Satoru Ozono

Reduced mastication stimulates impairment of spatial memory and degeneration of hippocampal neurons in aged SAMP8 mice

The involvement of reduced mastication in senile dementia was evaluated by examining the effect of cutting off the upper molars (molarless) on spatial memory and numbers of hippocampal neurons in aged SAMP8 mice. Molarless mice showed a decrease in both learning ability in a water maze and neuron density in the hippocampal CA1 region compared with control mice. These changes increased the longer the molarless condition persisted. The data suggest a possible link between reduced mastication and hippocampal neuron loss that may be one risk factor for senile impairment of spatial memory.

Impairment of spatial memory and changes in astroglial responsiveness following loss of molar teeth in aged SAMP8 mice

In order to evaluate the mechanism(s) responsible for senile impairment of cognitive function as a result of reduced mastication, the effects of the loss of the molar teeth (molarless condition) on the hippocampal expression of glial fibrous acidic protein (GFAP) and on spatial memory in young adult and aged SAMP8 mice were studied using immunohistochemical and behavioral techniques. Aged molarless mice showed a significantly reduced learning ability in a water maze test compared with age-matched control mice, while there was no difference between control and molarless young adult mice. Immunohistochemical analysis showed that the molarless condition enhanced the age-dependent increase in the density and hypertrophy of GFAP-labeled astrocytes in the CA1 region of the hippocampus. These effects increased the longer the molarless condition persisted. When the extracellular K+ concentration ([K+]o) was increased from 4 to 40 mM for hippocampal slices in vitro, the mean increase in the membrane potential was about 57 mV for fine, delicate astrocytes, the most frequently observed type of GFAP-positive cell in the young adult mice, and about 44 mV for the hypertrophic astrocytes of aged mice. However, there was no significant difference in resting membrane potential between these cell types. The data suggest that an impairment of spatial memory and changes in astroglial responsiveness occur following the loss of molar teeth in aged SAMP8 mice.

The molarless condition in aged SAMP8 mice attenuates hippocampal Fos induction linked to water maze performance

The involvement of dysfunctional teeth in senile hippocampal activity was evaluated by examining, in aged SAMP8 mice, the effect of cutting off the upper molars (molarless condition) on hippocampal induction of the protein product, Fos, of the immediate early gene, c-fos, and on spatial performance in a water maze. The molarless condition caused a reduction in the number of Fos-positive cells in the hippocampal CA1 region, in which Fos immunoreactivity was localized in the cell nuclei. This effect was more pronounced the longer the molarless condition persisted. The suppression of both learning ability and Fos induction in the CA1 induced by the molarless condition was considerably reduced by restoring the lost molars with artificial crowns. Taken together with the plethora of research showing a relationship between stress, aging and hippocampal function and our past findings [Brain Res. 1999; 826: 148-53; Behav. Brain Res. 2000;108: 145-55; Exp. Gerontol. 2001; 36:283-95], the present results suggest the detrimental effects of a reduction in chewing on hippocampal processing in aged SAMP8 mice that would be linked with stress induced by the molarless condition.

Changes in the septohippocampal cholinergic system following removal of molar teeth in the aged SAMP8 mouse.

We investigated the effect of dysfunctional teeth on age-related changes in the septohippocampal cholinergic system by assessing acetylcholine (ACh) release and choline acetyltransferase (ChAT) activity in the hippocampus and ChAT immunohistochemistry in the medial septal nucleus and the vertical limb of the diagonal band in young-adult and aged SAMP8 mice after removal of their upper molar teeth (molarless condition). Aged molarless mice showed decreased ACh release and ChAT activity in the hippocampus and a reduced number of ChAT-immunopositive neurons in the medial septal nucleus compared to age-matched control mice, whereas these effects were not seen in young-adult mice. The results suggest that the molarless condition in aged SAMP8 mice may enhance an age-related decline in the septohippocampal cholinergic system.

Restoration of BRAK / CXCL14 gene expression by gefitinib is associated with antitumor efficacy of the drug in head and neck squamous cell carcinoma.

Clinical efficacy of gefitinib (ZD1839, Iressa), which is an inhibitor specific for epidermal growth factor (EGF) receptor tyrosine kinase, has been shown in non‐small‐cell lung carcinoma patients with EGF receptor mutations, so these mutations are useful marker(s) to find a responder for the drug. Recent studies have shown that the EGF receptor gene mutation is rare in squamous cell carcinoma in the esophageal and head and neck regions. We previously reported that the expression of the chemokine BRAK/CXCL14 in head and neck squamous cell carcinoma (HNSCC) cells was down‐regulated by EGF treatment, and that forced expression of BRAK in tumor cells decreased the tumorigenicity of the cells in xenografts. Thus, we investigated the relationship between restoration of BRAK expression by gefitinib and the efficacy of the drug for tumor suppression. We found that EGF down‐regulated BRAK expression through the MEK–extracellular signal regulated kinase pathway and that this down‐regulated expression was restored by gefitinib in vitro. Oral administration of gefitinib significantly (P < 0.001) reduced tumor growth of xenografts of three HNSCC cell lines (HSC‐2, HSC‐3, and HSC‐4), in female athymic nude mice, accompanied by an increase in BRAK expression specifically in tumor tissue. This tumor‐suppressing effect of the drug was not observed in the case of BRAK non‐expressing cells. Furthermore introduction of BRAK shRNA vector reduced both the expression levels of BRAK in HSC‐3 cells and the antitumor efficacy of gefitinib in vivo. Our data showing an inverse relationship between BRAK expression levels in tumor cells and the tumor growth rate indicate that the gefitinib‐induced increase in BRAK expression is beneficial for tumor suppression in vivo. (Cancer Sci 2009)

