Protein-polynucleotide scattering centers as a protein structure probe

When certain basic globular proteins are mixed with nucleic acids near a critical concentration ratio, large, low density scattering centers of about 10⁹ particle weight are created. Scattering from these complexes is altered when thermally inactivated proteins are substituted for enzymes in their native, globular conformation. Scattering data from heat-treated ribonuclease and lysozyme mixed with four different synthetic homopolyribonucleotides are reported. The concentration of nucleic acid necessary to produce maximum scattering from a heat-treated protein sample is shown to be a direct indication of the amount of enzyme that remains biologically active after being heated.     

Altered Sensitivity to Retinoid-Induced Apoptosis Associated with Changes in the Subcellular Distribution of Bcl-2

In the acute promyelocytic leukemia cell line NB4, Bcl-2 downregulation occurred as a late event of retinoid-induced differentiation. In the maturation-resistant NB4-R1 subclone, retinoids failed to downregulate Bcl-2 even in the situation of apoptosis massively induced by pan-agonists and RXR-selective agonists. We observed that NB4 and NB4-R1 cells differed with respect to the intracellular localization of Bcl-2 which showed a perinuclear localization in NB4-R1 cells, while Bax was broadly expressed in the cytoplasm and to only a minor extent in the perinuclear area. Therefore, the distinct intracellular localization of Bcl-2 and Bax was in general nonoverlaping. Bcl-2 remained massively expressed until cell disruption. Bax was not significantly upregulated in cells committed to death. However, Bax localization changed from a diffuse pattern to concentrate in few specific cytoplasmic area at a stage preceding the formation of apoptotic bodies. A human Bcl-2 transgene was transiently overexpressed in NB4-R1 cells which showed increased resistance to apoptosis induced by retinoids. Stably transfected clones of NB4-R1 cells showed an increased expression of Bcl-2 and a marked resistance to apoptosis. Interestingly, the overexpression of Bcl-2 restored a pattern of uniform Bcl-2 labeling in the cytoplasm and, remarkably, the colocalization of Bcl-2 with Bax. This work demonstrates that the ability of retinoid-induced cells to undergo apoptosis depends on the level of expression and the functional interaction between Bcl-2 and Bax.     

Effectiveness of Hospital-Wide Methicillin-Resistant Staphylococcus aureus (MRSA) Infection Control Policies Differs by Ward Specialty

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of preventable nosocomial infections and is endemic in hospitals worldwide. The effectiveness of infection control policies varies significantly across hospital settings. The impact of the hospital context towards the rate of nosocomial MRSA infections and the success of infection control is understudied. We conducted a modelling study to evaluate several infection control policies in surgical, intensive care, and medical ward specialties, each with distinct ward conditions and policies, of a tertiary public hospital in Sydney, Australia. We reconfirm hand hygiene as the most successful policy and find it to be necessary for the success of other policies. Active screening for MRSA, patient isolation in single-bed rooms, and additional staffing were found to be less effective. Across these ward specialties, MRSA transmission risk varied by 13% and reductions in the prevalence and nosocomial incidence rate of MRSA due to infection control policies varied by up to 45%. Different levels of infection control were required to reduce and control nosocomial MRSA infections for each ward specialty. Infection control policies and policy targets should be specific for the ward and context of the hospital. The model we developed is generic and can be calibrated to represent different ward settings and pathogens transmitted between patients indirectly through health care workers. This can aid the timely and cost effective design of synergistic and context specific infection control policies.     

The combination of trimethoprim and sulfamethoxazole in the treatment of urinary tract infection

In a series of 52 patients the combination of trimethoprim and sulfamethoxazole was used for the treatment of urinary tract infection and the results are analyzed with respect to the clinical diagnosis and bacterial etiology. There was complete agreement between in vitro sensitivity and clinical response except in the case of one strain of Streptococcus fecalis. The combination of drugs was effective against some bacterial strains which were resistant to the commonly used antimicrobial agents.     

LPS-induced biomarkers in mice: a potential model for identifying insulin sensitizers

The contribution of nutrient overload and associated inflammation to insulin resistance has highlighted several therapeutic targets including c-Jun N-terminal kinase (JNK) and S6 kinase (S6K). To investigate how a lipopolysaccharide (LPS)-mediated inflammatory response may modulate pathways implicated in insulin resistance, we characterized the LPS-induced changes in key biomarkers. Administration of 0.06-4 mg/kg LPS to C57BL/6 mice stimulated increases in plasma levels of TNFalpha, IL-12p40, IL-6 and MCP-1 and in JNK activity as measured by phosphorylated c-Jun in fat. For the first time, we show that LPS induces S6K activity by up to 6.1-fold, as measured by the phosphorylation of S6 ribosomal protein in liver, and increases by up to 1.8-fold, plasma levels of the novel pro-inflammatory cytokine osteopontin which is implicated in the pathogenesis of insulin resistance. These novel findings suggest that LPS administration may form the basis of an acute in vivo pharmacodynamic model for therapies targeting multiple pathways implicated in insulin resistance.