bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolutionary aspects of positioning and identification of vertebrate limbs
Authors: TAMURA KOJI , KURAISHI RITSU , SAITO DAISUKE , MASAKI HIDEKI , IDE HIROYUKI , YONEI‐TAMURA SAYURI 
Published: March 2003

abstractEmerging developmental studies contribute to our understanding of vertebrate evolution because changes in the developmental process and the genes responsible for such changes provide a unique way for evaluating the evolution of morphology. Endoskeletal limbs, the locomotor organs that are unique to vertebrates, are a popular model system in the fields of palaeontology and phylogeny because their structure is highly visible and their bony pattern is easily preserved in the fossil records. Similarly, limb development has long served as an excellent model system for studying vertebrate pattern formation. In this review, the evolution of vertebrate limb development is examined in the light of the latest knowledge, viewpoints and hypotheses.
The cellular networks of normal ovine medial collateral and anterior cruciate ligaments are not accurately recapitulated in scar tissue
Authors: Lo Ian K. Y. , Ou Yong , Rattner John‐Paul , Hart David A. , Marchuk Linda L. , Frank Cyril B. , Rattner Jerome B. 
Published: March 2003

AbstractThe purpose of this study was to characterize the cellular organization of the ovine medial collateral ligament (MCL) and anterior cruciate ligament (ACL) and compare this organization with that found in ligaments undergoing healing. Indirect immunofluorescence microscopy, used in combination with antibodies to cytoskeletal proteins, was employed to visualize individual ligament cells. Normal ligaments contained fusiform cells arranged in rows, which were stacked at regular intervals across the body of the ligament forming a three‐dimensional cellular lattice. Each cell exhibited prominent cytoplasmic processes that extended for long distances through the extracellular matrix to adjacent cells, and these processes contained gap junctions. Thus the cells in rows and between rows were interconnected. The cells of the MCL and ACL scars were also arranged in rows, but these rows were shorter, irregularly arranged and closely packed into bundles resulting in tissue with a higher cellular density. In addition, cells transiting the cell cycle were detected in the scar but not in normal ligament. While the rows of cells in the normal ligament extended along the long axis of the ligament, the bundles of rows of ligament scar cells had a random orientation with respect to one another and to the region outside the scar. Over time both the ACL and the MCL scars displayed discontinuities in their cellular rows. In contrast to the scars of the MCL, which contained discontinuities filled with cellular projections and gap junctions, ACL scars contained discontinuities that were devoid of cells and gap junctions. These discontinuities as well as the differences between normal and scar cytoarchitecture may represent features of an inadequate healing response and/or may provide the structural basis for the altered biomechanics of healing ligaments.
Understanding Schwann cell–neurone interactions: the key to Charcot–Marie–Tooth disease?*
Authors: Maier Marcel , Berger Philipp , Suter Ueli 
Published: March 2003

AbstractCharcot–Marie–Tooth disease (CMT) comprises a heterogeneous group of disorders. The most frequent subtype is caused by increased PMP22 gene dosage or missense point mutations affecting the PMP22 gene (CMT type 1A; CMT1A). Animal models in rat and mouse with the corresponding PMP22 alterations are available and mimic many aspects of the human diseases. Detailed examinations of the animal mutants, together with complementary data from patients, point towards altered Schwann cell–neurone interactions as a major underlying mechanism of CMT1A and related hereditary neuropathies. This is evident from the finding that mutated proteins affecting either Schwann cells or neurones have a profound influence on their partner cells. Recently, a number of novel genes causing various forms of CMT have been identified which are expressed either mainly by Schwann cells and/or by the accompanying neurones. These genes can be viewed, in analogy to classic experiments routinely performed in lower vertebrates, as the result of a ‘functional screen’ revealing crucial players in the interactions between Schwann cells and neurones. Studying how Schwann cell and axon‐encoded proteins are functionally interconnected will be an exciting task for the future. It will not only yield insights into the molecular and cellular basis of neuropathies but also provide crucial information about the interplay between Schwann cells and neurones in general.
Functional and morphological consequences of removing astrocytes from the in vivo blood–brain barrier
Authors: Ray D. E. , Mavroudis G. , Prior M. J. W. , Guérin C. J. , Nolan C. C. 
Published: March 2003

