Higher Plasma Testosterone Levels Research Articles

The role of perinatal testosterone on exploratory behavior, sexual motivation, and spatial working memory in adult rats

Aim: Sex differentiation occurs during the perinatal period (four days before and after birth) in the rat brain. The brain remains a female brain unless exposed to testosterone, which gets metabolized to 17β-estradiol and dihydrotestosterone. While aromatase converts testosterone to 17β-estradiol, 5α-reductase converts testosterone to dihydrotestosterone. 17β-estradiol exerts its effects by binding to an estrogen receptor, whereas dihydrotestosterone via an androgen receptor. The role of dihydrotestosterone and 17β-estradiol during the organizational phase of brain differentiation was tested using adult rat behaviors. The study sought to examine the effects of perinatal manipulations on adult rat behaviors. Materials and methods: Timed-pregnant rats received either the vehicle (5% ethanol and 95% sesame oil), exemestane (4 mg/kg/ml; aromatase inhibitor), or flutamide (20 mg/kg/ml; androgen receptor blocker) subcutaneously during the last four days of pregnancy. Pups from each group continued to receive their treatments during the first four days after birth. From postnatal day 65, these animals were subjected to open field, sexual motivation, and spatial working memory tests. Results: Male rats receiving flutamide exhibited exploratory behavior significantly more compared to exemestane and control groups. Male rats receiving exemestane had substantially higher plasma testosterone and displayed an increased interest in the estrus rat than the control and flutamide group. Conclusion: Androgen receptor blockade resulted in increased exploratory behavior in male rats where 17β-estradiol was testosterone's primary metabolite. The blocking of aromatase using exemestane resulted in higher levels of plasma testosterone and enhanced sexual motivation in male rats. Thus, 17β-estradiol and dihydrotestosterone's presence during the organizational phase is essential for normal socio-sexual and exploratory behaviors.

Associations between plasma testosterone levels and season, nutritional status, age, and body size in free-ranging male Asian black bears (Ursus thibetanus) in central Honshu, Japan

Testosterone is an important regulator of male reproduction in terms of spermatogenesis and physiological changes in the accessory reproductive organs. Despite the important role of the testosterone level in male reproduction, testosterone levels vary among male bears even during the breeding season, and the causative underlying factors remain unknown. We postulated that testosterone levels are higher during the breeding season than during other seasons in free-ranging male bears, and that testosterone levels increase with advancing age, larger body size, and better nutritional status. We assessed potential factors (season, time of sampling, body condition index, head circumference, and age) associated with the testosterone level in 80 blood samples collected from free-ranging Asian black bears (Ursus thibetanus) captured in barrel traps in the Ashio–Nikko Mountains and Okutama Mountains in central Honshu Island, Japan. The plasma testosterone level was higher during the breeding season (May–July) than during the non-breeding season (August–November). The body condition index was significantly and positively associated with the plasma testosterone level. None of the other factors were significantly associated with the plasma testosterone level. Therefore, the body condition index may be essential for maintaining high plasma testosterone levels. These findings imply that testosterone secretion might be activated in free-ranging males during the breeding season, and animals with good nutritional status may be able to maintain high plasma testosterone levels. This study uncovered an association between nutritional conditions and reproductive activity in male bears.

Targeted differential illumination improves reproductive traits of broiler breeder males

