Nucleus of the solitary tract in the C57BL/6J mouse: Subnuclear parcellation, chorda tympani nerve projections, and brainstem connections.

The nucleus of the solitary tract (NST) processes gustatory and related somatosensory information rostrally and general viscerosensory information caudally. To compare its connections with those of other rodents, this study in the C57BL/6J mouse provides a subnuclear cytoarchitectonic parcellation (Nissl stain) of the NST into rostral, intermediate, and caudal divisions. Subnuclei are further characterized by NADPH staining and P2X2 immunoreactivity (IR).

The effect of beta-bungarotoxin, or geniculate ganglion lesion on taste bud development in the chick embryo.

Chick taste bud (gemmal) primordia normally appear on embryonic day (E) 16 and incipient immature, spherical-shaped buds at E17. In ovo injection of beta-bungarotoxin at E12 resulted in a complete absence of taste buds in lower beak and palatal epithelium at developmental ages E17 and E21. However, putative gemmal primordia (solitary clear cells; small, cell groupings) remained, lying adjacent to salivary gland duct openings as seen in normal chick gemmal development.

Brain-derived neurotrophic factor-, neurotrophin-3-, and tyrosine kinase receptor-like immunoreactivity in lingual taste bud fields of mature hamster after sensory denervation.

Unlike lingual taste buds in most mammals, fungiform buds on the anterior tongue of mature hamster survive sensory denervation. The role of the neurotrophin ligands, brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), and their respective tyrosine kinase (Trk) receptors, TrkB and TrkC, in denervated taste buds is not known. The present report investigates changes in the degree of gemmal cell immunoreactivity (IR) (i.

Brain-derived neurotrophic factor-, neurotrophin-3-, and tyrosine kinase receptor-like immunoreactivity in lingual taste bud fields of mature hamster.

The neurotrophins brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), as well as their respective tyrosine kinase (Trk) receptors, TrkB and TrkC, influence peripheral target cell innervation, survival, and proliferation. In the mature taste system the role of neurotrophins and their receptors is not known. The mature hamster is an intriguing model because anterior lingual fungiform, unlike posterior lingual foliate and circumvallate, taste buds survive denervation.

Fingerprinting taste buds: intermediate filaments and their implication for taste bud formation.

Intermediate filaments in taste organs of terrestrial (human and chick) as well as aquatic (Xenopus laevis) species were detected using immunohistochemistry and electron microscopy. During development, the potential importance of the interface between the taste bud primordium and non-gustatory adjacent tissues is evidenced by the distinct immunoreactivity of a subpopulation of taste bud cells for cytokeratins and vimentin. In human foetuses, the selective molecular marker for taste bud primordia, cytokeratin 20, is not detectable prior to the ingrowth of nerve fibres into the epithelium, which supports the hypothesis that nerve fibres are necessary for initiating taste bud development.

Taste cell function. Structural and biochemical implications.

Maintenance of constant relations between receptor cell types and branching from a single gustatory nerve fiber during normal cell turnover and regeneration requires cell-cell recognition likely mediated by timed expression of molecules at surfaces of taste bud cells, nerve endings, and in extracellular matrix. These processes assure stability of gustatory quality representation during intragemmal remodeling. Coincidentally, features of gemmal cell lifespan, including elongation, differentiation, and migration prior to apoptosis, must also be orchestrated by molecular signals.

Organization of geniculate and trigeminal ganglion cells innervating single fungiform taste papillae: a study with tetramethylrhodamine dextran amine labeling.

Single gustatory nerve fibers branch and innervate several taste buds. In turn, individual taste buds may receive innervation from numerous gustatory nerve fibers. To evaluate the pattern of sensory innervation of fungiform papilla-bearing taste buds, we used iontophoretic fluorescent injection to retrogradely label the fibers that innervate single taste papillae in the hamster.

Distribution of vimentin in the developing chick taste bud during the perihatching period.

The tissue environment within which taste bud cells develop has not been wholly elaborated. Previous studies of taste bud development in vertebrates, including the avian chick, have suggested that taste bud cells could arise from one, or several tissue sources (e.g.

