Biomedical subjects

S Leclerc

Publications and source records attributed to S Leclerc.

53 records · Page 3Linked to original sources

PubMed1995

Imperforate anus, malrotation and Hirschsprung's disease: a rare association.

The association of imperforate anus with anomalies of rectal innervation is very rare. Moreover, malrotation only rarely accompanies these malformations. We report 2 patients with this unusual triple association and its impact on their management. Retrospectively both patients presented at birth with the same radiological picture of distended distal colon and right-sided small bowel location. We discuss the importance of a systematic search for associated intestinal malformations in cases of imperforate anus in order to avoid serious complications and to choose the optimal operative strategy.

Anastomosis, Surgical↗

PubMed1995

Selective splenic artery embolization or use of polyglycolic acid mesh in children with severe splenic trauma.

Children with splenic trauma are managed conservatively in most circumstances, and the need for surgical intervention is very rare. When surgical exploration in mandatory, splenic preservation is a worthwhile objective, using various suture methods, biomaterials, or resorbable prostheses. We present our experience over the past year with 5 severe splenic injuries. Three of these patients were treated operatively with a resorbable mesh, while the other two were managed percutaneously by selective embolization of the splenic artery under fluoroscopic control. We describe the embolization technique with its advantages, good outcome with low morbidity, and low economic and social cost.

Adolescent↗

PubMed1995

Overlapping cis-acting elements located in the first intron of the gene for type I 3 beta-hydroxysteroid dehydrogenase modulate its transcriptional activity.

High levels of expression for the gene encoding human type I 3 beta-hydroxysteroid dehydrogenase (3 beta-HSDI) have been detected in placenta and skin but not in adrenals, which, however, express high levels of type II 3 beta-HSD. In this study, we addressed the issue of whether the differential pattern of cell-specific expression for type I 3 beta-HSD can be explained by the differential utilization of cis-acting regulatory elements present in the 3 beta-HSDI gene regulatory sequences. Deletion analyses indicated that removal of intron 1 strongly impaired the transcriptional activity directed by the 3 beta-HSDI basal promoter. Consequently, we focused our attention to the characterization of the 128 base pair first intronic sequence from the 3 beta-HSDI gene. A single protected region, designated the 3 beta I-A element, was identified by DNase I footprinting. Gel mobility shift assays indicated that at least four nuclear proteins with distinct biochemical and binding properties possess the ability to bind the 3 beta I-A element to produce four DNA-protein complexes (R1 to R4). However, the one producing R1, a 37-kilodalton protein that has been found in both human choriocarcinoma JEG-3 and adrenal cortex adenocarcinoma SW13 cells, as well as in all tested tissue culture cells, clearly accounts for the major 3 beta I-A-binding species. Site-directed mutagenesis provided the evidence that the 3 beta I-A element acts positively on the 3 beta-HSD-I gene promoter-mediated transcriptional activity upon transient transfection of both JEG-3 and SW13 cells. No homology has been found between the 3 beta I-A element and target sequences for other known transcription factors. In addition, of the four proteins binding the 3 beta I-A element, that producing R2 was identified as the positive transcription factor Sp1, whereas the identity of the remaining factors is still unknown. This is consistent with the presence of an Sp1 motif overlapping the 3 beta I-A element in intron 1, therefore pointing toward an important function played by this particular region in 3 beta-HSDI basal, but not cell-specific, gene expression.

3-Hydroxysteroid Dehydrogenases↗

PubMed1994

The rat growth hormone proximal silencer contains a novel DNA-binding site for multiple nuclear proteins that represses basal promoter activity.

