Depression and cardiovascular risk-association among Beck Depression Inventory, PCSK9 levels and insulin resistance.

BACKGROUND: Depression and cardiovascular disease (CVD) are among the most common causes of disability in high-income countries, depression being associated with a 30% increased risk of future CV events. Depression is twice as common in people with diabetes and is associated with a 60% rise in the incidence of type 2 diabetes, an independent CVD risk factor. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a key regulator of low-density lipoprotein cholesterol, has been related to a large number of CV risk factors, including insulin resistance. Aim of this study was to investigate whether the presence of depression could affect PCSK9 levels in a population of obese subjects susceptible to depressive symptoms and how these changes may mediate a pre-diabetic risk. RESULTS: In 389 obese individuals, the Beck Depression Inventory (BDI-II) was significantly associated with PCSK9 levels. For every one-unit increment in BDI-II score, PCSK9 rose by 1.85 ng/mL. Depression was associated also with the HOMA-IR (homeostatic model assessment index of insulin resistance), 11% of this effect operating indirectly via PCSK9. CONCLUSIONS: This study indicates a possible mechanism linking depression and insulin resistance, a well-known CV risk factor, providing evidence for a significant role of PCSK9.

Direct potentiometric information on total ionic concentrations.

Polymeric membrane ion-selective electrodes exhibit an apparently super-Nernstian response at low sample activities if inner solutions are used that induce strong zero-current fluxes of primary ions toward the inner compartment. This is due to the limited ion fluxes in the aqueous boundary layer near the membrane. In the presence of labile complexes, the effective flux rate is increased and the emf depends on the total concentration of the ions. The concept is illustrated experimentally with calcium-selective electrodes based on the ionophore N,N-dicyclohexyl-N',N'-dioctadecyl-3-oxapentanediamide (ETH 5234) that either respond to total or free ion concentrations. Samples can be distinguished that contain varying levels of total calcium but are all buffered with EDTA to the same free calcium concentration of 5 x 10(-8) M.

Improved detection limits and sensitivities of potentiometric titrations.

Zero-current ion fluxes through polymer membranes of ion-selective electrodes (ISEs) may lead to biased endpoints of potentiometric titrations. The bias is eliminated, and the sensitivity of the end-point detection is improved through reducing transmembrane ion fluxes by an appropriate choice of the inner solution. Surprisingly, ISE membranes that have a significant primary ion flux toward the inner solution show much larger sensitivities than expected by titration theory; however, depending on the experimental conditions, their application may bias the endpoint. With the optimal systems, endpoint detection is now possible with total sample concentrations below 10(-6) M, as demonstrated by the titration of EDTA with a Pb2+ solution.

Potentiometric polymeric membrane electrodes for measurement of environmental samples at trace levels: new requirements for selectivities and measuring protocols, and comparison with ICPMS.

It is here established that potentiometric polymeric membrane electrodes based on electrically neutral ionophores are useful analytical tools for heavy metal ion determinations in drinking water at nanomolar total concentrations. This means that they can compete with the most sophisticated techniques of instrumental analysis. With optimized ion-selective membranes based on the lead-selective ionophore 4-tert-butylcalix[4]arenetetrakis(thioacetic acid dimethylamide) as model example, a number of native and spiked drinking water samples are potentiometrically assessed for lead, and the results compared with ICPMS measurements. The goal of this work is to demonstrate that detection limits in real world samples are routinely achieved that are, with 1.5 ppb, at least 10-fold lower than the lead action limit imposed by the U.S. Environmental Protection Agency (15 ppb). In contrast to earlier reports, different conditioning and measuring protocols are followed, and membranes and inner filling solution of optimized composition are used. The sensors are shown to be useful for the speciation analysis of lead in water as well. Typical water samples are acidified to pH 4 to assess total lead rather than free, uncomplexed lead. For lead concentrations above 2 ppb, the values compare very well with ICPMS. Main interferences are found to be H+ and Cu2+, although Cu2+ only shows significant interference at levels around or above its own action limit (1.3 ppm), in which case the water sample would anyway show quality problems. An explicit, simplified flux model targeted to the practical use of these sensors explains the extent of expected interference. Sensors are shown to require a higher selectivity than predicted by models not considering ion fluxes, since in dilute samples, the counterdiffusion flux of lead from the membrane into the sample becomes potential determining. The model and experiments shown here are a foundation for future trace level applications of potentiometric polymeric membrane electrodes.

Continuous monitoring of plant water potential.

Plant water potential was monitored continuously with a Wescor HR-33T dewpoint hygrometer in conjunction with a L51 chamber. This commercial instrument was modified by replacing the AC-DC mains power converter with one stabilized by zener diode controlled transistors. The thermocouple sensor and electrical lead needed to be thermally insulated to prevent spurious signals. For rapid response and faithful tracking a low resistance for water vapor movement between leaf and sensor had to be provided. This could be effected by removing the epidermis either by peeling or abrasion with fine carborundum cloth. A variety of rapid plant water potential responses to external stimuli could be followed in a range of crop plants (sunflower (Helianthus annuus L., var. Hysun 30); safflower (Carthamus tinctorious L., var. Gila); soybean (Glycine max L., var. Clark); wheat (Triticum aestivum L., var. Egret). These included light dark changes, leaf excision, applied pressure to or anaerobiosis of the root system. Water uptake by the plant (safflower, soybean) mirrored that for water potential changes including times when plant water status (soybean) was undergoing cyclical changes.