Artificial targeted illumination has a pivotal role in reproductive processes of poultry. The light-absorption mechanism in birds consists of 2 main components: the eye (retinal photoreceptors) and extraretinal photoreceptors located in the brain. Previous studies conducted on hens have shown that photostimulation of brain extraretinal photoreceptors elevates reproductive activity, whereas retinal photostimulation suppresses it. We tested the effect of targeted differential photostimulation (TDP) on reproductive activities of broiler breeder males. Fifty broiler breeder roosters (Ross), 21 wk of age, were divided into 5 environmentally controlled light-treatment rooms (n = 10) equipped with individual cages. Rooms 1 and 2 had 2 parallel lighting systems consisting of red light (630 nm) and green light (514 nm), and rooms 3 and 4 had parallel red and blue (456 nm) lighting systems. Room 5, illuminated with white light, served as the control. Birds of all groups were kept under short day (6L:18D) for 2 wk with both lighting systems in each treatment room turned on. At 23 wk of age, birds were photostimulated by gradually increasing one of the lighting systems to 14 h of light in each room, while the other lighting system was left on short day (6L:18D). Weekly semen samples were collected until 65 wk of age and analyzed for volume, motility, concentration and vitality. Monthly blood samples were drawn for plasma hormone assays. At 65 wk of age, roosters were euthanized and hypothalamus, pituitary gland, retina and testes samples were taken for mRNA expression analysis. TDP using long-day red light and short-day green light significantly increased reproductive performance, manifested by higher semen volume, motility and concentration, and testis weight; furthermore, this group had higher plasma testosterone levels, higher GnRH mRNA expression in the hypothalamus, lower levels of aromatase in the testes, and lower mRNA expression of hypothalamic serotonin transporter, and of pituitary prolactin and its receptors in the testes. This is the first study showing a positive effect of TDP on reproduction of broiler breeder roosters.

Gonad development and reproductive hormones of invasive silver carp (Hypophthalmichthys molitrix) in the Illinois River.

Reproduction is a major component of an animal's life history strategy. Species with plasticity in their reproductive biology are likely to be successful as an invasive species, as they can adapt their reproductive effort during various phases of a biological invasion. Silver carp (Hypophthalmicthys molitrix), an invasive cyprinid in North America, display wide variation in reproductive strategies across both their native and introduced ranges, though the specifics of silver carp reproduction in the Illinois River have not been established. We assessed reproductive status using histological and endocrinological methods in silver carp between April and October 2018, with additional histological data from August to October 2017. Here, we show that female silver carp are batch spawners with asynchronous, indeterminate oocyte recruitment, while male silver carp utilize a determinate pattern of spermatogenesis which ceases in the early summer. High plasma testosterone levels in females could be responsible for regulating oocyte development. Our results suggest that silver carp have high spawning activity in the early summer (May-June), but outside of the peak spawning period, female silver carp can maintain spawning-capable status by adjusting rates of gametogenesis and atresia in response to environmental conditions, while males regress their gonads as early as July. The results of this study are compared to reports of silver carp reproduction in other North American rivers as well as in Asia.

Juvenile Type Granulosa Cell Tumor

Abstract Granulosa cell tumor is a type of neoplasm, which represents 2-5% of all ovarian cancers. About 5% of these tumors are juvenile- type and usually occur to girls before puberty and to women younger than thirty years of age. There are signs premature puberty or premature emergence of secondary sexual characteristics with irregular vaginal bleeding that occur to these kind of patients. To the rare cases, like this, the occurrence of granulosa cell tumors can cause the appearance of hyperandrogenism with high levels of plasma testosterone, leading to virilization which happened to this female patient. We will present the female patient who was 35 years old and which was originally hospitalized to the Clinic for Haematology Clinical Center Kragujevac, because of extreme fatigue accompanied by dizziness. During diagnostics the patient underwent to the complete gynecological examination. After gynecological examinations and necessary diagnostic procedures, it was decided continuing the treatment at the Clinic of Gynecology and Obstetrics Clinical Center Kragujevac, where she underwent a total abdominal hysterectomy with bilateral salpingo- oophorectomy for suspected uterine neoplasm. Histopathological analysis of the obtained material confirmed the presence of follicular cysts of both ovaries and juvenile type granulosa cell tumor on the right ovary; the uterus was enlarged with multiple fibroid tumors. Granulosa cell tumor should be suspected in the cases of girls and young females if there is present an ovarian cyst paired with signs of preterm puberty or hyperestrogenism. In this case, the presence of granulosa cell tumor was masked by signs of hyperandrogenism, which is not so typical, as well as the presence of uterine fibroids who have actually been the main cause for surgical treatment.

