Effects of DC Magnetic Fields on Magnetoliposomes.

The potential use of magnetic nanoparticles (MNPs) in biomedicine as magnetic resonance, drug delivery, imagenology, hyperthermia, biosensors, and biological separation has been studied in different laboratories. One of the challenges on MNP elaboration for biological applications is the size, biocompatibility, heat efficiency, stabilization in physiological conditions, and surface coating. Magnetoliposome (ML), a lipid bilayer of phospholipids encapsulating MNPs, is a system used to reduce toxicity. Encapsulated MNPs can be used as a potential drug and a gene delivery system, and in the presence of magnetic fields, MLs can be accumulated in a target tissue by a strong gradient magnetic field. Here, we present a study of the effects of DC magnetic fields on encapsulated MNPs inside liposomes. Despite their widespread applications in biotechnology and environmental, biomedical, and materials science, the effects of magnetic fields on MLs are unclear. We use a modified coprecipitation method to synthesize superparamagnetic nanoparticles (SNPs) in aqueous solutions. The SNPs are encapsulated inside phospholipid liposomes to study the interaction between phospholipids and SNPs. Material characterization of SNPs reveals round-shaped nanoparticles with an average size of 12 nm, mainly magnetite. MLs were prepared by the rehydration method. After formation, we found two types of MLs: one type is tense with SNPs encapsulated and the other is a floppy vesicle that does not show the presence of SNPs. To study the response of MLs to an applied DC magnetic field, we used a homemade chamber. Digitalized images show encapsulated SNPs assembled in chain formation when a DC magnetic field is applied. When the magnetic field is switched off, it completely disperses SNPs. Floppy MLs deform along the direction of the external applied magnetic field. Solving the relevant magnetostatic equations, we present a theoretical model to explain the ML deformations by analyzing the forces exerted by the magnetic field over the surface of the spheroidal liposome. Tangential magnetic forces acting on the ML surface result in a press force deforming MLs. The type of deformations will depend on the magnetic properties of the mediums inside and outside the MLs. The model predicts a coexistence region of oblate-prolate deformation in the zone where χ = 1. We can understand the chain formation in terms of a dipole-dipole interaction of SNP.

Aphasia due to lesions of the kinesthetic speech areas.

The study of two groups of right handed aphasics, group A and group B, is presented. Each group was formed by four subjects, both groups showed an aphasic syndrome craracterized by alteration in the efferent sphere of oral and written language, principally in the latter. There was almost no alteration in the sensory interchange sphere, except for a right hypoesthesia and astereognosis in two subjects of each group. The aspect in which both groups differed profoundly was the efferent sphere of written language. Group B patients could not write with the dominant hand because of a right hemiplegia. Nevertheless, they could do it with the left, nondominant hand. Group A patients were unable to write with either hand in spite of the absence of motor deficit or incoordination which could explain this inability. The different possible topographical localizations responsible for the deficit are analyzed. It is concluded that there are three main possibilities that could explain the writing difficulty found in group B patients: a) a lesion located in the white frontal matter of the left hemisphere just underneath the kinesthetic area; b) a lesion in the kinesthetic dominant area itself; c) a lesion in the dominant cerebral hemisphere white matter underlying the primary receptor somesthetic and the primary effector areas, but without directly involving them, and extending also in depth toward the anterior third of the corpus callosum. Any one of these lesions could impair the transmission of information from the dominant kinesthetic hand area to the primary effector motor area of both cerebral hemispheres.

A new method for the examination of language in aphasics: internal and external reliability coefficients.

A new method is presented to test language, worked out by one of the authors (R.R.L.). Briefly, it consists of the systematic and ordered exploration of the functions from the cortical sensory and motor areas, the interchange of the sensorial information from the sensory to the motor areas. Nine patients with different aphasic syndromes were examined independently from each other. The test was divided in two ranks; the sensory interchange and the motor-oral-manual. The Spearman Correlation Coefficient and its statistical meaning was calculated for each rank. For the internal reliability tests, the results achieved by two successive examination on the same patient were compared by the same explorer. For the external reliability, the results from two sucessive tests on the same patient were compared by two different explorers. The Spearman Correlation Coefficient rate in all the cases varied between 1 and 0.88 with a probability of more than 0.0005 and high statistical significance, with exception of the motor rank of case 4, where it was 0.87 with a probability of more than 0.005 and less than 0.0005 with still some statistical meaning.