Biomedical subjects
Publications and source records attributed to A Keenan.
The spectrum of prompt conversion electrons emitted by excited 254No nuclei has been measured, revealing discrete lines arising from transitions within the ground state band. A striking feature is a broad distribution that peaks near 100 keV and comprises high multiplicity electron cascades, probably originating from M1 transitions within rotational bands built on high K states.
Understanding the fundamental excitations of many-fermion systems is of significant current interest. In atomic nuclei with even numbers of neutrons and protons, the low-lying excitation spectrum is generally formed by nucleon pair breaking and nuclear vibrations or rotations. However, for certain numbers of protons and neutrons, a subtle rearrangement of only a few nucleons among the orbitals at the Fermi surface can result in a different elementary mode: a macroscopic shape change. The first experimental evidence for this phenomenon came from the observation of shape coexistence in 16O (ref. 4). Other unexpected examples came with the discovery of fission isomers and super-deformed nuclei. Here we find experimentally that the lowest three states in the energy spectrum of the neutron deficient nucleus 186Pb are spherical, oblate and prolate. The states are populated by the alpha-decay of a parent nucleus; to identify them, we combine knowledge of the particular features of this decay with sensitive measurement techniques (a highly efficient velocity filters with strong background reduction, and an extremely selective recoil-alpha-electron coincidence tagging methods). The existence of this apparently unique shape triplet is permitted only by the specific conditions that are met around this particular nucleus.
OBJECTIVE: Our purpose was to determine whether preterm birth of twins is associated with an increased risk of preterm birth in a subsequent singleton pregnancy. STUDY DESIGN: The Medical University of South Carolina perinatal database was accessed to identify a cohort of patients who were delivered of twins followed by a singleton gestation (1981 to 1993). Maternal transports were excluded to minimize referral bias. Preterm birth was defined as < 37 weeks' gestation. Relative risks with 95% confidence intervals were calculated. RESULTS: One hundred forty-four patients were identified who were delivered of twins followed by a singleton gestation. Preterm delivery occurred in 86 (59.7%) of the twins and 21 (14.6%) of the subsequent singletons. Preterm birth of twins was associated with a significantly increased risk of preterm delivery in a subsequent singleton pregnancy (relative risk 2.87, 95% confidence interval 1.02 to 8.09). In the subset of women who were delivered of twins at < 30 weeks' gestation, 42% of the subsequent singletons were delivered preterm (relative risk 6.11, 95% confidence interval 2.07 to 18.02). The relative risk of preterm birth of a singleton after delivery of twins between 30 and 34 weeks' gestation was 3.63 (95% confidence interval 1.02 to 12.92). However, if the preceding twins delivered between 34 and 37 weeks' gestation, the relative risk of preterm birth of the subsequent singleton was not significantly increased (relative risk 1.42, 95% confidence interval 0.40 to 5.01). CONCLUSIONS: Preterm birth of twins before 34 weeks' gestation is associated with a significant risk for preterm delivery in a subsequent singleton pregnancy. The magnitude of risk increases with decreasing gestational age of the preceding twin delivery.
Transforming growth factor-alpha (TGF alpha) is a cytokine secreted by stimulated alveolar macrophages (AM) in vitro and after in vivo particulate or hyperoxia exposure and has been implicated in the processes of postnatal lung development. It is unknown if AM TGF alpha secretion changes during normal postnatal lung development. After sacrifice of New Zealand white rabbits on postnatal d 0-2, 5-7, 9-10, 14, 21, and 28 and > 4 mo (adult), AM were isolated by discontinuous density centrifugation and placed in culture in the presence or absence of concanavalin A (ConA) for 24 h. Media were collected, and the concentration and isoforms of TGF alpha in AM media samples were determined by an epidermal growth factor/TGF alpha radioreceptor assay and Western immunodetection, respectively. TGF alpha was present in media of AM from the 1.06 and 1.08 g/dL Percoll densities, but not in the 1.10 g/dL density. Statistically significant differences in TGF alpha secretion by unstimulated and ConA-stimulated AM at the various ages were not detected until d 14 (p < 0.02). Western blot analysis of unstimulated AM media samples from d 0-7 rabbits demonstrated the presence of TGF alpha isoforms at 46, 30, and 14.3 kD. At later postnatal ages (> or = d 9), a single 14.3-kD isoform was present. In contrast, analysis of ConA-stimulated AM media samples showed TGF alpha isoforms at 46, 30, and 14.3 kD for all ages; however, the 6-kD mature isoform was present only in juvenile (d 28) and adult media.(ABSTRACT TRUNCATED AT 250 WORDS)
OBJECTIVE: This study was performed to determine the risks associated with antepartum cervical examination in women with multifetal gestations attending a specialized antepartum Twin Clinic. STUDY DESIGN: Patients followed up in a specialized Twin Clinic from 1988 through 1991 (N = 89) received extensive preterm birth prevention education and routine cervical examination at each clinic visit. Obstetric outcome was compared between these patients and 288 other twin gestations followed up in the high-risk obstetric clinics between 1981 and 1991. In these control twin gestations cervical examination was done for obstetric indications only. RESULTS: Comparisons between the 89 Twin Clinic attendees and the 288 controls followed up in the high-risk obstetric clinic revealed no significant differences in patient demographics, medical complications, or infectious morbidity. Importantly, premature rupture of membranes was significantly less frequent in the Twin Clinic group, who had 7.6 +/- 3.2 (mean +/- SD) cervical examinations per patient. CONCLUSION: Routine cervical examination in multifetal gestations is not associated with increased rates of premature rupture of membranes or other obstetric complications.
