Biomedical subjects
Publications and source records attributed to A G Lee.
Patients often present to primary care physicians with acute or chronic red eyes. Benign conditions may be evaluated and treated by primary care practitioners. Red eyes due to serious conditions may be vision threatening and require early detection and referral.
BACKGROUND: There has been little previous study reporting the eye findings and presentation of elderly patients with myasthenia gravis. The purpose of this study was to review the findings and course of myasthenia gravis after the sixth decade of life. METHODS: Retrospective observational case series. The authors reviewed the clinical records of 27 patients with onset of myasthenia gravis at age 60 years or more who were seen at a tertiary care academic ophthalmology centre in Houston between January 1992 and March 1999. The diagnosis of myasthenia gravis was based on conventional clinical and laboratory criteria. RESULTS: Twenty patients (74%) were men. Of the 16 patients who underwent testing for anti-acetylcholine receptor antibodies, 11 (69%) were seropositive. Concurrent thyroid disease was found in seven patients (26%), including five (71%) of the seven women. No patient had thymoma. Sixteen patients (59%) manifested generalized symptoms during follow-up; 12 did so within 1 year of disease onset. Patients responded well to both anticholinesterase and corticosteroid therapy. At the most recent follow-up visit 18 patients (67%) were clinically improved, and no patient was clinically worse. INTERPRETATION: Myasthenia gravis in this study was characterized by a male predominance, high rate of concurrent thyroid disease, high rate of progression to mild generalized symptoms, absence of thymoma, good response to medical therapy and minimal life-threatening complications. Clinicians should consider the diagnosis of myasthenia gravis in an older patient presenting with diplopia or ptosis.
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OBJECTIVE: The authors describe nine new cases of acute multifocal placoid pigment epitheliopathy (AMPPE) with associated central nervous system (CNS) involvement and permanent visual sequelae. The study includes a review of the literature and discussion of evaluation, management, and treatment options. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Nine patients were identified with AMPPE and CNS involvement in addition to 22 patients reviewed in the literature. MAIN OUTCOME MEASURES: A review of nine patients with AMPPE and CNS involvement was performed. Charts were reviewed for age, gender, preceding viral prodromes, visual acuity, ophthalmologic examination findings, CNS findings, and treatment. RESULTS: Thirty-one patients (nine new patients) were diagnosed with AMPPE and various degrees of CNS involvement. Ages ranged from 8 to 54 years, with an average of 27 years. Twenty-one males (68%) and 10 females (32%) were identified. Eleven patients (35%) had antecedent viral illnesses. Visual acuity was variable and ranged from 20/20 to count fingers. The spectrum of CNS findings ranged from headaches to sagittal sinus thrombosis. CONCLUSIONS: Acute multifocal placoid pigment epitheliopathy can be associated with CNS abnormalities and permanent visual deficits. Neuroimaging, lumbar puncture, and cerebral angiography analysis provide useful diagnostic tools when CNS involvement is suspected. Intravenous corticosteroids and collaboration with neurovascular colleagues should be considered in these situations. In cases complicated by CNS arteritis, immunosuppressive agents can be a beneficial adjunct to corticosteroids.
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OBJECTIVE: To report two cases of cerebral venous sinus thrombosis with papilledema and visual loss that improved after endovascular stent placement. MATERIALS AND METHODS: Retrospective case series from a tertiary ophthalmic center. RESULTS: Two cases of venous sinus occlusion treated with angioplasty and stenting are described. Both cases experienced improvement in optic disc edema and visual function following the procedures. CONCLUSION: Endovascular stent placement may relieve increased intracranial pressure and papilledema caused by cerebral sinus thrombosis and may prevent further visual loss.
INTRODUCTION: Idiopathic facial nerve palsy is a common neurologic condition but episodes of ophthalmoplegia in these patients are uncommon. MATERIALS AND METHODS: Retrospective case series. RESULTS: Three patients with facial nerve palsy with unusual features, including ophthalmoplegia, are described. CONCLUSION: Recurrent episodes, familial tendency, and associated ophthalmoplegia are uncommon in patients with idiopathic facial nerve palsy.
OBJECTIVE: To correlate the clinicopathologic and radiographic features characteristic of orbital solitary fibrous tumor (SFT). METHODS: The diagnostic features and clinical outcome of seven adults with orbital SFT are retrospectively outlined. Orbital imaging was performed by ultrasonography, computed tomography, or magnetic resonance imaging. Some cases were imaged by multiple modalities. Histopathologic examination of each tumor specimen included standard light and immunohistochemical stains. RESULTS: Heterogeneous internal composition was better appreciated on magnetic resonance imaging than on computed tomography. All cases undergoing magnetic resonance imaging showed T1 isointensity and T2 hypointensity relative to gray matter. Strong, generalized immunohistochemical reactivity to vimentin and CD34 validated the diagnosis of SFT and differentiated the specimens from other spindle cell neoplasms. After complete tumor resection, our patients remain tumor free with postoperative intervals of 15 to 45 months. CONCLUSIONS: Solitary fibrous tumor has now been reported in 26 orbits. No physical finding is pathognomonic, but several imaging traits are highly characteristic. Intralesional image heterogeneity and a predominantly low T2 signal intensity are distinctive of SFT. Complete tumor resection and immunohistologic specimen evaluation are emphasized. Clinicians should consider the diagnosis of SFT when confronted with an adult patient having an orbital soft tissue mass demonstrating the distinctive magnetic resonance imaging findings.
