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E Pattou

Publications and source records attributed to E Pattou.

At least 19 recordsLinked to original sources
PubMed1993

Preferential distribution of C-terminal fragments of [hydroxyproline9]LHRH in the rat hippocampus and olfactory bulb.

Several molecular forms related to the decapeptide LHRH were characterized and quantified in various brain structures of intact and castrated male and female rats. Distinct moieties were separated by high performance liquid chromatography (HPLC) and radioimmunoassayed against anti-LHRH antibodies of different specificities. The hypothalamus contained the highest concentration of LHRH-like material detected by the antisera. The predominant (89%) molecular form recovered from that structure was LHRH itself; 9% of the material corresponded to [hydroxyproline9]LHRH ([Hyp9]LHRH), an endogenous posttranslational product of the LHRH precursor, and the residual immunoreactivity was accounted for by C-terminal fragments of both decapeptides, as assessed after labelling HPLC columns with appropriate synthetic or endogenous hypothalamic peptides. The proportions were the same in both sexes and were not affected by castration, in spite of a lesser overall LHRH activity in females and in castrates. LHRH and [Hyp9]LHRH were also detected in the olfactory bulb and the hippocampus. In these structures however, most (97%) LHRH-related molecules corresponded to C-fragments derived from [Hyp9]LHRH, whereas only very few fragments derived from the nonhydroxylated decapeptide were found. Sex or castration affected neither total nor relative concentrations of LHRH-derived molecules in the olfactory bulb and the hippocampus. Taken altogether, these observations are suggestive of a different LHRH metabolic regulation in neurons projecting to either the median eminence or extrahypothalamic areas. In the latter case, larger amounts of the LHRH precursor appear processed to [Hyp9]LHRH. Recovery of relatively high concentrations of [Hyp9]LHRH C-fragments in the olfactory bulb and the hippocampus reflects the higher resistance of the Hyp9-Gly10-NH2 than the Pro9-Gly10-NH2 peptide bond to hydrolysis by the postproline cleaving enzyme. In view of reports that intracerebral administration of C-terminal fragments of LHRH are able to trigger sex behavior, our finding that extrahypothalamic structures contain relatively high concentrations of the [Hyp9]LHRH-derived, more stable C-fragments suggests that these catabolites may have a role in the regulation of sex behavior.

Amino Acid Sequence↗
PubMed1992

Precursor and deaminated forms of both luteinizing hormone-releasing hormone (LHRH) and (hydroxyproline9)LHRH are present in the rat hypothalamus.

A naturally occurring analog of the decapeptide luteinizing hormone-releasing hormone ([Hyp9]LHRH) has been described previously in the hypothalamus of several mammals. It derives from post-translational hydroxylation of the LHRH proline9 residue. In the present work, intermediate LHRH precursors exhibiting both Pro9 or Hyp9 residues in the LHRH sequence were characterized in the rat hypothalamus. Hydroxylation of the Pro9 residue can thus be assumed to occur at an early stage of post-translational maturation. Deaminated, free acid forms of both native decapeptides were also detected. They correspond most likely to catabolites from incompletely processed precursors.

Amino Acid Sequence↗
PubMed1992

A second endogenous molecular form of mammalian hypothalamic luteinizing hormone-releasing hormone (LHRH), (hydroxyproline9)LHRH, releases luteinizing hormone and follicle-stimulating hormone in vitro and in vivo.

In vitro and in vivo release of pituitary hormones were studied in the presence of (hydroxyproline9)LHRH ((Hyp)LHRH), a newly characterized endogenous molecular form of LHRH. Results were compared to those obtained with LHRH itself. (Hyp)LHRH, as LHRH, stimulated both luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release in a homothetic manner. The hydroxylated compound was, however, 24 times (in vitro) and 5 times (in vivo) less potent than LHRH. The lower activity of (Hyp)LHRH than of LHRH in the in vitro assay correlated well with a 28-fold lesser potency in a binding test using pituitary membrane preparations. The higher relative potency and the prolonged effect of (Hyp)LHRH in the in vivo test were related to a lesser susceptibility of the hydroxylated form to proteolytic degradation. Effects of LHRH and of (Hyp)LHRH were not additive, both peptides were equally able to desensitize gonadotrophs to a subsequent challenge by the other. Taken together, these observations suggest that both forms of LHRH act at the same receptor site. The lesser affinity of the hydroxylated compound is compensated to a certain extent by its higher resistance to enzymatic degradation. It is concluded that in spite of its lesser potency, (Hyp)LHRH may participate in the regulation of gonadotropins.

