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Biomedical subjects

D Fang

Publications and source records attributed to D Fang.

At least 19 recordsLinked to original sources
PubMed2005

Bioleaching of Cr from tannery sludge: the effects of initial acid addition and recycling of acidified bioleached sludge.

A technologically feasible process called bioleaching was used to remove Cr from tannery sludge with Acidithiobacilli TS6 bacteria in this study. The buffering capacity of tannery sludge and municipal sewage sludge were compared. The effects of initial sulfuric acid addition on bioleaching process and influences of recycle rate of acidified bioleached sludge on subsequent bioleaching reaction were examined. The quantities of initial sulfuric acid addition ranged from 0 to 0.185 ml g(-1) dry sludge. Recycle rate (V(beleached/V(total)) was controlled at 1/3, 1/2, 3/5 and 2/3. We found that tannery sludge had a higher buffering capacity than sewage sludge. The results showed that there was an increase in the rates of pH reduction and Cr solubilization with the increase of initial sulfuric acid addition. The suitable quantity of sulfuric acid addition was 0.185 ml g(-1) dry sludge at the beginning of the first bioleaching process. After 10 days of bioleaching, pH reached 1.5 and almost 100% of Cr could be leached in this case. Besides, an evidently dividing point pH 2.0 was found to be the threshold value for considerable Cr solubilization during the leaching reaction. Recycle experiments confirmed that the application of the method by recycling acidified sludge to launch subsequent bioleaching is feasible. The optimal recycle rate of acidified sludge for consecutive leaching of Cr from tannery sludge is 2/3.

Acidithiobacillus↗
PubMed2001

Cbl promotes ubiquitination of the T cell receptor zeta through an adaptor function of Zap-70.

Triggering of the T cell antigen receptor (TCR).CD3 complex induces its ubiquitination. However, the molecular events that lead to ubiquitin conjugation to these cell surface molecules have not been defined. Here we report that Cbl, a RING-type E3 ubiquitin-protein ligase, promotes ubiquitination of TCR zeta chain, which requires its functional variant Src homology 2 domain and an intact RING finger. The tyrosine kinase Zap-70, which binds to both TCR zeta and Cbl, plays an adaptor role in these events. Mutations in TCR zeta, Zap-70, or Cbl that disrupt the interaction between TCR zeta and Zap-70 or between Zap-70 and Cbl reduce ubiquitination of TCR zeta. Our results suggest a novel mechanism by which Cbl negatively regulates T cell development and activation by inducing ubiquitination of the TCR.CD3 components.

Cell Line↗
PubMed2001

DNA sequencing by capillary electrophoresis using mixtures of polyacrylamide and poly(N,N-dimethylacrylamide).

The possibility of using polymer mixtures with different chemical compositions as a DNA sequencing matrix by capillary electrophoresis (CE) has been exploited. Polyacrylamide (PAM, 2.5%, w/v) having a molecular mass of 2.2 x 10(6) has been mixed with poly(N,N-dimethylacrylamide) (PDMA) having molecular masses of 8000, 470000 and 2.1 x 10(6) at concentrations of 0.2, 0.5 and 1% (w/v). Unlike polymer mixtures of the same polymer with different molecular masses, the use of polymer mixtures with different chemical compositions encounters an incompatibility problem. It was found that the incompatibility increased with increasing PDMA molecular mass and PDMA concentration, which resulted in decreased efficiency in DNA sequencing. Also, the incompatibility had a more pronounced effect on the efficiency as the base number was increased. However, by choosing a low-molecular-mass PDMA of 8000 and a low concentration of 0.2% (w/v), the incompatibility of PAM and PDMA has been alleviated. At the same time, the advantage of using polymer mixtures revealed a higher efficiency for such a polymer mixture when compared with PAM. The mixture also endowed the separation medium with a dynamic coating ability. An efficiency of over 10 x 10(6) theoretical plates per meter has been achieved by using the bare capillaries without the additional chemical coating step.

Acrylamides↗
PubMed2001

DNA sequencing by capillary electrophoresis using copolymers of acrylamide and N,N-dimethylacrylamide.

