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Biomedical subjects

B K Young

Publications and source records attributed to B K Young.

At least 19 recordsLinked to original sources
PubMed2006

Creation of hot radiation environments in laser-driven targets.

A hot radiation environment, produced by maximizing laser-energy deposition into a small, high- "can," is a platform being developed for investigations of material properties under extreme conditions. In such small targets, almost doubling the laser energy results in only an incremental increase in the x-radiation flux, and almost no increase in the maximum achieved radiation temperature. That most of this additional laser energy is not deposited within the target is a direct consequence of laser-plasma interactions (LPI) outside of the target, which result in high-angle beams never entering the target late in the laser pulse. Accounting for these processes in the modeling results in quantitative agreement for the first time with experiments using very small cans. These findings have provided the scientific foundation for modifying the target geometry to mitigate the LPI and to achieve higher radiation temperatures.

Journal Article↗
PubMed2005

Radiation-driven hydrodynamics of high- hohlraums on the national ignition facility.

The first hohlraum experiments on the National Ignition Facility (NIF) using the initial four laser beams tested radiation temperature limits imposed by plasma filling. For a variety of hohlraum sizes and pulse lengths, the measured x-ray flux shows signatures of filling that coincide with hard x-ray emission from plasma streaming out of the hohlraum. These observations agree with hydrodynamic simulations and with an analytical model that includes hydrodynamic and coronal radiative losses. The modeling predicts radiation temperature limits with full NIF (1.8 MJ), greater, and of longer duration than required for ignition hohlraums.

Journal Article↗
PubMed2004

Endoscopic closure of fetal membrane defects: comparing iatrogenic versus spontaneous rupture cases.

OBJECTIVE: Currently, physicians manage preterm premature rupture of membranes (PPROM) by expectant management or termination of the gestation. A therapy aimed at sealing membranes would be optimal to maintain the pregnancy and achieve a normal neonate. Our objective was to compare an endoscopic technique for intrauterine closure of fetal membrane defects after both iatrogenic and spontaneous rupture of membranes. METHODS: Our technique was performed on four patients experiencing PPROM spontaneously and four patients after genetic amniocentesis. Intrauterine endoscopy allowed direct visualization of membrane defects. Rapid sequential injections of platelets, fibrin glue and powdered collagen slurry were administered at the site of the defect and of trocar placement. Sonography for amniotic fluid index, nitrazine and fern testing and pad count were performed after each procedure at three intervals: immediately post-procedure, and after 24 and 48 h. RESULTS: Eight patients underwent endoscopic intrauterine sealing of ruptured membranes between 16 and 24 weeks of gestation: four were spontaneous ruptures and four were ruptures post-amniocentesis. In the post-amniocentesis group, three patients delivered viable infants at 26, 32 and 34 weeks. In one patient, the membranes ruptured again 12 h after the sealing procedure and she decided to undergo termination of pregnancy. Of the four spontaneous rupture patients, two experienced preterm labor and delivery within 2 days of the procedure. One patient was diagnosed with fetal demise 12 h post-procedure, and one patient delivered a neonate at 31 weeks of gestation with severe respiratory distress syndrome. CONCLUSIONS: This technique for sealing ruptured membranes is effective after amniocentesis, but may not be of benefit with spontaneous rupture.

Abortion, Induced↗
PubMed2003

Perinatal outcomes in monoamniotic gestations.

