Female canaries produce eggs with greater amounts of testosterone when exposed to preferred male song

Male birdsong has a great influence in the stimulation of female reproduction. However, female physiological responsiveness to song may depend on the degree of complexity of male song. This is expected because females of iteroparous organisms may increase their fitness by matching their reproductive investment to the predicted value of each reproductive attempt. To the extent that the expression of male ornaments is a signal of male quality, we expect females to increase their investment when paired to highly ornamented males. However, female investment may be cryptic and difficult to detect, such as androgen content in the eggs. In this study, we exposed female canaries (Serinus canaria) to attractive and unattractive song repertoires using a crossover design. As predicted, females invested greater concentrations of testosterone in their eggs when exposed to attractive repertoires than when exposed to unattractive repertoires. This implies that song repertoires convey important information about the reproductive value of a given male and suggests that testosterone deposition in egg yolk may be costly.     

Signaling Pathways That Control the Growth and Survival of Prostate Carcinoma Cells in the Absence of Androgens

Androgen-dependent human prostate adenocarcinoma cell line LNCaP was used to study the effect of androgen deprivation on the cell response to TNF-related cytokines. Several signaling pathways were implicated in cell survival in the absence of androgens. In androgen-deprived LNCaP cells, TNF- and TRAIL stimulated the cell growth and activated the mitogenic and antiapoptotic signaling pathways involving NF-B, STAT3, PI3K, and -catenin. The results suggested a role of cytokines in the survival of prostate adenocarcinoma cells deprived of androgens in vitro.     

BCL-2 in prostate cancer: a minireview

Prostate cancer progression and the development of androgen-independent prostate cancer have been largely related to a number of genetic abnormality that affect not only the androgen receptor but also crucial molecules involved in the regulation of survival or apoptotic pathways. One of these molecules, the pro-survival protein BCL-2, has been associated with the development of androgen-independent prostate cancer due to its high levels of expression in androgen-independent tumors in advanced stages of the pathology. The upregulation of BCL-2 after androgen ablation in prostate carcinoma cell lines and in a castrated-male rat model further established a connection between BCL-2 expression and prostate cancer progression. This review focuses on the experimental evidence that associates BCL-2 expression with prostate carcinogenesis and cancer progression, and analyzes the evidence that links the phosphatidylinositol 3-kinase (PI 3-kinase)/nuclear factor kappa B (NF-B) survival pathway with the upregulation of BCL-2. The way in which hormone ablation influences this survival pathway and the potential application of novel therapeutic strategies to overcome this anti-apoptotic mechanism is examined.     

The brain-pituitary-gonadal axis in the rainbow trout,Salmo gairdneri: Gonadal hormones and the maturation of gonadotropic cells

Summary Intact and castrated juvenile male rainbow trout (Salmo gairdneri) were treated with testosterone and gonadotropic hormone (GTH) to determine the maturational effects of these hormones on the GTH-cells. Electron-microscopic studies of the GTH-cells revealed that GTH and testosterone in intact animals, and testosterone in castrated fish, caused GTH-cell maturation: These cells now displayed the same appearance as GTH-cells in adult trout, including the presence of globules, a well-developed Golgi apparatus and rough endoplasmic reticulum, all of which were absent in GTH-cells of control animals. Animals with stimulated GTH-cells also had an increased GTH content of the pituitary; release of GTH could not be demonstrated. Animals treated with GTH exhibited an accelerated development of the testes, resulting in complete gametogenesis and elevated plasma testosterone levels. These results indicate that exogenous steroids as well as endogenous gonadal steroids can stimulate the full development of GTH-cells and accelerate GTH synthesis. The significance of this stimulating effect of the gonadal hormones with respect to the development of the brain-pituitary-gonadal axis and the onset of puberty is discussed.The results were presented as a poster at the 11th conference of the European Society of Comparative Endocrinology, Jerusalem, August 10–14, 1981     

