Defects in energy metabolism in either the retina or the immediately adjacent retinal pigment epithelium (RPE) underlie retinal degeneration, but the metabolic dependence between retina and RPE remains unclear. Nitrogen-containing metabolites such as amino acids are essential for energy metabolism. Here, we found that 15N-labeled ammonium is predominantly assimilated into glutamine in both the retina and RPE/choroid ex vivo. [15N]Ammonium tracing in vivo show that, like the brain, the retina can synthesize asparagine from ammonium, but RPE/choroid and the liver cannot. However, unless present at toxic concentrations, ammonium cannot be recycled into glutamate in the retina and RPE/choroid. Tracing with 15N-labeled amino acids show that the retina predominantly uses aspartate transaminase for de novo synthesis of glutamate, glutamine, and aspartate, whereas RPE uses multiple transaminases to utilize and synthesize amino acids. Retina consumes more leucine than RPE, but little leucine is catabolized. The synthesis of serine and glycine is active in RPE but limited in the retina. RPE, but not the retina, uses alanine as mitochondrial substrates through mitochondrial pyruvate carrier. However, when the mitochondrial pyruvate carrier is inhibited, alanine may directly enter the retinal mitochondria but not those of RPE. In conclusion, our results demonstrate that the retina and RPE differ in nitrogen metabolism and highlight that the RPE supports retinal metabolism through active amino acid metabolism.

OBJECTIVEThe first attempt to cannulate the foramen ovale is oftentimes unsuccessful and requires subsequent reattempts, thereby increasing the risk of an adverse event and radiation exposure to the patient and surgeon. Failure in cannulation may be attributable to variation in soft-tissue–based landmarks used for needle guidance. Also, the incongruity between guiding marks on the face and bony landmarks visible on fluoroscopic images may also complicate cannulation. Therefore, the object of this study was to assess the location of the foramen ovale by way of bony landmarks, exclusive of soft-tissue guidance.METHODSA total of 817 foramina ovalia (411 left-sided, 406 right-sided) from cranial base images of 424 dry crania were included in the study. The centroid point of each foramen ovale was identified. A sagittal plane through the posterior-most molar (molar plane) and a coronal plane passing through the articular eminences of the temporal bones (inter-eminence plane) were superimposed on images. The distances of the planes from the centroids of the foramina were measured. Also, counts were taken to assess how often the planes and their intersections crossed the boundary of the foramen ovale.RESULTSThe average distance between the molar plane and the centroid of the foramen was 1.53 ± 1.24 mm (mean ± SD). The average distance between the inter-eminence plane and the centroid was 1.69 ± 1.49 mm. The molar and inter-eminence planes crossed through the foramen ovale boundary 83.7% (684/817) and 81.6% (667/817) of the time, respectively. The molar and inter-eminence planes passed through the boundary of the foramen together 73.5% (302/411) of the time. The molar and inter-eminence planes intersected within the boundary of the foramen half of the time (49.4%; 404/817).CONCLUSIONSThe results of this study provide a novel means of identifying the location of the foramen ovale. Unlike the soft-tissue landmarks used in the many variations of the route of Härtel, the bony landmarks identified in this study can be palpated, marked on the face, appreciated fluoroscopically, and do not require any measurement from soft-tissue structures. Utilizing the molar and inter-eminence planes as cannulation guides will improve the approach to the foramen ovale and decrease the amount of radiation exposure to both the patient and surgeon.

Inferior vena cava (IVC) variations signify predisposition to deep vein thrombosis and may complicate retroperitoneal surgeries including abdominal aortic surgery and nephrectomy. Failure to recognize such variations may predispose the patient to life‐threatening complications. Despite their clinical significance, few studies have detailed variations from direct observation. This study assessed 36 cadavers for variations of the IVC and left renal vein. Prevalence was determined for the following variations: double IVC, isolated left IVC, retroaortic left renal vein, and circumaortic renal vein. Two of the 36 cadavers (5.6%) were variant. The variations included a double IVC (1:36; 2.8%) and a retroaortic left renal vein (1:35; 2.9%). There were no occurrences of an isolated left IVC or a circumaortic renal vein (0:36; 0% and 0:35; 0%, respectively). Further, the double IVC and the retroaortic left renal vein were accompanied by regional pathologies—both having kidney pathology and one with an abdominal aortic aneurysm. The results of this study suggest that, IVC variations are rare and, when an IVC variation is discovered, there is typically an attending urinary system pathology.Support or Funding InformationWest Virginia University, West Liberty University, NASA West Virginia Space Grant Consortium and West Virginia Research Challenge FundThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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Trigeminal neuralgia is characterized by debilitating facial pain. The treatment for trigeminal neuralgia often involves the introduction of a surgical tool through the foramen ovale and porus trigeminus (PT). Though several studies have recently described the anatomy of the foramen ovale, few have described the PT. This study analyzed 53 PT for area, height, width, and circularity among both left‐ and right‐sided PT from females and males. There were no statistically significant differences in the area, height, width, and circularity of the PT between sexes (U=258, p=0.42; U=255, p=0.38; U=298, p=0.99; U=295.5, p=0.95). Similarly, paired t‐tests revealed no significant differences between sides with regard to area (t=1.35; p=0.19) and height (t=0.40; p=0.69). However, there were significant differences between sides with regard to width (t=2.19; p=0.04) and circularity (t=3.38; p=0.003). The average left‐sided PT width was 6.6±2.4mm (Mean±SD) whereas the average right‐sided PT width was 7.7±1.6mm. With regard to surgical implications, right‐sided PT may provide slightly greater freedom with regard to the angle of approach to the PT.Support or Funding InformationFunding: WV Research Challenge Fund [HEPC.dsr.17.06]This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.