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P Nicolas

Publications and source records attributed to P Nicolas.

At least 19 recordsLinked to original sources
PubMed1995

Separation of oviposition-stimulating peptides and myotropic factors from head extracts of Galleria mellonella L.: comparative effects of myotropic and non-myotropic factors on egg laying.

Methanolic extracts from heads of the wax moth, Galleria mellonella L. contain several factors that stimulate oviposition of virgin females in vivo and spontaneous contractions of the oviduct in vitro of the cricket, Gryllus bimaculatus. The myotropic and egg-laying activities behaved distinctly during all steps of purification, including fractionation on reverse-phase high-performance liquid chromatography. A novel neuropeptide was isolated from Galleria mellonella. The peptide does not increase the motility of isolated cricket oviducts. Among 13 other myotropic or non-myotropic factors studied, none were found to be as potent as the new peptide in stimulating egg-laying activity. The dose-response curves of myotropic and non-myotropic factors indicate that (i) proctolin, L-glutamate, octopamine, leucokinin-VI, leucopyrokinin, ecdysone and 20-hydroxy-ecdysone, or equivalent structures, might be involved in Galleria mellonella oviposition control, and (ii) that only the novel wax moth neuropeptide has the ability to trigger egg laying in that insect. The significance of these findings is discussed.

Amino Acid Sequence↗
PubMed1995

Ex vivo studies of polymorphonuclear neutrophils from patients with early-onset periodontitis (III). CR3 and LFA-1 expression by peripheral blood and gingival crevicular polymorphonuclear neutrophils.

In this study, we assessed the LFA-1 (CD18/CD11a) and CR3 (CD18/CD11b) expression on peripheral polymorphonuclear leukocytes (PB-PMN) and crevicular fluid polymorphonuclear leukocytes (CF-PMN), by subjects with a healthy periodontium (n = 7), gingivitis (n = 8), early-onset periodontitis (n = 17) and adult periodontitis (n = 8). Using flow cytometry analysis, the %s of CD18, CD11a and CD11b positive cells and the absolute numbers of fluorescent molecules were determined. No significant difference could be found among the 4 groups, for these 2 kinds of parameters, in PB-PMN or CF-PMN. However, a great difference could be noted between the results obtained from PB-PMN and those obtained from CF-PMN. The %s of positive CF-PMN were significantly lower than those of PB-PMN for the 3 sub-units (p < 0.001). The levels of CD18 and CD11b expressed by CF-PMN were higher than those expressed by PB-PMN and the difference was significant for CD11b (p < 0.001). On the contrary, the level of CD11a expressed on CF-PMN was significantly lower than that expressed by PB-PMN (p < 0.001). Hence, our current results show that early-onset periodontitis PMN can be quite normal and this fact is not surprising insofar as, in our study, these cells were perfectly functional and all the subjects were in good health. We concluded that the analysis of the leukocyte adhesion receptors expression on PB-PMN does not appear useful for helping to establish a differential diagnosis between the different forms of periodontitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

The vertebrate peptide antibiotics dermaseptins have overlapping structural features but target specific microorganisms.

