Circadian periodicity of the cell kinetics of rat molar periodontal ligament

Roberts, W. Eugene; Aubert, Maryse; Sparaga, John M.; Smith, Ricky K.

doi:10.1016/0002-9416(79)90028-9

Cited by 19 publications

(20 citation statements)

References 16 publications

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“…The present study reveals an average labeling index of about 5-6% along a surface of continuous, relatively rapid bone formation (Fig. Circadian periodicity of labeling and mitotic activity along a slowly resorbing surface is maximal during the light cycle (resting period for nocturnal animals) [9]. Thus, proliferation of fibroblastlike cells in rat molar PDL appears to be directly related to the rate of osseous accretion along the adjacent alveolar bone surface.…”

Section: Discussionsupporting

confidence: 51%

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Circadian rhythm of mechanically mediated differentiation of osteoblasts

1984

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Rats entrained to alternating 12 h light/dark periods were sacrificed at hourly intervals over one complete circadian cycle. Each animal was injected with 3H-Thymidine 1 h before death. Autoradiographs of serial sections of maxillary first molar periodontal ligament (PDL) were prepared. Nuclear volume was determined for labeled fibroblastlike PDL cells along a physiological bone forming surface. Preosteoblasts (large nuclei), the immediate proliferating precursors of osteoblasts, were found to synthesize DNA primarily during the environmental light period and divide during the subsequent dark cycle. Less differentiated precursor cells (small nuclei), the proliferating predecessors of preosteoblasts, were in S phase primarily during the dark period and divided in the following light cycle. Since previous studies have indicated, the stress/strain-mediated increase in nuclear size to form preosteoblasts also requires about 8-12 h, the least complex osteoblast differentiation model, which is consistent with the present data, is a 60 h sequence involving at least four cell types and five alternating dark/light cycles. The principal rate-limiting step in osteoblast differentiation is the mechanically related shift in nuclear size (change in genomic expression) associated with formation of preosteoblasts.

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Section: Discussionsupporting

confidence: 51%

“…Roberts et al [9] observed a 3H-thymidine labeling index of about 1% for unstimulated PDL adjacent to a slowly resorbing surface, whereas resting and slowly forming surfaces were about 2% labeled. The present study reveals an average labeling index of about 5-6% along a surface of continuous, relatively rapid bone formation (Fig.…”

Section: Discussionmentioning

confidence: 99%

Circadian rhythm of mechanically mediated differentiation of osteoblasts

1984

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“…The circadian controls for this study are reported in detail elsewhere [16]. For the four 10 a.m. shamtreated controls there were no significant differences, although a slight tendency toward increased mitotic activity was noted.…”

Section: Resultsmentioning

confidence: 92%

Cell kinetics of the initial response to orthodontically induced osteogenesis in rat molar periodontal ligament

Smith

Roberts

1980

Calcif Tissue Int

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Initial cell kinetics (15 min-20 h) of mechanically induced osteogenesis was studied with 3H-thymidine (3H-Tdr) autoradiography. Continuous orthodontic force elicited a three-stage cell proliferative reaction within rat molar periodontal ligament (PDL): (a) brief, generalized response, characterized by a burst of mitotic activity from 75 min to 2 h and a cyclic change (decrease, increase and return to control levels) in percent labeled cells from 15 to 2 h; (b) transient, generalized response, involving an increased mitotic index (MI) from 2 to 13 h, associated with elevated labeling index (LI) from 6 to 12 h; and (c) sustained, localized osteogenic response (12 h to several days) in which cell proliferation was confined primarily to the immediate area of new bone formation. These results suggest that the initial effect of mechanical perturbation on relatively quiescent adult bone progenitor cells is a generalized, transient release of G1 and G2 blocked cells. This response may correlate clinically with the regional acceleration phenomenon (RAP), which follows bone trauma, fracture, or surgical injury.

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“…Diurnal variations have also been reported in bone and cartilage formation (Simmons, 1962(Simmons, , 1992Simmons and Nichols, 1966;Roberts et al, 1979;Petrovic et al, 1981;Stutzmann and Petrovic, 1984;Mühlbauer and Fleisch, 1990;Yosipovitch et al, 1995). In mandibular condylar cartilage, diurnal variations in cellular proliferation and collagen synthesis have been shown in growing rats (Oudet et al, 1984;Saeki, 1995).…”

Section: Introductionmentioning

confidence: 87%

“…Simmons (1962) demonstrated the existence of diurnal rhythm in mitotic activity in epiphysial growth cartilage. As described earlier, many different organs show diurnal rhythm in mitotic activity (Roberts et al, 1979). Some investigators have reported that the proliferating activity is up to 30% higher in the light period (resting period of animals) than in the dark period (active period of animals) in normal rats (Oudet et al, 1984).…”

Section: Growth Of the Condylementioning

confidence: 96%

Diurnal Variation in the Response of the Mandible to Orthopedic Force

et al. 2002

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Bone and cartilage metabolism is known to be more active during rest than during periods of activity. The purpose of this study was to examine the hypothesis that mandibular retractive force could be more effective when applied to rats during rest. Mandibular retractive force caused a considerable reduction in the condylar length in experimental groups, and the magnitude of this reduction was greater in the Light-period (08:00-20:00) group than in the Dark-period (20:00-08:00) group. The differentiation and proliferation of chondrocytes were inhibited in animals in the Light-period group, compared with those in the Dark-period group. These results suggest that the orthopedic effects of mandibular retractive force vary depending on the time of day the force is applied, and that such force may be more effective while animals are resting than while they are active.

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Circadian periodicity of the cell kinetics of rat molar periodontal ligament

Cited by 19 publications

References 16 publications

Circadian rhythm of mechanically mediated differentiation of osteoblasts

Circadian rhythm of mechanically mediated differentiation of osteoblasts

Cell kinetics of the initial response to orthodontically induced osteogenesis in rat molar periodontal ligament

Diurnal Variation in the Response of the Mandible to Orthopedic Force

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