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Biomedical subjects

D Weinstein

Publications and source records attributed to D Weinstein.

At least 19 recordsLinked to original sources
PubMed2005

Influence of tissue conductivity anisotropy on EEG/MEG field and return current computation in a realistic head model: a simulation and visualization study using high-resolution finite element modeling.

To achieve a deeper understanding of the brain, scientists, and clinicians use electroencephalography (EEG) and magnetoencephalography (MEG) inverse methods to reconstruct sources in the cortical sheet of the human brain. The influence of structural and electrical anisotropy in both the skull and the white matter on the EEG and MEG source reconstruction is not well understood. In this paper, we report on a study of the sensitivity to tissue anisotropy of the EEG/MEG forward problem for deep and superficial neocortical sources with differing orientation components in an anatomically accurate model of the human head. The goal of the study was to gain insight into the effect of anisotropy of skull and white matter conductivity through the visualization of field distributions, isopotential surfaces, and return current flow and through statistical error measures. One implicit premise of the study is that factors that affect the accuracy of the forward solution will have at least as strong an influence over solutions to the associated inverse problem. Major findings of the study include (1) anisotropic white matter conductivity causes return currents to flow in directions parallel to the white matter fiber tracts; (2) skull anisotropy has a smearing effect on the forward potential computation; and (3) the deeper a source lies and the more it is surrounded by anisotropic tissue, the larger the influence of this anisotropy on the resulting electric and magnetic fields. Therefore, for the EEG, the presence of tissue anisotropy both for the skull and white matter compartment substantially compromises the forward potential computation and as a consequence, the inverse source reconstruction. In contrast, for the MEG, only the anisotropy of the white matter compartment has a significant effect. Finally, return currents with high amplitudes were found in the highly conducting cerebrospinal fluid compartment, underscoring the need for accurate modeling of this space.

Anisotropy↗
PubMed2005

Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb.

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.

Journal Article↗
PubMed2005

Atomic-scale visualization of inertial dynamics.

The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.

Journal Article↗
PubMed2005

Clocking femtosecond X rays.

Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

Journal Article↗
PubMed2005

Extracorporeal ultrafiltration for acute exacerbations of chronic heart failure: report from the Acute Dialysis Quality Initiative.

This report from a work group affiliated with the Acute Dialysis Quality Initiative is a critical assessment of the use of extracorporeal ultrafiltration (UF) in the management of acutely decompensated heart failure (HF). In addition to assessing UF in this setting, the report also provides background information on HF, including classification, pathophysiology, and the importance of concomitant renal failure. A summary of important results from clinical trials in this area is provided, along with a discussion of technical considerations. Finally, specific recommendations for future clinical evaluations are given.

Heart Failure↗
PubMed2002

Acute and chronic effects of methamphetamine on tele-methylhistamine levels in mouse brain: selective involvement of the D(2) and not D(3) receptor.

We have explored the role of endogenous dopamine in the control of histaminergic neuron activity in mouse brain regions evaluated by changes in tele-methylhistamine (t-MeHA) levels. In vitro, methamphetamine released [(3)H]noradrenaline but failed to release [(3)H]histamine from synaptosomes. In vivo, methamphetamine enhanced t-MeHA levels by about 2-fold with ED(50) values of approximately 1 mg/kg in caudate putamen, nucleus accumbens, cerebral cortex, and hypothalamus. This response selectively involved the D(2) and not the D(3) receptor as indicated by its blockade by haloperidol and by its persistence after administration of nafadotride, a D(3) receptor preferential ligand, or in (-/-) D(3) receptor-deficient mice. The t-MeHA response to methamphetamine was delayed compared with the locomotor-activating effect of this drug, suggesting that it is of compensatory nature. In agreement, ciproxifan, an inverse agonist known to enhance histamine neuron activity, decreased the hyperlocomotion induced by methamphetamine. Repeated methamphetamine administration resulted in the expected sensitization to the hyperlocomotor effect of the drug but did not modify either the ED(50) or the E(max) regarding t-MeHA levels. However, it resulted in an enhanced basal t-MeHA level (+30-40%), which was sustained for at least 11 days after withdrawal in hypothalamus, striatum, and cerebral cortex and suppressed by haloperidol. Hence, both the acute and chronic administration of methamphetamine enhance histamine neuron activity, presumably in a compensatory manner. Repeated methamphetamine administration also resulted in a modified balance in the opposite influences of dopamine and serotonin on histaminergic neurons as revealed by the enhanced response to haloperidol and abolished response to ketanserin, respectively.

