Purpose-To develop and test a time-efficient, free-breathing, whole-heart T 2 mapping technique at 3.0T.Methods-ECG-triggered three-dimensional images were acquired with different T 2 preparations at 3.0T during free breathing. Respiratory motion was corrected with a navigatorguided motion correction framework at near perfect efficiency. Image intensities were fit to a mono-exponential function to derive myocardial T 2 maps. The proposed approach (3D-FB-MoCo) was studied in ex-vivo hearts and kidneys, healthy volunteers and canines with acute myocardial infarction (AMI).Results-Ex-vivo T 2 values from proposed 3D T 2 -prep GRE was not different from 2D SE (p=0.7) and T 2 -prep bSSFP (p=0.7). In volunteers, compared to the proposed approach (3D-FBMoCo) and breath-held 2D T 2 -prep bSSFP (2D-BH), non-motion-corrected (3D-FB-Non-MoCo) myocardial T 2 was longer, had larger coefficient-of-variation (COV) and lower image quality (IQ) score (T 2 =40.3 ms, COV=38% and IQ=2.3, all p<0.05). Conversely, the mean and COV and IQ of 3D-FB-MoCo (T 2 =37.7 ms, COV=17% and IQ=3.5.) and 2D-BH (T 2 =38.0 ms, COV=15% and IQ=3.8) were not different (p=0.99, p=0.74, and p=0.14, respectively). In AMI, T 2 values and edema volumes from 3D-FB-MoCo and 2D-BH approaches were closely correlated (R 2 =0.88 and 0.96, respectively). Conclusion-The proposed whole-heart T 2 mapping approach can be performed within 5 minutes with similar accuracy to 2D-BH T 2 mapping approach.

We developed a simple, direct and cost-effective approach to search for the most likely target genes of a known microRNA (miRNA) in vitro. We term this method ‘labeled miRNA pull-down (LAMP)’ assay system. Briefly, the pre-miRNA is labeled with digoxigenin (DIG), mixed with cell extracts and immunoprecipitated by anti-DIG antiserum. When the DIG-labeled miRNA and bound mRNA complex are obtained, the total cDNAs are then subcloned and sequenced, or RT–PCR-amplified, to search for the putative target genes of a known miRNA. After successfully identifying the known target genes of Caenorhabditis elegans miRNAs lin-4 and let-7 and zebrafish let-7, we applied LAMP to find the unknown target gene of zebrafish miR-1, which resulted in the identification of hand2. We then confirmed hand2 as a novel target gene of miR-1 by whole-mount in situ hybridization and luciferase reporter gene assay. We further validated this target gene by microarray analysis, and the results showed that hand2 is the top-scoring among 302 predicted putative target genes. We concluded that LAMP is an experimental approach for high-throughput identification of the target gene of known miRNAs from both C. elegans and zebrafish, yielding fewer false positive results than those produced by using only the bioinformatics approach.

Transcription factor Six1a plays important roles in morphogenesis, organogenesis, and cell differentiation. However, the role of Six1a during zebrafish cranial muscle development is still unclear. Here, we demonstrated that Six1a was required for sternohyoideus, medial rectus, inferior rectus, and all pharyngeal arch muscle development. Although Six1a was also necessary for myod and myogenin expression in head muscles, it did not affect myf5 expression in cranial muscles that originate from head mesoderm. Overexpression of myod enabled embryos to rescue all the defects in cranial muscles induced by injection of six1a-morpholino (MO), suggesting that myod is directly downstream of six1a in controlling craniofacial myogenesis. However, overexpression of six1a was unable to rescue arch muscle defects in the tbx1- and myf5-morphants, suggesting that six1a is only involved in myogenic maintenance, not its initiation, during arch muscle myogenesis. Although the craniofacial muscle defects caused by pax3-MO phenocopied those induced by six1a-MO, injection of six1a, myod or myf5 mRNA did not rescue the cranial muscle defects in pax3 morphants, suggesting that six1a and pax3 do not function in the same regulatory network. Therefore, we proposed four putative regulatory pathways to understand how six1a distinctly interacts with either myf5 or myod during zebrafish craniofacial muscle development.

Myocardial blood flow (MBF) is the critical determinant of cardiac function. However, its response to increases in partial pressure of arterial CO 2 (PaCO 2 ), particularly with respect to adenosine, is not well characterized because of challenges in blood gas control and limited availability of validated approaches to ascertain MBF in vivo. Methods: By prospectively and independently controlling PaCO 2 and combining it with 13 N-ammonia PET measurements, we investigated whether a physiologically tolerable hypercapnic stimulus (;25 mm Hg increase in PaCO 2 ) can increase MBF to that observed with adenosine in 3 groups of canines: without coronary stenosis, subjected to non-flow-limiting coronary stenosis, and after preadministration of caffeine. The extent of effect on MBF due to hypercapnia was compared with adenosine. Results: In the absence of stenosis, mean MBF under hypercapnia was 2.1 6 0.9 mL/min/g and adenosine was 2.2 6 1.1 mL/min/g; these were significantly higher than at rest (0.9 6 0.5 mL/min/g, P , 0.05) and were not different from each other (P 5 0.30). Under left-anterior descending coronary stenosis, MBF increased in response to hypercapnia and adenosine (P , 0.05, all territories), but the effect was significantly lower than in the left-anterior descending coronary territory (with hypercapnia and adenosine; both P , 0.05). Mean perfusion defect volumes measured with adenosine and hypercapnia were significantly correlated (R 5 0.85) and were not different (P 5 0.12). After preadministration of caffeine, a known inhibitor of adenosine, resting MBF decreased; and hypercapnia increased MBF but not adenosine (P , 0.05). Conclusion: Arterial blood CO 2 tension when increased by 25 mm Hg can induce MBF to the same level as a standard dose of adenosine. Prospectively targeted arterial CO 2 has the capability to evolve as an alternative to current pharmacologic vasodilators used for cardiac stress testing.