The physiological significance of the occurrence of sequence similar antimicrobial peptides in frog skin, as the bombinins in Bombina, the magainins in Xenopus, and the dermaseptins in Phyllomedusa, is a major unanswered question. Dermaseptins s1, s2, s3, s4, and s5, a family of cationic (lysine-rich), amphipathic antifungal peptides of 28-34 residues were thus synthesized, purified to homogeneity, and evaluated for their growth-inhibition activity in vitro against various pathogenic microorganisms. Although all five of these peptides shared a similar spectrum of lytic activity against the filamentous fungi that are responsible for opportunistic lethal infections that follow the immunodeficiency syndrome or the use of immunosuppressive agents, they exhibited marked differences in their potencies to arrest the growth of Gram-positive and Gram-negative pathogenic bacteria and yeasts. Likewise, whereas dermaseptins s1 and s5 were devoid of hemolytic activity, dermaseptin s4 caused lysis of erythrocytes at micromolar concentrations. The dermaseptins exhibited dramatic synergy of action upon combination, resulting in some cases in a 100-fold increase in antibiotic activity of the mixture over the activity of the peptides separately. Shortening the peptide chain of dermaseptin s3 to dermaseptin s3-(1-16)-NH2 did not affect the antimicrobial potency of the peptide. Further reduction of the chain length yielded peptide derivatives gradually showing reduced activity. Surprisingly, however, analogs of dermaseptin s3 as shorter as 10-12 residues in length remained fully active against Enterococcus faecalis, Cryptococcus neoformans, and against Aeromonas caviae, the causal agent of red-leg disease in amphibians. Overall, these results suggest that, despite 40% sequence similarities, the dermaseptins have distinct spectra of anti-microbial activity and may act in concert to circumvent host invasion by providing frogs with a better shielding against a broad array of microorganisms. They also demonstrate the potential usefulness of short analogs of these peptides as potential candidates for biorational design of germicides.

Amino Acid Sequence↗
PubMed1994

Skin peptide tyrosine-tyrosine, a member of the pancreatic polypeptide family: isolation, structure, synthesis, and endocrine activity.

Pancreatic polypeptide, peptide tyrosine-tyrosine (PYY), and neuropeptide tyrosine (NPY), three members of a family of structurally related peptides, are mainly expressed in the endocrine pancreas, in endocrine cells of the gut, and in the brain, respectively. In the present study, we have isolated a peptide of the pancreatic polypeptide family from the skin of the South American arboreal frog Phyllomedusa bicolor. The primary structure of the peptide was established as Tyr-Pro-Pro-Lys-Pro-Glu-Ser-Pro-Gly-Glu10-Asp-Ala-Ser-Pro-Glu-Glu- Met-Asn- Lys-Tyr20-Leu-Thr-Ala-Leu-Arg-His-Tyr-Ile-Asn-Leu30-Val-Thr- Arg-Gln-Arg-Tyr-NH2 . This unusual peptide, named skin peptide tyrosine-tyrosine (SPYY), exhibits 94% similarity with PYY from the frog Rana ridibunda. A synthetic replicate of SPYY inhibits melanotropin release from perifused frog neurointermediate lobes in very much the same way as NPY. These results demonstrate the occurrence of a PYY-like peptide in frog skin. Our data also suggest the existence of a pituitary-skin regulatory loop in amphibians.

Amino Acid Sequence↗
PubMed1994

Spectrum of antimicrobial activity and assembly of dermaseptin-b and its precursor form in phospholipid membranes.

Dermaseptins are 27-34 amino acid antimicrobial peptides that irreversibly inhibit growth of pathogenic filamentous fungi, in addition to their ability to inhibit the growth of bacteria, yeasts, and protozoa. Synthetic peptides, with sequences corresponding to dermaseptin-b (DS-b) and its N-terminal extended precursor form dermaseptin-B (DS-B), were synthesized and investigated with respect to their spectrum of antimicrobial activity and their mode of interaction with model membranes composed of PS or PC/PS phospholipids. We found that DS-B is much more potent than DS-b against all microorganisms tested. Furthermore, despite significant structural identity between DS-b and DS-S (Pouny et al., 1992), only the former is highly effective at inhibiting the growth of filamentous fungi. The peptides were labeled selectively at their N-terminal amino acid with either 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) or rhodamine fluorescent probes, which facilitated the determination of their partition coefficients with phospholipid membranes and their organization in their membrane-bound state. The partition coefficients of DS-B are 10-fold higher than those of DS-b and DS-S, with both acidic and zwitterionic phospholipid vesicles. This may explain the ability of DS-B to permeate both types of vesicles efficiently. Furthermore, while both DS-b and DS-B interact with phospholipid membranes in a noncooperative manner, they are self-associated in their membrane-bound state. This noncooperative binding probably prevents aggregation of the peptides on the surface of outer bacterial membranes, and assists them in efficiently diffusing into the inner target membranes. The exceptional property of DS-B to bind strongly to phospholipid membranes and to form small bundles correlates with its high potential to kill yeast and filamentous fungi. As a molecular model, dermaseptins may be of potential interest in drug design, particularly in antifungal warfare.

