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Biomedical subjects

L Carmichael

Publications and source records attributed to L Carmichael.

At least 55 records · Page 3Linked to original sources
PubMed1987

External vibratory acoustic stimulation near term: fetal heart rate and heart rate variability responses.

Twenty-five pregnant women between 36 and 40 weeks' gestational age were studied to examine effects of a 5-second external vibratory acoustic stimulus on the fetal heart rate and fetal heart rate variability. There was an immediate significant increase in the basal heart rate, which persisted for 1 hour after the stimulus, compared to that of the control subjects. There was also a significant increase in the total time during which accelerations occurred for the first 20 minutes after the stimulus. There were no changes in computer-derived indices of fetal heart rate variability. Maternal blood pressure and heart rate were not altered following vibratory acoustic stimulus. We hypothesize that external vibratory acoustic stimulus causes a change from a state of sleep to a state of wakefulness in near term healthy fetuses.

Acoustic Stimulation↗
PubMed1987

Human fetal responses to vibratory acoustic stimulation from twenty-six weeks to term.

Eighty-three healthy pregnant women between 26 and 40 weeks' gestational age were studied to examine effects of a 5-second external vibratory acoustic stimulus on the fetal heart rate, fetal breathing, and gross fetal body movement patterns. There was an immediate fetal heart rate response, following stimulus, characterized by an increase in duration of fetal heart rate accelerations from 26 weeks to term with an increase in basal fetal heart rate after 30 weeks. There was also a delayed response after 33 weeks' gestation, which consisted of an increase in the number of fetal heart rate accelerations and the incidence of gross fetal body movements for up to 1 hour after a 5-second stimulus with the electronic artificial larynx. Term (36 to 40 weeks) fetuses made breathing movements more irregularly after vibratory acoustic stimulation. We suggest that human fetal responses to stimulation with the electronic artificial larynx may reflect a functional maturation of the fetal central nervous system.

Acoustic Stimulation↗
PubMed1987

Cerebral oxidative metabolism in fetal sheep with multiple-dose ethanol infusion.

Cerebral oxidative metabolism and cotylendonary blood flow were measured in 10 unanesthetized fetal sheep (127 to 132 days' gestation) during a control period, after the first, third, and fourth infusions of four doses of 0.5 gm of ethanol per kilogram of maternal body weight infused into the ewe during 5 hours, and 24 hours after ethanol infusion. Preductal arterial and sagittal vein blood samples were analyzed for oxygen content, blood gases, pH, and ethanol. Cerebral and cotylendonary blood flow were measured with a radioactive microsphere technique. Fetal blood gases and pH changed little with the ethanol infusions, although PaO2 and oxygen content decreased 24 hours after ethanol infusion. Cotylendonary blood flow, which was decreased after the third and fourth ethanol infusions, did not account for these delayed hypoxemic changes. Similarly, cerebral oxidative metabolism was decreased when measured after each of the ethanol infusions, with no dose response or tolerance evident. This noted fall in fetal cerebral oxidative metabolism appears to be a direct depressant effect that was maximal at rather low fetal ethanol levels, which, if prolonged, might well affect cerebral growth and development. Recovery of cerebral metabolic function appeared complete by 24 hours. However, relative fetal hypoxemia was evident at this time, the mechanism of which remains to be determined.

Animals↗
PubMed1986

Effects of vibratory acoustic stimulation on human fetal breathing and gross fetal body movements near term.

Twenty-five pregnant women between 36 and 40 weeks' gestational age were studied to examine effects of a 5-second external vibratory acoustic stimulus on fetal breathing and gross fetal body movement patterns. When the study period was compared with the control period, there was an immediate significant decrease in the incidence of fetal breathing movements that persisted for 1 hour after the stimulus. Moreover the fetal breathing pattern was more irregular for the hour after the stimulus. There was also a significant but delayed increase in the incidence of gross fetal body movements that persisted for 1 hour after the stimulus. We hypothesize that an external vibratory acoustic stimulus causes a change from a state of sleep to a state of wakefulness in near-term healthy fetuses.

Acoustic Stimulation↗
PubMed1986

Analysis of fetal activity and maternal and fetal heart rate using a laboratory minicomputer.

Using a PDP-11 minicomputer, a system was developed for real-time acquisition of fetal breathing, body movement, and heart rate data. Analogue event pulses were input electronically to a DR-11 16 channel A/D, D/A interface and the event times were measured using an AR-11 real-time clock. Event times were stored for comprehensive off-line analysis and useful data summaries were also provided on-line. The on-line printouts enabled investigators to examine the quality of the data at the time of the study. The system has resulted in faster data acquisition and analysis and greater accuracy of measurement.

Computers↗
PubMed1985

The distribution of accelerations of the human fetal heart rate at 38 to 40 weeks' gestational age.

