Distinctive autoradiographic patterns of glycine incorporation in rat enamel and dentine matrices

Young, Richard W.; Greulich, Richard C.

doi:10.1016/0003-9969(63)90068-2

Cited by 68 publications

(14 citation statements)

References 24 publications

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“…Radioactive tracers of certain substances in the dentin can then be used as an indicator of the appearance and disappearance of the tracer itself from the body as a whole. 3H-amino acids, particularly glycine and proline, have been used in radioautographic studies as precursors to dentinal proteins, presumably mainly collagen (Carneiro and Leblond, 1959;Leblond, 1963;Young and Greulich, 1963;Weinstock and Leblond, 1974). These labeled amino acids are incorporated by the odontoblasts, and within a short time they are seen as an intensely labeled band of protein (collagen) in the dentin which neither turns over nor redistributes, but which remains in that position for the life of the tooth.…”

Section: Discussionmentioning

confidence: 98%

“…Despite the presence of cellular processes, the calcified collagen of dentin is remarkably stable and resists turnover of its organic constituents (Young and Greulich, 1963). Thus, dentin serves as a n almost permanent history of events which occur systematically, such as the changes at birth, which are recorded as the neonatal line separating prenatal from postnatal dentin.…”

Section: Discussionmentioning

confidence: 99%

“…the parathyroid gland (Nakagami et al, 1971), the labeled secretion product is delivered from the cells and is lost from the system. In bone and dentin, however, some of the secreted proteins become part of a collagenous matrix adjacent to the cells which is transformed into a mineralized record of labeled proteins produced by the cells (Carneiro and Leblond, 1959;Young and Greulich, 1963;Weinstock and Lebond, 1974). Enamel on the other hand, does not behave in this manner, since the secreted matrix proteins tend to disperse from the initial site of deposition and randomize throughout the previously secre:ed enamel layer (see reviews in Leblond and Warshawsky, 1979;Warshawsky, 1979).…”

mentioning

confidence: 96%

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Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of ³H‐labeled proline and tyrosine

Josephsen

Warshawsky

1982

Am. J. Anat.

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After injection of labeled precursors such as 3H-proline or 3H-tyrosine into rats, the incisor dentin contains a continuous and stable record of precursor incorporation into labeled proteins. This record was visualized and quantitated with radioautography in order to evaluate the quantitative changes in enamel where newly secreted proteins randomize with older proteins and both are eventually lost. Up to 4 hours after injection, the pulse-dose was incorporated as a highly labeled band of predentin. The band was entirely within calcified dentin at 2 days and was further removed from new predentin by 4 and 8 days. Dentin which formed proximal to the heavily labeled band contained an amount of radioactivity reflecting the level of labeled precursor available at that time. A standardizing factor for experimental error was obtained by quantitating the reaction in the heavily labeled band, and a post-pulse incorporation factor was determined from the amount of radioactivity added per day as weakly labeled dentin. The variation within the heavily labeled band was assumed to reflect experimental error. The number of grains in the bands were averaged from 4 hours to 8 days to give the standardizing factor. This was multiplied by the ratio of enamel to dentin counts in the same section to obtain a corrected enamel count. In this way the coefficient of variation was improved from a high of 17.2% in uncorrected enamel counts to 2.4% in corrected counts. The post-pulse incorporation factor was higher with tyrosine than with proline. With proline it amounted to 5% increase per day from 1 to 4 days and 2.5% per day from 4 to 8 days after injection. In addition, with 3H-proline the incorporation into predentin increased from 30 minutes to 4 hours. With tyrosine, the counts increased from 30 minutes to 1 hour, but decreased by nearly one third from 1 to 4 hours. This was interpreted as a loss of short-lived matrix proteins including procollagen peptides produced during conversion from procollagen to tropocollagen in the predentin.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 96%

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Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of ³H‐labeled proline and tyrosine

Josephsen

Warshawsky

1982

Am. J. Anat.

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“…The phenomenon of diffusion and apparent randomization of silver grains over enamel in radioautographs over long intervals following single injections of radioactive amino acids has been noted by several workers (reviewed in Young and Greulich, 1963;Leblond and Warshawsky, 1979;Warshawsky, 1979). Among reasons given to explain this unusual movement of labeling include that it is: 1) an artifact caused by fixatives "pushing" freely diffusable labeled material out of the appositional band into deeper regions of the enamel (reviewed in Young and Greulich, 1963); 2) an expression of the globular nature of enamel proteins and their arrangement in a thixotropic gel, which allows free mixing of all components (Eastoe, 1979); 3) an expression of movement of label along an attenuating Tomes' process (Leblond and Warshawsky, 1979;Warshawsky, 1979;Warshawsky and Josephsen, 1981); and 4) an expression of the differential migratory behavior of two classes of enamel proteins in which newly synthesized and relatively hydrophobic amelogenins are deposited at rod and interrod growth sites, whereas newly synthesized and relatively hydrophilic enamelins move into deeper regions of enamel to coat the surfaces of growing hydroxyapatite crystal .…”

