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Ultrastructural obsevations on synaptic ribbons in the pineal organ of the goldfish.
Synaptic ribbons in the pineal organ of the goldfish were examined electron microscopically with particular attention to their topography. These structures were formed of parallel membranes, which were poorly preserved with OsO4 fixation and could be extracted from thin sections with pronase indicating their proteinaceous nature. Synaptic ribbons were closely apposed to the plasma membrane bordering dendrites of ganglion cells, but were also related to processes of both photoreceptor and supportive cells. Their close proximity to invaginations of the plasma membrane and portions of the endoplasmic reticulum suggest that they are involved in the turnover of cytoplasmic membranes. Tubular and spherical organelles of unknown function are also described.
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Electron microscopic study of the origin and formation of Reissner's fiber in the subcommissural organ of Cebus apella (Primates, Platyrrhini).
Two kinds of secretion are formed in cells of the subcommissural organ (SCO) of Cebus apella. The "light secretion" is found in saccules originating from the endoplasmic reticulum. This secretion is stored in the peripheral portion of the cells and is not involved in formation of Reissner's fiber (RF). In close association with the Golgi complex, electron-dense granules are developed, containing a finely granular substance. These granules accumulate beneath the apical plasmalemma of the cell. Their content is discharged into the third ventricle, where it occurs in the form of a thin layer of secretion. This material appears to constitute the RF at the level of the entrance to the mesencephalic aqueduct.
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The ventricular surface of the subcommissural organ: a scanning and transmission electron microscopic study.
The subcommissural organ of the rat has been studied by a combination of light, scanning and transmission electron microscopy. Special attention has been paid to the appearance of the ventricular surface of the organ. The ependyma-derived cells on the surface of the organ are extremely long with a width which diminishes steadily from the base, where the nucleus is situated, to the ventricular surface. This results in a fan-shaped arrangement of cells, the cytoplasm of each cell reaching the surface of the ventricular system. The apical surface of the cell has small ciliated extensions 1-1.5 micrometers in diameter protruding into the ventricular lumen. With conspicuous rough endoplasmic reticulum and Golgi apparatus, and microtubules in profusion, the subcommissural organ cells possess the hallmarks of active secreting cells. The surface of the cells shows pinocytic vesicles-suggesting exchange of materials with the cerebrospinal fluid.
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Synaptic ribbons during postnatal development of the pineal gland in the golden hamster (Mesocricetus auratus).
Synaptic ribbons, functionally enigmatic structures of mammalian pinealocytes, were studied during the postnatal development of the pineal gland in the golden hamster (Mesocricetus auratus). On day 4 post partum, synaptic ribbons appear in cells that have already started to differentiate into pinealocytes. Between days 4 and 9, an increase in the number of synaptic ribbons occurs, concomitant with the continuing differentiation of the pineal tissue. Between days 9 and 16, when differentiation of this tissue is almost completed, the number of synaptic ribbons decreases and approaches that characteristic of the adult pineal gland. During development, the synaptic ribbons increase in length, and dense core vesicles are frequently found in the vicinity of these structures. It is assumed that a functional relationship exists between dense core vesicles and the synaptic ribbons, which are considered to be engaged in a certain form of secretory activity of the mammalian pineal gland.
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Regenerative Neurology and Regenerative Cardiology: Shared Hurdles and Achievements.
From the first success in cultivation of cells in vitro, it became clear that developing cell and/or tissue specific cultures would open a myriad of new opportunities for medical research. Expertise in various in vitro models has been developing over decades, so nowadays we benefit from highly specific in vitro systems imitating every organ of the human body. Moreover, obtaining sufficient number of standardized cells allows for cell transplantation approach with the goal of improving the regeneration of injured/disease affected tissue. However, different cell types bring different needs and place various types of hurdles on the path of regenerative neurology and regenerative cardiology. In this review, written by European experts gathered in Cost European action dedicated to neurology and cardiology-Bioneca, we present the experience acquired by working on two rather different organs: the brain and the heart. When taken into account that diseases of these two organs, mostly ischemic in their nature (stroke and heart infarction), bring by far the largest burden of the medical systems around Europe, it is not surprising that in vitro models of nervous and heart muscle tissue were in the focus of biomedical research in the last decades. In this review we describe and discuss hurdles which still impair further progress of regenerative neurology and cardiology and we detect those ones which are common to both fields and some, which are field-specific. With the goal to elucidate strategies which might be shared between regenerative neurology and cardiology we discuss methodological solutions which can help each of the fields to accelerate their development.
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Ultrastructural features of pituicytes in the neural lobe of adult rats.
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Schmidt-Lantermann incisures in the central nervous system.
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Ultrastructure of the human atrioventricular node.
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[The early phases of cilia formation and the problem of the origin of the basal body].
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Dark and light somatotroph cells in the adenohypophysis of the mouse.