Glycoprotein synthesis in the subcommissural organ of the chick embryo. I. An ontogenetical study using specific antibodies.
TL;DR: In this article, the specificity of the antibodies was controled by immunostaining and by a competition test between lectins (Concanavalin A-Con A- and wheat germ agglutinin-WGA-) and antibodies (A74 IgG).
Abstract: Antibodies were raised in rabbit against crude subcommissural organ (SCO) extract of 19 day old chick embryos. After absorption with crude brain extract, the IgG fraction was purified by ion exchange chromatography. The specificity of the antibodies was controled by immunostaining and by a competition test between lectins (Concanavalin A-Con A- and wheat germ agglutinin-WGA-) and antibodies (A74 IgG).
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TL;DR: The subcommissural organ (SCO) is a phylogenetically ancient and conserved structure that is one of the first brain structures to differentiate and may participate in different processes such as the clearance of certain compounds from theCSF, the circulation of CSF, and morphogenetic mechanisms.
Abstract: The subcommissural organ (SCO) is a phylogenetically ancient and conserved structure. During ontogeny, it is one of the first brain structures to differentiate. In many species, including the human, it reaches its full development during embryonic life. The SCO is a glandular structure formed by ependymal and hypendymal cells highly specialized in the secretion of proteins. It is located at the entrance of the aqueduct of Sylvius. The ependymal cells secrete into the ventricle core-glycosylated proteins of high molecular mass. The bulk of this secretion is formed by glycoproteins that would derive from two different precursors of 540 and 320 kDa and that, upon release into the ventricle aggregate, form a threadlike structure known as Reissner's fiber (RF). By addition of newly released glycoproteins to its proximal end, RF grows caudally and extends along the aqueduct, fourth ventricle, and the whole length of the central canal of the spinal cord. RF material continuously arrives at the dilated caudal end of the central canal, known as the terminal ventricle or ampulla. When reaching the ampulla, the RF material undergoes chemical modifications, disaggregates, and then escapes through openings in the dorsal wall of the ampulla to finally reach local blood vessels. The SCO also appears to secrete a cerebrospinal fluid (CSF)-soluble material that is different from the RF material that circulates in the ventricular and subarachnoidal CSF. Cell processes of the ependymal and hypendymal cells, containing a secretory material, terminate at the subarachnoidal space and on the very special blood capillaries supplying the SCO. The SCO is sequestered within a double-barrier system, a blood-brain barrier, and a CSF-SCO barrier. The function of the SCO is unknown. Some evidence suggests that the SCO may participate in different processes such as the clearance of certain compounds from the CSF, the circulation of CSF, and morphogenetic mechanisms.
185 citations
TL;DR: The SCO is sequestered within a double-barrier system of unknown functional significance, thereby indicating the unique character of this circumventricular organ.
Abstract: Publisher Summary This chapter highlights the cell biology of the subcommissural organ (SCO) and discusses its structure–function relationships to provide a basis for further experimental work. SCO is a complex of nonneuronal secretory cells covering and penetrating the posterior commissure. This complex protrudes toward the third ventricle, occupies the posterior portion of the diencephalic roof caudal to the pineal organ, and marks the entrance to the Sylvian aqueduct. SCO is formed by two populations of secretory cells, which, in many species, are arranged into two distinct layers: the ependyma and the hypendyma. The bulk of the secretory products of the SCO, apparently a complex containing different glycoproteins, are released into the ventricular cerebrospinal fluid (CSF). In the ventricle, the secretion is condensed into a thread-like structure, Reissner's fiber (RF) that terminates in the ampulla caudalis of the central canal. The blood vessels of the SCO represent a highly specialized vascular structure within the CNS. The SCO is sequestered within a double-barrier system of unknown functional significance, thereby indicating the unique character of this circumventricular organ.
121 citations
TL;DR: The immunocytochemical study of the bovine SCO using an anti-RF serum showed that the secretory material present in the rough endoplasmic reticulum (RER), secretory granules and in RF is strongly immunoreactive.
86 citations
TL;DR: This work has identified a novel gene, otoc1, which encodes the zebrafish ortholog of Oc90, and suggests that Otoc1 may serve to nucleate calcium carbonate mineralization of aragonitic otoliths.
Abstract: Within the vestibular system of virtually all vertebrate species, gravity and linear acceleration are detected via coupling of calcified masses to the cilia of mechanosensory hair cells. The mammalian ear contains thousands of minute biomineralized particles called otoconia, whereas the inner ear of teleost fish contains three large ear stones called otoliths that serve a similar function. Otoconia and otoliths are composed of calcium carbonate crystals condensed on a core protein lattice. Otoconin-90 (Oc90) is the major matrix protein of mammalian and avian otoconia, while otolith matrix protein (OMP) is the most abundant matrix protein found in the otoliths of teleost fish. We have identified a novel gene, otoc1, which encodes the zebrafish ortholog of Oc90. Expression of otoc1 was detected in the ear between 15 hpf and 72 hpf, and was restricted primarily to the macula and the developing epithelial pillars of the semicircular canals. Expression of otoc1 was also detected in epiphysis, optic stalk, midbrain, diencephalon, flexural organ, and spinal cord. During embryogenesis, expression of otoc1 mRNA preceded the appearance of omp-1 transcripts. Knockdown of otoc1 mRNA translation with antisense morpholinos produced a variety of aberrant otolith phenotypes. Our results suggest that Otoc1 may serve to nucleate calcium carbonate mineralization of aragonitic otoliths.
