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Biomedical subjects

Z Huang

Publications and source records attributed to Z Huang.

At least 145 records · Page 8Linked to original sources
PubMed2000

Host suppressors in Arabidopsis thaliana of mutations in the movement protein gene of Cauliflower mosaic virus.

A novel genetic screen was used to identify host factors in Arabidopsis thaliana that suppress mutations in the Cauliflower mosaic virus (CaMV) movement protein gene (gene I). A series of small mutations was made in gene I and the mutations were tested for their suitability in a suppressor screen. The first round of screening yielded only revertants or second-site mutations in gene I. A derivative of one of the second-site mutant viruses (N7) that was delayed in symptom production was used in a second round of screening for suppressor plants that accelerated symptom production. Two candidate suppressor plants were found that accelerated by 1 to 4 days the first appearance of symptoms caused by the mutant viruses. One of the suppressors (5-2), called asc1 (acceleration of symptoms by CaMV N7), was mapped to chromosome 1. Two additional loci that differentially affect N7 virus susceptibility in the parental Columbia and Ler ecotypes were mapped to chromosomes 3 and 4 by quantitative trait locus (QTL) analysis.

Arabidopsis↗
PubMed2000

Increased susceptibility to ischemia-induced brain damage in transgenic mice overexpressing a dominant negative form of SHP2.

Cell culture studies have established SH2 domain-containing protein tyrosine phosphatase-2 (SHP2) as an important factor in growth factor and cytokine-activated signaling pathways. However, the significance of SHP2 in the mammalian central nervous system (CNS) is not known since early embryonic lethality occurs in shp2 null mice. To bypass this embryonic lethality, transgenic animals containing a catalytically inactive mutant of SHP2 (SHP2-CS) under the control of a nestin intron II/thymidine kinase minimal promoter were generated. In the developing CNS of these animals, although high-level transgene expression was detected in the neuroepithelium, there was no obvious abnormality in progenitor cell proliferation or migration. In the adult brain, high-level transgene expression was detected in the subventricular zone, rostral migratory stream, dentate gyrus of hippocampus, and cerebellum. Because SHP2 function is likely important in cell survival pathways, we used a focal cerebral ischemia model to examined whether SHP2 is important during CNS injury. Ischemia-induced damage and neuronal death was found to be significantly greater in nestin-SHP2-CS mice than in wild-type littermates. These findings indicate that SHP2 is a required factor in signaling pathway(s) important for neuronal survival.

Animals↗
PubMed2000

Endothelial nitric oxide synthase-dependent cerebral blood flow augmentation by L-arginine after chronic statin treatment.

Nitric oxide, a product of nitric oxide synthase activity, relaxes vascular smooth muscle and elevates brain blood flow. We evaluated the importance of eNOS to cerebral blood flow augmentation after L-arginine infusion and increases in flow after eNOS upregulation in SV-129 mice. Blood flow was measured by laser-Doppler flowmetry before and after L-arginine infusion (450 mg/kg during a 15-minute period) or measured by 14C-iodoamphetamine indicator fractionation or 14C-iodoantipyrine tissue equilibration techniques. rCBF increased by 26% (laser Doppler flowmetry) after L-arginine infusion but did not change in mutant mice deficient in eNOS expression. After eNOS upregulation by chronic simvastatin treatment (2 mg/kg subcutaneously, daily for 14 days), L-arginine amplified and sustained the hyperemia (38%) and increased absolute brain blood flow from 86 +/- 7 to 119 +/- 10 mL/100 g per minute. Furthermore, pretreatment with simvastatin enhanced blood flow within ischemic brain tissue after middle cerebral artery occlusion. Together, these findings suggest that eNOS activity is critical for blood flow augmentation during acute L-arginine infusion, and chronic eNOS upregulation combined with L-arginine administration provides a novel strategy to elevate cerebral blood flow in the normal and ischemic brain.

Animals↗
PubMed2000

Suppressing complexity via the slaving principle

The complexity of a nonlinear dynamic system can be suppressed by adding an external period force with appropriate choice of frequency and amplitude directly on the slowly changing variable of the system. Numerical results indicate that the method not only can suppress chaos but also is robust to the additive external noise.