Cell-type-specific expression of the rat growth hormone (rGH) gene is determined by the interaction of both positive as well as negative regulatory proteins with cis-acting elements located upstream of the rGH mRNA start site. We have recently shown that the rat liver transcription factor NF1-L binds to the proximal rGH silencer (called silencer-1) to repress its transcriptional activity. However, this single factor proved to be insufficient by itself to confer cell-specific gene repression. We therefore attempted to identify other regulatory proteins interacting with silencer 1, which might be needed to achieve full cell-specific repression of that gene. A common recognition site for three yet uncharacterized nuclear proteins (designated as SBP1, SBP2 and SBP3) which bind a DNA sequence adjacent to the NF1-L-binding site in the rGH silencer-1 element were identified. UV crosslinking of DNA/protein complexes and nuclear protein fractionation/renaturation from SDS/polyacrylamide gels further indicated that the molecular masses for SBP1-3 are 41, 26 and 17 kDa respectively, the major species being the 26-kDa protein (SBP2) which account for 83% of the shifted SBP double-stranded oligonucleotide in gel mobility-shift assays. For this reason, most of this study focussed on the characterization of SBP2. We demonstrated that binding of NF1-L and SBP2 to their respective recognition sequence is a mutually exclusive event. Although an SBP-binding activity has been found in every non-pituitary tissue or cell line tested, no such activity could be detected in either rat pituitaries or rat pituitary GH4C1 cells. Insertion of the SBP element upstream of the basal promoter of the mouse p12 heterologous gene resulted in a consistent decrease in chloramphenicol acetyl transferase reporter gene expression following transient transfections in non-pituitary cells only, suggesting that the related SBP1-3 proteins might be involved in generally repressing gene transcription in a cell-specific manner.

Animals↗

PubMed1994

Inhibition of cyclin-dependent kinases by purine analogues.

While testing purines related to the non-specific protein kinase inhibitors N6-dimethylaminopurine and N6-(delta 2-isopentenyl)adenine as potential inhibitors of the p34cdc2/cyclin B kinase, we discovered a compound with high specificity, 2-(2-hydroxyethylamino)-6- benzylamino-9-methylpurine (olomoucine). Kinetic analysis of kinase inhibition reveals that olomoucine behaves as a competitive inhibitor for ATP and as a non-competitive inhibitor for histone H1 (linear inhibition for both substrates). The kinase specificity of this inhibition was investigated for 35 highly purified kinases (including p34cdk4/cyclin D1, p40cdk6/cyclin D3, cAMP-dependent and cGMP-dependent kinases, eight protein kinase C isoforms, calmodulin-dependent kinase II, myosin light-chain kinase, mitogen-activated S6 kinase, casein kinase 2, double-stranded RNA-activated protein kinase, AMP-stimulated kinase, eight tyrosine kinases). Most kinases are not significantly inhibited. Only the cell-cycle regulating p34cdc2/cyclin B, p33cdk2/cyclin A and p33cdk2/cyclin E kinases, the brain p33cdk5/p35 kinase and the ERK1/MAP-kinase (and its starfish homologue p44mpk) are substantially inhibited by olomoucine (IC50 values are 7, 7, 7, 3 and 25 microM, respectively). The cdk4/cyclin D1 and cdk6/cyclin D3 kinases are not significantly sensitive to olomoucine (IC50 values greater than 1 mM and 150 microM, respectively). N6-(delta 2-Isopentenyl)adenine is confirmed as a general kinase inhibitor with IC50 values of 50-100 microM for many kinases. The purine specificity of cyclin-dependent kinase inhibition was investigated: among 81 purine derivatives tested, only C2, N6 and N9-substituted purines exert a strong inhibitory effect on the p34cdc2/cyclin B kinase. An essentially similar sensitivity to this olomoucine family of compounds was observed for the brain-specific cdk5/p35 kinase. Structure/activity relationship studies allow speculation on the interactions of olomoucine and its analogues with the kinase catalytic subunit. Olomoucine inhibits in vitro M-phase-promoting factor activity in metaphase-arrested Xenopus egg extracts, inhibits in vitro DNA synthesis in Xenopus interphase egg extracts and inhibits the licensing factor, an essential replication factor ensuring that DNA is replicated only once in each cell cycle. Olomoucine inhibits the starfish oocyte G2/M transition in vivo. Through its unique selectivity olomoucine provides an anti-mitotic reagent that may preferentially inhibit certain steps of the cell cycle.

Animals↗

PubMed1994

Minimally conjoined omphalopagi: a consistent spectrum of anomalies.

