Nano-silver in drinking water and drinking water sources: stability and influences on disinfection by-product formation.

Nano-silver is increasingly used in consumer products from washing machines and refrigerators to devices marketed for the disinfection of drinking water or recreational water. The nano-silver in these products may be released, ending up in surface water bodies which may be used as drinking water sources. Little information is available about the stability of the nano-silver in sources of drinking water, its fate during drinking water disinfection processes, and its interaction with disinfection agents and disinfection by-products (DBPs). This study aims to investigate the stability of nano-silver in drinking water sources and in the finished drinking water when chlorine and chloramines are used for disinfection and to observe changes in the composition of DBPs formed when nano-silver is present in the source water. A dispersion of nano-silver particles (10 nm; PVP-coated) was used to spike untreated Ottawa River water, treated Ottawa River water, organic-free water, and a groundwater at concentrations of 5 mg/L. The diluted dispersions were kept under stirred and non-stirred conditions for up to 9 months and analyzed weekly using UV absorption to assess the stability of the nano-silver particles. In a separate experiment, Ottawa River water containing nano-silver particles (at 0.1 and 1 mg/L concentration, respectively) was disinfected by adding sodium hypochlorite (a chlorinating agent) in sufficient amounts to maintain a free chlorine residual of approximately 0.4 mg/L after 24 h. The disinfected drinking water was then quenched with ascorbic acid and analyzed for 34 neutral DBPs (trihalomethanes, haloacetonitriles, haloacetaldehydes, 1,1 dichloro-2-propanone, 1,1,1 trichloro-2-propanone, chloropicrin, and cyanogen chloride). The results were compared to the profile of DBPs obtained under the same conditions in the absence of nano-silver and in the presence of an equivalent concentration of Ag(+) ions (as AgNO3). The stability of the nano-silver dispersions in untreated Ottawa River water, with a dissolved organic carbon concentration of 6 mg/L, was significantly higher than the stability of the nano-silver dispersions in distilled, organic-free water. Nano-silver particles suspended in the groundwater agglomerated and were quickly and quantitatively removed from the solution. Our data confirm previous observations that natural dissolved organic matter stabilizes nano-silver particles, while the high-ionic strength of groundwater appears to favor their agglomeration and precipitation. As expected, nano-silver was not stable in Ottawa River water through the chlorination process, but survived for many days when added to the Ottawa River water after treatment with chlorine or chloramines. Stirring appeared to have minimal effect on nano-silver stability in untreated and treated Ottawa River water. The profile of DBPs formed in the presence of nAg differed significantly from the profile of DBPs formed in the absence of nAg only at the 1 mg/L nAg concentration. The differences observed consisted mainly in reduced formation of some brominated DBPs and a small increase in the formation of cyanogen chloride. The reduced formation of brominated congeners may be explained by the decrease in available bromide due to the presence of Ag(+) ions. It should be noted that a concentration of 1 mg/L is significantly higher than nAg concentrations that would be expected to be present in surface waters, but these results could be significant for the disinfection of some wastewaters with comparably high nano-silver concentrations.

A history of caloric restriction induces neurochemical and behavioral changes in rats consistent with models of depression.

A history of dieting is common in individuals suffering from eating disorders for which depression and mood disturbances are also comorbid. We investigated the effect of a history of caloric restriction (HCR) in rats that involved cyclic food restriction and refeeding with varying levels of access to palatable food (PF) on: 1) responses to the SSRI, fluoxetine; 2) monoamine levels in brain regions central to the control of feeding, reward, and mood regulation; and 3) behavioral tests of anxiety and depression. HCR coupled with intermittent but not daily access to PF exaggerated rats' anorectic response to fluoxetine (p<0.05); was associated with a significant 71% and 58% reduction of 5-HT and dopamine, respectively, in the medial prefrontal cortex; and induced behaviors consistent with models of depression. HCR, irrespective of access to PF, abolished the strong association between 5-HT and dopamine turnover in the nucleus accumbens in control rats (r=0.71 vs. -0.06, p<0.01). Access to PF, irrespective of HCR, reduced hypothalamic dopamine. Together, these findings suggest that a history of frequent food restriction-induced weight fluctuation imposes neurochemical changes that negatively impact feeding and mood regulation.

A data analysis algorithm for programmed field-flow fractionation.

