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PubMed1993

The influence of elective amniotomy on fetal heart rate patterns and the course of labor in term patients: a randomized study.

OBJECTIVES: Our study was designed to evaluate the effects of routine elective amniotomy on the frequency and severity of abnormal fetal heart rate patterns and on the course of labor and the need for oxytocin augmentation. STUDY DESIGN: A randomized, controlled trial was conducted at term in patients in active labor who were randomly selected to undergo elective amniotomy (amniotomy group) or left intact with amniotomy reserved for specific indications (intact group). RESULTS: Four hundred fifty-nine patients were studied (235 in the amniotomy group vs 224 in the intact group). Average cervical dilatation at rupture was 5.5 cm in the amniotomy group and 8.1 cm in the intact group. Analysis of fetal heart rate revealed more mild and moderate variable decelerations in the active phase of labor in the amniotomy group but no difference in the frequency of more severe decelerations or operative deliveries. In the intact group the need for oxytocin was twice as common (76 in the intact group vs 36 in the amniotomy group, p = 0.000005), and the active phase of labor was considerably longer (5 hours 56 minutes in the intact group vs 4 hours 35 minutes in the amniotomy group). Neonatal outcome was similar in the two groups. CONCLUSIONS: Elective amniotomy appears to increase the likelihood of umbilical cord compression in the active phase of labor and results in more mild and moderate variable decelerations, but it does not result in more severe abnormal fetal heart rate patterns or more operative intervention. Elective amniotomy does, however, shorten the active phase of labor and decreases the need for oxytocin augmentation.

Amnion↗
PubMed1994

Computerized analysis of fetal heart rate variation in postterm pregnancy: prediction of intrapartum fetal distress and fetal acidosis.

OBJECTIVE: Our purpose was to evaluate whether computerized analysis of fetal heart rate variation may improve fetal surveillance in postterm pregnancy. STUDY DESIGN: Three hundred thirty-seven pregnant women who were delivered after 41 weeks' gestation and who had 610 antenatal tests were included in this study. Fetal tests included a nonstress test with a computerized analysis of the fetal heart rate, Doppler examination of the umbilical artery, and a biophysical profile, performed every 2 to 4 days. Induction of labor was performed when the fetal heart rate variation was reduced (< 30 msec), when fetal heart rate decelerations appeared, or when the amniotic fluid index was < or = 5. The results of the fetal surveillance tests were compared with the results of the intrapartum fetal heart rate monitoring and with the metabolic status of the babies at delivery. Sensitivity and specificity of the various tests in predicting intrapartum fetal distress and acidosis at delivery were described by means of the receiver-operator characteristic curve. RESULTS: Ten of 12 fetuses with reduced fetal heart rate variation had a trial of labor. Nine of these 10 fetuses had fetal distress during labor. Seven of the 12 fetuses with reduced fetal heart rate variation were acidotic at delivery (umbilical artery pH < 7.2). Overall, there were 10 acidotic fetuses at delivery in the study group. Only two of them had an umbilical systolic/diastolic ratio > 95th percentile, three had an amniotic fluid index < or = 5, and five had fetal heart rate decelerations before labor. Fetuses who demonstrated an abnormal intrapartum fetal heart rate tracing or who were acidotic at delivery had a significantly higher rate of reduced fetal heart rate variation or decelerations before labor. The largest area under the receiver-operator curve curve for predicting fetal acidosis at delivery or fetal distress during labor was achieved by means of computerized analysis of fetal heart rate variation. CONCLUSION: A computerized numeric analysis of fetal heart rate variation may improve fetal surveillance in postterm pregnancy.

Acidosis↗
PubMed1995

Longitudinal measurement of amniotic fluid index in postterm pregnancies and its association with fetal outcome.

