Dual flaA1 flaB1 mutant of Serpulina hyodysenteriae expressing periplasmic flagella is severely attenuated in a murine model of swine dysentery

The motility imparted by the periplasmic flagella (PF) of Serpulina hyodysenteriae is thought to play a pivotal role in the enteropathogenicity of this spirochete. The complex PF are composed of multiple class A and class B polypeptides. Isogenic strains containing specifically disrupted flaAl or flaB1 alleles remain capable of expressing PF, although such mutants display aberrant motility in vitro. To further examine the role that these proteins play in the maintenance of periplasmic flagellar structural integrity, motility, and fitness for intestinal colonization, we constructed a novel strain of S. hyodysenteriae which is deficient in both FlaA1 and FlaB1. To facilitate construction of this strain, a chloramphenicol gene cassette, with general application as a selectable marker in prokaryotes, was developed. The cloned flaAl and flaB1 genes were disrupted by replacement of internal fragments with chloramphenicol and kanamycin gene cassettes, respectively. The inactivated flagellar genes were introduced into S. hyodysenteriae, and allelic exchange at the targeted chromosomal flaA1 and flaB1 loci was verified by PCR analysis. Immunoblots or cell lysates with antiserum raised against purified FlaA or FlaB confirmed the absence of the corresponding sheath and core proteins in this dual flagellar mutant. These mutations selectively abolished the expression of the targeted genes without affecting the synthesis of other immunologically related FlaB proteins. The resulting flaA1 flaB1 mutant exhibited altered motility in vitro. Surprisingly, it was capable of assembling periplasmic flagella that were morphologically normal as evidenced by electron microscopy. The virulence of this strain was assessed in a murine model of swine dysentery by determining the incidence of cecal lesions and the persistence of S. hyodysenteriae in the gut. Mice challenged with the wild-type strain or a passage control strain showed a dose-related response to the challenge organism. The dual flagellar mutant was severely attenuated in murine challenge experiments, suggesting that the FlaA1 and FlaB1 proteins are dispensable for flagellar assembly but critical for normal flagellar function and colonization of mucosal surfaces of the gastrointestinal tract. This strain represents the first spirochete engineered to contain specifically defined mutations in more than one genetic locus.     

Behavioral and cardiovascular responses to interpersonal challenges among male offspring of essential hypertensives.

Behavioral, cardiovascular, and self-report measures of cognitive and affective responses to 2 interpersonal challenges were examined among 20 men with a positive (FH+) and 20 with a negative (FH–) family history of hypertension. Heart rate (HR) and blood pressure (BP) were measured throughout the laboratory session; Ss were requested to self-report positive and negative conditions, state anger, and state anxiety that occurred during interactions with a male and female confederate. Behavioral responses to interpersonal tasks were videotaped, coded, and categorized into 4 major groupings (positive verbal, positive nonverbal, negative verbal, and negative nonverbal). FH+ individuals exhibited significantly higher resting HR and systolic BP reactivity to both interactions than FH– counterparts. Analyses of behavioral responses for both interactions revealed significantly more negative verbal and nonverbal behavior and less positive nonverbal behavior among FH+ as compared with FH– Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rule-based supervisory control of a two-link flexible manipulator

In this paper, we propose a two level hierarchical control strategy to achieve accurate end-point position of a planar two-link flexible manipulator. The upper level consists of a feedforward rule-based supervisory controller that incorporates fuzzy logic, whereas the lower level consists of conventional controllers that combine shaft position-endpoint acceleration feedback for disturbance rejection properties and shaping of the (joint) actuator inputs to minimize the energy transferred to the flexible modes during commanded movements. The effectiveness of this hierarchical control strategy is verified by experimental results for various movements of the links, in various configurations. In particular, we illustrate how the hierarchical intelligent control strategy performs better than conventional control techniques for endpoint position control in the presence of flexure effects.     

Interlaboratory ring test of time-resolved fluoroimmunoassays for zeranol and alpha-zearalenol and comparison with zeranol test kits.

