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Biomedical subjects

J Fu

Publications and source records attributed to J Fu.

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

CFTR chloride channel regulation by an interdomain interaction.

The cystic fibrosis gene encodes a chloride channel, CFTR (cystic fibrosis transmembrane conductance regulator), that regulates salt and water transport across epithelial tissues. Phosphorylation of the cytoplasmic regulatory (R) domain by protein kinase A activates CFTR by an unknown mechanism. The amino-terminal cytoplasmic tail of CFTR was found to control protein kinase A-dependent channel gating through a physical interaction with the R domain. This regulatory activity mapped to a cluster of acidic residues in the NH(2)-terminal tail; mutating these residues proportionately inhibited R domain binding and CFTR channel function. CFTR activity appears to be governed by an interdomain interaction involving the amino-terminal tail, which is a potential target for physiologic and pharmacologic modulators of this ion channel.

Adenosine Triphosphate↗
PubMed1999

Electron crystal structure of an RNA polymerase II transcription elongation complex.

The structure of an actively transcribing complex, containing yeast RNA polymerase II with associated template DNA and product RNA, was determined by electron crystallography. Nucleic acid, in all likelihood the "transcription bubble" at the active center of the enzyme, occupies a previously noted 25 A channel in the protein structure. Details are indicative of a roughly 90 degrees bend of the DNA between upstream and downstream regions. The DNA apparently lies entirely on one face of the polymerase, rather than passing through a hole to the opposite side, as previously suggested.

Crystallography↗
PubMed1999

Yeast RNA polymerase II at 5 A resolution.

Appropriate treatment of X-ray diffraction from an unoriented 18-heavy atom cluster derivative of a yeast RNA polymerase II crystal gave significant phase information to 5 A resolution. The validity of the phases was shown by close similarity of a 6 A electron density map to a 16 A molecular envelope of the polymerase from electron crystallography. Comparison of the 6 A X-ray map with results of electron crystallography of a paused transcription elongation complex suggests functional roles for two mobile protein domains: the tip of a flexible arm forms a downstream DNA clamp; and a hinged domain may serve as an RNA clamp, enclosing the transcript from about 8-18 residues upstream of the 3'-end in a tunnel.

Crystallography, X-Ray↗
PubMed1999

Role of ERAB/L-3-hydroxyacyl-coenzyme A dehydrogenase type II activity in Abeta-induced cytotoxicity.

Endoplasmic reticulum-associated amyloid beta-peptide (Abeta)-binding protein (ERAB)/L-3-hydroxyacyl-CoA dehydrogenase type II (HADH II) is expressed at high levels in Alzheimer's disease (AD)-affected brain, binds Abeta, and contributes to Abeta-induced cytotoxicity. Purified recombinant ERAB/HADH II catalyzed the NADH-dependent reduction of S-acetoacetyl-CoA with a Km of approximately 68 microM and a Vmax of approximately 430 micromol/min/mg. The contribution of ERAB/HADH II enzymatic activity to Abeta-mediated cellular dysfunction was studied by site-directed mutagenesis in the catalytic domain (Y168G/K172G). Although COS cells cotransfected to overexpress wild-type ERAB/HADH II and variant beta-amyloid precursor protein (betaAPP(V717G)) showed DNA fragmentation, cotransfection with Y168G/K172G-altered ERAB and betaAPP(V717G) was without effect. We thus asked whether the enzyme might recognize alcohol substrates of which the aldehyde products could be cytotoxic; ERAB/HADH II catalyzed oxidation of a variety of simple alcohols (C2-C10) to their respective aldehydes in the presence of NAD+ and NAD-dependent oxidation of 17beta-estradiol. Addition of micromolar levels of synthetic Abeta(1-40) to purified ERAB/HADH II inhibited, in parallel, reduction of S-acetoacetyl-CoA (Ki approximately 1.6 microM), as well as oxidation of 17beta-estradiol (Ki approximately 3.2 microM) and (-)-2-octanol (Ki approximately 2.6 microM). Because micromolar levels of Abeta were required to inhibit ERAB/HADH II activity, whereas Abeta binding to ERAB/HADH II occurred at much lower concentrations (Km approximately 40-70 nM), the latter more closely simulating Abeta levels within cells, Abeta perturbation of ERAB/HADH II was likely to result from mechanisms other than the direct modulation of enzymatic activity. Cells cotransfected to overexpress ERAB/HADH II and betaAPP(V717G) generated malondialdehyde-protein and 4-hydroxynonenal-protein epitopes, which were detectable only at the lowest levels in cells overexpressing either ERAB/HADH II or betaAPP(V717G) alone. Generation of such toxic aldehydes was not observed in cells contransfected to overexpress Y168G/K172G-altered ERAB and betaAPP(V717G). We conclude that the generalized alcohol dehydrogenase activity of ERAB/HADH II is central to the cytotoxicity observed in an Abeta-rich environment.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1999

