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S Dufour

Publications and source records attributed to S Dufour.

81 records · Page 5Linked to original sources
PubMed1986

Role of a major cell-substratum adhesion system in cell behavior and morphogenesis.

Fibronectins are multifunctional glycoproteins involved in the embryogenesis and in multiple physiological processes. Most of their functions derive from interactions of these glycoproteins with the cell surface. Fibronectin and their cell surface receptor constitute the major cell-substratum adhesion that plays a key role in cell adhesion, cell spreading and cell motility, particularly during embryonic development. Additionally, other functions of fibronectins are due to their ability to ban a great variety of macromolecules contained in an extracellular matrix and in plasma. In particular, the interaction of fibronectins with the cell surface, collagen, fibrin and fibrinogen are involved in physiological processes such as hemostasis, wound healing and phagocytosis.

Animals↗
PubMed1985

Increase in brain and pituitary radioimmunoassayable gonadotropin releasing hormone (GnRH) in the European silver eel treated with sexual steroid or human chorionic gonadotropin.

In the female silver eel, a single estradiol 17 beta (E2) injection significantly increased radioimmunoassayable GnRH (IRGnRH) in the di- and mesencephalon and also in the telencephalon and olfactory lobes, during the first following days; after a chronic estradiol treatment, the pituitary IRGnRH was doubled. In the male silver eel, a single injection of human chorionic gonadotropin (hCG), which is able to induce a progressive testicular development and a durable increase in androgens production, produced a long-term effect on IRGnRH: IRGnRH was significantly increased in the same brain areas as in E2-treated females; a more important rise (10-fold) was observed for pituitary IRGnRH, probably reflecting the accumulation of GnRH in the axonal endings which directly innervate the pituitary in teleosts. These results suggest a positive effect of sexual steroids on GnRH synthesis but not release in the silver eel.

Animals↗
PubMed1983

Effects of steroid hormones on pituitary immunoreactive gonadotropin in European freshwater eel, Anguilla anguilla L.

The low pituitary immunoreactive gonadotropin (IR GTH) contents of immature female or male freshwater eels were strongly increased after intraperitoneal injections of estradiol. Using female eels, the effect was shown to be dose dependent. In neither sex was modification of pituitary IR GTH observed after progesterone treatment; a very small increase (significant in females but not in males) was produced by cortisol. An important sexual difference occurred with testosterone, which strongly stimulated pituitary IR GTH level in male but not in female eels. The possibility of a low central aromatase activity responsible for the lack of effect of testosterone in the female eel is discussed. Circulating IR GTH levels were very low in steroid-treated eels, as in controls, indicating a weak GTH release. Thus, as in juvenile, immature fish from other species, a sexual steroid stimulated eel pituitary GTH content; the peculiarity of the apparent "blockade" of eel sexual development appears not related to a lack of sensitivity of gonadotropin synthesis to the positive feedback of a sexual steroid.

Anguilla↗
PubMed1983

Development of a heterologous radioimmunoassay for eel (Anguilla anguilla) gonadotropin.

A heterologous radioimmunoassay (RIA) for eel gonadotropin (GTH) was developed, using an antiserum to the beta subunit of carp GTH (cGTHbeta). Partially purified eel GTH preparations or crude eel pituitary extracts produced partial cross-reactions: the inhibition curves reached a plateau before complete inhibition of the binding of the tracer and the slopes were lower than those for cGTH. However, the parallelism between the inhibition curves produced by all the eel samples allowed estimation of their GTH activity relative to an eel GTH standard; under these conditions, the RIA exhibited good reproducibility within and between assays. Three different RIA systems for cGTHbeta using different antisera gave similar estimations of immunoreactive GTH (irGTH) content of eel GTH preparations and pituitary extracts. The specificity of teh heterologous RIA for eel GTH was first assessed by comparing RIA and bioassay data: as with carp pituitary extracts, no significant difference was found between immunological and biological estimations of GTH activity for partially purified or crude pituitary extracts from normal female eel. Further validation of the specificity of the RIA for eel GTH was provided by the variation of the eel pituitary irGTH content under different hormonal treatments: a significant increase in female eel pituitary irGTH content was produced by treatment with estradiol-17 beta or with carp pituitary extract, a result in agreement with previous histological reports of Olivereau and collaborators. The heterologous RIA for eel GTH, in view of its sensitivity, reproducibility, and specificity, is a useful tool for physiological studies in the eel.

Anguilla↗
PubMed1982

Presence and distribution of radioimmunoassayable LHRH in the European eel, Anguilla anguilla.

Eel brain contains a factor which exhibited a complete cross-reaction in a radioimmunoassay (RIA) for mammalian luteinizing hormone-releasing hormone (LHRH) and which exhibited a behavior similar to that of synthetic mammalian LHRH on Sephadex G-25. Eel brains contained 920 +/- 135 pg of this LHRH-like immunoreactive factor (IR-LHRH); 75% of immunoreactivity was present in the di- and mes-encephalon, 21% in the telencephalon and 4% in the hind-brain. Thus, IR-LHRH in eel brain exhibited a much wider distribution than in mammalian brain. Pituitary also contained a large amount of IR-LHRH (304 +/- 69 pg) at a concentration even higher than in median hypothalamic lobe; this result is probably related to the fact that, in teleost, median eminence is included into the pituitary. An immunoreactive substance was also present in the blood. In conclusion, the lack of sexual development and the low gonadotropic function in the eel, are apparently not related to an absence of LHRH.

Anguilla↗
PubMedDate not supplied

Chromatographic and immunological evidence for mammalian GnRH and chicken GnRH II in eel (Anguilla anguilla) brain and pituitary.

Gonadotropin-releasing hormone (GnRH) peptides in the brain and pituitary of the European eel (Anguilla anguilla) were investigated by reverse phase high performance liquid chromatography (HPLC) and radioimmunoassay with region-specific antisera. Two GnRH molecular forms were demonstrated in brain and pituitary extracts. One form eluted in the same position as synthetic mammalian GnRH on HPLC and was recognized by antibodies directed against the NH2 and COOH termini of mammalian GnRH as well as by antibodies to the middle region. The second form eluted in the same position as synthetic chicken GnRH II and was recognized by specific antibodies to this molecule. Salmon GnRH and chicken GnRH I were not detected. The occurrence of mammalian GnRH in teleost fish suggests that this molecular form is more ancient than was previously suspected and arose earlier than in primitive tetrapods, or that it has arisen in the eel through random mutation of salmon GnRH. The lack of salmon GnRH in the eel brain indicates that this molecular form is not common to all teleost species. The finding in eel brain of chicken GnRH II, which has previously been described in species of Mammalia, Aves, Reptilia, Amphibia, Osteichthyes, and Chondrichthyes, supports our hypothesis that this widespread structural variant may represent an early evolved and conserved form of GnRH.

Anguilla↗
PubMedDate not supplied

Organizational support of the clinical nurse specialist role: a nursing research and professional development directorate.

Administrative support is essential for optimal utilization of the Clinical Nurse Specialist (CNS) resource. It has been linked to successful role implementation, role efficacy and job satisfaction. The article addresses how a Nursing Research and Professional Development Directorate (NRPD) provides administrative support of the CNS role. The impact of the directorate on the role functions of practitioner, consultant, educator and researcher is delineated. Specific challenges to the CNS role and organizational benefits are described. A model of organizational support of the CNS, based on the concepts of collaboration and peer mentorship, is proposed. The model emphasizes mutual goal setting to achieve both organizational and professional objectives.

Humans↗