OBJECTIVE: Our objective was to explore the association between maternal ethnicity and maternal antepartum complications of pregnancy, maternal sociodemographic factors, and newborn characteristics with the incidence of hyaline membrane disease. STUDY DESIGN: By using a retrospective cohort analysis the incidence of hyaline membrane disease was determined for 2295 preterm infants. The study population consisted of all live, inborn infants delivered vaginally from 1982 to 1987. Statistical differences were assessed by use of chi 2 and Student's t tests. A logistic regression procedure determined the relationship of ethnicity and hyaline membrane disease after the study was controlled for all other significant population differences. RESULTS: The differences between black and white populations in marital status, were statistically significant years of education, prolonged rupture of membranes, anemia, and chronic hypertension were statistically significant. Infants of black mothers were diagnosed with hyaline membrane disease less often than infants of white mothers (overall and at each gestational age interval). After the study was controlled for population differences, infants of black mothers were still found to experience hyaline membrane disease less often. CONCLUSION: These data suggest that hyaline membrane disease occurs less frequently, is less severe, and is accompanied by fewer related complications in black preterm infants.
Few authors have published investigations regarding a possible association between preeclampsia and changing paternity. This study employs an epidemiological approach to explore the relationship between severe preeclampsia and changes in paternity patterns among multigravidae in a Caribbean community (Guadeloupe, French West Indies). Multiparae who were diagnosed with preeclampsia or eclampsia with fetal complications (transfer of their infants in the Neonatal Department) and controls were examined (134 mothers' interviews). Information concerning paternity for the index and previous pregnancies was collected from three groups: women with pregnancy-induced hypertension (PIH); women with chronic hypertension (CH); and a control group consisting of women without hypertension during pregnancy. In 21/34 (61.7%) of PIH mothers, the father of the current pregnancy was different than that of the former, compared to 4/40 (10%) among CH and 10/60 (16.6%) in the controls (P < 0.0001). Moreover, considering three and four consecutive pregnancies, there was a significant trend (P < 0.005 and P < 0.02) for an increase in PIH with having a different father in each successive pregnancy. Patterns of changing paternity were significantly correlated with pregnancy-induced hypertension in multiparae but not with chronic hypertension and controls.
OBJECTIVE: To determine whether a specialized, multidisciplinary twin clinic could reduce rates of very low birth weight (VLBW) and perinatal mortality. Multifetal gestations account for only 1% of all pregnancies, yet are responsible for nearly 10% of all perinatal mortality. Very low birth weight (less than 1500 g) infants are the major contributors to this increased perinatal mortality rate. METHODS: Eighty-nine twin pairs followed in the Twin Clinic since 1988 were compared with 51 contemporary twin pairs who did not attend the Twin Clinic. Patients not attending the Twin Clinic were attended in the high-risk clinic by the obstetric residents and faculty. All maternal transports were excluded. Aspects of prenatal care emphasized in the Twin Clinic that differed from the high-risk clinic included consistent evaluation of maternal symptoms and cervical status by a single certified nurse-midwife, intensive preterm birth prevention education, individualized modification of maternal activity, increased attention to nutrition, and tracking of clinic non-attenders. RESULTS: There were no differences between the groups in demographic characteristics, adequacy of prenatal care, or antepartum complications. However, Twin Clinic attenders had lower rates of VLBW infants, neonatal intensive care unit admission, and perinatal mortality. CONCLUSIONS: These improvements in perinatal outcome for twin gestations are attributed to intensive preterm birth prevention education, individualization of prenatal care, and frequent maternal assessment by a consistent care provider. This approach reduced the rate of very early preterm delivery and its neonatal sequelae.
Explore the source record for details and available documents.
Explore the source record for details and available documents.