Identified taste bud cell proliferation in the perihatching chick.

Developing taste buds in the anterior mandibular floor of perihatching chicks were studied by high voltage electron microscopic autoradiography in order to identify proliferating gemmal cell types. Montaged profiles of 29 taste buds in five cases euthanized between embryonic day 21 and posthatching day 2 were analyzed after a single [3H]thymidine injection administered on embryonic day 16, 17 or 18. Results showed that dark cells comprised 55% of identified (n = 900 cells) and 62% of labeled (n = 568 cells) gemmal cells as compared with light, intermediate, basal or perigemmal bud cells.

Neural cell adhesion molecule, neuron-specific enolase and calcitonin gene-related peptide immunoreactivity in hamster taste buds after chorda tympani/lingual nerve denervation.

Hamster fungiform papilla taste buds persist in an atrophic form following sensory denervation. While atrophic and innervated taste buds are morphologically similar, it is not known whether their gemmal cells have similar molecular characteristics. Three neurochemicals, neural cell adhesion molecule, neuron-specific enolase, and calcitonin gene-related peptide have been implicated in trophic phenomena, synaptogenesis and cell recognition in neurons and sensory neuroepithelia.

Taste bud cell generation in the perihatching chick.

Chick taste bud primordia initially appear in late gestation on embryonic day 17 (E17), 4 days before hatching. To track DNA synthesis and subsequent taste bud cell proliferation between E17 and the second day post-hatching (H2), single 25 muCi injections of tritiated thymidine (specific activity = 72.5 Ci/mmol) were administered in ovo during E15, E16, E17 or E18.

Ontogenesis and taste bud cell turnover in the chicken. I. Gemmal cell renewal in the hatchling.

Taste bud cell turnover rate was examined in oral epithelium of the precocial chick, which at hatching contains the adult complement of taste buds. Forty newly hatched chicks received single or double pulse injections of tritiated thymidine (specific activity was 6.7 Curies/millimole; dosage was 0.

Aspects of vertebrate gustatory phylogeny: morphology and turnover of chick taste bud cells.

The taste bud is a receptor form observed across vertebrates. The present report compares chick taste buds to those of other vertebrates using light and electron microscopy. Unlike mammals, but common to many modern avians, the dorsal surface of chick anterior tongue lacks taste papillae and taste buds.

The effect of neonatal capsaicin treatment on gustatory behavior in the albino rat.

Small-diameter fibers present in gustatory peripheral nerves have historically been suspected of relaying information about the bitter quality of a taste stimulus. Neonatally injected capsaicin irreversibly destroys a proportion of unmyelinated C- and some A delta-fibers. Consummatory responses to increasing concentrations of quinine and other chemical solutions following neonatal capsaicin injection were compared to those of untreated and vehicle-injected control Sabra albino rats.

Ultrastructure of palatal taste buds in the perihatching chick.

Palatal taste buds of perihatching chicks were examined by electron microscopy. Four intragemmal cell types were characterized. 1) Light: with voluminous, electron-lucent cytoplasm containing scattered free ribosomes, rough and smooth endoplasmic reticulum, plump mitochondria, sparse perinuclear filaments, occasional Golgi bodies, and numerous clear and dense-cored vesicles.

Behavioral reactions to gustatory stimuli in young chicks (Gallus gallus domesticus).

Freely-moving, posthatch chicks were individually presented 2 concentrations each of quinine, citric acid, fructose, sucrose, sodium saccharin, and distilled water and their behavioral reactions were videotaped and analyzed. Already during the first posthatch day distinct rejection responses to quinine and citric acid could be recognized. Prolonged head shaking and beak clapping episodes were the most dominant features of these reactions.

Olfactory function following late repair of choanal atresia.

Results of olfactory function tests (threshold determination and odor identification) in three cases of bilateral and one case of unilateral choanal atresia are reported. All four patients underwent successful repair of choanal atresia at relatively advanced ages (8 to 31 years). Test results showed that patients who had suffered from bilateral atresia had permanent olfactory deficits, while the patient who had suffered from unilateral atresia appeared to have normal olfactory acuity.

