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Biomedical subjects

T Bertrand

Publications and source records attributed to T Bertrand.

7 recordsLinked to original sources
PubMed2000

Substrate-induced fit of the ATP binding site of cytidine monophosphate kinase from Escherichia coli: time-resolved fluorescence of 3'-anthraniloyl-2'-deoxy-ADP and molecular modeling.

The conformation and dynamics of the ATP binding site of cytidine monophosphate kinase from Escherichia coli (CMPK(coli)), which catalyzes specifically the phosphate exchange between ATP and CMP, was studied using the fluorescence properties of 3'-anthraniloyl-2'-deoxy-ADP, a specific ligand of the enzyme. The spectroscopic properties of the bound fluorescent nucleotide change strongly with respect to those in aqueous solution. These changes (red shift of the absorption and excitation spectra, large increase of the excited state lifetime) are compared to those observed in different solvents. These data, as well as acrylamide quenching experiments, suggest that the anthraniloyl moiety is protected from the aqueous solvent upon binding to the ATP binding site, irrespective of the presence of CMP or CDP. The protein-bound ADP analogue exhibits a restricted fast subnanosecond rotational motion, completely blocked by CMP binding. The energy-minimized models of CMPK(coli) complexed with 3'-anthraniloyl-2'-deoxy-ADP using the crystal structures of the ligand-free protein and of its complex with CDP (PDB codes and, respectively) were compared to the crystal structure of UMP/CMP kinase from Dictyostelium discoideum complexed with substrates (PDB code ). The key residues for ATP/ADP binding to CMPK(coli) were identified as R157 and I209, their side chains sandwiching the adenine ring. Moreover, the residues involved in the fixation of the phosphate groups are conserved in both proteins. In the model, the accessibility of the fluorescent ring to the solvent should be substantial if the LID conformation remained unchanged, by contrast to the fluorescence data. These results provide the first experimental arguments about an ATP-mediated induced-fit of the LID in CMPK(coli) modulated by CMP, leading to a closed conformation of the active site, protected from water.

Adenosine Triphosphate↗
PubMed2000

Sleep in subjects with autistic disorder: a neurophysiological and psychological study.

Polysomnography (EOG, EEG, EMG) was carried out in 17 male children and adolescents with autistic disorder, in seven patients with mental retardation and fragile X syndrome, and in five age- and sex-matched normal male subjects. Density of rapid eye movements was not significantly different in the three groups of subjects; however, some sleep parameters such as time in bed, sleep period time, and total sleep time were significantly lower in subjects with autistic disorder than in normal controls; moreover, patients with autistic disorder showed values of sleep period time, first REM latency and percent (%) sleep stage 1 lower than those of patients with fragile X syndrome with mental retardation. Density of muscle twitches was significantly higher in patients with autistic disorder than in normal controls. In contrast only minor differences were observed between patients with autistic disorder and those with fragile X syndrome with mental retardation. Furthermore, some psychoeducational profile-revised items such as perception and eye-hand coordination, showed significant correlation with some sleep parameters (time in bed, sleep latency, stage shifts, first REM latency and wakefulness after sleep onset). Childhood Autism Rating Scale (CARS) scores to visual response and non-verbal communication showed significant correlation with some tonic sleep parameters, such as sleep period time, wakefulness after sleep onset, and total sleep time. Relating to people and activity level items were found to be significantly correlated with rapid eye movement density. Our results suggest the existence of a sleep pattern in autistic patients different from that observed in subjects with mental retardation and from that of normal controls. In addition, these findings indicate that sleep parameters in these patients are correlated with some psychological indices generally used for the diagnosis of autistic disorder; for this reason, polysomnographies might be useful in the comprehension of the neurophysiological mechanisms underlying this condition.

Adolescent↗
PubMed1997

[Description of the prismation method in the rehabilitation of low visions of macular origin].

GOALS: This work aimed at presenting an original rehabilitation method based on the prismation available for patients with organic lesions of the macula. We report results obtained in our first series of patients. MATERIAL AND METHODS: The treatment was given to 14 patients, 7 women and 7 men, aged from 68 to 92 years, with an average age of 81.64, followed in "Low Vision" consultation, and suffering from bilateral macular diseases. All the patients with age-related macular degeneration developed retinal correspondences. They all received a bilateral prismation over their old correction. The orientation of the prisms taking into account the eccentric fixations. The criteria chosen for surveillance were binocular subjective and objective acuity, contrast sensitivity and vision of colours. RESULTS: For all the patients concerned, the method led to an immediate subjective improvement of the visual function. Tolerance to optical support was improved. The patients recovered better self-sufficiency in their daily life. The objective binocular for VA was improved by at least one line for 92.86% of the patients, by at least 2 lines for 42.85% and by 3 lines for 7.14%. The binocular contrast sensitivity was better for all the patients. Regarding the vision of binocular colours, the examination performance time was improved for all the patients. CONCLUSIONS: Prismation allows optimal use of the corresponding eccentric fixation areas. It appears as an interesting new therapeutic method for patients with macular-related low vision. It is complementary to rehabilitation treatment of such patients.

Aged↗