| 2. |
- Naredi, Peter, 1955, et al.
(författare)
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Aggregation of microspheres in blood flow measurements.
- 1991
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Ingår i: International journal of microcirculation, clinical and experimental / sponsored by the European Society for Microcirculation. - 0167-6865. ; 10:2, s. 169-80
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Tidskriftsartikel (refereegranskat)abstract
- The aggregation of NEN-TRAC radionuclide-labeled 15 microns resin microspheres was studied in vitro and in vivo. In vitro, the control group not agitated at all was compared with groups subjected to agitation with a Vortex Shaker or agitation with first a Vortex shaker and then a sonification bath. Loading the microspheres in a catheter made agitation unnecessary (5.6 +/- 1.7 aggregates/100 spheres and 2.3 +/- 0.5 microspheres/aggregate). Sonification increased aggregation when the solution was drawn into 1 cc syringes (13.7 +/- 2.6 aggregates/100 spheres and 2.8 +/- 1.2 microspheres/aggregate). In vivo less aggregates were observed. Loading the microspheres into PK 50 catheters and then injecting them into the left ventricle of the heart after agitation in a Vortex shaker for 1 min minimized aggregation (1.6 +/- 1.0 aggregates/100 spheres and 2.2 +/- 0.4 spheres/aggregate). Sonification increased both the number of aggregates and the number of spheres in each aggregate significantly (10.0 +/- 3.1 aggreates/100 spheres and 2.8 +/- 1.3 spheres/aggregate). Aggregates of 10 to 40 microspheres were occasionally observed. When the microspheres were injected into the aorta at the level of the diaphragm, one large aggregate (approximately 50 spheres) was seen. The handling of the microsphere solution is important to prevent aggregation and the treatment recommended by the manufacturer does not seem to be the optimal. Large aggregates, which are rare, might embolize the precapillary arteries. Small aggregates are more common and they might result in disproportionately fewer microspheres in vessels than their actual blood flow. This would make the microsphere method less reliable in blood flow measurements.
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| 3. |
- Ponten, I., et al.
(författare)
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SPECTROSCOPIC STUDIES OF THE TRANS ADDUCTS DERIVED FROM (+)-ANTI-BENZO A PYRENE-7,8-DIHYDRODIOL-9,10-EPOXIDE AND (-)-ANTI-BENZO A PYRENE-7,8-DIHYDRODIOL-9,10-EPOXIDE AND THE OLIGONUCLEOTIDE 5'-D(CCTATAGATATCC)
- 1994
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Ingår i: Carcinogenesis. - : Oxford University Press (OUP). - 0143-3334 .- 1460-2180. ; 15:10, s. 2207-2213
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Tidskriftsartikel (refereegranskat)abstract
- The oligonucleotide 5'-d(CCTATAGATATCC) has been reacted with the (+)- or (-)-enantiomers of trans-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-and (-)-anti-BPDE respectively]. Consistent with previous studies employing single-stranded oligonucleotides, adduct formation of both anti-BPDE enantiomers preferentially involved trans-addition of the C10 position of the diol-epoxide to the exocyclic nitrogen of deoxyguanosine [in the following abbreviated as (+)-BPDE(t)-N-2-G and (-)-BPDE(t)-N-2-G adducts respectively]. The unmodified or (+)-BPDE(t)-N-2-G-modified oligonucleotide was allowed to form duplexes with the complementary sequence 5'-d(GGATATCTATAGG) or sequences in which C has been replaced with T, G or A and analysed with regard to thermal stability. The presence of a (+)-BPDE(t)-N-2-G adduct in oligonucleotide duplexes substantially decreased the value of the melting point relative to the corresponding unmodified duplex. In mismatched complexes containing the (+)-BPDE(t)-N-2-G adduct, a further decrease in thermal stability was observed. The presence of a (+)-BPDE(t)-N-2-G adduct did not seem to change the extent of hyperchromicity (approximate to 20%) upon melting. 5'-d(GGATATCTATAGG) or strands in which C was replaced with T,G or A were gradually added to (+)- or (-)-BPDE(t)-N-2-G-modified oligonucleotides and the fluorescence emission intensity was determined. In all cases with (+)-BPDE(t)-N-2-G, except when C was replaced with A in the complement, the fluorescence intensity steadily decreased and became constant at equal strand concentrations. When a strand containing A in place of C was gradually added to the (+)-BPDE(t)-N-2-G oligonucleotide, a marked increase in the fluorescence intensity was observed (>3-fold). In contrast, addition of strands containing A, T or G to the (-)-BPDE(t)-N-2-G-modified oligonucleotide increased tbe fluorescence intensity from 1.5- to >5-fold. Addition of the fully complementary sequence to the (-)-BPDE(t)-N-2-G-containing oligonucleotide resulted in reduced fluorescence, however less pronounced than with the (+)-BPDE(t)-N-2-G-modified analogue. Significant changes in spectral properties of the adducts were observed in the duplexes. The absorption and fluorescence excitation maxima of the single-stranded (+)-BPDE(t)-N-2-G-modified oligonucleotide were at 353 nm. Insertion of C or A opposite the adduct caused a significant shift of these maxima to shorter wavelengths (347-348 nm). Addition of acrylamide, a fluorescence quencher, reduced the fluorescence intensity in all cases, but to variable extents. The adducts not quenchable by acrylamide demonstrate spectral properties similar to those of the single-stranded (+)-BPDE(t)-N-2-G-modified oligonucleotide.
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