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Biomedical subjects

M Kamoun

Publications and source records attributed to M Kamoun.

At least 19 recordsLinked to original sources
PubMed2005

[Retinal detachment after Excimer laser (myopic LASIK or PRK). A retrospective multicentric study: 15 cases].

INTRODUCTION: Refractive surgery by LASIK or photorefractive keratectomy (PRK) generaly aims at a myopic population that has a high probability of developing rhegmatogenous retinal detachment (RD). The authors report a multicenter study with 15 cases of RD appearing after refractive surgery by Excimer laser and discuss the role played by the techniques used. MATERIAL AND METHODS: Five centers fitted with nine Excimer laser devices took part in this study. Of 22,700 eyes undergoing refractive myopic surgery during the period 1994-2002, 15 eyes developed rhegmatogenous RD. The average age of the patients with RD was 37 years. The average myopia was 13.5 D. RD occurred a mean of 20 months after refractive laser. RESULTS: Fifteen eyes of 13 patients developed a rhegmatogenous RD, two of which were bilateral. Eight of these cases had LASIK surgery and six had photorefractive keratectomy; one of the latter patients was retreated with LASIK because of substantial regression after PRK. RD was total or subtotal in five eyes, partial superior with a temporal tear in six eyes, and nasal in three eyes. One case with inferior RD, two cases with giant retinal tear and one case with posterior tear were also repaired. Fourteen eyes were suitable for operation. The retina was reattached in 12 cases. Mean postoperative visual acuity was 7/10. DISCUSSION: The occurrence of rhegmatogenous RD in the myopic population is estimated at 2.2%. It is estimated at 0.1% in the emmetropic population. The Excimer laser, through its thermic effects, shock wave, traumatism undergone by the suction ring at the time of LASIK surgery, could increase this risk in myopic patients. A review of the literature cast doubt on the cause and effect hypothesis. Personal and multicenter studies (including ours) show that the frequency rate of rhegmatogenous RD after Excimer laser is equivalent and even lower than that estimated with an emmetropic population. The low percentage of RD after Excimer surgery found in the literature as well as in our study (<0.1%) may be explained by patient selection, the systematic monitoring of the peripheral fundus, and the prophylactic treatment of degenerative lesions by photocoagulation. In RD surgery, the cornea must be manipulated carefully, a case of flap dehiscence has been reported in the literature. CONCLUSION: Refractive surgery by LASIK or PRK for severe myopia increases the risk of RD. Systematically monitoring the peripheral fundus and preventive photocoagulation have mitigated its occurrence, and the risk incurred in the myopic population has fallen to the emmetropic population's rate. Nevertheless, candidates for LASIK or PRK surgery must be informed because severe myopia constitutes a non-negligible risk factor.

Adult↗
PubMed2004

[Simultaneous bilateral rhegmatogenous retinal detachment. 7 case studies].

PURPOSE: Simultaneous bilateral rhegmatogenous retinal detachments are rare. The purpose of our study was to examine the incidence, predictive factors, surgical results and prognosis of these retinal detachments. PATIENTS AND METHODS: A retrospective analysis of the medical records of 468 consecutive patients, 7-89 years of age (mean, 45.7 years), undergoing surgery for rhegmatogenous retinal detachment between 1993 and 2000. RESULTS: During this period, a total of 497 operations for rhegmatogenous retinal detachment were done. Thirty-two patients had bilateral rhegmatogenous retinal detachment. Simultaneous detachments were observed in seven patients (1.5%). In four cases, the diagnosis of retinal detachment was fortuitous. In fact, most patients presented with unilateral symptoms. The mean age (35 years) of patients suffering from simultaneous bilateral rhegmatogenous retinal detachment was younger than that of patients with unilateral or consecutive bilateral retinal detachments. Five patients were myopic. Multiple round retinal holes were the most frequent lesions responsible for retinal detachment. A preoperative proliferative vitreoretinopathy was found in 57% of cases. The retina was reattached in nine cases (81%). CONCLUSION: Simultaneous bilateral rhegmatogenous retinal detachment is usually found in relatively young myopic patients with atrophic retinal holes. They are rare but severe because of their frequent association with preoperative proliferative vitreoretinopathy.

