The international scientific conference on camels 10-12 may (2006), Saudia Arabia.P 1484-1494
Anatomical and Histological Studies on the Parathyroid gland of the Camel (Camelus Dromadrius)
By
Metwally, M.A.M and **Attia, H.F.A*
* Dept. Anatomy &Embryology ** Dept. Histology &Cytology
Faculty of Vet. Med. Benha University, Egypt
Summary
This study was carried out on the anatomical structure, position and dimension of the parathyroid gland. Also this study was attended to the histological, histochemical and ultrastructure of the cells of the parathyroid gland. It was seen at the dorsal border on the cranial pole of the thyroid gland as definite circumscribed structure. Also the gland is located as separate parathyroid structure in the architecture of the thyroid gland. The gland separated from the architecture of the thyroid gland by CT capsule. The gland parenchyma consisted of two groups of cells; chief cells which were numerous and classified to light and dark cells and oxyphilic cells that were fewer in number andrandomly distributed between the chief cells.
Introduction
The camel is considered one of the most important domestic animals throughout the Arabian countries especially in Egypt. Since the camel was accommodated to the all types of climatic conditions, in addition to the meat, hide and milk that given by the camel(Attia, 2000). The parathyroid gland cells give parathyroid hormone which had a great role in the regulation of the calcium metabolism inside the body The parathyroid gland secretion (parathyroidhormone) play an important role in keeping calcium level within normal inside the blood and compensate any disturbance in calcium in case of some metabolic disorders as hypocalcaemia (Mayer, Ramberg , Kronfeld, Buckle, Sherwood, Aurbach and Potis 1969and Potts, Defots, Buckle, Sherwood and Aurbach 1968) . The parathyroid glands are essential for life in most animals and human. The cat is the exception where bilateral thyroidectomy is not life threatening. (Bienzle ,1993). Few studies were carried out on the camel's parathyroid gland (Nagabal , Sudhakar, Yashwant and Dhingra 1989), buffalo ( El-Zoghby, 2004) and goat (Roy, Saigal and Nanda 1984 and Bareedy,1987).
Materials & Methods
The parathyroid gland of 20 mature camel of both sex, their ages ranges from 1-12 years. The specimens were collected from different abattoirs,immersed in Susa fluid fixative, dehydrated in ascending grades of alcohols, cleared in xylene and embedded in paraffin then Cuted at 4-5 U. The anatomical,histological, histochemical and ultrastructure of the parathyroid glands were studied using different histological stains. Hematoxyline & Eosin (Harris, 1898) for general character , Crossmon,s trichrome ( Crossmon's, 1937) for identification of collagen fibers and Silver impergination technique ( Gomori, 1937) for identification of reticular fibers and combination of PAS and alcian blue ( Mowry ,1956) for identification of both acid and neutral mucopolysacharides.Small piece of the external and internal parathyroid gland are put in 2.5% gluteraldehyde for the TEM in AlmazaMilitaryVeterinaryHospital using Sumy Electron Optics SEO at 25 Kv. A very small pieces of 1x1x1 mm were fixed in 2.5% glutaraldehyde in 1M phosphate buffer (pH. 7.3) for 24 hours then post fixed in cold 1M phosphate buffered 1% osmium tetroxide (pH. 7.3) for 3 hours, rinsed in phosphate buffer for 30 minutes then dehydrated (Hayat,1986)Semi-thin sections were stain by Toluidine blue. Ultra thin sections were obtained and mounted on copper grids then stained with uranyl acetate and lead citrate (Reynolds,1965).
Results
1- Anatomical structure
The parathyroid gland was large in size in comparison to the other glands in the different animals. It was located at the dorsal border of the thyroid gland (Fig.1). The gland was situated in a depression inside the architecture of the thyroid gland near the cranial pole. Each gland was separated from the architecture of the thyroid gland by thin CT capsule that was easily identified and distinguished from the thyroid capsule (Fig.2).
The length, width and thickness of the parathyroid gland were measured by using advanced computer program. The gland length was 14 mm , width was 5 mm and its thickness was variable from 3-6 mm. these dimension were represented the mean dimension of the 20 parathyroid glands.
