Biomedical subjects

I Watanabe

Publications and source records attributed to I Watanabe.

At least 19 recordsLinked to original sources

PubMed2006

Nd:YAG laser penetration into cast titanium and gold alloy with different surface preparations.

This study investigated the effect of surface preparation on the Nd:YAG laser penetration into cast titanium and gold alloy. Cast blocks of each metal were given four different surface preparations: (i) coloured with black marker; (ii) air-abraded with 50 microm Al2O3; (iii) ground with SiC points and (iv) polished with 1 microm Al2O3 (mirror-polished). Two blocks with each of the surface preparations were abutted and laser-welded at their interface using the voltages of 210-260 V in increments of 10 V. After the welded blocks were mechanically separated, the laser penetration was measured using computer graphics. Regardless of the surface preparation, an increase in voltage increased the laser penetration for both metals. The laser penetration into titanium prepared with black marker and air-abrasion was significantly deeper than into the titanium ground with SiC points and mirror-polished. Although there were no statistical differences in penetration among the surface preparations for the gold alloy, the penetration in the mirror-polished specimens was shallower than any of the other preparation methods at higher voltages of 240-260 V. The results obtained in this study suggested that broken metal frameworks with finished surfaces should be painted with black marker or air-abraded before laser welding.

Air↗

PubMed2006

Palatine mucosa of aging and experimentally induced diabetic aging rabbits: light-microscopic, scanning electron microscopic and transmission electron microscopic qualitative study.

BACKGROUND: Data associating palatine mucosa, microvascular architecture, aging and diabetes mellitus are few, so the aim of the present study was to examine these conditions structurally and ultrastructurally. METHODS: We used 18 female rabbits, aged about 2 years at the beginning of the experiment, distributed into 2 groups: aging diabetic and aging animals, prepared by three different methodologies: light microscopy, scanning electron microscopy and transmission electron microscopy. The samples were stained with hematoxylin-eosin for light microscopy, and for scanning electron microscopy, we used Mercox Cl-2B vascular corrosion casts. For transmission electron microscopy, the specimens were fixed and embedded in Epon 812 resin. RESULTS: Under light microscopy, we noted small amounts of underdeveloped connective papillae and significant flattened areas through the epithelium-connective tissue interface in the aging diabetic group. Larger blood vessels were deeply located in the palatine mucosa, branching off in the direction of the epithelium-connective tissue interface. Capillaries followed the interface contour. In both groups, vascular corrosion casts revealed capillaries sprouting out in disorganized rows but parallel between themselves. 'Hair-pin' capillary loops and convoluted capillary loops were noted. CONCLUSION: The aging diabetic group showed rarefying microvasculature areas with complex tortuous capillary loops. Transmission electron microscopy results showed that the aging diabetic group presented small cytoplasmatic projections directed to the vessel lumen and micropinocytic vesicle, i.e. caveolas. Epithelium-connective tissue interface, connective papillae, microangioarchitecture, and information about endothelial cells alterations were observed in the aging diabetic and aging animals.

Age Factors↗

PubMed2005

Trypanosoma cruzi: preliminary investigation of NADH-positive and somatostatin-immunoreactive neurons in the myenteric plexus of the mouse colon during the infection.

In this paper, the distribution of NADH-positive and somatostatin (SOM) immunoreactive neurons in the myenteric plexus of the colon of mice infected with Trypanosoma cruzi was studied. Ten young, male, BALB/c mice were inoculated with the Y strain of T. cruzi, 60 days previously (chronic phase of the infection). Another 10 mice were uninfected controls. Distal and proximal colonic neurons from five chronically infected mice and their controls were stained using the NADH-diaphorase method. Quantitative results showed a significant decrease of 39% in the number of neurons in the proximal colon of infected mice and 58% in the distal colon (p<0.05). SOM was localized in five animals from each group by light microscopy, using an indirect immunofluorescence technique. It was observed that there were far fewer nerve cells and fibres and less intensely stained neuron bodies and varicose SOM-positive nerve fibres in both, control and chronic infected mice. These findings could be related to the disturbances in intestinal motility observed in patients in the chronic phase of Chagas' disease.

Animals↗

PubMed2005

Penetration depth into dental casting alloys by Nd:YAG laser.

