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Biomedical subjects

Kiyoshi Koyano

Publications and source records attributed to Kiyoshi Koyano.

At least 19 recordsLinked to original sources
PubMed2006

Protein phosphatase regulation by PRIP, a PLC-related catalytically inactive protein--implications in the phospho-modulation of the GABAA receptor.

PRIP, phospholipase C related, but catalytically inactive protein was first identified as a novel inositol 1,4,5-trisphosphate binding protein. It has a number of binding partners including protein phosphatase (PP1 and 2A), GABAA receptor associated protein, and the beta subunits of GABAA receptors, in addition to inositol 1,4,5-trisphosphate. The identification of these molecules led us to examine the possible involvement of PRIP in the phospho-regulation of the beta subunits of GABAA receptors using hippocampal neurons prepared from PRIP-1 and 2 double knock-out (DKO) mice. Experiments were performed with special reference to the dephosphorylation processes of the beta subunits. The phosphorylation of beta3 subunits by the activation of protein kinase A in cortical neurons of the control mice continued for up to 5 min, even after washing out of the stimulus, followed by a gradual dephosphorylation. That of DKO mice gradually increased in spite of the lower phosphorylation levels induced by the stimulation. There was little difference in the amount of cellular cyclic AMP and protein kinase A activity between the control and mutant mice, indicating that phosphatases such as PP1 and PP2A are primarily involved in the difference. The time course of PP1 activity changes in the vicinity of the receptors in control mice corresponded to the phosphorylation of PRIP, while that of the mutant mice decreased with the period of the incubation. This is a good agreement with the suggestion that PRIP binds to and inactivates PP1, which is regulated by the phosphorylation of PRIP at threonine 94. These results suggest that PRIP plays an important role in controlling the dynamics of GABAA receptor phosphorylation by through PP1 binding and, therefore, the efficacy of synaptic inhibition mediated by these receptors.

Animals↗
PubMed2006

The contribution of platelet-derived growth factor, transforming growth factor-beta1, and insulin-like growth factor-I in platelet-rich plasma to the proliferation of osteoblast-like cells.

The aim of this study was to investigate the effect of platelet-rich plasma (PRP) on the proliferation of osteoblast-like cells in vitro. PRP was prepared using a centrifuge; the number of platelets (n = 32) and the levels of platelet-derived growth factor-AB (PDGF-AB), transforming growth factor-beta1 (TGF-beta1), and insulin-like growth factor-I (IGF-I) were measured (n = 16). For the proliferation assay, SaOS-2 was cultured in the presence of platelet-poor plasma (PPP), whole blood, or PRP. The cell number was counted after 36 and 72 hours. To investigate the effect of each growth factor, the cells were cultured with PRP in the absence or presence of neutralizing antibodies, and counted as described. The mean platelet count of PRP was 1546.36 +/- 382.25 x 10(3)/microL, and the mean levels of PDGF-AB, TGF-beta1 and IGF-I were 0.271 +/- 0.043, 0.190 +/- 0.039, and 0.110 +/- 0.039 ng/1500 x 10(3) platelets, respectively. Cell proliferation was enhanced in all PRP groups in a dose-dependent manner, and all neutralizing antibodies significantly suppressed proliferation compared with the PRP group, lacking antibody, at 36 hours. However, at 72 hours, the neutralizing antibodies of PDGF and TGF-beta1, but not IGF-I, significantly suppressed proliferation. These results show the beneficial abilities of PRP in the proliferation of osteoblast-like cells from the standpoint of growth factors, including the contribution of each factor.

Adult↗
PubMed2005

Type II/III Runx2/Cbfa1 is required for tooth germ development.