An algorithm that employs numerical integration for analysis of field-flow fractionation (FFF) data is presented. The algorithm utilizes detector response, field strength, and channel flow rate data, monitored at discrete time intervals during sample elution to generate a distribution of sample components according to particle size or molecular weight. The field strength and channel flow rate may either be held constant or programmed as functions of time, and it is not necessary for these programs to follow specific mathematical functions. If experimental conditions are monitored during a run, the algorithm can account for any deviation from nominal set conditions. The algorithm also allows calculation of fractionating power for the actual conditions as monitored during the run. The method provides greatly increased flexibility in the application of the FFF family of techniques. It removes the limitations on experimental conditions incurred by adherence to analytically available solutions to FFF theory, allowing ad hoc variation of field strength and other experimental parameters as necessary to increase sensitivity and specificity of the method. An implementation of the algorithm is described that is independent of the FFF technique (i.e., independent of field type) and mode of operation. To reduce computation time, it uses mathematical techniques to reduce the required number of numerical integrations. This is of particular importance when the perturbations to ideal FFF theory, such as those due to the effects of hydrodynamic lift forces, particle-wall or particle-particle interactions, and secondary relaxation, necessitate relatively lengthy numerical calculations.

RECODE: a database of frameshifting, bypassing and codon redefinition utilized for gene expression.

The RECODE database is a compilation of 'programmed' translational recoding events taken from the scientific literature and personal communications. The database deals with programmed ribosomal frameshifting, codon redefinition and translational bypass occurring in a variety of organisms. The entries for each event include the sequences of the corresponding genes, their encoded proteins for both the normal and alternate decoding, the types of the recoding events involved, trans-factors and cis-elements that influence recoding. The database is freely available at http://recode.genetics. utah.edu/.

ODNBase--a web database for antisense oligonucleotide effectiveness studies. Oligodeoxynucleotides.

SUMMARY: ODNBase is a database of antisense oligodeoxynucleotides targeted to mammalian mRNAs that were reported in the literature. It includes the oligo sequences tested, the measured effectiveness, the RNA that was targeted, the type of measurement assay used, the oligo concentration applied, and the reference for each oligo. It provides a searchable interface by motif content, activity level, applied concentration and RNA name. Oligo lists matching search criteria can be downloaded in a spreadsheet compatible format.

Identification of sequence motifs in oligonucleotides whose presence is correlated with antisense activity.

Design of antisense oligonucleotides targeting any mRNA can be much more efficient when several activity-enhancing motifs are included and activity-decreasing motifs are avoided. This conclusion was made after statistical analysis of data collected from >1000 experiments with phosphorothioate-modified oligonucleotides. Highly significant positive correlation between the presence of motifs CCAC, TCCC, ACTC, GCCA and CTCT in the oligonucleotide and its antisense efficiency was demonstrated. In addition, negative correlation was revealed for the motifs GGGG, ACTG, AAA and TAA. It was found that the likelihood of activity of an oligonucleotide against a desired mRNA target is sequence motif content dependent.

A software system for data analysis in automated DNA sequencing.

Software for gel image analysis and base-calling in fluorescence-based sequencing consisting of two primary programs, BaseFinder and GelImager, is described. BaseFinder is a framework for trace processing, analysis, and base-calling. BaseFinder is highly extensible, allowing the addition of trace analysis and processing modules without recompilation. Powerful scripting capabilities combined with modularity and multilane handling allow the user to customize BaseFinder to virtually any type of trace processing. We have developed an extensive set of data processing and analysis modules for use with the program in fluorescence-based sequencing. GelImager is a framework for gel image manipulation. It can be used for gel visualization, lane retracking, and as a front end to the Washington University Getlanes program. The programs were designed using a cross-platform development environment, currently allowing them to run in Windows NT, Windows 95, Openstep/Mach, and Rhapsody. Work is ongoing to deploy the software on additional platforms, including Solaris, Linux, and MacOS. This software has been thoroughly tested and debugged in the analysis of >2 million bp of raw sequence data from human chromosome 19 region q13. Overall sequencing accuracy was measured using a significant subset of these data, consisting of approximately 600 sequences, by comparing the individual shotgun sequences against the final assembled contigs. Also, results are reported from experiments that analyzed the accuracy of the software and two other well-known base-calling programs for sequencing the M13mp18 vector sequence. [The sequence data described in this paper have been submitted to the GenBank data library under accession no. AF025422]

Subcutaneous infusion of r-hirudin does not inhibit neointimal proliferation after angioplasty of the subclavian artery in cholesterol-fed rabbits.

