Fine structure of degeneration and regeneration in denervated rabbit vallate taste buds.
01 Nov 1970-Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology (John Wiley & Sons, Ltd)-Vol. 168, Iss: 3, pp 393-413
TL;DR: Taste buds of rabbit circumvallate papillae were studied with the electron microscope at intervals from six hours to 11 weeks after section of the glossopharyngeal nerve distal to the petrosal ganglion was affected, showing degeneration as early as 12 hours and disappearing by 48 hours.
Abstract: Taste buds of rabbit circumvallate papillae were studied with the electron microscope at intervals from six hours to 11 weeks after section of the glossopharyngeal nerve distal to the petrosal ganglion. Nerve endings were first affected, showing degeneration as early as 12 hours and disappearing by 48 hours. Rapid loss of cells and of all buds by ten days followed. Numerous inclusion bodies within type I and type II cells were interpreted as autophagic activity in type II cells and both phagocytic and autophagic activity in type I cells. Type III cells were lost primarily by pyknosis, and phagocytized by type I cells. No clear evidence of dedifferentiation, or extrusion of dead cells, was observed.
Regenerated nerves appeared beneath the epithelium at 21 days but new buds first appeared at 25 days, after nerves had penetrated the basement membrane. Intimate contact of nerves with epithelial cells appears to be a precondition for taste bud renewal. Early appearance of cells resembling basal cells (type IV) followed by relatively simultaneous appearance of type I, II and III suggest independent origins for these three types. The data support a humoral hypothesis of trophic action but do not rule out a role for impulse transmission.
Citations
More filters
TL;DR: In rats, some Type III cells accumulate serotonin but do notexpress PGP 9.5, whereas others express PGP 7.5 but doNot accumulate amines, and the serotonin‐immunoreactive taste cells exhibit two morphological varieties.
Abstract: Taste buds contain a variety of morphological and histochemical types of elongate cells. Serotonin, neuron-specific enolase (NSE), ubiquitin carboxyl terminal hydrolase (PGP 9.5), and neural cell adhesion molecule (N-CAM) all have been described as being present in the morphologically defined Type III taste cells in rats. In order to determine whether these substances coexist in a single cell, we undertook immunohistochemical and ultrastructural analysis of taste buds in rats. Double-label studies show that PGP 9.5 and NSE always colocalize. In contrast, PGP 9.5 and serotonin seldom colocalize. Further, whereas the serotonin-immunoreactive cells are always slender and elongate, the PGP 9.5/NSE population comprise two morphological types--one slender, the other broader and pyriform. Although gustducin-immunoreactive taste cells appear similar in overall shape to the pyriform PGP 9.5/NSE population, gustducin never colocalizes with PGP 9.5 or NSE. The serotonin-immunoreactive taste cells have an invaginated nucleus, synaptic contacts with nerve fibers, and taper apically to a single, large microvillus. These are all characteristics of Type III taste cells described previously in rabbits (Murray [1973] Ultrastructure of Sensory Organs I. Amsterdam: North Holland. p 1-81). PGP 9.5-immunoreactive taste cells exhibit two morphological varieties. One type is similar to the serotonin-immunoreactive population, containing an invaginated nucleus, synapses with nerve fibers, and a single large microvillus. The other type of PGP 9.5-immunoreactive taste cell has a large round nucleus and the apical end of the cell tapers to a tuft of short microvilli, which are characteristics of Type II taste cells. Thus, in rats, some Type III cells accumulate serotonin but do not express PGP 9.5, whereas others express PGP 9.5 but do not accumulate amines. Similarly, Type II taste cells come in at least two varieties: those immunoreactive for gustducin and those immunoreactive for PGP 9.5.
252 citations
Additional excerpts
...…January 2000; Revised 13 April 2001; Accepted 14 August 2001 © 2001 WILEY-LISS, INC. differences represent separate cell lineages within a bud (De Lorenzo, 1963; Beidler and Smallman, 1965; Farbman, 1965a,b, 1971, 1980; Graziadei, 1969; Fujimoto and Murray, 1970; Murray, 1973; Delay et al., 1986)....
[...]
TL;DR: The model of chemosensory processing in the taste bud presented here can now be explored in great detail and indicates a potential for intriguing peripheral integrative mechanisms, including cross-talk between taste cells, summation of chemoreceptor responses by interneurons, and centrifugal control of taste buds via efferent input from the CNS.
