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At least 235 records · Page 13Linked to original sources
PubMed1992

Comparative studies of protein biosynthesis: the main experimental parameters in pulse and pulse-chase experiments must be standardized.

The influence of experimental conditions was investigated in pulse and pulse-chase experiments involving L-[35s]methionine incorporation by isolated rat hepatocytes. The incorporation of the labelled amino acid must be linear as a function of dose and time, and similar hepatocyte densities should be used to compare radioactive uptake. High hepatocyte densities give greater precision. In pulse-chase experiments, it was shown that a pool of free radioactivity moves progressively during the chase phase from the intracellular compartment. Protein-associated radioactivity must therefore be expressed as a function of both total radioactive uptake and total labelled protein.

Albumins↗
PubMed1997

Multicenter study on the clinical value of fetal pulse oximetry. I. Methodologic evaluation. The French Study Group on Fetal Pulse Oximetry.

OBJECTIVE: Our purpose was to evaluate the feasibility of intrapartum fetal pulse oximetry, the distribution of fetal oxygen saturation values, and the relationship with the neonatal outcome in a population with an abnormal fetal heart rate. STUDY DESIGN: A prospective multicenter observational study was performed from June 1994 to November 1995. Fetal oxygen saturation was continuously recorded with use of a Nellcor N-400 fetal pulse oximeter in case of an abnormal fetal heart rate during labor. Simultaneous readings of fetal oxygen saturation and fetal blood analysis were obtained at inclusion and before birth. Feasibility, adverse effects, distribution of fetal oxygen saturation values, and relationship with neonatal outcome were assessed. RESULTS: One hundred seventy-four patients were included. From 172 attempted sensor placements, the procedure was impossible in three cases and fetal oxygen saturation values were obtained in 164 cases (95.3%). Physicians considered sensor placement an easier task than an attempt at fetal blood analysis (easy in 87.5% vs 78.9% for fetal blood analysis, p = 0.03). The mean reliable signal time (+/- SD) was 64.7% +/- 32% during the first stage. There were no serious adverse effects in the study population. The mean fetal oxygen saturation during the first stage of labor was 42.2% +/- 8.0% (10th to 90th percentile range 30% to 53%). Fetal oxygen saturation was significantly correlated with scalp pH (r = 0.29, p = 0.01) but not with neonatal umbilical artery pH or gas values. There was a significant association between low fetal oxygen saturation (< 30%) and poor neonatal condition. CONCLUSION: The feasibility of fetal pulse oximetry is satisfactory in clinical practice. It is easy to use and provides a fair rate of recorded values, even in a population with suspicion of fetal distress. A low fetal oxygen saturation is significantly associated with an abnormal neonatal outcome.

Adult↗
PubMed2002

Paired pulse facilitation is turned into paired pulse depression in hippocampal slices after epilepsy induced by 4-aminopyridine in vivo.

Modifications in synaptic plasticity seem to play a key role in the origin and persistence of epilepsy. 4-Aminopyridine (4-AP) induces intense and long lasting epileptic seizures and neurodegeneration when applied into the hippocampus in vivo, effects that seem to be mediated by overactivation of glutamate receptors due to the enhancement of glutamate release from nerve endings. We have studied presynaptic modifications of CA1 responses, using the paired pulse paradigm, in hippocampal slices obtained from 4-AP-treated rats killed during epileptic activity (ex vivo). The paired pulse facilitation (PPF) observed in control slices with interstimulus intervals of 10-30 ms was changed into paired pulse depression (PPD) after 100 microM 4-AP added in vitro. A strikingly similar change was observed in the ex vivo slices even though 4-AP was no longer present in the tissue. We conclude that the facilitation of glutamate release induced by 4-AP becomes chronic after a transient exposure to the drug. This suggests that the facilitated neurotransmitter release induced by 4-AP triggers a more permanent plastic change that may be responsible for the persistence of epilepsy.

4-Aminopyridine↗
PubMed1997

Depth of morphologic skin damage and viability after one, two, and three passes of a high-energy, short-pulse CO2 laser (Tru-Pulse) in pig skin.

