Browsing by Subject "Lizard"

Now showing 1 - 4 of 4
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    Fine autoradiographical study on scale morphogenesis in the regenerating tail of lizards
    (Murcia : F. Hernández, 1994) Alibardi, Lorenzo
    Regenerating scales in lizards originate as pockets in the epidermis instead of epidermal elevations as during embryo development. The morphogenesis of scales in the regenerating tail of the lizards. Anolis and Lamphropholis was studied after peritoneal injection of 3~-thymidineT. he tracer was localized in the forming epidermis after progressive post-injection times, by means of autoradiographY on plastic sections. After 4-5 hours post-injection of H-thymidine, the radioactivity was localized in the basal layer. After 2 to 4 days postinjection labelled cells were seen in the basal and intermediate spinosus layers but not in the uppermost keratinizing layers. Labelled cells were seen in the differentiating cornifying layers (pre-B and pre-a) 6-8 days post-injection. At 12-14 days post-injection almost no radioactivity was seen in the basal layer or in the living part of the epidermis. A few labelled cells were present in the dense keratinizing layers of the sloughing wound and interscale lacunar layers. This study shows that scale formation and morphogenesis in the regenerating tail is brought about by a localized cell proliferation along the regenerating epidermis. In the forming scales the percentage of labelled cells in the distal side (future dorsal part of the new scale) is much higher than in the proximal side (the future ventral side of the scale), so that overlapped scales are generated.
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    Modifications of the dermis during scale regeneration in the lizard tail
    (Murcia : F. Hernández, 1994) Alibardi, Lorenzo
    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 scales
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    Observations on proliferating sheath cells in the regenerating nerves of lizard
    (Murcia : F. Hernández, 1996) Alibardi, Lorenzo
    The proliferation of sheath cells (Schwann and endoneurium) of growing nerves has been studied by autoradiography after 3~-thymidinead ministration to lizards (Anolis carolinensis and Lampropholis delicata) with regenerating tails. Schwann cells of regenerating nerves derive from the multiplication of resident cells within the growing nerves, but labelled Schwann cells derived from the regenerative blastema also appear to ensheath the new axons. Endoneurium cells of growing nerves derive from the blastema around the nerves more than from dividing and migrating cells of the original endoneurium. After 6-20 days post-injection the number of labelled sheath cells in the older proximal regenerated nerves increased due to local division and migration. In the proximal spinal ganglia which innervate the regenerating tail some satellite cells, but not neurons, took up 3~-thymidinaen d multiplied.
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    The distribution of vasotocin and mesotocinimmunoreactivity in the hypothalamic magnocellularneurosecretory nuclei of the Saharan herbivorous lizard,Uromastix acanthinurus Bell, 1825 (Sauria-Agamidae)
    (Murcia : F. Hernández, 2010) Barka-Dahane, Zohra; Bendjelloul, Mounira; Estabel, Jeanne; Exbrayat, Jean-Marie
    An immunohistochemical study of themagnocellular neurosecretory nuclei was performed inthe hypothalamus of the desert lizard Uromastixacanthinurususing polyclonal antibodies againstarginine vasotocin (AVT), mesotocin (MST) andneurophysins I and II (NpI, NpII). AVT- and MST-immunoreactivities were localized in individual neuronsof the supraoptic, periventricular, and paraventricularnuclei and in scattered neurosecretory cells. Thesupraoptic nuclei (SONs) can be subdivided into rostral,medial and caudal portions. The rostral portion of theSONs was called the SON-ventral aggregation (V SON)because the neurosecretory neurons are present in theventral part of the hypothalamus along the optic chiasma(OC). Their perikarya and fibres were only AVT-ir. Themedial part of the SONs was constituted of two clustersof neurosecretory neurons located in the two lateral endsof the OC to form the SON-lateral aggregations (LSON). In the caudal end of the last one, some MST-irperikarya appeared. The caudal part of the SONs wasconstituted of a dorso-lateral aggregation (D SON) of ir-neurons spreading over the lateral forebrain bundle(LFB). AVT- and MST- perikarya were observed in thiscaudal portion of the SONs, AVT-ir neurons being morenumerous. AVTergic and MSTergic magnocellularneurons were present in the periventricular nuclei(PeVNs). Parvocellular and magnocellular AVT- andMST-ir were observed in the paraventricular nuclei(PVNs). The fibres emerging from the magnocellularneurons which belong to these nuclei and the scatteredcells ran along the hypothalamic floor and entered themedian eminence (ME) to end in the neural lobe ofhypophysis. As a rule, immunoreactivity was alsoobserved in all the regions of the forebrain withvasotocinergic and mesotocinergic perikarya and fibres.The immunoreactive distribution was similar to thatdescribed in other reptiles.