Biomineralization by silica (chalcedony) in human brain from elderly patients

MARÍA PRADO FIGUEROA; JUVENAL SANCHEZ; SANDRO CASAVILCA

Bregenz

Simposio; The Tenth International Symposium on Neurobiology and Neuroendocrinology; 2010

University of North Dakota School of Medicine & Health Sciences

ABSTRACT Silicon (Si) is an essential nutrient of fundamental importance to human biology. Aluminum and Si accumulations have been detected in senile plaques and neurofibrillary tangle-bearing neurons and in normal elderly brains by a combination of scanning electron microscopy and X-ray spectrometry (EDS-SEM) (Candy et al., 1985). These inorganic elements are related to pathological changes in the cerebral cortex. The presence of chalcedony (an oxide silicon mineral, SiO2) was also found in human brains from elderly people, by using a mineralogical microscope (Prado-Figueroa et al., 2008). Chalcedony is a microcrystalline fibrous form of silica and consists of nanoscale intergrowths of quartz and moganite (Heaney & Post, 1992). This paper documents the visualization of chalcedony by using a Leica TCS ¨C SP2 Laser Scanning Confocal Microscope (LSCM). Three ion lasers were used: Ar 488; He/Ne 543 and He/Ne 633. Sections of human brain were collected after autopsy from elderly patients (mean, 81 years old) from INEN (Lima, Per¨²). The autofluorescent character of chalcedony allowed us to obtain three-dimensional images of the crystals, by using a Leica software. The mature prismatic chalcedony was observed in the cerebral cortex and cerebellum, they are rhombohedral crystals of about 30 ¦Ìm in size, distributed in patches or aggregates. A less mature chalcedony (silica polymorph) of about 1 or 2 ¦Ìm in size, pinacoid (acicular shape) crystals, were also detected nearby. These crystals can be differentiated by using an argon laser with two emission bands. It may also be suggested that chalcedony perhaps enters the tissues as a supersaturated silica fluid or gel, through open spaces, and finally precipitates as a mature prismatic crystal from a prior silica polymorph, growing as a crystal aggregate in an appropriate pH/Eh environment. An important role is played by SiO2 accumulation, pH and Eh, suggesting neurons and nerves are being replaced by SiO2 and they are becoming mineralized.