Biomedical subjects

Yoshiaki Shimada

Publications and source records attributed to Yoshiaki Shimada.

17 recordsLinked to original sources

PubMed2006

Bilateral optic neuropathy associated with multiple myeloma.

A 51-year-old man had reduced vision and bilateral optic disc swelling as the initial clinical manifestation of multiple myeloma. Brain imaging failed to disclose any abnormalities. Before any therapy was begun, visual function began to improve substantially. Three months after chemotherapy was started, visual function and optic disc appearance returned to near normal. There were no features to suggest polyneuropathy-organomegaly-endocrinopathy-M protein-skin changes (POEMS) syndrome. Visual loss in myeloma is usually caused by compression or infiltration of the optic nerves by tumor. The mechanism of the optic neuropathy in this case remains unknown.

Diagnosis, Differential↗

PubMed2005

Synthesis and biological activity of novel 4,4-difluorobenzazepine derivatives as non-peptide antagonists of the arginine vasopressin V1A receptor.

To find potent and selective antagonists of the arginine vasopressin (AVP) V1A receptor, optimization studies of compounds structurally related to (Z)-N-{4'-[(4,4-difluoro-5-carbamoylmethylidene-2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl)carbonyl]phenyl}carboxamide were performed. The synthesis and pharmacological properties of these compounds are described. We first investigated the effect of the carboxamide moiety, and found that a 2-methylfuran-3-carbonyl group at this position increased V1A binding affinity and selectivity for the V1A receptor versus the V2 receptor. The amino group of the 5-carbamoylmethylidene moiety was also examined, and a 4-piperidinopiperidino group was found to be optimal at this position. The hemifumarate of compound 12l (YM218) was shown to exhibit potent binding affinity, V1A receptor selectivity, and in vivo antagonist activity.

Animals↗

PubMed2005

Changes in multifocal electroretinograms induced by transpupillary thermotherapy.

OBJECTIVE: To determine retinal function after transpupillary thermotherapy (TTT) for subfoveal choroidal neovascularization using multifocal electroretinograms (mfERGs). METHODS: Multifocal electroretinograms were recorded before and after TTT (wavelength, 810 nm; diameter, 3 mm; duration, 60 seconds; power, 350 mW) in 9 eyes in 9 patients with subfoveal choroidal neovascularizations. The stimulus consisted of 7 hexagons; the central hexagon covered the laser-irradiated area and the surrounding 6 hexagons covered the nonirradiated area. Each recording was completed within 1 minute, and mfERGs were recorded periodically during the first 60 minutes after TTT and also at 24 hours and 1 week after TTT. RESULTS: The amplitude of mfERGs from irradiated areas was significantly reduced at 1 minute after TTT (P< .01) and then recovered soon. The peak time was prolonged at 15 minutes after TTT (P< .01), recovered to pre-TTT levels at 60 minutes, and then was prolonged again at 24 hours (P< .05) and 1 week (P< .05) after TTT. The mfERGs in nonirradiated areas were unchanged during the observational period. CONCLUSIONS: We found amplitude reduction in central focal ERGs at 1 minute after TTT, transient peak-time delay at 15 minutes, and a delay at 24 hours. Early reduction is probably directly caused by an increase in temperature during TTT as previously reported in focal flicker ERGs. Peak-time delays at 15 minutes and 24 hours may be caused by other factors, such as increased intracellular calcium (Ca(2+)), the release of nitric oxide or heat shock proteins, vasodilation, or change in choroidal neovascularization. Our findings indicate that recording mfERGs may be a useful tool for evaluating TTT procedures.

Adult↗

PubMed2005

Spatial and temporal properties of interocular timing differences in multifocal visual evoked potentials.

The multifocal VEPs (mfVEPs) obtained from the right and left eyes are practically identical in shape and amplitude, however small differences in the implicit times (ITs) have been reported. We have analyzed the ITs in detail to show that they are dependent on the radial location of the stimulus in the visual field. The differences are large, up to 8.3 ms, near the horizontal meridian, and are probably due to differences in the distances of the nasal and temporal ganglion cell axons from the optic disc. The intraretinal conduction velocity of ganglion cell axons, determined by dividing the axonal length to the optic disc by the ITs, was 0.29 m/s at an eccentricity of 0.5-1.4 degrees and 1.39 m/s at 8-12 degrees .

