Serum antioxidant activity (AOA) was examined in 35 healthy subjects and 111 patients with chronic renal failure (CRF), consisting of 13 patients in the predialysis stage, 11 requiring the start of regular dialysis therapy (RDT) and 87 undergoing RDT. Serum AOA was determined by assaying serum activity to inhibit malondialdehyde (MDA) generation. AOA levels were significantly lower in CRF patients, and the lowest levels were noticed in patients with uremic symptoms requiring the start of RDT. These levels were restored to a subnormal level during RDT. Defective serum AOA appears to be an endogenous metabolic consequence in uremia. Sera with low AOA tended to show high MDA levels, indicating that patients with low serum AOA were susceptible to cellular injury by lipid peroxidation. It is proposed that defective serum AOA may contribute to a certain uremic toxicity through peroxidative cell damage.

Montmorillonite dissolution under highly alkaline conditions (pH = 13.3; I = 0.3 M) was investigated by bulk dissolution methods and in situ atomic force microscopy (AFM). In bulk dissolution experiments, initial SiO2 concentrations were high, and a steady state was reached after 136 h. The dissolution rates derived from the edge surface area (ESA) at the steady-state condition at 30, 50 and 70°C were 3.39 x 10−12, 1.75 × 10−11 and 5.81 × 10−11 mol/m2 s, respectively. The AFM observations were conducted under three conditions: (Run I) short-term in situ batch dissolution at RT; (Run II) long-term in situ flow-through dissolution at RT; and (Run III) long-term batch dissolution at 50°C. The observed reductions in montmorillonite particle volume for Runs I and II were due primarily to edge-surface dissolution. The ESA-based dissolution rate for Run I (10−9 mol/m2 s) was three orders of magnitude faster than that for Run II (10−12 mol/m2 s). The rate obtained for Run II corresponded to the rate at the steady-state conditions in the bulk dissolution experiments. A small number of etch pits developed in Run III slightly increased the ESA of montmorillonite since most of the montmorillonite particles were separated into monolayers lacking three-dimensional periodicity. The ESA-based dissolution rate for Run III was 2.26 × 10−11 mol/m2 s. Dissolution rates based on long-term AFM observations could be directly compared with steady-state rates obtained from bulk dissolution experiments. The AFM observations indicated that dissolution occurred at edge surfaces; therefore, the ESA should be used to calculate the dissolution rate for montmorillonite under alkaline conditions. Dissolution rates of individual particles with different morphologies estimated by AFM were similar to rates estimated from bulk dissolution experiments.

Urinary alpha 1-microglobulin (U-A1M) was measured in healthy term infants on days 1, 4, 7, 14, 28, 90 and 180 of life. U-A1M was high until day 14 and declined thereafter. It was significantly correlated with urinary beta 2-microglobulin (U-B2M) throughout the study, but not with serum A1M on days 1 or 7. Similar to U-B2M, U-A1M in the clinically stable term infants with intrauterine growth retardation (n = 4-7) was not elevated on days 1-7. In the sick infants who needed immediate resuscitation at birth (n = 4-8), U-A1M was well as U-B2M was high on days 1-7 and then decreased to normal levels, suggesting that U-A1M can be used as a sensitive marker of acute proximal tubular damage and its recovery. These observations indicate that U-A1M is a useful index of proximal tubular function in early infancy.

Routine urinalysis is performed as a screening test for urinary tract infection (UTI), but is not very reliable. We assessed the usefulness of microscopic examination of unspun urine using a disposable slide with counting chambers for the diagnosis of UTI caused by a variety of species of bacilli. One hundred and seventy-two urine samples were obtained from 113 subjects (60 male and 53 female), including 84 inpatients, aged 20-96 years. The urine samples were examined for bacteriuria and pyuria using a counting chamber, and the reliability of this method in predicting significant bacteriuria defined by routine urine culture and Gram stain of urine smears was analyzed. Significant bacteriuria was diagnosed in 68 urine samples, including 34 from indwelling catheters, from 52 patients mostly having underlying diseases. Only 12 of the positive urine samples contained E. coli, with a variety of other bacilli including cocci found in the rest. The counting chamber method detected bacteriuria in 64 of these 68 positive samples (sensitivity = 94%). Specificity was 88%. While the sensitivity and specificity of pyuria (WBC > 10 microliters-1) were 79 and 71%, respectively, both sensitivity and negative predictive value were as high as 97% when bacteriuria or pyuria was present. We demonstrated that urine microscopy on a disposable counting chamber is a simple, sensitive and time- and cost-saving method for the diagnosis of UTI caused by a variety of bacterial species including cocci.

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