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H Cao

Publications and source records attributed to H Cao.

At least 127 records · Page 7Linked to original sources
PubMed1999

Sequence motifs and free energies of selected natural and non-natural nucleosome positioning DNA sequences.

Our laboratories recently completed SELEX experiments to isolate DNA sequences that most-strongly favor or disfavor nucleosome formation and positioning, from the entire mouse genome or from even more diverse pools of chemically synthetic random sequence DNA. Here we directly compare these selected natural and non-natural sequences. We find that the strongest natural positioning sequences have affinities for histone binding and nucleosome formation that are sixfold or more lower than those possessed by many of the selected non-natural sequences. We conclude that even the highest-affinity sequence regions of eukaryotic genomes are not evolved for the highest affinity or nucleosome positioning power. Fourier transform calculations on the selected natural sequences reveal a special significance for nucleosome positioning of a motif consisting of approximately 10 bp periodic placement of TA dinucleotide steps. Contributions to histone binding and nucleosome formation from periodic TA steps are more significant than those from other periodic steps such as AA (=TT), CC (=GG) and more important than those from the other YR steps (CA (=TG) and CG), which are reported to have greater conformational flexibility in protein-DNA complexes even than TA. We report the development of improved procedures for measuring the free energies of even stronger positioning sequences that may be isolated in the future, and show that when the favorable free energy of histone-DNA interactions becomes sufficiently large, measurements based on the widely used exchange method become unreliable.

Animals↗
PubMed1999

Site-directed mutagenesis evidence for arginine-384 residue at the active site of maize branching enzyme II.

Essential arginine residues are suggested to be located at the active sites of maize branching enzymes (BE) based on the evidence that two arginine residues are conserved in all BE from various species and that as little as one arginine residue is located at the active site of maize BE by phenylglyoxal (PGO) modification. To determine the exact location of the active-site arginine residue in BE, we employed peptide mapping and site-directed mutagenesis approaches. A single trypsin-digested, [14C]PGO-labeled peptide was purified from maize BEII by two rounds of HPLC separation, but we failed to obtain amino acid sequencing information. Site-directed mutagenesis was then used to create one mutant (arginine-384 to alanine-384), R384A. Immunoblotting result showed that BEII protein was expressed at a similar level in the wild type and the R384A mutant. However, BE activity in the R384A mutant was only 1.4% of the wild type. These results support the conclusion that the conserved arginine-384 residue is important in BEII catalysis.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1999

Characterization of a functional relationship between hepatocyte growth factor and mouse bone marrow-derived mast cells.

During the early stage (at 4 weeks) of interleukin-3 (IL-3)-induced development, mouse bone marrow-derived mast cells (BMMC) express alpha 4, alpha 5 and alpha 6 integrins, whereas with further maturation beyond 10 weeks, only alpha 5 integrin remains stably expressed. Hepatocyte growth factor (HGF) modulates the growth and movement of diverse cell types upon binding to its receptor, encoded by the proto-oncogene c-met. We report here the expression of c-met by BMMC throughout the course of their development. In addition, HGF stimulated migration of early week-4 BMMC, but not of the later stage week-10 BMMC, on fibronectin and laminin substrates. The developmental stage-dependent effect of HGF on BMMC was due to specific stimulation of the migratory function of alpha 4 and alpha 6, but not alpha 5 integrins. In addition, HGF had no effect on BMMC growth, either alone or in combination with IL-3. While HGF is stimulatory of the migratory function of BMMC, our results show that BMMC in turn can modulate HGF function. Thus, upon activation via the IgE receptors, BMMC released proteases that abolished HGF activities. Analyses of the degradation products by two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot using antisera prepared against recombinant HGF and the kringle 3 domain of HGF revealed specific degradation of HGF alpha but not beta/beta' subunits. Therefore, our results suggest that: 1) the motogenic effect of HGF on BMMC varies according to the stage of their development, 2) HGF stimulation of BMMC migration is due to selective activation of alpha 4 and alpha 6, but not alpha 5 integrin function, and 3) there exists a two-way relationship between BMMC and HGF such that HGF stimulates the beta 1 integrin-mediated migratory function of BMMC, which can, in turn, modulate HGF function by release of serine proteases.

