Recovery of atrophic parotid glands in rats fed a liquid diet by switching to a pellet diet

Objective: In this study, we aimed to clarify how parotid glands, made atrophic by a liquid diet, recover after diet change. Design: Seven-week-old male Wistar rats were fed a pellet (control group) or a liquid diet (experimental group) for the first 14 days. Thereafter, all animals were fed a pellet diet for up to 14 days (days 0-14). The parotid glands were removed, weighed and examined histologically and ultrastructurally. Immunohistochemistry was performed for BrdU, a marker of proliferating cells, and Casp-3, a marker of apoptotic cells. Results: Feeding of a liquid diet for 14 days induced atrophy of the parotid glands. Histologically, acinar cells were small on day 0, compared with the control group. After changing the diet from liquid to pellet form, acinar cells increased in size over time, recovering nearly fully by day 7. Many BrdU-positive acinar cells were observed in the glands in the experimental group on days 1 and 3. Although more acinar cells were Casp-3-positive compared with the control group on day 0, there was no difference between the two groups after the diet change. Ultrastructurally, the cellular organelles did not exhibit a substantial alteration, except for an increase in secretory granules following diet change. Conclusions: Our findings suggest that atrophic parotid glands are able to recover to their normal size by switching the diet from liquid to pellet form and that an increase in both the size and number of acinar cells plays an important role in this recovery process

Acinar cell response to liquid diet during rats' growth period differs in submandibular and sublingual glands from that in parotid glands

Continuously feeding a liquid diet to growing rodents strongly inhibits parotid gland growth, due to suppressed growth of acinar cells. This study investigated whether a liquid diet had a similar effect on submandibular and sublingual glands of growing rats. Rats were weaned on day 21 after birth and then fed a pellet diet in the control group and a liquid diet in the experimental group for 0, 1, 2, 4, and 8 weeks. Their submandibular and sublingual glands were excised, weighed, and examined histologically, immunohistochemically (using antibodies to 5'-bromo-2-deoxyuridine and cleaved caspase 3), and ultra structurally. The submandibular glands did not significantly differ between the control and experimental groups at all tested points. Only at Week 8, acinar cell area and 5'-bromo-2-deoxyuridine-labeling index of acinar cells in sublingual glands were significantly lower in the experimental group than in the control group. These results show that a liquid diet during rats' growth period had no effect on acinar cells in their submandibular glands, and only a slight effect on acinar cells in their sublingual glands of growing rats, in contrast to the marked effect of a liquid diet on parotid glands

Growth of rat parotid glands is inhibited by liquid diet feeding

This study investigated how liquid diet feeding affects the growth of parotid glands. We weaned 21-day-old rats and thereafter fed them a pellet diet (control group) or a liquid diet (experimental group) for 0, 1, 2, 4, or 8 weeks. Their parotid glands were excised, weighed, examined, and tested for 5-bromo-2'-deoxyuridine (BrdU) and cleaved caspase-3 (Casp-3) as markers of proliferation and apoptosis, respectively. Parotid gland weights were consistently smaller in experimental animals than in controls. Morphometrical analysis showed that control group acinar cells increased in area during the experiment, but experimental group acinar cells were almost unchanged. Labeling indices of BrdU in acinar cells in both groups declined during the experiment, but were consistently lower in the experimental group than in controls. Casp-3-positive acinar cells were rare in both groups, which consistently express significantly similar Casp-3 levels. Ultrastructurally, terminal portions of the experimental parotid glands consisted of a few acinar cells that were smaller than those in controls. Control acinar cells showed mitotic figures within short experimental periods, but not in experimental glands. These observations indicate that liquid diet feeding inhibits growth of parotid glands in growing rats through suppression of growth and proliferation of individual acinar cells, but not through apoptosis. (C) 2015 Elsevier Ltd. All rights reserved

