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PubMed2006

Solid state NMR at high magic angle spinning frequencies: dipolar chemical shift correlation with adiabatic inversion pulse based RF pulse schemes.

The efficacy of hetero- and homonuclear dipolar recoupling employing tanh/tan adiabatic inversion pulse based RF pulse schemes has been examined at high magic angle spinning (MAS) frequencies via numerical simulations and experimental measurements. An approach for minimising the recoupling RF power level is presented, taking into consideration the spinning speed, the range of resonance offsets and H(1) inhomogeneities and the available RF field strength. This involves the tailoring of the frequency and amplitude modulation profiles of the inversion pulses. The applicability of tanh/tan pulse based dipolar recoupling schemes to spinning speed regimes where the performance with conventional rectangular pulses may not be satisfactory is demonstrated.

Carbon Isotopes↗
PubMed1987

Auditory unit responses to single-pulse and twin-pulse microwave stimuli.

Responses of units in the cat cochlear nucleus to single microwave pulses with different durations and to twin microwave pulses with different interpulse delays are used to study microwave hearing. Inferred threshold specific absorption rate is less than 6 mW/g; inferred threshold specific absorption, less than 0.5 microJ/g. The existence of responses from units with characteristic frequencies (CFs) from 931 Hz to 25.5 kHz is not consistent with a primary role for head resonance in microwave hearing. Patterns of response amplitude have a periodicity of 1/CF and are fully explained by frequency content of the pulse stimulus and signal processing of the auditory system. For pulses shorter than about 0.24/CF, it is shown that response amplitude is predictably proportional to pulse energy.

Animals↗
PubMed2004

Production of hepatitis B surface antigen-pulsed dendritic cells from immunosuppressed murine hepatitis B virus carrier: evaluation of immunogenicity of antigen-pulsed dendritic cells in vivo.

Vaccines containing hepatitis B surface antigen (HBsAg) induce antibody to HBsAg (anti-HBs) in most normal individuals and protects them from hepatitis B virus (HBV) infection. However, these vaccines are not efficient at inducing anti-HBs in immunosuppressed individuals, especially in immunosuppressed HBV carriers. The aim of this study was to prepare and to assess the efficacy of a dendritic cell (DC)-based vaccine in an immunosuppressed HBV transgenic mouse (HBV-Tg), an animal model of the HBV carrier state. In order to prepare immunosuppressed HBV-Tg, HBV-Tg were injected with FK-506, an immunosuppressive agent, once daily, intraperitoneally for 15 days. Spleen cells of immunosuppressed HBV-Tg expressed very little mRNAs for interleukin-2 and interferon-gamma. DCs were isolated from the spleen of immunosuppressed HBV-Tg and cultured with HBsAg (100 microg) for 48 h to prepare HBsAg-pulsed DCs. Immunosuppressed HBV-Tg expressing HBsAg in the sera were administered with HBsAg-pulsed DCs or unpulsed DCs or HBsAg in adjuvant for different durations. Immunosuppressed HBV-Tg (n = 8) twice administered with HBsAg-pulsed DCs expressed anti-HBs in the sera within 6 weeks of first injection. Seven of eight immunosuppressed HBV-Tg remained positive for anti-HBs in the sera for the next 12 weeks of observation in spite of receiving daily injection of FK-506 for the entire duration. However, immunosuppressed HBV-Tg administered with unpulsed DCs or HBsAg in adjuvant did not express anti-HBs in the sera. The data show that DCs from immunosuppressed HBV-Tg can be loaded with HBsAg to prepare immunogenic HBsAg-pulsed DCs. HBsAg-pulsed DCs induced anti-HBs in immunosuppressed HBV-Tg. This approach may be of use to induce and maintain anti-HBs in immunosuppressed human HBV carriers.

Animals↗
PubMed1996

Synaptic release rather than failure in the conditioning pulse results in paired-pulse facilitation during minimal synaptic stimulation in the rat hippocampal CA1 neurones.

In this paper we report our observations of the relationship of paired-pulse facilitation (PPF) with synaptic release or release failure at small numbers of synaptic sites. Minimal stimulation protocols were employed to enable the activation of only one or a few axons which synapse onto CA1 pyramidal cells in the hippocampus. Excitatory postsynaptic currents (EPSCs) in response to paired stimulation were measured. On the analysis of the data, we examined the effects of failure and synaptic release on PPF, and found that PPF was observed as a decrease in failures of synaptic release in response to test stimuli which were preceded by conditioning stimuli that evoked synaptic release. The test-pulse failure rate following conditioning pulse failures was indistinguishable from the overall conditioning pulse failure rate. It is postulated that the mechanism of paired-pulse facilitation is presynaptic and associated with successful synaptic release in response to the conditioning stimulus.

