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Biomedical subjects

D K Lee

Publications and source records attributed to D K Lee.

At least 73 records · Page 4Linked to original sources
PubMed1999

Different upstream transcriptional activators have distinct coactivator requirements.

Activated transcription by RNA polymerase II (Pol II) requires coactivators, one of which is the SRB/mediator. Whereas Srb4, an essential subunit of the SRB/mediator, is broadly required for Pol II transcription in yeast, we have shown that it is dispensable for the transcriptional activation of some genes. Here, we show that transcriptional activation by different natural activators, and by artificial recruitment of various transcription factors, have very different degrees of Srb4 independence. These data, and the analysis of an rgr1 mutant, point to an Rgr1 subcomplex of the SRB/mediator as the mechanistic route of activation by Srb4-independent activators in vivo.

Carrier Proteins↗
PubMed1999

Two related G protein-coupled receptors: the distribution of GPR7 in rat brain and the absence of GPR8 in rodents.

GPR7 and GPR8, orphan G protein-coupled receptor (GPCR) genes, expressed in the brain and periphery share highest sequence identity to each other and significant similarity with opioid and somatostatin receptors. To further our knowledge of GPR7's physiological function, we performed in situ hybridization analyses of rat brain to reveal specific patterns of expression in the brain. GPR7 mRNA was found to be discretely localized in areas of the amygdala, hippocampus, hypothalamus and cortex. We previously reported that GPR7 was highly conserved in both human and rodent orthologs while GPR8 was not found in the rodent [9]. We speculated that GPR8 originated after the divergence of the human and rodent. Using primers designed from human GPR8, we isolated lemur GPR8 and subsequently aligned human, monkey, and lemur GPR8 orthologs to design primers recognizing highly conserved regions of GPR8. Using these primers, orthologs of GPR7 and GPR8 were isolated by the PCR from rabbit, tree shrew, and flying lemur, as well as GPR7 in the rat. Subsequent analysis of the clones obtained demonstrated that both GPR7 and GPR8 sequences were highly conserved amongst the species studied, but a rodent GPR8 was not isolated. The absence of a GPR8 gene in the rodent suggests that GPR8 originated from gene duplication of GPR7 after the rodent line diverged from the rabbit, tree shrew, flying lemur, lemur, monkey and human lines. In addition, the taxonomic distribution of GPR8 is consistent with molecular studies grouping rabbits with primates, tree shrews and flying lemurs rather than with rodents.

Amino Acid Sequence↗
PubMed1999

Antitumor activity of 4-phenyl-1-arylsulfonylimidazolidinone, DW2143.

We examined the ability of sulfonylurea derivative, DW2143 (4-phenyl-1-[1-(4-aminobenzoyl)-indoline-5-sulfonyl]-4,5-dihydro-2-imida zolone hydrochloride), to inhibit the growth of tumor cells in vitro and in vivo. When its anti-proliferative activities were tested on five murine tumor (B 16, Colon26, E1-4, 3LL and P388) and nine human tumor (BxPC-3, HepG2, Lovo, MCF-7, NCI-H69, SW480, WiDR, KB and KBV20C) cells of diverse tissue origins, the in vitro antitumor activities of DW2143 were comparable to those of doxorubicin against all tumor cell lines. In addition, the anti-proliferative activities of DW2143 against KBV20C, a vincristine-resistant cell line, are similar or superior to those of doxorubicin. When the in vivo antitumor activities using three murine tumor cells were tested after oral administration of DW2143, a wide range of tumor growth inhibition was observed. Tumor growth inhibition against 3LL at doses of 50 and 100 mg/kg DW2143 was 84.3% and 47.2%, respectively, which was comparable or superior to those of doxorubicin (5 mg/kg). Tumor growth inhibition of B16 at a dose of 100 mg/kg in the DW2143-treated group was 42% as compared to 54% for doxorubicin (5 mg/kg). When mice implanted with Colon26 were tested, tumor growth inhibition at a dose of 80 mg/kg DW2143 was 36% as compared with 37% for doxorubicin (5 mg/kg). Taken together, these results indicate that the novel sulfonylurea derivative, DW2143, is an attractive candidate for further development as a useful oral anticancer drug.

