This study was undertaken to determine the effects of soft diet on the masticatory function, as well as the growth and development of the rat mandibular ramus. Four-week-old male Wistar rats, immediately after weaning, were randomly divided into hard (H) and soft (S) diet groups. They were further subdivided into five small groups by age; five-week-old to nine-week-old groups. The muscle function was examined on the basis of the creatine kinase (CK) activity in the masticatory muscles. Morphological changes of the mandibular ramus were measured on radiographs, while changes in the internal structure of the ramus were studied using decalcified sections. The CK activity in the masticatory muscles initially increased in both the H and S groups. However, at six weeks the CK activity in Group H reached a steady level. The activity in Group S continued to increase until seven weeks, and then finally equalled that of the Group H level at eight weeks. Morphologically, the vertical dimensions of the coronoid process, mandibular notch, and condylar process were larger in Group H. In contrast, the horizontal dimensions of these structures were larger in Group S. Histologically, partially mineralized bone was recognized at each masticatory muscle attachment site in both groups. However, mineraized bone seen in Group H was more conspicuous than in Group S. In other areas of the mandible, Group H had a higher level of mineralized bone throughout the experimental period, while the S group had a higher level of partially mineralized bone. In conclusion, Group S showed maldevelopment of the mandible deficiency and low bone metabolism.

Differences in immune responses between immunized and non-immunized mice were studied with special reference to tumor-infiltrating lymphocytes (TIL), using inbred WHT/Ht mice with spontaneously developing transplantable squamous cell carcinoma. After inoculating 1×10⁶ tumor cells, a lymphocyte-proliferating response was observed in the spleens and regional lymph nodes of both immunized and non-immunized mice. Histological examination showed marked infiltration of lymphoid cells into tumor tissues of immunized mice, but was much less in non-immunized mice. Lymphocyte subset analysis by a fluorescent antibody method and FACScan indicated that TIL in the immunized mice consisted mostly of surface-Ig⁺, Mac-1⁺ and asialo GM1⁺ cells. This almost completely agreed with the distribution of spleen cells. However, in non-immunized mice, Lyt-1⁺ and L3T4⁺ cells were dominant, differing from the distribution of spleen cells. Furthermore, the killer activity of these TIL and spleen cells against syngeneic tumor cells was studied by ⁵¹Cr release assay. Results showed that TIL and spleen cells of immunized mice had cytolytic, natural killer, and ADCC activities, but none of these could be detected in the non-immunized mice.

The above findings suggest that infiltration of TIL is an expression of immune response of the tumor-bearing host against tumor-rejection antigens. At the site of tumor transplantation in immunized mice various effector cells having anti-tumor activity act toward tumor rejection.

Hydroxyapatite (HA) particles are frequently used in reconstruction of the jaw and augmentation of the alveolar ridge for defects and atrophy caused by various factors. However, postoperative displacement or dispersion of HA particles has been a problem in clinical application of these particles. A number of attempts have been undertaken to solve this problem.

In this study, application of was attempted for implantation an expanded polytetrafluoroethylene (EPTFE) tube, a vascular prosthesis tube, in the subperiosteal region and in the artificial defect of rabbit mandible, with a view of retaining the stability of the site treated with HA particles. The morphological stability after implantation was evaluated by an image analysis system. The results obtained are as follows:

Implantation of an EPTFE tube resulted in retention of excellent morphological stability of the site treated. New bone formation was found inside the porous structure and in the internal space of the EPTFE tube. These findings demonstrated that the implant and mandibular bone are fused together by new bone tissue.

These results suggest that this tube of synthetic material is useful and helps maintain the morphology of HA particles, and also has high compatibility with tissue.