Impaired activity of endothelium-derived nitric oxide in Type I (insulin-dependent) diabetes mellitus will cause an increased vascular tone. Considering the lower production of nitric oxide in veins ...than in arteries, an impaired activity would have less vasoconstrictive effect in veins. The reported minimally changed total plasma volume in diabetes might, therefore, indicate a redistribution of blood volumes from the arterial to the venous side of the circulation. This could be more pronounced in patients with microalbuminuria.
In 16 normoalbuminuric and 16 microalbuminuric Type I diabetic patients and 16 individually matched healthy control subjects, venous and arterial blood volumes, venous myogenic response and arterial distensibilities were assessed in the upper arm using an electrical bio-impedance method.
In diabetic patients, the venous blood volume and venous myogenic response were increased (p < 0.02 and p < 0.05, respectively), whereas the arterial blood volume did not change. Moreover, in diabetic patients the distensibility of the large arteries was decreased (p < 0.05) but increased in the total arterial bed (p < 0.05). Therefore, the distensibility of the small arteries must have been increased. No differences were found between normoalbuminuric and microalbuminuric diabetic patients.
The increase in venous blood volume and myogenic response and the decrease in distensibility of the large arteries in the upper arm are in agreement with the expected shift towards venous blood volume distribution in Type I diabetes with and without microalbuminuria. Furthermore, they support the haemodynamic hypothesis of the pathogenesis of diabetic microangiopathy.
The purpose of this study was to evaluate in a prospective, double-blind, placebo-controlled study the effect of long-term (2-year) lisinopril treatment on cardiovascular end-organ damage in patients ...with previously untreated isolated systolic hypertension (ISH). All patients with ISH were derived from a population screening program. End-organ damage measurements, done initially and after 6 and 24 months of treatment, included measurements of aortic distensibility and echocardiographic left ventricular mass index (LVMI) and diastolic function. Blood pressure was measured by office and ambulatory measurements. Of the 97 subjects with ISH selected from the screening, 62 (30 lisinopril) completed the study according to protocol. Office blood pressure decreased in both groups, but ambulatory results significantly decreased with lisinopril-treatment only. Aortic distensibility increased significantly with lisinopril, as opposed to a decrease in placebo-treated subjects. The main effect of increased distensibility occurred between 6 and 24 months, whereas ambulatory blood pressure changed mainly in the first 6 months of treatment. LVMI decreased in both treatment groups, with a significantly higher reduction in lisinopril-treated subjects. Left ventricular diastolic function showed no significant changes in either group. The vascular pathophysiologic alterations of ISH-a decreased aortic distensibility-can be improved with long-term lisinopril treatment, whereas values deteriorate further in placebo-treated subjects. These results, in one of the first studies including subjects with previously untreated ISH only, indicate that lisinopril treatment might favorably influence the cardiovascular risk of ISH.
Due to the results of antihypertensive intervention studies, isolated systolic hypertension (ISH) has gained new interest lately. Yet, apart from increased aortic stiffness, the specific ...pathophysiological features of ISH have remained largely undetermined. Therefore, we investigated the elastic properties of the vascular bed of an upper arm segment in uncomplicated ISH patients and matched normotensive controls using an electrical bioimpedance technique. Compared with the controls, the compliance of the arterial bed as a whole at normotensive blood pressure level was on the average 108.0% higher (p < 0.005) in the hypertensive patients. The blood volume of the arterial bed as a whole at operating blood pressure level and that of the larger arteries were significantly higher (40.5%, p < 0.05, and 40.5%, p < 0.01, respectively). The same held true for the venous blood volume (64.4%, p < 0.05), and for the width of the arterial compliance-pressure relation (34.6%, p < 0.01). We concluded that ISH is a separate pathophysiological entity in which all parts of a peripheral vascular bed are changed and the decreased buffering function of the aorta and large arteries is partly compensated for by an increase in small artery compliance.
Several studies have demonstrated the beneficial effects of 3 hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors on vascular properties, but little is known about treatment ...intensification. We compared patients in whom statins were started (INITIAL,
n=30) for hypercholesterolaemia (>6.5 mmol l
−1) with a matched patient group of long-time statin users, with similar baseline characteristics for lipids, intima-media thickness (IMT), and pulse wave velocity, in whom treatment with statins was intensified (LONG-TERM,
n=54). At baseline and after 1 year, lipid profile, IMT of the carotid and femoral arteries, aortic distensibility using pulse-wave velocity and various properties of the peripheral vascular bed using a recently developed bio-impedance method were measured. After 1 year the relative changes in lipid profile were significantly better in the INITIAL compared with the LONG-TERM-group. The relative changes in IMT of the mean internal carotid and common femoral arteries significantly differed between the INITIAL and LONG-TERM-group (−8 and +11%, −11 and +22%, respectively). After 1 year, in both groups, most other vascular wall characteristics were unaltered compared with baseline. In conclusion, the beneficial structural alterations of the vascular wall were greater after starting than after intensifying already existing lipid-lowering treatment. This suggests that other effects of HMG-CoA reductase inhibitors than lipid-lowering alone must be involved in vascular changes.
