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Presence and seasonal distribution of putative sex steroid binding molecules in the testis of the lizard, Podarcis s. sicula
No full textEXTRABULBAR OLFACTORY SYSTEM AND NERVUS TERMINALIS FMRFAMIDE IMMUNOREACTIVE COMPONENTS IN XENOPUS LAEVIS ONTOGENESIS.
No full textThe extrabulbar olfactory system (EBOS) is a collection of nerve fibers which originate from primary olfactory receptor-like neurons
and penetrate into the brain bypassing the olfactory bulbs. Our description is based upon the application of two neuronal tracers (biocytin,
carbocyanine DiI) in the olfactory sac, at the cut end of the olfactory nerve and in the telencephalon of the developing clawed frog. The
extrabulbar olfactory system was observed already at stage 45, which is the first developmental stage compatible with our techniques; at
this stage, the extrabulbar olfactory system fibers terminated diffusely in the preoptic area. A little later in development, i.e. at stage 50, the
extrabulbar olfactory system was maximally developed, extending as far caudally as the rhombencephalon. In the metamorphosing specimens,
the extrabulbar olfactory system appeared reduced in extension; caudally, the fiber terminals did not extend beyond the diencephalon. While a
substantial overlapping of biocytin/FMRFamide immunoreactivity was observed along the olfactory pathways as well as in the telencephalon,
FMRFamide immunoreactivity was never observed to be colocalized in the same cellular or fiber components visualized by tracer molecules.
The question whether the extrabulbar olfactory system and the nervus terminalis (NT) are separate anatomical entities or represent an integrated
system is discussed
Development and distribution of FMRFamide-like immunoreactivity in the toad (Bufo bufo) brain
No full textBy using immunohistochemistry, we studied the development and distribution of the FMRFamide-like immunoreactive (ir) neuronal system in the toad brain during the ontogeny. In addition to this, experimental evidence was provided to show that the rostral forebrain-located FMRFamide neurons originate in the olfactory placode and then migrate into the brain along the olfactory pathway. During early development, within the brain, FMRFamide-ir perikarya first appeared in the periventricular hypothalamus. Later in development, FMRFamide-ir cells were visualized in the rostralmost forebrain simultaneously with similar ir cells in the developing olfactory mucosa. Selective ablation of the olfactory placode(s), prior to the appearance of the first FMRFamide-ir cells in the brain, resulted in the total absence of ir cells in the telencephalon (medial septum and mediobasal telencephalon) of the operated sides(s). The preoptic-suprachiasmatic-infundibular hypothalamus-located FMRFamide-ir neurons were not affected by olfactory placodectomy, arguing that they do not originate in the placode. This result points to the placode as the sole source of such neurons in the rostral forebrain. (C) 2001 Elsevier Science B.V. All rights reserved
Developmental changes in mammalian and chicken-II gonadotropin-releasing hormone-like immunoreactivities in the brain of Rana esculenta
No full text
Immunoreactive mammalian and chicken-II GnRHs in Rana esculenta brain during development
No full textTwo forms of gonadotropin-releasing hormone (mammalian, mGnRH and chicken-II, cGnRH-II) were measured by radioimmunoassay in the nasal area (containing peripheral terminal nerve), brain and pituitary of Rana esculenta during larval development, metamorphosis, and until prior to becoming reproductively active. Small amounts of both forms of GnRH were first detected in the brain extract of early tadpoles (stage 26-27, when hindlimbs begin to develop). Later, there was a gradual, but constant, stage-dependent increase in the brain content of GnRHs, with the most remarkable increase recorded at postclimax and in young frogs. In tadpoles, postclimax froglets, and young frogs, the brain concentration of mGnRH was higher than that of cGnRH-II, with a ratio of approximately 2:1 in favor of mGnRH. In juveniles, however, the brain extract contained more cGnRH-II than mGnRH. No GnRH immunoreactivity was detected in the nasal area until stage 31. In successive stages of development, however, only mGnRH was present in the nasal area, and this confirmed our previous immunohistochemical analysis which showed that the peripheral terminal nerve contains only mGnRH-immunoreactive neurons and fibers. Although both GnRH forms were detected in the anterior (telencephalon, diencephalon) and posterior (mesencephalon, rhombencephalon) brain halves from juveniles, mGnRH content predominated in the anterior half whereas in the posterior half cGnRH-II was present in greater amounts. Pituitaries from male and female postclimax froglets and young frogs contained both forms of GnRH in a ratio of approximately 10:1 in favor of mGnRH. This finding may shed light on the question of which GnRH(s) regulate gonadotropin release from the pituitary. The developmental changes in GnRH-immunoreactive content of the brain and pituitary have been discussed in the light of functional maturation of the brain-pituitary-gonad axis
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