Response of Merkel cells in the palatal rugae to the continuous mechanical stimulation by palatal plate

Abstract

Abstract(1) Objective: The aim of the present study was to investigate the behavior of Merkel cells which have been suggested to be mechanoreceptors that exist in extensive amounts in the palatal rugae, due to the continuous mechanical stimulation exerted by the palatal plate.(2) Design:Forty golden 8-weeks-old hamsters were used in this experiment. The palatal plate was made of adhesive resin (4-META/MMA-TBB) and it was set o n the palate of the animal for 1, 4 and 7 days. In order to achieve a continuous pressure over the mucosa underlying palatal plate, the palatal plates were pressed against the palatal mucosa and fixed to the posterior teeth using the same adhesive resin d escribed above. To exert a continuous pressure, a 0.8 mm prominence on the internal surface of the palatal plate was created at the middle portion of the fourth palatal ruga. Thereafter, the number of Merkel cells in the mucosa was calculated by immunohistochemical observation. Furthermore, the electron microscopic features of Merkel cells were examined regarding the cell profile, continuity of the cell membrane, mitochondria , nerve tissues, the number of cell processes, neurosecretory granules in the cyt oplasm and the nuclear -cytoplasmic (N/C) ratio. The d ata were analyzed using Bonferroni's multiple comparison procedure and Fisher's exact test. The level of significance was 0.05 in all analyses.(3) Results:1. There was significant deference among the control and any of the treated groups on the number of CK20 positive Merkel cells (p<0.05) and that numbers were decreased at the sites where continuous mechanical stimulation was exerted. 2. A degeneration of the cytoplasm mitochondria and nerve endings , and a decrease in both the number of neurosecretary granules and cell processes were observed. Furthermore, the presences of nuclear chromatin aggregation and fragmentation were recognized.

Effects of the long-term anosmia combined with vision deprivation on the taste sensitivity and feeding behavior of the rainbow trout Parasalmo (=Oncorhynchus) mykiss

“…The oral gustatory system is responsible for obtaining informa tion about taste properties of an object, whereas the oral tactile system assesses the object's texture proper ties and location. It is considered that the mouth cav ity of animals is the zone where mechanical impacts are the main and most frequently occurring type of stimuli (Ishizaki et al, 2006). The chemical (gusta tory) and mechanical (tactile) stimuli are perceived when a food object is retained in the fish mouth cavity.…”

Morphological and molecular changes in denture‐supporting tissues under persistent mechanical stress in rats

“…Following the procedure of Ishizaki et al. (4), each animal was placed under anaesthesia with an intraperitoneal injection of 0·2 mL thiopental sodium (RAVONAL)* per 100 g body weight and a precision non‐pressure impression of the upper jaw of each animal was taken using a vinylsilicon impression material (Exafine) † . An ultrahard plaster (New Fujirock) † cast was then made.…”

“…We used the palatal plate, according to the method of Ishizaki et al. (4), who investigated the responses of Merkel cells because of the continuous mechanical stimulation exerted by the plate. The experimental palatal plate used in this study was made from 4‐META resin in accordance with the method of Ishizaki et al.…”

“…The upper dentures subjected to functional stresses have the potential to cause various kinds of problems, such as white spots, inflammation/ulceration of mucous membranes and/or resorption of alveolar bone in denture‐supporting tissues. Many histological studies have investigated phenomena that occur in denture‐supporting tissues and have demonstrated the deformation of rete ridges of the epithelium (1–3), the degeneration of epithelial cells (3), decreased numbers of sensory cells (4), irregularities in cell layers (5) and changes in the numbers of osteoblasts and osteoclasts according to the intensity of pressure (2, 6). Furthermore, Atasever et al.…”

Merkel Cells in Somatosensation

“…Since their discovery in 1875, Merkel cells have been proposed to function as mechanosensory cells based on their morphology and location (Merkel, 1875;reviewed in Tachibana and Nawa, 2002;Halata et al, 2003 (Ishizaki et al, 2006). Extracellular recordings were made from individual somatosensory afferents using a semiintact preparation consisting of mouse hairy skin innervated by the saphenous nerve.…”