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H Jiang

Publications and source records attributed to H Jiang.

At least 505 records · Page 28Linked to original sources

Subtraction hybridization identifies a novel melanoma differentiation associated gene, mda-7, modulated during human melanoma differentiation, growth and progression.

Cultured human melanoma cells lose proliferative capacity and terminally differentiate after treatment with the combination of recombinant human fibroblast interferon (IFN-beta) and mezerein (MEZ). Subtraction hybridization of cDNA libraries prepared from actively proliferating human H0-1 melanoma cells from cDNA libraries produced from H0-1 cells treated with IFN-beta + MEZ identifies a novel melanoma differentiation-associated (mda) cDNA, mda-7, that displays elevated expression in differentiation inducer-treated H0-1 cells. mda-7 encodes a novel protein of 206 amino acids with a predicted size of 23.8 kDa. The level of mda-7 mRNA is elevated in actively proliferating normal human melanocytes versus primary and metastatic human melanomas. In the Matrigel-assisted melanoma progression model, mda-7 expression decreases in early vertical growth phase primary human melanoma cells selected for autonomous or enhanced tumor formation in nude mice. Treatment of human melanomas with IFN-beta + MEZ, and to a lesser extent with MEZ, results in growth suppression and induced or enhanced mda-7 expression. Immunoprecipitation analyses using peptide-derived rabbit polyclonal antibodies detect increases in mda-7 protein, and a higher molecular weight protein of approximately 90 to 100 kDa, in MEZ and IFN-beta + MEZ treated H0-1 cells. mda-7 is a highly conserved gene with an homologous sequence in the genome of yeast. Transfection of mda-7 expression constructs into H0-1 and C8161 human melanoma cells reduces growth and inhibits colony formation. These results confirm that mda-7 has antiproliferative properties in human melanoma cells and in this context may contribute to terminal cell differentiation. The mda-7 gene may also function as a negative regulator of melanoma progression.

Amino Acid Sequence↗

Involvement of Ral GTPase in v-Src-induced phospholipase D activation.

An early response to the tyrosine kinase activity of v-Src is an increase in phospholipase D (PLD) activity, which leads to the generation of biologically active lipid second messengers, including phosphatidic acid, lysophosphatidic acid and diacylglycerol. We have recently demonstrated that v-Src-induced PLD activity is mediated by Ras, although Ras involvement was indirect, requiring a cytosolic factor for PLD activation. Ras interacts with and activates Ral-GDS, the exchange factor responsible for the activation of Ral GTPases. Here we report that this newly identified Ras/Ral signalling pathway mediates PLD activation by v-Src. PLD activity could be precipitated from v-Src-transformed cell lysates with immobilized RalA protein and with an anti-Ral antibody. A mutation to the region of RalA analogous to the 'effector domain' of Ras did not reduce the ability of RalA to complex with PLD, although deletion of a Ral-specific amino-terminal region did. Overexpression of RalA potentiated PLD activation by v-Src, and expression of dominant negative RalA mutants inhibited both v-Src- and v-Ras-induced PLD activity. Thus RalA is involved in the tyrosine kinase activation of PLD through its unique N terminus, and that PLD is a downstream target of a Ras/Ral GTPase cascade.

3T3 Cells↗

Cell cycle gene expression and E2F transcription factor complexes in human melanoma cells induced to terminally differentiate.

