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Concept: Double variation


A unique anatomical variation of the suprascapular notch was discovered in one scapula from 610 analyzed by three-dimensional CT reconstruction. Two bony bridges were found, converting it into a double suprascapular foramen, in the left upper extremity of an 56-year-old Caucasian female. This variation might be a risk factor for suprascapular nerve entrapment. Suprascapular nerve running through inferior suprascapular foramen was discovered. Suprascapular vessels passed through superior suprascapular foramen (artery lay medially and vein laterally). A new hypothesis of double suprascapular foramen formation (mechanism of creation) is presented based on recent anatomical findings (e.g., the discovery in 2002 of the anterior coracoscapular ligament). Knowledge of the anatomical variations described in this study should be helpful in arthroscopic and open procedures at the suprascapular region and also confirms the safety of operative decompression for the suprascapular nerve.

Concepts: Blood vessel, Observation, Anatomy, Supraspinatus muscle, Suprascapular nerve, Suprascapular notch, The Double, Double variation


Substantial inter-individual variations in exercise economy exist even in highly trained endurance athletes. The variation is believed to be determined partly by intrinsic factors. Therefore, in the present study, we compared exercise economy in V2-skating, double poling, and uphill running. Ten highly trained male cross-country skiers (23 ± 3 years, 180 ± 6 cm, 75 ± 8 kg, VO2peak running: 76.3 ± 5.6 mL·kg(-1)·min(-1)) participated in the study. Exercise economy and VO2peak during treadmill running, ski skating (V2 technique) and double poling were compared based on correlation analysis. There was a very large correlation in exercise economy between V2-skating and double poling (r = 0.81) and large correlations between V2-skating and running (r = 0.53) and double poling and running (r = 0.58). There were trivial to moderate correlations between exercise economy and the intrinsic factors VO2peak (r = 0.00-0.23), cycle rate (r = 0.03-0.46), body mass (r = -0.09-0.46) and body height (r = 0.11-0.36). In conclusion, the inter-individual variation in exercise economy could be explained only moderately by differences in VO2peak, body mass and body height. Apparently other intrinsic factors contribute to the variation in exercise economy between highly trained subjects.

Concepts: Mass, Human height, Correlation and dependence, Ski, Skiing, Ski touring, Telemark skiing, Double variation


Repetitive elements are now known to have relevant cellular functions, including self-complementary sequences that form double stranded (ds) RNA. There are numerous pathways that determine the fate of endogenous dsRNA, and misregulation of endogenous dsRNA is a driver of autoimmune disease, particularly in the brain. Unfortunately, the alignment of high-throughput, short-read sequences to repeat elements poses a dilemma: Such sequences may align equally well to multiple genomic locations. In order to differentiate repeat elements, current alignment methods depend on sequence variation in the reference genome. Reads are discarded when no such variations are present. However, RNA hyper-editing, a possible fate for dsRNA, introduces enough variation to distinguish between repeats that are otherwise identical.

Concepts: DNA, Gene, Genetics, Genome, Series, RNA, RNA virus, Double variation


Due to the technical improvements, anatomical variations of the small arteries, those were previously reported on cadaveric series, can also be evaluated on CT angiography. Absence of the anterior inferior cerebellar artery (AICA) is the most common variation of the AICA. Duplication and fenestration of the AICA can be rarely seen. In this report, two new variations, early bifurcation and double origin of the AICA, were described on CT angiography.

Concepts: Atherosclerosis, Atheroma, Cerebellum, Posterior inferior cerebellar artery, Anterior inferior cerebellar artery, Inferior cerebellar veins, Double variation, Vestibular nuclei