Animals↗
PubMed1999

Selective incorporation and specific cytocidal effect as the cellular basis for the antimelanoma action of sulphur containing tyrosine analogs.

Tyrosine analogs are good candidates for developing melanoma chemotherapy because melanogenesis is inherently toxic and uniquely expressed in melanocytic cells. Sulphur containing substrate (tyrosine) analogs, N-acetyl-4-S-cysteaminylphenol (NAcCAP) and N-propionyl-4-S-cysteaminylphenol (NPrCAP), have been shown to have potent antimelanoma activity in mice bearing melanoma. Both NAcCAP and NPrCAP show selective cytotoxicity towards melanoma cell lines. But the mechanism leading to selectivity is not clear as these drugs are also toxic to other cell lines to a lesser extent. Here we show that these drugs have both cytostatic and cytocidal effects, which could account for this. Cytostatic effect is suggested by DNA flow cytometry. The drug causes cell cycle changes in four human cell lines (normal skin fibroblasts, HeLa cells, and melanoma cell lines, C32 and SK-MEL-23) in a dose-dependent manner blocking cells in S phase with concomitant decrease in the number of cells in G1 phase. There is also a gradual decrease in cells in G2 + M phases. The dose-concentration curves give IC50 values in the range of 50-400 microM and the melanotic melanoma cell line SK-MEL-23 has the lowest IC50 value consistent with our hypothesis that these drugs are selective towards melanoma cells. The concentration-dependent accumulation of cells in S phase suggest a cytostatic effect as a consequence of inhibition of DNA synthesis in agreement with [3H] thymidine incorporation assay. There is a highly specific uptake of [14C]NAcCAP and irreversible damage to DNA synthesis machinery in SK-MEL-23 cells, indicating a melanotic-specific cytocidal effect as well. Trypan blue exclusion study and competitive inhibition assay indicated that visible cytocidal effect occurs slowly and oxidative stress resulting from tyrosinase mediated oxidation of the drug appears to be the underlying mechanism. The primary antimelanoma effect of cysteaminylphenols derives from a selective cytostatic effect, but is followed by a specific cytocidal action rendering the drugs useful for targeted melanoma chemotherapy.

Animals↗
PubMed1999

Artificial DNAs with metal-assisted base pairs.

Two types of artificial beta-C-nucleosides, 2 and 3, were newly synthesized, which possess a metal chelating site (2-aminophenol and catechol, respectively) at the nucleobase moiety. These nucleosides are expected to form metal-assisted base pairs in oligonucleotides and thereby to control high-order structures and functions of DNAs.

Aminophenols↗
PubMed1999

Participation of dynamin in the biogenesis of cytoplasmic vesicles.

Dynamin is a 100-kDa GTPase that has been implicated in endocytosis. To extend our understanding of its cellular functions, we have microinjected specific affinity-purified anti-dynamin antibodies into cultured mammalian epithelial cells. Using this approach, dynamin function can be inhibited specifically and rapidly in single cells. Effects of microinjected inhibitory antibodies on distinct endocytic processes and plasmalemmal morphology were then assayed by fluorescence microscopy (FM) and ultrastructural analysis. Micro-injected antibodies inhibit the clathrin-mediated endocytosis of fluorophore-labeled transferrin and cause a marked invagination of the plasma membrane. Many of these long plasmalemmal invaginations had clathrin-coated pits along their cytoplasmic surface. A number of distinct noncoated pits resembling plasmalemmal caveolae also accumulated in anti-dynamin antibody-injected cells. Further, the cellular uptake of cholera toxin B, which normally occurs by the internalization of caveolae, was inhibited in these cells. In support of these observations, immunoisolation techniques, double-label immuno-FM, and immunoelectron microscopy (immuno-EM) provided biochemical and morphological evidence that dynamin associates with plasmalemmal caveolae. Together, these observations indicate that dynamin mediates scission from the plasma membrane of both clathrin-coated pits and caveolae during distinct endocytic processes. These results demonstrate that dynamin isoforms are involved in an additional endocytic process that is distinct from clathrin-mediated endocytosis and provide significant insights into the molecular mechanisms governing the GTP-mediated internalization of caveolae. Evidence is provided demonstrating that dynamin isoforms have a differential distribution in mammalian cells. Targeting information for these isoforms is provided at least in part by regions of alternative splicing. Thus, the different dynamin isoforms may be localized to distinct cellular compartments but provide a similar scission function during the biogenesis of nascent cytoplasmic vesicles.

