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Biomedical subjects

Y W Wong

Publications and source records attributed to Y W Wong.

At least 19 recordsLinked to original sources
PubMed2006

Expression of insulin-like growth factor binding protein-3 in pterygium tissue.

BACKGROUND: Pterygium is a fibrovascular overgrowth from the conjunctiva onto the cornea. The pathogenesis of this common ocular surface disorder is not well understood and the only treatment is surgical removal. METHODS: DNA microarray analysis of primary pterygium tissue was carried out using uninvolved conjunctiva tissue as a comparison for gene expression levels. Real time polymerase chain reaction (PCR) was used to verify the mRNA level of expression for genes changed in pterygium. Western blot analysis and immunohistochemistry showed protein expression levels and the tissue distribution. RESULTS: Microarray analysis revealed that mRNA levels of a number of genes were changed in primary pterygium. In particular the gene for insulin-like growth factor binding protein-3, (IGFBP3), which modulates the effects of insulin-like growth factor on cells was significantly decreased. Both the message and protein expression of IGFBP3 in pterygium were decreased compared to normal, uninvolved conjunctiva. CONCLUSION: Decreased levels of IGFBP3 protein have been strongly correlated with the presence of cancer. Identification of the low level of expression of IGFBP3 in pterygium suggests that the pathway controlling cell proliferation has lost an important control mechanism, which may explain the continued growth of pterygium.

Adult↗
PubMed2005

Effect of segmental artery ligation on the blood supply of the thoracic spinal cord during anterior spinal surgery: a quantitative histomorphological fresh cadaver study.

STUDY DESIGN: Human cadaver quantitative morphometric analysis of the blood vessels in the spinal cord after ligation of segmental arteries. OBJECTIVES: To investigate the effect of ligation of segmental arteries on the quantity and density of the blood vessels in the spinal cord. SUMMARY OF BACKGROUND DATA: Ligation of segmental arteries is often used in the anterior approach for correction scoliosis. However, whether or not segmental artery ligation is liable to deny the spinal cord an adequate blood supply, thus leading to paraplegia, still remains controversial. METHODS: Eleven fresh cadavers were divided into control, unilateral, and bilateral groups. For the unilateral and bilateral groups, 5 segmental vertebral arteries (T7-T11) were ligated unilaterally and bilaterally, respectively. Then, the number and density of blood vessels at different levels in the 3 groups were measured. RESULTS: Compared to that of the corresponding level in the control group, the number of blood vessels at T5 to L1 all decreased in the ligation groups. And significant differences were found at T8 (82.80 +/- 16.36), T10 (77.80 +/- 19.80), and T11 (99.20 +/- 14.85) levels, compared to those of the corresponding levels in the control group: T8 (175.80 +/- 8. 31), T9 (176.40 +/- 32. 33), T10 (171.40 +/- 9. 73), and T11 (189.20 +/- 15. 92). Further decrease was found at each corresponding level in the bilateral group, and significant differences were found at T8 (65.80 +/- 15.55), T9 (24.80 +/- 13.43), T10 (0), T11 (0), and T12 (0) levels. Similar results were obtained with regard to the density of blood vessels. Significant differences were found at T11 (1.246 +/- 0.112) and L1 (1.349 +/- 0.109) in the unilateral group, and T9 (0.260 +/- 0.088), T10 (0), T11 (0), T12 (0), and L1 (0.147 +/- 0.117) in the bilateral group compared to those of the corresponding levels in the control group: T9 (1.810 +/- 0.202), T10 (1.833 +/- 0.175), T11 (2.308 +/- 0.335), T12 (2.510 +/- 0.617), and L1 (2.193 +/- 0.033). CONCLUSIONS: This study suggests that the more levels the ligation encompasses, the higher the risk of spinal cord damage. Therefore, caution should be taken when several segmental arteries are to be ligated in the clinical setting. What is more, bilateral ligation, which is worse than unilateral ligation, can lead to a significant decrease in the number and density of blood vessels of the spinal.

Adolescent↗
PubMed2004

A prospective comparison of the coronal deformity correction in thoracic scoliosis using four different instrumentations and the fulcrum-bending radiograph.

