Impact of antimicrobial stewardship program-driven educational intervention for vancomycin loading dose on mortality.

BACKGROUND: Although the loading dose (LD) of vancomycin (VCM) contributes to its efficacy, it may not be conducted adequately. Herein, the objective was to evaluate the effect of LD on patient prognosis using therapeutic drug monitoring by pharmacists and elucidate the impact of an antimicrobial stewardship program (ASP)-driven educational intervention on the LD implementation rate and patient prognosis. MATERIALS AND METHODS: First, a retrospective cohort study was conducted involving 121 adult patients administered with VCM and compared with 28-day mortality in LD and non-LD groups. To avoid confounding, the propensity score method was employed. Second, post-training with ASP-driven lectures, a questionnaire survey was conducted for healthcare workers, including physicians, nurses, and pharmacists. The rates of VCM LD implementation and 28-day mortality were compared during a period of one year and 9 months between the pre-ASP (n = 38) and post-ASP (n = 33) groups. RESULTS: After propensity score matching, the 28-day mortality in the LD group was significantly improved, suggesting that the early increase in blood levels of VCM due to an LD is an important factor influencing patient prognosis. After the lecture, a questionnaire survey revealed that the understanding rates of "well" and "slightly well" for educational lectures exceeded 80% of all healthcare workers. The rate of LD implementation significantly increased to 63.6% (21/33) in the post-ASP group compared with 31.6% (12/38) in the pre-ASP group (p = 0.007), and the 28-day mortality declined from 23.7% (9/38) to 6.1% (2/33) (p = 0.041). CONCLUSION: This method of ASP-driven educational intervention would facilitate LD implementation, improving patient prognosis.

Human RAD50 makes a functional DNA-binding complex.

The MRE11-RAD50-NBS1 (MRN) complex has several distinct functions in DNA repair including important roles in both non-homologous end-joining (NHEJ) and homologous recombination (HR). The biochemical activities of MR(N) have been well characterized implying specific functional roles for the components. The arrangement of proteins in the complex implies interdependence of their biochemical activities making it difficult to separate specific functions. We obtained purified human RAD50 and observed that it binds ATP, undergoes ATP-dependent conformational changes as well as having ATPase activity. Scanning force microscopy analysis clearly showed that RAD50 binds DNA although not as oligomers. RAD50 alone was not functional in tethering DNA molecules. ATP increased formation of RAD50 multimers which were however globular lacking extended coiled coils, in contrast to the MR complex where ATP induced oligomers have obvious coiled coils protruding from a central domain. These results suggest that MRE11 is important in maintaining the structural arrangement of RAD50 in the protein complex and perhaps has a role in reinforcing proper alignment of the coiled coils in the ATP-bound state.

Efficient transgene expression by alleviation of translational repression in plant cells.

Global translational repression under abiotic stress influences translation of both endogenous and transgene mRNAs. Even in plant cell culture, hypoxia and nutrient deficient stress arise during the growth process. In this study, we first demonstrated the existence of global translational repression in Arabidopsis T87 cultured cells over a time course following inoculation. Next, we performed genome-wide analysis, which revealed that the translational states of endogenous mRNAs differed significantly between growth and stationary phase cells. This analysis showed that translation from most mRNAs was repressed upon stationary phase. Otherwise, a part of mRNA including alcohol dehydrogenase (ADH) gene was recalcitrant to the repression. Furthermore, by polysome analysis and followed quantitative reverse transcription PCR analysis of transformants having 5'untranslated regions (UTRs) of ADH or translationally repressed At3g47610 mRNA fused to reporter gene, we demonstrated that polysomal associations of reporter mRNAs were in accordance with those the mRNAs from which their 5'UTR derived, suggesting that the 5'UTR is an important determinant of the translational state of mRNAs in stationary phase cells. Finally, we demonstrated the effectiveness of 5'UTR of ADH mRNA in transformants derived from the BY-2 tobacco cell line. These results suggested that 5'UTR of ADH mRNA would be a useful element for efficient transgene expression upon stationary phase.

Ataxia telangiectasia-mutated (ATM) kinase activity is regulated by ATP-driven conformational changes in the Mre11/Rad50/Nbs1 (MRN) complex.

The Ataxia Telangiectasia-Mutated (ATM) protein kinase is recruited to sites of double-strand DNA breaks by the Mre11/Rad50/Nbs1 (MRN) complex, which also facilitates ATM monomerization and activation. MRN exists in at least two distinct conformational states, dependent on ATP binding and hydrolysis by the Rad50 protein. Here we use an ATP analog-sensitive form of ATM to determine that ATP binding, but not hydrolysis, by Rad50 is essential for MRN stimulation of ATM. Mre11 nuclease activity is dispensable, although some mutations in the Mre11 catalytic domain block ATM activation independent of nuclease function, as does the mirin compound. The coiled-coil domains of Rad50 are important for the DNA binding ability of MRN and are essential for ATM activation, but loss of the zinc hook connection can be substituted by higher levels of the complex. Nbs1 binds to the "closed" form of the MR complex, promoted by the zinc hook and by ATP binding. Thus the primary role of the hook is to tether Rad50 monomers together, promoting the association of the Rad50 catalytic domains into a form that binds ATP and also binds Nbs1. Collectively, these results show that the ATP-bound form of MRN is the critical conformation for ATM activation.

