Number Of Spicules Research Articles

A spiculated mass target model for clinical image quality control in digital mammography.

Quality assurance of breast imaging has a long history of using test objects to optimize and follow up imaging devices. In particular, the evaluation of new techniques benefits from suitable test objects. The applicability of a phantom consisting of spiculated masses to assess image quality and its dependence on dose in flat field digital mammography (FFDM) and digital breast tomosynthesis systems (DBT) is investigated. Two spiculated masses in five different sizes each were created from a database of clinical tumour models. The masses were produced using 3D printing and embedded into a cuboid phantom. Image quality is determined by the number of spicules identified by human observers. The results suggest that the effect of dose on spicule detection is limited especially in cases with smaller objects and probably hidden by the inter-reader variability. Here, an average relative inter-reader variation of the counted number of 31% was found (maximum 83%). The mean relative intra-reader variability was found to be 17%. In DBT, sufficiently good results were obtained only for the largest masses. It is possible to integrate spiculated masses into a cuboid phantom. It is easy to print and should allow a direct and prompt evaluation of the quality status of the device by counting visible spicules. Human readout presented the major uncertainty in this study, indicating that automated readout may improve the reproducibility and consistency of the results considerably. A cuboid phantom including clinical objects as spiculated lesion models for visual assessing the image quality in FFDM and DBT was developed and is introduced in this work. The evaluation of image quality works best with the two larger masses with 21 spicules.

The spatial structure (3D) and mechanical properties of the sponge Spongilla lacustris L. (Porifera: Spongillida) skeleton as a potential tensegral architecture

Complex biological systems often provide ready solutions for contemporary engineering. One such organism might be sponges, primitive, tissueless animals whose evolution over 600 million years has allowed them to become highly specialized. An example of such an organism is the freshwater sponge Spongilla lacustris L., an organism that filters water. This study aimed to investigate the 3D structure of the aforementioned sponge using a broad spectrum of techniques such as Microcomputed Tomography (µCT), Scanning Electron Microscopy (SEM), Confocal Laser Scanning Microscopy (CLSM), and Light Microscopy. Additionally, these techniques have been used to correlate sponge architecture with mechanical properties using the concept of tensegrity, i.e., the feature of architectural structures that self-stabilize by balancing multidirectional, often opposing, tensile and compressive forces. A more detailed look at the structure of the sponge skeleton reveals that it is based on two elements: rigid siliceous spicules, chitin in in fibres with cementing collagen-type spongin material. The coexistence of these elements in the sponge structure determines the mechanical properties and, consequently, the sponge skeleton’s postulated tensegrity. Our observations indicate that the integrity of loose megascleres is realized by sponging material surrounding the bundles of spicules. Our distinction of skeletal elements was determined by the number of spicules in the bundle, the direction of spicule position relative to the main body axis, and the way the elements were connected. The arrangement of the bundles described above has important implications for the mechanical properties of the sponge skeleton and, consequently, for the tensegrity hypothesis.

Solar Chromospheric Network as a Source for Solar Wind Switchbacks

Recent studies suggest that the magnetic switchbacks (SBs) detected by the Parker Solar Probe carry information on the scales of solar supergranulation (large scale) and granulation (medium scale). We test this claim using high-resolution Hα images obtained with the visible spectropolarimeters of the Goode Solar Telescope in Big Bear Solar Observatory. As possible solar sources, we count all the spicule-like features standing along the chromospheric networks near the coronal hole boundary visible in the Hα blue-wing but absent in the red-wing images and measure the geometric parameters of dense sections of individual flux tubes. Intervals between adjacent spicules located along the chromospheric networks are found in the range of 0.4–1.5 Mm (0.°03–0.°12) tending to be smaller than the medium scale of SBs. Interdistances between all pairs of the flux tubes are also counted and they appear in a single peak distribution around 0.7 Mm (0.°06) unlike the waiting-time distribution of SBs in a scale-free single power-law form. The length-to-diameter ratio of the dense section of flux tubes is as high as 6–40, similar to the aspect ratio of SBs. The number of spicules along a network can be as high as 40–100, consistent with numerous SBs within a patch. With these numbers, it is argued that the medium scale of SBs can be understood as an equilibrium distance resulting from a random walk within each diverging magnetic field funnel connected to the chromospheric networks.

