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Safety and efficacy of hepatitis B surface antigen-pulsed dendritic cells in human volunteers.

Hepatitis B surface antigen (HBsAg)-pulsed murine spleen dendritic cells (DCs) have shown tremendous therapeutic potentials in chronic hepatitis B virus (HBV) carriers however, there has been no study regarding the feasibility of using HBsAg-pulsed DCs in human. Five human healthy volunteers with no apparent concomitant diseases were enrolled in this study. DCs were enriched from peripheral blood of each volunteer in endotoxin-free and sterilized conditions. HBsAg-pulsed DCs were prepared by culturing DCs with a commercial-available human grade vaccine containing HBsAg. After assessing the expression of HLA DR and CD86 on HBsAg-pulsed DCs, 5 million HBsAg-pulsed DCs were injected intradermally, once, to each volunteer. The volunteers were serially observed for safety and efficacy of administration of HBsAg-pulsed DCs. No evidence of physical, biochemical, and immunological abnormalities were documented in any volunteer during the next 28 days following administration of HBsAg-pulsed DCs. A single administration of HBsAg-pulsed DCs resulted in upregulation of anti-HBs in two anti-HBs(+) volunteers. Moreover, anti-HBs were detected in two anti-HBs(-) volunteer, 2 weeks after administration of HBsAg-pulsed DCs. This study provides the scientific and ethical basis for using HBsAg-pulsed DCs for therapeutic and prophylactic purposes in patients with chronic hepatitis B and non-responders to hepatitis B vaccine, respectively.

Journal Article↗

Background gradient suppression in stimulated echo NMR diffusion studies using magic pulsed field gradient ratios.

By evaluating the spin echo attenuation for a generalized 13-interval PFG NMR sequence consisting of pulsed field gradients with four different effective intensities (F(p/r) and G(p/r)), magic pulsed field gradient (MPFG) ratios for the prepare (G(p)/F(p)) and the read (G(r)/F(r)) interval are derived, which suppress the cross term between background field gradients and the pulsed field gradients even in the cases where the background field gradients may change during the z-store interval of the pulse sequence. These MPFG ratios depend only on the timing of the pulsed gradients in the pulse sequence and allow a convenient experimental approach to background gradient suppression in NMR diffusion studies with heterogeneous systems, where the local properties of the (internal) background gradients are often unknown. If the pulsed field gradients are centered in the tau-intervals between the pi and pi/2 rf pulses, these two MPFG ratios coincide to eta=G(p/r)/F(p/r)=1-8/[1+(1/3)(delta/tau)(2)]. Since the width of the pulsed field gradients (delta) is bounded by 0< or =delta< or =tau, eta can only be in the range of 5< or =-eta< or =7. The predicted suppression of the unwanted cross terms is demonstrated experimentally using time-dependent external gradients which are controlled in the NMR experiment as well as spatially dependent internal background gradients generated by the magnetic properties of the sample itself. The theoretical and experimental results confirm and extend the approach of Sun et al. (J. Magn. Reson. 161 (2003) 168), who recently introduced a 13-interval type PFG NMR sequence with two asymmetric pulsed magnetic field gradients suitable to suppress unwanted cross terms with spatially dependent background field gradients.

Diffusion↗

Over-pulsing degrades activated iridium oxide films used for intracortical neural stimulation.

Microelectrodes using activated iridium oxide (AIROF) charge-injection coatings have been pulsed in cat cortex at levels from near-threshold for neural excitation to the reported in vitro electrochemical charge-injection limits of AIROF. The microelectrodes were subjected to continuous biphasic current pulsing, using an 0.4V (versus Ag|AgCl) anodic bias with equal cathodal and anodal pulse widths, for periods up to 7h at a frequency of either 50Hz or 100Hz. At charge densities of 3mC/cm(2), histology revealed iridium-containing deposits in tissue adjacent to the charge-injection sites and scanning electron microscopy of explanted electrodes revealed a thickened and poorly adherent AIROF coating. Microelectrodes pulsed at 2mC/cm(2) or less remained intact, with no histologic evidence of non-biologic deposits in the tissue. AIROF microelectrodes challenged in vitro under the same pulsing conditions responded similarly, with electrodes pulsed at 3mC/cm(2) showing evidence of AIROF delamination after only 100s of pulsing at 100Hz (10,000 pulses total), while electrodes pulsed at 2mC/cm(2) for 7h at 50Hz (1.3 x 10(6) pulses total) showed no evidence of damage. In vitro electrochemical potential transient measurements in buffered physiologic saline indicate that polarizing the AIROF beyond the potential window for electrolysis of water (-0.6 to 0.8V versus Ag|AgCl) results in the observed degradation.

