Limb Structures Research Articles

A Single-Center Experience with Kidney Transplantation in the Verteberal, Anal, Cardiac, Tracheoesophageal, Renal, and Limb Birth Detects (VACTERL) Association

VACTERL association is a nonrandom association of birth defects in vertebral, anal, cardiac, tracheoesophageal, renal, and limb structures. Renal anomalies are observed in ∼60%–90% of VACTERL patients. We present 3 cases to demonstrate the clinical and surgical challenges that these patients present for renal transplantation. One pediatric and 2 adult patients with the VACTERL association were transplanted at a single center; their follow-up times were 6 years, 4 years, and 3 months. Only 1 of them had a suitable native bladder to receive the kidney graft; the other 2 required bladder augmentation, 1 of which was performed after the loss of the first graft. None of these patients had an uneventful posttransplantation course. Two patients had acute rejection episodes, and 2 had reoperations for urologic complications. One patient needed a surgical intervention owing to a sigmoid prolapse. All 3 grafts worked at last examination. The 2 patients with bladder reconstructions and longer follow-ups suffered recurrent pulmonary and urinary infections and had been hospitalized several times during each posttransplantation year. In conclusion, multiorgan involvement in VACTERL patients greatly complicates medical care after transplantation; urinary tract reconstruction seems to be essential before transplantation.

Design of Limb of 2R2T 4-DoF Symmetrical Parallel Manipulators

A systematic methodology is presented for design of 2R2T 4-DoF symmetrical parallel manipulators, based on the screw theory. Through analyse the given constraints of the moving platform, using the screw theory and the reciprocal screw theory. According to the reciprocal product between kinetic screw and constraint screw in screw theory, this method firstly creates possible limb structures and then generates different models of mechanism. enumerate the limb twist system. Based on the limb twist system, design the feasible limb structures and the potentially parallel manipulators.

Forward kinematic problem of 5-RPUR parallel mechanisms (3T2R) with identical limb structures

This paper investigates the formulation of the forward kinematic problem of the 5-DOF parallel mechanisms performing three translation and two independent rotations with identical limb structures. The mathematical framework used in this paper is based on algebraic geometry where the forward kinematic problem is explored in a seven-dimensional kinematic space by the means of the so-called Study parameters. In this paper, the algorithms proposed for obtaining the forward kinematic expression is based on two approaches which differ by their concept of eliminating passive variables. The first one is based on the application of the so-called resultant method and the second one, as a novel approach referred to as linear implicitization algorithm, uses an elimination procedure based on solving several systems of linear equations. The forward kinematic problem is solved using the homotopy continuation and it is revealed that it has 1680 finite solutions. Moreover, the forward kinematic problem is studied in three-dimensional Euclidean space where a class of simplified designs are proposed which admit a simpler formulation for the forward kinematic problem. Finally, based on the simplified designs, for a nearly general design a univariate expression of degree 220 is obtained.

Looking proximally and distally: 100 years of limb regeneration and beyond

The experimental study of amphibian limb regeneration spans most of the 20th century and the first decade of the 21st century. We first review the major questions investigated over this time span: (1) the origin of regeneration blastema cells, the mechanism of tissue breakdown that liberates cells from their tissue organization to participate in blastema formation, (3) the mechanism of dedifferentiation of these cells, (4) how the blastema grows, (5) how the blastema is patterned to restore the missing limb structures, and (6) why adult anurans, birds and mammals do not have the regenerative powers of urodele salamanders. We then look forward in a perspective to discuss the many unanswered questions raised by investigations of the past century, what new approaches can be taken to answer them, and what the prospects are for translation of basic research on limb regeneration into clinical means to regenerate human appendages.

Kinetics of jump landing in agility dogs

A recent survey reported an increased risk of injury in dogs participating in agility, a competitive canine sport involving different jumping activities. The aim of this study was to quantify the kinetic parameters during jump landing for commonly used obstacle types. It was hypothesised that with increasing obstacle height, the vertical force and vertical and accelerative horizontal impulse will increase as a result of a lengthened aerial phase, a more acute landing angle and the need to convert potential into forwards kinetic energy. Simultaneous kinetic and kinematic data were recorded from 11 competition agility dogs jumping over obstacle combinations of different height and inter-obstacle distance. Speed and landing angle of the second of the two consecutive jumps were successfully controlled by obstacle height and distance between obstacles. Statistical analysis showed differences between obstacles for peak vertical force, vertical impulse and accelerative horizontal impulse (increasing values with more acute landing angles). Extremely high peak vertical force was observed in the forelimbs (4.5 times bodyweight) when landing from a hurdle jump at high speed. Further detailed studies into the consequences for internal limb structures are warranted in order to clarify how this might be related to injury.

