A histological study of the long‐term response to trauma of squamate integument

Maderson, P. F. A.; Baranowitz, Steven; Roth, Sanford I.

doi:10.1002/jmor.1051570202

Cited by 38 publications

(41 citation statements)

References 16 publications

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“…Similar epidermal infolding is typical for the origin of large, flat and non-overlapping scales (e.g. neck and head scales) in lepidosaurian reptiles (Alibardi, personal observations) and regenerating scales in lizards (Bryant and Bellairs 1967;Maderson et al 1978;Alibardi 1994aAlibardi , 1994bAlibardi , 1995 and Sphenodon (Alibardi, unpublished observations). In most lepidosaurian embryos, the scale anlagen appears as small epidermal bumps in the initially flat epidermis (Maderson 1965(Maderson , 1985Liu and Maneely 1969;Dhouailly 1975).…”

Section: Formation Of Scutes and Dermal Ossificationmentioning

confidence: 93%

Morphogenesis of shell and scutes in the turtle Emydura macquarii

Alibardi¹,

Thompson²

1999

Aust. J. Zool.

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Formation of the scutes and dermis of the embryonic shell of the turtle Emydura macquarii was studied using light and electron microscopy. Shell morphogenesis begins at embryonic stage 15 and the shape of the shell is mostly completed by embryonic stage 19. The carapace anlagen arises as a thickening of the skin in the dorsal part of the mid-trunk region between the anterior and posterior limbs. This thickening extends ventro-laterally to form ridges at the margins of the carapace. Each ridge forms as a thick epidermal placode over a condensation of mesenchymal cells. The epidermis behind the advancing margins of the carapace is cuboidal or columnar but does not form placodes. The margins of the carapace expand rapidly in all directions. The plastron anlagen is derived from epidermal cells localised in the latero-ventral regions between the fore- and hind-limbs. Plastron placodes are present laterally, while the mid-ventral and central epidermis remains cuboidal or columnar but does not form placodes at embryonic stage 16. The plastron thickening rapidly moves from a latero-ventral position to a flat ventral position between embryonic stages 16 and 19. Dermal–epidermal anchoring complexes occur throughout placodes of both the carapace and plastron, but are rare in non-placode areas. The accumulation of a dense mesenchyme beneath the shell epidermis forms a dermal cushion that surrounds the body cavity. The superficial dermis close to the epidermis is made of mesenchymal fibroblasts at embryonic stage 19, although the inner-most areas contain bipolar fibroblasts and extracellular fibrils. Scutes with serrations at their borders form as invaginations of the epidermis into the dermis in the mid-dorsal areas of the embryo at embryonic stages 18–19. Dermal–epidermal anchoring complexes are located around the infoldings that form the scutes of the hinge region. The epidermis of the shell has 2–3 suprabasal cells at embryonic stages 19–22, and lacks keratinisation before embryonic stage 22 when it has 4–6 suprabasal layers with 2–3 external layers made of flat cells. The dermis thickens and has numerous collagen fibrils after embryonic stage 19. The formation of dermal bones begins at embryonic stage 18–19 in the plastron. Only small areas of the carapace near to the bridge have begun to form dermal bone at embryonic stage 19. Calcification begins at embryonic stage 19, but is still incomplete at embryonic stages 24–25.

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Section: Formation Of Scutes and Dermal Ossificationmentioning

confidence: 93%

Morphogenesis of shell and scutes in the turtle Emydura macquarii

Alibardi¹,

Thompson²

1999

Aust. J. Zool.

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“…Papillar growth in Sphenodon punctatus (Fig. 8) is not accompanied by lacunar tissue hypertrophy, as it is in lizards (Maderson et al, 1978a;Maderson, 1985).…”

Section: Epidermal Cell Activity Over the Prescaling And Scaling Caudmentioning

confidence: 91%

“…It has long been known that the former involves a folding of embryonic integument (Maderson, 1965), quite different than the "carving-out" of new scales by epidermal pegs invading the dermal tissues during the latter (Maderson et al, 1978a). Those LM studies revealed that, concomitant with either scale embryogenesis or neogenesis, the epidermis enters, or reenters, the shedding cycle (Maderson et al, 1998), although in the embryo the outermost components of the first epidermal generation differentiate beneath a periderm, while scale neogenesis occurs beneath a WE.…”

mentioning

confidence: 99%

Observations on the histochemistry and ultrastructure of regenerating caudal epidermis of the tuatara Sphenodon punctatus (Sphenodontida, Lepidosauria, Reptilia)