Dental pulp can be a good candidate for nerve grafting in a xeno-graft model

Dental pulp is discarded after extirpation of dental pulp and after tooth extraction. However, it contains nerve tissue abundantly and could be used more effectively. This study was designed to examine whether a dental pulp could be a candidate of donor for nerve grafting in xenografting model. The dental pulp was obtained from a human vital extracted tooth for orthodontic treatment, and treated with freezing and thawing method for reducing antigenicity. The treated sample was inserted into chitosan mesh tube for easy suturing, and then the complex was implanted into transected sciatic nerve in Sprague-Dawley (SD) rats (dental pulp group). As controls, chitosan tubes with and without sciatic nerve harvested from another SD rats were implanted (isograft group and tube group, respectively). As early as four weeks after grafting, regenerating axons accompanied by host Schwann cells were found to grout out through basal laminae by electron microscopy. The intact structure of basal laminae at this period suggested that they were derived from the original structure of donor graft. Twelve weeks after grafting, sporadic axonal regeneration was confirmed by light microscopy in the dental pulp group. Thirty-two weeks after implantation, aggregation of axons was observed in this group and matched that in isograft group. The average diameter of axons in dental pulp group was comparable to that in isograft group, whereas number of minifascicles and axon proportion were smaller. It was suggested that some delay occurred in dental pulp group because of the phagocytosis and absorption of tissue debris components remained after the freezing and thawing treatment. These findings clearly demonstrate that even dental pulp can act as conduits for regenerating axons

Odontoclasts in the Chinook salmon differ from mammalian odontoclasts by exhibiting a great proportion of cells with high nuclei number

Odontoclasts resorbing teeth are multinucleated cells. Previously, the authors have investigated the distribution of number of nuclei per human odontoclast and showed that the mean number of nuclei per cell is 5.3, the median is 4, and 93.8% of cells have 10 or fewer nuclei. Teleost odontoclasts have features similar to those of mammals; however, the distribution of number of nuclei per cell remains unknown. The present study aimed to examine the distribution of number of nuclei per odontoclast in a teleost fish, Chinook salmon, Oncorhynchus tshawytscha (Walbaum), and to clarify the difference of number of nuclei in odontoclasts between Chinook salmon and humans. The maxillae and mandibles of Chinook salmon were fixed, decalcified, and embedded in Epon 812. Specimens were serially sectioned into 0.5- m semithin sections and examined by light microscopy. Cells possessing a brush border adjacent to a resorptive lacuna were identified as odontoclasts, and 246 odontoclasts were investigated to determine the distribution of nuclei per cell. The mean number of nuclei per cell was 21.8 and the median was 17; only 24.4% of odontoclasts had 10 or fewer nuclei, and 95.5% had 50 or fewer nuclei. These results suggest that the range for the number of nuclei per odontoclast in Chinook salmon is greater than that in humans

Features of the clear zone of odontoclasts in the Chinook salmon (Oncorhynchus tshawytscha)

This study aims to clarify the features of the clear zone of odontoclasts on shedding teeth of a teleost fish, Chinook salmon, Oncorhynchus tshawytscha (Walbaum), using a light microscope to determine the orientation between a cell body and a resorptive lacuna, followed by transmission electron microscopy. Ultrathin sections of LR White embedded material were incubated in rabbit anti-actin polyclonal antibody and then were incubated with 15 nm gold-conjugated goat anti-rabbit IgG. The clear zones of odontoclasts showed a variable structure with electron-dense structures on sections, but distinct clear zones were not always seen on odontoclasts. In odontoclasts sectioned in the direction perpendicularly to the surface of a resorptive lacuna, some cells showed a wide clear zone, but two types of clear zones were usually observed: a part composed of some cytoplasmic processes and one composed of several complicatedly interwoven processes. Gold particles were localized on the clear zones, especially in electron-dense structures; very few gold particles were detected in ruffled borders. These results show that the clear zone of odontoclasts in Chinook salmon contains actin. Our results suggest that the clear zone of an odontoclast in Chinook salmon is not always a wide annular structure

