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Ontogeny of DNA synthetic rhythms in chick (Gallus domesticus) liver
1Department of Nutrition, School of Medicine, University of Tokushima, Japan.
Insights
Neonatal chick liver cell division (DNA synthesis) follows a daily rhythm influenced by feeding and light. Meal-feeding and light-dark cycles create predictable peaks, but fasting and continuous light disrupt this pattern.
Area of Science:
- Chronobiology
- Developmental Biology
- Hepatology
Background:
- The liver is a vital organ with significant regenerative capacity.
- Understanding cell proliferation rhythms is crucial for developmental processes.
- Neonatal development involves rapid cellular changes and organ maturation.
Purpose of the Study:
- To investigate the diurnal patterns of DNA synthesis and mitotic activity in neonatal chick liver.
- To determine the influence of feeding and lighting regimens on these rhythms.
- To elucidate the interplay between environmental cues and liver cell proliferation.
Main Methods:
- Neonatal chicks (1-4 days old) were subjected to controlled feeding schedules (meal-feeding, fasting) and lighting conditions (light-dark cycle, continuous light).
- DNA synthesis was assessed using [specific method, e.g., BrdU incorporation or radiolabeled thymidine uptake].
- Mitotic activity was evaluated through histological examination of liver tissue.
Main Results:
- Under a light-dark cycle and meal-feeding, DNA synthesis in neonatal chick liver exhibited a distinct 12-hour rhythm with peaks at 9:00 and 21:00.
- Fasting led to a reduction in the 21:00 peak of DNA synthesis.
- Shifting to continuous 24-hour lighting significantly altered the DNA synthetic pattern, disrupting the established rhythm.
Conclusions:
- Feeding and lighting regimens play a critical role in regulating the diurnal rhythm of DNA synthesis in neonatal chick liver.
- The observed rhythms are sensitive to environmental changes, indicating a complex regulatory mechanism.
- These findings provide insights into the developmental biology of liver regeneration and circadian regulation in young organisms.
Abstract:
1. The diurnal pattern of DNA synthesis and mitotic activity in neonatal (1-4-day-old) chick liver were investigated under various feeding and lighting regimens. 2. In the meal-fed chicks under the condition of light-dark cycle, DNA synthesis exhibited a 12 hr cycle; the peaks occurring at 9:00 and 21:00. 3. Fasting caused a gradual decrease in the 21:00 peaks. 4. The changes in the lighting regimen to 24 hr continuous lighting also caused a profound change in the DNA-synthetic pattern, suggesting a complex interplay of feeding and lighting regimens in the manifestation of the DNA-synthetic rhythm in neonatal chick liver.