Search PubMed⌕ Search

Biomedical subjects

T Moreau

Publications and source records attributed to T Moreau.

At least 91 records · Page 5Linked to original sources
PubMed1994

New substrates of papain, based on the conserved sequence of natural inhibitors of the cystatin family.

A series of peptide substrates with different fluorogenic leaving groups has been synthesized. The peptide moiety in these substrates mimics a highly conserved sequence (QVVAG) in the natural reversible inhibitors of cysteine proteinases, the cystatins, that participates to the tight binding of target proteinases. This sequence is invariably cleaved at the A-G bond when synthetic peptides containing it were incubated with papain. AEC and AMC fluorophores were therefore attached to the Ala residue to construct new substrates for cysteine proteinases. The solubility of the resulting substrates was improved by attaching a N-terminal gluconoyl group, or by introducing an arginyl residue at P5 (nomenclature of Schechter I, Berger A (1967) Biochem Biophys Res Commun 27, 157-162). Neither induced significant changes in the kcat/Km values with papain. Those values were all in the 10(5) M-1 s-1 range. The kcat/Km was increased 10-50-fold by using substrates with intramolecularly quenched fluorescence. With these, the enzyme specificity on both sides of the scissile bond can be investigated. The substrate Abz-QVVAGA-EDDnp is among the most sensitive papain substrates ever reported, with a kcat/Km value of 29 10(6) M-1 s-1. The positioning and conformation of the bound QVVA moiety within the active site of papain were predicted by molecular modelling using the X-ray coordinates of a peptide inhibitor-papain complex.

Amino Acid Sequence↗
PubMed1994

Test of homogeneity of binary data with explanatory variables.

Apparent heterogeneity of the risk of a disease in different groups may be explained by subject-specific risk factors unequally distributed in these groups. We propose a score test of homogeneity that allows adjustment for known risk factors of the disease. The test is based on a random-effect logistic regression model and requires only simple computations in addition to a conventional logistic regression method. The score test is applied to the study of geographical heterogeneity of cognitive impairment in elderly using a sample of 3,318 subjects scattered in 75 parishes. It is shown that an apparent heterogeneity disappears when taking into account subject-specific risk factors. This test may also be useful for studying familial aggregation of a disease.

Epidemiologic Methods↗
PubMed1994

Measurement of respiratory impedance by forced oscillation: comparison of the standard and head generator methods.

Physiological and clinical studies have shown that the standard method of measuring respiratory impedance by forced oscillation leads to less efficient control of the upper airway shunt effect than the head generator method. To test the effects of these two techniques in epidemiological studies, we compared, in a sample of 73 French agricultural workers, the values obtained with each method for five forced oscillation parameters: resistance, frequency dependence of resistance, inertance, compliance and resonant frequency. For these comparisons, subjects were classified according to four respiratory status factors: smoking status, cough, expectoration and airway obstruction assessed from the maximum expiratory flow volume curve. Logistic regression models using the set of four forced oscillation parameters (excluding resonant frequency, which is derived from compliance and inertance) were then used to analyse the ability of each method to classify the subjects in each group. Significant differences between the two methods were observed for the mean values obtained for all five parameters. However, when each parameter was considered separately, the correlations between the values for each method were significant. Each method possessed the necessary ability to separate subjects into our group classification, but the significant relationships were not always found for the same parameters. Finally, logistic regression models showed that the two methods led to almost the same classification of the subjects. According to our results, the standard method of applying forced oscillation at the mouth seems an acceptable device for measuring respiratory impedance for epidemiological purposes.

Airway Obstruction↗
PubMed1993

A new, sensitive fluorogenic substrate for papain based on the sequence of the cystatin inhibitory site.

