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Articles by C Lee
Total Records ( 8 ) for C Lee
  S. F Thieme , T. R. C Johnson , C Lee , J McWilliams , C. R Becker , M. F Reiser and K. Nikolaou
 

OBJECTIVE. The purpose of this study was to assess the feasibility and diagnostic value of dual-energy CT iodine mapping at pulmonary CT angiography.

SUBJECTS AND METHODS. Ninety-three patients underwent CT angiography with the dual-energy technique on a dual-source CT scanner. Postprocessing was used to map iodine in the lung parenchyma on the basis of its spectral behavior, and image quality was assessed by two readers. Iodine distribution patterns were rated as homogeneous, patchy, or circumscribed defects. Conventional CT angiographic images reconstructed from the same data sets were reviewed for the presence and localization of pulmonary embolism, whether embolic occlusion was partial or complete, and the presence of changes in the lung parenchyma. Dual-energy perfusion findings were correlated with the CT angiographic and lung-window CT findings in per-patient and per-segment analyses.

RESULTS. Iodine distribution was homogeneous in 49 patients, of whom CT angiography showed no pulmonary embolism in 46 patients and nonocclusive pulmonary emboli in three patients. Images of 29 patients showed a patchy pattern; 24 of these patients had no pulmonary embolism, and five had nonocclusive pulmonary emboli with solely nonocclusive intravascular clots. Images of 15 patients showed segmental or subsegmental defects; four of these patients had evidence of pulmonary embolism, and 11 had occlusive pulmonary emboli with at least one occlusive clot in the pulmonary vasculature.

CONCLUSION. Dual-energy CT is reliable in the detection of defects in pulmonary parenchymal iodine distribution that correspond to embolic vessel occlusion.

  E Gorell , C Lee , C Munoz and A. L. S. Chang
 

Objective  To investigate whether the adoption of Western culture is associated with attitudes and practices promoting sun exposure among Asian Americans.

Design  Survey conducted from November 28, 2007, to January 28, 2008.

Setting  Primarily northern California community groups via online survey.

Participants  Adult volunteers who self-identified as Asian American.

Main Outcome Measures  Results based on 546 questionnaires returned.

Results  The overall response rate was 74.4%. Multivariate regression analysis controlling for age and skin type showed that westernization (as determined by generation in the United States, location raised, or self-rated acculturation) was associated with attitudes and behaviors promoting sun exposure (including the belief that having a tan is attractive, negative attitudes toward use of sunscreen and sun protective clothing, and increased weekend sun exposure, lying out to get a tan, and tanning bed use) at a level of P < .05.

Conclusions  Our data suggest that adoption of Western culture may be associated with attitudes and behaviors promoting sun exposure among Asian Americans. This group should be targeted by dermatologists for increased education regarding sun protection, solar damage, and skin cancer prevention and detection.

  R. W.K Chiu , H Sun , R Akolekar , C Clouser , C Lee , K McKernan , D Zhou , K. H Nicolaides and Y.M. D. Lo
 

Background: Noninvasive prenatal diagnosis of trisomy 21 (T21) has recently been shown to be achievable by massively parallel sequencing of maternal plasma on a sequencing-by-synthesis platform. The quantification of several other human chromosomes, including chromosomes 18 and 13, has been shown to be less precise, however, with quantitative biases related to the chromosomal GC content.

Methods: Maternal plasma DNA from 10 euploid and 5 T21 pregnancies was sequenced with a sequencing-by-ligation approach. We calculated the genomic representations (GRs) of sequenced reads from each chromosome and their associated measurement CVs and compared the GRs of chromosome 21 (chr21) for the euploid and T21 pregnancies.

Results: We obtained a median of 12 x 106 unique reads (21% of the total reads) per sample. The GRs deviated from those expected for some chromosomes but in a manner different from that previously reported for the sequencing-by-synthesis approach. Measurements of the GRs for chromosomes 18 and 13 were less precise than for chr21. z Scores of the GR of chr21 were increased in the T21 pregnancies, compared with the euploid pregnancies.

