Cynthia Corbitt

Antiestrogenic glyceollins suppress human breast and ovarian carcinoma tumorigenesis

Purpose: We have identified the phytoalexin compounds glyceollins I, II, and III, which exhibit marked antiestrogenic effects on estrogen receptor function and estrogen-dependent tumor growth in vivo. The purpose of this study was to investigate the interactions among the induced soy phytoalexins glyceollins I, II, and III on the growth of estrogen-dependent MCF-7 breast cancer and BG-1 ovarian cancer cells implanted in ovariectomized athymic mice. Experimental Design: Four treatment groups for each cell line were used: vehicle control, 20 mg/kg/mouse/d glyceollin mixture injection, 0.72 mg estradiol (E2) implant, and E2 implant + 20 mg/kg/mouse/d glyceollin injection. Results: Treatment with glyceollin suppressed E2-stimulated tumor growth of MCF-7 cells (−53.4%) and BG-1 cells (−73.1%) in ovariectomized athymic mice. These tumor-inhibiting effects corresponded with significantly lower E2-induced progesterone receptor expression in the tumors. In contrast to tamoxifen, the glyceollins had no estrogen-agonist effects on uterine morphology and partially antagonized the uterotropic effects of estrogen. Conclusions: These findings identify glyceollins as antiestrogenic agents that may be useful in the prevention or treatment of breast and ovarian carcinoma.

Opioid receptor densities analyzed across seasons in the POM and VTA of the dark-eyed junco, Junco hyemalis

The motivation of songbirds to sing is influenced by two brain regions, the medial preoptic area (POM) and ventral tegmental area (VTA), which are located outside the song control system itself. These areas receive opioidergic innervation. Furthermore, the opioid enkephalin has been proposed to play a role in the reward for singing. In order to determine whether seasonal changes in song output relate to seasonal changes in opioid receptor (OR) densities in the POM and VTA, we measured the densities of micro, delta, and kappa subtypes in these brain regions in adult male dark-eyed juncos (Junco hyemalis) sampled in spring (singing), summer (singing and breeding), and fall (no singing). Receptor densities in the rostral and caudal portions of the POM were measured separately because these subregions are thought to predominantly influence appetitive and consumatory sexual behaviors, respectively. delta ORs were generally denser than micro or kappa in both parts of the POM and micro ORs were denser than the other subtypes in the VTA. Densities of micro ORs in the POM were higher in the summer than in spring or fall, although this difference was statistically significant only for cPOM (p=0.002). In rPOM, kappa OR densities tended to be higher in spring and summer than fall, although this pattern did not reach statistical significance (p=0.057). In contrast, kappa OR densities were lowest in the VTA during the summer compared to spring and fall, although this pattern did not reach statistical significance, either (p=0.094). Results obtained for cPOM micro ORs suggest a heightened reward potential for sexual behavior during the breeding season.

Age-Related Difference in Size of Brain Regions for Song Learning in Adult Male Dark-Eyed Juncos (Junco hyemalis)

In seasonally breeding adult male songbirds, the volumes of several song control regions (SCRs) change seasonally in parallel with plasma testosterone (T) levels and decrease following gonadectomy. Testosterone treatment to castrates prevents this decrease, indicating T dependency. During the breeding season, second-year (SY: birds entering their first breeding season) free-ranging male Dark-eyed Juncos (Junco hyemalis) have smaller testes than older (after second-year, ASY: birds entering at least their second breeding season) birds. SY males also have lower plasma T concentrations than ASY males at the beginning of the breeding season. We investigated differences in song structure of the two age groups and the relationship between age differences in gonadal function and SCR sizes. The average number of syllables per song, syllable duration, trill rate, song duration, and variability in song duration were age-independent. Two brain regions that are thought to be involved primarily in song learning and perception were 13 and 18% larger, respectively, in SY than in ASY males, the opposite of what would be expected based solely on reproductive measures (testis mass and cloacal protuberance width). In contrast, the volumes of two regions that directly control song expression did not differ with age. The lack of age-related size differences in regions that are required for song production may indicate that male juncos of all ages have similar brain space requirements for motor production. Where there were size differences, they were restricted to regions primarily controlling vocal behavior acquisition/perception, suggesting that first time breeders need more brain space than experienced breeders to acquire crystallized song and/or acoustically perceive aspects of their environment.

