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G A Williams

Publications and source records attributed to G A Williams.

At least 37 records · Page 2Linked to original sources
PubMed2001

Using meta computing tools to facilitate large-scale analyses of biological databases.

Given the high rate at which biological data are being collected and made public, it is essential that computational tools be developed that are capable of efficiently accessing and analyzing these data. High-performance distributed computing resources can play a key role in enabling large-scale analyses of biological databases. We use a distributed computing environment, Legion, to enable large-scale computations on the Protein Data Bank (PDB). In particular, we employ the Feature program to scan all protein structures in the PDB in search for unrecognized potential cation binding sites. We evaluate the efficiency of Legion's parallel execution capabilities and analyze the initial biological implications that result from having a site annotation scan of the entire PDB. We discuss four interesting proteins with unannotated, high-scoring candidate cation binding sites.

Algorithms↗
PubMed2001

Cone-based vision of rats for ultraviolet and visible lights.

Rats (Rattus norvegicus) have two classes of cone, one containing an ultraviolet (UV)-sensitive photopigment and the other housing a pigment maximally sensitive in the middle (M) wavelengths of the visible spectrum. The manner in which signals from these two cone types contribute to rat vision was investigated through recordings of a gross electrical potential (the electroretinogram, ERG) and behavioral discrimination tests. Spectral sensitivity functions obtained from both types of measurement indicate clear contributions from each of the cone classes, but there is a marked enhancement of the relative sensitivity to UV light in the behavioral index; for instance, under some photopic test conditions, rats are approximately equally sensitive to middle-wavelength and UV lights. In adaptation tests, thresholds for UV and M lights were found to be differentially elevated in the presence of chromatic adapting backgrounds, thus providing the possibility that signals from the two cones could be used by the rat visual system to support color discriminations. Evidence of dichromatic color vision in the rat was subsequently obtained from tests of wavelength discrimination.

Adaptation, Ocular↗
PubMed2001

Drug approval summaries: arsenic trioxide, tamoxifen citrate, anastrazole, paclitaxel, bexarotene.

This report summarizes information on drugs recently approved by the Food and Drug Administration, Office of Drug Evaluation I, Division of Oncology Drug Products. Five applications supporting new claims will be discussed: Trisenox (arsenic trioxide) for induction of remission and consolidation in patients with acute promyelocytic leukemia who are refractory to, or have relapsed from, retinoid and anthracycline chemotherapy, and whose disease is characterized by the presence of the t(15;17) translocation or PML/RAR-alpha gene expression; Nolvadex (tamoxifen citrate) in women with ductal carcinoma in situ, following breast surgery and radiation, to reduce the risk of invasive breast cancer; Arimidex (anastrazole) for first-line treatment of postmenopausal women with hormone receptor positive or hormone receptor unknown locally advanced or metastatic breast cancer; Taxol (paclitaxel), 175 mg/m(2) by 3 h infusion in combination with cisplatin for first-line treatment of advanced ovarian cancer; and Targretin gel (bexarotene) for the topical treatment of cutaneous lesions in patients with stage IA and IB cutaneous T-cell lymphoma who have not tolerated other therapies or who have refractory or persistent disease. Information provided includes rationale for drug development, study design, efficacy and safety results, and pertinent literature references.

Anastrozole↗
PubMed2000

Effect of perifoveal tissue dissection in the management of acute idiopathic full-thickness macular holes.

OBJECTIVE: To evaluate the efficacy of perifoveal tissue dissection (PTD) on patients undergoing pars plana vitrectomy for idiopathic macular holes of less than 1-year's duration. METHODS: Pars plana core vitrectomy was performed on 107 eyes of 104 consecutive patients with acute idiopathic macular holes. One cohort had routine PTD. In the other cohort, no attempt was made to strip preretinal tissue. Follow-up was longer than 6 months (follow-up range, 6 to 36 months). RESULTS: Overall, 95 (89%) of all macular holes were closed. Visual acuity improved 2 lines or more of the Snellen letter chart in 91 eyes (85%). A postoperative visual acuity of 20/50 or better was achieved in 79 eyes (74%). A transient increase in intraocular pressure (230 mm Hg) developed in 25 eyes (23.4%). In 6 eyes (5.6%) a retinal detachment developed. One eye had retinal pigment epithelial changes and 1 patient reported peripheral field loss. No statistically significant differences were noted between eyes having PTD and those without PTD for any outcome measure. CONCLUSION: In this series, no beneficial or adverse effect could be demonstrated by performing PTD in eyes undergoing pars plana core vitrectomy for acute idiopathic macular holes.

