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Biomedical subjects

G Wong

Publications and source records attributed to G Wong.

At least 19 recordsLinked to original sources
PubMed2001

Truncated trkB.T1 is dominant negative inhibitor of trkB.TK+-mediated cell survival.

Truncated trkB.T1 (T1) neurotrophin receptor inhibits full-length trkB.TK+ (TK+) signaling. At least two possible mechanisms have been proposed for this action: T1 could trap the ligand or function as a dominant negative receptor. To differentiate between these possibilities we have studied survival of serum-deprived PC12-trkB cells stably expressing TK+. PC12-trkB cells were observed to display constitutive trkB kinase activity which leads to survival of a cell subpopulation in the absence of added brain-derived neurotrophic factor (BDNF) and serum. Exogenous BDNF significantly increased cell survival, and this increase was inhibited by BDNF neutralizing antibody. The antibody treatment had no effect on the constitutive TK+ activity. Transfected T1 completely inhibited survival by BDNF or constitutive trkB kinase activity in PC12-trkB cells similarly to tyrosine kinase inhibitor K252a. In addition, T1 coimmunoprecipitated with TK+ and inhibited its autophosphorylation by BDNF. These data suggest that truncated T1 inhibits TK+ signaling by dominant negative action.

Animals↗
PubMed2001

Increased expression of neuronal Src and tyrosine phosphorylation of NMDA receptors in rat brain after systemic treatment with MK-801.

We have observed that systemic treatment with the uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 increases Src expression and NMDA receptor phosphorylation in rat brain. A partial cDNA encoding rat neuronal Src was isolated and its sequence was used to design specific oligonucleotide probes. Systemically administered MK-801 (5 mg/kg for 4 h) increased by 28+/-4% mRNA expression of neuronal Src in the superficial layers of the parietal cortex. This effect was observed at doses as low as 0.2 mg/kg. A similar, although more modest, induction was observed 6 h after phencyclidine (15 mg/kg) administration, but not after high doses of memantine and ketamine. The MK-801-induced effect was not blocked by pretreatment with clozapine. Consistent with the increase in mRNA levels, cortical Src protein was increased to 186 +/- 24% of control 24 h after MK-801 treatment. Total cellular Src activity was also increased in parietal cortex homogenates 4 h after MK-801 (5 mg/kg). Moreover, MK-801 treatment (0.5 mg/kg and 5 mg/kg for 4 h) increased tyrosine phosphorylation, but not protein levels, of the NMDA receptor subunit NR2A. These results provide evidence for a contribution of Src and tyrosine phosphorylation of NMDA receptors in the pharmacological actions of uncompetitive NMDA receptor antagonists.

Amino Acid Sequence↗
PubMed2001

Uncompetitive antagonists of the N-methyl-D-aspartate (NMDA) receptors alter the mRNA expression of proteins associated with the NMDA receptor complex.

N-methyl-D-aspartate (NMDA) receptor function appears to be under complex control during physiological and pharmacological states. We have investigated the effects of acute administration of uncompetitive NMDA receptor antagonists on mRNA levels of NMDA receptor subunits and on molecules known to cluster or phosphorylate the receptor utilizing in situ hybridization on rat brain sections. A high dose (5 mg/kg; 4 hr) of dizocilpine (MK-801) decreased mRNA levels of NMDA receptor subunits NR2C and NR2B in the entorhinal and parietal cortices, respectively. MK-801 increased mRNA levels of synapse-associated protein-90/postsynaptic density-95 (SAP90/PSD-95) and a gamma-isoform of protein kinase C (PKCgamma) in cortical regions. Synapse-associated protein-97 (SAP97) mRNA levels were increased in the entorhinal cortex layer III after MK-801 or after relatively high doses of other uncompetitive NMDA receptor antagonists: phencyclidine (15 mg/kg; 6 hr) and memantine (50 mg/kg; 6 hr). Memantine also increased SAP97 mRNA expression in other cortical regions, but this effect was not observed with MK-801 or phencyclidine. NMDA receptor uncompetitive antagonists alter the expression of multiple receptor components and such events may ultimately play a role in adaptation or toxic responses.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Single-dose toxicity study of hepatic intra-arterial infusion of doxorubicin coupled to a novel magnetically targeted drug carrier.

