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BackgroundThe relationship of cholesterol homeostasis and carotid intima-media thickness (cIMT) is unknown. To address this, we assessed markers of cholesterol homeostasis (serum plant sterols and cholesterol precursor concentrations as surrogate measures of cholesterol absorption and synthesis, respectively) and cIMT in a middle-aged, statin-naive population.MethodsIn this prospective study of primary prevention cIMT was measured by ultrasound in 583 hospital employees aged 25-60 years without prevalent cardiovascular disease or lipid-modifying medication. The serum concentrations of plant sterols (as markers of cholesterol absorption) were measured by gas-liquid chromatography. Lathosterol serum concentrations were quantitated to assess hepatic cholesterol synthesis.ResultscIMT correlated positively with serum cholesterol (r = 0.22, PConclusionsIn this population without prevalent cardiovascular diseases or lipid-modifying medication, markers of increased endogenous cholesterol synthesis correlated positively with cIMT, while markers of cholesterol absorption showed a weakly negative correlation. These data suggest that not only total serum cholesterol levels but also differences in cholesterol homeostasis are associated with cIMT.

Absorption lines of HDO and H2O have been detected in a 0.23-wave number resolution spectrum of the dark side of Venus in the interval 2.34 to 2.43 micrometers, where the atmosphere is sounded in the altitude range from 32 to 42 kilometers (8 to 3 bars). The resulting value of the deuterium-to-hydrogen ratio (D/H) is 120 +/- 40 times the telluric ratio, providing unequivocal confirmation of in situ Pioneer Venus mass spectrometer measurements that were in apparent conflict with an upper limit set from International Ultraviolet Explorer spectra. The 100-fold enrichment of the D/H ratio on Venus compared to Earth is thus a fundamental constraint on models for its atmospheric evolution.

We have detected the 3 nu 2 band of CH3D in the spectrum of Neptune near 1.6 micrometers recorded at a spectral resolution of 4 cm-1 with the Cassegrain Fourier Transform Spectrometer at the 3.6 m Canada-France-Hawaii Telescope (CFHT) on Mauna Kea. Our analysis of this spectrum, using spectral synthesis techniques, yielded a CH3D/CH4 ratio of 6(+6)(-4) x 10(-4), which corresponds to a global D/H ratio for Neptune of 1.2(+1.2)(-0.8) x 10(-4), if CH3D is in isotopic fractionation equilibrium with HD. This value is about an order of magnitude larger than an earlier estimate by Orton et al. based on deconvolution measurements of unresolved molecular emission in the 8-10 micrometers region. Comparison of this new determination with previous studies of CH3D in the outer solar system shows that, as in the case of Uranus, the D/H on Neptune is strongly enhanced over that found on Jupiter and Saturn and is comparable to the D/H in methane on Titan and in terrestrial methane and water.

We have estimated the D/H ratio that may have been present in the primitive ices in the protosolar nebula. Using observations of the CH3D/CH4 ratio in the outer planets, we developed two simple but limiting models which constrain the amount of dilution that deuterated volatiles which were contributed to the planetary atmospheres by evaporated primordial ices may have undergone by mixing with the original hydrogen envelopes. The models suggest that the D/H ratio in these ices was probably somewhere between a few times 10(-4) and 10(-3). These planetary-atmosphere-derived results are compared with other solar system bodies thought to contain primitive material and with D/H ratios observed in interstellar polyatomic molecules.

A new atlas of CH(4) lines in the 1120-1800-cm(-1) region has been generated, based on laboratory spectra taken with a Nicolet interferometer at 0.06-cm(-1) resolution with 635-cm path length at pressures of 0.98 Torr, 4.86 Torr, and 19.97 Torr. A compilation of line positions and line intensities includes 1339 CH(4) lines, several hundred of which have not been previously observed.

We have just completed a series of determinations of the CH3D/CH4 ratio in the atmospheres of Saturn, Titan and Uranus. These results, coupled with the work of other investigators, suggest that the Solar System contains at least two distinctly different primordial reservoirs of deuterium: that contained in gaseous hydrogen and that contained in the volatiles which have been maintained at low temperatures or isolated from hydrogen; for example, trapped in cold, solid material. Both of these reservoirs were established before the formation of the Solar System.

The 3-0 rotation-vibration band of carbon monoxide in the near-infrared spectrum of Titan has been identified, and a reflecting layer model mixing ratio of carbon monoxide to molecular nitrogen of 6 x 10(-5) has been determined. This result supports the probable detection of carbon dioxide by Samuelson and his co-workers and strengthens possible analogies between the atmosphere of Titan and conditions on primitive Earth.

Deuterium on Mars has been detected by the resolution of several Doppler-shifted lines ofHDO near 3.7 micrometers in the planet's spectrum. The ratio of deuterium to hydrogen is (9 +/- 4) x 10(-4); the abundance of H(2)0 was derived from lines near 1.1 micrometers. This ratio is enriched on Mars over the teiluric value by a factor of6 +/- 3. The enrichment implies that hydrogen escaped more rapidly from Mars in the past than it does now, consistent with a dense and warm ancient atmosphere on the planet.