Acute Disease↗
PubMed2000

Nonsurgical management of macular hemorrhage secondary to retinal artery macroaneurysms.

OBJECTIVE: To report visual acuity outcomes of nonsurgical management of macular hemorrhage secondary to retinal artery macroaneurysms. METHODS: Forty-one patients at multiple centers with macular hemorrhage secondary to retinal artery macroaneurysms managed with observation alone were reviewed. Time to clearance of macular hemorrhage, visual acuity at final follow-up, and presence or absence of macular pigmentary changes after absorption of the hemorrhage were recorded for each patient. RESULTS: On initial examination, visual acuity was 20/200 or worse in all except 4 patients (3 with 20/70, 1 with 20/80). At an average follow-up of 15. 7 months, a final visual acuity of 20/40 or better was achieved in 15 eyes (37%), between 20/50 and 20/100 in 12 (29%), and 20/200 or worse in 14 (34%). Macular pigmentary abnormalities were noted after clearance of the hemorrhage in 23 (56%) of 41 cases, and these eyes generally had worse visual acuity outcomes. CONCLUSIONS: In eyes with macular hemorrhage secondary to retinal artery macroaneurysms managed with observation alone, good visual acuity outcomes can often be achieved. Poorer visual acuity outcomes are associated with macular pigmentary changes after resorption of blood. Arch Ophthalmol. 2000;118:780-785

Adult↗
PubMed2000

Vitrectomy for diffuse diabetic macular edema associated with a taut premacular posterior hyaloid.

PURPOSE: To evaluate the role of vitrectomy in eyes with diffuse diabetic macular edema associated with a taut posterior hyaloid. METHODS: Records of 55 eyes of 50 patients with diabetic retinopathy and diffuse clinically significant diabetic macular edema who underwent vitrectomy with stripping of the premacular posterior hyaloid were reviewed. In all 55 eyes, diffuse diabetic macular edema was present on contact lens examination and confirmed with fluorescein angiography. On fundus examination, the premacular posterior hyaloid was attached and appeared taut. RESULTS: The mean preoperative best-corrected visual acuity was 20/160, and the mean final best-corrected visual acuity was 20/80 (P <.0001, Wilcoxon signed rank test), with 27 (49.1%) of the 55 eyes demonstrating improvement in best-corrected visual acuity of 2 or more lines. Fifty-two (94.5%) of the 55 vitrectomized eyes showed improvement in clinically significant macular edema and in 45 eyes (81.8%) the macular edema resolved completely during a mean period of 4.5 months (range, 1 to 13 months). Eyes with macular ischemia and preoperative best-corrected visual acuity of 20/200 or less tended to respond less favorably to vitrectomy than eyes lacking these characteristics. All eyes had at least 6 months of follow-up after surgery, with a mean follow-up of 23.2 months. CONCLUSION: In eyes with persistent diffuse diabetic macular edema with a taut premacular posterior hyaloid face unresponsive to laser therapy, vitrectomy with removal of the posterior hyaloid appears to be beneficial in some cases. Careful selection of eyes with favorable preoperative clinical characteristics may improve surgical outcomes.

Adult↗
PubMed2000

A new approach to stage 3 macular holes.

PURPOSE: The purpose of this article is to demonstrate the feasibility of a surgical approach that might be possible in an office setting for idiopathic stage 3 macular holes. The posterior hyaloid of the vitreous and perihole tissue is enzymatically manipulated to create an atraumatic posterior vitreous separation and may stimulate cell proliferation to close macular holes. DESIGN: Prospective noncomparative interventional case series. PARTICIPANTS: Nine eyes of eight patients with idiopathic stage 3 macular holes were treated. METHODS: The patients were treated with an injection of 0.4 IU of autologous plasmin enzyme into the midvitreous cavity and lavage of the vitreous cavity with an infusion light pipe and vitreous cutter followed by filling 70% to 80% of the vitreous cavity with 14% C3F8 and head-down positioning. MAIN OUTCOME MEASURES: Posterior vitreous detachment, macular hole closure, and vision improvement. RESULTS: Eight of nine eyes showed a spontaneous posterior vitreous detachment. One eye required minimal suction of less than 50 mmHg to elevate the posterior hyaloid off the retinal surface. Eyes were followed for a minimum of 6 months. All holes closed, and there was an average visual acuity improvement of four lines. The average surgical time for this procedure was 20 minutes. CONCLUSIONS: Autologous plasmin enzyme-assisted vitreous surgery techniques can reduce operative time, expense, and patient inconvenience while maintaining excellent surgical results, which may allow office-based vitreous surgery for idiopathic stage 3 macular holes.

