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Microsomal triglyceride transfer protein (MTP) plays a central role in the synthesis of lipoproteins by shuttling lipids between phospholipid membranes to apoB. We have examined the effect of three MTP gene variants, -493G > T, Q95H and H297Q, in 2831 healthy UK middle-aged men. The rare allele frequencies were: 0.25 (95% CI 0.24-0.26) for -493T, 0.054 (95% CI 0.05-0.06) for 95H and 0.32 (95% CI 0.31-0.33) for 297Q. The three variants were in strong allelic association in all pairwise combinations ( p < 0.001). None of the variant sites were associated with significant differences in cholesterol, triglyceride, apoB or apoAI levels. When stratified by tertiles of triglycerides for the H297Q variant alone there was a significant effect on apoB levels in men in the top tertile ( p = 0.01). Considering the -493G > T and H297Q genotype in combination on baseline levels, individuals with three or four rare alleles had 6.6% higher mean apoB levels compared to the rest ( p = 0.007). Therefore, homozygosity for 297Q at higher triglyceride (Tg) levels, or in combination with -493G > T, is associated with a raising effect on apoB levels, suggesting the importance of modest differences in MTP activity in determining hepatic secretion of lipoproteins in healthy men.

We have presented the first rheological studies conducted on a series of side chain dendritic polymers (SCDP) which are produced by copolymerization of dendritic dilos of the second, third, and fourth generation with different semiregid and flexible diisocyanates. The SCDPs, consisting of polyurethane main chain and polyether side chains, obeyed time/temperature superposition. The shift factors as a function of temperature were fitted to the so-called WLF equation. Some results suggested that the dendritic side groups have a distinct effect on the elastic part of the complex modulus, whereas the effect on the viscous part seemed to be small. At low frequencies, SCDPs behaved almost like classical viscous liquids (theory:  G‘ ~ ω² and G‘ ‘ ~ ω; experiment:  G‘ ~ ω^1.5-1.8 and G‘ ‘ ~ ω). At the intermediate frequencies, the experimental exponent was 0.8, which is higher than the theoretical value of 0.5 predicted within the Rouse model. The zero shear viscosities were generated from the low limiting values of η‘(ω). For the dendritic macromonomers the viscosity increased with the generation number. For the dendritic polymers, however, the reversed trend was observed; the relative increase of the viscosity upon polymerization is smaller for dendritic polymers of higher generation side groups. These results were discussed in terms of the shielding effect of the dendritic side groups. Furthermore, it was demonstrated that the rheology of the SCDPs can be regulated by the choice of the diisocyanate, i.e., by changing the flexibility of the main chain.

The influence of physical aging on viscoelastic behaviour of heterogeneous amorphous polyblends of ABS and polycarbonate was studied by means of stress relaxation experiments at different temperatures. The stress relaxation data of the constituent phases ABS and PC are found to be in agreement with the universal description of relaxation behaviour of amorphous polymers at the onset of the glass-rubber transition. The regimes where master curve construction by time-temperature and time-aging time superposition is permitted could be deduced for the thermorheologically complex polyblends. It is shown that the relaxation curves of the ABS/PC blends can be calculated by means of a quasi-elastic extension of the van der Poel-model using the stress relaxation data of the constituent phases and their volume fractions.

In linear viscoelastic investigations the frequency dependence of the phase shift between stress and strain appears to be very characteristic of the molecular structure of the material. This function is also a good approximation of the slope of the double logarithmic plot of the absolute value of the shear modulusGd vs. the angular frequency?. The product (Gd/p) sin 2d comes very close to the relaxation spectrumH(t), witht = 1/?, in all physical states of the material.