PubMed Health⌕ Search

Biomedical subjects

B Mercer

Publications and source records attributed to B Mercer.

35 records · Page 2Linked to original sources
PubMed1996

Expression of the SM22alpha promoter in transgenic mice provides evidence for distinct transcriptional regulatory programs in vascular and visceral smooth muscle cells.

SM22alpha is a putative calcium-binding protein that is expressed in cardiac, smooth, and skeletal muscle lineages during mouse embryogenesis and in adult smooth muscle cells (SMC). To define the mechanisms that regulate smooth muscle-specific gene transcription, we isolated the SM22alpha gene and analyzed its 5'-flanking region for elements that direct smooth muscle expression in transgenic mice. Using a series of promoter deletions, a region of the SM22alpha promoter containing 445 base pairs of 5'-flanking sequence was found to be sufficient to direct the specific expression of a lacZ transgene in mouse embryos in the vascular smooth, cardiac, and skeletal muscle lineages in a temporospatial pattern similar to the endogenous SM22alpha gene. However, in contrast to the endogenous gene, transgene expression was not detected in venous, nor visceral SMCs. This SM22alpha-lacZ transgene was therefore able to distinguish between the transcriptional regulatory programs that control gene expression in vascular and visceral SMCs and revealed heretofore unrecognized differences between these SMC types. These results suggest that distinct transcriptional regulation programs control muscle gene expression in vascular and visceral SMCs.

Animals↗
PubMed1995

Associations between adverse perinatal outcome and serially obtained second- and third-trimester maternal serum alpha-fetoprotein measurements.

OBJECTIVE: Our purpose was to determine whether third-trimester maternal serum alpha-fetoprotein predicts adverse perinatal outcome and whether use of both second- and third-trimester maternal serum alpha-fetoprotein enhances the positive predictive value for various abnormal outcomes. STUDY DESIGN: A cohort study with obstetric outcome assessed by chart analysis after delivery was performed at Regional Medical Center (Memphis, Tennessee), a hospital staffed by university-based physicians serving a large urban population with many indigent patients. A total of 650 women attending prenatal clinics in the above setting with a singleton pregnancy without a neural tube defect, contributing a maternal blood samples in both the second and third trimesters, and delivered in the above hospital participated. Various pregnancy outcomes were correlated with maternal serum alpha-fetoprotein levels in the second and third trimesters and in both. RESULTS: In the third trimester no significant associations were found between maternal serum alpha-fetoprotein elevations and pregnancy complications. In the second trimester elevation ( > or = 2.0 multiples of the median) were, by contrast, significantly associated with preterm premature rupture of the membranes, preterm birth, and low birth weight. No association was found with certain other complications. When second-trimester data were grouped according to the types of complications occurring in individual women, only preterm premature rupture of the membrane proved statistically significant. CONCLUSIONS: Second-trimester but not third-trimester maternal serum alpha-fetoprotein is significantly elevated with preterm premature rupture of the membranes, preterm birth, and low birth weight; in this cohort study no association was found with preeclampsia, oligohydramnios, or polyhydramnios.

Cohort Studies↗
PubMed1995

The preterm prediction study: significance of vaginal infections. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network.

OBJECTIVE: Our purpose was to evaluate the association of bacterial vaginosis, trichomonas vaginitis, and monilial vaginitis with spontaneous preterm birth at < 35 weeks 0 days. STUDY DESIGN: A total of 2929 women at 10 centers were studied at 24 and 28 weeks' gestation by Gram stain of vaginal smear, wet mount, and 10% potassium hydroxide preparations to detect vaginal infections. RESULTS: The rates of detected infection at 24 and 28 weeks, respectively, were bacterial vaginosis 23.4% and 19.4%, trichomonas 3.3% and 2.7%, and monilia 21.1% and 19.5%. The occurrence of bacterial vaginosis at 28 weeks was associated with an increased risk of spontaneous preterm birth, odds ratio 1.84 (95% confidence interval 1.15 to 2.95, p < 0.01). Detection of Trichomonas vaginalis (by wet mount) or monilia (by potassium hydroxide preparation) had no significant associations with preterm birth. CONCLUSION: The presence of bacterial vaginosis at 28 weeks' gestation is associated with an increased risk of spontaneous preterm birth.

