Biomedical subjects

P De Mazancourt

Publications and source records attributed to P De Mazancourt.

6 recordsLinked to original sources

PubMed2005

Childhood hypophosphatasia due to a de novo missense mutation in the tissue-nonspecific alkaline phosphatase gene.

Hypophosphatasia is an inherited disorder due to mutations in the bone alkaline phosphatase (ALPL) gene. We report here a patient with childhood hypophosphatasia diagnosed at 1.4 yr because of pectus excavatum, large anterior fontanel, rachitic skeletal changes, and low serum alkaline phosphatase. Sequencing of the ALPL gene produced evidence of two distinct missense mutations, E174K (c.571G>A), of maternal origin, and a de novo mutation, M45I (c.186G>C). The study of various microsatellite polymorphisms ruled out false paternity and therefore confirmed that M45I occurred de novo in the paternal germline or in the early development of the patient. Site-directed mutagenesis showed that M45I results in the absence of in vitro alkaline phosphatase activity, suggesting that the mutation is a severe allele. In conclusion, childhood hypophosphatasia in this patient is the result of compound heterozygosity for the moderate mutation E174K and a novel severe de novo mutation M45I.

Adolescent↗

PubMed2003

Two novel fibrinogen variants found in patients with pulmonary embolism and their families.

BACKGROUND: The occurrence of dysfibrinogen is quite rare in comparison with other hemostatic defects, specially in cases of venous thrombosis. OBJECTIVES: Fibrinogen is known to have multiple functions, which are not evaluated by simple coagulation testing. We have used gel electrophoresis to search for new mutations. PATIENTS AND METHODS: Specimens of purified fibrinogen from 217 consecutive patients with familial or recurrent or early thrombosis and from 490 control subjects were evaluated by electrophoresis. Plasma fibrinogen levels and coagulation-dependent tests (electromechanical and optical coagulometric determinations, immunological measurement, thrombin and Reptilase(R) times) were normal. RESULTS: Two novel familial variants were detected. For a 42-year-old patient, an in-frame 117 base pair insertion in the Aalpha-chain gene caused a 5-kDa mobility shift of the Aalpha chain. This corresponds to a 39 amino acid duplication in the connector domain (fibrinogen Champagne au Mont d'Or). This pattern was also found in the patient's mother and child. A second 31-year-old patient presented an extra band under non-reducing conditions, 30 kDa larger than HMW fibrinogen and reacting with antifibrinogen antibodies (fibrinogen Lozanne). A heterozygous 5909A-->G mutation was found on the Bbeta-chain gene leading to heterozygous Bbeta Tyr236--> stop codon. The predicted truncated Bbeta chain could participate in chain assembly. Two family members were also affected, one of whom had suffered early venous thrombosis. CONCLUSIONS: Electrophoretic testing of apparently normal fibrinogens can reveal new variants which may be clinically relevant.

Adult↗

PubMed2001

Rapid and sensitive high-performance liquid chromatographic method for simultaneous determination of retinol, alpha-tocopherol, 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 in human plasma with photodiode-array ultraviolet detection.

A new rapid and sensitive high-performance liquid chromatographic method using 0.5 ml of plasma has been developed for the simultaneous determination of retinol (vitamin A), alpha-tocopherol (vitamin E), 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3. The eluate was monitored with a photodiode-array detector with two fixed wavelengths (267 nm for vitamin D, 292 nm for alpha-tocopherol and retinol). For all compounds, including internal standards, the method provides extraction recoveries greater than 81%. Detection limits were equal to or lower than 1.5 microg/l for the 4 vitamins. Linearity of standards was excellent (r>0.999 in all cases). Intra-day and inter-day precision were generally acceptable; the intra-dayassay C.V. was 3/4 7.7 for all compounds and the inter-day-assay C.V. was <9.2% except for the lower concentrations of 25-hydroxyvitamin D3, 25-hydroxyvitamin D2 and alpha-tocopherol (10.8, 11.8 and 11.9, respectively). The important properties of the present method are its ease of use, its rapidity, since sample preparation was achieved in 15 min and all the compounds were eluted in less than 15 min, and its small sample volume required (=0.5 ml), which enables it to be used in pediatric practice.

