A preliminary report on the fine structure of Tripneustes esculentus eggs.

The fine structure of Tripneustes esculentus eggs was studied with the aid of an electron microscope. Cells obtained from this West Indies sea urchin showed cortical granules, mitochondria forming a rosette around lipid granules, endoplasmic reticula, Golgi apparatus and annulated lamellae. These structures appear identical to those seen in eggs of the Atlantic sea urchin: Arbacia punctulata.     

Fibrin membrane endowed with biological function. III. Fixing living cells in fibrin gel without impairing their functions

Summary Chlorella cells, sea urchin eggs and Paramecium were embedded in fibrin gel which was formed by fibrinogen-fibrin conversion in the presence of thrombin. The embedded Chlorella cells retain the ability of photosynthesis by illumination. The embedded sea urchin eggs develop to normal blastulae and gastrulae. Samples of Paramecium survive for more than several h beating their cilia. It is suggested that this technique of fixing living cells is useful for handling free cells as a mass like a tissue, and for holding free cells in micrurgical experiments.     

Zinc increases the longevity of unfertilized sea urchin eggs

Summary We have found that Zn²⁺ prevented lysis of unfertilized sea urchin eggs, and the eggs retained the ability to form fertilization membranes and to divide. SDS polyacrylamide gel electrophoresis showed that proteolysis of several proteins accompanied egg lysis, but Zn²⁺ inhibited this proteolysis. Therefore, Zn²⁺ blocks protease activity directly or indirectly and thereby prolongs the longevity of unfertilized sea urchin eggs.     

Denaturation map of the ribosomal DNA of Lytechinus variegatus sperm.

Electron microscopy of the partially heat denatured ribosomal DNA (rDNA) from sea urchin (Lytechinus variegatus) sperm has demonstrated that it consists of repeating units of 3.6 +/- 0.2 micron, corresponding to a mol.wt of 7.2 +/- 0.4 x 10(6). Based on differential denaturability, each repeat unit is divided into 2 regions. The larger region of 2.47 +/- 0.11 micron (mol.wt 4.9 +/- 0.22 x 10(6)) corresponds in length to the ribosomal precursor RNA of sea urchins and the smaller, GC-rich, subunit of 1.16 +/- 0.09 micrometer (mol.wt 2.3 +/- 0.18 x 10(6)) is presumed to contain non-transcribed spacer sequences.     

Végétativisation de l'œuf de l'oursin par la Phénazone

Summary Phenazone employed in various concentrations on the eggs of the sea urchin,Paracentrotus lividus, has a powerful vegetalizing effect on their development. The role of the interference between phenazone and synthetic process of specific proteins is considered.     

Free choline in sea urchin embryos (Paracentrotus lividus)

Summary A sensitive radio-enzymatic assay for choline, applied to extracts of developing sea urchin embryos, revealed that free choline in eggs declines during cleavage and rises abruptly previous to gastrulation, indicating an important shift in choline metabolism between these two stages.     

Chymotrypsin-like and trypsin-like protease activities in the sea urchin (Hemicentrotus pulcherrimus) egg

Proteolytic activities in extracts of sea urchin eggs were examined using SDS (sodium dodecyl sulphate)-polyacrylamide gels. In the unfertilized eggs, proteases were detected as bands corresponding to the molecular weights of 40 kD and 26 kD on the gelatin gel, and 35 kD and 30 kD on the casein gel. Using various protease inhibitors, it was found that 40 kD, 30 kD, and 26 kD are chymotrypsin-like proteases and that 35 kD is a trypsin-like protease. The activity of the 40 kD chymotrypsin-like protease was found to be almost completely lost after insemination.     

Chymotrypsin-like and trypsin-like protease activities in the sea urchin (Hemicentrotus pulcherrimus) egg.

Proteolytic activities in extracts of sea urchin eggs were examined using SDS (sodium dodecyl sulphate)-polyacrylamide gels. In the unfertilized eggs, proteases were detected as bands corresponding to the molecular weights of 40 kD and 26 kD on the gelatin gel, and 35 kD and 30 kD on the casein gel. Using various protease inhibitors, it was found that 40 kD, 30 kD, and 26 kD are chymotrypsin-like proteases and that 35 kD is a trypsin-like protease. The activity of the 40 kD chymotrypsin-like protease was found to be almost completely lost after insemination.     

Effets de l'actinomycine D sur le développement normal et sur les modifications expérimentales de la morphogénèse de l'oeuf de l'oursinParacentrotus lividus

Summary In the presence of actinomycin D (20–40 µg/ml), the development of the eggs of the sea urchin,Paracentrotus lividus, is slowed from the late morula and stopped at the blastula stage. The development is immediately stopped in the blastula treated with actinomycin D (20–40 µg/ml). The inhibitory effects of actinomycin D are prevented by deoxyribonucleic acid. Actinomycin D does not exert animalizing or vegetalizing effects. However, the enhancing of vegetalizing action of lithium and the weakening of animalizing effects of zinc ions and Evans blue have been observed in the presence of actinomycin D. These observations may reflect some difference in the state of dependence of differentiation of entomesodermic and ectodermic structures towards the nucleus.     