Copolymers of acrylamide (AM) and N,N-dimethylacrylamide (DMA) with AM to DMA molar ratios of 3:1, 2:1 and 1:1 and molecular weights of about 2.2 MDa were synthesized. The polymers were tested as separation media in DNA sequencing analysis by capillary electrophoresis (CE). The dynamic coating ability of polydimethylacrylamide (PDMA) and the hydrophilicity of polyacrylamide (PAM) have been successfully combined in these random copolymers. A separation efficiency of over 10 million theoretical plates per meter has been reached by using the bare capillaries without the additional polymer coating step. Under optimized separation conditions for longer read length DNA sequencing, the separation ability of the copolymers decreased with decreasing AM to DMA molar ratio from 3:1, 2:1 and 1:1. In comparison with PAM, the copolymer with a 3:1 AM:DMA ratio showed a higher separation efficiency. By using a 2.5% w/v copolymer with 3:1 AM:DMA ratio, one base resolution of 0.55 up to 699 bases and 0.30 up to 963 bases have been achieved in about 80 min at ambient temperatures.

Acrylamides↗
PubMed2001

Fast DNA sequencing up to 1,000 bases by capillary electrophoresis using poly(N,N-dimethylacrylamide) as a separation medium.

Poly(N,N-dimethylacrylamide) (PDMA) with a molecular mass of 5.2 x 10(6) g/mol has been synthesized and used in DNA sequencing analysis by capillary electrophoresis (CE). A systematic investigation is presented on the effects of different separation conditions, such as injection amount, capillary inner diameter, polymer concentration, effective separation length, electric field and temperature, on the resolution. DNA sequencing up to 800 bases with a resolution (R) limit of 0.5 (and 1,000 bases with a resolution limit of 0.3) and a migration time of 96 min was achieved by using 2.5% w/v polymer, 150 V/cm separation electric field, and 60 cm effective separation length at room temperature on a DNA sample prepared with FAM-labeled--21M13 forward primer on pGEM3Zf(+) and terminated with ddCTP. Ultrafast and fast DNA sequencing up to 420 and 590 bases (R > or = 0.5) were also achieved by using 3% w/v polymer and 40 cm effective separation length with a separation electric field of 525 and 300 V/cm, and a migration time of 12.5 and 31.5 min, respectively. PDMA has low viscosity, long shelf life and dynamic coating ability to the glass surface. The unique properties of PDMA make it a very good candidate as a separation medium for large-scale DNA sequencing by capillary array electrophoresis (CAE).

Acrylamides↗
PubMed2001

Separation of double-stranded DNA fragments by capillary electrophoresis in interpenetrating networks of polyacrylamide and polyvinylpyrrolidone.

Mixtures of two polymers with totally different chemical structures, polyacrylamide and polyvinylpyrrolidone (PVP) have been successfully used for double-stranded DNA separation. By polymerization of acrylamide in a matrix of PVP solution, the incompatibility of these two polymers was suppressed. Laser light scattering (LLS) studies showed that highly entangled interpenetrating networks were formed in the solution. Further systematic investigation showed that double-stranded DNA separation was very good in these interpenetrating networks. With a concentration combination of as low as 2% w/v PVP (weight-average molecular mass Mr = 1 x 10(6) g/mol) + 1% w/v polyacrylamide (Mr = 4 x 10(5) g/mol), the 22 fragments in pBR322/HaeIII DNA, including the doublet of 123/124 bp, have been successfully separated within 6.5 min. Under the same separation conditions, similar resolution could only be achieved by using polyacrylamide (Mr = 4 x 10(5) g/mol) with concentrations higher than 6% w/v and could not be achieved by using only PVP (Mr = 1 x 10(6) g/mol) with a concentration as high as 15% w/v. It is noted that the interpenetrating network formed by 2% PVP and 1% polyacrylamide has a very low viscosity and can dynamically coat the inner wall of a fused-silica capillary. The separation reached an efficiency of more than 10(7) theoretical plate numbers/m and a reproducibility of less than 1% relative standard deviation of migration time in a total of seven runs. The interpenetrating network could stabilize polymer chain entanglements. Consequently, the separation speed was increased while retaining resolution.

Acrylic Resins↗
PubMed2001

Expression of microtubule-associated protein 2 in benign and malignant melanocytes: implications for differentiation and progression of cutaneous melanoma.