Animals↗
PubMed1999

Discovery of a receptor related to the galanin receptors.

We report the isolation of a cDNA clone named GPR54, which encodes a novel G protein-coupled receptor (GPCR). A PCR search of rat brain cDNA retrieved a clone partially encoding a GPCR. In a library screening this clone was used to isolate a cDNA with an open reading frame (ORF) encoding a receptor of 396 amino acids long which shared significant identities in the transmembrane regions with rat galanin receptors GalR1 (45%), GalR3 (45%) and GalR2 (44%). Northern blot and in situ hybridization analyses revealed that GPR54 is expressed in brain regions (pons, midbrain, thalamus, hypothalamus, hippocampus, amygdala, cortex, frontal cortex, and striatum) as well as peripheral regions (liver and intestine). In COS cell expression of GPR54 no specific binding was observed for 125I-galanin. A recent BLAST search with the rat GPR54 ORF nucleotide sequence recovered the human orthologue of GPR54 in a 3.5 Mb contig localized to chromosome 19p13.3.

Amino Acid Sequence↗
PubMed1999

Identification and cloning of three novel human G protein-coupled receptor genes GPR52, PsiGPR53 and GPR55: GPR55 is extensively expressed in human brain.

The G protein-coupled receptor (GPCR) family share a structural motif of seven transmembrane segments with large numbers of conserved residues in those regions. Here, we report the identification and cloning of two novel human intronless GPCR genes, GPR52, GPR55 and a pseudogene PsiGPR53. GPR55 was identified from the expressed sequence tags (EST) database whereas GPR52 and pseudogene PsiGPR53 originated from the high throughput genome (HTG) database. A partial cDNA clone obtained from the IMAGE Consortium of GPR55 was used to screen a human genomic library to acquire the full length gene. GPR52 and PsiGPR53 were amplified from human genomic DNA using primers based on the HTG sequences. GPR55 and GPR52 encode receptors of 319 and 361 amino acids, respectively. GPR55 gene was mapped to chromosome 2q37, using fluorescence in situ hybridization (FISH), and its mRNA transcripts have been detected in the caudate nucleus and putamen, but not in five other brain regions. Human receptors showing the highest amino acid identity to GPR55 include P2Y5 (29%), GPR23 (30%), GPR35 (27%) and CCR4 (23%). GPR52 gene localized to chromosome 1q24 shares the highest identity with GPR21 (71%), histamine H2 (27%) and 5-HT4 (26%) human receptors. PsiGPR53 is a pseudogene mapped to chromosome 6p21 that demonstrates the highest similarity to the MRG (35%), MAS (28%) and C5a (24%) human receptor genes.

Amino Acid Sequence↗
PubMed1999

Identification of a signal transducer and activator of transcription (STAT) binding site in the mouse metallothionein-I promoter involved in interleukin-6-induced gene expression.

Mechanisms of regulation of mouse metallothionein (MT)-I gene expression in response to bacterial endotoxin-lipopolysaccharide (LPS) were examined. Northern blot analysis of hepatic MT-I mRNA in interleukin (IL)-6 or tumour necrosis factor (TNF)-receptor type I knock-out mice demonstrated that IL-6, not TNF-alpha, is of central importance in mediating hepatic MT-I gene expression in vivo after LPS injection. In vivo genomic footprinting of the MT-I promoter demonstrated a rapid increase, after LPS injection, in the protection of several guanine residues in the -250 to -300 bp region of the MT-I promoter. The protected bases were within sequences which resemble binding sites for the signal transducers and activators of transcription (STAT) transcription factor family. Electrophoretic mobility-shift assays using oligonucleotides from footprinted MT-I promoter regions showed that injection of LPS resulted in a rapid increase in the specific, high-affinity, in vitro binding of STAT1 and STAT3 to a binding site at -297 bp (TTCTCGTAA). Western blotting of hepatic nuclear proteins showed that the time-course for changes of total nuclear STAT1 and STAT3 after LPS injection paralleled the increased complex formation in vitro using this oligonucleotide, and binding was specifically competed for by a functional STAT-binding site from the rat alpha2-macroglobulin promoter. Furthermore, the MT-I promoter -297 bp STAT-binding site conferred IL-6 responsiveness in the context of a minimal promoter in transient transfection assays using HepG2 cells. This study suggests that the effects of LPS on hepatic MT-I gene expression are mediated by IL-6 and involve the activation of STAT-binding to the proximal promoter.

