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R Lapointe

Publications and source records attributed to R Lapointe.

At least 37 records · Page 2Linked to original sources
PubMed1997

Interference of HIV-1 Nef in the sphingomyelin transduction pathway activated by tumour necrosis factor-alpha in human glial cells.

OBJECTIVE: The HIV-1 nef gene product, thought to interact with mediators of cell signalling, is overexpressed during the restricted HIV-1 infection of human astrocytes. This infection can be reactivated following exposure to tumour necrosis factor (TNF)-alpha. We examined the possibility that Nef alters the TNF-alpha-induced cell signalling in astroglioma cells through the sphingomyelin pathway. METHODS: Sphingomyelinase activation by TNF-alpha was analysed in U251MG glial cells constitutively expressing Nef and compared with U251MG cells stably transfected with the expression vector alone. The consequent effect on the cellular proliferative response and induction of nuclear factor NF-kappa B and AP-1 binding activities were examined. RESULTS: A marked enhancement in the levels of ceramide, a product of the sphingomyelin hydrolysis, was observed in U251MG-Nef upon stimulation with TNF-alpha. In contrast, ceramide levels in control cells were barely increased under similar conditions. A concomitant reduction of sphingomyelin level occurred in U251MG-Nef cells. In addition, the reduced survival rate of U251MG cells resulting from TNF-alpha activation was prevented in the presence of Nef. Furthermore, electrophoretic mobility shift assays indicated that nef expression inhibits AP-1 activation without altering the induction of NF-kappa B. CONCLUSION: These results strongly suggest that nef expression in U251MG cells modulates the sphingomyelinase signalling pathway triggered by TNF-alpha, thus leading to important modifications in the activation and proliferation of glial cells. They also provide new insights to explain the widespread reactive astrogliosis observed in AIDS-associated neuropathological disorders.

Cells, Cultured↗
PubMed1997

[Congenital duodenal diaphragm in an adult associated with an abnormal location of Vater's ampulla: a case report and review of the literature].

Web-related duodenal obstruction in the adult is rare, so is the anomalous location of the ampulla of Vater in the third part of the duodenum. A woman who harboured both anomalies is described and the literature reviewed. The diagnosis, often made at laparotomy, mandates an exploratory duodenotomy. The best treatment consists of partial excision of the web and transverse closure of the duodenum. A duodenojejunostomy or duodenoduodenostomy, or both, are acceptable therapies. The anomalous location of the ampulla of Vater in the third part of the duodenum does not require treatment.

Ampulla of Vater↗
PubMed1996

HIV-1 LTR activity in human CD40-activated B lymphocytes is dependent on NF-kappaB.

CD40-stimulated human B lymphocytes are highly permissive to a productive infection by the human immunodeficiency virus type 1. In these cells, nuclear factors involved in activation of the HIV-1 LTR, which contains the transcriptional control elements of the virus, are unknown. Transient expression assays with plasmids containing deleted parts of the LTR region linked to a reporter gene showed that the NF-kappaB binding site was essential for HIV-1 LTR activity in CD40-stimulated B lymphocytes. In addition, electrophoretic mobility shift and supershift assays revealed that important NF-kappaB binding activity composed of at least p50, p65, and c-Rel NF-kappaB subunits was present in nuclei of CD40-stimulated B cells. These results confirm at a molecular level the ability of HIV-1 to replicate in B cells and that this activity is strongly associated with NF-kappaB.

B-Lymphocytes↗
PubMed1996

Tyrosine kinase and cAMP-dependent protein kinase activities in CD40-activated human B lymphocytes.

In vitro, human B lymphocytes undergo long-term proliferation when activated through CD40, a protein expressed on their cell surface. The nature of CD40-dependent signals in proliferating fresh human Epstein-Barr virus-negative B lymphocytes is currently unknown. In this study, a CD40-dependent B cell culture system was used to examine the role of different signal transduction elements. Protein kinase C (PKC) depletion generated by a long-term phorbol 12 myristate 13-acetate treatment had weak effects on proliferation. Rather, tyrosine phosphorylation was shown to be directly involved in mediating CD40-dependent signals. The use of the protein tyrosine kinase (PTK)-specific inhibitor herbimycin A dramatically decreased cellular proliferation without altering the activity of the human immunodeficiency virus-1 long terminal repeat (HIV-1 LTR), a promoter largely dependent on the binding of nuclear factor kappa B (NF- kappa B). In contrast, the cAMP-dependent protein kinase specific inhibitor H-89 totally inhibited HIV-1 LTR activity at a concentration as low as 100 nM without affecting cellular proliferation. Electrophoretic mobility shift assay (EMSA) and supershift assay using an NF-kappa B binding sequence from the kappa light chain as a probe, revealed that both p65 (RelA) and c-Rel were present in CD40-stimulated B cells. While PKC depletion did not alter the NF-kappa B level, treatment of B lymphocytes with H-89 or herbimycin A provoked a decrease in the NF-kappa B level. These observations establish the importance of different signal transducing pathways leading to CD40 activation of B lymphocytes.