Journal Article↗
PubMed2000

Three-dimensional analysis of harmonic generation in high-gain free-electron lasers

In a high-gain free-electron laser (FEL) employing a planar undulator, strong bunching at the fundamental wavelength can drive substantial bunching and power levels at the harmonic frequencies. In this paper we investigate the three-dimensional evolution of harmonic radiation based on the coupled Maxwell-Klimontovich equations that take into account nonlinear harmonic interactions. Each harmonic field is a sum of a linear amplification term and a term driven by nonlinear harmonic interactions. After a certain stage of exponential growth, the dominant nonlinear term is determined by interactions of the lower nonlinear harmonics and the fundamental radiation. As a result, the gain length, transverse profile, and temporal structure of the first few harmonics are eventually governed by those of the fundamental. Transversely coherent third-harmonic radiation power is found to approach 1% of the fundamental power level for current high-gain FEL projects.

Journal Article↗
PubMed2000

Structural characterization of the released polysaccharide of desiccation-tolerant Nostoc commune DRH-1.

The structure of the viscous extracellular polysaccharide (glycan) of desiccation-tolerant Nostoc commune DRH-1 was determined through chromatographic and spectroscopic methods. The polysaccharide is novel in that it possesses a 1-4-linked xylogalactoglucan backbone with D-ribofuranose and 3-O-[(R)-1-carboxyethyl]-D-glucuronic acid (nosturonic acid) pendant groups. The presence of D-ribose and nosturonic acid as peripheral groups is unusual, and their potential roles in modulating the rheological properties of the glycan are discussed. Nosturonic acid was present in the glycans of N. commune from diverse geographic locations, suggesting that this uronic acid is an integral component of this cosmopolitan anhydrophile.

Carbohydrate Conformation↗
PubMed2000

Nuclear matrix attachment regions of human papillomavirus type 16 repress or activate the E6 promoter, depending on the physical state of the viral DNA.

Two nuclear matrix attachment regions (MARs) bracket a 550-bp segment of the long control region (LCR) containing the epithelial cell-specific enhancer and the E6 promoter of human papillomavirus type 16 (HPV-16). One of these MARs is located in the 5' third of the LCR (5'-LCR-MAR); the other lies within the E6 gene (E6-MAR). To study their function, we linked these MARs in various natural or artificial permutations to a chimeric gene consisting of the HPV-16 enhancer-promoter segment and a reporter gene. In transient transfections of HeLa cells, the presence of either of these two MARs strongly represses reporter gene expression. In contrast to this, but similar to the published behavior of cellular MARs, reporter gene expression is stimulated strongly by the E6-MAR and moderately by the 5'-LCR-MAR in stable transfectants of HeLa or C33A cells. To search for binding sites of soluble nuclear proteins which may be responsible for repression during transient transfections, we performed electrophoretic mobility shift assays (EMSAs) of overlapping oligonucleotides that represented all sequences of these two MARs. Both MARs contain multiple sites for two strongly binding proteins and weak binding sites for additional factors. The strongest complex, with at least five binding sites in each MAR, is generated by the CCAAT displacement factor (CDP)/Cut, as judged by biochemical purification, by EMSAs with competing oligonucleotides and with anti-CDP/Cut oligonucleotides, and by mutations. CDP/Cut, a repressor that is down-regulated during differentiation, apparently represses HPV-16 transcription in undifferentiated epithelials cells and in HeLa cells, which are rich in CDP/Cut. In analogy to poorly understood mechanisms acting on cellular MARs, activation after physical linkage to chromosomal DNA may result from competition between the nuclear matrix and CDP/Cut. Our observations show that cis-responsive elements that regulate the HPV-16 E6 promoter are tightly clustered over at least 1.3 kb and occur throughout the E6 gene. HPV-16 MARs are context dependent transcriptional enhancers, and activated expression of HPV-16 oncogenes dependent on chromosomal integration may positively select tumorigenic cells during the multistep etiology of cervical cancer.

Base Sequence↗
PubMed2000

Body distribution of poly-DL-lactide-poly(ethylene glycol) microspheres with entrapped leptospira interrogans antigens following intravenous and oral administration to guinea-pigs.