BACKGROUND: CO2 laser energy is absorbed by water, which is present in all tissue. The depth of penetration of CO2 lasers is narrow with minimal reflection, scatter, or transmission. However, thermal damage has limited the usefulness of conventional, continuous-wave CO2 lasers for debridement as demonstrated by wound healing studies. The development of high-energy CO2 lasers, with pulse durations that are less than the thermal relaxation time of tissue, have made vaporization of skin for resurfacing and wound debridement possible because of the decreased risk of thermal damage. OBJECTIVE: This study was performed to evaluate thermal damage produced by a CO2 laser. METHODS: Routine histopathologic examination and nitroblue-tetrazolium chloride (NBTC) staining were used to evaluate the depth of tissue damage and viability in weanling pig skin after one, two, and three passes of the laser. RESULTS: At a pulse energy of 300 mJ, with a pulse duration of 60 microseconds, one pass of the laser produced vaporization of the epidermis with minimal thermal damage. Two passes produced areas of denatured collagen with loss of viable cells in the superficial papillary dermis. Three passes extended the damage into the papillary dermis. CONCLUSION: Hyalinization of collagen appears to correspond well with the level of thermal damage as measured by NBTC staining. Our findings suggest that the energy necessary to vaporize the dermis may be greater than that needed to vaporize epidermis.

Animals↗
PubMed2003

Improving W-band pulsed ENDOR sensitivity--random acquisition and pulsed special TRIPLE.

Two approaches for improving the signal-to-noise ratio (S/N) of W-band pulsed electron-nuclear double resonance (ENDOR) spectra are presented. One eliminates base-line problems while the other enhances the ENDOR effect. High field ENDOR spectra measured at low temperatures often suffer from highly distorted base-lines due to the heating effect of the RF pulses that causes some detuning of the cavity and therefore leads to a reduction in the echo intensity. This is a severe problem because it often masks broad and weak ENDOR signals. We show that it can be eliminated by recording the ENDOR spectrum in a random, rather than the standard sequential variation of the RF frequency. The S/N of the ENDOR spectrum can be significantly enhanced by the application of the pulse analog of the continuous wave (CW) special TRIPLE experiment. While this experiment is not applicable in the solid state at conventional X-band frequencies, at W-band it is most efficient. We demonstrate the efficiency of the special TRIPLE Davies and Mims experiments on single crystals and orientationally disordered systems.

Copper↗
PubMed2003

Variable pulse frequency-doubled Nd:YAG laser versus flashlamp-pumped pulsed dye laser in the treatment of port wine stains.

The flashlamp-pumped pulsed dye laser (FPDL) is regarded as the gold standard in the treatment of port wine stains. The purpose of this prospective, intra-individual, comparative clinical study was to investigate whether a frequency-doubled variable pulsed Nd:YAG laser (frequency-doubled Nd:YAG) is equally as safe and effective as established lasers. Forty-three patients with port wine stains were included in the study. Test treatments were performed using the frequency-doubled Nd:YAG laser (532 nm; 4 mm psi; 5-50 ms; 5.5 to 15 J/cm2) versus the FPDL (585 nm; 450 micros; 7 mm psi; 6 J/cm2). After 6 weeks, a full lesional treatment was performed using the device and the parameters showing the best clearance and the fewest side effects. The clearance of the lesions was generally good to fair. With the exception of poor results at 5 ms and 5.5 J/cm2 with the frequency-doubled Nd:YAG laser, there were no significant differences between the two laser devices. Scar formation, nevertheless, occurred in only 3% of the FPDL-treated sites versus up to 18% of the frequency-doubled Nd:YAG sites, increasing with pulse duration. In port wine stains, the FPDL remains the therapy of choice because of the somewhat better results and a lower frequency of side effects, especially scarring.

Adolescent↗
PubMed1977

Turbulence measurement by the pulse luminescence method using a nitrogen pulse laser.

In order to visualize and measure with ease the velocity distribution and diffusion of turbulent flow, the pulse luminescence method was investigated. Turbulence intensity was obtained from the turbulent diffusion patterns by Taylor's diffusion theory. Apparatus was developed for easier measurement. A nitrogen pulse laser was used for instantaneous, high-power excitation. With the use of a night vision scope a bright image was recorded by a TV camera and video tape recorder. The optimum concentration of LC-G1A luminescent particles was about 0-05% wt for the measurement. High fidelity of the particles as an indicator of the fluid velocity was confirmed. It was demonstrated that the turbulence intensity could be visualized and measured quantitatively by the pulse luminescence method.

