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PubMed1988

Divergent effects of the antiestrogen tamoxifen and of estrogens on luteinizing hormone (LH) pulse frequency, but not on basal LH levels and LH pulse amplitude in men.

We studied the role of estrogens on LH pulse modulation in men in two ways. Firstly, we compared LH pulse frequency and amplitude in 13 normal men before and after 6 weeks administration of the antiestrogen tamoxifen (10 mg twice daily). Secondly, we compared LH pulse frequency and amplitude between a group of 10 agonadal men not receiving sex steroid treatment and a group of 9 agonadal men (male to female transsexuals) continuously treated with 50 micrograms ethinyl estradiol/day. Tamoxifen administration to normal men resulted in a significant rise in the mean serum LH level from 5.7 +/- 1.3 (+/- SD) to 10.1 +/- 2.4 U/L, which was associated with significant increases in LH pulse frequency (from 4.2 +/- 1.5 to 5.8 +/- 1.7/7 h) and LH pulse amplitude (from 3.8 +/- 0.9 to 4.6 +/- 0.7 U/L). In the group of agonadal men the mean LH pulse frequency was 6.8 +/- 1.5/7 h, while it was 5.9 +/- 1.7/7 h in the estrogen-treated agonadal group (P = NS). The mean serum LH level and LH pulse amplitude were, however, significantly lower in the estrogen-treated agonadal men than in the agonadal men (14.7 +/- 7.0 vs. 34.3 +/- 8.6 and 4.1 +/- 1.8 vs. 7.4 +/- 1.8 U/L, respectively). We conclude that estrogens reduce basal LH levels and LH pulse amplitude. With regard to the modulation of LH pulse frequency our data provide contradictory results. While an antiestrogen increased LH pulse frequency in normal men, estrogen alone produced no change in LH pulse frequency in agonadal men. The study design in the agonadal men ignores the possible interaction of the two major testicular hormones (estradiol and testosterone) on gonadotropin secretion. Therefore, a possible explanation for this discrepancy in the effects of antiestrogen and estrogen could be an interaction between estrogens and androgens on gonadotropin secretion at the level of the LHRH pulse generator.

Adult↗
PubMed2006

Reproducibility of automated pulse wave velocity measurement during exercise. Running head: pulse wave velocity during exercise.

Pulse wave velocity measurement is used as an index of arterial stiffness. The purpose was to evaluate the reproducibility of pulse wave velocity measurement at rest, during exercise and recovery from exercise, using an automated device. Twelve healthy young adults (mean age 22.0 +/- 3.1 yrs) underwent an upright submaximal cycle test on two separate occasions, one week apart. Pulse wave velocity, systolic and diastolic blood pressures and heart rate were assessed at rest, during the last 2 min of exercise and 10 min later. Pulse wave velocity was measured on the upper limb and the forearm by the cross-correlation function of photoplethysmography and Doppler signals. Brachial artery pulse wave velocity was calculated from upper limb and forearm pulse wave velocities. No significant difference was found on duplicate measurements of heart rate, systolic and diastolic blood pressures at rest, during exercise and recovery, showing that pulse wave velocity was measured under similar conditions. Coefficient of variation for upper limb and forearm pulse wave velocities ranged from 2.9 to 5.9% at rest and during recovery, and were respectively 2.9% and 8.3% during exercise. However, coefficient of variation for brachial pulse wave velocity was 7.7 and 10.3% at rest, 15.7% during exercise, and 5.8% during recovery. During exercise, pulse wave velocity measurements were satisfying, but indirect assessment of brachial artery pulse wave velocity showed poor reproducibility. Thus, upper limb and forearm pulse wave velocities may be used during exercise to assess the effect of training or drugs on arterial wall mechanical properties.

Adult↗
PubMed1988

Effects of pulse frequency on single-unit baroreceptor activity during sine-wave and natural pulses in dogs.

