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T Moreau

Publications and source records attributed to T Moreau.

At least 19 recordsLinked to original sources
PubMed2001

Purification and characterization of active recombinant rat kallikrein rK9.

The rat tissue kallikrein rK9 is most abundant in the submandibular gland and the prostate. It has been successfully expressed in the Pichia pastoris yeast expression system. A full-length cDNA coding for the mature rK9 was fused in frame with yeast alpha-factor cDNA. The fusion protein was secreted into the medium with high yield without being processed by the yeast KEX2 signal peptidase. Mature rK9 was efficiently released from the fusion protein by trypsin and was purified to homogeneity by one-step affinity chromatography using soya bean trypsin inhibitor (SBTI) as affinity ligand. The identity of the recombinant enzyme was checked by N-terminal amino acid sequencing, Western blot analysis and kinetic studies. The dual trypsin- and chymotrypsin-like enzymatic specificity of rK9 was assessed by determining specificity constants (k(cat)/K(m)) for the hydrolysis of fluorogenic substrates, the peptide sequences of which were derived from proparathyroid hormone (pro-PTH) and from semenogelin-I. Our results confirmed the presence of an extended binding site in the rK9 active site. We also identified a far more sensitive substrate of this enzyme than those previously described, Abz-VKKRSARQ-EDDnp, which was hydrolysed with a catalytic efficiency k(cat)/K(m) of 420000 M(-1)s(-1). Finally, we showed that four of the five major proteins contained in secretions of rat seminal vesicles were rapidly degraded by recombinant rK9.

Amino Acid Sequence↗
PubMed2001

Subsite specificity of trypanosomal cathepsin L-like cysteine proteases. Probing the S2 pocket with phenylalanine-derived amino acids.

The S2 subsite of mammalian cysteine proteinases of the papain family is essential for specificity. Among natural amino acids, all these enzymes prefer bulky hydrophobic residues such as phenylalanine at P2. This holds true for their trypanosomal counterparts: cruzain from Trypanosoma cruzi and congopain from T. congolense. A detailed analysis of the S2 specificity of parasitic proteases was performed to gain information that might be of interest for the design of more selective pseudopeptidyl inhibitors. Nonproteogenic phenylalanyl analogs (Xaa) have been introduced into position P2 of fluorogenic substrates dansyl-Xaa-Arg-Ala-Pro-Trp, and their kinetic constants (Km, kcat/Km) have been determined with congopain and cruzain, and related host cathepsins B and L. Trypanosomal cysteine proteases are poorly stereoselective towards D/L-Phe, the inversion of chirality modifying the efficiency of the reaction but not the Km. Congopain binds cyclohexylalanine better than aromatic Phe derivatives. Another characteristic feature of congopain compared to cruzain and cathepsins B and L was that it could accomodate a phenylglycyl residue (kcat/Km = 1300 mM-1.s-1), while lengthening of the side chain by a methylene group only slightly impaired the specificity constant towards trypanosomal cysteine proteases. Mono- and di-halogenation or nitration of Phe did not affect Km for cathepsin L-like enzymes, but the presence of constrained Phe derivatives prevented a correct fitting into the S2 subsite. A model of congopain has been built to study the fit of Phe analogs within the S2 pocket. Phe analogs adopted a positioning within the S2 pocket similar to that of the Tyr of the cruzain/Z-Tyr-Ala-fluoromethylketone complex. However, cyclohexylalanine has an energetically favorable chair-like conformation and can penetrate deeper into the subsite. Fitting of modeled Phe analogs were in good agreement with kinetic parameters. Furthermore, a linear relationship could be established with logP, supporting the suggestion that fitting into the S2 pocket of trypanosomal cysteine proteases depends on the hydrophobicity of Phe analogs.

Animals↗
PubMed2001

Insulin-like growth factor binding proteins (IGFBPs) as potential physiological substrates for human kallikreins hK2 and hK3.

