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D Lee

Publications and source records attributed to D Lee.

At least 163 records · Page 9Linked to original sources
PubMed2000

Numerical simulation of flow fields in a tube with two branches.

In the present study, a numerical calculation procedure based on the finite volume method was employed to simulate flow fields in double-branched tubes. The configuration was a tube with two vertical branches; the two branches were either on the same side or on the opposite side. The study focused on the baseline flow fields and the possible flow interaction between the two branches. The branching ratio and the branch /main tube diameter ratio were fixed in this study. The results showed that when the two branches were on the same side, the low/oscillating shear regions were found on the ventral walls of the branches and on the dorsal wall of the main tube distal to the branches. The flow field proximal to each branch was similar to that in a single-branched tube when the two branches were distant. When the branches were on the opposite side with the staggering distance S=0 (symmetric case), the low/oscillating shear regions were found on the lateral walls of the main tube. As S increased, the interaction between the two branches weakened, the low/oscillating shear regions were found on the lateral walls of the main tube to the side of the second branch. The flow field near the branch was significantly different from that of a single-branched tube. Care should be taken on localization of plaques in multi-branched vessels due to the flow pattern change. The numerical results were qualitatively consistent with what observed experimentally, by other investigators.

Humans↗
PubMed2000

Sodium channels in central neurons of the tobacco budworm, Heliothis virescens: basic properties and modification by scorpion toxins.

Voltage-activated sodium channels in central neurons of larval and adult Heliothis virescens were characterized using whole-cell patch clamp techniques. Macroscopic currents showing rapid activation and inactivation kinetics were uniformly sensitive to tetrodotoxin (IC(50)=1.9nM). Currents began to activate at voltage steps to -45mV and reached half maximal at -30mV. Fast inactivation was evident at voltages as negative as -75mV and reached half maximal at -50mV. Full recovery from inactivation occurred within 1 to 2ms. Currents in larval neurons exhibited similar properties to those of adult neurons, except for the rate of fast inactivation (t(1)), which was significantly slower in larval neurons. The biophysical properties of sodium channels remained unchanged for up to 3days in culture. Two insecticidal neurotoxins, LqhalphaIT and AaIT, produced distinctly different modifications of H. virescens sodium channels. LqhalphaIT slowed channel inactivation, while AaIT specifically shifted voltage-dependent activation to more negative potentials. Overall, the results indicate that sodium channels in H. virescens neurons exhibit biophysical characteristics similar to those of vertebrates, yet possess pharmacological uniqueness with respect to scorpion toxin modification.

Journal Article↗
PubMed2000

Development of an objective structured assessment of technical skills for obstetric and gynecology residents.

OBJECTIVE: To develop an objective structured assessment for evaluating surgical skills of obstetrics and gynecology residents and to evaluate the reliability and validity of the assessment. METHODS: A seven-station, objective, structured assessment of technical skills was administered to 24 residents. The test included laparoscopic procedures (port placement, salpingostomy, suturing, vessel ligation) and open abdominal procedures (hypogastric ligation, repair of enterotomy, salpingo-oophorectomy.) All surgical tasks were done on pigs. Residents were timed and assessed at each station using three methods of scoring, a task-specific checklist, global rating scale, and pass-fail grade. RESULTS: Assessment of construct validity (the ability of the test to discriminate among residency levels) found significant differences on the checklist and the global rating scale by residency level. Reliability indices calculated with Cronbach's alpha were 0.89 for the global rating scale and 0.89-0.95 for the individual skills checklists. Interrater reliability was 0.87 for the global rating scale and 0.78-0.98 for the checklists. CONCLUSION: Objective, structured assessment of technical skills can assess residents' surgical skills with high reliability and validity. These assessments have possible application for identifying residents who need additional training and might provide a mechanism to ensure competence of surgical skills.

Adult↗
PubMed2000

Phenolic compounds from the leaves of Cornus controversa.

Two novel phenolic compounds from the leaves of Cornus controversa (Cornaceae) were characterized as (-)-2,3-digalloyl-4-(E)-caffeoyl-L-threonic acid and (-)-2-galloyl-4-(E)-caffeoyl-L-threonic acid, using spectroscopic methods.

Phenols↗
PubMed2000

Learning of spatial and temporal patterns in sequential hand movements.