Animals↗
PubMed1999

Cytotoxic constituents from the roots of Anthriscus sylvestris.

Activity-guided fractionation of the roots of Anthriscus sylvestris resulted in the isolation and characterization of five cytotoxic compounds, deoxypodophyllotoxin (1), falcarindiol (2), and angeloyl podophyllotoxin (5) from the hexane soluble fraction and morelensin (3), bursehernin (4) from the chloroform soluble fraction. It is the first report of the occurrence of compound 5 in nature.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Effectiveness of preoperative transarterial chemoembolization in presumed inoperable hepatoblastoma.

PURPOSE: To evaluate the effectiveness and therapeutic role of preoperative transarterial chemoembolization (TACE) of hepatoblastoma. MATERIALS AND METHODS: Four patients (one boy, three girls) with unresectable hepatoblastoma were treated twice with preoperative TACE in an effort to improve the surgical and clinical outcome. The patients ranged in age from 8 to 27 months (mean, 15 months). The first TACE was performed superselectively in tumor feeding arteries. The second TACE was performed 3 weeks later. Surgical hepatic resection was performed 1 month after the second TACE. Contrast-enhanced computed tomography (CT) was used to evaluate changes in size, volume, internal texture, and margin of the masses. The toxicity of the chemotherapeutic drugs was evaluated by blood chemistry analysis (AST/ALT, alpha-FP) performed before and after TACE, and after surgery. RESULTS: TACE allowed subsequent surgical resection in all four patients, who remained disease free 16-52 months after operation. There were no major problems related to TACE. There was no chemotherapeutic agent toxicity from TACE. The average largest diameters and volumes of the tumors decreased by 31% (8.3 to 5.6 cm) and 69% (317 to 93 cm2), respectively. CONCLUSION: TACE provided subsequent successful surgical resection and good long-term results in all four patients. The hepatoblastomas were initially considered inoperable because of extensive hepatic involvement and indistinct margins.

Antineoplastic Agents↗
PubMed1999

Attention activates winner-take-all competition among visual filters.

Shifting attention away from a visual stimulus reduces, but does not abolish, visual discrimination performance. This residual vision with 'poor' attention can be compared to normal vision with 'full' attention to reveal how attention alters visual perception. We report large differences between residual and normal visual thresholds for discriminating the orientation or spatial frequency of simple patterns, and smaller differences for discriminating contrast. A computational model, in which attention activates a winner-take-all competition among overlapping visual filters, quantitatively accounts for all observations. Our model predicts that the effects of attention on visual cortical neurons include increased contrast gain as well as sharper tuning to orientation and spatial frequency.

Attention↗
PubMed1999

Formulation development of allopurinol suppositories and injectables.

Allopurinol was formulated into injectable and suppository dosage forms. The injectable formulation was prepared by dissolving allopurinol in a cosolvent system consisting of dimethyl sulfoxide (DMSO) and propylene glycol (v/v = 50/50). The stability of allopurinol in the cosolvent system was studied under accelerated storage conditions, and results indicate first-order degradation kinetics with an activation energy of 24.3 kcal/mol. The development of suppository dosage forms was performed by formulating allopurinol with polyethylene glycol (PEG) mixtures of different molecular weights. In vitro release profiles of suppositories formulated with different polyethylene bases were obtained in the pH 7.4 buffer solution using the USP 23 paddle method at 100 rpm. Results indicate that the release rate of the suppository formulations containing PEG 1500/PEG 4000 at the ratio (w/w) of 2.5/10 to 10/2.5 appeared to be similar. However, the addition of sodium lauryl sulfate in the suppository decreased the release rate of allopurinol significantly. A future study to establish in vitro/in vivo correlation (iv/ivc) is suggested.