Animals↗
PubMed2000

Postpartum umbilical cord blood collection for transplantation: a comparison of three methods.

OBJECTIVE: This study was undertaken to compare 3 methods of collection of human umbilical cord blood. STUDY DESIGN: Seventy-five women with uncomplicated vaginal deliveries were divided equally into 3 groups. One of 3 cord blood collection methods was applied to each woman. Method 1 was collection of cord blood into a standard donation blood bag. Methods 2 and 3 used a syringe to perform a sodium chloride solution flush and drain, which included withdrawal of cord blood by a syringe until the delivery of the placenta, followed by flushing through a catheter one of the umbilical arteries with sodium chloride solution and collection of the cord blood either into an open sterile container (method 2) or into a standard donation blood bag (method 3). Analyses included comparisons among the 3 groups of volume collected, total number of white blood cells, and bacterial contamination rates (positive culture results). In addition a correlation was made between the different variables and the collected cord blood nucleated cells. RESULTS: Cord blood collection by the blood bag method (method 1), which is presently the standard clinical practice, resulted in a mean blood volume of 76.4 +/- 32.1 mL and a mean total white blood cell count of 835 +/- 507 x 10(6) cells. With collection methods 2 and 3, in which as much blood as possible was withdrawn by syringe while the placenta was still in utero followed by a second collection after infusion of the umbilical artery with sodium chloride solution, the mean volume collected was significantly higher (P <.05) at 174.4 +/- 42.8 mL and 173.7 +/- 41.3 mL, respectively, with significantly higher (P <.001) mean total white blood cell counts of 1624 +/- 887 x 10(6) cells and 1693 +/- 972 x 10(6) cells, respectively. A direct correlation was observed between the cord blood volume collected and placental weight, whereas no correlations were observed with maternal age, pregnancy duration, or the neonate's weight. Bacterial contamination was significantly higher (P =.04) in cord blood collections obtained by method 2 (48%) than by methods 1 (16%) and 3 (19%). CONCLUSIONS: The syringe-assisted sodium chloride solution flush collection method with a blood bag (method 3) was found to be the most effective method for human umbilical cord blood collection. This method doubles the total white blood cells collected with respect to current yields, which may make cord blood transplantation applicable for adults.

Adult↗
PubMed2000

Indomethacin for preterm labor: a randomized comparison of vaginal and rectal-oral routes.

OBJECTIVE: To compare the efficacy of intravaginal and intrarectal plus oral indomethacin for the treatment of preterm labor. METHODS: Between December 1996 and November 1998, 46 eligible gravidas admitted with singleton pregnancies and idiopathic preterm labor before 33 gestational weeks were randomized to receive 200 mg of intravaginal or intrarectal plus oral indomethacin. RESULTS: Twenty-three subjects were allocated to each study group. The interval from initiation of treatment to delivery was significantly longer in the intravaginal indomethacin group (26.5 +/- 5.7 versus 12.6 +/- 3.7 days; P =.007). Delivery was delayed by more than 7 days in 18 of 23 subjects (78%) in the intravaginal indomethacin group compared with ten (43%) in the intrarectal plus oral indomethacin group (P =.03). Birth weights were significantly higher (2306 +/- 436 versus 1862 +/- 232 g; P =.002) and hospitalization in a neonatal intensive care unit (NICU) (3.1 +/- 0.8 versus 9.3 +/- 3. 7 days; P =.001) and mechanical ventilation (1.4 +/- 0.2 versus 5.3 +/- 1.6 days; P =.001) were significantly shorter in the intravaginal indomethacin group. CONCLUSION: Intravaginal indomethacin is more effective than intrarectal plus oral application in delaying preterm labor and is associated with higher birth weights, shorter NICU stays, and shorter intervals of mechanical ventilation.