This study investigated the effect of laser-beam welding conditions [voltage (V) and spot diameter (mm)] on the penetration depth into dental casting alloys. Castings (3.0 mm x 8.0 mm x 50 mm) were prepared from the metals used in this study: commercially pure titanium (CP Ti), Ti-6Al-4V, Ti-6Al-7Nb, cobalt-chromium alloy (Co-Cr) and Type IV gold alloy. Two cast blocks of each metal were butted against one another at the 8.0 x 50-mm surfaces. They were then welded at their interface under the following conditions: voltage of 160-340 V, spot diameter of 0.4-1.6 mm, and pulse duration of 10 ms. After laser welding, the blocks were separated, and the penetration depth into each alloy was measured. The data were analyzed with the use of ANOVA at the p < 0.05 level of significance. The penetration depths were as follows: CP Ti (0.29-6.45 mm), Ti-6Al-4V (0.32-5.24 mm), Ti-6Al-7Nb (0.34-5.65 mm), Co-Cr (0.24-6.15 mm), and Type IV gold alloy (0.12-5.22 mm). The voltage and spot diameter affected the penetration depth into the metals tested. When the voltage increased and the spot diameter decreased, the penetration depth increased for each metal. Selecting suitable conditions for laser welding to obtain sufficient penetration depth for the optimal thickness of the metal is important when welding prostheses.

Dental Alloys↗

PubMed2005

Synaptic contacts established by inferior alveolar nerve fibres in the paratrigeminal nucleus: an electron microscopic study in the rat.

A quantitative evaluation of the types of synaptic contacts from afferent fibres in the paratrigeminal nucleus after partial pulpectomy was compared with that after transection of the inferior alveolar nerve (IAN), using transganglionic degeneration. Degenerating terminals with a marked increase in axoplasmic electron opacity were observed bilaterally in the paratrigeminal nucleus of rats submitted to either partial pulpectomy or IAN transection. The total number of degenerating terminals observed after partial pulpectomy was 53% of that for IAN transection. This suggests a considerable contribution of tooth pulp afferent fibres in the total number of synaptic contacts in the intermediate and caudal parts of the paratrigeminal nucleus. In both the partial pulpectomy and IAN-transected groups, the majority of these synapses formed single asymmetric contacts with intermediate and distal dendritic segments, and accounted for 74% of all classified contacts. The remaining 26% of contacts occurred with proximal dendritic segments, dendritic spines, perikaryon, normal terminals and double post-synaptic elements. There was no statistically significant difference in the number of synaptic contacts for each type of synapse, with the exception of contacts with dendritic spines in the contralateral side, between the partially pulpectomised and IAN-transected groups.

Animals↗

PubMed2005

Does incineration turn infectious waste aseptic?

Incineration of infectious waste is considered to be biologically safe. We performed basic experiments to confirm that bacillus spores are killed by incineration in a muffle furnace. Biological samples containing 10(6) spores of Bacillus stearothermophilus were placed in stainless steel Petri dishes and then into hot furnaces. The furnace temperature and duration of incineration were 300 degrees C for 15 min, 300 degrees C for 30 min, 500 degrees C for 15 min, 500 degrees C for 30 min and 1100 degrees C for 3 min. We confirmed that all spores of B. stearothermophilus were killed at each of these settings. The effect of incineration seems to be equivalent to that of sterilization, based on the satisfactory sterilization assurance level of 10(-6).

Geobacillus stearothermophilus↗

PubMed2005

Multi-unit fixed partial denture for a bilateral cleft palate patient: a clinical report.

Patients with cleft palates eventually require definitive fixed or removable dental prostheses after the maintenance of arch alignment and occlusal relationship during adolescence. This case report presents application of a resin composite veneered fixed partial denture utilized as a definitive prosthesis for a bilateral cleft palate patient after stable occlusion had been established orthodontically. The composite veneered long span fixed partial denture provides adequate aesthetics and function.

Adult↗

PubMed2004

Mechanical strength of laser-welded cobalt-chromium alloy.