OBJECTIVE: A comprehensive review of monoamniotic twin gestations reported between 1990 and 2002 was performed to estimate current perinatal mortality and morbidity rates, as well as the predictive value of an antenatal diagnosis of cord entanglement for poor obstetric outcomes. METHOD: A Medline literature review using the search term 'monoamniotic' and limited to articles published in the English language between 1990 and 2002 was performed. RESULTS: A total of 133 continuing, non-conjoined twin monoamniotic pregnancies with delivery information were identified. Perinatal loss per 2-week interval was relatively constant at 2-4% from 15 to 32 weeks. However, of the 131 fetuses reaching 33 weeks, the percentage loss significantly increased to 11.0% at 33-35 weeks and 21.9% at 36-38 weeks compared to that at 30-32 weeks. Overall perinatal mortality was 23.3%. Of all losses, 61.2% involved both twins and 38.8% involved only one fetus. Cord entanglements were documented antenatally in 22.6% of reports. There was a statistically significant decrease in the average number of neonatal intensive care unit days for non-anomalous neonates (10.6 +/- 7.7 vs. 32.6 +/- 32.0), average gestational age at the time of delivery (30.4 +/- 7.6 vs. 32.6 +/- 4.1), as well as a decrease in the prevalence of total (8.3% vs. 27.7%) and non-anomalous (7.0% vs. 21.6%) perinatal mortality in pregnancies with an antenatal diagnosis of cord entanglement compared to those without the antenatal diagnosis of cord entanglement. The presence of fetal anomalies was associated with a 42.9% perinatal mortality rate. CONCLUSIONS: Contrary to previous reports, there is a significant increase in the incidence of perinatal loss beyond 32 weeks among monoamniotic twins, suggesting that delivery after corticosteroid therapy should be strongly considered at this gestational age.

Female↗
PubMed2000

Change in cervical length after cerclage as a predictor of preterm delivery.

OBJECTIVE: To determine whether the degree of cervical lengthening after cerclage and whether serial follow-up measurements of cervical length after cerclage are predictive of pregnancy outcome. METHODS: Eighty women whose primary physician determined that a prophylactic (n = 50) or urgent cerclage (n = 30) was indicated had transvaginal ultrasonographic evaluation before and after cerclage. Thereafter, most women had three additional transvaginal ultrasound examinations until 32 weeks' gestation. At each examination, the mean of three measurements was calculated. Statistical analyses were done by t test, analysis of variance, and logistic regression, with significance set at P <.05. RESULTS: The mean +/- standard deviation precerclage cervical length was 27.2 +/- 10.3 mm and after cerclage was 34.1 +/- 9.9 mm (n = 80, P <.001, paired t test). No significant association was found (r = -0.26) between the difference in cervical length (postcerclage - precerclage lengths) and pregnancy outcome. Patients with a prophylactic cerclage had a mean cervical length that was consistently longer in patients delivering at term compared with those who delivered preterm at 20 to 32 weeks' gestation. In the urgent cerclage group a significant difference in cervical length between those who delivered at term compared with preterm was evident only at 28 to 32 weeks. CONCLUSION: The increase in cervical length after cerclage is not predictive of term delivery. Serial cervical length measurements in the late second or early third trimester predict preterm birth but could provide earlier warning in patients with a prophylactic cerclage than in patients with urgent cerclage.

Adult↗
PubMed2000

Minimally invasive endoscopy in the treatment of preterm premature rupture of membranes by application of fibrin sealant.

We report only the 3rd case of closure of amniorrhexis following genetic amniocentesis. Our technique is the first to use endoscopic visualization of the rupture site and apply maternal platelets and fibrinogen/thrombin (Hemaseel Haemacure Corp Sarasota F1). The patient underwent repair at 20.6 weeks, 26 days after spontaneous rupture of membranes post-amniocentesis. At the time of the procedure the amniotic fluid index was 1 cm. Patient was delivered at 32.3 weeks secondary to complications of diabetes and severe preeclampsia. The neonate had APGARS of 7 at 1 min and 8 at 5 min and was discharged home on Day 21 of life.

Adult↗
PubMed2000

Management of cervical cerclage at term: remove the suture in labor?

