Varying Appearances of Calcification in Human Pineal Gland: A Light Microscopic Study

Transcription

1 Dixit, D.P. et al 17 J Anat. Soc. India 50(1) (2001) Varying Appearances of Calcification in Human Pineal Gland: A Light Microscopic Study Koshy, S. and Vettivel S.K. Department of Anatomy, Christian Medical College, Vellore, INDIA For Reprints, request the first author. Abstract. Pineal glands were collected from accident deads during autopsy. The subjects were South Indians. There were no histological postmortum changes. The glands were processed for light microscopy. Eight micron sections were cut and stained. Capsule, septa, lobules, and corpora aranacea were observed. The pineal parenchyma had light and dark pinealocytes. Intrapineal and extrapineal calcified concretions were present. Intrapineal concretions were in the parenchyma, where in younger age groups and among the pinealocytes, the concretions were of globular pattern but in older age groups and among glial fibres, these were of concentric lamellar pattern. Extrapineal concretions were adjacent to the capsule and were concentric lamellar only. Key words : Calcification, concretions, corpora aranacea, glial fibres, parenchyma, pineal gland, pinealocytes. Introduction : The pineal gland (epiphysis cerebri) contains cords and follicles of pinealocytes and neuroglia. Septa extend into it from the surrounding piamater. Pinealocytes form the pineal parenchyma. Neuroglial cells, partially separating the pinealocytes, are like astrocytes (Williams et al. 1989). Brain sands, corpora aranacea, or acervuli are calcified concretions in the pineal gland, presence of which is known since the discovery of the pineal gland and have been investigated over 400 years in animals and in human. They are visible in imaging techniques and help as a midline landmark. There are intrapineal calcifications as well as extrapineal calcifications. Calcified deposits seen in the choroid plexus of lateral ventricles, meninges, and elsewhere in the habenular commissure are extrapineal calcification; and those within the pineal parenchyma are intrapineal calcification. Occasionally these are absent in some specimens. Only a few studies on the concretions, suggested a fresh study. Therefore, the morphology of the pineal calcified concretions were studied. Materials and Methods : Forty pineal glands were collected from accident deads within five to six hours after death during autopsy. There were no histological postmortum changes. Age of the subjects ranged from one to eighty years. The subjects were South Indians in decade wise age groups. Pineal glands were removed from the brain along with the superior colliculus, so that the pineal recess of the third ventricle was also included. Pineal glands were put in Bouin s fluid. After fixation, the specimens were processed for light microscopy. Eight micron serial sections were cut and stained. Staining methods used were (1) Haematoxylin and eosin, (2) Masson s fontanna method for melanin, (3) Heidenhains iron haemotoxylin for secretory materials, and (4) Mallory s phosphotungstic acid haematoxylin for neuroglial cells and nerve fibres. Observations : Pineal gland had a well defined capsule (piamater) and from the capsule septa extended into the parenchyma dividing it into lobules (Fig. 1). The lobular pattern was not well defined in older age groups. Parenchyma consisted of mainly two types of pinealocytes, light pinealocytes and dark pinealocytes (Fig 2). Besides these cells, there were glial cells (Fig. 2). Corpora aranacea were a constant feature as age advanced. Corpora aranacea were in two locations, intrapineal in the pineal parenchyma and extrapineal in the pineal capsule (Fig. 3). These calcified deposits were of two patterns, one was a globular pattern and the other was a concentric lamellated pattern. The extrapineal were of concentric lamellated pattern only. The intrapineal were of two types, the globular type seen, where pinealocytes were present and in younger age groups, and the concentric lamellated type seen around glial fibres and in older age groups. Corpora aranacea appeared in a gland of 12 year. Globular pattern of calcification was chiefly in younger age groups and among large amount of pinealocytes (Fig. 4). As age advanced, there were areas of more glial fibres, and of glial cyst with central coagulum and surrounding glial fibres (Fig. 5). Peripheral to the glial fibre tissue were areas of pinealocytes. In the areas of more glial fibres, large amount of concentric lamellated crystals of corpora aranacea were present in areas of less pinealocytes and more glial fibres (Fig. 6). Discussion : Corpora aranacea are composed of calcium and magnesium salts, Polypeptide hormones, J. Anat. Soc. India 50(1) (2001)