We have designed and tested a new papain substrate with intramolecularly quenched fluorescence. It is based on a highly conserved sequence in all members of the cystatin superfamily that participates in the inhibition of cysteine proteinases. This substrate, O-aminobenzoyl (Abz)-QVVAGA-ethylenediamine-2-4-dinitrophenyl (EDDnp) is very sensitive to papain with a second-order rate constant kcat/Km of 3.1 10(7) M-1S-1. It is also efficiently hydrolyzed by cathepsin L, although the kcat/Km for this proteinase is about 60-fold lower than that for papain. This change is due to a decrease in kcat, the Km's are almost identical. This allows clear functional discrimination between these two proteinases, and may lead to the development of selective inhibitors for individual cysteine proteinases. Unlike most commonly used papain substrates, Abz-QVVAGA-EDDnp is not hydrolyzed by trypsin. The papain cleavage site was identified as the A-G bond by N-terminal amino acid sequencing. The use of sensitive and specific substrates such as the one described here will prove invaluable for investigating cysteine proteinase activities in parasite infections. The close interaction between papain or cathepsin L with Abz-QVVAGA-EDDnp is compared to that with cystatin inhibitors, which all include a QxVxG consensus segment in their structure.

Amino Acid Sequence↗
PubMed1993

Environmental exposure to cadmium and human birthweight.

Fetal toxicity of cadmium (Cd) is well documented in rodents. However, little information is available regarding the human fetus. To investigate the effect of low levels of Cd on the human placenta and the consequences on birthweight, we conducted a study of 102 mothers and their newborns in an obstetrical care unit. Placental and hair samples were collected at delivery to determine Cd concentrations. The main finding of this study was the relationship between a decrease in birthweight and an increase of newborn hair Cd which varied in the presence of placental calcification. In cases of parenchymal calcifications, placental Cd levels were higher (Wilcoxon test, P < 0.05) and newborn hair Cd levels were lower (Wilcoxon test, P < 0.01) than in the absence of calcification. These relationships remained significant even after taking into account smoking habits and gestational age. In the presence of calcification, an increase in the level of Cd in newborn hair was related to a decrease in birthweight which was independent of placental Cd concentration (rpartial = -0.49, P < 0.01). In the absence of calcification, a decrease in birthweight was observed for the upper values of newborn hair Cd (r = -0.44, P < 0.05 when Cd > or = 0.3 ppm). The difference in birthweight between infants in the first and last quartiles of newborn hair Cd was 472 g in cases of calcifications and 122 g in the absence of calcification. Other placental parameters were not significantly related to placental Cd concentration.

Birth Weight↗
PubMed1993

Interaction between cystatin-derived peptides and papain.

The interaction between papain and synthetic peptides which tentatively mimic cystatin surfaces was investigated both enzymatically and structurally. Measurements of dissociation equilibrium constants for the interaction of papain with these peptides modified by successive deletions or substitutions demonstrated that the QVVAG segment, which is highly conserved throughout members of the cystatin superfamily, is essential for the interaction. The glycyl-containing (N-terminal) fragments and PW-containing (C-terminal) fragments were found to be of lesser importance, since each could be deleted without significantly modifying the interaction. These fragments improved the stability of the interacting QVVAG region, which appeared to be substrate-like in all peptides tested, as it was cleaved at the A-G bond upon peptide-papain interaction. Replacement of the A residue at the scissile bond of the QVVAG by a blocked cysteinyl residue reduced the rate of cleavage of the susceptible bond and therefore shifted the resulting peptide from a substrate to an inhibitor. Derivatization of this substituted peptide at its N- and C-terminal ends by fluoresceinyl groups resulted in a dramatic decrease in the Ki to 0.5 microM. This improvement in the inhibitory properties of the substituted and derivatized peptides was correlated with structural changes as analyzed by molecular dynamic calculations. The results were compared to those proposed for the mechanisms of inhibition by natural inhibitors of the cystatin superfamily.

Amino Acid Sequence↗
PubMed1993

Upper limb injuries and handedness plasticity.

In a questionnaire survey of 9591 men between 17 and 27 years of age, there was an association between present handedness score and report of an earlier injury causing a temporary shift of hand use. The proportion of weak right-handers was higher among those who reported injuries. Overall, there was no association between left-handedness and injuries. Nevertheless, injuries occurring before the school attendance age, which concerned only a very small fraction of the respondents, were associated with an increased frequency of left-handedness. The data emphasize the plasticity of human handedness, and do not suggest that innate left- or non-right-handedness is a risk factor for accident occurrence.

