Prolactin and the shared regulation of parental care and cooperative helping behavior in white-browed sparrow weaver societies.

Most recent models of the partitioning of reproduction attempt to explain patterns of skew on the assumption that dominant individuals have complete control over breeding opportunities within the group, but may nevertheless concede a share of direct reproduction to subordinates as an incentive to remain peacefully in the association. Although these models may be applicable to some animal societies, we argue that they fail to provide a comprehensive theory of skew. Instead, we suggest that subordinates may often be able to claim unsanctioned reproduction for themselves, but will be forced to exercise a degree of reproductive restraint lest they incite ejection by the dominant. Reproductive skew, in other words, may reflect the threat of ejection (inducing subordinate restraint) rather than the threat of subordinate departure (inducing reproductive concessions by dominants). We present a simple ESS model of reproductive skew under these circumstances, which demonstrates that a shift in emphasis from reproductive concessions by dominants to reproductive restraint on the part of subordinates, radically alters the predictions of skew models. High group productivity, high relatedness and (when group members are related) strong ecological constraints are all expected to lead to reduced skew (the opposite conclusions to those of previous, concession-based analyses). The reason is that these factors reduce the benefits (or increase the costs) of ejection to the dominant, who therefore does best to tolerate more subordinate reproduction.

Delayed Breeding Affects Lifetime Reproductive Success Differently in Male and Female Green Woodhoopoes

Cooperative breeding among birds is at its most extreme in white-winged choughs ( Corcorax melanorhamphos ). Choughs have never been observed to breed successfully without helpers, and reproductive success increases linearly across all group sizes (maximum = 16). Further, helpers contribute to every aspect of reproduction, including nest building and incubation. Here we show that the contribution of young helpers (one year old and less) to incubation depends on the group in which they live. In small groups (3-5 birds), young helpers contribute as much to incubation as older birds, but in large groups they contribute little. In large groups, help increases sharply with age. Old birds contribute equally, regardless of group size. Although choughs generally do not lose body mass over incubation, young helpers lose mass in proportion to the amount of incubation they perform, independent of any effect of group size. This provides evidence that helpers in cooperatively breeding birds suffer costs from providing help additional to the costs incurred from remaining philopatric. It also demonstrates that the needs of the group influence whether young birds provide help.

The present investigation was performed to elucidate the mechanism of the suppression of ovarian follicular development and maturation in lactating rats. Administration of bromocriptine (CB-154) to lactating rats did not increase basal levels of LH, FSH, inhibin and estradiol-17β in the plasma, nor did it initiate follicular development and maturation, though plasma levels of prolactin and progesterone were markedly decreased by CB-154. The effects of high levels of plasma prolactin and progesterone on secretion of gonadotropins and ovarian hormones as well as follicular development and maturation were examined using postpartum non-lactating pituitary grafted rats. Plasma levels of LH, estradiol-17 β and inhibin as well as the number of antral follicles increased significantly in postpartum non-lactating pituitary grafted rats when compared with those in control lactating rats, though high levels of plasma prolactin and progesterone were maintained in both groups. These results indicate that high levels of prolactin and progesterone do not suppress follicular development nor do they suppress secretion of LH in the postpartum rat. The suckling stimulus suppresses follicular development and maturation probably through severe inhibition of LH secretion from the pituitary gland.

Serum prolactin (PRL) and TSH basal levels and the responses of serum PRL and TSH to thyrotropin releasing hormone (TRH) were investigated by radioimmunoassay in patients with breast cancer, who were classified in the following four groups : New T13, M0 breast cancer patients (N = 70), M1 or recurrent breast cancer patients (N = 50), locally advanced breast cancer patients (N = 8) and post-biopsied breast caner patients (N =28).Serum samples were taken 7 times before and for 3 hours after administration of TRH (0.5mg, i.v.). These were examined for basal and peak values, and reaction patterns.PRL levels : Patients with locally advanced and post-biopsied breast cancer indicated high PRL levels in the basal and peak values (P < 0.01), and showed an excessive-prolonged pattern to TRH.TSH levels : Patients with locally advanced and M1 or recurrent breast cancer indicated high TSH levels in the basal and peak values and showed an excessive-prolonged pattern to TRH.To examine the detailed variations within the group of the patients with recurrent breast cancer, they were classified in the following 3 subgroups : locoregional recurrent breast cancer (N =10), skeletal metastatic breast cancer (N = 22), and visceral metastatic breast cancer (N =6).The locoregional recurrent patients showed high PRL levels in the basal and peak values. The skeletal metastasized patients with breast cancer tended to show high TSH levels in the basal and peak values.To comfirm whether local (intercostal nerve) stimulation gives any effect on high serum PRL levels in the patients with locally advanced breast cancer, epidural anesthesia was performed 24 hours in accordance with Keegan's dermatome.As a result, basal PRL values tended to decrease in the cases blocked satisfactorily, but peak PRL values indicated no change even though blocked satisfactorily. It might be caused by short anesthetic duration.Post-biopsied breast cancer patients indicated also high PRL levels in the basal and peak values, but compared post-biopsied breast cancer to post-biopsied benign mammary tumor, both indicated increment of serum PRL peak values. High serum PRL levels of post-biopsied breast cancer patients might be caused by manipulation of biopsy itself.