1. Previous studies using sine-wave pulses have shown that changes in pulse frequency do not alter single-unit activity per unit time. Since baroreceptor activity is phasic with most of the activity occurring in systole, we reasoned that the lack of effect of pulse frequency is due to the associated reciprocal change in duration of systole with sine-wave pulses. Therefore, we tested the hypothesis that change in frequency using natural arterial pulses alters baroreceptor unit activity per unit time. 2. In chloralose-anaesthetized dogs the isolated carotid sinus was connected to an electromagnetic pressure converter driven by a voltage generator that controlled pulse pressure and sine-wave pulse rate. To generate a natural pulse the converter was driven by the output from the pressure channel used to record arterial pressure. Systolic and diastolic pressures were maintained constant by a pressurized air source and an adjustable control on the voltage generator. The rate of natural pulses was decreased by electrical stimulation of the peripheral right vagus nerve which slowed the heart rate of the dog. 3. Decreases in sine-wave rate by approximately 73 pulses/min (from 156 +/- 2 to 83 +/- 1 pulses/min) at a mean pressure of 114 +/- 8 mmHg (n = 13) did not alter activity per unit time (28 +/- 3 vs. 29 +/- 3 spikes/s). 4. In contrast, decreases in natural pulse rate by an average of 78 pulses/min (from 182 +/- 7 to 104 +/- 15 pulses/min) at a comparable mean pressure (104 +/- 7 mmHg) (n = 9) decreased activity per unit time by 28% from 32 +/- 4 to 23 +/- 4 spikes/s (P less than 0.05). Similar findings were observed in five of six single units using an intact (normally perfused) carotid sinus preparation in dogs with heart block and cardiac pacing. 5. The results indicate that a change in natural pulse rate is an important determinant of single-unit baroreceptor activity.

Action Potentials↗
PubMed2001

Histologic evaluation of skin damage after overlapping and nonoverlapping flashlamp pumped pulsed dye laser pulses: A study on normal human skin as a model for port wine stains.

BACKGROUND AND OBJECTIVE: In the treatment of port wine stains (PWS) with the flashlamp pumped pulsed dye laser (FPPDL), no consensus exists about overlapping of pulses. The advantage of overlapping pulses is homogeneous lightening of the PWS; the risk is redundant tissue damage. The aim of this study was to determine the histopathologic effect on human skin of pulsed dye laser pulses with various degrees of overlap, with normal human skin as a model for PWS. STUDY DESIGN/MATERIALS AND METHODS: Eighteen healthy white volunteers were irradiated with pulsed dye laser pulses with increasing radiant exposure and with different degrees of overlap. Biopsy samples were taken and histologically analysed. RESULTS: Overlapping of pulses on normal human skin enhances depth of vascular damage with approximately 30%. Adjacent pulses also show this effect. We found no histologic signs of serious damage to epidermis or dermal connective tissue by using radiant exposure levels of 6-8 J/cm(2), regardless of pulse application. CONCLUSIONS: Reasoning that the mechanism of tissue injury is comparable for normal and PWS skin, we conclude that it is safe to treat PWS with overlapping FPPDL pulses to achieve homogeneous lightening.

Abdomen↗
PubMed1992

Controlled trial of pulse methylprednisolone versus two regimens of pulse cyclophosphamide in severe lupus nephritis.

Pulse cyclophosphamide is more effective than prednisone alone in preventing renal failure in lupus nephritis. We undertook a randomised, controlled trial to find out whether pulse methylprednisolone could equal pulse cyclophosphamide in preserving renal function in patients with lupus nephritis, and whether there was a difference between long and short courses of pulse cyclophosphamide in preventing exacerbations. 65 patients (60 female, 5 male; median [range] age 29 [10-48] years) with severe lupus nephritis were assigned randomly to monthly pulse methylprednisolone for 6 months (25 patients), monthly pulse cyclophosphamide for 6 months (20), or monthly cyclophosphamide for 6 months followed by quarterly pulse cyclophosphamide for 2 additional years (20). Patients treated with pulse methylprednisolone had a higher probability of doubling serum creatinine than those treated with long-course cyclophosphamide (p less than 0.04). Risk of doubling creatinine was not significantly different between short and long course cyclophosphamide. However, patients treated with short-course cyclophosphamide had a higher probability of exacerbations than those treated with long-course cyclophosphamide (p less than 0.01). An extended course of pulse cyclophosphamide is more effective than 6 months of pulse methylprednisolone in preserving renal function in patients with severe lupus nephritis. Addition of a quarterly maintenance regimen to monthly pulse cyclophosphamide reduces the rate of exacerbations.

