The number of neurons in the brain increases over time, even in adults. This phenomenon, known as “neurogenesis”, is associated with neural stem cells present only in the dentate gyrus of the hippocampus. However, the frequency of neurogenesis is regulated by various factorsand mastication has been suggested as one such factor. In the present study, we examined the effects of varying the input of masticatory stimulation on neural stem cells using feed with different degrees of hardness. Male C57BL/5 mice were used in a comparative study. After weaning at 3weeks old, experimental mice were fed a soft or hard diet for 4 or 11weeks. To study the dynamic behavior of neural stem cells, the expression of two markers （nestin, a neural stem/progenitor cell marker; and doublecortin, a microtubule-associated protein） was quantitatively analyzed via immunostaining, whereas gene expression was analyzed by real-time polymerase chain reaction （RT-PCR）. Immunostaining-based quantification and gene expression analysis by RT-PCR revealed the decreased expression of markers in the hippocampus in the soft diet group compared to that in the hard diet group. Based on these results, the repression of neurogenesis by a soft diet was associated with changes in neural stem cells in the hippocampus and the frequency of neurogenesis.

Autografts, which are commonly used for alveolar bone regeneration, often utilize the ilium and jaw bones as alternative bone graft materials. Maxillary and mandibular bones are developmentally derived from neural crest-derived cells (NCDCs), while the majority of trunk and limb bones are derived from mesoblast cells. Consequently, the host bone graft material might differ in developmental origin from the recipient bone. With such a potential mismatch in practical terms, it is unclear whether genuine jaw bone can be regenerated. We hypothesized that bones derived from NCDCs and mesoblast cells show different capacities for in vivo bone healing. To investigate this proposal, we undertook bone graft experiments using a murine model. We first perforated a 2-mm diameter area in both the frontal and parietal bones, which are derived from NCDCs and mesoblast cells, respectively; then we grafted various source materials into each bone defect. Mice were euthanized at 2 weeks after grafting, and histological analyses and immunohistochemistry were performed to evaluate differences in bone healing based on the various combinations of graft and recipient bones. The frontal bone was found to heal faster than the parietal bone. Parietal bone defects transplanted with maxillary and mandibular bone grafts exhibited closure, whereas iliac and femoral bone grafts did not result in full healing. Immunostaining for osteopontin also demonstrated good bone regeneration in the parietal bone defects using maxillary and mandibular bone graft materials. These results suggest that maxilla and mandible bones exhibit NCDC properties with an enhanced healing potential. We conclude that maxillary and mandibular bones are effective bone graft and graft bed materials.

Introduction: Mandibular growth is believed to be strongly related to mastication. Furthermore, mandibular condylar cartilage is known to be derived from neural crest cells. We examined whether the degree of chewing affects condylar cartilage growth of the mandible. Methods: Mice were fed diets with varying hardness. Genes specific to neural crest-derived cells were measured by real-time polymerase chain reaction to compare the expression changes between the mandibular and tibia cartilages. The mandibular condylar cartilage was then evaluated histologically, and proliferation was evaluated using proliferating cell nuclear antigen. Immunostaining was conducted for osteopontin, type X collagen, and Musashi1, and real-time polymerase chain reaction was used to assess the expression levels of osteopontin and type X collagen. Results: Markers including P75, Wnt-1, Musashi1, and Nestin were upregulated in the mandibular condylar cartilage as compared with the tibial cartilage. Histologic assessment of the mandibular cartilage showed that the hypertrophic chondrocyte zone was statistically significantly thicker in mice fed a hard diet. Chondrocyte proliferation and Musashi1 expression were lower in mice fed a hard diet. After 4 weeks, numerous osteopontin and type X collagen-positive cells were observed in mice fed a mixed diet. Conclusions: Mastication affects the balance between differentiation and proliferation in the mandibular condylar cartilage. This phenomenon might be attributed to the presence of neural crest-derived cells.

The purpose of this study was to assess the recovery of experimentally induced alveolar bone loss and the destruction of periodontal tissue induced by histological and morphometric examinations.Experimental periodontal disease was induced using the wire ligation between the upper first and second molars for two weeks.Bone loss and the structures of periodontal tissues were examined immediately after the removal of the wire ligation and at one week after the ligation.MicroCT analysis indicated that the decreased mass of alveolar bone induced using the wire ligation signifi cantly recovered at one week after the removal of the ligation.Histological examination indicated the reappearance of transseptal ligaments and alveolar bones.These results suggest that this model might be useful to examine the regeneration process of periodontal tissue destructed by periodontal disease.

BACKGROUND In the clinical field of jawbone formation, the use of autogenous bone as the graft material is the gold standard. However, there are some problems with this technique, such as risk of infection on the donor side, the limited amount of available bone mass, and marked resorption of the grafted bone. We investigated the potential for using teeth as a bone graft material for jawbone formation because the dental pulp contains stem cells, including undifferentiated neural crest-derived cells. METHODS Alveolar bone defects were created in Wistar rats, and the defects were filled with either tooth or iliac bone graft material, or left as controls. The potential for using teeth as a bone graft material for jawbone formation was measured using real-time polymerase chain reaction, microcomputed tomography, and histologic analysis. RESULTS Polymerase chain reaction revealed that the expressions of P75, P0, nestin, and musashi-1 were significantly higher in teeth than in mandibular bone and iliac bone grafts. Hematoxylin and eosin staining and microcomputed tomography showed that at 8 weeks, tooth graft material produced a similar amount of new bone compared to iliac bone graft material. Osteopontin was expressed in both the tooth and iliac bone graft material at 6 and 8 weeks after surgery. Dentin sialoprotein was expressed in the tooth graft material in the new bone at 6 weeks only. CONCLUSION These results indicate that teeth may be an alternative material to autogenous bone for treating alveolar bone defects by grafting.

Foal heat diarrhea (FHD) is a major factor in the management of foals between 2 and 3 wk of age. The objective of this on-farm study was to determine the efficacy of postpartum anthelmintic treatment of mares for reducing the incidence and/or the severity of FHD in foals caused by parasitic infestation. Twenty-four Quarter Horse mares and their foals were alternately assigned to a treated or non-treated group according to expected foaling date. Treatment consisted of oral administration of Zimectrin® (Farnam Companies, Inc., Phoenix, AZ) to the dam within 12 h post-foaling. From d l through 25, foals were weighed, and vital signs and severity or absence of diarrhea were recorded. Incidence scores of 0 to 3 were assigned to each foal based on severity of diarrhea: 0 = no affliction and 3 = severe, watery diarrhea. There was no difference in incidence scores because of treatment; however, there was a trend for foals from treated mares to experience more severe diarrhea with a shorter duration. There was no difference in BW gain related to treatment or nontreatment of mares. Postpartum administration of Zimectrin to mares did not significantly decrease the incidence or severity of diarrhea in foals. Additionally, it did not affect growth rate of foals. The trend for foals from treated mares to have a shorter duration of FHD may be beneficial to farm managers who spend time and money treating and cleaning foals.