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At least 289 records · Page 16Linked to original sources
PubMed2004

Reproducibility of arterial stiffness indices (pulse wave velocity and augmentation index) simultaneously assessed by automated pulse wave analysis and their associated risk factors in essential hypertensive patients.

Arterial stiffness is a strong determinant of cardiovascular risk. Pulse wave velocity (PWV) and the augmentation index (AIx) are widely used as arterial stiffness indices. We studied the reproducibility of these indices and their association with cardiovascular risk factors in hypertensives. We measured brachial blood pressure (BP), brachial-ankle PWV (baPWV) and carotid AIx (cAIx) twice (at the baseline and 4 weeks after the baseline) using an automatic device in 103 hypertensives. The mean intraobserver-intersession difference was 29.0 cm/s with an SD of 201.6 cm/s for baPWV, and 0.5% with an SD of 5.9% for cAIx, and the Bland-Altman plots demonstrated the good reproducibility of baPWV and cAIx. Both baPWV and cAIx (the average of the 1st and the 2nd measurements) were significantly correlated with age, systolic BP (SBP), and pulse pressure (all, p <0.005); however, these factors were not correlated with each other (r =0.06, NS). cAIx was correlated with height, heart rate (HR), total cholesterol, and low density lipoprotein cholesterol (LDL-C) (all, p <0.05). In multiple regression analysis, age, SBP, and HR emerged as significant independent predictors of baPWV (adjusted R(2)=0.43, p <0.0001), while height, SBP, HR, and LDL-C emerged as significant independent predictors of cAIx (adjusted R(2)=0.58, p <0.0001). Both PWV and AIx measured using an automatic device were fairly reproducible, and their associated risk factors appeared to be different. Automated simultaneous measurement of these arterial stiffness indices may be useful for risk stratification of hypertensives.

Aged↗
PubMed2004

Compact optical system for pulse-to-pulse laser beam quality measurement and applications in laser machining.

Fluctuations in beam quality (M2) have been observed on a pulse-to-pulse basis from an industrial Nd:YAG laser. This was achieved with a compact multiplane imaging method incorporating quadratically distorted diffraction gratings, which enabled simultaneous imaging of nine planes on a single CCD array. With this system, we measured across a range of beam qualities with an associated error (in M2 variation) of the order of 0.7%. Application of the system to fiber-optic beam delivery and laser drilling is demonstrated.

Journal Article↗
PubMed2006

Numerical simulation of the amplification of a short laser pulse by a ytterbium doped amplifier longitudinally pumped by short pump pulses.

A simple and original derivation making it possible to analytically compute the performances achievable with an end pumped ytterbium (Yb) amplifier pumped by a pump pulse and seeded by a laser pulse both shorter than the upper-level lifetime is presented. This may be useful when amplifiers or lasers are pumped by a Ti:sapphire laser. The case of a Yb:YAG amplifier is numerically investigated and it is shown that, in these conditions, the resulting efficiency can reach quantum efficiency.

Journal Article↗
PubMedDate not supplied

Correlation between oxygen consumption and photobleaching during in vitro photodynamic treatment with ATX-S10.Na(II) using pulsed light excitation: dependence of pulse repetition rate and irradiation time.

We revealed that in ATX-S10.Na(II)(13,17-bis (1-carboxypropionyl) carbamoylethyl-8-etheny-2-hydroxy-3-hydroxyiminoethylidene-2,7,12,18-tetraethyl porphyrin sodium)-mediated photodynamic therapy using 667 nm nanosecond-pulsed light excitation at a peak intensity of 2.0 MW/cm(2), phototoxicity increased with decreasing pulse repetition rate in the range of 5-30 Hz for A549 cell cultures. To examine the relation between the reaction mechanism and measured phototoxicity, we carefully measured the kinetics of photochemical oxygen consumption and photobleaching during irradiation of ATX-S10.Na(II)-sensitized A549 monolayer cultures. Measurements of oxygen consumption with a microelectrode, which was performed just above the cells, showed that there was no significant difference between the magnitudes of decrease in oxygen at the three repetition rates at the same cumulative fluence. Loss of ATX-S10.Na(II) fluorescence intensity also exhibited little repetition rate dependence when compared at the same cumulative fluence. We investigated the correlation between oxygen consumption and photobleaching during irradiation and obtained "fluorescence-oxygen diagrams." The diagrams showed dynamic changes between oxygen-dependent and oxygen-independent photobleaching at the higher repetition rates of 10 and 30 Hz, whereas such change was not clearly seen over the whole irradiation time at 5 Hz. These results suggest that the reduced phototoxicity at high repetition rates might be due to an oxygen-independent reaction. We presumed that the change in the reaction mechanism was associated with the local concentrations of the photosensitizer and oxygen in cells during irradiation.