OBJECTIVE: Our purpose was to study the association between dynamic changes in serial amniotic fluid index measurements and adverse fetal outcome in postterm pregnancies. STUDY DESIGN: Serial amniotic fluid index values were obtained semiweekly in 139 reliably dated, uncomplicated, singleton pregnancies at > 41 weeks' gestation. Adverse fetal outcome was defined by the presence of moderate or thick meconium, fetal heart rate decelerations, cesarean delivery for fetal distress, neonatal intensive care unit admission, and perinatal mortality. RESULTS: Prominent changes in the amniotic fluid index (i.e., > 50% increase or decrease) had no association with adverse fetal outcome irrespective of rate of change, provided the final value remained > 5.0 cm. A significant association with fetal heart rate decelerations and the presence of meconium was detected only in patients whose final amniotic fluid index was < or = 5.0 cm (p = 0.007 and p = 0.003, respectively). CONCLUSION: Irrespective of the rate of change in amniotic fluid index, postterm pregnancies are significantly associated with potential complications such as fetal heart rate decelerations and meconium staining when the final amniotic fluid index is < or = 5.0 cm.

Amniotic Fluid↗
PubMed1989

Exploratory analysis of time-dependent risk for infection, rejection, and death after cardiac transplantation.

Data from 95 heart transplantations performed at The Johns Hopkins Hospital from July 1983 to October 1988 were analyzed to detect patterns of morbidity and mortality. Using nonparametric techniques, hazard functions were determined for all deaths and for deaths due to infection or rejection. The rates of rejection and infection (episodes per patient-month) were determined within each of ten intervals following transplantation. A total of 19 deaths, 281 rejection episodes, and 180 distinct infections were available for analysis during a follow-up of 1 to 62 months. The hazard function for rejection appeared biphasic, with a rapidly decelerating early phase during the first year followed by a constant late phase. The hazard function for infection was triphasic, with a delayed, decelerating early phase, a period of increased risk approximately 2 years after operation, and finally a late constant phase. Both infection and rejection rates (episodes per patient-month) were biphasic, with rapidly decelerating early phases and constant late phases. Multiple regression analysis demonstrated that eventually nonsurviving patients had significantly higher rates of rejection and infection during both the early and late phases compared with survivors. The increased rate of rejection among nonsurvivors was evident throughout follow-up, although no deaths were attributable directly to rejection after the first 8 months. These data suggest that a complex interrelationship between infection and rejection determines late survival after cardiac transplantation and that aggressive treatment of late rejection predisposes toward death from infection.

Actuarial Analysis↗
PubMed1987

The action of sphingomyelinase from Bacillus cereus on ATP-depleted bovine erythrocyte membranes and different lipid composition of liposomes.

The presence of cholesterol or phosphatidylethanolamine in sphingomyelin liposomes enhanced 2- to 10-fold the breakdown of sphingomyelin by sphingomyelinase from Bacillus cereus. On the other hand, the presence of phosphatidylcholine was either without effect or slightly stimulative at a higher molar ratio of phosphatidylcholine to sphingomyelin (3/1). In the bovine erythrocytes and their ghosts, the increase by 40-50% or the decrease by 10-23% in membranous cholesterol brought about acceleration or deceleration of enzymatic degradation of sphingomyelin by 50 or 40-50%, respectively. The depletion of ATP (less than 0.9 mg ATP/100 ml packed erythrocytes) enhanced K+ leakage from, and hot hemolysis (lysis without cold shock) of, bovine erythrocytes but decelerated the breakdown of sphingomyelin and hot-cold hemolysis (lysis induced by ice-cold shock to sphingomyelinase-treated erythrocytes), either in the presence of 1 mM MgCl2 alone or in the presence of 1 mM MgCl2 and 1 mM CaCl2. Also, ATP depletion enhanced the adsorption of sphingomyelinase onto bovine erythrocyte membranes in the presence of 1 mM CaCl2 up to 81% of total activity, without appreciable K+ leakage and hot or hot-cold hemolysis. These results suggest that the presence of cholesterol or phosphatidylethanolamine in biomembranes makes the membranes more susceptible to the attack of sphingomyelinase from B. cereus and that the segregation of lipids and proteins in the erythrocyte membranes by ATP depletion causes the deceleration of sphingomyelin hydrolysis despite the enhanced enzyme adsorption onto the erythrocyte membranes.

Adenosine Triphosphate↗
PubMed1979

Transport of local anaesthetics across chromatophore membranes.

