A comparison of maternal calcium and magnesium levels in pre-eclamptic and normotensive pregnancies: an observational case-control study.

OBJECTIVE: Supplementing pregnant women at high risk of developing pre-eclampsia with calcium may reduce the incidence of the disease. This study examines differences in serum and hair concentrations of calcium and magnesium between women with pre-eclamptic and normotensive pregnancies. DESIGN: Observational case-control study. SETTING: Two teaching hospitals in Cape Town, South Africa. POPULATION: Women with pre-eclamptic (N = 96) or normotensive (N = 96) pregnancies, who delivered a single, live infant. METHODS: Demographic and current pregnancy details were retrieved from clinical notes. Each participant completed a dietary questionnaire. Venous blood samples were taken from each participant to assess serum calcium and magnesium concentrations. Hair samples were obtained from all participants and calcium and magnesium levels were measured by inductively coupled plasma optical emission spectrometry (ICPOES). MAIN OUTCOME MEASURE: Hair and serum calcium and magnesium concentrations were compared between women with pre-eclamptic and normotensive pregnancies. RESULTS: Diet and socio-economic status in the two groups were similar. There was no significant difference in the hair calcium level between women with pre-eclamptic [1241 parts per million (ppm); range, 331-4654 ppm] and normotensive (1146 ppm; range, 480-4136 ppm) pregnancies (P = 0.5). Hair calcium levels in both groups were not affected by HIV infection. CONCLUSION: Woman with pre-eclampsia showed no difference in chronic calcium status relative to normotensive women. This finding does not support the current belief that the mechanism by which calcium supplementation reduces the risk of developing pre-eclampsia is by correcting a nutritional deficiency.

Antibacterial effects of theaflavin and synergy with epicatechin against clinical isolates of Acinetobacter baumannii and Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia and Acinetobacter baumannii are recognised as important nosocomial pathogens; however, due to their intrinsic resistance to multiple antibiotics, treatment options are limited. Polyphenols from black tea have been shown to possess antibacterial action. In this study, the antibacterial effects of various concentrations of theaflavin as well as combinations of theaflavin and epicatechin were determined using the disk diffusion assay. The results showed strong antibacterial activity of theaflavin against eight clinical isolates of S. maltophilia and A. baumannii. Significant synergy (P≤0.05) was also observed between theaflavin and epicatechin against all isolates. Although the mechanisms for this activity and synergy are not well understood, the clinical potential is clear and further research is recommended to determine the modes of action.

Micro-fluidic and lab-on-a-chip technology.

By reducing the operational dimensions of a conventional macrofluidic-based system down to the micron scale, one can not only reduce the sample volume, but also access a range of unique characteristics, which are not achievable in conventional macro-scale systems. This chapter will discuss the unique properties of miniaturised systems based on micro-fluidic and Lab-on-a-Chip technology and consider how these may influence the overall performance associated with chemical and biological processing. Some consideration will also be given to the selection of materials and/or surface modifications that will be proactive in exploiting the high surface area and thermal and mass transfer properties, to enhance process performance.

Combinatorial synthesis in micro reactors.

This article reviews the current and future applications of micro reactors in the field of combinatorial chemistry and drug discovery. Liquid phase reactions have been used to illustrate the advantages of performing chemical reactions in micro reactors which illustrate that reactions can be performed very rapidly in high yield to enable the preparation of combinatorial libraries of structurally related compounds.

Maternal and neonatal hair mercury concentrations: the effect of dental amalgam.