The purpose of this study was to investigate the effect of the output energy of laser welding and welding methods on the joint strength of cobalt-chromium (Co-Cr) alloy. Two types of cast Co-Cr plates were prepared, and transverse sections were made at the center of the plate. The cut surfaces were butted against one another, and the joints welded with a laser-welding machine at several levels of output energy with the use of two methods. The fracture force required to break specimens was determined by means of tensile testing. For the 0.5-mm-thick specimens, the force required to break the 0.5-mm laser-welded specimens at currents of 270 and 300 A was not statistically different (p > 0.05) from the results for the nonwelded control specimens. The force required to break the 1.0-mm specimens double-welded at a current of 270 A was the highest value among the 1.0-mm laser-welded specimens. The results suggested that laser welding under the appropriate conditions improved the joint strength of cobalt- chromium alloy.

Biocompatible Materials↗

PubMed2004

Effect of heat treatments on machinability of gold alloy with age-hardenability at intraoral temperature.

OBJECTIVE: This study investigated the effect of heat treatment on the machinability of heat-treated cast gold alloy with age-hardenability at intraoral temperature using a handpiece engine with SiC wheels and an air-turbine handpiece with carbide burs and diamond points. METHODS: Cast gold alloy specimens underwent various heat treatments [As-cast (AC); Solution treatment (ST); High-temperature aging (HA), Intraoral aging (IA)] before machinability testing. The machinability test was conducted at a constant machining force of 0.784N. The three circumferential speeds used for the handpiece engine were 500, 1,000 and 1,500 m/min. The machinability index (M-index) was determined as the amount of metal removed by machining (volume loss, mm(3)). The results were analyzed by ANOVA and Scheffé's test. RESULTS: When an air-turbine handpiece was used, there was no difference in the M-index of the gold alloy among the heat treatments. The air-turbine carbide burs showed significantly (p<0.05) higher M-indexes than the diamond points after any heat treatments. With the SiC wheels, increasing the circumferential speed increased the M-index values for each heat treatment. The specimens heat-treated with AC, HA and IA had similar M-indexes at the lower speeds (500 and 1,000 m/min). The ST specimens exhibited the lowest M-index at the lower speeds. However, at the highest speed (1,500 m/min), there were no significant differences in the M-indexes among the heat treatments except for HA, which showed the highest M-index. CONCLUSION: There was no effect of heat treatment on the machinability of the gold alloy using the air-turbine handpiece. The heat treatments had a small effect on the M-index of the gold alloy machined with a SiC wheel for a handpiece engine.

Body Temperature↗

PubMed2004

Cytotoxicity of commercial and novel binary titanium alloys with and without a surface-reaction layer.

Titanium-based alloys form a surface reaction layer when cast. This study investigated the effect of the surface reaction layer on the cytotoxicity of novel Ti-based binary alloys. The cytotoxicities of the novel alloys were compared with commercially pure titanium, Ti-6Al-4V and Ti-6Al-7Nb. Cast discs with or without the reaction layer were first tested for cytotoxicity, then for elemental release into cell-culture medium. The elements released into the extracts were measured by means of an inductively coupled plasma atomic emission spectrometer. The commercial and novel binary Ti-based alloys showed no statistically significant cytotoxicity, although some trends were noted for several alloys. The presence of the reaction layer did not significantly alter the cytotoxicity. These favourable biocompatibility results show that these novel alloys have promise for use in dental restorations.

Alloys↗

PubMed2004

Mechanical properties of cast Ti-6Al-4V-XCu alloys.

The mechanical properties of Ti-6Al-4V-XCu (1, 4 and 10 wt% Cu) alloys were examined. The castings for each alloy were made in a centrifugal titanium casting machine. Two shapes of specimens were used: a dumbbell (20 mm gauge length x 2.8 mm diameter) for mechanical property studies, and a flat slab (2 mm x 10 mm x 10 mm) for metallography, microhardness determination and X-ray diffractometry. Tensile strength, yield strength, modulus of elasticity, elongation and microhardness were evaluated. After tensile testing, the fracture surfaces were observed using scanning electron microscopy. The tensile strengths of the quaternary alloys decreased from 1016 MPa for the 1% Cu alloy to 387 MPa for the 10% Cu alloy. Elongation decreased with an increase in the copper content. The 1% Cu alloy exhibited elongation similar to Ti-6Al-4V without copper (3.0%). The results also indicated that the copper additions increased the bulk hardness of the quaternary alloy. In particular, the 10% Cu alloy had the highest hardness and underwent the most brittle fracture. The mechanical properties of cast Ti-6Al-4V alloy with 1 and 4% Cu were well within the values for existing dental casting non-precious alloys.

