The availability of subtype-specific agonists and antagonists for somatostatin (SS) receptors (SSTRs) will be important for elucidation of the function of each receptor isoformin vivo.A SS analog, ...des-AA1,2,5-D-Trp8, IAmp9SS (CH275), has been shown previously to bind preferentially to SSTR1. In this report, we identify structural determinants in the ligand and receptor responsible for the selective binding of CH275 to SSTR1 by modifying both the ligand and the receptor. We propose that IAmp9in CH275, like Lys9in SS, interacts with Asp137 in the middle of the third transmembrane domain of SSTR1 to form an ion pair, while other residues unique to SSTR1 conbribute to binding selectivity of CH275 for SSTR1. Replacement of Asp137 with Asn resulted in loss of binding of radiolabeled SS and decreased potencies of both SS and CH275 to induce a change in the extracellular acidification rate measured by microphysiometry. The structural determinants for specific binding to SSTR1 were mapped in chimeric SSTR1/SSTR2 receptors. One chimera, 2β, with theN-terminus to second transmembrane domain (TM2) from SSTR2 and the remainder of the receptor from SSTR1, had low affinity for CH275. Furthermore, when a single residue, Leu107, in TM2 of SSTR1 was replaced with Phe, the corresponding residue in SSTR2, a 20-fold decrease in affinity for CH275 with no significant change in affinity for SS was observed. A reciprocal change from Phe to Leu in the chimeric receptor 2β resulted in a 10-fold increase in affinity for CH275. Thus, Leu107 is an important determinant for CH275 binding to SSTR1. To identify the moiety in CH275 which could interact with Leu107, a new analog des-AA1,2,5-D-Trp8, Amp9SS was prepared. This analog bound to both SSTR1 and SSTR2 with similar affinities; thus, subtype selectivity was lost. Collectively, these data support a binding model for CH275 in which the positively charged IAmp interacts with the negatively charged Asp137 in TM3 of SSTR1 and the isopropyl group of IAmp forms a hydrophobic interaction with Leu107 in TM2.
Alternative processing of the RNA transcribed from the calcitonin gene appears to result in the production of a messenger RNA in neural tissue distinct from that in thyroidal 'C' cells. The thyroid ...mRNA encodes a precursor to the hormone calcitonin whereas that in neural tissues generates a novel neuropeptide, referred to as calcitonin gene-related peptide (CGRP). The distribution of CGRP-producing cells and pathways in the brain and other tissues suggests functions for the peptide in nociception, ingestive behaviour and modulation of the autonomic and endocrine systems. The approach described here permits the application of recombinant DNA technology to analyses of complex neurobiological systems in the absence of prior structural or biological information.
LHRH antagonists compete with endogenous LHRH for binding to receptors on pituitary gonadotrophs and thereby inhibit gonadotropin secretion and, consequently, gonadal function. We studied the ...pituitary and gonadal suppression following single doses and short term administration (1-3 weeks) of a recently developed LHRH antagonist in normal men. First, the antagonist Nal-Glu (Ac-D2Nal1, D4ClPhe2,D3Pal3,Arg5,DGlu6(AA),DAla10LHRH ), was given as a single sc injection to five normal men at three dose levels of 1, 5, and 20 mg (study I). Serum FSH, immunoreactive LH (IR-LH), bioactive LH (bio-LH), testosterone, and estradiol were measured before and at frequent intervals for 48 h after Nal-Glu administration. Mean serum FSH decreased (P less than 0.001) by 28.9 +/- 5.4% (+/- SE), 38.2 +/- 7.9%, and 44.5 +/- 3.6% after the 1-, 5-, and 20-mg doses, respectively. Mean serum IR-LH decreased (P less than 0.001) by 39.0 +/- 13.8%, 53.2 +/- 10.0%, and 53.1 +/- 14.4% after the three doses. Serum bio-LH levels and the ratio of bio-LH/IR-LH decreased (P less than 0.001) after the 20-mg dose by 87.8% and 78.5%, respectively. Serum testosterone levels decreased (P less than 0.001) more than 78.5% after all Nal-Glu doses. The duration of testosterone suppression, but not the nadir reached, was dose dependent (P = 0.012). Serum estradiol levels also decreased (P less than 0.001), but the rate of decrease was slower than that of serum testosterone. The apparent plasma disappearance half-life of Nal-Glu after administration of 5 mg was 12.8 +/- 2.7 h. The Nal-Glu antagonist also was given daily as a single sc injection of 5 mg to eight normal men for 21 days (study II) or twice daily to five men for 7 days (study III). In study II, serum FSH, IR-LH, bio-LH, testosterone, estradiol, and 17-hydroxy-progesterone were measured daily, immediately before the next injection, and on days 1, 7, and 21 in frequent blood samples drawn for 24 h. The mean serum testosterone level in study II decreased (P less than 0.001) from 17.6 +/- 2.2 to 4.1 +/- 1.0 nmol/L on day 1, increased (P less than 0.05) between days 2 and 8, and then progressively decreased to below 2 nmol/L from day 18 until 24 h after the end of the study. Serum FSH, IR-LH, and bio-LH levels paralleled those of testosterone.
