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Biomedical subjects

D M Albert

Publications and source records attributed to D M Albert.

At least 523 records · Page 29Linked to original sources
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Epidemiologic aspects of uveal melanoma.

Although the underlying cause or causes of uveal melanoma have yet to be elucidated, important insights may be gained by examining the epidemiologic features of the disease. Uveal melanoma is an uncommon cancer with an incidence of only six cases per million population per year. It is most often diagnosed in the sixth decade and is somewhat more common in males. Apart from sporadic reports of family clusters, uveal melanoma is not considered an inherited disease. Whether some environmental exposure triggers the development of uveal melanoma remains an open question. Sunlight has been proposed as an environmental risk factor because sunlight is known to cause melanoma of the skin and both diseases are rare in nonwhite races. Unlike cutaneous melanoma, however, rates have not been increasing over time and do not vary by latitude. This paper evaluates the available evidence for sunlight and other potential risk factors for uveal melanoma, highlighting areas requiring further research.

Female↗
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Magnetic resonance imaging and spectroscopy of intraocular tumors.

Proton magnetic resonance imaging (1H MRI) has emerged as a clinically useful tool for the diagnosis of intraocular tumors. During the last four years 1H MRI characteristics, including spin-lattice relaxation times (T1) and spin-spin relaxation times (T2), have been established for several types of tumors. The introduction of surface coils to the imaging process has significantly improved the quality of intraocular MR images, leading some clinicians to suggest that 1H MR images are preferable to CT scans. Another MRI technique, in which sodium-23 (23Na) is imaged rather than protons, is now under development as tool for intraocular diagnosis. The potential of 23Na MRI depends upon the high concentration and "visibility" of sodium in the vitreous body, and upon the apparent differences in sodium behavior in normal cells vs. tumor cells. The metabolism of normal ocular tissues and intraocular tumors may be probed noninvasively with phosphorus-31 MR spectroscopy (31P MRS). Much progress has been made during the last few years in understanding the appearance of 31P MR spectra of many types of healthy and diseased cells and tissues. Clinical application of this technique to the diagnosis and monitoring of intraocular tumors following conservative treatment will be dependent upon the development of spectroscopy techniques that collect information from the volume of interest (tumor) only.

Cell Nucleus↗
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A historical review of sympathetic ophthalmia and its epidemiology.

Sympathetic ophthalmia was given its complete clinical description by William Mackenzic in 1840, and fully described in terms of its histopathology by Ernst Fuchs in 1905. A review of epidemiologic data from the 19th and 20th centuries reveals that acceptable statistical studies have yet to be carried out, but suggests that the disease has always been of extremely low incidence. Further, there does not appear to be a markedly decreased incidence in the "modern era." The etiology of the disease remains elusive, although the pathogenesis appears to be due to delayed hypersensitivity (cell-mediated immunity), possibly directed at a surface membrane antigen that is shared by photoreceptors, retinal pigment epithelium and choroidal melanocytes. The only effective therapy remains preventive enucleation of the injured eye, despite modern usage of immunosuppressive agents. Studies have suggested that early enucleation of a blind exciting eye can improve the prognosis for the sympathizing eye.

Antigens, Surface↗
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Secondary optic nerve tumors.

Secondary tumors of the optic nerve are more common than primary optic nerve tumors. The involvement of the optic nerve may arise from direct invasion from intraocular malignancies, from hematopoietic malignancy, from meningeal carcinomatosis, or from distant primary tumors. Orbital tumors rarely invade the optic nerve, and brain tumors involve it only in their late stages.

Cranial Nerve Neoplasms↗
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Origins and evolution of the Lancaster Course in ophthalmology.

The Lancaster Course was created in 1945 to meet a need for training in the basic sciences of ophthalmology. At that time the course was designed particularly for young physicians who were discharged from the Armed Services at the end of World War II. For nearly five decades, the course has been given each summer at Colby College in Waterville, Maine, with the participation of some of the most illustrious figures in ophthalmology. It has undergone numerous changes in faculty and student body, having become less directed toward the experienced physician and more toward the beginning resident. What has not changed in the informal environment combined with intensive study, which allows students to learn basic sciences and to interact with outstanding leaders in ophthalmology.

