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Biomedical subjects

M Akao

Publications and source records attributed to M Akao.

At least 37 records · Page 2Linked to original sources
PubMed1999

cGMP modulation of Ca2+ sensitivity in airway smooth muscle.

A beta-escin-permeabilized canine tracheal smooth muscle preparation was used to test the hypothesis that cGMP decreases Ca2+ sensitivity in airway smooth muscle primarily by inhibiting the membrane receptor-coupled mechanisms that regulate Ca2+ sensitivity and not by inhibiting Ca2+/calmodulin activation of the contractile proteins. 8-Bromo-cGMP (100 microM) had no effect on the free Ca2+ concentration-response curves generated in the absence of muscarinic receptor stimulation. In the presence of 100 microM ACh plus 10 microM GTP, 8-bromo-cGMP (100 microM) caused a rightward shift of the free Ca2+ concentration-response curve, significantly increasing the EC50 for free Ca2+ from 0.35 +/- 0.03 to 0.75 +/- 0.06 microM; this effect of 8-bromo-cGMP was concentration dependent from 1 to 100 microM. 8-Bromo-cGMP (100 microM) decreased the level of regulatory myosin light chain (rMLC) phosphorylation for a given cytosolic Ca2+ concentration but had no effect on the amount of isometric force produced for a given level of rMLC phosphorylation. These findings suggest that cGMP decreases Ca2+ sensitivity in canine tracheal smooth muscle primarily by inhibiting the membrane receptor-coupled mechanisms that modulate the relationship between cytosolic Ca2+ concentration and rMLC phosphorylation.

Animals↗
PubMed1999

[A patient operated for occlusion of the superior mesenteric artery].

A 40-year-old woman presented with fever, dysarthria, and left hemiparesis. Diagnostic imaging detected an infarction in the right cerebrum; lupus anticoagulant was positive. A T4N3M0 adenocarcinoma coexisted in the left lung, which was irradiated once. Two days later, the superior mesenteric artery was occluded. The bowel was widely resected but she died of hepatic infarction. The lung cancer may have triggered catastrophic antiphospholipid syndrome.

Adenocarcinoma↗
PubMed1998

Pneumothorax due to hemangiopericytoma metastasis from the thigh.

A 25-year-old female had malignant hemangiopericytoma of the right thigh resected. Three years later, right pneumothorax developed, necessitating a thoracotomy. A 3-cm bulla was discovered on the lower right pulmonary lobe and was subsequently resected. Microscopy showed tumor cells which were positive for actin, but negative for epithelial membrane antigen, vimentin, and factor VIII-related antigen--features compatible with those of the thigh. The patient has been free of the disease for five years. Pertinent literature reveals similar cases with hemangioendothelioma but offers few reports on pneumothorax caused by metastatic hemangiopericytoma.

Adult↗
PubMed1998

Tissue reaction of hydroxyapatite sol to rat molar pulp.

Hydroxyapatite sol was prepared by dispersing unheated hydroxyapatite microcrystals into distilled water. A suspension of hydroxyapatite heated at 800 degrees C (HAp-800 degrees C) in distilled water was used as a comparative material. These were characterized by X-ray diffractometry, SEM and electroconductivity measurements. 0.001 ml of each material was injected into the upper first molar pulp of rats. After 7-14 days post-operatively, the group with hydroxyapatite sol showed slight inflammation in the pulp cavities and a highly calcified tubular dentine bridge was observed. Osteodentine had developed and adhered to the surface of the hydroxyapatite microcrystals. Matrix vesicles were observed in the extracellular matrix between collagen fibrils and electron-dense granules. After 28 days, the inflammation completely disappeared and tubular dentine was observed below the osteodentine. Acid phosphates (ACPase) activity was detected along all biosynthesizing pathways in odontoblast-like cells. Localized dehydrogenate (LDH) activity indicated phagocytosis of hydroxyapatite microcrystals by odontoblasts. In the group with HAp-800 degrees C after 7-14 days post-operatively, the inflammation was moderate. After 28 days, relatively fewer calcified dentine tubules were observed. ACPase activity was detected only along the membranes bounding cytoplasmatic vacuoles. It was concluded that hydroxyapatite sol is a safe biomaterial for use as dental pulp and induces early formation of dentine-bridge more so than HAp-800 degrees C.

Journal Article↗
PubMed1998

Antisporulating and respiration-inhibitory effects of essential oils on filamentous fungi.

