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Biomedical subjects

R Huang

Publications and source records attributed to R Huang.

At least 37 records · Page 2Linked to original sources
PubMed2002

Center for Synchrotron Biosciences' U2B beamline: an international resource for biological infrared spectroscopy.

A synchrotron infrared (IR) beamline, U2B, dedicated to the biomedical and biological sciences has been constructed and is in operation at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory. The facility is operated by the Center for Synchrotron Biosciences of the Albert Einstein College of Medicine in cooperation with the NSLS. Owing to the broadband nature of the synchrotron beam with brightness 1000 times that of conventional sources, Fourier transform IR spectroscopy experiments are feasible on diffraction-limited sample areas at high signal-to-noise ratios and with relatively short data-acquisition times. A number of synchrotron IR microscopy experiments that have been performed in the mid-IR spectral range (500-5000 cm(-1)) are summarized, including time-resolved protein-folding studies in the microsecond time regime, IR imaging of neurons, bone and other biological tissues, as well as imaging of samples of interest in the chemical and environmental sciences. Owing to the high flux output of this beamline in the far-IR region (50-500 cm(-1)), investigations of hydrogen bonding and dynamic molecular motions of biomolecules have been carried out from 10 to 300 K using a custom-made cryostat and an evacuated box. This facility is intended as an international resource for biological IR spectroscopy fully available to outside users based on competitive proposal.

Bone and Bones↗
PubMed2001

Embryonic central nervous system angiogenesis does not involve blood-borne endothelial progenitors.

We asked, whether, in the blood of avian embryos, endothelial precursor cells circulate that actually contribute to the growing vascular system in and around the central nervous system (CNS). We compared the morphology and distribution of QH1-positive cells after transplantation of quail paraxial mesoderm, after blood transfusion, in quail-chick parabiosis, or after quail bone-marrow transplantation. After head mesoderm transplantation from quail to chick, we observed sprouting endothelial cells (ECs), capillary tube formation, and chimeric endothelial lining of large arteries in the host brain. These QH1-positive quail cells showed EC morphologies that demonstrated three different aspects of CNS angiogenesis: invasion by means of filopodia, clonal proliferation and tube formation, and integration into preexisting EC layers. After blood transfusion or in chick-quail parabiosis, blood-borne QH1+ cells were found in the lumen of but not integrated into the wall of the host vascular system. Neither were QH1+ cells observed in the capillary walls of parabiotic chick chorioallantoic membranes. In both cases, the quail cells showed typical macrophage morphology. In chicks that had received quail bone marrow transplants onto their chorioallantoic membranes, QH1+ cells with macrophage, but not EC shape were occasionally seen near the inoculation site. We conclude that (1) blood-borne cells do not become ECs or directly contribute to angiogenesis inside, or in vascular plexuses around the CNS during embryonic development; (2) blood-borne cells do not contribute to the intraneural macrophage population of the embryonic CNS.

Afferent Pathways↗
PubMed2001

Simultaneous detection of multiple cytokines from conditioned media and patient's sera by an antibody-based protein array system.

We have developed a novel technique for high-throughput simultaneous screening of multiple cytokine expression based on a protein array system. Our method has the advantage of showing the specificity of enzyme-linked immunosorbent assays, sensitivity of enhanced chemiluminescence (ECL), and high-throughput of microspot. In this system, the cytokine array membranes were created by spotting capture antibodies onto the membranes. The membranes were then incubated with biological samples such as conditioned media and patient's sera. The bound proteins were then recognized by biotin-conjugated antibodies and detected by horseradish peroxidase-conjugated streptavidin coupled with ECL. Experiments demonstrated that 24 cytokines from conditioned media and patient's sera could be simultaneously detected using this new approach. This methodology should allow us to develop many high-density protein array systems to detect a variety of proteins. To validate and quantitate the expression of key molecules in a wide range of samples, we have developed conditioned medium arrays to evaluate hundreds and even thousands of samples from individual cells and patients in a single microarray. The combinations of protein arrays and conditioned medium arrays or serum arrays will provide a powerful tool to identify the protein expression profiles and rapidly validate their expression in many types and numbers of samples.

Antibodies↗
PubMed2001

An Arabidopsis mutant cex1 exhibits constant accumulation of jasmonate-regulated AtVSP, Thi2.1 and PDF1.2.

