Cytochemical Studies of Ameloblasts and the Surface Layer of Enamel of the Rat Incisor at the Maturation Stage

Takano, Yoshiro

doi:10.1679/aohc1950.42.11

Cited by 33 publications

(19 citation statements)

References 40 publications

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“…These findings suggest that some P/Q-rich SCPPs assemble a structure or a space between the hypermineralizing tooth surface and overlying epithelium. This space is probably important for providing cell-tooth adhesion and for the inhibition of spontaneous calcification to facilitate the transportation of ions and organic molecules between tooth and dental epithelium [Takano, 1979;Al Kawas and Warshawsky, 2008]. Thus, I refer to these proteins as hypermineralization SCPPs and distinguish them from enamel matrix SCPPs.…”

Section: P/q-rich Scpp Genes and Hypermineralized Tissuesmentioning

confidence: 99%

The SCPP Gene Family and the Complexity of Hard Tissues in Vertebrates

Kawasaki¹

2011

Cells Tissues Organs

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Diverse hard tissues constituted a tooth-like skeletal element in extinct jawless vertebrates. Today, similar tissues are found in our teeth. These tissues mineralize in the extracellular matrix and involve various macromolecules. Among these molecules are secretory calcium-binding phosphoproteins (SCPPs) coded by genes that arose by duplication. Although the repertoire of SCPPs may vary in different lineages, some SCPPs are unusually acidic and are thought to participate in the mineralization of a collagenous matrix, principally either bone or dentin. Other SCPPs are rich in Pro and Gln (P/Q) and are employed to form the tooth surface. In tetrapods, the tooth surface is usually covered with enamel which develops in a matrix comprised of P/Q-rich SCPPs. By contrast, the tooth surface tissue in teleosts is called enameloid and it forms in a dentin-like collagenous matrix. Despite the difference in their matrix, both enamel and enameloid mature into hypermineralized inorganic tissues. Notably, some P/Q-rich SCPP genes are primarily expressed at this stage and their proteins localize between the tooth surface and overlying dental epithelium. Moreover, an orthologous gene is used for maturation of these 2 different tissues. These findings suggest distinct roles of acidic and P/Q-rich SCPPs during the evolution of hard tissues. Acidic SCPPs initially regulated the mineralization of bone, dentin, or a similar ancient collagenous tissue through interaction with calcium ions. P/Q-rich SCPPs arose next and originally assembled a structure or a space that facilitated the hypermineralization of dentin or a dentin-like tissue. Subsequently, some P/Q-rich SCPPs were coopted for the mineralizing enamel matrix. More recently, however, many SCPP genes were lost in toothless birds and mammals. Thus, it appears that, in vertebrates, the phenotypic complexity of hard tissues correlates with gain and loss of SCPP genes.

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Section: P/q-rich Scpp Genes and Hypermineralized Tissuesmentioning

confidence: 99%

The SCPP Gene Family and the Complexity of Hard Tissues in Vertebrates

Kawasaki¹

2011

Cells Tissues Organs

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“…x 3,800 nized as a thin layer, about 2,am thick, showing an intense affinity to hematoxylin but no affinity to silver. Electron microscopically, the ILC consisted of a ruthenium red or chromic phosphotungstic acid positive material, i.e., proteoglycans (LUFT, 1971;TAKANO, 1979) and of a few fine collagen fibrils distributed at random.…”

Section: Laver Of Cementurn 465mentioning

confidence: 99%

The innermost layer of cementum in rat molars : Its ultrastructure, development, and calcification.

Yamamoto

1986

Arch. Histol. Jap., Arch. Histol. Jpn

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“…There is additional evidence suggesting that ameloblasts also form exportable proteins after the enamel layer has developed to its full thickness (Weinstock, 1972;Warshawsky, 1979;Warshawsky and Josephsen, 1981). The exact chemical nature of these proteins remains obscure, but it is believed that they may represent components of a basal-lamina-like structure which appears on the surface of the enamel near the beginning of the maturation stage of amelogenesis (Weinstock, 1972;Takano, 1979). It is also possible that a portion of these proteins could constitute newly formed enzymes such as proteases ("amelogenases") which some workers believe are secreted extracellularly to cleave the amelogenins into small molecular weight fragments thereby promoting enamel maturation (reviewed in Carter et al, 1984;Crenshaw and Bawden, 1984).…”

mentioning

confidence: 99%

Immunocytochemical and radioautographic evidence for secretion and intracellular degradation of enamel proteins by ameloblasts during the maturation stage of amelogenesis in rat incisors

Nanci¹,

Slavkin²,

Smith³

1987

Anat. Rec.

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In the continuously erupting rat incisor the ameloblasts progress through distinct stages associated with the secretion and maturation of enamel. We have examined the possibility that the so-called "postsecretory" ameloblasts of the maturation stage of amelogenesis remain biosynthetically active and are engaged in the synthesis, secretion, and degradation of enamel gene products. The ultrastructural distribution of antigenic sites for enamel proteins was studied within enamel organ cells during the early maturation stage of amelogenesis in rat incisors by using the protein A-gold immunocytochemical technique and rabbit polyclonal antibodies developed against mouse amelogenins. All regions of amelogenesis from late secretion through the first complete modulation from ruffle-ended to smooth-ended ameloblasts were examined. Specific immunolabelling was found within the rough endoplasmic reticulum, Golgi saccules, secretory granules, and lysosomes of ameloblasts throughout these regions. The heaviest intracellular immunolabelling was found within secretory granules and lysosomes (multivesicular type). Quantitative analyses showed that the Golgi saccules and the multivesicular lysosomes of modulating ameloblasts were generally less immunoreactive compared to similar organelles in ameloblasts secreting the inner enamel layer. Radioautographic studies confirmed that ameloblasts of the maturation stage incorporated 3H-leucine and 3H-methionine and secreted labelled proteins into the enamel layer. Grain counts indicated that ameloblasts from the first ruffle-ended band incorporated about two-fold less 3H-methionine and secreted about tenfold less labelled proteins into the enamel compared to ameloblasts secreting the inner enamel layer. The results of this study confirm that ameloblasts do not terminate biosynthesis and secretion of enamel proteins once the final layer has been deposited on the surface of the developing enamel. They continue to form and release new proteins during the maturation stage which intermix with older proteins laid down initially during the secretory stage of amelogenesis. Secretory activity for enamel proteins has been detected in ameloblasts up to at least the second ruffle-ended phase of maturation, at which point the enamel matrix is partially soluble in EDTA.

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Cytochemical Studies of Ameloblasts and the Surface Layer of Enamel of the Rat Incisor at the Maturation Stage

Cited by 33 publications

References 40 publications

The SCPP Gene Family and the Complexity of Hard Tissues in Vertebrates

The SCPP Gene Family and the Complexity of Hard Tissues in Vertebrates

The innermost layer of cementum in rat molars : Its ultrastructure, development, and calcification.

Immunocytochemical and radioautographic evidence for secretion and intracellular degradation of enamel proteins by ameloblasts during the maturation stage of amelogenesis in rat incisors

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