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Biomedical subjects

N Zhang

Publications and source records attributed to N Zhang.

At least 163 records · Page 9Linked to original sources
PubMed1997

Electrochemical and histomorphometric evaluation of the TiNiCu shape memory alloy.

By means of electrochemical and quantitative histomorphometric methods, the corrosion resistance and tissue biocompatibility of Ti50Ni50 and Ti50Ni50-xCux (x = 1, 2, 4, 6, 8) were investigated. It is discovered that the repassivation potential of Ti50Ni50-xCux (x = 2, 4, 6, 8) alloys is about 200 mV higher than that of Ti50Ni50 alloy. Namely, the addition of Cu raises the repassivation potential of TiNi shape memory alloys and improves their corrosion resistance. Pitting potentials of Ti50Ni50 and Ti50Ni50-xCux (x = 1, 2, 4, 6, 8) alloys increase with solution pH value, but the repassivation potentials keep constant. The adding of Cu has no obvious influence on pitting potential (Epit) of TiNi alloys, meanwhile, the corrosion potential and corrosion rate of Ti50Ni50-xCux (x = 1, 2, 4, 6, 8) alloys are irrelevant to its Cu content and the values are almost the same as those of TiNi alloys. The connective tissue layer covering the plates is statistically significantly thicker for Ti50Ni42Cu8 plates (p < 0.05) than that of Ti50Ni50, Ti50Ni48Cu2, Ti50Ni44Cu6 plates after one month. The numbers of connective tissue cells, polynucleated cells, macrophages and round cells are higher for Ti50Ni42Cu8 plates than those of the other three types of plates, but no statistically significant differences are detected. There are no significant differences on tissue reaction parameters after two and three months among four alloys. After one, two and three months implantation, no corrosion is observed on the plates surfaces. A preliminary conclusion can be drawn that Ti50Ni50-xCux (x = 2, 6, 8) shape memory alloys have good biocompatibility.

Alloys↗
PubMed1997

[Malignant changes in laryngeal papilloma with 13 case reports].

The 13 cases of malignant changes in 43 cases of laryngeal papilloma are reported. The rate of malignant change was 30. 2%. Laryngeal papilloma with epithelial atypia has proclaimed the onset of carcinoma. Therefore, high attention should be paid on its treatment. The safe margin on the operation of the malignant change case should be kept above 0.5 cm and radiation should be followed after the operation. It was invalid by using only radiation treatment. The pathogenesis and diagnosis of malignant change in laryngeal papillomas were also discussed in this article.

Adult↗
PubMed1996

Retrovirus-mediated gene expression in hematopoietic cells correlates inversely with growth factor stimulation.

Cells of the hematopoetic system, especially hematopoietic progenitor and stem cells, are perceived as ideal targets for human gene therapy. In this report, the stability of retrovirus-mediated gene expression driven by three different potent promoters has been examined in purified human CD34+ cells. The promoters, murine stem cell virus (MSCV) long terminal repeat (LTR) and pgk, show gene expression in 10 times more hematopoietic colonies derived from CD34+ cells than the commonly used Moloney murine leukemia virus (Mo-MLV) LTR. Quantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis, however, demonstrates that the levels of gene expression in retrovirus-transduced cells decrease with time in long-term bone marrow cultures and in suspension cultures containing hematopoietic growth factors. Removal of hematopoietic growth factors from the suspension culture medium was associated with a decrease in cell proliferation and differentiation, but with stable gene expression. Retrovirus-mediated gene expression is, therefore, inversely related to proliferation and differentiation of the transduced CD34+ cells. These observations may have implications in future design and implementation of human gene therapy protocols.

Animals↗
PubMed1996

Three distinct domains in the HOX-11 homeobox oncoprotein are required for optimal transactivation.

