Effects of learning and movement frequency on polyrhythmic tapping performance.

This study examined the effect of learning a complex bimanual coordination task at different movement frequencies. 30 subjects performed 5:3 polyrhythmic tapping at either high, medium, or low movement frequency on a rhythmic synchronization task and then reproduced the polyrhythmic pattern repeatedly in the spontaneous task. Analysis showed that practice on the synchronization task qualitatively changed correct responses into anticipatory ones. The synchronization learning of the polyrhythm caused the anticipatory responses and so, may involve memorization of serial positions within the polyrhythm. Also, more anticipatory responses were indicated in performance at the medium and low frequencies than at the high frequency on the synchronization task. In addition, deviations of taps from expected tapping positions were observed in performance of the spontaneous task at the high frequency. These results suggest that the movement frequency qualitatively influenced the learning of this bimanual coordination. Especially at the high frequency, frequent shifts to other coordination patterns occurred on the spontaneous task. This means that the performance at higher frequency is more strongly affected by entrainment between the two hands.

Pattern formation in polyrhythmic tapping at a self-paced tempo.

The present study examined the pattern formation in complex bimanual coordination at a self-paced tempo. 10 subjects performed two motor tasks in a self-paced situation, a single-rhythmic tapping with the preferred hand and a 3:2 polyrhythmic tapping with the right hand taking the faster beat. To clarify the process of polyrhythmic pattern formation, the transition routes of frequency ratios were analyzed. Analysis showed that a 3:2 pattern was formed by transition repeatedly shifting among 1:1, 2:1, and 3:1 patterns. Consequently, transitions were induced from a simple dissipative structure to a more complex dissipative structure. This process could be represented as a shift from lower- to higher-order ratios in the Farey tree. Furthermore, close relationships were indicated between personal tempo in the polyrhythmic tapping with the faster hand and in the single-rhythmic tapping.

Postoperative posterior retinal holes after pars plana vitrectomy for primary retinal detachment.

BACKGROUND: Although retinal breaks occur frequently during vitrectomy, the postoperative occurrence of new retinal holes close to the vascular arcade after vitrectomy for rhegmatogenous retinal detachment rarely has been reported. METHODS: Three patients with rhegmatogenous, retinal detachment were treated by vitrectomy. More than 49 days after vitrectomy, posterior retinal holes with no retinal detachment occurred halfway between the vascular arcade and the chorioretinal scar around the extrusion hole or the primary retinal tear. RESULTS: These new holes were effectively managed with photocoagulation. CONCLUSION: New hole formation could be caused by the technique of the internal drainage, the contraction of the photocoagulation scar, or epiretinal membrane contraction. Another possibility is that new holes occur through two opposite tangential traction contractile forces: one induced by the contraction of the photocoagulation scar, the other caused by the contraction of the premacular cortical vitreous attached to the vascular arcade.

Relationship between cataracts and epilation in atomic bomb survivors.

Among 1713 atomic bomb survivors who underwent ophthalmological examinations from 1963-1964, the risk of cataract formation per unit dose of radiation was significantly greater for those who reported hair loss of 67% or more after exposure (the epilation group) than for those who reported less or no hair loss (the no-epilation group) (P < 0.01). Such an epilation effect has also been associated with leukemia mortality and the frequency of chromosome aberrations. Although this might be interpreted as indicating differential sensitivity to radiation between the epilation group and the no-epilation group, it could also be explained by imprecision in dose estimates. We have calculated that a 48% random error in DS86 dose estimates could be in accordance with the dose-response relationship for the prevalence of cataracts in the epilation group or the no-epilation group. Possible mechanisms for variation in radiosensitivity are discussed.

Computerized tomography of two patients with morning glory syndrome.

Morning glory syndrome (MGS), an uncommon optic disc anomaly, is characterized by a funnel-shaped, excavated optic disc surrounded by chorioretinal pigmentary disturbance. Generally, it is an isolated ocular abnormality. The authors describe two patients in whom MGS developed in association with brain abnormalities. In both cases, there was enlargement of the optic nerve that showed increased radiodensity similar to that of sclera and cavum vergae in the brain cavity present in computerized tomography (CT). To our knowledge, the coexistence of MGS, cavum vergae and an enlarged retrobulbar optic nerve showing increased radiodensity have not been previously reported. The findings suggest that MGS may be based on a developmental anomaly involving the brain, and the enlarged optic nerve may be associated with sclera because of the isodensity in CT.

Retinal detachment with tear in the posterior fundus following ocular contusion.

