triki ahmed - Academia.edu (original) (raw)

Papers by triki ahmed

Research paper thumbnail of Genetic characterization of clade B measles viruses isolated in Tunisia and Libya 2002–2009 and a proposed new subtype within the B3 genotype

Research paper thumbnail of The First Genome-Wide Scan in a Tunisian Family With Generalized Epilepsy With Febrile Seizure Plus (GEFS

Journal of Child Neurology, 2010

Generalized epilepsy with febrile seizure plus (GEFS+) is an autosomal dominant disorder. In the ... more Generalized epilepsy with febrile seizure plus (GEFS+) is an autosomal dominant disorder. In the literature, 5 responsible genes were identified and 2 novel susceptibility loci for GEFS+ at 2p24 and 8p23-p21 were reported, indicating the genetic heterogeneity of this disorder. The aim of this report is to identify the responsible loci in a large affected Tunisian family by performing a 10cM density genome-wide scan. The highest multipoint logarithm of odds (LOD) score (1.04) was found for D5S407 in the absence of recombination. Two other interesting regions were found around marker D19S210 (LOD=0.799) and D7S484 (LOD=0.61) markers. To fine map these loci, additional markers in 2 regions on 5q13.3 and 7p14.2 were analyzed and positive LOD scores for both loci were obtained. Sequencing of the Sodium channel subunit beta-1 gene (SCN1B) (19q13.1) showed the absence of any causal mutation. Our findings emphasized the genetic heterogeneity of febrile seizures.

Research paper thumbnail of Genetic screening of two Tunisian families with generalized epilepsy with febrile seizures plus

European Journal of Neurology, 2009

Background and purpose: Febrile Seizure can be associated with heterogeneous epilepsy phenotypes... more Background and purpose: Febrile Seizure can be associated with heterogeneous epilepsy phenotypes regrouped in a syndrome called generalized epilepsy with febrile seizures plus (GEFS+). The aim of this report is to search for the gene responsible for GEFS+ in two affected Tunisian families.Methods: Microsatellite marker analysis was performed on the known FS and GEFS+ loci. According to the results obtained by statistical analyses, GABRG2 on GEFS+3 locus and SCN1A on GEFS+2 locus were considered as two of the potential candidate genes and were tested for mutations by direct sequencing.Results and conclusions: The mutation analysis and statistical test of the GABRG2 gene revealed a disease association with rs211014 in intron 8 (χ2 = 5.25, P = 0.021). A sequencing analysis of the SCN1A gene was performed for the two tested families and showed a known mutation (c.1811G>A) and a putative disease-associated haplotype in only one family. Our results support that SCN1A is the responsible gene for GEFS+ in one of the two studied Tunisian families and suggest a positive association of an intronic SNP in the GABRG2 gene in both families.

Research paper thumbnail of Severe MDC1A Congenital Muscular Dystrophy Due to a Splicing Mutation in the LAMA2 Gene Resulting in Exon Skipping and Significant Decrease of mRNA Level

Research paper thumbnail of Intercell Interference Coordination Algorithms in OFDMA Wireless Systems

Research paper thumbnail of Imputing censored data with desirable spatial covariance function properties using simulated annealing

Journal of Geographical Systems, 2010

When measurements of values that are less than the limit of detection are reported as not detecte... more When measurements of values that are less than the limit of detection are reported as not detected, the data are referred to as censored. The non-recording of values below the limit of detection is common in soil science research although modelling data affected by censoring can be problematic. This paper develops and tests a modified version of Spatial Simulated Annealing, called Simulated Annealing by Variogram and Histogram form, for drawing values for censored points given a mixed set of observed and censored data. The algorithm aims to maximise the goodness of fitting between the experimental and theoretical variograms (by allowing variation in its parameters) while the imputed values are constrained to a target histogram form. In practice, the experimental histogram is estimated by transforming the available data (interval and exact observations) to quantiles and fitting a plausible distribution. The theoretical distribution of the data is used to constrain the variogram fitting. The proposed simulated annealing method is designed to find the optimal spatial arrangement of values, given by the lowest errors in variogram and histogram fitting and kriging prediction. The accuracy of the method proposed is assessed on a simulated data set in which the censored point values are known and compared with the Spatial Simulated Annealing algorithm. According to the results obtained, the Simulated Annealing by Variogram and Histogram form (SAVH) approach can be recommended as a useful tool for the analysis of spatially distributed data with censoring.