Adolescent↗
PubMed1996

Present day pacemakers for pulse generator exchange: is 3.5 V a sufficient nominal setting for the pulse amplitude? Thera Pacemaker Study Group.

Projected pacemaker longevity is calculated according to the nominal setting, which is 3.5 V for pulse amplitude in most present day pacemakers. The aim of this study was to test whether the nominal ventricular output setting of 3.5 V and 0.4 ms provides a 100% safety margin if these pacemakers are connected to implanted ventricular pacing leads. The study included 24 patients undergoing pulse generator exchange. The new pacemaker was either a Thera DR (n = 21) or Thera SR (n = 3) device. Ventricular pacing leads were implanted 70 +/- 38 months previously. Intraoperative measurements included pacing threshold at 0.5-ms pulse duration, impedance, and R wave amplitude. To achieve a 100% safety margin with 3.5 V, the cut-off pacing threshold is 1.7 V. At discharge it was assessed whether ventricular pulse amplitude remained at < or = 3.5 V or was programmed to > 3.5 V. At pulse generator exchange, pacing threshold was 1.2 +/- 0.5 V, including four patients with pacing thresholds > 1.7 V. Impedance was 587 +/- 189 omega and R wave amplitude was 12.8 +/- 4.8 mV. At discharge, ventricular pulse amplitude remained at the nominal setting in 13 patients, including 2 patients with high pacing thresholds at pacemaker exchange, and was programmed to < 3.5 V in 7 patients. Ventricular pulse amplitude was programmed to > 3.5 V in four patients. Two of these patients had high pacing thresholds (> 1.7 V/0.5 ms) at pulse generator exchange; the other two patients were programmed to > 3.5 V, although 3.5 V already provided a 100% safety margin. After pulse generator exchange, 92% of the patients could be paced with a 3.5-V pulse amplitude. Pacemakers were programmed in four patients > 3.5 V, but in only two of them to obtain a sufficient safety margin. High pacing thresholds at pulse generator exchange did not generally predict high pacing thresholds at discharge.

Aged↗
PubMed1995

A novel electrophysiological approach to monitor pulse by pulse the concentration of released noradrenaline at the presynaptic alpha 2-adrenoceptors of sympathetic nerves in rat tail artery.

