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Biomedical subjects

L Mercier

Publications and source records attributed to L Mercier.

At least 37 records · Page 2Linked to original sources
PubMed1994

Ontogenetic variations in auditory arousal threshold during sleep.

Developmental variations in auditory arousal thresholds during sleep were investigated in four groups of normal male subjects--children, preadolescents, adolescents, and young adults. Arousal thresholds were determined during NREM and REM sleep for tones presented via earphone insert on a single night following two adaptation nights of undisturbed sleep. Age-related relationships were observed for both awakening frequency and stimulus intensity required to effect awakening, with awakenings occurring more frequently in response to lower stimulus intensities with increasing age. Although stimulus intensities required for awakening were high and statistically equivalent across sleep stages in nonadults, higher intensity stimuli were required in Stage 4 relative to Stage 2 and REM sleep in adults. These results confirm previous observations of marked resistance to awakening during sleep in preadolescent children and suggest that processes underlying awakening from sleep undergo systematic modification during ontogenetic development.

Adolescent↗
PubMed1994

Validation of the Box and Block Test as a measure of dexterity of elderly people: reliability, validity, and norms studies.

Manual dexterity is a skill frequently evaluated in rehabilitation to estimate hand function. Several tests have been developed for this purpose, including the Box and Block Test (BBT) that measures gross manual dexterity. The goal of the present study was to verify the test-retest reliability and construct validity of the BBT with subjects aged 60 and over with upper limb impairment. The second objective of this research was to develop normative data based on a random sample of healthy elderly community-living individuals. The results show that the test-retest reliability is high (intraclass correlations coefficients of 0.89 to 0.97) and the validity of the test is shown by significant correlations between the BBT, an upper limb performance measurement and a functional independence measurement. The norms will help rehabilitation clinicians to differentiate better between real difficulties and those that may be attributed to normal aging.

Activities of Daily Living↗
PubMed1993

Norethindrone alters apolipoprotein E concentration and isoform expression in rat plasma high-density lipoproteins.

The administration of norethindrone, a synthetic progestin, to female rats caused marked decreases in the cholesterol and protein contents of high-density lipoproteins (HDL). A 84% decrease in the total apolipoprotein (apo) E of HDL was associated with a 80% decrease in the proportions of apoE isoforms E1 and E2, whereas E3 and E4 were unchanged. This appears to be the first demonstration of hormonally-induced modification of the apoE phenotype.

Animals↗
PubMed1993

Monoclonal antibodies against methionyl recombinant human prolactin.

Hybridoma cell lines producing monoclonal antibody (Mab) against recombinant human prolactin (rhPrl) were established from fusion between X63-Ag8 myeloma cells and Balb/c mice splenocytes. Four Mabs numbered I to IV were selected by ELISA, purified and characterized. All these Mabs were of the Ig1 kappa isotype and able to recognize oxidized as well as reduced rhPrl. As shown by a competitive inhibition assay, Mab IV did not compete with any of the three others. Moreover, both rhPrl and hPrl extracted from human pituitaries, were recognized equally by this Mab. Properties displayed by Mab IV make it very attractive for the evaluation of prolactin levels by sandwich immunoassays.

Animals↗
PubMed1993

Sleep patterns in reading disabled children.

Sleep patterns in reading disabled (n = 24) and normal control (n = 15) 8-10-year-old boys were compared to examine suggested relationships among sleep, maturational and cognitive processes. Sleep was recorded in the laboratory for four consecutive nights (two adaptation, two baseline) using standard polysomnography. Analyses revealed variations across nights for both groups reflecting adaptation to the sleep laboratory, but such effects were attenuated in reading disabled subjects. Group comparisons on baseline sleep measures (nights 3 and 4 collapsed) revealed that reading disabled children showed significantly more stage 4 sleep, less rapid eye movement (REM) sleep, a longer REM onset latency and, related to this, an extended initial non-REM (NREM) cycle. Chronic sleep deprivation and maturational delay are prominent among factors that could result in such variations in sleep architecture, and these factors, alone or in combination, could impair information processing and contribute to cognitive deficits noted in reading disabled children.