Cell Line, Tumor↗
PubMed2004

Averaging keyhole pulse sequence with presaturation pulses and EXORCYCLE phase cycling for dynamic contrast-enhanced MRI.

The purpose of this study was to design a keyhole pulse sequence for quantitative 2D dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) based on a spoiled gradient echo T1-weighted acquisition. Saturation recovery was applied to achieve a linear correlation between signal intensity and contrast agent concentration in an arterial input function (AIF) while simultaneously removing time-of-flight effect. To remove ghosting artifacts arising from incomplete presaturation, EXORCYCLE phase cycling with averaging was applied to the pulse sequence. RF spoiling by radiofrequency switching with the synthesizer can be combined with EXORCYCLE phase cycling. Images affected by the large difference in signal intensity before and after contrast agent administration with the keyhole technique were improved by interleaving of peripheral lines of k-space with groups of central lines. Both peripheral and central lines were renewed during the dynamic scan. AIFs were obtained from the rat abdominal aorta with this keyhole sequence.

Animals↗
PubMedDate not supplied

Optimal pulse sequence for ferumoxides-enhanced MR imaging used in the detection of hepatocellular carcinoma: a comparative study using seven pulse sequences.

OBJECTIVE: To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs). MATERIALS AND METHODS: Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 micromol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333-8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TRinfinity/TE39 and 98), T2*-weighted gradient- recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis. RESULTS: Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others. CONCLUSION: T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxidesenhanced MR imaging in the detection of HCCs.

Adult↗
PubMed2006

Superthreshold behavior of ultrasound-induced lung hemorrhage in adult rats: role of pulse repetition frequency and pulse duration.

OBJECTIVE: The purpose of this study was to enhance the findings of an earlier ultrasound-induced lung hemorrhage study (Ultrasound Med Biol 2003; 29:1625-1634) that estimated pressure thresholds as a function of pulse duration (PD: 1.3, 4.4, 8.2, and 11.6 micros; 2.8 MHz; 10-s exposure duration [ED]; 1-kHz pulse repetition frequency [PRF]). In this study, the roles of PRF and PD were evaluated at 5.9 MPa, the peak rarefactional pressure threshold near that of the ED50 estimate previously determined. METHODS: A 4 x 4 factorial design study (PRF: 50, 170, 500, and 1700 Hz; PD: 1.3, 4.4, 8.2, and 11.6 mus) was conducted (2.8 MHz; 10-s ED). Sprague Dawley rats (n = 175) were divided into 16 exposure groups (10 rats per group) and 1 sham group (15 rats); no lesions were produced in the sham group. Logistic regression analysis evaluated significance of effects for lesion occurrence, and Gaussian tobit analysis evaluated significance for lesion depth and surface area. RESULTS: For lesion occurrence and sizes, the main effect of PRF was not significant. The interaction term, PRF x PD, was highly significant, indicating a strong positive dependence of lesion occurrence on the duty factor. The main effect of PD was almost significant (P = .052) and thus was included in the analysis model for a better fit. CONCLUSIONS: Compared with the findings from a PRF x ED factorial study (J Ultrasound Med 2005; 24:339-348), a function that considers PRF, PD, and ED might yield a sensitive indicator for consideration of a modified mechanical index, at least for the lung.

Age Factors↗
PubMed1992

Non-invasive assessments of compliance of the aortic wind-kessel in man derived from pulse pressure/storage volume ratio and from pulse wave velocity.