Omphalapagus twins constitute less than one third of all siamese twins. Most omphalopagi are attached by a skin bridge that often contains hepatic tissue. Only four cases of omphalopagi attached by an intestinal bridge have been reported. The authors present two additional cases of conjoined twins minimally attached by a small bowel and bladder bridge. In both instances, the spectrum of anomalies included a ruptured omphalocele and imperforate anus with cloacal anomalies. The attachment consisted of an open urachal remnant joining the two bladders, and the short small bowel of twin A attached to the terminal ileum of twin B. Separation was uneventful. For one set of twins, the case part of the proximal colon of twin B was used to lengthen the bowel of twin A. Three of the twins survived and underwent additional procedures for repair of the cloacal anomalies. All four previously reported cases of minimally conjoined omphalopagi presented with a remarkably similar spectrum of anomalies. All had ruptured omphaloceles, imperforate anus with cloacal anomalies, and urachal anomalies. Intestinal connection was consistently at a point corresponding to the Meckel diverticulum site of twin B, with blood supply to the small bowel of twin A, probably via the vitelline artery. The consistent spectrum of anomalies encountered with minimally conjoined omphalopagi allows planning of separation. Caution is required to avoid overlooking the patent urachus, and intestinal lengthening procedures based on the vitelline artery become an important consideration.

Anus, Imperforate↗

PubMed1992

Transcription of the mouse secretory protease inhibitor p12 gene is activated by the developmentally regulated positive transcription factor Sp1.

We have previously shown that a trans-acting protein produced in some tissue culture cells positively control the transcriptional activity directed by the mouse p12 promoter. This nuclear protein exerts its positive activity by interacting with a regulatory sequence designated p12.A and located between the TATA and CCAAT box elements on the p12 gene promoter. Using DNase I and dimethyl sulfate methylation interference footprinting techniques coupled with gel retardation assays, we found evidence that the protein which binds to the p12.A element is the well-known transcription factor Sp1. Mutational analysis in transient transfection assays confirmed the positive activity exerted by this protein in every cell line tested. In agreement with this observation, we detected a p12.A-Sp1 binding activity in nuclear extracts prepared from all cell lines used. However, a similar binding activity could not be detected in a number of nuclear extracts prepared from normal mouse tissues. In this report, we provide the evidence that the lack of Sp1-binding activity results from the degradation of Sp1 in the kidney, liver, and pancreas of the mouse.

Animals↗

PubMed1991

Purification of a human glucocorticoid receptor gene promoter-binding protein. Production of polyclonal antibodies against the purified factor.

The glucocorticoid receptor (GR) is an essential protein involved in mediating glucocorticoid-regulated gene transcription. The cellular GR concentration is modulated by a number of factors including glucocorticoids, which are capable of down-regulating their own receptor concentration. To further study this phenomenon, the human GR (hGR) gene promoter was isolated and was shown to contain the sequences essential for glucocorticoid-dependent down-regulation in CV-1 cells by gene transfer. Further transfections performed with the hGR gene demonstrated that the nucleotide sequence between -250 and -750 is implicated in the down-regulation of the hGR by hormone. The promoter region of human GR is extremely rich in G+C sequences which are known to be involved in the regulation of many housekeeping genes such as GR, as well as a number of cellular oncogenes. Using a combination of partial purification of DNA-binding proteins, DNA-protein interaction by gel shift analysis and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we have identified a protein factor (GRF-1) of 95 kDa which interacts with the human GR gene fragment implicated in homologous down-regulation. Polyclonal antibodies were then raised against the protein following purification. This method of purification and identification may be universally applied to purify and characterize unknown factors which may be involved in the regulation of genes such as hGR gene.

Amino Acid Sequence↗

PubMed1991

Differential regulation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase chimeric gene by human mineralocorticoid hormone-receptor complexes.

