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M Olivereau

Publications and source records attributed to M Olivereau.

At least 37 records · Page 2Linked to original sources
PubMed1985

Distribution of cell types and aromatase activity in the sculpin (Myoxocephalus) pituitary.

Although aromatase activity is exceptionally high in the teleost pituitary, it is not known which of the secretory cell types are responsible. Pituitary glands from the longhorn sculpin (Myoxocephalus octodecimspinosus) were sectioned transversely into "cephalic" and "caudal" fragments and cultured for 24 hr in medium containing [7-3H]androstenedione. Radiolabeled estrone and estradiol-17 beta production were measured as an estimate of aromatization. In order to determine the distribution pattern of different cell types, the in situ pituitary and dissected fragments were analyzed by standard cytological procedures. Further verification of cell function was obtained by somatostatin (SRIF) and corticotropin-releasing factor (CRF) immunocytochemistry. Estrogen yields obtained from caudal fragments in two separate experiments averaged four times higher per milligram protein than yields from matched cephalic fragments. In addition, female glands synthesized significantly more estrogen than those of males. Due to an anteroflexion of the longitudinal axis and a disposition of the gonadotropic (GTH) cells at the periphery of the gland and surrounding the neurointermediate lobe (NIL), the classical subdivisions of the teleost adenohypophysis were not strictly applicable to the sculpin. The predominance of growth hormone (GH) secreting cells in the caudal fragment suggests their participation in aromatization, a finding which is consistent with a previous study of rodent pituitary; however, a role for gonadotropes and other hypophysial cells in this transformation cannot be ruled out.

Adrenocorticotropic Hormone↗
PubMed1984

Immunocytochemical identification of CRF-like and SRIF-like peptides in the brain and the pituitary of cyprinid fish.

Single and double immunocytochemical techniques were applied to the brain and pituitary of carps and goldfish. With the use of antiserum raised against synthetic corticotropin-releasing factor (CRF), immunoreactive perikarya were observed in the nucleus praeopticus and the nucleus praeopticus periventricularis. CRF-like-immunoreactive hypothalamic nerve fibers reach the pituitary. In cyprinids, some fine fibers enter the rostral neurohypophysis bordered by prolactin- and ACTH cells. Other thicker fibers extend ventrocaudally into the neurointermediate lobe. This CRF-like system appears to differ from the SRIF-like system, which is restricted to the proximal pars distalis of the pituitary containing somatotrophs.

Animals↗
PubMed1984

Somatostatin in the brain and the pituitary of some teleosts. Immunocytochemical identification and the effect of starvation.

Immunocytochemical investigations show that somatostatin (SRIF)-like immunoreactive material is present in the brain and the pituitary of nine different species of teleosts. In the brain, immunoreactive perikarya and fibers are observed in the preoptic periventricular nucleus, the entopeduncular nucleus, the anterior periventricular nucleus, and the nucleus lateralis tuberis. In the pituitary, SRIF-like-immunoreactive fibers occur in the proximal pars distalis (PPD), which contains the growth hormone (GH)-secreting cells. Nerve fibers are scattered among GH cells (cyprinids), or end on the basal lamina at the neuroglandular interface of the PPD (eel, salmonids). In the eel, the proximal neurohypophysis does not penetrate deeply into the PPD that is very poorly vascularized. In some species, e.g. Myoxocephalus, SRIF-like immunoreactive fibers are also observed in the caudal neurohypophysis, and even among MSH cells of the pars intermedia. In long-term starved carps and eels, the amount of SRIF-like material in the pituitary is clearly reduced. A possible role of SRIF in the concomitant stimulation of GH cells is discussed.

Animals↗
PubMed1983

Response of prolactin cells to environmental calcium in the eel (Anguilla anguilla L.).

