Immunodetection of FGF1-2 and FGFR1-2 indicates that these proteins disappear in the wound epidermis and blastema of the scarring limb in lizard

In lizards while the tail broadly regenerates after amputation the limb generally forms short scarring outgrowths FGFs are important growth factors that are present in regenerating tissues and appear to stimulate tail regeneration in lizards In the limb immunohistochemistry at days post amputation indicates that FGFs and FGFR are present with different intensity in the wound regenerating epidermis and sparsely in connective muscle and cartilaginous cells of the healing tissues of the stump However the immunofluorescence study indicate that FGF and FGF receptors are little or no immunodetectable at days post amputation especially in the wound epidermis when the limb blastema is turning into a scarring connective tissue of the short limb outgrowth Western blot analysis shows no low MW bands for FGF and altered or degraded bands of FGFR in the limb at days post amputation when scarring is taking place The present observations indicate that the disappearance of these proteins is related to loss of cell proliferation that leads to the failure of limb regeneration in lizards The study further stress the essential role of FGFs and their receptors in the stimulation of organ regeneration in lizards and likely in other amniote

Evolutionary origin and diversification of epidermal barrier proteins in amniotes.

The evolution of amniotes has involved major molecular innovations in the epidermis. In particular, distinct structural proteins that undergo covalent cross-linking during cornification of keratinocytes facilitate the formation of mechanically resilient superficial cell layers and help to limit water loss to the environment. Special modes of cornification generate amniote-specific skin appendages such as claws, feathers, and hair. In mammals, many protein substrates of cornification are encoded by a cluster of genes, termed the epidermal differentiation complex (EDC). To provide a basis for hypotheses about the evolution of cornification proteins, we screened for homologs of the EDC in non-mammalian vertebrates. By comparative genomics, de novo gene prediction and gene expression analyses, we show that, in contrast to fish and amphibians, the chicken and the green anole lizard have EDC homologs comprising genes that are specifically expressed in the epidermis and in skin appendages. Our data suggest that an important component of the cornified protein envelope of mammalian keratinocytes, that is, loricrin, has originated in a common ancestor of modern amniotes, perhaps during the acquisition of a fully terrestrial lifestyle. Moreover, we provide evidence that the sauropsid-specific beta-keratins have evolved as a subclass of EDC genes. Based on the comprehensive characterization of the arrangement, exon-intron structures and conserved sequence elements of EDC genes, we propose new scenarios for the evolutionary origin of epidermal barrier proteins via fusion of neighboring S100A and peptidoglycan recognition protein genes, subsequent loss of exons and highly divergent sequence evolution

Performance and stability of sewage sludge digestion under CO2 enrichment: a pilot study

Carbon dioxide (CO2) injection in anaerobic digestion has recently been proposed as an interesting possibility to boost methane (CH4) recovery from sludge and organic waste by converting a greenhouse gas into a renewable resource. This research assessed the effects of exogenous CO2 injection on performance and process stability of single-phase continuous anaerobic digesters. Two pilot scale reactors treating sewage sludge were operated for 130 days. One reactor was periodically injected with CO2 while the other acted as control. Two injection frequencies and injection devices were tested. The results indicated that CO2 enrichment allowed an increase in CH4 production of ca. 12%, with a CH4 production rate of 371 ± 100 L/(kgVSfed⋅d) and a CH4 concentration of ca. 60% when dissolved CO2 levels inside the test reactor were increased up to 1.9-fold. Results also indicated an improvement in process resilience to temporary overloads and no impacts on stability parameters

Modifications of the dermis during scale regeneration in the lizard tail

During scale morphogenesis in the regenerating tail of lizards (Anolis and Lampropholis) the structure of the dermis undergoes changes in relation to the ingrowth of epidermal papillae to form the new scales. Cell proliferation in the dermis, as revealed by the uptake of 3~-thymidinei,s high in the prescaling region of the regenerating tail but lower than the proliferation in the epidermis. Under the epidermis of the scaling region dermal cell proliferation rapidly drops down under the distal (apical) and proximal (caudal) sides of the infoldin epidermal papillae. Dermal fibroblasts take up g ~ - p r o l i n ein high amounts, especially in the forming deep dermal layer, where many collagen fibrils are laid down forming dense connective. Electron microscopic study revealed that ((anchoring filaments~li nk the basement membrane of the epidermis with the deep dermis, in particular in the sinking hnge region. As a result of the higher proliferation of the epidermis with respect to the dermis (heterochrony) and the presence of dermo-epithelial eanchoring filarnents», the superficial laminar epidermis sinks into the dermis to produce new scales. The epidermal downpushing is evidenced by a characteristic distortion of the dermal fibrils under the distal and the proximal sides, and in the hinge region of the forming scale

Observations on Lumbar Spinal Cord Recovery after Lesion in Lizards Indicates Regeneration of a Cellular and Fibrous Bridge Reconnecting the Injured Cord