OBJECTIVE: To evaluate maternal and fetal hair mercury levels in relation to the placement of dental amalgam tooth restorations. DESIGN: Cross sectional study involving women who never had dental amalgam restorations placed, women who had amalgam restorations placed before pregnancy and women who had restorations placed during the index pregnancy. SETTING: North of England Maternity Hospital. SAMPLE: Fifty-three healthy women who delivered healthy babies at term. METHODS: Maternal and fetal hair was collected in a standardised manner in the first few days following delivery. MAIN OUTCOME MEASURES: Maternal and neonatal hair mercury concentrations. RESULTS: When compared with women without restorations, there was a significant increase in the maternal hair mercury concentration in women who had dental amalgam placed outside of the index pregnancy and also in women who had dental amalgam placed during the index pregnancy. The fetal hair mercury concentration was significantly higher in babies when mothers had been exposed to dental amalgam either before pregnancy or during pregnancy compared with unexposed babies. There was no difference in the maternal or fetal hair mercury levels in the groups of patients who had dental amalgam placed before or during pregnancy. CONCLUSIONS: Maternal and fetal hair mercury levels were significantly higher in women who previously had dental amalgam restorations placed. There was no evidence that placement of dental amalgam restorations in pregnant women who had already similar restorations increased the maternal or fetal hair mercury level.

An analysis of maternal and fetal hair lead levels.

Lead contamination of the environment is an important public health consideration. There is evidence of declining blood lead levels in Britain, however, there is still concern about chronic exposure of the fetus and young children to low levels of lead and the effect that this has on neurodevelopment. Hair lead levels have been found to correlate well with body lead contamination. This study is the first to document the level of hair lead in pregnant women and their babies from an urban British population. There was no evidence of toxic maternal lead levels and the fetus is protected by the placental barrier.

The selenium status of women with a history of recurrent miscarriage.

OBJECTIVE: To assess the relationship between selenium levels in human blood and hair, and the risk of recurrent miscarriages. DESIGN: Case-control study. PARTICIPANTS: Two groups of non-pregnant women: 18 women with one or more successful pregnancies and no history of miscarriage (control group); 26 women with a history of recurrent miscarriage (> or = 3) with no subsequent successful pregnancies (study group). METHODS: Samples of venous blood and scalp hair were collected and the selenium content analysed by inductively coupled plasma mass spectrometry. RESULTS: No significance difference was found between the level of selenium in the blood samples of the women in each group. There was a significant reduction in the mean hair selenium level in the recurrent miscarriage group compared with the control group (0.14 microg/g vs 0.34 microg/g). Further analysis of the recurrent miscarriage group revealed no relationship between levels of serum or hair selenium with parity. There was a significantly greater proportion of women in the control group who ate cereals, vitamin supplements, and liver or kidney. CONCLUSION: There was evidence of selenium deficiency in women with recurrent miscarriages compared with a control group of women with a good reproductive performance. This difference was seen in hair samples but not serum samples and therefore may not represent a simple nutritional deficiency. The importance of selenium deficiency in miscarriage has still not been determined.

Mercury and selenium concentrations in maternal and neonatal scalp hair: relationship to amalgam-based dental treatment received during pregnancy.

Mercury and selenium concentrations were determined in scalp hair samples collected postpartum from 82 term pregnancy mothers and their neonates. Maternal mercury and selenium had median concentrations of 0.39 microg/g (range 0.1-2.13 microg/g) and 0.75 microg/g (range 0.1-3.95 microg/g), respectively, and corresponding median neonatal values were 0.24 microg/g (range 0.1-1.93 microg) and 0.52 microg/g (range (0.1-3.0 microg/g). Amalgam-based restorative dental treatment received during pregnancy by 27 mothers (Group I) was associated with significantly higher mercury concentrations in their neonates (p < 0.0001) compared to those born to 55 mothers (Group II) whose most recent history of such dental treatment was dated to periods ranging between 1 and 12 yr prior to pregnancy. In the Group I mother/neonate pairs, amalgam removal and replacement in 10 cases was associated with significantly higher mercury concentrations compared to 17 cases of new amalgam emplacement. Selenium concentrations showed no significant intergroup differences. However, the selenium/mercury molar ratio values were lowest in the Group I neonates, compared to their mothers and to the Group II mother/neonate pairs. This ratio decreased as mercury concentration increased, and this interrelation was statistically significant in both groups of mother/neonate pairs. The data from this preliminary study suggest that amalgam-based dental treatment during pregnancy is associated with higher prenatal exposure to mercury, particularly in cases of amalgam removal and replacement. The ability of a peripheral biological tissue, such as hair, to elicit such marked differences in neonatal mercury concentrations provides supporting evidence of high fetal susceptibility to this form of mercury exposure. The data are discussed in relation to the differences between maternal and fetal mercury metabolisms and to mercury-selenium metabolic intereactions in response to mercury exposure.