Research paper thumbnail of A two-stage stochastic integer programming approach as a mixture of Branch-and-Fix Coordination and Benders Decomposition schemes

We present an algorithmic approach for solving two-stage stochastic mixed 0-1 problems. The first... more We present an algorithmic approach for solving two-stage stochastic mixed 0-1 problems. The first stage constraints of the Deterministic Equivalent Model have 0-1 variables and continuous variables. The approach uses the Twin Node Family (TNF) concept within the algorithmic framework so-called Branch-and-Fix Coordination for satisfying the nonanticipativity constraints, jointly with a Benders Decomposition scheme for solving a given LP model at each TNF integer set. As an illustrative case, the structuring of a portfolio of Mortgage-Backed Securities under uncertainty in the interest rate path along a given time horizon is used. Some computational experience is reported.

Research paper thumbnail of P0368 WILSON DISEASE: TUNISIAN PAEDIATRIC EXPERIENCE

Journal of Pediatric Gastroenterology and Nutrition, 2004

Research paper thumbnail of Do we know all there is to know about Familial Adenomatous Polyposis

Gastroenterologie Clinique Et Biologique, 2007

Familial Adenomatous Polyposis (FAP) and Attenuated FAP (AFAP) are caused by a germline mutation ... more Familial Adenomatous Polyposis (FAP) and Attenuated FAP (AFAP) are caused by a germline mutation in the Adenomatous polyposis coli (APC) gene. Recently, a new pathway characterized by a biallelic mutation in the MYH gene, with a recessive model of inheritance was discovered for this inherited syndrome. This report describes a Tunisian patient with an attenuated FAP phenotype, presenting seven colon polyps and an adenocarcinoma but no detectable germline mutations in the FAP target genes. A well known somatic mutation was found in the APC mutation cluster region (MCR). This case shows that further studies are needed to fully understand all the pathways of the FAP syndrome.

Research paper thumbnail of Seroepidemiology of hepatitis B, C and delta viruses in Tunisia

Transactions of The Royal Society of Tropical Medicine and Hygiene, 1997

Serum samples from 33 363 healthy people inTunisia have been tested for serological markers of he... more Serum samples from 33 363 healthy people inTunisia have been tested for serological markers of hepatitis B, C and delta viruses (HBV, HCV and HDV). Hepatitis B surface antigen (HBsAg) was detected in 65% of sera. The overall seroprevalence of HBV was 37.5%.Vertical and perinatal transmission of HBV in the first 3 months of life occurred in only 0.4% of 177 mother and child pairs. HBV seroprevalence was 10.7% in infants under 5 years old and increased with age rapidly till 25 years of age and then more slowly in adulthood, reaching 54% for people aged over 40 years. HBsAg seropositivity varied throughout the country, ranging from 3% to 13% with higher prevalences in the south and central-west regions. Overall seronrevalences for HDV and HCV were 17.7% and 0.4%. resnectivelv. HDV sunerinfection occurred later &an HBV and increased with age in parallel with HBV. &e;all, H6V and Hl3V infections had different geographical distributions throughout the country. The study confirmed the high prevalence of HBV infection in Tunisia; it occurs mainly in children and teenagers, and vertical and perinatal transmission of HBV does not annear to be sipnificant. HDV sunerinfection is auite common in Tunisia and occurs in almost 44% of i&viduals infected with HBV. In contrast, seropr&alence of HCV in theTunisian general population was low (0.4%).These results indicate differences in the distribution of the viruses and/or different routes of transmission.

