Changes in Plasma Testosterone Levels and Brain AVT Cell Number during the Breeding Season in the Green Treefrog

Eastern Highlands and Central Australian dingoes housed in Canberra do not have a testicular cycle. They are spermatogenically active and capable of mating with oestrous females and fathering young all year. They do exhibit a breeding season (April-June) but this is entirely governed by the female. During the breeding season testosterone levels rise; this is thought to be influenced by the presence of an oestrous female and copulation. There are indications that captive dingoes in Central Australia may have a testicular cycle. Colony dingoes showed little interest in and do not mate with an oestrous domestic female at times other than January-July. They also become almost aspermous outside the breeding season. In contrast, Central Australian dingoes housed in Canberra are spermatogenically active and capable of successful matings all year.

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Testosterone Does not Increase in Response to Conspecific Challenges in the White-Bellied Antbird (Myrmeciza Longipes), A Resident Tropical Passerine

The Auk ◽

10.1093/auk/123.1.61 ◽

2006 ◽

Vol 123 (1) ◽

pp. 61-66

Author(s):

Bradley C. Fedy ◽

Bridget J. M. Stutchbury

Keyword(s):

Breeding Season ◽

Temperate Zone ◽

Plasma Testosterone ◽

Tropical Species ◽

Zone Model ◽

Territorial Aggression ◽

Social Instability ◽

Testosterone Levels ◽

Testosterone Secretion ◽

Removal Experiments

Abstract Resident tropical passerines that exhibit year-round territorial aggression do not fit well into the temperate-zone model, because testosterone does not increase substantially during the breeding season. We studied patterns of testosterone secretion in the White-bellied Antbird (Myrmeciza longipes), a resident tropical species in Panama that maintains territories year-round and is capable of aggression throughout the year, regardless of its stage of reproduction. Levels of plasma testosterone were low (mean = 0.30 ng mL−1) throughout the breeding and nonbreeding seasons and did not differ between them. Testosterone also did not increase in response to simulated conspecific intrusions. When we used temporary removal experiments to induce natural, extended conflict between males, testosterone levels did not increase in response to the extended social instability that resulted. White-bellied Antbirds demonstrate an apparent uncoupling of testosterone and territorial aggression throughout the year. La Testosterona no Aumenta como Respuesta a Desafíos de Individuos Coespecíficos en Myrmeciza longipes, un Paserino Residente de la Zona Tropical

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A Comparison of Plasma Testosterone and Progesterone Levels in The Thredbo and Duckmaloi River Platypuses Over a Twelve Month Cycle.

Australian Mammalogy ◽

10.1071/am98311 ◽

1998 ◽

Vol 20 (2) ◽

pp. 305

Author(s):

L. Hinds ◽

D. Goldney

Keyword(s):

Blood Sample ◽

Breeding Season ◽

Blood Cells ◽

Peak Plasma ◽

Plasma Testosterone ◽

Plasma Progesterone ◽

Breeding Potential ◽

Testosterone Levels

A 1-2 ml blood sample was removed from the bill sinus of 208 captured platypuses from the Duckmaloi and Thredbo Rivers over the period January 1991-March 1993. Platypuses from the Duckmaloi were sampled monthly during 1992 and in February, August and December from the Thredbo River in the same year. The numbers and sex of platypuses sampled are recorded in the following Table. Samples were stored on ice and plasma separated from blood cells within 24 hours of sampling by centrifugation for I0 minutes and the supernatant stored at -20°C. The changes in plasma testosterone and progesterone for platypuses from both rivers were compared over a 12 month cycle. The levels of these two hormones were considerably less in the breeding season in the Thredbo River platypuses than in those from the Duckmaloi River. Peak plasma progesterone levels of the order of 90 ng/ml were measured in the Duckmaloi River females compared to levels of <5 ng/ml in Thredbo River females. Male plasma testosterone levels in animals from the Duckmaloi River peaked around 15 ng/ml, whereas Thredbo River males had levels of around 6 ng/mI. These data suggest that over the period of the two year study, platypus breeding potential in the Thredbo River was significantly impaired.

