Tail Axis Research Articles

Evaluation of the electromyography activity of hindlimb muscles during core exercises in horses

IntroductionTherapeutic exercise is key in rehabilitation programs, so they must be specific, individualised, and reasoned. Biomechanical studies using surface electromyography have allowed us to make an evidence-based selection of the most appropriate exercises for each patient. The literature describes different electromyography activities in many muscles during different exercises, including walking, trotting, galloping, poles, and slopes, among others, but research on exercises performed in standing horses is lacking. Inclusion in rehabilitation programs of these exercises is based on an effect extrapolated from an anatomical and biomechanical concept of the muscles and not on surface electromyography evidence. This study evaluated the effect of six therapeutic exercises commonly used in horse rehabilitation programs on four muscles (m. gluteus medius, m. tensor fasciae latae, m. biceps femoris, and m. gracilis), to objectively measure the activity they generate by surface electromyography. Material and methodsSix horses performed six selected core exercises: axial tail traction, lateral tail traction, lateral tail traction to the contralateral side, lumbosacral flexion, lumbosacral extension, and caudal weight displacement. The activity was recorded by surface electromyography in four hindlimb muscles, including the m. gluteus medius, m. tensor fasciae latae, m. biceps femoris, and m. gracilis, and the signal registered was rectified and smoothed using the root mean square (RMS) algorithm. Finally, the data obtained was subjected to a statistical analysis using an ANOVA for the differential voltage factor followed by a Duncan multiple range analysis to determine which muscles activated each exercise. ResultsMaximum activity was observed for m. gluteus medius with lateral tail traction (41.55 μV) and lumbosacral flexion (46.72 μV); m. tensor fasciae with lateral tail traction (40.63 μV); m. biceps femoris with lumbosacral flexion (22.22 μV); and m. gracilis with axial tail traction (39.48 μV), lateral tail traction to the contralateral side (56.43 μV), lumbosacral flexion (68.72 μV), and caudal weight displacement (41.12 μV). ConclusionsM. biceps femoris was moderately activated during lumbar flexion, indicating it is not as relevant in pelvic stability as previously assumed. M. gluteus medius, m. biceps femoris, and m. gracilis activity during lumbar flexion suggests their potential involvement in the stability of the lumbosacral region. m. gracilis exhibited more activity than expected, indicating a significant role in pelvis and hip stability.

The Wagging Plasma Tail of Comet C/2020 S3 (Erasmus)

Long-period comet C/2020 S3 (Erasmus) reached perihelion at 0.398 au on UT 2020 December 12.67, making it a bright, near-Sun object. Images taken between 2020 mid-November and December using the HI-1 camera and COR2 coronagraph on board STEREO-A, as well as the LASCO/C3 coronagraph on board SoHO, show significant variations in the plasma tail position angles. To analyze these variations, a simple technique was developed to calculate the aberration angles. These angles are defined as the angle between the Sun–comet line and the tail axis, measured in the orbital plane. The aberration angles were found to range from 1.°2 to 46.°8, with an average (median) value of approximately 20.°3 (16.°3). By considering the aberration angles, the solar wind radial velocities during the observations were inferred to range from 73.9 to 573.5 km s−1, with a mean (median) value of approximately 205.5 km s−1 (182.3 km s−1). Throughout the observations, two periods were identified where the tails showed forward tilting, which cannot be explained by aberration alone. In one case, this anomalous position angle was sustained for at least 11 days and is possibly due to corotating interaction regions. In the other case, the tail exhibited dramatic excursions from 180° to 150° back to 210° over a limited period of around 34 hr. This behavior is tentatively explained as a consequence of the interaction with a halo coronal mass ejection that was launched from NOAA Active Region 12786 and arrived at comet C/2020 S3 during the time when the tail displayed its wagging behavior.