Child↗
PubMed1990

Bacterial production and purification of recombinant human prolactin.

Escherichia coli cells transformed with a recombinant plasmid (pT7L) containing the coding sequence of human prolactin (hPrl) expressed a new protein. This protein, comigrating with human Prl on sodium dodecyl sulfate (SDS)-polyacrylamide gels, represented 50% of the total bacterial extract. Immunoprecipitation of [35S]methionine-labeled bacterial lysate with a rabbit antiserum to hPrl followed by SDS-polyacrylamide gel electrophoresis (PAGE) analysis showed that the major component had a Mr identical to that of standard hPrl. The majority of the recombinant hPrl (r-hPrl) accumulated in inclusion bodies. Analysis of these inclusion bodies by SDS-PAGE under nonreducing conditions showed that they are composed mostly of fully reduced monomers. Solubilization of the inclusion bodies and protein denaturation were performed in 8 M urea. Refolding during the renaturation procedure was confirmed by SDS-PAGE under nonreducing conditions. r-hPrl was further purified by gel permeation chromatography on a fast protein liquid chromatography column. More than 95% of the molecules were recovered as oxidized monomeric forms. The refolded molecule was tested for its bioactivity in the Nb2 lymphoma mitogenic assay. The dose-response curves obtained with either r-hPrl or pituitary-derived hPrl showed a complete parallelism. Furthermore, Nb2 cell proliferation was completely blocked by addition of hPrl antiserum to both preparations. Recombinant hPrl is identical to natural hPrl except for an additional methionine group at the amino terminal end.

Amino Acid Sequence↗
PubMed1989

Differential modulation of gene induction by glucocorticoids and antiglucocorticoids in rat hepatoma tissue culture cells.

Studies of glucocorticoid and antiglucocorticoid induction of tyrosine aminotransferase (TAT) in two rat hepatoma cell lines (Fu5-5 and HTC) are described. These studies revealed several phenomena that are not consistent with the current models of steroid hormone action: (a) TAT induction occurred at glucocorticoid levels below those required for comparable receptor occupancy in Fu5-5, but not in HTC, cells; (b) the ability of antiglucocorticoids to induce TAT is higher in Fu5-5 than in HTC cells; (c) the values of the amount of TAT agonist activity with the antiglucocorticoid dexamethasone 21-mesylate and of log10 of the dexamethasone concentration required for half-maximal induction of TAT were not constant over time but varied in a linear, reciprocal manner. This modulation was seen for several glucocorticoids and antiglucocorticoids at the level of both TAT enzyme and mRNA but not for two other glucocorticoid inducible genes in the same cells. These results, plus the fact that a similar difference in the concentration required for half-maximal TAT induction in Fu5-5 cells was seen for both glucocorticoids and cyclic AMP, argue that the modulation occurs at some point distal to receptor-steroid complex binding to the biologically active nuclear sites but proximal to translation of TAT mRNA. In order to explain these results, it is pointed out that models involving second messengers are entirely appropriate for steroid hormone action. The participation of a modulated trans-acting factor in such a model may explain the above results.

Animals↗
PubMed1989

Molecular cloning and characterization of two forms of trout growth hormone cDNA: expression and secretion of tGH-II by Escherichia coli.

We constructed a cDNA library using mRNA isolated from rainbow trout pituitaries. Two types of cDNA clones encoding growth hormone (GH) were isolated and their complete nucleotide sequences determined. Twenty seven nucleotide substitutions in the coding region and 108 in the noncoding region distinguish the cDNAs of trout GH-I and II. Both cDNAs encode polypeptides of 210 amino acids, including a putative signal peptide of 22 amino acids, which differ by 12 residues. In both trout and salmon, GH-I mRNA is predominant, which suggests that the variation in the amount of secreted GH originates from a transcriptional event. Moreover, comparison of rainbow trout and chum salmon GH reveals that, in both cases, the predominant GH-I has mutated less than its GH-II counterpart. Mature tGH-II was expressed in Escherichia coli using the pIN-III-ompA-Hind secretion vector.

