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PubMedDate not supplied

Transient synchronous intrapartum late deceleration patterns of concordant twins due to maternal-related etiologies.

An unusual case is presented in which intrapartum electronic fetal heart rate (FHR) monitoring of concordant monochorionic twins at 39 weeks gestation revealed two separate occurrences of transient synchronous repetitive late deceleration patterns of both fetal heart rates. Both episodes were considered due to correctable maternal-related etiologies. Each of these occurrences resolved immediately with correction of the respective underlying etiologies, and the subsequent FHR tracings were reactive.

Adult↗
PubMed1999

Deceleration-dependent shortening of the QT interval: a new electrocardiographic phenomenon?

In clinical cardiology, deceleration-dependent QT interval shortening is considered to be an extraordinary electrocardiographic phenomenon. We present an early premature born 4-year-old African-American girl with complications related to her premature birth, developmental delay, and several episodes of cardiac arrest. An episode of severe transient bradyarrhythmia was documented on Holter monitoring. The unique feature of the rhythm strips was paradoxical gradual shortening of the QT interval to 216 ms with accompanying transient T-waves abnormalities. The activation of the Ik, ACh due to an unusually high vagal discharge to the heart is proposed as a possible mechanism responsible for both slowing of the heart rate and shortening of the QT interval.

Bradycardia↗
PubMed1992

Folding of RNase T1 is decelerated by a specific tertiary contact in a folding intermediate.

The replacement of tryptophan 59 of ribonuclease T1 by a tyrosine residue does not change the stability of the protein. However, it leads to a strong acceleration of a major, proline-limited reaction that is unusually slow in the refolding of the wild-type protein. The distribution of fast- and slow-folding species and the kinetic mechanism of slow folding are not changed by the mutation. Trp-59 is in close contact to Pro-39 in native RNase T1 and probably also in an intermediate that forms rapidly during folding. We suggest that this specific interaction interferes with the trans----cis reisomerization of the Tyr-38-Pro-39 bond at the stage of a native-like folding intermediate. The steric hindrance is abolished either by changing Trp-59 to a less bulky residue, such as tyrosine, or, by a destabilization of folding intermediates at increased concentrations of denaturant. Under such conditions folding of the wild-type protein and of the W59Y variant no longer differ. These results provide strong support for the proposal that trans----cis isomerization of Pro-39 is responsible for the major, very slow refolding reaction of RNase T1. They also indicate that specific tertiary interactions in folding intermediates do exist, but do not necessarily facilitate folding. They can have adverse effects and decelerate rate-limiting steps by trapping partially folded structures.

Models, Molecular↗
PubMed1994

Intact disulfide bonds decelerate the folding of ribonuclease T1.

Disulfide bonds in a folding protein chain are equivalent to prematurely formed native-like tertiary interactions. We investigated whether the mechanism of protein folding is changed by the presence of disulfide bonds. As a model we used the S54G/P55N-variant of ribonuclease T1, a protein with two disulfide bonds and a single cis proline (Pro39), and we measured both the direct and the proline-limited folding reactions before and after breaking of the disulfide bonds. The folding kinetics were compared under refolding conditions, in the regions of the urea-induced unfolding transitions of the two forms, and under unfolding conditions. The kinetics in the transition regions were analyzed on the basis of a three-species mechanism and all microscopic rate constants of folding and of prolyl isomerization could be determined as a function of the urea concentration from the measured rates and amplitudes. These kinetic analyses indicated that the disulfide bonds can be rather unfavorable for the folding of S54G/P55N-ribonuclease T1. Under strongly native conditions they retard the rate-limiting trans-->cis isomerization of Pro39 because they allow the rapid formation of partially ordered structure prior to the proline-limited refolding reaction. Under unfolding conditions the isomerization of Pro39 is not affected. The direct unfolding and refolding reactions in the transition region of polypeptide chains with correct prolyl isomers are also decelerated when the disulfide bonds are present. These changes in the folding kinetics are possibly related to the decrease in chain flexibility that is caused by the disulfide bonds. A high flexibility is probably important throughout folding, and in the case of ribonuclease T1 a premature locking of tertiary contacts by intact disulfide bonds can interfere unfavorably with both the direct and the proline-limited folding reactions.

Amino Acid Isomerases↗
PubMed1988

Transient growth deceleration in normal short children. A potential source of bias in growth studies.

We have examined the records of 21 short children evaluated for growth hormone deficiency and found not to be deficient. Their growth velocity was evaluated for at least 6 months, both before and after testing. Without any specific therapeutic intervention, growth velocity was significantly higher after testing, as compared with before. We attribute this apparent "therapeutic" effect of testing to a selection bias, due to the fact that, in normal clinical practice, children are selected for testing immediately following a period of slow growth, and that decelerations of growth are very often transient. Studies of growth-stimulating treatments using children as their own controls should, for this reason, be interpreted with caution.

Adolescent↗
PubMed1986

Compensatory maturational deceleration of growth or "catch-down growth" in patients with congenital adrenal hyperplasia after delayed initiation of therapy.