Animals↗
PubMed2002

Inversion profiles of adiabatic inversion pulses for flowing spins: the effects on labeling efficiency and labeling accuracy in perfusion imaging with pulsed arterial spin-labeling.

The inversion profile of adiabatic inversion pulses is essential to the accuracy of perfusion measurement with pulsed arterial spin-labeling (ASL). In this paper, the inversion profiles for flowing spins were investigated using a numerical solution of the modified Bloch equations including a term for moving spins. Inversion profiles for spins flowing at a constant or varying velocity were examined for hyperbolic secant (HS) and frequency-offset corrected inversion (FOCI) pulses. Distortions of the inversion profiles were found for both pulses with spins flowing within physiological velocity range. The effects of the distorted profiles on labeling efficiency and labeling accuracy in the application of pulsed ASL perfusion imaging were analyzed. These effects should be taken into account in ASL techniques, in order to obtain robust and accurate perfusion measurements.

Blood Flow Velocity↗
PubMed2006

Differential pulse voltammetry and additive differential pulse voltammetry with solvent polymeric membrane ion sensors.

The ion transfer across the water-solvent polymeric membrane interface is investigated by using a new device based on a modification of a commercial ion-selective electrode body that permits the accommodation of a platinum counter electrode inside the inner filling solution compartment and, therefore, use of a four-electrode potentiostat with ohmic drop compensation. This device is used here to apply two different double potential pulse techniques--differential pulse voltammetry and additive differential pulse voltammetry--which are more advantageous than other voltammetric techniques, such as normal pulse voltammetry or cyclic voltammetry, for the determination of the characteristic electrochemical parameters of the system. This is due to the concurrence of two factors in these double potential pulse techniques, the peak-shaped response together with a considerable reduction of undesirable current contributions.

Ions↗
PubMed1988

High-resolution separation and accurate size determination in pulsed-field gel electrophoresis of DNA. 2. Effect of pulse time and electric field strength and implications for models of the separation process.

Bacteriophage DNAs annealed into linear oligomeric concatemers were used to examine the quantitative pulsed-field gel electrophoretic behavior of different-sized DNAs as a function of electrical field strength and pulse time. Three zones of resolution are observed for increasingly larger DNAs. In the first two zones, the electrophoretic mobility decreases linearly with increasing DNA size. The separation in zone 2 is roughly twice that in zone 1. The largest DNA molecules do not resolve at all and migrate in a compression zone. Mobility in zone 1 increases linearly with the electric field strength and decreases with the inverse of the pulse time. The behavior of DNA in zone 2 is qualitatively similar. However, the effect of field strength and pulse time on the separations in each zone is quite different. The results for zone 1 are generally consistent with the predictions of several existing physical models of pulsed-field gel electrophoresis, but no model accounts for all of the observed behavior in the three zones.

Bacteriophages↗
PubMed2004

Reflectance pulse oximetry from core body in neonates and infants: comparison to arterial blood oxygen saturation and to transmission pulse oximetry.

OBJECTIVE: To compare pulse oximetry oxygen saturation (SpO(2)) measured by a novel reflectance method from core body to arterial oxygen saturation (SaO(2)) in neonates and infants. Transmission pulse oximetry (TPO) was measured for comparison. STUDY DESIGN: We monitored 18 infants by the two pulse oximeters simultaneously. The reflectance pulse oximetry (RPO) (PRO2, ConMed, Utica, NY) was measured on the upper back or chest, while the TPO (N395-Nellcor, Pleasanton, CA) was measured from the finger of the infant on the left hand or feet. Data from the two methods were compared to functional SaO(2) derived from blood sample drawn from arterial line for patient care and measured by a Co-oximeter (Ilex, Instrument Lab. Lexington, MA). The potential advantage of the RPO is demonstrated in a case of a premature infant with hypovolemic shock, where SaO(2) or TPO could not be obtained but oximetry was available from the RPO. RESULTS: We used for analysis 56 RPO and 32 TPO measurements. SpO(2) obtained from the RPO was 88.3+/-9.8%, from the TPO 84.2+/-10.1%, and functional SaO(2) was 88.2+/-11.7%, with correlation coefficient of 0.93 and 0.88, respectively (p<0.0001). The mean difference (bias) and standard deviation of the differences (precision) between the RPO and the TPO compared to functional SaO(2) were -0.09+/-4.5% and 1.26+/-5.9% and the absolute errors were 3.2+/-3.1%, and 4.4+/-4.0%, respectively. The accuracy of both RPO and TPO was diminished when SaO(2) was <85%, but only the RPO remained correlated with the functional SaO(2). CONCLUSIONS: Reflectance pulse oximetry measured from core body of neonates and infants is accurate and reliable and is comparable to the transmission SpO(2) when compared to functional SaO(2). We speculate that the reflectance method might be advantageous in cases of poor peripheral perfusion in neonates and infants.

