A holistic approach for determining the entomopathogenic potential of Bacillus thuringiensis strains

The cry gene content of Bacillus thuringiensis subsp. aizawai HD-133 was analyzed by a combination of high-pressure liquid chromatography (HPLC) and exclusive PCR. A total of six cry genes were detected in genomic DNA purified from HD-133, four from the cry1 family (cry1Aa, cry1Ab, cry1C, and cry1D) as well as a gene each from the cry2 (cry2B) and the cry1I families. To directly determine which genes were expressed and crystallized in the purified parasporal inclusions, solubilized and trypsinized HD-133 crystals were subjected to chromatographic separation by HPLC. Only three proteins, Cry1Ab, Cry1C, and Cry1D, were found, in a 60/37/3 ratio. Dot blot analysis of total mRNA purified from HD-133 showed that both the cry2B and cry1I genes, but not the cry1Aa gene, were transcribed. Cloning and sequencing of the cry1Aa gene revealed an inserted DNA sequence within the cry coding sequence, resulting in a disrupted reading frame. Taken together, our results show that combining crystal protein analysis with a genetic approach is a highly complementary and powerful way to assess the potential of B. thuringiensis isolates for new insecticidal genes and specificities. Furthermore, based on the number of cryptic genes found in HD-133, the total cry gene content of B. thuringiensis strains may be higher than previously thought.     

Effect of high fat corn oil, olive oil and fish oil on phospholipid fatty acid composition in male F344 rats

Venous stasis associated with prolonged bed rest can enhance the risk of deep venous thrombosis (DVT). Pneumatic compression of the lower extremities can reduce this risk by preventing venous stasis. When selecting a method of leg compression for their patients, physicians must chose between two distinctly different types of compression devices. One device applies pressure with a single-chambered sleeve to the below knee region while the other applies pressure in a sequential gradient fashion from the ankle to the thigh. The current prospective study was designed to evaluated the ability of two such devices to increase blood flow in the profunda femoral vein. Venous blood flow velocity, compression time, and vein diameter were measured in nine normal experimental subjects using an Accuson duplex-Doppler before, during and after leg compression. Compression with the single-chambered device produced a significant rise in venous blood flow velocity; however, this could not be maintained and our results indicate a higher average velocity was achieved with the sequential gradient device. The sequential gradient device also moved a greater volume of blood and achieved a higher average blood flow rate. The time between deflation of the sleeve and return of a phasic respiratory signal was greater after compression with the sequential gradient device. These results suggest that sequential gradient compression produces the type of hemodynamic alterations needed to reduce the risk of DVT by achieving a sustained increase in venous blood flow and more completely emptying of the veins in the leg.     

Free vibration and stability behaviour of uniform beams and columns on nonlinear elastic foundation

Free vibration and stability behaviour of uniform beams and columns on nonlinear elastic foundation are evaluated using a finite element formulation. Numerical results are presented for various end boundary conditions with varying foundation parameters.     

Functional analysis of the DNA-packaging/terminase protein gp17 from bacteriophage T4

In bacteriophage T4, the terminase complex constituted by the large subunit gp17 (69 kDa) and the small subunit gp16 (18 kDa) is a critical component of the ATP-driven DNA-packaging pump that translocates DNA into an empty capsid shell. Evidence suggests that the large subunit gp17 is the critical component and consists of a number of the functional sites required for DNA-packaging. It exhibits a terminase activity that introduces non-specific cuts into DNA, a portal vertex binding site that allows linkage of cleaved DNA to an empty prohead, an in vitro DNA-packaging activity, and an ATPase activity. In addition, a consensus metal-binding motif and two consensus ATP-binding sites have been identified by sequence analysis. In order to understand the mechanism of action of the multifunctional gp17, we developed an expression-based selection strategy to select for mutants that are defective in terminase function. Characterization of one of the mutants revealed a unique phenotype in which a single H436R mutation resulted in a dramatic loss of both the terminase and the DNA-packaging functions. Indeed, in vivo substitution of H436 with any of the 12 amino acids for which a suppressor is available was lethal to T4 development. According to one hypothesis, H436 is part of a metal-binding motif that is essential for gp17 function. This hypothesis was tested by introducing mutations at each of the three histidine pairs, the H382-X2-H385 pair, the H411-X2-H414 pair and the H430-X5-H436 pair, which constitute the histidine-rich region near the C terminus of gp17. A mutation at either the H411 pair or the H430 pair resulted in a loss of gp17 function, whereas a mutation at the H382 pair had no effect. In addition to the putative metal-binding motif, substitutions at residue K166 within the putative N terminus-proximal ATP-binding site also resulted in a loss of gp17 function. We propose that a metal-binding motif involving the histidine residues within the sequence H411-X2-H414-X15-H430-X5-H436 is essential for gp17 function. Metal-terminase interactions may be required for structural alignment and stabilization of functional sites in phage T4 terminase and other double-stranded DNA phage terminases.     

Nutrient composition and biological evaluation of mesta (Hibiscus sabdariffa) seeds

Differently substituted flavanones were isolated from Leguminosae and their antibacterial activity was comparatively studied against methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MICs) of phytochemical flavanones to clinical isolates of MRSA were determined by a serial agar dilution method. The structure-activity relationship has indicated that 2',4'- or 2',6'-dihydroxylation of the B ring and 5,7-dihydroxylation of the A ring in the flavanone structure are important for significant anti-MRSA activity and that substitution with a certain aliphatic group at the 6- or 8-position also enhances the activity. Among the thirteen flavanones tested, tetrahydroxyflavanones with these structural characteristics isolated from Sophora exigua and Echinosophora koreensis showed intensive activity to inhibit the growth of all MRSA strains at 3.13-6.25 micrograms/ml. The present hydroxyflavanones would be useful in the phytotherapeutic strategy against MRSA infections.     

A Comparative Study of Explicit Frequency and Conventional Signal Representations for Speech Recognition

Krishnan, S., and Rao, P. V. S., A Comparative Study of Explicit Frequency and Conventional Signal Representations for Speech Recognition,Digital Signal Processing6(1996), 249–264.The performance of a speech recognition system depends to a large extent on the signal representation strategy. It is therefore important to evaluate various signal representations, with a view to comparing their relative performance on speech recognition tasks. Various comparative studies have been reported earlier in the literature in this respect. However, these studies are limited to comparing some subsets of representations on different kinds of recognition tasks. In this sense, they preclude a fair comparison of the representations on the same task. In contrast, we attempt here a systematic and fairly comprehensive comparison of signal representations along various dimensions (frequency and amplitude scales, speaker normalization, and two statistical classifiers) on a standard (TIMIT) speech database. This study shows that the line spectrum pair frequency representation augmented with spectral amplitudes yields the best recognition performance.     

A knowledge-based approach for script recognition without training

The approach described is based on an empirical parametric model for the handwriting recognition system. The parameters are so chosen and quantized as to retain only broad shape information, ignoring writer-dependent and other variability. Concatenation of character prototypes generates archetypal reference words for recognition, and training is unnecessary. The recognition scores exceed 90%