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Biomedical subjects

L Gauthier

Publications and source records attributed to L Gauthier.

At least 55 records · Page 3Linked to original sources
PubMed1994

Properties of a Streptococcus salivarius spontaneous mutant in which the methionine at position 48 in the protein HPr has been replaced by a valine.

HPr is a protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) that participates in the concomitant transport and phosphorylation of sugars in bacteria. In gram-positive bacteria, HPr is also reversibly phosphorylated at a seryl residue at position 46 (Ser-46) by a metabolite-activated ATP-dependent kinase and a Pi-dependent HPr(Ser-P) phosphatase. We report in this article the isolation of a spontaneous mutant (mutant A66) from a streptococcus (Streptococcus salivarius) in which the methionine at position 48 (Met-48) in the protein HPr has been replaced by a valine (Val). The mutation inhibited the phosphorylation of HPr on Ser-46 by the ATP-dependent kinase but did not prevent phosphorylation of HPr by enzyme I or the phosphorylation of enzyme II complexes by HPr(His-P). The results, however, suggested that replacement of Met-48 by Val decreased the affinity of enzyme I for HPr or the affinity of enzyme II proteins for HPr(His-P) or both. Characterization of mutant A66 demonstrated that it has pleiotropic properties, including the lack of IIILman, a specific protein of the mannose PTS; decreased levels of HPr; derepression of some cytoplasmic proteins; reduced growth on PTS as well as on non-PTS sugars; and aberrant growth in medium containing a mixture of sugars.

Bacterial Proteins↗
PubMed1994

Use of desmopressin acetate to reduce blood transfusion requirements during cardiac surgery in patients with acetylsalicylic-acid-induced platelet dysfunction.

OBJECTIVE: To determine whether desmopressin acetate (DDAVP) has the ability to reduce blood loss in patients with a known bleeding tendency. DESIGN: A randomized, double-blind, placebo controlled study. SETTING: A university teaching hospital. PATIENTS: Men under the age of 70 years who had taken acetylsalicylic acid within 7 days of scheduled coronary artery bypass surgery. Patients with an abnormal hematologic profile or a history of bleeding or who were receiving heparin or undergoing repeat coronary bypass surgery were excluded. Forty-four patients were randomized with restriction in blocks of 10; 20 received DDAVP and 24 received a placebo. MAIN OUTCOME MEASURES: Blood loss and blood transfusion requirements. RESULTS: Patients treated with DDAVP lost significantly (p < 0.01) less blood than those receiving a placebo (1543 mL versus 2376 mL respectively). Nineteen patients had a blood loss of more than 2000 mL; 15 of these were in the placebo group. Significantly (p < 0.02) fewer patients receiving DDAVP required blood transfusion (9 versus 18). CONCLUSIONS: DDAVP reduces blood loss during cardiac bypass surgery in patients who have taken acetylsalicylic acid within 7 days before operation.

Aspirin↗
PubMed1993

In vivo detection of waste water and industrial effluent genotoxicity: use of the Newt Micronucleus Test (Jaylet Test).

The genotoxic potential of various waste waters has been evaluated in a micronucleus test using amphibian larvae. Genotoxicity was detected after dilution, in waste water from tanneries and from various petrochemical industries. Further studies have shown that sample treatment used for in vitro testing may affect the genotoxic response. Sterilization by gamma irradiation lowered genotoxic activity. Furthermore, microfiltration of effluent and extraction of organic micropollutants on XAD-4 resins, lead to the preparation of extracts which are not fully representative of the initial water sample. Testing of concentrates, as required for in vitro studies, will limit the scope of a survey to that part of the organic matter that can be recovered by concentration techniques. Many of the problems encountered in in vitro genotoxicity studies of waters, may be circumvented with direct testing on aquatic organisms. Thus, there is no need to concentrate or sterilise a sample. The tests can be carried out with intact animals, thus taking into account uptake and elimination, internal transport and metabolism. Finally, in vivo test-systems, such as the Newt Micronucleus Test, are more relevant to eukaryotes than bacterial assays and are suitable to assess the real impact of genotoxins discharged in the aquatic environment.

Animals↗
PubMed1993

Mechanisms that generate human immunoglobulin diversity operate from the 8th week of gestation in fetal liver.