Liquid-Saturated Hydrocarbons Resulting from Pyrolysis of the Marine Coccolithophores Emiliania huxleyi and Gephyrocapsa oceanica.

: Two nanoplanktonic marine coccolithophores, Emiliania huxleyi and Gephyrocapsa oceanica, were grown at 23 degrees C with a 16-hour light and 8-hour darkness regimen. The cells were dried at room temperature and then subjected to pyrolysis at 100 degrees to 500 degrees C under anoxygenic conditions to produce hydrocarbons. Temperature-dependent profiles of the liquid-saturated hydrocarbons (saturates) produced during pyrolysis were very similar for the two strains, although the total amount was higher in E. huxleyi than in G. oceanica. The amount of saturates produced was only 0.05% to 0.15% below 200 degrees C, but about 2.1% to 2.8% at 300 degrees C. Their major components were normal alkanes in a series ranging from nC(11) to nC(35) with the predominant peak at nC(15). At 400 degrees and 500 degrees C most of saturates transformed into gaseous compounds. The major saturates identified in all pyrolysates were normal C(31) monounsaturated and diunsaturated alkenes, a series of normal alkanes, phytenes, C(28) sterenes, and steranes. Profiles of saturates in gas chromatography-mass spectroscopy varied with increasing pyrolysis temperature and also differed between E. huxleyi and G. oceanica. The two coccolithophores are useful candidates for the production of renewable liquid fuel through pyrolysis-especially E. huxleyi, which has higher production. The results also provide information for further studies on the characterization, source, and paleogeographic distribution of marine sediment.

Journal Article↗
PubMed1999

Expression of a conifer glutamine synthetase gene in transgenic poplar

The assimilation of ammonium into organic nitrogen catalyzed by the enzyme glutamine synthetase (GS; EC 6.3.1.2) has been suggested to be the limiting step for plant nitrogen utilization (H-M. Lam et al. 1995, Plant Cell 7: 887-898). We have developed a molecular approach to increase glutamine production in transgenic poplar by the overexpression of a conifer GS gene. A chimeric construct consisting of the cauliflower mosaic virus 35S promoter fused to pine cytosolic GS cDNA and nopaline synthetase polyadenylation region was transferred into pBin19 for transformation of a hybrid poplar clone (INRA 7171-B4, Populus tremula x P. alba) via Agrobacterium tumefaciens. Transformed poplar lines were selected by their ability to grow on selective medium containing kanamycin. The presence of the introduced gene in the poplar genome was verified by Southern blotting and polymerase chain reaction analysis. Transgene expression was detected in all selected poplar lines at the mRNA level. The detection of the corresponding polypeptide (41 kDa) and increased GS activity in the transgenics suggest that pine transcripts are correctly processed by the angiosperm translational machinery and that GS1 subunits are assembled in functional holoenzymes. Expression of the pine GS1 gene in poplar was associated with an increase in the levels of total soluble protein and an increase in chlorophyll content in leaves of transformed trees. Furthermore, the mean net growth in height of GS-overexpressing clones was significantly greater than that of non-transformed controls, ranging from a 76% increase in height at 2 months to a 21.3% increase at 6 months. Our results suggest that the efficiency of nitrogen utilization may be engineered in trees by genetic manipulation of glutamine biosynthesis.

