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Biomedical subjects

David Wong

Publications and source records attributed to David Wong.

At least 37 records · Page 2Linked to original sources
PubMed2004

Results of thoracoscopic instrumented fusion versus conventional posterior instrumented fusion in adolescent idiopathic scoliosis undergoing selective thoracic fusion.

STUDY DESIGN: Retrospective review of 31 consecutive female patients with adolescent idiopathic scoliosis undergoing selective thoracic fusion. OBJECTIVE: To compare safety and efficacy of two techniques in treating adolescent idiopathic scoliosis undergoing selective thoracic fusion. SUMMARY OF BACKGROUND DATA: There is paucity in the literature comparing posterior versus thoracoscopic instrumented fusion in scoliosis. METHODS: Nineteen patients (group 1) underwent posterior instrumented fusion. Twelve patients (group 2) had thoracoscopic anterior instrumented fusion. All patients had a minimum of 25 months of follow-up observation. RESULTS: Both groups were similar in terms of age at menarche and surgery. Preoperative Cobb angles in the coronal (erect and bending) and sagittal planes did not differ between the two groups. Group 1 patients had higher estimated blood loss (P = 0.006). Operative time (P < 0.001) and intensive care unit stay (P = 0.01) were longer in group 2 patients. There was no difference in parenteral analgesia requirement. There were no complications in group 1. Complications in group 2 included lobar collapse (1) and scapula winging (1). Improvement in scoliosis among group 1 patients averaged 77 (1 week), 72 (6 months), and 67% (most recent follow-up review). In group 2 patients, mean improvement in scoliosis was 66 (1 week), 62 (6 months), and 62% (most recent follow-up review). The differences between the two groups in terms of scoliosis improvement were not significant. Thoracic kyphosis (T2-T12) did not increase significantly with thoracoscopic versus posterior instrumentation. No significant change in lumbar lordosis (T12-S1) was noted with either procedure. CONCLUSIONS: The efficacy of thoracoscopic surgery was similar to standard posterior procedures. Advantages included lower intraoperative blood loss. The longer operative time and intensive care unit stay were attributed to the steep learning curve of this technique.

Adolescent↗
PubMed2004

A randomized controlled trial of combined 5-fluorouracil and low-molecular-weight heparin in management of established proliferative vitreoretinopathy.

OBJECTIVE: To determine the efficacy of a combination of 5-fluorouracil and low-molecular-weight heparin (LMWH) to improve the outcome of surgery for established proliferative vitreoretinopathy (PVR). DESIGN: Double-masked, prospective, randomized, placebo-controlled clinical trial. SETTING: Three tertiary-referral teaching hospital vitreoretinal surgical units. PATIENTS: One hundred fifty-seven patients with established PVR (grade C, anterior or posterior) undergoing vitrectomy surgery. INTERVENTION: All patients underwent vitreoretinal surgery and silicone oil exchange with or without membrane peeling and/or retinectomy. Patients were randomly allocated to perioperative infusion with or without 5-fluorouracil (200 microg/ml) and LMWH (5 IU/ml) in Hartmann's solution for 1 hour. OUTCOME MEASURES: The primary outcome measure was defined as posterior retinal reattachment after removal of silicone oil without any reoperations at 6 months. Secondary outcome measures recorded were posterior retinal reattachment, localized/tractional retinal detachment, visual acuity, macular pucker, hypotony, glaucoma, keratopathy, and cataract. Removal of silicone oil and reoperations were also recorded. RESULTS: Overall, at 6 months 84% of patients had full retinal reattachment and 94% had stable posterior retinal reattachment. There was no significant difference in success in the primary outcome measure (56%, treatment group; 51%, placebo group; P = 0.59) or in secondary outcome measures or rates of complications. Secondary macular pucker occurred less often in the treatment group (6% vs. 17% at 6 months, P = 0.068). CONCLUSIONS: A perioperative infusion of combined 5-fluorouracil and LMWH does not significantly increase the success rate of vitreoretinal surgery for established PVR.

Aged↗
PubMed2003

Tamponade properties of double-filling with perfluorohexyloctane and silicone oil in a model eye chamber.