The repertoire of immunoglobulin expressed very early in human development was approached by cloning and sequencing 55 rearranged and 11 germ-line VH transcripts, after amplification by polymerase chain reaction of cDNA libraries derived from two fetal livers at 8 and 13 weeks of gestation. All families with the exception of VH2, were expressed as soon as 8 weeks, with preferential usage of certain germ-line genes. Very few somatic mutations, randomly localized, were identified. By contrast, in a series of clones derived from the same VDJ rearrangement using the VH6 family, extensive mutations had taken place, mostly accumulated in the third complementarity-determining region (CDR3) suggesting that the specialized enzymatic machinery was at hand very early during human development. Some other characteristics of the fetal repertoire also emerged, namely increased usage of JH3 and JH2, as compared to the adult pattern, where JH4 is dominant and reduced length of the D/CDR3 regions. All D gene families were identified, and their usage frequently involved D-D fusions. N diversity was present very early, and increased with age. Identification of germ-line transcripts pertaining to all six VH families including pseudogenes, in the E55 library, revealed a population very different as compared to rearranged gene transcripts. This suggests that a large portion of VH locus is accessible for transcription, bringing no evidence of correlation between preferential rearrangement of a given VH gene and its localization in the locus.

Antibody Diversity↗
PubMed1993

Amphibian micronucleus test(s): a simple and reliable method for evaluating in vivo genotoxic effects of freshwater pollutants and radiations. Initial assessment.

A micronucleus test was developed using larvae from two urodele amphibians (Pleurodeles waltl and Ambystoma mexicanum) and an anuran (Xenopus laevis). The methods for maintenance of adults, egg laying, and rearing the larvae are described, and the conditions required for optimal response are given for each of these species. The tests are carried out during a period of intense erythropoiesis when red blood cells are actively dividing in circulating blood. The micronuclei are observed on blood smears. The genotoxic effects of X-rays were evaluated at 12 different doses over a range of 6-1200 rad. All doses, even the very low dose of 6 rad, gave positive results. The test substances were added to the water in which the larvae were reared, and the results obtained after treatment for 12 days and/or 8 days with 47 different chemical compounds are listed. Detailed results are given as the lowest concentration producing a positive response or the highest concentration producing a negative response. The reliability of the test system using the newt is now well established, while the tests using the other two amphibian species are still under evaluation. Integration of this test in a test battery for quality control of water would aid the evaluation of risks to human health, as well as the protection of aquatic ecosystems.

Ambystoma mexicanum↗
PubMed1993

Rapid transfusion of packed red blood cells: effects of dilution, pressure, and catheter size.

STUDY OBJECTIVE: To examine flow rates and quantify red blood cell (RBC) destruction using various catheter sizes, pressures, and dilutions in the transfusion of packed RBCs. DESIGN: Study equipment was identical to that used in clinical practice. Laboratory tests consisting of plasma free hemoglobin, hematocrit, RBC count, and plasma potassium were used to assess RBC destruction. Statistical analysis was performed using the two-tailed Student's t-test. Statistical significance was considered to be .05. INTERVENTION: Packed RBCs were transfused in vitro through 16-, 18-, 20-, and 22-gauge catheters using no pressure, 150 mm Hg, and 300 mm Hg pressure as well as dilutions of 0, 100, and 250 mL normal saline. OUTCOME MEASURES: Flow rates in milliliters per minute were recorded for all combinations. The extent of RBC destruction was estimated using RBC count, hematocrit, plasma free hemoglobin, and serum potassium. RESULTS: Increases in flow rates of tenfold simply by diluting the units with 250 mL normal saline and sevenfold with the application of a pressure device were seen at all catheter sizes. The combination of both dilution and pressure increased flow rates 33-fold, varying between 70 and 300 mL/min for 22- and 16-gauge catheters, respectively. No significant difference in RBC destruction was seen among the four catheter sizes. CONCLUSION: Flow rates of packed RBCs sufficient for volume resuscitation can be achieved using 20- and 22-gauge catheters without evidence of increased RBC destruction. When it is impossible to obtain large-bore venous access or when such access would necessitate a delay of five to ten minutes, smaller catheters used in conjunction with dilution, pressure, or both should be considered.

Catheterization↗
PubMed1992

[Post-varicella disciform keratitis].

Varicella disciform stromal keratitis is rare. It occurs several weeks or months after the skin rash. We report 4 cases in children, two of whom developed one or more recurrent episodes. Treatment based on local steroids was long and difficult to dose. One case treated with oral aciclovir did not show a better clinical course than the other patients.

Chickenpox↗
PubMed1992

[Psychotherapy in child incest: the dangers of a psychic break].