Defects in cellular differentiation are a common occurrence in human cancers. The combination of recombinant human fibroblast interferon (IFN-beta) and the antileukemic compound mezerein (MEZ) results in an irreversible loss of proliferative capacity and terminal cell differentiation in H0-1 human melanoma cells. In contrast, either agent alone induces reversible growth arrest and/or specific components of the differentiation process without inducing terminal differentiation. The current study investigates changes in cell cycle, cell cycle gene expression and E2F transcription factor complex formation during the processes of reversible and irreversible (terminal) differentiation. Induction of both terminal differentiation and reversible differentiation (MEZ treatment) results in a temporal decrease in DNA synthesis and the percentage of cells in S phase and a decrease in the expression of cell cycle and growth regulated genes, including cdc2, cyclin A, cyclin B, histone H1, histone H4, nm23-H1, p53 and c-myc. Persistent gene expression changes occur in terminally differentiated cells, but not in reversibly differentiated cells. H0-1 cells contain several E2F binding activities, including uncomplexed E2F, an E2F-p107-cyclin A-cdk2 kinase complex and an Rb-E2F complex. Induction of growth arrest by MEZ results in a slow migrating gelshift band that contains E2F associated with the pRb2/p130 protein. There is also a loss of the Rb-E2F complex. Induction of terminal differentiation after treatment with IFN-beta + MEZ generates a second pRb2/p130-E2F complex that migrates considerably faster than the pRb2/p130-E2F complex resulting from growth arrest. The slower migrating complex may contribute to growth arrest, whereas the faster migrating complex may play a role in terminal differentiation. Our results demonstrate that terminal cell differentiation involves a co-ordinate and continuous suppression of a number of cell cycle and growth related genes and results in the development of a novel E2F transcription factor complex not apparent in growth arrested and reversibly differentiated human melanoma cells.

CDC2 Protein Kinase↗

Object-related activity revealed by functional magnetic resonance imaging in human occipital cortex.

The stages of integration leading from local feature analysis to object recognition were explored in human visual cortex by using the technique of functional magnetic resonance imaging. Here we report evidence for object-related activation. Such activation was located at the lateral-posterior aspect of the occipital lobe, just abutting the posterior aspect of the motion-sensitive area MT/V5, in a region termed the lateral occipital complex (LO). LO showed preferential activation to images of objects, compared to a wide range of texture patterns. This activation was not caused by a global difference in the Fourier spatial frequency content of objects versus texture images, since object images produced enhanced LO activation compared to textures matched in power spectra but randomized in phase. The preferential activation to objects also could not be explained by different patterns of eye movements: similar levels of activation were observed when subjects fixated on the objects and when they scanned the objects with their eyes. Additional manipulations such as spatial frequency filtering and a 4-fold change in visual size did not affect LO activation. These results suggest that the enhanced responses to objects were not a manifestation of low-level visual processing. A striking demonstration that activity in LO is uniquely correlated to object detectability was produced by the "Lincoln" illusion, in which blurring of objects digitized into large blocks paradoxically increases their recognizability. Such blurring led to significant enhancement of LO activation. Despite the preferential activation to objects, LO did not seem to be involved in the final, "semantic," stages of the recognition process. Thus, objects varying widely in their recognizability (e.g., famous faces, common objects, and unfamiliar three-dimensional abstract sculptures) activated it to a similar degree. These results are thus evidence for an intermediate link in the chain of processing stages leading to object recognition in human visual cortex.

Adult↗

Diminished teratogenicity of retinoid X receptor-selective synthetic retinoids.

One feature that contraindicates the wide therapeutic use of retinoids is their teratogenicity. Synthetic retinoids are distinguishable from each other on the basis of their partial or exclusive preference in binding and activation of all-trans retinoic acid receptors (RARs) or retinoid X receptors (RXRs). Using mouse embryo limb bud cells in micromass cultures as a bioassay, we examined the inhibitory activities of a number of standard and novel retinoids on chondrogenic cell differentiation. Transient cotransfection of HeLa cells was used to measure the ability of each retinoid to induce transcription of a reporter gene by activating RAR alpha, RAR beta, RAR gamma, or RXR alpha chimeric constructs. All retinoids in this study that activated RARs to any degree in the cotransfection assay also inhibited chondrogenesis in vitro, whereas retinoids that were either specific for RXR or inactive in the cotransfection assay did not. The activity of RAR-selective agonists and the inactivity of RXR-specific agonists in the cotransfection assay correlated well with the relative teratogenicity of six of the representative retinoids studied when orally administered at day 11 to pregnant ICR mice.

Animals↗

Selective coupling of beta 2-adrenergic receptor to hematopoietic-specific G proteins.

