Lorenzo Alibardi

..The study of the molecules involved in the dermo-epidermal interactions in reptilian skin and the molecular biology of epidermal proteins are among the most urgent future areas of research in the biology of reptilian skin...

..These data on apteric epidermis support the hypothesis of an evolution of the apteric and interfollicular epidermis from the expansion of hinge regions of protoavian archosaurians...

..In therapsids-mammals, mutations of the ancestral proteins formed the high glycine-tyrosine or the high cysteine proteins but no core-box was produced in the matrix proteins of the hard corneous material of mammalian derivatives...

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..The rapid replacement of setae ensures the continuous usage of the gecko's adhesive devices, the pad lamellae, during most of their active life...

..No cross-reactivity was seen using an antibody against feather beta-keratin, indicating absence of a common epitope between snake and feather keratins...

..The association of caspase-14 with keratohyalin and trichohyalin granules may indicate a specific role of caspase-14 in the maturation of these keratinocyte-specific structures...

..Thus, the shell makes the animal more streamlined for swimming...

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..The role of cells of the IRS in sculpturing the fiber cuticle and in the mechanism of shedding that allows the exit of hair on the epidermal surface in mammals are discussed...

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..It is speculated that the progressive reduction of the extended dermal papilla of reptilian scales into small and deep papillae of therapsid reptiles produced hairs in mammals...

..The latter evolved as glycine-tyrosine-rich, sulphur-rich, and ultra-sulphur-rich proteins that are used for building hairs, horns and nails...

..Observed differences between posttrauma scale neogenesis and scale embryogenesis are responses to functional problems involved in, respectively, restoring, or forming, a barrier to CWL while accommodating rapid somatic growth...

..A discussion of the role of gap and tight junctions during feather morphogenesis is presented...

..The specificity for turtle beta-keratin suggests that the antiserum recognizes some epitope/s specific for chelonians beta-keratins, and that it also variably recognizes other reptilian and avian beta-keratins...

..In general a thin cortex is formed in those sections of the rachis where barbs are absent, and the feather keratin positive layer increases in the basal part of the feather, the calamus...

..In conclusion, our study suggests that proteins with epitopes that they have in common with cornification proteins of mammalian epidermis are also present in the epidermis of turtle...

..The data on the ultrastructural localization of hair keratin homologs facilitate a comparison of lizard claws and mammalian hard epidermal appendages containing hair keratins...

..The role of the cornified pulp epithelium is to limit water loss and to form a microbe barrier before the mature feather is moulted...

..The modality of cornification in feathers is compared to the process of hard cornification of reptilian scales and claws and mammalian hairs and nails...

..Beta-keratins may have both a fibrous and a matrix role in forming the hard texture of corneoum scales in this ancient species, as well as in more recently evolved reptiles...

..It is unknown whether sulphur is derived from either sulphated mucins, or disulphide bonds in aggregated keratins, or specific sulphur-rich proteins...

..The hypothesis indicates that in a following stage, the medulla was obliterated or replaced by cortical cells while the external part of the cortex formed a cuticular surface due to the different growth rate with inner root sheath cells...

..The production of beta-defensins from granulocytes would allow protection of exposed tissues from microbial invasion avoiding a persistent inflammation, a process that leads to tissue regeneration...

..The latter has invaginated in association with the collar epidermis from which feathers were produced...

..The stratified layers gradually disappear toward the growing border of the shell. The mode of growth of horny scutes in these different species of chelonians is discussed...

..In birds, a small beta-keratin has allowed the formation of feathers. It is suggested that beta-keratins represent the reptilian counterpart of keratin associated or matrix proteins present in mammalian hairs, claws, and horns...

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..This study indicates that a functional stratum corneum in the epidermis of amniotes originates only after the association of matrix and corneous cell envelope proteins with the original keratin scaffold of keratinocytes...

..Feather morphogenesis suggests possible stages for feather evolution and diversification from hair-like outgrowths of the skin found in fossils of pro-avian archosaurians...

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..The present study suggests that FGFs produced in the regenerating epidermis, spinal cord and nerves can stimulate tail regeneration in lizards...

..Eventually, the disappearance of wedge cell scaffolding determines the regular spacing of barbs attached to the rachis in order to form a close vane...

