[Cytological reactions in the pars intermedia of the hypophysis of the salpa, Boops salpa L. (a marine teleost fish, Sparidse) to variations in salinity]

Immunocytochemical and ultrastructural characterization of the cell types in the adenohypophysis of Sparus aurata L. (teleost)

The structure and immunocytochemistry of the adenohypophysis of sexually mature male specimens of Sparus aurata (gilthead sea bream) were studied. The adenohypophysis was composed of rostral pars distalis (RPD), proximal pars distalis (PPD), and pars intermedia (PI). In the RPD the prolactin cells were organized into follicles which occupied a very reduced area as corresponds to that in saltwater fishes; the corticotropic cells were surrounding the pars nervosa branches and the prolactin follicles. The PPD showed somatotropic, gonadotropic, and thyrotropic cells. The somatotropic cells were isolated, clustered, or surrounding the pars nervosa branches. Only one polymorphic cell type of gonadotropic cells was found in the PPD ventral and dorsal areas and around the PI. The PI was composed mainly of melanotropic cells and a PAS-positive cell layer adjacent to the neurohypophysis. The ultrastructure of the presumptive endocrine cells was reported and their distribution was discussed in relation to those of other teleosts.

Stress-induced elevation of plasma alpha-MSH and endorphin in brown trout, Salmo trutta L

Handling and confinement caused a pronounced elevation in the plasma cortisol levels of brown trout. This response was more rapid, and the elevation greater, at 13.4 than at 5 degrees although basal cortisol levels were also higher at the warmer water temperature. The large increase in plasma cortisol caused by handling and confinement was not accompanied by any changes in the plasma levels of either alpha-MSH or endorphin. However, when handling and confinement was combined with a thermal shock, not only was there a rapid and pronounced elevation in plasma cortisol, but there were also concomitant and sustained rises in the plasma levels of both alpha-MSH and endorphin. The levels of a alpha-MSH and endorphin induced by the thermal shock were considerably higher than those recorded in long-term, black-adapted brown trout, the only other circumstance in fish known to cause an elevation of the plasma levels of these two peptides. These results indicate that handling and confinement only activated the corticotrophs of the pars distalis, not the melanotrophs of the neurointermediate lobe, whereas when combined with a thermal shock, both cell types were activated.

Isolation of the biosynthetic products of the PAS positive pars intermedia cells in the cichlid teleost Sarotherodon mossambicus

The pars intermedia of teleosts contains two types of granular cells with the predominant type being similar to the pars intermedia cells in other vertebrate groups and containing peptides derived from the pro-opiomelanocortin precursor molecule. The function and products of the second cell type, the PAS positive cells, are unknown. This study reports on the identification of biosynthetic products of the PAS positive cells of the cichlid teleost Sarotherodon mossambicus. The experimental regimen took advantage of earlier morphometric analyses which showed marked differences in metabolic activity of the PAS positive cells resulting from adaptation to different background colours and illumination. Autoradiography at the light microscopic level showed that both cell types of the pars intermedia incorporate labeled amino acids during in vitro incubation. To identify the products synthesized by the PAS positive cells, labeled products of the pars intermedia tissue were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high-pressure liquid chromatography. Comparison of pulse incubations of pars intermedia tissue of fish adapted to different backgrounds and conditions of illumination revealed that an increase in the number and metabolic activity of the PAS positive cells, as deduced from morphometric data, was paralleled by an increase of the amount of label incorporated into 27K and 25K molecules. Pulse--chase experiments with pars intermedia lobes of white and black background adapted fish showed that these two products, unlike the other newly synthesized products, were not involved in any precursor-product relationship. Our data, therefore, suggest that the 27K and 25K peptides were synthesized by the PAS positive cells.