Adult↗

PubMed2005

Stereoselective synthesis of methyl (Z)-(4,4-difluoro-2,3,4,5-tetrahydro-1H-1-benzazepin-5-ylidene)acetate using a dianion Horner-Wadsworth-Emmons reagent.

Stereoselective synthesis of methyl (Z)-(4,4-difluoro-2,3,4,5-tetrahydro-1H-1-benzazepin-5-ylidene)acetate (1a) is described. Z-selectivity of the Horner-Wadsworth-Emmons (HWE) reaction was obtained based on an investigation of the reaction conditions for introduction of a methylidene group onto the 5-position of benzazepine.

Acetates↗

PubMed2005

Preparation of highly potent and selective non-peptide antagonists of the arginine vasopressin V1A receptor by introduction of a 2-ethyl-1H-1-imidazolyl group.

To find a new series of arginine vasopressin (AVP) V1A receptor antagonists, the influence of the 2-phenyl group of 2-phenyl-4'-[(2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl)carbonyl]benzanilide (7) was investigated. Replacement of the 2-phenyl group by a 2-ethyl-1H-imidazol-1-yl group was effective in yielding a V1A-selective compound. Moreover, this imidazolyl group was introduced in the same position in YM-35471 (6), and further studies of these compounds were performed. Consequently, we found that the (Z)-4'-({4,4-difluoro-5-[(N-cyclopropylcarbamoyl)methylene]-2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl}carbonyl)-2-(2-ethyl-1H-1-imidazol-1-yl)benzanilide (9f) exhibited highly potent affinity and selectivity, and was the most potent antagonist for the V1A receptor among our compounds. The synthesis and pharmacological evaluation of these compounds are described in this paper.

Antidiuretic Hormone Receptor Antagonists↗

PubMed2004

Multifocal electroretinograms combined with periodic flashes: direct responses and induced components.

PURPOSE: To investigate the retinal responses generated by flash interactions in a recently introduced "global (full-screen) flash" stimulus paradigm to record the multifocal electroretinogram (mfERG). METHODS: Five normal individuals were studied with stimulation combining multifocal (pseudorandom) flashes with interleaved global (periodic, full-screen) flashes. The intensities of the two flashes were independently varied. Two distinct first-order response components were obtained: the mean response to the focal flashes (referred to as the direct response, DR) and the effect of the focal flash on the responses evoked by the global flash (the induced component, IC). RESULTS: Increasing the global flash luminance reduced DR amplitude and shortened DR implicit time. IC amplitude peaked with a moderate global flash (1.33-2.67 cd.s/m2). With a global flash of the right intensity, a weak focal flash could evoke a considerable IC even when the DR was barely detectable. Moderate global flashes maximized the IC, and its intersubject variability was reduced at lower focal flash luminances. IC topography had a large naso-temporal asymmetry. CONCLUSIONS: While the DR is the average response generated by the local flashes regardless of the context of preceding and following flashes, the IC represents the difference in the global flash response in the presence and absence of the preceding focal flash. As the focal flashes were always preceded by the periodically occurring global flashes, the DR reflects the resulting adapted or desensitized state of the retinal patch. The pure, nonlinear IC is thought to reflect predominantly inner retinal function.

Adult↗

PubMed2003

Kinetics of indocyanine green dye after intraocular surgeries using indocyanine green staining.

OBJECTIVE: To determine the elimination kinetics of indocyanine green (ICG) after intraocular operations using ICG staining. METHODS: Intraocular fluorescence of ICG was determined using the ICG angiographic mode of a scanning laser ophthalmoscope (in vivo) and fluorescence microscopy (in vitro) after circular curvilinear capsulorhexis with ICG staining during cataract surgery and internal limiting membrane (ILM) peeling with ICG staining during macular hole surgery. SUBJECTS: We studied 9 eyes of 7 patients with white cataracts and 14 eyes of 14 patients with idiopathic macular holes. RESULTS: Scanning laser ophthalmoscopy revealed fluorescence in the anterior segment of patients with cataracts on the first postoperative day, and fluorescence remained for a mean +/- SD of 6.0 +/- 2.2 days postoperatively. Scanning laser ophthalmoscopy also revealed fluorescence in the posterior pole of patients with macular holes, and it remained for a mean +/- SD of 2.7 +/- 1.4 months postoperatively. Fluorescence microscopy showed fluorescence of the entire tissues, suggesting that ICG had stained not only the surface of the membranes but had also entered them. In both operations, visual outcomes were not significantly different from the results obtained without ICG. CONCLUSIONS: Because entire tissues were stained, the differences in ICG kinetics might also be caused by factors other than differences in stainability, such as the environment surrounding the tissues or molecular structural differences between the lens capsule and the ILM. Although we found complete disappearance of fluorescence and good functional recovery, the longer resident time of the dye after macular hole surgery may suggest a potential risk to intraocular tissues.