Environmental physiology of the teleostean thyroid gland: a review

Synopsis Recent studies of thyroid hormone function are reviewed as they relate to the environmental physiology of teleost fish. In addition, reports dealing with the apparent interdependence of thyroid gland function with that of other endocrine glands are discussed with emphasis on the interrelated endocrine response associated with changing physiological status of teleosts.Seasonal changes in thyroid gland activity are described in several species. Although seasonal alterations in apparent thyroid status are concomitant with changes in ambient temperature, photoperiod and/or gonadal status, their biological significance is not fully understood and direct relationships are for the most part, not proven. Similarly, most reports of thyroid involvement in gonadal development or maturation are based on indirect evidence of the relationship. The exception to this is a study in immature or hypophysectomized goldfish in which thyroxine (T₄) was shown to promote ovarian development and maturation, possibly acting collateralistically or synergistically with gonadotropin. Even in this study it is not clear whether the T₄ effect is a direct action on the ovarian tissue or an indirect action via the regulation of metabolites necessary for gonad metabolism. Integumentary silvering and retinal porphyropsin formation in salmonids are stimulated by administration of T₄ or thyroid extracts. Administration of T₄ or triiodothyronine (T₃) enhances skeletal and somatic growth in some teleostean species, although the effect on somatic growth is most pronounced when these hormones act synergistically with somatotropin (STH) or androgens. The growth-promoting effects of T₄ and T₃ may be linked to their apparent involvement in lipid, carbohydrate, protein and vitamin metabolism. alterations in apparent thyroid activity concomitant with changes in ambient temperature have been reported (for example correlated with seasonal ambient thermal changes), although there are marked contradictions in data presented by different investigators. Reported temperature-related effects on thyroid function are probably secondary responses of thyroid metabolism to altered temperatures. Evidence of a direct rate of thyroid hormones in the regulation of migration (and associated behavioural modifications), salmonid smoltification, oxygen consumption, and osmotic or ionic regulation although highly suggestive in a number of areas is inconclusive and requires further critical experimental evaluation.The pituitary control (by thyrotropin) of thyroid secretion of T₄ is convincingly shown in several teleosts, and evidence of an inhibitory hypothalamic control of thyrotrop activity is highly suggestive in some species. A thyrotropic effect of somatotropin preparations is well established in several teleostean species; the effect does not appear to be related to contamination of the somatotropin preparations with thyrotropin, and may be an important consideration in explaining the apparently related involvement of T₄ (or T₃) and somatotropin in growth and metabolism. The apparent thyrotropic property of some gonadotropin preparations, shown in several teleostean species, requires further investigation before the doubts regarding hormone preparation purity can be satisfied. Recent studies of effects of prolactin on thyroid function are highly suggestive of an inhibitory role of prolactin in peripheral monodeiodination of T₄ to T₃ which secondarily affects thyroid activity in some species. There is no evidence of a direct involvement of corticotropin, melanotropin or fractions of these molecules on thyroid function in teleosts. Moreover, the little evidence in support of a role of gonadal or adrenocortical steroids in thyroid control is either often contradictory or indirect and needs to be evaluated further.Interlake epizootiological studies of thyroid dysfunction in Great Lakes salmonids provide substantive evidence for the presence of a ubiquitous waterborne goitrogen(s) in the Great Lakes environs. The nature of the goitrogen(s), whether naturally-occurring or a man-introduced toxicant, remains to be determined but the possible existence of waterborne goitrogens in natural water systems and their possible effects on experimental studies of teleostean thyroid function have to be evaluated further. If goitrogens are a common component of aquatic environments their presence could explain some of the data discrepancy among different groups of investigators, and could account for some of the apparent seasonal change in teleost thyroid physiology.     

In vitro effects of beta-endorphin on testicular release of androgens in the lizard podarcis sicula raf

The effects of the proopiomelanocortin-derived opioid peptide, beta-endorphin (β-EP), and of the opioid antagonist, naloxone (NAL), on both basal and pituitary-stimulated androgen secretion from superfused quiescent and active testes were assessed in the adult lizard, Podarcis sicula. In the absence of the homologous pituitary, in vitro treatment with β-EP and/or NAL did not affect basal secretion of androgens from quiescent and active testes. Conversely, in the presence of the homologous pituitary, treatment with β-EP brought about a decrease in androgen secretion in active testes, but no effect on quiescent ones Naloxone counteracted the inhibitory effect of β-EP in active testes, and enhanced maximal pituitary-stimulated secretion of androgens in quiescent but not in active testes. The effects produces by β-endorphin and naloxone were reversible. These results suggest that, in this lizard, opioids might be involved in the control of androgen release. The lack of effect of β-EP and naloxone when added directly to the testes seems to suggest that the opioid agonist and antagonist act on androgen release by modulating pituitary gonadotrophin output. © 1996 Wiley-Liss, Inc.     