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TL;DR: The preparation of a series of normal stages of the chick embryo does not need justification at a time when chick ernbryos are not only widely used in descriptive and experimental embryology but are proving to be increasingly valuable in medical research, as in work on viruses and cancer.
Abstract: FORTY-FIVE FIGURES The preparation of a series of normal stages of the chick embryo does not need justification at a time when chick ernbryos are not only widely used in descriptive and experimental embryology but are proving to be increasingly valuable in medical research, as in work on viruses and cancer. The present series was planned in connection with the preparation of a new edition of Lillie’s DeueZopmerzt of the Chick by the junior author. It is being published separately to make it accessible immediately to a large group of workers. Ever since Aristotle “discovered” the chick embryo as the ideal, object for embryological studies, the embryos have been described in terms of the length of time of incubation, and this arbitrary method is still in general use, except for the first three days of incubation during which more detailed characteristics such as the numbers of somites are applied. The shortcomings of a classification based on chronological age are obvious to every worker in this field, for enormous variations may occur in embryos even though all eggs in a setting are plmaced in the incubator at the same time. Many factors are responsible for the lack of correlation between chronological and structural age. Among these are : genetic differences in the rate of development of different breccls (eg., the embryo of the White Leghorn breed develops more 49
12,079 citations
TL;DR: In this article, a series of normal stages of the chick embryo is described in terms of the length of time of incubation, except for the first three days during which more detailed characteristics such as the number of somites are applied.
Abstract: FORTY-FIVE FIGURES The preparation of a series of normal stages of the chick embryo does not need justification at a time when chick ernbryos are not only widely used in descriptive and experimental embryology but are proving to be increasingly valuable in medical research, as in work on viruses and cancer. The present series was planned in connection with the preparation of a new edition of Lillie’s DeueZopmerzt of the Chick by the junior author. It is being published separately to make it accessible immediately to a large group of workers. Ever since Aristotle “discovered” the chick embryo as the ideal, object for embryological studies, the embryos have been described in terms of the length of time of incubation, and this arbitrary method is still in general use, except for the first three days of incubation during which more detailed characteristics such as the numbers of somites are applied. The shortcomings of a classification based on chronological age are obvious to every worker in this field, for enormous variations may occur in embryos even though all eggs in a setting are plmaced in the incubator at the same time. Many factors are responsible for the lack of correlation between chronological and structural age. Among these are : genetic differences in the rate of development of different breccls (eg., the embryo of the White Leghorn breed develops more 49
7,180 citations
TL;DR: The subcommissural organ (SCO) is a phylogenetically ancient and conserved structure that is one of the first brain structures to differentiate and may participate in different processes such as the clearance of certain compounds from theCSF, the circulation of CSF, and morphogenetic mechanisms.
Abstract: The subcommissural organ (SCO) is a phylogenetically ancient and conserved structure. During ontogeny, it is one of the first brain structures to differentiate. In many species, including the human, it reaches its full development during embryonic life. The SCO is a glandular structure formed by ependymal and hypendymal cells highly specialized in the secretion of proteins. It is located at the entrance of the aqueduct of Sylvius. The ependymal cells secrete into the ventricle core-glycosylated proteins of high molecular mass. The bulk of this secretion is formed by glycoproteins that would derive from two different precursors of 540 and 320 kDa and that, upon release into the ventricle aggregate, form a threadlike structure known as Reissner's fiber (RF). By addition of newly released glycoproteins to its proximal end, RF grows caudally and extends along the aqueduct, fourth ventricle, and the whole length of the central canal of the spinal cord. RF material continuously arrives at the dilated caudal end of the central canal, known as the terminal ventricle or ampulla. When reaching the ampulla, the RF material undergoes chemical modifications, disaggregates, and then escapes through openings in the dorsal wall of the ampulla to finally reach local blood vessels. The SCO also appears to secrete a cerebrospinal fluid (CSF)-soluble material that is different from the RF material that circulates in the ventricular and subarachnoidal CSF. Cell processes of the ependymal and hypendymal cells, containing a secretory material, terminate at the subarachnoidal space and on the very special blood capillaries supplying the SCO. The SCO is sequestered within a double-barrier system, a blood-brain barrier, and a CSF-SCO barrier. The function of the SCO is unknown. Some evidence suggests that the SCO may participate in different processes such as the clearance of certain compounds from the CSF, the circulation of CSF, and morphogenetic mechanisms.
185 citations
124 citations