Runx2/Cbfa1 is an essential transcription factor for osteoblast differentiation and bone formation. Runx2/Cbfa1 knockout mice showed both a complete lack of ossification and the developmental arrest of tooth germ. We here report Runx2/Cbfa1 isoform-type specific functional roles in the development of tooth germ by the administration of antisense phosphorothioate oligodioxynucleotides (S-ODNs) into cultured mouse mandibles. The administration of type II/III Runx2/Cbfa1 antisense S-ODNs into the culture media resulted in an arrest of tooth germ growth at the bud-like stage in cultured mandible taken from the 11-day-old embryos, while also causing the inhibition of the differentiation of odontogenic cells into ameloblast and odontoblast in cultured tooth germs taken from the 15-day-old embryos. The expression of dentin matrix protein 1, dentin sialophosphoprotein, amelogenin, and ameloblastin was shown to be markedly suppressed in cultured tooth germ by the semi-quantitative RT-PCR. Meanwhile, no developmental arrest of tooth germ, no inhibition of gene expression, or differentiation of odontogenic cells was observed in samples treated with the type I Runx2/Cbfa1 antisense S-ODNs. The same findings were also observed in either the control or the sense and random sequence S-ODNs-treated samples. These data indicate that the type II/III Runx2/Cbfa1 isoform is closely related to the development and differentiation of tooth germ.

Animals↗
PubMed2005

The effect of platelet-rich plasma on the cellular response of rat bone marrow cells in vitro.

The aim of this study was to investigate the effect of platelet-rich plasma (PRP) on the proliferation and the differentiation of rat bone marrow cells (RBMCs). PRP, platelet-poor plasma (PPP), and bone marrow cells were derived from the rats (hearts and tibia) and the cells were cultured with or without PRP or PPP (0 [control]), 0.2 approximately 10 microL/mL). The proliferation of RBMCs was measured on days 2 and 4, and alkaline phosphatase (ALP) staining and activity measurement were evaluated to determine the effect of PRP on the differentiation on days 4 and 8. PRP enhanced the proliferation significantly compared to the control group (P < .05). These enhancements were greater than ones induced by the addition of PPP. ALP staining appeared to show that PRP decreased the number of ALP positive cells and ALP activity significantly (P < .05). Our results demonstrate that PRP stimulates the proliferation but suppresses the differentiation of RBMCs.

Alkaline Phosphatase↗
PubMed2005

Fabrication of hydroxyapatite block from gypsum block based on (NH4)2HPO4 treatment.

The aim of this study was to evaluate the feasibility of fabricating low-crystalline, porous apatite block using set gypsum as a precursor based on the fact that apatite is thermodynamically more stable than gypsum. When the set gypsum was immersed in 1 mol/L diammonium hydrogen phosphate aqueous solution at 100 degrees C, it transformed to low-crystalline porous apatite retaining its original shape. The transformation reaction caused a release of sulfate ions due to an ion exchange with phosphate ions, thus leading to a decrease in the pH of the solution. Then, due to decreased pH, dicalcium phosphate anhydrous--which has similar thermodynamic stability at lower pH--was also produced as a by-product. Apatite formed in the present method was low-crystalline, porous B-type carbonate apatite that contained approximately 0.5 wt% CO3, even though no carbonate sources--except carbon dioxide from air--were added to the reaction system. We concluded therefore that this is a useful bone filler fabrication method since B-type carbonate apatite is the biological apatite contained in bone.

Bone Substitutes↗
PubMed2004

Effect of the difference of bone turnover on peri-titanium implant osteogenesis in ovariectomized rats.

High and low bone turnover situations, both of which are typically observed as postmenopausal and senile osteoporosis, were created by ovariectomy (OVX), and then an investigation of whether or not the difference of bone turnover affected peri-titanium (Ti) implant osteogenesis in rats was conducted. Female rats were divided into four groups. The experimental and control groups underwent OVX or sham operations at 15 or 27 weeks of age, as high or low bone turnover groups, respectively. Ti implants were inserted into the tibiae at 30 weeks, then fluorochromes were injected 10 or 20 days after the implantation for histometry. The implants were retained for 30 days and then ground sections were prepared. Afterward, the cortical bone growth rate, bone contact ratio (BCR) of the implant in both the cortical bone area and medullary canal area, and the average trabecular bone thickness around the implant were evaluated. Biochemical markers of bone turnover were also measured. Biochemical measurements indicated both increasing osteocalcin production in OVX rats and decreasing tartrate-resistant acid phosphatase activity in the low-turnover group. Histometrical measurements showed decreasing cortical growth and low BCR in the medullary canal of the low-turnover group. The high-turnover group demonstrated BCR as high as that of the control group. There was no significant difference in the average trabecular bone thickness around the implant among the groups. As a result, two types of osteoporotic situations were confirmed and it was shown that the difference of bone turnover was clearly due to the diverse osteogenesis around the Ti implant.