Evaluation of PCSK9 levels and its genetic polymorphisms in women with polycystic ovary syndrome

Dyslipidemia is one of the common metabolic disorders in Polycystic Ovary Syndrome (PCOS). Proprotein convertase subtilisin kexin type 9 (PCSK9) is a new component of lipid metabolism and correlated to the development of dyslipidemia and atherosclerosis. This protein acts by preventing the recycling of LDL receptors (LDL-r) back to the cell surface and thus generates higher levels of LDLc. The objective of this study was to evaluate the PCSK9 polymorphisms rs505151 (c.2009A>G), rs562556 (c.1420A>G) and rs11206510 (T>C) and plasma PCSK9 levels in PCOS. A group of women with PCOS (n=97), and a group of healthy women (control, n=99) were selected. Biochemical parameters were determined by using Vitros system and polymorphisms were assessed by TaqMan SNP Genotyping Assays. Plasma PCSK9 levels or PCSK9 polymorphisms were not associated with PCOS. The genotype rs11206510TT was associated with higher levels of PCSK9 in both groups. The population investigated (PCOS+control groups) with the rs505151AA genotype presented higher HDLc levels. The GG genotype regarding rs562556 polymorphism was associated with higher HDLc in PCOS group, while the AA genotype carriers had higher plasma testosterone levels when evaluated all women in a same group. The results were the same by comparing recessive and dominant model despite PCOS or both groups altogether. Our results suggest that PCSK9 is not altered specifically in PCOS, but it could be associated with in lipid and androgen metabolism in Brazilian women.

Abnormal lipid/lipoprotein metabolism and high plasma testosterone levels in male but not female aromatase-knockout mice

Sex steroid hormones, such as estrogen and testosterone, are believed to play important roles in lipid metabolism. To elucidate the effects of estrogen depletion on lipid metabolism in male and female mice, we used aromatase-knockout (ArKO) mice, in which Cyp19 gene disruption prevented estrogen synthesis in vivo. These mice were divided into the following 4 groups: male and female ArKO mice and male and female wild-type (WT) mice. These mice were fed a normal-fat diet (13.6% fat) ad libitum. At 159 days after birth, the mice were tested for liver and plasma lipid content and hepatic hormone receptor- and lipid/lipoprotein metabolism-related gene expression. Interestingly, we found that hepatic steatosis was accompanied by markedly elevated plasma testosterone levels in male ArKO mice but not in female ArKO mice. Plasma lipoprotein profiles exhibited concurrent decreases in LDL- and small dense LDL-triglyceride (TG) levels in male ArKO mice. Moreover, male mice, but not female mice, exhibited marked elevations in androgen receptor (AR), sterol regulatory element-binding protein 1 (SREBP1), and CD36 expression. These results strongly suggest that Cyp19 gene disruption, which induces a sexually dimorphic response and high plasma testosterone levels in male mice, also induces hepatic steatosis.

Correlation Between Personality Traits and Testosterone Concentrations in Healthy Population.

Objective:High plasma testosterone levels have been associated with aggression, sexual behaviour and social status. The aim of this paper was to study the correlation between basal plasma testosterone levels and personality variables in healthy participants.Materials and Methods:Fifty-four participants were randomly enrolled into this study. Basal plasma testosterone levels were measured between 8:30 am and 10 am. After 24 hours of blood drawing, each subject completed personality questionnaires.Results:Positive correlation between basal plasma testosterone levels and anti-social personality traits in both genders was observed (r = 0.336 and P < 0.018). Also, a positive correlation was observed between basal plasmatestosterone levels and criminal thinking traits (r = 0. 376, P < 0.05) and Millon compulsive (r = 0.386, P < 0.010) in both genders. In female participants, a positive correlation between basal plasmatestosterone levels and psychoticism (r = 0. 25, P < 0.019) and Cloninger AUTO TCI (r = 0.507, P < 0.004) was observed. In males participants positive correlation between baseline plasmatic Testosterone levels and Millon Antisocial trait (r = 0. 544, P < 0.19) and Millon Hypomania trait (r = 0. 485, P < 0.41) and Millon Drug Abuse trait (r = 0.632, P < 0.05) was reported.Conclusion:Our results suggest gender differences in clinical and personality variables related with basal plasma testosterone level. In men, high plasma testosterone levels were associated with clinical traits, substance abuse and hypomania. Women with higher basal testosterone levels showed higher scores on personality self-direction traits.

