Localization of serotonin in cleavage embryos of Ophryotrocha labronica La Greca and Bacci

Abstract

Serotonin distribution in early Ophryotrocha embryos was investigated with fluorescence microscopy based on formaldehyde gas treatment of the embryos, and with light- and electron-microscopic autoradiography after the embryos had been treated withH-5-hydroxytryptophan.Sections of early cleavage embryos showed serotonin-specific fluorescence all over the blastomeres, but it was mainly concentrated on yolk granules, and to a lesser degree on lipid drops and vacuoles. In 2-8 cell embryos, marked regional concentration of serotonin fluorescence was noticeable along the completed cleavage furrows.The autoradiographs confirmed the picture of the yolk granules as the principal site of serotonin formation and serotonin accumulation; considerable amounts were also associated with their decomposition products, i.e. lipid drops, vacuoles, and vesicles, whereas major cell organelles, e.g. mitochondria, were almost totally lacking. Of cytoplasmic structures in the blastomeres without apparent yolk granule origin, only microfilaments, particularly those amassed along the cleavage furrow, showed consistent and significant association with formed serotonin. This suggests a connexion between serotonin and microfilaments and might imply that in early embryo cells the fundamental contractile machinery is controlled by serotonin gradually released from the yolk granules.Within the blastomere nuclei, moderate amounts of serotonin were demonstrated with both fluorescence microscopy and autoradiography.The monoamine oxidase (MAO) inhibitor catron (phenylisopropylhydrazine), used to intensify the autoradiographic picture of serotonin in the Ophryotrocha embryos, markedly increased intragranular serotonin accumulation, but also retarded yolk granule disintegration and delayed the cell cleavage process. In embryos barely able to cleave after treatment with catron, ultrastructural analysis demonstrated that membrane formation at cell cleavage depends on influx of material from the nearby disintegrating yolk granules.

Annelida: Polychaeta

“…This compound caused retardation of development and exogastrulation in Nereis succinea (Henley, 1946) and Ophryotrocha labronica (Emanuelsson, 1971). Emanuelsson ( 1971 ) postulated that yolk granules may be the site of action of lithium chloride in other sensitive systems. There was also an increase in the number of lipid droplets; Henley (1946) also reported a change in the number and distribution of lipid droplets in Nereis.…”

Serotonin as a Differentiation Signal in Early Neurogenesis

“…Although the exact developmental roles played by the monoamines have yet to be specified, evidence has been presented for their involvement in cell division, motility, and morphogenetic cell movements during cleavage and gastrulation [8][9][10][11]14,18,55], closure of the neural tube [28], development of photoreceptors [60], and differentiation of neuroblastoma and glioma cells [17.31.35,37, 43,45-47],…”

Localization of serotonin and its possible role in early embryos of Tritonia diomedea (Mollusca: Nudibranchia)

“…It is well known that such pretreatment specifically increases the level of intracellular 5-HT (Emanuelsson 1974(Emanuelsson , 1992Wallace 1982; Sakharov Table 1 The action of 5-HT and its agonists on the sensitivity of Tritonia embryos to ritanserin (10 µM). This staining indicates the presence of an endogenous 5-HT-like substance (probably 5-HT itself) for four reasons.…”