Mechanisms of isoniazid resistance in Mycobacterium tuberculosis: enzymatic characterization of enoyl reductase mutants identified in isoniazid-resistant clinical isolates

Hepatocyte growth factor (HGF) decreases transforming growth factor beta1 (TGFbeta1) levels in the liver and attenuates hepatic fibrosis caused by dimethylnitrosamine in rats. In the liver, HGF is presumed to act predominantly on parenchymal cells, and TGFbeta1 is produced mainly by mesenchymal cells. In hepatic fibrosis, stellate cells play a central role with undergoing activation, which also occurs when the cells are cultured on plastic. Thus, we wondered if HGF could act directly on stellate cells. c-Met was detected in rat stellate cells activated by culture for 10 days, but not in the cells cultured for 3 days. Specific binding of HGF to the activated cells was determined, and Scatchard analysis indicated an apparent Kd of 1.5 nM. c-Met mRNA was detected in freshly isolated stellate cells from rats treated with carbon tetrachloride for 8 weeks, but not in those cells from normal rats. These results indicate that stellate cells express c-met when activated in vitro and in vivo. HGF enhanced TGFbeta1 production and DNA synthesis in the activated cells.     

Identity elements and aminoacylation of plant tRNATrp

Mutation of the Arabidopsis thaliana tRNA (Trp)(CCA) anticodon or of the A73 discriminator base greatly diminishes in vitro aminoacylation with tryptophan, indicating the importance of these nucleotides for recognition by the plant tryptophanyl-tRNA synthetase. Mutation of the tRNA (Trp)(CCA) anticodon to CUA so as to translate amber nonsense codons permits tRNA (Trp)(CCA) to be aminoacylated by A.thaliana lysyl-tRNA synthetase. Thus, translational suppression by tRNA (TRP)(CCA) observed in plant cells includes significant incorporation of lysine into protein.     

Thermal degradation of the concrete roof of high-level waste storage tank

The DOE's high-level waste storage tank (HLWST) sites consist of single- and double-shell concrete tanks covered with soil overburden. Due to the high temperature (212 °F and above) of the liquid-filled waste, the concrete walls and domed roofs are expected to endure thermal degradation which, in turn, may lead to cracking of the concrete. A remote video camera inspection of one such HLWST indicated some ‘irregularities’ on the inner surface of the tank dome. A finite element model using ADINA was developed to simulate the field conditions including concrete strength deterioration. The model was first validated against the results obtained from tests conducted on a 1/10th-scale model. The analysis was then extended to study the actual field behavior. The results confirmed the overall structural integrity of the tank by considering the global response of the tank and a detailed analysis of likely crack patterns in the dome area. The paper describes the complexities in validating the scale model as well as prototype response.     

An instrument with digital readout for indirect determination of kVp

An electronic instrument with digital readout has been designed and constructed for indirect determination of the kVp applied to diagnostic x-ray tubes. The signals from two detectors exposed simultaneously to a differentially filtered x-ray beam are processed by analog computing circuitry to yield an output signal directly proportional to the applied peak kilovoltage. Theory and preliminary results are presented and discussed.