Implanting hydroxyapatite-mineralized tough hydrogel into osteochondral defects of rabbits, osteogenesis spontaneously penetrates into the gel matrix owing to the semi-permeablility of the hydrogel. The gradient layer (around 40 μm thick) contributes quite strong bonding of the gel to bone. This is the first success in realizing the robust osteointegration of tough hydrogels, and the method is simple and feasible for practical use

Peroxidasin is a novel protein combining peroxidase and extracellular matrix motifs. Hemocytes differentiate early from head mesoderm, make peroxidasin and later phagocytose apoptotic cells. As hemocytes spread throughout the embryo, they synthesize extracellular matrix and peroxidasin, incorporating it into completed basement membranes. Cultured cells secrete peroxidasin; it occurs in larvae and adults. Each 1512 residue chain of the three‐armed, disulfide‐linked homotrimer combines a peroxidase domain with six leucine‐rich regions, four Ig loops, a thrombospondin/procollagen homology and an amphipathic alpha‐helix. The peroxidase domain is homologous with human myeloperoxidase and eosinophil peroxidase. This heme protein catalyzes H2O2‐driven radioiodinations, oxidations and formation of dityrosine. We propose that peroxidasin functions uniquely in extracellular matrix consolidation, phagocytosis and defense.

No abstract

A collagen‐like protein was identified from the otoliths of the chum salmon, Oncorhynchus keta. The otolith, composed mainly of calcium carbonate with small amount of organic matrices, is formed in the inner ear and serves as a part of the hearing and balance systems. Although the organic matrices may play important roles in the growth of otolith, little is known about their chemical nature and physiological function. In this study, a major organic component of the otolith, designated otolin‐1, which may serve as a template for calcification, was purified. The sequences of two tryptic peptides from otolin‐1 revealed high homology with parts of a saccular collagen which had been described previously [Davis, J.G., Oberholtzer, J.C., Burns, F.R. & Greene, M.I. (1995) Science267, 1031–1034]. Cloning of a cDNA coding for otolin‐1 revealed that the deduced amino‐acid sequence contained a collagenous domain in the central part of the protein. Although collagen is the most abundant structural protein in the animal body, otolin‐1 mRNA was expressed specifically in the sacculus. Immunohistochemical studies showed that otolin‐1 is synthesized in the transitional epithelium and transferred to the otolith and otolithic membrane. This is the first report concerning characterization of a structural protein containing many tandem repeats of the sequence, Gly‐Xaa‐Yaa, typical for collagen from the biomineral composed of calcium carbonate.

In teleosts, a considerable part of the body calcium is found in the scales. Associated with the scales are osteoblasts and osteoclasts, and during periods of high calcium demand such as during sexual maturation or starvation, the scales can be resorbed and thereby act as an internal calcium reservoir. In mammalian bone tissue, the activity of an acid phosphatase (ACP) isoenzyme, tartrate resistant acid phosphatase (TRACP), can be used as a marker for osteoclastic activity. In the present study, an evaluation of TRACP as a marker for osteoclastic activity in teleost scales has been performed. ACP and TRACP was histologically localized at resorption sites around the edge of the scales as well as at resorption holes in the scales. The optimal conditions for biochemical measurements of ACP and TRACP activity were found to be pH 5.3, 10 mM paranitrophenylphosphate, incubated for 30 min at room temperature, and 10 mM tartrate added when required. Using TRACP as a marker, estradiol-17β (E2) was found to increase the proportion of scales being resorbed, as well as the number and size of resorption sites per scale. Also, the scales of E2-treated fish showed weaker staining for calcium. Together, the obtained data indicate that estradiol-17β induces osteoclastic activity in teleost scales, resulting in increased resorption of the scales. A period of refeeding following a period of starvation did not have detectable effects on the scale osteoclastic activity and scale resorption.

No abstract

Background: An oxidized guanine, 8-oxo-7,8-dihydroguanine, induces base mispairing, thereby altering genetic information. Results: Human MTH3 degrades 8-oxoguanine-containing nucleoside diphosphates to prevent misincorporation of 8-oxoguanine into DNA and RNA. Conclusion: MTH3 is closely related to MTH1 and MTH2 but differs in substrate specificity. Significance: MTH3 may be involved in maintaining the high fidelity of DNA replication as well as transcription under oxidative stress.

The symmetrical body of flatfish larvae dramatically changes into an asymmetrical form after metamorphosis. Eye migration results in the most significant asymmetrical development seen in any vertebrate. To understand the mechanisms involved in eye migration, bone and cartilage formation was observed during metamorphosis in laboratory-reared Japanese flounder, Paralichthys olivaceus, by using whole-body samples and histological sections. Most of the hard tissues of the cranium (parasphenoid, trabecular cartilage, supraorbital canal, and supraorbital bar) exist symmetrically in the larval period before metamorphosis and develop by twisting in the same direction as that in which the eye migrates. An increase in skin thickness beneath the eye was observed only on the blind side at the beginning of eye migration; this was the first definitive difference between the right and left sides of the body. The pseudomesial bar, a peculiar bone present only in flatfishes, developed from this thick skin and grew dorsad. Novel sac-like structures were found and named retrorbital vesicles. The retrorbital vesicle of the blind side grew larger and faster than that of the ocular side when the right eye moved most dramatically, whereas no difference was observed between the volume of right and left connective tissue in the head. The asymmetrical presence and growth of the pseudomesial bar together with inflation of the retrorbital vesicle on the blind side may be responsible for right eye migration during metamorphosis in the Japanese flounder.