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J Rivier

Publications and source records attributed to J Rivier.

At least 73 records · Page 4Linked to original sources
PubMed1996

The effect of 'Astressin', a novel antagonist of corticotropin releasing hormone (CRH), on CRH-induced seizures in the infant rat: comparison with two other antagonists.

Corticotropin releasing hormone (CRH) has both neuroendocrine effects, promoting ACTH release from the anterior pituitary, and neurotransmitter properties, acting on specific neuronal populations. A recently designed CRH analogue has been shown to be highly potent in preventing activation of pituitary CRH receptors. The efficacy of this compound, 'Astressin', in blocking the effects of CRH in the central nervous system (CNS) has not been determined. CRH induces prolonged amygdala-origin seizures in neonatal and infant rats. This model was used in the current study, to compare Astressin to alpha-helical CRH-(9-41), and to [D-Phe12, Nle21.38, C-MeLeu37]CRH-(12-41), i.e. D-Phe-CRH-(12-41). Astressin (3 or 10 micrograms) was infused into the cerebral ventricles of infant rats prior to CRH infusion. Both doses of the analogue significantly delayed the onset of CRH-induced seizures when given 15, but not 30 min before CRH. No effect of the lower Astressin dose on seizure duration was demonstrated; the higher dose prevented seizures in 2/12 rats, and delayed seizure onset in the others (22.7 +/- 5 min vs 10.1 +/- 1.3 min). In the same paradigm, 10 micrograms of alpha-helical CRH-(9-41) and 5 micrograms of D-Phe-CRH-(12-41) had comparable effects on seizure latency and duration. Electroencephalograms confirmed the behavioral effects of Astressin. Therefore, in a CNS model of CRH-mediated neurotransmission, the potency of Astressin is not substantially higher than that of alpha-helical CRH (9-41) and D-Phe-CRH-(12-41).

Animals↗
PubMed1995

Potent, structurally constrained agonists and competitive antagonists of corticotropin-releasing factor.

Predictive methods, physicochemical measurements, and structure activity relationship studies suggest that corticotropin-releasing factor (CRF; corticoliberin), its family members, and competitive antagonists (resulting from N-terminal deletions) usually assume an alpha-helical conformation when interacting with the CRF receptor(s). To test this hypothesis further, we have scanned the whole sequence of the CRF antagonist [D-Phe12,Nle21,38]r/hCRF-(12-41) (r/hCRF, rat/human CRF; Nle, norleucine) with an i-(i + 3) bridge consisting of the Glu-Xaa-Xaa-Lys scaffold. We have found astressin [cyclo(30-33)[D-Phe12,Nle21,38,Glu30,Lys33]r/ hCRF(12-41)] to be approximately 30 times more potent than [D-Phe12,Nle21,38]r/hCRF-(12-41), our present standard, and 300 times more potent than the corresponding linear analog in an in vitro pituitary cell culture assay. Astressin has low affinity for the CRF binding protein and high affinity (Ki = 2 nM) for the cloned pituitary receptor. Radioiodinated [D-125I-Tyr12]astressin was found to be a reliable ligand for binding assays. In vivo, astressin is significantly more potent than any previously tested antagonist in reducing hypophyseal corticotropin (ACTH) secretion in stressed or adrenalectomized rats. The cyclo(30-33)[Ac-Pro4,D-Phe12,Nle21,38,Glu30,Lys33++ +]r/hCRF-(4-41) agonist and its linear analog are nearly equipotent, while the antagonist astressin and its linear form vary greatly in their potencies. This suggests that the lactam cyclization reinstates a structural constraint in the antagonists that is normally induced by the N terminus of the agonist.

Adrenalectomy↗
PubMed1995

A new family of Conus peptides targeted to the nicotinic acetylcholine receptor.