Journal Article↗
PubMed1999

Limited genetic variation in Lacerta mixta and its parthenogenetic daughter species: evidence from cytochrome b and ATPase 6 gene DNA sequences.

Little mtDNA variation was observed among populations of the bisexual Caucasian rock lizard Lacerta mixta and unisexual L. dahli and L. armeniaca. Three haplotypes were detected in L. mixta and the maximum pairwise difference among the samples was 0.67%. No intra- and interspecific variation was found among populations of either L. armeniaca or L. dahli. Moreover, both unisexual species were identical to one of the three haplotypes of L. mixta. The limited variation in L. mixta is likely the result of bottleneck effect, although the small sample size may also be responsible. The lack of variation in the unisexual was attributed to the restricted variation among the maternal parents, limited involvement of females in the hybridization, and recent origin.

Adenosine Triphosphatases↗
PubMed1999

Discriminating and locating character covariance: an application of permutation tail probability (PTP) analyses.

The ability of permutation tail probability (PTP) analyses to discriminate between character covariance and noise is investigated with both hypothetical and published data sets. PTP is shown to be a powerful tool, not only for detecting character covariance, but also for locating that covariance on trees. PTP is especially useful for evaluating DNA sequence data that may have a high level of homoplasy. A three-step PTP procedure for locating covaried characters is presented.

Animals↗
PubMed1999

A stop-codon mutation in the human mtDNA cytochrome c oxidase I gene disrupts the functional structure of complex IV.

We have identified a novel stop-codon mutation in the mtDNA of a young woman with a multisystem mitochondrial disorder. Histochemical analysis of a muscle-biopsy sample showed virtually absent cytochrome c oxidase (COX) stain, and biochemical studies confirmed an isolated reduction of COX activity. Sequence analysis of the mitochondrial-encoded COX-subunit genes identified a heteroplasmic G-->A transition at nucleotide position 6930 in the gene for subunit I (COX I). The mutation changes a glycine codon to a stop codon, resulting in a predicted loss of the last 170 amino acids (33%) of the polypeptide. The mutation was present in the patient's muscle, myoblasts, and blood and was not detected in normal or disease controls. It was not detected in mtDNA from leukocytes of the patient's mother, sister, and four maternal aunts. We studied the genetic, biochemical, and morphological characteristics of transmitochondrial cybrid cell lines, obtained by fusing of platelets from the patient with human cells lacking endogenous mtDNA (rho0 cells). There was a direct relationship between the proportion of mutant mtDNA and the biochemical defect. We also observed that the threshold for the phenotypic expression of this mutation was lower than that reported in mutations involving tRNA genes. We suggest that the G6930A mutation causes a disruption in the assembly of the respiratory-chain complex IV.

Adult↗
PubMed1999

Characterization of MAP kinase and PKC isoform and effect of ACE inhibition in hypertrophy in vivo.

Protein kinase C (PKC) and mitogen-activated protein (MAP) kinase activation appear important in conferring hypertrophy in vitro. However, the response of PKC and MAP kinase to stimuli known to induce hypertrophy in vivo has not been determined. We recently demonstrated that pressure-overload hypertrophy induced a transiently transfected gene driven by an hypertrophy responsive enhancer (HRE) through a marked increase in binding activity of its interacting nuclear factor (HRF). These data suggested that the HRE/HRF could serve as a target for evaluating the signal transduction events responsible for hypertrophy in vivo. Accordingly, we characterized MAP kinase and PKC isoform activation, injected HRE driven reporter gene expression, and HRF binding activity in rat hearts subjected to ascending aortic clipping or sham operation in the presence of the angiotensin-converting enzyme (ACE) inhibitor fosinopril, hydralazine, or no treatment. Analyses showed that PKC-epsilon and MAP kinase were acutely activated following ascending aortic ligature and that fosinopril significantly inhibited but did not completely abrogate PKC-epsilon and MAP kinase activation. However, fosinopril completely prevented pressure overload-mediated induction of HRE containing constructs and obviated increased HRF binding activity. These results suggest a direct relationship between ACE activity and HRE/HRF-mediated gene activation and imply that PKC-epsilon and MAP kinase may be involved in transducing this signal.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

