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Biomedical subjects

M O Tso

Publications and source records attributed to M O Tso.

At least 181 records · Page 10Linked to original sources
PubMed1977

Retinoblastoma and intracranial malignancy.

The occurrence of independent brain tumors in two patients with retinoblastoma is described. One patient with well-differentiated biliteral retinoblastomas developed, over two years later, a pineal tumor but no other metastatic lesions. The pineal tumor was composed of small neuroblastic cells and a second population of larger cells with vesicular nuclei and more abundant cytoplasm. This feature is not characteristic of either primary or metastatic retinoblastoma. In the second patient the symptoms of a brain tumor led to the discovery of a small uniocular, well-differentiated retinoblastoma. The brain tumor was retrochiasmal, highly differentiated (showing areas of photoreceptor differentiation), and interpreted as an ectopic nonmetastatic retinoblastoma. The possible histogenetic origins of the brain tumors are discussed. Patients who develop symptoms of a brain tumor after a prolonged interval since the treatment of their ocular tumors should be suspected of harboring a second intracranial primary.

Brain Neoplasms↗
PubMed1977

Mesectodermal leiomyoma of the ciliary body: a tumor of presumed neural crest origin.

Two benign tumors of the ciliary body diagnosed as neurogenic tumors by light microscopy were shown by electron microscopy to be composed of smooth muscle cells with unusual morphologic features. The light-microscopic appearance of a background fibrillary matrix imparting a "neural" appearance was the result of the interweaving of myriad cell processes filled with thin cytoplasmic filaments possessing fusiform densities. The perikaryon of the tumor cells was relatively free of filaments and displayed mitochondria and stacks of rough-surfaced endoplasmic reticulum suggestive of Nissl substance. The basis for these remarkable "hybrid" tumor cells--combining myogenic and neurogenic characteristics--is believed to reside in the neural crest origin of the smooth muscle of the ciliary body (mesectoderm). The histogenetic implications of mesectodermal tissue and the tumors that it spawns are discussed.

Adult↗
PubMed1977

Fluorescein pattern of the choriocapillaris in the neonatal rhesus monkey.

Seven neonatal rhesus monkeys were studied by serial fundus photography and fluorescein angiography at weekly intervals during the first 12 weeks of life. The neonatal rhesus showed little pigmentation of the fundus during the first six weeks of life. The fluorescein angiograms showed a definite sequential as well as segmental filling pattern at the level of the choriocapillaris. This filling pattern was based on individual units called lobules. In addition there was a segmental flow in the macula; that is, the nasal macula filled before the temporal macula.

Animals↗
PubMed1977

Experimental macular edema after lens extraction.

Macular edema has been observed frequently in man after cataract extraction, but pathogenic mechanisms remain unclear. Seven eyes of four young adult rhesus monkeys underwent lens extraction. The retinas and maculae of these eyes were examined by ophthalmoscopy fundus photography, fluorescein angiography, light and electron microscopy, and the horseradish peroxidase tracer technique. In the macular region, the blood-retinal barrier at the retinal vasculature was disrupted in three of the seven eyes. All three eyes had had vitreous loss during lens extraction. Horseradish peroxidase was observed both intracellularly and extracellularly in the maculae. In contrast, the blood-retinal barrier at both the retinal pigment epithelium and the retinal vasculature of the peripheral retina in most eyes was intact. We conclude that macular edema secondary to lens extraction is due to disruption of the blood-retinal barrier at the levels of the retinal vasculature and the retinal pigment epithelium.

Animals↗
PubMed1977

Experimental allergic optic neuritis in guinea pigs: preliminary report.

An experimental model for acute allergic optic neuritis was produced in adult strain 13 guinea pigs by sensitization with isogenic spinal cord emulsion in complete Freund's adjuvant. These animals exhibited two distinct clinical patterns: (1) "retrobulbar optic neuritis," with a diminished pupillary response to light despite a normal fundus, and (2) "neuroretinitis," with a diminished pupillary response associated with hyperemia and swelling to the disc and juxtapapillary retinal edema. Histopathologic study of those animals with "retrobulbar neuritis" revealed that some had no abnormalities in the optic nerve or chiasm, but showed foci of mononuclear cell infiltration in the brain. Others had a mononuclear cell infiltration localized to the retrobulbar portion of the optic nerve and chiasm with multiple foci of axial and periaxial demyelination. Similar pathologic changes were present in the animals with "neuroretintis", but the lesions were located just behind the lamina scleralis. These animals also exhibited marked swelling of the axons at the lamina retinalis. On examination by light microscopy, the alterations in the region of optic nerve head appeared characteristic of papilledema.

