varying of index −α∈(−1,0) as x↓0. We also analyse the boundary case, α=0, when Π¯α is slowly varying at 0. When α∈(0,1), we show that (tΠ¯α(Xα(t)))−1 converges in distribution, as t↓0, to the random variable (Sα(1))α. This latter random variable, as a function of α, converges in distribution as α↓0 to the inverse of an exponential random variable. We prove these convergences, also generalised to functional versions (convergence in D[0,1]), and to trimmed versions, whereby a fixed number of its largest jumps up to a specified time are subtracted from the process. The α=0 case produces convergence to an extremal process constructed from ordered jumps of a Cauchy subordinator. Our results generalise random walk and stable process results of Darling, Cressie, Kasahara, Kotani and Watanabe.

Meeting Review: 2018 International Workshop on Structure and Function of the Lentiviral gp41 Cytoplasmic Tail.

Recent developments in defining the role of the lentiviral envelope glycoprotein (Env) cytoplasmic tail (CT) in Env trafficking and incorporation into virus particles have advanced our understanding of viral replication and transmission. To stimulate additional progress in this field, the two-day International Workshop on Structure and Function of the Lentiviral gp41 Cytoplasmic Tail, co-organized by Eric Freed and James Hoxie, was held at the National Cancer Institute in Frederick, MD (26–27 April 2018). The meeting served to bring together experts focused on the role of gp41 in HIV replication and to discuss the emerging mechanisms of CT-dependent trafficking, Env conformation and structure, host protein interaction, incorporation, and viral transmission. The conference was organized around the following three main hot topics in gp41 research: the role of host factors in CT-dependent Env incorporation, Env structure, and CT-mediated trafficking and transmission. This review highlights important topics and the advances in gp41 research that were discussed during the conference.

Nonionic Glycolipids for Chromium Flotation- and Emulsion (W/O and O/W)-Based Bioactive Release.

Biosourced surfactants are endeavored as a green alternative to biosurfactants and petrochemical surfactants having industrial utilization. Nine glycolipids with headgroup and chain length variation were derived from renewable resources like vegetable oils, carbohydrates, and amino acids. The concentration-dependent interfacial activity, foamability, wetting power, emulsification power, and solubilization capacities of glycolipids were investigated to provide a structure-activity relationship. Later, the metal flotation and emulsification experiments were performed. In general, for metal flotation, the surfactant should contain a hydrophobic tail, hydrophilic head, and chelating function. In the present investigation, it was observed that the headgroup of a glycolipid can serve as a hydrophilic head as well as perform a chelating function. Moreover, heat energy generated from the sunlight was utilized for metal flotation. Additionally, these glycolipids are capable to form stable sunflower oil-water (W/O and O/W) emulsions. The mechanical and thermal stabilities and hydrophobic chain length dependency of the prepared emulsions at different water volume fractions are explored. Furthermore, encapsulation and release of water-soluble (riboflavin and l-ascorbic acid) and oil-soluble (curcumin and α-tocopherol) bioactives in glycolipid emulsions were monitored. Thus, glycolipids under investigation had shown the possibility for pretreatment of chromium-containing wastewaters and bioactive-loaded emulsions toward the controlled release.

Robust Estimation Using Modified Huber’s Functions With New Tails

ABSTRACTIt is traditionally believed that robustness is obtained by sacrificing efficiency. Estimators with high breakdown point and high efficiency are therefore highly desirable. We investigate a new estimation procedure based on Huber’s robust approach, but with tail functions replaced by the exponential squared loss. The tuning parameters are data-dependent to achieve high efficiency even in nonnormal cases. In the regression framework, we show that our hybrid estimator is of high efficiency, reaching the highest asymptotic breakdown point of 50%. We have also established the -consistency and asymptotic normality of our estimator under regularity conditions. Extensive numerical studies are carried out to compare the performances of our method and other existing methods in terms of the standard errors and relative efficiency, and the results reveal that the newly proposed method has smaller standard errors and higher relative efficiency than its competitors when the sample size is sufficiently large. Finally, we present three real examples for demonstration. Supplementary materials for the article are available online.

