Quail and other short-lived birds
Introduction
The Japanese quail model system has been characterized during aging; many of the age-related changes found in mammalian neuroendocrine systems are mirrored in this species. Further, this species has two distinct advantages over mammalian models. First, hypothalamic systems exhibit neuroplasticity; even senescent males respond to testosterone replacement therapy with full recovery of reproductive behavior. This behavioral recovery is accompanied by restoration of specific hypothalamic neuropeptide systems, which regulate both sexual behavior and GnRH, thereby allowing identification of these neural systems. Further, males possess a cloacal gland, which similar to the prostate gland is androgen responsive. The second unique advantage to the avian model is a dynamic bone physiology, especially in females because the hollow bones serve as a depot for minerals used in egg production. As a result, aging females develop bone fragility; they have been well characterized as a model for hormone effects on osteoporosis and the role of vitamin D.
It appears that critical neuroregulatory systems, specifically catecholamine (norepinephrine [NE] and dopamine [DA]), aromatase enzyme (AROM) and opioid peptide (β-endorphin [END] and met-enkephalin [ENK]) systems must also remain young in order to prolong reproductive function. In the case of testosterone replacement therapy and restoration of male sexual behavior in the quail, it appears that these systems remain plastic and continue to respond to exogenous steroids, even in senescent animals. Therefore, rescue of these systems through steroid hormone replacement provides a tool for investigating systems affected by the process of aging and determining the processes involved in restoring some of their function.
Section snippets
Of quail and terns!
The Common Tern is a shore bird with a relatively long life span. This species exhibits clear and very interesting age-related changes in breeding strategies and behavior (Nisbet, 1989). As the pairs return from migration to their breeding grounds, the older pairs set about courtship and nesting immediately. These pairs, by virtue of their rapid nesting are able to select the prime territories for their nests. In addition, their immediate nesting allows the young to be hatched earlier and
Lifetime patterns in reproduction in the Japanese quail (Coturnix japonica)
The timing of the age-related decline is both species specific and varies with the individual (Ottinger et al., 1995, Nisbet, 1999). Japanese quail reach puberty about 6–8 weeks of age and attain full adult function within 2–3 weeks, with females maturing slightly later than males. Quail exhibit relatively high fertility and egg production and remain reproductive if maintained on a long photoperiod. On this regimen, females have a lifespan of 2.5 to 3 years, whereas males live 3–5 years (Ottinger,
Aging of hypothalamic systems: restoration by steroids?
Our approach has been to study hypothalamic systems in young reproductive quail and then compare these findings to senescent individuals. As mentioned earlier, the age-related decline in fertility in male quail coincides with decreasing reproductive behavior; both precede measurable hormone changes. Reproductive behavior therefore provides an index of reproductive status. Once separated according to behavioral activity, we found that sexually active males retained relatively higher circulating
Specific changes in the GnRH-I system during aging
In rats, age-related changes are relatively subtle in the female's GnRH system (Rubin et al., 1984, Leranth et al., 1986). However, there were morphological changes found in the synapses of GnRH neurons (Witkin, 1989). In birds, we have studied chicken GnRH-I, which is the biologically active form of the peptide. In quail, GnRH-I cell bodies are concentrated more rostral (preoptic-lateral septal; POA-SL region) and project to the median eminence (ME) (Sharp et al., 1990, Dunn et al., 1993).
Summary
In summary, gonadal steroids are likely to be a key element in the process of aging as they reflect hypothalamic and pituitary regulation and in turn modulate hypothalamic regulatory systems that impact behavioral and endocrine responses. In quail, testosterone is required for AROM and AVT immunoreactivity in the Preoptic area. In aging male quail, there is loss of AROM and AVT in the POA, which are restored with exogenous testosterone treatment. The POA-SL is also the site of GnRH-I cell
Acknowledgements
There have been a number of collaborators, graduate students, and post-doctoral fellows involved in this research. Some of them are cited in the text and others are referenced. This work would not have been possible without them. Support for this work was provided by the University of Maryland Agriculture Experiment Station, USDA-NRI grants # 88-37242 and 92-37203-7742 (MAO) and NATO CRG. 92-1267 (MAO and GCP).
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Age-related histomorphometric and ultrastructural changes in the Sertoli cells of Japanese quail (Coturnix Coturnix japonica)
2021, Tissue and CellCitation Excerpt :Currently a great deal of research on the reproductive biology of birds is conducted using the Japanese quail (Balthazart and Ball, 1998; Huss et al., 2008; Ottinger et al., 2004). Japanese quail are small seasonally breeding galliform birds with relatively high fertility, egg production and reproductive capability under artificial conditions (Ottinger, 2001). During ageing, the reproductive behavior of the male Japanese quail decreases, followed by a loss of fertility and regression of the testicular germinal epithelium, leading to a decline in the production of spermatozoa (Eroschenko et al., 1977; Humphreys, 1975; Ottinger, 2001).
Age dependent variations in the deep brain photoreceptors (DBPs), GnRH-GnIH system and testicular steroidogenesis in Japanese quail, Coturnix coturnix japonica
2018, Experimental GerontologyCitation Excerpt :Declining hypothalamic response to gonadal steroids appears to be an early event in aging in both quail and domestic chickens (Williams and Sharp, 1978; Ottinger et al., 1997a, 1997b). In males, this is accompanied by decreased male sexual behavior and in females egg production becomes increasingly irregular (Palmer and Bahr, 1992; Ottinger, 2001). Further, altered hypothalamic neurotransmitters and neuropeptides appear to be fundamental to the functional changes inherent in the cascade of events leading to reproductive failure (Ottinger et al., 1997a, 1997b).
Birds as models for the biology of aging and aging-related disease: An update
2018, Conn's Handbook of Models for Human AgingFunctional and Anatomic Correlates of Neural Aging in Birds
2018, Veterinary Clinics of North America - Exotic Animal PracticeCitation Excerpt :As such, poultry have an excellent model understanding some of the basic biology of osteoporosis and ovarian cancer. Short-lived male birds also show evidence of aging, particularly in endocrine and behavioral components of reproduction.17,18 This includes decreased sperm production and increased sperm abnormalities over time.11,19
Locally elevated cortisol in lymphoid organs of the developing zebra finch but not Japanese quail or chicken
2016, Developmental and Comparative ImmunologyCitation Excerpt :Hatchling finches were collected from nest boxes on the day of hatch (P0, or posthatch day 0), and juveniles (still housed with parents) were collected at P30, which is approximately one-third of the age of sexual maturity (gonads mature at approximately P90). Japanese quail and chickens are born feathered, mobile, with open eyes, and able to actively forage for themselves (McNabb and McNabb, 1977; Nichelmann and Tzschentke, 2002; Ottinger, 2001). These functional physiological systems come at the cost of reduced post-hatch growth rates (Ricklefs, 1979).
The evolution of prolonged life after reproduction
2015, Trends in Ecology and EvolutionCitation Excerpt :However, in some circumstances reproductive senescence is accelerated relative to somatic senescence leading to a PRLS. At first glance, PRLSs appear to be widespread and have been documented across a wide range of taxonomic groups [11,13,33,34] and in both males and females [35,36]. These patterns have led some authors to suggest that PRLSs are not an evolutionary oddity [9,12] and do not require special adaptive explanations [8,37].