Shigeo Takeuchi

Cause of the memory effect observed in alkaline secondary batteries using nickel electrode

Abstract The cause of the memory effect observed in alkaline-type rechargeable batteries such as nickel–cadmium and nickel–hydrogen batteries was studied using a positive capacity-limited nickel–cadmium cell and AAA-type commercially available nickel–cadmium and nickel–hydrogen batteries. From the X-ray diffraction (XRD) analysis, γ-NiOOH was observed on the nickel electrode in a charged state after repeating shallow discharge cycling of the cells or overcharging. This γ-NiOOH is initially formed at the collector side of the electrode and it then grows to the solution side during shallow discharge cycling. When the amount of γ-NiOOH formed is small, only β-NiOOH can be detected by conventional XRD, even when the memory effect is observed. In this case, γ-NiOOH can be detected by shaving the surface of the electrode, using an emery paper to remove the β-NiOOH covering. This γ-NiOOH disappeared within a few cycles of the normal charge–discharge cycling and the memory effect disappeared. It is concluded that the cause of the memory effect is mainly due to the formation of γ-NiOOH.

Adrenergic neurotransmitters and calcium ionophore‐induced situs inversus viscerum in Xenopus laevis embryos

Xenopus laevis embryos at the blastula–early tail bud stage were exposed to norepinephrine or octopamine dissolved in culture saline until they reached the larval stage. The left–right asymmetry of the heart and gut was then examined. We found that these adrenergic neurotransmitters induced situs inversus in the heart and/or gut in up to 35% of tested neurula embryos. Norepinephrine‐induced situs inversus was blocked by the α‐1 adrenergic antagonist prazosin. Furthermore, A23187, a calcium ionophore, also increased the incidence of situs inversus up to 54% when late‐neurula embryos were exposed to the solution. A23187 treatment initiated before neural groove formation was less effective. The incidence of situs inversus induced by these reagents decreased towards the control level (2.2%, 25 untreated embryos out of 1127 embryos in total) in embryos past the stage of neural tube closure. In the present experiments we obtained 22 gut‐only situs inversus embryos having an inverted gut and a normal heart. In contrast, such embryos were not observed among the 1127 untreated embryos. An adrenergic signal mediated by an increase in intracellular free calcium may be involved in the asymmetrical visceral morphogenesis of Xenopus embryos.

Optic chiasm in the species of order Clupeiformes, family Clupeidae: Optic chiasm of Spratelloides gracilis shows an opposite laterality to that of Etrumeus teres

In most teleost fishes, the optic nerves decussate completely as they project to the mesencephalic region. Examination of the decussation pattern of 25 species from 11 different orders in Pisces revealed that each species shows a specific chiasmic type. In 11 species out of the 25, laterality of the chiasmic pattern was not determined; in half of the individuals examined, the left optic nerve ran dorsally to the right optic nerve, while in the other half, the right optic nerve was dorsal. In eight other species the optic nerves from both eyes branched into several bundles at the chiasmic point, and intercalated to form a complicated decussation pattern. In the present study we report our findings that Spratelloides gracilis, of the order Clupeiformes, family Clupeidae, shows a particular laterality of decussation: the left optic nerve ran dorsally to the right (n=200/202). In contrast, Etrumeus teres, of the same order and family, had a strong preference of the opposite (complementary) chiasmic pattern to that of S. gracilis (n=59/59), revealing that these two species display opposite left–right optic chiasm patterning. As far as we investigated, other species of Clupeiformes have not shown left–right preference in the decussation pattern. We conclude that the opposite laterality of the optic chiasms of these two closely related species, S. gracilis and E. teres, enables investigation of species-specific laterality in fishes of symmetric shapes.

Morphometry of cellular protrusions of mesodermal cells and fibrous extracellular matrix in the primitive streak stage chick embryo

SummaryChick mesodermal cells, having become invaginated and beginning to locomote prior to the formation of the mesodermal cell layer at an early primitive streak stage, extend many filopodia and flatten themselves against the basal surface of the epiblast. Morphometry on scanning electron micrographs of chick mesodermal cells revealed two statistically significant tendencies. Each cell took an extended form and protruded filopodia, preferably along its major axis, suggesting that the force extending the cell body was generated by both ends rich in filopodia. The cells also tended to protrude filopodia most frequently in a direction away from Hensens node. The orientation of the fibrous extracellular matrix (fECM), running on the basal surface of the epiblast, was assessed quantitatively, and it was proved statistically that the orientation of the fECM was radial around the primitive streak: With an immunogold staining technique, fECM, to which the filopodia of the mesodermal cells attached frequently and closely, was confirmed to be rich in fibronectin (FN). These results lead us to conclude that the mesodermal cells in chick gastrula were guided to locomote towards the periphery of the area pellucida by FN-rich fECM laid on the basal surface of the epiblast, and that this movement was due to an in vivo locomotive mechanism using filopodia.

Invasion and migration of a single chick pre-streak stage epiblast cell in vitro: Its implication to the primitive streak formation

To investigate the contribution of the epiblast cell behavior to the primitive streak formation, we examined the motility of a single epiblast cell from pre‐streak stage embryo in vitro. On the substratum that was evenly coated with laminin gel, epiblast cells attached well to the gel and one or a few very long and broad cellular processes protruded from their spherical cell bodies; however, they hardly locomoted on it. Unexpectedly, after overnight culture, half of the single cells dissolved the laminin gel beneath them to make well‐like holes, and invaded in the holes. On the substratum lined parallel with the fibrous laminin gels supplemented with fibronectin, they locomoted actively in accordance with the alignment. That is, they were subjected to contact guidance. In locomotion they looked like snails, extending one or a few long and broad processes in a forward direction from the spherical cell bodies. However, on the substratum lined with laminin or fibronectin only, they did not locomote actively. Individual chick pre‐streak epiblast cells had already been committed to invade, and their migratory nature existed in each cell, even though they were isolated from the epithelial sheet. The implication of these findings on the cellular basis of primitive streak formation will be discussed.

Effects of Bromo-Cyclic GMP and Bromo-Cyclic AMP on Embryonic Development of Xenopus laevis

Abstract Low molecular signalling molecules such as cAMP and cGMP are expected to have important functions in early morphogenetic processes in animal development. We examined the effect of 8-bromo-cyclic GMP (Br-cGMP) on Xenopus embryogenesis, using 8-bromo-cyclic AMP (Br-cAMP) as a reference. When Xenopus gastrulae were cultured in the medium which contained these analogues, their development was affected in specific and dosage-dependent manners: While Br-cAMP induced anomaly only in head part (swelling of myelencephalon with enlarged ventricle), Br-cGMP induced shortening in body length often accompanied by bending of the cephalo-caudal axis. In embryos treated with Br-cGMP at a high dose, cellular movement was inhibited as revealed by SEM and this resulted in the formation of tadpoles with unclosed yolk plug. Br-cGMP at lower doses induced severe inhibition of the development of notochord and muscles. Since HPLC analyses revealed that both analogues were uptaken into embryonic cells, we assumed that the morphological effects observed were induced by the interference of the normal functioning of cGMP and cAMP, respectively, by Br-cGMP and Br-cAMP. Based on the results obtained, we assume that while cGMP is involved mainly in the differentiation of mesodermal structures, especially in formation of notochord and muscles, cAMP is involved mainly in the differentiation of neural structures.