The coupling of the beta 2-adrenergic receptor (AR) to the alpha subunits of the Gq class of G proteins was investigated in a cotransfection system. COS-7 cells cotransfected with the beta 2-AR cDNA and the G alpha 15 or G alpha 16 cDNA showed marked norepinephrine-induced increases in accumulation of inositol phosphates in a concentration-dependent manner. However, cells cotransfected with the cDNA encoding G alpha q, G alpha 11, or G alpha 14 instead of G alpha 16 gave no ligand-dependent activation of phospholipase C (PLC). The facts that the beta-AR agonist isoprenaline can also induce activation of PLC in cells coexpressing beta 2-AR and G alpha 16 and that the beta 2-AR-specific antagonist propranolol can block norepinephrine-induced activation of PLC in these cotransfected cells further indicate that it is the beta 2-AR that mediates the activation of phospholipase C in these cotransfected cells. To test the possibility of involvement of G beta gamma, a G beta gamma antagonist, G gamma 3 mutant with substitution of a Ser residue for the C-terminal Cys residue, was used because this protein, when expressed in COS-7 cells, can inhibit only G beta gamma-mediated but not G alpha-mediated activation of PLC. The result that the G gamma 3 mutant could not inhibit beta 2-adrenergic receptor-mediated activation of PLC in cells cotransfected with the G alpha 16 cDNA suggests that G beta gamma is unlikely to be a major mediator of beta 2-adrenergic receptor-induced activation of PLC. Thus, we conclude that the beta 2-adrenergic receptor can specifically couple to G alpha 15 and G alpha 16, but not to G alpha q, G alpha 11, or G alpha 14 to activate PLC.

Animals↗

The melanoma differentiation-associated gene mda-6, which encodes the cyclin-dependent kinase inhibitor p21, is differentially expressed during growth, differentiation and progression in human melanoma cells.

The combination of recombinant human fibroblast interferon (IFN-beta) and the antileukemic compound mezerein (MEZ) induces terminal differentiation with an irreversible loss of proliferative capacity in human melanoma cells. Using subtraction hybridization, cDNAs were identified that display enhanced expression in terminally differentiated and growth arrested human melanoma cells (Jiang and Fisher, 1993; Jiang et al., 1994a). A specific melanoma differentiation-associated (mda) cDNA, mda-6, is described whose expression inversely correlates with melanoma progression and growth. mda-6 is identical to WAF1/CIP1/SDI1 that encodes the M(r) 21,000 protein (p21) that is an inhibitor of cyclin-dependent kinases. Actively growing normal melanocyte, SV40-immortalized human melanocyte and dysplastic nevus cell lines synthesize elevated levels of mda-6 mRNA; whereas, actively proliferating radial and early vertical growth phase primary melanomas as well as metastatic human melanoma cells produce reduced levels of mda-6 mRNA. Treatment of primary and metastatic human melanoma cells with IFN-beta + MEZ results in growth inhibition and an increase in mda-6 expression. mda-6 expression also increases when human melanoma cells are grown to high saturation densities or when grown in serum-free medium. Using anti-p53 and anti-p21 antibodies, an inverse correlation is found between p53 and p21 protein levels during growth arrest and differentiation. Induction of growth arrest and terminal differentiation in H0-1 human melanoma cells by IFN-beta + MEZ results in a temporal decrease in wild-type p53 protein levels with a corresponding increase in p21 levels. In the Matrigel-assisted melanoma progression model, mda-6 expression decreases in early vertical growth phase primary human melanoma cells selected for autonomous or enhanced tumor formation in nude mice. In metastatic human melanoma cells displaying a loss of metastatic potential resulting from introduction of a normal human chromosome 6, mda-6 mRNA levels increase. Taken together, these studies indicate that mda-6 (p21) may function as a negative regulator of melanoma growth, progression and metastasis.

Amino Acid Sequence↗

Different alpha 1-adrenergic receptor sequences required for activating different G alpha subunits of Gq class of G proteins.

In order to understand the specific interactions between receptors and guanine nucleotide-binding regulatory protein (G proteins), we attempted to delineate the alpha 1 B-adrenergic receptor sequences involved in activation of the alpha subunits of the Gq class of G proteins. A number of specific mutations were introduced into the third inner loop of the receptor, and the mutants were tested for their abilities to activate different G alpha subunits of the Gq class. Our results indicate that the receptor sequences required for activating G alpha q/11, G alpha 14, or G alpha 16 are different. The sequence extending from residues Lys240 to His252 is required for activation of G alpha q/11, but not for activation of G alpha 14 or G alpha 16. Two segments in the third loop of the receptor are required for activation of G alpha 14: one is located at the N terminus of the loop ending at residue Asn226, and the other is located at the C terminus of the loop starting from residue Ser278. The latter contains a BBXXB motif, which is apparently critical for G alpha 14 coupling, but not for G alpha 16 or G alpha q/11 coupling. Furthermore, the three amino acids stretch (Tyr217 to Val219) included in the N-terminal segment is not only required for G alpha 14 coupling, but also for G alpha q/11 coupling. It may be involved to some extent in G alpha 16 coupling as well.