A free-swimming tadpole model based on immersed boundary-lattice Boltzmann method and its application

A two-dimensional (2D) free-swimming tadpole model is built in this study using the immersed boundary-lattice Boltzmann method. The tadpole is developed by connecting a passive elliptical head with a beating tail. This developed tadpole is capable of controlling the tail swing amplitude to change the swimming speed and achieve the desired swimming direction by attaching an angle offset on the tail axis. The hydrodynamics of the proposed tadpole model in swimming is investigated by regulating the width of the confined space. To be specific, three points are summarized below. First, a lower swimming speed will be produced in a narrower channel under the identical swimming pattern. Second, under the effect of a slight swing strength, a small-scale disturbance is triggered to the surrounding fluid, and a small swimming speed will be generated. Third, a relatively small or excessive swimming speed adversely affects the stability of its swimming. Moreover, a perception-response strategy for the tadpole is further formulated to achieve its autonomous locomotion control. A virtual perceptive field is proposed as the visual range, which is conducive to implementing tadpole motion control based on a set of mechanical response rules. With the above-mentioned improvements, the tadpole can effectively achieve obstacle avoidance in sophisticated obstacle array environments and tracking sine curve routines. Accordingly, this study can provide a valuable reference for the theoretical design of underwater bionic tadpole-like robots.

The Role of Posterior Neural Plate-Derived Presomitic Mesoderm (PSM) in Trunk and Tail Muscle Formation and Axis Elongation.

Elongation of the posterior body axis is distinct from that of the anterior trunk and head. Early drivers of posterior elongation are the neural plate/tube and notochord, later followed by the presomitic mesoderm (PSM), together with the neural tube and notochord. In axolotl, posterior neural plate-derived PSM is pushed posteriorly by convergence and extension of the neural plate. The PSM does not go through the blastopore but turns anteriorly to join the gastrulated paraxial mesoderm. To gain a deeper understanding of the process of axial elongation, a detailed characterization of PSM morphogenesis, which precedes somite formation, and of other tissues (such as the epidermis, lateral plate mesoderm and endoderm) is needed. We investigated these issues with specific tissue labelling techniques (DiI injections and GFP+ tissue grafting) in combination with optical tissue clearing and 3D reconstructions. We defined a spatiotemporal order of PSM morphogenesis that is characterized by changes in collective cell behaviour. The PSM forms a cohesive tissue strand and largely retains this cohesiveness even after epidermis removal. We show that during embryogenesis, the PSM, as well as the lateral plate and endoderm move anteriorly, while the net movement of the axis is posterior.

Seeking Sense in the Hox Gene Cluster.

The Hox gene cluster, responsible for patterning of the head-tail axis, is an ancestral feature of all bilaterally symmetrical animals (the Bilateria) that remains intact in a wide range of species. We can say that the Hox cluster evolved successfully only once since it is commonly the same in all groups, with labial-like genes at one end of the cluster expressed in the anterior embryo, and Abd-B-like genes at the other end of the cluster expressed posteriorly. This review attempts to make sense of the Hox gene cluster and to address the following questions. How did the Hox cluster form in the protostome-deuterostome last common ancestor, and why was this with a particular head-tail polarity? Why is gene clustering usually maintained? Why is there collinearity between the order of genes along the cluster and the positions of their expressions along the embryo? Why do the Hox gene expression domains overlap along the embryo? Why have vertebrates duplicated the Hox cluster? Why do Hox gene knockouts typically result in anterior homeotic transformations? How do animals adapt their Hox clusters to evolve new structural patterns along the head-tail axis?

An Exploratory Study on Vectorcardiographic Identification of the Site of Origin of Focally Induced Premature Depolarizations in Horses, Part I: The Atria.