Amino Acid Sequence↗
PubMed1989

Rainbow trout prolactin cDNA cloning in Escherichia coli.

We describe the isolation and characterization of a cDNA for trout prolactin (tPrl). An extensive analysis of tPrl recombinant clones by restriction analysis and sequencing revealed the presence of only one form of tPrl mRNA. The deduced protein sequence consists of 210 amino acids, including a signal peptide of 23 amino acids. The amino acid sequence of the mature protein is compared among teleosts and mammals, showing two domains of strong similarity that may be involved in biological activity.

Amino Acid Sequence↗
PubMed1988

Inverse correlation between dexamethasone 21-mesylate agonist activity and sensitivity to dexamethasone for induction of tyrosine aminotransferase in rat hepatoma cells.

Previous results demonstrated that both the level of induction of the liver specific enzyme tyrosine aminotransferase (TAT) by the irreversible antiglucocorticoid dexamethasone 21-mesylate (Dex-Mes) and the concentration of the reversible glucocorticoid dexamethasone (Dex) required for 50% of maximal TAT induction (i.e. EC50) were different in HTC and Fu5-5 rat hepatoma culture cells. In the present study, a retrospective analysis of these two parameters over an 8 yr period indicates that the absolute values of both parameters varied within each cell line over time in a reversible manner. The variation of both parameters appears to be causally related since a linear, reciprocal relationship exists between the amount of Dex-Mes agonist activity and log10 (Dex EC50) in both cell lines (correlation coefficient is -0.896 for n = 46). This relationship was independent of changes in basal TAT level, culture medium, and serum lot. Results with cloned HTC cells indicate that these temporal variations are not due to fluctuations in the relative abundance of two cell populations displaying either high or low amounts of agonist activity with Dex-Mes. While these analyses relied on the detection of enzyme levels, the amount of TAT mRNA is shown to parallel the enzyme levels. Thus the variation in parameters of TAT induction by Dex and by Dex-Mes appears to be modulated at a pre-translational step. Such variations have not previously been observed for the control of specific gene transcripts by other steroid hormones and may be related to the known differences in agonist activity seen for most antisteroids in various systems.

Animals↗
PubMed1988

A simple method for the preparation of the covalently closed circular form of plasmid DNA.

We describe a simple, rapid, inexpensive method for isolation of covalently closed circular plasmid DNA. The method involves the electrophoresis of crude DNA preparations in an agarose gel, electrotransfer onto a dialysis membrane and elution of the highly purified circular covalently closed plasmid DNA. Native and recombinant plasmid DNA have been purified by this method and shown to be suitable for restriction enzyme digestion and transformation of bacteria. The yield of this rapid purification procedure makes it a good alternative method to standard centrifugation in cesium chloride ethidium bromide gradients.

DNA, Circular↗
PubMed1987

Nutritional dependence of the effect of estrogen on fat cell lipoprotein lipase.

We investigated the effects of ethynylestradiol (EE) at low dose (1.2 micrograms/day) injected s.c. for 10 days on lipoprotein lipase (LPL) in fat cells of female rats fed a standard diet (5% lipid, 49.5% glucid, 23.5% protein) as a function of the nutritional state. EE caused a 150% increase in LPL activity in the fed state, and a 65% decrease in the fasting state, resulting in a large increment in the physiological feeding-fasting difference. Feeding the rats a diet supplemented with 20% lard reversed the estrogen-dependent LPL increase in the fed state. Under all experimental conditions, EE caused a depletion of fat stores and an increase in plasma levels of triacyglycerol.

