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Biomedical subjects

P F Lopez

Publications and source records attributed to P F Lopez.

51 records · Page 3Linked to original sources
PubMed1992

Phenotypic similarities between Stargardt's flavimaculatus and pattern dystrophies.

Some heredomacular diseases share ophthalmoscopic and morphologic similarities despite being nosologically distinct. In part, this may arise from pathologic reaction patterns such as lipopigment accumulation and drusen deposition which are common to a variety of disorders of the photoreceptor--retinal pigment epithelium--Bruch's membrane complex. Two of these disorders, Stargardt's flavimaculatus and the pattern dystrophies of the retinal pigment epithelium may be especially difficult to differentiate clinically since they are characterised by both a similar ophthalmoscopic appearance and considerable inter and intrafamilial variation in their expression. Stargardt's flavimaculatus may, however, be distinguished from the retinal pigment epithelial pattern dystrophies by certain clinical and morphological features that are outlined below.

Diagnosis, Differential↗
PubMed1992

Peripapillary subretinal neovascularization. A review.

Peripapillary choroidal neovascularization is an important feature in the pathogenesis and treatment of a number of disorders affecting the optic nervehead and adjacent chorioretinal areas. Although less well understood than its macular counterpart, peripapillary subretinal neovascularization possesses characteristic clinical and histopathologic features that directly affect its prognosis and management. This review provides a summary of the diseases in which peripapillary subretinal neovascularization occurs and an overview of studies on the natural history, clinicopathologic findings, and therapy. In addition, a pathogenetic model of peripapillary subretinal neovascularization is discussed based on these findings.

Choroid Neoplasms↗
PubMed1991

Bone marrow transplant retinopathy.

Five of eight patients (62%) who survived at least six months after autologous or allogeneic bone marrow transplantation for acute leukemia developed occlusive microvascular retinopathy. Treatable retinal microangiopathy included a high incidence (80%) of clinically significant macular edema and one case of proliferative retinopathy with subhyaloid hemorrhage. The bone marrow transplant protocol required high-dose cytarabine hydrochloride and 1,200 cGy of total body irradiation. The development of radiation retinopathy after such low doses of teletherapy suggests that high-dose chemotherapy may increase the susceptibility for the development of retinopathy at otherwise safe radiation doses.

Adolescent↗
PubMed1991

Pathologic features of surgically excised subretinal neovascular membranes in age-related macular degeneration.

The histopathologic features of ten consecutive surgically excised subfoveal neovascular membranes from patients with age-related macular degeneration were examined. Ultrastructural features included the following in decreasing order of frequency: endothelium-lined vascular channels, new collagen, fibrocytes, retinal pigment epithelium, erythrocytes, and myofibroblasts. Chronic inflammatory cells were frequently evident and included macrophages, lymphocytes, and plasma cells. Basal laminar deposit or diffuse drusen were observed in six of the membranes. Photoreceptors and Bruch's membrane were each observed in three of the specimens, but were not associated with decreased postoperative visual acuity. Fibrin was observed in eight membranes, either within the stroma of the membrane or in association with subretinal hemorrhage.

Age Factors↗
PubMed1990

Autosomal-dominant fundus flavimaculatus. Clinicopathologic correlation.

The authors report the first clinicopathologic study of autosomal-dominant fundus flavimaculatus with late-onset atrophic macular degeneration in a 62-year-old man. Results of histopathologic examination disclosed the retinal pigment epithelium (RPE) to be distended by a periodic acid-Schiff (PAS)-positive, acid mucopolysaccharide-negative material. Transmission electron microscopy showed marked accumulation of lipofuscin and melanolipofuscin granules within the RPE. The different modes of genetic transmission and ultrastructural heterogeneity suggest that fundus flavimaculatus is a clinical syndrome representing several genetically and mechanistically distinct disorders whose common end-stage is a topographically similar accumulation of lipofuscin.

Fluorescein Angiography↗
PubMed1988

Topographic analysis and visual acuity after radial keratotomy.

Using a computerized corneal topographic mapping system that allows detailed examination of the corneal curvature in the vicinity of the visual axis, we identified separate regions of differing corneal curvature in three of 11 eyes after radial keratotomy. In these eyes, the excellent uncorrected visual acuity appeared to be inconsistent with the postoperative spherical equivalent as determined by refraction and corneal curvature by standard keratometer measurements. The distinct regions of corneal curvature appeared to serve as alternative effective optical zones, thus allowing the patients to have excellent visual acuity. In essence, the cornea became a multifocal lens. Although degradation in the contrast of the image as well as monocular diplopia are possible, our patients had no significant complaints.

