The effects of a photoperiod reduction in the entrainment of circadian rhythms of systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and spontaneous locomotor activity (SLA) were determined in conscious Wistar rats by using radiotelemetry. Two groups of seven rats were maintained in a 12:12-h light-dark (12L/12D) photoperiod for 11 wk and then placed in a reduced ph...

A new model to analyse reciprocal transfer experiments to assess stages of photoperiod sensitivity in Antirrhinum has been validated in the present study. Flowering time and leaf numbers data of Antirrhinum cultivars Chimes White, Liberty White, Ariane, Winter Euro Rose, Sonnet and Rocket Orchid were used for the validation of the model. Six plants of each cultivar were transferred from LD to S...

Manipulation of photoperiod may provide a noninvasive, easily implemented, effective method to improve immune status and enhance the efficiency of production. The objective of this study was to evaluate the impact of manipulation of photoperiod on endocrine and immune responses of pregnant sows and their offspring. At d 83 of gestation, sows were moved to gestation stalls and kept on a photoper...

Previously, we found that, unlike adults, adolescent male dark-eyed juncos (Junco hyemalis) maintained large Area X volumes despite having low plasma testosterone concentrations. Other studies indicate that photoperiod may act independently of testosterone to modulate vocal control region (VCR) volumes in adult songbirds. In the present study, we investigated the effects of testosterone and pho...

The role of photoperiod in the induction of diapause in eggs laid by field-collected adult Aedes sollicitans mosquitoes was examined at different temperatures. Short-day photoperiods induced a much higher incidence of diapause at 15 degrees than at 22 degrees C, whether eggs were 0, 1, 2, 3, 4 or 5 days old postoviposition on exposure. A 6-week exposure to a 6:18 to 10:14 (L:D) photoperiod at 1...

12 month photoperiod cycle, normal yearly cycles compressed into 9 and 6 months, and a constant 12 hour light/12 hour dark regime and the effects of these experimental photoperiod regimes on the times of spawning of both male and female rainbow trout. Spawning was advanced by 6 weeks under the 9 months photoperiod regime, and by 12 weeks under the 6 month regime in comparison with the normal cy...

The effect of the hormones triiodothyronine (T3) and melatonin on antioxidant defense system was studied in 6-propyl thiouracil (6-PTU)-treated or photoperiod-exposed teleost Anabas testudineus. 6-PTU (2 microg/g) treatment or photoperiod exposure (24 h) increased malondialdehyde (MDA) and conjugated dienes (CD) concentrations, indicating increased lipid peroxidation (LPO) in the experimental c...

Birds respond to environmental changes by modulating their levels of plasma corticosterone, a stress hormone produced by the adrenal glands. Baseline levels of corticosterone and the magnitude of adrenocortical response to acute stress are known to vary seasonally. Photoperiod is one of several potential factors which could affect the seasonal modulation of corticosterone secretion. In this stu...

Diurnally active golden spiny mice (Acomys russatus) and nocturnal common spiny mice (Acomys cahirinus) coexist in hot rocky deserts of Israel. Diurnal and nocturnal activities expose these species to different climatic conditions. Nonshivering thermogenesis (NST) capacity of individuals of both species immediately upon removal from the field exhibited seasonal changes, with no significant inte...

Variation in maize for response to photoperiod is related to geographical adaptation in the species. Maize possesses homologs of many genes identified as regulators of flowering time in other species, but their relation to the natural variation for photoperiod response in maize is unknown. Candidate gene sequences were mapped in four populations created by crossing two temperate inbred lines to...