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Biomedical subjects

T Hikichi

Publications and source records attributed to T Hikichi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Usefulness of endoscopic ultrasonographic analysis of variceal hemodynamics for the treatment of esophageal varices.

The correlation of between the endoscopic findings of esophageal varices and endoscopic ultrasound findings of the collaterals outside the esophageal wall in patients with portal hypertension remains unclear. We investigated the relationship between esophageal varices and the collaterals by endoscopy and endoscopic ultrasound. Moreover, we investigated the correlation between the collaterals around the esophagus and recurrence of esophageal varices in patients with portal hypertension who had undergone endoscopic injection sclerotherapy. The collaterals were divided into two groups: 1; those with peri-esophageal collateral veins (peri-ECVs) adjacent to the muscularis externa of the esophagus, and 2; those with para-esophageal collateral veins (para-ECVs) distal to the esophageal wall without contact with the muscularis externa. Peri- and para-ECVs were scored as mild or severe according to the stage of development. According to endoscopy, the varix form was significantly larger in severe peri-ECVs group than in mild peri-ECVs group. In contrast, the varix form did not differ significantly between the mild and severe para-ECVs group. The prevalence of perforating veins increased according to the varix form. With regard to variceal recurrence, in patients with variceal recurrences, EUS findings included a significantly higher incidence of severe-type peri-ECVs, a significantly larger number of perforating veins, and a significantly larger diameter of perforating veins compared with patients without recurrence. Moreover, when EUS found the abnormalities when no endoscopic recurrence was found, the results were the almost same as the findings when EUS was performed at the same time when endoscopic recurrence was found. In conclusion, the presence of severe peri-ECVs and large perforating veins in the esophageal wall strongly correlates with occurrence and recurrence of esophageal varices in patients with portal hypertension. An understanding of these EUS abnormalities on the basis of hemodynamics around the esophagus is thought to be important for management of esophageal varices in patients with portal hypertension.

Collateral Circulation↗
PubMed2001

New graphics models for PC based ocular surgery simulator.

High-end graphics workstations (GWS) have been used for surgical simulators utilizing Computer Graphics (CG) and Virtual Reality (VR) technologies. This is because the simulators need lots of computing power, mainly for collision detection among objects modeled as a set of polygons. In this paper, we propose to use mathematical functions to model objects for collision detection. However, for graphic display we continue to use polygonal representation. Using the new model, we have developed a PC based ocular surgery simulator, which creates realistic surgery image in real-time. The computation time was found to be much lower than that in the conventional method.

Computer Graphics↗
PubMed2001

[Immunohistochemical study of idiopathic and secondary epiretinal membrane].

PURPOSE: We investigated the immunohistochemical features of surgically resected idiopathic epiretinal membranes(ERMs) and secondary ERMs with regard to posterior vitreous detachment(PVD). METHODS: Six specimens of idiopathic epiretinal membranes(3 eyes with complete PVD, 2 eyes with partial PVD, and one eye with no PVD) and 3 specimens of secondary ERMs(all eyes with complete PVD) were immunohistochemically studied. We used type I, II, III, IV collagen and fibronectin to study extracellular components, and glial fibrillary acidic protein(GFAP), S 100 protein, vimentin, and so forth to study cellular components. RESULTS: All the specimens of idiopathic ERMs had the major components of the lamellar stained by type II collagen antibody, and one out of 3 specimens of secondary ERMs had a minor component stained by type II collagen antibody. Compared with idiopathic ERMs with complete PVD, 2 out of 3 specimens of idiopathic ERMs with partial PVD or no PVD contained rather thick collagen lamellar. CONCLUSION: There was difference between specimens of idiopathic ERMs and specimens of secondary ERMs in staining by type II collagen antibody, supposed by vitreous, in this study. Idiopathic ERM with attached posterior vitreous membrane may cause growth of collagen.