In this work, a new family of Conus peptides, the alpha A-conotoxins, which target the nicotinic acetylcholine receptor, is defined. The first members of this family have been characterized from the eastern Pacific species, Conus purpurascens (the purple cone); three peptides that cause paralysis in fish were purified and characterized from milked venom. The sequence and disulfide bonding pattern of one of these, alpha A-conotoxin PIVA, is as follows: [formula: see text] where O represents trans-4-hydroxyproline. The two other peptides purified from C. purpurascens venom are the under-hydroxylated derivatives, [Pro13]alpha A-conotoxin PIVA and [Pro7,13]alpha A-conotoxin PIVA. The peptides have been chemically synthesized in a biologically active form. Both electrophysiological experiments and competition binding with alpha-bungarotoxin demonstrate that alpha A-PIVA acts as an antagonist of the nicotinic acetylcholine receptor at the postsynaptic membrane.

Amino Acid Sequence↗
PubMed1995

Potent pituitary-gonadal axis suppression and extremely low anaphylactoid activity of a new gonadotropin releasing hormone (GnRH) receptor antagonist "azaline B".

We report here the biological characterization of azaline B, a new gonadotropin releasing hormone (GnRH) receptor antagonist, with the following amino acid sequence: [Ac-D-Nal1, D-Cpa2, D-Pal3, Aph5(atz), D-Aph6(atz), Ilys8, D-Ala10]-GnRH. Azaline B was shown to suppress several reproductive processes in rats including ovulation, and had very low anaphylactoid activity compared with other GnRH antagonists. Azaline B inhibited histrelin (a GnRH agonist)-mediated follicle stimulating hormone (FSH) and luteinizing hormone (LH) release from cultured rat pituitary cells. Three antagonists ([Nal-Glu]-GnRH, [Nal-Lys]-GnRH ("antide"), and azaline B) inhibited 0.1 nM histrelin-mediated gonadotropin release to baseline levels with EC50 values of approximately 0.6 nM. Azaline B, when injected s.c. into rats on the afternoon of proestrus, was more potent at inhibiting ovulation than either [Nal-Glu]-GnRH or [Nal-Lys]-GnRH. The relative order of antiovulatory potencies of the three antagonists was azaline B > [Nal-Glu]-GnRH > [Nal-Lys]-GnRH. Similar azaline B potency was shown by its ability to suppress gonadotropin levels in castrated rats. The improved selectivity of azaline B was demonstrated when it was compared with other GnRH antagonists in the cutaneous anaphylactoid assay (local wheal response) in rats. Results with azaline B were not significantly different from results with vehicle in this assay. [Nal-Glu]-GnRH was more than twice as potent as [Nal-Lys]-GnRH in stimulating a wheal response. Furthermore, the maximal wheal response produced by azaline B was only 0.6 times that of [Nal-Lys]-GnRH, currently one of the most selective antagonists identified. Finally, both azaline B and [Nal-Lys]-GnRH were much less potent than [Nal-Glu]-GnRH in the guinea pig cardiopulmonary anaphylactoid assay after i.v. administration. These data show that azaline B is a potent and selective GnRH receptor antagonist with little or no anaphylactoid activity in animal models, and therefore has potential for use in the treatment of many reproductive endocrine disorders, as well as for use as a contraceptive.

Amino Acid Sequence↗
PubMed1995

Ligand requirements of the human corticotropin-releasing factor-binding protein.

CRF-binding protein (CRF-BP), identified as a 37-kilodalton human serum protein, binds human (h) CRF (Kd = 0.17 +/- 0.01 nM) and blocks hCRF's ability to stimulate ACTH release by pituitary cells in vitro. The present study examines ligand requirements of CRF-BP by testing the affinity of recombinant CRF-BP for synthetic analogs of CRF and peptides in the CRF family. The relative affinities of various fragments of hCRF or related peptides for CRF-BP indicate that residues 9-28 are crucial for ligand binding. CRF-BP binds human/rat CRF and urotensin-I with high affinity, sauvagine with moderate affinity, and ovine (o) CRF with low affinity. The marked difference in the affinity of CRF-BP for oCRF (Ki = 1100 +/- 97 nM) compared to hCRF (Ki = 0.17 +/- 0.01 nM), when considered with the importance of the central domain, suggests that amino acids 22, 23, and/or 25 are critical for binding. Altering oCRF residues 22, 23, or 25 individually or collectively to match those of hCRF increases the affinity of CRF-BP for these ligands; [Ala22, Arg23, Glu25]oCRF, in which all three of these central amino acids are substituted by their hCRF counterparts, binds CRF-BP with an affinity equal to that of hCRF. CRF-BP has differential affinities for CRF receptor antagonists, binding alpha-helical CRF-(9-41) with high affinity and [D-Phe12, Nle21,38]hCRF-(12-41) with low affinity. Thus, the structural requirements for binding to CRF-BP can clearly be distinguished from those for CRF receptor recognition of both agonists and antagonists. Peptides such as hCRF-(9-33), with low biological activity but which retain high affinity for the binding protein, can competitively override the effects of CRF-BP to block CRF-induced ACTH secretion, raising the possibility that whereas endogenous CRF-BP serves to limit the distribution or duration of action of CRF, specific pharmacological inhibitors of the ligand-binding protein interaction might be used to therapeutically elevate free CRF levels.