Adolescent↗
PubMed2002

Identification and sequencing of HLA-B*0714 and B*2718 alleles and novel exon 1 sequences of B*0709 and B*2714 alleles in potential bone marrow donors.

Sequence specific oligonucleotide probe hybridization and sequence specific primer PCR typing of volunteer bone marrow donors suggested the presence of variants of known HLA-B alleles in two individuals. PCR products encompassing HLA-B locus exons 1, 2, and 3 were prepared, subcloned and sequenced. A Hispanic individual had a novel B*07 allele (B*0714) and a Chinese individual had a novel B*27 allele (B*2718). In two other individuals, a previously unknown sequence of exon 1 was determined for HLA-B*0709 (African American) and B*2714 (Native American). These findings further illustrate the substantial genetic variation present at the HLA-B locus within human populations. We discuss the structural variation in the protein sequence for these HLA-B alleles and its potential functional effects.

Asian People↗
PubMed2002

New HLA-B alleles identified and sequences extended in potential bone marrow donors: B*5804, B*4418, B*1558, and B*4805.

Nucleic acid-based methods for allele identification have revealed more than 470 polymorphic variants at the HLA-B locus. Screening of potential bone marrow donors with sequence specific primer polymerase chain reactions and sequence specific oligonucleotide probe hybridization assays revealed apparent variants within the B*58, *44, *15, and *48 allele groups. DNA sequencing of cloned DNA identified the new alleles B*5804, B*4418, and B*1558 within these groups and observed new sequence information for the previously reported allele B*4805. These findings further extend our knowledge of the substantial genetic variation present at the HLA-B locus within human populations.

Alleles↗
PubMed2002

A nonsense mutation in exon 3 results in the HLA-B null allele B*5127N.

A new HLA-B null allele has been identified within the B*51 group by combined serological and molecular typing of an Italian Caucasoid family. Serological data indicated that the proband typed homozygous for A2 and B60. Confirmatory typing using sequence specific oligonucleotide hybridization (SSPOH) detected a second B allele within the B*51 group. Allele specific typing (SSP) for B*51 subtypes, including the known B*5111N allele, was performed, and typing results were consistent with B*5101, suggesting the presence of a new null variant. Cloning and sequencing of this allele identified a B*5101 variant with a nonsense mutation in exon 3. This new null allele has been designated B*5127N. The combined use of serologic and DNA-based typing methods facilitates the identification of null and low-expression alleles. An overview of null alleles of class I HLA is presented.

Base Sequence↗
PubMed2002

[Intumescent cataract with ocular hypertony].

INTRODUCTION: Intumescent cataract with ocular hypertony is a medicosurgical emergency. The purpose of our study is to define the clinical and therapeutic particularities of these cataracts. MATERIAL AND METHODS: This retrospective study includes 40 consecutive patients with angle closure secondary to intumescent cataract. All patients were examined between 1st January 1998 and 30 October 2000. RESULTS: The patient population consisted of 28 women (70%) and 12 men ranging in age from 59 to 88 years (mean age: 78 years). Preoperative visual acuity was negative in 17% of cases and limited to light perception in 83% of cases. Ocular pressure varied from 25 to 68 mmHg. Patients underwent surgery one to 23 days after diagnosis. Surgical techniques consisted in extracapsular cataract extraction with (35%) and without (65%) intraocular lens. Preoperative complications were: vitreous loss in 20% of cases and expulsive haemorrhage in 2 cases (5%). Postoperative visual acuity improved in 70% of cases. COMMENT AND CONCLUSION: Intumescent cataract with ocular overpressure gives therapeutic problems, which can be prevented by a preoperative hypotony. Functional results of this study encouraged us to operate the intumescent cataract even if visual acuity is bad.

