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Biomedical subjects

A Lejeune

Publications and source records attributed to A Lejeune.

At least 37 records · Page 2Linked to original sources
PubMed1989

A spectrophotometric assay for the cyclization activity of cyclomaltohexaose (alpha-cyclodextrin) glucanotransferase.

A cyclomaltohexaose (alpha-cyclodextrin) determination method which is both highly reproducible and selective is described. It involves the formation of an inclusion complex between the cyclodextrin and methyl orange under conditions of low pH (1.2) and low temperature (16 degrees C) and is useful for the assay of cyclodextrin glucanotransferase activity. The formation of the inclusion complex causes a decrease in absorbance of the methyl orange solution and this is monitored at a wavelength of 505 nm. The decrease in absorbance is linearly correlated with the cyclomaltohexaose concentration in the range of 0.25 optical density unit and 0.30 mM cyclomaltohexaose. The specificity of the test for cyclomaltohexaose is high, with only limited interference by linear oligosaccharides and other cyclodextrins: cyclomaltoheptaose and cyclomaltooctaose cause absorbance variations of 16 and 5%, respectively, of the response of maltohexaose. The formation of the complex is instantaneous and the complex is stable in time, provided the temperature is constant. The presence of methyl orange does not hinder enzymatic activity determination. The reaction is stopped by acidification and absorbance is measured at the fixed temperature of 16 degrees C. Possible interferences inherent to the composition of the sample itself can be suppressed by running appropriate controls and calculating a corrected optical density. This colorimetric method is simple and should be versatile in assaying diverse cyclomaltohexaose glucanotransferase enzymes.

Azo Compounds↗
PubMed1989

[Current trends in experimental peripheral nerve regeneration].

Large posttraumatic defects in the peripheral nervous system need to discover methods to solve the demand of nerve grafts. There is no definite answer now. The authors present a model for nervous regeneration studies. Experiments are performed in the Wistar rat. A venous isograft is used to bridge defects of various size in a divided rat sciatic nerve. The venous tube is a guide for axonal regeneration. In one series, the tube is filled with physiological saline and, in a second one, neonatal Schwann cells are injected in the venous isograft. Results recorded are a combination of quantitative methods: neurophysiology and morphometry. The injection of neonatal Schwann cells is able to stimulate nerve regeneration but not completely.

Animals↗
PubMed1988

Characterization and expression in Escherichia coli of an endoglucanase gene of Pseudomonas fluorescens subsp. cellulosa.

An endoglucanase gene of Pseudomonas fluorescens subsp. cellulosa present on plasmid pRUCL150 and expressed in Escherichia coli was subcloned in plasmid pBR322. Plasmid pRUCL153 contained the smallest DNA insert (2.9 kb) with endoglucanase activity. The plasmids directed the synthesis of a mostly periplasmic enzyme in E. coli and the level of enzyme activity was comparable in several strains. Analysis by non-denaturing polyacrylamide gel electrophoresis of the endoglucanase produced with various recombinant plasmids showed that it was unique. The endoglucanase gene on plasmid pRUCL153 was localized by physical mapping of independent transposon Tn5 insertions. Hence, its size was estimated to be approx. 1.3 kb. In vivo radioactive labelling of plasmid-encoded proteins using minicells, followed by denaturing polyacrylamide gel electrophoresis, allowed us to determine the size of the endoglucanase: Mr 40,000 for the precursor and Mr 38,000 for the mature enzyme. It was demonstrated that no cellulase operon, but a single gene, was cloned. The direction of transcription of the gene was determined by placing it under the control of the promoter of the lactose operon.

Cellulase↗
PubMed1988

Characterization of an Endoglucanase from Pseudomonas fluorescens subsp. cellulosa Produced in Escherichia coli and Regulation of the Expression of Its Cloned Gene.

Several enzymatic properties of an endoglucanase produced in Escherichia coli by a gene from Pseudomonas fluorescens subsp. cellulosa were investigated. Gel filtration revealed a single peak of M(r) 36,000 with endoglucanase activity. The pH optimum of the enzyme was 7.0. Carboxymethyl cellulose and barley beta-glucan (mixed beta-1,3 and 1,4 linkages) were good substrates, but not laminarin (beta-1,3 linkages), amylose, filter paper, microcrystalline cellulose (Avicel), or cellotriose. The mode of action was typical of an "endo"-acting enzyme. Taken together, these properties do not correspond to those of any of the endoglucanases described in P. fluorescens subsp. cellulosa. Consequently, the gene was designated egIX. The enzyme was sensitive to end-product inhibition by cellobiose but was only moderately inhibited by glucose. The enzyme was formed constitutively in E. coli throughout the growth phase. Urea had no effect on endoglucanase synthesis, but glucose acted as a catabolite repressor. The formation of the enzyme in E. coli was partially dependent on cyclic AMP.