BLM-DNA2-RPA-MRN and EXO1-BLM-RPA-MRN constitute two DNA end resection machineries for human DNA break repair.

Repair of dsDNA breaks requires processing to produce 3'-terminated ssDNA. We biochemically reconstituted DNA end resection using purified human proteins: Bloom helicase (BLM); DNA2 helicase/nuclease; Exonuclease 1 (EXO1); the complex comprising MRE11, RAD50, and NBS1 (MRN); and Replication protein A (RPA). Resection occurs via two routes. In one, BLM and DNA2 physically and specifically interact to resect DNA in a process that is ATP-dependent and requires BLM helicase and DNA2 nuclease functions. RPA is essential for both DNA unwinding by BLM and enforcing 5' → 3' resection polarity by DNA2. MRN accelerates processing by recruiting BLM to the end. In the other, EXO1 resects the DNA and is stimulated by BLM, MRN, and RPA. BLM increases the affinity of EXO1 for ends, and MRN recruits and enhances the processivity of EXO1. Our results establish two of the core machineries that initiate recombinational DNA repair in human cells.

Development and application of a simple LC-MS method for the determination of plasma maraviroc concentrations.

Maraviroc is an orally available antagonist of the CCR5 chemokine receptor, which acts as a human immunodeficiency virus type 1 (HIV-1) coreceptor. Binding of maraviroc to this receptor blocks HIV-1 attachment to the coreceptor and prevents HIV-1 from entering host cells. Maraviroc does not require intracellular processing to exert this activity. Drug interaction studies have shown changes in maraviroc exposure when given with other anti-HIV medications, and thus quantification of maraviroc in human plasma is important to manage drug interactions and to evaluate the relationship between plasma concentrations and treatment response. We developed a conventional LC-MS method for determining plasma maraviroc concentrations, validated by estimating precision and accuracy for inter- and intraday analysis in the concentration range of 0.011-2.188 µg/ml. The calibration curve was linear within this range. The average accuracy ranged from 92.7% to 99.7%, while the relative standard deviations of both inter- and intraday assays were less than 7.1%. Recovery of maraviroc exceeded 86.7%. Our LC-MS method provides a conventional, accurate and precise way to determine the maraviroc concentration in human plasma. This method enables dose adjustment based on monitoring plasma maraviroc concentrations and permits management of drug interactions and toxicity.

High performance liquid chromatography using UV detection for the simultaneous quantification of the new non-nucleoside reverse transcriptase inhibitor etravirine (TMC-125), and 4 protease inhibitors in human plasma.

Etravirine (TMC-125, ETV) is a second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) that demonstrates potent activity against NNRTI-resistant strains of human immunodeficiency virus type-1 (HIV-1). Thus, ETV has been used in combination with ritonavir-boosted protease inhibitor (PI) and integrase inhibitor for therapy-experienced HIV-1-infected patients. On the other hand, as ETV is a substrate and inducer of cytochrome P450 3A4 (CYP3A4), ETV may induce metabolism of PI and alter the concentrations of co-administered PIs. In order to ensure optimal drug efficacy and prevention of resistance, it is essential to monitor plasma concentrations of ETV and PIs. Here we describe the application of HPLC with UV detection for the simulataneous assay of ETV and 4 PIs, darunavir (DRV), atazanavir (ATV), ritonavir (RTV) and lopinavir (LPV). In this study, the calibration curve of each drug was linear with the average accuracy ranging from 93.6 to 110.9%. Both intra- and interday coefficients of variation for each drug were less than 11.6%. The mean recovery of all drugs ranged from 88.0 to 97.5%. The limit of quantification was 0.04, 0.04, 0.04, 0.05 and 0.07 microg/ml for ETV, DRV, ATV, RTV and LPV, respectively. These results demonstrate that our HPLC-UV method can be used for routine determination of plasma concentrations of ETV and 4 PIs in clinical settings.

RAD50, an SMC family member with multiple roles in DNA break repair: how does ATP affect function?