Sporulation of four species of filamentous fungi, namely Aspergillus fumigatus, Fusarium solani, Penicillium expansum and Rhizopus oryzae, was suppressed by gaseous contact with citron, lavender and thyme oils and, to a lesser extent, by that of perilla and tea tree oils. Lemongrass and cinnamon bark oils were scarcely active. The antisporulating effect of the essential oils was not observed when they were applied as a solution, indicating that their vapours were the active form. Moreover, exposure of fungal cultures to vapours of the active essential oils caused curling of the tips of aerial hyphae (R. oryzae) or incomplete development of conidiophores (A. fumigatus). These antisporulating effects of the vapourizing essential oils seemed to be correlated with their respiration-inhibitory activity, rather than with their growth-inhibitory activity.

Fungi↗
PubMed1998

KATP channels are common mediators of ischemic and calcium preconditioning in rabbits.

Calcium preconditioning (CPC), like ischemic preconditioning (IPC), reduces myocardial infarct size in dogs and rats. ATP-sensitive potassium (KATP) channels induce cardioprotection of IPC in these animals. To determine whether KATP channels mediate both IPC and CPC, pentobarbital sodium-anesthetized rabbits received 30 min of coronary artery occlusion followed by 180 min of reperfusion. IPC was elicited by 5 min of occlusion and 10 min of reperfusion, and CPC was elicited by two cycles of 5 min of calcium infusion with an interval period of 15 min. Infarct size expressed as a percentage of the area at risk was 38 +/- 3% (mean +/- SE) in controls. IPC, CPC, and pretreatment with a KATP channel opener, cromakalim, all reduced infarct size to 13 +/- 2, 17 +/- 2, and 12 +/- 3%, respectively (P < 0.01 vs. controls). Glibenclamide, a KATP channel blocker administered 45 min (but not 20 min) before sustained ischemia, attenuated the effects of IPC and CPC (31 +/- 4 and 41 +/- 6%, respectively). Thus KATP channel activation appears to contribute to these two types of cardioprotection in rabbits.

Adenosine Triphosphate↗
PubMed1998

pH and carbonate levels in developing enamel.

Our earlier studies showed that the surface of developing and calcifying enamel changes its pH alternatively along the tooth axis when stained with pH indicating dyes. Based on the pH conditions, the enamel at this stage was distinguished as neutral zone (N1 and N2) and acid zone (A1 and A2). The aim of the present study was to correlate changes of pH with proteolytic activity and crystal size of the calcifying bovine enamel. Specimens of developing bovine enamel were separated into four maturing stages using pH staining methods. Crystal chemistry of the developing enamel was investigated using thermogravimetry (TGA), ICP emission spectrometry, X-ray diffractometry (XRD) and infrared spectroscopy (IR). Previous biochemical analysis of proteolytic enzyme activity from enamel indicated that the optimal pH of the major protease was approximately pH 6.0, coinciding with the pH of the A1 zone. IR, TGA and XRD analyses showed that most of the organic components of the enamel decomposed at 580 degrees C. Higher levels of carbonate were observed in the secretory stages than in mature enamel. The Ca/P molar ratio of the enamel apatite was lower than the stoichiometric value of 1.67. These results suggest that growth and maturation of enamel apatite crystals is related to a decrease in the carbonate level and appear to be related to the alternative calcification and decomposition of enamel proteins.

Ameloblasts↗
PubMed1998

[Thoracoscopic repair of diaphragmatic eventration sustained at knife injury: a case report].

A 46-year-old male taxi driver was stabbed onto the left chest while on duty. On arrival soon after, he was hemodynamically stable. Computed tomography showed omental prolapse into the left thorax through the diaphragm. On the 11th day, he underwent thoracoscopy revealing omental prolapse via a 3-cm rent in the left diaphragm, which was reduced manually. The diaphragmatic orifice was lifted and debrided with suturing using a stapling cutter. The post-operative course was uneventful. Finger palpation through the orifice enabled safe suturing of the left diaphragm facing the omentum, the colon, and the stomach, all of which may suffer iatrogenic injury.

Endoscopy↗
PubMed1997

Myocardial ischemia induces differential regulation of KATP channel gene expression in rat hearts.

The cardiac ATP-sensitive potassium (KATP) channel is thought to be a complex composed of an inward rectifier potassium channel (Kir6.1 and/or Kir6.2) subunit and the sulfonylurea receptor (SUR2). This channel is activated during myocardial ischemia and protects the heart from ischemic injury. We examined the transcriptional expression of these genes in rats with myocardial ischemia. 60 min of myocardial regional ischemia followed by 24-72 h, but not 3-6 h, of reperfusion specifically upregulated Kir6.1 mRNA not only in the ischemic (approximately 2.7-3.1-fold) but also in the nonischemic (approximately 2.0-2.6-fold) region of the left ventricle. 24 h of continuous ischemia without reperfusion also induced an increase in Kir6.1 mRNA in both regions, whereas 15-30 min of ischemia followed by 24 h of reperfusion did not induce such expression. In contrast, mRNAs for Kir6.2 and SUR2 remained unchanged under these ischemic procedures. Western blotting demonstrated similar increases in the Kir6.1 protein level both in the ischemic (2.4-fold) and the nonischemic (2.2-fold) region of rat hearts subjected to 60 min of ischemia followed by 24 h of reperfusion. Thus, prolonged myocardial ischemia rather than reperfusion induces delayed and differential regulation of cardiac KATP channel gene expression.