In 13 healthy volunteers a computerized experimental set-up was used to measure the electrical impedance of the upper arm at changing cuff pressure, together with the finger arterial blood pressure ...in the contralateral arm. On the basis of a model for the admittance response, the arterial blood volume per centimeter length (1.4 +/- 0.3 ml/cm), the venous blood volume as a percentage of the total blood compartment (49.2 +/- 12.6%), and the total arterial compliance as a function of mean arterial transmural pressure were estimated. The effective physiological arterial compliance amounted to 2.0 +/- 1.3 microliters.mmHg-1.cm-1 and the maximum compliance to 33.4 +/- 12.0 microliters.mmHg-1.cm-1. Additionally, the extravascular fluid volume expelled by the occluding cuff (0.3 +/- 0.3 ml/cm) was estimated. These quantities are closely related to patient-dependent sources of an unreliable blood pressure measurement and vary with changes in cardiovascular function, such as those found in hypertension. Traditionally, a combination of several methods is needed to estimate them. Such methods, however, usually neglect the contribution of extravascular factors.
Calcium antagonists have antihypertensive and antianginal properties. In heart failure, however, their use can be hazardous, as systolic function can deteriorate. This may not be true of the new ...calcium antagonist mibefradil, which has a new chemical structure. Calcium antagonists may also be beneficial for diastolic left ventricular function in coronary artery disease. To investigate the possible effects of mibefradil on diastolic left ventricular function, we performed the present study as a multicenter, double-blind,placebo-controlled, multiple-dose safety trial. Fifteen patients with New York Heart Association (NYHA) class II or III for dyspnea and depressed ejection fraction (<40%) due to a previous myocardial infarction were investigated. The measured nuclear angiographic parameters included ejection fraction (EF), peak ejection rate (PER), and peak filling rate (PFR). Systolic and diastolic blood pressure (SBP, DBP) and heart rate (HR) were also obtained. Group I (5 patients) received placebo medication; group IIA (6 patients) received mibefradil 6.25, 12.5, or 25 mg/day; and group IIB (4 patients) received mibefradil 50 or 100 mg/day. Measurements were made before and after the first dose and after 1 week of treatment before and after the final dose. Mibefradil clearly decreased HR (repeated-measures analysis of variance p < 0.05). No statistically significant effects of mibefradil were noted on SBP or DBP or on systolic and diastolic left ventricular function. In our study conditions, mibefradil caused no worsening of systolic function and preserved diastolic function in short-term treatment of patients with decreased EF and heart failure.
The significance of age-related changes in arterial stiffness has remained largely uncertain in healthy subjects. This appears to be partly due to difficulties in the interpretation of methods for ...measuring arterial stiffness in vivo. Therefore, a recently developed electrical bioimpedance method was used for studying elastic properties of a vascular bed as a function of age. In 66 healthy subjects, aged 22-82 years, we investigated the vascular bed of an upper arm segment. This vascular bed showed an age-related decrease in the venous blood volume (r = -0.31, p < 0.01) and in the distensibility, the inverse of stiffness, of the larger arteries (r = -0.38, p < 0.001). The distensibility of the arterial bed as a whole at normotensive blood pressure, however, appeared to increase with age (r = 0.32, p < 0.005). The arterial and venous blood volumes, arterial compliance and extravascular fluid volume were significantly higher in the males than in the females. Practically all investigated vascular properties appeared to be related with height, body mass or body mass index. We concluded that comparative studies concerning vascular properties should preferably be performed in subjects matched as to age, gender, height and body mass. In healthy subjects the smaller arteries adjust to the age-related decrease in large artery distensibility by means of an age-related increase in distensibility. These age-related changes in arterial distensibility are caused by changes in the females, and seem to be associated with age-related changes in body mass index rather than with aging per se.
To define exactly the onset of late diastolic filling with respect to atrial contraction, the atrial contribution (AC) to left ventricular filling was quantified in 34 patients with a variety of ...diseases using radionuclide angiography. From the time-activity curve and its first derivative, a flow-volume loop was constructed. Using the flow-volume loop, the period between minimal flow and the moment of maximal end-diastolic counts was defined as the AC-interval and correlated with the PQ-interval on the electrocardiogram. The relative filling volumes within these time periods were closely related in all patients (r = 0.99, P < 0.0001). The correlation between the PQ-interval and AC-interval was also statistically significant (r = 0.82, P < 0.0001). In a subset of patients, the PQ-interval and AC-interval were not exactly the same. In these patients, the AC-interval was always longer than the PQ-interval, indicating the existence of passive diastasis flow before the onset of atrial contraction. This was more apparent in patients with low heart rates than in those with high heart rates. Despite the close correlation between the PQ-interval on the electrocardiogram and the AC-interval of the flow-volume loop, they may represent different entities. We conclude that the PQ-interval is better than the AC-interval for determining the moment of onset of atrial activity during radionuclide angiography.
Degenerate Bose-Fermi gases in microgravity Herr, W.; van Zoest, T.; Gaaloul, N. ...
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference,
2009-June
Conference Proceeding
Summary form only given. Bose Einstein condensates (BEC) opened the way for realization of atomic ensembles with Heisenberg limited uncertainty. In microgravity extremely dilute samples of BEC can be ...obtained and observed after a free evolution on timescales of seconds. Applications range from atom optics to matter wave interferometry. This has led us to realize a BEC of 10000 87Rb atoms in microgravity. The experimental results (to be published) establish the fact, that in a microgravity environment ultra-large condensates (Icircosl.5 mm) after a free evolution of 1 second can be observed. In particular, microgravity provides mass independent confining potential which is very important for the research on a mixture of quantum gases. We aim to realize a new setup for multispecies experiments, which can be used in catapult mode doubling the time for microgravity to 9 seconds. The experiment is planned to use 87 Rb and 40 K as degenerate Bose and Fermi gases respectively and can be used to carry out experiments on interferometry, Bose-Fermi mixtures and tests of the weak equivalence principle in quantum domain. Up to date progress and future prospects of this ambitious and technically challenging project will be presented.
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