Biomedical subjects

E Kim

Publications and source records attributed to E Kim.

At least 109 records · Page 6Linked to original sources

PubMed2000

9:00-9:15. Antiangiogenic Treatment with Endostatin Results in Uncoupling of Blood Flow and Glucose Metabolism in Human Tumors.

Endostatin is a novel antiangiogenic agent currently in phase I trials. In the context of this trial, we are evaluating the use of non-invasive imaging with PET to determine the relationship between tumor blood flow and glucose metabolism in imaged tumors from treated patients.Ten patients have been treated with escalating daily iv Endostatin doses of 30 to 180 mg/m(2). PET images were obtained before the start of therapy and again after 28 days of treatment. Each patient was scanned with Oxygen-15 labeled water for estimation of tumor blood flow and Flourine-18 labeled FDG to estimate tumor metabolic activity. In most cases, two distinct tumor-bearing sites were analyzed in each patient. Thus, a total of 19 tumors were imaged. Regional blood flow and standard uptake values (SUV) were computed at baseline and 28 days post treatment and the percentage change in blood flow and SUV plotted as a function of Endostatin dose.Both blood flow and glucose metabolism in the imaged tumors were observed to increase in patients treated with </=60 mg/m(2)/d, but became uncoupled in the tumors imaged from patients treated at the 180 mg/m(2)/d dose level. Thus, in patients receiving Endostatin at a dose of 180 mg/m(2)/d, blood flow decreased but glucose metabolism increased. This relationship is displayed in Figure 1 below.

Journal Article↗

PubMed2000

9:30-9:45. First Pass FDG Measured Blood Flow in Tumors: A Comparison with O-15 Labeled Water Measured Blood Flow.

The purpose of this study was to determine if the first-pass of FDG can be used to measure regional blood flow in tumors in the absence of perfusion imaging with a known blood flow tracer.PET scans were obtained in patients being evaluated for tumor perfusion and metabolism in a Phase I dose escalating protocol for Endostatin, a novel antiangiogenic agent. A two minutes perfusion scan was done with a bolus injection of 60 mCi of O-15 labeled water followed by a 10 mCi dose of FDG and four sequential scans consisting of a first pass two minutes scan and three 15 minutes scans. Regions of interest were drawn on two tumor sites for each scan. Blood flow was computed using a one-compartment model previously published by the authors. Linear regression analysis was carried out between the first pass FDG measured blood flow and O-15 measured blood flow (Figure 1).Blood flow estimated from the first pass of FDG was linearly correlated with O-15 measured blood flow with an intercept of 0.01, slope of 0.86, and r squared regression coefficient of 0.74 (R = 0.86) for blood flow values of up to 0.6 ml/min/gm of tissue. These results suggests that in the absence of a perfusion tracer, the first pass of FDG provides an estimate of perfusion in a tumor within the limitations of incomplete extraction of FDG compared to O-15 water.

Journal Article↗

PubMed2000

Reconstitution of an ATM-dependent checkpoint that inhibits chromosomal DNA replication following DNA damage.

Cell cycle checkpoints lead to the inhibition of cell cycle progression following DNA damage. A cell-free system derived from Xenopus eggs has been established that reconstitutes the checkpoint pathway inhibiting DNA replication initiation. DNA containing double-strand breaks inhibits replication initiation in a dose-dependent manner. Upon checkpoint activation, a prereplicative complex is assembled that contains ORC, Cdc6, Cdc7, and MCM proteins but lacks Cdc45. The checkpoint is ATM dependent. Cdk2/CyclinE acts downstream of ATM and is downregulated by Cdk2 phosphorylation on tyrosine 15. Cdk2AF/CyclinE is refractory to checkpoint signaling, and Cdc25A overrides the checkpoint and restores DNA replication. This report provides the description of a DNA damage checkpoint pathway that prevents the onset of S phase independently of the transcriptional function of p53 in a vertebrate organism.

Androstadienes↗

PubMed2000

Effect of a global regulatory gene, afsR2, from Streptomyces lividans on avermectin production in Streptomyces avermitilis.

The global regulatory gene, afsR2, from Streptomyces lividans was previously reported to highly stimulate two structurally unrelated antibiotics, actinorhodin and undecylprodigiosin, in both S. lividans and its close relative S. coelicolor. Production of eight avermectin components was also improved in S. avermitilis: the use of wild-type S. avermitilis and its high-producing mutant, transformed by introduction of multiple copies of afsR2, increased the total avermectin productions by 2.3-fold and 1.5-fold, respectively.