Aged↗
PubMed2000

Surgical repair of full-thickness idiopathic macular holes associated with significant macular drusen.

OBJECTIVE: To evaluate the visual and anatomic results of surgically repaired macular holes in eyes with intermediate or large-sized macular drusen. DESIGN: Retrospective noncomparative case series. PARTICIPANTS: Thirty-four eyes of 32 patients undergoing macular hole surgery with preoperative intermediate or large-sized macular drusen as defined by the Age-Related Eye Disease Study (AREDS). INTERVENTION: Pars plana vitrectomy for standard macular hole repair performed by multiple surgeons. MAIN OUTCOME MEASURES: Visual acuity, anatomic hole closure. RESULTS: Initial hole closure failed in 8 eyes (24%) overall, 5 of 28 eyes (18%) with AREDS category 2 drusen and 3 of 6 eyes (50%) with category 3 drusen (P = 0.1263). Final macular hole closure was seen in 93% of category 2 and 67% of category 3 eyes (P = 0.1347). Mean final visual acuity was 20/60 overall, 20/60 for category 2, and 20/50 for category 3 eyes. CONCLUSIONS: A trend of reduced initial macular hole closure was seen in eyes with significant macular drusen. Reoperation improved closure rates. If closure was accomplished, visual outcomes were excellent.

Aged↗
PubMed2000

Evidence for a role of HLA DRB1 alleles in the control of IgE levels, strengthened by interacting TCR A/D marker alleles.

BACKGROUND: MHC class II alleles at human chromosome 6p21.1 and alleles in the TCR A/D locus at human chromosome 14q11.2 have been implicated in susceptibility to specific allergies and the modulation of total serum IgE. It has also been hypothesized that HLA and TCR allelic interactions may have a strong influence on predisposition to allergic disease. OBJECTIVE: This study was performed to investigate the influence of HLA-DRB and DQB1 alleles and D14S50 alleles (adjacent to TCR A/D locus on 14q11.2), individually and in-combination, on total serum IgE levels, and on the development of specific allergies. METHODS: We performed an association study between HLA-DRB, HLA-DQB1 polymorphisms, D14S50 alleles, total serum IgE expression and specific allergies to house dust mite, grass pollens and cat fur. A sample of 181 individuals was drawn from a larger set of 2415 adults, sampled at random from a district in Nottingham. RESULTS: Strong association was observed between HLA-DRB1*0701 allele and high total serum IgE expression (P < 0.001). D14S50 alleles alone showed no evidence for independent association. However, there was a significant interaction between DRB1*0701 and D14S50 allele 170 such that, when both were present, there was a further increase in total serum IgE levels. CONCLUSION: This study suggests that DRB1*0701 allele is involved in the modulation of total serum IgE, and that there is an interaction between DRB1*0701 and a marker adjacent to TCR A/D in the control of IgE expression.

Adolescent↗
PubMed2000

External versus internal approach to the removal of metallic intraocular foreign bodies.

OBJECTIVE: To review the management of metallic intraocular foreign bodies (IOFB) at a single institution and to compare the use of internal and external approaches for their removal. SUBJECTS AND METHODS: A retrospective review was conducted on 70 eyes from 70 patients who underwent surgical removal of a metallic IOFB with either an internal (vitrectomy followed by forceps or internal magnet use) or external approach (large electromagnet) by seven vitreoretinal surgeons at a single institution between 1973 and 1996. Visual acuity and complications occurring with the two approaches were the main outcome measures studied. RESULTS: Overall, patients showed significant improvement in visual acuity following surgical intervention (P < 0.001) despite widely varying surgical techniques. When the authors compared patients treated with an external versus an internal approach they found no statistically significant difference with regard to visual outcome and a trend toward a higher rate of postoperative endophthalmitis in the external approach group. CONCLUSION: Surgical removal of metallic IOFB results in significant visual improvement. The external approach to the removal of magnetic metallic IOFB remains a viable treatment option in select cases.

