Biomedical subjects

Fan Zhang

Publications and source records attributed to Fan Zhang.

At least 145 records · Page 8Linked to original sources

PubMed2003

A 12-week, double-blind comparison of olanzapine vs haloperidol in the treatment of acute mania.

BACKGROUND: This randomized controlled trial compares the efficacy and safety of olanzapine vs haloperidol, as well as the quality of life of patients taking these drugs, in patients with bipolar mania. METHODS: The design consisted of 2 successive, 6-week, double-blind periods and compared flexible dosing of olanzapine (5-20 mg/d, n = 234) with haloperidol (3-15 mg/d, n = 219). RESULTS: Rates of remission (Young-Mania Rating Scale score of < or =12 and 21-item Hamilton Rating Scale for Depression score of < or =8 at week 6) were similar for olanzapine- and haloperidol-treated patients (52.1% vs 46.1%, respectively; P =.15). For the subgroup of patients whose index episode did not include psychotic features, rates of remission were significantly greater for the olanzapine group compared with the haloperidol group (56.7% vs 41.6%, P =.04). Relapse into an affective episode (mania and/or depression) occurred in 13.1% and 14.8% of olanzapine- and haloperidol-treated patients, respectively (P =.56). Switch to depression occurred significantly more rapidly with haloperidol than with olanzapine when using survival analysis techniques (P =.04), and significantly more haloperidol-treated patients experienced worsening of extrapyramidal symptoms, as indicated by several measures. Weight gain was significantly greater in the olanzapine group compared with the haloperidol group (2.82 vs 0.02 kg, P<.001). The olanzapine group had significant improvement in quality of life on several dimensions compared with the haloperidol group. CONCLUSIONS: These data suggest that olanzapine does not differ from haloperidol in achieving overall remission of bipolar mania. However, haloperidol carries a higher rate of extrapyramidal symptoms, whereas olanzapine is associated with weight gain.

Acute Disease↗

PubMed2003

Change in pH-dependent membrane insertion characteristics of trichosanthin caused by deletion of its last seven C-terminal amino acid residues.

Trichosanthin (TCS) is a type I ribosome-inactivating protein (RIP) that can selectively kill some types of cells at low concentration (0.1-1 nM). The pH-dependent membrane insertion ability of TCS makes it possible that the internalized toxin avoids degradation in lysosomes and further undergoes transportation into the cytosol by some still unidentified mechanism. Here, we show that deletion of C-terminal residues affects interactions of modified TCS (C7-TCS) with lipids and reduces its pH-dependent membrane insertion ability. Fluorescence measurements indicate that at low pH C7-TCS undergoes profound conformational changes that causes exposure of a hydrophobic region and leads to oligomerization of the C7-TCS molecules. The results suggest that the membrane insertion of TCS at low pH might be important for translocation of TCS into the cytosol, which is important for exertion of the RIP activity of TCS. Deletion of the last seven C-terminal residues of TCS would reduce both its RIP activity in vitro and cytotoxicity in vivo, with the degree of decrease being more significant for the cytotoxicity in vivo.

Amino Acid Sequence↗

PubMed2003

Distribution and characterization of over 1000 T-DNA tags in rice genome.

We generated T-DNA insertions throughout the rice genome for saturation mutagenesis. More than 1,000 flanking sequences were mapped on 12 rice chromosomes. Our results showed that T-DNA tags were not randomly spread on rice chromosomes and were preferentially inserted in gene-rich regions. Few insertions (2.4%) were found in repetitive regions. T-DNA insertions in genic (58.1%) and intergenic regions (41.9%) showed a good correlation with the predicted size distribution of these sequences in the rice genome. Whereas, obvious biases were found for the insertions in the 5'- and 3'-regulatory regions outside the coding regions both at 500-bp size and in introns rather than in exons. Such distribution patterns and biases for T-DNA integration in rice are similar to that of the previous report in Arabidopsis, which may result from T-DNA integration mechanism itself. Rice will require approximately the same number of T-DNA insertions for saturation mutagenesis as will Arabidopsis. A database of the T-DNA insertion sites in rice is publicly available at our web site (http://www.genomics.zju.edu.cn/ricetdna).

DNA, Bacterial↗

PubMed2003

Trichosanthin induces leakage and membrane fusion of liposome.