Aged↗
PubMed2000

Cyanide-bridge Fe-Fe and Fe-Co molecular squares: structures and electrochemistry of

Cyanide-bridged iron-iron and iron--cobalt molecular squares of [Fe(II/4)(mu-CN)4(bpy)8[(PF6)4 x 4H2O (1), [Fe(II/2)Co(II/2)(mu-CN)4(bpy)8](PF6)4 x 3CHCl3 x 2CH3CN (2), and [Fe(II/2)Co(III/2)(mu-CN)4(bpy)8](PF6)6 x 2CHCl3 x 4CH3NO2 (3) (bpy =2,2'-bipyridine) were prepared. X-ray structure analyses for 1-3 were performed and their electrochemistry was studied. In 1-3, four metal ions are bridged by cyanide groups to form tetranuclear macrocycles ("molecular squares"). Each metal ion in the square is six-coordinate: four of the coordination sites are occupied by the nitrogen atoms of two of bpy ligands and the remaining cis coordination sites are occupied by cyanide-carbon or cyanide-nitrogen atoms. In 1, Fe-C (cyanide) (1.899(4)-1.927(4)A) and Fe-N(cyanide) (1.929(4)-1.950(4)A) distances are typical of low-spin Fe2+ ions. In 2, Fe-C(cyanide) and Co(2+)-N(cyanide) bond lengths are in the range 1.919(5)-1.963(5)A and 1.850(5)-2.017(5) A, respectively: in contrast, shorter bond lengths are observed for the metal to cyanide-carbon and cyanide-nitrogen (1.878(7)- 1.893(7) A) in 3. As a result, the molecular squares in 1. 2, and 3 have sides of 4.947(1)4.986(1) A, 5.001(1)-5.053(1) A, and 4.910(1)-4.918(1) A, respectively. Magnetic susceptibility measurements revealed that the Fe2+ and Co3- ions in 1 and 3 are diamagnetic, while the high-spin Co2+ ions in 2 are weakly coupled through the low-spin Fe2 ions. Cyclic voltammograms of the squares are presented, and the electrochemically generated mixed-valent species [Fe(II/2)Fe(III/2)(mu-CN)4(bpy)8]6+ was discussed in terms of the intervalence transfer band.

Journal Article↗
PubMed2000

Vitreous surgery simulator.

OBJECTIVE: To reduce the surgical risks to patients and expose surgeons to surgical experience and complications, we have developed a practical system of vitreous surgery using virtual-reality technology. METHODS: The system is composed of high-resolution color stereo binoculars, haptic devices, foot switches, and a high-speed graphics computer. To simulate vitreous surgery, we created several virtual patient eyes with retinal diseases such as preretinal membranes and subretinal neovascular tissue at the fovea. RESULTS: The simulator provided the trainees with an operating environment similar to an actual one, and allowed them to learn to maneuver surgical instruments and remove proliferative tissue on the retina, under the retina, or both. This system allowed surgeons to avoid iatrogenic complications through visual signs such as retinal hemorrhage when the instrument contacted the retinal surface. CONCLUSIONS: This simulator may not only be suitable for residents to learn ocular surgical techniques but may also allow veteran surgeons to develop new surgical methods and skills.

Computer Simulation↗
PubMed2000

Scanning laser ophthalmoscope correlations with biomicroscopic findings and foveal function after macular hole closure.

OBJECTIVE: To investigate the relation between foveal findings and visual function in eyes with a resolved idiopathic macular hole after vitreous surgery. METHODS: We divided 28 eyes with postoperative idiopathic macular hole resolution into 3 groups based on postoperative biomicroscopic foveal findings of complete closure, partial closure, or atrophic closure. To evaluate foveal retinal function, scanning laser ophthalmoscope (SLO) microperimetry was performed preoperatively and 6 months postoperatively. RESULTS: Postoperatively in 18 eyes (64%), the foveal images became normal or almost normal and were classified as having complete closure, 6 eyes (21%) were classified as having partial closure, and 4 eyes (14%) as having atrophic closure. The corresponding visual acuity levels 6 months postoperatively were, respectively, 0.10, 0.35, and 0.64 (P<.01) based on LogMAR analysis. Preoperative SLO microperimetry detected an absolute scotoma at the bottom of all macular holes; postoperatively, the absolute scotoma disappeared in the 18 eyes with complete hole closure, but a relative scotoma was detected in 6 eyes. Of 6 eyes with partial closure, 1 had an absolute scotoma and 5 had a relative scotoma. An absolute scotoma was detected in 4 eyes with atrophic closure. CONCLUSIONS: After macular hole closure, SLO findings correlate both with biomicroscopic findings and foveal function. Better anatomical foveal recovery in eyes after macular hole closure results in better improvement of vision than in eyes in which the foveal anatomical findings are not as good.