Speed and accuracy in performing a complex movement sequence improve with practice. To examine how the temporal and spatial patterns of movement sequence are learned, the sequence of target locations and the consistency in the timing of target presentation were manipulated independently while subjects produced a series of visually guided hand movements. When the sequence of target locations and the timing of target presentation followed a consistent pattern, performance for a particular movement sequence improved with practice for both temporal and spatial movement parameters. However, when the same temporal and spatial patterns were recombined with a phase shift, there was a small but consistent deficit in performance. These results suggest that whereas spatial and temporal patterns in a learned movement sequence can be recombined flexibly, optimal performance is obtained for a specific spatio-temporal pattern of movement sequence. Whereas subjects were largely aware of the spatial and temporal patterns, they were unaware of the phase-shift, suggesting that learning of a specific spatio-temporal pattern was implicit.

Hand↗
PubMed2000

Phosphatidylcholine metabolism in human endothelial cells: modulation by phosphocholine.

Phosphatidylcholine is the principal phospholipid in mammalian tissues, and a major source for the production of arachidonic acid. In this study, the effect of exogenous phosphocholine, a precursor of phosphatidylcholine biosynthesis, on the metabolism of phosphatidylcholine in human umbilical vein endothelial cells was investigated. Incubation of endothelial cells with exogenous phosphocholine at concentrations of 1 to 5 mM was found to inhibit choline uptake and its subsequent incorporation into phosphatidylcholine. Phosphocholine appeared to inhibit choline uptake in a competitive manner. Since phosphatidylcholine is metabolized mainly by the action of phospholipase A2, with the release of arachidonic acid and other fatty acids, the effect of phosphocholine on arachidonic acid release in endothelial cells was also examined. The induction of arachidonic acid release by ATP was enhanced in cells treated with 1 mM phosphocholine. In vitro assays of phospholipase A2 activity in cells incubated with phosphocholine, however, did not produced any significant change in the activity of this enzyme. The results of this study show that phosphocholine modulates the biosynthesis and catabolism of phosphatidylcholine in an indirect manner.

Adenosine Triphosphate↗
PubMed2000

Familial thrombophilia and retinal vein occlusion.

PURPOSE: To perform a pilot study on the prevalence of familial thrombophilia in all cases of retinal vein occlusion with no known risk factors. METHODS: Over the 1 year study period 71 patients presented with a new diagnosis of retinal vein occlusion (age 28-90 years). Fifty-five (77%) were excluded because of local predisposing factors. The remaining 16 (23%) had a full risk factor history taken and blood investigations of rheological factors and thrombophilia including tests for the factor V Leiden mutation, prothrombin G20210A allele and hyper-homocystinemia. RESULTS: Of those with no local predisposing factors, 3 patients had antiphospholipid antibodies, 3 had raised fibrinogen levels, 4 had hyper-homocystinemia and 1 was heterozygous for the Leiden mutation. Other lifestyle risk factors such as obesity, smoking and a positive family history of venous thrombosis were not uncommon. No patient had the prothrombin G20210A variant. CONCLUSIONS: It seems likely that several risk factors, both genetic and acquired, need to be present for thrombosis to occur. In investigating a new patient with a retinal vein occlusion one should test for hypertension, glaucoma and diabetes mellitus. Estimation of plasma viscosity and a full blood count are cheap investigations which may reveal neoplasia or vasculitis, and lipid levels should be estimated. In a young patient or one with an unexpected vein occlusion and a personal or family history of thrombosis, a hypercoagulable state may rarely be identified. This additional testing should include testing for antiphospholipid antibodies and a full thrombophilia screen including the factor V Leiden mutation, homocysteine and the prothrombin variant as part of a clinical trial. Until the role of these markers in thrombosis is better defined in relation to causation of retinal vein occlusion and treatment has been shown to improve outcome, we can not recommend them for routine testing. If a hereditary defect is found, referral should be made to a hematologist and consideration given to anticoagulation and screening of family members to prevent further thrombotic episodes. Retinal vein occlusions are multifactorial in origin except in rare cases.

Adult↗
PubMed2000

Stabilized plasmid-lipid particles for systemic gene therapy.

