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Biomedical subjects

T Shibuya

Publications and source records attributed to T Shibuya.

At least 91 records · Page 5Linked to original sources
PubMed1997

Prosthetic replacement of the hip in dogs using bioactive bone cement.

Total hip arthroplasties were performed in dogs using bioactive bone cement consisting of silane treated CaO-MgO-SiO2-P2O5-CaF2 glass powder as the filling particles and bisphenol-a-glycidyl methacrylate based resin as the organic matrix, and the outcomes were compared with the results of polymethylmethacrylate bone cement. The mechanical properties of the bioactive bone cement were stronger than the mechanical properties of polymethylmethacrylate bone cement. The bonding strength of the bioactive bone cement to bone in dogs' femora increased with time, reaching 4.7 MPa at 6 months, whereas that of polymethylmethacrylate bone cement did not increase, remaining at 1.0 MPa. Results of histologic examination showed direct bonding between the bioactive bone cement and bone, and the bony trabeculae around the cement mantle grew with time. However, in polymethylmethacrylate bone cement, an intervening soft tissue layer was evident at the bone cement interface. Direct bonding of the bioactive bone cement at the interface through an apatite layer of 30 microm in thickness was shown through observation with the scanning electron microscopy. Using this bioactive bone cement in clinical settings may help alleviate serious problems associated with cemented total hip arthroplasty, such as aseptic loosening of the implant and mechanical failure of the bone cement.

Acetabulum↗
PubMed1997

Longitudinal evaluation of time related bone remodeling after cementless total hip arthroplasty.

Bone remodeling after cementless total hip arthroplasty was evaluated by dual energy x-ray absorptiometry in a longitudinal study of 32 hips. After insertion of a fully porous surface anatomic stem made of cobalt chromium, bone mineral density was analyzed until at least 2 years postoperatively. Bone remodeling was evaluated in terms of regional bone density changes in the seven adjacent periprosthetic zones as well as the global change in bone density distribution over the entire periprosthetic area. At 12 months after the operation, the averaged regional bone mineral density in all seven zones showed a rapid decrease, ranging from 9% to 24% of the bone mineral density present at 2 weeks postoperatively. Thereafter, the bone density change appeared to be stabilized. The global change in the bone density distribution was expressed as two summarizing statistical indexes derived from principal component analysis: the first index represents the change of average bone mineral density over the entire periprosthetic area, and the second represents the severity of bone mineral density decrease in the proximal area versus the distal area. The second index proved that more bone density reduction occurred in the proximal area, but this was variable among patients and correlated significantly with the stem size and the initial bone mineral density in the distal part of the periprosthetic area. This longitudinal dual energy x-ray absorptiometry study suggests that a large part of the bone remodeling after cementless hip arthroplasty ceases within 1 year postoperatively, and stem size and the initial bone density around the distal portion are important considerations for predicting the proximal bone density decrease during the early rapid remodeling period.

Absorptiometry, Photon↗
PubMed1997

Rehabilitation of patients with extended facial and craniofacial resection.

Surgery of benign and malignant disease of the nose and sinuses can result in disfigurement and disability. Many patients have speech, mastication, and swallowing problems, anosmia, and pain. If the orbit is retained, visual loss, dystopia, diplopia, and epiphora can occur. This study reviews the senior author's experience with 34 patients over the last 18 years. Group and case analyses demonstrate that in patients with cancer, the eye can be preserved if one anatomical boundary is retained beyond a negative frozen section margin. Dystopia can be prevented by reconstruction of the floor with skin and fascial grafts or flaps. Epiphora can be reduced by repair of the medial canthus and dacryocystorhinostomy. Evidence is presented for prosthetic management of speech and swallowing and restoration of cheek contour. Case examples are used to illustrate the surgical techniques.

Adolescent↗
PubMed1997

Synthesis of glycosyl-trehaloses by cyclomaltodextrin glucanotransferase through the transglycosylation reaction.

Cyclomaltodextrin glucanotransferase from Bacillus stearothermophilus produced a series of glycosyl-trehaloses through the transglycosylation reaction with cyclomaltohexaose as the glycosyl donor and trehalose as its acceptor. After beta-amylase treatment, five species of glycosyl-trehaloses were isolated by column chromatography. After chemical and enzymatic analyses, it was concluded that these oligosaccharides were alpha-maltosyl alpha-D-glucopyranoside, alpha-maltotriosyl alpha-D-glucopyranoside, alpha-maltosyl alpha-maltoside, alpha-maltotriosyl alpha-maltoside, and alpha-maltotriosyl alpha-maltotrioside. These were not hydrolyzed by salivary amylase, artificial gastric juice, or pancreatic amylase, however they were hydrolyzed by enzymes of the small intestine.

