摘要:

AbstractUnilateral interruption of the chorda‐lingual nerve led to a loss of most epithelial axons and to the deterioration of fungiform taste buds in the anterior portion of the tongue of albino rats, mongolian gerbils, and golden hamsters. By three weeks after surgery the following percentages of fungiform taste buds had completely disappeared: 71% in gerbils, 28% in rats, and 26% in hamsters. Residual taste buds were classified into two groups: atrophic taste buds and taste bud remnants. Atrophic taste buds were smaller than normal and typically had no visible taste pore, although they retained the characteristic oval shape of a taste bud and numerous elongated cells. Taste bud remnants were non‐oval fragments of taste buds with few elongated cells. Specific markers for elongated taste cells (monoclonal antibodies to keratin 19) confirmed that atrophic taste buds, as well as some taste bud remnants, had elongated taste cells. By 180 days after chorda‐lingual nerve transection, 44% of rat fungiform taste buds had disappeared; morphometric analysis of the 311 residual taste buds established that 241 atrophic taste buds and 69 taste bud remnants were, respectively, 50% and 75% smaller than the average volume of 480 normal taste buds. The aggregate loss of gustatory tissue, calculated from the shrinkage of residual taste buds and the volume lost by the outright disappearance of many taste buds, was 88% for gerbils, 72% for rats, and 65% for hamsters. Evaluation in gerbils of the co‐occurrence of taste buds and axons suggests residual taste buds were neurotrophically supported. Every gerbil fungiform papilla that lacked axons lacked a taste bud. Every fungiform papillae that had a residual taste bud had axons; axons were absent from 22% of empty fungiform papillae. Diminished numbers of gustatory neurotrophic axons could account for both the loss of fungiform taste buds and the reduced volume of residual taste buds. © 1993 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070260302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe lingual epithelium is innervated by special sensory (taste) and general sensory (trigeminal) nerves that transmit information about chemical stimuli introduced into the mouth to the higher brain centers. Understanding the cellular mechanisms involved in eliciting responses from these nerves requires a detailed understanding of the contributions of both the paracellular and transcellular pathways. In this paper we focus on the contribution of these 2 pathways to the responses of salts containing sodium and various organic anions in the presence and absence of amiloride. Electrophysiological recordings from trigeminal nerves, chorda tympani nerves, and isolated lingual epithelia were combined with morphological studies investigating the location (and permeability) of tight junctions, the localization of amiloride‐inhibitable channels, and Na‐K‐ATPase in taste and epithelial cells. Based on these measurements, we conclude that diffusion across tight junctions can modulate chorda tympani and trigeminal responses to sodiumcontaining salts and rationalize the enhancement of taste responses to saccharides by NaCl. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070260303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe fine structure of the taste buds of circumvallate papillae of two strains of mice was studied by electron microscopy. Mice anesthetized with ketamine were perfused through the heart with a double aldehyde mixture in cacodylate buffer and the tissues embedded in Epon. Semi‐serial sections were employed. The morphology and relationships of cell types are consistent with the majority of descriptions of mammalian taste buds served by the ninth cranial nerve. Cells of type II are particularly well documented, as the stages in their origin, maturation and degeneration could be followed. Significant differences, however, relate to cell type I. These cells contain large dense‐cored granules, contrasted with the more irregular and somewhat larger dark granules of the type I cells in the rabbit. These granules do not produce a dense homogenous product for the pore, as seen in the rabbit. Rather the pore substance consists of small, empty vesicles in a diffuse dark matrix. These granules are only moderately larger than the dense‐cored vesicles of the type III cells. All features of the type III cell were demonstrated, although no instance of a complete cell was seen in any section. No significant differences were noted between the two strains of mice. Intimate proximity of a nerve to a cell nucleolus, suggestive of a trophic pathway, is illustrated. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070260304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe presence of glutamate immunoreactivity (glu‐IR) in the nerve fibers of the mudpuppy taste bud was investigated by electron microscopy. Pre‐embedding staining with avidinbiotin‐peroxidase complex (ABC) and post‐embedding staining with 5 mm colloid gold conjugates were used separately to identify immuno‐stained structures. We have found the following: 1) the majority of the nerve fibers innervating the mudpuppy taste bud are unmyelinated; 2) about 85% of nerve fibers located at the base of the taste bud and about 60% of the nerve fibers located between the taste cells show glu‐IR by pre‐embedding staining; 3) there is a preferential staining of the glu‐IR in the nerve fibers of the mudpuppy taste bud; and 4) the distribution of the colloidal gold particles in the nerve fibers is 1.5 to 2 times denser than that of the staining in the connective tissue background or cellular profiles of taste cells. From the distribution and pattern of the nerve fibers obtained in the thick and thin sections, we conclude that the mudpuppy taste bud is innervated by glutamate‐containing unmyelinated nerve fibers. © 19