Administration, Intravaginal↗
PubMed2000

Attention-deficit hyperactivity disorder and posttraumatic stress disorder: differential diagnosis in childhood sexual abuse.

Attention-deficit hyperactivity disorders (ADHD) and posttraumatic stress disorder (PTSD) are the most commonly diagnosed disorders in sexually abused children (SAC). There is a high degree of symptom overlap and comorbidity between these disorders, and differential diagnosis can be confusing. Current diagnostic criteria do not include PTSD as a differential diagnosis for ADHD, nor do existing assessment guidelines address these diagnostic similarities. This may have serious implications for SAC. This literature review describes the psychological impact of child sexual abuse and possible consequences for misdiagnosing ADHD in SAC. A comparison of criteria from the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (American Psychiatric Association, 1994) criteria for ADHD and PTSD is presented, and commonalities are discussed. On the basis of this comparison, recommendations are made for improving clinical decision-making and for facilitating differential diagnosis. Routine inquiry about traumatic experiences in children presenting with ADHD symptoms is suggested to increase accuracy in differential diagnosis.

Attention Deficit Disorder with Hyperactivity↗
PubMed2000

Lead-field bases for electroencephalography source imaging.

In recent years, significant progress has been made in the area of electroencephalography (EEG) source imaging. Source localization on simple spherical models has become increasingly efficient, with consistently reported accuracy of within 5 mm. In contrast, source localization on realistic head models remains slow, with subcentimeter accuracy being the exception rather than the norm. A primary reason for this discrepancy is that most source imaging techniques are based on lead fields. While the lead field for simplified geometries can be easily computed analytically, an efficient method for computing realistic domain lead fields has, until now, remained elusive. In this paper, we propose two efficient methods for computing realistic EEG lead-field bases: the first is element oriented and the second is node oriented. We compare these two bases, discuss how they can be used to apply recent source imaging methods to realistic models, and report timings for constructing the bases.

Biomedical Engineering↗
PubMed1999

Expression of the imprinted H19 oncofetal RNA in epithelial ovarian cancer.

STUDY: To examine the expression of the imprinted maternally expressed H19 gene in benign, low malignant potential (borderline) and malignant surface epithelial ovarian tumors. DESIGN: In situ hybridization for H19 RNA using S-labeled and digoxigenin-labeled probes was performed on paraffin sections of ovarian surface epithelial tumors. The serous tumors included nine section cystadenomas, twelve serous tumors of low malignant potential and twenty serous carcinomas, grade I-IIII (FIGO classification). A smaller group included two mucinous cystadenomas, four mucinous tumors of low malignant potential and two mucinous cystadenocarcinomas. RESULTS: H19 expression was found to be positive in 6/9 (67%) serous cystadenomas, 9/12 (75%) of serous tumors of low malignant potential and 13/20 (65%) of invasive serous carcinomas. Expression in mucinous tumors was confined to the stroma beneath the epithelial lining. CONCLUSION: H19 is expressed in the majority of serous epithelial tumors. Taking into consideration the high percentage of H19 expressing serous ovarian neoplasms we suggest that H19 RNA may be used as an adjuvant tumor marker for the diagnosis and mainly for staging and follow-up of patients with serous ovarian carcinoma.

Adenocarcinoma↗
PubMed1999

Perionychial infections associated with sculptured nails.