Jasmonates (JA) act as a regulator in plant growth as well as a signal in plant defense. The Arabidopsis vegetative storage protein (AtVSP) and plant defense-related proteins thionin (Thi2.1) and defensin (PDF1.2) have previously been shown to accumulate in response to JA induction. In this report, we isolated and characterized a novel recessive mutant, cex1, conferring constitutive JA-responsive phenotypes including JA-inhibitory growth and constitutive expression of JA-regulated AtVSP, Thi2.1 and PDF1.2. The plant morphology and the gene expression pattern of the cex1 mutant could be phenocopied by treatment of wild-type plants with exogenous JA, indicating that CEX1 might be a negative regulator of the JA response pathway.

Adenosine Triphosphatases↗
PubMed2001

Connexin 43 (cx43) enhances chemotherapy-induced apoptosis in human glioblastoma cells.

Stable re-expression of connexin 43 (cx43) in human glioblastoma suppresses transformation and tumorigenicity. The present study was designed to examine the role of cx43 in chemotherapy-induced apoptosis. Expression of cx43 in human glioblastoma cells significantly increased sensitivity to several common chemotherapeutic agents, including etoposide, paclitaxel (Taxol) and doxorubicin, compared with control-transfected cells. The increased sensitivity to chemotherapeutic agents resulted from apoptosis as evidenced by Hoechst dye staining, TUNEL assay and annexin V assay. These cx43-mediated effects were coupled with decreased expression of the specific apoptosis inhibitor bcl-2. Over-expression of bcl-2 in cx43-transfected cells partially confers the resistance to apoptosis induced by etoposide, suggesting that the cx43-mediated apoptosis to chemotherapeutic agents is regulated in part through the down-regulation of bcl-2 expression. Furthermore, the cx43-mediated apoptosis in response to chemotherapeutic drugs may not be linked to increased gap junctional communication in cx43-transfected cells. Our results demonstrate a new role of cx43 in the mediation of apoptosis during chemotherapy.

Antineoplastic Agents↗
PubMed2001

Antagonists of calcium fluxes and calmodulin block activation of the p21-activated protein kinases in neutrophils.

Neutrophils stimulated with fMLP or a variety of other chemoattractants that bind to serpentine receptors coupled to heterotrimeric G proteins exhibit rapid activation of two p21-activated protein kinases (Paks) with molecular masses of approximately 63 and 69 kDa (gamma- and alpha-Pak). Previous studies have shown that products of phosphatidylinositol 3-kinase and tyrosine kinases are required for the activation of Paks. We now report that a variety of structurally distinct compounds which interrupt different stages in calcium/calmodulin (CaM) signaling block activation of the 63- and 69-kDa Paks in fMLP-stimulated neutrophils. These antagonists included selective inhibitors of phospholipase C (1-[6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione), the intracellular Ca(2+) channel (8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate), CaM (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide; N-(4-aminobutyl)-5-chloro-1-naphthalenesulfonamide; trifluoperazine), and CaM-activated protein kinases (N-[2-(N-(chlorocinnamyl)-N:-methylaminomethyl)phenyl]-N-[2-hydroxyethyl]-4-methoxybenzenesulfonamide). This inhibition was dose-dependent with IC(50) values very similar to those that interrupt CaM-dependent reactions in vitro. In contrast, less active analogues of these compounds (1-[6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-2,5-pyrrolidinedione; N-(6-aminohexyl)-1-naphthalenesulfonamide; N-(4-aminobutyl)-1-naphthalenesulfonamide; promethazine; 2-[N-(4-methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzyl-amine]) did not affect activation of Paks in these cells. CaM antagonists (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide; trifluoperazine), but not their less-active analogues (N-(6-aminohexyl)-1-naphthalenesulfonamide; promethazine), were also found to block activation of the small GTPases Ras and Rac in stimulated neutrophils along with the extracellular signal-regulated kinases. These data strongly suggest that the Ca(2+)/CaM complex plays a major role in the activation of a number of enzyme systems in neutrophils that are regulated by small GTPases.

Animals↗
PubMed2001

Design of a microfabricated magnetic cell separator.

A new magnetic separation idea utilizing several ideas from microfabrication and nanomagnetics is presented. The basic idea comes from our earlier work using asymmetry in obstacles and Brownian motion to effect separation of objetcs [10] by moving them in streams whose angle to the hydrodynamic average velocity is a function of the diffusion coefficient of the object. The device we propose here is not technically a Brownian ratchet device but uses the idea of force which acts at angle to the hydrodynamic flow. In our case, the force is generated by a magnetic field gradient which comes from an array of magnetized wires which lie at an angle 0 to a hydrodynamic field flow. The sum of the hydrodynamic force and the magnetic force create a new vector which as in the case of the Brownian ratchet moves the cell out of the main stream direction.