Blood Gas Monitoring, Transcutaneous↗
PubMed2003

Microresurfacing using the variable-pulse erbium:YAG laser: a comparison of the 0.5- and 4-ms pulse durations.

BACKGROUND: Laser resurfacing has become less popular because of its long recovery time, significant discomfort, and potential risks. Microsurfacing employs the use of single-pass erbium:YAG (Er:YAG) "mini peels," which may be performed serially. OBJECTIVE: The purpose of this study was to evaluate the efficacy and patient acceptance of microresurfacing Er:YAG peels in treating facial photodamage. The variable-pulse Er:YAG system was used and was allowed a comparison of the 0.5- and 4-ms pulse widths. METHODS: Six female patients underwent eight microresurfacing peels in a split-face fashion using the 0.5- and 4.0-ms pulse durations of a variable-pulse Er:YAG laser. Patients returned at postoperative Days 3 to 4 and 7 for clinical evaluation and Mexameter measurements. RESULTS: There were no significant differences in healing or postoperative erythema between the 0.5- and 4-ms pulse durations on postoperative Day 7. The average time to reepithelialization was 3.6 days. In a 1-year postoperative interview, four of six patients said that they would undergo the peel again periodically, and five of six stated they had maintained some level of improvement. CONCLUSION: Microresurfacing is an effective and well-tolerated procedure. Benefits include its tolerability under topical anesthesia, limited down time, and high patient satisfaction.

Cosmetic Techniques↗
PubMed1990

Duration of phasic electrical activity of the hypothalamic gonadotropin-releasing hormone pulse generator and dynamics of luteinizing hormone pulses in the rhesus monkey.

The secretion of luteinizing hormone (LH) by the pituitary gland is a pulsatile phenomenon. In the rhesus monkey, each pulse of LH in the peripheral circulation is associated with a characteristic increase in multiunit electrical activity (MUA) recorded from the medial basal hypothalamus. These "volleys" of electrical activity initiate the release of gonadotropin-releasing hormone (GnRH) into the pituitary portal circulation from the terminals of neurosecretory cells. Their duration varies from 1-3 min in normal, adult intact females to 10-25 min in long-term ovariectomized monkeys. A variety of pharmacological interventions also modify volley duration. The purpose of this investigation was to determine the physiological significance of alterations in volley duration. The dynamics of LH pulses in ovariectomized animals were observed in a number of experimental circumstances in which MUA volley duration was reduced from a maximum of 23 min to a minimum of 4 min without significantly altering their frequency. The magnitude of each LH pulse was assessed by calculating the area under the curve delineated by the time course of LH above baseline. In eight experiments, a linear regression of these values on volley duration failed to reveal a significant correlation between MUA volley duration and the magnitude of LH pulses. These results suggest that all of the GnRH secreted per pulse is released at the onset of each MUA volley, the remainder of the increase in electrical activity having no further action on GnRH secretion, although effects on other systems cannot be excluded.

Activity Cycles↗
PubMed2005

Successful treatment of a patient with severe Churg-Strauss syndrome by a combination of pulse corticosteroids, pulse cyclophosphamide, and high-dose intravenous immunoglobulin.

A 24-year-old woman with a 4-year history of bronchial asthma suffered from bloody sputum, numbness of the extremities, elevated eosinophil count, and hypoxemia. A diagnosis of alveolar hemorrhage was made by bronchoalveolar lavage. Echocardiogram revealed severe hypokinesis of the left ventricular wall. Her respiratory condition deteriorated despite administration of pulse corticosteroids. A second pulse corticosteroids and pulse cyclophosphamide followed by high-dose intravenous immunoglobulin brought about a dramatic improvement of alveolar hemorrhage, cardiac impairment, and peripheral neuropathy. Levels of antimyeloperoxidase-antineutrophil cytoplasmic antibodies, soluble thrombomodulin, soluble interleukin-2 receptor, eosinophil cationic protein were elevated and returned to the normal range in remission. The combination of pulse corticosteroids, pulse cyclophosphamide, and high-dose intravenous immunoglobulin seemed effective for the acute phase of severe Churg-Strauss syndrome.

