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D Porquet

Publications and source records attributed to D Porquet.

At least 37 records · Page 2Linked to original sources
PubMed1999

Growth hormone inhibits rat liver alpha-1-acid glycoprotein gene expression in vivo and in vitro.

The gene encoding alpha-1-acid glycoprotein (AGP), one of the major acute-phase proteins, is positively controlled at the transcriptional level by cytokines (interleukin-1 [IL-1], IL-6, and tumor necrosis factor alpha) and glucocorticoids. Here, we show that growth hormone (GH) treatment of isolated rat hepatocytes in vitro reduces AGP messenger RNA (mRNA) expression. AGP gene expression remained inducible by IL-1, IL-6, and phenobarbital (PB) in GH-treated hepatocytes. Interestingly, the repressive effect of GH on AGP gene expression was also observed in vivo: liver AGP mRNA content was strongly increased in hypophysectomized rats, and GH treatment of these animals led to a decrease in mRNA to levels lower than those in untreated control animals. Moreover, the inhibitory effect of GH mainly occurs at the transcriptional level and can be observed as little as 0.5 hours after GH adding in vitro to isolated hepatocytes. These results show negative regulation of AGP gene expression and strongly suggest that GH is a major endogenous regulator of constitutive AGP gene expression. Moreover, transfection assays showed that the region of the AGP promoter located at position -147 to -123 is involved in AGP gene regulation by GH. Furthermore, GH deeply modifies the pattern of nuclear protein binding to this region. GH treatment of hypophysectomized rats led to the release of proteins of 42 to 45 and 80 kd and to the binding of proteins of 48 to 50 and 90 kd.

Animals↗
PubMed1999

Insulin assays and reference values.

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.

C-Peptide↗
PubMed1997

Reduced final height and indications for insulin resistance in 20 year olds born small for gestational age: regional cohort study.

OBJECTIVE: To investigate whether the association between low birth weight and increased risk of developing impaired glucose tolerance, insulin resistance, hypertriglyceridaemia, and hypertension in middle age is apparent by the age of 20 in people born small for gestational age. DESIGN: Regional cohort study. SETTING: Maternity registry, Haguenau, France. SUBJECTS: 236 full term singleton babies born small for gestational age (birth weight or length, or both, below third centile) during 1971-8 and 281 with normal birth weight (between 25th and 75th centile). All subjects were contacted and evaluated at a mean (SD) age of 20.6 (2.1) years. MAIN OUTCOME MEASURES: Adult height; concentrations of glucose, insulin, and proinsulin during an oral glucose tolerance test; lipid and fibrinogen concentrations; and blood pressure. RESULTS: After sex and target height were adjusted for, subjects who had been born small for gestational age were significantly shorter at age 20 than those with a normal birth weight (men 4.5 cm shorter (95% confidence interval 6.0 to 3.0 cm); women 3.94 cm shorter (5.2 to 2.7 cm)). After sex and body mass index were adjusted for, mean plasma glucose concentration 30 minutes after a glucose load, fasting insulin concentration (in women), and insulin and proinsulin concentrations 30 and 120 minutes after a glucose load were significantly higher in subjects who had been born small for gestational age than in those with a normal birth weight. Mean lipid and fibrinogen concentrations and blood pressure were not different between the two groups. CONCLUSIONS: Intrauterine growth retardation has long term consequences such as reduced final height Raised insulin and proinsulin concentrations are present in young adults born small for gestational age and could be markers of early changes in insulin sensitivity.

Adolescent↗
PubMed1997

Gene expression of a protein, JB70, related to rat alpha1-acid glycoprotein in Euglena gracilis.

Antibodies directed against rat alpha1-acid glycoprotein (AGP) recognize a 70 kDa antigen, designated JB70, present in extracts of achlorophyllous Euglena gracilis cells as well as in their culture medium. By using 2-dimensional electrophoresis, JB70 appears to be composed of two acidic polypeptides. Additionally, Northern blot analysis reveals the presence in E. gracilis cells of a 2.3 kb mRNA hybridizing with a cDNA probe specific for rat AGP mRNA. Moreover, elevated mRNA levels are detected in dexamethasone-treated E. gracilis cells, indicating a response to this inducer similar to that observed for hepatic AGP. These results strongly suggest that polypeptides closely related to hepatic rat AGP are expressed in E. gracilis cells. They also indicate that, like other gene families implicated in natural defense processes such as heat-shock protein and metallothionein genes, the AGP gene appears to be conserved down to this early diverging eucaryote.

