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...son and Shine, 1997; Thomas et al., 2001). Food availability has long been considered the ultimate environmental factor influencing breeding seasons in seasonally breeding birds (Horá̌k et al., 2015; =-=Lack, 1968-=-; Murton and Westwood, 1977; Wingfield, 1983). As most passerines do not store large amounts of energy, timing energetically costly breeding with periods of peak food abundance is crucial. This is esp...

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...ssor and increase glucocorticoid secretion (Fokidis et al., 2012; Lynn et al., 2010). Glucocorticoids, including corticosterone (CORT), negatively affect reproduction by inhibiting HPG axis activity (=-=Sapolsky et al., 2000-=-; Schoech et al., 2009) and thus could potentially serve as mediators between energetic state and reproductive function. Few studies, however, have examined the effects of food restriction simultaneou...

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...any animals, the decision of when to breed is a critical one because timing reproduction to coincide with favorable environmental conditions can substantially impact reproductive success and fitness (=-=Both et al., 2006-=-; Davies and Deviche, 2014; Olsson and Shine, 1997; Thomas et al., 2001). Food availability has long been considered the ultimate environmental factor influencing breeding seasons in seasonally breedi...

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...y 2014, at which time they were naturally exposed to a nonstimulating photoperiod. Birds were caught using food-baited traps and were sexed based on plumage coloring, and aged based on molt patterns (=-=Pyle, 1997-=-). Only post-second year (i.e. hatched in 2012 or earlier) males were selected. Birds were transported to Arizona State University Animal Care Facilities and placed in visually isolated, individual ca...

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... true for females, who experience an additional energetic cost associated with egg formation (Nager, 2006). During periods of energetic scarcity, birds may delay egg laying and have smaller clutches (=-=Meijer et al., 1990-=-; Rodenhouse and Holmes, 1992), whereas food supplementation can result in birds advancing laying and producing larger clutches (Ruffino et al., 2014). Food availability, therefore, acts both as the u...

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...5) 218, 2694-2704 doi:10.1242/jeb.123323 Th e Jo u rn al o f Ex p er im en ta lB io lo g y proGnRH, GnIH, NPY) plus one extra series. Sections were placed in wells containing cryoprotectant solution (=-=Watson et al., 1986-=-) and kept at −20°C until immunolabeling. Testis histology For measurement of the diameter of seminiferous tubules, one right and one left testis section from each bird, stained with hematoxylin and e...

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...l., 2010; Pérez-Rodríguez et al., 2006). A role for glucocorticoids in suppressing HPG axis activity is also well studied in avian species (Deviche et al., 2012; Kwok et al., 2007; Lynn et al., 2010; =-=Wingfield et al., 1982-=-). We hypothesized that an increase in plasma CORT during food restriction contributes to inhibition of the HPG axis. However, we found no effect of food restriction on plasma CORT and the data theref...

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...o influence their activity (Dawson and Sharp, 2007), and there is some evidence that the effects of nutritional signals are mediated at the hypothalamic level. Gonadotropin-inhibitory hormone (GnIH) (=-=Tsutsui et al., 2000-=-), which inhibits both LH release from the pituitary gland and GnRH cells directly (for reviews, see Clarke, 2011; Kriegsfeld et al., 2015; Tsutsui, 2009; Tsutsui et al., 2010, 2012), is one potential...

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...e, 1997; Thomas et al., 2001). Food availability has long been considered the ultimate environmental factor influencing breeding seasons in seasonally breeding birds (Horá̌k et al., 2015; Lack, 1968; =-=Murton and Westwood, 1977-=-; Wingfield, 1983). As most passerines do not store large amounts of energy, timing energetically costly breeding with periods of peak food abundance is crucial. This is especially true for females, w...

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...not closely associated with gonadal development. This situation is commonly observed in other photoperiodic species, especially in those such as the house finch that are double-brooded (Dawson, 1983; =-=Wingfield, 1984-=-). This fluctuation has been hypothesized to serve changing behavioral needs during territorial defense, courtship and nesting activity (Wingfield et al., 1987), but the mechanism responsible for thes...

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... a critical one because timing reproduction to coincide with favorable environmental conditions can substantially impact reproductive success and fitness (Both et al., 2006; Davies and Deviche, 2014; =-=Olsson and Shine, 1997-=-; Thomas et al., 2001). Food availability has long been considered the ultimate environmental factor influencing breeding seasons in seasonally breeding birds (Horá̌k et al., 2015; Lack, 1968; Murton ...