[A preliminary study on the genetic susceptibility of asthma in a Chinese population].

OBJECTIVE: To study the asthma genetic susceptibility by way of ccandidate region so as to accumulate data on the related loci in Chinese population and determine whether genetic susceptibility to asthma is linked to the chromosome region. METHODS: One hundred ninety-two samples from 32 families were collected from Zhaoan county in Fujian province. Two Rsa I polymorphic sites within uncoded region of the high-affinity IgE receptor beta chain gene (Fc(epsilon) RI-beta) located on chromosome 11q13 were detected by PCR/Rsa I restriction endonuclease digestion. The polymorphic markers D5S436 and D5S393 within chromosome 5q31-33 were amplified by PCR incorporated with radioactive isotope. The asthma family samples were compared with unrelated samples randomly selected from general population. RESULTS: Genotypes containing A allele within intron 2 polymorphic site of Fc(epsilon) RI-beta gene were associated with asthma (P<0.05,OR = 2.039). Significant difference in the level of total serum IgE was noted among three genotypes of intron 2 polymorphic site of Fc(epsilon) RI-beta gene (P<0.05). The association between A allele and elevated total serum IgE was also significant (P<0.05, RR = 1.361). No relationship between exon 7 polymorphic site of Fc epsilonRI-beta gene and asthma was shown. By sib-pair analysis, significant evidence for linkage to asthma was observed with D5S436 (P<0.05) but not with D5S393. No significant linkage to total serum IgE was identified with both of these markers. CONCLUSION: The above-accumulated data suggested that both Fc epsilonRI-beta gene and chromosome 5q31-33 could be very attractive candidate gene and region for further studies in Chinese population, and to confirm these preliminary results, more markers within these regions merit testing in additional population samples.

Adolescent↗
PubMed1999

[Vector construction for embryonic stem cell gene targeting of site specific point mutation mouse coagulation factor IX gene].

OBJECTIVE: To construct the recombinant vectors for embryonic stem(ES) cell gene targeting which contain the mouse coagulation factor IX (F IX) gene modified by PCR site-directed mutagenesis. METHODS: Three site specific point mutations were introduced into exon 8 of mouse F IX gene respectively. The replacement targeting vectors were constructed and transfected into ES cells. The drug-resistant cell clones were picked after drug selection. RESULTS: The construction of targeting vectors was successful and several drug-resistant ES cell clones were gained. CONCLUSION: The site specific point mutation system can modify human gene in vitro more accurately. It is useful in the setting up of animal models.

Animals↗
PubMed1999

[Perioperative use of peripherally inserted central catheter for parenteral nutrition in patients with abdominal malignancy].

OBJECTIVE: To evaluate the use of peripherally inserted central catheter(PICC) in perioperative patients with abdominal malignancies for parenteral nutrition. METHODS: PICC was performed in 33 patients while subclavicular vein insertion in 30 patients for comparison in order to analyse prospectively the advantages and disadvanges of PICC. RESULTS: There was no difference in the rate of success of catheter placement and infection between PICC and the "subclavicular" insertion (P > 0.05), but PICC had significantly longer indwelling time than that of the "subclavicular" insertion (P < 0.05). There were less risks associated with PICC insertions, but the flow rate of was lower(p < 0.05). CONCLUSIONS: PICC can be widely used on account of its longer indwelling time, easy and safe insertion.

