Words similar to estrus
Example sentences for: estrus
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Sixty grams is confirmed as a critical body mass for induction of estrus in juvenile female opossums as identified in our previous study [ 7 ] . Somatic growth and attainment of a threshold body mass or energy reserves are known requisites for puberty in many mammals including the tammar wallaby [ 26 ] , sheep [ 27 28 ] , and several species of rodents [ 1 ] , but these factors seldom act independently of environmental factors such as photoperiod [ 26 27 ] or social cues [ 3 29 ] . The opossum is unusual in this regard, because social cues in the form of male pheromone appear to stimulate both somatic growth and ovarian activation.
Subsequent to early studies that established the pheromonal qualities of male urine to synchronize estrous cycles of laboratory mice [ 2 ] , sexual maturation in female mice was shown to be accelerated by male pheromones [ 3 ] and retarded by female pheromones [ 4 ] . Pheromonal induction of first estrus in juvenile females has been reported in a variety of other mammals including prairie voles [ 5 ] , pigs [ 6 ] , and opossums [ 7 ] .
Females lack an estrous cycle and anestrous adults are dependent upon direct contact with a non-volatile male pheromone for induction of estrus [ 8 ] . Hormonal control of scentmarking and sexual behavior of this species (hereinafter, opossum) has been described in some detail [ 9 10 ] . Estrus is induced when females nuzzle scentmarks from the androgen-dependent suprasternal (chest) gland [ 10 11 ] . Nuzzling delivers nonvolatile chemical signals to the vomeronasal organ (VNO) [ 12 ] and surgical removal of the VNO prevents induction of estrus by scentmarks alone [ 13 ] , although cautery ablation of the VNO fails to prevent ovarian activation and ovulation in females that are caged with adult males [ 14 ] . While anestrous adults are reliant on male pheromone for reproductive activation, spontaneous postlactational estrus occurs in the absence of direct contact with male pheromone [ 15 ] .
The animals (two at each time of the cycle) were sacrificed on proestrus (P1000 and 2000 h), estrus (E0200 and E1000 h), diestrus I (DI, 1100 h) and diestrus II (DII, 1100 h).
Plasma concentrations of estradiol in opossums are low (<15 pg/ml) during anestrus and are elevated (>20 pg/ml) only during estrus [ 15 ] . Mean plasma estradiol concentrations as high as 58 pg/ml have been reported in estrous females [ 25 ] , but a gradual increase in circulating estradiol during pheromonal induction of estrus in opossums has not been described.
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