Journal Article↗

PubMed2000

A supernumerary tooth fused to the facial surface of a maxillary permanent central incisor: case report.

A case of a supernumerary tooth fused to the facial surface of a maxillary permanent central incisor is reported. Root canal therapy on the maxillary central incisor was performed due to pulpal communication between the supernumerary tooth and the maxillary central incisor after removing the supernumerary tooth structure. The communication was sealed with mineral trioxide aggregate. The difference between fusion and gemination is discussed.

Aluminum Compounds↗

PubMed2000

Combined antitumor effects of an adenoviral cytosine deaminase/thymidine kinase fusion gene in rat C6 glioma.

OBJECTIVE: In this study, we investigated the feasibility of a double-suicide gene/prodrug therapy, involving direct introduction of the herpes simplex virus Type 1 thymidine kinase (TK) gene and the Escherichia coli cytosine deaminase (CD) gene, via a recombinant adenoviral vector, and ganciclovir (GCV) and/or 5-fluorocytosine (5-FC) treatment, in a rat C6 glioma model. METHODS: Efficient gene transfer and transduction of C6 glioma cells via a recombinant adenovirus were evaluated by infecting cells with adenovirus bearing the beta-galactosidase gene and then staining cells with X-5-bromo-4-chloro-3-indolyl-13-D-galactoside. CD/TK expression in cells infected with adenovirus bearing the CD/TK gene (ad-CD/TK) was examined by immunoblotting analysis. For in vitro cytotoxicity experiments, the cells were infected with ad-CD/TK or ad-deltaE1 (as a control). After the addition of a variety of concentrations of GCV and 5-FC, either separately or in combination, cell viability was determined by staining the cells with crystal violet solution 6 days after infection. For in vivo antitumor experiments, 1x10(5) cells were stereotactically injected into the right caudate-putamen of female Wistar rat brains. At 3 days after implantation, 1x10(8) plaque-forming units of ad-CD/TK or ad-deltaE1 (as a control) were stereotactically injected into the tumors and GCV (25 mg/kg) and 5-FC (250 mg/kg), alone or in combination, were intraperitoneally administered. Animals were then killed, and tumor volumes were measured by determining the tumor area in every fifth section, using a light microscope. RESULTS: C6 glioma cells were efficiently transduced with recombinant adenoviral vector at multiplicities of infection of 200 or more. In vitro cytotoxicity of GCV and/or 5-FC, either alone or in combination, was exclusively observed in the cells transduced with ad-CD/TK. Obvious cytotoxicity (>50% inhibition) was observed in the presence of 5-FC at concentrations greater than 30 microg/ml or GCV at concentrations greater than 0.3 microg/ml at a multiplicity of infection of 100. Additionally, cytotoxicity in the presence of both GCV and 5-FC was greater than that after single-prodrug treatments, indicating additive effects of the prodrug treatments. In in vivo experiments, the tumor volumes of the rats treated with GCV or 5-FC alone after ad-CD/TK injection (59.1+/-4.6 and 57.4+/-7.1 mm3, respectively) were significantly smaller than that of the control rats (157+/-8.9 mm3, P<0.05). Furthermore, the tumor volume of the rats treated with GCV and 5-FC in combination was 14.7+/-1.8 mm3. CONCLUSION: These results demonstrated the efficient transduction of C6 glioma cells with a recombinant adenovirus and the additive effects of CD/TK fusion gene/GCV/5-FC treatment, compared with single-gene therapy with the TK or CD gene. Therefore, our data suggest that the direct administration of a double-suicide gene/prodrug therapy has great potential in the treatment of brain tumors.

Adenoviridae↗

PubMed2000

Performance on the three-point Vernier alignment or acuity test as a function of age: measurement extended to ages 5 to 9 years.

The three-point Vernier alignment (or acuity) test was conducted on children from 5 to 9 years old. There is a significant difference between the 5-9 year old subjects and those in age groups 10 to 19 and 20 to 29 years in Vernier performance. These data were also compared with previously published data from older subjects (up to age 70). We conclude that Vernier function has not fully matured within the age range of 5 to 9 years; this finding is consistent with previous results reported in the literature.

Adolescent↗

PubMed2000

The Shank family of scaffold proteins.

