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C Hubert

Publications and source records attributed to C Hubert.

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

Measurement of respiratory impedance by forced oscillation: comparison of the standard and head generator methods.

Physiological and clinical studies have shown that the standard method of measuring respiratory impedance by forced oscillation leads to less efficient control of the upper airway shunt effect than the head generator method. To test the effects of these two techniques in epidemiological studies, we compared, in a sample of 73 French agricultural workers, the values obtained with each method for five forced oscillation parameters: resistance, frequency dependence of resistance, inertance, compliance and resonant frequency. For these comparisons, subjects were classified according to four respiratory status factors: smoking status, cough, expectoration and airway obstruction assessed from the maximum expiratory flow volume curve. Logistic regression models using the set of four forced oscillation parameters (excluding resonant frequency, which is derived from compliance and inertance) were then used to analyse the ability of each method to classify the subjects in each group. Significant differences between the two methods were observed for the mean values obtained for all five parameters. However, when each parameter was considered separately, the correlations between the values for each method were significant. Each method possessed the necessary ability to separate subjects into our group classification, but the significant relationships were not always found for the same parameters. Finally, logistic regression models showed that the two methods led to almost the same classification of the subjects. According to our results, the standard method of applying forced oscillation at the mouth seems an acceptable device for measuring respiratory impedance for epidemiological purposes.

Airway Obstruction↗
PubMed1993

Functional analysis of the human somatic angiotensin I-converting enzyme gene promoter.

Angiotensin I-converting enzyme (ACE) is a key enzyme in the regulation of systemic blood pressure and plays a major role in the renin-angiotensin and bradykinin-kinin systems, at the luminal surface of the vascular endothelia. To identify the promoter region, the transcription regulatory elements and the cell specificity of the ACE gene, five successive DNA deletions of the 5' upstream region (-1214, -754, -472, -343, -132 bp relative to the start site of transcription) were isolated and fused in sense and antisense orientations to the bacterial chloramphenicol acetyltransferase (CAT) reporter gene in the promoterless plasmid pBLCAT3. Promoter activities were measured in transient transfection assays using three different cell lines from rabbit endothelium (RE), human embryocarcinoma (Tera-1) and hepatocarcinoma cells (HepG2). All five fragments of the ACE promoter region directed expression of the CAT gene when transfected into the endothelial and the embryocarcinoma cells, which contain endogenous ACE mRNA and express ACE activity. In contrast only minimal levels of promoter activity were obtained on transfection into hepatocarcinoma cells in which endogenous ACE mRNA and ACE activity were not detected. Transfection of RE and Tera-1 cells demonstrated that promoter activity was defined by the length of the ACE promoter sequence inserted into the construct. The 132 bases located upstream from the transcription start site were sufficient to confer ACE promoter activity, whereas the sequences upstream from -472 bp and between -343 bp and -132 bp were responsible for a decrease of promoter activity. Furthermore, the minimal 132 bp of the ACE promoter contains elements which direct cell-specific CAT expression. In addition, the DNA transfection study in the presence of dexamethasone suggested that the potential glucocorticoid regulatory elements, located in the sequence of the ACE promoter, are not functional.

Angiotensin I↗
PubMed1992

Functional study of the germinal angiotensin I-converting enzyme promoter.

Polymerase chain amplification experiments indicate that the germinal specific promoter of the angiotensin I-converting enzyme (ACE) is completely extinguished in somatic tissues. Despite this very strict specificity of expression, the germinal ACE promoter is active in transient transfection experiments in two somatic cell lines and one cell line of germinal origin. The analysis of the promoter shows the existence two regulatory elements within the first 350 bp: a proximal positive element and a distal negative element.

Animals↗
PubMed1991

Structure of the angiotensin I-converting enzyme gene. Two alternate promoters correspond to evolutionary steps of a duplicated gene.

Overlapping genomic clones containing the entire sequence of the human angiotensin I-converting enzyme (ACE) gene were isolated from a lamda phage human DNA library. This gene spans 21 kilobases (kb) and comprises 26 exons, ranging in size from 88 to 481 base pairs. Intron-exon boundaries were sequenced and the relative positions of the exons were mapped. The two different mRNAs transcribed from the ACE gene were assigned to their respective exons. The large endothelial type ACE mRNA (4.3 kb long) is transcribed from exon 1 to exon 26, excluding exon 13. The 3-kb long testicular ACE mRNA is transcribed from exon 13 to exon 26. Exon 13 encodes for the 67 amino acids of the NH2-terminal region of the testicular ACE, whereas downstream exons encode a sequence common to both isozymes. The gene duplication suggested by the internal homology of the endothelial ACE mRNA is now confirmed by the presence of two homologous clusters of eight exons (exons 4-11 and exons 17-24) having similar sizes and codon phases at exon-intron boundaries. The presence of two alternate promoters was investigated by ribonuclease protection assays. The different 5' ends of the two ACE transcripts revealed a promoter for the endothelial ACE mRNA in the 5'-flanking region of the first exon and a promoter for the testicular ACE mRNA situated in intron 12.