BACKGROUND: Thrombin, a potent stimulator of smooth muscle cell proliferation and inhibitor of endothelial cell growth, has been implicated as an important mediator of restenosis after angioplasty. Acute administration of the thrombin inhibitor r-hirudin reduced restenosis in animal models of angioplasty, possibly by inhibiting smooth muscle cell proliferation. Because thrombin-induced proliferation requires prolonged exposure to the agonist, it was hypothesized that a greater reduction in lesion size could be achieved by chronic administration of r-hirudin. OBJECTIVE: To determine whether prolonged treatment with r-hirudin would reduce lesion size and improve vascular function in a rabbit model of neointimal proliferation. METHODS: Male New Zealand white rabbits were fed a high-cholesterol diet for 4 weeks, after which they were subjected to balloon injury of the left subclavian artery. The rabbits were assigned to one of three groups: control (no drug); acute r-hirudin treatment (0.33 mg/kg intravenously plus 0.48 mg/kg per h subcutaneously for 24 h); or chronic r-hirudin treatment (0.33 mg/kg intravenously plus 0.6 mg/kg per h subcutaneously for 28 days). After surgery the rabbits were fed a normal diet and killed 30 days later. Left (angioplastied) and right (control) subclavian arteries were removed for morphological and functional analysis. RESULTS: Angioplasty in control, untreated rabbits produced large neointimal lesions [15.0 +/- 1.8% of the area within the external elastic lamina (EEL)], comprised mainly of smooth muscle cells (34 +/- 16 cells/section) and lipid-rich macrophage or foam cells (118 +/- 51 cells/section). Acute r-hirudin treatment neither inhibited smooth muscle cell proliferation (35 +/- 12 cells/section) nor reduced neointimal lesion size (23.5 +/- 4.6% of the area within the EEL). Chronic r-hirudin treatment significantly increased the number of proliferating cells (55 +/- 15 cells/section, P < 0.05) and the size of the lesions (28.5 +/- 5.6% of the area within the EEL, P < 0.05). Further more, treatment with r-hirudin appeared to exacerbate, rather than improve, angioplasty-induced functional alterations. CONCLUSIONS: Prolonged treatment with r-hirudin neither inhibits vascular smooth muscle cell proliferation in rabbits after angioplasty of the left subclavian artery nor reduces the size of neointimal lesions. Furthermore, treatment with r-hirudin might impair endothelial cell function after angioplasty. This suggests that prolonged thrombin inhibition using this r-hirudin regimen is not suitable as an antirestenotic intervention.

Automatic matrix determination in four dye fluorescence-based DNA sequencing.

The four dye fluorescence detection strategy is a widely used approach to automated DNA sequence analysis. An important aspect of data processing in this approach is the multicomponent analysis to deduce the concentrations of four fluorophores from fluorescence emission intensities at four different wavelengths. This requires knowledge of the correct transformation matrix M. The matrix M is a function both of the fluorophores employed and the fluorescence detection system. M is typically determined either by a calibration process with individual dyes, or by choosing four well-separated individual peaks corresponding to the four different dyes. Both are time-consuming and complicated procedures for routine use. An automatic scheme for finding M directly from raw sequence data is presented here. This facilitates data analysis and the underlying algorithm may also find utility in other multispectral applications.

Characterization of the morphological and functional alterations in rabbit subclavian artery subjected to balloon angioplasty.

BACKGROUND: A number of experimental models for the study of the pathogenesis of the restenotic process have been developed, although many fail to correlate the time courses of both functional and morphological alterations following balloon injury. Our aim was to develop a rabbit model of balloon injury, which studied both of these alterations in detail. METHODS: Male New Zealand White rabbits (12 weeks old) were fed a high-cholesterol diet for 4 weeks, after which they were subjected to balloon injury of the left subclavian artery. After surgery the animals were returned to a normal diet and sacrificed 2, 7, 15 or 30 days after angioplasty. Two further groups of animals were sacrificed either after 4 weeks of high-cholesterol feeding (no angioplasty) or 2 days after a sham angioplasty operation. Angioplasty-induced changes in vasoconstrictor [to 5-hydroxytryptamine (5-HT) and KCl] and endothelium-dependent (ACh and calcimycin) and endothelium-independent (sin-1) vasodilator responses were assessed in isolated vessel rings. Morphological analysis of the size and composition of neointima was also made at each timepoint. RESULTS: Hypercholesterolaemia reduced the responsiveness of the subclavian arteries to the endothelium-dependent vasodilators carbachol and calcimycin; however, this responsiveness was restored after 7 days of a normal diet. The response to carbachol remained depressed in angioplastied arteries until 30 days after angioplasty, whereas recovery of relaxation to calcimycin was unaffected by angioplasty. Responses to 5-HT, KCl and sin-1 were unchanged by either hypercholesterolaemia or angioplasty. Morphological studies demonstrated the development of neointima in all rabbits after 7 days, reaching a maximum size after 15 days. All neointima stained for a smooth muscle actin. Accumulation of macrophages appeared in the media after 7 days and was present in the neointima after 15 days, and subsequently declined. Proliferating smooth-muscle cells were evident in the media 2 days after angioplasty, and in the neointima fro 7 days onwards. CONCLUSION: In the rabbit subclavian artery, we have developed a model that describes fully the temporal development and characteristics of an intimal cellular response and functional changes following balloon injury.

A food-safety curriculum for second- and third-grade elementary students.