Poly-DL-lactide-poly(ethylene glycol) (PELA) microspheres with entrapped antigens were administered intravenously and orally into guinea-pigs to quantitatively determine the in-vivo distribution and release profiles. PELA microspheres containing 125I-labelled outer-membrane protein Leptospira interrogans antigens (125I-OMP) were prepared by double-emulsion solvent extraction procedure, and characterized with respect to size, morphology and in-vitro release profiles. The fractured sections of liver and spleen were inspected by scanning electron microscopy, which indicated that microspheres had successfully been entrapped within the above tissues after intravenous injection and oral administration. At predetermined intervals, the blood and such tissues as the liver, spleen, kidney, thyroid, small intestine and mesentery were collected, and the radioactivity was measured by gamma scintillation counting. Following intravenous administration, 56.7% of administered microspheres were accumulated in immunization-related tissues, and 40.1% of microspheres were located in the liver and spleen. However, there was limited uptake efficiency (8.33%) following oral administration, and 49.5% of the absorbed microspheres were located in the intestinal mucosa. Compared with in-vitro release, the in-vivo release profiles of 125I-OMP from PELA microspheres, determined from the decreasing radioactivity in the above tissues, were much faster and the burst effect was higher. Antigen-loaded PELA microspheres were efficiently entrapped within immunization-related tissues after intravenous administration, but orally administered PELA microspheres showed limited uptake efficiency. Further investigation is needed to improve intestinal absorption.

Administration, Oral↗
PubMed2000

[A study of transgenic IFV cattle integrated with human serum albumin gene].

The mammary gland expression vector (pcDNA 3.1-GCALBm) containing the full-length sequence of human serum albumin (hALB) cDNA and intron 1 as well as the goat beta-casien gene promoter and 5' up-stream regulatory sequence was constructed. The vector was micro-injected into bovine IVF eggs. The embryos were in vitro cultured to the late stage of morulae, and then few embryo cells were aspirated for the implantation detection of target gene integration and SRY DNA sequence using nested-PCR. Afterwards, ten integrated embryos were selected to transfer into eight recipients and three were pregnant. The pregnant rate was 37.5%(3/8). However, two were miscarried in mid-trimester but one was pregnant at term to deliver a male transgenic cattle integrated with hALB mini-gene. The transgenic efficiency was 12.5% (1/8).

Animals↗
PubMed2000

[Methods for microdissection-PCR-silver stain technique in paraffin-embedded tissue sections].

OBJECTIVE: To use the microdissection-PCR-silver stain technique in the paraffin- embedded tissue sections and analyze the microsatellite instability in colorectal cancer. METHODS: By microdissection technique, the lymphocytes and mesenchymal cells, normal mucous epithelial cells, displasia, adenoma, and carcinoma cells were recovered from paraffin-embedded tissue sections. The cells were digested by protinase K; the cell lysates were used as PCR template and the PCR products were analysed by denatured polyacrylamide gel electrophoresis and silver stain. Four microsatellite loci, TGF-betaRII(A)(10), hMSH(2)(A)(26)-Bat-26, hMSH(3)(A)(8), hMSH(6)(C)(8), were analyzed. RESULTS: In all 28 specimens, hMSH(3)(A)(8) and hMSH(6)(C) 8) loci were amplified successfully. TGF-betaRII(A)10), Bat-26 had consistent amplification in 23/28, 22/28 specimens, respectively. And Bat-26 microsatellite instability was found in carcinoma cells in 5 specimens, and in adenoma cells in one of the 5 specimens. CONCLUSION: Microdissection-PCR silver stain technique can be used in paraffin-embedded tissue sections with satisfactory results. This method can be employed in analyzing microsatellite instability in colorectal carcinoma.

Colorectal Neoplasms↗
PubMed2000

[The correlation of cytokines TNF alpha, IFN-gamma, Epo with anemia in rheumatoid arthritis].

