An inversion recovery (180°-TI-90°) imaging pulse sequence was used to measure the T1 relaxation times: eight inversion times (TI) that ranged from 0.5 to 15 s were applied. Echo time was 4 ms. A Carr-Purcell-Meiboom-Gill

spin-echo imaging pulse sequence was used to measure T2 relaxation times [21]. A train of 16 echoes was acquired and the delay (τ) between 180° pulses was 10 ms. Single exponential relaxation times were calculated from experimental data using Bruker Paravision software. learn more Fourier-transformed, 3D MRI data were visualized using Amira imaging PC-based software (Visage Imaging, Inc., San Diego, CA, USA). This allowed 2D slices to be viewed from any angle within the 3D data set and regions of interest segmented, finite element meshes were generated and then surface rendered. Thus anatomy could be visualized and volumetric measurements determined. Quail eggs between Incubation Day 0 and 3 were exposed to a high static 7 T magnetic field, linear magnetic

field gradients (with maximum gradient amplitude of 200 mT/m) and 300 MHz rf pulses for several hours (average of 7 h) (test group). This long exposure time was to determine whether the high magnetic fields had any adverse affects upon embryonic development. Eggs removed from the incubator for the same period of time but not subjected to external magnetic fields made up the control group. After MRI scanning, test and control eggs were returned to the incubator until Day 7. A third

group of eggs (incubator Oligomycin A datasheet Cyclin-dependent kinase 3 group) remained continuously in the incubator until Day 7. At Day 7, the quail embryos were removed from the three groups of eggs, fixed in 4% paraformaldehyde in 0.1 M phosphate-buffered saline (PBS) and left overnight at 4°C. The specimens were then washed with PBS. These embryos were observed under a microscope to assess and record the developmental stage using Hamburger/Hamilton staging [22] to monitor whether development was normal. The main aim of the study was to undertake longitudinal μMRI studies of quail embryos developing within their eggs and then quantify the developmental changes in the embryos and the extra- and non-embryonic regions. Six eggs were studied over an 8-day period. On the day the eggs arrived (Day 0), they were imaged using 3D RARE-8 MRI sequence. This fast spin-echo imaging sequence takes about 35 min to obtain, after which the eggs were placed in the incubator. Consecutive 3D images were acquired at 24-h periods. Representative MRI images are shown in Fig. 1, Fig. 2 and Fig. 3; all these images are from the same egg. Images with equivalent letters were acquired at the same time points and originate from the same MRI data set. Fig. 1 displays a 2D vertical slice from the whole egg; Fig. 2 shows 2D images of the sagittal plane through the developing quail embryo; and Fig. 3 is a 3D surface rendering of various components after segmentation using Amira software.