HOX-11 (tcl-3) is a homeobox oncogene isolated from the breakpoint region of the t(10;14) chromosomal translocation recurring in T-cell acute lymphoblastic leukemia. Here we demonstrate that the HOX-11 homeoprotein mediates transactivation of reporter genes through various promoters in both mammalian and yeast cells. By deletion analysis, the transactivation domains of HOX-11 have been mapped to three amino acid stretches in the homeoprotein, the glycine-proline-rich region at the amino terminus, the homeodomain and the glutamine-rich region at the carboxyl terminus. The three distinct functional domains of HOX-11 act in concert for optimal transactivation. In addition, the homeodomain of HOX-11 appears to be differentially utilized in a promoter-dependent manner. Our data support the notion that the HOX-11 homeoprotein functions as an oncogenic transcription activator in leukemogenesis.

3T3 Cells↗
PubMed1996

Genetic typing by capillary electrophoresis with the allelic ladder as an absolute standard.

We demonstrate a genetic typing method based on capillary electrophoresis/laser-induced fluorescence (CE-LIF). VNTR polymorphism in the human D1S80 locus was studied. A pooled allelic ladder, which contains the 27 most common human alleles, was used as the absolute standard. Extracted genomic DNA from an individual was amplified by polymerase chain reaction (PCR). Typing can be accomplished by co-injection of the PCR product and the D1S80 ladder and then running CE. Separation by a polymer solution of poly(ethylene oxide) in uncoated fused-silica capillaries allows high-resolution, repeated runs in the same capillary. Sensitive detection with minimal sample preparation is possible by using ethidium bromide as the intercalating dye. Statistical analysis of the data indicates a high level of confidence in matching the bands despite variations in the injection process or in the CE system. Future adaptation to a multiple-capillary array system should allow high-speed, high-throughput operation.

Alleles↗
PubMed1996

Induction of p53 and increased sensitivity to cisplatin in ataxia-telangiectasia cells.

Several reports have demonstrated a defective p53 response to ionizing radiation exposure in ataxia-telangiectasia (A-T) cells. On the other hand, p53 induction was normal after u.v. irradiation, an agent to which A-T cells are not hypersensitive. We show here that A-T cells are more sensitive than normal lymphoblastoid cells to cisplatin treatment but the rate of induction of p53 by cisplatin is similar in both cell types. In addition, the half-life of p53, both in the induced and uninduced forms, is the same in A-T and normal lymphoblastoid cells. The use of a reporter assay to determine the functional status of p53 confirmed the results obtained in the induction experiments with cisplatin. These results demonstrate that p53 induction status in A-T cells does not correlate with sensitivity to the inducting agent and there is no inherent defect in the turn-over of p53 in the induced or uninduced states in A-T.

Animals↗
PubMed1996

Characterization of the 5' flanking region of the human MnSOD gene.

Human manganese-containing superoxide dismutase (MnSOD) is a nuclear encoded mitochondrial protein that scavenges potentially toxic superoxide radicals by dismuting O2- to O2 plus H2O2. To understand the molecular mechanism governing the transcriptional regulation of the human MnSOD gene, I have isolated and sequenced a genomic clone containing the 5' flanking region of the human MnSOD gene. One major transcription start site was mapped by primer extension to a guanine residue 67 base pairs upstream from the translation start site. Eight putative Sp1 binding elements and one AP1 consensus sequence, but no TATA or CAAT box, were found in the promoter region. Furthermore, a series of chimerical/CAT reporter gene constructs were used to transfect human hepatocellular carcinoma(HepG2) human neuroblastoma and human skin fibroblast cell lines to characterize the promoter and regulatory region of the human MnSOD gene. The results show that human MnSOD gene expression is governed by one promoter and that the basic promoter is located between nucleotides -34 and +38. The results also indicate that both positive and negative elements are involved in the regulation of the cell-type specific expression of the human MnSOD gene. The functional studies indicate that the Sp1 binding sites or G+C rich regions play an important role in regulation of expression of the human MnSOD gene in vivo.