Animals↗
PubMed1992

[New data on a second endogenous molecular form of mammalian hypothalamic LHRH, (hydroxyproline 9) LHRH].

An endogenous hydroxylated form of LHRH, (Hyp) LHRH, is able to displace LHRH bound to pituitary membrane preparations. In parallel, it stimulates release of both LH and FSH from pituitary cells in primary culture. The potency ratio of (Hyp)LHRH is approximately 1:20 and 1:5 with respect to the native decapeptide when peptidasic degradation is or is not inhibited. This correlates with a greater resistance of (Hyp) LHRH towards enzymatic degradation; in contrast to LHRH, the C-terminal (residues 6 to 10) end of (Hyp) LHRH is not degraded and generates C-terminal fragments which account for 64% of the LHRH immunoreactivity in extrahypothalamic areas as the hippocampus. Besides its weak gonadotropin releasing activity and its action or its localization in peripheral organs (placenta, gonads), a major role of the hydroxylated decapeptide may thus be to serve as a precursor of smaller active fragments on targets other than pituitary receptors.

Animals↗
PubMed1990

The helminth Schistosoma mansoni expresses a peptide similar to human beta-endorphin and possesses a proopiomelanocortin-related gene.

Opioid peptides, a group of transmitter substances with a high degree of phylogenic conservation, have many different functions, including a role in modulation of cells of the immune system. We have postulated the existence of such peptides in the parasite Schistosoma mansoni in view of their possible role in host-parasite interactions. In this report we show that beta-endorphin, which is a member of the opiate family and is derived from the proopiomelanocortin (POMC) precursor, is present in S. mansoni. Southern blots of cercarial genomic DNA, hybridized with two oligonucleotide probes complementary to highly conserved POMC sequences, showed a POMC-related gene in this trematode. Northern blot analysis of adult worm RNA indicated that this gene was actively transcribed. Significant amounts of beta-endorphin, adrenocorticotropin (ACTH), and alpha-melanocyte stimulating hormone (alpha-MSH) were detected in all developmental stages of the parasite by radioimmunoassays with the use of antisera to human peptides. By means of reverse-phase high-performance liquid chromatography (HPLC), we found that the parasite beta-endorphin-like material and the human opiate have a high degree of homology. These results appear to constitute the first demonstration of a POMC-related gene transcribed in an invertebrate.

Adrenocorticotropic Hormone↗
PubMed1986

Effects of estradiol and progesterone on immunoreactive forms of hypothalamic luteinizing hormone-releasing hormone.

In order to investigate mechanisms underlying the ovarian steroid action on hypothalamic luteinizing hormone-releasing hormone (LHRH) neurons, LHRH and a higher immunoreactive molecular form (MW 1,800 daltons) of the decapeptide were immunoassayed with antibodies of different specificities in hypothalamic subcellular fractions, after molecular sieve filtration on Biogel P4 columns equilibrated with 0.2 N acetic acid containing 0.02% sodium azide. The study was performed in ovariectomized (OVX), ovariectomized estradiol-implanted (OVX + E2) or OVX + E2 progesterone one-treated rats (OVX + E2 + P). The animals were killed before or during the circadian luteinizing hormone (LH) surge. The amount of LHRH-like immunoreactivity recovered from the synaptosomal fraction was slightly increased in OVX + E2-implanted animals but very markedly augmented in OVX + E2 + P-treated rats. In contrast, the higher molecular form recovered from a high-speed supernatant was markedly decreased in OVX + E2 + P-treated rats when compared to the other groups. At the time of maximal LH release induced by E2 + P administration, hypothalamic LHRH was markedly depleted, whereas the larger molecular form was notably augmented. The data suggest that ovarian steroids not only influence release of hypothalamic LHRH but also the processing of LHRH precursor forms.

Animals↗
PubMed1986

[Different immunoreactive forms of hypothalamic LHRH].