Animals↗
PubMed2001

Hydrogen peroxide promotes transformation of rat liver non-neoplastic epithelial cells through activation of epidermal growth factor receptor.

Previous studies demonstrated that hydrogen peroxide (H(2)O(2)) is a tumor promoter in the rat liver epithelial cell line T51B. We investigated the pathway linking H(2)O(2) to tumor promotion. H(2)O(2) can directly induce tyrosine phosphorylation of epidermal growth factor receptor (EGFR). H(2)O(2) and epidermal growth factor exerted similar effects on the induction of early growth response genes, disruption of gap junction communication, triggering of calcium inflow, and promotion of transformation. Furthermore, the effect of H(2)O(2) on tumor promotion was blocked by abrogation of EGFR activation. Our results suggested that tumor promotion by H(2)O(2) is mediated mainly through activation of EGFR in T51B cells.

Animals↗
PubMed2001

Enhanced apoptosis under low serum conditions in human glioblastoma cells by connexin 43 (Cx43).

Connexin 43 (Cx43), a structural component of gap junctions, is believed to function as a tumor suppressor gene. Previously, we showed that expression of Cx43 suppresses cell proliferation and tumorigenicity of human glioblastoma cells [Huang et al., Cancer Res 58:5089-5096, 1998] and enhances apoptosis in response to chemotherapeutic agents [Huang et al., Int J Cancer 92:130-138, 2001]. In the present study, we demonstrated that expression of Cx43 in human glioblastoma cells potentiated an apoptotic program under low-serum conditions. The Cx43-mediated effect was coupled with a decreased expression of the specific apoptosis-inhibitor bcl-2. Overexpression of bcl-2 in Cx43-transfected cells conferred resistance to apoptosis induced under low-serum conditions, suggesting that the Cx43-mediated apoptosis under low-serum conditions is regulated, in part, through the downregulation of bcl-2 expression. Furthermore, application of the phosphatidylinositol-3'-OH kinase inhibitor LY294002 specifically induced apoptosis in Cx43-transfected cells. Our results demonstrate a new role of Cx43 in the mediation of apoptosis under low serum conditions.

Apoptosis↗
PubMed2001

Molecular and cellular analysis of embryonic avian tongue development.

Signalling cascades first described in Drosophila have been found to regulate patterning and outgrowth in a number of structures in higher vertebrates. We sought to determine whether the evolutionarily conserved genes were important during the development of the tongue. In situ hybridisation was used to determine the temporo-spatial expression of a panel of conserved genes. Histological examination and incorporation of BrdU were used to determine the mechanism by which the tongue develops. We show that evolutionarily conserved genes were expressed in distinct dynamic patterns during tongue development. Sonic Hedgehog (Shh) and Patched (Ptc) were found only in the dorsal tongue epithelium. Shh expression was only observed in the suprabasal layers, whereas Ptc was observed in both basal and suprabasal layers. Cell division in the epithelium was concentrated in regions devoid of Shh. Expression of bone morphogenetic protein-7 (BMP) was identical to that of Shh. Shh and Ptc expression were never detected in the mesenchyme. Ectopic expression of Noggin (a potent antagonist of the BMPs) caused severe abnormalities in tongue morphology, including swelling of the mesenchymal component and a thickening of the epithelial layer. Data from this study suggests that the epithelium and mesenchyme express quite different genes during development. However BMP activity acts to inhibit growth in both tissues.

Activins↗
PubMed2001

Factors affecting performance on the American Board of Surgery in-training examination.

BACKGROUND: Surgical programs use the American Board of Surgery In-Training Examination (ABSITE) in several ways, including for promotion and retention decisions. The purpose of this study was to identify the combination of factors that explain residents' successful performance on the ABSITE. METHODS: Fifty-one surgical residents completed questionnaires, and information was gathered about their previous ABSITE performance, anxiety, probationary status, amount of study, amount of sleep before examination, confidence, and attendance at conference. RESULTS: An analysis of the data for those with experience taking the examination (n = 34) indicated that the combination of conference attendance (26.3%), previous performance (16.5%), probationary status (10.4%), amount of sleep (9.8%), and amount of study (8%) were significant in explaining a total of 71% of the variance in ABSITE scores. Amount of study (+0.32, P = 0.011), confidence (+0.36, P = 0.005), and conference attendance (+0.51, P = 0.001) were significantly correlated with ABSITE performance. CONCLUSIONS: Several factors contribute to residents' successful ABSITE performance. These findings may lead to improved examination performance and application of knowledge, both during residency and throughout their career.