B-Lymphocytes↗
PubMed1996

The hepatic microcirculation in the isolated perfused human liver.

In cirrhosis, capillarization of sinusoids could result in impaired exchanges between the hepatocytes and the blood perfusing the liver and contribute to liver failure irrespective of the metabolic capacity of the liver. To characterize anomalies of the hepatic microcirculation, we used the multiple-indicator dilution approach in isolated perfused livers obtained from patients with cirrhosis at the time of transplantation, and from organ donors with normal or near-normal livers or hepatic steatosis. In organ donors, the sinusoidal volume and the permeability of sinusoids to albumin, sucrose, and water were found to be comparable to that of normal dog and rat livers. The sinusoidal volume and the extravascular volume (EVV) accessible to diffusible tracers were larger after hepatic artery than after portal vein injection, probably because of an unshared arterial sinusoidal bed. In cirrhotic livers, two kinds of alterations were found: the appearance of a barrier between the sinusoids and the hepatocytes (capillarization) and intrahepatic shunts. The extravascular space accessible to albumin decreased with increasing severity of cirrhosis, and the diffusion of sucrose in the space of Disse showed a barrier-limited pattern, instead of the normal flow-limited behavior. In cirrhotic livers, a correlation was found between the hepatic extraction of indocyanine green (ICG) and the extravascular space accessible to albumin (r = .84, P < .05), suggesting that the impaired access of this protein-bound dye to the hepatocyte surface contributed to its impaired elimination. Intrahepatic shunts were found between portal and hepatic vein (21% +/- 16% of portal flow), but not between hepatic artery and hepatic veins. We conclude that (1) the behavior of diffusible tracers in human livers with normal liver architecture is comparable to that reported in normal animals; (2) the permeability of sinusoids in cirrhotic livers is abnormal, (3) permeability changes are related to changes in liver function in cirrhosis.

Adolescent↗
PubMed1996

[Reduction of blood loss in orthotopic liver transplantation with the use of aprotinin].

UNLABELLED: The impact of aprotinin on blood losses during orthotopic liver transplantation (OLT) has been studied retrospectively. PATIENTS AND METHODS: From September 1984 to July 1995, 152 patients underwent 168 OLT in our center. Seventy three patients (group I) received epsilon-aminocaproic acid as an antifibrinolytic agent and 95 patients (group II) received aprotinin. RESULTS: There was a significant reduction in the mean duration of the surgery (I = 743 +/- 25 min; II = 302 +/- 10 min; p < 0.001) and in the post reperfusion time (I = 282 +/- 13 min; II = 126 +/- 6 min; p < 0.001) in the group II. The need for blood products during the operation was also reduced (blood units; I = 21.7 +/- 2.3 units; II = 4.6 +/- 0.4 units; p < 0.001). There was less infectious and hemorrhagic complications requiring reoperation in group II. We have not seen an increased incidence of thrombotic complications in the patients receiving aprotinin. Other variables such as the use of hemoclips, veno-venous bypass and the type of preservation solution were also considered. CONCLUSION: Aprotinin use during OLT is efficient and superior to epsilon-aminocaproic acid in reducing blood losses. Combined with the non-utilisation of a veno-venous by-pass and the use of hemoclips, it helps reduce the operating time and the postoperative complications.

Adult↗
PubMed1996

Clearance by the liver in cirrhosis. III. Propranolol uptake by the isolated perfused human liver.

