Koji Wada

Extracellular matrix formation by amebocytes during epithelial regeneration in the pearl oysterPinctada fucata

SummaryTo identify the cells which produce the extracellular matrix during bivalve wound healing, we observed epithelial regeneration inPinctada fucata and evaluated the ability of amebocytes to produce the matrix in vitro. Between days 1 and 3 after an ovary was implanted with abiotic material (a shell ball) via an incision, agranular amebocytes formed a sheath, consisting of 10–20 cell layers, between the implant and incised ovarian tissue. Extracellular matrix was deposited in the spaces between the amebocytes in the sheath. At the incised follicle, gonadal epithelial cells were attached to the newly formed matrix. When a mantle allograft (2 mm square) was implanted with abiotic material to bring them into close contact, epithelial cells emigrated from the allograft along the surface of the abiotic material where they attached to the newly formed matrix at the sheath of amebocytes. In vitro, agranular amebocytes formed a matrix composed of fibrils with a diameter of 20 nm during a 6-day culture period. Pepsin-digested extract of the cell layer forming the matrix gave protein bands with electrophoretic mobilities identical to α- and β-sized components of a collagen purified from this animal. The matrix exhibited immunoreaction to antiserum raised against the collagen and was stained by alcian bluc. Thus, the agranular amebocyte apparently has the ability to produce an extracellular matrix containing collagen and possibly proteoglycan(s).

STUDIES ON THE MINERALIZATION OF THE CALCIFIED TISSUE IN MOLLUSCS-I

1) Relationships among the epithelial cells and their products were investigated in the homoplastic transplantation between the Japanese pearl oyster Pinctada martensii. 2) In mineralization of molluscan shells, groups of the metachromatic granules in various sizes appeared first on the surface of an inserted glass in contact with epithelial cells and subsequently became homogeneous. 3) Fibrous deposits formed on an inserted glass appear to be alike in the elongation and tension of regenerated epithelium. 4) Mounds grown on the fibrous deposits consisted of dendritic spherical crystalline aggregates of shell substances and increased larger in dimension than overlying epithelial cells. 5) Mineral crystals in mounds were in granular, needle-like and rhombic shapes-among individual materials and neighboring areas of a single material.

STUDIES ON THE MINERALIZATION OF THE CALCIFIED TISSUE IN MOLLUSCS-II

1) Experiments of crystal growth on inserted coverslips between shell valve and mantle of Pinctada martensii were carried out with the adminstration of tetracycline hydrochloride. 2) The fluorophore was incorporated into mineral crystals. 3) Localization of the fluorophore appears to be closely related to the mode of growth of mineral crystal and to mineralization of lamellae. 4) Discussion on crystal growth was attempted by the aid of tetracycline adminestered.