Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogenic bacterium that causes severe diseases in humans. For decades, MRSA has acquired substantial resistance against conventional antibiotics through regulatory adaptation, thereby posing a challenge for treating MRSA infection. One of the emerging strategies to combat MRSA is the combinatory use of antibacterial agents. Based on the dramatic change in phospholipid fatty acid (PLFA) composition of MRSA in previous results, this study investigated branched-chain amino acid derivatives (precursors of fatty acid synthesis of cell membrane) and discovered the antimicrobial potency of D-norvaline. The compound, which can act synergistically with oxacillin, is among the three leucine-tRNA synthetase inhibitors with high potency to inhibit MRSA cell growth and biofilm formation. PLFA analysis and membrane properties revealed that D-norvaline decreased the overall amount of PLFA, increasing the fluidity and decreasing the hydrophobicity of the bacterial cell membrane. Additionally, we observed genetic differences to explore the response to D-norvaline. Furthermore, deletion mutants and clinically isolated MRSA strains were treated with D-norvaline. The study revealed that D-norvaline, with low concentrations of oxacillin, was effective in killing several MRSA strains. In summary, our findings provide a new combination of aminoacyl-tRNA synthetase inhibitor D-norvaline and oxacillin, which is effective against MRSA.
In this paper, we describe a hybrid ZF-SD method. The method is based on dimensionality reduction via predecoding and cancellation of those symbols that can be quickly and reliably detected by a linear decoder. The proposed method shows BER performance similar to SD but with much lower computational complexity than SD.
In order to investigate the effects of different culture media containing various concentrations of epidermal growth factor (EGF) and chondroitin sulfate (CDS) on the growth of cultured corneal endothelial cell, pig corneal endothelial cells were used for this study. The cells were divided into 7 groups and each group was cultured with a medium containing: 1. Eagle's minimal essential medium with Earle's salt (EMEM) only; 2. EMEM + EGF (10 ng/ml); 3. EMEM + EGF (100 ng/ml); 4. EMEM + CDS (1 mg/ml); 5. EMEM + CDS (25 mg/ml); 6. EMEM + EGF (10 ng/ml) + CDS (1 mg/ml); 7. EMEM + EGF (100 ng/ml) + CDS (25 mg/ml), respectively. The results are shown below: (1) High concentration of EGF (100 ng/ml) stimulated the growth of pig corneal endothelial cells, shortened doubling time and the cells reached confluence earliest in group 3. But a low concentration of EGF (10 ng/ml) showed no effects on the growth of pig corneal endothelial cells. (2) A high concentration of CDS (25 mg/ml) might retard the growth of pig corneal endothelial cell, but a low concentration of CDS (1 mg/ml) has no retarding effects on the growth of pig corneal endothelial cells. (3) A high concentration of EGF could "antagonize" the CDS induced growth retarding effects of endothelial cells. (4) Those cells cultured with a medium containing high concentrations of EGF had more mitotic activity, including many prominent binuclear and polynucleolar cells. (5) The cells cultured with a medium containing high concentrations of CDS showed a more flat-shaped morphology under observation with a phase contrast microscope.(ABSTRACT TRUNCATED AT 250 WORDS)
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