Many zeranol immunoassay test kits cross-react with toxins formed by naturally occurring Fusarium spp. fungi, leading to false-positive screening results. This paper describes the evaluation and application of recently published, dry reagent time-resolved fluoroimmunoassays (TR-FIA) for zeranol and the toxin alpha-zearalenol. A ring test of bovine urine fortified with zeranol and/or alpha-zearalenol in four European Union National Reference Laboratories demonstrated that the TR-FIA tests were accurate and robust. The alpha-zearalenol TR-FIA satisfactorily quantified alpha-zearalenol in urine fortified at 10-30 ng ml(-1). The specificity-enhanced zeranol TR-FIA accurately quantified zeranol in the range 2-5 ng ml(-1) and gave no false-positive results in blank urine, even in the presence of 30 ng ml(-1) alpha-zearalenol. Zeranol TR-FIA specificity was demonstrated further by analysing incurred zeranol-free urine samples containing natural Fusarium spp. toxins. The TR-FIA yielded no false-positive results in the presence of up to 22 ng ml(-1) toxins. The performance of four commercially available zeranol immunoassay test kits was more variable. Three kits produced many false-positive results. One kit produced only one potential false-positive using a protocol that was longer than that of the TR-FIA. These TR-FIAs will be valuable tools to develop inspection criteria to distinguish illegal zeranol abuse from contamination arising from in vivo metabolism of Fusarium spp. toxins.     

Wireless LAN Security: Things You Should Know about WLAN Security

Given the well-publicised security holes in baseline wireless LAN (WLAN) standards, just how should security-conscious network managers proceed with safeguarding their wireless environments?     

Extending the color gamut and dynamic range of an sRGB image using a residual image

Image sources, such as digital camera captures and photographic negatives, typically have more information than can be reproduced on a photographic print or a video display. The information that is lost during the tone/color rendering process relates to both the extended dynamic range and color gamut of the original scene. In conventional photographic systems, most of this additional information is archived on the photographic negative and can be accessed by adjusting the way the negative is printed. However, most digital imaging systems have traditionally archived only a rendered video RGB image. As a result, it is not possible to make the same sorts of image manipulations that historically have been possible with conventional photographic systems. This suggests that there would be an advantage to storing images using an extended dynamic range/color gamut color encoding. However, because of file compatibility issues, digital imaging systems that store images using color encoding other than a standard video RGB representation (e.g., sRGB) would be significantly disadvantaged in the marketplace. In this article, we describe a solution that has been developed to maintain compatibility with existing file formats and software applications, while simultaneously retaining the extended dynamic range and color gamut information associated with the original scenes. With this approach, the input raw digital camera image or film scan is first transformed to the scene‐referred ERIMM RGB color encoding. Next, a rendered sRGB image is formed in the usual way and stored in a conventional image file (e.g., a standard JPEG file). A residual image representing the difference between the original extended dynamic range image and the final rendered image is formed and stored in the image file using proprietary metadata tags. This provides a mechanism for archiving the extended dynamic range/color gamut information, which is normally discarded during the rendering process, without sacrificing interoperability. Appropriately enabled applications can decode the residual image metadata and use it to reconstruct the ERIMM RGB image, whereas applications that are not aware of the metadata will ignore it and only have access to the sRGB image. The residual image is formed such that it will have negligible pixel values for those portions of the image that lie within the sRGB gamut, and will therefore be highly compressible. Tests on a population of 950 real customer images have demonstrated that the extended dynamic range scene information can be stored with an average file size overhead of about 8% compared to the sRGB images alone. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 251–266, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10160     

Toward the reduction of population obesity: Macrolevel environmental approaches to the problems of food, eating, and obesity.

The authors reviewed the evidential basis of three environmental approaches to reducing population obesity: What are the effects of (a) taxing or subsidizing foods, (b) manipulating the ease of food access, and (c) restricting access to certain foods? A narrative review evaluated evidence using National Heart, Lung, and Blood Institute criteria. There was strong evidence that subsidization influences food purchases, but not necessarily food consumption or body weight. Ease of food access may influence food purchases, and possibly food intake and body weight. Data on restriction were lacking. More studies are needed to justify that altering these macro-environmental variables will necessarily reduce population obesity. A proposed conceptual model posits that the steps through environmental interventions may exert intended and unintended influences on body weight and obesity prevalence. Contemplated policy changes should weigh scientific evidence with social judgments and values concerning changes to the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)