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Biomedical subjects

J Sahel

Publications and source records attributed to J Sahel.

At least 37 records · Page 2Linked to original sources
PubMed2000

Characterization of the intermolecular associations of the dystrophin-associated glycoprotein complex in retinal Müller glial cells.

The abnormal retinal neurotransmission observed in Duchenne muscular dystrophy patients has been attributed to altered expression of C-terminal products of the dystrophin gene in this tissue. Müller glial cells from rat retina express dystrophin protein Dp71, utrophin and the members of the dystrophin-associated glycoprotein complex (DGC), namely beta-dystroglycan, delta- and gamma-sarcoglycans and alpha1-syntrophin. The DGC could function in muscle as a link between the cystoskeleton and the extracellular matrix, as well as a signaling complex. However, other than in muscle the composition and intermolecular associations among members of the DGC are still unknown. Here we demonstrate that Dp71 and/or utrophin from rat retinal Müller glial cells form a complex with beta-dystroglycan, delta-sarcoglycan and alpha1-syntrophin. We also show that beta-dystroglycan is associated with alpha-dystrobrevin-1 and PSD-93 and that anti-PSD antibodies coimmunoprecipitated alpha-syntrophin with PSD-93. By overlay experiments we also found that Dp71and/or utrophin and alpha-dystroglycan from Müller cells could bind to actin and laminin, respectively. These results indicate that the DGC could have both structural and signaling functions in retina. On the basis of our accumulated evidence, we propose a hypothetical model for the molecular organization of the dystrophin-associated glycoprotein complex in retinal Müller glial cells, which would be helpful for understanding its function in the central nervous system.

Actins↗
PubMed2000

Expression of Dp71 in Müller glial cells: a comparison with utrophin- and dystrophin-associated proteins.

PURPOSE: The abnormal retinal electrophysiology observed in patients with Duchenne muscular dystrophy (DMD) has been attributed to an altered expression of C-terminal products of the dystrophin gene. It has been shown that Dp260 is expressed by photoreceptor cells, whereas Dp71 is present in glial cells. The present study was intended to identify all known members of the dystrophin superfamily and their associated proteins expressed in Müller glial cells (MGC). METHODS: The expression of the proteins and of their messengers was studied in MGC cultures from 2-week-old rats, by polymerase chain reaction amplification, Western blot analysis, and immunocytochemistry. An immunocytochemical localization of the proteins was also performed on enzymatically dissociated Müller cells from adult rat retinas. RESULTS: MGCs expressed a spliced isoform of Dp71 called Dp71f, as well as utrophin, beta-dystroglycan, delta and gamma-sarcoglycans, and alpha1-syntrophin. In morphologically preserved differentiated Müller cells, Dp71f was localized in clusters, utrophin was diffusely distributed in the cytoplasm, and dystrophin-associated proteins (DAPs) were membrane-bound. Most of these proteins were preferentially expressed in the vitread portion of the cells. Dp71f and utrophin expression was restricted to MGCs, whereas all DAPs were also present in other retinal cell types. CONCLUSIONS: The exclusive localization of Dp71f and utrophin in MGCs suggests that these proteins, together with DAPs, play a specific role in these cells. Further knowledge of possible interactions of these proteins within a functional complex may provide new insights into the molecular basis of the electroretinogram phenotype in DMD.

Animals↗
PubMed2000

Human platelet suspension stimulates porcine retinal glial proliferation and migration in vitro.

PURPOSE: To characterize the cellular and molecular mechanisms underlying the efficacy of autologous platelet suspension adjuvant therapy in the treatment of macular hole. METHODS: Platelet suspensions were: paid from whole blood samples obtained from informed volunteers. For proliferation assays, platelet suspensions or purified growth factors were added to semi-confluent cultures of porcine real glial cells for 24 hours, followed by [3H]thymidine for 15 hours, after which time cells were washed, solubilized, and counted for uptake of radioactive tracer. For cell migration assays, confluent glial cultures were scrape wounded and maintained in the presence or absence of platelet suspension or identified platelet constituents. Cell migration into the denuded area was scored as a function of time. In certain cases, specific pharmacologic inhibitors of growth factor action were added at the same time as platelet adjuvant or growth factors. RESULTS: Platelet suspension adjuvant induced strong mitogenic and chemotactic responses in cultured glia, in a dose-dependent manner. Maximal incorporation of thymidine was two- to threefold that of control levels, with an ED50 approximately 5 x 10(6) platelets/ml, and migration was enhanced up to 80-fold after 48 hours. Platelet suspension-induced proliferation was completely blocked by addition of 25 microM genistein, a tyrosine kinase receptor inhibitor. However, the same concentration only partially blocked the cell migration response. Addition of any single growth factor or protein identified from ELISA analysis, or a combination of all factors, did not significantly stimulate proliferation or cell migration. CONCLUSIONS: Human platelet suspensions exert both proliferative and chemotactic influences on retinal glial cells in vitro, suggesting that the same responses may occur in platelet-induced macular hole repair in humans. Growth factors or proteins that have been identified within the suspensions do not mimic these responses in vitro, implying that additional currently unidentified trophic activities are also present.

