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S Kumasaka

Publications and source records attributed to S Kumasaka.

11 recordsLinked to original sources
PubMed2000

Quantitative analysis using the star volume method applied to skeleton patterns extracted with a morphological filter.

In this study, a morphological filter was combined with star volume analysis and applied to digital images to determine its potential usefulness in assessing trabecular structure. Three digital "geometric" test patterns (square, rectangle, circle) were created on a CRT (cathode ray tube). Each shape was arranged into five groups by size to yield 15 final "skeletal" patterns that were subsequently assessed with star volume analysis. Also, three digital X-ray images (background, soft tissue, bone block) were processed with a morphological filter to create three sets of 11 skeletal patterns each. These patterns were also assessed with star volume analysis and the ratio of extracted skeletal elements (in pixel numbers) to total pixel numbers was expressed as the pixel percentage. Star volume analysis was then applied to these digital skeletal images to yield the volume of extracted "skeletal" trabecular elements (Vsk) and the volume of nonskeletal (marrow space) elements (Vsp). The Vsk and Vsp were compared for all the different skeletal patterns. The pixel percentages were then compared to the star volume results for the X-ray test patterns. The Vsk decreased and Vsp increased as the number of operations (n) increased for both digital X-ray images and the geometric test patterns when the X-ray images were depicted by pixel percentages. Also, all true bone test patterns were clearly different both visually and quantitatively when compared to the noise skeletons extracted from background and soft tissue. Therefore, as Vsk was increased, so was connectivity. It can be concluded that the application of morphological filters and star volume analysis may be a useful tool in quantitatively determining the characteristics and continuity of trabecular skeletal structures. Further studies involving a larger number of bone samples and using models to compare measurements of calculated versus actual volume should reveal the true potential of this method for evaluating bone structure and its relationship to bone strength and also increase the tools available for evaluating bone diseases such as osteoporosis.

Femur↗
PubMed2000

Morphologically extracted trabecular skeleton superimposed upon digital radiograph structure.

The purpose of this study was to employ a morphological filter to digital X-ray images to extract the morphology of trabecular structures in a clearly understandable visual format. This study compares the trabecular skeleton extracted by a morphological filter to the original digital radiographic image by superimposing the images. A morphological filter (a combination of a single structuring element and a skeleton operation) based on a mathematical morphology theory was used to extract the skeletal pattern of trabecular bone from a digital X-ray image of a human femoral neck. Subset images with different operation numbers (n = 1, n = 2) were obtained, and then each image was superimposed on the original digital radiographic image using the superimpose function of a workstation. The extracted trabecular skeleton pattern was fairly consistent with the trabecular structure seen on the digital image according to the opinion of seven dentomaxillofacial radiologists. In their opinion, the majority of the structural elements were reproduced on the extracted skeleton. However, accurate skeleton elements were not extracted in the region of dense trabecular structure. The morphological filter was able to extract a large portion of the bone trabecular structure as a binary skeletal pattern image from trabecular bone on digital X-ray image, but more work is needed to improve the assessment of dense trabeculae.

Computers↗
PubMed2000

Myasthenia gravis associated with reduced masticatory function.

This paper describes a case of myasthenia gravis in a 38-year-old woman who first consulted a dentist and then an oral surgeon because of chewing difficulty. Although myasthenia gravis commonly presents with diplopia, ptosis, or both as initial symptoms, chewing difficulty is rare. The patient was given steroid therapy and underwent thymectomy. Changes in bite force were monitored during treatment. The bite force was low when a high titer of anti-acetylcholine receptor antibody (11.0 nmol/l, normal <0.2) was found in the blood, but increased after the titer had decreased (1.5 nmol/l) in response to therapy.

Adult↗
PubMed1999

Novel mechanisms involved in superoxide anion radical-triggered Ca2+ release from cardiac sarcoplasmic reticulum linked to cyclic ADP-ribose stimulation.