Animals↗
PubMed1999

Prevalence and risk factors of behavioral and emotional problems among Chinese children aged 6 through 11 years.

OBJECTIVE: To examine the prevalence and risk factors of behavioral and emotional problems in Chinese children. METHOD: A sample of 2,940 children aged 6 through 11 years was randomly drawn from household registers in Shandong Province of China. Parents completed the Child Behavior Checklist (CBCL) and a structured self-rating questionnaire. RESULTS: The mean CBCL Total Problems score was 16.1 (SD = 14.0). There was no significant age effect on the Total Problems score; boys scored significantly higher than girls (17.2 versus 15.0; F = 24.94, p < .01). The overall prevalence rates of behavioral problems were 12.5% for boys and 8.3% for girls (chi 2 = 14.23, p < .01). Logistic regression analysis showed that a number of parental, prenatal, perinatal, and postnatal factors were significantly associated with increased risk of children's behavioral problems. CONCLUSIONS: The prevalence of parent-reported behavioral problems in Chinese children is lower than those found in other countries. Of multiple psychosocial and biological factors associated with children's behavioral problems, separation or divorce of parents is the most significant factor.

Behavioral Symptoms↗
PubMed1999

Purification and molecular genetic characterization of ZPU1, a pullulanase-type starch-debranching enzyme from maize.

This study identified and purified specific isoamylase- and pullulanase-type starch-debranching enzymes (DBEs) present in developing maize (Zea mays L.) endosperm. The cDNA clone Zpu1 was isolated based on its homology with a rice (Oryza sativa L.) cDNA coding for a pullulanase-type DBE. Comparison of the protein product, ZPU1, with 18 other DBEs identified motifs common to both isoamylase- and pullulanase-type enzymes, as well as class-specific sequence blocks. Hybridization of Zpu1 to genomic DNA defined a single-copy gene, zpu1, located on chromosome 2. Zpu1 mRNA was abundant in endosperm throughout starch biosynthesis, but was not detected in the leaf or the root. Anti-ZPU1 antiserum specifically recognized the approximately 100-kD ZPU1 protein in developing endosperm, but not in leaves. Pullulanase- and isoamylase-type DBEs were purified from extracts of developing maize kernels. The pullulanase-type activity was identified as ZPU1 and the isoamylase-type activity as SU1. Mutations of the sugary1 (su1) gene are known to cause deficiencies of SU1 isoamylase and a pullulanase-type DBE. ZPU1 activity, protein level, and electrophoretic mobility were altered in su1-mutant kernels, indicating that it is the affected pullulanase-type DBE. The Zpu1 transcript levels were equivalent in nonmutant and su1-mutant kernels, suggesting that coordinated regulation of ZPU1 and SU1 occurs posttranscriptionally.

Amino Acid Sequence↗
PubMed1999

Identification of the soluble starch synthase activities of maize endosperm.

