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Naoki Sasaki

Publications and source records attributed to Naoki Sasaki.

16 recordsLinked to original sources
PubMed2006

Hydrodynamic properties of DNA and DNA-lipid complex in an elongational flow field.

The aim of this study was to determine the difference between hydrodynamic properties of DNA-cetyltrimethylammonium (CTA) complex and those of DNA, which may be related to the difference in fibre-forming ability of DNA-CTA from that of DNA. Responses of DNA and DNA-CTA complex to an elongational flow field were investigated. In both solution systems, results suggesting a coil-stretch transition were obtained. From a critical strain rate value, the radius of gyration of DNA-CTA molecules in ethanol-glycerol solution was revealed to be 0.3-0.5 times of that of DNA in aqueous NaCl solution. Shear viscosity of DNA-CTA solution was much smaller than that of DNA solution, also suggesting a smaller size of DNA-CTA in ethanol-glycerol solution than that of DNA in aqueous NaCl solution. The plateau birefringence value of the DNA-CTA system, a parameter that indicates the local molecular conformation and the molecular arrangement, was only about 1/10 of that of the DNA system. There is an empirically determined molecular model of DNA-CTA complex in which a DNA molecule is sheathed by a cylindrical crust made of CTA chains. This structure reduces the DNA molecular density in a pure elongational flow field region but cannot explain the observed reduction of birefringence intensity. The small plateau birefringence value of DNA-CTA compared with that of DNA was attributed to the reduced molecular polarizability by the particular conformation of DNA molecules and CTA chains in the DNA-CTA system such as that expected by the conformational models.

Animals↗
PubMed2006

AC electroosmotic micromixer for chemical processing in a microchannel.

A rapid micromixer of fluids in a microchannel is presented. The mixer uses AC electroosmotic flow, which is induced by applying an AC voltage to a pair of coplanar meandering electrodes configured in parallel to the channel. To demonstrate performance of the mixer, dilution experiments were conducted using a dye solution in a channel of 120 microm width. Rapid mixing was observed for flow velocity up to 12 mm s(-1). The mixing time was 0.18 s, which was 20-fold faster than that of diffusional mixing without an additional mixing mechanism. Compared with the performance of reported micromixers, the present mixer worked with a shorter mixing length, particularly at low Peclet numbers (Pe < 2 x 10(3)).

Diffusion↗
PubMed2006

A method on strain measurement of HAP in cortical bone from diffusive profile of X-ray diffraction.

Bone tissue is a composite material composed of hydroxyapatite (HAp) and collagen matrix. As HAp is a crystalline structure, an X-ray diffraction method is available to measure the lattice strain of HAp crystals. However, mineral particles of HAp in bone have much lower crystallinity than usual crystalline materials, which show a diffusive intensity profile of X-ray diffraction. It is not easy to determine quantitatively an infinitesimal strain of HAp from the peak position of diffusive profile. In order to improve the accuracy of strain measurement of HAp in bone tissue and to obtain reproducible results, this paper proposes an X-ray diffraction method applied to a diffusive profile for low crystallinity. This method is to estimate the lattice strain of HAp using not a peak position but a whole diffraction profile. In this experiment, a strip specimen of 28 x 8 x 2 mm was made from bone axial, outside circumferential and cross-sectional circumferential region in the cortical bone of bovine femur. The X-ray diffraction measurements were carried out before and after applying an external load. As a result, the precision of strain measurement was much improved by this method. Although a constant value of macroscopic strain was applied in the specimen, the lattice strain had a lower value than the macroscopic strain and had a different value in each specimen.

Animals↗
PubMed2006

Practical tips for modified dorsolumbar epidural anesthesia in cattle.

