Mechanistic and structural studies on legumain explain its zymogenicity,distinct activation pathways,and regulation

The cysteine protease legumain plays important functions in immunity and cancer at different cellular locations, some of which appeared conflicting with its proteolytic activity and stability. Here, we report crystal structures of legumain in the zymogenic and fully activated form in complex with different substrate analogs. We show that the eponymous asparagine-specific endopeptidase activity is electrostatically generated by pH shift. Completely unexpectedly, the structure points toward a hidden carboxypeptidase activity that develops upon proteolytic activation with the release of an activation peptide. These activation routes reconcile the enigmatic pH stability of legumain, e.g., lysosomal, nuclear, and extracellular activities with relevance in immunology and cancer. Substrate access and turnover is controlled by selective protonation of the S1 pocket (K_M) and the catalytic nucleophile (k_cat), respectively. The multibranched and context-dependent activation process of legumain illustrates how proteases can act not only as signal transducers but as decision makers.     

Single time point measurement by C2 or C3 is highly predictive in cyclosporine area under the curve estimation immediately after lung transplantation

Abstract: Background: The two h post-dose cyclosporine (CsA) concentration has been advocated as the optimal time point measurement for CsA area under the curve (AUC) estimation after solid organ transplantation. The aim of the study was to investigate whether intensified CsA monitoring is necessary, or if a single time point measurement is accurate to estimate the AUC in the very early period following lung transplantation (LuTX). Methods: Within the first two wk following transplantation, daily AUCs were calculated by serial CsA measurements at zero, one, two, three, four, and six h (C0–C6) in 12 consecutive lung transplant recipients. Correlation of single CsA measurements and AUC as well as linear regression analysis was performed to evaluate the most predictive single CsA blood level regarding the AUC. Results: A total of 606 CsA concentration measurements were performed and the 101 corresponding AUCs were calculated for each patient. Mean AUC was 3443 ± 1451 μg/L. C0: 361 ± 118 μg/L, C1: 481 ± 231 μg/L, C2: 682 ± 314 μg/L, C3: 715 ± 347 μg/L, C4: 658 ± 271 μg/L, C6: 571 ± 260 μg/L. The correlation of CsA serum levels with AUC was the lowest at trough levels (C0) with a correlation coefficient (r = 0.31) and highest at three h (C3: r = 0.89) and two h (C2: r = 0.88). Conclusions: Similar to a stable post-transplant period, CsA trough levels turned out to have poor correlation with the corresponding AUC early after LuTX. The highest correlation of C3 with the AUC may be explained by delayed intestinal resorption immediately post-operative, however C2 is a peer parameter. Optimum AUCs and corresponding C2 or C3 levels in the immediate post-operative phase however remain to be determined.     

Are neurology residents in the United States being taught defensive medicine?

OBJECTIVE: To study whether and how fear of litigation and defensive medicine are communicated during residency training and to assess whether this affects residents' attitudes. METHODS: Neurology residents in the US (n=25) and, as a control group, Neurology residents training in Germany (n=42) were asked to rate multiple items regarding litigation, defensive strategies and how often these issues are raised by teaching physicians. Statistic analysis was performed using nonparametric tests. RESULTS: Residents in both countries indicated that litigation is an "important problem", although US residents stated this significantly more often (p<0.001). Initiation of tests motivated mainly by fear of litigation (p=0.004) and explicit teaching of defensive strategies by teaching physicians (p<0.02) were reported more often by US residents. CONCLUSION: Neurology residents in both the US and Germany perceive a litigational threat, but significantly less so in Germany. This difference may result at least in part from teaching of defensive strategies reported more often in US programs.     

Comparison of 2 different protocols for ingestion of low-attenuating oral contrast agent for multidetector computed tomography of the abdomen

OBJECTIVE: To evaluate 2 different oral contrast application protocols concerning degree of intestinal contrast filling and distension in multidetector computed tomography. METHODS: Examinations of 260 patients were retrospectively analyzed. Group 1 (n = 205) was prepared with 1000 mL of water with 28 g of dissolved mannitol which was ingested for 1 hour; group 2 (n = 55) was prepared with 2000 mL of water containing 56 g of mannitol which was ingested for 2 hours. Small intestine was divided into 4 quadrants; colon was divided into 4 segments. Contrast filling and distension of bowel loops were graded with a 3-point scale and compared using chi2 testing. RESULTS: Besides the right upper quadrant, no significant differences in contrast filling and distention were found for small bowel segments. Colonic segments were significantly better contrast filled and distended in group 2 (0.001 < P < 0.025). CONCLUSIONS: A higher amount of water with 28 g/L of mannitol and a prolonged ingestion of oral contrast media result in significantly better contrast filling and bowel distension in the ileocecal region, the colon, and the rectum.