The excitatory junction current (EJC) evoked by electrical stimulation of postganglionic sympathetic nerves of rat tail artery with 100 pulses at 2 Hz, at 1.3 mmol/l external Ca2+, was used as a measure of the per pulse release of ATP. In controls the EJCs were initially facilitated, then gradually depressed during the stimulus train. The first EJC was slightly depressed by the alpha 2-adrenoceptor antagonist yohimbine, but starting from the 4th pulse the EJCs were enhanced. Yohimbine increased the early facilitation without markedly modifying the subsequent depression. The yohimbine-induced enhancement of EJCs caused by pulses 11-100 was, thus, constant. The noradrenaline reuptake blocker cocaine depressed the EJCs, abolished the early facilitation and slightly enhanced the depression. These effects of cocaine were reversed by further addition of yohimbine. The alpha 2-adrenoceptor agonist xylazine (1 and 10 mumol/l) dose dependently depressed the EJCs starting from the first pulse. The inhibitory effect of 1 mumol/l xylazine, but not that of 10 mumol/l xylazine, declined with train length. The inhibition of individual EJCs caused by activation of presynaptic alpha 2-adrenoceptors was used to monitor the concentration of released noradrenaline at these receptors. The ratio of individual EJCs in the presence and absence of yohimbine was assumed to reflect, pulse by pulse, the relative concentration of released noradrenaline at the presynaptic alpha 2-adrenoceptors, and hence termed [NA]alpha 2. For comparison, the concentration of endogenous noradrenaline was monitored electrochemically by differential pulse amperometry with a carbon fibre microelectrode; this signal is termed [NA]CF. [NA]alpha 2 and [NA]CF grew during the first 7-10 or 14-16 pulses, respectively, and then remained relatively constant throughout the stimulus train. Cocaine caused [NA]alpha 2 and [NA]CF to continue to grow during the first 35 and 50 pulses, and enhanced their peak levels by 180% and 320%, respectively. For comparison with the effects on the EJCs mediated via presynaptic alpha 2-adrenoceptors, those caused by varying external Ca2+ level were examined. At 0.65 mmol/l Ca2+ the amplitude of the first EJC was smaller than that at 1.3 mmol/l Ca2+, but the facilitation of later EJCs was enhanced and the subsequent depression reduced. An increase in external Ca2+ to 2.6 mmol/l had the opposite effects. All effects on EJCs caused by changes in external Ca2+ were maximal for the first EJC and then declined with the train length.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed2006

Asymmetric pulses in cochlear implants: effects of pulse shape, polarity, and rate.

Existing cochlear implants stimulate the auditory nerve with trains of symmetric biphasic (BP) pulses. Recent data have shown that modifying the pulse shape, while maintaining charge balance, may be beneficial in terms of reducing power consumption, increasing dynamic range, and limiting channel interactions. We measured thresholds and most comfortable levels (MCLs) for various 99-pulses-per-second (pps) stimuli. "Pseudomonophasic (PS)" pulses consist of a brief phase of one polarity followed immediately by a longer and lower-amplitude phase of the opposite polarity. We focused on a novel variant of PS pulses, termed the "delayed pseudomonophasic (DPS)" stimulus, in which the longer phase is presented midway between the short phases of two consecutive pulses. DPS pulse trains produced thresholds that were more than 10 dB lower than those obtained with BP pulses. This reduction was much greater than the 0- to 3-dB drop obtained with PS pulses and was still more than 6 dB when a pulse rate of 892 pps was used. A study of the relative contributions of the two phases of DPS suggested that the short, high-amplitude phase dominated the perceived loudness. This study showed major threshold and MCL reductions using a DPS stimulus compared to the widely used BP stimulus. These reductions, which were predicted by a simple linear filter model, might lead to considerable power savings if implemented in a cochlear implant speech processor.

Adult↗
PubMed1989

Photoendocrine transduction in cultured chick pineal cells. III. Ouabain (or dark) pulses can block, overcome, or alter the phase response of the melatonin rhythm to light pulses.

A photoentrainment pathway, circadian pacemakers, and the apparatus for regulated melatonin production all reside within chick pineal cells. Pulses of white light (L), or darkness (D), or ouabain (Ob), in otherwise constant red light, induce phase-dependent phase shifts in the rhythm of melatonin output displayed by these cells in static culture. The phase response curves (PRCs) (which describe the relationship between the phase at which a pulse is given and the resulting phase shift) for Ob and for D are quite similar, and differ from the PRC for L pulses. Here, we describe the effects of pulses of Ob, L, and D, in combination, on subsequent phase of the melatonin rhythm. Ob pulses can block, overcome, or alter the phase response to light pulses, depending on the phases and concentrations used. Under appropriate conditions, D pulses can, like Ob, convert the phase response to a light pulse from phase delays to phase advances. Such alterations in the response to a second pulse (L) caused by a first pulse (Ob or D) implies a rapid resetting of the phase of the underlying pacemaker. The interactions of Ob, L, and D are consistent with, but do not require, the convergence of their entrainment pathways on the same oscillating component of the pacemaker.