Adult↗

PubMed2003

Removal of lens material dropped into the vitreous cavity during cataract surgery using an optical fiber-free intravitreal surgery system.

We describe a technique for removing lens fragments dropped into the vitreous cavity during cataract surgery using an optical fiber-free intravitreal surgery system (OFFISS) that was developed for bimanual vitrectomy. The dropped nucleus was removed by 2-port corneal vitrectomy using the OFFISS in 3 patients during complicated cataract surgery. No complications occurred, and good visual recovery was achieved. The OFFISS provided a good view of the fundus without fiber optics and allowed the use of 2 ports for vitrectomy through the corneal wound. This technique is suitable for cataract surgeons who have not been trained in 3-port pars plana vitrectomy.

Cataract Extraction↗

PubMed2003

Stray light-induced multifocal electroretinograms.

PURPOSE: To evaluate the characteristics of stray light-induced response in multifocal ERG (mfERG) elicited by the stimulus falling on the disc. METHODS: A patient with an enlarged optic disc (4 x 4 disc diameters of disc of normal fellow eye) and four normal volunteers served as subjects. The mfERGs elicited by different stimulus intensities (0.67-4.67 cd-sec/m(2)) were recorded from the patient, and the mfERGs obtained with stimuli on the enlarged optic disc. For comparison, full-field pseudorandom ERGs (ffprERGs) were also recorded in all subjects. The first-order kernels (K1) and the second-order kernels (K2.1) were analyzed. RESULTS: A small and delayed K1 was recorded on the enlarged disc, but K2.1 was flat on the disc at all intensities. The implicit time of K1 at lower intensities was longer than at higher intensities. ffprERGs at very low intensities in the patient and normal subjects were similar to the mfERG on the disc (delayed K1 associated with flat K2.1). CONCLUSIONS: The responses elicited by stimulating the disc were delayed in K1 and flat in K2.1. Because similar ffprERGs were observed at very low intensities, it is likely that an optic disc with high reflectance scattered the stimulus light to create a weak full-field stimulus. Thus, care must be taken when focal lesions are investigated with mfERGs.

Adult↗

PubMed2003

Multifocal electroretinograms in cases of central areolar choroidal dystrophy.

PURPOSE: To study multifocal electroretinograms (mfERG) in patients with early-stage central alveolar choroidal dystrophy (CACD) with well-demarcated atrophic areas. METHODS: Eight eyes of eight patients with CACD (ages, 47-67 years) and 20 normal control subjects were examined. The first- and second-order kernels (K1 and K2) were extracted from the responses elicited by 61 standard hexagonal elements of a visual response imaging system. The amplitudes and peak times of the focal responses at various retinal eccentricities were studied. RESULTS: The amplitudes of K1 were reduced in the visibly atrophic areas, and they were also decreased in areas with no visible atrophy. The peak time was slightly delayed in many loci, but the delay was not as long as that in congenital stationary night blindness or diabetic retinopathy. The amplitude of K2 was very small in the central and peripheral areas, but the K2/K1 ratio in both areas was not significantly reduced, compared with that in normal subjects. CONCLUSIONS: Although the atrophic area was ophthalmoscopically well demarcated in patients with CACD, the abnormality of retinal function extended beyond the borders of the ophthalmoscopic and angiographic lesions. The retinal dysfunction outside the atrophic areas suggests a centrifugal progression of the disease, and abnormal K2 and K1 with preserved K2/K1 ratio are consistent with a presynaptic mechanism for the retinal dysfunction in this disease.

Adult↗

PubMed2003

Preparation of non-peptide, highly potent and selective antagonists of arginine vasopressin V1A receptor by introduction of alkoxy groups.

