Steps in the bacterial flagellar motor

The bacterial flagellar motor is a highly efficient rotary machine used by many bacteria to propel themselves. It has recently been shown that at low speeds its rotation proceeds in steps [Sowa et al. (2005) Nature 437, 916--919]. Here we propose a simple physical model that accounts for this stepping behavior as a random walk in a tilted corrugated potential that combines torque and contact forces. We argue that the absolute angular position of the rotor is crucial for understanding step properties, and show this hypothesis to be consistent with the available data, in particular the observation that backward steps are smaller on average than forward steps. Our model also predicts a sublinear torque-speed relationship at low torque, and a peak in rotor diffusion as a function of torque

A Turbulent Origin for Flocculent Spiral Structure in Galaxies

The flocculent structure of star formation in 7 galaxies has a Fourier transform power spectrum for azimuthal intensity scans with a power law slope that increases systematically from -1 at large scales to -1.7 at small scales. This is the same pattern as in the power spectra for azimuthal scans of HI emission in the Large Magellanic Clouds and for flocculent dust clouds in galactic nuclei. The steep part also corresponds to the slope of -3 for two-dimensional power spectra that have been observed in atomic and molecular gas surveys of the Milky Way and the Large and Small Magellanic Clouds. The same power law structure for star formation arises in both flocculent and grand design galaxies, which implies that the star formation process is the same in each. Fractal Brownian motion models that include discrete stars and an underlying continuum of starlight match the observations if all of the emission is organized into a global fractal pattern with an intrinsic 1D power spectrum having a slope between 1.3 and 1.8. We suggest that the power spectrum of optical light in galaxies is the result of turbulence, and that large-scale turbulent motions are generated by sheared gravitational instabilities which make flocculent spiral arms first and then cascade to form clouds and clusters on smaller scales.Comment: accepted for ApJ, 31 pg, 9 figure

TES-1/Tes and ZYX-1/Zyxin protect junctional actin networks under tension during epidermal morphogenesis in the C. elegans embryo

Acknowledgments cDNA clones for hmr-1, ajm-1, zyx-1, zoo-1, hmp-1, and tes-1 (yk collection) were provided by Yuji Kohara (National Institute of Genetics). A.M.L., Y.Z., B.G.L., S.C.T.M., and J.H. were supported by NIH grant R01GM058038 and NIH MIRA R35GM145312 awarded to J.H.; S.C.T.M. was supported by a Gilliam Fellowship from the Howard Hughes Medical Institute and by an Advanced Opportunities Fellowship and a COVID-19 dissertation completion fellowship from the University of Wisconsin-Madison; S.B. and A.A. were supported by NIH MIRA R35GM134865 awarded to A.A.; J.D.W. was supported by NIH grant F32GM122372 and by NIH grant R01GM104032 and the Army Research Office Multidisciplinary University Research Initiative W911NF1410403 awarded to M.L.G.; and B.G. and M.M.S. were supported by NIH MIRA R35GM134838 awarded to B.G. and NIH grant F32GM119348 awarded to M.M.S. Some strains were provided by the Caenorhabditis Genetics Center (CGC; https://cbs.umn.edu/cgc/home), which is funded by the NIH Office of Research Infrastructure Programs (P40 OD010440).Peer reviewedPostprin

Imported Melioidosis, Israel, 2008

In 2008, melioidosis was diagnosed in an agricultural worker from Thailand in the southern Jordan Valley in Israel. He had newly diagnosed diabetes mellitus, fever, multiple abscesses, and osteomyelitis. Burkholderia pseudomallei was isolated from urine and blood. Four of 10 laboratory staff members exposed to the organism received chemoprophylaxis, 3 of whom had adverse events

A community-based lifestyle and weight loss intervention promoting a Mediterranean-style diet pattern evaluated in the stroke belt of North Carolina: the Heart Healthy Lenoir Project

Abstract Background Because residents of the southeastern United States experience disproportionally high rates of cardiovascular disease (CVD), it is important to develop effective lifestyle interventions for this population. Methods The primary objective was to develop and evaluate a dietary, physical activity (PA) and weight loss intervention for residents of the southeastern US. The intervention, given in eastern North Carolina, was evaluated in a 2 year prospective cohort study with an embedded randomized controlled trial (RCT) of a weight loss maintenance intervention. The intervention included: Phase I (months 1–6), individually-tailored intervention promoting a Mediterranean-style dietary pattern and increased walking; Phase II (months 7–12), option of a 16-week weight loss intervention for those with BMI ≥ 25 kg/m2 offered in 2 formats (16 weekly group sessions or 5 group sessions and 10 phone calls) or a lifestyle maintenance intervention; and Phase III (months 13–24), weight loss maintenance RCT for those losing ≥ 8 lb with all other participants receiving a lifestyle maintenance intervention. Change in diet and PA behaviors, CVD risk factors, and weight were assessed at 6, 12, and 24 month follow-up. Results Baseline characteristics (N = 339) were: 260 (77 %) females, 219 (65 %) African Americans, mean age 56 years, and mean body mass index 36 kg/m2. In Phase I, among 251 (74 %) that returned for 6 month follow-up, there were substantial improvements in diet score (4.3 units [95 % CI 3.7 to 5.0]), walking (64 min/week [19 to 109]), and systolic blood pressure (−6.4 mmHg [−8.7 to −4.1]) that were generally maintained through 24 month follow-up. In Phase II, 138 (57 group only, 81 group/phone) chose the weight loss intervention and at 12 months, weight change was: −3.1 kg (−4.9 to −1.3) for group (N = 50) and −2.1 kg (−3.2 to −1.0) for group/phone combination (N = 75). In Phase III, 27 participants took part in the RCT. At 24 months, weight loss was −2.1 kg (−4.3 to 0.0) for group (N = 51) and −1.1 kg (−2.7 to 0.4) for combination (N = 72). Outcomes for African American and whites were similar. Conclusions The intervention yielded substantial improvement in diet, PA, and blood pressure, but weight loss was modest. Trial registration clinicaltrials.gov Identifier: NCT0143348