Carbohydrate Sequence↗
PubMed1997

Chromosome 17 copy numbers and incidence of p 53 gene deletion in gastric cancer cells. Dual color fluorescence in situ hybridization analysis.

Tumor tissue samples were obtained from each of ten patients with stomach cancer who had undergone surgery. The simultaneous detection of signals from 17 alpha pericentromeric and 17 p 13.1 loci after hybridization with the appropriate probes was carried out on 100-200 tumor cells in each case. The copy number category (i.e., monosomy, disomy, trisomy, and so on) was defined as described by Waldman et al., and the deletion of a gene of interest was defined as described by Matsumura et al. The copy number category was monosomic in seven and disomic in three out of ten cases. The frequency of the copy number 2 (two centromeric signals per nucleus) was lower in tumor cells than in control cells that comprise normal gastric epithelium cells and cells from a normal fibroblast cell line. The copy numbers 3, 4, 5, and above (polysomy) were more frequent in tumor cells, whereas no normal cells having three or more centromeric signals per nucleus was present in the control. Incidence of p 53 gene deletion in ten patients ranged from 55.4% to 90.0%, and from 1.5% to 30.7% if nuclei having three or more copy numbers were taken into consideration. The mean incidence of the p 53 deletion was significantly higher in the differentiated type than in the undifferentiated type of carcinoma (p < 0.02). Various types in the combination pattern of 17 alpha centromere/17 p 13.1 signals were observed, and the most frequent pattern in the ten cases was a combination of 1/1. The deletion of chromosome 17 p may play an important role in carcinogenesis of the stomach.

Adenocarcinoma↗
PubMed1997

Changes in nitric oxide generated by the oxidation of oxymyoglobin by nitrite.

We found that nitric oxide (NO) was produced during the oxidation of oxymyoglobin by nitrite, by using a NO-selective electrode system, which enabled us to measure NO in phosphate solution, continuously and quantitatively. When 500 microM nitrite was added in the solution of oxymyoglobin (65 microM in heme), oxymyoglobin was oxidized to metmyoglobin in a sigmoidal manner. During the reaction, NO was generated quickly at the initial lag phase, and reached its peak (NO approximated to 30 microM), before the burst oxidation of oxymyoglobin occurred. Then, NO content was gradually decreased. By the addition of the increased concentration of nitrite (1 mM or 2 mM) to oxymyoglobin solution (65 microM in heme), the production rate of NO was much accelerated and the amounts of NO were increased, in good accordance with the accelerated oxidation of oxymyoglobin by nitrite. These results suggest that NO is involved in the oxidation of oxymyoglobin by nitrite.

Animals↗
PubMed1997

Intracerebral monoamine concentration after ventriculoperitoneal shunting in the congenital hydrocephalus rat.

This study investigated the relationship between neurotransmitters and improvement of symptoms after ventriculoperitoneal shunting in congenital hydrocephalus (LEW-HYR) rats. Twenty-four patent hydrocephalus rats, aged 12-14 days, were randomly assigned to the following four groups: ventriculoperitoneal shunt group, obstructed shunt group, burr hole group, and no treatment group. In addition, six normal rats served as control group. Head to body length ratio was measured before and 7 days after the procedures. Coordination movement was evaluated on the 7th postoperative day. High performance liquid chromatography (HPLC) was used to measure the concentrations of dopamine (DA), norepinephrine (NE), serotonin, homovanillic acid (HVA), 3-methoxyl-4-hydroxyphenylenglycol, 5-hydroxy-indolacetic acid (5-HIAA), and 3,4-dihydroxyphenylacetic acid in the whole cerebral cortex, the thalamus and hypothalamus, the midbrain, the lower brainstem, the cerebellum, and the striatum. Fluorohistochemical studies were also performed. Significant improvements were observed in body proportion and coordination movement in the ventriculoperitoneal shunt group compared to the burr hole group and the no treatment group. HPLC and fluorohistochemical studies revealed that concentrations of NE in the thalamus and hypothalamus and DA in the striatum were significantly lower in the burr hole group and the no treatment group. Concentrations of HVA and 5-HIAA in the cerebellum were significantly lower in the control group. The present study indicates that ventriculoperitoneal shunting may improve the changes in concentrations of neurotransmitter in specific neurons caused by hydrocephalus, and this may contribute to the improvement of the symptoms.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1997

Production of nitric oxide (NO) during the oxidation of human oxyhemoglobin by nitrite: application of a NO-selective electrode for the measurement of NO.