Simple SummaryArrhythmias are common in horses, but in order to offer adequate treatment, the anatomical location from where the arrhythmia originates must first be known. The objective of this study was to differentiate between the various anatomical origins of atrial premature depolarizations and to further differentiate these from normal sinus rhythm based upon the vectorcardiography characteristics of seven horses without cardiovascular disease. With vectorcardiography, the magnitude and direction of the cardiac electrical forces were derived from an electrocardiographic recording and were plotted in three dimensions. The three directions were represented by the right–left axis, head–tail axis, and dorsoventral axis. Under general anaesthesia, atrial premature depolarizations were induced by pacing inside the heart, guided by a 3D mapping system that allowed us to see the 3D position of the pacing catheter inside the heart in real-time. An adapted statistical test optimized for spherical data was used to demonstrate that the maximal directions of the first and second half of the P wave showed significant differences between the paced locations and between the paced complexes and sinus rhythm. The current study provides a practical approach to identifying the approximate site of origin of an atrial arrhythmia using a custom 12-lead ECG.In human cardiology, the anatomical origin of atrial premature depolarizations (APDs) is derived from P wave characteristics on a 12-lead electrocardiogram (ECG) and from vectorcardiography (VCG). The objective of this study is to differentiate between anatomical locations of APDs and to differentiate APDs from sinus rhythm (SR) based upon VCG characteristics in seven horses without cardiovascular disease. A 12-lead ECG was recorded under general anaesthesia while endomyocardial atrial pacing was performed (800–1000 ms cycle length) at the left atrial free wall and septum, right atrial free wall, intervenous tubercle, as well as at the junction with the cranial and caudal vena cava. Catheter positioning was guided by 3D electro-anatomical mapping and transthoracic ultrasound. The VCG was calculated from the 12-lead ECG using custom-made algorithms and was used to determine the mean electrical axis of the first and second half of the P wave. An ANOVA for spherical data was used to test if the maximal directions between each paced location and the maximal directions between every paced location and SR were significantly (p < 0.05) different. Atrial pacing data were not available from the LA septum in three horses, the intervenous tubercle in two horses, and from the LA free wall in one horse. The directions of the maximal electrical axes showed significant differences between all paced locations and between the paced locations and SR. The current results suggest that VCG is useful for identifying the anatomical origin of an atrial ectopy.

A Tail of Two Clumps

We present two axisymmetric simulations of a high velocity clump in a photoionized region: one for the case of a uniform, low density environment and a second one for the case of a clump first traveling within a high density medium and then emerging into a low density environment. We show that the second scenario results in the production of an axial tail of dense material with a linear velocity vs. position ramp (with zero velocity at the high/low density environment transition). This material comes from a confined bow shock (produced by the clump when it was within the dense cloud) that emerges into the low environmental density region.

Bisphenol A exposure induces apoptosis and impairs early embryonic development in Xenopus laevis.

Bisphenol A (BPA), an endocrine-disrupting chemical that is largely produced and used in the plastics industry, causes environmental pollution and is absorbed by humans through consumption of food and liquids in polycarbonate containers. BPA exerts developmental and genetic toxicities to embryos and offsprings, but the embryotoxicity mechanism of this chemical is unclear. This study aimed to explore the toxic effect of BPA on embryonic development and elucidate its toxicity mechanism. Embryos of Xenopus laevis as a model were treated with different concentrations (0.1, 1, 10, and 20μM) of BPA at the two-cell stage to investigate the developmental toxicity of BPA. Embryonic development and behaviors were monitored 24h-96h of BPA exposure. BPA concentrations greater than 1μM exerted significant teratogenic effects on the Xenopus embryos, which showed short tail axis, miscoiled guts, and bent notochord as the main malformations. The 20μM BPA-treated embryos were seriously damaged in all aspects and exhibited deformity, impaired behavioral ability, and tissue damage. The DNA integrity and apoptosis of the Xenopus embryos were also investigated. Exposure to BPA concentrations higher than 0.1μM significantly induced DNA damage (p<0.05). The 10 and 20μM BPA-treated embryos exhibited higher levels of cleaved caspase-3 protein than the control. The ratios of bax/bcl-2 mRNA were significantly higher in the 10μM and 20μM-treated embryos than the ratio in the control group. Overall, data indicated that BPA can delay the early development, induce DNA damage and apoptosis, and eventually cause multiple malformations in Xenopus embryos.

Structure and mechanism of DNA delivery of a gene transfer agent

Alphaproteobacteria, which are the most abundant microorganisms of temperate oceans, produce phage-like particles called gene transfer agents (GTAs) that mediate lateral gene exchange. However, the mechanism by which GTAs deliver DNA into cells is unknown. Here we present the structure of the GTA of Rhodobacter capsulatus (RcGTA) and describe the conformational changes required for its DNA ejection. The structure of RcGTA resembles that of a tailed phage, but it has an oblate head shortened in the direction of the tail axis, which limits its packaging capacity to less than 4,500 base pairs of linear double-stranded DNA. The tail channel of RcGTA contains a trimer of proteins that possess features of both tape measure proteins of long-tailed phages from the family Siphoviridae and tail needle proteins of short-tailed phages from the family Podoviridae. The opening of a constriction within the RcGTA baseplate enables the ejection of DNA into bacterial periplasm.

