The aim of the present experiment was to determine the growth hormone (GH) and prolactin (PRL) secretions in relation to the milk yield of lambed sheep used for milk under different photoperiodic conditions. The study was carried out at the Experimental Station of the Department of Sheep and Goat Breeding of the Agricultural University in Krakow, using 60 Polish Long-wool sheep assigned to thre...

Adult male rose ringed parakeets were exposed to very long photoperiod (22 hr L: 2 hr D) and very short photoperiod (2 hr L: 22 hr D) daily for 60 days during different phases of the annual testicular cycle. Adrenal activities of the experimental birds were compared with that of parallel held natural photoperiodic birds. Marked atrophy of adrenocortical cells was noted in the glands of long pho...

C. nipponensis Photoperiod is an important factor influencing many biological processes including population dynamics of many insect species in temperate zones. To determine the population response of Chrysoperla nipponensis under altered conditions (high temperature and short photoperiod) and to test whether the short photoperiod was suitable for artificial storage, the life table data of were...

Photoperiod is one of the major environmental factors determining time to flower initiation and first flower appearance in plants. In chickpea, photoperiod sensitivity, expressed as delayed to flower under short days (SD) as compared to long days (LD), may change with the growth stage of the crop. Photoperiod-sensitive and -insensitive phases were identified by experiments in which individual p...

Individuals of numerous species limit energy expenditure during winter by inhibiting reproduction and other nonessential functions. To time these adaptations appropriately with the annual cycle, animals rely on environmental cues that predict, well in advance, the onset of winter. The most commonly studied environmental factor that animals use to time reproduction is photoperiod. Rodents housed...

Variation in complex physiological pathways has important effects on human function and medical treatment. Complex pathways involve cells at multiple locations, which serve different functions regulated by many genes and include complex neuroendocrine pathways that regulate physiological function. One of two competing hypotheses regarding the effects of selection on complex pathways predicts th...

INTRODUCTION Shift workers-e.g., health care professionals, truck drivers, and factory workers-are forced to maintain daily cycles at odds with their natural circadian rhythms and as a consequence need to frequently readjust these cycles. This shift work-induced circadian desynchrony (CD) is associated with increased sleep disorders and with alcohol abuse. Nonetheless, it has proven difficult t...

Ware JV, Nelson OL, Robbins CT, Jansen HT. Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment. Am J Physiol Regul Integr Comp Physiol 303: R890–R902, 2012. First published September 12, 2012; doi:10.1152/ajpregu.00313.2012.—Seasonal cycles of reproduction, migration, and hibernation are often synchronized to changes in day...

The molecular basis of seasonal or nonseasonal breeding remains unknown. Although laboratory rats are generally regarded as photoperiod-insensitive species, the testicular weight of the Fischer 344 (F344) strain responds to photoperiod. Recently, it was clarified that photoperiodic regulation of type 2 iodothyronine deiodinase (Dio2) in the mediobasal hypothalamus (MBH) is critical in photoperi...

the main purpose of this study was to evaluate the influence of the photoperiod on the seminal traits of crossbreed wool-producing rams throughout on year period. for the effect of photoperiod two periods were considered: decreasing daylight length (summer and autumn) and increasing daylight length (winter and spring). for the study 5 baluchi × moghani (bl×mg) and 5 arkharmerino × moghani (am×m...