Two unusual cases of rhegmatogenous retinal detachment following contusion to the eyeball showed retinal tears at the posterior fundus close to the optic disc and the large retinal blood vessels. In both cases, the tears were not detected immediately after the injury due to a coexisting vitreous hemorrhage. Both patients were successfully treated by pars plana vitrectomy, air-fluid exchange, and endolaser photocoagulation. During vitrectomies, an adhesion of the vitreous to the flap or the operculum of the tear was observed, with detachment of the remainder of the posterior vitreous from the retina. Vitrectomy allowed a more complete resolution of posterior tractional forces than scleral buckling, and eliminated the vitreous hemorrhage.

Did atomic bomb radiation influence the incidence of retinoblastoma in Nagasaki and Hiroshima?

The authors studied the effect of atomic bomb radiation in Nagasaki and Hiroshima on the incidence of retinoblastoma by examining the history of exposure to atomic bomb radiation among the grandparents and parents of retinoblastoma patients in Nagasaki and Hiroshima. Of 85 patients born in Nagasaki Prefecture from 1965 to 1986 and in Hiroshima Prefecture from 1966 to 1986, 42 had records to whether or not their grandparents and parents had been exposed to atomic bomb radiation. Seven had parents or grandparents exposed to atomic bomb radiation. These patients showed neither a high incidence of bilateral retinoblastoma nor a family history of retinoblastoma, although a higher incidence of cancer in the family history was found in the exposed group. Exposure to radiation showed no correlation with the onset of retinoblastoma. Moreover, the incidence of retinoblastoma in Nagasaki and Hiroshima Prefectures was almost the same as the average incidence in Japan. The authors failed to find evidence of increased incidence of retinoblastoma in the offspring of those exposed to atomic bomb radiation in Nagasaki and Hiroshima. However, this does not mean that the effect of radiation on the occurrence of retinoblastoma can be ruled out.

[A case of radiation cataract resulting from accidental irradiation of radioisotope].

We studied light and electron microscopic findings in one case of cataract resulting from accidental radioisotope irradiation. A 53-year-old male, a radiographer, was irradiated by Ga-citrate which dropped accidentally into his left eye during a radioisotope procedure. Subsequently opacity appeared in the posterior and anterior subcapsular area of the left lens and increased in intensity. Intracapsular cataract extraction was performed one and a half years after the accident. The extracted lens was studied by light and transmission electron microscopy. Epithelial cells showed frequent stratification in some sites and disappeared in others in the equatorial region. Wedl cells and vacuoles were also seen in the posterior subcapsular area. Degeneration of lens fibers, including multilayered whorls, were observed in the cortex.

Inositol phosphate-diacylglycerol signaling pathway in regulation of intraocular pressure.

To clarify the role of the inositol phosphate diacylglycerol (PI) signaling pathway in the regulation of intraocular pressure (IOP), we examined the effects of the tumor promoter phorbol ester (PMA) and Ca ionophore A23187 on IOP responses in albino rabbits. It was known that PMA stimulates protein kinase C (PKC) directly and that A23187 elevates intracellular Ca2+ concentration. In this study, the topical application of 10 microM PMA or 15 microM A23187 slightly reduced IOP. However, when both 10 microM PMA and 15 microM A23187 were topically applied the IOP was significantly reduced between 2 and 10 hours after A23187 application. The maximum IOP decrease was 5.0 mmHg at 3 hours. This decrease was inhibited by pretreatment with 0.5 microM staurosporin, a PKC inhibitor. These findings suggest that the PI signaling pathway somehow mediates aqueous dynamic changes in the eye.

[Fluorescein fundus angiography of optic nerve head in primary open angle glaucoma and low tension glaucoma].

Fluorescein fundus angiography was performed at angle of 20 degrees in the 58 low tension glaucoma (LTG) eyes (30 cases) and 77 primary open angle glaucoma (POAG) eyes (41 cases) and the relation of the optic nerve head fluorescein changes to visual field disturbances (stage classification of Kosaki) was compared between POAG and LTG groups. The filling defect of fluorescein in the deep area and the decrease in number of superficial capillaries were observed in the optic nerve head. The filling defect area of fluorescein in the optic nerve head corresponding to Bjerrum scotoma was recognized even in the mild visual field disturbance cases of both LTG and POAG. The following findings were noted in both LTG and POAG cases; expansion of the filling defect area and the decrease in number of superficial capillaries in the same area with progression of visual field disturbances. Filling defect area of fluorescein of the optic nerve head accorded with visual field disturbance area in 19 LTG eyes (32.8%) and 61 POAG eyes (79.2%). On the contrary, the filling defect area of the optic nerve head was wider than the visual disturbance area in 37 LTG eyes (63.8%) and 16 POAG eyes (20.8%). These findings suggest that blood circulatory disorders of the optic nerve head occurred earlier in LTG than in POAG and that the development of LTG might be closely associated with the blood circulatory disorders.

