Claw Development Research Articles

Construction of a soil clod recognition bench-scale experiment for discrete element method modeling of tilling phenomena

Rotary claws are used to break soil into small pieces and plow the soil flat. In this study, rotary claw development in tiller machines was evaluated using both equipment and the discrete element method (DEM). However, evaluation through equipment is imprecise and time consuming. Although DEM is an effective method for modeling the movement of granular materials, it requires numerous parameters to ensure accuracy, which must be determined through experimental evaluation and comparison. To resolve this concern, an image processing method was developed that leverages point cloud data obtained from a depth camera to capture changes in soil shape, distribution, and soil clod size before and after tilling. The effect of soil moisture content and claw rotation speed on soil clod formation and decomposition was evaluated. The experimental results show that the location, number, and soil clod size vary with soil moisture content and claw rotation speed. The results were compared with the DEM simulation to reconcile differences and confirm the feasibility of the proposed method. The model experiment system for soil clods and the image processing method facilitates a quantitative comparison between experimental and DEM simulated soil dispersal, which accelerates the search for DEM parameters to reproduce the tilling.

Characterization of novel cell-penetrating peptides derived from the capsid protein of beak and feather disease virus

Beak and feather disease virus (BFDV) is a 17-20 nm icosahedral virus belonging to the Circoviridae family. Psittacine beak and feather disease (PBFD) is caused by BFDV and its common symptoms include abnormal feather, beak, and claw development, as well as immunosuppression in various bird species. In this study, novel cell-penetrating peptides (CPPs) in the capsid protein (Cap) of BFDV were identified through bioinformatic analyses, after which they were experimentally characterized. The cell-penetrating activities of both CPP1 and CPP2 of BFDV were analyzed through flow cytometry and image analysis. The internalization of CPP1 and CPP2 was both dose- and time-dependent but their uptake efficiencies varied depending on the cell type. The cell-penetrating activities of BFDV CPP1 and CPP2 were both superior to that of a typical CPP-TAT originating from the viral protein of human immunodeficiency virus. The cellular uptake of 5 μM CPP1 was close to that of 25 μM TAT, albeit with less cytotoxicity. Using the identified CPPs, the pc-mCheery, pc-Rep, and pc-Cap plasmids were successfully delivered into the target cells for expression. Moreover, both the replication-associated protein with the tag and the Cap protein with the tag could also be successfully delivered into the cells by CPP1 and CPP2. Multiple endocytosis pathways and direct translocation were involved in the cell internalization of CPP1 and CPP2. Furthermore, the delivery of the apoptin gene using CPP1 and CPP2 effectively triggered apoptosis, thus confirming the potential of these CPPs as delivery vehicles. Similarly, green fluorescent protein (GFP) fused with CPP1 or CPP2 at their N-terminus successfully entered the cells. However, the cell internalization efficiency of CPP2-GFP was higher than that of CPP1-GFP. Taken together, our findings demonstrated that both CPP1 and CPP2 of BFDV have promising potential as novel CPPs.

Timing of organogenesis underscores the evolution of neonatal life histories and powered flight in bats.

Bats have undergone one of the most drastic limb innovations in vertebrate history, associated with the evolution of powered flight. Knowledge of the genetic basis of limb organogenesis in bats has increased but little has been documented regarding the differences between limb organogenesis in bats and that of other vertebrates. We conducted embryological comparisons of the timelines of limb organogenesis in 24 bat species and 72 non-bat amniotes. In bats, the time invested for forelimb organogenesis has been considerably extended and the appearance timing of the forelimb ridge has been significantly accelerated, whereas the timing of the finger and first appearance of the claw development has been delayed, facilitating the enlargement of the manus. Furthermore, we discovered that bats initiate the development of their hindlimbs earlier than their forelimbs compared with other placentals. Bat neonates are known to be able to cling continuously with their well-developed foot to the maternal bodies or habitat substrates soon after birth. We suggest that this unique life history of neonates, which possibly coevolved with powered flight, has driven the accelerated development of the hindlimb and precocious foot.