Adipose Tissue↗
PubMed1986

Antiglucocorticoid steroids have increased agonist activity in those hepatoma cell lines that are more sensitive to glucocorticoids.

FU5-5 rat hepatoma (Reuber H35) cells are hypersensitive in that the same percentages of full induction of tyrosine aminotransferase (TAT) occur at much lower concentrations of glucocorticoids than in the related HTC rat hepatoma (Morris) cells. Unexpectedly, these hypersensitive FU5-5 cells also exhibited more agonist activity with the affinity labeling antiglucocorticoids cortisol 21-mesylate and dexamethasone 21-mesylate than did HTC cells (Mercier et al., Endocrinology 112, 601-609 [1983]). In the present study, several other antiglucocorticoids (11-desoxycortisone, progesterone, dexamethasone oxetanone, and RU 486 in addition to dexamethasone 21-mesylate) and the antiandrogen cyproterone acetate were examined to see if chemically unreactive, reversible antisteroids also would exhibit an altered activity (i.e. increased agonist activity) in FU5-5 cells. Each antiglucocorticoid examined did display a 2-fold increased amount of agonist activity in FU5-5 cells, as compared to HTC cells; only RU 486 was predominantly an antagonist in FU5-5 cells but the potency of RU 486 was about 9-fold less than in HTC cells. Dexamethasone, and especially progesterone, was metabolized in FU5-5 and HTC cells. However, differential metabolism in FU5-5 vs HTC cells cannot account for the increased induction of TAT in FU5-5 cells since the amount of agonist activity seen for dexamethasone mesylate (or its metabolites) depended not on the cell type used but rather on the glucocorticoid inducible enzyme monitored, i.e. TAT or glutamine synthetase. The combined data suggest that the hypersensitivity of FU5-5 cells towards glucocorticoid induction of TAT may be linked with the ability of both reversible and irreversible antiglucocorticoids to display increased TAT agonist activity in FU5-5 cells. This behavior was somewhat steroid specific since the antiandrogen cyproterone acetate did not display increased TAT agonist activity in FU5-5 cells compared to HTC cells and was only 2-fold less effective as an antiglucocorticoid in FU5-5.

Animals↗
PubMed1986

Effects of 2-fluoroestradiol on lipid metabolism in the ovariectomized rat.

Biological activities of estrogen molecules are altered by fluorination of ring A, and the resulting impairment to form catechols. 2-fluoroestradiol (2-F-E2) has been found to be devoid of carcinogenic action despite its high estrogenic potency; its metabolic effects are so far unknown. This study was designed to investigate the effects of 2-F-E2 on lipid metabolism, as compared to those of estradiol-17 beta(E2). Ovariectomized rats received E2 or 2-F-E2 by s.c. injection at a dose of 60 micrograms for three consecutive days. Parameters measured were weights of parametrial fat depots, fat cell volumes, levels of triacylglycerol and acylcholesterol in plasma, and enzymatic responses to the estrogens in isolated parametrial fat cells as evaluated in terms of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) activities. 2-F-E2 and E2 were found to produce comparable decreases in fat depots, cell volumes and plasma levels of acylcholesterol whereas plasma triacylglycerol was unchanged. Both estrogens decreased LPL, and increased HSL activities to the same extent. Thus, 2-F-E and E2 exhibited comparable effects on lipid metabolism. These effects appeared to depend mainly on the estrogenic potency of these molecules, and to be distinct from their carcinogenic action. Despite its high estrogenic potency, 2-F-E2 was found to be slightly less estrogenic than E2.

Adipose Tissue↗
PubMed1985

Formation of a fluorescent glucocorticoid receptor-steroid complex in HTC cell cytosol.

An intensely fluorescent rhodamine derivative of dexamethasone (i.e. Dex-C2-Rho) was synthesized. Dex-C2-Rho possessed high affinity for HTC cell glucocorticoid receptors in cell-free systems. Whole cell activity and receptor affinity of Dex-C2-Rho were both much lower, apparently due to problems with cell permeability and/or metabolism. A specific, fluorescent receptor-steroid complex at concentrations as low as 1 X 10(-9) M could readily be observed with crude HTC cell receptors after removal of the free Dex-C2-Rho. This appears to be the first report of a fluorescent glucocorticoid receptor-steroid complex.

