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Biomedical subjects

I Le Blanc

Publications and source records attributed to I Le Blanc.

15 recordsLinked to original sources
PubMed2001

HTLV-1 structural proteins.

HTLV-1 structural proteins do not appear to ensure virus transmission as efficiently as most other retrovirus structural proteins do, whereas all other retroviruses can be transmitted via either free virions or cell-to-cell contacts, infection by HTLV-1 by free virions is very inefficient, and effective infection requires the presence of HTLV-1 infected cells. This characteristic feature of HTLV-1 provides a unique tool which can be used to analyse retrovirus cellular transmission in the absence of simultaneous cell-free infection. Here we summarise what is known about HTLV-1 structural proteins and identify the questions about these proteins which remain to be answered.

Amino Acid Sequence↗
PubMed2000

A 37 base sequence in the leader region of human T-cell leukaemia virus type I is a high affinity dimerization site but is not essential for virus replication.

Mutagenesis has demonstrated a region in the human T-cell leukaemia virus type I (HTLV-I) 5' leader RNA which, when deleted, abolishes stable RNA dimer formation in vitro. We have further mapped, using both in vitro transcribed and synthesized RNA, this site to a 37 base region, which dimerizes with high affinity. When deleted from an HTLV-I Gag-Pol-expressing plasmid which was co-transfected with an envelope protein expressor to produce virions capable of single round infection, the dimer linkage deletion did not affect viral protein production. In addition, virus infectivity was only slightly reduced, to approximately 75-80% of the wild-type.

5' Untranslated Regions↗
PubMed1999

Early assembly step of a retroviral envelope glycoprotein: analysis using a dominant negative assay.

As for most integral membrane proteins, the intracellular transport of retroviral envelope glycoproteins depends on proper folding and oligomeric assembly in the ER. In this study, we considered the hypothesis that a panel of 22 transport-defective mutants of the human T cell leukemia virus type 1 envelope glycoprotein might be defective in ER assembly. Upon cell cotransfection with wild-type envelope, however, the vast majority of these transport-defective mutants (21 of 22) exerted a specific trans-dominant negative effect. This effect was due to random dimerization of the mutated and wild-type glycoproteins that prevented the intracellular transport of the latter. This unexpected result suggests that association of glycoprotein monomers precedes the completion of folding. The only mutation that impaired this early assembly was located at the NH2 terminus of the protein. COOH-terminally truncated, soluble forms of the glycoprotein were also trans-dominant negative provided that their NH2 terminus was intact. The leucine zipper-like domain, although involved in oligomerization of the envelope glycoproteins at the cell surface, did not contribute to their intracellular assembly. We propose that, at a step subsequent to translation, but preceding complete folding of the monomers, glycoproteins assemble via their NH2-terminal domains, which, in turn, permits their cooperative folding.

Amino Acid Substitution↗
PubMed1999

The Y-S-L-I tyrosine-based motif in the cytoplasmic domain of the human T-cell leukemia virus type 1 envelope is essential for cell-to-cell transmission.

The human T-cell leukemia virus type 1 (HTLV-1) transmembrane glycoprotein has a 24-amino-acid cytoplasmic domain whose function in the viral life cycle is poorly understood. We introduced premature-stop mutations and 18 single-amino-acid substitutions into this domain and studied their effects on cell-to-cell transmission of the virus. The results show that the cytoplasmic domain is absolutely required for cell-to-cell transmission of HTLV-1, through amino acids which cluster in a Y-S-L-I tyrosine-based motif. The transmission defect in two motif mutants did not result from a defect in glycoprotein incorporation or fusion. It appears that the Y-S-L-I tyrosine-based motif of the HTLV-1 glycoprotein cytoplasmic domain has multiple functions, including involvement in virus transmission at a postfusion step.

Amino Acid Motifs↗
PubMed1999

Multiple functions for the basic amino acids of the human T-cell leukemia virus type 1 matrix protein in viral transmission.

We studied the involvement of the human T-cell leukemia virus type 1 (HTLV-1) Gag matrix protein in the cell-to-cell transmission of the virus using missense mutations of the basic amino acids. These basic amino acids are clustered at the N terminus of the protein in other retroviruses and are responsible for targeting the Gag proteins to the plasma membrane. In the HTLV-bovine leukemia virus genus of retroviruses, the basic amino acids are distributed throughout the matrix protein sequence. The HTLV-1 matrix protein contains 11 such residues. A wild-type phenotype was obtained only for mutant viruses with mutations at one of two positions in the matrix protein. The phenotypes of the other nine mutant viruses showed that the basic amino acids are involved at various steps of the replication cycle, including some after membrane targeting. Most of these nine mutations allowed normal synthesis, transport, and cleavage of the Gag precursor, but particle release was greatly affected for seven of them. In addition, four mutated proteins with correct particle release and envelope glycoprotein incorporation did not however permit cell-to-cell transmission of HTLV-1. Thus, particle release, although required, is not sufficient for the cell-to-cell transmission of HTLV-1, and the basic residues of the matrix protein are involved in steps that occur after viral particle release.

Amino Acid Sequence↗
PubMed1994

[Anorectal manometry and ileo-anal anastomosis: pre- and postoperative manometric comparison].