Insulin-like growth factors (IGFs) are important growth regulators of both normal and malignant prostate cells. Their action is regulated by six insulin-like growth factor binding proteins (IGFBPs). The proteolytic cleavage of IGFBPs by various proteases decreases dramatically their affinity for their ligands and therefore enhances the bioavailability of IGFs. To elucidate the putative biological role of prostatic kallikreins hK2 and hK3 (prostate-specific antigen) in tumour progression, we analyzed the degradation of IGFBP-2, -3, -4 and -5 by these two tissue kallikreins. We found that hK3, already characterized as an IGFBP-3 degrading protease, cleaved IGFBP-4 but not IGFBP-2 and -5, whereas hK2 cleaved all of the IGFBPs much more effectively, and at concentrations far lower than those reported for other IGFBP-degrading proteases. The proteolytic patterns after cleavage of IGFBPs by hK2 and hK3 were similar and were not modified in the presence of IGF-I. Heparin, but not other glycosaminoglycans, enhanced dramatically the ability of hK3 but not hK2 to degrade IGFBP-3 and IGFBP-4. More importantly, the IGFBP fragments generated by hK2 and hK3 had no IGF-binding capacity, as assessed by Western ligand blotting. Our results suggest that the prostatic kallikreins hK2 and hK3 may influence specifically the tumoral growth of prostate cells through the degradation of IGFBPs, to increase IGF bioavailability.

Binding Sites↗
PubMed2001

A semiparametric approach for the two-sample comparison of survival times with long-term survivors.

In the two-sample comparison of survival times with long-term survivors, the overall difference between the two distributions reflects differences occurring in early follow-up for susceptible subjects and in long-term follow-up for nonsusceptible subjects. In this setting, we propose statistics for testing (i) no overall, (ii) no short-term, and (iii) no long-term difference between the two distributions to be compared. The statistics are derived as follows. A semiparametric model is defined that characterizes a short-term effect and a long-term effect. By approximating this model about no difference in early survival, a time-dependent proportional hazards model is obtained. The statistics are obtained from this working model. The asymptotic distributions of the statistics for testing no overall or no short-term effects are ascertained, while that of the statistic for testing no long-term effect is valid only when the short-term effect is small. Simulation studies investigate the power properties of the proposed tests for different configurations. The results show the interesting behavior of the proposed tests for situations where a short-term effect is expected. An example investigating the impact of progesterone receptors status on local tumor relapse for patients with early breast cancer illustrates the use of the proposed tests.

Biometry↗
PubMed2001

A method for shortening instruments using the Rasch model. Validation on a hand functional measure.

BACKGROUND: Many measurement instruments, particularly measures of hand functional ability, frequently comprise a large number of items. Reduced versions of these instruments can facilitate their use. This work proposes a new method for shortening an instrument. METHODS: The method proposed was based on a scale of item difficulty calculated using the Rasch model. It was applied on a hand functional measure comprising 67 tests. The sample included 194 patients with hand lesions. The shortened instrument obtained was compared with those provided by classic methods used in the literature, with item random choice, and with shortened versions proposed by four independent experts, two rehabilitation physicians and two occupational therapists, who are clinicians familiar with the tool. All the statistical analyses were carried out on a random sub-group of two-thirds of the sample. A cross validation was then carried out on the remaining third. RESULTS: The reduction obtained had score non significantly different from that of the original instrument. In addition, the intra-class correlation coefficient and the Cronbach alpha coefficient were high. Among the different degrees of reduction investigated, the 12-item version seemed to be appropriate. Our method appeared to provide better results in terms of discriminant validity and internal validity than the choices of the four experts. The reductions produced were also better than those obtained by classic methods based on principal component analysis and multiple linear regression, as well as those obtained by random choices of items. CONCLUSION: The method presented is pertinent and useful. The reduction obtained appeared to be better than the choices of experts and the reductions provided by classic methods. The method could be used in other fields.

Accidents↗
PubMed2001

[Multiple sclerosis: spontaneous course, natural history].

Globally, the course and prognosis of multiple sclerosis are heterogeneous, and generally considered to be unpredictable. Advances in statistical techniques have made it possible to analyze representative cohorts of patients to clearly delineate the overall prognosis of the disease, beyond individual variations. For each individual however, there appears to be a steady progression as shown by serial quantified neurological examinations. At the present time early prediction of outcome remains impossible. In the near future, new imaging techniques may provide a solution to this problem allowing selection of patients at risk who could benefit from early treatment.