Identification of genes controlled by LMX1B in E13.5 mouse limbs

During limb development, the dorsal limb mesenchyme expression of the transcription factor LMX1B is required for dorsoventral limb patterning. In mice, Lmx1b mutations result in the mirror-image duplication of ventral limb structures and loss of dorsal limb structures. Heterozygous LMX1B mutations in humans cause the Nail-Patella Syndrome characterized by limb, kidney, and eye developmental defects. We used DNA microarrays to compare the mRNAs in E13.5 mouse Lmx1b mutant and wild-type limbs. We report 14 genes that require Lmx1b for their normal expression in the dorsal limb or the restriction of their expression to the ventral limb.

X-ray micro-tomography of Carboniferous stem-Dictyoptera: new insights into early insects

Computer reconstructions of Archimylacris eggintoni, a Carboniferous stem-group dictyopteran ('roachoid'), are presented. A siderite-hosted specimen was scanned using high-resolution X-ray microtomography (µCT), and a 'virtual fossil' was created with a resolution of 17.7 µm. This has revealed the morphology in great detail, including adhesive limb structures indicative of climbing and specializations for rapid movement. The antennae are filiform, and the mandibles are comparable to those of certain extant cockroaches, suggesting a similar generalist, saprophagous diet. The reconstruction reveals a high degree of specialization, and provides insights into the mode of life of these common Palaeozoic insects. Further µCT study of insect fossils has the potential to supplement wing venation with new characters, and hence improve fossil insect phylogenies.

The Clinical Relevance of Teaching the Medial line Theme of the Lower Limb to Future Healthcare Professionals

ObjectiveThis project investigated the current common overview approaches to lower limb anatomy teaching and suggests an alternative technique. Introduction. The overview of the lower limb is often described as thigh, leg and foot regions, and subdivided into anterior, posterior, medial and lateral compartments. This method guarantees all structures of the lower limb are taught. Virtually all healthcare institutions have had to distill anatomy into accelerated courses.MethodsLiterature search was conducted regarding teaching techniques of the lower limb and morphology of 60 dissected embalmed cadavers was observed to assess patterns which correlate with common clinical conditions and techniques.ResultsLiterature review revealed no specific teaching techniques. However, observations commonly revealed compartment and/or systems layout. Dissections revealed an overwhelming number of clinically important structures along the medial line of the lower limb. Reinforcement or stability structures, venous access, arterial supply, and nerves were emphasized greater along the medial line versus the lateral line.DiscussionAnatomy courses have resulted in less student‐instructor contact time. Specific techniques would aid the efficiency of learning. This project demonstrates that emphasizing lower limb structures along the medial line would be a useful technique teaching future clinicians.

Automatic Detection of Limb Prominences in 304 Å EUV Images

A new algorithm for automatic detection of prominences on the solar limb in 304 Å EUV images is presented, and results of its application to SOHO/EIT data discussed. The detection is based on the method of moments combined with a classifier analysis aimed at discriminating between limb prominences, active regions, and the quiet corona. This classifier analysis is based on a Support Vector Machine (SVM). Using a set of 12 moments of the radial intensity profiles, the algorithm performs well in discriminating between the above three categories of limb structures, with a misclassification rate of 7%. Pixels detected as belonging to a prominence are then used as the starting point to reconstruct the whole prominence by morphological image-processing techniques. It is planned that a catalogue of limb prominences identified in SOHO and STEREO data using this method will be made publicly available to the scientific community.