The aim of this study was to evaluate the physiological and manometric changes of anorectal function after proctocolectomy and ileal J pouch anastomosis performed in 13 patients. A short muscular rectal cuff was conserved in the first 5 patients, mucosectomy was performed in the next patients (Group M), and the entire rectum and proximal portion of the anal canal (1 mm above the dentate line) were resected without mucosectomy (Group WM) in the most recent patients. With a median postoperative follow-up of 18 months, anorectal continence was perfect in 9 patients, and minimal incontinence were observed in 4 patients (2 patients in Group M, and 2 patients in Group SM). In Group M, the resting lower anal canal pressure was significantly decreased after the operation and was less than the postoperative resting lower anal canal pressure observed in Group SM. The resting upper anal canal pressure in continent patients was inferior to the postoperative values measured in patients with minimal incontinence. In all the groups, no change in squeeze pressure was observed after the operation. During the postoperative period, the rectoanal inhibitory reflex was absence in all patients. The volume necessary for sensation threshold was increased after the operation, in the same number of patients in Group M and SM, and more frequently in continent patients compared with patients with soiling. The absence of muscular rectal cuff and mucosectomy seems to provide best results than rectal cuff preservation. After the operation, a marked decrease in the resting pressure and an increase in the volume necessary to onset of threshold sensation, were associated with the presence of minimal incontinence.

Adult↗
PubMed1993

Measuring the rupture stress point of biological sealant-collagen bonding: validation of a technique used after hepatectomy.

The aim of this experimental study was to measure the rupture stress point of a fibrin clot situated on a liver, in realistic surgical conditions. The experimental method was carried out with a machined wooden cylinder bonded on the liver, connected with a wire to a setup and pulled at a constant speed, and a sensor was placed on the wire measuring the applied strength. This method, realized in the dog, made it possible to validate a precise and reproducible method designed for testing the adhesive characteristics of biological sealant-collagen bonding on the liver.

Adhesiveness↗
PubMed1992

[Disorders of relaxation of the lower esophageal sphincter appearing after resection of a mid-thoracic esophageal pulsion diverticulum].

A pulsion diverticulum of the mid-thoracic oesophagus was resected because of severe dysphagia. A subdiverticular myotomy was associated for the treatment of non-propagated oesophageal contractions, without oesophageal low-sphincter abnormalities. Three months post-operatively, the dysphagia was still present and manometry showed the absence of lower sphincter relaxation after 45 percent of deglutitions; a lower oesophageal sphincter myotomy was performed, resulting in correction of the dysphagia and of the sphincter relaxation abnormalities. The deficit of the inhibitory nervous mechanism, responsible for abnormalities of lower oesophageal sphincter relaxation, was present in the entire intramural oesophageal plexus, but, was not symptomatic at the level of the IOS prior to resection of the diverticulum.

Acute Disease↗
PubMed1992

[Disorders of relaxation of the lower esophageal sphincter after resection of mediothoracic esophageal pulsion diverticulum].

A pulsion diverticulum of the mid-thoracic oesophagus was resected because of severe dysphagia. A subdiverticular myotomy was associated for the treatment of non-propagated oesophageal contractions, without oesophageal low-sphincter abnormalities. Three months post-operatively, the dysphagia was still present and manometry showed the absence of lower sphincter relaxation after 45 percent of deglutitions; a lower oesophageal sphincter myotomy was performed, resulting in correction of the dysphagia and of the sphincter relaxation abnormalities. The deficit of the inhibitory nervous mechanism, responsible for abnormalities of lower oesophageal sphincter relaxation, was present in the entire intramural oesophageal plexus, but, was not symptomatic at the level of the IOS prior to resection of the diverticulum.

Diverticulum, Esophageal↗
PubMed1991

[Gastric volvulus secondary to para-esophageal and sliding hiatal hernias].

Gastric volvulus is not a rare condition and 350 authentic cases have been documented in the adult population. Most often, gastric volvulus was associated with a large paraoesophageal hernia (40%). We report seven new cases of gastric volvulus: 5 were due to a large paraoesophageal hernia, 1 to mixed hiatus hernia, and 1 to a sliding hiatus hernia. We did not observe any cases of acute strangulation with gastric necrosis. The lesions were reversible in the three cases of acute and four cases of chronic gastric volvulus. Surgical treatment included gastric volvulus reduction and repair of hiatus hernia without gastric resection. Surgical treatment of paraoesophageal hiatus hernia is mandatory to reduce the incidence of gastric volvulus. The possibility of gastric volvulus with hiatus hernia must be recognized.

Female↗
PubMed1990

[The role of colorectal resection in severe constipation after promontory rectopexy].

Abdominal rectopexy to the promontory is an effective treatment for total rectal prolapse, internal procidentia and solitary ulcer. This paper is designed to stress the risk of severe constipation following rectopexy, a complication which required surgical resection in 5 cases. This raises the problems of the physiological mechanisms of this complication, the definition of a possible high risk population (young women, patients who were constipated preoperatively?), and an alternative to promontory rectopexy: sacral fixation of the rectum, associated sigmoidectomy, Delorme's operation?

Adult↗
PubMed1990

[Carney's triad: a new case associated with adrenal cortex adenoma].

Carney's triad is a combination of at least 2 of 3 tumor sites: multiple gastric leiomyoblastoma, pulmonary chondroma and paraganglioma, most often extra-adrenal and secreting. Thirty-three cases have been published; we report a new case in a 20 year-old woman, with multiple gastric leiomyoblastomas, liver metastasis, and bilateral pulmonary chondroma. The research of paraganglioma, in regard to Carney's disease, led to the discovery of corticoadrenal adenoma.

Adenoma↗
PubMed1990

[Pancreatico-pleural fistula in chronic pancreatitis].

Seven patients presented with a pancreatic pleural fistula in the context of chronic pancreatitis. The diagnosis was made by analysis of the pleural effusion and by endoscopic retrograde pancreatography which opacified the fistula in six cases. Surgical procedure (five resections, one Roux-en-Y drainage and one resection associated with Roux-en-Y drainage) was guided by the morphology of the pancreatic duct and the presence of pseudocysts. All patients were successfully treated by surgery.

Adult↗