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OBJECTIVE: To report visual loss resulting from chiasmal involvement by primary central nervous system lymphoma (PCNSL). MATERIALS AND METHODS: Case report. RESULTS: A patient with the acquired immune deficiency syndrome (AIDS) presented with visual loss resulting from PCNSL involving the optic chiasm. The clinical findings, neuroimaging, pathology, and treatment of this patient are described. CONCLUSIONS: Although rare, clinicians should consider PCNSL in the differential of a hypothalamic/chiasmal mass, especially in a patient with AIDS.
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All biological membranes contain lipids that prefer to adopt a non-bilayer phase. Recent results suggest that, in the thylakoid membrane, membrane proteins force all the lipids to adopt a bilayer structure, and that the non-bilayer-forming lipids in the thylakoid membrane serve to drive the formation of membrane stacks.
We have studied the effects of aromatic residues at the ends of peptides of the type Ac-KKGL(n)()WL(m)()KKA-amide on their interactions with lipid bilayers as a function of lipid fatty acyl chain length, physical phase, and charge. Peptide Ac-KKGFL(6)WL(8)FKKA-amide (F(2)L(14)) incorporated into bilayers of phosphatidylcholines containing monounsaturated fatty acyl chains of lengths C14-C24 at a peptide:lipid molar ratio of 1:100 in contrast to Ac-KKGL(7)WL(9)KKA-amide (L(16)) which did not incorporate at all into dierucoylphosphatidylcholine [di(C24:1)PC]; Ac-KKGYL(6)WL(8)YKKA-amide (Y(2)L(14)) incorporated partly into di(C24:1)PC. Lipid-binding constants relative to that for dioleoylphosphatidylcholine (C18:1)PC were obtained using a fluorescence quenching method. For Y(2)L(14) and F(2)L(14), relative lipid-binding constants increased with increasing fatty acyl chain length from C14 to C24; strongest binding did not occur at the point where the hydrophobic length of the peptide equalled the hydrophobic thickness of the bilayer. For Ac-KKGYL(9)WL(11)YKKA-amide (Y(2)L(20)), increasing chain length from C18 to C24 had little effect on relative binding constants. Anionic phospholipids bound more strongly than zwitterionic phospholipids to Y(2)L(14) and Y(2)L(20) but effects of charge were relatively small. In two phase (gel and liquid crystalline) mixtures, all the peptides partitioned more strongly into liquid crystalline than gel phase; effects were independent of the structure of the peptide or of the lipid (dipalmitoylphosphatidylcholine or bovine brain sphingomyelin). Addition of cholesterol had little effect on incorporation of the peptides into lipid bilayers. It is concluded that the presence of aromatic residues at the ends of transmembrane alpha-helices effectively buffers them against changes in bilayer thickness caused either by an increase in the chain length of the phospholipid or by the presence of cholesterol.
The conventional model for transport of Ca(2+) by the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum (SR) involves a pair of binding sites for Ca(2+) that change upon phosphorylation of the ATPase from being high affinity and exposed to the cytoplasm to being low affinity and exposed to the lumen. However, a number of recent experiments suggest that in fact transport involves two separate pairs of binding sites for Ca(2+), one pair exposed to the cytoplasmic side and the other pair exposed to the lumenal side. Here we show that the carbodiimide 1-ethyl-3-[3-(dimethylamino)-propyl] carbodiimide (EDC) is membrane-impermeable, and we use EDC to distinguish between cytoplasmic and lumenal sites of reaction. Modification of the Ca(2+)-ATPase in sealed SR vesicles with EDC leads to loss of ATPase activity without modification of the pair of high affinity Ca(2+)-binding sites. Modification of the purified ATPase in unsealed membrane fragments was faster than modification in SR vesicles, suggesting the presence of more quickly reacting lumenal sites. This was confirmed in experiments measuring EDC modification of the ATPase reconstituted randomly into sealed lipid vesicles. Modification of sites on the lumenal face of the ATPase led to loss of the Ca(2+)-induced increase in phosphorylation by P(i). It is concluded that carboxyl groups on the lumenal side of the ATPase are involved in Ca(2+) binding to the lumenal side of the ATPase and that modification of these sites leads to loss of ATPase activity. The presence of MgATP or MgADP leads to faster inhibition of the ATPase by EDC in unsealed membrane fragments than in sealed vesicles, suggesting that binding of MgATP or MgADP to the ATPase leads to a conformational change on the lumenal side of the membrane.
59-year-old man with a history of mycosis fungoides developed loss of visual acuity and visual field in the left eye. Epiretinal lesions were present in the right eye and multifocal choroidal lesions, optic disc edema, and vitritis were present in the left eye. A diagnostic vitrectomy was performed and cytologic examination of the vitreous confirmed the diagnosis of T-cell lymphoproliferative disorder. Systemic and intrathecal chemotherapy resulted in marked improvement in ocular signs and symptoms. At last follow-up, the patient was found to have improved visual acuity in the left eye; however, significant worsening of his systemic condition developed and he died shortly thereafter.