Aged↗
PubMed2000

Effects of peroxynitrite on rabbit cornea.

BACKGROUND: Nitric oxide (NO) reacts rapidly with the superoxide anion to generate peroxynitrite, which has been found in the aqueous humor in eyes with uveitis. We evaluated the functional and anatomic effects of peroxynitrite on rabbit cornea. METHODS: One eye of each rabbit received an anterior chamber injection of 3-morpholinosydonimine N-ethylcarbamide (SIN-1), which simultaneously generates both NO and the superoxide anion. The corneal thickness was measured using an ultrasonic pachymeter before and after the injection. The eyes were fixed and the corneal specimens were prepared for electron microscopy. RESULTS: Anterior chamber injections of SIN-1 caused a significant increase in the corneal thickness (25.1+/-3.0 microm) 30 min after injection. Transmission electron microscopy showed swollen mitochondria and large vacuoles in the cytoplasm, and scanning electron microscopy revealed obscuring of the mosaic pattern by increased ruffling of endothelial cell surface and borders. CONCLUSION: The results suggest that peroxynitrite generated in the aqueous humor may cause corneal endothelial cell damage, which leads to transient corneal edema.

Animals↗
PubMed2000

Suppression of conditioned fear by administration of CRF receptor antagonist CP-154,526.

In order to examine the involvement of corticotropin-releasing hormone (CRF) receptor in the formation of anxiety, we investigated whether CRF receptor antagonist CP-154,526 suppressed conditioned fear stress. First, rats were individually subjected to 30 min of footshock. Twenty-four hours after footshock, the rats were again placed in the chamber and observed for 5 min without shock. CP-154,526 was administered 30 min before placing the rats in the chamber again. After that, CP-154,526 was once more administered 30 min before applying footshock. Administration of CP-154,526 30 min both before conditioned fear stress (placing the rats inside the cage but not applying footshock) and before actual footshock significantly reduced freezing behavior. These results show that CP-154,526 blocked both the acquisition and expression of conditioned fear, thus suggesting that the CRF receptor might be related to anxiety.

Animals↗
PubMed2000

Intravitreal injection of hyaluronidase cannot induce posterior vitreous detachment in the rabbit.

PURPOSE: To investigate whether intravitreal injection of hyaluronidase can induce posterior vitreous detachment (PVD) in the rabbit. METHODS: One eye each of 12 New Zealand white rabbits received intravitreal injection via the pars plana of 20 IU of hyaluronidase (0.1 mL reconstituted in sterile balanced salt solution [BSS]) into the midvitreous cavity. The fellow eye of each rabbit received a vitreous injection of 0.1 mL of BSS. At 3 and 6 months after intravitreal injection, four and eight rabbits were killed, respectively, and the eyes were enucleated. After fixation, scanning electron microscopy was performed to study the vitreoretinal interface. RESULTS: At 3 and 6 months after injection, scanning electron microscopy showed that the retinal surfaces in eyes that received either hyaluronidase or BSS were covered with vitreous collagen fibers. No eyes, even those that received hyaluronidase over a period of 6 months, had the smooth retinal surface consistent with a bare internal limiting lamina that suggests the development of PVD. CONCLUSION: Hyaluronidase cannot induce PVD in the rabbit over a 6-month period after vitreous injection.

Animals↗
PubMed1999

Suppression of conditioned fear by administration of CCKB receptor antagonist PD135158.

In order to examine the involvement of CCK in the formation of anxiety, we have investigated whether CCKB receptor antagonist PD135158 suppressed conditioned fear stress. Rats were individually subjected to 30 min of inescapable electric footshock in a chamber with a grid floor. First, the rats were individually subjected to 30 min of footshock. Twenty-four h after the footshock, the rats were again placed in the chamber and observed for 5 min without shocks. PD135158 was administered 30 min before placing the rats in the chamber again. Secondly, PD135158 was administered 30 min before footshock. Thirdly, PD135158 was administered 5 min after footshock. Administration of PD135158 30 min before conditioned fear stress significantly reduced freezing behavior. Administration of PD135158 30 min before footshock also significantly reduced freezing behavior. But, administration of PD135158 5 min after footshock did not significantly reduce freezing behavior. PD135158 blocked not only the acquisition but also the expression of conditioned fear. These results suggest that the CCKB receptor might play an important role in conditioned fear stress and that it might be related to anxiety.

