Biomedical subjects

Yutaka Yamada

Publications and source records attributed to Yutaka Yamada.

14 recordsLinked to original sources

PubMed2006

Effects of bioactive glass on bone augmentation within a titanium cap in rabbit parietal bone.

BACKGROUND: The condition of alveolar bone influences the success and subsequent esthetics of implant treatment. This study investigated the early effects of bioactive glass (BG) on bone augmentation within a hemispherical titanium cap in rabbit parietal bone. METHODS: Twelve adult male Japanese white rabbits were used. One titanium cap (test site) was packed with BG in a collagen gel, and the other (control site) was packed with the collagen gel alone. After 1 and 3 months, animals were euthanized, and the experimental area was examined using fluorescence and light microscopy. RESULTS: Newly generated bone was observed at 1 and 3 months of healing. Although bone was also generated without BG, newly mineralized bone was generated sooner with BG present for guided bone augmentation than without BG. At 1 and 3 months, the BG was not bioabsorbed completely, and some particles remained. CONCLUSION: New bone is generated at an early stage of bone formation using BG for bone augmentation.

Animals↗

PubMed2006

Effects of different sizes of beta-tricalcium phosphate particles on bone augmentation within a titanium cap in rabbit calvarium.

This study evaluated the effects of different sizes of beta-TCP particles on bone augmentation within a titanium cap. In 20 rabbits, the calvarium was exposed and a circular groove was prepared. After marrow penetration, a standardized hemispherical titanium cap was placed in the circular grove. The cap was filled with small-sized (100-250 microm) or medium-sized (250-500 microm) beta-TCP particles for the experimental site and without beta-TCP for the control site. After one and three months of healing, the animals were euthanized and examined histologically. There was a statistically significant difference in the amount of mineralized bone generated between the experimental and control groups in the three-month specimens. Furthermore, the medium-sized particles showed significantly more mineralized bone than did the small-sized particles. Based on these findings, we suggested that beta-TCP might be effective for bone formation and that medium-sized particles are more useful than small-sized particles in bone maturation.

Animals↗

PubMed2005

Three-dimensional evaluation for augmented bone using guided bone regeneration.

OBJECTIVE: This study evaluated new bone regeneration beyond the skeletal envelope within an occlusive titanium cap on rabbit calvaria using microfocus computed tomography images. METHODS: In 10 rabbits, the calvaria was exposed and a circular groove was prepared. After penetrating the marrow, a standard hemispherical titanium cap was placed in the groove and covered with a cutaneous flap. After 1 or 3 months, the animals were killed and the calvariae and titanium caps were dissected. After taking microfocus computed tomography images of the specimens, histological sections were made. The specimens were observed using three-dimensional images constructed from the microfocus computed tomography images, and the histological sections were examined to compute bone parameters. RESULTS: The three-dimensional images and histological specimens showed that new bone formed in flat, cup-like, and dome shapes. The bone parameters trabecular thickness and the proportion of marrow space to the capacity of the titanium cap increased, whereas bone density decreased, and there were significant differences between the 1- and 3-month groups. DISCUSSION: First, a cylinder of new bone formed from the existing bone. Gradually, bone formed along the cap wall and the new tissue formed in a crater indented centrally. Finally, the new tissue formed in the shape of a dome. CONCLUSION: Trabecular bone formed along the wall of the titanium cap, and bone filled the inside of the cap within 3 months.

Animals↗

PubMed2004

A new method for preparing plan-view TEM specimen of multilayered films using focused ion beam.

A new method is proposed for preparing plan-view specimens of a CeO(2)/Gd(2)Zr(2)O(7) multilayer on a metal substrate using focused ion beam milling. In the plan-view specimen, a membrane from the surface region of the CeO(2) to the Gd(2)Zr(2)O(7) layer was thinned to electron transparence so that the entire span of the multilayer can be observed in a single sample. The in-plane alignments of the CeO(2) layer and the Gd(2)Zr(2)O(7) layer were analysed using selected-area diffraction patterns (SADPs). The boundaries between the CeO(2) grains were also examined using SADPs.

Microscopy, Electron, Transmission↗

PubMed2004

Specimen preparation for high-resolution transmission electron microscopy using focused ion beam and Ar ion milling.

