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Biomedical subjects

J Charlier

Publications and source records attributed to J Charlier.

At least 19 recordsLinked to original sources
PubMed1992

Acetylornithine deacetylase, succinyldiaminopimelate desuccinylase and carboxypeptidase G2 are evolutionarily related.

The nucleotide (nt) sequence of the Escherichia coli argE gene, encoding the acetylornithine deacetylase (AO) subunit, has been established and corresponds to a 43-kDa (M(r) 42,320) polypeptide. The enzyme has been purified to near homogeneity and it appears to be a dimer consisting of two 43-kDa subunits. The amino acid sequence deduced from the nt sequence was compared to that of the subunit of E. coli succinyldiaminopimelate desuccinylase (the dapE gene product involved in the diaminopimelate pathway for lysine biosynthesis), since both enzymes share functional and biochemical features. Significant similarity covering the entire sequence allows us to infer a common origin for both deacylases. This homology extends to the Pseudomonas sp. G2 carboxypeptidase (G2CP); this or a functionally related enzyme may be responsible for the minor AO activity found in organisms relying on ornithine acetyltransferase for ornithine biosynthesis.

Amidohydrolases↗
PubMed1992

[Evaluation of spatial discrimination performances of newborn infants with the visual pursuit of structured stimuli].

Pursuit eye movements have been recorded with the photo-oculographic technique from newborn infants during the presentation of stimulations specific for spatial discrimination functions. 72.5 per cent of 51 subjects whose eye movements have been recorded have successfully followed stimuli of spatial frequency up to 0.4 cycles per degree. Estimations of grating visual acuity are similar to those provided by the preferential looking technique.

Eye Movements↗
PubMed1992

Visual acuities and scotomas after one week levodopa administration in human amblyopia.

The authors previously showed that a single dose of levodopa improves the contrast sensitivity and decreases the size of fixation point scotomas in amblyopic patients. In the present study, they investigated the effect of levodopa after 1 wk of daily administration using a cross-over, double masked design. The decrease of fixation point scotomas was confirmed with automatic static perimetry. An improvement of visual acuity occurred in 70% of the patients after 1 wk of levodopa administration compared to only 22% in the authors' previous study using one single dose. The improvements in visual acuities and visual fields persisted even after the levodopa administration was completed.

Administration, Oral↗
PubMed1991

Static flicker perimetry in glaucoma and ocular hypertension.

The visual threshold for standard and flickering targets was determined and compared in 8 glaucoma patients, 8 glaucoma suspects and 13 normal controls. Using a Goldmann size III standard white light target, 25 points in the central 30 degrees of the visual field were tested. The location of these points was designed to reflect areas of the visual field commonly affected by glaucomatous damage. The same determinations were then repeated with the test target flickering at 25 Hz. All glaucoma patients had elevation of the visual threshold compared to normal controls for both standard and flickering targets. The absolute value of threshold elevation was not significantly different between standard and flickering lights. However, when larger targets were used, flicker thresholds were an average 8 dB higher (p less than 0.05) in the glaucoma patients compared to the normals, suggesting improved identification of glaucomatous damage with the use of larger flickering targets.

Adult↗
PubMed1990

[A new technic for recording eye movements by image processing. Principle and method].

Nowadays, electro-oculography remains the only clinical method for ocular movement recording which is largely used in daily practise, but it has many drawbacks and limits. Till now the photo-oculographic technics have been only applied in laboratory conditions. A new differential photo-oculographic procedure is presented. This optical method is based upon the measurement of gaze direction and ocular movement amplitude from the relative pattern of five reflected corneal dots and pupil image which are located in two different optical plans. The authors relate in detail the recording devices and processing materials for the computerized analysis of video signals. The preliminary results confirm the real advantages of the method which allows to record all sorts of ocular movements in clinical conditions.

Eye Movements↗
PubMed1990

[Comparative study of electrooculographic and photooculographic recordings].

The authors present the results of clinical application of a new invasive real time method for ocular movement recording. There is an optical system which measures the gaze direction from the video signals of five reflected corneal dots and pupil image. Their study is based upon 110 simultaneous P.O.G. - E.O.G. recordings of normal beings or patients having various oculomotor troubles. It appears that the heavy odds of such a new method is obvious. It allows to obtain an absolute measurement of eye positions in relation to the basic line whatever the pattern and axis of the moving may be. A quantitative evaluation of all movement parameters is in progress. It still remains to solve the problem of large deviations and the wearing of optical correction during the examination.

Electrooculography↗
PubMed1989

[Asymmetry of visual perceptive activity of faces and emotional facial expressions].

