Which hyperparathyroid state is better for bone densitometry in uremic patients?
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Bone Density↗
Biomedical subjects
A Fournier
Publications and source records attributed to A Fournier.
Binding profile of a selective calcitonin gene-related peptide (CGRP) receptor antagonist ligand, [125I-Tyr]hCGRP8-37, in rat brain and peripheral tissues.
The calcitonin gene-related peptide (CGRP) C-terminal fragment human CGRP8-37 acts as a potent antagonist of various in vitro and in vivo effects of CGRP. Its iodinated counterpart, [125I-Tyr] hCGRP8-37, binds with high affinity (KD values between 7.5 x 10(-11)-2.1 x 10(-10) M) to what is apparently a single class of CGRP receptors in brain, atrium and vas deferens membrane preparations. The relative potencies of various CGRP-related fragments and analogs in competing for [125I-Tyr]hCGRP8-37 binding sites were similar in these three preparations, with hCGRP alpha being the most potent competitor, followed by unlabeled hCGRP8-37, the linear agonist [acetamidomethyl-cysteine2,7] hCGRP alpha, and finally by rat amylin-amide and salmon calcitonin. Competition profiles suggested the existence of a single affinity site (except in the case of hCGRP alpha, for which competition binding data were best fitted to two apparent affinity constants in all three tissues), whereas rat amylin-amide revealed two affinity constants in the rat brain. Guanylylimidodiphosphate (100 microM) failed to alter specific [125I-Tyr]hCGRP8-37 binding in the various tissues studied here. Quantitative receptor autoradiography in the rat brain revealed [125I-Tyr]hCGRP8-37 binding sites mostly concentrated in the nucleus accumbens (shell), caudate putamen (tail), amygdaloid body, pontine nuclei, cerebellum and inferior olive, whereas lower quantities of sites were present in the olfactory tubercle, nucleus accumbens (core), medial geniculate, superior colliculus, temporal cortex, inferior colliculus, lateral lemniscus, vestibular nuclei and principal sensory trigeminal nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Conformational and biological studies of neuropeptide Y analogs containing structural alterations.
We evaluated the alpha-helix content, the biological activities and the affinities of a series of neuropeptide Y (NPY) analogs containing structural alterations, mainly in the central portion of the molecule for which a putative alpha-helix arrangement has been proposed. First, we investigated the conformational and pharmacological characteristics of derivatives containing the N-terminal tetrapeptide linked to C-terminal peptide-amide segments of various lengths. In some of these, the missing portion was replaced with epsilon-aminocaproic acid, a flexible arm-linker. Data revealed that (1-4)-Aca-(18-36)NPY is a discontinuous analog almost as potent as the native peptide in a pharmacological preparation enriched in Y2 receptors (rat vas deferens), whereas it is about 5 times less potent in a Y1 bioassay (rabbit saphenous vein). This analog showed a similar profile in [125I]PYY binding assays performed in rat frontoparietal cortex (Y1) and hippocampus (Y2) membrane preparations. In a series of truncated derivatives obtained with the successive removal of the 5-13 to 5-17 segments of the NPY molecule, no apparent correlation was observed between the affinity or potency in bioassays and the alpha-helix content, as measured by circular dichroism spectroscopy. Other truncated analogs, obtained by linking the C-terminal 31-36 fragment to various N-terminal tetrapeptides were also investigated. None showed any affinity in brain membrane preparations (frontoparietal cortex and hippocampus) or activity in the rat vas deferens bioassay. However, a weak short-lasting contraction was measured with some of these analogs in the rabbit saphenous vein, thus suggesting that the 1-4 and 31-36 segments of the molecule contains pharmacophores recognized by the Y1 receptor subtype. The contribution of the arginine residues also was evaluated in relation with the alpha-helix. Their successive substitution with lysine, an excellent helix-promoter, showed that the replacement of Arg-19 or Arg-25, two residues found in the putative alpha-helix, gave active analogs. Furthermore, the substitution of Arg-19 with lysine increased the activity in the rat vas deferens as well as the affinity in the brain membrane binding assays. On the other hand, the substitution of Arg-33 produced a weak agonist, whereas the replacement of Arg-35 generated an inactive analog in the Y2-pharmacological preparation and a very weak competitor in the CNS binding assays. Interestingly, this latter analog was still active in the rabbit saphenous vein, thus identifying the position 35 as an additional potential target for the development of Y1 versus Y2 specific molecules.(ABSTRACT TRUNCATED AT 400 WORDS)
Amino Acid Sequence↗
Differential transcription of multiple copies of a silk worm gene encoding tRNA(Gly1).