Alloys↗

PubMed2003

Molecular cloning and expression of a Kv1.1-like potassium channel from the electric organ of Electrophorus electricus.

Electrocytes from the electric organ of Electrophorus electricus exhibited sodium action potentials that have been proposed to be repolarized by leak currents and not by outward voltage-gated potassium currents. However, patch-clamp recordings have suggested that electrocytes may contain a very low density of voltage-gated K(+) channels. We report here the cloning of a K(+) channel from an eel electric organ cDNA library, which, when expressed in mammalian tissue culture cells, displayed delayed-rectifier K(+) channel characteristics. The amino-acid sequence of the eel K(+) channel had the highest identity to Kv1.1 potassium channels. However, different important functional regions of eel Kv1.1 had higher amino-acid identity to other Kv1 members, for example, the eel Kv1.1 S4-S5 region was identical to Kv1.5 and Kv1.6. Northern blot analysis indicated that eel Kv1.1 mRNA was expressed at appreciable levels in the electric organ but it was not detected in eel brain, muscle, or cardiac tissue. Because electrocytes do not express robust outward voltage-gated potassium currents we speculate that eel Kv1.1 channels are chronically inhibited in the electric organ and may be functionally recruited by an unknown mechanism.

Amino Acid Sequence↗

PubMed2003

Prognostic factors in resection of pulmonary metastasis from colorectal cancer.

BACKGROUND: The aim of this retrospective study was to evaluate characteristics of primary colorectal cancer and pulmonary metastases in order to identify prognostic factors for overall survival and risk factors for further intrapulmonary recurrence after resection of pulmonary metastases from colorectal cancer. METHODS: Forty-nine patients who underwent resection of pulmonary metastases from colorectal cancer were reviewed. The factors assessed were age, sex, pathological findings of the original colorectal cancer (depth, lymphatic invasion, venous invasion, lymph node metastasis, differentiation, Dukes' stage) and pulmonary metastasis (maximum tumour size, number of tumours, completeness of resection), serum carcinoembryonic antigen level, previous hepatectomy for liver metastases, and surgical procedure for resection of pulmonary metastasis. Overall survival and intrapulmonary recurrence were also reviewed. RESULTS: Survival rates after resection of pulmonary metastases were 78 per cent at 3 years and 56 per cent at 5 years. Solitary pulmonary metastases were significantly correlated with survival (P = 0.049). The pathological features of the primary colorectal cancer had no impact on survival. Histologically incomplete resection of pulmonary metastasis significantly correlated with pulmonary re-recurrence (P = 0.034). CONCLUSION: Long-term survival can be expected after complete resection of pulmonary metastases arising from colorectal cancer, especially in patients with a solitary pulmonary metastasis.

Adult↗

PubMed2003

Cortical reorganization in training.

Plasticity within the human central motor system occurs and has been studied with transcranial magnetic stimulation in patients with amputations, spinal cord injuries, and ischemic nerve block. These studies have identified a pattern of motor system reorganization that results in enlarged muscle representation areas and large motor evoked potentials (MEPs) for muscles immediately proximal to the lesion. Some of these changes are apparent minutes after ischemic nerve block, weeks after spinal cord injury, and as early as six months after amputation.These studies motivated us to study the cortical motor reorganization after finger movement training in normals and after anastomosis of intercostal nerves to the musculocutaneous nerve in young patients with cervical root avulsions due to a traumatic motorcycle injury.

Accidents, Traffic↗

PubMed2002

Induction of vasculogenesis in breast cancer models.

