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Biomedical subjects

D Robert

Publications and source records attributed to D Robert.

At least 325 records · Page 18Linked to original sources
PubMedDate not supplied

Molecular quantum similarity measures tuned 3D QSAR: an antitumoral family validation study.

In this work, a new methodology to construct a tuned QSAR model is presented, which is based on a convex set formalism. The present procedure continues previous 3D QSAR studies, performed using molecular quantum similarity measures (MQSM). With this new computational tool, the efficiency of MQSM applied to QSAR analysis is significantly improved. A reliable QSAR model is obtained using convex linear combinations of different kinds of MQSM, corresponding to different quantum-mechanical operators related to the quantum similarity integral. The active compounds studied here, as a case study, are a set of antitumor agents, the camptothecin molecule and analogues, and the property evaluated is the topoisomerase-I inhibition activity. Before performing a tuned QSAR analysis with this particular molecular set, a simple QSAR study for all the different possible types of MQSM is carried out. In addition, another application of MQSM is presented, to determine which method can be used to optimize molecular structures in order to reproduce experimental molecular geometries as well as possible.

Animals↗
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Three-dimensional quantitative structure-activity relationships from tuned molecular quantum similarity measures: prediction of the corticosteroid-binding globulin binding affinity for a steroid family.

Predictive models based on tuned molecular quantum similarity measures and their application to obtain quantitative structure-activity relationships (QSAR) are described. In the present paper, the corticosteroid-binding globulin binding affinity of a 31 steroid family is studied by means of a multilinear regression using molecular descriptors derived from mixed steric-electrostatic quantum similarity matrixes as parameters, obtaining satisfactory predictions. A systematic procedure to treat outliers by using triple-density quantum similarity measures is also presented. This method depicts an alternative to the grid-based QSAR techniques, providing a consistent approach that avoids problematic result dependency on the grid parameters.

In Vitro Techniques↗
PubMedDate not supplied

Quantification of the influence of single-point mutations on haloalkane dehalogenase activity: a molecular quantum similarity study.

Controlled modifications in certain protein amino acid residues can lead to changes in their function and stability. Amino acid structural features and their relation to these changes were examined by using quantum molecular similarity techniques. The effect of deliberate mutations in position 172 of the haloalkane dehalogenase enzyme, yielding to variations on the dehalogenation of 1,2-dibromoethane, was studied qualitatively and quantitatively using molecular quantum similarity techniques. A valuable classification of the residues according to their effect on activity was obtained by representing the optimal two-dimensional classical scaling solution. In addition, satisfactory quantitative relationships were found, comparable to those attained by previous studies on this same data set using other techniques. Molecular quantum similarity analysis provides a consistent, unbiased, and homogeneous set of molecular descriptors and is a feasible alternative to the use of physicochemical properties.

Hydrolases↗
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Renal function and urinary excretion of electrolytes in patients receiving cyclic parenteral nutrition.

BACKGROUND: Long-term parenteral nutrition (LTPN) has been shown to induce renal impairment and bone demineralization. However, the mechanism of both injuries has not been clarified. METHODS: This prospective study was performed in 16 patients with short bowel syndrome, aged 28 to 63 years, who had received LTPN for 31 +/- 7 months. Urinary excretion of electrolytes were measured before (diurnal, 12 hours) and during (nocturnal, 12 hours) parenteral nutrition. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured in the morning after the nutritional bag supply. RESULTS: Mean GFR was 86 +/- 7 mL/min/1.73 m2 and ERPF was 412 +/- 31 mL/min/1.73 m2. Decreased GFR was present in 9 patients. There was no relation between renal function and age or the duration of LTPN. Urine volume and excretion of urea, creatinine, sodium, magnesium, and phosphate but not potassium increased significantly in nocturnal urine compared with diurnal urine. On the basis on 24-hour calciuria, 7 patients were normocalciuric (NCa) whereas 9 were hypercalciuric (HCa). Both had excessive nocturnal calciuria, but only the HCa group had diurnal hypercalciuria, the calcium supply being identical. Bone mineral density (BMD) was slightly, although not significantly, higher in NCa group, but in all patients BMD correlated significantly with calciuria. Serum parathyroid hormone and vitamin D were not different in the two groups. CONCLUSIONS: In patients receiving LTPN, renal function is frequently impaired, by a mechanism which remains unclear. In nocturnal cyclic mode of nutrition, urinary volume and electrolyte excretion occurred predominantly during the infusion, but some patients have diurnal hypercalciuria. In these patients a defect in renal calcium reabsorption or more likely the inability of bone to retain the infused calcium may be responsible for bone demineralization.

