Mechanistic analysis of a synthetic inhibitor of the Pseudomonas aeruginosa LasI quorum-sensing signal synthase

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen responsible for many human infections. LasI is an acyl-homoserine lactone synthase that produces a quorum-sensing (QS) signal that positively regulates numerous P. aeruginosa virulence determinants. The inhibition of the LasI protein is therefore an attractive drug target. In this study, a novel in silico to in vitro complementation was applied to screen thiazolidinedione-type compounds for their ability to inhibit biofilm formation at concentrations not affecting bacterial growth. The compound (z)-5-octylidenethiazolidine-2, 4-dione (TZD-C8) was a strong inhibitor of biofilm formation and chosen for further study. Structural exploration of in silico docking predicted that the compound had high affinity for the LasI activity pocket. The TZD-C8 compound was also predicted to create hydrogen bonds with residues Arg30 and Ile107. Site-directed mutagenesis (SDM) of these two sites demonstrated that TZD-C8 inhibition was abolished in the lasI double mutant PAO-R30D, I107S. In addition, in vitro swarming motility and quorum sensing signal production were affected by TZD-C 8, confirming this compound alters the cell to cell signalling circuitry. Overall, this novel inhibitor of P. aeruginosa quorum sensing shows great promise and validates our mechanistic approach to discovering inhibitors of LuxI-type acyl-homoserine lactone synthases.

How do radiologists evaluate osteonecrosis?

OBJECTIVES

Management of patients with osteonecrosis of the hip remains controversial and challenging. Because the prognosis and treatment are determined in large part by the stage and extent of the disease, it is important to use a reliable and efficient method for evaluation and staging. The objective of this study was to determine how musculoskeletal (MSK) radiologists evaluate osteonecrosis and whether this evaluation is adequate.

MATERIALS AND METHODS

A 12-part questionnaire was designed to determine how MSK radiologists evaluate patients with osteonecrosis of the femoral head (ONFH). This was sent to 888 members of the Society of Skeletal Radiology.

RESULTS

One hundred and twenty-one members responded to essentially all questions. Patients were evaluated using plain radiographs and MRI. All agreed that it is clinically important to determine the extent of necrosis and joint involvement, and 115 (95 %) stated that this should be part of the radiologists' evaluation. However, only 55 (46 %) said that in practice they used a specific system of classification, and most of these used the Ficat and Arlet classification, which does not indicate the extent of involvement. One hundred and seven (88 %) respondents included a simple visual estimate of the extent of involvement, and a small number added a specific measurement of lesion size. The majority indicated that they were infrequently consulted about which imaging studies should be obtained.

CONCLUSIONS

Although radiologists recognize the clinical importance of determining the extent of necrosis and joint involvement in patients with ONFH, in practice the methods used to evaluate these patients often do not accomplish this satisfactorily. The use of an effective classification, which includes both stage and extent of involvement, should be stressed, as it will lead to improved treatment of patients with ON. Physicians who order imaging studies for patients with ON should be encouraged to consult routinely with their radiology colleagues regarding which studies to request, as well as on the interpretation of these studies.

200 MeV proton radiography studies with a hand phantom using a prototype proton CT scanner

Proton radiography has applications in patient alignment and verification procedures for proton beam radiation therapy. In this paper, we report an experiment which used 200 MeV protons to generate proton energy-loss and scattering radiographs of a hand phantom. The experiment used the first-generation proton computed tomography (CT) scanner prototype, which was installed on the research beam line of the clinical proton synchrotron at Loma Linda University Medical Center. It was found that while both radiographs displayed anatomical details of the hand phantom, the energy-loss radiograph had a noticeably higher resolution. Nonetheless, scattering radiography may yield more contrast between soft and bone tissue than energy-loss radiography, however, this requires further study. This study contributes to the optimization of the performance of the next-generation of clinical proton CT scanners. Furthermore, it demonstrates the potential of proton imaging (proton radiography and CT), which is now within reach of becoming available as a new, potentially low-dose medical imaging modality.