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...o experience an additional energetic cost associated with egg formation (Nager, 2006). During periods of energetic scarcity, birds may delay egg laying and have smaller clutches (Meijer et al., 1990; =-=Rodenhouse and Holmes, 1992-=-), whereas food supplementation can result in birds advancing laying and producing larger clutches (Ruffino et al., 2014). Food availability, therefore, acts both as the ultimate factor and as a proxi...

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...iction treatment (time 0), after 4 weeks of treatment, and after 7 weeks of treatment. The amount of furcular fat was visually estimated using a scale of 0–5, with 0 for no fat and 5 for bulging fat (=-=Helms and Drury, 1960-=-). As the pectoral muscles are the largest store of protein in birds, their size was estimated using a scale of 0–3, with 0 for concave pectoral muscles and a prominent keel and 3 for convex pectoral ...

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...in an alcohol/dry ice slurry. They were kept at −80°C until sectioned. Brains were cryostatsectioned coronally (25 µm thick sections) at −20°C using the canary brain stereotaxic atlas as a reference (=-=Stokes et al., 1974-=-). Sections were collected in five parallel series, one for each immunocytochemical procedure (GnRH, 2700 RESEARCH ARTICLE The Journal of Experimental Biology (2015) 218, 2694-2704 doi:10.1242/jeb.123...

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...cted by food availability. Cloacal protuberance size usually varies in parallel with testis size (Perfito et al., 2005; Small et al., 2008) and both are influenced by circulating testosterone levels (=-=Deviche and Cortez, 2005-=-). Although food-restricted finches had lower plasma testosterone than ad libitum-fed finches, it appears that the precise relationship between plasma testosterone and cloacal protuberance growth is s...

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...he peptide as a result of decreased transport and/or secretion (Foster et al., 1988), and decreased cGnRH-ir perikaryon number can occur with increased cellular activation and release of the peptide (=-=Lee et al., 1990-=-). Inhibited secretion of GnRH, rather than increased production of GnRH, is a probable explanation based on the observation that food restriction did not influence hypothalamic proGnRH-ir expression,...

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...ubules are the sites of spermatogenesis, these data suggest that food restriction reduced sperm production. Body condition in free-living house finches correlates positively with plasma testosterone (=-=Duckworth et al., 2001-=-). Consistent with this observation, food-restricted finches were in lower body condition and had lower plasma testosterone than ad libitum-fed finches. Chronic food restriction (Davies et al., 2015a;...

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...Gonadotropin-inhibitory hormone (GnIH) (Tsutsui et al., 2000), which inhibits both LH release from the pituitary gland and GnRH cells directly (for reviews, see Clarke, 2011; Kriegsfeld et al., 2015; =-=Tsutsui, 2009-=-; Tsutsui et al., 2010, 2012), is one potential candidate in this mediation. Short-term energy deprivation stimulates GnIH activity in the Pekin duck, Anas platyrhynchos domestica (Fraley et al., 2013...

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...t al., 2014; Jawor et al., 2006; Perfito et al., 2011). In domestic chickens, Gallus gallus domesticus, food restriction alters the LH response of the pituitary gland to GnRH (Bruggeman et al., 1998; =-=Tanabe et al., 1981-=-). To our knowledge, the HPG axis responsiveness of male birds under different energetic states has only been investigated in Abert’s towhees, Melozone aberti (Davies et al., 2015b). As the coordinati...

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...vestigating the effects of food availability on female birds, which, because of a higher energy investment in reproduction, are likely to be even more sensitive to fluctuations in energy homeostasis (=-=Ball and Ketterson, 2008-=-; Caro, 2012; Caro et al., 2009; Farner and Follett, 1979). Conclusions The energetic condition of house finches influences testicular development and function. These effects may result from inhibitio...

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...corticoid secretion (Fokidis et al., 2012; Lynn et al., 2010). Glucocorticoids, including corticosterone (CORT), negatively affect reproduction by inhibiting HPG axis activity (Sapolsky et al., 2000; =-=Schoech et al., 2009-=-) and thus could potentially serve as mediators between energetic state and reproductive function. Few studies, however, have examined the effects of food restriction simultaneously on plasma CORT and...