Ten different tRNA(Gly1) genes from the silk worm, Bombyx mori, have been cloned and characterized. These genes were transcribed in vitro in homologous nuclear extracts from the posterior silk gland (PSG) or nuclear extracts derived from the middle silk gland or ovarian tissues. Although the transcription levels were much higher in the PSG nuclear extracts, the transcriptional efficiency of the individual genes followed a similar pattern in all the extracts. Based on the levels of in vitro transcription, the ten tRNA(Gly1) genes could be divided into three groups, viz., those which were transcribed at very high levels (e.g., clone pR8), high to medium levels (e.g., pBmi1, pBmp1, pBmh1, pBmt1) and low to barely detectable levels (e.g., pBms1, pBmj1 and pBmk1). The coding sequences of all these tRNA genes being identical, the differential transcription suggested that the flanking sequences modulate their transcriptional efficiency. The presence of positive and negative regulatory elements in the 5' flanking regions of these genes was confirmed by transcription competition experiments. A positive element was present in the immediate upstream A+T-rich sequences in all the genes, but no consensus sequences correlating to the transcriptional status could be generated. The presence of negative elements on the other hand was indicated only in some of the genes and therefore may have a role in the differential transcription of these tRNA(Gly1) genes in vivo.
Animals↗
[Factors of resistance to the treatment of hypertension. They are multiple, but often controllable, without therapeutic escalation].
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Antihypertensive Agents↗
Relaxation by dexamethasone of isolated guinea-pig airways precontracted with endothelin-1.
Dexamethasone (1-100 microM) produced concentration-dependent relaxations of isolated guinea-pig tracheal and bronchial strips precontracted with endothelin-1 (100 nM), which were not affected by the removal of the epithelium. Dexamethasone neither induced relaxation of tissues precontracted with carbachol (0.1 microM) or KCl (25 mM) nor inhibition of endothelin-1 (1-100 nM)-induced peak contractions after 10-min preincubation of the tissues with dexamethasone. These findings indicate that acute corticosteroid treatment can reverse the bronchoconstrictor action of endothelin-1.
Animals↗
D-myo-inositol 1,2,6-trisphosphate blocks neuropeptide Y-induced facilitation of noradrenaline-evoked vasoconstriction of the mesenteric bed.
Perfusion of the rat mesenteric bed with 0.1 or 10 nM neuropeptide Y potentiated the noradrenaline-induced increase in mesenteric pressure; the peptide did not modify basal perfusion pressure. While perfusion with 0.1 nM neuropeptide Y significantly increased the maximal noradrenaline-evoked vasoconstriction without modifying its EC50, 10 nM neuropeptide Y potentiated the maximal noradrenaline effect and significantly shifted its concentration-response curve to the left. Perfusion with 1-10 microM D-myo-inositol 1,2,6-trisphosphate (alpha-trinositol) reduced, in a concentration-dependent fashion, the neuropeptide Y-induced potentiation of the noradrenaline-evoked vasoconstriction without altering the potency or maximal response evoked by the catecholamine alone. Perfusion with 0.1 nM neuropeptide Y plus 1 microM alpha-trinositol completely abolished the neuropeptide Y-induced facilitation of the noradrenaline effect. alpha-Trinositol 1 microM in the presence of 10 nM neuropeptide Y caused a nonparallel rightward shift of the noradrenaline concentration-response curve as compared to that obtained in the presence of 10 nM neuropeptide Y alone. The alpha-trinositol blockade of the facilitatory action of neuropeptide Y was reversible.