Animals↗
PubMed2003

Treatment of facial telangiectasia with variable-pulse high-fluence pulsed-dye laser: comparison of efficacy with fluences immediately above and below the purpura threshold.

BACKGROUND: : Pulsed-dye laser treatment has been shown to be highly effective for the treatment of facial telangiectasia. Posttreatment purpura after such treatment has limited patient acceptance of the procedure. OBJECTIVE: : To determine whether purpura-free treatment with recently introduced variable-pulsed pulsed-dye lasers can effectively reduce facial telangiectasia. METHODS: : This was a prospective, randomized, controlled, nonblinded trial. Eleven patients received variable-pulse pulsed-dye laser treatment with and without induction of purpura. Telangiectasia were graded on a "telangiectasia density scale," on which a 1 signified extremely fine, sparsely distributed telangiectasia, and 5 referred to thick, ropelike telangiectasia covering the affected area. For each subject, two areas on either side of the facial midline with equivalent telangiectasia density ratings were randomized to the purpura and purpura-free treatment groups, respectively. All treatments used a 7-mm spot size and a 10-ms pulse duration. The fluence associated with the purpura threshold for each patient was determined in test areas. Purpura-free treatment entailed a fluence 1.0 J/cm2 less than the purpura threshold, and purpura-level treatment entailed a fluence 0.5 J/cm2 greater than the threshold. RESULTS: : Six weeks after a single purpura-free treatment, mean telangiectasia ratings were reduced from 2.7 to 2.4. Purpura-level treatments resulted in a decrease to 1.4 from the same baseline. Thicker, denser telangiectasia appeared to benefit more from purpura-level treatment (a mean telangiectasia density scale reduction of 1.7) than finer, sparser telangiectasia (a mean reduction of 0.8). In 81% of cases, both investigators and patients rated the side treated with purpura as undergoing a greater reduction in telangiectasia density. CONCLUSION: : Although facial telangiectasia do improve after a single purpura-free treatment with the variable-pulse pulsed-dye laser, they improve more after purpura is induced. Purpura-free and purpura-level treatments may be close to equivalent for treating fine telangiectasia, but purpura-level treatments have a distinct advantage for treating thicker telangiectasia. Significantly, the variable-pulse pulsed-dye laser offers patients the option of effective treatment of some telangiectasia without bruising.

Adult↗
PubMed1994

A review of the principles of pulse oximetry and accuracy of pulse oximeter estimates during exercise.

This article reviews the principles of pulse oximetry and assesses the accuracy of pulse oximeter measurements obtained during exercise, based on reports of 10 studies that evaluated 24 pulse oximeters. Nine of the studies used cycle exercise, and 1 study utilized treadmill running for mode of activity. Subject populations included patients with cardiovascular or pulmonary disorders, nondisabled individuals, and athletes. Studies were performed under normoxic and hypoxic conditions, and 5 of the 10 studies validated 18 pulse oximeters at arterial oxyhemoglobin saturation (%HbO2) levels of < or = 78%. Sixteen of the 24 pulse oximeters (67%), from 7 of the 10 studies, observed pulse oximeter estimates (%SpO2) during exercise to be accurate, at least when %HbO2 was > or = 85% in nonsmokers. However, the degree of accuracy of the pulse oximeters was variable, even among the same models. Recent studies suggest the current generation of finger-probe-equipped pulse oximeters may be more accurate than ear-probe-equipped models. We recommend that clinicians carefully secure the probe; monitor signal strength; be wary of %SpO2 values of < or = 68% to 78% to avoid undetected severe hypoxemia; and be alert to whether a patient is a smoker, in which case %SpO2 will likely be overestimated. Researchers interested in using pulse oximeter estimates should validate their particular pulse oximeter(s) via arterial blood sampling.

Diagnostic Errors↗
PubMed1999

A comparison of the long-pulse and short-pulse Alexandrite laser hair removal systems.

