Relevance of mating-associated stimuli, ovulation, and the progesterone receptor for the post-coital inhibition of estrous behavior in the female rabbit

Estrous female domestic rabbits (Oryctolagus cuniculus) display scent marking (“chinning”) and sexual receptivity. Mating induces ovulation, which occurs approximately 12 h later, and also decreases chinning and receptivity. In the present study, we explored the participation of mating-associated stimuli, ovulation, and the progesterone receptor (PR) in mediating such behavioral effects. We found that copulatory stimuli were not necessary, and that ovulation alone was sufficient, as these behavioral changes were replicated in unmated females by intravenous administration of human chorionic gonadotropin (hCG). The post-mating administration (s.c.) of 5 μg/day estradiol benzoate (EB), prevented the decline in chinning and receptivity. A lower dose of EB (1 μg/day) had no effect, nor did the antiprogestin RU486 (20 mg, s.c., administered 3 h before mating). However, the combination of a single pre-mating administration of RU486 plus the post-mating administration of 1 μg/day EB completely blocked the decline in estrous behavior. We propose that PR activation around the time of mating and a post-mating decline in ovarian estradiol secretion and/or estradiol responsiveness act in parallel to terminate estrus in this species.     

刺五加花粉活力和柱头可授性的研究

用TTC法测定了刺五加花粉的活力和寿命,用联苯胺一过氧化氢法、开花后套袋法测定了其柱头可授期,用扫描电子显微镜观察了刺五加柱头的亚显微形态特征。结果表明,刺五加长花丝植株的花粉活力比中花丝植株的高;花粉活力及其下降快慢随生境不同而有所差异;通常情况下,花粉寿命约4天。刺五加长花丝植株的柱头一直不具有可授性;中花丝植株和短花丝植株的柱头,因所处生镜不同,在开花后5-7、6-8、或7-9天具可授性;生境越郁闭,柱头具可授性的时间越晚。具可授性的柱头有独特的形态特征,即：柱头外翻、5或4裂、湿性、乳突细胞呈猫耳朵状。     

Factors influencing the onset and duration of receptivity of female purple rock crabs, Hemigrapsus sexdentatus (H. Milne Edwards, 1837) (Brachyura: Grapsidae)

The effects of males, field, and laboratory conditions on the receptivity of females were tested in the New Zealand purple rock crab Hemigrapsus sexdentatus. Onset and duration of female receptivity is of interest because it influences the time available for mating and therefore the operational sex ratio (OSR), male-male competition, and the extent of sperm competition. Females were receptive once a year for a short time prior to oviposition. The breeding season was highly synchronised and lasted for about 3 weeks (from the end of March to mid-April; southern autumn), after which, almost all females carried eggs. We found few receptive females in the field (0% to 4.9%) during the breeding season despite a large number of crabs examined (935 in 1999 and 555 in 2000), suggesting that females are receptive for less than a day. The onset of the breeding season was the same for the wild crabs and those held in field cages, but the duration of receptivity increased to several days for caged females. The onset of the breeding season of females in the laboratory was earlier compared to females in the field and had, overall, a longer breeding season. Females isolated from males stayed receptive significantly longer (5.5 days) than females caged with males (3.3 days), suggesting that the duration of female receptivity is adjusted according to the presence or absence of males. Our results suggest that females have some control over their receptivity in relation to male presence, and this could influence the outcome of sexual selection.     

Hormonal status and test condition, but not sexual experience, modulate partner preference in female rats

A series of experiments was conducted to determine the contributions of hormonal status, test condition, and sexual experience to the display of partner preference by female rats. Preference for a sexually active male rat over a sexually receptive female rat was assessed in independent groups of female rats tested in a condition limiting physical contact (No Contact) and a condition allowing for sexual interaction (Contact). Although hormonal status and test condition influenced the preference for a sexually active male, repeated testing and sexual experience had no effect. Experiment 1 demonstrated that independent of test condition, preference for the male is stronger in estrogen- and progesterone-primed rats than in rats receiving the vehicle. Moreover, independent of hormone condition, rats tested in the No Contact condition exhibit a stronger preference for the male than rats tested in the Contact condition, reflecting in part the active pacing of mating stimulation by sexually receptive rats tested in the Contact condition. Experiment 2 showed that the overall pattern of partner preference in proestrous and diestrous rats was similar to that observed in ovariectomized, estrogen- and progesterone-primed, and oil-treated rats, respectively. In Experiment 3, rats primed with estrogen alone did not exhibit a preference for the male even though fully receptive. Experiments 4 and 5 demonstrated that sexual experience does not affect the expression of preference for the male in estrogen- and progesterone-primed rats. The present findings demonstrate that the female rat's preference for the male is stable across repeated tests and is not affected by sexual experience. Our results also confirm that gonadal hormones influence the expression of a preference for a sexually active male versus a sexually receptive female and demonstrate that the magnitude of preference is modulated by test conditions.     

