Journal of medical and dental sciences
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We have proposed a concept that prolonged rhythmic gum chewing causes a suppressed nociceptive flexion reflex via the serotonergic (5-HT) descending inhibitory pathway. However, the mechanism of activation of the 5-HT system by gum chewing remains undetermined. Several human and animal studies have reported that a direct connection exists between the prefrontal cortex (PFC) and 5-HT neurons in the dorsal raphe nucleus; therefore, we hypothesized that activation of the PFC region might be responsible for augmented 5-HT activity. ⋯ A significant increase in oxyHb level was observed in the ventral part of PFC compared with the dorsal part of PFC. We confirmed the previous results in that the nociceptive flexion reflex was significantly suppressed and the 5-HT level in blood was significantly increased following prolonged gum chewing. These results support the hypothesis that activation of the ventral part of PFC during gum chewing evokes augmented activity of 5-HT neurons in the dorsal raphe nucleus, which in turn suppress nociceptive responses.
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Diffuse noxious inhibitory control (DNIC) is thought to be mediated by neural networks in supraspinal brain structures. The descending antinociceptive system (DAS) is an important component of the DNIC neural network, but the precise structure of the neural network and the related neurotransmitters have not been examined. ⋯ The results show that clinical doses of DEX and PE inhibit DNIC, thereby affecting and modulating the intrinsic pain inhibition system. These findings suggest that adrenergic neurons are involved in DNIC.
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A porous hydroxyapatite/collagen composite (HAp/Col) was developed that consists of hydroxyapatite nanocrystals and atelocollagen. In this study, cylindrical (diameter: 5 mm, height: 3 mm) porous HAp/Col implants with different pore sizes (diameter: 160 or 290 microm) were prepared, and the influences of pore size and implanted volume were evaluated using a rabbit bone defect model. In the implant groups, one or three (diameter: 5 mm, total height: 9 mm) implants were transplanted into bone holes created in the anteromedial site of the proximal tibiae, while a group without implantation was used as a control. ⋯ At twelve weeks, four implant groups showed repair of cortical defects and implant absorption, which was thought to be the result of natural bone remodeling mechanisms. The control group showed bone formation developed from the periosteum without bone induction in the marrow cavity, and at four weeks, the bone hole was almost healed. pQCT analysis revealed that the expansion rates of bone tissue were higher in the large-pore implant groups than in the small-pore groups. These data demonstrate the osteoconductivity of porous HAp/Col and the importance of its porous structure.
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People have the opportunity to inhale inorganic dusts under various environments. Inorganic dust exposures as a result of occupational exposure may induce or modulate pulmonary fibrosis. We analyzed the deposition of elements in lung tissues of patients with idiopathic pulmonary fibrosis (IPF) and compared element deposition with chronic hypersensitivity pneumonitis (chronic HP) and collagen vascular diseases (CVD). ⋯ The silicon (Si)/sulfur (S) ratio and aluminium (AI)/S ratio were increased in IPF independent of occupational exposure. A point elemental analysis showed that the major compound of the particles was aluminium-silicate in IPF. These results suggest that unrecognized dust exposures are relatively common in some IPF patients and aluminium-silicate could be associated with the disease process of IPF.
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To reveal roles of neurotrophic factors in plastic changes of the primary afferent neurons following nerve injury, we investigated expression of glial cell line-derived neurotrophic factor (GDNF) as well as nerve growth factor (NGF) in a neuropathic pain model of the rat. The rats exhibited hyperalgesia and allodynia on the injured left side for at least 2 weeks after chronic constrictive injury to the sciatic nerve. ⋯ In contrast, the amount of NGF in DRGs was unchanged in spite of disturbance of NGF transport in the nerve. The present results suggest that decreased expression of GDNF takes some part in development and/or maintenance of neuropathic pain.