Cutaneous melanocytic neoplasms are known to acquire variable characteristics of neural crest differentiation. Melanocytic nevus cells in the dermis and desmoplastic melanomas often display characteristics of nerve sheath differentiation. The extent and nature of neuronal differentiation characteristics displayed by primary and metastatic melanoma cells are not well understood. Here, we describe induction of a juvenile isoform of microtubule-associated protein 2 (MAP-2c) in cultured metastatic melanoma cells by the differentiation inducer hexamethylene bisacetamide. Up-regulation of this MAP-2 isoform, a marker for immature neurons, is accompanied by extended dendritic morphology and down-regulation of tyrosinase-related protein 1 (TYRP1/gp75), a melanocyte differentiation marker. In a panel of cell lines that represent melanoma tumor progression, MAP-2c mRNA and the corresponding approximately 70-kd protein could be detected predominantly in primary melanomas. Immunohistochemical analysis of 61 benign and malignant melanocytic lesions showed abundant expression of MAP-2 protein in melanocytic nevi and in the in situ and invasive components of primary melanoma, but only focal heterogeneous expression in a few metastatic melanomas. In contrast, MAP-2-positive dermal nevus cells and the invasive cells of primary melanomas were TYRP1-negative. This reciprocal staining pattern in vivo is similar to the in vitro observation that induction of the neuronal marker MAP-2 in metastatic melanoma cells is accompanied by selective extinction of the melanocytic marker TYRP1. Our data show that neoplastic melanocytes, particularly at early stages, retain the plasticity to express the neuron-specific marker MAP-2. These observations are consistent with the premise that both benign and malignant melanocytes in the dermis can express markers of neuronal differentiation.

Acetamides↗
PubMed2001

Results of surgical resection of patients with primary lung cancer: a retrospective analysis of 1,905 cases.

BACKGROUND: Surgical resection, combined therapies, and lymphadenectomy are extensively utilized in the treatment of patients with lung cancer. In the present study, we summarized the clinical data of patients with primary lung cancer after surgical resection alone or combined with adjuvant therapy, and evaluate the main factors influencing long-term survival. METHODS: A retrospective review of 1,905 consecutive patients with primary lung cancer treated at the Cancer Institute of the Chinese Academy of Medical Sciences from March 1961 through December 1995 was performed. Statistical analysis was done using STATA software. The survival rate was estimated using the life-table method. Survival differences were performed using the log-rank test. The modified 1997 TNM staging system was used. RESULTS: There was a 12.28% morbidity rate and a 1.31% hospital mortality in our series. The 5-year survival rate for the complete resection was 49.5% and for the palliative resection 18.8% (p < 0.01). The 5-year survival rate was 72.0% in stage IA and 61.0% in stage IB (p < 0.05), 32.9% in stage IIA and 34.5% in stage IIB, 22.6% in stage IIIA and 15.9% in stage IIIB (p < 0.05), and 7.1% in stage IV. CONCLUSIONS: Multiple factors influence the long-term survival of patients with primary lung cancer after surgery. They include TNM staging, the extent of surgical resection (complete or palliative), resection margin (positive or negative), pathologic type of tumors, and type of resection.

Adult↗
PubMed2001

Regulation of tyrosinase-related protein-2 (TYRP2) in human melanocytes: relationship to growth and morphology.

Treatment of human melanoma cells with the differentiation-inducing agent hexamethylene bisacetamide (HMBA) results in reciprocal changes in expression of melanocyte-specific genes tyrosinase-related proteins-1 and -2 (TYRP1 and TYRP2). In this study, we investigated the effects of HMBA on cultured neonatal human cutaneous melanocytes. Flow cytometric analysis showed that HMBA inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-dependent growth of melanocytes by reducing the population of cells entering the DNA synthesis phase of cell cycle. Melanocyte growth inhibition was accompanied by an increase in the number of cells exhibiting polydendritic morphology. This morphologic change was less pronounced when HMBA was added to melanocytes in the absence of TPA. Northern blot analyses of total cellular RNA showed that expression of microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), TYRP1, Silver (SILV/Pmel17) gene was down-regulated by HMBA, while TYRP2 mRNA was up-regulated (> 10-fold). When the inducer was added to cells in the absence of TPA, there was > 50-fold increase in TYRP2 mRNA with a moderate increase in MITF, tyrosinase and SILV gene mRNAs and complete repression of TYRP1 gene. Studies using inhibitors for protein kinases involved in cell signaling pathways suggested that stress-activated kinase p38 and mitogen-activated protein kinase kinase MEK are involved in TPA-independent regulation of TYRP2 expression in melanocytes. These data show that treatment of proliferating melanocytes with the differentiation inducer HMBA results in a distinct change in morphology and up-regulation of TYRP2, while quiescent melanocytes respond by a dramatic increase in expression of TYRP2 without change in morphology. These results suggest an inverse relationship of TYRP2 gene regulatory mechanisms to melanocyte growth regulatory pathways.

