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Biomedical subjects

R O Davis

Publications and source records attributed to R O Davis.

At least 73 records · Page 4Linked to original sources
PubMed1989

A comparison of perinatal outcome in patients undergoing contraction stress testing performed by nipple stimulation versus spontaneously occurring contractions.

Perinatal outcomes were analyzed in 848 high-risk pregnancies managed with a prospective weekly contraction stress testing protocol. In 615 patients the last test was performed by a nipple stimulation protocol whereas 233 patients had sufficient spontaneous contractions for performance of the test. All patients were either delivered of their infants or admitted for delivery within 7 days of the last test. The results of the last test were compared to various perinatal outcome parameters. There was no significant difference in perinatal outcomes between the two groups.

Breast↗
PubMed1989

Indomethacin-induced oligohydramnios.

A case of reversible indomethacin-induced oligohydramnios is presented. This case suggests a relationship between the dose of indomethacin and the quantity of amniotic fluid.

Adult↗
PubMed1989

Prematurity, postdates, and growth retardation: the influence of use of ultrasonography on reported gestational age.

The preterm and postterm delivery rates and the percentage of infants with intrauterine growth retardation are dependent on the gestational age recorded at delivery. At our institution a sharp increase in the preterm delivery rate and a coincident decrease in the postterm delivery rate and the rate of intrauterine growth retardation were noted. Over a 3-year period, while the characteristics of the obstetric population changed only slightly, the gestational age distribution shifted, with a decrease in the mean gestational age of about 1 week and a risk in the reported preterm delivery rate from 12% to 17%. About 15% of this rise was explained by an increase in obstetric interventions, and another 15% can be explained by changes in the way physicians rounded off gestational age. The majority of the increase in the preterm delivery rate was related to changes involving ultrasonographic examinations. These changes included a greater percentage of the population examined, trends toward earlier examinations, a tendency for the physicians to use ultrasonography rather than the last menstrual period in choosing the final gestational age, the use of different standards, an increase in the number of structures measured, and the weight given to various structures for determination of gestational age. It is apparent that changes in use of ultrasonography had a profound effect on the reported gestational age distribution at our institution.

Birth Weight↗
PubMed1989

Preliminary results from the Collaborative Alabama and Scandinavian Study of Successive Small-for-Gestational Age Births.

The study "Successive Small-for-Gestational Age Births" (SGA study) was initiated and is sponsored by the National Institutes of Health (N.I.H.) in the U.S.A. Its purpose is to describe and characterize the different types of intra-uterine growth retardation and their consequences, to assess the associated risk factors, and to provide a basis for preventive measures. Starting in 1986, it runs concurrently in Bergen and Trondheim (Norway), Uppsala (Sweden) and Birmingham, Alabama (U.S.A.), recruiting pregnant para 1 and 2 mothers at high risk of having an SGA birth and a random (control) sample of the total pregnant population. Data collection will end in late 1989, when the last-born children have reached 13 months of age. At the present symposium, investigators from all four study centers and the N.I.H. described the study design and discussed problems of methodology. Strict standardization of parameters to determine gestational age (ultrasound, menstrual dates) is a prerequisite for comparison of results over time and between study centers. Some preliminary results were presented.

Alabama↗
PubMed1989

Computer-aided sperm analysis (CASA): image digitization and processing.

The active undulations of a sperm flagellum are a basic expression of cell vitality. They reflect a number of intracellular processes, and also reveal the interaction between the sperm and its environment. The pattern of sperm-head motion during locomotion is a hydrodynamic consequence of the behavior of the flagellum. Hence, studies of sperm-head motion should provide insights into cellular function and membrane integrity. Because of its importance in fertility, considerable attention is devoted to the analysis of sperm-head motion at both a clinical and basic biological level. Historically, such work has been done by hand. Recently, new, computer-aided sperm analysis (CASA) systems have become available to automate this process. These new systems promise to advance the study of cell behavior because they facilitate the objective collection of large amounts of data at relatively low cost. At present, however, few workers understand the relative strengths and limitations of such systems. There is a tendency to uncritically accept CASA results because they are computer generated. In this article, we describe how CASA systems work, and discuss several technological and methodological problems which can produce spurious results. We argue for the development of optical, machine, and specimen preparation standards which will facilitate inter-laboratory comparisons of CASA data.