Effects of vinclozolin, an anti-androgen, on affiliative behavior in the Dark-eyed Junco, Junco hyemalis.

Endocrine disrupting chemicals (EDCs) produce changes in physiology and behavior via diverse mechanisms including acting as hormone mimics or antagonists, affecting intracellular signaling pathways, and altering hormone production pathways. The fungicide vinclozolin acts as an anti-androgen and is known to affect affiliative behaviors in rodents, fish and amphibians. To investigate the possible effects of exposure to EDCs on reproductive behavior in a wild population of songbirds, we examined the effects of vinclozolin in wild-caught Dark-eyed Juncos (Junco hyemalis). For this and many other temperate songbird species, testosterone has powerful activational effects on affiliative behaviors in adulthood. We hypothesized that vinclozolin would affect male behaviors associated with female preference. Male juncos received daily oral gavage for 10 weeks with 2mM vinclozolin in vehicle or vehicle alone. Juncos were photostimulated (16L:8D) to induce breeding behavior. Each pair of a treated and non-treated male was presented to an estrogen-primed female to assess female preference. Seven of eight females exhibited a strong preference for a male exposed to vinclozolin over a control male (p=0.01). The only significant difference in measured male behaviors was increased beak wiping in controls (p=0.006) and there was no difference in gonad size or brain weight (p>0.05 for each). Our data suggest that estrogen-primed female juncos prefer to associate with male juncos exposed to this anti-androgen. This finding demonstrates that environmentally occurring anti-androgens can affect the social behavior of this species. To our knowledge, this is the first study to show that vinclozolin has effects on the social behavior of songbirds.

Reproductive aging in Japanese quail, Coturnix japonica is associated with changes in central opioid receptors.

Quantitative in vitro autoradiography was used to measure specific mu and delta opioid receptor densities in regions of the Japanese quail, Coturnix japonica, brain that regulates reproductive endocrine and behavioral responses to determine the possible involvement of the opioid system in reproductive decline seen during aging. Densities were measured in selected brain regions of young sexually active (YAM), young photoregressed (YPM), old reproductively senescent (OIM) male, young active (YF), and old senescent female (OF) Japanese quail. Medial and lateral septum (SM, SL), medial preoptic area (POM), and n. intercollicularis (ICo) were of particular interest for reproductive responses. Similar to previous observations, mu and delta opioid receptors showed differential distributions in the areas measured. Some age-related changes were observed, with lower SM mu receptor densities in aged males (OIM) than females or young males (YAM). Densities of mu receptors in the POM and in other areas examined did not vary with sex or age. Similarly, OIM males had lower densities of delta receptors in the SM than young males (YAM and YPM); POM delta receptor densities were also low in OIM males compared to the YPM males, and YAM males were intermediate. Interestingly, photoregressed males (YPM) had higher SL delta receptor densities than any other group. Thus there were age-related differences detected in mu receptor densities among groups in the SM of OIM relative to other groups; and the mu and delta receptor densities did not differ in females with brain region. Additionally for delta receptors specifically, YF and OF did not differ from OIM for any brain region and similarly had lower densities of delta receptors compared to YAM males. These data provide support for regional differences in opioid receptor distribution and for age- and sex-related differences in delta opioid receptor densities. The direction of change presents an interesting dichotomy in that, compared to young active males, delta opioid receptor densities increased with loss of reproductive function in the YPM, whereas receptor densities decreased in the OIM. Plasma androgen levels were relatively low in both these groups compared to the young active males. This observation suggests that there is an age-related loss in the ability of this receptor system to respond to circulating and centrally produced steroid hormones in the POM and in some septal regions, compared to young animals that are responding to environmental cues. Furthermore, these data support an active role of the opioid peptide system in the inhibition of the reproductive axis in photoregression.