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Ignoring the challenge? Male black redstarts ( Phoenicurus ochruros ) do not increase testosterone levels during territorial conflicts but they do so in response to gonadotropin-releasing hormone

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2011.0098 ◽

2011 ◽

Vol 278 (1722) ◽

pp. 3233-3242 ◽

Cited By ~ 62

Author(s):

Beate Apfelbeck ◽

Wolfgang Goymann

Keyword(s):

Breeding Season ◽

Gonadotropin Releasing Hormone ◽

Plasma Testosterone ◽

Releasing Hormone ◽

Social Challenges ◽

Testosterone Levels ◽

Territorial Conflicts ◽

Territory Defence ◽

Simulated Territorial Intrusion ◽

Territorial Intrusion

Competition elevates plasma testosterone in a wide variety of vertebrates, including humans. The ‘challenge hypothesis’ proposes that seasonal peaks in testosterone during breeding are caused by social challenges from other males. However, during experimentally induced male–male conflicts, testosterone increases only in a minority of songbird species tested so far. Why is this so? Comparative evidence suggests that species with a short breeding season may not elevate testosterone levels during territory defence. These species may even be limited in their physiological capability to increase testosterone levels, which can be tested by injecting birds with gonadotropin-releasing hormone (GnRH). We studied two populations of black redstarts that differ in breeding altitude, morphology and the length of their breeding season. Unexpectedly, males of neither population increased testosterone in response to a simulated territorial intrusion, but injections with GnRH resulted in a major elevation of testosterone. Thus, black redstarts would have been capable of mounting a testosterone response during the male–male challenge. Our data show, for the first time, that the absence of an androgen response to male–male challenges is not owing to physiological limitations to increase testosterone. Furthermore, in contrast to comparative evidence between species, populations of black redstarts with a long breeding season do not show the expected elevation in testosterone during male–male challenges.

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Experimentally Elevated Plasma Testosterone Levels Do Not Influence Singing Behaviour of Male Blue Tits (Parus caeruleus) During the Early Breeding Season

Ethology ◽

10.1111/j.1439-0310.2006.01254.x ◽

2006 ◽

Vol 112 (10) ◽

pp. 984-992 ◽

Cited By ~ 14

Author(s):

Hansjoerg P. Kunc ◽

Katharina Foerster ◽

Etiënne L. M. Vermeirssen ◽

Bart Kempenaers

Keyword(s):

Breeding Season ◽

Plasma Testosterone ◽

Parus Caeruleus ◽

Elevated Plasma ◽

Testosterone Levels ◽

Blue Tits

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Extended light period in the maternal circadian cycle impairs the reproductive system of the rat male offspring

Journal of Developmental Origins of Health and Disease ◽

10.1017/s2040174420000975 ◽

2020 ◽

pp. 1-8

Author(s):

Fernanda Mithie Ogo ◽

Glaucia Eloisa Munhoz Lion Siervo ◽

Ana Maria Praxedes de Moraes ◽

Katia Gama de Barros Machado ◽

Suellen Ribeiro da Silva Scarton ◽

...

Keyword(s):

Reproductive System ◽

System Development ◽

Sperm Count ◽

Cell Number ◽

Male Offspring ◽

Constant Light ◽

Plasma Testosterone ◽

Circadian Cycle ◽

Pregnant Rats ◽

Testosterone Levels

Abstract Alterations in the circadian cycle are known to cause physiological disorders in the hypothalamic–pituitary–adrenal and the hypothalamic–pituitary–gonadal axes in adult individuals. Therefore, the present study aimed to evaluate whether exposure of pregnant rats to constant light can alter the reproductive system development of male offspring. The dams were divided into two groups: a light–dark group (LD), in which pregnant rats were exposed to an LD photoperiod (12 h/12 h) and a light–light (LL) group, in which pregnant rats were exposed to a photoperiod of constant light during the gestation period. After birth, offspring from both groups remained in the normal LD photoperiod (12 h/12 h) until adulthood. One male of each litter was selected and, at adulthood (postnatal day (PND) 90), the trunk blood was collected to measure plasma testosterone levels, testes and epididymis for sperm count, oxidative stress and histopathological analyses, and the spermatozoa from the vas deferens to perform the morphological and motility analyses. Results showed that a photoperiod of constant light caused a decrease in testosterone levels, epididymal weight and sperm count in the epididymis, seminiferous tubule diameter, Sertoli cell number, and normal spermatozoa number. Histopathological damage was also observed in the testes, and stereological alterations, in the LL group. In conclusion, exposure to constant light during the gestational period impairs the reproductive system of male offspring in adulthood.