Amino Acid Sequence↗
PubMed1994

Antagonism between T3 and amiodarone on the contractility and the density of beta-adrenoceptors of chicken cardiac myocytes.

3,3',5-Triiodothyronine (T3), at 10(-8) M, potentiated by 26.4-30.9% the isoproterenol-mediated inotropic effect in chick embryo cardiac myocytes in culture. Amiodarone (10(-6) M) decreased this response by 44.6% only in cells cultured with serum, where the T3 concentration was 10(-13) M. Amiodarone inhibited the potentiating effect of T3. Amiodarone alone had no influence on the beta-adrenoceptor density in cells cultured in serum-free medium. This confirms that the effects of amiodarone on cardiac beta-adrenoceptors are T3 dependent. T3 increased the density of beta-adrenoceptors through two concentration ranges, with an initial 30% increase between 10(-14) and 10(-11) M, followed by a second increase until 10(-7) M. Amiodarone not only inhibited the first positive effect of T3 but also decreased beta-adrenoceptor density far below the control value. The second positive T3 effect was also inhibited by 50% by amiodarone. This study suggests that T3 might increase the number of cell-surface beta-adrenoceptors and modify their cellular traffic through at least two mechanisms, one assumed to be non-genomic, the other being genomic, and that amiodarone could affect the two mechanisms differently.

Adrenergic beta-Antagonists↗
PubMed1994

Precursors of vertebrate peptide antibiotics dermaseptin b and adenoregulin have extensive sequence identities with precursors of opioid peptides dermorphin, dermenkephalin, and deltorphins.

The dermaseptins are a family of broad spectrum antimicrobial peptides, 27-34 amino acids long, involved in the defense of the naked skin of frogs against microbial invasion. They are the first vertebrate peptides to show lethal effects against the filamentous fungi responsible for severe opportunistic infections accompanying immunodeficiency syndrome and the use of immunosuppressive agents. A cDNA library was constructed from skin poly(A+) RNA of the arboreal frog Phyllomedusa bicolor and screened with an oligonucleotide probe complementary to the COOH terminus of dermaseptin b. Several clones contained a full-length DNA copy of a 443-nucleotide mRNA that encoded a 78-residue dermaseptin b precursor protein. The deduced precursor contained a putative signal sequence at the NH2 terminus, a 20-residue spacer sequence extremely rich (60%) in glutamic and aspartic acids, and a single copy of a dermaseptin b progenitor sequence at the COOH terminus. One clone contained a complete copy of adenoregulin, a 33-residue peptide reported to enhance the binding of agonists to the A1 adenosine receptor. The mRNAs encoding adenoregulin and dermaseptin b were very similar: 70 and 75% nucleotide identities between the 5'- and 3'-untranslated regions, respectively; 91% amino acid identity between the signal peptides; 82% identity between the acidic spacer sequences; and 38% identity between adenoregulin and dermaseptin b. Because adenoregulin and dermaseptin b have similar precursor designs and antimicrobial spectra, adenoregulin should be considered as a new member of the dermaseptin family and alternatively named dermaseptin b II. Preprodermaseptin b and preproadenoregulin have considerable sequence identities to the precursors encoding the opioid heptapeptides dermorphin, dermenkephalin, and deltorphins. This similarity extended into the 5'-untranslated regions of the mRNAs. These findings suggest that the genes encoding the four preproproteins are all members of the same family despite the fact that they encode end products having very different biological activities. These genes might contain a homologous export exon comprising the 5'-untranslated region, the 22-residue signal peptide, the 20-24-residue acidic spacer, and the basic pair Lys-Arg.

Amino Acid Sequence↗
PubMed1994

Structure, synthesis, and activity of dermaseptin b, a novel vertebrate defensive peptide from frog skin: relationship with adenoregulin.