The brain tissues of the rat and mouse express two types of corticosteroid binding proteins, the glucocorticoid (GR) and aldosterone (MR) receptors. Unlike the type II (GR) receptor, type I receptor has a high affinity for aldosterone (ALDO) and corticosterone and is structurally similar to the kidney mineralocorticoid receptor (MR). The results reported in this study provide direct evidence for the interaction of dexamethasone (DEX), triamcinolone acetonide (TA), dexamethasone-21-mesylate (DXM) and 11-deoxycorticosterone (DOC) with human MR expressed in cells by transient co-transfection of a hMR expression vector. The interactions of hMR with DEX, TA, DXM, DOC, promegestone (R5020) and methyltrienelone (R1881) were measured by trans-activation of mouse mammary tumor virus long terminal repeat fused to bacterial chloramphenicol acetyltransferase (MMTV-tk-CAT) in gene co-transfection experiments and by cell free hormone binding assay. The incubation of various steroid hormones in the presence of [3H]ALDO in a competition assay with extracts prepared from HeLa cells co-transfected with hMR expression vector, showed that hMR expressed under these conditions has a high relative affinity for DEX which is similar to ALDO, TA and DOC. Incubation with DXM under these conditions showed very little competition, as was observed with R1881 and R5020. Incubation of the co-transfected cells with DEX, ALDO, DOC, R5020, TA, R1881 and DXM demonstrated that the level of trans-activation did not reflect the previously observed order of binding affinity for the hMR. The level of transactivation was always higher with DEX and TA compared to ALDO and DOC. Analysis of the binding of labeled glucocorticoid regulatory element (GRE) and hMR incubated with DEX, ALDO and DXM by gel shift analysis demonstrated that the trans-activation of MMTV-tk-CAT by hMR is a result of the interaction of hMR with GRE in the MMTV-LTR.

Animals↗

PubMed1991

Human glucocorticoid receptor gene promotor-homologous down regulation.

To study the regulation of the human glucocorticoid receptor (hGR), we characterized the promoter region by primer extension, S1 nuclease mapping and by DNA sequencing. We found that the promoter is extremely G + C rich (72% GC content) and contains a "TAATA" and a "CAT" box, eight "GGGCGG", three "CCGCCC" and two "CACCC" motifs and a motif similar to the glucocorticoid responsive element (GRE) which included two interchanged nucleotides "TCTTGT". In contrast to other steroid receptor genes, exon I or GHGR contains the major part of the 5' non-coding sequences of hGR mRNA while exon II contains coding sequences for the first 394 amino acid residues of the A/B region of hGR. The major transcriptional start site was found to be 134 bp upstream of the ATG initiation codon. Transfection of HeLa cells with plasmids containing various deletions of GHGR promoter fused to a promoterless CAT vector suggested the region between -470 and -1030, at the 5' end of the mRNA start site, to contain sequences required for down regulation by hormone.

Amino Acid Sequence↗

PubMed1987

Morphological and electrophysiological characteristics of somatosensory thalamocortical axons studied with intra-axonal staining and recording in the cat.

The intracortical arborizations of thalamocortical fibers arising from the ventroposterolateral (VPL) nucleus in the cat were studied following intra-axonal injections of horseradish peroxidase (HRP). The axons were impaled 1.5 to 3 mm below the surface of the cortex, identified electrophysiologically by stimulating the VPL nucleus and functionally by stimulating the somatic receptive field with natural stimuli. Many of the results obtained in a previous study using similar techniques (Landry and Deschênes 1981) were confirmed by the present experiments. Fibers activated by cutaneous stimulation arborized either in area 3b or 1 but some did send branches to both areas. Also, the intracortical arborization of a rapidly adapting cutaneous afferent fiber in area 2 is described. The size and tangential extent of the fiber in area 2 are similar to those arborizing in other areas of the primary somatosensory cortex and consist of multiple patches separated by uninvaded gaps. One fiber activated by stimulation of deep tissue receptors gave rise to two bushes that arborized along a rostrocaudal axis exclusively in area 3b. Terminal boutons and varicosities were found mostly in layers VI, IV, the bottom third of III and the upper portion of V, but some fibers did send a few collateral branches to layer II and the bottom part of layer I. The results suggest that in the forebrain representation, the same modality and submodality can be recorded in more that one cytoarchitectonic area but that areas 3b, 1 and 2 should not be considered as a single functionally homogeneous area. Counts of terminals suggest that a single fiber arborizing in area 1 makes as many as 3 times the number of synapses made in area 2 or 3b. Since fibers appear to be modality and submodality specific, if convergence of modality, submodality and/or body areas occur in the cortex, then this must be preferentially, but not exclusively, done by thalamic fibers of different functions which arborize in the same cytoarchitectonic area and synapse upon a shared postsynaptic target. In the same experiments intra-axonal recordings revealed the presence of two hyperpolarizing after potentials elicited by a preceding action potential. The first after potential was associated with a decrease in excitability of the fiber and an increase in membrane resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

PubMed1985

High density lipoprotein cholesterol, habitual physical activity and physical fitness.

