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Prospective study of port wine stain treatment with dye laser: comparison of two wavelengths (585 nm vs. 595 nm) and two pulse durations (0.5 milliseconds vs. 20 milliseconds).

BACKGROUND AND OBJECTIVES: The conventional pulsed-dye laser (wavelength 585 nm, pulse duration 0.5 milliseconds) is seen as the standard treatment for port wine stains (PWS). Using the pulsed-dye laser at wavelengths of 590, 595, and 600 nm and at varying pulse durations of 1.5-40 milliseconds is one of the newest developments in the field, the therapeutic value of which has been examined in only a few studies. Treatment of PWS with short- and long-pulse dye lasers. Comparison of two wavelengths (585 nm vs. 595 nm) and two pulse durations (0.5 milliseconds vs. 20 milliseconds). STUDY DESIGN/MATERIALS AND METHODS: Fifteen patients with untreated PWS were included in a randomized prospective study with three different laser settings. Patients underwent one treatment session. The following treatment parameters were chosen at a uniform spot size of 7 mm: (1) 585 nm/0.5 milliseconds/5.5 J/cm(2), (2) 595 nm/0.5 milliseconds/5.5 J/cm(2), and (3) 595 nm/20 milliseconds/13 J/cm(2). The clearance as well as side effects was evaluated. All treatments were performed with cold air-cooling. Follow-up took place immediately, 2 days and 4 weeks after the treatment. The PWS was assigned a clearance score (CS) from 1 to 4 (1 = poor to 4 = excellent). RESULTS: Descriptively, 585 nm/0.5 milliseconds generated the best average CS of 2.7, followed by 595 nm/20 milliseconds (2.5) and 595 nm/0.5 milliseconds (1.6)); statistically, there is no difference between the CS of 585 nm/0.5 milliseconds and 595 nm/20 milliseconds. The best lightening rates overall were achieved in purple PWS (CS = 3.5) versus red (CS = 2.5) and pink (CS = 2.0). Purple PWS responded best to 585 nm/0.5 milliseconds; red and pink PWS yielded similar results with 585 nm/0.5 milliseconds and 595 nm/20 milliseconds. The setting, 595 nm/0.5 milliseconds was clearly not as effective as the other laser settings. Purpura, pain, and crusting were most commonly reported after treatments with 585 nm/0.5 milliseconds (93%/93%/33%), closely followed by treatments at 595 nm/20 milliseconds (86%/93%/20%). The settings 595 nm/0.5 milliseconds yielded the lowest rate of adverse effects (67%/60%/0%). Hypopigmentation only occurred in one case (585 nm/0.5 milliseconds), and there were no reports of hyperpigmentation or scarring. CONCLUSIONS: With respect to treating PWS, the conventional pulsed-dye laser set to 585 nm/0.5 milliseconds yields a significantly greater clearance rate than it does at a setting of 595 nm (with the same pulse duration, fluence, and spot size), although the former also entails the highest spectrum of adverse effects. In this study, purple PWS treated at these parameters showed the best results. In dealing with pink PWS, the results were similar to those of the conventional pulsed-dye laser when the pulse duration was increased to 20 milliseconds and fluence was increased. As a rule, the clearance rate corresponded to the extent of the postoperative purpura.

Adolescent↗

Design of adiabatic pulses for fat-suppression using analytic solutions of the Bloch equation.

Discrimination between signals produced by fat and by water is an important issue in MRI. One efficient approach is to perform fat-suppression by selective inversion. This technique exploits the transition region of a selective RF pulse to invert the longitudinal lipid magnetization while leaving the magnetization of the water protons untouched. The damaging effects of RF field inhomogeneity may be overcome by using pulses based on the adiabatic fast passage principle (AFP). In particular, the well-known sech/tanh adiabatic pulse is a robust and efficient pulse that is obtained as an analytic solution of the Bloch equation. In this paper, a wider class of analytic solutions of the Bloch equation is presented of which the sech/tanh driving function is merely a particular case. The new pulse exhibits an asymmetric distribution of magnetization with one transition sharper than the other. The sharper transition can be used to perform the required selective discrimination between signals. The resulting pulse features excellent adiabatic behavior. Moreover, the transition width of the new pulse can be reduced by a factor of about 2/3 with respect to an equal-duration sech/tanh pulse. The performance of the new pulse is compared with a similar sech/tanh pulse with the aid of a practical design example.

