Ontogeny of immunoreactive somatolactin cells in the pituitary of gilthead sea bream ( Sparus aurata L., Teleostei)

 This is the first report on the identification of somatolactin (SL) cells during the early developmental stages of the teleost fish Sparus aurata. The SL cells were followed from newly hatched until 46 months. SL cells were immunocytochemically identified at light microscopical level with anti-cod SL in the developing pituitary using the peroxidase-antiperoxidase method. SL cells first appeared in newly hatched specimens, in which the pituitary gland lacked the neurohypophysis. They were scarce and located from the middle to the posterior region of the adenohypophysis. As the fish developed, the cells progressively increased in number and surrounded the developing neurohypophysis, which could be distinguised from 12-day-old larvae onwards in the caudal region of the gland. From 51 days onwards, SL cells were found in a discontinuous layer surrounding the neurohypophysis branches that entered the pars intermedia as clustered or isolated cells among non-SL-immunoreactive cells of the pars intermedia, and in the proximal pars distalis. The somatolactin-immunoreactive cells are periodic acid-Schiff-positive only in the adult stages. These data confirm, previous findings concerning the presence of two molecular forms of SL, glycosylated and nonglycosylated, in this species. Accepted: 4 April 1997     

Ontogeny of immunoreactive somatolactin, prolactin and growth hormone secretory cells in the developing pituitary gland of Cichlasoma dimerus (Teleostei, Perciformes)

Prolactin, growth hormone and somatolactin constitute a hormone family because they are structurally related and are secreted by acidophilic cells of different regions of the adenohypohyisis. In this work, we report the ontogeny of ir-prolactin, ir-growth hormone and ir-somatolactin cells in the developing pituitary gland of the cichlid fish Cichlasoma dimerus (Teleostei; Perciformes). Antisera raised against fish pituitary hormones were used. In this species hatching occurs 54 hs after fertilization and the three different cell types were recognized two days later. The neurohypophysis was recognized on day 14 after hatching and in later stages it began to show the characteristic deep interdigitations of the adults. On day 42 (juvenile stage) the distribution of ir-PRL, ir-GH and ir-SL showed the pattern described for adults of this species. The ir-SL cells were not PAS-positive in larvae as they are in adults. This would suggest the presence of a nonglycosilated form of somatolactin in early stages of development which may coexist in adults with a glycosilated form. The appearence of these hormones so early in development suggest their importance in the survival of fish larvae but further studies focused on the ontogeny of hypothalamic factors that regulate their synthesis and secretion must be performed. Accepted: 30 January 2001     

Immunocytochemical and ultrastructural characterization of somatolactin cells from the gilthead sea bream ( Sparus aurata L., Teleostei): an ontogenic study (from newly hatched to adults)

For the first time, somatolactin (SL) cells have been ultrastructurally identified and characterized during the ontogeny of gilthead sea bream, Sparus aurata, using specimens ranging in age from hatching to 15 months. The SL cells were identified by an immunogold method using anti-cod SL serum. The SL-immunoreactivity was mostly located on the secretory granules of the cells, although some vesicles of variable size and shape with a medium electron-dense content, and some irregular secretory granules and polymorphic or very irregular masses that can arise from the fusion of several secretory granules, also presented immunogold labeling. In adults, the SL cells were mainly found in the pars intermedia, where they were organized in discontinuous cell cords lying against the neurohypophysis or surrounding the neurohypophyseal branches. Some SL cells, however, appeared isolated or in small groups in the pars intermedia, in the proximal pars distalis and, rarely, in the rostral pars distalis. The SL cells were variable in shape, with processes directed towards the neurohypophysis or blood vessels, or intermingling among other adenohypophyseal cells. The secretory granules were mostly round, although some were oval, bilobate or pear-shaped, with a homogeneous, very electron-dense content and a narrow, dense or clear, halo. Different SL cell populations can be distinguished according to secretory granule size. Our findings indicate that SL is stored in the secretory granules and released by exocytosis. SL cells showing involutive features were only found in adults. SL cells can be ultrastructurally identified in one-day-old larvae although similar characteristics to those found in adults can be positively identified only after 4 days. Secretory granules increased in number, size and heterogeneity during development. Synaptic-like structures between axon terminals of the neurohypophysis and the SL cells were found in larvae from one-day-old onwards. In juveniles of 118 days of age, two different populations of secretory granules (immunogold-labeled and non-immunogold-labeled) can be found in the same or different SL cells, findings that suggest the existence of two different molecular forms of SL at this age. There was a clear increase in the complexity of the pituitary gland and in the heterogeneity of the SL cells during development, the latter observation probably reflecting different functional cell stages or production of SL molecules. Accepted: 22 January 2001     