1. Both simple amines and tertiary amino local anaesthetics give rise to an accelerated decay of the absorption change of added pH indicator dyes and a decelerated decay of the endogenous carotenoid absorption band shift, following short flash excitation of Rhodopseudomonas sphaeroides chromatophores. 2. With increasing medium pH, lower concentrations of amine or local anaesthetics are effective. 3. The order of potency of the local anaesthetics concurs with their reported membrane/buffer partition coefficients and concentrations required for action potential blockade in nerve fibres. 4. The data are taken as evidence for rapid transport of the free base across the chromatophore membrane and relatively slow penetration of the protonated local anaesthetic. Protolytic reactions complete the effective dissipation of the trans-membrane pH gradient. 5. Benzocaine, with its unusually low pKa and the quaternary derivative, chloropromazine methiodide do not display this type of behaviour. 6. In the presence of membrane potential-collapsing agents, such as valinomycin/K+ or thiocyanate ions, local anaesthetics decelerate the decay of the cresol red change but have no effect on the carotenoid shift decay. It appears that transport of the unprotonated local anaesthetic although electrically neutral, requires the presence of a membrane potential. 7. In contrast, the non-anaesthetic amines act independently of the membrane potential. 8. Ca2+ interferes with the mechanism of local anaesthetic deceleration of the cresol red change decay in the presence of valinomycin/K+ or thiocyanate but not with other anaesthetic or amine reactions.

Bacterial Chromatophores↗
PubMed1996

Allosteric and competitive interactions of 2 alpha-(2',2'-disubstituted- hydroxy-ethoxy)tropane and its optical isomers at rat central muscarinic acetylcholine receptors.

Both allosteric and competitive interactions of 2 alpha-(2',2'-disubstituted-hydroxy-ethoxy)tropane (2 alpha-DHET) and its four optical isomers with muscarinic acetylcholine receptors in rat cerebral cortex were investigated. 2 alpha-DHET and its optical isomers allosterically decelerated the dissociation of bound [3H]N-methylscopolamine in a concentration-dependent manner, but these compounds failed to decelerate the dissociation of bound [3H]quinuclidinyl benzilate. The potencies of 2 alpha-DHET and its optical isomers to decelerate the dissociation of bound [3H]N-methylscopolamine were not differed significantly, but the competitive binding potencies of these compounds were significantly different. The order of potencies of 2 alpha-DHET and its four optical isomers to inhibit the binding of [3H]quinuclidinyl benzilate to central muscarinic acetylcholine receptors was 1S-2 alpha-2'R > 1R-2 alpha-2'R > 2 alpha-DHET > 1S-2 alpha-2'S > 1R-2 alpha-2'S the isomer with 1S-2 alpha-2'R configuration was about two orders of magnitude more potent than the isomer with 1R-2 alpha-2'S configuration. The allosteric potencies were found not to be correlated with their competitive binding potencies.

Allosteric Regulation↗
PubMed1977

Elective induction of labor conducted under lumbar epidural block. II. Labor induction by amniotomy and intravenous prostaglandin.

Labor was electively induced at term in 117 clinically normal nulliparae and parous women by combining low amniotomy with intravenous administration of prostaglandin F2 alpha (n = 64) or prostaglandin E2 (n = 53). Analgesia was obtained by continuous lumbar epidural block with bupivacaine. The procedure was very effective in producing vaginal delivery within 24 h after prostaglandin infusion (n = 115), but it was accompanied by an extremely high incidence of uterine hypertonus. Tentative explanations for the transient uterine hyperstimulation are a direct stimulatory effect of the local anesthetic on the contractility of the myometrial fiber and/or a temporarily higher amount of circulating oxytocic compound reaching the myometrium due to local vasodilatation as a result of sympathetic nerve blockade. In some cases uterine hypertonus was associated with slowing of the basal fetal heart rate and, when severe, with the appearance of late deceleration patterns and fetal acidosis. In other cases the fetal heart rate deceleration is explained by the toxic effect of bupivacaine on the myocard. Since both the myometrial hyperactivity and the FHR alterations were temporary, fetal biochemical parameters were unaffected at completion of the first stage of labor. Because with intravenous prostaglandin uterine hyperstimulation is more difficult to avoid and regional analgesia further increases the hazard of both hypertonus and fetal heart rate deceleration, the combined application of an intravenous prostaglandin and continuous epidural analgesia should not be introduced into obstetrical practice.

