Influence of pH and temperature on the growth of and toxin production by neurotoxigenic strains of Clostridium butyricum type E

Strains of Clostridium butyricum that produce botulinal toxin type E have been implicated in outbreaks of foodborne botulism in China, India, and Italy, yet the conditions that are favorable for the growth and toxinogenesis of these strains remain to be established. We attempted to determine the temperatures and pH levels that are most conducive to the growth of and toxin production by the six strains of neurotoxigenic C. butyricum that have been implicated in outbreaks of infective and foodborne botulism in Italy. The strains were cultured for 180 days on Trypticase-peptone-glucose-yeast extract broth at various pHs (4.6, 4.8, 5.0, 5.2, 5.4, 5.6, and 5.8) at 30 degrees C and at various temperatures (10, 12, and 15 degrees C) at pH 7.0. Growth was determined by checking for turbidity; toxin production was determined by the mouse bioassay. We also inoculated two foods: mascarpone cheese incubated at 25 and 15 degrees C and pesto sauce incubated at 25 degrees C. The lowest pH at which growth and toxin production occurred was 4.8 at 43 and 44 days of incubation, respectively. The lowest temperature at which growth and toxin production occurred was 12 degrees C, with growth and toxin production first being observed after 15 days. For both foods, toxin production was observed after 5 days at 25 degrees C. Since the strains did not show particularly psychrotrophic behavior, 4 degrees C can be considered a sufficiently low temperature for the inhibition of growth. However, the observation of toxin production in foods at room temperature and at abused refrigeration temperatures demands that these strains be considered a new risk for the food industry.     

ARL1 and membrane traffic in Saccharomyces cerevisiae

To examine the functions of the Arf-like protein, Arl1p, in Saccharomyces cerevisiae, a null allele, arl1delta::HIS3, was constructed in two strains. In one background only, loss of ARL1 resulted in temperature-sensitive (ts) growth (suppressed on high-osmolarity media). Allelic variation at the SSD1 locus accounted for differences between strains. Strains lacking ARL1 exhibited several defects in membrane traffic. First, arl1delta strains secreted less protein as measured by TCA-precipitable radioactivity found in the media of [(35)S]-labelled cells. A portion of newly synthesized carboxypeptidase Y (CPY) was secreted rather than correctly targeted to the vacuole. Uptake of the fluid-phase marker, lucifer yellow, was reduced. All these phenotypes were exacerbated in an ssd1 background. The ts phenotype of the arl1deltassd1 strain was suppressed by YPT1, the yeast Rab1a homologue, suggesting that ARL1 and YPT1 have partially overlapping functions. These findings demonstrate that ARL1 encodes a regulator of membrane traffic.     

Copper adaptation and methylotrophic metabolism in Candida boidinii

The importance of the antioxidant enzyme superoxide dismutase (CuZnSOD) in the metabolic switch from normotrophic to methylotrophic conditions was studied in the facultative methylotrophic yeast Candida boidinii. Copper adaptation was performed to qualify C. boidinii as a suitable cellular system to study the effect of induction of CuZnSOD, and other biochemical components along the copper detoxification system, on methanol adaptation. Copper adaptation results in the induction of CuZnSOD peroxidase activity as well as of glutathione. The effects at the metabolic level of exposure to both copper and methanol were also studied: the results suggest that the effect on antioxidant enzyme levels as a function of the change of trophic condition are predominant with respect to the effects of copper administration. Thus, the methanol-dependent induction of such enzymes is likely to provide a sufficient protection for the cells against toxic effects depending on copper administration. Administration of copper under methylotrophic conditions decreases the growth rate in spite of the high levels of antioxidant enzymes that are elicited by copper treatment. The adaptation to methanol metabolism was studied alsoafter methanol-independent induction of CuZnSOD, glutathione and catalase levels, obtained by exposure to high copper concentrations in glucose-containing medium. The metabolic changes induced by copper are persistent over several re-inoculations in normo-cupric glucose medium, thus allowing the study of the glucose-to-methanol switch on cells exhibiting high levels of antioxidant enzyme activities. Under such conditions the lag time observed during the transition from normotrophic to methylotrophic conditions is strongly reduced.     