Aged↗
PubMed2001

Cellular and molecular parameters in human renal allograft rejection.

Acute rejection of human renal allografts is frequent postransplantation complication. In addition, it is a risk factor for chronic rejection, the most common cause of failure of long-term allografts. Renal allografts are rejected as a result of an immune response directed against alloantigens on the graft that are absent from the host, and the most important of these are the HLA antigens. The application of molecular diagnostic methods has revealed a differential intra-renal gene expression of cytokines, chemokines and their receptors, and cytotoxic attack molecules in acute and chronic rejection processes. Differential expression of T cell costimulatory molecules B7 and CD40/CD40L, and endothelium adhesion molecules ICAM-1 and VCAM-1 has also been reported during acute rejection. These molecules play an important role in mediating the recruitment of lymphocytes into rejecting allografts and costimulation of T cell activation. Based on experimental data, it seems that it is likely that the blockade of T cell costimulatory pathways can be used in human in the future to selectively prevent transplant rejection without generally suppressing the immune system.

B7-1 Antigen↗
PubMed2001

Validation of DNA-based HLA-A and HLA-B testing of volunteers for a bone marrow registry through parallel testing with serology.

A total of 42,160 individuals were typed for HLA-A and HLA-B by both serology and PCR-based typing. The HLA assignments included all of the known serological equivalents. The majority of the individuals (99.9%) were from U.S. minority population groups. The serologic typing was performed between 1993 and 1997 at the time of recruitment for the National Bone Marrow Program (NMDP) registry. The polymerase chain reaction (PCR)-based typing was carried out in two phases. In phase I, DNA typing was performed by PCR using sequence-specific oligonucleotide probes (PCR-SSOP) or PCR using sequence-specific primers (PCR-SSP) without knowledge of the serologic assignments. Discrepancies were identified between the serologic and DNA assignments in 24% of the volunteers (8% of volunteers differed for only HLA-A assignments, 13% for HLA-B, and 3% for both HLA-A and -B) and a potential explanation was assigned each discrepant serology/DNA pair. In phase II, a random sampling scheme was used to select a statistically significant number of individuals for repeat DNA typing from each of these categories. The categories included antigens missed by serology, nonexpressed (null) alleles, PCR amplification failures, misassignment of antigens and nomenclature issues. Only a single individual was found to carry a null allele. DNA-based testing correctly typed nearly 99% of the donors at HLA-A, more than 98% at HLA-B, and more than 97% at both HLA-A and -B validating this methodology for registry typing.

Bone Marrow Examination↗
PubMed2001

Novel HLA-B alleles identified in potential marrow donors: B*3917, B*1405 and B*3528.

Sequence-specific oligonucleotide probe hybridization and sequence-specific primer polymerase chain reaction (PCR) typing of volunteer bone marrow donors suggested the presence of variants of known HLA-B alleles in five individuals. PCR products encompassing HLA-B locus exons 1 through 3 were prepared and subcloned. Three African-American individuals had a novel HLA-B*39 allele (B*3917), and another African-American was found to have a novel HLA-B*14 allele (B*1405). In a third individual of Hispanic origin, a novel HLA-B*35 allele (B*3528) was identified. These findings further illustrate the substantial genetic variation present at the HLA-B locus within human populations.

Alleles↗
PubMed2000

Detection of anti-HLA antibody by flow cytometry in patients with a left ventricular assist device is associated with early rejection following heart transplantation.

