Two-pion-exchange potential in a quasistatic two-Skyrmion system.
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Journal Article↗
Biomedical subjects
M Oka
Publications and source records attributed to M Oka.
Palytoxin: a potent stimulator of catecholamine release from cultured bovine adrenal chromaffin cells.
The effect of palytoxin (PTX), a potent marine toxin, on catecholamine release from cultured bovine adrenal chromaffin cells was examined. PTX at concentrations of over 10(-9) M induced catecholamine release dose-dependently. About 40-50% of the total cellular catecholamine was released during 20-min incubation with 3 x 10(-8) M PTX. PTX-induced catecholamine release was dependent on both extracellular Na+ and Ca2+, and was inhibited by organic and inorganic Ca2+ channel blockers, but not by tetrodotoxin. PTX-induced increase in 45Ca2+ influx into the cells, which was associated with catecholamine release, was also inhibited by these Ca2+ channel blockers. These results indicated that PTX-induced catecholamine release was mediated by activation of Na(+)-dependent, tetrodotoxin (TTX) insensitive voltage-dependent Ca2+ channels.
Acrylamides↗
Biodegradable screw fixation of rabbit tibia proximal osteotomies.
The purpose of this study was to evaluate a biodegradable poly(L-lactide) (P-L-LA) screw for osteosynthesis under a load-bearing condition. A proximal tibial osteotomy on 25 rabbits was fixed with a biodegradable screw made of P-L-LA. A follow-up study was done at 1, 2, 4, 8, and 16 weeks. In another 25 rabbits, the tibial osteotomy was fixed with stainless steel (SUS) screws of the same size as the P-L-LA screws with a similar follow-up period. Radiographic, histological, microradiographic, and oxytetracycline-labeling studies showed healing of the osteotomy within 4 to 8 weeks. The displacement of fragments and the mass of newly formed bone around the screws were measured by histomorphometric analysis. There was no significant difference in the displacement of the fragments in these two groups and new bone was more abundantly detected in the P-L-LA group than in the SUS group. Histologically, no inflammatory lesion was detected in either group. All osteotomies united without delay and the displacement was minimal, although no external support was applied and the rabbits were allowed to move freely after the operation. The results of this study suggest a possible use for a P-L-LA screw in the clinical treatment of human bone fractures.
Animals↗
Poly(vinyl alcohol) hydrogel as an artificial articular cartilage: evaluation of biocompatibility.
We have developed a new poly(vinyl alcohol) hydrogel (PVA-H) of increased physical strength through a new manufacturing process. Its mechanical properties have been found to be preferable as a substitute for articular cartilage. To evaluate its biocompatibility as an artificial articular cartilage, a series of in vivo tests within the intraarticular, as well as the intramuscular, environment were conducted. Tissue reactions of cartilage, bone, synovium, and muscle to PVA-H were studied histologically. In the experimental group, in which PVA-H was implanted, inflammatory reactions of all of these tissues were very slight. In the control group, in which ultra-high molecular weight polyethylene (UHMWPE) was implanted, although tissue reactions of bone and muscle were as slight as in the experimental group, those of cartilage and synovium were somewhat more conspicuous. By way of these findings, the better biocompatibility of PVA-H was documented.
Animals↗
A heat-generating bioactive glass-ceramic for hyperthermia.
Glass plates of the chemical composition: CaO (29.0), SiO 2 (31.0), Fe 2O 3 (40.0), B 2O 3 (3.0), P 2O 5 (3.0) in weight ratio were heated to 1050 degrees C at a rate of 5 degrees C/min and then cooled to laboratory temperature. The resulting glass-ceramic containing magnetite and wollastonite crystals showed high-saturation magnetization. The bonding ability of this new glass-ceramic to bone tissue was evaluated using rabbit tibiae, and compared with glass of the same composition. This glass-ceramic formed a Ca, P-rich layer on its surface and bonded tightly with bone within 8 weeks of implantation. However, the glass did not form this Ca, P-rich layer, nor had it bonded with bone at 25 weeks. The bone-heating ability of this glass-ceramic was investigated by applying a max. 300-Oe, 100-kHz magnetic field. The granules of the glass-ceramic filled in the rabbit tibiae heated the whole surrounding bone to more than 42 degrees C and maintained this temperature for 30 min. Bioactive ceramics reinforce the mechanical strength of bone tissue. Furthermore, this heat-generating bioactive glass-ceramic can be used for hyperthermic treatment of bone tumors.