Probing Coronal Magnetic Fields with Sungrazing Comets: H i Lyα from Pickup Ions

Observations of sungrazing comets can be used to probe the solar corona, to study the composition of the comets, and to investigate the plasma processes that govern the interaction between the coronal plasma and cometary gas. UVCS observations of the intensities and line profiles of H i Lyα trace the density, temperature, and outflow speed of the corona. Analysis of H i Lyα observations of comet C/2002 S2 showed a surprising split in the comet's Lyα tail and an asymmetry of redshifted and blueshifted emission across the tail axis. It was suggested that the velocity structure might result from a population of neutrals produced by charge transfer between pickup ions and cometary neutrals. Here we present numerical simulations of the H i Lyα intensity and velocity centroid for sungrazing comets under the assumptions that the magnetic field and solar wind are radial. The models qualitatively reproduce the observations of Comet C/2002 S2 and potentially explain the split tail morphology that was seen in C/2002 S2 and also C/2001 C2. They also match the observed red- and blueshifts, though the solar wind velocity needed to explain the blueshift implies strong Doppler dimming and requires a higher outgassing rate to match the light curve. However, the models do not match the observations in detail, and we discuss the remaining discrepancies and the uncertainties in the model. We briefly discuss the implications for other UVCS comet observations and sungrazing comet observations with the Metis coronagraph.

Structure, rheological and responsive properties of a new mixed viscoelastic surfactant system

A new viscoelastic surfactant system based on a mixture of cationic (n-dodecylpyridinium chloride) and anionic (potassium oleate) surfactants was prepared. The effect of the concentration of cationic surfactant at constant concentration of anionic surfactant on the structure and rheological properties was investigated. A transition from spherical to cylindrical micelles was observed upon increasing content of cationic surfactant. SANS data revealed that the cylindrical micelles have an elliptical cross-section with a major axis close to double length of oleate tail and minor axis close to the double length of n-dodecyl tail suggesting that the both surfactants are segregated in some way within the micelles. The local segregation of surfactants was confirmed by 1H NMR NOESY data. The rheological data show that the viscosity goes through maximum with increasing content of cationic surfactant, which is due to the growth of micelles in length (before the maximum) and their branching (after the maximum). A maximum viscosity was found at a molar ratio between cationic and anionic surfactants equal to 0.3. The mixed surfactant system was shown to be responsive to hydrocarbons, since added n-decane induced a decrease of viscosity by 5 orders of magnitude as a result of transformation of long cylindrical micelles into ellipsoidal microemulsion droplets as was evidenced by SANS.

Relationship between testicular and epididymal biometry compared to semen quality in Yankasa rams

This study examined the relationship between the testicular and epididymal biometry compared to semen characteristics in Yankasa rams. Fifteen apparently healthy rams aged between 1-2 years with average weight of 20 kg were used for the study. They were acclimated for four weeks, screened and treated against endo and ecto parasite. They were kept in small ruminant pens under zero grazing, fed with hay, ground nut leaves/straw ‘harawa’ and wheat offal with water supplied ad-libitum. The scrotal circumference was measured in centimeters using a measuring tape. The testicular length (L), width (W), depth and epididymal head axis, length and tail axis were measured by caliper and testicular volume and weight were calculated by formula methods. Semen samples were collected using an electro-ejaculator and immediately evaluated for colour, volume, motility, pH, sperm concentration, sperm morphology and live/dead ratio. The right testicular and epidydimal biometry were non significantly greater than that of the left. Semen parameters correlate positively (right testicules, r=0.225) and (left testicles, r=0.346) with testicular volume except for bent tail, coil tail and motility. The left epididymal head’s long axis and right epididymal tail axis showed significant positive correlation (r= 0.55) with semen parameters and right epididymal head’s long axis and left epididymal tail axis showed negative correlation with semen characteristics. It was concluded that testicular and epididymal biometry increase with increase testicular function and output.

Developmental Biology: Reissner’s Fiber and Straightening of the Body Axis

A straight longitudinal body axis supports efficient directed locomotion of fish and other vertebrates. Newresearch demonstrates that Reissner's fiber, an enigmatic structure within the spinal central canal, is essential for development of an extended trunk to tail axis.