Adipose Tissue↗

Perfusion imaging using FOCI RF pulses.

Pulsed arterial spin-tagging techniques for perfusion measurements (e.g., echo planar MR imaging and signal targeting with alternating radiofrequency (EPISTAR), flow-sensitive alternating inversion recovery (FAIR), quantitative imaging of perfusion using a single subtraction (QUIPPS), uninverted FAIR (UNFAIR)) generally use hyperbolic secant (HS) pulses for spin inversion. The performance of these techniques depends on the inversion efficiency, as well as the sharpness of the slice profiles. Frequency offset corrected inversion (FOCI) pulses, a recently proposed HS variant, can provide slice profiles with edges that can be up to 10 times sharper than those obtained with conventional HS pulses. In this communication, the implementation and application of the C-shape FOCI pulse for perfusion imaging in rat brain with the FAIR technique is summarized. Despite providing a more rectangular slice profile than a conventional HS pulse, it is demonstrated both theoretically and experimentally that the FAIR perfusion signal is not increased by using a FOCI tagging pulse. However, the use of a FOCI inversion pulse is shown to significantly minimize static signal subtraction errors that are common with conventional HS pulses. Finally, the suitability of the pulse for perfusion studies is demonstrated, in vivo, on rat brain.

Animals↗

A computer algorithm for differentiating valid from distorted pulse oximeter waveforms in neonates.

Current pulse oximeter technology is fraught with a significant false alarm rate. This is mainly due to motion artifacts at the sensor site which distort the pulse waveform and render the computation of SaO2 invalid. If the pulse waveform could be automatically recognized as either normal or distorted, then only valid SaO2 values would be displayed. We observed that the systolic upstroke time (Sy) of the pulse waveform has a narrow and consistent range in normal appearing pulses. The systolic upstroke time (Sy) is the time from the onset of systole to the peak of the pulse waveform. Comparison of a preset range of Sy was made against Sy obtained by computer analysis of each pulse waveform. Visual examination of 14,090 pulses was carried out to determine the sensitivity and false positive rate of the algorithm. Sensitivity of computer detection of valid pulses was 92% with a positive predictive value of 92%. When used on line for continuous recording of SaO2 in patients, this simple algorithm has the potential to decrease the false alarm rate of pulse oximeters and improve the accuracy of long-term SaO2 recordings.

Algorithms↗

J pulses for multiplet-selective NMR.

Exact product operator solutions have been obtained for the evolution of weakly coupled spin-(1/2) I(m)S(n) systems during arbitrary RF irradiation of one spin. These solutions, which completely characterize the nature of J-coupling modulation during RF pulses, show that significant exchange occurs between single-spin magnetization and two-spin product operator states when the RF field strength is comparable to the coupling. In particular, a long (t(p) = [2J](-1) s), low-power (B(1) = J/2 Hz), constant amplitude pulse applied on resonance to one spin in an IS system completely interconverts the spinstates S(z) <--> 2S(x)I(z) and S(x) <--> 2S(z)I(z) when the RF is applied to the S spins, and interconverts S(x) <--> 2S(y)I(y) in 100% yield when the RF is applied to the I spins. Thus, these "J pulses," which select a bandwidth approximately equal to J Hz, may replace any combination of a (2J)(-1) delay period and a consecutive hard 90 degrees pulse in any polarization transfer or multiple quantum sequence. Although these rectangular pulses are highly frequency selective, in general they increase the replaced (2J)(-1) period by only a modest 40%, a time saving of a factor of 5 compared to existing pulses exhibiting the same selectivity. In favorable cases, there is no increase in duration of a pulse sequence using a particular type of J pulse, the 90(J) variety, which accomplishes the third spin state transformation listed above. J pulses will be advantageous for systems subject to rapid signal loss from relaxation and more generally for the enhanced operation of pulse sequences via the use of J modulation during RF irradiation.

