Biomedical subjects

E Richard

Publications and source records attributed to E Richard.

At least 19 recordsLinked to original sources

PubMed2006

[Cholinesterase inhibitors in dementia: the precarious balance between efficacy and safety].

Cholinesterase inhibitors are widely prescribed in patients with Alzheimer's disease. Recently it has become clear that using these medications increases the risk of serious adverse events like cardiac arrhythmias, and some studies report a much-increased mortality in the treatment group on comparison with the placebo group. In the light of the at best, modest, treatment effects, we advocate that the safety of cholinesterase inhibitors should be the subject of continuing, intense scrutiny. Efforts should be made to delineate the profile of a true 'cholinergic deficiency syndrome', in order to be able to prescribe these medications to a group of patients in whom the benefits outweigh the risks.

Alzheimer Disease↗

PubMed2004

Hematopoietic stem cell gene therapy of murine protoporphyria by methylguanine-DNA-methyltransferase-mediated in vivo drug selection.

Erythropoietic protoporphyria (EPP) is an inherited defect of the ferrochelatase (FECH) gene characterized by the accumulation of toxic protoporphyrin in the liver and bone marrow resulting in severe skin photosensitivity. We previously described successful gene therapy of an animal model of the disease with erythroid-specific lentiviral vectors in the absence of preselection of corrected cells. However, the high-level of gene transfer obtained in mice is not translatable to large animal models and humans if there is no selective advantage for genetically modified hematopoietic stem cells (HSCs) in vivo. We used bicistronic SIN-lentiviral vectors coexpressing EGFP or FECH and the G156A-mutated O6-methylguanine-DNA-methyltransferase (MGMT) gene, which allowed efficient in vivo selection of transduced HSCs after O6-benzylguanine and BCNU treatment. We demonstrate for the first time that the correction and in vivo expansion of deficient transduced HSC population can be obtained by this dual gene therapy, resulting in a progressive increase of normal RBCs in EPP mice and a complete correction of skin photosensitivity. Finally, we developed a novel bipromoter SIN-lentiviral vector with a constitutive expression of MGMT gene to allow the selection of HSCs and with an erythroid-specific expression of the FECH therapeutic gene.

Animals↗

PubMed2003

Lentivirus-mediated gene transfer of uroporphyrinogen III synthase fully corrects the porphyric phenotype in human cells.

Congenital erythropoietic porphyria (CEP) is an inherited disease due to a deficiency in the uroporphyrinogen III synthase, the fourth enzyme of the heme biosynthesis pathway. It is characterized by accumulation of uroporphyrin I in the bone marrow, peripheral blood and other organs. The prognosis of CEP is poor, with death often occurring early in adult life. For severe transfusion-dependent cases, when allogeneic cell transplantation cannot be performed, the autografting of genetically modified primitive/stem cells may be the only alternative. In vitro gene transfer experiments have documented the feasibility of gene therapy via hematopoietic cells to treat this disease. In the present study lentiviral transduction of porphyric cell lines and primary CD34(+) cells with the therapeutic human uroporphyrinogen III synthase (UROS) cDNA resulted in both enzymatic and metabolic correction, as demonstrated by the increase in UROS activity and the suppression of porphyrin accumulation in transduced cells. Very high gene transfer efficiency (up to 90%) was achieved in both cell lines and CD34(+) cells without any selection. Expression of the transgene remained stable over long-term liquid culture. Furthermore, gene expression was maintained during in vitro erythroid differentiation of CD34(+) cells. Therefore the use of lentiviral vectors is promising for the future treatment of CEP patients by gene therapy.

Adult↗

PubMed2002

[Rivastigmine for Alzheimer disease; evaluation of preliminary results and of structured assessment of efficacy].