25-Hydroxyvitamin D 2↗

PubMed1996

Site-related differences in G-protein alpha subunit expression during adipogenesis in vitro: possible key role for Gq/11 alpha in the control of preadipocyte differentiation.

G protein alpha subunits were compared by immunoblotting in preadipocytes and adipocytes from rat subcutaneous and epididymal adipose tissue at three steps of adipogenesis. The most striking difference concerned the Gq/11 alpha subunits whose expression decreased during preadipocyte differentiation in subcutaneous cells while it remained constant in epididymal cells. The PKC inhibitor CGP 41251 increased glycerol 3-phosphate dehydrogenase activity (EC 1.1.1.8), a late marker of differentiation, in epididymal preadipocytes but not in subcutaneous cells. There was no difference in the proliferation capacities between subcutaneous and epididymal preadipocytes: in both cells, CGP 41251 led to the same decrease in [(3)H]thymidine incorporation and, at confluence, the amounts of Gq/11 alpha subunits were equivalent. No major site-related difference was found in the amounts of Gs and Gi alpha during adipogenesis. Thus, compared to epididymal preadipocytes, the higher capacity of subcutaneous preadipocyte to differentiate seems to be correlated with the decrease in Gq/11 alpha expression and the decreased Gq/11 mediated PKC activation.

Adipocytes↗

PubMed1995

Direct control of a large conductance K(+)-selective channel by G-proteins in adrenal chromaffin granule membranes.

We report here the presence of a Ca(2+)-independent K(+)-channel of large conductance in adrenal chromaffin cell secretory vesicle membranes which is controlled by inhibitory as well as stimulatory heterotrimeric GTP-binding proteins. Using antibodies against specific alpha subunits for immunoblot analysis, we were able to identify the presence of the inhibitory G(i)2 and G(i)3 subtypes, as well as the stimulatory G(o) and Gs subtypes, but not G(i)1 in adrenal chromaffin granules. Furthermore, functional analysis of the K(+)-channel incorporated into planar lipid bilayers showed that GDP beta S and GTP gamma S have opposite effects on channel activity inducing interconversions between a low and a high open-probability state. Consistent with these findings, the same antibodies antagonized the effects of the nonhydrolyzable analogues on the open probability of the K(+)-channel.

Adrenal Medulla↗

PubMed1994

Rat preadipocyte adenylyl cyclase: influence of fat localization and androgenic status.

The influence of androgenic status on basal and stimulated cAMP production, adenylyl cyclase activities and immunoblot quantified GS alpha and Gi alpha 2 subunits of the adenylyl cyclase regulatory proteins were compared in confluent preadipocytes from subcutaneous (SC) and deep-intraabdominal (epididymal) fat deposits. Maximal cAMP response to isoproterenol was lower in SC than in epididymal preadipocytes. After castration, this site-specific difference was suppressed. cAMP response to 2-chloroadenosine, which was identical in the two types of preadipocytes, was decreased by castration in epididymal cells but not in SC cells. The catalytic activity of adenylyl cyclase and its maximal response to GTP were higher in epididymal than in SC preadipocytes. This response to GTP was decreased by castration in epididymal preadipocytes while it remained unchanged in SC preadipocytes. The catalytic activity of adenylyl cyclase was unchanged by androgenic status whatever the cell localization. Levels of GS alpha quantified by immunoblotting were not modified whatever the androgenic status and cell origin. Levels of Gi alpha 2 were not affected by the androgenic status as well, but were lower in SC than in epididymal cells. This study shows that components of the adenylyl cyclase system in preadipocytes are differently regulated by the androgenic status depending on the anatomical origin of the cells.

Adenylyl Cyclases↗