Adolescent↗
PubMed1993

[Association of amyotrophic lateral sclerosis and multiple sclerosis].

A twenty-five year old woman developed a progressive right hemiparesis which remitted within three months, without treatment. The diagnosis was a first relapse of multiple sclerosis. After a 10 year fully asymptomatic period, the patient developed weakness of the legs with falls and swallowing difficulties. Fasciculations and amyotrophy were present in the limbs and the tongue. There were no sensory abnormalities. The electromyogram confirmed the peripheral neurogenic degeneration with signs of anterior horn involvement. Motor and sensory nerve conductions were normal. Muscle weakness and atrophy increased in the limbs and the bulbar territory and the patient died nine months later. The autopsy showed characteristic "old" plaques of multiple sclerosis in the cerebrum with anterior horn cell and pyramidal tracts degeneration, typical of amyotrophic lateral sclerosis, in the spinal cord. Although exceptional, this association of amyotrophic lateral sclerosis and multiple sclerosis leads to the discussion of an etiological immunological dysregulation common to these two diseases.

Adult↗
PubMed1993

Aryl hydrocarbon hydroxylase activity in human placenta and threatened preterm delivery.

Induction of aryl hydrocarbon hydroxylase (AHH) activity in the placenta has been well documented. This enzyme may be induced by a variety of Polycyclic Aromatic Hydrocarbons (PAHs) and the AHH inducibility is associated with harmful effects of environmental chemicals. Toxic effects of PAHs in tissues such as placenta have been demonstrated to be due to their metabolites, epoxides, which interact with DNA. Thus, environmental PAHs may be related to its alterations in fetal development. Founded on these findings the PAH metabolites could interfere with the normal course of the pregnancy and may be an aborticide, a teratogen or a carcinogen. We hypothesize that low increased activity of placental Aryl Hydrocarbon Hydroxylase (AHH) may be an important determinant of human fetotoxicity. The present investigation was designed to examine the possible implications of PAH exposure at environmental exposure levels on the normal course of the pregnancy using AHH induction as an indicator of PAH exposure. Threatened Preterm Delivery (TPD) was used as an index of problems in the normal course of pregnancy. A group of forty pregnancies at term with TPD was compared with eighty controls for placental AHH induction. Macroscopic placental examination was also performed. A significant increase in prevalence of placental AHH induction with TPD was shown (Odds-Ratio = 2.8; 95% confidence bounds [1.3-6.2]; chi 2 = 6.7 p < 0.01). No such increases were found associated with placental pathology. When taking into account the group of placenta without basal plate calcifications, the significant increase in prevalence of placental AHH induction with TPD above mentioned was greatly increased (Odds-Ratio = 8.9; 95% confidence bounds [2.4-32.9]; chi 2 = 11.1 p < 0.001) controlling for gestational age. The increase in prevalence of placental AHH induction with TPD disappeared when taking into account the subgroup with basal plate or parenchyma calcifications. It is hypothesized that the high estrogen and progesterone at term may explain these associations.

Adult↗
PubMed1992

Inhibition of rat tissue kallikrein gene family members by rat kallikrein-binding protein and alpha 1-proteinase inhibitor.

The regulation of tissue kallikrein activity by plasma serine proteinase inhibitors (serpins) was investigated by measuring the association rate constants of six tissue-kallikrein family members isolated from the rat submandibular gland, with rat kallikrein-binding protein (rKBP) and alpha 1-proteinase inhibitor (alpha 1-PI). Both these serpins inhibited kallikreins rK2, rK7, rK8, rK9 and rK10 with association rate constants in the 10(3)-10(4) M-1.s-1 range, whereas only 'true' tissue kallikrein rK1 was not susceptible to alpha 1-PI. This results in slow inhibition of rK1 by plasma serpins, which could explain why this kallikrein is the only member of the gene family identified so far that induces a transient decrease in blood pressure when injected in minute amounts into the circulation.