Magnetic Resonance Spectroscopy↗

Determination of quadrupole parameters with a composite pulse for spurious signal suppression.

Spurious signals such as the piezoelectric signal from a ferroelectric crystal or the ringing signal from the NMR probe head tuned for low gyromagnetic ratio nuclei are often observed in pulsed NMR. Both signals are cancelled using the Hahn echo sequence with appropriate phase cyclings. The present paper applies a composite-pulse sequence to cancel the ringing signal. The main advantage of this sequence over the Hahn echo sequence is in the simplicity of optimizing the line intensity: the optimization of only one pulse duration for this sequence but of two pulse durations and the interpulse delay for the Hahn echo sequence. We are interested in half-integer quadrupole spins (I = 3/2, 5/2, 7/2, and 9/2), which means that we must consider the first-order quadrupole interaction during the pulses. For simplicity, we deal mainly with spin I = 3/2 nuclei. Since the central-line intensity depends on the ratio of the quadrupole coupling constant (QCC) to the amplitude of the RF pulse, we can determine the QCC from a featureless lineshape by fitting the variation of the experimental central-line intensity for increasing pulse duration with theoretical results. Contrary to the one-pulse sequence where the central-line intensity is proportional to the pulse duration if the latter is short, there is no such condition with the composite-pulse sequence. In other words, this sequence does not allow us to quantify the relative spin populations in powders. The size of the sample must be much smaller than that of the RF coil in order for the RF magnetic field to become homogeneous for the sample. We used (87)Rb (I = 3/2) in an aqueous solution of RbCl and in RbNb2O5F powder, (131)Xe (I = 3/2) of xenon gas physisorbed in Na-Y zeolite, and (23)Na (I = 3/2) in two well-known powders (NaNO3 and NaNO2) to support our theoretical result.

Journal Article↗

A comparison of paired-pulsed facilitation of AMPA and NMDA receptor-mediated excitatory postsynaptic currents in the hippocampus.

Paired-pulse facilitation of excitatory synaptic transmission was investigated in the CA1 region of rat hippocampal slices using whole-cell patch-clamp recording. To optimise the measurement of excitatory synaptic transmission, gamma-amino-butyric acid (GABA)-mediated synaptic inhibition was eliminated using both GABAA and GABAB antagonists. Pure alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents (EPSCs) were then isolated pharmacologically. Paired-pulse facilitation of either AMPA or NMDA receptor-mediated EPSCs (EPSCA and EPSCN, respectively) was investigated using two stimuli of identical strength delivered at intervals of between 25 and 1000 ms. The paired-pulse facilitation profiles of both EPSCA and EPSCN were similar. Paired-pulse facilitation of EPSCA was independent of holding potential. In contrast paired-pulse facilitation of EPSCN was markedly voltage-dependent; maximum facilitation was recorded at hyperpolarised membrane potentials. At positive membrane potentials there was little or no paired-pulse facilitation and, in most neurones, paired-pulse depression was observed. Voltage-dependence of paired-pulse facilitation of EPSCN was similar in the presence of nominal absence of Mg2+ in the bathing medium, and was unaffected by extensive dialysis of neurones with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). These data are consistent with a presynaptic locus for paired-pulse facilitation of EPSCA. However, paired-pulse facilitation of EPSCN involves postsynaptic factors.

Animals↗

Local intraarterial thrombolysis: in vitro comparison between automatic and manual pulse-spray infusion.

PURPOSE: Manual and automatic pulse-spray infusion techniques are compared in vitro to evaluate the efficacy of thrombolysis and the distribution of urokinase and saline solution within thrombus using a pulse-spray catheter. METHODS: A pulse-spray catheter was introduced into a human thrombus within a stenotic flow model. Automatic and manual pulsed infusion of urokinase and automatic pulsed infusion of saline solution were compared. To quantify the efficacy of thrombolysis, pressure gradients were recorded proximal and distal to the thrombus and during the course of infusion. Distribution of infused urokinase was assessed radiographically. RESULTS: The fastest and most homogeneous dissolution of the thrombus was achieved with automatic pulsed infusion of urokinase, shown by decreasing transthrombotic pressure gradients (p < 0.001, Wilcoxon, matched pairs). Manual pulsed infusion of urokinase or saline solution resulted in inhomogeneous thrombus dissolution and delayed thrombolysis. CONCLUSION: Application of automatic pulse-spray injectors seems beneficial for more effective and homogeneous intraarterial pulse-spray thrombolysis when compared with conventional manual pulsed technique.