ATP-Binding Cassette Transporters↗
PubMed1997

Inhibition of sarcolemmal Na+,K+-ATPase activity reduces the infarct size-limiting effect of preconditioning in rabbit hearts.

BACKGROUND: The inhibition of sarcolemmal Na+,K+-ATPase activity is closely related to ischemic myocardial cell injury. However, the involvement of this enzyme in preconditioning has not been determined. METHODS AND RESULTS: We assessed the effect of ischemia on sarcolemmal Na+,K+-ATPase activity. Control and preconditioned rabbits were subjected to 0, 10, 20, 30, and 60 minutes of coronary occlusion. Ten to 60 minutes of ischemia reduced Na+,K+-ATPase activity, whereas preconditioning preserved the activity of this enzyme only during the first 20 minutes of ischemia. To determine whether the preservation of Na+,K+-ATPase activity in the early phase of ischemia contributed to limiting the infarct size, additional rabbits underwent 30 minutes of occlusion followed by 3 hours of reperfusion with or without pretreatment with digoxin, an inhibitor of Na+,K+-ATPase. Infarct size in animals pretreated with digoxin in the absence of preconditioning did not differ from that in controls. It was markedly reduced by preconditioning, whereas digoxin reduced the infarct size-limiting effect. Moreover, preconditioning increased sarcolemmal Na+-Ca2+ exchange activity in rabbits subjected to 20 minutes of ischemia, whereas digoxin diminished this increase. CONCLUSIONS: Preconditioning preserves the ischemia-induced reduction in sarcolemmal Na+,K+-ATPase activity in the early phase of ischemia in rabbit hearts. Inhibition of Na+,K+-ATPase activity reduces the infarct size-limiting effect of preconditioning with a loss of increased Na+-Ca2+ exchange activity, implying that this preservation is responsible for the cardioprotective effect of preconditioning.

Animals↗
PubMed1997

K(ATP) channels contribute to the cardioprotection of preconditioning independent of anaesthetics in rabbit hearts.

The contribution of ATP sensitive potassium (K(ATP)) channels to the infarct-size limiting effect of preconditioning is considered to be anaesthetic-dependent in the rabbit heart. It has previously been reported that ischaemic preconditioning prevents ischaemia-induced reductions in activities of sarcolemmal adenylate cyclase (AC) and Na+, K(+)-ATPase. Anaesthetic dependency of the role of K(ATP) channels in the preservation of these enzyme activities, induced by ischaemic preconditioning, as well as that induced by activation of A1-adenosine receptors, was examined in rabbits anaesthetized with either pentobarbital or ketamine-xylazine and subjected to 20 min of regional ischaemia. Adenylate cyclase and Na+, K(+)-ATPase activities were lower in the ischaemic than in the non-ischaemic region of the hearts in control rabbits, but not in animals subjected to ischaemic preconditioning, or those pretreated with the A1-adenosine receptor agonist R(-)-N6-(2-phenylisopropyl) adenosine. The protective effects of both ischaemic preconditioning and A1-adenosine receptor activation were prevented by 6 mg/kg, but not 3 mg/kg, of the K(ATP) channel blocker, glibenclamide, in rabbits anaesthetized with pentobarbital, while these effects were prevented by 3 mg/kg of the blocker in rabbits anaesthetized with ketamine-xylazine. Moreover, K(ATP) channel opener, cromakalim, prevented the ischaemia-induced decreases in enzymatic activities in rabbits subjected to either type of anaesthesia. Thus, although the antagonistic effect of glibenclamide is blunted under pentobarbital, compared to ketamine-xylazine anaesthesia, K(ATP) channels contribute to preservative actions independent of the type of anaesthesia in the rabbit heart.

Adenosine Triphosphate↗
PubMed1997

Preparation and mechanical properties of calcium phosphate/copoly-L-lactide composites.