Life-history theory predicts that individuals should adapt their parental investment to the costs and benefits of the current reproductive effort. This could be achieved by modulating the hormonal stress response, which may shift energy investment away from reproduction and redirect it toward survival. In birds, this stress response consists of a release of corticosterone that may be accompanied by a decrease in circulating prolactin, a hormone involved in the regulation of parental care. We lack data on the modulation of the prolactin stress response. In this study, we tested the hypothesis that individuals should modulate their prolactin stress response according to the fitness value of the current reproductive effort relative to the fitness value of future reproduction. Specifically, we examined the influence of breeding status (failed breeders vs. incubating birds) and body condition on prolactin and corticosterone stress responses in a long-lived species, the snow petrel Pagodroma nivea. When facing stressors, incubating birds had higher prolactin levels than failed breeders. However, we found no effect of body condition on the prolactin stress response. The corticosterone stress response was modulated according to body condition but was not affected by breeding status. We also performed an experiment using injections of adrenocorticotropic hormone (ACTH) and found that the modulation of the corticosterone stress response was probably associated with a reduction in ACTH release by the pituitary and a decrease in adrenal sensitivity to ACTH. In addition, we examined whether prolactin and corticosterone secretion were functionally linked. We found that these two hormonal stress responses were not correlated. Moreover, injection of ACTH did not affect prolactin levels, demonstrating that short-term variations in prolactin levels are not governed directly or indirectly by ACTH release. Thus, we suggest that the corticosterone and prolactin responses to short-term stressors are independent and may therefore mediate some specific components of parental investment in breeding birds. With mounting evidence, we suggest that examining both corticosterone and prolactin stress responses could be relevant to parental investment in vertebrates.

Prolactin (PRL) plays an important role in mammary epithelial cell development and lactation. Increased levels of PRL are observed in human breast cancer, but the underlying mechanism and prognostic significance of PRL are still controversial. In this study, we sought to determine the significance of PRL in Chinese postmenopausal women with breast cancer. Plasma PRL levels in 326 healthy individuals and 333 postmenopausal breast cancer patients were analyzed. Immunohistochemical staining of cytoplasmic prolactin receptor (PRL-R) was performed. Moreover, the relationships between plasma PRL and clinicopathological parameters as well as survival in breast cancer patients were evaluated. We found that high plasma levels of PRL was more common in breast cancer patients than in healthy individuals. We also observed that high level of PRL was associated with adverse prognostic factors, such as larger tumor size, more lymph node metastasis, advanced tumor stage, negative estrogen receptor (ER) expression, and negative progesterone receptor (PR) expression of breast cancer. Kaplan-Meier analysis showed that high plasma level of PRL correlated with poor disease-free and overall survival, while Cox regression models demonstrated that high plasma level of PRL was an independent prognostic marker for disease-free survival. The rate of PRL-R positivity among those with high plasma PRL was significantly higher than that of patients with low PRL (P < 0.05). The plasma PRL level and PRL-R expression in tumor tissue may be prognostic for Chinese postmenopausal women with breast cancer. The inhibition of PRL and PRL-R signaling is a potential therapeutic approach for endocrine therapy in breast cancer.

Selection should favor flexibility in reproductive tactics when the combination of sexual traits and reproductive behaviors that achieve the highest fitness differs between males within a population. Understanding the functional significance of variation in male reproductive tactics can provide insight into their evolution. Male house finches (Carpodacus mexicanus) in a Montana population display continuous variation in parental tactics: males with more elaborated (redder) plumage color provide little or no parental care compared to less elaborated (dull) males. Here, we first determined whether elevation of prolactin (a pituitary hormone) was related to variation in male parental tactics and, second, we used the relationship between prolactin levels and parental behavior to investigate why redder males avoid a high investment in parental care. We found that prolactin elevation was closely associated with paternal care. In addition, males with redder plumage color had low prolactin levels, whereas dull males, which provision twice as frequently, had high levels of prolactin. We also found that male condition was unrelated to plumage color but negatively related to prolactin levels. These results suggest that the low provisioning of redder males was not due to physiological constraints, but instead reflected a tactic to avoid the costs associated with parental care. The condition benefits accrued by redder males may explain their higher post-breeding survival compared to dull males. Moreover, dull males were previously shown to have higher pairing success than redder males, suggesting that the relationship between male plumage color and parental care may reflect individually optimized parental tactics.

Comparative studies of social insects and birds show that the evolution of cooperative and eusocial breeding systems has been confined to species where females mate completely or almost exclusively with a single male, indicating that high levels of average kinship between group members are necessary for the evolution of reproductive altruism. In this paper, we show that in mammals, the evolution of cooperative breeding has been restricted to socially monogamous species which currently represent 5 per cent of all mammalian species. Since extra-pair paternity is relatively uncommon in socially monogamous and cooperatively breeding mammals, our analyses support the suggestion that high levels of average kinship between group members have played an important role in the evolution of cooperative breeding in non-human mammals, as well as in birds and insects.