Neuroendocrine correlates of behavioral polymorphism in white-throated sparrows

Interspecific differences in the neuropeptide systems of the lateral septum (LS) often parallel differences in social behavior. In rodents, some closely related species that differ in aggressive behavior also differ according to the level of vasopressin (VP) innervation of the LS. In songbirds, the neuropeptides vasotocin (VT) and vasoactive intestinal peptide (VIP) affect aggression when administered directly to the LS. Here, we tested whether the density of VT or VIP innervation of the LS reflects patterns of intraspecific behavioral polymorphism in male and female white-throated sparrows (Zonotrichia albicollis), in which the "white-stripe" (WS) morph behaves more aggressively than the "tan-stripe" (TS) morph. We found that the WS birds had more VT-immunoreactivity (IR) than the TS birds in the ventrolateral subdivision of the caudal LS (LSc.vl) and in the medial portion of the bed nucleus of the stria terminalis (BSTm). In addition, the TS birds had more densely stained VIP-IR in the LSc.vl than the WS birds. Males had more VT-IR than females in the LSc.vl and BSTm, and more VIP-IR in the LSc.vl. We also report sex and morph differences in VIP-IR in the basal hypothalamus, where VIP is synthesized and released into the portal vasculature. Males had nearly twice as many VIP-immunoreactive (ir) neurons in the infundibular nucleus than did females, and birds of the WS morph had more densely stained VIP-IR in the median eminence than TS birds. Our results support the hypothesis that differences in these neuropeptide systems underlie inter- and intraspecific differences in social behavior across vertebrates.     

Caenorhabditis elegans germline patterning requires coordinated development of the somatic gonadal sheath and the germ line

Interactions between the somatic gonad and the germ line influence the amplification, maintenance, and differentiation of germ cells. In Caenorhabditis elegans, the distal tip cell/germline interaction promotes a mitotic fate and/or inhibits meiosis through GLP-1/Notch signaling. However, GLP-1-mediated signaling alone is not sufficient for a wild-type level of germline proliferation. Here, we provide evidence that specific cells of the somatic gonadal sheath lineage influence amplification, differentiation, and the potential for tumorigenesis of the germ line. First, an interaction between the distal-most pair of sheath cells and the proliferation zone of the germ line is required for larval germline amplification. Second, we show that insufficient larval germline amplification retards gonad elongation and thus delays meiotic entry. Third, a more severe delay in meiotic entry, as is exhibited in certain mutant backgrounds, inappropriately juxtaposes undifferentiated germ cells with cells of the proximal sheath lineage, leading to the formation of a proximal germline tumor derived from undifferentiated germ cells. Tumors derived from dedifferentiated germ cells, however, respond to the proximal interaction differently depending on the mutant background. Our study underscores the importance of strict developmental coordination between neighboring tissues. We discuss these results in the context of mechanisms that may underlie tumorigenesis.     

Social signals influence hormones independently of calling behavior in the treefrog (Hyla cinerea)

Social signals play an important role in regulating hormone-behavior relationships. In anurans (frogs and toads), acoustic signals are an essential aspect of reproductive behavior; however, the physiological consequences of receiving social signals has remained largely undescribed. Each night for 5, 10, or 20 days, we presented acoustically isolated male treefrogs with a conspecific mating chorus, an array of tones, or no sound. We recorded calling rate of individuals throughout the experiment and collected blood before and after treatment. Days of stimulus exposure had no effect on any dependent measure. Acoustic treatment influenced steroid levels; testosterone, dihydrotestosterone, and corticosterone increased only in the group exposed to the chorus. Chorus-exposed males also showed an increase in stimulus-evoked calling. We found no correlation between androgens and calling within each treatment group. In addition, noncallers in the chorus group had higher levels of androgens than males in the tone or no sound groups. Further, chorus-exposed males with zero, low, or high rate of calling had similar levels of androgens. These data indicate that social signals increase circulating androgens independently of calling behavior. Elevated corticosterone associated with chorus reception did not inhibit calling behavior, and corticosterone showed no correlation with androgen levels.