Preliminary studies into the direct interfacing of a microreactor to a gas chromatographic instrument.

The paper reports on a preliminary study into the coupling of a microreactor to a GC-FID, using a standard GC needle as the interface between the microreactor and the injection port of a conventional GC. Using the injection needle as the ground electrode, electroosmotic flow was used to control the injection of reagent/sample into the GC. Photolithographic and wet etching techniques were used to fabricate the microreactor (channels 200 microns id, 100 microns deep) in a borosilicate glass substrate. The results of the effects of voltage and injection times on the response signal are presented. The critical obstacles to overcome were the backpressure posed by the carrier gas disrupting the liquid flow in the channels and reservoirs of the microreactor and the need to thermally insulate the microreactor, to prevent evaporation of solvent and reagents from the device.

The generation of concentration gradients using electroosmotic flow in micro reactors allowing stereoselective chemical synthesis.

The stereoselective control of chemical reactions has been achieved by applying electrical fields in a micro reactor generating controlled concentration gradients of the reagent streams. The chemistry based upon well-established Wittig synthesis was carried out in a micro reactor device fabricated in borosilicate glass using photolithographic and wet etching techniques. The selectivity of the cis (Z) to trans (E) isomeric ratio in the product synthesised was controlled by varying the applied voltages to the reagent reservoirs within the micro reactor. This subsequently altered the relative reagent concentrations within the device resulting in Z/E ratios in the range 0.57-5.21. By comparison, a traditional batch method based on the same reaction length, concentration, solvent and stoichiometry (i.e., 1.0:1.5:1.0 reagent ratios) gave a Z/E in the range 2.8-3.0. However, when the stoichiometric ratios were varied up to ten times as much, the Z/E ratios varied in accordance to the micro reactor i.e., when the aldehyde is in excess, the Z isomer predominates whereas when the aldehyde is in low concentrations, the E isomer is the more favourable form. Thus indicating that localised concentration gradients generated by careful flow control due to the diffusion limited non-turbulent mixing regime within a micro reactor, leads to the observed stereo selectivity for the cis and trans isomers.

Electric field-induced mobilisation of multiphase solution systems based on the nitration of benzene in a micro reactor.

This paper describes the electric field-induced flow characteristics of multiphase solutions in a micro reactor device using the nitration of benzene as a model process. Photolithographic and wet etching techniques were used to fabricate the micro reactor (channels, 200 microns id, 100 microns deep) in a borosilicate glass substrate. The results focus specifically on the flow parameters of reagents/reactants (i.e., voltage, solution concentration and pH ranges and current-voltage relationships) used in this study. The benzene was introduced and mobilised by electroosmotic flow (EOF), as a microemulsion using an appropriate surfactant (sodium dodecyl sulfate), whilst the nitronium ions, produced in situ from mixed H2SO4-HNO3 (the nitrating agent), underwent electrophoretic-induced (electrokinetic) mobility. A co-surfactant, butan-1-ol, was used owing to (a) its relative solubility in the aqueous surfactant solution, (b) its ability to aid the solubilization of benzene, (c) the provision of a water-rich (oil-in-water) rather than oil-rich (water-in-oil) microemulsion system and (d) its lack of significant adverse effects on the EOF. The optimum conditions used for the nitration of benzene within the micro reactor were a run of the microemulsion as main reagent stream, then three 30 s segmented injections of mixed acid, with a 5 s push of the microemulsion into the system after each injection, and then a 60 s stopped-flow reaction time before driving reaction product segments to a collection reservoir.

The preparation of a series of nitrostilbene ester compounds using micro reactor technology.