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...hibitory hormone (GnIH) (Tsutsui et al., 2000), which inhibits both LH release from the pituitary gland and GnRH cells directly (for reviews, see Clarke, 2011; Kriegsfeld et al., 2015; Tsutsui, 2009; =-=Tsutsui et al., 2010-=-, 2012), is one potential candidate in this mediation. Short-term energy deprivation stimulates GnIH activity in the Pekin duck, Anas platyrhynchos domestica (Fraley et al., 2013), and GnIH can stimul...

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...es not support the proposition that food restriction increased hypothalamic GnRH production. In mammals, energy deficits influence the activity of the HPG axis by acting primarily on the GnRH system (=-=Wade et al., 1996-=-). This system is speculated to also be the primary site of regulation in birds, but there is little research to resolve this. We sought to identify potential hypothalamic mediators of GnRH activity i...

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...current study again suggests either species differences or differences due to experimental design. Hypothalamus-mediated effects of energetic deficit As is commonly the case in photoperiodic species (=-=Dawson and Goldsmith, 1997-=-; Hahn and Ball, 1995; Saldanha et al., 1994), the hypothalamic expression of GnRH in the house finch changes seasonally, increasing in preparation for breeding (through increased synthesis) and decre...

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...y, timing energetically costly breeding with periods of peak food abundance is crucial. This is especially true for females, who experience an additional energetic cost associated with egg formation (=-=Nager, 2006-=-). During periods of energetic scarcity, birds may delay egg laying and have smaller clutches (Meijer et al., 1990; Rodenhouse and Holmes, 1992), whereas food supplementation can result in birds advan...

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...gest store of protein in birds, their size was estimated using a scale of 0–3, with 0 for concave pectoral muscles and a prominent keel and 3 for convex pectoral muscles that protrude above the keel (=-=Salvante et al., 2007-=-). At each of these three time points, cloacal protuberance width (±0.1 mm) was also measured using digital calipers. Blood sampling and hormone challenges The effect of food restriction on the plasma...

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...1). Food availability has long been considered the ultimate environmental factor influencing breeding seasons in seasonally breeding birds (Horá̌k et al., 2015; Lack, 1968; Murton and Westwood, 1977; =-=Wingfield, 1983-=-). As most passerines do not store large amounts of energy, timing energetically costly breeding with periods of peak food abundance is crucial. This is especially true for females, who experience an ...

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...nfluencing the HPG axis. By contrast, a perceptual pathway (visual cues) appears to participate in food availability-mediated effects on the HPG axis in the spotted antbird, Hylophylax n. naevioides (=-=Hau et al., 2000-=-). Whether this is also the case in house finches is not known. Indeed, food restriction in the present study resulted in energetic deficit as indicated by decreased fat and muscle stores. However, fo...

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...ilability may influence the HPG axis activity at levels other than the hypothalamus. The sensitivity of the pituitary gland to GnRH, or of the testes to LH, may be regulated by environmental factors (=-=Jawor et al., 2006-=-; Perfito et al., 2011). This sensitivity can be probed using hormonal challenges, in which subjects receive GnRH or LH, and the downstream hormonal response, either LH or testosterone, is then measur...

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...mary proximate signal. In opportunistic species, food restriction can inhibit HPG axis activity. For example, in the zebra finch, Taeniopygia guttata, food restriction leads to underdeveloped testes (=-=Perfito et al., 2008-=-) and in the red crossbill, Loxia curvirostra, it attenuates long day-induced LH secretion (Hahn, 1995). Whether similar inhibition of the HPG axis occurs in more strictly photoperiodic avian species ...

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...bility on female birds, which, because of a higher energy investment in reproduction, are likely to be even more sensitive to fluctuations in energy homeostasis (Ball and Ketterson, 2008; Caro, 2012; =-=Caro et al., 2009-=-; Farner and Follett, 1979). Conclusions The energetic condition of house finches influences testicular development and function. These effects may result from inhibition of the entire HPG axis throug...

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...1997). We therefore propose that prior to photostimulation, GnRH in the present study increased through renewed synthesis associatedwith the development of photosensitivity (Dawson andGoldsmith, 1997;=-=Deviche et al., 2000-=-; Parry et al., 1997; Stevenson et al., 2012), and that during photostimulation, food restriction decreased GnRH secretion, resulting in increased brain GnRH stores and a larger number of visible cGnR...

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... hormone (FSH) (Hattori et al., 1986; Sharp et al., 1990). In male birds, LH and FSH act on the gonads to increase testosterone production and secretion. The overall result is increased gonadal size (=-=Farner and Follett, 1979-=-; Farner and Gwinner, 1980) and an increase in testosterone-mediated secondary sex characteristics and behavior (Kirby and Froman, 2000). The effects of food availability on the HPG axis have been pri...