Adult↗
PubMed1982

Heart rate mechanisms in instrumental conditioning reinforced by petting in dogs.

The aim of this experiment was to determine heart rate (HR) responses during conditioned stimuli (CS) and the petting reward (US) delivered by the experimenter to the dogs after performance of the instrumental conditioned response (CR). It was found that in five dogs for which petting served as a positive reinforcement the delivery of petting was accompanied by cardiac deceleration followed by sudden acceleration at the moment of petting withdrawal. Presentation of CS evoked heart rate deceleration until performance of the first CR. At the start of performance of CRs, heart rate accelerated. It was suggested that heart-rate deceleration is an important component of cardiac response to petting reward and, that probably, it is associated with the hedonic aspect of the reinforcement.

Animals↗
PubMed1990

The shape of the cumulative food intake curve in humans, during basic and manipulated meals.

The shape of the cumulative food intake curve of normal weight and obese women was studied during solid food lunches, artificially prolonged meals, and energetically enriched meals eaten in a laboratory setting. Subjects (86 normal weight, 50 obese) displayed consistent eating behaviour over 3-6 repeated meals, with marked differences between individuals. Aspects of eating behaviour were reflected in decelerated and nondecelerated (or linear) cumulative intake curves depending on changes or no changes in eating rate during the course of a meal, respectively. A change in eating rate was generally related to decrease in bite size, with bite rate remaining constant, from the third temporal quarter of the meal onwards, resulting in a decelerated cumulative intake curve. The nondecelerated (linear) cumulative intake curve does not show this change in eating rate: in the first three temporal quarters bite size and bite rate were constant, whereas in the fourth temporal quarter bite size decreased slightly, compensated by a small increase in bite rate. Intraindividual ranges for meal parameters such as chewing time per bite, bite interval and initial eating rate indicated consistency of individual eating behaviour. In manipulation experiments with a subset of 21 subjects in which meals were artificially prolonged by an interval of 8 min, the cumulative intake curves did not differ significantly from the original cumulative intake curves in 10 nondecelerated (linear) eaters, but showed a change towards nondecelerated curves in 8 out of 11 decelerated eaters.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Physiological and psychological differentiation of bidirectional baroreceptor carotid manipulation in humans.

We investigated a phase-related-external-suction (PRES) method of bidirectional carotid stimulation which, unlike other methods, is not readily discriminable for direction (excitation vs. inhibition). Thirty-two subjects were first given 128 6-s PRES trials (64 each excitatory and inhibitory) which were signaled by two tones of differing frequency. There followed a 20-trial discrimination phase where subjects' task was to identify excitatory and inhibitory PRES trials (randomly presented) in terms of the two tone signals. Physiological (HR) discrimination was bidirectional (deceleration and acceleration for excitatory and inhibitory PRES trials, respectively), reflex-like (no habituation), but asymmetrical in magnitude (larger decelerations than accelerations), and topography (e.g., presence of a short latency deceleration). Group psychological discrimination was absent, although two subjects had a 100% hit rate on the discrimination test. There were, however, no systematic HR changes associated with these two subjects. Finally, the small-magnitude (2-3 bpm) physiological HR reflex was markedly augmented by what appeared to be a psychological, attentional factor. Accordingly, while the results indicated a dissociation between physiological and psychological differentiation, there was also evidence of a psychological factor (attention) influencing a physiologically induced reflex.

Adult↗
PubMed1988

Transition dynamics between pursuit and fixation suggest different systems.

The offset of smooth pursuit eye movements is very different from the onset. The onset eye velocity is characterized by overshoot and ringing before settling to steady-state velocity. Yet, at pursuit offset, the eye velocity returns smoothly to zero. One reason for this difference may be that the pursuit system is nonlinear and behaves differently during acceleration and deceleration. After testing four subjects, we found no difference between acceleration and deceleration ringing dynamics, except for decelerations to 0 +/- 2 deg/sec, suggesting that around zero velocity, the central nervous system switches off pursuit and adopts fixation. This supports the idea that fixation and pursuit represent different neurological systems.