Implications of spicule activity on coronal loop heating and catastrophic cooling

ABSTRACT We report on the properties of coronal loop foot-point heating with observations at the highest resolution, from the CRisp Imaging Spectro-Polarimeter located at the Swedish 1-m Solar Telescope and co-aligned NASA Solar Dynamics Observatory observations, of Type II spicules in the chromosphere and their signatures in the extreme ultraviolet (EUV) corona. Here, we address one important issue, as to why there is not always a one-to-one correspondence, between Type II spicules and hot coronal plasma signatures, i.e. beyond TR temperatures. We do not detect any difference in their spectral properties in a quiet Sun region compared to a region dominated by coronal loops. On the other hand, the number density close to the foot-points in the active region is found to be an order of magnitude higher than in the quiet Sun case. A differential emission measure analysis reveals a peak at ∼5 × 105 K of the order of 1022 cm−5 K−1. Using this result as a constraint, we conduct numerical simulations and show that with an energy input of 1.25 × 1024 erg (corresponding to ∼10 RBEs contributing to the burst) we manage to reproduce the observation very closely. However, simulation runs with lower thermal energy input do not reproduce the synthetic AIA 171 Å signatures, indicating that there is a critical number of spicules required in order to account for the AIA 171 Å signatures in the simulation. Furthermore, the higher energy (1.25 × 1024 erg) simulations reproduce catastrophic cooling with a cycle duration of ∼5 h, matching a periodicity we observe in the EUV observations.

The mechanical influence of bone spicules in the osteochondral junction: A finite element modelling study.

While much has been done to study how cartilage responds to mechanical loading, as well as modelling such responses, arguably less has been accomplished around the mechanics of the cartilage-bone junction. Previously, it has been reported that the presence of bony spicules invading the zone of calcified cartilage, preceded the formation of new subchondral bone and the advancing of the cement line (Thambyah and Broom in Osteoarthr Cartil 17:456-463, 2009). In this study, the morphology and frequency of bone spicules in the cartilage-bone interface of osteochondral beams subjected to three-point bending were modelled, and the results are discussed within the context of biomechanical theories on bone formation. It was found that the stress and strain magnitudes, and their distribution were sensitive to the presence and number of spicules. Spicule numbers and shape were shown to affect the strain energy density (SED) distribution in the areas of the cement line adjacent to spicules. Stresses, strains and SED analyses thus provided evidence that the mechanical environment with the addition of spicules promotes bone formation in the cartilage-bone junction.

On the Possibility of Heating the Solar Corona by Heat Fluxes from Coronal Magnetic Structures

We estimate the role of heat flux from hot magnetic loops and open flux tubes into the surrounding corona as a possible source of heating of the corona. We show that hot magnetic-flux tubes (Type-II spicules) provide a more efficient source of coronal heating than hot magnetic loops, as the closed magnetic structure of a loop substantially restricts the heat flux into the corona. In order to compensate for radiation and thermal-conduction losses, approximately $10^{4}$ Type-II spicules with a temperature of several million Kelvin are required, which is about 1% of the number of spicules simultaneously observed on the solar disk. Our analysis shows that the principal source of energy that heats the coronal plasma is photospheric convection, which generates electric currents of about $10^{10}$ – $10^{12}$ A in magnetic loops and spicules. Dissipation of the currents increases significantly in the partially ionized plasma, i.e. when ion–atom collisions and the associated Cowling conductivity occur. This results in two important effects: heating of plasma in magnetic structures up to several million Kelvin, and ejection of hot plasma from open magnetic-flux tubes to the corona, replenishing the corona with hot plasma. The ejection of hot plasma results from the heating of the spicule foot-point by electric-current dissipation, which grows with a sporadic increase in the velocity of photospheric convection, for example, due to five-minute oscillations or the Rayleigh–Taylor instability. As a result, the rate of heating the photospheric foot-points of the spicules by ring currents exceeds radiation losses, which leads to a jump in the pressure gradient and the ejection of hot plasma into the corona from the open tips of the magnetic-flux tubes.