The growth pattern is reported of 16 patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency in whom therapy was started after the age of 3 years. Treatment was initiated at a mean chronological age (CA) of 4.7 years (range 3.0-7.2) and at a mean bone age (BA) of 10.4 years (range 10.2-13.2). It consisted of hydrocortisone (mean dosage 26 mg/m2) or prednisone (8.7 mg/m2) in all, and of fluorohydrocortisone (0.05-0.1 mg daily) in five patients. At the last examination the mean duration of therapy was 5.2 years, the mean CA 10.0 years, and the mean BA 12.6 years. In 13 of the 16 patients a "catch-down growth" pattern was observed, which was characterised by a decrease in height (expressed as SDS) for CA, a deceleration of bone maturation and increase of height (SDS) for BA, and an improvement in predicted height (Bayley-Pinneau).

Adolescent↗
PubMedDate not supplied

Heart rate deceleration is not an orienting reflex; heart rate acceleration is not a defensive reflex.

Graham and Clifton (1966) proposed an integration of Sokolov's theory of orienting and defensive reflexes with the stimulus intake/rejection dichotomy of the Laceys. This integration consisted of hypothesizing that heart rate deceleration is a measure of the orienting reflex, and that cardiac acceleration is a measure of the defensive reflex. This article demonstrates that Graham and Clifton failed to establish a valid integration of these two theories. This failure is a consequence of 1) their misconstruing Sokolov's theory, and 2) an inaccurate and selective review of the research literature then available. Consideration of more recent research would seem to rule out the possibility that their thesis was correct in spite of these flaws in its derivation. Cardiac responding in the OR context thus remains open to further investigation and interpretation.

Acoustic Stimulation↗
PubMed2001

Physiological effects of constant versus decelerating inflation flow in patients with chronic obstructive pulmonary disease under controlled mechanical ventilation.

OBJECTIVE: To study the cardiorespiratory effects of inspiratory flow rate and waveform in COPD patients. DESIGN: Prospective physiological investigation with randomized allocations of experimental conditions. SETTING: A 14-bed medical ICU in a 1000-bed university hospital. PATIENTS AND PARTICIPANTS: Ten COPD intubated, sedated and paralyzed patients with chronic obstructive pulmonary disease (COPD), mechanically ventilated for acute respiratory failure. INTERVENTIONS: In volume-controlled mode, three inflation flow rates of 0.40, 0.70, and 1.10 l/s for 20 min with a constant (CF) or a decelerating (DF) inflation flow profile. Each patient received all six experimental conditions in a random order. Tidal volume and respiratory frequency were similar during the experimental conditions. MEASUREMENTS AND RESULTS: Arterial blood gases, hemodynamics ( n=8), and respiratory mechanics were measured with zero end expiratory pressure. Between flow rates the median (25th-75th percentiles) values of PaO(2)/FIO(2) were 232 (132-289), 253 (161-338), 231 (163-352) for CF and 253 (143-331), 249 (164-360), 231 mmHg (187-351), for DF, respectively; the maximal airway pressures were 25.6, 28.3, 34.6 cmH(2)O for CF and 21.7, 29.6, 34.8 cmH(2)O for DF, respectively, the mean airway pressures were 8.9, 6.1, 5.4 cmH(2)O for CF and 9.1, 7, 6.5 cmH(2)O for DF, respectively. CONCLUSIONS: Changing the ventilator in volume-controlled mode with a DF or CF profile has no significant cardiorespiratory effect in intubated COPD patients mechanically ventilated for acute respiratory failure.

Aged↗
PubMed2003

Mid-systolic septal deceleration. A new sign of left ventricular outflow tract obstruction obtained by color-coded tissue Doppler echocardiography.

Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by the presence of a dynamic left ventricular outflow tract gradient. We studied septal longitudinal motion by color coded tissue Doppler echocardiography in a 69-year old HOCM patient during and after catheter based treatment by trans coronary alcohol ablation of septal hypertrophy. The presence of dynamic left ventricular outflow tract obstruction was associated with a characteristic abrupt mid-systolic septal deceleration pattern in the tissue Doppler velocity trace. Five weeks after treatment, this pattern was no longer visible at rest.

Aged↗
PubMed1999

Heart rate deceleration during the grasping reflex.

UNLABELLED: Heart rate changes were measured as a psychophysiological indicator during grasping reflex in 27 full-term healthy newborns at 2.5-50 h after birth. A significant heart rate deceleration accompanied the grasping response. CONCLUSION: Reflex grasping of a mother's hand, as a component of human attachment behaviour, may have a positive calming effect on the infant's state and could have therapeutic value for high risk mother-infant dyads.

Electrocardiography↗
PubMed1989

Pacing lead fracture after a deceleration injury.

Acute pacemaker malfunction is potentially lethal. A high index of suspicion must be maintained in physicians caring for traumatized patients utilizing permanent pacing systems. We present a case of transvenous pacemaker lead fracture sustained in a vehicular deceleration injury.

