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  • 1
    Electronic Resource
    Electronic Resource
    Early organization of the pituitary gland in Sparus aurata L. (Teleostei) An ultrastructural study (1996)
    Springer
    Anatomy and embryology 193 (1996), S. 441-452 
    Details
    ISSN: 1432-0568
    Keywords: Pituitary gland ; Development ; Ultrastructure ; Sparus aurata (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185875
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  • 2
    Electronic Resource
    Electronic Resource
    Ontogeny of some endocrine cells of the digestive tract in sea bass (Dicentrarchus labrax): An immunocytochemical study (1994)
    Springer
    Cell & tissue research 277 (1994), S. 373-383 
    Details
    ISSN: 1432-0878
    Keywords: Endocrine cells ; Gut ; Ontogeny ; Regulatory peptides ; Immunocytochemistry ; Dicentrarchus labrax (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Serotonin- and ten peptide-immunoreactive (IR) cell types were identified in the digestive tract of sea bass (Dicentrarchus labrax L.) larvae of four morphofunctional phases ranging in age from hatching to 61 days. The sequence of appearance and location of endocrine cells during ontogenetic development of the larvae was determined. The differentiation of endocrine cells followed a distal-proximal gradient in the gut which paralleled the morphofunctional differentiation. Serotonin-IR cells were identified in the last portion of the digestive tract from phase I onwards and in the gastric region from phase III, before these regions were morphofunctionally differentiated; met-enkephalin-IR cells were identified from phase II onwards in both the differentiated rectum and the undifferentiated intestine; cholecystokinin (CCK)- and synthetic human gastrin-34-IR cells were located only in the intestine and first found in the undifferentiated intestine of phase II; human gastrin-17-, peptide YY (PYY)- and neuropeptide Y (NPY)-IR cells appeared in the intestine from phase II and in stomach in phase IV, when it showed gastric glands; pancreatic polypeptide (PP)- and glucagon-IR cells were observed in both intestine and stomach, but insulin- and somatostatin-IR cells only in stomach, from phase III, during which the intestine but not the stomach was differentiated. PP- and PYY-, PP- and glucagon-, and PYY- and glucagon-like immunoreactivities coexisted from their first appearance in some cells of the gut.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327785
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  • 3
    Electronic Resource
    Electronic Resource
    Electron-microscopic immunocytochemical study of the endocrine pancreas of sea bass (Dicentrarchus labrax) (1993)
    Springer
    Cell & tissue research 274 (1993), S. 303-314 
    Details
    ISSN: 1432-0878
    Keywords: Endocrine pancreas ; Peptides ; Ultrastructure ; Immunogold labeling ; Sea bass ; Dicentrarchus labrax ; (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Insulin (B)-, somatostatin 25 (SST-25) (D1)-, somatostatin 14 (SST-14) (D2)-, glucagon (A)-, and glucagon PP/PYY/NPY (PP-like)-immunoreactive cells in islets of sea bass (Dicentrarchus labrax) were characterized according to their ultrastructure and immunogold labeling. Cells labeled with antisera to bonito and salmon insulin had numerous secretory granules with a small halo and round core, and a few with wide halo and round or crystalloid core. Gold particles were found throughout the granule in tissue labeled with the former but only in the core in tissue labeled with the latter. D1 cells had large granules with a medium electron-dense content and some with a darker core. D2 had smaller medium or high electron-dense secretory granules than D1 cells, located mainly in cell periphery. Glucagon-immunoreactive cells contained some granules with a polygonal core that was heavily labeled and other granules with a round core with no or hardly any labeling. Glucagon and PP-like immunoreactivity were co-localized in secretory granules, in which the gold particles showed no different distribution with the various antisera used. PYY-immunoreactive granules were also found in nerve endings. All the pancreatic endocrine cell types showing involutive characteristics are found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318749
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  • 4
    Electronic Resource
    Electronic Resource
    Ontogeny of the endocrine pancreas in sea bass (Dicentrarchus labrax): an ultrastructural study. I. The primordial cord and the primitive, single and primordial islets (1994)
    Springer
    Cell & tissue research 276 (1994), S. 309-322 
    Details
    ISSN: 1432-0878
    Keywords: Endocrine pancreas ; Ontogeny ; Ultrastructure ; Dicentrarchus labrax (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The primordial cord and the primitive, single and primordial islets present in the 3 earliest stages of the developing endocrine pancreas of sea bass were studied ultrastructurally. The primordial cord consisted of type I and II cells and was included in the gut. Besides these cell types, X cells were seen in the primitive islet. The single islet was made up of type I, II, III and IV cells. A correlation between these endocrine cell-types and cells previously identified immunocytochemically, was established. Type I, II, III and IV cells, correlated respectively with SST-25-, insulin-, SST-14- and glucagon-immunoreactive cells, and could be related to the D1, B, D2 and A cells, respectively, of older larvae and adult sea bass. Each cell type shows characteristic secretory granules from its first appearance. A progressive development of the organelles and an increase in the number and size of the secretory granules, whose ultrastructure also varied, was observed in the endocrine cells of the primordial cord and the succeeding islets. In 25-day-old larvae at the beginning of the fourth developmental stage, the primordial islet, the first ventral islet found, was close to a pancreatic duct and blood vessel, and consisted of type I and II cells whose ultrastructure was similar to that of the type I and II cells in the primordial cord. These data suggest a ductular origin for the pancreatic endocrine cells in the ventral pancreas. It is suggested that although endocrine cells undergo mitosis, their increase in number during the earliest development stages is principally due to the differentiation of surrounding cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306116
