Chromosome-level genome assembly and annotation of rare and endangered tropical bivalve, Tridacna crocea.

Tridacna crocea is an ecologically important marine bivalve inhabiting tropical coral reef waters. High quality and available genomic resources will help us understand the population structure and genetic diversity of giant clams. This study reports a high-quality chromosome-scale T. crocea genome sequence of 1.30 Gb, with a scaffold N50 and contig N50 of 56.38 Mb and 1.29 Mb, respectively, which was assembled by combining PacBio long reads and Hi-C sequencing data. Repetitive sequences cover 71.60% of the total length, and a total of 25,440 protein-coding genes were annotated. A total of 1,963 non-coding RNA (ncRNA) were determined in the T. crocea genome, including 62 micro RNA (miRNA), 58 small nuclear RNA (snRNA), 83 ribosomal RNA (rRNA), and 1,760 transfer RNA (tRNA). Phylogenetic analysis revealed that giant clams diverged from oyster about 505.7 Mya during the evolution of bivalves. The genome assembly presented here provides valuable genomic resources to enhance our understanding of the genetic diversity and population structure of giant clams.

Effects of Gestational Magnetic Resonance Imaging on Methylation Status of Leptin Promoter in the Placenta and Cord Blood.

Over the past two decades, magnetic resonance imaging (MRI) has been widely used for diagnosis in gestational women. Though it has several advantages, animal and human studies on the safety of MRI for the fetus remain inconclusive. Epigenetic modifications, which are crucial for cellular functioning, are prone to being affected by environmental changes. Therefore, we hypothesized that MRI during gestation may cause epigenetic modification alterations. Here, we investigated DNA methylation patterns of leptin promoter in the placenta and cord blood of women exposed to MRI during gestation. Results showed that average methylation levels of leptin in the placenta and cord blood were not affected by MRI. We also found that the methylation levels in the placenta and cord blood were not affected by different magnetic fields (1.5T and 3.0T MRI). However, if pregnant women were exposed to MRI at 15 to 20 weeks of gestation, the methylation level of leptin in cord blood was visibly lower than that of pregnant women exposed to MRI after 20-weeks of gestation (P = 0.037). mRNA expression level of leptin in cord blood was also altered, though mRNA expression of leptin in the placenta was not significantly affected. Therefore, we concluded that gestational MRI may not have major effects on the methylation level of leptin in cord blood and the placenta except for MRI applied before 20 weeks of gestation.

[Diagnostic role of contrast-enhanced whole-heart coronary magnetic resonance angiography in the evaluation of coronary artery disease].

OBJECTIVE: To prospectively evaluate the diagnostic effectiveness of contrast-enhanced whole-heart coronary magnetic resonance angiography (CE-CMRA) in patients with suspected coronary artery disease (CAD) with conventional coronary angiography as the reference standard. METHODS: A total of 72 subjects with suspected CAD scheduled for conventional coronary angiography underwent 3.0-T contrast-enhanced whole-heart CE-MRA. The imaging quality, diagnostic performance and accuracy of CE-MRA for detecting significant stenoses ( ≥ 50%) in coronary arteries were compared with that of quantitative coronary angiography (QCA). RESULTS: The whole-heart CE-MRA examinations were successfully completed in 65 patients. Among 809 segments with a reference luminal diameter ≥ 1.5 mm on CAG, 105 segments on CE-MRA were evaluated as nonassessable(13.0%) and 704 segments assessable.If 105 nonassessable segments on CE-MRA were considered to have significant stenoses, CE-MRA correctly identified CAD in 36/38 patients and correctly ruled out CAD in 21/27 patients. CE-MRA yielded 93.8%, 85.4%, 53.2% and 98.9% for diagnostic sensitivity, specificity, positive predicative value(PPV) and negative predicative value(NPV) on the basis of per-segment versus 94.7%, 77.8%, 85.7% and 91.3% respectively on the basis of per-patient. CONCLUSION: CE-CMRA provides sufficiently high sensitivity and NPV, but moderate specificity and PPV for the diagnosis of CAD.It may be used as an optional imaging modality for CAD screening.

Distinction between postoperative recurrent glioma and radiation injury using MR diffusion tensor imaging.

INTRODUCTION: This study aims to evaluate the differentiated effectiveness of MR diffusion tensor imaging (DTI) to postoperative recurrent glioma and radiation injury. METHODS: Conventional MRI and DTI examination were performed using Siemens 3.0 T MR System for patients with new contrast-enhancing lesions at the site of treated tumor with postoperative radiotherapy. The region of interest was manually drawn on ADC and FA maps at contrast-enhancing lesion area, peri-lesion edema, and the contra-lateral normal white matter. Then ADC and FA values were measured and, the ADC ratio and FA ratio were calculated. Twenty patients with recurrent tumor and 15 with radiation injury were confirmed by histopathologic examination (23 patients) and clinical imaging follow-up (12 patients), respectively. The mean ADC ratio and FA ratio were compared between the two lesion types. RESULTS: The mean ADC ratio at contrast-enhancing lesion area was significantly lower in patients with recurrent tumor (1.34 ± 0.15) compared to that with radiation injury (1.62 ± 0.17; P < 0.01). The mean FA ratio at contrast-enhancing lesion area was significantly higher in patients with recurrent tumor (0.45 ± 0.03) compared to that with radiation injury (0.32 ± 0.03; P < 0.01). Neither mean ADC ratio nor FA ratio in edema areas had statistical difference between the two groups. A recurrent tumor was suggested when either ADC ratio <1.65 or/and FA ratio >0.36 at contrast-enhancing lesion area according to the receiver operating characteristics curve analysis. Three patients with recurrent tumor and two with radiation injury were misclassified. CONCLUSION: DTI is a valuable method to distinguish postoperative recurrent glioma and radiation injury.