Stabilizing selection on behavior and morphology masks positive selection on the signal in a salamander pheromone signaling complex

Natural selection maintains the integration and coordination of sets of phenotypic characters that collectively perform a task. In functional complexes in which characters span molecular to behavioral levels of organization, we might then expect similar modes of selection to produce similar patterns in evolutionary divergence at each level. To test this expectation, we diagnosed selection at behavioral, morphological, and molecular levels for courtship pheromone signaling by plethodontid salamanders. At the levels of morphology and behavior tens of millions of years of stasis (stabilizing selection) occur on each side of a transition from vaccination to olfactory delivery modes. As a proxy for the molecular level, we used plethodontid receptivity factor (PRF), a protein that is an active component of the pheromone. We cloned PRF from 12 Plethodon spp. spanning the delivery transition and obtained multiple alleles from each individual surveyed. Analyses of 61 alleles for PRF identified elevated nonsynonymous over synonymous substitution rates along lineages in a molecular phylogeny, and at 8% of sites in the protein, indicating that positive (directional) selection has acted on this vertebrate pheromone gene. Structural models showed PRF is in a family of cytokines characterized by a four-alpha-helix bundle. Positive selection in PRF was associated with receptor binding sites that are under purifying selection in other cytokines of that family. The evolutionary dynamics of the plethodontid pheromone delivery complex consists of stabilizing selection on morphological and behavioral aspects of signal delivery but positive selection on the signal mediated by receptors. Thus, different selection modes prevail at different levels in this reproductive functional complex. Evolutionary studies of integrated sets of characters therefore require separate analyses of selective action at each level.     

Pathology and ultrastructure of Hz-2V infection in the agonadal female corn earworm,Helicoverpa zea

The pathology and ultrastructure of the reproductive tract of Hz-2V-infected female corn earworm moths, Helicoverpa zea, were studied. The identity of malformed reproductive tissues found in virus-infected moths was determined by examining these tissues in moths that were infected with the virus at different life stages. Malformation of reproductive tissues in the progeny of virus-infected female moths was first observed by 3 days post-pupation (dpp), indicating that virus replication had altered the differentiation of these tissues very early on in their development. The ultrastructure of the grossly malformed agonadal reproductive tissues from insects aged 3-10dpp revealed the absence of the cuticular lining found in the oviducts of normal moths, and the proliferation of epithelial cells in these infected oviduct tissues. In addition, large quantities of virus were found aggregated into a large mass in the lumen of the malformed cervix bursa of 10dpp agonadal female pharate adult moths. Prior to eclosion, the virus in the cervix bursa was observed separated into spherical masses, which are thought to exude through the ductus bursa and collect over the vulva, forming a viral "waxy plug" that is likely to play an important role in virus transmission.     

Prenatal stress alters reproductive responses of rats in behavioral estrus and paced mating of hormone-primed rats

Adult female offspring of dams exposed to gestational stress (prenatal stress, PNS) may show altered reproductive behavior, exploration in novel environments, and/or social interactions than do their non-PNS counterparts. These behavioral differences may be more readily observed in a seminatural, paced mating paradigm, in which females have greater control of their sexual contacts, than in a standard mating situation. Adult offspring of dams exposed to restraint and lights for 45 min on Gestational Days 14-20 (PNS) were compared with those not subjected to stress (non-PNS, control condition). The motor, reproductive, and sociosexual behaviors of hormone-primed (Experiment 1) or cycling adult offspring in behavioral estrus (Experiment 2) were examined following 20 min of restraint stress under bright lights (postnatal stress). Hormone-primed PNS rats displayed less motor behavior in a novel arena than did non-PNS rats. In a standard mating test, hormone-primed PNS females tended to be more aggressive toward the male than were non-PNS rats. In a seminatural mating situation, hormone-primed PNS females showed increased avoidance behavior, such as longer latencies to the initial intromission, greater return latencies following mounts and intromissions, and more exiting subsequent to mounts and intromissions, than did non-PNS rats. PNS rats in behavioral estrus had decreased incidence and intensity of lordosis, and fewer solicitation behaviors, in both standard or paced mating situations, in which latency to and number of mounts were also increased. Thus, hormone-primed PNS rats exposed to restraint showed more avoidance behaviors in paced mating situations, while cycling PNS rats in behavioral estrus had greater disruption of reproductive responses in standard or paced mating paradigms than did non-PNS control rats.     