Conclusions: Massively parallel sequencing-by-ligation of maternal plasma DNA was effective in identifying T21 fetuses noninvasively. The quantitative biases observed among the GRs of certain chromosomes were more likely based on analytical factors than biological factors. Further research is needed to enhance the precision for measuring for the representations of chromosomes 18 and 13.

  J. R Edwards , A. H O'Donnell , R. A Rollins , H. E Peckham , C Lee , M. H Milekic , B Chanrion , Y Fu , T Su , H Hibshoosh , J. A Gingrich , F Haghighi , R Nutter and T. H. Bestor
 

Abnormalities of genomic methylation patterns are lethal or cause disease, but the cues that normally designate CpG dinucleotides for methylation are poorly understood. We have developed a new method of methylation profiling that has single-CpG resolution and can address the methylation status of repeated sequences. We have used this method to determine the methylation status of >275 million CpG sites in human and mouse DNA from breast and brain tissues. Methylation density at most sequences was found to increase linearly with CpG density and to fall sharply at very high CpG densities, but transposons remained densely methylated even at higher CpG densities. The presence of histone H2A.Z and histone H3 di- or trimethylated at lysine 4 correlated strongly with unmethylated DNA and occurred primarily at promoter regions. We conclude that methylation is the default state of most CpG dinucleotides in the mammalian genome and that a combination of local dinucleotide frequencies, the interaction of repeated sequences, and the presence or absence of histone variants or modifications shields a population of CpG sites (most of which are in and around promoters) from DNA methyltransferases that lack intrinsic sequence specificity.

  D Kang , S Cho , C Lee , J. G Myoung and J. Na
 

Kang, D., Cho, S., Lee, C., Myoung, J-G. and Na, J. 2009. Ex situ target-strength measurements of Japanese anchovy (Engraulis japonicus) in the coastal Northwest Pacific. – ICES Journal of Marine Science, 66: 1219–1224.

The Japanese anchovy (Engraulis japonicus) is an important species in regard to the fisheries and ecology of the coastal Northwest Pacific. Measurements of ex situ target strength (TS; dB re 1 m2) were made on live anchovy using 38, 120, and 200 kHz split-beam echosounders. The fish were tethered using small hooks attached to their mouths. During the acoustic measurements, an underwater video camera was used to continuously monitor fish behaviour and tilt-angle (). Data for 35 individual anchovy ranging from immature to adult sizes (total lengths LT = 4.8–12.2 cm) were analysed. Least-squares regression fits of TS vs. log(LT) were: TS38 kHz = 20 log(LT) – 65.8 (r2 = 0.82), TS120 kHz = 20 log(LT) – 68.4 (r2 = 0.84), and TS200 kHz = 20 log(LT) – 69.1 (r2 = 0.71). The LT vs. wet weight (W; g) relationship for these fish was W = 0.0036 LT3.204. The mean for anchovy swimming freely in a large seawater tank was 9.1° (s.d. = 13.1°). These ex situ measurements of TS, LT, W, and can be applied to improve acoustic estimates of Japanese anchovy biomass.

  R Zhong , C Lee and Z. H. Ye
 

We report the genome-wide analysis of direct target genes of SND1 and VND7, two Arabidopsis thaliana NAC domain transcription factors that are master regulators of secondary wall biosynthesis in fibers and vessels, respectively. Systematic mapping of the SND1 binding sequence using electrophoretic mobility shift assay and transactivation analysis demonstrated that SND1 together with other secondary wall NACs (SWNs), including VND6, VND7, NST1, and NST2, bind to an imperfect palindromic 19-bp consensus sequence designated as secondary wall NAC binding element (SNBE), (T/A)NN(C/T) (T/C/G)TNNNNNNNA(A/C)GN(A/C/T) (A/T), in the promoters of their direct targets. Genome-wide analysis of direct targets of SND1 and VND7 revealed that they directly activate the expression of not only downstream transcription factors, but also a number of non-transcription factor genes involved in secondary wall biosynthesis, cell wall modification, and programmed cell death, the promoters of which all contain multiple SNBE sites. SND1 and VND7 directly regulate the expression of a set of common targets but each of them also preferentially induces a distinct set of direct targets, which is likely attributed to their differential activation strength toward SNBE sites. Complementation study showed that the SWNs were able to rescue the secondary wall defect in the snd1 nst1 mutant, indicating that they are functionally interchangeable. Together, our results provide important insight into the complex transcriptional program and the evolutionary mechanism underlying secondary wall biosynthesis, cell wall modification, and programmed cell death in secondary wall-containing cell types.