Recently, there have been reports of postnatal vasculogenesis in cases of ischaemia models. The aim of the present study is to provide evidence of postnatal vasculogenesis in breast-cancer-bearing mice. Based on cell surface antigen expression, we isolated endothelial precursor cells from bone marrow, peripheral blood and tumour-infiltrating cells from mice that had received six human breast cancer xenografts. In all three areas (bone marrow, peripheral blood and tumour-infiltrating cells), endothelial precursor cell population was elevated in all transplanted mice. Differentiation and migration activities of endothelial precursor cells were measured by comparing levels of the endothelial precursor cell maturation markers Flk-1, Flt-1, Tie2, VE-cadherin and CD31 among these three areas. The endothelial precursor cell population was 14% or greater in the gated lymphocyte-size fraction of the inflammatory breast cancer xenograft named WIBC-9, which exhibits a hypervascular structure and de novo formation of vascular channels, namely vasculogenic mimicry (Shirakawa et al, 2001). In vitro, bone marrow-derived endothelial precursor cells from four human breast cancer xenografts proliferated and formed multiple clusters of spindle-shaped attaching cells on a vitronectin-coated dish. The attaching cells, which incorporated DiI-labelled acetylated low-density lipoprotein (DiI-acLDL) and were negative for Mac-1. The putative bone marrow derived endothelial precursor cell subset, which was double positive of CD34 and Flk-1, and comparative bone marrow derived CD34 positive with Flk-1 negative subset were cultured. The former subset incorporated DiI-acLDL and were integrated with HUVECs. Furthermore, they demonstrated significantly higher levels of murine vascular endothelial growth factor and interleukin-8 in culture supernatant on time course by enzyme-linked immunosorbent assay. These findings constitute direct evidence that breast cancer induces postnatal vasculogenesis in vivo.

Animals↗

PubMed2002

Non-Fermi-liquid spin dynamics in CeCoGe3-xSi(x) for x = 1.2 and 1.5.

Muon spin relaxation has been measured in CeCoGe3-xSi(x) at the magnetic/nonmagnetic boundary compositions of x = 1.2 and x = 1.5. Both the alloys are found to exhibit an ordered region and a disordered region. At x = 1.2, short-range magnetic ordering is observed below 0.86 K in the ordered region. The disordered region is paramagnetic and the muon spin-lattice relaxation rate lambda2 in this region displays non-Fermi-liquid (NFL) spin dynamics, i.e., the power law lambda2 proportional to T0.72 which shows the formation of Griffiths phase. lambda2 in the x = 1.5 alloy displays logarithmic (NFL) scaling below 1 K, in agreement with the theory of a T = 0 K magnetic transition.

Journal Article↗

PubMed2002

Machinability of cast commercial titanium alloys.

This study investigated the machinability of cast orthopedic titanium (metastable beta) alloys for possible application to dentistry and compared the results with those of cast CP Ti, Ti-6Al-4V, and Ti-6Al-7Nb, which are currently used in dentistry. Machinability was determined as the amount of metal removed with the use of an electric handpiece and a SiC abrasive wheel turning at four different rotational wheel speeds. The ratios of the amount of metal removed and the wheel volume loss (machining ratio) were also evaluated. Based on these two criteria, the two alpha + beta alloys tested generally exhibited better results for most of the wheel speeds compared to all the other metals tested. The machinability of the three beta alloys employed was similar or worse, depending on the speed of the wheel, compared to CP Ti.

Alloys↗

PubMed2002

Elevated concentrations of trace elements in Caspian seals (Phoca caspica) found stranded during the mass mortality events in 2000.

Concentrations of V, Mn, Fe, Cr, Co, Cu, Zn, As, Se, Mo, Ag, Cd, Tl, Hg, Pb, and organic mercury (Org-Hg) were determined in liver, kidney, and muscle of healthy Caspian seals ( Phoca caspica) collected in 1998. These concentrations were compared with those of seals infected with canine distemper virus (CDV) found stranded along the coastal areas in 2000. Concentrations of toxic elements (As, Ag, Cd, Tl, Hg, Pb, and Org-Hg) in Caspian seals stranded in 2000 were comparable or lower than those of samples collected in 1998 and in other pinnipeds. Thus it may be inferred that these elements were not the causative agents in the deaths of the seals. In contrast, concentrations of Zn and Fe were much higher in diseased Caspian seals than those in other pinnipeds. Zinc concentrations in all tissues of Caspian seals also increased during 1993-2000. Furthermore, negative correlations were found between blubber thickness and hepatic and renal Zn concentrations. These results imply the disturbance in homeostatic control and nutritional status of essential elements in Caspian seals stranded in 2000.

Animals↗