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Biomedical subjects

J W Simon

Publications and source records attributed to J W Simon.

At least 19 recordsLinked to original sources
PubMed2002

Bilateral lateral rectus resection for residual esotropia.

PURPOSE: Residual or recurrent esotropia is a common problem following bilateral medial rectus recessions for esotropia, and various surgical techniques have been advocated. We have favored bilateral lateral rectus resections. METHODS: We reviewed our results in 25 patients, aged 7 to 89 months (mean 27 months), with a follow-up of 7 to 95 months (mean 39 months) following the second surgery. Survival analysis was used, with success (survival) defined as alignment within 10 PD at last follow-up. RESULTS: Median survival was 84 months with an estimated mean survival of 55 months. There are 15 of 25 patients (60%) currently successful. There were 8 undercorrections and 2 overcorrections. Three patients, included among those not successful, required a third procedure. Survival was similar to previous reports of primary esotropia and consecutive exotropia. CONCLUSIONS: Our results suggest that bilateral lateral rectus resection is a reasonable surgical option in the treatment of residual esotropia following recessions of both medial recti.

Child↗
PubMed2001

Commonly missed diagnoses in the childhood eye examination.

Early and accurate detection of eye disorders in children can present a challenge for family physicians. Visual acuity screening, preferably performed before four years of age, is essential for diagnosing amblyopia. Cover testing may disclose small-angle or intermittent strabismus. Leukocoria, which is detected with an ophthalmoscope, may indicate retinoblastoma or cataract. Children with glaucoma may have light sensitivity and enlargement of the cornea, and conjunctivitis that does not respond quickly to treatment may reflect more serious ocular inflammation. Children with serious eye injuries often present to the primary care physician. Nystagmus and many systemic conditions are associated with specific eye findings.

Amblyopia↗
PubMed2001

Analysis of the structure, substrate specificity, and mechanism of squash glycerol-3-phosphate (1)-acyltransferase.

BACKGROUND: Glycerol-3-phosphate (1)-acyltransferase(G3PAT) catalyzes the incorporation of an acyl group from either acyl-acyl carrier proteins (acylACPs) or acyl-CoAs into the sn-1 position of glycerol 3-phosphate to yield 1-acylglycerol-3-phosphate. G3PATs can either be selective, preferentially using the unsaturated fatty acid, oleate (C18:1), as the acyl donor, or nonselective, using either oleate or the saturated fatty acid, palmitate (C16:0), at comparable rates. The differential substrate specificity for saturated versus unsaturated fatty acids seen within this enzyme family has been implicated in the sensitivity of plants to chilling temperatures. RESULTS: The three-dimensional structure of recombinant G3PAT from squash chloroplast has been determined to 1.9 A resolution by X-ray crystallography using the technique of multiple isomorphous replacement and provides the first representative structure of an enzyme of this class. CONCLUSIONS: The tertiary structure of G3PAT comprises two domains, the larger of which, domain II, features an extensive cleft lined by hydrophobic residues and contains at one end a cluster of positively charged residues flanked by a H(X)(4)D motif, which is conserved amongst many glycerolipid acyltransferases. We predict that these hydrophobic and positively charged residues represent the binding sites for the fatty acyl substrate and the phosphate moiety of the glycerol 3-phosphate, respectively, and that the H(X)(4)D motif is a critical component of the enzyme's catalytic machinery.

Amino Acid Sequence↗
PubMed2001

The prevalence of uveitis in juvenile rheumatoid arthritis.

BACKGROUND: Because asymptomatic uveitis has been an important cause of visual loss in children with juvenile rheumatoid arthritis, periodic ophthalmologic screenings of such patients have been recommended. Recently, some authors have found a decreased prevalence of uveitis in children with juvenile rheumatoid arthritis. METHODS: We studied a total of 76 patients (63 girls and 13 boys, aged 1 to 16 years), referred to 3 pediatric ophthalmology practices between March 1976 and October 1999. Follow-up examinations were performed at intervals of 3 to 6 months according to current guidelines, during the following 6 months to 23 years (mean, 55 months). RESULTS: Uveitis developed in 10 children (13%). Of these 10 children, 2 were symptomatic (blurred vision, discomfort) and 7 were diagnosed with uveitis at the initial visit. Only 1 patient had asymptomatic uveitis after initial negative findings on screening examination. Final visual acuity for all the compliant children in the uveitis group was better than 20/30. DISCUSSION: The prevalence of uveitis in our study is similar to rates found by other recent authors. This decrease may reflect a tendency for systemic medications to prevent the development of ocular inflammation. We believe that screening guidelines should be reevaluated, especially for asymptomatic children with negative findings on initial examinations.

Adolescent↗
PubMed2001

Recurrent endogenous candidal endophthalmitis in a premature infant.