Adult↗
PubMed1994

Lupus-related myelitis: serial MR findings.

PURPOSE: To correlate the MR findings in transverse myelitis secondary to systemic lupus erythematosus with clinical findings during disease exacerbation and remission. METHODS: Four patients (ages 33 to 47 years) with episodes of transverse myelitis secondary to systemic lupus erythematosus were identified. Three patients had recurrent transverse myelitis episodes (one patient with two recurrences), for a total of eight episodes. MR examinations (six after contrast administration) were performed during each transverse myelitis episode, as well as during four periods of remission (in three patients) after therapy with steroids and/or immunosuppressive agents. MR examinations were reviewed for the presence of spinal cord enlargement, intramedullary signal abnormality, and contrast enhancement. RESULTS: Prolongation of T1 or T2 signal (or both) was seen in eight episodes (100%). Spinal cord enlargement was seen in six (75%) of eight transverse myelitis episodes, although it was mild during two episodes. Contrast enhancement was seen in three of six transverse myelitis episodes (dense, inhomogeneous enhancement during two episodes in one patient, and a small focus of enhancement in one patient). During periods of remission, spinal cord diameter returned to normal, and no contrast enhancement was seen, although abnormal signal was present in three examinations performed within 2 months of a transverse myelitis episode. CONCLUSION: Spinal cord widening and signal abnormalities are common MR findings during episodes of transverse myelitis related to systemic lupus erythematosus, and contrast enhancement is less frequently seen. Improvement or resolution of these findings correlates with clinical improvement.

Adrenal Cortex Hormones↗
PubMed1994

Prevention of neonatal group B streptococcal infection.

The optimal clinical strategy to prevent neonatal group B streptococcal infection has not been established. The Maternal-Fetal Medicine Units Network assessed the feasibility of a randomized clinical trial to compare the effectiveness of two methods of prevention of streptococcal infection. The attack rates of early-onset group B streptococcal disease were estimated for the following: 1) a hypothetical program of universal prenatal screening and selective intrapartum chemoprophylaxis, and 2) a hypothetical program of selective intrapartum chemoprophylaxis based on clinical risk factors. Sample size requirements were calculated for a clinical trial to detect a significant difference in attack rates between the two hypothetical programs. Similar low attack rates using both strategies would require extremely large sample sizes to detect differences between programs. Until a satisfactory, rapid diagnostic test for intrapartum group B streptococcal carrier status is developed and clinical strategies are tested in populations with varying carriage frequencies, institutions will need to individualize their approaches to prevent early-onset neonatal group B streptococcal disease.

Algorithms↗
PubMed1992

Serial thoracic versus abdominal circumference ratios for the prediction of pulmonary hypoplasia in premature rupture of the membranes remote from term.

OBJECTIVES: The purpose of this study was to evaluate the fetal thoracic versus abdominal circumference ratio in the prediction of pulmonary hypoplasia after preterm premature rupture of the membranes. STUDY DESIGN: A standard curve of thoracic versus abdominal circumference ratio versus gestational age was derived from 120 uncomplicated pregnancies. Thoracic versus abdominal circumference ratio and amniotic fluid estimations were obtained serially in 16 women with premature rupture of the membranes at less than 26 weeks' gestation. RESULTS: An abnormal thoracic versus abdominal circumference ratio predicted lethal pulmonary hypoplasia in six infants. A progressive decline in thoracic versus abdominal circumference ratio was identified in all of these patients. Six of eight women with persistent oligohydramnios had abnormal thoracic versus abdominal circumference ratios and lethal pulmonary hypoplasia. Two surviving infants had restriction deformities and pulmonary complications. CONCLUSIONS: In the setting of premature rupture of the fetal membranes at less than 26 weeks, serial thoracic versus abdominal circumference ratio measurement is a reliable predictor of pulmonary hypoplasia. Persistent oligohydramnios is ominous because of the risk of restriction deformities and pulmonary complications in the survivors.