OBJECTIVE: To elucidate the characteristics of anemia of chronic disease(ACD) in rheumatoid arthritis(RA), and the role of TNF alpha, IFN-gamma and Epo in the pathogenesis of ACD. METHOD: Serum TNF alpha and IFN-gamma levels in RA patients and serum Epo levels in RA with ACD were measured by ELISA. Serum iron status profile in RA patients were also detected. The effects of TNF alpha and IFN-gamma on cobalt-induced erythropoietin production in human hepatic cancer cells(HepG2) were examined. The effect of TNF alpha and IFN-gamma erythroid colony formation (CFU-E and BFU-E) of normal bone marrow cells, and the effect of serum from RA patients and Epo on CFU-E yields of RA bone marrow cells. RESULT: Serum TNF alpha or IFN-gamma in RA and RA with ACD patients were higher than those in normal controls, and were inversely correlated with hemoglobin, and serum iron levels. Serum Epo levels in ACD patients were lower than those in iron-deficiency anemia patients with comparable hemoglobin level. TNF alpha and IFN-gamma could specifically inhibit cobalt-induced Epo production in HepG2 cells, and suppressed normal bone marrow BFU-E and CFU-E growth in a dose-dependent manner. Bone marrow CFU-E yields of RA patients were also suppressed by their own serum. The inhibitory effects of TNF alpha, IFN-gamma or serum from RA patients on erythroid colony formation could be corrected by the addition of rhEpo. CONCLUSION: It suggested that there were hematopoietic inhibiting factors in the serum of RA patients. TNF alpha or IFN-gamma was involved in the pathogenesis of anemia in RA patients. Administration of rhEpo might be beneficial for anemia of RA patients.

Adolescent↗
PubMed2000

[Mixing of Cunninghamia lanceolata with Michelia macclurei and restoration of self-sustaining mechanism in G. lanceolata plantation].

The formation of self-sustaining mechanism is one of the major objectives for the sustainable management of plantations. In this study, the incorporation of different proportions of native Michelia macclurei into Cunninghamia lanceolata plantation was practiced to restore the degraded C. lanceolata plantation, and the comparison of nutrient cycling characteristics and soil nutrient concentrations was made among four types of plantation stand with different mixed rate of native M. macclurei representing four different restoration stages of degraded C. lanceolata plantations. With the increase of the proportion of M. macclurei in the plantation, the litterfall and returned nutrients N, P, K, Ca and Mg increased. The nutrient cycling efficiency increased significantly, e.g., that of N and Mg increased from about 0.1 for the degraded pure C. lanceolata plantation to above 0.5 for the pure M. macclurei plantation. Soil organic matter and nutrients also elevated. It is suggested that the self-sustaining mechanism of the C. lanceolata plantation forest gradually reformed as the proportion of native M. macclurei mixed in the plantation increased. The criteria to determine the proportion of native broad-leaved tree species mixed in C. lanceolata plantations for the purpose of sustainable management should be based on whether the self-sustaining mechanism was reformed and whether the soil nutrient status was improved.

Biomass↗
PubMed2000

[Decomposition process of Chinese fir stump roots and changes of nutrient concentration].

With space as a substitute for time, the changes of the density of stump sapwoods and heartwoods, and the releasing process of major nutrients during the decomposition of Chinese fir stump roots were investigated. The yearly loss rate of the densities of sapwoods and heartwoods was 2.767 x 10(-2) and 2.255 x 10(-2) respectively during decomposition. The contents of N and P in sapwoods and roots decreased continually, while those in heartwoods increased during the first stage of decomposition, and then decreased. The K concentration in stump roots decreased remarkably during first two years, and the content of organic substances decreased during the whole decomposition process. The N, P and K concentrations in roots, were higher than those in stump sapwoods and heartwoods at the beginning of decomposition, but bet content of organic substance was opposite.

Abies↗
PubMed2000

[Species composition and distribution of algae in semi-desert algal crusts].