OBJECTIVE: Evaluation of the initial experiences with rivastigmine in Alzheimer's disease. DESIGN: Retrospective. METHOD: Data were collected from patients with Alzheimer's disease who were treated with rivastigmine between 1 October 1998-30 November 1999 at the Memory Disorders Outpatients Clinic at the Academic Medical Centre or the Slotervaart Hospital, both in Amsterdam, the Netherlands. Before, and 6 months after treatment, the course of the disease was evaluated using clinimetric scales relating to cognitive functions, behavioural abnormalities and instrumental daily functions. The treatment results were considered to be 'favourable' if they corresponded with a disease course seen in less than 10% of untreated Alzheimer patients. RESULTS: During the study period, 53 patients were treated, 36 women and 17 men, with a mean age of 77 years (range: 57-89). Follow-up data were incomplete for four patients. Of the remaining patients, 27 (55%; 95% CI: 40-69) withdrew from treatment during the first 6 months, mainly because of gastrointestinal side-effects. Of the other 22 patients (45%; 31-60) 18 continued with rivastigmine treatment (18/49 = 37%; 23-52), and in three of these patients the disease course was favourable (3/49 = 6%; 1-17). CONCLUSION: In daily practice, over 50% of the patients were unable to tolerate rivastigmine. Structured evaluation of treatment efficacy was feasible in this population. Treatment with rivastigmine seemed to be beneficial in a small proportion of the patients.

Activities of Daily Living↗

PubMed2001

[Family with malaria: from the asymptomatic to life-threatening].

Five members of a Dutch family of Nigerian origin (three girls aged 1, 6 and 8 years and their parents, mother aged 32 and father aged 41 years), had been infected with Plasmodium falciparum during a visit to Nigeria. The mildest infection could be treated at home with oral medication. The severest case had to be admitted to the paediatric intensive care unit for respiratory support and exchange transfusions. Four patients were treated with quinine. A combination of atovaquone and proguanil was added, resulting in a quick decline of the parasitaemia. Whenever a patient is suspected of malaria, laboratory tests should be carried out immediately and treatment should be started as soon as possible, in order to prevent possible complications. The early recognition of any of the alarm symptoms, for example, lowered consciousness, abnormal respiratory movements, cold extremities, convulsions, hypoglycaemia, severe anaemia and a high parasitaemia, whether at casualty or the general practitioner's surgery is crucial.

Adult↗

PubMed2001

Screening for PS1 mutations in a referral-based series of AD cases: 21 novel mutations.

BACKGROUND: Mutations in the presenilin-1 gene (PS1) account for a majority of patients with early-onset familial AD. However, the clinical indications and algorithms for genetic testing in dementia are still evolving. METHODS: The entire open reading frame of the PS1 gene was sequenced in a series of 414 consecutive patients referred for diagnostic testing, including 372 patients with AD and 42 asymptomatic persons with a strong family history of AD. RESULTS: Forty-eight independent patients screened had a PS1 mutation including 21 novel mutations. In addition, 3% of subjects (11/413) had a known polymorphism, the Glu318Gly substitution. The majority of the mutations were missense substitutions but there were three insertions and Delta exon 10 mutation. With six exceptions (codons 35, 178, 352, 354, 358, and 365) most of the mutations occurred at residues conserved in the homologous PS2 gene or in PS1 of other species. CONCLUSIONS: Eleven percent of a referral-based series of patients with AD can be explained by coding sequence mutations in the PS1 gene. The high frequency of PS1 mutations in this study indicates that screening for PS1 mutations in AD is likely to be successful, especially when directed at patients with a positive family history with onset before 60 years (90% of those with PS1 mutations were affected by age 60 years). This will also have significance for the secondary identification of at-risk relatives who might be candidates for future prophylactic therapies for AD.

Adult↗

PubMed2001

Control of conformational equilibria in the human B2 bradykinin receptor. Modeling of nonpeptidic ligand action and comparison to the rhodopsin structure.