Eye Movements↗
PubMed1995

A sulfated chitin, SCM-chitin III, inhibits the clearance of human erythrocytes from the blood circulation in erythrocyte-transfused SCID mice.

Recently, we have developed a SCID mouse model in which circulating red blood cells (RBC) are entirely substituted with RBCs from other animals like bovine (Bo) or human (Hu). The relatively short life time, especially of Hu-RBCs, in the SCID mouse, however, is a major obstacle in this model. The present study was performed to examine whether a low-toxic sulfated chitin, carboxymethyl chitin III (SCM-chitin III), which has heparin-like structures in the molecule (heparinoid), could inhibit the Hu-RBC clearance in RBC-transfused SCID mice. When Hu-RBCs were transfused simultaneously with SCM-chitin III, their life time in the blood circulation was prolonged significantly. Sulfated chitosan (S-chitosan) showed only a weak decelerating activity on the clearance of Hu-RBCs. Carboxymethyl chitin (CM-chitin), which was used as an unsulfated control compound, had no effect on the Hu-RBC clearance. Another sulfated polysaccharide, dextran sulfate, though this showed some adverse effects, such as anti-coagulant and anti-platelet aggregation, also exhibited a potent decelerating activity on Hu-RBC clearance. Clearance deceleration by these sulfated polysaccharides was primarily attributable to the inhibition of RBC uptake by cultured macrophages.

Animals↗
PubMed1993

The bilateral reach to grasp movement.

This study investigated the kinematic organization of bilateral reach to grasp movements. In Experiment 1 non-homologous bilateral movements were performed. One limb reached to grasp an object using whole hand prehension; the contralateral limb simultaneously reached to grasp an object using precision grip. Corresponding unilateral movements were assessed. Movement duration for each limb in the bilateral condition was similar. However, with earlier temporal settings for peak wrist acceleration and velocity, the limb performing precision grip showed a longer approach (deceleration) phase to the object. Unilateral precision grip movements showed a longer movement duration and deceleration phase than unilateral whole hand prehension movements. In Experiment 2 homologous bilateral movements were assessed. Both limbs performed either a reach and whole hand prehension or a reach and precision grip. Again the precision grip movements showed longer movement and deceleration times. Experiment 3 consisted of bilateral non-homologous pointing movements and a pointing movement with one limb while reaching to grasp with the contralateral limb. It was found that the earlier temporal settings of peak acceleration and velocity with the precision grip limb of the non-homologous bilateral task (Expt. 1) were largely due to the performance of distal grasping actions. It is concluded that a kinematic parameterization which is independent to each limb is evident for bilateral tasks which require functionally independent actions.

Adolescent↗
PubMed1996

Prehension with trunk assisted reaching.

For prehensile tasks, where objects are located beyond the normal reaching space, the trunk is bent forward to assist in the transport of the wrist to the object. Such task behaviors raise complex motor control issues such as how is the trunk movement incorporated into the motor plan. In this experiment, seated subjects were asked to reach and grasp a small and a large object placed on a table located beyond their maximal reach. Forward trunk bending was required to extend the reach distance. For such reaching movements, the wrist velocity consisted of a bell shape profile similar to those seen when the arm is the sole transport agent. In most trials, the trunk was the first to initiate movement, although there was no strict pattern of initiation order. The transport data showed that trunk and arm movement components were decoupled at the end of the reach. While the object was being grasped and lifted, the trunk continued moving for approximately 180 ms after the grasp. Wrist deceleration time expressed in absolute and relative values was sensitive to object size. The time from maximum peak aperture to the end of wrist movement also was significantly longer for grasping the small compared to the large object. No such relationships were observed for the trunk. Temporal coupling was only observed between the grip and wrist transport component. Time to maximum aperture was significantly correlated with time to peak wrist deceleration and only rarely with time to trunk deceleration peak. When the trunk participates in the transport of the wrist to an object, these findings suggest that only the wrist component is directly related to the achievement of the grasp. While the trunk assisted the arm to reach the object, the kinematic parameter recorded did not reveal any evidence of direct coupling. The presented data suggests that the planning takes place at the level of the hand and that endpoint is the primary variable controlled.