Amino Acid Sequence↗

The nature and distribution of the innervation of human supraspinal and interspinal ligaments.

STUDY DESIGN: To use fresh, human supraspinal and interspinal ligaments and document their innervation. OBJECTIVES: To characterize the innervation of the human supraspinal and interspinal ligaments. SUMMARY OF BACKGROUND DATA: The nature and distribution of the innervation of spinal ligaments remains unknown. METHODS: Sections of spinal ligaments were labeled with a fluorescent antibody against neurofilament proteins and observed with a confocal microscope. RESULTS: The ligaments were found to be well innervated. Innervation was equally distributed along the ligament, symmetrically distributed between left and right sides, and more densely distributed in the periphery. Pacinian corpuscles were scattered randomly, close to blood vessels, whereas Ruffini corpuscles were in the periphery, close to the collagen bundles. CONCLUSIONS: Human supraspinal and interspinal ligaments are well innervated. This innervation might form the basis of neurologic feedback mechanisms for the protection and stability of the spine. These mechanisms might also be important in the development of diseases such as scoliosis.

Adult↗

Ras mediates the activation of phospholipase D by v-Src.

We demonstrated previously that v-Src activates a phospholipase D (PLD) activity (Song, J., Pfeffer, L.M., and Foster, D.A. (1991) Mol. Cell. Biol. 11, 4903-4908) and that this activation is dependent upon a G protein(s) (Jiang H., Alexandropoulos, K., Song, J., and Foster, D.A. (1994) Mol. Cell. Biol. 14, 3676-3682). An in vitro PLD assay was developed to study G protein involvement in v-Src-induced PLD activity. Maximal PLD activity in membranes isolated from v-Src-transformed cells was dependent upon both GTP and cytosol. In this report, we present three lines of evidence demonstrating that v-Src-induced PLD activity is mediated by Ras. First, a neutralizing Ras monoclonal antibody (Y13-259) inhibits PLD activity in membranes isolated from v-Src-transformed Balb/c 3T3 cells. Second, immobilized Ras protein depleted cytosol of the ability to stimulate PLD activity. This effect was dependent upon preloading immobilized Ras with GTP. Last, expression of a dominant negative Ras mutant in v-Src-transformed cells reduced PLD activity to the level observed in the nontransformed parental cells. These data establish a novel role for Ras in the regulation of PLD activity.

3T3 Cells↗

Homology dependence of UvsX protein-catalyzed joint molecule formation.

The bacteriophage UvsX protein is a "strand transferase" that promotes the pairing of homologous single and double-stranded DNAs. The efficiency of UvsX protein-mediated joint molecule formation between supercoiled duplex DNA and oligonucleotides is shown to have a sharp dependence on the degree of homology. The reaction proceeded efficiently with oligonucleotides containing 32 homologous positions but not with oligonucleotides containing only 24 homologous bases. This was shown to reflect an intrinsic homology requirement for the formation of stable joint molecules and was not caused by poor binding of the protein to short single-stranded DNAs. Even a single mismatch located in the middle of a region of 40 homologous nucleotides had a detectable effect on the efficiency of pairing. An in vitro recombinationally initiated DNA synthesis reaction that mimics the "secondary mode" of phage T4 DNA replication exhibited the same homology dependence.

Adenosine Triphosphatases↗

Placental transfer and developmental effects of 9-cis retinoic acid in mice.