A prototypic study of the molecular mechanisms of activation or inactivation of peptide hormone G protein-coupled receptors was carried out on the human B2 bradykinin receptor. A detailed pharmacological analysis of receptor mutants possessing either increased constitutive activity or impaired activation or ligand recognition allowed us to propose key residues participating in intramolecular interaction networks stabilizing receptor inactive or active conformations: Asn(113) and Tyr(115) (TM III), Trp(256) and Phe(259) (TM VI), Tyr(295) (TM VII) which are homologous of the rhodopsin residues Gly(120), Glu(122), Trp(265), Tyr(268), and Lys(296), respectively. An essential experimental finding was the spatial proximity between Asn(113), which is the cornerstone of inactive conformations, and Trp(256) which plays a subtle role in controlling the balance between active and inactive conformations. Molecular modeling and mutagenesis data showed that Trp(256) and Tyr(295) constitute, together with Gln(288), receptor contact points with original nonpeptidic ligands. It provided an explanation for the ligand inverse agonist behavior on the WT receptor, with underlying restricted motions of TMs III, VI, and VII, and its agonist behavior on the Ala(113) and Phe(256) constitutively activated mutants. These data on the B2 receptor emphasize that conformational equilibria are controlled in a coordinated fashion by key residues which are located at strategic positions for several G protein-coupled receptors. They are discussed in comparison with the recently determined rhodopsin crystallographic structure.

Amino Acid Sequence↗

PubMed2001

[Evaluation of the therapeutic effects in individual patients with Alzheimer disease].

Rivastigmine was recently licensed for treatment of Alzheimer's disease on the basis of large double-blind placebo-controlled clinical trials. However, it is difficult to determine the clinical relevance for individual patients from the results of this type of clinical trial. With the help of standardised measurements in individual patients the clinical relevance can be better established. In order to avoid extra burden on patients, caregivers and doctors, these measurements should be simple. A combination of three clinimetrical scales for cognition, ability to perform daily activities and behaviour, which takes about 15 min to complete, appears to be efficient. Comparison of these data with data from a group of untreated Alzheimer's patients can give an impression of the efficacy of the medication. With the use of goal-attainment scaling, measurements can be individualised even more. This approach allows the clinician, in consultation with the caregiver and the patient, to make an informed decision about whether or not to continue treatment.

Activities of Daily Living↗

PubMed2001

Correction of deficient CD34+ cells from peripheral blood after mobilization in a patient with congenital erythropoietic porphyria.

Congenital erythropoietic porphyria (CEP) is an inherited disease due to a deficiency in the uroporphyrinogen III synthase (UROS), the fourth enzyme of the heme pathway. It is characterized by accumulation of uroporphyrin I in the bone marrow, peripheral blood, and other organs. The onset of most cases occurs in infancy and the main symptoms are cutaneous photosensitivity and hemolysis. For severe transfusion-dependent cases, when allogeneic cell transplantation cannot be performed, autografting of genetically modified primitive/stem cells is the only alternative. In the present study, efficient mobilization of peripheral blood primitive CD34(+) cells was performed on a young adult CEP patient. Retroviral transduction of this cell population with the therapeutic human UROS (hUS) gene resulted in both enzymatic and metabolic correction of CD34(+)-derived cells, as demonstrated by the increase in UROS activity and by a 53% drop in porphyrin accumulation. A 10-24% gene transfer efficiency was achieved in the most primitive cells, as demonstrated by the expression of enhanced green fluorescent protein (EGFP) in long-term culture-initiating cells (LTC-IC). Furthermore, gene expression remained stable during in vitro erythroid differentiation. Therefore, these results are promising for the future treatment of CEP patients by gene therapy.

Antigens, CD34↗

PubMed2001

Gene therapy of a mouse model of protoporphyria with a self-inactivating erythroid-specific lentiviral vector without preselection.

