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    Dominique Porquet

    We measured serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin concentrations on a bioMérieux Mini Vidas system in a pediatric population ranging in age from 1 to 19 years. Reference intervals were... more
    We measured serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin concentrations on a bioMérieux Mini Vidas system in a pediatric population ranging in age from 1 to 19 years. Reference intervals were established separately for females and males, with stratification by age group and by Tanner's pubertal stage. FSH values were higher in females than in males, and were lowest in both sexes of age class 2 (4–8 years), increasing thereafter to the upper limit for stage PIV (females) and stage PV (males). LH values showed a similar pattern of change: concentrations were lowest for class 1 (1–3 years) and class 2 (4–8 years), and highest for stage PII (females) and stage PV (males). No significant difference was observed according to gender. Prolactin values did not differ markedly according to gender or pubertal status.Clin Chem Lab Med 2007;45:541–5.
    Insulin is produced by beta cells in pancreatic islets of Langherans via a complex process of proteolytic conversion. A precursor molecule, proinsulin, is transported to the Golgi apparatus where it is packed into secretory granules.... more
    Insulin is produced by beta cells in pancreatic islets of Langherans via a complex process of proteolytic conversion. A precursor molecule, proinsulin, is transported to the Golgi apparatus where it is packed into secretory granules. Maturation of the secretory granules is associated with conversion of proinsulin to insulin and C-peptide by enzymatic cleavage. Secretion of insulin into the bloodstream is accompanied by the release of small amounts of proinsulins. Insulin immunoassays consist of radioimmunoassays using polyclonal antisera which cross-react with proinsulins, and two-site assays using monoclonal antibodies. These immunometric assays have led to improvements in specificity and sensitivity as compared to radioimmunoassays. To determine reference values and limits, insulinaemia must be measured in normoglycaemic subjects with a normal body weight. Moreover, as insulinaemia is most often measured during stimulation tests, reference values must also be determined for the most common tests such as the oral glucose tolerance test or the intravenous glucose tolerance test. We report the analytical characteristics of insulin assays and review reference values and their interpretation. Wide-scale use of insulin assays remains a subject of research rather than a diagnostic application. Spontaneous hypoglycaemia, a disorder which can be caused by hyperinsulinism, insulinoma, insulin autoimmune syndrome and non-insulin-mediated factors, is almost the only clinical indication for the measurement of plasma insulin. Diabetes is diagnosed solely on the basis of chronic hyperglycaemia. Thus, measurement of plasma insulin has no clinical value in the diagnosis or management of diabetic patients, with the exception of rare cases including the syndrome of severe insulin resistance and abnormalities in beta-cell secretory products. Otherwise, insulin measurement is used in experimental investigations to study the pathophysiology of various disorders, especially diabetes. The reference and range of plasma insulin values are not yet clearly established, and the range of concentrations reported in the literature remains unsatisfactory. There is a need to standardise results and thereby improve comparability among studies.
    ABSTRACT The authors bring out the useful data for the diagnosis and management of diabetes mellitus
    ABSTRACT
    Pindolol, propranolol, practolol, N-isopropyl-p-nitrophenyl-ethanolamine (INPEA), d and l-alprenolol were injected into the lateral cerebral ventricle of the anaesthetized rat. Except for INPEA, which has no action at the doses used,... more
    Pindolol, propranolol, practolol, N-isopropyl-p-nitrophenyl-ethanolamine (INPEA), d and l-alprenolol were injected into the lateral cerebral ventricle of the anaesthetized rat. Except for INPEA, which has no action at the doses used, these various beta-blocking agents produce a dose-related fall in blood pressure. D-alprenolol and practolol seem to be the least active of the hypotensive agents. Our results show some relationship between the beta-blocking potency of the drugs studied and the hypotension induced when they were injected in the lateral ventricle.
    Recently, the role of the peroxisome proliferator-activated receptor alpha (PPARalpha) in the hepatic inflammatory response has been associated to the decrease of acute phase protein transcription, although the molecular mechanisms are... more
    Recently, the role of the peroxisome proliferator-activated receptor alpha (PPARalpha) in the hepatic inflammatory response has been associated to the decrease of acute phase protein transcription, although the molecular mechanisms are still to be elucidated. Here, we were interested in the regulation by Wy-14643 (PPARalpha agonist) of alpha1-acid glycoprotein (AGP), a positive acute phase protein, after stimulation by Dexamethasone (Dex), a major modulator of the inflammatory response. In cultured rat hepatocytes, we demonstrate that PPARalpha inhibits at the transcriptional level the Dex-induced AGP gene expression. PPARalpha exerts this inhibitory effect by antagonizing the CCAAT/enhancer binding protein (C/EBPbeta) transcription factor that is involved in Dex-dependent up-regulation of AGP gene expression. Overexpression of C/EBPbeta alleviates the repressive effect of PPARalpha, thus restoring the Dex-stimulated AGP promoter activity. Furthermore, glutathione-S-transferase GST ...