Our purpose was to attempt to determine the role of astrocytes in the maintenance and repair of the blood–brain barrier in adult F344 rats. Systemic administration of the glyceraldehyde‐3‐phosphate dehydrogenase inhibitor S‐alpha‐chlorohydrin produces selective destruction of astrocytes within specific brain stem nuclei (Cavanagh et al. Neuropath. Appl. Neurobiol. 19, 1993). At appropriate dose levels (140–160 mg/kg i.p.) other brain areas are undamaged, which allows the full time course of the response of sensitive areas to be studied in rats showing relatively little functional impairment. All experiments were carried out in accordance with UK Home Office requirements. Lesion development was followed by in vivo Magnetic Resonance Imaging, by post mortem immunohistochemistry and confocal microscopy, or electron microscopy. Barrier function was studied by the permeation of fluorescent conjugated dextrans of 3–500 KDa molecular weight given intravenously 1 h before perfusion with fixative, and visualised by confocal microscopy (Guérin et al. Neurosci. 103, 2001).Astrocytic death was seen throughout areas such as the inferior colliculi and vestibular nuclei over 6–24 h and was followed by secondary neuronal death and a microglial reaction from 48 h. After a delay of about 12 h following the loss of astrocytes, endothelial cells become permeable to dextran for up to 4 d and then recovered. This recovery was seen in the absence of direct contact with astrocytes, as determined by immunohistochemistry and electron microscopy.Since chlorohydrin does not increase endothelial monolayer permeability in vitro (Romero et al. Neurotoxicol. 18, 1997), we hypothesise that this transient loss of barrier function in vivo represents a partial dedifferentiation in response to loss of astrocytic contact. The subsequent restoration of endothelial barrier function in areas devoid of astrocytes represents the first in vivo demonstration that direct astrocytic contact is not needed for establishment of the blood–brain barrier.
Complementary actions of VEGF and angiopoietins on blood vessel permeability and growth in mice
Authors: Thurston G. 
Published: March 2003

The families of vascular endothelial growth factors (VEGFs) and angiopoietins regulate blood vessel growth, maturation and function via distinct endothelial‐cell specific tyrosine kinase receptors. We have gained some insight into the actions of these growth factors by comparing 2 systems in which VEGF or angiopoietin‐1 (Ang1) was overexpressed in mice. In one set of studies we compared the blood vessels in the skin of transgenic mice in which VEGF, angiopoietin‐1, or both factors, were expressed locally under the keratin‐14 (K14) promoter. Mice overexpressing VEGF (K14‐VEGF) had numerous tortuous capillary‐sized skin vessels which were leaky to the plasma tracer Evans blue under baseline conditions and became even leakier in response to inflammatory stimuli such as topical mustard oil. The dermis of K14‐VEGF mice was increased in thickness and contained numerous infiltrating leukocytes. In contrast mice overexpressing angiopoietin‐1 had increased size of vessels in the skin without a significant increase in vessel number. Furthermore the skin vessels in K14‐Ang1 mice were less leaky than those of wild‐type mice in response to inflammatory stimuli and did not leak under baseline conditions. The dermal thickness was normal and there were normal dermal leukocytes. In double transgenic mice overexpressing both factors, both the size and number of skin vessels were increased, however, the vessels were not abnormally leaky under baseline or inflammatory conditions and the dermis was relatively normal. In a second set of studies we compared the effects of systemically delivered VEGF or angiopoietin‐1 using an adenoviral‐mediated system to produce the factors in vivo. Intravenous injection of adenovirus encoding VEGF (Ad‐VEGF) into mice resulted in widespread tissue oedema within 1–2 d after administration. In contrast injection i.v. of Ad‐Ang1 resulted in the skin vessels becoming less leaky in response to topical inflammatory stimuli or local injection of VEGF. The decreased leakage in the skin vessels was found at one day after Ad‐Ang1 injection, was not accompanied by morphologic changes, and was reproduced by systemic administration of recombinant Ang1 proteins. Thus overexpression of VEGF appears to promote growth of new vessels accompanied by plasma leakage and inflammation, whereas overexpression of Ang1 promotes the enlargement of existing vessels and a decrease in inflammation induced leakage. Further understanding of the interrelationship of these factors during normal development could lead to their application in the treatment of ischaemic diseases.Studies were supported in part by NIH HL59157.
Aquaporin‐4 water channel expression in human vasogenic brain oedema
Authors: Geeson F. , Saadoun S. , Papadopoulos M. C. , Bell B. A. , Davies D. C. 
Published: March 2003

