A multiple linear regression approach to the estimation of carboxylic acid ester and lactone alkaline hydrolysis rate constants.

Pesticides, pharmaceuticals, and other organic contaminants often undergo hydrolysis when released into the environment; therefore, measured or estimated hydrolysis rates are needed to assess their environmental persistence. An intuitive multiple linear regression (MLR) approach was used to develop robust QSARs for predicting base-catalyzed rate constants of carboxylic acid esters (CAEs) and lactones. We explored various combinations of independent descriptors, resulting in four primary models (two for lactones and two for CAEs), with a total of 15 and 11 parameters included in the CAE and lactone QSAR models, respectively. The most significant descriptors include pKa, electronegativity, charge density, and steric parameters. Model performance is assessed using Drug Theoretics and Cheminformatics Laboratory's DTC-QSAR tool, demonstrating high accuracy for both internal validation (r2 = 0.93 and RMSE = 0.41-0.43 for CAEs; r2 = 0.90-0.93 and RMSE = 0.38-0.46 for lactones) and external validation (r2 = 0.93 and RMSE = 0.43-0.45 for CAEs; r2 = 0.94-0.98 and RMSE = 0.33-0.41 for lactones). The developed models require only low-cost computational resources and have substantially improved performance compared to existing hydrolysis rate prediction models (HYDROWIN and SPARC).

Extracorporeal shock wave lithotripsy treatment of spinal cord injury patients.

A total of 32 male patients with spinal cord injury underwent extracorporeal shock wave lithotripsy. The mean stone burden was 2.9 cm. (range 0.2 to 8.0 cm.) per renal unit. Of 41 renal units 27 (66 per cent) required ancillary endourological procedures preoperatively and 32 (78 per cent) required a single treatment with extracorporeal shock wave lithotripsy. Urine cultures were positive in 30 of 32 patients (94 per cent) before treatment. All patients with positive preextracorporeal shock wave lithotripsy urine cultures also had positive cultures after treatment. Followup (3-month) was available for 26 of 41 renal units (63 per cent) and showed 19 (73 per cent) to be free of stones or without any radiographic evidence of calcification overlying the collecting system. Seven staghorn calculi were treated with extracorporeal shock wave lithotripsy without prior debulking procedures. Two partial staghorn calculi were treated and rendered free of stones. None of the 5 kidneys with full staghorn calculi was rendered free of stones. We conclude that extracorporeal shock wave lithotripsy is effective for the treatment of unbranched and partial staghorn calculi in the spinal cord injury patient. However, extracorporeal shock wave lithotripsy alone is less effective for the treatment of full staghorn calculi.

Renal pelvic pressures during extracorporeal shock-wave lithotripsy.

Renal pelvic pressures were studied in 4 patients with indwelling nephrostomy tubes undergoing extracorporeal shock-wave lithotripsy (ESWL). The pressures were monitored by attaching the patients' nephrostomy tubes to an electrical pressure transducer. Three of these patients had ureteral stents placed to prevent outflow obstruction from disintegrated stone fragments. The mean pelvic pressure increased from 17.0 cm H2O at the start to 52 cm H2O at the conclusion of ESWL. Two hours post-ESWL, the pressures declined to a mean of 27.0 cm H2O. The maximum pelvic urine volume as determined by aspirating the nephrostomy tubes at the conclusion of the procedure was 6 cc. The observed rise in pelvic pressure may be explained by a sustained contraction of the pelvic smooth musculature.