Animals↗
Bone-bonding ability of P2O5-free CaO.SiO2 glasses.
An apatite- and wollastonite-containing glass-ceramic (A.W-GC) has been reported to form a tight bond with living bone through an apatite layer formed on its surface. This layer is considered to be formed by dissolution of Ca2+ and HSiO3- ions from the glass-ceramic into the surrounding body fluids. In order to confirm this proposed mechanism for the surface reaction of A.W-GC, three kinds of glass in the systems CaO-SiO2, CaO-SiO2-CaF2, and CaO-SiO2-P2O5 were implanted into the tibiae of rabbits for 3 or 8 weeks. Contact microradiography and SEM-EPMA showed that all three kinds of glass formed a Ca,P-rich layer in combination with a Si-rich layer on their surfaces within 3 weeks and formed a direct bond with bone via these layers. The detaching test, performed 8 weeks after implantation, showed that the loads required to detach the implants from the bone were almost equal for the phosphorus-free and the phosphorus-containing glasses. It was concluded that even P2O5-free CaO.SiO2 glass formed a Ca,P-rich layer on its surface and bonded tightly with living bone. If glasses and glass-ceramics release at least Ca2+ and HSiO3- ions, this would be sufficient for them to form the Ca,P-rich layer on their surfaces in vivo, enabling them to bond directly with bone.
Animals↗
Low wear rate of UHMWPE against zirconia ceramic (Y-PSZ) in comparison to alumina ceramic and SUS 316L alloy.
Partially stabilized zirconia ceramic is being recognized among ceramics for its high strength and toughness. With this ceramic, is possible to manufacture a 22-mm-size femoral head for low friction arthroplasty of the hip joint in association with an ultra-high-molecular-weight polyethylene socket. Wear-resistant properties of zirconia ceramic were screened on two principally different wear devices. Sterile calf bovine serum, physiological saline, and distilled water were chosen as the lubricant fluid media. Depending on the lubricant medium, the wear factor of polyethylene against zirconia ceramic counterfaces was 40 to 60% less than that against alumina ceramic counterfaces, and 5 to 10 times lower than with the SUS316L metal counterfaces. Polyethylene wear against metal was more susceptible in saline in which it had 2 to 3 times higher wear rate than with serum. On the other hand, different fluid media had little effect on polyethylene wear against ceramic counterfaces. In each set of tests, the wear factor obtained on an unidirectional wear device showed 10 to 15 times higher values, in comparison to the wear factor estimated on a reciprocating wear device.
Alloys↗
Occlusal contact area and temporomandibular joint symptoms.
A new method for quantitative occlusal measurement is presented. In this study occlusal contact areas in 79 patients with or without temporomandibular joint symptoms were assessed from the simple wax bite. The area of occlusion has showed no distinct differences between the two groups. The occlusal contacts did not show any significant correlations with temporomandibular joint dysfunctions.
Adolescent↗
Involvement of central cholinergic mechanism in RU-24969-induced behavioral deficits.