A number of brain lesions result in brain oedema formation. This oedema is considered to be vasogenic in nature, resulting from breakdown of the blood–brain barrier. Brain microvessels are surrounded by astrocyte foot processes that express the water channel protein aquaporin 4 (aqp4). Aqp4 has been implicated in the formation of vasogenic oedema in animal models, but little is known about its involvement in vasogenic oedema in man. Therefore formalin‐fixed samples of a variety of brain lesions that give rise to brain oedema were obtained from 17 patients who underwent craniotomy at atkinson morley’s hospital during 1993–9. Immunocytochemistry was then performed on the samples using a polyclonal aqp4 antibody (ab3068, chemicon) visualised with immunoperoxidase and diaminobenzidine hydrochloride. In histologically normal cerebral cortex (n = 1) aqp4 immunoreactivity was restricted to astrocyte foot processes lining the pial membrane and surrounding some microvessels. In contused cortex (n = 3) astrocyte aqp4 expression was up‐regulated in accordance with the degree of tissue damage and the severity of oedema, assessed by contrast enhancement on ct. Aqp4 immunoreactivity was not present in nonastrocytic tumour cells including adenocarcinoma (n = 4), meningioma (n = 4), oligodendroglioma (n = 1) and medulloblastoma (n = 1). However diffuse aqp4 immunoreactivity was present in cells with the morphology of reactive astrocytes at the periphery of these tumours and occasionally ‘trapped’ within them. In addition up‐regulation of aqp4 immunoreactivity was observed in astrocyte end feet surrounding the microvessels in the perimeningioma cortex. Diffuse aqp4 immunoreactivity was observed in a subependyal astrocytoma (n = 1). Strong aqp4 immunolabelling of astrocytes was observed in cerebral cortex affected by bacterial meningitis (n = 1). Up‐regulation of aqp4 immunoreactivity was also observed in the foot processes of astrocytes lining the pial membrane and surrounding microvessels in this tissue. Up‐regulation of aqp4 immunoreactivity was not observed in brain tissue affected by subarachnoid haemorrhage (n = 1), from a patient who did not show any evidence of oedema on ct. Therefore brain lesions with different aetiologies that result in vasogenic brain oedema appear to cause a similar up‐regulation of aqp4 expression in astrocytes associated with the lesions. These results suggest that aqp4 up‐regulation in astrocytes may be part of a ‘final common pathway’ leading to oedema formation.
Patterning of the axial musculature in the developing chick embryo (Gallus)
Authors: Adds P. J. , Robson L. G. 
Published: March 2003

While the development and patterning events of the skeletal, myogenic and connective tissues of the developing limb buds of the chick have been relatively well studied, there is little known about the formation of the epaxial muscles and tendons. The epaxial muscles form the postvertebral muscle groups and develop from the myotome of the somite. The myotome develops from myogenic precursors migrating from the dorsomedial lip of the dermomyotome. These myogenic cells differentiate in a cranial to caudal sequence with the muscle fibres also orientated in a cranial to caudal direction.Here we use immunohistological staining both in whole mount and in transverse sections of chick embryos from various stages of development. Antibodies to the myosin heavy chain or tenascin were used to visualise the development of the epaxial muscles and tendons.The first myotomal muscle fibres are differentiated by Hamburger and Hamilton (H & H) stage 10 in the cranial somites, and differentiation proceeds caudally until at least H & H stage 22–23. Further development of the epaxial muscles does not take place until H & H stage 26–27 with the splitting of the myotome into the individual muscles. We demonstrate how the myotome splits into the individual muscles and how some muscle fibres become reorientated into a more oblique orientation. This delayed development and reorientation of muscle fibres is unique to the epaxial muscles.
The F‐actin cytoskeleton of neurons following microinjection with the small GTPase V14 RhoA
Authors: Bird M. M. 
Published: March 2003