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  • 5
    Electronic Resource
    Electronic Resource
    Ontogeny of the endocrine pancreas in sea bass (Dicentrarchus labrax): an ultrastructural study. II. The big and secondary islets (1994)
    Springer
    Cell & tissue research 276 (1994), S. 323-331 
    Details
    ISSN: 1432-0878
    Keywords: Endocrine pancreas ; Ontogeny ; Ultrastructure ; Dicentrarchus labrax (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The big and secondary islets of sea bass larvae were characterized ultrastructurally from, 25 to 60 days after hatching. From the 25th day, big islets consisted of inner type II and III, external type I and peripheral type IV cells. From the 55th day, type V cells appeared in limited peripheral areas. Secondary islets, first found in 32-day-old larvae, were made up of inner type II and III, external type I, and peripheral either type IV and V cells (type I islets), or only type V cells (type II islets). Type I cells contained secretory granules with a fine granular, low-medium electron-dense material, whereas the secretory granules of type II cells were smaller and had a high electron-dense core with diffused limits; needle and rod-like crystalloid contents were occasionally found. Type III secretory granules posessed a homogeneous, high or medium electron-dense material with or without a clear halo. Type IV cells had secretory granules with a polygonal dense core embedded in a granular matrix and granules containing a high or medium electron-dense material. Type V cells had secretory granules with a fine granular, high or medium electron-dense content. These cell-types correlated with cells previously identified immuno-cytochemically, as regards to their distribution in the islets, and related to those characterized ultrastructurally in adult specimens. Thus, types I, II, III, IV and V correspond to D1, B, D2, A and PP cells, respectively. From the 32nd day onwards, endocrine cells of all the different types were found grouped, type V cells also being observed in isolation close to pancreatic ducts and/or blood vessels. Small groups consisting of type I and II cells were found in 40-day-old larvae. A mitotic centroacinar ductular cell containing some secretory granules similar to those of type I cells, was seen adjacent to a type I cell. As the larvae grew older, the endoplasmic reticulum developed, the number of free ribosomes decreased, and the number and size of the secretory granules increased. Dark type I, II, III, IV and V cells were found in the islets and cell clusters from the 55th day onwards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306117
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  • 6
    Electronic Resource
    Electronic Resource
    Ontogeny of the endocrine pancreas in sea bass (Dicentrarchus labrax) (1992)
    Springer
    Cell & tissue research 270 (1992), S. 339-352 
    Details
    ISSN: 1432-0878
    Keywords: Endocrine pancreas ; Ontogeny ; Regulatory peptides ; Immunocytochemistry ; Dicentrarchus labrax (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The development of the endocrine pancreas of the teleost sea bass (Dicentrarchus labrax, L.) was examined from hatching to 61 days, using the peroxidase-antiperoxidase technique for light microscopy. Mammalian and bonito insulin (mI and bI)-, salmo somatostatin-25 (SST-25)-, somatostatin-14 (SST-14a and b)-, glucagon-, bovine pancreatic polypeptide (PP)-, peptide tyrosine-tyrosine (PYY)- and salmo neuropeptide Y (NPY)-like immunoreactivity was demonstrated. Four ontogenetic stages were established according to the organization and immunostaining of the endocrine cells. One cell strand or primordial cord showing mI/bI- and SST-25/SST-14a-like immunoreactivity was first found at hatching in the dorsal epithelium of the anterior zone of the midgut (stage 1). One primitive islet, comprising outer SST-25/SST-14a- and inner mI/bI- and SST-14a/ SST-14b-immunoreactive cells, was found in 2- to 5-day-old larvae (stage 2). One single islet, in which glucagon-immunoreactive cells appear in the periphery, was found in larvae from 9 to 20 days after hatching (stage 3). One big islet containing, in addition, PP-immunoreactive cells in the outer region and slender cell processes which showed PYY-like immunoreactivity, was found from 25 to 61 days after hatching. During this period, primordial islets, composed of SST-25- and bI-immunoreactive cells, and clustered or isolated pancreatic endocrine cells, close to the pancreatic duct, as well as small and intermediate islets (secondary islets), in which glucagon, PP, PYY and NPY seem to be co-localized, were progressively found (stage 4). The origin of the endocrine pancreas of sea bass, and the ontogenetic and phylogenetic significance, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328018
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