Penetration of model beta-blockers, propranolol, oxprenolol, metaprolol, and nadolol, into dimyristoylphosphatidylcholine (DMPC) monolayers cast on a pH 7.4 phosphate buffer (mu = 0.155 adjusted with NaCl) at 25 degreesC was monitored using a film balance equipped with a Wilhelmy plate for measuring changes in surface pressure. Drug solution (pH 7.4) is injected below the surface of the monolayer. The difference in surface pressure, Delta pi, for each drug concentration added to the monolayer was measured at equilibrium. Delta pi increased with increasing drug concentration. Consistent with the relative lipophilicities, the Delta pi vs drug concentration slopes were as follows: propranolol > metaprolol > oxprenolol > nadolol. The intrinsic surface activity of the beta-blockers was also determined in the absence of the lipid. Differential scanning calorimetry (DSC) measurements were also made on DMPC bilayers in the above buffer. DMPC suspended in buffered drug solutions were scanned over a temperature range of 5 degrees to 40 degreesC at a scan rate of 0.091 degreesC/min. The DSC studies indicate that the DMPC thermotropic phase behavior is modulated by these compounds as follows: propranolol >> metaprolol congruent with oxprenolol > nadolol which agrees with reported partition coefficients as well as the above Delta pi observations. However, an accounting of the intrinsic surface activity of these compounds results in a lower than expected affinity for the DMPC monolayer.
The aim of this study was to evaluate the consequence of changing land use from agriculture land to other use purposes with respect to OCPs non-cancer and cancer risk on human health, based on concentrations of DDTs and HCHs in soils collected from 55 locations representing 12 different land use types. There were no non-cancer risks of DDTs and γ-HCHs on adults and children, and there were very low cancer risks of DDD, o,p'-DDE, DDT, α-HCH, β-HCH, γ-HCH based on their total concentrations in all samples. Nonetheless, there were significant correlations of DDT to its metabolites (DDE and DDD) (r = 0.506 and r = 0.648) and DDE to DDD (r = 0.438) both at p < 0.01. OCP levels should be routinely monitored in different environmental media and food in order to verify whether there is fresh input. Their potential risks on human health should also be assessed.
All too often, waste authorities either assume that they know enough about their bulky waste stream or that it is too insignificant to deserve attention. In this paper, we use Hong Kong as an example to illustrate that official bulky waste figures can actually be very different from the reality and therefore important waste management decisions made based on such statistics may be wrong too. This study is also the first attempt in Hong Kong to outline the composition of bulky waste. It was found that about 342tonnes/day of wood waste were omitted by official statistics owing to incomplete records on actual bulky waste flow. This is more than enough to provide all the feedstock needed for one regular-sized wood waste recycling facility in Hong Kong. In addition, the proportion of bulky waste in the municipal solid waste (MSW) streams in Hong Kong should be about 6.1% instead of the officially stated 1.43%. Admittedly, there are limitations with this study. Yet, present findings are suggestive of significant MSW data distortion in Hong Kong.
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