Amino Acid Sequence↗
PubMed1994

Decreased release of gonadotropin-releasing hormone during the preovulatory midcycle luteinizing hormone surge in normal women.

To investigate the contribution of hypothalamic gonadotropin-releasing hormone (GnRH) secretion to the midcycle gonadotropin surge in the human, the response of luteinizing hormone (LH) to competitive GnRH receptor blockade achieved by administration of a range of doses of a pure GnRH antagonist was used to provide a semiquantitative estimate of endogenous GnRH secretion. The LH response to 5, 15, 50, and 150 micrograms/kg s.c. of the NAL-GLU GnRH antagonist ([Ac-D-2Nal1,D-4ClPhe2,-D-Pal3,Arg5,D-4-p-met hoxybenzoyl-2-aminobutyric acid6,D-Ala10]GnRH, where 2Nal is 2-naphthylalanine, 4ClPhe is 4-chlorophenylalanine, and 3Pal is 3-pyridylalanine) was measured in normal women in the early and late follicular phases of the menstrual cycle, at the time of the midcycle LH surge and in the early luteal phase. LH decreased in a dose-response fashion after administration of the GnRH antagonist in all cycle phases (P < 0.0001). When this suppression was expressed as maximum percent inhibition, there was no difference in response during the early and late follicular and early luteal phases. However, at the midcycle surge, there was a leftward shift of the dose-response curve with significantly greater suppression of LH at the lower antagonist doses in comparison to the other cycle phases (P < 0.005), but no difference at the highest dose. Thus, we draw the following conclusions. (i) There is a consistently greater degree of LH inhibition by GnRH antagonism at the midcycle surge at submaximal degrees of GnRH receptor blockade than at other phases of the menstrual cycle in normal women. (ii) This leftward shift of the dose-response relationship to GnRH receptor blockade suggests that the overall amount of GnRH secreted at the midcycle surge is less than at other cycle stages. (iii) These data confirm the importance of pituitary augmentation of the GnRH signal at the time of the midcycle gonadotropin surge in the human.

Adolescent↗
PubMed1994

Conformationally restricted competitive antagonists of human/rat corticotropin-releasing factor.

Corticotropin releasing factor (CRF) is a 41-peptide amide which stimulates the release of ACTH (Vale et al. Science 1981, 213, 1394). CRF has been postulated to assume an alpha-helical conformation upon binding to its pituitary receptor (Hernandez et al. J. Med. Chem. 1993, 36, 2860). We have exploited this hypothesis in the design of a limited series of cyclic analogues and have taken into consideration the effects of side-chain deletion (Alanine scan, Kornreich et al. J. Med. Chem. 1992, 35, 1870) as well as of changes in chirality (Rivier et al. J. Med. Chem. 1993, 36, 2851), with the rationale that side chains necessary for binding could also be replaced by side-chain bridges. In particular, we have used computer modeling to predict likely side chain bridging opportunities and evaluated the effects of such replacements by correlating biological results with those derived from CD spectroscopy. We have synthesized 38 monocyclic peptide amides, competitive antagonists of human/rat CRF, using solid-phase methodology on MBHA resin. After purification by preparative RP-HPLC, the peptides were analyzed by RP-HPLC and capillary zone electrophoresis and characterized by mass spectroscopy and amino acid analysis. CRF antagonists were tested for their ability to interfere with CRF-induced release of ACTH by rat anterior pituitary cells. In most cases, one of the bridge heads was located at a position where substitution by a D-residue was tolerated (i.e., positions 12 and 20). It has become clear that careful optimization of bridge length and chirality is critical. This is best exemplified by the fact that out of the 38 analogues that were synthesized and tested, only two, [cyclo(20-23)[DPhe12,Glu20,Lys23, Nle21,38]h/rCRF12-41 and cyclo(20-23)[DPhe12,Glu20,Orn23,Nle21,38] h/rCRF12-41], were found to be more potent (3 and 2 times, respectively) than [DPhe12,Nle21,38]h/rCRF12-41, the parent compound. Six analogues belonging to two different families were found to be half as potent as the standard, 18 had 2-20% of the potency of the standard, and the others were significantly less potent. CD results of all analogues in 50% TFE (a concentration of TFE that induced nearly maximum helicity of [DPhe12,Nle21,38]h/rCRF12-41) suggest that while helicity may be an important factor for CRF analogue recognition, little correlation is found between percent helicity as determined by spectral deconvolution and biological activity in vitro.

