Mossbauer Studies of Healthy Brain Tissue

Magnetic resonance imaging of a normal human brain (material of the Department of Neurology, Medical University of Warsaw, Poland). Arrows show the location of GP—globus pallidus, HP—hippocampus (a—coronal section), and SN—substantia nigra (b—saggital section). 

An excess of free radicals may destroy cell membranes, and thus lead directly to the death of cells [3]. Studies dealing with the role of iron, which may be involved in oxidative stress in the human brain, are therefore of ultimate importance. 

There are about 4g of iron in the human body. Sixty percent of this iron is found in hemoglobin, and the remaining 40% is found mainly in liver, spleen, heart, muscles, and brain. The distribution of iron in the brain differs between various brain structures. There are about ISO ng of iron per mg of wet tissue in substantia nigra and globus pallidus, and only about 50 ng of iron per mg of wet tissue in the hippocampal cortex [4-7]. The weight of tissue samples that can be used in MS studies is at most I g so that less than about 50-200 pg of natural iron (l-4pg of Fe ) could be present in each sample. In order to study such low concentrations of iron, the MS measurements have to be performed in a highly iron-clean environment. This demands iron-free counter and cryostat windows and iron-free sample holders. In the Mossbauer studies reported here, Mossbauer spectra measured with a sample holder filled with distilled water proved that, indeed, the background, measured without tissues, was very tiny, effectively nonexistent, in these experiments [8]. 

Mossbauer spectra of three brain structures SN, GP, and HP were obtained at 4.1 K, 90 K, and also at room temperature for lyophilized samples. All brain samples were obtained from autopsies performed within 48 h after death and were kept in liquid nitrogen until assayed or lyophilized. Formalin-fixed brain samples were not used, as preliminary measurements showed that this form of storage caused significant changes in the iron composition, which were proportional to the time the tissues had been stored in formalin [9]. 

All Mossbauer spectra of the measured tissues presented an asymmetric doublet at room temperature and at 90 K, and a sextet at 4.1 K. Typical Mossbauer spectra of SN, GP, and HP obtained at 90 K are shown in Fig. 16.2, and a typical Mossbauer spectrum of SN obtained at 4.1 K is shown in Fig. 16.3. 

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