Animals↗
The rabbit saphenous vein: a tissue preparation specifically enriched in NPY-Y1 receptor subtype.
Neuropeptide Y (NPY), a co-transmitter in noradrenergic sympathetic nerves of the cardiovascular system, was tested on isolated segments of rabbit saphenous vein. NPY caused strong, long lasting and concentration dependent contraction resistant to adrenergic blockade. PYY, a NPY related peptide, shared this property. As pressor agents, both peptides were about 100-fold more potent than norepinephrine and at their highest concentrations caused a contraction of a similar magnitude as NE. Gradual shortening of N-terminal end of the NPY molecule caused major loss of potency and reduction of intrinsic activity; which suggests that the entire molecule is required to produce full biological activity in this vascular preparation. Addition of [Leu31,Pro34]pNPY, a NPY analog with specific agonist properties at Y1 receptors, mimicked the effect of NPY whereas NPY (13-36), a selective agonist at Y2 receptors, caused a 2 log unit shift to the right of the concentration response curve. These results suggest that the vasoconstrictor effect of NPY in rabbit saphenous vein results from a direct effect on smooth muscle cells and that the receptors involved are of the Y1 subtype.
Animals↗
Evaluation of truncated neuropeptide Y analogues with modifications of the tyrosine residue in position 1 on Y1, Y2 and Y3 receptor sub-types.
Substitutions of the tyrosine residue in position 1 of truncated neuropeptide Y (N-terminal fragment 1-4 linked to C-terminal fragment 18-36 by the epsilon-aminocaproic acid) produced analogues that compete for specific [125I]polypeptide YY (PYY) binding in the frontoparietal cortex (Y1-enriched) with a profile best fitted to a two site-model with KD values in the low and high nM range, respectively. In the hippocampal membrane preparations (Y2-enriched), halogen substitutions on the aromatic ring generated analogues with competition profiles best fitted to a one-site model, revealing differences between the two binding assays and the interaction of these analogues with the Y1 and Y2 receptor sub-types. In the rat vas deferens (Y2-enriched), all truncated analogues inhibited the twitch response with similar or slightly weaker potency than the native molecule. In contrast, these molecules were markedly less potent than neuropeptide Y (NPY) in the rabbit saphenous vein (Y1-enriched) and the rat distal colon (Y3-enriched). Some of the truncated analogues were inactive at up to microM concentrations in the rat distal colon, demonstrating the distinct structural requirement of the receptor sub-type present in this bioassay. These results revealed that amino acid residues between positions 5 and 17 are critical for the maintenance of optimal affinity for the NPY receptors present in the rabbit saphenous vein and the rat distal colon.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Regulation of neuronal alpha-melanocyte-stimulating hormone by neuropeptide Y. In vitro and in vivo studies.
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Animals↗
Purification of a galanin receptor from pig brain.
A galanin receptor protein was solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) from pig brain membranes and then purified by single-step affinity chromatography. The product exhibits saturable and specific binding for galanin with a binding activity of 17 nmol/mg of protein and a dissociation constant (Kd) of 10 nM. This represents a 300,000-fold purification over the detergent-solubilized fraction with a final recovery of 31% of the initial membrane galanin binding activity. Gel electrophoresis of the affinity-purified material showed a single polypeptide of 54 kDa by silver staining and after radioiodination. Cross-linking of a purified fraction affinity-labeled with 125I-labeled galanin revealed a single band for the galanin-receptor complex at 57 kDa. The general binding characteristics of the purified preparation appeared to be identical to those of the crude soluble material as far as specificity toward galanin and the structural requirement for galanin are concerned. In contrast, unlike the CHAPS-soluble galanin receptor, binding of 125I-labeled galanin to the purified galanin receptor was not sensitive to guanine nucleotides, suggesting that dissociation of the inhibitory guanine nucleotide binding protein from the galanin receptor occurred during purification. The purification to homogeneity of a galanin receptor paves the way toward its sequencing and cloning.
