Photo‐reversal of the circadian rhythm in the proliferative activity of the mouse small intestine

Abstract

Mice (C57B1) were placed for 35 days in a room with reversed light cycle; lights came on at 1800 hours and off at 0600 hours. At six hour intervals throughout the day three mice were injected with tritiated thymidine and sacrificed 30 minutes later. Crypts were dissected for radioautography and determination of disintegrations per minute per crypt, the number of cells in mitosis and the number of cells synthesizing DNA was determined. The results reported clearly demonstrate reversal of the circadian rhythm in the parameters tested.

Is There Circadian Variation in Villus Height in Rat Small Intestine?

“…The fact that villus height is in a relatively steady state throughout the day and night implies that the rate of cell exfoliation from the villi is approximately equal to the rate of recruitment of new cells from the crypts. This is consistent with the mechanisms suggested by Clarke (1973) and Cheng & Leblond (1974), and is further supported by the observation by Potten & Allen (1977) that cell loss is maximal in the mouse during the early hours of the morning, this coinciding with the time of maximal cell production reported by Sigdestad & Lesher (1971). Hence, the driving force for cell extrusion is likely to be directly associated with upward migration although it is not necessarily a passive process (Potten & Allen, 1977).…”

Studies on the Mechanism of Diurnal Variation of Proliferative Indices in the Small Bowel Mucosa of the Rat

“…In respect of renewing cell populations such as that of the small bowel mucosa, few workers have assessed such data as cell cycle phase durations derived from FLM curves in the light of possible diurnal variation in proliferative rates or in phase durations. Despite early claims to the contrary (Pilgrim, Erb & Maurer, 1963), the detailed work of Sigdestad and Lesher (Sigdestad, Bauman & Lesher, 1969;Sigdestad & Lesher, 1970, 1971 has established that a definite diurnal rhythm of proliferative activity occurs in the small bowel mucosa of the mouse.…”

Influence of Secretin and Pentagastrin on the Circadian Rhythm of Cell Proliferation in the Intestinal Mucosa in Rats

“…The use of tritiated thymidine for the labeling of the DNA-synthetizing cells and for the determination of the phases in the cell cycle demonstrated a nocturnal increase of the percentage of labeled cells during night in fasting mice [24], A simultaneous increase of the percentage of mitosis was observed [22], The photoreversibility of this rhythm suggested the circadian origin of the varia tion [23], The simultaneous increase of LI and MI was explained by two events: a nocturnal increase in the number of proliferative cells [11] and a shorter duration of the cell cycle time during the night with a shortening of G1 and G2 phases [24], In fed rats, circadian rhythms in mitotic activity and 3H-thymidine uptake were observed [21,26] with conflicting results. Scheving et al [21] found a diurnal peak for LI and MI between 11.00 a.m. and 4.00 p. m., whereas T utton [26] calculated a shorter cell cycle time during the night and obtained a maximal MI between 6.00 a.m. and 10.00 a.m.…”

“…Secretin was found to inhibit the fundic hypertrophy secondary to Pentagastrin-induced hypertrophy [23] and to suppress the Pentagastrin effect on duodenal and ileal fragments [13].…”