Evolutionary changes of Hox genes and relevant regulatory factors provide novel insights into mammalian morphological modifications.

The diversity of body plans of mammals accelerates the innovation of lifestyles and the extensive adaptation to different habitats, including terrestrial, aerial and aquatic habitats. However, the genetic basis of those phenotypic modifications, which have occurred during mammalian evolution, remains poorly explored. In the present study, we synthetically surveyed the evolutionary pattern of Hox clusters that played a powerful role in the morphogenesis along the head–tail axis of animal embryos and the main regulatory factors (Mll, Bmi1 and E2f6) that control the expression of Hox genes. A deflected density of repetitive elements and lineage‐specific radical mutations of Mll have been determined in marine mammals with morphological changes, suggesting that evolutionary changes may alter Hox gene expression in these lineages, leading to the morphological modification of these lineages. Although no positive selection was detected at certain ancestor nodes of lineages, the increased ω values of Hox genes implied the relaxation of functional constraints of these genes during the mammalian evolutionary process. More importantly, 49 positively‐selected sites were identified in mammalian lineages with phenotypic modifications, indicating adaptive evolution acting on Hox genes and regulatory factors. In addition, 3 parallel amino acid substitutions in some Hox genes were examined in marine mammals, which might be responsible for their streamlined body.

X-Ray Reflectometry of DMPS Monolayers on a Water Substrate

The molecular structure of dimyristoyl phosphatidylserine (DMPS) monolayers on a water substrate in different phase states has been investigated under normal conditions by X-ray reflectometry with a photon energy of ~ 8 keV. According to the experimental data, the transition from a two-dimensional expanded liquid state to a solid gel state (liquid crystal) accompanied by the ordering of the hydrocarbon tails of the DMPS molecule occurs in the monolayer as the surface pressure rises. The monolayer thickness is (20 +/- 3) Angstrom and (28 +/- 2) Angstrom in the liquid and solid phases, respectively, with the deflection angle of the molecular tail axis from the normal to the surface in the gel phase being (26 +/- 8) deg. At least a twofold decrease in the degree of hydration of the polar lipid groups also occurs under two-dimensional monolayer compression. The reflectometry data have been analyzed using two approaches: under the assumption about the presence of two layers with different electron densities in the monolayer and without any assumptions about the transverse surface structure. Both approaches demonstrate satisfactory agreement between themselves in describing the experimental results.

GEMINGA’S PUZZLING PULSAR WIND NEBULA

ABSTRACT We report on six new Chandra observations of the Geminga pulsar wind nebula (PWN). The PWN consists of three distinct elongated structures—two ≈ 0.2 d 250 pc long lateral tails and a segmented axial tail of ≈ 0.05 d 250 pc length, where d 250 = d / ( 250 pc ) . The photon indices of the power-law spectra of the lateral tails, Γ ≈ 1 , are significantly harder than those of the pulsar ( Γ ≈ 1.5 ) and the axial tail ( Γ ≈ 1.6 ). There is no significant diffuse X-ray emission between the lateral tails—the ratio of the X-ray surface brightness between the south tail and this sky area is at least 12. The lateral tails apparently connect directly to the pulsar and show indications of moving footpoints. The axial tail comprises time-variable emission blobs. However, there is no evidence for constant or decelerated outward motion of these blobs. Different physical models are consistent with the observed morphology and spectra of the Geminga PWN. In one scenario, the lateral tails could represent an azimuthally asymmetric shell whose hard emission is caused by the Fermi acceleration mechanism of colliding winds. In another scenario, the lateral tails could be luminous, bent polar outflows, while the blobs in the axial tail could represent a crushed torus. In a resemblance to planetary magnetotails, the blobs of the axial tail might also represent short-lived plasmoids, which are formed by magnetic field reconnection in the relativistic plasma of the pulsar wind tail.