Adrenal Cortex Hormones↗
PubMed2006

Accuracy of a third (Dolphin Voyager) versus first generation pulse oximeter (Nellcor N-180) in predicting arterial oxygen saturation and pulse rate in the anesthetized dog.

OBJECTIVE: To compare the accuracy of a 3rd (Dolphin Voyager) versus 1st generation pulse oximeter (Nellcor N-180). STUDY DESIGN: Prospective laboratory investigation. ANIMALS: Eight adult dogs. METHODS: In anesthetized dogs, arterial oxygen saturation (SpO(2)) was recorded simultaneously with each pulse oximeter. The oxygen fraction in inspired gas (FiO(2)) was successively reduced from 1.00 to 0.09, with re-saturation (FiO(2) 0.40) after each breathe-down step. After each 3-minute FiO(2) plateau, SpO(2) and pulse rate (PR) were compared with the fractional arterial saturation (SaO(2)) and PR determined by co-oximetry and invasive blood pressure monitoring, respectively. Data analysis included Bland-Altman (B-A) plots, Lin's concordance correlation factor (rho(c)), and linear regression models. RESULTS: Over a SaO(2) range of 33-99%, the overall bias (mean SpO(2) - SaO(2)), precision (SD of bias), and accuracy (A(rms)) for the Dolphin Voyager and Nellcor N-180 were 4.3%, 4.4%, and 6.1%, and 3.2%, 3.0%, and 4.3%, respectively. Bias increased at SaO(2) < 90%, more so with the Dolphin Voyager (from 1.6% to 8.6%) than Nellcor N-180 (from 3.2% to 4.5%). The SpO(2) readings correlated significantly with SaO(2) for both the Dolphin Voyager (rho(c) = 0.94) and Nellcor N-180 (rho(c) = 0.97) (p < 0.001). Regarding PR, bias, precision, and accuracy (A(rms)) for the Dolphin Voyager and Nellcor N-180 were -0.5, 4.6, and 4.6 and 1.38, 4.3, and 4.5 beats minute(-1), respectively. Significant correlation existed between pulse oximeter and directly measured PR (Dolphin Voyager: rho(c) = 0.98; Nellcor N-180: rho(c) = 0.99) (p < 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: In anesthetized dogs with adequate hemodynamic function, both instruments record SaO(2) relatively accurately over a wide range of normal saturation values. However, there is an increasing overestimation at SaO(2) < 90%, particularly with the Dolphin Voyager, indicating that 3rd generation pulse oximeters may not perform better than older instruments. The 5.4-fold increase in bias with the Dolphin Voyager at SaO(2) < 90% stresses the importance of a 93-94% SpO(2) threshold to ensure an arterial saturation of >or=90%. In contrast, PR monitoring with both devices is very reliable.

Anesthesia↗
PubMed2003

532-nm Nd:YAG and 595-nm pulsed dye laser treatment of leg telangiectasia using ultralong pulse duration.

BACKGROUND: Telangiectatic leg veins have been treated using lasers with variable success. OBJECTIVE: We aimed to examine the efficacy and tolerability of a 595-nm pulsed dye laser (PDL) and a 532-nm Nd:YAG laser using ultralong pulse duration to improve leg telangiectasias with a single treatment. METHODS: Ten subjects with leg telangiectasias up to 1.0 mm in diameter participated in the study. The telangiectatic patch was divided into two approximately equal adjacent areas. The first area was treated with a 532-nm Nd:YAG laser at a fluence of 20 J/cm2 and a pulse duration of 50 ms using a contact cooling device. The second area was treated with a 595-nm PDL at a fluence of 25 J/cm2 and a pulse duration of 40 ms using cryogen spray precooling. Each area was treated once only. Photographic evaluation was used for an assessment of response. RESULTS: Two of 10 subjects had less than 25%, 3 had 25% to 50%, 2 had 50% to 75%, and 3 had more than 75% improvement after single treatment with a 532-nm Nd:YAG laser. Similarly, 2 of 10 subjects had less than 25%, 2 had 25% to 50%, and 6 had 50% to 75% improvement with the 595-nm PDL. Hyperpigmentation occurred in one subject treated with the 532-nm Nd:YAG laser and two subjects treated with the 595-nm PDL. No blistering, crusting, hypopigmentation, or scarring were observed. CONCLUSION: Both lasers using ultralong pulse width improved leg telangiectasias after a single treatment with minimal adverse reactions.

Adult↗
PubMed2004

Long-pulsed (6-ms) pulsed dye laser treatment of rosacea-associated telangiectasia using subpurpuric clinical threshold.