Shank proteins make up a new family of scaffold proteins recently identified through their interaction with a variety of membrane and cytoplasmic proteins. Shank polypeptides contain multiple sites for protein-protein interaction, including ankyrin repeats, an SH3 domain, a PDZ domain, a long proline-rich region, and a SAM domain. Binding partners for most of these domains have been identified: for instance, the PDZ domain of Shank proteins interacts with GKAP (a postsynaptic-density protein) as well as several G-protein-coupled receptors. The specific localization of Shank proteins at postsynaptic sites of brain excitatory synapses suggests a role for this family of proteins in the organization of cytoskeletal/ signaling complexes at specialized cell junctions.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Transfer of SV40 temperature-sensitive early gene into human epidermal keratinocytes by the recombinant adenovirus vector.

We constructed a recombinant adenovirus vector that contained the origin-defective SV40 early gene, coding temperature-sensitive T antigen. This vector transferred the SV40 early gene into human epidermal keratinocytes with high efficiency. T antigen conferred the ability of keratinocytes to grow with limited differentiation in the presence of serum and high calcium concentration at the permissive temperature (34 degrees C), although normal keratinocytes were induced to differentiate and stop growing under the same conditions. The serum/Ca++-resistant cells did not proliferate at the nonpermissive temperature (40 degrees C), indicating that they depended on T antigen for their proliferation. The temperature-sensitive T antigen dissociated from the tumor suppressor gene products, p53, at 40 degrees C. The serum/Ca++-resistant cells still had the ability to proceed to terminal differentiation when injected into SCID mice as cultured keratinocytes. However, they did not form an apparent basal layer. This indicated that the tissue remodeling process in the serum/Ca++-resistant keratinocytes was abnormal. All of these epidermoid cysts disappeared within 8 wk and no tumor developed for 6 mo. We consider that deltaE1/SVtsT is a useful tool to examine multistep carcinogenesis of human epithelial cells in vitro.

Adenoviridae↗

PubMed2000

The three point vernier alignment or acuity test (3Pt VA test): an analysis of variance.

A very useful clinical vernier acuity or vernier alignment test has been developed in this and associated laboratories over a span of two decades. We seek to refine further this test, to seek internal inconsistencies and to optimize parameters used in a variety of devices and environments. Vernier testing, and many aspects of this work have been considered by numerous able scientists over a long time period (not reviewed here), but none have encountered conditions faced by this group, particularly in the developing world. The three point vernier alignment (acuity) threshold test (3Pt VeA test) employed here has broad applications; it can be used as a clinical test of vision status, for triage, and as a reference standard for vision testing (in general). As one example, if sufficient luminance is employed, the test is applicable in the presence of truly dense media disorders, even advanced leucomas, mature cataracts, intraocular bleeds, as well as combinations of these disorders, with or without a window to the retina. Only retinal and centrally-based neural disorders, eccentricity from fixation, and about 50% of hypermature cataracts affect outcomes. With minor alterations, this test can be employed to assess the visual field. An analysis of variance (ANOVA) was performed on a defined set of parameters, to enable us to understand better the special properties and requirements associated with this test. Results are not significantly altered between ages 10-94 years (not assessed here). Employing settings well above threshold for test spot detection and well separated individual test spots, changes in test spot luminance, or background luminance (or adaptation level), contrast, veiling glare, test spot size, clear and variously degraded images, seem not to affect meaningfully measured outcomes. If an observer can define well a center of gravity for each test spot viewed, he can align the three points with remarkable precision.

Adult↗

PubMed2000

Functional analysis of androgen receptor N-terminal and ligand binding domain interacting coregulators in prostate cancer.

Several new androgen receptor (AR) coregulators, including ARA70, ARA55, ARA54, ARA160 and ARA24, associated with the N-terminal or the ligand-binding domain (LBD) of AR, have been identified by our group. We first identified the AR-LBD coregulators ARA70, ARA55, and ARA54. Our previous reports suggest that ARA70 can enhance the androgenic activity of 17 beta-estradiol (E2) and antiandrogens toward AR. It is of interest to compare and determine if the specificity of sex hormones and antiandrogens can be modulated by different coregulators. Our results indicate that, ARA70 is the best coregulator for increasing the androgenic activity of E2. Only ARA70 and ARA55 were able to significantly increase the androgenic activity of hydroxyflutamide, the active metabolite of a widely-used antiandrogen for the treatment of prostate cancer. Furthermore, our results suggest that among the LBD coregulators, ARA70 has a relatively high specificity for AR in the human prostate cancer cell line DU145. Together, our data suggest that the androgenic activity of some sex hormones and antiandrogens can be modulated by selective AR coactivators. In addition to the AR-LBD associated proteins, ARA24 and ARA160 have been identified as AR coregulators, interacting with the AR N-terminal instead of the LBD. Functional analysis revealed that the AR N-terminal coregulator ARA160 could cooperate with the AR LBD-associated coregulator ARA70. Our data indicate that ARA24 could also interact with AR, and that this binding is decreased by an expanding poly-glutamine (Q) length within AR. The length of the poly-Q stretch in the AR N-terminal domain is inversely correlated with the transcriptional activity of AR. Our data suggest that optimal AR transactivation may require interaction of AR with AR coregulators. The identification of factors or peptides that can interrupt androgen-mediated AR-ARA interactions may be useful in the development of better antiandrogens for treating androgen-related diseases, such as prostate cancer.