There seems to be a consensus today by which a child, who is a victim of incest or sexually abused, must be directed to therapy in order that he or she provides a factual account of the traumatism and, by the same token, exorcises it. The authors deplore the widespread use of this destabilizing method. They emphasize that, for many children, recovery is achieved more successfully through "repression" (in the psychoanalytical sense of the term). After having obtained disclosure from the child, the authors argue that it is preferable for the intervenor to create the appropriate therapeutic conditions allowing the child to positively bury the event and move on with his or her life.

Child↗
PubMed1991

The presence of two forms of the phosphocarrier protein HPr of the phosphoenolpyruvate:sugar phosphotransferase system in streptococci.

The protein, HPr, a necessary component of the phosphoenolpyruvate phosphotransferase system (PTS) in bacteria, was purified from Streptococcus salivarius by column chromatography. The purified preparation gave only one band when analyzed by sodium dodecylsulfate gel electrophoresis or by isoelectric focusing in polyacrylamide gel (pI = 4.85). However, electrophoresis in Tris-containing buffers under non-denaturing conditions revealed 2 bands that could be phosphorylated by PEP in the presence of enzyme I of the PTS or by ATP with the HPr kinase. Homogeneous preparations of these 2 forms could be obtained by preparative electrophoresis. Each preparation exhibited only 1 band when analyzed by electrophoresis under non-denaturing conditions, indicating that the doublet observed before preparative electrophoresis was not an electrophoretic artefact. The electrophoretic mobility of each protein was not modified following heat-treatment at 100 degrees C for 20 min or storage at -40 degrees C for several months. Both HPr proteins catalyzed in vitro the PEP-dependent phosphorylation of glucose, but at a rate slightly lower than that observed with a preparation of HPr containing both forms of the protein. Both forms were also able to transfer the phosphate group from PEP to the other specific PTS proteins known in S salivarius. Rabbit polyclonal antibodies directed against each form reacted with both proteins. The presence of the 2 forms of HPr was detected in fresh cellular extracts of S salivarius; however, their intracellular ratio varied according to growth conditions. A doublet was also found in many other streptococcal species tested (S mutans, S sobrinus, S sanguis, S thermophilus, S bovis, S rattus) and also in L lactis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

HPr polymorphism in oral streptococci is caused by the partial removal of the N-terminal methionine.

HPr is a small phosphocarrier protein of the bacterial phosphoenolpyruvate:sugar phosphotransferase system involved in the transport and phosphorylation of sugars. It has recently been reported that streptococci possess two forms of HPr having identical biochemical properties. In this communication, we show by N-terminal amino-acid sequencing and by ion-spray mass spectroscopy that these two forms differ by the presence or the absence of the N-terminal methionine.

Amino Acid Sequence↗
PubMed1991

Treatment of Alzheimer's disease: hopes and reality.

The relative failure of symptomatic therapeutic trials for Alzheimer's disease using non-selective cholinergic agonists brings about the need for longitudinal studies with parallel designs aimed at disease stabilization, using trophic substances or amyloid suppressors.

Alzheimer Disease↗
PubMed1991

Spatial disorientation in persons with early senile dementia of the Alzheimer type.

Although spatial disorientation is frequently observed in persons with Alzheimer disease, it is not well understood. A descriptive study was conducted to examine spatial skills associated with spatial orientation. Spatial tasks were selected and grouped into three types of spatial skills: perceptual, cognitive, and functional. These spatial tasks were administered to a group of 15 persons with senile dementia of the Alzheimer type (SDAT) (early Alzheimer disease) and a group of 15 control subjects. The results indicated that the subjects with SDAT were impaired on half of the perceptual spatial tasks and all of the cognitive spatial tasks. On the functional spatial tasks, however, the subjects with SDAT showed impaired skills in the new environment but intact skills in familiar environments. Spatial disorientation poses a danger and limits a person's ability to independently perform daily activities that require navigation outside of the home. Occupational therapy should therefore include the assessment of spatial orientation skills in persons who are in the early stages of dementia.

Activities of Daily Living↗
PubMed1990

A IIIman protein is involved in the transport of glucose, mannose and fructose by oral streptococci.