Research paper thumbnail of Le diabète insipide central chez l'enfant : étude de six observations

IntroductionThe central insipid diabetes (DIC) is defined by the excretion — abnormally important... more IntroductionThe central insipid diabetes (DIC) is defined by the excretion — abnormally important — of dilute urines at an absolute or relative deficiency in endogen vasopressin and susceptible to exogen vasopressin.

Research paper thumbnail of A putative disease-associated haplotype within the SCN1A gene in Dravet syndrome

Biochemical and Biophysical Research Communications, 2011

Dravet syndrome (DS), previously known as severe myoclonic epilepsy of infancy, is one of the mos... more Dravet syndrome (DS), previously known as severe myoclonic epilepsy of infancy, is one of the most severe forms of childhood epilepsy. DS is caused by a mutation in the neuronal voltage-gated sodium-channel alpha-subunit gene (SCN1A). However, 25-30% of patients with DS are negative for the SCN1A mutation screening, suggesting that other molecular mechanisms may account for these disorders. Recently, the first case of DS caused by a mutation in the neuronal voltage-gated sodium-channel beta-subunit gene (SCN1B) was also reported. In this report we aim to make the molecular analysis of the SCN1A and SCN1B genes in two Tunisian patients affected with DS. The SCN1A and SCN1B genes were tested for mutations by direct sequencing. No mutation was revealed in the SCN1A and SCN1B genes by sequencing analyses. On the other hand, 11 known single nucleotide polymorphisms were identified in the SCN1A gene and composed a putative disease-associated haplotype in patients with DS phenotype. One of the two patients with putative disease-associated haplotype in SCN1A had also one known single nucleotide polymorphism in the SCN1B gene. The sequencing analyses of the SCN1A gene revealed the presence of a putative disease-associated haplotype in two patients affected with Dravet syndrome.

Research paper thumbnail of Genetic characterization of clade B measles viruses isolated in Tunisia and Libya 2002–2009 and a proposed new subtype within the B3 genotype

Research paper thumbnail of The First Genome-Wide Scan in a Tunisian Family With Generalized Epilepsy With Febrile Seizure Plus (GEFS

Journal of Child Neurology, 2010

Generalized epilepsy with febrile seizure plus (GEFS+) is an autosomal dominant disorder. In the ... more Generalized epilepsy with febrile seizure plus (GEFS+) is an autosomal dominant disorder. In the literature, 5 responsible genes were identified and 2 novel susceptibility loci for GEFS+ at 2p24 and 8p23-p21 were reported, indicating the genetic heterogeneity of this disorder. The aim of this report is to identify the responsible loci in a large affected Tunisian family by performing a 10cM density genome-wide scan. The highest multipoint logarithm of odds (LOD) score (1.04) was found for D5S407 in the absence of recombination. Two other interesting regions were found around marker D19S210 (LOD=0.799) and D7S484 (LOD=0.61) markers. To fine map these loci, additional markers in 2 regions on 5q13.3 and 7p14.2 were analyzed and positive LOD scores for both loci were obtained. Sequencing of the Sodium channel subunit beta-1 gene (SCN1B) (19q13.1) showed the absence of any causal mutation. Our findings emphasized the genetic heterogeneity of febrile seizures.