Androgen Antagonists↗

PubMed2000

Mutant p53: "gain of function" through perturbation of nuclear structure and function?

Mutant p53 not simply is an inactivated tumor suppressor, as at least some mutant p53 proteins exhibit oncogenic properties. Mutant p53 thus is the most commonly expressed oncogene in human cancer. Accordingly, the expression of mutant p53 in tumors often correlates with bad prognosis, and expression of mutant p53 in p53-negative tumor cells enhances their transformed phenotype. The molecular basis for this "gain of function" is not yet understood. However, the finding that mutant p53 tightly associates with the nuclear matrix in vivo, and with high affinity binds to nuclear matrix attachment region (MAR) DNA in vitro, suggests that these activities are connected and may result in perturbation of nuclear structure and function in tumor cells. MAR-binding of mutant p53 most likely is due to conformation-selective DNA binding by mutant p53, i.e. the specific interaction of a given mutant p53 protein with regulatory or structural genomic DNA elements that are able to adopt specific non-B-DNA conformations. In support to this assumption, human mutant p53 (Gly(245)-->Ser) was shown to bind to repetitive DNA elements in vivo that might be part of MAR elements. This further supports a model according to which mutant p53, by interacting with key structural components of the nucleus, exerts its oncogenic activities through perturbation of nuclear structure and function. J. Cell. Biochem. Suppl. 35:115-122, 2000.

Animals↗

PubMed1999

Maintenance of genomic integrity by p53: complementary roles for activated and non-activated p53.

In this review we describe the multiple functions of p53 in response to DNA damage, with an emphasis on p53's role in DNA repair. We summarize data demonstrating that p53, through its various biochemical activities and via its ability to interact with components of the repair and recombination machinery, actively participates in various processes of DNA repair and DNA recombination. An important aspect in evaluating p53 functions arises from the finding that the p53 core domain harbors two mutually exclusive biochemical activities, sequence-specific DNA binding, required for its transactivation function, and 3'->5' exonuclease activity, possibly involved in various aspects of DNA repair. As modifications of p53 that lead to activation of its sequence-specific DNA-binding activity result in inactivation of its 3'-> 5' exonuclease activity, we propose that p53 exerts its functions as a 'guardian of the genome' at various levels: in its non-induced state, p53 should not be regarded as a non-functional protein, but might be actively involved in prevention and repair of endogenous DNA damage, for example via its exonuclease activity. Upon induction through exogenous DNA damage, p53 will exert its well-documented functions as a superior response element in various types of cellular stress. The dual role model for p53 in maintaining genomic integrity significantly enhances p53's possibilities as a guardian of the genome.

Animals↗

PubMed1999

Influence of promoter DNA topology on sequence-specific DNA binding and transactivation by tumor suppressor p53.

Transcriptional activation by the tumor suppressor p53 is regulated at multiple levels, including posttranslational modifications of the p53 protein, interaction of p53 with various regulatory proteins, or at the level of sequence-specific DNA binding to the response elements in p53's target genes. We here propose as an additional regulatory mechanism that the DNA topology of p53-responsive promoters may determine the interaction of p53 with its target genes. We demonstrate that sequence-specific DNA binding (SSDB) and transcriptional activation by p53 of the mdm2 promoter is inhibited when this promoter is present in supercoiled DNA, where it forms a non-B-DNA structure which spans the p53-responsive elements. Relaxation of the supercoiled DNA in vitro resulted in conversion of the non-B-DNA to a B-DNA conformation within the mdm2 promoter, and correlated with an enhanced SSDB of p53 and an elevated expression of a reporter gene. In contrast, sequence specific DNA binding and transcriptional activation of the p21 promoter were not inhibited by DNA supercoiling. We propose that conformational alterations within p53-responsive sites, which either promote or prohibit sequence specific DNA binding of p53, are an important feature in orchestrating the activation of different p53 responsive promoters.

Binding Sites↗

PubMed1999

Heterogeneous Catalysis with Cross-Linked Lyotropic Liquid Crystal Assemblies: Organic Analogues to Zeolites and Mesoporous Sieves.