STUDY DESIGN: A prospective study on comparing coronal deformity correction in thoracic scoliosis using four different instrumentations. OBJECTIVES: To compare the ability of four different instrumentation systems in correcting thoracic scoliosis based on the curve flexibility as reviewed by the fulcrum-bending radiograph. SUMMARY OF BACKGROUND DATA: The fulcrum-bending radiograph has been shown to be able to accurately reflect the flexibility of thoracic curves, and the fulcrum bending correction index (FBCI) predicts the amount of correction achieved by current surgical techniques. By recruiting curves of known flexibility, the efficacy of the different instrumentations in correcting coronal deformity can be truly compared. METHODS: A consecutive series of 127 patients with idiopathic scoliosis were treated by one of four implants: CD-Horizon (CD-H), Moss Miami (MM), TSRH, and ISOLA. All surgeries were performed by the same group of surgeons using the respective recommended techniques. FBCI was used to compare the correction achieved by these implants. RESULTS: The mean FBCI/correction rate was 101.0%/57.9% in the TSRH group, 103.5%/58.5% in ISOLA, 109.1%/67.6% in CD-H, and 100.2%/62.7% in the MM group. The correction rate was significantly (P < 0.05) higher in the CD-H group than those in the TSRH and ISOLA groups, while the differences in the FBCI between the four implants were not statistically significant. CONCLUSIONS: When curve flexibility is taken into account, despite differences in material and design of four commonly used instrumentations, their ability to correct thoracic scoliosis is the same. Future studies describing surgical correction results should be based on the FBCI.

Adolescent↗
PubMed2003

Isokinetic and isometric lifting capacity of Chinese in relation to the physical demand of job.

The aim of the study was to formulate normative data for the lifting capacities of a normal Chinese population, in order to establish a basic foundation for further studies and to investigate the relationship between individual attributes including age, gender, height, weight, job physical demand and each type of lifting capacity. Isokinetic and isometric lifting strength at low, waist and shoulder assessment levels were measured using the LIDO Workset II based on a sample of 93 normal Chinese adults (63 men and 30 women) between the ages of 21-51. The 50th percentile score for adult Chinese female's lifting strength was 17.71% lower than the American female while the adult Chinese male's lifting strength was 14.94% lower than the American male. Lifting forces were higher in the 20-40 year age group. The isometric work mode had considerable impact on the lifting capacities, with shoulder level having the highest lifting capacities. The gender and body weight had a significant positive correlation to lifting capacity while job physical demand had a moderate correlation. Age and body heights were weakly correlated to lifting capacity.

Adult↗
PubMed2003

Pyoderma gangrenosum in a thoracotomy wound associated with a pulmonary cavitating lesion.

We present a patient with both pyoderma gangrenosum in a thoracotomy wound and a pulmonary cavitating lesion with the histological features of Wegener's granulomatosis. An ulcer with blue undermined edges developed in our patient's thoracotomy scar after a lobectomy was carried out for the cavitating lung lesion and c Antineutrophil Cytoplasmic Antibodies (cANCA), which is highly specific for active Wegener's granulomatosis but was negative at the time of her skin lesion. This suggests that our patient had cutaneous pyoderma gangrenosum rather than cutaneous Wegener's granulomatosis, although the two conditions may occasionally have similar clinical and histological features.

Aged↗
PubMed2003

Rapid manufacturing techniques in the development of an axial blood pump impeller.

This paper presents a comparison of manufacturing techniques used in the development of an axial blood pump impeller. In this development process the impeller was designed and its performance was evaluated with the aid of computational fluid dynamics (CFD). Prototypes of those designs where the CFD results show promise were needed in sufficient quantities at a low cost for experimental validation of the CFD results. As the impeller is less than 16 mm in diameter with a maximum blade thickness of about 1.5 mm, innovative manufacturing techniques are explored in this paper to determine the best process for quick fabrication of prototypes that are dimensionally accurate, structurally robust and low in cost. Four rapid prototyping techniques were explored. The completed parts were compared on the basis of manufacturing time, quality and strength of parts obtained, manufacturing cost and also in vitro performances. Based on these studies, it was concluded that selective laser sintering (SLS) is the most appropriate method for the quick production of prototype parts for evaluation of pump performance.

Blood Flow Velocity↗
PubMed2002

Quantification of mouse glial cell-line derived neurotrophic factor family receptor alpha 2 alternatively spliced isoforms by real time detection PCR using SYBR Green I.