Successful treatment of blood disorders by gene therapy has several complications, one of which is the frequent lack of selective advantage of genetically corrected cells. Erythropoietic protoporphyria (EPP), caused by a ferrochelatase deficiency, is a good model of hematological genetic disorders with a lack of spontaneous in vivo selection. This disease is characterized by accumulation of protoporphyrin in red blood cells, bone marrow, and other organs, resulting in severe skin photosensitivity. Here we develop a self-inactivating lentiviral vector containing human ferrochelatase cDNA driven by the human ankyrin-1/beta-globin HS-40 chimeric erythroid promoter/enhancer. We collected bone marrow cells from EPP male donor mice for lentiviral transduction and injected them into lethally irradiated female EPP recipient mice. We observed a high transduction efficiency of hematopoietic stem cells resulting in effective gene therapy of primary and secondary recipient EPP mice without any selectable system. Skin photosensitivity was corrected for all secondary engrafted mice and was associated with specific ferrochelatase expression in the erythroid lineage. An erythroid-specific expression was sufficient to reverse most of the clinical and biological manifestations of the disease. This improvement in the efficiency of gene transfer with lentiviruses may contribute to the development of successful clinical protocols for erythropoietic diseases.

Animals↗

PubMed2001

Treatment of post-haemorrhage ventricular dilatation with an Ommaya's reservoir: management and outcome of 64 preterm infants.

Over a 5-year period, an Ommaya's reservoir has been inserted in a single neurosurgical centre in each of 64 preterm infants with post-haemorrhage ventricular dilatation (PHVD). Their mean gestational age at birth was 29.2 weeks. The average age at reservoir insertion was 24 days. Seventeen infants received a fibrinolytic agent through the reservoir. Infections occurred in 14 patients. Two patients died after handling of their reservoirs. Thirty-one of the 45 survivors required a shunt placement. After a follow-up ranging from 6 months to more than 4 years, 17 of 43 patients have severe sequelae or are handicapped. Compared with the results of other studies, our experience does not suggest that treatment of PHVD with an Ommaya's reservoir is beneficial in term of mortality, shunt placement, and/or neurological outcome. The place of Ommaya's reservoir among the various means of managing PHVD should be carefully evaluated, as should the best way of using this appliance safely.

Catheters, Indwelling↗

PubMed2001

Mutations in the open reading frame of the beta-site APP cleaving enzyme (BACE) locus are not a common cause of Alzheimer's disease.

Amyloid beta-peptide (Abeta) plays a central role in the pathogenesis of Alzheimer's disease (AD). The gene encoding the beta-site APP cleaving enzyme (BACE), one of two enzymes that sequentially cleave the beta-amyloid precursor protein to generate Abeta, has recently been cloned. We tested the hypothesis that BACE might be genetically associated with AD by linkage analysis (56 pedigrees), by direct nucleotide sequencing of the entire open reading frame (20 subjects with familial AD, and 10 subjects with sporadic AD) and by allelic association analysis (155 AD cases and 173 non-demented controls). Our results revealed no evidence for either genetic linkage or allelic association between BACE and AD, and no coding sequence mutations were detected in the open reading frame of the BACE gene. These data suggest that while BACE protein plays an important role in the pathogenesis of AD, and may be a robust therapeutic target, it is unlikely to be a major AD susceptibility locus.

Aged↗

PubMed2001

Successful therapeutic effect in a mouse model of erythropoietic protoporphyria by partial genetic correction and fluorescence-based selection of hematopoietic cells.

Erythropoietic protoporphyria is characterized clinically by skin photosensitivity and biochemically by a ferrochelatase deficiency resulting in an excessive accumulation of photoreactive protoporphyrin in erythrocytes, plasma and other organs. The availability of the Fech(m1Pas)/Fech(m1Pas) murine model allowed us to test a gene therapy protocol to correct the porphyric phenotype. Gene therapy was performed by ex vivo transfer of human ferrochelatase cDNA with a retroviral vector to deficient hematopoietic cells, followed by re-injection of the transduced cells with or without selection in the porphyric mouse. Genetically corrected cells were separated by FACS from deficient ones by the absence of fluorescence when illuminated under ultraviolet light. Five months after transplantation, the number of fluorescent erythrocytes decreased from 61% (EPP mice) to 19% for EPP mice engrafted with low fluorescent selected BM cells. Absence of skin photosensitivity was observed in mice with less than 20% of fluorescent RBC. A partial phenotypic correction was found for animals with 20 to 40% of fluorescent RBC. In conclusion, a partial correction of bone marrow cells is sufficient to reverse the porphyric phenotype and restore normal hematopoiesis. This selection system represents a rapid and efficient procedure and an excellent alternative to the use of potentially harmful gene markers in retroviral vectors.