Reuse of voucher specimens provides insights into the genomic associations and taxonomic value of wing colour and genitalic differences in a pest group (Lepidoptera: Tortricidae: Choristoneura)

AbstractSubtle morphological differences can be essential to diagnosing closely related species, and an understanding of the genetic basis of these characters can contribute to understanding their divergences. We used voucher specimens from previous genetic analyses of population structure to subsequently analyse genome‐wide associations linking morphology to genetic variation in spruce budworms, a group of economically important and morphologically similar forest pests. In particular, we assessed the taxonomic value and genetic architecture of two morphological traits (wing pattern and genitalic spicule abundance) that have been reported to differ among spruce budworm species. Our results suggest that phallic spicule number has greater taxonomic utility than wing pattern for distinguishing Choristoneura fumiferana (Clemens) from Choristoneura occidentalis occidentalis Freeman and Choristoneura occidentalis biennis Freeman. However, there was considerable overlap among taxa for all phenotypic characters analysed. In a genome‐wide association study, wing pattern variation was significantly associated with four single nucleotide polymorphism (SNP) loci, including two adjacent SNPs. One SNP was flanked by sequence resembling RNA‐directed DNA polymerase from mobile element jockey‐like. This locus is a promising candidate for the study of wing pattern development in spruce budworms, as jockey‐like transposable elements and polymerases have documented roles in wing spot production in other Lepidoptera. Our study links classical taxonomic characters and genomic data to provide insights into the potential genetic architecture of species differences. It also demonstrates previously untapped morphological and taxonomic value in voucher specimens from earlier molecular genetic analyses.

Nitrogen and sulfur Association: Effects on Yield Components and Physical Attributes of Wheat Seeds

The aimed to evaluate the effect of different nitrogen doses in association with sulfur fertilization on yield components and seeds physic-quality attributes. The experimental design was randomized blocks, arranged in a 3 × 5 × 2 factorial design (cultivar × nitrogen doses × sulfur management), with four replications. The analysis of variance revealed that wheat cultivars × sulfur management interaction was significant for height insert of main spike. Interaction was verified between cultivars × nitrogen doses for number of tillers per plant and number of spikes per m2. The nitrogen doses × sulfur management interaction was significant for number of tillers per plant. Interaction between cultivars × nitrogen doses were observed for number of spicules per spikes and number of seeds per spike. Nitrogen fertilization has different effects on wheat cultivars. The cultivar ‘TBIO Sinuelo’ presents greater seeds yield with improvement of nitrogen fertilization doses. High nitrogen doses provide increasing of wheat seeds yield. Nitrogen doses influence differently on yield components of wheat. Number of tillers per plant is correlated with seeds yield. Physical attributes of wheat seeds are not influenced by nitrogen doses increasing. Sulfur fertilization promotes tillering and increment of number of spicules per spike. The cultivar ‘TBIO Sinuelo’ presents higher weight per 1000 seeds, followed by ‘Jadeíte 11’, and ‘TBIO Sintonia’.

Clinical markers of cerebellar tremor of the upper limb

Hypermetric tremor, from cerebellar origin, directly relate to iterative hypermetria by delayed antagonist correction at each movement, is a frequent neurological disorder, which can cause significant functional and social disability. Nowadays, the clinical evaluation of tremors relies mainly on subjective rating tools. The purpose of the study was to develop quantitative markers of hypermetric tremor of the upper limb to help clinicians with diagnosis, follow-up and assessment of treatment effects. We prospectively analyzed data from two volumetric tests (30 seconds and 5 table-to-mouth tests), a device for evaluating rapid alternating pronosupination movements “the Hand Tapper” (large/small movements ratios) and spiralography (number of spikes per turn and symmetry coefficient). We compared these parameters in three populations: 18 patients (age: 63 ± 16 years) with upper limb cerebellar tremor, 15 patients with Parkinson's disease with predominant tremor (67 ± 7 years) and 18 healthy subjects (age: 63 ± 15 years). At the volumetric tests, the height of remaining water is measured in the polystyrene cup (90 mm height) after each test. For the 30 seconds posture test (H30): cerebellar = 41.2 ± 8.5 mm, parkinson = 82.9 ± 4.5 mm, healthy subjects = 90.0 ± 0.0 mm, ( P cerebellar vs parkinson = 2 × 10 −5 ) and for the 5 table-to-mouth back and forth movements test (HX5): cerebellar = 27.3 ± 7.6 mm, parkinson = 88.7 ± 0.3 mm, healthy subjects = 89.9 ± 0.1 mm ( P cerebellar vs parkinson = 10 −11 ). At the “Hand Tapper”, the large/small pronosupination movements ratios (L/S) were: cerebellar = 65.0 ± 4.6%, parkinson = 50.2 ± 2.2%, healthy subjects = 47.9 ± 3.0% ( P cerebellar vs parkinson = 0.01). At the spiralography, the number of spikes per turn were: cerebellar = 10.7 ± 1.7; parkinson 6.1 ± 1.3; healthy subjects = 2.0 ± 0.3 ( P cerebellar vs parkinson = 0.03). The height of remaining water on volumetric tests, L/S ratios with Hand Tapper, and the number of spicules on spiralography seem to be representative markers of cerebellar hypermetry, compared to “parkinsonism”. Explorations of diagnostic performances of these parameters and correlations with the severity of the tremor will be the subject of a future analysis.