OBJECTIVE: To assess the risks and benefits to patients who carry to term after undergoing a Shirodkar cerclage where the cerclage is not removed until the patient presents in labor. METHODS: A retrospective analysis was conducted examining all patients who underwent a Shirodkar cerclage employing a 5 mm Mersilene band. All the cerclages were placed by a single operator over a twenty five year span, from 1/01/74 till 10/01/98. Only patients who delivered vaginally or were allowed a trial of labor were included. In all cases, the cerclage was removed under regional anesthesia after the patient presented to the hospital in labor. RESULTS: Ninety six cerclage procedures were performed over that period. Eighty two pregnancies qualified for review. Sixty two patients delivered vaginally (76%). Nine cesareans were indicated for failure to progress in labor (11%) with cervical dystocia possibly implicated in one. There were no cases of ruptured uteri or the development of uterine windows. Of the 82 pregnancies there were five cases (6%) of minor cervical laceration. CONCLUSION: Allowing patients to proceed to labor with a Shirodkar, cerclage in place, does not increase the risks of cervical dystocia, cervical laceration, or uterine rupture above the reported incidence for these complications in patients in whom the cerclage is removed prophylactically.

Cervix Uteri↗
PubMed1999

Change in cervical length after prophylactic cerclage.

OBJECTIVE: To determine changes in length of incompetent cervices after cerclage, using transvaginal ultrasound. METHODS: Patients were enrolled in a prospective, observational study under an Institutional Review Board-approved protocol. McDonald or Shirodkar sutures were placed according to physician preference. Pre- and postcerclage cervical lengths were measured within 72 hours of the procedure. At each examination, the first measurement was discarded, and a mean of the subsequent three measurements was calculated. RESULTS: Twenty-one Shirodkar and ten McDonald operations were done. The mean (+/- standard deviation) precerclage cervical length was 2.7+/-0.9 cm and the postcerclage cervical length was 3.6+/-0.9 cm (P<.001, paired t test). CONCLUSION: Prophylactic cerclage results in measurable increases in cervical length, which might contribute to the success of the procedure. Further study is needed to determine whether the degree of cervical lengthening after cerclage predicts term delivery.

Adult↗
PubMed1999

Intra amniotic candidiasis. Case report and meta-analysis of 54 cases.

We present a case of mid pregnancy loss with retained intrauterine contraceptive device associated with fetal Candida infection. Review of English literature identified 53 additional cases of fetal candidal infection, with 17 associated with an IUCD in situ. The presence of an IUCD was associated with delivery at a statistically significant earlier gestational age when compared to cases not associated with an IUCD (23.3 +/- 4.9 vs 31.6 +/- 7.0, p < 0.001). Seventy-seven percent of fetal candidal infections associated with an IUCD were systemic (heart, brain, liver, gastrointestinal, lung) compared to 33% of cases not associated with an IUCD. In contrast to bacterial intraamniotic infections there was a low incidence of maternal febrile morbidity. An hypothesis as to the pathogenesis of Candidal infections in the presence and absence of an IUCD is offered as well as a paradigm for the management of the gravid patient with an IUCD in situ.

Adult↗
PubMed1997

Neuropsychiatric adverse effects of antiparkinsonian drugs. Characteristics, evaluation and treatment.

Parkinson's disease (PD) is a progressive neurological condition that causes considerable disability in the elderly. Drugs used to treat PD, such as levodopa, offer symptomatic relief but often have neuropsychiatric adverse effects, most prominently psychosis and delirium. Aged patients and those with dementia are particularly vulnerable to these adverse effects. Evaluating PD patients with drug-induced neuropsychiatric adverse effects is made difficult by their complex clinical presentations. The treatment of drug-induced psychosis and delirium begins with manipulating the antiparkinsonian drug regimen, but this frequently worsens motor function. Atypical antipsychotics such as clozapine have been successfully employed to treat the psychosis without worsening the motor disability. Patient intolerance of clozapine therapy has prompted open-label studies with newer agents such as risperidone, remoxipride, zotepine, mianserin and ondansetron.

Aging↗
PubMed1996

Flutamide-induced liver toxicity including fatal hepatic necrosis.

