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Biomedical subjects

J Hamada

Publications and source records attributed to J Hamada.

156 records · Page 9Linked to original sources
PubMed1984

A multi-stage model for border contrast.

A multi-stage model has been constructed. In this model, the first level is expressed by a convolution of the physical luminance function with a line spread function whose parameters depend on luminance. The second level extracts the gradient of the response that is processed at the first level. The third level detects, as edges, the inflection points of the response that is processed at the first level. The fourth level averages the response gradients over each interval between the edges, while keeping the total magnitude of the final response within the interval the same as those of the initial response at the first level. The model was applied to border contrast phenomena as described by Bergström (1966).

Darkness↗
PubMed1983

[Lightness decrease of the total area accompanying simultaneous lightness contrast].

Matches to the Munsell Lightness Scale were made in the two areas in a contrast-inducing pattern whose luminance difference was less than about 10%, and were compared with those of two uniform luminance field of corresponding luminances. The results showed (1) the simultaneous lightness contrast appeared in the contrast-inducing pattern, (2) the high luminance area in the contrast-inducing pattern appeared darker than the uniform luminance field of the same luminance. The lightness decrease in the high luminance area could be explained neither by Békésy's neural units model nor by Stevens' power transformation model, since Békésy's model predicts that high luminance area should appear lighter than the corresponding uniform luminance pattern, while Stevens' model expected the identical lightnesses between the two areas. In order to explain both the simultaneous lightness contrast and the lightness decrease, it was introduced a new model which included not only the antagonistic excitation and inhibition depending upon luminance-intensity, but also the non-antagonistic inhibition which is dependent upon the luminance-difference.

Adult↗
PubMed1980

[An inducing mechanism of the Craik-O'Brien and the Cornsweet effects (author's transl)].

The effect of edges on apparent lightness of the uniform luminous field was investigated in the so-called Craik-O'Brien and Cornsweet patterns as compared with that in the edgeless uniform field. It was found that white edge in the Craik-O'Brien pattern of Type II as well as a black edge in that of Type I lowered or darkened apparent lightness of the field on both side of the edge. The so-called Craik-O'Brien effect was due to assymmetry of the edge-effect on the two sides. The darkening effect of the white edge was explained by the antagonistic lateral inhibition. The same effect of the black edge was explained by a newly introduced concept of non-antagonistic inhibition. The Cornsweet effect was a combination of two edges, white and black, but not simply a summation but a complicated interaction of them.

Form Perception↗
PubMedDate not supplied

Recurrences after the open Bankart repair: a potential risk with use of suture anchors.

Eighty-seven consecutive patients were treated with an open Bankart repair for traumatic, recurrent anterior instability of the shoulder. Forty-six of these patients underwent a transosseous suture technique. Forty-one patients were operated on with suture anchors. After follow-ups that ranged from 18 to 85 months, 7 of the 87 patients showed signs of recurrence and another 14 patients reported apprehension. Compared with the 66 patients without residual instability, these 21 patients were more likely to have been operated on with suture anchors (P < .05), had a greater incidence of hypermobility in joints other than the shoulder (P < .05), and had had a greater number of preoperative episodes (P < .05). In light of this data we recommend the transosseous suture technique for open Bankart repairs. In addition, a cautious and extensive capsular repair may be required when a patient reports frequent subluxations preoperatively or has hypermobility in some joints, if not in the shoulder per se.

Adolescent↗
PubMedDate not supplied

Inhibitory effects of malotilate on in vitro invasion of lung endothelial cell monolayer by human oral squamous cell carcinoma cells.

We have previously reported that malotilate (MT) inhibited the invasion and metastasis of rat mammary carcinoma cells through the modification of host endothelial cells. In this study, we examined the inhibitory effects of MT on invasion of human cancer, using five oral squamous cell carcinoma cells (SAS, Ca9-22 and HSC-2, -3 and -4). MT did not affect the growth of these tumor cells and the invasion of reconstituted basement membrane, Matrigel. In an in vitro invasion assay using rat lung endothelial (RLE) cells, invasion of tumor cells which had been treated with MT (10 ng/ml, 24 h) was not affected; however, when RLE cells had been treated with MT, invasion was significantly inhibited in three cell lines (SAS, Ca9-22 and HSC-4) and a tendency to inhibition was also observed in other cell lines. Electron-microscopical examination of the RLE monolayer treated with MT (MT-RLE) showed the development of gap and tight junction-like structures. Subsequently, junction-associated proteins, connexin 43, zonula occludin and desmoglein, were examined by Western blotting. Protein levels of connexin 43 and zonula occludin were elevated dose dependently, and connexin 43 was chronologically enhanced by MT whereas desmoglein was not. The enhanced gap junctional communication of MT-RLE cells was observed in the scrape-loading assay using lucifer yellow CH. These results suggest that MT promotes the development of cell-to-cell adhesion, e. g. gap junction and tight junction in endothelial cells, resulting in the inhibition of invasion by the tumor cells.