Eye movements were studied in 40 right-handed subjects during perception of symmetrical chimerical faces. These movements were recorded using an original system based on a differential optical method for the detection of corneal reflection and of the pupil made shiny. Under basal conditions, the first fixation was usually located in the left visual hemifield. The subjects spent more time gazing at the right hemiface (P less than 0.04). This visuo-spatial asymmetry in favour of the left hemispace was increased when the subject was requested to determine the emotional expressions of a new series of faces (P less than 0.002). Compared with basal conditions, the increase in the percentage of time spent in the left area was significant (P less than 0.035). An analysis performed on the first 3 seconds confirmed and amplified the differences observed. These results can partly be explained by reading habits and exploratory activity for symmetrical shapes. However, activation of the right hemisphere, specialized in the perception of faces and facial expressions, probably influenced visual exploration by drawing attention to the left area and favouring the left visual hemifield.

Adult↗
PubMed1987

Lysyl-tRNA synthetase from Escherichia coli K12. Chromatographic heterogeneity and the lysU-gene product.

In contrast with most aminoacyl-tRNA synthetases, the lysyl-tRNA synthetase of Escherichia coli is coded for by two genes, the normal lysS gene and the inducible lysU gene. During its purification from E. coli K12, lysyl-tRNA synthetase was monitored by its aminoacylation and adenosine(5')tetraphospho(5')adenosine (Ap4A) synthesis activities. Ap4A synthesis was measured by a new assay using DEAE-cellulose filters. The heterogeneity of lysyl-tRNA synthetase (LysRS) was revealed on hydroxyapatite; we focused on the first peak, LysRS1, because of its higher Ap4A/lysyl-tRNA activity ratio at that stage. Additional differences between LysRS1 and LysRS2 (major peak on hydroxyapatite) were collected. LysRS1 was eluted from phosphocellulose in the presence of the substrates, whereas LysRS2 was not. Phosphocellulose chromatography was used to show the increase of LysRS1 in cells submitted to heat shock. Also, the Mg2+ optimum in the Ap4A-synthesis reaction is much higher for LysRS1. LysRS1 showed a higher thermostability, which was specifically enhanced by Zn2+. These results in vivo and in vitro strongly suggest that LysRS1 is the heat-inducible lysU-gene product.

Adenine Nucleotides↗
PubMed1986

alpha-Difluoromethylornithine induces protective immunity in mice inoculated with Plasmodium berghei sporozoites.

Mice inoculated weekly with Plasmodium berghei sporozoites while under treatment with alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, developed protective immunity against subsequent challenge with this parasite. The percentage of mice protected was similar whether DFMO alone (55%) or DFMO + chloroquine (65%) was used. With chloroquine alone, only 12% of mice were protected. This protection was long-lasting (at least six months). The immunity protected against sporozoites but not against erythrocytic form inoculation. It is suggested that this protection is induced by antigens released from exoerythrocytic schizonts whose further development is inhibited by DFMO.

Animals↗
PubMed1985

[Methods of stimulation in visual electrophysiology].

After introducing physical and physiological stimulation parameters, the authors present different techniques and discuss their clinical usefulness for the investigation of the visual system: flashes: chiefly 'ganzfeld' stimulators (whole field or local stimulation). A solution using optic fibres incorporated in a sclero-corneal electrode built in our laboratory is presented; patterns: bars or chekerboards, especially on TV screens. Advantages and inconveniences of video images are discussed; other techniques: essentially endocular laser interference fringes, electrical stimulations, high level flashes for ERP and binocular studies, particularly dynamic random dot pattern EVP. In conclusion, the necessity for the careful control of stimulation characteristics and for a strategy suitable for clinical examination is discussed.

Brain↗
PubMed1979

Arginyl-tRNA synthetase from Escherichia coli K12. Purification, properties, and sequence of substrate addition.

Arginyl-tRNA synthetase from Escherichia coli K12 has been purified more than 1000-fold with a recovery of 17%. The enzyme consists of a single polypeptide chain of about 60 000 molecular weight and has only one cysteine residue which is essential for enzymatic activity. Transfer ribonucleic acid completely protects the enzyme against inactivation by p-hydroxymercuriben zoate. The enzyme catalyzes the esterification of 5000 nmol of arginine to transfer ribonucleic acid in 1 min/mg of protein at 37 degrees C and pH 7.4. One mole of ATP is consumed for each mole of arginyl-tRNA formed. The sequence of substrate binding has been investigated by using initial velocity experiments and dead-end and product inhibition studies. The kinetic patterns are consistent with a random addition of substrates with all steps in rapid equilibrium except for the interconversion of the cental quaternary complexes. The dissociation constants of the different enzyme-substrate complexes and of the complexes with the dead-end inhibitors homoarginine and 8-azido-ATP have been calculated on this basis. Binding of ATP to the enzyme is influenced by tRNA and vice versa.

Amino Acids↗