Animals↗

Pulse replications and spatially differentiated structure formation in one-dimensional lattice dynamical system.

Replication and differentiation of pulses are studied through a simple dynamical system on a one-dimensional lattice. Depending on the parameter values, our proposed system exhibits the following types of pulse replications: (I) each pulse replicates by itself, (II) each pulse replicates if two or more pulses collide each other, and (III) pulses replicate by the organization of pulse generators. Moreover, replicated pulses construct the spatial-temporal pattern when the number of pulses is large. By selecting local objects in such spatial-temporal patterns and replanting them numerically, it is found that there are two types differentiated local structures: one that continues the production of pulses and the other that does not.

Diffusion↗

Slice profile optimization in arterial spin labeling using presaturation and optimized RF pulses.

OBJECTIVE: An important source of error in arterial spin labeling (ASL) is incomplete static tissue subtraction due to imperfect slice profiles. This effect can be reduced by saturating the spins in the imaging area prior to labeling. In this study, the use of optimized presaturation is compared with the use of optimized RF pulses for minimizing this error. MATERIALS AND METHODS: Different methods for optimizing presaturation were simulated by numerical solution of the Bloch equation. Presaturation was optimized by changing the number of presaturation pulses, their position in the pulse sequence and the area of the crusher gradients following each saturation pulse. It was also investigated whether the use of optimized presaturation could reduce the tag gap needed to ensure complete static tissue subtraction. Simulation results were verified using phantom and in vivo studies at 3T. RESULTS: In proximal inversion with control for off-resonance effects, optimized presaturation could reduce the necessary tag gap to 15% of the imaging slab for experiments using standard RF pulses, while c-FOCI RF pulses could reduce it to 11%. In flow-sensitive alternating inversion recovery, a single presaturation pulse could reduce the inversion width to 122% of the imaging slab and neither multiple presaturation pulses nor optimized RF pulses could reduce it further. CONCLUSION: Optimized presaturation can reduce the necessary inversion width to the same level as if using optimized RF pulses and can, therefore, be used to optimize ASL sensitivity. Furthermore, optimized presaturation can reduce the B(1)-dependent sensitivity in static tissue subtraction.

Adult↗

Role of pulse shape in cell membrane electropermeabilization.

The role of the amplitude, number, and duration of unipolar rectangular electric pulses in cell membrane electropermeabilization in vitro has been the subject of several studies. With respect to unipolar rectangular pulses, an improved efficiency has been reported for several modifications of the pulse shape: separate bipolar pulses, continuous bipolar waveforms, and sine-modulated pulses. In this paper, we present the results of a systematic study of the role of pulse shape in permeabilization, cell death, and molecular uptake. We have first compared the efficiency of 1-ms unipolar pulses with rise- and falltimes ranging from 2 to 100 micros, observing no statistically significant difference. We then compared the efficiency of triangular, sine, and rectangular bipolar pulses, and finally the efficiency of sine-modulated unipolar pulses with different percentages of modulation. We show that the results of these experiments can be explained on the basis of the time during which the pulse amplitude exceeds a certain critical value.

Animals↗

Millisecond measurement of transport during and after an electroporation pulse.

Electroporation involves the application of an electric field pulse that creates transient aqueous pathways in lipid bilayer membranes. Transport through these pathways can occur by different mechanisms during and after a pulse. To determine the time scale of transport and the mechanism(s) by which it occurs, efflux of a fluorescent molecule, calcein, across erythrocyte ghost membranes was measured with a fluorescence microscope photometer with millisecond time resolution during and after electroporation pulses several milliseconds in duration. One of four outcomes was typically observed. Ghosts were: (1) partially emptied of calcein, involving efflux primarily after the pulse; (2) completely emptied of calcein, involving efflux primarily after the pulse; (3) completely emptied of calcein, involving efflux both during and after the pulse; or (4) completely emptied of calcein, involving efflux primarily during the pulse. Partial emptying, involving significant efflux during the pulse, was generally not observed. We conclude that under some conditions transport caused by electroporation occurs predominantly by electrophoresis and/or electroosmosis during a pulse, although under other conditions transport occurs in part or almost completely by diffusion within milliseconds to seconds after a pulse.

