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Biomedical subjects

S Magni

Publications and source records attributed to S Magni.

At least 19 recordsLinked to original sources
PubMed2000

Reaction centre accessibility. I. Calculation of reaction centre congestion and influence of structure flexibility

The fate of a reaction depends on many factors like the electronic reactivity of the ground state molecules, conformation/configuration needs and solvent influence. It is often impossible to predict with any certainty the result, in terms of yield and products, of the interaction between two reactants. Thus the role of reaction centre accessibility is definitely determining but is itself difficult to determine. Nevertheless, within the framework of reaction product prediction it is essential to search for an acceptable solution of predictive modelling. A new approach to both the calculation of steric congestion near reaction centres and its regulation is presented as a first step towards the prediction of centre accessibility. The approach is based on a two dimensional representation of molecules and on the calculation of the steric congestion of each branch, calculated by means of intersecting circles that indicate the extent of the reactivity space and the congestion space.

Journal Article↗
PubMed2000

Reaction centre accessibility. II. Role of reaction centre congestion in the calculation of reaction centre accessibility

Accessibility to reaction centres is as important as electronic reactivity in determining the success of a reaction. The possibility of its calculation becomes a necessary requisite in the prediction of reaction products. Using a recently proposed approach to the calculation of reaction centre congestion based on a two dimensional representation of molecules, a new system has been realised that can quickly evaluate the desired accessibility. The system is based on the simulation of the steric interaction between reactants in different orientations. The calculation of an interaction energy for each orientation and their combination permits the approximate estimation of the reaction probability for the steric factors concerned. Even though all the operations were performed using a two-dimensional representation the results are encouraging. It is obvious that at this level it is impossible to predict face accessibility preference.

Journal Article↗
PubMed1992

Evaluation of treatments for the vaccination against hepatitis B + thymopentine.

We have studied a series of 43 patients--who were suffering from uremia, subject to hemodialysis treatment, resulting seronegative to the test for HBV and who had never been vaccinated before--considering the HBS antibody as seroconversion index. We subdivided our patients into three groups, according to the treatment employed. First group: French vaccine; 2nd group: French vaccine+thymopenthine; 3rd group: recombining DNA vaccine+thymopentine. From a statistical point of view, in the 3rd group we obtained a significant seroconversion in terms of patients, if compared with the other groups.

Adult↗
PubMed1979

Radial maze type as a determinant of the choice behavior of rats.

Spatial memory of rats was examined in two types of radial mazes in which animals had to obtain food from 6-, 8-, or 12-different arms without repeating choices. In Maze 1 with tubular channels closed at the far end rats returned to the central platform by backing out from the just visited alley. In Maze 2 the tubular channels were equipped with one-way doors at both ends and the central platform was raised 5 cm above the floor. Rats leaving the far end of the alley returned to the central platform through a circular hole in its center. Performance was almost perfect in both apparatuses, but rats preferred to enter adjacent alleys in Maze 1 and widely separated alleys in Maze 2. These behaviors were significantly different from computer-simulated random choice from the set of correct solutions of the task. It is concluded that Maze 2 is better suited for repeated experiments with the same animal because the obligatory return to the center of the platform precludes the simplification of the task by response chaining.

Animals↗
PubMed1976

[Permanent endocardiac electric stimulation. Observations on 1125 patients (1 January 1966-31 August 1974)].

The authors report on nine years' experience with permanent endocardial pacing in the treatment of various conduction disturbances. Their experiences relate to 1125 patients; 2208 pacers were used. The age of the patients ranges from 60 to 80 (85%), 15% referring to the left decades, minimum 17 - maximum 94. Fixed rate pacers were used in 41% of cases, QRS synchronous or QRS inhibited pacers were used in 59%. Average life of pacers varies from 8.5 to 28.3 months; the average life of fixed rate pacers is higher. Complications and causes of failures, among which electrode dislodgement is the most relevant and frequent, as well as the relative therapeutical treatments, are described. Early mortality is about 1% and late mortality 8-9%: the survival rate calculated altogether after 9 years' treatment with implantable pervenous pacing is about 24%.

Adolescent↗
PubMedDate not supplied

Activation of the complement system during immunotherapy of cancer with interleukin-2: a possible explanation of the capillary leak syndrome.

The capillary leak syndrome, responsible for fluid loss into the interstitial space, represents one of the major cardiovascular toxicities of IL-2 during the immunotherapy of cancer. The mechanisms involved in the increased vascular permeability have still to be better understood. The present study was carried out to investigate the role of the complement system in mediating the IL-2 vascular toxicity. The study was performed in metastatic renal cancer patients, treated with IL-2 through a 24-hour i.v. infusion at a daily dose of 3 x 10(6) U/m2 for 5 consecutive days, corresponding to one IL-2 course. Six IL-2 courses were evaluated. C3 and C4 were measured daily during IL-2 infusion, and 2 and 5 days after its interruption. IL-2 administration induced a significant decrease in both C3 and C4 mean levels, which became within the normal range 5 days after the end of IL-2 infusion. These results show that IL-2 administration may directly activate the complement system through the classical pathway, which might play a role in determining the increased vascular permeability.

Capillary Permeability↗