Matthijs A. Zandbergen

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Primary pituitary cell cultures from sexually mature adult male African catfish, Clarias gariepinus, were used to study the regulation of LH biosynthesis by sex steroids. The cell cultures were exposed to testosterone (T), estradiol (E(2)), or 5alpha-dihydrotestosterone (DHT), a nonaromatizable analogue of T, and to the likewise nonaromatizable(More)
Unlike nonhuman primates, songbirds learn to vocalize very much like human infants acquire spoken language. In humans, Broca's area in the frontal lobe and Wernicke's area in the temporal lobe are crucially involved in speech production and perception, respectively. Songbirds have analogous brain regions that show a similar neural dissociation between vocal(More)
Two GnRH peptides have recently been identified in brain extracts of the African catfish, chicken-II GnRH ([His5,Trp7,Tyr8]GnRH, cGnRH-II) and catfish GnRH ([His5,Asn8]GnRH, cfGnRH). Using three experimental approaches, we investigated whether both peptides are involved in the regulation of pituitary gonadotropin secretion. First, the presence of cfGnRH and(More)
Mammalian gonadotropin-releasing hormone receptors (GnRH-Rs) differ from other G protein-coupled receptors in lacking the intracellular C-terminus and in showing an exchange of two otherwise highly conserved Asp (D) and Asn (N) residues in transmembrane domains (TMD) 2 and 7, respectively. However, the first GnRH-R characterized from a nonmammalian(More)
Parrots and songbirds learn their vocalizations from a conspecific tutor, much like human infants acquire spoken language. Parrots can learn human words and it has been suggested that they can use them to communicate with humans. The caudomedial pallium in the parrot brain is homologous with that of songbirds, and analogous to the human auditory association(More)
The development of the catfish gonadotropin-releasing hormone (cfGnRH) fiber network in the pituitary of male African catfish (Clarias gariepinus) was investigated in relation to puberty. Double immunolabeling studied by confocal laser scanning microscopy revealed a concomitant development of gonadotropes and of pituitary cfGnRH innervation during the first(More)
The effects of two endogenous steroids on the maturation of the catfish GnRH and the chicken GnRH-II system in the African catfish were investigated. Immature fish (2 weeks of age, which is before sexual differentiation; thus male and female genotypes present) were fed with food pellets containing either testosterone (T), 11beta-hydroxyandrostenedione (OHA)(More)
Like many other songbird species, male zebra finches learn their song from a tutor early in life. Song learning in birds has strong parallels with speech acquisition in human infants at both the behavioral and neural levels. Forebrain nuclei in the 'song system' are important for the sensorimotor acquisition and production of song, while caudomedial pallial(More)
Interrenal-like tissue in male African catfish is localized in paired organs, situated retroperitoneally anterior of the kidney. Histological and enzyme-histochemical (3β-hydroxysteroid dehydrogenase) reactions were carried out on sections of these organs in order to localize steroid-producing cells. In vitro incubations were carried out to determine the(More)
The effect of testosterone (T), 11-ketotestosterone (KT) and estradiol (E(2)) on the development of the catfish gonadotropin-releasing hormone system (cfGnRH) of male African catfish (Clarias gariepinus), at the onset of puberty [between 10 and 12 weeks post hatching (ph)] was investigated. The cfGnRH neurons, located in the ventral forebrain, were(More)