On the pH-responsive, charge-selective, polymer-brush-mediated transport probed by traditional and scanning fluorescence correlation spectroscopy.

The complete and reversible charge-selective sequestration of fluorophores by a weak polyelectrolyte brush, poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA) was demonstrated using fluorescence correlation spectroscopy (FCS). The chemistry and thickness of the weak polyelectrolyte PDMAEMA was tuned reversibly between neutral and cationic polymer forms. Thus, by switching the pH successively, the brush architecture was tuned to selectively trap and release anionic dye probes while continuously excluding cationic molecules. In addition, line-scan FCS was implemented and applied for the first time to a synthetic polymer system and used to identify a new, slower diffusion time on the order of seconds for the sequestered anionic probe under acidic conditions. These results, which quantify the selective sequestration properties of the PDMAEMA brush, are important because they enable a better understanding of transport in polymers and establish a spectroscopic means of evaluating materials with proposed applications in separations science, charge storage/release, and environmental remediation.

Analysis of western redcedar (Thuja plicata Donn) heartwood components by HPLC as a possible screening tool for trees with enhanced natural durability.

A method is described for the quantitative analysis of seven known compounds, specifically plicatic acid, thujaplicatin methyl ether, beta-thujaplicin, gamma-thujaplicin, beta-thujaplicinol, thujic acid, and methyl thujate, in the ethanol extract of second growth western redcedar heartwood (Thuja plicata Donn) by high-performance liquid chromatography using diode array detection. The para bromo phenacyl ester of crotonic acid is synthesized for use as the internal standard for the method. Separation of compounds covering a wide range of polarities is achieved using an Inertsil ODS 3 3-micro column. Twenty seven second growth trees ranging in age from 40 to 125 years, originating from the coastal and interior regions of British Columbia, are selected for analysis and profiled using the described method. Samples consisting of five growth rings each are analyzed from the heartwood-sapwood boundary to the pith for each tree. Substantial variation in most heartwood compounds are detected within and between trees within a region. Significant variation in beta-thujaplicin, the ratio between gamma- and beta-thujaplicin, and methyl thujate is detected between coastal and interior populations.

Health, equity, and reproductive risks in the workplace.

Potential exposure to occupational reproductive hazards raises complex questions regarding health and gender discrimination in the workplace. On the one hand, growing scientific evidence suggests that workplace exposures to either sex can cause a wide range of disorders ranging from infertility to adverse pregnancy outcomes. On the other hand, policies alleging to protect workers from reproductive risks have often reinforced gender inequalities in the workplace. This article sheds new light on this continuing debate through an examination of the policy insights suggested by a recent study of reproductive hazard policies in Massachusetts. In what ways do policies evidenced in this study reflect or differ from historical patterns of protectionism? The article presents a political-legal review of reproductive hazard policies in the workplace, then examines the policy implications of the Massachusetts study, and finally presents the prescriptions for change that are implied by both the historical and contemporary evidence.

The renin-angiotensinogen reaction during pregnancy and oral contraception: estimation of kinetic parameters by an autologous plasma renin assay.

A method has been developed which allows estimation of the kinetic parameters of the plasma renin-angiotensinogen reaction from data obtained by autologous renin assays at several plasma dilutions. The quantitative aspects of the renin-angiotensin system were examined in 28 plasma samples from 23 healthy, normotensive pregnant women. They were compared with 20 women who were not pregnant, of whom 12 were taking oral contraceptives and eight were not. In the first 3 months of pregnancy, there was a sharp increase in plasma renin activity and concentration. Plasma angiotensinogen rose steadily throughout pregnancy. The higher concentrations of renin and angiotensinogen would lead to an increase in angiotensin formation with potentially adverse consequences. However, this increase may be reduced by the fall in the affinity between renin and angiotensinogen which is suggested by the present observation that the Michaelis-Menten constant (Km) attained values five to six times higher than those seen in women not taking oral contraceptives. The smaller increases in plasma renin and angiotensinogen induced by oral contraceptives were less effectively compensated by lower affinity. Circumstantial evidence is provided which suggests that the observed high Km values may be due to oestrogen/pregnancy-induced synthesis of an angiotensinogen with a lower affinity for renin.

Reduced activation and affinity of renin during pregnancy and oral contraception: determination of kinetic parameters by a fully autologous plasma renin assay.

In healthy normotensive pregnancy, a complex functional network develops between the cardiovascular system, the volume and composition of the extracellular fluid and the renin-angiotensin system (RAS). Cardiac output and heart rate increase, but blood pressure is reduced. The kidneys increase in size and both the glomerular filtration rate and renal blood flow increase early. Renal tubular water and sodium reabsorption is even more enhanced, so that the total body water of mother and foetus rises in the course of pregnancy by 6-8 litres. Plasma osmolality falls by about 10 mosm/kg. yet total body sodium increases by about 1 mol. Understandably, in the face of such complex fluid and pressure adjustments, data on the changes of the RAS in normal pregnancy are often contradictory. However, there is general agreement that the angiotensinogen and inactive renin in plasma are greatly raised. Most groups have also found a considerable increase in active renin. These changes could lead to higher rates of angiotensin I (AI) formation (and hence high circulating angiotensin II levels), with adverse consequences for mother and foetus. The high proportion of inactive renin may reflect a reduction in the rate of activation of prorenin in order to avoid these consequences. This reduction may involve kallikreins which have been listed amongst the putative in vivo activators of prorenin. Excessive AI formation in pregnancy could also be avoided by the production of functionally different renins or angiotensinogens. Such changes will be difficult to detect with assays which require addition of extraneous renin or angiotensinogen.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of chlorinated phenols in surface-treated lumber by HPLC.

A solution of internal standard in acetonitrile is used to extract samples of wood from lumber which had been commercially treated with chlorinated phenols. The tetrachlorophenol(TCP) and pentachlorophenol( PCP) were analytically separated from each other and from the other wood extractive compounds using a high performance liquid chromatograph (HPLC). The ultraviolet (UV) absorptions of the TCP, PCP, and internal standard were automatically measured as they eluted. The UV absorption peaks were integrated, and the amounts of TCP and PCP present were calculated with a dedicated microcomputer. Compared with the method previously used, this method is faster (up to 144 samples per 48 hours), has the same accuracy and precision, and it is linear over the concentration range used.