The Morphological Observation Of The Structural Features And Somatostatin Expression In Elder Rat Pineal Body

Objective: The mammalian pineal body is an important neuroendocrine organ which can secrete various monoamines and polypeptide hormones. Along with the growth of the age, there are structural changes and functional decline on pineal body. This research is to discover the subtle and ultramicro structural features on elderly rat pineal body and the change of somatostatin expression by means of light and electro microscopy technique. It can provide the morphological data to research the relationship between structure and function of pineal body in depth.Methods:1 Experimental Animal and MaterialsThe fivetin healths elder SD rats (24-month-old), four adult rats (3-month-old), male or female, provided by Hebei medical university laboratory animal center. intravenous injection in enterocoelia for anesthesia with 6% chloral hydrate (0.5ml/100g), intubation and perfusion with 0.9% physiological saline through ascending aorta rapidly. And it takes about 2 to 3 hours to perfuse it with mixed fixatives of 3% paraformaldehyde and 1% glutaraldehyde in 4℃. After decollation and removing the brain, cut down the superficial part of the pineal body and soak it into the mixed fixatives of 3% paraformaldehyde and 1% glutaraldehyde (4℃) with 48 hours to prepare the light and electro microscopy sample.2 Sample preparation and observation with light microscopeThe pineal body sample paraffin embeds with tissue slice, HE staining and light microscope observation to indicate the fine structure of pineal body.3 Immunohistochemical staining and observation with light microscopeThe pineal body which is paraffin embeds with tissue slice, carrying out the somatostatin immunohistochemical staining, observing the somatostatin and its receptor expression with light-microscope, showing the reaction of all kinds of cells in pineal body tissue. .4 Preparation and observation for the transmission electron microscope sample Prepare pineal body tissue sample for transmission electron microscope observation, the ultra-sections of pineal body were observed with transmission electron microscope, which show the ultra-structural characteristics of the elder rat pineal body tissue.Results:1 Through HE staining and light-microscope observation on the paraffin embedding tissue sections:The pineal body is consisting of parenchyma and mesenchyma. The parenchyma mainly concludes pinealocytes and a small quantity of glial cells; the mesenchyma is the loose connective tissue. There are more pinealocytes which are closely-arranged and have the round nucleus and the obvious nucleolus in adult rat group. There are less pinealocytes which are loosely-arranged. In cytoplasm of pinealocyte has lipid droplets, accompanied with obvious connective tissue hyperplasia.2 Observation on the frozen section of the immunohistochemical staining with light microscope:In adult rat pineal body section, the positive cells and positive reactive products of somatostatin immune mainly distributed in cytoplasm of pinealocytes, and there are immune reactive positive fibers in pineal body parenchyma. In elder rat pineal body section, the somatostatin immune reactive positive cells are similar with the control group. The positive cells are pinealocytes. The expression of somatostatin immune positive reactive products was not only in cytoplasm, but also in nucleus.3 Observation on the ultra-sections with transmission electron microscope: There is pineal body sac on the elder rat pineal body. The chief cell of pineal body is pinealocyte, have two or more processes. The intercellular tubules are presence along pineal cells in quantity. The tubules and the pineal body sac, perivascular space, connective tissue space are connected each other. The irregular nucleus of pinealocyte shows the nucleus lobular, the ruga which is formed by nuclear membrane sag, and the obviously increased heterochromatin. Even the chromatin appears the edge set phenomenon. Some pinealocytes show ultra-structural changes as apoptosis. Partial mitochondria of some cells are swelling and deforming, with the crest cytolysis. The common and a few Cysts lined of endoplasmic reticulum and Golgi complex take expansion. Secondary lysosomes and multivesicular bodies are increased. Even it takes plenty of deposition of lipofuscin particles. The blood capillary of rat pineal body is fenestrated type capillary. There is obvious basement membrane on the blood capillary endothelium. The pericytes are also fairly common in connective tissue space around the blood capillary.Conclusion:1 The rat pinealocytes are the immune response positive cells for somatostatin. The elder rat pinealocytes have the increased somatostatin expression which appears on cytoplasm and nucleus.2 The elder rat pineal body appears obvious fine and ultra- structural change. It shows on the decline of pinealocytes, the increasing of connective tissue stromal elements, the deposition of lipid material inside and outside the pinealocytes and the form of lipofuscin particles and plaque.3 The tissue structure of pineal body, especially the morphological changes of pinealocytes, may have the relation with progressive decline of elder rat pineal function.