Accidents, Traffic↗
PubMed1990

Computer analysis of antepartum fetal heart rate: 2. Detection of accelerations and decelerations.

Based upon a previously described procedure for automated baseline determination in antepartum fetal heart rate recordings, a programme has been developed for recognition of accelerations and decelerations. Detection of these deviations from the baseline depends on criteria for amplitude and duration, with special account for signal loss. The described automated analysis provides an objective tool for description of antepartum fetal heart rate patterns. A first evaluation with respect to its capacity to discriminate between different fetal heart rate patterns in relation to fetal rest-activity patterns shows promising results.

Female↗
PubMed1988

Pressure influences the rate of fibrin polymerization: decompression accelerates, compression decelerates.

We report here that the rate of fibrin polymerization is accelerated by decompression: the rate is essentially doubled by reducing the pressure by one-half (380 torr, 14.7 PSI or 1/2 ATM) and increased by 3.6 times with respect to the control at 25 torr (0.48 PSI or 1/30th ATM). We also report here that the rate of fibrin polymerization is decelerated by compression; at 5.2 X 10(5) torr (10,000 PSI or 680 ATM) polymerization is inhibited and/or reversed.

Animals↗
PubMed1976

The effect of voluntary control of heart rate deceleration on skin conductance level: an example of response fractionation.

Twenty-four undergraduate male volunteers participated in an experimental designed to assess the effect of voluntary control of heart rate deceleration on skin conductance level. One group of subjects received heart rate feedback training and a second group performed a tracking task. Because heart-rate feedback was presented via a visual display, the tracking task group was included to control for display monitoring influences on heart rate. Results demonstrated feedback mediated acquisition of learned control of heart rate slowing. More importantly, the heart-rate slowing performance was accompanied by increases in skin conductance level. This 'fractionation' of physiological responding suggests the presence of a physiological response pattern which may counter initial attempts to produce greater magnitude slowing effects.

Arousal↗
PubMed1992

How useful are acceleration- and deceleration-based Doppler indices? A trial on patients with percutaneous transluminal angioplasty.

The usefulness of indices commonly used in Doppler sonography is limited; the aim of this study was to investigate if inclusion of systolic acceleration and deceleration patterns in Doppler indices will result in practical diagnostic advantages. Systolic delay time index (SDTI) and height-width index (HWI) are compared to Gosling's pulsatility index (PI) and to PI-based damping factors (DF) in patients with isolated lesions in the distal superficial femoral artery before and after percutaneous transluminal angioplasty (PTA). Before PTA, all indices distal to the lesion differ significantly from proximal indices. After successful PTA, none of the indices is able to detect the PTA outcome with sufficient sensitivity. The additionally defined curve broadening index (CBI) shows a 100% sensitivity for detecting PTA success in the examined patient population.

Aged↗
PubMedDate not supplied

Component analysis and stimulus control assessment of a behavior deceleration treatment package.

A treatment package that included two setting condition manipulations and visual occlusion was implemented to gain control over the high-intensity screaming and whining of a 16-year-old female with developmental disabilities. The study included an analysis of the individual and combined components of the treatment package and a stimulus control analysis of three salient features of the visual occlusion apparatus (i.e., opaque screen, secured helmet, and cranial pressure). Results showed that the treatment package occasioned a deceleration in the two targeted vocal behaviors and a reduction in the amount of time the participant was required to wear the occlusion apparatus. An analysis of the apparatus suggested that the critical element needed to control inappropriate vocalizations appeared to be cranial pressure, which was naturally produced by the helmet. Consequently, the helmet was eliminated and cranial pressure was produced by a woman's headband. Follow-up data, collected 1, 2, and 3 months after termination of systematic intervention, revealed near-zero levels of screaming and whining behaviors. A 9-month follow-up investigation involving the removal and subsequent reinstatement of the headband procedure supported the use of the headband for the maintenance of behavioral gains.

Adolescent↗
PubMed1995

Deceleration vs. acceleration: a haemodynamic parameter in the assessment of vascular reactivity. A preliminary study.

The parameter deceleration vs. acceleration (dc/ac) as derived from the instantaneous peak velocity is obtained by dividing the descending and ascending slopes of plotted velocity curves. Blood velocities were recorded with a specially designed continuous-wave ultrasonic Doppler unit which provides: the instantaneous peak velocity, the instantaneous mean velocity, the acceleration, and an indication of volume flow. A physical meaning to the dc/ac parameter is given through an analysis, based on an electrical model, of a small portion of an artery. This gives a simple relationship which only takes account of the assumed vascular resistances. Measurements were performed in 67 male subjects; 39 were normotensive control subjects and 28 had established moderate hypertension. In both groups there was an increase of dc/ac in passing from the supine to the erect position, the increase being more accentuated by hypertension. The variation of dc/ac with age was significantly different in both groups. The results suggest that this parameter is a sensitive indicator of variations in vascular reactivity and as an indicator of structural changes in the arterial wall.

Adolescent↗