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H Han

Publications and source records attributed to H Han.

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

Role of the tyrosine kinase pyk2 in the integrin-dependent activation of human neutrophils by TNF.

Secretion of inflammatory products from neutrophils can be induced by a combination of signals from ligated integrins and receptors for soluble, physiological agonists such as TNF. Here we identify pyk2 in primary human neutrophils; localize it to focal adhesions and podosomes; and demonstrate its tyrosine phosphorylation, activation, and association with paxillin during stimulation of adherent cells by TNF. Tyrphostin A9 emerged as the most potent and selective of 51 tyrosine kinase inhibitors tested against the TNF-induced respiratory burst. Tyrphostin A9 inhibited TNF-induced tyrosine phosphorylation of pyk2 without blocking the cells' bactericidal activity. Wortmannin, an inhibitor of phosphatidylinositol-3-kinase, potently blocked the TNF-induced respiratory burst and selectively inhibited tyrosine phosphorylation of pyk2. Thus, pyk2 appears to play an essential role in the ability of neutrophils to integrate signals from beta(2) integrins and TNF receptors.

Androstadienes↗
PubMed1999

The mandibular foramen: an anatomic study and its relevance to the sagittal ramus osteotomy.

The sagittal split ramus osteotomy is the most commonly used procedure to reposition the mandible surgically. Because it is more technically difficult and associated with a higher incidence of complications compared with other mandibular osteotomies, thorough knowledge of the anatomy of the mandibular ramus is a prerequisite. Anatomic measurements related to the mandibular foramen were obtained from 57 formalin-preserved non-Asian hemimandibles. As shown in previous reports, great variability was noted in the position of the mandibular foramen. However, these studies utilized Asian mandibles with a clear discrepancy in key anatomic measurements in comparison with the authors' data. This brings into question the validity of these earlier studies when applying their data to non-Asian groups. The "fade-out" point of the internal oblique ridge was found not to be a reliable anatomic reference for placement of the horizontal osteotomy along the medial ramus. Thus, familiarity with the described relationships of the mandibular foramen will assist in performing properly a sagittal split of the ramus and will reduce the chance for an unfavorable split.

Adult↗
PubMed1999

[Association of glucokinase gene with gestational diabetes mellitus in Chinese].

OBJECTIVE: To evaluate the role of glucokinase(GCK) gene in the pathogenesis of gestational diabetes mellitus (GDM) in Chinese. METHODS: Two microsatellite polymorphisms, GCK1 and GCK2 which located at approximately 10 Kb 3' and 6 Kb 5', respectively, of the human glucokinase gene on chromosome 7p13, were genotyped in 40 unrelated gestational diabetics and 43 controls. RESULTS: Four alleles (A, B, C, D) and seven genotypes were identified at the GCK1 locus. There was no significant difference in allele and genotype frequency between GDM and control groups at the GCK1 locus. For GCK2, four alleles(1,2,3,4) and eight genotypes were detected. When compared with control subjects, the GDM group had a much less frequency of the allele 2 (51.3% vs 69.8%, chi 2 = 5.965, P = 0.015), and a much more frequency of allele 3(31.3% vs 17.4%, chi 2 = 4.321, P = 0.038). Nine haplotypes of GCK1 and GCK2 were observed and haplotype B/2 was much less in GDM group(1.9% vs 19.4%, RR = 0.078 6, P = 0.003). Among the GDM patients, comparing with carriers of other alleles, the carriers of allele 3 of GCK2 locus had significantly elevated fasting and 2 hour's blood glucose levels during OGTT, and their insulin levels at 2nd and 3rd hour during the OGTT test were significantly decreased. Our results suggest that GCK gene was associated with Chinese GDM, and haplotype of GCK1/GCK2 B/2 was a protective factor for GDM.

Adult↗
PubMed1998

Overexpression of the sarcolemmal calcium pump in the myocardium of transgenic rats.