Bacteriophage lambda↗
PubMed1990

An insertion/deletion polymorphism in the angiotensin I-converting enzyme gene accounting for half the variance of serum enzyme levels.

A polymorphism consisting of the presence or absence of a 250-bp DNA fragment was detected within the angiotensin I-converting enzyme gene (ACE) using the endothelial ACE cDNA probe. This polymorphism was used as a marker genotype in a study involving 80 healthy subjects, whose serum ACE levels were concomitantly measured. Allele frequencies were 0.6 for the shorter allele and 0.4 for the longer allele. A marked difference in serum ACE levels was observed between subjects in each of the three ACE genotype classes. Serum immunoreactive ACE concentrations were, respectively, 299.3 +/- 49, 392.6 +/- 66.8, and 494.1 +/- 88.3 micrograms/liter, for homozygotes with the longer allele (n = 14), and heterozygotes (n = 37) and homozygotes (n = 29) with the shorter allele. The insertion/deletion polymorphism accounted for 47% of the total phenotypic variance of serum ACE, showing that the ACE gene locus is the major locus that determines serum ACE concentration. Concomitant determination of the ACE genotype will improve discrimination between normal and abnormal serum ACE values by allowing comparison with a more appropriate reference interval.

Adult↗
PubMed1990

The angiotensin I-converting enzyme (kininase II): progress in molecular and genetic structure.

The complete amino acid sequence of the human angiotensin I-converting enzyme (ACE) has been determined by protein sequencing of the purified kidney enzyme and cDNA cloning in endothelial cell libraries. The ACE molecule comprises 1,306 amino acids. It possesses a signal peptide of 29 residues cleaved off during maturation. The enzyme is most likely anchored to the plasma membrane by a short transmembrane domain situated near the carboxy-terminal extremity. Interestingly, the molecule presents a high degree of internal homology between two large peptidic domains. Each of these domains contains short sequences identical to zinc binding and active site sequences of other zinc metallopeptidases and therefore bears a putative active site. However, earlier experiments indicate only one zinc atom bound per molecule of ACE. Competitive inhibitors seem to interact with a unique class of high-affinity binding site. These observations may suggest that, despite the duplicated structure of the enzyme, there is only one functional active site per molecule of ACE. The respective role of the two homologous domains in this active site remains to be determined. A single gene coding for ACE is present in humans, transcribed as a 4.3-kilobase mRNA species in endothelial cells. In other studies, evidence for a genetic polymorphism in plasma ACE levels has been obtained by analyzing a large group of "healthy" nuclear families. A familial association of plasma ACE levels was observed. A major gene effect can possibly explain part of the interindividual variability observed in this enzyme.

Amino Acid Sequence↗
PubMed1989

The testicular transcript of the angiotensin I-converting enzyme encodes for the ancestral, non-duplicated form of the enzyme.

The endothelial angiotensin I-converting enzyme (ACE) is organized in two large homologous domains, each bearing a putative active site. However, only one of these sites is probably involved in catalyzing the conversion of angiotensin I into angiotensin II. The testicular form of ACE is equally active, encoded by the same gene, but translated from a shorter mRNA. Molecular cloning of the human testicular ACE cDNA indicates that the mRNA codes for 732 residues (vs 1306 in endothelium). The testicular transcript corresponds to the 3' half of the endothelial transcript and encodes one of the two homologous domains of endothelial ACE, preceded by a short specific sequence. This 5' specific sequence contains 228 nucleotides and encodes 67 amino acids, including the putative signal peptide followed by a serine/threonine-enriched region, presumably glycosylated. The testicular transcript corresponds to the ancestral, non-duplicated form of the ACE gene. Since the carboxyl-terminal domain of the endothelial ACE is expressed in the testicular enzyme, it is likely that it bears the active site in both forms.

Amino Acid Sequence↗
PubMed1989

Computed tomography of retained abdominal sponges and towels.

The diagnosis of retained sponges and towels a year or more after surgery is often very difficult. We describe the computed tomographic (CT) findings in 4 patients with this complication; 2 cases of retained sponges and 2 cases of retained towels. While the CT appearance of the retained sponges was not specific, the particular appearance of the retained towels had not been previously described. This appearance is characteristic enough to suggest the correct diagnosis before reoperation.

Abdomen↗
PubMed1989

The angiotensin converting enzyme in the kidney.

