Can meconium in the amniotic fluid injure the fetal brain?
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Amniotic Fluid↗
Biomedical subjects
L D Montgomery
Publications and source records attributed to L D Montgomery.
Pelvic blood pooling of men and women during lower body negative pressure.
INTRODUCTION: The objective of this study was to investigate possible gender differences in the hemodynamic responses of the lower body during lower body negative pressure (LBNP). METHODS: In this study, 17 women (mean age = 56 yrs) and 15 men (mean age = 55 yrs) underwent a 15 min exposure to -50 mm Hg LBNP. A Beckman (BR-100) Impedance Plethysmograph was used to measure each subject's leg and pelvic blood flow and pooling during the LBNP test. RESULTS: The women had an 83% greater increase in blood volume in the pelvic region than men as a result of the LBNP exposure. Women and men had similar increases in leg blood volume as a result of the 15 min exposure to -50 mm Hg. There was no significant gender difference in the decreased amount of blood flow to the leg or pelvic regions by the end of -50 mm Hg LBNP. CONCLUSIONS: These results demonstrate that women have greater blood pooling in the pelvic region compared to men when exposed to -50 mm Hg LBNP. These results should be considered when designing life-support equipment for men and women pilots and astronauts, especially the designing of anti-G and Space Shuttle re-entry garments.
Aged↗
Massive fetomaternal hemorrhage treated with serial combined intravascular and intraperitoneal fetal transfusions.
One of the many causes of fetal hydrops is fetomaternal hemorrhage. This report presents a pregnancy with fetomaternal hemorrhage that was treated with serial combined intravascular and intraperitoneal fetal transfusions, resulting in a good outcome. A 26-year-old woman seen for ultrasonographic evaluation was found to have a fetus with hydrops fetalis. Fetal blood sampling demonstrated severe fetal anemia (hematocrit 16.4%). The initial Kleihauer-Betke test result on maternal blood was 6% fetal cells. The fetus was transfused five times over a 24-day period by means of a combined intravascular and intraperitoneal route. The fetus also received one platelet transfusion for thrombocytopenia. The pregnancy resulted in a good fetal outcome without the need for postpartum transfusion. This case represents successful treatment of fetal anemia and nonimmune hydrops with a serial combined intravascular and intraperitoneal transfusion technique.
Adult↗
Meconium inhibits the contraction of umbilical vessels induced by the thromboxane A2 analog U46619.
OBJECTIVE: Our objective was to study the direct effects of meconium on isolated umbilical artery and vein in vitro. STUDY DESIGN: Intact umbilical artery and vein rings were suspended in 5 ml organ baths containing kreb's solution (pH 7.2, 37 degrees C; bubbled with 2.5% oxygen and 8.07% carbon dioxide, balance nitrogen) for isometric tension recording. Meconium alone (final bath concentration 1%), centrifuged and filtered meconium, and meconium with the lipid fraction removed (separated into < 30,000 kd and > 30,000 kd) were added to the baths. Some vessels were also incubated in 1% meconium for 30 minutes, after which the meconium was washed out. Concentration-response curves to U46619 were obtained. The negative log of the concentration that evokes 50% of the maximal contraction was determined. RESULTS: Umbilical artery and vein had no sustained response to meconium. Tension that developed by rings exposed to meconium was significantly less than control at all concentrations of U46619. There was some loss of the efficacy of meconium after centrifugation-filtration and washing out. Meconium without the lipid fraction had less inhibitory effect than did native meconium. CONCLUSIONS: Meconium does not cause sustained contraction of umbilical artery and vein in vitro. It does, however, inhibit the contractile effect of U46619 in both umbilical artery and vein smooth muscle. The inhibitory activity of meconium appears to be concentrated in the lipid fraction.
15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
Rheoencephalographic and electroencephalographic measures of cognitive workload: analytical procedures.