Two noninvasive methods for assessment of the compliance (1/E') of the aortic windkessel in man are presented and were tested for their ability to detect increases in stiffness of the aorta induced by atropine (0.012 and 0.024 mg/kg sequentially) in the presence and absence of a beta-blockade with propranolol 240 mg (n = 9). Method A, based on the calculation of the relation between pulse pressure and systolic storage volume of the aorta, requires measurement of blood pressure, systolic and diastolic time intervals and stroke volume. Method B, based on measurement of pulse wave velocity along the aorta also requires several anthropometric data (body surface area, age). Both methods were able to detect a dose-dependent increase in E' following atropine injections; method A has greater relative changes than method B. The average maximal increases were 90 and 40 percent of the baseline before atropine. The daily baselines of E' averaged 0.6 Torr x cm-3 for method A and 0.9 Torr x cm-3 for method B. Propranolol itself did not influence E' but dampened the atropine effects. The results from method A and B were correlated with r = 0.70 and 0.60 resp. (p < 0.01). The results suggest the use of these relatively simple techniques for evaluation of aortic compliance under influence of varying pathophysiological conditions or/and pharmacological interventions.

Aorta↗
PubMedDate not supplied

[Ultrasound Doppler sonography in obstetrics. A comparison between simple Doppler methods (continuous or pulsed Doppler) and the duplex system (combination of B-image and pulse Doppler)].

120 pregnant women between the 26th and 42nd week of gestation have been examined using simple Doppler-units with pulsed- or continuous-wave technique and duplex Doppler-units (combined B-mode and pulsed-wave Doppler). The umbilical and uterine arteries were measured with both units in a semi-recumbent position at the same time by the same examiner. Only ideal flow profiles were taken to calculate the S/D-ratio. Our results were correlated to the fetal outcome, to all cases of pre-eclampsia and to all cases of intra-uterine growth retardation. Except in one of these cases we got the majority of pathological results using simple Doppler-units. Only in pre-eclampsia the duplex Doppler-units had the majority of pathological results. Even in normal fetal outcome the majority of simple Doppler-unit results are pathological. This finding is due to the impossibility to localize the vessel exactly using simple Doppler-units. Sensitivity is higher in simple Doppler-techniques (74.3% to 52.9%), specificity is higher in duplex Doppler-technique (77.9% to 52.6%).

Female↗
PubMed1994

Pulse-first heterofusion of cells by electric field pulses and associated loading of macromolecules into mammalian cells.

Exposing cells to brief, high-intensity electrical field pulses can lead to the permeabilization of their plasma membranes. This electro-induced permeated state of the cell membrane is reversible and leads to cell fusion; i.e., the electropermeabilized state if fusogenic. The size of cells intended for fusing, however, limits the obtention of viable hybrids when there is a wide range of cell sizes. We report here that electrofusion of cells of different origins and sizes (hamster fibroblasts and red blood cell ghosts) can be easily obtained. Due to size differences, the optimum electric field conditions for their permeabilization and the maintenance of their integrity are observed to be different (10 pulses, 100 microseconds duration, 1.2 kV/cm for Chinese hamster ovary [CHO] kV/cm for erythrocyte ghosts). Cells and ghosts are electropermeabilized separately and kept at low temperature. Their fusion is then induced by the creation of contact between them by gentle centrifugation. This process takes advantage of the long-lived fusogenicity of the electropermeabilized cell membrane. An immediate consequence is the introduction of macromolecules into mammalian cells. This is obtained by fusing cells with pre-loaded erythrocyte ghosts. Under optimum conditions, penetration of large quantities of FITC-dextran (70 kDa) and beta-galactosidase into 90%-95% of CHO cells while preserving their viability has been observed.

Animals↗
PubMed1994

[Noninvasive patient observation in veterinary medicine: pulse oximetry and capnography. I. Pulse oximetry].