Immunohistochemical studies and experiments with microdissected nephron segments indicate that the angiotensin I converting enzyme (ACE) in the kidney is expressed in the vascular endothelial cells of the renal vessels and in the epithelial cells of the proximal convoluted tubule and the pars recta. Angiotensin converting enzyme is a membrane-bound zinc metallopeptidase and the primary structure has recently been determined by protein sequencing and molecular cloning. It is probably anchored to the cell membrane by a single, short, transmembrane domain located near the carboxy-terminal extremity. The larger, externally situated, amino-terminal part of the molecule is organized in two large, highly homologous domains, each with a putative active site. The function of the endothelial enzyme in the renal vessels is primarily related to angiotensin II (Ang II) formation. However, its level of expression in renal vessels, especially at the glomerular level, appears to be very low in the adult human kidney, and there is evidence that the conversion of angiotensin I (Ang I) may be a rate-limiting step in Ang II formation in the kidney. The vascular enzyme may also contribute to the inactivation of kinins in the peritubular circulation. In the epithelial cells of the proximal tubule, ACE is present in both the brush border and the basolateral membrane. Although the basolateral enzyme may be involved in Ang II formation in the peritubular interstitium, the function of the enzyme on the brush border is unknown. The effects of ACE inhibitors on renal function are primarily, if not exclusively, related to Ang II suppression and perhaps kinin potentiation in the renal circulation.

Endothelium, Vascular↗
PubMed1989

The peculiar characteristics of the amino acid sequence of angiotensin I-converting enzyme, as determined by cDNA cloning of the human endothelial enzyme.

The angiotensin-I converting enzyme (ACE) is a membrane bound zinc metallopeptidase of the vascular endothelial cell. Recently, the complete amino-acid sequence of human ACE has been determined by protein sequencing and cDNA cloning in endothelial cell libraries. The ACE is encoded from a 4.3 kb transcript and comprises 1,306 amino acids. The molecule comprises a signal peptide of 29 residues cleaved off during maturation. It is most likely anchored by a short transmembrane domain situated near the carboxyterminal extremity. Interestingly, the molecule presents a high degree of internal homology between two large peptidic domains. Each of these domains contains short sequences identical to zinc binding and active site sequences of other zinc metallopeptidases and therefore bears a putative active site. The ACE gene results probably from duplication and fusion of a more ancestral gene, coding for a putative nonduplicated enzyme. However, despite the duplicated structure of ACE, it has been reported that there is only one zinc atom bound per molecule. Competitive inhibitors seem to interact with a unique high affinity binding site. Therefore, there is only one active site in ACE whose location remains to be determined.

Amino Acid Sequence↗
PubMed1989

[Post-transfusion cytomegalovirus infection in premature infants weighing less than 1,500 g].

The incidence of cytomegalovirus (CMV) infection among 107 low birth weight transfused infants (birth weight less than or equal to 1,500 g) admitted to an intensive care nursery over an 18 month period was evaluated. The diagnosis of CMV infection was based on specific serologic tests (presence of IgM, increased IgG by ELISA technic) and identification of the virus in the urine. During the first 8 months, the infants received untested blood and CMV disease occurred in 8 infants out of 44 (18.2%). During the following 10 months, all transfusions performed in 63 infants were supposed to be CMV negative. However, 32 infants received untested blood due to emergency, and 5 of them developed a CMV infection (15.6%). Finally, only 31 infants received CMV negative blood without any case of CMV infection. These data clearly demonstrate that, considering the severity of the CMV disease in the premature infants, transfusions should be performed with CMV negative blood products.

Cytomegalovirus↗
PubMed1988

Recent data on the structure of rabbit milk protein genes and on the mechanism of the hormonal control of their expression.

Mammary explants or isolated mammary cells from rabbit have been cultured in the presence of insulin, prolactin and cortisol alone or in combination. The cellular content in alpha s1-casein, beta-casein and whey acidic protein (WAP) mRNA have been evaluated using the corresponding cDNA as probes. In all cases alpha s1-casein mRNA was the most abundant and WAP mRNA the least abundant mRNA. The three genes showed essentially similar dependency towards hormones. Prolactin stimulated mRNA accumulation and insulin and cortisol amplified this stimulation. The induction by prolactin was rapid whereas stimulation by insulin was slower. Fragments of rabbit genomic DNA inserted in lambda phage and containing alpha s1-casein, and WAP genes have been cloned. The primary sequence around the CAP site of the three genes has been established. A comparison of the sequences located upstream from the CAP site shows several striking homologies with the corresponding genes from cow, rat and guinea-pig. This suggests that these sequences participate in the transcriptional control of the genes by hormones. The mechanism involved in the transduction of the prolactin message to milk protein genes in unknown. Using mammary explants in culture, several classical mechanisms of transduction have been examined. Phorbol ester, phorbol -12, 13-dibutyrate (PdiBu) inhibited prolactin action. However, another tumor promoter, 12-O-tetradecanoyl phorbol-13-acetate (TPA), did not alter prolactin action. Kinase C inhibitor H7 did not prevent prolactin action and did not overcome the inhibition by PdiBu. Kinase C is therefore not essential for the transduction of the prolactin message to milk protein gene. Neomycin, which inhibits phosphatidylinositol hydrolysis by phosphorylase C, prevented prolactin action, whereas other inhibitors of phosphatidylinositol metabolism remained uneffective. Degradation of phosphatidylinositol is therefore likely not an essential step of prolactin action on milk protein genes. Inhibitors of tyrosine kinase and phosphatase exhibited a poor capacity to modify the prolactin response. Hence, transduction mechanisms using tyrosine kinase activity likely cannot account for prolactin action.

Animals↗