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Comparative ultrastructural observations on the pineal organ of the pipefish, Syngnatus acus, and the seahorse, Hippocampus hudsonius.
A comparative ultrastructural study was made of the pineal organ of two related species of the Syngnathidae, the pipefish, Syngnathus acus, and the seahorse, Hippocampus hudsonius. Both species have a relatively small pineal organ, which ultrastructurally shows several similarities with the pineal of other teleosts. In the pineal organ of Syngnathus acus, the photoreceptor cells have well-developed outer segments consisting of about 15 to 60 saccules. The pineal supporting cells are characterized by the presence of numerous myeloid bodies. In Hippocampus hudsonius the pineal outer segments are scarce and poorly developed; generally, they show not more than 20 saccules. The apical parts of the supporting cells contain dense-core vesicles with a diameter varying from 100 to 180 nm. Corresponding vesicles were not observed in the pineal organ of Syngnathus acus. Arguments are presented for the suggestion that the pineal organ of the Syngnathidae, in spite of its relatively small size, still has a functional significance. In Syngnathus acus, light reaching the pineal organ directly might have a regulating effect on pineal activity. In Hippocampus hudsonius, however, light acting directly on the pineal organ appears to have minor effect on pineal function.
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Differentiation of human anterior hypophysial cells during fetal life.
This paper deals with cell differentiation in the anterior hypophysis of the human fetus, as may be stated by electronmicroscopy. In the 9 cm fetus the greater number of cells are devoid of granules; this was the reason for their being considered as nondifferentiated cells. A small number of cells however contain granules which vary from cell to cell in number and size and may be considered as cells with different functions. Usually the granules secreted within the same cell have very close diameters. The number of such cells increases with the age of the fetus; thus, in 170 mm fetal length there remain very few nondifferentiated cells. Some cells have their granules located centrally, while in others they are closer to the cell membrane, suggesting that the product of cell secretion is extruded in the nearby lumen of capillaries. The shape of the cells, their location, as well as the features of the cell organelles are similar to those described for adults, but in the fetus they are proportionally fewer. The electronmicroscopic pattern does not seem to be a sufficient criterion for the specification of the type of cells, except ACTH-MSH secreting cells.
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Electron microscopic observation on rat ovaries in different stages of development and steroidogenesis.
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Some light- and electron-microscopical observations on the pars tuberalis of the pituitary gland of the rabbit.
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Intercisternal parallel filaments in the endoplasmic reticulum in cells of the rat subcommissural organ.
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[Peculiar neuronal cells in the ependyma of the central canal of Salamandra maculosa].
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An electron microscopic study of the neuroglia during postnatal development of the rat cerebrum.
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The fine structure of some intraganglionic alterations. Neurofibrillary tangles, granulovacuolar bodies and "rod-like" structures as seen in Guam amyotrophic lateral sclerosis and parkinsonism-dementia complex.
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[On the fine structure of the subformical organ of the cat. 3. Nerve and glial cells].
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Amino acid neurotoxicity: intracellular sites of calcium accumulation associated with the onset of irreversible damage to rat cerebellar neurones in vitro.
Electron microscopy and the combined oxalate-pyroantimonate technique were used to locate calcium in intracerebellar nucleus neurones of rat cerebellar slices subjected to a neurotoxic concentration of N-methyl-D-aspartate. After a sub-lethal exposure period (5 min) calcium pyroantimonate deposits were found in swollen cisterns of the Golgi apparatus and, in lesser amounts, in the nuclei. Deposits were more prominent in the nuclei after a just-lethal exposure (10 min) when they were additionally observed within a population of swollen mitochondria and also apparently free in the dendritic and somatic cytoplasm. The results support the proposal that amino acid neurotoxicity is a consequence of an intracellular Ca2+ overload brought about by excessive Ca2+ influx.