[Endocarditis due to Bacteroides fragilis revealed by portal thrombosis: a case report].
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Aged↗
Biomedical subjects
M Tessier
Publications and source records attributed to M Tessier.
Abdominal skin temperature variation in healthy broiler chickens as determined by thermography.
Abdominal skin temperature of healthy broiler chickens was determined by thermography to estimate the normal range of between- and within-bird temperature variation. Effects of potential confounding factors, such as bird's contention duration, abdominal side, age, and time of day, were also estimated. Mean skin temperature was estimated from thermogram pictures by computer image analysis of a predetermined abdominal area. Results demonstrated that skin temperature was not significantly affected by contention duration. However, skin temperature was higher on the right abdominal side in younger birds and at 1200 h. Between- and within-bird variation in healthy birds was small (< 0.5 degrees C) when age, abdominal side, and time of day were taken into account. This work suggests that skin temperature measurement using thermography can be adapted for the study of skin temperature in broiler chickens.
Abdomen↗
Structure-based chimeric enzymes as an alternative to directed enzyme evolution: phytase as a test case.
Thermostability is a key feature for commercially attractive variants of the fungal enzyme phytase. In an initial set of experiments, we restored ionic interactions and hydrogen bonds on the surface of Aspergillus terreus phytase, which are present in the homologous but more thermostable enzyme from A. niger. Since these mutations turned out to be neutral, we replaced-in the same region and based on the crystal structure of A. niger phytase-entire secondary structure elements. The replacement of one alpha-helix on the surface of A. terreus phytase by the corresponding stretch of A. niger phytase resulted in an enzyme with improved thermostability and unaltered enzymatic activity. Surprisingly, the thermostability of this hybrid protein was very similar to that of A. niger phytase, although the fusion protein contained only a 31 amino acid stretch of the more stable parent enzyme. This report provides evidence that structure-based chimeric enzymes can be used to exploit the evolutionary information within a sequence alignment. We propose this method as an alternative to directed enzyme evolution if due to expression constraints the screening of large mutant populations is not feasible.
Amino Acid Sequence↗
Active site residue 297 of Aspergillus niger phytase critically affects the catalytic properties.
The wild-type phytases from the Aspergillus niger strains NRRL 3135 and T213 display a three-fold difference in specific activity (103 versus 32 U/mg protein), despite only 12 amino acid differences that are distributed all over the sequence of the protein. Of the 12 divergent positions, three are located in or close to the substrate binding site. Site-directed mutagenesis of these residues in A. niger T213 phytase showed that the R297Q mutation (R in T213, Q in NRRL 3135) fully accounts for the differences in catalytic properties observed. Molecular modelling revealed that R297 may directly interact with a phosphate group of phytic acid. The fact that this presumed ionic interaction - causing stronger binding of substrates and products - correlates with a lower specific activity indicates that product (myo-inositol pentakisphosphate) release is the rate-limiting step of the reaction.
6-Phytase↗
[Influence of biotic and abiotic factors on the morphology and reproduction of Suaeda maritima on a salt marsh].
The aim of this study was to estimate the influence of biotic and abiotic factors on Suaeda maritima reproduction on a salt marsh. Individuals of Suaeda maritima were submitted in natural conditions to four series of densities (100, 1,000, 4,000 and 8,000 plants/m2). When density increases, individuals tend to be less or non-branched, while individual biomass decreases. Consequently, individual seed production decreases as density increases. Despite morphological modifications, Suaeda maritima present density-dependent mortality. For a unit area, total biomass and seed production are higher at intermediate density (1,000 plants/m2). Environmental factors could interfere with self-thinning. They seem to limit the effect of competition on mortality and to have an influence on individual and total seed production. This experiment stressed the importance of a biotic factor such as intra-specific competition, which occurs at the same time as abiotic factors, in Suaeda maritima dynamics in the field.
Biomass↗
Parallel gene expression monitoring using oligonucleotide probe arrays of multiple transcripts with an animal model of focal ischemia.
