Biology subjects

Dzowo, Y.

Publications and source records attributed to Dzowo, Y..

3 recordsLinked to original sources

bioRxiv2024

Death in the taste bud: Morphological features of dying taste cells and engulfment by Type I cells

Taste buds comprise 50-100 epithelial derived cells, including glial-like cells (Type I) and two types of receptor cells (Types II and III). All of these taste cells are renewed throughout the life of an organism from a pool of uncommitted basal cells. Immature cells enter the bud at its base, maturing into one of the three mature cell types. How taste cells die and/or exit the bud, as well as the role of the glial-like cells in this process, remains unclear. Here we present morphological data obtained through Serial Blockface Scanning Electron Microscopy of murine circumvallate taste buds, revealing taste cells at the end of their life. Cells we identify as dying share morpholowgical features typical of apoptosis: swollen endoplasmic reticulum, large lysosomes, degrading organelles, distended outer nuclear membranes, heterochromatin reorganization, cell shrinkage, and cell and/or nuclear fragmentation. Most early stage dying cells have Type II cell morphologies, while a few display Type III cell features. Many dying cells maintain contacts with nerve fibers, but those postsynaptic fibers often appear to be detached from the main trunk of an afferent nerve. Dying cells, like mature Type II and III taste cells, are surrounded by glial-like Type I cells. In many instances Type I cells appear to be engulfing their dying neighbors, suggesting for them a novel, phagocytic role. Surprisingly, virtually no Type I cells display features of apoptosis, although they reportedly have the shortest residence time in taste buds. The ultimate fate of Type I cells therefore remains unknown. Table of Contents EntryO_ST_ABSMain PointsC_ST_ABSO_LIDying taste cells display morphologies consistent with apoptosis. C_LIO_LIGlial-like Type I cells engulf dying neighbors, perhaps acting as "undertakers." C_LIO_LIWe find no dying Type I cells--all early dying cells are taste transducing Type II or III cells. C_LI

neuroscience↗

bioRxiv2021

Taste Bud Connectome: Implications for Taste Information Processes

Taste buds contain 3 types of morphologically identifiable mature cells, 2 of which mediate transduction of specific taste qualities: Type III cells transduce sour while Type II cells transduce either sweet, bitter or umami. A long-standing controversy is whether the nerve fibers innervating these cells are wired specifically, in a labeled-line fashion, or non-specifically, leading to broad responsiveness across taste qualities, the so-called across-fiber system of encoding. Using serial blockface scanning electron microscopy through 5 circumvallate mouse taste buds, we reconstructed the patterns of connectivity of nerve fibers as well as the degree of potential interaction between the two types of taste transducing cells. Type II and Type III cells share few points of contact with one another, and display no morphologically identifiable synapses, suggesting limited direct interaction between these cell types. Of the 127 nerve fibers that make synaptic contacts with taste cells in the sampling volume, about 70% (n=91) synapse with only one taste cell. Of the remaining 36 fibers, 4 synapse with both Type II and Type III cells, the remainder synapsing exclusively with multiple Type II taste cells or multiple Type III cells. Since Type II and Type III cells transduce different taste qualities, the few mixed fibers do not follow a labeled-line organization according to taste quality information and show that connectional specificity in taste buds is not absolute. Significance StatementTaste buds, the sensory end organs for the sense of taste, contain multiple types of sensory cells, with each responding to one of the primary tastes: salt, sweet, sour, bitter and umami. A long-standing question is whether each type of taste cell is wired specifically to a unique set of nerve fibers conveying a "labeled-line" message to the brain. Using serial sections, we determined the neural connectivity in mouse circumvallate taste buds. The majority of individual nerve fibers connect to a single type of taste cell, but 3.1% of the fibers branch to receive input from taste cells known to have different specificities. Thus taste cannot entirely be carried along nerve fibers dedicated to single taste qualities.

neuroscience↗

bioRxiv2019

Three-Dimensional Reconstructions of Mouse Circumvallate Taste Buds Using Serial Blockface Scanning Electron Microscopy: I. Cell Types and the Apical Region of the Taste Bud

Taste buds comprise four types of taste cells: 3 mature, elongate types: Type I, Type II, Type III; and basally-situated, immature post-mitotic Type IV cells. We employed serial blockface scanning electron microscopy to delineate the characteristics and interrelationships of the taste cells in the circumvallate papillae of adult mice. Type I cells have an indented, elongate nucleus with invaginations, folded plasma membrane, and multiple apical microvilli in the taste pore. Type I microvilli may be either restricted to the bottom of the pore or extend outward reaching midway up into the taste pore. Type II cells (aka receptor cells) are characterized by a large round or oval nucleus, a single apical microvillus extending through the taste pore, and specialized \"atypical\" mitochondria at functional points of contact with nerve fibers. Type III cells (aka \"synaptic cells\") are elongate with an indented nucleus, possess a single, apical microvillus extending through the taste pore and are characterized by a small accumulation of synaptic vesicles at points of contact with nerve fibers. About one-quarter of Type III cells also exhibit an atypical mitochondrion amidst the presynaptic vesicle clusters at the synapse. Type IV cells (non-proliferative \"basal cells\") have a nucleus in the lower quarter of the taste bud but have a foot process extending to the basement membrane often contacting nerve processes along the way. Type I cells represent just over 50% of the population, whereas Type II, Type III, and Type IV (basal cells) represent 19%, 15%, and 14% respectively.

neuroscience↗