Like parent, like child – Ontogenetic development of claws of intertidal arthropods (Acari, Oribatida) from different ecological niches

The shape of claws of adult air-breathing intertidal oribatid mites shows a strong correlation with ecology. As nothing is known about juvenile characteristics of this trait, the ontogenetic development of these attachment devices was studied for the first time with comprehensive geometric morphometric methods. In nine investigated species, claws of immature stages can be classified into the same ecological categories as adults, i.e. juveniles of several rock-dwelling species already show higher and stronger curved claw shapes with smaller claw angles, while juvenile instars of the single investigated mangrove-dwelling species possess lower and less curved claws with wider claw angles. For each species, claw curvature is almost static during the complete development and claw length grows directly proportional with increasing body size. Developmental changes in body size and weight are thus mainly compensated by a simple relative growth in size. Despite the finding that claw shapes of early developmental stages are already classifiable into ecological categories, their shapes also change slightly during development to become more ‘rock’, ‘mix’ or ‘mangrove’-like, respectively. The present results demonstrate that ecology is also the most important factor in shaping the claws of immatures and that attachment in the intertidal environment is vital for the survival of each mobile stage.

Utilizing In Vivo Postnatal Electroporation to Study Cerebellar Granule Neuron Morphology and Synapse Development.

Neurons undergo dynamic changes in their structure and function during brain development to form appropriate connections with other cells. The rodent cerebellum is an ideal system to track the development and morphogenesis of a single cell type, the cerebellar granule neuron (CGN), across time. Here, in vivo electroporation of granule neuron progenitors in the developing mouse cerebellum was employed to sparsely label cells for subsequent morphological analyses. The efficacy of this technique is demonstrated in its ability to showcase key developmental stages of CGN maturation, with a specific focus on the formation of dendritic claws, which are specialized structures where these cells receive the majority of their synaptic inputs. In addition to providing snapshots of CGN synaptic structuresthroughout cerebellar development, this technique can be adapted to genetically manipulate granule neurons in a cell-autonomous manner to study the role of any gene of interest and its effect on CGN morphology, claw development, and synaptogenesis.

Immunolocalization of corneous beta proteins of the Epidermal Differentiation Complex in the developing claw of the alligator

Knowledge on the sharpness, mechanical and hydration resistance of the corneous material of claws requires information on its constituent proteins. The present immunohistochemical study has localized some of the main corneous beta proteins (CBPs, formerly termed beta-keratins) indicated to be present in alligator claws only by genomic data. Using specific antibodies we show the immunolocalization of representative claws CBPs of the Epidermal Differentiation Complex (Beta A1 group) during late stages of claw development in alligator. Intense but asymmetric proliferation, revealed by 5BrdU-immunolabeling, determines the formation of a curved dorsal part (unguis) and a linear ventral part (sub-unguis). The large beta-cells generated in the unguis and their packing into a solid corneous layer occur before thinner beta-cells appear in the sub-unguis. In the latter, CBPs are also immune-detected but with less intensity compared to the unguis, and corneocytes remain separated and desquamate. It is suggested that at the tip of the developing claw beta-corneocytes move downward into the initial part of the sub-unguis. This circular movement contributes to sharpen the claw as these cells fully cornify and are desquamated from the sub-unguis. Corneocytes of the unguis contain 10−16 kDa proline-serine-rich proteins that also possess high percentages of glycine, cysteine, tyrosine, valine and leucine. Cysteines likely give rise to numerous SS bonds in the constituent hard horny material, tyrosine contribute to packing proteins into a dense horny material while glycine, valine and leucine increase the hydrophobic property of claws in these water-adapted predators.

Evaluation of claw development in giant freshwater prawn, Macrobrachium rosenbergii (de Man, 1879)

Dynamics of claw development in Macrobrachium rosenbergii (de Man, 1879) was evaluated through monosex culture. The segregated males and females were stocked separately in two earthen ponds of 200 m2 area, at a density of 2.5 m-2 and reared for 3 months. Percentage contribution of claw weight to body weight (PCB) increased from 8.96 to 14.4% in the first month, but the change was minimal (14.4 to 17.19%) during the rest of the culture period. In order to delineate the relationship further, the data obtained was pooled together and classified into different classes based on the body weight (class interval 10 g). Interestingly, PCB in males decreased gradually upto 30 - 40 g weight class and then increased considerably for higher weight classes. But for females, the increase in PCB was marginal.