Segmental dorsolumbar epidural anesthesia has been considered difficult to perform. The purpose of this study was to determine whether or not it is difficult for beginners to learn how to do modified dorsolumbar epidural anesthesia of cattle. Thirty cattle were divided into two groups, young (n = 8) and adult (n = 22), according to their age and body weight, and 0.12% new methylene blue (NMB) was injected into the first interlumbar (L1.L2) epidural space by four fifth-year veterinary school students who had never performed this method. After a 1 hour lecture on the modified dorsolumbar epidural anesthesia procedure which included basic anatomy and skills, each student successfully performed the procedure. In the young group, the NMB solution was distributed between the periosteum and the epidural fat (BPF) in one half and between the epidural fat and the dura mater (BFD) in the other half of the cattle. In about 60% (13/22) of the adult group, the NMB solution distributed as BFD type. This study showed that the modified dorsolumbar epidural anesthesia procedure is easy for beginners to perform if they overcome their fear about the deeper insertion of the epidural needle with basic anatomical knowledge and a little experience.

Age Factors↗
PubMed2006

Mathematical description of stress relaxation of bovine femoral cortical bone.

In 1993 we proposed an empirical formula for describing the relaxation modulus of cortical bone based on the results of stress relaxation experiments performed for 1 x 10(5) sec: [E(t) = E0{A exp[ -(t/tau1)beta] + (1 - A) exp(-t/tau2)}, (0 < A, beta <1 and tau1 << tau2) where E0 is the initial value of the relaxation modulus, A is the portion of the first term, tau1 and tau2 are characteristic relaxation times, and beta is a shape factor [Sasaki et al., J. Biomechanics 26 (1993), 1369]. Although the relaxation properties of bone under various external conditions were described well by the above equation, recent experimental results have indicated some limitations in its application. In order to construct an empirical formula for the relaxation modulus of cortical bone that has a high degree of completeness, stress relaxation experiments were performed for 6 x 10(5) seconds. The second term in the equation was determined as an apparently linear portion in a log E(t) vs t plot at t>1 x 10(4) sec. The same plot for experiments performed for 6 x 10(5) seconds revealed that the linear portion corresponding to the second term was in fact a curve with a large radius of curvature. On the basis of this fact, we proposed a second improved empirical equation E(t) = E0{A exp [ -(t/tau1)beta] + (1 - A) exp[-(t/tau2)gamma]}, (0<A, beta, gamma <1) to describe the stress relaxation of cortical bone. The early stage of the stress relaxation process, which could not be expressed by the first, is well described by the second equation.

Animals↗
PubMed2005

Use of 13C-acetate breath test for assessment of gastric emptying in horses.

This study aimed to establish and standardize a breath test that uses 13C-acetate in a liquid diet for evaluation of gastric emptying in horses. Seven adult healthy thoroughbreds were used in this study. They were given 13C-acetate (125 mg, 250 mg, or 500 mg) in a test meal (2000 ml liquid diet) via an intranasal catheter. 13C concentrations in the exhaled CO2 were measured in samples taken before and after test meal administration using an infrared absorption spectroscope. In the 500 mg 13C-acetate group, Delta13CO2 showed a steep gradient immediately after meal administration compared to the 125 mg and 250 mg groups. Therefore, t(max) in the 500 mg group was easier to determine than in the 125 mg and 250 mg groups. In the 500 mg group, GEC, half-empty time (t1/2), calculated t(max) (t(lag)), and t(max) were 1.95 +/- 0.28 (mean +/- SD), 229.2 +/- 57.0 (min), 139.2 +/- 22.2 (min), and 124.0 +/- 28.4, respectively. Differences in CV observed in the 500 mg group were lower than those in the 125 mg and 250 mg groups. This study demonstrates that the 13C-acetate breath test is useful for evaluating gastric emptying in horses since it is non-invasive and does not require set up of special facilities or equipment. Optimum evaluation of gastric emptying in horses can be achieved with 500 mg of 13C-acetate given in a liquid diet.

Acetates↗
PubMed2005

Effects of mosapride, a 5-hydroxytryptamine 4 receptor agonist, on electrical activity of the small intestine and cecum in horses.