Ontogeny of immunoreactive somatolactin cells in the pituitary of gilthead sea bream (Sparus aurata L., Teleostei)

This is the first report on the identification of somatolactin (SL) cells during the early developmental stages of the teleost fish Sparus aurata. The SL cells were followed from newly hatched until 46 months. SL cells were immunocytochemically identified at light microscopical level with anti-cod SL in the developing pituitary using the peroxidase-antiperoxidase method. SL cells first appeared in newly hatched specimens, in which the pituitary gland lacked the neurohypophysis. They were scarce and located from the middle to the posterior region of the adenohypophysis. As the fish developed, the cells progressively increased in number and surrounded the developing neurohypophysis, which could be distinguised from 12-day-old larvae onwards in the caudal region of the gland. From 51 days onwards, SL cells were found in a discontinuous layer surrounding the neurohypophysis branches that entered the pars intermedia as clustered or isolated cells among non-SL-immunoreactive cells of the pars intermedia, and in the proximal pars distalis. The somatolactin-immunoreactive cells are periodic acid-Schiff-positive only in the adult stages. These data confirm, previous findings concerning the presence of two molecular forms of SL, glycosylated and nonglycosylated, in this species.     

Immunocytochemical and ultrastructural characterization of somatolactin cells from the gilthead sea bream (Sparus aurata L., Teleostei): an ontogenic study (from newly hatched to adults)

For the first time, somatolactin (SL) cells have been ultrastructurally identified and characterized during the ontogeny of gilthead sea bream, Sparus aurata, using specimens ranging in age from hatching to 15 months. The SL cells were identified by an immunogold method using anti-cod SL serum. The SL-immunoreactivity was mostly located on the secretory granules of the cells, although some vesicles of variable size and shape with a medium electron-dense content, and some irregular secretory granules and polymorphic or very irregular masses that can arise from the fusion of several secretory granules, also presented immunogold labeling. In adults, the SL cells were mainly found in the pars intermedia, where they were organized in discontinuous cell cords lying against the neurohypophysis or surrounding the neurohypophyseal branches. Some SL cells, however, appeared isolated or in small groups in the pars intermedia, in the proximal pars distalis and, rarely, in the rostral pars distalis. The SL cells were variable in shape, with processes directed towards the neurohypophysis or blood vessels, or intermingling among other adenohypophyseal cells. The secretory granules were mostly round, although some were oval, bilobate or pear-shaped, with a homogeneous, very electron-dense content and a narrow, dense or clear, halo. Different SL cell populations can be distinguished according to secretory granule size. Our findings indicate that SL is stored in the secretory granules and released by exocytosis. SL cells showing involutive features were only found in adults. SL cells can be ultrastructurally identified in one-day-old larvae although similar characteristics to those found in adults can be positively identified only after 4 days. Secretory granules increased in number, size and heterogeneity during development. Synaptic-like structures between axon terminals of the neurohypophysis and the SL cells were found in larvae from one-day-old onwards. In juveniles of 118 days of age, two different populations of secretory granules (immunogold-labeled and non-immunogold-labeled) can be found in the same or different SL cells, findings that suggest the existence of two different molecular forms of SL at this age. There was a clear increase in the complexity of the pituitary gland and in the heterogeneity of the SL cells during development, the latter observation probably reflecting different functional cell stages or production of SL molecules.     