Humans↗

Pulse oximeters demonstrate different responses during hypothermia and changes in perfusion.

PURPOSE: Several new pulse oximeters using updated algorithms are marketed as being resistant to motion and hypoperfusion. The purpose of this study was to compare the performance of three pulse oximeters under conditions of hypothermia and altered perfusion. METHODS: Ten male volunteers were enrolled in this study after Institutional approval and obtaining informed consent. The probe of the Dolphin 2100, Nellcor N-595, or Masimo SET radical version 4.2 was attached to the left index finger. Time from 'power on' to acquire the pulse wave and oxygen saturation (SpO2), time from the application of air tourniquet with 250 mmHg on the upper arm to loss of pulse wave and SpO2, and time from the release of the tourniquet to acquire the pulse wave and SpO2 were measured. Then, the patient's left hand and arm were cooled gradually to 27 degrees C dermal temperature in a room at 19 degrees C. The temperatures at loss of the pulse wave and SpO2 were recorded. RESULTS: The Nellcor N-595 was the slowest to detect SpO2 and pulse wave at 'power on'. The Masimo SET showed pulse wave and SpO2 longer than the other two monitors after 'tourniquet on'. The Nellcor N-595 was the fastest to show pulse wave and SpO2 following tourniquet release. CONCLUSION: The Masimo SET was the slowest to respond to the changes in perfusion, and the Nellcor N-595 responded the fastest. However, the Nellcor N-595 was the slowest to show SpO2 and pulse wave at 'power on'.

Adult↗

[The use of pulse oximetry in prilocaine induced methemoglobinemia].

During the last 15 years pulse oximetry has become a widely accepted method of monitoring during general and local anaesthesia. Pulse oximeters measuring with two wave-lengths are considerably affected by dyshaemoglobin. At concentrations up to 30%, CO-Hb cannot be distinguished from O2-Hb. Met-Hb, even in low concentrations, leads to a constant error of measurement; some authors recommended exploiting this for estimation of the Met-Hb concentration. To prove the aim of the present study was to test whether this error in measurement can be defined with one formula for different pulse oximeters. PATIENTS AND METHODS. In a prospective, randomized, double-blind study, 171 non-smoking patients with healthy lungs (ASA 1-3) who had received a plexus block for hand surgery were investigated. After premedication with 3.75-15 mg medazolam p.o. each patient received a total of 6 1O2 via a Hudson mask during the investigation. After 10 min the following pulse oximeters were put on the index finger: (1) Ohmeda BIOX 3700e, (2) Critikon Oxyshuttle, (3) Nellcor N 180. Simultaneously a venous blood sample was taken and analysed immediately with a Radiometer OSM3. The procedure was repeated 15, 30, 60 and 120 min after the plexus block. In 41 patients the plexus block was carried out with lidocaine (6 mg/kg body weight) and in 130 patients, with prilocaine (7 mg/kg body weight). RESULTS. There were no significant differences in age, sex and risk groups between the lidocaine and the prilocaine group. In the lidocaine group we were able to show that hyperoxic conditions can be maintained for 2 h with the method described. In the lidocaine group none of the pulse oximeters showed a psO2 less than 99%. Our results show significant differences between the three pulse oximeters. Therefore, in contrast to the convention followed in the literatur, the relation between Met-Hb and psO2 under hyperoxic conditions must be described with different formulas for each pulse oximeter as follows: (1) Ohmeda BIOX 3700e: Met-Hb = (101-psO2).0.6 (r = 0.94); (2) Critikon Oxyshuttle: Met-Hb = (101-psO2).0.7 (r = 0.83); (3) Nellcor N 180: Met-Hb = (101-psO2).0.9 (r = 0.92). DISCUSSION. Our results show that it is not possible to describe the connection between Met-Hb and psO2 for all pulse oximeters with only one formula, but it is possible to set up different formulas with good correlations for each of the three pulse oximeters. The reasons for the different sensitivity are probably the different algorithms used by the manufacturers. In spite of the good correlations we can not recommend Met-Hb estimation by pulse oximetry measurement with two wave-lengths, because the distinction of hypoxia and Met-Hb its not possible when hyperoxic conditions are not stable as they were in our controlled study. A low psO2 measured in patients with normal arterial blood gases can be an indication of Met-Hb, but the exact measurement of dyshaemoglobin is only possibly by using a co-oximeter.