Animals↗
Conformational characterization by circular-dichroism spectroscopy of various fragments and analogs of calcitonin-gene-related peptide.
A conformational study by circular-dichroism spectroscopy of calcitonin-gene-related peptide (CGRP) and related fragments and analogs was carried out in structure-promoting solvent mixtures. The structural characterization of rat CGRP alpha and the two isoforms of human CGRP, alpha and beta, revealed that these peptides possess very similar conformational features. The far-ultraviolet circular-dichroism spectra, in pure water, of human CGRP alpha, (hCGRP alpha), [Acm-Cys2,7]hCGRP alpha, various fragments and analogs indicated that these peptides exhibited predominantly a random-coil conformation. The addition of increasing concentrations of 1,1,1,3,3,3-hexafluoro-2-propanol to the peptide solutions resulted in a transition from a random-coil conformation to a stabilized alpha-helical structure. The substantial loss of helical content measured with [Acm-Cys2,7]hCGRP alpha, [Acm-Cys2,7]hCGRP-(1-24)-CONH2 and hCGRP-(8-37), compared to hCGRP alpha, suggested that the N-terminal disulfide bridge of hCGRP alpha is essential for adopting a highly stabilized alpha-helical conformation. Moreover, the lower helical content of hCGRP-(8-37), as compared to [Acm-Cys2,7]hCGRP alpha, as well as spectroscopic results measured with various fragments and analogs of hCGRP-(8-37) revealed that N-terminal residues found in the peptide segment 1-12 are important for the full conservation of the amphiphilic alpha-helix. In addition, the similar alpha-helical content of hCGRP-(8-37) and hCGRP-(8-18) indicated that the C-terminal segment 19-37 is not essential for the stabilization of the alpha-helix structure.
Amino Acid Sequence↗
Interaction of benzene 1,2,4-trisphosphate with inositol 1,4,5-trisphosphate receptor and metabolizing enzymes.
In a wide variety of cells, inositol 1,4,5-trisphosphate (InsP3) is an important second messenger involved in the regulation of intracellular Ca2+ concentration. InsP3 interacts with specific receptors and triggers the release of sequestered Ca2+ from an internal store. We have synthesized a structural analogue of InsP3 by phosphorylation of the free hydroxyl groups of 1,2,4-benzenetriol with dibenzylphosphorochloridate. The product benzene 1,2,4-trisphosphate (BzP3) was shown to interact with InsP3 receptor and InsP3 metabolizing enzymes of bovine adrenal cortex. BzP3 competitively blocked InsP3 binding to adrenal cortex microsomes with a half-maximal efficiency at 34 microM. This affinity was about 10,000 times lower than that of InsP3 for its receptor. The Ca2+ releasing activity of BzP3 on the same microsomal preparation was monitored with the fluorescent indicator fura-2. BzP3 had no agonistic effect on this activity but it was able to inhibit InsP3-induced Ca2+ release in a dose-dependent manner. The activity of InsP3 phosphatase was also studied. BzP3 inhibited the activity of the phosphatase with a half-maximal efficiency of 32 microM. BzP3 was also able to inhibit the activity of the cytosolic InsP3 kinase with a half-maximal efficiency of 6.1 microM. These results show that BzP3 is interacting with the three specific recognition sites for InsP3 in the bovine adrenal cortex. The inhibitory effect of this compound is relatively more potent on the metabolizing enzymes than on the Ca(2+)-mobilizing receptor.
Adrenal Glands↗
Can ethnic differences in men's preferences for women's body shapes contribute to ethnic differences in female adiposity?
