A Subtype of Olfactory Bulb Interneurons Is Required for Odor Detection and Discrimination Behaviors.

UNLABELLED: Neural circuits that undergo reorganization by newborn interneurons in the olfactory bulb (OB) are necessary for odor detection and discrimination, olfactory memory, and innate olfactory responses, including predator avoidance and sexual behaviors. The OB possesses many interneurons, including various types of granule cells (GCs); however, the contribution that each type of interneuron makes to olfactory behavioral control remains unknown. Here, we investigated the in vivo functional role of oncofetal trophoblast glycoprotein 5T4, a regulator for dendritic arborization of 5T4-expressing GCs (5T4 GCs), the level of which is reduced in the OB of 5T4 knock-out (KO) mice. Electrophysiological recordings with acute OB slices indicated that external tufted cells (ETCs) can be divided into two types, bursting and nonbursting. Optogenetic stimulation of 5T4 GCs revealed their connection to both bursting and nonbursting ETCs, as well as to mitral cells (MCs). Interestingly, nonbursting ETCs received fewer inhibitory inputs from GCs in 5T4 KO mice than from those in wild-type (WT) mice, whereas bursting ETCs and MCs received similar inputs in both mice. Furthermore, 5T4 GCs received significantly fewer excitatory inputs in 5T4 KO mice. Remarkably, in olfactory behavior tests, 5T4 KO mice had higher odor detection thresholds than the WT, as well as defects in odor discrimination learning. Therefore, the loss of 5T4 attenuates inhibitory inputs from 5T4 GCs to nonbursting ETCs and excitatory inputs to 5T4 GCs, contributing to disturbances in olfactory behavior. Our novel findings suggest that, among the various types of OB interneurons, the 5T4 GC subtype is required for odor detection and discrimination behaviors. SIGNIFICANCE STATEMENT: Neuronal circuits in the brain include glutamatergic principal neurons and GABAergic interneurons. Although the latter is a minority cell type, they are vital for normal brain function because they regulate the activity of principal neurons. If interneuron function is impaired, brain function may be damaged, leading to behavior disorder. The olfactory bulb (OB) possesses various types of interneurons, including granule cells (GCs); however, the contribution that each type of interneuron makes to the control of olfactory behavior remains unknown. Here, we analyzed electrophysiologically and behaviorally the function of oncofetal trophoblast glycoprotein 5T4, a regulator for dendritic branching in OB GCs. We found that, among the various types of OB interneuron, the 5T4 GC subtype is required for odor detection and odor discrimination behaviors.

Elemental distributions and microtensile bond strength of the adhesive interface to normal and caries-affected dentin.

The aim of this study was to evaluate the microtensile bond strength (microTBS) and the elemental contents of the adhesive interface created to normal versus caries-affected dentin. Extracted human molars with coronal carious lesions were used in this study. A self-etching primer/adhesive system (Clearfil Protect Bond) was applied to flat dentin surfaces with normal and caries-affected dentin according to the manufacturer's instructions. After 24 h water storage, the bonded specimens were cross-sectioned and subjected to a microTBS test and electron probe microanalysis for the elemental distributions [calcium (Ca), phosphorus (P), magnesium (Mg), and nitrogen (N)] of the resin-dentin interface after gold sputter-coating. The microTBS to caries-affected dentin was lower than that of normal dentin. The demineralized zone of the caries-affected dentin-resin interface was thicker than that of normal dentin (approximately 3 microm thick in normal dentin; 8 microm thick in caries-affected dentin), and Ca and P in both types of dentin gradually increased from the interface to the underlying dentin. The caries-affected dentin had lost most of its Mg content. The distributions of the minerals, Ca, P, and Mg, at the adhesive interface to caries-affected dentin were different from normal dentin. Moreover, a N peak, which was considered to be the collagen-rich zone resulting from incomplete resin infiltration of exposed collagen, was observed to be thicker within the demineralized zone of caries-affected dentin compared with normal dentin.

Evaluation of in vitro secondary caries using confocal laser scanning microscope and X-ray analytical microscope.

PURPOSE: To evaluate in vitro secondary caries formation and inhibition by using a confocal laser scanning microscope (CLSM), and further map the calcium distribution with an X-ray analytical microscope (XAM). MATERIALS AND METHODS: 36 box-shaped cavities were prepared on bovine root dentin and restored with Fuji II, Fuji II LC (improved), or Clearfil Liner Bond 2V system with a non-fluoride releasing resin-based composite; Clearfil AP-X was used as a negative control. After immersion in a buffered demineralizing solution of 50 mmol/L of acetic acid adjusted to pH 4.5 for 3.5 days, longitudinal half sections were cut through each restoration and polished for analysis under CLSM. In order to confirm the CLSM results, the same samples were subsequently examined by means of the X-ray analytical microscope (XAM). The values of the outer lesions and the inhibition zones obtained by the two different CLSM and XAM measurements were then analyzed by one-way ANOVA, Fisher's PLSD Test at the 95% level of confidence and correlation coefficient. RESULTS: Inhibition zones and outer lesions were clearly detected under CLSM around the glass-ionomer and resin-modified glass-ionomer restorations. As expected, an inhibition zone was not detected adjacent to the resin-based composite restoration. Additionally, using the transmission x-ray images of XAM, the inhibition zones were observed as high density areas, and the outer lesions as low density areas. The width of the inhibition zones and the depth of the outer lesions measured under the CLSM were similar to those obtained from the XAM.