A recently refined technique for microinjecting proteins into small cells (Bird et al. J. Anat.198, 2001) has been used to examine changes in the morphology and F‐actin cytoskeleton of cultured spinal cord neurons following microinjection of IgG alone or in conjunction with V14 Rhoa, a small gtpase known to cause changes in the actin cytoskeleton.Dissociated cell cultures from embryonic chick spinal cord (E7) were plated out onto glass coverslips in Ham’s F12 culture medium, incubated at 37 °C and re‐fed at intervals of 72 h. After 10 d in culture iindividual neurons were microinjected with V14RhoA (1 mg/mL), and/or IgG (to identify injected cells). The cultures were incubated at 37 °C for a further 20 min before fixation in 3.7% formaldehyde. The cells were washed permeabilised with 0.2% Triton X‐100 in PBS and then washed prior to immersion in buffer containing TRITC‐labelled phalloidin and FITC‐labelled anti rat IgG. The cultures were mounted in Mowiol containing a grain of antiquench and viewed on a confocal laser microscope.Microinjected cells showed spread of injectate throughout the cell body and into the proximal parts of the major dendrites. On the rare occasions when the nucleus was injected IgG did not escape into the cytoplasm. In control cells the F‐actin was concentrated close to the cell membrane in cell bodies and in specific parts of the growth cone. When cells were injected with V14RhoA there was an increase in the number of actin containing microspikes on the cell soma and major dendrites close to the origin of the presumptive axon. Near the substrate increased numbers of podosomes were also observed. More varicosities were found in both axons and dendrites after injection with V14RhoA.The changes in the F‐actin cytoskeleton after V14RhoA injections were observed within 30 min of the injections. Although some of the changes were similar to those observed in fibroblasts others, such as the presence of varicosities, were unique to neurons.
Astrocyte–endothelial interactions and blood–brain barrier permeability*
Authors: Abbott N. Joan 
Published: March 2003

AbstractThe blood–brain barrier (BBB) is formed by brain endothelial cells lining the cerebral microvasculature, and is an important mechanism for protecting the brain from fluctuations in plasma composition, and from circulating agents such as neurotransmitters and xenobiotics capable of disturbing neural function. The barrier also plays an important role in the homeostatic regulation of the brain microenvironment necessary for the stable and co‐ordinated activity of neurones. The BBB phenotype develops under the influence of associated brain cells, especially astrocytic glia, and consists of more complex tight junctions than in other capillary endothelia, and a number of specific transport and enzyme systems which regulate molecular traffic across the endothelial cells. Transporters characteristic of the BBB phenotype include both uptake mechanisms (e.g. GLUT‐1 glucose carrier, L1 amino acid transporter) and efflux transporters (e.g. P‐glycoprotein). In addition to a role in long‐term barrier induction and maintenance, astrocytes and other cells can release chemical factors that modulate endothelial permeability over a time‐scale of seconds to minutes. Cell culture models, both primary and cell lines, have been used to investigate aspects of barrier induction and modulation. Conditioned medium taken from growing glial cells can reproduce some of the inductive effects, evidence for involvement of diffusible factors. However, for some features of endothelial differentiation and induction, the extracellular matrix plays an important role. Several candidate molecules have been identified, capable of mimicking aspects of glial‐mediated barrier induction of brain endothelium; these include TGFβ, GDNF, bFGF, IL‐6 and steroids. In addition, factors secreted by brain endothelial cells including leukaemia inhibitory factor (LIF) have been shown to induce astrocytic differentiation. Thus endothelium and astrocytes are involved in two‐way induction. Short‐term modulation of brain endothelial permeability has been shown for a number of small chemical mediators produced by astrocytes and other nearby cell types. It is clear that endothelial cells are involved in both long‐ and short‐term chemical communication with neighbouring cells, with the perivascular end feet of astrocytes being of particular importance. The role of barrier induction and modulation in normal physiology and in pathology is discussed.
Quantifying temporal bone morphology of great apes and humans: an approach using geometric morphometrics
Authors: Lockwood Charles A. , Lynch John M. , Kimbel William H. 
Published: March 2003