A novel antimicrobial peptide, designated dermaseptin b, was isolated from the skin of the arboreal frog Phyllomedusa bicolor. This 27-residue peptide amide is basic, containing 3 lysine residues that punctuate an alternating hydrophobic and hydrophilic sequence. In helix-inducing solvent, dermaseptin b adopts an amphipathic alpha-helical conformation that most closely resembles class L amphipathic helixes, with all lysine residues on the polar face of the helix. The peptide exhibits growth inhibition activity in vitro against a broad spectrum of pathogenic microorganisms including yeast and bacteria as well as various filamentous fungi that are responsible for severe opportunistic infections accompanying acquired immunodeficiency syndrome and the use of immunosuppressive agents. Maximized pairwise sequence alignment of dermaseptin b and dermaseptin s, a 34-residue antimicrobial peptide previously isolated from Phyllomedusa sauvagii, reveals 81% amino acid identity. No other significant similarity was found between dermaseptin b and any prokaryotic or eukaryotic protein, but similarity was found with adenoregulin (38% amino acid postional identity), a 33-residue peptide that enhances binding of agonists to the A1 adenosine receptor. The synthetic replicates of dermaseptin b and adenoregulin displayed similar but nonidentical spectra of antimicrobial activity, and both peptides were devoid of lytic effect on mammalian cells. Accordingly, the observation that adenoregulin enhances binding of agonists to the adenosine receptor may in fact be a consequence of its ability to alter the structure of biological membranes and to produce signal transduction via interactions with the lipid bilayer, bypassing cell surface receptor interactions.

Amino Acid Sequence↗
PubMed1994

Distribution of TRH-potentiating peptide (Ps4) and its receptors in rat brain and peripheral tissues.

TRH-potentiating peptide (Ps4) is a peptide originally isolated from bovine hypothalamus, which corresponds to the deduced rat prepro-TRH-(160-169) sequence. We have examined the distribution of Ps4 and [125I-Tyr0]Ps4 binding sites in various rat tissues. Very high specific binding of [125I-Tyr0]Ps4 was observed in pituitary membranes. Almost identical relative magnitude of binding was found in spinal cord, hypothalamus, hippocampus and olfactory lobe. In addition, a high density of Ps4 binding sites was demonstrated in urogenital organs. The observed distribution pattern of Ps4 in brain tissues was similar to that reported for TRH, with high concentrations in the hypothalamus and significant amount in spinal cord and olfactory lobe. These findings support the hypothesis that the TRH-potentiating peptide could act as neuromodulator or neurotransmitter in the central nervous system (CNS). In peripheral tissues, very low concentrations of Ps4 were detected except in testis which seems to be the major locus for Ps4 biosynthesis. This study demonstrated for the first time that TRH-potentiating peptide and its receptors are widely distributed in the CNS and peripheral tissues.

Animals↗
PubMed1994

Mechanism of delta-opioid receptor selection by the address domain of dermenkephalin.

Dermenkephalin (Tyr-D-Met-Phe-His-Leu-Met-AspNH2) is a highly potent and selective delta-opioid peptide isolated from frog skin. It was recently recognized that the C-terminus His4-Leu5-Met6-Asp7NH2 of dermenkephalin was responsible for the addressing of the peptide towards the delta-opioid receptor. In order to investigate the role played by residues 4, 5 and 6 in this 'delta address', we synthesized and evaluated 20 new analogues for their ability to displace tritiated ligands from mu- and delta-opioid sites. Results showed that position 4 of dermenkephalin contributes to delta selectivity independently of delta-opioid receptor binding by preventing a high affinity mu binding. Position 5 requires a hydrophobic side chain to enhance delta affinity. A high delta affinity was obtained with any amino acids introduced in position 6 suggesting that residue 6 serves as a neutral spacer. Thus, the main features responsible for the high delta-opioid selectivity of dermenkephalin are electrostatic repulsions with the mu-opioid receptor, additional hydrophobic interactions with the delta-opioid receptor and folding of the C-terminal domain.