  C Lee , Q Teng , W Huang , R Zhong and Z. H. Ye
 

Xylan is the second most abundant polysaccharide in dicot wood. Unraveling the biosynthetic pathway of xylan is important not only for our understanding of the process of wood formation but also for our rational engineering of wood for biofuel production. Although several glycosyltransferases are implicated in glucuronoxylan (GX) biosynthesis in Arabidopsis, whether their close orthologs in woody tree species are essential for GX biosynthesis during wood formation has not been investigated. In fact, no studies have been reported to evaluate the effects of alterations in secondary wall-associated glycosyltransferases on wood formation in tree species. In this report, we demonstrate that PoGT47C, a poplar glycosyltransferase belonging to family GT47, is essential for the normal biosynthesis of GX and the normal secondary wall thickening in the wood of the hybrid poplar Populus alba x tremula. RNA interference (RNAi) inhibition of PoGT47C resulted in a drastic reduction in the thickness of secondary walls, a deformation of vessels and a decreased amount of GX in poplar wood. Structural analysis of GX using nuclear magnetic resonance (NMR) spectroscopy demonstrated that the reducing end of GX from poplar wood contains the tetrasaccharide sequence, β-d-Xylp-(1->3)--l-Rhap-(1->2)--d-GalpA-(1->4)-d-Xylp, and that its abundance was significantly decreased in the GX from the wood of the GT47C-RNAi lines. The transgenic wood was found to yield more glucose by cellulase digestion than the wild-type wood, indicating that the GX reduction in wood reduces the recalcitrance of wood to cellulase digestion. Together, these results provide direct evidence demonstrating that the PoGT47C glycosyltransferase is essential for normal GX biosynthesis in poplar wood and that GX modification could improve the digestibility of wood cellulose by cellulase.

  Z Tang , P Arjunan , C Lee , Y Li , A Kumar , X Hou , B Wang , P Wardega , F Zhang , L Dong , Y Zhang , S. Z Zhang , H Ding , R. N Fariss , K. G Becker , J Lennartsson , N Nagai , Y Cao and X. Li
 

Platelet-derived growth factor CC (PDGF-CC) is the third member of the PDGF family discovered after more than two decades of studies on the original members of the family, PDGF-AA and PDGF-BB. The biological function of PDGF-CC remains largely to be explored. We report a novel finding that PDGF-CC is a potent neuroprotective factor that acts by modulating glycogen synthase kinase 3β (GSK3β) activity. In several different animal models of neuronal injury, such as axotomy-induced neuronal death, neurotoxin-induced neuronal injury, 6-hydroxydopamine–induced Parkinson’s dopaminergic neuronal death, and ischemia-induced stroke, PDGF-CC protein or gene delivery protected different types of neurons from apoptosis in both the retina and brain. On the other hand, loss-of-function assays using PDGF-C null mice, neutralizing antibody, or short hairpin RNA showed that PDGF-CC deficiency/inhibition exacerbated neuronal death in different neuronal tissues in vivo. Mechanistically, we revealed that the neuroprotective effect of PDGF-CC was achieved by regulating GSK3β phosphorylation and expression. Our data demonstrate that PDGF-CC is critically required for neuronal survival and may potentially be used to treat neurodegenerative diseases. Inhibition of the PDGF-CC–PDGF receptor pathway for different clinical purposes should be conducted with caution to preserve normal neuronal functions.

 
 
 
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