Animals↗
PubMed1989

Maternal serum alpha-fetoprotein prenatal screening for Down syndrome.

The relationship between maternal serum alpha-fetoprotein (MSAFP) levels, maternal age and Down syndrome risk factors were studied in the greater Birmingham and North Alabama areas. After adjustment for race and maternal weight, 3.84 percent of women in this study were determined to have Down syndrome risk factors equal to or greater than that of a 35 year old woman with a normal pregnancy. Maternal weight adjustment was of special importance, reducing the number of MSAFP values considered low from 5.12 percent to 3.40 percent. The use of race and area specific medians was also important in the use of prenatal MSAFP screening for Down syndrome affected pregnancies.

Body Weight↗
PubMed1989

Sonographic measurements and ratios in fetuses with Down syndrome.

Ultrasound measurements of 15 fetuses with trisomy 21 detected during the 17th week of gestation were matched retrospectively to those of 45 normal controls. We compared nine standard ultrasound measurements of the fetal head, abdomen, and femur in these two groups. The fetuses with trisomy 21 had significantly shorter mean femur lengths, narrower occipitofrontal diameters, and increased biparietal diameter (BPD)/femur length and abdominal circumference/femur length ratios. An increased BPD/femur length ratio was the ultrasound finding that best predicted a fetus with Down syndrome. A BPD/femur length ratio of 1.80 or higher was 40% sensitive and 97.8% specific in predicting Down syndrome, and had a false-positive rate of only 2.2%. An increased second-trimester BPD/femur length ratio measured by ultrasound may prove beneficial as an additional screening test for Down syndrome.

Down Syndrome↗
PubMed1987

Amniotic fluid alpha-fetoprotein levels and pregnancy outcome.

Elevated and low levels of maternal serum alpha-fetoprotein in the midtrimester of pregnancy have been linked with adverse events in later gestation, such as fetal and neonatal deaths, chromosomal abnormalities, and low birth weight infants. It is not known if this same association with poor pregnancy outcome is also true of amniotic fluid alpha-fetoprotein. In this study, alpha-fetoprotein was obtained from the fluid of 1060 women undergoing genetic amniocentesis for advanced maternal age. Poor pregnancy outcome was defined as (1) a fetal or neonatal death, (2) preterm delivery, or (3) low birth weight infants. Amniotic fluid alpha-fetoprotein was compared to each type of adverse outcome. No significant association with a poor pregnancy outcome in later gestation was noted. Although serum alpha-fetoprotein in the midtrimester of pregnancy may relate to certain poor outcomes in later gestation, midtrimester amniotic fluid alpha-fetoprotein offers no predictive value for the course of events in later gestation.

Amniocentesis↗
PubMed1986

Digital signal processing in studies of animal acoustical communication, including human speech.

The study of animal acoustical communication and other biological signals like cardiopulmonary cycles and neurological waves has advanced rapidly in the last few years. Progress has been stimulated by dramatic improvements in transducers, recorders, computers, and digital signal processing (DSP) techniques. Nevertheless, many biologists cannot take advantage of these new techniques and technology because mainframe computer usage is expensive and DSP theory is buried in highly technical engineering and mathematical journals. Recently, new developments in microcomputer hardware and commercially available DSP software have greatly improved this picture. Nevertheless, DSP theory remains largely inaccessible to the non-specialist. In this paper, selected areas of DSP theory are surveyed in relation to a common biological signal processing problem, namely, the analysis of animal acoustical signals. Signal digitization techniques are described, including the concepts of word-width, sample rate, and data encoding. An overview of the mathematical models developed for human speech encoding and analysis is presented. Finally, selected DSP techniques used in the time and frequency domains, including digital filtering, spectral analysis, and dynamic time warping are reviewed.

Animals↗
PubMed1986

The Personal Acoustics Lab (PAL): a microcomputer-based system for digital signal acquisition, analysis, and synthesis.