BACKGROUND: Patients with a left ventricular assist device (LVAD) as a bridge to heart transplantation (HT) often have elevated levels of panel reactive antibodies (PRA). The clinical significance of anti-human histocompatibility leukocyte antigen (HLA) antibodies detected by flow cytometry in PRA negative patients remains unclear. METHODS: Eighteen patients who underwent LVAD placement as a successful bridge to HT had standard anti-human globulin complement-dependent cytotoxicity and retrospective flow cytometry assays performed to detect class I anti-HLA antibodies. A positive flow result was defined as a fluorescent ratio of 23:1 versus a negative control. RESULTS: Six patients had anti-HLA antibodies detected by flow cytometry. Univariate analysis demonstrated more moderate-severe rejection episodes (ISHLT > or = IIIA) at 2 months (0.83+/-0.75 vs. 0; P=0.04) and a trend toward decreased time to first rejection (61+/-17 vs. 225+/-62 days; P=0.06) in these patients. No differences were observed in donor-recipient HLA mismatch or 1 year Kaplan-Meier survival between patients with or without anti-HLA antibodies. CONCLUSION: Despite a negative PRA, LVAD patients with class I anti-HLA antibodies detected by flow cytometry have a greater incidence of moderate-severe rejection in the first 2 months after HT. Flow cytometry may be a useful clinical tool in screening PRA negative LVAD patients before transplantation. Patients with positive anti-HLA antibody screening by flow cytometry may require more intensive immunosuppression in the early post-HT period.

Adult↗
PubMed2000

Mechanisms of suppression of experimental autoimmune encephalomyelitis by intravenous administration of myelin basic protein: role of regulatory spleen cells.

Experimental allergic encephalomyelitis (EAE) can be downregulated by intravenous (iv) administration of myelin basic protein (MBP). In this report we show that downregulation of EAE by two 500-microgram doses of MBP administered iv before immunization was associated with reduced encephalitogenicity of both spleen and lymph node cells (day 12 postimmunization) in adoptive transfer studies. However, efficient downregulation of EAE by two 500-microgram iv doses of MBP on days 10 and 11 after active immunization (at the time of disease onset) was associated with no significant change in the encephalitogenicity of lymph node cells, but a complete abrogation of the ability of spleen cells (both at day 12 postimmunization) to transfer EAE compared to controls. Furthermore, coculture of spleen cells from rats tolerized by iv MBP on days 10 and 11 after active immunization with MBP with MBP-reactive T cells resulted in a decreased ability of the spleen T cells to transfer EAE compared to effector cells in monoculture. In contrast, coculture of MBP-reactive T cells with spleen cells from rats tolerized by iv MBP on days 14 and 7 before active immunization resulted in increased disease in recipient rats. These results suggest that reversal of clinical EAE by iv injection of MBP at the time of disease onset is due at least in part to a T cell control mechanism located in the spleen and suggest the presence of splenocyte regulatory cells that can suppress the ability of encephalitogenic T cells to induce EAE.

Adoptive Transfer↗
PubMed2000

Large-scale DNA-based typing of HLA-A and HLA-B at low resolution is highly accurate specific and reliable.

DNA-based typing of HLA class I alleles of the HLA-A and HLA-B loci using sequence-specific oligonucleotide primers and/or probes has been used for the large-scale typing of individuals for the National Marrow Donor Program unrelated donor registry. Typing was performed by 16 laboratories at a low level of resolution (e.g. A*01, B*07). The results of blinded quality control analysis for the first 12 months of the project show the typing to be highly accurate, specific and reliable. The total error rate based on 11,545 HLA-A and 11,428 HLA-B assignments was 1.1% for HLA-A and 1.9% for HLA-B. This level of accuracy is particularly remarkable because the quality control samples could not be distinguished from 64,180 donor samples tested at the same time by the laboratories.

Bone Marrow Transplantation↗
PubMed2000

A novel HLA-B*40 allele and novel exon 1 sequences of two B*40 alleles identified in potential marrow donors.