Animals↗
PubMed2000

[Small bowel perforation and occlusion after migration of biliary and cystogastric prosthesis].

We report on two cases of intestinal complications associated with the migration of biliary and cystogastrostomy stents. In the first case, intestinal perforation occurred after migration of an Amsterdam type biliary stent. In the second case, a double pig tail endoprosthesis induced intestinal occlusion which was successfully managed without surgery. Complications after intestinal migration of biliopancreatic stents are very rare and usually involve the colon. Our observations point out the potential gravity of intestinal migration of biliopancreatic stents and, as in the second case, the possible resolution of stent related intestinal occlusion after medical management.

Aged↗
PubMed1999

Results of proton therapy of uveal melanomas treated in Nice.

PURPOSE: To present the first results of uveal melanomas treated with the Medicyc Cyclotron 65 MeV proton beam facility in Nice, analyzing the factors that affect the cause-specific survival (CSS), metastatic rate, and reporting the visual outcome. METHODS AND MATERIALS: This study concerns 538 patients referred by French institutions between June 1991 and December 1996. The eye and tumor parameters were measured using ultrasonography and angiography. Since 1994, CT scans were performed in most patients to help determine the axial length and the shape of the ocular globe. Tantalum clips were inserted around the tumor by the referring ophthalmologist. There were 349 posterior pole tumors (64.9%), 130 equatorial tumors (24.1%), and 59 ciliary body tumors (11%). Two hundred four patients (37.9%) had T1 or T2 tumors, and 334 patients (62.1%) had T3 or T4 tumors. The median tumor diameter was 14.6 mm, and the median tumor height was 5.1 mm. All patients received 52 Gy (57.20 Gy Co-equivalent dose) on 4 consecutive days. The data were analyzed by December 1997. RESULTS: The CSS was 77.4% at 78 months, the overall survival was 73.8% and the local control was 89.0%. The CSS was not influenced by the patient age or the site of the tumor. It was 81.5% for T1 and T2 tumors, versus 75% for T3 and T4 tumors (P = 0.035). It was found that the tumor diameter, rather than the height, was the most important parameter affecting outcome. The metastatic rate was 8%. It depended on the T stage, tumor diameter and thickness, but not the tumor site. Thirty-eight enucleations were performed, most of them due to tumor progression and/or glaucoma. One-third of the patients in whom visual acuity was adequately scored before and after treatment had a stable, if not improved vision, and half the patients retained useful vision after treatment. CONCLUSION: The outcome of patients suffering from uveal melanoma and treated with high-energy protons compares favorably with other techniques of treatment. The tumor dimensions affected CSS and metastatic rate. Even though two-thirds of patients had posterior pole tumors, half of them retained useful vision.

Age Factors↗
PubMed1999

Ability of retinal Müller glial cells to protect neurons against excitotoxicity in vitro depends upon maturation and neuron-glial interactions.

Glutamate is the most abundant excitatory amino acid in the central nervous system. It has also been described as a potent toxin when present in high concentrations because excessive stimulation of its receptors leads to neuronal death. Glial influence on neuronal survival has already been shown in the central nervous system, but the mechanisms underlying glial neuroprotection are only partly known. When cells isolated from newborn rat retina were maintained in culture as enriched neuronal populations, 80% of the cells were destroyed by application of excitotoxic concentrations of glutamate. Massive neuronal death was also observed in newborn retinal cultures containing large numbers of glia, or when neurons were seeded onto feeder layers of purified cells prepared from immature (postnatal 8 day) rat retina. When newborn retinal neurons were seeded onto feeder layers of purified glial cells prepared from adult retinas, application of excitotoxic amino acids no longer led to neuronal death. Furthermore, neuronal death was not observed in mixed neuron/glial cultures prepared from adult retina. However, in all cases (newborn and adult) application of kainate led to amacrine cell-specific death. Activity of glutamine synthetase, a key glial enzyme involved in glutamate detoxification, was assayed in these cultures in the presence or absence of exogenous glutamate. Whereas pure glial cultures alone (from young or adult retina) showed low activity that was not stimulated by glutamate addition, mixed or co-cultured neurons and adult glia exhibited up to threefold higher levels of activity following glutamate treatment. These data indicate that two conditions must be satisfied to observe glial neuroprotection: maturation of glutamine synthetase expression, and neuron-glial signalling through glutamate-elicited responses.