A rapid interview protocol supporting patient-centered quality improvement: hearing the parent's voice in a pediatric cancer unit

BACKGROUND: The Institute of Medicine's 2001 report on quality delimits six dimensions of optimal care: safety, effectiveness, efficiency, timeliness, patient centeredness, and equity. In fall 2001 parents of pediatric cancer patients were interviewed to determine how well they thought these dimensions were addressed with respect to medication administration. Immediate goals were to identify system weaknesses and devise strategies to prevent future errors. A higher-order goal was to develop and demonstrate a model protocol for rapid-cycle interview assessments. METHODS: Hematology/oncology directors worked with a research expert to develop a semistructured interview protocol. After training, which included directed reading, oral instruction, and role-playing, a convenience sample of 20 English- and Spanish-speaking parents of inpatients was recruited. Parents were asked to characterize current medication administration practices and to describe problems that they had experienced or witnessed. Rapid content analysis techniques were used to identify issues of importance to the parents. FINDINGS: Parents' medication concerns centered on their children's comfort. Parents called for communication improvements, standardization of all nursing procedures and techniques, and a guide or an outline providing a clear understanding of what to expect when and from whom. Viewing these concerns in relation to the Institute of Medicine's quality domains allowed the department to frame an improvement action plan aligned with organizational and national priorities. IMPLICATIONS: With good supervision and limited focused training, inexperienced staff can successfully administer semistructured qualitative interviews and help analyze findings for rapid cycle improvement purposes. The protocol can be adapted for use in organizations interested in rapid qualitative assessments of patient and parent preferences.     

Discrete Green's methods and their application to two-dimensional phase unwrapping

A fully self-contained discrete framework with discrete equivalents of Stokes's, Gauss's, and Green's theorems is presented. The formulation is analogous to that of continuous operators, but totally discrete in nature, and the exact relationships derived are shown to hold provided that a set of predefined rules is followed in building discrete contours and domains. The method allows for an analytical rigor that is not guaranteed if one translates the classical continuous formulations onto a discretized approximated framework. We clarify several issues related to the use of discrete operators, which may play a crucial role in specific applications such as the two-dimensional phase-unwrapping problem, chosen as our main application example, and we show that reconstruction on irregular domains and/or in the presence of undersampling and noise is better formulated in the discrete framework than in the continuous domain.     

First observation of the fourth neutral polarization point in the atmosphere

In the clear sky there are three commonly known loci, the Arago, Babinet, and Brewster neutral points, where the skylight is unpolarized. These peculiar celestial points, bearing the names of their discoverers, have been the subject of many ground-based investigations, because their positions are sensitive indicators of the amount and type of atmospheric turbidity. According to theoretical considerations and computer simulations, there should exist an additional neutral point approximately opposite to the Babinet point, which can be observed only at higher altitudes in the air or space. Until now, this anonymous "fourth" neutral point has not been observed during air- or space-borne polarimetric experiments and has been forgotten, in spite of the fact that the neutral points were a basic tool in atmospheric research for a century. Here, we report on the first observation of this fourth neutral point from a hot air balloon. Using 180 degrees-field-of-view imaging polarimetry, we could observe the fourth neutral point at 450, 550, and 650 nm from different altitudes between 900 and 3500 m during and after sunrise at approximately 22 degrees - 40 degrees below the anti-solar point along the anti-solar meridian, depending on the wavelength and solar elevation. We show that the fourth neutral point exists at the expected location and has characteristics similar to those of the Arago, Babinet, and Brewster points. We discuss why the fourth neutral point has not been observed in previous air- or space-borne polarimetric experiments.     

Laguerre-Gauss and Bessel-Gauss beams in uniaxial crystals

A simple correspondence between the paraxial propagation formulas along the optical axis of a uniaxial crystal and inside an isotropic medium is found in the case of beams with linearly polarized circularly symmetric boundary distributions. The electric fields of the ordinary and the extraordinary beams are related to the corresponding expressions in a medium with refractive index n(o) and n(e)2/n(o), where n(o) and n(e) are the ordinary and the extraordinary refractive indexes, respectively. Closed-form expressions for Laguerre-Gauss and Bessel-Gauss beams propagating through an anisotropic crystal are given.     

Rasch-transformed raw scores and Two-way ANOVA: a simulation analysis

This article demonstrates, through the exposition of underestimated variable effects or spurious interaction effects, the inherent inadequacy of untransformed 0-1 raw scores for analysis via Two-Way analysis of variance (ANOVA). The pioneering work in this field, conducted in the 1990's by Dr. Susan Embretson of the University of Kansas, USA, is highlighted, and the eminent suitability of Rasch transformations of 0-1 raw scores for analysis via Two-Way ANOVA is also demonstrated. In this study Monte Carlo techniques or simulations are utilized to determine the precise psychometric conditions under which differences between raw scores and Rasch transformations of those raw scores are detectable via Two-Way ANOVA. This study partially replicates Dr. Embretson's studies, and also defines the extent of underestimation and spuriousness which ensue when uniform or skewed distributions of item difficulties are used instead of normal distributions, and misfitting raw data are utilized instead of fitting data.