High density oligonucleotide arrays offer tremendous potential to study gene changes occurring in disease states. The authors described the first case of using a custom designed high density oligonucleotide probe array containing 750 genes to monitor the changes in mRNA transcript levels occurring after focal ischemia for a period of 3 hours. Permanent middle cerebral artery occlusion in the rat resulted in neuronal degeneration in the dorsolateral cortex and striatum over a time course of 24 hours. Comparing the changes in hybridization levels in the frontal and parietal cortices and the striatum, between the ipsilateral and contralateral sides of the brain using the probe arrays resulted in the up-regulation of 24 genes, which showed greater than a twofold change. Very few genes were found to be downregulated after the ischemic insult. Many of the immediate early genes (IEGs) such as c-fos, NGFI-A, NGFI-C, and Krox-20 were found to be robustly upregulated in the three different regions studied. Other genes that were up-regulated in perifocal regions included Arc, Inhibin-beta-A, and the phosphatases MKP-1 and MKP-3. The hybridization signal intensity from the probe arrays enabled quantification of many genes relative to one another, and robust changes in expression were obtained with very little interanimal variability. Furthermore, the authors were able to validate the increased expression of NGFI-C and Arc using in situ hybridization. This represented the first example of using high density oligonucleotide probe arrays in studying the expression of many genes in parallel and in discrete brain regions after focal ischemia.
Animals↗
Optimization of the catalytic properties of Aspergillus fumigatus phytase based on the three-dimensional structure.
Previously, we determined the DNA and amino acid sequences as well as biochemical and biophysical properties of a series of fungal phytases. The amino acid sequences displayed 49-68% identity between species, and the catalytic properties differed widely in terms of specific activity, substrate specificity, and pH optima. With the ultimate goal to combine the most favorable properties of all phytases in a single protein, we attempted, in the present investigation, to increase the specific activity of Aspergillus fumigatus phytase. The crystal structure of Aspergillus niger NRRL 3135 phytase known at 2.5 A resolution served to specify all active site residues. A multiple amino acid sequence alignment was then used to identify nonconserved active site residues that might correlate with a given favorable property of interest. Using this approach, Gln27 of A. fumigatus phytase (amino acid numbering according to A. niger phytase) was identified as likely to be involved in substrate binding and/or release and, possibly, to be responsible for the considerably lower specific activity (26.5 vs. 196 U x [mg protein](-1) at pH 5.0) of A. fumigatus phytase when compared to Aspergillus terreus phytase, which has a Leu at the equivalent position. Site-directed mutagenesis of Gln27 of A. fumigatus phytase to Leu in fact increased the specific activity to 92.1 U x (mg protein)(-1), and this and other mutations at position 27 yielded an interesting array of pH activity profiles and substrate specificities. Analysis of computer models of enzyme-substrate complexes suggested that Gln27 of wild-type A. fumigatus phytase forms a hydrogen bond with the 6-phosphate group of myo-inositol hexakisphosphate, which is weakened or lost with the amino acid substitutions tested. If this hydrogen bond were indeed responsible for the differences in specific activity, this would suggest product release as the rate-limiting step of the A. fumigatus wild-type phytase reaction.
6-Phytase↗
Sauna-induced myocardial ischemia in patients with coronary artery disease.