Lasers↗
PubMed2005

Effectiveness of photodynamic therapy with topical 5-aminolevulinic acid and intense pulsed light versus intense pulsed light alone in the treatment of acne vulgaris: comparative study.

BACKGROUND: Photodynamic therapy (PDT) involves the activation of a photosensitizing agent by light to produce oxygen intermediates that destroy target tissues. Topical 5-aminolevulinic acid (ALA) is converted to protoporphyrin IX, a very potent photosensitizer, which accumulates in human skin, particularly in the epidermis and its appendages. OBJECTIVE: To study the effect of PDT in acne vulgaris using topical ALA and intense pulsed light (IPL). METHODS: Thirteen individuals with varying degrees of acne were treated after a 3-week washout period. Twenty percent ALA hydrochloride (DUSA Pharmaceuticals, Wilmington, MA, USA) was applied to half of the face, and after 3 hours, the whole face was exposed to intense pulsed light (Quantum SR, Lumenis, Santa Clara, CA, USA) using a 560 nm cutoff filter starting at a fluence of 26 J/cm. The procedure was done twice at 2-week intervals, and the patients were clinically evaluated on the second, fourth, and eighth weeks. RESULTS: All patients had no apparent improvement on the second week on both facial halves. In fact, some of the patients developed acute acneiform eruptions on the side treated with ALA. By the fourth week, however, most of the patients had visible improvement of facial acne that was more significant on the ALA-treated side of the face. This persisted until the eighth week post-treatment. On the other hand, the facial half treated with intense pulsed light only showed a return to baseline of their facial acne. CONCLUSION: ALA-IPL are beneficial in the management of acne vulgaris and may be used in combination with other forms of acne treatment or may be an alternative treatment for patients who do not want to take systemic retinoids.

Acne Vulgaris↗
PubMed2006

The effect of varying pulse duration, wavelength, spot size, and fluence on the response of previously treated capillary vascular malformations to pulsed-dye laser treatment.

Modern lasers allow different parameters to be altered in an effort to gain further improvement in otherwise resistant capillary vascular malformations (CMs). The aim of this study was to examine the effect of changing the pulse duration, wavelength, spot size, and fluence on the color and capillary architecture of 585-nm pulsed-dye, laser-resistant CMs. Eighteen patients were assessed with a depth measurement videomicroscope (DMV) before and after 12 test patches with ScleroPlus and V-Beam lasers at specified parameters. In the majority of the test patch areas, there was little improvement after treatment. However, 44% of patients had greater than 75% clearance in at least 1 test patch site. This study demonstrates that both lasers can achieve further lightening in 585 nm 0.45 msec pulsed-dye laser-resistant CMs. However, in CMs consisting of small-diameter deep vessels, further improvement is unlikely.

Capillaries↗
PubMed2004

Energy-landscape-model analysis for irreversibility and its pulse-width dependence in cells subjected to a high-intensity ultrashort electric pulse.

We provide a simple, but physical analysis for cell irreversibility and apoptosis in response to an ultrashort (nanosecond), high-intensity electric pulse. Our approach is based on an energy landscape model for determining the temporal evolution of the configurational probability function p(q). The primary focus is on obtaining qualitative predictions of a pulse width dependence to apoptotic cell irreversibility that has been observed experimentally. The analysis couples a distributed electrical model for current flow with the Smoluchowski equation to provide self-consistent, time-dependent transmembrane voltages. The model captures the essence of the experimentally observed pulse-width dependence, and provides a possible physical picture that depends only on the electrical trigger. A number of interesting features are predicted.

Biophysics↗
PubMed1991

Potential errors in pulse oximetry. I. Pulse oximeter evaluation.

There is no absolute reference for oxygen saturation, although multiwavelength in vitro oximeters are accepted as the 'gold standard'. Regardless of whether fractional or functional saturation is used by manufacturers to calibrate their oximeters, evaluation against fractional saturation is recommended since this is the clinically relevant variable. The use of standard notation and comparisons based on bias and precision is recommended. The accuracy of pulse oximetry is intrinsically limited by the use of only two wavelengths, and is dependent on the initial calibration population. The empirical algorithms used to convert the signal to its 'readout value' and the quality control of hardware may both be important sources of variability between oximeters. Change in blood temperature may introduce errors in pulse oximeter and in vitro oximeter saturation readings, but these will be clinically insignificant. Changes in blood pH should not decrease pulse oximetry accuracy.