The relationships between habitual physical activity and fitness parameters and fasting serum high density lipoprotein cholesterol (HDL-C), total cholesterol (TC), and triglycerides (TG) were assessed in 357 men aged 30-59 years (mean 44, SD 5). A progressive submaximal power output test (PWC150), a 1-min sit-up test, and a 3-day activity energy expenditure record were obtained for each subject. HDL-C, TG, and HDL-C/TC were significantly associated with the fitness indices (PWC150 and sit-ups), but not with the mean daily energy expenditure computed from a 3-day activity record. However, when the subjects were stratified according to the maximal level of intensity reported in the work and leisure energy expenditure record, a relationship between maximal exercise or work intensity and the concentration of HDL-C and TG, and the ratio HDL-C/TC was found. When adjusted by multiple regression procedures for age, alcohol consumption, cigarette smoking, socio-economic status, fatness level, and TC, or TG, or HDL-C, as appropriate, these relationships became nonsignificant, with the exception of TG and PWC150. These results suggest that habitual physical activity of light intensities is not a major determinant of HDL-C, TC, and HDL-C/TC; it could, however, have a small but significant role in TG. In addition, data suggest that periods of exercise of higher intensity, i.e. with an energy cost of about 6 mets and more, could be a sensible mean to influence serum blood lipid levels.

Adult↗

PubMed1983

Association between serum high-density lipoprotein cholesterol and body composition in adult men.

The relationships between measurements of body composition and fasting serum high-density lipoprotein cholesterol (HDL-C) were assessed in 357 men aged 30 to 59 years. The sum of six skinfolds (triceps, biceps, subscapular, suprailiac, abdominal and medial calf), body density through underwater body weighing, lean body mass (kg), body-fat mass, and percent body fat, all three derived from the Siri equation, were obtained. Effects of age, sex, alcohol consumption, cigarette smoking, socioeconomic status, triglycerides, total cholesterol and current energy expenditure were statistically removed through multiple regression procedures. HDL-C was significantly associated with weight, weight/height, weight/height11, weight/height16, body density, body-fat mass, sum of six skinfolds, but not with height alone or lean body mass. These results suggest that, among the body composition measurements, the adipose component is the major contributor to the low but significant association between HDL-C and weight.

Adult↗

PubMedDate not supplied

[Multinucleate cells angiohistiocytoma].

INTRODUCTION: Multinucleate cell angiohistiocytoma is a rare entity. We report two unusual cases of this lesion. CASE REPORT: A 39 year-old man had presented since two years an arciform papular eruption of the forehead. A 40 year-old woman had a disseminated maculo-papular eruption since three years. Histological examination of skin samples of the two patients showed a dermal small vessel proliferation, associated with multinucleate cells, and confirmed the diagnosis of multinucleate cell angiohistiocytoma. DISCUSSION: Our cases, typical histologically, have unusual clinical presentation (first case observed in a man, and the second in a disseminated form). Multinucleate cell angiohistiocytoma is a rare benign vascular proliferation individualized in 1985. Clinically, the lesion consists in small circumscribed papules. Acral sites and notably of the dorsum of the hands are the more frequent topography. It generally occurs in women aged over 50 years. Histologically, there is a dermal proliferation of capillaries and venules, and a fibrosis associated with the interstitial mononucleate cells and multinucleate cells.

Adult↗

PubMedDate not supplied

Properties and potential-applications of chemical inhibitors of cyclin-dependent kinases.