It has been suggested that cyclic adenosine 5'-diphosphoribose (cADPR) directly activates the cardiac isoform of the ryanodine receptor (RyR)/Ca2+ release channel. We have previously shown that selective activation of RyR/Ca2+ release channel by superoxide anion radical (O2.-) is dependent of the presence of calmodulin and identified calmodulin as a functional mediator of O2.- -triggered Ca2+ release through the RyR/Ca2+ release channel of cardiac sarcoplasmic reticulum (SR). We now demonstrate that although the effect of O2.- on Ca2+ efflux from RyR/Ca2+ release channel at higher concentrations ( >5 microM) is due to its ability to produce a loss in function of calmodulin thereby decreasing calmodulin inhibition, O2.- radicals at lower concentrations (<5 microM) may be able to stimulate Ca2+ release only in the presence of calmodulin from the SR via increased cADPR synthesis; it is also shown that cADPR is a modulator that can activate the Ca2+-release mechanism when it is in a sensitized state by the presence of calmodulin, possibly, at physiological concentration. In addition, the SR vesicles immediately upon addition of cADPR, but not NAD+, did exhibit Ca2+ efflux stimulation. When heart homogenate was incubated with O2.-, conversion of NAD+ into cADPR was stimulated; the reduction of homogenate Ca2+ uptake (by increasing Ca2+ efflux through RyR/Ca2+ release channel) occurred. Thus O2.- radical is responsible for cADPR formation from NAD+ in the cellular environment outside of the SR of heart muscle. The results presented here provide the first evidence of a messenger role for O2.- radical in cADPR-mediated Ca2+ mobilization in myocardium.

Adenosine Diphosphate Ribose↗
PubMed1998

Inhibition by midazolam of the adrenergic function in the isolated canine mesenteric vein.

BACKGROUND: Midazolam has been reported to cause hypotension or to depress sympathetic activity following intravenous injection. However, little information is available concerning the mechanism of these effects. The aim of the present study was to determine the effects of midazolam on release of noradrenaline (NA) at nerve terminals and on receptors in the venous smooth muscle. METHODS: The effect of midazolam at nerve terminals was examined by measuring the amount of NA release from superfused canine mesenteric vein helical strips during electrical stimulation (ES; 5 Hz, 2 ms, 9 V). The NA was quantified by high-performance liquid chromatography with electrochemical detection; tension development evoked by ES was also recorded simultaneously. In a separate series of experiments, ring preparations from the isolated vein were mounted in Krebs-Ringer solution for isometric tension recording to assess the effect of midazolam on alpha-adrenoceptors. RESULTS: Application of tetrodotoxin (10(-6) M) or replacement of superfusate with Ca(2+)-free solution decreased both the release of NA and the tension development evoked by ES. Yohimbine (5 x 10(-8) M) increased the ES-evoked release of NA, whereas it decreased tension development in the vein strips. Midazolam (10(-4) M) did not affect either the basal release of NA or the basal tension, but inhibited both the NA release (P < 0.01) and the tension development (P < 0.01) during ES; midazolam at 10(-5) M inhibited the tension development (P < 0.05) but had no effect on NA release. In the ring preparations, midazolam (10(-5) and 10(-4) M) attenuated responses to NA (a mixed alpha 1- and alpha 2-adrenoceptor agonist, 10(-8) to 10(-3) M), phenylephrine (the alpha 1-adrenoceptor agonist, 10(-8) to 10(-3) M) and 5-bromo-6-[2-imidazolin-2yl-amino]-quinoxaline (UK14304; the alpha 2-adrenoceptor agonist, 10(-7) to 10(-3) M) in a dose-dependent manner. CONCLUSION: The data obtained in the present study suggest that midazolam at 10(-4) M may reduce venous tone by inhibiting the release of NA from sympathetic nerve endings and both alpha 1- and alpha 2-adrenoceptor mediated smooth muscle contractions. It is also postulated that a stage of the post-receptor transduction mechanism linked to the venous smooth muscle contraction may be more sensitive to midazolam than the NA release mechanism at nerve terminals since midazolam at the low concentration tested inhibited ES-evoked tension development with no effect on the release of NA.

Adrenergic Antagonists↗
PubMed1997

Initial investigation of mathematical morphology for the digital extraction of the skeletal characteristics of trabecular bone.

OBJECTIVE: To develop a filter utilizing mathematical theory to extract the skeletal patterns of trabecular bone. METHODS: Studies of morphology in the extraction of patterns of calcification in mammograms provided the theoretical framework. Using these studies as a basis, a morphological filter was applied to extract skeletal patterns from digital images of trabecular bone. Sequential images (subset) were combined in a structured fashion to create an aggregate (sumset) which compared with the original images, skeleton and line skeleton images. RESULTS: Binary images of the skeletal patterns in continuous, round and mesh-like forms were obtained from the original images by processing with the skeleton operation using a disc-shaped single structuring element. The line skeleton operation using line structuring elements with constant directions allowed the extraction of linear and discontinuous patterns. Both the skeleton and line skeleton operations extracted binary subset images which depicted skeletal patterns correlating with the operation sequence. CONCLUSIONS: Modification of the morphological filter enhanced the extraction of skeletal characteristics of trabecular bone. A morphological filter may be a useful adjunct in computer-aided structural analysis of bone.