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... the zebra finch, Taeniopygia guttata, food restriction leads to underdeveloped testes (Perfito et al., 2008) and in the red crossbill, Loxia curvirostra, it attenuates long day-induced LH secretion (=-=Hahn, 1995-=-). Whether similar inhibition of the HPG axis occurs in more strictly photoperiodic avian species in response to decreased food availability is uncertain. Non-photoperiodic signals are generally thoug...

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...contrast to testicular size, cloacal protuberance growth in finches was not affected by food availability. Cloacal protuberance size usually varies in parallel with testis size (Perfito et al., 2005; =-=Small et al., 2008-=-) and both are influenced by circulating testosterone levels (Deviche and Cortez, 2005). Although food-restricted finches had lower plasma testosterone than ad libitum-fed finches, it appears that the...

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... al., 1986; Sharp et al., 1990). In male birds, LH and FSH act on the gonads to increase testosterone production and secretion. The overall result is increased gonadal size (Farner and Follett, 1979; =-=Farner and Gwinner, 1980-=-) and an increase in testosterone-mediated secondary sex characteristics and behavior (Kirby and Froman, 2000). The effects of food availability on the HPG axis have been primarily investigated in opp...

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...tic deficit. European starlings, Sturnus vulgaris, with reduced body mass as a result of experimentally changing the daily duration of food availability also have underdeveloped testes (Dawson, 1986; =-=Meijer, 1991-=-), but testis growth is unaffected by food availability in Abert’s towhees (Davies et al., 2015a). Seasonal testicular growth is primarily due to proliferation of Sertoli cells, which make up the majo...

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...tudies, increased hypothalamic cGnRH-ir perikaryon number (under short-day conditions) was interpreted to reflect cellular build-up of the peptide as a result of decreased transport and/or secretion (=-=Foster et al., 1988-=-), and decreased cGnRH-ir perikaryon number can occur with increased cellular activation and release of the peptide (Lee et al., 1990). Inhibited secretion of GnRH, rather than increased production of...

Citation Context

... either species differences or differences due to experimental design. Hypothalamus-mediated effects of energetic deficit As is commonly the case in photoperiodic species (Dawson and Goldsmith, 1997; =-=Hahn and Ball, 1995-=-; Saldanha et al., 1994), the hypothalamic expression of GnRH in the house finch changes seasonally, increasing in preparation for breeding (through increased synthesis) and decreasing at the end of t...

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...n and secretion. The overall result is increased gonadal size (Farner and Follett, 1979; Farner and Gwinner, 1980) and an increase in testosterone-mediated secondary sex characteristics and behavior (=-=Kirby and Froman, 2000-=-). The effects of food availability on the HPG axis have been primarily investigated in opportunistically breeding birds, in which food rather than photoperiod may serve as a primary proximate signal....

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... neuropeptide that may be involved in transducing metabolic information to GnRH cells. The orexigenic role of NPY is well known (Bungo et al., 2011; Bechtold and Loudon, 2013; Davies andDeviche, 2015;=-=Kuenzel et al., 1987-=-; Richardson et al., 1995) and there are potential links between NPY cells and GnRH release (Contijoch et al., 1993; McShane et al., 1992) as well as between NPY and GnIH activity (Klingerman et al., ...

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...bolic hormones may cause indirect effects. In particular, decreased food availability may in some circumstances be perceived as a stressor and increase glucocorticoid secretion (Fokidis et al., 2012; =-=Lynn et al., 2010-=-). Glucocorticoids, including corticosterone (CORT), negatively affect reproduction by inhibiting HPG axis activity (Sapolsky et al., 2000; Schoech et al., 2009) and thus could potentially serve as me...

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...vailability of energy) or through indirect perceptual effects (visual and tactile pathways) remains a matter of debate (Hahn et al., 2005). Avian testes in vitro respond directly to metabolic stress (=-=McGuire et al., 2013-=-), and in mammals, the administration of glucose (Ohkura et al., 2000) and fatty acids (Garrel et al., 2011) can alter LH secretion. Generally consistent with these observations, in the European starl...

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... be involved in transducing metabolic information to GnRH cells. The orexigenic role of NPY is well known (Bungo et al., 2011; Bechtold and Loudon, 2013; Davies andDeviche, 2015;Kuenzel et al., 1987; =-=Richardson et al., 1995-=-) and there are potential links between NPY cells and GnRH release (Contijoch et al., 1993; McShane et al., 1992) as well as between NPY and GnIH activity (Klingerman et al., 2011). The GnIH–NPY axis ...