Investigation of prepubertal sex differences in wheel running and social behavior in three mouse strains

Sex differences in social behaviors exist in mammals during adulthood, and further evidence suggests that sex differences in behavior are present before sexual maturity. In order to model behavioral disorders in animals, it is important to assess baseline sex-related behavioral differences, especially when studying disorders for which sex-related behavioral effects are expected. We investigated the effect of sex on behavior in three strains of prepubertal mice (C57BL/6, CFW, and CF1) using a wheel-running assay. We found no significant sex differences in latency to run on the wheel or total duration of wheel running within each strain. During the social interaction test, there were no differences between the sexes in latency or total duration of contact or following between a subject and a novel mouse. We also evaluated behavioral patterns of wheel running and stereotypical behaviors such as burrowing and grooming. Both sexes showed characteristic wheel-running behavior, spending the majority of each trial interacting with the wheel when it was free and more time performing other activities (e.g., stereotypical behaviors, general locomotion) when it was jammed. These results provide evidence that, among various strains of prepubertal mice, baseline sex-related behavioral differences are not strong enough to influence the measured behaviors.

Androgen receptor location in the dark-eyed junco using a probe for in situ hybridization histochemistry generated from zebra finch cDNA

Due to the role of sex steroids, namely testosterone (T), in the development and production of song in songbirds, androgen receptor (AR) densities in the brain regions controlling this behavior (i.e., the song control system) have long been studied. Many methods have been used to determine AR density and location to investigate the functional role of T in song development and production; however, a riboprobe developed from zebra finch (Taeniopygia guttata) cDNA was shown to be much more sensitive than previous methods. The zebra finch is a common model for song development and is sexually dimorphic, but does not breed seasonally or display seasonal changes in song control region volume. In this study, we used this riboprobe for in situ hybridization histochemistry (ISHH) to describe AR mRNA location in the brain of the dark-eyed junco (Junco hyemalis), a seasonally breeding model for which T has been shown to be important. Additionally, we provide a detailed comparison of AR mRNA location between these species. We found that this probe is indeed highly sensitive. We detected AR mRNA in four major regions of the song control system (HVC, MAN, RA and Area X). Additionally, we found that the location of AR mRNA in other regions varied only slightly between these two species. These findings suggest that this method is suitable for use across songbirds and it could be useful in the ongoing attempts to elucidate the roles of sex steroid hormones on the development of this and other sex steroid dependent behaviors in songbirds.

The Fringes of Mammalness, the Platypus and Monotreme Biology

The platypus, Ornithorhynchus anatinus, is one of the best examples of confounding paradoxes in the natural sciences; early anatomists and scientists relegated the first specimens to the company of the unholy marriages of fish and monkey bodies that made mermaids and the vast plethora of chimeras produced by the early entrepreneurial manufacturers of scientific souvenirs in the eighteenth and nineteenth centuries. Disbelief and acrimony have become, over the centuries, gratitude and celebration for the existence and survival of the platypus and its close relatives, the short and long-beaked echidnas, the sole living representatives of monotremes, one of the three main branches of the crown-group Mammalia. The extraordinary morphology of monotremes is reflected by their mythical names (echidna was the mother of Chimera in Greek mythology); yet these very real, and rare, animals are not well known to most non-Australians. The present book by Tom Grant is “aimed predominantly at the lay person” and the book is streamlined along that concept; references are omitted from the text and a section on Questions and Answers reflects what might be asked by the general public. This much revised fourth edition is indeed a different book from the preceding versions, The Platypus: A Unique Mammal, published by UNSW Press between 1984 and 1995 (Grant 1995). Previous editions organized the chapters into seasons (winter through autumn) and covered various physiological, life history, and environmental topics relevant to each time of year. This seasonal arrangement has been replaced with a more traditional one and several topics have been added. The introductory chapter covers the general anatomy and distribution of the platypus and in part that of the echidnas. This opening chapter is followed by seven chapters dealing with breeding biology, the venomous system, sensory physiology, energetics and foraging, general ecology, conservation of the living platypus, and phylogeny and evolution of the platypus and allied monotremes. A perusal at the back of the book of the “Selected References,” which are organized by chapter, indicates that a fair percentage of the citations across all of the chapters have been published in the last decade. For example, one of the more important basic scientific findings since the last edition, the presence J Mammal Evol (2008) 15:289–290 DOI 10.1007/s10914-008-9078-6