The total number of spicules on the solar surface and their role in heating and mass balanace in the solar corona

A critical review of determinations of the number of spicules is presented, and the role of both classical and Type 2 spicules in heating and mass balance in the corona is considered. The total number of Type 2 spicules is determined, together with the upward fluxes of energy and mass to which they give rise. The total number of Type 2 spicules on the solar surface is found to be ~105, close to values obtained in other studies. The associated particle flux toward the corona is 2.5 × 1014 cm−2 s−1, an order of magnitude lower than the corresponding flux for classical spicules. The associated energy flux is 104 erg cm−2 s−1, an order of magnaitude lower than estimates obtained in other studies. The results indicate that Type 2 spicules can supply the mass lost from the corona, but are not able to fully explain coronal energy losses.

Posidonia oceanica meadows as sponge spicule traps

A quantitative study on the sponge spicules present in a series of horizontal core samples, taken at different levels, from a 1.5 m thick living matte within the Posidonia oceanica meadow of Prelo Bay (Eastern Ligurian Sea), has been performed. Sponge spicule amounts were evaluated by microscopical and chemical analyses. From the superficial samples the spicule number decreased until 60–80 cm depth to increase progressively until the deepest studied layer, 140 cm depth. The same results were obtained from the trend of spicule volume and biogenic silica tested by chemical analysis. Among the recognisable spicule types, the most common are oxeas, followed by tylostyles, achantostyles and strongyles. However, oxeas, tylostyles and achantostyles showed the same trend of the entire spicule population, whereas strongyles had an opposite trend with a maximum value at the 80–100 cm depth. According to the hypothesis that the amount of spicules in the sediment is proportional or at least related to the sponge biomass existing in the surrounding area, our data suggest that the sponge assemblage of Prelo Bay should not have been constant in the past 100–200 years. Our hypothesis is that the rapid urban and industrial development that occurred along the Ligurian coast after the Second World War, particularly in the 1960s, had an important impact on the sponge assemblages of the area.

Solar spicules and jets

In order to clear up the origin and possibly explain some solar limb and disc spicule quasi-periodic recurrences produced by overlapping effects, we present a simulation model assuming quasi- random positions of spicules. We also allow a set number of spicules with different physical properties (such as: height, lifetime and tilt angle as shown by an individual spicule) occurring randomly. Results of simulations made with three different spatial resolutions of the corresponding frames and also for different number density of spicules, are analyzed. The wavelet time/frequency method is used to obtain the exact period of spicule visibility. Results are compared with observations of the chromosphere from i/ the Transition Region and Coronal Explorer (TRACE) filtergrams taken at 1600 angstrom, ii/ the Solar Optical Telescope (SOT) of Hinode taken in the Ca II H-line and iii/ the Sac-Peak Dunn’s VTT taken in H? line. Our results suggest the need to be cautious when interpreting apparent oscillations seen in spicule image sequences when overlapping is present, i.e. ; when the spatial resolution is not enough to resolve individual components of spicules.

Contribution to the modeling of solar spicules

Solar limb and disk spicule quasi-periodic motions have been reported for a long time, strongly suggesting that they are oscillating. In order to clear up the origin and possibly explain some solar limb and disk spicule quasi-periodic recurrences produced by overlapping effects, we present a simulation model assuming quasi-random positions of spicules. We also allow a set number of spicules with different physical properties (such as: height, lifetime and tilt angle as shown by an individual spicule) occurring randomly. Results of simulations made with three different spatial resolutions of the corresponding frames and also for different number density of spicules, are analyzed. The wavelet time/frequency method is used to obtain the exact period of spicule visibility. Results are compared with observations of the chromosphere from (i) the Transition Region and Coronal Explorer (TRACE) filtergrams taken at 1600 Å, (ii) the Solar Optical Telescope (SOT) of Hinode taken in the Ca II H-line and (iii) the Sac-Peak Dunn’s VTT taken in Hα line. Our results suggest the need to be cautious when interpreting apparent oscillations seen in spicule image sequences when overlapping is present, i.e., when the spatial resolution is not enough to resolve individual components of spicules.

