Methods for Serial Sectioning of the Brain Using a Meat Slicer and for Manufacture of the Permanent Specimens of Brain Slices

Abstract

It is important for the medical students to understand the horizontal planes of human normal brain. Particularly in recent decades, the popularization of magnetic resonance images has made the horizontal planes of brain more necessary. Color atlas of neuroanatomy or plastic models of brain have been widely used for this purpose. However, they are as nor realistic neither accurate as the human brain specimens. Thus, it is necessary to make educational tools of the human brain specimens. In most cases, brains are serially sectioned with 10 mm-thickness, but this is not sufficient for the close observation. Brains can be serially sectioned with 1 mm-thickness by using a polycut or cryomacrotome. However, those equipments cost high and the samples should be treated for a long period of time before serial sectioning. If the brain slices are preserved in the preservative solution, they can be easily damaged. In order to overcome this problem, the plastination method which allows plastic to penetrate into brain tissues was developed. However, this method costs high and requires the complex technique. Thus, we attempted to develop a rapid way to make the permanent specimens of brain slices with reasgnable efforts using synthetic resin.

A brain of 41 years old man cadaver was taken out and soaked in 10% formalin solution. The embedding box was made of acryl plate and acryl cylinder. An amount of 20% gelatin solution was poured into the embedding box and solidified to make gelatin bottom. The brain was put on the gelatin bottom, while the brain direction was adjusted for horizontal serial sectioning of the brain. 25% gelatin solution is poured and solidified to make gelatin cover. A brain block including brain, gelatin bottom and cover was extracted from the embedding box and the brain block was soaked in 10% formalin solution to make it suitably solid. The brain block was fixed on a meat slicer and serially sectioned at 5 mm-thickness to make 28 brain slices. The brain slices were dehydrated in glycerin solution, which was subsequently removed using paper towel. The permanent specimen molds were made of glass plate and acryl plates. An amount of synthetic resin mixture was poured into the permanent specimen mold and solidified to make synthetic resin bottom. Each brain slice was put on the resin bottom. Synthetic resin mixture was poured and solidified to make synthetic resin cover. Each permanent specimen including brain slice, synthetic resin bottom and cover is extracted from the permanent specimen mold. Margins of the permanent specimens of brain slices were trimmed using an electric acryl cutter and surfaces of the permanent specimens were grinded using an electric sandpaper machine and an electric polishing machine. Signs of the numbers and directions of brain slices were attached on the permanent specimens.

Twenty eight horizontal brain slices were made; and each brain slice was processed to make a permanent specimen, so that 28 permanent specimens of brain slices were prepared. The permanent specimens showed the clean surfaces of brain slices with discrimination of the gray and white matters. Using the methods which have been developed in this research, the permanent specimens of brain slices can be made with relatively low cost and little time consuming, which will be practically helpful for neuroanatomy education.