In order to further understand the use of antepartum fetal heart rate monitoring we measured the distribution, in time, of two, three, or five fetal heart rate accelerations of greater than or equal to 15 bpm for greater than or equal to 15 seconds and of greater than or equal to 10 bpm for greater than or equal to 6 seconds in 12 healthy pregnant women at 38 to 40 weeks' gestation. The length of time necessary to measure 50% or 95% of intervals containing five accelerations would be substantially reduced by changing to a definition of two or three accelerations. However, an observation interval of at least 80 minutes is required to include the longest time interval of two, three, or five accelerations. These data may suggest new strategies for decreasing time and expense of fetal heart rate testing.

Female↗
PubMed1984

The effects of maternal hyperoxia on fetal breathing movements in third-trimester pregnancies.

Fetal breathing movements and gross fetal body movements were observed before, during, and after maternal hyperoxia induced by inhalation of 50% oxygen in 14 women with normal term pregnancies. Studies were performed with real-time B-scan linear-array ultrasound and were standardized for time of day, maternal nutritional status, postprandial interval, and length of observation. Each study included a 30-minute baseline, followed by 15 minutes of hyperoxia, and 45 minutes of continued monitoring. No significant changes occurred in the mean incidences of fetal breathing movements, gross fetal body movements, the mean breathing rate, or breath interval variability, as analyzed in 5-minute epochs. Maternal PO2, as measured by transcutaneous electrodes, increased to the maximum level after 5 minutes of hyperoxia (155% over control levels). The breathing activity of normal third-trimester fetuses appears to be stimulated maximally in the second and third postprandial hours and cannot be further increased by maternal hyperoxia. This protocol represents a possible clinical strategy for investigating fetuses at risk for intrauterine hypoxia, provided that similar experimental conditions are maintained.

Female↗
PubMed1984

Absence or impaired response of fetal breathing to intravenous glucose is associated with pulmonary hypoplasia in congenital myotonic dystrophy.

Two fetuses of a patient affected with myotonic dystrophy were studied ultrasonically from 28 to 34 weeks' gestation. After a 1-hour observation period, an intravenous injection of 25 gm of 50% glucose solution was given to the mother. Fetal breathing movements were 0% during the control period and increased to only 10% at 90 minutes after the injection of glucose; the episode lasted approximately 30 minutes. The infants, who were delivered at 33 and 35 weeks, had generalized hypotonia, normal arterial cord blood gases, and died shortly after birth from pulmonary insufficiency, in spite of maximum ventilatory support. Postmortem pulmonary hypoplasia was confirmed by a lung weight/body weight ratio of less than 0.019. We postulate that fetal breathing activity and its response to the injection of glucose may be a potential clinical test by which normal fetuses can be differentiated from fetuses affected by neuromuscular disorders, including myotonic dystrophy.

Adult↗
PubMed1984

Maternal glucose injections do not alter the suppression of fetal breathing following maternal ethanol ingestion.

In order to determine whether intravenous injections of glucose could reverse the effects of maternal ingestion of ethanol (0.25 gm/kg), glucose (25 gm intravenously) or an equal volume of saline solution was administered to eight pregnant women at 37 to 40 weeks' gestation after ingestion of ethanol. Fetal breathing movements were abolished within 30 minutes after ingestion of ethanol and were not increased by maternal intravenous injections of glucose. Maternal heart rate was increased by ethanol. The disposition of ethanol in maternal blood was not altered by injection of glucose, and fetal gross body movements were not influenced by maternal ingestion of ethanol or by injections of glucose after ethanol.

Blood Glucose↗
PubMed1984

Fetal breathing, gross fetal body movements, and maternal and fetal heart rates before spontaneous labor at term.

In order to examine patterns of fetal breathing and body movements and fetal and maternal heart rates near term, we studied 28 healthy pregnant women over 24-hour observation intervals at 38 to 40 weeks' gestation. There was a significant decrease in the incidence of fetal breathing movements during the last 3 days before spontaneous parturition at term, but there was no significant difference in the patterns of gross body movements or fetal and maternal heart rates. We concluded that, prior to spontaneous labor at term, there is a normal decrease in the incidence of fetal breathing movements but no similar change in the incidence of gross fetal body movements. This study suggested that the presence of gross fetal body movements is a more consistent index of fetal health before spontaneous labor at term.

Female↗
PubMed1984

Effect of intravenous glucose injection on human maternal and fetal heart rate at term.

The effects of maternal intravenous glucose administration (25 gm) on maternal heart rate, fetal heart rate, gross fetal body movements, and fetal heart rate accelerations was measured in 11 healthy pregnant women at 38 to 40 weeks' gestational age. Mean maternal heart rate increased from 78.3 +/- 0.8 bpm during the control period to 82.7 +/- 0.5 bpm at 30 to 85 minutes following glucose injections (p less than 0.01). Mean fetal heart rate rose from 137.8 +/- 0.4 bpm to 142.4 +/- 0.3 bpm at 50 to 95 minutes following injections (p less than 0.001). The incidence of gross fetal body movements and the number, duration, and amplitude of fetal heart rate accelerations did not change following glucose injection. We conclude that maternal glucose administration near term results in a small but significant increase in the mean maternal heart rate and fetal heart rate and no change in the incidence of gross fetal body movements or in fetal heart rate accelerations.