Acceleration↗
PubMed1990

Quantification of aortic regurgitation using continuous and pulsed wave Doppler echocardiography.

In a prospective blind study, continuous and pulsed wave Doppler echocardiography were used to predict the severity of angiographically assessed aortic regurgitation in 36 patients. High quality continuous wave spectral recordings of the regurgitant jet were obtained in 32 patients but four patients with mild aortic regurgitation had dropout of high velocity signals precluding accurate assessment. The deceleration slope of the peak to end-diastolic velocity measured by continuous wave Doppler, and pulsed wave Doppler mapping of the regurgitant jet in the left ventricle were compared with angiographic severity. The deceleration slope was significantly steeper in patients with severe rather than mild or moderate aortic regurgitation (3.65 +/- 1.04 vs. 1.89 +/- 0.42 vs. 1.52 +/- 0.59 m sec-2). A decay slope of greater than 3 m sec-2 was observed only in patients with 3+ or 4+ aortic regurgitation and a decay slope less than 1.2 m sec-2 was seen only in mild 1+ aortic regurgitation but there was considerable overlap between groups, making it difficult in individual cases to assess severity on the basis of the continuous wave deceleration slope. The pulsed wave Doppler technique was more time consuming, added little to the continuous wave Doppler assessment and underestimated severe regurgitation in almost 50% of cases. Hence, there are significant problems using either Doppler technique in quantitatively assessing aortic regurgitation.

Adolescent↗
PubMed1982

Age effects on heart rate, sustained potential, and P3 responses during reaction-time tasks.

Relationships between physiological responses and slowed reaction time (RT) among elderly subjects were tested in 48 healthy young, middle-aged, and elderly men (mean ages 24, 45, and 71 years) using simple and choice RT tasks. There were age reductions in P3 amplitude and heart rate (HR) deceleration, but no effects of age on P3 latency. Sustained potential (SP or CNV) amplitude paradoxically increased with age, possibly indicating weaker inhibitory function. P3 amplitude, SP amplitude, and HR deceleration were most strongly correlated with RT among younger subjects, but SP amplitude was correlated with RT in the elderly group during the choice task. HR deceleration shared a small amount of variance with SP amplitude and RT in the young group. There was no HR-SP-RT relationship in the older groups. Choice-simple task differences in P3 amplitude and RT were correlated in the young and elderly groups. The results suggest that HR, SP, and P3 responses may reflect physiological processes related to the slower RTs of healthy elderly subjects.

Action Potentials↗
PubMed1976

Organismic, stimulus and task determinants of phasic and tonic heart rate and skin conductance changes.

The effects of three variables (perceptual style 'leveling--sharpening', stimulus intensity and task) on tonic and phasic heart rate and skin conductance responses were studied. 24 levelers and 24 sharpeners received a series of 25 auditory stimuli under two instructions (task): in one task subject had to listen carefully to possible small differences between tones (intake task) and in the other task the subject had to count back silently and could neglect the tones (rejection task). One third of each group received tones of 50 dB, one third 75 dB and one third 100 dB. Results show that task has a strong effect on tonic responses in the direction predicted from Lacey's intake--rejection hypothesis. There is hardly any effect of task on phasic responses: only at the first trial heart rate tends to decelerate more in the intake than in the rejection task. Stimulus intensity does not influence tonic responses but very strongly affects phasic responses: deceleration to 50 and 75 dB, acceleration to 100 dB. GSR amplitude increases monotonically as a function of stimulus intensity. There is no difference between levelers and sharpeners with regard to tonic responses. Concerning phasic heart rate, sharpeners decelerate more than levelers and levelers have greater GSRs than sharpeners. It is suggested that tonic changes are relatively more under cognitive control, whereas phasic changes are more of a non-cognitive reflex-like nature. A relationship between the distinction arousal-activation as proposed by Pribram and McGuinness (1975) and the results of this experiment was suggested.

Acoustic Stimulation↗