The toxicity of a single hepatic intra-arterial administration of doxorubicin (DOX) coupled to a magnetically targeted drug carrier (MTC) was evaluated in a swine model. MTC is a microparticle composite of elemental iron and activated carbon. MTC-DOX is a new formulation of doxorubicin absorbed to the MTC and is designed for site-specific delivery to a solid tumor in the presence of an externally applied magnetic field. The magnetic field induces extravasation of MTCs through the vascular wall, leading to localization and retention in the tissue at the targeted site. Eighteen swine were assigned to 6 treatment groups, including 3 control groups (vehicle control, doxorubicin, MTC), and 3 experimental groups that received the MTC-DOX preparation. Animals were given a single administration of test article, evaluated over 28 days, and then sacrificed. Signs of toxicity were monitored via clinical status, total body weight, gross and microscopic pathology, and serum chemistries. Angiography was used to determine the extent of any embolization present. There were no adverse effects observed in the DOX-alone group. Biologically significant, treatment-related gross and microscopic lesions were limited to the targeted area of the liver only in groups receiving > or =75 mg of MTC (with or without doxorubicin). The severity of liver necrosis correlated to the severity of embolization following treatment. Doxorubicin was not freely circulating in any of the MTC-DOX groups, suggesting successful localization to the targeted site. The no-adverse-effect level (NOAEL) was determined to be the MTC-DOX low-dose group.

Angiography↗
PubMed2000

Phototransduction in transgenic mice after targeted deletion of the rod transducin alpha -subunit.

Retinal photoreceptors use the heterotrimeric G protein transducin to couple rhodopsin to a biochemical cascade that underlies the electrical photoresponse. Several isoforms of each transducin subunit are present in the retina. Although rods and cones seem to contain distinct transducin subunits, it is not known whether phototransduction in a given cell type depends strictly on a single form of each subunit. To approach this question, we have deleted the gene for the rod transducin alpha-subunit in mice. In hemizygous knockout mice, there was a small reduction in retinal transducin alpha-subunit content but retinal morphology and the physiology of single rods were largely normal. In homozygous knockout mice, a mild retinal degeneration occurred with age. Rod-driven components were absent from the electroretinogram, whereas cone-driven components were retained. Every photoreceptor examined by single-cell recording failed to respond to flashes, with one exception. The solitary responsive cell was insensitive, as expected for a cone, but had a rod-like spectral sensitivity and flash response kinetics that were slow, even for rods. These results indicate that most if not all rods use a single transducin type in phototransduction.

Animals↗
PubMed2000

Randomized phase III study comparing Best Supportive Care to Biafine as a prophylactic agent for radiation-induced skin toxicity for women undergoing breast irradiation: Radiation Therapy Oncology Group (RTOG) 97-13.

PURPOSE: To determine if Biafine compared to Best Supportive Care (BSC) is effective in minimizing or preventing radiation-induced dermatitis in women undergoing breast irradiation. METHODS AND MATERIALS: Patients were randomized between Biafine (n = 83) vs. BSC (n = 89). The institutions identified preference for BSC at the time of randomization. A no-treatment arm was allowed (16% received no treatment). Patients were instructed to apply randomized product three times a day, but not within 4 h of their daily RT session. Application began following their first radiation treatment and continued 2 weeks postradiation. Skin dermatitis was scored weekly utilizing the RTOG and ONS (Oncology Nursing Society) skin toxicity scales, a weekly patient satisfaction and quality-of-life questionnaire. RESULTS: Using the RTOG toxicity scale there was no overall difference for maximum dermatitis during RT between Biafine and BSC (p = 0.77). There was no difference in maximum toxicity by arm or breast size. There was an interaction between breast size and toxicity, with large-breasted women exhibiting more toxicity. Large-breasted women receiving Biafine were more likely to have no toxicity 6 weeks post RT. CONCLUSION: There was no overall difference between BSC and Biafine in the prevention, time to, or duration of radiation-induced dermatitis.