Two non-invasive continuous techniques for monitoring the respiratory function during anaesthesia have been established during the last year: pulse oximetry for monitoring the adequate oxygen supply and capnography for measuring the carbon dioxide elimination. In human medicine both are accepted as essential monitors with great reliability. Whether clinical use and interpretation can be transferred to animals without any restrictions will be discussed by looking on the physical and engineering background as well as the physiologic interpretation of the measured variable and their capability to detect critical events during administration of anaesthesia. Part I: Pulse oximetry measures the arterial oxygen saturation continuously and non-invasively. Its application in veterinary medicine must be discussed critically concerning the method as well as the interpretation. The information obtained is very different during injectable and inhalant anaesthesia. Respiratory depression is easy to detect while the animal breathes room air spontaneously. Is the inspired air enriched with oxygen, like during inhalant anaesthesia, normal values of oxygen saturation can mask the respiratory insufficiency and may give a false sense of security.

Anesthesia↗
PubMed1993

Skin graft take and healing following 193-nm excimer, continuous-wave carbon dioxide (CO2), pulsed CO2, or pulsed holmium: YAG laser ablation of the graft bed.

BACKGROUND: Ablative lasers have been used for cutaneous surgery for greater than two decades since they can remove skin and skin lesions bloodlessly and efficiently. Because full-thickness skin wounds created after thermal laser ablation may require skin grafting in order to heal, we have examined the effect of the residual laser-induced thermal damage in the wound bed on subsequent skin graft take and healing. In a pig model, four different pulsed and continuous-wave lasers with varying wavelengths and radiant energy exposures were used to create uniform fascial graft bed thermal damage of approximately 25, 160, 470, and 1100 microns. Meshed split-thickness skin graft take and healing on the thermally damaged fascial graft beds were examined on a gross and microscopic level on days 3 and 7, and then weekly up to 42 days. RESULTS: Laser-induced thermal damage on the graft bed measuring greater than 160 +/- 60 microns in depth significantly decreased skin graft take. Other deleterious effects included delayed graft revascularization, increased inflammatory cell infiltrate at the graft-wound bed interface, and accelerated formation of hypertrophied fibrous tissue within the graft bed and underlying muscle. CONCLUSIONS: Ablative lasers developed for cutaneous surgery should create less than 160 +/- 60 microns of residual thermal damage to permit optimal skin graft take and healing. Pulsed carbon dioxide and 193-nm excimer lasers may be valuable instruments for the removal of full-thickness skin, skin lesions, and necrotic tissue, since they create wound beds with minimal thermal damage permitting graft take comparable to that achieved with standard surgical techniques.

Animals↗
PubMedDate not supplied

[The dependence of the biological effect of electron radiation on the pulse repetition rate. The dependence of mortality and life span in rats on the radiation dose and pulse repetition rate].

Quantitative regularities have been established for mortality and life-span of rats in relation to the pulse recurrence frequency (3-2400 s-1) of electron radiation with electron energies of 25 and 50 MeV. Electrons with pulse recurrence frequencies of 600 and 1200 s-1 have shown a higher biological effectiveness.

Animals↗
PubMed1994

Estimates of pulse wave velocity and measurement of pulse transit time in the human cerebral circulation.

Knowledge of the velocity with which pressure and flow waves travel within the arterial tree has been fundamental to the understanding of important hemodynamic parameters, such as vessel wall elastance, impedance and reflection coefficients for the systemic circulation. To our knowledge, however, this pulse wave velocity (PWV) has not been previously measured for the human cerebral circulation. In this study, we estimate the PWV from 88 measurements during normocarbia and 95 measurements during hypocarbia in six healthy human volunteers. The measurements consisted of time delays between velocity waveforms obtained simultaneously from the cervical carotid artery and the ipsilateral middle cerebral artery. An estimation of the distance between these sites as 10 centimeters yielded a PWV of 12.8 m/s for both levels of pCO2. Vessel elasticity could then be estimated between 17 and 34 dyne/cm2.10(6). These values of PWV are among the highest of those found in the peripheral circulation, and may have implications for the interpretation of the shape of the cerebral pressure and flow waveforms.

Adult↗
PubMed1981

The reactions of the 2'-deoxyadenosine electron adduct in aqueous solution. The effects of the radiosensitizer p-nitroacetophenone. A pulse spectroscopic and pulse conductometric study.