    The syncytiotrophoblast is the major component of the human placenta as it is involved in the feto-maternal exchanges and the secretion of pregnancy-specific hormones. In normal placenta, the multinucleated syncytiotrophoblast is formed... more
    The syncytiotrophoblast is the major component of the human placenta as it is involved in the feto-maternal exchanges and the secretion of pregnancy-specific hormones. In normal placenta, the multinucleated syncytiotrophoblast is formed by fusion of mononuclear cytotrophoblast cells. In trisomy 21-affected placenta, we show that it exists a defect (or a delay) in the syncytiotrophoblast formation and a decrease of the production of pregnancy-specific hormones. We show that it is related to the over expression of the SOD-1 located on chromosome 21. These results will be of help for the understanding of maternal hormonal markers of fetal trisomy 21 and the consequences of the placental defects on the fetal development.
    Puberty corresponds to the development of gonads and secondary sexual characteristics, and on a biological point of view, to the functional maturation of the gonadal axis. Puberty begins at the age of 11.5 to 12 years in males and 10.5 to... more
    Puberty corresponds to the development of gonads and secondary sexual characteristics, and on a biological point of view, to the functional maturation of the gonadal axis. Puberty begins at the age of 11.5 to 12 years in males and 10.5 to 11 years in females. Depending on secondary sexual characteristics, particularly pubic pilosity, puberty is classified in five stages (Tanner's stages). During puberty growth velocity increases in response to gonadal steroid secretion. From a biochemical point of view, three steps are involved in the development of the hypothalamo-hypophysogonadal axis: 1. nocturnal hypothalamic GnRH secretion increases and becomes pulsatile (a peak every 60 to 90 min); 2. the pituitary gonadotrophins FSH and LH follow the same pattern of secretion as GnRH; increase of GnRH and FSH/LH secretion is due to a decrease in hypothalamo-hypophysal sensitivity to the negative feed back exerted by circulating gonadal steroids; 3. secretion of estradiol in females and te...
    The serum level of rat alpha 1-acid glycoprotein is significantly increased by treatment with phenobarbital, and in vivo studies have shown that phenobarbital seems to act mainly at the transcriptional level. To show the direct mediating... more
    The serum level of rat alpha 1-acid glycoprotein is significantly increased by treatment with phenobarbital, and in vivo studies have shown that phenobarbital seems to act mainly at the transcriptional level. To show the direct mediating effect of phenobarbital on alpha 1-acid glycoprotein gene expression, we investigated the ability of primary cultured rat hepatocytes to respond to in vitro phenobarbital administration. Phenobarbital increased both alpha 1 acid glycoprotein secretion and corresponding mRNA levels in primary rat hepatocytes cultured on matrigel. Used in combination with interleukin-1, interleukin-6 and dexamethasone, phenobarbital had an additive or synergistic effect on alpha 1-acid glycoprotein synthesis. These results show that (a) phenobarbital acts directly on hepatocytes by increasing alpha 1-acid glycoprotein gene expression and (b) this effect is mediated by a specific mechanism independent of pathways involved in alpha 1-acid glycoprotein induction by inter...
    The ability of the fetal rat to respond to interleukin 1 beta (IL1 beta) by expressing alpha 1-acid glycoprotein (AGP) was investigated. Eight and 20 h after injection of 7 ng IL1 beta into 19-day fetuses, liver AGP mRNA increased by a... more
    The ability of the fetal rat to respond to interleukin 1 beta (IL1 beta) by expressing alpha 1-acid glycoprotein (AGP) was investigated. Eight and 20 h after injection of 7 ng IL1 beta into 19-day fetuses, liver AGP mRNA increased by a factor of 66 and 82 respectively, while serum AGP levels increased by a factor of 3 and 5. Similar treatment of the mothers altered in the fetuses neither AGP serum levels nor the amount of liver AGP mRNA. The induction of AGP gene expression in the fetal liver in response to IL1 beta was similar to that observed in the adult liver. These results demonstrate that at day 19 the fetal rat liver has acquired a mature acute-phase system.