BACKGROUND: The use of perfluorohexyloctane as a heavier-than-water tamponade for long-term use is limited by its tendency to dispersion and associated intraocular inflammation. Double-filling with silicone oil and F6H8 produces a united, two-layer bubble, appearing as a single bubble. This has been proposed as a method of improving the utility of F6H8 as a tamponade. METHODS: A surface modified polymethylmethacrylate model eye chamber was double-filled with perfluorohexyloctane and silicone oil to approximate a 90% fill. The proportion of silicone oil was increased in a stepwise fashion. A qualitative comparison of surface contact at each stage was made. Chambers with one, two or no indent were used. Dispersion by agitation of the chamber was assessed. RESULTS: With less than 20% silicone oil it was difficult to force the two liquids to make contact. With more oil they united in the form of a single bubble joined at an interface. Once joined, the sides of the single bubble were drawn away from the wall of the chamber. As the proportion of silicone oil increased the area of lost contact increased and progressed inferiorly. Compared to F6H8 alone the double-fill reduced dispersion. CONCLUSION: Silicone oil and F6H8 can unite to form a single bubble that changes the effectiveness of either tamponade agent on their own. The double-fill needs to have enough silicone oil to form a single bubble, but this needs to be kept as low as possible to avoid progressive loss of lateral tamponade. It does not provide good simultaneous superior and inferior tamponade. The double-fill reduces dispersion.

Drug Therapy, Combination↗
PubMed2003

Effects of the matricellular protein SPARC on human retinal pigment epithelial cell behavior.

PURPOSE: To determine the effects of the matricellular protein SPARC (Secreted Protein, Acidic and Rich in Cysteine) on human retinal pigment epithelial (HRPE) cell behavior in vitro. METHODS: Proliferation and migration assays were performed on HRPE cells exposed to various concentrations of SPARC. Additionally, HRPE cells were seeded on top of collagen matrices (a 2D model of the retinal scarring disorder known as proliferative vitreoretinopathy or PVR) and were exposed to SPARC over a 7 day period. Changes in matrix contraction were recorded. RESULTS: HRPE cell proliferation was significantly inhibited at 1 and 10 microg/ml SPARC (p<0.01). SPARC protein did not stimulate HRPE cell migration at any of the concentrations used. SPARC did not significantly affect fibronectin-induced HRPE cell migration at SPARC concentrations up to 10 microg/ml. HRPE cell-seeded collagen matrices demonstrated a significant inhibition of matrix contraction by 1 and 10 microg/ml SPARC (t-test; p<0.02 and 0.001, respectively) compared to controls. CONCLUSIONS: SPARC protein has anti-proliferative effects on HRPE cells in vitro. In addition, SPARC appears to have an inhibitory effect on HRPE-mediated contraction of 2D collagen matrices. These results are consistent with an important role for SPARC in modulating cell behavior in vitro and may indicate a role for SPARC in modifying HRPE cell activities during the development of PVR and other proliferative retinal diseases.

Adult↗
PubMed2003

Trypan blue staining in vitreoretinal surgery.

PURPOSE: To evaluate the efficacy of trypan blue for staining the internal limiting membrane (ILM) and epiretinal membranes (ERM) in vitreoretinal surgery. DESIGN: Prospective noncomparative case series. PARTICIPANTS: Fifty eyes of 50 patients with macular pucker (n = 22), macular hole (n = 18), or a combination (n = 2), proliferative vitreoretinopathy (n = 5), or diabetic retinopathy (n = 3). METHODS: Trypan blue 0.2% was used to stain the ILM or ERM during vitreoretinal surgery. MAIN OUTCOME MEASURES: The intraoperative visibility of the membranes was scored as poor, moderate, good, or excellent. RESULTS: The application of trypan blue onto the ILM or the ERM resulted in a useful bluish staining, facilitating the identification, delineation, and removal of the membranes in all surgeries. No residual staining or adverse effects related to the dye were observed. CONCLUSIONS: Trypan blue stains both ILM and ERM and might be an useful tool in vitreoretinal surgery.

Adult↗
PubMed2003

The role of Tim9p in the assembly of the TIM22 import complexes.

Tim9p is located in the soluble 70-kDa Tim9p-Tim10p complex and the 300-kDa membrane complex in the mitochondrial TIM22 protein import system, which mediates the import of inner membrane proteins. From a collection of temperature-sensitive mutants, we have analyzed two in detail. tim9-3 contained two mutations and tim9-19 contained one mutation, all located near the 'twin CX3C' motif that is conserved in the small Tim proteins. As a result, the import components in the tim9-3 mutant mitochondria were severely reduced and assembled into complexes of aberrant sizes. Protein import was severely reduced and Tim9p and Tim10p binding to in vitro imported ADP/ATP carrier was impaired. In the tim9-19 mutant mitochondria, the 300-kDa membrane complex was assembled, although the soluble 70-kDa Tim9p-Tim10p complex was not detectable. Protein import was decreased only two-fold. When coexpressed in Escherichia coli, tim9-19 and TIM10 proteins failed to assemble into a 70-kDa complex. Our findings suggest that residues near the 'twin CX3C' motif are important for the assembly of Tim9p in both the Tim9p-Tim10p complex and the 300-kDa membrane complex.