Animals↗
PubMed1976

Chalcosis in the human eye. A clinicopathologic study.

A clinicopathologic study of eight human eyes containing intraocular copper foreign bodies was undertaken. These foreign bodies, which had been retained in the eyes from three weeks to 22 years, were analyzed by atomic-absorption spectrophotometry and x-ray diffraction to determine their chemical composition. Copper deposits in Descemet membrane, vitreous, internal limiting membrane of the retina, and fibrous capsule around the foreign bodies could be demonstrated by rhodanine, rubeanic acid, and alizarin blue stains and were correlated with clinical findings and pathologic changes. Eyes with foreign bodies containing more than 85% copper tended to show more disseminated copper deposits. Eyes with alloy containing less than 85% copper showed more localized deposits of copper. Retinal structures were well preserved, even in an eye with an intraocular copper foreign body that had been retained for 22 years.

Adolescent↗
PubMed1976

A light microscopic, autoradiographic study of axoplasmic transport in the optic nerve head during ocular hypotony, increased intraocular pressure, and papilledema.

Cyclocryotherapy of the monkey eye reliably produces transient increased intraocular pressure followed by prolonged hypotony, during which papilledema occurs. Axoplasmic transport was studied while the intraocular pressure was both increased and decreased after cyclocryotherapy by autoradiography following the intravitreal injection of tritiated leucine and proline. Surgical fistulization of the anterior chamber was also used to produce hypotony and papilledema. Significant alterations of both the rapid and the slow components of axoplasmic transport were demonstrated in the nerve head during increased intraocular pressure, and in ocular hypotony with papilledema.

Animals↗
PubMed1976

The architecture of the choriocapillaris at the posterior pole.

The afferent and efferent vessels as well as the choriocapillaris in the human posterior pole, studied in flat preparations, paraffin sections, and Epon sections, formed relatively discrete units of organization which we called lobules. A lobule is a segment of the choriocapillaris supplied centrally by a precapillary arteriole and demarcated peripherally by a ring of postcapillary venules. Observations on the choroidal phase of fundus fluorescein angiography indicated that blood entering a lobule did not intermingle with blood from adjoining lobules. The choriocapillaris in the posterior pole of the human eye, with its supplying and draining vessels, appeared as a mosaic of adjoining lobules that function independently.

Arteries↗
PubMed1976

Distribution of axonal and glial elements in the rhesus optic nerve head studied by electron microscopy.

Quantitative measurements of the composition of axonal bundles were made from electron micrographs for six levels within the intraocular portion of the optic nerve head of the rhesus moneky. The proportion of the areas occupied by axonal cytoplasm, glial cytoplasm, mitochondria, and myelin was calculated. Average axonal diameters were determined at each location. Axonal bundles acquired progressively more interaxonal glial tissue as they passed posteriorly from the region of the optic disk toward the optic nerve. Mitochondria were present within axons in increased numbers in the lamina choroidalis and lamina scleralis, and there may be focal expansions and constrictions of axons in the same regions. The overall cross-sectional area of the intraocular portion of the optic nerve expanded posterior to Bruch's membrane in part because of the addition of the interaxonal glial tissue.

Animals↗
PubMed1976

Electron microscopic study of human papilledema.

Papilledema associated with neoplastic invasion of the orbit in the optic disks of two patients was found and examined by light and electron microscopy. Pathologic changes in the optic nerve head and nerve included axonal degeneration and mild interstitial edema. Axonal swelling appeared to be the major factor in the overall increase in tissue volume of the optic nerve head. Vascular and perivascular glial alterations were nonspecific.

Adult↗
PubMed1976

Experimental papilledema produced by cyclocryotherapy.