Organic, nanoporous heterogeneous catalysts based on a carboxylate-containing, amphiphilic mesogen catalyze the Knoevenagel condensation (see schematic representation). These networks maintain their order in solution and can be recycled. Enhanced basicity, excellent site accessibility, and substrate size exclusion are features of these nanostructured systems.

Journal Article↗

PubMed1999

Heme oxygenase-2 expression at rat neuromuscular junctions.

The neuromuscular junction is specialized for rapid transmission of electrical signals. Nitric oxide synthase (NOS) is concentrated at the junction, and NO modulates transmission and could influence signaling pathways. Increasing evidence suggests that carbon monoxide (CO) serves as a neurotransmitter, and heme oxygenase (HO), the enzyme that catalyzes the formation of CO, is often colocalized with NOS. Immunoreactivity for HO-2 was present at rat neuromuscular junctions of leg muscles and persisted in denervated muscle indicating the localization of the enzyme to the postsynaptic surface. In contrast, HO-2 immunoreactivity was absent from the en grappe and orbital en plaque endplates of extraocular muscle (EOM), while only the global en plaque endplates possessed HO-2 immunoreactivity. The difference between EOM and leg endplates may arise from EOM's unique physiology. The presence of HO-2 at neuromuscular junctions suggests CO could serve as a pre- and post-synaptic messenger.

Animals↗

PubMed1999

Characterization of the Shank family of synaptic proteins. Multiple genes, alternative splicing, and differential expression in brain and development.

Shank1, Shank2, and Shank3 constitute a family of proteins that may function as molecular scaffolds in the postsynaptic density (PSD). Shank directly interacts with GKAP and Homer, thus potentially bridging the N-methyl-D-aspartate receptor-PSD-95-GKAP complex and the mGluR-Homer complex in synapses (Naisbitt, S., Kim, E., Tu, J. C. , Xiao, B., Sala, S., Valtschanoff, J., Weinberg, R. J., Worley, P. F., and Sheng, M. (1999) Neuron 23, 569-582; Tu, J. C., Xiao, B., Naisbitt, S., Yuan, J. P., Petralia, R. S., Brakeman, P., Doan, A., Aakalu, V. K., Lanahan, A. A., Sheng, M., and Worley, P. F. (1999) Neuron 23, 583-592). Shank contains multiple domains for protein-protein interaction including ankyrin repeats, an SH3 domain, a PSD-95/Dlg/ZO-1 domain, a sterile alpha motif domain, and a proline-rich region. By characterizing Shank cDNA clones and RT-PCR products, we found that there are four sites for alternative splicing in Shank1 and another four sites in Shank2, some of which result in deletion of specific domains of the Shank protein. In addition, the expression of the splice variants is differentially regulated in different regions of rat brain during development. Immunoblot analysis of Shank proteins in rat brain using five different Shank antibodies reveals marked heterogeneity in size (120-240 kDa) and differential spatiotemporal expression. Shank1 immunoreactivity is concentrated at excitatory synaptic sites in adult brain, and the punctate staining of Shank1 is seen in developing rat brains as early as postnatal day 7. These results suggest that alternative splicing in the Shank family may be a mechanism that regulates the molecular structure of Shank and the spectrum of Shank-interacting proteins in the PSDs of adult and developing brain.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Cloning and characterization of T-cell lymphoma invasion and metastasis 2 (TIAM2), a novel guanine nucleotide exchange factor related to TIAM1.

TIAM1 is a guanine nucleotide exchange factor that was identified in a screen for genes that increase the invasiveness of T lymphoma cell lines (Habets et al., 1994, Cell 77(4): 537-549). We have identified a gene, T-cell lymphoma invasion and metastasis 2 (HGMW-approved symbol TIAM2), with significant identity to the carboxyl-terminal region of the TIAM1 and mapped it to 6q25. TIAM2 is expressed as an approximately 3.3-kb transcript in cerebrum and as an approximately 4.4-kb transcript in the cerebellum and testis. The approximately 4. 4-kb message encodes a longer form of the approximately 3.3-kb mRNA predicted protein, and both contain homology to the Dbl-homologous region (70%) and Pleckstrin-homologous (54%) regions of TIAM1. We have purified TIAM2 and shown it to have GDP-GTP exchange activity. In situ hybridizations demonstrate TIAM2 expression in the E13.5 telencephalon of mouse embryos and in the cerebral cortex, hippocampus, and ependyma of adult mouse brains.

Amino Acid Sequence↗