Biological Transport↗

Correlation between electric field pulse induced long-lived permeabilization and fusogenicity in cell membranes.

Electric field pulses have been reported to induce long-lived permeabilization and fusogenicity on cell membranes. The two membrane property alterations are under the control of the field strength, the pulse duration, and the number of pulses. Experiments on mammalian cells pulsed by square wave form pulses and then brought into contact randomly through centrifugation revealed an even stronger analogy between the two processes. Permeabilization was known to affect well-defined regions of the cell surface. Fusion can be obtained only when permeabilized surfaces on the two partners were brought into contact. Permeabilization was under the control of the pulse duration and of the number of pulses. A similar relationship was observed as far as fusion is concerned. But a critical level of local permeabilization must be present for fusion to take place when contacts are created. The same conclusions are obtained from previous experiments on ghosts subjected to exponentially decaying field pulses and then brought into contact by dielectrophoresis. These observations are in agreement with a model of membrane fusion in which the merging of local random defects occurs when the two membranes are brought into contact. The local defects are considered part of the structural membrane reorganization induced by the external field. Their density is dependent on the pulse duration and number of pulses. They support the long-lived permeabilization. Their number must be very large to support the occurrence of membrane fusion.

Animals↗

Biological effect of pulsed dose rate brachytherapy with stepping sources if short half-times of repair are present in tissues.

PURPOSE: To explore the possible increase of radiation effect in tissues irradiated by pulsed brachytherapy (PDR) for local tissue dose rates between those "averaged over the whole pulse" and the instantaneous high dose rates close to the dwell positions. Increased effect is more likely for tissues with short half-times of repair of the order of a few minutes, similar to pulse durations. METHODS AND MATERIALS: Calculations were done assuming the linear quadratic formula for radiation damage, in which only the dose-squared term is subject to exponential repair. The situation with two components of T1,2 is addressed. A constant overall time of 140 h and a constant total dose of 70 Gy were assumed throughout, the continuous low dose rate of 0.5 Gy/h (CLDR) providing the unitary standard effects for each PDR condition. Effects of dose rates ranging from 4 Gy/h to 120 Gy/h (HDR at 2 Gy/min) were studied, covering the gap in an earlier publication. Four schedules were examined: doses per pulse of 0.5, 1, 1.5, and 2 Gy given at repetiton frequencies of 1, 2, 3, and 4 h, respectively, each with a range of assumed half-times of repair of 4 min to 1.5 h. Results are presented for late-responding tissues, the differences from CLDR being two or three times greater than for early-responding tissues and most tumors. RESULTS: Curves are presented relating the ratio of increased biological effect (proportional to log cell kill) calculated for PDR relative to CLDR. Ratios as high as 1.5 can be found for large doses per pulse (2 Gy) if the half-time of repair in tissues is as short as a few minutes. The major influences on effect are dose per pulse, half-time of repair in tissue, and--when T1/2 is short--the instantaneous dose rate. Maximum ratios of PDR/CLDR occur when the dose rate is such that pulse duration is approximately equal to T1/2. As dose rate in the pulse is increased, a plateau of effect is reached, for most T1/2s, above 10 to 20 Gy/h, which is therefore radiobiologically equivalent to the highest HDR. A stepping source of 1 curie carries a sphere of "HDR" of radius 20 mm with it in its track through tissue. High ratios of PDR/LDR effect can be avoided by keeping dose per pulse below 1 Gy. CONCLUSIONS: Therefore, about 75% of the total dose is delivered at HDR in a PDR implant of moderate volume, reducing to 40% as the source decays from 1 to 0.3 curies. Even so, restricting the dose per pulse to 0.5 or 0.6 Gy should avoid ratios of increased effect larger than about 10%. It appears likely that PDR delivered by stepping source might behave more like HDR than LDR, especially for tissues with a substantial component of repair of very short T1/2.