Educational Measurement↗
PubMed2001

Direct electrochemistry and electrocatalysis with horseradish peroxidase in Eastman AQ films.

Stable films made from ionomer poly(ester sulfonic acid) or Eastman AQ29 on pyrolytic graphite (PG) electrodes gave direct electrochemistry for incorporated enzyme horseradish peroxidase (HRP). Cyclic voltammetry of HRP-AQ films showed a pair of well-defined, nearly reversible peaks at about -0.33 V vs. SCE at pH 7.0 in blank buffers, characteristic of HRP heme Fe(III)/Fe(II) redox couple. The electron transfer between HRP and PG electrode was greatly facilitated in AQ films. The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (k(s)) and formal potential (E(o')) were estimated by fitting the data of square-wave voltammetry (SWV) with nonlinear regression analysis. Reflectance absorption infrared (RAIR) and UV-Vis absorption spectra demonstrated that HRP retained a near native conformation in AQ films. The embedded HRP in AQ films retained the electrocatalytic activity for oxygen, nitrite and hydrogen peroxide. Possible mechanism of catalytic reduction of H(2)O(2) with HRP-AQ films was proposed.

Catalysis↗
PubMed2001

Assignment of the disulfide bonds of huwentoxin-II by Edman degradation sequencing and stepwise thiol modification.

A novel strategy combining Edman degradation and thiol modification was developed to assign the three disulfides of huwentoxin-II (HWTX-II), an insecticidal peptide purified from the venom of the spider Selenocosmia huwena. Phenylthiohydantoin (Pth) derivatives of Cys and the elimination product, dehydroalanine (DeltaSer), can be observed in the Cys cycles during Edman degradation of native HWTX-II. The appearance of two products indicates that the disulfides of HWTX-II were split and that the free thiol group of the second half cystine has been generated. Information about the nature of the disulfide bridges of HWTX-II could be obtained from the sequencing signal if the nascent thiols were modified stepwise by 4-vinylpyridine. Using this method the disulfide bridges of HWTX-II were assigned as Cys4-Cys18, Cys8-Cys29 and Cys23-Cys34, which is different from that seen in HWTX-I, a neurotoxic peptide from the same spider. Using this strategy, one can assign the disulfide bonds of small proteins by sequencing and modification n - 1 times, where n is the number of disulfide bonds in the protein. The above assignment of the disulfide bonds of HWTX-II was confirmed by MALDI-TOF MS of tryptic fragments of HWTX-II. Some disulfide interchanging during proteolysis was observed by monitoring the kinetics of proteolysis of HWTX-II by MALDI-TOF MS.

Amino Acid Sequence↗
PubMed2001

Fetal iliac angle measurements by three-dimensional sonography.

OBJECTIVE: To determine the technical reliability of fetal iliac angle measurements by three-dimensional sonography as a prenatal marker for Down syndrome. METHODS: Three-dimensional multiplanar views of the fetal pelvis were used to standardize iliac angle measurements from 35 normal second-trimester pregnancies. Measurement reliability for a single examiner and between two different examiners were analyzed by intraclass correlation. Normal iliac angle measurements were compared to those obtained from 16 fetuses with trisomy 21. RESULTS: The mean axial angle for normal fetuses was 79 +/- 5.5 degrees, which was significantly less than that observed in fetuses with trisomy 21 (87.7 +/- 4.9 degrees ) (P < 0.001). Iliac angles did not correlate with gestational age. Axial angles were reproducible between two examiners who measured the same multiplanar view of the pelvis. Inter- and intraobserver reliability were also acceptable after a standardized multiplanar view was independently obtained by each examiner (intraclass correlation = 0.91 for both). Coronal angles were unreliable because of difficulties with finding a reproducible measurement plane. For a false-positive rate of 5%, an axial angle threshold of 87 degrees correctly identified 56% of fetuses with trisomy 21. CONCLUSION: Axial iliac angle measurements are reliable by standardized three-dimensional multiplanar views of the pelvis and can be used to identify some fetuses at increased risk for trisomy 21.

Adult↗
PubMed2001

Impact of technetium-99m sestamibi imaging on the emergency department management and costs in the evaluation of low-risk chest pain.