A new version of the convexification method for a 1D coefficient inverse problem with experimental data

A new version of the convexification method is developed analytically and tested numerically for a 1D coefficient inverse problem in the frequency domain. Unlike the previous version, this one does not use the so-called ‘tail function’, which is a complement of a certain truncated integral with respect to the wave number. Globally strictly convex cost functional is constructed with the Carleman weight function. Global convergence of the gradient projection method to the correct solution is proved. Numerical tests are conducted for both computationally simulated and experimental data.

Positive Charge of Arginine Residues on Histone H4 Tail Is Required for Maintenance of Mating Type in Saccharomyces cerevisiae.

Transcriptional gene silencing is regulated by the chromatin structure, which is by various factors including histones. Saccharomyces cerevisiae contains transcriptionally silenced regions such as telomeric regions and hidden mating (HM) loci. The positively-charged amino acids on the histone H4 tail were reported to be critical for the telomeric silencing in yeast, by interacting with Dot1, a specific methyltransferase for the 79th. lysine on histone H3. However, Dot1 did not affect gene silencing within HM loci, but whether the positively-charged amino acids on the H4 tail affect HM silencing has not been defined. To elucidate the function of the H4 tail on HM silencing, we created several MATa-type yeast strains bearing the substitution of arginine with alanine or lysine on the histone H4 tail and checked the sensitivity of MATa-type yeast to alpha pheromone. The arginine point mutants substituted by alanine (R17A, R19A, and R23A) did not show sensitivity to alpha pheromone, but only two arginine mutants substituted by lysine (R17K and R19K) restored the sensitivity to alpha pheromone-like wild type. These data suggested that the basic property of arginine at 17th and 19th positions in the histone H4 tail is critical for maintaining HM silencing, but that of the 23rd arginine is not. Our data implicated that the positive charge of two arginine residues on the histone H4 tail is required for HM silencing in a manner independent of Dot1.

Structural Diversity of Nucleosomes Characterized by Native Mass Spectrometry.

Histone tails, which protrude from nucleosome core particles (NCPs), play crucial roles in the regulation of DNA transcription, replication, and repair. In this study, structural diversity of nucleosomes was investigated in detail by analyzing the observed charge states of nucleosomes reconstituted with various lengths of DNA using positive-mode electrospray ionization mass spectrometry (ESI-MS) and molecular dynamics (MD) simulation. Here, we show that canonical NCPs, having 147 bp DNA closely wrapped around a histone octamer, can be classified into three groups by charge state, with the least-charged group being more populated than the highly charged and intermediate groups. Ions with low charge showed small collision cross sections (CCSs), suggesting that the histone tails are generally compact in the gas phase, whereas the minor populations with higher charges appeared to have more loosened structure. Overlapping dinucleosomes, which contain 14 histone proteins closely packed with 250 bp DNA, showed similar characteristics. In contrast, mononucleosomes reconstituted with a histone octamer and longer DNA (≥250 bp), which have DNA regions uninvolved in the core-structure formation, showed only low-charge ions. This was also true for dinucleosomes with free DNA regions. These results suggest that free DNA regions affect the nucleosome structures. To investigate the possible structures of NCP observed in ESI-MS, computational structural calculations in solution and in vacuo were performed. They suggested that conformers with large CCS values have slightly loosened structure with extended tail regions, which might relate to the biological function of histone tails.

CCL19 with CCL21-tail displays enhanced glycosaminoglycan binding with retained chemotactic potency in dendritic cells.

CCL19 is more potent than CCL21 in inducing chemotaxis of human dendritic cells (DC). This difference is attributed to 1) a stronger interaction of the basic C-terminal tail of CCL21 with acidic glycosaminoglycans (GAGs) in the environment and 2) an autoinhibitory function of this C-terminal tail. Moreover, different receptor docking modes and tissue expression patterns of CCL19 and CCL21 contribute to fine-tuned control of CCR7 signaling. Here, we investigate the effect of the tail of CCL21 on chemokine binding to GAGs and on CCR7 activation. We show that transfer of CCL21-tail to CCL19 (CCL19CCL21-tail ) markedly increases binding of CCL19 to human dendritic cell surfaces, without impairing CCL19-induced intracellular calcium release or DC chemotaxis, although it causes reduced CCR7 internalization. The more potent chemotaxis induced by CCL19 and CCL19CCL21-tail compared to CCL21 is not transferred to CCL21 by replacing its N-terminus with that of CCL19 (CCL21CCL19-N-term ). Measurements of cAMP production in CHO cells uncover that CCL21-tail transfer (CCL19CCL21-tail ) negatively affects CCL19 potency, whereas removal of CCL21-tail (CCL21tailless ) increases signaling compared to full-length CCL21, indicating that the tail negatively affects signaling via cAMP. Similar to chemokine-driven calcium mobilization and chemotaxis, the potency of CCL21 in cAMP is not improved by transfer of the CCL19 N-terminus to CCL21 (CCL21CCL19-N-term ). Together these results indicate that ligands containing CCL21 core and C-terminal tail (CCL21 and CCL21CCL19-N-term ) are most restricted in their cAMP signaling; a phenotype attributed to a stronger GAG binding of CCL21 and defined structural differences between CCL19 and CCL21.