Trichosanthin (TCS) is a ribosome inactivating protein with multiple pharmacological properties. Here the interaction between TCS and a phospholipid bilayer is investigated to provide evidence for membrane translocation mechanism of TCS. The results show that TCS can destabilize liposomes made by phospholipids with negatively charged head group. The destabilization effect is pH-dependent and happens only under acidic conditions. Membrane fusion is also seen to accompany the destabilizing process. The interaction between a phospholipid bilayer and C7, a mutant of TCS with 7 residues at its C-terminus deleted, has been investigated. Deleting the C-terminus almost completely abolishes the destabilizing effect of TCS on the phospholipid bilayer, which implicates the C-terminus in the interaction between trichosanthin and the membrane.

Amino Acid Sequence↗

PubMed2003

Nitric oxide synthesis influences the renal vascular response to heme oxygenase inhibition.

We studied the effects of the heme oxygenase (HO) inhibitor stannous mesoporphyrin (SnMP; 40 micromol/kg i.v.) on renal hemodynamics in anesthetized rats with and without 48-h pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthesis. SnMP decreased renal blood flow (RBF) and increased renal vascular resistance (RVR) in both groups. The SnMP-induced reduction of RBF in L-NAME-pretreated rats was more prominent than in rats without pretreatment (43 +/- 7 vs. 13 +/- 3%) as was the SnMP-induced elevation of RVR (87 +/- 31 vs. 14 +/- 5%). The renal vasoconstrictor effect of SnMP is linked, in part, to amplification of prevailing neurohormonal constrictor mechanisms, since in L-NAME-pretreated rats it was prevented by concurrent administration of prazosin or losartan. However, SnMP (15 micromol/l) also elicits vasoconstriction in isolated, pressurized renal interlobular arteries and the response is more intense in vessels obtained from L-NAME-pretreated rats than from rats without pretreatment. These data indicate that the status of NO synthesis conditions the vascular response to HO inhibition in the rat kidney.

Animals↗

PubMed2003

The overexpression of cyclo-oxygenase-2 in chronic periodontitis.

BACKGROUND: The objective of this prospective cross-sectional study was to determine if cyclo-oxygenase-2, or COX-2, is overexpressed in the inflamed gingival tissue of patients diagnosed as having moderate-to-severe chronic periodontitis, or CP. METHODS: The authors evaluated clinical measures, crevicular fluid and gingival biopsy specimens from patients with moderate or severe CP (n = 16) and from healthy volunteers (n = 8). Patients were diagnosed as having CP based on clinical attachment loss, or CAL, of at least 5 millimeters at two sites in each quadrant and on evidence of alveolar bone loss as assessed from standard periapical or bite-wing radiographs. Healthy patients exhibited no sites with CAL of more than 2 mm and no evidence of alveolar bone loss. The authors used standard techniques to perform biochemical measures. RESULTS: Levels of interleukin-1 beta, or IL-1beta, in crevicular fluid were more than doubled in the CP group (P < .05). The amounts of COX-2 mRNA and protein also were elevated in gingival tissues from subjects with CP compared with those from healthy subjects. To gain further mechanistic insights, the authors conducted in vitro studies. The results showed that lipopolysaccharide and tumor necrosis factor alpha, or TNF-alpha, induced COX-2 in macrophages, while IL-1beta and TNF-alpha induced COX-2 in oral epithelial cells. CONCLUSIONS: Taken together, these results suggest that levels of COX-2 in gingivae reflect clinical measures of periodontitis and gingival inflammation. CLINICAL IMPLICATIONS: The discovery of increased levels of COX-2 in inflamed gingival tissue suggests that COX-2 represents a pharmacological target for the prevention or treatment of CP.

Adult↗

PubMed2003

Comparison of risperidone and olanzapine in the control of negative symptoms of chronic schizophrenia and related psychotic disorders in patients aged 50 to 65 years.

BACKGROUND: This analysis compares the efficacy of risperidone and olanzapine in controlling negative and positive symptoms of chronic psychosis in older patients. METHOD: Post hoc assessments were made in a subset of risperidone-treated (N = 19) and olanzapine-treated (N = 20) older patients (aged 50 to 65 years) from a large international, multicenter, parallel, double-blind, 28-week study of patients aged 18 to 65 years (N = 339) randomly assigned to receive risperidone (4-12 mg/day) or olanzapine (10-20 mg/day). Assessments were made using repeated-measures analysis. RESULTS: At both 8 weeks and 28 weeks, the magnitude of changes in Positive and Negative Syndrome Scale (PANSS) positive symptom subscale scores did not differ between treatment groups (8 weeks: risperidone, -6.5; olanzapine, -6.8, p = .866; 28 weeks: risperidone, -6.5; olanzapine, -7.0; p = .804). However, by the 8-week timepoint, olanzapine had reduced PANSS negative subscale scores significantly more than risperidone (-8.8 vs. -4.9, p = .032). By the 28-week endpoint, olanzapine had continued to maintain significantly greater reduction in baseline-to-endpoint PANSS negative scores (-8.1 vs. -3.5, p = .032) and led to significantly greater reduction in scores on the Scale for the Assessment of Negative Symptoms (SANS) dimensions of affective flattening (-5.2 vs. -0.6, p = .033) and alogia (-3.8 vs. -0.3, p = .007). Patients in the olanzapine treatment group also demonstrated numerically greater reduction of both SANS summary (-3.7 vs. -1.0, p = .078) and SANS composite scores (-14.1 vs. -4.1, p = .075). CONCLUSION: These data demonstrate that, in older patients with schizophrenia and related psychotic disorders, risperidone and olanzapine have approximately equal efficacy in controlling positive symptoms. However, olanzapine appears to be more efficacious in maintaining control over negative symptoms.

