| 1. |
- Forsell, Johan, et al.
(författare)
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Role of the pineal organ in the photoregulated hatching of the Atlantic halibut
- 1997
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Ingår i: International Journal of Developmental Biology. - 0214-6282. ; 41:4, s. 591-595
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Tidskriftsartikel (refereegranskat)abstract
- The timing of hatching in the Atlantic halibut (Hippoglossus hippoglossus) has been suggested to be regulated by environmental light conditions. However, the photosensory organ that perceives the triggering light has not been identified. In the present study, we investigated the morphogenesis of the pineal organ and the neurochemical differentiation of photoreceptors in the pineal organ and the retina of the Atlantic halibut during embryonic development. Immunocytochemical techniques were used for detection of integral protein components of the phototransduction process: opsins, arrestin (S-antigen) and α-transducin. We also studied the expression of serotonin (5-HT), a precursor of the neurohormone melatonin known to be synthesized by pineal photoreceptors. In the pineal anlage, opsin immunoreactive (ir) cells appear at 11 days post-fertilization (pf), arrestin, α-transducin and serotonin ir cells appear at 14 days pf; hatching took place 15 days pf. The retina contained no immunoreactive cells in embryos or in newly hatched larva. During this period, the pineal anlage is morphologically discernible only as a wedge-shaped region in the diencephalic roof, where elongated cells are aligned with their long axes converging toward a centrally located presumptive pineal lumen. The results show that the pineal photoreceptors contain serotonin and molecules involved in the phototransduction cascade before hatching. We suggest that the pineal organ has the capacity to perceive and mediate photic information before hatching in halibut embryos, and may thereby influence the timing of hatching.
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| 2. |
- Holmqvist, Bo I., et al.
(författare)
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Hypophysiotrophic systems in the brain of the Atlantic salmon. Neuronal innervation of the pituitary and the origin of pituitary dopamine and nonapeptides identified by means of combined carbocyanine tract tracing and immunocytochemistry
- 1995
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Ingår i: Journal of Chemical Neuroanatomy. - 0891-0618. ; 8:2, s. 125-145
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Tidskriftsartikel (refereegranskat)abstract
- The neuroanatomical organization of neurons projecting to the pituitary and the origin of pituitary dopamine and nonapeptides were investigated in the brain of the Atlantic salmon (Salmo salar). Carbocyanine tract tracing in combination with tyrosine hydroxylase, arginine vasotocin and isotocin immunocytochemistry for double labelling revealed a previously unknown organization of hypophysiotrophic cell groups and their extrahypothalamic projections, and provide the first direct identification in a teleost fish of the origin of the dopaminergic and nonapeptidergic innervation of the pituitary. The present data include identification of (1) hypophysiotrophic neurons in the ventral telencephalon and in the periventricular preoptic nucleus, (2) large (magnocellular) vasotocinergic hypophysiotrophic neurons in the most rostral extension of the preoptic area, (3) a distinct neuronal group located in a supraoptic/suprachiasmatic position in the anterior periventricular nucleus, that seems to be the major source of dopaminergic innervation of the pituitary, (4) the nonapeptidergic hypophysiotrophic neurons in the preoptic nucleus, (5) hypophysiotrophic neurons in the ventral and posterior hypothalamus of which some are of liquor-contacting type, (6) projections from hypophysiotrophic and non-hypophysiotrophic neurons in the preoptic nucleus to extrahypothalamic areas such as thalamic and periventricular pretectal nuclei, and (7) subdivisions within the preoptic nucleus that exhibit different combinations of hypophysiotrophic and extrahypothalamic efferent connections. Together with previous studies of retinohypothalamic projections and neurochemical organization of hypothalamic/preoptic areas, the present data suggest that the preoptic nucleus and the anterior periventricular nucleus in teleosts possess functional subdivisions with features that resemble those of the paraventricular, supraoptic and suprachiasmatic nuclei of other vertebrates. In the Atlantic salmon, specific dopaminergic and nonapeptidergic neuronal subdivisions are proposed to play a role for photoperiod control of endocrine activity.
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| 3. |
- Holmqvist, Bo, et al.
(författare)
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Subcellular localization of neuronal nitric oxide synthase in the brain of a teleost; an immunoelectron and confocal microscopical study
- 1997
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Ingår i: Brain Research. - 0006-8993. ; 745:1-2, s. 67-82
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Tidskriftsartikel (refereegranskat)abstract
- The subcellular localization of neuronal nitric oxide (NO) synthase (NOS)-immunoreactive (NOSir) elements in the brain of the Atlantic salmon was investigated by means of electron microscopy and confocal laser scanning microscopy. NOSir structures are present only in neuronal elements. In neuronal processes, strong NOS immunoreactivity was mainly localized within synaptic vesicles or seen as a dense accumulation associated with the plasma membrane of dendrites and at terminal formations. NOSir precipitate was also associated with microtubuli and mitochondrial outer membranes. The highest accumulation of NOS immunoreactivity was found in dendrites located in close apposition to immunonegative myelinated or unmyelinated neural processes. Several NOSir and unmyelinated immunonegative profiles formed synaptic specializations. Immunonegative neurons in contact with NOSir processes always contained round clear synaptic vesicles. In neuronal somata, strong NOS immunoreactivity was localized in the cristae of some large mitochondria, whereas vacuoles and the endoplasmic reticulum showed a relatively weak staining. Confocal microscopic analysis of NOS immunofluorescence showed a corresponding subcellular localization of NOS in different brain regions, but also indicated the presence of NOS axosomatic terminals. Our data show that specific neurons contain a neuronal NOS-like molecule which to a high degree is stored in vesicles and is accumulated at various sites along the neuronal processes or at specific synaptic terminal formations. Thus, NO may be formed and exert its actions at various sites along the processes of NOS-synthesizing neurons. The present study provides evidence at the ultrastructural level that NO may play a messenger role in neural circuits involved in visual and hypophysiotrophic brain functions.
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