This study identified the complement of soluble starch synthases (SSs) present in developing maize (Zea mays) endosperm. The product of the du1 gene, DU1, was shown to be one of the two major soluble SSs. The C-terminal 450 residues of DU1 comprise eight sequence blocks conserved in 28 known or predicted glucan synthases. This region of DU1 was expressed in Escherichia coli and shown to possess SS activity. DU1-specific antisera detected a soluble endosperm protein of more than 200 kD that was lacking in du1- mutants. These antisera eliminated 20% to 30% of the soluble SS activity from kernel extracts. Antiserum against the isozyme zSSI eliminated approximately 60% of the total soluble SS, and immunodepletion of du1- mutant extracts with this antiserum nearly eliminated SS activity. Two soluble SS activities were identified by electrophoretic fractionation, each of which correlated specifically with zSSI or DU1. Thus, DU1 and zSSI accounted for the great majority of soluble SS activity present in developing endosperm. The relative activity of the two isozymes did not change significantly during the starch biosynthetic period. DU1 and zSSI may be interdependent, because mutant extracts lacking DU1 exhibited a significant stimulation of the remaining SS activity.

Amino Acid Sequence↗
PubMed1999

The hepatic nuclear factor-1alpha G319S variant is associated with early-onset type 2 diabetes in Canadian Oji-Cree.

Mutations in the gene encoding hepatic nuclear factor-1alpha (HNF-1alpha) have been found in patients with maturity-onset diabetes of the young. We identified a new variant in the HNF-1alpha gene, namely G319S, in Ontario Oji-Cree with type 2 diabetes. G319S is within the proline II-rich domain of the trans-activation site of HNF-1alpha and alters a glycine residue that is conserved throughout evolution. S319 was absent from 990 alleles taken from subjects representing six other ethnic groups, suggesting that it is private for Oji-Cree. We found that 1) the S319 allele was significantly more prevalent in diabetic than nondiabetic Oji-Cree (0.209 vs. 0.087; P = 0.000001); 2) S319/S319 homozygotes and S319/G319 heterozygotes, respectively, had odds ratios for type 2 diabetes of 4.00 (95% confidence interval, 2.65-6.03) and 1.97 (95% confidence interval, 1.44-2.70) compared with G319/G319 homozygotes; 3) there was a significant difference in the mean age of onset of type 2 diabetes, with G319/G319, S319/G319, and S319/S319 subjects affected in the fifth, fourth, and third decades of life, respectively. In subjects with type 2 diabetes, we also found significantly lower body mass index and significantly higher post-challenge plasma glucose in S319/S319 and S319/G319 compared with G319/G319 subjects. Finally, among nondiabetic subjects, S319/G319 heterozygotes had significantly lower plasma insulin than G319/G319 homozygotes. The presence of the private HNF-1alpha G319S variant in a large number of Oji-Cree with type 2 diabetes and its strong association with type 2 diabetes susceptibility are unique among human populations. Also, G319S is associated with a distinct form of type 2 diabetes, characterized by onset at an earlier age, lower body mass, and a higher postchallenge plasma glucose.

Adolescent↗
PubMed1999

Cloning and expression of a novel chicken sulfotransferase cDNA regulated by GH.

We have used mRNA differential display to compare gene expression in normal and GH receptor-deficient dwarf chickens, and report here the characterization of one differentially expressed gene, which shows significant sequence identity to the sulfotransferase gene family. Partial cDNA clones were isolated from a chicken liver cDNA library and an additional sequence was obtained using 5' rapid amplification of cDNA ends. A complete cDNA probe hybridizes to three transcripts (2.4, 2.0 and 1.45 kb) on Northern blots of chicken liver RNA, which differ in the length of the 3' untranslated region. All three transcripts are expressed at higher levels in normal vs dwarf chickens, as expected for a GH-regulated gene. The expression of this sulfotransferase mRNA was also detected in skeletal muscle, but not other tissues. The administration of GH to chickens increased the hepatic expression within 1 h, suggesting this sulfotransferase could be directly regulated by GH. Sulfotransferase activity, using estradiol or corticosterone as substrate, is detected in cells transfected with an expression vector containing the full-length cDNA. The sequence of this sulfotransferase does not show significant similarity with any subfamily of the sulfotransferases and its endogenous substrate is presently unknown. However, we speculate that GH activation of sulfotransferase activity could play a role in reducing concentrations of growth-antagonistic steroid hormones in GH target tissues. These results demonstrate the usefulness of differential display in this model system to identify genes that play a role in mediating GH action.