Brachytherapy↗

New pulse sequences for T1- and T1/T2-contrast enhancing in NMR imaging.

Improved pulse sequences DIFN (abbreviation of the words: DIFferentiation by N pulses), 90 degrees - tau1 - 180 degrees tau1 - . . . 180 degrees - tau1 with optimised time intervals tau1- for T1 measurement and contrast enhancing in NMR imaging are presented. The pulse sequences DIFN have a better sensitivity to T1 than the well-known pulse sequence SR. In contrast to the IR pulse sequence, the information given by the DIFN pulse sequence is more reliable, because the NMR signal does not change its sign. For a given time interval tau0 < or = (0.1 - 0.3) T(1) the DIFN pulse sequences serve as T1-filters. They pass the signal components with relatively short T1 < T(1) and suppress the components with relatively long T1 < T(1). The effects of the radiofrequency field inhomogeneity and inaccurate adjusting of pulse lengths are also considered. It is also proposed in this work to use the joint T1T2-contrast in NMR imaging obtained as a result of applying the DIFN pulse sequences in combination with the well-known Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence. The region of interest, where the contrast should be especially enhanced, is specified by the two times at which measurements are performed, which allow the amplitudes of pixels to reach some defined levels by spin-lattice and spin-spin relaxation.

Computer Simulation↗

Ambulatory pulse pressure as predictor of outcome in older patients with systolic hypertension.

We enrolled 808 older patients with isolated systolic hypertension (160 to 219/71 <95 mm Hg) to investigate whether ambulatory measurement of pulse pressure and mean pressure can refine risk stratification. The patients (> or =60 years) were randomized to nitrendipine (10 to 40 mg/day) with the possible addition of enalapril (5 to 20 mg/day) or hydrochlorothiazide (12.5 to 25 mg/day) or to matching placebos. At baseline, pulse pressure and mean pressure were determined from six conventional blood pressure (BP) readings and from 24-h ambulatory recordings. With adjustment for significant covariables, we computed mutually adjusted relative hazard rates associated with 10 mm Hg increases in pulse pressure or mean pressure. In the placebo group, the 24-h and nighttime pulse pressures consistently predicted total and cardiovascular mortality, all cardiovascular events, stroke, and cardiac events. Daytime pulse pressure predicted cardiovascular mortality, all cardiovascular end points, and stroke. The hazard rates for 10 mm Hg increases in pulse pressure ranged from 1.25 to 1.68. Conventionally measured pulse pressure predicted only cardiovascular mortality with a hazard rate of 1.35. In the active treatment group compared with the placebo patients, the relation between outcome and ambulatory pulse pressure was attenuated to a nonsignificant level. Mean pressure determined from ambulatory or conventional BP measurements was not associated with poorer prognosis. In conclusion, in older patients with isolated systolic hypertension higher pulse pressure estimated by 24-h ambulatory monitoring was a better predictor of adverse outcomes than conventional pulse pressure, whereas conventional and ambulatory mean pressures were not correlated with a worse outcome.

Aged↗

The role of the laser pulse duration in infrared matrix-assisted laser desorption/ionization mass spectrometry.

The role of the laser pulse duration in matrix-assisted laser desorption/ionization mass spectrometry with infrared lasers (IR-MALDI-MS) emitting in the 3 microm wavelength range has been evaluated. Mass spectrometric performance and characteristics of the IR-MALDI process were examined by comparing a wavelength-tuneable mid-infrared optical parametric oscillator (OPO) laser of 6 ns pulse duration, tuned to wavelengths of 2.79 and 2.94 microm, with an Er:YAG laser (lambda = 2.94 microm) with two pulse durations of 100 and 185 ns, and an Er:YSGG laser (lambda = 2.79 microm) with a pulse duration of 75 ns. Threshold fluences for the desorption of cytochrome C ions were determined as a function of the laser pulse duration for various common IR-MALDI matrices. For the majority of these matrices a reduction in threshold fluence by a factor of 1.2-1.9 was found by going from the 75-100 ns long pulses of the Erbium lasers to the short 6 ns OPO pulse. Within the experimental accuracy threshold fluences were equal for the 100 and the 185 ns pulse duration of the Er:YAG laser. Some pronounced pulse duration effects related to the ion formation from a glycerol matrix were also observed. The effect of the laser pulse length on the duration of ion emission was furthermore investigated.

