Search

Phylogenetic analyses were carried out using various reconstructed datasets to examine the quality and quantity of information for each region in the sea urchin mitochondrial genome. Smaller sized data produced no reliable results. As the data size increased, orders were organized into individual clades. An almost exact relationship between orders was acquired from an apploximately 6500-bp dataset from the ND protein group, but it was not perfect. Probably, the entire mitochondrial genome or a larger dataset will be required to accurately determine phylogenetic relationships of sea urchins., Departmental Bulletin Paper, 原著, 2019年度神奈川大学総合理学研究所共同研究助成論文

In this activity, the eggs and sperm of sea urchins were used for the study of fertilization and embryogenesis. These sea urchin gametes are a favorite material for the observation of the processes of fertilization, cleavage, embryogenesis and larval development in senior high school and university biology courses. In Japan, some sea urchin programs are also occasionally incorporated into junior high school courses. In this article, we present practical examples of observations and experiments regarding sea urchin adults, fertilization and early development. These were successfully carried out in an elementary school classroom. Questionnaire survey responses from children showed that they gained an appreciation for the fact that successive bodies of animals could be created by their continuous development from fertilized eggs. The educational effect of the program on children was that it taught them about not only the mystery of the birth and growth of a life form but also the relevance of marine ecology to the promotion of education-oriented local revitalization in Noto.

The animal pole region of the sea urchin larva is composed of the thickened animal plate, and the apical ganglion formed by several serotonergic cells. Recent studies have revealed many genes involved in the differentiation and construction of these structures. However, the cellular basis of specification process is largely unknown. To understand how these structures are specified, we tried to clarify the properties of animal hemisphere by manipulative methods. The isolation experiments revealed that some cytoplasmic factors responsible for the thickening of the ectodermal epithelium form a gradient from the animal pole toward the equator. The deletion experiments showed that an1 blastomeres are required for the formation of animal plate and apical ganglion. Recombination and transplantation experiments suggested that the presumed thickening factors are easily inactivated by the vegetal signal, and that a low concentration of thickening factors promotes the differentiation of serotonergic cells, while the factors inhibit serotonergic cell differentiation at higher concentrations. Further, pulse treatment with animalizing or vegetalizing reagent showed that the specification process terminates during the mesenchyme blastula stage. Based on these results, we propose a model that explains the experimentally caused changes in the size of animal plate and in the width of apical ganglion.

Recent studies have uncovered the gene regulatory network that operates in the process of endoderm specification in the sea urchin embryo. However, it is still unknown how the presumptive endodermal tissue is allocated to three parts of digestive tract (esophagus, stomach, and intestine). In this study, early stage embryos were treated with chemicals that disturb the signaling involved in the endoderm specification, and the change in volumes of three parts of the digestive tract was monitored. The obtained results showed the existence of a mechanism that allocates the presumptive endodermal tissue to the esopahgus and stomach at a constant volume ratio. It was also found that Notch signaling is involved in the specification process of intestinal cells, and that the intestinal cells were specified independently of the esophagus and stomach at a later stage. Further, whole-mount in situ hybridization revealed that Endo16, a specific marker of the vegetal plate, was expressed irrespectively of the vegetal plate formation; Endo16 expressing cells newly appeared at the base of the archenteron after the vegetal plate had invaginated into the blastocoel. Based on these results, a model for the allocation of presumptive endodermal tissue to three parts of the digestive tract is presented.

第28回宇宙利用シンポジウム (2012年1月23-24日. 日本学術会議), 港区, 東京都, Space Utilization Research (January 23-24, 2012. Science Council of Japan), Minato-ku, Tokyo Japan, 資料番号: SA6000032056, レポート番号: L16

We organized a working group for studying the reproduction and continuity of life under the space environment. The aim of our project is to get deep insight into the effect of space environment from various aspects, such as basic life science, applied reproductive biology, and medical sciences. This year, our group has discussed about the following research projects. First, the effects of gravity on behavior of mouse were examined. When mouse was exposed to 3G serious effects were observed in amount of food consumption, feeding period and posture resulting in loss of weight. Second, we demonstrated progesterone and melatonin both accelerated hyperactivation of sperm motility. Since hyper gravity modifies various kinds of reproduction relating hormones it could be assumed that hyper gravity might affect reproduction via modification of sperm hyperactivation. Third, apoptosis occurred during spermatogenesis especially in spermatocyte stage. Space environment might affect the function of sperm selection by modifying the apoptosis. In addition we discussed about diffusion of ATP (Adenosine Triphosphate) in sperm flagella and human sexuality. We move ahead on these projects to space experiment., 資料番号: AA0063706069

In sea urchin embryo, the skeletogenic cells are called primary meshenchymen cells derived from micromeres at 16-cell stage. We reported a promotive effect of hypergravity in the low serum concentration culture of the skeletogenic cells. In this condition, cultured skeletogenic cells were so sensitive that they showed a clear difference of skeletogenesis also for the different substrate of culture plate. The decrease of spicule number by the inhibitor of Ca(2+)-channel is recovered under hypergravity condition. The culture in low Ca(2+) concentration also decreased the number of formed spicule and the number was recovered under hypergravity, too. These results show the possibility that the Ca(2+) uptake is one of a candidate process that is affected by hypergravity condition. The spicule also contains spicule matrix proteins. The expression of their mRNA under hypergravity was examined and the level was not different from control condition., 資料番号: AA0063349095