Animals↗

PubMed2000

The binding site of human adenosine deaminase for CD26/Dipeptidyl peptidase IV: the Arg142Gln mutation impairs binding to cd26 but does not cause immune deficiency.

Human, but not murine, adenosine deaminase (ADA) forms a complex with the cell membrane protein CD26/dipeptidyl peptidase IV. CD26-bound ADA has been postulated to regulate extracellular adenosine levels and to modulate the costimulatory function of CD26 on T lymphocytes. Absence of ADA-CD26 binding has been implicated in causing severe combined immunodeficiency due to ADA deficiency. Using human-mouse ADA hybrids and ADA point mutants, we have localized the amino acids critical for CD26 binding to the helical segment 126-143. Arg142 in human ADA and Gln142 in mouse ADA largely determine the capacity to bind CD26. Recombinant human ADA bearing the R142Q mutation had normal catalytic activity per molecule, but markedly impaired binding to a CD26(+) ADA-deficient human T cell line. Reduced CD26 binding was also found with ADA from red cells and T cells of a healthy individual whose only expressed ADA has the R142Q mutation. Conversely, ADA with the E217K active site mutation, the only ADA expressed by a severely immunodeficient patient, showed normal CD26 binding. These findings argue that ADA binding to CD26 is not essential for immune function in humans.

Adenosine Deaminase↗

PubMed2000

Regulation of epiblast cell movements by chondroitin sulfate during gastrulation in the chick.

Avian gastrulation is dependent on the ingression of outer layer cells into the interior of the embryo by means of a transient structure referred to as the primitive streak. As the growing streak progresses through the central area pellucida of the blastoderm, selective de-epithelialization of epiblast cells results in the initial migratory cells of the primitive mesoderm and endoderm. Here, we have examined the possibility that extracellular matrix molecules of the epiblast basal lamina influence the selection of streak-specific epiblast cells. By using whole embryo culture, we have found that removal of chondroitin sulfate glycosaminoglycans at gastrulation stages leads to defective streak formation. In situ hybridization with streak-specific markers in these embryos reveals ectopic patterns of gene expression, suggesting that differentiation of primitive streak precursors in the pregastrula epiblast is independent of normal streak morphogenesis. In addition, in vitro assays with chondroitin sulfate containing matrices suggest that specific cells of the epiblast are inhibited from joining the streak during gastrulation. Taken together, these results indicate that the presence of chondroitin sulfate in the epiblast basal lamina facilitates the allocation of cells to the primary germ layers by preventing ectopic axis formation.

Animals↗

PubMed2000

Potential relationship between genotype and clinical outcome in propionic acidaemia patients.

Propionic acidaemia (PA) is an autosomal recessive disorder caused by mutations in either of the PCCA or PCCB genes which encode the alpha and beta subunits, respectively, of the mitochondrial enzyme propionyl-CoA carboxylase (PCC). In this work we have examined the biochemical findings and clinical outcome of 37 Spanish PA patients in relation to the mutations found in both PCCA and PCCB genes. We have detected 27 early-onset and 101 late-onset cases, showing remarkably similar biochemical features without relation to either the age of onset of the disease or the defective gene they have. Twenty-one of the patients have so far survived and three of them, now adolescents, present normal development. Different biochemical procedures allowed us to identify the defective gene in 9 PCCA deficient and 28 PCCB deficient patients. Nine putative disease-causing mutations accounting for 77.7% of mutant alleles were identified among PCCA deficient patients, each one carrying a unique genotypic combination. Of PCCB mutant alleles 98% were characterised. Four common mutations (ins/del, E168K, 1170insT and A497V) were found in 38/52 mutant chromosomes investigated, whereas the remainder of the alleles harbour 12 other different mutations. By examining the mutations identified both in PCCA and PCCB genes and the clinical evolution of patients, we have found a good correlation between certain mutations which can be considered as null with a severe phenotype, while certain missense mutations tend to be related to the late and mild forms of the disease. Expression studies, particularly of the missense mutations identified are necessary but other genetic and environmental factors probably contribute to the phenotypic variability observed in PA.

