Effects of Methallibure (ICI 33,828) on the pars distalis of pituitary, testis and thumb pad of the green frog, Rana esculenta L.

Rastogi, Rakesh K.; Chieffi, G.; Marmorino, C

doi:10.1007/bf00335642

Cited by 14 publications

(1 citation statement)

References 16 publications

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“…Furthermore, forearm width and nuptial pad number are androgen dependent and function in mating (Emerson et al 1999; Epstein and Blackburn 1997; Lynch and Blackburn 1995; Rastogi and Chieffi 1971; Thomas and Licht 1993; Thomas et al 1993; van Wyk et al 2003; Wetzel and Kelley 1983). We show that these traits are reduced in intersex individuals, suggesting that intersex toads do not build hypertrophied musculature or develop nuptial pads typically associated with normal levels of androgens and properly functioning testes (Lee and Correales 2002).…”

Section: Discussionmentioning

confidence: 99%

Agriculture Alters Gonadal Form and Function in the Toad Bufo marinus

McCoy

Bortnick²,

Campbell³

et al. 2008

Environ Health Perspect

116

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BackgroundMany agricultural contaminants disrupt endocrine systems of wildlife. However, evidence of endocrine disruption in wild amphibians living in agricultural areas has been controversial. Typically, studies on the effects of pollutants on wildlife attempt to compare polluted with unpolluted sites.ObjectivesWe took a novel approach to address this question by explicitly quantifying the relationship between gonadal abnormalities and habitats characterized by differing degrees of agricultural activity.MethodsWe quantified the occurrence of gonadal abnormalities and measures of gonadal function in at least 20 giant toads (Bufo marinus) from each of five sites that occur along a gradient of increasing agricultural land use from 0 to 97%.ResultsThe number of abnormalities and frequency of intersex gonads increased with agriculture in a dose-dependent fashion. These gonadal abnormalities were associated with altered gonadal function. Testosterone, but not 17β-estradiol, concentrations were altered and secondary sexual traits were either feminized (increased skin mottling) or demasculinized (reduced forearm width and nuptial pad number) in intersex toads. Based on the end points we examined, female morphology and physiology did not differ across sites. However, males from agricultural areas had hormone concentrations and secondary sexual traits that were intermediate between intersex toads and non-agricultural male toads. Skin coloration at the most agricultural site was not sexually dimorphic; males had female coloration.ConclusionsSteroid hormone concentrations and secondary sexual traits correlate with reproductive activity and success, so affected toads likely have reduced reproductive success. These reproductive abnormalities could certainly contribute to amphibian population declines occurring in areas exposed to agricultural contaminants.

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Section: Discussionmentioning

confidence: 99%

Agriculture Alters Gonadal Form and Function in the Toad Bufo marinus

McCoy

Bortnick²,

Campbell³

et al. 2008

Environ Health Perspect

116

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The control of spermatogenesis in the green frog, Rana esculenta

et al. 1976

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The process o f spermatogenesis in Rana esculenta (living in the surroundings of Naples) resurges gradually i n the spring months, proceeds actively through the summer and declines gradually in the winter months reaching an almost total "quiescence" for a short length of time. The repeating from year to year with a distinct regularity of spermatogenetic cycle suggests that environmental cues play a role in timing its various phases. Both temperature and photoperiod appear to be potential modifiers of spermatogenetic activity in this species. It is, however, probable that photoperiod acts only in a permissive way to facilitate the temperature response which seems to be the more direct modifier of the testicular activity.The proliferation of primary spermatogonia seems to be favoured by only low temperatures. The formation of secondary spermatogonia, and primary and secondary spermatocytes occurs when there occurs a gradual increase in the ambient temperature, day length and gonadotropin secretion. This period is characterized by very low plasma level of testosterone, that, through the reduced negative feedback to the hypothalamus, favours an increased secretion of FSHlike gonadotropin. Spennatid formation is entirely androgen-dependent as confirmed by the use of a specific antiandrogen, cyproterone acetate. In fact spermatid formation naturally occurs in a period when plasma level of testosterone is increasing and pituitary gonadotrops are declining in their secretory activity. In this period the ambient temperature and the photoperiod gradually decline.The importance of lateral eyes and the pineal gland in the mediation of influence of photic cues has been shown. It seems that without either the eyes or the pineal gland both light and temperature are completely ineffective in stimulating the early spermatogenesis, which shows the permissive role of light on temperature influence upon spermatogenesis.Hypophysectomy impairs spermatogenesis, which can be restored by a replacement therapy with homoplastic pituitary extract. Testosterone alone does not restore spermatogenesis except enhancing spermatid formation. Pituitary extract stimulates mitotic activity of spermatogonia and formation of primary and secondary spermatocytes. Testosterone is not involved because the stimulatory effects of pituitary extract are only marginally blocked by the antiandrogen. In fact spermatogonial multiplication is partially inhibited, while spermatid formation is totally blocked, indicating that ICSH-like gonadotropin acts upon the formation of spermatids through the stimulation of testosterone production.Thus i t has been found that there exists a complex interaction between the environmental factors and the "endogenous hormonal trigger" that subsequently steps into the regulation of spermatogenesis.A wealth of information on the reproduc-for reviews). Rana esculenta has a potentive patterns in amphibians has shown tially continuous type of spermatogenesis that species inhabiting cold zones have a (Galgano, '35 151

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The Effect of Sex Steroids on Primary and Secondary Sex Differentiation in the Sexually Dichromatic Reedfrog (Hyperolius argus: Hyperolidae) from the Arabuko Sokoke Forest of Kenya

Hayes

Menendez

1999

General and Comparative Endocrinology

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Effects of Methallibure (ICI 33,828) on the pars distalis of pituitary, testis and thumb pad of the green frog, Rana esculenta L.

Cited by 14 publications

References 16 publications

Agriculture Alters Gonadal Form and Function in the Toad Bufo marinus

Agriculture Alters Gonadal Form and Function in the Toad Bufo marinus

The control of spermatogenesis in the green frog, Rana esculenta

The Effect of Sex Steroids on Primary and Secondary Sex Differentiation in the Sexually Dichromatic Reedfrog (Hyperolius argus: Hyperolidae) from the Arabuko Sokoke Forest of Kenya

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