The plasma membrane calmodulin-dependent calcium ATPase (PMCA) is a calcium-extruding enzyme controlling Ca2+ homeostasis in nonexcitable cells. However, its function in the myocardium is unclear because of the presence of the Na+/Ca2+ exchanger. We approached the question of the physiological function of the calcium pump using a transgenic "gain of function" model. Transgenic rat lines carrying the human PMCA 4 cDNA under control of the ventricle-specific myosin light chain-2 promoter were established, and expression in the myocardium was ascertained at the mRNA, protein, and functional levels. In vivo hemodynamic measurements in adult homozygous animals showed no differences in baseline and increased cardiac performance recruited by volume overload compared with controls. No differences between transgenic and control cardiomyocytes were found in patch clamp voltage dependence, activation/inactivation behavior of the L-type Ca2+ current, or fast [Ca2+]i transients (assessed by the Fura-2 method). To test whether the PMCA might be involved in processes other than beat-to-beat regulation of contraction/relaxation, we compared growth processes of neonatal transgenic and control cardiomyocytes. A 1.6- and 2.3-fold higher synthesis rate of total protein was seen in cells from transgenic animals compared with controls on incubation with 2% FCS for 24 hours and 36 hours, respectively. An effect of similar magnitude was observed using 20 micromol/L phenylephrine. A 1.4-fold- and 2.0-fold-higher protein synthesis peak was seen in PMCA-overexpressing cardiomyocytes after stimulation with isoproterenol for 12 hours and 24 hours, respectively. Because pivotal parts of the alpha- and beta-adrenergic signal transduction pathways recently have been localized to caveolae, we tested the hypothesis that the PMCA might alter the amplitude of alpha- and beta-adrenergic growth signals by virtue of its localization in caveolae. Biochemical as well as immunocytochemical studies suggested that the PMCA in large part was colocalized with caveolin 3 in caveolae of cardiomyocytes. These results indicate that the sarcolemmal Ca2+-pump has little relevance for beat-to-beat regulation of contraction/relaxation in adult animals but likely plays a role in regulating myocardial growth, possibly through modulation of caveolar signal transduction.

Animals↗
PubMed1998

NMR-Based model of a telomerase-inhibiting compound bound to G-quadruplex DNA.

The single-stranded (TTAGGG)n tail of human telomeric DNA is known to form stable G-quadruplex structures. Optimal telomerase activity requires the nonfolded single-stranded form of the primer, and stabilization of the G-quadruplex form is known to interfere with telomerase binding. We have identified 3,4,9, 10-perylenetetracarboxylic diimide-based ligands as potent inhibitors of human telomerase by using a primer extension assay that does not use PCR-based amplification of the telomerase primer extension products. A set of NMR titrations of the ligand into solutions of G-quadruplexes using various oligonucleotides related to human telomeric DNA showed strong and specific binding of the ligand to the G-quadruplex. The exchange rate between bound and free DNA forms is slow on the NMR time scale and allows the unequivocal determination of the binding site and mode of binding. In the case of the 5'-TTAGGG sequence, the ligand-DNA complex consists of two quadruplexes oriented in a tail-to-tail manner with the ligand sandwiched between terminal G4 planes. Longer telomeric sequences, such as TTAGGGTT, TTAGGGTTA, and TAGGGTTA, form 1:1 ligand-quadruplex complexes with the ligand bound at the GT step by a threading intercalation mode. On the basis of 2D NOESY data, a model of the latter complex has been derived that is consistent with the available experimental data. The determination of the solution structure of this telomerase inhibitor bound to telomeric quadruplex DNA should help in the design of new anticancer agents with a unique and novel mechanism of action.

Anthracenes↗
PubMed1998

Investigations of azapeptides as mimetics of Leu-enkephalin.

Solution syntheses of azapeptide pentamers 2, 3, and 4 were accomplished. The binding affinity of these azapeptides and azatide 1 were examined in the context of monoclonal antibody 3-E7 known to strongly bind the [Leu5]enkephalin sequence.

Enkephalin, Leucine↗
PubMed1998

Inhibition of TCR/CD3-mediated signaling by a mutant of the hematopoietically expressed G16 GTP-binding protein.