In cirrhosis, intrahepatic shunts and capillarization of sinusoids can result in impaired extraction of substrates by the liver irrespective of the metabolic capacity of the liver (intact hepatocyte theory). To evaluate the role of anomalies of uptake in impaired drug disposition, we studied the steady-state hepatic clearance and single-pass hepatic uptake of propranolol in isolated perfused livers obtained from patients with cirrhosis at the time of transplantation and from organ donors with normal liver architecture. The kinetics of propranolol transport in the liver were characterized by means of the multiple-indicator dilution technique, and the outflow pattern of propranolol in the hepatic veins was resolved into throughput material, which had swept past the hepatocytes along with albumin, and returning material, which had entered the cells but returned in the outflow after escaping cellular sequestration and metabolism. The steady-state clearance of propranolol was decreased in cirrhotics compared with organ donors, and the outflow profile differed between the two groups. In cirrhotic livers, half of the propranolol in the outflow consisted of throughput material and the other half of returning material; in organ donors, all of the propranolol in the outflow was returning material. In the presence of albumin and alpha 1-acid glycoprotein in the perfusate, about 80-85% of propranolol was protein bound; removal of albumin and alpha 1-acid glycoprotein from the perfusate it cirrhotic livers resulted in an increase in the free fraction of propranolol, an increase in steady-state extraction, and a decrease in the throughput component of propranolol in the outflow. We conclude that impaired uptake of protein-bound propranolol, as a result of capillarization and intrahepatic shunts, contributes to its impaired elimination in cirrhosis.

Biological Transport↗
PubMed1995

Bronchogenic cyst of the right hemidiaphragm.

A rare case of bronchogenic cyst of the right hemidiaphragm is reported. The literature is reviewed briefly. Clinical presentation, diagnosis, and treatment of this entity are discussed further.

Bronchogenic Cyst↗
PubMed1995

[Role of extracorporeal shock wave lithotripsy in the treatment of common bile duct and intrahepatic calculi].

The management of intrahepatic and common bile duct stones has been modified by the advent of endoscopic sphincterotomy and percutaneous extraction through a T-tube tract or transhepatic access. Occasionally, nonoperative extraction is incomplete. The use of extracorporeal lithotripsy is reviewed in this setting. From May 1990 to February 1994, 18 patients (age 68.4 +/- 4.6 years) were treated by extracorporeal shockwave lithotripsy combined with endoscopic sphincterotomy and retrograde extraction or percutaneous approach. 72% of patients had previously undergone a cholecystectomy and 44% exploration of the common duct. Patients were submitted to 1.56 +/- 0.17 session of lithotripsy (5.546 +/- 701 shockwaves). Hospital stay was 19.5 +/- 3.3 days. After the lithotripsy, 1.17 +/- 0.19 endoscopic or percutaneous procedures per patient were necessary to clear the biliary tract. Seventy-eight percent of patients became stone-free. The five failures were treated by endobiliary prosthesis (n = 4) or cholecystectomy and bile duct exploration (n = 1). Lithotripsy in association with the usual therapeutic modalities contributes to clearing the bile duct from stones and avoids surgery in the majority of patients. A multidisciplinary approach is necessary in order to obtain those results.

Aged↗
PubMed1994

Productive infection of normal CD40-activated human B lymphocytes by HIV-1.

OBJECTIVE: Antigen-driven B-cell proliferation and maturation occur in germinal centres present in lymphoid tissues. This process is highly dependent on functional interactions between B and T lymphocytes. In vitro activation of CD40 present on B cells mimics B cell-T interactions and allows the proliferation of normal Epstein-Barr virus (EBV)-negative B lymphocytes. In HIV-1-seropositive individuals, B cells become exposed to free viral particles and to infected T lymphocytes while migrating through germinal centres. The effect of HIV-1 viral exposure on CD40-activated B lymphocytes was therefore examined. METHODS: Freshly isolated B lymphocytes were cultured in vitro through activation of CD40. B-cell proliferation, HIV-1 infectivity and viral production were monitored following B-lymphocyte exposure to HIV-1. In addition, HIV-mediated fusion between infected B cells and uninfected CD4+ T lymphocytes was assessed in a coculture assay. RESULTS: EBV-negative, CD40-activated human B lymphocytes were directly infected by HIV-1. The infection significantly reduced their proliferation rate. Viral production was detected in B-cell culture supernatant. Numerous fusion events indicated that HIV-1 infection of B lymphocytes could spread to T lymphocytes following HIV-1-mediated fusion of these two cell types. CONCLUSION: In view of the importance of B cell-T cell interactions in the maintenance of a functional immune system, disruption of B-lymphocyte development could have direct implications on the course of AIDS progression.

