Circadian variation in cell proliferation and maturation

Refsum, Sigvald; Håskjold, Erling; Bjerknes, Rolf; Iversen, Olav Hilmar

doi:10.1007/bf02899550

Cited by 11 publications

(3 citation statements)

References 23 publications

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“…The effect is more pronounced for the MR than for the LI. The results support the theory of Refsum et al (17) that even regeneration depends on a diurnal synchronizing factor.…”

Section: Resultssupporting

confidence: 91%

Time Dependency in the Regenerative Response to Injury of the Rat Corneal Epithelium

Sandvig

Haaskjold

Refsum

1994

Chronobiology International

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In the present study a central corneal epithelial defect (diameter 3.5 mm) was made in both eyes at 12:00 h in one group of rats and at 24:00 h in another group to see if the regenerative proliferation is influenced by circadian rhythms. The labeling index and the mitotic rate were registered at 4-h intervals in the perilimbal conjunctiva, the limbal area, and different parts of the cornea from the following morning until noon the day after that. The most pronounced regenerative proliferation was seen in the midperipheral and peripheral cornea. The regenerative response occurred in both groups 24-28 h after the injury, but was highly influenced by the normal circadian rhythms, especially with regard to the mitotic rate. The results support the theory that even regeneration is influenced by a circadian proliferative factor.

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“…The effect is more pronounced for the MR than for the LI. The results support the theory of Refsum et al (17) that even regeneration depends on a diurnal synchronizing factor.…”

Section: Resultssupporting

confidence: 91%

Time Dependency in the Regenerative Response to Injury of the Rat Corneal Epithelium

Sandvig

Haaskjold

Refsum

1994

Chronobiology International

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“…In vivo, signals mediated by the central nervous system are believed to stimulate cell proliferation. This stimulus is possibly regulated by locally acting growth-inhibitors, chalones, which are produced by the mature cell compartment of the corneal epithelium (Iversen 1981; Refsum et al 1991). The in vitro observation of an increased proliferation of corneal and conjunctival epithelial cells in the control eyes, accompanied by a simultaneous decrease in the number of cells per vision field, may be explained by loss of the mature cell population and delayed maturation of epithelial cells, leading to a decrease in locally produced growth-inhibitory substances.…”

Section: Discussionmentioning

confidence: 99%

“…migration followed by DNA-synthesis and mitotic activity (Haaskjold et al 1989). In vivo studies of the normal and regenerating rat corneal epithelium have demonstrated a prominent circadian variation, which possibly is controlled by the central nervous system (Refsum et al 1991). Recently, cell-kinetic studies of the proliferative responses in corneal, limbal, and conjunctival cell populations have suggested that these epithelia are influenced by the same growth-suppressing factors (Haaskjold et al 1989).…”

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confidence: 99%

Cell kinetics of normal and healing rat corneal epithelium during organ culture

Hjortdal

Haaskjold

Sørensen

et al. 1993

Acta Ophthalmologica

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Local epithelial proliferation in corneal, limbal, and conjunctival rat epithelium was investigated during organ culture of corneo-scleral shells, by relating the number of tritium labelled cells to the total number of cells (labelling index). The changes in labelling index after a mechanically induced central corneal abrasion were also studied. Local labelling indices were measured 2 h, 1, 2, 4 and 7 days after incubation. The average labelling index increased in un-abraded specimens 4-fold after 4 days of incubation, while the total number of cells only decreased 30-50%. In eyes with a central corneal abrasion the labelling index increased 10-fold in the surrounding epithelial cells after 1 day. The labelling index of the limbal and conjunctival epithelial cells increased to the same extent after 2 days of incubation. The finding of a reduced total number of cells and an increased cell proliferation in un-abraded eyes may be explained by increased loss of mature cells normally producing growth-inhibitory substances (chalones). Alternatively, the culture medium may contain an excess of growth-stimulatory substances. The results also suggest that the proliferative response spreads in a centrifugal direction during in vitro healing of a central corneal abrasion.

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Circadian rhythm of cell division

Smaaland

1996

Progress in Cell Cycle Research

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Circadian variation in cell proliferation and maturation

Cited by 11 publications

References 23 publications

Time Dependency in the Regenerative Response to Injury of the Rat Corneal Epithelium

Time Dependency in the Regenerative Response to Injury of the Rat Corneal Epithelium

Cell kinetics of normal and healing rat corneal epithelium during organ culture

Circadian rhythm of cell division

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