Amino Acid Sequence↗
PubMed1999

Effects of nitric oxide inhibitor on prostacyclin biosynthesis in portal hypertensive rats.

OBJECTIVE: To evaluate the effects of nitric oxide inhibitor on prostacyclin (PGI2) biosynthesis and the role of PGI2 in hyperhemodynamics of portal hypertension. METHODS: Sprague Dawley rats were divided into four groups: intrahepatic portal hypertension (IHPH) by injection of CCl4, prehepatic portal hypertension (PHPH) by stenosis of the portal vein, end-to-side portacaval shunt (PCS), and sham-operated controls (SO). Animals of each group were subdivided into 2 groups: systemic administration of nitric oxide inhibitor L-NMMA and vehicle. The radioactive microsphere method was used for hemodynamic study. The level of plasma PGI2 (6-keto-PGF1 alpha) was measured by radioimmunoassay. RESULTS: The characteristics of hyperdynamic circulatory state including increased cardiac output and splanchnic blood flow, decreased mean arterial blood pressure, total peripheral vascular resistance, and splanchnic vascular resistance were observed in IHPH, PHPH and PCS rats. The magnitude of hyperhemodynamics was in the order of PCS > PHPH > IHPH rats. The hyperdynamic circulatory state in IHPH, PHPH and PCS rats could be effectively reversed by L-NMMA to the baseline values of hemodynamics in SO rats. The baseline concentrations of plasma 6-keto-PGF1 alpha (ng/ml) in PHPH, IHPH, PCS, and SO rats were 6.93 +/- 2.43, 5.09 +/- 2.27, 2.36 +/- 1.01 and 1.56 +/- 0.61, respectively. The concentrations of plasma 6-Keto-PGF1 alpha in PHPH, IHPH and PCS rats were significantly higher than those in SO rats. Moreover, the concentrations were significantly higher in PHPH and IHPH rats than in PCS rats (P < 0.05). After administration of L-NMMA, the concentrations of plasma 6-Keto-PGF1 alpha (ng/ml) in PHPH, IHPH, PCS and SO rats were 7.69 +/- 2.98, 5.68 +/- 2.66, 5.50 +/- 0.79, 5.02 +/- 2.86, respectively. As compared to the baseline value, the concentrations of 6-keto-PGF1 alpha rats were slightly increased in IHPH, PHPH rats (P > 0.05), but significantly increased in PCS and SO rats (P < 0.05). CONCLUSIONS: In this study, the hyperdynamic circulatory state in portal hypertensive rats and portacaval shunt rats was completely reversed by L-NNMA to normal, but the level of 6-keto-PGF1 alpha was still elevated. The results indicate that PGI2 is not involved in hyperhemodynamics of portal hypertension.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

An ultrasound scoring system for the diagnosis of liver fibrosis and cirrhosis.

OBJECTIVE: To establish noninvasive semiquantitative ultrasonic criteria for evaluating liver fibrosis and differentiating cirrhosis from chronic hepatitis. METHODS: A total of 66 HBsAg positive patients (chronic hepatitis 42 patients, cirrhosis 24) were included. Ultrasonography was performed 24 hours before liver biopsy. A fibrotic scoring system was used to evaluate the ultrasound findings in contrast with fibrotic stages in each patient. RESULTS: The total liver fibrotic scores had a significantly positive correlation with the histological liver fibrotic stage (r = 0.952, P < 0.001); the stage of histological liver fibrosis (Y) was calculated by the total fibrotic scores (X) according to the experiential formula: Y = X/2 -2; receiver operating curves (ROC) showed that the best cut-off values for differentiating cirrhosis from chronic hepatitis was 10 with a sensitivity of 87.8% and a specificity of 97.6%. CONCLUSIONS: The total fibrotic scores of ultrasonic dimensional image provide a semiquantitative marker to evaluate liver fibrosis and differentiate cirrhosis from chronic hepatitis.

