Limitations of Parenchymal Volume Analysis for Estimating Split Renal Function and New Baseline Glomerular Filtration Rate After Radical Nephrectomy.

PURPOSE: Accurately predicting new baseline glomerular filtration rate (NBGFR) after radical nephrectomy (RN) can improve counseling about RN vs partial nephrectomy. Split renal function (SRF)-based models are optimal, and differential parenchymal volume analysis (PVA) is more accurate than nuclear renal scans (NRS) for this purpose. However, there are minimal data regarding the limitations of PVA. Our objective was to identify patient-/tumor-related factors associated with PVA inaccuracy. MATERIALS AND METHODS: Five hundred and ninety-eight RN patients (2006-2021) with preoperative CT/MRI were retrospectively analyzed, with 235 also having NRS. Our SRF-based model to predict NBGFR was: 1.25 × (GlobalGFRPre-RN × SRFContralateral), where GFR indicates glomerular filtration rate, with SRF determined by PVA or NRS, and with 1.25 representing the median renal functional compensation in adults. Accuracy of predicted NBGFR within 15% of observed was evaluated in various patient/tumor cohorts using multivariable logistic regression analysis. RESULTS: PVA and NRS accuracy were 73%/52% overall, and 71%/52% in patients with both studies (n = 235, P < .001), respectively. PVA inaccuracy independently associated with pyelonephritis, hydronephrosis, renal vein thrombosis, and infiltrative features (all P < .03). Ipsilateral hydronephrosis and renal vein thrombosis associated with PVA underprediction, while contralateral hydronephrosis and increased age associated with PVA overprediction (all P < .01). NRS inaccuracy was more common and did not associate with any of these conditions. Even among cohorts where PVA inaccuracy was observed (22% of our patients), there was no significant difference in the accuracies of NRS- and PVA-based predictions. CONCLUSIONS: PVA was more accurate for predicting NBGFR after RN than NRS. Inaccuracy of PVA correlated with factors that distort the parenchymal volume/function relationship or alter renal functional compensation. NRS inaccuracy was more common and unpredictable, likely reflecting the inherent inaccuracy of NRS. Awareness of cohorts where PVA is less accurate can help guide clinical decision-making.

Broader than expected tolerance for substitutions in the WCGPCK catalytic motif of yeast thioredoxin 2.

Thioredoxins constitute a key class of oxidant defense enzymes that facilitate disulfide bond reduction in oxidized substrate proteins. While thioredoxin's WCGPCK active site motif is highly conserved in traditional model organisms, predicted thioredoxins from newly sequenced genomes show variability in this motif, making ascertaining which genes encode functional thioredoxins with robust activity a challenge. To address this problem, we generated a semi-saturation mutagenesis library of approximately 70 thioredoxin variants harboring mutations adjacent to their catalytic cysteines, making substitutions in the Saccharomyces cerevisiae thioredoxin Trx2. Using this library, we determined how such substitutions impact oxidant defense in yeast along with how they influence disulfide reduction and interaction with binding partners in vivo. The majority of thioredoxin variants screened rescued the slow growth phenotype that accompanies deletion of the yeast cytosolic thioredoxins; however, the ability of these mutant proteins to protect against H2O2-mediated toxicity, facilitate disulfide reduction, and interact with redox partners varied widely, depending on the site being mutated and the substitution made. We report that thioredoxin is less tolerant of substitutions at its conserved tryptophan and proline in the active site motif, while it is more amenable to substitutions at the conserved glycine and lysine. Our work highlights a noteworthy plasticity within the active site of this critical oxidant defense enzyme.