CHANDRA OBSERVATIONS OF OUTFLOWS FROM PSR J1509–5850

ABSTRACT PSR J1509–5850 is a middle-aged pulsar with a period of P ≈ 89 ms and spin-down power of erg s−1, at a distance of about 3.8 kpc. We report on deep Chandra X-ray Observatory observations of this pulsar and its pulsar wind nebula (PWN). In addition to the previously detected tail extending up to 7′ southwest from the pulsar (the southern outflow), the deep images reveal similarly long, faint, diffuse emission stretched toward the north (the northern outflow) and the fine structure of the compact nebula (CN) in the pulsar vicinity. The CN is resolved into two lateral tails and one axial tail pointing southwest (a morphology remarkably similar to that of the Geminga PWN), which supports the assumption that the pulsar moves toward the northeast. The luminosities of the southern and northern outflows are about and erg s−1, respectively. The spectra extracted from four regions of the southern outflow do not show any softening with increasing distance from the pulsar. The lack of synchrotron cooling suggests a high flow speed or in situ acceleration of particles. The spectra extracted from two regions of the northern outflow show a hint of softening with distance from the pulsar, which may indicate slower particle propagation. We speculate that the northern outflow is associated with particle leakage from the bow-shock apex into the ISM, while the southern outflow represents the tail of the shocked pulsar wind behind the moving pulsar. We estimate the physical parameters of the observed outflows and compare the J1509–5850 PWN with PWNe of other supersonically moving pulsars.

Extra-embryonic Wnt3 regulates the establishment of the primitive streak in mice

The establishment of the head to tail axis at early stages of development is a fundamental aspect of vertebrate embryogenesis. In mice, experimental embryology, genetics and expression studies have suggested that the visceral endoderm, an extra-embryonic tissue, plays an important role in anteroposterior axial development. Here we show that absence of Wnt3 in the posterior visceral endoderm leads to delayed formation of the primitive streak and that interplay between anterior and posterior visceral endoderm restricts the position of the primitive streak. Embryos lacking Wnt3 in the visceral endoderm, however, appear normal by E9.5. Our results suggest a model for axial development in which multiple signals are required for anteroposterior axial development in mammals.

Plasma distribution of Comet ISON (C/2012 S1) observed using the radio scintillation method

We report the electron density in a plasma tail of Comet ISON (C/2012 S1) derived from interplanetary scintillation (IPS) observations during November 1–28, 2013. Comet ISON showed a well-developed plasma tail (longer than 2.98×107km) before its perihelion passage on November 28. We identified a radio source whose line-of-sight approached the ISON’s plasma tail in the above period and obtained its IPS data using the Solar Wind Imaging Facility at 327MHz. We used the Heliospheric Imager onboard the Solar-Terrestrial Relation Observatory to distinguish between the cometary tail and solar eruption origins of their enhanced scintillation. From our examinations, we confirmed three IPS enhancements of a radio source 1148–00 on November 13, 16, and 17, which could be attributed to the disturbance in the cometary tail. Power spectra of 1148–00 had the steeper slope than normal ones during its occultation by the plasma tail. We estimated the electron density in the ISON’s plasma tail and found 84cm-3 around the tail axis at a distance of 3.74×107km from the cometary nucleus and an unexpected variation of the electron density in the vicinity of the tail boundary.

Transcriptomic analysis of tail regeneration in the lizard Anolis carolinensis reveals activation of conserved vertebrate developmental and repair mechanisms.

Lizards, which are amniote vertebrates like humans, are able to lose and regenerate a functional tail. Understanding the molecular basis of this process would advance regenerative approaches in amniotes, including humans. We have carried out the first transcriptomic analysis of tail regeneration in a lizard, the green anole Anolis carolinensis, which revealed 326 differentially expressed genes activating multiple developmental and repair mechanisms. Specifically, genes involved in wound response, hormonal regulation, musculoskeletal development, and the Wnt and MAPK/FGF pathways were differentially expressed along the regenerating tail axis. Furthermore, we identified 2 microRNA precursor families, 22 unclassified non-coding RNAs, and 3 novel protein-coding genes significantly enriched in the regenerating tail. However, high levels of progenitor/stem cell markers were not observed in any region of the regenerating tail. Furthermore, we observed multiple tissue-type specific clusters of proliferating cells along the regenerating tail, not localized to the tail tip. These findings predict a different mechanism of regeneration in the lizard than the blastema model described in the salamander and the zebrafish, which are anamniote vertebrates. Thus, lizard tail regrowth involves the activation of conserved developmental and wound response pathways, which are potential targets for regenerative medical therapies.