Estrogen Receptor Alpha as a Mediator of Life-History Trade-offs.

Trade-offs between competitive and parental strategies often are mediated by sex steroids. The mechanisms underlying steroid signaling and metabolism may therefore serve as targets of disruptive selection that leads to alternative behavioral phenotypes. White-throated sparrows exhibit two color morphs that differ in both competitive and parental behavior; white-striped (WS) birds engage in more territorial singing, whereas tan-striped (TS) birds provision nestlings more often. Although WS birds have higher levels of plasma testosterone (T) and estradiol than do TS birds, experimental equalization of these hormones does not abolish morph differences in singing. Neural sensitivity to sex steroids may differ between the morphs because the gene for estrogen receptor alpha (ERα) has been captured by a chromosomal rearrangement found only in the WS birds. We recently showed that expression of this gene differs between the morphs and may drive the behavioral polymorphism. First, the ERα promoter region contains fixed polymorphisms that affect transcription efficiency in vitro. Second, in a free-living population, local expression of ERα depends strongly on morph and predicts both territorial singing and parental provisioning. Differential ERα expression is particularly striking in the medial amygdala; WS birds have three times more ERα mRNA than do TS birds. This difference persists during the non-breeding season and is unaffected by exogenous T treatment. Finally, preliminary data generated by RNA-seq confirm that ERα expression in MeA is both differentially expressed and correlated with territorial singing. Together, these results suggest that ERα may be a target of disruptive selection that leads to alternative behavioral strategies. Our future directions include a more detailed analysis of the ERα promoter regions to determine the molecular basis of differential expression as well as gene network analyses to identify genes connected to ERα.

Enhanced mesenteric arterial responsiveness to angiotensin II is androgen receptor-dependent in prenatally protein-restricted adult female rat offspring.

Gestational protein restriction results in intrauterine growth restriction and hypertension in adult female growth-restricted rats. Enhanced vascular responsiveness to angiotensin II is observed, and blockade of the renin-angiotensin system abolishes hypertension in adult growth-restricted rats, suggesting that the renin-angiotensin system contributes to intrauterine growth restriction-induced hypertension. Moreover, growth-restricted adult rats have higher plasma testosterone levels, and antiandrogen treatment abolishes hypertension, indicating an important role for testosterone. We hypothesized that androgens may play a pivotal role in the enhanced responsiveness to Ang II and hypertension. Female offspring of pregnant rats fed 20% protein (control) or 6% protein diet (protein restricted), at 6 mo of age, were studied. Plasma testosterone and mean arterial pressure in protein-restricted offspring were significantly higher compared to controls. Flutamide treatment (10 mg/kg/day subcutaneously for 10 days) reduced mean arterial pressure in protein-restricted offspring but was without significant effect in controls. Vascular Agtr1/Agtr2 ratio was significantly higher in protein-restricted offspring, an effect that was reversed by flutamide. Flutamide treatment did not have any effect on Agtr1/Agtr2 ratio in controls. Enhanced contractile response to angiotensin II in mesenteric arteries was observed in protein-restricted offspring compared with control. Flutamide treatment reversed the enhanced contractile response to angiotensin II in protein-restricted offspring without significant effect in controls. Vascular reactivity to phenylephrine was similar between the control and protein-restricted offspring with and without flutamide treatment, suggesting that enhanced contractile response and flutamide's reversal effect is specific to angiotensin II. These results suggest that prenatally protein-restricted rats exhibit an enhanced responsiveness to angiotensin II that is testosterone-dependent.