Acid Phosphatase↗
PubMed2004

Simvastatin promotes osteogenesis around titanium implants.

OBJECTIVES: Hydroxymethylglutaryl-coenzyme A reductase inhibitors, the so-called statins, have been widely used for hyperlipidemic patients, and it was recently reported that it promoted bone formation. In the present study, we examined the effect of simvastatin on the promotion of osteogenesis around titanium implants. MATERIALS AND METHODS: Ten 30-week-old rats received pure titanium implants in both tibiae, and were then divided into experimental and control groups. The experimental group was administered simvastatin daily. Thirty days later, all animals were killed and then specimens were prepared. The bone contact ratio (BCR) to the implant and bone density (BD) around the implant, as well as histological findings, were obtained. RESULTS: In the control group, newly formed bone could be seen around the implants. It was seen to be in direct contact with the implant surface, but otherwise unmineralized connective tissue was occasionally interposed. In the medullary canal, a scanty amount of bone trabeculae was observed. In the experimental group, in contrast, thicker bone trabeculae were abundantly seen in the medullary canal and showed a mesh-like structure. In the histometrical observations, both BCR and BD of the experimental group were significantly greater than those of the control group. CONCLUSION: The administration of simvastatin increases the value of both BCR and BD. This drug may have the potential to improve the nature of osseointegration.

Animals↗
PubMed2003

Leptin modulates behavioral responses to sweet substances by influencing peripheral taste structures.

Leptin is a hormone that regulates body weight homeostasis mainly via the hypothalamic functional leptin receptor Ob-Rb. Recently, we proposed that the taste organ is a new peripheral target for leptin. Leptin selectively inhibits mouse taste cell responses to sweet substances and thereby may act as a sweet taste modulator. The present study further investigated leptin action on the taste system by examining expression of Ob-Rb in taste cells and behavioral responses to sweet substances in leptin-deficient ob/ob, and Ob-Rb-deficient db/db mice and their normal litter mates. RT-PCR analysis showed that Ob-Rb was expressed in taste cells in all strains tested. The db/db mice, however, had a RT-PCR product containing an abnormal db insertion that leads to an impaired shorter intracellular domain. In situ hybridization analysis showed that the hybridization signals for normal Ob-Rb mRNA were detected in taste cells in lean and ob/ob mice but not in db/db mice. Two different behavioral tests, one using sweet-bitter mixtures as taste stimuli and the other a conditioned taste aversion paradigm, demonstrated that responses to sucrose and saccharin were significantly decreased after ip injection of leptin in ob/ob and normal littermates, but not in db/db mice. These results suggest that leptin suppresses behavioral responses to sweet substances through its action on Ob-Rb in taste cells. Such taste modulation by leptin may be involved in regulation for food intake.

Animals↗
PubMed2003

Conditioned taste aversion learning in leptin-receptor-deficient db/db mice.

The db/db mouse has defective leptin receptors. The defects lead to impairments of leptin regulation of food intake and body weight, and result in the expression of diabetic symptoms such as hyperinsulinemia, hyperglicemia, and extreme obesity. Recent studies have proposed that leptin may also affect memory and learning processes. To examine this possibility, we compared the ability of leptin-receptor-deficient db/db mice and their normal lean litter mates to form and extinguish a conditioned taste aversion (CTA) for saccharin. We used a short-term (10 s) lick test and a long-term (48 h) two bottle preference test for measurement of consumption of test solutions. On the first day after conditioning to avoid saccharin, the db/db mice showed preference scores for saccharin as low, and aversion thresholds for sucrose lower than that of the lean mice. During the extinction test trials beginning from the second up to the 30th day after conditioning, numbers of licks and preference scores for aversive saccharin and sucrose appeared to be larger, and recovered faster to the control levels in db/db mice. These results indicate that db/db mice with leptin-receptor-deficiency may show equal capacity to form CTAs for saccharin, greater generalization from saccharin to sucrose, and a faster rate of extinction. This suggests that disruption of leptin signalling does not inhibit acquisition of CTA learning, but impairs its extinction. This differential contribution of the leptin system on CTA processes may be due to differential distribution of leptin receptors in the CTA-related brain areas.

