Impact of Changes in Sugar Exudate Created by Biological Damage to Tomato Plants on the Persistence of Escherichia coli O157:H7

ABSTRACT: The survival of enteric pathogens on vegetable leaves improves due to presence of phytopathogens. Phytopathogen damage alters the microenvironment on the leaf surface. The objective of this study was to identify differences in sugar concentrations in tomato leaves damaged by biotropic plant pathogens and determine if these differences affect Escherichia coli O157:H7 survival. E. coli O157:H7 survived better on tomato plants damaged by Xanthomonas campestris than on healthy plants (P = 0.012). The most common sugars and sugar alcohols in the damaged leaf exudate were glucose, fructose, inositol, and sucrose. The abundance of sucrose and inositol differed between the healthy and infected plants (P < 0.05). In this study, it was found that phytopathogen damaged plants increased sugar availability on the leaf surface for E. coli O157:H7 to proliferate. Keeping plants free from biological damage can limit the amount of leaching of sugars that could allow human pathogens to proliferate. There is the possibility of increasing food safety of vegetable products by limiting phytopathogenic damage to plants.     

Involving Support Partners in Obesity Treatment.

In this study, the authors examined whether the number or success of weight loss partners influences participants' outcomes in behavioral weight loss treatment. Overweight participants (n = 109) assigned to an exercise intensive group in a larger trial were encouraged to invite up to 3 partners to attend treatment. Weight losses at 6, 12, and 18 months were not associated with the number of partners (0-3) but were associated with the weight loss success of the partners. Participants with at least 1 successful partner (weight loss ≥10% at 6 months) lost significantly (p = .004) more weight at 6, 12, and 18 months than those with no successful partners and those without partners. Interclass correlations of weight change between participants and their partner(s) were strong at all time points (ps     

Dynamics of rotating paramagnetic particle chains simulated by particle dynamics,Stokesian dynamics and lattice Boltzmann methods

Paramagnetic particles, when subjected to external unidirectional rotating magnetic fields, form chains which rotate along with the magnetic field. In this paper three simulation methods, particle dynamics (PD), Stokesian dynamics (SD) and lattice Boltzmann (LB) methods, are used to study the dynamics of these rotating chains. SD simulations with two different levels of approximations—additivity of forces (AF) and additivity of velocities (AV)—for hydrodynamic interactions have been carried out. The effect of hydrodynamic interactions between paramagnetic particles under the effect of a rotating magnetic field is analyzed by comparing the LB and SD simulations, both of which include hydrodynamic interactions, with PD simulations in which hydrodynamic interactions are neglected. It was determined that for macroscopically observable properties like average chain length as a function of Mason number, reasonable agreement is found between all the three methods. For microscopic properties like the force distribution on each particle along the chain, inclusion of hydrodynamic interaction becomes important to understand the underlying physics of chain formation. Any opinion, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.     

Mild enzymatic isolation of mannan and glucan from yeast Saccharomyces cerevisiae

An enzymatic procedure to isolate polysaccharides from the yeast saccharomyces cerevisiae was developed which would both be environmentally friendly and preserve the native structure of the polymers. Two proteases and three enzyme cocktails were employed. To isolate the cell wall polysaccharides, the cell walls were first separated from the internal components by mechanical cell disruption. The quality of cell disruption was investigated for four types of glass beads with diameters from 0.25 – 1.5 mm and monitored via the inner cellular proteins released. With large glass beads (Ø = 0.75 – 1.5 mm) both brewer's and baker's yeast cells exhibited more than 90% cell disruption after as little as 12 min, whereas disruption was still incomplete with smaller beads. The isolated cell wall material was purified on microporous membranes, freeze-dried and then incubated with enzymes. Proteases caused protein lysis in the outer cell wall and released soluble mannan. The insoluble glucan was separated by centrifugation and the mannan was purified by dialysis or chromatography. In the digestion with proteases, complete conversion was achieved at concentrations higher than 240 mg g^–1 of cell wall material within 26 h. Cell walls from baker's yeast had to undergo a preliminary extraction with petroleum ether. Complete conversion was only possible with one of the enzyme cocktails investigated, and this was achieved after as little as 6 h for cell walls from both baker's and brewer's yeast. The activity of the two other enzyme cocktails investigated was weaker, with brewer's yeast cell walls generally reacting more readily than those of baker's yeast.     