The present study was undertaken to investigate the role of cholinergic mechanisms in the behavioral effects of RU-24969, a compound with serotonin1B (5-HT1B) receptor agonist properties. RU-24969 caused an increase in locomotion (2-5 mg/kg IP) and an impairment of spontaneous alternation (SA) behavior in a T-maze (0.5-2.0 mg/kg IP) in mice, effects that were also induced by the cholinergic hypofunction with scopolamine treatment (0.5-5.0 mg/kg IP), an acetylcholine (ACh) receptor antagonist. The impairment of the SA behavior by RU-24969 was enhanced by scopolamine. Both the hyperlocomotion and the SA impairment by RU-24969 were markedly reduced by propranolol (20 mg/kg IP) which has 5-HT1A/5-HT1B receptor antagonist properties, as well as by physostigmine (0.05-0.2 mg/kg IP), an ACh esterase inhibitor, and oxotremorine (0.005-0.01 mg/kg IP), an ACh receptor agonist. Moreover, these behavioral deficits of RU-24969 were diminished in mice pretreated intracerebroventricularly with AF64A (30 nmol/body), a presynaptic cholinergic neurotoxin, whereas scopolamine induced the deficits even in animals with the same treatment. These results suggest that the serotonergic behavioral deficits observed after RU-24969 treatment may be caused by an inhibition of ACh release through its action on the presynaptic receptor (particularly RU-24969-sensitive sites) localized on the cholinergic terminals.
Animals↗
Incorporation of cortical bone autografts following intraoperative extracorporeal irradiation in rabbits.
In an experimental study using 60 rabbits, a cortical bone segment of the unilateral tibial diaphysis was resected, irradiated extracorporeally, and reimplanted immediately as an autograft. The subsequent process of graft incorporation was examined over a 26-week period by roentgenography, histology, and histomorphometry. The irradiation doses were 0 (control), 50, 100, and 200 Gy. Roentgenographic and histologic examinations revealed that cortical bone autografts irradiated at 50 to 200 Gy were incorporated in the same manner as non-irradiated controls. By histomorphometry, the mean unresorbed fraction of the grafts at 6 weeks post-implantation was estimated to be 88.4% for the control group and 89.4% for the 200 Gy group. That of 26 weeks postimplantation was 17.5% for the control and 28.5%, 26.1%, and 27.8% for the 50, 100, and 200 Gy groups, respectively. Cumulative new bone formation showed a similar but inverse pattern of difference between the control and irradiated groups at 26 weeks. However, these differences were not statistically significant and were considered to be slight when compared with the overall similarity of the process. The total cross-sectional area of cortical bone at 26 weeks was similar to that of the contralateral side in all groups. In none of the adopted evaluation methods was any difference detected among the three irradiated groups with different doses. The results of this study suggest that extracorporeal irradiation of autografts at the specified doses impairs possible cellular contribution of the grafted marrow to the incorporation process, but does not interfere with the contribution of the matrices. The results provide useful information concerning the method of limb salvage surgery using intraoperatively-irradiated autografts.
Animals↗
Pneumoparotis, an unusual occurrence of parotid gland swelling during dental treatment. Report of a case with a review of the literature.
A 24-year-old male with pneumoparotis caused by the use of an air syringe during a routine restorative dental procedure during clinical training is presented. Reflux of air into the parotid gland due to increasing pressure is a rare cause of acute parotid swelling.--A discussion of this unusual case and review of the literature including its differential diagnosis and management form the basis of this report. Judicious use of intra-oral dental instruments using compressed air or gas is advised.
Adult↗
Benign mesenchymoma of the tongue. Report of a case, with review of the literature.
A benign mesenchymoma of the dorsal midtongue in an 88-year-old woman is presented. The tumour was excised under local anaesthesia, and microscopic examination revealed cartilage, bone, striated muscle, peripheral nerve, adipose and myxoid tissue, and blood vessels in addition to fibrous tissue. Eight cases including ours were found in the literature.
Aged↗
Analysis and prevention of spinal column deformity following cervical laminectomy. I. Pathogenetic analysis of postlaminectomy deformities.