Humans↗
PubMed1989

Electrical pulse train and single pulse stimulation of the small intestine: acute and chronic studies in the dog.

In vitro tests have shown that electric currents may lead either to relaxation or contraction of the bowel wall. Because voluntary changes of the intestinal motility could be useful in the treatment of intestinal disorders, we investigated the reactions elicited by electrostimulation of the small intestine in the intact animal. Stimulating electrodes, electroenteromyogram electrodes, and pressure monitoring tubes were used to instrument a 5-cm segment of the proximal jejunum in five dogs in acute studies and in two dogs in chronic studies. Single pulses of 200 ms elicited a pulsatile pressure increase of 10-35 mm Hg. Pulse train stimulation was followed by a more complex reaction. Trains of 500-microseconds, 910-Hz pulses at 30 mA evoked a 50-80 mm Hg pressure increase, 1-ms, 10-Hz trains caused an initial relaxation, followed by a pressure increase during stimulation and a further pressure increase after termination of the burst. These reactions were similar to those observed by Campbell working with colon in vitro. The chronic fasted animals reacted to 500 microseconds, 910-Hz, 25-mA stimulation with a mean pressure increase of 26 mm Hg (n = 10) and to 200-microseconds, 1.67-kHz, 30 mA stimulation with 28 mm Hg (n = 16). In the fasted animals a pressure increase during stimulation predominated (Campbell type I), whereas in the fed animal an additional off response after termination of the stimulation was the most common type of reaction (Campbell type II). Initial relaxation (Campbell type III) could be elicited by 1-ms, 10-Hz trains.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Intracellular kinetics of ATX-S10.Na(II) and its correlation with photochemical reaction dynamics during a pulsed photosensitization process: effect of pulse repetition rate.

Although photodynamic therapy with pulsed light excitation has interesting characteristics, its photosensitization mechanism has not been fully elucidated. In this study, we showed that the intracellular kinetics of ATX-S10.Na(II), a lysosomal sensitizer, was closely related to photochemical reaction dynamics during photodynamic treatment of A549 cells with nanosecond pulsed light. Fluorescence microscopy revealed that at high frequencies of 10 and 30 Hz the sensitizer initially localized mainly in lysosomes but that it started to be redistributed to the cytosol in certain ranges of radiant exposures. These ranges were found to coincide with a regime of fluorescence degradation with limited oxygen consumption. On the other hand, at 5 Hz, there was no such a discontinuous behavior in the sensitizer redistribution characteristics throughout the period of irradiation; this was consistent with the fact that no reaction switching was observed. Two possible reasons for the appearance of the regime with limited oxygen consumption are discussed: participation of an oxygen-independent reaction and change in the microenvironment for the sensitizer caused by lysosomal photodamage. The pulse frequency-dependent intracellular kinetics of the sensitizer also explains our previous results showing higher cytotoxicity at 5 Hz than at 10 and 30 Hz.

Adenocarcinoma↗
PubMed1989

Pulse oximetry at the roadside: a study of pulse oximetry in immediate care.

The measurement of tissue oxygen saturation with a pulse oximeter is of proved value in the hospital setting. The development of a portable oximeter has allowed this investigation to be performed during the prehospital phase of a patient's care. Pulse oximetry was performed at the roadside in 25 patients with abnormal trauma scores and found to be of benefit in detecting and monitoring hypoxia in patients with airway obstruction, depressed respiration due to head injury, and, in particular, with closed chest injuries. There were no practical difficulties associated with the use of the instrument either at the roadside or in a moving ambulance. The portable pulse oximeter is a valuable aid in the prehospital monitoring of patients with trauma.

Accidents, Traffic↗
PubMed2000

Short-term fasting selectively suppresses leptin pulse mass and 24-hour rhythmic leptin release in healthy midluteal phase women without disturbing leptin pulse frequency or its entropy control (pattern orderliness).