Analysis of radiofrequency energy stored in the altered shapes: Stomatocyte–echinocyte of human erythrocytes

The aim of this study is to analyze the electromagnetic energy stored in stomatocyte, erythrocyte and echinocyte cells exposed to a linearly polarized electromagnetic plane wave at 900, 1800 and 2450 MHz radiofrequency signals. This analysis can provide a better understanding of the order of appearance of altered shapes of erythrocytes (RBC) in the stomatocyte–echinocyte transition under radiofrequency exposure in terms of the deposited electromagnetic energy. For this purpose we use a realistic geometrical cell model based on parametric equations that allow for continuous transformations between normal erythrocytes and three stomatocyte subclasses with different degree of invagination and also between normal erythrocytes and echinocytes with an arbitrary number of spicules. We use a finite element technique with adaptive meshing for calculating the electromagnetic energy deposited on the different regions of the cell models. It is found that the echinocyte cell stores the minimum electromagnetic energy and therefore from an energetic point of view it would be the most stable and preferred cell state when this electromagnetic energy is the predominant energy component.

Pruritic and nociceptive sensations and dysesthesias from a spicule of cowhage.

Although the trichomes (spicules) of a pod of cowhage (Mucuna pruriens) are known to evoke a histamine-independent itch that is mediated by a cysteine protease, little is known of the itch and accompanying nociceptive sensations evoked by a single spicule and the enhanced itch and pain that can occur in the surrounding skin. The tip of a single spicule applied to the forearm of 45 subjects typically evoked 1) itch accompanied by nociceptive sensations (NS) of pricking/stinging and, to a lesser extent, burning, and 2) one or more areas of cutaneous dysesthesia characterized by hyperknesis (enhanced itch to pricking) with or without alloknesis (itch to stroking) and/or hyperalgesia (enhanced pricking pain). Itch could occur in the absence of NS or one or more dysesthesias but very rarely the reverse. The peak magnitude of sensation was positively correlated for itch and NS and increased (exhibited spatial summation) as the number of spicules was increased within a spatial extent of 6 cm but not 1 cm. The areas of dysesthesia did not exhibit spatial summation. We conclude that itch evoked by a punctate chemical stimulus can co-exist with NS and cutaneous dysesthesias as may occur in clinical pruritus. However, cowhage itch was not always accompanied by NS or dysesthesia nor was a momentary change in itch necessarily accompanied by a similar change in NS or vice versa. Thus there may be separate neural coding mechanisms for itch, nociceptive sensations, and each type of dysesthesia.

Shapes of Red Blood Cells: Comparison of 3D Confocal Images with the Bilayer-Couple Model

Cells and organelles are shaped by the chemical and physical forces that bend cell membranes. The human red blood cell (RBC) is a model system for studying how such forces determine cell morphology. It is thought that RBCs, which are typically biconcave discoids, take the shape that minimizes their membrane-bending energies, subject to the constraints of fixed area and volume. However, recently it has been hypothesized that shear elasticity arising from the membrane-associated cytoskeleton (MS) is necessary to account for shapes of real RBCs, especially ones with highly curved features such as echinocytes. In this work we tested this hypothesis by following RBC shape changes using spherical harmonic series expansions of theoretical cell surfaces and those estimated from 3D confocal microscopy images of live cells. We found (i) quantitative agreement between shapes obtained from the theoretical model including the MS and real cells, (ii) that weakening the MS, by using urea (which denatures spectrin), leads to the theoretically predicted gradual decrease in spicule number of echinocytes, (iii) that the theory predicts that the MS is essential for stabilizing the discocyte morphology against changes in lipid composition, and that without it, the shape would default to the elliptocyte (a biconcave ellipsoid), (iv) that we were able to induce RBCs to adopt the predicted elliptocyte morphology by treating healthy discocytes with urea. The latter observation is consistent with the known connection between the blood disease hereditary elliptocytosis and spectrin mutations that weaken the cell cortex. We conclude that while the discocyte, in absence of shear, is indeed a minimum energy shape, its stabilization in healthy RBCs requires the MS, and that elliptocytosis can be explained based on purely mechanical considerations.