Adolescent↗
PubMed2000

Soccer ball-related retinal injuries: a report of 13 cases.

PURPOSE: To describe the clinical characteristics and management of retinal injuries caused by soccer ball impact as well as the mechanism of injury, prognostic features, risk factors, and possible prevention strategies. METHODS: Thirteen cases of soccer ball injuries from retina referral practices were retrospectively reviewed, with attention to the mechanism of associated ocular complications and the anatomic and visual outcomes. RESULTS: Soccer ball injuries occurred in both male and female patients (9 male, 4 female) with ages ranging from 8 to 21 years (median 14 years). These patients were observed from 0 to 64 months (median follow-up, 8 months). Four patients had traumatic macular holes, two eyes had retinal detachment associated with retinal dialysis, two had retinal tears associated with hemorrhage, one had a choroidal rupture, and one had only vitreous hemorrhage and Berlin's edema. Although six eyes had some degree of traumatic retinal pigment epitheliopathy, it was the primary diagnosis in only three. Visual acuity at presentation ranged from 20/20 to count fingers, with 7/13 (54%) having 20/200 or worse vision. Seven eyes underwent surgical procedures; the remainder were observed. Final visions ranged from 20/20 to count fingers, with 3/13 (23%) having 20/200 or worse vision. Six eyes (46%) improved by two or more lines by the last follow-up. CONCLUSION: Soccer ball-related ocular injuries disproportionately affect young players, are more frequent in females than previously reported, and have more severe visual consequences than previously recognized. Injury prevention strategies to minimize contact between the eye and the soccer ball may reduce the incidence and severity of eye injuries.

Adolescent↗
PubMed1999

Results after lens extraction in patients with diabetic retinopathy: early treatment diabetic retinopathy study report number 25.

OBJECTIVE: To assess the visual results after surgical lens removal in patients with diabetic retinopathy. DESIGN: A multicenter randomized clinical trial designed to assess the effect of photocoagulation and aspirin in patients with mild to severe nonproliferative or early proliferative diabetic retinopathy and/or macular edema. PARTICIPANTS: Of the 3711 patients enrolled in the Early Treatment Diabetic Retinopathy Study, lens surgery was performed on 205 patients (270 eyes) during follow-up that ranged from 4 to 9 years. OUTCOME MEASUREMENTS: Visual acuity, macular edema status, and degree of diabetic retinopathy. In addition, risk factors associated with lens extraction and with poor postoperative visual acuity (worse than 20/100) were assessed. RESULTS: The risk of lens extraction increased with increasing age, female sex, and baseline proteinuria. Ocular variables associated with increased risk of lens surgery included poor baseline visual acuity and vitrectomy performed during the course of the study. At 1 year after lens surgery, visual acuity improvement of 2 or more lines from preoperative levels occurred in 64.3% of the operated-on eyes assigned to early photocoagulation and 59.3% of eyes assigned to deferral of photocoagulation. In eyes assigned to early photocoagulation, 46% of eyes achieved visual acuity better than 20/40; 73%, better than 20/100; and 8%, 5/200 or worse at 1 year after surgery. Visual acuity results for eyes assigned to deferral of laser photocoagulation at 1 year were not as favorable; 36% achieved visual acuity better than 20/40; 55%, better than 20/100; and 17%, 5/200 or worse at 1 year after surgery. Evaluation of 1-year postoperative visual acuities for all eyes with mild to moderate nonproliferative diabetic retinopathy at the annual visit before lens surgery showed that 53% were better than 20/40; 90%, better than 20/100; and 1%, 5/200 or worse. However, for eyes with severe nonproliferative or worse retinopathy at the annual visit before lens surgery, only 25% were better than 20/40; 42%, better than 20/100; and 22%, 5/200 or worse at 1 year after lens surgery. There was little change in visual acuity between 1 and 2 years postoperatively. Increased severity of retinopathy and poor visual acuity before surgery were associated with visual acuity of worse than 20/100 at 1 year after surgery. Lens surgery was associated with a borderline statistically significant increased risk of progression of diabetic retinopathy in the adjusted analyses (P = .03). No statistically significant long-term increased risk of macular edema was documented after lens surgery. CONCLUSIONS: Visual acuity results after lens surgery in patients in the Early Treatment Diabetic Retinopathy Study were better than published results for similar patients. This may be because of more intensive photocoagulation for lesions of diabetic retinopathy in the Early Treatment Diabetic Retinopathy Study than in previously reported studies. Although patients with severe nonproliferative retinopathy or worse before lens surgery had poorer visual results, visual improvement was seen in 55% of these patients at 1-year follow-up. The main causes of poor visual results in eyes after lens surgery were complications of proliferative retinopathy and/or macular edema.