Adult↗

PubMed2003

[Preliminary study on HLA-B genotyping by oligonucleotide chips].

HLA genes constitute a highly polymorphic multigene system. In the present study, HLA-B oligonucleotide chips were manufactured by using a set of sequence-specific oligonucleotide probes derived from polymorphic regions in exon 2 and exon 3 of HLA-B gene spotted by microarrayer onto the aldehyde modified glass slides. In addition, the sequenced HLA-B gene clones used as standard samples were amplified from exon 2 and exon 3 by PCR. Together with the correct hybridization and wash conditions, the PCR products were bound with the array probes on the chip, and the hybridization patterns were transformed to HLA-B genotypes. The results showed that the genotypes of standard samples by the HLA-B oligonucleotide chips were completely identical with the sequenced clones. In conclusion, the oligonucleotide chip method presented here for HLA-B genotyping is a rapid, accurate, sensitive and attractive high throughput biochemical way.

Genotype↗

PubMed2003

[HLA-A genotyping by oligonucleotide arrays].

OBJECTIVE: To investigate HLA genotyping by oligonucleotide arrays. METHOD: Unsymmetrical PCR was used to amplify HLA-A gene exon 2, 3. The PCR products were used as templates for hybridization. The oligonucleotide probes were spotted on glass to make microarrays. High signal and specific probes were selected. The effects of the length and location of probes on hybridization signal were studied. A set of computer software was designed for scanning and genotype differentiation. RESULT: The genotypes of 30 samples analyzed by microarray showed concordance to that by SBT and PCR-SSP. CONCLUSION: HLA-A genotyping by oligonucleotide array is a good method with advantage of high speed, low cost and high flux.

Genotype↗

PubMed2003

[Application of Ac/Ds transposon system to genetate marker gene free transgenic plants in rice].

It is critical to generate marker gene free transgenic plants for retransformating or eliminating the potential harmfulness of marker gene and its product. In this study, Ac/Ds transposon system was developed for removal of hpt selection marker gene to obtain marker-free transgenic plants in rice ( Oryza sativa L.). Ds element containing the interesting gene bar was constructed next to the selection marker gene hpt to get Ds-T-DNA. Rice plants were transformed by Agrobacterium tumefaciens EHA105 containing Ac-T-DNA and Ds-T-DNA respectively. Rice plant containing single copy Ac-T-DNA was crossed with plant containing single copy Ds-T-DNA to obtain the F1 plant containing both Ac and Ds elements. F1 plant was self-crossed to produce F2 progeny in which T-DNA insert and transposed Ds element segregated independently. Two plants contained Ds element but no hpt marker gene in total 100 F2 plants. The result indicated that Ac/Ds transposon system could be used as a vector system for generating marker gene free transgenic plants in rice.

Agrobacterium tumefaciens↗

PubMed2002

Down-regulation of caspase 3 in breast cancer: a possible mechanism for chemoresistance.

Caspase-3 is a member of the cysteine protease family, which plays a crucial role in apoptotic pathways by cleaving a variety of key cellular proteins. Caspase-3 can be activated by diverse death-inducing signals, including the chemotherapeutic agents. The purpose of this study was to determine the levels of caspase-3 expression in breast tumor samples and to determine whether alterations in its expression can affect their ability to undergo apoptosis. Primary breast tumor and normal breast parenchyma samples were obtained from patients undergoing breast surgery and the expression of caspases-3 was studied. Similarly, normal mammary epithelial cells and several established mammary cancer cell lines were studied for caspases-3 expression by reverse transcriptase-polymerase chain reaction, Northern blot analysis, and Western blot analysis. Approximately 75% of the tumor as well as morphologically normal peritumoral tissue samples lacked the caspase-3 transcript and caspase-3 protein expression. In addition, the caspases-3 mRNA levels in commercially available total RNA samples from breast, ovarian, and cervical tumors were either undetectable (breast and cervical) or substantially decreased (ovarian). Despite the complete loss of caspase-3, the expression levels of other caspases, such as caspase-8 and caspase-9, were normal in all of the tumor samples studied. The sensitivity of caspase-3-deficient breast cancer (MCF-7) cells to undergo apoptosis in response to doxorubicin and other apoptotic stimuli could be augmented by reconstituting caspase-3 expression. These results suggest that the loss of caspases-3 expression may represent an important cell survival mechanism in breast cancer patients.