Animals↗
PubMed2003

Experimental and numerical investigations of axisymmetric wave propagation in cylindrical pipe filled with fluid.

Acoustic wave propagation in fluid-filled cylindrical pipe with arbitrary thickness is investigated numerically and experimentally. The vibrational properties of the coupled fluid-pipe system are evaluated by a layerwise approach, which is similar to the finite-strip method. In this approach, the thick cylindrical wall is divided into a number of thin cylindrical layers in the thickness direction. The displacements in the thickness direction for each layer are approximated by linear-shape functions. The governing equation is obtained by using an energy minimization principle. The dispersion curves, distribution of vibrational energy between pipe wall and contained fluid, and displacement fields are examined. The dependence of the dispersion curves on wall thickness is discussed. Two PZT ring transducers adhered to the outer surface of pipe are used as source and receiver, respectively. The propagating waves generated by burst signals are measured. To localize transient signal both in time and frequency domains, the discrete wavelet transform is applied to decomposing the receiving signal into several components. Each component is limited to a narrower bandwidth. Therefore the frequency-dependent group velocity is estimated. The experimental and numerical results are compared.

Journal Article↗
PubMed2002

Reperfusion response changes induced by repeated, sustained contractions in normal human masseter muscle.

The purpose was to evaluate the intramuscular reperfusion response characteristics associated with repeated isometric contractions in normal human masseter. Intramuscular blood volume was quantified with a near-infrared spectroscopic device that measured the total haemoglobin (Hb) concentration in the muscle. Electromyographic (EMG) activity from the masseter and total bite forces were also recorded. Sixteen healthy volunteers, eight females and eight males, without masticatory muscle pain participated. They were asked first to clench their teeth for as long as possible at 50% of their maximum voluntary contraction (MVC). This was followed by a 60s rest and then immediately by a standard clenching task (50% MVC for 30s) and a 60s recovery period, immediately after which they were asked to repeat exactly the same procedure, with a final 5 min recovery period after the second 30s contraction. Bite force, EMG and Hb concentration were measured continuously and the duration of the two endurance tasks and the amplitudes of all recorded signals were compared (first trial versus second trial). Specifically, the difference between the lowest Hb (trough) seen during the standardised 30s contractions and the highest (peak) seen just after them was assessed. The trough-to-peak difference in Hb concentration of the second standard contraction task was significantly smaller than that of the first standard task (P<0.05, paired t-test). These data show that with sustained effort the post-contraction vasodilatory reperfusion responses of the human masseter are diminished, suggesting a progressive desensitisation of the vasodilatory system.

Adult↗
PubMed2002

Difference in penetration of horseradish peroxidase tracer as a foreign substance into the peri-implant or junctional epithelium of rat gingivae.

Horseradish peroxidase (HRP) tracer was applied to the gingival sulcus of implants or natural teeth at 5, 25, or 50 mg/ml to investigate the sealing capacities of the peri-implant epithelium (PIE) and junctional epithelium (JE); the extent of HRP penetration was observed under electron microscopy. A Ti-6Al-4V implant was inserted either immediately (immediate implantation) or 2 weeks (delayed implantation) after extraction of the maxillary left first molar of rats. The JE of the right molar was used as a control. Although the whole PIE of undecalcified sections appeared to be attached to the implant surface, electron microscopically, the internal basement lamina (IBL) and hemidesmosomes were deficient in the coronal-middle region of the PIE. There were extensive extracellular deposits of HRP in the intercellular spaces between PIE cells, and HRP was blocked to some extent by the lamina lucida and lamina densa of the external basal lamina and basal cell junction. HRP was detected in the connective tissue under the PIE, but was not found in the connective tissue under the JE. Intracellularly, HRP was found in the vesicles and granules of PIE cells and JE cells. These were fewer in number in PIE cells than in JE cells. There were no differences between the findings for immediate and delayed implantation. The results indicate that a deficiency in the IBL permitted penetration of HRP from the gingival sulcus into the connective tissue under the PIE, and suggest that the endocytotic capacity of PIE cells is inferior to that of JE cells.