PURPOSE: To describe hepatic injuries in three patients who received flutamide prior to and during radiation treatment to make radiation oncologists aware of the need for careful monitoring of liver function during use of this drug. METHODS AND MATERIALS: The records of three patients who developed abnormal liver function tests while undergoing total androgen suppression (TAS), as well as the literature concerning flutamide toxicity were reviewed and summarized. RESULTS: Three of 34 patients treated with a TAS regimen incorporating flutamide developed significant hepatic abnormalities: elevated transaminases [2] and fatal hepatic necrosis [1]. Following the discontinuation of flutamide, two patients recovered fully. Unfortunately, the third patient's hepatic function continued to deteriorate, which culminated in his death. Transient elevations in serum transaminases, which do not exceed four times the upper limits of normal, are common and apparently without clinical significance. Unfortunately, idiosyncratic serious and/or fatal liver damage can occur. Significant liver toxicity may be obviated by monitoring of liver function tests (LFT) early in the course of flutamide therapy. CONCLUSION: The incidence of hepatic toxicity associated with flutamide may be higher than previously suggested. To prevent the development of serious hepatic dysfunction, all patients receiving flutamide should be monitored clinically for signs and symptoms referable to hepatic injury and with serial LFT. We recommend baseline LFT followed by serial LFT at weeks 2, 4, 6, and 8 from the start of treatment with flutamide. Flutamide should be stopped promptly if significant liver abnormalities are detected.

Adenocarcinoma↗
PubMed1996

Tachycardia as the sole fetal heart rate abnormality after funipuncture.

BACKGROUND: Fetal bradycardia is a common complication of funipuncture. We present a case of fetal exsanguination in which fetal tachycardia was the sole fetal heart rate abnormality. CASE: Funipuncture was performed at 32 weeks' gestation for evaluation of Rh isoimmunization. A persistent fetal tachycardia ensued and, although there was no immediate ultrasound evidence of bleeding, repeat ultrasonography revealed active bleeding at the puncture site. A neonate with an initial hematocrit of 42% was delivered by cesarean. Despite aggressive replacement of blood products, a repeat hematocrit was only 35% and a severe, persistent coagulopathy ensued. The newborn died 18 hours after delivery. Autopsy findings were consistent with neonatal coagulopathy. CONCLUSION: Although fetal bleeding is usually a common, relatively benign complication of funipuncture, streaming may not always be detected on ultrasonographic examination. Our case demonstrates that fetal tachycardia may be the only sign of fetal hemorrhage.

Adult↗
PubMed1994

The role of nitric oxide in the pathogenesis of preeclampsia.

OBJECTIVE: Nitric oxide, a potent vasodilator released by endothelial cells, inhibits platelet aggregation and adhesion to vascular endothelial surfaces. Because endothelial cell damage is considered pivotal in the pathogenesis of preeclampsia, this study was initiated to determine whether nitric oxide production is decreased in patients with preeclampsia. STUDY DESIGN: Twenty-six patients with preeclampsia (as defined by a blood pressure > or = 140 mm Hg systolic or 90 mm Hg diastolic plus proteinuria, > or = 300 mg per 24 hours or > or = 2+ by dipstick, both occurring on two occasions > or = 4 hours apart) and 26 normotensive women with singleton gestations in the third trimester were studied. Because nitric oxide is spontaneously oxidized to both nitrite and nitrate, two analytic assays were used serially. Serum nitrite levels were initially determined with the Greiss reagent and subsequently analyzed with Escherichia coli nitrate reductase. RESULTS: With the Greiss reagent alone the mean +/- SEM of serum nitrite level in 26 patients with preeclampsia was significantly decreased compared with 26 normotensive patients (3.46 +/- 1.43 mumol/L vs 4.65 +/- 0.85 mumol/L, p = 0.02). With the addition of the nitrate reductase enzyme of Escherichia coli the mean +/- SEM of serum nitrite level in 26 preeclamptic patients was again significantly decreased compared with 26 normotensive patients (20.04 +/- 1.25 mumol/L vs 27.38 +/- 2.23 mumol/L, p = 0.02). One patient with the syndrome of hemolysis, elevated liver enzymes, and low platelets demonstrated a concurrent decrease in serum nitrite over a 2-week period, emphasizing the relationship of nitric oxide to the pathophysiologic features of the syndrome. CONCLUSIONS: Circulating levels of nitrite are decreased in patients with preeclampsia. These data support the concept that diminished nitric oxide synthesis contributes to the pathophysiologic changes seen in preeclampsia.