Amino Acid Sequence↗
PubMed2002

Use of perfluorohexyloctane as a long-term internal tamponade agent in complicated retinal detachment surgery.

PURPOSE: To report the use of perfluorohexyloctane, a liquid semifluorinated alkane that is heavier than water, as an internal tamponade agent in surgery for complicated retinal detachments. DESIGN: A consecutive interventional case series from three study centers. METHODS: In 23 consecutive eyes (23 patients, 19 men and four women, mean +/- standard deviation (SD) age of 58.5 years +/- 16.1) perfluorohexyloctane was used for long-term internal tamponade. Included were eyes with complicated retinal detachment involving the lower two quadrants of the fundus. Excluded were patients with diseases in the fellow eye or severe systemic disease. A pars plana vitrectomy was performed, including membrane peeling and retinotomy where necessary. RESULTS: The mean duration for perfluorohexyloctane being left in situ was 76 days (SD 37.64) (range, 35-202 days). Four weeks following the removal of perfluorohexyloctane 19 of the 23 patients had total reattachment of the retina; three eyes had a recurrence of retinal detachment. One patient was lost to follow-up. The mean follow-up after perfluorohexyloctane removal was 97 days (range, 48 to 169 days). Cataract formation or progression was noted in nine of the 10 eyes. There were two cases with high intraocular pressures. Dispersion into small droplets was observed as early as 3 days postoperatively in three of the 23 patients. At least 12 of the 23 patients had an obvious dispersion by the time of perfluorohexyloctane removal. There was no sign of optic atrophy, retinal necrosis, or retinal vascular occlusion. CONCLUSION: Perfluorohexyloctane was tolerated as a long-term internal tamponade agent without obvious signs of damage to the retina or optic disk. Of all the complications noted, the most common was that of dispersion of the perfluorohexyloctane bubble into droplets.

Cataract↗
PubMed2002

Rhegmatogenous retinal detachment after transscleral local resection of choroidal melanoma.

OBJECTIVE: To report on the incidence and outcome of rhegmatogenous retinal detachment after transscleral local resection of choroidal melanoma. DESIGN: Prospective, noncomparative, interventional case series. PARTICIPANTS: One hundred fifty-six patients with choroidal melanoma treated by transscleral local resection between January 1993 and June 2000. INTERVENTION: Transscleral choroidectomy or cyclochoroidectomy for uveal melanoma, with ocular decompression by single-port pars plana vitrectomy and, in most patients, adjunctive ruthenium plaque radiotherapy. MAIN OUTCOME MEASURES: Incidence of rhegmatogenous retinal detachment according to predictive factors and outcomes reported in terms of anatomic success, visual acuity, and ocular conservation. RESULTS: Rhegmatogenous retinal detachment occurred in 28 (18%) eyes and was significantly more common in patients with thick tumors (Cox univariate analysis, P = 0.001) and in males (Cox univariate analysis, P = 0.013), with posterior tumor extension being of borderline significance (Cox univariate analysis, P = 0.069). Surgical treatment of the retinal detachment was performed in 25 patients; it was undertaken at our center in 22 patients and at the referring hospital in 3 patients. Anatomic success was achieved in 21 (84%) of these 25 patients, with 7 eyes retaining counting fingers vision, and 3 eyes seeing 6/60 or better. Ten eyes treated for retinal detachment were enucleated because of recurrent tumor (four eyes), retinal detachment (three eyes), wound dehiscence (one eye), phthisis (one eye), and poor visual acuity (one eye). Eleven eyes known to have a retinal tear underwent prophylactic vitreoretinal surgery at the end of the local resection, with only one (9%) of these subsequently developing retinal detachment. CONCLUSIONS: Rhegmatogenous retinal detachment after transscleral choroidectomy or cyclochoroidectomy for uveal melanoma is a serious complication requiring early vitreoretinal surgery.

Adolescent↗
PubMed2002

Apoptosis, proliferation and p12(doc-1) profiles in normal, dysplastic and malignant squamous epithelium of the Syrian hamster cheek pouch model.