Corticotropin releasing factor (CRF) is a 41-residue peptide, capable of stimulating the secretion of corticotropin (ACTH)-like and beta-endorphin-like immunoreactivity from the adenohypophysis. Low ...doses of CRF (0.0015-0.15 nM) given intracerebroventricularly (i.c.v.) produced changes in electrographic activity suggestive of increased arousal. Higher doses of CRF (1.5-3.75 nM) induced, over a period of 3-7 h, electrographic and behavioral signs of seizure activity indistinguishable from those which occur following electrical 'kindling' of the amygdala.
Gonadotropin releasing hormone (GnRH), as well as an antagonist Ac-D2Nal,1 D4ClPhe,2 D3Pal,3 NicLys,5 DNicLys,6 ILys,8 DAla10 GnRH.HOAc (1) and a superagonist DTrp6, Pro9-NHEtGnRH (2), have been ...electrochemically driven across excised hairless mouse skin. Determined by HPLC analysis, the delivery rate from aqueous solution into isotonic saline at 0.5 mA cm-2 was as high as 19 nM cm-2 h-1 for 2. Because of its insolubility in water, analogue 1 could only be delivered from an acidic donor solution. Analogue 2 was also delivered in pulsatile fashion using current on/off cycles. For all three peptides, passive transport was negligible and stability is evident when in contact with the stratum corneum. Slow metabolism occurs when GnRH contacts the dermal side of hairless mouse skin.
Dispersed pituitary cells of the goldfish were incubated with biotinylated D-Lys6, Pro9-N-ethylamide salmon gonadotropin-releasing hormone (sGnRH-A) then avidingold (10 nm), and were fixed, embedded ...and sectioned. Cells were identified as gonadotrophs, somatotrophs, or prolactin cells using specific hormone antisera and protein-A gold (20 nm) as a marker. Attachment of the biotinylated sGnRH-A to the pituitary cell sections was determined by scanning cell surfaces for the smaller gold particles using the transmission electron microscope. Attachment was observed on gonadotrophs and somatotrophs, but was negligible on prolactin cells. Preincubation with unlabelled salmon gonadotropin-releasing hormone or chicken II gonadotropin-releasing hormone, or omission of the salmon gonadotropin-releasing hormone analog, prevented the reaction. The direct visualization of specific gonadotropin-releasing hormone receptors on gonadotrophs and somatotrophs supports the existence of direct stimulatory actions of gonadotropin-releasing hormone on gonadotropin and somatotropin release in gold-fish.
L’objectif de cette étude est de disposer de données qualitatives et quantitatives sur la contamination de l’environnement intérieur hospitalier, microbiologique et chimique, afin d’évaluer ...l’exposition du personnel, des visiteurs et des patients et la variabilité spatio-temporelle de la contamination.
L’étude s’est déroulée dans différents lieux des CHU de Rennes et de Nancy : hall d’accueil, salle de soins infirmiers, salle de réveil post-opératoire, chambre d’un patient, unité de désinfection des endoscopes, laboratoire de parasitologie et salle de découpe de plâtres. Deux campagnes de prélèvement ont eu lieu en été 2014 et en hiver 2015. Les méthodes de prélèvement étaient nombreuses et complémentaires (Fig. 1). L’analyse des données a été réalisée sous IBM SPSS grâce au test de Mann-Whitney et le coefficient de corrélation de Pearson.
Les concentrations d’aldéhydes, de composés organiques volatils (COV) et semi-volatils étaient faibles à très faibles dans les 2 établissements. Étaient détectables, mais sans différences globales entre les 2 établissements : la contamination fongique (m=226UFC/m3 ; p=0,97) ou bactérienne (m=352UFC/m3 ; p=0,14), les particules PM2,5 (m=2,1μg/m3 ; p=0,97) et PM10 (m=6,6μg/m3 ; p=0,84). Sur le plan saisonnier, la contamination fongique était plus importante en été pour les 2 établissements (p=0,002). La contamination bactérienne ne varie pas significativement entre les locaux (p=0,14) contrairement à la contamination fongique (p=0,02) et particulaires PM2,5 (p=0,01) ou PM10 (p=0,01). Cette dernière est plus importante dans le hall (m=879UFC/m3), le laboratoire de parasitologie (m=333UFC/m3) et la salle de plâtre (m=310UFC/m3). Nous ne retrouvons pas de corrélation significative entre le nombre de personnes, le taux de CO2, l’humidité relative et le dénombrement bactérien ou fongique. Néanmoins nous retrouvons une relation forte entre la température du local et la contamination bactérienne (r=0,7, p=0,008) ou la contamination fongique (r=0,56, p=0,045) d’une part, et entre la contamination fongique et les PM10 (r=0,52, p=0,022) d’autre part.
Notre étude montre une très faible contamination par les aldéhydes, COV et sCOV comparativement à d’autres lieux publics. La forte variabilité spatio-temporelle de la contamination fongique et particulaire est liée à la saison, à l’activité et à la ventilation.