Animals↗
PubMed1992

Vitamin B12 among parturients and their newborns and its relationship with birthweight.

Vitamin B12 (Cobalamin) is an essential nutrient in the diet of humans, particularly during pregnancy, nevertheless very few epidemiological studies have been reported, particularly concerning variation factors. The purpose of this study is to assess the role of vitamin B12 on birthweight after taking into account potential confounders, such as obstetrical, socioeconomic, and biological factors which will be identified. This study was conducted on 188 single births occurring during a 5-month period in an obstetrical care unit in Paris. Vitamin B12 plasma levels and folate plasma levels of mothers and cords along with haematological parameters were measured. Social and obstetrical features of the mothers as well as their tobacco exposure and alcohol consumption were recorded. Cord blood vitamin B12 levels were highly correlated with maternal levels (r = 0.63, P less than 0.001) and were 2-3-fold higher. Three variation factors of vitamin B12 were identified: maternal age, ethnicity and tobacco exposure. Negative correlations between birthweight and vitamin B12 levels were observed only among the smoker group (r mothers = -0.46, P less than 0.05 and r cords = -0.42, P less than 0.05). After adjustment for ethnicity and parity, birthweight remained negatively linked to vitamin B12 in smokers. This relationship could suggest that the availability of vitamin B12 for fetal development depends on certain biological factors present only in mothers who smoked. We hypothesized this relationship could be explained, in part, by lipid metabolism, particular to smokers.

Adult↗
PubMed1992

An immunochemical approach to investigating the mechanism of inhibition of cysteine proteinases by members of the cystatin superfamily.

Antibodies were raised against a synthetic dodecameric peptide KGAGQVVAGPWK (K12K), encompassing sequences thought to be important for the function of the cysteine proteinase inhibitors of the cystatin superfamily. These antibodies specifically recognized molecules of family 3, i.e., kininogens, in the serum of seven mammalian species tested in this study. The only notable exception was that of rat thiostatin (T kininogen) which is structurally related to the kininogen family. The antibodies also discriminated between family 2 (cystatins) and family 3 (kininogens) of the cystatin superfamily, since neither chicken cystatin nor human and rat cystatins C and S, which all belong to family 2 were recognized. The cystatin-like inhibitory domains resulting from fragmentation of human low molecular weight kininogen by bovine trypsin, were still recognized by antibodies, indicating that discrimination does not require two neighbouring inhibitory sites on the kininogen heavy chain. The antibodies blocked the capacity of kininogens to inhibit papain, suggesting that they recognize a conformational epitope at or near the kininogen inhibitory sites. The inhibitory properties of family 2 cystatins remained unchanged, confirming that members of this family do not interact with anti K12K antibodies. These antibodies are thus a new tool able to discriminate functionally and structurally between the members of the cystatin superfamily.

Amino Acid Sequence↗
PubMed1992

Protein products of the rat kallikrein gene family. Substrate specificities of kallikrein rK2 (tonin) and kallikrein rK9.