Adult↗
PubMedDate not supplied

Shoshin beriberi: an unusual complication of prolonged parenteral nutrition.

After 4 weeks of total parenteral nutrition (TPN), a 12-yr-old girl exhibited an acute heart failure with high cardiac output, anuria, and severe lactic acidosis. The clinical, hemodynamic, and biological data suggested the diagnosis of shoshin beriberi which was proved by the low erythrocyte transketolase activity with elevated "TPP effect" and by the dramatic improvement of the patient after thiamin administration. Thiamin deficiency and severe neurological disorders have been described during long-term parenteral nutrition. To our knowledge, this is the first report of the cardiovascular complication of this vitamin deprivation in long-term TPN.

Acidosis↗
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Hepatic cytolytic and cholestatic changes related to a change of lipid emulsions in four long-term parenteral nutrition patients with short bowel.

Long-term parenteral nutrition hepatic-related impairment is commonly reported and diversely explained. However, with a low cyclic caloric intake (100% to 130% of basal metabolism calculated with the Harris-Benedict formula) consisting of two-thirds glucose, one-third lipid, and 0.20 to 0.25 g of nitrogen per kilogram per day, these complications were infrequent in a clinical practice of home long-term parenteral nutrition. Retrospectively, it was noticed that the switch from Intralipid 20% to Ivelip 20% at the same amount was followed within 2 months by four cases of jaundice in a population of four home long-term parenteral nutrition patients with short bowel disease. Hepatic disturbances were characterized by cytolysis and cholestasis and were reversible after switching from Ivelip 20% back to Intralipid 20%. Neither viral, nor biliary, nor septic etiologies were detected. The exact pathological mechanism remains unknown. The basal composition of both lipid emulsions seems to be identical: soy oil emulsion emulsified by egg phospholipids. However, some differences exist such as the size of particles, the presence of sodium oleate in Ivelip 20%, and the purification process of lecithin. These may explain the difference in hepatic tolerance during long-term parenteral nutrition.

Adult↗
PubMedDate not supplied

[Kurt Goldstein: from aphasia to linguistics].

The authors try to take into account Kurt Goldstein's contribution on the subject of aphasia. They introduce the significance of the phenomenological approach of the language leading them toward the structuralist theme.

Aphasia↗
PubMedDate not supplied

Evaluation of an intermittent flow oxygen system.

A new portable intermittent-demand flow oxygen system triggered by the differences of temperature detected at the nose by two small thermistors has been evaluated on 16 patients. Compared to an ordinary constant-flow cannula, the mean oxygen saving of the intermittent flow system was 50%.

Adult↗
PubMedDate not supplied

[Indications of home assisted ventilation by tracheostomy for non-paralytic chronic respiratory insufficient patients (author's transl)].

Based on a 15-year study, the indication of assisted ventilation at home is discussed. It depends on the seriousness of the C.R.I. (dyspnea, repeated acute failures, PaCO2 greater than or equal to 55 Torr). The only possible course is ventilation by tracheostomy. The best indication is represented by pure restrictive syndromes. On the contrary, the indication should be considered with extreme caution in obstructive syndromes.

Airway Resistance↗
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[Technic and supervision of home assisted ventilation (H.A.V.) in tracheostomized chronic respiratory insufficient (C.R.I.) patients (author's transl)].

With 200 patients during the last 15 years the daily use of apparatus and supervision modalities, as described in the present work, has shown that H.A.V. is entirely possible in tracheostomized C.R.I. patients. Rather strict conditions must be respected (as with hemodialysis at home) if H.A.V. is to be medically and materially successful. The expenses involved can vary greatly according to the medical and material management (choice of study material, economic maintenance, minimal oxygen consumption through proper adjustment...). Finally, the use of assisted ventilation requires a choice amont several adjustment possibilities which are still subject to evolution.

Home Nursing↗
PubMedDate not supplied

[Results of home assisted ventilation of non-paralytic and tracheostomized chronic respiratory insufficient patients (author's transl)].

The following results have been obtained from a study of 118 tracheostomized patients ventilated at home: --Survival on the whole is generally prolonged. --The prognosis of tracheostomized subjects with restrictive syndrome is totally modified in length and quality when the patients are ventilated. --In the case of obstructive syndrome, the length and quality of survival are probably increased. However, it seems that assisted ventilation at home leads only to the disappearance of asphyxiating paroxysms and right cardiac failure. It does not seem to prevent the unrelenting evolution of the disease.

Adult↗