Endogenous Candida endophthalmitis resulting from candidemia in low-birth-weight infants usually occurs as a retinochoroiditis, which is effectively treated with systemic antifungal agents. We report a case of Candida endophthalmitis that recurred 4 months after completion of systemic antifungal therapy. The recurrent Candida infection affected primarily the iris and lens, rather than the retina and choroid. Vitrectomy was required for diagnosis and treatment.

Amphotericin B↗
PubMed2001

Acquired esotropia: subjective and objective outcomes.

PURPOSE: The measurement of outcomes of pediatric therapy will be increasingly important to third-party payers as they allocate health care resources. We undertook this study to assess the effectiveness of treatment of acquired esotropia, as measured subjectively by parents and objectively by examination. METHODS: A chart review was used to gather objective clinical data from all patients presenting between 1994 and 1995 with esotropia after their first birthday. Parents' impressions of the quality and impact of treatment were tabulated by using a telephone questionnaire. RESULTS: Of 48 patients studied (mean age, 3.8 years; 44 months' follow-up), the 26 with amblyopia were effectively treated in 81% of cases. Mean esotropic angles decreased, with glasses and/or surgery, from 33.1 to 4.9 PD at distance and from 40.0 to 11.4 PD at near. The average estimated cost of care was 547 dollars per patient per year. Parents considered treatment "extremely important" to their child's future happiness and success in 90% of cases. CONCLUSION: Our experience has shown that treatment of acquired esotropia in childhood, while relatively inexpensive, is highly effective, both objectively and subjectively.

Child↗
PubMed2001

Bilateral ectopia lentis as a presenting feature of medulloepithelioma.

Ectopia lentis may be a feature of numerous systemic and ocular disorders. Kivela and Tarkkanen described an 8-year-old girl with medulloepithelioma who presented with ectopia lentis and a mass behind the temporal iris. Shields reported 2 children with medulloepithelioma who had ectopia lentis associated with neovascular glaucoma. To date, there has been no report of a child with ectopia lentis as the only presentation of an intraocular tumor. We present 2 children with malignant medulloepitheliomas who presented in this fashion.

Child, Preschool↗
PubMed2001

Crystallization and preliminary X-ray analysis of the glycerol-3-phosphate 1-acyltransferase from squash (Cucurbita moschata).

Glycerol-3-phosphate 1-acyltransferase (E.C. 2.3.1.15; G3PAT) catalyses the incorporation of an acyl group from either acyl-acyl carrier proteins (acylACPs) or acylCoAs into the sn-1 position of glycerol 3-phosphate to yield 1-acylglycerol 3-phosphate. Crystals of squash G3PAT have been obtained by the hanging-drop method of vapour diffusion using PEG 4000 as the precipitant. These crystals are most likely to belong to space group P2(1)2(1)2(1), with approximate unit-cell parameters a = 61.1, b = 65.1, c = 103.3 A, alpha = beta = gamma = 90 degrees and a monomer in the asymmetric unit. X-ray diffraction data to 1.9 A resolution have been collected in-house using a MAR 345 imaging-plate system.

Acyltransferases↗
PubMed2000

Kinetic mechanism of NADH-enoyl-ACP reductase from Brassica napus.

Enoyl-ACP reductase, a component of fatty acid synthase, is a target for anti-microbial agents and herbicides. Here we demonstrate the kinetic mechanism to be a compulsory-order ternary complex with NADH binding before the acyl substrate. Matrix-assisted laser desorption ionisation mass spectrometry analysis of enzymatically and synthesised crotonyl-ACP substrate showed the former to contain a single acyl group, whereas the latter contained up to four additional crotonylations. The use of authentic crotonyl-ACP will be important in future kinetic and crystallographic studies.

Binding, Competitive↗
PubMed2000

Treatment of subtotal medial rectus myectomy complicating functional endoscopic sinus surgery.

During the past 2 decades, the introduction of functional endoscopic sinus surgery (FESS) has dramatically improved the treatment of sinus disorders. However, a variety of orbital complications have been reported, including optic nerve damage, hemorrhage, infection, compromise of the lacrimal drainage apparatus, and strabismus. At least 10 cases have reported damage to the medial rectus muscle. (1-8) Treatment options for such patients have been limited, especially because most are adults at risk for anterior segment ischemia after transposition of vertical rectus muscles. We describe 2 patients whose medial rectus myectomies were repaired by using nonabsorbable "hang-back" sutures in combination with a botulinum toxin (Botox) injection of the antagonist lateral rectus muscle. Good primary position alignment was achieved in both patients, and one patient was able to regain binocular function. We recommend this surgical approach, especially in patients at increased risk for anterior segment ischemia.

Adult↗
PubMed2000

Bilateral lateral rectus recession for consecutive exotropia.

