Central benzodiazepine receptors in human brain: estimation of regional Bmax and KD values with positron emission tomography.

Studies of central benzodiazepine receptors in the human brain in vivo are now possible using positron emission tomography (PET) and [11C]flumazenil. With the aim of measuring Bmax and Kd in brain regions, we used a two-injection [11C]flumazenil (at high and low specific radioactivity, respectively) pseudo-equilibrium paradigm to evaluate, in seven unmedicated healthy volunteers, the relative merits of three 'reference' structures (pons, hemispheric white matter and corpus callosum) in which the free radioligand concentration in brain tissue was estimated 15-40 min after i.v. injection of the radioligand. By means of high-resolution PET, the Bmax and Kd were calculated for each subject in 18 gray matter structures, based on a two-point Scatchard plot. We found that the use of the corpus callosum as reference often resulted in spurious Bmax and Kd values. The pons was the best reference structure because it provided satisfactory Bmax values (closest to in vitro data) and most consistent Kd values, and was the region easiest to sample on PET images. The pattern of regional Bmax was consistent with that expected from in vitro studies, with values highest in the cerebral cortex, intermediate in the cerebellum, and lowest in the striatum and the thalamus. The Kd values were uniform among regions and were consistent with earlier in vitro and in vivo data. This work documents the feasibility of estimating Bmax and Kd of central benzodiazepine receptors in multiple brain regions for clinical research.     

FM sonography in diffuse liver disease: prospective assessment and blinded analysis

FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease.     

The clinical utility of risk factor data

Epidemiological data on risk factors may be used by clinicians to help diagnose the presence of a disease or assess the probability of its developing in the future. However, the use of risk factor data in this way has not been well evaluated. In this report, relationships are derived between common epidemiological measures of association, such as risk ratios, and common clinically useful measures, such as the operating characteristics of tests. These indicate that even a risk factor with a high relative risk may not be effective when used clinically.     

Percutaneous nephrolithotomy: perspectives for the future. Analysis of 250 cases in 3 years' experience

The authors report their experience of percutaneous nephrolithotomy over a period of three years. The analysis of the first 250 cases performed reveals a low morbidity, with serious complications in 1% of cases, and an acceptable complete success rate of 83%. The indications for percutaneous nephrolithotomy have been modified since the opening of an extracorporeal lithotripsy unit. The choice between the two techniques depends on their efficacy and their expected morbidity based on four criteria: the volume, chemical composition and site of the stone and the morphology of the upper urinary tract. Percutaneous nephrolithotomy is the treatment of choice for large stones (greater than 2.5 cm), hard stones or those formed proximally to a stenotic lesion of the urinary tract, which can then be dilated at the same procedure. A combination of the two methods is sometimes uses to treat staghorn calculi with a success rate of 80%. On the other hand, very large staghorn calculi with caliceal branches are best treated by open surgery.     

Phenotypic and proliferative properties of Schwann cells from nerves of diabetic patients.

The phenotypic (morphologic and antigenic) properties and mitotic index of cultured Schwann cells obtained by dissecting nerves from six diabetic patients were studied. These features were compared with those of Schwann cells cultured in vitro from six normal control nerves. Preservation of the specific antigenic properties of cells, identified with rabbit antiserum as bovine protein S-100, was documented by immunofluorescence with monoclonal antibodies against laminin, fibronectin, histocompatibility antigens HLA-A, B, C and -DR, HNK-1 antigen and the human receptor for nerve growth factor. The cell proliferation index was assessed by incorporation of bromodeoxyuridine. The results of the study showed that the mitotic capacities of Schwann cells from diabetic nerves cultured in vitro remained comparable with those of normal control cells. As regards phenotypic characteristics, no modifications were detectable by immunofluorescence. These findings suggest that the phenomena of demyelination and remyelination, sometimes with onion bulb features, which can be observed in some cases of diabetic neuropathy, are not due to a primary dysfunction of the Schwann cells but are secondary to axonal degeneration.