Bone Density↗
PubMed1990

[A study of development and lesion of dental hard tissue. Quantitative analysis of trace elements (Cd, Zn, Pb and Cu) in different geological areas of Japan].

Trace elements (Cd, Zn, Pb and Cu) levels were determined in lower deciduous incisors which were collected from four areas (Sapporo, Yokosuka, Nagano and Kitakyushu) in Japan. Samples were divided into enamel and dentin, and dissolved with nitric and dried at 80 degrees C. Each element was separated chromatographically using an acetone-HCL gradient solution with a cation exchange resin and then analyzed by atomic absorption spectrophotometry. The results were as follows: 1. Ca, P, Ca/P ratio levels showed no significant differences among four areas. 2. In the enamel, (1) Cd levels of each area were 0.593 micrograms/g (Yokosuka) greater than 0.315 micrograms/g (Sapporo) greater than 0.261 micrograms/g (Nagano) greater than 0.222 micrograms/g (Kitakyushu). (2) Zn levels of each area were 174.912 micrograms/g (Nagano) greater than 157.473 micrograms/g (Yokosuka) greater than 150.971 micrograms/g (Kitakyushu) greater than 128.980 micrograms/g (Sapporo). (3) Pb levels of each area were 8.412 micrograms/g (Kitakyushu) greater than 7.925 micrograms/g (Yokosuka) greater than 5.426 micrograms/g (Sapporo) greater than 4.285 micrograms/g (Nagano). (4) Cu levels of each area were 9.276 micrograms/g (Kitakyushu) greater than 6.928 micrograms/g (Nagano) greater than 6.178 micrograms/g (Yokosuka) greater than 4.389 micrograms/g (Sapporo). 3. In the dentin, (1) Cd levels of each area were 0.214 micrograms/g (Sapporo) greater than 0.184 micrograms/g (Kitakyushu) greater than 0.145 micrograms/g (Nagano) greater than 0.119 micrograms/g (Yokosuka). (2) Zn levels of each area were 124.152 micrograms/g (Yokosuka) greater than 112.242 micrograms/g (Nagano) greater than 111.952 micrograms/g (Sapporo) greater than 111.456 micrograms/g (Kitakyushu). (3) Pb levels of each area were 3.584 micrograms/g (Kitakyushu) greater than 3.019 micrograms/g (Yokosuka) greater than 1.819 micrograms/g (Sapporo) greater than 1.523 micrograms/g (Nagano). (4) Cu levels of each area were 3.734 micrograms/g (Kitakyushu) greater than 2.221 micrograms/g (Nagano) greater than 2.098 micrograms/g (Yokosuka) greater than 1.664 micrograms/g (Sapporo). Therefore, the results suggest that the trace elements levels in deciduous teeth depended on the environmental condition of each area and the deciduous teeth could be a useful material as an environmental contamination indicator.

Cadmium↗
PubMedDate not supplied

Oligodontia: a radiographic comparison of subjects with Down syndrome and normal subjects.

Panoramic radiographs and clinical records were used to investigate developmentally absent permanent teeth in 98 subjects with Down syndrome (trisomy-21). This retrospective study was based on the records and panoramic radiographs of subjects from approximately five years of age (the age at which mineralization of the permanent tooth germ could be identified) through to their most recent records. The time period covered by records ranged from 6 to 28 years. The majority of subjects with Down syndrome (63%) exhibited oligodontia, and many subjects were missing two or more teeth (53%). The most frequently absent teeth were the lower lateral incisors (23.3%), the upper second premolars (18.2%), the upper lateral incisors (16.5%), and the lower second premolars (15.3%). In general, the distribution of the developmentally absent teeth was similar for teeth in homologous positions (i.e., left and right canines, etc.) on either side of the midline or between the maxilla and the mandible. The only significant exceptions to this pattern were seen with the central incisors and the second molar. This study's findings suggest a high risk of oligodontia in subjects with Down syndrome.

Anodontia↗