OBJECTIVE: To examine the effects of various doses of mosapride, a 5-hydroxytryptamine 4 receptor agonist, on motility of the small intestine and cecum in horses by use of electrical activity and to determine the dose that provides the optimal response. ANIMAL: 6 healthy adult Thoroughbreds. PROCEDURE: Electrical activity of the small intestine and cecum was recorded before and after mosapride administration by use of an electrogastrograph. Mosapride (0.5, 1, 1.5, and 2 mg/kg) was dissolved in 200 mL of water and administered orally to horses through a nasogastric tube. Three hours after drug administration, mean amplitude of electrical activity calculated for a period of 30 minutes was expressed as the percentage of the mean amplitude of electrical activity for a period of 30 minutes before drug administration. RESULTS: Mosapride administered orally increased the percentage of the mean amplitude of electrical activity in the small intestine and cecum in a dose-dependent manner. Mean +/- SD values differed significantly for 1, 1.5, and 2 mg/kg (127.0 +/- 12.5%, 137.7 +/- 22.2%, and 151.1 +/- 24.0%, respectively) in the small intestine and for 1.5 and 2 mg/kg (130.1 +/- 34.5% and 151.6 +/- 45.2%, respectively) in the cecum. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of results of this study clearly documents that mosapride promotes motility in the small intestine and cecum of horses and that the optimal orally administered dosage is 1.5 to 2 mg/kg. Therefore, mosapride may be useful for treatment of horses with gastrointestinal tract dysfunction.

Animals↗
PubMed2004

Memory effect in the chain-collapse process in a dilute polymer solution.

The effect of temperature perturbation on a single-chain-collapse process was studied for poly(methyl methacrylate) with the molecular weight M(w)=1.05 x 10(7) in the mixed solvent of tert-butyl alcohol+water (2.5 vol %). In the chain-collapse process after a quench from the theta; temperature to a temperature T(1), the temperature was changed from T(1) to T(2) at the time t(1) after the quench and returned to T(1) at the time t(1)+t(2). In the three stages at T(1), T(2), and T(1), measurements of the mean-square radius of gyration of polymer chains were carried out by static light scattering and the chain-collapse process was represented by the expansion factor as a function of time. An effect of chain aggregation on the measurements was negligibly small because of the very slow phase separation. For the negative temperature perturbation (T(1)>T(2)), the chain-collapse processes observed in the first and third stages were connected smoothly and agreed with the collapse process due to a single-stage quench to T(1). A memory of the chain collapse in the first stage at T(1) was found to persist into the third stage at the same temperature T(1) without being affected by the temperature perturbation of T(2) during t(2). The memory effect was observed irrespective of the time period of t(2). The positive temperature perturbation (T(1)<T(2)) showed an acceleration of the chain-collapse process.

Journal Article↗
PubMed2004

Anisotropic viscoelastic properties of cortical bone.

Relaxation Young's modulus of cortical bone was investigated for two different directions with respect to the longitudinal axis of bone (bone axis, BA): the modulus parallel (P) and normal (N) to the BA. The relaxation modulus was analyzed by fitting to the empirical equation previously proposed for cortical bones, i.e., a linear combination of two Kohlraush-Williams-Watts (KWW) functions (Iyo et al., 2003. Biorheology, submitted): E(t)=E0 (A1 exp[-(t/tau1)beta]+(1-A1) exp[-(t/tau2)gamma]), [0 < A1, beta, gamma < 1], where E0 is the initial modulus value E0. Tau1 and tau2(>>tau1) are characteristic times of the relaxation, A1 is the fractional contribution of the fast relaxation (KWW1 process) to the whole relaxation process, and beta and gamma are parameters describing the shape of the relaxation modulus. In both P and N samples, the relaxation modulus was described well by the empirical equation. The KWW1 process of a P sample almost completely coincided with that of an N sample. In the slow process (KWW2 process), there was a difference between the relaxation modulus of a P sample and that of an N sample. The results indicate that the KWW1 process in the empirical equation represents the relaxation in the collagen matrix in bone and that the KWW2 process is related to a higher-order structure of bone that is responsible for the anisotropic mechanical properties of bone.