Acetamides↗
PubMed2001

Proteolysis-independent regulation of PI3K by Cbl-b-mediated ubiquitination in T cells.

Cbl-b, a ring-type E3 ubiquitin protein ligase, is implicated in setting the threshold of T lymphocyte activation. The p85 regulatory subunit of phosphatidylinositol 3 kinase (PI3K) was identified as a substrate for Cbl-b. We have shown that Cbl-b negatively regulated p85 in a proteolysis-independent manner. Cbl-b is involved in the recruitment of p85 to CD28 and T cell antigen receptor zeta through its E3 ubiquitin ligase activity. The enhanced activation of Cbl-b(-/-) T cells was suppressed by the inhibition of PI3K. The results suggest a proteolysis-independent function for Cbl-b in the modification of protein recruitment.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Prostate-specific antigen, testosterone, sex-hormone binding globulin and androgen receptor CAG repeat polymorphisms in subfertile and normal men.

The aim of this study was to understand the androgen-related factors which may regulate concentrations of the tumour marker, prostate-specific antigen (PSA). We therefore measured the serum concentrations of total and free testosterone and of sex hormone-binding globulin (SHBG) and determined the androgen receptor (AR) gene CAG repeat length, then compared these values to total and free PSA concentrations in 91 subjects with proven fertility, and 112 subfertile men with defective spermatogenesis. Concentrations of free testosterone and total testosterone, adjusted for SHBG, were 17-20% lower in subfertile men compared with those in their fertile counterparts. This subtle, but highly significant (P < 0.001), difference in testosterone between fertile and subfertile men was accentuated by the positive correlation between testosterone and AR gene CAG repeat length in fertile, but not subfertile, subjects. In subfertile subjects, testosterone strongly correlated (r = 0.354, P < 0.001) with PSA concentrations, and independent of testosterone, total PSA negatively correlated (r = -0.229, P = 0.011) with AR CAG length. Overall our data suggest that, firstly, PSA correlates with testosterone only in an environment of relatively low androgenicity, such as in subfertile men. Secondly, in such a low androgenic environment, short CAG tracts (associated with high AR activity) correlate positively with PSA concentrations. These results suggest that interpretation of PSA is best made in conjunction with testosterone concentrations and AR CAG length.

Adult↗
PubMed2001

[HCV core protein activates expression of vascular endothelial growth factor in HepG(2) cells].

OBJECTIVE: To explore the effect of HCV core protein on vascular endothelial growth factor (VEGF) in HepG(2) cells. METHODS: The HCV core gene cDNA was recoverd by PCR, and cloned into PBK-CMV. The recombinant plasmid (PBK-HCVc) and the vector-alone were transfected into HepG(2) cells with liposome. After being selected with G418,resistant colonies were obtained. The reverse transcription PCR and Western blot was analyzed to show HCV core protein expression. VEGF was analyzed by immunohistochemical and Western blot; VEGF mRNA was analyzed by in situ hybridization and reverse transcription PCR. RESULTS: The results suggest that the recombinant plasmid could express HCV core protein efficiently under the control of vector's promoter. The VEGF of HepG(2)-C cells was higher than that of HepG(2)-CMV. CONCLUSIONS: HCV C protein can activates the expression of VEGF in HepG(2) cells and may contributes to viral carcinogenesis.

Endothelial Growth Factors↗
PubMed2001

[Establishment and implication of an assay for high density lipoprotein phospholipids in human serum].

OBJECTIVE: To develop an assay for high density lipoprotein phospholipids in human serum based on ascorbutate reduction method. METHODS: HDLs were separated from apolipoprotein B-containing lipoproteins by precipitation of phosphotungstic acid and magnesium chloride. Phospholipids of HDL were extracted by ethanol/ether, and dried. After the dried phospholipids were digested by sulphuric acid and perchloric acid, the color was developed by adding ammonium molybdate in ascorbutate. The levels of high density lipoprotein phospholipids (HDL-PL) were measured by spectrophotometry at 700 nm. RESULTS: The coefficients of variation (CV) were 3.6% and 3.7% within two batches of assays. Recovery of isolated HDL-PL added to serum ranged from 98% to 107%, averagely 103%. The established assay for human serum HDL-PL was used to measure the serum levels of 30 hypercholesterolemic subjects, 30 hypertriglyceridemic subjects, 30 combined hyperlipidemic subjects, and 30 normolipidemic subjects. The hypertriglyceridemic subjects had lower HDL-PL level than normolipidemic subjects and hypercholesterolemic subjects (The P values are 0.005 and 0.007 respectively). CONCLUSION: A simple and specific method for assay of HDL-phos-pholipids in human serum has been developed. The above data collected by the use of this method demonstrate the closer relationship between human HDL-PL metabolism and triglyceride metabolism, suggesting that lower HDL-PL level might serve as an index in the assay for type IV hyperlipidemia.