Alveolar bone regeneration using absorbable poly(L-lactide-co-ɛ-caprolactone)/β-tricalcium phosphate membrane and gelatin sponge incorporating basic fibroblast growth factor

The aim of this study was to evaluate the effects of combining a porous poly(L-lactide-co-epsilon-caprolactone)/beta-tricalcium phosphate membrane and gelatin sponge incorporating basic fibroblastic growth factor (bFGF) on bone regeneration in mandibular ridges. Four full-thickness saddle-type defects (10 mm long x 5 mm deep) were symmetrically created in both edentulous mandibular alveolar ridges of 6 beagles. The dome-shaped membrane was secured to each defect site, and a gelatin sponge containing 200 microg bFGF was implanted on the left side of each defect (experimental group). Only the membranes (control group) were secured to the defect sites on the right. Three and 6 months later, 3 animals were killed. Bone regeneration was analyzed by soft X-ray photographs, micro-computed tomography (CT) images, and peripheral quantitative CT (pQCT), and then examined histologically. Soft X-ray examination revealed an increase in new bone volume in the experimental group 6 months postoperatively. pQCT showed that immature bone density was higher in the experimental group. Micro-CT images revealed well formed new bone along the original contour of the dome-shaped membrane in the experimental group. Histologically, inflammatory infiltration of tissue surrounding the membranes was slight. These results suggest that combining the poly(L-lactide-co-epsilon-caprolactone)/beta-tricalcium phosphate membrane and bFGF-gelatin sponge is promising for alveolar ridge reconstruction.

Enhanced Regeneration of Critical Bone Defects Using a Biodegradable Gelatin Sponge and β-Tricalcium Phosphate with Bone Morphogenetic Protein-2

We examine the osteogenicity of a sponge biomaterial consisting of a biodegradable mixture of gelatin and β-tricalcium phosphate (βTCP) that bound bone morphogenetic protein 2 (BMP-2) in critical-sized bone defects in rats. Gelatin-βTCP sponges containing either phosphate buffered saline or incorporating BMP-2 are implanted into 5 mm diameter bone defects created in rat mandibles. We assess the defects biweekly for 8 weeks following implantation. There is significantly higher osteoinductive activity and significantly more Gla-osteocalcin content at bone-defect healing sites treated with gelatin-βTCP sponges incorporating BMP-2 than there is in those treated with sponges that did not contain BMP-2. Histologically, new bone that contains bone marrow and that is connected to the original bone almost entirely replaces the regenerated bone. These results show that biodegradable gelatin-βTCP incorporating BMP-2 is osteogenic enough to promote healing in large bone defects.

Stimulation of sodium current by cyclic AMP is mediated through protein phospyorylation inEuhadra neurons

The protein kinase inhibitors, protein kinase inhibitor isolated from rabbit muscle and isoquinolinesulfonamide, abolished the inward Na current which was elicited by cAMP.

Modification of the Na+,K+-pump of glial cells within cobalt-induced epileptogenic cortex of rat

Abstract The characteristics of a glial Na+,K+-pump dependent on extracellular K+ within epileptogenic cortex were studied electrophysiologically, biochemically and histochemically in vitro using slices from cobalt-induced epileptogenic cortex of rat. When the extracellular K+ concentration ([K+]o) was varied between 4 and 40 mM, the mean slope of membrane potential plotted against [K+]o was about 57 mV in glia from the normal cortex (tissue A) and about 44 mV in glia from the epileptogenic cortex (tissue B); whereas no significant difference in the resting membrane potential of these tissues was observed. In glia from tissue B, a marked transient hyperpolarization above control level was caused by replacement of elevated [K+]o with the normal medium. Ouabain abolished these phenomena observed in glia from tissue B, but had no effect on the membrane potential during normal [K+]o. Reduction of extracellular Na+, Ca2+ and Cl− did not significantly affect the membrane potential of glia from either tissue. In tissue A, the cells marked by intracellular injection of horseradish peroxidase after intracellular recording were protoplasmic astrocytes; in tissue B, fibrous astrocytes with abnormal processes predominated. K+-dependent stimulation of Na+,K+-ATPase activity of the astrocyte-enriched fraction and its membrane preparation from tissue B was much larger than that from tissue A. A certain amount of the reaction product of K+-pNPPase activity was seen on glial plasma membrane within tissue B but not on that from tissue A. The above findings suggest that a glial Na+,K+-pump within actively firing epileptogenic cortex may be modified to increase in its activity.

SLOW INDUCTION OF GELATINASE B mRNA BY ACIDIC CULTURE CONDITIONS IN MOUSE METASTATIC MELANOMA CELLS

Gelatinase B has been thought to be a key enzyme for degradation of extracellular matrix in tumour invasion and metastasis. In this study, we examined the effect of acidic culture medium (pH5.9) on the expression of gelatinase B mRNA in mouse metastatic melanoma cell line (B16‐F10). Using reverse transcription‐polymerase chain reaction (RT‐PCR) analysis, we found that gelatinase B was induced by the acidic culture medium at 24h, and then gradually diminished to 72h. By gelatin zymographic analysis, gelatinase B was first detected at 24h, continued to increase and then reached a plateau at around 48h. These results suggest that the induction of gelatinase B secretion by acidic culture medium occurs as a result of the gene expression.