This investigation demonstrates the feasibility of mental workload assessment by rheoencephalographic (REG) and multichannel electroencephalographic (EEG) monitoring. During the performance of this research, unique testing, analytical and display procedures were developed for REG and EEG monitoring that extend the current state of the art and provide valuable tools for the study of cerebral circulatory and neural activity during cognition. REG records are analyzed to provide indices of the right and left hemisphere hemodynamic changes that take place during each test sequence. The EEG data are modeled using regression techniques and mathematically transformed to provide energy-density distributions of the scalp electrostatic field. These procedures permit concurrent REG/EEG cognitive testing not possible with current techniques. The introduction of a system for recording and analysis of cognitive REG/EEG test sequences facilitates the study of learning and memory disorders, dementia and other encephalopathies.
Adult↗
Seroprevalence of human immunodeficiency virus among inpatient pretrial detainees.
Medical records of inpatients discharged from a forensic unit in Columbia, South Carolina, from January 1991 to December 1991 were reviewed to determine the incidence of human immunodeficiency virus (HIV) seropositivity. Results were linked to age, gender, ethnicity, history of intravenous drug use, and Axis I diagnoses. HIV status was obtained for 74 percent of patients 18 to 55 years of age. The incidence of HIV seropositivity among patients tested was 5.5 percent, which is greater than 40 times the incidence for the general population in South Carolina. Intravenous drug use was reported for 33 percent of the seropositive males. We conclude that inpatient pretrial detainees are at increased risk for HIV infection. HIV testing should be mandated at all facilities housing detainees. Further studies are needed to determine any factors about these patients that can be linked to seropositivity.
AIDS Serodiagnosis↗
Effect of smoking cessation upon circulatory responses to reactive hyperemia and cold pressor stress.
Local and sympathetic nervous system stress tests were administered prior to and following a 5-d smoking cessation program to determine the effects of short term smoking cessation upon peripheral circulation. Reactive hyperemia (RH) tests were performed on the forearm as a local dilatory stressor. Finger blood flow responses to cold pressor (CP) stresses were used to access stimulation of the sympathetic nervous system. Measures of heart rate and total forearm or finger blood flow, pulse volume and rate of blood delivery were obtained continuously during each stress test. Smoking cessation produced a significant decrease (0.01 < p < 0.05) in heart rate during both the RH and CP test sequences. Grouped mean peak forearm blood flow (Mean difference = 2.11 ml.100 ml-1.min-1; p < 0.05) and pulse volume (Mean difference = 0.04 ml.100 ml-1.pulse-1; p < 0.01) were both significantly greater following occlusion during the post-cessation RH tests than during the similar test before smoking cessation. Both finger pulse volume and rate of blood delivery were significantly greater (0.01 < p < 0.05) during the recovery portion of the post-cessation CP tests than during the same period of the pre-cessation tests. Thus, smoking cessation significantly altered both the locally mediated and central nervous system controlled responses to externally applied stressors.
Aged↗
Body volume changes during simulated microgravity I: Technique and comparison of men and women during horizontal bed rest.
It has been hypothesized that many of the adaptive processes that occur in man during exposure to microgravity involve the rapid headward shift of fluids during the first few hours of spaceflight. Impedance plethysmography was used to measure lower body volume changes in men and women during horizontal bed rest simulated microgravity. Segmental volumes calculated from the leg impedance values are compared to similar volumes determined from detailed anthropometric measurements. The results of this experiment indicate that men and women respond differently to bed rest and that impedance plethysmography can be used to quantify the extent of fluid redistribution in the body during actual or simulated microgravity in a manner that corresponds well with anthropometric determinations.
Anthropometry↗
Body volume changes during simulated microgravity. II: Comparison of horizontal and head-down bed rest.
Changes in segmental fluid volume were measured in 10 male subjects during 7 d of either horizontal (0 degrees) or antiorthostatic (-6 degrees) head-down bed rest as part of the Joint U.S./U.S.S.R. Hypokinesia Program. Impedance plethysmography (IPG) was used to measure leg, pelvic, thoracic, and arm volume changes prior to, during, and following bed rest. Results of this study demonstrate that antiorthostatic bed rest produces a larger and more persistent thoracic fluid shift than horizontal bed rest. Segmental volume responses found during this investigation are compared to those obtained during other simulated or actual space-flight experiments. Antiorthostatic thoracic volume changes from this study were found to closely approximate those estimated to take place in space while leg volume changes produced by either 0 degrees or -6 degrees bed rest were much less than those observed by others in the microgravity environment.