Adrenocorticotropic Hormone↗
PubMed1994

Characterization of a novel and potent corticotropin-releasing factor antagonist in rats.

The present study examined the ability of two analogs of human/rat corticotropin-releasing factor (h/rCRF), [Met18, Lys23, Glu27,29,40, Ala32,41, Leu33,36,38] h/rCRF9-41 (alpha-hel CRF9-41) and [D-Phe12, Nle21,38, C alpha MeLeu37] h/rCRF12-41 (D-Phe CRF12-41), to antagonize CRF- and stress-induced behavioral changes in rats. The potency and duration of action of D-Phe CRF12-41 in vivo was compared with that of alpha-hel CRF9-41, the most effective CRF antagonist studied to date. When administered i.c.v., both CRF antagonists dose-dependently reduced the locomotor activity induced by rat CRF (0.5 microgram/rat i.c.v.) and attenuated the social stress-induced anxiogenic-like effect, as measured by the elevated plus-maze. However D-Phe CRF12-41 was 5 times more potent and remained effective for a longer period (> 1.5 hr) than alpha-hel CRF9-41. High doses of alpha-hel CRF9-41 (25 micrograms/rat), by itself, exhibited weak agonist effects, which were not observed with D-Phe CRF12-41 at the same doses. These results demonstrate that a N-terminus-shortened CRF antagonist that encompasses the substitution D-Phe12 has significantly higher biological potency and an extended duration of action without intrinsic agonist effects in these in vivo systems. The availability of potent and effective CRF antagonists will provide valuable tools for exploring the functional role of brain CRF and may ultimately lead to an understanding of the biological basis of stress-related illnesses.

Amino Acid Sequence↗
PubMed1994

Pharmacological comparison of two corticotropin-releasing factor antagonists: in vivo and in vitro studies.

The present study compared the effects of two analogs of corticotropin-releasing factor (CRF), [D-Phe12,Nle21,38, C alpha MeLeu37]CRF12-41 (D-PheCRF12-41) and alpha helical CRF9-41, as antagonists of CRF in in vivo and in vitro assays. In halothane-anesthetized rats, intracerebroventricular (i.c.v.) administration of both analogs inhibited the activation of locus coeruleus (LC) neuronal discharge produced by CRF (3.0 micrograms, i.c.v.). LC activation by hypotensive stress elicited by intravenous (i.v.) infusion of nitroprusside was antagonized by the same doses of the CRF antagonists that were effective in antagonizing CRF, suggesting that the receptors involved in LC activation by CRF and by hypotensive stress are similar. However, D-PheCRF12-41 was approximately 100 times more potent than alpha helical CRF9-41 when administered i.c.v. The IC50 values for D-PheCRF12-41 as an antagonist of CRF and of nitroprusside were 0.16 and 0.14 microgram, i.c.v., respectively. The IC50 values for alpha helical CRF9-41 as an antagonist of CRF and of nitroprusside were 18 and 27 micrograms, i.c.v., respectively. In contrast, D-PheCRF12-41 was only slightly more potent than alpha helical CRF9-41 in antagonizing CRF-stimulated cyclic AMP production in rat brain homogenates, with IC50s of 78 +/- 15 and 260 +/- 30 nM for D-PheCRF12-41 and alpha helical CRF9-41, respectively. Moreover, the antagonists had similar affinities for CRF binding sites in rat brain homogenates, with Kis of 15.5 +/- 4 nM and 10.3 +/- 6 nM for D-PheCRF12-41 and alpha helical CRF9-41, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1993

Role of CRF in stress-related alterations of gastric and colonic motor function.

