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Computer modeling of aggregate exposure provides the capability to estimate the range of doses that can occur from product use and to understand the relative importance of different routes of exposure. This paper presents an assessment of aggregate occupational exposure to two glycol ethers used as solvents in floor maintenance products for industrial and institutional facilities, using a simulation tool named PROMISE. Three commercial floor-care products were assumed to be applied in sequence--a floor stripper, then a floor cleaner, and lastly a protective coating. The glycol ethers modeled were ethylene glycol butyl ether (EGBE) in the floor stripper and in the floor cleaner, and dipropylene glycol methyl ether (DPGME) in the coating. Modeling uncertainty was assessed through a comparison of the PROMISE inhalation exposure estimates with those from an independent model (MCCEM), and parameter uncertainty was investigated using PROMISE software's Monte Carlo simulation capabilities. Modeling results indicated that inhalation is the dominant exposure route. The predicted average air concentration and inhalation dose from PROMISE agreed with the second model (MCCEM) within 10%. Monte Carlo simulation indicated that the upper end of the aggregate-dose distribution for the scenario was more than 50% higher than the value of the point estimate. The modeled 8-h TWA concentrations for EGBE and DPGME were lower than the corresponding permissible exposure limits American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLV) by at least a factor of 20, indicating that under the assumed conditions workplace exposures to glycol ethers are below levels of concern.

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Polyethylene terephthalate (PET) due to its physicochemical properties, especially regidity and glass-like transparency is widely used as food packaging material. The relevant legislation states that substances may not migrate from food contacting materials in quantities that may cause undesirable changes in organoleptic properties of food coming into contact with such material. The lists of substances authorized for food contact plastic materials and requirements for the final product were established. The requirements concern global migration limits (60 mg/kg or 10 mg/dm2) and specific migration limits (SML) set for substances which, when migrate into food in grater quantities may cause risk for human health. For the products manufactured from PET the specific migration limits were set for terephthalic acid (7.5 mg/kg), for isophthalic acid (5 mg/kg), for isophthalic acid dimethyl ester (0.05 mg/kg) and for ethylene and diethylene glycol (30 mg/kg). PET may undergo thermal degradation resulting in formation of acetaldehyde, which may influence organoleptic characteristics of packaged foods changing taste and smell.

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We have investigated the freezing tolerance of rat pancreatic islets. Freshly isolated rat pancreatic islets were divided into three groups based on their longest diameter (small; 100 - 200 microns, medium; 201 - 300 microns, large; > 300 microns). They were then cryopreserved at a slow cooling rate (-0.3 degrees C/min) in the presence of dimethyl sulfoxide (Me2SO) or ethylene glycol (EG). After storage at -196 degrees C for 1 - 4 weeks, they were thawed and their ability to secrete insulin in response to fluctuations in glucose concentration was examined during three consecutive static incubations in vitro (1st; 2.8 mM, 2nd; 16.7 mM, 3rd; 2.8 mM). Morphological examination of the beta-granule population was determined by image analysis, and correlation with islets size was analyzed. The amount of insulin released from large-sized islets was significantly suppressed in EG (p < 0.05) and Me2SO (p < 0.01) groups compared to unfrozen islets. However, the mean volume of the large-sized islets isolated from one rat accounted for 43.0% of the total volume. On the other hand, the amount of insulin released from small- and medium-sized islets did not differ from those of unfrozen islets, and their mean volumes were 13.2 and 43.8% respectively. The percentage of cells with beta-granules was significantly correlated with size in both EG (r = -0.52) and Me2SO (r = -0.35) groups, but no significant correlation was observed in the unfrozen islets groups. These findings suggest that large-sized islets are more susceptible to freezing injury than small- or medium-sized islets. Moreover, the volume distribution of isolated islets indicated that it may be important to retain the ability of insulin secretion from the large-sized islets.

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Results are presented for the purity of three commercial brands of the Ca chelator EGTA [ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid] as determined with pH-metric and oxalate precipitation methods and other techniques. The effect that the observed degree of hydration (2-4%) has on calculated values for [Ca2+] in Ca-EGTA solutions is described with reference to a theoretical dose-response relationship. In addition to the corrections for purity, the adjustments necessary to allow for ionic strength and the correction of pH readings to yield true [H+] activity or concentration values are described. These several corrections result in both a shift and a shape change for the dose-response curve compared with the curve calculated without these corrective procedures. Some authors have already taken some of these aspects into account, but this has not generally been made clear in the literature heretofore. The points raised may help to account for the wide variation of reported [Ca2+] ranges for Ca-sensitive cellular processes.

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Reagent-grade ethylene glycol has been shown to contain substantial amounts of aldehydes, peroxides, iron, and uv-absorbing hydrocarbons. These impurities can be removed by reduction with sodium borohydride, dilution with H2O, passing through a train of four columns, and filtering through a 0.45-micron filter. The product is stable for at least several months and perhaps much longer; storage under nitrogen in acid-washed dark bottles is preferable. Ten liters of 25% (v/v) aqueous ethylene glycol can easily be purified in about 1 week using equipment commonly available in a biochemical laboratory. This purification is also applicable to aqueous glycerol.

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