Amino Acid Sequence↗
PubMed1994

Analysis of structural requirements for TRH-potentiating peptide receptor binding by analogue design.

Previous studies established that the [125I-Tyr0]Ps4 derivative of TRH-potentiating peptide (Ps4), Ser-Phe-Pro-Trp-Met-Glu-Ser-Asp-Val-Thr, displays high affinity and selectivity for an orphan membrane receptor in rat anterior pituitary. To identify the sites in Ps4 that determine receptor binding affinity, we have synthesized and screened a panel of 15 single-point substituted analogues for their ability to displace bound [125I-Tyr0]Ps4. The affinity of [Tyr0]Ps4 for rat anterior pituitary membranes [inhibitory constant (Ki), approximately 5 nM] was drastically reduced by the substitution of either Tyr0 with Gly or Asp8 with Asn (Ki approximately 95 and approximately 51 nM, respectively). Deamination of [Tyr0]Ps4 also sharply reduced affinity (Ki approximately 1100 nM). In contrast, Ser1-->Ala, Pro3-->Ala and Thr10-->Val substitutions led to analogues showing a tenfold increase in binding affinity relative to the parent peptide. The change of Phe2-->Leu, Trp4-->Ala, Glu6-->Gln, Val9-->Thr and carboxamidation of Thr10 had no effect on binding affinity. The data suggest that substitutions of the amino-terminal group, Asp8 and Tyr0, have a marked effect on the ability of [Tyr0]Ps4 to compete with [125I-Tyr0]Ps4 for binding to TRH-potentiating peptide pituitary receptor.

Amino Acid Sequence↗
PubMed1994

Modulation of the biological activity of thyrotropin-releasing hormone by alternate processing of pro-TRH.

Thyrotropin-releasing hormone prohormone contains multiple copies of TRH linked together by connecting sequences. Like other plurifunctional prohormone proteins, pro-TRH undergoes differential proteolytic processing in various tissues to generate, beside authentic TRH, several other novel peptides corresponding to C-terminally extended forms of TRH and connecting fragments. The pro-TRH connecting peptides are, together with TRH, predominant storage forms of TRH-precursor related peptides in the rat hypothalamus. Connecting peptides are co-localized with TRH in the median eminence nerve endings and co-released through a mechanism involving voltage-operated Ca2+ channels. The connecting peptide Ps4 is involved in potentiation of the action of TRH on thyrotropin hormone release by pituitary in vitro and in vivo through interactions with a specific pituitary cell receptor coupled to dihydropyridine and omega-connotoxin sensitive Ca2+ channels of the L-type. It also causes dose-dependent increases in the steady state levels of mRNAs of TSH and prolactin through stimulation of the respective gene promoter activities. These findings indicate that Ps4 and TRH, two peptides which originate from a single multifunctional biosynthetic precursor, can function on the same target tissues in a coordinate manner to promote hormonal secretion. This suggests that differential processing of the TRH prohormone may have the potential to modulate the biological activities of TRH.

Amino Acid Sequence↗
PubMed1994

Kinetics of a new iodolabeled MAO-B inhibitor in the rat brain and in cultured astrocytes.

3-Bromobenzyloxy phenyloxy hydroxymethyl propanol was labelled with iodine-125. Labeling yield was approximately 92%. Using HPLC and an RP18 column, Iodo*MD (MW = 412) was obtained at no-carrier-added conditions (specific activity 125 Ci/mmole). Biochemical experiments were carried out in vitro and showed a Ki for MAO-B of 5.4 nM and of 5000 for MAO-A (RA/B = 926). Using ex vivo kinetic inhibition in rat (dose: 5 mg/kg p.o.), the results demonstrated a strong similarity of action with BromoMD and IodoMD, with an inhibition percentage that decreased with time (91% at 1 hour, 48% at 8 hours, 2% at 24 hours). The rat brain Iodo*MD concentration was maximal after the first pass and inhibition decreased slowly with time (T1/2 = 1.8 hours). Uptake and wash-out of Iodo*MD was studied on two-day-old rat astrocytes in culture. Half-times of uptake and efflux were respectively 2.5 minutes and 7.5 minutes. The use of metabolic inhibitors (KCN and Digoxin) suggested the absence of any active transport. Binding studies with various concentration of cold MD 360194 showed that at 10(-8) M the uptake decreased significantly. Rats were dissected at different times post i.v. injection (0-2 hours), and the principal organs and brain were obtained (the brain was separated into 7 pieces). Radioactivity was concentrated mainly in the liver (24.6 +/- 4%), fat (12.4 +/- 3.4%) and muscles (18.4 +/- 3%). In the brain the concentration was approximately 1.2 +/- 0.3% within 30 minutes post i.v. injection and 0.84 +/- 0.15% thereafter. The hypothalamus and striatum were two-fold more active than the cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Propanol↗
PubMed1992