Tramadol abuse has become a crisis in Egypt and many other Middle Eastern countries. Tramadol abuse is associated with sexual dysfunction and male infertility, according to recent animal and human studies. The objective of this study was to compare tramadol abuse patients and healthy controls regarding free testosterone and prolactin levels and semen analysis. Sixty patients with opiate use disorders attributed to tramadol (OUD-T) based on Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) diagnostic criteria and 30 healthy controls were included in the study. Sociodemographic and clinical data and urine, blood, and semen samples were collected from patients and controls for assessment. Compared with controls, OUD-T patients had higher prolactin and lower free testosterone levels. Patients with OUD-T were more likely to have lower sperm count and higher abnormal motility and forms of sperms compared with controls. Patients with OUD-T were found to be more likely to have lower free testosterone levels and lower sperm counts and vitality, and higher prolactin levels and sperm abnormal forms compared with controls.

Prolactin is associated with both maternal and paternal care and appears important in developing a bond between parent and infant. In contrast with oxytocin, another hormone important in infant care, there is scant information on the role of prolactin in maintaining adult heterosexual relationships. We present here the first results demonstrating a relationship between prolactin levels and sexual and contact affiliation behavior in a pair-bonded species. We studied cotton-top tamarins, a socially-monogamous, cooperatively-breeding primate. We measured chronic urinary prolactin levels over a four week period to include the entire female ovulatory cycle and correlated prolactin levels in males and females with simultaneous measures of contact affiliation and sexual behavior. Current mothers who were no longer nursing displayed lower amounts of sexual behavior and proximity than non-breeding females and also had marginally lower levels of prolactin. The prolactin levels of males and females were similar within pairs, and variation in prolactin levels for both sexes was explained both by the amount of sexual behavior and contact affiliation. The results parallel a previous study that compared oxytocin levels with sociosexual behavior in the same species, and supports the hypothesis that both prolactin and oxytocin are involved in pair-bonding as well as in infant care.

Testosterone, social status and parental care in a cooperatively breeding bird

Background: Taking into consideration the pulsatile secretion of prolactin, a single prolactin measurement may not be adequate to confirm abnormal prolactin level. Objectives: The present study aimed to compare prolactin serum levels in the morning and in the evening in women suspected of hyperprolactinemia. Methods: This descriptive cross-sectional study recruited women presenting to the laboratory for measurement of prolactin. In patients with symptoms of hyperprolactinemia and elevated early morning serum prolactin, a new sample was obtained in the evening. Women with a clinical history of hyperprolactinemia, pituitary adenoma and galactorrhea were excluded. Prolactin was measured by chemiluminescence method. A P value less than 0.05 was defined as statistically significant. Results: From 109 women with morning hyperprolactinemia, 52 (41.71%) had normal evening prolactin levels and 57 (58.29%) had high prolactin levels in the evening. The mean percentage of reduction in prolactin levels in the evening compared to the morning, in women with normal evening prolactin was significantly more than those who had high evening prolactin levels. Of women who had normal prolactin levels in the evening, 30.77% had normal mean levels of prolactin in the morning, as well. Conclusions: Prolactin levels of women were significantly higher in the morning than those in the evening. In 42% of the patients with borderline morning hyperprolactinemia (about twice the normal upper limit), evening prolactin levels return to normal. Therefore, single measurements may not be enough for the diagnosis of hyperprolactinemia and a criterion for treatment, particularly in the absence of galactorrhea in women with abnormal uterine bleeding.

Aims: This study aimed to investigate the relationship between prolactin (PRL) levels and inflammatory markers in women with polycystic ovary syndrome (PCOS) compared to controls.. Methods: A total of 120 women, 60 with PCOS and 60 controls, were included in this study. The participants were divided into four groups based on their PRL levels: hyperprolactinemia PCOS, normal PRL PCOS, hyperprolactinemia controls, and normal PRL controls. The levels of various inflammatory markers, including C-reactive protein (CRP), Hb, red cell distribution width (RDW-SD), mean platelet volume (MPV), and platelet distribution width (PDW), were measured and compared between the groups. The correlation between PRL levels and inflammatory markers was also analyzed. Results: The results show that the mean value of CRP was higher in the PCOS group with hyperprolactinemia (2.15±1.61) compared to the PCOS group with normal PRL levels (1.68±1.19), but the difference was not statistically significant (p=0.432). The correlation results show that there was a statistically significant negative correlation between PRL levels and Hb (r=-0.313, p=0.015) and a positive correlation between PRL levels and RDW-SD (r=0.352, p=0.006) in PCOS patients. In PCOS patients, higher PRL levels were associated with increased RDW-SD, decreased Hb levels, decreased platelet count, and increased MPV and PDW. However, there was no significant correlation between PRL levels and inflammatory markers in the control group. Conclusion: The results of this study suggest that higher PRL levels may be associated with increased inflammation in PCOS patients. However, further research is needed to understand the underlying mechanisms and potential clinical implications of these associations.

Physiological mechanisms mediating patterns of reproductive suppression and alloparental care in cooperatively breeding carnivores