Role of Thin Fimbriae in Adherence and Growth of Acinetobacter calcoaceticus RAG-1 on Hexadecane

Acinetobacter calcoaceticus RAG-1, a hydrocarbon-degrading bacterium which adheres avidly to hydrocarbons and other hydrophobic surfaces, possesses numerous thin fimbriae (ca. 3.5-nm diameter) on the cell surface. MR-481, a nonadherent mutant of RAG-1 which is unable to grow on hexadecane under conditions of limited emulsification and low initial cell density, lacks these fimbriae. Prolonged incubation of MR-481 in hexadecane medium enriched for partial adherence revertants. The reappearance of thin fimbriae was observed in all such revertant strains. RAG-1 cells and partial revertant strains were agglutinated in the presence of antibody, whereas MR-481 cells were not. Another mutant, AB15, which was previously isolated on the basis of its nonagglutinability in the presence of antibody, also lacked thin fimbriae and was conditionally nonadherent. Furthermore, strain AB15 was unable to grow on hexadecane medium. Adherence of RAG-1 cells to hexadecane was considerably reduced after shearing treatment. The material removed from the cell surface by shearing of RAG-1 and the partial revertant strains yielded a single antigenic band in RAG-1 and partial revertant strains, as observed by crossed immunoelectrophoresis. This band was absent in both fimbriae-less mutants, MR-481 and AB15. The data demonstrate that the thin fimbriae of RAG-1 (i) are a major factor in adherence to polystyrene and hydrocarbon, (ii) may be crucial in enabling growth of cells on hexadecane, and (iii) constitute the major cell surface agglutinogen.

Experimental demonstration of X-ray drive enhancement with rugby-shaped hohlraums

Rugby-shaped hohlraums have been suggested as a way to enhance x-ray drive in the indirect drive approach to inertial confinement fusion. This Letter presents an experimental comparison of rugby-shaped and cylinder hohlraums used for D2 and D3He-filled capsules implosions on the Omega laser facility, demonstrating an increase of x-ray flux by 18% in rugby-shaped hohlraums. The highest yields to date for deuterium gas implosions in indirect drive on Omega (1.5x10{10} neutrons) were obtained, allowing for the first time the measurement of a DD burn history. Proton spectra measurements provide additional validation of the higher drive in rugby-shaped hohlraums.

Collective dynamics of complex plasma bilayers

A classical dusty plasma experiment was performed using two different dust grain sizes to form a strongly coupled asymmetric bilayer (two closely spaced interacting monolayers) of two species of charged dust particles. The observation and analysis of the thermally excited particle oscillations revealed the collective mode structure and dispersion (wave propagation) in this system; in particular, the existence of the theoretically predicted k=0 energy (frequency) gap was verified. Equilibrium molecular-dynamics simulations were performed to emulate the experiment, assuming Yukawa-type interparticle interaction. The simulations and analytic calculations based both on lattice summation and on the quasilocalized charge approximation approach are in good agreement with the experimental findings and help in identifying and characterizing the observed phenomena.

Beam-plasma instabilities in a 2D Yukawa lattice

We consider a 2D Yukawa lattice of grains, with a beam of other charged grains moving in the lattice plane. In contrast to Vlasov plasmas, where the electrostatic instability excited by the beam is only longitudinal, here both longitudinal and transverse instabilities of the lattice phonons can develop. We determine and compare the transverse and longitudinal growth rates. The growth rate spectrum in wave number space exhibits remarkable gaps where no instability can develop. Depending on the system parameters, the transverse instability can be selectively excited.

Image-guided near-infrared fluorescent sentinel lymph node mapping in human breast cancer