PURPOSE: Sauna bathing is a popular recreational activity that is generally considered to be safe. However, there have been case reports of adverse cardiac events. We sought to determine whether sauna use caused myocardial ischemia in patients with coronary artery disease. METHODS: Sixteen patients with proven coronary artery disease were submitted to three conditions (rest, exercise, and sauna bathing) with continuous electrocardiographic (ECG) monitoring and regular blood pressure measurements. During each condition, patients were injected with Tc-99 sestamibi followed by nuclear scintigraphic imaging. Perfusion defect scores were calculated in 15 patients. RESULTS: Sauna bathing was well tolerated. There was a mean (+/- SD) increase in heart rate of 32% +/- 20% in the sauna (resting mean heart rate = 60 +/- 9 beats per minute vs sauna mean heart rate = 79 +/- 11 beats per minute, P <0.001) and a 13% +/- 6% drop in systolic blood pressure (resting mean systolic blood pressure = 142 +/- 14 mm Hg vs sauna mean systolic blood pressure = 123 +/- 15 mm Hg, P <0.001). There were no arrhythmias or ECG changes in the sauna. Compared with rest, there was significant ischemia during sauna bathing (average perfusion defect score at rest = -0.44 vs average sauna score = -0.93, P <0.001). The perfusion defect score in the sauna was worse than the resting score in 14 of the 15 patients. Sauna-associated perfusion defect scores were highly correlated with exercise-induced scores (R2 = 0.65, P <0.001). CONCLUSION: In patients with stable coronary artery disease, sauna use is clinically well tolerated but is associated with scintigraphically demonstrated myocardial ischemia.
Aged↗
Biophysical characterization of fungal phytases (myo-inositol hexakisphosphate phosphohydrolases): molecular size, glycosylation pattern, and engineering of proteolytic resistance.
Phytases (myo-inositol hexakisphosphate phosphohydrolases) are found naturally in plants and microorganisms, particularly fungi. Interest in these enzymes has been stimulated by the fact that phytase supplements increase the availability of phosphorus in pig and poultry feed and thereby reduce environmental pollution due to excess phosphate excretion in areas where there is intensive livestock production. The wild-type phytases from six different fungi, Aspergillus niger, Aspergillus terreus, Aspergillus fumigatus, Emericella nidulans, Myceliophthora thermophila, and Talaromyces thermophilus, were overexpressed in either filamentous fungi or yeasts and purified, and their biophysical properties were compared with those of a phytase from Escherichia coli. All of the phytases examined are monomeric proteins. While E. coli phytase is a nonglycosylated enzyme, the glycosylation patterns of the fungal phytases proved to be highly variable, differing for individual phytases, for a given phytase produced in different expression systems, and for individual batches of a given phytase produced in a particular expression system. Whereas the extents of glycosylation were moderate when the fungal phytases were expressed in filamentous fungi, they were excessive when the phytases were expressed in yeasts. However, the different extents of glycosylation had no effect on the specific activity, the thermostability, or the refolding properties of individual phytases. When expressed in A. niger, several fungal phytases were susceptible to limited proteolysis by proteases present in the culture supernatant. N-terminal sequencing of the fragments revealed that cleavage invariably occurred at exposed loops on the surface of the molecule. Site-directed mutagenesis of A. fumigatus and E. nidulans phytases at the cleavage sites yielded mutants that were considerably more resistant to proteolytic attack. Therefore, engineering of exposed surface loops may be a strategy for improving phytase stability during feed processing and in the digestive tract.
6-Phytase↗
Isolation and characterization of the carotenoid biosynthesis genes of Flavobacterium sp. strain R1534.
The Gram-negative bacterium Flavobacterium sp. strain R1534 is a natural producer of zeaxanthin. A 14 kb genomic DNA fragment of this organism has been cloned and a 5.1 kb piece containing the carotenoid biosynthesis genes sequenced. The carotenoid biosynthesis cluster consists of five genes arranged in at least two operons. The five genes are necessary and sufficient for the synthesis of zeaxanthin. The encoded proteins have significant homology to the crtE, crtB, crtY, crtI and crtZ gene products of other carotenogenic organisms. Biochemical assignment of the individual gene products was done by HPLC analysis of the carotenoid accumulation in Escherichia coli host strains transformed with plasmids carrying deletions of the Flavobacterium sp. strain R1534 carotenoid biosynthesis cluster.
Alkyl and Aryl Transferases↗
Gene cloning, purification, and characterization of a heat-stable phytase from the fungus Aspergillus fumigatus.