    Diabetic patients receiving insulin therapy generally develop anti-insulin antibodies that must be eliminated, usually by extraction with polyethylene glycol (PEG), before determining the concentration of free (active) insulin in plasma.... more
    Diabetic patients receiving insulin therapy generally develop anti-insulin antibodies that must be eliminated, usually by extraction with polyethylene glycol (PEG), before determining the concentration of free (active) insulin in plasma. We describe a new method for removing such antibodies, with the use of Protein A coupled to Sepharose microspheres. The results correlate well with those by the PEG method, although values are systematically higher or lower for given samples, according to the initial titer of the antibody measured in terms of binding capacity. Further studies are required to clarify this observation.
    Lipogenesis from U(14C) lactate was studied in hepatocytes isolated from obese Zucker rats (fa/fa) their lean littermates (Fa/?) and Sprague Dawley rats. The distribution of radioactive carbon between the glycerol and the fatty acid... more
    Lipogenesis from U(14C) lactate was studied in hepatocytes isolated from obese Zucker rats (fa/fa) their lean littermates (Fa/?) and Sprague Dawley rats. The distribution of radioactive carbon between the glycerol and the fatty acid moieties of the acylglycerols were studied. Radioactive lactate was better utilized for glycerol formation than it was for fatty acid formation in the obese rats. However, when oleate was added to the hepatocytic incubation medium, radioactive lactate was preferentially incorporated into the fatty acid moiety of the acylglycerols. Zucker obesity classified as a "metabolic obesity" by Meyer (1) depends upon abnormalities in carbohydrate metabolism associated with increased lipogenesis. This might be explained by biochemical shifts in the utilization of nutrients (2). Among the nutrients, lactate seems to be a better source of carbon than glucose for lipid synthesis (3). It has been shown that there is an increased hepatic portal blood concentration of lactate several hours after eating: about 4 mM in Wistar rats (4) and 10-15 mM in obese Zucker rats (3). We are interested in determinating the incorporation of carbon from lactate either into glycerol or into fatty acyl moieties of hepatic acylglycerols, and in determining the influence of exogenous fatty acids on acylglycerol synthesis, since a high level of circulating fatty acids in Zucker obese rats has been reported (5). Our purpose was to determine the incorporation of lactate into glycerol and fatty acyl moieties of acylglycerols, under the influence of oleate. Hepatocytes were isolated from ad libitum fed obese Zucker rats (fa/fa), their lean littermates (Fa/?) and Sprague-Dawley rats (SD). Incorporation of lactate was studied for three hours, in order to exclude short-term regulation effects and to allow oleate to be distributed into all cellular compartments.
    Pregnancy-associated plasma protein-A and -A2 (PAPPA and PAPPA2) are proteases that cleave IGF binding proteins (IGFBPs) and thereby increase the bioavailability of growth factors. PAPPA has long been recognized as a marker of fetal... more
    Pregnancy-associated plasma protein-A and -A2 (PAPPA and PAPPA2) are proteases that cleave IGF binding proteins (IGFBPs) and thereby increase the bioavailability of growth factors. PAPPA has long been recognized as a marker of fetal genetic disorders and adverse pregnancy outcomes. In contrast, although PAPPA2 is also highly expressed in human placenta, its physiological importance is not clear. To establish whether mice will be a useful model for the study of PAPPA2, we compared the patterns of expression of PAPPA2 in the placentae of mouse and human. We show, for the first time, that Pappa2 is highly expressed in mouse placenta, as is the case in humans. Specifically, it is expressed at the interface of the maternal and fetal layers of the mouse placenta at all gestational stages studied (10.5–16.5 days post coitum). Similarly, PAPPA2 is expressed in the syncytiotrophoblast layer of human placental villi and is also detected in some invasive extravillous trophoblasts in the first ...
    Numerous data suggest that impaired growth hormone secretion in short children is usually related to abnormal regulation of the hormone at the hypothalamic level. In order to improve our understanding of neurohypothalamic dysfunction in... more
    Numerous data suggest that impaired growth hormone secretion in short children is usually related to abnormal regulation of the hormone at the hypothalamic level. In order to improve our understanding of neurohypothalamic dysfunction in short children, we measured basal and peak (after l–dopa stimulation) plasma growth hormone-releasing hormone levels in 43 prepubertal children. Among them, in 23 children suspected of having hypothalamic growth hormone dysregulation, growth hormone-releasing hormone values were significantly higher than those observed in normal short stature children (n=20), no longer correlated with peak growth hormone following l–dopa, and negatively correlated with growth velocity. This suggests that a predominant inhibitor of growth hormone secretion, such as an increase in somatostatin tone, might be prevalent in a large number of children with partial growth hormone deficiency and suspected hypothalamic growth hormone dysregulation. Journal of Endocrinology (1...