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Background: Breast cancer surgery is presently performed without real-time image-guidance. We have developed a novel optical imaging system for image-guided surgery that uses invisible near-infrared (NIR) fluorescent light to highlight structures on the surgical field with high sensitivity, specificity, and contrast. We have also performed the first human clinical trial of the imaging system in women undergoing SLN mapping for breast cancer. Methods: We used a portable imaging system with an articulating arm that has 6 degrees of freedom, high power LED light source, custom optics, custom software, and sterile drape. The imaging system provided simultaneous and real-time imaging of color video and NIR fluorescence at up to 15 frames per second. N = 6 women with biopsy- confirmed breast cancer undergoing SLN mapping gave informed consent. All subjects received conventional mapping with Tc-99m sulfur colloid using a handheld gamma probe as well as NIR fluorescence-guided SLN mapping using a mixture of indocyanine green (ICG) diluted to a final concentration of 10 μM in human serum albumin (ICG:HSA). Results: The imaging system was easy to position in the operating room, with the articulating arm providing 50” horizontal reach and 70” vertical reach. Working distance to the patient was 18”. NIR fluorescence excitation was 20 mW/cm2 at 760 nm. NIR-depleted white light was 40,000 lux. A total of 1.6 ml of ICG:HSA was injected intra-tumorally and peri-tumorally and the site massaged for 5 min. 8 of 9 SLNs identified by Tc- 99m sulfur colloid were also identified by NIR fluorescence. However, NIR fluorescence identified an SLN, confirmed to have cancer in it, that was not identified by Tc-99m sulfur colloid. These differences were consistent with asynchrony in the injection techniques. Unlike the gamma-ray probe, NIR fluorescence provided high-resolution, large area optical imaging of the surgical field, and helped guide surgical resection. Conclusions: In this 6-patient pilot study, a novel NIR fluorescence optical imaging system was used for the first time, and provided real-time image-guided surgery for SLN mapping of breast cancer.

No significant financial relationships to disclose.

β-Galactosidase activity and H(2)S production in an experimental oral biofilm

We recently suggested that oral malodor production involves two steps: (i) deglycosylation of glycoproteins and (ii) proteolysis and amino acid utilization of the protein core to yield volatiles such as volatile sulfide compounds (VSCs). Our aim was to test the hypothesis that β-galactosidase activity and VSC production occur in distinct areas of the biofilm by two different bacterial populations. Biofilms were grown anaerobically for seven days with or without antibiotics (i.e. vancomycin and metronidazole). Biofilms were stained for β-galactosidase activity and VSC production and studied using confocal laser scanning microscopy. Results showed that β-galactosidase activity occurs in the outer layers and disappears following vancomycin addition, whereas VSC production occurs deeper within the biofilm and disappears following metronidazole application. These findings suggest that β-galactosidase activity is produced mainly by Gram-positive oral bacteria at the outer portion of the biofilm, and VSC production occurs in the deeper layers by Gram-negative oral bacteria.

Calcium-alginate coated, whey protein-based microspheres: preparation, some properties and opportunities

An 'all aqueous' encapsulation process followed by a heat treatment was used to prepare calcium-alginate-coated, whey protein-based, water insoluble microspheres containing micronized calcium carbonate as a model core. Results obtained with this process were compared to those obtained with a similar process in which chemical cross-linking was utilized. At an initial core load of 25 or 50% (w/w), core retention ranged from 84.2-95.12% and was not significantly affected by the initial core load or by the cross-linking method. Regardless of the cross-linking method, protein retention during the process was high and ranged from 78.2-87.5%. Outer topography of the microspheres was not influenced by the cross-linking method, however, at a given composition, the inner structure of heat treated microspheres differed from that obtained with chemically-cross-linked microspheres. Swelling properties of denovo microspheres were affected by pH. Results indicated that the micronized calcium carbonate could be used as a porogenic core. Removal of the core, by an acid treatment, allowed preparing microporous delivery devices. In addition to offer opportunities for encapsulation and delivery of crystalline core, the investigated process can provide means to prepare 'ghost' microporous delivery systems that can, in potential, be loaded, following their preparation, with sensitive core materials at conditions that favour the stability and functionality of this core.

Dust measurements in tokamaks (invited)

Dust production and accumulation present potential safety and operational issues for the ITER. Dust diagnostics can be divided into two groups: diagnostics of dust on surfaces and diagnostics of dust in plasma. Diagnostics from both groups are employed in contemporary tokamaks; new diagnostics suitable for ITER are also being developed and tested. Dust accumulation in ITER is likely to occur in hidden areas, e.g., between tiles and under divertor baffles. A novel electrostatic dust detector for monitoring dust in these regions has been developed and tested at PPPL. In the DIII-D tokamak dust diagnostics include Mie scattering from Nd:YAG lasers, visible imaging, and spectroscopy. Laser scattering is able to resolve particles between 0.16 and 1.6 microm in diameter; using these data the total dust content in the edge plasmas and trends in the dust production rates within this size range have been established. Individual dust particles are observed by visible imaging using fast framing cameras, detecting dust particles of a few microns in diameter and larger. Dust velocities and trajectories can be determined in two-dimension with a single camera or three-dimension using multiple cameras, but determination of particle size is challenging. In order to calibrate diagnostics and benchmark dust dynamics modeling, precharacterized carbon dust has been injected into the lower divertor of DIII-D. Injected dust is seen by cameras, and spectroscopic diagnostics observe an increase in carbon line (CI, CII, C(2) dimer) and thermal continuum emissions from the injected dust. The latter observation can be used in the design of novel dust survey diagnostics.