Abdominal Neoplasms↗
PubMed1999

[A study of mitoxantrone with other chemical agents in treating 126 cases of adult acute myeloid leukemia].

OBJECTIVE: To estimate the effect of mitoxantrone with other chemical agents in treating adult acute myeloid leukemia. METHODS: 126 inpatients diagnosed as acute myeloid leukemia between January 1993 to December 1997 were treated with mitoxantrone with other chemical agents. 85 had not been treated previously, (untreated) while 51 were relapsing or resistant to previous treatment. RESULTS: The complete response rate among untreated and the relapsing/resistant groups were 44.7% and 27.5%; while the partial response rate were 20.0%, 9.8% respectively. 4 patients were in the untreated group died early. The main side-effect of mitoxantrone is bone marrow depression which led to fever and bleeding with rates of 40.4%, 24.3%. The non-bone marrow side-effects were tolerable. Damage to the liver was a prominent occurrence 31.8%. CONCLUSION: mitoxantrone was effective as the first line anti-tumor drug with other chemical agents in treating adult acute myeloid leukemia, its side-effects were mild.

Adolescent↗
PubMed1999

[Effect of tian ma cu zhi chongji medicinal granules (TMCZCJ) on blood rheology in hypostasis rats due to stagnation of liver-qi and learning-memory disorder in cerebral ischemia-reperfusion mice].

OBJECTIVE: To investigate the effect of TMCZCJ on the blood rheology in hypostasis rats due to stagnation of the liver-qi and on the learning-memory disorder in cerebral ischemia-reperfusion mice. METHOD: The models of hypostasis due to stagnation of the liver-qi were made by combining irritation with hypodemic injected adrenalin and ice-bath in rats, and the models of learning-memory disorder were made by repeatedly ligating-reperfusing the bilateral carotid in mice. The hypostasis rats and learning-memory disorder mice were perorally administrated TMCZCJ(7.7, 15.4 g.kg-1) once a day, for fourteen consecutive days. RESULT: TMCZCJ can significantly reduce plasma viscosity, blood viscosity and reduced viscosity in hypostasis rats. It can also improve the latent learning-memory capability and memory gain-repetition ability in water-maze for cerebral ischemia-reperfusion mice. CONCLUSION: TMCZCJ can improve remarkably blood rheology in hypostasis rats and learning-memory disorder in cerebral ischemia-reperfusion mice.

Animals↗
PubMed1999

[Study of mutagenesis of two procarcinogens in human amnion cells using a shuttle vector pWB1].

Using 2 x 10(-5) mol/ml beta-NF (beta-naphthoflavone) to induce FL cells to express cytochrome P450 isozymes at a reasonable level, we have studied the mutagenesis of two procarcinogens, aflatoxin B1 and benzo (alpha)pyrene, at four different doses. Except for their top doses, all other doses induced mutation in target gene SupF carried by plasmid pWB1 at the frequency of 10(-4), which is higher than the spontaneous mutation frequency (7.61 x 10(-6)). Aflatoxin B1 demonstrated normal effect-dose relationship. Meanwhile no mutant was detected in their correspondent negative controls. All the results suggest that shuttle vector pWB1 can be conveniently used for detection of procarcinogens and study of their mutagenesis mechanisms in human cells.

Aflatoxin B1↗
PubMed1999

[Studies on reduction of Au3+ by bacteria for preparing gold catalyst].

The strain D01, screened from different source bacterial strains, has relatively strong ability of adsorbing Au3+. The strain D01 was identified as Bacillus megatherium D01 and still grew well in the medium containing 600 mg/L Au3+. The results of electrochemical reaction indicated that the strain D01 had a strong ability of reduction. It could reduce the Au3+/alpha-Fe2O3(precursor of the gold catalyst) to highly dispersive Au0/alpha-Fe2O3 catalyst which could catalyze the reaction of CO + O2-->CO2.

Adsorption↗