The Great Divides: Ardipithecus ramidus Reveals the Postcrania of Our Last Common Ancestors with African Apes

Genomic comparisons have established the chimpanzee and bonobo as our closest living relatives. However, the intricacies of gene regulation and expression caution against the use of these extant apes in deducing the anatomical structure of the last common ancestor that we shared with them. Evidence for this structure must therefore be sought from the fossil record. Until now, that record has provided few relevant data because available fossils were too recent or too incomplete. Evidence from Ardipithecus ramidus now suggests that the last common ancestor lacked the hand, foot, pelvic, vertebral, and limb structures and proportions specialized for suspension, vertical climbing, and knuckle-walking among extant African apes. If this hypothesis is correct, each extant African ape genus must have independently acquired these specializations from more generalized ancestors who still practiced careful arboreal climbing and bridging. African apes and hominids acquired advanced orthogrady in parallel. Hominoid spinal invagination is an embryogenetic mechanism that reoriented the shoulder girdle more laterally. It was unaccompanied by substantial lumbar spine abbreviation, an adaptation restricted to vertical climbing and/or suspension. The specialized locomotor anatomies and behaviors of chimpanzees and gorillas therefore constitute poor models for the origin and evolution of human bipedality.

Solution Structure and Phylogenetics of Prod1, a Member of the Three-Finger Protein Superfamily Implicated in Salamander Limb Regeneration

BackgroundFollowing the amputation of a limb, newts and salamanders have the capability to regenerate the lost tissues via a complex process that takes place at the site of injury. Initially these cells undergo dedifferentiation to a state competent to regenerate the missing limb structures. Crucially, dedifferentiated cells have memory of their level of origin along the proximodistal (PD) axis of the limb, a property known as positional identity. Notophthalmus viridescens Prod1 is a cell-surface molecule of the three-finger protein (TFP) superfamily involved in the specification of newt limb PD identity. The TFP superfamily is a highly diverse group of metazoan proteins that includes snake venom toxins, mammalian transmembrane receptors and miscellaneous signaling molecules.Methodology/Principal FindingsWith the aim of identifying potential orthologs of Prod1, we have solved its 3D structure and compared it to other known TFPs using phylogenetic techniques. The analysis shows that TFP 3D structures group in different categories according to function. Prod1 clusters with other cell surface protein TFP domains including the complement regulator CD59 and the C-terminal domain of urokinase-type plasminogen activator. To infer orthology, a structure-based multiple sequence alignment of representative TFP family members was built and analyzed by phylogenetic methods. Prod1 has been proposed to be the salamander CD59 but our analysis fails to support this association. Prod1 is not a good match for any of the TFP families present in mammals and this result was further supported by the identification of the putative orthologs of both CD59 and N. viridescens Prod1 in sequence data for the salamander Ambystoma tigrinum.Conclusions/SignificanceThe available data suggest that Prod1, and thereby its role in encoding PD identity, is restricted to salamanders. The lack of comparable limb-regenerative capability in other adult vertebrates could be correlated with the absence of the Prod1 gene.

In Situ Hybridization on Ant Ovaries and Embryos

The detection of transcript distribution throughout a fixed tissue is a major step in studying the transcriptional activity of target genes and their function. In situ hybridization specifically detects the spatial distribution of RNA transcripts using an antisense RNA probe. This protocol describes the preparation of digoxigenin-labeled antisense RNA probes and their hybridization to complementary mRNA sequences; expression can then be localized using an antibody against digoxigenin conjugated to a chromogenic enzyme. In ants, this method can be applied to visualize cell populations of interest among other populations in a tissue, such as insect ovaries, or in the whole organism, such as insect embryos. Specific markers (e.g., genes known to be expressed in particular clusters of cells) can be cloned and used as probes to study the distribution and development of germline cells (e.g., nanos, vasa), neurons (repo), or limb structures (e.g., distal-less). Various markers might also allow the study of oogenesis (nanos, par-1, oskar), segmentation in the embryo (e.g., engrailed, wingless), or other developmental processes.