Laser-assisted hair removal has been reported previously with the Nd:YAG laser, the long-pulse ruby laser, the long-pulse Alexandrite laser, and the short-pulse Alexandrite laser. Results with all these lasers have been successful; however, it has been postulated that the long-pulse Alexandrite laser would have a lower complication rate and greater efficacy at identical fluences than the short-pulse Alexandrite laser. The authors chose to compare directly the pulsed Alexandrite lasers for speed of application, complications, and results. Eighteen patients who desired hair removal were entered into the study. There were 10 female and 8 male patients, with a mean age of 36 years. All skin types from Fitzpatrick classes I through VI were treated. The body areas treated consisted of the face, ears, neck, back, arms, upper thighs, bikini lines, legs, and breasts. One side of the body was treated with the short-pulse (2-msec) Alexandrite laser (Sharplan Epitouch 5100). The other half was treated with a long-pulse (20-msec) Alexandrite laser. Both lasers were set at the same fluence for each patient. Patients reported a 60% to 80% reduction in hair growth at 6 months. Both sides were identical with regard to return of hair growth and complications such as hypopigmentation. Both the long- and short-pulse Alexandrite laser systems yielded an effective method of hair reduction with minimal complications. Equal results and complications were obtained with the two systems. The only exception was that the length of the procedure was shorter with the short-pulse Alexandrite laser.

Adult↗
PubMed2004

Ultrashort laser pulses and electromagnetic pulse generation in air and on dielectric surfaces.

Intense, ultrashort laser pulses propagating in the atmosphere have been observed to emit sub-THz electromagnetic pulses (EMPS). The purpose of this paper is to analyze EMP generation from the interaction of ultrashort laser pulses with air and with dielectric surfaces and to determine the efficiency of conversion of laser energy to EMP energy. In our self-consistent model the laser pulse partially ionizes the medium, forms a plasma filament, and through the ponderomotive forces associated with the laser pulse, drives plasma currents which are the source of the EMP. The propagating laser pulse evolves under the influence of diffraction, Kerr focusing, plasma defocusing, and energy depletion due to electron collisions and ionization. Collective effects and recombination processes are also included in the model. The duration of the EMP in air, at a fixed point, is found to be a few hundred femtoseconds, i.e., on the order of the laser pulse duration plus the electron collision time. For steady state laser pulse propagation the flux of EMP energy is nonradiative and axially directed. Radiative EMP energy is present only for nonsteady state or transient laser pulse propagation. The analysis also considers the generation of EMP on the surface of a dielectric on which an ultrashort laser pulse is incident. For typical laser parameters, the power and energy conversion efficiency from laser radiation to EMP radiation in both air and from dielectric surfaces is found to be extremely small, < 10(-8). Results of full-scale, self-consistent, numerical simulations of atmospheric and dielectric surface EMP generation are presented. A recent experiment on atmospheric EMP generation is also simulated.

Journal Article↗
PubMed1982

Regulation of immune response by preadministration of cells briefly pulsed with antigen in vitro. I. Suppression of IgE antibody response by antigen pulsed spleen cells.

The intravenous administration of syngeneic spleen cells (SPCs) briefly pulsed with antigen in vitro, results in a profound state of IgE antibody unresponsiveness. In Balb/c mice, the primary response of anti-DNP, anti-beef insulin and anti-ovalbumin IgE antibody is completely suppressed by the administration of antigen-pulsed spleen cells, 1 X 10(7), 5 X 10(7) and 1 X 10(8), respectively. This suppression is antigen specific and effects both primary and secondary immune responses. Furthermore, the immune response to dinitrophenylated Keyhole limpet hemocyanin (DNP-KLH) is most extensively suppressed by DNP-KLH pulsed SPCs, intermediately suppressed by KLH-pulsed SPCs and minimally suppressed by dinitrophenylated mouse gamma globulin or dinitrophenylated mouse serum albumin pulsed SPCs. Suppressing directly cells specific for hapten and carrier, hapten carrier protein pulsed SPCs would caused the additive suppressive effect. The suppression is induced strongly by the intravenous administration of antigen pulsed spleen cells, slightly by the subcutaneous administration and is not induced by the intravenous administration of antigen solution in phosphate buffer saline. This suppression may be mediated by either of two different mechanisms: one of them is responsible for the immediate tolerance which is induced without any suppressor cells 1 day after the administration of antigen pulsed SPCs, and the other is responsible for the suppression transferred by suppressor cells or factors to normal mice 7 days after the administration of antigen pulsed SPCs. This method in which IgE antibody response is suppressed by the administration of cells briefly pulsed in vitro with antigen, provides a powerful tool to analyze the first step of antigen specific suppression developed in vivo by conventional antigens.