In the United States, obesity is more common among black and Hispanic than white women. One putative cause of this difference is different cultural norms for attractiveness. Two studies assessed ethnic differences in men's perceptions of the attractiveness of females of varying sizes. In the first, 108 men recruited on the New York subway were shown sets of silhouettes depicting female bodies varying in fatness and were asked to pick the silhouette they found most attractive. They were also asked to indicate the thinnest and fattest figures they would consider dating. A measure of "latitude of acceptance" was computed as the difference between the thinnest and fattest figures considered. Results indicated no relationship between ethnicity and preference (F = 1.383, p = .257) or "latitude" (F = .102, p = .903). In Study 2, "personal advertisements" placed by 373 black, 1915 white, 110 Hispanic, and 30 Asian men from 35 newspapers and magazines were coded as: 1) thinness preferred; 2) no information on weight preference; 3) fatness preferred; or 4) states weight or looks unimportant. Results indicated a statistically significant but small association between ethnicity and preference (chi2 = 49.55, df = 9, p < .00001). Relative to white and Asian men, black and Hispanic men more frequently requested fat women, Hispanic men less frequently requested thin women, and black men more frequently stated that looks or weight did not matter. Ethnicity explained only 2.1% of the variance in preference. Thus, it seems unlikely that ethnic differences in men's preferences for women's body shapes contribute substantially to ethnic differences in female adiposity.
Adipose Tissue↗
Synthesis of a hydrophilic affinity matrix for the purification of the vasoactive intestinal peptide receptor.
Vasoactive intestinal peptide (VIP) was assembled on a polyacrylamide gel using a combination of the Boc and Fmoc peptide synthesis strategies. Before the synthesis, the polymeric matrix functionalized with sarcosine methylester was treated with ethylenediamine in order to form primary amine reaction sites (0.3 mmol/g). Then a six-carbon spacer arm, Boc-aminocaproic acid, was coupled to the gel after activation with benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP) reagent. After acidolysis of the Boc protecting group, the derivative Boc-asparaginyl (xanthenyl)-4-(oxymethyl)phenylacetic acid was introduced into the polyacrylamide resin. Leucine-27 and isoleucine-26 were incorporated into the peptide chain as Boc-protected derivatives while the subsequent amino acids were all introduced as Fmoc residues. All couplings were achieved with BOP reagent in presence of diisopropylethylamine. The synthesis proceeded easily and only asparagine-9 required a double coupling step. After completion of the VIP assemblage, the side-chain protecting groups were removed by reaction with trifluoroacetic acid containing appropriate scavengers. A sample of peptide-resin was treated with hydrofluoric acid and the quality of the synthetic VIP-COOH material, obtained after cleavage, was assessed by reverse-phase HPLC and fast atom bombardment mass spectrometry. The compatibility with aqueous solutions of the polyacrylamide resin loaded with VIP (0.15 mmol/g), as well as its ability to be utilized as an affinity matrix for VIP receptors, was demonstrated using solubilized receptor preparation made from porcine liver membrane. After a single-step affinity chromatography, no binding activity was anymore detectable in the pass-through fraction.(ABSTRACT TRUNCATED AT 250 WORDS)
Acrylic Resins↗
CGRP 8-37[correction of 8-27] blocks the inhibition of gastric emptying induced by intravenous injection of alpha-CGRP in rats.
The receptor subtype mediating rat alpha-calcitonin gene-related peptide (alpha-CGRP)-induced inhibition of gastric emptying of a non nutrient solution was tested in conscious rats using the CGRP1 receptor antagonist, CGRP 8-37, and the CCK antagonist, MK-329. Intravenous injection of alpha-CGRP (0.5 micrograms) decreased gastric emptying to 26.5 +/- 5.8% from 46.4 +/- 3.9% in vehicle-treated group. Intravenous injection of CGRP 8-37 (15 micrograms) did not influence gastric emptying but completely prevented alpha-CGRP inhibitory effect whereas the 47% delay in gastric emptying induced by intravenous cholecystokinin-8 (CCK, 0.25 microgram) was not modified. The CCK antagonist, MK-329 (1 mg) reversed CCK- but not alpha-CGRP-induced delay in gastric emptying. These results demonstrate that CGRP 8-37 is a specific tool to block alpha-CGRP inhibitory action on gastric motor function and suggest that gastric stasis elicited by peripheral injection of alpha-CGRP may involve an interaction with a CGRP1 receptor subtype.