New artificial bone materials were prepared using calcium phosphates, hydroxyapatite and beta-tricalicum phosphate, and copoly-L-lactide, CPLA. Calcium phosphate powder and CPLA were mixed at 453 K for 10 min with various mixing ratios. Scanning electron microscope observations indicated that the composites of beta-tricalicum phosphate and CPLA were homogeneously dispersed and highly adhesive. Young's modulus of the composites was the same as bone, and bending strength was over half that of bone. The improvement of Young's modulus compared to the original two materials was due to a composite effect. The composites are expected to be usable as artificial bone materials.

Journal Article↗
PubMed1997

Tissue reactions to various percutaneous materials with different surface properties and structures.

Tissue responses to various percutaneous materials with different surface properties and structures were investigated. Dense hydroxyapatite (HA), tricalcium phosphate (TCP), glassy carbon (GC), and 2 types of porous HA were used. Cutaneous and subcutaneous tissues were tightly attached to the surface of the penetrating portion of an HA percutaneous device (PD). Neither bacterial infection nor serious epidermal downgrowth were observed in the area surrounding the shaft of the HA-PD. At the margin of the epidermis, fibroblasts and collagen fibrils of fibrous connective tissue were well oriented and formed perpendicular to the shaft. The tissue response to the TCP was mild and nearly the same as that to the HA. The GC induced serious epidermal downgrowth and inflammatory cell infiltration. In contrast to dense HA-PD, the insertion of both types of porous HA-PDs, 1 with a spongy structure and 1 with close pores was followed by acute infection within 1 month. Based upon these results, it was concluded that the dense HA was the best percutaneous material of those tested.

Animals↗
PubMed1997

[Report of questionnaire about enterohemorrhagic Escherichia coli cases caused in the area including Sakai City in 1996].

Many outbreaks of EHEC O157 were occurred in Japan in 1996. There was the biggest outbreak involving approximately 6000 victims in area of Sakai City. We conducted a questionnaire survey on the EHEC infection to the physicians who treated these patients and the microbiologists. For physicians we asked mainly clinical manifestation of patients they observed and treatment they did and their outcome (Answer A). Microbiologists were also required to answer the opinion about treatment (Answer B). Eighty-five of physicians replied about their 222 patients and 209 of microbiologists answered their opinions. In this report we summarized the data and obtained following results: 1) We observed higher frequency of HUS/TTA complication in female than male. 2) Higher HUS/TTP complication was accompanied with patients complained symptoms of fever, bloody diarrhea, and general fatigue. 3) The most patients (96%) were received antimicrobial agents, especially fosfomycin (84%), followed by new quinolon (17.8%) and Cefems (12.2%). Later starting of treatment with antimicrobial agents than 7 days from onset of symptoms increased HUS/TTP complication. 4) Anti-diarrhoeal agents seems to be one of risk factors for HUS/TTP complications.

Adolescent↗
PubMed1997

Preparation and characterization of double layered coating composed of hydroxyapatite and perovskite by thermal decomposition.

A new modified thermal decomposition method is described for preparing a double layered coating on titanium plates which includes an initial perovskite (CaTiO3) layer followed by a hydroxyapatite (HA) layer on top. The characterization of the coating was studied by X-ray diffractometry and infrared spectroscopy and indicated that the double layer consisted of carbonate HA and CaTiO3 and the thickness of the layer was 4 microns. The coating was performed on the inner surfaces of 50-200 microns sized pores and was also consistent in the smallest of the pores even those of 50 microns. Bone formation was examined in canines at 2-32 week intervals and was dominant on coated plates and in large-sized pores before 16 weeks. However, after 16 weeks bone ingrowth was similar in non-coated and coated plates and in all pore sizes. The results indicated that HA could only influence early bone ingrowth, though good bone ingrowth into small pores indicated that HA exhibited enhanced osteocompatibility. Our methodology ensured the stability of the HA layer consequently minimizing the problems associated with HA loss.

Animals↗
PubMed1997

[A case of traumatic cardiac contusion accompanied by the rupture of pericardium].

We experienced a case of traumatic cardiac contusion accompanied by the rupture of the pericardium after multiple blunt trauma sustained in a traffic accident. A 26-year-old woman who had suffered from blunt chest and abdominal trauma was admitted to our hospital, being unconscious with multiple severe injuries including pelvic fracture, bilateral hemothorax, and multiple fractures in the extremities. The patient was in a shock status. We performed the transcatheter arterial embolization of the internal iliac arteries to control the bleeding, when aortography showed that the contrast media extravasated toward the left thoracic cavity. Immediately, an operation for blunt chest trauma was performed. Blood was flooding out of the ruptured pericardium because of the contusion of myocardium. The postoperative course was uneventful. Blunt chest trauma is usually accompanied by multisystem injury. Therefore, it is imperative to determine the priority of treatment based on preoperative examination in patients having multiple injuries.

Abdominal Injuries↗