Shika Kiso Igakkai zasshi = Japanese journal of oral biology最新文献

Effects of oxygen on growth of Streptococcus mutans Ingbritt (serotype c) were examined. The strain could be passaged under aerobic conditions at 37 degrees C in a peptone/yeast extract medium containing 0.2% glucose. Although the growth rate was slightly retarded under aerobic conditions (the doubling time, 60 min; 45 min under anaerobic conditions), the increment of cellular dry weight change was 35 g per mole of glucose under both conditions. To investigate such aerotolerance in growth as indicated by these results, oxygen metabolism was compared between aerobically and anaerobically grown cells. No difference was observed in the apparent rate of superoxide production or superoxide dismutation. However, aerobically grown cells showed a higher activity of hydrogen peroxide reduction with glucose as substrate and accumulated a lower level of hydrogen peroxide when incubated with glucose under aerobic conditions. In addition, hydrogen peroxide added to the medium was less inhibitory to anaerobic growth when aerobic cells were used as the inoculum. These results indicate that aerotolerance of S. mutans Ingbritt can be ascribed at least in part to its hydrogen peroxide reducing activity which is elevated under aerobic conditions.

The present study aims to understand the three-dimensional structure of the osteoclast during locomotion. The osteoclasts were gained from the bone marrow cells of new born ddY mouse. These osteoclasts were seeded onto dentine slices and then cultured for 48 hrs. The cells were examined using transmission electron microscopy. The osteoclast seen in this study had an irregular outline and had shifted from previously formed lacunae. This cellular extension was seemed to be lamellipodia. According to these results, the osteoclasts seen in present study were determined to have been during locomotion. The ruffled border of the osteoclast was composed of both finger-like processes and plate-like ones. The plate-like processes were observed in the almost newly formed lacuna. The complicated interwoven membranous gatherings were observed at two extensive areas of the cell body situated in the previously formed lacuna. It is postulated that these structures are related to the incoming and outgoing of the cell membranes of the ruffled border in accordance with cell locomotion.

We conducted an investigation of the relation between dentofacial skeletal patterns and the deflection of the roots of mandibular canines and premolars. Data on root deflection, rated as mesial, distal, or undeflected, were obtained from orthopantomographs taken of 130 patients who were judged to meet certain criteria on their initial orthodontic examinations. The significance of the relation between these data and the dentofacial patterns, determined by radiographic cephalometric analysis, was then examined statistically. This determined that in cases of severe mandibular prognathism (ANB less than -2 degrees), the roots of 1st and 2nd premolars exhibited significantly more mesial deflection. This result suggests that the mesial deflection of these roots is caused by the differential growth rates of basal and alveolar bone in cases of severe mandibular prognathism.

The cellular proteins of hamster tongue squamous cell carcinoma and epithelial dysplastic lesions induced by 9,10-dimethyl-1,2-benzanthracend (DMBA) were analyzed by two-dimensional isoelectric focusing-sodium dodecyl sulfate gel electrophoresis. Many of the polypeptides were common to these lesions. However, there were thirteen main polypeptides which differed between normal tongue mucosa and tongue carcinoma. In the carcinoma, eight polypeptides (5.2/53 K, 5.8/47 K, 6.9/46 K, 6.9/50 K, 7.1/55 K, 7.2/46 K, 7.3/75 K, 7.4/48 K, pI/MW) were decreased and three polypeptides (4.9/32 K, 6.3/50 K, 7.2/60 K) were increased in an amount. The remaining two polypeptides (4.8/37 K, 4.9/36 K) that were not normally present were appeared in carcinoma, but these two new polypeptides were not specific to carcinoma because they were also present in dysplastic lesions. There were marked differences in the polypeptide between various degree of dysplastic lesions and carcinoma on the one hand and normal mucosa on the others. These results suggests that two-dimensional electrophoresis may have usefulness in further research on transformations from normal mucosa to malignant cancer cells.

The ultrastructure of the articular fibrous zone of the rat mandibular condyle was observed at 3 and 6 weeks of age in order to investigate the histological changes that occur during the establishment of mastication after suckling. We divided the articular fibrous zone into two layers (F1 layer and F2 layer). The F1 layer was composed of fibroblast-like cells, macrophage-like cells, and the matrix which consisted of granular or fibrillar material, loosely arranged small bundles of collagen fibrils with uniform thickness of 30-50 nm, and independent microfibrils. The F1 layer was continuous with the synovial membrane without any distinct boundary in its peripheral area. Mitotic figures could infrequently be observed in the fibroblast-like cells. The cells in the F2 layer closely resembled fibroblasts. The matrix in the F2 layer mostly consisted of densely arranged bundles of collagen fibrils which are not of uniform diameter ranging 40-100 nm. Elastic fibers occurred among the collagen fibrils. The F1 layer which was observed clearly at 3 weeks almost disappeared at 6 weeks of age. It is confirmed that the F1 layer resembling the synovial membrane exists over the condyle up to the weaning period about 3 weeks of age but it degenerates before 6 weeks of age when the masticatory function is established.

Two different patterns of rhythmical jaw movements (RJM) resembling masticatory movements were evoked by stimulation of the cerebral cortex in the rat. The first type of RJM was evoked from the primary jaw motor area, and it always began with a sustained jaw-opening and consisted of high frequency (5-7 Hz) simple opening-closing movements of the jaw. The anterior digastric electromyographic (EMG) activity showed discharges apparently time-locked to each stimulus pulse. The second type of RJM was evoked from the ventral part of the insular cortex. In contrast to the first type of RJM, the second type started with a jaw closing movement in many cases. This type of RJM had large and complex lateral and sagittal movements and the frequency of RJM was low (3-4 Hz). The digastric EMG activity did not show the stimulus-locked component. The pattern of these RJM did not depend on the intensity or frequency of stimulation, but on the site stimulated. These two cortical RJM areas appeared to work independently from each other, because ablation of one area did not affect the pattern of the RJM evoked from the other cortical area.