Education, Medical, Continuing↗
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Histopathology of the ears, eyes, and brain in Norrie's disease (oculoacousticocerebral degeneration).

Norrie's disease is an x-linked recessive disorder characterized by progressive oculoacousticocerebral degeneration. The light and electron microscopic changes in the temporal bones, eyes, and brain of an affected 77-year-old man who suffered from bilateral profound sensorineural hearing loss, blindness, and mental retardation are described. The inner ears showed marked atrophy of the stria vascularis, severe degeneration of hair cells and cochlear neurons, and connective tissue proliferation in the spiral ganglion, osseous spiral lamina, and walls of the membranous vestibular labyrinth. The eyes showed detached retinae, dense proliferation of fibrillary glial cells in the retina and vitreous, severe atrophy of the optic nerves, and degenerative hyalinization of blood vessels. This case is the first published report of the histopathology of the inner ear in Norrie's disease.

Aged↗
PubMedDate not supplied

Treatment of metastatic uveal melanoma: review and recommendations.

This article reviews the published clinical responses of metastatic uveal melanoma and metastatic cutaneous melanoma with visceral involvement to current therapeutic protocols. Despite isolated patient responses to systemic treatment, no effective treatment currently exists for metastatic uveal melanoma. However, several new approaches involving interferons and interleukin and combination chemotherapy have shown some activity against metastatic cutaneous melanoma. The effectiveness against metastatic uveal melanomas has not been determined. A new approach to intrahepatic administration of chemotherapy also warrants further evaluation because of the high incidence of hepatic involvement with metastatic uveal melanoma. When an effective systemic treatment is found, early administration as an adjuvant to primary treatment may provide the best strategy for control of systemic spread.

Antineoplastic Combined Chemotherapy Protocols↗
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Trilateral retinoblastoma: insights into histogenesis and management.

Trilateral retinoblastoma (TRb) is a syndrome involving midline intracranial malignancies in children with the heritable form of retinoblastoma. All cases of TRb reported from 1971 to 1997 were reviewed. The histopathologic findings, clinical features, treatment modalities, and survival rates from 80 cases were evaluated. Histopathologic findings from intracranial malignancies demonstrated primitive neuroectodermal tumors in 61.5% of cases. Various degrees of neuronal or photoreceptor differentiation were seen in the other 38.5% of cases. Autopsy, histopathologic, and radiologic examinations did not show a more definitive site of origin of these intracranial tumors, although "pinealoblastoma" was often the diagnosis reported. These findings, together with analysis of the histopathologic similarities among human primitive neuroectodermal tumors, pinealoblastoma, retinoblastoma, and ependymoblastoma, suggest that TRb more likely arises from a germinal layer of predisposed primitive subependymal neuroblasts that are not necessarily destined for pineal or photoreceptor differentiation. Trilateral tumors have also been found in transgenic mice expressing the simian virus 40 T-antigen. Transgenic murine intracranial tumors are primitive neuroectodermal tumors arising from the subependymal layer. Transgenic mice with the murine interphotoreceptor cell binding protein promoter and simian virus 40 T-antigen also develop pineal tumors. Trilateral retinoblastoma is usually fatal, with an average survival time of 11.2 months. Therapies include radiation, systemic chemotherapy, intrathecal chemotherapy, and surgical resection/craniotomy in combination with radiation and/or chemotherapy. Survival may be prolonged with combination chemotherapy (24.6 months) and if neuroradiologic screening identifies TRb before symptoms are present (23.5 months). Recent success with platinum-based chemoreduction of intraocular retinoblastoma may indicate a similar role for platinum-based chemotherapy in the treatment of TRb. Routine central nervous system imaging should be considered in the management of TRb.

Animals↗
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Retinoblastoma in transgenic mice: models of hereditary retinoblastoma.