A series of compounds structurally related to 4'-[(4,4-difluoro-5-methylidene-2,3,4,5-tetrahydro-1H-1-benzoazepin-1-yl)carbonyl]benzanilide were synthesized and evaluated for arginine vasopressin (AVP) antagonistic activity. Compounds with alkoxy groups (especially ethoxy group) at the 2'-position of benzanilide possessed potent affinity and selectivity for the V1A receptor versus V2 receptor. Further study has shown that the introduction of 4,4-dimethylaminopiperidino and morpholino groups at carbonylmethylene exhibited more potent affinity and selectivity for V1A receptors. Consequently, we found that the (Z)-4'-([4,4-Difluoro-5-[(4-dimethylaminopiperidino)carbonylmethylene]-2,3,4,5-tetrahydro-1H-1-benzoazepin-1-yl]carbonyl)-2-ethoxybenzanilide monohydrochloride (8d) and the (Z)-4'-[(4,4-Difluoro-5-morpholinocarbamoylethylene-2,3,4,5-tetrahydro-1H-1-benzoazepin-1-yl)carbonyl]-2-ethoxybenzanilide (8q) exhibited potent and selective V1A receptor antagonist activity. The synthesis and pharmacological properties of these compounds are detailed in this paper.

Acetic Acid↗

PubMed2002

New system for fiberoptic-free bimanual vitreous surgery.

OBJECTIVES: To describe a new system for fiberoptic-free bimanual vitrectomy and to present the outcome of 37 eyes with preretinal membranes due to diabetic retinopathy or proliferative vitreoretinopathy that underwent surgery using this system. METHODS: The system consists of a 40-diopter aspheric field lens suspended from the operating microscope and a prismatic inverting device. The aspheric lens is placed above the cornea, and the illumination from the operating microscope creates an inverted image of the fundus, which is made erect by an inverter system. No fiberoptics are required, and both hands are free to use 2 microinstruments. MAIN OUTCOME MEASURES: The practical utility of this system and its surgical results and complications. RESULTS: The system was used successfully in all cases. Membrane dissection and hemostasis were performed without incident. An improvement in visual acuity of 2 or more lines was found in 30 of 37 eyes. Five eyes did not reveal change of 2 or more lines, and 2 eyes had a decrease in visual acuity of more than 2 lines. There was no evidence of phototoxicity. CONCLUSION: This system is very useful for bimanual vitrectomy.

Diabetic Retinopathy↗

PubMed2002

Transparent irrigation cannula for bimanual lens cortex removal.

A transparent irrigation cannula was developed to facilitate bimanual removal of subincisional lens cortex after phacoemulsification. The cannula allows visualization of the proximal cortex and provides ample inflow to maintain an inflated anterior chamber even at a high aspiration pressure.

Catheterization↗

PubMed2002

[The concept of induced components in multifocal electroretinograms].

PURPOSE: In the late period of a multifocal electroretinogram (mfERG) waveform, higher order-kernels copy themselves. These images are called projection components(or induced components), and contribute to the particular waveform of mfERG. I describe this feature, which the developer of the multifocal technique was fully aware of. METHOD: Inter-kernel comparisons were made of mfERGs, focusing on the characteristics and influence of induced components. RESULTS AND DISCUSSION: Even though induced components have never been described or discussed in detail in Japan, they are certainly one of the key elements in learning how the multifocal technique works and what the difference is between multifocal and conventional ERGs.

Electroretinography↗

PubMed2002

[A probable case of Creutzfeldt-Jakob disease with electroretinogram alterations].

Although visual disturbance is recognized as a clinical feature of Creutzfeldt-Jakob disease (CJD), lesions within the retina have to date, recorded little attention. In this single case study, we report a case of retinopathy observed in a 72-year-old female patient with CJD. The patient admitted to the hospital complaining of a 2-month history of visual disturbance, dysarthria, and gait disorder. Electroencephalogram showed periodic synchronous discharges synchronizing with myoclonic jerks. Electroretinogram (ERG) using single bright flash in a dark-adapted state demonstrated the absence of b-wave in both eyes. One month later, ERG could no longer record a-wave of the right eye. The absence of b-wave on ERG indicated a disorder within the inner layer of the retina, furthermore lesions detected in the occipital lobe were considered too mild to have elicited such visual disorder. We further conclude that retinopathy may be found in CJD and can progress in retrograde from ganglion cells to photoreceptors. Although the frequency of retinopathy among the CJD population is unclear, detailed clinical observation and analysis of ERG in patients with visual disorders of unknown cause is extremely important for both the screening and exclusion of CJD.

Aged↗

PubMedDate not supplied

Bilateral spontaneous hyphema with uveitis in a young girl.

A healthy 5-year-old girl presented with bilateral hyphema as an initial symptom of uveitis. The ocular findings and the patient's age suggested that the uveitis was due to juvenile rheumatic arthritis or chronic iridocyclitis.

Arthritis, Juvenile↗