The finding of heat-stable enzymes or the engineering of moderately thermostable enzymes into more stable ones by random or site-directed mutagenesis has become a main priority of modern biotechnology. We report here for the first time a heat-stable phytase able to withstand temperatures up to 100 degrees C over a period of 20 min, with a loss of only 10% of the initial enzymatic activity. The gene (phyA) encoding this heat-stable enzyme has been cloned from Aspergillus fumigatus and overexpressed in Aspergillus niger. The enzyme showed high activity with 4-nitrophenyl phosphate at a pH range of 3 to 5 and with phytic acid at a pH range of 2.5 to 7.5.
6-Phytase↗
[Incidence of homeopathic treatment with cuprum 4 CH on the intestinal transit of mouse: preliminary study].
An homeopathic treatment with cuprum 4 CH, 24 and 5 hours before neostigmine (50 micrograms/kg/IP) administration has been done in the mouse. This treatment significantly reduces (Kruskal-Wallis: p less than 0.02) the faciliting action of neostigmine on intestinal transit.
Animals↗
Conversion-electron Mössbauer spectroscopy studies in amorphous Tb-Fe films.
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Journal Article↗
The limited photochemical activity of solid aggregated forms of bovine rhodopsin.
The visual pigment rhodopsin has been purified and depleted of detergent. Under these conditions, the pigment strongly aggregates. When dried, a significant fraction of these aggregates appear insensitive to light. We have characterized them by means of absorption and photoacoustic spectroscopies and we find that their photochemical behavior is best explained by a limited activity that does not reach photointermediates beyond the lumirhodopsin step in the bleaching sequence of rhodopsin. We interpret this result as an indication of a significant conformational change of the protein during the transition from lumi- to meta-rhodopsin.
Animals↗
[Adolescence and sexuality : the stakes in prevention.].
Studies of adolescent girls underline the limits of clinical services in the prevention of undesired pregnancies. This article concerns a study carried out at the St-Denis Youth Clinic with the aim of collecting data to permit the development of adequate preventive measures in work with the adolescent population. The author deals with factors linked to the development of the adolescent personality and presents two theories explaining preventive behaviour. She gives an account of evaluations of current practices in Quebec in relation to sexuality and contraception, and suggests avenues to pursue at different levels of prevention.
English Abstract↗
[The St-Denis youth clinic.].
The Clinique des Jeunes St-Denis was founded in 1977 to provide complete medical and psychosocial services to young clients in matters of sexuality. The work assumed by a multi-disciplinary team has provided its members with an opportunity for growth and allowed them to investigate the different aspects of their work load. The actual clinical needs and the effective treatment are discussed : abortion, incest, sexually transmitted diseases, etc. Groups are formed in order to perceive the adolescent as a whole and not only its sexual dimension ; and a concern for preventive action is always present. A research on these matters has been initiated.
English Abstract↗
Are interactions with phospholipids responsible for pharmacological activities of cardiotoxins?
Cardiotoxins are small basic proteins (7 000 daltons) that are found in the venoms of Elapidae snakes. Although they are structurally close to alpha-neurotoxins present in the same secretions, their activity is related to their ability to interact with every cell membrane inducing, near micromolar concentration, the modification of its biological properties and/or physical structure. The mode of action of cardiotoxins, on a molecular level, is still under investigation. However, lipid-protein interactions are more and more involved in their binding to membrane and in their activities. Using new experimental data a better definition of phospholipid-cardiotoxin interaction is arrived at and a tentative molecular explanation of the pharmacological activities of these proteins is presented and discussed.
Amino Acid Sequence↗
Amino-acids condensations in the preparation of N alpha-9-fluorenylmethyloxycarbonylamino-acids with 9-fluorenylmethylchloroformate.
Synthesis of N alpha-9-fluorenylmethyloxycarbonyl (Fmoc) amino-acids by reaction of free amino-acids (glycine and alanine) with 9-fluorenylmethylchloroformate leads to formation of small amounts of Fmoc-dipeptide which are difficult to eliminate by crystallization. The alternative way to prepare Fmoc-amino-acids by reacting the Fmoc-chloride first with sodium azide and then with the free amino-acid eliminates this side reaction, at least for glycine and alanine.
Amino Acids↗