Journal Article↗
PubMed1988

Aspirin dose, bleeding time, platelet adhesion and aggregation in cerebral thrombosis.

Bleeding time, platelet aggregation and platelet adhesiveness were measured before and after each of 11 consecutive therapeutic sequences in 17 patients who had recently suffered a cerebro-vascular accident of atheromatous ischemic origin. The first 10 sequences were each of 15 days duration and during the first 8 of these, aspirin was increased with each sequence from 300 mg/2 days to 3 g/day. During the 10th sequence a placebo was given. The final sequence (11th) lasted 3 months and during this time the dose of aspirin was fixed at 1 g/day. Significant modification of platelet aggregation was obtained with 300 mg/2 days, platelet adhesiveness was significantly modified with 500 mg/2 days while significant bleeding time modification required a minimum 500 mg/day. The results did not vary significantly with higher doses of acetylsalicylic acid (ASA). Only the results for the platelet aggregation were individually reproducible. There was no statistical correlation between the results of the tests. As far as the 3 tests are considered, the best efficiency is obtained with the therapeutic range of 500 mg to 1 g/day.

Adolescent↗
PubMed1987

Evidence for two mechanisms of human erythrocyte endocytosis by Entamoeba histolytica-like amoebae (Laredo strain).

A study of the ultrastructural aspects of endocytosis of human erythrocytes by Entamoeba histolytica-like amoebae (Laredo) revealed two different mechanisms of endocytosis. First, there is classical phagocytosis which consists of the formation of a phagocytotic pseudopod. This process begins with the engulfment of the red blood cell followed by its entrapment in a food vacuole of the same size as the erythrocyte. It is then digested in the food vacuole. The second means of endocytosis is achieved through a preliminary lytic attack on the red blood cell. Following attachment of the prey to the attacking cell, dendritic extensions elongate from the surface of the amoeba at the site of attachment. Intense folding and liquefaction of the red blood cell membrane is then observed. The fluid membrane is then sucked into the amoeba through a pinocytotic-like channel. The end result is the formation of small vacuoles in the amoeba's cytoplasm, filled with the digested red blood cell.

Animals↗
PubMed1986

Bovine herpesvirus-1 and Pasteurella haemolytica aerobiology in experimentally infected calves.

Eight calves (2 calves in each of 4 groups) were exposed to an aerosol of bovine herpesvirus-1 (BHV-1) and 4 days later to an aerosol of Pasteurella haemolytica. Samples of tracheal and exhaled air were taken simultaneously beginning 1 day before viral exposure and once a day up to 3 to 4 days after the bacterial exposure. Samples were also taken during the period of aerosol exposure. Only 0.04% to 0.42% of P haemolytica-carrying droplets of the bacterial aerosol passed beyond the cranial part of the respiratory tract to the trachea. Nevertheless, numbers of bacteria as few as 1 bacterium/L of tracheal air were sufficient to produce fatal disease in the lungs of BHV-1-infected calves. In 1 of 4 groups, BHV-1 was isolated from most daily samples of exhaled and tracheal air. Pasteurella haemolytica was isolated 7 times more frequently from air when calves were kept at 1 C than when calves were kept at 23 C. The number of P haemolytica-carrying droplets in exhaled air was low (less than 1/L of air); however, samples obtained during the time that calves were coughing contained up to 10 P haemolytica-carrying droplets/L of air. It was learned that the cranial part of the respiratory tract serves as an efficient filter on inhalation and exhalation, but this filter is deficient in the animal when coughing occurs. This process expels infective droplets of size suitable for inhalation by other cattle in close proximity.

Aerosols↗
PubMed1978

[Interhemispheric disconnection syndrome with diagonistic dyspraxia in the course of Marchiafava-Bignami disease].

The probable diagnosis of Marchiafava-Bignami disease was made in a chronic alcoholic patient because of the rapid onset of signs of inter-hemisphere disconnection. These inclused left visual and tactile anomia, difficulty of a limb to imitate postures presented in the contralateral visual half-field, constructional apraxia of the right hand, agraphia of the left hand, left auditive extinction in the dichotic test, difficulty in responses of the left limbs to verbal orders, which the authors propose to name left "aphasic apraxia" and a bimanual asynergia, sometimes presenting an aspect of diagonistic dyspraxia. These symptoms clearly show the competence of the left hemisphere for verbal tasks, or more generally, those of an imaginary or conceptual nature, and that of the right hemisphere for visiopatial tasks, or more generally, those required by concrete situations.

Agraphia↗