Adult↗

The role of GABAergic inhibition in shaping directional selectivity of bat inferior collicular neurons determined with temporally patterned pulse trains.

This study examined the role of GABAergic inhibition in shaping directional selectivity of neurons in the inferior colliculus of the big brown bat, Eptesicus fuscus. When determined with temporally patterned pulse trains at different pulse repetition rates, 93 inferior colliculus neurons displayed three types of directional selectivity curves. A directionally selective curve always showed a maximum to a certain azimuthal angle (the best angle). A hemifield curve showed a maximum to a range of contralateral azimuthal angles. A non-directional curve did not show a maximum to any particular azimuthal angles. Directional selectivity curves of 42% neurons changed from hemifield or non-directional to directionally selective and the best angles of 16-21% neurons shifted toward the midline with increasing pulse repetition rate of pulse trains. Directional selectivity curves of most (74%) neurons that discharged impulses to each pulse of a pulse train also became sharper with increasing pulse repetition rate of pulse trains. Bicuculline application produced more pronounced broadening of directional selective curves of inferior colliculus neurons at higher than at lower pulse repetition rates. As a result, pulse repetition rate-dependent directional selectivity of inferior colliculus neurons was abolished. Possible mechanisms and biological significance of these findings are discussed.

Action Potentials↗

Synchronization of Na/K pump molecules by a train of squared pulses.

We experimentally studied the Na/K pump currents evoked by a train of squared pulses whose pulse-duration is about the time course of Na-extrusion at physiological conditions. The magnitude of the measured pump current can be as much as three-fold of that induced by the traditional single pulse measurement. The increase in the pump current is directly dependent on the number of pre-pulses. The larger the number of the pre-pulses is, the higher the current magnitude can be obtained. At a particular number of pre-pulses, the pump current becomes saturated. These results suggest that a large number of pre-pulses may synchronize the pump molecules to work at the same pace. As a result, the pump molecules may extrude Na ions at the same time corresponding to the stimulation pulses, and pump in K ions at the same time during the pulse intervals. Therefore, the measured pump current is three-fold of that measured by a single pulse where the outward and inward pump currents are canceled each other.

Animals↗

Reduction of laser-induced pathologic tissue injury using pulsed energy delivery.

Continuous-wave (CW) laser irradiation of cardiovascular tissues is characterized by 2 distinctive histologic findings: a superficial zone of coagulation necrosis and a subjacent zone of polymorphous lacunae. The present investigation was designed to determine whether such injury could be eliminated by altering the temporal profile of laser energy delivery. One hundred forty-five myocardial slices were irradiated with an air-tissue interface using CW laser irradiation at wavelengths of 488 to 515 nm (argon), 1,064 nm (Nd-YAG) and 10,600 nm (CO2). Pulsed laser irradiation included 248 nm (excimer); 355, 532 and 1,064 nm (Nd-YAG); and 515 nm (mode-locked argon). Energy profiles in the pulsed mode included a range of repetition rates (1 Hz to 256 MHz), pulse duration (0.2 to 358 ns) and pulse energies (2 nJ to 370 mJ). Resultant average powers were 0.1 to 38 W. Grossly visible charring of myocardial tissue was observed at all laser wavelengths when the laser energy profile was CW or pulsed at high repetition rates (more than 2 KHz) and low pulse energies (less than 3 mJ) independent of the wavelengths used. In contrast, when laser energy was pulsed at low repetition rates (less than 200 Hz) and large pulse energies (more than 10 mJ), neither gross nor histologic signs of thermal injury were observed. Pathologic injury associated with laser-induced tissue ablation may thus be substantially reduced by use of pulsed energy delivery at low repetition rates. Potential advantages of pulsed laser energy include a more benign healing process, a less thrombogenic surface, and improved preservation of structural tissue integrity.