Antigens, CD↗
PubMed1994

Properties of a Streptococcus salivarius spontaneous mutant in which the methionine at position 48 in the protein HPr has been replaced by a valine.

HPr is a protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) that participates in the concomitant transport and phosphorylation of sugars in bacteria. In gram-positive bacteria, HPr is also reversibly phosphorylated at a seryl residue at position 46 (Ser-46) by a metabolite-activated ATP-dependent kinase and a Pi-dependent HPr(Ser-P) phosphatase. We report in this article the isolation of a spontaneous mutant (mutant A66) from a streptococcus (Streptococcus salivarius) in which the methionine at position 48 (Met-48) in the protein HPr has been replaced by a valine (Val). The mutation inhibited the phosphorylation of HPr on Ser-46 by the ATP-dependent kinase but did not prevent phosphorylation of HPr by enzyme I or the phosphorylation of enzyme II complexes by HPr(His-P). The results, however, suggested that replacement of Met-48 by Val decreased the affinity of enzyme I for HPr or the affinity of enzyme II proteins for HPr(His-P) or both. Characterization of mutant A66 demonstrated that it has pleiotropic properties, including the lack of IIILman, a specific protein of the mannose PTS; decreased levels of HPr; derepression of some cytoplasmic proteins; reduced growth on PTS as well as on non-PTS sugars; and aberrant growth in medium containing a mixture of sugars.

Bacterial Proteins↗
PubMed1994

Iatrogenic injury to the bile duct: a working classification for radiologists.

PURPOSE: To assess the usefulness of the Bismuth classification method in the preoperative localization of iatrogenic bile duct lesions with cholangiography and to correlate these cholangiographic findings with surgical findings. MATERIALS AND METHODS: The records of 33 patients who underwent open or laparoscopic cholecystectomy and who sustained injuries to the biliary tract during the course of these procedures were reviewed retrospectively. The accuracy of the cholangiographic localization of bile duct injury was assessed with the Bismuth classification method, which is based on the localization of the traumatic lesion according to the distance from the biliary confluence. RESULTS: An exact correspondence between cholangiographic and surgical findings was found in 85% of the subjects. A minimal discrepancy was found in the remainder. There was no interobserver variation. CONCLUSION: The use of the Bismuth classification method appears to be an accurate and practical method for the grading of postoperative bile duct lesions with cholangiography.

Bile Ducts↗
PubMed1994

Postoperative changes, complications, and recurrent disease after Whipple's operation: CT features.

Whipple's operation consists of resection of the pancreatic head and duodenum, followed by pancreaticojejunostomy, choledochojejunostomy, and gastrojejunostomy or duodenojejunostomy. Indications include neoplasms of the periampullary region, symptomatic chronic pancreatitis, and, occasionally, trauma CT is useful in diagnosing postoperative complications and in detecting disease recurrence during long-term follow-up. This complex surgical procedure causes alterations of the normal anatomy, which may lead to difficulty interpreting images. Familiarity with the appearance of postoperative changes and common complications and with patterns of disease recurrence is a prerequisite to accurate interpretation of CT scans in these patients.

Choledochostomy↗
PubMed1994

[Experience with the transjugular intrahepatic portocaval shunt].

Liver transplantation and the intrahepatic shunt have changed the management of variceal hemorrhage and refractory ascites. The purpose of this work is to review the results obtained with intrahepatic shunting. From January 1991 to May 1993, 45 patients underwent a transjugular intrahepatic portosystemic shunt. In 23 patients, liver insufficiency was considered moderate and in 21 severe. Indications for the procedure were: variceal bleeding (23), refractory ascites (19) and portal hypertensive gastritis (3). The portocaval gradient was lowered from 24.2 +/- 5.1 mm Hg to 12.9 +/- 3.9 (-47%). The procedure was effective in 78% of variceal bleeders and in 89% of patients with ascites. Thirty-day mortality was 22%. One-year survival was 39%. Liver failure or severe encephalopathy occurred in 27% of patients. Four patients (9%) presented intra-abdominal bleeding. Four patients developed renal failure. Transjugular intrahepatic portosystemic shunts are effective in lowering portal pressure and controlling complications of portal hypertension. However, important side effects are present and controlled studies are required to evaluate this new treatment.

Aged↗
PubMed1994

[Cystic tumors of the pancreas: apropos of 36 cases].