OBJECTIVES: To assess the impact of rest sestamibi scanning on emergency physicians' (EPs') diagnostic certainty and decision making (as assessed by the hypothetical disposition of patients) for 69 consenting stable patients with suspected acute cardiac ischemia and nondiagnostic electrocardiograms. The resultant impact on costs was examined as a secondary outcome. METHODS: Patients with suspected acute cardiac ischemia were injected with 25 mCi of sestamibi within two hours of active pain in one of three emergency department study sites. The probability of acute myocardial infarction (AMI) and unstable angina (UA), and hypothetical disposition decisions were recorded immediately before and after physicians were notified of scan results. Changes in disposition were classified as optimal or suboptimal. For the cost determinations, a cost-based decision support program was used. RESULTS: For the subgroup found to be free of acute cardiac events (ACEs) (n = 62), the EPs' post-sestamibi scan probabilities for AMI decreased by 11% and UA by 18% (p < 0.001 for both conditions). In seven patients with ACEs, the post-scan probabilities of AMI and UA increased, but neither was statistically significant. Scan results led to hypothetical disposition changes in 29 patients (42%), of which 27 (93%) were optimal (nine patients were reassigned to a lower level of care, two to a higher level, and 16 additional patients to "discharge-home" status). The strategy of scanning all patients who were low to moderate risk for acute cardiac ischemia would result in an increase of direct costs of care of $222 per patient evaluated, due to added cost of sestamibi scanning. CONCLUSIONS: Sestamibi scanning results appropriately affected the EPs' estimates of the probability of AMI and UA and improved disposition decisions. Scanning all low-risk patients would likely be associated with increased costs at this medical center.

Angina, Unstable↗
PubMed2001

Patterning of fast and slow fibers within embryonic muscles is established independently of signals from the surrounding mesenchyme.

During embryonic development, and before functional innervation, a highly stereotypic pattern of slow- and fast-contracting primary muscle fibers is established within individual muscles of the limbs, from distinct populations of myoblasts. A difference between the fiber-type pattern found within chicken and quail pectoral muscles was exploited to investigate the contributions of somite-derived myogenic precursors and lateral plate-derived mesenchymal stroma to the establishment of muscle fiber-type patterns. Chimeric chicken/quail embryos were constructed by reciprocal transplantation of somites or lateral plate mesoderm at stages prior to muscle formation. Muscle fibers derived from quail myogenic precursors that had migrated into chicken stroma showed a quail pattern of mixed fast- and slow-contracting muscle fibers. Conversely, chicken myogenic precursors that had migrated into quail stroma showed a chicken pattern of nearly exclusive fast muscle fiber formation. These results demonstrate in vivo an intrinsic commitment to fiber-type on the part of the myoblast, independent of extrinsic signals it receives from the mesenchymal stroma in which it differentiates.

Animals↗
PubMed2001

Effectiveness of interferon-alfa and mid-cycle chemotherapy added to an anthracycline-based regimen in the treatment of aggressive non-Hodgkin's lymphoma.

Interferon-alfa in combination with cytotoxic chemotherapy has been shown to be effective in treating certain types of non-Hodgkin's lymphoma (NHL) (1). However, there is no published data on upfront induction treatment of aggressive NHL with IFN-alfa containing regimens. Studies have also shown that one can overcome regrowth resistance by administering mid-cycle agents which slow tumor proliferation between courses of cytotoxic therapy (2). Based on this, we treated 32 consecutive patients between 1/93 and 9/96 with a regimen containing cyclophosphamide 750 mg/m2, mitoxantrone 12 mg/m2, and teniposide 60 mg/m2 IV on day 1 with prednisone 100 mg PO given on days 1-5. On day 15, patients received vincristine 1.4 mg/m2 (2 mg max.) and bleomycin 10 units/m2 IV. Interferon-alfa-2b 5x10(6) units/m2 SQ was administered on days 22-26. The median age was 55 (range 26-83), M:F ratio was 2.5:1, and the median International Prognostic Index was 2. 38% of patients had stages I-II and 62% had stages III-IV disease. Fifty-nine percent of the patients achieved a complete response, 22% a partial response, and 19% had progressive disease. The overall survival (OS) was 81% and the progression free survival (PFS) was 56% at 4.3 years. There were no severe (grade IV) hematologic, flu-like, GI and infectious toxicities from IFN-alpha. Leukopenia was the main severe toxicity related to the chemotherapy regimen (days 1-15), but not IFN-alpha. Severe infection secondary to the chemotherapy regimen occurred in one patient. Interferon-alfa-2b and mid-cycle chemotherapy added to an anthracycline based regimen is effective induction treatment for patients with aggressive NHL. The OS and PFS using this regimen, based on regrowth resistance, appears to be at least as or more effective than CHOP therapy for this group of patients. Severe toxicities were rare.

Adult↗