Abdomen↗
PubMed1991

Severe preeclampsia in the second trimester: recurrence risk and long-term prognosis.

A total of 125 women with severe preeclampsia that developed in the second trimester underwent follow-up for an average of 5.4 years. Seventeen women had no further pregnancies and 108 had 169 subsequent pregnancies: 59 (35%) were normotensive and 110 (65%) were complicated by preeclampsia (32% of these developing in the second trimester, 32% at 28 to 36 weeks, and 36% at 37 to 40 weeks). Overall, 21% of subsequent pregnancies were complicated by severe preeclampsia in the second trimester. Forty-four patients (35%) had chronic hypertension, the highest incidence being in those with recurrent severe preeclampsia in the second trimester and the lowest in those with only normotensive subsequent pregnancies (67% vs 4%, p less than 0.0001). Long-term maternal complications included two maternal deaths and two other patients with end-stage renal disease requiring dialysis. We conclude that these women are at increased risk for repeat preeclampsia, particularly in the second trimester, and are at increased risk for chronic hypertension and maternal mortality and morbidity.

Adult↗
PubMed1991

Labor induction with continuous low-dose oxytocin infusion: a randomized trial.

One hundred twenty-three women were randomized to receive either of two regimens of oxytocin for labor induction. Sixty-one received a low-dose regimen, with oxytocin increases at intervals of not less than 60 minutes. Patients with unripe cervices received prolonged low-dose oxytocin priming before membrane rupture. Sixty-two others received a traditional protocol, with oxytocin increased every 20 minutes as required. Both groups had amniotomy when deemed safe and feasible. Oxytocin was adjusted for uterine hyperstimulation or abnormal fetal heart rate patterns in 29 and 58% of low-dose and traditional protocol subjects, respectively (P less than .001, odds ratio 3.6). No significant increase in time to delivery was seen with low-dose oxytocin infusion. Cesarean delivery and cesareans for fetal distress were more frequent in the traditional protocol group. This study demonstrates that a continuous low-dose protocol for oxytocin induction of labor is effective in establishing active labor and achieving vaginal delivery in women with both ripe and unripe cervices. It is also associated with fewer episodes of uterine hyperstimulation requiring adjustments of oxytocin infusion than is the traditional protocol of this institution.

Adult↗
PubMed1988

Primary thrombocythemia in pregnancy: a report of two cases.

We report two cases of primary thrombocythemia diagnosed during pregnancy. One patient developed transient visual field defects. She was treated with plateletpheresis at term and delivered of a normal child by cesarean section. The second patient was not treated. Intrauterine fetal death occurred at 36 weeks' gestation from multiple placental infarcts. In cases of primary thrombocythemia, we suggest close monitoring of both mother and fetus throughout pregnancy.

Adult↗
PubMed1988

Gastroschisis: ultrasonographic diagnosis, perinatal embryology, surgical and obstetric treatment and outcomes.

The embryology and onset time of gastroschisis are poorly understood. This paper reviews 22 cases of the condition seen at the Children's Hospital of Eastern Ontario between 1975 and 1986. Sixteen cases were judged to be of the perinatal and 6 of the early type. Ultrasonography revealed the actual time of development in one case and the probable time in another. In 20 cases the defect was closed primarily and in 2 by a staged procedure (Silon pouch). Nineteen infants (86.4%) survived. In all cases the umbilical vasculature was normal and all were right-sided. Other anomalies were rare and less important. Two clear examples of rupture of the umbilical ring are documented. Ultrasonography had been performed in 10 infants, usually for intrauterine growth retardation, and gastroschisis was diagnosed in 4 of these. Delivery was by cesarean section in six. Marked meconium staining occurred in 16 (73%), 7 of whom had subglottic aspiration of meconium. The average birth weight was 2480 g. Ultrasonography is recommended in all cases of intrauterine growth retardation with careful examination of the umbilical area to establish the presence and time of onset of gastroschisis. Vaginal delivery appears to be the route of choice for delivery.