Chemotropic Receptor Deleted In Colorectal Cancer (DCC) Prevents Translation Initiation By Directly Inhibiting Ribosome Function

Axonal outgrowth and guidance is dictated by a variety of chemotropic signals. Netrin receptors at the growth cones of developing neurons function to attract or repel outgrowth during commissure formation. The dependence receptor Deleted in Colorectal Cancer (DCC) is activated by netrin‐1, and dimerization initiates a variety of responses, including activation of Src tyrosine kinases and focal adhesion kinase. Prior to netrin‐1 activation, the monomeric C‐terminal tail of DCC binds to 80S ribosomes and prevents polysome formation. DCC activation and dimerization releases 80S ribosomes for translation initiation, presumably to promote axonal outgrowth. The C‐terminal tail of DCC is a 35 kDa protein that is composed of three domains (P1‐3) and is predicted 91% unstructured. Dimerization is facilitated by the P3 domain, while the P1 domain binds to the 60S subunit protein, ribosomal protein L5 (rpL5). Yet, the exact mechanism of how the DCC C‐terminal tail inhibits translation is unknown. Titrating the full‐length C‐terminal tail into translation‐competent lysates, we found that the tail specifically inhibits eukaryotic translation, and inhibits protein synthesis of messages that use both cap‐dependent and internal ribosome entry site translation initiation. Hence, we propose that the DCC C‐terminal tail functions primarily through binding the ribosome, not eukaryotic initiation factors. In fact, we have evidence from co‐sedimentation and gel filtration chromatography studies to show that the full‐length tail binds to the small and large subunits, as well as the 80S ribosome in the absence of mRNA. We propose a mechanism by which the C‐terminal tail blocks the decoding groove of the 80S ribosome to stall the apo‐80S complex. Our hypothesis is supported by data showing the P1 domain (and its interaction with rpL5) is not solely responsible for the decrease in translation, and thus the P2‐3 domains are also important for function. Collectively, our results support the idea that the DCC C‐terminal tail inhibits translation by effectively preventing ribosomes from binding to messages, until receptor dimerization and release of 80S ribosomes. Thus chemoattraction via netrin‐induced DCC receptor dimerization might lead to a global (not message‐specific) increase in localized protein synthesis at axonal growth cones.Support or Funding InformationHoward Hughes Medical Institute, Janelia Farm Visiting Scientists Program & Metropolitan State University of Denver Provost GrantThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Convexification of a 3-D coefficient inverse scattering problem

A version of the so-called “convexification” numerical method for a coefficient inverse scattering problem for the 3D Helmholtz equation is developed analytically and tested numerically. Backscattering data are used, which result from a single direction of the propagation of the incident plane wave on an interval of frequencies. The method converges globally. The idea is to construct a weighted Tikhonov-like functional. The key element of this functional is the presence of the so-called Carleman Weight Function (CWF). This is the function which is involved in the Carleman estimate for the Laplace operator. This functional is strictly convex on any appropriate ball in a Hilbert space for an appropriate choice of the parameters of the CWF. Thus, both the absence of local minima and convergence of minimizers to the exact solution are guaranteed. Numerical tests demonstrate a good performance of the resulting algorithm. Unlikeprevious the so-called tail functions globally convergent method, we neither do not impose the smallness assumption of the interval of wavenumbers, nor we do not iterate with respect to the so-called tail functions.