Neurturin (NTN) belongs to the glial cell-line derived neurotrophic factor (GDNF) family of growth factors. Both NTN and GDNF have been shown to potently prevent the degeneration of dopaminergic neuron in vitro and in vivo. The GDNF family receptor alpha 2 (GFR alpha-2) is the preferred receptor for NTN. In addition to the known full-length isoform (GFR alpha-2a), we have previously reported the isolation of two novel alternatively spliced isoforms (GFR alpha-2b and GFR alpha-2c). All three isoforms are expressed in all mammalian tissues examined, including human fetal brain. However, the expression levels of these isoforms have yet to be quantified. In this report, we have developed a real time polymerase chain reaction (PCR) detection method using SYBR Green I to detect the expression levels of the three splice variants (GFR alpha-2a, GFR alpha-2b and GFR alpha-2c). Of the three isoforms, GFR alpha-2a was found to be the most abundant receptor expressed in the whole murine brain. The real time PCR detection method using SYBR Green I developed in this report can be used to unambiguously quantitate expression levels of the GFR alpha-2 isoforms and can be extended to the quantitation of other alternatively spliced isoforms.

Alternative Splicing↗
PubMed2002

A computational study of the effects of inlet guide vanes on the performance of a centrifugal blood pump.

This article presents computational studies on the effects of inlet guide vanes (IGVs) on the flow pattern and shear stress in a centrifugal blood pump. The effect of IGVs is to introduce a pre-swirl to fluid particles entering the impeller with the intention that the fluid particles will travel along the blade profile. Currently, most commercial centrifugal blood pumps employ straight radial impeller blades that are not hydrodynamically ideal for a good flow pattern within the blade passage. Flow separation and formation of vortices within the blade passage are believed to increase the degree of hemolysis and thrombosis. These are causes for blood clotting that will lead to malfunctioning of ventricular assist devices. Four IGVs of different geometrical profiles have been numerically investigated using a commercial software program CFX-Tascflow. The pump is operated at 2,000 rpm, and the results revealed that the relative flow patterns in the blade passage have been dramatically altered. The size of the vortices was reduced, and the pressure contours indicated a gradual rise from the impeller leading edge to the trailing edge. However, inclusion of IGV causes a drop in the pressure head generated. Higher frictional losses are incurred as fluid particles passed through the IGV. In addition, the IGV modifies the inlet velocity triangles, and this also contributes to a drop in the pressure head generated that is consistent with Euler's pump theory. The change in the flow patterns and the gradual variation of the pressure contours have led to lower shear stress within the blade passages as compared to the case without IGVs.

Blood Flow Velocity↗
PubMed2002

Numerical investigation of the effect of blade geometry on blood trauma in a centrifugal blood pump.

Fluid dynamic forces in centrifugal blood pump impellers are of key importance in destruction of red blood cells (RBCs) because high rotational speed leads to strong interaction between the impeller and the RBCs. In this paper, three-dimensional models of five different blade geometries are investigated numerically using the commercial software CFX-TASCflow, and the streaklines of RBCs are obtained using the Lagrangian particle tracking method. In reality, RBCs pass through the pump along complicated paths resulting in a highly irregular loading condition for each RBC. In order to enable the prediction of blood damage under the action of these complex-loading conditions, a cumulative damage model for RBCs was adopted in this paper. The numerically simulated percent hemoglobin (%HB) released as RBCs traversed the impeller and volute was examined. It was observed that the residence time of particles in the blade passage is a critical factor in determining hemolytic effects. This, in turn, is a function of the blade geometry. In addition, it was observed that the volute profile is an important influence on the computed HB% released.

Computer Simulation↗
PubMed2002

Lichen sclerosus. A review.

Lichen sclerosus is a chronic inflammatory skin condition that can cause substantial physical and psychological morbidity. It most commonly affects women in the anogenital region, but may affect any area of skin in either sex at any age. Not only does it cause itching and soreness, but also urinary and sexual problems. There is an increased risk of developing squamous cell carcinoma in the genital area in both female and male sufferers, thus long term follow-up may be justified. The aetiology of Lichen sclerosus is unknown but genetic factors play a role, and chronic infection had been postulated but not proven. The association with autoimmune disease is also well recognized. The mainstay of treatment for genital lichen sclerosus is potent topical steroid. Surgery may be required only to relieve the effect of scarring. Current research to understand the pathogenesis of disease may allow us to target specific intervention in the future.

Female↗
PubMed2001

Evaluation of various evoked potential techniques for spinal cord monitoring during scoliosis surgery.