Diagnostic Imaging↗
PubMed2001

[Daily life activities and multiple sclerosis].

The onset of Multiple Sclerosis usually concerns young adults who are making plans for their life. The personal, familial, professional plans must be adapted to the course of the disease. This adapted daily life must be as normal as possible to prevent the social loneliness which is the principal complication of Multiple Sclerosis. Three frequent situations of daily life have recently been studied in Multiple Sclerosis. Pregnancy is permitted. There is a dramatic decrease of the relapse rate during pregnancy but an obvious increase after delivery. Pregnancy has no influence on disability. Vaccinations do not favor the onset or the worsening of Multiple Sclerosis according to studies with large number of patients (in particular hepatitis B vaccination). Stress is not able to trigger the onset or relapses of Multiple Sclerosis. Stress could even protect against relapses. The Multiple Sclerosis daily life does not need to take specific precautions which would expose to the marginalization of patients.

Activities of Daily Living↗
PubMed2000

Relapses and progression of disability in multiple sclerosis.

BACKGROUND: The influence of the patterns of onset of multiple sclerosis and relapses of the disease on the time course of irreversible disability is controversial. METHODS: In 1844 patients with multiple sclerosis who were followed for a mean (+/- SD) of 11 +/- 10 years, we determined the time of the clinical onset of the disease, the initial course (relapsing-remitting or progressive) and the subsequent course (relapsing-remitting, secondary progressive, or primary progressive), the times of relapses, the time to the onset of irreversible disability, and the time course of progressive, irreversible disability. We used three scores on the Kurtzke Disability Status Scale (range, 0 to 10, with higher scores indicating more severe disability) as measures of the severity and progression of disability: a score of 4 (limited walking ability but able to walk for more than 500 m without aid or rest), a score of 6 (ability to walk with unilateral support no more than 100 m without rest), and a score of 7 (ability to walk no more than 10 m without rest while leaning against a wall or holding onto furniture for support). We used Kaplan-Meier analyses to determine the influence of relapses on the time to the onset of irreversible disability. RESULTS: The median times from the onset of multiple sclerosis to the assignment of a score of 4, a score of 6, and a score of 7 on the disability scale were longer among the 1562 patients with a relapsing-remitting onset of disease (11.4, 23.1, and 33.1 years, respectively) than among the 282 patients who had progressive disease from the onset (0.0, 7.1, and 13.4 years, respectively; P<0.001 for all comparisons). In contrast, the times from the assignment of a score of 4 to a score of 6 were similar in the two groups (5.7 and 5.4 years, P=0.74). The time course of progressive, irreversible disease among patients with the primary progressive type of multiple sclerosis was not affected by the presence or absence of superimposed relapses. CONCLUSIONS: Among patients with multiple sclerosis, relapses do not significantly influence the progression of irreversible disability.

Adolescent↗
PubMed2000

Does selenium reduce the risk of threatened preterm delivery associated with placental cytochrome P450-1A1 activity?

Selenium (Se), an essential trace element in human nutrition, is thought to have an important role in the prevention of oxygen damage by organic hydroperoxides generated by oxidative metabolism. Epidemiological studies have shown an association between placental cytochrome P450-1A1 (CYP1) activity and threatened preterm delivery (TPD), and other experimental studies have shown alterations in fetal development with CYP1 activity or toxicity. The present study examined the possible protective effect of selenium on the potential toxicity of maternal exposure to polycyclic aromatic hydrocarbons (PAHs) on the normal course of pregnancy. Placental CYP1 activity was used as a risk factor resulting from maternal exposure to PAHs. TPD occurrence was used as a general indicator of troubles in the normal course of pregnancy. A group of TPD patients and a group of controls were selected from 178 pregnant women attending obstetrical care in a maternity hospital. Selenium concentrations in maternal plasma were lower in the TPD group: 63.7 ng/ml (CI 95% confidence bounds = 43.6-82.2) vs 69.2 ng/ml (CI 95% confidence bounds = 49. 3-96.3) (t test, P<0.01). When placental CYP1 was induced, an association between TPD and selenium was found, with an increase of 10 ng/ml for the latter. An adjusted odds ratio of 0.55 (CI 95% confidence bounds = 0.34-0.88; chi(2), P<0.01) was estimated. When placental CYP1 was not activated, the odds ratio was estimated at 0.99 (CI 95% confidence bounds=0.95-1.03; NS). This epidemiologic finding suggests that antioxidant Se status may be a protective factor against the potential toxic effect of PAHs on the normal course of pregnancy. The downward trend that we observed supports the hypothesis that the one-electron pathway metabolism of PAHs may explain a large fraction of TPD and some preterm deliveries.