Nuclear resonant scattering experiment with fast time response: Photonuclear excitation of Hg201

Nuclear resonant excitation of the 29.19-keV level in $^{229}$Th with high-brilliance synchrotron- radiation and detection of its decay signal, are proposed with the aim of populating the extremely low-energy isomeric state of $^{229}$Th.The proposed experiment, known as nuclear resonant scattering (NRS), has the merit of being free from uncertainties about the isomer level energy. However, it requires higher time resolution and shorter tail in the response function of the detector than that of conventional NRS experiments because of the short lifetime of the 29.19-keV state. We have fabricated an X-ray detector system which has a time resolution of 56 ps and a shorter tail function than the previously reported one. We have demonstrated an NRS experiment with the 26.27-keV nuclear level of $^{201}$Hg for feasibility assessment of the $^{229}$Th experiment. The NRS signal is clearly distinct from the prompt electronic scattering signal by the implemented detector system. The half-life of the 26.27-keV state of $^{201}$Hg is determined as 629 $\pm$ 18 ps which is better precision by a factor three than that reported to date.

A Failsafe for Sensing Chromatid Tension in Mitosis with the Histone H3 Tail in Saccharomyces cerevisiae.

Mitotic fidelity is ensured by achieving biorientation on all paired chromosomes. The key signal for proper chromosome alignment is the tension between sister chromatids created by opposing poleward force from the spindles. In the budding yeast, the tension-sensing function requires that the Shugoshin protein, Shugoshin 1, be recruited to the centromeres and the neighboring pericentric regions. Concerted actions integrating proteins at centromeres and pericentromeres create highly specific Shugoshin 1 domains on mitotic chromosomes. We have previously reported that an important regulatory region on histone H3, termed the tension-sensing motif (TSM), is responsible for retaining Shugoshin 1 at pericentromeres. The TSM is negatively regulated by the acetyltransferase Gcn5p, but the underlying mechanism was elusive. In this work, we provide evidence that, when the TSM function is impaired, the histone H3 tail adopts a role that complements the damaged TSM to ensure faithful mitosis. This novel function of the H3 tail is controlled by Gcn5p, which targets selective lysine residues. Mutations to K14 and K23 ameliorate the mitotic defects resulting from TSM mutations. The restoration of faithful segregation is accompanied by regaining Shugoshin 1 access to the pericentric regions. Our data reveal a novel pathway for mitotic Shugoshin 1 recruitment and further reinforce the active role played by chromatins during their segregation in mitosis.

ITERATED FAILURE RATE MONOTONICITY AND ORDERING RELATIONS WITHIN GAMMA AND WEIBULL DISTRIBUTIONS

Stochastic ordering of random variables may be defined by the relative convexity of the tail functions. This has been extended to higher order stochastic orderings, by iteratively reassigning tail-weights. The actual verification of stochastic orderings is not simple, as this depends on inverting distribution functions for which there may be no explicit expression. The iterative definition of distributions, of course, contributes to make that verification even harder. We have a look at the stochastic ordering, introducing a method that allows for explicit usage, applying it to the Gamma and Weibull distributions, giving a complete description of the order of relations within each of these families.

Exact Bounds on the Inverse Mills Ratio and Its Derivatives

The inverse Mills ratio is $$R:=\varphi /\Psi $$ , where $$\varphi $$ and $$\Psi $$ are, respectively, the probability density function and the tail function of the standard normal distribution. Exact bounds on R(z) for complex z with $$\mathfrak {R}z\geqslant 0$$ are obtained, which then yield logarithmically exact upper bounds on high-order derivatives of R. These results complement the many known bounds on the (inverse) Mills ratio of the real argument. The main idea of the proof is a non-asymptotic version of the so-called stationary-phase method. This study was prompted by a recently discovered alternative to the Euler–Maclaurin formula.

Proposals of probability measures suitable for accounting data based bankruptcy models

Financial distress and bankruptcy modeling represents large and important field of economic research topics. This paper concerns with general structure of score oriented models in form of linear or affine forms built upon data available from standard accounting reports. For illustration purposes, we present well-known models, i.e. Altman, Neumaier, Ohlson, and Zmijewski one. However, the paper is focused mainly to probabilistic framework, which is getting more actual attention in practice for company financial health quantitative analysis, now. At first, the logit and probit transformations used for Ohlson, and Zmijewski model, respectively, are presented, as well as one model for calculation of probability of company default based upon Z-score values. Our contribution to this field is presented in the central part of the paper. We assume the score value to be an outcome of a random variable, which is introduced by its cumulative distribution function. This function is constructed systematically as a piecewise smooth function collected from three branches. Two of them, there are tail functions, belong to exponencial family. Whereas the central branch is specified as a linear function. At each joint, which is related to model grey zone bound, point smoothness of two adjacent branches is maintained by specific boundary conditions applied. Several cumulative distribution functions are presented, together with their probability density functions. Next, we select a SME ranked company, and apply the proposed technique to company survival analysis, as well as an analysis of company default probabilities. All calculations were performed by sw Mathematica.