STUDY DESIGN: This prospective study compared the outcomes of different evoked potential (EP) techniques for intraoperative spinal cord monitoring. OBJECTIVES: To evaluate the reliability of different EP techniques administered during scoliosis surgery. SUMMARY OF BACKGROUND DATA: A number of different methods of intraoperative spinal cord monitoring are available. Because each has its own advantages and limitations, multimodal spinal cord monitoring has been proposed to improve monitoring reliability. MATERIALS AND METHODS: Cortical somatosensory-evoked potential (CSEP), cortical motor-evoked potential (CMEP), spinal somatosensory-evoked potential (SSEP), and spinal cord-evoked potential (SCEP) were applied simultaneously to 30 patients undergoing surgical correction for spinal deformity. The presence of the EP waveforms and their reproducibilities over separate tests were compared. In addition, the monitoring outcomes were evaluated with the clinical results. RESULTS: Of the 30 patients, CSEP waveforms were successfully recorded in 28 cases (93%), SCEP in 25 cases (83%), CMEP in 24 cases (80%), and SSEP in 21 cases (70%). Latencies of each EP technique showed no significant variability. However, amplitudes showed significant differences between different techniques. SCEP and CMEP showed clearer waveforms of greater amplitude that could be detected faster than CSEP and SSEP waveforms. SCEP and SSEP waveforms were more easily influenced by the surgical procedure. CONCLUSION: CSEP and CMEP are recommended for routine monitoring, so that both ascending and descending tracts are monitored. If adequate signals for either of these proposed monitoring methods cannot be easily obtained, SSEP can substitute for CSEP, whereas SCEP can substitute for CMEP.

Adolescent↗
PubMed2001

Effect of stimulus pulse duration on intraoperative somatosensory evoked potential (SEP) monitoring.

The effect of the stimulus duration on the amplitude and latency of intraoperative somatosensory evoked potential (SEP) was studied in 30 patients with idiopathic scoliosis undergoing surgery. Constant current square-wave electrical stimulation was applied to the posterior tibial nerve at a rate of 5.1 Hz. The effects of both the pulse duration and the stimulus current density on the intraoperative SEP were evaluated. Amplitudes and latencies of SEP were analyzed by one-way parametric analysis of variance. SEP signal recording was found to be difficult if the stimulus duration was less than 0.05 ms. The stimulus duration had no significant effect on the latencies of the SEP, but the amplitude of the SEP showed significant changes with differing stimulus durations. The SEP amplitudes were found with significant increases in pulse durations less than 0.3 ms. Stimulus pulse duration has a significant effect on SEP amplitude, and this should be taken into consideration during intraoperative SEP monitoring. A pulse duration of 0.3 ms is recommended for SEP using posterior tibial nerve stimulation.

Adolescent↗
PubMed2001

Back muscle contraction patterns of patients with low back pain before and after rehabilitation treatment: an electromyographic evaluation.

The aims of this study were to conduct a comparative investigation of muscle function between patients with low back pain (LBP) and healthy persons, and to determine whether intensive rehabilitation can change back muscle contraction synergy. Twenty healthy persons and 20 patients with chronic LBP were asked to perform symmetrical and asymmetric tasks. The patients with LBP were tested in the weeks immediately before and after 12 weeks of LBP rehabilitation. Tasks include "carrying" weights up and down and with a 45 degrees left rotation. Eight-channel surface electromyographic electrodes were placed on the surface of paraspinal muscles over the lumbar region. Correlations between the right and left corresponding muscles and between values before and after treatment were determined. Lifting capacity for patients with LBP were also measured before and after treatment. Results from electromyographic profiles showed that the muscle activity strategies varied between healthy persons and patients with LBP. The correlation coefficients for spinal muscles have shown very reproducible intrasubject muscle contraction synergies. Unbalanced electromyographic patterns found in patients with LBP given symmetrical tasks were not affected by rehabilitation treatment.

Adult↗
PubMed2001

Effect of stimulation parameters on intraoperative spinal cord evoked potential monitoring.

The purpose of this study was to investigate the effects of the stimulus parameters on spinal cord evoked potential (SCEP) and to recommend a practical epidural stimulation protocol for intraoperative spinal cord monitoring. This prospective study compared the latencies and amplitudes of SCEP obtained on epidural stimulation of 30 patients with scoliosis under anesthesia using different stimulus pulse duration and stimulation rates. SCEP was found to be undetectable with shorter stimulus duration (<0.05 ms). The SCEP latencies did not show any significant difference among different stimulation parameters. However, the SCEP amplitude showed significant changes with differing stimulus durations. The SCEP amplitudes were found to significantly decrease when the pulse durations become shorter than 0.2 ms. Stimulus parameters showed significant effects on SCEP amplitude but not latency. Stimulus rates in the range of 21 to 61 Hz are equivalent for quick and reliable detection of SCEP. Considering the short latency of SCEP, a pulse duration of 0.2 ms is recommended for SCEP using epidural stimulation.

Adolescent↗