Adult↗
PubMed2000

Incidence of multiple sclerosis in Dijon, France: a population-based ascertainment.

Incidence of multiple sclerosis (MS) was prospectively determined within the population of the city of Dijon (94,000 inhabitants under 60 years old) at 47 degrees northern latitude, in Burgundy, France. All the incident cases were diagnosed according to the criteria of Poser, associated to the study of cerebrospinal fluid, evoked potentials and cerebral magnetic resonance imaging. Diagnosis was assessed in all the cases by a neurologist working either in the University Hospital (four neurologists) or in private offices (seven neurologists). The ascertainment was performed on a full 5-year period, from 1993 to 1997. Twenty-one cases were diagnosed in the population of 94,000 inhabitants, with an incidence of 6.1/100,000/year in women, 3.3/100,000/year in men and 4.3/100,000/year in both sexes. The sex-ratio female/male was 2.5. Our data are similar to those of the literature, in particular in countries around the Burgundy area. Our data allow evaluation of the burden of MS in our area and allow evaluation of the changes of incidence in the future.

Adolescent↗
PubMed2000

[Can the prognosis of multiple sclerosis be predicted?].

Though the global course of the disease is well known when considering large cohorts of patients, it is rather difficult to make a prognosis for a given patient. It is essential however to predict the course of the disease as early as possible in order to be able to give the patient the right treatment at the right time. Age at disease onset is one of the most important clinical predictive factors, as this has been proved by various analyses. The earlier the disease onset, the better the prognosis. The inaugural symptom of optic neuritis, the long interval between the first two relapses, a remitting form at onset are predictive factors of a good evolution. A normal brain magnetic resonance imaging performed on the occasion of a first isolated sign of the central nervous system is the marker of a good prognosis. Conversely, the presence of oligoclonal bands in the cerebrospinal fluid and the increase of IgG index increase the risk of occurrence of a second relapse. The new techniques of magnetic resonance imaging and the exhaustive initial clinical examination using several classifications of disability will allow a better prognosis for a given patient.

Brain↗
PubMed1999

Variation over time of the effects of prognostic factors in a population-based study of colon cancer: comparison of statistical models.

The authors compare the performance of different regression models for censored survival data in modeling the impact of prognostic factors on all-cause mortality in colon cancer. The data were for 1,951 patients, who were diagnosed in 1977-1991, recorded by the Registry of Digestive Tumors of Côte d'Or, France, and followed for up to 15 years. Models include the Cox proportional hazards model and its three generalizations that allow for hazard ratio to change over time: 1) the piecewise model where hazard ratio is a step function; 2) the model with interaction between a predictor and a parametric function of time; and 3) the non-parametric regression spline model. Results illustrate the importance of accounting for non-proportionality of hazards, and some advantages of flexible non-parametric modeling of time-dependent effects. The authors provide empirical evidence for the dependence of the results of piecewise and parametric models on arbitrary a priori choices, regarding the number of time intervals and specific parametric function, which may lead to biased estimates and low statistical power. The authors demonstrate that a single, a priori selected spline model recovers a variety of patterns of changes in hazard ratio and fits better than other models, especially when the changes are non-monotonic, as in the case of cancer stages.

Aged↗
PubMed1999

[Dental amalgam and multiple sclerosis: what is the connection?].