Cyclocryotherapy was a reliable method of producing prolonged decreased intraocular pressure and papilledema in the rhesus monkey. Histologic changes in papilledema caused by decreased pressure were indistinguishable from those in papilledema from increased intracranial pressure. Electron microscopic observations in papilledema after cyclocryotherapy suggested that the principal morphologic alteration in the optic disk is axonal swelling. Additionally, many mitochondria accumulated in some swollen axons. These changes, observed at the ultrastructural level, suggest that alternations of axoplasmic transport may play a significant role in the pathogenesis of swelling of the disk.

Animals↗
PubMed1976

A light microscopic, autoradiographic study of axoplasmic transport in the normal rhesus optic nerve head.

A systematic study of axoplasmic transport in the normal optic nerve head is essential to the understanding of the role of this process in the pathogenesis of disease of the optic nerve. Twenty-one eyes from normal adult rhesus monkeys were subjected to intravitreal injections of tritiated leucine (3H) or proline (3H). Light microscopic autoradiographs were prepared on these eyes and optic nerves six hours to 60 days after injection. The isotope that was incorporated in cytoplasmic components associated with the slow phase of axoplasmic transport (3H leucine) became concentrated in the temporal region of the optic nerve head, unevenly distributed within axons in the axonal bundles, and apparently accumulated in axons or glial cells, or both, in the lamina choroidalis and scleralis as a broad pulse of isotope moved across the optic nerve head. Several anatomic factors, including the distribution of macular fibers, increasing amounts of glial cells within the same axonal bundles as the optic nerve passed from the lamina retinalis to the lamina scleralis, and the abrupt addition of myelin sheaths to axons behind the lamina scleralis, contributed to the complex distribution of isotope in the normal optic nerve head. Glial cell labeling was especially prominent with 3H proline.

Animals↗
PubMed1975

Is there a blood-brain barrier at the optic nerve head?

The retina and optic nerve have been demonstrated to possess a blood-brain barrier that prevents the passive passage of protein and certain dyes from the blood vessels into the extracellular space. Our observations suggest that an exception is present at the normal optic disc. Using horseradish peroxidase as a tracer for electron microscopy and the normal rhesus monkey as the experimental animal, we have demonstrated that in certain regions of the optic nerve head, horseradish peroxidase from the blood stream reaches the axons of the optic nerve through the border tissue of Elschnig from the adjacent choridal tissues. A barrier formed by a series of cell junctions between glial cells at the edge of the optic disc prevented spread of the tracer from the optic disc into the subretinal space.

Animals↗
PubMed1975

Congenital grouped pigmentation of the retina. Histopathologic description and report of a case.

Gross examination of an eye removed at autopsy from a 4-year-old child with congenital heart disease revealed typical grouped pigmentation of the retina. Routine light microscopy and flat preparation of the retinal pigment epithelium demonstrated the lesions to consist of focal areas of increased concentration of pigment granules in otherwise normal retinal pigment epithelial cells. The pigment granules were large and football shaped. The overlying photoreceptors showed no abnormalities, possibly explaining the clinical features of normal visual acuity and visual fields in this patient. We believe that this is the first histologic description of congenital grouped pigmentation reported in the English literature. A differential diagnosis and brief review of the pertinent literature are also presented.

Child, Preschool↗
PubMed1975

Histologic localization of sodium fluorescein in human ocular tissues.

We studied the distribution pattern of sodium fluorescein in human eyes microscopically. The ciliary body showed early and diffuse leakage, with staining of the basement membrane of the nonpigmented ciliary epithelium, indicating movement of fluorescein from the ciliary body into the aqueous humor. After five minutes the iris stroma stained with fluorescein, probably from the aqueous humor. The retinal vessels and retinal pigment epithelium were impermeable to fluorescein. Corresponding to the background fluorescence seen in fluorescein angiography, fluorescence was present in Bruch's membrane and in the stroma of the inner one third of the choroid. Drusen stained most intensely in areas of greatest PAS positively. Early fluorescence of the optic disk was the result of intravascular perfusion of the dye. Minimal diffusion of fluorescein from the fenestrated choroidal vessels across the border tissue of Elschnig into the peripheral optic nerve bundles was observed. Late fluorescene of the optic disk was due mainly to fluorescein staining of the lamina scleralis and glial columns.

Eye↗