Adult↗
PubMed1999

[Differential diagnosis in patients with tuberculous meningitis and cryptococcal meningitis].

OBJECTIVE: To search for the main differential points in clinical and CSF changes between patients with tuberculous meningitis (TBM) and cryptococcal meningitis (CCM). METHODS: Fifty three cases of TBM and 55 cases of CCM who admitted to hospital from February 1983 to December 1997 were investigated retrospectively. Main symptoms, signs and CSF changes before administration of specific antibiotics were compared. RESULTS: 9%(5/53) TBM and 49% (27/55) CCM patients had headache without fever at the onset. The incidences of symptoms of failing eyesight, hearing loss and paralysis of extremities were 13% (7/53) and 36%(20/55), 2% (1/53) and 16% (9/55), and 19% (10/53) and 0 in TBM and CCM patients respectively. The rate and the degrees of optic papilla edema in CCM patients (66%, 16/36 slight, 13/36 moderate, and 7/36 serious) were significantly higher and more serious than that in TBM (15%, 8/8 slight). The patients with initial CSF pressure over 400 mm H2O were 11% and 90% in TBM and CCM. All but 20 CCM patients had elevation of CSF protein content, and 45% (24/53) TBM and 9%(5/55) CCM were > 2 g/L. CONCLUSIONS: This study shows that the most important differences between TBM and CCM are: headache not accompanied by fever at the onset, failing eyesight, striking elevation of initial CSF pressure, moderately and serious degree of optic papilla edema, normal CSF protein content occurs usually in CCM more than those in TBM patients. On the other hand, striking elevation of CSF protein content (> 2 g/L) occurs usually in TBM patients.

Adolescent↗
PubMed1999

[IL-12 gene treatment of hepatocellular carcinoma: experimental study].

OBJECTIVE: To investigate the inhibitory effects of retrovirus vector containing IL-12 gene on hepatoma growth in vivo and to explore a new approach of gene therapy to hepatocellular carcinoma (HCC). METHODS: Retrovirus vector containing IL-12 gene was constructed and transfected into packaged cell PA317. Positive PA317 was injected into the rat which suffered from experimental HCC and its anti-tumor effects and immunity changes were recorded. RESULTS: The packaged cell PA317 containing IL-12 gene could inhibit the proliferation of hepatocellular cell line CBRH3. The rats injected at day 1 or 3 can survive permanently, while those injected at day 5 or 7 can survive longer than those not injected. However, tumor generated in rats injected with blank control or package cells containing retroviral vector without IL-12 gene (P < 0.01). CONCLUSIONS: Package cells transfected with retroviral vector containing IL-12 either injected to the hepatoma tissue locally or given splenic exercises anti-hepatoma effects efficiently. The direct intrasplenic injection route is new, safe and effective.

Animals↗
PubMed1999

[Applied anatomic study on intraorbital and intraethmoidal parts of ethmoidal artery].

OBJECTIVE: In order to provide anatomic data for operation of ethmoidal sinus and optic canal decompression. METHOD: Using microanatomic method, the intraorbital and intraethmoidal parts of ethmoidal arteries were observed and measured. RESULT: The length of intraorbital segment of anterior ethmoidal artery was 5.16 +/- 1.24 mm, and its diameter was 0.56 +/- 0.17 mm; the length of intraorbital segment of posterior ethmoidal artery was 9.08 +/- 2.29 mm, with diameter 0.37 +/- 0.14 mm. The ethmoidal artery, nerve and vein were surrounded by fascial sheath which could extend to ethmoidal sinus. Three variants of ethmoidal arteries could be found: It passed through bony canal; It went between the superior wall of ethmoidal cell and ethmoidal mucosa; One part went through bony canal, but the other did not. CONCLUSION: It was important to find ethmoidal artery in operation of ethmoidal sinus and optic canal decompression.

Adult↗