Retinoblastoma, the most common intraocular malignancy ill childhood, has served as a paradigm for the study of genetic mechanisms of oncogenesis. The retinoblastoma susceptibility gene RB1 was the first tumor suppressor gene to be cloned, and genetic and molecular biologic studies of this tumor have greatly expanded the understanding of the mechanics of tumorigenesis. Human retinoblastoma has essentially no naturally occuring animal counterpart. The development of transgenic murine models of retinoblastoma have created an experimental tool for manipulation of a tumor gene system in vivo. These models have also enabled studies of new therapeutic modalities. This review outlines the development of the transgenic murine models of retinoblastoma, together with the genetic mechanisms of retinoblastoma origin. Current therapeutic innovations developed by means of the transgenic models are described.

Animals↗
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A human DNA segment with properties of the gene that predisposes to retinoblastoma and osteosarcoma.

The genomes of various tumour cells contain mutant oncogenes that act dominantly, in that their effects can be observed when they are introduced into non-malignant cells. There is evidence for another class of oncogenes, in which tumour-predisposing mutations are recessive to wild-type alleles. Retinoblastoma is a prototype biological model for the study of such recessive oncogenes. This malignant tumour, which arises in the eyes of children, can be explained as the result of two distinct genetic changes, each causing loss of function of one of the two homologous copies at a single genetic locus, Rb, assigned to the q14 band of human chromosome 13. Mutations affecting this locus may be inherited from a parent, may arise during gametogenesis or may occur somatically. Those who inherit a mutant allele at this locus have a high incidence of non-ocular, second tumours, almost half of which are osteosarcomas believed to be caused by the same mutation. Here we describe the isolation of a complementary DNA segment that detects a chromosomal segment having the properties of the gene at this locus. The gene is expressed in many tumour types, but no RNA transcript has been found in retinoblastomas and osteosarcomas. The cDNA fragment detects a locus spanning at least 70 kilobases (kb) in human chromosome band 13q14, all or part of which is frequently deleted in retinoblastomas and osteosarcomas.

Chromosome Deletion↗
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Retinoblastoma and angiogenesis activity.

Aqueous humor from 30 enucleated retinoblastoma-bearing eyes and 9 cell cultures of retinoblastoma were tested for angiogenesis activity using capillary endothelial cell migration assays. Aqueous from 90% of retinoblastoma eyes stimulated endothelial cell migration, compared with 25% of control eyes. Five of nine retinoblastoma cultures stimulated endothelial cell migration and five showed chorioallantoic membrane (CAM) neovascularization when compared with positive controls for angiogenesis activity. These results suggest an inverse relation between the length of time in culture and the ability of these cells to stimulate angiogenesis using these assays. Cells in culture for short periods of time gave positive test results, whereas continuous cell lines of retinoblastoma were consistently negative. While aqueous humor from retinoblastoma-bearing eyes demonstrated significant angiogenesis activity, cultured retinoblastoma cells show this only in early passages. Several possible explanations for this are considered.

Aqueous Humor↗
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Perfluoroether liquid as a long-term vitreous substitute. An experimental study.

A commercial perfluoroether liquid, Fomblin-H Fluorinated Fluid, which is transparent and viscous, was investigated as a possible long-term vitreous substitute. The material belongs to a family of perfluorocarbon derivatives that are generally inert and nontoxic. A space for the vitreous substitute was created in rabbit eyes by a vitreous compression technique using perfluoropropane gas. Fomblin caused gliosis of the retina at 1 month after intravitreous injection. Preretinal membrane formation and retinal disorganization and detachment occurred in two of four eyes enucleated at 3 months, and in all five eyes enucleated at 4 or 6 months. Vacuoles presumably filled with Fomblin were localized histopathologically within the retina. In control eyes injected with medical-grade silicone oil, abnormalities were limited to moderate edema of the nerve fiber and ganglion cell layer. Fomblin was not as well-tolerated by the rabbit retina as was medical-grade silicone oil. Fomblin is not a suitable vitreous substitute.

Animals↗
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Proton beam irradiation for treatment of experimental human retinoblastoma.