Molecular mechanisms of membrane interaction at implantation

Successful pregnancy is dependent upon the implantation of a competent embryo into a receptive endometrium. Despite major advancement in our understanding of reproductive medicine over the last few decades, implantation failure still occurs in both normal pregnancies and those created artificially by assisted reproductive technology (ART). Consequently, there is significant interest in elucidating the etiology of implantation failure. The complex multistep process of implantation begins when the developing embryo first makes contact with the plasma membrane of epithelial cells within the uterine environment. However, although this biological interaction marks the beginning of a fundamental developmental process, our knowledge of the intricate physiological and molecular processes involved remains sparse. In this synopsis, we aim to provide an overview of our current understanding of the morphological changes which occur to the plasma membrane of the uterine endothelium, and the molecular mechanisms that control communication between the early embryo and the endometrium during implantation. A multitude of molecular factors have been implicated in this complex process, including endometrial integrins, extracellular matrix molecules, adhesion molecules, growth factors, and ion channels. We also explore the development of in vitro models for embryo implantation to help researchers investigate mechanisms which may underlie implantation failure. Understanding the precise molecular pathways associated with implantation failure could help us to generate new prognostic/diagnostic biomarkers, and may identify novel therapeutic targets. Birth Defects Research (Part C) 108:19–32, 2016. © 2016 Wiley Periodicals, Inc.     

Genotypic variation in the effect of salinity on fertility in rice

The effect of salinity on the reproductive physiology of five rice genotypes (IR54, IR26, IR2153-26-3-5-2, IR15324-117-3-2-2 and BR6), was investigated by treatment from panicle initiation with sodium concentrations of 20, 35 or 50 mol m^-3 in an artificial seawater. In an experiment conducted in a glasshouse, plant height and dry weight were little affected by the treatments. There was, however, genotypic variation in the extent of the sodium accumulation, with IR15324-117-3-2-2 containing the highest and IR2153-26-3-5-2 the lowest concentrations: sodium concentrations were higher in older than younger leaves.Salinity delayed flowering, reduced the number of productive tillers, the number of fertile florest per panicle, the weight per grain and the grain yield: effects on grain yield were very much more severe than on vegetative growth. Panicle length was also reduced as was the number of primary branches in a panicle: again there was genotypic variation in the response of these characters to salinity, with the number of branches in IR2153-26-3-5-2 being particularly sensitive.The concentration of sodium increased in the pollen, stigmas, lemmas and paleas with each increment of external salinity. The highest concentrations of sodium in pollen and stigmas was recorded in IR54 and IR15324-117-3-2-2. Pollen viability, whether tested with the tetrazolium salt thiazolyl blue (3-{4,5-dimethylthiazolyl-2}-2,5-diphenyl monotetrazolium bromide or MTT), germination on stigmas, growth through the stylar tissue or F₁ seed set, was reduced particularly in those genotypes accumulating most sodium. At all three salt levels, a genotype which accumulated more Na in its pollen produced less-viable pollen than those with less Na in their pollen. Since the amount of Na in the pollen was highly correlated with the Na in the flag leaf, assessment of flag leaf Na should prove a useful indicator of the likely pollen viability. Stigmatic receptivity was also reduced, when estimated either from germination of viable pollen on stigmas of salt-grown plants, its growth through the stylar tissue or F₁ seed set. The reduction of seed set in crosses suggested that the overall consequences of salinity are dominated by effects on panicle development, stigmas and grain filling rather than on pollen.Analysis of the data suggests that genotypic variation exists in the extent to which salinity affects aspects of the plants reproductive physiology and development: this variation might be used in attempts to enhance the resistance of rice to salinity.