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The larva of the sand dollar Peronella japonica lacks a mouth and gut, and undergoes metamorphosis into a juvenile sand dollar without feeding. In the present study, it was found that thyroid hormones accelerate the metamorphosis of P. japonica larvae. The contents of thyroid hormones in larvae increased gradually during development. Thiourea and potassium perchlorate, inhibitors of thyroid hormone synthesis, delayed larval metamorphosis and simultaneously repressed an increase in the content of thyroxine in the larval body. These results suggest that the P. japonica larva has a system for synthesis of thyroid hormones that act as factors for inducing metamorphosis.

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The exogastrula-inducing activity of the blastocoelic fluid of sea urchin embryo was demonstrated by adding it to the culture medium of the late blastula stage. The active substance was separated by gel filtration and ultrafiltration, and its molecular weight was found to be in the range from 10,000 to 50,000. The activity was destroyed by trypsin and heat treatment. Since the treated embryos developed normally into pluteus larvae, except for the extrusion of archenteron toward the outside, the morphogenetic activity of the blastocoelic fluid was assumed to be exerted on the endoderm. Close examination of the exogastrulation process suggests that the evagination was due to some force pushing the endodermal plate toward the outside of the embryo.Gastrulation is the first remarkable morphogenetic event in the embryonic development of sea urchins. The mechanism of this process has not been sufficiently elucidated. Normal gastrulation of sea urchin embryos can easily be disturbed by vegetalizing agents such as lithium (Herbst, 1892; cf. Gustafson, '65) and chloramphenicol (Horstadius, '63; Fujiwara and Yasumasu, '74) and by chilling (Waterman, '34; Takahashi et al., '77), resulting in exogastrulation. These disturbances in normal development elicited by foreign srbstances suggest that there may possibly be some intrinsic controlling factorb), which can be affected by the external environment. In this regard, some morphogenetic factors have been reported in the unfertilized egg homogenate of sea urchin (Horstadius et al., '67; Josefsson and Horstadius, '69).On the other hand, Dan and Okazaki ('56) pointed out the importance of pseudopodia protruding from the secondary mesenchyme cells in the second step of gastrulation, by causing exogastrulation by affecting the attachment of pseudopodia to the roof of the blastocoel by either Ca deficiency or protease treatment. The same results were also reported independently by Gustafson and Kinnader ('56) from the cinematographic studies. Recently, it was reported by Berg and Akin ('71) that the blastocoelic fluid of blastula may have a special role in gastrulation. According to these authors, the gastrulation of sea urchin embryos reared in a culture medium containing blastocoelic fluid was arrested; permanent blastulae were maintained, and occasionally exogastrulae were formed as the blastocoelic fluid was made more dilute.It is thus conceivable that the blastocoelic fluid as an intrinsic factor may have an effect on the growth of secondary mesenchyme cells or on the movement of the invaginating cells of the endodermal plate. In this preliminary experiment, we attempted to isolate the active component(s) of blastocoelic fluid that induces exogastrulation, so as to characterize the intrinsic factors affecting gastrulation in sea urchin embryos, and also tried to analyze the process of exogastrulation. MATERIALS AND METHODSThe eggs of Anthocidaris crassispina obtained by introducing 0.53 M KC1 into the coelom were cultured after fertilization in normal sea water in th...

A man in his 80s was administered lenvatinib to treat multiple hepatocellular carcinomas. After starting lenvatinib, he was admitted to our hospital for fever and epigastric tenderness. Conjunctival icterus and conjunctival pallor were observed. Computed tomography showed high density areas in his tumors which were suggestive of intratumoral hemorrhage and tumor rupture. As a result, the patient underwent an emergent angiography and arterial embolization.