    During human pregnancy, the trophoblast develops from differentiation of cytotrophoblast cells into an endocrine active syncytiotrophoblast. In culture, isolated mononuclear cytotrophoblasts aggregate and then fuse to form a syncytium,... more
    During human pregnancy, the trophoblast develops from differentiation of cytotrophoblast cells into an endocrine active syncytiotrophoblast. In culture, isolated mononuclear cytotrophoblasts aggregate and then fuse to form a syncytium, reproducing the in vivo process. In this study, we examined the effect of low oxygen tension (approximately 9%, hypoxia) compared to standard conditions (approximately 19% oxygen, normoxia) on these cellular events. Under hypoxia, syncytial formation was less frequently observed, cell staining and electron microscopy revealed that cytotrophoblasts remain aggregated, with a positive proliferative cell nuclear antigen (PCNA) immunostaining. Desmoplakin and E-cadherin, both known to disappear with cytotrophoblast fusion, showed persistent expression in hypoxic cells after 3 days of culture. In contrast, the expression of actin and ezrin, two cytoskeletal proteins, was unchanged. hCG secretion and hPL expression were both decreased in hypoxic cells, reflecting a reduced syncytial formation. Thus, on day 3, the mean values for hCG secretion were 1,100 +/- 155 and 289 +/- 26 mlU/mL in normoxic and hypoxic conditions, respectively. The reduced cell fusion process as well as hCG secretion and hPL expression under hypoxia were reversed by reoxygenation of the cells. We conclude that under hypoxia, the formation of functional syncytiotrophoblast is impaired due to a defect in the cytotrophoblast fusion process. This may explain the observation of a higher number of cytotrophoblast cells and a reduced syncytial layer in placentas of some pathological pregnancies.
    In order to gain a better understanding on the possible role of retinoic acid (RA) on human GH secretion, we have characterized the expression of its nuclear receptors in somatotropic adenoma cell extracts. By immunoblotting with rabbit... more
    In order to gain a better understanding on the possible role of retinoic acid (RA) on human GH secretion, we have characterized the expression of its nuclear receptors in somatotropic adenoma cell extracts. By immunoblotting with rabbit polyclonal antibodies directed against RAR alpha, beta, and gamma and RXR alpha and beta, we could only detect the presence of RAR alpha and RXR alpha proteins. The predominant expression of RXR alpha was confirmed at the mRNA level by Northern and slot-blot analysis. We then investigated the effect of RA on GH synthesis in cell culture of adenomatous somatotrophs. In cultured cells, RA (1 microM) stimulated GH secretion, increased intracellular GH content and GH mRNA levels within 72 h, suggesting a modulation of GH synthesis by RA.
    Methylmalonyl-CoA mutase (MCM) apoenzyme deficiency is a rare metabolic disease that may result in distinct biochemical phenotypes of methylmalonic acidemia (MMA), namely mut(o) and mut-. We analyzed a cohort of 40 MCM-deficient patients... more
    Methylmalonyl-CoA mutase (MCM) apoenzyme deficiency is a rare metabolic disease that may result in distinct biochemical phenotypes of methylmalonic acidemia (MMA), namely mut(o) and mut-. We analyzed a cohort of 40 MCM-deficient patients with MMA affected by either the mut(o) or the mut- form of the disease. By direct sequencing of cDNA and gDNA of the MUT gene, we detected 42 mutations, 29 of which were novel mutations. These included five frameshift mutations (insertion, deletion, or duplication of a single nucleotide), five sequence modifications in consensus splice sites, six nonsense and 12 missense mutations, and a large genomic deletion including exon 12. We explored how the 12 novel missense mutations might cause the observed phenotype by mapping them onto a three-dimensional model of the human MCM generated by homology with the P. shermanii enzyme. In this work we update the spectrum of MCM mutations (n=84), and then discuss their prevalence and distribution throughout the coding sequence in relation to the enzyme structure.
    In order to assess the value of urinary growth hormone (GH) as a reflection of central GH release, 42 prepubertal children with short stature and without organic disease were studied. A nocturnal GH profile and L-dopa and GH-releasing... more
    In order to assess the value of urinary growth hormone (GH) as a reflection of central GH release, 42 prepubertal children with short stature and without organic disease were studied. A nocturnal GH profile and L-dopa and GH-releasing hormone (GHRH) tests were performed. Urinary GH was measured by means of a direct immunoradiometric method we have developed, using two monoclonal antibodies. Nocturnal urinary GH values correlated positively with plasma GH values expressed as the area under the curve (r = 0.76; p = 0.0001) or mean peak amplitude (r = 0.73; p = 0.0001). Also, urinary GH values correlated positively with peak plasma GH levels during the GHRH test (r = 0.64; p = 0.001). In contrast, no correlation was observed between peak plasma GH and urinary GH during the L-dopa test (r = 0.29; p = 0.11). This suggests a specific but as yet undetermined effect of L-dopa on urinary GH secretion.