The radioimmunological detection of higher molecular weight (HMW) forms of LHRH is attempted in acidic extracts of the rat hypothalamus. Three antibodies are used: antibodies directed against the N or the C terminal part of LHRH (N-or C-antibodies) and recognizing synthetic LHRH molecules with N or C peptidic extensions; one conformational antibody accepting none modification of LHRH extremities. Hypothalamic LHRH immunoreactivity is distributed between three peaks after molecular sieve filtration. The first one (peak I) is eluted in the void volume of the column. Its apparent molecular weight is estimated to 26,000 daltons. Its detection is possible with the N-antibody only. The second one (peak II) is eluted before the total volume of the column. The third one (peak III) is eluted like synthetic LHRH. Its detection is easy with all antibodies. Nevertheless, it is more important with the N-antibody. This peak corresponds to the native LHRH. The excess of the N-immunoreactivity has not been yet elucidated. Several immunological detections for the peak II also: easily detected by the N-antibody, it is partially recognized by the C-antibody. By using different molecular sieve filtrations, ion exchange or affinity chromatographies, it is suggested that molecules detected with the C-antibody could correspond to C-terminal catabolites of LHRH. Molecules recognized with the N-antibody would be a LHRH sequence extended on the C-part with 1,800 daltons for the apparent molecular weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Mapping of LH-RH-containing projections to the mediobasal hypothalamus by differential deafferentation experiments.

Luteinizing hormone-releasing hormone (LH-RH) was immunoassayed in several hypothalamic structures of male rats after complete, anterior, posterior or lateral deafferentation of that structure performed with a rotating knife, as well as after discrete frontal or sagittal transections placed with a glass knife in various parts of the mediobasal hypothalamus (MBH). Survival time in all cases was two weeks. Taken together, the results indicate that most fibers containing LH-RH and originating in the preoptic area of the hypo-thalamus (APO) take a lateral course upon leaving that structure and travel along the medial forebrain bundle (MFB). Along that tract, they proceed caudally over some distance and enter the median eminence from the side; fibers innervating the posterior median eminence bend back towards the midline at a more posterior level than those terminating in the zona externa. A limited amount of fibers also reaches the median eminence from a midsagittal location. In addition, a few medial arcuate-median eminence connections may account for the small proportion of MBH LH-RH spared by complete, anterolateral or lateral transections. Projections to the organum vasculosum laminae terminalis, whether proceeding from the APO in an independent manner or as collaterals of fibers terminating in the median eminence, are unaffected by any of the transections tested. A partly common organization pattern of fibers supplying the median eminence in several neuropeptides (for instance somatostatin, CRF, cholecystokinin or dynorphin) is suggested.

Afferent Pathways↗
PubMed1983

Biphasic pattern of follicle stimulating and luteinizing hormone responses to gonadotropin-releasing hormone in vitro.

Increasing concentrations of LHRH or its active analog des-gly10 (D-ala6) LHRH induced a bimodal pattern of FSH and LH release from incubated male rat pituitaries. A low amplitude response (40% increase of LH over baseline levels) was observed for concentrations of LHRH and the agonist in the range of 10(-12) and 10(-13) M respectively. After a plateau of gonadotropin stimulation, a further high amplitude response (180-240% increase over baseline levels) occurred between 3.10(-10) and 10(-8) for LHRH and 3.10(-11) and 3.10(-9) M for des-gly10 (D-ala6) LHRH. Corresponding half maximal effective concentrations (ED50) were 2 and 0.3 nM respectively. Stimulation of FSH release closely paralleled that of LH. The low amplitude, high apparent affinity response was only obtained when the peptides were diluted in low concentrations of acidic tissue extracts. A preliminary study indicated that this method of dilution minimized peptide loss by adsorption. In addition, the low amplitude, high affinity response was never observed on pituitaries sampled from castrates. These experiments suggest the presence of two distinct populations of LHRH recognition sites on pituitary gonadotrophs. Under our experimental conditions, the appearance of the higher affinity response was dependent upon prior exposure to sex steroids. This could be due to a direct action of the steroid on the expression of a high affinity LHRH receptor.

Animals↗
PubMed1982

Further evidence for the existence of opiate binding sites on neurosecretory LHRH mediobasal hypothalamic terminals.