Animals↗
PubMed1996

Purification and partial characterization of a 31-kDa cysteine endopeptidase from germinated barley.

Proteolytic enzymes hydrolyze cereal seed storage proteins into small peptides and amino acids, which are very important for seed germination and the malting process. A cysteine-class endopeptidase was purified from 4-d-germinated barley (Hordeum vulgare L. cv. Morex). Four purification steps were used, carboxymethyl cellulose cation-exchange chromatography, chromatofocusing, size-exclusion chromatography, and electroelution from a polyacrylamide gel. The endopeptidase was most active at pH 4.5. It's isoelectric point (pI) was 4.4, as determined by isoelectric focusing, and it's SDS-PAGE molecular size was 31 kDa. The enzyme specifically hydrolyzed peptide bonds when the S2 site contained relatively large hydrophobic amino acids. The N-terminal amino acid sequence residues (1-9) of the 31-kDa endopeptidase had high homology to those of the EP-A and EP-B cysteine proteinases reported previously. The 31-kDa endopeptidase had a hydrolytic specificity similar to that of the Morex green malt 30-kDa endopeptidase we characterized previously, and also reacted with the antibody raised against the purified 30-kDa proteinase, but the two had different mobilities on non-denaturing PAGE. The hydrolytic specificities of both 30- and 31-kDa endopeptidases are such that both would very quickly cleave hordein (barley storage) proteins to small glutamine- and proline-rich peptides that could be quickly degraded to amino acids by barley exopeptidases.

Antimicrobial Cationic Peptides↗
PubMed1996

Identification and genetic analysis of wunen, a gene guiding Drosophila melanogaster germ cell migration.

We describe a novel genetic locus, wunen (wun), required for guidance of germ cell migration in early Drosophila development. Loss of wun function does not abolish movement but disrupts the orientation of the motion causing the germ cells to disperse even though their normal target, the somatic gonad, is well formed. We demonstrate that the product of this gene enables a signal to pass from the soma to the germ line and propose that the function of this signal is to selectively stabilize certain cytoplasmic extensions resulting in oriented movement. To characterize this guidance factor, we have mapped wun to within 100 kb of cloned DNA.

Alleles↗
PubMed1996

Two new saponins, congmuyenosides A and B, from the leaves of Aralia elata collected in Heilongjiang, China.

Two new triterpenoidal saponins, congmuyenosides A and B, were isolated from the leaves of Aralia elata collected in Heilongjiang Province, China, and established as 3-O-[beta-D-glucopyranosyl(1-->2)][beta-D-glucopyranosyl-(1-->3)]- beta-D-glucopyranosyl hederagenin and 3-O-[beta-D-glucopyranosyl(1-->2))] [beta-D-glucopyranosyl(1-->3)-beta-D-glucopyranosyl(1-->3 )]-beta-D-glucopyranosyl hederagenin, respectively, on the basis of chemical and spectral evidence.

Carbohydrate Sequence↗
PubMed1996

[Correlation analysis of the changes of EEG mapping and the changes of CT scan in patients with senile dementia].

OBJECTIVE: To observe the changes of EEG mapping and CT scan and analyse the correlation between the changes of the function presented by EEG mapping and morphology presented by CT. METHODS: The absolute power of EEG mapping and 9 parameters of CT in 30 normal controls and 31 patients with senile dementia were measured. The correlation was analysed quantitatively with multiple stepwise regression method. RESULTS: The EEG mapping of senile dementia revealed a diffuse increase in delta, theta power and decreased alpha power in most areas. CT scan showed cortical and subcortical atrophy in brain. There were positive correlations between the increase of delta power and lateral fissure, and between the increase of delta power and average cerebral sulcus. There was a negative correlation between the decrease of alpha power and the increase of lateral fissure. CONCLUSION: The EEG mapping and CT in patients with senile dementia are different from those in normal elderly. There is a correlation between the changes of EEG mapping and CT scan.