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...sonally breeding, photoperiodic male songbird, the house finch, Haemorhous mexicanus (Müller 1776). Male house finches exhibit increased HPG axis activity and gonadal growth in response to long days (=-=Cho et al., 1998-=-; Hamner, 1966, 1968). To determinewhether adequate energetic balance is necessary during this time to stimulate the HPG axis, we manipulated food availability in captive birds exposed to long days. W...

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...re mediated at the hypothalamic level. Gonadotropin-inhibitory hormone (GnIH) (Tsutsui et al., 2000), which inhibits both LH release from the pituitary gland and GnRH cells directly (for reviews, see =-=Clarke, 2011-=-; Kriegsfeld et al., 2015; Tsutsui, 2009; Tsutsui et al., 2010, 2012), is one potential candidate in this mediation. Short-term energy deprivation stimulates GnIH activity in the Pekin duck, Anas plat...

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...oductive development is seasonally activated through the hypothalamic–pituitary–gonadal (HPG) axis, with long days stimulating gonadotropin-releasing hormone-I (GnRH) secretion from the hypothalamus (=-=Follett et al., 1977-=-; for review, see Dawson, 2015). GnRH stimulates the anterior pituitary gland to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (Hattori et al., 1986; Sharp et al., 1990). In ...

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... al., 2011; Bechtold and Loudon, 2013; Davies andDeviche, 2015;Kuenzel et al., 1987; Richardson et al., 1995) and there are potential links between NPY cells and GnRH release (Contijoch et al., 1993; =-=McShane et al., 1992-=-) as well as between NPY and GnIH activity (Klingerman et al., 2011). The GnIH–NPY axis is thus hypothesized to play an important role in relating energy homeostasis to reproduction (Davies and Devich...

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...nce the HPG axis activity at levels other than the hypothalamus. The sensitivity of the pituitary gland to GnRH, or of the testes to LH, may be regulated by environmental factors (Jawor et al., 2006; =-=Perfito et al., 2011-=-). This sensitivity can be probed using hormonal challenges, in which subjects receive GnRH or LH, and the downstream hormonal response, either LH or testosterone, is then measured (Bergeon Burns et a...

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...us (Follett et al., 1977; for review, see Dawson, 2015). GnRH stimulates the anterior pituitary gland to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (Hattori et al., 1986; =-=Sharp et al., 1990-=-). In male birds, LH and FSH act on the gonads to increase testosterone production and secretion. The overall result is increased gonadal size (Farner and Follett, 1979; Farner and Gwinner, 1980) and ...

Citation Context

...sui, 2009; Tsutsui et al., 2010, 2012). Neuropeptide Y (NPY) is another neuropeptide that may be involved in transducing metabolic information to GnRH cells. The orexigenic role of NPY is well known (=-=Bungo et al., 2011-=-; Bechtold and Loudon, 2013; Davies andDeviche, 2015;Kuenzel et al., 1987; Richardson et al., 1995) and there are potential links between NPY cells and GnRH release (Contijoch et al., 1993; McShane et...

Citation Context

...cision of when to breed is a critical one because timing reproduction to coincide with favorable environmental conditions can substantially impact reproductive success and fitness (Both et al., 2006; =-=Davies and Deviche, 2014-=-; Olsson and Shine, 1997; Thomas et al., 2001). Food availability has long been considered the ultimate environmental factor influencing breeding seasons in seasonally breeding birds (Horá̌k et al., 2...

Citation Context

...d under energetic deficit. European starlings, Sturnus vulgaris, with reduced body mass as a result of experimentally changing the daily duration of food availability also have underdeveloped testes (=-=Dawson, 1986-=-; Meijer, 1991), but testis growth is unaffected by food availability in Abert’s towhees (Davies et al., 2015a). Seasonal testicular growth is primarily due to proliferation of Sertoli cells, which ma...

Citation Context

...food availability in Abert’s towhees (Davies et al., 2015a). Seasonal testicular growth is primarily due to proliferation of Sertoli cells, which make up the majority of the mass in developed testes (=-=Deviche et al., 2011-=-; Young et al., 2001). In this study, we found that the smaller testes under food restriction can be at least partially attributed to smaller seminiferous tubules. As seminiferous tubules are the site...

