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Ameloblast apoptosis and IGF-1 receptor expression in the continuously erupting rat incisor model (1999)

Joseph, B. K. ; Harbrow, D. J. ; Sugerman, P. B. ; [et al.]

Springer

Apoptosis 4 (1999), S. 441-447

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ISSN: 1573-675X

Keywords: ameloblasts ; amelogenesis ; apoptosis ; insulin-like growth factor.

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract Enamel-producing cells (ameloblasts) pass through several phenotypic and functional stages during enamel formation. In the transition between secretory and maturation stages, about one quarter of the ameloblasts suddenly undergo apoptosis. We have studied this phenomenon using the continuously erupting rat incisor model. A special feature of this model is that all stages of ameloblast differentiation are presented within a single longitudinal section of the developing tooth. This permits investigation of the temporal sequence of gene and growth factor receptor expression during ameloblast differentiation and apoptosis. We describe the light and electron microscopic morphology of ameloblast apoptosis and the pattern of insulin-like growth factor-1 receptor expression by ameloblasts in the continuously erupting rat incisor model. In the developing rat incisor, ameloblast apoptosis is associated with downregulated expression of the insulin-like growth factor-1 receptor. These data are consistent with the hypothesis that ameloblasts are “hard wired” for apoptosis and that insulin-like growth factor-1 receptor expression is required to block the default apoptotic pathway. Possible mechanisms of insulin-like growth factor-1 inhibition of ameloblast apoptosis are presented. The rat incisor model may be useful in studies of physiological apoptosis as it presents apoptosis in a predictable pattern in adult tissues.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009600409421

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Anionic copolymerization of styrene and 1,1-diphenylethylene (1966)

Ureta, E. ; Smid, J. ; Szwarc, M.

New York : Wiley-Blackwell

Journal of Polymer Science Part A-1: Polymer Chemistry 4 (1966), S. 2219-2228

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ISSN: 0449-296X

Keywords: Physics ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Kinetics of anionic copolymerization of styrene (S) and 1,1-diphenylethylene (D) were investigated in THF. The rate constant of addition of D to living polystyrene was found to be k1,2 ± = 250 l./mole-sec. for , Na+ ion-pair, and that for the free , Na+ ion is k1,2-∼400,000 l./mole-sec. Both values refer to 25°C. The addition of styrene to —D-, Na+ was found to be reversible: and k2,1 was determined by three different methods to be ∼0.5-0.7 l./mole-sec. Studies performed in a stirred-flow reactor led to k-21 = 13 sec. -1 and K21 ∼ 5 × 10-2 l./mole. An alternating copolymer is obtained in the presence of a large excess of 1,1-diphenylethylene.

Additional Material: 3 Ill.