Animals↗
Localization and characterization of PACAP receptors in the rat cerebellum during development: evidence for a stimulatory effect of PACAP on immature cerebellar granule cells.
Pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptors are abundant in the brain and particularly in the cerebellum of adult rats. In contrast, the occurrence of PACAP binding sites has not been investigated during ontogenesis. The aim of the present study was to determine the distribution and biochemical characteristics of PACAP binding sites in the rat cerebellum during postnatal development, and to examine the effect of PACAP on immature cerebellar granule cells. Autoradiographic studies revealed that PACAP binding sites are transiently expressed in a germinative matrix of the cerebellar cortex, the external granule cell layer, and in the medulla, from postnatal days 8 to 25. A population of PACAP binding sites persisted in the internal granule cell layer in the mature cerebellum. Emulsion-coated cytoautoradiography, performed on cultured immature granule cells from eight-day-old rat cerebellum, demonstrated that transient PACAP binding sites are expressed by cerebellar immature granule cells. Biochemical characterization of binding revealed the occurrence of two classes of PACAP recognition sites exhibiting, respectively, high (Kd = 0.39 +/- 0.08 nM) and low (Kd = 21.2 +/- 9.4 nM) affinity for PACAP27. The two naturally occurring forms PACAP38 and PACAP27 were equipotent in competing for [125I]PACAP27 binding. In contrast, the [Des-His1]PACAP38 analog was eight times less efficient and vasoactive intestinal polypeptide only induced weak displacement of the binding. Exposure of cultured immature granule cells to PACAP27 resulted in a dose-dependent stimulation of the production of cAMP, indicating that PACAP binding sites represent authentic receptors positively coupled to adenylate cyclase. These results show that PACAP receptors are actively expressed in the cerebellum of rats during postnatal development. The presence of functional PACAP receptors in the external granule cell layer suggests that PACAP may play a role in the control of proliferation and/or differentiation of granule cells.
Adenylyl Cyclases↗
Predictive factors for spontaneous closure of atrial septal defects diagnosed in the first 3 months of life.
OBJECTIVES: To establish the rate of spontaneous closure of atrial septal defects diagnosed before age 3 months, 101 infants (mean age 26 days) with an interatrial shunt confirmed by Doppler echocardiography were followed up for an average of 265 +/- 190 days. BACKGROUND: Even if interatrial shunts in the newborn are frequently encountered, little is known about their natural history. METHODS: Defect diameter on two-dimensional echocardiography and width of color flow jet were measured in the subcostal view. Right and left ventricular diameters and atrial septal curvature were also studied. Kaplan-Meier curves were obtained to predict age of spontaneous closure in relation to initial defect diameter. RESULTS: There was no significant correlation between the diameter of the atrial septal defect and right ventricular/left ventricular ratio or type of septal curvature (vertical or concave toward the left atrium). The classic predominance of girls over boys was observed only for defects > 5 mm. An overall rate of spontaneous closure of 87% was observed. Frequency and timing of closure were inversely correlated to atrial septal defect diameter: closure occurred in 100% (32 of 32) of defects in group 1 (diameter < 3 mm), 87% of defects (39 of 45) in group 2 (diameter 3 to 5 mm), 80% of defects (16 of 20) in group 3 (diameter 5 to 8 mm). Spontaneous closure did not occur in four patients of group 4 (defect > or = 8 mm) during an average follow-up interval of 417 days (range 294 to 597 days). CONCLUSIONS: These results suggest that infants with an atrial septal defect < 3 mm need not be followed up as 100% of these defects will be closed by age 18 months; those with a defect 3 to 5 or 5 to 8 mm should be evaluated by the end of the 12th and the 15th month, respectively, when > 80% of these defects will be closed. An atrial septal defect with a diameter > or = 8 mm may have little chance of closing spontaneously and the possibility of surgical correction should be considered. Defects < 3 mm probably do not constitute a cardiac malformation in light of their natural evolution and gender distribution.
Age Factors↗