We show in this article that the transport of glucose, mannose and fructose by the phosphoenolpyruvate: mannose phosphotransferase system of oral streptococci requires the participation of a protein component that we have called IIIman. This protein was purified from Streptococcus salivarius by chromatography on DEAE-cellulose, DEAE-TSK, hydroxyapatite, and Dyematrex Green A. The purified protein migrated as a 38,900 molecular weight protein on a sodium dodecyl sulfate polyacrylamide gel. However, electrophoretic analysis of phosphoproteins and Western blot experiments indicated the presence in membrane-free cellular extracts of S. salivarius of 2 different forms of IIIman having molecular weights of 38,900 and 35,200. The presence of the high-molecular-weight form of IIIman was observed by immunodiffusion, Western blot and phosphorylation by [32]PEP in S. salivarius, Streptococcus mutans, Streptococcus sobrinus, and Streptococcus lactis but not in Streptococcus faecium, Staphylococcus aureus, Bacillus subtilis and Lactobacillus casei. Antibodies directed against the IIIman of S. salivarius did not react with the IIIman of Escherichia coli.

Bacterial Proteins↗
PubMed1990

Control of sugar utilization in oral streptococci. Properties of phenotypically distinct 2-deoxyglucose-resistant mutants of Streptococcus salivarius.

The physiological and biochemical characterization of Streptococcus salivarius mutants isolated by positive selection for resistance to 0.5 mM 2-deoxyglucose in the presence of lactose are reported. We found 2 classes of mutants following a series of experiments that included: growth rate determinations, uptake studies, measurement of phosphotransferase system (PTS) activities and detection of the IIIman proteins by Western blotting and analysis of [32P]PEP-phosphorylated proteins. Class 1 mutants did not possess the low-molecular-weight form of IIIman. They did not grow on mannose and were unable to transport 2-deoxyglucose. On the other hand, class 2 mutants possessed the 2 forms of IIIman, grew readily on mannose and transported 2-deoxyglucose, albeit at a lower rate than the parental strain. Both classes of mutants exhibited abnormal growth in media containing mixtures of sugars. Moreover, derepression of genes coding for catabolic enzymes was observed in all the mutant strains. Our data suggested that the role of the mannose PTS in the control of sugar utilization in S. salivarius is complex and may involve the participation of several components.

Deoxyglucose↗
PubMed1990

Assessment of functional changes in Alzheimer's disease.

Functional difficulties occur in all patients with Alzheimer's disease. Instrumental skills (shopping, handling money) are involved first, then self-care activities (toileting, dressing). Drug trials in intermediate stage Alzheimer's disease should monitor self-care activities with structured diaries and rating scales.

Alzheimer Disease↗
PubMed1990

[Bilateral corneal neovascularization and floppy eyelid syndrome. A case report].

The conjunctival and corneal lesions usually observed in the floppy eyelid syndrome are benign and reversible as soon as the specific treatment of superior palpebral hyperlaxity is performed. A case of bilateral corneal vascularization, a rare but severe complication of floppy eyelid syndrome is reported. The floppy eyelid syndrome was identified late because keratoconjunctivitis was clinically predominant and palpebral tonicity was not initially considered. The treatment of palpebral hyperlaxity was the prerequisite for good results with keratoplasty.

Aged↗
PubMed1989

Use of newt larvae for in vivo genotoxicity testing of water: results on 19 compounds evaluated by the micronucleus test.

The micronucleus test using erythrocytes of Pleurodeles waltl larvae (Amphibian, Salamandridae) was used to detect the genotoxic activity of various substances. Most of them were known (or suspected) to be mutagenic or carcinogenic in mammals. Larvae were reared in water containing either a test chemical (experimental group) or in control water and the levels of micronucleated red blood cells (RBCs) compared between the two groups. Aroclor 1254, butylated hydroxyanisole, phenobarbital and 12-O-tetradecanoyl-phorbol-13-acetate produced negative results, while acridine orange, benzo[alpha]pyrene, epsilon-caprolactam, cyclophosphamide, diethyl sulphate, epichlorhydrin, ethidium bromide, ethyl methanesulphonate, ethylene dibromide (dibromoethane), N-ethyl-N'-nitro-N-nitrosoguanidine, N-ethyl-N-nitrosourea, hexamethylphosphoramide, 3-methyl cholanthrene, pyrene and o-toluidine gave positive responses. The results were compared with published data from other tests used to detect the clastogenic or mutagenic properties of chemicals. We suggest that the newt micronucleus test could be used to monitor aquatic pollution, and/or for the quality control of drinking water. Pleurodele larvae may also prove to be of value for the detection of carcinogenic/clastogenic substances dissolved in water.

Animals↗