Animals↗
PubMed1999

Posterior vitreous detachment induced by injection of plasmin and sulfur hexafluoride in the rabbit vitreous.

PURPOSE: To investigate whether an injection of plasmin and sulfur hexafluoride (SF6) can induce posterior vitreous detachment (PVD) without vitrectomy. METHODS: One eye each of 15 New Zealand white rabbits was assigned to one of three groups. Eyes in group 1 received a vitreous injection of 1 unit of human plasmin (0.1 mL reconstituted in balanced salt solution) and 0.5 mL of SF6; eyes in group 2 received a vitreous injection of plasmin alone; eyes in group 3 received a vitreous injection of SF6 alone. Seven days after injection, all animals were monitored electroretinographically and killed, and the eyes were enucleated. After fixation, scanning electron microscopy was performed. RESULTS: In group 1 eyes, the retinal surface was smooth except for the vitreous base, which showed complete separation of the vitreous cortex from the retina, indicating PVD. In group 2 and 3 eyes, sparse collagen fibers remained on the retinal surface. CONCLUSION: Vitreous injection of plasmin combined with SF6 can induce PVD without vitrectomy.

Animals↗
PubMed1998

Wound healing of scleral self-sealing incision: a comparison of ultrasound biomicroscopy and histology findings.

PURPOSE: The goal of this study was to compare the morphologic findings of wound healing in scleral self-sealing incisions using ultrasound biomicroscopy and histology. METHODS: Using a slit-knife, we made a scleral self-sealing incision in the rabbit eye. At various time points postoperatively, ultrasound biomicroscopy was performed to evaluate wound healing; the eyes then were enucleated and studied histologically. We also performed ultrasound biomicroscopy at various time points postoperatively in patients who received a scleral self-sealing incision during cataract surgery. RESULTS: In rabbit eyes, on days 1 and 2 postoperatively, we detected the scleral wound; thereafter, detection became increasingly difficult. On day 7 postoperatively, the wound was undetectable. By light-microscopic observation, the scleral wound was open at 1 day postoperatively. On day 2 postoperatively, fibrovascular tissue barely extended into the wound; on day 5 postoperatively, connective tissue extended through the full thickness of the wound. On day 7 postoperatively, the connective tissue became dense and aligned with the lamella. In human eyes, using ultrasound biomicroscopy, the scleral incision was detectable until 5 days postoperatively, but undetectable at 7 days postoperatively. CONCLUSIONS: Ultrasound biomicroscopy demonstrates the stages of wound healing of scleral self-sealing incisions. We believe that careful observation is necessary for approximately 7 days following self-sealing incision cataract surgery.

Animals↗
PubMed1998

[Suppression of conditioned fear by administration of CCKB receptor antagonist PD135158].

The aim of this study is to determine whether or not CCKB receptor antagonist PD135158 suppresses conditioned fear. Rats were individually subjected to 30 min of inescapable electric footshock in a chamber with a grid floor. PD135158 or the vehicle was administered 30 min before placing the rats in the shock chamber again. The rats were observed for 5 min without receiving shock. The administration of PD135158 30 min before conditioned-fear stress significantly reduced freezing behavior. PD135158 blocked the expression of conditioned fear. PD135158 was again administered 30 min before footshock. Then, the rats were individually subjected to 30 min of inescapable electric footshock in the shock chamber. Twenty-four hours after receiving footshock, the rats were again placed in the shock chamber and observed for 5 min without shock administration. The administration of PD135158 30 min before footshock significantly reduced conditioned freezing. PD135158 blocked the anxiety of conditioned fear. PD135158 blocked not only the anxiety, but also the expression of conditioned fear. These results suggest that CCKB receptor might play an important role in conditioned-fear stress. They indicate that CCKB receptor is related to anxiety.

Animals↗
PubMed1997

Transient shallow anterior chamber induced by supraciliary fluid after vitreous surgery.