Cystadenomas and cystadenocarcinomas are rare cystic tumors of pancreas. Clinicopathological features and treatment of these neoplasms have been studied in 36 patients over a 10-year period (1983-1993). There were 19 cystadenomas (CA) either serous (n = 13) or mucinous (n = 6) and 17 cystadenocarcinomas (CAC). Eighteen CA (95%) were found in women. CAC were found equally between both sexes. Median age was 63 years and was the same for CA and CAC. Ultrasound gave correct diagnosis of CA or CAC in 64% and CT-scan in 77%. The majority of CAC (n = 15) were localized in the head of the pancreas. CA had no preferential localization. 24 patients (66%) underwent including resection (n = 20) and biopsy (n = 4). Four other patients had a percutaneous biopsy and 8 were observed. Hospital mortality was 8%. Complications included gastric atony (n = 4) and pancreatic fistula (n = 2). Four-year actuarial survival is 63% for resected CAC and 100% for resected CA. In conclusion, most cystic pancreatic tumors are found in women. Malignant lesions are found predominately in the head of the pancreas. Modern imaging technics combined with clinical presentation are reliable in obtaining a diagnosis. Resection remains the treatment of choice.

Adult↗
PubMed1994

Transhepatic portal vein stenting for treatment of ruptured duodenopancreatic varices in a patient with chronic pancreatitis.

BACKGROUND: Portal vein obstruction with secondary variceal bleeding in the setting of chronic pancreatitis has not been recognized as frequently as splenic vein occlusion. This condition can be difficult to diagnose and treat. METHODS: A 54-year old man was referred for massive recurrent endoscopy-negative upper-gastrointestinal bleeding. The diagnosis of duodenopancreatic varices was finally made. Direct portography showed a high-grade stenosis of the proximal portal vein that was dilated and stented with a balloon expandable prosthesis. RESULTS: The gradient across the stenosis fell from 9 to 2 mm Hg. Bleeding stopped. After 7 months of follow-up, the patient has experienced no rebleeding, and a Doppler examination is normal. CONCLUSIONS: In patients with chronic pancreatitis and upper gastrointestinal tract bleeding of unknown origin, obstruction of one of the major splanchnic veins must be excluded. Portal vein dilatation and stenting appears to be a safe procedure with good short-term results.

Angioplasty, Balloon↗
PubMed1993

Altered expression of several genes in IIIManL-defective mutants of Streptococcus salivarius demonstrated by two-dimensional gel electrophoresis of cytoplasmic proteins.

Mannose, glucose and fructose are transported in Streptococcus salivarius by a phosphoenolpyruvate:mannose phosphotransferase system (PTS) which consists of a membrane-bound Enzyme II (EII) and two forms of IIIMan having molecular weights of 38,900 (IIIManH) and 35,200 (IIIManL), respectively. We have previously reported the isolation of spontaneous mutants lacking IIIManL and showed that they exhibit higher beta-galactosidase activity than the parental strain after growth on glucose, and that some of them constitutively express a fructose PTS which is induced by fructose in the parental strain. In an attempt to determine whether the expression of other genes is affected by the mutation and what the physiological link is between them, we examined three S. salivarius IIIManL-defective mutants (strains A37, B31 and G29) and the parental strain using two-dimensional gel electrophoresis after growth of the cells on a variety of sugars. After growth on glucose, five new proteins were detected in the cytoplasm of the three mutants. Two of these proteins were induced in the parental strain by galactose or oligosaccharides containing galactose, and one was specifically induced by melibiose. The other two proteins were not detected in the parental strain under any of the growth conditions tested. Two other proteins were only detected in glucose-grown cells of mutant A37, and a protein associated with the metabolism of fructose was constitutively expressed in mutants B31 and G29. Moreover, we have found that under identical growth conditions the amounts of several other proteins which were detected in the parental strain were either increased or decreased in the mutants. Globally, our results have indicated that (1) the expression of several genes was affected in the spontaneous IIIManL-defective mutants; (2) some of the proteins abnormally produced in the mutants were specifically induced in the parental strain by sugars; (3) the phenotypic modifications observed in the mutants were of two types: most were observed solely after growth of the cells on glucose whereas the others were glucose-independent; and (4) the mutants shared common phenotypic traits, but also exhibited idiosyncratic characteristics.

Bacterial Proteins↗