Urolithiasis is one of the most common urologic diseases in industrialized societies. More than 80% of renal stones are composed of calcium oxalate, and small changes in urinary oxalate concentrations affect the risk of stone formation. Elucidation of the source of oxalate and its mechanism of transport is crucial for understanding the etiology of urolithiasis. Sources of oxalate can be both endogenous and exogenous. With regard to oxalate transport, tests were carried out to prove the function of solute-linked carrier 4 (SLC4) and SLC26. The molecular mechanism of urolithiasis caused by SLC4 and SLC26 is still unclear. The growing number of studies on the molecular physiology of SLC4 and SLC26, together with knockout genetic mouse model experiments, suggest that SLC4 and SLC26 may be a contributing element to urolithiasis. This review summarizes recent research on the sources of oxalate and characterization of the oxalate transport ionic exchangers SLC4 and SLC26, with an emphasis on different physiological defects in knockout mouse models including kidney stone formation. Furthermore, SLC4 and SLC26 exchangers provide new insight into urolithiasis and may be a novel therapeutic target for modification of urinary oxalate excretion.

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This paper studies both vibroacoustics and aeroacoustics of a centrifugal fan casing; the aim of this study is to explore a methodology to make quantitative predictions of fan casing noise. The spectra of the fan noise and casing vibration were firstly presented; discrete components related to the rotational frequency protrude in the spectra, especially the blade passing frequency (BPF). Computational fluid dynamics (CFD) technique was used to obtain the three-dimensional unsteady turbulent internal flow. Attention was paid to the pressure fluctuations on the volute wall; the shapes of pressure fluctuation were nearly sinusoidal in nature, with the BPF as the primary frequency. On the vibroacoustic side, Fast Fourier Transform (FFT) was applied to the time series of pressure fluctuations to extract the BPF component. A finite element analysis (FEA) model of the casing structure was constructed, and was validated by experimental modal analysis. The harmonic dynamic response of the casing structure was calculated with the BPF pressure fluctuation component as the excitation. The vibration results were then taken as the velocity (Neumann) boundary condition for the noise radiation model which was built in boundary element method (BEM), and the sound radiation was calculated. On the aeroacoustic side, the BPF component of pressure fluctuations was modeled as acoustic dipole source, and sound radiation was also solved by BEM. Results show that the sound pressure level (SPL) of vibroacoustics is fairly small compared to the aeroacoustic counterpart. This study shows that CFD, FEA together with BEM can be used to numerically predict BPF casing noise of turbomachinery successfully.

L e t t e r t o t h e E d i t o rDear Sir, We herein describe an unexpected case of severe perineal pain that gradually developed into urinary incontinence following a single 10-mg intravenous injection of dexamethasone sodium phosphate.A 25-year-old man was scheduled for nasal septal reconstruction and maxillary sinus cyst removal via reconstruction under nasal endoscope. Before the induction of anaesthesia in the operating room, a single 10-mg dose of dexamethasone sodium phosphate (product batch no.: 1208296432, Chen Xin Pharmaceutical Co Ltd, Jining, China) was administered intravenously to the patient. The patient immediately complained of severe itching, burning and numbness, which were confined to the perineal region. General anaesthesia was induced to relieve his discomfort. The patient was extubated at the end of the 1-hour surgery and recovered from the effects of anaesthesia without complaints of discomfort at the perineal region.Urinary incontinence developed 3 hours after surgery, and the patient described his urination as uncontrolled and intermittent, not accompanied by urination urgency and urodynia. Physical examination revealed that the bladder was not filled. The patient refused urethral catheterisation and bladder imaging. Nevertheless, the symptoms and condition gradually improved within 1 hour, and the patient fully recovered 28 hours postoperatively.However, 42 hours after surgery, the patient developed itching and urticaria of the skin on his anterior chest. As this occurrence was thought to be due to drug allergy, the attending doctor administered a 10-mg dose of dexamethasone sodium phosphate for anti-allergy treatment. The discomfort at the perineal region immediately reoccurred and the patient again developed gradual urinary incontinence in the following 3 hours. He recovered within the next 18 hours without any sequelae, and was discharged from the hospital on postoperative Day 4.The mechanism of urinary incontinence is unclear in this case. We suspect that phosphate ester could have led to dysfunction of the pudendal nerve, which controls the sensory perception in the perineal region and urination. Various measures are available to prevent perineal discomfort, including administration of dexamethasone after induction of anaesthesia, administration of fentanyl prior to dexamethasone and dilution of dexamethasone to be given as a slow bolus.(1-3) We opine that corticosteroid phosphate esters play an important role in the development of urinary incontinence. Therefore, careful attention should be paid to the rare adverse effects of dexamethasone sodium phosphate and the prevention of such occurrences.Yours sincerely,