A new, integrated digital signal processing (DSP) system, the Personal Acoustics Lab (PAL), is described. This microcomputer-based system is suitable for analogue signal digitization at rates from several samples per hour to 150,000 samples per second in 12- or 16-bit words. Data may be acquired on one to sixteen single-ended A/D, or one to eight double-ended A/D channels in bipolar or unipolar modes. Digitized data may be reconverted to analogue signals using one or two D/A channels. An external clock and trigger and two bidirectional digital ports are provided. Integrated PAL-ILS software commands perform all necessary DSP functions, including: data editing, time- and frequency-domain graphical display, plotting, filtering, Fourier and Hilbert transforms, linear predictive coding, auto- and cross-correlation, and summary statistics. The system is suitable for biological and engineering DSP applications. Output from selected PAL-ILS software commands is illustrated using a bioacoustical example.

Animals↗
PubMed1985

Decreased levels of amniotic fluid alpha-fetoprotein associated with Down syndrome.

Low maternal serum alpha-fetoprotein levels have been associated with fetal aneuploidies. Amniotic fluid alpha-fetoprotein levels have been reported to be low with Down syndrome (trisomy 21) but not with other fetal trisomies. We compared the amniotic fluid alpha-fetoprotein levels from 25 cases of autosomal trisomy (18 of trisomy 21, four of trisomy 13, three of trisomy 18) diagnosed by midtrimester fetal cytogenetic studies with those from matched, cytogenetically normal pregnancies. With these normal pregnancies used as controls, statistical analyses were performed on the data for all the trisomic fetuses, on the data for trisomy 21 only, and on the data for trisomies 13 and 18 combined. Amniotic fluid alpha-fetoprotein levels were significantly lower in the 25 trisomic cases compared with controls, 0.77 +/- 0.34 versus 1.03 +/- 0.34 mg/dl (p less than 0.001). However, further analysis revealed that the difference was due to the trisomy 21 data alone. In the trisomy 21 cases there was a significant difference for alpha-fetoprotein levels between cases and controls (p less than 0.001), whereas there was no difference for the combined trisomy 13 and 18 cases compared to controls (p greater than 0.40). These findings suggest that the low maternal serum levels of alpha-fetoprotein reported in cases of Down syndrome may be related to reduced amniotic fluid concentrations. However, the reduced maternal serum alpha-fetoprotein levels reportedly associated with trisomies 13 and 18 do not seem to be explained by low amniotic fluid concentrations.

Adult↗
PubMed1985

Fatal meconium aspiration syndrome occurring despite airway management considered appropriate.

A combined obstetric-pediatric approach to tracheal toilet is said to prevent serious cases of the potentially fatal meconium aspiration syndrome. After delivery of the head a DeLee trap is used to suction the oropharynx and nasopharynx. Immediately following delivery, endotracheal suction is performed in an effort to remove any remaining meconium-stained amniotic fluid. Although routinely using this approach, we continue to have occasional cases of fatal meconium aspiration syndrome. Therefore, we reviewed the outcome of infants born through meconium-stained fluid. During a 5-year period, 1420 (15%) of 9299 live-born infants had meconium-stained fluid. Thirty (2.1%) of these 1420 developed meconium aspiration syndrome and 12 (40%) died; eight received a postmortem examination. Four had unequivocal evidence of meconium aspiration, two had large numbers of intra-alveolar squamous cells, and two had no evidence of aspiration. We conclude that aggressive airway management during and immediately after delivery does not always prevent fatal meconium aspiration syndrome.

Amniotic Fluid↗
PubMed1985

Real-time analysis of sperm motion using automatic video image digitization.

A methodology is described for automatic, real-time analysis of sperm movement characteristics. Video micrographic images of spermatozoa are digitized, compressed, and then analyzed using a Motion Analysis Corporation Expert Vision system. The system includes a VP-100 video processor, a video camera, and a Sun-2/120 minicomputer. Algorithms for detection of and discrimination among sperm are described, and desirable operating characteristics of the system are considered. Salient parameters which characterize the kinematics of sperm swimming trajectories are discussed.

Analog-Digital Conversion↗