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Biomedical subjects

P J Placek

Publications and source records attributed to P J Placek.

At least 19 recordsLinked to original sources
PubMed1993

Stimulus speed and order of presentation effect the visually released predatory behaviors of the praying mantis Sphodromantis lineola (Burr.).

To assess the role of stimulus speed and order on the predatory behaviors of the praying mantis Sphodromantis lineola (Burr.), tethered adult females were presented with various flat black stimuli (lures) by means of a variable speed mechanical arm. Lure speed had a dramatic effect on mantis behavior: mantises emitted significantly more strikes to a 6 x 6 mm square and to 'worm' lures (i.e. length > width = 6 mm) moving at 34.3 cm/sec than they did to 'antiworm' lures (i.e. width > length = 6 mm), or to slower moving lures. These effects were consistent over lure directions (0-75 degrees relative to the mantis' long axis), and background patterns. On the other hand, mantises emitted significantly more approaching behavior to lures moving at 12 cm/sec than to lures moving at 36 cm/sec. This suggests that S. lineola extract distance information from retinal image velocity, as do other insects. Stimulus order also effected mantis predatory behavior: for instance, mantises were more likely to track a lure without striking at it on the first trial than on subsequent trials. However, after the first trial, they were also more likely to freeze (become immobile) when a lure was presented. Mantises were also less likely to strike at a preferred lure if it was preceded by one or two non-preferred lures. In a final experiment, intact, freely moving mantises were placed in an arena, presented with adult crickets, and video taped. The behaviors of the freely moving mantises were congruent with those of the tethered mantises in the previous experiments. This series of experiments demonstrates that the information processing capabilities of S. lineola are more complex than generally depicted, however, they can be explained by assuming a neural organization similar to that of other insects such as flies (Diptera) and dragonflies (Odonata).

Animals↗
PubMed1991

How frequently are home pregnancy tests used? Results from the 1988 National Maternal and Infant Health Survey.

Many women use commercially available home pregnancy tests to determine their pregnancy status before seeking professional health care. Despite the increasing popularity of these products, no national estimates have been reported to date on their frequency of use. We analyzed available data from the 1988 National Maternal and Infant Health Survey to determine the frequency of use of home pregnancy tests during recent pregnancies of women of varying sociodemographic backgrounds. Approximately 33 percent (N = 4700) of the women surveyed used such a device. Use was most frequent among women who were white, married, over age 39 years, highly educated, or had a high family income. We conclude that home pregnancy testing appears to be a frequent procedure, especially among women of high socioeconomic background.

Adolescent↗
PubMed1991

The 1988 National Maternal and Infant Health Survey: design, content, and data availability.

The 1988 National Maternal and Infant Health Survey was conducted by the National Center for Health Statistics to study factors related to poor pregnancy outcome, such as adequacy of prenatal care; inadequate and excessive weight gain during pregnancy; maternal smoking, drinking, and drug use; and pregnancy and delivery complications. The survey is a nationally representative sample of 11,000 women who had live births, 4000 who had late fetal deaths, and 6000 who had infant deaths in 1988. Mothers were mailed questionnaires based on information from certificates of live birth, reports of fetal death, and certificates of infant death. Information supplied by the mother, prenatal care providers, and hospitals of delivery was linked with the vital records to expand knowledge of maternal and infant health in the United States. Data collection from the Longitudinal Followup of mothers in the survey began in January 1991. It provides information on health and development of low- and very low-birthweight babies, child care and safety, maternal health, maternal depression, and plans for adoption and foster care. Both surveys will provide useful data for clinicians in maternal and child health.

Data Collection↗
PubMed1991

1989 U.S. cesarean section rate steadies--VBAC rate rises to nearly one in five.

The 25 years of rising cesarean delivery rates in the United States may have finally run their course. In 1989 the rate of 23.8 cesareans per 100 deliveries was not significantly different from 24.7 in 1988, 24.4 in 1987, or 24.1 in 1986. The 1989 primary rate of 17.1 first cesareans per 100 women with no previous cesarean was also not significantly different from 17.5 for 1988, or 17.4 for 1987 and 1986. The percentage of vaginal births after cesarean section per 100 deliveries showed a remarkable rise between 1988 and 1989--from 12.6 percent in 1988 to 18.5 percent in 1989. Data are from the National Hospital Discharge Survey conducted by the National Center for Health Statistics, Centers for Disease Control.

Adult↗
PubMed1990

Use of diagnostic ultrasound, X-ray examinations, and electronic fetal monitoring in perinatal medicine.

Obstetrical technologies such as electronic fetal monitoring (EFM) and selected diagnostic imaging procedures can be integral components of perinatal care. The Center for Devices and Radiological Health, a unit within the Food and Drug Administration, collaborated with the National Center for Health Statistics in the design and conduct of a National Maternal and Infant Health Survey to collect information from prenatal care providers, hospitals, and mothers on the use of EFM, diagnostic ultrasound, and x-ray examinations during pregnancy, labor, and delivery. A pretest, conducted some months before the survey began, showed that 78.8% of the pregnancies surveyed received a diagnostic ultrasound examination during pregnancy. Approximately 58.3% of the ultrasound-exposed mothers had two or more such examinations. Approximately 10.1% of the ultrasound examinations were performed in the first trimester of pregnancy, 57.0% in the second trimester, and 32.9% in the third trimester. The most common indication for an ultrasound examination was to establish dates or gestational age. Approximately 15.3% of the pregnancies surveyed received an x-ray examination. Approximately 74.6% of the pregnancies were monitored with EFM during labor. External EFM was used alone during 54.9% of the labors and along with internal EFM during 19.7% of the labors. The implications of these pretest findings are discussed, along with a review of the medical literature on the safety and effectiveness of these medical device technologies.