9-cis retinoic acid (RA) is a naturally occurring isomer of all-trans RA. While both isomers can bind with high affinity and activate RA receptors, only 9-cis RA is the specific ligand for the retinoid X receptors. 9-cis RA has also been shown to be much more potent than all-trans RA in inducing digit duplication in the chick embryo wing bud. To gain further insight into its mechanisms, here we investigated the teratogenic activity in pregnant mice of 9-cis RA and compared it with those of all-trans RA and 13-cis RA. Using frequency and severity of limb reduction defects as well as palatal clefts in the resultant fetuses as indicators, we found that orally administered 9-cis RA was one-half as potent a teratogen as all-trans RA. That 9-cis RA was intrinsically less active than all-trans RA was deduced by comparing the inhibitory activities of the two retinoids in the limb bud mesenchymal cell micromass cultures using chondrogenesis as an end-point. Since placental transfer of cis isomers of RA is generally poor, we monitored the identities and amounts of retinoids in the embryo after administration of 9-cis RA to the mother. We found that 9-cis RA undergoes extensive metabolism and isomerization during absorption resulting in a number of metabolites in the maternal circulation within 30 min after administration. Although some of these metabolites remain to be identified, the most abundant RA isomers in the plasma coeluted with 13-cis RA.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Drug-Induced↗

Analogue of aspartate and glutamate active at synapses are attractants for Escherichia coli.

1. This research was carried out to compare Escherichia coli bacteria with animals in their response to L-aspartate and L-glutamate and their analogues. 2. Various analogues of aspartate and glutamate known to be neurotransmitters at synapses were shown to be attractants for E. coli. 3. The amino acid sequences of the animal receptors and the bacterial receptor, however, have no detectable relationship. Based on the amino acid sequence, evolutionarily the two systems appear not to be related.

Animals↗

Absence of relaxation to lactate in human placental vessels of pregnancies with severe preeclampsia.

OBJECTIVE: Our objective was to determine whether the observed relaxation to lactate and other agents in placental vessels of normal pregnancies is altered in severe preeclampsia. STUDY DESIGN: Isolated placental arteries and veins from women with severe preeclampsia and uncomplicated term pregnancies were precontracted with prostaglandin F2 alpha under 5% oxygen and 5% carbon dioxide with the balance nitrogen (Po2 35 to 38 torr) and then exposed to lactate (1 to 10 mmol/L, pH 7.4, n = 8 to 15), arachidonic acid (0.01 to 10 mumol/L, n = 6 to 13), nitroglycerin (1 nmol to 1 mumol/L, n = 4 to 12), or forskolin (0.01 to 10 mumol/L, n = 6 to 9). The response to lactate was also examined in placental vessels from appropriate-for-gestational-age preterm deliveries (n = 8) for comparison with a similar group with severe preeclampsia (n = 8). The t test and analysis of variance statistics were used. RESULTS: Relaxation to lactate was markedly inhibited in both placental arteries and veins of women with severe preeclampsia compared with vessels from uncomplicated term or preterm pregnancies. Responses to the other relaxing agents were not altered in the severely preeclamptic vessels. CONCLUSIONS: In severe preeclampsia absence of lactate-induced dilatation of placental vessels may contribute to the fetal complications associated with impaired blood flow and vasospasm.

Adult↗

Quantitative and dynamic MRI of neuroprotection in experimental stroke.

Experimental studies of stroke in animal models have traditionally relied on histological endpoints for the measurement of neuroprotection. In this study, we used in vivo and dynamic MRI to quantify the neuroprotective effects of the non-competitive NMDA antagonist MK801. Four hours of occlusion followed by 6 h of reperfusion was performed in a rabbit model of focal cerebral ischemia. Spin-echo T2-weighted (T2W) MRI was used to quantify ischemic lesion volumes. Hemispheric measurements of perfusion deficits were assessed by using dynamic susceptibility-contrast MRI to map the first-pass transit of injected GdDTPA. Histological correlates of infarction were quantified using tetrazolium staining. Animals treated with 2 mg/kg MK801 infused immediately post-occlusion (n = 6) were compared with untreated controls (n = 8). T2W MRI scans obtained after 6 h of reperfusion showed high-intensity lesions in the ischemic basal ganglia and cortex. MK801-treated animals showed significantly decreased lesion volumes compared to untreated controls (7.3 +/- 3.2% treated vs 20.7 +/- 4.8% control, p < 0.05). Lesion volumes measured with MRI were significantly correlated with tetrazolium-defined infarct volumes (r = 0.766, p = 0.004). Dynamic MRI demonstrated the phenomenon of delayed hypoperfusion in the ischemic hemisphere during the late reperfusion phase; relative cerebral blood volume (rCBV) was 45.2 +/- 10.3% in untreated animals. MK801 slightly improved these deficits although the differences did not reach statistical significance (rCBV = 77.0 +/- 9.7%, p = 0.128).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

HPLC investigation on Ni(II)-mediated DNA damage in the presence of t-butyl hydroperoxide and glutathione.