Adult↗

PubMed2000

Studies on the mechanism of a fatal clarithromycin-pimozide interaction in a patient with Tourette syndrome.

The authors report in detail the case of a 27-year-old man who experienced sudden cardiac death 2 days after coprescription of the neuroleptic pimozide and the macrolide antibiotic clarithromycin after the documentation of a prolonged QT interval. To determine the prevalence of this interaction, the authors referred to the Spontaneous Reporting System of the Food and Drug Administration and identified one similar case in which clarithromycin was coprescribed with pimozide and sudden cardiac death occurred shortly thereafter. In addition, the search identified 39 cases of cardiac arrhythmia associated with pimozide, 11 with pimozide alone, and 6 with clarithromycin alone, 1 of which had a positive rechallenge. The mechanism of the interaction between clarithromycin and pimozide seems to involve the inhibition of the hepatic metabolism of pimozide by the macrolide. The authors demonstrated that clarithromycin is able to inhibit the metabolism of pimozide in human liver microsomal preparations (K(i) = 7.65 +/- 1.18 microM) and that pimozide, but not clarithromycin or its primary metabolite, is able to prolong the electrocardiac QT interval in a dose-dependent manner in the isolated perfused rabbit heart. The increase was 9.6 +/- 1.1% in male hearts (N = 5) and 13.4 +/- 1.2% in female hearts (N = 4) (p < 0.05).

Adolescent↗

PubMed1999

Cysteine 530 of the human estrogen receptor alpha is the main covalent attachment site of 11beta-(aziridinylalkoxyphenyl)estradiols.

The efficiency of 11beta-[p(aziridinylethoxy)phenyl]estradiol 1 and 11beta-[p(aziridinylpentoxy)phenyl]estradiol 2 affinity labeling of the estrogen receptor alpha (ERalpha) was evaluated on the basis of their capacity to inhibit [(3)H]estradiol binding to lamb and human ERalphas. Relative to RU 39 411 (11beta-[p(dimethylaminoethoxy)phenyl]estradiol), the most closely related and chemically inert analogue of 1, the two electrophiles irreversibly inhibited [(3)H]estradiol binding to the lamb ERalpha. The fact that the compound effects were prevented (i) when the ERalpha hormone-binding site was occupied by estradiol and (ii) when the ERalpha-containing extracts were pretreated with methyl methanethiosulfonate (an SH-specific reagent) suggested that the compounds specifically alkylated ERalpha at cysteine residues. Wild-type human ERalpha was alkylated as efficiently as lamb ER, whereas the quadruple cysteine --> alanine mutant, in which all cysteines of the hormone-binding domain (residues 381, 417, 447, and 530) were changed to alanines, showed no significant electrophile labeling. The single C530A mutant was much less sensitive to the action of the electrophiles than the three other single mutants (C381A, C417A, and C447A). Moreover, analysis of the three double mutants (C381A/C530A, C417A/C530A, and C447A/C530A) showed that only the C381A/C530A mutant was less susceptible to electrophile labeling than the single C530A mutant. We concluded that in the hormone-binding pocket C530 was the main covalent attachment site of aziridines 1 and 2, whereas C381 could be a secondary site. These results agreed with the crystal structure of the hormone-binding domain of the human ERalpha bound to estrogen or antiestrogen, since C381 and C530 appeared to be (i) located in structural elements involved in delineating the hormone-binding pocket and (ii) in spatial proximity to each other, which was closer in the crystal structure of the ER:antiestrogen complex than in that of the ER:estrogen complex. Since C530 and C381 were also the main and secondary covalent attachment sites of tamoxifen aziridine (a nonsteroidal affinity-labeling agent), we propose a selective mode of superimposition of tamoxifen-class antiestrogens with RU 39 411-class antiestrogens, which could account for the relative positioning of the two types of ligands in the ERalpha hormone-binding pocket.

Animals↗