Aspirin↗
PubMed1999

Vitrectomy for chronic pseudophakic cystoid macular edema.

PURPOSE: We report the results of pars plana vitrectomy for chronic pseudophakic cystoid macular edema unresponsive to medical treatment. METHODS: Retrospective analysis of 23 consecutive eyes of 23 patients with chronic pseudophakic cystoid macular edema was performed. Eyes with vitreous incarceration into the cataract wound or vitreous-cornea contact were excluded from the study. Preoperatively, all eyes had cystoid macular edema confirmed on fluorescein angiography and were unresponsive to medical treatment. Pars plana vitrectomy was performed using standard techniques and vitreous adhesions to the iris, intraocular lens, or both were lysed if present. RESULTS: The mean interval between cataract surgery and vitrectomy was 32.3+/-30.9 months (median, 20 months; range, 3 to 110 months). The vitreous was adherent to the iris or intraocular lens in 12 eyes (52.2%) and was present in the anterior chamber with no evidence of adhesions in seven eyes (30.4%). In four eyes (17.4%) the vitreous was posterior to the iris plane with no adhesions to anterior segment structures. The median preoperative best-corrected visual acuity was 20/200, and the median final postoperative best-corrected visual acuity was 20/60 (P<.0001) after a mean follow-up of 30.2+/-31.2 months (median, 14 months; range, 2 to 109 months). Final best-corrected visual acuity improved by a mean of 3.3+/-2.6 Snellen lines, with a median percent change of 70% (mean, 57.3%; range, 0% to 99%). In all 23 eyes the cystoid macular edema resolved postoperatively by biomicroscopic examination in a mean period of 3.3 months (median, 2 months; range, 1 to 12 months). CONCLUSIONS: In pseudophakic eyes with chronic cystoid macular edema unresponsive to medical treatment, vitrectomy resulted in resolution of the cystoid macular edema with improved visual acuity in some cases. Clinical improvement may occur in eyes with no apparent vitreous disturbance.

Aged↗
PubMed1999

Potential utility of left heart contrast agents in diagnosis of myocardial rupture by 2-dimensional echocardiography.

This case illustrates the use of intravenous injections of a contrast agent during 2-dimensional echocardiography in a patient with myocardial rupture after myocardial infarction. Intravenous injections of echocardiographic contrast agents may have potential use in the identification of intrapericardial hemorrhage after myocardial infarction caused by myocardial rupture or development of ventricular pseudoaneurysm.

Aged↗
PubMed1999

Successful closure of traumatic macular holes.

PURPOSE: To establish the efficacy of vitreoretinal surgery without the use of transforming growth factor-beta or autologous platelet concentrate in the repair of traumatic macular holes. METHODS: This retrospective review consisted of 16 eyes from 16 consecutive patients treated by five vitreoretinal surgeons at a single institution between 1993 and 1997. Intervention included pars plana vitrectomy with creation of posterior vitreous detachment, placement of 14% to 16% C3F8 gas, and postoperative face-down positioning. Ten eyes received intraoperative autologous plasmin to facilitate formation of posterior vitreous detachment. Main outcome measures were anatomic closure rate and visual outcome. RESULTS: Anatomic closure of the macular holes was achieved in 15 (94%) of 16 eyes, with an average follow-up of 7 months. Six (38%) eyes achieved visual acuity of 20/40 or better. Visual acuity improved by 2 or more lines in 11 (69%) of 16 eyes. The average preoperative logMAR-converted visual acuity of 20/175 improved to 20/60 postoperatively. CONCLUSION: Traumatic macular holes can be closed successfully with substantial visual recovery without the use of transforming growth factor-beta or platelet concentrate.

Adolescent↗