By using a nitric oxide (NO) selective electrode system. NO produced during the oxidation of human hemoglobin by nitrite was monitored. When 160 microM oxyhemoglobin (in heme) was reacted with 500 microM nitrite. NO was generated quickly at the initial lag phase of the oxidation of oxyhemoglobin by nitrite and decreased gradually during the second burst phase of the reaction. While the oxidation of oxyhemoglobin by nitrite proceeded in a sigmoidal manner including the initial lag phase and second burst phase. The maximal amount of NO produced under this condition was estimated to be 48 microM. According to the increase of nitrite concentrations added, the amounts of NO produced at the initial phase increased, being in good accordance with the increased rate of the oxidation of oxyhemoglobin. These results strongly suggest the critical role of NO in the oxidation mechanism of oxyhemoglobin by nitrite.

Electrodes↗
PubMed1997

Contralateral hip in patients with unilateral nontraumatic osteonecrosis of the femoral head.

To clarify the risk of the development of osteonecrosis of the femoral head in the contralateral hip of patients with unilateral nontraumatic osteonecrosis of the femoral head, a followup study was performed using magnetic resonance imaging. Forty-six asymptomatic contralateral hips with no evidence of osteonecrosis on magnetic resonance imaging, in patients with unilateral osteonecrosis, were subjects of this study. The period from the onset of unilateral osteonecrosis to entrance in this study ranged from 1 month to 20 years (mean, 3.1 years). There were 29 males and 17 females ranging in age from 16 to 71 years (mean, 41 years). Twenty-three patients had previous steroid therapy for various conditions: 16 had alcoholism and 7 had no etiologic factors. The followup term ranged from 3 to 8 years (average, 5.5 years). During the followup period, 1 patient (2%) had a band of low signal intensity demarcating the lesion of normal fat intensity on T1 weighted images, which progressed to collapse of the femoral head. These results suggest that in unilateral osteonecrosis cases, osteonecrosis rarely develops in the contralateral hip that has appeared normal on magnetic resonance imaging. The contralateral hip with a negative magnetic resonance imaging scan is not in Stage 0 of osteonecrosis, but is normal.

Adolescent↗
PubMed1997

Enumerating suboptimal alignments of multiple biological sequences efficiently.

The multiple sequence alignment problem is very applicable and important in various fields in molecular biology. Because the optimal alignment that maximizes the score is not always biologically most significant, providing many suboptimal alignments as alternatives for the optimal one is very useful. As for the alignment of two sequences, this suboptimal problem is well-studied, but for the alignment of multiple sequences, it has been considered impossible to investigate such suboptimal alignments because of the enormous size of the problem. The optimal multiple alignment can be obtained with A* algorithm, and an efficient algorithm for the k shortest paths problem on general graphs is discovered recently. We extend these algorithms for computation of set of all aligned groups of residues in optimal and suboptimal alignments, and for enumeration of suboptimal alignments. The suboptimal alignments are numerous. Thus we discuss what kind of suboptimal alignment is unnecessary to enumerate, and propose an efficient technique to enumerate only necessary alignments. The practicality of these algorithms are demonstrated through experiments. Moreover, the property of suboptimal alignments of multiple sequences are also examined through experiments.

Algorithms↗
PubMed1996

Dose-dependent induction of recessive mutations with N-ethyl-N-nitrosourea in primordial germ cells of male mice.

Using a specific locus test, we previously found that N-ethyl-N-nitrosourea (ENU) induces recessive mutations at a relatively high rate in male mouse primordial germ cells (PGC) at 8.5, 10.5 and 13.5 days of development (G8.5, G10.5 and G13.5). A large difference was observed on the induced mutation rate between 30 and 50 mg/kg ENU in 10.5-day PGC. We therefore carried out specific locus tests to ascertain whether ENU induces recessive mutations in a dose-dependent manner in G8.5 and G10.5 PGC. We also gave multiple doses of 25 mg/kg ENU using an 18-h interval, the approximate doubling time of PGC at these developmental stages, to test for an additive effect on the induced mutations rate. A dose-dependent induction of recessive mutations by ENU was observed in both G8.5 and G10.5 PGC, and multiple dosing of 25 mg/kg ENU showed an additive effect. Comparing these results to data on spermatogonial stem cells, we conclude the capacity to repair ENU-induced premutagenic damages is less effective in male mouse PGC at these developmental stages than in spermatogonial stem cells.

Animals↗
PubMed1996

Hemostasis activation during sclerotherapy of lower extremity varices.