Nutritional signals strongly regulate neuroendocrine axes, such as those subserving release of LH, GH, and TSH, presumptively in part via the adipocyte-derived neuroactive peptide leptin. In turn, leptin release is controlled by both acute (fasting) and long-term (adipose store) nutrient status. Here, we investigate the neuroendocrine impact of short-term (2.5-day) fasting on leptin release in healthy young women studied in the steroid-replete midluteal phase of the normal menstrual cycle. Eight women each underwent 24-h blood sampling at 10-min intervals during a randomly ordered 2.5-day fasting vs. fed session in separate menstrual cycles. Pulsatile leptin release was quantified by model-free Cluster analysis, the orderliness of leptin patterns by the approximate entropy statistic, and nyctohemeral leptin rhythmicity by cosinor analysis. Mean (24-h) serum leptin concentrations fell by 4.6-fold during fasting; namely, from 15.2+/-2.3 to 3.4+/-0.6 microg/L (P = 0.0007). Cluster analysis identified 13.9+/-1.1 and 14.3+/-1.1 leptin peaks per 24 h in the fed and fasting states (P = NS), and unchanging leptin interpeak intervals (89+/-5.4 vs. 92+/-5.3 min). Leptin peak area declined by 4.2-fold (155+/-21 vs. 37+/-7 area units, P = 0.004), due to a reduction in incremental leptin pulse amplitude (4.4+/-0.7 vs. 1.0+/-0.13 microg/L, P = 0.0011). The cosine amplitude and mesor (mean) of the 24-h leptin rhythm decreased by 4-fold, whereas the acrophase (timing of the nyctohemeral leptin peak) remained fixed. The approximate entropy of leptin release was stable, thus indicating preserved orderliness of leptin release patterns in fasting. Cross-correlation analysis revealed both positive (fed) and negative (fasting) leptin-GH relationships, but no leptin-LH correlations. In summary, short-term (2.5-day) fasting profoundly suppresses 24-h serum leptin concentrations and pulsatile leptin release in the sex steroid-sufficient midluteal phase of healthy women via mechanisms that selectively attenuate leptin pulse area and incremental amplitude. In contrast, the pulse-generating, nyctohemeral phase-determining, and entropy-control mechanisms that govern 24-h leptin release are not altered by acute nutrient restriction at this menstrual phase. Leptin-GH (but not leptin-LH) showed nutrient-dependent positive (fed) and negative (fasting) cross-correlations. Whether similar neuroendocrine mechanisms supervise altered leptin signaling during short-term nutrient restriction in men, children, or postmenopausal women is not known.

Adult↗
PubMed2003

Wavelength-tunable optical short-pulse generation by mutual pulse injection seeding of two gain-switched Fabry-Perot laser diodes.

A simple and robust system is presented to generate wavelength-tunable optical short pulses by use of two gain-switched Fabry-Perot laser diodes in a mutual pulse injection-seeding scheme. The operating wavelength of the optical pulses is flexibly selected by adjustment of a tunable filter, and its intensity is enhanced with an erbium-doped fiber amplifier. The side-mode suppression ratio achieved by the system is larger than 26 dB over a wavelength region of 25 nm and higher than 31 dB within an 18-nm wavelength.

Journal Article↗
PubMed2003

Dual-pulse laser-induced breakdown spectroscopy with combinations of femtosecond and nanosecond laser pulses.

Nanosecond and femtosecond laser pulses were combined in an orthogonal preablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS) configuration. Even without full optimization of interpulse alignment, ablation focus, large signal, signal-to-noise ratio, and signal-to-background ratio enhancements were observed for both copper and aluminum targets. Despite the preliminary nature of this study, these results have significant implications in the attempt to explain the sources of dual-pulse LIBS enhancements.

Journal Article↗
PubMed2003

High-conversion-efficiency optical parametric chirped-pulse amplification system using spatiotemporally shaped pump pulses.

High-conversion-efficiency, high-stability optical parametric chirped-pulse amplification is demonstrated with a spatiotemporally shaped pump laser system. Broadband 5-mJ pulses are produced at a 5-Hz repetition rate with a pump-to-signal conversion efficiency of 29% and energy stability better than 2% rms. To our knowledge this is the highest conversion efficiency and stability achieved in an optical parametric chirped-pulse amplification system.

Journal Article↗