Section: Degradation Of Enamel Proteinsmentioning

confidence: 93%

Degradation and loss of matrix proteins from developing enamel

et al. 1989

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The pattern and timing of the breakdown and loss of matrix proteins were studied in developing rat incisor enamel using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), fluorography, radioautography, and in vitro incubations of proteins isolated from freshly dissected, crushed pieces of enamel. For biochemical studies, the technique of Robinson et al. (1974, 1977, 1983) was used to transect the enamel organ and enamel into a series of strips at 1 mm intervals along the length of the tooth. The proteins in each strip were extracted and either quantified by Lowry analysis or applied to 12% slab (enamel) or 5-15% continuous gradient (enamel organ) SDS-polyacrylamide gels and separated by electrophoresis. The biochemical studies indicated that the amount of protein contained within an enamel strip increased gradually by volume across the secretory stage, reached a peak early during the maturation stage, and then declined rapidly thereafter. The distribution of enamel proteins on SDS-polyacrylamide gels changed markedly throughout this period. These changes included increases and decreases in the intensity of staining of proteins at certain molecular weights (e.g., 18 kDa) and the appearance and disappearance of some proteins not seen clearly near the start of the secretory stage of amelogenesis (e.g., 32 and 10 kDa). Labeling studies with 35S-methionine suggested that the "stacked" arrangement of proteins typical of forming enamel (secretory stage) actually represented a very dynamic association of proteins, with new ones being added at the top of the stack and then breaking down with time to become those seen at lower molecular weights. Across the secretory stage, new proteins were always added to the top of the stack, but during early maturation this activity slowed dramatically, allowing the breakdown of aging proteins to be visualized more clearly. Radioautographic studies with 3H-methionine indicated that the breakdown of newly secreted proteins also was correlated with a movement of label from the site of secretion into deeper, previously unlabeled, areas of forming enamel. In vitro studies revealed that the rate and degree of breakdown of enamel proteins varied markedly, depending on the stage of amelogenesis from which the proteins were extracted. Secretory stage enamel proteins showed slow in vitro degradation with accumulation of proteins near 18 kDa. Early maturation stage enamel proteins showed more rapid breakdown with little accumulation of proteins near 18 kDa, whereas late maturation stage enamel proteins showed complete degradation by 2 days of incubation in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)

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“…In bone and dent ln, some of the secreted proteins become part of a collageno~s uatrix which 18 transformed into mineralized products of the cells (Carneiro and Leb1ond.' 1959;Young and Greulich, 1963;Weinstock and Leblond, 1974).…”

Section: Response Of the Enamel Organ And Ename! To Drilling Proceduresmentioning

confidence: 99%

In vivo experimentation on rat incisor enamel organs through a surgical window

McKee

Warshawsky

1984

Anat. Rec.

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Experimental agents administered systemically are costly and often toxic to animals. An in vivo technique has been developed whereby a surgical window in the alveolar bone allows selected areas of the rat incisor enamel organ and underlying enamel to be exposed to various drugs, radiolabeled molecules, and molecular weight markers. Sherman rats weighing 100 gm were anesthetized and the inferior surface of each hemimandible was surgically exposed. A slow‐speed dental hand drill was used to drill a small hole through the alveolar bone overlying the secretion or maturation zones of the enamel organ. The wound was closed and during recovery the mechanical trauma to the underlying tissue moved away from the hole due to the continuous eruption of the tooth. Two to 5 days later the hole was reexposed and microinjections of 3H‐proline, 125I‐salmon calcitonin, vinblastine sulphate, and normal saline (as control) were administered through the hole with a micro‐manipulator and a microliter syringe. Radioautographic detection of 3H‐proline incorporation in secretory ameloblasts and enamel at 10 minutes, 30 minutes, 1 hour, 4 hours, 1 day, and 2 days after microinjection was identical to that obtained previously by systemic injection. Two hours after microinjection of vinblastine sulphate the cellular response was again identical to that following systemic injection; 125I‐salmon calcitonin (M.W. ∼ 3,600D) was used as a molecular weight marker and was seen to diffuse into the enamel of the maturation zone at 10 minutes after microinjection. This study has demonstrated the feasibility of this new technique for experimentation on rat incisor enamel organs.

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Distinctive autoradiographic patterns of glycine incorporation in rat enamel and dentine matrices

Cited by 68 publications

References 24 publications

Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of ³H‐labeled proline and tyrosine

Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of ³H‐labeled proline and tyrosine

Degradation and loss of matrix proteins from developing enamel

In vivo experimentation on rat incisor enamel organs through a surgical window

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Distinctive autoradiographic patterns of glycine incorporation in rat enamel and dentine matrices

Cited by 68 publications

References 24 publications

Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of 3H‐labeled proline and tyrosine

Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of 3H‐labeled proline and tyrosine

Degradation and loss of matrix proteins from developing enamel

In vivo experimentation on rat incisor enamel organs through a surgical window

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Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of ³H‐labeled proline and tyrosine

Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of ³H‐labeled proline and tyrosine