    Serum human growth hormone (hGH) levels were measured with three different commercial kits, comprising a radioimmunoassay (RIA) (bioMérieux, Marcy-l'Etoile, France,... more
    Serum human growth hormone (hGH) levels were measured with three different commercial kits, comprising a radioimmunoassay (RIA) (bioMérieux, Marcy-l'Etoile, France, 'bmpoly') and two immunoradiometric assays (IRMA) (bioMérieux, 'bmmono', and CIS bioInternational, Gif-sur-Yvette, France, 'cismono'). Samples were collected after various stimulation tests [arginine-insulin, growth hormone-releasing hormone (GHRH), L-dopa and glucagon-beta-axolol] from children who were undergoing evaluation for short stature. Values obtained with the IRMAs were consistently lower than those obtained with the RIA. Furthermore, the cismono/bmmono and cismono/bmpoly values ratios were always significantly higher when samples were collected during GHRH stimulation than during the other stimulation tests. These data indicate that GHRH could induce a particular form of hGH molecule (in nature or in amount), recognized by the monoclonal antibodies in the cismono kit and that a specific form of hGH may be released by GHRH stimulation.
    Hyperglycosylated human chorionic gonadotropin (H-hCG) is secreted by the placenta in early pregnancy. Decreased H-hCG levels have been associated with abortion in spontaneous pregnancy. We retrospectively measured H-hCG and dimeric hCG... more
    Hyperglycosylated human chorionic gonadotropin (H-hCG) is secreted by the placenta in early pregnancy. Decreased H-hCG levels have been associated with abortion in spontaneous pregnancy. We retrospectively measured H-hCG and dimeric hCG in the sera of 87 in vitro fertilization patients obtained in the 3 weeks following embryo transfer and set the results in relation to pregnancy outcome. H-hCG and dimeric hCG were correlated (r(2) = 0.89), and were significantly decreased in biochemical pregnancy (2 microg/l and 18 IU/l, respectively) compared to early pregnancy loss (22 microg/l and 331 IU/l) and ongoing pregnancy (32 microg/l and 353 IU/l). Only H-hCG tended to discriminate between these last two groups.
    Serum IGF-1 level declines with advancing age and is a reliable index of protein-energy undernutrition in elderly patients in a metabolically stable condition. We have examined the value of IGF-1 as an indicator of malnutrition in elderly... more
    Serum IGF-1 level declines with advancing age and is a reliable index of protein-energy undernutrition in elderly patients in a metabolically stable condition. We have examined the value of IGF-1 as an indicator of malnutrition in elderly patients during recovery within 1 month after surgery for a hip fracture and we have studied the relationship between changes in IGF-1 levels, nutritional status and inflammatory reaction during 2 month follow up. Forty elderly patients (mean age 84.0+/-1.9) were nutritionally assessed upon admission to our rehabilitation unit (D0) then monthly (D30-D60) by measurement of anthropometric and biological parameters. Two groups of patients were defined on the basis of mid-arm circumference (MAC) and tricipital skinfold thickness (TST) measurement at D0: group 1, undernourished (n=13) and group 2, normally nourished (n=27). Changes in anthropometric and biological parameters during the study were compared between these two groups of patients. IGF-1 level was significantly lower in group 1 (79.5+/-9.1 vs 108+/-8.6 ng/ml, P<0.05) while usual serum protein levels were in the same range in the two groups. Orosomucoid level significantly decreased during 2 month follow-up in group 2 (P<0.01), CRP level decreased but not significantly. TST and MAC decreased in group 2 (respectively P<0.02 and P<0.05) while anthropometric parameters tended to slightly increase in group 1 in relation with an increase in caloric intake (P<0.05). IGF-1 level increased significantly during the study in group 2 (P<0.05) and was significantly lower in patients with complications occurring between D0 and D30 in comparison with patients without complications (respectively P<0.05 at D0, P<0.02 at D30). IGF-1 level correlated with body mass index, MAC, TST, muscle midarm circumference, albumin and transthyretin levels. Changes in IGF-1 levels positively correlated with those in transthyretin levels and negatively with those in orosomucoid levels. IGF-1 level seems a reliable index of protein-energy under-nutrition in elderly patients in the recovery period after surgery for a hip fracture. This marker is influenced by the inflammatory reaction. Decline of inflammatory reaction, rather than change in nutritional status, is responsible for the variation in IGF-1 level during a 2 month follow-up.

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