Seasonal Fluctuations of Sex Steroid Hormones in Indian Major Carp Catla Catla in Khouzestan, Iran

Catla (Catla catla) is one of the most important species of cyprinids in terms of economic and nutritional value that was considered as aquaculture candidate in Khozaestan province (Iran). In this study, 40 female and male Catla broodstocks (imported from India), were studied during year (summer 2011 to spring 2012). Seasonally, blood sampling was collected with heparinated syringe followed by catching and anesthesia. Levels of steroid hormones (testosterone, 17β-estradiol and progesterone) were measured by RIA. Results showed significant differences in all sex steroids during seasonal sampling (P<0.05). High plasma testosterone levels were measured in both sexes (female: 0.13 ± 0.03 ng/ml and male: 0.16 ± 0.04 ng/ml) in the course of the sexual maturation at the end of winter. Highest female plasma levels of 17 β-estradiol (128.50 ± 26.60 ng/ml) was measured in fall. Progesterone also significantly increased at winter (1.32 ± 0.22 ng/ml) in female broodstocks (P<0.05). All broodstocks were ripe and ready to breeding in winter. Water temperature was higth (29.88 ± 1.42) in summer which declined to (14.63 ± 0.47) in winter. According to the results, climatic conditions (Temperature) had a great impact on broodstocks Gonad development via involving of hormones in Khuzestan.

Maternal corticosterone elevation during egg formation in chickens (Gallus gallus domesticus) influences offspring traits, partly via prenatal undernutrition

The relationship between maternal stress during pregnancy in humans and the subsequent physical and mental health disorders in their children has inspired a wide array of studies on animal models. Almost all of these studies have used mammalian species, but more recently oviparous species in which the embryo develops outside the mother’s body have received more attention. These new models facilitate disentangling of the underlying mechanism due to the accessibility of the prenatal environment, the egg. Studies in birds have found that maternal stress during egg formation induces phenotypic alterations in the offspring that hatch from these eggs. However, different offspring traits have been measured in different studies and potential underlying mechanisms are barely addressed. In this study we experimentally manipulated maternal corticosterone levels in laying hens. We found that mothers with experimentally elevated plasma corticosterone levels produced offspring that are smaller at hatching, less competitive, less fearful, have lower immunocompetence and higher plasma testosterone levels, as well as an alteration of visually guided behavioural lateralization. Earlier we have showed that eggs produced by these corticosterone treated mothers were lighter and contained lower concentrations of testosterone and progesterone in the yolk. While yolk hormones showed no correlation with any offspring traits, egg mass correlated positively with offspring’s body mass from hatching until 10days of age and hatching mass correlated positively with the offspring’s ability to compete for food, indicating that prenatal under nutrition might mediate some effects of maternal stress.

Testosterone secretion in elite adolescent swimmers does not modify bone mass acquisition: a 1-year follow-up study

To investigate whether high plasma testosterone (T) levels affect areal bone mineral density (aBMD), bone geometry, and bone remodeling in young elite female swimmers (SW). Cross-sectional and 1-year follow-up study. Pediatric endocrinology and gynecology units. Twenty-five SW and 21 control subjects (CON) with breast stages IV or V (mean age 15.3 ± 1.3 y). None. Clinical and biologic parameters, aBMD, and bone geometry. Two groups of SW were constituted on the basis of total T level. High T level SW (HSW; n = 15) presented higher T than SW with normal T (NSW; n = 10) and CON (0.63 ± 0.17; 0.36 ± 0.07, and 0.38 ± 0.14 ng/mL, respectively). The SHBG level (62.1 ± 18.7 vs. 43.3 ± 19.8 nmol/L) and the LH/FSH ratio (1.7 ± 1.1 vs. 0.9 ± 0.5) were higher, and menstrual disorders (60% vs. 23.8%) were more frequent in HSW than CON, and no difference was observed between the three groups for other sex hormones and insulin-like growth factor (IGF) 1 or IGF-binding protein 3. SW presented lower fat mass in the whole body and higher lean mass in the upper limbs only. aBMD was only modestly increased in the upper limbs in the SW groups, but no other bone-specific differences (aBMD, bone geometry, bone turnover markers) were demonstrated between SW and CON at baseline or for aBMD after 1 year in a subgroup of participants. High plasma T levels have no detectable effect on bone mass and bone geometry in SW during the period of peak bone mass acquisition.

