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841.
The investigation of the essential oil from Molopospermum peloponnesiacum roots afforded, in addition to some well known terpenoids, two aromatic aldehydes, which were found for the first time as volatile oil components. Their structures were elucidated by spectroscopic methods. The formation of these aldehydes during steam distillation from unstable precursors is discussed. 相似文献
842.
Robert Huber Helge Meggers Karl-Heinz Baumann Maureen E. Raymo Rüdiger Henrich 《Palaeogeography, Palaeoclimatology, Palaeoecology》2000,160(3-4):193-212
We present measurements of the maximum diameter of the planktonic foraminifer Neogloboquadrina pachyderma sin. from six sediment cores (Ocean Drilling Program sites 643, 644, 907, 909, 985 and 987) from the Norwegian–Greenland Sea. Our data show a distinct net increase in mean shell size of N. pachyderma sin. at all sites during the last 1.3 Ma, with largest shell sizes reached after 0.4 Ma. External factors such as glacial–interglacial variability and carbonate dissolution alone cannot account for the observed variation in mean shell size of N. pachyderma sin. We consider the observed shell size increase to mirror an evolutionary trend towards better adaptation of N. pachyderma sin. to the cold water environment after 1.1–1.0 Ma. Probably, the Mid Pleistocene climate shift and the associated change of amplitude and frequency of glacial–interglacial fluctuations have triggered the evolution of this planktonic foraminifer. Oxygen and carbon stable isotope analyses of different shell size classes indicate that the observed shell size increase could not be explained by the functional concept that larger shells promote increasing sinking velocities during gametogenesis. For paleoceanographic reconstructions, the evolutionary adaptation of Neogloboquadrina pachyderma sin. to the cold water habitat has significant implications. Carbonate sedimentation in highest latitudes is highly dependent on the presence of this species. In the Norwegian–Greenland Sea, carbonate-poor intervals before 1.1 Ma are, therefore, not necessarily related to severe glacial conditions. They are probably attributed to the absence of this not yet polar-adapted species. Further, transfer function and modern analog techniques used for the reconstruction of surface water conditions in high latitudes could, therefore, contain a large range of errors if they were applied to samples older than 1.1–1.0 Myrs. 相似文献
843.
The “expensive tissue hypothesis” states that large brains are active at high metabolic rates, which have to be financed by a significant trade-off with other organs such as the alimentary tract. Recent morphological findings on primate brains and guts support this idea also considering the importance of high-energy diets as a possible driving power of this process. However, the trade-off correlation between brain and alimentary tract, the essence of the “expensive tissue hypothesis”, has not yet been tested using molecular data to complement morpho-functional findings. We therefore hypothesize that the activity of marker proteins expressed both in brain and alimentary tract should parallel functional morphology in organs at the molecular level. Thus, in animals feeding on hard to digest diet, we would expect a high concentration per unit mass of that marker protein in the digestive tract and reversely a lower concentration in the brain. In contrast, in animals feeding on easily-digested, high-energy food we would expect the reverse pattern. Recent preliminary studies suggest that carbonic anhydrase II (CA-II) could act as a marker. The enzyme concentration was found to increase in the brain with higher cerebral activity from cattle to humans and to reversely decrease in salivary secretions. The reverse concentration of CA-II in saliva and brains of cattle and primates might be the first molecular evidence of the validity of the “expensive tissue hypothesis”. 相似文献
844.
Production of poly-D(-)-3-hydroxybutyrate and poly-D(-)-3-hydroxyvalerate by strains ofAlcaligenes latus 总被引:2,自引:0,他引:2
Alcaligenes latus strains can accumulate poly-D(-)-3-hydroxybutyrate (PHB) up to about 85% of cell dry weight. The abilities to store poly-D(-)-3-hydroxyvalerate (PHV) of three strains ofA. latus were investigated. With Na-propionate as PHV precursor, strainA. latusDSM 1122 had better PHV accumulation ability than strainsA. latusDSM 1123 and 1124. StrainA. latus DSM 1123 could store PHV when Na-valerate but not Na-propionate served as the PHV precursor. PHB and PHV accumulation byA. latus DSM 1124 rapidly increased when propionic acid and acetic acid were together added to the fermentor. This increase was not obtained in the culture shaker flask and fermentor growing the same strain when Na-propionate alone served as a PHV precursor. 相似文献