We have developed a focused ion beam (FIB)-Ar ion-milling technique for high-resolution transmission electron microscopy. A micrometresized specimen was mounted on a cross section of metal foil of a few micrometres thick, using FIB microsampling. Following this, a 2 degrees wedgeshaped part was made in the specimen using FIB. Finally, the specimen was milled using an Ar ion beam to remove the FIB-damaged layers. We applied the FIB-Ar ion milling technique to a CeO(2)/Gd(2)Zr(2)O(7) multilayer specimen, resulting in the crystal lattice fringes of both layers being clearly observable in comparison to a specimen finished using a Ga ion beam at an accelerating voltage of 10 kV.

Argon↗

PubMed2004

Comparisons of the skeletal muscle metabolic abnormalities in the arm and leg muscles of patients with chronic heart failure.

BACKGROUND: It has been suspected for some time that patients with chronic heart failure (CHF) have abnormal muscle metabolism, so in the present study the muscle metabolism of the arm and leg were compared by (31)P magnetic resonance spectroscopy ((31)P-MRS) to examine the relationship to exercise tolerance. METHODS AND RESULTS: The study group comprised 13 patients and 11 normal controls. Calf-plantar and forearm-wrist flexion were performed to evaluate the metabolic capacity assessed as the phosphocreatine breakdown rate (PCr-slope) and muscle pH at a submaximal (70% peak) work rate (submax-pH). Exercise of both the arm and leg resulted in an earlier decrease in PCr and muscle pH in patients with CHF compared with controls. There were significant correlations between peak oxygen uptake (peak V(O2)) and the PCr-slope in both limbs in patients with CHF (forearm: r=0.63, p<0.05; calf: r=0.60, p<0.05), but no correlations in normal controls. There was a close correlation between the ventilatory anaerobic threshold (AT) and the PCr-slope in the calf (r=0.85, p<0.01), but not in the forearm in patients with CHF. Submax-pH in both upper and lower limbs was not significantly correlated to peak V(O2) or AT in either patients with CHF or controls. CONCLUSIONS: Although metabolic abnormalities during exercise are seen in both arms and legs, leg muscle abnormalities, in particular, are closely related to systemic exercise intolerance in patients with CHF.

Arm↗

PubMed2004

Comparative study on Tp53 gene mutations in lung tumors from rats exposed to 239Pu, 237Np and 222Rn.

The tumor suppressor gene Tp53 was analyzed by polymerase chain reaction-amplification of genomic DNA extracted from paraffin-embedded tissue sections of rat lung tumors to compare mutations that occurred after inhalation exposures to plutonium dioxide, neptunium dioxide, or radon and radon progenies. Exons 5 to 8 of the gene were amplified in 16 plutonium-, 23 neptunium- and 15 radon-induced lung tumors, and their polymerase chain reaction products were examined for mutations by single strand conformational polymorphism analysis and direct sequencing method. Two point mutations were detected in the plutonium-induced tumors, i.e., a guanine to adenine transition at codon 219 of exon 6 and a cytosine to thymine transition at codon 266 of exon 8. Although only one point mutation was found at codon 175 of exon 5 (cytosine to thymine transition) from neptunium-induced tumors, no mutations were detectable from radon-induced tumors. These results indicate that the abnormalities of the Tp53 gene might not be so critical for the pulmonary carcinogenesis after the inhalation of different alpha emitters, even though the presence and frequencies of the Tp53 gene mutations were different.

Administration, Inhalation↗

PubMed2004

Angiotensin converting enzyme genotype influences the response to the angiotensin II receptor antagonist losartan in patients with hypertension.

To examine whether the response to the angiotensin II receptor antagonist losartan varies depending on the angiotensin converting enzyme (ACE) genotype, we prospectively studied the effect of losartan in 42 hypertensive patients (20 men, 22 women; mean age: 60.4 years). After a 4-week observation period, losartan was administered at 50 mg/day and blood pressure was measured every 2 to 4 weeks for 12 weeks. Among the 42 patients, 19, 11, and 12, respectively, had the II, ID, and DD ACE genotypes. The baseline plasma ACE activity in patients with the ID or DD genotype was significantly higher than that in patients with the II genotype (13.8 +/- 4.2 vs. 9.6 +/- 2.3 IU/l; p = 0.0002). However, age, gender, baseline systolic and diastolic blood pressure (SBP/DBP), and body mass index (BMI) were not different among the groups. After 12 weeks of treatment with losartan alone, DBP in the ID+DD group was significantly higher than that in the II group (85.0 +/- 9.0 vs. 77.8 +/- 9.6 mmHg, p = 0.018), while the percent reduction in DBP in the ID+DD group was significantly smaller than that in the II group (7.9 +/- 8.8 vs. 14.3 +/- 10.1%, p = 0.035). Multiple regression analysis showed that the significant predictors of the DBP at 12 weeks were age (p = 0.030), ACE genotype (p = 0.029) and baseline DBP (p = 0.0001). The ACE genotype may be a determinant of the response to losartan in hypertensive patients.

