Ready-to-eat shrimp as an international vehicle of antibiotic-resistant bacteria

The occurrence of antibiotic-resistant bacteria in foods of animal origin is a potential health threat because resistance can be transferred among bacteria, and antibiotic-resistant pathogens may not respond to antibiotic treatments. Thirteen brands of ready-to-eat shrimp representing four countries of origin were obtained from local grocery stores. Total heterotrophic plate counts were determined, and antibiotic-resistant bacteria were isolated. Total heterotrophic colony counts ranged from 3.3 to 5.6 log CFU/g, which was within approved quality limits. A total of 1,564 isolates representing 162 bacterial species were recovered during screening of resistance to 10 antibiotics: ampicillin, ceftriaxone, chloramphenicol, clindamycin, erythromycin, nalidixic acid, streptomycin, tetracycline, trimethoprim, and vancomycin. Six hundred fifty-seven (42%) of the isolates and 131 (81%) of the species had acquired resistance to antibiotics. Numerous resistant human pathogens were isolated, including Escherichia coli, Enterococcus spp., Salmonella, Shigella flexneri, Staphylococcus spp., and Vibrio spp. Nonresistant Yersinia spp. also were isolated. Ready-to-eat shrimp is sold with instructions to thaw the product before serving, which may result in consumer exposure to antibiotic-resistant bacteria. Widespread trade of this product provides an avenue for international dissemination of antibiotic-resistant pathogens.     

View angle effects in the radiometric measurement of plant canopy temperatures

The thermal infrared sensor response from a wheat canopy was extremely non-Lambertian because of spatial variations in energy flow processes; the effective radiant temperature of the sensor varied as much as 13°C with changing view angle. This variation of sensor response was accurately quantified (root-mean-square of deviations between theoretical and measured responses reduced to 1.1°C) as a function of vegetation canopy geometry, vertical temperature distribution of canopy components, and sensor view angle. The results have important implications for optimizing sensor view angles for remote sensing missions.     

Prostaglandins promote and block adipogenesis through opposing effects on peroxisome proliferator-activated receptor gamma

Fat cell differentiation is a critical aspect of obesity and diabetes. Dietary fatty acids are converted to arachidonic acid, which serves as precursor of prostaglandins (PGs). PGJ2 derivatives function as activating ligands for peroxisome proliferator-activated receptor gamma (PPAR gamma), a nuclear hormone receptor that is central to adipogenic determination. We report here that PGF2 alpha blocks adipogenesis through activation of mitogen-activated protein kinase, resulting in inhibitory phosphorylation of PPAR gamma. Both mitogen-activated protein kinase activation and PPAR gamma phosphorylation are required for the anti-adipogenic effects of PGF2 alpha. Thus, PG signals generated at a cell surface receptor regulate the program of gene expression required for adipogenesis by modulating the activity of a nuclear hormone receptor that is directly activated by other PG signals. The balance between PGF2 alpha and PGJ2 signaling may thus be central to the development of obesity and diabetes.     

Detection and Evaluation of Plant Stresses for Crop Management Decisions

The ability to quantitatively assess crop conditions using remotely sensed data would not only improve yield forecasts but would also provide information that would be useful to farm managers in making day-to-day management decisions. Experiments were conducted using ground-based radiometers to relate spectral response to crop canopy characteristics. It was found that radiometrically measured crop temperature, when compared with a reference temperature, was related to the degree of plant stress and could indicate the onset of stress. Reflectance based vegetation indices, on the other hand, were not sensitive to the onset of stress but were useful in evaluating the consequences of stress as expressed in changing quantities of green phytomass. Anatomical and physiological changes occur within plant cells when plants are stressed and increase the amount of reflected radiation. However, canopy geometrical changes may alter the amount of radiation that reaches a radiometer, complicating the interpretation of spectral response to stress. Timeliness, frequency of coverage, andresolution are three factors that must be considered when satellite-based sensors are used to evaluate crop conditions for farm management applications.     

Rapid determination of sanitizer concentration using impedance-based methods

Chlorine, iodophor, and quaternary ammonium solutions of various concentrations were assayed with rapid test kits and with three Bactometer impedimetric test codes (the impedance, conductance, and capacitance test codes). An initial study was conducted to determine which test code was most suitable for each sanitizer. Impedance was shown to be the best for sodium hypochlorite solutions, conductance for iodophor solutions, and capacitance for quaternary ammonium solutions. When Bactometer results were compared with test kit results, linear regression revealed strong correlations for all three sanitizer solutions. For sodium hypochlorite concentrations of 0 to 100 ppm and 100 to 1,000 ppm, R2 values of 0.87 and 0.99, respectively, were obtained. For iodophor concentrations between 25 to 150 ppm, an R2 value of 0.95 was obtained. For quaternary ammonium compound concentrations of 100 to 1,000 ppm, an R2 value of 0.94 was obtained. The impedimetric methods proved to be simple and rapid (6 min) alternatives for measuring concentrations of the sanitizer solutions with a high level of certainty (P < 0.0002). The Bactometer will save time when multiple samples are tested.     

Diurnal Patterns of Wheat Spectral Reflectances

Spectral reflectances of Produra wheat were measured at 13 different times of the day at Phoenix, Arizona, on April 14, 1979 using a nadir-oriented hand-held 4-band radiometer which had bandpass characteristics similar to those on current LANDSAT satellites. Different sun altitude and azimuth angles caused significant diurnal changes in radiant return in both visible and near-IR regions of the spectrum and in several vegetation indices derived from them. The magnitude of these changes were related to different canopy architecture, percent cover, and green leaf area conditions. Spectral measurements taken at each time period were well correlated with green leaf area index but the nature of the relationship changed significantly with time of day. Thus a significant bias in the estimation of green leaf area index (GLAI) from remotely sensed spectral data could occur if sun angles are not properly accounted for.     

Electrosorption of tert-butyl compounds on Hg from aqueous Na2SO4 solution: tert-butylamine

The adsorption of tert-butylamine (TBUNH₂) at the Hg/0.5 M aqueous Na₂SO₄ polarized interface has been studied by means of electrocapillary measurements. Adsorption has been found to follow a Frumkin isotherm with interaction parameter corresponding to particle-particle attraction. Adsorption is congruent neither with respect to charge nor with respect to potential, but the model of two capacitors in parallel is much better approached, especially at positive rational potentials. The positive value of the interaction parameter is explained in terms of unfavourable solvent-adsorbate surface interactions, slightly dependent on the electric field. The fundamental adsorption parameter of TBUNH₂ are compared with data previously obtained for TBUOH. The behaviour of TBUNH₂ at the air-solution interface seems to exclude any specific interaction between the Hg surface and NH₂ group; the differences between TBUNH₂ and TBUOH are probably to be related to the different nature of the particle-particle interactions.     

On the relationship between global and local controllability

Given a pair(X ⁰,D), whereX ⁰ is a vector field andD is a family of vector fields on a manifoldM, we can define a system affine in the control, i.e., the new family of all the vector fields of the formX ⁰ +uX, whereX ∈D andu is a real parameter. Such a system will be called globally controllable if each state is reachable from each other, whenever unbounded values foru are allowed. It is proved that a system affine in the control is globally controllable if and only if in any set of a suitable partition ofM there exist points locally controllable with bounded values foru. Further, it is proved that, under more restrictive assumptions, global controllability implies the existence of points locally controllable at a fixed time with bounded values foru. In the case of simply connected manifolds, a full equivalence among all the forms of controllability considered here is obtained.