Abdominal Muscles↗
PubMed1977

A study of confabulation.

Confabulation consequent to organic amnesia is a well-described clinical finding. A number of plausible theories of confabulation have been proposed, but the various claims and counterclaims have not been systematically tested. A standardized test battery that included four different kinds of questions plus measures of suggestibility and the tendency to utilize external cues was administered to ten amnesic patients who demonstrated varying degrees of confabulation. One additional patient, whose clinical condition changed dramatically during his hospital course, received the battery on a number of occasions. Differences among patients were found in overall performance, degree of confabulation, and ability to use cues. Hypothesized relationships between confabulation and suggestibility, degree of memory disorder, and degree of disorientation were not confirmed. However, confabulation proved to be strongly related to the inability to withhold answers, to monitor one's own responses and to provide verbal self-corrections. These results suggest a tentative model of the process of confabulation as well as a number of useful clinical signs indicationg recovery from amnesia.

Adult↗
PubMedDate not supplied

Fetal membrane histology in preterm premature rupture of membranes: comparison to controls, and between antibiotic and placebo treatment. The National Institute of Child Health and Human Development Maternal Fetal Medicine Units Network, Bethesda, MD, USA.

The objectives of this study were to test the hypotheses that antibiotic therapy will alter the histologic appearance of fetal membranes in preterm premature rupture of membranes (pPROM), and that the membrane histology will demonstrate distinct differences between term and preterm rupture of membranes. We also wished to test interobserver variability of pathologists. Placental membranes were sampled from 268 women participating in a randomized placebo-controlled trial of antibiotic therapy for pPROM at 24-32 weeks of gestation (cases) and from 4 control groups who were not in the randomized trial: (1) preterm labor without pPROM (n = 21), (2) term labor (n = 65), (3) term PROM (n = 21), and (4) term cesarean section (n = 27). The cases and controls were scored for 40 histologic features by pathologists blinded to the identity of each sample (case or control). pPROM histology of samples from patients receiving antibiotics and those receiving placebo was compared using a chi-squared test and with control groups using logistic regression. There were no histological differences between pPROM cases treated with antibiotic and those receiving placebo, nor with respect to duration of membrane rupture greater or less than 48 h. Concordance among pathologists was low for features other than acute inflammation. Logistic regression analysis controlled for race and pathologist, and demonstrated that all of the control groups had significantly fewer common markers of acute inflammation when compared with the pPROM cases. This study suggests that histopathologic evidence of infection is seen more frequently with pPROM than in preterm or term controls. The histologic features used in this study cannot be used to determine the effectiveness of antibiotic therapy.

Adult↗
PubMedDate not supplied

Histologic features of chorioamnion membrane rupture: development of methodology.

This study developed a set of histologic features that will allow subclassification of placentas with preterm premature rupture of membranes. Placentas were obtained from patients participating in a multi-institutional NICHD Maternal-Fetal Medicine Unit Network study of antimicrobial therapy after preterm premature rupture of membranes. The rupture site was sampled by inking the open sac margin and rolling a membrane strip in four quadrants from the ink to the placental margin. Independently, four pathologists used a provisional feature list to score the slides from 15 placentas. A concordance analysis was performed on those results. With those results, the slides were reviewed concurrently to discover the source of disagreements and to revise the feature list. The sampling method frequently demonstrated a rupture site with histology distinct from that of the remainder of the membranes. After review of the preliminary scoring results, 29 features of membrane histology present in preterm premature rupture could be objectively described with agreement among four pathologists. The feature list allows both novel and commonly recognized histologic features of fetal membranes to be recorded with objectivity. This list, with the described sampling technique, is presented as a tool for clinical correlation in studies of membrane rupture, especially in preterm, premature rupture.

Amnion↗