Adult↗
Simultaneous use of rheoencephalography and electroencephalography for the monitoring of cerebral function.
Many of the changes in human performance under stress or in hazardous environments may be attributed, in part, to altered cerebral functions. These changes may take place in either the cerebral neurologic or cerebral circulatory systems. Investigation of the interaction between intracranial blood flow and neural activity during these exposures would provide a better understanding of the human response to these conditions. Experimental and analytical procedures are described whereby the combination of rheoencephalography (REG) and electroencephalography (EEG) may provide additional information during the study of cerebral function. Examples are given to demonstrate the simultaneous use of these techniques during mental arithmetic and antiorthostatic bed rest. Results of these tests in both the time and frequency domains show that REG and EEG can be used to provide graded quantitative measures of cerebral responses to externally applied stressors.
Cerebrovascular Circulation↗
Cortical localization of cognitive function by regression of performance on event-related potentials.
This paper demonstrates a new method of mapping cortical localization of cognitive function, using electroencephalographic (EEG) data. Cross-subject regression analyses are used to identify cortical sites and post-stimulus latencies where there is a high correlation between subjects' performance and their cognitive event-related potential (ERP) amplitude. The procedure was tested using a mental arithmetic task and was found to identify essentially the same cortical regions that have been associated with such tasks on the basis of research with patients suffering localized cortical lesions. Thus, it appears to offer an inexpensive, noninvasive tool for exploring the dynamics of localization in neurologically normal subjects.
Adult↗
Hemodynamic responses to seated and supine lower body negative pressure: comparison with +Gz acceleration.
Hemodynamic changes between upright and supine lower body negative pressure (LBNP) to levels of -70 mm Hg were compared in 8 subjects (5 males, 3 females) and correlated with their findings during simulated Shuttle reentry acceleration with a slow onset rate of 0.002 G/s (1,020 s to peak +2 Gz) and during gradual onset exposures (0.03 G/s) to +3 Gz and +4 Gz. Six of the 8 subjects were able to tolerate 2 min at peak +2 Gz, 2-5 min at +3 Gz, and 1-2 min at +4 Gz. Heart rate (HR) at any given level of upright LBNP regularly exceeded supine levels. HR change at -50 mm Hg in upright subjects (+47.7 bpm from 74.1 +/- 1.9 (M +/- S.E.) bpm, control) was 2.6 times greater than in supine subjects (+18.3 bpm from 64.8 +/- 2.8 bpm, control). HR values at -40 mm Hg supine (73.7 +/- 2.6) matched seated upright pre-LBNP control levels (74.1 +/- 1.9 bpm), while values at -70 mm Hg supine (102.5 +/- 4.4 bpm) were not significantly different from those at -40 mm Hg upright (103.1 +/- 4.0 bpm). Peak HR during +3 Gz (145.8 +/- 7.7 bpm) and +4 Gz (152.3 +/- 6.5 bpm) significantly exceeded recorded supine and upright LBNP levels, whereas values at +2 Gz (104.8 +/- 5.5 bpm) closely matched those at -40 mm Hg upright (103.1 +/- 4.0 bpm) and -70 mm Hg supine (102.5 +/- 4.4 bpm). Supine LBNP HR changes in this relatively small group of subjects closely matched those previously reported in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
An impedance device for study of multisegment hemodynamic changes during orthostatic stress.
Definition of multisegment hemodynamic changes that take place in the body would provide a more complete understanding of the physiologic responses to various orthostatic stress techniques. A self-contained impedance device is described which may be used to measure the electrical transmission characteristics produced by blood flow and volume changes in six segments of the human body during head-up tilt, bed rest, and lower body negative pressure. The device consists of a module that contains the electronics for the impedance system, a separate controller/multiplexer, a personal computer interface/analog to digital conversion/power supply system, and the associated computer control software. The instrument is linear over a range of 0 to 200 ohms; provides analog outputs of base impedance, phase angle, pulsatile impedance change, and the first derivative of the pulsatile impedance changes; and can be used to automatically record basal impedance values into spread-sheet format with cycle times between 12 s and 1 h. Typical results are presented to illustrate its application in aerospace research.