BACKGROUND: There is some debate concerning a possible relationship between dental fillings and multiple sclerosis. Many patients ask their dentist to remove fillings. TOXICITY: Dental fillings contain mercury (more than 50%) which can cross the blood-brain barrier. Massive mercurial intoxication is neurotoxic both for the central and peripheral nervous system. Dental fillings release as much mercury in 24 hours as is ingested in a normal meal, i.e. a level well under the neurotoxicity level. RELATIONSHIP: Mercurial poisoning is histologically, clinically, immunologically, and toxicollogically different from multiple sclerosis. Based on data available today, it is not warranted to propose removing dental fillings.

Dental Amalgam↗
PubMed1999

Unobserved covariates in the two-sample comparison of survival times: a maximum efficiency robust test.

In analysing a clinical trial with the logrank test, the hazards between the two groups are usually assumed to be proportional. Nevertheless, this hypothesis is no longer valid with unobserved covariates. As a consequence, there is a loss of power of the logrank test for testing the null hypothesis H(0) of no treatment effect. We propose a test suited for taking into account unobserved covariates. The proposed approach is based on a proportional hazard frailty model whereby the omitted covariates are considered as an unobserved frailty variable. The procedure is as follows. In a first step, the weighted logrank test optimal for testing H(0) against a general proportional hazard frailty model is obtained and its specialization for a gamma frailty variable is derived. In a second step, the proposed test is obtained by combining the maximin efficiency robustness principle and the gamma frailty distribution properties. Simulation studies investigate the power properties of the test for different frailty distributions. A breast cancer clinical trial is analysed as an example. The proposed test might be recommended rather than the logrank for practical situations in which one expects heterogeneity related to omitted covariates.

Breast Neoplasms↗
PubMed1999

Discussion

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Journal Article↗
PubMed1999

New, sensitive fluorogenic substrates for human cathepsin G based on the sequence of serpin-reactive site loops.

Cathepsin G has both trypsin- and chymotrypsin-like activity, but studies on its enzymatic properties have been limited by a lack of sensitive synthetic substrates. Cathepsin G activity is physiologically controlled by the fast acting serpin inhibitors alpha1-antichymotrypsin and alpha1-proteinase inhibitor, in which the reactive site loops are cleaved during interaction with their target enzymes. We therefore synthesized a series of intramolecularly quenched fluorogenic peptides based on the sequence of various serpin loops. Those peptides were assayed as substrates for cathepsin G and other chymotrypsin-like enzymes including chymotrypsin and chymase. Peptide substrates derived from the alpha1-antichymotrypsin loop were the most sensitive for cathepsin G with kcat/Km values of 5-20 mM-1 s-1. Substitutions were introduced at positions P1 and P2 in alpha1-antichymotrypsin-derived substrates to tentatively improve their sensitivity. Replacement of Leu-Leu in ortho-aminobenzoyl (Abz)-Thr-Leu-Leu-Ser-Ala-Leu-Gln-N-(2, 4-dinitrophenyl)ethylenediamine (EDDnp) by Pro-Phe in Abz-Thr-Pro-Phe-Ser-Ala-Leu-Gln-EDDnp produced the most sensitive substrate of cathepsin G ever reported. It was cleaved with a specificity constant kcat/Km of 150 mM-1 s-1. Analysis by molecular modeling of a peptide substrate bound into the cathepsin G active site revealed that, in addition to the protease S1 subsite, subsites S1' and S2' significantly contribute to the definition of the substrate specificity of cathepsin G.

Amino Acid Sequence↗
PubMed1999

Modeling of high-cost patient distribution within renal failure diagnosis related group.

Modeling by mixed-distribution was proposed in order to analyze heterogeneity of costs and length of stays within Diagnosis Related Groups (DRGs). A mixed-distribution model based on Weibull distributions was applied to 791 discharge abstracts of French DRG no. 450 (Health Care Financing Administration 3 DRG no. 316 "Renal failure") from a national database. Three subgroups of cost and length of stay were identified. Except for age, clinical criteria significantly linked with the long-stay subgroup were the same as those associated with the high-cost subgroup: acute renal failure, intensive care, infectious complications, and vascular investigations. The identification of factors associated with high costs, based on the proposed model, will allow physicians to understand more accurately how their choice of specific procedures influences hospital costs.

Costs and Cost Analysis↗