Masaaki Morisawa

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Spermatozoa that are quiescent in electrolyte and nonelectrolyte solutions isotonic to seminal plasma show motility when the semen is diluted with hypotonic solution in freshwater teleosts (four species tested) and with hypertonic solution in marine teleosts (five species tested). Decrease or increase, respectively, in osmolality of the environment may be(More)
The larvae of the ascidian Ciona intestinalis from which the chorion with the test cells and follicle cells were removed developed normally without the test cells until the early tailbud stage. A number of round-shaped cells morphologically similar to the test cells but with different lectin affinities and autofluorescence, then appeared on the neck region(More)
At ejaculation, human sperm are considered to be mechanically trapped and become immotile in the semen coagulum by binding to semenogelins (Sgs) from the seminal vesicle and zinc ions from the prostate. However, the physiological combined roles of the protein and heavy metal on sperm motility are unknown. Here, we have first demonstrated that Sg I alone,(More)
Chemotactic swimming behaviors of spermatozoa toward an egg have been reported in various species. The strategies underlying these behaviors, however, are poorly understood. We focused on two types of chemotaxis, one in the siphonophores and the second in the ascidians, and then proposed two models based on experimental data. Both models assumed that the(More)
The sperm-activating and -attracting factor released from the eggs of the ascidians Ciona intestinalis and Ciona savignyi requires extracellular Ca(2+) for activating sperm motility and eliciting chemotactic behavior of the activated sperm toward the egg. Here, we show that modulators of the store-operated Ca(2+) channel, SK&F96365, Ni(2+),(More)
Morphological changes in the tunic layers and migration of the test cells during swimming period in the larva of the ascidian, Ciona intestinalis, were observed by light and electron microscopy. The swimming period was divided into three stages. In stage 1, further formation of juvenile tunic layer started only in the larval trunk and neck region. In stage(More)
In salmonid fishes, rainbow trout and masu salmon, and the plecoglossid fish, ayu, seminal plasma had an osmolality around 300 mosmol kg-1 isotonic to the blood plasma, and contained a higher concentration of potassium than the blood plasma. Spermatozoa of salmonid fishes were motile when semen was diluted 1:100 with solutions of sodium chloride or(More)
In the ascidian Ciona intestinalis (and C. savignyi), sperm-activating and -attracting factor (SAAF) is released from the egg at fertilization and stimulates both Ca(2+) influx and a transient increase in cAMP level of the sperm, leading to the activation of sperm motility (M. Yoshida et al., 1994, Dev. Growth Differ. 36, 589-595). In this paper we show in(More)
The male reproductive organ of rainbow trout and chum salmon consists of a pair of testes and sperm ducts. Spermatozoa in the distal portion of the sperm ducts exhibit full motility in the K+-free medium. However, spermatozoa from the testis were almost immotile in this medium. This suggests that the spermatozoa acquire a capacity for movement during their(More)