ISSN:1059-910X    

DOI:10.1002/jemt.1070260305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe distribution of acetylcholinesterase (AChE), NADH dehydrogenase (NADHd), and cytochrome oxidase (CO) was determined in the nucleus of the solitary tract (NST) in the golden hamster. Histochemical staining was compared to cytoarchitectonic subdivisions of the NST (Whitehead: J. Comp Neurol. 276:547–572, 1988) and to terminal fields of primary afferents of the nerves that innervate the tongue. These three histochemical methods resulted in differential staining patterns within the NST that were related to certain subdivisions. Transganglionic transport of horseradish peroxidase (HRP) was used to determine the central projections of the chorda tympani (CT), the lingual branch of the trigeminal (L‐V), and the lingual‐tonsilar branch of the glossopharyngeal nerves (L‐IX). Alternate or the same brain sections were processed to reveal transported HRP, and NADHd or AChE levels. Increased staining of the neuropil with NADHd and AChE was coincident with the dense part of the afferent terminal fields of all three nerves in the NST and the laterally adjacent dorsomedial part of the spinal trigeminal nucleus. CO showed this pattern only for the most rostral part of the CT field. The densest AChE staining coincided with gustatory afferent terminal fields. The histochemical staining facilitated the interpretation of the organization of the NST. For example, at caudal levels of the gustatory NST, it is suggested that taste processing is localized predominately in the medial part of the rostral central, and somatosensory processing in the rostral lateral subdivision. AChE or NADHd staining should facilitate studies of connections, topography, and neuroplastic changes of the gustatory NST. © 1993 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070260306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractHRP histochemistry and microelectrode mapping were combined to study the sizes, shapes, and orientations of neuronal cell bodies and dendrites located at sites of taste‐elicited single unit activity in the nucleus of the solitary tract (NST). Cells responding to sapid stimulation of the anterior tongue were extracellularly recorded using micropipettes containing HRP. Iontophoretic injection of the marker at the recording sites resulted in small (50–200 μm diameter) opaque zones bordered by a small number (2–15) of neurons with Golgi‐like filling of their cell bodies, dendrites, and to some extent, their axons. The cell bodies were near (50–250 μm) the injection sites into which they sent labelled dendrites. Two broad categories of neurons were typically filled.Elongate cellshad oval‐ to spindle‐shaped cell bodies oriented mediolaterally. Two primary dendrites extended 100–300 μm from the cell body, one medially and one laterally, and branched within a cylindrical dendritic field oriented mediolaterally. A minority of the HRP‐filled elongate cells had unusually long rostrally or caudally directed dendritic branches.Stellate cellshad oval, round, triangular, or polygonal cell bodies and 3–5 primary dendrites coursing 200–300 μm in all directions and branching as unoriented, spheroidal fields. A minority of stellate cells had relatively unbranched wavy dendrites, resembling tentacles, while others had unusually small cell bodies (10–15 μm diameter), small dendrites, and locally arborizing axons. Of 151 labelled cells, all but 12 were remarkably confined to the rostral NST. Nearly 90% were concentrated in therostral centralcytoarchitectonic subdivision, where stellate cells predominated, or in therostral lateralsubdivision, where elongate cells predominated. These morphological types of neurons, filled at neurophysiological recording sites, are compared with cell types identified in previous light and electron microscopic studies of the cytoarchitecture, connections, and synaptic organization of the gustatory

ISSN:1059-910X    

DOI:10.1002/jemt.1070260307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractKidneys of anesthetized rats were perfused with digitonin to extract cytosolic proteins of glomerular podocytes so that the remaining intracellular structures could be examined by three‐dimensional stereo high‐resolution scanning electron microscopy (HRSEM). Cytoskeleton, consisting of microtubules and intermediate filaments, was preserved with each applied concentration of digitonin. High concentrations of digitonin (1.0 mg/ml) produced a corrugated appearance in plasma membranes likely due to the formation of digitonin‐cholesterol complexes. At 1.0 mg/ml digitonin, the Golgi complex became vesicularized, and mitochondria were well extracted and their ultrastructure preserved. Lower concentrations of digitonin (0.1 and 0.2 mg/ml) were less disruptive to both the plasma membrane and the Golgi complex. Mitochondria, rough endoplasmic reticulum, coated vesicles, nuclear membrane, and chromatin were well preserved. Extraction with digitonin, at the optimal concentration and perfusion time, simultaneously maintains both the cytoskeleton and membranous organelles inside the cell and provides a method to elucidate the interactions between these two components. Furthermore, digitonin extraction should preserve antigenic sites, thereby allowing the localization of intracellular proteins by backscattered electron imaging of immunogold labels in the scanning electron microscope. © 1993 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070260308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:1059-910X    

DOI:10.1002/jemt.1070260301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY