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Biomedical subjects

Hiroshi Ujiie

Publications and source records attributed to Hiroshi Ujiie.

11 recordsLinked to original sources
PubMed2005

Rheological analyses of coagulation of blood from different individuals with special reference to procoagulant activity of erythrocytes.

In our previous papers, we reported that factor IX (FIX), when activated by erythrocyte membranes, causes coagulation. We have identified and characterized the FIX-activating enzyme located in normal human erythrocyte membranes. In this paper, to examine physiological and pathological significances of procoagulant activity of erythrocytes, coagulation of blood obtained from different individuals was analyzed by means of a rheological technique. In more than 65% of subjects including normals and patients, the initiation of coagulation seemed to be governed by erythrocytes. Coagulation of whole blood and platelet-free plasma supplemented with erythrocytes had a tendency to occur rapidly in the elderly. It was suggested that the concentration of FIX-activating enzyme on erythrocyte membranes for aged donors was somewhat higher than that for young ages. Propagation reactions on erythrocyte membranes (i.e. factor X activation leading to thrombin generation after FIX activation) was slower than that on platelet membranes. Moreover, the propagation reaction on erythrocyte membranes was greatly dependent on individuals, whereas that on platelet membranes was not so much. Our study demonstrates that the activation of FIX by erythrocytes and subsequent propagation reaction on platelet membranes may be important for initiating and controlling blood coagulation reactions.

Adult↗
PubMed2004

Continuous laryngoscopic vocal cord monitoring for vascular malformation surgery in the medulla oblongata: technical note.

OBJECTIVE: Resection of lesions located in the medulla oblongata may result in significant morbidity. The most lethal complications are swallowing disturbances, which can lead to aspiration pneumonia. To prevent this problem, the lower cranial nerves can be mapped with recording needles placed in the posterior pharyngeal wall and the tongue. However, mapping alone is not sufficient to preserve the lower cranial nerves and swallowing functions. To overcome this problem, we attempted to devise a method to intraoperatively monitor vocal cord movements with a laryngoscope. We used this method, in addition to other types of brainstem mapping, in three cases. METHODS: Recording needles were inserted into the posterior pharyngeal wall and the tongue, to record the responses of Cranial Nerves IX and XII. A laryngoscope was inserted orally, for direct observation of vocal cord movements, and was maintained until the end of the operation. The floor of the fourth ventricle was stimulated with a monopolar stimulator. Somatosensory evoked potentials, auditory evoked potentials, and motor evoked potentials were simultaneously monitored. RESULTS: We were able to confirm synchronized vocal cord adduction with stimulation of the expected vagal trigonum location and to monitor rhythmic vocal cord movements during spontaneous respiration. In all three cases, we removed the lesions without postoperative complications. CONCLUSION: In addition to intraoperative vocal cord monitoring with a laryngoscope, we could safely determine the optimal location for the first incision in the floor of the fourth ventricle. Potentially lethal postoperative complications can be avoided with brainstem mapping and vocal cord monitoring.

Brain Mapping↗
PubMed2004

Rabbit aneurysm model mediated by the application of elastase.

The concentrations and application methods of elastase in the rabbit aneurysm model were optimized to control the initiation of aneurysms and to cause rupture in a stepwise, controlled fashion. The common carotid artery of male Japanese albino rabbits was exposed. No aneurysm was generated if the adventitia was not dissected. After gentle removal of the adventitia, a two-fold dilution series of elastase was applied to the lesion and observed over a period of 2 hours. Various stages of aneurysmal lesions, from spindle-shaped enlargement to rupture, were produced in proportion to the elastase concentration. Application of elastase stock solution (5 U/mg of type I porcine pancreatic elastase) resulted in rupture within 30 minutes in all six animals. Elastase 1:2 solutions caused oozing in all animals, but subsequent rupture in only three of six animals. Histological examination found serious destruction of the internal elastic lamina and media, with expansion of the very thin wall. Elastase 1:4 to 1:16 solutions caused spindle-like distention of the entire artery and the development of tortuosity at the lesion. Elastase 1:32 or weaker solutions caused only localized dilatations. Overall, the destruction of the tunica media became less severe with decreased elastase concentration. Furthermore, the bursting pressure of the aneurysms decreased with increasing elastase concentrations. In particular, aneurysms produced by the elastase 1:2 solution ruptured at less than 150 mmHg, whereas aneurysms induced by the elastase 1:4 or weaker solutions did not rupture within the physiological range of blood pressure. The present aneurysm model requires shorter preparation time and enables accurate control of aneurysm development and rupture.

Aneurysm↗
PubMed2004

[Biocompatibility of ePTFE modified by ion beam irradiation].

Expanded polytetrafluoroethylene (ePTFE) is a stable polymer and widely used as a prosthesis because of its chemical inertness. However, ePTFE as an artificial dura mater is often associated with postoperative leakage of the cerebrospinal fluid (CSF) due to its very low adhesiveness to fibrin glue and surrounding tissue. To overcome this shortcoming the authors examined the effects of ion beam irradiation to ePTFE surface. The surfaces of ePTFE were irradiated with 150keV--He+, Ne-, Ar+ and Kr+ ions with fluences of 1 x 10(14), 5 x 10(14) and 1 x 10(15) ions/cm2. L929 fibroblasts were cultured for 24 hours on ePTFE sheets that had both ion beam irradiated and un-irradiated regions. It was confirmed that fibroblasts still adhered to the ion beam irradiated area. This phenomenon was observed under different condition of ion beam irradiation. Adhesive strength of fibrin glue to ion beam irradiated ePTFE was evaluated by tensile strength and burst pressure test using ePTFE patch. Both tensile strength and burst pressure were remarkably enhanced by ion beam irradiation. SEM study indicated that fibrin glue infiltrated and anchored into the gaps induced by the ion beam irradiation. Thus ion beam irradiation improved biocompatibility of the surface of ePTFE.

Biocompatible Materials↗
PubMed2004

[Ion-beam irradiated ePTFE for the therapy of intracranial aneurysms].

Intracranial aneurysms are frequently treated with either microsurgical clipping or endovascular coiling. However, as so called broad-neck aneurysms are not suitable for these treatment options, a wrapping technique using muslin gauze, muscle piece, ePTFE is applied for such cases. The material for aneurysmal wrapping demands both stable adherence and no reactive inflammatory response such as inert artificial wall. Authors have developed a new improved ePTFE by ion-beam irradiation technique that is biologically inert and able to adhere firmly to surrounding tissue. Based on the last studies, Ar+ ion at an energy of 150 keV with a fluence of 5 x 10(14) ions/cm2 was chosen to irradiate ePTFE. A cell adhesion test and direct implantation of ion-beam irradiated ePTFE as wrapping material to rabbit common carotid arteries (CCA) were examined. It was demonstrated that the surface of ion-beam irradiated ePTFE exhibits remarkably greater adhesion and promotes cell proliferation on the surface more effectively than that of non-irradiated ePTFE. The carotid artery well-wrapped by ion-beam irradiated ePTFE strongly adhered to the mural wall and induced little inflammatory reaction. The results of this investigation indicate that application of this technology would offer the best means for aneurysm wrapping.

Animals↗
PubMed2003

Essential role of Gap junctions in NO- and prostanoid-independent relaxations evoked by acetylcholine in rabbit intracerebral arteries.

BACKGROUND AND PURPOSE: Direct intercellular communication via gap junctions may play a central role in endothelium-dependent relaxations that are mediated by a conducted hyperpolarization and do not involve the synthesis of NO and prostanoids. In the present study, inhibitory peptides homologous to the Gap27 domain of the second extracellular loop of connexin37/connexin43 and connexin40, designated as 37,43Gap27 and 40Gap27, respectively, were used to evaluate the role of this mechanism in intracerebral arteries. METHODS: Isolated rings of rabbit middle cerebral artery were constricted by histamine (10 micromol/L) in the presence of N(G)-nitro-L-arginine methyl ester (300 micromol/L) and indomethacin (10 micromol/L). Concentration-relaxation curves for acetylcholine were constructed in the presence and absence of 37,43Gap27 and 40Gap27. Specific antibodies were used to delineate the distribution of connexin37, connexin40, connexin43, and connexin45 within the arterial wall. RESULTS: Individually, 37,43Gap27 and 40Gap27 minimally affected endothelium-dependent relaxations to acetylcholine at concentrations of 300 micro mol/L, whereas their combination (at 300 micromol/L each) inhibited the maximal response by approximately 70% and increased the EC50 value for relaxation by approximately 15-fold. In endothelium-denuded rings, this peptide combination did not attenuate responses to sodium nitroprusside, an exogenous source of NO. Gap junction plaques, whose incidence was highest in endothelium, were constructed from connexin40 and connexin43 in the media and connexin37, connexin40, and connexin43 in the endothelium. CONCLUSIONS: The findings confirm that direct communication via gap junctions contributes to agonist-induced relaxations of intracerebral arteries. More than one connexin subtype appears to participate in such responses.

Acetylcholine↗
PubMed2003

[Ion-beam irradiated ePTFE for an artificial dura mater].

Expanded polytetrafluoroethylene (ePTFE) is a stable polymer and widely used as a prosthesis because of its chemical inertness. However, ePTFE as an artificial dura mater is often associated with postoperative leakage of the cerebrospinal fluid (CSF) due to its very low adhesiveness to fibrin glue and surrounding tissue. The surfaces of ePTFE were modified by ion-beam irradiation in order to improve tissue adhesiveness. The morphological changes of ePTFE that was irradiated with 150 keV-He+, Net, Ar+ and Kr+ ions applied at a rate of 1 x 10(14), 5 x 10(14) and 1 x 10(15) ions/cm2 were examined with scanning electron microscopy. Next, surrounding tissue reactions to the implanted ePTFE into the rabbit calvarial defects were analyzed at intervals from 1 week up to 1 month. The micromesh structures of the ePTFE were destroyed by ion-beam irradiation, and the depth and width of the gaps increased with heavy particle ion and irradiated fluence. In an implantation study using experimental rabbits, a dura defect was patched with four types of ion-beam irradiated ePTFE with different in irradiation fluence. A CSF leakage was observed in the rabbit covered with non-irradiated ePTFE, but, CSF leakage did not occur in any of the rabbits covered with ion-beam irradiated ePTFE that adhered in a water-tight manner to surrounding tissues. Histological study indicated that fibroblast-like cells had infiltrated and anchored the gaps in the ion-beam irradiated ePTFE. Ar+ or Kr+ with 1 x 10(15) ions/cm2 irradiated ePTFE had the highest adhesiveness and produced the best healing of dura defects.

Animals↗
PubMed2002

Optic nerve arteriovenous malformation causing optic apoplexy: case report.

OBJECTIVE AND IMPORTANCE: Vascular malformations in the optic pathway are rare. Only one case of pathologically confirmed arteriovenous malformation (AVM) of the optic nerve has been reported previously. We document the case of a patient with an optic nerve AVM who presented with optic apoplexy that was diagnosed with the use of magnetic resonance imaging. CLINICAL PRESENTATION: A 15-year-old girl developed left visual disturbance of sudden onset while playing badminton. A magnetic resonance imaging scan disclosed left optic nerve swelling and intraoptical hemorrhage, although an angiogram did not reveal abnormal vessels. INTERVENTION: The patient underwent total removal of the hematoma and tangles of the abnormal vessels in the left optic nerve, which was diagnosed pathologically as an AVM. The patient recovered visual acuity, but the left visual field defect remained unchanged. CONCLUSION: Along with cavernous malformations and optic gliomas, AVMs can be a rare cause of optic nerve apoplexy. T2-weighted magnetic resonance imaging is useful in rendering the diagnosis of an optic nerve AVM, observed as a mass lesion consisting of serpiginous, tangled, low-intensity bands. Early surgical treatment is recommended to obtain a rapid recovery.

Adolescent↗
PubMed2002

Endogenous nitric oxide synthesis differentially modulates pressure-flow and pressure-conductance relationships in the internal and external carotid artery circulations of the rat.

The role of endogenous nitric oxide (NO) synthesis was investigated in the regulation of the internal (ICA) and external carotid artery (ECA) beds of ventilated, anesthetized rats in a model in which the left common carotid artery was perfused from the aorta via an extracorporeal circuit under conditions of non-pulsatile controlled flow. The territories supplied by the extracranial ICA and ECA were studied separately following occlusion of the appropriate artery. An inhibitor of nitric oxide synthesis, N(G)-monomethyl-L-arginine (L-NMMA), and the NO synthase substrate L-arginine were administered via a jugular venous catheter. NO synthesis exerted an important influence on the pressure-flow relationships of the ICA and ECA circulations as L-NMMA increased input perfusion pressure at any given flow rate. However, in the presence of NO synthesis, hydraulic conductance increased rapidly with flow in the ICA, thereby stabilizing perfusion pressures over a wide range of flow rates, whereas this phenomenon was not evident in the ECA territory. Differences between the two circulations were further emphasized by observations that L-arginine antagonized the systemic hemodynamic response to L-NMMA and its effects on the conductance of the ECA bed, whereas the effects of L-NMMA were irreversible in the ICA territory.

Animals↗