..Putative COM-mossy fibers reach the granule areas of the DCN, including unipolar brush cell dendrites, another possible excitatory commissural pathway...

..The evolution of these small proteins represents the more recent variation of the process of cornification in vertebrates...

..Pyramidal cells convey an excitatory signal from the DCN to higher mesencephalic nuclei for further elaboration of the acoustic signal...

..These small proteins produce a hard type of corneous material due to their dense packing among cytokeratin filaments...

..Nevertheless, the mechanism of redistribution of such proteins during maturation of monotreme keratinocytes is different from, perhaps more primitive, or less specialized, than that in the epidermis of eutherian mammals...

..This result indicates that beta-keratins among different reptilian groups posses different immunoreactive regions...

..The evolution of these small proteins in lepidosaurians, chelonians and archosaurians represent the next step to understand the evolution of cornification in reptiles and derived amniotes (birds and mammals)...

..Based on comparative studies of reptilian and mammalian skin, a speculative hypothesis on the evolution of the IRS and hairs from the skin of synapsid reptiles is presented...

..It is suggested that the shedding complex in lepidosaurian reptiles has evolved after the production of a histidine-rich protein and of a beta-keratin layer beneath the former alpha-layer...

..The review concludes by stressing the importance of the lizard model of tissue regeneration for medical studies and applications...

..The contribution of lipids or lipoprotein to the initial aggregation of beta-keratin molecules is discussed...

..The latter are not contacted by large mossy-like glycine terminals...

..The study also suggests that more forms of beta-keratins (more than three different types) are present in the epidermis of snakes...

..The latter contains lipids and eventually flakes off, determining shedding of the above outer corneous layer in late spring or summer...

..These observations suggest that low amounts of matrix proteins are present among keratin bundles of avian keratinocytes and that keratohyalin granules are absent...

..This process initially produced variably branched down feathers and later, after barb ridge fusion, a rachis. From the modulation in the pattern of barb ridge formation various pennaceous feathers later evolved...

..This observation suggests that histidine-labeled material contributes to the formation of long keratin filaments with axial orientation that are utilized for the elongation of barb and barbule cells...

..Therefore, together with trichohyalin, the cross-linking due to involucrin is also responsible for the mechanical resistance of the corneous trabeculae present among the empty spaces of the medulla of the human hair...

..The terminals branching off each seta may derive from the organization of the cytoskeleton and from the mechanical separation of keratin bundles located at the terminal apex of setae...

..These observations will allow focusing efforts of biochemical substrate screening on a subset of proteins localizing to distinct compartments of terminally differentiated keratinocytes...

..These immunocytochemical results suggest that the 3-nm beta keratin filaments of the reptilian integument are phylogenetically related to those found in avian epidermal appendages...

..We have also identified the colocalization of alpha-tubulin with keratin in the cortical region of the oocyte, in particular when the cortex is engaged in the uptake of the yolk proteins...

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..Although the cell membrane of superficial corneous cells of amphibian epidermis became thicker, the absence of loricrine immunolabelling suggests that a cell corneous envelope containing this protein is not present or undetectable...

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..The latter is shed at hatching leaving the pointed claw made of harder corneous layers in the unguis side of the claw...

..The cross-reactivity of the beta-antibody, produced against a chick scale keratin, further shows that avian and crocodilian hard (beta) keratins share common antigenic sites, reflecting a phylogenetic affinity between these taxa...

..The present study suggests that, in the epidermis of lepidosaurian reptiles, the synthesis of a histidine-rich protein is involved in the formation of the shedding layer and, as in mammals, in a-keratinization...

..In conclusion, beta-keratin, histidine-rich, and sulfur-rich proteins contribute to form snake microornamentations...

..The present study suggests that octopus cells are a special type of excitatory D-multipolar neuron confined to the octopus cell area and mainly innervated by glutamatergic cochlear nerve terminals...

..The synthesis of beta-keratin from its mRNA occurs among ribosomes or is associated with the surface of beta-keratin filaments...

..PCR analysis showed that the genes are presumably located in tandem along the DNA and are transcribed from the same DNA strand like in avian beta-keratins...

..This region was possibly present in basic reptiles that originated reptiles and birds...