Developmental mechanisms underlying differential claw expression in the autopodia of geckos.

BackgroundThe limb and autopodium are frequently employed to study pattern formation during embryonic development, providing insights into how cells give rise to complex anatomical structures. With regard to the differentiation of structures at the distal tips of digits, geckos constitute an attractive clade, because within their ranks they exhibit multiple independent occurrences of claw loss and reduction, these being linked to the development of adhesive pads. The developmental patterns that lead to claw loss, however, remain undescribed. Among geckos, Tarentola is a genus characterized by large claws on digits III and IV of the manus and pes, with digits I, II, and V bearing only vestigial claws, or lacking them entirely. The variable expression of claws on different digits provides the opportunity to investigate the processes leading to claw reduction and loss within a single species.ResultsHere, we document the embryonic developmental dynamics that lead to this intraspecifically variable pattern, focusing on the cellular processes of proliferation and cell death. We find that claws initially develop on all digits of all autopodia, but, later in development, those of digits I, II, and V regress, leading to the adult condition in which robust claws are evident only on digits III and IV. Early apoptotic activity at the digit tips, followed by apoptosis of the claw primordium, premature ossification of the terminal phalanges, and later differential proliferative activity are collectively responsible for claw regression in particular digits.ConclusionsClaw reduction and loss in Tarentola result from differential intensities of apoptosis and cellular proliferation in different digits, and these processes have already had some effect before visible signs of claw development are evident. The differential processes persist through later developmental stages. Variable expression of iteratively homologous structures between digits within autopodia makes claw reduction and loss in Tarentola an excellent vehicle for exploring the developmental mechanisms that lead to evolutionary reduction and loss of structures.Electronic supplementary materialThe online version of this article (doi:10.1186/s13227-015-0003-9) contains supplementary material, which is available to authorized users.

Frizzled6 Deficiency Disrupts the Differentiation Process of Nail Development

Nails protect the soft tissue of the tips of digits. The molecular mechanism of nail (and claw) development is largely unknown, but we have recently identified a Wnt receptor gene, Frizzled6 (Fzd6) that is mutated in a human autosomal-recessive nail dysplasia. To investigate the action of Fzd6 in claw development at the molecular level, we compared gene expression profiles of digit tips of wild-type and Fzd6−/− mice, and show that Fzd6 regulates the transcription of a striking number of epidermal differentiation-related genes. Sixty-three genes encoding keratins, keratin associated proteins, and transglutaminases and their substrates were significantly down-regulated in the knockout mice. Among them, four hard keratins, Krt86, Krt81, Krt34 and Krt31; two epithelial keratins, Krt6a and Krt6b; and transglutaminase1 were already known to be involved in nail abnormalities when dysregulated. Immunohistochemical studies revealed decreased expression of Krt86, Krt6b and involucrin in the epidermal portion of the claw field in the knockout embryos. We further showed that Dkk4, a Wnt antagonist, was significantly down-regulated in Fzd6−/− mice along with Wnt, Bmp and Hh family genes; and Dkk4 transgenic mice showed a subtly but appreciably modified claw phenotype. Thus, Fzd6-mediated Wnt signaling likely regulates the overall differentiation process of nail/claw formation.

Development, comparative morphology and cornification of reptilian claws in relation to claws evolution in tetrapods

The development of claws in different reptiles and their cornification are analyzed using histological, ultrastructural and autoradiographic methods. Claws develop at the tip of digits in relation to the growth of the terminal phalanx and appear as modified scales. The apical epidermis of digit becomes thickened and is associated with a mesenchymal condensation or a dense mesenchyme. The dorsal side of the digit becomes the unguis while the ventral side becomes the sub-unguis. The corneous layer in the unguis is thicker than in the sub-unguis and accumulates hard-keratin while corneocytes remain separated or partially fused. Bundles of hard-keratin tend to accumulate in parallel orientation with respect to the surface and are directed toward the claw tip. The sub-unguis is formed by a softer corneous material and by a much thinner hard-keratin layer. Autoradiography after tritiated thymidine and histidine injection indicates that the growth of reptilian claws occurs along the entire epidermis of the claw. A proximal matrix zone for cell proliferation like in mammalian nails and claws is therefore absent in claws of reptiles. This observation indicates that the pattern of growth of reptilian and probably avian claws is different from that of mammals.