Cell Signaling Regulation of Vertebrate Limb Growth and Patterning

Limb development is a well-coordinated three-dimensional process in which limb-bud outgrowth and patterning along the different axes of development are intimately linked through interactions of the signaling molecules that mediate the function of three key signaling centers. The vertebrate limb develops from a primordial embryonic limb bud, consisting of a homogeneous mesoderm core covered by an ectodermal jacket, and development of the limb bud is an autonomous process controlled by these signaling centers, which are formed through epithelial-mesenchymal interactions. The major signaling centers in the limb each direct limb development along one of the three axes: proximodistal (from shoulder to digit tip), anteroposterior (from digit 1, or thumb, to digit 5, or small finger) and dorsoventral (from the dorsum to the palm of the hand) (Table I). View this table: TABLE I Signaling Pathways During Embryogenesis These signaling centers were identified by classic embryological experiments; recent molecular genetic studies in both the mouse and the chick have revealed signaling molecules that mediate the functions of these centers1. Although they only act early in the limb bud, these signaling centers have a profound influence on limb morphology by providing positional cues that determine the shape and spatial organization, as well as the temporal order of formation, of limb structures such as bones and tendons. We will describe several of the known links between the different development axes and give examples of the ways in which genetic mutations or disrupted embryonic development can affect these signaling events and cause longitudinal deficiencies and other malformations in humans and in mouse genetic mutants. The first signaling center to appear is the apical ectodermal ridge (AER), which is a thickened epithelial structure at the distal tip of the limb bud. In human embryos, limb initiation occurs at twenty-six days post coitum; in the mouse, the limb bud …

Cre/lox recombination in the lower urinary tract

Tbx18 is a T-Box transcription factor that has specific expression and indispensible function in the lower urinary tract. Here, we report the generation and characterization of a bacterial artificial chromosome (BAC) transgene expressing Cre under the control of Tbx18 regulatory elements. When crossed to the ROSA26R-lacZ reporter mice, the Tbx18-Cre transgene mediates loxP recombination in the mesenchymal derivatives in the lower urinary tract, especially in the smooth muscle cells (SMCs) and the stromal cells. There is no expression of this transgene in the urothelium or in the kidney. This Tbx18-Cre transgene recapitulates the endogenous Tbx18 expression in the urinary system and can be used for the study of the development, physiology, and diseases in the urinary tract. Its additional expression in the epicardium, limb, vibrissae, and other structures would be useful for studies in the relevant fields.

Notes on chydorid endemism in continental Africa: Matralona gen. n., a monotypic Alonine from the Fouta Djalon Plateau (Guinea, West Africa) (Crustacea: Cladocera: Anomopoda)

A study of the morphology of Alona simonei Dumont, 1981, here emended to Alona simoneae, from the ancient Fouta Djalon Plateau in Guinea (West Africa) reveals unique limb structures. We allocate this species to the monotypic Matralona gen. n. and consider it a relict of an Alona-like clade. Matralona gen. n. is another example of divergence in limb morphology among externally similar Aloninae. Separation of this monotypic genus is based on more than autapomorphies alone and we include arguments for significant isolation from the ancestral stock. Within the Aloninae, Matralona gen. n. shows closest affinities with the Australasian genus Armatalona Sinev, 2004. Both taxa may share a common ancestor. Matralona gen. n. is one of the most peculiar African Chydoridae with no close relatives on the continent. We discuss a few areas of endemism in Chydoridae that begin to emerge on continental Africa.

The role of early development in mammalian limb diversification: A descriptive comparison of early limb development between the natal long‐fingered bat (Miniopterus natalensis) and the mouse (Mus musculus)

Comparative embryology expands our understanding of unique limb structures, such as that found in bats. Bat forelimb digits 2 to 5 are differentially elongated and joined by webbing, while the hindlimb digits are of similar length in many species. We compare limb development between the mouse and the Natal long-fingered bat, Miniopterus natalensis, to pinpoint the stage at which their limbs begin to differ. The bat forelimb differs from the mouse at Carollia stage (CS) 14 with the appearance of the wing membrane primordia. This difference is enhanced at CS 15 with the posterior expansion of the hand plate. The bat hindlimb begins to differ from the mouse between CS 15 and 16 when the foot plate undergoes a proximal expansion resulting in digit primordia of very similar length. Our findings support recent gene expression studies, which reveal a role for early patterning in the development of the bat limb.

Ectopic Meis1 expression in the mouse limb bud alters P-D patterning in a Pbx1-independent manner