We have investigated the role of the hematopoietically expressed G16 GTP-binding protein on T cell activation. We constructed transfectants of Jurkat T cells that express a function-deficient mutant of G alpha 16 predicted to prevent activation of this G protein. Upon stimulation with anti-CD3 epsilon antibodies, mutant G alpha 16 transfectants display a profound defect in the production of IL-2 and IL-10, as well as in the expression of CD69. In contrast, the phorbol 12-myristate 13-acetate (PMA)-induced IL-10 production and CD69 expression, and the ionomycin plus PMA-induced IL-2 production are not affected. Consistent with the reduction in cytokine production is the inhibition of early signaling events in the mutant G alpha 16-expressing cells. There are significant reductions in anti-epsilon-induced tyrosine phosphorylation of zeta, epsilon, ZAP-70, and phospholipase C gamma 1, as well as in intracellular Ca2+ mobilization. In accordance with the effects on tyrosine phosphorylation is the reduction of TCR/CD3-mediated Fyn and Lck activities in G alpha 16 mutant cells. Even though the mechanism through which the G alpha 16 mutant mediates inhibition of T cell activation is not known, the data suggest a model where G proteins become activated upon TCR/CD3 engagement and regulate the activation of tyrosine kinases and subsequent downstream signaling events that lead to the activation of cytokine genes.

Alanine↗
PubMed1998

5'-Amino acid esters of antiviral nucleosides, acyclovir, and AZT are absorbed by the intestinal PEPT1 peptide transporter.

PURPOSE: General use of nucleoside analogues in the treatment of viral infections and cancer is often limited by poor oral absorption. Valacyclovir, a water soluble amino acid ester prodrug of acyclovir has been reported to increase the oral bioavailability of acyclovir but its absorption mechanism is unknown. This study characterized the intestinal absorption mechanism of 5' -amino acid ester prodrugs of the antiviral drugs and examined the potential of amino acid esters as an effective strategy for improving oral drug absorption. METHODS: Acyclovir (ACV) and Zidovudine (AZT) were selected as the different sugar-modified nucleoside antiviral agents and synthesized to L-valyl esters of ACV and AZT (L-Val-ACV and L-Val-AZT), D-valyl ester of ACV (D-Val-ACV) and glycly ester of ACV (Gly-ACV). The intestinal absorption mechanism of these 5' -amino acid ester prodrugs was characterized in three different experimental systems; in situ rat perfusion model, CHO/hPEPT1 cells and Caco-2 cells. RESULTS: Testing 5' -amino acid ester prodrugs of acyclovir and AZT, we found that the prodrugs increased the intestinal permeability of the parent nucleoside analogue 3- to 10-fold. The dose- dependent permeation enhancement was selective for L-amino acid esters. Competitive inhibition studies in rats and in CHO cells transfected with the human peptide transporter, hPEPT1, demonstrated that membrane transport of the prodrugs was mediated predominantly by the PEPT1 H+/dipeptide cotransporter even though these prodrugs did not possess a peptide bond. Finally, transport studies in Caco-2 cells confirmed that the 5' - amino acid ester prodrugs enhanced the transcellular transport of the parent drug. CONCLUSIONS: This study demonstrates that L-amino acid-nucleoside chimeras can serve as prodrugs to enhance intestinal absorption via the PEPT1 transporter, providing a novel strategy for improving oral therapy of nucleoside drugs.

Acyclovir↗
PubMed1998

Active domains of human papillomavirus type 11 E1 protein for origin replication.

Viral proteins E1 and E2 are essential for transient human papillomavirus (HPV) DNA replication. E1 is a multifunctional protein which can bind DNA and complex with E2, has ATPase and helicase activities, and interacts with DNA polymerase alpha-primase. E2 is a transactivator-repressor protein, playing an important role in replication and transcriptional regulation. A series of deletion mutants of HPV-11 E1 were constructed and tested in functional assays to define those domains of HPV-11 E1 which are important for binding to the origin DNA and E2. The domain of HPV-11 E1 involved in binding to the origin was located between aa 186 and 649, and that for binding to E2 was between aa 346 and 649. Since E1 binds to the origin more efficiently in the presence of E2, we also mapped the DNA binding domain of E1 in the presence of E2, and found that when binding was enhanced, the region of E1 involved in binding was similar to that observed with E1 alone. The same deletion mutation constructs of E1 were subcloned into an expression vector for use in transient replication assays to study the effect of the deletions on the replication of the origin DNA in vivo and the data suggest that the C-terminal domain contains important functions for replication.

