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Biomedical subjects

C Ramon

Publications and source records attributed to C Ramon.

24 records · Page 2Linked to original sources
PubMed1983

Muscle pathway geometry in the heart wall.

Muscle fiber pathways in the heart wall are described. Procedures are introduced which permit data to be standardized from cadaver and animal hearts fixed at different points of the cardiac cycle or obtained in vivo from patients with different ejection fractions and heart masses. Design criteria are also developed here to construct a hypothetical standard left ventricle to compare the data from different hearts. The equations allow the nested set of toroidal fiber-shells to be depicted with typical muscle fiberpaths. With this formulation the heart wall and typical elements in it can be shown computergraphically as they move from the contracted state to the distended. Man-made fiber structures that simulate the fail-safe shockload absorbing features of the heart can now be designed and tested computergraphically by use of the mathematical procedures described here.

Animals↗
PubMed1981

Inhibition of growth rate of Escherichia coli induced by extremely low-frequency weak magnetic fields.

Cultures of Escherichia coli kept at 0 degree C in a phosphate buffer solution were exposed to a sinusoidal weak 60- or 600-Hz magnetic field of strength 2 X 10(-3) Tesla. A decrease of more than 40% in bacterial count was observed after a 60-h exposure to the magnetic field. Electron micrographs of exposed bacteria show ruptured cell walls, possibly due to the breaking away of flagella under the influence of the sinusoidally varying electromotive force.

Cell Membrane↗
PubMedDate not supplied

On the influence of volume currents and extended sources on neuromagnetic fields: a simulation study.

The influence of volume currents on the magnetic field is an important question in magnetoencephalography since the spherical volume conductor is still widely used for source localization. In theory, the magnetic field of a radial dipole in a homogeneous sphere is zero. In realistic models of the head, the field is suppressed when compared with a tangential dipole. To determine the influence of the volume currents, this suppression ratio (magnetic field of the radial dipole divided by the field of the tangential dipole) needs to be quantified. Large-scale finite element method models of the human head and the rabbit head were constructed and the suppression ratio was computed. The computed suppression value of 0.28 in the rabbit head was similar to the previously measured experimental value. In the human head, an average suppression ratio of 0.19 +/- 0.07 was found for different regions and depths in the gray matter. It was found that the computed magnetic field of radial sources varied significantly with the conductivities of the surrounding tissues where the dipole was located. We also modeled the magnetic field of an epileptic interictal spike in a finite element model of the rabbit head with a single dipole and with extended sources of varying length (1-8 mm). The extended source models developed were based on invasive measurements of an interictal spike within the rabbit brain. The field patterns of the small (1-2 mm) extended sources were similar to a single dipolar source and begin to deviate significantly from a dipolar field for the larger extended sources (6-8 mm).

Animals↗
PubMedDate not supplied

The influence of local tissue conductivity changes on the magnetoencephalogram and the electroencephalogram.

We examined the influence of local tissue conductivity changes in the vicinity of a dipolar source on the neuromagnetic field and the electric scalp potential using a high resolution finite element method model of the human head. We found that the topology of both the electric scalp potential and the neuromagnetic field (and consequently dipole localization) is influenced significantly by conductivity changes only in voxels adjacent to the source. Conductivity changes in these voxels yield a greater change in the amplitude of the magnetic field (and consequently in the dipole strength) than in the amplitude of the electric potential.

Action Potentials↗
PubMedDate not supplied

Peptide mapping characterization by capillary electrophoresis of a human monoclonal anti-Rh(D) antibody produced for clinical study.

CE has been employed for peptide mapping characterization of the light chain of a human anti-Rhesus (D) (Rh[D]) antibody presently undergoing clinical evaluation. In the presence of an ion-pairing agent used to increase resolution, reproducible maps were obtained within 55 min after injection of 12 fmol of protein. CE has also been employed as a direct and quick screening tool for purity evaluation of the tryptic peptides obtained from reversed-phase high-performance liquid chromatography (RP-HPLC) prior to sequence analysis. Post-translational modifications of the protein were determined by identification of the cysteine residues implicated in disulfide linkages.

Amino Acid Sequence↗