Animals↗
PubMed2003

Clinical utility of aortic pulses and pressures calculated from applanated radial-artery pulses.

Brachial artery cuff blood pressures are but approximations of central aortic pressures. The actual pressures against which the left ventricle must pump would be useful clinical information if obtained noninvasively. Our aim was to determine the clinical utility of aortic pulses and pressures calculated from noninvasively obtained radial-artery pulses. Radial-arterial pulses were recorded by applanation and calibrated with arm/cuff oscillometric pressures. Aortic pulses and pressures were calculated from the radial pulses by Fourier analysis and transfer functions. These calculated aortic pulses were compared with directly recorded aortic pulses by a transducer-tip catheter in a series of 50 patients undergoing cardiac catheterization. The correlation coefficient (r) of the measured versus the calculated aortic systolic blood pressure was +0.89, but the scatter was large (standard deviation of the differences=+/-11.3 mm Hg). The pulse pressure correlations were less good (r=+0.79) and also had a large scatter (+/-13.6 mm Hg). The average calculated pulse pressure was 11.5 mm Hg lower than the measured value because the cuff diastolic blood pressures, used to calibrate the radial pulses, were systematically higher than those in the aorta (8.9 mm Hg). Multivariable analysis incorporating height, age, heart rate, and ejection fraction as additional, independent variables eliminated mean differences between the new "predicted" and measured pressures, significantly improved correlation coefficients, and reduced the scatter. However, the improvements were small. The inaccuracy of the oscillometric cuff method for measuring arm blood pressure appears to be the limiting factor in the prediction of clinically useful, noninvasive aortic pressures.

Adult↗
PubMed1993

Attenuated luteinizing hormone (LH) pulse amplitude but normal LH pulse frequency, and its relation to plasma androgens in hypogonadism of obese men.

To evaluate the effects of obesity on the hypothalamo-pituitary-testicular axis, we compared total and free (FT) testosterone (T), androstenedione, dehydroepiandrosterone and its sulfate, and 5 alpha-androstane-3 alpha, 17 beta-diol glucuronide, and estradiol levels in a group of 35 obese [body mass index (BMI), > 30] men (aged 17-61 yr) to levels in a nonobese control group. We observed a highly significant negative correlation (P < 0.001) between plasma (F)T levels and BMI and a significant positive correlation (P < 0.01) between E2 levels and BMI. There were no differences between the obese and the nonobese men in levels of androstenedione, dehydroepiandrosterone sulfate, and 5 alpha-androstane-3 alpha, 17 beta-diol glucuronide. Insulin levels were significantly higher in obese men and were significantly (P < 0.02) correlated with the waist hip girth ratio. To evaluate the role of the hypothalamo-pituitary complex in the decreased (F)T levels in obese men, diurnal (0800-2000 h) LH pulsatility was studied in eight obese middle-aged men and eight age-matched controls. The pulsatility of plasma cortisol levels was also studied. Whereas LH pulse frequency was similar in the obese and control subjects, mean diurnal LH levels, mean diurnal LH pulse amplitude, and the sum of all diurnal LH pulse amplitudes and secretory masses were significantly lower in the obese than in the controls. Moreover, there was a highly significant correlation between the sum of LH pulse amplitudes and plasma (F)T levels. This decrease in LH pulse amplitude is not an isolated phenomenon of hypothalamo-pituitary dysfunction in obese men, because the pulse amplitude of plasma cortisol levels was also decreased. The decreased LH pulse amplitude together with the normal respond of Leydig cells to hCG stimulation reported in the literature suggest by inference that the decreased FT levels in obese men are the consequence of a hypogonadotropism. The decreased LH pulse amplitude and the decreased amplitude of cortisol pulses, and hence probably of ACTH pulses, point toward a general alteration of hypothalamo-pituitary function in obese men.