Animals↗
PubMed1997

Retinoic acid stimulates growth hormone synthesis in human somatotropic adenoma cells: characterization of its nuclear receptors.

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.

Acromegaly↗
PubMed1997

A thyroxine dosage of 8 micrograms/kg per day is appropriate for the initial treatment of the majority of infants with congenital hypothyroidism.

UNLABELLED: The adequate L-thyroxine dosage for the initial treatment of infants with congenital hypothyroidism is a subject of controversy. Some recommend higher dosages (> 10 micrograms/kg/day) to ensure adequate levels, while others advocate lower dosages to permit normalisation of thyroid status. The aim of this study was to evaluate the results of a treatment strategy using an initial dosage of 7.5-8.0 micrograms/kg per day, TSH measurements being taken at 15 and 30 days of treatment. Fifty one newborns infants with primary congenital hypothyroidism detected by neonatal screening were treated with the same therapeutic strategy. A mean L-thyroxine dosage of 7.9 micrograms/kg per day at the onset of treatment and 6.6 micrograms/kg/d at 2 months, normalised the FT4 and FT3 levels at 15 days in 100% and TSH levels at 2 months in 90% of cases. Many patients showed elevated levels of FT4 and a systematic higher initial dosage could expose many infants to a dangerous hyperthyroidism. Patients with abnormal TSH levels at 2 months already had higher TSH levels in the first 8 weeks of life and, despite higher L-thyroxine dosage, also exhibited lower FT4 and FT3 levels. These patients who needed an early increase in dosage had already shown a more profound ante and neonatal hypothyroidism. This subgroup of patients require a higher dosage of thyroxine and early assessment of FT4, FT3 and TSH levels are required for optimum dosage choice. CONCLUSION: Even though a subgroup of patients may require a higher dosage of L-thyroxine, an initial dosage of 7.5-8.0 micrograms/kg per day, with an early assessment of FT4, FT3, and TSH levels, is adequate for the treatment of the majority of infants with congenital hypothyroidism.

Congenital Hypothyroidism↗
PubMed1997

Fetal fibronectin in the cervical secretion predicts accurately the onset of labor at term.

OBJECTIVE: The objective of our study was to check if presence of fetal fibronectin in the cervical secretion of full term patient predicts accurately the onset of labour at term. STUDY DESIGN: 78 women in the term period were included in the study, serial samples for fetal fibronectin were assessed, each patient underwent spontaneous labour, delay between last sample and delivery were analysed. RESULTS: Patient with positive fetal fibronectin delivered within 3 +/- 1.9 days where as patient with negative fetal fibronectin delivered within 5.7 +/- 3.9 days (P = 0.01). CONCLUSION: Presence of fetal fibronectin in cervical secretions seems to be a powerful tool to predict in a short delay the onset of labour at term, it should be used in conjunction with clinical and fetal assessment data.

Adult↗
PubMed1997

Real time validation of paediatric biochemical reports using the Valab-Biochem system.

Validation of biochemical reports must be fast and clinically accurate to be of assistance to clinicians. Considerable skill is required to analyse the consistency of different data in the report and to consider influences on the data. When performed throughout the day, such analysis is time-consuming and uncertain. We therefore decided to use a computer-assisted validation system, Valab-Biochem. Its decisions result from a decision tree based primarily on the intrinsic consistency of the data, validation ranges and patients' sex, age and hospital ward. Three hundred randomly chosen reports were simultaneously submitted to Valab-Biochem and to five biologists in order to analyse the computer's findings. The sensitivity of Valab-Biochem was 80% compared to biologists' consensus decision, which was taken as the gold standard. The specificity was 78%. This system provided autonomous assessment of the reports and could be used as an initial screen to assist biologists and focus attention on potentially inconsistent reports.

Artificial Intelligence↗
PubMed1996

EGF increases retinoid X receptor-alpha expression in human trophoblastic cells in culture: relationship with retinoic acid induced human chorionic gonadotropin secretion.