Major advances have been made in the understanding of the pathophysiology of stress-related alteration of gut function. A wealth of information indicates that CRF is involved in the central mechanisms by which stress inhibits gastric emptying while stimulating colonic motor function. CRF acts in the PVN to trigger both the inhibition of gastric emptying and the stimulation of colonic motor function in response to stress, in addition to previously established endocrine and behavioral responses. Preliminary evidence exists that CRF acts in the locus coeruleus to induce a selective stimulation of colonic transit without influencing gastric emptying. The central actions of CRF to alter gastric and colonic motor function are conveyed by autonomic pathways and are unrelated to the associated stimulation of pituitary hormone secretion. The demonstration that central CRF plays a role in mediating gastric stasis resulting from surgery, peritonitis or high levels of central interleukin-1 provides new insight into the mechanisms involved in gastric ileus induced postoperatively or by infectious disease. Likewise, the demonstration that CRF in the PVN and locus coeruleus induce the anxiogenic and colonic motor responses to stress and that colonic distention activates neurons in the locus coeruleus opens new avenues for the understanding of the pathogenesis of a subset of IBS patients with colonic hypersensitivity associated with psychopathological disturbance and diarrhea-predominant symptoms.

Animals↗
PubMed1993

Single point D-substituted corticotropin-releasing factor analogues: effects on potency and physicochemical characteristics.

In an attempt to determine which conformational parameters are important for the biological activity of ovine corticotropin-releasing factor (oCRF), we have synthesized in significant amounts (50-200 mg) and characterized chemically, structurally (CD), and biologically, oCRF analogues with substitution of each amino acid by its corresponding D-isomer. Out of 37 of these analogues, three were found to be equipotent to, or twice as potent as, oCRF, 13 had potencies in the range from 10 to 60%, 17 had potencies ranging from 1 to 10%, and the four others had potencies less than 0.5%. None of the analogues antagonized oCRF-induced release of ACTH in vitro at concentrations > or = 1000 oCRF. Since antagonists to CRF action can be generated by deletion of the first 8-14 residues, a series of CRF antagonists which exhibit significantly higher in vitro and in vivo biological potency than [Met18,Lys23,Glu27,29,40,Ala32,41,-Leu33,3 6,38] h/rCRF, [alpha-helical-CRF9-41], is also described. [D-Phe12,Nle21,38,Arg36]h/rCRF, in particular, was found to be ca. 15 times more potent than alpha-helical-CRF9-41 in vitro. In the rat, however, this analogue was about as effective as alpha-helical-CRF9-41 in blocking CRF-induced decrease in mean arterial blood pressure and increase in heart rate. Its potency in blocking epinephrine release by CRF was not significantly different from that of alpha-helical-CRF9-41. In the adrenalectomized rat, [Lys36]alpha-helical-CRF(9-41) (1.7 mg/kg) blunted the effect of endogenous CRF over a 90-min period; by comparison, a similar dose of alpha-helical-CRF9-41 was effective for less than 1 h.

Adrenocorticotropic Hormone↗
PubMed1993

Synthesis and relative potencies of new constrained CRF antagonists.