Two closely related kallikrein-like proteinases having little activity toward the standard synthetic amide substrates of tissue kallikreins were isolated from the rat submandibular gland. They were found to be the protein products of the rKlk2 (tonin) and the rKlk9 genes by amino acid sequence analysis (nomenclature of the genes and proteins of the kallikrein family is according to the proposal of the discussion panel from the participants of the KININ '91 meeting held Sept. 8-14, 1991, in Munich, Germany). These two proteinases of similar structure also had very similar physicochemical properties. They differed from other kallikrein-related proteinases in having high pHi values of 6.20 (rK2) and 6.85 (rK9). Kallikrein rK2 was purified as a single peptide chain, whereas rK9 appeared as a two-chain protein after reduction. Their enzymatic properties were also very similar and differed significantly from those of other rat kallikrein-related proteinases. Unlike the five other kallikrein-related proteinases we have purified so far, kallikrein rK9 was not inhibited by aprotinin. rK9 also differed from rK2 by its tissue localization. The prostate gland contained only rK9 where it was the major kallikrein-like component. The amino acids preferentially accommodated by the proteinase S3 to S2' subsites were identified using synthetic amide and protein substrates. Unlike other kallikrein-related proteinases, rK2 had a prevalent chymotrypsin-like specificity, whereas rK9 had both chymotrypsin-like and trypsin-like properties. Both rK2 and rK9 preferred a prolyl residue in position P2 of the substrate and did not accommodate bulky and hydrophobic residues at that position, as did most of the other kallikrein-related proteinases. This P2-proline-directed specificity is necessary for processing the precursors of several biologically active peptides. Subsites accommodating residues COOH-terminal to the scissile bond were also important in determining the overall substrate specificity of these proteinases. rK2 and rK9 both showed a preference for hydrophobic residues in P2'. Other subsites upstream of the S3 subsite were found to intervene in substrate binding and hydrolysis. The restricted specificity of rK2 and rK9 is consistent with the presence of an extended substrate binding site, and hence with a processing enzyme function. Their P1 specificities enabled both proteinases to release angiotensin II from angiotensinogen and from angiotensinogen I, but rK9 was at least 100 times less active than rK2 on both substrates. The substrate specificities of rK2 and rK9 were correlated with key amino acids defining their substrate binding site.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

Functional diversity of proteinases encoded by genes of the rat tissue kallikrein family.

A group of proteinases closely related to tissue kallikrein was purified from the rat submandibular gland. Physicochemical characterization of these proteinases, including amino terminal sequencing, allowed correlation with the genes of the rat kallikrein family. In spite of their similar structure, these proteinases have different substrate specificities and different susceptibilities to inhibitors which suggest that they do not share the same biological function. Kallikrein-like proteinases also have restricted specificities that are probably related to their extended substrate binding site. This makes them good candidates for processing inactive protein or peptide precursors into biologically active peptides. A general approach to identifying the putative biological substrates of individual proteinases based on analysis of the specific cleavage of synthetic and natural peptide substrates by kallikrein-related proteinases is described.

Amino Acid Sequence↗
PubMed1992

Placental aryl hydrocarbon hydroxylase activity and placental calcifications.

Induction of aryl hydrocarbon hydroxylase (AHH) activity in the placenta as a result of maternal exposure to polycyclic aromatic hydrocarbons contained in cigarette smoke has been well documented. Furthermore, calcifications are more prevalent in the placentas of pregnant smokers than in those of non-smokers. The present study examines whether this latter relationship could be explained by the induction of AHH activity in the placenta. AHH levels were determined at birth in 141 unselected pregnant women admitted for delivery. Macroscopic placental examination was performed for vascular lesions, abnormalities of placental shape, of the cord and parameters of placental maturity such as basal and parenchymatous calcifications. Significant increases in the prevalence of calcifications of the placental basal plates and parenchyma with the induction of placental AHH were found. A similar significant association between smoking and AHH activation was also observed. These findings remained unchanged when controlling for smoking status assessed both by questionnaire and presence of cotinine in mother's urine. Moreover, the apparent association between smoking 'factor' and calcifications disappeared when controlling for AHH induction. Therefore, the association between smoking and placental calcifications previously related could be mediated by the AHH induction.

Aryl Hydrocarbon Hydroxylases↗
PubMed1992

Cystatin mimicry by synthetic peptides.

Synthetic peptides which tentatively mimic the cystatin inhibitory surface were used to study the mechanism of inhibition of cysteine proteinases by their natural inhibitors. The inhibitory properties of these peptides depend mainly on the presence of the QxVxG consensus sequence. N and C-terminal peptide derivatives bearing large hydrophobic groups showed dramatically improved inhibition. Molecular dynamic studies after energy minimization showed that the non covalent interaction between these hydrophobic groups induced the formation of a loop structure which probably favours inhibition. Antibodies were raised against one of these peptides, which recognized kininogens in the serum of all mammal species tested, but not cystatins from family two.

Animals↗