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Articles by K Choi
Total Records ( 5 ) for K Choi
  B Lu , N Congdon , X Liu , K Choi , D. S. C Lam , M Zhang , M Zheng , Z Zhou , L Li , A Sharma and Y. Song
 

Objective  To study the associations between near work, outdoor activity, and myopia among children attending secondary school in rural China.

Methods  Among a random cluster sample of 1892 children in Xichang, China, subjects with an uncorrected acuity of 6/12 or less in either eye (n = 984) and a 25% sample of children with normal vision (n = 248) underwent measurement of refractive error. Subjects were administered a questionnaire on parental education, time spent outdoors, and weekly time spent engaged in and preferred working distance for a variety of near-work activities.

Results  Among 1232 children with refraction data, 998 (81.0%) completed the near-work survey. Their mean age was 14.6 years (SD, 0.8 years), 55.6% were girls, and 83.1% had myopia of –0.5 diopters or less (more myopia) in both eyes. Time and diopter-hours spent on near activities did not differ between children with and without myopia. In regression models, time spent on near activities and time outdoors were unassociated with myopia, adjusting for age, sex, and parental education.

Conclusions  These and other recent results raise some doubts about the association between near work and myopia. Additional efforts to identify other environmental factors associated with myopia risk and that may be amenable to intervention are warranted.

  M Zhang , N Congdon , L Li , Y Song , K Choi , Y Wang , Z Zhou , X Liu , A Sharma , W Chen and D. S. C. Lam
 

Objective  To study the effect of myopia and spectacle wear on bicycle-related injuries in rural Chinese students. Myopia is common among Chinese students but few studies have examined its effect on daily activities.

Methods  Data on visual acuity, refractive error, current spectacle wear, and history of bicycle use and accidents during the past 3 years were sought from 1891 students undergoing eye examinations in rural Guangdong province.

Results  Refractive and accident data were available for 1539 participants (81.3%), among whom the mean age was 14.6 years, 52.5% were girls, 26.8% wore glasses, and 12.9% had myopia of less than –4 diopters in both eyes. More than 90% relied on bicycles to get to school daily. A total of 2931 accidents were reported by 423 participants, with 68 requiring medical attention. Male sex (odds ratio, 1.55; P < .001) and spectacle wear (odds ratio, 1.38; P = .04) were associated with a higher risk of accident, but habitual visual acuity and myopia were unassociated with the crash risk, after adjusting for age, sex, time spent riding, and risky riding behaviors.

Conclusion  These results may be consistent with data on motor vehicle accidents implicating peripheral vision (potentially compromised by spectacle wear) more strongly than central visual acuity in mediating crash risk.

  K. M Kim , H Cho , K Choi , J Kim , B. W Kim , Y. G Ko , S. K Jang and Y. K. Kim
 

During or right after mRNA export via the nuclear pore complex (NPC) in mammalian cells, mRNAs undergo translation mediated by nuclear cap-binding proteins 80 and 20 (CBP80/20). After CBP80/20-dependent translation, CBP80/20 is replaced by cytoplasmic cap-binding protein eIF4E, which directs steady-state translation. Nonsense-mediated mRNA decay (NMD), one of the best-characterized mRNA surveillance mechanisms, has been shown to occur on CBP80/20-bound mRNAs. However, despite the tight link between CBP80/20-dependent translation and NMD, the underlying molecular mechanism and cellular factors that mediate CBP80/20-dependent translation remain obscure. Here, we identify a new MIF4G domain-containing protein, CTIF (CBP80/20-dependent translation initiation factor). CTIF interacts directly with CBP80 and is part of the CBP80/20-dependent translation initiation complex. Depletion of endogenous CTIF from an in vitro translation system selectively blocks the translation of CBP80-bound mRNAs, while addition of purified CTIF restores it. Accordingly, down-regulation of endogenous CTIF abrogates NMD. Confocal microscopy shows that CTIF is localized to the perinuclear region. Our observations demonstrate the existence of CBP80/20-dependent translation and support the idea that CBP80/20-dependent translation is mechanistically different from steady-state translation through identification of a specific cellular protein, CTIF.

  J. H Ahn , J. H Bae , Y. S Lee , K Choi , T. S Bae and J. H. Wang
  Background

An anterolateral approach to the tibial tunnel of posterior cruciate ligament reconstruction is used to reduce the sharpness of the graft-tunnel angle, the so-called killer turn effect. However, with the anterolateral approach, the tunnel might be widened into an ovoid shape because of the small angle between the tunnel and the anterolateral cortex.

Hypothesis

The fixation strength of the posterior cruciate ligament graft in the tibial tunnel will be weaker in the anterolateral approach compared with the anteromedial approach.

Study Design

Controlled laboratory study.

Methods

Twenty paired cadaveric tibias were used. Tibial tunnels were made using following approaches: an anteromedial approach for 10 tibias and an anterolateral approach for 10 tibias. The anterior cortex-tunnel angle and the diameter of the tunnel entrance were measured by 2-dimensional computed tomographic scans. After fixation of the Achilles tendon allograft with a biodegradable screw, the maximal strength of the graft at failure was measured using a materials testing machine.

Results

The mean cortex-tunnel angle was 47.5° ± 9.3° in the anteromedial approach group and 28.3° ± 7.4° in the anterolateral approach group. The mean long diameter of the tunnels in the anteromedial approach group was 10.6 ± 1.0 mm and in the anterolateral approach group it was 14.0 ± 1.5 mm. These two parameters showed statistically significant differences between the 2 groups (P < .01). The mean maximum load at failure for the anteromedial approach group was 385.4 ± 139.7 N, and for the anterolateral approach group it was 225.1 ± 144.1 N. This difference was statistically significant (P = .021).

Conclusion

The anterolateral approach resulted in a tunnel with a wider entrance, a more acute cortex-tunnel angle, and a lower maximal load at failure compared with tunnels created using the anteromedial approach.

Clinical Relevance

The use of additional fixation methods, such as post ties or ligament washers and screws, should be considered when using an anterolateral approach for tibial tunnel of posterior cruciate ligament reconstruction.

  K Choi , Y. H Ahn , D. L Gibbons , H. T Tran , C. J Creighton , L Girard , J. D Minna , F. X. F Qin and J. M. Kurie
 

Notch signaling is activated in a subset of non-small cell lung cancer cells because of overexpression of Notch3, but the role of Notch ligands has not been fully defined. On the basis of gene expression profiling of a panel of non-small cell lung cancer cell lines, we found that the predominant Notch ligands were JAG1, JAG2, DLL1, and DLL3. Given that Notch ligands reportedly have overlapping receptor binding specificities, we postulated that they have redundant biological roles. Arguing against this hypothesis, we found that JAG1 and JAG2 were differentially regulated; JAG1 expression was dependent upon epidermal growth factor receptor (EGFR) activation in HCC827 cells, which require EGFR for survival, whereas JAG2 expression was EGFR-independent in these cells. Furthermore, HCC827 cells underwent apoptosis following depletion of JAG1 but not JAG2, whereas co-culture experiments revealed that depletion of JAG2, but not JAG1, enhanced the ability of HCC827 cells to chemoattract THP-1 human monocytes. JAG2-depleted HCC827 cells expressed high levels of inflammation-related genes, including interleukin 1 (IL1) and a broad range of IL1-regulated cytokines, which was attenuated by inhibition of IL1 receptor (IL1R). Our findings suggest that JAG1 and JAG2 have distinct biological roles including a previously undiscovered role for JAG2 in regulating the expression of cytokines that can promote antitumor immunity.

 
 
 
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