Animals↗
PubMed1999

Effect of autologous platelet concentrate in surgery for idiopathic macular hole: results of a multicenter, double-masked, randomized trial. Platelets in Macular Hole Surgery Group.

OBJECTIVE: To evaluate prospectively the efficacy and safety of autologous platelet concentrate (APC) as an adjuvant in surgery for idiopathic macular hole. DESIGN: Multicenter, double-masked, randomized clinical trial. SETTING: Four university-based ophthalmology clinics. PARTICIPANTS: One hundred ten patients with stage 3 or 4 idiopathic full-thickness macular holes of less than 3 years' duration were randomized (53 eyes to the platelet group and 57 eyes to the control group). INTERVENTIONS: Standardized macular hole surgery versus surgery combined with injection of an APC. In all cases, the procedure consisted of three-port pars plana vitrectomy, posterior hyaloid separation, and nonexpansile fluid-gas exchange. After the fluid-gas exchange, patients were randomized to receive either injection of an APC or no adjunctive treatment. After surgery, patients were positioned face down for 12 days. Platelet counts showed that the concentrates contained a mean of 96.106 platelets (range, 82-102). MAIN OUTCOME MEASURES: Anatomic and functional evaluations were performed at 1, 3, and 6 months after surgery in a double-masked fashion by an independent observer. The main outcome was reapposition of the edge of the macular hole 1 month after surgery. Secondary outcomes were anatomic status at 3 and 6 months, changes in Early Treatment Diabetic Retinopathy Study score, and complications. RESULTS: One month after surgery, the anatomic success rate in the platelet group was 52 of 53 (98%; 95% confidence interval, 0.90-1.00) versus 47 of 57 (82%; 95% confidence interval, 0.70-0.91) in the control group (P = 0.009, Fisher's exact test; relative risk, 0.11; 95% confidence interval, 0.01-0.81). Visual acuity was not significantly different between the two groups at any timepoint. There were no complications specifically attributable to the platelet injection. CONCLUSION: Injection of APC improved significantly the anatomic success rate of surgery for idiopathic macular holes of less than 3 years' duration, but postoperative visual acuity of the platelet group was not statistically different from the control group.

Aged↗
PubMed1999

Chronic pancreatitis and inflammatory bowel disease: true or coincidental association?

OBJECTIVE: Several cases of pancreatitis have been described during the course of Crohn's disease (CD) or ulcerative colitis (UC), but many of them were related to either biliary lithiasis or drug intake. We tried to evaluate the clinical and morphological features of so-called idiopathic pancreatitis associated with inflammatory bowel disease and to define their pathological characteristics. METHODS: Chronic idiopathic pancreatitis was diagnosed on the basis of abnormal pancreatograms suggestive of chronic pancreatitis associated with or without impaired exocrine pancreatic function, or pathological examination in patients undergoing pancreatic resection. We found 6 patients presenting with features of chronic idiopathic pancreatitis and UC and 2 patients with CD seen between 1981 and 1996 in three hospital centers of the south of France. A review of the literature has identified 6 cases of pancreatitis associated with UC and 14 cases of pancreatitis associated with CD based on the above criteria. RESULTS: Hyperamylasemia was not a sensitive test since it was present in 44% and 64% of patients with UC or CD. In UC, pancreatitis was a prior manifestation in 58% of patients. In contrast, the pancreatitis appeared after the onset of CD in 56% of the cases. In patients with UC, pancreatitis were associated with severe disease revealed by pancolitis (42%) and subsequent surgery. Bile duct involvement was more frequent in patients with UC than with CD (58% vs 12%) mostly in the absence of sclerosing cholangitis (16% vs 6%). Weight loss and pancreatic duct stenosis were also more frequent in UC than in CD (41% vs 12% and 50% vs 23%, respectively). Pathological specimens were analyzed in 5 patients and demonstrated the presence of inter- and intralobular fibrosis with marked acinar regression in 3 and the presence of granulomas in 2 patients, both with CD. CONCLUSIONS: Pancreatitis is a rare extraintestinal manifestation of inflammatory bowel disease. Chronic pancreatitis associated with UC differs from that observed in CD by the presence of more frequent bile duct involvement, weight loss, and pancreatic duct stenosis, possibly giving a pseudotumor pattern.