Prolactin (PRL) cell activity was investigated in eels kept in fresh water (FW), deionized water (DW) supplemented or not with Ca (2 mM), in Ca-enriched FW (10 mM), in normal (Ca 3.4 mM) or Ca-free 1/3 sea water (SW), and in SW (Ca 10.2 mM) or Ca-free SW (Ca 0.15 mM). Light-microscopic studies, including measurement of the nuclear area and cell height, showed that PRL cell activity, reduced in DW, is not affected by Ca supplementation. Activity is reduced in Ca-enriched FW, in 1/3 SW and in SW, conditions inducing an increase in the plasma sodium level. The lack of calcium in saline environments partly suppresses the nuclear atrophy occurring in SW. There is no significant correlation between external or total plasma calcium concentration and PRL cell activity. In artificial Ca-free SW, eels show a rapid increase in plasma osmolarity and sodium levels; there is a significant negative correlation between these two plasma values and the nuclear area or cell height of PRL cells. As in some other teleosts, plasma osmolarity and plasma sodium seem to play a more important role than external or internal calcium in controlling PRL secretion. This correlation is not apparent in eels kept in SW, having unstimulated PRL cells but active calcium-sensitive (Ca-s) cells in the pars intermedia.

Anguilla↗
PubMed1983

Response of prolactin cells in the goldfish adapted to diluted seawater with or without calcium.

The activity of prolactin (PRL) cells was investigated in goldfish gradually adapted to diluted (30%) artificial seawater (ASW) or directly immersed in 23% ASW and in similar saline solutions free of calcium. When Ca2+ is omitted, PRL cells appear slightly more active than those in saline solutions with calcium, nuclear areas having intermediate values between those in freshwater (FW) and those in diluted SW. Nuclear areas are also slightly larger in Mg-free SW. Other signs of stimulation are not apparent. These data are compared to those obtained in other teleost species. The lack of stimulation in PRL cells of goldfish adapted to deionized water (DW) suggests that calcium plays a minor role in controlling prolactin secretion in this teleost.

Animals↗
PubMed1983

Immunocytochemistry of gonadotropic cells in the pituitary of some teleost species.

An antiserum (anti-sGTH) raised against salmon gonadotropin (SG-G100) was tested on pituitary sections of Sarotherodon mossambicus, Carassius auratus, Anguilla anguilla (intact and estradiol-treated to induce the development of the gonadotropic (GTH) cells), Salmo trutta fario, and a protandric marine teleost (Sarpa salpa, Sparidae). Using an immunoenzymologic technique, anti-sGTH stained GTH and thyrotropic (TSH) cells in the species studied. Anti-sGTH stained the granulated GTH cells in S. trutta fario and S. salpa; the vacuolated cells remained faintly stained or unlabeled in most cases. The results are discussed in the light of cytological, ultrastructural, and biochemical data which suggest that two forms of GTH cells may be present in some teleost pituitaries.

Animals↗
PubMed1983

[Ultrastructure of prolactin cells and survival of Gambusia sp. (teleost fish) in deionized water enriched in calcium or sodium].

The ultrastructure of the prolactin (PRL) cells of Gambusia was studied in animals kept in deionized water (EDes) and in EDes supplemented either with Ca2+ (10,2 and 15,3 mM) or with Na+ (10,2 and 15,3 mM). In environments supplemented with CaCl2 the maximal survival was 40 days. The stimulation of PRL cells was similar to that described in EDes. On the contrary, in environments supplemented with NaCl, 50% of the animals are still alive after 45 days. PRL cells are slightly stimulated and their ultrastructural aspect is similar to that observed in controls kept in freshwater. The significance of these results is discussed in relation with our present knowledge of the pituitary control of osmoregulation in teleost fish.

Animals↗
PubMed1983

Ultrastructural changes in the pars intermedia of the goldfish kept in calcium-free environments.

The PAS-positive-calcium-sensitive (Ca-s) cells of the pars intermedia (PI) were studied in goldfish kept in fresh water (FW), deionized water (DW), 1/3 sea water (SW) and 1/3 Ca-free SW. Ultrastructural studies show that Ca-s cells of control goldfish kept in FW have a low activity with elongated or deeply indented nuclei. This activity is slightly reduced after 19 days in 1/3 SW. A considerable stimulation of most Ca-s cells is noted in goldfish kept in DW for 20 or 40 days. The stimulation is similar in 1/3 Ca-free SW, but it affects sometimes a smaller percentage of cells and may be less marked in peripheral areas of the PI. Exocytotic figures are more numerous in Ca-s cells of goldfish in 1/3 Ca-free SW than in DW. A basal lamina is rarely present and direct contacts between PI cells and nervous tissue are frequent, although a single synaptic contact with a type B fiber was observed. MSH cells are not affected in goldfish kept in DW. They are stimulated in 1/3 Ca-free SW: the physiological significance of this response remains unclear. Few agranular (Agr) cells are scattered in the PI. Evident changes are not observed in the different environments. The present ultrastructural data support the hypothesis that the Ca-s cells of the PI secrete a factor involved in calcium regulation in some teleosts.