Research paper thumbnail of Genetic screening of two Tunisian families with generalized epilepsy with febrile seizures plus

European Journal of Neurology, 2009

Background and purpose: Febrile Seizure can be associated with heterogeneous epilepsy phenotypes... more Background and purpose: Febrile Seizure can be associated with heterogeneous epilepsy phenotypes regrouped in a syndrome called generalized epilepsy with febrile seizures plus (GEFS+). The aim of this report is to search for the gene responsible for GEFS+ in two affected Tunisian families.Methods: Microsatellite marker analysis was performed on the known FS and GEFS+ loci. According to the results obtained by statistical analyses, GABRG2 on GEFS+3 locus and SCN1A on GEFS+2 locus were considered as two of the potential candidate genes and were tested for mutations by direct sequencing.Results and conclusions: The mutation analysis and statistical test of the GABRG2 gene revealed a disease association with rs211014 in intron 8 (χ2 = 5.25, P = 0.021). A sequencing analysis of the SCN1A gene was performed for the two tested families and showed a known mutation (c.1811G>A) and a putative disease-associated haplotype in only one family. Our results support that SCN1A is the responsible gene for GEFS+ in one of the two studied Tunisian families and suggest a positive association of an intronic SNP in the GABRG2 gene in both families.

Research paper thumbnail of Severe MDC1A Congenital Muscular Dystrophy Due to a Splicing Mutation in the LAMA2 Gene Resulting in Exon Skipping and Significant Decrease of mRNA Level

Research paper thumbnail of Intercell Interference Coordination Algorithms in OFDMA Wireless Systems

Research paper thumbnail of Imputing censored data with desirable spatial covariance function properties using simulated annealing

Journal of Geographical Systems, 2010

When measurements of values that are less than the limit of detection are reported as not detecte... more When measurements of values that are less than the limit of detection are reported as not detected, the data are referred to as censored. The non-recording of values below the limit of detection is common in soil science research although modelling data affected by censoring can be problematic. This paper develops and tests a modified version of Spatial Simulated Annealing, called Simulated Annealing by Variogram and Histogram form, for drawing values for censored points given a mixed set of observed and censored data. The algorithm aims to maximise the goodness of fitting between the experimental and theoretical variograms (by allowing variation in its parameters) while the imputed values are constrained to a target histogram form. In practice, the experimental histogram is estimated by transforming the available data (interval and exact observations) to quantiles and fitting a plausible distribution. The theoretical distribution of the data is used to constrain the variogram fitting. The proposed simulated annealing method is designed to find the optimal spatial arrangement of values, given by the lowest errors in variogram and histogram fitting and kriging prediction. The accuracy of the method proposed is assessed on a simulated data set in which the censored point values are known and compared with the Spatial Simulated Annealing algorithm. According to the results obtained, the Simulated Annealing by Variogram and Histogram form (SAVH) approach can be recommended as a useful tool for the analysis of spatially distributed data with censoring.

Research paper thumbnail of A two-stage stochastic integer programming approach as a mixture of Branch-and-Fix Coordination and Benders Decomposition schemes

We present an algorithmic approach for solving two-stage stochastic mixed 0-1 problems. The first... more We present an algorithmic approach for solving two-stage stochastic mixed 0-1 problems. The first stage constraints of the Deterministic Equivalent Model have 0-1 variables and continuous variables. The approach uses the Twin Node Family (TNF) concept within the algorithmic framework so-called Branch-and-Fix Coordination for satisfying the nonanticipativity constraints, jointly with a Benders Decomposition scheme for solving a given LP model at each TNF integer set. As an illustrative case, the structuring of a portfolio of Mortgage-Backed Securities under uncertainty in the interest rate path along a given time horizon is used. Some computational experience is reported.

Research paper thumbnail of P0368 WILSON DISEASE: TUNISIAN PAEDIATRIC EXPERIENCE

Journal of Pediatric Gastroenterology and Nutrition, 2004

Research paper thumbnail of Do we know all there is to know about Familial Adenomatous Polyposis

Gastroenterologie Clinique Et Biologique, 2007

Familial Adenomatous Polyposis (FAP) and Attenuated FAP (AFAP) are caused by a germline mutation ... more Familial Adenomatous Polyposis (FAP) and Attenuated FAP (AFAP) are caused by a germline mutation in the Adenomatous polyposis coli (APC) gene. Recently, a new pathway characterized by a biallelic mutation in the MYH gene, with a recessive model of inheritance was discovered for this inherited syndrome. This report describes a Tunisian patient with an attenuated FAP phenotype, presenting seven colon polyps and an adenocarcinoma but no detectable germline mutations in the FAP target genes. A well known somatic mutation was found in the APC mutation cluster region (MCR). This case shows that further studies are needed to fully understand all the pathways of the FAP syndrome.

