3,134 publications from this institution
Increased pulse pressure (PP) is an independent marker of cardiovascular risk, mainly for myocardial infarction, congestive heart failure, and cardiovascular deaths. Moreover, reduced circadian blood pressure (BP) variation is a potential risk factor for the development of diabetic complications, as patients with type 2 diabetes mellitus (DM) show a progressive loss of nocturnal BP decline. Accordingly, we aimed to compare the circadian pattern of ambulatory BP variability between hypertensive patients with and without DM. We analyzed 2,756 BP profiles sampled from 1,418 patients (234 complicated with DM) with grade 1–2 hypertension (641 mean), 52.6±13.8 years of age. BP was measured by ambulatory monitoring (ABPM) at 20-min intervals from 07:00 to 23:00 hours and at 30-min intervals at night for 48 consecutive hours. Physical activity was simultaneously monitored every minute by wrist actigraphy, and the information used to determine diurnal and nocturnal means of BP for each patient according to individual resting time. Circadian parameters established by population multiple-component analysis were compared between patients with and without DM by nonparametric testing. Patients with DM, either untreated or evaluated under antihypertensive medication, are characterized by a significant increase in systolic BP, mainly during nocturnal resting hours, as compared to hypertensive patients without DM. The nocturnal mean of diastolic BP was, however, similar between groups, while the diurnal mean was significantly reduced in DM. Accordingly, there was a highly significant increase in PP across the 24 hours in both untreated (5.6 mm Hg in 24-hour mean, P<0.001) and treated patients with DM (6.4 mm Hg, P<0.001), as compared to patients without DM. Results from this study on hypertensive patients evaluated by 48-hour continuous ABPM and with nocturnal BP mean calculated individually according to actual resting time determined by actigraphy, indicates a highly significant increase of PP in patients with DM. Results also corroborate the significant reduction in day/night variation of systolic and diastolic BP in DM, reflecting a higher tendency towards a nondipper profile among patients with DM. The elevation in PP and the lack of a proper nocturnal decline in BP should be taking into account for the treatment of hypertensive patients with DM. Am J Hypertens (2004) 17, 214A–214A; doi: 10.1016/j.amjhyper.2004.03.571
Studies based on office blood pressure measurements concluded that parity has significant effects on blood pressure during pregnancy. The authors evaluated possible differences in the circadian pattern of blood pressure as a function of parity in normotensive women systematically studied by ambulatory blood pressure monitoring. They analyzed 1400 blood pressure series sampled for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery in 234 women. The circadian pattern of blood pressure variation for each group (nulliparous vs. multiparous) and trimester of gestation was established by population multiple‐component analysis. A highly statistically significant circadian pattern, described by a model that includes components with periods of 24 and 12 hours, was demonstrated for systolic and diastolic blood pressure for both groups of pregnant women in all trimesters (p<0.001). There was no significant difference in 24‐hour mean among groups divided by parity at any stage of pregnancy (p>0.315). Data obtained from systematic ambulatory monitoring in normotensive pregnant women indicate the lack of differences in blood pressure according to parity. Reference thresholds for blood pressure in pregnancy could thus be developed as a function of rest‐activity cycle and gestational age only, independent of parity.
We describe a hands-on experience designed for students in an upper-division undergraduate analytical laboratory for the UV–vis spectrophotometric determination of phosphorus in natural waters using a current microextraction technique. The method is based on the formation of a colored ion pair and its subsequent extraction in a microdrop of organic solvent. The proposed laboratory experiment allows the students to gain experience in developing a green sample preparation approach. Furthermore, the extraction of a colored product allows them to better understand different issues that govern solvent microextraction. Optimization of some experimental parameters and the chemical analysis of natural waters are also addressed in this laboratory experiment.
PartitionTest test suite
In the present work, we study the effects that aggregation of humic acids in seawater, and its adsorption to surfaces, can have on the determination of Cu and Pb accumulation by phytoplankton within the context of metal bioavailability studies, using the diatom Thalassiosira weissflogii. Two methods commonly used for collection of algae to analyse metal content, filtration and centrifugation, were compared, and a procedure to differentiate the metal internalized by the alga from that adsorbed to cell walls-washing with 0.01 M ethylenediaminetetraacetic acid (EDTA)- was optimized for its use in seawater and in the presence of humic acids. The present results highlight the possibility of obtaining biased results if filtration is used to isolate the algae, and show that centrifugation is a more suitable procedure minimizing contribution of particulate and colloidal forms of metals to the measured cellular and intracellular metal contents. Thus a combination of centrifugation to isolate the algae from the medium with a 10 minutes washing with a washing agent composed of EDTA 0.01 M at pH 8 and NaCl and KCl to 0.5 M ionic strength is recommended to extract metals adsorbed to the surfaces of marine phytoplankton for a seawater containing humic substances. The importance of discriminating between internalized metal and total cellular metal in bioavailability studies is noted, given the different effects of humic substances on metal accumulation in the different cellular pools.