Alibardi

Maderson

2003

Journal of Morphology

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Study of the histology, histochemistry, and fine structure of caudal epidermal regeneration in Sphenodon punctatus through restoration of a scaled form reveals that the processes involved resemble those known in lizards. Following establishment of a wound epithelium (WE), subjacent scale neogenesis involves epidermal downgrowths into the dermis. Although the process is extremely slow, and most new scales do not overlap, their epidermal coverings reestablish epidermal generation (EG) formation. As in lizards, the flat, alpha-keratogenic, WE cells contain lipids as revealed by their affinity for Sudan III. A few mucous cells that store large PAS-positive mucus-like granules also occur in WE. During differentiation of WE cells, among the bundles of 70-nm tonofilaments are many lamellar bodies (LBs) and mucous granules (MGs) that discharge their contents into the cytoplasm and extracellular spaces producing a strongly PAS-positive keratinized tissue. Richness of epidermal lipids coexistent with mucus is a primitive characteristic for amniote vertebrates, probably related to functions as a barrier to cutaneous water loss (CWL). As scale neogenesis begins, beneath the superficial WE appear 3-5 layers of irregularly shaped cells. These contain tonofilament bundles surrounded by small, round keratohyalin-like granules (KHLGs) and a keratinized matrix with beta-keratin packets and a 3-5-nm thick keratin granulation. This mixture of alpha- and beta-keratogenic capacities resembles that seen in the innermost cells of a normal tuatara epidermal generation. As in the latter, but in contrast to both normal and regenerating lizard epidermis, no definable shedding complex with interdigitating clear layer and oberhautchen cells occurs (Alibardi and Maderson, 2003). The tortuous boundaries, and merging beta-keratin packets, identify subjacent keratinizing cells as precursors of the typical stratified, squamous beta-layer seen in long-term regenerated caudal skin wherein the entire vertical sequence of epidermal layers resembles that of normal scales. The sequence of events in caudal epidermal regeneration in S. punctatus resembles that documented for lizards. 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.

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“…Despite of this, the epidermal layers are produced in the same sequence and cytological differentiation as in the normal renewal phase of adult scales (Maderson et al 1978;Alibardi 2001Alibardi , 2012. Initially, the epidermis folds inward as pegs that penetrate into the dermis, while the central region begins to form new differentiating layers (Fig.…”

Section: Scales Pads and Claws Of A Carolinensismentioning

confidence: 94%

Review: mapping epidermal beta-protein distribution in the lizard Anolis carolinensis shows a specific localization for the formation of scales, pads, and claws

Alibardi

2015

Protoplasma

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The epidermis of lizards is made of multiple alpha- and beta-layers with different characteristics comprising alpha-keratins and corneous beta-proteins (formerly beta-keratins). Three main modifications of body scales are present in the lizard Anolis carolinensis: gular scales, adhesive pad lamellae, and claws. The 40 corneous beta-proteins present in this specie comprise glycine-rich and glycine-cysteine-rich subfamilies, while the 41 alpha-keratins comprise cysteine-poor and cysteine-rich subfamilies, the latter showing homology to hair keratins. Other genes for corneous proteins are present in the epidermal differentiation complex, the locus where corneous protein genes are located. The review summarizes the main sites of immunolocalization of beta-proteins in different scales and their derivatives producing a unique map of body distribution for these structural proteins. Small glycine-rich beta-proteins participate in the formation of the mechanically resistant beta-layer of most scales. Small glycine-cysteine beta-proteins have a more varied localization in different scales and are also present in the pliable alpha-layer. In claws, cysteine-rich alpha-keratins prevail over cysteine-poor alpha-keratins and mix to glycine-cysteine-rich beta-proteins. The larger beta-proteins with a molecular mass similar to that of alpha-keratins participate in the formation of the fibrous meshwork present in differentiating beta-cells and likely interact with alpha-keratins. The diverse localization of alpha-keratins, beta-proteins, and other proteins of the epidermal differentiation complex gives rise to variably pliable, elastic, or hard corneous layers in different body scales. The corneous layers formed in the softer or harder scales, in the elastic pad lamellae, or in the resistant claws possess peculiar properties depending on the ratio of specific corneous proteins.

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A histological study of the long‐term response to trauma of squamate integument

Cited by 38 publications

References 16 publications

Morphogenesis of shell and scutes in the turtle Emydura macquarii

Morphogenesis of shell and scutes in the turtle Emydura macquarii

Observations on the histochemistry and ultrastructure of regenerating caudal epidermis of the tuatara Sphenodon punctatus (Sphenodontida, Lepidosauria, Reptilia)

Review: mapping epidermal beta-protein distribution in the lizard Anolis carolinensis shows a specific localization for the formation of scales, pads, and claws

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