The influence of compression sclerotherapy upon hemostasis activation was investigated in 41 consecutive patients with lower extremity varices by serial measurement of thrombin-antithrombin III complexes (TAT), D-dimer, fibrinogen and C-reactive protein (CRP). Blood sampling was carried out before operation and on the 7th and 28th post-operative day in patients randomly assigned to either the control group (n = 18), in which high ligation of sapheno-femoral junction and local excision of varices were performed, or the sclerotherapy group (n = 23) in which the comparable surgical intervention and compression sclerotherapy using hypertonic saline were performed simultaneously. In both groups, the TAT, D-dimer and fibrinogen concentrations at day 7 were significantly elevated compared to the value before operation while CRP showed no significant change during the observation period. In the sclerotherapy group, higher incidence of superficial thrombosis was observed and the TAT concentration at day 7 was significantly higher than that in the control group (p < 0.01), and the TAT at day 28 was still significantly elevated compared to the pre-operative level (p < 0.05). However, no relationship between TAT and D-dimer concentrations and the extent of superficial thrombosis was observed. We conclude that compression sclerotherapy for lower extremity varices causes latent activation of coagulation system and can be a risk factor for venous thromboembolism.

Antithrombin III↗
PubMed1996

Simultaneous determination of alpha-tocopherol and alpha-tocopherolquinone by high-performance liquid chromatography and coulometric detection in the redox mode.

A simple, selective and highly sensitive assay method for the simultaneous determination of alpha-tocopherol and alpha-tocopherolquinone in plasma or erythrocyte membrane by high-performance liquid chromatography (HPLC) with a series of multiple coulometric working electrodes (CWE) was investigated. For good separation of alpha-tocopherol and alpha-tocopherolquinone, an MC MEDICAL C18 reversed-phase column and a mobile phase consisting of 96% methanol [methanol-HPLC-grade distilled water (96:4, v/v)] with 40 mM sodium perchlorate were used. Also, selective, highly sensitive and simultaneous detection of these substances was performed in redox mode using a series of four CWE. In this detection mode, the first, second and third CWE were set at -0.45 V for pre-reaction and to prevent interference, the fourth CWE was used as an electrode for actual measurement with its potential set at +0.40 V against a palladium reference electrode. The detection limits were 50-100 pg. Excellent chromatograms of alpha-tocopherol and alpha-tocopherolquinone were obtained within 8 min. The usefulness of reversed-phase HPLC with the redox detection mode was confirmed by application to the determination of the concentrations of alpha-tocopherol and alpha-tocopherolquinone in a crude ethanol-hexane extract of rat plasma or erythrocyte membrane. These findings suggest that reversed-phase HPLC with the redox detection mode using a series of four CWE is applicable to study the preventive effect of alpha-tocopherol on lipid peroxidation.

Animals↗
PubMed1996

Mechanical and biological properties of two types of bioactive bone cements containing MgO-CaO-SiO2-P2O5-CaF2 glass and glass-ceramic powder.

In this study two types of bioactive bone cement containing either MgO-CaO-SiO2-P2O5-CaF2 glass (type A) or glass-ceramic powder (type B) were made to evaluate the effect of the crystalline phases on their mechanical and biological properties. Type A bone cement was produced from glass powder and bisphenol-a-glycidyl methacrylate (BIS-GMA) resin, and type B from glass-ceramic powder containing apatite and wollastonite crystals and BIS-GMA resin. Glass or glass-ceramic powder (30, 50, 70, and 80 by wt %) was added to the cement. The compressive strength of type A (153-180 MPa) and B (167-194 MPa) cement were more than twice that of conventional polymethylmethacrylate (PMMA) cement (68 MPa). Histological examination of rat tibiae showed that all the bioactive cements formed direct contact with the bone. A reactive layer was seen at the bone-cement interface. In specimens with type A cement the reactive layer consisted of two layers, a radiopaque outer layer (Ca-P-rich layer) and a relatively radiolucent inner layer (low-calcium-level layer). With type B cement, although the Ca-P-rich layer was seen, the radiolucent inner layer was absent. Up to 26 weeks there was progressive bone formation around each cement (70 wt %) and no evidence of biodegradation. The mechanical and biological properties of the cements were compared with those of a previously reported bone cement containing MgO-free CaO-SiO2-P2O5-CaF2 glass powder (designated type C).

Animals↗
PubMed1996

Bone-bonding behavior of plasma-sprayed coatings of BioglassR, AW-glass ceramic, and tricalcium phosphate on titanium alloy.