The structure of 'stabilized plasmid-lipid particles' (SPLP) and their properties as systemic gene therapy vectors has been investigated. We show that SPLP can be visualized employing cryo-electron microscopy to be homogeneous particles of diameter 72 +/- 5 nm consisting of a lipid bilayer surrounding a core of plasmid DNA. It is also shown that SPLP exhibit long circulation lifetimes (circulation half-life >6 h) following intravenous (i.v.) injection in a murine tumor model resulting in accumulation of up to 3% of the total injected dose and concomitant reporter gene expression at a distal (hind flank) tumor site. In contrast, i v. injection of naked plasmid DNA or plasmid DNA-cationic liposome complexes did not result in significant plasmid delivery to the tumor site or gene expression at that site. Furthermore, it is shown that high doses of SPLP corresponding to 175 microg plasmid per mouse are nontoxic as assayed by monitoring serum enzyme levels, whereas i.v. injection of complexes give rise to significant toxicity at dose levels above 20 microg plasmid per mouse. It is concluded that SPLP exhibit properties consistent with potential utility as a nontoxic systemic gene therapy vector.

Animals↗
PubMed2000

Dopamine induces a biphasic modulation of hypothalamic ANF neurons: a ligand concentration-dependent effect involving D5 and D2 receptor interaction.

Increasing evidence now suggests that more than one subtype of dopamine receptors is co-expressed in some of the central neurons. The neurobiological effects on the host cells when these receptors are concurrently activated by their common physiological ligand, dopamine, however, remains elusive. Among the members of the family of dopamine receptors, coupling of D1-like dopamine receptors to Gs and D2-like receptors to Gi proteins are known to augment or suppress cellular functions respectively, through modulation of adenylyl cyclase activity and consequently cAMP generation. Simultaneous activation of D1 and D2 receptors in transfected cell lines expressing the two cloned receptors, however, produced antagonistic effects. This is in contrast to in vivo studies, in which concurrent activation of D1-like and D2-like receptors by their respective agonists may induce synergistic or antagonistic effects or both. We report here that in long-term rat hypothalamic cell cultures, activation of both D1-like (D1 and D5) and D2 receptors on atrial natriuretic factor-producing neurons by dopamine yields a biphasic response. The response is ligand concentration-dependent and involves type II adenylyl cyclases. This process is mediated primarily through antagonistic and synergistic interactions of D5 and D2 receptors as the event is mimicked by the concurrent activation of these two receptors co-transfected in CHO cells. Our present findings suggest a novel action of dopamine, and the biochemical processes involved may underlie some of the pharmacological actions of atypical anti-psychotic drugs. Molecular Psychiatry (2000) 5, 39-48.

1-Methyl-3-isobutylxanthine↗
PubMed2000

Glucocorticoid modulation of dopamine mediated effects on hypothalamic atrial natriuretic factor neurons.

Dopamine (DA) plays an important role in cognition, neuroendocrine functions and psychosis.1,2 Whilst stress adversely affects some of these functions, its neurobiological basis remains unclear.3 In the rat hypothalamus, a concurrent activation of D5and D2 receptors by dopamine produces a biphasic effect on the function of atrial natriuretic factor (ANF) neurons.4 Whereas low doses (10-8 and 10-7 M) of DA suppress the release and pro-ANF mRNA expression, high doses (10-6 and 10-5 M) of the amine produce an opposite effect through the interaction of D5 and D2 receptors. We report here that the augmenting effect of DA on the hypothalamic neurons is inhibited by a synthetic glucocorticoid, dexamethasone (DM), in both time-dependent and dose-related manner with an EC50 of 0.1 nM. Furthermore, the inhibition is blocked by 100 nM of RU38486 (P<0.01), a glucocorticoid receptor antagonist, but not by an equivalent dose of RU28318, a mineralocorticoid receptor antagonist. In contrast, DM failed to modulate low doses (10(-8) to 10(-7) M) of DA-induced suppression of ir-ANF release and pro-ANF mRNA expression that was mediated primarily through D2 receptors. We conclude that glucocorticoids markedly alter DA-induced biphasic effects by down-regulating D5, but not D2, receptor-mediated neurobiological events. Hence, in severe stress, high levels of circulating glucocorticoids may render dopamine to act as a potent suppressor of neurons that possess both D5 and D2 receptors. The possibility that this novel mechanism of stress hormone or glucocorticoids may, in part, undermine DA-mediated neurophysiology in critical regions of the brain, which links to psychosis now needs to be considered.

Animals↗
PubMed2000

Transcriptional responses to growth factor and G protein-coupled receptors in PC12 cells: comparison of alpha(1)-adrenergic receptor subtypes.

