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Chordomas are rare bony neoplasms usually unassociated with a familial tumor predisposition syndrome. The peak incidence of this midline axial skeletal tumor is in adulthood but when very young children are affected, consideration should be given to occurrence within the tuberous sclerosis (TS) complex, especially when presenting in neonates <3 months of age. To call attention to this association, we present a brachyury-immunopositive chordoma occurring in the skull base of a 2-month-old male infant who was later realized to have metastases to the subcutaneous tissues and lungs, as well as rhabdomyoma of the heart and renal cysts/angiomyolipomas, that is, characteristic features of the TS complex. We review the limited literature on this topic.

In hospitalized patients, over 50% of cases of acute kidney injury (AKI) are caused by renal ischemia [1][2][3] . A recent study of hospitalized patients revealed that only a mild increase in serum creatinine levels (0.3 to 0.4 mg/dl) is associated with a 70% greater risk of death than in persons without any increase 1 . Along these lines, surgical procedures requiring cross-clamping of the aorta and renal vessels are associated with a renal failure rates of up to 30% 4 . Similarly, AKI after cardiac surgery occurs in over 10% of patients under normal circumstances and is associated with dramatic increases in mortality. AKI are also common complications after liver transplantation. At least 8-17% of patients end up requiring renal replacement therapy To elucidate mechanisms of renal injury due to ischemia and possible therapeutic strategies murine models are intensively required [7][8][9][10][11][12][13] . Mouse models provide the possibility of utilizing different genetic models including gene-targeted mice and tissue specific gene-targeted mice (creflox system). However, murine renal ischemia is technically challenging and experimental details significantly influence results. We performed a systematic evaluation of a novel model for isolated renal artery occlusion in mice, which specifically avoids the use of clamping or suturing the renal pedicle 14 . This model requires a nephrectomy of the right kidney since ischemia can be only performed in one kidney due to the experimental setting. In fact, by using a hanging-weight system, the renal artery is only instrumented once throughout the surgical procedure. In addition, no venous or urethral obstruction occurs with this technique. We could demonstrate time-dose-dependent and highly reproducible renal injury with ischemia by measuring serum creatinine. Moreover, when comparing this new model with conventional clamping of the whole pedicle, renal protection by ischemic preconditioning is more profound and more reliable. Therefore his new technique might be useful for other researchers who are working in the field of acute kidney injury. Video LinkThe video component of this article can be found at https://www.jove.com/video/2549/ ProtocolGeneral remarks. All operations should be performed under an upright dissecting microscope (Leica) and by using a surgical coagulator. The mice in the experimental groups should be matched in age and weight to ensure comparability of the results. Temperature, blood pressure, anesthesia and fluid administration should be stable and monitored during the experiment.

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