The study of the use of specific staining in the observation of neuronal cells and myelin fibers of the cerebellum in the stages of pheasant embryos to one-day-old chicks.

Aim: Pheasant is a pleasant bird whose long and magnificent tail distinguishes it from other types of birds. The cerebellum is organized in the form of leaves that are located in a row in the rostrocaudal axis of the brain. Myelin is the twisting of the plasma membrane of the oligodendrocyte and Schwann cells around an axon, which insulates it and increases the speed of nerve current conduction. Due to the importance and fundamental role of the nervous system, many studies have been done on the nervous system of mammals and other birds, but no research has been done on the development of the pheasant's nervous system, therefore, this research is proposed. Material and methods: In this study, sixty fertilized pheasant eggs were used. Healthy eggs were placed in the automatic incubator and head sampling was done on different days of the embryo from the 7th day and the one-day-old chick. The specimens were immediately fixed in 10% neutral buffered formalin solution for 24-48 hours and then submitted to the dehydration process by passing them through a series of ascending ethanol alcohol each for two hours (70, 80, 90 and 100%) and then specimens were cleared in xylene for one hour after that embedded in paraffin wax and then the blocks were sectioned by microtome at 5μm thickness. First, all tissue sections were stained with Hematoxylin and Eosin for histological structure, and then to identify myelin fibers and glial cells, sections were stained with special stain; Luxal Fast Blue Cresyl Etch Violet and Mallory's Phosphotungstic Acid-Hematoxylin dyes. Results: In the cerebellum of a 7-day-old pheasant fetus, myelin fibers were seen in the form of very thin short strands among the primary nerve cells in an irregular and scattered manner. With increasing fetal age, the density, and probably the length of myelin fibers and the size of nerve cells increased also, the spatial arrangement of myelin fibers was seen in the form of regular thickness and almost from the 17-day embryo of the pheasant onwards, the regular arrangement of these fibers led to the recognition of the white and gray matter of the cerebellum. In 19-day-old pheasant embryo onwards, the regular arrangement of these fibers caused a clear recognition of the white and gray matter of the cerebellum, which until now from this age, they were not distinguishable, but empty spaces between myelin fibers were observed. Conclusion: The results showed that myelin and glial cells start to form in the pheasant cerebellum from the age of 7 and as the embryo ages, these cells become bigger and completely fill the space between the neurons. Also, myelin fibers were first observed in the form of very thin and scattered threads at the age of 7 embryos and As the embryo ages, these fibers become denser and finally, in the white matter of the cerebellum of a day-old chick, they find a spatial arrangement in the form of very thick and regular bundles. [ABSTRACT FROM AUTHOR]