Allopurinol↗
PubMed1999

Bacterial DNA in mixed cholesterol gallstones.

OBJECTIVE: Numerous investigators have proposed a role for bacteria in biliary lithogenesis. We hypothesized that bacterial DNA is present in gallstones, and that categorical differences exist between gallstone type and the frequency of bacterial sequences. METHODS: Polymerase chain reaction (PCR) was used to amplify bacterial 16S rRNA and uidA (encoding Escherichia coli [E. coli] beta-glucuronidase) genes in different types of gallstones. PCR products were sequenced. RESULTS: Bacterial 16S rRNA and uidA DNA sequences in E. coli were detected in all brown pigment, common bile duct, and mixed cholesterol gallstones (n = 14). In contrast, only one (14%) of seven pure cholesterol gallstones yielded a PCR product. Most (88%) mixed cholesterol gallstones yielded PCR amplification products from their central, as well as their outer, portions. Sequenced products possessed 88-98% identity to 16S rRNA genes of E. coli and Pseudomonas species. CONCLUSIONS: Bacterial DNA sequences are usually present in mixed cholesterol (to 95% cholesterol content), brown pigment, and common bile duct, but rarely in pure cholesterol gallstones. The presence of bacterial beta-glucuronidase is also suggested. The role of bacteria and their products in the formation of mixed cholesterol gallstones, which comprise the majority of cholesterol gallstones, warrants further study.

Adult↗
PubMed1999

Cholesterol removal from homogenized milk with beta-cyclodextrin.

This study was carried out to determine optimum conditions of five different factors (beta-cyclodextrin concentration, mixing temperature, mixing time, centrifugal force, and centrifugation time) in reduction of cholesterol in 3.6% fat, homogenized milk by application of beta-cyclodextrin. beta-Cyclodextrin at 0.5 to 1.5% provided 92.2 to 95.3% removal of cholesterol when mixed at 10 degrees C for 10 min. Among other factors, mixing time (5 to 20 min) did not significantly affect cholesterol removal. Removal was enhanced with increasing centrifugal forces up to 166x g (95.9%) but decreased thereafter. Various centrifugation times (5 to 20 min) did not have significant effects. Based on these results, we suggest that the optimum conditions for the process are addition of 1.5% beta-cyclodextrin, mixing temperature of 10 degrees C, 10-min mixing time, and centrifugation at 166x g for 10 min.

Animals↗
PubMed1999

Tenosynovial giant cell tumor of finger, localized type: a case report.

The authors report a typical case of tenosynovial giant cell tumor of the right middle finger of a 31-year-old man. Histologically, this tumor is characterized by a discrete proliferation of rounded synovial-like cells accompanied by a variable number of multinucleated giant cells, inflammatory cells, and xanthoma cells. Clinicopathologically, this tumor is a benign lesion that nonetheless possesses a capacity for local recurrence. Local excision with a small cuff of normal tissue is the treatment of choice in this tumor.

Adult↗
PubMed1999

Attentional capacity is undifferentiated: concurrent discrimination of form, color, and motion.

We report a series of experiments on the concurrent discrimination of form, color, and motion attributes. All tasks involved joint discrimination of attributes, and positions and were highly demanding of attention. We quantified interference between concurrent discriminations by establishing the attention-operating characteristic. Interference was indistinguishable for similar and dissimilar task combinations (form-form, color-color, motion-motion, and color-form, color-motion, motion-color, and motion-form, respectively). These results suggest strongly that different visual discriminations draw on the same attentional capacity--in other words, that the capacity of visual attention is undifferentiated.

Attention↗
PubMed1999

Ovarian teratomas appearing as solid masses on ultrasonography.