Animals↗
PubMed1985

[Characterization of specific receptors for estradiol, induction of vitellogenin and its mRNA in the liver of rainbow trout (Salmo gairdnerii)].

In all egg laying vertebrates, synthesis and use of vitellogenin (Vg) are intimately bound to the active phase of reproduction. In the liver of the rainbow trout (Salmo gairdnerii), Vg synthesis is influenced by estradiol (E2) which, we believe, acts through the classical mechanism of steroid hormone action. After binding of the hormone to a soluble specific receptor protein, the estradiol-receptor complex can interact with chromatin and modulate the expression of Vg genes, leading to increased synthesis of specific mRNA and Vg. We show here: (i) the presence of specific oestrogen receptors (dissociation constant KD congruent to 1.5 X 10(-9) M for E2) in the cytosol of the male trout liver. (ii) The male liver, offering, an ideal experimental control of "zero" background, we followed-in the liver of male trout--the kinetics of induction of Vg mRNA by hybridization with Vg cDNA, after E2 stimulation, and (iii) the apparition of Vg in the serum by using an original rocket immuno-electrophoretic technique. The male trout liver vitellogenin model and the original techniques we developed will be very useful to study the influence of endogenous and exogenous factors on the different steps (receptors, transcription, translation) of vitellogenesis regulation.

Animals↗
PubMed1984

Glucocorticoid versus antiglucocorticoid activity: can a single functional group modification of glucocorticoid steroids always convey antiglucocorticoid activity?

Single functional group modifications of glucocorticoid steroids have been performed in an effort to obtain antiglucocorticoids with high affinity and specificity for glucocorticoid receptors. This approach tests the hypothesis that the structural determinants of biological activity and receptor binding are independent so that modification of more potent glucocorticoids could yield more potent antiglucocorticoids . In this study, a new functional group capable of conferring antiglucocorticoid activity has been identified, i.e. the spiro C-17 oxetan -3'-one group. Using three glucocorticoids of greatly different potency ( deacylcortivazol greater than dexamethasone greater than cortisol), we examined the effects of incorporation of the oxetanone group and the previously described, alkylating C-21 mesylate group on steroid affinity for receptors and biological activity. In both series of modified steroids, the receptor affinity of the derivatives paralleled that of the parent steroids. The biological activities of the dexamethasone and cortisol derivatives were predominantly or totally antagonistic, while both deacylcortivazol derivatives were full agonists. We conclude that antiglucocorticoid activity can arise from the incorporation of a single functional group into glucocorticoid steroid structures, but that the expression of agonist vs. antagonist activity is determined by a balance of structural group determinants which are not restricted to a common region of the steroid. Within a given class of derivatives, receptor affinity correlated with the amount of agonist activity. The structure-activity relationships for dexamethasone oxetanone and deacylcortivazol mesylate were studied in detail. Dexamethasone oxetanone is a potent antiglucocorticoid in HTC cells. [3H]Dexamethasone oxetanone binds to cell-free glucocorticoid receptors with a Kd of 3.2 X 10(-8) M. No specific antiglucocorticoid binder was detected. Direct binding experiments with [3H]dexamethasone oxetanone as well as indirect studies of the kinetics of cell-free competition of [3H]dexamethasone binding demonstrated that dexamethasone oxetanone binds to receptors faster (by about a factor of 2) and dissociates from receptors much faster than does dexamethasone. Deacylcortivazol mesylate was a more potent agonist and binder to receptors than dexamethasone, but displayed no irreversible interactions with HTC cell receptors under those conditions that afforded a covalent receptor-steroid complex with the closely related dexamethasone mesylate.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