Raptorial Legs and Claws Are Not Influenced by Food Condition in Nymphal Stages of <I>Lethocerus deyrolli</I> (Heteroptera: Belostomatidae)

Previous studies have suggested that the developmental pattern of insect body parts is influenced by food conditions during the nymphal stages. In this study, we compared the developmental patterns of five body parts (body length, fore-femur length, mid-femur length, hind-femur length, and angle of claw) in the predatory insect Lethocerus deyrolli Vuillefroy fed three diets (tadpoles, Odonata nymphs, and tadpole–Odonata nymph mixture) during the nymphal stages. Significant age by sex interactions were detected in body length, fore-femur length, mid-femur length, and hind-femur length, indicating developmental patterns of these traits varied between sexes. Significant age by food interactions were detected in body length and hind-femur length and were marginally significant in mid-femur length, showing developmental patterns of these traits varied among food types. None of the interactions were significant in angle of the claw. A predation experiment was performed using double-claw nymphs as a control and one-claw nymphs (adult type) as a treatment. Double-claw nymphs successfully caught both large and small tadpoles, whereas one-claw nymphs caught small tadpoles more frequently than large tadpoles. Our results suggest that the claw development, which is very likely related to predatory function, may be less affected by nutritional conditions, and that double claws during nymphal stages may be indispensable to increased predation success.

Studies on the development of the claws in new born calves of different breeds and crossbreds using Dual Energy X-Ray Absorptiometry (DXA)

Abstract. This study evaluated claw development in 199 calves of different genetic background during the first 70 days of life. Dual Energy X-Ray Absorptiometry (DXA) was found to be a useful tool for this purpose. By the means of DXA, in humans as in animals, body constitution and composition can be examined in vivo. Thus, the whole body or body regions can be analyzed for the content of fat tissue, lean tissue, bone mineral content and bone mineral density. Large differences in claw parameters were observed, depending on the position of the claws, sex and breed, including interaction effects between gender and breeds. In all four pairs of claws, the medial claws had significantly higher contents of bone mineral than the lateral claws. All fore claws had a higher density than hind claws. Male calves showed significantly higher values than females in all measured parameters. Comparing breeds and crossbreds, pure German Holsteins had the lowest values in all parameters with exception of the R-value. Within breeds/crossbreds and gender various interactions could be found. Calves of first lactation cows had lower values than calves of elder cows. Calves with a small birth weight and calves originating of a multiple birth had significantly lower values of the scanned parameters than calves with higher birth weight or monoparous calves.

Studies on the growth and the development of the Claw capsule in new born calves of different breeding lines using linear measurements

Abstract. This study evaluated claw development in 80 calves of different genetic background during the first 70 days of life. Linear claw measurements were found to be useful tools for this purpose. Large differences in claw parameters were observed, depending on the position of the claws, gender and breeding line, including interaction effects between gender and breeding line. In all four pairs of claws, the medial claws were longer than the lateral claws. Claw width is significantly wider in lateral claws, both hind and fore. Male calves showed significantly higher values than females in most measured parameters except bulb length and angle of the bulb. Comparing breeding lines, significant differences in some parameters (claw width, length of the diagonal, sole length, axial wall length) were found, which are in discussion to be important in claw soundness. Older cows produced calves with larger claws than calves of younger cows.