Angiotensin I↗

Augmented experimental pulse-spray thrombolysis with tissue plasminogen activator, enabling dose reduction by one or more orders of magnitude.

PURPOSE: To critically evaluate and optimize methodologic details of pulse-spray thrombolysis with tissue plasminogen activator (tPA) in a subacute rabbit inferior vena cava thrombosis model. MATERIALS AND METHODS: Occlusive inferior vena cava thrombi were produced in 104 rabbits and 2 days later were treated for 1 hour with pulse-spray thrombolysis using tPA. Methodologic variables included pulse frequency, concentration and amount of tPA, infusion versus pulse therapy, and admixture of heparin. After the rabbits were killed, residual thrombus was weighed. RESULTS: The authors' earlier standard regimen (3 mg of tPA in 6 mL of heparinized saline, 0.2-mL hand pulses, frequency 1 pulse per 2 minutes) produced 60% mean lysis. Optimization involved increasing the pulse frequency to two per minute and decreasing tPA concentration by 98% to 0.01 mg/mL, modifications that produced 22% more thrombolysis, despite 92% reduction in amount of tPA to 0.25 mg. CONCLUSION: Consistent with the in vitro work of other investigators, a roughly bell-shaped dose-response curve was elicited in vivo for pulse-spray with tPA. By diluting tPA to an optimal level, and increasing pulse frequency to two per minute, thrombolysis was markedly augmented. These results suggest that the conventional dose of tPA used for clinical pulse-spray thrombolysis can be reduced by one to two orders of magnitude, possibly markedly reducing procedural risk.

Animals↗

Pulsed electrospray for mass spectrometry.

Pulsed electrospray has been developed and been reported for the first time. This new technique is based on the principle of pulsed ion sources, combined with the conventional electrospray. The pulsed ion spray was realized by a homemade pulsed HV circuit and was monitored by a digital microscope and an oscilloscope. Results show that the pulsed ESI device can be operated under proper conditions for a clear on-and-off spray process and that the device was kept in good electric contact for electrospray when pulsed HV was on. A pulsed ion current and pulsed mass spectra can be achieved with this pulsed ESI device. Furthermore, it has been noted that, under the same conditions (i.e., shape and size of sprayer tip, distance from sprayer tip to sampling nozzle, and other parameters for mass spectrometer), stable electrospray could be obtained for lower flow rates with a pulsed spray device. This experimental fact indicates the possible reduction in the total sample consumed could be realized by exploiting this novel design.

Spectrometry, Mass, Electrospray Ionization↗

Field study of pulsed air sparging for remediation of petroleum hydrocarbon contaminated soil and groundwater.

Recent laboratory-scale studies strongly suggested an advantage to operating air-sparging systems in a pulsed mode; however, little definitive field data existed to support the laboratory-scale observations. This study aimed to evaluate the performance of a field-scale pulsed air-sparging system during a short-term pilot test and during long-term system operation. The air-sparging system consisted of 32 sparging points and had been previously operated in a continuous mode for two years before the field study was performed. The field study used instruments with continuous data logging capabilities to monitor the dynamic responses of groundwater and soil vapor parameters to air injection. The optimum pulsing frequency was based on the evidence that the hydrocarbon volatilization and oxygen dissolution rates dramatically dropped after the air-sparging system reached steady state. The short-term pilot test results indicated a substantial increase in hydrocarbon volatilization and biodegradation in pulsed operation. On the basis of the results of the pilottest, the air-sparging system was set to operate in a pulsed mode at an optimum pulsing frequency. Operation parameters were collected 2, 8, and 12 months after the start of the pulsed operation. The long-term monitoring results showed thatthe pulsed operation increased the average hydrocarbon removal rate (kg/day) by a factor of up to 3 as compared to the previous continuous operation. The pulsed air sparging has resulted in higher reduction rates of dissolved benzene, toluene, ethylbenzene, and xylenes (BTEX) than were observed during the continuous operation. Among BTEX, benzene's reduction rate was the highest during the pulsed air-sparging operation.