Postlaminectomy deformities were simulated in the cervical or cervicothoracic spine by the use of a displacement incremental method based on finite-element analysis combined with composite material and spanning element theory. The simulation analyses revealed that the primary cause of postlaminectomy deformity was the resection of one or more spinous processes and/or posterior ligaments (ie, ligamenta flava, supraspinous, and interspinous ligaments). After their removal, the tensile stresses that were preoperatively distributed through the posterior ligaments were transferred to the facets. This led to an imbalance of the stresses on the spinal bodies, causing deformity. The gravitational center of the head determined whether the deformity would develop as a kyphosis or increasing lordosis. As the elastic modulus of the soft tissue composites (eg, end plates, ligaments, and facets) increased, a kyphotic deformity changed gradually from swan-neck deformity, to extreme kyphotic deformity with a large curvature, and finally to a straightening deformity. Progressive kyphotic deformity is found only in children.
Adult↗
Role of L3T4+ and Lyt-2+ T cell subsets in protective immune responses of mice against infection with a low or high virulent strain of Toxoplasma gondii.
In order to elucidate the role of T cell subsets in protective immunity against infection with high virulent and low virulent strains of Toxoplasma gondii, monoclonal antibodies specific for T cell subsets were injected into mice before immunization or challenge infection. Treatment of mice with monoclonal antibody to either L3T4+ or Lyt-2+ T cells before they were immunized with Toxoplasma cell homogenate prepared from high virulent RH strain tachyzoites markedly reduced survival after mice were challenged with low virulent bradyzoites of the Beverley strain. Thus, induction of protective immunity against bradyzoites of the Beverley strain requires the presence of both L3T4+ and Lyt-2+ T cells. In contrast, mice injected with living bradyzoites of the low virulent Beverley strain after immunization with Toxoplasma cell homogenate acquired protective immunity against high virulent tachyzoites of the RH strain. Lyt-2+ T cells alone appear to be final effector cells for protection against the challenge with high virulent RH strain tachyzoites, since treatment of the bradyzoite-immune mice with anti-Lyt-2 antibody, but not anti-L3T4 antibody, before challenge significantly increased mortality.
Animals↗
[Effect of AS-2646, a novel antiulcer agent on gastric mucosal defensive factors in rats].
The effects of AS-2646 on the acute gastric mucosal lesions induced by various noxious agents and the gastric mucosal defensive factors were studied in rats, and the following results were obtained: 1) AS-2646 (5-100 mg/kg, p.o.) dose-dependently inhibited the formation of the mucosal lesions induced by ethanol, ethanol-HCl, taurocholate-HCl and serotonin, and its anti-lesion spectrum was the widest among the compounds (cimetidine, pirenzepine, sulpiride and prostaglandin E1) examined here. 2) AS-2646 (5-10 mg/kg, p.o.) not only improved the changes of gastric mucosal hemodynamics induced by the blood removal and/or the reserpine treatment, but also inhibited the mucosal lesions induced by them. 3) AS-2646 (2-20 mg/kg, p.o.) antagonized the decrease in the surface gastric mucus and mucosal hexosamine contents induced by stress and/or aspirin. 4) AS-2646 (2-20 mg/kg, p.o.) caused no significant effect on the gastric mucosal prostaglandin E2 levels. 5) AS-2646 inhibited Campylobacter pylori in vitro. These results indicate that AS-2646 may be useful as a novel antiulcer drug with the defensive factor-potentiating and anti-Campylobacter pylori effects.
Animals↗
[Catecholamine secretion from adrenal chromaffin cells].