Spicule formation by the cultured micromere of sea urchin was used as a model for the morphogenesis in biomineralization to be adapted as an experimental system in space. Several experiments were carried out in the different gravity environment to examine a role of gravity in the cells isolated from whole embryo and reported that spicule elongation was suppressed in the experiments of centrifugation, clinostat and the parabolic flight. The spicules of sea urchin larvae consist of calcite with magnesium and organic substances, called spicule matrix proteins. To examine the detail of the effect of these gravity conditions, RT-PCR was used to measure the level of expression of spicule matrix proteins in the cultured cells under each condition. The expression of one spicule matrix protein (SM30) was suppressed under the centrifugal condition. It also suppressed in the cells whose spicule elongation was suppressed in the culture on the ground after the parabolic flight. These results demonstrate that each gravity condition can effect on the gene expression of spicule matrix protein., 資料番号: AA0046917010

第27回宇宙利用シンポジウム (2011年1月24日-25日, 宇宙航空研究開発機構宇宙科学研究所相模原キャンパス), 相模原市, 神奈川県, The Twenty-seventh Space Utilization Symposium (January 24-25, 2011. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, Sea urchin and other echinoderm animals have calcitic endoskeleton. In sea urchin embryo, skeletogenesis starts at late gastrula stage and then the spicules grow up to larval skeletons. The skeletogenic cells are called primary mesenchyme cells derived from micromeres at 16-cell stage. We already reported a promotive effect of hypergravity on skeletogenesis in the culture of the skeletogenic cells with low concentration of horse serum. For the culture of skeletogenic cells, micromeres isolated by sucrose gradient are used. In this study, we examined more simple method to isolate skeletogenic cells. In calcium deficient seawater, embryos developed without cell adhesion and failed to form blastura. At the time of hatching, most cells were dispersed but mesenchyme cells attached on the substrate. By the gentle stream, dissociated cells were removed and mesenchyme cells left on the bottom were used for the culture. These mesenchyme sometimes contained not only skeletogenic cells but also secondary mesenchyme cells. This isolation method is simple and possibly is useful to improve a procedure of the gravity experiment., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0065129071

Sea urchin and other echinoderm animals have calcitic endoskeleton. In sea urchin embryo, skeletogenesis starts at late gastrula stage and then the spicules grow up to larval skeletons. The skeletogenic cells are called primary mesenchyme cells derived from micromeres at 16-cell stage. We already reported a promotive effect of hypergravity on skeletogenesis in the 0.25 percent horse serum culture of the skeletogenic cells. In this condition, cultured skeletogenic cells are so sensitive that they show a clear difference of skeletogenesis under the hypergravity though it is difficult to detect significant difference in the culture medium containing 4 percent horse serum. In 0.25 percent serum, the number of spicule is less than that in 4 percent serum under 1 xg condition. It recovers to the similar level significantly even in 0.25 percent under hypergravity (100 xg). In this study, we examined the effect of hypergravity on the spicule formation of the sea urchin embryo. The embryos cultured under hypergravity showed some abnormal skeletogenesis. The elongation of two arm rods (post oral rod) was suppressed in 80 percent of embryos under 100 xg condition. Under 5 xg condition most of them developed into normal larvae, but additional branching, abnormal partial thickening and excess spicule formation were observed. It is considered that spicule formation in embryo is accepting not only direct hypergravity effect but also indirect effect via surrounding tissues. The excess spicule formation observed in the embryo is correspond to the increase of spicule in the culture experiment and supposed to be one direct effect of hyper gravity., 資料番号: AA0063706057

Gonads of sea urchin Strongylocentrotus nudus were salted with 10, 15, and 20% NaCl and stored at 5°C for about 27 weeks. During storage, composition of lipid of the salted gonads was analyzed. TBA value and contents of VBN, carbonyl, and oxo-acid were also determined, The content of triglyceride, a principal component of non-polar lipids, of salted gonads decreased during storage, while that of free fatty acid increased. The changes in the contents of these lipid classes occurred noticeably in the sample with NaCl added at a higher concentration. The contents of phosphatidylcholine and phosphatidylethanolamine, major components of polar lipids, decreased, being accompanied with formations of lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine. A larger amount of LPC was accumulated in the sample with NaCl added at higher concentration. Fatty acid composition of the total lipid in all samples remained almost unchanged during storage. However, percentages of C20:4 and C20:5 decreased in the polar lipid fraction, while it increased in the non-polar lipid fraction. These results suggested that the lipid deterioration of salted gonads of sea urchin during storage was caused through a hydrolytic reaction rather than oxidative one.

Unfertilized and fertilized eggs at every developmental stages of the sea urchin, Hemicentrotus pulcherrimus, were first immersed in hypotonic sea water; then centrifugalized in that condition with a force of about 1300 x G for ten minutes. These eggs were fixed withBouin's solution at each stage of development and sectioned with ordinary paraffin method.The sectioned preparations were stained with the Lillie's PAS method.By the centrifugation, the cortical cytoplasm was clearly observed "both in living and sectioned prepartions. The thickness calculated is about less than 4 tim. In this experiment, the behavior of the cytoplasmic granules stained with PAS method were discussed.