Primary processes of the thermal degradation of HET acid containing unsaturated polyester cured with styrene

The primary processes of thermal degradation of 1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic (HET) group containing unsturated polyesters cured with styrene were investigated. DTA traces in nitrogen atmosphere showed a much more pronounced endothermic reaction as the chlorine content in the unsaturated polyester resin decreased. This could be associated to the unzipping of the polystyrene units which is interfered by hexachlorocyclopentadiene ejected during degradation. Actually the styrene formation is prevented in a certain range of temperature due to the interaction with hexachlorocyclopentadiene. This was proved by on-line mass spectroscopic analysis of the degrading polymer.     

Investigation of the action of flame retardants in cellulose. I. Investigation of the flame retardant action of 2,2′-oxybis(5,5-dimethyl-1,3,2-dioxaphosphorinane-2,2′-disulfide) in cellulose

Pyrolysis experiments were performed in high vacuum and under reduced air pressure (100 Pa). The volatile products of pure cellulose and cellulose containing various amounts of flame retardant 2,2′-oxybis (5,5-dimethyl-1,3,2-dioxaphosphorinane-2,2′-disulfide), i.e., Sandoflam 5060 of Sandoz AG, were studied by means of gas chromatography in combination with mass spectroscopy. The volatile products were characterized with infrared spectroscopy. The studied revealed that the incorporation of the flame retardant enhanced the water release and shifted the onset of this reaction to lower temperature. On the basis of these findings an explanation for the mechanism of flame retardancy in generated cellulose fibers modified with this particular flame retardant is attempted. From experiments with different residual air pressure the influence of oxygen on the primary processes of the pyrolytic degradation of cellulose is being discussed.     

Accumulation and Toxicity of Superparamagnetic Iron Oxide Nanoparticles in Cells and Experimental Animals

The uptake and distribution of negatively charged superparamagnetic iron oxide (Fe₃O₄) nanoparticles (SPIONs) in mouse embryonic fibroblasts NIH3T3, and magnetic resonance imaging (MRI) signal influenced by SPIONs injected into experimental animals, were visualized and investigated. Cellular uptake and distribution of the SPIONs in NIH3T3 after staining with Prussian Blue were investigated by a bright-field microscope equipped with digital color camera. SPIONs were localized in vesicles, mostly placed near the nucleus. Toxicity of SPION nanoparticles tested with cell viability assay (XTT) was estimated. The viability of NIH3T3 cells remains approximately 95% within 3–24 h of incubation, and only a slight decrease of viability was observed after 48 h of incubation. MRI studies on Wistar rats using a clinical 1.5 T MRI scanner were showing that SPIONs give a negative contrast in the MRI. The dynamic MRI measurements of the SPION clearance from the injection site shows that SPIONs slowly disappear from injection sites and only a low concentration of nanoparticles was completely eliminated within three weeks. No functionalized SPIONs accumulate in cells by endocytic mechanism, none accumulate in the nucleus, and none are toxic at a desirable concentration. Therefore, they could be used as a dual imaging agent: as contrast agents for MRI and for traditional optical biopsy by using Prussian Blue staining.     

Structure-cytotoxicity studies on alkyl lysophospholipids and some analogs in leukemic blasts of human origin in vitro

Eleven lipids have been tested for cytotoxic (trypan blue dye exclusion) activity in cells from eight freshly explanted human leukemias in vitro. 4-Aminomethyl-1-[2,3-(di-N-decyloxy)N-propyl]-4-phenylpiperidine (CP-46,665), 1-mercapto-hexadecyl-2-methoxymethyl-rac-glycero-3-phosphocholine (BM 41.440), the 2-acetamide analog of platelet-activating factor (PAF) and 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH₃) were found among the most active compounds. 2-Lysophosphatidylcholine (2-LPC) showed the lowest activity. However, in addition there was variation among the results regarding the activity of the 1-octadecyl-rac-glycero-3-phosphocholine (ET-18-OH) and its D- and L-forms, but a significantly higher cytotoxic activity of D-ET-18-OH compared with L-ET-18-OH on the basis of 2-LPC as control after an incubation time of 48 hr. We conclude that with the limited number of structures available, this type of study is not sufficient to yield further information about the mode of the accumulation and toxicity of this type of lipids.     

Site-directed mutants of the cAMP receptor protein-DNA binding of five mutant proteins

Oligonucleotide-directed mutagenesis was employed to generatemutants of the cAMP receptor protein (CRP) of Escherichia coli.The mutant proteins were purified to homogeneity and testedfor stability and DNA binding. It is shown that mutations atthe position of Arg¹⁸⁰ abolish specific DNA binding, whereasthose at the position Arg¹⁸⁵ have very little effect. Both positionshave previously been implicated as crucial for the specificinteraction between CRP and DNA. The Ser¹²⁸ Ala mutant showsa slight reduction in DNA binding affinity relative to wild-type.All mutants investigated show similar stability profiles towild-type CRP with respect to thermolysin proteolysis as a functionof temperature.     

Identification and composition of turnip root lipids

Two varieties of turnip, Laurentian and Wye, were examined for their lipid and fatty acid composition. Lipids extracted with 80% ethanol contained variable quantities of phosphatidic acid, which was considered to be an artifact. Crude lipids were fractionated by TLC, and fatty acids and sterols were analyzed by GLC. Among the common phospholipids, cardiolipid and phosphatidyl glycerol were abundant components. Linolenic acid comprised 60% of the total fatty acids. β-Sitosterol was the principal sterol, and about half of the carotenoids was lycopene. No great differences between the two varieties studied were observed however. Contribution No. 53 of the Food Research Institute, Canada Department of Agriculture, Ottawa.