Aged↗

PubMed2003

Effects of occlusiveness of a titanium cap on bone generation beyond the skeletal envelope in the rabbit calvarium.

We evaluate the effects of occlusiveness of a titanium cap on bone generation beyond the skeletal envelope. In eight rabbits, the calvarial bone was exposed and a circular groove was prepared with a trephine drill. After marrow penetration, a standardized hemispherical titanium cap, either with or without small holes (1.5 mm in diameter), was then placed into the bone and covered by a cutaneous flap. After 1 month or 3 months of healing, the animals were euthanized and examined histologically. The percentage area of newly generated tissue consisting of mineralized bone and marrow spaces in each section was calculated relative to the area bounded by the hemispherical shape of the titanium cap and the parent bone; this latter volume was taken to be 100%. Furthermore, the cross-sectional areas of generated mineralized bone expressed as percentages of the total tissue area generated within each space were determined. In the 1-month specimens, there was no statistically significant difference between the two caps in the amount of tissue generated, 54.7%+/-12.2% with holes vs. 60.4%+/-8.8% without holes (p=0.225). However, in the 3-month specimens, we observed a significant difference between the caps (55.9%+/-7.4% with holes vs. 89.9%+/-6.5% without holes, P<0.05). Also, there was a statistically significant difference between 1- and 3-month specimens in the amount of tissue generated under the cap without holes (60.4%+/-8.8% vs. 89.9%+/-6.5%, P<0.05). Although there was no significant difference in the relative amount of mineralized bone generated between the caps with holes and those without holes in the 1-month specimens (27.7%+/-4.8% vs. 30.8%+/-6.4%, P=0.225), there was a statistically significant difference between the two caps in the 3-month specimens (24.3%+/-4.1% with holes vs. 34.0%+/-8.6% without holes, P<0.05). A substantial ingrowth of fibrous connective tissue through the holes appeared to prevent further new tissue generation in a defined area adjacent to the bone surface. We concluded that total occlusiveness, sufficient stiffness of the cap, as well as the passage of time will allow predictable mineralized bone augmentation to occur in spaces beyond the skeletal envelope.

Animals↗

PubMed2003

The specific induction of osteosarcomas in different mouse strains after injections of 239Pu citrate.

Lifetime bone tumor induction by the injection of a bone-seeking alpha emitter, 239Pu citrate, was compared among 630 female mice from three strains (C3H/He, C57BL/6 and B6C3F1) showing different genetic backgrounds for carcinogenesis. Bone tumors, mostly osteosarcomas, appeared early during the period from 200 to 600 days after the injection, showing an almost similar dose responsiveness with a peak incidence of 50% to 63% at skeletal doses of 2-3 Gy, in all mouse strains. The primary sites of bone tumors from these strains were also predominantly distributed in 80% to 90% of the skeletal bones, which had well-developed trabecular bone surfaces and large vascular sinusoids. The frequency of lymphoid neoplasms was significantly lower than the control values, and some appeared earlier at the higher injected doses than those of the controls. Fewer or no myeloid leukemias were found in all the control and injected animals, and the incidences of other solid tumors decreased, reaching zero at doses where the maximum incidences of bone tumors were noted. These findings indicate that osteosarcoma is the only specific tumor commonly observed among different mouse strains following the injection of soluble plutonium compounds.

Animals↗

PubMed2003

Comparisons of pulmonary carcinogenesis in rats following inhalation exposure to plutonium dioxide or X-ray irradiation.