Substrate Determinants and Developmental Rate of Claw Asymmetry in American Lobsters, Homarus Americanus

Abstract A new index was used to describe and quantify claw asymmetry for American lobsters, Homarus americanus. Length : width (L:W) ratios were calculated for each claw, and a measure of claw asymmetry (Ca) was computed as the percent reduction in the claw with the smaller L:W ratio. Fourth stage (first benthic stage) lobsters had relatively symmetrical claws, with L:W ratios of 4.3 in the cutter and 4.1 in the crusher claw, and a corresponding Ca value of 5.4%. Hatchery animals that could not differentially exercise one claw maintained a low average Ca value (2.5%). In adult animals, the L:W ratio decreased to a minimum of 2.7 for cutter claws, and 2.0 for crusher claws, giving a Ca value of 25.9%. This method was then used to assess claw development in animals exposed to one of four different natural substrates (cobble, shell, sand, and plant) in a hatchery setting. The development of claw asymmetry is known to be a function of increased exercise in one claw, and substrates allowing for more exercise ...

Development and evolution of the mammalian limb: adaptive diversification of nails, hooves, and claws.

Paleontological evidence indicates that the evolutionary diversification of mammals early in the Cenozoic era was characterized by an adaptive radiation of distal limb structures. Likewise, neontological data show that morphological variation in distal limb integumentary appendages (e.g., nails, hooves, and claws) can be observed not only among distantly related mammalian taxa but also among closely related species within the same clade. Comparative analysis of nail, claw, and hoof morphogenesis reveals relatively subtle differences in mesenchymal and epithelial patterning underlying these adult differences in distal limb appendage morphology. Furthermore, studies of regulatory gene expression during vertebrate claw development demonstrate that many of the signaling molecules involved in patterning ectodermal derivatives such as teeth, hair, and feathers are also involved in organizing mammalian distal limb appendages. For example, Bmp4 signaling plays an important role during the recruitment of mesenchymal cells into the condensations forming the terminal phalanges, whereas Msx2 affects the length of nails and claws by suppressing proliferation of germinal epidermal cells. Evolutionary changes in the form of distal integumentary appendages may therefore result from changes in gene expression during formation of mesenchymal condensations (Bmp4, posterior Hox genes), induction of the claw fold and germinal matrix (shh), and/or proliferation of epidermal cells in the claw matrix (Msx1, Msx2). The prevalence of convergences and parallelisms in nail and claw structure among mammals underscores the existence of multiple morphogenetic pathways for evolutionary change in distal limb appendages.

Effect of stage of development and pre-natal nutrition on hoof characteristics of fetal sheep

Lameness is a major welfare problem in farm animals and poor hoof (claw) health frequently causes painful lesions. Such lesions frequently arise from damage to the underlying dermal and epidermal soft tissues causing impaired production of the horn on the external surface of the claw (Budras et al., 1998) Precisely timed interactions between embryonic dermis and epidermis, are essential for normal development and function in other integumental tissues such as the hair follicle (Galbraith, 1998), but have not been confirmed for claw tissue. The time course of development of cellular and extra-cellular structures has not been described, nor has the question of whether fetal prenatal claw development may be affected by undernutrition of the ewe such as frequently occurs in extensive production systems. The aims of the study were to investigate external physical dimensions and internal cellular development of fetal claws and how these may be influenced by stage of gestation and maternal nutrition.

Muscle Restructuring in Crustaceans: Myofiber Death, Transfiguration and Rebirth

Research on the dimorphic claws of the snapping shrimp Alpheus has revealed moult-associated changes in structure and biochemical composition—including atrophy and biochemical modification—of claw muscle fibers during morphological transformation of a claw from a pincer to a snapper. Electrophysiology, SDS-PAGE gel electrophoresis, and immunocytochemistry were used to analyze changes in claw closer muscle function and composition during the transformation process. Remodification of closer muscle during claw transformation, involving the complete loss of a central section of fast-contracting fibers and their replacement through enlargement of existing slowly-contracting segments of the muscle, may mimic similar muscle modifications during initial claw development. Exposure of intact animals to environmental ecdysteroid hormones accelerated the rate of these changes. These processes appear to be a product of a remarkable trophic plasticity of crustacean skeletal muscle first discovered by Skinner.