Proton beam irradiation was used to treat human retinoblastoma (Y-79 cell line) grown subcutaneously in the athymic "nude" mouse. Thirty-four tumors were included in the experimental groups, of which twenty-three were irradiated and eleven served as controls. Tumors were irradiated with protons produced at the 160 megavolts Harvard cyclotron. The dose delivered to the tumor ranged from 7.5 to 27.5 proton gray in a single treatment, and 25.0 proton gray delivered in two fractions separated by 24 hours. Reduction of tumor growth was significantly greater than controls (p less than 0.001) with treatment doses greater than or equal to 17.5 proton gray. Histologic examination revealed a marked decrease of mitotic activity in all specimens examined 48 hours after treatment at these higher doses. Total regression without evidence of remaining malignant cells was noted in three tumors treated at 17.5 proton gray or above. Our results indicate that human retinoblastoma in a murine host, with a tumor mass similar to that seen in a clinical setting, is sensitive to radiation by high energy protons.

Animals↗
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Development of the outer plexiform layer in albino rats.

The development of the outer plexiform layer (OPL) at the posterior pole was studied in albino rats, ages 1 to 18 days. Light microscopic observations were consistent with previous reports that within the first postnatal week neuroepithelial cells migrate into outer and inner nuclear layers with formation of the intervening OPL. The relation of neural and glial cells was consistent with the suggestion of others that guidance by glial cells influences the radial organization of the developing neural retina. The new observations presented in this paper raise the possibility that the horizontal orientation of neural processes in the outer plexiform layer depends upon guidance of glial cells.

Animals↗
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Astrocytic hamartoma in tuberous sclerosis mimicking necrotizing retinochoroiditis.

A pale, elevated peripapillary lesion discovered in a young child with no family history of phakomatoses, grew larger, caused vitreous hemorrhage and underwent necrosis. Secondary inflammation developed in the eye, finally producing rubeosis irides with elevated intraocular pressure and a blind, painful eye which required enucleation. Clinically, the lesion was variably diagnosed and treated as toxoplasmosis and toxocara canis. These diagnoses were made despite low titres, a negative ELISA test and a normal eosinophil count. On histopathologic examination, a diagnosis of toxocara canis was entertained, although no remnants of the organism could be found in serial sections. Years later, when a family history of tuberous sclerosis became apparent, a diagnosis of astrocytic hamartoma of the retina with secondary hemorrhage and inflammation was made on the basis of re-examination of the pathologic specimen and special stains.

Adult↗
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Prolonged survival of a child with metastatic retinoblastoma.

A boy was discovered to have retinoblastoma in his right eye at age 29 months. The eye was enucleated and showed invasion of the choroid and optic nerve on examination. Bone marrow aspiration was negative in January 1981. Orbital recurrence was noted 1 month later and bone marrow aspiration was positive 2 months later. MAD-DOC chemotherapy and radiation therapy to the right orbit and brain were initiated immediately. The tumor has remained in remission since completion of the chemotherapy 18 months later. A preleukemic syndrome occurred in July 1984, and a successful bone marrow transplantation was performed in November 1984. He resumed normal growth and has remained well. Metastatic retinoblastoma should no longer be thought of as invariably fatal.

Child, Preschool↗
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Epithelial downgrowth--fistula repair and keratoplasty.

Eight patients with leaking fistulas from epithelial downgrowth were repaired by various techniques. Wide excision of the fistula and replacement with a graft, followed by a conjunctival flap, proved to be the most satisfactory technique for dealing with the fistula. However, this subset of patients responded to fistula closure with a much worse secondary glaucoma than downgrowth patients in general. Fifteen patients with proven epithelial down-growth received penetrating keratoplasty. Eleven of these grafts failed within a year, but there was no regrowth of epithelium on the back of the graft in at least two patients. In spite of generally discouraging results, we recommend immediate closure of epithelialized fistula to avoid even more severe complications in the future. We also recommend keratoplasty, repeated if necessary, in severe corneal edema. Both situations may eventually require radical glaucoma surgery and/or keratoprosthesis.

Adult↗