A novel microscopic assay for oral malodor-related microorganisms

Previous research has shown that the production of volatile sulfide compounds (VSC) by oral bacteria is associated with oral malodor. In the present study, we report a novel technique (microscopic sulfide assay (MSA)) for the quantification of VSC-producing oral microorganisms. The MSA was performed by overnight incubation of saliva samples in the presence of ferrous sulfate and sodium thiosulfate, followed by digital analysis of cells stained black due to cell-associated precipitation of ferric sulfide. This method was found to correlate significantly with oral malodor parameters, including mean odor judge scores (two judges, r = 0.48 and p = 0.001) and Halimeter® readings (r = 0.53 and p < 0.001), in a group of 42 subjects. As compared with odor judge scores as the gold standard, the new MSA technique yielded a diagnostic accuracy of 0.7 (ROC, p = 0.023). Results indicate that the MSA may serve as a diagnostic technique for assessing oral malodor levels and aid in identifying the particular bacteria involved in this condition.

Expression using vectors with phage lambda regulatory sequences

In the expression system described here, plasmids (pSKF) utilize regulatory signals--such as the powerful promoter pL--from the bacteriophage lambda. Transcription from pL can be fully repressed and plasmids containing it are thus stabilized by the lambda repressor, cI. The repressor is supplied by an E. coli host which contains a integrated copy of a portion of the lambda genome. This so-called defective lysogen supplies the lambda regulatory proteins cI and N but does not provide the lytic components that would normally lead to cell lysis. Thus, cells carrying these plasmids can be grown initially to high density without expression of the cloned gene and subsequently induced to synthesize the product upon inactivation of the repressor. This system also ensures that pL-directed transcription efficiently traverses any gene insert, which is accomplished by providing the phage lambda antitermination function, N, to the cell and by including on the pL transcription unit a site necessary for N utilization (Nut site). The N protein interacts with and modifies the RNA polymerase at the Nut site so as to block transcription termination at distal sites in the transcription unit. In order to express the coding sequence, efficient ribosome-recognition and translation-initiation sites have been engineered into the pL transcription unit. Expression occurs after temperature or chemical induction inactivates the repressor (see first and second basic protocols). Restriction endonuclease sites for insertion of the desired gene have been introduced both upstream and downstream from an ATG initiation codon. Thus, the system allows either direct expression or indirect expression (via protein fusion) of any coding sequence, thereby potentially allowing expression of any gene insert. Protocols describe direct expression of "authentic" gene products, as well as heterologous genes fused to highly expressed gene partners generates chimeric proteins that differ from the native form. In the latter case, the fusion partner can be removed to obtain an unfused version of the gene product.

Ground state of magnetic dipoles on a two-dimensional lattice: structural phases in complex plasmas

We study analytically and by molecular dynamics simulations the ground state configuration of a system of magnetic dipoles fixed on a two-dimensional lattice. We find different phases, in close agreement with previous results. Building on this result and on the minimum energy requirement we determine the equilibrium lattice configuration, the magnetic order (ferromagnetic versus antiferromagnetic), and the magnetic polarization direction of a system of charged mesoscopic particles with magnetic dipole moments, in the domain where the strong electrostatic coupling leads to a crystalline ground state. Orders of magnitudes of the parameters of the system relevant to possible future dusty plasma experiments are discussed.

Diagnosis of cystic fibrosis in the Republic of Ireland: epidemiology and costs

There were four objectives in this study: (1) determine the incidence of cystic fibrosis (CF) in Ireland; (2) estimate the cost of diagnosing CF; (3) clarify the characteristics and outcomes of the nationwide diagnostic efforts and (4) identify disparities. Surveys were conducted to determine the number, methods, costs and outcomes for sweat tests in Ireland from 2001 through 2003. The results allowed us to determine that Ireland's CF incidence is the world's highest at 1:1353. The average cost for diagnosis was Euro 2663 per patient. Analyses of data in The Cystic Fibrosis Registry of Ireland revealed longer delays when diagnosis followed respiratory symptoms, rather than gastrointestinal signs, and also in girls compared to boys, particularly those presenting with respiratory symptoms. Although expenditures for diagnosing of CF in Ireland are relatively modest, the high incidence and age of diagnosis, as well as gender-related disparities, are sufficient to warrant investment in national newborn screening.