Humans↗
PubMed2001

[Color reaction of chromogenic reagent O-hydroxybenzenediazoaminoazobenzene with thallium (III) and its application].

The chromogenic reaction of the O-hydroxybenzenediazoaminoazobenzene (O-HDAA) with thallium was studied in this paper. In the presence of Triton X-100 and SDBS and in ammonia medium of 0.54-1.1 mol.L-1, O-HDAA reacts with thallium (III) to form a stable red complex with molar radio of 1:5. The apparent molar absorptivity is 1.4 x 10(5) L.mol-1.cm-1 at the maximum absorption wavelength of 520 nm. Beer's law is obeyed in the concentration range of 0-600 micrograms.L-1 Tl(III). The method has been applied to the direct determination of trace amounts of thallium in waste water and in geological samples by using polyurethane foam to absorb and separate Tl(III) with satisfactory results.

Color↗
PubMed2000

Expression and Up-regulation of alternatively spliced transcripts of melastatin, a melanoma metastasis-related gene, in human melanoma cells.

Loss of expression of a novel suppressor of metastasis, melastatin (MLSN1), has recently been reported to correlate with metastatic potential of melanoma cells. Using differential display analysis, we identified MLSN1 among genes overexpressed in pigmented metastatic human melanoma cells treated with the differentiation inducer hexamethylene bisacetamide (HMBA). In this study, we show that multiple short transcripts of MLSN1 are present in melanocytes and pigmented metastatic melanoma cell lines while the full-length 5. 4-kb mRNA is detectable only in melanocytes. Treatment of pigmented melanoma cells with the differentiation-inducing agent, HMBA, results in up-regulation of the 5.4-kb MLSN1 mRNA as well as short RNAs. Analysis of a panel of nonpigmented primary and metastatic melanoma cell lines showed weak expression of a 1.8-kb mRNA in a few melanoma cell lines. Northern blot and RT-PCR analyses with DNA probes and oligonucleotide primers that correspond to distinct regions of full-length MLSN1 mRNA indicated that the short transcripts contained sequences corresponding primarily to either 5'- or 3'-end of the 5.4-kb mRNA. HMBA appears to up-regulate MLSN1 transcripts derived mainly from the 5'-end. Modulators of cAMP and protein kinase C pathways had no significant effect on MLSN1 expression. Our data show that multiple MLSN1 transcripts, both constitutively expressed and inducible, are present in cultured pigmented melanoma cells, and suggest that MLSN1 expression can be regulated at the level of both transcription and mRNA processing.

Alternative Splicing↗
PubMed2000

Cbl-b, a RING-type E3 ubiquitin ligase, targets phosphatidylinositol 3-kinase for ubiquitination in T cells.

Cbl-b is implicated in setting the threshold of T lymphocyte activation. In Cbl-b-deficient T cells, the activation of Vav, a guanine nucleotide exchange factor, is significantly enhanced. The molecular mechanism underlying Cbl-b-regulated Vav activation was unclear. Here it is shown that Cbl-b interacts with and induces ubiquitin conjugation to the p85 regulatory subunit of phosphatidylinositol 3-kinase, an upstream regulator of Vav. A functional RING finger of Cbl-b was essential for p85 ubiquitination. However, a loss of function mutation at the well-conserved amino-terminal variant src homology (SH) 2 domain of Cbl-b did not affect its ligase activity. A distal carboxyl-terminal proline-rich region in Cbl-b was mapped to contain the primary binding sequences for the SH3 domain of p85. Deletion of either the distal proline-rich region in Cbl-b or the SH3 domain of p85 severely reduced ubiquitin conjugation to p85. The data suggest a molecular link for Cbl-b-mediated negative regulation of Vav, with phosphatidylinositol 3-kinase as a direct target for Cbl-b E3 ubiquitin ligase.

Adaptor Proteins, Signal Transducing↗