Influence of Environmental Lighting on Decidualization in the Rat

Darkness-Elicited Changes in Rat Reproduction Not Mediated by Pineal Gland

“…These findings are quite in accordance with those o 1 Mitchell and Yochim [1970]. who reported that pinealectomy does not alter the effects of a very short daily photoperiod (2hL/22hD) on length of gestation or time of delivery.…”

Fetal and Placental Growth in the Rat following Differential Reduction of Litter Size

“…In the control group of the first experi ment in the present study no significant correla tion could be demonstrated between fetal weight and litter size, although that between placental weight and litter size was highly sig nificant. The observation that birth weight is inversely related to litter size (4,16,24) is confounded in the present context by the fact that large litters have a shorter gestation period (5,10,20,24) which would tend to make these neonates lighter at birth.…”

A method for regulating the duration of pregnancy and the time of parturition in Sprague-Dawley rats (Charles River CD strain)

“…The bimodal distribution of parturitions on Days 22 and 23 of pregnancy that we found in females that did not undergo a shift of the dark period throughout pregnancy has been reported by several investigators that have used 14 : 10 (light : dark) photoperiods throughout pregnancy, in contrast to our light schedule of and have studied different strains of rats 12 : 12 hr, than Sprague-Dawley. Mitchell and Yochim (1970), using the Holtzman rat strain, found a bimodal distribution of parturitions (Day 22 ϭ 38%, Day 23 ϭ under the 14 : 10 light photoperiod and Lincoln 51%) and Porter (1976Porter ( , 1979, using the Wistar strain, reported distributions of parturitions on Day 22 from 0800 to and on Day 23 from 0200 to 1800 hr with the majority of these parturitions occur-1400 hr ring in the middle of these periods. Day-22 deliveries were all in the light phase whereas Day-23 deliveries started during the dark phase but also were mainly during the light phase.…”

“…Day-22 deliveries were all in the light phase whereas Day-23 deliveries started during the dark phase but also were mainly during the light phase. Mitchell and Yochim (1970) have shown that with light phases of (and 14 hr ) all parturitions occur during the light phase 22 hr but are distributed over Days 21, 22, and 23. Dukes, Chester, and Atkinson (1974) Gilbert, Rosenwasser, and Adler (1985), who used a 14 : 10 photoperiod cycle (lights on at ), and found that 80% 0930 hr (23/29) of the Sprague-Dawley females gave birth between on Day 22.…”