AbstractThe hominid temporal bone offers a complex array of morphology that is linked to several different functional systems. Its frequent preservation in the fossil record gives the temporal bone added significance in the study of human evolution, but its morphology has proven difficult to quantify. In this study we use techniques of 3D geometric morphometrics to quantify differences among humans and great apes and discuss the results in a phylogenetic context. Twenty‐three landmarks on the ectocranial surface of the temporal bone provide a high level of anatomical detail. Generalized Procrustes analysis (GPA) is used to register (adjust for position, orientation and scale) landmark data from 405 adults representing Homo, Pan, Gorilla and Pongo. Principal components analysis of residuals from the GPA shows that the major source of variation is between humans and apes. Human characteristics such as a coronally orientated petrous axis, a deep mandibular fossa, a projecting mastoid process, and reduced lateral extension of the tympanic element strongly impact the analysis. In phenetic cluster analyses, gorillas and orangutans group together with respect to chimpanzees, and all apes group together with respect to humans. Thus, the analysis contradicts depictions of African apes as a single morphotype. Gorillas and orangutans lack the extensive preglenoid surface of chimpanzees, and their mastoid processes are less medially inflected. These and other characters shared by gorillas and orangutans are probably primitive for the African hominid clade.
Sonic hedgehog: restricted expression and limb dysmorphologies
Authors: Hill Robert E. , Heaney Simon J. H. , Lettice Laura A. 
Published: March 2003

AbstractSonic hedgehog, SHH, is required for patterning the limb. The array of skeletal elements that compose the hands and feet, and the ordered arrangement of these bones to form the pattern of fingers and toes are dependent on SHH. The mechanism of action of SHH in the limb is not fully understood; however, an aspect that appears to be important is the localized, asymmetric expression of Shh. Shh is expressed in the posterior margin of the limb bud in a region defined as the zone of polarizing activity (ZPA). Analysis of mouse mutants which have polydactyly (extra toes) shows that asymmetric expression of Shh is lost due to the appearance of an ectopic domain of expression in the anterior limb margin. One such polydactylous mouse mutant, sasquatch (Ssq), maps to the corresponding chromosomal region of the human condition pre‐axial polydactyly (PPD) and thus represents a model for this condition. The mutation responsible for Ssq is located 1 Mb away from the Shh gene; however, the mutation disrupts a long‐range cis‐acting regulator of Shh expression. By inference, human pre‐axial polydactyly results from a similar disruption of Shh expression. Other human congenital abnormalities also map near the pre‐axial polydactyly locus, suggesting a major chromosomal region for limb dysmorphologies. The distinct phenotypes range from loss of all bones of the hands and feet to syndactyly of the soft tissue and fusion of the digits. We discuss the role played by Shh expression in mouse mutant phenotypes and the human limb dysmorphologies.
Copper‐binding proteins in ectomycorrhizal fungi
Authors: HOWE REBECCA , EVANS R. L. , KETTERIDGE S. W. 
Published: March 2003

SUMMARYThe presence of copper‐binding proteins produced in response to added copper was examined in isolates of Laccaria laccata (Scop, ex Fr.) Cooke and Paxillus involutus (Batsch ex Fr.) Fr. taken from copper‐contaminated and uncontaminated sites, and in a single isolate of Scleroderma citrinum Pers. from a contaminated site. Two isolates of Laccaria (GLac4 and ELacl) grew better in 1–5 miu and 2–5 niM copper than a third (Lac3G) and were considered to be more tolerant. Amongst five isolates of P. involutus, three (WJPax2R, GPaxRSp2 and Pax4) were capable of growth in media containing 4–0 mM copper and were regarded as tolerant. All isolates of both Laccaria and Paxillus were capable of some growth in 2–5 mM copper, but S. citrinum was much more copper‐sensitive and the concentration had to be reduced at least 10‐fold before any growth occurred. Tolerance of isolates was not related to whether they were taken from copper‐contaminated or uncontaminated sites. Copper‐binding proteins were detected in response to copper in the culture media in the two tolerant isolates of Laccaria (GLac4 and ELacl) but not in the least tolerant isolate. In Paxillus, similar proteins were found in two tolerant isolates (GPaxRSp2 and Pax4) but not in WJPax2R, which was also regarded as tolerant, nor in any of the less tolerant isolates. Copper‐binding proteins were not detected in S. citrinum. The copper‐binding protein purified from the Laccaria isolate ELacl appeared as a single band in modified SDS‐PAGE electrophoresis. Its molecular mass and spectral characteristics were consistent with it being a metallothionein.