Research paper thumbnail of Seroepidemiology of hepatitis B, C and delta viruses in Tunisia

Transactions of The Royal Society of Tropical Medicine and Hygiene, 1997

Serum samples from 33 363 healthy people inTunisia have been tested for serological markers of he... more Serum samples from 33 363 healthy people inTunisia have been tested for serological markers of hepatitis B, C and delta viruses (HBV, HCV and HDV). Hepatitis B surface antigen (HBsAg) was detected in 65% of sera. The overall seroprevalence of HBV was 37.5%.Vertical and perinatal transmission of HBV in the first 3 months of life occurred in only 0.4% of 177 mother and child pairs. HBV seroprevalence was 10.7% in infants under 5 years old and increased with age rapidly till 25 years of age and then more slowly in adulthood, reaching 54% for people aged over 40 years. HBsAg seropositivity varied throughout the country, ranging from 3% to 13% with higher prevalences in the south and central-west regions. Overall seronrevalences for HDV and HCV were 17.7% and 0.4%. resnectivelv. HDV sunerinfection occurred later &an HBV and increased with age in parallel with HBV. &e;all, H6V and Hl3V infections had different geographical distributions throughout the country. The study confirmed the high prevalence of HBV infection in Tunisia; it occurs mainly in children and teenagers, and vertical and perinatal transmission of HBV does not annear to be sipnificant. HDV sunerinfection is auite common in Tunisia and occurs in almost 44% of i&viduals infected with HBV. In contrast, seropr&alence of HCV in theTunisian general population was low (0.4%).These results indicate differences in the distribution of the viruses and/or different routes of transmission.

Research paper thumbnail of Le diabète insipide central chez l'enfant : étude de six observations

IntroductionThe central insipid diabetes (DIC) is defined by the excretion — abnormally important... more IntroductionThe central insipid diabetes (DIC) is defined by the excretion — abnormally important — of dilute urines at an absolute or relative deficiency in endogen vasopressin and susceptible to exogen vasopressin.

Research paper thumbnail of A putative disease-associated haplotype within the SCN1A gene in Dravet syndrome

Biochemical and Biophysical Research Communications, 2011

Dravet syndrome (DS), previously known as severe myoclonic epilepsy of infancy, is one of the mos... more Dravet syndrome (DS), previously known as severe myoclonic epilepsy of infancy, is one of the most severe forms of childhood epilepsy. DS is caused by a mutation in the neuronal voltage-gated sodium-channel alpha-subunit gene (SCN1A). However, 25-30% of patients with DS are negative for the SCN1A mutation screening, suggesting that other molecular mechanisms may account for these disorders. Recently, the first case of DS caused by a mutation in the neuronal voltage-gated sodium-channel beta-subunit gene (SCN1B) was also reported. In this report we aim to make the molecular analysis of the SCN1A and SCN1B genes in two Tunisian patients affected with DS. The SCN1A and SCN1B genes were tested for mutations by direct sequencing. No mutation was revealed in the SCN1A and SCN1B genes by sequencing analyses. On the other hand, 11 known single nucleotide polymorphisms were identified in the SCN1A gene and composed a putative disease-associated haplotype in patients with DS phenotype. One of the two patients with putative disease-associated haplotype in SCN1A had also one known single nucleotide polymorphism in the SCN1B gene. The sequencing analyses of the SCN1A gene revealed the presence of a putative disease-associated haplotype in two patients affected with Dravet syndrome.