Adult↗
PubMed1994

Fetal cardiac effects of oral ritodrine tocolysis.

The beta-sympathomimetic oral tocolytic ritodrine can cause maternal tachycardia and hypotension, and may cross the placenta. A new echocardiographic technique has been developed to explore fetal and placental ritodrine effects. Values in 76 healthy historic controls were compared to 18 studies in 16 patients performed while receiving stable oral ritodrine therapy, measured both at baseline and 30 minutes after a dose. Data collected included maternal pulse and blood pressure (BP), fetal cerebral and umbilical Doppler waveforms, and fetal heart rate. A new index of fetal myocardial contractility, combined ventricular shortening fraction, was derived from two-dimensionally directed M-mode. Maternal pulse and BP, fetal heart rate and heart size, and all Doppler indices were normal, without demonstrable dose-response effects. In the control subjects, combined ventricular shortening fraction fell with increasing gestational age (combined ventricular shortening fraction = -0.27 estimated gestational age + 49; r = 0.27; P < or = 0.02; standard error of the estimate, 11%). However, combined ventricular shortening fraction in ritodrine patients was abnormally decreased in 72% of cases. The mean index in normal subjects was 43 +/- 5%, but in ritodrine patients it was only 31%. We conclude that a history of premature labor or oral ritodrine, or both, is associated with reduced shortening fraction. Since there was no change in placental resistance, cerebral hypoxia, fetal heart rate, or heart size (preload), then low shortening fraction may be due to increased fetal systemic vascular resistance (BP) or decreased myocardial contractility.

Administration, Oral↗
PubMed1993

Synthesis of alpha 1-antichymotrypsin and alpha 1-antitrypsin by human trophoblast.

alpha 1-Antichymotrypsin (alpha 1-ACHY) and alpha 1-antitrypsin (alpha 1-AT) are closely related glycoprotein protease inhibitors, present in plasma and other extracellular fluids, that neutralize proteases released by leukocytes in response to trauma and inflammatory stimuli. Both inhibitors are synthesized primarily by hepatocytes, although lower levels of synthesis by monocytes and breast and intestinal epithelial cells have been demonstrated. Recently, the immunohistochemical localization of alpha 1-AT and alpha 1-ACHY in intrauterine and extrauterine human trophoblastic tissue has been reported. In the present study, we have sought to determine whether human trophoblast is also able to synthesize alpha 1-AT and alpha 1-ACHY. Messenger RNA for both inhibitors was found by Northern blotting in chorionic villi obtained from first trimester and term placenta. Substantial differences in messenger levels for both inhibitors among individual placentas were noted. alpha 1-ACHY and alpha 1-AT messenger was also present in trophoblast cells in primary culture. Synthesis of alpha 1-AT and alpha 1-ACHY protein was demonstrated by SDS-PAGE after immunoprecipitation of [35S]-labeled alpha 1-AT and alpha 1-ACHY from conditioned media of trophoblast cells in culture metabolically labeled with [35S]-methionine. It is of some interest that the M(r) of the alpha 1-AT and alpha 1-ACHY secreted by trophoblast were 50,000 and 49,000, respectively, compared with 54,000 and 68,000 for these proteins in plasma (or secreted by HepG2 human hepatoma and MCF-7 human breast cancer cells).(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