Animals↗
PubMed2004

[The efficacy of Shakuyaku-Kanzo-to for peripheral nerve dysfunction in paclitaxel combination chemotherapy for epithelial ovarian carcinoma].

Shakuyaku-Kanzo-to was first medicated for muscular pain which was called Komuragaeri, and it has been reported that it is effective for peripheral nerve dysfunction such as arthralgia and numbness. Recently, Paclitaxel (T) and Carboplatin (J) combination chemotherapy (TJ chemotherapy) has been a standard first-line chemotherapy for epithelial ovarian carcinoma. For the arthralgia and muscular pain occurring in TJ chemotherapy, non-steroid-anti-inflammatory drugs (NSAIDs), Vitamin B12 (VB12) and Shakuyaku-Kanzo-to are the major medications. In this study, we examined twenty-one cases in which arthralgia and muscular pain occurred in TJ chemotherapy (including 16 cases as first-line chemotherapy). In all cases, patients took 7.5 g of Shakuyaku-Kanzo-to orally per day for eight days. We investigated the efficacy of Shakuyaku-Kanzo-to retrospectively with the following results. In nine cases (43%), Shakuyaku-Kanzo-to was effective in reducing pain. Especially in TJ chemotherapy as first-line chemotherapy, Shakuyaku-Kanzo-to was even more effective in reducing pain. We suggested that Paclitaxel combination chemotherapy with Shakuyaku-Kanzo-to taken orally is a more safe and tolerable way to reduce pain in epithelial ovarian carcinoma.

Adult↗
PubMed2004

[Clinical study on the efficacy of weekly paclitaxel administration for platinum-resistant epithelial ovarian carcinoma].

OBJECTIVE: Recently, paclitaxel (T) and carboplatin (J) combination chemotherapy has been a standard first-line chemotherapy for epithelial ovarian cancer and has improved its prognosis. But we have many chemoresistant cases, and we examined the efficacy of weekly, single-agent, paclitaxel administration. METHODS: Seven cases were included in this study. In all cases weekly paclitaxel administration (weekly-T chemotherapy) was performed because of the resistance to pre-treated platinum-based chemotherapy. In all cases the clinical stage was III c, and the histologic types consisted of four serous adenocarcinomas and three clear cell carcinomas. The number of courses and regimens in pre-treated chemotherapy was 8 to 16 (median 9) and 1 to 3 (median 2). Performance status (PS) was more than 2 in four cases. During weekly-T chemotherapy, 80 mg/m2 of paclitaxel was intravenously administered weekyl for 1-hour three times over two weeks, and next administration was performed two weeks later. 2 to 7 (mean 3.9) courses of weekly-T chemotherapy were performed in this study. RESULTS: The treatment outcomes of weekly-T chemotherapy were 2 partial remission (PR), 3 no change (NC) and 2 progressive disease (PD). Though peripheral neuropathy occurred in five cases (71%), the drug for neuropathy needed to be administered in only one case (14%). While the toxicity of hemoglobin was worse than grade 3 in 13 courses (48%), hematological and non-hematological toxicity was mild. CONCLUSION: The findings suggested that weekly-T chemotherapy was effective for heavily treated ovarian cancer patients in terms of both toxicity and quality of life (QOL).

Adult↗
PubMed2003

Elongational flow studies on conformational change in DNA induced by DNA-binding protein HU.