Primary stabilisation for tail avulsion in 15 cats

To evaluate the effects of a primary tail stabilisation technique in relieving pain and supporting nerve recovery in cats that have lost voluntary motor function and pain sensation in the tail without caudal nerve transection. Retrospective review of medical records and preoperative diagnostic tests, including clinical examination results and tail radiographs of cats suffering from tail avulsion with loss of pain perception in the tail between 2009 and 2015. Cats with open tail fracture, tail wounds that necessitated an amputation or caudal nerve root transection were excluded. Tail reconstruction was performed, after surgical exploration, with two nylon sutures. Fifteen cats were included, all of which had lost voluntary motor function in the tail and 8 of 15 were urinary incontinent. After surgery, 11 cats recovered voluntary tail function and pain sensation within 14 to 90 days (mean 39 days). Five of the eight previously incontinent cats recovered urinary continence within a month of surgery. The reported method of primary tail stabilisation is associated with recovery of lost function in the majority of cats presenting with tail avulsions, loss of pain sensation in the tail but without caudal nerve root transection. A comparison study is required to determine whether these results are superior to conservative management.

Recursion versus tail recursion over [formula omitted

We characterize the intrinsically recursive functions over the algebraic closure of a finite field in terms of Turing machine complexity classes and derive some structural properties about the family of such functions. In particular, we show that the domain of convergence of any partial recursive function is again recursive, and, under complexity-theoretic hypotheses, that the class of tail recursive functions is strictly smaller than the class of recursive functions (cf. Theorems 5.4, 5.2, and Section 8).Underlying these results is the “meta-result” that we can perform a limited amount of arithmetic inside the field itself, with no access to a separate sort of natural numbers.

Lateral movements of a massive tail influence gecko locomotion: an integrative study comparing tail restriction and autotomy

Tails are an intricate component of the locomotor system for many vertebrates. Leopard geckos (Eublepharis macularius) possess a large tail that is laterally undulated during steady locomotion. However, the tail is readily shed via autotomy, resulting in the loss of tail function, loss in body mass, and a cranial shift in the center of mass. To elucidate the function of tail undulations, we investigated changes in limb kinematics after manipulating the tail artificially by restricting tail undulations and naturally by removing the tail via autotomy. Restricting tail undulations resulted in kinematic adjustments similar to those that occur following tail autotomy, characterized by more flexed hind limb joints. These data suggest that effects of autotomy on locomotion may be linked to the loss of tail movements rather than the loss of mass or a shift in center of mass. We also provide empirical support for the link between lateral tail undulations and step length through the rotation of the pelvic girdle and retraction of the femur. Restriction and autotomy of the tail limits pelvic rotation, which reduces femur retraction and decreases step length. Our findings demonstrate a functional role for tail undulations in geckos, which likely applies to other terrestrial vertebrates.

Formation and function of sperm tail structures in association with sperm motility defects.

Male infertility is an increasing problem partly due to inherited genetic variations. Mutations in genes involved in formation of the sperm tail cause motility defects and thus male infertility. Therefore, it is crucial to understand the protein networks required for sperm differentiation. Sperm motility is produced through activation of the sperm flagellum, which core structure, the axoneme, resembles motile cilia. In addition to this, cytoskeletal axonemal structure sperm tail motility requires various accessory structures. These structures are important for the integrity of the long tail, sperm capacitation, and generation of energy during sperm passage to fertilize the oocyte. This review discusses the current knowledge of mechanisms required for formation of the sperm tail structures and their effect on fertility. The recent research based on animal models and genetic variants in relation to sperm tail formation and function provides insights into the events leading to fertile sperm production. Here we compile a view of proteins involved in sperm tail development and summarize the current knowledge of factors contributing to reduced sperm motility, asthenozoospermia, underline the mechanisms which require further research, and discuss related clinical aspects on human male infertility.