The Influence of Synoptic-scale Air Flow and Local Circulation on the Dust Layer Height in the North of the Taklimakan Desert

The present study investigates the influences of synoptic-scale air flows and local wind circulations on the dust layer height (DLH) in the Taklimakan Desert, based on lidar observations performed in the north of the desert in March 2003. The DLH fluctuates approximately every three days between 2500 m (above sea level) and 5000 m, including diurnal variations. Meteorological analyses and numerical simulations show that the three-day fluctuation of DLH corresponds with variations in synoptic-scale air flows over the Taklimakan Desert, and the diurnal variations are linked to downdrafts and updrafts that are formed over the north of the desert as part of local circulations. When strong northerly winds prevail in the upper troposphere and a developed valley wind blows toward the Tienshan Mountains in the lower troposphere, the downdrafts strengthen in the middle troposphere over the north of the desert, lowering the DLH to about 2500 m. In contrast, the DLH rises to about 5000 m when the updrafts develop between strong southerly winds in the upper troposphere and a developed mountain wind blowing from the Tienshan Mountains. Simulations for the local circulation behavior without the presence of the Tienshan Mountains demonstrate that the valley and mountain winds on the southern slope of the Tienshan Mountains control the intensity of the downdrafts and updrafts, thereby influencing the DLH over the north of the Taklimakan Desert.     

Hydrolysis of di-n-butyl phthalate, butylbenzyl phthalate and di(2-ethylhexyl) phthalate in human liver microsomes

Diester phthalates are industrial chemicals used primarily as plasticizers to import flexibility to polyvinylchloride plastics. In this study, we examined the hydrolysis of di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP) in human liver microsomes. These diester phthalates were hydrolyzed to monoester phthalates (mono-n-butyl phthalate (MBP) from DBP, mono-n-butyl phthalate (MBP) and monobenzyl phthalate (MBzP) from BBzP, and mono(2-ethylhexyl) phthalate (MEHP)) by human liver microsomes. DBP, BBzP and DEHP hydrolysis showed sigmoidal kinetics in V-[S] plots, and the Hill coefficient (n) ranged 1.37-1.96. The S₅₀, V_max and CL_max values for DBP hydrolysis to MBP were 99.7 μM, 17.2 nmol min⁻¹ mg⁻¹ protein and 85.6 μL min⁻¹ mg⁻¹ protein, respectively. In BBzP hydrolysis, the values of S₅₀ (71.7 μM), V_max (13.0 nmol min⁻¹ mg⁻¹ protein) and CL_max (91.3 μL min⁻¹ mg⁻¹ protein) for MBzP formation were comparable to those of DBP hydrolysis. Although the S₅₀ value for MBP formation was comparable to that of MBzP formation, the V_max and CL_max values were markedly lower (<3%) than those for MBzP formation. The S₅₀, V_max and CL_max values for DEHP hydrolysis were 8.40 μM, 0.43 nmol min⁻¹ mg⁻¹ protein and 27.5 μL min⁻¹ mg⁻¹ protein, respectively. The S₅₀ value was about 10% of DBP and BBzP hydrolysis, and the V_max value was also markedly lower (<3%) than those for DBP hydrolysis and MBzP formation for BBzP hydrolysis. The ranking order of CL_max values for monoester phthalate formation in DBP, BBzP and DEHP hydrolysis was BBzP to MBzP ? DBP to MBP > DEHP to MEHP > BBzP to MBP. These findings suggest that the hydrolysis activities of diester phthalates by human liver microsomes depend on the chemical structure, and that the metabolism profile may relate to diester phthalate toxicities, such as hormone disruption and reproductive effects.     

Human UDP-glucuronosyltransferase isoforms involved in bisphenol A glucuronidation

Bisphenol A (BPA) is one of a number of potential endocrine disruptors which may affect normal hormonal function. In this study, human UDP-glucuronosyltransferase (UGT) isoforms involved in BPA glucuronidation were studied by kinetic analyses using human liver microsomes and recombinant human UGTs expressed in insect cells (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B4, UGT2B7, UGT2B15 and UGT2B17). BPA glucuronidation was catalyzed by UGT1A1, UGT1A3, UGT1A9, UGT2B4, UGT2B7 and UGT2B15 as well as by human liver microsomes. Among these UGTs, UGT2B15 showed the highest activity of BPA glucuronidation at low- (1.0 microM) and high- (20 microM) substrate concentrations. Kinetic analyses of BPA glucuronidation were performed by constructing Michaelis-Menten and Eadie-Hofstee plots. The kinetic profile of BPA glucuronidation by pooled human liver microsomes and UGT2B15 was monophasic, the K(m) and V(max) values were 6.39 microM and 4250 pmol min(-1)mg(-1)protein for pooled human liver microsomes, and 8.68 microM and 873 pmol min(-1)mg(-1)protein for UGT2B15, respectively. The K(m) values for BPA glucuronidation by pooled human liver microsomes and UGT2B15 were similar. These findings demonstrate that BPA is mainly glucuronidated by UGT2B15 in human liver microsomes, and suggest that this UGT isoform plays important roles in the detoxification and elimination of BPA.     

Fine-scale flower-visiting behavior revealed by using a high-speed camera

Most estimations of the pollination efficiency of insects have been based on observation by the naked human eye. However, insect behaviors are often too rapid to analyze sufficiently this way. Here we demonstrate the use of high-speed cameras to analyze the fine-scale behaviors of Macroglossum pyrrhosticta, Xylocopa appendiculata, and Papilio dehaanii when visiting Clerodendrum trichotomum. The fine-scale nectar drinking time, number of contacts with anthers and/or stigmas, and frequencies of body part contact with anthers and/or stigmas differed significantly among pollinator species. Pollination efficiency was not equal among pollinators. In addition, M. pyrrhosticta made the least number of contacts with anthers and/or stigmas even though it showed the highest visitation frequency. These results demonstrate that when examined from the viewpoint of rapid visitation behaviors, pollination dynamics differ among pollinator species, and flower visits and pollination rates are not equal.