Citation Context

... but intermediate metabolic hormones may cause indirect effects. In particular, decreased food availability may in some circumstances be perceived as a stressor and increase glucocorticoid secretion (=-=Fokidis et al., 2012-=-; Lynn et al., 2010). Glucocorticoids, including corticosterone (CORT), negatively affect reproduction by inhibiting HPG axis activity (Sapolsky et al., 2000; Schoech et al., 2009) and thus could pote...

Citation Context

...2015; Tsutsui, 2009; Tsutsui et al., 2010, 2012), is one potential candidate in this mediation. Short-term energy deprivation stimulates GnIH activity in the Pekin duck, Anas platyrhynchos domestica (=-=Fraley et al., 2013-=-), and GnIH can stimulate food intake in birds and mammals (for reviews, see Clarke et al., 2012; Kriegsfeld et al., 2015; Tsutsui, 2009; Tsutsui et al., 2010, 2012). Neuropeptide Y (NPY) is another n...

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...lasma CORT in other species (Lynn et al., 2010; Pérez-Rodríguez et al., 2006). A role for glucocorticoids in suppressing HPG axis activity is also well studied in avian species (Deviche et al., 2012; =-=Kwok et al., 2007-=-; Lynn et al., 2010; Wingfield et al., 1982). We hypothesized that an increase in plasma CORT during food restriction contributes to inhibition of the HPG axis. However, we found no effect of food res...

Citation Context

...han increased production of GnRH, is a probable explanation based on the observation that food restriction did not influence hypothalamic proGnRH-ir expression, which correlates with GnRH production (=-=Parry et al., 1997-=-). We therefore propose that prior to photostimulation, GnRH in the present study increased through renewed synthesis associatedwith the development of photosensitivity (Dawson andGoldsmith, 1997;Devi...

Citation Context

...hat of the testis. In contrast to testicular size, cloacal protuberance growth in finches was not affected by food availability. Cloacal protuberance size usually varies in parallel with testis size (=-=Perfito et al., 2005-=-; Small et al., 2008) and both are influenced by circulating testosterone levels (Deviche and Cortez, 2005). Although food-restricted finches had lower plasma testosterone than ad libitum-fed finches,...

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...gen for 3 min. NPY The median eminence (ME) was used as a landmark for identifying the infundibular nucleus/median eminence area, the region where NPY cells involved in HPG axis activation are found (=-=Walsh and Kuenzel, 1997-=-). The primary antibody (Bachem Laboratories, Torrence, CA, USA) was used at a 1:20,000 dilution in 0.3% PBT. The blocking serum and secondary antibody solutions were the same as in the proGnRH staini...

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...han ad libitum-fed finches, it appears that the precise relationship between plasma testosterone and cloacal protuberance growth is somewhat dissociated, an observation that is not without precedent (=-=Wingfield et al., 2012-=-). This dissociation may result from the threshold level of plasma testosterone necessary to stimulate cloacal protuberance growth being lower than that necessary for testis growth. The absence of a p...

Citation Context

...t al., 2010, 2012). Neuropeptide Y (NPY) is another neuropeptide that may be involved in transducing metabolic information to GnRH cells. The orexigenic role of NPY is well known (Bungo et al., 2011; =-=Bechtold and Loudon, 2013-=-; Davies andDeviche, 2015;Kuenzel et al., 1987; Richardson et al., 1995) and there are potential links between NPY cells and GnRH release (Contijoch et al., 1993; McShane et al., 1992) as well as betw...

Citation Context

...easured (Bergeon Burns et al., 2014; Jawor et al., 2006; Perfito et al., 2011). In domestic chickens, Gallus gallus domesticus, food restriction alters the LH response of the pituitary gland to GnRH (=-=Bruggeman et al., 1998-=-; Tanabe et al., 1981). To our knowledge, the HPG axis responsiveness of male birds under different energetic states has only been investigated in Abert’s towhees, Melozone aberti (Davies et al., 2015...

Citation Context

...ggeman et al., 1998; Tanabe et al., 1981). To our knowledge, the HPG axis responsiveness of male birds under different energetic states has only been investigated in Abert’s towhees, Melozone aberti (=-=Davies et al., 2015-=-b). As the coordination of breeding with energetically favorable conditions is crucial, we hypothesized that there are multiple sites of regulation on the HPG axis, and that altering the sensitivity o...

