The measurement of specific dynamic action in fishes.

Specific dynamic action (SDA) is the postprandial increase in oxygen uptake. Whereas it is easy to measure in fishes that remain calm and motionless during the entire digestion period, spontaneous locomotor activity is a frequent problem that leads to overestimation of SDA amplitude and magnitude (area under the curve, bound by the standard metabolic rate, SMR). Few studies have attempted to remove the effect of fish activity on SDA. A new method, non-parametric quantile regression, is described to estimate SDA even when pronounced circadian activity cycles are present. Data from juvenile Atlantic cod Gadus morhua are used to demonstrate its use and advantages compared with traditional techniques. Software (scripts in the R language) is provided to facilitate its use.

"Single-exposure" dual energy digital radiography in the detection of pulmonary nodules and calcifications.

We studied the detectability of mineralized and non-mineralized simulated pulmonary nodules with dual energy digital radiography. "Soft tissue" and "bone" images (pixel size = 0.2 mm, 10 bits deep) were obtained with subtraction image processing after a single simultaneous exposure (100 kVp, 8 mAs, 17 mR skin exposure dose) of two storage phosphors with an interleaved 0.9 mm copper wafer. Three classes of paraffin-based nodules (0.5 to 3.0 cm) of varying mineral concentration (0, 120 and 190 mg/cm3 K2HPO4) were randomly positioned on the chest wall of two healthy volunteers to simulate calcified and non-calcified nodules. The average receiver operating characteristics (ROC) area of six readers (n = 2880 observations) showed that digital "bone" images (ROC area: 0.77 +/- 0.03) were significantly better (P less than 0.04) than conventional radiographs (OC Film, Lanex medium screens, 141 kVp, 19 mR skin exposure dose) (ROC area: 0.71 +/- 0.05) in detecting calcification in nodules. The unsubtracted digital images of lower kilovoltage were not superior to the 141 kVp conventional radiographs in a subgroup of two readers (ROC area: 0.73 +/- 0.02). Digital "soft tissue" images were equivalent to conventional chest radiographs in detecting soft tissue pulmonary nodules (ROC areas: 0.92 +/- 0.04 and 0.92 +/- 0.05, respectively.

Glial cells metabolically cooperate: a potential requirement for gene replacement therapy.

Immunofluorescently labeled glial cells are shown by radioautography to metabolically cooperate with hypoxanthine phosphoribosyltransferase-deficient fibroblasts. The observations of cooperation without cell contact and of incorporation gradients around the glial cells suggest that cooperation occurs through extracellular transport of radiolabeled purine compounds. The transfer of radiolabeled adenine, adenosine, or methylthioadeninosine is supported by the quantitative loss of cooperation when the recipient cell is also deficient in enzymes required for adenine or adenosine salvage. The demonstration of glial cell cooperation provides impetus for current research toward gene replacement therapy for the neurologic symptoms of the Lesch-Nyhan syndrome.

Predictive value of image-guided adrenal biopsy: analysis of results of 101 biopsies.

A retrospective study of 97 patients undergoing 101 image-guided adrenal biopsies (IGABs) was performed to analyze the effects of specific pathologic results on test characteristics. Three categories of pathologic results (benign adrenal tissue, malignant tissue, and nondiagnostic) were compared with outcomes. Diagnostic samples were obtained in 86% of cases. Among 72 patients with proved outcomes, IGAB had an accuracy of 96%, a sensitivity of 93%, and a negative predictive value of 91% (92% in patients with bronchogenic carcinoma). In this subset of patients, 33 had biopsy specimens that contained benign adrenal tissue. In these 33 patients, three masses (each smaller than 3 cm) proved malignant. In the 14 patients with nondiagnostic samples, two masses proved malignant. Obtaining benign adrenal tissue was highly predictive of benignity, even in the setting of lung cancer. The authors conclude that IGAB is an accurate procedure in both oncologic and nononcologic patients. However, when the biopsy specimen does not contain benign adrenal tissue or malignant cells, repeat percutaneous biopsy or surgery should be considered.