The synthesis of stilbene esters using Wittig chemistry has been used to illustrate the generic diversity micro reactors offer in terms of chemical control and rapid method development. The micro reactor consisted of a 'T' design based on channel geometries 200 microns wide and 100 microns deep, etched into borosilicate glass and sealed with a borosilicate top plate using a thermal bonding technique. The movement of the reagent and products was achieved using electroosmotic flow (EOF), assisted by the incorporation of micro porous silica frits within the micro-channels to allow accurate solution control. To optimise the operating conditions methyl 4-formylbenzoate, premixed with sodium methoxide, was reacted with 2-nitrobenzyl-triphenylphosphonium bromide in dry degassed MeOH using flow conditions for both reagents of 0.40 microL min-1 for 20 min. A product yield of 70% (2:1 reaction stoichiometry with the aldehyde in excess) was obtained representing a 10% increase compared with the traditional batch synthesis. To demonstrate the capability of micro reactors to perform atom efficient synthesis a series of experiments based on an injection methodology (optimised to 30 s) were performed in the micro reactor at 1:1 stoichiometry resulting in a yield of 59%. Finally, the capability of micro reactors to perform a series of analogue reactions was investigated. The yields for a further three aldehydes indicated that the technology will be suitable for the development of automated device to support the generation of combinatorial libraries and rapid high throughput synthetic methods.

Antioxidant activity related to copper binding of native prion protein.

We have developed a method to affinity-purify mouse prion protein (PrP(c)) from mouse brain and cultured cells. PrP(c) from mouse brain bound three copper atoms; PrP(c) from cultured cells bound between one and four copper atoms depending on the availability of copper in the culture medium. Purified PrP(c) exhibited antioxidant activity, as determined by spectrophotometric assay. Incubation of PrP(c) with the neurotoxic peptide, PrP106-126, inactivated the superoxide dismutase-like activity. Culture experiments showed that PrP(c) protects cells against oxidative stress relative to the amount of copper it binds. These results suggest that PrP(c) is a copper-binding protein which can incorporate varying amounts of copper and exhibit protective antioxidant activity.

The aldol reaction of silyl enol ethers within a micro reactor.

We have demonstrated the use of silyl enol ethers in the aldol reaction within a micro reactor. Quantitative conversion of the silyl enol ether to a beta-hydroxyketone was observed in a 20 min period compared to traditional batch systems, where quantitative yields were only obtained when extended reaction times of 24 h were employed.

Electrical currents and liquid flow rates in micro-reactors.

For micro-reactor devices in which liquids are pumped by electro-osmotic flow (EOF), in situ monitoring of the electrical currents in the channel networks provides a valuable diagnostic tool. We demonstrate here that the voltage-current characteristics of a micro-reactor channel network can be accurately modelled using measurements of the full 3-D geometry of the channel network, the liquid conductivity and the channel wall-liquid surface conductivity. It is shown that surface conductivity provides a significant contribution to the overall measured electrical currents in channel networks for which the ratio of surface area to volume is high. Following correction for surface conductivity, the electrical currents are proportional to the liquid volumetric flow rates measured in the different branches of the channel network. The constant of proportionality is related to the zeta potential of the channel wall-liquid surface. Measurements of the variation of electrical currents and volumetric flow rates as a function of the applied voltages allows the determination of the surface conductivity and zeta potential within the micro-reactor which enables the prediction of the voltages required to produce the desired flow rates in any channel section. In situ logging of the electrical currents, incorporated within the control system, allows continuous monitoring of the liquid flow rates during micro-reactor operation.

Kumada-Corriu reactions in a pressure-driven microflow reactor.

Reaction rates for the Kumada reaction (of Grignard reagents with aryl halides) catalysed by an immobilised nickel(II) catalyst have been shown to be enhanced when the reaction is carried out in a pressure driven microreactor (internal diameter 100-200 microm) rather than with conventional batch reaction techniques.

The investigation of an equilibrium dependent reaction for the formation of enamines in a microchemical system.

The paper describes the equilibrium dependant reaction for the formation of enamines in a microchemical system utilising electroosmotic flow (EOF) for fluid mobilisation. The authors have shown that the reaction can be carried out without the presence of a Lewis acid catalyst, in addition the enamine intermediate was synthesised at room temperature using mild solvent conditions. A 42% conversion of cyclohexanone into the enamine has been achieved to date.