Adolescent↗
PubMed1999

[A new mode of recording retinal activity: multifocal ERG].

Global ERG recordings are only modified in conditions with diffuse or extensive retinal involvement. The use, over the last 6 months, of a new functional testing device: VERIS (visual evoked response imaging system) allows accurate detection and quantification of localized retinal function defects. Our preliminary experience shows that a careful preparation of subjects, standardized testing protocols and a good understanding of the device technology, especially software parameters are mandatory. We report our results on a series of 28 normal volunteers, grouped by age and describe the various graphic presentation of data collected. This technology should allow accurate detection and quantification of retinal functional defects in patients with age related macular degeneration as well as evaluation of visual function in retinitis pigmentosa patients before and after photoreceptor transplantation.

Adult↗
PubMed1999

[Central retinal vein occlusion and opto-ciliary shunts. An angiographic diagnosis].

Opto-ciliary shunts are compensatory bypass channels from the retinal venous system to the choroidal veins in case of long standing central retinal vein occlusion. Indocyanine green angiography with the Scanning Laser Ophtalmoscope may be helpful to differentiate acquired optociliary shunts from retinal or choroidal arteriovenous malformations.

Choroid↗
PubMed1999

[Pancreatic intubation by endoscopy in chronic calcifying pancreatitis].

BACKGROUND: The aim of our study was to assess the efficacy of endoscopic pancreatic stenting on pain and frequency of acute pancreatitis in patients with calcifying chronic pancreatitis. PATIENTS: Between 1987 and 1996, 70 patients underwent endoscopic management for calcifying chronic pancreatitis. RESULTS: Endoscopic stent placement was successful in 59 patients (85%). 46 patients were followed for a mean duration of 29 +/- 26.4 months after stent removal. The presence of pancreatic pseudocysts in 26 patients appeared to modify pain improvement rate but did not influence the decrease in the frequency of acute pancreatitis. An improvement of pancreatic pain occurred at the end of stenting and after removal of the stent in respectively 44% and 38% of the patients without pseudocysts and in 85% (P < 0.02) and 65% of the patients presenting with pancreatic pseudocysts. Before stenting, 43/70 (61%) patients had at least two episodes of acute pancreatitis. After removal of the stent, only 5/46 (11%) had one episode of acute pancreatitis. Improvement of weight loss and diabetes was observed in respectively 28 cases (52%), 7 cases (39%) at the end of pancreatic stenting and was still persisting in 21 (51%) and 5 cases (26%) after removal of the stent. CONCLUSION: After pancreatic stenting, the improvement of pain appears to be moderate in the absence of pancreatic pseudocyst. Nevertheless, the improvement of pain is maintained after stent removal. Moreover, the frequency of acute pancreatitis is significantly decreased after pancreatic stenting.

Adult↗
PubMed1999

[Natural history of non alcoholic and non familial chronic pancreatitis. Results of a multicentre study].

UNLABELLED: The natural history and complications of non alcoholic chronic pancreatitis (NACP) is poorly understood compared to that of alcoholic chronic pancreatitis (ACP). PATIENTS AND METHODS: From April 1993 to April 1996, 77 patients with NACP were prospectively evaluated in 17 French centres. This population was compared to a cohort of 417 patients with ACP. RESULTS: No significant difference was observed with respect to mean age between NACP and ACP (43 +/- 20 vs 44 +/- 11 years, respectively). The median patient follow-up time was also comparable: 7 years (1-28) and 6 years (1-34) respectively for NACP and ACP. There were significantly more males in the ACP group (9/1 in ACP group and 1.3/1 in NACP group; P<10(- 7) ). Patients with NACP were less likely to have calcifications (58% vs 77%; P=0.01), pseudocysts (19 vs 47%, P<0.001), portal vein thrombosis (5 vs 16%, P<0.02). Importantly, patients with NACP required less surgical procedures than those with ACP (26% vs 44%, P=0.004). The actuarial death rate at 15 years was 0% in the NACP group compared to 20.5% in those with ACP (no CP related death). CONCLUSION: NACP has a less severe disease progression, fewer complications and requires less surgical interventions than ACP. The lower actuarial survival rate in patients with ACP correlates with the extra-pancreatic complications encountered in patients with alcohol related diseases and not with the evolution of CP itself.

Adolescent↗