Animals↗
PubMedDate not supplied

Unsaturated fatty acid feeding prevents the development of acute hepatitis in Long-Evans cinnamon (LEC) rats.

To investigate the effects of dietary alpha-linolenic acid (18:3, n-3; alpha-LNA) and linoleic acid (18:2, n-6; LA) on the development of hereditary hepatitis, we compared incidences and grades of acute hepatitis between the Long-Evans cinnamon (LEC) rats fed with safflower oil-supplemented diet and perilla oil-supplemented diet. Both safflower and perilla oil supplemented diets reduced the incidence of hepatitis and significantly prolonged its onset as compared to the non-supplemented conventional diet. No significant difference was observed between safflower and perilla oil diets in the rats of incidence of hepatitis. At the age of 16 weeks, just before the onset of hepatitis, serum levels of transaminase (AST, ALT) and concentration of copper in rats fed with both test diets were significantly reduced as compared with that of rats fed alpha-linolenate and linoleate have an inhibitory effect on the development of hepatitis in LEC rats due to the prevention of serum copper elevation.

Acute Disease↗
PubMedDate not supplied

The utility of the microcrystalline cellulose sphere as a particulate embolic agent: an experimental study.

BACKGROUND AND PURPOSE: Although various particulate materials have been developed as embolization agents, their biocompatibility remains unclear. We used an animal model to examine the possibility of using FDA-approved microcrystalline cellulose spheres (CELPHERE) as solid embolic material for the permanent occlusion of blood vessels. METHODS: Angiographic and histologic studies in 12 canine renal arterial systems were conducted to evaluate the performance of CELPHERE beads at 1 hour, and at 4 and 12 weeks after embolization. RESULTS: The CELPHERE beads traveled to vessels with diameters approximating their own. Larger vessels were occluded by aggregations of beads. There was no disruption of vessel walls and no evidence of perivascular hemorrhage or inflammatory changes. CONCLUSION: Because CELPHERE beads are easy to handle, highly biocompatible, and have few adverse effects, they are suitable for intravascular applications.

Angiography↗
PubMedDate not supplied

Embolization with cellulose porous beads, I: An experimental study.

PURPOSE: To study the possibility of using cellulose porous beads (CPBs) as a solid embolic material for the permanent occlusion of blood vessels. METHODS: Unilateral renal arteries of 12 adult mongrel dogs were embolized with CPBs. Selective renal angiograms were obtained immediately, 1 hour, 4 weeks, and 12 weeks after the embolization. The dogs were killed 1 hour (n = 4), 4 weeks (n = 4), or 12 weeks (n = 4) after the procedure. The kidneys were removed en bloc and examined histologically. RESULTS: The CPBs were easily injected through a microcatheter, were readily controlled with radiodensity, and did not adhere to the catheter. Renal angiograms obtained after embolization disclosed complete occlusion of the renal artery. Microscopically, the CPBs traveled to vessels with approximately the same diameter size. Larger vessels were occluded by aggregations of particles that left no open spaces. We found no disruption of the vessel wall, no evidence of perivascular hemorrhage, and no inflammatory changes of the vessel wall or the surrounding tissues. CONCLUSION: The CPBs were easy to use; they reached distal sites and produced a homogeneous and permanent occlusion without specific inflammatory changes. The good results of this experimental study led to a clinical trial of CPBs.

Animals↗
PubMedDate not supplied

Embolization with cellulose porous beads, II: Clinical trial.

PURPOSE: To evaluate the clinical applicability of cellulose porous beads (CPBs) as an embolic material for permanent vascular occlusion. METHODS: Embolization with CPBs was performed in 16 patients, six with meningioma of the sphenoid wing, two with meningioma of the falx, three with meningioma of the tentorium, two with dural arteriovenous fistula, one with paraganglioma, and two with spinal arteriovenous malformation. Surgical specimens were examined histologically. RESULTS: No complications were encountered in any of the 16 patients. Angiograms obtained after embolization showed satisfactory vascular stasis in all cases. Histologic examination of surgical specimens disclosed that vessels having approximately the same caliber as the CPB particles were occluded without stretching of the vessel wall. Larger vessels were occluded by aggregates of many particles, which left no open spaces. Although a few inflammatory cells were seen in the thrombosed vessels, inflammation evoked by CPB was mild and did not extend to either the vessel wall or to surrounding tissues. CONCLUSION: CPBs were easy to inject through microcatheters, traveled to distal sites, and produced homogeneous and peripheral embolization without inflammatory changes different from other embolic materials. CPBs are a good embolic material for permanent occlusion in the clinical setting.

Adolescent↗