Biomedical subjects

T Masuda

Publications and source records attributed to T Masuda.

906 records · Page 51Linked to original sources

PubMedDate not supplied

[Effect of vesnarinone on the myocardial force-length relationship in the in situ canine left ventricle].

The left ventricular (LV) end-systolic force-diameter (Fes-Des) relationship was used to examine the effect of a new positive inotropic agent (vesnarinone) on the contractility of the beta-blocked canine left ventricle. Seven adult mongrel dogs were implanted with ultrasonic crystals to measure the LV diameter and a micromanometer to measure LV pressure. Beta-adrenergic and vagal blockades were induced with intravenous propranolol (2 mg/kg) and atropine (0.2 mg/kg), respectively, and preload was decreased by inferior vena caval occlusion. The slope (Ec) and extrapolated diameter intercept (Do) of the LV Fes-Des relationship were derived from the end-systolic data obtained in the control, beta-blocked state, after sulfolane infusion, and after infusion of vesnarinone (3 mg/kg) dissolved in sulfolane. Ec was used as a new index of LV myocardial contractility. After vesarinone infusion, the LV Fes-Des relationship seemed to be nearly linear, and its Ec value was significantly increased by 18% (68.4 +/- 15.4 vs 80.4 +/- 21.8 g/cm, p < 0.05) without changes in heart rate, whereas Do did not change (1.74 +/- 0.44 vs. 1.70 +/- 0.42 cm). These results indicate that vesnarinone significantly enhances myocardial contractility in the beta-blocked canine left ventricle.

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PubMedDate not supplied

Analysis of p53 abnormalities in endoscopic gastric biopsies.

We performed immunohistochemical staining for p53 in 152 endoscopic gastric biopsy specimens, including 39 adenomas, 80 carcinomas, and 33 cases of regenerative atypia. Direct DNA sequencing of exons 5,7 and 8 of the p53 gene was performed on 8 specimens. Nuclear p53 immunoreactivity was observed in 36 of 80 carcinomas, 7 of 39 adenomas and none of the cases of regenerative atypia. Three of the adenomas demonstrated diffuse or focal p53 immunoreactivity. All three cases were associated with severe degrees of epithelial dysplasia, and two of them harbored carcinoma on subsequent polypectomy. Among 6 p53 positive carcinomas and adenomas sequenced, 3 showed DNA mutations, all G:C to A:T transitions. These results indicate that positive p53 immunoreactivity in intraepithelial atypical cells on gastric biopsies represents true dysplasia or carcinoma rather than regenerative atypia.

Adenocarcinoma↗

PubMedDate not supplied

Preliminary comparison of mineralizing multilayer cultures formed by primary fetal bovine mandibular osteoblasts grown on titanium, hydroxyapatite, and glass substrates.

Bone formation at implant surfaces may be directly influenced by effects of the implant material on osteoblast behavior. Cell culture models of osteoblast physiology may be used to investigate the interaction of osteoblastic cells with various surfaces. In this study, primary cultured fetal bovine mandibular osteoblastic cells were cultured on titanium, ceramic hydroxyapatite, and glass coverslip surfaces to allow for the comparison of the mineralizing matrix elaborated by osteoblasts grown on different implant material surfaces. Morphologic and immunohistochemical analysis revealed the similar formation of multilayered, mineralizing cultures on these three surfaces. The qualitative similarity of the matrix formed on these culture surfaces may reflect similar qualitative in vivo responses of bone to titanium and hydroxyapatite implants.

Animals↗

PubMedDate not supplied

Cell and matrix reactions at titanium implants in surgically prepared rat tibiae.

The tissue response of rat tibiae to the surgical placement of commercially pure titanium implants was examined at 2, 6, 10, and 28 days. The transcortical placement of 1.5-mm x 2-mm implants resulted in the apposition of threaded implant surfaces within cortical and cancellous regions of the tibia. In all regions, evidence of bone formation was obtained through pre-embedding fracture of the implant from the bone tissue interface. Scanning electron microscopy examination of early responses revealed a fibrin clot and rapid formation of a loosely organized collagenous matrix. Many extravasated blood cells contacted the implant surface. At day 6, a more organized matrix containing many blood vessels opposed the implant surfaces, and few extravasated blood cells remained in contact with the implant surface. By day 10, the surgical wound was filled with woven bone that approximated the contours of the threaded implant. Later, few cells were attached to the retrieved implants. The consolidation of the forming matrix was clearly evident at 28 days. The tissue interface was an amorphous matrix that revealed the surface characteristics of the machined implant. Light microscopic analysis of ground sections indicated that, from day 6 onward, cells morphologically consistent with the osteoblastic phenotype were predominant within the gap between the surgical margin and implant surface. Osteoblastic cells had achieved the formation of an osteoid seam upon which bone formation progressed. The matrix that had formed represented woven bone containing many osteocytes. At day 6, evidence of remodeling was observed at sites distant from the surgical site, and by day 28 osteoclastic activity was observed at trabecular sites adjacent to the implant surface. The rat tibia model provides evidence of rapid formation of bone at implant surfaces.

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PubMedDate not supplied

Generalizations regarding the process and phenomenon of osseointegration. Part I. In vivo studies.

The clinical success of endosseous implants is associated with the formation and maintenance of bone at implant surfaces. Histologic analyses have indicated that bone formation at a variety of implant surfaces is a continuous process that supports long-term functional integration. Based on in vivo observations, several generalizations have been derived regarding the nature of the interface. Experimental descriptions indicate that the implantbone interface may be characterized in spatial and temporal terms as discontinuous. Biomechanical tests of the bone associations with implants demonstrate that the chemical composition and the surface topography of the implant influence the rate and extent of bone formation at implant surfaces. The precise character and functional attributes of this interface are the focus of this investigation. Many technical difficulties are associated with its structural and chemical characterization in vivo. Despite the technically difficult nature of this type of analysis and the limitations of current histologic examinations and biomechanical tests, in vivo models of osseointegration are necessary experimental tools for the continued empirical development of clinical implant applications.

Animals↗

PubMedDate not supplied

Generalizations regarding the process and phenomenon of osseointegration. Part II. In vitro studies.

In this review, the appropriate use of cell culture to evaluate substrate effects on osteoblast behavior during the process of osseointegration has been considered in the context of existing reports. The interactions of osteoblasts with different substrates can be measured in terms of cytotoxicity, attachment, proliferation, and differentiation. The osteoblast culture systems that produce an osteoblast matrix opposing implant material substrates provide one model for evaluating the implant-bone interface. Alterations in osteoblast behavior at different culture substrates may reflect clinical determinants of bone formation at these substrates in vivo; however, cell responses in vitro have not been compared or correlated with in vivo outcomes. Legitimate interpretations of in vitro experiments are discussed in terms of practical, technical, and biologic limitations presented by the cell culture approach. Cell culture provides access to molecular and cellular information that fosters nanostructural engineering approaches to implant design and significant hypotheses to be tested in vivo. In this way, cell culture offers unique insights into the process and phenomenon of osseointegration.

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