Base Sequence↗

PubMed2002

TGF-beta induced G(1) cell cycle arrest requires the activity of the proteasome pathway. Transforming growth factor.

Transforming growth factor-beta (TGF-beta) induces a potent G(1)/S-phase cell cycle arrest of epithelial cells by inhibiting the activities of cyclin D- and cyclin E-associated kinase complexes. Downregulation of the kinase activities is mediated by induction of cyclin dependent kinase (CDK) inhibitor p15(Ink4b) which blocks CDK4 and CDK6 kinases and leads to binding of p27(Kip1) to CDK2-cyclin E complex. Levels of several of these factors are controlled by the ubiquitin-proteasome pathway. We demonstrate here that proteasomal inhibitors release the cells from TGF-beta imposed G(1)-phase arrest and instigate the entry of the cells into S-phase. Proteasomal inhibitors are shown to specifically increase the activity of the cyclin D-kinase complex by increasing the levels of p27(Kip1) and cyclin D and by maintaining CDK4/6 protein levels leading to phosphorylation of the retinoblastoma protein without increasing cyclin E-associated kinase activity. The results indicate caution in the potential therapeutic use of the proteasome inhibitors due to unscheduled initiation of DNA replication in the presence of a physiological growth inhibitor.

Animals↗

PubMed2002

Proteasomal activity modulates TGF-ss signaling in a gene-specific manner.

Transforming growth factor-beta (TGF-beta) signaling relies on Smad-signaling pathway controlled in part by the proteasome. Here we demonstrate that inhibition of the proteasome function in mink epithelial cells accumulates both positive and negative modulators of TGF-beta signaling, phospho-Smad2 and SnoN. Inhibition of the proteasome led to abrogation of TGF-beta target gene regulation in a gene-specific manner. While regulation of p15Ink4b and myc by TGF-beta are lost, PAI-1 induction, previously shown to occur in a Smad3-dependent manner, was not affected by treatment of the cells with the proteasomal inhibitor MG132. The results suggest that proteasomal activity is required for TGF-beta signaling in a gene-specific manner.

Animals↗

PubMed2002

Transfection of CYP4A1 cDNA increases vascular reactivity in renal interlobar arteries.

20-HETE, a cytochrome P-450 4A (CYP4A1)-derived arachidonic acid metabolite, is a major eicosanoid formed in renal and extrarenal microcirculation. 20-HETE inhibits Ca(2+)-activated K(+) channels in vascular smooth muscle cells and thereby may modulate vascular reactivity. We transfected renal interlobar arteries with an expression plasmid containing the cDNA of CYP4A1, the low-K(m) arachidonic acid omega-hydroxylase, and examined the consequences of increasing 20-HETE synthesis on constrictor responses to phenylephrine. CYP4A1-transfected interlobar arteries demonstrated a twofold increase in CYP4A protein levels and 20-HETE production compared with arteries transfected with the empty plasmid; they also showed increased sensitivity to phenylephrine, as evidenced by a decrease in EC(50) from 0.37 +/- 0.04 microM in plasmid-transfected arteries to 0.07 +/- 0.01 microM in CYP4A1-transfected arteries. The increased sensitivity to phenylephrine was greatly attenuated by N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS), a selective inhibitor of 20-HETE synthesis, and by 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid, a specific 20-HETE antagonist. This effect of DDMS was reversed by addition of 20-HETE, further substantiating the notion that increased levels of 20-HETE contribute to the increased sensitivity to phenylephrine in vessels overexpressing CYP4A1. These data suggest that 20-HETE of vascular origin sensitizes renal vascular smooth muscle to phenylephrine.

Amides↗

PubMed2002

Serine 577 is phosphorylated and negatively affects the tRNA binding and eIF2alpha kinase activities of GCN2.