Effects of supplementation with preferred foods on the reproductive axis of American Goldfinches (Spinus tristis)

Numerous field studies indicate that food supplementation of birds can advance laying date. In addition, laboratory studies, though less common, suggest that altering the amount of food, the predictability of food, or food type can affect reproductive physiology. American Goldfinches ( Spinus tristis , formerly Carduelis tristis (L., 1758)) breed in late summer when thistle (Cynareae) seeds become abundant, suggesting that specific food types may affect their reproductive physiology. We tested whether supplementation with preferred seeds would affect reproductive physiology of male and female American Goldfinches. Birds were photostimulated and fed a standard pellet diet, or supplemented with a variety of preferred seeds. Supplemented females developed larger ovarian follicles. Supplemented males had higher levels of plasma testosterone, but only if they were also housed with a female. These results suggest that preferred seed types can act as a supplementary cue in this species, and fine-tune photoperiod-driven changes in reproductive physiology.

Factors affecting individual variation in nest-defense intensity in colonially breeding Black-tailed Gulls (Larus crassirostris)

The physiological state of parent birds combined with the value of their clutch may affect the intensity of their nest defense. In colonially breeding birds, nest-defense intensity may also be affected by the behavior of neighbors. We investigated individual variation in the nest-defense intensity among colonial Black-tailed Gulls ( Larus crassirostris Vieillot, 1818) over 2 years. Only 30%–40% of males attacked a decoy of an egg predator (Large-billed Crow ( Corvus macrorhynchos Wagler, 1827)), and the other males and females rarely attacked. Males attacking the decoy had higher levels of plasma testosterone than males that did not attack. Each male’s, but not female’s, nest-defense intensity was consistent throughout the incubation period and also across years. The intensity was not related to egg-laying date, clutch size, or age of offspring. The intensity was likely to be higher when individuals had one or more neighbors, representing higher nest-defense intensity in the year where gulls had larger number of adjacent neighboring nests (5.23 nests), but this trend was not observed in the year where they had smaller number of the neighboring nests (3.73 nests). Thus, in addition to testosterone levels, behavior of neighbors also influences the nest-defense intensity.

Androgen-dependence of male-typical sexual and aggressive behaviors inParoedura picta; A comparative study in gecko lizards