The lumbar spinal cords of lizards were transected, but after the initial paralysis most lizards recovered un-coordinated movements of hind limbs. At 25-45 days post-lesion about 50% of lizards were capable of walking with a limited coordination. Histological analysis showed that the spinal cord was transected and the ependyma of the central canal formed two enlargements to seal the proximal and distal ends of the severed spinal cord. Glial and few small neurons were formed while bridge axons crossed the gap between the proximal and the distal stumps of the transected spinal cord as was confirmed by retrograde tract-tracing technique. The bridging fibers likely derived from interneurons located in the central and dorsal grey matter of the proximal spinal cord stump suggesting they belong to the local central locomotory pattern generator circuit. The limited recovery of hind limb movements may derive from the regeneration or sprouting of short proprio-spinal axons joining the two stumps of the transected spinal cord. The present observations indicate that the study on spinal cord regeneration in lizards can give insights on the permissive conditions that favor nerve regeneration in amniotes

Immunolocalization of a beta-defensin (Tu-BD-1) in the skin and subdermal granulocytes of turtles indicate the presence of an antimicrobial skin barrier

The resistance of turtle skin to infections is likely due to the production of a thick corneous layer but also of soluble antimicrobial molecules released in the stratum corneum. The present study has determined the localization of beta-defensin peptides previously identified by biomolecular analysis in turtle skin. After the production of a specific antibody for one peptide indicated as Ts-BD-1, light and ultrastructural localization indicates that the peptide is mainly present in some variably dense primary granules of granulocytes. These cells are sparse in the connective tissues and within blood vessels present in the dermis and subdermal inter-muscular connective tissue. A weak labeling is also present in the epidermis, especially localized in sparse secretory granules discharged among corneocytes of the stratum corneum. This localization suggests that antimicrobial peptides are common constituents of the narrow extracellular spaces located among superficial corneocytes where bacteria or their remnants are frequently detected. The study suggests that turtle beta-defensins are mainly contained in granulocytes involved in the immunological surveillance of the skin and that they become active after skin wounding

Fine structure of juvenile feathers of the zebrafinch in relation to the evolution and diversification of pennaceous feathers

Journal of submicroscopic cytology and patholog

Introduction to the Study on Regeneration in Lizards as an Amniote Model of Organ Regeneration

Initial observations on the regeneration of the tail in lizards were recorded in brief notes by Aristotle over 2000 years ago, as reported in his book, History of Animals (cited from [...

Proliferating Cells in Knee Epiphyses of Lizards Allow for Somatic Growth and Regeneration after Damage

After bone damage, fracture or amputation, lizards regenerate a variable mass of cartilaginous and fibro-cartilaginous tissues, depending from the anatomical site and intensity of inflammation. Aside tail and vertebrae, also long bones and knee epiphyses can regenerate a relative large mass of cartilage after injury. Regeneration is likely related to the persistence of stem cells in growing centers of these bones, localized in the epiphyses of femur, tibia and fibula. The epiphyses form ossified secondary centers in adults but a few progenitor cells remain in the articular cartilage and growth plate, allowing a continuous growth during most lifetime of lizards. The present Review indicates that putative progenitor/stem cells, identified by long labeling retaining of 5-bromo-deoxy-uridine (5BrdU) and immunolocalization of telomerase, remain localized in the articular cartilage and growth plates of the femur and tibia. These cells are re-activated after limited epiphyses damage or amputation of the distal part of the femur or tibia-fibula, and can re-form cartilaginous epiphyses. Regenerating chondrocytes show an intense proliferation and the production of new extracellular matrix components such as collagen VI, chondroitin sulfate proteoglycan, and hyaluronate receptors. The molecular factors at the origin of the chondrogenic potential of the articular cartilage, growth plates, and the periosteum in lizard bones remain to be studied

Immunolocalization of Keratin-associated beta-proteins (beta-keratins) in pad lamellae of geckos suggest that glycine-cysteine-rich proteins contribute to their flexibility and adhesiveness

The epidermis of digital pads in geckos comprises superficial microornamentation from the oberhautchen layer that form long setae allowing these lizards to climb vertical surfaces. The betalayer is reduced in pad lamellae but persists up to the apical free margin. Setae are made of different proteins including keratin\u2010associated beta\u2010proteins, formerly indicated as beta\u2010keratins. In order to identify specific setal proteins the present ultrastructural study on geckos pad lamellae analyzes the immunolocalization of three beta\u2010proteins previously found in the epidermis and adhesive setae of the green anolis. A protein rich in glycine but poor in cysteine (HgG5\u2010like) is absent or masked in gecko pad lamellae. Another protein rich in glycine and cysteine (HgGC3\u2010like) is weakly present in setae, oberhautchen and beta\u2010layer. A glycine and cysteine medium rich beta\u2010protein (HgGC10\u2010 like) is present in the lower part of the beta\u2010layer but is absent in the oberhautchen, setae, and mesos layer. The latter two proteins may form intermolecular bonds that contribute to the flexibility of the corneous material sustaining the setae. The pliable alpha\u2010layer present beneath the thin beta\u2010layer and in the hinge region of the pad lamellae also contains HgGC10\u2010like proteins. Based on the possibility that some HgGC3\u2010like or other cys\u2010rich beta\u2010proteins are charged in the setae it is suggested that their charges influence the mechanism of adhesion increasing the induction of dipoles on the substrate and enhancing attractive van der Waals forces