Histological structure
The gland was situated in a depression inside the architecture of the thyroid gland near the cranial pole. Each gland was separated from the architecture of the thyroid gland by thin CT capsule that was easily identified and distinguished from the thyroid capsule. The gland was consisted of stroma and parenchyma , the gland stroma was represented by thin CT capsule that consisted of collagen and reticular fibers , from the capsule , thin and short CT septa was extended into the substance of the gland that divided it into incomplete compartment ( Fig.1). The gland parenchymaconsisted of densely packed cellular structure that were arranged in different forms , including; cords , follicles and anastomosing cords. Only few cells were arranged singly and were scattered throughout the whole gland especially near the center (Fig.2).
The parenchymal cells were two types of cells, chief cells and oxyphilic cells. The chief cells were abundant and widely distributed throughout the gland. The cells were round to ovoid in shape, lightly stained cytoplasm and basophilic, round, vesicular and centrally located nuclei. Most of the chief cells were located around the blood capillaries and sinusoids (Fig.3). The oxyphilic cells were fewer in number and mostly located as single cells. The cells were characterized by darklystained, centrally located nuclei and eosinophilic, granular cytoplasm. The oxyphilic cells were seen to be larger than that of the chief cells (fig.3). Their cytoplasm was PAS positive. Numerous fibroblast cells were found distributed between the architecture of the gland (Fig.2 and 3).The interstitial CT was highly vascular and mainly consisted of reticular and collagen fibers that enclosed the cells of the parenchyma (Fig.4 and 5).
Ultrastructure
a-Light chief cell
These cells were characterized by their shape which was cuboidal to columnar in shape with large pale round to ovoid nuclei. Abundant translucent cytoplasm. Few round and elongated mitochondria , slightly dialated Gologi apparatus, ribosomes and polysomes. RER are present mainly with short cisternae. Secretory granules of various numbers were seen distributed throughout the cytoplasm. Small cytoplasmic projections with tortosity were recorded. Few fat globules were located within the cytoplasm with different densities ( Fig.67) .
b-Dark chief cells
The cells were smaller that that of the light chief cells and mainly distributed among them. It had round to ovoid or ellipsoid nucleus. Abundant ER and golgi apparatus, free ribosomes and polysomes. Large secretory granules were distributed allover the cells and mainly above the nucleus. Large fat globules were located distributed throughout the cytoplasm.( Fig.8).
2- Oxyphilic cells
The cells were larger than the other cells. The abundant cytoplasm was tightly packed with numerous mitochondria. Poorly developed Golgi apparatus and glycogen particles was located between the mitochondria. The nuclei was large, intended and of eccentric position. Poorly developed secretory granules.Numerous large fat globules distributed in the cytoplasm.( Fig.9).
Discussion
Parathyroid glands in most animal species consist of two pairs of glands situated in the anterior cervical region and internal parathyroid gland inside the architecture of the thyroid gland (Smithcors 1964). Also, our work indicated the same findings, but the internal parathyroid gland was not circumscribed and imposible to find it macroscopically.The camel parathyroid gland was mainly identical in histological structure to the other mammals ( Nagabal , Sudhakar, Yashwant and Dhingra 1989) in camel , ( Charles , Adalbert and Clarence 1965) in cow and ( Roy , Sagial and Nada 1984) in goat
Calcium ion plays a key role in many fundamental biologic processes including muscle contraction, blood coagulation, enzyme activity, neural excitability, hormone release, and membrane permeability, in addition to being an essential structural component of the skeleton. Therefore, the precise control of calcium ion in extracellular fluids is vital to the health of humans and animals. To maintain a constant concentration of blood calcium, despite marked variations in intake and excretion, endocrine control mechanisms have evolved that consist primarily of the interactions of three major hormones. Although the direct roles of parathyroid hormone (PTH), calcitonin (CT), and vitamin D frequently are emphasized in the control of blood calcium, other hormones such as adrenal corticosteroids, estrogens, thyroxine, somatotropin, and glucagon may contribute to the maintenance of calcium homeostasis under certain conditions (Chen , Hayakawa , Emura , Ozawa , Taguchi , Yano and Shoumura 2001)
The fine structure of the parathyroid gland cells were discussed by many authors ( El-Zoghby,2004) in buffalo, (Berdahl and Boquist 1973) in dog (Fujimoto, Matsukawa, Inubushi, Satoh and Yamagiwa 1967)in horse and rat (Utsumi , Moriguchi , Takahashi , Kinoshita , Togari , Mizutani , Ohno 2004).
