NMR-based metabolomics reveals that conjugated double bond content and lipid storage efficiency in HepG2 cells are affected by fatty acid cis/trans configuration and chain length

In the present study the metabolic response to various fatty acids was investigated in HepG2 cells by using a (1)H NMR-based approach. To elucidate the effect of cis/trans configuration, the cells were exposed to either oleic acid (C18:1 cis-9), elaidic acid (C18:1 trans-9), vaccenic acid (C18:1 trans-11), linoleic acid (C18:2), or palmitic acid (C16:0), and multivariate data analysis revealed a strong effect of fatty acid on the lipophilic metabolite fraction. Inspection of the spectra revealed that the difference between the observed responses could be ascribed to the appearance of resonances from conjugated double bonds (5.65, 5.94, and 6.28 ppm) in cells exposed to vaccenic acid, revealing that vaccenic acid upon uptake by the HepG2 cells is converted into a conjugated fatty acid. Upon exposure of the HepG2 cells to either butyric acid (C4:0), caproic acid (C6:0), lauric acid (C12:0), myristic acid (C14:0), or palmitic acid (C16:0), an effect of fatty acid length was also evident, and data indicated that short-chain fatty acids (C4-C6) are immediately converted, whereas medium-long-chain fatty acids (C12-16) are incorporated into triglycerides and deposited in the cells. In conclusion, the present study demonstrates that (1)H NMR spectroscopy is a useful method for studying the uptake of fatty acids in in vitro cells.     

Relationships between a terrain-based hydrologic model and patch-scale vegetation patterns in an arctic tundra landscape

Implicit in the relationship between vegetation patterns and landforms is the influence of topography on the water regime at the patch scale. Hence, based on the numerous process-based studies linking plant structure and function to water in the arctic, we hypothesize that the general pattern of arctic landscapes can be explained by a mesotopographic variable such as water drainage. In this paper, we test this hypothesis by examining the spatial relationship between patterns of vegetation and the water regime in a small watershed in northern Alaska. Using gridded elevation data, we develop a model (T-HYDRO) to generate a 2-dimensional water flow field for the watershed and compare this to vegetation patterns as given by 1) a vegetation map developed from aerial photographs in conjunction with extensive field sampling; and 2) a normalized difference vegetation index (NDVI). Our results show that it is possible to account for about 43% of the spatial variance in NDVI, which supports our hypothesis. In spite of its limitations, the correspondence of patterns presented in this paper provides encouraging evidence that we can find simple approaches to stratify landscapes and that it is possible to overcome the frequently made assumption of spatial homogeneity in ecosystems modeling.     

Origin of multiexponential T(2) relaxation in muscle myowater.

To obtain a further understanding of the nature of the multiexponential T(2) relaxation seen in muscle tissue water (myowater), relaxation measurements were carried out on whole, minced, and homogenized pork of three different qualities with regard to water-holding capacity (normal, red soft exudative, and dark firm dry). Whole, minced, and homogenized pork all resulted in multiexponential T(2) relaxation (three components) independently of the quality, even though microscopic studies on homogenized meat revealed considerable disruption of the macroscopic structure. This states that the relaxation behavior in meat cannot be explained by intra-/extracellular compartmentalization of the water as suggested in earlier studies. Subsequent studies of T(2) relaxation in either whole meat, where the structure integrity was changed by the introduction of dimethyl sulfoxide (membrane disruption) or urea (protein denaturation), or minced meat with added NaCl (inter-/intraprotein interactions) lead to the suggestion that in whole meat (i) the fastest relaxation component reflects water tightly associated with macromolecules, (ii) the intermediate relaxation component reflects water located within highly organized protein structures, for example, water in tertiary and/or quaternary protein structures and spatials with high myofibrillar protein densities including actin and myosin filament structures, and (iii) the slowest relaxation component reflects the extra-myofibrillar water containing the sarcoplasmatic protein fraction. Finally, relaxation patterns in heat-set gels of superprecipitated actomyosin and bovine serum albumin similar to that identified in whole meat support the proposed nature of T(2) relaxation in muscle myowater.     

Structural analogues of homoeriodictyol as flavor modifiers. Part III: short chain gingerdione derivatives

In order to find new flavor modifiers, various short chain gingerdione derivatives were synthesized as structural analogues of the known bitter masker homoeriodictyol and evaluated by a sensory panel for masking and sweetness enhancing activities. 1-(4-Hydroxy-3-methoxyphenyl)hexa-3,5-dione ([2]-gingerdione) and the homologue 1-(4-hydroxy-3-methoxyphenyl)hepta-3,5-dione ([3]-gingerdione) at concentration ranges 50-500 mg kg (-1) showed the most promising masking activity of 20-30% against bitterness of a 500 mg kg (-1) aqueous caffeine solution. Additionally, both compounds were able to reduce the bitterness of a 5 mg kg (-1) quinine solution by about 20%; however, the bitter tastes of salicine, the model peptide H-Leu-Trp-OH, and KCl solutions were not reduced. Whereas for bitter masking activity a vanillyl moiety seems to be important, some of the tested isovanillyl isomers showed an interesting sweet enhancing effect without exhibiting a significant intrinsic sweetness. The isomer 1-(3-hydroxy-4-methoxyphenyl)hexa-3,5-dione ([2]-isogingerdione) at 100 mg kg (-1) caused a significant and synergistic increase of 27% of sweet taste of a 5% sucrose solution.