Interaction of DNA-binding protein HU from Bacillus stearothermophilis (HUBst) with coliphage T2 DNA was investigated by observing an elongational flow-induced birefringence, Deltan, of a T2-phage DNA aqueous solution at various HU concentrations. Localized flow birefringence was observed in the pure elongational flow region, and the strain rate dependence of Deltan had a critical strain rate epsilon;(c) for the appearance of flow birefringence at all of the HU concentrations examined, indicating that a coil-stretch transition occurred at epsilon;(c) in each DNA-HU system. For strain rates larger than epsilon;(c), Deltan increased rapidly and then gradually, approaching a plateau value. The value of epsilon;(c) increased with an increase in HU concentration. Analysis based on the relationship between epsilon; (c) and the Rouse-Zimm relaxation time revealed that the increase in epsilon;(c)with increase in HU can be explained by the decrease in the size of the DNA-HU complex. The plateau birefringence value, Deltan(p), decreased at small HU concentrations but did not change at larger HU concentrations. Considering that Deltan(p) is related to the orientational order parameter of segments, it was concluded that there were at least two stages in the process of compaction of DNA induced by HU.

Bacterial Proteins↗
PubMed2003

Analgesic effect of caudal epidural ketamine in cattle.

This study was performed to clarify the analgesic effect of ketamine injected into the first intercoccygeal (Co1-Co2) epidural space in standing cattle. Five adult cows were randomly received 3 treatments at least 1 week interval: 5, 10 and 20 mL of 5% ketamine. Sedation, analgesia, ataxia and other effects on cardiopulmonary and rumen functions were assessed before ketamine administration and until 120 min. The analgesia without sedation was shown at tail and perineum about 5 min after all three treatments. The duration of analgesia was significantly increased according to the volume of ketamine (p<0.01). There was a similar tendency of ataxia with individual variation. There were minimal effects on cardiopulmonary and rumen functions. The present study showed that caudal epidural ketamine administration induced analgesia without sedation in cows, and the duration of analgesia was dose dependent with ataxia. However, the duration of analgesia after 5 and 10 mL ketamine administration is short for common surgical procedures and pain relief of perineum. Further studies are needed to prolong the duration of analgesia without side effects.

Analgesia, Epidural↗
PubMed2002

Compact form of DNA induced by DNA-binding protein HU.

Interaction of DNA-binding protein HU from Bacillus stearothermophilus (HUBst) with coliphage T2 DNA was investigated by means of a single-duplex DNA chain visualization method using fluorescence microscopy. Fluorescence microscopic images of coliphage T2 DNA molecules were observed as a function of HUBst concentration. The average fluorescence image size of T2 DNA decreased with increase in HUBst concentration to a size comparable to that of a DNA globule induced by polyethylene glycol (PEG) and multivalent cation (MVC). The change to globule-like DNA proceeded gradually and monotonously, in contrast to the coil-globule transition of DNA induced by PEG and MVC. The histogram of the fluorescence image length was essentially a single-modal one throughout the process of conformational change. These results indicate that the process of shrinking of DNA from a random coil to a globule-like one is not of a transitional nature. The interaction of HUBst with DNA and the mechanism of shrinkage are concluded to be different from those of PEG-induced and MVC-induced coil-globule transition of DNA.

Bacterial Proteins↗
PubMed2002

Atomic force microscopic studies on the structure of bovine femoral cortical bone at the collagen fibril-mineral level.

The structure of cortical bone at the collagen-mineral level was investigated by means of atomic force microscopy. Surfaces of the specimens treated with collagenase and ethylenediaminetetraacetic acid (EDTA) were examined. Images of blob-like objects observed in intact specimen became clearly outlined after collagenase treatment; the sizes of the blob decreased, suggesting that each blob had been fragmented by the collagenase treatment. Following EDTA treatment of an intact specimen, an image of thread-like objects appeared; the thread was partly constructed by trains of blobs and the other parts of the threads had a periodic pattern along its longer axis. The period was almost equal to the collagen D-period of the Hodge-Petruska model, indicating that the threads are collagen fibrils and that the blobs are related to the mineral phase in bone. It was concluded that minerals were deposited on and along collagen fibrils. A decorated collagen fibril model for the spatial relationship between mineral and collagen fibril was proposed. According to our model, the mineral inside the collagen fibril is about one forth of the extrafibrillar mineral.

Journal Article↗