Transcriptional responses to growth factor and G protein-coupled receptors were compared in PC12 cells using retroviral luciferase reporters. In cells stably expressing alpha(1A)-adrenergic receptors, norepinephrine activated all five reporters [AP1 (activator protein-1), SRE (serum response element), CRE (cyclic AMP response element), NFkappaB) (nuclear factor-kappaB), and NFAT (nuclear factor of activated T cells)], whereas nerve growth factor (NGF) and epidermal growth factor activated only AP1 and SRE. Activation of P2Y2 receptors by UTP did not activate any reporters. Protein kinase C inhibition blocked NFkappaB activation by norepinephrine, but potentiated CRE. Mitogen-activated protein kinase kinase inhibition blocked AP1 activation by norepinephrine, but also potentiated CRE. p38 mitogen-activated protein kinase inhibition reduced most norepinephrine responses, but not NGF responses. inhibition of Src eliminated SRE responses to norepinephrine and NGF, and reduced all responses except CRE. Phosphatidylinositol 3-kinase inhibitors markedly potentiated CRE activation by norepinephrine, with only small effects on the other responses. Comparison of the three human subtypes showed that the alpha(1A) activated all five reporters, the alpha(1B) showed smaller effects, and the alpha(1D) was ineffective. Cell differentiation caused by norepinephrine, but not NGF, was reduced by all inhibitors studied. These experiments suggest that alpha(1A)-adrenergic receptors activate a wider array of transcriptional responses than do growth factors in PC12 cells. These responses are not linearly related to second messenger production, and different subtypes show different patterns of activation.

Animals↗
PubMed2000

Comparison of flow cytometric assays with isotopic assays of (51)chromium-labeled cells for estimation of red cell clearance or survival in vivo.

BACKGROUND: A comparison was made between flow cytometric and conventional radioisotopic assays in the determination of the clearance or survival of small volumes of (51)chromium-labeled D+ red cells after injection into volunteers. STUDY DESIGN AND METHODS: Four clearance studies were performed using 4 mL of autologous D+ cells coated with anti-D at two concentrations (5 or 10 microg anti-D/mL red cells) transfused to two subjects at separate times. Five survival studies were carried out using 5 mL of frozen-thawed D+ cells transfused to five D- subjects with no detectable anti-D. Sequential blood samples were taken for gamma counting and flow cytometry. Several methods were used to stain the transfused red cells, and the data were analyzed by using three flow cytometers. RESULTS: The determination of red cell clearance or survival by radioactivity measurements gave results consistent with published data. However, none of the flow cytometric assays exhibited the necessary sensitivity or accuracy in quantitation of the rare events to provide reliable data for the calculation of the initial clearance rate, the red cell half-life, or the mean cell lifespan, although rough estimates of red cell clearance were obtained in some subjects. This inability to accurately enumerate rare fluorescence-labeled cells was due mainly to the presence of "background" events, which were a considerable problem in some samples, when the coating level of anti-D was less than 3000 molecules of IgG per cell. CONCLUSION: Flow cytometry may enable the crude estimation of the percentage of small volumes (<5 mL) of transfused D+ red cells, but in this study it was found that this method was not sufficiently accurate to determine the initial clearance rate, red cell half-life, or mean cell lifespan. If the proportion of transfused cells in the recipient is about 0.2 percent or less, the use of radioisotopes for labeling cells for quantitative in vivo red cell clearance or survival data should remain the method of choice.

Blood Volume↗
PubMed2000

Cryptotia.

Explore the source record for details and available documents.

Child↗
PubMed2000

Magnetic resonance imaging in patients with central nervous system pathology: a comparison of OptiMARK (Gd-DTPA-BMEA) and Magnevist (Gd-DTPA).

RATIONALE AND OBJECTIVES: The objective of the two pivotal phase 3 studies was to evaluate the safety and efficacy of OptiMARK (Gd-DTPA-bis(methoxyethylamide) [Gd-DTPA-BMEA]) compared with Magnevist (Gd-DTPA) in magnetic resonance imaging of the central nervous system. METHODS: Two multicenter, randomized, double-blind, parallel group studies were conducted in 395 patients with known or suspected central nervous system pathology. Subjects were randomized to receive a single 0.1 mmol/kg intravenous injection of either Gd-DTPA-BMEA or Gd-DTPA. The safety of Gd-DTPA-BMEA and Gd-DTPA was monitored for up to 72 hours after study drug administration. Precontrast and postcontrast administration magnetic resonance scans were acquired using identical imaging planes and techniques. RESULTS: No deaths or unexpected adverse events were reported in either group. A comparison of adverse events by intensity and relation demonstrated no statistically significant differences between the two groups. Gd-DTPA-BMEA and Gd-DTPA were equivalent with respect to confidence in diagnosis, conspicuity, and border delineation. CONCLUSIONS: Gd-DTPA-BMEA and Gd-DTPA demonstrated comparable efficacy profiles, and the safety profiles were considered similar.