Quantitative 3-dimensional profiling of channel networks within transparent lab-on-a-chip microreactors using a digital imaging method.

We have developed a method for the quantitative 3-dimensional profiling of micron sized channel networks within optically transparent "lab-on-a-chip" microreactor devices. The method involves capturing digitised microscope images of the channel network filled with an optically absorbing dye. The microscope is operated in transmission mode using light filtered through a narrow bandpass filter with a maximum transmission wavelength matching the wavelength of the absorbance maximum of the dye solution. Digitised images of a chip filled with solvent and dye solution are analysed pixel by pixel to yield a spatially resolved array of absorbance values. This array is then converted to optical path length values using the Beer-Lambert law, thereby providing the 3D profile of the channel network. The method is capable of measuring channel depths from 10 to 500 microm (and probably even smaller depths) with an accuracy of a few percent. Lateral spatial resolution of less than 1 microm is achievable. It has been established that distortion of the measured profiles resulting from a mismatch in refractive index between the dye solution and the glass of the microreactors is insignificant. The method has been successfully used here to investigate the effects of thermal bonding and etch time on channel profiles. The technique provides a convenient, accurate and non-destructive method required to determine channel profiles; information which is essential to enable optimisation of the operating characteristics of microreactor devices for particular applications.

Functional and structural differences between the prion protein from two alleles prnp(a) and prnp(b) of mouse.

The prion protein is a glycoprotein expressed by neurones and other cells. In its holo-form it binds copper and exhibits superoxide dismutase activity. Studies in mice have led to the description of two distinct alleles. Differences in these alleles are linked to long and short incubation times following infection with scrapie. We studied recombinant mouse protein corresponding to the products of either allele and two intermediates carrying single amino-acid residue substitutions. The different forms of the prion protein exhibited differences in superoxide dismutase (SOD) activity and conformation. Intermediates with single substitutions were less stable than either allelic product. The findings provide insight into the differences between the two alleles and might have consequences for understanding differences in susceptibility to prion disease.

Correlation between plasma total homocysteine and copper in patients with peripheral vascular disease.

BACKGROUND: Increased concentrations of both plasma total homocysteine and copper are separately associated with cardiovascular disease. Correlations between plasma total homocysteine, trace elements, and vitamins in patients with peripheral vascular disease have not been investigated. METHODS: The concentrations of trace elements in plasma were determined by the multielement analytical technique of total-reflection x-ray fluorescence spectrometry. Plasma total homocysteine was determined by HPLC. RESULTS: In the univariate and multivariate regression analyses, copper was positively correlated with plasma total homocysteine in all subjects (coefficient +/- SE, 0.347 +/- 0.113; P = 0.0026 and coefficient +/- SE, 0.422 +/- 0.108; P = 0.0002, respectively), and in patients with peripheral vascular disease (coefficient +/- SE, 0.370 +/- 0.150; P = 0.016; and coefficient +/- SE, 0.490 +/- 0.151; P = 0.0025, respectively). Correlation between copper and plasma total homocysteine was not detected in healthy control subjects. The concentration of calcium in plasma (67.5 vs 80. 8 microg/g) was significantly lower in the patients than in the control subjects (P = 0.02). When the patients were divided into groups, the patients with suprainguinal lesions had significantly higher copper concentrations (P = 0.04) and significantly lower selenium and calcium concentrations (P = 0.01 and 0.008, respectively) than the healthy subjects. Patients had higher concentrations of autoantibodies against oxidized LDL and concentrations of thiobarbituric acid-reactive substance than the healthy subjects (P <0.0001 and P = 0.001, respectively). The concentrations of plasma total homocysteine and alpha-tocopherol were significantly higher, and the concentrations of vitamin B(6) and beta-carotene were lower in the patients than the healthy subjects. CONCLUSION: Our findings suggest that the atherogenicity of homocysteine may be related to copper-dependent interactions.