Ultrastructure and cytochemistry study of Eimeria sparis (Protozoa: Apicomplexa) stages from the intestine of gilthead sea bream Sparus aurata L. (Pisces: Teleostei)

The ultrastructure and cytochemistry of merogonial, gamogonial, and early sporogonial stages of Eimeria sparis in the intestine of Sparus aurata were studied. Mature stages showed the typical pellicle, which was lost in some transitional stages. An apparent unit membrane was seen in some immature stages. A parasitophorous vacuole, sometimes with membrane vesicular invaginations, was usually observed. We propose that the stages located over the epithelium and the so-called epicellular stages be termed supraepithelial stages. Endomerogony was observed in intraepithelial and supraepithelial positions. Intraepithelial stages apparently starting ectomerogony were also detected. Electron-dense granules similar to wall-forming-like bodies of types 1 and 2 were observed. Microgametes exhibited two flagella. Cytochemistry study revealed scarce polysaccharides, if any, in merogonial stages and in microgamonts. The occurrence of polysaccharides and amylopectin granules increased progressively in macrogamonts, macrogametes, zygotes, and early oocysts. Lipidic droplets were scarce or absent in merogonial stages and abundant in maturing macrogamonts. Some glycoproteins were demonstrated in certain merogonial stages. Received: 30 January 1996 / Accepted: 12 August 1996     

Ultrastructure and cytochemistry study of Goussia sparis (Protozoa: Apicomplexa) stages from the intestine of the gilthead sea bream Sparus aurata L. (Pisces: Teleostei)

 The ultrastructure and cytochemistry of merogonial and gamogonial stages and early unsporulated oocysts of Goussia sparis in the intestine of Sparus aurata were studied. The typical pellicle was observed in some stages. The different stages might appear in intraepithelial or supraepithelial positions, but they were always intracellular. First steps of two apparently different endomerogonies were observed in intra- and supraepithelial positions, respectively. An apparent ectomerogony also occurred in supraepithelial stages. Developing macrogamonts showed surface invaginations and were densely packed with ribosomes, well-developed rough endoplasmic reticulum, mitochondria, amylopectin granules, lipidic droplets, and wall-forming-like bodies. The latter could participate in the formation of the oocyst wall. Abundant and large mitochondria, together with residual nuclei, appeared in advanced microgamonts. Microgametes showed two flagella with microtubul arranged according to the typical pattern. An increase in polysaccharide content was observed with coccidian development, reaching a maximum in zygotes and unsporulated oocysts. Received: 30 January 1996 / Accepted: 8 July 1996     

An immunocytochemical study of the development of the olfactory system in the three-spined stickleback (Gasterosteus aculeatus L., Teleostei).

Summary Antisera against a variety of substances have been found to produce an identical immunoreaction in the developing olfactory system of a teleost, the three-spined stickleback (Gasterosteus aculeatus). The label is localized in the olfactory placode, the olfactory nerve and those parts of the secondary olfactory tracts which constitute the dorsal descending fascicles and the ventral descending fibers of the medial olfactory tract. The label was first detected 3 days after fertilization (3D) in the olfactory placode where labeled supporting cells were observed. At 4D, the label was observed at the site of the developing olfactory bulbs. At 7D, the olfactory placode lost the direct contact with the brain and the labeled olfactory nerve became visible. At the same time, the medial olfactory tract emerged from the bulbs, and contacts with cells in the nucleus of the terminal nerve were observed. The development of the medial olfactory tract proceeded caudally, and by the end of I OD, the olfactory tract reached the periventricular hypothalamus. Pre-absorption of the antisera with the respective antigens did not abolish the capacity of the antisera to produce the label. The immunoreaction is thus not specific for the antigens against which the antisera have been raised. Yet the label produced by the immunoreaction is an extremely reliable marker for the primary olfactory tract, and the only existing marker by which secondary olfactory tracts can be visualized.     

