Somatotropic effects of exogenous prolactin and growth hormone in juvenile lizards (Lacerta s. sicula)

Licht, Paul; Hoyer, H. E.

doi:10.1016/0016-6480(68)90090-7

Cited by 36 publications

(3 citation statements)

References 6 publications

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“…in humans: Kanaley et al, 1997;Gustafsson et al, 1999). If juveniles are already secreting high levels of growth factors (Licht and Hoyer, 1968;Rousseau and Dufour, 2007), they may not be able to produce more, or receptors may be near saturation such that higher concentrations have little to no effect. All of these possibilities warrant further investigation.…”

Section: Discussionmentioning

confidence: 99%

Exercise training reveals trade-offs among endurance performance and immune function, but not growth, in juvenile lizards

Husak

Roy

Lovern

2017

Journal of Experimental Biology

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Acquired energetic resources allocated to a particular trait cannot then be re-allocated to a different trait. This often results in a trade-off between survival and reproduction for the adults of many species, but such a trade-off may be manifested differently in juveniles not yet capable of reproduction. Whereas adults may allocate resources to current and/or future reproduction, juveniles can only allocate to future reproduction. Thus, juveniles should allocate resources toward traits that increase survival and their chances of future reproductive success. We manipulated allocation of resources to performance, via endurance exercise training, to examine trade-offs among endurance capacity, immune function and growth in juvenile green anole lizards. We trained male and female captive anoles on a treadmill for 8 weeks, with increasing intensity, and compared traits with those of untrained individuals. Our results show that training enhanced endurance capacity equally in both sexes, but immune function was suppressed only in females. Training had no effect on growth, but males had higher growth rates than females. Previous work showed that trained adults have enhanced growth, so juvenile growth is either insensitive to stimulation with exercise, or they are already growing at maximal rates. Our results add to a growing body of literature indicating that locomotor performance is an important part of life-history trade-offs that are sex and age specific.

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Section: Discussionmentioning

confidence: 99%

Exercise training reveals trade-offs among endurance performance and immune function, but not growth, in juvenile lizards

Husak

Roy

Lovern

2017

Journal of Experimental Biology

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“…Fig. 11) starting in late July showed testicular development to stage 3 after three months (Licht & Hoyer, 1968).…”

Section: Testicular Cycles Regulation Of Testicular Activity In Lacertamentioning

confidence: 94%

Influence of photoperiod and temperature on testicular recrudescence and body growth in the lizards, Lacerta sicula and Lacerta muralis

1969

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With 1 plate and 16 figures in the text)Annual testicular cycles in the lizards Lacerta sicula and L. muralis appear to be regulated by the interaction between seasonal changes in body temperature and an endogenous rhythmicity in thermal responsiveness. Photoperiodism does not appear to be an important factor; i.e. testicular activity does not appear to be regulated by daylength.Following testicular regression in July, the lizards are refractory to sexual Stimulation by high temperatures (i.e. normal preferred levels) for about five months. High temperatures accelerate gonadal regression and prevent recrudescence during late summer. Reduced temperatures stimulate testicular enlargement and spermatid formation during the autumn; this recrudescence can be blocked by treatment with testosterone. Very low temperatures suppress gonadal activity during mid-winter.Maintenance of lizards at constant high temperatures (33°C) starting in July suppresses testicular recrudescence until December. Also, testicular collapse occurs in lizards transferred to high temperatures after recrudescence has started. The gonads are stimulated by exogenous gonadotropins at 33°C during the fall indicating that high temperatures reduce circulating levels of gonadotropins.The refractoriness to high temperatures is "spontaneously" terminated during midwinter (December) under a wide range of photo-thermal conditions. Low temperatures may accelerate the termination of refractoriness. Thereafter, high temperatures stimulate, and are required for the final development of the testes and accessory sexual structures, Thus, the increase in body temperature following hibernation times the onset of breeding in the spring.Temperature also has a marked influence on appetite and growth, independent of photoperiod. Weight gains are greater at 33" than at 2O"C;At 33" there is a tendency for abdominal fat bodies to enlarge but with little hepatic growth; whereas, the reverse occurs at 20°C.

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“…The first study explicitly demonstrating a key role of GH in the control of overall growth in tadpoles and frogs used transgenic Xenopus that overexpress the cDNA-encoding GH [26]. In reptiles, GH has also been shown to increase appetite and growth [lizard: [27]; turtle: [28]].…”

Section: Gh Regulation Of Growth and Metabolismmentioning

confidence: 99%

Comparative Aspects of GH and Metabolic Regulation in Lower Vertebrates

Rousseau

Dufour

2007

Neuroendocrinology

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In all vertebrates, the regulations of growth and energy balance are complex phenomena which involve elaborate interactions between the brain and peripheral signals. Most vertebrates adopt and maintain a life style after birth, but lower vertebrates may have complex life histories involving metamorphoses, migrations and long periods of fasting. In order to achieve the complex developmental programs associated with these changes, coordinated regulation of all aspects of energy metabolism is required. Somatotropic axis (somatostatin (SRIH) growth hormone (GH) and insulin-like growth factor 1 (IGF1), is known to be involved in the regulation of growth and energy balance. Interestingly, recent studies showed that additional factors such as pituitary adenylate cyclase-activated polypeptide (PACAP), corticotropin-releasing hormone (CRH), ghrelin and leptin could also have major roles in the control of growth and metabolism in lower vertebrates (fish, amphibians and reptiles). This mini-review will survey the function of GH and metabolic regulation in lower vertebrates.

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Somatotropic effects of exogenous prolactin and growth hormone in juvenile lizards (Lacerta s. sicula)

Cited by 36 publications

References 6 publications

Exercise training reveals trade-offs among endurance performance and immune function, but not growth, in juvenile lizards

Exercise training reveals trade-offs among endurance performance and immune function, but not growth, in juvenile lizards

Influence of photoperiod and temperature on testicular recrudescence and body growth in the lizards, Lacerta sicula and Lacerta muralis

Comparative Aspects of GH and Metabolic Regulation in Lower Vertebrates

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