Two series of CRF antagonists with N alpha- and C alpha-methylated alanine and leucines were evaluated for their biological activities in vitro and in vivo in several systems. The poly-N-methylated analogue of alpha-helical-CRF9-41, [N alpha MeLeu10,15,27,37,N alpha MeAla22,32,41]-alpha-Hel-CRF9-41, was found to be considerably less potent than the parent non-N-methylated analogue. This result was expected on the basis that alpha-helicity was thought to be required for biological activity and the prediction that backbone substitutions on the nitrogen have a tendency to break alpha-helices (a hypothesis that was confirmed by circular dichroism). Next, a series of constrained analogues of the potent CRF antagonist, [DPhe12,Nle21,38]h/rCRF12-41, was synthesized that contained C alpha-methylleucine and/or C alpha-methylalanine (Aib) residues at selected positions. Because C alpha-methylation is recognized to increase alpha-helicity, and because there is now strong NMR data suggesting that residues 6-36 assume a well-defined alpha-helix, it was expected that these analogues would be more potent. Although usual solid-phase peptide synthesis procedures were followed, success in coupling the C alpha-methyl amino acids was obtained only with a 1:1 mixture of BOP/HOBt. In vitro potencies of the synthesized compounds were measured in a collagenase-dispersed anterior pituitary cell culture bioassay. Monosubstituted analogues were shown to be twice to one fourth as potent as the parent compound; while the pluri-substituted peptides were slightly less potent. This decrease in potency might be correlated to an unexpected lower helical content of the pluri-substituted compounds (as determined by CD spectroscopy), as it was suggested that the bioactive conformation of the CRF was predominantly alpha-helical. Interestingly, one analogue, [DPhe12,Nle21,38,C alpha-MeLeu37]h/rCRF12-41, was found to be more potent and longer acting than the parent compound in two in vivo assays measuring ACTH release after intravenous administration to adrenalectomized rats and reversal of stress-induced delay in gastric emptying in the rat after intracisternal administration. The molecular basis for this increased duration of action and potency is being investigated.

Adrenalectomy↗
PubMed1993

High-performance liquid chromatography of amino acids, peptides and proteins. CXXVIII. Effect of D-amino acid substitutions on the reversed-phase high-performance liquid chromatography retention behaviour of neuropeptide Y[18-36] analogues.

The reversed-phase high-performance liquid chromatographic (RP-HPLC) gradient elution behaviour of a series of peptides related to Neuropeptide Y (NPY) has been investigated. The peptides studied included NPY, NPY[13-36], NPY[18-36] and a series of 16 analogues of NPY[18-36], each with a single D-amino acid substitution. Chromatographic parameters which relate to the interactive contact area and the binding affinity have been evaluated with two different stationary phase ligands and two organic modifiers. The results demonstrate that D-amino acid substitutions in the sequence region encompassing amino acid residues NPY[27-31] of these NPY[18-36] peptides significantly influence the interactive behaviour of these peptides relative to the unsubstituted NPY[18-36] molecule, while substitutions in the N- and C-terminal regions had little effect. Further, these results indicate that, in hydrophobic environments, NPY[18-36] adopts a significant degree of secondary structure which is severely disrupted by the presence of the D-amino acids in the central portion of the molecule.

Acetonitriles↗
PubMed1993

Molecular and functional characterization of GnRH receptors cloned from rat pituitary and a mouse pituitary tumor cell line.

A cDNA for a GnRH receptor (mtGnRH-R) was obtained from a mouse gonadotropic pituitary cell line (alpha T3-1) by expression cloning. This full-length cDNA was subsequently used as a probe to clone a rat pituitary GnRH receptor (rGnRH-R). The two receptors differ by 13 amino acids and are 100% identical to those recently reported. The analysis of the cloned receptors by photoaffinity-labeling followed by SDS-PAGE reveals a major band of approximately 70 kDa. This is in contrast to the native rat pituitary and mouse alpha T3-1 receptors whose major labeled species migrate with an apparent size of approximately 45 kDa. Functional studies reveal that both receptors, when transiently expressed in COSM6 cells, can bind GnRH with high affinity and transduce the stimulation of IP3 accumulation in response to GnRH.

Affinity Labels↗
PubMed1993

Rapid regression of uterine leiomyomas in response to daily administration of gonadotropin-releasing hormone antagonist.

