Cidofovir transport in the pigmented rabbit conjunctiva

PURPOSE: To characterize cidofovir (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine) transport in the pigmented rabbit conjunctiva and to evaluate the formulation influence on its transport. METHODS: The excised pigmented rabbit conjunctiva was mounted in the modified Ussing chamber. Cidofovir transport was initiated by applying 3H-cidofovir to the donor compartment and assayed by measuring the radioactivity accumulated in the receiver fluid over 180 min. RESULTS: Cidofovir flux in the mucosal-to-serosal direction increased proportionally with drug concentration over the 0.01 to 1 mM range. Cidofovir transport (0.01 mM) at 37 degrees C in the mucosal-to-serosal direction was not significantly different from that in the opposite direction or from that at 4 degrees C. Hypotonicity (80 mOsm/kg), 0.5% EDTA, and 0.0125% benzalkonium chloride increased the apparent permeability coefficient of cidofovir 3, 21, and 49 times, respectively. This was accompanied by a corresponding 43%, 86%, and 96% reduction in the transconjunctival electrical resistance over 180 min. The reduction in transepithelial electrical resistance elicited by hypotonicity was reversible. There was a good correlation between apparent permeability coefficient and the transconjunctival conductance, suggesting that cidofovir may undergo paracellular passive diffusion in the conjunctiva. CONCLUSION: Cidofovir transport in the rabbit conjunctiva may be via paracellular passive diffusion. Formulation changes may improve cidofovir absorption from the conjunctival route.     

Synthesis of DHPA analogs and their inhibitory activities of human recombinant S-adenosyl-L-homocysteine hydrolase

We report syntheses of DHPA analogs, e.g., 9-(3-formyl-2,3-dihydroxypropyl)adenine (FDHPA) and 9-(3-formyl-2,3-dihydroxypropyl)hypoxanthine (FDHPI). Among these DHPA analogs, FDHPA behaved as an irreversible inactivator of human recombinant SAH hydrolase.     

SAW气体传感器的转换机制

讨论了在SAW气体的传感器中把化学信号(气体浓度)转换成物理信号(SAW相速度变化)的机制以及将它们彼此分离开来的方法.     

浅谈入世后我国农产品质量安全和标准体系建设

<正> 随着农业发展进入新的阶段,农产品质量安全已成为制约我国农业和农村经济发展的突出问题。特别是WTO成立以来,伴随着农产品贸易的自由进程,传统的关税壁垒作用在逐步减弱,以控制农产品质量安全为中心的技术性壁垒的作用在逐步加强,围绕农产品质量安全而产生的贸易摩擦乃至争端呈增长趋势。我国加入WTO之后,无论是农产品的国内市场,还是面对国际农产品贸易,都不可避免地要被卷入这场新的国际角逐。     

Concentration distribution of antioxidant additive BHT in polypropylene after heating

The concentration distribution of an antioxidant 2,6-di-tert-butyl-p-cresol (BHT) in the polypropylene (PP) after heating the film containing BHT for a long period of time in succession was studied with use of the rolled film method. The film of 0.003 cm in thickness containing uniformly 710 mg kg^?1 of BHT was wound tightly around a glass tube. At the beginning, BHT was distributed uniformly in all layers, and after a given time of the heat treatment at 70–100°C, a remarkable alteration of the concentration distribution of BHT in PP took place. The relations between BHT concentration and the distance from the surface were shown by parabolic curves after heating. The BHT concentration was always kept at almost zero concentration at the surface layer of the rolled film. Assuming that the diffusion obeys Fick's law, the diffusion coefficients at 70, 80, 90, and 100°C were estimated to be 1.05, 4.17, 8.69, and 24.7 × 10^?9 cm² s^?1, respectively. The activation energy was calculated as 105 kJ mol^?1.     

Thermal decomposition of aluminium hydroxycarboxylates—lactate,citrate and tartrate

The thermal transformation of anhydrous alumina obtained by the decomposition of the lactate, citrate and tartrate of aluminium has been examined by thermal analysis(TGA and DTA), infrared spectrophotometry and X-ray diffraction study. It is found that under an atmosphere of air the thermal decomposition of aluminium hydroxycarboxylates to anhydrous amorphous alumina, which transforms to α-alumina via γ-, δ- and θ-aluminas, proceeds as follows for Al[CH₃CH(OH)COO]₃, the decomposition of skeleton and the combustion of its decomposition products; for Al[CH₂C(OH)CH₂(COO)₃] and Al₂{[CH(OH)COO]₂}₃, dehydroxylation, decomposition of skeleton and the combustion of its decomposition products.     

An optical 90°-hybrid balanced receiver module using a planarlightwave circuit

An optical 90°-hybrid coherent receiver module is constructed that uses the planar lightwave circuit technique. The module consists of an optical 90°-hybrid silica planar waveguide and two 14 GHz balanced O/E converters; the solder-bump technique is employed. For both sets of paths between the optical coupler and the twin-p-i-n photodetector pairs, the effective propagation time differences were reduced to within 4 ps. A 10 Gb/s BPSK homodyne detection experiment confirms the feasibility of the receiver