Equipment Design↗
A system to measure lower body volume changes during rapid onset high-G acceleration.
A specialized four-channel impedance plethysmograph is described that can be used to measure calf, thigh, and abdominal volume changes during rapid onset rate centrifuge acceleration. Typical results are presented to demonstrate its application to research and the design and assessment of countermeasures to enhance man's performance in the high-G environment.
Acceleration↗
Body volume changes during simulated weightlessness: an overview.
It has been hypothesized that many of the adaptive processes that occur in man during exposure to space involve the rapid headward shift of tissue fluids, blood, and other fluids during the first few hours of spaceflight. A total of 53 men and women between the ages of 22 and 55 years were tested during four bed rest studies lasting between 4 h and 7 d to define the segmental volume changes that took place during simulated weightlessness. Impedance plethysmography can be used to measure baseline resistance (Ro) changes of the calf, thigh, total leg, pelvic, torso, and arm segments before, during, and after each bed rest exposure. Records of Ro were analyzed to determine the fluid volume and volume change of each segment during each test sequence.
Adaptation, Physiological↗
Cardiovascular dynamics associated with tolerance to lower body negative pressure.
The purpose of this investigation was to identify cardiovascular responses associated with tolerance to lower body negative pressure (LBNP). In this study, 18 men, ages 29-51 years, were categorized as high (HT) or low (LT) LBNP tolerant based on a graded presyncopal-limited LBNP exposure criterion of -60 mm Hg relative to ambient pressure. Groups were matched for physical characteristics and preLBNP cardiovascular measurements, with the exceptions of greater (p less than 0.05) end-diastolic volume and cardiac output in the HT group. During peak LBNP, cardiac output was similar (NS) in both groups, although the HT group displayed a greater heart rate (p less than 0.05). In both groups, venous return appeared to limit cardiac output resulting in decreased arterial pressure. Tolerance to LBNP did not appear solely dependent on the absolute amount of blood pooled in the legs since the HT group demonstrated a greater (p less than 0.05) peak LBNP-induced increase in midthigh-leg volume. Greater tolerance to LBNP was associated with a larger preLBNP cardiac output reserve and higher compensatory increases in heart rate and peripheral resistance.
Adult↗
Studies on prenatal and postnatal development in rats exposed to 60-Hz electric fields.
A series of three experiments was performed to determine the effects of 30-day exposures to uniform 60-Hz electric fields (100 kV/m) on reproduction and on growth and development in the fetuses and offspring of rats. In the first experiment, exposure of females for 6 days prior to and during the mating period did not affect their reproductive performance, and continued exposure through 20 days of gestation (dg) did not affect the viability, size, or morphology of their fetuses. In the second experiment, exposure of the pregnant rat was begun on 0 dg and continued until the resulting offspring reached 8 days of age. In the third experiment, exposure began at 17 dg and continued through 25 days of postnatal life. In the second and third experiments, no statistically significant differences suggesting impairment of the growth or survival of exposed offspring were detected. In the second experiment, a significantly greater percentage of the exposed offspring showed movement, standing, and grooming at 14 days of age than among-sham-exposed offspring. There was a significant decrease at 14 days in the percentage of exposed offspring displaying the righting reflex in the second experiment and negative geotropism in the third experiment. These differences were all transient and were not found when the animals were tested again at 21 days of age. Evaluation of the reproductive integrity of the offspring of the second experiment did not disclose any deficits.
Age Factors↗
Thermoregulatory responses of rats to varying environmental temperatures.
The peripheral (tail) circulatory responses of six male albino rats were measured at ambient temperatures between 5 and 40 degrees C, using impedance plethysmography. Each animal was anesthetized, instrumented, and placed in a thermal environmental chamber to reach equilibrium. Tail blood flow, respiration rate, heart rate, core temperature, and tail skin temperature were then monitored at each ambient temperature. The mean tail blood flow was significantly higher (p less than 0.05) at 5 degrees C than at 10 degrees C. The mean blood flow increased significantly (p less than 0.01) at each of the temperatures above 10 degrees C. Tail skin temperature and internal body (core) temperature increased significantly with increasing ambient temperature.
Animals↗