Interrelationship of Lighting Regimen and Virus Infection to Diurnal Rhythms in Liver Components Associated with Protein Metabolism in the Chick

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Abstract
The interrelationships of lighting regimen and virus infection to diurnal rhythms of liver components were studied. Progressive within-day sampling of tissues of cockerel chicks conditioned to 12-hour light/dark (LD) and 24-hour (LL) lighting regimens and infected with Newcastle disease virus (NDV) showed that these exogenous and endogenous agents significantly affected diurnal rhythm patterns of liver weight, protein, DNA, RNA and free amino acids. Under the LL regimen the NDV increased liver weights, desynchronized DNA patterns and depressed RNA and free amino acid levels as compared with control values. Under the LD regimen diurnal patterns of these parameters were held in reasonable synchronization to controls. This breakdown in patterns is attributed to the additive effects of the stress of constant lighting plus the stress of the infection. Sampling periods spaced at 12-hour intervals are believed to be the minimal requirement to establish normal control rhythms and the presence of abnormal diurnal patterns resulting from unknown exogenous or endogenous agents which might confound treatment effects.