The effect of palytoxin (PTX) on catecholamine (CA) secretion from cultured bovine adrenal chromaffin cells was examined. PTX (greater than 10(-10) M) induced CA secretion concentration-dependently. About 40-50% of the total cellular CA was secreted during a 20 min incubation with 3 x 10(-8) M PTX. PTX caused increases in [22Na](+)- and [45Ca](2+)-influxes into the cells, which were not affected by TTX. PTX-induced CA secretion and [22Na](+)- and [45Ca](2+)-influxes were significantly inhibited by quinidine and aprindine, antiarrhythmic drugs. Ca(2+)-channel blockers such as nifedipine, verapamil, Co2+, and Cd2+ inhibited both CA secretion and [45Ca](2+)-influx induced by PTX. These results indicated that PTX-induced CA secretion was mediated by activation of Na(+)-dependent, TTX-insensitive voltage-dependent Ca(2+)-channels. PTX-induced [22Na](+)-influx was inhibited by amiloride, an inhibitor of the Na(+)-H+ exchange system, suggesting that the Na(+)-H+ exchange mechanism might be involved in PTX-induced [22Na](+)-influx into the cells. The effects of flavonoids on CA secretion from permeabilized adrenal chromaffin cells were examined. CA secretion from the cells in response to a direct Ca2+ challenge was inhibited by quercetin (greater than 10(-5) M) and apigenin (greater than 10(-5) M). These flavonoids also inhibited phorbol ester TPA-induced CA secretion. Therefore, the inhibitory effects of flavonoids on CA secretion were thought to be attributed to their inhibitory effects on PKC.
Acrylamides↗
Pharmacological study on Ba2(+)-stimulated catecholamine secretion from cultured bovine adrenal chromaffin cells: possible relation of Ba2+ action to Ca(2+)-activated secretory mechanism.
The stimulatory action of Ba2+ on catecholamine secretion from cultured bovine adrenal chromaffin cells was studied to elucidate a possible relationship between Ba2+ action and the Ca2(+)-mediated secretory mechanism. Catecholamine secretion was dramatically stimulated by Ba2+ in the absence of external Ca2+, and this stimulatory action was observed in a concentration-dependent manner. Ba2+ evoked the concomitant release of dopamine beta-hydroxylase in a similar manner to the Ca2(+)-dependent secretion. The stimulation of catecholamine secretion by low concentrations of Ba2+ was markedly inhibited by protein kinase inhibitors, polymyxin B and trifluoperazine (TFP). The inhibitory action of polymyxin B, but not that of TFP, on the Ba2+ action was attenuated by elevating the concentration of Ba2+ in the incubation mixture. The stimulatory action of Ba2+ was enhanced by a protein kinase C activator, 12-O-tetradecanoylphorbol 13-acetate (TPA). In contrast to the acute effect of TPA, chronic exposure of chromaffin cells to high concentration of TPA reduced catecholamine secretion stimulated by Ba2+ as well as high K+ and carbamylcholine. These findings suggest the possibility that Ba2+ may activate Ca2(+)-mediated secretory processes presumably through its action on protein kinase C, thus resulting in the stimulation of catecholamine secretion from bovine adrenal chromaffin cells.
Adrenal Medulla↗
Idebenone inhibits catecholamine secretion through its blocking action on Ca2+ channels in cultured adrenal chromaffin cells.
The effect of idebenone, an agent improving cerebral metabolism, on catecholamine secretion was examined using primary cultures of bovine adrenal chromaffin cells. Catecholamine secretion evoked by acetylcholine was markedly inhibited by idebenone, and this effect was concentration-dependent. In contrast, other cerebral metabolism-improving agents, such as hopantenate and propentofylline, failed to cause any significant effect on the secretion in the same concentration range. Furthermore, idebenone inhibited the secretion evoked by high K+, veratridine, and Ba2+, but failed to inhibit the secretion evoked by the Ca(2+)-ionophore A23187. Idebenone also inhibited the radioactive Ca2+ uptake stimulated by acetylcholine or high K+ under the conditions in which its inhibitory action on the secretion was observed. Nifedipine, a typical voltage-dependent Ca2+ channel blocker, inhibited the secretion evoked by high K+, and this inhibitory action on the secretion was markedly reduced by the presence of idebenone. The present results suggest that idebenone may inhibit the influx of extracellular Ca2+ into the cells presumably through its blocking action on the voltage-dependent Ca2+ channels, resulting in the inhibition of catecholamine secretion in the adrenal chromaffin cell.
Acetylcholine↗