Adult↗
PubMed2000

Effects of CEES on inflammatory mediators, heat shock protein 70A, histology and ultrastructure in two skin models.

Chemical warfare threats require the development of diverse models for the assessment of countermeasures. Human skin products, Skin2 (differentiating keratinocytes on a fibroblast-collagen matrix) and EpiDerm (differentiating keratinocytes) were exposed (2 h) to the sulfur mustard 2-chloroethyl ethyl sulfide (CEES, 1-2 mg l(-1) min(-1)) in humidified air or to humidified air alone. Tissues were evaluated histologically, ultrastructurally and for viability 22 h later; media and tissues were also analyzed for inflammatory mediators. Histology showed that CEES induced the separation of dermal and epidermal regions in Skin2 with severe damage to basal keratinocytes. Histology and electron microscopy of both products revealed condensation of nuclear chromatin, retraction of spinous processes, collapse of the tonofibrillar network and cytoplasmic vacuolization and blebbing in those cells with loss of pseudobasement membrane integrity. Exposure of Skin2 to CEES increased extracellular interleukin-1alpha (IL-1alpha), prostaglandin-E2 (PGE2) and especially IL-1 receptor antagonist (IL-1Ra) release (56,334 vs 84,614 pg ml(-1)), but decreased interleukin-6 (IL-6, 4,755 vs 351 pg ml(-1)). Exposure of EpiDerm to CEES led to unaffected extracellular and reduced intracelluar IL-1alpha (371 vs 92 pg ml(-1)). Extracellular IL-1Ra greatly increased (2,375 vs 24,875 pg ml(-1)), whereas cellular levels decreased (16,5425 vs 96,625 pg ml(-1)). Extracellular (224 vs 68 pg ml(-1)) and intracellular (485 vs 233 pg ml(-1)) soluble interleukin-1 receptor H (sIL-1RII) decreased. Prostanglandin E2 increased (1,835 vs 2,582 pg ml(-1)), whereas heat shock protein 70A (Hsp70A) remained statistically unchanged (57,000 vs 96,000 pg ml(-1)). Failure to obtain a heat shock response to CEES may contribute to the susceptibility of tissue to the alkylating agent. Consistent and marked responses of cellular and extracellular IL-1Ra to CEES suggest a potential for use as a tissue status marker and primary antiinflammatory regulator in skin.

Biomarkers↗
PubMed2000

Transgenic mice overexpressing truncated trkB neurotrophin receptors in neurons show increased susceptibility to cortical injury after focal cerebral ischemia.

It has been suggested that the increased production of endogenous BDNF after brain insults supports the survival of injured neurons and limits the spread of the damage. In order to test this hypothesis experimentally, we have produced transgenic mouse lines that overexpress the dominant-negative truncated splice variant of BDNF receptor trkB (trkB.T1) in postnatal cortical and hippocampal neurons. When these mice were exposed to transient focal cerebral ischemia by occluding the middle cerebral artery for 45 min and the damage was assessed 24 h later, transgenic mice had a significantly larger damage than wild-type littermates in the cerebral cortex (204 +/- 32% of wild-type, P = 0.02), but not in striatum, where the transgene is not expressed. Our results support the notion that endogenously expressed BDNF is neuroprotective and that BDNF signaling may have an important role in preventing brain damage after transient ischemia.

Alternative Splicing↗
PubMed2000

Molecular effects of the psychotropic NMDA receptor antagonist MK-801 in the rat entorhinal cortex: increases in AP-1 DNA binding activity and expression of Fos and Jun family members.