Delivery, Obstetric↗
PubMed1989

X-ray examinations during pregnancy: National Natality Surveys, 1963 and 1980.

Based on 1963 and 1980 National Natality Surveys, the rate of medical x-ray examinations during pregnancy per 100 mothers fell 34.2 percent. A decrease in chest x-ray examinations accounted for almost all of the decline in total x-ray examinations. The reductions were greater for older mothers and those who were not White. While the number of births fell from 4,071,000 in 1963 to 3,612,000 in 1980, the number of pelvimetry examinations actually increased by 45,000.

Adult↗
PubMed1988

Vaginal birth after cesarean (VBAC) in the 1980s.

The incidence of vaginal birth after cesarean (VBAC) and characteristics of VBAC births are investigated using 1980-85 National Hospital Discharge Survey Data collected by the National Center for Health Statistics. Only 3.4 per cent of mothers with previous cesarean delivery had VBAC in their subsequent 1980 delivery; this increased to 6.6 per cent in 1985. Because VBAC is a relatively infrequent event, 1980-85 data were combined and indicate that in this period 4.9 per cent of mothers with previous cesarean had a vaginal birth in their subsequent delivery. Combined 1980-85 VBAC rates are under 10 per cent for all age, race, marital status, region, hospital size, hospital ownership, and expected source of payment groups. Between 1980 and 1985, over 1.4 million repeat cesareans were performed for mothers having a live birth. Evidence suggests that potentially over 500,000 of these repeat cesareans could have been VBACs (over and above the 74,000 VBACs which occurred). VBAC mothers' mean length of hospital stay is 3.2 days, which compares closely with 3.0 days for other vaginal deliveries, but both contrast sharply with 5.6 days for repeat cesareans and 6.0 days for primary cesareans. Except for the uterine scar from the previous cesarean, VBAC mothers appear to have about the same history and frequency of complications as mothers with other vaginal deliveries. If the 500,000 repeat cesareans had been VBACs, surgical fees and costs for 1.2 million days of hospital stay would have been averted over the 1980-85 period.

Adult↗
PubMed1988

Recent patterns in cesarean delivery in the United States.

The United States cesarean rate has risen from 5.5 per 100 deliveries in 1970 to 24.1 per 100 deliveries in 1986 according to the National Hospital Discharge Survey. Less than 10 per cent of mothers have a vaginal birth after a prior cesarean. Women spend an average of 5.0 days in the hospital for a cesarean delivery, but only 2.6 days for a vaginal delivery. The rise in cesareans is partly responsible for a concurrent increase in postpartum sterilization. If age-specific cesarean rates continue the steady pattern of increase observed since 1970, 40 per cent of births could be by cesarean by the year 2000.

Cesarean Section↗
PubMed1987

Comparisons of national cesarean-section rates.

Our study of cesarean rates in 19 industrialized countries of Europe, North America, and the Pacific revealed sharp differences in rates, ranging from a low of 5 (Czechoslovakia) to a high of 18 (United States) per 100 hospital deliveries in 1981. Differences in cesarean rates according to maternal age, parity, and complications of pregnancy and childbirth reflected national differences in obstetrical practice. For example, the percentage of mothers who had a vaginal birth after a previous cesarean section was only 5 in the United States as compared with 43 in Norway, where the cesarean rate was half that in the United States. Despite the wide range of cesarean rates, almost all the countries studied have had consistent increases over the past decade, and the annual rate of increase for all countries appears to be converging. The steady pace of increase in developed countries, combined with comparable or even higher rates of cesarean delivery now being reported in less developed countries, underscores the need for the medical community to consider the appropriateness of this continued rise in the number of cesarean deliveries.

Australia↗
PubMed1987

Trends in the United States cesarean section rate and reasons for the 1980-85 rise.

The rate of cesarean section delivery in the United States rose from 4.5 per 100 deliveries in 1965 to 22.7 in 1985, and in 1985 an estimated 851,000 live births were cesarean deliveries, according to data from the National Hospital Discharge Survey. This increase has been observed for all ages, and within all regions of the country. The rate for teenagers and mothers aged 20 to 29 was five to six times as high in 1985 as in 1965, and four times as high for mothers aged 30 years and older. Repeat cesareans account for an increasing share of all cesarean deliveries; in 1985 one in three cesareans were repeats. The increase in the cesarean rate of 6.2 percentage points between 1980 and 1985 (from 16.5 to 22.7) was partitioned according to five complications of delivery recorded on hospital discharge records: previous cesarean delivery, breech presentation, dystocia, fetal distress, and all other complications. Nearly half (48 per cent) of the increase was associated with previous cesarean delivery, 29 per cent with dystocia, 16 per cent with fetal distress, 5 per cent with breech presentation, and 2 per cent with all other complications.

Adolescent↗