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Biomedical subjects

G Longhi

Publications and source records attributed to G Longhi.

At least 19 recordsLinked to original sources
PubMed2000

Theoretical and experimental studies for the interpretation of vibrational circular dichroism spectra in the CH-stretching overtone region

Two theoretical models for the interpretation of the existing data of CH-stretching overtones' vibrational circular dichroism data are presented. The first model is based on the quantum mechanical Van Vleck contact transformation theory and is applied to the full vibrational problem, the second is based on classical trajectories calculations, by which we treat a simplified three-degrees of freedom Hamiltonian. The latter allows one to derive a qualitative but efficacious picture of the behavior of coupled anharmonic oscillators. In this framework, we analyze the Poincare Surfaces of Section, and calculate the Fourier Cross Spectra of coupled CH-stretchings. Values for the harmonic frequencies and anharmonicities are derived from absorption spectra in the near infrared on partially deuterated compounds. The effect of large amplitude, low-frequency puckering or twisting modes on the ensemble of coupled CH-stretching is taken into account. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗
PubMed2000

Investigations on the mobility of the glycosidic linkage in sucrose by study of the phase space structure of a two-degrees of freedom model.

Using the theoretical Ramachandran (phi, psi) maps reported in the literature for sucrose in vacuo and in aqueous solution, we constructed a two-degrees of freedom model in which the glucose and fructose units are substituted by pseudo-atoms. The complete dynamics of this model is studied numerically at fixed energies. Use is made of the graphic method of the Poincaré surfaces of section in phase space and of the Lissajous maps in configuration space. The reduction to just two degrees of freedom allows one to deal with all initial conditions in phase space, whereas the results of molecular dynamics calculations with all internal degrees of freedoms and with the explicit consideration of solvent molecules are taken into account via effective kinetic and potential energy terms. The conformational isomerization mechanism is investigated by singling out the most reactive trajectories in phase space that are associated with the so-called reactive islands and with the resonances found between the phi and psi motions.

Carbohydrate Conformation↗
PubMed1977

Giant spinal extradural cyst.

A case of giant extradural cyst in a 13-year-old girl is described. The cyst was formed by the arachnoid membrane which extruded through a wide lumbar dural defect. It extended from the midthoracic region down to the sacral canal. At operation a large portion of the cystic wall was removed, but the dural defect was not repaired. Two spino-peritoneal shunts were left in place to drain both the intradural and the extradural spaces. The treatment has proved successful during the 20 months that the patient has been observed.

Adolescent↗
PubMed1975

Energy metabolism of isolated rat thymus cells.

The energy metabolism of rat thymus cells has been investigated using preparations of isolated cells obtained by mechanical treatment of whole organs. The addition of glycolytic substrates such as glucose, pyruvate and lactate stimulates the endogenous respiration of these cells by 50%. On the other hand, succinate, glutamate and malate do not produce any effect. Oligomycin (10 mug/ml) inhibits both endogenous and glucose stimulated respiration by about 40%; 2, 4-DNP (50 muM) increases by 100% glucose induced respiration. The results obtained by using mitochondrial and glycolytic inhibitors as well as aminoxyacetic acid (AOA) and following pyridine nucleotides redox changes, support the idea that in thymus cells glucose is able to induce a great enhancement of O2 consumption both by raising the level of endogenous pyruvate and feeding the mitochondrial respiratory chain with cytosolic reducing equivalents, through an active malate-aspartate shuttle. Thymus cells exhibit a high Pasteur effect (74%). Both AOA and 2,4 DNP are able to stimulate aerobic lactate accumulation by 200% and 100% respectively, indicating that either the redox or phosphate potential do influence the rate of aerobic glycolysis in isolated thymus cells. Similar experiments are also reported on other cells with well known biochemical characteristics.

Animals↗