Opiate binding sites as well as LHRH and SRIF content were evaluated in mediobasal hypothalamus (MBH) from normal male rats and animals subjected to anterolateral deafferentation of the hypothalamus. A 87 and 44% depletion of LHRH and SRIF content respectively and a 50% decrease in the number of specific opiate binding sites was observed in the deafferented MBH. Dopa-decarboxylase activity remained unchanged. These data indicate that presynaptic opiate binding sites are present on LHRH and SRIF mediobasal hypothalamic nerve endings.

Animals↗
PubMed1981

Occurrence of higher molecular forms of LHRH in fractionated extracts from rat hypothalamus, cortex and placenta.

Separation of higher molecular forms of LHRH-like immunoreactive material was attempted in homogenates and subcellular fractions of hypothalamus, cerebral cortex and placenta. Physiological activity was checked by means of antibodies directed against different sequences of LHRH and shown to recognize synthetic LHRH analogs extended on either C- or N-terminal portions of the molecule. After molecular-sieve filtration, 2 peaks of immunoreactive material corresponding apparently to sequences of LHRH extended on the C terminus were recovered. Peak I, with a molecular weight of about 26 000 dalton, was found exclusively in a cytoplasmic and axoplasmic supernatant (S2), where it migrated alone with microsomes. Peak II (1800 dalton) was present both in S2 and in a synaptosomal fraction (P2) corresponding to nerve endings. Native LHRH was almost exclusively recovered from the synaptosomal fraction. Extracts from placenta or cerebral cortex contained little or no native LHRH; in contrast, a small amount of immunoreactive material corresponding to peak II was detected in the cerebral cortex, and fairly large amounts of both putative precursors were found in the placenta. Chromatography of tissues containing no LHRH, such as cerebellum or liver, yielded no immunoreactive material at either elution site, thus suggesting specific detection of LHRH-like material under our experimental conditions. The present data suggest that 2 higher molecular forms, one slightly heavier than the native peptide itself, and another corresponding to a much larger protein, could represent LHRH precursors and are present in the hypothalamus as well as the cerebral cortex and the placenta.

Animals↗
PubMed1980

Kinetic characteristics of LH and FSH responses to LHRH in incubated pituitaries from ovariectomized or ovariectomized, estrogen-implanted rats.

Incubated pituitary halves from ovariectomized, estrogen-implanted female rats were shown to be much more sensitive to LHRH than pituitaries from castrated, nontreated animals. LHRH in a concentration of 1,885 pg/ml increased the release of LH and FSH from 7.3 +/- 0.9 and 0.91 +/- 0.13 ng/h/hemipituitary respectively to 21.4 +/- 1.9 and 1.97 +/- 0.18 ng/h in animals implanted with the steroid. In contrast, 5,000 pg/ml of LHRH increased LH secretion from 3.4 +/- 0.3 to 8.4 +/- 0.4 ng/h in ovariectomized, nontreated animals. In pituitaries from both steroid and nontreated animals a highly significant dose response for LH and FSH secretion to the actual concentration of LHRH measured in each incubation tube by radioimmunoassay was observed. When expressed as percent of the corresponding control release, maximal stimulation of LH and FSH was comparable. Pituitaries from implanted animals provided a very sensitive bioassay for LHRH, in which amounts of the peptide lower than 100 pg/ml were detected. The apparent responsiveness to LHRH of pituitaries from estradiol-treated rats was found to be over 20 times greater than that of pituitaries from nontreated castrates.

Animals↗
PubMed1976

Brain serotonin and estradiol retention in the hypothalamus and pituitary of the rat.

In order to investigate whether the capacity of hypothalamic and anterior pituitary tissue to concentrate and retain estradiol is affected by serotonin (5-HT), 3H-estradiol (3HE2) retention in these structures was measured after 5-HT synthesis inhibition by either parachlorophenylalanine (PCPA) or 6-fluoro-tryptophane (6 FTrp), or after destruction of midbrain raphe nuclei containing 5-HT cell bodies, as well as after administration of the 5-HT precursor 5-hydroxytryptophane (5-HTP). No modification in 3HE2 retention was observed after tryptophane hydroxylase inhibitors of raphe lesions; administration of the precursor only increased the steroid retention at very high, nonphysiological dose levels. It is concluded that the interaction of 5-HT with gonadotropic release cannot be accounted for by a direct effect on specific estrogenic receptors, but occurs at a different level of gonadotropic release regulating structures or directly on LH-RH neurons.

5-Hydroxytryptophan↗