Early organization of the pituitary gland in Sparus aurata L. (Teleostei) An ultrastructural study

The cell organization of the pituitary gland and the relationship between neurohypophysis and adenohypophysis in the early developmental stages of the gilthead sea bream, Sparus aurata, were studied by electron microscopy. In newly hatched larvae, the pituitary gland was embedded in the ventral floor of the diencephalon and separated from the hypothalamus by a continuous basal lamina. Elongated mesenchymal cells next to the ventral surface were observed. At this stage, there was no neurohypophysis and the adenohypophysis consisted of undifferentiated endocrine cells with small scarce secretory granules and a few stellate cells, with no distinctive zonation. An incipient neurohypophysis was present in 1-day-old larvae. The first evagination of the neurohypophysis into the adenohypophysis were observed in 2-day-old larvae and developed progressively with age, being deeper in the caudal zone. Two regions in the adenohypophysis, one anterior — the presumptive pars distalis — and one posterior — the presumptive pars intermedia — were found in 2-day-old larvae. Three regions (rostral and proximal pars distalis and pars intermedia) were clearly distinguishable in 4-day-old larvae. The ultrastructural features of the pituitary endocrine cells varied during gland differentiation, with the secretory granules gradually increasing in number and size, accompanying organelle development. Nevertheless, even in the oldest larvae studied (65 days), undifferentiated cells similar to those in the earliest stages were observed. The first blood vessels appeared in the neurohypophysis around 16 days after hatching. During early development, the pituitary gland progressively emerged from the ventral floor of the brain. By 16 days, the principal pattern of the pituitary gland architecture appeared to be established.     

An immunohistochemical analysis of the ontogeny, distribution and coexistence of 12 regulatory peptides and serotonin in endocrine cells and nerve fibers of the digestive tract of the turbot, Scophthalmus maximus (Teleostei)

 The ontogeny of endocrine cells and nerve fibers containing immunoreactivities for 12 regulatory peptides and serotonin was studied in the digestive tract of a flatfish, the turbot (Scophthalmus maximus), using antisera specific for mammalian and teleostean hormones. Transient insulin-immunoreactive (-IR) endocrine cells were detected from day 5 to day 10 in stomach and intestine I. Somatostatin (SOM)-IR cells appeared at day 8 in the stomach anlage and intestine I. In contrast to the islet cells, they reacted with antisera against mammalian (m) SOM-14 and salmon (s) SOM-25. Infrequent nerve fibers reacting only with anti-mSOM-14 appeared around day 24. Thus, different forms of SOM seem to be present in the gastro-entero-pancreatic system and the enteric nervous system. Neuropeptide Y (NPY)-, salmon pancreatic polypeptide (sPP)- and mPP-immunoreactivities coexisted thoughout development. In entero-endocrine cells, NPY/PP-immunoreactivity was first observed at day 8 and around day 24 in enteric nerve fibers. Glucagon (GLUC)-IR entero-endocrine cells appeared at day 5. No coexistence of NPY/PP- and GLUC-immunoreactivities was observed. The first insulin-like growth factor I (IGF-I)-IR cells were identified around day 8. They seemed to contain none of the other peptides. Their number and distribution exhibited great interindividual differences. Vasoactive intestinal polypeptide (VIP)-IR entero-endocrine cells appeared as late as around day 24. The first VIP-IR nerve fibers, however, were identified at day 5. Infrequent neurotensin (NT)-IR cells appeared along the intestine around day 10 and NT-IR nerve fibers at day 17. The first serotonin (SER)-IR cells were observed in the stomach anlage around day 10 and SER-IR nerve fibers at day 15 thoughout the gastro-intestinal tract. Gastrin (GAS)/cholecystokinin (CCK)-IR cells appeared around day 11 in stomach and intestine I. The first substance P (SP)-IR enteric nerve fibers were detected around day 8 and SP-IR endocrine cells at day 11. Pancreastatin (PST)-IR cells were identified in the stomach anlage and intestine I around day 8 and contained NT-, GAS/CCK- and SER-immunoreactivities in coexistence. Thus, several developmental phases can be distinguished: (1) at the onset of exogenous feeding only transient INS-IR cells and VIP-IR nerve fibers are present; (2) a differentiated entero-endocrine system establishes during the early phase of exogenous feeding; (3) before the final differentiation of stomach and gut GAS/CCK-IR cells appear; (4) after metamorphosis most of the different types of regulatory peptide-containing nerve fibers develop, probably setting up the fine regulation of gastro-intestinal blood flow and motility. Accepted: 24 June 1996