Cyclin-dependent kinases (CDKs) trigger and co-ordinate the cell division cycle phases. They also play a role in neuronal cells and in the control of transcription. Intensive screening has led in the past few years to the identification of a series of chemical inhibitors of CDKs. Some of these compounds display remarkable selectivity and efficiency (IC50 <25 nM). Many have been co-crystallised with CDK2, and their atomic interactions with the kinase have been analysed in detail: all are located in the ATP-binding pocket of the enzyme. These inhibitors are antimitotic, they arrest cells in G1 and, at higher doses, in G2/M. Furthermore, they facilitate or even trigger apoptosis in proliferating cells. In contrast, they protect neuronal cells from apoptosis. The potential use of these inhibitors is being extensively evaluated in cancer chemotherapy (clinical trials, Phase I and II). Possible clinical applications are being investigated in other fields: cardiovascular (restenosis, tumoural angiogenesis, atherosclerosis), nephrology (glomerulonephritis), dermatology (psoriasis), parasitology (unicellular parasites such as Plasmodium, Trypanosoma, Toxoplasma, etc.), neurology (Alzheimer's disease), viral infections (cytomegalovirus, human immunodeficiency virus, herpes). We anticipate the discovery of novel selective and powerful inhibitors in the near future, and hope for their efficient applications in various human diseases.

Cell Division↗

PubMedDate not supplied

Search for androgen response elements in the proximal promoter of the canine prostate arginine esterase gene.

We have demonstrated the binding of the recombinant DNA binding domain of the rat androgen receptor to a DNA sequence of the canine prostate arginine esterase gene and have determined the functional significance of this sequence in transient transfection experiments. One of the binding sites was localized to a region (-172 to -148 bp) containing the sequence AGGACAACAGGTGTT that has 73% homology with the prostate-specific antigen (PSA) androgen response element (ARE) found at a similar position in the PSA promoter. Competition experiments showed that the androgen receptor had an approximately 100-fold more affinity for the PSA ARE than for the arginine sequence at -172 to -148. Transient cotransfection of 5'-deletion mutants of the arginine esterase promoter and 5'-flanking sequences driving the activity of the reporter gene along with the rat androgen receptor expression vector yielded only negligible inductions of chloramphenicol acetyl transferase (CAT) activity when dihydrotestosterone (DHT) was added to the culture medium. The introduction of one to four repeats of the -172 to -148 sequence of the arginine esterase gene upstream of the basal promoter of the mouse p12 gene in p12.108 also resulted in a minimal induction of CAT activity compared with a 10-fold induction of PSA AREs under similar conditions. These results suggest that the regulation of the canine arginine esterase gene by androgens is most probably achieved by mechanisms that differ from the ones prevailing with the human PSA and kallikrein-2 (hKLK2) genes.

Androgens↗

PubMedDate not supplied

Transcriptional regulation of the alpha 4 integrin subunit gene in the metastatic spread of uveal melanoma.

Recently, expression of the alpha 4 integrin subunit has been shown to be inversely correlated with the invasive potential of B16 mouse epidermal melanoma. The purpose of this study was to establish whether expression of the human alpha 4 integrin subunit gene might be similarly regulated in human uveal melanoma which has varying degrees of invasiveness, and whether such modifications are determined by alterations in the transcriptional activity directed by the alpha 4 gene promoter. Two metastatic variants (MH5 and MH10) derived from a human uveal melanoma (SP6.5) were used. Expression studies were performed by transiently transfecting each of these cell lines with recombinant plasmids bearing various lengths of the alpha 4 promoter fused to the CAT reporter gene, and were further validated by Northern blot analyses of the alpha 4 transcript. Both transient transfection and mRNA analyses provided evidence that the transcriptional activity directed by the alpha 4 promoter sequences extending up to position -76 and -120 was indeed inversely correlated to the potential of uveal melanoma to yield metastasis. Experiments in electrophoretic mobility shift assay (EMSA) demonstrated that binding of the nuclear proteins that likely account for transcription of the alpha 4 gene to alpha 4.1 (namely Bp1, Bp2, Bp4, and Bp5) was dramatically reduced in uveal melanoma, but not in normal uveal melanocytes. These results highlight the fundamental function the alpha 4 integrin subunit may play in the ability of tumor cells to evade the primary tumor and form metastasis.

Adolescent↗