Animals↗
PubMed1982

Calcium-sensitive cells of the pars intermedia and osmotic balance in the eel. I. Responses to changes in the environmental calcium and magnesium.

The structure of the PAS-positive calcium-sensitive (Ca-s) cells of the pars intermedia was investigated in eels kept in deionized water (DW) or fresh water (FW) supplemented with Ca2+ of Mg2+ x Ca2+ (2mM) reduces considerably the response to DW; plasma osmolarity, Na+ and Ca2+ levels are not significantly affected. In eels adapted to DW for 21 or 28 days, showing highly stimulated Ca-s cells, an addition of CaCl2 for 2 days inhibits the release of granules, but does not immediately block their synthesis and the mitotic activity. The nuclear area is reduced, osmolarity and plasma sodium increase, but the rise in calcium is not always significant. Magnesium, at a 10-fold greater concentration than in FW (2mM), slightly inhibits the release of secretory granules without reducing other indicators of stimulation. In Ca-enriched FW, the Ca-s cells appear inactive. These data show that the PAS-positive cells in the pars intermedia of the eel are calcium-sensitive, similar to those of the goldfish; their role in calcium regulation is briefly discussed.

Animals↗
PubMed1982

Calcium-sensitive cells of the pars intermedia and osmotic balance in the eel. II. Response to calcium-free sea water.

Freshwater eels were adapted to calcium-free sea water (SW) or 1/3 Ca-free SW. Survival was generally poor in Ca-free SW, although three eels were still in good condition after 19-30 days; survival in 1/3 Ca-free SW was excellent. Osmotic disturbances (increase of plasma osmolarity and sodium levels), which initially occur in Ca-free SW, were no longer detectable after 19-30 days, or in eels in 1/3 Ca-free SW after one month. Plasma calcium sharply decreases initially; it is less depressed after 19-30 days and in 1/3 Ca-free SW. Alterations in the mucus production may be involved in the osmotic changes. Under these conditions no clear stimulation of the calcium-sensitive (Ca-s) cells of the pars intermedia was registered, but in Ca-free SW (1/3 or full strength) the inhibitory effect normally observed in SW does not occur. In a hyperosmotic environment, other ion(s), possibly magnesium, may reduce the response of the Ca-s cells to a lack of environmental calcium.

Anguilla↗
PubMed1982

Response of calcium-sensitive cells in the pars intermedia of the goldfish adapted to diluted sea water with different calcium and magnesium contents.

Goldfish kept in diluted Ca-free sea water (SW) (23 or 30%) or in Ca-Mg-deficient SW (23%) have a limited survival, release large amounts of mucus, and show spasmodic seizures. Plasma calcium decreases. The PAS-positive calcium-sensitive (Ca-s) cells of the pars intermedia show a low activity in diluted SW and in 23% Mg-free SW. In diluted Ca-free SW, Ca-s cells are stimulated, but cell hypertrophy is not uniform and often restricted to an area adjacent to the proximal pars distalis. Nuclear hypertrophy is significant in the reactive area, although less pronounced or even absent at the periphery of the lobe. Mitotic activity occurs in the Ca-s cells of goldfish gradually adapted to diluted Ca-free SW and Ca-Mg- deficient SW, and sacrificed after 19 and 28 days, respectively. A general stimulation of the Ca-s cells, which remains less intense than that in goldfish kept in deionized water (DW), appears unable to ensure the survival of the goldfish in an isosmotic Ca-free environment containing Mg2+ (0.1, 12 or 16.8 mM). These data are compared with those obtained in the eel kept in Ca-free SW.

Acclimatization↗
PubMed1981

Ultrastructural changes in the calcium-sensitive (PAS-positive) cells of the pars intermedia of eels kept in deionized water and in normal and concentrated sea water.