Animals↗

Stimulus parameters affecting paired-pulse depression of dentate granule cell field potentials. II. Low-frequency stimulation.

Low frequency (1 Hz) stimulation of the perforant path produces a depression in the population spike (PS) of dentate granule cell field potentials and also may affect the strength of paired pulse depression. The effects of 1 Hz stimulation (30 s train) on paired pulse depression (20 and 200 ms interpulse intervals, IPI) were evaluated in the unanesthetized rat under two conditions: (i) when the stimulus intensity of both pulses was increased simultaneously (5-100%); and (ii) when the stimulus intensity of the first (conditioning) pulse was increased (5-100%), while the stimulus intensity of the second (test) pulse was held constant (50%). The test PS amplitude was predicted based upon either the conditioning PS amplitude at the end of the 1 Hz train or upon the additive effects of paired pulse depression and 1 Hz stimulation. These predicted values then were assessed for the best fit to observed values following 1 Hz trains. Under both stimulus conditions, the 1 Hz depression in the conditioning PS amplitude exhibited characteristics that were identical to late paired pulse depression recorded before the train. A decrease in the test PS amplitude also was observed following 1 Hz stimulation at the 20 and 200 ms IPIs. The best fit to observed values of the test PS at the end of 1 Hz trains was provided by estimates based upon the additive effects of 1 Hz stimulation and paired pulse depression. These results indicate that the strength of paired pulse depression in the unanesthetized rat is unchanged following 1 Hz stimulation, and further, that the 1 Hz depression in dentate granule cell field potentials most likely reflects the cumulative influence of late paired pulse depression.

Action Potentials↗

Enhancement of paired-pulse depression in the dentate gyrus in vivo by the NMDA antagonist, MK-801, and electrical kindling.

We have previously demonstrated that late paired-pulse depression of dentate granule cell field potentials decreases when stimulus intensity is increased from moderate to high levels. Voltage-dependent N-methyl-D-aspartate (NMDA) currents are increasingly activated within this stimulus range, and are enhanced following the development of kindled seizures. The NMDA antagonist, MK-801 (0.25 and 1.0 mg/kg, i.p.), was used in the present experiments to evaluate the contribution of NMDA currents to the loss of late paired-pulse depression at high stimulus intensities in naive and kindled rats. Paired-pulse stimulus intensity functions were obtained from animals prepared with chronic electrodes in the perforant path and dentate gyrus. MK-801 administration had no effect on the stimulus intensity function for early paired-pulse depression (20-30 ms interpulse intervals, IPI) in either preparation. Late paired-pulse depression (150-500 ms IPI) was significantly enhanced in naive rats by MK-801. In contrast, MK-801 had no effect on the potentiation of late paired-pulse depression recorded from kindled animals. These findings suggest that the ability of NMDA currents to reduce the strength of late paired-pulse depression in naive animals is altered following the development of kindled seizures. A decrease in late paired-pulse depression was observed at high stimulus intensities under all experimental conditions. The latter findings indicate that the processes responsible for the reduction in late paired-pulse depression at high stimulus intensities are unaffected by either NMDA or kindling-induced modulation of late paired-pulse depression.

Animals↗

Microstructural musical linguistics: composers' pulses are liked most by the best musicians.