Air↗

Study of the mechanisms of flux enhancement through hairless mouse skin by pulsed DC iontophoresis.

Enhanced iontophoretic transport using pulsed DC is usually explained by citing the observed decrease in skin resistance caused by an increase in AC pulse frequency at very small currents. Alternately, it has been suggested that the "on-to-off" nature of pulsed DC imparts an "impact energy" to the fluid, thereby increasing transport. This report provides a test of these mechanisms for enhanced delivery via pulsed iontophoresis. The DC resistance of hairless mouse skin during continuous and pulsed DC iontophoresis is measured as a function of time for selected pulse frequencies and duty cycles using current densities ranging from 0.1 to 1.0 mA/cm2. As a test of the impact energy mechanism, the iontophoretic transport of 14C-glucose measured with pulsed DC is compared with similar data obtained previously using continuous DC. It is suggested that pulsed current can yield lower resistance and enhanced drug delivery provided that (a) the "steady-state" current during the "on" phase of the pulse is very small and (b) the frequency is low enough to allow depolarization of the skin during the "off" phase of the pulse. The glucose transport results suggest that the "impact energy" concept does not apply to iontophoresis.

Animals↗

Factors influencing fetal pulse oximetry performance.

Fetal pulse oximetry shares many problems with traditional pulse oximetry, but also poses unique challenges that may compromise accurate SpO2 determination and data availability. The purpose of this review is to characterize the factors that may influence fetal pulse oximetry and their relationship to sensor design. A review of the literature of pulse oximetry identifies the factors that have been shown to influence fetal pulse oximetry performance, as well as other factors from traditional pulse oximetry that may also be expected to have an effect. Sensor design choices, including monitoring site, wavelength, and configuration, are related to the incidence and mitigation of these factors. Sensor designs may be characterized by monitoring site, means of retention, and operating mode (reflectance versus transmission). The factors influencing fetal pulse oximetry may be categorized as follows: fetal physiology, tissue characteristics at the monitoring site, sensor-tissue interface, and external influences. Monitoring site selection is of paramount importance in reducing the impact of interfering factors on fetal pulse oximetry performance. Many factors of importance in traditional pulse oximetry have yet to be characterized as far as their potential for interference in fetal pulse oximetry.

Equipment Design↗

Should pulse pressure become part of the Framingham risk score?

An increased pulse pressure suggests aortic stiffening. New evidence also suggests that pulse pressure is a more sensitive measure of risk than other indexes of blood pressure in middle-aged and older persons. The objective of the study was to relate pulse pressure to the risk of cardiovascular events in the general population, and to assess whether pulse pressure could improve the Framingham risk prediction. A total of 378 men and 391 women over the age of 50 years (mean 62.7 years) were followed. Sex-specific Framingham cardiovascular risk scores were derived from age, systolic pressure, diastolic pressure, total and HDL cholesterol, smoking status and the presence or absence of diabetes mellitus. The cutoff points used to develop a pulse pressure score were calculated by determining the percentile points corresponding to the blood pressure categories in the Framingham risk score. We calculated relative hazard rates by multiple Cox regression. After a median follow-up of 7.2 years (range: 11 months-15 years), a total of 148 cardiovascular events occurred. In Cox regression analysis, a 10 mmHg higher pulse pressure was associated with 31% (P<0.0001) increase in the risk for cardiovascular events (fatal and nonfatal) after adjustment for sex, age, total and HDL cholesterol, smoking and the presence of diabetes mellitus. After adjustment for the aforementioned risk factors, a one-point increment in the blood pressure and pulse pressure scores was associated with a 40 and 48% (both P<0.0001) increase in the risk of fatal and nonfatal cardiovascular events, respectively. When both the blood pressure and pulse pressure scores were forced into a Cox model, only the pulse pressure score remained statistically significant (P<0.0001) with a relative hazard rate of 1.37 (CI: 1.16-1.69). These prospective data suggest that pulse pressure may improve the Framingham risk prediction among middle-aged and older individuals. Further studies, especially in the Framingham cohort, are warranted.

Age Factors↗