Histological aspect of the effects of soft food on major salivary glands

The modern Japanese population favors soft foods, which do not demand extensive mastication. However, daily intake of soft foods is considered to have unfavorable influences on the mind and body. This is especially within the oral maxillofacial region. Consequently, many studies using experimental animals, feed a liquid or powdered diet and indicate that soft foods negatively affect the jaw bones, masseter muscle, and temporomandibular joint. Furthermore, since a report by Hall and Schneyer in 1964, the effects of soft foods on salivary glands have been under investigation. Soft food intake induces atrophic alteration to the parotid glands in adult animals. In these glands, shrinkage, suppression of proliferation, and apoptotic deletion of acinar cells were observed. In growing animals fed soft foods, parotid gland growth is inhibited through the suppression of an increase of acinar cell size and of acinar cell proliferation, but not through apoptosis. These findings support that unfavorable effects on parotid glands are induced by the intake of soft food regardless of growing or mature phases. However, different observations exist between these two phases. Despite accumulated knowledge on parotid glands, the debate whether soft food affects submandibular and sublingual glands remains controversial. It is the case that many studies agree soft food unfavorably affects parotid glands to a greater extent than submandibular and sublingual glands. This article reviews the histological effects of soft food on major salivary glands and introduces recent data from our research group

Mineralization process during acellular cementogenesis in rat molars: a histochemical and immunohistochemical study using fresh-frozen sections.

This study was designed to detect tissue non-specific alkaline phosphatase (TNSALP) by Azo-dye staining, calcium by glyoxal bis (2-hydroxyanil) (GBHA) staining, bone sialoprotein (BSP) and osteopontin (OPN) by immunoperoxidase staining in developing rat molars, and also to discuss the mineralization process during acellular cementogenesis. To restrain a reduction in histochemical and immunohistochemical reactions, fresh-frozen undemineralized sections were prepared. Where the epithelial sheath was intact, TNSALP reaction was observed in the dental follicle, but not in the epithelial sheath. With the onset of dentin mineralization, the BSP- and OPN-immunoreactive, initial cementum layer appeared. At this point, cementoblasts had shown intense TNSALP reaction and GBHA reactive particles (=calcium-GBHA complex) appeared on the root surface. With further development, the reaction of TNSALP and GBHA became weak on the root surface. Previous studies have shown that the initial cementum is fibril-poor and that matrix vesicles and calciferous spherules appear on the root surface only during the initial cementogenesis. The findings mentioned above suggest that: during the initial cementogenesis, cementoblasts release matrix vesicles which result in calciferous spherules, corresponding to the GBHA reactive particles. The calciferous spherules trigger the mineralization of the initial cementum. After principal fiber attachment, mineralization advances along collagen fibrils without matrix vesicles

Regeneration of myoepithelial cells in rat submandibular glands after yttrium aluminium garnett laser irradiation

The regeneration of myoepithelial cells in rat submandibular salivary gland after partial irradiation with yttrium aluminium garnett (YAG) laser was investigated. The irradiated glands were examined immunohistochemically for actin, histochemically for alkaline phosphatase (ALP), and by transmission electron microscopy (TEM). In control glands, myoepithelial cells were positive for actin and ALP. Electron microscopically, the positive reaction for actin was associated with the myofilaments of myoepithelial cells, and the plasma membrane of myoepithelial cells was positive for ALP. One day after YAG laser irradiation, the irradiated region was necrotic. By 5 days, duct-like structures and epithelial clusters were observed at the interface between the necrotic zone and the remaining undamaged glands; immature acini appeared after 7 days. No reaction in duct-like structures or epithelial clusters to actin or ALP was recognizable by 5 days. However, at 7 days, actin and ALP-positive spindle cells appeared at the periphery of the duct-like structures and immature acini. After 10 days, both actin-positive and ALP-positive cells increased in number. These observations indicate that during regeneration, actin-positive and ALP-positive cells regenerate myoepithelial cells, and it is suggested that this differentiation to myoepithelial cells is closely related to that of luminal to acinar cells. In addition, TEM observations indicate that regenerated myoepithelial cells originated from the basal cells of duct-like structures