In the present study, the effect of retinoic acid (RA) and epidermal growth factor (EGF) on the functions of human trophoblastic cells in culture were analysed. In these cells, RA potentiated the hCG secretion increase induced by EGF. To gain a better understanding of such a synergistic effect, the expression of retinoic acid receptors (RAR alpha and beta) and retinoid X receptor (RXR alpha) was studied by immunoblotting in RA- and EGF-treated cells. EGF treatment specifically increased the level of RXR alpha protein and RXR alpha transcripts. In parallel, we demonstrated that the choriocarcinoma cells JEG 3, which respond to RA by an increase in hCG secretion, express constitutively high levels of RXR alpha protein. Furthermore, RXR alpha-transfected trophoblastic cells also become RA responsive for hCG secretion. All these data suggest that RXR alpha expression is modulated by EGF, and may be involved in the effect of RA on hCG secretion.

Cell Line, Transformed↗
PubMed1996

Hypoxia impairs cell fusion and differentiation process in human cytotrophoblast, in vitro.

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.

Actins↗
PubMed1996

Evaluation of clinical and laboratory parameters during 2 years of growth hormone treatment in prepubertal children with chronic renal failure.

UNLABELLED: Twelve prepubertal children with chronic renal failure (CRF) were treated with human growth hormone (GH) (1.2 IU/kg/week) for 2 years. High doses of GH clearly increased growth velocity, from 3.8 +/- 1.3 to 9.6 +/- 1.5 (P = 0.0001) and 6.9 +/0 0.8 cm/year (P = 0.0001) after the 1st and 2nd year of treatment, respectively, leading to a mean height gain of 1.4 SD. During the 1st year of treatment the height increment, expressed in SDS, correlated negatively with chronological age (P = 0.003). Basal insulin-like growth factor 1 (IGF 1) levels were normal or elevated (7/12 patients) and correlated positively with the overnight integrated GH concentration (r = 0.68, P < 0.001). Basal insulin-like growth factor binding protein 3 (IGF-BP3) levels were elevated in 8/12 patients. GH induced a significant increase in IGF 1 and IGF-BP3 levels; IGF 1 peaked after 6 months (when growth velocity was optimal) and IGF-BP3 peaked after 12 months. The mean glomerula filtration rate, measured by inulin clearance and corrected for body surface area, fell after the 1st year of treatment, and significantly so at the end of the 2nd year (P = 0.02). CONCLUSION: Early initiation of GH therapy during CRF may prevent severe growth retardation and allow these children to attain normal height before dialysis and transplantation.

Area Under Curve↗
PubMed1996

Vitamin A and retinoic acid stimulate within minutes cAMP release and growth hormone secretion in human pituitary cells.

In order to gain a better understanding on the possible role of vitamin A (VA) and retinoic acid (RA) on human growth hormone (GH) secretion, we used the physiological model of pituitary cells perifusion. In perifused cells from pituitary somatotropic adenomas, RA induced within minutes a peak of GH secretion. This effect was dose dependent, maximal effect being observed with 100 nM. The GH release was associated with a discharge of cAMP delayed by 4 to 8 minutes relative to the GH surge. Similar results were obtained after VA stimulation. Our observations provide the first evidence of an action of VA and RA on cAMP production. They suggest a role of RA and VA in the regulation of human GH secretion via the cAMP dependent pathway.

Adult↗
PubMed1995

Evaluation of liver toxicological effects induced by polyalkylcyanoacrylate nanoparticles.

Intravenous administration of drug-loaded polyalkylcyanoacrylate (PACA) nanoparticles is followed by a rapid uptake by the tissues of the reticuloendothelial system, mainly the liver. Nevertheless, it is so far unknown whether chronic administration of nanoparticles can lead to damage to the liver cells. We have studied the subacute toxicological effects of these drug carriers in a rat in vivo/ex vivo model. Nanoparticles were administered intravenously at a total dose of 200 mg/kg for 14 days (10 individual doses of 20 mg/kg). Hepatocytes were then isolated. Levels of alpha 1-acid glycoprotein secretion increased while albumin secretion decreased in hepatocytes from rats treated with PACA nanoparticles. In addition, glucose production due to the fructose metabolism was lowered. Treated rats induced a temporary increase and hyposialyation of serum alpha 1-acid glycoprotein. These effects were reversible 15 days after the treatment was concluded. Finally, the involvement of Kupffer cells and polymer degradation products was studied in vitro. Modifications of hepatocyte protein synthesis related to the treatments were only observed when direct contact between nanoparticles and hepatocytes existed. Kupffer cells and polymer degradation products did not mediate the hepatocyte response to nanoparticles in vitro. In conclusion, modifications in hepatic function after chronic administration of PACA nanoparticles have been detected by the use of very sensitive models for detecting hepatoxicity. These effects were, however, found to be reversible when the treatment was stopped.

Animals↗