During limb development, expression of the TALE homeobox transcription factor Meis1 is activated by retinoic acid in the proximal-most limb bud regions, which give rise to the upper forelimb and hindlimb. Early subdivision of the limb bud into proximal Meis-positive and distal Meis-negative domains is necessary for correct proximo-distal (P-D) limb development in the chick, since ectopic Meis1 overexpression abolishes distal limb structures, produces a proximal shift of limb identities along the P-D axis, and proximalizes distal limb cell affinity properties. To determine whether Meis activity is also required for P-D limb specification in mammals, we generated transgenic mice ectopically expressing Meis1 in the distal limb mesenchyme under the control of the Msx2 promoter. Msx2:Meis1 transgenic mice display altered P-D patterning and shifted P-D Hox gene expression domains, similar to those previously described for the chicken. Meis proteins function in cooperation with PBX factors, another TALE homeodomain subfamily. Meis-Pbx interaction is required for nuclear localization of both proteins in cell culture, and is important for their DNA-binding and transactivation efficiency. During limb development, Pbx1 nuclear expression correlates with the Meis expression domain, and Pbx1 has been proposed as the main Meis partner in this context; however, we found that Pbx1 deficiency did not modify the limb phenotype of Msx2:Meis1 mice. Our results indicate a conserved role of Meis activity in P-D specification of the tetrapod limb and suggest that Pbx function in this context is either not required or is provided by partners other than Pbx1.

Disruption of an AP-2α binding site in an IRF6 enhancer is associated with cleft lip

Previously we have shown that nonsyndromic cleft lip with or without cleft palate (NSCL/P)1, is strongly associated with SNPs in Interferon Regulatory Factor 6 (IRF6)2. Here, multispecies sequence comparisons identify a common SNP (rs642961, G>A) in a novel IRF6 enhancer. The A allele is significantly overtransmitted (P=1×10−11) in families with NSCL/P, in particular with cleft lip (CL) but not cleft palate. Further, there is a dosage effect of the A allele, with the relative risk for CL 1.68 for the AG genotype and 2.40 for the AA genotype. EMSA and ChIP assays demonstrate that the risk allele disrupts the binding site of transcription factor AP-2α and expression analysis in the mouse localizes the enhancer activity to craniofacial and limb structures. Our findings place IRF6 and AP-2α in the same developmental pathway and identify a high frequency variant in a regulatory element contributing substantially to a common, complex disorder.

The Mouse Limb Anatomy Atlas: An interactive 3D tool for studying embryonic limb patterning

BackgroundThe developing mouse limb is widely used as a model system for studying tissue patterning. Despite this, few references are available that can be used for the correct identification of developing limb structures, such as muscles and tendons. Existing textual references consist of two-dimensional (2D) illustrations of the adult rat or mouse limb that can be difficult to apply when attempting to describe the complex three-dimensional (3D) relationship between tissues.ResultsTo improve the resources available in the mouse model, we have generated a free, web-based, interactive reference of limb muscle, tendon, and skeletal structures at embryonic day (E) 14.5 . The Atlas was generated using mouse forelimb and hindlimb specimens stained using immunohistochemistry to detect muscle and tendon. Limbs were scanned using Optical Projection Tomography (OPT), reconstructed to make 3D models and annotated using computer-assisted segmentation tools in Amira 3D Visualisation software. The annotated dataset is visualised using Java, JAtlasView software. Users click on the names of structures and view their shape, position and relationship with other structures within the 3D model and also in 2D virtual sections.ConclusionThe Mouse Limb Anatomy Atlas provides a novel and valuable tool for researchers studying limb development and can be applied to a range of research areas, including the identification of abnormal limb patterning in transgenic lines and studies of models of congenital limb abnormalities. By using the Atlas for "virtual" dissection, this resource offers an alternative to animal dissection. The techniques we have developed and employed are also applicable to many other model systems and anatomical structures.

All‐trans retinoic acid‐induced ectopic limb and caudal structures: Murine strain sensitivities and pathogenesis

Treatment of pregnant mice at the egg cylinder stage with retinoic acid (RA) has caused ectopic hindlimbs in the offspring. Proposed causes of ectopic hindlimbs include homeotic transformation or multiple axis formation. Two mouse strains were determined to be divergent in susceptibility to this malformation (C57BL/6N, highly sensitive; SWV/Fnn, less sensitive). Ectopic limbs were hindlimbs (expressing Pitx1 and Tbx4 but not Tbx5), yet they also expressed the predominantly forelimb Hoxb8. Ectopic body axis formation was indicated by gene expression for ectopic primitive streaks, notochords, and nodes, as well as inhibition of anterior visceral endoderm and mesodermal migration. The earlier in development that embryos were examined, the higher the rate of ectopic hindlimb development and axis formation. Ectopic axis formation and cell migration inhibition had the same strain susceptibility as the dysmorphogenesis. We propose that all extra hindlimbs were derived from ectopic axis formation, perturbation of which is genetic background dependent.