Blood Glucose↗
PubMed1984

Accelerations of the human fetal heart rate at 38 to 40 weeks' gestational age.

In order to document the normal structure and pattern of fetal heart rate accelerations near term, we measured fetal heart rate and fetal movements for 24-hour observation intervals in 12 healthy pregnant women at 38 to 40 weeks' gestation. There were 34 accelerations per hour on the average with a mean amplitude of 22.8 bpm and a mean duration of 40.7 seconds. The longest time between successive accelerations was 37 minutes. There was a significant negative correlation between the mean daily maximum amplitude of accelerations and the mean daily fetal heart rate (r = -0.84). Fetal heart rate acceleration patterns suggested a prolonged period of fetal wakefulness during the late evening.

Electrocardiography↗
PubMed1984

Antisperm responses in male dogs with chronic Brucella canis infections.

Male Beagles infected with Brucella canis for greater than or equal to 3 months developed serum antibodies that agglutinated normal canine spermatozoa. Titers were highest in dogs that had been infected for 4 to 6 months. Lower spermagglutinin titers were detected in sera collected 10 months after inoculation. Antibodies were also observed in seminal plasma of chronically infected dogs. Seminal plasma from infected, but not from clinically normal dogs, caused head-to-head agglutination of normal sperm. In contrast to macroagglutination of sperm by serum antibodies, agglutination by seminal plasma antibodies was detected only by microscopic examination. Seminal plasma agglutinins were not inactivated by heat (56 C, 1 hour) or by reduction with 2-mercaptoethanol. When seminal plasma and sperm were mixed with 2 hemolytic units of guinea pig complement, spermatozoa were not inactivated. Spermagglutinin activity was present in the first 2 spectral absorption peaks of Sephadex G-200 fractionated seminal plasma. Fractions that had the highest spermagglutinin titers contained mostly immunoglobulin A. Seminal plasma from infected dogs also contained cytophilic factors for normal splenic macrophages that caused sperm adherence to macrophages. Dogs with a bacteremia lasting greater than 4 months had cutaneous delayed-type hypersensitivity reactions when tested with soluble canine testicular extracts. Reactions did not occur in normal dogs. Dogs with testicular atrophy had the most severe skin test responses. Seemingly, isoimmune responses to sperm antigens are involved in infertility caused by B canis infection of male dogs.

Agglutinins↗
PubMed1983

Effect of maternal ethanol ingestion on fetal breathing movements, gross body movements, and heart rate at 37 to 40 weeks' gestational age.

The effect of maternal ingestion of ethanol (0.25 gm/kg) on fetal breathing movements, gross fetal body movements, and fetal heart rate was studied in 11 healthy pregnant women at 37 to 40 weeks' gestation. Fetal breathing movements were almost abolished within 30 minutes of the alcoholic drink and remained significantly decreased for 3 hours. The incidence of gross fetal body movements before or after ethanol was not different from that on the control day, and the fetal heart rate was not changed after maternal ingestion of ethanol.

Adult↗
PubMed1982

Influence of maternal heart rate and gross fetal body movements on the daily pattern of fetal heart rate near term.

Continuous measurements of fetal heart rate (FHR), gross fetal body movements, fetal breathing movements, and maternal heart rate (MHR) were made for 24-hour observation intervals in 11 pregnant women at 38 to 40 weeks. There was a significant positive correlation between each mother's daily mean MHR and her fetus' daily mean FHR. There was a trough in mean hourly FHR between 0200 and 0600 hours and a trough in mean hourly MHR between 2400 and 0700 hours. Mean hourly FHR both during and between times of gross fetal body movements was significantly correlated to mean hourly MHR. At term, the mean FHR is strongly influenced by the mean MHR and the presence or absence of gross fetal body movements.

Circadian Rhythm↗
PubMed1982

Effects of intravenous glucose injections on human fetal breathing movements and gross fetal body movements at 38 to 40 weeks' gestational age.

Fetal breathing movements and gross fetal body movements were studied subsequent to the intravenous injection of either 25 gm of glucose or an equal volume of normal saline solution in 10 healthy women with uncomplicated pregnancies at 38 to 40 weeks' gestation. The incidence of fetal breathing increased from 17.5% during the control period to 54.9% after glucose injection. Neither glucose nor saline solution had any effect on the incidence of gross fetal body movements. All fetuses made some breathing movements during any 15-minute interval between 30 and 75 minutes after glucose injection. These data suggest a useful strategy for clinical measurement of fetal breathing activity near term.

Apgar Score↗
PubMed1982

Patterns of gross fetal body movements over 24-hour observation intervals during the last 10 weeks of pregnancy.

Continuous measurements of gross fetal body movements were made with an ultrasonic real-time scanner for periods of 24 hours in 31 women. Fetuses made 0 to 130 gross fetal body movements per hour which accounted for 0% to 50% of the time. At 38 to 39 weeks' gestational age, fetuses demonstrated a peak in activity between 2100 and 0100 hours. The longest period of complete absence of gross fetal body movements was 75 minutes. Maternal meals and glucose concentrations did not influence gross fetal body movements.

Activity Cycles↗