OBJECTIVE: To create and implement a food-safety curriculum for second- and third-grade elementary students. DESIGN/SUBJECTS: One pilot study and one expanded study were conducted in two elementary schools (106 students) and nine elementary schools (455 students), respectively. In both studies the subjects selected were determined by their enrollment in the classes. The expanded program targeted third-grade students and fourth-grade students in the English as a Second Language program in ethnically and racially diverse areas. INTERVENTION: An educational curriculum entitled "Discovering Food Safety--Detective Mike Robe's Fantastic Journey" was administered to the target audiences. OUTCOME MEASURES: A pretest and a posttest containing the same questions were delivered to the students before and after curriculum administration. Students were not given the answers to the questions, that is, the graded tests were not returned. Different evaluation sheets were designed for students and teachers and the program was rated using a hedonic scale. STATISTICAL ANALYSES: Results were analyzed using the Student's t test. RESULTS: Pretests and posttests were administered in each study. Test scores increased significantly in the expanded study and the pilot study after the programs were implemented. Student and teacher evaluations indicated that they were extremely satisfied with the curriculum. APPLICATIONS/CONCLUSIONS: A food-safety curriculum was designed that met the needs of the target audience and had successful results. The program appeared to be effective for populations of diverse backgrounds.

An adaptive, object oriented strategy for base calling in DNA sequence analysis.

An algorithm has been developed for the determination of nucleotide sequence from data produced in fluorescence-based automated DNA sequencing instruments employing the four-color strategy. This algorithm takes advantage of object oriented programming techniques for modularity and extensibility. The algorithm is adaptive in that data sets from a wide variety of instruments and sequencing conditions can be used with good results. Confidence values are provided on the base calls as an estimate of accuracy. The algorithm iteratively employs confidence determinations from several different modules, each of which examines a different feature of the data for accurate peak identification. Modules within this system can be added or removed for increased performance or for application to a different task. In comparisons with commercial software, the algorithm performed well.

Kinetics of degradation of "short-" and "long-lived" proteins in cultured mammalian cells.

Two distinct classes of protein referred to as short- and long-lived (Poole and Wibo, 1973) were found in pulse-chased HeLa S-3 and BHK 21/C13 cells. From experiments with pulse times ranging from 1 min to 20 h, a clear inverse correlation emerged between the pulse length and the percentage of protein which was hydrolysed intracellularly in the first h of chase. Using a 5 min pulse labelling with 3H-leucine, cells were either harvested immediately or after a 2 h chase. Approximately 35% of the label incorporated by cells was lost in a 2h chase; however, electrophoretic separation of cytosol and residual cytoplasmic fractions revealed no significant alteration in their protein profiles. The technique of selectively labelling "short" and "long-lived" proteins, which implies qualitative differences between then, is more readily interpreted as an artificial polarisation of a declining statistical probability curve of proteolysis with time which is similar for all nascent proteins.

Amino acid analogues: uptake, pool formation and incorporation of phenylalanine and two halogenated derivatives in cultured mammalian cells.

HeLa cells take up Phe and two of its ring halogenated derivatives (pFPhe and pClPhe) with rpaidity, concentrating them against the external medium both at 4 and 37 degrees C. The majority of amino acid (greater than 90%) is accumulated without energy expenditures at 4 degrees C, and can be quickly discharged by normal cell washing procedures in saline. At 37 degrees C the freely-diffusible (FDP) pool is accompanied by another which develops more slowly and cannot diffuse out freely during washings with saline but is extractable with trichloracetic acid (the slowly-diffusible pool, SDP, or more conventionally, the acid-soluble pool). Both of the analogues produced larger pools of the latter type than Phe itself from external concentrations ranging from 10(-5) to 10(-3) M. The incorporation of pFPhe into proteins over these same concentrations ranged from 30 to 90--95% of Phe incorporation, whereas pClPhe showed negligible incorporation. From these and similar analyses it can be concluded that amino acid pools form largely independently of protein synthesis, but bear a close relationship with the external amino acid concentration. The fraction of total uptake into cellular pools entering the SDP was relatively constant over a wide range of external concentrations. pFPhe incorporation into cellular proteins produced the same labelling distribution of Phe. It appears to ener all proteins, the vast majority of which have similar half-lives and turnover rates to Phe proteins. In competition, little or no interference was experienced between the analogue and Phe in uptake and pool formation until excessive amounts of one or the other were present (50--100x). By contrast, incorporation of pFPhe into protein was markedly reduced by the presence of Phe. However, the development of normal or large pools of pFPhe or Phe in cells prior to 3H-Phe incorporation did not affect the linear incorporation pattern of the radioisotope into protein. The relationship of pools to protein synthesis is discussed, and it is concluded that, although the SDP could contain potential precursor molecules for protein synthesis, it does not usually act as the direct supplier of amino acid for protein synthesis. Alternative explanations for precursor supply are discussed.