ABSTRACT
Radiation is a common tool in the treatment of brain tumors that induces neurological deficits as a side effect. Some of these deficits appear to be related to the impact of radiation on the neurogenic niches, producing a drastic decrease in the proliferative capacity of these regions. In the adult mammalian brain, the subventricular zone (SVZ) of the lateral ventricles is the main neurogenic niche. Neural stem/precursor cells (NSCs) within the SVZ play an important role in brain repair following injuries. However, the irradiated NSCs' ability to respond to damage has not been previously elucidated. In this study, we evaluated the effects of localized radiation on the SVZ ability to respond to a lysolecithin-induced demyelination of the striatum. We demonstrated that the proliferation rate of the irradiated SVZ was increased after brain damage and that residual NSCs were reactivated. The irradiated SVZ had an expansion of doublecortin positive cells that appeared to migrate from the lateral ventricles toward the demyelinated striatum, where newly generated oligodendrocytes were found. In addition, in the absence of demyelinating damage, remaining cells in the irradiated SVZ appeared to repopulate the neurogenic niche a year post-radiation. These findings support the hypothesis that NSCs are radioresistant and can respond to a brain injury, recovering the neurogenic niche. A more complete understanding of the effects that localized radiation has on the SVZ may lead to improvement of the current protocols used in the radiotherapy of cancer.
Subject(s)
Cerebral Ventricles/radiation effects , Demyelinating Diseases/metabolism , Neural Stem Cells/radiation effects , Animals , Cell Differentiation/physiology , Cell Differentiation/radiation effects , Cell Movement/physiology , Cell Movement/radiation effects , Cell Proliferation , Cerebral Ventricles/metabolism , Cerebral Ventricles/pathology , Demyelinating Diseases/pathology , Humans , Male , Mice , Mice, Inbred C57BL , Microscopy, Electron, Transmission , Neural Stem Cells/cytologyABSTRACT
It has been demonstrated that the exposure of biological systems to magnetic fields (MFs) can produce several beneficial effects: tissue recovery in chronic wounds, re-establishment of blood circulation after tissue ischemia or in necrotic tissues, improvement after epileptic episodes, angiogenesis, etc. In the current study, the effects of extremely low frequency (ELF) MF on the capillaries of some circumventricular organs (CVOs) are demonstrated; a vasodilator effect is reported as well as an increase in their permeability to non-liposoluble substances. For this study, 96 Wistar male rats (250 g body mass) were used and divided into three groups of 32 rats each: a control group (no treatment); a sham ELF-MF group; and an experimental group subjected to ELF-MF (120 Hz harmonic waves and 0.66 mT, root mean square) by the use of Helmholtz coils. All animals were administered colloidal carbon (CC) intravenously to study, through optical and transmission electron microscopy, the capillary permeability in CVOs and the blood-brain barrier (BBB) in brain areas. An increase in capillary permeability to CC was detected in the ELF-MF-exposed group as well as a significant increase in vascular area (capillary vasodilation); none of these effects were observed in individuals of the control and sham ELF-MF groups. It is important to investigate the mechanisms involved in the phenomena reported here in order to explain the effects of ELF-MF on brain vasculature.
Subject(s)
Blood-Brain Barrier/physiology , Capillaries/radiation effects , Capillary Permeability/radiation effects , Magnetic Fields , Animals , Blood-Brain Barrier/radiation effects , Carbon , Cerebral Ventricles/blood supply , Cerebral Ventricles/radiation effects , Male , Rats , Rats, WistarABSTRACT
Se desarrolló un método de Braquiterapia del espacio subaracnoideo mediante la introducción de un coloide de FostatoCrómico 32P (CROP) en el LCR. Se usaron 90 conejos y los coloides fueron inyectados por vía cisternal, Se comprobó la distribución uniforme y permanencia del CROP en la pia-aracnoides de todo el espacio subaracnoideo y superficie cortical y en el epéndimo ventricular mediante autorradiografías y cortes histológicos con técnica de stripping film. La distribución del 32P en hígado (10 por ciento ), bazo (7 por ciento ) y médula ósea (2 por ciento) y otros órganos no provoca efectos significativos. Se comprueba la tolerancia neurológica perfecta para los coloides de partículas finas de menos de 100 nm (CROP), y la neurotoxicidad de los coloides de partículas grandes mayores a 100 nm.. Con altas dosis los estudios histológicos demostraron la ausencia de edema o de lesiones en células y tejido nerviosos. Hasta 6 meses de observación ninguno de los animales mostró trastornos neurológicos atribuíbles al CROP, ni con la repetición de sus aplicaciones