Abstract: New technologies in neurophysiology and ultrastructural research are bringing about rapid advances in our understanding of taste, particularly at the cellular level. The model of chemosensory processing in the taste bud presented here can now be explored in great detail. The synaptic organization of the taste bud indicates a potential for intriguing peripheral integrative mechanisms, including cross-talk between taste cells, summation of chemoreceptor responses by interneurons (basal cells) in the taste bud, and centrifugal control of taste buds via efferent input from the CNS. Figure 2 summarizes these findings. The existence of voltage-gated ionic channels on taste cells and their unequal distribution in apical and basolateral membrane suggests mechanisms for chemosensory transduction: A primary event in the transduction process for many taste stimuli is likely to be the closure of apical potassium channels, thus leading to a depolarizing receptor potential. The closure of these apical potassium channels is probably mediated via cyclic nucleotides or intracellular Ca2+.
201 citations
TL;DR: The ultrastructural features of murine vallate taste bud cells and their associated synapses have been examined in thin and thick sections with conventional transmission electron microscope and high‐voltage electron microscopy.
Abstract: The ultrastructural features of murine vallate taste bud cells and their associated synapses have been examined in thin and thick sections with conventional transmission electron microscopy and high-voltage electron microscopy. Computer-assisted reconstructions from serial sections were utilized to aid in visualization of taste bud cell-nerve fiber synapses. We have classified taste bud cells on the basis of previously established criteria-namely, size of the nucleus, shape and density of chromatin, density of cytoplasm, and presence or absence of dense-cored or clear vesicles, other cytoplasmic organelles, and synaptic foci. Both dark cells and light cells are present, as well as cells with intermediate morphological characteristics. Synapses were observed from taste bud cells onto nerve fiber processes. In virtually all instances, synapses are associated with the nuclear region of the taste cell. These synapses are characterized by the presence of 40-70 nm clear vesicles embedded in a thickened presynaptic membrane separated from the postsynaptic membrane by a 16-30 nm cleft. Synapses are not unique to any particular cell type. Dark, intermediate, and light cells all synapse onto nerve fibers. Two general types of synapses exist: spot (or macular) and fingerlike. In the latter, the postsynaptic region of the neuronal process protrudes into an invagination of the taste cell membrane. Differences in synaptic morphology are not correlated with taste cell type. In some cases a single taste cell was observed to possess both macular and fingerlike synapses adjacent to one another, forming a synaptic complex onto a single neuronal process. On the basis of the presence of synaptic contacts, we conclude that both "dark" and "light" cells are gustatory receptors.
177 citations
TL;DR: The presence and the function of muscie innervation have a variety of in de pen dentiy exerted long term effects on the motoneurone itself, and on the physiological and anatomical state of the muscle.
Abstract: In addition to their responsibility for the minute to minute control of behavior and homeostasis, nerve cells are important in maintaining the long term stability of structure and function of the nervous system and the cells it innervates. The trophic action of motor nerve cells on skeletal muscles is a well known example of such an activity. Miledi (270) defined trophic actions as due to "an influence of the nerve not mediated by impulses," but it has recently been suggested that only some of the classical trophic effects on skeletal muscle are exerted independently of nerve im pulses and/or muscle contraction. For example, direct electrical stimulation of a denervated muscle may reverse the development of denervation hypersensitivity (83, 241). The presence and the function of muscie innervation have a variety of in de pen dentiy exerted long term effects on the motoneurone itself, and on the physiological and anatomical state of the muscle. For example, botulinus toxin affects most of the trophic actions of the nerve except the maintenance of end plate cholinesterase (82), preganglionic cholinergic nerves form functional synapses on frog skeletal muscle but do not induce endpiate cholinesterase (223), and adrenergic nerves can prevent denervation fibrillation without forming functional synapses (265). Similarly com plex sets of interactions have been described elsewhere in the peripheral and auto nomic nervous systems, and within the brain as well.
165 citations
TL;DR: The lifespan of cells in the mouse taste bud was examined with high‐voltage electron microscopic (HVEM) autoradiography (ARG) after giving a single injection of 3H‐thymidine to identify and characterize labeled cells.
Abstract: The lifespan of cells in the mouse taste bud was examined with high-voltage electron microscopic (HVEM) autoradiography (ARG) after giving a single injection of 3H-thymidine. Animals were killed at 1 hour, 6 hours, 12 hours, 24 hours, and then daily up through 10 days postinjection. Lingual tissues were prepared for HVEM ARG so that we could identify and characterize labeled cells. Four categories of taste cells were identified: basal, dark, intermediate, and light cells. Basal cells were polygonal cells located near the basolateral sides of the taste buds and were characterized primarily by the presence of filaments attached to the nuclear envelope. Dark and light cells had the typical features described by previous authors. Intermediate cells had features in between those of dark and light cells. Over 90% of the cells labeled in the first 2 days following injection of 3H-thymidine were basal cells. Labeled dark cells appeared 6 hours after injection, reached their peak incidence at the fourth day postinjection, and then gradually decreased. Labeled intermediate cells were identified after the appearance of dark cells (12 hours) and reached a peak incidence at the fifth day after injection of 3H-thymidine. Lastly, labeled light cells were first observed on the fourth day postinjection and continued to increase until the tenth day, when they constituted 45% of the labeled cells. These data support the hypothesis that there is one cell line in the mouse vallate taste bud that undergoes morphological changes in its lifespan.