Citation Context

...y that energetic factors regulate GnRH function indirectly, i.e. by acting at the testicular rather than hypothalamic level. Steroid feedback by testosterone negatively affects hypothalamic cGnRH-ir (=-=Deviche et al., 2006-=-). As food-restricted birds had lower plasma testosterone than ad libitum-fed birds, a decrease in gonadal steroid feedback may have stimulated GnRH synthesis. Again, however, the observation that pro...

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...rmal rabbit blocking serum. Sections were incubated in chromagen for 3.5 min. ProGnRH Again, the TrSM was used as a landmark for identifying the POA. The primary antibody (1947; Roberts et al., 1989; =-=Dutlow et al., 1992-=-) was used at a 1:1000 dilution in 0.3% PBT. The blocking serum used was normal horse serum (Vector Laboratories) at a 1:33 dilution in 0.3% PBT. The secondary antibody used was biotinylated horse ant...

Citation Context

...y acts as a proximate cue to affect breeding through direct metabolic effects (availability of energy) or through indirect perceptual effects (visual and tactile pathways) remains a matter of debate (=-=Hahn et al., 2005-=-). Avian testes in vitro respond directly to metabolic stress (McGuire et al., 2013), and in mammals, the administration of glucose (Ohkura et al., 2000) and fatty acids (Garrel et al., 2011) can alte...

Citation Context

...photoperiodic male songbird, the house finch, Haemorhous mexicanus (Müller 1776). Male house finches exhibit increased HPG axis activity and gonadal growth in response to long days (Cho et al., 1998; =-=Hamner, 1966-=-, 1968). To determinewhether adequate energetic balance is necessary during this time to stimulate the HPG axis, we manipulated food availability in captive birds exposed to long days. We hypothesized...

Citation Context

...study may reflect lower plasma LH, resulting in attenuated stimulation of Leydig cells. Supporting this hypothesis, other avian studies found that food restriction can decrease plasma LH (Hahn, 1995; =-=Kobayashi et al., 2002-=-). Alternatively or additionally, food restriction may decrease the sensitivity of Leydig cells to LH. The present results do not favor this hypothesis because LH administration had a similar relative...

Citation Context

... the hypothalamic level. Gonadotropin-inhibitory hormone (GnIH) (Tsutsui et al., 2000), which inhibits both LH release from the pituitary gland and GnRH cells directly (for reviews, see Clarke, 2011; =-=Kriegsfeld et al., 2015-=-; Tsutsui, 2009; Tsutsui et al., 2010, 2012), is one potential candidate in this mediation. Short-term energy deprivation stimulates GnIH activity in the Pekin duck, Anas platyrhynchos domestica (Fral...

Citation Context

...photostimulation, GnRH in the present study increased through renewed synthesis associatedwith the development of photosensitivity (Dawson andGoldsmith, 1997;Deviche et al., 2000; Parry et al., 1997; =-=Stevenson et al., 2012-=-), and that during photostimulation, food restriction decreased GnRH secretion, resulting in increased brain GnRH stores and a larger number of visible cGnRH-ir perikarya in food-restricted than in ad...

Citation Context

... al., 2011). This sensitivity can be probed using hormonal challenges, in which subjects receive GnRH or LH, and the downstream hormonal response, either LH or testosterone, is then measured (Bergeon =-=Burns et al., 2014-=-; Jawor et al., 2006; Perfito et al., 2011). In domestic chickens, Gallus gallus domesticus, food restriction alters the LH response of the pituitary gland to GnRH (Bruggeman et al., 1998; Tanabe et a...

Citation Context

... food availability on female birds, which, because of a higher energy investment in reproduction, are likely to be even more sensitive to fluctuations in energy homeostasis (Ball and Ketterson, 2008; =-=Caro, 2012-=-; Caro et al., 2009; Farner and Follett, 1979). Conclusions The energetic condition of house finches influences testicular development and function. These effects may result from inhibition of the ent...

Citation Context

...Short-term energy deprivation stimulates GnIH activity in the Pekin duck, Anas platyrhynchos domestica (Fraley et al., 2013), and GnIH can stimulate food intake in birds and mammals (for reviews, see =-=Clarke et al., 2012-=-; Kriegsfeld et al., 2015; Tsutsui, 2009; Tsutsui et al., 2010, 2012). Neuropeptide Y (NPY) is another neuropeptide that may be involved in transducing metabolic information to GnRH cells. The orexige...