OBJECTIVE: The efficacy of acute and sustained pituitary gonadotropin down-regulation by the Nal-Glu GnRH antagonist (Nal-Glu) was evaluated in the treatment of uterine leiomyomas. DESIGN: Prospective, open clinical trial. PATIENTS: Seven normally cycling women with symptomatic leiomyomas. INTERVENTIONS: Nal-Glu (50 micrograms/kg per day) was administered subcutaneously for 3 months. MAIN OUTCOME MEASURES: Baseline ultrasound examinations were obtained and repeated monthly throughout treatment. Each leiomyoma was mapped and measured in three dimensions. Blood samples were drawn daily for 7 days, weekly for 4 weeks, and monthly for the remaining 2 months. RESULTS: Mean leiomyoma size decreased 52.8 +/- 7.3% (means +/- SD) after 1 month of therapy and remained unchanged for the remainder of the study. Serum levels of E2 (35.9 +/- 11.8 to 9.3 +/- 0.8 pg/mL, 131.7 +/- 43.3 to 34.0 +/- 1.4 pmol/L), estrone (37.3 +/- 7.5 to 13.0 +/- 2.5 pg/mL, 138.1 +/- 27.7 to 48.1 +/- 9.1 pmol/L), and P (1.6 +/- 1.1 to 0.3 +/- 0.01 ng/mL, 5.0 +/- 3.6 to 0.9 +/- 0.04 nmol/L) declined rapidly (within 48 hours) and remained suppressed throughout treatment. Serum LH, FSH, androstenedione, T, and DHEA levels did not change significantly. In two subjects who did not have surgical removal, leiomyomas grew to original size within the 1st month off drug. Six patients remained amenorrheic and the other subject spotted during the last 2 months of therapy. CONCLUSIONS: Continuous treatment with Nal-Glu induces immediate and sustained pituitary-gonadal down-regulation that results in regression in leiomyoma size. By circumventing GnRH agonist-induced pituitary-ovarian up-regulation, GnRH antagonists may prove to be superior tools in the medical management of leiomyomas.

Adult↗
PubMed1993

Coupling of hormonal stimulation and transcription via the cyclic AMP-responsive factor CREB is rate limited by nuclear entry of protein kinase A.

Cyclic AMP (cAMP) regulates a number of eukaryotic genes by mediating the protein kinase A (PKA)-dependent phosphorylation of the CREB transcription factor at Ser-133. In this study, we test the hypothesis that the stoichiometry and kinetics of CREB phosphorylation are determined by the liberation and subsequent translocation of PKA catalytic subunit (C subunit) into the nucleus. Using fluorescence imaging techniques, we observed that PKA was activated in a stimulus-dependent fashion that led to nuclear entry of C subunit over a 30-min period. The degree of CREB phosphorylation, assessed with antiserum specific for CREB phosphorylated at Ser-133, correlated with the amount of PKA liberated. The time course of phosphorylation closely paralleled the nuclear entry of the catalytic subunit. There was a linear relationship between the subsequent induction of the cAMP-responsive somatostatin gene and the degree of CREB phosphorylation, suggesting that each event--kinase activation, CREB phosphorylation, and transcriptional induction--was tightly coupled to the next. In contrast to other PKA-mediated cellular responses which are rapid and quantitative, the slow, incremental regulation of CREB activity by cAMP suggests that multifunctional kinases like PKA may coordinate cellular responses by dictating the kinetics and stoichiometry of phosphorylation for key substrates like CREB.

Animals↗
PubMed1993

Evidence for a common neural mechanism mediating growth hormone-releasing factor-induced and somatostatin-induced feeding.

We have previously reported that the somatotropin regulatory peptides, growth hormone-releasing hormone (GRF) and somatostatin (SS) increase feeding when applied centrally in low picomole-range doses. The similarity between the dose-response characteristics and photoperiod sensitivities of these two peptide's feeding effects, together with indirect evidence suggesting that these peptides interact functionally within the hypothalamus, suggests that GRF and SS may induce feeding via a common neural mechanism. The present studies sought to investigate this possibility. In the first experiment combined intracerebroventricular (icv) injections of optimal doses of GRF and SS were found to be less potent than icv injections of GRF or SS alone, suggesting that the mechanisms mediating GRF-induced and SS-induced feeding are not totally independent. In further studies, icv injections of antiserum raised against SS blocked GRF-induced feeding. In contrast, icv injections of antiserum raised against GRF were ineffective in blocking SS-induced feeding. These results suggest that SS may act downstream to GRF in a putative neural feeding mechanism which utilizes both peptides. The possible anatomical basis for such a feeding mechanism involving GRF and SS is discussed.

Animals↗