Binding Sites↗
PubMed1998

LIM protein KyoT2 negatively regulates transcription by association with the RBP-J DNA-binding protein.

The RBP-J/Su(H) DNA-binding protein plays a key role in transcriptional regulation by targeting Epstein-Barr virus nuclear antigen 2 (EBNA2) and the intracellular portions of Notch receptors to specific promoters. Using the yeast two-hybrid system, we isolated a LIM-only protein, KyoT, which physically interacts with RBP-J. Differential splicing gave rise to two transcripts of the KyoT gene, KyoT1 and KyoT2, that encoded proteins with four and two LIM domains, respectively. With differential splicing resulting in deletion of an exon, KyoT2 lacked two LIM domains from the C terminus and had a frameshift in the last exon, creating the RBP-J-binding region in the C terminus. KyoT1 had a negligible level of interaction with RBP-J. Strong expression of KyoT mRNAs was detected in skeletal muscle and lung, with a predominance of KyoT1 mRNA. When expressed in F9 embryonal carcinoma cells, KyoT1 and KyoT2 were localized in the cytoplasm and the nucleus, respectively. The binding site of KyoT2 on RBP-J overlaps those of EBNA2 and Notchl but is distinct from that of Hairless, the negative regulator of RBP-J-mediated transcription in Drosophila. KyoT2 but not KyoT1 repressed the RBP-J-mediated transcriptional activation by EBNA2 and Notch1 by competing with them for binding to RBP-J and by dislocating RBP-J from DNA. KyoT2 is a novel negative regulatory molecule for RBP-J-mediated transcription in mammalian systems.

Amino Acid Sequence↗
PubMed1998

A novel homozygous missense mutation in the apo A-I gene with apo A-I deficiency.

We analyzed the genetic defect in a 67-year-old Japanese male patient with apolipoprotein (apo) A-I and high density lipoprotein (HDL) deficiencies, corneal opacities, and coronary artery disease. The plasma concentrations of apoA-I and HDL cholesterol were 2.9 to 7.3 mg/dL and 0.08 to 0.19 mmol/L, respectively. The lecithin:cholesterol acyltransferase (LCAT) activity and cholesterol esterification rate were <40% of normal control values. LCAT mass was 550% of normal control. Sequence analysis of polymerase chain reaction-amplified DNA of the proband's apoA-I gene showed a homozygous T-to-A transition resulting in the substitution of Val 156 with Glu (apoA-I Oita). Direct sequencing of samples obtained from other family members showed that the brother was homozygous, whereas the son was a heterozygous carrier of apoA-I Oita. The heterozygote for apo A-I Oita showed nearly 60% of normal apoA-I and normal HDL cholesterol levels. In vivo turnover studies in rabbits demonstrated that the variant apoA-I was rapidly cleared from plasma compared with normal human apoA-I. Our data suggest that the Val156Glu substitution is associated with apoA-I and HDL deficiency, partial LCAT deficiency, and corneal opacities and that Val156 of apoA-I may play an important role in apoA-I function.

Aged↗
PubMed1998

[The determination of diuron and chlortoluron residues in beef and beef products by high performance liquid chromatography].

Amethod for the determination of diuron and chlortoluron in beef and beef products with high performance liquid chromatography is described. The sample was extracted with a mixture of acetonitrile and methanol (50:50, V/V). After filtration, the filtrate was defatted with petroleum ether, then water was added and further extracted with chloroform. The chloroform collected was evaporated in a rotary evaporator(45 degrees C). The residue was dissolved in acetonitrile-methanol(50:50, V/V) mixture, poured into an Al2O3 column and eluted with the same mixture. The eluate was collected for HPLC analysis. The analytical column was Selectosil C18 (5 microns, 250 mm x 4.6 mm i.d.), mobile phase was methanol-water(60:40, V/V) and detection wavelength was UV-245 nm. The minimum amounts of detection were 0.4 ng for diuron and 0.5 ng for chlortoluron. Recoveries were 87.34%-87.64% for diuron and 88.78%-91.94% for chlortoluron.

Animals↗
PubMed1997

Cloning of P2XM, a novel human P2X receptor gene regulated by p53.