Protein kinase GCN2 regulates translation initiation by phosphorylating eukaryotic initiation factor 2alpha (eIF2alpha), impeding general protein synthesis but specifically inducing translation of GCN4, a transcriptional activator of amino acid biosynthetic genes in Saccharomyces cerevisiae. GCN2 activity is stimulated in amino acid-deprived cells through binding of uncharged tRNA to a domain related to histidyl tRNA synthetase. We show that GCN2 is phosphorylated by another kinase on serine 577, located N-terminal to the kinase domain. Mutation of Ser-577 to alanine produced partial activation of GCN2 in nonstarved cells, increasing the level of phosphorylated eIF2alpha, derepressing GCN4 expression, and elevating the cellular levels of tryptophan and histidine. The Ala-577 mutation also increased the tRNA binding affinity of purified GCN2, which can account for the elevated kinase activity of GCN2-S577A in nonstarved cells where uncharged tRNA levels are low. Whereas Ser-577 remains phosphorylated in amino acid-starved cells, its dephosphorylation could mediate GCN2 activation in other stress or starvation conditions by lowering the threshold of uncharged tRNA required to activate the protein.

Mass Spectrometry↗

PubMed2002

Probing domain swapping for the neuronal SNARE complex with electron paramagnetic resonance.

Highly conserved soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) proteins control membrane fusion at synapses. The target plasma membrane-associated SNARE proteins and the vesicle-associated SNARE protein assemble into a parallel four-helix bundle. Using a novel EPR approach, it is found that the SNARE four-helix bundles are interconnected via domain swapping that is achieved by substituting one of the two SNAP-25 helices with the identical helix from the second four-helical bundle. Domain swapping is likely to play a role in the multimerization of the SNARE complex that is required for successful membrane fusion. The new EPR application employed here should be useful to study other polymerizing proteins.

Cyclic N-Oxides↗

PubMed2002

The four-helix bundle of the neuronal target membrane SNARE complex is neither disordered in the middle nor uncoiled at the C-terminal region.

Assembly of the SNARE complex is an essential step for membrane fusion and neurotransmitter release in neurons. The plasma membrane SNAREs syntaxin 1A and SNAP-25 (t-SNAREs) and the delivery-vesicle SNARE VAMP2 (or v-SNARE) contain the "SNARE regions" that essentially mediate SNARE pairing. Using site-directed spin labeling and EPR distance measurement we show that two identical copies of the SNARE region from syntaxin 1A intertwine as a coiled coil near the "ionic layer" region. The structure of the t-SNARE complex appears to be virtually identical to that of the ternary SNARE complex, except that VAMP2 is substituted to the second copy of syntaxin 1A. Furthermore, it appears that the coiled coil structure is maintained up to residue 259 of syntaxin 1A, identical to that of the ternary complex. These results are somewhat contradictory to the previous reports, suggesting that the t-SNARE complex has the disordered midsection (Xiao, W. Z., Poirier, M. A., Bennett, M. K., and Shin, Y. K. (2001) Nat. Struc. Biol. 8, 308-311) and the uncoiled C-terminal region (Margittai, M., Fasshauer, D., Pabst, S., Jahn, R., and Langen, R. (2001) J. Biol. Chem. 276, 13169-13177). The newly refined structure of the t-SNARE complex provides a basis for the better understanding of the SNARE assembly process. It also provides possible structural-functional clues to the membrane fusion in the v-SNARE deleted fusion models.

Amino Acid Sequence↗

PubMed2002

No evidence for hypermethylation of the hSNF5/INI1 promoter in pediatric rhabdoid tumors.

The hSNF5/INI1 gene on chromosome 22 has been implicated as a tumor suppressor gene in pediatric rhabdoid tumor, an aggressive malignancy that generally occurs in the first two years of life. The most common sites for tumor development are the brain and kidney. We and other investigators have identified deletions and mutations of the INI1 gene in the majority of rhabdoid tumors of the central nervous system, kidney, and extrarenal tissues. At least 20% of cases do not have genomic alterations of INI1, although expression at the RNA or protein level may be decreased. The aim of this study was to determine whether hypermethylation or mutation of the 5' promoter region of INI1, or hypermethylation of CpG dinucleotides in a GC-rich repeat region within the first intron, could account for the decreased expression of INI1 observed in these tumors. We employed bisulfite modification, polymerase chain reaction, and sequence analysis to determine the methylation status of the cytosine nucleotides in the predicted promoter region of the INI1 gene, and two GC repeat regions in intron 1. DNA from 24 tumors with or without coding-sequence mutations was analyzed. None of the tumors demonstrated methylation of the promoter or intron 1 regions. This mechanism is unlikely to account for the inactivation of INI1 in rhabdoid tumors without coding-sequence mutations. One tumor demonstrated a potential mutation in the promoter region, but further studies are required for determining its functional significance.

5' Untranslated Regions↗