Studies of L-phenylalanine production by immobilised aminoacylase in stabilized calcium alginate beads

Aminoacylase I (EC 3.5. 1.14) was immobilised by entrapment in uncoated calcium alginate beads and calcium alginate beads coated with chitosan, polyethyleneimine and polyethyleneimine-glutaraldehyde for the production of L-phenylalanine by the hydrolysis of a racemic mixture of N-acetyl-DL-phenylalanine. The operational stability, thermal stability, effects of pH and temperature and kinetic constants, K_m and V_max values of free and immobilised enzymes were studied. Scanning electron micrographs revealed differences in the structures of the surfaces of coated and uncoated beads. Chitosan-coated calcium alginate beads was found to be the best among the immobilised systems studied. The activity and the optimum temperature of immobilised aminoacylase were higher than those of the free enzyme. In addition, the beads showed stable activity under operational conditions. The immobilised aminoacylase lost about 20% of its initial activity after ten cycles of reuse. Polyethyleneimine and polyethyleneimine-glutaraldehyde treatments were also found to enhance the operational stability of the enzyme but its activity was greatly reduced.     

Hydroxyurea accelerates the loss of epidermal growth factor receptor genes amplified as double-minute chromosomes in human glioblastoma multiforme

OBJECTIVE: We sought to determine whether hydroxyurea could accelerate the loss of amplified epidermal growth factor receptor (EGFR) genes from glioblastoma multiforme (GBM). There is good reason to think that elimination of amplified EGFR genes from GBMs will negatively impact tumor growth. Hydroxyurea has previously been shown to induce the loss of amplified genes from extrachromosomal double minutes (dmin) but not from chromosomal homogeneously staining regions. METHODS: Pulsed-field gel electrophoresis and Southern blot hybridization were used to demonstrate EGFR genes amplified as dmin. Giemsa-stained metaphase spreads were prepared in an attempt to visualize dmin. A GBM cell line containing amplified EGFR genes was treated continuously in vitro with 0 to 150 mumol/L hydroxyurea, and slot blot analysis was used to show the loss of amplified EGFR genes. RESULTS: Amplified EGFR genes were found on dmin in 4 of 11 (36%) fresh human GBM biopsy specimens. None of the GBMs contained EGFR genes amplified as homogeneously staining regions. Amplified dmin were not microscopically visible when stained with Giemsa because of their small size. Slot blot analysis showed that these low doses of hydroxyurea accelerated the loss of amplified EGFR genes in a dose- and time-dependent fashion. Pulsed-field gel electrophoresis and Southern blot analysis confirmed that EGFR gene loss was accompanied by amplified dmin loss in a dose-dependent fashion. CONCLUSION: These studies suggest the potential use of low-dose hydroxyurea in the treatment of GBMs.     

An outbreak of vancomycin-resistant Enterococcus faecium in liver transplant recipients

Vancomycin-resistant Enterococcus faecium (VREF) has become a significant nosocomial pathogen for immunosuppressed patients. During a 5-month period in 1993, 8 cases of invasive infection with VREF (7 with bacteremia) were identified in liver transplant recipients, half of whom were adults. Epidemiology and microbiology studies were designed to identify the source and to determine the risk factors for this infection. Overall mortality was 50% (3 adults and 1 child). Mortality in bacteremic patients was 57%. A case-control study showed that cases were more likely to have been treated with a third-generation cephalosporin or vancomycin and to have undergone more than four biliary tract procedures. Environmental surveillance cultures yielded only one VREF isolate from a rectal temperature probe, but this device was used in only 2 of the cases. Cultures from all surgery and radiology suites were negative. All VREF isolates were genotyped by contour-clamped homogenous electric field electrophoresis of chromosomal DNA restriction fragments. These studies showed that a single clone was responsible for the outbreak, although other clones could be detected in the hospital. After implementing strict contact isolation on the liver transplant unit, only 1 additional patient with VREF was identified during this outbreak. In conclusion, it was found that antibiotic use and biliary tract manipulation were risk factors for developing invasive infections with VREF after liver transplantation. Optimal treatment is still unclear but most likely includes a combination of two or more antibiotics. Prompt institution of infection control measures can preclude rapid spread of this nosocomial pathogen.     

