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Biomedical subjects

D Violon

Publications and source records attributed to D Violon.

At least 19 recordsLinked to original sources
PubMed2001

Stabilization of the hydrophilic sphere of non-ionic monomers: are all protected in a similar way?

The present study attempts to investigate whether incorporation of a methyl group as second substituent in the tertiary amido group of the two benzamide side chains of iobitridol (Xenetix) increases the stability of the hydrophilic sphere around this molecule as claimed by its manufacturer, and whether this hydrophilic sphere is unique to this particular molecule or to what extent other monomer non-ionic contrast media show this feature. Five non-ionic monomer contrast medium molecules, ioversol, iohexol, iobitridol, ioxilan and iopromide, were studied. Barriers to the rotation of acetanilide and benzamide side chains, and to the rotation of the amide bond in the benzamide chains, were calculated at a semi-empirical quantum mechanical level of theory with the Mopac/Ampac computer program. The five studied contrast medium molecules showed very similar energy barriers to the rotation of complete substituent chains (benzamide and acetanilide) around their bond with the benzene ring. The magnitude of the barriers fell in the range of values mentioned in the literature. In conclusion, introduction of a methyl group as second substituent in the tertiary amido group of the benzamide substituent chains of iobitridol does not increase the studied rotation barriers, i.e. it does not seem to stabilize the hydrophilic sphere to a greater extent compared with similar monomer non-ionic molecules. The sphere is shown to exist in all five analysed molecules. Introduction of a group with a more hydrophobic character has to be considered and eventually questioned, bearing in mind that a more hydrophilic molecule interacts to a lesser degree with body systems.

Contrast Media↗
PubMed1999

Multiple regression analysis of octanol/water partition coefficients of non-ionic monomeric radiographic contrast media with the combination of three molecular descriptors.

A multiple non-linear regression equation is calculated for the correlation of the octanol/water partition coefficient of nine non-ionic monomeric radiographic contrast media molecules with a combination of three molecule describing parameters (heat of formation, dipole and ovality). Good correlation is obtained (proportion of variance explained, R2, is 0.9093). This simple equation can be used prospectively in the design of new compounds analogous to the used series. It was used to calculate prospectively the partition coefficient of another compound of the same family, iomeprol.

Chemical Phenomena↗
PubMed1999

Renal failure and iodinated contrast media. A review.

Contrast medium-induced renal failure is reported to be a very frequent adverse effect (up to 70% incidence) that often goes undetected. Consequences are sometimes very dramatic and can even lead to irreversible renal damage and renal dialysis. Basically, four groups of mechanisms will be considered: decrease of renal perfusion and increased vascular resistance, glomerular injury, tubular injury, and obstructive nephropathy. Many risk factors are discussed, but the most important is believed to be preexisting renal insufficiency. Preventive measures are discussed. Principally, maintaining good hydration of the patient and avoiding supplementary risk factors in excess of a possible preexisting renal damage are advocated.

Contrast Media↗
PubMed1997

Computation of the solvent-accessible surface area of monomer nonionic contrast media. Consequences for used probe radius in the study of hydrophilic characteristics.

RATIONALE AND OBJECTIVES: The solvent-accessible surface areas of different monomer nonionic contrast media were calculated for different probe radii. By correlating these areas with an experimental (octanol/water partition coefficient) and a calculated parameter (COMB-C), implications for the radius of the probe volume are pointed out. METHODS: The solvent-accessible surface areas of seven monomer nonionic iodinated contrast media were calculated with GEPOL (a program able to calculate various molecular surfaces and volumes) for a wide range of probe radii of the solvent. These areas were correlated with the octanol/ water partition coefficient and COMB-C, a parameter describing the spatial distribution of the hydrophilic elements of a molecule. RESULTS: The correlation coefficients of the solvent-accessible surface areas (determined with the different probe radii) with the octanol/water partition coefficient and of the solvent-accessible surface areas (determined with the same probe radii) with COMB-C were good. This correlation was better for probe raddi of 3 A or more. CONCLUSIONS: COMB-C, a parameter designed earlier, correlated well with the hydrophilia of a monomer nonionic contrast molecule. It was shown that a probe radius of at least 3 A should be used when correlations with hydrophilic characteristics are studied, rather than a probe radius of 1.5 A, which is generally used in assessment of solubilities of molecules in biologic environment. Implications are discussed.