The reactions of the one electron adduct of 2'-deoxyadenosine dA(-), in aqueous solutions have been studied using pulse radiolysis techniques with optical absorption and conductivity detection. The dA(-) radical anion itself shows a weak and featureless optical absorption at greater than 300 nm. It reacts rapidly with H20 (k equals 6 x 10(4)M(-1)s(-1); t1/2 equals 210 ns) to yield at least three different protonated structures (dAH., dA'H., dA"H.). In neutral solutions the most important of these (dAH., lambda(max) equals 315 nm) decays by a first order process (t1/2 approximately equal to 9 microseconds). In basic solutions dAH. undergoes on OH- catalysed rearrangement into another neutral radical (dA"'H., lambda(max) equals 355 nm; k(dAH. plus OH-) equals 1.7 x 10(8)M(-1)s(-1)). p-Nitroacetophenone (PNAP) reacts rapidly with the protonated electron adducts of 2'-deoxyadenosine (k equals 5 x 10(9)M(-1)s(-1)). An electron transfer occurs with dAH to yield PNAP and a reoxidized form of 2'-deoxyadenosine. As indicated by its pK value of 8.8 the latter is not, however, simply a repaired 2'-deoxyadenosine molecule, but is suggested to include the elements of water. Species dA"'H.(and dA'H.) react with PNAP in a process which is clearly not an electron transfer but likely an addition reaction.

Acetophenones↗
PubMed2007

Central pulse wave velocity is responsible for increased brachial-ankle pulse wave velocity in subclinical hypothyroidism.

OBJECTIVE: Subclinical hypothyroidism affects 5-15% of the general population, and is associated with increased morbidity from cardiovascular disease. We recently reported a significant increase in brachial-ankle pulse wave velocity (baPWV), a parameter of arterial stiffening and an independent predictor for the presence of cardiovascular disease, in subclinical hypothyroidism. The current study was performed to assess which arterial segment is responsible for enhanced baPWV in subclinical hypothyroidism. PATIENTS AND METHODS: Central PWV (PWV in heart-femoral segments), peripheral PWV (PWV in femoral-ankle segments), and baPWV were measured in subclinical hypothyroid patients and normal subjects. RESULTS: Central PWV, baPWV, and peripheral PWV were significantly higher in subclinical hypothyroid patients than in normal subjects. BaPWV was significantly and positively correlated with central and peripheral PWV in both groups. However, a significant and positive correlation between central and peripheral PWV in normal subjects was not found in subclinical hypothyroid patients. Moreover, stepwise regression analysis showed that the association of central PWV with baPWV was stronger than that of peripheral PWV, whereas in normal subjects central PWV was not associated with baPWV. CONCLUSIONS: Our results demonstrate that central and peripheral PWV are significantly higher in subclinical hypothyroid patients, and that the increase in baPWV depends more strongly on central PWV than on peripheral PWV in these patients. This suggests that increased elastic arterial stiffening of the aorta, rather than of peripheral muscular arteries, might be more responsible for increased general arterial stiffening in subclinical hypothyroid patients.

Ankle↗
PubMed1977

Distortion of non-invasive cardiac pulse curves. A capillary-damped pick-up and a calibration unit forapex cardiograms and other pulse curves.

A calibration unit and a capillary-damped pick-up, of funnel type, intended for apex cardiograms and other non-invasive cardiac pulse curves are presented. The physical properties of a recording system, suitable for non-invasive cardiac diagnostic techniques, are reviewed. In 4 identical recording units consisting of a funnel with and without capillary damping, connected via air transmission to a transducer, the overamplification in the underdamped systems varied between 2-4 and 4-3, and in the capillary-damped systems between 1-1 and 1-2. The capillary damping gave an approximately linear relation between phase shift and frequency in the high frequency range with a calculated delay of about 4ms. The low frequency time constant in the systems varied between 1-9 and 4-6 s, depending on the amplifier setting used, which for sine curves of frequency 0-5 and 2 Hz means an apparent prematurity for their maxima and minima varying between 53 and 1 ms, this being larger with lower frequency time constants and lower frequency curves.

Amplifiers, Electronic↗