Adolescent↗
PubMed2006

Brachial-ankle pulse wave velocity is an independent risk factor for microalbuminuria in patients with essential hypertension--a Japanese trial on the prognostic implication of pulse wave velocity (J-TOPP).

Brachial-ankle pulse wave velocity is a new measure of arterial stiffness. The clinical significance of brachial-ankle pulse wave velocity as a measure of early vascular damage remains unclear. We examined the hypothesis that higher brachial-ankle pulse wave velocity is associated with a much greater risk of albuminuria by employing a cohort of 718 never-treated hypertensive patients registered in a prospective study. The 718 patients consisted of 500 patients with normoalbuminuria (69.6%), 191 patients with microalbuminuria (26.6%) and 27 patients with macroalbuminuria (3.8%). The prevalence of microalbuminuria increased with a graded increase in brachial-ankle pulse wave velocity (17.6, 22.8, 28.2 and 39.6%, p < 0.0001). The prevalence of macroalbuminuria remained constant until the third grade group of the brachial-ankle pulse wave velocity but increased significantly in the highest grade group compared with the lower grade groups (2.3, 3.2, 2.3, 9.9%, p < 0.0001). Age, systolic and diastolic blood pressure, pulse pressure, heart rate, and fasting glucose concentration were also significantly increased with an increase in brachial-ankle pulse wave velocity (p < 0.0001 for all). Multiple logistic regression analysis has shown that systolic blood-pressure, fasting blood glucose, and brachial-ankle pulse wave velocity are significant risk factors for microalbuminuria. After adjusting for other risk factors, the odds ratio for an increase of 200 cm/s in brachial-ankle pulse wave velocity was 1.192 (95% confidence interval: 1.022-1.365; p < 0.05). These data suggest that brachial-ankle pulse wave velocity is an independent risk factor for microalbuminuria and could be used as a marker for early vascular damage in never-treated hypertensive patients.

Adult↗
PubMed1994

Changes in pulse transit time and pulse rate as markers of arousal from sleep in normal subjects.

1. Obstructive sleep apnoea and its variants often provoke hundreds of short arousals that lead to the most important symptom, disabling hypersomnolence. The measurement of sleep in these conditions requires the documentation of these short arousals and this is conventionally done by manual inspection of the sleeping EEG, a laborious procedure. 2. Other markers of 'arousal', that are easier to measure and document, include several cardiovascular signals that change as part of the orienting reflex: pulse rate rise, blood pressure rise, skin vasoconstriction, for example. 3. Pulse transit time (measured as the interval from the ECG R-wave until the arrival of the pulse pressure wave at the periphery, about 250 ms) varies inversely with blood pressure and provides a beat-to-beat estimation of blood pressure changes. 4. In eight normal subjects we have assessed the relationship between transient EEG arousals of different length (provoked by external stimuli) and changes in both pulse transit time and heart rate. 5. Significant falls in pulse transit time occurred in response to external stimuli [15.1 (SEM 1.4) ms], indicating a rise in blood pressure, and were significant even when there was no discernible change in the EEG [9.9 (SEM 2.6) ms]. Significant changes in heart rate also occurred [10.3 (SEM 1.2) beats/min], but were slightly less sensitive than changes in pulse transit time. 6. Changes in pulse transit time (and to a lesser extent pulse rate) are sensitive markers of EEG arousal. As such they should be useful to include when monitoring sleep and its disorders, particularly since pulse transit time recorders can easily be made portable for home use.

Adult↗