Bilateral lesions of suprachiasmatic nuclei affect circadian rhythms in [³H]‐thymidine incorporation into deoxyribonucleic acid in mouse intestinal tract, mitotic index of corneal epithelium, and serum corticosterone

Abstract

Investigations into the role of the suprachiasmatic nuclei (SCN) in the coordination of circadian rhythms have presented differing results. Several reports have shown that ablation of the suprachiasmatic nuclei (SCNA) alters the phase and amplitude of rhythms but does not abolish them. The present study investigates the effect of SCNA on the rhythms in cell proliferation in various regions of the intestinal tract as measured by the incorporation of [3H]-thymidine into deoxyribonucleic acid, in the mitotic activity of the corneal epithelium, and in serum corticosterone levels. The study involved mice with verified lesions of the SCN (six to 13 mice per time point) and control groups of both sham-operated and unoperated mice (seven of each per time point). The mice were killed in groups that represented seven time points over a single 24 hr span (3 hr intervals with the 0800 hr sampled both at start and end of the series). The tissues examined were the tongue, esophagus, gastric stomach, and colon for DNA synthesis, the corneal epithelium for mitotic index, and blood serum for corticosterone level. The most consistent result of SCNA was a phase advance in the rhythms in cell proliferation in the tongue, esophagus, gastric stomach, colon, and corneal epithelium. A reduction in rhythm amplitude occurred in the tongue, esophagus, and corneal epithelium; however, there was an amplitude increase for the stomach, colon, and serum corticosterone. The mesor (rhythm-adjusted mean) was increased by SCNA in all tissues except the corneal epithelium. These findings further support the role of the suprachiasmatic nuclear area in the control of rhythms in cell proliferation and corticosterone production, by acting as a "phase-resetter" and as a modulator of rhythm amplitude.

Circadian-independent cell mitosis in immortalized fibroblasts

“…For example, the period of the cell cycle could be regulated by the 24-h rhythm of body temperature or hormone levels controlled by the SCN. The phase and amplitude of rhythms of cell division are altered in SCN-lesioned mice, suggesting that the circadian system can regulate cell proliferation in vivo (56). A previous study also showed that the circadian rhythm of circadian gene mutant primary fibroblasts acquired the periodicity of the host rhythm when the fibroblasts were transplanted into wild-type mice (57).…”

Chronobiology of Aging: A Mini-Review

“…3 H]-thymidine incorporation into the DNA of different organs (tongue, esophagus, gastric stomach, and colon) and of the mitotic index of the corneal epithelium of female BD2Fl mice after bilateral lesioning of the suprachiasmatic nuclei was later demonstrated [29] . The most consistent result was a phase advance in the rhythms in cell proliferation in the tongue, esophagus, gastric stomach, colon, and corneal epithelium, and a reduction in the circadian amplitude detected in the tongue, esophagus, and corneal epithelium.…”

Cross-talks between Circadian Timing System and Cell Division Cycle Determine Cancer Biology and Therapeutics

“…Even the suprachiasmatic nuclei (SCN) do not seem to be indispensable for rhythmic divisions to occur in synchrony in mouse intestine or corneal epithelium (Scheving et al 1983), as well as in mouse bone marrow (Filipski et al 2004a). In a study involving 52 mice with histologically proven SCN ablation and 34 sham-operated controls kept under LD 12:12 synchronization, the rest-activity cycle was suppressed in all of the mice with SCN ablation whereas the plasma corticosterone rhythm persisted yet with a nonsinusoidal pattern, a damped amplitude, and a phase-advance by a few hours (Filipski et al 2004a).…”