Cornea↗
PubMed1987

Linear nevus sebaceous syndrome. A review.

We report a case of linear nevus sebaceous syndrome with large areas of calcification involving multiple layers of the posterior aspects of both eyes. This patient had a normal neurological examination despite dysplastic brain changes. We discuss and review the multiple clinical presentation and embryopathogenesis of this disorder.

Calcinosis↗
PubMed1986

Dependence of initiation of an innocent bystander cytotoxicity reaction on the association of viral antigens and tumor cell membranes in mice.

In chemically induced mouse mammary tumors in BALB/c mice, no murine mammary tumor virus (MuMTV) antigens could be detected in the tumor cell membranes. In contrast, in mammary tumors of spontaneous appearance in BALB/cfC3H mice neonatally infected with MuMTV, viral antigens could be detected by immunofluorescence. Specific activation of immune spleen lymphocytes in vitro by homologous tumor cell membrane preparations resulted in an innocent bystander cytotoxicity reaction in BALB/c mice bearing either the chemical- or virus-induced mammary tumors. Non-tumor bearers did not respond in this reaction. The cytotoxicity effector cell was a nylon-adherent Thy 1.2+, Lyt 1+, Lyt 2+ lymphocyte. Induction of the reaction in the chemically induced mammary tumor bearers was related to tumor-associated antigens, but in the mice with MuMTV-induced tumors, it was possible that all responses were solely due to viral antigens. Biochemical analyses using immunoprecipitation techniques indicated that the major external glycoprotein of MuMTV (gp52) was present in the tumor cell membrane preparations. Preincubation of the cell membranes of virus-induced tumors with anti-MuMTV completely blocked the capacity of this preparation to induce the cytotoxicity. Preabsorption of the anti-MuMTV with purified MuMTV removed all the blocking activity of these sera, indicating that the antigenic determinants recognized were of viral origin. However, purified MuMTV failed by itself to elicit the innocent bystander cytotoxicity. This observation indicates that an association with membranes was necessary for the viral antigens to initiate and/or effect this cell-mediated immune reaction.

Animals↗
PubMed1986

Leber's optic neuropathy. New observations.

Leber's disease is a hereditary optic neuropathy characterized by a triad of ocular fundus changes, including circumpapillary telangiectatic microangiopathy, pseudoedema of the nerve fiber layer around the disc, and absence of peripapillary staining on fluorescein angiography. We report two families in which the first afflicted member had insufficient fundus changes to enable a diagnosis of Leber's disease. However, the presence of telangiectatic microangiopathy in either a symptomatic or asymptomatic family member established the diagnosis of Leber's optic nerve disease under these circumstances. These observations suggest that circumpapillary telangiectatic microangiopathy is a genetic marker and may not always be a pathogenetic predeterminant of Leber's optic neuropathy. In view of our findings, we propose the term "typical Leber's disease" for patients demonstrating the characteristic fundus triad and the term "atypical Leber's disease" for patients who lack diagnostic fundus changes but who have a family member with classic telangiectatic microangiopathy.

Adult↗
PubMed1984

Antigenic determinants in a virus-induced mouse mammary tumor recognized by cell-mediated immune assays.

Purified tumor cell membrane (PTCM) fractions from spontaneous BALB/cfC3H mammary adenocarcinomas elicit blastogenic responses in spleen cells of tumor-bearing mice. Previous studies have demonstrated that splenic T-cells are the major responding cell population but have not clarified whether the antigens responsible for the reactions are exclusively viral in origin or may involve nonviral tumor-associated antigens (TAA). Pretreatment of PTCM preparations with polyvalent anti-murine mammary tumor virus (MuMTV) completely obliterated the ability of PTCM to stimulate an innocent bystander cytotoxicity reaction; however, it reduced the blastogenic response by only 60%, suggesting that the two assays may measure different antigenic reactivities. The specificity of the anti-MuMTV blocking for viral antigens was demonstrated by the complete absorption of the serum-blocking reaction with purified MuMTV particles in the cytotoxicity assay; however, absorption was only partial in the blastogenesis assay. Incubation with purified Rauscher murine leukemia virus particles failed to absorb the neutralizing effect of the sera. These data suggest that putative TAA can be detected in the blastogenesis assay but not in the cytotoxicity reaction. Ammonium sulfate-precipitated immunoglobulin fractions of sera from tumor-bearing BALB/cfC3H mice (TBMS) completely blocked the stimulatory potential of PTCM in both the blastogenesis and the cytotoxicity assays. In the reciprocal experiment to that described above, preabsorption of TBMS immunoglobulins with purified MuMTV completely removed the inhibition of the cytotoxicity but again only partially restored the blastogenic response. The reaction could be completely restored by preabsorption of TBMS with PTCM. These results support the contention of nonvirion antigen involvement in the blastogenesis reaction. In conclusion, these two assay systems detect different antigenic determinants on the MuMTV-expressing tumor cell membranes. Both viral and other antigens appear to be relevant in this model system, and serum factors present in the immunoglobulin fractions of tumor-bearing mice can inhibit T-cell responses directed at either kind of antigenic moieties.