Bragg curve spectroscopy in a 4π geometry

Ionization counters employing Bragg curve spectroscopy have been constructed for use in a 4π geometry. These detectors compare very favorably in terms of both energy and charge resolution with small solid angle devices. These detectors have a large dynamic range because they are backed by scintillation detectors, and are thus capable of detecting and identifying particles with energies from 1 MeV/nucleon up to 200 MeV/nucleon.     

External threat and the definition of deviance.

Studied how task-oriented groups of 5 members each responded to threats. 240 17–30 yr old males joined task groups to evaluate the case histories of juvenile delinquents and make correctional treatment recommendations to criminal justice authorities during a 55-min discussion period conducted by an observer. One member of the team was a confederate. During the 1st 30 min of group interaction, groups experienced a mild-threat condition (a criminal justice authority indicated he had to leave to observe another group and said that the group should probably not continue), a strong-threat condition (the authority said that the group should not continue), or no threat (the authority simply left the meeting). Discussion was allowed to continue, and at the end of the meeting Ss were asked if they would like to remain members of the group; each S was extensively interviewed after the meeting. Results show that level of threat was directly related to the extent of rejection and negative definition; noncomformity to the central task norm was not systematically related to deviant status; high-status actors were more involved in the rejection of the deviant; sociometric rejection of the deviant was accompanied by negative definition in the strong-threat condition; and the level of group solidarity was related to the extent of rejection and negative definition. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Think Small for Big Impact

Molecular engineering has emerged as an approach to integrate molecular‐level science and engineering to develop solutions to urgent societal problems. It aims to bring together molecular design—both rational and evolutionary, chemistry, and assembly to achieve new (bio)materials and device functionality. Molecular engineering also aims to bring researchers together to create new research interfaces between computation, machine learning, (bio)chemical synthesis and technology creation perspectives to accelerate new technologies for water and energy resources, information security, and human health.     

Continuous Software Process Improvement Requires Organisational Learning: An Australian Case Study

The study reported in this paper suggests that in order to achieve optimal benefits from implementing process improvement programs, organisations must move towards becoming what is termed a learning organisation. Software process assessment leads to the identification and selection of key activities for improvement and the continuous application of improvements to match business needs (ISO/IEC 1996). Continuous improvement requires a commitment to learning on the part of the organisation (Garvin 1993). A model to help identify evidence of learning (the Organisational Learning Evaluation Cycle [OLEC] has been developed and empirically tested in the study. We have found evidence to suggest that the case study organisation had not moved through all three of Garvin's (1993) overlapping phases of organisational learning and as a result the firm's improvement program did not achieve optimal benefits for the organisation. The paper concludes by discussing why significant improvement in performance was not achieved.     

Turbulence as a source of excessive baseline noise during high-speed isocratic and gradient separations using absorption detection

The occurrence of turbulent flow conditions in the connection tubing or at the entrance of the detection flow cell has been identified as a potential source of excessive detector noise in the signal of the diode array UV-absorption detector flow cell of a commercial HPLC system used to perform high-speed separations on wide-bore columns (4.6 mm i.d.). This excessive noise was found to occur abruptly if the flow rate is increased beyond a certain critical value or during gradient runs, if the mobile phase viscosity falls below a certain critical value. Several detector cells of different dimensions were studied to investigate the dependency of the effect on the detector cell design and the system tubing. Evidence for the turbulent flow origin of this noise is that its onset always occurred at a given fixed value of the Reynolds number. This critical Reynolds number could also be used to predict the onset of detector noise during gradient elution runs. Second, evidence for the turbulent flow origin of the noise was that it could be reliably eliminated using a flow splitter after the column to reduce the flow rate below its critical value before entering the detector. The loss in separation efficiency and detection sensitivity accompanying this flow splitting solution was found to be so small that it does not weigh up against the huge advantage of the possibility to eliminate the excessive detector noise.