Interaction between visual and olfactory stimuli during host-finding by leafhopper,Dalbulus maidis (Homoptera: Cicadellidae)

Virtually nothing is known about the role plant volatiles play in host-finding by Homoptera in the Suborder Auchenorrhyncha. In laboratory bioassays, we examined the influence of plant volatiles on orientation and postcontact behaviors of the leafhopper,Dalbulus maidis, and determined the relationship between visual and olfactory stimuli during host-finding. When compared to the number of contacts made with reflected green light in the presence of a hexane control,D. maidis made more contacts when exposed to volatile extracts from its preferred host, maize; a similar number of contacts when exposed to volatiles from a marginal host, gamagrass; and fewer contacts when exposed to volatiles from a nonhost, sorghum. There was no difference between males and females in the number of contacts made with green light when exposed to maize volatiles compared to hexane alone. More contacts were made with green light than with white light of similar intensity, both in the presence and in the absence of olfactory stimuli; however, maize volatiles acted as a Synergist by increasing the number of contacts leafhoppers made with green light. After contacting the green light, exposure of maize volatiles significantly increased, relative to hexane, the amount of stationary time, but did not influence the amount of time spent moving, the distance traveled, or the speed while moving when within the boundaries of the green light. This study provides the first evidence for an interaction between visual and olfactory stimuli during host-finding for a leafhopper and also for olfactory mediation of postcontact behaviors not associated with feeding.     

Design improvement using process capability data

Historical process capability data (PCD) is commonly used during product design. Such data can be stored in a formal database known as a process capability database (PCDB). PCD is primarily used during product design to allocate tolerances or forecast and manage manufacturing variation. However using a PCDB for these purposes alone does not exploit its full potential. This paper describes a method by which PCD can be applied to predict product performance variation early in the design process, thus saving time and reducing subsequent redesign costs. More specifically it describes the use of PCD during the initial design stage to predict how the product will operate, in terms of functional reliability, after it has been manufactured. An illustrative example based on the design of an electrical connector is provided. In this case connector beam normal force is a strong indicator of connector reliability and the example shows how the variation of this normal force can be predicted during initial connector design.     

Measurement of Q degradation due to polarisation mode dispersion using multiple importance sampling

Multiple importance-sampling (IS) is used to measure the Q degradation due to the polarisation mode dispersion generated by three programmable DGD elements with uniform polarisation coupling between sections. The measured Q-penalty probability distribution extends to <10/sup -17/ with only 1800 experimental samples.     

Family planning: an essential component of prenatal care

This nation's traditional approach to improving maternal and infant health has been prenatal care. But evidence is mounting that additional progress in reducing maternal and infant morbidity and mortality will depend, at least in part, on the care that a woman receives before she conceives. The studies reviewed in this paper indicate that increasing the interval between deliveries and preventing or delaying pregnancies among women at high risk could lower the rate of low birthweight (LBW). Since reducing the rate of unintended pregnancies would also reduce the number of pregnancies in women at high risk of LBW because of race, age, late or no prenatal care, and unhealthy behaviors, the prevention of unintended pregnancies would also reduce LBW. Unfortunately, prenatal care, as experienced by many women, devotes little attention to these family planning issues. Many women do not realize the importance of family planning to their own health and that of their children. Prenatal care providers should include instruction about the importance of pregnancy planning and encourage women to continue receiving health care between pregnancies. If the health of women and infants is to be improved, society must be willing to provide health services to women of reproductive age even when they are not pregnant.