BACKGROUND: The pulsed dye laser (PDL), especially the 585-nm short-pulse width (450 micros) laser, has been extensively used in the treatment of facial telangiectasias. However, the resultant posttreatment purpura lasts for days and may not be cosmetically acceptable. OBJECTIVE: To examine the effect of long-pulsed (6 ms) PDL at subpurpuric clinical threshold in the treatment of rosacea-associated telangiectasia. METHODS: Twelve patients with rosacea-associated telangiectasia were recruited into the study. We used the 595-nm PDL at a pulse duration of 6 ms and titrated the fluence between 7 and 9 J/cm2 to produce immediate purpura lasting only a few seconds. Pretreatment cooling was achieved by cryogen spray. Assessment was made by comparing pretreatment and posttreatment photographs. Patients were evaluated 6 to 8 weeks after one PDL treatment. Results were reported as the percentage of reduction in the number of telangiectasias. Patients were asked for their own evaluation of improvement after treatment in terms of excellent, moderate, or poor outcome. Side effects such as pigmentary disturbance and scarring were also documented. RESULTS: Two of 12 patients had more than 75% improvement. Another two had 50% to 75% improvement, and five had 25% to 50% improvement. Overall, 9 (75%) of 12 patients had more than 25% improvement after a single treatment of PDL. None of the patients reported any lasting posttreatment purpura or complications. CONCLUSION: The long-pulsed 595-nm PDL using subpurpuric clinical threshold was effective for treatment of rosacea associated telangiectasia.

Adult↗
PubMed2003

Viability of cancer cells exposed to pulsed electric fields: the role of pulse charge.

The goal of this study was to collect a comprehensive set of data that related lethal effects of electric fields to the duration of the pulse. Electric pulses of different strengths and durations were applied to a suspension of HEp-2 cells (epidermoid carcinoma of the human larynx) using a six-needle electrode array connected through an autoswitcher to a square wave generator. Pulse durations varied from 50 micros to 16 ms and the ranges of electric field were adjusted for each duration to capture cell viabilities between 0% and 100%. After pulsation, cells were incubated for 44 h at 37 degrees C, and their viability was measured spectrophotometrically using an XTT assay. For each pulse duration (d), viability data were used to determine the electric field that killed half of the cells (E50). When plotted on logarithmic axes, E50 vs. d was a straight line, leading to a hyperbolic relationship: E50=const/d. This relationship suggests that the total charge delivered by the pulse is the decisive factor in killing HEp-2 cells.

Carcinoma, Squamous Cell↗
PubMedDate not supplied

Time resolved properties of acoustic pulses generated in water and in soft tissue by pulsed proton beam irradiation--a possibility of doses distribution monitoring in proton radiation therapy.

Time-resolved acoustic pulses generated in water and in soft tissue by pulsed proton beam irradiation were observed. The spatial resolution of depth dose distribution in the clinically applied beam intensity is estimated about 3 mm by means of TOF measurement. The dependence of the acoustic signal intensity on the temperature of medium was examined. Proportionality of acoustic pulse intensity to absorbed dose per pulse was confirmed as well. These results suggest the possibility of clinical application to monitor dose distribution in the patient's body during irradiation of pulsed proton beam.

Humans↗
PubMed1975

Computation of aortic pulse wave velocity and aortic pulse wave velocity and aortic extensibility from pressure gradient measurements.

This study is concerned with the computation of aortic pulse wave velocity based on simultaneous recordings of the aortic pressure gradient and first-time derivative of aortic pressure. These variables were recorded by means of a double-lumen catheter introduced in the aorta of four anesthetized closed chest dogs, and connected to critically damped manometer systems. Results of aortic pulse wave velocity were then compared: (i) to the true phase velocity obtained from spectra of apparent phase velocity, and (ii) to the pulse wave velocity computed from the time shift between maximum slopes of the pressure wave. From the aortic valves to 37 cm down the aortic trunk, pulse wave velocity increased from 410-460 cm/s to approximately 600-800 cm/s. Based on the wave propagation equation presented of Bramwell and Hill (Bramwell, J.C., and Hill, A. V. 1922. Proc. R. Soc. 93, 298-306), volumetric extensibility coefficients were computed from pulse wave velocity data. Results indicated that, from the aortic valves to 37 cm down to the aorta, the mean volumetric extensibility decreased from 0.43-0.56% deltaV/cm H2O to 0.16-0.25% deltaV/cm H2O (1 cm H2O = 94.1 N/m2).

Animals↗