PURPOSE: To report the mechanism of transient shallow anterior chamber after vitreous surgery for proliferative diabetic retinopathy. METHOD: Using ultrasound biomicroscopy, we examined a patient with transient shallow anterior chamber after vitreous surgery for proliferative diabetic retinopathy. RESULTS: On the day after surgery, slit-lamp examination disclosed a shallow anterior chamber that persisted for 1 week and deepened thereafter. Ultrasound biomicroscopy 5 days postoperatively disclosed a narrow angle in the peripheral anterior chamber and supraciliary fluid. At 14 days postoperatively, suprachoroidal fluid could not be detected, and the angle was wide. CONCLUSION: The shallow anterior chamber in this patient was caused by supraciliary fluid after vitreous surgery.

Aged↗
PubMed1997

Association between the short-term natural history of diabetic macular edema and the vitreomacular relationship in type II diabetes mellitus.

PURPOSE: The authors ascertain the association between the short-term natural history of untreated diabetic macular edema and the vitreomacular relationship. METHODS: The authors prospectively studied 82 type II diabetic patients with clinically significant macular edema over a six-month period. They used multiple linear regression analysis to evaluate the effect of ten variables on the short-term natural history of macular edema 6 months after diagnosis: age; gender; diabetes duration at diagnosis of macular edema; hemoglobin A1; insulin use; presence of proteinuria; presence of systemic hypertension, cardiac disorders, or both; degree of diabetic retinopathy; history of panretinal photocoagulation; and vitreomacular relationships, as determined by present lens biomicroscopy. RESULTS: At study entry, 22 (27%) eyes had vitreomacular separation and 60 (73%) eyes did not. Macular edema spontaneously resolved in 27 (33%) eyes 6 months after diagnosis. Of the 22 eyes with vitreomacular separation at study entry, 12 (55%) had spontaneous resolution of macular edema after 6 months, whereas only 15 of 60 (25%) of the eyes with vitreomacular adhesion at study entry had spontaneous resolution (P = 0.01). Stepwise regression analysis indicated that vitreomacular separation (P = 0.01) and diabetes duration (P = 0.03) contribute to resolution of macular edema. Of the 27 eyes with resolved macular edema, 17 (63%) had improved visual acuity of more than two lines, whereas no eyes had improved visual acuity if macular edema persisted. The prevalence of improved visual acuity of more than two lines was significantly higher in eyes with vitreomacular separation at study entry (36%, 8/22) than in eyes without (15%, 9/60; P = 0.04). CONCLUSION: Our findings suggest that vitreomacular separation may promote the spontaneous resolution of diabetic macular edema and consequently improve visual acuity.

Adolescent↗
PubMed1997

Copper-ion-catalyzed vitreous liquefaction in vivo.

To investigate copper-ion (Cu2+)-catalyzed vitreous liquefaction in vivo, Cu2+ solution (10 mumol) was injected into the vitreous cavity of rabbits. At 24 h after the injection, the gel and liquid vitreous were weighed, and the percent of vitreous liquefaction was calculated. Cu2+ injection resulted in liquefaction of 58% of the vitreous, although control eyes had 12% liquefaction (p < 0.1). The vitreous liquefaction was more pronounced in the presence of exogenous ascorbic acid. However, the addition of mannitol, a hydroxyl-radical-specific scavenger, significantly suppressed the Cu(2+)-catalyzed vitreous liquefaction. The free radicals generated by the Cu(2+)-catalyzed oxidation system may cause vitreous liquefaction in vivo.

Animals↗
PubMed1997

Role of the vitreous and macular edema in branch retinal vein occlusion.

BACKGROUND AND OBJECTIVE: To determine the relationship between macular edema associated with branch retinal vein occlusion (BRVO) and the condition of the vitreous. PATIENTS AND METHODS: The authors retrospectively studied 58 patients (58 eyes) who underwent vitreous examination. The eyes were classified as having vitreomacular attachment (VMA) or vitreomacular separation (VMS), and were divided into two groups based on the mean age of the patients. RESULTS: Macular edema was found in 39 (67%) of the eyes. The prevalence of VMA was 81% (22 of 27 eyes) in group 1 (patients who were 64 years old or younger) and 45% (14 of 31 eyes) in group 2 (patients who were older than 64 years). Although no significant relationship was found, 77% (17 of 22) of the eyes with VMA in group 1 had macular edema. The incidence of macular edema was significantly higher in eyes with VMA (93%, 13 of 14) than in eyes with VMS (41%, 7 of 17, P = .009) in group 2. CONCLUSION: The authors' findings suggest that VMA may influence the presence of macular edema associated with BRVO.

Adult↗