Computer Systems↗
PubMed1997

Analysis of the factors influencing the osmolality of eight monomeric nonionic iodinated contrast medium molecules.

RATIONALE AND OBJECTIVES: Because the measured osmolality of a contrast medium solution differs considerably from the theoretical one, the author analyzed the relative influence of various parameters on the experimental osmolality and derived an equation permitting the prospective calculation of the real osmolality of monomeric nonionics. The author discusses the consequences of the results. MATERIALS: Eight monomer nonionic iodinated molecules (ioversol, iohexol, P-569, iobitridol, P-530, iopamidol, and iopromide) were analyzed. A parameter combining the hydrophilic and the hydrophobic aspects of these molecules was calculated, the relative weight of each composing term was calculated with the multiple nonlinear regression technique. RESULTS: The regression equation was determined based on seven compounds. A high proportion of explained variance was achieved. The prediction for ioxilan (with the lowest osmolality of the eight molecules) yielded a good result, confirming that structural influences determine the osmolality of a molecule. CONCLUSIONS: The study of the parameters influencing the osmolality of eight nonionic iodinated monomer contrast medium molecules led to the development of a regression equation. It is shown that both the hydrophilic and hydrophobic characteristics of a molecule are important in the determination of the osmolality. This equation can be useful prospectively.

Contrast Media↗
PubMed1996

Correlation of some geometric parameters derived from molecular models of monomer nonionic contrast medium molecules with their octanol/water partition coefficient.

RATIONALE AND OBJECTIVES: The author geometrically quantifies the concept of hydrophilic facial and lateral protection of the benzene ring in nonionic monomer contrast medium molecules and verifies the validity of its incorporation in the design theory. The author also correlates this quantification with the octanol/water partition coefficient. METHODS: Six monomer nonionic contrast medium molecules were studied using simple measuring techniques with respect to some geometric parameters quantifying the hydrophilic protection of the hydrophobic zones. The results were processed to obtain a quantifying parameter, which was correlated subsequently with the corresponding octanol/water partition coefficients. RESULTS: A high correlation (r = 0.90) of the developed quantifying parameter with log-P was calculated; its reliability is high. CONCLUSIONS: The validity of the faciality/laterality concept and of its incorporation in the design theory was shown.

Contrast Media↗
PubMed1996

Application of the lateral/facial protection model to a new molecule, iobitridol.

RATIONALE AND OBJECTIVES: The author applies the model quantifying lateral/facial protection of the benzene ring of monomer nonionic contrast media molecules to a new molecule, iobitridol, to confirm the validity of the model and the importance of the facial/lateral protection in the design theory. MATERIALS AND METHODS: A tridimensional model of iobitridol was built, the appropriate measurements were taken, and the previously proposed parameter, COMB-C, was calculated. With the linear regression equation calculated on the basis of the data of six other molecules (and COMB-C as the independent variable), the log-p was calculated prospectively and compared with the known experimental log-p. RESULTS: It was found that the calculated log-p matches the experimental log-p. CONCLUSIONS: The proposed model describing the overall distribution of hydrophilic groups around the benzene ring accurately predicts the log-p of a new molecule, thereby confirming the validity of the model.

Contrast Media↗
PubMed1992

Adrenal cortical carcinoma: a case report.

We present a case of adrenocortical carcinoma. Excretory urography and sonography revealed a left adrenal mass, which was confirmed by computer tomography and further delineated by arteriography. Complete surgical resection was possible. A summary of the clinical and radiological data is included.

Adrenal Cortex Neoplasms↗
PubMed1982

Traumatic rupture of the ascending aorta: a case report.

A patient with a rupture of the ascending aorta after a non-penetrating chest trauma is presented. The aortic tear, angiographically demonstrated, was situated just above the left coronary ostium. Only three examples of angiographically established cases of rupture of the ascending aorta were found in the literature. The point that the distal tip of the catheter should be placed proximally in the ascending aorta, is emphasized After operation the patient went well.

Accidents, Traffic↗