The durability of a fluoride-releasing resin adhesive system to dentin.

The durability of a fluoride-free (SE Bond) and a fluoride-containing (KBF) self-etching primer/ adhesive system were compared by measuring the microtensile bond strengths (microTBS) of these adhesive systems to human dentin in vitro. After bonding, the restored teeth were serially sectioned into multiple slabs that were trimmed to a 1 mm2 cross-sectional area at the bonded interface. For the three and six month specimens, half were fully covered with nail varnish (SE+, KBF+), while the other half were incubated at 37 degrees C in water without any protective varnish (SE-, KBF-). The microTBS of the one-day specimens were 44.6 +/- 11.2 MPa for SE Bond and 39.8 +/- 8.0 MPa for KBF (p > 0.05). When unprotected specimens were incubated in water for three and six months, the microTBS fell to 26.3 +/- 8.8 MPa and 23.6 +/- 10.7 MPa for SE-, respectively, but did not change in the specimens protected with nail varnish (SE+, 41.9 +/- 12.8 MPa and 41.8 +/- 9.8 MPa, respectively). In contrast, in specimens bonded with a fluoride-containing resin, KBF, the bond strengths of the unprotected specimens did not change over three and six months KBF-. Values were 32.4 +/- 6.1 MPa and 36.8 +/- 2.3 MPa, respectively. Similarly, varnish-protected KBF+ specimens did not change over three and six months (39.3 +/- 13.6 MPa and 40.9 +/- 14.7 MPa, respectively). The results indicate that decreases in bond strength over six months' storage are water-dependent but can be prevented by using fluoride-containing resins.

[Non-randomized clinical study comparing chemotherapy plus radiotherapy with radiotherapy alone in neoadjuvant therapy for oral cancer].

Neoadjuvant therapy plays an important role for organ preservation and survival rate in the treatment of oral cancer. We clinically compared the effect of neoadjuvant radiotherapy and chemoradiotherapy in patients with oral cancer. We retrospectively examined 47 patients diagnosed with oral squamous cell carcinoma who underwent neoadjuvant therapy followed by curative surgery in the oral and maxillofacial surgery department of Ehime University Hospital. We divided them into two groups: radiotherapy alone (24 cases) and chemoradiotherapy (23 cases). The patients in the radiotherapy group underwent irradiation of 32.6 +/- 5.0 Gy (mean +/- SD). The patients in the chemoradiotherapy group received a low-dose fraction of cisplatin (8 mg/mm2/day, 5 days a week; total dose: 139.4 +/- 67.1 mg) and 5-fluorouracil (300 mg/mm2/day, 5 days a week; total dose: 5,900 +/- 1,839.8 mg) combined with simultaneous irradiation of 31.0 +/- 3.2 Gy. None of the 24 patients had a complete response to radiotherapy alone and 12 (50%) had a partial response. Six (26%) of the 23 patients had a complete response to chemoradiotherapy and 12 (52%) had a partial response. The primary control rate (82.6%) to chemoradiotherapy was higher than that (67.5%) to radiotherapy alone although no significant difference was found. The 5-year survival rate was 64.3% in the radiotherapy group and 62.8% in the chemoradiotherapy group. The findings of the present study suggest that while the combination of radiation and cisplatin/5-fluorouracil in neoadjuvant therapy for oral cancer may not bring a significant benefit to improve survival rate, the primary local control rate is improved in comparison with radiotherapy alone.

Long-term durability of resin dentin interface: nanoleakage vs. microtensile bond strength.

This study tested the hypothesis that long-term durability of resin bonds to dentin is directly related to the nanoleakage of dentin bonding systems. Extracted human third molars were ground flat with 600-grit SiC paper under running water to expose middle dentin. Clearfil Liner Bond 2V (LB2V) or Fluoro Bond (FB) was applied to dentin surfaces according to the manufacturer's instructions. A crown was built-up with Clearfil AP-X resin composite, and the specimens were stored in water for 24 hours at 37 degrees C. The bonded assemblies were vertically sectioned into approximately 0.7 mm thick slabs and trimmed for microtensile bond test. All slabs were immersed in individual bottles of water at 37 degrees C, which was changed every day. Specimens were incubated for one day, and three, six, and nine months, and at the specified time period, they were randomly divided to two subgroups: 50% AgNO3 and the control. In the 50% AgNO3 subgroup, the slabs were immersed for one hour in 50% AgNO3, followed by exposure in a photo-developing solution for 12 hours just prior to debonding. The specimens in the control subgroup were soaked in water until debonding. Then, all specimens were subjected to microtensile bond testing. The debonded specimens of the AgNO3 subgroup had micrographs subjected to image analysis by NIH Image PC (Scion, Fredrick, MD, USA), and the area of silver penetration was quantitated. The bond strength data and silver penetration areas were subjected to two- and three-way ANOVA and Fisher's PLSD test at the 95% level of confidence. Regression analysis was used to test the relationship between bond strengths and the silver penetration area at each time period. For both adhesive systems, the bond strengths gradually decreased over time, although there were no statistically significant differences in the FB bond strength among the four time periods tested (p>0.05). Silver penetration in specimens bonded with LB2V and FB gradually increased over time. Regression analysis showed a higher correlation between bond strength and silver penetration at 9 months for specimens bonded with LB2V (R2=0.844) than at shorter time periods. The authors speculate that hydrolytic degradation within the hybrid layer gradually increased due to water penetration through nanoleakage channels, resulting in lower bond strengths and interfacial failure after as little as nine months.