By use of HPLC with UV and electrochemical detection, the present study demonstrates that reaction of Ni2+ with t-butyl hydroperoxide in the presence of glutathioine (GSH) generates 8-hydroxy-2'-deoxyguanosine (8-OH-dG) from 2'-deoxyguanosine (dG) and from dG residues in calf thymus DNA at physiological pH. No significant amount of 8-OH-dG was generated in the absence of GSH, indicating an important role of GSH in enhancing the reactivity of Ni2+ toward lipid hydroperoxide to oxidize dG or dG residues in DNA. The rate of dG conversion to 8-OH-dG depends on the concentration of the reagents. During a two hour incubation of 0.75 mM dG, 10 mM t-butyl hydroperoxide, 1 mM Ni2+, and 2 mM GSH at room temperature under ambient air, dG was converted to 8-OH-dG with a yield of about 0.2%. For dG residues in DNA, 24 hour incubation at 37 degrees C yielded 0.1% 8-OH-dG. The 8-OH-dG generation from both dG and dG residues in DNA was inhibited by superoxide dismutase, catalase, and ethanol (hydroxyl radical scavenger), implying the involvement of oxygen free radicals in the 8-OH-dG generation process. The metal ion chelators, deferoxamine and EDTA, efficiently inhibited the 8-OH-dG formation. Similar results were obtained for the conversion of dG residues in calf thymus DNA to 8-OH-dG. Electrophoretic assays of DNA strand breaks showed that Ni2+ caused DNA double-strand breaks in the presence of t-butyl hydroperoxide and GSH. Because GSH is ubiquitously present in cellular systems at relatively high concentration, and the exposure of cells to Ni2+ results in the generation of lipid hydroperoxides, the 8-OH-dG generation and DNA double-strand breaks caused by the reaction of Ni2+ with lipid hydroperoxides in the presence of GSH may be an important mechanism in Ni(2+)-induced carcinogenesis. The inhibitory effect of chelators suggests a possible prevention strategy against Ni(2+)-induced toxicity and carcinogenesis.

8-Hydroxy-2'-Deoxyguanosine↗

Interferon beta-1b reduces interferon gamma-induced antigen-presenting capacity of human glial and B cells.

Interferon (IFN) beta-1b has been shown to alter the course of multiple sclerosis and to inhibit MHC class II expression, but its effect on antigen presentation has not been examined in a functional assay (Neurology 43 (1993) 655-661). The effect of IFN beta-1b on alloantigen presentation by human antigen-presenting cells (APC) including human fetal astrocytes (HFA) and microglia was examined. The effect of IFN beta-1b on the ability of B cells to present tetanus toxoid (TT) to TT-specific T cell lines was also examined. APC were pre-treated with IFN gamma (100 units/ml), IFN beta-1b (10-2000 units/ml), or a combination of IFN gamma and IFN beta-1b for 3 days and washed thoroughly prior to culture with allogeneic peripheral blood lymphocytes (PBL) for a period of 6 days. Lymphocyte proliferation was then measured by tritiated thymidine uptake. Treatment of the APC with IFN beta-1b resulted in a reduction in the IFN gamma-enhanced alloantigen-induced T cell responses. This reduction ranged between 50 and 70%, was associated with a 30-50% reduction in HLA class II (DR) and 35-40% reduction in ICAM-1 expression on the HFA used as APC. IFN beta-1b pretreatment of B cells reduced their constitutive and IFN gamma enhanced capacity to present TT to TT-specific T cell lines by 50-80%. This was associated with a 30 +/- 11% mean reduction in class II (DR) expression and approximately 50 +/- 1% reduction in ICAM-1 expression in IFN beta-1b + IFN gamma-treated B cells compared to IFN gamma-treated B cells (mean of three experiments).(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvants, Immunologic↗