Western music is a combination of notated structure plus microstructure. Composers' pulses, as precise microstructural functions, were tested with five groups of subjects of graded musical proficiency: (1) 10 famous artists including Vladimir Ashkenazy, Yehudi Menuhin, Paul Badura-Skoda and others; (2) 14 Julliard School of Music graduate students; (3) 19 Manhattan School of Music graduate students; (4) 51 Australian conservatory students; and (5) 41 non-music students (total, 135 subjects). Composers' pulses consist of combined amplitude and timing warps specific to each composer--the composer's pulse matrix. Each subject listened to and scored 40 versions of 10 short music examples (not selected by the author) of eight bars each, composed by Beethoven, Mozart, Haydn and Schubert, performed by computer, in which composers' pulses, as developed by Clynes (1983, 1985a,b, 1986, 1987), were incorporated in a two-level hierarchic pulse configuration, and interchanged. Each example was heard with the pulses of those four composers in turn, in quasi-random sequence, one performance thus incorporating the "right" pulse and three the "wrong" ones. Results show dramatically that the greater the musical proficiency, the more marked the preference for the "right" pulse (p < .0001). Non-musicians as a group showed a similar tendency of preference, but typically to a considerably less pronounced degree. Further studies suggest that longer excerpts (32 bars) and repeated hearing would help non-musicians also to better understand composers' pulses. A theory of music as a double stream is introduced. The results suggest that the composers' pulse matrices posited by Clynes as a first approximation are in fact appropriately meaningful. Brain function aspects of the meaningful discrimination of such tiny time differences are discussed.

Adolescent↗

Enhanced responsiveness to parathyroid hormone and induction of functional differentiation of cultured rabbit costal chondrocytes by a pulsed electromagnetic field.

Pulsed electromagnetic fields promote healing of delayed united and ununited fractures by triggering a series of events in fibrocartilage. We examined the effects of a pulsed electromagnetic field (recurrent bursts, 15.4 Hz, of shorter pulses of an average of 2 gauss) on rabbit costal chondrocytes in culture. A pulsed electromagnetic field slightly reduced the intracellular cyclic adenosine 3',5'-monophosphate (cAMP) level in the culture. However, it significantly enhanced cAMP accumulation in response to parathyroid hormone (PTH) to 140% of that induced by PTH in its absence, while it did not affect cAMP accumulation in response to prostaglandin E1 or prostaglandin I2. The effect on cAMP accumulation in response to PTH became evident after exposure of the cultures to the pulsed electromagnetic field for 48 h, and was dependent upon the field strength. cAMP accumulation in response to PTH is followed by induction of ornithine decarboxylase, a good marker of differentiated chondrocytes, after PTH treatment for 4 h. Consistent with the enhanced cAMP accumulation, ornithine decarboxylase activity induced by PTH was also increased by the pulsed electromagnetic field to 170% of that in cells not exposed to a pulsed electromagnetic field. Furthermore, stimulation of glycosaminoglycan synthesis, a differentiated phenotype, in response to PTH was significantly enhanced by a pulsed electromagnetic field. Thus, a pulsed electromagnetic field enhanced a series of events in rabbit costal chondrocytes in response to PTH. These findings show that exposure of chondrocytes to a pulsed electromagnetic field resulted in functional differentiation of the cells.

Alprostadil↗

A prospective randomized evaluation of biphasic versus monophasic waveform pulses on defibrillation efficacy in humans.

Biphasic waveforms have been suggested as a superior waveform for ventricular defibrillation. To test this premise, a prospective randomized intraoperative evaluation of defibrillation efficacy of monophasic and biphasic waveform pulses was performed in 22 survivors of out of hospital ventricular fibrillation who were undergoing cardiac surgery for implantation of an automatic defibrillator. The initial waveform used in a patient for defibrillation testing, either monophasic or biphasic, was randomly selected. Subsequently, each patient served as his or her own control for defibrillation testing of the other waveform. The defibrillation threshold was defined as the lowest pulse amplitude that would effectively terminate ventricular fibrillation with a single discharge delivered 10 s after initiation of an episode of ventricular fibrillation induced with alternating current. Each defibrillation pulse was recorded oscilloscopically, and defibrillation pulse voltage, current, resistance and stored energy were measured. Fifteen (68%) of the 22 patients had a lower defibrillation threshold with the biphasic pulse, 3 (14%) had a lower threshold with the monophasic pulse and 4 (18%) had equal defibrillation thresholds (within 1.0 J) regardless of waveform. The mean leading edge defibrillation threshold voltage was 317 +/- 105 V when the monophasic pulse was used and 267 +/- 102 V (16% less) when the biphasic pulse was used (p = 0.008). Mean leading edge defibrillation threshold current was 7.9 +/- 3.7 A when the monophasic pulse was used and 6.8 +/- 3.8 A (14% less) when the biphasic pulse was used (p = 0.051).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