Alloys↗
PubMed2002

A study of the initial attachment and subsequent behavior of rat oral epithelial cells cultured on titanium.

BACKGROUND: The seal between an implant and the oral epithelium is an important factor for successful implant therapy. The purpose of this study was to evaluate the initial attachment and subsequent behavior of rat oral epithelial (OE) cells on pure titanium (Ti) used for dental implants. METHODS: OE cells derived from 4-day-old rats were cultured on Ti, polystyrene culture dishes, and glass coverslips. The number of attached cells, cell areas, number of colonies, and proliferation rates were measured. Additionally, immunostaining of vinculin and laminin-5 (LN5) was performed, and LN5-immunoreactive areas were measured. RESULTS: After 24 hours of culture, there were fewer cells attached to the Ti than to the polystyrene dishes or glass coverslips, and the area of cells was greater on the polystyrene than on the Ti or glass. OE cells reached their maximum proliferation rate after 48 hours of culture on the polystyrene and glass, and after 72 hours on Ti. LN5 was deposited behind cells as they migrated, and the LN5-immunoreactive area was smaller on Ti than on polystyrene after 96 hours of culture. CONCLUSIONS: The initial attachment of OE cells to Ti was inferior to that on polystyrene or glass, and the OE cell migration area indicated by the deposition of LN5 was smaller on Ti than on the other materials. Therefore, this study suggests that further improvement of Ti surface properties is needed for rapid attachment and spreading of oral epithelium to dental implants.

Analysis of Variance↗
PubMedDate not supplied

In situ expression of heat shock proteins, Hsc73, Hsj2 and Hsp86 in the developing tooth germ of mouse lower first molar.

This study examined the detailed gene expression pattern of three different heat shock proteins (HSPs), Hsc73, Hsj2, and Hsp86, by means of an in situ hybridization method. Hsc73, Hsj2, and Hsp86 were shown in our previous study to be differentially expressed in the mouse embryonic mandible at day 10.5 (E10.5) gestational age. These HSP genes showed similar expression patterns during development of the mouse lower first molar. HSPs-expressing cells were widely distributed in both the epithelial and underlying ectomesenchymal cells at E10.5, and then were slightly localized at E12 in an area where the tooth germ of the lower first molar is estimated to be formed. A strong expression of HSPs was observed in the tooth germ at E13.5. At the cap stage, HSPs were expressed in the enamel organ and dental papilla. At the bell stage, HSPs were distinctly expressed in the inner enamel epithelium and dental papilla cells facing the inner enamel epithelial layer, which later differentiate into ameloblasts and odontoblasts, respectively. This study is the first report in which Hsc73, Hsj2, and Hsp86 were distinctly expressed in the developing tooth germ, thus suggesting these HSPs are related to the development and differentiation of odontogenic cells.

Animals↗
PubMedDate not supplied

In vitro study of a mandibular implant overdenture retained with ball, magnet, or bar attachments: comparison of load transfer and denture stability.

PURPOSE: When implants are used to support a removable overdenture, the optimal stress distribution to minimize both forces on the implants and denture movement is desirable. This study compared the stress patterns generated around implants and denture movement among three retention systems. MATERIALS AND METHODS: Two root-form implants were anchored in a mandibular model made of resin, and a removable overdenture on which all experiments were performed was fabricated. The surface of the model was covered with a layer of impression material to simulate oral mucosa. Ball/ O-ring, bar/clip, and magnetic attachments were used. A vertical force was applied to the left first molar and gradually increased from 0 to 50 N in 5-N steps. The resultant stress distribution and denture movement were evaluated. RESULTS: The ball/O-ring attachment transferred the least stress to both implants and produced less bending moment than the bar/clip attachment. Vertical force applied to the bar/clip attachment created immediate stress patterns of greater magnitude and concentration on both implants. CONCLUSION: This in vitro study suggested that the use of the ball/O-ring attachment could be advantageous for implant-supported overdentures with regard to optimizing stress and minimizing denture movement.

Analysis of Variance↗