In anurans, circulating levels of androgens influence certain secondary sexual characteristics that are expressed only during the breeding season. We studied the contractile properties of external oblique muscles (used to power sound production) in a species of North American gray tree frog, Hyla chrysoscelis, during the breeding season and also in testosterone-treated captive males and females...

An attempt was made to determine the cyclicity in yak through plasma progesterone estimation during breeding season as well as non-breeding season because silent or non-detected estrus is very common in this species. Blood samples were collected from yak (n = 8) during peak breeding season (July to November) and from the same animals in non-breeding season (February to March) at a two-day inter...

Vertebrates show a diverse array of social behaviors associated with territoriality. Field and laboratory experiments indicate that underlying themes-including mechanisms-may exist. For example in birds, extensive evidence over many decades has implicated a role for testosterone in the activation of territorial aggression in reproductive contexts. Territoriality at other times of the year appea...

Effects of Body Condition Recent University of Arkansas research determined the interactive effects of forage environment and body condition on the calving rate of beef cows. multiparous beef cows (1/4 to 3/8 Brahman) were managed to achieve marginal (4.7) or good (6.6) body condition scores (BCS) over approximately 5 months before the initiation of the breeding season. growth, endophyte acres ...

The aim of this study was to investigate the seasonal expression of androgen receptor (AR), estrogen receptors α and β (ERα and ERβ) and aromatase cytochrome P450 (P450arom) mRNA and protein by real-time PCR and immunohistochemistry in the wild ground squirrel (WGS) testes. Histologically, all types of spermatogenic cells including mature spermatozoa were identified in the breeding season (Apri...

The aim of this study was to elucidate the regulatory role of androgen in the follicular development of wild female ground squirrels. Immunohistochemical staining of FSHR, LHR, P450c17, P450arom, androgen receptor (AR), estrogen receptors (ERa and ERb) were executed in ovaries of female ground squirrels from both breeding and nonbreeding seasons. In addition, total ovarian proteins were extract...

This study was performed in adult male goats in which seasonal variations were abolished by rapid alternations of long days and short days. These treatments have been shown previously to prevent seasonal changes in the hypothalamo-pituitary axis and to maintain testis weight and sperm production at a high level. The experimental groups were exposed for 3 years to an alternation of either a 1 mo...

The aim of this study was to investigate the presence of nerve growth factor (NGF) and its receptors tyrosine kinase A (TrkA) and p75 in the ovaries of the wild ground squirrels during the breeding and nonbreeding seasons. In the breeding period, NGF, TrkA and p75 were immunolocalized in granulosa cells, thecal cells, interstitial cells and luteal cells whereas in the nonbreeding period, both o...

The wild ground squirrel is a typical seasonal breeder. In this study, using RT-PCR, western blot and immunohistochemistry, we investigated the mRNA and protein expressions of androgen receptor (AR), estrogen receptors α and β (ERα and ERβ) and aromatase cytochrome P450 (P450arom) in the medial preoptic area (MPOA) of hypothalamus of the wild male ground squirrel during the breeding season (Apr...

The pattern of fine-scale genetic structure in a population may reflect current biological processes of the species, such as natal dispersal, the breeding system and demography. We investigated the spatial distribution of nests and fine-scale genetic structure during two breeding seasons in a population of a weakly territorial, flock-living passerine bird, the vinous-throated parrotbill, Parado...