Noncompetitive NMDA receptor antagonists such as phencyclidine and MK-801 produce psychotropic symptoms that closely resemble schizophrenic psychosis and induce the expression of immediate early genes in limbic cortical areas. We are concentrating on analyzing molecular and physiological effects that these drugs produce in the entorhinal cortex and on the potential connection between these effects and the psychotic symptoms. We show here that MK-801 increases the DNA binding activity of the activator protein-1 (AP-1) complex in the entorhinal cortex. We also observed increased expression of mRNAs for Fos and Jun transcription factor family members c-Fos, FosB, Fra-2, and JunB, as well as Fos family proteins in the entorhinal cortex after MK-801 administration. This suggests that the activated AP-1 complex consists of these transcription factors. Genes regulated by the AP-1 complex in the entorhinal cortex might be involved in the pathophysiology of psychotic behavior and are potential targets for new antipsychotic drugs.

Animals↗
PubMed2000

Developing a tobacco survey for deaf youth.

Formidable barriers hinder use of standard data collection methods among deaf youth. Culturally and linguistically sensitive data collection strategies are needed to identify the unmet health and programming needs of this population. Unfortunately, researchers often fail to describe the issues involved in developing such targeted methods. The authors describe development of a culturally appropriate data collection instrument for a study of tobacco-related knowledge, attitudes, and practices among deaf youth. The instrument uses interactive multimedia technology to administer a questionnaire translated into the primary languages used by the Deaf. The procedures taken to accommodate this technology to these languages and to Deaf culture are described. This process yielded useful insights with respect to data collection not only among the Deaf, but among other frequently overlooked and underserved populations as well.

Adolescent↗
PubMed2000

A functional genomic study of the effects of antipsychotic agent chlorpromazine in PC12 cells.

Expression profiling using methods of functional genomics can be used to investigate changes in gene transcription induced by drug treatment, which may lead to discovery of new potential drug targets. Antipsychotic agents alleviate symptoms of schizophrenia but the mechanism behind their clinical efficacy is unclear. We have used the PC12 cell line as a model to characterize effects of the antipsychotic drug chlorpromazine on gene expression using high-density complementary DNA array filters prepared from a rat brain entorhinal cortex complementary DNA library. Chlorpromazine treatment positively regulated the expression of several clones, five of which were selected for further characterization. Northern blotting experiments confirmed the increased expression of these genes after chlorpromazine treatment. Sequencing revealed that two clones were cytochrome c oxidase and three were novel genes. Characterization of the function of these genes could increase our understanding of the mechanisms of action of antipsychotic drugs, and might be beneficial for the development of more effective agents.

Animals↗
PubMed2000

Comparison of the pharmacokinetics and phototoxicity of protoporphyrin IX metabolized from 5-aminolevulinic acid and two derivatives in human skin in vivo.

Our novel approach was to compare the pharmacokinetics of 5-aminolevulinic acid (ALA), ALA-n-butyl and ALA-n-hexylester induced protoporphyrin IX (PpIX), together with the phototoxicity after photodynamic therapy (PDT) in human skin in vivo, using iontophoresis as a dose-control system. A series of four increasing doses of each compound was iontophoresed into healthy skin of 10 volunteers. The kinetics of PpIX metabolism (n = 4) and the response to PDT (n = 6) performed 5 h after iontophoresis, were assessed by surface PpIX fluorescence and post-irradiation erythema. Whilst ALA-induced PpIX peaked at 7.5 h, highest PpIX fluorescence induced by ALA-n-hexylester was observed at 3-6 h and no clear peak was seen with ALA-n-butylester. With ALA-n-hexylester, more PpIX was formed after 3 (P < 0.05) and 4.5 h, than with ALA or ALA-n-butylester. All compounds showed a linear correlation between logarithm of dose and PpIX fluorescence/phototoxicity at 5 h, with R-values ranging from 0.87 to 1. In addition, the ALA-n-hexylester showed the tendency to cause greater erythema than ALA and ALA-n-butylester. Fluorescence microscopy (n = 2) showed similar PpIX distributions and penetration depths for the three drugs, although both ALA esters led to a more homogeneous PpIX localization. Hence, ALA-n-hexylester appears to have slightly more favorable characteristics for PDT than ALA or ALA-n-butylester.

