Monitoring of radio frequency tissue ablation in an interventional magnetic resonance environment. Preliminary ex vivo and in vivo results

RATIONALE AND OBJECTIVES: The authors evaluate the feasibility of monitoring radio frequency (RF) ablation in an interventional, open-configuration, 0.5-tesla magnetic resonance (MR) environment. METHODS: Ex vivo and in vivo RF coagulation necrosis were induced in porcine paraspinal muscle tissue using a 300 kHz monopolar RF generator applying 5 to 20 W over 3 to 9 minutes. Images were acquired simultaneous to RF application, after RF application, and in an intermittent mode (60 seconds of RF followed by 15 seconds of MR imaging). Temperature changes were monitored based on amplitude (ex vivo) and phase alterations (in vivo) of a T1-weighted graded refocused echo (GRE) sequence enabling an update every 2.5 seconds. A standardized color-coded subtraction technique enhanced signal changes. Additionally, T2- and T1-weighted spin echo (SE) images were acquired with and without intravenous contrast. Macroscopic coagulation size was compared with lesion size seen on MR images. RESULTS: Although lesion diameters were related directly to applied RF power, the application mode had no significant impact on coagulation size (P > 0.05). As could be expected, MR imaging during RF ablation resulted in major image distortion. Radio frequency effects were seen on images acquired in the continuous and intermittent modes. Coagulation size seen on GRE images correlated well with macroscopy both ex vivo (r = 0.89) and in vivo (r = 0.92). Poorer correlation was found with postinterventional SE sequences (r = 0.78-0.84). CONCLUSIONS: Magnetic resonance monitoring of RF effects is feasible both ex vivo as well as in vivo using temperature-sensitive sequences in an open-configuration MR environment.     

Isolation of type II epithelial cells from rabbit fetal lungs by adherence on an IgG-coated surface

The lung is comprised of about 40 different cell types, of which only 15% are type II cells. These are the major, if not the sole, source of synthesis and secretion of lung surfactant. To date a large number of methods have been described for the isolation of pure populations of type II cells using a wide variety of techniques, but most of these have employed differential centrifugation methods and have used adult rodents. The present study reports the isolation of type II cells from fetal rabbit lungs by the immunoglobin G plating method. Pure populations of fetal type II cells in high yield and with good viability were obtained by the procedure for the first time from rabbit fetal tissue.     

PCR analysis of microsatellite DNA markers: possibility of erroneous determination of genotypes

A comparative study of two techniques for the PCR genotyping of highly polymorphic tandem repeats was carried out by the example of a triplet repeat in the myotonin protein kinase gene. Sequencing denaturing gels were shown to yield more precise results in the analysis of amplification products.     

Structures of the O-antigens of Proteus bacilli belonging to OX group (serogroups O1-O3) used in Weil-Felix test

Structures of the O-specific polysaccharide chains of lipopolysaccharides from Proteus group OX strains (serogroups O1-O3) used as antigens in Weil-Felix test for diagnosis of rickettsiosis, were established. From them, the acid-labile polysaccharide of Proteus vulgaris OX19 (O1) is built up of the following branched pentasaccharide repeating units connected via a phosphate group: [structure in text] where QuiNAc stands for 2-acetamido-2,6-dideoxyglucose (N-acetylquinovosamine). The basis of serospecificity of the Proteus group OX antigens and their cross-reactivity with human anti-rickettsial antibodies is discussed.     

Body size, mating success and advantage of large flies in Drosophila bipectinata species complex

Mating success of large and small flies of Drosophila malerkotliana and D. bipectinata was studied using multiple, male and female choice methods. In multiple choice method the large male mated with large female and small male paired with small female. In female choice method, large male was successful in mating with female irrespective of its size while in male choice method, preferential mating occurred between large male and large female as well as small male and small female. The consequence of such non-random mating in the presence of male rivarly and preferential mating has been discussed.