Radiation-induced pulmonary carcinogenesis was compared in female Wistar rats following either inhalation exposure to alpha-emitting (239)PuO(2) aerosols, whole-body or thoracic X-ray irradiation. Dose-dependent survival reduction was correlated with increased malignant lung tumors at doses over 0.45 Gy, reaching the maximum incidence of 90% at 6.6-8.5 Gy in (239)Pu-exposed rats. While the differential dose responses for each histopathological type of tumors were noted, almost 70-80% were carcinomas among all of the primary tumors from (239)Pu-exposed rats. As the dose response curves for lung carcinomas were compared, the slope of the fit linear equation and the calculated relative effectiveness for 50% incidence of lung carcinomas were approximately 11-times as high in (239)Pu-exposure as those of thoracic X-irradiation. The numbers of tumor lesions distributed in the lung per tumor-bearing animal were about 2-fold more in (239)Pu-exposed rats, while the proportions of their histopathological types were similar between (239)Pu-exposure and X-irradiation. These results indicate that the magnitudes of the relative effectiveness or risk for pulmonary carcinogenesis are greater in (239)Pu-exposure than X-irradiation, and that radiation-induced lung tumors appear to originate mostly from the same target epithelial cells.

Adenoma↗

PubMed2003

The effects of twisting and type of aspiration needle on the efficiency of transvaginal ultrasound-guided ovum pick-up in cattle.

The effects of twisting and type (single- or double-lumen) of aspiration needle on the efficiency of transvaginal ultrasound-guided ovum pick-up (US-guided OPU) were investigated in cattle. The first study using slaughterhouse ovaries revealed that twisting of the needle during follicle aspiration improved the oocyte recovery rate without deleterious effects on the attachment of cumulus layers. Vacuum pressure affected the oocyte recovery and cumulus attachment, regardless of the needle type. The needle type did not affect the oocyte recovery or cumulus attachment with an optimized vacuum pressure. In the second study, US-guided OPU was performed in live cows using two types of needles with a vacuum pressure of 75 mmHg. The needle type did not affect the oocyte recovery or cumulus attachment of the recovered oocytes. The results revealed that twisting of the needle is effective in follicle aspiration, and suggested that a single-lumen needle is as useful as a double-lumen needle for US-guided OPU in cattle.

Animals↗

PubMed2002

Immunohistochemical study on cellular origins of rat lung tumors induced by inhalation exposures to plutonium dioxide aerosols as compared to those by X-ray irradiation.

Immunohistochemical examinations were performed on rat pulmonary tumors induced by inhalation exposures to 239PuO2 aerosols, or by X-ray-irradiation to identify and compare cellular origins or, in turn, target cells at risk for radiation carcinogenesis. Both plutonium-induced and X-ray-induced pulmonary tumors appeared to occur from the lower respiratory tract epithelium through bronchioles into alveoli, and were histopathologically diagnosed as adenoma, adenocarcinoma, adenosquamous carcinoma, and squamous cell carcinoma. Immunohistochemical staining of neoplastic lesions using rabbit polyclonal antibodies to rat surfactant apoprotein A specific for alveolar type II pneumocytes, and Clara cell antigen specific for nonciliated bronchiolar Clara cells, showed that most of the adenomatous and adenocarcinomatous lesions from plutonium-exposed or X-irradiated rats were positive for either or both antigens, while, in contrast, adenosquamous and squamous lesions were mostly negative for both antigens. Even though there were some differences in the proportions and distributions of immunoreactive cells between plutonium- and X-ray-induced tumors and among neoplastic lesions, the results indicate that radiation-induced pulmonary adenomas and adenocarcinomas mostly originate from either alveolar type II pneumocytes or bronchiolar Clara cells, while adenosquamous and squamous carcinomas may be derived from the other epithelial cell components, or might have lost specific antigenicity during their transforming differentiation.

Administration, Inhalation↗

PubMed2002

Effects of ipriflavone on bone augmentation within a titanium cap in rabbit calvaria.

Ipriflavone (7-isopropoxyisoflavone, IP), a drug used in the treatment of osteoporosis, may promote bone formation during bone remodeling. IP has been shown to accelerate both the activity of, and formation of mineralized nodules by a human osteosarcoma cell line at an early stage. However, the direct effects of IP on bone augmentation have not been investigated. The purpose of this study was to determine whether IP induces bone augmentation within a titanium cap in rabbit calvaria at an early stage. Five adult male Japanese white rabbits were used. One cap (test site) was packed with IP in a collagen gel, and the other (control site) was packed with the collagen gel alone. After the one- and three-month healing periods, we measured the newly generated tissue and bone within the titanium caps. The amount of newly generated tissue within the titanium caps of the control sites was higher than the tests sites after one month and three months. However, the percentage of newly generated bone/bone marrow in the newly generated tissue at the test sites was higher than for the control sites after one month and three months. These results suggest that IP affects the quality of bone augmentation at an early stage.

Animals↗