Through cloning of functional p53-binding sites (p53-tagged sites) from the human genome, we isolated a novel gene inducible by wild-type p53. Its cDNA sequence contained an open reading frame encoding a 431-amino acid peptide that showed a significant homology with members of the P2X family. This protein also revealed a similarity to RP-2, a gene activated in thymocytes undergoing programmed cell death. Northern blot analysis showed that it was expressed predominantly in skeletal muscle. Hence, we designated the gene P2XM (P2X specifically expressed in skeletal muscle). P2XM was localized to chromosomal band 22q11, where frequent loss of heterozygosity has been observed in rhabdoid tumors. Although we detected no genetic alteration in the coding sequences, one of four rhabdomyosarcoma cell lines examined had completely lost expression of this gene. Furthermore, a minor splice variant lacking a part of exon 1 that would encode residues corresponding to transmembrane domain M1 was relatively more abundant in two of seven sarcoma cell lines, one of which was derived from a rhabdomyosarcoma, and the other was derived from an osteosarcoma. The results suggest that P2XM may play a significant role in the proliferation and/or differentiation of skeletal muscle cells and that its altered expression may be involved in the development of some sarcomas.

Alternative Splicing↗
PubMed1997

Redox-regulated signaling by lactosylceramide in the proliferation of human aortic smooth muscle cells.

Previously, our laboratory reported that lactosylceramide (LacCer) stimulated human aortic smooth muscle cell proliferation via specific activation of p44 mitogen-activated protein kinase (MAPK) in the p21(ras)/Raf-1/MEK2 pathway and induced expression of the transcription factor c-fos downstream to the p44 MAPK signaling cascade (Bhunia A. K., Han, H., Snowden, A., and Chatterjee S. (1996) J. Biol. Chem. 271, 10660-10666). In the present study, we explored the role of free oxygen radicals in LacCer-mediated induction of cell proliferation. Superoxide levels were measured by the lucigenin chemiluminescence method, MAPK activity was measured by immunocomplex kinase assays, and Western blot analysis and c-fos expression were measured by Northern blot assay. We found that LacCer (10 microM) stimulates endogenous superoxide production (7-fold compared with control) in human aortic smooth muscle cells specifically by activating membrane-associated NADPH oxidase, but not NADH or xanthine oxidase. This process was inhibited by an inhibitor of NADPH oxidase, diphenylene iodonium (DPI), and by antioxidants, N-acetyl-L-cysteine (NAC) or pyrrolidine dithiocarbamate. NAC and DPI both abrogated individual steps in the signaling pathway leading to cell proliferation. For example, the p21(ras).GTP loading, p44 MAPK activity, and induction of transcription factor c-fos all were inhibited by NAC and DPI as well as an antioxidant pyrrolidine dithiocarbamate or reduced glutathione (GSH). In contrast, depletion of GSH by L-buthionine (S, R)-sulfoximine up-regulated the above described signaling cascade. In sum, LacCer, by virtue of activating NADPH oxidase, produces superoxide (a redox stress signaling molecule), which mediates cell proliferation via activation of the kinase cascade. Our findings may explain the potential role of LacCer in the pathogenesis of atherosclerosis involving the proliferation of aortic smooth muscle cells.

Acetylcysteine↗
PubMed1997

Palliation of AIDS-related primary lymphoma of the brain: observations from a multi-institutional database.