Adult↗
PubMed2000

Induction of cAMP response element modulator (CREM) and inducible cAMP early repressor (ICER) expression in rat brain by uncompetitive N-methyl-D-aspartate receptor antagonists.

The N-methyl-D-aspartate (NMDA) subtype of glutamate receptor mediates fast excitatory neurotransmission, and agents that attenuate this function are neuroprotective, anesthetic, and psychotropic. To determine whether cAMP regulatable transcription factors play a role in the neurochemical actions of agents acting through NMDA receptors, the effects of the acute administration of uncompetitive and competitive antagonists on the expression of cAMP response element modulator (CREM) and inducible cAMP early repressor (ICER) transcription factors were examined. In situ hybridization to rat brain sections revealed that ICER mRNA expression was significantly increased by uncompetitive NMDA receptor antagonists (MK-801, phencyclidine, ketamine, memantine) but not by the competitive antagonist CPP [(+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid] or other psychotropic agents (clozapine, haloperidol, desipramine). Major brain regions where ICER transcripts were increased were the hippocampus, parietal cortex layers IV and VI, temporal cortex, cingulate cortex, thalamus, and granule cell layer of the olfactory bulb. Northern and Western blot analyses indicated that CREM mRNA and protein, respectively, were also increased after MK-801 treatment, but ICER isoforms predominate during both basal and induced conditions. MK-801 also transiently increased the binding of proteins to cAMP response element, which was supershifted by anti-CREM antibody, indicating that increased mRNA and protein levels have functional consequences on gene transcription. These results provide evidence for the involvement of CREM and ICER family transcription factors in the pharmacologic effects of uncompetitive NMDA receptor antagonists.

Animals↗
PubMed1999

Analysis of gene expression data using self-organizing maps.

DNA microarray technologies together with rapidly increasing genomic sequence information is leading to an explosion in available gene expression data. Currently there is a great need for efficient methods to analyze and visualize these massive data sets. A self-organizing map (SOM) is an unsupervised neural network learning algorithm which has been successfully used for the analysis and organization of large data files. We have here applied the SOM algorithm to analyze published data of yeast gene expression and show that SOM is an excellent tool for the analysis and visualization of gene expression profiles.

Algorithms↗
PubMed1999

Expression of the naturally occurring truncated trkB neurotrophin receptor induces outgrowth of filopodia and processes in neuroblastoma cells.

We have investigated the effects of the truncated trkB receptor isoform T1 (trkB.T1) by transient transfection into mouse N2a neuroblastoma cells. We observed that expression of trkB.T1 leads to a striking change in cell morphology characterized by outgrowth of filopodia and processes. A similar morphological response was also observed in SH-SY5Y human neuroblastoma cells and NIH3T3 fibroblasts transfected with trkB.T1. N2a cells lack endogenous expression of trkB isoforms, but express barely detectable amounts of its ligands, brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4). The morphological change was ligand-independent, since addition of exogenous BDNF or NT-4 or blockade of endogenous trkB ligands did not influence this response. Filopodia and process outgrowth was significantly suppressed when full-length trkB.TK+ was cotransfected together with trkB.T1 and this inhibitory effect was blocked by tyrosine kinase inhibitor K252a. Transfection of trkB.T1 deletion mutants showed that the morphological response is dependent on the extracellular, but not the intracellular domain of the receptor. Our results suggest a novel ligand-independent role for truncated trkB in the regulation of cellular morphology.

3T3 Cells↗
PubMed1999

The development and validation of the coping inventory for prodromes of mania.

This study described the construction and validation of the Coping Inventory for Prodromes of Mania (CIPM)-a newly developed instrument aimed at assessing how manic depressive sufferers dealt with their prodromes of mania. Two hundred and six subjects completed a 40-item measure of coping responses to prodromes of mania, a measure of social functioning and a mood measure. The CIPM yielded four empirically derived subscales: stimulation reduction, problem-directed coping, seeking professional help, denial or blame. All of these subscales provided good reliability and acceptably high internal consistency data. There was also some evidence of good validity of the CIPM.

Adaptation, Psychological↗