Event Abstract Back to Event Androgen-dependence of male-typical sexual and aggressive behaviors in Paroedura picta; A comparative study in gecko lizards Alison Golinski1*, Lukas Kubicka2, Tracy Brynildsen3, Lukas Kratochvil2 and Henry John-Alder3 1 Rutgers, The State University of New Jersey, Graduate Program in Endocrinology and Animal Biosciences, United States 2 Charles University in Prague, Department of Ecology, Czechia 3 Rutgers, The State University of New Jersey, Department of Ecology, Evolution & Natural Resources, United States Androgens mediate the expression of sexual and aggressive behaviors in all classes of vertebrates, but temporal associations between androgens and behavioral expression as well as the types of behaviors affected are quite variable, even among closely related species. Previous studies on two species of eyelid gecko lizards (Eublepharidae), demonstrated that the expression of aggressive behavior requires high levels of plasma testosterone (T), but the T-dependence of sexual behavior is more complicated. Courtship requires high T in Eublepharis macularius, but this phase of sexual behavior has been evolutionarily lost and cannot be induced by T in Coleonyx elegans. Nevertheless, the mounting phase of male sexual behavior persists in castrated males of both species. Although these two species have evolved differently with regard to courtship, they share T-dependence of aggression and persistent mounting in the absence of T. In the present study, we examined activational effects of T on behavior in Madagascar Ground Geckos (Gekkonidae: Paroedura picta). Like C. elegans, P. picta does not express the courtship behavior. In sexually mature lizards, T was manipulated to create 5 groups: intact control males and females, castrated males with and without T-replacement, females with T-supplementation. Social interactions were staged 6 months post-treatment and analyzed using JWatcher™ software. Aggressive behavior was expressed in both sexes of P. picta when plasma T was high. Mounting was induced by T in females, but in contrast to the eublepharids, mounting was suppressed by castration and restored by replacement of T in males. Our findings suggest these species have evolved differences in androgenic control of male sexual behavior. However, discrepancies in the latent period between treatment and behavioral trials raise the possibility that T-independence of mounting behavior in past studies may be due to a prolonged activational "memory” in the weeks following castration. Acknowledgements Supported by Fulbright (AG) and by the Czech Science Foundation, project no. 206/09/0895 (LK). Keywords: Coleonyx elegans, Eublepharis macularius, activation, Lizard, organization, Testosterone Conference: ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology, Ann Arbor, United States, 11 Jul - 13 Jul, 2011. Presentation Type: Poster Topic: Reproduction Citation: Golinski A, Kubicka L, Brynildsen T, Kratochvil L and John-Alder H (2011). Androgen-dependence of male-typical sexual and aggressive behaviors in Paroedura picta; A comparative study in gecko lizards. Front. Endocrinol. Conference Abstract: ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology. doi: 10.3389/conf.fendo.2011.03.00012 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Jul 2011; Published Online: 09 Aug 2011. * Correspondence: Ms. Alison Golinski, Rutgers, The State University of New Jersey, Graduate Program in Endocrinology and Animal Biosciences, New Brunswick, NJ, United States, kubickalukas@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Alison Golinski Lukas Kubicka Tracy Brynildsen Lukas Kratochvil Henry John-Alder Google Alison Golinski Lukas Kubicka Tracy Brynildsen Lukas Kratochvil Henry John-Alder Google Scholar Alison Golinski Lukas Kubicka Tracy Brynildsen Lukas Kratochvil Henry John-Alder PubMed Alison Golinski Lukas Kubicka Tracy Brynildsen Lukas Kratochvil Henry John-Alder Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

A twice-a-day feeding regimen optimizes performance in broiler breeder hens

To evaluate the effects of different methods of feed allocation on performance, plasma hormone concentration, and ovarian morphology, an experiment was conducted using 32 Cobb 500 broiler breeder hens. The experiment was started at 27 wk and lasted to 39 wk of age. Feeding regimens included: i) hens with an ad libitum feeding program, ii) hens that received their restricted feed once a day, iii) hens that received their restricted feed twice a day, and iv) hens that received their restricted feed 3 times a day. Each hen was assumed as an experimental unit and treatments were replicated 8 times. Daily egg production, BW, and egg and yolk weights were measured. Two blood samples were taken 3 and 6 h after the first feed allocation every 2 wk. Plasma samples were assayed for glucose, triacylglycerol (TAG), cholesterol, as well as leptin-like concentration, glucagon, triiodothyronine, thyroxine, progesterone, estradiol, and testosterone. Liver, abdominal fat pad, and ovary were collected at necropsy. Ovaries were weighed and follicles were characterized as large yellow follicles, small yellow follicles, and large white follicles. Results showed inferior egg production in ad libitum-fed birds along with high levels of plasma glucose, TAG, cholesterol, leptin-like concentration, and testosterone. Twice-a-day-fed birds produced more egg in the entire production period than once-a-day-fed birds. Better performance of twice-a-day-fed hens was associated with lower plasma glucose, TAG, and leptin-like concentration, whereas their estradiol and glucagon were higher than once-a-day-fed hens. Results obtained in our study suggest that allocation of restricted feed 2 times a day may alleviate or delay lipotoxicity development and improve reproductive performance in broiler breeder hens.