Radiation-related ophthalmological changes and aging among Hiroshima and Nagasaki A-bomb survivors: a reanalysis.

The relationship of ionizing radiation to the age-related ophthalmological findings of the 1978-1980 ophthalmological examination of A-bomb survivors of Hiroshima and Nagasaki has been reanalyzed using DS86 eye organ dose estimates. The main purpose of this reevaluation was to determine whether age and radiation exposure, as measured using the recently revised dosimetry information (DS86), have an additive, synergistic, or antagonistic effect. The data in this study are limited to axial opacities and posterior subcapsular changes, for which a definite radiation-induced effect has been observed in Hiroshima and Nagasaki A-bomb survivors. The best model fitting for axial opacities gives a significant positive effect for both linear dose and linear age-related regression coefficients and a significant negative effect for an interaction between radiation dose and age. Such a negative interaction implies an antagonistic effect in that the relative risks in relation to radiation exposure doses become smaller with an increase in age. On the other hand, the best-fitting relationship for posterior subcapsular changes suggested a linear-quadratic dose and linear age-related effect. The estimate of the quadratic dose coefficient shows a highly negative correlation with age, but the negative quadratic dose term is extremely small and is of little biological significance.

Leukemic involvement of the optic nerve.

We studied five cases of leukemia with invasion of the optic disk and optic nerve. Two patients had acute lymphoblastic leukemia and three had acute myelogenous leukemia. All patients received intrathecal injections of chemotherapeutic drugs including methotrexate, cytarabine, and prednisolone. Three patients underwent irradiation therapy of the whole brain and optic nerve. While initial improvement in the ophthalmic abnormalities, such as optic disk edema, flame-shaped retinal hemorrhages, and dilation of the retinal vein, was noted, optic atrophy was later found in all eyes.

A Fukuyama type of congenital muscular dystrophy associated with atypical gyrate atrophy of the choroid and retina. A case report.

A three-year-ten-month old boy with the Fukuyama type of congenital muscular dystrophy (FCMD), early onset of muscular hypotonia, severe mental retardation, a slow progressive course and a characteristic fundus appearance similar to that of gyrate atrophy is described. Hyperornithinaemia and iminoglycinuria were not noted. To our knowledge, this is the first reported case of FCMD associated with atypical gyrate atrophy of the choroid and retina.

Ophthalmologic changes related to radiation exposure and age in adult health study sample, Hiroshima and Nagasaki.

A 2-year ophthalmologic study of age and radiation-related ophthalmologic lesions among the atomic bomb survivors in Hiroshima and Nagasaki was conducted in 1978-80. The study sample in both cities was composed of all persons exposed to 100+ rad, their controls, and all other persons with a previous record of axial opacities or posterior subcapsular changes. Most of the losses were due to persons who refused to participate or for whom it was not possible to arrange for an ophthalmologic examination at the time of the regularly scheduled medical examination. It should be emphasized, however, that the loss of persons in both the control and the 100+ rad groups did not change systematically with increasing age by city. Increased lenticular opacities, other lens changes, and loss of visual acuity and accommodation occurred with increasing age in both exposed and control subjects as manifestations of the normal aging process. A highly significant excess risk for all age categories in the 300+ rad group in comparison to those in the control group was observed for both axial opacities and posterior subcapsular changes in Hiroshima, but not in Nagasaki. A stronger radiosensitive aging effect for persons who were under 15 years old at the time of the bombing (ATB) was observed for both axial opacities and posterior subcapsular changes in Hiroshima.

Free amino acid concentrations in blood cells of two brothers with gyrate atrophy of the choroid and retina with hyperornithinaemia.

In this study we selected blood cells as accessible tissues and measured the free amino acid concentrations in erythrocytes, lymphocytes, and granulocytes of two patients with gyrate atrophy with hyperornithinaemia. We found that ornithine concentrations were elevated in blood cells, to different degrees depending on the type of cell, and that aspartic acid concentrations were low in erythrocytes. We also investigated the fluctuation of free amino acid concentrations in blood cells up to 24 h after the oral administration of ornithine. The ornithine concentration in the blood cells of the patients reached a peak 2 h after the oral administration, and remained high for at least 4 h, although after 2 h the concentration curves differed in the three types of cells.