Adult↗
PubMed2000

The Becker technique for otoplasty: modified and revisited with long-term outcomes.

OBJECTIVES: To demonstrate a modification of the Becker technique for otoplasty and to evaluate the long-term results. STUDY DESIGN: Case series with follow-up survey assessment. METHODS: A sample of 16 patients treated by a single surgeon at an academic pediatric referral center who met the inclusion criteria was reviewed for surgical results and patient/parental satisfaction. RESULTS: A total of 30 ears underwent repair. Patients ranged from 4 to 17 years (mean age, 8.2 y) with an average follow-up of 4.6 years. One patient had an immediate postoperative hematoma from blunt trauma that was treated with good long-term results. No cases required revision surgery. Preservation of the antihelix with good to excellent ear symmetry was obtained in all patients at follow-up. All patients were happy or very happy with the surgical procedure. All patients had at least five of the six criteria for surgical success as defined by the survey. CONCLUSIONS: This modification of the Becker technique of otoplasty is efficacious for correction of protruding ears with excellent long-term results.

Adolescent↗
PubMed2000

Characterization of two highly polymorphic human tryptase loci and comparison with a newly discovered monkey tryptase ortholog.

Tryptases are serine proteases involved in mast cell-mediated inflammatory responses which represent potential targets of drugs against diseases such as asthma, arthritis and inflammatory bowel disease. In order to interpret pharmacodynamic data on the tryptase inhibitors undergoing clinical trials, we defined the genetic variability of the tryptase 1 (TPS1) and tryptase 2 (TPS2) loci by screening a reference population of 32 individuals representing three major ethnic groups (Caucasian, African American, Asian). Using overlapping PCR products, we resequenced the entire tryptase genes with the only exclusion of TPS2 intron 1 and 20 bp of TPS2 5' untranslated region included in exon 1 and we identified 21 novel single nucleotide polymorphisms in TPS1 and 17 single nucleotide polymorphisms plus a large polymorphic deletion in the TPS2 gene. We also compared the type, frequency and distribution of single nucleotide polymorphisms in TPS1 and TPS2 and we observed that the polymorphism frequency within these two loci is unexpectedly high (approximately 1 SNP every 90 bp) and that some of the allele frequencies differ significantly among the three ethnic groups. Based on differences observed in preclinical studies using a cynomolgus monkey (Macaca fascicularis) asthma model system, we investigated the difference between monkey and human tryptase genes in order to better understand the mechanism of action of our tryptase inhibitors.

Amino Acid Sequence↗
PubMed2000

An update on "special stain" histochemistry with emphasis on automation.

For nearly 100 years, pathologists have utilized "special histochemical stains" to assist in tissue-based diagnosis. As illustrated in Figures 1 and 2, histochemical stains have been used to identify infectious microorganisms (e.g., Mycobacterium tuberculosis with acid-fast bacillus (AFB) stain), to detail inflammatory stromal or structural alterations (e.g., fibrosis in liver cirrhosis with Masson trichrome), to identify microanatomic sites of disease (e.g., basement membrane in glomerulonephritis with Jones methenamine silver), to identify abnormal chemical deposits (e.g., iron in hemochromatosis with Prussian blue stain), or abnormal immune deposits (e.g., amyloid via Congo red stain). The current surgical pathology laboratory may employ a repertoire of 20 to 25 "special stains" to ensure the full diagnostic complement. While the diagnostic repertoire and the biochemical recipes for the stains are now a well-established, codified part of surgical pathology, there is an ever-moving, leading edge of new developments including new reagents, applications, and methods. This review seeks to update the reader on some of the new applications including both new reagents and methods. Particular emphasis will be placed on the recent technologic advance of automating special stains in kinetic-mode (1-4). The authors consider in turn: 1. In brief, the "news" (recent literature review) of new staining applications; 2. In greater detail, two new applications for detection of Microsporidia and Helicobacer pylori; 3. The new technologic advancement of kinetic mode automation of special stains.

Automation↗