Epidermal keratinization in the salamander and a comparison with other amphibia

Spearman, R. I. C.

doi:10.1002/jmor.1051250202

Cited by 46 publications

(19 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This chemical affinity forms an electron-dense material under the electron microscope, such as in hair cortical and cortex cells (Filshie & Rogers 1962;Spearman 1968;Fraser et al 1972). In fact, both osmium and especially lead are absorbed in matrix proteins in hairs cortex and in cuticle where high amount of cysteine and especially of cystine (disulfide bonds) are present.…”

Section: Corneous Proteins Of the Claw And Comparison To Amniote Clawsmentioning

confidence: 99%

Cornification in the claw of the amphibianXenopus laevis(Pipidae, Anura) and comparison with claws in amniotes

Alibardi

2010

Italian Journal of Zoology

View full text Add to dashboard Cite

An ultrastructural, immunocytochemical and electrophoretic study on keratinocytes forming the corneous layer of claws in the frog Xenopus laevis has been conducted in order to analyze the process of cornification in amphibians and compare it with cornification in amniote claws. During claw differentiation pre-corneous keratinocytes accumulate dense corneous bundles containing keratin filaments and inter-keratin material. Ribosomes are associated with keratin bundles, suggesting that neo-synthesized matrix molecules are rapidly aggregated onto the keratin filaments, turning the complex into an amorphous, electron-dense, and resistant horny material. Most proteins of the claw are acidic to neutral keratins of 45-66 kDa, but other protein spots outside the molecular weight range of keratins are also present. These proteins of 16-17 kDa with pI at 7.0-7.3 contain little histidine and may represent 'amphibian keratin associated proteins' (aKAPs). The association of keratins and aKAPs determine the formation of the hard corneous material of claws and likely of the other corneous structures present in amphibian skin, such as the horny beak and horny nuptial pads. The cornification in amphibian claws, compared to the process of cornification present in amniote claws, shows common aspects, but is more simplified in amphibians.

show abstract

Section: Corneous Proteins Of the Claw And Comparison To Amniote Clawsmentioning

confidence: 99%

Cornification in the claw of the amphibianXenopus laevis(Pipidae, Anura) and comparison with claws in amniotes

Alibardi

2010

Italian Journal of Zoology

View full text Add to dashboard Cite

show abstract

“…Also, no cell corneus envelope, the 10 -15 nm plasmalemmal thickening due to the deposition of envelope proteins (Mehrel et al, 1990;Resing and Dale, 1991), is formed in the external keratinocytes of N. forsteri. The reaction to sulfhydryl groups suggests that, like in amphibians, the mature keratin filaments are not very crosslinked and that many sulfhydryl groups remain (soft keratin; Spearman, 1968;Matoltsy, 1987). In hard keratinized layers of amniotes, sulfhydryl groups disappear, being substituted by disulfide groups.…”

Section: Keratinization In Lungfish Epidermismentioning

confidence: 99%

Keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri (dipnoi)

Alibardi

Joss

2003

Journal of Morphology

View full text Add to dashboard Cite

The differentiation of the epidermis in sarcopterigian fish may reveal some trend of keratinization followed by amphibian ancestors to adapt their epidermis to land. Therefore, the process of keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri was studied by histochemistry, electron microscopy, and keratin immunocytochemistry. The epidermis is tri-stratified in a 2-3-month-old tadpole but becomes 6-8 stratified in young adults. Keratin filaments increase from basal to external cells where loose tonofilament bundles are present. This is shown also by the comparison of positivity to sulfhydryl groups and increasing immunoreactivity to alpha-keratins in more external layers of the epidermis. Two broad-spectrum anti alpha-keratin monoclonal antibodies (AE1 and AE3) stain all epidermal layers as they do in actinopterigian fish. In the adult epidermis, but not in that of the larva, the AE2 antibody (a marker of keratinization in mammalian epidermis) often immunolabels more heavily the external keratinized layers where sulfhydryl groups are more abundant. Mucous granules are numerous and concentrate on the external surface of the epidermis to be discharged and contribute to cuticle formation. Keratin is therefore embedded in a mucus matrix, but neither compact keratin masses nor cell corneous envelope were seen in external cells. It is not known whether specific matrix proteins are associated with mucus. There was no immunolocalization of the keratin-associated proteins, filaggrin and loricrin, which suggests that the epidermis of this species lacks the matrix and cell corneus envelope proteins characteristic of that of amniotes. In conclusion, while specific keratins (AE2 positive) are probably produced in the uppermost layers as in amphibian epidermis, no interkeratin, matrix proteins seem to be present in external keratinocytes of the lungfish other than mucus.

show abstract

“…In all amniotes, the last supra‐basal layers of the epidermis are cornified, meaning they are formed of dead cells filled entirely with alpha‐keratin filaments coated with specific amorphous proteins and lipids, providing a barrier to water loss. In a variety of living amphibians, such as toads, a ‘stratum corneum‐like’ layer exists, but it is only one to three cell depths, and nuclear remnants still persist (Spearman, 2005). In all vertebrates, the corneal epithelium is un‐cornified and is protected only by tears.…”

Section: Introductionmentioning

confidence: 99%

A new scenario for the evolutionary origin of hair, feather, and avian scales

2009

View full text Add to dashboard Cite

In zoology it is well known that birds are characterized by the presence of feathers, and mammals by hairs. Another common point of view is that avian scales are directly related to reptilian scales. As a skin embryologist, I have been fascinated by the problem of regionalization of skin appendages in amniotes throughout my scientific life. Here I have collected the arguments that result from classical experimental embryology, from the modern molecular biology era, and from the recent discovery of new fossils. These arguments shape my view that avian ectoderm is primarily programmed toward forming feathers, and mammalian ectoderm toward forming hairs. The other ectoderm derivatives -scales in birds, glands in mammals, or cornea in both classes -can become feathers or hairs through metaplastic process, and appear to have a negative regulatory mechanism over this basic program. How this program is altered remains, in most part, to be determined. However, it is clear that the regulation of the Wnt/ beta-catenin pathway is a critical hub. The level of beta-catenin is crucial for feather and hair formation, as its down-regulation appears to be linked with the formation of avian scales in chick, and cutaneous glands in mice. Furthermore, its inhibition leads to the formation of nude skin and is required for that of corneal epithelium. Here I propose a new theory, to be further considered and tested when we have new information from genomic studies. With this theory, I suggest that the alpha-keratinized hairs from living synapsids may have evolved from the hypothetical glandular integument of the first amniotes, which may have presented similarities with common day terrestrial amphibians. Concerning feathers, they may have evolved independently of squamate scales, each originating from the hypothetical roughened beta-keratinized integument of the first sauropsids. The avian overlapping scales, which cover the feet in some bird species, may have developed later in evolution, being secondarily derived from feathers.

show abstract

Epidermal keratinization in the salamander and a comparison with other amphibia

Cited by 46 publications

References 25 publications

Cornification in the claw of the amphibianXenopus laevis(Pipidae, Anura) and comparison with claws in amniotes

Cornification in the claw of the amphibianXenopus laevis(Pipidae, Anura) and comparison with claws in amniotes

Keratinization of the epidermis of the Australian lungfish Neoceratodus forsteri (dipnoi)

A new scenario for the evolutionary origin of hair, feather, and avian scales

Contact Info

Product

Resources

About