Present evidence indicates that the parathyroid glands contain two types of secretory cell concerned with the elaboration on one hormone. The chief cells were present in different forms, as that was present in the parathyroid of humans and animals are composed of chief cells in various stages of secretory activity and in transition to oxyphil cells in certain species.(Capen 1975). Experimental and pathologic evidence has accumulated to suggest that certain fine structural characteristics of chief cells are associated with different stages of synthetic and secretory activity (Capen 1971 , Roth and Capen 1974 , Jamali , Hayakawa , Chen , Ozawa , Taguchi , Yano , Emura and Shoumura 2000,and Betea, Bradwell, Harvey, Mead, Schmidt-Gayk, Ghaye, Daly, and Beckers 2004 ).The chief cells of the parathyroid gland classified under light microscope into light and dark cells ( Bensley 1947 and Krook 1957).
Chief cells in the active stage of the secretory cycle occur less frequently in the parathyroid glands of most species under normal conditions. The cytoplasm of active chief cells has an increased electron density owing to the close proximity of organelles, numerous secretion granules, overall density of the cytoplasmic matrix, and loss of glycogen particles and lipid bodies (Roth and Capen 1974, Yano Hayakawa, Emura, Chen, Ozawa, Taguchi1 and , Shoumura 2002 and Rangoonwala , Suryawanshi , Pandey 2004 ), this finding was homologous to our results, that the dark chief cells had the character of active cells.
A second cell type in the parathyroid glands of certain animal species and humans is the oxyphil cell. Oxyphil cells are not present in the human fetal parathyroid gland. They first appear in late childhood and increase in number with advancing age, often forming nodules in parathyroid of older persons. Nakagami , Yamazaki and Tsunoda (1968) and Fleischer, Becker, Hamele-Bena, Breen, and Silverberg (2004).They are absent in parathyroids of the rat, chicken, and many species of lower animals.( Cortelyou and McWhinnie 1967 and Fujii , 1972). Oxyphil cells are observed either singly or in small groups interspersed among chief cells. They are larger than chief cells, and their abundant cytoplasmic area is filled with numerous large, often bizarre-shaped mitochondria. Glycogen particles and free ribosomes are interspersed among the mitochondria. Granular endoplasmic reticulum, Golgi apparatuses, and secretory granules are poorly developed in oxyphil cells of normal parathyroid gland,( Capen, 1971)suggesting that oxyphil cells do not have an active function in the biosynthesis of parathyroid hormone. Associated with the marked increase in mitochondria, oxyphil cells have been shown histochemically to have a higher oxidative and hydrolytic enzyme activity than chief cells ( Balogh and Cohen, 1961).Cells are observed with cytoplasmic characteristics intermediate between those of chief and oxyphil cells, suggesting that oxyphil cells represent structurally and functionally modified chief cells. These transitional oxyphil cells have numerous mitochondria, but other organelles are present, including granular endoplasmic reticulum, Golgi apparatuses, and secretory granules. The significance of oxyphil cells in the pathophysiology of the parathyroid glands has not been elucidated, but they do not appear to be active in the synthesis of parathyroid hormone.Oxyphils are not altered in response to either shortterm hypocalcemia or hypercalcemia in animals,(Capen 1971).
On the other hand some authors described some cells rich mitochondria as intermediate cells or transitional oxyphils cells ( Munger and Roth 1963) and Weymouth and Sheridan 1966 and Altenabr and Seifert 1971) or it may be described as oxyphil-chif cells ( Black 1969 ) and ( Munger and Roth 1963).
The cell membrane of the chief cells appeared tortous , this may be due to expulsion of the hormone from the active cell membrane , in which the secretory granules fused with it , whereas the granules content released into the extra cellular space ( Thiele and Wermbter1974 and Palade 1975) , on the other hand Capen, 1971 suggested that the complex interdigitation of the plasna membrane are a direct effect of the low calcium concentration of the ambient calcium, the low calcium concentration may induce synthesis of the plasma membrane and may lead to increase permeability. The cell membrane tortousity may be affected according to the level of hormone and activity of the gland cells (Nakanishi , Sawamoto , Kawashima , Kuwamura , Yamate 2004).
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