Regeneration and sex-biased transformation of the sexually dimorphic pincer claw in adult snapping shrimps

Adult snapping shrimps Alpheus heterochelis have paired asymmetric claws, a large snapper which is similar in the sexes, and a much smaller pincer which is sexually dimorphic. The male pincer is slightly more hypertrophied compared to the female and therefore intermediate in size between the female pincer and the snapper. This has led to the suggestion that female pincer, male pincer and snapper represent a continuum in claw development. To test this possibility we examined regenerating snappers and found them to pass through a pincer-like stage in both sexes. In males they transiently possess the pincer-characteristic setose fringe. As well, the regenerating closer muscle shows a band of fast fibers reminiscent of the pincer closer muscle in both sexes. Since the male pincer more closely resembles the snapper in external and internal morphology than the female pincer, its transformation to a snapper may be more easily precipitated. To test this possibility we cut the snapper dactyl and this triggered transformation of the pincer to a snapper in 84% of male shrimps but only in 28% of female shrimps. During the intermolt in which the snapper dactyl is cut, axon numbers on the pincer side exceeded those on the snapper side in males but not in females. Since this shift in axon numbers favoring the pincer side occurs well before the pincer transforms to a snapper at the next molt it may signal transformation. J. Exp. Zool. 279:356–366, 1997. © 1997 Wiley-Liss, Inc.

Critical period for determining claw asymmetry in developing lobsters

AbstractThe pair of enlarged chelipeds or claws in the lobster Homarus americanus is differentiated into a major crusher claw with a closer muscle of slow fibers only and a minor cutter claw with a closer muscle of predominatly fast fibers. Claw placement is random and can be controlled by removing one claw in the juvenile 4th or 5th stage. This induces the contralateral intact claw to become a cruscher, while the regenerated claw develops into a cutter (Emmel, '08). Rearing lobsters with a substrate (oyster chips) promotes the development of class asymmetry, whereas a substrate‐free environment (smooth surface) promotes the development of paired cutter claws (Lang et al., '78). Consequently, by rearing lobsters with or without a substrate at selected periods of juvenile development, we have delimited the critical period for claw determination to the 5th stage. During this 2‐week period, the presence of a substrate for a period of at least five days is necessary for the development of claw asymmetry.

Muscle and Muscle Fiber Type Transformation In Clawed Crustaceans

SYNOPSIS. The first pair of thoracic limbs in many crustaceans is elaborated into claws in which the principal muscle is the closer. Changes in the fiber composition of the closer muscle during claw development, regeneration and reversal are reviewed here and the hypothesis is advanced that such changes are nerve-dependent. In adult lobsters, Homarus amencanus , the paired claws and closer muscles are bilaterally asymmetric, consisting of a minor or cutter claw with predominantly fast fibers and a small ventral band of slow and a major or crusher claw with 100% slow fibers. Yet in the larval and early juvenile stages the paired claws and closer muscles are symmetric consisting of a central band of fast fibers sandwiched by slow. Differentiation into a cutter or crusher muscle during subsequent juvenile development is by appropriate fiber type transformation. Experimental manipulation of the claws or the environment in early juvenile stages when the claws are equipotent revealed that the determination of claw and closer muscle asymmetry is dependent on the convergence of neural input from the paired claws: the point of convergence most likely being the CNS. Bilaterally symmetrical input results in the development of paired cutter claws while bilaterally asymmetric input gives rise to dimorphic, cutter and crusher claws. In the northern crayfish, Orconectes rusticus , where the paired claws are bilaterally similar, the closer muscle transforms its central band of fast fibers to slow, both during primary development and regeneration. Whether these fiber type transformations are nerve-dependent is unknown. In adult snapping shrimps, Alpheus sp., the paired claws and closer muscles are asymmetric: the minor or pincer claw has a central band of fast fibers flanked by slow while the major or snapper claw has 100% slow fibers. Claw reversal occurs with removal of the snapper resulting in the transformation of the existing pincer to a snapper and the regeneration of a new pincer at the old snapper site. Transformation of the closer muscle from pincer to snapper type is by degeneration of the fast fiber band and hypertrophy of the slow fibers. Claw transformation can be either prevented if the pincer nerve is sectioned at the time of snapper removal or promoted if the snapper nerve is sectioned: both results implicating a neural basis for muscle transformation.