Unstable drift mode driven by shear plasma flow in solar spicules

Context. The lower solar atmosphere contains at any moment a large number of spicules comprising plasma that moves towards the upper layers with typical axial velocities of 20−30 km s −1 . It is expected that these flows as well as the plasma density are inhomogeneous in the perpendicular direction. The presence of such a density gradient implies the existence of drift waves, while the inhomogeneity of the flow velocity can cause the growth of such modes. Aims. The stability of the drift waves will be discussed within the two-fluid theory taking into account the ion temperature and the stress tensor effects. Methods. An analytical linear normal mode analysis is used within the local approximation. Results. A detailed derivation of the hot ion contribution is performed. A dispersion equation is derived and the stability/instability conditions are discussed in detail for the parameter range appropriate for solar spicules. The drift mode appears to be highly unstable for typical spicule characteristic lengths of the density and the shear flow gradients, i.e. in the range of a few hundred meters up to a few kilometers, yielding wave frequencies of the order of a few Hz. Conclusions. Hence, the waves and the instabilities develop at reasonable time scales regarding the life times of spicules that are measured in minutes.

The reliability of measuring physical characteristics of spiculated masses on mammography

The goal of this study was to assess the reliability of measurements of the physical characteristics of spiculated masses on mammography. The images used in this study were obtained from the Digital Database for Screening Mammography. Two experienced radiologists measured the properties of 21 images of spiculated masses. The length and width of all spicules and the major axis of the mass were measured. In addition, the observers counted the total number of spicules. Interobserver and intraobserver variability were evaluated using a hypothesis test for equivalence, the intraclass correlation coefficient (ICC) and Bland-Altman statistics. For an equivalence level of 30% of the mean of the senior radiologist's measurement, equivalence was achieved for the measurements of average spicule length (p<0.01), average spicule width (p = 0.03), the length of the major axis (p<0.01) and for the count of the number of spicules (p<0.01). Similarly, with the ICC analysis technique "excellent" inter-rater agreement was observed for the measurements of average spicule length (ICC = 0.770), the length of the major axis (ICC = 0.801) and for the count of the number of spicules (ICC = 0.780). "Fair to good" agreement was observed for the average spicule width (ICC = 0.561). Equivalence was also demonstrated for intraobserver measurements. Physical properties of spiculated masses can be measured reliably on mammography. The interobserver and intraobserver variability for this task is comparable with that reported for other measurements made on medical images.

Echinocyte Shapes: Bending, Stretching, and Shear Determine Spicule Shape and Spacing

We study the shapes of human red blood cells using continuum mechanics. In particular, we model the crenated, echinocytic shapes and show how they may arise from a competition between the bending energy of the plasma membrane and the stretching/shear elastic energies of the membrane skeleton. In contrast to earlier work, we calculate spicule shapes exactly by solving the equations of continuum mechanics subject to appropriate boundary conditions. A simple scaling analysis of this competition reveals an elastic length Λ el, which sets the length scale for the spicules and is, thus, related to the number of spicules experimentally observed on the fully developed echinocyte.

Disruption of Primary Mesenchyme Cell Patterning by Misregulated Ectodermal Expression ofSpMsxin Sea Urchin Embryos

The patterning of the mesoderm of the sea urchin embryo is a classical paradigm of epithelial mesenchymal interactions in organogenesis, yet little is known of its molecular basis. Here we address the role of the homeobox gene,SpMsx,a member of the highly conservedMsxgene family, in this process.Msxgenes have been shown to function in the dorsoventral patterning of the central nervous system inDrosophilaand in a variety epithelial–mesenchymal interactions in vertebrates. We showed previously that theSpMsxgene is expressed during embryogenesis in a complex and dynamic pattern consistent with roles in the development of subpopulations of endoderm, mesoderm, and oral ectoderm. To perturb this pattern of expression and thus probe the function ofSpMsx,we injectedSpMsxmRNA into single-cell zygotes and monitored development morphologically and with a series of territory-specific molecular markers. RT-PCR analysis revealed that injectedSpMsxtranscripts persisted at least until the gastrula stage in amounts comparable to endogenous levels. Injected embryos exhibited deficiencies in the organization of primary and secondary mesenchyme cells within the blastocoelic cavity, as well as abnormalities in spicule number and shape. Defects in the endoderm were also common, including reduced or absent archenterons. Micromere transplantation experiments revealed that the defects in skeletogenic mesenchyme patterning were non-cell autonomous, consistent with findings that cell–cell interactions between ectoderm and the progenitors of the skeletogenic mesenchyme, the primary mesenchyme cells (PMCs), are important both for PMC guidance and spicule morphogenesis. Our data, taken together with observations in other organisms on the role ofMsxgenes in embryonic signaling processes, particularly involving the BMP pathway, suggest thatSpMsxmay be a part of the mechanism by which the ectoderm influences both the arrangement of primary mesenchyme cells within the blastocoel and the shapes of the skeletal rods.