The ultrastructure of the calcium-sensitive (Ca-s) (PAS-positive) cells of the pars intermedia was investigated in eels kept in hypo- and hyperosmotic environments. Although the cells were moderately active in fresh water (FW), they were highly stimulated in deionized water (DW) and displayed an enlarged Golgi apparatus, a distinct rough endoplasmic reticulum, few secretory granules, some microtubules and an extended area of contact with the basal lamina that separates nervous and glandular tissues. Some mitosing cells were seen. A similar picture was observed in eels kept in sea water (SW) for 45 days, returned to FW and subsequently to DW for 21 days. In SW (20 and 33%), and particularly in concentrated SW (50, 60 and 63%), the Ca-s cells were inactive. Their granules were significantly smaller than in eels kept in FW, and the area of contact with the basal lamina was greatly reduced. However, signs of granule-release were seen in eels adapted to 50 and 60% SW. Nerve fibers rarely contacted the Ca-s cells and did not synapse with them. The ultrastructural data support the hypothesis that the Ca-s cells of Anguilla, like those of Carassius, are involved in ionic regulation. MSH cells were not greatly affected by the present experiments.

Animals↗
PubMed1981

Specific effect of calcium ions on the calcium-sensitive cells of the pars intermedia in the goldfish.

Cytological changes in the calcium-sensitive (Ca-s) cells (formerly termed PAS-positive cells) of the pars intermedia were investigated in the goldfish after adaptation to deionized water (DW), with or without addition of sodium, potassium and magnesium. These ions were added as chloride salts at concentrations similar to those present in fresh water (FW). The marked stimulation of the Ca-s cells is not inhibited in DW supplemented with Na+ (0.35 mM/l), K+ (0.05 mM/l), and Mg2+ (0.2 mM/l) for a period of 24 days. The inhibition of the response to DW with calcium chloride (2 mM/l). These data show that chloride ions are not responsible for the regression of the Ca-s cells observed in goldfish kept in DW supplemented with calcium chloride. The effect of calcium ions on the Ca-s cells appears to be specific. These results support the hypothesis that the Ca-s cells synthesize a factor (hypercalcin?) involved in calcium regulation, and that its release is influenced by the calcium content of the environment. The role of the pars intermedia in calcium metabolism is strengthened by the present results. Biochemical data suggest the presence of a hypercalcemic factor in the pituitary of fish (Parsons et al. 1978) and are in agreement with the present cytological findings.

Animals↗
PubMed1981

[Response of the pars intermedia of the goldfish pituitary to deionized water, buffered or not, and to calcium and magnesium supplementation (author's transl)].

In the goldfish, one cell type of the pars intermedia, slightly PAS positive, is highly stimulated in deionized water (E Dés). This response is not influenced by the pH of the water (E Dés pH 5.3, E Dés buffered with imidazole pH 6.7) for 20 days. Stimulation is prevented when the E Dés is supplemented with CaCl2 (2mM), but it is not affected by the addition of MgCl2 (2 mM). When goldfish are kept in E Dés for 20 days, and subsequently in E Dés supplemented with calcium gluconate (1 mM), a granule storage occurs in the cytoplasm of the enlarged cells within 48 hours. These cells are therefore sensitive to the lack or presence of calcium in the environment. The term of calcium-sensitive (Ca-s) cells appears justified in the goldfish, as in the eel; their putative role in the control of the pigmentation is not evident.

Animals↗
PubMed1980

Responses of MSH and prolactin cells to 5-hydroxytryptophan (5-HTP) in amphibians and teleosts.

Injection of 5-hydroxytryptophan (5-HTP), a precursor of serotonin, induces dispersion of melanin in the amphibians, Pleurodeles waltlii (Urodela) and Xenopus laevis (Anura), in the goldfish, Carassius auratus, and in the carp, Cyprinus carpio. It is accompanied by a dispersion of erythrophore pigments. In the pituitaries of Pleurodeles and goldfish, a stimulation of MSH cells, characterized by a significant nuclear hypertrophy, is also observed; in Carassius, MSH cells may become degranulated. Serotonin appears to exert a stimulating effect on MSH release in lower vertebrates. Swimming behavior is disturbed in the goldfish and the carp; gaseous metabolism in the swim-bladder may be affected by injection of 5-HTP, as previously reported in the eel. Prolactin (PRL) cells appear activated, but remain granulated in the treated goldfish. No clear response of PRL cells to injection of 5-HTP can be observed in Pleurodeles. A possible role of serotonin in Pleurodeles submitted to an experimental aeroionization is briefly discussed.

5-Hydroxytryptophan↗