Adenocarcinoma↗
PubMedDate not supplied

Choroidal hypoperfusion after surgical excision of subfoveal neovascular membranes in age-related macular degeneration.

PURPOSE: To study the choroidal circulation after surgical excision of subfoveal choroidal neovascular membranes (SFCNVM) in age-related macular degeneration (ARMD). METHODS: Twelve eyes of eleven patients with ARMD that underwent surgical excision of SFCNVMs were evaluated with stereoscopic color fundus photography, stereoscopic fluorescein angiography (FA) and scanning laser ophthalmoscope-indocyanine green videoangiography (SLO-ICGv). The patients were followed for a mean of 7.9 months (range 2 to 14 months). RESULTS: Preoperatively, all eyes had angiographic evidence of a SFCNVM, with SLO-ICGv showing the presence of a choriocapillary blush. Postoperatively, stereoscopic color fundus photographs documented that the bed of the surgical excision was characterized by an absence of visible retinal pigment epithelial (RPE) pigmentation in all eyes. Stereoscopic FA of the excision bed revealed choriocapillary hypofluorescence with visible dye perfusion in the underlying medium and large choroidal vessels in all eyes. SLO-ICGv of the excision bed disclosed the presence of perfused medium and large choroidal vessels, but a marked choroidal hypofluorescence with loss of the choriocapillary and small choroidal vascular filling within the excision bed in eleven of the twelve eyes. CONCLUSION: Our results indicate that both choriocapillary and small choroidal vascular filling is frequently abnormal or absent in the bed of surgically excised subfoveal neovascular membranes in ARMD. This finding, which may represent either pathologic or iatrogenic choriocapillary and small choroidal vascular atrophy or occlusion with preservation of perfusion in the underlying medium and large choroidal vessels, may influence structural and visual recovery after submacular surgery for ARMD, despite RPE transplantation or regeneration.

Aged↗
PubMedDate not supplied

Spinal cord involvement in encephalocraniocutaneous lipomatosis.

Encephalocraniocutaneous lipomatosis is a rare hamartomatosis involving the craniofacial region and the central nervous system. The most prominent clinical features are large areas of scalp alopecia, soft subcutaneous craniofacial masses, lipomas, connective tissue nevi of the eyelids and surrounding areas, pterygium-like choriostoma of the ocular conjunctiva, mental retardation, motor deficit, and seizures. Of the eight patients reported previously, three had spinal cord evaluations and two had evidence of lipomatosis. We report the third patient with this association, review the literature of encephalocraniocutaneous lipomatosis, and stress the importance of spinal cord evaluation during the newborn period.

Adolescent↗
PubMedDate not supplied

Subregions of differing refractive power within the clear zone after experimental radial keratotomy.

After radial keratotomy (RK), some patients experience a mild decrease in best corrected visual acuity, visual distortion, or monocular diplopia. These optical effects of radial keratotomy are best explained by subregions of different refractive powers within the surgery-free clear zone. To investigate the topography of the clear zone, we performed four- and eight-incision radial keratotomy in eight cadaver eyes. After radial keratotomy, we found subregions within the clear zone of two types: 1) small, very flat regions at the ends of the radial incisions (seven of eight eyes), and 2) a series of concentric rings centered on the visual axis with a continuously progressive decline in refractive power toward the periphery of the clear zone (all eyes). The clear zone after radial keratotomy is often nipple-shaped, with a more myopic segment centrally and a more hyperopic region near the periphery of the clear zone.

Cornea↗
PubMedDate not supplied

Tissue plasminogen activator in the surgical excision of subfoveal choroidal neovascular membranes.

We investigated the use of tissue plasminogen activator (t-PA) as an adjunct to the surgical removal of subfoveal choroidal neovascular membranes. t-PA in a concentration of 6 micrograms/0.1 cc dissolved the fibrin rim surrounding recent subfoveal membranes but was less effective on more mature lesions. t-PA may be a useful intraoperative tool to limit the damage to surrounding structures during the surgical excision of recent subfoveal choroidal neovascular membranes with surrounding fibrin rims.

Adult↗