The purposes of this study were to evaluate the prevalence and imaging characteristics of ovarian teratomas that appear as solid masses on ultrasonography and to compare the ultrasonographic imaging features of the tumors with their pathologic findings. The ultrasonographic images of 202 ovarian teratomas were reviewed retrospectively. Solid-appearing masses were selected from among them and were evaluated in terms of internal echotexture, the presence or lack of peripheral hypoechogenicity, posterior sonic attenuation, and tumoral calcification. Seventy-six (37.6%) masses of 202 belonged to the atypical solid-appearing masses on ultrasonography. Of 76 masses, 57 (75.0%) had peripheral hypoechogenicity; 38 masses had well-defined thin hypoechoic rims, whereas 19 had poorly demarcated peripheral hypoechogenicity. Posterior sonic attenuation was evident in 18 (23.7%) masses. The presence of peripheral hypoechogenicity, which is suggestive of the fluid portion of the tumor, might be one of the characteristic findings of solid-appearing ovarian teratomas on ultrasonography.

Adolescent↗
PubMed1999

Characterization of antiallodynic actions of ALE-0540, a novel nerve growth factor receptor antagonist, in the rat.

There is growing evidence that nerve growth factor (NGF) may function as a mediator of persistent pain states. We have identified a novel nonpeptidic molecule, ALE-0540, that inhibits the binding of NGF to tyrosine kinase (Trk) A or both p75 and TrkA (IC50 5.88 +/- 1. 87 microM, 3.72 +/- 1.3 microM, respectively), as well as signal transduction and biological responses mediated by TrkA receptors. ALE-0540 was tested in models of neuropathic pain and thermally-induced inflammatory pain, using two routes of administration, a systemic i.p. and a spinal intrathecal (i.th.) route. Morphine was also tested for comparison in the antiallodynia model using mechanical stimuli. We show that either i.p. or i.th. administration of ALE-0540 in rats produced antiallodynia in the L5/L6 ligation model of neuropathic pain. The calculated A50 values (and 95% confidence intervals) for ALE-0540 administered i.p. and i. th. were 38 (17.5-83) mg/kg and 34.6 (17.3-69.4) microgram, respectively. ALE-0540 given i.th., at doses of 30 and 60 microgram, also blocked tactile allodynia in the thermal sensitization model. Although morphine displayed greater potency [A50 value of 7.1 (5.6-8. 8) mg/kg] than ALE-0540 in anti-allodynic effect when given i.p. to L5/L6-ligated rats, it was not active when administered i.th. These data suggest that a blockade of NGF bioactivity using a NGF receptor antagonist is capable of blocking neuropathic and inflammatory pain and further support the hypothesis that NGF is involved in signaling pathways associated with these pain states. ALE-0540 represents a nonpeptidic small molecule which can be used to examine mechanisms leading to the development of agents for the treatment of pain.

Analgesics↗
PubMed1998

Benzylimidazolines as h5-HT1B/1D serotonin receptor ligands: a structure-affinity investigation.

Benzylimidazolines may represent a class of 5-HT1D ligands that has yet to be exploited. On the basis of a previous report that the 2-(substituted-benzyl)imidazoline alpha-adrenergic agonist oxymetazoline (8) binds with high affinity at calf brain 5-HT1D receptors, we explored the structure-affinity relationships of a series of related derivatives. Each of the aromatic substituents was removed and then reinstated in a systematic manner to determine the influence of the individual substituents on binding. It was found that all of the aromatic substituents of 8 act in concert to impart high affinity. However, although the 3-hydroxy group could be removed without significantly reducing affinity for h5-HT1D (i.e., human 5-HT1Dalpha) receptors, this modification reduced h5-HT1B (i.e., human 5-HT1Dbeta) receptor affinity by nearly 50-fold. The 2, 6-dimethyl groups also contribute to binding but seem to play a greater role for h5-HT1B binding than h5-HT1D binding. With the appropriate structural modifications, several compounds were identified that display 20- to >100-fold selectivity for h5-HT1D versus h5-HT1B receptors. Preliminary functional data suggest that these compounds behave as agonists. Given that 5-HT1D agonists are currently being explored for their antimigraine action and that activation of h5-HT1B receptors might be associated with cardiovascular side effects, h5-HT1D-selective agents may offer a new lead for the development of therapeutically efficacious agents.

Adrenergic alpha-Agonists↗