Reduced Mastication Impairs Memory Function

Mastication is an indispensable oral function related to physical, mental, and social health throughout life. The elderly tend to have a masticatory dysfunction due to tooth loss and fragility in the masticatory muscles with aging, potentially resulting in impaired cognitive function. Masticatory stimulation has influence on the development of the central nervous system (CNS) as well as the growth of maxillofacial tissue in children. Although the relationship between mastication and cognitive function is potentially important in the growth period, the cellular and molecular mechanisms have not been sufficiently elucidated. Here, we show that the reduced mastication resulted in impaired spatial memory and learning function owing to the morphological change and decreased activity in the hippocampus. We used an in vivo model for reduced masticatory stimuli, in which juvenile mice were fed with powder diet and found that masticatory stimulation during the growth period positively regulated long-term spatial memory to promote cognitive function. The functional linkage between mastication and brain was validated by the decrease in neurons, neurogenesis, neuronal activity, and brain-derived neurotrophic factor (BDNF) expression in the hippocampus. These findings taken together provide in vivo evidence for a functional linkage between mastication and cognitive function in the growth period, suggesting a need for novel therapeutic strategies in masticatory function-related cognitive dysfunction.

Activation of phosphoipase D by platelet-derived growth factor (PDGF) in rat C6 glioma cells: Possible role in mitogenic signal transduction

The effects of platelet-derived growth factor (PDGF) on phospholipase D (PLD) activity and deoxyribonucleic acid (DNA) synthesis in rat C6 glioma cells have been investigated. Pretreatment of serum-starved C6 cells with PDGF results in enhanced choline production and the phosphatidylethanol (PEt) formation in the presence of ethanol, indicating the activation of PLD acting on phosphatidylcholine (PC). The dose-response curve for choline generation and DNA synthesis were comparable. In addition, the effects of PDGF on both PEt formation and [3H]thymidine incorporation into acid-precipitable material was blocked by the potent protein kinase C (PKC) inhibitor 1-(5-isoquinolinesulphonyl)-2-methylpiperazine (H-7) but not by N-(2-guanidinoethyl)-5-isoquinolinesulphonamide (HA1004), a relatively weak inhibitor of PKC, suggesting that PDGF plays an important role as a positive regulator of glioma cell growth via a PLD-mediated mitogenic signal transduction cascades, which depends largely on the activation of PKC.

Enhanced Anti-tumour Effect of Cisplatin with Low-voltage Electrochemotherapy in Hamster Oral Fibrosarcoma

The aim of this study was to determine the effects of low-voltage electrochemotherapy with intraperitoneal cisplatin on hamster oral fibrosarcoma. Oral fibrosarcoma was transplanted sub-mucosally into the cheek pouch mucosa of 100 hamsters. After transplantation, the hamsters were randomly divided into four equal groups. These groups received no treatment (D-E-); 2 mg/kg body weight cisplatin treatment without electroporation (D+E-); electroporation without cisplatin treatment (D-E+);or 2 mg/kg body weight cisplatin treatment followed by electroporation (D+E+). Electrical pulse treatment together with cisplatin injection markedly reduced the size of the tumour, whereas cisplatin injection or electrical pulse treatment alone did not. These results clearly indicate that the anti-tumour effect of cisplatin on hamster oral fibrosarcoma was considerably potentiated or enhanced by the administration of local electrical pulses at low voltages.

Nucleus ^{26}O: A Barely Unbound System beyond the Drip Line

The unbound nucleus ^{26}O has been investigated using invariant-mass spectroscopy following one-proton removal reaction from a ^{27}F beam at 201  MeV/nucleon. The decay products, ^{24}O and two neutrons, were detected in coincidence using the newly commissioned SAMURAI spectrometer at the RIKEN Radioactive Isotope Beam Factory. The ^{26}O ground-state resonance was found to lie only 18±3(stat)±4(syst)  keV above threshold. In addition, a higher lying level, which is most likely the first 2^{+} state, was observed for the first time at 1.28_{-0.08}^{+0.11}  MeV above threshold. Comparison with theoretical predictions suggests that three-nucleon forces, pf-shell intruder configurations, and the continuum are key elements to understanding the structure of the most neutron-rich oxygen isotopes beyond the drip line.

Electrospray droplet impact secondary ion mass spectrometry using a vacuum electrospray source

RATIONALE

In electrospray droplet impact (EDI) developed in our laboratory, an atmospheric pressure electrospray source has been used. To increase the ion beam intensity and reduce the evacuation load, a vacuum electrospray cluster ion source using a silica capillary was developed.

METHODS

A silica capillary with a tip inner diameter of 8 µm was used for vacuum electrospray using aqueous 10% methanol. To stabilize the flow rate of the liquid for nano-electrospray, a home-made constant pressure liquid pump was also developed.

RESULTS

By using the silica tip nano-electrospray emitter and a constant pressure pump, stable electrospray with flow rate of 22 nL/min was realized without using any heating system such as laser irradiation. Comparative study of mass spectra obtained by atmospheric pressure EDI (A-EDI) and vacuum EDI (V-EDI) was made for various samples such as thermometer molecule, peptide, polystyrene, Alq(3), NPD, C(60), indium, and SiO(2). V-EDI showed slightly milder ionization than A-EDI.

CONCLUSIONS

Because V-EDI gave higher target current (5-10 nA) than A-EDI (a few nA at most), V-EDI secondary ion mass spectrometry (SIMS) would be a useful technique for the surface and interface analysis.