The bone-bonding behavior of three kinds of bioactive ceramics coated on titanium alloy by the plasma-spray technique was investigated. Titanium alloy (Ti-6A1-4V) coated with BioglassR (45S5), apatite-wollastonite containing glass ceramic (AW), or beta-tricalcium phosphate (TCP) was prepared, and rectangular specimens were implanted into the tibial bones of mature male rabbits, which were sacrificed 8 or 24 weeks after implantation. The tibiae containing the implants were dissected out and subjected to detachment tests to measure the failure load. The bone-implant interface was investigated by Giemsa surface staining, contact microradiography, and scanning electron microscopy-electron probe microanalysis (SEM-EPMA). Eight weeks after implantation, the failure loads for implants coated with BioglassR, AW, and TCP were 1.04 +/- 0.94, 2.03 +/- 1.17, and 3.91 +/- 1.51 kg, respectively, and 24 weeks after implantation, the respective failure loads were 2.72 +/- 1.33, 2.39 +/- 1.30, and 4.23 +/- 1.34 kg. Failure loads of AW- and TCP-coated implants did not increase significantly with time. After the detachment test, breakage of the coating layer was observed. Bioactive ceramics can act as stimulants that induce bonding between bone and metal implants. However, failure load of metal implants coated with the bioactive ceramics was lower than that of bulk AW or TCP. It appears impossible to obtain a higher failure load using a bioactive-ceramic coating on titanium alloy. Histologically, the coating layer was found to become detached from the metal implant and the bone tissue bonded to the coating layer. SEM-EPMA observation revealed breakage of the coating layer, although bonding between bone and the coating layer was evident. A Ca-P-rich layer was observed at the interface between bone and the AW coating, and a Ca-P-rich and a Si-rich layer were observed at the interface between bone and the BioglassR coating. For clinical application, it would seem better to use coated metal implants for short-term implantation. However, there is a possibility of breakage of the coating layer because of both dissolution of the bioactive ceramic and mechanical weakness at the interface between the coating layer and the metal implant.

Alloys↗
PubMed1996

Bone bonding behavior of titanium and its alloys when coated with titanium oxide (TiO2) and titanium silicate (Ti5Si3).

It has been proposed that the essential requirement for artificial materials to bond to living bone is the formation of bonelike apatite on their surfaces in the body. Recent studies have shown that titanium hydrogel and silica gel induce apatite formation on their surface in a simulated body fluid. In this study, the influence of titanium oxide and titanium silicate on the bonding of titanium alloys to bone was studied. Rectangular implants (15 x 10 x 2.2 mm) of titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were implanted into the tibial metaphyses of mature rabbits. At 8 and 24 weeks after implantation, the tibiae containing the implants were dissected out and subjected to a detaching testing. The failure load for titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were, respectively, 0.68 +/- 0.48, 0.22 +/- 0.46, 0.67 +/- 0.59, 2.18 +/- 0.71 and 2.03 +/- 0.41 kgf at 8 weeks, and 2.7 +/- 0.91, 2.58 +/- 1.29, 2.38 +/- 0.41, 3.79 +/- 1.7, and 2.79 +/- 0.87 kgf at 24 weeks after implantation. Histological examination by Giemsa surface staining, CMR, and SEM-EPMA revealed the coated titanium alloy implants directly bonded to bone tissue during early implantation. A Ca-P layer was observed at the interface of the coated implants and the bone. The results of this study indicated that TiO2 and Ti5Si3 can enhance the early bonding of titanium alloys to bone by inducing a Ca-P layer (chemical apatite) on the surface of titanium alloys. It also is suggested that the direct bone contact occurs in relation to the calcium and phosphorus adsorption onto the surface of the titanium passive layer formed during long-term implantation.

Alloys↗
PubMed1996

Osteogenic differentiation of cultured marrow stromal stem cells on the surface of bioactive glass ceramics.

To investigate the significance of apatite-wollastonite-containing glass ceramic (AW ceramic) surfaces and the biological apatite layer formed on these surfaces, rat marrow cell culture, which shows osteogenic differentiation, was carried out on four different culture substrata (control culture dish, two AW ceramics, each having a different surface roughness, and a ceramic on which an apatite layer was formed. A culture period of 2 weeks in the presence of beta-glycerophosphate, ascorbic acid, and dexamethasone resulted in abundant mineralized nodule formations that were positive for alkaline phosphatase (ALP) stain on all substrata. The stain on the apatite-formed AW ceramic was the most intense, the enzyme activity being about twice that of the control culture dish, which had the lowest stain and activity of the four substrata. Northern blot analysis of bone Gla protein (BGP) showed the same tendency, that is, the amount of BGP mRNA from cultured cells on the apatite-formed AW ceramics was the highest and the mRNA on the control dish was the lowest. These data indicate that the glass ceramic surface promotes osteoblastic differentiation and that the promotion can be further enhanced by the formation of a biological apatite layer on the ceramic surface.

Alkaline Phosphatase↗