Long-term effects of gustatory neurectomy on fungiform papillae in the young rat.

Recent evidence from mature hamster fungiform papillae indicates that following denervation taste buds are present from 21 to 330 days in the absence of discernible intragemmal nerve fibers. In contrast, most prior taste bud degeneration studies focused on shorter survival times. The present inquiry in young rats examined the issue of postneurectomy buds, in which regeneration of the resected chorda tympani or facial nerves was prevented and anterior tongue tissue examined over a range of relatively long survival times (30-90 days).

Central distribution and efferent origins of facial nerve branches in the chicken.

The central afferent distribution and the origins of visceromotor and somatomotor components of greater superficial petrosal (GSP), chorda tympani (CT), and hyomandibular (Hy) branches of the facial nerve were analyzed by the transganglionic and retrograde transport of horseradish peroxidase. Labelled sensory afferent fascicles of the GSP collected dorsomedial to the spinal trigeminal complex and passed caudally as the tractus solitarius. Fine-grain terminal fields were evident in ipsilateral n.

Taste bud development in chickens (Gallus gallus domesticus).

Oral epithelium in the anterior mandibular glands region was examined in embryonic, hatchling, and mature chickens to establish the timing of morphologic events during taste bud ontogeny. Hematoxylin-and-eosin-stained sections (10 microns) from 27 Anak (broiler breed) chickens were examined serially, and buds were quantified at 16-20 days of incubation (E) and, posthatch days 1 and 50-60. Taste buds were first recognized at the beginning of E17 as small clusters of cells in the basal epithelium.

Chorda tympani innervation of anterior mandibular taste buds in the chicken (Gallus gallus domesticus).

While the mammalian chorda tympani innervates taste buds on the anterior two-thirds of the tongue, the chorda tympani of chickens does not enter the tongue, but rather is reported to supply the oral epithelium of the lower beak subjacent to the tongue. This study in the chicken investigated whether the integrity of taste buds in the lower beak is normally dependent upon innervation by the chorda tympani. Following unilateral ligation and removal of a large section of the chorda tympani, animals were sacrificed at 11, 14, and 21 days postoperatively.

Central afferent connections and origin of efferent projections of the facial nerve in the chicken (Gallus gallus domesticus).

The central afferent connections and origin of efferent projections of the facial nerve in the adult domestic chicken were studied by anterograde and retrograde transport of horseradish peroxidase from the geniculate ganglion. Ipsilateral afferent projections were traced caudal to the level of entrance of the facial nerve and into tractus solitarius (TS), located dorsomedial to the spinal trigeminal nuclear complex. At several rostrocaudal levels in the medulla, fibers exited from TS and terminated in n.

Behavioral displays to gustatory stimuli in newborn rat pups.

These experiments examine behavioral responses to taste stimuli in newborn rat pups during the first 4 postnatal days. Motor displays in the face and head regions of 90 neonate rats were recorded during 60-sec observation periods in a double-blind setting. Stimuli, presented as single droplets to the lips, included 2 concentrations each of sucrose, sodium saccharin, citric acid, quinine, and distilled water.

Influence of intake of sweet solutions on the analgesic effect of a low dose of morphine in randomly bred rats.

The time course for the development of morphine tolerance, following prolonged sweet intake, was examined in randomly bred Sabra rats. Exposure to 3% glucose in 6 mM saccharin solution increased drinking by about three times as compared to rats supplied only with water. Suppression of the analgesic effect of morphine was already detectable after 24 h of intake and became progressively more marked within the next 5 weeks.

Number and distribution of taste buds in the oral cavity of hatchling chicks.

The location and number of taste buds were mapped in palatal epithelia of one-day old chicks and bud widths measured. Bud counts additionally were recorded for the tongue, and floor of the lower beak. An average of 316 taste buds was observed in the oral cavity of which 69%, 29% and 2% were distributed across oral epithelium in the upper beak (palate), lower beak and posteroventrolateral region of the anterior tongue, respectively.