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PLASMA TESTOSTERONE LEVELS IN DONKEYS IN THE TROPICS

Journal of Endocrinology ◽

10.1677/joe.0.0740151 ◽

1977 ◽

Vol 74 (1) ◽

pp. 151-152 ◽

Cited By ~ 2

Author(s):

S. GOMBE ◽

C. B. KATONGOLE

Keyword(s):

Breeding Season ◽

Adult Male ◽

Laboratory Animals ◽

Plasma Testosterone ◽

Free Access ◽

Testosterone Levels ◽

Animal Physiology ◽

Basal Plasma ◽

The Tropics

Department of Animal Physiology, University of Nairobi, Chiromo, Nairobi, Kenya (Received 1 February 1977) The concentration of testosterone in the plasma of most male domestic and laboratory animals, for example bulls (Thibier, 1975), boars (Andresen, 1976) and rats (Mock, Kamel, Wright & Frankel, 1975) is usually in excess of 10 nmol/l. In seasonal breeders such as sheep, values as high as 90 nmol/l have been reported in the summer before the breeding season (Falvo, Buhl, Reimers, Foxcroft, Dunn & Dziuk, 1975). In contrast, Katongole (1971) found that in a temperate summer, plasma testosterone concentrations in Equidae, including the donkey, were 4·5 nmol/l or less. It was, therefore, of interest to investigate whether the basal plasma testosterone concentrations in donkeys would be higher and more stable in the tropics. Six potent adult male donkeys were kept in a large pen, fed rhode grass and given free access to salt and water. Blood

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INFLUENCE OF METYRAPONE ON PLASMA CONCENTRATIONS OF TESTOSTERONE AND ANDROSTENEDIONE IN MAN

Acta Endocrinologica ◽

10.1530/acta.0.0680576 ◽

1971 ◽

Vol 68 (3) ◽

pp. 576-584 ◽

Cited By ~ 5

Author(s):

K. O. Nilsson ◽

B. Hökfelt

Keyword(s):

Body Weight ◽

Male Patient ◽

Gradual Increase ◽

Plasma Concentrations ◽

Plasma Testosterone ◽

Testosterone Levels ◽

Basal Plasma ◽

Normal Males ◽

A Minor ◽

Secondary Hypogonadism

ABSTRACT Metyrapone was administered either orally, 750 mg every four h, in a total of six doses, or intravenously 30 mg per kg body weight as a four h infusion. In three males with normal endocrine functions, metyrapone given orally or intravenously induced a fall in plasma testosterone and an elevation of androstenedione within 2–8 h. When metyrapone was administered to a patient given dexamethasone to suppress endogenous ACTH production, the androstenedione levels did not alter whereas the testosterone levels showed a slight, transient decrease. In two normal females metyrapone administration was followed by a marked increase in plasma androstenedione whereas testosterone showed only a minor, gradual increase. In one male patient with Addison's disease the basal plasma testosterone was normal whereas the level of androstenedione was low. Following metyrapone intravenously, there was a slight suppression of plasma testosterone but no change in the androstenedione concentration. In one patient with primary hypogonadism, two with secondary hypogonadism and two with Klinefelter's syndrome the plasma testosterone was low under basal conditions and did not change following metyrapone. Basal plasma androstenedione was within the range for normal males and increased markedly following metyrapone in all the cases.

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Effects of oestradiol benzoate (OeB) and human chorionic gonadotrophin (hCG) on the testes and accessory sex glands of the rat

Acta Endocrinologica ◽

10.1530/acta.0.0960273 ◽

1981 ◽

Vol 96 (2) ◽

pp. 273-280 ◽

Cited By ~ 1

Author(s):

Mridula Chowdhury ◽

Robert Tcholakian ◽

Emil Steinberger

Keyword(s):

Treated Group ◽

Inhibitory Effect ◽

Male Rats ◽

Plasma Testosterone ◽

Control Group ◽

Intact Male ◽

Intact Control ◽

Testosterone Levels ◽

Oestradiol Benzoate ◽

Direct Inhibitory Effect

Abstract. It has been suggested that treatment of intact male rats with oestradiol benzoate (OeB) causes an interference with testosterone (T) production by the testes by a direct inhibitory effect on steroidogenesis. To test this hypothesis, different doses (5, 10 or 25 IU) of hCG were administered concomitantly with 50 μg of OeB to adult intact or hypophysectomized male rats. The testicular and plasma testosterone, and serum hCG levels were determined. The sex accessory weights were recorded. In the intact OeB-treated group of animals, hCG stimulated both the secondary sex organs and plasma testosterone levels above the intact control group. However, in hypophysectomized animals, although plasma testosterone levels increased above that of intact controls, their secondary sex organ weights did not. Moreover, inspite of high circulating hCG levels, the testicular testosterone content and concentration remained suppressed in OeB-treated animals. The reason for such dichotomy of hCG action on OeB-treated animals is not clear at present.

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The Immediate Effect of HCG Upon Plasma Testosterone Levels in the Bull

Acta Veterinaria Scandinavica ◽

10.1186/bf03548665 ◽

1981 ◽

Vol 22 (3-4) ◽

pp. 403-408 ◽

Cited By ~ 1

Author(s):

A. Sundby

Keyword(s):

Plasma Testosterone ◽

Testosterone Levels

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