PURPOSE: To catalogue the presenting symptoms of patients with AIDS who are presumed to have primary central nervous system lymphoma (PCNSL). To document the palliative efficacy of cranial irradiation (RT) relative to the endpoints of complete and overall response for the respective symptoms. METHODS: An analysis of 163 patients with AIDS-related PCNSL who were evaluated at nine urban hospitals was performed. These patients were treated for PCNSL after the establishment of a tissue diagnosis or on a presumptive basis after failing empiric treatment for toxoplasmosis. All patients were treated between 1983 and 1995 with radiotherapy (median dose-fractionation scheme = 3 Gy x 10) and steroids (>90% dexamethasone). Because multiple fractionation schemes were used, prescriptions were converted to biologically effective doses according to the formula, Gy10 = Total Dose x (1 + fractional dose/alpha-beta); using an alpha-beta value of 10. RESULTS: The overall palliative response rate for the entire group was 53%. In univariate analysis, trends were present associating complete response rates with higher performance status (KPS > or = 70 vs. KPS < or = 60 = 17% vs. 5%), female gender (women vs. men = 29% vs. 8%), and the delivery of higher biologically effective doses (BED) of RT (Gy10 > 39 vs. < or = 39 = 20% vs. 5%). In multivariate analysis of factors predicting complete response, both higher KPS and higher BED retained independent significance. A separate univariate analysis identified high performance status (KPS > or = 70 vs. KPS < or = 60 = 71% vs. 47%), and young age (< or = 35 vs. > 35 = 61% vs. 40%) as factors significantly correlating with the endpoint of the overall response. In multivariate analysis, high performance status and the delivery of higher biologically effective doses of irradiation correlated significantly with higher overall response rates. CONCLUSION: Most AIDS patients who develop symptoms from primary lymphoma of the brain can achieve some palliation from a management program that includes cranial irradiation. Young patients with excellent performance status are most likely to respond to treatment. The delivery of higher biologically effective doses of irradiation also may increase the probability of achieving a palliative response.

Acquired Immunodeficiency Syndrome↗
PubMed1997

The effect of perfusion on T1 after slice-selective spin inversion in the isolated cardioplegic rat heart: measurement of a lower bound of intracapillary-extravascular water proton exchange rate.

Many NMR measurements of cardiac microcirculation (perfusion, intramyocardial blood volume) depend on some kind of assumption of intracapillary-extravascular water exchange rate, e.g., fast exchange. The magnitude of this water exchange rate, however, is still unknown. The intention of this study was to determine a lower limit for this exchange rate by investigating the effect of perfusion on relaxation time. Studies were performed in the isolated perfused cardioplegic rat heart. After slice-selective inversion, the spin lattice relaxation rate of myocardium within the slice was studied as a function of perfusion and compared with a mathematical model which predicts relaxation rate as a function of perfusion and intracapillary-extravascular exchange rate. A linear relationship was found between relaxation rate T(-1) and perfusion P normalized by perfusate/tissue partition coefficient of water, lambda: deltaT(-1) = m x deltaP/lambda with 0.82 < or = m < or = 1.06. Insertion of experimental data in the model revealed that a lower bound of the exchange rate from intra- to extravascular space is 6.6 s(-1) (4.5 s(-1), P < 0.05), i.e., the intracapillary lifetime of a water molecule is less than 150 ms (222 ms, P < 0.05). Based on this finding, the T1 mapping after slice-selective inversion could become a valuable noncontrast NMR method to measure variations of perfusion.

Animals↗
PubMed1997

Rapsyn and agrin slow the metabolic degradation of the acetylcholine receptor.

Rapsyn is a 43-kDa cytoplasmic protein that clusters nicotinic acetylcholine receptors (AChR) in the postsynaptic membrane. Here we examine the effect of rapsynmediated AChR clustering on the metabolic stability of the AChR. When transfected into QT-6 fibroblasts, cell surface AChRs (alpha, beta, epsilon, and delta subunit combination) pulse labeled with 125I-alpha-bungarotoxin were degraded with a half-life of 16.4 +/- 1.1 h (mean +/- SEM). Cotransfection of rapsyn with AChR caused extensive AChR clustering and increased AChR half-life to 20.5 +/- 1.0 h. Anti-AChR antibodies such as mab 35 cause an increased AChR degradation often associated with myasthenia gravis: 80.8 +/- 2.5% of AChRs labeled at zero time were degraded over a 12-h period. Contransfection of rapsyn reduced this AChR loss to 66.4 +/- 3.8%. Rapsyn also reduced normal AChR degradation, from 53.2 +/- 2.1 to 44.2 +/- 2.2%. Muscle cell lines from wild-type myotubes displayed few AChR clusters, but treatment with neural agrin increased the number of AChR clusters 30-fold. Clustering was accompanied by reductions in AChR degradation (both in the presence and absence of mab 35) similar in magnitude to those produced by overexpression of rapsyn in QT-6 cells. In rapsyn-deficient myotubes, treatment with neural agrin neither caused AChR clustering nor reduced AChR degradation. Thus neural agrin may slow AChR degradation by inducing the rapsyn-dependent clustering of AChRs.

Agrin↗