INTRODUCTION: Treatment of consecutive exotropia after bilateral medial rectus recessions has been rarely studied. Though several series have reported results of medial rectus advancement, none has described results of lateral rectus recessions. METHODS: We reviewed our results in 31 patients who underwent bilateral lateral rectus recessions for consecutive exotropia after bilateral medial rectus recessions. Mean follow-up was 30 months (range, 1-140 months) after the exotropia repair. RESULTS: At last follow-up, 20 of 31 patients (65%) had deviations of less than or equal to 10 PD. Limitation of adduction was not apparent. DISCUSSION: Cooper's dictum states that lateral rectus recession should be performed instead of medial rectus advancement. Our results suggest that this approach is generally successful. The outcome after exotropia repair in consecutive deviations is comparable to that after repair of primary exotropia.

Adolescent↗
PubMed2000

Crystallization of the NADP-dependent beta-keto acyl-carrier protein reductase from Brassica napus.

The NADP-dependent beta-keto acyl-carrier protein reductase (BKR) from Brassica napus has been crystallized by the hanging-drop vapour-diffusion method using polyethylene glycol of average molecular weight 1500 as the precipitant. The crystals belong to the hexagonal space group P6(4)22, with unit-cell parameters a = b = 129. 9, c = 93.1 A, alpha = beta = 90, gamma = 120 degrees. Calculated values for V(m), the use of rotation and translation functions and consideration of the packing suggest that the asymmetric unit contains a monomer. The crystals diffract to beyond 2.8 A resolution and are more amenable to X-ray diffraction analysis than those reported previously for the Escherichia coli enzyme. The structure determination of B. napus BKR will provide important insights into the catalytic mechanism of the enzyme and into the evolution of the fatty-acid elongation cycle by comparisons with the other oxidoreductase of the pathway, enoyl acyl-carrier protein reductase (ENR).

3-Oxoacyl-(Acyl-Carrier-Protein) Reductase↗
PubMed2000

Mutagenesis of squash (Cucurbita moschata) glycerol-3-phosphate acyltransferase (GPAT) to produce an enzyme with altered substrate selectivity.

In an attempt to rationalize the relationship between structure and substrate selectivity of glycerol-3-phosphate acyltransferase (GPAT, 1AT, EC 2.3.1.15) we have cloned a number of cDNAs into the pET overexpression system using a PCR-based approach. Following assay of the recombinant enzyme we noted that the substrate selectivity of the squash (Cucurbita moschata) enzyme had altered dramatically. This form of GPAT has now been crystallized and its full three-dimensional structure elucidated. Since we now have two forms of the enzyme that display different substrate selectivities this should provide a powerful tool to determine the basis of the selectivity changes. Kinetic and structural analyses are currently being performed to rationalize the changes which have taken place.

Arabidopsis↗
PubMed1999

Developmental delay and poverty in the strabismus clinic.

BACKGROUND: Strabismus and poverty are more common among developmentally delayed children. Poverty is difficult to define, but qualification for Medicaid benefits has been used as an indicator in the past. METHODS: There was a retrospective review of 95 patients with strabismus younger than 7 years who were seen in the Department of Pediatric Ophthalmology at the Albany Medical Center for a 12-month period and were reviewed for the presence or absence of developmental delay. These patients were selected from 2 groups: one with Medicaid coverage and one without. RESULTS: Developmental delays were noted in 13 patients without Medicaid (27.0%) and in 26 patients with Medicaid (55.3%) (P = .0096). Patients with Medicaid were less likely to name Allen pictures by age 3 years (P = .0003). CONCLUSIONS: Poverty is more commonly associated with delays in patients with strabismus, and this should alert ophthalmologists who work with Medicaid patients to seek to identify the presence of developmental delay in managing the care of these patients.

Child↗
PubMed1998

cDNA cloning of Brassica napus malonyl-CoA:ACP transacylase (MCAT) (fab D) and complementation of an E. coli MCAT mutant.

The GenBank database was searched using the E. coli malonyl CoA:ACP transacylase (MCAT) sequence, for plant protein/cDNA sequences corresponding to MCAT, a component of plant fatty acid synthetase (FAS), for which the plant cDNA has not been isolated. A 272-bp Zea mays EST sequence (GenBank accession number: AA030706) was identified which has strong homology to the E. coli MCAT. A PCR derived cDNA probe from Zea mays was used to screen a Brassica napus (rape) cDNA library. This resulted in the isolation of a 1200-bp cDNA clone which encodes an open reading frame corresponding to a protein of 351 amino acids. The protein shows 47% homology to the E. coli MCAT amino acid sequence in the coding region for the mature protein. Expression of a plasmid (pMCATrap2) containing the plant cDNA sequence in Fab D89, an E. coli mutant, in MCAT activity restores growth demonstrating functional complementation and direct function of the cloned cDNA. This is the first functional evidence supporting the identification of a plant cDNA for MCAT.

Acyl-Carrier Protein S-Malonyltransferase↗