An in vivo method for measuring the adsorption of plasma proteins to titanium in humans

A novel method of collecting in vivo plasma proteins of humans from osteotomies prepared during insertion of an oral implant is described. A rod containing a collecting portion with a predetermined surface is introduced into the osteomy, removed, and transferred for enzyme-linked immunosorbent assay analysis. Two experiments were used to examine the feasibility of the method. In the first, titanium (Ti) rods with different roughness were exposed for 10 min to the blood. Blasted and acid-etched surfaces adsorbed four times more and acid-etched surfaces adosorbed two times more plasma proteins as compared to machined surfaces. In the second experiment, blasted and acid-etched rods were wetted for 10 s prior to the insertion. The adsorption for fibronectin, albumin, fibrinogen, and IgG was enhanced significantly compared with nonwetted rods. These results are discussed in the light of previous methods used in studies on adsorption. Thus, use of the collecting instrument enables aspects of human plasma-implant interface to be studied in a more realistic manner.

In celebration of the 100th anniversary of the lipid hypothesis of atherosclerosis

This year marks the 100th anniversary of the publication of Anitschkow's classic paper proposing the central role of hypercholesterolemia in atherogenesis. We at the Journal of Lipid Research take this occasion to acknowledge the debt we all owe to Anitschkow and his colleagues for getting us on the right track. As discussed below in detail, his contributions were insightful and went well beyond simply pinpointing hypercholesterolemia as a major etiologic factor. Anitschkow's work led him to define most of the key elements in the initiation and evolution of lesions in animal models of atherogenesis.

Development of a Head Scanner for Proton CT

We describe a new head scanner developed for Proton Computed Tomography (pCT) in support of proton therapy treatment planning, aiming at reconstructing an accurate map of the stopping power (S.P.) in a phantom and, in the future, in patients. The system consists of two silicon telescopes which track the proton before and after the phantom/patient, and an energy detector which measures the residual energy or range of the proton to reconstruct the Water Equivalent Path Length (WEPL) in the phantom. Based on the experience of the existing prototype and extensive Geant4 simulations and CT reconstructions, the new pCT scanner will support clinically useful proton fluxes.

Evaluation of plant and fungal extracts for their potential antigingivitis and anticaries activity

The link between diet and health has lead to the promotion of functional foods which can enhance health. In this study, the oral health benefits of a number of food homogenates and high molecular mass and low molecular mass fractions were investigated. A comprehensive range of assays were performed to assess the action of these foods on the development of gingivitis and caries using bacterial species associated with these diseases. Both antigingivitis and anticaries effects were investigated by assays examining the prevention of biofilm formation and coaggregation, disruption of preexisting biofilms, and the foods' antibacterial effects. Assays investigating interactions with gingival epithelial cells and cytokine production were carried out to assess the foods' anti- gingivitis properties. Anti-caries properties such as interactions with hydroxyapatite, disruption of signal transduction, and the inhibition of acid production were investigated. The mushroom and chicory homogenates and low molecular mass fractions show promise as anti-caries and anti-gingivitis agents, and further testing and clinical trials will need to be performed to evaluate their true effectiveness in humans.

Chance and serendipity in science: two examples from my own career

The usual scientific paper follows a rather narrowly (but not ever rigidly) defined pattern. Both the author and the journal like to see a linear logical presentation of a "story." Seldom does the paper give the reader the "backstory." Where did the idea come from in the first place? How many false leads led down blind alleys? What happened by chance and what by logical planning? Was there an element of serendipity involved? Perhaps as we enter the paperless era and do not have to count words quite so religiously, it may be possible to encourage a more freewheeling scientific paper, but for now, we have to rely on the historians of science and/or those who "tell all" about their own research. "Reflections" seems an appropriate space for the latter. I have chosen two scenarios from my own career in which happy accidents played important roles but, unhappily, received little recognition in my published papers.