Disruption of the homeostatic balance between proliferation and apoptosis is widely believed to contribute to human oral carcinogenesis. Using the Syrian hamster oral cancer model, we examined normal, hyperplastic, dysplastic and malignant oral epithelium for the fraction of apoptotic, proliferating and p12(doc-1) expressing keratinocytes using the TUNEL assay, as well as PCNA and p12(doc-1) immunostaining, respectively. The percentage of TUNEL positive cells progressively increased from normal to dysplastic epithelium (P<0.0019), but returned to normal keratinocyte levels in the malignant epithelium (P<0.20). However, PCNA positive cells increased progressively through hamster oral malignant progression (P<0.0012). The overall ratio of apoptotic to proliferating keratinocytes remains similar until the transition between dysplastic and malignant epithelium, where the ratio is markedly reduced (P<0.05). p12(doc-1) labeling demonstrated a similar expression pattern (P<0.008). This study demonstrates that apoptosis, proliferation and the expression of p12(doc-1) reflects alterations reported during human oral carcinogenesis and supports the use of the Syrian hamster model for the further examination of these pathways.

Animals↗
PubMedDate not supplied

Current preoperative testing practices in ambulatory surgery are widely disparate: a survey of CAS members.

PURPOSE: Routine preoperative testing has been criticized as having little impact on perioperative outcomes. The purpose of this study is to identify the current practice of preoperative testing in ambulatory surgery. METHODS: A standard questionnaire was sent to all active members of the Canadian Anesthesiologists' Society (CAS). The study inquired into the anesthesiologist's preoperative testing practice in healthy patients and patients with stable medical conditions undergoing ambulatory surgery. RESULTS: Of 1,335 mailed questionnaires, a total 617 respondents who reported their participation in ambulatory surgical care were received. Eighty percent [95% confidence interval (CI) 76.5-83.2] of the respondents indicated that, if testing had to be ordered in asymptomatic patients undergoing low-risk ambulatory surgery, it would be due to the patient's clinical indications while others indicated it would be the result of following institutional guidelines (15.1%, 95% CI 12.2-17.9), and even fewer attributed it to a "routine" testing practice (0.5%, 95% CI 0-1.14). Forty-four percent (95% CI 39.8-47.8) of the anesthesiologists indicated that age alone is not a criterion when they required a preoperative electrocardiogram (ECG) while others reported various cut-points (> 65; > 55; > 45; > 40 yr) for ECG ordering for asymptomatic patients undergoing the low-risk ambulatory surgery. About 40% (95% CI 35.7-43.5) of the anesthesiologists had no specific concern about eliminating preoperative testing in ambulatory surgery. CONCLUSION: Our survey has documented marked disparities in the practices of preoperative testing. A large proportion of the anesthesiologists indicated that age alone is not a criterion for preoperative ordering of ECG. Many anesthesiologists had no concern about eliminating preoperative testing in low-risk ambulatory surgery.

Age Factors↗
PubMedDate not supplied

Pseudophakic retinal detachment.

Pseudophakic retinal detachment is a rare, but potentially serious, complication of cataract surgery. The incidence of pseudophakic retinal detachment following current surgical techniques of cataract extraction, including extracapsular cataract extraction by nuclear expression and phacoemulsification, is lower than that found after intracapsular cataract extraction. The risk of pseudophakic retinal detachment appears to be increased in myopic patients, in those patients in whom vitreous loss had occurred at the time of cataract surgery, and in patients undergoing Nd:YAG posterior capsulotomy. Most cases present to the clinician when the macula is already detached and the central vision is affected. When evaluating patients with pseudophakic retinal detachment, the fundal view is often impaired by anterior or posterior capsular opacification, reflections related to the intraocular lens, or poor mydriasis. Scleral buckling, pneumatic retinopexy, and primary pars plana vitrectomy, with or without combined scleral buckling, are the surgical techniques used to treat pseudophakic retinal detachment. Anatomical success rates are high after vitreo-retinal surgery for pseudophakic retinal detachment, although a smaller proportion of patients recover good vision following surgery.

Cataract Extraction↗
PubMedDate not supplied

Congenital scoliosis in a quarter horse filly.

A 4-week old Quarter Horse filly was evaluated for abnormal gait and lateral deviation of the cervical spine. Physical examination findings prompted radiographs and computed tomography of the thoracic vertebral column which revealed hypoplasia of several thoracic vertebral bodies and resultant scoliosis of the thoracic vertebral column and deviation of the left and right hemithoraces and associated ribs. Collectively, radiography and computed tomography provided an accurate description of the vertebral malformations resulting in scoliosis in this foal.

Animals↗