Twenty-two species of algae, including 10 Cyanophyta, 4 Chlorophyta, 6 Bacillariophyta and 2 Euglenophyta, were isolated and identified from the semi-desert algal crusts in Shapotou, Ningxia Autonomous Region. The relationship between algae and soil matrix was studied by grinding and superprobe, and the distribution of algal species in eight layers of crusts was examined under light and scanning electron microscopes. It was found that the algae exhibited a layer-typed distribution in intermicron, and the layers of algal crust from surface to inner were in order of inorganic mineral protection layer(ca. 0.02 mm), alga-enriched layer(0.02-2.5 mm) and sparse algae layer(2.5-5.0 mm). The filaments of algae were united with clay mineral by the polysaccharides and protein of their sheath, or extended directly into mineral granules to network and band sand and soil particles.

Climate↗
PubMed2000

[Dynamics of phenolics content of Chinese fir stump-roots and the rhizosphere soil and it's allelopathy].

Studies on the releasing pattern of phenolics during the decomposition of Chinese fir stump-root and on its allelopathy show that the phenolics contents in stump-roots decreased with their decomposition. Roots had a higher content of phenolics than heart stumps, and edge stumps had the least. The phenolics was released during decomposition, and accumulated in the soils around stump-roots. Pot culture experiment showed that phenolics affected the germination of Chinese fir seeds. The correlation analysis between the density of Chinese fir stump-root and the tree height and base diameter (BD) of its saplings proved that Chinese fir stump-roots had a negative impact on the growth of the next generation of Chinese fir plantations. It is suggested that the traditional operation of Chinese fir plantations should be reformed, and the stump-roots should be cleared from woodland before reforestation.

Phenols↗
PubMed2000

Adenovirus-mediated transfer of beta-galactosidase and prourokinase genes into vein grafts.

OBJECTIVE: To study the feasibility of adenovirus mediated gene transfer into vein grafts and the role of the prourokinase gene in protecting vein grafts from thrombosis. METHODS: Fifty-two Wistar rats underwent implantation of reversed autologous jugular vein interposition grafts in the common carotid arteries. Jugular veins were excised and distended with solution containing three different adenovirus vectors (Adv5-CMV, group I; Adv5-CMV/LacZ, group II; Adv5-CMV/Pro-UK, group III) for 30 min, then the jugular veins were reversed and interposed into the divided carotid arteries, and end-to-end anastomoses were performed. The amount of 51Cr-labeled platelets in vein grafts of group I and group III was counted 24 hours postoperatively. On the 14th day, the vein grafts were harvested to examine beta-galactosidase activity and prourokinase (Pro-UK) activity and observe thrombosis in vein grafts. RESULTS: Extensive blue coloration in the area of intima and media of each vein graft in group II was observed. No blue coloration was seen in group I. Pro-UK activity was not detected in the vein grafts of group I. In group III, the amount of Pro-UK gene expression was 308 IU/g tissue. The amount of 51 Cr labeled platelets in group I and group II was (123.7 +/- 19.4) x 10(6)/g dry wt, (34.4 +/- 5.3) x 10(6)/g dry wt, respectively. The thrombosis rate and occlusion rate of the vein grafts in group I were 30% and 10%, respectively. In group III, all vein grafts were patent and free of thrombosis. CONCLUSIONS: Ex vivo gene transfer before vein grafting is feasible using replication deficient recombinant adenovirus and results in a high level of gene expression in vivo. Direct transfer of the Pro-UK gene into vein grafts may prevent thrombosis.

Adenoviridae↗
PubMed2000

[Observation on dynamic changes of serum procollagen III, hyaluronic acid and laminin in rats with hepatic fibrosis treated with Hujin pill].

OBJECTIVE: To study the dynamic changes of serum procollagen III (PCIII), hyaluronic acid (HA) and laminin (LN) in rats with hepatic fibrosis treated with Hujin pill (HJP). METHODS: The classic model of hepatic fibrosis induced by CCl4 were used in the observation. The serum PCIII, HA and LN were determined by radioimmunoassay (RIA). RESULTS: HJP could reduce the serum HA, LN content significantly, as compared with the control group, the difference was significant (P < 0.05, P < 0.01). Its long-term therapeutic effect was better than that of colchicine. It could maintain the serum PCIII stable in hepato-fibrotic stage (9-12 weeks), as compared with the normal control group, the difference was insignificant (P > 0.05). CONCLUSION: HJP could retard the liver fibrosis, and has good preventive and therapeutic effect on liver fibrosis in rats.

Animals↗