Aged↗
PubMed1996

Microrough surface of metallic biomaterials: a literature review.

In this paper, four aspects of microrough surface of metallic biomaterials are reviewed: i.e., the preparation of microrough surface, the technology of surface roughness measurement, the parameters of roughness and the bio-effect of microrough surface. Microrough surfaces (roughness below 50 microns) are easily prepared and conveniently detected in practice. Microrough surfaces allow early better adhesion of mineral ions or atoms, biomolecules, and cells, form firmer fixation of bone or connective tissue, result in thinner tissue-reaction-layer with inflammatory cells decreased or absent, and prevent microorganism adhesion and plaque accumulation, when compared with the smooth surfaces.

Biocompatible Materials↗
PubMed1996

[The effects of a single active ingredient (T4) of Tripterygium Wilfordii Hook on the production of tumor necrosis factor by the peripheral blood mononuclear cells and synovium cells of rheumatoid arthritis patients].

Encouraged by good therapeutic results of the semipurified preparations of Tripterygium Wilfordii Hook (TWH) (code name T4) a single-active ingredient of TWH with the code name of T4 was obtained. The in vitro effects of T4 on the bioactivity of TNF produced by PBMC of normal subjects (n = 10) and RA patients (n = 6) or the RA digested synovium single cells (DSSC) were studied. The results showed that under pretreatment of PBMC of healthy persons with T4 (35 ng/ml) for two hours, TNF were reduced to 36.13 +/- 1.75% in comparison with the control of 63.33 +/- 2.51% (P < 0.001), with an inhibition rate of 40.31%. Similarly, the inhibition rate for the PBMC of RA patients (P < 0.001), was 25.54%. The fact that coculture of PBMC and T4 for 6 hours instead of treatment with T4 for 2 hours caused an inhibition rate of 40.51% (P < 0.01), might indicate that time of interaction was also a factor of importance. T4 also reduced TNF secretion by RA-DSSC from 72.1 +/- 6.1% to 51.6 +/- 2.0% with an inhibition rate of 28.4%. The aformentioned indicates that T4 appears to possess suppressive actions on production of TNF by PBMC and DSSC of RA patients. Therefore, it is possible that T4 may be used clinically for RA patients.

Adult↗
PubMed1996

[Loss of alveolar attachments in smoker's lungs and its relation to small airway abnormalities].

The alveolar attachments and small airway abnormalities in the lungs of smokers were measured by computerized imaging to study the relationship between loss of alveolar attachments and small airway abnormalities, the smoker's lungs were divided into three groups: no emphysema (NE), centrilobular emphysema (CLE) and panlobular emphysema (PLE). The distance between normal alveolar attachments (Distance) and percent abnormal alveolar attachments (% Abnormal) in CLE were significantly higher than in NE (P < 0.05 and P < 0.01), and no significant difference in the number of normal alveolar attachments in the 3 groups. The small airway wall area (WA) and deformity index (DI) in CLE differed significantly from MA and DI in NE (P < 0.05 for all). There were no differences between PLE and NE in these indices. Distance and % Abnormal correlated significantly with WA and DI, but the correlations were shown only in CLE. We concluded that alveolar attachment destruction in smoker's lungs was closely associated with small airway abnormalities, which indicated the different patterns of emphysema, CLE and PLE, probably have different pathogenesis respectively.

Adult↗
PubMed1996

[Replantation of 45 digits in 26 children: a long-term follow-up].