Characterization of receptors for thyrotropin-releasing hormone-potentiating peptide on rat anterior pituitary membranes.

Previous studies (Bulant, M., Delfour, A., Vaudry, H., and Nicolas, P. (1988) J. Biol. Chem. 263, 17189-17196; Bulant, M., Roussel, J. P., Astier, H., Nicolas, P., and Vaudry, H. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 4439-4443) have shown that post-translational processing of rat thyrotropin-releasing hormone prohormone (pro-TRH) generates, besides thyrotropin-releasing hormone (TRH), a connecting decapeptide corresponding to prepro-TRH-(160-169), i.e. Ser-Phe-Pro-Trp-Met-Glu-Ser-Asp-Val-Thr. This peptide, which is named TRH-potentiating peptide (Ps4), is co-localized with TRH in the median eminence nerve endings and is involved in potentiation of the action of TRH on thyrotropin hormone release by pituitary in vitro and in vivo. To characterize the receptor(s) for TRH-potentiating peptide in the pituitary, a highly potent and metabolically stable derivative of Ps4, [I-Tyr0]Ps4, was radioiodinated. Binding of [125I-Tyr-0]Ps4 to rat pituitary membrane homogenates was specific, saturable, reversible, and linear with membrane protein concentration. Equilibrium measurements performed over a large range of concentrations revealed a single homogeneous population of high affinity binding sites (Kd = 0.22 nM; Bmax = 517 fmol/mg of membrane proteins). Several naturally occurring neuropeptides and hormones, including TRH, did not compete with [125I-Tyr0]Ps4 in the binding, which suggests the binding sites are specific to Ps4. Using C-terminal deletion analogs of [Tyr0]Ps4, we further showed the critical role the C-terminal residues Thr10, Val9, and Asp8 play in conferring high binding affinity and selectivity. Binding site tissue distribution and cross-reactivity binding studies suggest that the action of TRH-potentiating peptide is mediated through interaction with a specific pituitary cell-surface receptor which differ from those for TRH. [I-Tyr0]Ps4 reported in this paper, through its high binding affinity and specificity, its very low nonspecific binding, its high resistance to enzymatic degradation, and its high potentiating action in vitro should allow further progress in understanding the in vivo physiological function of Ps4.

Amino Acid Sequence↗
PubMed1992

Isolation and amino acid sequence of the TRH-potentiating peptide from bovine hypothalamus.

A neuropeptide termed TRH-potentiating peptide, which potentiates TRH-evoked thyrotropin secretion by antehypophysis in vitro, was isolated from an acetonic powder of bovine hypothalamus. The peptide was purified to homogeneity by a 3-step protocol involving molecular sieve filtration, ion-exchange chromatography and reverse phase high performance liquid chromatography. The complete amino acid sequence of the decapeptide was determined as Ser-Phe-Pro-Trp-Met-Glu-Ser-Asp-Val-Thr by automated Edman degradation with a solid-phase sequencer. Bovine TRH-potentiating peptide is structurally identical to Ps4, a decapeptide which was deduced from the cDNA encoding the rat TRH precursor. This study provides for the first time a direct chemical evidence for the existence of non-TRH peptides originating from posttranslational processing of the TRH precursor in vivo.

Amino Acid Sequence↗