Colorants acides et détermination embryonnaire chez les Echinodermes

Summary The effects of three dyes with carboxyl groups are been studied on the developing eggs of the sea urchin,Paracentrotus lividus. Uranin and rose Bengal are both some derivative of the xanthene. Chrome violet CG is a carboxyl derivative of pararosolic acid. In dilute solutions these three dyes induce the development of radial larvae. At higher concentration, uranin and rose Bengal are very effective animalizing agents. Rose Bengal is more active than uranin. Rose Bengal differs from uranin by the fixation of halogens on the molecule of dye which increase the acidity of the carboxyl group. It appears that animalizing activity runs parallel with acidity. The results of these experiments are discussed in relation to the animalizing effects of various acid sulfonated dyes. The possible significance of the combinations between acid dyes and basic components of the cells in the animalization is considered.     

Binding of Lens culinaris lectin to sea urchin embryo chromatin.

Lentin binds specifically to sea urchin embryo chromatin. This binding is saturable and inhibited by alpha-methyl-mannose. Scatchard plot analysis of the binding reaction suggests a single binding site.     

Teratogenic effect of tolbutamide on the development of the sea urchin embryo (Paracentrotus lividus lamarck)

Summary The hypoglycemic agent tolbutamide was tested for its action on the cleavage and differentiation of the sea urchin embryo. Tolbutamide effects a strong selective action on the endoderm which becomes suppressed.     

Involvement of a sperm aminopeptidase in fertilization of the sea urchin

Summary Inhibitory efficiencies of bestatin methyl ester and its nine analogs for sea urchin sperm aminopeptidase activity were similar to the efficiency of the same compounds as inhibitors either of sperm respiration or of fertilization. This suggests that a sperm aminopeptidase plays a role in fertilization in the sea urchin, possibly through its involvement in sperm respiration.Acknowledgment. We are grateful to Dr Wataru Tanaka of Nippon kayaku co. for his gifts of bestatin and its analogs. We are also indebted to Mrs Akiko Tsuchida-Watanabe for her technical assitance, and to the staff of Asamushi Marine Biological Station, Tohoku University, where part of this work was carried out. This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.     

Acid release at meiotic maturation of oocytes in the polychaete annelid Sabellaria alveolata.

ABout 1 pmole of acid per egg is released when prophasic oocytes undergo maturation under the action of sperm, proteases or ionophore A 23187. No similar acid release occurs at fertilization of matured oocytes. These findings are compared with data on Urechis and sea urchin.     

Sea urchin embryo as a model for analysis of the signaling pathways linking DNA damage checkpoint,DNA repair and apoptosis

DNA integrity checkpoint control was studied in the sea urchin early embryo. Treatment of the embryos with genotoxic agents such as methyl methanesulfonate (MMS) or bleomycin induced the activation of a cell cycle checkpoint as evidenced by the occurrence of a delay or an arrest in the division of the embryos and an inhibition of CDK1/cyclin B activating dephosphorylation. The genotoxic treatment was shown to induce DNA damage that depended on the genotoxic concentration and was correlated with the observed cell cycle delay. At low genotoxic concentrations, embryos were able to repair the DNA damage and recover from checkpoint arrest, whereas at high doses they underwent morphological and biochemical changes characteristic of apoptosis. Finally, extracts prepared from embryos were found to be capable of supporting DNA repair in vitro upon incubation with oligonucleotides mimicking damage. Taken together, our results demonstrate that sea urchin early embryos contain fully functional and activatable DNA damage checkpoints. Sea urchin embryos are discussed as a promising model to study the signaling pathways of cell cycle checkpoint, DNA repair and apoptosis, which upon deregulation play a significant role in the origin of cancer. Received 10 April 2007; accepted 23 April 2007     

Effects of Ca2+ and Mg2+ on motility of sea urchin spermatozoa

Summary Swimming speed of sea urchin spermatozoa, measured by a light scattering technique, did not change with 0-20 mM Ca²⁺ in the medium. The speed was maximum at the normal concentration of Mg²⁺ (49 mM) in sea water.Supported by grants-in-aid from the Ministry of Education, Science and Culture, Japan, and a grant from the Ford Foundation.     

Effets de la 2-mercaptopropionyl-glycine sur la différenciation de l'œuf d'oursin

Summary 2-Mercaptopropionyl-glycine (Thiola) exerted a strong animalizing action on the development of the sea urchin,Paracentrotus lividus. The action of Thiola on the synthesis of superficial and cortical cellular structures newly synthesized during the segmentation is suggested. These changes may alter the circulation of morphogenetic substances between blastomeres.     

Acid release at meiotic maturation of oocytes in the polychaete annelidSabellaria alveolata

Summary About 1 pmole of acid per egg is released when prophasic oocytes undergo maturation under the action of sperm, proteases or ionophore A 23187. No similar acid release occurs at fertilization of matured oocytes. These findings are compared with data onUrechis and sea urchin.     

Effects of zinc and lithium ions on the strengthening cell adhesion in sea urchin blastulae

Summary Cellular adhesion in sea urchin blastulae, normal and vegetalized by treatment with lithium ions, strengthened as development proceeded. This tendency was arrested in the embryos animalized by treatment with zinc ions.The authors thank Mr T. Shinkai and S. Sone for their technical assistance.     

The problem of sea urchin egg fertilization and its implications for biological studies.

The analysis of sea urchin egg fertilization shows that several phenomena common to other biological systems are involved: cell recognition, cell fusion, exocytosis and initiation of mitotic activity. Both the role of calcium ions in cell fusion and exocytosis and the function of the cell surface in the initiation of mitotic activity appear to have general applicability. The study of fertilization can contribute to the elucidation of these processes and, reciprocally, progress in this field can help to advance our understanding of the mechanisms of fertilization in sea urchins and other organisms.