Twenty eight children with 47 amputated digits were replanted by the authors from 1978 to 1985. Among them 18 cases with 37 replanted digits was from 1 to 4 years old. The average age was 4.3 yrs. Forty six digits were salvaged, with survival rate of 97.8%. Twenty-six cases with 45 replanted digits have been examined from 9 to 15 years postoperatively. The follow-up rate was 92.8%. The hand functions assessed by criteriae of nakamura and tamai were excellent in 24 and good in 2 with out fair or poor grade. The two-point discrimination discrimination distance between 2-4 mm was 85%, The long term cosmetic appearance were good. The pulps of fingers were full and had rich blood supply. The satisfactory rate amounted to 96%. The excellent result obtained was due to strict adherence to the rules for replantation in childed cases: precise repair of all kinds of tissues and strict operative skill. The bone should be shortened less than 5 mm only. The follow-up X ray films taken from 9 to 15 years postoperatively showed the average shortening of the operated hand was 4 mm in comparison with the contralateral side. The lengths of the replanted phalanges were 3.8 mm shorter than the contralateral one. It means the absolute shortening during operation has no change while the lengths of the hand have some compensation in the process of growth. Those digits amputated at the interphalangeal joints had an average shortening of total hand length of 10.2 mm. Most joints were fused. The fact demonstrate that in joint amputation case the articular surface of proximal phalanx can be shortened while the distal articular joint surface should be preserved for preservation of epiphysis.

Amputation, Traumatic↗
PubMed1995

Tyrosine phosphorylation is required for up-regulation of the HOX-11 (TCL-3) homeobox proto-oncogene in T cells.

HOX-11 (TCL-3) is a homeobox proto-oncogene isolated from the breakpoint region of the t(10;14) chromosomal translocation associated with pediatric T-cell acute leukemia. To better understand the transcriptional regulation of the HOX-11 gene in response to extracellular signals, the levels of HOX-11 RNA were examined in normal and leukemic human T cells upon phytohemagglutinin and hematopoietic growth factor stimulation. While individual hematopoietic growth factors tested did not show any effect on HOX-11 gene expression, a drastic increase in HOX-11 RNA was observed under the induction of phytohemagglutinin. In the presence of cycloheximide, a protein synthesis inhibitor, phytohemagglutinin-induced HOX-11 up-regulation was suppressed, indicating that HOX-11 acts as a delayed early response gene which requires protein synthesis. The HOX-11 gene expression was also suppressed by the tyrosine kinase inhibitors tryphostin and lavendustin A. Our data therefore suggest that the delayed early response of HOX-11 up-regulation in T cells requires a tyrosine phosphorylation signal.

Base Sequence↗
PubMed1995

Preparation of antisera to recombinant, soluble N-acetylglucosaminyltransferase V and its visualization in situ.

N-Acetylglucosaminyltransferase V (GlcNAc-T V) is a glycosyltransferase which transfers N-acetylglucosamine in beta(1,6) linkage to the alpha(1,6)-linked mannose residue of Asn-linked oligosaccharides. This enzyme is characterized by several unusual properties: GlcNAc-T V is the largest lumenal Golgi glycosyltransferase described thus far, and its multiple mRNA transcripts range from 4.5 to about 9.5 kb; GlcNAc-T V mRNA and activity are regulated by the src tyrosine kinase signalling pathway; in brain tissue, large levels of GlcNAc-T V mRNA are present, but only relatively low levels of catalytic activity can be detected; a lectin-resistant cell line, Lec4A, expresses active GlcNAc-T V which is mislocalized intracellularly. In addition, the cell surface oligosaccharide products of this enzyme have been hypothesized to regulate intercellular adhesion. In order to devise specific inhibitors of this enzyme it is necessary to understand its physical structure and how structural changes can influence its activity and localization. We have expressed milligram amounts of a soluble form of recombinant rat GlcNAc-T V, purified it from CHO cell-conditioned media, and used it to prepare specific antisera. This antisera binds selectively to GlcNAc-T V and has been used to visualize B-16 mouse melanoma cell GlcNAc-T V on immunoblots after SDS-PAGE. When the antisera was used in immunofluorescence microscopy experiments on permeabilized B-16 and baby hamster kidney cells, intense, specific staining was observed in intracellular structures which appear to correspond to the Golgi apparatus.

Animals↗