The protein complex including Mre11, Rad50, and Nbs1 (MRN) functions in DNA double-strand break repair to recognize and process DNA ends as well as signal for cell cycle arrest. Amino acid sequence similarity and overall architecture make Rad50 a member of the structural maintenance of chromosome (SMC) protein family. Like SMC proteins, Rad50 function depends on ATP binding and hydrolysis. All current evidence indicates that ATP binding and hydrolysis cause architectural rearrangements in SMC protein complexes that are important for their functions in organizing DNA. In the case of the MRN complex, the functional significance of ATP binding and hydrolysis are not yet defined. Here we review the data on the ATP-dependent activities of MRN and their possible mechanistic significance. We present some speculation on the role of ATP for function of the MRN complex based on the similarities and differences in the molecular architecture of the Rad50-containing complexes and the SMC complexes condensin and cohesin.

RAD50 and NBS1 form a stable complex functional in DNA binding and tethering.

The RAD50/MRE11/NBS1 protein complex (RMN) plays an essential role during the early steps of DNA double-strand break (DSB) repair by homologous recombination. Previous data suggest that one important role for RMN in DSB repair is to provide a link between DNA ends. The striking architecture of the complex, a globular domain from which two extended coiled coils protrude, is essential for this function. Due to its DNA-binding activity, ability to form dimers and interact with both RAD50 and NBS1, MRE11 is considered to be crucial for formation and function of RMN. Here, we show the successful expression and purification of a stable complex containing only RAD50 and NBS1 (RN). The characteristic architecture of the complex was not affected by absence of MRE11. Although MRE11 is a DNA-binding protein it was not required for DNA binding per se or DNA-tethering activity of the complex. The stoichiometry of NBS1 in RMN and RN complexes was estimated by SFM-based volume analysis. These data show that in vitro, R, M and N form a variety of stable complexes with variable subunit composition and stoichiometry, which may be physiologically relevant in different aspects of RMN function.

New lycorine-type alkaloid from Lycoris traubii and evaluation of antitrypanosomal and antimalarial activities of lycorine derivatives.

A new lycorine derivative LT1 (4) was isolated from the aerial part and bulbs of Lycoris traubii Hayward (Amaryllidaceae). Its structure including absolute configuration was established by spectroscopic analysis and semi-synthesis to be 1-O-(3'S)-hydroxybutanoyllycorine. Some lycorine ester derivatives including LT1 were examined for their inhibitory activity against Trypanosoma brucei brucei, the parasite associated with sleeping sickness, and against Plasmodium falciparum, the causative agent of malaria. Among them, 2-O-acetyllycorine (6) showed the most potent activity against parasitic T. b. brucei, and LT1 (4), 1-O-(3'R)-hydroxybutanoyllycorine (8), 1,2-di-O-butanoyllycorine (11), and 1-O-propanoyllycorine (12) showed significant activity against P. falciparum in an in vitro experiment.

Phytochemical and biological investigation of Hymenocallis littoralis SALISB.

A phytochemical investigation of the bulbs and flowers of Hymenocallis littoralis SALISB., cultivated in Egypt, was carried out, which resulted in the isolation of four alkaloids, lycorine (1), hippeastrine (2), 11-hydroxyvittatine (3), and (+)-8-O-demethylmaritidine (4), and of two flavonoids, quercetin 3'-O-glucoside (5), and rutin (6). The volatile constituents of the plant flowers were analyzed for the first time by GC/MS, which led to the identification of 26 known compounds (Table 1). Finally, the antimicrobial activity of the petroleum ether extract of the flowers of H. littoralis was investigated.

RNAi knock-down of ENOD40s leads to significant suppression of nodule formation in Lotus japonicus.

ENOD40 is one of the most intriguing early nodulin genes that is known to be induced very early in response to interaction of legume plants with symbiotic Rhizobium bacteria, but its function in the nodulation process is still not known. Lotus japonicus has two ENOD40 genes: LjENOD40-1 is abundantly induced in very early stages of bacterial infection or Nod factor application, whereas LjENOD40-2 is abundantly expressed only in mature nodules. We generated transgenic lines of L. japonicus with an RNAi (RNA interference) construct that expresses hairpin double-stranded RNA for LjENOD40-1 to induce sequence-specific RNA silencing. In the transgenic plants, expression of both LjENOD40-1 and -2 was significantly reduced, and no accumulation of ENOD40 transcripts was detected upon Mesorhizobium loti inoculation. The transgenic plants exhibited very poor nodulation (only 0-2 nodules per plant) and could not grow well without additional nitrogen supply. Analysis of segregation in the T(2) progeny indicated that the suppression of nodulation is perfectly linked with the presence of the transgene. Microscopic observation of the infection process using lacZ-labeled M. loti, together with expression analysis of infection-related nodulin genes, demonstrated that ENOD40 knock-down did not inhibit the initiation of the bacterial infection process. In contrast, nodule primordium initiation and subsequent nodule development were significantly suppressed in the transgenic plants. These results clearly indicate that ENOD40 is required for nodule initiation and subsequent organogenesis, but is not involved in early infection events.