Summary
The asymmetric endostyle in the larval amphioxus (Branchiostoma lanceolatum) was examined by light-and electron-microscopic cytochemistry (peroxidase; incubation in diaminobenzidine) and autoradiography (incubation in 125I-). Compared to the adult the same cellular zones were also found in the larval endostyle, with the exception of zone 1, which was absent. The corresponding adult and larval zones had a similar morphology. All cells in zones 5a, 5b, and 6 were reactive for peroxidase. A reaction product was also present in the lateral 2 to 3 cell rows of zone 3. The dense reaction product was located on the inner surface of membranes of the rough endoplasmatic reticulum, Golgi apparatus and vesicles, and multivesicular bodies as well as on the outer surface of the luminal plasma membrane. An incomplete row of granule-containing, peroxidase-negative cells was located between zones 5b and 6. After incubation of larvae in sea water containing 125I-, autoradiographic grains were selectively concentrated over the lumen at the apical surface of all peroxidase-positive zones. The highest grain density occurred in relation to zone 5a, which in the adult has been recognized as the iodination center. Few grains were located over the cytoplasm. Methimazole, an inhibitor of peroxidase, abolished the cytochemical reaction and the appearance of autoradiographic grains. The observations indicate that iodination in the larval endostyle takes place extracellularly and is catalyzed by peroxidase bound in the plasma membrane.
Similar content being viewed by others
References
Barrington EJW (1957) The distribution and significance of organically bound iodine in the ascidian ciona intestinalis. J Mar Biol Ass U.K. 36:1–16
Barrington EJW (1958) The localization of organically bound iodine in the endostyle of Amphioxus. J Mar Biol Ass U.K. 35:117–129
Barrington EJW (1959) Some endocrinological aspects of the protochordata. In: A Gorbman (ed) Comparative endocrinology, Wiley, N.Y. pp 250–282
Barrington EJW, Thorpe A (1965) The identification of monoiodotyrosine, diiodotyrosine and thyroxine in extracts of the endostyle of the ascidian Ciona intestinalis. Proc R Soc Ser B 171:136–149
Björkman U, Ekholm R, Denef J-F (1981) Cytochemical localization of hydrogen peroxide in isolated thyroid follicles. J Ultrastruct Res 74:105–115
Dunn AD (1974) Ultrastructural autoradiography and cytochemistry of iodine-binding cells in ascidian endostyle. J Exp Zool 188(1):103–123
Dunn AD (1980) Properties of an iodinating enzyme in the ascidian endostyle. Gen Comp Endocrinol 40:484–493
Ekholm R (1981) Iodination of thyroglobulin. An intracellular or extracellular process? Mol Cell Endocrinol 24:141–163
Ericson LE, Fredriksson G, Öfverholm T (1985) Ultrastructural localization of the iodination centre in the endostyle of the adult Branchiostoma lanceolatum. Cell Tissue Res 241:267–273
Fredriksson G, Ericson R, Olsson R (1984) Iodine binding in the endostyle of larval Branchiostoma lanceolatum (Cephalochordata). Gen Comp Endocrinol 56:117, 177–184
Fredriksson G, Ericson LE, Öfverholm T (1985) Ultrastructural demonstration of iodine-binding and peroxidase activity in the endostyle of Oikopleura dioica. (Appendicularia). Gen Comp Endocrinol: (in press, Vol 58)
Fujita H, Nanba H (1971) Fine structure and its functional properties of the endostyle of ascidians, Ciona intestinalis. A part of phylogenetic studies of the thyroid gland. Z Zellforsch 121:455–469
Fujita H, Sawano F (1979) Fine structural localization of endogenous peroxidase in the endostyle of ascidians, Ciona intestinalis. A part of phylogenetic studies of the thyroid gland. Arch Histol Jpn 42:319–326
Kobayashi H, Tsuneki K, Akiyoshi H, Kobayashi Y, Nozaki M, Ouji M (1983) Histochemical distribution of peroxidase in ascidians with special reference to the branchial sac. Gen Comp Endocrinol 50(2):172–187
Monaco F, Dominici R, Andreoli M, De Pirro R, Roche J (1981) Thyroid hormone formation in thyroglobulin synthesized in the amphioxus Branchiostoma lanceolatum. Comp Biochem Physiol B 70B:341–343
Nunez J, Pommier J (1982) Formation of thyroid hormones. Vit Horm 39:175–229
Olsson R (1963) Endostyles and endostylar secretions: A comparative study. Acta Zool 44(2):299–328
Olsson R (1969) General review of the endocrinology of the Protochordata and Myxinoidea. Gen Comp Endocrinol, Suppl 2:485–499
Olsson R (1983) Club-shaped gland and endostyle of larval Branchiostoma lanceolatum (Cephalochordata). Zoomorphology 103(2):1–13
Salvatore G (1969) Thyroid hormone biosynthesis in Agnatha and Protochordata. Gen Comp Endocrinol, Suppl 2:535–550
Strum JM, Karnowsky MJ (1970) Cytochemical localization of endogenous peroxidase in thyroid follicle cells. J Cell Biol 44:655–666
Thomas IM (1956) The accumulation of radioactive iodine by Amphioxus. J Mar Biol Ass U.K. 35:203–210
Thorndyke M (1978) Evidence for a mammalian thyroglobulin in the endostyle of the ascidian Styela clava. Nature 271:61–62
Thorndyke MC, Probert L (1979) Calcitonin-like cells in the pharynx of the ascidian Styela clava. Cell Tissue Res 203:301–309
Thorpe A, Thorndyke MC, Barrington EJW (1972) Ultrastructural and histochemical features of the endostyle of the ascidian Ciona intestinalis with special reference to the distribution of bound iodine. Gen Comp Endocrinol 19:559–571
Tice LW, Wollman SH (1974) Ultrastructural localization of peroxidase on pseudopods and other structures of the typical thyroid epithelial cell. Endocrinology 94:1555–1567
Tsuneki K, Kobayashi H, Ouji M (1983) Histochemical distribution of peroxidase in amphioxus and cyclostomes with special reference to the endostyle. Gen Comp Endocrinol 50(2):188–200
Wijhe JW v (1914) Studien über Amphioxus. I, Mund und Darmkanal während der Metamorphose. Verh Kon Akad Wetensch (2 Sect), 18 nr 1, Amsterdam, pp 1–84
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Fredriksson, G., Öfverholm, T. & Ericson, L.E. Electron-microscopic studies of iodine-binding and peroxidase activity in the endostyle of the larval amphioxus (Branchiostoma lanceolatum). Cell Tissue Res. 241, 257–266 (1985). https://doi.org/10.1007/BF00217169
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00217169