Sequence-specific oligonucleotide probe hybridization and sequence-specific primer polymerase chain reaction (PCR) typing suggested the presence of variants of HLA-B*40 in three individuals. Two were part of 3,500 potential marrow donors being screened for the National Marrow Donor Program, while the third was a clinical specimen. PCR products encompassing HLA-B locus exons 1 through 3 were prepared and subcloned. In one individual, a native of the Pacific Islands, sequencing revealed a novel HLA-B*40 allele (B*4023). In two other individuals, a previously unknown exon 1 sequence was determined for HLA-B*4016 (ethnicity unknown) and B*4020 (Hispanic). These findings further illustrate the substantial genetic variation present at the HLA-B locus within human populations.

Alleles↗
PubMed2000

Novel HLA-B*15 alleles identified in potential marrow donors.

Several methods for low-resolution class I typing of potential bone marrow donors are available. The National Marrow Donor Program (NMDP) has initiated pilot projects for large-scale DNA-based class I typing to initially characterize donors. Sequence-specific oligonucleotide probe hybridization and sequence-specific primer polymerase chain reaction (PCR) screening of 3,500 NMDP potential donors suggested the presence of variants of known HLA-B*15 variants in 3 donors. PCR products encompassing HLA-B locus exons 1 through 3 were prepared and subcloned. Sequencing revealed 3 alleles differing from known HLA-B*15 alleles by nucleotide substitutions resulting in predicted novel HLA-B antigens. The new alleles occur in distinct ethnic groups. These findings further illustrate the substantial genetic variation present at the HLA-B locus within human populations.

Alleles↗
PubMed2000

Reduced mobilization of CD34+ stem cells in advanced human immunodeficiency virus type 1 disease.

Granulocyte colony-stimulating factor (r-met Hu G-CSF; filgrastim; 10 microgram/kg/day for 7 days) was used to mobilize CD34+stem cells into the peripheral blood of human immunodeficiency virus type 1 (HIV-1)-infected individuals and a group of HIV-1-uninfected donors as a measure of immunologic reserve in HIV-1-infected people. G-CSF mobilized CD34+ cells of HIV-1-infected individuals with cell counts >500 CD4+ cells/mm3, as well as in HIV-1-uninfected donors. In contrast, CD34 cell mobilization was significantly blunted in HIV-1-infected individuals with cell counts <500 CD4+ cells/mm3 (<200 cell days vs. >650 cell days, P<.0005, compared with the >500 CD4+ cell cohort). At least 1.75x10(7) CD34 cells were harvested by leukapheresis from patients in each study cohort. CD34+ cell viability and the ability to differentiate precursor cells into myeloid and erythroid progenitor cells were not affected by HIV-1 infection.

Adult↗
PubMed2000

Hepatosplenic gamma-delta T-cell lymphoma as a late-onset posttransplant lymphoproliferative disorder in renal transplant recipients.

We report 2 cases of renal transplant recipients in whom hepatosplenic gamma-delta T-cell lymphoma (gamma-delta HSTCL) developed 5 and 10 years after transplantation. Both patients had marked hepatosplenomegaly, B symptoms (weight loss, fever, and night sweats), and abnormal peripheral blood findings, including anemia in both, thrombocytopenia and leukoerythroblastic changes in 1, and leukocytosis in the other. Markedly atypical lymphoid infiltrate of intermediate to large cells was observed in the spleen, liver, and bone marrow. The malignant cells showed typical immunophenotype of gamma-delta T cells (CD2+, CD3+, CD4-, CD8-, CD7+, gamma-delta T-cell receptor-positive, and alpha-beta T-cell receptor-negative) with clonal T-cell receptor gene rearrangement and were of the V-delta-1 subset. In addition, the cells contained a cytolytic granule-associated protein, TIA-1, and Fas ligand, indicating cytotoxic T-cell differentiation. The malignant T cells in both cases were of host tissue origin. Both cases were negative for Epstein-Barr virus genome using Southern blot analysis. The patients did not respond to reduction of immunosuppression. Despite initial response to chemotherapy, both patients died within 6 months of diagnosis. Our findings indicate that gamma-delta HSTCL can occur as a late complication in transplant recipients.

Adult↗