162 citations
References
More filters
TL;DR: In this article, the authors refer to polymorphic dense bodies which appear normally in peribiliary (or pericanalicular) positions in liver cells as lysosomes and show that the enzyme product of acid phosphatase is found exclusively in these bodies.
Abstract: De Duve and his colleagues, a few years ago, originated the concept of lysosomes based on the biochemical analysis of isolated cytoplasmic particles (1). He reported that a number of hydrolytic enzymes are concentrated in a fraction consisting of small subcellular units which sediments between the usual mitochondrial and microsomal fractions. Subsequent to this discovery, some of these properties have been demonstrated in hepatic pericanalicular dense bodies, and Essner and Novikoff (2), using the electron microscope, have shown that the enzyme product of acid phosphatase is found exclusively in these bodies. They have also found that a variety of pigment granules in human liver cells possess both the fine structure characteristic of dense bodies and the acid phosphatase activity of lysosomes (3). In this report we shall refer to polymorphic dense bodies which appear normally in peribiliary (or pericanalicular) positions in liver cells as lysosomes. This is in keeping with what is now the usual practice among cytologists. Admit tedly the identification would be more definite if parallel cytochemical studies had been done to determine the presence or absence of acid phosphatase and other acid hydrolases. The microbody, as distinct from the lysosome, is a cytoplasmic particle 0.4 to 0.6 micron in
722 citations
TL;DR: These studies suggest that the cells within the taste bud, as well as the nerves, undergo considerable change with time, and Corresponding changes in function are considered.
Abstract: Colchicine blocks mitotic division of the epithelial cells surrounding the taste bud of the rat tongue. Response to chemical stimulation decreases 50 per cent 3 hours after colchicine injection as measured by recording the electrical activity from the taste nerve bundle. Radioautography, using tritiated thymidine, shows that those epithelial cells surrounding the taste bud divide and that some of the daughter cells enter the taste bud and slowly move toward the center. The life span of the average cell is about 250 ± 50 hours, although some cells have a much shorter and others a much longer life span. These studies suggest that the cells within the taste bud, as well as the nerves, undergo considerable change with time. Corresponding changes in function are considered.
566 citations
TL;DR: The patches of neuronal plasmalemma associated with subsurface cisterns may, therefore, have special properties because of this association, resulting in a non-uniform neuronal surface.
Abstract: Subsurface cisterns (SSC's) are large, flattened, membrane-limited vesicles which are very closely apposed to the inner aspect of the plasma membranes of nerve cell bodies and the proximal parts of their processes. They occur in a variety of vertebrate and invertebrate neurons of both the peripheral and central nervous systems, but not in the surrounding supporting cells. SSC's are sheet-like in configuration, having a luminal depth which may be less than 100 A and a breadth which may be as much as several microns. They are separated from the plasmalemma by a light zone of ∼50 to 80 A which sometimes contains a faint intermediate line. Flattened, agranular cisterns resembling SSC's, but structurally distinct from both typical granular endoplasmic reticulum (ER) and from Golgi membranes, also occur deep in the cytoplasm of neurons. It is suggested that membranes which are closely apposed may interact, resulting in alterations in their respective properties. The patches of neuronal plasmalemma associated with subsurface cisterns may, therefore, have special properties because of this association, resulting in a non-uniform neuronal surface. The possible significance of SSC's in relation to neuronal electrophysiology and metabolism is discussed.
410 citations
TL;DR: The nerve endings about the external hair cells of the organ of Corti in the guinea pig have been studied by means of serial sections, and plastic reconstructions, and three kinds of nerve endings were found most often.
243 citations
TL;DR: DNA-protein coacervates containing colloidal gold particles were readily phagocytized by strain L fibroblasts and served as markers which permitted the demonstration of the evolution of digestive vacuoles to multivesicular bodies and finally to dense bodies.
Abstract: DNA-protein coacervates containing colloidal gold particles were readily phagocytized by strain L fibroblasts. During the subsequent digestion process, the gold particles served as markers which permitted the demonstration of the evolution of digestive vacuoles to multivesicular bodies and finally to dense bodies. Acid phosphatase and esterolytic activity was present in these structures. The hydrolytic enzymes were apparently brought to the phagocytotic vacuoles in small vesicles originating in the Golgi region. These vesicles entered the vacuoles prior to the digestion of the coacervates and the appearance of positive cytochemical reactions. The cytoplasmic dense bodies frequently merged with the phagocytotic vacuoles. This was demonstrated by prelabeling the dense bodies with colloidal iron prior to phagocytosis of the coacervates. In addition, evidence is presented for the interrelationship of the phagocytotic and autophagic pathways.
227 citations