Freezability of Iberian ibex ( Capra pyrenaica) spermatozoa according to the glycerolization temperature and plasma testosterone concentration

Ibex spermatozoa can be successfully frozen using glycerolated media. However, no information is available regarding the most effective method of glycerol addition in this species. The aim of the present work was to evaluate the effect of the glycerolization temperature on the response to freezing–thawing of ibex spermatozoa collected by electroejaculation. The effect of the interaction glycerolization temperature x plasma testosterone concentration was also evaluated. The spermatozoa used in this work came from six adult ibexes maintained in captivity. Each ejaculate was divided into two aliquots in a Tris–egg yolk-based medium. One fraction was subjected to single step dilution with 5% glycerol at room temperature (23 °C). The other fraction was diluted in two steps, first by dilution at room temperature with an extender identical to that described above but without glycerol, followed by the addition of glycerol after cooling to 5 °C. The glycerolization temperature did not affect any sperm variable after thawing. Heterospecific artificial insemination involving domestic goats, revealed no differences in the fertilization rate for frozen–thawed spermatozoa diluted by the one or two step procedures (18.2% vs. 20.0%). The interaction glycerolization temperature x plasma testosterone concentration had no affect on the freezing–thawing of the sperm cells. The results revealed, however, that high plasma testosterone levels during the pre-rutting season may interfere with the freezing–thawing process, having a negative influence on sperm cryosurvival.

Effects of in vivo testosterone manipulation on ovarian morphology, follicular development, and follicle yolk testosterone in the homing pigeon

To date, our understanding of the function of testosterone in female reproductive physiology is only marginal although there are indications that testosterone is involved in modulating follicular recruitment, growth, atresia, and ovulation. Studies elevating testosterone in breeding female birds have, in most instances, found detrimental effects, such as delayed clutch initiation or decreased clutch size. In our previous study, testosterone treatment of female homing pigeons delayed clutch initiation without diminishing fecundity. In this study, we explore whether the observed effect might have been caused by testosterone influencing follicle maturation or ovulation. We implanted mature female pigeons with testosterone prior to pairing, which resulted in constant elevation of circulating testosterone concentrations within the physiological range. We killed females after they had laid the first egg and measured ovarian and follicular development. Ovarian mass and pre-hierarchical yolky follicles were not affected by the treatment; however, testosterone females produced smaller and lighter preovulatory follicles. High plasma testosterone levels at oviposition or a strong temporal increase in testosterone were negatively related to mass and diameter of second follicles. We proposed that sustained elevation of testosterone delays follicular maturation, potentially via negative feedback on the hypothalamo-pituitary-gonadal axis. Furthermore, to gain better insight into the regulation of yolk hormone acquisition, we measured testosterone concentrations in the preovulatory follicles. We found no differences between treatment groups but follicle yolk contained much higher levels of testosterone than yolk of un-incubated eggs, suggesting that hormone measurements performed after oviposition do not correctly reflect maternal allocation.

Effects of Androgens and Oestrogens on the Behaviour of Chicks in an Imprinting Situation

The behavioural effects of testosterone propionate (TP), 5alpha-dihydrotestosterone (DHT) and oestradiol benzoate (OB) were investigated in day-old chicks during imprinting sessions to a duck model. TP increased the duration of peeping while inhibiting the following reaction and the twitters. DHT had more or less the same effects while OB induces the reverse behavioural changes. The behavioural effects of hormone injections agree with behavioural sex differences observed in non-injected animals: males peep more than females which on the other hand produce more twitters. This could be related to sex differences in the hormonal status of the birds at hatching, as it is known that during incubation male chick embryos have higher plasma testosterone levels than females of corresponding ages.