2 18 produced by pineal neuroglia and neurons, combined with specific protein carriers. They are released by exocytosis, together with fragments of vasicular membranes, the latter forming exocytotic debris. When released, the complex is believed to dissociate, hormones being exchanged for calcium ions. The calcium carrier complex so formed is, in the pineal, deposited concentrically around exocytotic debris as corpora aranacea (Lukaszyk and Rieter, 1975). Presence of calcified concretions need not reflect a pathological state as these pineal glands were collected from accident deads, whose health status was unknown and who probably were of normal health. The degree of calcification invariably increases from younger to older age groups and occasionally, corpora aranacea are absent in some adult specimens as according to Krabbe (1955). The morphology of corpora aranacea shows variations in the present study. Calcification occurs not only in the pineal gland but also in the capsule. Vigh et al. (1998) reported the presence of calcium alongside the cell membranes and that meningeal corpora aranacea are in the form of concentric lamellae & intrapineal as globular. But in the present study, as age advances, the intrapineal concretions are of concentric lamellar pattern. Thus, probably the morphology of intrapineal conceretions changes as age advances, globular pattern in younger age groups & concentric lamellar pattern in older age groups. As age advances, the number of pinealocytes decreases and glial fibres increase. The pattern of intrapineal concretions also changes. Globular type of calcified deposits are seen where large amount of pineal parenchyma is present and in younger age groups; whereas concentric lamellated type of calcified deposits are usually associated with large amounts of glial fibres and in older age groups. Humbert and Pevet (1995) observed in aging rats two types of calcification by electron microscopic and electron diffraction methods, an amorphous type with concentric layers and crystalline type with needle shaped crystals and stated that the genesis takes place in dark pinealocytes, which contains more calcium and that once formed the concretions reach extracellular space. The amount of calcarous deposits do not seem to significantly increase as age advanced but the pattern of deposit differs. Kodaka et al (1994) stated that initial human calcification is as calcified pinealocytes, which grow appositionally forming concentric laminations and then simple calcospherulites aggregated with each other and that some of them become numerous aggregated concretions, others individually develop scallopshaped concentric laminations and become lobated calcospherulites. Cytoplasmic microacervuli are localized ultrastructurally in pineal gland from age of 2 days to 86 years; microacervuli are barely present or frequently absent in the oldest subjects; their involvement in the secretory activity rather than in gland atrophy suggests a close relationship between cytoplasmic microacervuli and intermediate microfilaments and a possible role of the cytoskeleton in the formation of corpora aranacea (Gallinai et al. 1989). Where the concretions occur adjacent to pinealocytes, it is crystalline, needle shaped & globular (Fig. 3) while adjacent to glial fibres or other connective tissue, it is amorphous, concentric & lamellar (Fig. 6). To conclude, (1) Pinealocytes are abundant in younger age groups, where the concretions are in the form of crystalline globular pattern. (2) As age advances, pinealocytes decrease and glial fibres increase. Secretory products of pinealocytes are less so that the concretions are modified to amorphous concentric lamellar pattern. References : 1. Galliani, I., Frank, F., Gobbi, P., Giangaspero, F. and Falcieri, E. (1989): Histochemical and ultrastructural study of human pineal gland in the course of aging. Journal of Submicroscopic Cytology and Pathology. 21(3): Humbert, W. and Pevet, P. (1995): Calcium concretions in the pineal gland of aged rats: an ultrastructural and microanalytical study of their biogenesis: Cell & Tissue Research 279(3): Kodaka, T., Mori, R., Debari, K. and Yamada, M. (1940): Scanning electron microscopy and electron probe microanalysis studies of human pineal concretions. Journal of Electron Microscopy (Tokyo) 43(5): Krabbe, K.H. (1995): Development of the pineal organ and a rudimentary parietal eye in some birds Journal of Comparative Neurology 103: Lukaszyk, A. and Rieter, R.J. (1975): Histophysiological evidence for the secretion of polypeptides by the pineal gland. American Journal of Anatomy 103: Vigh, B., Szel, A., Debreceni, K., Fejer, Z., Manzano e Silva, M.J. and Vigh-Teichmann, I. (1998): Comparative histology of pineal calcification: History and Histopathology 13(3): Willaims, P.L., Warwick, R., Dyson, M. and Bannister, L.H.: Gray s Anatomy. In: The Endocrine System. 37 th Edn, Churchill Livingstone, London, pp (1989). J. Anat. Soc. India 50(1) (2001)

3 Fig. 1. Lobular appearance of pineal parenchyma (100 X). Capsule C Septa S Lobule L Fig. 2. Cells in parenchyma (1000 X). Dark pinealocyte Square Light pinealocyte Thick arrow Glial cell Thin arrow

4 Fig. 3. Extrapineal calcification in capsule (100 X). Concentric lamellar pattern Thick arrow (LC) Fig. 4. Intrapineal calcification in parenchyma (100 X). Globular pattern (arrow) surrounded by pinealocytes

5 Fig. 5. Increased glial fibres with glial cyst (100 X) Area of glial fibres F Glial cyst C Fig. 6. Intrapineal calcification in parenchyma (100 X) Concentric lamellar pattern (arrow) surrounded by glial fibres (F)