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... is well known (Bungo et al., 2011; Bechtold and Loudon, 2013; Davies andDeviche, 2015;Kuenzel et al., 1987; Richardson et al., 1995) and there are potential links between NPY cells and GnRH release (=-=Contijoch et al., 1993-=-; McShane et al., 1992) as well as between NPY and GnIH activity (Klingerman et al., 2011). The GnIH–NPY axis is thus hypothesized to play an important role in relating energy homeostasis to reproduct...

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...ivated through the hypothalamic–pituitary–gonadal (HPG) axis, with long days stimulating gonadotropin-releasing hormone-I (GnRH) secretion from the hypothalamus (Follett et al., 1977; for review, see =-=Dawson, 2015-=-). GnRH stimulates the anterior pituitary gland to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (Hattori et al., 1986; Sharp et al., 1990). In male birds, LH and FSH act on ...

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... of debate (Hahn et al., 2005). Avian testes in vitro respond directly to metabolic stress (McGuire et al., 2013), and in mammals, the administration of glucose (Ohkura et al., 2000) and fatty acids (=-=Garrel et al., 2011-=-) can alter LH secretion. Generally consistent with these observations, in the European starling, decreased access to food affected gonadal maturation only when birds also lost body mass (Meijer, 1991...

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...on from the hypothalamus (Follett et al., 1977; for review, see Dawson, 2015). GnRH stimulates the anterior pituitary gland to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (=-=Hattori et al., 1986-=-; Sharp et al., 1990). In male birds, LH and FSH act on the gonads to increase testosterone production and secretion. The overall result is increased gonadal size (Farner and Follett, 1979; Farner and...

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...uenzel et al., 1987; Richardson et al., 1995) and there are potential links between NPY cells and GnRH release (Contijoch et al., 1993; McShane et al., 1992) as well as between NPY and GnIH activity (=-=Klingerman et al., 2011-=-). The GnIH–NPY axis is thus hypothesized to play an important role in relating energy homeostasis to reproduction (Davies and Deviche, 2014).Received 18 April 2015; Accepted 23 June 2015 1School of L...

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...se finch that are double-brooded (Dawson, 1983; Wingfield, 1984). This fluctuation has been hypothesized to serve changing behavioral needs during territorial defense, courtship and nesting activity (=-=Wingfield et al., 1987-=-), but the mechanism responsible for these fluctuations is unclear. Cloacal protuberance growth did not mirror that of the testis. In contrast to testicular size, cloacal protuberance growth in finche...

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...bert’s towhees (Davies et al., 2015a). Seasonal testicular growth is primarily due to proliferation of Sertoli cells, which make up the majority of the mass in developed testes (Deviche et al., 2011; =-=Young et al., 2001-=-). In this study, we found that the smaller testes under food restriction can be at least partially attributed to smaller seminiferous tubules. As seminiferous tubules are the sites of spermatogenesis...

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...ggeman et al., 1998; Tanabe et al., 1981). To our knowledge, the HPG axis responsiveness of male birds under different energetic states has only been investigated in Abert’s towhees, Melozone aberti (=-=Davies et al., 2015-=-b). As the coordination of breeding with energetically favorable conditions is crucial, we hypothesized that there are multiple sites of regulation on the HPG axis, and that altering the sensitivity o...

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...and tactile pathways) remains a matter of debate (Hahn et al., 2005). Avian testes in vitro respond directly to metabolic stress (McGuire et al., 2013), and in mammals, the administration of glucose (=-=Ohkura et al., 2000-=-) and fatty acids (Garrel et al., 2011) can alter LH secretion. Generally consistent with these observations, in the European starling, decreased access to food affected gonadal maturation only when b...

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...a 1:200 dilution in normal rabbit blocking serum. Sections were incubated in chromagen for 3.5 min. ProGnRH Again, the TrSM was used as a landmark for identifying the POA. The primary antibody (1947; =-=Roberts et al., 1989-=-; Dutlow et al., 1992) was used at a 1:1000 dilution in 0.3% PBT. The blocking serum used was normal horse serum (Vector Laboratories) at a 1:33 dilution in 0.3% PBT. The secondary antibody used was b...

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...rences or differences due to experimental design. Hypothalamus-mediated effects of energetic deficit As is commonly the case in photoperiodic species (Dawson and Goldsmith, 1997; Hahn and Ball, 1995; =-=Saldanha et al., 1994-=-), the hypothalamic expression of GnRH in the house finch changes seasonally, increasing in preparation for breeding (through increased synthesis) and decreasing at the end of the breeding season as a...