Two cases of perionychial infections associated with the use of sculptured fingernails are presented. Both patients developed paroncyhia necessitating incision and drainage. One patient, a diabetic, had a concomitant subungual abscess and felon which required repeat drainage and debridement as well as intravenous antibiotics over an extended period for complete resolution. Sculptured fingernails may be risk factors for the development of digit infections through various mechanisms, and users of these cosmetic devices, especially diabetics and immunocompromised people, should be made aware of their potential for infectious complications.

Acrylates↗
PubMed1999

Breast fibroadenoma: mapping of pathophysiologic features with three-time-point, contrast-enhanced MR imaging--pilot study.

The capability of three-time-point, gadolinium-enhanced magnetic resonance imaging to depict vascular permeability and extracellular volume fraction of breast fibroadenoma was evaluated with histopathologic correlation. This method demonstrated an even distribution of high extracellular volume fraction and low to moderate microvascular permeability in these common breast lesions, providing a nonsurgical means of improving the accuracy of diagnosis of fibroadenoma.

Adult↗
PubMed1998

High risk pregnancy outcome by route of delivery.

This review examines the preferred route of delivery in accordance with neonatal and maternal outcome of three high risk pregnancy conditions: multiple pregnancy; delivery after cesarean section; and delivery of infants with macrosomia to mothers with gestational diabetes mellitus. The most common feature of all these conditions is the lack of information, based on large prospective controlled studies, available to the treating physician for choosing the delivery route of choice and for minimizing morbidity and mortality of both infant and mother.

Delivery, Obstetric↗
PubMed1997

Effect of epidural analgesia on duration and outcome of induced labor.

OBJECTIVE: To evaluate the effect of epidural block on the duration of labor and maternal and fetal outcome in induced-labor patients. METHOD: 210 women admitted for induction of labor at a level III university hospital, during the year 1991, were studied. Of these, 112 were given an epidural block and 98 served as controls. Outcome measures studied were: induction time and time in labor, c-section and instrumental delivery rates, intra-partum and post-partum complications, and Apgar scores at 1 and 5 min. RESULT: Multiple regression analysis revealed that epidural analgesia, before and after adjustment for confounding factors, significantly prolonged labor time (P < 0.0001) and was associated with an increase in instrumental delivery rates (P < 0.04). A significant reduction in intra-partum complication rate (FHR changes, meconium) was observed (OR = 0.32; P < 0.03), while c-section rate and Apgar scores were not found to be influenced by epidural analgesia. CONCLUSION: Epidural anesthesia, significantly prolongs labor time in induced patients. While instrumental delivery was more prevalent in these parturients, c-section rate was not increased and intra-partum complications were significantly reduced in these patients.

Adult↗
PubMed1997

High risk pregnancy outcome following induction of labour.

OBJECTIVE: To evaluate whether induction of labour, performed in a high risk obstetric population, when medically indicated, carries an increased risk for operative delivery and maternal and fetal complications. The secondary goal was to study the effect of the various induction methods used on these outcomes and labour time. STUDY DESIGN: This study was carried out at a level [1] university hospital. A group of 210 women who were induced for various indications, were compared to our general parturient population. Main outcome measures were cesarean section (CS) and instrumental delivery rates, intra-partum and post-partum complications, APGARs 1' and 5' and labour time by induction method. RESULTS: No significant increase in the rates of primary CS (8.6 vs. 7.1%) and instrumental delivery (15.7 vs. 12.7%), were found in the induction high risk group as compared to our general obstetric population. Intra-partum complications and fetal outcome were comparable in both groups. A comparison of methods of induction used (oxytocin, PgE2, Amniotomy) revealed a less favorable outcome with the oxytocin induction method which showed an elevated intra-partum complication rate (P < 0.01) and a tendency toward lower Apgar scores and higher CS rate. CONCLUSIONS: Induction of labour performed in a high-risk obstetric population is safe, carrying no significant increase in CS and neonatal complication rates. Of the three methods of induction used, oxytocin induction showed the least favorable outcome for both mother and her offspring.

Adult↗