Inhibition of neuroinflammation in BV2 microglia by the biflavonoid kolaviron is dependent on the Nrf2/ARE antioxidant protective mechanism

Kolaviron is a mixture of bioflavonoids found in the nut of the West African edible seed Garcinia kola, and it has been reported to exhibit a wide range of pharmacological activities. In this study, we investigated the effects of kolaviron in neuroinflammation. The effects of kolaviron on the expression of nitric oxide/inducible nitric oxide synthase (iNOS), prostaglandin E2 (PGE2)/cyclooxygenase-2, cellular reactive oxygen species (ROS) and the pro-inflammatory cytokines were examined in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. Molecular mechanisms of the effects of kolaviron on NF-B and Nrf2/ARE signalling pathways were analysed by immunoblotting, binding assay, and reporter assay. RNA interference was used to investigate the role of Nrf2 in the anti-inflammatory effect of kolaviron. Neuroprotective effect of kolaviron was assessed in a BV2 microglia/HT22 hippocampal neuron co-culture. Kolaviron inhibited the protein levels of NO/iNOS, PGE2/COX-2, cellular ROS and the proinflammatory cytokines (TNFα and IL-6) in LPS-stimulated microglia. Further mechanistic studies showed that kolaviron inhibited neuroinflammation by inhibiting IB/NF-B signalling pathway in LPS-activated BV2 microglia. Kolaviron produced antioxidant effect in BV2 microglia by increasing HO-1 via the Nrf2/ antioxidant response element (ARE) pathway. RNAi experiments revealed that Nrf2 is need for the anti-inflammatory effect of kolaviron. Kolaviron protected HT22 neurons from neuroinflammation-induced toxicity. Kolaviron inhibits neuroinflammation through Nrf2-dependent mechanisms. This compound may therefore be beneficial in neuroinflammation-related neurodegenerative disorders

Search for Colour Singlet and Colour Reconnection Effects in Hadronic Z Decays at LEP

A search is performed in symmetric 3-jet hadronic Z decay events for evidence of colour singlet production or colour reconnection effects. Asymmetries in the angular separation of particles are found to be sensitive indicators of such effects. Upper limits on the level of colour singlet production and colour reconnection effects are established for a variety of models

The metabolic syndrome and neuropathy: Therapeutic challenges and opportunities

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110888/1/ana23986.pd

Bacterial Chemotaxis in an Optical Trap

An optical trapping technique is implemented to investigate the chemotactic behavior of a marine bacterial strain Vibrio alginolyticus. The technique takes the advantage that the bacterium has only a single polar flagellum, which can rotate either in the counter-clock-wise or clock-wise direction. The two rotation states of the motor can be readily and instantaneously resolved in the optical trap, allowing the flagellar motor switching rate to be measured under different chemical stimulations. In this paper the focus will be on the bacterial response to an impulsive change of chemoattractant serine. Despite different propulsion apparati and motility patterns, cells of V. alginolyticus apparently use a similar response as Escherichia coli to regulate their chemotactic behavior. Specifically, we found that the switching rate of the bacterial motor exhibits a biphasic behavior, showing a fast initial response followed by a slow relaxation to the steady-state switching rate . The measured can be mimicked by a model that has been recently proposed for chemotaxis in E. coli. The similarity in the response to the brief chemical stimulation in these two different bacteria is striking, suggesting that the biphasic response may be evolutionarily conserved. This study also demonstrated that optical tweezers can be a useful tool for chemotaxis studies and should be applicable to other polarly flagellated bacteria

The internal structure of poly(methyl methacrylate) latexes in nonpolar solvents

Hypothesis: Poly(methyl methacrylate) (PMMA) latexes in nonpolar solvents are an excellent model system to understand phenomena in low dielectric media, and understanding their internal structure is critical to characterizing their performance in both fundamental studies of colloidal interactions and in potential industrial applications. Both the PMMA cores and the poly(12-hydroxystearic acid) (PHSA) shells of the latexes are known to be penetrable by solvent and small molecules, but the relevance of this for the properties of these particles is unknown. Experiments: These particles can be prepared in a broad range of sizes, and two PMMA latexes dispersed in n-dodecane (76 and 685 nm in diameter) were studied using techniques appropriate to their size. Small-angle scattering (using both neutrons and X-rays) was used to study the small latexes, and analytical centrifugation was used to study the large latexes. These studies enabled the calculation of the core densities and the amount of solvent in the stabilizer shells for both latexes. Both have consequences on interpreting measurements using these latexes. Findings: The PHSA shells are highly solvated (∼85% solvent by volume), as expected for effective steric stabilizers. However, the PHSA chains do contribute to the intensity of neutron scattering measurements on concentrated dispersions and cannot be ignored. The PMMA cores have a slightly lower density than PMMA homopolymer, which shows that only a small free volume is required to allow small molecules to penetrate into the cores. Interestingly, the observations are essentially the same, regardless of the size of the particle; these are general features of these polymer latexes. Despite the latexes being used as a model physical system, the internal chemical structure is complex and must be fully considered when characterizing them